A process for producing lighter olefins

Abstract

The present disclosure relates to a process for producing lighter olefins in a fluid catalytic cracking (FCC) unit. The process enhances lighter olefin production from low-value paraffinic naphtha, thereby significantly enhancing the profitability of the FCC process.

Description

[0001] A PROCESS FOR PRODUCING LIGHTER OLEFINS

[0002] FIELD

[0003] The present disclosure relates to petroleum refining. More particularly, the present disclosure relates to a process for producing lighter olefins.

[0004] DEFINITIONS

[0005] As used in the present disclosure, the following terms are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used indicate otherwise.

[0006] Fluid catalytic cracking (FCC): The term “Fluid catalytic cracking” refers to a petrochemical process that is used to convert heavy hydrocarbon fractions from crude oil into lighter products such as gasoline, diesel, and other olefins. The process uses a catalyst to facilitate the breaking (cracking) of large hydrocarbon molecules into smaller ones.

[0007] Light paraffinic naphtha: The term “Light paraffinic naphtha” refers to a type of petroleum distillate that falls within the lighter fractions of crude oil, wherein the lighter fractions include hydrocarbons with carbon numbers ranging from Cs to C7.

[0008] FCC Riser: The term “FCC riser” is a crucial unit that maximizes the efficiency and yield of the FCC process. Its design and operating conditions directly impact product quality and quantity.

[0009] Retrofitting: The term “retrofitting” refers to retrofitting of an FCC (Fluid Catalytic Cracking) unit that involves upgrading or modifying existing equipment and processes to improve efficiency, increase product yield, enhance operational flexibility, or meet new environmental regulations.

[0010] BACKGROUND

[0011] The background information herein below relates to the present disclosure but is not necessarily prior art.

[0012] Fluid Catalytic Cracking (FCC) has long been a central process in petroleum refining, primarily employed to convert heavy hydrocarbon feed, such as vacuum gas oil and atmospheric residue, into lighter, more valuable products like gasoline, diesel, and liquefied petroleum gas (LPG). Conventional FCC units have been optimized to maximize gasoline production, reflecting the market demands of past decades. However, in recent years, the global petrochemical industry has experienced a significant shift in product demand, with increasing emphasis on light olefins, particularly ethylene (C2) and propylene (C3). These light olefins are essential building blocks for a wide range of polymers, chemicals, and other petrochemical derivatives. This changing market demand has highlighted the limitations of conventional FCC technology, which is inherently less effective at producing high yields of light olefins from standard hydrocarbon feed.

[0013] One of the primary challenges in adapting FCC operations for enhanced light olefin production lies in the nature of the hydrocarbon feed. Light paraffinic naphtha, a refinery stream composed mainly of C5-C7 paraffins and iso-paraffins with a boiling range of approximately 25 °C to 100°C, is generally considered a low-value product. Although it is abundantly available in refineries, it is typically underutilised, often being sent to hydrogen plants, blended into gasoline, or mixed with lower-quality naphtha streams. Conventional FCC units are designed to process heavier, more complex hydrocarbons, and light paraffinic naphtha does not readily undergo cracking under standard operating conditions. The strong carbon-carbon bonds and lack of reactive sites in these paraffins result in low conversion efficiency, producing only small amounts of valuable light olefins when processed in conventional FCC setups.

[0014] Additionally, conventional FCC processes are not tailored to selectively crack lighter paraffinic hydrocarbons. Existing catalyst formulations and operating conditions favour the production of gasoline and heavier products, while generating higher quantities of less valuable by-products, such as fuel gas and coke. As a result, conventional FCC units fail to achieve high selectivity toward ethylene and propylene, representing a missed opportunity for refineries to convert a low-value stream into high-demand petrochemical products. From both economic and environmental perspectives, these limitations are significant. Conventional steam cracking, the conventional method for producing light olefins from naphtha, is highly capital and energy-intensive, requiring substantial infrastructure investment and operating costs.

[0015] Therefore, there is felt a need to provide a process for producing lighter olefins that obviates the drawbacks mentioned hereinabove or at least provides an alternative solution. OBJECTS

[0016] Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:

[0017] 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.

[0018] An object of the present disclosure is to provide a process for producing lighter olefins by using light paraffinic naphtha as a feed in FCC units.

[0019] Another object of the present disclosure is to provide a process that increases the flexibility of FCC operations to use a broader range of hydrocarbon feed.

