Selective Production of Platform Chemicals from Low-Temperature Pyrolysis of Biomass Mediated by Exogenous Acid-Intrinsic Base Balance br

The catalytic activity of intrinsic alkali and alkaline earth metals (AAEM) in biomass has been usually considered as anegative factor affecting the fast pyrolysis of biomass. Herein, thisnegative factor was turned into a positive one using 0.4%H2SO4impregnation of pinewood, which can achieve the directionalpyrolysis of pinewood into levoglucosan at low temperatures.Pyrolysis of 0.4%H2SO4-impregnated pinewood at 300 degrees Cdrastically improved the yield of levoglucosan from 2.3 to 53.6%while suppressing the formation of small oxygenates, non-condensable gases, and char. The introduction of the desiredamount of exogenous H2SO4combined with intrinsic AAEM inraw biomass, namely, exogenous acid-intrinsic base balance, wasessential to achieve the directional pyrolysis of biomass at low temperatures to form levoglucosan. Exogenous H2SO4accounted forthe low-temperature activation of cellulose to form levoglucosan, while intrinsic AAEM were responsible for inhibiting thedehydration reactions to form levoglucosenone and char. Compared with the pyrolysis of raw pinewood at 500 degrees C, pyrolysis of 0.4%H2SO4-impregnated pinewood at 300 degrees C reduced the heat requirement by 78.5%. The kinetic analysis demonstrated that 0.4%H2SO4impregnation improved the activation energy for pyrolysis of pinewood. In situ DRIFT experiment combined with two-dimensional perturbation correlation infrared spectroscopy (2D-PCIS) analysis showed that H2SO4can achieve the low-temperatureactivation of cellulose within pinewood to form levoglucosan. AAEM can inhibit the intramolecular dehydration of the C3 hydroxylgroups and C2 hydrogen atoms in the levoglucosan end/levoglucosan to form levoglucosenone and char. Thisfinding provides asimple and energy-saving approach to achieve directional conversion of biomass into platform chemicals via low-temperature pyrolysi