Oxalic Acid Dissolution of Mixed Oxide Dehydrogenation Catalysts
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Solution Overview
Problem
Current methods for removing mixed oxide catalysts from reactors and piping in oxidative dehydrogenation processes are inefficient and can result in the formation of harmful catalyst dust, with limited use of oxalic acid for solubilization and no effective means to disperse alumina supports.
Innovation Solution
Contacting the catalysts, comprising specific metal oxide compositions, with an oxalic acid solution at elevated temperatures to dissolve and remove them, along with agitation to enhance the process, allowing for the separation of valuable metals and alumina supports.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If physical treatment methods are used to remove catalysts and residues, then removal can be achieved, but harmful catalyst dust is formed
Solution Approach 1:
The invention changes the chemical state of the catalyst from solid particulate form to dissolved ionic form by treating it with oxalic acid solution. This parameter change from solid to dissolved state eliminates dust formation while maintaining effective catalyst removal, as the catalyst components (Mo, V, Nb, Te oxides) dissolve into the acid solution rather than becoming airborne particles.
Solution Approach 2:
The invention replaces mechanical/physical removal methods with a chemical dissolution process. Instead of using physical treatment that generates dust, the catalyst is chemically dissolved in oxalic acid solution, substituting a mechanical system with a chemical system that achieves the same removal goal without harmful byproducts.
2Productivity
If conventional cleaning methods are used, then catalyst removal is achieved, but the process is inefficient and time-consuming
Solution Approach 1:
The invention optimizes the chemical parameters of the cleaning process by using oxalic acid at specific concentrations (0.5-5 M) and temperatures (20-100°C), which dramatically accelerates the dissolution rate of the catalyst components. This parameter optimization enables complete catalyst removal in significantly reduced time compared to conventional methods, improving cleaning efficiency while minimizing time loss.
3Productivity
If strong acids are used to dissolve catalysts, then complete removal is achieved, but damage to reactor components occurs
Solution Approach 1:
The invention selects oxalic acid as the dissolving agent, which has optimal parameters for selectively dissolving catalyst components (Mo, V, Nb, Te oxides) while being sufficiently mild to avoid damaging reactor components. The acid concentration is controlled at 0.5-5 M, and temperature at 20-100°C, creating a parameter window that achieves complete catalyst removal while preserving reactor integrity.
Solution Approach 2:
Oxalic acid acts as an intermediary substance that facilitates the removal of catalyst components without directly attacking the reactor structure. It selectively interacts with the metal oxide catalyst components, forming soluble complexes, while its mild nature prevents harmful reactions with stainless steel or other reactor materials, thus protecting component integrity.
4Productivity
If oxalic acid is used to dissolve catalysts, then catalyst removal is achieved, but alumina support dissolution may occur
Solution Approach 1:
The invention carefully controls the parameters of oxalic acid treatment (concentration 0.5-5 M, temperature 20-100°C, time sufficient for catalyst dissolution) to create selective dissolution conditions. Under these parameters, the catalyst active components (Mo, V, Nb, Te oxides) dissolve rapidly, while alumina support remains largely intact due to its lower reactivity with oxalic acid under these controlled conditions, minimizing support loss.
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
Effectively dissolves the catalysts and supports in oxalic acid solutions, preventing dust formation and enabling efficient cleaning of reactors and piping, while maintaining the integrity of stainless steel components and allowing for the recovery of valuable metals.
Implementation Method 1
contacting the catalyst with from 10 to 100 mL of not less than a 0.5 molar solution typically not less than 1 M up to the solubility limit of oxalic acid in an aqueous solution at the temperature of treatment per g of catalyst at a temperature from 20°C up to the boiling temperature of a saturated solution preferably greater than 60°C most preferably greater than 80°C for a period of time for at least 1 hour in some cases 20 or more hours; wherein contacting the catalyst comprises dissolving the catalyst in the solution of oxalic acid
Data Source
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AI summary
Oxidative dehydrogenation catalysts comprising mixed oxides of Mo, V, Nb, Te and optionally a promoter may be dissolved in aqueous solutions of oxalic acid. This permits the removal of catalyst and catalyst residues from reactors for the oxidative dehydrogenation of paraffins and particularly ethane.