Catalytic reforming of toluene as tar model compound: Effect of Ce and Ce–Mg promoter using Ni/olivine catalyst

• Ce and Mg promoters enhancing Ni/olivine catalysts in toluene conversion.
• Ni–Ce–Mg/olivine having highest toluene conversion and energy yield.
• Ni–Ce–Mg/olivine resistant to 10 ppm H2S poison.
• Ni–Ce–Mg/olivine resistant to deactivation.

Tar produced by biomass gasification as a route of renewable energy must be removed before the gas can be used. This study was undertaken using toluene as a model tar compound for evaluating its steam reforming conversion with three Ni-based catalysts, Ni/olivine, Ni–Ce/olivine and Ni–Ce–Mg/olivine. Effects of Ce and Mg promoters on the reaction activity and coke deposition were studied. Overall the performance of Ce and Mg promoted Ni/olivine catalysts is better than that of only Ce promoter and Ni/olivine alone. The experimental results indicate that Ni–Ce–Mg/olivine catalysts could improve the resistance to carbon deposition, enhance energy gases yield and resist 10 ppm H2S poison at 100 mL min−1 for up to 400 min. Furthermore, the activity of catalysts was related to the steam/carbon (S/C) ratios; at S/C ratio = 5, T = 790 °C, space velocity = 782 h−1 and t = 2 h, the Ni–Ce–Mg/olivine system yielded 89% toluene conversion, 5.6 L h−1 product gas rate, 62.6 mol% H2 content and 10% (mol useful gas mol−1 toluene) energy yield. Moreover, at low S/C ratio, it had higher reaction activity and better ability to prevent coking. There is a small amount of carbon deposition in the form of amorphous carbon after 7 h. Various characterization techniques such as XRD, FTIR and thermogravimetric were performed to investigate the coke deposition of Ni/olivine, Ni–Ce/olivine and Ni–Ce–Mg/olivine. It is suggested that 3% Ni-1% Ce-1% Mg/olivine was the most promising catalyst due to its minimum coke amount and the lower activation energy of coke burning.