Raney Nickel Pretreatment for Reduced DCH in Adiponitrile Hydrogenation
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Solution Overview
Problem
Existing processes for the hydrogenation of adiponitrile to hexamethylenediamine using Raney nickel catalysts suffer from high formation of diaminocyclohexane (DCH) as a side product, making separation difficult and increasing purification costs and energy consumption.
Innovation Solution
The use of a Raney nickel catalyst modified by pre-treatment with carbon monoxide or carbon dioxide in a liquid medium, either prior to or during hydrogenation, to reduce DCH formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Raney nickel catalyst is used for hydrogenation of adiponitrile, then catalytic activity is achieved, but diaminocyclohexane formation increases
Solution Approach 1:
The Raney nickel catalyst is pre-treated with carbon monoxide or carbon dioxide in a liquid medium before use in the hydrogenation reaction. This preliminary treatment modifies the catalyst surface properties to reduce its ability to catalyze the formation of diaminocyclohexane while maintaining its activity for hexamethylenediamine production
Solution Approach 2:
The invention changes the physical-chemical parameters of the catalyst by exposing it to carbon monoxide or carbon dioxide in a liquid medium. This treatment alters the catalyst's surface characteristics and electronic properties, thereby changing its selectivity to favor hexamethylenediamine formation over diaminocyclohexane formation
2Productivity
If diaminocyclohexane is formed as side product, then hydrogenation reaction proceeds, but separation difficulty increases
Solution Approach 1:
The catalyst is pre-treated to prevent or reduce the formation of diaminocyclohexane before the main hydrogenation reaction occurs. By modifying the catalyst properties in advance, the harmful side reaction is suppressed, avoiding the creation of separation problems downstream
3Productivity
If conventional hydrogenation process is used, then hexamethylenediamine is produced, but purification costs increase
Solution Approach 1:
The catalyst undergoes preliminary treatment with carbon monoxide or carbon dioxide to establish selective properties before the hydrogenation reaction. This pre-modification ensures that the reaction produces minimal diaminocyclohexane, thereby reducing the energy and cost requirements for subsequent purification steps
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
Significantly reduces DCH formation, improving catalyst selectivity and maintaining catalytic activity, thereby facilitating easier purification of hexamethylenediamine with reduced capital and energy costs.
Implementation Method 1
hydrogenation of adiponitrile in the presence of a Raney nickel catalyst
Implementation Method 2
hydrogenation of adiponitrile to give a cyclic diamine, diaminocyclohexane (DCH)... in the presence of a catalyst based on optionally doped Raney nickel
Data Source
AI summary
The present invention relates to a process for the preparation of hexamethylenediamine by hydrogenation of adiponitrile in the presence of a Raney nickel catalyst, wherein a Raney nickel catalyst modified by treatment with carbon monoxide or carbon dioxide in a liquid medium is used.