CA1256845A - Shock calcined crystalline silica catalysts - Google Patents

Abstract

SHOCK CALCINED CRYSTALLINE SILICA CATALYSTS

ABSTRACT OF THE DISCLOSURE
A process for producing a thermally shock calcined crystalline silica comprising (A) precalcining a crystalline silica at a relatively low temperature, (B) very rapidly increasing the temperature of the crystalline silica to a relatively high temperature for a short period of time, and (C) rapidly cooling the crystalline silica. The resulting crystalline silica is catalytically active for hydrocarbon conversion reactions and is particularly selective for the production of para-xylene from a reaction mix of toluene and a methylating agent.

Description

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The present invention relates to a crystalline silica and especially to a crystalline silica which is catalyticallY active and selective in methylation reactions.

A process for selectively producing para-xylene is disclosed in United States Patent 4,270,017. Para-xylene is selectively prepared by reacting toluene and a methylating agent in the pre~ence of a phosphorus modified catalyst comprising a silica polymorph intermixed with an inorganic refractory oxide.
United States Patents 4,325,929 and 4~344/927 relate to a process for hydrothermally preparing a silica polymorph which is described as suitable for use in aromatic alkylation.

-1- '3 ~L25~;~345 United States Patent 4,362,653 discloses a catalyst composite comprising a silica polymorph and the use of the catalyst in a hydrocarbon reforming processO
Crystalline silicas and their use as alkylation catalysts are disclosed in United States Patent 4,283,306.
The patent additionally teaches the use of various promoters combined with the catalysts.
Hydrogenation catalysts are disclosed in United States Patent 4,387,258 which relates to palladium or platinum promoters deposited on a low acidity silica polymorph/silicalite/high silica zeolite.
The present invention seeks to provide crystalline sllica ~or use in catalytically promoting the conversion oE
hydrocarbons.
Further this invention seeks to provide a cata-lytically active crystalline silica that is selective for the production of para-xylene.
Additionally, this invention seeks to provide a process for the production of para-xylene using catalysts containing said crystalline silica.
Moreover, this invention seeks to provide a process for producing a crystalline silica.
The invention provides a crystalline silica activa-ted by shock calcination. Typically, the crystalline silica is produced by a method comprising the steps of : (1) precalcining the crystalline silica at a relatively low temperature, (2) rapidly heating the crystalline silica to a relatively high calcination temperature and maintaining the high calcina-tion temperature for a relatively short period of time and (3) rapidly cooling the crystalline silica. When used as a catalyst for hydrocarbon conversion reactions, the crystalline silica is generally eombined with a porous refractory oxide and, optionally, with a promoter.
The invention additionally provides a method of alkylating an aromatic compound which comprises contacting an aromatic compound with a C~ to C10 hydrocarbon in the presence of a catalyst comprising a thermally shock calcined crystalline silica.
This invention provides a method for thermally shoek calcining crystalline silica; crystalline silicas activated by such a method; catalysts produeed therefrom, and a method of using sueh catalysts for hydrocarbon eonversion reaetions, particularly for alkyl.atiny an aromatlc eompound with a Cl to C10 hydroearbon.
Any of the known erystalline silicas may be thermally shock caleined in accordance with the process herein to produee a catalyst which may be used in hydroearbon conversion reactions.
The preferred crystalline silica composition herein is charaeterized by pores of uniform diameter of 6A or less, and even more preferably 5A to 6A and is prepared by ealeining a erystalline hydrated alkylonium silica 1 ~2S6~

11 prepared by hydrothermal crystallization fxom a reaction

2 mixture containiny as essential reagen~s, water, amorphous

3 silica and a quarternary ammonium compound, for example,

4 tetraethyl ammonium hydroxide, at a p~ of at least 10. The

5 compound thus formed is calcined to decompose the alkylonium

6 moieties present. The crystalline silica exhibits no ion

7 exchange properties; however, because of its uniform pore

8 structure it is capable of making size-selective separations

9 of molecular species.
0 The crystalline silica produced from the 11 above-described mixture has a topological type of 12 tetrahedral ~ramework, which contains a large ~raction of 13 five-membered rings o~ silica-oxygen tetrahedra. The 14 framework comprises a three-dimensional system of intersect-15 ing channels which are defined as ten rings of oxygen atoms 16 extending in three directions. Precursor organic nitrogen 17 ions which occupy the intersecting channels are removed by 18 heating or in the alternative, by extracting with an acid to 19 yield the desired crystalline silica. The resulting void 20 volume occupies approximately 33 percent of the crystal ~1 structure, and the three-dimensional channel is wide enough 22 to absorb organic molecules having up to about 6A in æ diameter. The crystalline silicas, herein, degrade to glass 24 products and dense crystalline silica above about 2,732F.
~_ The crystalline silica employed in this invention ~6 is analogous to highly siliceous alkali silicates which form 27 as insoluble compounds during extended hydrothermal 28 digestion. The organic agent, in the ~orm of a nitrogen ~9 compound incorporated as a cation during crystallization of 30 the crystalline silicas herein, becomes a source of 3~j~

