Improving the activity and long-term durability of the Ni/Al2O3 catalyst in the low-temperature steam reforming of highly concentrated volatile organic compounds

Abstract

Highly concentrated volatile organic compounds (VOCs), a precursor of PM2.5, are released from car-painting booths, laundries, printing presses, and refineries. H2, as an eco-friendly substitute to fossil fuels, can be produced by the steam reforming of highly concentrated VOCs. However, catalyst deactivation caused by coke accumulation is a serious issue in relation to steam-reforming reactions. A series of 15Ni-M/Al2O3 (M = 5 wt% of Ce, La, Sm, Fe, Tb, Ca, Mn, Sr, V, Hf, and Cs) has been synthesized to investigate their catalytic activity during the steam reforming of the highly concentrated toluene, xylene, and butyl acetate (6000–7000 ppm) mixture released from car-painting booths. The influence of the reaction conditions is studied at T = 400–600 °C, steam-to-carbon ratio (S/C) = 3–15, and gas-hourly-space-velocity (GHSV) = 15,000–40,000 h−1. NiCe/Al2O3 shows the optimal H2 yield and VOC conversion of 91 % and 99 %, respectively, at 550 °C, an S/C of 6, and a GHSV of 15,000 h−1 among all the prepared catalysts. Under the same reforming conditions, the unpromoted Ni/Al2O3 catalyst exhibits an H2 yield and VOC conversion of 73 % and 75 %, respectively. The NiCe/Al2O3 catalyst shows a stable H2 yield and VOC conversion over a 100 h reaction period, with a maximum coking rate of 1.80 mgc gcat-1h−1. The superior catalytic performance and durability of the NiCe/Al2O3 catalyst are associated with its low acidity, strong metal–support interaction, high metal dispersion with a small Ni crystallite size, high Ni0 (77 %) and Ce+3 (80 %) content, and abundant oxygen vacancies (91.4 %).

Keywords

• Coking
• Catalyst synthesis
• H2 production
• VOCs
• Steam reforming
• Stability