Description:FIELD OF THE INVENTION:
The present invention relates to a process for producing aromatics and Liquified Petroleum Gas from aromatic feedstock. More particularly, the present invention relates to a method of producing products comprising high concentration of monoaromatic products like benzene, toluene, xylene (BTX) and Liquified Petroleum Gas (LPG) from light cycle oil by using mix of metal modified mesoporous ZSM-5 zeolite additive catalyst and fluid catalytic cracking catalyst.

BACKGROUND OF THE INVENTION:
Conventionally benzene, toluene and xylene have been produced by catalytic reforming of naphtha and later on extracting benzene, toluene and xylene from naphtha reformate product.

However, conventional methods of producing aromatic products involves using hydrogen and costly noble metal based catalysts, so method for producing aromatic products without hydrogen and noble metal based catalyst reduces cost of production of benzene, toluene and xylene.

Fluid catalytic cracking (FCC) is a process, majorly producing gasoline and LPG by catalytic cracking of vacuum gas oil. Other than gasoline, light cycle oil and slurry oil products are also obtained in FCC process.

Particularly, among these products, Light cycle oil contains a large amount (60% or more) of aromatic components of one or more aromatic ring compounds and hence Light cycle oil is suitable feedstock for producing benzene, toluene and xylene through catalytic cracking route. However, compared to naphtha reforming process, light cycle oil consists of other contaminants such as sulphur, nitrogen which acts as contaminant for catalyst, so for process of converting light cycle oil to benzene, toluene and xylene requires more robust catalyst for sustaining these contaminants. With optimized and robust catalyst, Catalytic cracking of light cycle oil in fluidized bed is a promising route for producing Benzene, toluene and xylene.

EP2351820A2 discloses a method for producing aromatic products (benzene/toluene/xylene) and olefin products from oils produced by a fluidized catalytic cracking process.

EP2412785 B1 discloses a method for producing a BTX fraction from a fraction containing a light cycle oil (LCO) produced in an FCC unit.

WO2017093056A1 discloses a process for producing LPG and BTX from hydrocarbon feed having polyaromatics. During the process, the hydrocarbon feed is subjected to hydrocracking wherein a light distillate stream is obtained, which is further subjected to hydrocracking to obtain LPG and BTX streams. The prevalent hydrocracking conditions are as follows: temperature ranging between 300-500 °C and pressure ranging between 1-25 MPa. The catalyst employed for second hydrocracking step is ZSM-5 based, having silica to alumina ratio ranging between 30-100. Further, the overall LPG yield reported is more than 70 wt.%, whereas monoaromatic yield is more than 20 wt.%.

CN113462430B discloses a method for producing low carbon olefin and aromatic hydrocarbon. The method includes the following sequence of operations: hydrocracking LCO followed by second separation (second oil-gas product), and mixing the second oil-gas product with first oil-gas product (obtained from heavy hydrocarbon catalytic cracking) followed by series of rectification separation, gas separation and aromatic extraction separation. The disclosure mentions the catalytic cracking catalyst to include zeolite such as ZSM-5 and which may be optionally modified by a metal component.

WO2009087576A2 discloses a process for fluid catalytic cracking of hydrocarbon feed. The catalytic composition used herein comprises a basic material and at least one intermediate or small pore zeolite. The catalytic composition also comprises less than 15% (or substantially free of) large pore zeolite. The basic material includes transition metal, whereas the at least one intermediate or small pore zeolite includes ZSM-5. The process further (vaguely) discusses about using a hydrocarbon feed which seems to be feed agnostic. However, it specifically mentions VGO and/or hydrotreated VGO as the preferred feed.

Prior art mainly discusses process of producing benzene, toluene, xylene using two-step process, where in the first step hydrotreating of light cycle oil is carried out followed by catalytic cracking of hydrotreated light cycle oil or hydrocracking of hydrogenated light cycle to produce benzene, toluene and xylene. Accordingly, there is a need to develop a simple one-step catalytic cracking process without hydrogenation of light cycle oil to produce Benzene, toluene and xylene and Liquified petroleum gas.
SUMMARY OF THE INVENTION:
The present invention provides a process for production of benzene, toluene, xylene and Liquified petroleum gas by catalytic cracking of light cycle oil without hydrogenation of light cycle oil using metal modified mesoporous ZSM-5 zeolite additive catalyst in one step process.

