CA1207697A - Selective dewaxing of hydrocarbon oil using surface modified zeolites - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A method for selectively dewaxing a waxy hydro-carbon oil feedstock comprising contacting said waxy hydrocarbon oil stock in the presence of hydrogen with a zeolite (1) which has been chemically modified by reaction, under dry, anhydrous conditions, with an organosilane wherein the zeolite has some reactive sites capable of reacting with the organosilane and where said organosilane is: (a) capable of entering into the channels of the zeolite and chemically reacting with the reactive sites present therein, as well as (b) reacting with hydroxyl groups present on the external surface of said zeolite, and (2) which has been loaded with a catalytically active hydrogenating metal component; which contacting is con-ducted under conditions of pressure, temperature and liquid flow velocities sufficient to effect the hydro-dewaxing. Preferably the organosilane modified zeolite, either before or after the deposition of the catalytic metal component may be heated to an elevated temperature in an inert or reducing atmosphere.

Description

~LZ~ t7 1 DEscRIprrI _ OF THE INVENTION

2 A method is described for selectively dewaxing

3 a waxy hydrocarbon oil feedstock which method comprises

4 contacting said waxy hydrocarbon oil stock in the presence

5 of hydrogen with a zeolite (l) which has been chemically * 6 modified by reaction, under dry, anhydrous conditions, L 7 with an organosilane wherein the zeolite has some sites . ~ ~ capable of reacting with the organosilane and wherein g said organosilane is: ~a) capable of entering into the 10 channels of the zeolite and chemically reacting with the 11 reactive sites present therein, as well as (b) reacting 12 with hydroxyl groups present on the external surface 13 oE said zeolite, and (2) which has been loaded with a 14 catalytically active hy~rogenating metal component;
15 said contacting being conducted under conditions of 16 pressure, temperature and liquid flow velocities suffi-17 cient to effect the hydrodewaxing. Preferably the 18 organosilane modified zeolite, either beore or after 19 the deposition of the catalytic metal component may 20 be heated to an elevated temperature in an inert or 21 reducing atmosphere This heating may be conducted as 22 an independent operation or may be conducted in situ 23 in the catalytic dewaxing environment. In either case, 24 the atmosphere employed is inert or reducing and is 25 preferably hydrogen or contains hydrogen. Such deliberate 26 or in situ heating is conducted to form a stable surface 27 resulting from condensationpolymerization reactions. The 28 temperatures Ghosen for imparting this stability are 29 usually at or above the temperature of the subsequent 30 catalytic process, but, preferably about 300 to 500C, 31 more preferably 400 to 500C.
32 The waxy hydrocarbon oil which is dewaxed 33 may be any natural or synthetic hydrocarbon oil~ pre-34 ferably a waxy petroleum oil, most preferably a waxy 35 specialty oil such as a lube or transformer oil.
36 Under certain conditions, treatment with 37 organosilanes rnay improve the hydrodewaxing selectivity 38 and activity maintenance of zeolites known to have some , 7~9~7 1 utility for this process. Furthermore, zeolites which are 2 known to have little or no hydrodewaxing selectivity can 3 be converted to this use by treatment with organosilanes.

Silylation of surfaces has been practiced

6 extensively since the early 1950's. USP 2,722,504

7 to Fleck described methods for improving the organo-

8 philicity of catalysts and adsorbents by treating with

9 compounds of the general type RlR2R3Six where RlR2 and R3 may be organic non-hydrolyzable moieties and x is a 11 hydrolyzable group including halogens, alkoxy and other 1~ groups which separate from silicon in the presence of 13 water. Though Fleck did not describe the reaction, the 14 surface hydroxyls of insulating surfaces like silica, alumina, magnesia and zeolites, may interact with such 16 silanes in the following way~

17 si(S) _ O + RlR2R3SiX Si(s) - O - siRlR2R3 18 H +HX

19 ~s) denotes a surface silicon Many variations on this reaction with other silicon 21 reagents and other suraces but particularly silica have 22 been studied, see: "Study of the Surface and Bulk 23 Hydroxyl Groups of Silica by Infra-red Spectra and D2O
24 Exchange", Kiselev et al, Trans. Farad. Soc. 60, 2254 (1964); "Reactions of Chlorosilanes with Silica Surfaces"
26 ~air et al, J. Phys. Chem. 73 #7, 2372 July 1969; t'Reac-~7 tions of Chloromethyl Silanes with Hydrated Aerosil 28 SilicasW Armestea~ et al, Trans. FaradO Soc. 63, 2549 29 (1967); "Adsorption and Reaction of Methylchlorosilanes at an 'Aerosill Surface" Evans et alj J. Catalysis 11, 31 336-341 (196~).
32 More recently, patents have been issued per-33 taining to the reactions of organosilanes with zeolites 34 and the subsequent benefits of this treatment.
USP 3,682,996 issued to Kerr claims a æeolite '7~3t7 1 ester product (more properly described as a silicon ether) 2 derived from the reaction between a silane containing an 3 available hydrogen atom and an aluminosilicate zeolite.

O-AL Oj~ Si O + RXSiH4_x O-AL T - si o 6 O E~ O O SiRX

7 where x is between 1 and 4 and where R is independently at 8 least one organic radical, suitably aryl, alkyl, acyl, 9 aralkyl but preferably alkyl because the pore structure will more readily accept alkylsilanes than arylsilanes.
11 Apart from these classes of silanes Rerr makes a reference 12 to one other silane not fitting this formula, hexamethyl 13 disilazane. Kerr does not disclose or claim usage of 1~ halosubstituted silanes.
The reactions described by Kerr all occur under 16 vacuum conditions wherein the outgassed H form ~eolite is 17 contacted with pure organosilane vapor or liqu;d at 18 various temperatures. Kerr discloses, but does not 19 demonstrate or claim, that the silylated zeolite may be used in catalytic applications, including "certain shape 21 selective catalyzed reactions".
22 USP 3,726,309 to Allum claims a product derived 23 from the reaction of an inorganic material containing 24 hydroxyl groups, including aluminosilicates, modified by treatment with an organic radical substituted silane.
26 Bound silicon ethers are formed by reaction with the 27 surface hydroxyl groups. -28 USP 3,658,696 to Shively claims an improved 29 separation process resulting from the reactions o ~eolite molecular sieves with organosilanes. The replacement of 31 OH radicals on the zeolite surface with silane radicals 32 si9nificantly affects the surface adsorption properties of 33 the molecular sieve because the hydroxyl groups are the 34 main centers of surface adsorption. In this instance 0~7t~7 bulky silanes were chosen which reacted with only the 2 external surface of the zeolite.
3 Zhomov et al, Katal, Pererab, Uylevodorad, 4 Syr'ya 1968 (2) 9 (from Ref. Zh . Khim 1969 abstract No. 4N196) used a methyl chlorosilane to change the - 6 properties of an aluminosilicate used to alkylate phenol 7 with a tetran~eric propylene.
8 USP 3,980,586 to Mitche]l claims a new product 9 resulting from a sequence of silylation/ calcination and steaming of a group of materials consis~ing of alumina, 11 silica alumina and aluminosilicates. Calcining continues 12 for a sufficient time and at high enough temperatures-to 13 remove all of any introduced organic or halogen substi-14 tuent (unlike Kerr, Mitchell has used a more general form of silanes which includes halogens). The amount of silane 16 used was sufficient to achieve about 1-5% of a new SiO2 17 layer. USP 4,080,284 to Mitchell claims the new materials 18 to be useEul for catalytic hydroconversion.
1~ USP 4,002,697 to Chen used a silane treatment on ZSM-5 to improve the yield of p-xylene from methylation of 21 toluene. In thi5 instance the silane was chosen so as to 22 interact only with the external surface.
23 USP 3,698,157 and USP 3,724,179 to Allen demon-24 strated that improved separation of Cg aromatics could be achieved by contacting alumino-silicate adsorbents with 26 organic radical or halo substituted silanes~
27 A lication of Silvlation to Elvdrodewaxina PP ~
28 Despite the wealth of work reported on silane 29 treated surfaces it had yet to be demonstrated that silylation can improve the hydrodewaxing activit:y of 31 zeolite based catalysts.
32 An ideal hydrodewaxing catalyst would have 33 several necessary chemical and physical features.
34 The zeolite would have a pore size which is large enough to admit waxy n-paraffins and slightly 36 branched paraffins but small enough to exclude, or diffuse 37 only slowly, "non paraffinic" oil molecules. The relative 38 rates of zeolite diffusion of waxy and non-waxy components ~ `';