[0020] Still another object of the present disclosure is to provide a process that efficiently converts the low-value feed (C5-C7 paraffinic) into higher-value products (ethylene and propylene).

[0021] Yet another object of the present disclosure is to provide a process for producing lighter olefins with reduced formation of undesirable by-products, such as fuel gas, while maximizing the yield of ethylene and propylene.

[0022] Still another object of the present disclosure is to provide a process that allows the retrofitting of existing FCC units for co-processing or exclusive processing of light paraffinic naphtha without significant hardware modifications.

[0023] Yet another object of the present disclosure is to provide a process that is economical, simple and environmentally friendly.

[0024] 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.

[0025] SUMMARY

[0026] The present invention relates to a process for producing lighter olefins from a hydrocarbon feed, the process comprising the steps: injecting a first hydrocarbon feed through the operative bottom of the riser of a fluid catalytic cracking (FCC) unit containing a catalyst for primary catalytic cracking to obtain a primary cracked product adsorbed on said catalyst, desorbing the primary cracked product by injecting a regenerated catalyst steam in a controlled manner within the riser to obtain a desorbed primary cracked product; and injecting a second hydrocarbon feed into a reaction zone of the riser maintaining predetermined cracking conditions for a secondary cracking of the desorbed primary cracked product to obtain the lighter olefins comprising propylene and ethylene.

[0027] In an embodiment, the first hydrocarbon feed and the second hydrocarbon feed are injected through an inlet spaced apart from the operative bottom of the riser and the reaction zone is adjacent to the operative bottom of the riser.

[0028] In an embodiment, the first hydrocarbon feed is selected from the group consisting of fuel gas, vacuum gas oil, cyclic oil, olefinic naphtha, coke, a paraffinic stream and a mixture thereof.

[0029] In an embodiment, the second hydrocarbon feed is selected from the group consisting of a paraffinic stream, an olefinic stream, and a mixture thereof.

[0030] In an embodiment, the reaction zone is a region within the riser, wherein the reaction equilibrium is modified by injection of the second hydrocarbon feed to enable the secondary cracking of the desorbed primary cracked products to obtain the lighter olefins.

[0031] In an embodiment, the predetermined cracking conditions include a predetermined riser outlet temperature, a predetermined riser pressure, a predetermined riser residence time, and a predetermined riser space velocity.

[0032] In an embodiment, a weight ratio of the second hydrocarbon feed to the first hydrocarbon feed is in the range of 1 : 1 to 3 : 1.

[0033] In an embodiment, a weight ratio of the catalyst to the hydrocarbon feed is in the range of 6: 1 to 15: 1.

[0034] In an embodiment, the predetermined riser outlet temperature is in the range of 500 °C to 600 °C, the predetermined riser pressure is in the range of 0 kg / cm2g to 3 kg / cm2g, and the predetermined residence time is in the range of 2 seconds to 8 seconds.

[0035] In an embodiment, the paraffinic stream contains a light paraffinic naphtha consisting of a C5-C7 paraffinic hydrocarbon stream and an isoparaffmic hydrocarbon stream and a mixture thereof. In an embodiment, the catalyst and the regenerated catalyst has a composition comprising silicon dioxide in an amount in the range of 45 wt% to 55 wt%, aluminium oxide in an amount in the range of 40 wt% to 50 wt%, iron in an amount in the range of 0.3 wt% to 0.4 wt%, boron oxide in an amount in the range of 0.3 wt% to 1 wt%, rare earth metal oxides in an amount in the range of 0.5 wt% to 0.7 wt%, sodium oxide in an amount in the range of 0. 1 wt% to 0.5 wt%, phosphorus pentoxide in an amount in the range of 0 ppmw to 5 ppmw, and titanium dioxide in an amount in the range of 0 ppmw to 1 ppmw.

[0036] In an embodiment, the catalyst and the regenerated catalyst has physical characteristics including a total surface area in the range of 160 m2 / g to 200 m2 / g, a micropore surface area in the range of 70 m2 / g to 100 m2 / g, a pore volume in the range of 0.3 cc / g to 0.5 cc / g, a pore radius is in the range of 15 A to 20 A, and a particle size is in the range of 65 pm to 80 pm.

