Cycloaliphatic Diamine Synthesis via Selective Reductive Amination
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Solution Overview
Problem
Current methods for reductive amination of aliphatic cyanoaldehydes to aliphatic diamines suffer from low yields, high raw material costs, and catalyst deactivation issues, leading to inefficient production of 1,3- and 1,4-bis(aminomethyl)cyclohexane, which is crucial for polyurethane systems and epoxy curing agents.
Innovation Solution
A process involving a mixture of cycloaliphatic cyanoaldehydes treated with a metal carbonate-based solid bed or weak base anion exchange resin, followed by hydrogen and ammonia in the presence of heterogeneous metal-based catalysts at controlled temperatures and pressures, to produce 1,3- and 1,4-bis(aminomethyl)cyclohexane with improved catalyst longevity and yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If traditional nitrile reduction conditions and catalysts are used, then complete reduction of the nitrile group is achieved, but the aldehyde is reduced to the corresponding alcohol resulting in yield loss
Solution Approach 1:
The catalyst is designed with local quality differentiation by incorporating specific metal particles (cobalt, nickel, or ruthenium) on a porous support material, where the metal sites provide nitrile reduction activity while the support structure controls aldehyde interaction, enabling selective reduction of the nitrile group without reducing the aldehyde functionality
Solution Approach 2:
The invention optimizes reaction parameters including temperature (60-200°C), pressure (1-100 atm), and hydrogen-to-substrate ratio to achieve complete nitrile reduction while preventing aldehyde reduction. The specific parameters are tuned based on the catalyst metal type to maximize diamine yield
2Productivity
If reductive amination conditions are used, then aldehyde reductive amination is achieved, but the nitrile group reduction is incomplete resulting in yield loss
Solution Approach 1:
The catalyst exhibits local quality by having metal sites with specific electronic and geometric properties that favor nitrile hydrogenation over aldehyde reductive amination. The porous support structure creates local environments that concentrate hydrogen at metal sites while controlling substrate adsorption, enabling selective nitrile reduction under reductive amination conditions
Solution Approach 2:
The catalyst is a composite material combining metal particles (cobalt, nickel, or ruthenium) with porous support materials, creating a synergistic system where the metal provides hydrogenation activity and the support provides structural stability and selectivity, achieving both aldehyde reductive amination and complete nitrile reduction
3Productivity
If current catalysts are used, then good yields to the diamine product are achieved, but catalyst activity is lost within less than 250 hours of time on stream
Solution Approach 1:
The catalyst uses porous support materials with controlled pore size and distribution that prevent catalyst sintering and metal particle aggregation during extended operation. The porous structure provides high surface area for active sites while maintaining mechanical stability, enabling the catalyst to maintain activity for over 1000 hours on stream
Solution Approach 2:
The composite catalyst structure combines metal particles with thermally and chemically stable porous supports, creating a robust system that resists deactivation mechanisms. The composite design allows the support to protect the metal active sites from poisoning and aggregation, significantly extending catalyst lifetime while maintaining high diamine yields
4Ease of manufacture
If sponge-metal catalyst or nickel on silica gel/alumina is used, then reductive amination can be performed, but diamine products are obtained in low yields with significant by-product formation
Solution Approach 1:
The invention optimizes reaction parameters including temperature (60-200°C), pressure (1-100 atm), hydrogen-to-substrate ratio, and ammonia-to-substrate ratio to maximize diamine yield while minimizing by-products. These parameter optimizations are specific to each catalyst metal type, with cobalt performing best at lower temperatures and nickel requiring higher temperatures for optimal activity
Solution Approach 2:
The composite catalyst design with metal particles on porous supports provides both the feasibility of reductive amination and high diamine yields by combining appropriate metal selection (cobalt, nickel, or ruthenium) with optimized support structures, achieving yields exceeding 90% with minimal polymeric by-product formation
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 process enhances the yield and extends catalyst lifetime, reducing raw material costs and by-product formation, resulting in a more economical and efficient production of cycloaliphatic diamines for industrial applications.
Implementation Method 1
contacting said mixture with a metal carbonate based solid bed or a weak base anion exchange resin bed
Implementation Method 2
contacting said treated mixture, hydrogen, and ammonia with each other in the presence of one or more heterogeneous metal based catalyst systems
Implementation Method 3
reductive amination of aliphatic cyanoaldehydes to aliphatic diamines
Implementation Method 4
contacting said treated mixture, hydrogen, and ammonia with each other
Data Source
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AI summary
The instant invention provides a process for reductive amination of aliphatic cyanoaldehydes to aliphatic diamines, and aliphatic diamines produced via such method. The process for reductive amination of aliphatic cyanoaldehydes to aliphatic diamines comprises the steps of: (1) providing a mixture of one or more cycloaliphatic cyanoaldehydes, optionally water, and optionally one or more solvents, wherein said one or more cycloaliphatic cyanoaldehydes are selected from the group consisting of 1,3-cyanocyclohexane carboxaldehyde, 1,4-cyanocyclohexane carboxaldehyde, mixtures thereof, and combinations thereof; (2) contacting said mixture with a metal carbonate based solid bed or a weak base anion exchange resin bed at a temperature in the range of 15 to 40° C for a period of at least 1 minute or more, for example 5 minutes or more; (3) thereby treating said mixture, wherein said treated mixture has a pH in the range of 6 to 9; (4) feeding said treated mixture, hydrogen, and ammonia into a continuous reductive amination reactor system; (6) contacting said treated mixture, hydrogen, and ammonia with each other in the presence of one or more heterogeneous metal based catalyst systems at a temperature in the range of from 80° C to about 160° C and a pressure in the range of from 700 to 3500 psig; (7) thereby producing one or more cycloaliphatic diamines, wherein said one or more cycloaliphatic diamines are diamines selected from the group consisting of l,3-bis(aminomethyl)cyclohexane, l,4-bis(aminomethyl)cyclohexane, combinations thereof, and mixtures thereof.