Augmented Acid Catalysts for Room Temperature Alkane Isomerization
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Solution Overview
Problem
Current acidic catalysts are ineffective in isomerizing alkanes at room temperature and oligomerizing methane efficiently, lacking the necessary superacidity and stability for these reactions.
Innovation Solution
Development of augmented acid catalysts using wet impregnation and vapor phase grafting techniques with aluminum halides on various supports, followed by HBr treatment to create catalysts with enhanced acidity, specifically AlBr3 and AlCl3 on supports like ZSM-5 and silica gel, which demonstrate superacidity and capability for methane oligomerization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional acidic catalysts are used, then the catalyst structure is simple and easy to manufacture, but the catalyst cannot achieve superacidity and cannot isomerize alkanes at room temperature
Solution Approach 1:
The patent creates composite catalyst systems by combining aluminum halide species (AlCl3, AlBr3) with solid support materials (silica gel, alumina, zeolites). This composite structure enables the catalyst to achieve superacidity while maintaining structural stability, allowing isomerization reactions to proceed at room temperature with high activity. The synergistic interaction between the aluminum halide and support material creates the necessary superacidic sites.
Solution Approach 2:
The patent modifies catalyst parameters by controlling the loading amount of aluminum halide species (5-50 wt%), adjusting the type of aluminum halide (AlCl3 vs AlBr3), and varying the support material properties. These parameter changes enable tuning of the catalyst's acidity strength to achieve superacidity, which is necessary for room temperature isomerization of alkanes.
2Productivity
If conventional acidic catalysts are used, then the catalyst preparation is simple, but the catalyst lacks superacidity and cannot efficiently oligomerize methane
Solution Approach 1:
The patent employs preliminary impregnation of aluminum halide species onto the support material, followed by controlled activation through exposure to moisture or water vapor. This preliminary preparation creates the superacidic sites in advance, enabling efficient methane oligomerization when the catalyst is subsequently used. The activation step transforms the impregnated aluminum halide into the active superacidic form.
Solution Approach 2:
The patent replaces conventional high-temperature thermal activation methods with a milder activation approach using controlled exposure to moisture or water vapor. This substitution allows the formation of superacidic sites at lower temperatures, maintaining the integrity of the support material and aluminum halide species while achieving the necessary catalyst activity for methane oligomerization.
3Reliability
If aluminum halide impregnation is performed with high loading, then catalyst acidity is enhanced, but catalyst stability and structural integrity deteriorate
Solution Approach 1:
The patent applies partial impregnation of aluminum halide species onto the support material, using optimized loading amounts (5-50 wt%) rather than maximum possible loading. This partial action ensures sufficient superacidic sites are created for high catalyst activity while preventing excessive aluminum halide deposition that would compromise the structural stability and porosity of the catalyst.
Solution Approach 2:
The patent creates localized superacidic sites at the interface between the aluminum halide species and the support material, rather than uniformly distributing aluminum halide throughout the entire catalyst structure. This local quality approach concentrates the acidity enhancement at active sites while preserving the overall structural integrity and porosity of the support material for reactant diffusion.
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 augmented acid catalysts achieve superacidity, enabling isomerization of n-butane into isobutane at room temperature and successful methane oligomerization, producing higher molecular weight hydrocarbons, with specific catalysts like AlBr3 on H-ZSM5 showing significant activity in oligomerization reactions.
Implementation Method 1
Wet impregnation techniques may be used with various solvents to prepare acid catalysts. For example, supports may be impregnated by the dissolved aluminum halide precursors
Implementation Method 2
Vapor phase grafting techniques may also be used to prepare acid catalysts. For example, supports and aluminum halide, separated by quartz wool, may be heated up to 300° C. inside an air free vessel or under an inert atmosphere, allowing aluminum halide vapor to react with the surface species of support
Implementation Method 3
Each of the HBr treatments occur at room temperature but may be performed at higher temperatures potentially enhancing the acidity of the catalyst. For example, the silica gel based initial catalyst species Gi may react with HBr to yield Ga as follows: Gi+HBr→Ga
Implementation Method 4
Certain acidic catalyst disclosed herein demonstrate super acidity and may be capable of isomerizing alkanes at room temperature
Implementation Method 5
Certain acidic catalyst disclosed herein may be useful in the oligomerization of methane
Data Source
AI summary
Methods of preparing an acidic catalyst are disclosed that include heating a metal halide to produce a vapor phase metal halide, contacting an initial support material with the vapor phase metal halide in a reaction vessel causing a first chemical reaction and producing an intermediate acidic catalyst, contacting the intermediate acidic catalyst with HBr causing a second chemical reaction and producing an acidic catalyst product which is both more acidic than the intermediate acidic catalyst and more acidic than the initial support material.