FIELD

The present disclosure relates to the field of petrochemical engineering. Particularly, the present disclosure relates to a fluid catalytic cracking process for obtaining cracked run naphtha from vacuum gas oil. BACKGROUND

Vacuum distillation of crude oil results in a variety of petroleum products with a wide range of molecular weights. The heavier hydrocarbon fractions, usually, the left-overs from vacuum distillation process are converted and refined into more valuable lower molecular weight hydrocarbons with the help of an fluid catalytic cracking (FCC) unit. The ever-increasing demand for gasoline has seen a surge in such refining units.

Vacuum Gas Oil (VGO), particularly comprising higher molecular weight or heavy hydrocarbons, is subjected to an fluid catalytic cracking (FCC) process, in the FCC unit, thereby producing or obtaining cracked run naphtha (CRN), fuel oil and offgas as the end- products. Typically, the CRN contains around 45-55% liquid olefins. When these liquid olefins come in contact with dissolved oxygen, they form hydro-peroxides as immediate products, which undergo further reactions to form insoluble oxidized species. These oxidized species include peroxides, aldehydes, acids, ketones, and components having a molecular weight in the range of 200-600 g/mol (commonly referred to as gum). The gum formation in the interior of the process units results in fouling. Although, rigorous exclusion of oxygen or the addition of anti-oxidants are enough to eliminate fouling, in some industrial situations oxygen ingress cannot be easily prevented. If the liquid olefin content in the CRN is brought down, the gum formation and hence, the fouling can be controlled.

Thus, there is felt a need to reduce the content of liquid olefins in the CRN. In order to meet this need, a separate hydrotreating unit for hydrogenation of olefins may be used. However, such units increase the overall cost.

There is, therefore, felt a need for a FCC process for the production of CRN that overcomes the above-mentioned drawback. 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 FCC process to produce cracked run naphtha with low olefinic content.

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

The present disclosure relates to a fluid catalytic cracking process for obtaining cracked run naphtha from vacuum gas oil.

Vacuum gas oil is subjected to the fluid catalytic cracking (FCC) process in the presence of a catalyst composition. The catalyst composition comprises an FCC catalyst (ECAT) and an additive, to obtain a resultant product containing cracked run naphtha with a liquid olefinic content less than 40 weight .

The amount of the FCC catalyst in the catalyst composition can be in the range of 85 wt% to 93 wt .

The additive comprises at least two zeolites and a rare earth metal promoter. The amount of the additive in the catalyst composition can be in the range of 7 wt% to 15 wt%.

The at least two zeolites can be selected from the group consisting of ferrierite (FER), zeolite Y, and ZSM-35.

The ratio of two zeolites in at least two zeolites can be 1 : 1. The rare earth metal promoter can be at least one selected from the group consisting of lanthanum (La), zinc (Zn), and gallium (Ga). The precursor for the rare earth metal promoter can be a nitrate salt of the rare earth metal.

The amount of the rare earth metal promoter in the additive can be in the range of 1 wt% to 10 wt% of the total amount of the additive.

The catalyst composition can include at least one phosphorus containing compound. The phosphorus containing compound can be present in an amount in the range of 1 wt% to 4 wt% of the total amount of the additive.

The phosphorus containing compound can be at least one selected from the group consisting of phosphoric acid, phosphates, phosphorous acid, phosphites, pyrophosphoric acid, pyrophosphate, polymeric phosphoric acid, polyphosphates, metaphosphoric acid, and metaphosphate.

The vacuum gas oil can be introduced into the reactor at a weight hourly space velocity ranging from 6 hr ^-1 to 10 hr ¹ .

DETAILED DESCRIPTION

The disclosure relates to a fluid catalytic cracking (FCC) process for obtaining cracked run naphtha with low olefinic content. In particular, the disclosure relates to a process that makes use of a catalyst composition comprising an FCC catalyst (ECAT) and an additive. The additive comprises at least two zeolites and a rare earth metal promoter.

The FCC catalyst can be present in an amount in the range of 85 wt% to 93 wt% of the catalyst composition. The additive can be present in an amount in the range of 7 wt% to 15 wt% of the catalyst composition.

The at least two zeolites can be selected from the group consisting of ferrierite (FER), zeolite Y, and ZSM-35.

The ratio of two zeolites in at least two zeolites can be 1 : 1 The rare earth metal promoter can be at least one selected from the group consisting of lanthanum (La), zinc (Zn), and gallium (Ga). The amount of the rare earth metal promoter in the additive can be in the range of 1 wt% to 10 wt% of the total amount of said additive.

The precursor for the rare earth metal promoter can be a salt of the rare earth metal, preferably a nitrate salt of the rare earth metal promoter. Additionally, the catalyst composition comprises at least one phosphorus containing compound.

The phosphorus containing compound can be present in an amount in the range of 1 wt% to 4 wt% of the total amount of the additive.

The phosphorus containing compound can be at least one selected from the group consisting of phosphoric acid, phosphates, phosphorous acid, phosphites, pyrophosphoric acid, pyrophosphate, polymeric phosphoric acid, polyphosphates, metaphosphoric acid, and metaphosphate.

