Description:FIELD OF THE INVENTION

The present invention discloses a process for preparation of a mesoporous nanosized beta zeolite which reduces mass transfer diffusion limitation by enhancing mesoporous surface area and reducing particle size of beta zeolite. More specifically, the present invention discloses a process for preparation of a mesoporous nano sized beta zeolite using a triple template approach having tetraethylammonium hydroxide, tetraethylammonium bromide and cetyltrimethylammonium bromide. Further, the present invention discloses preparation of catalytic cracking catalyst microspheres by using the mesoporous nano-sized beta zeolite.

BACKGROUND OF THE INVENTION

Beta zeolite is used as active cracking catalyst for hydrocarbon feedstocks such as vacuum gas oil, light cycle oil, diesel and kerosene. Beta zeolite consists of micropores typically smaller than 1 nm, which limits the diffusion of compounds within these pores and the size of molecules that can be catalyzed, for which the mass-transfer problem cannot be ignored when bulky molecules are involved in the reactions catalyzed by microporous beta zeolite. This diffusion limitation results in low hydrocarbon conversion and more coke formation. Some of the prior art documents are given below:

US20200156052 discloses a method for synthesizing a nano-sized mesoporous zeolite composition, the method comprising: mixing silica, a source of aluminum, and tetraethylammonium hydroxide to form an aluminosilicate fluid gel; drying the aluminosilicate fluid gel to form a dried gel mixture; subjecting the dried gel mixture to hydrothermal treatment to produce a zeolite precursor; adding cetyltrimethylammonium bromide (CTAB) to the zeolite precursor to form a templated mixture; subjecting the templated mixture to hydrothermal treatment to prepare a CTAB-templated zeolite; washing the CTAB-templated zeolite with distilled water; separating the CTAB-templated zeolite by centrifugation; and drying and calcining the CTAB-templated zeolites to produce a nano-sized mesoporous zeolite composition.
US20210001313 discloses a method for hydrocracking a hydrocarbon feedstock, the method comprising: contacting the hydrocarbon feedstock with a catalyst containing a nano-sized mesoporous zeolite composition under reaction conditions to produce a product stream containing at least 20 weight percent of hydrocarbons with one to four carbon atoms, wherein the nano-sized mesoporous zeolite composition is produced by a method including the steps of: mixing silica, a source of aluminum, and tetraethylammonium hydroxide to form an aluminosilicate fluid gel; drying the aluminosilicate fluid gel to form a dried gel mixture; subjecting the dried gel mixture to hydrothermal treatment to produce a zeolite precursor; adding cetyltrimethylammonium bromide (CTAB) to the zeolite precursor to form a templated mixture; subjecting the templated mixture to hydrothermal treatment to prepare a CTAB-templated zeolite; washing the CTAB-templated zeolite with distilled water; separating the CTAB-templated zeolite by centrifugation; and drying and calcining the CTAB-templated zeolites to produce a nano-sized mesoporous zeolite composition.
US10773248B2 discloses a process for upgrading heavy oil, the process comprising: reducing aromatics content in the heavy oil by contacting the heavy oil with a hydrocracking catalyst comprising one or more nano-sized, mesoporous zeolite particles each comprising: a microporous framework comprising a plurality of micropores having diameters of less than or equal to 2 nm and a BEA framework type; and a plurality of mesopores having diameters of greater than 2 nm and less than or equal to 50 nm; wherein the nano-sized, mesoporous zeolite particles have a particle size of less than or equal to 100 nm.
US20200368732 discloses a method for synthesizing nano-sized, mesoporous zeolite particles, the method comprising: combining a first mixture with one or more of a base or cetrimonium bromide to form a second mixture, wherein the first mixture comprises one or more nano-sized zeolite particles having a particle size of less than or equal to 100 nm; and heating the second mixture to an elevated temperature for a heating time period to form mesopores in the nano-sized zeolite particles.
