High-Purity Fluoromethane via Low-Chlorine Alumina Catalyst
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Solution Overview
Problem
The existing methods for producing fluoromethane as an etching gas result in contamination with impurities like methane, ethane, propane, and methyl chloride due to the use of hydrochloric acid-treated alumina catalysts, making it difficult to achieve high purity.
Innovation Solution
The method involves pyrolyzing a fluorine-containing methyl ether in the presence of an alumina catalyst with a chlorine content of 1.0 wt % or less, preferably using a γ-alumina catalyst, to produce a high-purity fluoromethane composition by avoiding hydrochloric acid treatment and utilizing a catalyst with minimal chlorine content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If an alumina catalyst is treated with hydrochloric acid to increase reaction activity, then the reaction activity is improved, but the purity of fluoromethane deteriorates due to contamination with methyl chloride and other impurities
Solution Approach 1:
The harmful chlorine component is extracted and removed from the alumina catalyst system. Instead of using hydrochloric acid-treated alumina catalyst which contains chlorine and produces methyl chloride impurities, the invention uses alumina catalyst free from chlorine treatment, thereby eliminating the source of contamination and achieving high purity fluoromethane production
Solution Approach 2:
The conventional approach of treating alumina with hydrochloric acid to enhance activity is inverted. The invention achieves high reaction activity without chlorine treatment by optimizing other catalyst properties and reaction conditions, thus avoiding the harmful side effect of methyl chloride formation while maintaining productivity
2Productivity
If hydrochloric acid-treated alumina catalyst is used, then the reaction proceeds efficiently, but the final product contains difficult-to-remove impurities like methyl chloride
Solution Approach 1:
The invention converts the harmful effect of chlorine-containing catalysts into a beneficial approach by deliberately avoiding chlorine treatment. This prevents the formation of harmful methyl chloride impurities from the start, eliminating the need for complex purification steps to remove these difficult-to-eliminate contaminants
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 effectively prevents contamination and achieves a fluoromethane composition with a purity of 99.999 mol % or more, suitable for use as a dry etching gas, by using an alumina catalyst with low chlorine content to minimize impurity presence.
Implementation Method 1
pyrolyzing in a gas phase a fluorine-containing methyl ether... in the presence of an alumina catalyst
Implementation Method 2
pyrolyzing in a gas phase a fluorine-containing methyl ether represented by Formula (1)
Data Source
AI summary
An object of the present invention is to provide a composition containing fluoromethane having high purity. A method for producing fluoromethane, comprising: pyrolyzing in a gas phase a fluorine-containing methyl ether represented by Formula (1):wherein R1 and R2 are the same or different, and each represents an optionally substituted linear or branched monovalent aliphatic hydrocarbon group, an optionally substituted monovalent aromatic hydrocarbon group, an optionally substituted monovalent cyclic aliphatic hydrocarbon group, hydrogen, or halogen, in the presence of an alumina catalyst to thereby obtain a mixed gas containing fluoromethane and acid fluoride, wherein: the alumina catalyst contains chlorine in an amount of 1.0 wt % or less.