Acidity-regulation for enhancing the stability of Ni/HZSM-5 catalyst for valeric biofuel production

[Display omitted] •The activity and stability of Ni/HZSM-5 are comparable to noble metals.•Deactivated Ni/HZSM-5 can be regenerated by calcinations followed by reduction.•Acidity-regulation by potassium addition leads to lighter coke component.•Acidity-regulation by potassium addition prolongs the catalyst lifetime. Valerate esters as a new class of cellulosic transportation fuels showed great industrial prospect. Here we developed a non-noble Ni/HZSM-5 bifunctional catalyst with excellent stability for the cascade transformation of levulinic acid to valerate esters. The acidity-regulation of Ni/HZSM-5 catalyst by potassium addition decreased the strong acidity, meanwhile tuned the proportion of Brönsted acidity/Lewis acidity. Coke analysis indicated that acidity-regulation by potassium addition changed the heavier coke component (alkylated poly-aromatics) to the lighter one (alkylated mono-aromatics), thus effectively prolonged the lifetime of Ni/HZSM-5 catalyst in fixed-bed reactor. The relationship of the nature of coke deposits and the acidity-regulation of catalysts could contribute to intensively understand the catalyst deactivation and the choice of stable catalyst for upgrading of biomass and its platform molecules.