Hydrotalcite as a deoxygenation catalyst in fast pyrolysis of biomass for the production of high quality bio-oil

摘要

Commercially available MG70 hydrotalcite (HT) has been investigated for its influence on the in-situ catalytic fast pyrolysis of beechwood. The investigations were performed both with an analytical Py-GC/MS (pyroprobe) and on a bench scale fluidized bed reactor at a pyrolysis temperature of 500 ?. The semi qualitative pyroprobe analysis was carried out for different catalyst to biomass (C/B) ratios and a ratio of 4 was found to be optimum. At this C/B ratio, the acids, anhydro-sugars and methoxy phenolics were more or less eliminated and HT facilitated the formation of alkylated cyclopentenones, cresols, methly furans and hydrocarbons. The application of HT in the bench scale fluidized bed reactor allowed for further analysis of the pyrolysis products: bio-oil, char, and gas. The semi qualitative GCMS analysis of bio-oil was in general agreement with the volatiles detected from Py-GC/MS analysis. In addition the catalyst was characterized by BET, XRD and TGA analysis. Overall an organic rich bio-oil with a yield of 9.5 wt%, higher heating value of 29.3 MJ/kg (as received) was obtained. The pH of the bio-oil increased from 3.2 to 6.0 and oxygen content reduced from 46.3 to 20.5 wt% (as received). The substantial increase in CO2 concentration in the pyrolysis gas also supported these findings. Overall, HT facilitated the formation of moderately deoxygenated compounds and they are of interest as they can be further processed downstream to produce bio-fuels.