CA1051463A

CA1051463A - Disproportionation of toluene

Info

Publication number: CA1051463A
Application number: CA216,011A
Authority: CA
Inventors: Roger A. Morrison
Original assignee: Mobil Oil Corp
Current assignee: ExxonMobil Oil Corp
Priority date: 1974-01-07
Filing date: 1974-12-13
Publication date: 1979-03-27
Also published as: FR2256908B1; DE2460539A1; NL7500123A; NL183238B; IT1028200B; JPS5096532A; ZA7531B; GB1463359A; DE2460539C2; FR2256908A1; NL183238C; BE824175A

Abstract

DISPROPORTIONATION OF TOLUENE

Abstract of the Disclosure Toluene is disproportionated in high yield with unusually low hydrogen consumption by the use of a specific group of catalysts. The operation is carried out in the vapor phase for extremely long on-stream periods and comprising contacting toluene at a temp-erature between 650°F. and 1000°F., a hydrogen to hydro-carbon mole ratio of between 0 and 5, a pressure between atmospheric and 1000 psig, and a weight hourly space velocity between about 1 and 20, with a catalyst com-prising a crystalline aluminosilicate zeolite of the ZSM-5 family which zeolite is at least partly in the hydrogen form.

Description

iO51~3 This invention is directed to the vapor-phase disproport-lonation of toluene.
AIkylation of aromatic hydrocarbons employing certain crystalline aluminosilicate zeolite catalysts is known in the art. For instance, U.S. Patent 3,521,897 describes liquid phase alkylation in the presence of crystalline aluminosilicates such as fau~asite, heuland-lte, clinoptilolite, mordenite, dachiardite, zeolite X and zeolite Y. m e temperature of such alkylation procedure does not exceed 600F., thereby maintaining patentee's preferable operating phase as substantially ; liquid. me use of such zeolites, and others, for liquid phase disporportionation of toluene is also known; for instance British Specifi-cation 1,210,786 discloses the catalysis of disproportionation of a 4:1 toluene trimethylbenzene mixture by zeolite ZSM~4.
U.S. Patent 3,551,509 discloses transalkylation between tri-methylbenzenes and toluene to yield xylenes and benzene in the presence of a crystalline aluminosillcate catalyst having pore openings of 8 to 15 Angstrom units and, preferably, containing Group VIII metals, hydrogen and rare earth cations. From the teaching of these patents, one would expect the rather large pore opening of 8 to 15 Angstrom units to be a requirement for effective disproportionation of aromatic hydrocarbons such as toluene.
Whilst the crystalline aluminosilicate catalysts proposed for such prior art methods provide satisfactory initial yields of desired products their catalytic aging properties generally are not sufficiently good to warrant commercial application.

-2-lO~t~
According to the present invention a process for disproport-ionating toluene comprises contacting toluene at a temperature between 650F. and 1000F., a hydrogen to hydrocarbon mole ratio of between 0 and 5, a pressure between atmospheric and 1000 psig, and a weight hourly space velocity between about 1 and 20, with a catalyst comprising a crystalline aluminosilicate zeolite of the ZSM~5 family which zeolite is at least parly in the hydrogen form.
Preferably the zeollte has undergone base exchange with iron, cobalt or nickel (which latter is particularly advantageous); high temperatures, particularly when accompanied by a reducing atmosphere, will of course usually bring about transmutation of such introduced metal to the non-cationic state by the time it is in use. Alternatively, however, the zeolite may be used in the substantially total hydrogen form, achieved by base exchange with hydrogen ions or their precursors (such as ammonium).
The preferred member of the ZSM~5 family is zeolite ZSM~5 itself, advantageously of silica/alumina ratio between 5 and 100.
The zeolite may be mixed with a binder to form a composite containing 30 to 90, preferably about 35 weight percent zeolite. A preferred binder is alumina.
Preferred operating conditions comprise a temperature of 750 to 900F, a pressure of 400 to 800 psig, and a hydrogen/hydrocarbon mole ratio of 0 to 4, even more preferably 0 to 3.
The ZSM~5 family of crystalline aluminosilicate zeolites includes zeolltes ZSM~5 and ZSM~ll, which may be represented by the general formulae, expressed in terms of m~le ratios of oxides in the anhydrous state, which follow:

