A critical review on sustainable biochar system through gasification: energy and environmental applications

This review lays great emphasis on production and characteristics of biochar through gasification. Specifically, the physicochemical properties and yield of biochar through the diverse gasification conditions associated with various types of biomass were extensively evaluated. In addition, potential application scenarios of biochar through gasification were explored and their environmental implications were discussed. To qualitatively evaluate biochar sustainability through the gasification process, all gasification products (i.e., syngas and biochar) were evaluated via life cycle assessment (LCA). A concept of balancing syngas and biochar production for an economically and environmentally feasible gasification system was proposed and relevant challenges and solutions were suggested in this review

Polar aprotic solvent-water mixture as the medium for catalytic production of hydroxymethylfurfural (HMF) from bread waste

Valorisation of bread waste for hydroxymethylfurfural (HMF) synthesis was examined in dimethyl sulfoxide (DMSO)-, tetrahydrofuran (THF)-, acetonitrile (ACN)-, and acetone-water (1:1v/v), under heating at 140°C with SnCl4 as the catalyst. The overall rate of the process was the fastest in ACN/H2O and acetone/H2O, followed by DMSO/H2O and THF/H2O due to the rate-limiting glucose isomerisation. However, the formation of levulinic acid (via rehydration) and humins (via polymerisation) was more significant in ACN/H2O and acetone/H2O. The constant HMF maxima (26-27mol%) in ACN/H2O, acetone/H2O, and DMSO/H2O indicated that the rates of desirable reactions (starch hydrolysis, glucose isomerisation, and fructose dehydration) relative to undesirable pathways (HMF rehydration and polymerisation) were comparable among these mediums. They also demonstrated higher selectivity towards HMF production over the side reactions than THF/H2O. This study differentiated the effects of polar aprotic solvent-water mediums on simultaneous pathways during biomass conversion

Microwave-assisted depolymerization of various types of waste lignins over two-dimensional CuO/BCN catalysts

© 2020 The Royal Society of Chemistry. Valorization of lignin to valuable chemicals and biofuels increases the economic viability of sustainable biorefineries. This work aimed at elucidating how the lignin structures recovered from various agricultural and industrial residues governed the downstream catalytic conversion. Three types of lignins, namely bio-enzymatic lignin (BL), organosolv lignin (OL), and Kraft lignin (KL), were fully characterized by HSQC-NMR, TGA, FTIR, and SEM to obtain a detailed description of their structures. In consideration of redox-active CuO and highly active carbon-modified boron nitride (BCN) in oxidative dehydrogenation, a two-dimensional CuO/BCN catalyst was prepared and explored in microwave-assisted lignin conversion to improve the yields of aromatic monomers. BL achieved the highest yield of monomers (10 wt%) over the CuO/BCN catalyst after the 3rd cycle in 30 min under mild conditions (200 °C). The yields of bio-oils reached 70 wt% in 10 min when BL and OL were used as the substrate. High efficiency of the microwave-assisted reaction was illustrated by comparing with that of the hydrothermal reaction. This work demonstrated strong dependence of the conversion efficiency on the interunit linkages and functional groups of lignin structures. The strong metal-support interaction between CuO and BCN not only facilitated lignin depolymerization via the promoted electron transfer, but also enhanced the stability of Cu catalysts under hydrothermal conditions. In addition, elucidation of the catalyst redox evolution shed light on the role of the CuO/BCN catalyst in lignin depolymerization in recycle runs

Effect of N2 flow rate on kinetic investigation of lignin pyrolysis

Fast pyrolysis of lignin can obtain valuable products such as bio-oil, bio-chemical, syngas, and biochar. In this study, two types of lignin known as brown solid from the byproduct of cellulosic ethanol fermentation and commercial dealkaline lignin from the papermaking process were used for pyrolysis in a 3-L batch reactor at 300–450 °C. The product composition in the liquid and gas phases were analyzed by using gas chromatography-mass spectrometry/Flame-ionization detector/thermal conductivity detector (GC-MS/FID/TCD). Increasing the N flow rate to 150 mL/min was sufficient to increase the production of bio-oil/bio-organics up to 15% for brown solid pyrolysis. In contrast, the biochemical production during dealkaline lignin pyrolysis was not sensitive to the change of the N flow rate. The amount of biochar produced in the pyrolysis (~60%) slightly changed at various pyrolysis temperature and gas flow rate, which could be due to the relatively low pyrolysis temperature that was insufficient to decompose the lignin. The GC-MS analysis also revealed that C7–C8 compounds, which represented the phenolic compounds, were the most abundant in the liquid products. Kinetic models of the pyrolysis were established based on the thermogravimetric analysis

Synthesis of MOF525/PEDOT Composites as Microelectrodes for Electrochemical Sensing of Dopamine

Dopamine (DA) is an important neurotransmitter responsible for the functions and activities of multiple systems in human. Electrochemical detection of DA has the advantages of fast analysis and cost-effectiveness, while a regular electrode probe is restricted to laboratory use because the probe size is too large to be suitable for an in vivo or in vitro analysis. In this study, we have developed porphyrin-based metal organic framework (MOF525) and poly(3,4-ethylenedioxythiophene) (PEDOT)-based composites to modify microelectrode for DA detection. Two types of PEDOT monomers with different functional groups were investigated in this study. By varying the monomer ratios, electrolyte concentrations, and electropolymerization temperature, it was found that the PEDOT monomer containing carboxylic group facilitated the formation of regular morphology during the electropolymerization process. The uniform morphology of the PEDOT promoted the electron transmission efficiency in the same direction, while the MOF525 provided a large reactive surface area for electrocatalysis of DA. Thus, the MOF525/PEDOT composite improved the sensitivity-to-noise ratio of DA signaling, where the sensitivity reached 11 nA/μM in a good linear range of 4–100 µM. In addition, porphyrin-based MOF could also increase the selectivity to DA against other common clinical interferences, such as ascorbic acid and uric acid. The as-synthesized microelectrode modified with MOF525/PEDOT in this study exhibited great potential in real time analysis