In an aspect, the present invention provides a process for producing benzene, toluene, xylene and LPG by catalytic cracking of an aromatic feedstock oil comprising:
Catalytic cracking of aromatic feedstock oil in fluidized bed reactor at reaction temperature of 500-700 °C, reaction pressure of 0.1-3 bar in presence of a catalyst comprising a mix of fluid catalytic cracking catalyst and a metal modified mesoporous ZSM-5 zeolite additive and the catalyst to oil(cat/oil) ratio is in a range of 5-10.

In another aspect, the present invention provides a process for preparing metal modified mesoporous ZSM-5 zeolite additive catalyst, comprising steps of:
a. desilication of ZSM-5 zeolite additive by adding sodium hydroxide solution of normality 0.1-1 N at temperature in a range of 50-150 °C and stirring for time in a range of 2-10 hours at speed in a range of 100-1000 rpm to obtain a desilicated ZSM-5 zeolite additive,
b. filtering and washing the desilicated ZSM-5 zeolite additive followed by drying at temperature in a range of 100-120 °C and calcining at temperature in a range of 500-600 °C to obtain a mesoporous ZSM-5 zeolite additive catalyst.
c. adding metal precursor to the mesoporous ZSM-5 zeolite additive catalyst and stirring the mixture at 60-80 °C for 1-3 hours at a speed of 300-700 rpm to obtain a metal impregnated mesoporous ZSM-5 zeolite additive catalyst.
d. filtering and washing the metal impregnated mesoporous ZSM-5 zeolite additive catalyst followed by drying at 100-120 °C and calcining at 500-600 °C to obtain the metal modified mesoporous ZSM-5 zeolite additive catalyst.

DETAILED DESCRIPTION OF THE INVENTION:
The invention will now be described in detail in connection with certain preferred and optional embodiments, so that various aspects thereof may be more fully interpreted and comprehended. However, any skilled person or artisan will appreciate the extent to which such embodiments could be generalized in practice.

It is further to be understood that all terminology used herein is for the purpose of describing embodiments only and is not intended to be limiting in any manner of the scope.

Unless defined otherwise, all technical and scientific expressions used herein have the same meaning as commonly understood by one of ordinary skill in the art to which embodiments of the invention pertains.

In describing and claiming the embodiments of the present invention, the following terminology will be used in accordance with the definitions set out below which are known in the state of art.

The singular forms “a,” “an,” and “the” include plural reference unless the context clearly dictates otherwise.

All modifications and substitutions that come within the meaning of the description and the range of their legal equivalents are to be embraced within their scope. A description using the transition “comprising” allows the inclusion of other elements to be within the scope of the invention.

In an aspect, the present invention provides a process for producing benzene, toluene, xylene and LPG by catalytic cracking of an aromatic feedstock oil comprising:
Catalytic cracking of an aromatic feedstock oil in a fluidized bed reactor at reaction temperature of 500-700 °C, reaction pressure of 0.1-3 bar in presence of a catalyst comprising a mix of fluid catalytic cracking catalyst and a metal modified mesoporous ZSM-5 zeolite additive and the catalyst to oil(cat/oil) ratio is in a range of 5-10.

In an embodiment of the present invention, aromatic feedstock is rich in di-aromatic ring hydrocarbons which is mainly Light cycle oil.

In an embodiment of the present invention, catalyst is a mixture of fluid catalytic cracking catalyst and the metal modified mesoporous ZSM-5 zeolite additive in a ratio of 80:20 to 30:70.

In another embodiment of the present invention, catalyst is a mixture of fluid catalytic cracking catalyst and metal modified mesoporous ZSM-5 zeolite additive in the ratio of 70:30 to 50:50.
In another embodiment of the present invention, the reaction temperature for catalytic cracking of light cycle oil is 500-600 °C and catalyst to oil ratio is 5-7.