3'7~

1 would be sufficiently different so as to favour the 2 selective conversion of the paraffinic species.
3 Further the ideal zeolite should have a rela-4 tively lo~ total population of acidic (hydroxyl) sites but also a finite concentration of highly acidic sites. Such 6 a system would be relatively hydrophobic to improve the 7 diffusional transport of paraffins to the active sites, 8 but the few highly acidic sites in the syste~ would be 9 very efficient in converting the paraffins to light gas products.
11 The dewaxed oil product from this process would 12 have to be stable and of high yield (comparable to ~olvent 13 dewaxing).
14 Most of these properties are not commonly associated with zeolites but one zeolite does stand out 16 as a system for hydrodewaxing and many other hydroconver-17 sion processes; Mobil's ZSM-5 (USP 3,702l886). ZSM-5 18 has a highly stable framework containing two types of 19 intersecting channels which have ten-membered ring openingsO These are therefore intermediate between those 21 of classical shape-selective zeolites with 8 membered 22 rings (zeolite A, erionite) and the larger pore 12 23 membered ring zeolites (faujasite, X,Y, mordenite and 24 fault free offretite).
ZSM-5 has two sets of channels, in one direction 26 the channels are sinusoidal with near circular openings 27 of about 0.55 nmO The other channels are straight with 28 elliptical cross section (o.52 - 0.58 nm) Nature 272~ 437 29 (1978) Further the zeolite can be crystallized with very high SiO2 contents giving it hydrophobic properties.
31 The success of ZSM-5 as a selective dewaxing catalyst 32 is that the zeolite imposes configurational diffusion 33 restrictions within the pores rather than by molecular 34 screening which is observed for the smaller pore, clas-sical, shape selective zeolites~
36 In the present case three zeolites have been 37 studied to determine the potential for improved hydro-38 dewaxing performance by silylation of zeolite. Two ~ . - .

( l of the zeolites (mordenite and offretite) have pore 2 diameters in the range known to be effective for hydro-3 dewaxing, although mordenite (6.96 x 5.81 elliptical) and 4 offretite (6~4 R circular) are both larger than ZSM-5 (5.5 A ci~cular and 5.4x5.7 R elliptical). The othe~
6 zeolite, zeolite Y, has a large pore (7.4R~ and is not 7 known to demonstrate shape selective properties.
8 Zeolite Y is one of the largest known 12 ring 9 zeolites and is used in hydrocracking applications where hydrocarbon molecules of various types and shapss 11 are converted. One useful feature of this type of struc-12 ture is that it has a, 3 dimensional network of connecting 13 supercages which not only permits organosilanes to be 14 readily adsorbed (see: "Modification of ~I Y Zeolites by Reaction with Tetramethylsilane" McAteer et al, ACS
16 Advances in Chem 121 1973, "Molecular Sieves" ed, WO M.
17 Merer & J. B. Uytterhoeven and "Sorption of Hydrocarbons 18 and Water in Silanated and Unsilanated Partial H-Forms of 19 Zeolite Y" Barrer et al, J. C. S. Faraday 1 75 (9) 2221 ~1979)) but could potentially be a surface network that 21 rapidly diffuses hydrocarbon (e.g~ wax) molecules although 22 these references do not teach, suggest or imply such a 23 use.
24 In principle each of these ~eolite systems could be improved by silylation since each has an inherently 26 larger pore than ZSM-5 and the systems are highly hydro-27 philic in their "as crystallized formsn.
28 In the present invention the use of such surface 29 modifi~d zeolites for catalytic dewaxing of waxy hydro-carbon oils is revcaled for the first time~
31 Thus thQ presen~ invention provides ~ meth~d for 3,, selectively dewax-~,ng a ~axy 33 hydrocarbon oil feedstock characterized by contactinq said 34 waxy hyd.ocarbon oil stock in the presence of bydrogen ;

9'7 - 6~

1 and under conditions of pressure, temperature ~nd flow 2 velocity sufficient to effect the dewaxing with a zeolite, 3 which zeolite (1) has been modified by reaction under 4 anhydrous conditions with an organosilane wherein the zeolite to be modified possesses ~eactive sites capable 6 of reacting with the organosilane and wherein the organo-7 silane is capable of entering into the channels of the 8 zeolite and reacting with the reactive sites present ~ therein as well as reacting with reactive sites present on the external surface of said zeolite and (2) has been 11 loaded with a catalytically active hydrogenating metal 12 component.
13 In another aspect of the invention) there is 1~ provided a method for surface modifying a large pore 1~ æeolite so ~s to produce a material retaining sufficient catalytically active sites to be suitable for use as a catalyst, 17 which method com~rises chemically modifyin~ said large pore 18 zeolite by reacting said zeolite under anhydrous conditions with 1~ an organosilane wherein the starting zeolite to be modified ~o possesses sites some of which are available for reaction with the 21 organosilane and wherein some of the sites hav~ been protected to 22 prevent reaction with the organosilane and wherein the 23 organosilane is capable of entering into the channels of the 24 zeolite and reacting with the available reactive sites present therein as well as reacting with reactive sites present on the 26 external surface of said zeolite.

28 Figure 1 shows the infrared spectrum of the 2~ vapor phase reaction of hexamethyldisiloxane, HMDSO
with H-zeolite Y (containing hydrogen bonded hydroxyls).
31 Figure 2 shows the infrared spectrum of the 32 vapor phase reaction of HMDSO with H-zeolite Y (containing 33 isolated sites).
3~ Figure 3 shows the infrared spectrum of vapo~

. .

~7~~

uhase reaction of dichlorodimethyl silane with H-zeolite Y
containing mixed isolated and hydrogen bonded hydroxylis.
Figure 4 shows the infrared spectrum of the vapor phase reaction of HMDSO with H-zeolite Y, containing reactive sites comprising a mixture of isolated hydroxylis and strained bridge sites arising from dahydroxylation of hydrogen bonded hydroxylis.
Figure 5 shows infrared spectrum of the adsorption of pyridine on HMD~ modified catalyst A-l.
Figure 6 shows the infrared spectrum of the vapor phase reaction of catalyst ~-1 (offretite) with HMDS~.
Figure 7 shows the dewaxing performance on Western Canadian 150N of Type B and modified Type B catalyst (from offretite) .
THE INVENTION
A method is described for selectively dewaxing a waxy hydrocarbon oil feedstock which method comprises contacting said waxy hydrocarbon oil stock in the presence of hydrogen with a xeolite (1) which has been chemically modified by reaction, under dry, anhydrous conditions, with an organosilane wherein the zeolite has some sites capable of reacting with the organosilane and wherein said organosilane is: (a) capable of entering into the channels of the zeolite and chemically reacting with the reactive sites present therein, as well ~s (b) reacting with hydroxyl groups present on the external surface of said zeolite, and (2) which has been loaded with a catalytically active hydrogenating metal component; said contactiny beiny conducted under conditions of pressure, temperature and liquid flow velocity sufficient to effect the hydrodewaxing.
In another aspect, the invention provides a method for surface modifying a large pore zeolite so as to produce a material retaining sufficient catalytically active sites to be suitable for use as a catalyst, which method comprises chemically modifying said large pore zeolite by reacting said zeolite under anhydrous conditions with an oryanosilane wherein the starting zeolite to be modified possesses sites some o~ which are - 7a -available for reaction with the organosilane and wherein some o~
the sites have been ~rotected to prevent reaction with the organosilane and wherein the organosilane is capable of entering into the channels of the zeolite and reacting with the available reactive sites present therein as well as reacting with reactive sites present on the external surface o~ said zeoliteO
In yet another aspect, the invention provides a method for surEace modifying a larye pore zeolite so as to produce a material retaining sufficient catalytically active sites to be suitable for use as a catalyst, which method comprises partially cation exchanging the zeolite, calcining and cooling under anhydrous conditions, reacting said zeolite under anhydrous conditions with an organosilane capable of entering into the channels of the zeolite and reacting with the reactive sites present therein as well as reacting with reactive sites present on the external surfaca of said zeolite, reexchanging the silylated zeolite and calcining in moist atmosphere the reexchanged zeolite to generate new sites which are catalytically active.
DESCRIP~ION OF OILS
The waxy oils which can be processed by these catalysts range from liyht middle distillates or heating oils, boiling in the range 200C - 385C, to heavy lube distillates and deasphalt~d vacuum residuum boiling up to 580C. Pra~erred oils are light and middle distillate '7 1 oils and raffinates, such as kerosene, lube or transformer 2 oils.
3 The oils used to exemplify catalyst performance 4 are described in detail in Table 1.
DESCRIPTION OF ZEOLITES
-6 The zeolite which is surface modified and 7 loaded with a catalytically active hydrogenatiny metal 8 component (or vice versa) may be any natural or synthetic 9 unfaulted alumino-silicate material such as mordenite, offretite, (both natural and synthetic), offretite type 11 zeolites, zeolite X, zeolite Y, zeolite L, zeolite omega, 12 etc.
13 For the purposes of the application, both 14 natural and synthetic zeolites are contemplated. Zeolite material embraced in this application fall into two broad 16 categories, those having an average pore size of about 17 7~ or greater, which are termed "large pore zeolites'~ and 18 those having an average pore size of less than about 7~, 19 which are termed "intermediate pore zeolites". Represen-tative of "large pore zeolites" are zaolite X, Y~ L, 21 omega. Representative of "intermediate pore zeolites" are 22 mordenite, offretite, offretite type zeolites, ZSM-5, 23 erionite.