; :

ZSM-5 ~051~63 O.9 + O.2M20 : A1203 : XsiO2 n wherein M is a cation, n is the valence of M and x is at least 5, and ZSM-ll o.g + 0.3 M20 : A1203 : y SiO2 n wherein M is a cation, n is the valence of M and y is from 2 to 90. ZSM~5 is described in U.S. Speciflcation 3,702,886, ZSM-ll in U.S. Specification

3,709,929.
In a preferred synthesized form, the zeolite ZSM~5 for use in the catalyst composition useful in this invention has the formula, in terms of mole ratios of oxldes in anhydrous state, as follows:

0.9 + 0.2M20 : Al203 : xSiO2 n wherein M is selected from the grouP consisting of a mixture of alkali metal cations, especially sodium, and tetraalkylammonium : cations, the alkyl groups of which preferably contain 2 to 5 carbon atoms, and x is at least 5. Particularly preferred is a zeolite havin~
the ~ormula in the anhydrous state as follows:

0 9 + 0.2M20 : Al203 : 5-lO0 SiO2 ,~ n ,~
~ The preferred as-synthesized form of ~eolite ZSM-ll for use in the , catalyst composition useful in this invention has the formula, in terms of mole ratios of oxides in the anhydrous state, as follows:

' ~ ~
~ -4-, , , , ,,, . ~, -.. .

~0514~;3 0.9 + 0.3M20 : Al203:20 to 90 SiO2 n wherein M is a mixture of at least one of the quaternary cations of a Group V-A element of the Periodic Table and alkali metal cations, especially sodium, the amount of quaternary metal cations being between lO and 90 percent of total cation. m us, the zeolite c~n be expressed by the following formula in terms of mole ratios of oxides, as follows:
O.9 + O.3 ~xXR4+1-xM20] : Al203 : 20 to 90 SiO2 n wherein R is an alkyl or aryl group having between l and 7 carbon atoms, M ls an alkali metal catlon, X is a group V-A element, especially a metal, and x is between 0.1 and 0.9.
For use in catalytic compositions in the process of the inventlon the original cations of the ZSM~5 family zeolite are replaced, in accordance with technlques well kncwn in the art, at least in part, by lon exchange with hydrogen or hydrogen precursor cations and/or non-noble metal lons of Group VIII of the Perlodic Table, i.e., nlckel, iron and/or cobalt. By the tine the catalyst has encountered process conditions at least a part, and probably a significant proportion of the metal introduced by exchange ls non-cationic. m e preferred metal ls nickel. m e preferred zeollte ls zeolite ZSM-5, which has elllptlcal pores of approximately 4.8 x 7.1 Angstrom units. As an alternatlve to ion exchange a certaln proportlon of hydrogen catlon sltes may be generated in the zeollte by thermal ~; 25 degradatlon of orlginally present tetralkylammonium catlons.
Members of the ahove family of zeolltes, designated herein as ZSM-5 and ZSM_11 have an eceptlonally high degree of thermal stability, which renders them particularly effective in processes _~

~: , . . .

l(~S3L4ti3 involving elevated temperatures. In this connection, this familyof zeolites appears to be one of the most stable knowr. to date. Nevertheless, the process of this invention is carried out at reactor bed temperatures not in excess of 1000F., which eliminates many undesirable reactions that occur in catalytic transalkylation of hydrocarbons carried out at higher temperatures. At reactor bed temperatures substantially above 1000F., the reactants and products undergo degradation resulting in the loss of desired products and reactants. Undesirable residues are formed from the degradation reactions. These degradation products may lead to the formation ofcoke,~ike deposites on the active surfaces of the catalyst which rapidly destroy the hi~h activity of the catalyst and greatly shorten lts effective life.

~0514~i3 Members of the above family of zeolites for use in the catalyst composition of the present invention possess definite distinguishing crystalline structures wh~se X-ray diffraction patterns show the f~llowing significant lines:

Interplanar Spacing d (A) Relative Intensity .`

11.1 + 0.2 11.0 + 0.2 S
:7~4 + 0.15 W
7'1 + 0.15 W
6.3 + 0.1 W
6.04+ 0.1 W
5.56 + 0.1 W
5.~ + 0.1 W

4~ + o.o8 w 425+ o.o8 w ,3.85+ 0.07 VS
3.71+ 0.05 S
i 20 ~3~04 + 0.03 2.99+ 0.02 W
2.9~ 0.02 W

, " '' , .
.

