CA1037014A - Preparation of hydrocarbon conversion catalysts - Google Patents

Abstract

PREPARATION OF HYDROCARBON CONVERSION CATALYSTS
Abstract of the Disclosure Zeolite containing catalyst compositions are prepared by partially crystallizing a zeolite precursor reaction mixture which contains zeolite seed particles capable of initiating the rapid crystallization of zeolite to form a zeolite suspended in an excess of aqueous alkali metal silicate solution. The crystallization reaction is terminated after the desired quantity of zeolite has been formed, and the excess silicate is gelled to form an amorphous hydrogel matrix therefor.
Preferably the process is conducted on a continuous basis.
The zeolites are useful as hydrocarbon conversion catalysts.

Description

37~4 The present invention relates to the preparation of hydrocarbon conversion catalysts, and more speciically to an improved method for preparing zeolite containing catalysts wherein crystalline aluminosilicate zeolite is dispersed in an inorganic oxide matrix.
For many years zeolite containing hydrocarbon conver-sion catalysts have been prepared by admixing an essentially fully crystalline aluminosilicate such as faujasite with amorphous inorganic oxides such as silica, silica-alumina, and alumina hydrogels. Typical prior art processes involve irst forming a batch of crystalline alumino silicate zeolite hy the hydrothermal reaction of silica, alumina, sodium hydroxide and water. Sub-sequent to obtaining the crystalline zeolite batch, the zeolite is recovered from its reaction medium (mother liquor) and com- -~bined with an amorphous gel component such as silica-alumina or silica-alumina hydrogel. The gelled zeolite-amorphous hydrogel composite is then washed to remove excess alkali metal salts, ion exchanged with polyvalent metal ions, and dried.
It has been found that the batchwise preparation of zeolite followed by incorporation in an amorphous gel matrix ::. . .. .
is a relatively expensive procedure from the standpoint of materials in that the excess sodium silicate solu~ion which results from the batchwise preparation of zeolite is normally ~
discarded. Furthermore, it is found that batch preparation of ~ -zeolite on a commercial scale, wherein literally tons of :
zeolite are formed, frequently leads to the preparation of ~
: .
~ products of varying quality.
;. : , Attempts to prepare zeolite catalysts on a commercial - -scale using essentially continuous processes have not been ~ practlcal, primarily due to the fact preparation of fully crystalline zeolite requires reaction periods substantially longer than the subsequent catalyst forming operation.

: ,: ~' ~03~0~4 It is therefore an object of the present in~ention to provide an improved method for prepariny zeolite containiny catalysts.
It is another object to provide a method by which con-ventional quantities of zeolite containing catalysts may be prepared on an essentially continuous basis.
It is a further object to provide a zeolite hydro-carbon conversion catalyst preparation method by which sub-stantially full utilization of raw materials may be effectively obtained.
These and still further objects o~ the present invention will become readily apparent to one skilled in the art from the following detailed description and specific examples.
Broadly, our invention comprises a procedure wherein a crystalline aluminosilicate zeolite procursor reaction mixture containing zeolite seed particles, i.e., nucleation centers, which are effective for initiating the rapid crystallization of zeolite, is reacted to form partially crystalline zeolite product, and subsequently the partially crystalline reaction mixture is diluted with water, and combined with gel forming components such as mineral acid, carbon dioxide and/or acid aluminum salts.
More specifically, we have found that commercial quantities of crystalline zeolite containing catalysts may be quickly and economically prepared by the following procedures : :
outlined belo~: -1. A zeolite precursor reaction mixture which contains alumina, silica, sodium hydroxide and water is admixed with amorphous si1ica-alumina seed particles, i.e., nucleation ; centers, which possess a particle size of below about 0.1 micron.

2. The precursor reaction mixture is reacted at a temperature of from about 90C. to reflux to obtain about

- 3 -::', ~

103~
15 to 100% crystallization of zeolite which is theoretically obtainable from the reactants present.
3. The partially crystallized zeolite reaction mixture is then diluted with sufficient water to dilute the excess sodium silicate present to a level of about 7 to 3~ by weight SiO2 basis. This Pilution also serves to quench the crystal-lization reaction by lowering the reaction ternperature to below about 50C.