CN111017954 relates to a preparation method of an open type macroporous Beta molecular sieve, belonging to the field of molecular sieve catalyst preparation; the method comprises the following steps: a) uniformly mixing deionized water, an aluminum source, an alkali source, a template agent, a filling agent, a silicon source and seed crystals, and then transferring the mixture to a crystallization kettle for crystallization; b) the crystallization conditions are as follows: crystallizing at 140-180 ? for 6-72 hours; the heating rate is not lower than 2 ?/min and not higher than 10 ?/min; c) when the pressure in the kettle rises to 0.2-0.4 MPa, the pressure is released and the amine and the water vapor are recovered; maintaining the pressure in the kettle at 0.2-0.4 MPa in the crystallization process; d) after crystallization is finished, the product slurry is rapidly cooled; and separating, washing, drying and roasting the crystallized product to obtain the open type macroporous Beta molecular sieve.
CN102211779 discloses a method for preparing beta zeolite. The method is low in cost and high in efficiency. The method specifically comprises the following steps of: adding a sodium source, an aluminum source, a template agent, and an organic accelerator and/or inorganic accelerator into water, stirring uniformly and mixing the mixture and a silicon source, and violently stirring until the system materials form a uniformly dispersed mixture; and crystallizing the reaction mixture and filtering a crystallization product, washing and drying to obtain the beta zeolite with relatively high crystallinity.
US20200325029 discloses a process for preparing a molecular sieve having mesopores, wherein said process comprises the following steps: mother liquor preparation step, wherein a mixture containing an alumina source, a silica source, a template agent, an optional alkali metal oxide source, optionally a third oxide (ZxOy, wherein Z is at least one selected from Mg, Ca, Zn, Ti, Fe, Ga, Ge, B, P, and rare-earth metals) source and water is crystallized under a crystallization condition to produce a crystallized mother liquor; said mother liquor preparation step preferably comprises a step of thermally activating a mixture of an alumina source, a template agent and an optional alkali metal oxide source and a step of crystallizing the thermally activated mixture together with a silica source, and optionally a third oxide source; said thermal activation is carried out at 50-160 °C., preferably 60-150 °C., more preferably 90-140 °C., further preferably 95-130 °C. for 2-24 hours, preferably 4-22 hours, more preferably 6-20 hours, further preferably 8-18 hours; and said crystallization is carried out at 120-180 °C., preferably 130-170 °C., more preferably 140-160 °C., further preferably 145-155 °C. for 24-150 hours, preferably 30-130 hours, more preferably 35-120 hours, further preferably 40-100 hours, further preferably 50-80 hours; filtration step, wherein the crystallized mother liquor is filtered to produce a filter cake having a dry basis content of 5 wt %-30 wt %, preferably 6 wt %-15 wt %; precursor preparation step, wherein said filter cake is directly calcined to produce a molecular sieve precursor; said calcination condition comprises: the calcination temperature is 400-600° C., preferably 450-550° C.; the heating rate upon calcination is 5 °C./minute-100 °C./minute, preferably 10° C./minute-50° C./minute, more preferably 20° C./minute-40 °C./minute, further more preferably 30° C./minute-40 °C./minute; the calcination time is 1 hour-20 hours, preferably 2 hours-16 hours, more preferably 5 hours-15 hours, further more preferably 6 hours-12 hours; hydrothermal treatment step, wherein said molecular sieve precursor is subjected to the hydrothermal treatment in an acidic aqueous solution having an inorganic acid and/or organic acid content of 0.01M-5M, preferably 0.05M-2M, more preferably 0.2M-1.5M, further preferably 0.5-1.2M, further more preferably 0.8-1.1M, in a liquid-solid volume ratio of 5-200, preferably 20-100, more preferably 40-80, further preferably 50-70, at 80 °C.-300 °C., preferably 100 °C.-200 °C., more preferably 120 °C.-180 °C., further preferably 140 °C.-160 °C., for 0.1 hour-24 hours, preferably 0.5 hour-18 hours, more preferably 1 hour-12 hours, more preferably 2 hours-10 hours; and finished product preparation step, wherein the hydrothermally treated product is filtered, optionally washed and dried, and further calcined, the calcination is preferably carried out at 400 °C.-600 °C. for 2-8 hours.
Still, there was a need to develop beta zeolite without said diffusion limitation, which results in high hydrocarbon conversion and less coke formation.

