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Hydrogenation of dinitriles on Raney-type Ni catalysts: kinetic and mechanistic aspects

Paper ID Volume ID Publish Year Pages File Format Full-Text
43169 45957 2009 9 PDF Available
Title
Hydrogenation of dinitriles on Raney-type Ni catalysts: kinetic and mechanistic aspects
Abstract

The mechanism of the hydrogenation of aliphatic C4–C6 dinitriles (succinonitrile, glutaronitrile, and adiponitrile) over Raney-type Ni catalysts was investigated in a fed-batch autoclave at 350 K and 5.0 MPa. The results are interpreted based on the strength of adsorption, the interaction with the solvent and intramolecular interactions. The kinetics of the hydrogenation of aliphatic dinitriles is highly dependent on the hydrocarbon chain length. Short dinitriles like succinonitrile adsorb stronger on the catalyst surface than longer dinitriles like adiponitrile. The yield of the intermediate aminonitriles decreases with increasing hydrocarbon chain length, due to the enhanced competitiveness of dinitrile and aminonitrile for the same active sites. It is proposed that the reactivity of dinitriles and aminonitriles is caused by difference in solvent interaction. It is remarkable that the stronger the adsorption, the higher the reactivity. The reactivity decreases in the order: succinonitrile > glutaronitrile > adiponitrile. In contrast, the reaction rate of the aminonitriles is fairly independent of the hydrocarbon chain length. The formation of undesired secondary amines in the form of cyclic compounds is under kinetic control and increases with decreasing chain length. It is found that adiponitrile can be very selectively hydrogenated to primary diamines. Promoting Raney-type Ni catalysts with traces of Mo, Cr or Fe enhances the performance in the hydrogenation of dinitriles. This gives the best opportunity for process improvement towards the desired primary amines.

Graphical abstractThe kinetics of the hydrogenation of aliphatic C4–C6 dinitriles over Raney-type Ni catalysts is highly dependent on the hydrocarbon chain length. Short dinitriles like succinonitrile adsorb stronger on the catalyst surface than longer dinitriles like adiponitrile. The yield of the intermediate aminonitriles decreases with increasing chain length. It is remarkable that the stronger the adsorption, the higher the reactivity. The reactivity decreases in the order: succinonitrile > glutaronitrile > adiponitrile. Figure optionsDownload full-size imageDownload as PowerPoint slide

Keywords
Raney-type catalysts; Dinitriles; Diamines; Nylon; Polyamides; Kinetics
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Hydrogenation of dinitriles on Raney-type Ni catalysts: kinetic and mechanistic aspects
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 352, Issues 1–2, 15 January 2009, Pages 193–201
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
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Full-text PDF Download
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