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Process for selectively producing light olefins in a fluid catalytic cracking process

A selectivity and olefin technology, applied in catalytic cracking, hydrocarbon cracking, hydrocarbon production, cracking, etc., can solve the problems of increasing olefin cost and low olefin selectivity

Inactive Publication Date: 2001-06-13
EXXON RES & ENG CO
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Furthermore, even if a particular catalyst balance maintains maximum total olefin production, olefin selectivity is generally low due to undesired side reactions such as overcracking, isomerization, aromatization, and hydrogen transfer reactions
Light saturated gases produced by undesired side reactions lead to increased costs of recovering the desired olefins

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1-12

[0022] The following example illustrates the critical process operating conditions used to maintain chemically pure propylene using a sample of ZCAT-40 (a catalyst containing ZSM-5) that has been steamed at 815.5°C for 16 hours to simulate commercial equilibrium Catalytically cracked naphtha. Comparing Examples 1 and 2, it can be seen that increasing the catalyst / oil ratio can improve the yield of propylene, but the purity of propylene will be sacrificed. Comparing Examples 3 and 4 and 5 and 6, it can be seen that lowering the partial pressure of the oil can greatly improve the propylene purity without compromising the propylene yield. Comparing Examples 7 and 8 and 9 and 10, it can be seen that increasing the temperature can improve both the yield and the purity of propylene. Comparing Examples 11 and 12 it can be seen that reducing catalyst residence time improves propylene yield and purity. Example 13 shows an example of high propylene yield and purity achieved at reactor...

Embodiment 14-17

[0028] Cracking of olefins and paraffins contained in naphtha streams (eg, FCC naphtha, coker naphtha) by small or medium pore size zeolites such as ZSM-5 can produce relatively large amounts of ethylene and propylene. Selectivity to ethylene or propylene or to propylene / propane varies with catalyst and process operating conditions. It has been found that the propylene yield can be increased by feeding steam to the reactor simultaneously with the catalytic naphtha fraction. The catalyst can be ZSM-5 or other small or medium pore size zeolites. Table 2 below illustrates the improvement in propylene yield obtained when 5% by weight steam is fed simultaneously with FCC naphtha containing 38.8% by weight olefins. Although the propylene yield increased, the propylene purity decreased. Therefore, other operating conditions need to be adjusted to maintain the target propylene selectivity.

[0029] Example

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PUM

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Abstract

Disclosed is a process for selectively producing C2-C4 olefins from a catalytically cracked or thermally cracked naphtha stream. The naphtha stream is contacted with a catalyst containing from about 10 to 50 wt.% of a crystalline zeolite having an average pore diameter less than about 0.7 nanometers at reaction conditions which include temperatures from about 500 to 650 DEG C and a hydrocarbon partial pressure from about 10 to 40 psia.

Description

field of invention [0001] The invention relates to a method for selectively producing C from naphtha streams derived from catalytic cracking or thermal cracking 2 -C 4 Alkenes method. The naphtha stream is contacted with a catalyst comprising from about 10 to 50% by weight crystalline zeolites having an average pore size below about 0.7 nm under reaction conditions comprising a temperature of from about 500 to 650°C and a hydrocarbon partial pressure of from 10 to 40 psia. Background of the invention [0002] The need for low-emission fuels has led to an increase in demand for light olefins used in alkylation, oligomerization, MTBE and ETBE synthesis processes. In addition, there is a growing demand for low-cost light olefins, especially propylene, which are used as feedstocks for the production of polyolefins, especially polypropylene. [0003] Fixed-bed dehydrogenation processes for light paraffins that can be used to increase olefin production have recently received re...

Claims

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Application Information

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IPC IPC(8): C07C4/04C07C4/06C07C11/02C10G11/02C10G11/04C10G11/05C10G35/02C10G35/04C10G35/06C10G35/095C10G51/02C10G51/04C10G57/02
CPCC10G51/023C10G57/02C10G2400/20C07C4/02
Inventor P·K·雷德威格J·E·艾斯皮林G·F·斯图恩兹W·A·沃啻特尔B·E·亨瑞
Owner EXXON RES & ENG CO
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