Hydrocarbon Cracking with Metathesis for Propene Yield
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Solution Overview
Problem
Conventional hydrocarbon cracking systems face challenges in achieving high selectivity and yield of propene and ethylene, often producing larger C5+ hydrocarbons that reduce the efficiency of these olefins production, and are limited by the use of specific feedstocks like naphtha streams or gas condensate streams.
Innovation Solution
A system integrating a hydrocarbon cracking process with a dual catalyst metathesis process, including a selective hydrogenation and isomerization unit (SHIU) to convert C4 effluents, ensuring a higher concentration of 2-butenes relative to 1-butene and isobutene, which shifts the metathesis process towards greater propene production and less ethylene production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional hydrocarbon cracking systems are used, then olefins such as ethylene and propene can be produced, but substantial amounts of C5+ hydrocarbons are also produced which reduce the selectivity and yield of propene and ethylene
Solution Approach 1:
The process separates the cracking effluent into different fractions (C2-C4 fraction and C5+ fraction) using a fractionation system. The C2-C4 fraction containing propene and ethylene is isolated and further processed, while the C5+ fraction is removed as a separate stream, preventing it from reducing the selectivity and yield of the desired olefins.
Solution Approach 2:
The harmful C5+ hydrocarbon fraction is extracted and removed from the cracking effluent through fractionation. This extracted fraction is then processed separately in a second cracking unit, allowing the main stream to proceed with high selectivity for propene and ethylene production without contamination from C5+ compounds.
2Productivity
If high-severity fluidized catalytic cracking (HS-FCC) systems are used to increase propene yield, then conversion levels for petroleum streams are enhanced, but the process still produces C5+ compounds that reduce overall selectivity
Solution Approach 1:
The cracking process is segmented into two separate units with different functions. The first HS-FCC unit operates at high conversion levels to maximize propene production. The effluent is then fractionated, and the C5+ fraction is separated and processed in a second cracking unit, allowing the first unit to maintain high selectivity while the second unit handles the C5+ compounds that would otherwise reduce overall selectivity.
3Productivity
If conventional cracking processes are used, then propene can be produced from limited feedstocks, but the process is restricted to specific feedstocks like naphtha streams or gas condensate streams
Solution Approach 1:
The system is designed with multi-functionality to handle various hydrocarbon feedstocks including naphtha, gas condensate, and other petroleum streams. The fractionation system can process different feed compositions, and the second cracking unit can convert C5+ fractions from different feed sources into valuable products, making the overall process adaptable to a broader range of feedstocks while maintaining propene production efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This integrated system enhances the yield and selectivity of propene by optimizing the ratio of butene isomers, allowing for increased production of propene from a broader range of hydrocarbon feedstocks, including naphtha and gas condensate streams, compared to conventional processes.
Implementation Method 1
a selective hydrogenation catalyst and is operable to convert 1,3-butadiene in the C4 effluent to 1-butene
Implementation Method 2
isomerize at least a portion of 1-butene in the C4 effluent or produced from hydrogenation of 1,3-butadiene to 2-butenes
Implementation Method 3
a metathesis catalyst and a cracking catalyst downstream of the metathesis catalyst to produce a metathesis reaction effluent comprising at least propene. The contacting with the metathesis catalyst may cause metathesis of at least a portion of the mixed butenes to ethylene and propene through metathesis
Implementation Method 4
the contacting with the cracking catalyst may cause at least a portion of C5+ olefins produced through metathesis to undergo cracking reactions to produce propene, ethylene, or both
Data Source
AI summary
Processes for producing olefins include passing a hydrocarbon feed to a hydrocarbon cracking unit that cracks the hydrocarbon feed to produce a cracker effluent, passing the cracker effluent to a cracker effluent separation system that separates the cracker effluent to produce at least a cracking C4 effluent including 1-butene, 1,3-butadiene, and isobutene, passing the cracking C4 effluent to an SHIU that contacts the cracking C4 effluent with hydrogen in the presence of a selective hydrogenation catalyst to produce a hydrogenation effluent having a 2-butenes concentration greater than or equal to the sum of the concentrations of 1-butene and isobutene. The processes include passing the hydrogenation effluent to a metathesis unit that contacts the hydrogenation effluent with a metathesis catalyst and a cracking catalyst downstream of the metathesis catalyst to produce a metathesis reaction effluent comprising at least propene.