Propylene Yield Improvement via Aromatic Extraction in Methanol Conversion
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Solution Overview
Problem
Existing processes for producing C2-C4 olefins, particularly propylene, from methanol and dimethyl ether, suffer from low yields due to the removal of gasoline-hydrocarbon-rich fractions and the negative impact of aromatics recycling, leading to reduced methanol availability and increased costs.
Innovation Solution
The process involves separating aromatics from the C5+ gasoline hydrocarbon mixture, returning the largely aromatics-free stream to the reactor, and producing a valuable aromatics stream, with less than 5% aromatics by weight in the recycling stream, to enhance propylene yield and reduce costs by using adiabatic reaction conditions and multiple series-connected zeolite catalyst reactors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the gasoline-hydrocarbon-rich fraction is removed from the process, then the propylene yield is improved, but the process loses valuable hydrocarbon resources and reduces overall productivity
Solution Approach 1:
The patent applies the discarding and recovering principle by separating aromatics from the gasoline-hydrocarbon-rich fraction and recovering them as a valuable product stream. Instead of discarding the entire fraction or recycling all components, the process selectively recovers aromatics through a second separation device, while the aromatics-free stream is returned to the reactor. This resolves the contradiction by recovering valuable resources that would otherwise be wasted, thereby improving overall productivity while maintaining propylene yield.
2Quantity of substance
If aromatics are recycled back to the reactor, then the liquid product is fully utilized, but aromatics consume methanol through alkylation reactions reducing propylene yield
Solution Approach 1:
The patent applies the taking out (extraction) principle by removing aromatics from the recycling stream through a second separation device before returning the gasoline fraction to the reactor. This extraction of aromatics prevents them from consuming methanol through alkylation reactions, thereby protecting propylene yield while still allowing the aromatics-free stream to be fully utilized in the reactor.
Solution Approach 2:
The process discards aromatics from the recycling loop and recovers them as a separate valuable product stream. This prevents the harmful effect of aromatics consuming methanol while maintaining the beneficial utilization of the gasoline fraction, resolving the contradiction between liquid product utilization and propylene yield.
3Measurement precision
If a second separation device is added to separate aromatics, then propylene yield is improved, but the device complexity and process costs increase
Solution Approach 1:
The patent introduces a second separation device that extracts aromatics from the gasoline-hydrocarbon-rich fraction. While this increases device complexity, it enables the dual benefit of improving propylene yield and recovering valuable aromatics as a separate product stream. The complexity is justified by the significant improvement in propylene yield and the creation of an additional valuable product.
Solution Approach 2:
The second separation device serves multiple functions: it removes aromatics to protect propylene yield, recovers valuable aromatics as a separate product stream, and enables the gasoline fraction to be fully recycled. This multi-functionality justifies the added complexity by delivering multiple benefits from a single additional unit.
4Stability of the object's composition
If the process operates isothermally with vacuum conditions, then reaction control is improved, but energy consumption and operating costs increase significantly
Solution Approach 1:
The patent changes the operating parameters from isothermal vacuum conditions to adiabatic atmospheric pressure operation. This parameter change significantly reduces energy consumption and operating costs while still achieving good reaction control through the use of shape-selective zeolite catalysts and optimized reaction conditions. The adiabatic operation eliminates the need for complex temperature control systems and vacuum equipment.
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 propylene yield by 6% and produces a valuable aromatics stream, while reducing the aromatics content in the gasoline product, improving overall process efficiency and economic value.
Implementation Method 1
the educt mixture is converted into a catalyst in at least one reactor A reaction mixture comprising low molecular weight olefins and gasoline hydrocarbons is implemented
Implementation Method 2
a reaction mixture comprising low molecular weight olefins and gasoline hydrocarbons is implemented, which is separated in a first separation device into a mixture rich in C 5- olefins, a mixture rich in C 5+ gasoline hydrocarbons and an aqueous phase
Implementation Method 3
using adiabatic reaction conditions and multiple series-connected zeolite catalyst reactors
Data Source
AI summary
The invention relates to producing C2-C4-olefins, in particular propylene, from an educt mixture containing water vapour and methanol and/or dimethyl ether, wherein the inventive method consists in transforming the educt mixture on a catalyst in a reactor into a reaction mixture containing low-molecular olefins and gasoline hydrocarbons, in separating said mixture in a first separation device into an olefin C5-rich mixture, a C5+- gasoline hydrocarbon-rich mixture and into a gaseous phase. In order to increase a propylene yield, the C5+- gasoline hydrocarbon-rich mixture is directed to a second separation device, wherein aromatics contained in the mixture are separated, and residue flow which is substantially aromatic-free is redirected at least partially to the reactor.