Shell Catalyst Coating for Methanol Oxidation Abrasion Resistance
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Solution Overview
Problem
Existing catalysts for oxidizing methanol to formaldehyde lack both high abrasion resistance and selectivity, and there is a need for improved catalysts that can maintain performance over time while avoiding the disadvantages of prior art.
Innovation Solution
A shell catalyst with a coating composition comprising oxides of molybdenum and iron, along with an organic binder and an inorganic adhesion-promoting component such as SiO2 sol, applied to an inert nonporous support body, which provides enhanced abrasion resistance and porosity for improved catalytic activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If impregnation process is used to apply active sites to porous support, then catalytic activity is improved through chemical-physical interactions, but abrasion resistance deteriorates
Solution Approach 1:
The patent uses a porous layer made of metal oxides (such as aluminum oxide, silicon oxide, zirconium oxide, titanium oxide) as the support structure for active sites. This porous layer provides both the necessary surface area for catalytic interactions and a robust structure that resists abrasion, unlike traditional porous supports that compromise strength for surface area.
Solution Approach 2:
The patent employs composite materials by combining the porous metal oxide layer with active catalytic sites (such as noble metals or metal compounds). This composite structure integrates the mechanical strength and stability of the porous oxide support with the catalytic functionality of the active sites, achieving both high abrasion resistance and catalytic activity.
2Strength
If coated catalyst with nonporous support is used, then abrasion resistance is improved, but catalytic activity deteriorates due to lack of porosity
Solution Approach 1:
The patent introduces a porous layer composed of metal oxides on the nonporous support surface. This porous structure provides the necessary porosity for reactant access and catalytic interactions while the underlying nonporous support maintains overall structural integrity and abrasion resistance.
Solution Approach 2:
The patent transitions from a purely nonporous surface to a structured porous layer by controlling the deposition and sintering processes. This dimensional transformation creates a hierarchical structure where the porous layer provides catalytic functionality while the nonporous substrate provides mechanical strength.
3Strength
If organic binder is used in coating composition, then adhesion and abrasion resistance are improved, but harmful emissions increase during heat treatment
Solution Approach 1:
The patent modifies the binder composition by using inorganic binders (such as waterglass, cements, or metal oxide precursors) instead of traditional organic binders. This parameter change in binder chemistry eliminates carbon-containing emissions during heat treatment while maintaining adhesion and abrasion resistance through inorganic bonding mechanisms.
Solution Approach 2:
The patent converts the potential harm of binder decomposition into a benefit by using inorganic binders that decompose into harmless or beneficial substances (such as water, oxygen, or metal oxides) during heat treatment. These decomposition products either evaporate harmlessly or contribute to the formation of the porous metal oxide structure.
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 abrasion resistance both before and after heat treatment, with a favorable pore structure that maintains catalytic activity for methanol oxidation to formaldehyde, offering improved durability and performance compared to prior catalysts.
Implementation Method 1
at least one sol component, especially SiO2 sol
Implementation Method 2
adhesion-promoting component, especially a sol component
Implementation Method 3
porous layer of the actual active material
Implementation Method 4
Molybdenum-iron catalysts for partial oxidation of methanol to formaldehyde
Implementation Method 5
partial oxidation of methanol to formaldehyde
Data Source
AI summary
The invention relates to a coated catalyst, especially for oxidation of methanol to formaldehyde, which, on an inert, preferably essentially nonporous, support body, has at least one coating which comprises, before the removal of the organic fractions of components b) and c): (a) oxides, or precursor compounds convertible to the corresponding oxides, of molybdenum and iron, where the molar ratio of Mo:Fe is between 1:1 and 5:1, and optionally further metallic components or metal oxide components or precursor compounds convertible to the corresponding oxides, (b) at least one organic binder, preferably an aqueous dispersion of copolymers, especially selected from vinyl acetate/vinyl laurate, vinyl acetate/ethylene, vinyl acetate/acrylate, vinyl acetate/maleate, styrene/acrylate or mixtures thereof, and (c) at least one further component selected from the group consisting of SiO2 sol or precursors thereof, Al2O3 sol or precursors thereof, ZrO2 sol or precursors thereof, TiO2 sol or precursors thereof, waterglass, MgO, cement, monomeric, oligomeric or polymeric silanes, alkoxysilanes, aryloxysilanes, acryloyloxysilanes, aminosilanes, siloxanes or silanols. Additionally described is a process for preparing the catalyst and its preferred use.