In this invention, the zeolites of either 26 category are treated with organosilanes under specific 27 conditions which were explained in greater detail above to 28 effect condensation and polymerization.
29 The organosilanes employed in the preparati~n of the catalyst useful in the process of the present 31 invention come from the classes:
32 Si Ry X4 y and (Rw X3-w Si)2 - Z; wherein:
33 y = 1 to 4; w = 1 to 3 34 R = alkyl, aryl, H, alkoxy, arylalkyl, and where R has from 1 to 10 carbon atoms; X = halide and X = Oxygen 36 or NH or substituted amines or amides.
37 Examples of useful organo silanes are: hexamethyl 38 disilazane hexamethyldisiloxane, dichlorodimethyl silane, 1~0'76'3'7 g 1 monochloro trimethyl silane, methoxyltrimethyl silane, 2 N-methyl-N-trimethyl silyl trifluoro acetamide.
3 The organosilanes found most useful in this 4 work are hexamethyl disiloxane (HMDSO) and hexamethyl disilazane (HMDS).

7 Typical conditions for hydrodewaxing with these - 8 catalyts are 250 - 450C, preferably 250 - 380C. The g lower temperatures are preferred so as to reduce non-selective cracking. Typical pressures employed are 11 200 - 2090 psig H2, preferably 300 - 1000 psig H2 and 12 most preferably 400 - 700 psig H2. Feed rates may range 13 from 0.1 to 100 LHSV, preferably 0.1 to lOo Excess 14 gas rates may range from 1000 - 20/000 SCF H2/BBL but preferably from 1000 - 5000 SCF H2/BBL.

17 The object of treating zeolite catalysts with 18 the organosilanes is to convert the surface from a 19 hydrophilic into a hydrophobic form and to reduce the zeolite pore size and pore volume.
21 If zeolites are crystallized with organic 22 templating ions such as tetramethyl ammonium ion, they 23 must be first treated so as to remove these species. In 24 general, zeolites are calcined to remove organic templates and/or to create enough sites for sllylation by using NH4~ ion exhange or other techniques known in the art.
27 The zeolite containing the organic templating 28 agent (such as tetramethylammonium) is exchanged, prior to 29 or after calcination to decompose the templating agent, for example with NH4+ to remove cations. The zeolite 31 is then preferably loaded with a catalytically active 32 hydrogenating metal component using a metal salt, prefer-33 ably where the metal is a cation.
34 The conversion into the form active for silyla-tion may also be done before metal loading, but it is 36 preferred that the metal be loaded on an NH4+ form of 37 the zeolite prior to the calcination step which leads to 38 the reactive form of the zeolite.

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l The metal salt is then reduced to elemental 2 metal using techniques known in the art. Group VI
3 and/or VIII metals can be used. Pt and Pd are particu-4 larly useful preferably in the range 0.1 to 2.0 wt % based on dry zeolite, more preferably 0.1 - 1.0 wt % and most S peferably 0.2 - 0.5 wt %.
7 Metal loading and ammonium exchange may also 8 follow in some instances procedures used to increase g SiO2/Al2O3 ratio such as H4 EDTA leaching or other techniques well known in the art. Metal loading may also ll follow the silylating step, which is discussed in detail 12 below, but preferably precedes the silylat;ng step.

14 After the zeolite has been exchanged and a metal salt has been deposited, the zeolite is then treated so as 16 to generate sites which will react with the organosilane.
17 The sites which so react are either isolated hydroxyl 18 groups and/or strained bridge sites~ For the purpose l9 of this specification the term "reactive site" will be understood to include isolated hydroxyl groups and 21 strained bridge site.
22 The method employed for the generation of 23 isolated hydroxyl group depends upon the type of zeolite 24 being employed and the organosilane used. An isolated site is one whlch has no close neighbors so that hydroxyl-~6 hydroxyl interaction are rninimal.
27 In zeolites which have low SiO2/Al2O, ratios 28 (i.e., high site densities) care must be taken to employ 29 methods which generate the desired isolated sites. Such 30 methods include calcination of an ammonium form æeolite 31 in a dry environment, for example, dry hydrogen, and 32 maintaining a moisture free surface (i.e~, a dry environ 33 ment) at all times prior to and during silylation.
Alternatively, isolated hydroxyl sites may be created by 35 permitting minirnal cation exchange thereby generating a 36 low density of hydroxyls reducing the possibility of 37 hydroxyl-hydroxyl interaction. Another method would be to 38 increase the silica to alumina ratio of the zeolite which D'~7 1 also reduces site populations and minimizes interactions.
2 The other type of reactive sites, the strained 3 bridge sites are generated from hydrogen bonded hydroxyl 4 sites by dehydroxylation. Hydrogen bonded hydroxyl sites may first be generated by calcining an ammonium form 6 zeolite in m~ist air and particularly by cooling in moist 7 air ater decomposition of the ammonium form to tempera-8 tures below 100C. If the population of hydroxyls so 9 generated is high enough then they may be close enough to each other to interact through hydrogen bonds~ Such 11 sites are essentially unreactive with silylating agents, 12 however, if this surface is again heated this time in a 13 dry environment to temperatures above about 300C these 14 sites collapse losing chemical water leaving behind a strained bridge site. This site is reactive with sily-16 lating agents. Dehydroxylation is schematically repre-17 sented below:

18 Si-0\ ~ Si 19 H ~ 0 + H2O
20 Si-0 heat - Si /
21 \ H

22 Mixtures of reactive sites ~isolated hydroxyls and 23 strained bridge sites) can be generated by varying the 24 conditions of dryness and activation temperature. --SILyLATIoN
26 Silylation is performed by contacting the 27 zeolite under anhydrous conditions with either vaporous or 2~ liquid organosilanes or by dissolving the organosilane in 29 a dry organi~ solvent, such as hexane, heptane, naphtha or lube oil, and contacting the solution with the 2eolite, 31 with or without the metal hydrogenation component present, 32 at from 20 to 500C depending on the zeolite being 33 treated and the silane used (as is explained in greater 34 detail below). The silylating solution will contain from about 0.01 to 20% silane, preferably 1 to 5% silane (by 36 volume).

