Zeolite Molded Article Mechanical Strength via pH-Controlled Washing
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Solution Overview
Problem
Conventional methods for producing zeolite molded articles lack satisfactory mechanical strength, which affects their performance as catalysts in producing ε-caprolactam through the Beckmann rearrangement reaction of cyclohexanone oxime.
Innovation Solution
A method involving hydrothermal synthesis of a mixture containing a silicon compound, water, and quaternary ammonium hydroxide, followed by filtration, washing, and calcination, to produce a zeolite molded article with improved mechanical strength, utilizing a pentasil-type zeolite structure like silicalite-1, and subsequent treatment with water vapor to enhance mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional hydrothermal synthesis method is used to produce zeolite molded article, then the production process is simple, but the mechanical strength of the zeolite molded article is not satisfactory
Solution Approach 1:
The patent applies preliminary action by performing washing steps before molding to remove quaternary ammonium hydroxide from the zeolite crystals. This pre-treatment ensures that the binding agents can properly adhere to the zeolite surface during molding, resulting in improved mechanical strength of the final molded article. The washing and drying steps are conducted before the molding operation to prepare the zeolite particles for optimal bonding.
Solution Approach 2:
The patent applies parameter changes by controlling the pH of the washing water and the washing conditions to optimize the removal of quaternary ammonium hydroxide while maintaining zeolite crystal integrity. By adjusting washing parameters (water-to-zeolite ratio, washing time, temperature), the method achieves sufficient removal of ammonium hydroxide to improve mechanical strength without requiring overly complex processing equipment or procedures.
2Reliability
If zeolite molded article with high mechanical strength is produced, then the catalytic performance in Beckmann rearrangement reaction is improved, but additional washing and drying steps are required
Solution Approach 1:
The washing and drying steps are performed as preliminary actions before molding to ensure proper adhesion of binding agents and achieve high mechanical strength. This sequencing allows the zeolite particles to be optimally prepared for molding, resulting in molded articles with sufficient mechanical strength that maintain high catalytic performance and selectivity in Beckmann rearrangement reactions without requiring post-processing modifications.
Solution Approach 2:
By optimizing washing parameters (using water with controlled pH, appropriate water-to-zeolite ratios, and controlled washing durations), the method achieves effective removal of quaternary ammonium hydroxide that would otherwise interfere with binding agent adhesion. This parameter optimization ensures high mechanical strength and reliable catalytic performance while keeping the washing process efficient and not excessively time-consuming.
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 method results in a zeolite molded article with excellent mechanical strength and high selectivity for ε-caprolactam production in the Beckmann rearrangement reaction, achieving good conversion rates of cyclohexanone oxime.
Implementation Method 1
subjecting a mixture of a silicon compound, water, and a quaternary ammonium hydroxide to a hydrothermal synthesis reaction
Implementation Method 2
contacting the calcined product with water vapor to improve the mechanical strength of the zeolite molded article
Implementation Method 3
using the zeolite molded article as a catalyst for producing ε-caprolactam by subjecting cyclohexanone oxime to a Beckmann rearrangement reaction
Data Source
AI summary
The present invention provides a method for producing a zeolite molded article having an excellent mechanical strength. The method for producing a zeolite molded article according to the present invention comprises the following steps (1) to (5) : (1) subjecting a mixture containing a silicon compound, water, and a quaternary ammonium hydroxide to a hydrothermal synthesis reaction; (2) filtering the reaction mixture containing crystals obtained in the step (1) to separate it into a concentrate containing crystals and a filtrate; (3) washing the concentrate containing crystals obtained in the step (2) with water until the pH at 25°C of the washed solution obtained by washing becomes 8.5 to 9.5; (4) molding the crystals obtained in the step (3); and (5) calcining the molded article obtained in the step (4). By using as a catalyst the zeolite molded article produced by such a method, ε-caprolactam is produced by Beckmann rearrangement reaction of cyclohexanone oxime in a gaseous phase.