In another aspect, the present invention provides a process for preparing metal modified mesoporous ZSM-5 zeolite additive catalyst, comprising steps of:
a. desilication of ZSM-5 zeolite additive by adding sodium hydroxide solution of normality in a range of 0.1-1 N at temperature in a range of 50-150 °C to obtain a desilicated ZSM-5 zeolite additive.
b. filtering and washing the desilicated ZSM-5 zeolite additive followed by drying at temperature in a range of 100-120 °C and calcining at temperature in a range of 500-600 °C to obtain a mesoporous ZSM-5 zeolite additive catalyst.
c. adding metal precursor to the mesoporous ZSM-5 zeolite additive catalyst and stirring the mixture at 60-80 °C to obtain a metal impregnated mesoporous ZSM-5 zeolite additive catalyst.
d. filtering and washing the metal impregnated mesoporous ZSM-5 zeolite additive catalyst followed by drying at 100-120 °C and calcining at 500-600 °C to obtain the metal modified mesoporous ZSM-5 zeolite additive catalyst.

In another embodiment of the present invention, desilication of ZSM-5 zeolite additive is done by adding sodium hydroxide solution of normality 0.1-1 N at temperature in a range of 50-150 °C and stirring for time in a range of 2-10 hours at speed in a range of 100-1000 rpm to obtain a desilicated ZSM-5 zeolite additive.

In another embodiment of the present invention, adding of metal precursor to the mesoporous ZSM-5 zeolite additive catalyst is followed by stirring the mixture at 60-80 °C for 1-3 hours at a speed of 300-700 rpm to obtain a metal impregnated mesoporous ZSM-5 zeolite additive catalyst.

In another embodiment of the present invention, the metal modified mesoporous ZSM-5 zeolite additive consists of 10-40% ZSM-5 zeolite.
In another embodiment of the present invention, the desilication of ZSM-5 zeolite additive is carried out using 0.1-0.3 N sodium hydroxide solution at temperature of 60-80 °C for 4-8 hours at stirring speed of 300-500 rpm.

In another embodiment of the present invention, the metal precursor is selected from zinc nitrate hexahydrate, zinc chloride and zinc sulphate monohydrate.

In another embodiment of the present invention, the ZnO is impregnated on mesoporous ZSM-5 zeolite additive in a range of 2-3 %.

EXAMPLES:

The present disclosure with reference to the accompanying examples describes the present invention. However, those of skill in the art should, in light of the present disclosure, appreciate that many changes can be made in the specific embodiments which are disclosed and still obtain a like or similar result without departing from the spirit and scope of the invention. It is understood that the examples are provided for the purpose of illustrating the invention only and are not intended to limit the scope of the invention in any way.

Example 1: Preparation of zinc modified ZSM-5 zeolite additive catalyst.
11 grams of Zinc nitrate hexahydrate is mixed with 200 grams of water followed by addition of 100 g of ZSM-5 zeolite additive which consists of 20% ZSM-5 zeolite and stirring the mixture at 60 °C for 1 hour at stirring speed of 500 rpm. After 1 hour of mixing, the catalyst is washed, filtered, dried at 120 °C and calcined at 500 °C and obtained catalyst is 3% zinc oxide modified ZSM-5 zeolite additive.

Example 2: Preparation of mesoporous ZSM-5 zeolite additive catalyst.
300 grams of 0.2 N sodium hydroxide solution is prepared. 100 grams of ZSM-5 zeolite additive which consists of 20% ZSM-5 zeolite is added in sodium hydroxide solution and resulting mixture is kept at temperature of 80 °C for 6 hours at stirring speed of 500 rpm. After mixing, the catalyst is washed, filtered, dried at 120 °C and calcined at 500 °C, obtained catalyst is mesoporous ZSM-5 zeolite additive.

Example 3: Preparation of zinc modified mesoporous ZSM-5 zeolite additive catalyst
300 grams of 0.2 N sodium hydroxide solution is prepared. 100 grams of ZSM-5 zeolite additive which consists of 20% ZSM-5 zeolite is added in sodium hydroxide solution and resulting mixture is kept at temperature of 80 °C for 6 hours at stirring speed of 500 rpm. After mixing, the catalyst is washed, filtered, dried at 120 °C and calcined at 500 °C, obtained catalyst is mesoporous ZSM-5 zeolite additive.

