Effect of pyrolysis conditions on environmentally persistent free radicals (EPFRs) in biochar from co-pyrolysis of urea and cellulose.

Biochar derived from nitrogen-rich pyrolysis of biomass can be used as a soil conditioner, but it contains a large amount of environmental persistent free radicals (EPFRs). EPFRs are a newly identified environmentally harmful substance, and the detection and research on EPFRs in nitrogen-rich pyrolyzed char is lacking. Biochars prepared from cellulose-urea mixtures at different temperatures, residence times, and urea ratios were analyzed in this study. EPFRs in biochar prepared at 500 °C had the highest spin concentrations. Substituted aromatic compounds were the precursors to the EPFRs. The types of EPFRs in biochars shifted from oxygen-centered at 400 °C to carbon- and oxygen-centered in the 450-600 °C range due to a reduction in oxygen-containing functional groups. Residence time experiments showed that most EPFRs formed in the first 5 min of pyrolysis. C was the main element used for the formation of EPFRs, while N content was negatively correlated with the concentration of EPFRs. Pyrolysis temperature was the key factor determining the types of EPFRs produced, while proportion of urea only affected the concentrations of EPFRs and not type. The results of this study are of great significance for understanding the environmental behavior of common EPFRs in nitrogen-rich biochar.

One-step synthesis of biomass-based sulfonated carbon catalyst by direct carbonization-sulfonation for organosolv delignification.

Biomass-based sulfonated carbon catalyst (SCC) was prepared from corncob via direct sulfuric acid carbonization-sulfonation treatment. Central composite design was used to evaluate temperature and time for optimizing SCC yield and sulfonic acid (SO3H) density. The SO3H groups were successfully introduced to the SCC as evidenced by FTIR and sulfur analysis. Numerical optimization results showed that 100 °C and 5.78 h are the optimal conditions for maximizing yield (61.24%) and SO3H density (1.1408 mmol/g). The highest ethanol organosolv lignin (EOL) yield of 63.56% with a substrate yield of 39.08% was achieved at 20% SCC loading in the ethanol organosolv delignification of lignocellulosic biomass. The FTIR spectra of the isolated lignin revealed typical features of G-lignin, indicating that no drastic changes took place in the lignin structure during the process. This study developed a simple one-step preparation method of SCC, which was successfully used as a catalyst in an organosolv delignification of biomass.

Synthesis and characterization of sulfonated activated carbon as a catalyst for bio-jet fuel production from biomass and waste plastics.

Sulfonated activated carbon-based catalysts were prepared by microwaved-assisted carbonization of phosphoric acid activated corncob followed by sulfonation using concentrated sulfuric acid. Sulfonation at different temperatures and times resulted in varied SO3H group density of the SAC catalysts. Sulfonation temperature showed a significant effect on the introduction of SO3H on the AC precursor while time had minor role. The SAC catalysts were characterized by means of N2 sorption analysis (specific surface area, pore-volume, average pore width), FTIR spectroscopy, SEM imaging, and sulfur analysis. The impact of catalysts SO3H density on the product distribution and bio-oil composition from the catalytic co-pyrolysis of Douglas fir and LDPE was evaluated. The highest bio-jet fuels (aromatics and C9-16 alkanes) obtained was 97.51% using the SAC catalyst sulfonated at 100 °C for 5 h. Results showed that SAC has great potential as catalyst in the co-pyrolysis of biomass and plastics for the production of jet-fuel range hydrocarbons.

Microwave-assisted synthesis of bifunctional magnetic solid acid for hydrolyzing cellulose to prepare nanocellulose.

The conventional studies on the preparation of nanocellulose used a high concentration of sulfuric acid that is difficult to remove and recover. A biochar-based solid acid with magnetic properties was developed to hydrolyze cellulose to prepare nanocellulose in this work. Two different methods were selected to investigate the properties of the synthesized magnetic carbon-based solid acids. The synthesized catalysts were characterized by SEM, TEM, XRD, NH3-TPD and FT-IR. The experimental results showed that two solid acids by the microwave-assisted synthesis had good magnetic properties by a magnet adsorption. Analysis by SEM and TEM showed that the two solid acids had rich pore structures. According to mineral element analysis, both solid acids contained high sulfur content. The solid acid was an amorphous carbon structural material with a surface rich in active groups. The catalytic activity of the biochar-based solid acids in cellulose hydrolysis to prepare nano-scale cellulosic material was evaluated. It was found that magnetic biochar-based solid acid (MBC-SA1) could achieve a high yield, which produced up to 57.68% for hydrolyzing cellulose into nanometers.

Catalytic fast pyrolysis of a wood-plastic composite with metal oxides as catalysts.

The catalytic fast pyrolysis of a poplar wood-polypropylene composite (WPP) was investigated using Py-GC/MS in the presence of ZnO, CaO, Fe2O3 and MgO. The synergistic effects between wood and plastic components in both non-catalytic and ZnO-catalyzed pyrolysis of WPP were studied. CaO facilitated the removal of oxygen due to its strong basicity, eliminating carboxylic acids and phenols from the products, while slightly increasing cyclopentanones and alkenes. MgO has weaker deoxygenation but stronger chain scission activities versus CaO, and significantly enhanced the alkene yields. Alkene yields were highest using ZnO among the four catalysts. ZnO increased ketone and phenol yields while reducing carboxylic acids. Aromatics were identified in the presence of Fe2O3. A synergistic effect between poplar wood and PP in the uncatalyzed pyrolysis of WPP increased the yields of carboxylic acids, phenols and light alkenes, while it reduced carbonyl-containing oxygenates such as aldehydes, ketones and furans. The synergy in the ZnO-catalyzed pyrolysis of WPP further enhanced the formation of monomeric phenols and alkenes.