Methanol-Ethanol Olefin Production With Flexible Recycle Splits
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Solution Overview
Problem
Existing processes for producing C2-C4 olefins from methanol struggle to vary the proportions of ethylene, propylene, and butenes in the product streams and require significant recycle streams and energy consumption.
Innovation Solution
A flexible process involving a dimethyl ether fixed bed reactor followed by an olefin fixed bed reactor, with controlled recycling and separation of hydrocarbon streams to achieve desired olefin proportions, reducing recycle stream volumes and energy demand.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If methanol is converted to C2-C4 olefins using conventional fixed bed reactors with zeolite catalysts at 480°C, then propylene production is achieved, but the proportions of ethylene, propylene, and butenes cannot be varied within wide ranges
Solution Approach 1:
The process is divided into two separate fixed bed reactor stages: a first reactor for methanol-to-dimethyl ether conversion and a second reactor for olefin production. This segmentation allows independent optimization of each stage and enables flexible control of product proportions by adjusting operating parameters in each reactor separately
Solution Approach 2:
The invention utilizes changes in temperature, pressure, and catalyst composition between the two reactor stages to control product distribution. By varying these parameters independently in each stage, wide ranges of ethylene, propylene, and butenes proportions can be achieved without increasing overall system complexity
2Productivity
If hydrocarbon recycle streams are used to increase olefin yield in MTP processes, then productivity is improved, but the volume of recycle streams and energy consumption increase significantly
Solution Approach 1:
The invention extracts and separates C2-C4 olefins from the product stream before they can be converted to heavier hydrocarbons or by-products. By removing these valuable olefins early in the process, the need for large recycle streams is eliminated, reducing both energy consumption and complexity while maintaining high productivity
Solution Approach 2:
The two-stage reactor system maintains continuous conversion of methanol to olefins with optimized residence times in each stage. This continuous action maximizes olefin yield without requiring recycle streams, as each stage is designed to perform its specific function efficiently in sequence
3Productivity
If hydrocarbon recycle streams are recycled into the MTO process to improve olefin production, then productivity increases, but the volume of recycle streams increases
Solution Approach 1:
C2-C4 olefins are extracted and separated from the reaction products in each stage, preventing them from being converted further or requiring recycle. This extraction approach maintains high olefin production volumes while minimizing the quantity of recycle streams needed
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
The process allows for varying ethylene, propylene, and butenes proportions in the product streams and significantly reduces recycle stream volumes and energy consumption by optimizing catalyst usage and recycling strategies.
Implementation Method 1
feeding a feed stream A comprising methanol, with or without ethanol, into a dimethyl ether fixed bed reactor and catalytically converting methanol to dimethyl ether
Implementation Method 2
mixing stream A1 with at least one hydrocarbon recycle stream R comprising C2-C6 hydrocarbons and catalytically converting it in an olefin fixed bed reactor to a crude product stream B comprising C2-C4 olefins
Implementation Method 3
cooling crude product stream B to obtain a hydrocarbon crude product stream C
Data Source
AI summary
The invention relates to a method for producing C2-C4 olefins from methanol and ethanol, said method having the steps of: A) feeding a methanol- and optionally ethanol-containing feed flow A into a dimethyl ether fixed-bed reactor and catalytically reacting methanol to form dimethyl ether, wherein a product flow A1 containing dimethyl ether, methanol, ethanol and steam is obtained; B) mixing the flow A1 with at least one hydrocarbon return flow R containing C2-C6 hydrocarbons and catalytically reacting the mixture in an olefin fixed-bed reactor to form a raw product flow B containing C2-C4 olefins, C5-C6 hydrocarbon and C7+ hydrocarbons; C) cooling the raw product flow B, wherein a hydrocarbon raw product flow C is obtained; D) separating the hydrocarbon raw product flow C in a propylene-containing value product flow, optionally an ethylene-containing value product flow, a butene-containing value product flow, at least one C5-C6 hydrocarbon-containing return flow and at least one C6+ hydrocarbon-containing auxiliary product flow; E) returning a part of the C2-C4 olefins and at least a part of the C5-C6 hydrocarbons as one or more hydrocarbon return flows in step B); F) recovering a propylene-containing value product flow, an ethylene-containing value product flow and optionally a butene-containing value product flow; G) discharging the C6+ hydrocarbon-containing auxiliary product flow; characterised in that the flow A, in relation to methanol and ethanol, contains <1 wt. % or 30 to 50 wt. % ethanol, wherein, in relation to 100 wt. % of the C2-C4 olefins recovered as value products, 30 to 60 wt. % ethylene, 30 to 60 wt. % propylene, and 0 to 30 wt. % butene are recovered as value products, and, in relation to the C2-C4 olefins contained in the raw product flow B, 0 to 40% of the ethylene, 40 to 90% of the propylene, and 0 to 100% of the butene are fed back in step B), or the flow A, in relation to methanol and ethanol, contains 1 to 30 wt. % ethanol, wherein, in relation to 100 wt. % of the C2-C4 olefins recovered as value products, 0 to 20 wt. % ethylene, 70 to 100 wt. % propylene, and 1 to 20 wt. % butene are recovered as value products, and, in relation to the 40 C2-C4 olefins contained in the raw product flow B, 0 to 100% of the ethylene, 0 to 20% of the propylene and 40 to 100% of the butene are fed back in step B).