Description:FIELD OF THE INVENTION

The present invention relates to catalytic cracking catalyst. Particularly, the present invention relates to a composite catalytic cracking catalyst for producing light olefins from heavy oil cracking. The present invention also relates to the process of preparing the composite catalytic cracking catalyst by mixing a diffusion improved zeolite-based catalyst and a fluid catalytic cracking catalyst.

BACKGROUND OF THE INVENTION

Heavy oil is a hydrocarbon with a boiling range of 360-540 degrees Celsius. When heavy oil undergoes cracking, it typically leads to lower conversion and a decrease in light olefins due to the larger size of the hydrocarbon molecules present in heavy oil. In a fluid catalytic cracking unit, heavy oil is cracked at high severity in the presence of an FCC catalyst primarily composed of Y zeolite as the active cracking component.

However, due to diffusion limitations, most heavy oil molecules are unable to be cracked in the Y zeolite pores. Additionally, the Y zeolite-based catalyst does not further crack molecules in the naphtha range into lighter olefin range molecules. Molecular sieves with an MFI structure, such as ZSM-5 zeolite, can be utilized in the conversion of hydrocarbon oil to generate lower olefins like ethylene and propylene. Nonetheless, ZSM-5, which has a pore size of 5.4 angstroms, also presents diffusion limitations for heavy or bulky hydrocarbons, leading to increased coke and light paraffin formation. Some of the prior art disclose cracking of the heavy hydrocarbon feeds into lighter hydrocarbons and method used for cracking of the heavy hydrocarbon feeds.

CN1245199A discloses a cracking catalyst contains P-contained zeolite and matrix material. Said zeolite contains silicoaluminate zeolite (85-99.9 wt.%) and phosphorus (0.1-15 wt.% counting in P2O5). In its P MAS-NMR spectrum, the peak area of the peaks whose chemical displacement is -0.05 +/- 0.2 ppm is not greater than 80% of total peak area, and the peak area of the peaks whose chemical displacement is -44.05 +/- 0.2 ppm, -20.05 +/- 0.2 ppm and -26.80 +/- 0.2 ppm is not less than 20% of total peak area. Its advantages are higher in catalytic activity and output rate of light oil.
WO2019243420A1 discloses a composition comprising a) a molding comprising a zeolitic material having an AEI-type framework structure, wherein the zeolitic material has a framework structure comprising Si, a trivalent element X, and oxygen, wherein the zeolitic material further comprises one or more alkali metals AM and/or one or more alkaline earth metals AEM; and b) a mixed metal oxide comprising chromium, zinc, and aluminum; and to a process for its production, as well as to the molding and the mixed metal oxide as such, respectively, as obtainable or obtained according to the inventive production process, as well as to the composition as obtainable or obtained according to the inventive production process. In addition to these, the present invention further relates to the use of the inventive composition as a catalyst or as a catalyst component, as well as to a process for preparing C2 to C4 olefins from a synthesis gas comprising hydrogen and carbon monoxide.

CN101767025A discloses a catalytic cracking catalyst preparation method is included in and introduces inorganic acid, clay slurry, molecular sieve pulp, boehmite, phosphorus-containing compound in the water, and making beating makes catalyst slurry and with the catalyst slurry drying; Wherein, boehmite was introduced before other all materials; Inorganic acid is introduced at twice, wherein once joins earlier among the clay slurry, introduces simultaneously with clay slurry then, and introducing once is not particularly limited in proper order in addition, joins the 25-67 weight % that mineral acid quantity among the clay slurry accounts for the total addition of inorganic acid.

CN102744094A discloses a phosphor and rare earth composite modification method of a molecular sieve comprises that an aluminum source on the surface of the molecular sieve is utilized for in situ synthesis of carbonate-ion-pillared Zn (Mg)/Al/La (Ce) ternary hydrotalcite; that dihydrogen-phosphate-ion-pillared hydrotalcite is prepared by employing an ion exchange method; and that a program heating calcination method is used to make P2O5, La2O3 or Ce2O3 be highly dispersed in the surfaces and pores of the molecular sieve, thereby improving the acidity of the molecular sieve. According to the method of the invention, the molecular sieve modified by hydrotalcite precursor method not only realizes high dispersion of active components, but also greatly improves the acidity and the stability of the molecular sieve, thereby providing a material with practical application values for preparing catalyst for catalytic cracking of heavy oil.