1 If the organosilane is not reacted directly with 2 the surface as a vapor or liquid then it may be used as an 3 organic solution where the solvent is preferably non polar 4 and non aromatic and should preferably contain no greater than 10 ppm water. Total free water content of both the 6 zeolite and the solvent should not exceed 10 ppm.
7 For example, acetone, toluene, ethylacetate 8 and 1,4 dioxane all react with zeolitic sites at condi-g tions needed to form a stable silylated surface and are therefore unsatisfactory solvents whereas n-hexane, 11 n~pentane, and carbon tetrachloride and white oils are 12 unreactive with the zeolite and for that reason are 13 satisfactory.
14 The concern with solvent dryness is not only that water will hydrolyse the silylating molecule because, 16 at least for hexamethyldisiloxane (HMDSO) this occurs only 17 slowly. The problem also is that water can interact with 18 the zeolite's reactive sites which could in turn alter 19 or block the reaction of the reactive sites with HMDSO
or other silylating agents. Surface moisture can block 21 access by the silylating agent to the internal reactive 22 sites thereby limiting silylation to the external reactive 23 sites.
24 Silylation is preferably performed after the catalyst has been loaded with metal and following at least 26 partial thermal decomposition (calcination) of ~he NH4+
27 sites ~nd complete decomposition of any organic nitrogen 28 templating agent.
2g The initial reaction at room temperature with isolated sites is to possibly form a surface "ether" link 31 through trimethylsilyl (TMS) groups like ~hose described 32 by Kerr in USP 3,682,9~6. For example, the reaction of a 33 reactive isolated hydroxyl site with ~MDSO would be:

34 Si(S)-OH ~ (cH3)3si-o-si(cH

2[Si(s) - o-si (CH3)] ~ H2O

0~

-- 1~

1 The reaction with strained bridge sites with 2 HMDSO could be exemplified by:

3 _Si Si-(CH3)3 Si o - si (CH3)3 4 O + O
Si / \ Si-(CH3)3 - Si-O-Si(CH3)3 6 It is expected that silylated species generated by either 7 of the above reaction sequences will experience some 8 form of condensation-polymerization reaction as temper-g ature increasesO
A possible condensation product is:
11 Scheme 1 12 / CH3 ~ C}l2 13 Si(s)-o-si CH3 Si(s)-O-Si - CH3 14 \ C~13 Heat CH2 + CH4 17 Si(s)-o-si CH3 Si(S)-O-Si CH3 18 \ CH3 ~ CH2 19 The condensed surface is expected to be stable in H2 atmospheres up to S50C. This type of surface is 21 therefore different from the surfaces described by both 22 USP 3,622,996 (pendant silyl groups) and Mitchell USP
23 3,980,586 but is similar to the secondary reaction product 24 observed by McAteer in the reaction of tetrame~hyl silane with H zeolite Y. (ACS advances in Chemistry Sieves No.
26 121, "Molecules Sieves" Edited: Meier & Uytterhoeven).
27 : Because of the relatiye ease with which the 28 internal reactive sites can be substituted by the silane 29 in large pore zeolites (because of the ease with which the silane can enter the pores of the zeolite) the initial 31 silylating contact;temperature may be low to moderate:i.e.
32 25 - 200C. This is to be con~ras~ed with small pore 33 zeolites which require higher contact temperatures because 34 of the difficulty encountered by the silane in difusing 1 to the reactive sitesO
2 In both cases (i.e. small and large pore 3 zeolites) the final state of the silylated surface (i~e., 4 the deyrees of condensation-polymerization) will be determined by the highest temperature that the surface - 6 experiences either during silylation, subsequent acti-7 vation or when the catalyst is employed on oil. Depending - 8 on pore size, condensation-polymerization reactions 9 between neighboring silyl groups themselves and also with unreacted sites may begin at about 25C ~large pore) and 11 becorne more extensive as the temperature is raised.
12 Condensation-polymerization may be conducted as 13 an independent operation or may be conducted in situ in 14 the catalytic dewaxing environment (as a direc~ conse-quence of the catalytic dewaxing process conducted at said 16 elevated temperatures). In either case, the atmosphere 17 employed is inert or reducing and is preferably hydrogen 1~ or contains hydrogen~ Such deliberate or in situ heating 19 is conducted to form a stable surface. The temperatures chosen for imparting this stability are usually at or 21 above the temperature of the subsequent catalytic process, 22 but preferably about 300 to 500C, more preferably about 23 400 to 500C.

Although a change in pore volume and sorption 26 properties are very desirable and is achieved by the 27 silylation of reactive sites it is also important that 28 some hydroxyl sites be protected so that ultimately the 29 modified catalyst is activeq There must be a balance 30-- between sufficient constriction and the retention of some 3I of the acidic hydroxyl sites.
32 If the organosilane used has easy access into 33 the pores of the zeolite, complete silylation of the 34 internal and external hydroxyl groups may be possible.
In such cases methods for protecting some 36 hydroxyl sites are needed. Such protection can be 37 achieved by generating a mixed population of isolated 38 hydroxyl sites (i.e., those which react with the organo-7/~

1 silane) and hydrogen bonded hydroxyl sites which do not ~ react strongly with organosilanes.) If too many non 3 reactive hydrogen bonded hydroxyl sites are generated the 4 surface can be subjected to dehydroxylation conditions which result in the generation of some strained bridge 6 sites which are reactive with the organosilane silylating 7 agents. Any hydrogen bonded hydroxyls remaining after 8 dehydroxylation are then available as the catalytically 9 active hydroxylsO Other methods of protection include blocking of the potential hydroxyl site with cations. For 11 example, a sodium form zeolite can be partially exchanged, 12 with NH4+ salt solutions, calcined to generate isolated 13 hydroxyl sites, treated with silylating agent under dry 14 conditions, then re-exchan~ed and calcined to generate new reactive hydroxyl sites.

17 Three series of catalysts were studied. The A
18 series are derived from Zeolite Y tlarge pore), the B
19 series from offretite (intermediate pore) and the C-series from mordenite (intermediate pore).
21 Material A = Na Zeolite Y
_ 22 Zeolite Y received from Union Carbid~ Corpora-23 tion in the Na form had the following oxide composition:
24 Na20~A1203 4-4 SiO2 8-9 H20 with a corresponding unit cell formula:
26 Na60[(A12)60(SiO2)132]o250 ~2 27 Catalyst A-1 28 Material A was exchanged in 0.5N NH~N03 at 29 reflux for 2 hr using a 10 volume excess of solution then filtered and washed in water.
31 The crystals were re-slurried in a two volume 32 excess of a dilute aqueous NH40H solution (pH 10) and 33 an aqueous solution containing about 0.15 wt% of Pd(~H3)4 34 C12 was added dropwise over a 5 hour period at room temperature to give a nominal loading of 0.25 wt ~ Pd.
36 After washing, filtering the sample was dried at 120C
37 (1 hr.) i.e., the sample contained NH4~ ion.

7~ 3~

1 Catalyst A-2 2 Calcination of A-l at 500C in moist air 3 (laboratory air with ambient humidity), 1 hour yielded 4 an NH4~ free catalyst with the oxide composition:
0.45 Na20 A1203~4-4 SiO2 - 6 The powder was pressed, crushed and screened to 7 7-14 mesh (Tyler) loaded into a reactor and reduced in 8 H2 at 400C. 55% of the sites were nominally in the 9 hydrogen form.
HMDS0 Modified A Catalysts 11 Catalyst A-2M
12 Preparation was exactly as for A-2 except 13 that after ~2 reduction, the catalyst was cooled to 40C
14 in moist air and treated with a solution of 5 volume %
hexamethyldisiloxane (HMDSO) in Primol 185 (a white oil 16 containing no aromatics or polars, see Table 1) at 1 v/v/h 17 for 5 hours at 40C. Following this~ the catalyst was 18 washed with Primol 185 for 2 hours at 1 v/v/h. Feed was 19 admitted at 350C (see Table 3). At this temperature considerable condensation-polymerization of the surface 21 silyl species is expected.
22 Catalyst A-lM(a) 23 The catalyst was prepared from ca~alyst A-l.
24 The A-l catalyst was air calcined at 250C, cooled in air then pressed, and screened to 7-14 mesh (Tyler) and 26 loaded into a reactor. At this stage 14% of all the sites 27 are no~inally in the hydrogen form. There it was dried in 28 N2 at 200C for 1 hour, then in dry H2 at 200C for 29 2 hours~ followed by treatment at 40C in 5% HMDS0/Primol 185 at 1 v/v/h for lOh; finally, the catalyst was heated 31 to 500C in H2 prior to admitting feed.
32 Catalyst A-lM(b) 33 After 160 hours on stream ~Western Canadian 34 600N) the catalyst (A-lM(a)) was cooled to 250C in 35 hydrogen and a solution of 5 vol. % HMDS0 was passed over 36 the catalyst at 1 v/v/h for 5 hoursO Feed was readmitted 37 and the temperature raised to 350C. Extensive conden-38 sation-polymerization is expec~ed under this treatment 39 condition.

