Insight into acid-base bifunctional catalysts for microalgae liquefaction and bio-oil pyrolysis: Product characteristics, energy recovery and kinetics

•SO3H/SBA-15-NH2 catalyst was prepared by functional groups grafting.•Hydrocarbon yield of ex situ upgrading of LBO (liquefied bio-oil) was prompted by SO3H/SBA-15-NH2 as well as SO3H/SBA-15.•Deoxygenation rate of non-catalytic LBO was optimized on SO3H/SBA-15-NH2.•HHV of DSO (dual-stage oil) was analogous to petroleum crude. The aim of this work was to enhance the hydrocarbon yield of Chlorella liquefaction and consecutive upgrading by a new class of acid-base bifunctional heterogeneous catalysts. A simple method of grafting -SO3H and -NH2 groups on the surface of clin/SBA-15 resulted in SO3H-SBA-15-NH2 catalysts. Oil yields of in situ and ex situ upgrading of LBO (liquefied bio-oil) were obtained on SO3H-SBA-15-NH2. On the optimized catalyst, the hydrocarbon yield was prompted to 68.34 %, the deoxygenation of noncatalytic LBO was up to 59.42 %, and the heat value of DSO (dual-stage oil) was 42.33 MJ/kg, which was analogous to that for petroleum crude. SO3H- played a predominant role in Chlorella decomposition, and NH2- showed a critical effect on LBO deoxygenation. The O/C ratio (0.086) of LBO was effectively reduced to 0.031−0.082 (in DSO). The activation energy of noncatalytic LBO to DSO pyrolysis was 92.42 kJ/mol at 70 % weight loss, which was attributed to the synergetic effect of acid and base sites on the catalyst. This ex situ catalytic approach reveals great potential for algae in fuel production.