The prior arts disclose various process for cracking of heavy oils and discloses catalyst for cracking the heavy oils. However, the prior arts do not disclose efficient methods and catalyst for increased cracking of the heavy oils with higher yield of lighter hydrocarbon. Further, the process for cracking of heavy oil as disclosed in prior arts are not cost effective and the catalyst as disclosed in the prior arts are not easily available.

Accordingly, to increase olefin production costs and widen the availability of these catalyst, strategies aimed at developing the improved catalyst are worked upon. One promising approach is utilizing process for developing diffusion improved catalytic cracking catalyst as a component for composite cracking catalyst for reduced diffusion limitation and enhanced light olefin yield in heavy oil cracking.

SUMMARY OF THE INVENTION

This summary is provided to introduce a selection of concepts in a simplified format that are further described in the detailed description of the invention.

In an aspect of the present invention, there is provided a process for preparing a composite catalytic cracking catalyst, the process comprising preparing a diffusion improved zeolite-based catalyst and mixing the diffusion improved zeolite-based catalyst and a catalytic cracking catalyst to obtain the composite catalytic cracking catalyst.

In another aspect of present invention, there is provided a process for preparing a composite catalytic cracking catalyst, wherein the preparation of the diffusion improved zeolite-based catalyst includes treating ZSM-5 zeolite with alkali solution. Followed by treating the alkali treated ZSM-5 zeolite with acid solution to obtain acid-alkali treated ZSM-5 zeolite.

The acid-alkali treated ZSM-5 zeolite is washed, filtered, and dried. The dried acid-alkali treated ZSM-5 zeolite is calcined to obtain mesoporous ZSM-5 zeolite. Followed by impregnating P2O5 to the mesoporous ZSM-5 zeolite using a phosphorus source to obtain a P2O5 impregnated mesoporous ZSM-5 zeolite and impregnating MgO to the P2O5 impregnated mesoporous ZSM-5 zeolite, wherein the P2O5 impregnated mesoporous ZSM-5 zeolite is added in a magnesium salt solution to prepare a solution mixture, wherein the solution mixture is kept at 50 oC to 70 oC for 2 hours to 4 hours, filtered, washed, and dried, and calcined to obtain MgO- P2O5 impregnated mesoporous ZSM-5 zeolite using a magnesium salt to obtain a P2O5-MgO impregnated mesoporous ZSM-5 zeolite, wherein the magnesium salt is selected from magnesium sulphate, magnesium chloride and magnesium citrate, wherein the phosphorus salt is selected from phosphoric acid, diammonium hydrogen phosphate or monoammonium phosphate.

To the P2O5-MgO impregnated mesoporous ZSM-5 zeolite, kaolin clay, an aluminium phosphate binder are mixed to obtain a catalyst slurry.

The catalyst slurry is subjected to spray drying to obtain a microsphere of P2O5-MgO impregnated mesoporous ZSM-5 zeolite catalyst and calcining the spray dried catalyst to obtain diffusion improved zeolite-based catalyst.

In another aspect of present invention, there is provided a process for preparing a composite catalytic cracking catalyst, wherein the catalytic cracking catalyst and diffusion improved zeolite-based catalyst are mixed to obtain the composite catalytic cracking catalyst.

In another aspect of present invention, there is provided a process for preparing a diffusion improved zeolite, wherein the alkali solution is selected from sodium hydroxide solution, potassium hydroxide solution or barium hydroxide solution, wherein the acid solution is selected from nitric acid, sulphuric acid, carbonic acid, acetic acid, or oxalic acid.

In another aspect of the present invention, there is provided a composite catalytic cracking catalyst for producing light olefins from heavy oil cracking, the catalyst comprising catalytic cracking catalyst and diffusion improved mesoporous zeolite-based catalyst are present in a ratio of 20:80 to 50:50.