[0037] In an embodiment, the process results in an increase in lighter olefin yield in the range of 10 % to 30 % compared to a conventional fluid catalytic cracking (FCC) operation using the same hydrocarbon feed. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING

[0038] Figure 1 illustrates an FCC unit for producing lighter olefins in accordance with the present disclosure

[0039] LIST OF REFERENCE NUMERALS USED IN DETAILED DESCRIPTION AND DRAWING

[0040] DETAILED DESCRIPTION

[0041] The present disclosure relates to petroleum refining. More particularly, the present disclosure relates to a process for producing lighter olefins. The detailed description will now be described in detail with an accompanying drawing.

[0042] Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.

[0043] The terminology used in the present disclosure is only for the purpose of explaining a particular embodiment, and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises," "comprising," “including,” and “having,” are open ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and / or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.

[0044] When an element is referred to as being "mounted on," “engaged to,” "connected to," or "coupled to" another element, it may be directly on, engaged, connected, or coupled to the other element. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed elements.

[0045] The terms first, second, third, etc., should not be construed to limit the scope of the present disclosure, as the aforementioned terms may be only used to distinguish one element, component, region, layer, or section from another component, region, layer, or section. Terms such as first, second, third, etc., when used herein, do not imply a specific sequence or order unless clearly suggested by the present disclosure.

[0046] Terms such as “inner,” “outer,” "beneath," "below," "lower," "above," "upper," and the like, may be used in the present disclosure to describe relationships between different elements as depicted from the figures.

[0047] Fluid Catalytic Cracking (FCC) is a key process in refineries, primarily used to convert heavy hydrocarbons into gasoline, diesel, and LPG. Conventional FCC units are designed to maximize gasoline production and are inefficient at producing light olefins such as ethylene and propylene, which are in growing demand for petrochemical applications. Light paraffinic naphtha, a low-value refinery by-product, is difficult to crack under standard FCC conditions due to strong carbon-carbon bonds and low reactivity, resulting in low olefin yields and higher amounts of less valuable by-products such as fuel gas and coke. Existing alternatives, such as steam cracking, are capital- and energy-intensive, and conventional FCC units fail to utilize light naphtha efficiently, leading to missed economic opportunities.

[0048] The present disclosure provides an FCC-based process that efficiently converts light paraffinic naphtha and other hydrocarbons into high yields of light olefins, including ethylene and propylene. By optimizing feed injection, steam injection, catalyst composition, and operating conditions such as temperature, pressure, and feed ratios, the process enhances selective cracking of lighter hydrocarbons, reduces the formation of unwanted by-products, and increases overall olefin yield. This approach allows refineries to convert low-value streams into high-demand petrochemical products in a cost-effective and energy-efficient manner. In an aspect, the present disclosure envisages a process for producing lighter olefins from a hydrocarbon feed. The process comprises the following steps: i. injecting a first hydrocarbon feed through the operative bottom of the riser of a fluid catalytic cracking (FCC) unit containing a catalyst for primary catalytic cracking to obtain a primary cracked product adsorbed on said catalyst; ii. desorbing said primary cracked product by injecting a regenerated catalyst steam in a controlled manner within said riser to obtain a desorbed primary cracked product; and iii. injecting a second hydrocarbon feed into a reaction zone of said riser, maintaining predetermined cracking conditions for secondary cracking of said desorbed primary cracked product to obtain the lighter olefins comprising propylene and ethylene.

[0049] In the first step of the process, the first hydrocarbon feed (120) is injected at the operative bottom of the riser of the fluid catalytic cracking (FCC) unit. The FCC unit is loaded with a catalyst. The catalyst used in the FCC is a modified catalyst having a predetermined metal composition. The catalyst is effectively used for catalytic cracking of the first hydrocarbon feed to obtain a primary cracked product adsorbed on the catalyst.

[0050] In an embodiment, the first hydrocarbon feed and the second hydrocarbon feed are injected through an inlet (112) spaced apart from the operative bottom of the riser (110) and the reaction zone is adjacent to the operative bottom of the riser (110).

[0051] In an embodiment, the first hydrocarbon feed is selected from the group consisting of fuel gas, vacuum gas oil, cyclic oil, olefinic naphtha, coke, a paraffinic stream and a mixture thereof.

[0052] In the second step of the process, the primary cracked product from the catalyst is desorbed by injecting a regenerated catalyst steam in a controlled manner into the riser to obtain a desorbed primary cracked product.

