DESC:
FIELD
The present disclosure relates to a fluid catalytic cracking process for preparing cracked run naphtha with low olefin content.
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 a fluid catalytic cracking (FCC) unit. The ever-increasing demand for gasoline has seen a surge in such refining units.
Vacuum Gas Oil (VGO), a component of the heavy hydrocarbons, is subjected to cracking in an FCC unit resulting in cracked run naphtha (CRN), fuel oil and offgas as the end-products. The cracked run naphtha (CRN) produced by the cracking of VGO, typically, contains around 45-55% liquid olefins. When these liquid olefins come in contact with dissolved oxygen, they form hydroperoxides as immediate products, which undergo further reactions to form insoluble oxidized species. These oxidized species that include peroxides, aldehydes, acids, ketones as well as components with molecular weights 200-600 g/mol are commonly referred to as gum. This insoluble 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, fouling can be controlled.
Thus, a need to reduce the liquid olefin content in CRN arises. To meet this need, a separate hydrotreating unit for hydrogenation of olefins may be used. However such units increase the overall cost.
Another technique includes the use of a rare earth metal promoter as an additive in combination with an FCC catalyst. It is found that this composite helps to lower the liquid olefin content and at the same time maintains/enhances the research octane number (RON).
CN102794195A suggests one such catalyst. The catalyst is prepared from the following raw materials in percentage by mass: 25-50% of aluminum trioxide hydrate on the basis of Al2O3, 1-5% of P on the basis of P2O5, 0.1-5% of rare-earth oxide on the basis of (rare-earth)2O3 and 50-75% of modified shape-selective molecular sieve. The catalyst has the advantages of high gasoline octane number, low olefin content, high gasoline yield and low dry gas yield. The rare earth component in the cracking catalyst restricts the formation of liquid olefins.
However, these catalysts show a tendency to lose the expensive rare earth metal component due to which the catalyst activity cannot be recovered. The catalyst is required to be replenished frequently. This increases the cost of the FCC process. Also, the loss of the rare earth component leads to a higher amount of liquid olefins in the CRN which, in turn, causes fouling of the process units.
Therefore, there is a need for an FCC process for the production of cracked run naphtha with low olefin content using a catalyst composition which has a long service life or can be recovered.
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 an FCC process to produce cracked run naphtha with low olefin content.
Another object of the present disclosure is to provide an FCC process that makes use of a non-rare earth metal promoter based catalyst composition.
Still another object of the present disclosure is to provide an FCC process that makes use of a non-rare earth metal promoter that has a long service life
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 disclosure relates to a fluid catalytic cracking (FCC) process for the production of cracked run naphtha with low olefin content.
Vacuum gas oil is subjected to a catalytic cracking process in a fixed bed down-flow reactor unit in the presence of a catalyst composition comprising a FCC equilibrated catalyst (ECAT) and an additive, wherein the additive comprises a zeolite and at least one non-rare earth metal promoter selected from the group consisting of Zn and Ga. The resultant product containing cracked run naphtha has a liquid olefinic content less than 45 wt%.
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.
The disclosure relates to a fluid catalytic cracking (FCC) process for production of cracked run naphtha with low olefin content. In particular, the disclosure relates to a process that makes use of an additive in combination with an FCC equilibrated catalyst (ECAT), the mixture thereof reduces the concentration of olefin in the cracked run naphtha prepared while processing a vacuum gas oil feedstock.
In an embodiment of the present disclosure, an FCC process for obtaining cracked run naphtha with low olefin content from vacuum gas oil is disclosed. The catalytic reactor, which is a fixed bed down-flow reactor, is maintained at a pressure in the range of 1 atm to 2 atm and temperature in the range of 400 °C to 700 °C. The feedstock is vacuum gas oil (VGO) obtained as a left-over from vacuum distillation of crude oil. The feedstock in-flow is maintained at 6 ml/hr and a weight hourly space velocity (WHSV) of 9 hr-1. An inert gas, a non-limiting example of which is nitrogen, is selected as a carrier gas. The VGO is contacted with a catalyst composition comprising an FCC equilibrated catalyst (ECAT) and an additive comprising a zeolite and at least one non-rare earth metal promoter, to obtain a resultant product containing cracked run naphtha having a liquid olefinic content less than 45 wt%. 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, SAPO17, SAPO-18, SAPO-34, SAPO-44, MCM-22, ZSM-Y and Beta. The non-rare earth metal promoter is at least one selected from a group consisting of Zn and Ga. In an embodiment, the precursor for the non-rare earth metal promoter is a salt of the non-rare earth metal. In an exemplary embodiment, the precursor of the non-rare earth metal promoter is a nitrate salt of the non-rare earth metal.
In one embodiment of the present disclosure, the FCC equilibrated catalyst, ECAT, is present in the range of 80 wt% to 93 wt% of the catalyst composition and the additive is present in the range of 7 wt% to 20 wt% of the catalyst composition.
In another embodiment of the present disclosure, the non-rare earth metal promoter in the additive used in the process is in the range of 1 wt% to 10 wt% of the additive.
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 an equilibrated catalyst 100% FCC equilibrated catalyst (ECAT). The liquid products obtained were weighed using an integrated balance. The liquid products were analyzed by SIMDIST (Simulated Distillation) and PIONA (paraffins, isoparaffins, olefins, naphthenes and aromatics) analyzers equipped with a pre-fractionator.