OBJECTIVE OF THE INVENTION

The principal objective of the present invention is to provide a composite catalytic cracking catalyst.

Another objective of the present invention is to provide a composite catalytic cracking catalyst for increased production of light olefins and improved heavy oil cracking.

Yet another objective of the present invention is to provide a process for preparing the composite catalytic cracking catalyst.

DETAILED DESCRIPTION OF THE INVENTION

For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiments in the specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated composition, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skilled in the art to which this invention belongs. The composition, methods, and examples provided herein are illustrative only and not intended to be limiting.

The articles “a”, “an” and “the” are used to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article.

The terms “comprise” and “comprising” are used in the inclusive, open sense, meaning that additional elements may be included. It is not intended to be construed as “consists of only”.

Throughout this specification, unless the context requires otherwise the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of a stated element or step or group of elements or steps but not the exclusion of any other element or step or group of elements or steps.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the disclosure, the preferred methods and materials are now described. All publications mentioned herein are incorporated herein by reference.

The terminology and structure employed herein is for describing, teaching, and illuminating some embodiments and their specific features and elements and does not limit, restrict, or reduce the spirit and scope of the invention.

The term “optionally,” as used in the present disclosure, means that a feature or element described as ‘optional’ within the context of the invention is not required for the invention to function as claimed. It indicates that the presence or absence of the described feature or element does not alter the fundamental operation or scope of the invention, and its inclusion or exclusion may be determined based on the specific requirements or preferences of a practitioner skilled in the art or the particular application in question.

As used herein, the term “Catalyst” refers to a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change.

As used herein, the term “Catalytic cracking” refers to Catalytic cracking is a process in which complex hydrocarbons are broken down into simpler molecules.

As used herein, the term “impregnation” refers to a process to cause a material to be filled or soaked with something.

As used herein, the term “spray drying” refers to an indirect granulation process that involves pumping slurry to an atomizer, where small spherical droplets are sprayed into a large chamber.

As used herein, the term “Calcination” refers to the process of heating of solids to a high temperature for the purpose of removing volatile substances, oxidizing a portion of mass, or rendering them friable.

As used herein, the term “heavy oil” refers toa highly viscous oil that cannot easily flow from production wells under normal reservoir conditions.”

The present invention discloses a process for preparing a composite catalytic cracking catalyst, the process comprising preparing a diffusion improved zeolite-based catalyst, mixing the diffusion improved zeolite-based catalyst and a cracking catalyst to obtain the composite catalytic cracking catalyst.

In an embodiment, the present invention provides the process for preparing a composite catalytic cracking catalyst, the process comprising preparing a diffusion improved zeolite-based catalyst, mixing the diffusion improved zeolite-based catalyst and a cracking catalyst to obtain the composite catalytic cracking catalyst, wherein preparation of the diffusion improved zeolite-based catalyst comprises treating ZSM-5 zeolite with alkali solution for 5 hours to 10 hours at 60 ºC to 90 ºC at a stirring speed of 500 rpm to 700 rpm, washing, filtering and drying the ZSM-5 zeolite at 110 °C to 130 °C for 5 hours to 7 hours to obtain alkali treated ZSM-5 zeolite, treating the alkali treated ZSM-5 zeolite with acid solution at 60 ºC to 80 ºC for 3 to 5 hours at a stirring speed of 500 rpm to 700 rpm to obtain acid-alkali treated ZSM-5 zeolite, washing with water, filtering, and drying the acid-alkali treated ZSM-5 zeolite at a temperature range from 110 °C to 130 °C for 5 hours, calcining the dried acid-alkali treated ZSM-5 zeolite at a temperature from 500 ºC- 600 ºC to obtain mesoporous ZSM-5 zeolite.