[0053] In the third step of the process, the second hydrocarbon feed is injected into the reaction zone of the riser at a predetermined cracking condition for a secondary cracking of the desorbed primary cracked product to obtain lighter olefins comprising propylene and ethylene. In an embodiment, the second hydrocarbon feed is selected from the group consisting of a paraffinic stream, an olefinic stream, and a mixture thereof.

[0054] In an embodiment, the paraffinic stream comprises a light paraffinic naphtha consisting of a C5-C7 paraffinic hydrocarbon stream, an iso-paraffinic hydrocarbon stream and a mixture thereof.

[0055] The paraffinic stream is typically derived from the crude oil distillation process, which is often underutilised in conventional refining operations and is commonly directed toward hydrogen generation units or used as a blending component in motor spirit. However, in the present FCC process, the paraffinic streams are effectively utilized as a primary or co-fed feedstock.

[0056] In an exemplary embodiment, the paraffinic stream of the second hydrocarbon feed contacts with a catalyst under optimized reaction conditions such as catalytic and thermal reaction conditions in the reaction zone, enabling its selective cracking into high-value lighter olefins such as ethylene and propylene.

[0057] In an exemplary embodiment, the paraffinic stream has a boiling range of approximately 25 °C to 100 °C.

[0058] In an embodiment, the reaction zone is a region within the riser, wherein the reaction equilibrium is modified by injection of said second hydrocarbon feed to enable said secondary cracking of said desorbed primary cracked products to obtain said lighter olefins.

[0059] The reaction zone in the riser is determined on the basis of the equilibrium condition inside the riser. Inside the riser, where the primary cracked product is formed during the catalyst desorption, is considered the reaction zone suitable for the secondary cracking. The second hydrocarbon feed, more particularly the paraffinic stream of the second hydrocarbon feed, is introduced at that particular reaction zone where the equilibrium of the riser shifts, which causes secondary cracking to establish, resulting in the higher propylene and ethylene yield. The desorption of primary cracked products from the catalyst can also be controlled by the amount of steam fed into the riser. The amount of steam can vary the partial pressure of the feed reactants and products inside the riser. The FCC unit is typically configured with a different riser section. The riser of the FCC unit is configured into three sections: a first zone (110a) that is the bottom section of the riser, a second zone (110b) that is the upper section of the riser and a separation zone (180).

[0060] The bottom zone (110a) of the riser (100) has a smaller diameter, which results in a higher linear velocity, lower residence time and better catalyst oil mixing. The first hydrocarbon feed, typically Vacuum Gas Oil (VGO), is injected at or near the bottom of this section along with regenerated hot catalyst. The high-velocity and turbulent conditions promote rapid vaporization and initial cracking reactions.

[0061] The second zone (110b) of the riser (110) transitions to a larger diameter, resulting in a lower velocity and optimum residence time. In this section, the second hydrocarbon feed (130) such as olefinic streams, may be co-fed or recycled to undergo selective cracking to lighter molecules. The reduced velocity minimizes back-mixing and excessive secondary cracking of desired light olefins. The separation zone (180) is the topmost section of the FCC unit (100). In the separation section, the riser outlet connects to cyclone separators (160) within the reactor vessel for rapid catalyst-vapor disengagement to limit post-riser reactions.

[0062] In exemplary embodiment, in the primary cracking, the vacuum gas oil or crude distillation residue, such as fuel gas, olefinic naphtha, undergoes primary cracking to obtain a light cyclic oil, full range naphtha and coke. Further, this light cyclic oil, and full range naphtha undergo secondary cracking in the reaction zone of the riser to yield more ethylene, propylene along with liquified petroleum gas (LPG) comprising propane, butane and butenes and dry gas or fuel gas.

[0063] The riser and the reaction zone in the riser ensure that the hydrocarbon feed is rapidly and uniformly mixed with the hot catalyst, promoting efficient initiation of the cracking reactions. This arrangement allows for enhanced contact between the hydrocarbon feed and the catalyst, providing optimal temperature and residence time conditions for the selective cracking of light paraffinic naphtha into lighter olefins such as ethylene and propylene. The reaction zone improves conversion efficiency and reduces the formation of undesirable by-products.

[0064] In an embodiment, the process of producing lighter olefins is carried out in two stages.