4. The diluted reaction mixture is then admixed with an acidic component such as mineral acids, (H2SO4HCl or NHO3), carbon dioxide and/or acid aluminum salts such as alum to gel the sodium silicate and thereby form an amorphous hydrogel matrix. At this pOiIIt additional aluminum containing compounds such as sodium aluminate or other catalyst components such as clay may be added to the reaction mixture to impart the desired concentration of amorphous alumina and/or clay to the catalyst composition.

5. The gelled composition is then formed into desired particles such as by spray drying, washed to remove soluble salts such as sodium or sul~ate ion, and dried to remove excess ;
moistu~e. Optionally, the composition may b~ ion exchanged with~ -stabilizing and/or catalytic promotor metal ions to enhance the stability and/or catalytic properties of the catalyst composition.
In a particularly preferred embodiment of the present , inven*ion the above outlined process is conducted on a con- ~-tinuous basis. Thus, for example, the zeolite crystallization .,,~
process which requires only a few minutes due to the presence -~
.~ - ., ~.
of highly active crystallization initiation seed particles, may be continuously performed in an elongated pipe type reactor. ~ -The reactor is maintained at a temperature of from about 95 to -., .
110C. at which crystallization of the faujasite rapidly takes '' "' ' ' ' ,.

~3~14 place. At the point in the reactor wherein khe desired deyree of crystallization has occurred, normally from about 15 to 100%
crystallization of theory, cold water is admitted to the reactor to lower the temperature of the reaction mixture to temperature of from about ~0 to 50C. This quenching water is added in amounts to achieve dilution of the excess silicate present in the faujasite reaction mixture to a level of from about 7 to 3% based on the weight of silicate present. I'he diluted zeolite reaction mixture is then admitted to a second elonyated reactor to which an acidic yelling component is continuously added. The gel reaction mass is then washed to remove excess alkali metal and other soluble salts, spray dried, ion exchanged and finally dried using conventional spray drying or other catalyst forming procedures.
~s indicated above, the zeolite precursor reaction mixture contains silica, alumina, water and alkali metal hydroxide. -~
In general the composition of the precursor reaction mixture '-~
will depend upon the precise type zeolite which is to be pro~
duced. For example, when it is desired to produce type X or Y
zeolite having a silica alumina ratio on the order of 2.5 to 6 the following ratios of ingredients may he utilized:
Ingredient Moles SiO2 2.5 to 16 ~
A123 1 to 1 -H2O 80 to 170 Na2O 3.0 7 On the other hand, when it is desired -to prepare type ~: zeolite, the following reaction ratio~s may be utilized: -'' ''',' '. ' '' ~7(~4 Ingredient Moles SiO2 1.5 to 2 A123 1 to 1 H2O 60 to 120 Na2O1.0 to 1.8 The silicate may be derived from any convenient source such as sodium silicate or particulate colloidal silicaS
which are readily available for many commercial sources. The alumina component is provided from any convenient source such as sodi um aluminate or other soluble aluminum salt such as aluminum sulfate, Al(NO3)3, AlC13.
The precursor reaction mixtures described in the above are combined with zeolite seed particles or nucleation centers which are capable of initiating the rapid crystalli~
zation of the crystalline aluminosilicate zeolite. Preferably -~
these seeds, i.e., nucleation centers, are silica-alumina ;
particles which are amorphous and which possess a particle size of below about 0.1 micron and a SiO2 to A12O3 ratio of 5 to 1. ~-~
The zeolite seeds are prepared in the form of an aqueous slurry by reacting the following ratio of ingredients:
Ingredient Moles ;
SiO2/A12O3 14 to 16 , :.,:-Na2O/~12O3 15 to 17 H2O/Na2O 19 to 21 The seed preparation mixture is reacted at a temperature , , of from about 15 to 20C. and allowed to stand 16-24 hours at room temperature. The resultant slurry which remains stable ~ ~-for a period o~ many weeks is then utilized to initiate the crystallization of zeolite from the precursor reaction mixture.
It is generally found that the seed slurry described ~ --above is added to the precursor reaction mixture in amounts ranging from about 5 to 20 parts by weight of the seed slurry

