FIELD

The present disclosure relates to a fluid catalytic cracking (FCC) process. BACKGROUND Propylene is an unsaturated organic compound having the chemical formula C3¾. It is the second most important starting product in the petrochemical industry after ethylene. It is used as a raw material for a wide variety of products. Nearly two-third of the demand for propylene is from plastic polypropylene manufacturers.

Propylene is obtained as a component of natural gas during oil and gas extraction. Alternatively, propylene can also be produced by catalytic cracking of the leftover of vacuum distillation of crude oil, i.e. Vacuum Gas Oil (VGO). Other competing products obtained during the catalytic cracking of VGO include gaseous olefins, light cycle oil (LCO), gasoline and allied products.

The demand for propylene is more as compared to the other cracked products. Various attempts have been made to increase the yield of propylene during cracking. Attempts have been made in the past to improve both the FCC process and the catalyst used in the FCC process. Though, an increase in the propylene yield was observed, the amount of propylene obtained was still low (typically less than 6 %).

Therefore, there is felt need for a fluid catalytic cracking process that results in a higher propylene yield.

OBJECTS

Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows.

It is an object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative.

An object of the present disclosure is to provide a fluid catalytic cracking process that results in an increased propylene yield in the resultant product. Another object of the present disclosure is to provide a fluid catalytic cracking process using a catalyst composition that increases the propylene yield.

Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure. SUMMARY

In accordance with one aspect of the present disclosure there is provided a fluid catalytic cracking (FCC) process. The process comprises contacting a feedstock containing vacuum gas oil (VGO) with a catalyst composition in an FCC reactor at pre-determined conditions to obtain a resultant product comprising 7 % to 16 % propylene. The catalyst composition comprises an FCC catalyst and an additive.

The additive used in the present disclosure comprises at least one zeolite loaded with at least one Group V element in an amount ranging from 0.1 % to 5 % of the total weight of the zeolite; and at least one metal promoter in an amount ranging from 1 % to 3 % of the total weight of the zeolite. Optionally, at least one excipient in a ratio of 1 : 1 to 2.5:1 with respect to the zeolite is also present in the additive. The Group V element is phosphorus, and the metal promoter is an element selected from the group consisting of magnesium, calcium, strontium, barium, copper, iron, nickel, zinc, gallium, indium, thallium and any of the lanthanide series metal.

DETAILED DESCRIPTION The disclosure will now be described with reference to the accompanying embodiments which do not limit the scope and ambit of the disclosure. The description provided is purely by way of example and illustration.

The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein. It is observed that fluid catalytic cracking (FCC) process of a feedstock containing VGO using conventional catalysts gives a low propylene yield (typically less than 6 %). It has been found that the addition of zeolite containing additives to the fluid catalytic cracking (FCC) catalyst results in an improved propylene yield. Accordingly, the present disclosure provides an FCC process using a catalyst composition resulting in a product having 7 % to 16 % propylene. The process includes the step of contacting a feedstock containing vacuum gas oil (VGO) with a catalyst composition in an FCC reactor at a pre-determined feed flow rate, a pre-determined weight hourly space velocity, a pre-determined temperature and a pre-determined pressure to obtain a product having 7 % to 16 % propylene.

The catalyst composition includes an FCC catalyst and an additive.

In an exemplary embodiment of the present disclosure, the FCC catalyst is FCC-e-Cat.

The ratio of the FCC catalyst to the additive is in the range of 90: 10 to 95:5, preferably, 93:7.

The additive used in the catalyst composition comprises:

· at least one zeolite loaded with

o at least one Group V element in an amount ranging from 0.1 % to 5 % of the total weight of the zeolite; and

o at least one metal promoter in an amount ranging from 1 % to 3 % of the total weight of the zeolite. In an exemplary embodiment of the present disclosure, the Group V element is phosphorus.

The metal promoter is at least one element selected from the group consisting of magnesium, calcium, strontium, barium, copper, iron, nickel, zinc, gallium, indium, thallium and any of the lanthanide series metals.

Preferably, the metal promoter is at least one element selected from the group consisting of magnesium, calcium, strontium and barium.

In another embodiment of the present disclosure, the metal promoter is a combination of zinc and gallium. The zeolite is at least one selected from the group consisting of ZSM-5, ZSM-11, ZSM-12, ZSM-48, ZSM-57, SAPO-5, SAPO-11, SAPO-17, SAPO-18, SAPO-34, SAPO-44, MCM- 22, an intergrowth of ZSM-11, zeolite Y and zeolite Beta.

Optionally, an excipient in a ratio of 1.1 to 2.5:1 with respect to the zeolite is also present in the catalyst composition of the present disclosure.

The excipient in accordance with the present disclosure is at least one selected from the group consisting of a binder, a filler and a matrix.

