Effect of Al2O3/MgO molar ratio on catalytic performance of Pt/MgO–Al2O3 catalyst in acetonitrile hydrogenation followed by Fourier transform infrared spectroscopy

• Pt / MgO-Al2O3 catalysts were investigated for acetonitrile hydrogenation.
• The selectivity towards primary amine is correlated with the Al/Mg ratio.
• Al/Mg ratio had a important impact on acid-base properties of the support.
• In-situ FTIR spectroscopy evidenced the formation of an intermediate species.
• Ketenimine is proposed as this species and is included in the reaction mechanism.

Catalytic performances of Pt based catalysts supported on (Al2O3)x (MgO)1−x oxides prepared by sol–gel techniques, with x varying from 0.25 to 0.75 were investigated for acetonitrile hydrogenation to check the influence of acid-base properties of the support. The results evidenced a correlation between these properties and the yield towards the primary amines, the most desired ones. Thus, the more basic the support is, the higher the production of primary amines will be. However, an optimal values for both activity and selectivity is obtained for 1% Pt/(Al2O3)0.25(MgO)0.75. Then, hydrogenation of acetonitrile was studied by in situ FTIR spectroscopy and the formation of an intermediate species that would lead to secondary and tertiary amines formation was observed on the catalysts. In accordance to previous reaction pathways, ketenimine (CH2CNH) was proposed as this species.

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