~568~i micropores when eleminated by combustion or extraction. The surface of these micropores are relatively free of hydroxyl groups. The isolated hydroxyl groups which are present provide a moderate acidic strength when the crystalline silica is thermally activated. The crystalline silica is a uniquely, active solid which is suitable for use as a catalyst component or in catalysts used in hydrocarbon reactions.
The crystalline silica provides not only the required surface for the catalyst precursor, but gives physical streng-th and stability to the catalyst material.
In addition, -thc cr~stalline silica has a lar~e surace area upon which the catal~st precursor is depositecl.
A crystalline silica suitable for use herein is described in United States Patent 4,334,927. The crystalline silica is prepared by hydrothermally crystallizing said crystalline silica from a silicate solution containing an organic agent, in combination with a base solution, and an acid solution. Crystallization is effected utilizing high shear mixing. The crystalline silica has as the four strongest d~values of its x-ray diffraction pattern, d = 11.05, d = 9.96, d = 3.82 and d = 3.34. The crystalline silica is designated as UCS-3.
Another suitable crystalline silica is described in United States Patent 4,325,929. The crystalline silica is prepared in accordance with the procedure of United States Patent 4,334,927 above with the following exception:
crystallization is effected by high shear mixing ~2S6~

followed by an unagitated period during the crystallization of said silica. The crystalline silica has as the four strongest d-values of its x-ray diffraction pattern, d =

10.9, d = 4.06, d = 3.83 and d = 3.33. The crystalline silica is designated as UCS-4.
A particularly preferred crystalline silica suitable for use herein which exhibits molecular sieve properties is termed silicalite. This material has a specific gravity at 25C. of 1.99 ~ 0.05 g/cc as measured by water displacement. After calcination at 600C. in air for 1 hour, silicalite has a specific gravity of 1.70 + 0.05 g/cc. The mean refractive index of silicali-te crystals measured as the synthesized form is 1.48 ~ 0.01, while the calcined form (600C. in air for 1 hour) is 1.39 -I- 0.01.
The ~-ray diEfraction pattern of silicalite after calcination in air at 600C. for 1 hour has as its six strongest lines or interplanar spacings d = 11.1 -~ 0.2, d =
10.0 + 0.2, d = 3.85 + 0.07, d = 3.82 + 0.07, d = 3.76 +
0.05 and d = 3.72 + 0.05.
The pore diameter of silicalite is about 6A and its pore volume is 0.18 cc/g as determined by adsorption.
The uniform pore structure of silicalite imparts size-selective molecular sieve properties to the composition.
These molecular sieve properties permit the separation of p-xylene from o-xylene, m-xylene and ethylbenzene. A more detailed description of silicalite including a method of how to prepare the composition is described in greater detail in United States Patent 4,061,724.

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1 The crystalline silicas herein exhibit molecular 2 sieve properties characteristic of certain crystalline 3 aluminosilicate compositions, but exhibit substantially none 4 of the ion-exchange properties which are essential to the aluminosilicates commonly referred to as zec,lites. The 6 lack of ion-exchange properties in the crystalline silicas 7 herein is due to the crystal lattîce structure of the 8 silicas which does not contain alumina as an integral part 9 of said crystal lattice.
Before the crystalline silica is subjected to

11 thermal shock treatment, the crystalline silica is first

12 precalcined at a temperature of from about 700F. to about

13 1,100F., preferably from about 70QF. to about 900F for

14 about 30 minutes to about 2 days. Desirably, the thermal

15 shock calcination of the crystalline silica is conducted at

16 a temperature that is at least 300 F., preferably at least 1~ 400F. higher than the precalcination temperature.
18 Precalcination facilitates a rapid temperature rise during 19 the subsequent thermal shock calcination by decreasing the 20 heat spent in vaporizing water and desorbing volatile 21 components. Additionally, precalcination avoids the forma- ¦
22 tion of aerosols initiated by the rapid evolution of vapors 23 within the crystalline silica aggregates and particles which 24 may cause fragmentation and fluidization of the crystalline 25 silica during subsequent shock calcination of the silica.
26 After the precalcination treatment, the 27 crystalline silica is subjected to thermal shock ~8 calcination. The thermal shock treatment of the crystalline 29 silica may be carried out in steam, air, ammonia~ carbon 30 dioxide, carbon monoxide or any inert atmosphere such as ~256~34~i 1 nitrogen, hydrogen, flue gas, argon, helium and mixtures 2 thereof, but it is preferably effected in air. In addition, 3 effluent gases from a combustion chamber may be utilized as 4 a source of direct-fired heat. For maximum efficiency in 5 transferring heat through the crystalline silica, the 6 crystalline silica is reduced to a particle size of less 7 than 6 mesh. At or above 7 or 8 mesh, heat transfer becomes 8 a problem and rapid transfer of heat throughout the 9 crystalline silica is difficult to achieve~ !
During thermal shock calcination, the crystalline 11 silica is subjected to a very rapid increase in temperature 12 wherein the elevated temperature is maintained for a rela-13 tively short period o~ time, bccause prolonged exposure o~
14 the crystalline silica to the relatively high, shock 15 calcination temperature would destroy the original structure }6 of the crystalline silica. Thus, it is critical that the

17 temperature increase very rapidly in the thermal shock

18 calcination of crystalline silicas herein to prevent

19 undesirable fusion and mineralization reactions from

20 occurring. The crystalline silica is heated to a tempera-

21 ture within the range of from about 1,900F. to about

22 2,300F., preferably from about 2,000F. to about 2,200F.

