Effect of Preparation Solvent and Calcination Atmosphere on Ni@SiO2 Catalyst for Simultaneous Production of Hydrogen and Carbon Nanotubes from Simulated Plastic Waste Syngas

SiO2 core supports are prepared via the Stober method with various synthesizing solvents. Then, a Ni shell is deposited on SiO2 by a deposition-precipitation method. The results illustrate that using isopropanol as the solvent governs the catalyst particle size with a superior dispersion and a high catalytic activity. Thus, the calcination atmosphere of the catalyst directly affects both the chemical state and the catalytic performance of the active sites. The Ni@SiO2-I-air (isopropanol) catalyst calcined by air with more Ni2+ facilitates the highest H-2 production of 142.2 mmol g(-1) h(-1) but provides a carbon nanotube (CNT) yield of only 7.6%. Most importantly, the Ni@SiO2-I-H-2 catalyst calcined by ambient H-2 is prone to form Ni-0 species, thus providing the best crystalline conversion and metal-support interaction, which benefits the production of CNTs to a maximum yield of 19.8% with a H-2 production of 122.8 mmol g(-1) h(-1).