Production Of Benzoic Acid Through Catalytic Transformation Of Sawdust

Biomass is an abundant renewable energy source and the only renewable organic carbon source that has a huge advantage in replacing fossil fuels as a source of fuel and chemicals.In this paper,the production of benzoic acid through catalytic transformation of biomass(sawdust)was put forward and achieved:(i)the catalytic pyrolysis of sawdust into aromatics;(ii)the dealkylation of heavier alkylaromatics to toluene;(iii)the liquid-phase oxidation of toluene-rich aromatics to benzoic acid.The results of the study include:1.Production of aromatic hydrocarbon mixture by catalytic pyrolysis of sawdust.The effects of the main reaction conditions and the addition of methanol on the catalytic pyrolysis of biomass were studied by using 1%Zn/HZSM-5 zeolite as catalyst.The maximum yield of the mixed aromatics was 23.2 wt%under the optimum reaction conditions(T = 450?,methanol/sawdust mass ratio of 1:1).The reactions involved include pyrolysis,decarbonylation,decarboxylation,dehydroxylation,aromatization and so on.It was also found that the addition of methanol was beneficial to increase the yield of aromatic hydrocarbons and reduce the coke deposition on the catalyst surface,which inhibited the deactivation of the catalyst.2.Production of toluene by the dealkylation of heavier alkylaromatics.Considering the complex composition of the aromatic hydrocarbon mixture obtained by the catalytic pyrolysis of sawdust,it is necessary to carry out the catalytic dealkylation process to improve the content of toluene.The reaction temperature and the effect of adding methanol on the dealkylation process were studied by using Re/HY molecular sieve as catalyst.The organic liquid yield was 52.3wt%under optimized reaction conditions(T = 530?,methanol addition of 30 wt%),consisting essentially of 46.1 wt%benzene,45.2 wt%toluene and 6.8 wt%xylene.The addition of methanol can significantly reduce the coke yield.3.Production of benzoic acid by liquid-phase oxidation of toluene-rich aromatic hydrocarbon mixtures.First,the catalyst screening was carried out.MnO2/NHPI was selected as the aromatics oxidation catalyst owing to high oxidation activity and containing free of chlorides.Secondly,the effects of temperature and reaction time on reactant conversion and product selectivity were investigated.The production of the desired benzoic acid from the sawdust-derived aromatics,with the benzoic acid selectivity of 85.1 C-mol%and nearly complete conversion of toluene,was achieved using the MnO2/NHPI catalyst at 100? for 5h.Under optimized conditions,the total yield of benzoic acid was 207.8 g/kg sawdust(sawdust/methanol mass ratio of 1:1.2).