Maleic anhydride hydrogenation to succinic anhydride over mesoporous Ni/TiO₂ catalysts: Effects of Ni loading and temperature

Catalytic hydrogenation of maleic anhydride for the production of succinic anhydride can be a viable alternative to the higher energetic demand route based in the dehydration of succinic acid. In this sense, the metallic Ni catalysts supported on mesoporous TiO₂ (anatase) substrate demonstrated to be very active and 100% selective in the liquid phase hydrogenation of maleic anhydride (MA) to succinic anhydride (SA). The catalysts, which were prepared via wet impregnation method with different Ni loading (5, 10 and 15 wt.%), were characterized by chemical analysis (ICP-AES), N₂ physical adsorption-​desorption, H₂-​temperature programmed reduction (H₂-​TPR)​, X-ray diffraction (XRD)​, high resolution transmission electron spectroscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS). The Ni species interaction with support was investigated by TPR and by performing five catalyst recycling tests. After catalyst activation by reduction, the increase of Ni particle size with an increase of Ni loading was relatively small (from 6.9 to 8.9 nm) due to enhance of the metal-support interaction. After the first catalytic cycle, the optimized 5%Ni/TiO₂ catalyst showed a small decrease in the Ni loading attributed to metal leaching during time course of reaction. Besides this, the 5%Ni/TiO₂ catalyst exhibited a good stability during five continuous cycles with a very high yield of SA after 5 cycles. Finally, temperature experiments performed for the best system shown that the reaction temperature does not affect the SA selectivity in the temperature range studied (323 K–398 K).