Deposition–precipitation approach for preparing core/shell SiO2@Ni-Rh nanoparticles as an advanced catalyst for the dehydrogenation of 2-methoxycyclohexanol to guaiacol

A novel core/shell nano-bimetallic catalyst SiO 2 @Ni-Rh was successfully prepared by deposition–precipitation method, using liquid ammonia as a precipitating agent. SEM, TEM, XRD, XPS, H 2 -TPR, H 2 -TPD and adsorption/desorption of nitrogen were employed to systematically investigate the surface morphology, size, chemical composition, reducibility, Ni dispersion and structure of the as-synthesized nanoparticles. It is found that the nickel and rhodium are uniformly dispersed on the silica surface to form core/shell SiO 2 @Ni-Rh nanoparticles with Ni atoms and Rh atoms as the outer shell and SiO 2 as the core, which possess high dispersion of Ni on the surface and high specific surface area (234.063 m 2 /g) of the catalyst with the mean particle size of ca. 130 nm. The dehydrogenation of 2-methoxycyclohexanol to guaiacol was used as the model reaction for evaluating the catalytic activity of the as-synthesized core/shell various Ni and Rh-containing bimetallic nanoparticles in a tubular stainless steel reactor. SiO 2 @15Ni-0.4Rh nanoparticles have exhibited remarkable catalytic performance, with 98.3% conversion and 93.6% selectivity of guaiacol, due to high dispersion of metal nanoparticles and synergistic effect of bimetallic Ni-Rh over the special core/shell SiO 2 @Ni-Rh by the addition of rhodium. Furthermore, turn over frequency value of SiO 2 @15Ni-0.4Rh nanoparticles achieves 0.47 s −1 , showing high catalytic efficiency. In general, the dehydrogenation of 2-methoxycyclohexanol over the core-shell-like SiO 2 @Ni-Rh nanoparticles in a continuous fixed-bed reactor is a more promising, high atom economy, high efficient, easy separation, environmental friendliness, green synthetic pathway of guaiacol.