[0065] In an exemplary embodiment, in the first stage, the first hydrocarbon feed, such as Vacuum Gas Oil (VGO), is injected to initiate primary cracking. In another exemplary embodiment, in the first stage, the vacuum gas oil and the paraffinic stream of the first hydrocarbon feed are co-injected to initiate primary cracking of the first hydrocarbon feed.

[0066] In yet another exemplary embodiment, in the first stage, only a paraffinic stream of the first hydrocarbon feed is injected to initiate the primary cracking.

[0067] The primary cracking is carried out in the operative bottom section of the riser reactor of a fluid catalytic cracking (FCC) unit. The resulting primary cracked product is transported upward through the riser and subsequently subjected to a desorption step, wherein the primary cracked product desorbs from the catalyst by means of a regenerated catalyst steam stream that is recirculated from the catalyst regenerator (170).

[0068] In the second stage, the second hydrocarbon feed is introduced into the reaction zone of the riser located above the first-stage cracking zone. In the reaction zone, the desorbed primary cracked product undergoes secondary catalytic cracking, thereby producing lighter olefins, including butenes, propylene and ethylene.

[0069] In an exemplary embodiment, in the second stage, the second hydrocarbon feed, such as the paraffinic stream, is introduced into the reaction zone of the riser for secondary cracking of the desorbed primary cracked product.

[0070] This two-stage feed injection strategy ensures that the first hydrocarbon feed and the second hydrocarbon experience optimal contact with the catalyst at multiple points along the riser, promoting selective formation of ethylene and propylene while minimizing the generation of undesired by-products such as coke and fuel gas. Thus, the process achieves improved conversion efficiency and higher light olefin yields.

[0071] In an exemplary embodiment, multiple feed streams are introduced into the FCC unit at different locations along the riser of the FCC unit to achieve staged catalytic cracking of the hydrocarbon feed. The hydrocarbon feed supplied to the FCC unit (100) includes the lighter paraffinic naphtha (130), which is injected into the riser’s bottom zone (110a), representing about 8 wt% to 12 wt% of the total feed. From the complete lighter paraffinic stream (130), one-third of the lighter paraffinic naphtha is co-injected along with the other first hydrocarbon feed (120) from the operative bottom of the riser (100) for primary cracking and two-thirds of the lighter paraffinic naphtha (130) is injected at an elevated section of the riser (100) for secondary cracking. A recycled butane-rich liquid stream, drawn from the bottom of the de-ethanizer (DE-C3) distillation column, is also injected into the riser at the bottom section of the riser and constitutes about 4 wt% to 6 wt% of the total feed. The fresh hydrocarbon feed (140), preheated in the feed pre-heater (135), contributes approximately 50 wt% of the total feed and is introduced at the lower section of the riser for initial cracking.

[0072] Further, medium-pressure steam (150), injected from the upper section of the FCC unit to aid in vaporization and stripping of hydrocarbons, accounts for about 22 wt% to 26 wt% of the total feed. Additionally, a slurry stream (190) recycled from the bottom of the main fractionator is introduced into the unit in an amount ranging from 8 wt% to 12 wt% of the total hydrocarbon feed. This multi-point feed injection configuration enables controlled contact between the feed and catalyst, promoting efficient vaporization, selective cracking, and enhanced yield of lighter olefins.

[0073] In an embodiment, the catalyst and the regenerated catalyst has a composition comprising, silicon dioxide (SiCh) in an amount in the range of 45 wt% to 55 wt%, aluminium oxide (AI2O3) in an amount in the range of 30 wt% to 50 wt%, iron oxide (Fe2C>3) in an amount in the range of 0 wt% to 0.8 wt%, boron oxide (B2O3) in an amount in the range of 0.3 wt% to 1 wt%, rare earth metal oxides is in an amount in the range of 0.5 wt% to 0.7 wt%, sodium oxide (Na2O) in an amount in the range of 0. 1 wt% to 0.5 wt%, phosphorus pentoxide (P2O5) in an amount in the range of 0 ppmw to 5 ppmw and titanium dioxide (Ti O 2) in an amount in the range of 0 ppmw to 1 ppmw.

[0074] In an embodiment, the catalyst used for cracking light paraffinic naphtha possesses the following physical characteristics: a total surface area in the range of 160 m2 / g to 200 m2 / g, a micropore surface area in the range of 70 m2 / g to 100 m2 / g, a pore volume in the range of 0.3 cc / g to 0.5 cc / g, a pore radius is in the range of 15 A to 20 A, and a particle size is in the range of 65 pm to 80 pm.

