Coupling of nitrobenzene hydrogenation and 1, 4-butanediol dehydrogenation for the simultaneous synthesis of aniline and γ-butyrolactone over copper-based catalysts

This study examined the role of the support material on the coupling of 1,4-butanediol (BDO) dehydrogenation and nitrobenzene (NB) hydrogenation over copper-based catalysts. The catalysts, 10Cu/MgO (10CM), 10Cu/Al₂O₃ (10CA), 10Cu/MgO-Al₂O₃ (10CMA), and 10Cu/SiO₂ (10CS), were prepared using the impregnation method. The coupling reaction results conducted at 250 °C were compared with those of the individual reactions. The individual BDO dehydrogenation to γ-butyrolactone (GBL) conversion (99%) and hydrogenation of NB to aniline (AN) conversion (85 %) were high over 10CS. In contrast, 10CA produced tetrahydrofuran (THF) as a major product from BDO. Interestingly, the coupling process over the 10CM catalyst produced the best performance in converting NB (65%) to AN (99%) and BDO (85%) to GBL (99%). The superior performance of Cu/MgO in coupling process catalyst is mainly due to the high hydrogen adsorption ability compared to the other catalysts under limited hydrogen environments, which helps retain the active hydrogen on the catalyst surface for a longer time. The characterization of the catalysts showed that a high basic nature and the optimal amount of active copper sites (Cu⁰/Cu¹⁺) are responsible for the best performance of 10CM, followed by 10CS and 10CMA.