1~514t;3 TABLE 1 (Cont'd) ZSM-ll Interplanar Spacing d(A) Relative Intensity 11.2 + .2 M
10.1 + .2 M
6.73 + .2 W

5.75 _ .1 W
5.61 + .1 W
5~03 + .1 W
4.62 + .1 W
4.39 + .o8 w 3. 86 + . 07 vs : 3 73 + 07 M

3.49 + .07 W
(3-07, 3.00~'.05 W
2.01 + .02 W
.

,' 105~463 These values were determined by standard techniques.
The radiation was the K-alpha doublet of copper, and a scinti-llation counter spectr~meter with a strip chart pen rec~rder was used. The peak heights, I, and the positions as a function of 2 times theta, where theta is the Bragg angle, were read from the spectrometer chart. Fr~m these, the relative in-tensities, 100 I/I~, where Io is the intensity of the strongest line or peak, and d (obs.), the interplanar spacing in A, cor-resp~nding t~ the rec~rded lines, were calculated. In Table 1 the relative intensities are given in terms of the symbols W=weak, M=medium, S=strong and VS=very str~ng. It should be understood that these X-ray diffraction patterns are charac-teristic of all the species ~f the above family of zeolites.
Ion exchange of the sodium ion with cations reveals substantially the ~ame pattern with some minor shifts in interplanar spacing ~d variation in relative intensity. Other minor variations can occur depending on the silicon to aluminum ratio of the particular ~ample, as well as if it has been sub~ected to thermal treatment.
Zeolite ZSM-5 for use in this invention can be ~O suitably prepared by prepa~ing a solution containing tetra-propylammonium hydroxide, sodium oxide, an oxide of aluminum, an oxide of silicon and water having a composition, in terms of mole r~tlos o~ oxides, falling within the ~oll~wing ranges:

.
.

_g_ ~0514~;3 _ Particularly Acceptable Preferred Preferred OH-/SiO2 0.7- 1.0 0.1-0.8 0.2-0.75 R4N+/ (R4N++Na) 0.2-0.95 0.3-0.9 0.4-0.9 sio2/A123 5 10- 60 10- 40 wherein R is propyl and maintaining the mixture until crystals of the zeolite are formed. It is noted that an excess of tetrapropylammonium hydroxide can be used which would raise the value of OH-/SiO2 above the ranges set forth above. The excess hydroxide, of course, does not participate in the reaction. Thereafter, the crystals are separated from the liquid and recovered. Typical reaction conditions conslst of heating the foregoing reaction mixture to a temperature of from about 100C to 175C for a period of time of from about six hours to 60 days. A more preferred temperature range is from about 150C to 175C with the amount of time ! at a temperature in such range being from about 12 hours to 8 days.
The digestion of the gel particles is carried out until crystals form. The solid product is separated from the reaction medium, as by cooling the whole to room temperature, ¦ - filtering, and water washing.
The foregoing product is dried, e.g. at 230F, for \ from about 8 to 24 hours. Of course, milder conditions may .
~I ~
. ~ .

- 105~4~;3 be employed if desired, e.g., room temperature under vacuum.
To prepare the preferred form of the ZSM-5 catalyst for use herein, the composition can be prepared utilizing materials which supply the appropriate oxide. Such composi-tions include sodium aluminate, alumina, sodium silicate, silica hydrosol, silicic gel, silicic acid, sodium hydr~xide and tetra-propylammonium compounds, e.g., tetrapropylammonium hydroxide.
It will be understood that each oxide component utilized in the reaction mixture for preparing a member of the ZSM-5 family can be supplied by one or more initial reactants and they can be mixed together in any order. For example, sodium oxide can be supplied by an aqueous solution of sodium hydroxide, or by an aqueous solution of sodium silicate; tetrapropylammonium cation can be 5upplled by the bromide salt. The hydrogen cation can be supplied by an aqueous solution of hydrogen chloride ~r ammonium salt, such as ammonium chloride or ammonium nitrate. The non-.
noble metal of Group VIII can be supplied by methods well known in the art, such as ion exchange, impregnation or vapor impregnation. me reaction mixture can be prepared either batchwise or continuously. Crystal sized and crystallization time of the ZSM-5 composition will vary with the nature Or the reaction mixture employed.
Zeolite ZSM~ll for use in this invention can be suitably prepared by preparing a solution containing (R4X)20, sodium oxide, an oxide of aluminum, an oxide of silicon and water and having a composition, in terms of mole ratios of oxides, falling within the following ranges:

105~63 - Broad Preferred SiO2/A1203 10 - 150 20 - go Na20/SiO2 0.05 - 0.7 0.05 - 0.4 (R4X)20/sio2 0.02 - 0.2 0.02 - 0.15 H20/Na20 50 - 800 100 - 600 wherein R4X is a cation of a quaternary comp~und of an element of Group V-A of the Periodic Table, maintaining the mixture until crystals of the zeolite are formed. Preferably, crystallization is performed under pressure in a n autocla~e or static bomb reactor. The temperature ranges from 100C. -200C. generally, but at lower temperatures e.g., about 100C., crystallization time is longer. m ereafter, the crystals are separated from the liquid and recovered.
The ZSM-ll composition can be prepared utilizing materials which supply the appropriate oxide. Such compositions lnclude sodium aluminate, sodium silicate, silica hydrosol, silica gel, silicic acid and sodium hydroxide. The quaternary compounds can be any elem~nt of Group V-A such as nitrogen, phosphorus, arsenic, antimony or bismuth. The compound is E~nerally expressed by the following formùla:

~; ( R - X _ ~ or R4X+

~- ~ 25 wherein X is an element of Group V-A of the Periodic Table and each R is an alkyl or aryl gr~up having between 1 and 7 .

~ -12-., , - ' , ., - ,. - : , , , , , .: .

~051463 carbon atoms. While normally each alkyl or aryl group will be the same, it is not necessary that each grou~ have the same number of carbon atoms in the chain. The oxide of the quaternary metal compound is generally supplied by introduc-ing into the reaction mixture a composition such as t~tra-methyl, tetraethyl, tetrapropyl or tetrabutyl metal hydroxide or chloride. In preparing an ammonium species, tetrabutyl ammonium chloride or hydroxide is especially useful. In pre-paring the phosphon~um species of the zeolite, tetrabutyl-phosphonium chloride is particularly desirable as a means of incorporating the quaternary metal compound in the zeolite.
The other metals o~ Group V-A behave similarly and thus zeolites containing the same can be prepared by the same manipulative procedure substituting the other Group V-A metal for phosphorus.
It ~hould be realized that the oxide can be supplied from more than one source. The reaction mixture can be prepared either batchwise or continuously. Crystal size and crystallization time of the new zeolite composition will vary with the nature of the reaction mixture employed and the crystallization con-ditions.
, . .. .... , .. _ _.. . . .
me ZSM~5 or ZSM~ll zeolite catalyst may be employed in combination with a support or binder material such as,for example, a porous inorganic oxide support or a clay binder. Non-limiting examples of such binder materials include alumina, zirconia, silica, magnesia, thoria, titania, boria and combinations thereof, generally in the form of dried inorganic oxide gels and gelatinous precipitates. Suitable clay materials include, by way of example, bentonite, and kieselguhr. The relative proportions of zeolite and binder may vary widely, with the ZSM-5 or ZSM-ll content ranging from about 30 to about 90 percent by weight, mor usually about 50 to about 80 percent, by weight of the composition.

105~63 By the present process, toluene concentrates of relatively low commercial value are converted to aromatic concentrates of high value, namely xylene which is essentially ethylbenzene free, and benzene.
A particulary noteworthy and advantageous feature of the present invention is the low hydrogen consumption of its process. It has prevously been standard operating practice in toluene disproportion-ation to empoy hydrogen-to-hydrocarbon ratios in the range o~ 5 to 10.
~he present process operates at hydrogen-to-hydrocarbon ratios below such range, values of 3 and 4 being perfectly adequate for excellent results; and, as can be seen from the Examples which follow, the use of hydrogen can be dispensed with entirely.

- . . . .. .
.. - .. - . .. . .. . .

~05~463 m e following specific examples will serve to il-lustrate the process of the present invention, without un-duly limiting same.