23 The crystalline silicas herein are thermally shock calcined

24 by relatively rapidly increasing the temperature to within

25 the range of 1,900F. to 2,300F. and maintaining the

26 crystalline silica at temperatures within that range for a

27 relatively short period of time, usually from about 0.1

28 second to about 20 minutes, preferably from about 0.5 second

29 to about 10 minutes, most preferably from 1 second to about

30 S minutes. Preferably the thermal shock calcination

31

32 l -8-!l ,, ~ s6~4s l mperature is increa8ed at a rate of from about 1P. per 2 second to about 200,000 F. per second, preferably from 3 about 1 F. per second to about l,000 F. per second~

4 One method of rapidly increasing the temperature 5 of the crystalline silica involves contacting a stream of 6 preheated air with a stream of fluidized crystalline silica 7 powder. The crystalline silica powder typically has a 8 particle size of less than l00 microns, preferably from 9 about 6 microns to about l00 microns, most preferably from 10 about 25 microns to about l00 microns, and is fluidized in a 11 flowing gas stream, for example an air stream. A
12 crystalline silica powder having a p~rticle size in this 13 range when mixed with a gas has the characteristics of a 14 fluid when transported through a tube or coil.
l~ A typical apparatus for contacting the air and 16 crystalline silica includes two high-temperature coils 17 connected in series and suspended in a furnace. Air, 18 preheated in the first coil, impinges at a right angle on a 19 stream of fluidized crystalline silica introduced through a 20 tee into the second coil. The crystalline silica is then 21 rapidly cooled, as by introducing a quench stream of cold 22 air into the effluent from the second coil.
23 Another efficient method of rapidly heating the 24 crystalline silica to the desired temperature is by blending ~5 the crystalline silica with a preheated solid silica sand in ~6 -a sand bath.
27 Although the invention is not to be held to any ~8 particular theory of operation, thermally shock calcining 29 the crystalline silicas herein is believed to alter the 30 crystalline silica surface acidity by the following ~2~ L5 1 mechanism: electron-deficient, Lewis-acid sites form when 2 surface hydroxyl groups combine and water is expelled.
3 Crystalline silica surface protonic-acid sites (Bronsted) 4 are eliminated as Lewis-acid sites are formed. The concen-tration of Lewis-acid sites may decrease as thermal mobility 6 rearranges the crystalli-ne-silica surface and the more~
7 active acid sites are eliminated. Thus, the thermal shock 8 calcination of the crystalline silicas herein selectively 9 eliminates the strongest acid sites on the crystalline 10 silica surface resulting in a crystalline silica with 11 slightly reduced catalytic activity but greatly enhanced 12 selectivity. Examples oE i~proved catalyst selectivity a~e 13 the cracking of hydrocarbons to selectively produce higher 14 proportions of intermediate molecular weight products and in 15 alky1ation reactions to the selective production of certain 16 isomers, for example, para-xylene in the reaction of toluene 17 with a methylating agent. The optimal thermal shock 1~ calcination temperature for the crystalline silica may vary 19 according to the type of crystalline silica, the desired 20 reaction, and the level of activity and selectivity desired.
21 After the thermal shock calcination step is 22 completed, it is important to rapidly cool the crystalline 23 silica to a temperature of about 1,000F. or lower. Rapid 24 cooling of the crystalline silica is necessary because 25 crystalline silicas are excellent thermal insulators and ~6 retai`n the high shock calcination temperatures for a period 27 of time sufficient to cause excess sintering and loss f 28 catalytic activity. The thermally shock calcined 29 crystalline silicas may be c~oled, for example, by passing 30 the thermally shock calcined crystalline silica through a l -10- ' 1 tube immersed in a water bath or by flowing the crystalline 2 silica particles o~er an inclined cooled metal plate or 3 through a rotating cooled tube. Another method of rapidly 4 reducing the temperature of the thermally shock calcined 5 crystalline silicas is by quenching the shock calcined 6 crystalline silica in a liquid medium, such as water.
7 The shock calcination treatment may be performed 8 on the crystalline silica alone, or if the crystalline 9 silica is to be used as a catalyst, in combination with a 10 porous refractory oxide and/or optionally a promoter, then 11 the treatment may be applied to composites containing such 12 components in combination with the crystalline silica. In 13 addition, ~he crystalline silic~ treated by shock 14 calcination may be completely or partially cation exchanged, 15 for example, with hydrogen, ammonium, or di- or trivalent 16 metal cations, such as rare earth metal or alkaline ~arth 17 metal cations for stability purposes or with cations of 18 palladium, platinum, nickel, etc., to provide a hydro-19 genation component~ Other metal cations which may be used 20 herein include chromium, iron, titanium and zirconium.
21 The crystalline silicas herein may be used alone, 22 in combination with a refactory oxide, in combination with a æ promoter or in combination with a refractory oxide and a 24 promoter. It should be noted that the use of refractory ~_ oxides and promoters herein is optional but preferred.
26 The crystalline silicas may be mixed with an 27 inorganic refractory oxide in the form of a hydrogel or sol 2~ such ax peptized boehmite alumina or colloidal silica. The 29 inorganic refractory oxides herein are preferably selected 30 from the group consisting of boehmite alumina, silica ~56F~

