Catalytic hydrocracking, hydrogenation, and isomerization reactions of model biomass tar over (W/Ni)-zeolites

Abstract

Producing bio-based aromatic substrates is becoming increasingly of (industrial) interest. In this mechanistic work, the gas phase conversion of the biomass tar chemical model compounds (5 wt% naphthalene/95 wt% 1-methylnaphthalene) over the different pristine/metal-modified zeolites in a continuous flow fixed bed reactor was investigated. Bifunctional redox acid process catalysts were synthesized by wet impregnation method. The effect of the W (/Ni) metal formulation additives to the pristine H-beta, H-USY, H-Y, and H-ZSM-5 in the hydrocracking, hydrogenation, and isomerization transformation reactions of the mixture under applied ambient pressure was firstly studied. Structure, texture, morphology, acidity, composition and properties were determined by various analytical techniques. Results showed that the highest catalytic activity with a comparison to others was established over the 20 wt% W-beta with 96.0 mol% of the selectivity to 2-methylnaphthalene, the 93.3 mol% reacted total reactant after the 24 h time on stream, where ethylene/propane were predominating (80.5 wt%), and facile manufacturing scalability. Detailed characterization methodologies have revealed that after the loading of W onto H-beta_support, a uniform functional distribution of particles, the dealumination of framework and strong interaction phenomena were observed, which led to an increase in the amount of Brønsted/Lewis/reduction surface sites, and hence, increase stability of the catalyst. In addition, equilibrium coke formation was detected, decreasing all estimated rates, undergoing also consequent external deactivation, blocking pores, and its burning-off regeneration being needed. While both spent W-modified (20 wt%)/unmodified H-beta/ZSM-5 exhibited the lowest carbon quantity, the same fresh materials possessed the uppermost hierarchy factors.