Pirólise de biomassa lignocelulósica auxiliada por micro-ondas para produção de bio-óleo

Abstract

A review of the main concepts about microwave-assisted pyrolysis of lignocellulosic bio-mass was performed. The aim of this study is to elucidate the main differences between conventional pyrolysis and microwave-assisted pyrolysis, presenting MAP as an alternative to the former. For this, data from several studies available in the literature were used, through which the results of this technique and its derivations were presented and dis-cussed. Thus, it was possible to show that: volumetric heating ensures better heat and mass transfer, resulting in a higher level of thermodegradation heating rates and microwave power, witch play a key role in advancing the degradation of lignocellulosic biomass; pa-rameters such as pyrolysis temperature, residence time and biomass composition exert a strong influence on the degradation process and influence the yield and quality of the products, but that the size of the particles that have negligible effects on the product yields. It is also demonstrated that, as in conventional pyrolysis, the bio-oil obtained presents un-desirable characteristics such as high acidity, high water content, high viscosity and density and low calorific capacity, characteristics that make the upgrading process indispensable. As a way to improve the quality of bio-oil, solutions involving the feed system, such as the addition of other materials giving rise to co-pyrolysis, and modification in the condensation system are presented. In addition, catalytic pyrolysis is presented as the most promising alternative for the improvement of bio-oil, whose ex-situ pathway stands out for favoring the contact of pyrolytic vapors with the active sites of the catalyst, thus requiring a smaller amount of catalyst, and for allowing a more precise temperature control, since this is done independently of the temperature control of the pyrolytic bed, leading to increased cataly-sis efficiency