1 hydrosol, colloidal silica and mixtures thereof. Other 2 inorganic refractory oxides include alumina, silica, 3 magnesia, beryllia, zirconia and mixtures thereof.
4 Normally, the crystalline silica and inorganic 5 refractory oxide are mixed in a weight ratio range of from 6 about 1:10 to about 10:1, preferably from about 1:4 to about 7 4:1.
B In order to provide suitable hydrocarbon 9 conversion, hydrodewaxing, desulfurization and denitro-10 genation activity, the crystalline silicas herein may be 11 composited with a minor amount of a promoter. The amount of 12 promoter incorporated into the final catalyst is typically ~3 from about 0.2 to about 35 weight percent, preferably from 14 abou~ 0.5 to about 25 weight percent of the catalyst.
15 For use in hydroconversion reactions, such as ¦
16 hydrodesulfurization and hydrodenitrogenation processes and 17 hydroconversion processes such as hydrocracking, hydro-18 isomerization, reforming etc., a promoter comprising a 19 hydrogenation component is composited with the crystalline 20 silica catalyst. Effective hydrogenat.ion components 21 comprise the Group IIB, Group VIB, and Group VIII metals as 22 disclosed in the Periodic _able of Elements, as published by 23 the Sargent-Welch Scientific Company. I
24 Hydrocarbon conversion reactions such as ~5 alkylation, isomerization, transalkylation, etc., may be 26 promoted by compositing the crystalline silica catalyst with ~7 one or more promoters selected from the group consisting of ~8 the Groups IB, IIA and VA and the rare earth elements of the 29 Periodic Table of Elements as above-described and preferably 30 compounds of phosphorus, magneslum, boron, antimony, I

~.256~5 1 arsenic and mixtures thereof. One especially preferred 2 alkylation promoter is a phosphorus compouncl.
3 Representative phosphorus compouncls include 4 derivatives of groups represented by the formulae PX3, RPX2, 2 3 3 O (X03)P~ R3P=0~ ~3P=S, R P02, RPS
6 RP~O)(OX)2, RP(S)(SX)3, R2P(O)OX, R~PtS)SX, ~P(OX)2, 7 RP(SX)2, ROP(OX)2, RSP(SX)2, (RS)2PSP(S~)2, and (RO)2POP
8 (OR)2 wherein R is alkyl or aryl and X is hydrogen, alkyl~ ¦
9 aryl or halide. These compounds include primary, secondary 10 or tertiary phosphines; tertiary phosphine oxides; tertiary 1~ phosphine sulfides; primary and secondary phosphonic acids 12 and their corresponding sulfur derivatives; esters of 13 phosphonic acids; the dialkyl alkyl phosphonates; alkyl dialkyl phosphonates, phosphinous acids, primary, secondary 15 and tertiary phosphites and esters thereof alkyl 16 dialkylphosphinites, dialkyl alkyl-phosphonites their esters 17 and sulfur derivatives.
18 other suitable phosphorus-containing compounds 19 include the phosphorus halides such as phosphorus 20 trichloride, phosphorus tribromide, phosphorus triiodide, 21 alkyl phosphorodichloriaes, dialkyl phosphorochlorides and 22 dialkyl phosphonochloridites. Preferred phosphorus-23 containing compounds include phosphoric acid, phosphorus 24 acid, and phosphate esters such as trimethylphosphate, 25 ethylphosphate, ethylphosphite, or monophenylphosphate, etc. I
26 and mixtures thereof.
27 Preferred catalysts for alkylation reactions 28 comprise about 5 to about 30 weight percent phosphorus on a 29 support comprising silica or-alumina and a shock calcined 30 silicalite, most preferably in a 1:4 to 4~i weight ratio.

.~5 .

