Novelty without nobility: Outstanding Ni/Ti-SiO2 catalysts for propylene epoxidation

An efficient gas-phase production of propylene oxide (PO) with noble metal-free catalysts could modify the industrial output of this valuable compound. We present a novel catalyst based on well-dispersed Ni nanoparticles loaded on a Ti-SiO2 support for the propylene epoxidation reaction using H2/O2 mixtures. XPS, High Resolution Transmission Electron Microscopy (HRTEM), and UV–Vis corroborate both the small size of Ni particles and the excellent dispersion and incorporation of Ti as tetrahedral single site species into the silica framework. The catalytic results under steady-state conditions at low temperature (200 °C) show high PO selectivity (around 85%) with a substantial propylene conversion (over 6%) and excellent H2 efficiency (~37%) using only 0.5 wt% of Ni on Ti-SiO2 (Ti/Si = 0.01 M ratio). In this work, we have also carried out a preliminary DFT study to gain understanding of the characteristics that make this nickel catalyst active and selective for the propene epoxidation reaction. We thank the Spanish Ministry of Economy and Competitiveness (MINECO), Spanish Ministry of Science, Innovation and Universities, Generalitat Valenciana and FEDER (CTQ2015-66080-R, RTI2018-095291-B-I00, MAT2017-87579-R, and PROMETEO/2018/076) for financial support. JFC thanks MINECO for a researcher formation grant (BES-2016-078079).