Jialong Xu,Liang Zhu,Wei Cai,Zixia Ding,Dengyu Chen,Wenbiao Zhang,Chuang Xing,Kaige Wang,Zhongqing Ma
The oxidative torrefaction pretreatment (OTP) is a promising approach to upgrade the quality of biomass. This work investigated the oxidative torrefaction mechanism based on the OTP experiment of biomass pseudo component (cellulose, hemicellulose, and lignin) at varying OTP temperatures and oxygen concentrations. Results showed that more mass of biomass was transferred into the torrefied gaseous and liquid products with OTP temperature and oxygen concentration increasing, remaining less mass in torrefied solid product. The element distribution in biomass pseudo component was optimized after OTP, presenting as the removal of oxygen element and the enrichment of carbon element. The variation of these two elements in hemicellulose after OTP was much higher than that of cellulose and lignin due to the more intensive thermal decomposition reaction in hemicellulose. The chemical compounds in torrefied liquid products from biomass pseudo component were highly differentiated with each other, the anhydrosugars (e.g., levoglucosenone (LGO) and levoglucosan (LG)) and furans (e.g., furfural (FF)) from OTP of cellulose, the furans (e.g., furfural (FF)) and acids (e.g., acetic acid (AA)) from OTP of hemicellulose, the phenols from OTP of lignin. The concentrations of the released gas components during OTP of biomass pseudo component were ranked as CO 2 > CO > H 2 ≈ CH 4 . The thermal degradation mechanism of biomass OTP was revealed.
To unveil the nitrogen migration and conversion characteristics, catalytic copyrolysis of biomass pseudo components and polyamide (PA) with different blend ratios (1:0, 5:1, 3:1, 1:1, 1:3, 1:5, 0:1) under an ammonia atmosphere was proposed to boost the yield of N-containing compounds (NCCs) and N-rich biochar. The evolution and distribution of NCCs in liquid, gas and biochar were systematically investigated with a combination of TG-MS, Py-GC/MS and EPR. Synergistic effects and possible reaction pathways were also evaluated. Experimental results showed that PA could obviously boost biomass conversion due to increasing the chance of secondary cleavage, and the comprehensive synergistic effect of biomass-derived H* radicals, acid sites of the catalyst and cracking reactions (-C-N and C-C bonds) that reduced the reaction energy barrier and enhanced the NH 3 and HCN yields. NH 3 comes from the amino acids that are released from the amino acid pyrolysis and hydrolysis of HCN on the surface of char, while HCN is from the secondary cracking of primary pyrolysis products. Adding biomass increased CO 2 , CO, CH 4 , C-O and C O emissions from co-pyrolysis. Additionally, significant synergetic effects were observed when Biomass/PA= 3:1, which improved the NCCs and pyridine yields by 78.58% and 48.23%, respectively, under the HZSM-5 catalyst. A lower proportion of PA addition facilitated the Maillard reaction and amide bond cleavage to enhance the NCCs content and suppressed π-conjugated ring structure compound evolution and coke-derived O-containing compound polymerization, while a higher content of PA was favorable for amine and diaza heterocycle compound formation. Moreover, the addition of PA reduced the HHV and N content in biochar, resulting in lower pyrrole-N content and graphitization degree due to secondary cross-polymerization reaction of reaction volatiles, but it enhanced the polarity due to higher oxygen content (14.98%).
Ming Huang,Liang Zhu,Wenbiao Zhang,Lingjun Zhu,Zhongqing Ma,Dengyu Chen
Co-feeding of waste plastics during biomass catalytic fast pyrolysis can improve remarkably the yield of aromatic hydrocarbons. In this work, the simulated biomass by using its model components of cellulose, xylan, and lignin at different proportions was Co-CFP with LDPE to investigate the synergistic reaction mechanism between biomass and low-density polyethylene (LDPE) over hierarchical HZSM-5. Results showed that biomass and its model components were oxygen-enriched feedstock, while LDPE was the hydrogen-enriched feedstock with H/C eff over 2. The synergistic effect between biomass model components and LDPE was ordered as cellulose and LDPE > xylan and LDPE > lignin and LDPE. Because pyrolysis of cellulose produced higher yield of furans than that of xylan and lignin which acted as the key synergistic compounds in Diels-Alder reaction to form light aromatics. The transfer of hydrogen free radical from the LDPE-derived hydrocarbons to the biomass-derived oxygenates promoted the deoxygenation reaction of oxygenates in hierarchical HZSM-5. Diels-Alder reaction between furans and olefins was the key synergistic reaction which highly improved the yield of hydrocarbon aromatics. In general, the difference of the pyrolysis oxygenated intermediate among the biomass pseudo components resulted in different yields of light aromatics, where cellulose presented highest extent of synergistic reaction to LDPE.
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