Efeito do pré-tratamento de biomassas lignocelulósicas com ultrassom nas frações de bio-óleo e biochar obtidos por pirólise

• Ano de defesa: 2025
• Autor(a) principal: Silva, Thalyta Fonseca
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Santa Maria; Brasil; Engenharia Química; UFSM; Programa de Pós-Graduação em Engenharia Química; Centro de Tecnologia
• Palavras-chave em Português: Biomassa lignocelulósica; Pré-tratamento; Pirólise; Ultrassom; Biocombustíveis; Lignocellulosic biomass; Pretreatment; Pyrolysis; Ultrasound; Biofuels; CNPQ::ENGENHARIAS::ENGENHARIA QUIMICA
• Link de acesso: http://repositorio.ufsm.br/handle/1/34566

The production of fuels with neutral or low carbon emissions through renewable resources, such as biomass, is an alternative to minimize dependence on fossil fuels and meet energy demand, as well as to reduce pollutant emissions. Pyrolysis is a thermochemical process for converting varied materials, including biomass, with thermal decomposition of organic compounds occuring under an inert atmosphere, forming heterogeneous products. To make the most of the biomass suitable, the pre-treatment step is essential, to fragment its three main constituents (cellulose, hemicellulose and lignin). The treatment of materials with ultrasound (US) has been studied as a rising process for the pretreatment of lignocellulosic biomass, due to its ability to overcome the recalcitrant nature of this material, promoting effects that affect the processes to which the material will be subjected. This study aimed to evaluate the effects of pretreatment with US under different conditions on bio-oil and biochar formed by pyrolysis of agricultural biomass from sugarcane straw (SS) and sugarcane bagasse (SB) and forest residues from pine wood (PWR) and eucalyptus wood (EWR). Furthermore, the aim was to characterize the biomass and products formed after the conversion process (bio-oil and biochar). Pre-treatments with US were performed using neutral (with ultrapure water), acidic (H2SO4 1 mol L-1) and alkaline (NaOH 1 mol L-1) pH conditions. After, pre-treated materials were subjected to pyrolysis to evaluate the characteristics of the liquid (bio-oil) and solid (biochar) products. The SS, SB, PWR and EWR biomasses were subjected to slow (SP) and fast (FP) pyrolysis at 400 to 600 ºC. Pretreatment with US was carried out at a frequency of 45 kHz, amplitude of 70%, 60 ºC for 30 min with water, H2SO4 and NaOH. Comparatively, all biomasses were also treated under the same conditions, without application of US (silent condition), at 60 ºC for 30 min. All pre-treated biomasses, with US and without US (silent) condition, were subjected to subsequent FP, at 600 ºC. For all biomasses, pretreatment with ultrapure water in US was effective in decreasing moisture content and decreasing the concentration of Ba, Ca, K, Mg, Na, Sr and Cl, and pretreatment with NaOH contributed to increasing ash content in most of them. Treatment with H2SO4 was effective for the removal of analytes in agricultural and woody biomass. Pretreatment of SS biomass contributed to an increase in bio-oil yield of approximately 18% with ultrapure water, 7% with acidic solution and 22% with alkaline solution. Alkaline treatment negatively influenced the yield of the liquid fraction for SB and PWR. For EWR, a higher bio-oil yield (78%) was observed in the pretreatment with ultrapure water with US. For SB and EWR, pretreatment was not favorable to increasing bio-oil yield in almost all conditions. For PWR there were no significant differences between the conditions evaluated. For all treatment conditions, bio-oil presented concentrations below the quantification limit for all elements evaluated, while in biochar, the conditions applied resulted in different effects, such as a decrease or an increase in the concentration of metals and ash, depending on the biomass, for some of the conditions studied.