In an embodiment of the present disclosure, the binder is pseudoboehmite.

In an embodiment of the present disclosure, the filler is alpha alumina. In an embodiment of the present disclosure, the matrix is silica.

The process in accordance with the present disclosure is carried out in the temperature range of 500 °C to 550 °C and pressure range of 0.5 atm to 2 atm. An inert gas, such as, nitrogen is used as a carrier gas. The feed flow rate is in the range of 5 ML/h to 7 ML/h and the weight hourly space velocity (WHSV) is in the range of 5.2 h ^"1 to 5.3 h ^"1 . The present disclosure is further described in light of the following laboratory experiments which are set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure. These laboratory scale experiments can be scaled up to industrial/commercial scale.

Experiment 1: This is a comparative experiment, in which the catalyst composition of the present disclosure is not used.

Fluid catalytic cracking of VGO as the feedstock was carried out in a fixed bed down-flow reactor unit with a high pressure liquid gas separator. The reaction parameters are summarized below in Table- 1.

Table- 1 Pressure 1 atmosphere

Carrier Gas Nitrogen

Feed VGO

Feed flow rate (ML/h) 6

WHSV (h ¹ ) 5.2 to 5.3

The liquid products obtained were weighed using an integrated balance. The liquid products were analyzed by Simulated Distillation of Petroleum Products (LTSIMDIST) and Paraffins, Iso-paraffins, Olefins Naphthenes and Aromatics (PIONA) analyzer equipped with a Prefractionator.

Table-2 below summarizes the amount of the different products obtained when the reaction was carried out using only the FCC catalyst (without the additive).

Table-2

*CRN=Cracked Run Naphtha,

**=propylene is a component of LPG

The yield of propylene using the FCC catalyst (having a composition as mentioned hereinabove) is 6.2 %, which is lower as compared to that of the yields of the other products obtained.

The feedstock, the reactor and the reaction parameters of the following experiments 2 to 24 are the same as that of the comparative experiment- 1.

The ratio of the FCC catalyst to the additive is 93:7, from experiments 2 onwards. Experiments 2 to 6:

In the experiments 2 to 6, an additive comprising ZSM-5 loaded with varying amounts of phosphorus were used along with the FCC catalyst of the comparative experiment, as given in Table-3 below. Phosphorus was loaded on ZSM-5 having S1O2/AI2O ₃ (ratio=23). The ZSM-5 was mixed with varying quantities of orthophosphoric acid and the resultant slurry was mixed thoroughly at 25 °C for 3 hours, dried by evaporation and finally calcined at 550 °C for 5 hours. The calcined sample obtained was then ground into fine powder and sieved to obtain particles in size ranging from 600 μιη to 800 μπι. Thereafter, the fine powder was pressed into pellets and used along with the FCC catalyst, as the catalyst composition.

Table-3

The amount of the different products obtained by using the catalyst composition of experiments 2 to 6 is given below in Table-4.

Table-4

*CRN=Cracked Run Naphtha **=propylene is a component of LPG

It is seen from Table-4 that higher yields of propylene are obtained, when zeolite and phosphorus was used along with the FCC catalyst. Highest yield of 12.8 % was obtained when the amount of phosphorus in the catalyst composition was 1 %. It is also seen that at higher amounts of phosphorus in the catalyst composition, there was a reduction in the propylene yield. This may be due to the higher suppression/moderation of acid sites, thereby reducing the number and the strength of the acid sites.

Experiments 7 to 10:

In the experiments 7 to 10, ZSM-5 loaded with phosphorus along with metal promoters (Group II metals) magnesium, calcium, strontium and barium in varying amounts were used as the additive along with the FCC catalyst as given in Table-5 below. Five grams of dried zeolite was mixed with the solution of nitrate of metal promoter (magnesium, calcium, strontium and barium) and orthophosphoric acid. The slurry obtained was stirred at room temperature for 3 hours. After 3 hours, the slurry was evaporated in a rotary evaporator that was maintained at 75 °C under vacuum. The dried sample obtained was calcined at 550 °C for 5 hours. The calcined sample obtained was then ground into fine powder and sieved to obtain particles in size ranging from 600 μιη to 800 μπι. Thereafter, the fine powder was pressed into pellets and used along with the FCC catalyst, as the catalyst composition.

Table-5

The amount of the different products obtained by using the catalyst composition of the experiments 7 to 10 are given below in Table-6. Table-6

*CRN=Cracked Run Naphtha,

**=propylene is a component of LPG

As seen from Table-6, the yield of propylene was highest, when calcium (see experiment 8) was used in the catalyst composition and the yield of propylene was least when barium (see experiment 10) was used in the catalyst composition.