Table 1: FCC Reaction Parameters
Temperature
(o C) Pressure Carrier Gas Feed Feed Flow Rate (ml/hr) WHSV (h-1)
530 1 atm Nitrogen VGO 6 9

The resultant products obtained in Example 1 and their percentage composition are discussed in Tables 4 and 5.
Example 2: Catalytic Cracking of VGO with 93% FCC ECAT and 7% P-ZSM-5 (Comparative Example)
ZSM-5 with Si/Al ratio of 23 was loaded with 1% phosphorus in the following manner. 10 g of ZSM-5 sample was mixed with 2.65 g ortho phosphoric acid solution and the resultant slurry was agitated thoroughly at 25 °C for 3 hours for allowing phosphorus to impregnate the zeolite. The resulting slurry was then 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, sieved to obtain particles having particle sizes ranging from 600 µm to 800 µm and pressed into pellets to obtain the final sample P-ZSM-5 (phosphorus impregnated ZSM-5). 93% of the catalyst used in Example 1 and 7% of P-ZSM-5 were mixed and the mixture was used as the catalyst in the present example and the catalytic cracking was carried out in a manner similar to Example 1. The resultant products obtained in Example 2 and their percentage composition are discussed in Tables 4 and 5.
Table 2 shows the composition of the samples as prepared in Example 1 and Example 2.

Table 2: FCC equilibrated catalyst (ECAT) and a composite of ECAT and ZSM-5 with P loading
Zeolite Metal Loading
Example 1 FCC ECAT 100% 0 %
Example 2 FCC ECAT (93 %) +
H-ZSM-5 (7 %) “P” : 7 %

Examples 3-6 were carried out using the process and catalyst composition in accordance with the present disclosure.
Examples 3-6: FCC of VGO with 93% FCC Equilibrated catalyst ECAT and 7% M-ZSM-5
ZSM-5 with Si/Al molar ratio of 23 was loaded with individual or a mixture of non-rare earth metal promoters, Zn and Ga as listed in Table 3. 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 ZSM-5 was added to this metallic salt solution and was made into a slurry. The slurry was agitated at 75 °C for 3 hours for allowing the non-rare earth metal promoters to impregnate into ZSM-5. The non-rare earth metal promoter impregnated ZSM-5 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, sieved to obtain particles having particle sizes ranging from 600 µm to 800 µm and pressed into pellets to obtain the final sample M-ZSM-5 (non-rare earth metal promoter impregnated ZSM-5). 93% of the catalyst used in Example 1 and 7% of M-ZSM-5 were mixed and the mixture was used as the catalyst in the present example and the FCC was carried out in a manner similar to Example 1. The resultant products obtained in Examples 3-6 and their percentage composition are discussed in Tables 4 and 5.
Table 3: Catalyst compositions used in Examples 3-6 with their metal loadings
Examples Zeolite Metal Loading
3 FCC-ECAT (93 %) + M-ZSM-5 (7 %) Zn 1 %
4 Ga 1%
5 Zn 1% + Ga 2%
6 Zn 4% + Ga 4 %
Table 4: Composition of the CRN from Example 1 and Examples 2-6
Examples Liquid Yield CRN LCO Bottoms Cracked Gases
Ex 1 75.4 25.4 25.0 25.0 24.6
Ex 2 65.7 17.7 23.6 24.4 34.3
Ex 3 60 17.94 19.44 22.62 40
Ex 4 75 17.4 17.7 39.9 25
Ex 5 64.8 17.04 18.47 29.29 35.2
Ex 6 74.8 20.04 20.64 34.10 25.2