In the present invention, a mesoporous nano sized beta zeolite is developed which reduces mass transfer diffusion limitation by enhancing mesoporous surface area and reducing particle size of beta zeolite.

OBJECTIVES OF THE INVENTION
The main objective of the present invention is to develop a mesoporous nano sized beta zeolite.

Another objective of the present invention is to develop a mesoporous nano sized beta zeolite which reduces mass transfer diffusion limitation by enhancing mesoporous surface area and reducing particle size of beta zeolite.

Another objective of the present invention is to develop a mesoporous nano sized beta zeolite using a triple template approach.

Another objective of the present invention is to develop a mesoporous nano sized beta zeolite using tetraethylammonium hydroxide, tetraethylammonium bromide and cetyltrimethylammonium bromide.

One another objective of the present invention is to prepare catalytic cracking catalyst microspheres by using the mesoporous nano-sized beta zeolite.

SUMMARY OF THE INVENTION
The present invention discloses a process for preparation of mesoporous nano-sized beta zeolite, comprising: preparing an aluminosilicate gel by mixing an alumina source, a silica source, sodium hydroxide, water, tetraethyl ammonium hydroxide (TEAOH), tetraethyl ammonium bromide (TEABr) and cetyltrimethylammonium bromide (CTAB); ageing the aluminosilicate gel at a temperature in the range of 20-50 ? for 5-15 hours followed by hydrothermal crystallization of the aluminosilicate gel at a temperature in the range of 130-150 ? for 15-25 hours to obtain a crystallized beta zeolite; filtering and washing the crystallized beta zeolite to obtain wet crystallized beta zeolite; and drying the wet crystallized beta zeolite at a temperature in the range of 100-120 ? for 7-9 hours followed by ammonia exchange with ammonium sulphate solution to obtain ammonia exchanged beta zeolite; calcining the ammonia exchanged beta zeolite at a temperature in the range of 500-550 °C for 2-4 hours to obtain the mesoporous nano-sized beta zeolite.
In an embodiment of the present invention, the alumina source is sodium aluminate or aluminium sulphate, and the silica source is colloidal silica or fumed silica.
In an embodiment of the present invention, molar ratio of SiO2/Al2O3 in the aluminosilicate gel is in a range of 20-40; molar ratio of TEAOH/SiO2 in the aluminosilicate gel is in the range of 0.01-0.1; molar ratio of CTAB/SiO2 in the aluminosilicate gel is in the range of 0.01-0.1; and molar ratio of TEABr/SiO2 in the aluminosilicate gel is in the range of 0.01-0.1.
In an embodiment of the present invention, molar ratio of CTAB:TEAOH:TEABr in the aluminosilicate gel is in the range of 0.2:1:0.2 to 0.8:1:0.8.
In an embodiment of the present invention, particle size of the mesoporous nano-sized beta zeolite is in the range of 5-40 nm.
In an embodiment of the present invention, mesopore surface area of the mesoporous nano-sized beta zeolite is in the range of 250-400 m2/g.
In an embodiment of the present invention, pore volume of the mesoporous nano-sized beta zeolite is in the range of 0.5-0.6 cc/g.
In an embodiment of the present invention, yield of the aluminosilicate gel in the mesoporous nano-sized beta zeolite is in a range of 90-95%.
In an embodiment of the present invention, the mesoporous nano-sized beta zeolite is used in preparation of catalytic cracking catalyst microspheres.
The present invention also discloses a process for preparation of catalytic cracking catalyst microspheres, comprising: preparing a catalyst slurry by mixing 15-25 wt% mesoporous nano-sized beta zeolite, 5-15 wt% ZSM-5 zeolite, 25-35 wt% Kaolin clay, 15-25 % ammonium polysilicate, 15-25% pseudo boehmite alumina, formic acid and water; spray drying the catalyst slurry to obtain the catalytic cracking catalyst microspheres.

