Acidity control of ruthenium pillared clay and its application as a catalyst in hydrogenation reactions

Aluminum pillared clay was used as a support for the preparation of catalysts containing ruthenium as active metal, in the presence or not of a promoter (tin) and an acid reducer (barium). The catalysts were characterized and tested for hydrogenation of dimethyl adipate reactions. The results showed a high conversion, typically above 95%. in all studied systems. This conversion occurs irrespectively of the presence of active metal; therefore, it may be due to the support's intrinsic activity. The acidity was identified as the main cause of this activity. A barium treatment of these catalysts significantly reduced this acidity, thus making more selective the available systems. The catalysts treated with barium reduced the formation of undesirable products up to 45%. Similarly, the presence of tin helped to obtain valuable products such as gamma-caprolactone and methyl caproate, which reached high selectivity values (18.6% and 16.9%, respectively). (C) 2009 Elsevier B.V. All rights reserved.