Hydrogen Selective Membranes for Olefin Production
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Solution Overview
Problem
Dehydrogenation, dehydrocyclization, and dehydrocyclodimerization processes are limited by thermodynamic constraints, including endothermic reactions and hydrogen formation, which restrict olefin and aromatics yields and throughput due to heat introduction and pressure limitations, and existing solutions like catalytic membrane reactors increase complexity and cost.
Innovation Solution
Incorporating small pore microporous inorganic non-metallic membranes into dehydrogenation processes to separate hydrogen from hydrocarbon streams at elevated temperatures, allowing for controlled hydrogen removal and maintaining reaction conditions during separation, thereby increasing conversion and reducing capital and operating costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hydrogen is removed from the reaction mixture to improve conversion and throughput, then olefin and aromatics production increases, but the process complexity and cost increase due to additional separation equipment
Solution Approach 1:
The patent combines the dehydrogenation reaction and hydrogen separation functions into a single integrated membrane reactor. The catalytic membrane performs both the dehydrogenation reaction and simultaneously separates hydrogen from the reaction mixture, eliminating the need for separate reaction and separation units. This integration resolves the technical contradiction by achieving high productivity through continuous hydrogen removal while avoiding the process complexity of multiple separate equipment units.
2Reliability
If the membrane separation unit is operated at lower temperatures (below 500°C) to protect membrane stability, then membrane lifespan is extended, but additional interstage heating is required which increases energy consumption and thermal cracking
Solution Approach 1:
The patent employs high-temperature stable inorganic membranes (such as zeolites or ceramic membranes) that can withstand dehydrogenation reaction temperatures of 500-750°C. This parameter change in membrane material properties allows the membrane separation unit to operate at elevated temperatures, eliminating the need for cooling and subsequent reheating, thereby reducing energy consumption and minimizing thermal cracking while maintaining membrane stability through material selection.
3Productivity
If dehydrogenation is performed at higher temperatures (500-750°C) to achieve viable conversion, then conversion per pass increases, but thermal cracking and coking increase which reduces selectivity
Solution Approach 1:
The patent extracts hydrogen from the reaction mixture continuously through the membrane separation function. By removing hydrogen as it is formed during dehydrogenation, the equilibrium is shifted toward higher olefin conversion without requiring excessively high temperatures. This extraction of the product (hydrogen) allows the system to achieve high conversion per pass at moderate temperatures, thereby reducing thermal cracking and coking while maintaining high productivity.
4Adaptability or versatility
If separate units are used for dehydrogenation and membrane separation to allow independent control, then process flexibility is improved, but capital cost and operating cost increase due to additional equipment
Solution Approach 1:
The patent merges the dehydrogenation reactor and membrane separation unit into a single integrated membrane reactor. The catalytic membrane is installed within the reactor, allowing simultaneous reaction and separation functions. This integration reduces capital cost by eliminating separate equipment while maintaining process flexibility through the ability to independently control reaction conditions and membrane separation parameters within the unified system.
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 significantly enhances olefin and aromatics production throughput, reduces compression requirements, and lowers costs by maintaining reaction conditions during separation, thus improving the economic viability of the processes.
Implementation Method 1
separating the first reaction mixture in a first membrane separation zone using a first small pore microporous inorganic non-metallic membrane with a pore size of less than or equal to 4 Å at a temperature of greater than 500° C. into a first permeate comprising hydrogen
Data Source
AI summary
A catalytic reactor and membrane separation process is described in which a hydrocarbon feed comprising at least one alkane or alkylaromatic is at least one of dehydrogenated, dehydrocyclized, or dehydrocyclodimerized in first and second reactors. The reaction mixtures are separated in first and second membrane separation zones using first and second small pore microporous inorganic non-metallic membrane with a pore size of less than or equal to 4 Å at a temperature of greater than 500° C. The membrane separation zones are separate from the reactors.