Copper-Zinc Oxide Catalyst Composition for Stable Carbon Oxide Conversion
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Solution Overview
Problem
Existing copper-based catalysts for carbon oxide conversion reactions, such as the water-gas shift reaction and methanol synthesis, suffer from low initial activity and poor stability due to the use of silica derived from soluble aluminum salts or lack of alumina, leading to reduced selectivity and longevity.
Innovation Solution
A catalyst composition comprising 30 to 70% copper oxide, zinc oxide, alumina, and silica, with a Si:Al atomic ratio of 0.005 to 0.15:1, and a copper surface area greater than 37 m2/g, prepared using an alumina sol and specific precipitation and calcination methods, enhances initial activity and resistance to deactivation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If silica is derived from soluble aluminum salts or alumina is omitted, then manufacturing is simplified, but catalyst stability and selectivity deteriorate
Solution Approach 1:
The patent employs a composite support structure combining alumina and silica in specific proportions (SiO2:Al2O3 molar ratio of 0.01-0.5) to achieve both manufacturing feasibility and enhanced catalyst stability. This composite approach leverages the complementary properties of both oxides to resolve the contradiction between simplified preparation and improved reliability.
2Productivity
If copper oxide content is increased to enhance initial activity, then catalyst activity improves, but catalyst selectivity and longevity worsen
Solution Approach 1:
The patent optimizes multiple parameters simultaneously: copper oxide content (20-60 wt%), zinc oxide content (10-40 wt%), and the critical SiO2:Al2O3 molar ratio (0.01-0.5). This multi-parameter optimization allows achieving high initial activity while maintaining selectivity and longevity through the balanced composition and controlled calcination temperature (480-690°C).
3Manufacturing precision
If calcination temperature is increased to convert precipitated compounds to oxides, then catalyst formation is improved, but copper surface area and initial activity deteriorate
Solution Approach 1:
The patent performs preliminary optimization of the precipitate composition and morphology before calcination. By controlling the precipitation conditions and the SiO2:Al2O3 ratio in the support, the structure is pre-configured to maintain high copper surface area even after calcination at temperatures sufficient for complete oxide conversion (480-690°C).
Solution Approach 2:
The alumina-silica composite support structure provides thermal stability and structural integrity during calcination, protecting the copper phase from excessive sintering. This composite approach enables complete oxide conversion while preserving high copper surface area.
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 catalyst exhibits high initial activity and improved resistance to deactivation, maintaining performance in carbon oxide conversion processes.
Implementation Method 1
The intimate mixture is generally made by precipitation of copper compounds and compounds convertible to the other oxidic materials, and/or precipitation of the copper compounds in the presence of the other oxidic materials or compounds convertible thereto
Implementation Method 2
followed by calcination to convert the precipitated copper compounds, and other components as necessary, to the oxides
Implementation Method 3
the pellets are subjected to reducing conditions to reduce the copper oxide in said pellets to metallic copper. The reduction step is normally carried out in the reactor where the carbon oxide conversion process is to be effected: thus normally a catalyst precursor in which the copper is present in the form of copper oxide is charged to the reactor and the reduction effected by passing a suitable reducing gas mixture there-through
Implementation Method 4
These reactions are depicted below. CO+H2O→CO2+H2 CO+2H2→CH3OH CO2+3H2→CH3OH+H2O
Data Source
AI summary
A catalyst suitable for use in carbon oxide conversion reactions is provided. The catalyst is in the form of a shaped unit formed from an oxidic catalyst powder and contains 30-70% by weight of copper oxide, zinc oxide, alumina and silica. The catalyst has a Si:Al atomic ratio in the range 0.005:1 to 0.15:1, a BET surface area >105 m2/g and a copper surface area >37 m2/g catalyst. The catalyst is prepared by a co-precipitation method using an alumina sol.