1 ~he alkylation process herein may effectively be 2 carried out by contacting an aromatic hydrocarbon and a C
3 to C10 hydrocarbon with the above-described crystalline 4 silica under alkylation reaction conditionsO
The aromatic hydrocarbon suitable for use 6 preferably is a member selected from the group consisting of 7 benzene, toluene, xylene, ethylbenzene, phenol, and cr~sol 8 and mixtures thereof. The preferred aromatic hydrocarbon is 9 toluene.
A wide variety of C1 to C10 hydrocarbons may be 11 used to alkylate the aromatic hydrocarbons herein. For 12 example, the C1 to C10 alkanes, C~ to C10 olefins, as well 13 as C1 to C10 alicyclic and alkenyl radicals ancl various 14 methylating agents may be used.
The shock calcined crystalline silicas may be used 16 alone or in combination with refractory oxides and/or 17 promoters for alkylation reactions. In an especially 18 preferred mode, toluene is selectively alkylated to 19 para-xylene by contacting toluene and a methylating agent 20 with a thermally shock calcined crystalline silica.
21 Optionally, the crystalline silica may contain phosphorus or 22 one or more of the other promoters described herein, 23 preferably in conjunction with an inorganic refractory oxide 24 such as alumina, silica, etc. The reaction is carried out 25 at a temperature of from about 700F. to about 1,150~F., 26 preferably from about 800F. to about 1,000F., at a 27 pressure of from about atmospheric pressure to about 250 28 p.s.i.a., preferably from ~bout 15 p.s.i.a. to about 100 29 p.s.i.a. The molar ratio of toluene to methylating agent ~2 ~25~ a5 l is normally from about 6:1 to about 1O2, preferably from2 about 3:1 ~o about l~
3 Suitable methylating agents include methanol, 4 methylchloride, methylbromide, dimethyl ether, 5 methylcarbonate, dimethylsulfide, etc. The mPthylation 6 reaction is accomplished using a weight hourly space 7 velocity (WHSV) of from about 1 to 20, especially from about 8 2 to about 10. Para-xylene is selectively produced in the 9 reaction; however, it should be noted that some ortho-xylene 10 and small amounts of meta-xylene may additionally be ll produced. Conventional methods may be used to separate the 12 xylene isomers or the undesirable isomers may be converted 13 to para-xylene in an isomerization process. The methylation 14 reaction herein may ~e carried out as a continuous, 15 semi-continuous or batch type operatiorl, using a fixed or 16 moving type catalyst system utilizing conventional 17 apparatus.
18 The invention is further illustrated by the 19 following examples which are illustrative of various aspects 20 of the invention and are not intended as limiting the scope 21 of the invention as defined ~y the appended claims.
22 Example I
23 A crystalline silica (silicalite) is prepared by 24 mixing l~100 ml of an alkaline solution containing sodium 26 silicate equivalent to the molar proportions: 100 moles of 26 SiO2t 30 moles of Na2O, and 1,390 moles of water, with 530 27 ml of an acidic solution containing components equivalent to 2~ the molar proportions: 16 moles of NaCl, sulfuric acid 29 equivalent to 21 moles H2SO4, and 710 moles of water. The 30 resulti.lg gel is mixed with an organic solution containing ~56~

1 59 grams of tri-n-propylamine (N(n-C3H7)3), 49 grams of ~¦
2 n-propylbromide tn-c3~7Br) and 94 grams of 2-butanone 3 (CH3COC2H5). The resulting mixturP is stirred and reflu~ed 4 24 hours at 180 F. Next, the vapor space is pressured to 600 p.s.i. with nitrogen and the temperature is increased to 6 320~ ~. to 330~ F. for 30 hours while stirring at about 200 7 rpm to form a crystalline silica. The solid product is 8 collected by filtration, washed with distilled water and 9 dried at 240 F.
Next, 1,000 ml of 2.0 M ammonium hydrogen sulfate 11 ~NH4HSO4) is prepared by dissolving 132 grams of ammonium 12 sulfate [(NH4)2SO~] iJI 800 ml of water to form a solution.
13 Next/ 28 ml of concentrated sulfuric acid (l-l2SO~) is added 14 to the solution and the solution is diluted to 1,000 ml with 15 water. I
1~ Then, 300 grams of the silicalite prepared in 17 accordance with the procedure described above is added to 1~ the ammonium hydrogen sulfate solution and heated at 170 F.
19 to ~00 F. with stirring for one hour. The acid treated 20 silicalite is collected by filtration, washed with barium 21 acetate lBa(C2H3O2)2] until the filtrate tests sulfate 22 ~SO4 ) free and dried at 230 F.
23 Exam~le II
24 Precalcined 70 wt. % Silicalite 26 Bonded With 30 wt % Alumina 26 The dried, acid treated silicalite produced in 27 Example I is blended with Catapal S alumina to form a powder 28 mixture containing 70 wt. % silicalite and 30 wt. % alumina.
29 A combustible porosity promoter equivalent to 10 wt. % of 30 the silicali~e composition on a dry weight basis is added to 31 *Trade Mark ll ~25~ 5 l the mixture by blending said mixtur~ with powdered micro-2 crystalline cellulose, manufactured by the FMC Corporation.
3 The above-described powdered mixture is converted 4 into a paste by mulling ~ith sufficient N/lO nitric acid ~as 5 7 ml of concentrated nitric acid per l,000 ml solution).
6 Next~ the paste is spread into a thin layer, dried at 7 300 F., calcined at 900 P~ for 2 hours, and then 8 granulated into 10130 mesh aggregates.
9 Example III
lO Shock Calcined 70 wt. % Silicalite ll Bond d With 30 wt. % Alumina 12 A portion of the granul~s produced in accordclnce 13 with the procedure of Example II is thermally shock calcined l4 by spreading the granules in l/8 inch layers in zirconia 15 combustion boats. The boats are placed into a preheated 16 Alundum tube. The average rate of temperature increase for lq the granules is 2 F./second in the tempera~ure interval of 18 1,550 F. to 2,160 F. The temperature is held at 2,160 F.
l9 to 2,190 F. for 4 minutes. Next, the silicalite-containing 20 catalyst is cooled from 2,190 F. to 1,790 F. at about 1.3 ~1 F./second by drawing the catalyst through a ceramic tube and 22 then quenched by dumping on a cold steel plate.
23 Example IV
24 Shock Calcined 70 wt. % Silicalite 25 Bonded With 30 wt % Alumina 26 A shock calcined, silicalite-containing catalyst 27 is prepared in accordance with the procedure of Example III
28 with the following exception:
29 The average rate of temperature increase is 2 D
30 F./second in the temperature interval of 1,550 F. to 2,280 31 *Trade Mark ~ -17- j ~256~d~5 1 F. and the temperature is held at 2,280~ F. to 2,350 F. for 2 3.25 minutes.
3 Example V
4 Precalcined 70 wt. % Silicalite Bonded With 30 wt. % Silica 6 The dried, acid txeated silicalite (80 grams3 7 produced in Example I is blended with 1.0 gram of micro- !
8 crystalline cellulose for 5 minutes. Next, 78 ml of silica 9 and sufficient water are added to the above powdered mixture 10 to form a paste and the resulting mixture is mulled for 5 11 minutes. Then, the paste is spread into a thin layerl dried 12 at room temperature, granu1ated into 10/30 mesh aggregrates 13 and calcin~d a~ 900 ~. for 2 hours.
14 The calcined granules are slurried in 500 ml of 15 2.0 M ammonium nitrate and allowed to stand overnight. The 16 granules are collected, as by filtration, washed twice with lq distilled water, dried at 230 F. and calcined at 900 F.
18 for 2 hours.
19 Example VI
20 Shock Calcined 70 wt. % Silicalite 21 Bonded with 30 wt. % Silica 22 A precalcined, silicalite-containing catalyst is 23 prepared in accordance with the procedure of Example V to 24 produce a shock calcined catalyst with the following ~5 exception:
2B A portion of the granules produced in accordance 27 with the procedure of Example V is thermally shock calcined 2~ by spreading the granules in 1/8 inch layers in zirconia 29 combustion boats. The boats are placed into a preheated 30 alundum tube. The average rate of temperature increase for 32 ' . I