Experiments 11 to 13:

The catalyst compositions of experiments 11 to 13 were prepared similarly as in experiments 7 to 10, except that instead of Group II metal salts, salts of nickel, iron and copper as the Metal Promoters were used, as given in Table-7 below.

Table-7

The amount of the different products obtained by using the catalyst composition of experiments 11 to 13 are given below in Table-8. Table-8

*CRN=Cracked Run Naphtha,

**=propylene is a component of LPG

It is clearly seen from Table-8 that higher yield of propylene was obtained when nickel, iron and copper were used in the catalyst composition. The highest yield of propylene was 15.1 %, when iron was incorporated in the catalyst composition (see experiment 12). Experiment 14:

Experiment 14 was similar to experiments 11 to 13, except that instead of nickel, iron and copper, a mixture of zinc and gallium was used as metal promoter 1 and metal promoter 2. The details of the additive are given below in Table-9.

Table-9

The amount of the different products obtained by using the catalyst composition of experiment 14 is given below in Table- 10. Table-10

*CRN=Cracked Run Naphtha,

**=propylene is a component of LPG

It is seen from Table-10 that there is an increase in the propylene yield when a mixture of zinc and gallium were used in the catalyst composition, as compared to the comparative experiment- 1.

Experiments 15 to 16:

The catalyst compositions of experiments 15 to 16 were prepared similar to experiments 11 to 13, except that instead of nickel, iron and copper; lanthanum and cerium were used as the metal promoters as given below in Table- 11.

Table-11

The amount of the different products obtained by using the catalyst compositions of experiments 15 to 16 are given below in Table- 12

Table-12

*CRN=Cracked Run Naphtha,

**=propylene is a component of LPG

It is seen from Table- 12 that there is an increase in the propylene yield when lanthanum and cerium were used in the catalyst composition, as compared to the comparative experiment. However, there is not a significant difference in the propylene yield when lanthanum and cerium were interchanged in the catalyst composition.

Experiments 17 to 22:

In experiments 17 to 22, extrudates of the additives were formed. H-ZSM-5 having S1O2/AI2O ₃ ratio of 23 was loaded with 1 % to 14 wt % of phosphorus. The loading of the phosphorus was carried as previously mentioned in the experiments 2 to 6. The phosphorus loaded zeolite was mixed thoroughly with 3.5 g of pseudoboehmite as the binder, for 3 hours to achieve a composite containing pseudoboehmite and zeolite in a ratio of 1.5: 1. Fifty percent solution of nitric acid in water was added to the composite containing pseudoboehmite and zeolite, under stirring. The final material obtained was extruded into 2 mm extrudates. The extrudates were calcined at a temperature of 700 °C for 5 hours and then used as the additive along with the FCC catalyst as the catalyst composition.

Table- 13 gives the amount of different products obtained by using the extrudates containing different amount of phosphorus.

Table-13

21 11 73.2 29.1 30.5 13.6 7.9 18.9

(Propylene: 7.7)

22 14 71.2 24.1 23.3 23.9 8.7 20.1

(Propylene: 8.6)

*CRN=Cracked Run Naphtha,

**=propylene is a component of LPG

It is seen from Table- 13 that propylene yield increases when phosphorus is used in the catalyst composition, as compared to the comparative experiment. Highest propylene yield was obtained when the amount of phosphorus was 1 % and a decrease in the propylene yield was observed when the amount of phosphorus was 5 % and more.

Experiments 23 and 24:

The experiments were similar to experiments 17 to 22, except that only phosphorus was used as given below in Table- 14.

Table-14

Table- 15 below provides the amount of different products obtained when using the catalyst composition as given in experiments 23 and 24.

Table-15

LCO 13.3 13.6

Bottoms 11.4 11.6

Cat/oil= the catalyst to the feedstock weight ratio

**=propylene is a component of LPG

From Table- 15, it is clear that there is an effective increase in the propylene yield even when diluted catalyst composition was used (pseudoboehmite used as an excipient), as compared to the comparative experiment- 1.

The fluid catalytic cracking process of the present disclosure results in a product having a high propylene yield. Use of calcium and iron in the catalyst composition gives the highest propylene yield (15.1 %). It is also found that addition of phosphorus (0.1 % to 5 %) in the catalyst composition gives high propylene yields, however, more than 5 % phosphorous in the catalyst composition, results in decreased propylene yield. This may be due to the higher suppression/moderation of acid sites, thereby reducing the number and the strength of the acid sites.

TECHNICAL ADVANCES AND ECONOMICAL SIGNIFICANCE

The process of the present disclosure described herein above has several technical advantages including, but not limited to, the realization of:

- a fluid catalytic cracking process resulting in a product having increased propylene yield; and

- a simple and economic process for obtaining high yield of propylene.

The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein. Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. The use of the expression "at least" or "at least one" suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.

Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.

The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values ten percent higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.

While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.