- 6 -~. '', 1037~4 per part by weight o~ the A12O3 present in the zeolite pre-cursor mixture. To prepare the partially crystalline zeolite product, the combined seed slurry and precursor reaction mixture is reacted for a period of from about 15 to 180 minutes at a temperature of about 90 to 110C. whereat a partially crystalline product was formed which contains from about 10 to 100% crystalline zeolite which is theoretically obtainable from the reaction mixture if the reaction were permitted to run to completion. As indicated above, water is then added to the reaction mixture to terminate the crystallization procedure and to further dilute the excess alkali metal silicate present. Generally sufficient water is added to lower the temperature at least to 50C and to dilute the silicate to a level wherein the aqueous solution of silicate contains from about 7 to 3~ sodium silicate.
The reaction slurry, after the partial crystallization has taken place, is then combined with an acid gelling agent.
These gelling agents may be selected from the group consisting of mineral acids such as sulfuric acid, hydrochloric acid -or nitric acid. Gelling agents such as carbon dioxide may also ~-be effectively used to gel the excess silicate. Furthermore, it is contemplated that acid aluminum salts such as alum may be utilized. Furthermore, it is sometimes found that a combination .
of gelling agents including acid and alum may be effectively used.
Furthermore, it is contemplated that additional catalyst ingred~ients, such as clay, may be effectively added to the gelled compositions in amounts ranging from about 25 to 50 by weight of the finished catalyst composition.
The gelation step is preferably conducted on a continuous basls and in connection with a c~ntinuous crystallization procedure such as outlined above. Furthermore, it is con- ~ -tem]~l~ed that the gelation p~ocedure may be conducted on a

- 7 -`., ~0370~L~
batchwise basis, however, the primary benefit obtained in the present invention results when a continuous overall catalyst preparation procedure is conducted.
Subsequent to gelation of the catalyst composition, the solid catalyst is recovered from the mother liquor and washed to remove soluble salts. Furthermore, the catalyst is ion exchanged with dilute ammonium salts such as dilute ammonium sulfate to further reduce the sodium level of the catalyst. The catalyst is then slurried and formed into catalyst particles of a desired configuration. In a particularly pre~
ferred practice o~ the invention, the catalyst slurry is spray dried to form microspheres having a particle size ranging from about 50 to 300 microns. Alternatively, the catalyst may be pilled or formed into granules having particle sizes on the order -of 1/8 to 1/4 inches in diameterO Subsequent to spray drying the catalyst may be further ammonium exchanged to remove addition-al alkali metal salts to a level below about .6~ Na20. The -catalyst may be ion exchanged with polyvalent metal ions such as rare earth ions to further enhance the stability of the catalytic 2~ properties of the catalyst composition.
The catalysts prepared in accordance with the present invention will generally contain from about 15 to 35~ by weight zeolite calculated on total weight basis. Furthermor~, the ;
catalyst may contain a matrix which is essentially synthetic or the matri~ may contain substantial quantities of clay such : as kaolin. The catalysts prepared in accordance with the present invention wherein faujasite is used as the zeolite and rare earth metal ions are exchanged therein are particularly effective for the catalytic cracking of h~idrocarbons. These 3Q catalysts possess both good catalytic activity and good attrition properties ~hen utilized in commercial cracking units. -Having described the basic aspects of the present ~ -' , '' :,.

