This is the third article in a review of patents issued in 2016 in the area of Fluid Catalytic Cracking (FCC). The first article in this series, Catalyst Additives, can be found here, the second part, Equilibrium Catalyst here, can be found . The summary below covers four patents related to the production of light olefins using octane additives and specific process systems.
Conventional techniques available to refiners having FCC units for increasing light olefin production (not employing significant capital expense), have included: (1) catalyst approaches, such as reducing the unit cell size of the Y-zeolite used, or employing octane additives to crack naphtha range material to light olefins; (2) modifying operating conditions to drive conversion levels up and increase olefinicities; and (3) combining hardware modifications and alternative feedstocks. This last option includes processing large amounts/quantities of Light Straight-Run Naphtha (LSN), Light Coke Naphtha (LCN) and Natural Gas Condensate (Liquid – NGL). Some new technologies are also available, however, due to the heat-balance constraints imposed by the processing of large quantities of light feedstocks, changes to the process and to hardware have been necessitated. To date, there have only been a very few of these units built and operated and the others are still in the R&D stage as there are still considerable issues with their development that need to be sorted-out/worked through.
The 2016 patents summarized in this article combine the use of octane additives along with process changes. First, each of the four patents employ octane additives in various amounts. However, three of the four also employ multiple reactors to provide flexibility to adjust the desired product mix. Further, two of the patents (US 9,284,495 & US 9,452,404) involve strategies of preferential catalyst loss to maintain a desired catalyst component mix. Interestingly, while the ‘495 Patent is based on the preferential loss of its ZSM-5 type component, either through catalyst design to make it softer or through attrition, the ‘404 Patent relies on the opposite. There, the ZSM-5 type component is of higher particle size and density than the Y-type zeolite component, so is preferentially retained in the unit.
The patents related to light olefins production are summarized below. Attached Table 1 lists relevant information on the patents. Table 2 contains a representative independent claim from each.
U.S. Patent No. 9,284,495 relates to a process of fluid catalytic cracking for maximizing propylene. The patent contains a single independent claim with 11 total. The claimed process utilizes a two-component catalyst system containing 75-99 wt% of a large pore zeolite and 1-25 wt% of a medium or small pore zeolite having an initial average particle diameter of at least about 20µ, where the residence time of the medium or small pore zeolite is adjusted so that the inventory is replaced within a 35 day period. In the process, the medium or smaller particles, which have an attrition rate higher than the large pore zeolite, can be withdrawn and fresh catalyst is added. Alternately, the medium or small pore zeolite can be attrited to a size less than 2 microns, and removed as normal catalyst losses. In any event, through attrition or withdrawal the catalyst system is adjusted to have a propylene yield of at least 12 wt%. When a two-reactor design is used, the second reactor typically holds unregenerated catalyst, particularly of the medium or small pore zeolite, since it is not thought to accumulate large levels of coke during the cracking operation.
U.S. Patent No. 9,328,293 describes a fluid catalytic cracking process for producing olefins in at least one riser using three feed streams, in order to affect the residence time in the riser. The patent contains three independent claims (1, 14, and 19), with a total of 20. In one embodiment, a first feed has a boiling point of 180 to 800°C. A second feed of C4+ olefins contains greater than 10 wt% butenes. The third feed, injected downstream of the second feed in the riser, is a naphtha stream containing oligomers of butenes. In another embodiment, the fluid catalytic cracking process likewise includes a three feed-stream system: a C4 hydrocarbon stream containing greater than 10 wt% of butenes; a feed stream having a boiling point of 180 to 800°C; and a naphtha stream containing 20 to 70 wt% of C5-10 olefins, where the injection point for the naphtha is downstream of the C4 hydrocarbon stream. The catalyst used is a two-component stream, where the first catalyst has pores with openings greater than about 0.7 nm, and a second catalyst having smaller openings than the first catalyst.
U.S. Patent No. 9,452,404 relates to a process of fluid catalytic cracking for maximizing light olefins. The patent contains a single independent claim with 17 total. Two reactors, (riser and countercurrent flow) are used with common product separations and catalyst regeneration. A two-component catalyst system is used, containing a Y-zeolite having smaller particles (first portion) with lower density, and ZSM-5 particles having larger particle size and higher density (second portion). A first hydrocarbon feed reacts with the first portion of the regenerated catalyst in the riser reactor. In the second, countercurrent reactor, the catalyst is separated into its components, and the second portion of the regenerated catalyst flow reacts with a second hydrocarbon feed. Product streams are produced in both reactors containing cracked hydrocarbon and catalyst, which are then both routed to a disengagement drum. A third stream of spent catalyst from the countercurrent reactor is also produced. The catalyst is separated from the hydrocarbon in the disengagement drum, with the catalyst then being routed to the catalyst regeneration vessel.
U.S. Patent No. 9,468,897 relates to an apparatus for catalytic cracking to maximize propylene and ethylene. The patent contains three independent claims (1, 9, and 13), with a total of 15 claims. The design includes a first and a second catalytic reactor for maximizing propylene and ethylene. The first reactor may be an FCC reactor processing feedstock such as VGO. The catalyst can be a single or multicomponent system; e.g., when single-component, it can contain a standard Y-type zeolite, active alumina matrix, filler, and binder. When a second catalyst component is present, it can also include a medium or small pore zeolite, such as ZSM-5. A fractionation zone containing a debutanizer treats the product of the first reactor. A separations or extraction unit accepts feed from the fractionation zone and recovers C4 and C5 olefin streams as products. A second catalytic reactor receives the extract streams for further cracking. The second reactor can be an additional FCC reactor or it can be an olefin cracking reactor or an oligomerization reactor.