-~ ZC)~7~

1 Product B: Offretite ~ Various synthetic offre~ites were prepared 3 by methods similar to those described by Jenkins (USP
4 3,578,398), Rubin (Canadian Pat 934,130) and especially by Whittam (GB 1,413,470).
~ 6 The synthetic offretite material used in this 7 example had the following typical anhydrous composition 8 in the range:
9 (Ko.7(TMA)0.3)2o- A1203 7.5 SiO2.
In the preparation of the synthetic offretite of 11 the examples, the ingredients were used in the following 12 molar ratio:
13 A12o3-3H2O (Bayerite) 14 KOH 16.1 TMACl 1.8 16 Colloidal SiO2 (as Ludox LS
17 30 ~t % SiO2) 20 lB H2O 414 19 The following example yields 250 gms of productO
Dissolve 274.4 gms KOH in 800 gms H2O~ Add 46.8 gms 21 A12o3-3H2o and heat to 80C with mixing until clear.
22 Cool to roo~ temperature. Add above mixture to 1200 yMS
23 of Ludox LS over 15 min. with stirring. Age the gel for 24 5 days. After 5 days add a solution of 59.1 gms TMACl in 600 gms H2O. Reflux mixture for 28-40 hrs. in a stirred 26 vessel. Filter and wash to ph<ll with de-ionized H2O.
27 Each of the offretite cataiysts was prepared in 28 the following general sequsnce:
29 (a) the zeolite was refluxed in a 10-20 volume excess of deionised water for 1 hour then filtered (or 31 centrifuged). This procedure was repeated twice.
32 (b) The zeolite was dried at 120C for 1 hour 33 then calcined in an air flow at 425C for 16 hours, at 34 550C for 1 hour and finally at 600C for 1 hour to decompose TMA ions.
36 (c) The zeolite was refluxed with stirring in a 37 10 volume excess of NH4No3 for 2 hrs.
38 Catalyst B-l was exchanged with 2.0 N NH4NO3, 7~S~

1 washed and dried at 120C then calcined at 550C in 2 moist air and reexchanged in 2.0N NEl4NO3 again for 2 3 hours.
4 s-2 was exchanged twice in 0.5N NH~NO3 but 5 without intermediate calcination.
6 B-3 was exchanged once with 0.5N NH~N03~
7 B-4 was prepared from material B by washing and 8 calcination as in steps a) and b) above, then by refluxing g with an H4 EDTA solution to yield a product having 16/1 silicon to alumina ratio. This material was then exchanged 11 with 0.5N NH4NO3 12 (d) Pt was exchanged onto the NH4~ form of 13 each zeolite. The zeolite was slurried with a 10 volume 14 excess of deionized water and about 1 volume of an aqueous solution of 0.025M Pt(NH3)4C12 was added incrementally 16 to the stirred slurry over a 7 hour period at room temper-17 ature then left to stir for an additional 16 hour. The 18 zeolite was then washed free of Cl with de-ionized water 19 and dried at 120C for 1 hour.
Preparation procedures and catalyst compositions 21 are summarized in Table 2. In all cases, the catalysts 22 were air calcined at 550C for 2 hrs. following Pt salt 23 exchange and formed into 7-14 mesh pellets.

TYPE B CATALYSTS (FROM OFFRETITE) 26 Catalx~t B-l _B-2 _ B-3 _ _ B-4 _ 27 NH4NO3 exchange No. of A exchanges/
28 Molarity/Reflux time (h) 2/2/2 2/0.5/2 1/0.5/2 1/0.5/2 29 Air calcination between exchanges C/h 550/2 none none none 31 K/wt ~ (anhydrous basis) 1.4 2.1 2.9 __ 32 KfAl 0.13 0~19 .26 ~~
33 Si/A12 8.1 8.1 7.5 17,2 34 Pt wt ~ (nominal) 0.5 0.5 0.5 0.5 35 All catalysts were reduced in the reactor in ~6 a flow of H2 ~t up to 400~C.

'76~7 , HMDSO Modified B Catal~
.
2Following the reduction in hydrogen at 400C
3 some of the B series catalysts were rnodified by treatment 4 with HMDSO at various temperatures and, of these caca-5 lysts, some were subsequently stripped again in H2 at 6 between 400 - 550C at 3000 SCF/BBL for 2 hours. Thus, 7 B-lM(300) refers to catalyst B-l, from Table ~ which has 8 been HMDSO modified at 300C; B-2M~25)H is a form of g the B-2 catalyst modified with HMDSO at 25C and post

10 hydrogen stripped at 550C, 3,000 SCF/BBL for 2 hrs,

11 pure H2.

12 All HMDSO treatments of catalysts were performed

13 in a dry H2 atmosphere at 50 psig using 5 vol. % HMDSO

14 in Primol 185 at 1 v/v/h for 5 hours.

15 B-lM(300)

16 The modification of B-l with HMDSO was performed

17 after the catalyst had been run in an oil, (Western

18 Canadian 150N) . To ensure that treatment was on an

19 essentially hydrocarbon free surface~ the B 1 catalyst

20 was first washed with naphtha and H2 steipped at 550C

21 for 2 hours. Then the catalyst was cooled to 300C

22 and 5% H~D50 in Primol 185 was admitted~

23 B-lM (300) H

24 Following a study on Western Canadian 150N,

25 the B-lM(300) catalyst was washed with naphtha then

26 hydrogen stripped at 550C for 2 hours.

27 B-2M ~25)H

28 ~ The modification of the B-2 catalys~ was

29 performed after the catalyst had been run in an oil

30 (Western Canadian 150N). The catalyst was washed with

31 naptha then H2 stripped at 550~C to remove hydrocarbon

32 residues prior to the HMDSO treatment at 25C. Following

33 H~DSO treatmentl the catalyst was again H2 stripped at

34 550C.
35B-4M (40) H
36The B 4 catalyst was modified with 1% vol. HMDS
37(hexa methyl disilazane) in Primol 185 at 40C on a 38 freshly hydrogen reduced surface ther~ H2 stripped at 7~

1 500C. After 500 hours on oil the catalyst was washed 2 with naphtha and hexane heated to 550C in H2 for 22 hrs.
3 and treated again with a 5% vol. HMDS~Primol 185 solution 4 at 40C. The surface was washed in naphtha and hexane once more and heated in H2 at 550C for 2 hours.
6 PRODUCT C:_ H-MOR~ENITE
7 Zeolon 900-H from the Norton Co. had the fol-8 lowing anhydrous oxide composition:
9 0-29 Na2O A1203-17.5 Si2 Catalyst C-l 11 Product C was exchanged at reflux with a 12 10 volume excess of 0.5N NH4NO3 for 2 hours, washed 13 free of NO3 then exchanged with 10 volume excess of 14 aqueous Pt(NH3)qC12 to give a nominal loading of 0.5 wt % Pt. After washing to remove Cl~, the catalyst 16 was air dried at 120C (1 hour) than air calcined at 17 550C for 2 hours and formed into 7-14 mesh pelletsO
18 The catalyst was reduced in the reactor at 19 400C in H2.
HMDSO Modified C-l Catalyst (C-lM (30~ ~
21 HMDSO trea~ment was performed after the catalyst 22 had been run in an oil (Western Canadian 150N). The 23 catalyst was washed with naphtha then H2 stripped at 24 550C to remove hydrocarbon residues prior to HMDSO
treatment. A 10 volume excess of the treat solution, 5%
26 HMDSO in Primol 185 was passed over the catalyst at 27 300C 9t 1.0 v/v/h.
2~ IR. MONITORING OF ORGANOSILANE REACTIONS
29 Transmission infrared spectroscopy is an excellent tool for monitoring the changes in acid site 31 type and density of zeolites because they are transparent 32 to IR above 1300cm~l where valence vibrations occur~

33 Highly transmitting spectra of 40-50 mg 2.5 cm diameter 34 discs of pressed catalyst can be obtained by evacuating 3S the disc at 140C to remove physically and hydrogen 36 bonded water. All spectra shown were recorded at room 37 temperature on a Beckman 4240 IR spectrometer.

