Carrier Pretreatment for Olefin Epoxidation Catalyst Stability
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Solution Overview
Problem
Existing olefin epoxidation catalysts face performance decline due to impurities in the carrier, leading to reduced selectivity and activity over time, necessitating increased reaction temperatures that are not always feasible.
Innovation Solution
A process involving the treatment of the carrier with a low-concentration salt solution to remove impurities such as sodium and other soluble species, improving catalyst stability and selectivity by using a salt solution with specific anions and cations at controlled temperatures and concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the reaction temperature is increased to maintain olefin oxide production as the catalyst ages, then the productivity is maintained, but the selectivity deteriorates
Solution Approach 1:
The carrier is pretreated with low-concentration salt solutions (0.01-0.05 M) containing specific anions (acetate, nitrate, perchlorate, borate, fluoride, chloride, bromide, iodide) before catalyst preparation. This preliminary treatment removes harmful ionizable species and creates a more stable surface environment, preventing the need for temperature increases during catalyst operation and maintaining both productivity and selectivity over time.
Solution Approach 2:
The invention changes the chemical composition parameters of the carrier surface by controlling the concentration and type of salt anions during pretreatment. By optimizing the salt concentration (low range: 0.01-0.05 M) and selecting specific anions that do not form strong surface complexes, the carrier surface properties are modified to enhance catalyst stability and maintain selectivity at constant operating temperatures.
2Reliability
If conventional carrier pretreatment with high-concentration salt solutions is used, then impurity removal is improved, but catalyst stability deteriorates due to formation of strong surface complexes
Solution Approach 1:
The invention inverts the conventional approach by using low-concentration salt solutions (0.01-0.05 M) instead of high-concentration solutions. This parameter change prevents the formation of strong surface complexes while still effectively removing harmful ionizable species. The low concentration ensures that salt anions do not strongly adsorb to the carrier surface, thereby improving catalyst stability without creating harmful surface complexes.
Solution Approach 2:
The invention converts the potential harm of salt anion adsorption into a benefit by using low concentrations of specific anions (acetate, nitrate, perchlorate, borate, fluoride, chloride, bromide, iodide) that have moderate adsorption strengths. These anions effectively remove harmful species during pretreatment but do not form persistent strong complexes that would destabilize the catalyst, thus turning a potential harmful effect into a beneficial cleaning action.
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 treatment process enhances catalyst stability and selectivity, allowing for prolonged operation at optimal conditions without the need for excessive temperature increases, thereby improving process efficiency and product yield.
Implementation Method 1
contacting the carrier, or the precursor thereof, with a treatment solution comprising a salt in a concentration of less than 0.015 molar at a temperature of greater than 40° C.
Implementation Method 2
the salt comprises an anion selected from halides, organic anions, inorganic carboxylates, oxyanions of elements from Groups IIIB to VIIB, Group IIIA, and Groups VA to VIIA of the Periodic Table of Elements, cyanate, isocyanate, cyanide
Data Source
AI summary
A process for treating a carrier, or a precursor thereof, to at least partly remove impurities from the carrier, or the precursor thereof, comprising: contacting the carrier, or the precursor thereof, with a treatment solution comprising a salt in a concentration of at most 0.05 molar, wherein the salt comprises a cation and an anion, and wherein the cation is selected from ammonium, phosphonium, organic cations and combinations thereof, and wherein the anion is selected from organic anions, inorganic carboxylates, oxyanions of elements from Groups IIIA through VIIA of the Periodic Table of Elements, and combinations thereof; and separating at least part of the treatment solution from the carrier, or the precursor thereof.