The catalyst composition can be prepared in the steps described herein below.

At least two zeolites are loaded with at least one rare earth metal promoter. A nitrate salt of the rare earth metal promoter is used as the precursor. A pre-determined amount of the nitrate salt is dissolved in a pre-determined amount of water to obtain a metallic salt solution. A predetermined amount of the at least two zeolites is added to the metallic salt solution to obtain a slurry. The slurry is agitated at a temperature in the range of 70°C to 80°C and for a time period in the range of 2 hours to 3 hours, to allow the rare earth metal promoter to impregnate into the zeolites to obtain a rare earth metal promoter impregnated zeolite slurry. The rare earth metal promoter impregnated zeolite slurry is further evaporated in a rotary evaporator maintained at a temperature in the range of 70°C to 80°C under vacuum to obtain a dried mass which is calcined at a temperature in the range of 500°C to 600°C for a time period in the range of 3 hours to 6 hours to obtain a calcined mass. The calcined mass is grounded into a fine powder, pressed into wafers and sieved to obtain particles having particle sizes ranging from 650 μπι to 800 μπι. These particles are mixed with ECAT to obtain the catalyst composition.

In accordance with the present disclosure, an FCC unit, which is a fixed bed down-flow reactor, is maintained at a pressure in the range of 1 atm to 2 atm and at a temperature in the range of 400°C to 700°C. A feedstock (vacuum gas oil), which is typically a left-over of a vacuum distillation unit (V.D.U), is introduced into the FCC unit at a pre-determined rate and at a pre-determined weight hourly space velocity (WHSV). An inert gas, particularly nitrogen, is selected as a carrier gas. The feedstock is contacted with the catalyst composition, to obtain a resultant product containing cracked run naphtha having a liquid olefinic content less than 40 wt%.

The pre-determined rate at which the feedstock can be introduced into the FCC unit is 12 ml/hr.

The pre-determined WHSV can be in the range of 6 hr ^-1 to 10 hr ¹ .

The catalyst composition of the present disclosure facilitates in reducing the concentration of olefin in the cracked run naphtha prepared while processing the feedstock, particularly vacuum gas oil, in the FCC unit. Reduction in the olefinic content facilitates in reducing or controlling the gum formation in the interior of the FCC unit or process units, due to which the fouling in the interior of the FCC unit or process units can be controlled.

The present disclosure is further described in light of the following experiments which are set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure. The following laboratory scale experiments can be scaled up to industrial/commercial scale:

EXAMPLES

Example-1: A comparative example for FCC of VGO with 100% conventional catalyst - FCC equilibrated catalyst (ECAT)

The FCC reaction was carried out using VGO as the feedstock. The reaction was carried out in a fixed bed down-flow reactor unit with a high pressure liquid gas separator. The reaction parameters are listed in Table 1.

The catalyst used was 100% FCC catalyst (ECAT). Table-1: FCC Reaction Parameters

Examples 2-9: FCC of VGO with 85 wt% FCC catalyst (ECAT) and 15 wt% additive

Two zeolites comprising FER with Si/Al molar ratio of 20 and ZSM-5 with Si/Al molar ratio of 30 were loaded with single rare earth metal promoter or mixture of rare earth metal promoters, as listed in Table-2. The nitrate salts of the metals were used as the precursor. 1.186 g of metal salts were dissolved in 30 ml of water and made into their respective solutions. 10 g of the two zeolites was added to this metallic salt solution to obtain a slurry. The slurry was agitated at 75 °C for 3 hours to allow the rare earth metal promoters to impregnate into the zeolites to obtain a rare earth metal promoter impregnated zeolite slurry. The rare earth metal promoter impregnated zeolite slurry was evaporated in a rotary evaporator maintained at 75 °C under vacuum to obtain a dried mass which was calcined at 550°C for 5 hours to result in a calcined mass. The calcined mass was ground into fine powder, pressed into wafers and sieved to obtain particles having particle sizes ranging from 650 μπι to 800 μπι. These particles were mixed with ECAT to obtain a catalyst composition, which was used in the FCC process carried out in a manner similar to Example- 1. The resultant products obtained in Examples 2-9 and their respective percentage composition are listed in Table-3.

Table-2: Catalyst compositions used in Examples 2-9 with their metal loadings.

5 FER and ZSM-35 1 wt% Zn and 2

wt% Ga

6 zeolite Y and 5 wt% La

ZSM-35

7 zeolite Y and 1 wt% Zn and 2

ZSM-35 wt% Ga

8 FER and zeolite Y 5 wt% La

9 FER and zeolite Y 1 wt% Zn and 2

wt% Ga

Table-3:

From Table-3, it is evident that using the catalyst composition prepared in Examples 2-9, the olefins content in the CRN is reduced as compared to that present in the feed-stock.

TECHNICAL ADVANCES AND ECONOMICAL SIGNIFICANCE The present disclosure described herein above has several technical advantages including, but not limited to, the realization of a fluid catalytic cracking (FCC) process that:

- provides cracked run naphtha with reduced olefinic content.

The foregoing description of the specific embodiments 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", should 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 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.