Propylene Yield Enhancement via Propane Dehydrogenation
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Solution Overview
Problem
Current processes for producing propylene from oxygenates, such as methanol and dimethyl ether, have a propylene yield below 70 mol%, limiting economic efficiency due to unused by-products and undesirable alkylation reactions within the MTP reactor.
Innovation Solution
A process that includes heterogeneously catalyzed conversion of oxygenates to propylene, followed by physical separation and recycling of by-products, with the addition of a propane dehydrogenation stage to further convert propane into propylene, enhancing yield and utilizing light by-products for propylene production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If MTP process is used to convert oxygenates to propylene, then propylene production is achieved, but propylene yield is limited to below 70 mol% due to by-product formation
Solution Approach 1:
The patent recovers propane from the separation train (which would otherwise be discarded as by-product) and feeds it to a propane dehydrogenation unit to convert it to propylene. This transforms waste material into valuable product, increasing overall propylene yield while reducing substance loss.
Solution Approach 2:
The patent introduces a propane dehydrogenation step that changes the chemical composition parameters of the process by converting propane to propylene through dehydrogenation reaction. This parameter change enables additional propylene production from by-products.
2Productivity
If MTP reactor operates to produce propylene, then short-chain olefins are produced, but undesirable alkylation reactions occur consuming methanol
Solution Approach 1:
The patent extracts propane from the product mixture in the separation train before it can undergo unwanted alkylation reactions in the MTP reactor. By removing propane early and processing it separately in a dehydrogenation unit, the harmful alkylation side-reactions are prevented and methanol is preserved for productive propylene synthesis.
3Productivity
If by-products are recycled to MTP reactor to increase propylene yield, then conversion efficiency improves, but alkylation reactions increase consuming more methanol
Solution Approach 1:
The patent converts the harmful effect of propane (which causes alkylation reactions when recycled) into a benefit by directing it to a propane dehydrogenation unit. This transforms the problematic by-product into additional propylene feedstock, turning a harmful recycling pathway into a beneficial one that increases propylene yield without methanol loss.
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
Significantly increases propylene yield by effectively recycling and utilizing by-products, improving economic efficiency and reducing undesirable reactions within the MTP reactor.
Implementation Method 1
heterogeneously catalyzed conversion of an educt mixture comprising water vapor and oxygenates, such as methanol and/or dimethyl ether, under oxygenate conversion conditions in an olefin synthesis reactor
Implementation Method 2
separation of the primary product using physical separation processes into one C 5- fraction, a C 5+ fraction and an aqueous phase
Implementation Method 3
separation of the C 5+ fraction by multistage distillation, comprising an entbutaner
Implementation Method 4
compression of the C 5 fraction in a first compressor
Implementation Method 5
separation of the compressed C 5 fraction in a first phase separation stage into a first gaseous compressor product and a first liquid compressor product
Implementation Method 6
feeding the first gaseous compressor product to a depropaner, whereby a C 3- fraction is obtained as the top product of the depropaner and a C 4 fraction is obtained as the bottom product
Data Source
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AI summary
A process and plant for the production of olefins from oxygenates such as methanol and/or dimethyl ether are proposed. In this process, the oxygenates are first converted in an olefin synthesis reactor to a primary product containing propylene, other olefins, paraffins, and aromatics. The primary product is then separated into hydrocarbon fractions of varying carbon chain lengths, yielding short-chain olefins, particularly propylene as the target product, as well as a propane fraction. This propane fraction is then reacted in a propane dehydrogenation stage, producing further propylene, which is also added to the propylene target product stream.