[0075] These physical properties are optimized to ensure sufficient accessibility of active sites, enhance diffusion of hydrocarbon molecules, and promote selective cracking reactions under FCC operating conditions.

[0076] In an embodiment, the predetermined cracking conditions include a predetermined riser outlet temperature, a predetermined riser pressure, a predetermined riser residence time, and a predetermined riser space velocity. In an embodiment, a weight ratio of the second hydrocarbon feed to the first hydrocarbon feed is in the range of 1 : 1 to 3 : 1.

[0077] In an embodiment, the weight ratio of the catalyst to the hydrocarbon feed is in the range of 6: 1 to 15: 1.

[0078] In an embodiment, the catalytic and thermal reaction conditions including the predetermined riser outlet temperature is in the range of 500 °C to 600 °C, the predetermined riser pressure is in the range of 0 kg / cm2g to 3 kg / cm2g, and the predetermined residence time is in the range of 2 seconds to 8 seconds.

[0079] In an exemplary embodiment, the predetermined riser outlet temperature is 565 °C, the predetermined riser pressure is 0.8 kg / cm2g, and the predetermined riser residence time is 2 seconds.

[0080] In an embodiment, a weight hourly space velocity is in the range 0.1 seconds"1to 10 seconds"1. In an exemplary embodiment, the weight hourly space velocity is in the range 0.5 seconds"1to 5 seconds"1.

[0081] In an embodiment, the catalyst used in the process helps in both heating and cracking of the paraffinic stream containing lighter paraffinic naphtha.

[0082] The catalyst, maintained at a high temperature, provides the heat required to vaporize the hydrocarbon feed and initiate cracking reactions as soon as the feed comes in contact with the catalyst. The active sites on the catalyst surface break the carbon-carbon bonds in the paraffinic molecules, forming lighter hydrocarbons such as ethylene and propylene. The specific composition and physical characteristics, help achieve efficient conversion with reduced coke and fuel gas formation. The catalyst remains active throughout the reaction and can be reused after regeneration, ensuring continuous operation and stable olefin yield.

[0083] In an embodiment, the process results in an increase in lighter olefin yield in the range of 10 % to 30 % compared to a conventional FCC operation using the same hydrocarbon feed.

[0084] In exemplary embodiment, the process yields around 19% to 25% propylene, 9% to 15% ethylene and 10% to 15% aromatics like benzene, toluene, and xylene.

[0085] The present disclosure is further described in light of the following experiments, which are set forth for illustration purposes only and not to be construed as limiting the scope of the disclosure. The following experiments can be scaled up to an industrial / commercial scale, and the results obtained can be extrapolated to an industrial scale

[0086] EXPERIMENTAL DETAILS:

[0087] Comparative example 1: conventional FCC operation using Vacuum Gas Oil (VGO) Feed.

[0088] The conventional FCC unit was evaluated using Vacuum Gas Oil (VGO) as the primary feed. The feed rate of Vacuum Gas Oil VGO was maintained at 265 tonnes per hour (TPH), corresponding to a volumetric flow rate of 310 m3 / h. The study was performed at different Riser Outlet Temperatures (ROT) ranging from 515°C to 565°C, wherein the FCC unit was loaded with the conventional catalyst. The resulting yield (in wt%) of VGO with the conventional catalyst and normal injection of VGO in the riser of the FCC are summarized in Table 1 below.

[0089] Table 1: Product Yield Distribution for Conventional FCC Operation with VGO Feed. Table 1 shows that in the conventional cracking process, the yield of propylene is limited as the riser outlet temperature increases, while the yield of the heavier hydrocarbon fractions such as full-range naphtha (FRN) and light cycle oil (LCO) decreases.

[0090] Comparative example 2: conventional FCC operation using Vacuum Gas Oil (VGO) Feed and light paraffinic naphtha (mixed pentanes) feed. The fluid catalytic cracking (FCC) unit was operated with a higher proportion of light paraffinic naphtha co-fed along with VGO to assess the effect of increased paraffinic feed ratio on product distribution. The light paraffinic naphtha feed rate was maintained at 32 tonnes per hour (TPH), equivalent to 50 m3 / h, while the vacuum gas oil feed rate was adjusted to 261 TPH (300 m3 / h). The total combined feed rate of VGO and light paraffinic naphtha was thus 293 tonnes per hour (350 m3 / h). The operation was carried out across a range of Riser Outlet Temperatures (ROT) between 515°C and 565°C, wherein the FCC unit was loaded with the conventional catalyst.

