Selective Dehydration of 2,3-Butanediol to 3-Buten-2-ol over In2O3 Catalyst

The selective dehydration of 2,3-butanediol (2,3-BDO) to 3-buten-2-ol (3B2oL) was investigated over indium oxide (In2O3) catalysts. The effect of different process parameters such as reaction temperature, weight hourly space velocity (WSHV), and carrier gas on the product distribution during the dehydration of 2,3-BDO was demonstrated. Highest selectivity to 3B2oL (70%) was achieved when the reaction was performed under a H-2 flow, with 81% single pass conversion of 2,3-BDO. In all these cases, the dehydrogenation of 2,3-BDO was found to be the prevalent side reaction to dehydration. An optimum operating temperature (290 degrees C) corresponding to the selective formation of 3B2oL was identified, as further increases in temperature promoted other parallel reaction routes, which decreased selectivity toward 3B2oL. Varying the synthesis precursors and calcination temperatures allowed us to prepare In2O3 catalysts with differing ratios and concentrations of acid/base sites, which had a significant impact on both the dehydration and dehydrogenation pathways and provides a way to control the selectivity toward the desired product. Higher calcination temperatures (550 degrees C) were found to produce optimal acid/base site ratios that not only significantly improved the dehydration rate to the desired 3B2oL product but also suppressed the dehydrogenation rate. On the basis of the catalytic results and corresponding product distribution, the detailed reaction mechanism corresponding to the selective dehydration of 2,3-BDO to 3B2oL is also discussed herein.