Preparations of C/SiC composites and their use as supports for Ru catalyst in ammonia synthesis

A series of C/SiC composites was successfully synthesized via the carbothermal reduction of carbonaceous silicon xerogel, which was prepared from the sol gel method by using tetraethoxysilane TEOS and saccharose as the raw materials The obtained samples were characterized by X ray powder diffraction XRD and N2 physical adsorption The specific surface areas of the as prepared C/SiC composites varied from 329 to 849 m2/g The average pore diameters and the total pore volumes were in the range of 4.5–7.6 nm and 0.53–1.12 cm3/g, respectively The as prepared C/SiC composites were proved to be effective supports for Ru catalysts for ammonia synthesis At 435 °C, 10.0 MPa and a N2/H2 (1/3) flow rate of 10 000 h−1, the optimum activity of 15.9% ammonia in the effluent was reached when C/SiC-5 (C/TEOS molar ratio = 5) was used as the catalyst support.

Graphical abstractThe catalytic activity of the C/SiC-supported Ru catalysts exceeds that of the traditional Fe-based catalyst (ICI-74-1) at lower temperatures. At 435 °C, 10.0 MPa and a N2/H2 (1/3) flow rate of 10 000 h−1, the optimum activity of 15.9% ammonia in the effluent can be reached when C/SiC-5 (C/TEOS molar ratio = 5) was used as the catalyst support, with the potassium promoter loaded to 16 wt%.Figure optionsDownload full-size imageDownload as PowerPoint slide