3 :037~14 invention, the following examples are given to illustrate specific embodiments thereof.
Example I
. . .
A series of catalyst samples was prepared usiny the teachings of our invention.
(a) Three samples of faujasite precursor reaction mixture as follows:
To 284 y of sodium aluminate solution containing 0.333 mole of A12O3 and 0.466 mole of Na2O, were added slowly with stirring to 1422 g of sodium silicate solution ha~ing a density of 1.360 g/cc and 954 g of water.
(b) A zeolite seed preparation was prepared as follows:
158 g o~ NaOH were added 558 g of H2O. This solution was heated to 80~C. at which point 26 g of C-31 A12O3 (65%
A1203) was added slowly and stirred until completely dissolved.
The solution was cooled to 15 C. and maintained at this temper-ature while 555 g o~ sodium silicate solution (27~ SiO2, 8 N2O) was slowly added. The resulting seed solution was allowed to sit for 16 hours prior to use.
(c) 248 g samples of the seed preparation were added to each o~ the above reaction mixture samples. The mixtures ~;
were heated at reflux (110C) for 1.5 hours.
(d) The heating was stopped and each sample was ~;; diluted with 4840 g of water having a temperatuxe of 40C. This addition of water resulted in dilution of the sodium silicate solution~in the reaction mixture to a level of 5.5% silica.
e) The mixtures were cooled to 80F and gelled with ;8% aluminum sulfate solution until the pH of the gelled mix~ures ~ reached~9.0 tSamPle 1), 10.0 (Sample 2)/ and 10.7 (Sample 3), ~ respectively. The samples were then aged for 1/2 hour. Additional aluminum sulfate (5~ solution) (50-100 g) was added to give a ~ 9 ~

' : : ; :' ' ' .' ,, ,: .~ -~037~1~
total silica to alumina ratio of 3:1.
(f) The samples were washed with 1~ 1H4)2S04 and rare earth exchanged with a rare earth C13 to yield catalyst samples having the following characteristics: , ~ ' Table' I

wt. % wt. % rare Surface Area Sample No. Zeolite ear'th oxide m2/a . _ 31 7.7 174 ' , 2 27 6.~ 158 3 35 8.0 200 The zeolite was a type Y zeolite having a SiO2/A12O3 ' ~ ' of 5/1.The zeolite content in the above samples was determined ~, , by x-ray dif~raction. ' Examp'le' II
A larger catalyst sample was prepared as follows: ;~ ' To 9.94 pounds of a sodium aluminate solution, which , ', , contained Q.333 mole of A12O3 and 0.466 mole of Na2O, 33.6 ~ ~
pounds o~ H2O and 58.3 pounds of sodium silicate solution - ,~, which contained 27% by wt. SiO2 and 8.2~6 by wt. Na20, were added. To this mixture 8.68 pounds of the zeolite seed pre- `, paration, prepared by the procedure of Example I (b), were added. The mixture was heated at reflux (110C) for 1.5 hours. ' ,' The heating was stopped and 175 pounds of H2O were added to dilute the reaction mixture~ The concentration of `~' ' ' excess silicate in the reaction mother liquid was 5.5 wto % SiO2. '' The mixture was cooled to 80F and gelled by the addition of ,, . - .
70 pounds of 5% aluminum sulfate solution. The pH of the mixture , ; was 10.7. The mixture was aged for 1/2 hour at a temperature of ~ -~ 80F.
After aging, an additional 2 pounds of A12(SO~)3 ', ; solution were added to yield a total SiO2/A12O3 ratio of 3/1. ,~ ' ' ' The product was washed with 10% (MH4)2SO4 and rare ' ' : .::: .
,-: :, - 10 - ' ' .':; '.
:
. ' . ..' :' .

l037a~

earth exchanged with rare earth C13. The product was spra~
dried to yield a catalyst haviny the following properties: , T ble'II

