Abstract:

Nickel-based supported molecular sieve catalysts were prepared by excessive impregnation with different auxiliary methods using molecular sieve as the carrier. The catalytic pyrolysis performance of the nickel-based molecular sieve catalysts on the hydrogen carrier of biomass tar aromatic hydrocarbon-toluene to produce hydrogen was studied in a fixed-bed reactor. The effects of different molecular sieves, auxiliary methods and process conditions were investigated, and the service life of the catalyst was studied. The catalysts were characterized by XRD, SEM and BET. The results showed that the Ni/HZSM-5 molecular sieve catalyst using HZSM-5(the ratio of silicon to aluminum was 25) zeolite as the carrier had the highest catalytic activity, through the ultrasonic-assisted impregnation method, and the ultrasonic time was 20 min, the ultrasonic power was 80 W, and the Ni loading was 8%. At 700℃ and 40 min, the yields of H₂ and CH₄ were 76.6 mL/g and 27.6 mL/g, respectirely, and the total gas yield reached 108.9 mL/g. The toluene conversion rate was 76.8%, and the carbon deposition was 238.2 mg/g. The specificsurface area, the total pore volume and the average pore size of the catalyst were 241.8 m²/g, 0.19 cm³/g and 3.16 nm, respectively. The Ni loading did not affect the crystal structure of HZSM-5 obviously, while it exhibited an excellent catalytic activity. The stability of Ni/HZSM-5 catalyst was improved, and the service life was also extended. The catalytic hydrogen production performance of toluene was better than that of tetralin, phenol and acetic acid.

Key words: nickel-based catalyst, catalytic pyrolysis, aromatics, hydrogen production