~ ~0'7~

1 Silylation of Zeolite Y
2 The following Figures 1-4 demonstrate the 3 importance of having reactive sites for silylation.
4 Figure 1 shows that vapor phase H~SO does not react readily with a hydroxyl form zeolite Y when the hydroxyls 6 are hydrogen bonded. It is seen that there is little or 7 no change in the zeolitic hydroxyl band en~elope centered 8 around 3600 cm~l. This broad feature (lack of distinct g peaks) is indicative of interacting (hydrogen bonded) hydroxyl groups in the supercages and B cages (truncated 11 octahedra) of zeolite Y. Such hydrogen bonded hydroxyls 12 are unreactive with the silylating agents, in this case 13 ~DSO, and are believed to be caused (in this case) by the 14 presence of moisture on the zeolite Y surface, On the other hand, discrete non-interacting 16 hydroxyl species were created by decomposing A-l, the 17 NH4 form zeolite Y under dry conditions (Figure 2).
18 The bands due to the stretching vibrations of external 19 hydroxyls 3740 cm~l, supercage hydroxyls 3650 cm-l and B cage hydroxyls 3550 cm~1 have been identified 21 before by Uytterhoeven et al (J. Phys Chem 69 (6) 2117 22 (1965))- Each species is clearly not hydrogen bonded 23 and each reacts extensively with HMDSO at 25C as evi-24 denced by the disappearance of the hydroxyl bands and the appearanca of new bands at 2980 cm~l and 2~20 cm-l due 26 to C-H stretching modes.
27 Further degassing and heatinc3 completely 28 eliminated all trace of the hydroxyl modes and the C-H
2g bands declined in intensity due to condensation-polymeri-zation.
31 Another example of the effect of surface 32 pre~reatment of an A-l material upon the ex~ent of 33 silylation is shown in Figure 3.

34 A-l was calcined in moist air (laboratory air containing ambient humidity) at 500C for 1 hr,, 36 cooled to room temperature (in effact generating A-7.) then 37 evacuated at 140C, A mixed population of hydrogen 38 bonded hydroxyls and isolated hydroxyls was generated ~2~7~;3~

1 (Figure 3A), Note that the population oE isolated 2 internal hydroxyls is considerably higher in the case of 3 A-2 (NaY exchanged in 0.5N ammonium nitrate) than for the 4 example shown in Figure 1 (NaY exchanged in 2.ON ammonium nitrate~. This surface was subsequently exposed to 15 6 torr of dichlorodimethylsilane vapor (a highly reactive 7 silylating reagent) for 12 mlnutes at room temperature - 8 then again evacuated at 140C to 5 x 10-3 torr for 1 g hr. The isolated sites were completely eliminated and new bands appeared near 2980 and 2920 cm~l indicating 11 5ilylation. However the population of hydrogen bonded 12 hydroxyls was unchanged (Figure 3B).
13 This example demonstrates that the co-genera-14 tion of hydrogen bonded hydroxyls and isolated hydroxyls can be used as an accurate control of the extent of 16 silylation, since it is clear that of the two only the 17 isolated hydroxyls react with the silylating agent added 18 to the system. The unreacted hydrogen bonded hydroxyls 19 remain and could provide catalytic activity.
However, a surface containing hydrogen bonded 21 hydroxyl species may be activated so as to be reactive 22 with organosilanes. This is achieved by dehydroxylating 23 these hydrogen bonded hydroxyl species.
24 This is demonstrated by Figure 4. ~ surface containing a mixed population of isolated hydroxyls, 26 NH4+ and hydrogen bonded hydroxyls (Figure 4A) was heated 27 at high temperature (500C) for 45 minutes under vacuum 28 (less than 10-3 Torr) yielding a low population o~ iso-29 lated sites, no hydrogen bonded sites and by inference a large population of strained bridge sites (Figure 4B).
31 Subsequent reaction of this surface with HMDSO vapor 32 produced a large population o~ chemisorbed silyl species 33 (bands at 2980 and 2920 cm 1) which is substantially 34 greater than would be expected had only the isolated species reacted. (Compare with the intensity of the 2980 36 and 2920 cm~l bands in Figure 2C).
37 Thus, for the purposes of this specification, 38 one or both of the two types of reactive sites should - 2~ ~

1 be generated to facilitate silylation.
2 As evidence of the completeness of the silyla-3 tion of decomposed A-l (hydrogen form, isolated hydroxyls), 4 by HMDSO, the subsequent adsorption of pyridine vapour by 5 the ~odified surface showed that adsorption occurred as 6 hydrogen-bonded pyridine and as Lewis adsorbed pyridine 7 but there were no sites for Bronsted adsorption by proton 8 exchange to form pyridinium ions (no band at 1540 cm~l) 9 (Figure 5).
The possibility that all Bronsted sites can be 11 eliminated in zeolite Y means that the hydrocracking 12 potential of the zeolite may also be destroyed, because 13 Bronsted sites are generally thought to be needed to 14 initiate C-C cleavage reactions.
Therefore methods for preserving catalytically 16 active hydroxyls are appropriate with zeolite Y and 17 other low silica to alumina ratio zeolites so that the 18 modified system can function as a surface which is both 19 diffusionally selective and catalytically active.
In one scenario a form of Na zeolite Y could 21 be partly exchanyed, calcined to generate isolated 22 hydroxyl sites, treated with a silylating agent under dry 23 conditions, then re-exchanged to expose new sites, 24 The level of exchange (e.g. ammonium exchange) of the original cationic species (i~e. Na in the case of 26 sodium Y) may also determine the population of isolated 27 hydroxyl species and therefore the extent of hydroxyl 28 silylation. If only a few hydroxyl sites are created they 29 may be, statistically far enough apart not to hydrogen bond even if the decomposition takes place in moîst air 31 (see Figure 3). At higher exchange levels more hydrogen 32 bonded species will be formed if the surface is calcined 33 and cooled under moist conditions ollowing the exchange 34 step.
A possible variation on this would be to use 36 NH4-~ as the blocking ion~ In this case, the population 37 of NH4+ relative to the acidic hydroxyl sites can be 38 controlled by the calcining temperature. After silyla-7~ ~

