Preparation and characterization of carbon based acid catalysts for the dehydration of 2-propanol

The catalytic conversion of 2-propanol on carbon based acid catalysts obtained by chemical activation of lignocellulosic waste with H3PO4 was investigated. The carbon acid catalysts were prepared in a single step, without the need for incorporating acid surface groups in a complementary step by chemical oxidation of the carbon surface. The porous structure was characterized by N-2 and CO2 adsorption, showing a strong dependence on the impregnation ratio. The surface chemistry was studied by XPS and TPD. A significant amount of phosphorus remains on the catalysts surface, as phosphate and/or polyphosphate esters, stable at relatively high temperature (<700 degrees C), despite the washing process carried out during the preparation of the catalysts. The total acidity and acid strength distribution were determined by NH3-TPD. The conversion of 2-propanol yielded only dehydration products, mainly propylene with very low amounts of di-isopropyl ether, confirming the acidic nature of the catalyst sites. The amount and strength of acid sites affected the catalytic activity but did not change significantly the apparent activation energy of the dehydration reaction. The catalysts were stable at the operation conditions. The presence of water vapor did not affect significantly the conversion and the product distribution. (C) 2008 Elsevier Ltd. All rights reserved.