A reaction mixture was prepared by intimately mixing two solutions at room temperature in 1/2 inch normal pipe thread Venturi mixing nozzle. m e two solutions were desig-nated as Solution A and S~lution B. Solution A was prepared by stirring int~ 72.2 lbs. of water 1.44 lb. of A12(S04)3-X H20 (MW = 595) 15.80 lb. of NaCl : 3.52 lb. of H2S04 (97%) Solution B was prepared by stirring into 52.8 lbs. of water 42.2 lb. of Q-brand water glass (28.9 wt.
SiO2, 8.9 wt. ~ Na20, balance H20) m e resulting mixture was discharged into a 30 gallon baffled pressure autoclave. Then 2.84 lbs. of tri-normal-pr~pylamLne were charged to the autoclave followed by 5.64 lbs. of methyl-ethy~ ketone and 2.44 lbs. of n-propyl bromide. The latter i 20 three organic materials mix and form an organic layer over-lylng the aqueous gel formed by the mixing of Solutions A and B. The aut~clave was then closed and heated with stirring at .~ .
a-rotor speed of 76 rpm for approximately 13.7 hours until the temperature reached about 320F. The autoclave was then main-tained at this temperature, without stirring, for 13 hours, after which it was opened to the atmosphere to flash off resi-dual organic matter and then cooled to room temperature.

- .

, ~ .

The product wa~ ~ c~arged fram the autoclave, water washed to 0.01 weight percent residual chloride (based on samples dried at 1100F.) and dried at 250F. The product obtained was crystalline and identified by X-ray analysis as ZSM-5. Phot~micrographs indicated that the crystallites were agglomerated and that the individual crystallites were 0.5 x 1 - micron thin platelets.
The crystalline product was then combined with alumina as follows: Highly pure A1203 was hydrated for 16 hours at 200F. producing a hydrate containing 53 percent water. This product was mixed with ZSM-5 crystallites to,, glve a paste containing about 39 percent water and extruded into a hydraulic extruder to produce 1/16" extrudate. The extrudate was dried,and calcined in air at 750F. for 3 hours.
m e calcined extrudate was ion exchanged by treatment four tlmes for 1 hour each at room temperature with 5 cc ~f 5 percent aqueous ammonium chloride per gram of ZSM-5. The extrudate was then washed with water at room temperature, after which it was exchanged by treatment for 4 hours at ~0 190F. with 5 cc of one normal aqueous nickel nitrate per gram of ZSM-5. The extrudate was then water washed free of nickel ions and then heated at 250F. and finally calcined in ' air at 1000F. for 3 hours. The resulting catalyst composition contained 65 weight percent ion-exchanged ZSM-5, 35 weight percent alumina and 0.49 weight percent nickel.

The extrudate catalyst composition of Example 1 was crushed t~ 28 x 60 - mesh particles and 1.7 grams (2.8 cc) -1~ ' 1~)51~3 thereof was diluted with 7.2 cc of 28 x 48 - mesh tubular alumina.
m e resulting catalyst composition was then heated at 900F. under a pressure of 400 psig with 162 cc/minute of hydrogen passèd there~hrough for one hour.

~OSi~63 An extrudate catalyst compositon was prepared as in Example 1 except that it was not ammonium chloride exchanged. m e extrudate was prepared and treated essentially as outlined in Example 2 and was placed in a closed, pressure reaction vessel as a fixed bed thereln. A charge of toluene was continuously fed to the reaction vessel (after being perked through silica gel) at a rate which maintained the WHSV at 1.4. m e reaction pressure was maintained at 600 psig and hydrogen was suppled to the reaction vessel to malntain a hydrogen to hydrocarbon mole ratio of 4:1. me initial temperature of the experiment was 747F. and the inttial material balance was 96.8. Examples 3 to 5 were established by periodically measuring reaction temperature (changed for Examples 4 and 5), reactlon material balance and analyzing reaction products. A summary of these experl~.ents appears ln Iable 4 below:

.