11 grams of Zinc nitrate hexahydrate is mixed with 200 grams of water followed by addition of 100 gram of mesoporous ZSM-5 zeolite additive prepared in previous step and stirring the mixture at 60 °C for 1 hour at stirring speed of 500 rpm. After 1 hour of mixing, the catalyst is washed, filtered, dried at 120 °C and calcined at 500 °C, obtained catalyst is 3% zinc oxide modified mesoporous ZSM-5 zeolite additive.

Example 4: Catalytic cracking of light cycle oil using fluid catalytic cracking catalyst and zinc modified ZSM-5 zeolite additive catalyst.
The catalyst obtained in example 1 is deactivated in Cyclic Deactivation unit at 815 °C for 10 hours in 100% steam. A commercial Fluid catalytic cracking catalyst is also deactivated in Cyclic Deactivation unit at 815 °C for 10 hours in 100% steam.

Catalytic cracking of light cycle oil is carried out in fluidized bed reactor at reaction temperature of 550 °C, reaction pressure of 1 bar and at cat/oil of 6. The catalyst used in catalytic cracking of light cycle oil was a mixture of 60% steam deactivated fluid catalytic cracking catalyst and 40% steam deactivated catalyst prepared in Example 1.

Example 5: Catalytic cracking of light cycle oil using fluid catalytic cracking catalyst and mesoporous ZSM-5 zeolite additive catalyst.
The catalyst obtained in example 2 is deactivated in Cyclic Deactivation unit at 815 °C for 10 hours in 100% steam. A commercial Fluid catalytic cracking catalyst is also deactivated in Cyclic Deactivation unit at 815 °C for 10 hours in 100% steam.

Catalytic cracking of light cycle oil is carried out in fluidized bed reactor at reaction temperature of 550 °C, reaction pressure of 1 bar and at cat/oil of 6. The catalyst used in catalytic cracking of light cycle oil was mixture of 60% steam deactivated fluid catalytic cracking catalyst and 40% steam deactivated catalyst prepared in Example 2.

Example 6: Catalytic cracking of light cycle oil using fluid catalytic cracking catalyst and zinc modified mesoporous ZSM-5 zeolite additive catalyst.
The catalyst obtained in example 3 is deactivated in Cyclic Deactivation unit at 815 °C for 10 hours in 100% steam. A commercial Fluid catalytic cracking catalyst is also deactivated in Cyclic Deactivation unit at 815 °C for 10 hours in 100% steam.
Catalytic cracking of light cycle oil is carried out in fluidized bed reactor at reaction temperature of 550 °C, reaction pressure of 1 bar and at cat/oil of 6. The catalyst used in catalytic cracking of light cycle oil was mixture of 60% steam deactivated fluid catalytic cracking catalyst and 40% steam deactivated catalyst prepared in Example 3.

Comparative example 1:
ZSM-5 zeolite additive is deactivated in Cyclic Deactivation unit at 815 °C for 10 hours in 100% steam. A commercial Fluid catalytic cracking catalyst is also deactivated in Cyclic Deactivation unit at 815 °C for 10 hours in 100% steam.
Catalytic cracking of light cycle oil is carried out in fluidized bed reactor at reaction temperature of 550 °C, reaction pressure of 1 bar and at cat/oil of 6. The catalyst used in catalytic cracking of light cycle oil was mixture of 60% steam deactivated fluid catalytic cracking catalyst and 40% steam deactivated ZSM-5 zeolite additive.

Experiments & Results:

Table 1: Properties of steam deactivated catalysts

Catalyst properties FCC catalyst Comparative example 1 Example -4 Example-5 Example 6
SiO2, wt% 44.84 89.4 83.4 78.43 72.3
Al2O3, wt% 50.26 4.5 4.1 4.3 3.88
ZnO , wt% 0 0 2.93 0 2.89
Micropore surface area, m2/g 70 94.6 72 89.6 65
External surface area, m2/g 48 40.2 38.2 74.5 63.2
Pore volume, cc/g 0.34 0.3 0.28 0.36 0.35