In an embodiment, the present invention provides the process for preparing a composite catalytic cracking catalyst, the process comprising preparing a diffusion improved zeolite-based catalyst, mixing the diffusion improved zeolite-based catalyst and a cracking catalyst to obtain the composite catalytic cracking catalyst , wherein preparation of the diffusion improved zeolite-based catalyst comprises treating ZSM-5 zeolite with alkali solution for 5 hours to 10 hours at 85 ºC to obtain alkali treated ZSM-5 zeolite, wherein treating the alkali treated ZSM-5 zeolite with acid solution at 70 ºC for 5 hours at a stirring speed of 600 rpm and washing, filtering and drying the ZSM-5 zeolite with alkali solution at 120 °C for 4 hours to 6 hours to obtain acid-alkali treated ZSM-5 zeolite, washing, filtering, and drying the acid-alkali treated ZSM-5 zeolite at a temperature range from 120 °C for a time period 4 hours to 6 hours, calcining the dried acid-alkali treated ZSM-5 zeolite at a temperature from 550 ºC to obtain mesoporous ZSM-5 zeolite.

Followed by impregnating P2O5 to the mesoporous ZSM-5 zeolite using phosphoric acid solution to obtain a P2O5 impregnated mesoporous ZSM-5 zeolite, to the P2O5 impregnated mesoporous ZSM-5 zeolite MgO is impregnated to using magnesium salt solution to obtain a P2O5-MgO impregnated mesoporous ZSM-5 zeolite.

Following mixing 20 % to 40% of a kaolin clay, 10% to 30% of an aluminium phosphate binder, 10% to 30% of a colloidal silica, and 30 % to 60% of the P2O5-MgO impregnated mesoporous ZSM-5 zeolite to obtain a catalyst slurry.

Spray drying the obtained catalyst slurry an inlet temperature of 400 oC to 500 oC and an outlet temperature of 100 oC to 200 oC to obtain a spray dried P2O5-MgO impregnated mesoporous ZSM-5 zeolite catalyst and calcining the spray dried catalyst at 500 ºC 600 ºC for 4 hours to10 hours to obtain diffusion improved zeolite-based catalyst.

In another embodiment, the present invention provides the a process for preparing a composite catalytic cracking catalyst, the process comprising preparing a diffusion improved zeolite-based catalyst, mixing the diffusion improved zeolite-based catalyst and a cracking catalyst to obtain the composite catalytic cracking catalyst, wherein the spray drying the obtained catalyst slurry at an inlet temperature of 450 oC and an outlet temperature of 150 oC to obtain a spray dried P2O5-MgO impregnated mesoporous ZSM-5 zeolite catalyst and calcining the spray dried catalyst at 550 ºC ºC for 4 hours to obtain diffusion improved zeolite-based catalyst.
In yet another embodiment, the present invention provides the process for preparing a composite catalytic cracking catalyst, the process comprising preparing a diffusion improved zeolite-based catalyst, mixing the diffusion improved zeolite-based catalyst and a cracking catalyst to obtain the composite catalytic cracking catalyst, wherein the mixing of catalytic cracking catalyst and diffusion improved zeolite-based catalyst are mixed in a ratio of 20:80 to 50:50 to obtain the composite catalytic cracking catalyst.

The catalytic cracking catalyst is prepared by the following steps mixing 20 % to 40% of a rare-earth exchanged USY zeolite, 25% to 40% of kaolin clay, 20% to 40% of pseudo boehmite, and 5% to 10% ammonium polysilicate to obtain a mixed catalyst slurry, spray drying the mixed catalyst slurry at an inlet temperature of 400 ºC to 500 ºC and an outlet temperature of 100 ºC to 200 ºC and calcining the catalyst slurry at a temperature from 500 ºC 600 ºC for 4 hours to 10 hours to obtain catalytic cracking catalyst.

In yet another embodiment, the present invention provides the process for preparing a composite catalytic cracking catalyst, the process comprising preparing a diffusion improved zeolite-based catalyst, mixing the diffusion improved zeolite-based catalyst and the cracking catalyst to obtain the composite catalytic cracking catalyst , wherein the P2O5 of a concentration from 0.5 wt% to 1.5 wt% is impregnated to the mesoporous ZSM-5 zeolite to obtain the P2O5 impregnated mesoporous ZSM-5 zeolite, wherein the MgO of a concentration from 0.1 wt% to 0.8 wt% is impregnated to the P2O5 impregnated mesoporous ZSM-5 zeolite.

