Modified Platinum Catalyst for Selective Nitro Reduction
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Solution Overview
Problem
The catalytic hydrogenation of aromatic and heteroaromatic nitro compounds to their corresponding amines is challenging due to the stability of hydroxylamine intermediates and the occurrence of unwanted side reactions with halogen or sulfur-containing substituents, leading to incomplete reduction and catalyst poisoning, which results in unsatisfactory yields and the need for excessive catalyst amounts.
Innovation Solution
A supported platinum catalyst is modified with a molybdenum compound and a phosphorus compound, where the phosphorus has an oxidation state of less than +5, specifically using hypophosphorous acid or its salts and orthomolybdate, to enhance the selective reduction of nitro compounds in the presence of halogen or sulfur-containing groups without drastic reaction conditions or excessive catalyst usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a supported platinum catalyst is used for hydrogenation of nitro compounds, then the reduction reaction can proceed, but unwanted side reactions occur with halogen or sulfur-containing substituents leading to catalyst poisoning and incomplete reduction
Solution Approach 1:
The patent modifies the catalyst by changing its chemical composition parameters - adding molybdenum compound and phosphorus compound (with phosphorus in oxidation state less than +5) to the supported platinum catalyst. This compositional modification alters the catalyst's properties to achieve selective reduction of nitro groups while preventing side reactions with halogen or sulfur-containing substituents.
Solution Approach 2:
The invention creates a composite catalyst system comprising platinum supported on a carrier, modified with molybdenum compound and phosphorus compound. This composite structure combines multiple components with complementary functions: platinum provides catalytic activity, while molybdenum and phosphorus modifications enhance selectivity and prevent catalyst poisoning by halogen or sulfur groups.
2Productivity
If conventional platinum catalysts are used, then hydrogenation can occur, but hydroxylamine intermediates accumulate due to their stability and incomplete reduction
Solution Approach 1:
The modification of the platinum catalyst with molybdenum and phosphorus compounds changes the catalytic parameters to favor complete reduction. The modified catalyst promotes the conversion of unstable intermediates (nitroso and hydroxylamine) to the final amine product, preventing their accumulation while maintaining efficient reaction rates.
3Quantity of substance
If standard catalyst amounts are used, then the process is economical, but unsatisfactory yields are obtained due to catalyst poisoning by sulfur or halogen groups
Solution Approach 1:
The chemical modification of the catalyst with molybdenum and phosphorus compounds enhances its resistance to poisoning by halogen or sulfur-containing groups. This parameter change in catalyst composition allows the use of standard catalyst amounts while achieving high yields, as the modified catalyst maintains its activity and selectivity even in the presence of these potentially deactivating substituents.
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 approach enables complete reduction of nitro compounds to amines with high yields and minimizes side reactions, ensuring maximum catalyst activity and preventing catalyst poisoning, even in the presence of halogen or sulfur-containing substituents, thereby improving the efficiency of the hydrogenation process.
Implementation Method 1
A process for the catalytic hydrogenation of an aromatic or heteroaromatic nitro compound to the corresponding amine in the presence of a platinum catalyst comprising elemental platinum on a support, characterized in that the platinum catalyst has been modified with a molybdenum compound and a phosphorus compound
Implementation Method 2
the hydrogenation of halogen-substituted aromatic nitro-compounds, substantially without simultaneous dehalogenation, utilizing supported platinum catalysts modified with a phosphorous compound
Data Source
AI summary
Aromatic or heteroaromatic nitro compounds are catalytically hydrogenated to the corresponding amines in the presence of a platinum catalyst comprising elemental platinum on a support; the platinum catalyst is modified with a molybdenum compound and a phosphorus compound wherein the phosphorus has an oxidation state of less than +5, e.g. hypophosphorous acid; the catalyst is particularly useful in the hydrogenation of nitro compounds with halogen and/or sulfur-containing substituents.