Simultaneous synthesis of aniline and γ-butyrolactone from nitrobenzene and 1,4-butanediol over Cu-CoO_x-MgO catalyst via catalytic hydrogen transfer process: Effect of calcination temperature

This study examined a hydrogen transfer reaction from 1,4-butanediol to nitrobenzene for γ-butyrolactone and aniline simultaneously over Cu-CoO_x-MgO catalysts. The catalyst was developed by co-precipitation followed by metal hydroxycarbonate mixing and calcination at three different temperatures (500, 700, and 900 °C). The hydrogenation of nitrobenzene to aniline and the dehydrogenation of 1,4-butanediol to γ-butyrolactone was accomplished in a gas-phase fixed-bed continuous reactor system at 250 °C. The catalyst Cu-CoO_x-MgO-500 calcined at 500 °C showed outstanding performance because of the higher copper dispersion and negligible spinel species (CuCo₂O₄ /MgCo₂O₄) compared to the other two catalysts. The order of activity decreased with increasing calcination temperature from 500° to 900°C. The activity trend followed the order, Cu-CoO_x-MgO-500 > Cu-CoO_x-MgO-700 > Cu-CoO_x-MgO-900. The effect of calcination on the catalytic properties was analyzed by atomic absorption spectroscopy elemental analysis, Brunauer-Emmett-Teller surface area, N₂O pulse chemisorption, temperature-programmed reduction-H₂, X-ray diffraction, and X-ray photoelectron spectroscopy. The results showed that Cu-CoO-MgO-500 exhibited more active copper sites (Cu⁰/Cu⁺¹) and optimal metal-support interactions that decrease the reduction temperature of copper. On the other hand, Cu-Co and Mg-Co spinel (CuCo₂O₄/MgCo₂O₄) content, which adversely affects the catalyst activity, increased with increasing calcination temperature. In summary, simultaneous hydrogenation and dehydrogenation reactions via hydrogen transfer reactions have potential commercial applications.