In still another embodiment, the present invention provides the process for preparing a composite catalytic cracking catalyst, the process comprising preparing a diffusion improved zeolite-based catalyst, mixing the diffusion improved zeolite-based catalyst and a cracking catalyst to obtain the composite catalytic cracking catalyst, wherein the alkali solution is in a concentration of 0.1N to 0.5 N and the alkali solution is selected from sodium hydroxide solution, potassium hydroxide solution or barium hydroxide solution, wherein the acid solution is in a concentration of 0.1N to 0.5 N and the acid solution is selected from nitric acid, sulphuric acid, carbonic acid, acetic acid, or oxalic acid.

In still another embodiment, the present invention provides the process for preparing a composite catalytic cracking catalyst, the process comprising preparing a diffusion improved zeolite-based catalyst, mixing the diffusion improved zeolite-based catalyst and a cracking catalyst to obtain the composite catalytic cracking catalyst, wherein the aluminium phosphate binder consists of 5 wt% to 20 wt% PO4 content.

The present invention also discloses a composite catalytic cracking catalyst for producing light olefins from heavy oil cracking, the catalyst comprising catalytic cracking catalyst and diffusion improved mesoporous zeolite-based catalyst are present in a ratio of 20:80 to 50:50.

In still another embodiment, the present invention provides a composite catalytic cracking catalyst for producing light olefins from heavy oil cracking, the catalyst comprising catalytic cracking catalyst and diffusion improved mesoporous zeolite-based catalyst are present in a ratio of 20:80 to 50:50, wherein the catalyst increases 10% to 15 % of light olefin yield and 2% to 3% of heavy oil conversion.

In still another embodiment, the present invention provides a composite catalytic cracking catalyst for producing light olefins from heavy oil cracking, the catalyst comprising catalytic cracking catalyst and diffusion improved mesoporous zeolite-based catalyst are present in a ratio of 20:80 to 50:50, wherein catalyst having mesoporous surface area to microporous surface area in a ratio of 0.5:1, wherein the composite catalyst is used for catalytic cracking of heavy hydrocarbon feedstocks having a Conradson carbon residue of 4 wt% to 10 wt%.

EXAMPLES

EXAMPLE 1: Preparation of mesoporous ZSM-5 zeolite.
600 grams of 0.2 N sodium hydroxide solution was prepared. 200 grams of ZSM-5 zeolite was added in sodium hydroxide solution and resulting mixture was kept at temperature of 85 °C for 5 hours at stirring speed of 600 rpm.

After mixing, the zeolite was washed, filtered and dried at 120 °C, obtained treated zeolite was treated with 0.2 N HNO3 solution at 70 °C for 5 hours at stirring speed of 600 rpm. After acid treatment, zeolite was washed, filtered, dried at 120 °C and calcined at 550 °C to obtain mesoporous ZSM-5 zeolite.

Example 2: Preparation of MgO- P2O5 impregnated mesoporous ZSM-5 zeolite.
36 gram of phosphoric acid was added in 400 ml of water to prepare phosphoric acid solution, in phosphoric acid solution, 200 grams of mesoporous ZSM-5 zeolite prepared in example 1 was added to obtain P2O5 impregnated mesoporous ZSM-5 zeolite.

6.25 gram of magnesium sulphate was added in 400 ml of water to prepare magnesium sulphate solution, 200 gram of obtain P2O5 impregnated mesoporous ZSM-5 zeolite was added in a magnesium sulphate solution and solution mixture was kept at 60 oC for 3 hours, after that solution mixture was filtered, washed, dried at 120 oC and calcined at 550 oC for 5 hours to obtain MgO- P2O5 impregnated mesoporous ZSM-5 zeolite.