Table 2: Light cycle oil properties

Parameter Unit Value
Density g/cc 0.97
IBP 0C 140
FBP 0C 372
Sulphur Wt% 2.1
Aromatic distribution
Monoaromatics Wt.% 13.5
Diaromatics Wt.% 74.9
Tri aromatics Wt.% 11.6

Table 3: Catalytic Cracking performance evaluation of catalysts

Catalyst Name Comparative example 1 Example 4 Example 5 Example 6
Feed Name Light Cycle oil Light Cycle oil Light Cycle oil Light Cycle oil
Reactor Temperature °C 550 550 550 550
Cat/Oil (wt/wt) 6 6 6 6
Yields (wt.%)
Dry Gas 2.79 3.24 4.78 4.95
LPG 3.46 4.63 18.22 22.38
Coke 10.42 9.34 13.87 11.36
Gasoline 48.99 47.67 50.01 48.16
LCO 30.25 27.43 10.46 10.62
CLO 4.09 7.69 2.65 2.25
Benzene 1.64 1.78 1.82 3.82
Toluene 5.66 7.99 8.78 12.89
Xylene 6.69 7.38 7.45 11.56
BTX 13.99 17.15 18.05 28.27 , Claims:1. A process for producing benzene, toluene, xylene (BTX) and LPG by catalytic cracking of an aromatic feedstock oil comprising:
catalytic cracking of an aromatic feedstock oil in a fluidized bed reactor at reaction temperature of 500-700 °C, reaction pressure of 0.1-3 bar in presence of a catalyst comprising a mix of fluid catalytic cracking catalyst and a metal modified mesoporous ZSM-5 zeolite additive and the catalyst to oil(cat/oil) ratio is in a range of 5-10.

2. The process as claimed in claim 1, wherein aromatic feedstock is rich in diaromatic ring hydrocarbons which is mainly Light cycle oil.

3. The process as claimed in claim 1, wherein the catalyst is a mixture of fluid catalytic cracking catalyst and the metal modified mesoporous ZSM-5 zeolite additive in a ratio of 80:20 to 30:70.

4. The process as claimed in claims 1-2, wherein catalyst is a mixture of fluid catalytic cracking catalyst and metal modified mesoporous ZSM-5 zeolite additive in the ratio of 70:30 to 50:50.

5. The process as claimed in claim 1, wherein reaction temperature for catalytic cracking of light cycle oil is 500-600 °C and catalyst to oil ratio is 5-7.

6. A process for preparing metal modified mesoporous ZSM-5 zeolite additive catalyst as defined in claim 1, comprising steps of:
a. desilication of ZSM-5 zeolite additive by adding sodium hydroxide solution of normality in a range of 0.1-1 N at temperature in a range of 50-150 °C to obtain a desilicated ZSM-5 zeolite additive,
b. filtering and washing the desilicated ZSM-5 zeolite additive followed by drying at temperature in a range of 100-120 °C and calcining at temperature in a range of 500-600 °C to obtain a mesoporous ZSM-5 zeolite additive catalyst.
c. adding metal precursor to the mesoporous ZSM-5 zeolite additive catalyst and stirring the mixture at 60-80 °C to obtain a metal impregnated mesoporous ZSM-5 zeolite additive catalyst.
d. filtering and washing the metal impregnated mesoporous ZSM-5 zeolite additive catalyst followed by drying at 100-120 °C and calcining at 500-600 °C to obtain the metal modified mesoporous ZSM-5 zeolite additive catalyst.

7. The process as claimed in claim 6, wherein the metal modified mesoporous ZSM-5 zeolite additive consists of 10-40% ZSM-5 zeolite.

8. The process as claimed in claims 6-7, wherein desilication of ZSM-5 zeolite additive is carried out using 0.1-0.3 N sodium hydroxide solution at temperature of 60-80 °C for 4-8 hours at stirring speed of 300-500 rpm.

9. The process as claimed in claims 6-8, wherein metal precursor is selected from zinc nitrate hexahydrate, Zinc chloride and zinc sulphate monohydrate.

10. The process as claimed in claims 6-9, wherein ZnO is impregnated on mesoporous ZSM-5 zeolite additive in a range of 2-3 %.