Catalytic pyrolysis of Napier grass with nickel-copper core-shell bi-functional catalyst

[Display omitted] •The Ni-Cu/mCMs catalysts gave a high efficiency for catalytic pyrolysis of Napier grass.•The Ni-Cu/mCMs catalyst remarkably increased alkyl-phenols up to four-fold.•The oxygen removal was about 24 % more than in the non-catalytic bio-oil. Nickel-copper (Ni-Cu) core-shell catalysts supported on phosphorus-modified carbon microspheres (mCMs) were prepared at three Ni/Cu mass ratios, and applied to the catalytic pyrolysis of Napier grass (Pennisetum purpureum) under atmospheric pressure. The catalytic pyrolysis was carried out inside a custom-built one-shot two-stage fixed-bed reactor. The catalyst structure was confirmed by X-ray photoelectron spectroscopy and X-ray absorption spectroscopy. Remarkably, the Ni-Cu/mCM catalysts increased the produced alkyl-phenols by up to fourfold, and these products are an excellent gasoline blend stock due to their high blending octane number. At the same time, the mass of undesired compounds in the bio-oil including alcohols, ketones, and furan were markedly decreased compared to the case without a catalyst. The oxygen content of the bio-oil was reduced by up to 24 % compared to the non-catalytic case. The hydrogen/carbon and oxygen/carbon molar ratios were also improved after all catalytic treatments. Finally, a reaction mechanism was proposed, including the pathways of oxygen removal through dehydration, decarbonylation, and dealkoxylation. The presence of NiO in the Ni-Cu/mCM catalyst promoted the alkylation reaction to yield more alkyl-phenols.