Zhao Sun,Hanpeng Liu,Sam Toan,Weizhi Shi,Dongfang Cheng,Zhiqiang Sun
Biomass to hydrogen production has been regarded as a potential approach for green hydrogen synthesis. However, carbon dioxide and bio-tar are inevitably produced, which critically restricts the refinement of biomass-derived syngas. In this study, deoxygenation-enhanced chemical looping biomass gasification (DE-CLBG) is proposed for hydrogen-rich syngas production together with CO2/H2O deoxygenation and catalytic bio-tar removal using the composite Fe/CaO as the deoxidizer. The DE-CLBG process is comprised of a deoxygenated gasification stage and a regeneration stage. During the deoxygenated gasification stage, the deoxidizer is converted under steam gasification via CaO + Fe + O2− → Ca2Fe2O5 with biochar generation; at the regeneration stage, biochar is further gasified with the achievement of deoxidizer reduction via Ca2Fe2O5 + C → CaO + Fe + COx. Experimental results show that the hydrogen production and maximum concentration upon applying 0.300 g of deoxidizer per g of biomass are 6.70 mmol and 89.61 vol%, which was increased by 287% and 27%, respectively, compared with the non-deoxygenated process. Results from the Mössbauer spectrum show that Fe0 is finally transformed into Fe3+ in the form of Ca2Fe2O5 and a small amount of Fe3O4, corresponding to the deoxygenation efficiency of 99.21%. The NMR results imply that aromatic carbon is the main form in biochar whether introducing deoxidizer or not, and deoxygenation can promote the removal of O-alkyl C.
The steel industry is responsible for 30 % of global industrial greenhouse gas emissions, which is mainly dependent on metallurgical coke utilization. Although biochar represents a promising carbon–neutral alternative, its suboptimal mechanical properties have hindered its direct substitution for conventional coke. This work introduces an innovative hydrothermal carbonization-repolymerization strategy to synthesize high-performance biocoke from sustainable feedstocks of oak residues and waste soybean oil. Our approach is centered on a novel and bio-based polymerization agent, synthesized by blending epoxidized soybean oil from oxidized waste oil and tannic acid extracted from oak residues in a 3:1 mass ratio. The epoxidized soybean oil-tannic acid effectively undergoes cross-linking reactions with oak biochar and oak bio-oil that both in-situ generated from the hydrothermal carbonization, resulting in a highly cross-linked biocoke. The ESO undergoes epoxy ring-opening in the cross-polymerization reaction, providing more reaction sites for cross-linked reactions. Moreover, the resulting biocoke shows a significant aromatization and graphitization structure. Therefore, the biocoke displays superior mechanical and thermochemical properties, including crushing strength (86.0 % of M 40 ), abrasion resistance (6.6 % of M 10 ), coke strength after reaction (64.2 %), and higher heating value (40.79 MJ/kg), meeting the performance of first-grade metallurgical coke. A cradle-to-gate LCA indicates that substituting 50 % of metallurgical coke by biocoke results in a reduction of CO 2 emissions of 622.8 kg for per ton of iron production. This study not only provides a novel polymerization strategy for producing metallurgical-grade biocoke but also highlights its potential to significantly reduce the carbon footprint of the steel industry.
The steel industry accounts for 30 % of global industrial greenhouse gas emissions, which is primarily attributed to the utilization of metallurgical coke. While carbon-neutral biochar is a material that rivals conventional coke, the inferior mechanical properties and higher preparation temperature limit biochar as an ideal alternative for metallurgical coke. Herein, ammonium octamolybdate is employed to transform birch residues into metallurgical-grade biocoke at low temperature. AOM affords advanced catalytic capacity during pyrolysis under a nitrogen-oxygen mixture, inducing the formation of superoxide free radicals on birch residues to produce 2,5-furandicarboxylic acid. The resulting 2,5-furandicarboxylic acid serves as a polymerization agent to facilitate the cross-polymerization between biochar and bio-oil for preparing biocoke. The produced biocoke displays superior 6.2 MPa of compressive strength, 59.2 % of coke strength after reaction, 92.28 % of mechanical durability, and 38.79 MJ/kg of higher heating value, close to first-grade metallurgical coke. Carbon emission analysis shows replacing 30 % of metallurgical coke by biocoke for 1 t of iron production reduces 419.43 kg of CO 2 emissions. This study presents a mild pyrolysis-polymerization strategy to produce densified metallurgical-grade biocoke for metallurgical coke alternative and underscores biocoke's potential for low-carbon production of the steel industry.
Green production process of high value-added bio-platform compounds is appealing yet challenging due to low catalyst performance and demand for acid or alkali conditions. Herein, we fabricated a tailored bio-tar derived super porous carbon material supported nano Pt catalyst via tuning the alkalinity by nitrogen doping. This novel catalyst realized an enhanced catalytic performance in selective oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) in alkaline free conditions, in which 97.8 % HMF conversion and 54.7 % FDCA selectivity were achieved under mild temperature (90 °C). The kinetic study revealed that the process is multi-step parallel reactions of 2,5-diformylfuran (DFF) and 5-formylfuran-2-carboxylic acid (FFCA) as intermediates from HMF, and the oxidation of carbonyl group in FFCA is the rate-determining step. This work provides a new synthesis method of low-cost catalyst by using organic waste and inspires a sustainable process for bio-platform compounds production with significant environmental benefits.
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