[0091] The resulting yield (in wt%) of VGO and light paraffinic naphtha with the conventional catalyst and normal injection in the riser of the FCC is summarized in Table 2 below.

[0092] Table 2:

[0093] Further, the resulting Table 3 (herein below) shows the yield (in wt%) of only light paraffinic naphtha when the riser was loaded with the conventional catalyst and injected normally in the riser.

[0094] Table 3:

[0095] Table 2 shows the yield of co-fed light paraffinic naphtha with VGO and Table 3 shows the actual results of light paraffinic naphtha yield under conventional cracking conditions.

[0096] From Table 3, it is evident that the light paraffinic naphtha passes through the FCC unit without undergoing effective cracking. The increase in the yield of Full-Range Naphtha indicates that the light paraffinic naphtha co-fed with the VGO primarily walks through the FCC unit without significant conversion. Further, the propylene yield enhancement is negligible.

[0097] Example 3: Production of Lighter Olefins in an FCC Unit loaded with the Catalyst in accordance with the present disclosure when feeding lighter paraffinic naphtha and Vacuum Gas Oil (VGO) at different locations of the riser of the FCC unit.

[0098] In the present example, the lighter paraffinic naphtha was fed along with Vacuum Gas Oil (VGO) in the FCC unit, loaded with the catalyst in accordance with the present discourse. The lighter paraffinic naphtha feed rate was maintained at 32 tonnes per hour (TPH), corresponding to 50 m3 / h, while the VGO feed rate was adjusted to 261 TPH (300 m3 / h). The total combined feed rate of VGO and the light paraffinic naphtha was maintained at 293 TPH (350 m3 / h).

[0099] The feed was injected at two different locations: the first feed, containing the mixture of light paraffinic naphtha and VGO, was fed from the bottom of the riser of the FCC unit, whereas the second feed, containing only lighter paraffinic naphtha, was fed in the reaction zone of the FCC unit. The riser was operated at Riser Outlet Temperatures (ROT) between 515 °C and 565 °C. The resulting yield (in wt%) of VGO and lighter paraffinic naphtha by using the catalyst of the present disclosure and injection into the reaction zone is summarized in Table 4 below.

[0100] Table 4:

[0101] Further, the resulting Table 5 (herein below) shows the yield (in wt%) of only lighter paraffinic naphtha when fed into the riser loaded with the catalyst in accordance with the present disclosure and when injected into the reaction zone of the riser.

[0102] Table 5: Tables 4 and 5 show an improved thermal cracking of the hydrocarbon feed. Specifically, Table 5 shows that the results of improved catalytic cracking of the lighter paraffinic naphtha into the lighter olefin comprising propylene.

[0103] The injection of the lighter paraffinic naphtha into the reaction zone carries out the secondary catalytic cracking that converts the full-range naphtha into lighter olefins. As a result, Table 5 shows an improvement in the yield of propylene by 10% to 23% when compared to the conventional FCC process. The results clearly show that when the light paraffinic naphtha is injected into the riser of the catalyst of the present disclosure, it effectively establishes the secondary cracking to obtain higher value products, such as LPG that includes ethylene, propylene, and butenes from the low value product (lighter paraffinic naphtha).

[0104] The consistent reduction in Full Range Naphtha (FRN) and Light Cycle Oil (LCO) across increasing riser outlet temperature indicates deeper hydrocarbon conversion. However, a marginal increase in Fuel Gas and Coke yields suggests intensified cracking activity.