~ Zeolite* Rare earth Surface Area Sample No. ' (wt'.)' oxide (wt.) (m2/g) ____ 4 32 4.0 413 *wt. % type Y zeolite calculated o,n basis of SiO2 and A12O3 content.
''E'xamp'le'III
The catalyst samples prepared in Examples I and II
were evaluatad for activity and selectively as catalytic cracking catalysts in a pilot unit operated at 920F, a catalyst to oil ratio of 4, and a we-ight hourly space velocity (WHSV) of 40 and 60. The feed stock was a West Texas Devonian gas oil having a boiling range of 653 to 931F. ,,~, Prior to testing, all catalyst samples wer~ deactivated by steaming at 1520F using 20~ steam, at atmospheric pressure ~or 12 hours. The results are set forth in Table III~
' T'able''I'II_ ' 20Sample No. ''%''Coke ~ Converstion ~ ~-1 5.3 88 2 3.9 82.6 3 ~.0 94 - ~ ', -4 ~ 2.78 84.6 ~ .
~ ~ ~ For purposes of comparison a sample of commercial ;~ ~ catalyst (CBZ-I) which contained rare earth exchanged type Y
,, zeolite was evaluated and compared with Sample 4 as set forth n~Table I~

, : : : .~ : : -~ 3a ~ "" ,' :: : ;. : .

;,,, ' . '':' , ' ~ ' ' - ': ,' ~ID37~
T:able IV
Sample No. 4 4 CBZ-l Conversion, Vol. % 83.0 82.0 72 H2, wt. % .043 .052 .037 Cl ~ C2, wt. % 2.07 2.21 2.2 Total C3, vol- % 12.7 10.7 10.1 C3=, vol. gO 11.4 9.5 8.3 Total C4, vol. % 16.4 15.7 11.2 C4=, vol. % 5.7 5.7 3.3 iC4, vol. % 9.5 9.1 6.8 C5 + Gasoline, vol. % 69.5 66.1 52.4 Coke, wt. % 4.9 5.9 5-7 " . . , - ", . ,-Gasoline/Conv. 0.83 0.81 0.80 gO Zeolite Promoter 32 32 16 : .
% Rare earth oxide 7.20 7.20 3.37 :

`; ' ' . .
::~ -, . . .

., .:
.: . ~ ,., .": , '', '.', . ", ', ',' '' '' `i' "' . ' :: , .. ~ . , :

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

~ ,,. : -: , ~

Claims (10)

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

1. A process for preparing crystalline aluminosilicate containing catalysts which comprise:
a) forming a zeolite precursor reaction mixture containing silica, alumina, sodium hydroxide and water and crystallization initiating amorphous silica-alumina nucleation centers having a particle size below about 0.1 micron;
b) heating said reaction mixture to a temperature of from about 90 to 110°C. for a period sufficient to produce about 15 to 100% crystalline zeolite theoretically available to said reaction mixture;
c) diluting said reaction mixture with sufficient water to yield a sodium silicate solution concentration of from about 3 to 7% by weight SiO2 in said reaction mixture and to lower the temperature of said reaction mixture to at least 50°C.;
d) gelling said reaction mixture with an acid gelling mixture to produce an amorphous hydrogel composite having crystalline zeolite dispersed therein; and e) washing and drying said composite to produce a particulate catalyst.

2. The process of claim 1 wherein the process is con-ducted on a continuous basis.

3. The process of claim 1 wherein the said crystalline zeolite is type X or Y zeolite having a silica to alumina ratio on the order of from about 2.5 to 6.

4. The method of claim 1 wherein said zeolite is type A zeolite.

5. The process of claim 1 wherein said gelling agent is selected from the group consisting of mineral acids, CO2, aluminum salts and mixtures thereof.

6. The method of claim 1 wherein said heating step is conducted for a period of from about 15 to 120 minutes under substantially plug flow reaction conditions.

7. The method of claim 1 wherein said composite is ammonium exchanged to lower the Na2O content thereof to below about 1% by weight.

8. The method of claim 7 wherein said ammonium exchanged product is exchanged with rare earth ions.

9. The method of claim 1 wherein said composite is spray dried to produce a microspheroidal product having a particle size on the order of 50 to 300 microns.

10. The method of claim 1 wherein said partially crystalline zeolite reaction mixture is admixed with from about 10 to 30% by weight clay.