Catalyst Article Forming via Plastic Mixture
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Solution Overview
Problem
Current methods for preparing metal-loaded molecular sieves for selective catalytic reduction (SCR) catalysts are complex, energy-intensive, and can result in residual metal precursors that poison ammonia slip catalysts, requiring additional processing steps and high-temperature equipment.
Innovation Solution
A method involving a plastic mixture of crystalline small or medium pore molecular sieves in H+ or NH4+ form, insoluble active metal precursors, an inorganic matrix, organic auxiliary agents, and an aqueous solvent with a solids content greater than 50% by weight, which is molded and calcined to produce a solid catalyst body, thereby promoting metal loading and reducing processing steps and energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional wet impregnation or ion exchange methods are used to prepare metal-loaded molecular sieves, then metal loading can be achieved, but the process becomes complex, energy-intensive, and requires additional heating steps and expensive equipment
Solution Approach 1:
The patent combines the molecular sieve synthesis step and the metal loading step into a single simultaneous process. The metal precursor is added to the synthesis slurry during crystallization, allowing both the molecular sieve framework formation and metal incorporation to occur together, thereby eliminating separate impregnation or ion exchange steps and reducing overall process complexity
Solution Approach 2:
The metal precursor is introduced into the synthesis slurry before the molecular sieve crystallization is complete. This preliminary action allows the metal to be incorporated into the molecular sieve structure during crystallization itself, rather than requiring subsequent post-synthesis treatment steps
2Reliability
If traditional methods with heating steps are used, then metal loading is achieved, but energy consumption increases and expensive high-temperature equipment is required
Solution Approach 1:
The molecular sieve crystallization process itself provides the conditions necessary for metal loading. The exothermic nature of crystallization and the aqueous slurry environment automatically create the conditions for metal precursor incorporation and conversion, eliminating the need for external heating equipment and additional energy input
3Reliability
If soluble metal precursors are used in traditional methods, then metal loading occurs, but residual precursors remain that can poison ammonia slip catalysts
Solution Approach 1:
The patent employs metal precursors that are completely consumed during the crystallization process. The metal is incorporated into the molecular sieve structure as it forms, leaving no residual precursor that could later poison ammonia slip catalysts. The precursor serves its purpose during synthesis and is then fully utilized
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 method allows for comparable SCR activity to traditional methods while avoiding the need for heating steps and expensive equipment, reducing water consumption, and mitigating poisoning effects on ammonia slip catalysts.
Implementation Method 1
a crystalline small pore or medium pore molecular sieve in an H+ or NH4+ form; (ii) an insoluble active metal precursor
Data Source
AI summary
The present disclosure relates to a method for forming a catalyst article comprising: (a) forming a plastic mixture having a solids content of greater than 50% by weight by mixing together a crystalline small pore or medium pore molecular sieve in an H+ or NH4+ form, an insoluble active metal precursor, an inorganic matrix component, an organic auxiliary agent, an aqueous solvent and optionally inorganic fibres; (b) moulding the plastic mixture into a shaped article; and (c) calcining the shaped article to form a solid catalyst body. The present disclosure further relates to a catalyst article, particularly a catalyst article which is suitable for use in the selective catalytic reduction of nitrogen oxides, and to an exhaust system.