'~ -18-.' `

l~Si4~3 Example No. 3 4 Material Balance 96.8 97.8 100.4 Temperature, F 747 773 800 Time on Stream~ hours 3.1 - -Product Distribution, weight percent Methane 0.1 - o. 0 Ethane 0.9 `0.2 o ., ~Propane 2.7 0.7 1.1 Isobutane 0.5 0.1 0.1 n-Butane o.6 o. l o. l C4 Olefins 0.03 Isopentane 0.2 0.01 n-Pentane 0. o4 3-Methylpentane Trace n-Hexane Trace Methyl-cyclohexane Trace Benzene 11. 6 13.0 17.7 c7 Paraffins ~.1 0. o4 Toluene 65. 8 68. o 56.6 ~ C8 Paraffins0.05 p- and m-xylenes12.0 12.6 16.0 o-xylene 3.3 3-4 5.2 Cg Aromatics 1.7 1.6 2.8 Clo~ Aromatics o.5 0.2 . . Toluene Reacted, weight percent 34.2 32.0 43.4 10514~3 An extrudate catalyst composition was prepared as in Example 1 e~cept that it was not nickel nitrate exchanged. The extrudate was prepared and treated essentially as in Example 2 and was placed in a closed, pressure reaction vessel as a flxed bed therein.
A charge of toluene was continuously fed to the reaction vessel (after being perked throuh silica gel) at a rate which maintained the WHSV at 1.4. m e reactlon pressure was maintained at 610 psig for Examples

6-8 and at 605 psig for Example 9. No hydrogen was supplied to the reaction vessel. m e initial temperature of the experiment was 700F.
and the initial material balance was 95.8. Examples 6 to 9 were establlshed by perlodically measuring reaction temperature (changed for Examples 7-9), reaction material balance and analyzing reaction proiuots. A summary of these experiments ~ppears in lable 5 below.

'', ' `:

1051~63 a~ ~ ~ ~ ~ ~i ~i ~1 ~

m ~ O ~ m U~ ~ , . . .

~I N m N G ~ m o ,~
,i m "

i o o o U~ m ~

~4 b ~ ~.1 h E~ E P.~ ~ E V P, O ~ C~ E~ 3 ~, ,- ~.

lOS14~i3 The catalyst composition employed according to the invention exhibits markedly improved aging properites. Instead of cycle periods of a few hours or days as has been the practice of the prior art, a cycle of weeks or months is possible. Furthermore it is easily and effectively regenerated utilizing adiabatic burning in the presence o~ an inert dry gas as an oxygen diluent. A suitable regeneration technique using an inert dry gas as an oxygen diluent may be according to the following schedule:

Mass Velocity, Reactor Inlet lb/hr-ft2 TimeTemperature7 F Air 1.5 675 11 4.0 800 11 ` 22.0 850 11 25.0 900 11 25.5 95 11 26.5 1000 11 ` 27.5 1000 28.0 End of regeneration Also, the catalyst composition employed in the ` process of this invention will withstand numerous regenera-tions without losing activity. Thus, it is contemplated that a catalyst life in commercial use may be several years.
, -, ,

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for effecting vapor-phase disporpor-tionation of toluene comprising contacting toluene at a temperature between 650° F. and 1000°F., a hydrogen to hydrocarbon mole ratio of between 0 and 5, a pressure between atmospheric and 1000 psig, and a weight hourly space velocity between about 1 and 20, with a catalyst comprising a crystalline aluminosilicate zeolite of the ZSM-5 family which zeolite is at least partly in the hydrogen form.

2. A process according to Claim 1 wherein said crystalline aluminosilicate has undergone base exchange with a non-noble metal of Group VIII of the Periodic Table.

3. A process according to claim 2 wherein the catalyst comprises said metal in non-cationic form.

4. A process according to claim 2 or claim 3 wherein said metal is nickel.

5. A process according to claim 1, 2 or 3, wherein said zeolite is ZSM-5 characterized by a SiO2:Al2O3 ratio between 5 and 100.

6. A process according to claim 1, 2 or 3, wherein the temperature is between 750°F. and 900°F. and the pressure is between about 400 and 800 psig.

7. A process according to claim 1, wherein said catalyst composition comprises between 30 and 90 weight percent zeolite, the balance a binder therefor.

8. A process according to claim 7 wherein said binder is alumina.

9. A process according to claim 8 wherein alumina binder constitutes about 35 weight percent of the catalyst composition.

10. A process according to claim 1, 2 or 3 wherein the zeolite is substantially completely in the hydrogen form.