l tion, the catalyst may be post calcined at ey 500C to 2 restore sites, rather than require another exchange as in 3 the Na bloclcing case.
4 In this case it would be important to insure that hydroxyl sites generated from NH4-~ decomposition 6 were not all consumed by possible bridging reactions with 7 neighboring silyl species.
8 A preferred way of preserving sites for hydro-g cracking activity of low SiO2/Al2O3 ratio zeolite cata-lysts (eg zeolite Y) would be to generate a mixed popula-11 tion of hydrogen bonded hydroxyls and discrete (isolated) 12 hydroxyl sites. A preferable method to accomplish this 13 end would be to first partially decompose an NH~+ form 14 zeolite Y and expose the newly formed hydroxyls to mois-ture thereby creating hydrogen bonded hydroxyls. This 16 is what is occurring with the catalyst of series A when 17 calcination is conducted in moist air followed subse-18 quently by the step of permitting the calcined material to l9 come to room temperature in moist air~ The same result would be achieved if the calcination was conducted under 21 anhydrous conditions but the subsequent cooling to room 22 temperature were conducted in the presence of a moist 23 atmosphere, for example, moist air (laboratory air 24 containing ambient humidity) or some other a~mosphere into which moisture has been introduced. The amount 26 of moisture and the duration of exposure of the ~eolite 27 to the moist atmosphere will determine the extent to 28 which the hydroxyl groups which are generated will be in 29 the hydrogen bonded form. Subsequent drying of this surface and decomposition of the rema;ning N~ sites 31 in a dry environment will generate other hydroxyls which 32 are isolated (nonhydrogen bonded) as well as strained 33 bridge sites from dehydroxylation of hydrogen bonded 34 hydroxyl sites. Both of these sites are available or reaction with HMDSO or other silylating agents providing 36 dry conditions are maintained.
37 The ratio of hydrogen bonded to reactive sites 38 ~isolated hydroxyls and strained bridge sites) will ~ 7 l determine the extent of silyation. The hydrogen bonded 2 hydroxyls remain after silylation and are effective as 3 sites for hydrocracking. It is left to the practi~ioner 4 to determine the degree and extent of generation of hydrogen bonded hydroxyls as may be required by his - 6 specific application. All that is required however is 7 that there be some protected, hydrogen bonded hydroxyls 8 which are unreactive with silylating agent and that there g be some reactive sites (isolated hydroxyls and/or strained bridge sites) generated which are reactive with silylating ll agents.
12 It should be noted that all silylating reactions 13 were performed on metal loaded zeolite Y, however this is 14 not critical to the successful practice of the invention.
The reactivity and extent of reaction of Y type materials 16 with HMDS and HMDSO was independent of the presence of 17 this metal, at least up to Pd loadings of 0.5 wt%.
18 Silylation of Offret_te l9 l~nlike the zeolite Y system, the reactions of 20 HMDS and HMDSO with the smaller pore H-form offretite 21 were always incomplete even at temperatures up to ~00C
~2 and on surfaces having mostly discrete (isolated) hydroxyl 23 species. With offretite, large populations of isolated 24 sites can be generated even after the hydroxylated form has been exposed to moisture. Thus the strategems 26 employed when dealing with large pore low silica alumina 27 ratio zeolites such as zeolite Y need not be utilized when 28 dealing with the intermediate pore zeolites such as 29 offretite where access of organosilanes into the pores may be thermally limited.
31 Despite the access problem, permanent changes in 32 the behaviour of offretite can be affected by silylating 33 at higher temperatures, as previously discussed. Again 34 the 3eolite must be predried to remove physically adsorbed and hydrogen bonded water to react any of the internal 36 sites.
37 The vapour phase reaction o HMDSO with a disc 3~ of catalyst B-l is shown in Figure 6~ The spectrum of '7 1 hydrogen form offretite is similar to that of offretite, 2 reported by Barthomeuf V. et al, J. Catal, 57, 136 ~1979).
3 Bands at 3610 and 3550 cm~1 are the O H stretching modes 4 of the hydroxyl species located in the channels and cages respectively, while the band at 3744 cm~l (B) is due to 6 external surface hydroxyl speciesO The admission of HMDSO
7 vapour to this surface at 25C had almost no effect on 8 the hydroxyls but a weak C-H band appeared near 2980 cm~
9 (Figure 6B).
Readmission of HMDSO at 25C followed by heating 11 to 300C did cause reaction of about 30% of each of 12 the hydroxyl types but the band due to C-H species was 13 still quite small (Figure 6C). If each hydroxyl had 14 been replaced by a TMS group, a much larger 2980 cm~l adsorption band would have been expected (see, for 16 example, the intensity at 2980 cm~l in the zeolite Y
17 series experiments shown in Figure 2)~
18 It is apparent that a simultaneous silylation 19 and condensation-polymerization must be taking place on offretite. In order to promote reaction the temperature 21 must be raised to minimize diffusional constraints but 22 in so doing the initial reaction products are made suf-23 ficiently energetic to extensively bridge with neighbour-24 ing sites.
Further heating of this surface at 550C in 26 H2 (Figure 6D) again reduced the hydroxyl population 27 and the C-H intensity also declined, consistent with 28 further bridging.

Performance of Untreated Catalysts A-2 31 The untreated catalyst, A-2 was contacted with 32 a Western Canadian 600N waxy raffinate at 300, 325 and 33 370C at 4,14 MPag H2 and 1.0 v/v/h (Table 3). The oily 34 fraction remaining, l.e. ~he stripped products, were still very waxy, indicative of a process which is not shape 36 selective for charge molecules.
37 In fact the SiO2 gel separations and a measured 38 wax content by solvent separation showed that A-2 is l actually anti-selective for wax because the products had 2 a higher concentrations of saturates than the feed.
3 Aromatics and polars were preferentially reacted. Since 4 aromatics and polars are generally among the larger molecular species, it is to be expected that the fraction 6 of product boiling roughly in the same range as the feed 7 should be low because molecules of all sizes and types 8 have access to the hydrocracking surface.
g At 370C reactor temperature the oil yield is only 35~. These results are entirely predictable for a ll large pore hydrophilic, acidic surface.
12 Performance of the Modified Catalyst (A-Z)M
13 HMDS0 treatment of the A-2 ~H form Y) catalyst l~ completely altered its hydrocracking characteristics on Western Canadian 600N waxy raffinate.
16 At 410C only 20% of the raffinate had been 17 converted to product boiling below the ibp o the feed 18 (Table 3). This is due in part to A-2 (HMDS0) being 19 catalytically selective for wax. Many molecules are now constrained by the modified pore and molecules with 21 narrower cross-section will be admitted preferentially.
22 As a consequence the pour point and wax content in the 23 products are reduced.
2~ Performance of the Mo ified Catalyst A-lM(a) The A l (HMDSO) catalyst was actually "modifiedn 26 twice. In case (a), the catalyst was first modified in 27 the form where the site population comprised 45% Na~, 2~ 41% NH4~ and 14% hydroxyls~ Since the hydroxyls were 29 generated by calcination in moist air then cooled in moist air they were hydrogen bonded so that subsequent reaction 31 with H~DSO should be minimal.
32 The catalyst was active but only slightly 33 selective for wax on Western Canadian 600N waxy raffinate 34 (Table 3) and except for a slight pour reduction the catalyst behaviour was like that of catalyst A-2 36 A-l~(b) 37 The surface was retreated with HMDS0/Primol 38 185, after in situ activation under dry conditions and ~LZ~'7~3~
!

1 following 160 hrs on Western Canadian 600N raffinate.
2 The sites generated by this procedure should be isolated 3 hydroxyls and strained bridge sites and, therefore, 4 reactive with HMDSO. The result was a dramatic improve-ment in performance (Table 3). The oil product yield was 6 relatively high and the pour point dropped to -2C at a 7 mild reactor condition (350C). In this form zeolite Y
8 behaves as a selective hydrodewaxing catalyst. The g relatively low reactor temperature required is evidence that excellent catalytic sites have been preserved.
11 Performance of Untreated Offretite Catalysts 12 The offretite catalysts B-l and B-2 both dewaxed 13 Western Canadian 150N, +6C pour point (Table 4, Figure 7) 14 and appeared to have similar but fairly low selectivity.
That is, yields of dewaxed oil after stripping for a given 16 pour point, were lower than would be obtained by solvent 17 dewaxing to the same pour pointO For example between ~6 18 and -20C pour point, about 10% dry wax can be recovered 19 by solvent dewaxing, so if the hydrodewaxing process were perfectly selective then there would be only 10%
21 conversion, i.e. a 90% dewaxed oil yield. Instead the 22 yield is below 80%. This low yield may be a rasult of the 23 pore being too large and/or to the participation of the 2~ external surface in hydrocracking.
Performance of the Modified Offretite Catalysts 26 The effects of the temperature required for 27 modification on the extent of silylation of ofretite 28 identified in the spectroscopic studies is again revealed 29 in the catalytic tests.
Thus catalyst B-2 M(25)H modified at only 25C
31 then post stripped in H2, had the same activity and 32 selectivity as the untreated parent, B-2 on Western 33 Canadian 150N, (Table 4). But the catalyst modified at 34 300C, B-l M(300) and its H2 stripped counterpar~ B 1 M(300)H both exhibited better selectivity, in accord with 36 the IR result that surface silylation is significant only 37 at higher te~peratures with offretite (Table 4, Figure 7)~

0~711:~3~

1 The yield of dewaxed oil for a yiven pour point 2 was about 5-7% higher for the high temperature modified 3 catalysts. Post H2 stripping at 550C further improved 4 performance of the 300C modified catalyst in that the activity was increased without loss of selectivity.
6 A highly condensed (bridged) surface structure 7 appears to be most desirable for improved dewaxing with 8 offretite. The bridged surface apparently remained stable g up to 550C in H2 which is higher than any temperature likely to be encountered in hydrocracking in a reducing 11 gas medium or under conditions of H2 stripping conceivably 12 needed to rejuvenate a catalyst.
13 The B-4M (40) H catalyst successfully dewaxed an 14 Arabian Light/Texas 150N raffinate blend ~rom ~33 to -~5C pour point. This catalyst also exhibited much 16 better activity maintenance on atmospheric light gas oil 17 than the B-3 catalyst (Table 5).
18 ~ordeni_ 19 A very brief 5tudy was conducted on a mordenite catalyst using conditions similar to those used with 21 offretite. Ayain high temperature modification with 22 HMDSO resulted in improved selectivity of dewaxed oil are 23 about 6-9% higher for a given product pour point with C-l 24 M(300) (Table 6)o t7~:3~

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Claims (35)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method for selectively dewaxing a waxy hydrocarbon oil feedstock characterized by contacting said waxy hydrocarbon oil stock in the presence of hydrogen and under conditions of pressure, temperature and flow velocity sufficient to effect the dewaxing with a zeolite, which zeolite (1) has been modified by reaction under anhydrous conditions with an organosilane wherein the zeolite to be modified possesses reactive sites capable of reacting with the organosilane and wherein the organo-silane is capable of entering into the channels of the zeolite and reacting with the reactive sites present therein as well as reacting with reactive sites present on the external surface of said zeolite and (2) has been loaded with a catalytically active hydrogenating metal component.

