Isomerization Zone Yield via C6 Removal and Low H2 Ratio
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Solution Overview
Problem
Current processes for converting iso-paraffins to normal paraffins in an isomerization zone have limited conversion rates, leading to high methane formation and increased recycle streams, utility costs, and difficulty in separating undesirable hydrocarbons like naphthenes and aromatics from the feed stream.
Innovation Solution
Removing C6 cyclic hydrocarbons from the feed stream and maintaining a hydrogen to hydrocarbon molar ratio of less than 0.2 in the isomerization zone at elevated temperatures, such as at least 176°C, to enhance the conversion of iC5 and iC6 hydrocarbons to normal paraffins while minimizing methane production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the temperature of the isomerization zone is increased to increase conversion rates, then the conversion of iso-paraffins to normal paraffins is improved, but the cracking of paraffins to lighter hydrocarbons and formation of methane increases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the temperature range (150-200°C) and hydrogen to hydrocarbon molar ratio (0.05-0.2) in the isomerization zone. These optimized parameters enable sufficient conversion of iso-paraffins to normal paraffins while preventing excessive cracking reactions that produce methane, thus resolving the contradiction between conversion rate and methane formation.
2Productivity
If the liquid hourly space velocity is lowered to increase conversion rates, then the conversion of iso-paraffins to normal paraffins is improved, but the residence time increases leading to more cracking reactions and methane production
Solution Approach 1:
The patent optimizes the liquid hourly space velocity parameter to fall within the range of 0.5-5 hr⁻¹. This optimized parameter allows adequate residence time for isomerization reactions to proceed effectively while preventing excessive residence time that would lead to cracking reactions and methane formation, thus resolving the contradiction between conversion rate and residence time.
3Productivity
If large recycle streams are used to achieve full conversion of iso-paraffins, then the conversion completeness is improved, but the device complexity and utility costs increase
Solution Approach 1:
The patent changes the operating parameters (temperature: 150-200°C, hydrogen to hydrocarbon ratio: 0.05-0.2, LHSV: 0.5-5 hr⁻¹) to achieve high conversion completeness in a single pass, eliminating or reducing the need for large recycle streams. This resolves the contradiction between conversion completeness and device complexity by achieving the same conversion target with simpler process configuration.
4Adaptability or versatility
If C6 cyclic hydrocarbons are present in the feed stream, then the feedstock versatility is maintained, but the separation of undesirable hydrocarbons becomes more difficult and conversion efficiency decreases
Solution Approach 1:
The patent applies extraction by removing C6 cyclic hydrocarbons from the feed stream before it enters the isomerization zone. This selective removal eliminates the interference that C6 cyclic hydrocarbons cause in the isomerization reaction, thereby improving the conversion efficiency of iso-paraffins while maintaining the ability to process various feedstock types through selective separation.
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 approach increases the yield of normal paraffins to at least 20% and reduces methane to less than 1.0% in the product stream, achieving a favorable ratio of normal paraffins to methane, thus reducing recycle streams and operational costs.
Implementation Method 1
In the isomerization zone, the non-normal paraffins are converted, in the presence of a catalyst, into normal paraffins
Implementation Method 2
The great bulk of the ethylene consumed in the production of the plastics and petrochemicals such as polyethylene is produced by the thermal cracking of higher molecular weight hydrocarbons
Implementation Method 3
Steam is usually mixed with the feed stream to the cracking reactor to reduce the hydrocarbon partial pressure and enhance olefin yield
Data Source
AI summary
A process for increasing a yield of an isomerization zone by removing at least a portion of the C6 cyclic hydrocarbons from a stream prior to it being passed into the isomerization zone. Additionally, disproportionation reaction selectivity is also increased, producing valuable C3 hydrocarbons and C4 hydrocarbons. Also, a higher ring opening conversion of C5 cyclic hydrocarbons is observed. The isomerization zone may have an average operating temperature of at least 176° C. and an outlet molar ratio of hydrogen to hydrocarbon feed in the isomerization zone is less than about 0.2.