Table 5: The composition of the individual components of CRN from Examples 1-6
Cracked Products Examples
Ex 1 Ex 2 Ex 3 Ex 4 Ex 5 Ex 6
n-Paraffins (wt%) 9.6 8.6 11.1 7.8 10.0 12.4
i-Paraffins (wt%) 3.0 4.3 4.0 4.2 2.9 3.3
Naphthenes (wt%) 5.1 8.6 12.0 13.2 13.3 14.7
i-Olefins (wt%) 17.0 13.1 9.5 14.5 10.9 11.9
Cyclo olefins (wt%) 17.3 15.7 10.3 12.7 11.3 10.2
n-Olefins (wt%) 11.9 12.0 10.0 17.4 12.5 12.6
Aromatics (wt%) 33.0 32.8 41.2 28.3 37.0 32.6
Others (wt%) 3.1 2.7 1.9 1.8 2.0 2.2
Total Olefins (wt%) 46.2 37.3 31.9 44.6 34.8 34.7
% Reduction compared to FCC ECAT - 19.1 30.9 3.3 24.7 24.7
From Table 5, it is evident that the olefin content in the final CRN is found to be less than 45 wt% for the catalyst used in Examples 2, 3, 5 and 6.
The process of the current disclosure, employing a catalyst composition comprising a non-rare earth metal promoter, is successful in achieving the desired results, i.e. an olefin content less than that obtained by FCC equilibrated catalyst, ECAT and ECAT with a phosphorus loaded additive.
TECHNICAL ADVANCES AND ECONOMICAL SIGNIFICANCE
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of:
? an FCC process that provides cracked run naphtha with low olefin content;
? an FCC process that makes use of a non-rare earth metal promoter based catalyst; and
? an FCC process that makes use of a metal promoter that has a long service life.
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 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. ,CLAIMS:1. A fluid catalytic cracking process for obtaining cracked run naphtha from vacuum gas oil, said process comprising treating the vacuum gas oil in a reactor maintained at a temperature in the range of 400 °C to 750°C and at a pressure ranging from 1 atm to 2 atm in the presence of a catalyst composition comprising a fluid catalytic cracking catalyst and an additive, wherein said additive comprises a zeolite and a non-rare earth metal promoter, the non-rare earth metal promoter being at least one selected from the group consisting of Zn and Ga, to obtain a resultant product containing cracked run naphtha having a liquid olefinic content less than 45 wt%.

2. The process as claimed in claim 1, wherein said fluid catalytic cracking catalyst is FCC equilibrated catalyst (ECAT) and is in the range of 80 wt% to 93 wt% and said additive in said catalyst composition is in the range of 7 wt% to 20 wt%.

3. The process as claimed in claim 2, wherein the FCC equilibrated catalyst (ECAT) is in an amount 93 wt% and said additive is an amount 7 wt%.

4. The process as claimed in claim 1, wherein said non-rare earth metal promoter in said additive is in the range of 1 wt% to 10 wt% of said additive.

5. The process as claimed in claim 1, wherein said 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, SAPO17, SAPO-18, SAPO-34, SAPO-44, MCM-22, ZSM-Y and Beta.

6. The process as claimed in claim 1, wherein the precursor for said non-rare earth metal promoter is a nitrate salt of said non-rare earth metal.