Example 3: Preparation of MgO- P2O5 impregnated mesoporous ZSM-5 additive.
132 gram of kaolin clay, 438 gram of aluminum phosphate binder and 600 gram of water was mixed and stirred for 30 minutes. Then 200 grams of MgO- P2O5 impregnated mesoporous ZSM-5 zeolite was added in slurry solution. This slurry solution was spray dried in counter current spray dryer at inlet temperature of 450 oC and outlet temperature of 150 oC. Microspheres obtained via spray drying was calcined at 550 oC for 4 hours to obtain MgO- P2O5 impregnated mesoporous ZSM-5 additive.
Example 4: Deactivation of MgO- P2O5 impregnated mesoporous ZSM-5 additive
MgO- P2O5 impregnated mesoporous ZSM-5 additive obtained in example 3 was hydrothermally deactivated in presence of 100% steam at 815 oC for 10 hours in cyclic deactivation unit.

Example 5: Preparation of composite catalyst.
60 wt% of catalytic cracking catalyst (FCC equilibrium catalyst from HPCL Mumbai refinery) and 40 wt% of ZSM-5 additive prepared in example 4 was mixed to obtain composite catalyst.

Comparative Example 1:
Commercial ZSM-5 additive (ZSM-5 additive obtained from HPCL Mumbai Refinery) was hydrothermally deactivated in presence of 100% steam at 815 oC for 10 hours in cyclic deactivation unit. 60 wt% catalytic cracking catalyst (FCC equilibrium catalyst from HPCL Mumbai refinery) was mixed with 40 wt% of hydrothermally deactivated commercial ZSM-5 additive to obtain composite catalyst.

Experiments and Results
For Catalytic cracking performance comparison, catalytic cracking experiments were carried out in fluidized bed micro-reactor at reaction temperature of 600 oC and cat/oil of 12 with comparative example 1 and Example 5 catalysts, results are given in table 2. Heavy oil properties are given in table 1. Catalyst properties are given in table 2.

In table 3, with inventive composite catalyst, light olefin yield is increased by 10-15%, heavy oil conversion is increased by 2-3%.

Table 1: Heavy oil properties
Feed Heavy oil
Density @ 15°C, g/cc 0.94
Sulphur, wt.% 2.51
Conradson carbon residue, wt.% 5
Distillation: ASTM 7169, wt.%
IBP 224.4
5 314.4
10 351.8
30 412.4
50 450.2
70 511.8
90 625.4
95 694.6

Table 2: Properties of Catalysts
Catalyst properties Commercial Fluid catalytic cracking catalyst Commercial ZSM-5 additive Example-3
Elemental analysis, wt%
SiO2 44.84 89.4 71.3
Al2O3 50.26 4.5 3.88
P2O5 0 5.20 3.74
Micropore surface area, m2/g 70 94.6 65
Mesopore surface area, m2/g 48 40.2 63.2
Pore volume, cc/g 0.34 0.3 0.45

Table 3: Catalytic cracking performance evaluation of catalyst for heavy oil cracking.
Catalyst Name Comparative example 1 Example 5
Feed Name Heavy oil Heavy oil
Reaction Temp., °C 600 600
Cat/oil 12 12
Conversion, wt% 79.70 83.00
YIELDS, wt%:
Coke 8.60 9.58
Dry Gas 6.13 9.43
LPG 30.89 40.29
Cracked naphtha 34.07 23.66
Light cycle oil 12.63 10.28
Resid 7.67 6.75
Ethylene 3.70 5.30
Propylene 11.99 18.12
C4 Olefins 10.10 13.17
Total light olefins 25.78 36.59
, Claims:1. A process for preparing a composite catalytic cracking catalyst, the process comprising:
preparing a diffusion improved zeolite-based catalyst; and
mixing the diffusion improved zeolite-based catalyst and a cracking catalyst to obtain the composite catalytic cracking catalyst.