[0105] TECHNICAL ADVANCEMENTS

[0106] The present disclosure described herein above has several technical advantages, including, but not limited to, the realization of a process for producing lighter olefins that:

[0107] • enhances lighter olefin production from low-value paraffinic naphtha, thereby significantly enhancing the profitability of FCC units;

[0108] • utilizes a catalyst to promote selective cracking of C5-C7 paraffinic hydrocarbons, resulting in higher conversion efficiency and improved product yields;

[0109] • increases the flexibility of FCC operations and enables the use of a broader range of hydrocarbon feed;

[0110] • can be implemented in retrofit capability in existing FCC units with minimal hardware changes;

[0111] • minimizes the formation of undesirable by-products, such as coke and dry gases, leading to a cleaner process with higher selectivity toward light olefins; and

[0112] • is economic.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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

CLAIMS:

1. A process for producing lighter olefins from a hydrocarbon feed, said process comprising the following steps: i. injecting a first hydrocarbon feed through the operative bottom of the riser of a fluid catalytic cracking (FCC) unit containing a catalyst for primary catalytic cracking to obtain a primary cracked product adsorbed on said catalyst; ii. desorbing said primary cracked product by injecting a regenerated catalyst steam in a controlled manner within said riser to obtain a desorbed primary cracked product; and iii. injecting a second hydrocarbon feed into a reaction zone of said riser, maintaining predetermined cracking conditions for secondary cracking of said desorbed primary cracked product to obtain the lighter olefins comprising propylene and ethylene.

2. The process as claimed in claim 1, wherein said first hydrocarbon feed and said second hydrocarbon feed are injected through an inlet spaced apart from the operative bottom of the riser and said reaction zone is adjacent to the operative bottom of said riser.

3. The process as claimed in claim 1, wherein said first hydrocarbon feed is selected from the group consisting of fuel gas, vacuum gas oil, cyclic oil, olefinic naphtha, coke, a paraffinic stream and a mixture thereof.

4. The process as claimed in claim 1, wherein said second hydrocarbon feed is selected from the group consisting of a paraffinic stream, an olefinic stream, and a mixture thereof.

5. The process as claimed in claim 1, wherein said reaction zone is a region within said riser, wherein the reaction equilibrium is modified by injection of said second hydrocarbon feed to enable said secondary cracking of said desorbed primary cracked products to obtain said lighter olefins.

6. The process as claimed in claim 1, wherein said predetermined cracking conditions include a predetermined riser outlet temperature, a predetermined riser pressure, and a predetermined riser residence time.

7. The process as claimed in claim 1, wherein a weight ratio of said second hydrocarbon feed to said first hydrocarbon feed is in the range of 1 : 1 to 3: 1.

8. The process as claimed in claim 1, wherein a weight ratio of said catalyst to said hydrocarbon feed is in the range of 6 : 1 to 15: 1.

9. The process as claimed in claim 6, wherein;• said predetermined riser outlet temperature is in the range of 500°C to 600°C;• said predetermined riser pressure is in the range of 0 kg / cm2g to 3 kg / cm2g; and• said predetermined residence time is in the range of 2 seconds to 8 seconds.

10. The process as claimed in claims 3 and 4, wherein said paraffinic stream contains a light paraffinic naphtha consisting of a C5-C7 paraffinic hydrocarbon stream, an isoparaffinic hydrocarbon stream and a mixture thereof.

11. The process as claimed in claim 1, wherein said catalyst and said regenerated catalyst comprise:• silicon dioxide (SiCh) in an amount in the range of 45 wt% to 55 wt%;• aluminium oxide (AI2O3) in an amount in the range of 40 wt% to 50 wt%;• iron (Fe) in an amount in the range of 0.3 wt% to 0.4 wt%;• boron oxide (B2O3) in an amount in the range of 0.3 wt% to 1 wt%;• rare earth metal oxides in an amount in the range of 0.5 wt% to 0.7 wt%;• sodium oxide (Na20) in an amount in the range of 0. 1 wt% to 0.5 wt%;• phosphorus pentoxide (P2O5) in an amount in the range of 0 ppmw to 5 ppmw; and• titanium dioxide (TiCh) in an amount in the range of 0 ppmw to 1 ppmw.

12. The process as claimed in claim 1, wherein said catalyst and said regenerated catalyst have the following characteristics:• total surface area is in the range of 160 m2 / g to 200 m2 / g;• micropore surface area is in the range of 70 m2 / g to 100 m2 / g;• pore volume is in the range of 0.3 cc / g to 0.5 cc / g;• pore radius is in the range of 15 A to 20 A; and • a particle size is in the range of 65 pm to 80 pm.

13. The process as claimed in any of the preceding claims results in an increase in lighter olefin yield in the range of 10 % to 30 % compared to a conventional FCC operation using the same hydrocarbon feed.

Images