Non-Linear Primary Alcohol Dehydration with Water-Injected FER/MFS Zeolite
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Solution Overview
Problem
Existing processes for producing alkenes from primary monoalcohols, particularly isobutanol, face challenges in achieving high conversion rates and selectivity for desired products like isobutene, with catalyst degradation and formation of undesired by-products due to water content and thermal instability.
Innovation Solution
A process utilizing a shaped catalyst based on zeolites with 8-oxygen ring channels and a silica binder, operating in the gas phase with controlled water content in the feed, achieves high alcohol conversion and selectivity for linear alkenes by preventing thermal degradation and reducing non-selective coke formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If water is added to the feed to improve productivity and isobutene selectivity, then conversion stability and selectivity improve, but catalyst degradation and formation of undesired by-products occur due to thermal instability
Solution Approach 1:
The patent optimizes the water content parameter in the feed to a specific range (5-15 wt%) to achieve the desired balance between conversion stability and catalyst stability. This parameter optimization allows the process to maintain high productivity while minimizing catalyst degradation and by-product formation.
Solution Approach 2:
The patent employs a composite catalyst system comprising a zeolite component (such as ZSM-5, ZSM-23, or Theta-1) combined with a binder material. This composite structure enhances the catalyst's thermal stability and resistance to degradation while maintaining its catalytic activity for alcohol conversion.
2Productivity
If high conversion rates are achieved, then productivity increases, but selectivity for desired products decreases due to formation of undesired by-products
Solution Approach 1:
The patent utilizes zeolite catalysts with specific pore structures (8-membered ring or 10-membered ring channels) that provide shape selectivity. The local geometric constraints within the zeolite pores favor the formation of desired linear alkene products while suppressing the formation of undesired by-products, thereby maintaining high selectivity even at high conversion rates.
Solution Approach 2:
The patent optimizes operating parameters including temperature (200-400°C), water content (5-15 wt%), and space velocity to achieve the optimal balance between conversion rate and product selectivity. These parameter adjustments ensure high alcohol conversion while maximizing selectivity for desired linear alkene products.
3Quantity of substance
If water content in feed is increased to prevent feed from drying out, then economic advantage is achieved, but isobutene selectivity compared to total butenes does not improve
Solution Approach 1:
The patent identifies and optimizes the water content parameter to a specific range (5-15 wt%) where the beneficial effect of preventing feed drying is maximized while the negative effect on isobutene selectivity is minimized. Within this optimized range, the process achieves both economic advantage and acceptable product selectivity.
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 achieves over 98% alcohol conversion and selectivity for linear alkenes greater than 97%, with improved thermal stability and reduced formation of undesired by-products, particularly at high temperatures.
Implementation Method 1
The invention relates to an isomerizing dehydration process for a feed comprising a primary monoalcohol... in the presence of a catalyst comprising at least one binder based on silica and at least one zeolite
Implementation Method 2
The addition of water... has the effect of improving productivity and isobutene selectivity... The process achieves over 98% alcohol conversion and selectivity for linear alkenes greater than 97%, with improved thermal stability
Data Source
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AI summary
The invention concerns a method for the isomerisation dehydration of a feedstock comprising a primary monoalcohol, alone or in a mixture, of formula R-CH2-OH, in which R is a non-linear alkyl radical of general formula CnH2n+1 where n is an integer between 3 and 20, said method taking place - in the gaseous phase at a weighted average temperature of between 275°C and 400°C, at a pressure of between 0.3 MPa and 1 MPa and at a WHSV (weight hourly space velocity) of between 5 and 10 h-1, - in the presence of a catalyst comprising at least one silica-based binder and at least one zeolite having at least a series of channels of which the opening is defined by an 8-oxygen ring (8MR), - method in which vaporised feedstock entering the reactor has a weight content of water of 4% to 35%.