~2s6~3~a5 1 the granules is 30 F.Jsecond. The temperature is held at 2 2,030 F. for 2 minutes. Next, the silicalite-containing 3 catalyst is quenched by dumping on a cold steel plate.
4 Example VII
Precalcined lO wt. % P2O5 on 65 wt. ~
6 Silicalite Bonded With 25 wt. ~ Silica 7 The dried, acid treated silicalite (26 grams) 8 produced in Example I is blended with 3.5 ml of 85~
9 phosphoric acid and 25 ml of silica to form a mixture and dried at 230 F. The resulting mixture is calcined at 900 1~ F. for two hours and then granulated into 10/30 mesh 12 aggregates. The catalyst contained 10 wt. ~ phosphorus as 13 P2~5.
]~ Exam~le VIII
Shock ('alcined 10 wt. % P2O5 on 1~; 65 wt. % Silicalite Bonded With 25 wt. % Silica 17 A precalcined, silicalite-containing catalyst is 18 prepared in accordanc~ with the procedure of Example VII to 19 produce a shock calcined catalyst with the following exception:
21 A portion of the precalcined granules are spread 22 in 1/8 inch layers in zirconia combustion boats. The boats 23 are placed into a preheated Alundum tube. The average rate 24 of temperature increase for the granules is 12 F./second.
The temperature is held in the temperature interval of from 2G 2,170 F. to 2,110 F. for 3 ~inutes. Next, the 27 silicalite-containing catalyst is quenched by dumping on a 28 cold steel plate. It should be noted that after shock 29 calcination, the above-dêscribed catalyst contains 8.5 Wt.%
phosphorus as P2O5.

1 Examples IX to XI

2 Toluene is selectively methylated to p~ra-xylen~

3 by feeding a 2:1 molar ratio of toluene and methanol respec-4 tively into a react.or containing the crystal:line silica 5 catalysts described in Table 1 below. The toluene and 6 methanol are fed into the reactor at atmospheric pressure, a 7 temperature of 1,000~ F and a weight hourly space velocity 8 (WHSV) of 4~ The catalysts used and results are describecl 9 and summari~ed in Table 1 below:

17 .
18 .

29 . 1.

l -20-~* ~ ~ ~
a~ . u~

u~
u~ o ~ ~
p æ~

~ ~
~ U) ~
~ ~ . o~
~ ~ ~ In a~ o~
~ ~ ~ ~, ~ ~ ~ ~ .

! ~ ~ ~
cr~ I
, ,, ~ a~
~ I l l ~
~DCO a .
~- ~
~ ~ ~ ~ r~ P~
~ d~
..
U~ .
$ ~
S~ a~ ~
q) ' ~
.~; ~ H
~1 (~ U~ H 1-1 V ~ . . .
~ ~ ~ ~a ~11 ~ .
o ~ ~ X

~25i6~

1 The above data prove that the catalysts containing 2 the th~rmally shock calcined crystalline silica (Examples X
3 and XIl are more selective to the production of para-xylene 4 as compared to the otherwise identical catalyst that does 5 not contain a thermally shock calcined crystalline silica 6 (Example IX). Also, the catalysts of Examples X and XI
7 evidence greater selectivity for xylene production than the 8 catalyst of Example IX.
9 Obviously, many modifications and variations of 10 the invention, as herein before set forth, may be made 11 without departing from the spirit and scope thereof, and 12 only such limitations should be imposed as are indicated in 13 the appended claims.

~2 23 .

~ ~'.

31 .