Table 1 FCC Patents — Light Olefins Production
|Patent Number||Inventor||Assignee||Title||Issue Date|
|U.S. 9,284,495||Upson et al.||UOP LLC||Maintaining Catalyst Activity For Converting A Hydrocarbon Feed||March 15, 2016|
|U.S. 9,328,293||Mehlberg et al.||UOP LLC||Fluid Catalytic Cracking Process||May 3, 2016|
|U.S. 9,452,404||Marri et al.||Lummus Technology Inc.||Fluid Cracking Process And Apparatus For Maximizing Light Olefins Or Middle Distillates And Light Olefins||September 27, 2016|
|U.S. 9,468,897||Liu et al.||UOP LLC||Process And Apparatus For Improving Light Olefin Yield From A Fluid Catalytic Cracking Process||October 18, 2016|
Table 2 Light Olefins Production
|Patent Number||Independent Claim|
|U.S. 9,284,495||Claim 1. A process for fluid catalytic cracking, comprising: contacting a hydrocarbon feed with a catalyst mixture in a reaction vessel wherein the catalyst mixture comprises 99-75% by weight of a large pore zeolite and 1-25% by weight of a medium or smaller pore zeolite having an initial average particle diameter of at least about 20 microns; withdrawing the medium or smaller pore zeolite from the reaction vessel and providing fresh catalyst to the reaction vessel at a rate to replace a catalyst inventory of the medium or smaller pore zeolite over a period of up to about 35 days, wherein the fresh catalyst comprises fresh medium or smaller pore zeolite, fresh large pore zeolite, or both; providing feed to a riser in the reaction vessel and obtaining a propylene yield of at least about 12% by weight; wherein the medium or smaller pore zeolite has a higher attrition rate than the large pore zeolite; and wherein the medium or smaller pore zeolite is attrited to a size less than 2 microns.|
|U.S. 9,328,293||Claim 1. A fluid catalytic cracking process, comprising: operating a reaction zone at conditions to facilitate olefin production and comprising at least one riser; receiving in the at least one riser: 1) a first feed having a boiling point of about 180 to about 800°C.; 2) a second feed comprising one or more C.sub.4+ olefins comprising more than about 10%, by weight, butenes; and 3) a third feed comprising a naphtha stream including oligomers of butenes; wherein the third feed is injected downstream of the second feed.|
|U.S. 9,328,299||Claim 1. A process for producing light olefins, comprising: passing a straight run naphtha stream to a first separation column to generate a first light stream comprising methylcyclopentane, and C5– hydrocarbons and a first heavy stream comprising cyclohexane, and C7+ heavier hydrocarbons; passing the first heavy stream to a hydrotreating unit to remove sulfur and other catalyst poisonous impurities to generate a treated heavy stream; passing the treated heavy stream to a second separation unit to generate an extract stream comprising heavier normal paraffins and a raffinate stream comprising cyclohexane and non-normal hydrocarbons; passing the extract stream, the first light stream to a cracking unit to generate light olefins; and passing the raffinate stream and a cracker heavy stream from a heavy cracking unit to a catalytic reforming unit to produce a product with an increased amount of aromatics.|
|U.S. 9,452,404||Claim 1. A process for the catalytic cracking of hydrocarbons, comprising: regenerating a spent catalyst comprising a first cracking catalyst having a first average particle size and density and a second cracking catalyst having a second average particle size and density in a catalyst regeneration vessel to form a regenerated catalyst comprising the first cracking catalyst and the second cracking catalyst, wherein the average particle size of the first cracking catalyst is less than the average particle size of the second cracking catalyst; contacting in co-current flow a first hydrocarbon feed with a first portion of the regenerated catalyst in a riser reactor to produce a first effluent comprising a first cracked hydrocarbon product and a spent mixed catalyst fraction; feeding a second portion of the regenerated catalyst to a second cracking reactor; concurrently in the second cracking reactor: separating the first cracking catalyst from the second cracking catalyst based on at least one of density and particle size; contacting in countercurrent flow a second hydrocarbon feed with the second cracking catalyst to produce a second cracked hydrocarbon product; recovering a second effluent from the second cracking reactor comprising the second cracked hydrocarbon product and the first cracking catalyst as an effluent from the upper portion of the second cracking reactor and recovering a third effluent comprising spent second catalyst from the bottom of the second cracking reactor feeding the first effluent and the second effluent to a disengagement vessel to separate the spent mixed catalyst fraction and the separated first cracking catalyst from the first and second cracked hydrocarbon products; feeding the separated catalysts from the disengagement vessel to the catalyst regeneration vessel as the spent catalyst.|
|U.S. 9,468,897||An apparatus for catalytic cracking, comprising: a first catalytic reactor for catalytically cracking a first hydrocarbon feed stream; a fractionation zone in downstream communication with the first catalytic reactor, said fractionation zone comprising a debutanizer column; a separation unit including a first distillation column in downstream communication with said debutanizer column for producing a first separated stream comprising C4 olefins and a second distillation column in downstream communication with said fractionation section for producing a second separated stream comprising C5 olefins and a recovery column in said separation unit for separating extractant from extract, said recovery column being in downstream communication with said first distillation column and said second distillation column; and a second catalytic reactor in downstream communication with an overhead line of said first distillation column and an overhead line of said second distillation column of the separation unit for cracking a second hydrocarbon feed stream comprising said first separated stream and said second separated stream.|