Investigation of the Reaction Network of Benzofuran Hydrodeoxygenation over Sulfided and Reduced Ni–Mo/Al2O3 Catalysts

The hydrodeoxygenation (HDO) network of benzofuran was investigated over alumina-supported Ni–Mo sulfided and reduced catalysts. The effect of reaction temperature, pressure, hydrogen sulfide feed concentration, and pretreatment procedure on the product distribution, hydrogenolysis, and hydrogenation activity of each catalyst was studied. The differences and similarities between the observed benzofuran HDO network and the networks proposed in the literature were examined. Parallels between HDO and hydrodenitrogenation (HDN) were investigated by comparing the benzofuran HDO findings with previous results obtained for indole HDN. Reaction studies were carried out in a fixed-bed vapor-phase reactor using a wide range of feed concentrations at 120–360°C and 300–800 psig. Over the sulfided catalyst, one major route is observed for the benzofuran HDO network; it starts with the hydrogenation of benzofuran to 2,3-dihydrobenzofuran followed by its hydrgenolysis to 2-ethylphenol. Over the reduced catalyst, however, an additional route is observed that begins with the hydrogenation of 2,3-dihydrobenzofuran. This route contains several other oxygen-containing intermediate species that are not observed over the sulfided catalyst, and hydrocarbon products are formed by this route at significantly lower temperatures. The product distribution for both catalysts is found to be a strong function of temperature and H2S feed concentration where the hydrogenolysis reactions were promoted and the hydrogenation reactions were inhibited by H2S in the feedstream.