2. The process as claimed in claim 1, wherein the preparation of the diffusion improved zeolite-based catalyst comprises the steps of:
a. treating ZSM-5 zeolite with alkali solution for 5 hours to 10 hours at 60 ºC to 90 ºC at a stirring speed of 500 rpm to 700 rpm, washing, filtering and drying the stirred ZSM-5 zeolite with alkali solution at 110 °C to 130 °C for a time period 5 hours to 7 hours to obtain alkali treated ZSM-5 zeolite;
b. treating the alkali treated ZSM-5 zeolite with acid solution at 60 ºC to 80 ºC for 3 to 5 hours at a stirring speed of 500 rpm to 700 rpm to obtain acid-alkali treated ZSM-5 zeolite;
c. washing with water, filtering, and drying the acid-alkali treated ZSM-5 zeolite at a temperature range from 110 °C to 130 °C for a time period 4 hours to 6 hours;
d. calcining the dried acid-alkali treated ZSM-5 zeolite at a temperature from 500 ºC 600 ºC to obtain mesoporous ZSM-5 zeolite;
e. impregnating P2O5 to the mesoporous ZSM-5 zeolite using a phosphorus salt solution to obtain a P2O5 impregnated mesoporous ZSM-5 zeolite;
f. impregnating MgO to the P2O5 impregnated mesoporous ZSM-5 zeolite, wherein the P2O5 impregnated mesoporous ZSM-5 zeolite is added in a magnesium salt solution to prepare a solution mixture, wherein the solution mixture is kept at 50 oC to 70 oC for 2 hours to 4 hours, filtering and washing the solution mixture, and drying at 120 oC and calcined at 550 oC for 5 hours to obtain MgO- P2O5 impregnated mesoporous ZSM-5 zeolite;
g. mixing 20 % to 40% of a kaolin clay, 10% to 30% of an aluminium phosphate binder, and 30 % to 60% of the P2O5-MgO impregnated mesoporous ZSM-5 zeolite to obtain a catalyst slurry;
h. spray drying the obtained catalyst slurry at an inlet temperature of 400 oC to 500 oC and an outlet temperature of 100 oC to 200 oC to obtain a spray dried P2O5-MgO impregnated mesoporous ZSM-5 zeolite catalyst; and
i. calcining the spray dried catalyst at 500 ºC to 600 ºC for 4 hours to10 hours to obtain diffusion improved zeolite-based catalyst.

3. The process as claimed in claim 2, wherein the P2O5 of a concentration from 0.5 wt% to 1.5 wt% is impregnated to the mesoporous ZSM-5 zeolite to obtain the P2O5 impregnated mesoporous ZSM-5 zeolite using phosphorus salt solution, wherein phosphorus salt is selected from phosphoric acid, diammonium hydrogen phosphate or monoammonium phosphate.

4. The process as claimed in claim 2, wherein the MgO of a concentration from 0.1 wt% to 0.8 wt% is impregnated to the P2O5 impregnated mesoporous ZSM-5 zeolite using the magnesium salt solution, wherein the magnesium salt is selected from magnesium sulphate magnesium chloride or magnesium citrate.

5. The process as claimed in claim 2, wherein the alkali solution is in a concentration of 0.1N to 0.5 N and the alkali solution is selected from sodium hydroxide solution, potassium hydroxide solution or barium hydroxide solution.

6. The process as claimed in claim 2, wherein the acid solution is in a concentration of 0.1N to 0.5 N and the acid solution is selected from nitric acid, sulphuric acid, carbonic acid, acetic acid, or oxalic acid.

7. The process as claimed in claim 2, wherein the aluminium phosphate binder consists of 5 wt% to 20 wt% PO4 content.

8. The process as claimed in claim 1, wherein the mixing of catalytic cracking catalyst and diffusion improved zeolite-based catalyst are mixed in a ratio of 20:80 to 50:50 to obtain the composite catalytic cracking catalyst.

9. A composite catalytic cracking catalyst for producing light olefins from heavy oil cracking, the catalyst comprising:
a) a catalytic cracking catalyst; and
b) a diffusion improved mesoporous zeolite-based catalyst as claimed in claims 2-7; wherein the catalytic cracking catalyst and diffusion improved zeolite-based catalyst are present in a ratio of 20:80 to 50:50.

10. The catalyst as claimed in claim 9, wherein diffusion improved zeolite-based catalyst having mesoporous surface area to microporous surface area in a ratio of 0.5:1.