DETAILED DESCRIPTION OF THE INVENTION
In the present invention, a mesoporous nano sized beta zeolite is developed which reduces mass transfer diffusion limitation by enhancing mesoporous surface area and reducing particle size of beta zeolite.

In an aspect of the present invention, the present invention discloses a process for preparation of mesoporous nano-sized beta zeolite, comprising:
a) preparing an aluminosilicate gel by mixing an alumina source, a silica source, sodium hydroxide, water, tetraethyl ammonium hydroxide, tetraethyl ammonium bromide and cetyltrimethylammonium bromide.
b) ageing the aluminosilicate gel at a temperature in the range of 20-50 ? for 5-15 hours followed by hydrothermal crystallization of the aluminosilicate gel at a temperature in the range of 130-150 ? for 15-25 hours to obtain a crystallized beta zeolite;
c) filtering and washing the crystallized beta zeolite to obtain wet crystallized beta zeolite; and
d) drying the wet crystallized beta zeolite at a temperature in the range of 100-120 ? for 7-9 hours followed by ammonia exchange with ammonium sulphate solution to obtain ammonia exchanged beta zeolite;
e) calcining the ammonia exchanged beta zeolite at a temperature in the range of 500-550 °C for 2-4 hours to obtain the H-form of the mesoporous nano-sized beta zeolite.
In a feature of the present invention, the alumina source is sodium aluminate or aluminium sulphate, and the silica source is colloidal silica or fumed silica.
In a feature of the present invention, molar ratio of SiO2/Al2O3 in the aluminosilicate gel is in a range of 20-40.
In a feature of the present invention, molar ratio of TEAOH/SiO2 in the aluminosilicate gel is in the range of 0.01-0.1.
In a feature of the present invention, molar ratio of CTAB/SiO2 in the aluminosilicate gel is in the range of 0.01-0.1.
In a feature of the present invention, molar ratio of TEABr/SiO2 in the aluminosilicate gel is in the range of 0.01-0.1.
In a feature of the present invention, molar ratio of CTAB:TEAOH:TEABr in the aluminosilicate gel is in the range of 0.2:1:0.2 to 0.8:1:0.8.
In a feature of the present invention, particle size of the mesoporous nano-sized beta zeolite is in the range of 5-40 nm.
In a feature of the present invention, mesopore surface area of the mesoporous nano-sized beta zeolite is in the range of 250-400 m2/g.
In a feature of the present invention, pore volume of the mesoporous nano-sized beta zeolite is in the range of 0.5-0.6 cc/g.
In a feature of the present invention, yield of the aluminosilicate gel in the mesoporous nano-sized beta zeolite is in a range of 90-95%.
In a feature of the present invention, the mesoporous nano-sized beta zeolite is used in preparation of catalytic cracking catalyst microspheres.
In another aspect of the present invention, the present invention discloses a process for preparation of catalytic cracking catalyst microspheres, comprising: preparing a catalyst slurry by mixing 15-25 wt% mesoporous nano-sized beta zeolite, 5-15 wt% ZSM-5 zeolite, 25-35 wt% Kaolin clay, 15-25 % ammonium polysilicate, 15-25% pseudo boehmite alumina, formic acid and water; spray drying the catalyst slurry to obtain the catalytic cracking catalyst microspheres;
In another aspect of the present invention, the present invention discloses a process for preparation of mesoporous nano-sized beta zeolite, comprising: preparing an aluminosilicate gel by mixing alumina source, silica source, sodium hydroxide, water, tetraethyl ammonium hydroxide, tetraethyl ammonium bromide and cetyltrimethylammonium bromide; ageing the aluminosilicate gel at a temperature in the range of 20-50 ? for 5-15 hours followed by hydrothermal crystallization of the aluminosilicate gel at a temperature in the range of 130-150 ? for 15-25 hours to obtain a crystallized beta zeolite; filtering and washing the crystallized beta zeolite to obtain wet crystallized beta zeolite; and drying the wet crystallized beta zeolite at a temperature in the range of 100-120 ? for 7-9 hours followed by three times ammonia exchange for sodium removal and calcination at a temperature in the range of 500-550 °C for 2-4 hours to obtain the mesoporous nano-sized beta zeolite.