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Claims (42)

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

1. A process for treating a microporous crystalline silica which comprises (a) precalcining a microporous crystalline silica at a temperature below the temperature to which the crystalline silica is heated in step (b) but sufficiently high to vaporize water and desorb volatile components;
(b) thermally shock calcining the precalcined crystalline silica by rapidly increasing the temperature of said precalcined crystalline silica at a rate between about 1° F./second and about 200,000° F./second to a relatively high temperature between about 1900°F. and about 2300°F.
and maintaining said relatively high temperature for a period of time between about 0.1 second and 20 minutes, said period of time being sufficiently short to avoid substantial sintering; and (c) cooling the thermally shock calcined crystalline silica at a rate sufficiently rapid to avoid substantial sintering and substantial loss of catalytic activity from said shock calcining.

2. A hydrocarbon conversion process comprising contacting a hydrocarbon feedstock under hydrocarbon conversion conditions with a catalyst including a microporous crystalline silica prepared by a process comprising:
(a) precalcining a microporous crystalline silica at a temperature below the temperature to which the microporous crystalline silica is heated in step (b) but sufficiently high to vaporize water and desorb volatile components;

Docket No. 0179004 (b) thermally shock calcining the precalcined microporous crystalline silica by rapidly increasing the tem-perature of said precalcined crystalline silica at a rate between 1°F./second and about 200,000° F./second to a relatively high temperature between about 1900° F. and about 2300° F.
and maintaining said relatively high temperature for a period of time between about 0.1 second and about 20 minutes, said period of time being sufficiently short to avoid substantial sintering; and (c) cooling the thermally shock calcined crystal-line silica at a rate sufficiently rapid to avoid substantial sintering and substantial loss of catalytic activity from said shock calcining.

3. A process for alkylating an aromatic hydrocarbon which comprises contacting said aromatic hydrocarbon with a C1 to C10 hydrocarbon under alkylation reaction conditions in the presence of an alkylation catalyst including a microporous crystalline silica prepared by a process comprising:
(a) precalcining a microporous crystalline silica at a temperature below the temperature to which the micro-porous crystalline silica is heated in step (b) but sufficient-ly high to vaporize water and desorb volatile components;
(b) thermally shock calcining the precalcined microporous crystalline silica by rapidly increasing the temperature of said precalcined microporous crystalline silica at a rate between about 1° F./second and about 200,000° F./second to a relatively high temperature between about 1900° F. and about 2300° F. and maintaining said relatively high temperature for a period of time between about 0.1 second and about 20 minutes, said period of time being sufficiently short to avoid substantial sintering; and (c) cooling the thermally shock calcined crystalline silica at a rate sufficiently rapid to avoid substantial sintering and substantial loss of catalytic activity from said shock calcining.

4. A process as defined by any one of claims 1 to 3 wherein said precalcination temperature is about 400° or more below said relatively high thermal shock calcination temperature.

5. A process as defined by any one of claims 1 to 3 wherein the temperature of said precalcined crystalline silica in step (b) is increased to said relatively high temperature at a rate of from about 1° F./second to about 1000° F./second and maintained at said relatively high temperature for about 0.5 second to about 10 minutes.

6. A process as defined by any one of claims 1 to 3 wherein said precalcined crystalline silica is thermally shock calcined by rapidly increasing the temperature of said precalcined crystalline silica to within the range of from about 2000° F. to about 2200° F. and maintaining that tem-perature for a time between about 1.0 second and about 5 minutes.

7. A process as defined by any one of claims 1 to 3 wherein said microporous crystalline silica is precalcined at a temperature in the range between about 700° F. to about 1100° F.

8. A process as defined by any one of claims 1 to 3 wherein said microporous crystalline silica comprises silicalite.

9. A process as defined by any one of claims 1 to 3 wherein said thermally shock calcined crystalline silica is rapidly cooled to a temperature below about 1000° F.

10. A process as defined by any one of claims 1 to 3 wherein said thermally shock calcined crystalline silica is rapidly cooled to a temperature below about 1000° F. by passing the thermally shock calcined crystalline silica through a tube immersed in water.

11. A process as defined by any one of claims 1 to 3 wherein said thermally shock calcined crystalline silica is rapidly cooled to a temperature below about 1000° F. by contacting the thermally shock calcined crystalline silica with a stream of cold air.

12. A process as defined by any one of claims 1 to 3 wherein said thermally shock calcined crystalline silica is rapidly cooled to a temperature below about 1000° F. by flowing the thermally shock calcined crystalline silica over an inclined, cooled metal plate.

13. A process as defined by any one of claims 1 to 3 wherein said thermally shock calcined crystalline silica is rapidly cooled to a temperature below about 1000° F. by quenching the thermally shock calcined crystalline silica in a liquid medium.

14. A process as defined by any one of claims 1 to 3 wherein said thermally shock calcined crystalline silica is rapidly cooled to a temperature below about 1000° F. by passing the thermally shock calcined crystalline silica through a rotating cooled tube.

15. A process as defined by claim 2 wherein said catalyst further includes a hydrogenation component and said hydrocarbon conversion process is selected from the group consisting of hydrodesulfurization, hydrodenitrogenation, hydrocracking, hydroisomerization and reforming.

16. A process as defined by claim 2 wherein said catalyst further includes a promoter selected from the group consisting of phosphorus components, magnesium components, boron components, antimony components, arsenic components and mixtures thereof, and said hydrocarbon conversion process is selected from the group consisting of alkylation, transalkyla-tion and isomerization.

