Cyclohexane Production via Benzene Hydrogenation and MCP Isomerization
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Solution Overview
Problem
The existing processes for producing cyclohexane from hydrocarbon mixtures containing benzene, methylcyclopentane, and dimethylpentane face challenges in separating cyclohexane from other components, particularly due to the similar boiling points of cyclohexane and dimethylpentane, leading to complex and costly separation processes.
Innovation Solution
A process involving the hydrogenation of benzene to cyclohexane and isomerization of methylcyclopentane to cyclohexane, with preliminary separation of dimethylpentane and optional removal of low boilers, using acidic ionic liquids as catalysts, to facilitate the recovery of cyclohexane and reduce the complexity of subsequent separation steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If cyclohexane is produced by hydrogenation of benzene from pure benzene feedstock, then high purity cyclohexane is obtained, but benzene availability is reduced and production costs increase due to competition with other benzene uses
Solution Approach 1:
The invention changes the feedstock parameter from pure benzene to hydrocarbon mixtures containing benzene, methylcyclopentane, and dimethylpentane. By accepting mixed feedstock and implementing a multi-step process with selective separation and dual-path conversion (hydrogenation of benzene to cyclohexane, isomerization of methylcyclopentane to cyclohexane), the process maintains high cyclohexane purity while utilizing available benzene more efficiently and reducing competition with other benzene uses.
2Manufacturing precision
If dimethylpentane is separated from cyclohexane after isomerization, then pure cyclohexane is obtained, but the separation process becomes complex and expensive due to similar boiling points
Solution Approach 1:
The invention applies preliminary separation of dimethylpentane from the hydrocarbon mixture before the isomerization step. By removing dimethylpentane early in the process (before methylcyclopentane is converted to cyclohexane), the subsequent separation burden is significantly reduced. The isomerization then converts methylcyclopentane to cyclohexane without generating new dimethylpentane, simplifying the final purification step.
Solution Approach 2:
The invention segments the cyclohexane production process into distinct stages: (1) preliminary separation of dimethylpentane, (2) hydrogenation of benzene to cyclohexane, (3) isomerization of methylcyclopentane to cyclohexane, and (4) final separation of cyclohexane from unreacted components. This segmentation allows each stage to be optimized independently, reducing overall process complexity.
3Manufacturing precision
If complete separation of dimethylpentane is performed before isomerization, then cyclohexane purity is improved, but energy consumption and equipment costs increase
Solution Approach 1:
The invention applies partial separation of dimethylpentane before isomerization rather than complete separation. The preliminary separation removes a sufficient portion of dimethylpentane to prevent it from interfering with the isomerization process and to simplify downstream separation, without performing exhaustive separation that would consume excessive energy. The remaining small amounts are handled efficiently in the final purification step.
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 process enables the production of high-purity cyclohexane with reduced energy consumption and equipment costs by pre-separating dimethylpentane before isomerization, thereby simplifying the separation of cyclohexane and minimizing the amount of dimethylpentane in the final product.
Implementation Method 1
a) Hydrogenation of a hydrocarbon mixture (HM1), where (HM1) i) benzene
Implementation Method 2
e) isomerization of the hydrocarbon mixture (HM2a) or optionally the hydrocarbon mixture (HM2b) in the presence of a catalyst to give a hydrocarbon mixture (HM3) which has an increased amount of cyclohexane
Implementation Method 3
c) separating a stream (S1) containing DMP and cyclohexane from the hydrocarbon mixture (KG2) via an outlet of the rectification column (D1)
Data Source
Figure 1~2
Figure 3~4
AI summary
The present invention concerns a process for preparing cyclohexane from methylcyclopentane (MCP) and benzene. In the present invention, MCP and benzene are constituents of a hydrocarbon mixture (KG1) also including dimethylpentanes (DMP), optionally cyclohexane and optionally at least one compound (low boiler) selected from non-cyclic C5-C6 alkanes and cyclopentane. First, benzene is reacted in a hydrogenation step to give cyclohexane (present in the hydrocarbon mixture (KG2)), while MCP is isomerized to cyclohexane in the presence of a catalyst, preferably an acidic ionic liquid. After the hydrogenation but before the isomerization, the dimethylpentanes (DMP) are removed, and initially the cyclohexane present in the hydrocarbon mixture (KG2) is removed together with DMP. This pre-isomerization cyclohexane can be freed of DMP again in a downstream step of rectification and isolated and/or returned to the cyclohexane preparation process. If the hydrocarbon mixture (KG1) comprises low boilers, they can be removed between DMP removal and MCP isomerization. Following the isomerization comes the isolation of the cyclohexane, with optional recycling of unisomerized MCP and any low boilers. The hydrocarbon mixture (KG1) preferably includes cyclohexane and/or low boilers, and so low-boiler removal between DMP removal before isomerization is a preferred operation. Also preferred is an additional removal of DMP from the cyclohexane - that is, the cyclohexane fraction arising from the benzene hydrogenation and possibly forming part of the starting mixture (KG1) is isolated and hence recovered.