Propene Epoxidation Methanol Washing for Titanium Zeolite Protection
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Solution Overview
Problem
Catalyst breakage occurs in fixed bed reactors during the epoxidation of propene with hydrogen peroxide using a shaped titanium zeolite catalyst, particularly due to the regeneration of acidic ion exchange resins used in the methanol recycling process.
Innovation Solution
The process involves periodically regenerating the acidic ion exchange resin by passing a solution of a regenerating acid through the resin bed and then washing it with methanol until the exiting methanol reaches a pH higher than 2.0 before reuse, ensuring the resin is adequately neutralized.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the acidic ion exchange resin is regenerated by passing regenerating acid through the resin bed, then the resin is restored for continued use, but the catalyst breaksage occurs due to residual acid in the resin bed
Solution Approach 1:
The patent applies preliminary action by washing the regenerated ion exchange resin with water or dilute acid before putting it back into service. This pre-treatment step removes residual regenerating acid from the resin bed, preventing catalyst breakage that would otherwise occur when the acid-containing resin contacts the titanium zeolite catalyst in subsequent epoxidation reactions.
Solution Approach 2:
The patent uses water or dilute acid as an intermediary substance to mediate between the regenerating acid and the catalyst. This intermediary washing step transfers residual acid from the resin bed to the washing liquid, which is then discarded, thereby protecting the catalyst from direct exposure to harmful acid levels.
2Object-affected harmful factors
If the resin bed is thoroughly washed to remove residual acid, then catalyst breakage is prevented, but additional washing steps increase process time and complexity
Solution Approach 1:
The patent applies partial action by implementing a washing step that achieves sufficient acid removal without requiring complete exhaustion of all residual acid. The washing continues until the effluent pH indicates adequate neutralization, providing a practical balance between thoroughness and process efficiency, avoiding unnecessarily complex extended washing procedures.
3Reliability
If the washing step is extended to ensure complete acid removal, then catalyst integrity is maintained, but production efficiency decreases due to longer downtime
Solution Approach 1:
The patent employs feedback control by monitoring the pH of the washing effluent to determine when the washing step is sufficient. When the effluent pH reaches a predetermined threshold indicating adequate acid removal, the washing step is terminated and the resin is returned to service. This feedback mechanism prevents both under-washing (which would harm the catalyst) and over-washing (which would unnecessarily extend downtime).
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 method reduces or prevents catalyst breakage, allowing for extended operation without significant pressure drops and maintaining catalyst integrity.
Implementation Method 1
passing a solution of a regenerating acid through the resin bed to provide a regenerated bed of ion exchange resin
Implementation Method 2
washing it with methanol until the exiting methanol reaches a pH higher than 2.0
Data Source
AI summary
In a process for the epoxidation of propene, comprising reacting propene with hydrogen peroxide in the presence of a methanol solvent and a shaped titanium zeolite epoxidation catalyst in a fixed bed reactor, recovering methanol from the reaction mixture, treatment of the recovered methanol by passing it through a bed of an acidic ion exchange resin and recycling the treated methanol to the epoxidation reaction, as well as regeneration of the acidic ion exchange resin, catalyst breakage can be reduced or avoided by washing the regenerated bed of an acidic ion exchange resin with methanol until the methanol exiting the resin bed has an apparent pH higher than 1.8 before methanol treated with the acidic ion exchange resin is recycled to the epoxidation reaction.