17. A process as defined by claim 3 wherein said aromatic hydrocarbon is selected from the group consisting of benzene, toluene, xylene, ethylbenzene, phenol, cresol and mixtures thereof.

18. A process as defined by claim 3 wherein said C1 to C10 hydrocarbon is selected from the group consisting of C1 to C10 alkanes, C2 to C10 olefins, C1 to C10 alicyclic radicals and C1 to C10 alkenyl radicals.

19. A process as defined by claim 3 wherein said alkyla-tion catalyst further includes an inorganic refractory oxide component and a phosphorus component.

20. A catalyst comprising a microporous crystalline silica prepared by the process comprising:
(a) precalcining a microporous crystalline silica at a temperature below the temperature to which the microporous crystalline silica is heated in step (b) but sufficiently high to vaporize water and desorb volatile components:
(b) thermally shock calcining the precalcined microporous crystalline silica by rapidly increasing the temperature of said precalcined crystalline silica at a rate between about 1° F./second and about 200,000° F./second to a relatively high temperature between about 1900° F. and about 2300° F. and maintaining said relatively high temperature for a period of time between about 0.1 second and about 20 minutes, said period of time being sufficiently short to avoid substantial sintering; and (c) cooling the thermally shock calcined crystalline silica at a rate sufficiently rapid to avoid substantial sintering and substantial loss of catalytic activity from said shock calcining.

21. A catalyst as defined by claim 20 wherein said precalcination temperature is about 400° or more below said relatively high thermal shock calcination temperature.

22. A catalyst as defined by claim 20 wherein the temperature of said precalcined crystalline silica in step (b) is increased to said relatively high temperature at a rate between about 1° F./second and about 1000° F./second and maintained at said relatively high temperature for a period of time between about 0.5 second and about 10 minutes.

23. A catalyst as defined by claim 20 wherein the temperature of said precalcined crystalline silica in step (h) is rapidly increased to a relatively high temperature between about 2000° F. and 2200° F. and maintained at said relatively high temperature for a period of time between about 1.0 second and about 5 minutes.

24. A catalyst as defined by claims 20 or 21 wherein said microporous crystalline silica is precalcined at a temperature in the range between about 700° F. and about 1100°
F.

25. A catalyst as defined by claim 20 wherein said thermally shock calcined crystalline silica is rapidly cooled to a temperature below about 1000° F.

26. A catalyst as defined by claims 20 or 25 wherein said thermally shock calcined crystalline silica is rapidly cooled to a temperature below about 1000° F. by passing the thermally shock calcined crystalline silica through a tube immersed in water.

27. A catalyst as defined by claims 20 or 25 wherein said thermally shock calcined crystalline silica is rapidly cooled to a temperature below about 1000° F. by contacting the thermally shock calcined crystalline silica with a stream of cold air.

28. A catalyst as defined by claims 20 or 25 wherein said thermally shock calcined crystalline silica is rapidly cooled to a temperature below about 1000° F. by flowing the thermally shock calcined crystalline silica over an inclined, cooled metal plate.

29. A catalyst as defined by claims 20 or 25 wherein said thermally shock calcined crystalline silica is rapidly cooled to a temperature below about 1000° F. by quenching the thermally shock calcined crystalline silica in a liquid medium.

30. A catalyst as defined by claims 20 or 25 wherein said thermally shock calcined crystalline silica is rapidly cooled to a temperature below about 1000° F. by passing the thermally shock calcined crystalline silica through a rotating cooled tube.

31. A catalyst as defined by claim 20 wherein said micro-porous crystalline silica comprises silicalite.

32. A catalyst as defined by claim 20 additionally including an inorganic refractory oxide component.

33. A catalyst as defined by claim 20 additionally including a hydrogenation component.

34. A catalyst as defined by claim 20 additionally including a promoter selected from the group consisting of phosphorus components, magnesium components, boron components, antimony components, arsenic components, and mixtures thereof.

35. A catalyst as defined by claim 20 additionally including alumina and a phosphorus component.

36. A process for selectively producing para-xylene which comprises contacting toluene with a methylating agent under methylation reaction conditions in the presence of the catalyst of claim 20.

37. A process as defined by claim 36 wherein said microporous crystalline silica comprises silicalite.

38. A process as defined by claim 37 wherein said methylating agent is selected from the group consisting of methanol, methylchloride, methylbromide, dimethyl ether, methylcarbonate and dimethylsulfide.

39. A process as defined by claim 38 wherein said catalyst further comprises alumina and a phosphorus component.

40. A process as defined by claim 39 wherein said phosphorous component is selected from the group consisting of phosphoric acid, phosphorus acid, phosphate esters and mixtures thereof.

41. A process as defined in claim 36, 37 or 38, wherein the methylation is carried out at a temperature of from about 700°F. to about 1,150°F., at a pressure of from about atmospheric pressure to about 250 p.s.i.a. and at a molar ratio of toluene to methylating agent of from about 6:1 to about 1:2.

42. A process as defined in claim 39 or 40, wherein the methylation is carried out at a temperature of from about 700°F. to about 1,150°F., at a pressure of from about atmospheric pressure to about 250 p.s.i.a. and at a molar ratio of toluene to methylating agent of from about 6:1 to about 1:2.