In one another aspect of the present invention, the present invention discloses a process for preparation of mesoporous nano sized beta zeolite using triple template approach, wherein the process comprises steps of: preparing an aluminosilicate gel by mixing alumina source, silica source, sodium hydroxide, water, tetraethyl ammonium hydroxide, tetraethyl ammonium bromide and cetyltrimethylammonium bromide. ageing aluminosilicate gel at 20-50 ? for 5-15 hour followed by hydrothermal crystallization of aluminosilicate gel at temperature of 130-150 ? for 15-25 hours; crystallized beta zeolite product is filtered, washed and dried at temperature 100-120 ? for 8 hours, followed by three times ammonia exchange for sodium removal followed by calcination at 500-550°C for 3 hours to obtain mesoporous nano sized beta zeolite.
EXAMPLES:
Example 1:
4.1 g of sodium aluminate was added into 67.94 g of water. 1.43 g of sodium hydroxide was added to the sodium aluminate solution. 7 g of tetraethyl ammonium hydroxide solution, 7 g of tetraethyl ammonium bromide solution and 12 g of cetyl trimethyl ammonium bromide were added in solution above and stirred for 30 minutes. 100 g of colloidal silica was added into the solution above to obtain aluminosilicate gel mixture, and the aluminosilicate gel mixture is stirred for 1 hour. Gel mixture is transferred in autoclave and aged at temperature of 40 ? for 12 hours. Aged aluminosilicate gel mixture was crystallized at 140 ? for 24 hours. Crystallized zeolite was filtered, washed and dried at 120 ?. Dried beta zeolite was ammonia exchanged using 5 wt% ammonium sulphate solution three times, ammonia exchanged beta zeolite was calcined at 500 ? for 5 hours in muffle furnace to obtain H form of the mesoporous nano-sized beta zeolite.
Example 2:
Beta zeolite from Example 1 was used in making catalytic cracking catalyst microspheres. 20 wt% beta zeolite prepared in Example 1, 10 wt% ZSM-5 zeolite (Commercial ZSM-5 zeolite), 30 wt% Kaolin clay, 20 % ammonium polysilicate, 20% pseudo boehmite alumina, formic acid and water was added to make catalyst slurry, this slurry was spray dried and catalytic cracking catalyst microspheres was obtained.
Catalytic cracking catalyst was hydrothermally deactivated at 810 ? for 5 hours in Cyclic deactivation unit using 100% steam. Catalytic cracking performance of the catalyst was tested in Catalytic Cracking Section unit. This unit consists of a fluidized bed reactor. Catalyst was tested for catalytic cracking of kerosene at reaction temperature of 600 ? and Catalyst/oil of 12.
Comparative Example 1:
Commercial beta zeolite was used in making catalytic cracking catalyst microspheres. 20 wt % commercial beta zeolite, 10 wt% ZSM-5 zeolite (Commercial ZSM-5 zeolite), 30 wt% Kaolin clay, 20 % ammonium polysilicate, 20% pseudo boehmite alumina, formic acid and water was added to make catalyst slurry, this slurry was spray dried, and catalytic cracking catalyst microspheres was obtained.
Catalytic cracking catalyst was hydrothermally deactivated at 810 ? for 5 hours in Cyclic deactivation unit using 100% steam. Catalytic cracking performance of the catalyst was tested in Catalytic Cracking Section unit. This unit consists of a fluidized bed reactor. Catalyst was tested for catalytic cracking of kerosene at reaction temperature of 600 ? and Catalyst/oil of 12.
Experiments & Results

