Rare-Earth Catalyst for Methanethiol Selectivity
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Solution Overview
Problem
Current methods for gas-phase catalytic hydrosulfurization of methanol to methanethiol face challenges in achieving high methanol conversion rates with high selectivity and low production of non-recoverable by-products, such as light compounds, particularly with catalysts like lanthanum oxide on alumina which have high methanol conversion but low methanethiol selectivity, and ceria which produces excessive methane.
Innovation Solution
A method using a catalyst comprising or consisting of rare-earth oxides, sulfides, or oxysulfides, with specific compositions like mixed oxides of lanthanum, cerium, and zirconium, supported on modified alumina, which improves selectivity and reduces non-recoverable products by up to 40%, allowing for a wider temperature range and flexible product direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a catalyst based on lanthanum oxide supported on alumina is used, then high methanol conversion is obtained, but methanethiol selectivity becomes very low
Solution Approach 1:
The patent uses composite catalyst materials combining rare-earth oxides (lanthanum, cerium, praseodymium, neodymium) with zirconium oxide and alumina support. This composite structure integrates the high conversion capability of lanthanum oxide with the selectivity-enhancing properties of zirconium oxide and rare-earth sulfides, resolving the contradiction between conversion rate and selectivity.
Solution Approach 2:
The patent modifies catalyst composition parameters by incorporating specific ratios of rare-earth oxides (La2O3: 1-50 wt%, CeO2: 1-50 wt%, Pr6O11: 0.1-20 wt%, Nd2O3: 0.1-20 wt%) and zirconium oxide (ZrO2: 10-90 wt%) to optimize both conversion and selectivity. The inclusion of sulfide phases (LaS, CeS, PrS, NdS) further tunes the catalyst properties to achieve balanced performance.
2Manufacturing precision
If ceria catalyst is used, then high adsorption of hydrogen sulfide and increased methanethiol selectivity are observed, but methane production increases excessively
Solution Approach 1:
The patent creates composite catalysts combining cerium oxide with zirconium oxide and rare-earth sulfides. This composite structure mitigates ceria's tendency to produce excessive methane by introducing zirconium oxide which suppresses methane formation while maintaining high methanethiol selectivity through the synergistic interaction of multiple active sites.
Solution Approach 2:
The patent creates different active sites within the catalyst structure with specialized functions: cerium oxide sites for hydrogen sulfide adsorption and methanethiol formation, zirconium oxide sites for suppressing methane production, and rare-earth sulfide sites for enhancing selectivity. This spatial differentiation of catalytic functions resolves the contradiction between selectivity and harmful by-product formation.
3Productivity
If conventional catalysts are used, then the reaction requires high temperatures, but this increases energy consumption and by-product formation
Solution Approach 1:
The patent develops composite catalysts with multiple active phases (rare-earth oxides, zirconium oxide, sulfides) that create synergistic effects, enabling the reaction to proceed at lower temperatures. The combination of these materials provides sufficient catalytic activity and selectivity without requiring excessive thermal energy, thus reducing energy consumption and minimizing by-product formation.
Solution Approach 2:
The patent introduces rare-earth sulfides (LaS, CeS, PrS, NdS) as intermediary active sites that facilitate the hydrosulfurization reaction at lower temperatures. These sulfide phases act as mediators between the reactants and the catalyst surface, enabling efficient reaction progress without requiring high temperature conditions.
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 significantly enhances methanethiol selectivity and productivity, reduces non-recoverable by-products, and allows for the recycling of dimethyl sulfide to increase overall methanethiol yield, while operating within a broader temperature range, making it more efficient and adaptable.
Implementation Method 1
gas-phase catalytic reaction of hydrogen sulfide with a compound of formula ROH, in the presence of a solid catalyst
Implementation Method 2
the adsorption of hydrogen sulfide during the hydrosulfurization reaction of methanol in the presence of different catalysts
Data Source
AI summary
A method for preparing a compound of formula RSH where R represents an alkyl group, by gas-phase catalytic reaction of hydrogen sulfide with a compound of formula ROH, in the presence of a solid catalyst, according to which method the reaction is performed in the presence of a catalyst which includes one or several pure or mixed rare-earth oxide(s), one or several pure or mixed rare-earth sulfide(s), or one or several pure or mixed rare-earth oxysulfide(s). When the rare earth is lanthanum, the catalyst is a mixed oxide of lanthanum and of at least one metal selected from rare earths or not and when the rare earth is cerium, the catalyst is supported on an alumina.