2. A method according to claim 1 further characterized in that the zeolite is (i) any natural or synthetic zeolite having an average pore diameter of from about 7.ANG. or greater or (ii) any natural or synthetic zeolite having an average pore diameter of less than about 7.ANG..

3. A method according to claims 1 or 2 further characterized in that the zeolite is either (i) Y, X, L, omega or (ii) offretite, mordenite, offretite type zeo-lites, ZSM-5, erionite.

4. A method according to claim 2 characterized in that the zeolite has been calcined and cooled in the presence of a moist atmosphere and subse-quently calcined and cooled under anhydrous conditions prior to being chemically modified by reaction under anhydrous conditions with an organosilane.

5. A method according to claim 4 characterized in that the silylated metal loaded zeolite is heated in an inert or reducing atmosphere prior to being exposed to waxy oil.

6. A method according to claim 1 further characterized in that the zeolite employed is zeolite Y, offretite or an offretite type zeolite.

7. A method according to claim 1 further characterized in that the organosilane employed has the formula SiRyX4-y or (RwX3-wSi)2-z wherein R is H or a C1-C10 alkyl, aryl, alkoxy or aralkyl, X is halogen, Z is O or NH or substituted amines or amides and Y is 1 to 4 and w = 1 to 3.

8. A method according to claim 6 further character-ized in that in the organosilane is hexamethyldisilazane (HMDS) or hexamethyl-disiloxane (HMDSO).

9. A method according to claim 1 further character-ized in that the catalytically active hydrogenating metal compound is selected from the group consisting of Group VI
and Group VIII metals of the Periodic Table.

10. A method according to claim 1 further charact-erized in that steps (a) and (b) of the zeolite modification sequence may be practiced in any order.

11. A method according to claim 1 further charact-erized in that the waxy hydrocarbon oil is a petroleum oil, a lube or transformer oil.

12. The method of claim 9 wherein the catalytically active hydrogenating metal compound is selected from the group consisting of platinum and palladium and wherein said catalytically active hydrogenating metal compound is present in the range of 0.1 to 2.0 wt.% based on dry zeolite.

13. The method of claim 12 wherein the catalytically active hydrogenating metal compound is present in the range of 0.2 to a . 5 wt.% based on dry zeolite.

14. The method of claim 2, wherein the zeolite has been calcined under anhydrous conditions and cooled in the presence of a moist atmosphere and subsequently calcined and cooled under anhydrous conditions prior to being chemically modified by reaction under anhydrous conditions with an organosilane.

15. The method of claim 5 wherein the heating in an inert or reducing atmosphere prior to being exposed to waxy oil is at a temperature of from about 300° to 500°C.

16. The method of claim 4 wherein the zeolite used is an ammonium from zeolite, and wherein said anhydrous calcination is to temperature above about 300°C.

17. A method for surface modifying a large pore zeolite so as to produce a material retaining sufficient catalytically active sites to be suitable for use as a catalyst, which method comprises chemically modifying said large pore zeolite by reacting said zeolite under anhydrous conditions with an organosilane wherein the starting zeolite to be modified possesses sites some of which are available for reaction with the organosilane and wherein some of the sites have been protected to prevent reaction with the organosilane and wherein the organosilane is capable of entering into the channels of the zeolite and reacting with the available reactive sites present therein as well as reacting with reactive sites present on the external surface of said zeolite.

18. The method of claim 17 wherein the protected sites which are prevented from reacting with the organosilane have been produced by the procedure of first calcining and cooling a cation exchanged zeolite either or both of such steps of calcination and cooling being conducted in the presence of a moist atmosphere followed by calcining and cooling under anhydrous conditions to yield a mixed population of protected, available and catalytically active sites on the zeolite prior to reacting said zeolite under anhydrous conditions with the organosilane.

19. The method of claim 17 wherein the protected sites which are prevented from reacting with the organosilane have been produced by the procedure of first calcining and cooling a cation exchanged zeolite in an anhydrous atmosphere and then exposing such zeolite to a moist atmosphere, followed by calcining and cooling the zeolite under anhydrous conditions to yield a mixed population of protected, available and catalytically active sites on the reactive zeolite prior to reacting said zeolite under anhydrous conditions with the organosilane.

20. The method of claim 18 wherein the first calcination is at a temperature of about 180°C and greater.

21 The method of claim 19 wherein the first calcination is at a temperature of about 180°C and greater.

22. The method of claim 18 wherein the cation exchanged zeolite is an ammonium form zeolite and wherein said first calcination is at a temperature of about 200°C or higher and said subsequent anhydrous calcination is to a temperature of about 300°C and higher.

23. The method of claim 19 wherein the cation exchanged zeolite is an ammonium form zeolite and wherein said first calcination is at a temperature of about 200°C and higher and said subsequent anhydrous calcination is to a temperature of about 300°C and higher.

24. A method for surface modifying a large pore zeolite so as to produce a material retaining sufficient catalytically active sites to be suitable for use as a catalyst, which method comprises partially cation exchanging the zeolite, calcining and cooling under anhydrous conditions, reacting said zeolite under anhydrous conditions with an organosilane capable of entering into the channels of the zeolite and reacting with the reactive sites present therein as well as reacting with reactive sites present on the external surface of said zeolite, reexchanging the silylated zeolite and calcining in moist atmosphere the reexchanged zeolite to generate new sites which are catalytically active.

25. The method of claim 24 wherein the silylated zeolite is heated in an inert or reducing atmosphere at from 300 to 500°C to promote condensation - polymerization of the silylated surface.

26. The method of claim 25 wherein the large pore zeolite is any natural or synthetic zeolite having an average pore diameter of from about 7.ANG. or greater.

27. The method of claim 26 wherein the large pore zeolite is Zeolite Y.

28. The method of claim 27 wherein silylation is performed by contacting the zeolite and the organosilane in the vapor or liquid form or dissolved in a dry non reactive organic solvent, at from 20 to 500°C.

29. The method of claim 28 wherein the organosilane is dissolved in the dry, non reactive organic solvent at a concentration of from 0.01 to 20 vol.% silane.

30. The method of claim 29 wherein the organosilane employed has the formula SiRyX4-y or (RwX3-wSi)2-z wherein R is H or a C1-C10 alkyl, aryl, alkoxy or aralkyl, X is halogen, Z is 0 or NH or substituted amines or amides and Y is 1 to 4 and w = 1 to 3.

31. The method of claim 30 wherein the organosilane is hexamethyl disilazane (HMDS) or hexamethyl disiloxane (HMDSO).

32. The method of claim 31 wherein either before or after silylation the zeolite has associated therewith a catalytically active hydrogenating component.

33. The method of claim 32 wherein the catalytically active hydrogenating component is selected from the group consisting of Group VI and Group VIII metals, their oxides and sulfides and mixtures thereof.

34. The method of claim 33 wherein the catalytically active hydrogenating component is present in the range of 0.1 to 2.0 wt.% based on dry zeolite.

35. The method of claim 34 wherein the catalytically active hydrogenating component is platinum or palladium.