Table 1: Comparison between properties of the commercial beta zeolite and the beta zeolite of the present invention
Properties Commercial beta zeolite Example 1
Framework SiO2/Al2O3 35 35.4
Micropore surface area, m2/g 467.3 433.16
Mesoporous surface area, m2/g 147.7 268.94
Pore volume, cc/g 0.31 0.58
Particle size, nm 120 29
Crystallinity, % 100 107

Table 2: Cracking performance evaluation of the catalysts prepared using commercial beta zeolite and beta zeolite of the present invention.
Catalyst Comparative Example 1 Example 2
Feed Kerosene Kerosene
Catalyst/Oil, wt/wt 12 12
Temperature, ? 600 600
Yield
(in wt%)
Dry Gas 8.08 8.88
LPG 53.99 57.70
Coke 3.07 2.81
Gasoline 31.82 27.67
LCO 2.29 2.60
Bottoms 0.74 0.34
Ethylene 4.6 5.42
Propylene 18.54 20.07
Butene 10.97 12.00
Light olefin yield 34.11 37.49

Advantages of the present invention.
The synthesized mesoporous nano-sized beta zeolite of the present invention is used in making catalytic cracking catalyst for Kerosene cracking. Due to the presence of mesopores in the mesoporous nano-sized beta zeolite, light olefin yield has increased by 3-4 wt%.
, Claims:1. A process for preparation of mesoporous nano-sized beta zeolite, comprising:
a) preparing an aluminosilicate gel by mixing an alumina source, a silica source, sodium hydroxide, water, tetraethyl ammonium hydroxide (TEAOH), tetraethyl ammonium bromide (TEABr) and cetyltrimethylammonium bromide (CTAB);
b) ageing the aluminosilicate gel at a temperature in the range of 20-50 ? for 5-15 hours followed by hydrothermal crystallization of the aluminosilicate gel at a temperature in the range of 130-150 ? for 15-25 hours to obtain a crystallized beta zeolite;
c) filtering and washing the crystallized beta zeolite to obtain wet crystallized beta zeolite; and
d) drying the wet crystallized beta zeolite at a temperature in the range of 100-120 ? for 7-9 hours followed by ammonia exchange with ammonium sulphate solution to obtain ammonia exchanged beta zeolite;
e) calcining the ammonia exchanged beta zeolite at a temperature in the range of 500-550 °C for 2-4 hours to obtain the mesoporous nano-sized beta zeolite.
2. The process as claimed in claim 1, wherein the alumina source is sodium aluminate or aluminium sulphate, and the silica source is colloidal silica or fumed silica.
3. The process as claimed in claims 1 and 2, wherein molar ratio of SiO2/Al2O3 in the aluminosilicate gel is in a range of 20-40; wherein molar ratio of TEAOH/SiO2 in the aluminosilicate gel is in the range of 0.01-0.1; wherein molar ratio of CTAB/SiO2 in the aluminosilicate gel is in the range of 0.01-0.1; and wherein molar ratio of TEABr/SiO2 in the aluminosilicate gel is in the range of 0.01-0.1.
4. The process as claimed in claim 1, wherein molar ratio of CTAB:TEAOH:TEABr in the aluminosilicate gel is in the range of 0.2:1:0.2 to 0.8:1:0.8.
5. The process as claimed in claim 1, wherein particle size of the mesoporous nano-sized beta zeolite is in the range of 5-40 nm.
6. The process as claimed in claim 1, wherein mesopore surface area of the mesoporous nano-sized beta zeolite is in the range of 250-400 m2/g.
7. The process as claimed in claim 1, wherein pore volume of the mesoporous nano-sized beta zeolite is in the range of 0.5-0.6 cc/g.
8. The process as claimed in claim 1, wherein yield of the aluminosilicate gel in the mesoporous nano-sized beta zeolite preparation process is in a range of 90-95%.
9. A process for preparation of catalytic cracking catalyst microspheres, comprising:
i. preparing a catalyst slurry by mixing 15-25 wt% mesoporous nano-sized beta zeolite, 5-15 wt% ZSM-5 zeolite, 25-35 wt% Kaolin clay, 15-25 % ammonium polysilicate, 15-25% pseudo boehmite alumina, formic acid and water;
ii. spray drying the catalyst slurry to obtain the catalytic cracking catalyst microspheres.