Hydrolysis of eucalyptus wood chips under hot compressed water in the presence of sulfonated carbon-based catalysts

Upgrading Pyrolytic Residue from End-of-Life Tires to Efficient Heterogeneous Catalysts for the Conversion of Glycerol to Acetins

Recovered carbon blacks (rCBs) produced from end-of-life tires using pyrolysis were transformed into solid acid catalysts for the synthesis of acetins, i.e., products with a wide spectrum of practical applications. Tuning the chemical properties of the surface of samples and introducing specific functional groups on the rCBs were achieved through carbon functionalization with concentrated H2SO4. The initial and modified rCBs were thoroughly characterized using techniques such as elemental analysis, potentiometric back titration, thermogravimetric technique, scanning and transmission microscopy, X-ray photoelectron spectroscopy, etc. The catalytic activities of the samples were measured via batch mode glycerol acetylation performed at 110 °C and compared to the catalytic performance of the functionalized commercial carbon black. The modified rCBs were found to show a significant catalytic effect in the tested reaction, giving high glycerol conversions (above 95%) and satisfactory combined yields of diacetins and triacetin (~72%) within 4 h; this behavior was attributed to the presence of -SO3H moieties on the surface of functionalized rCBs. The reusability tests indicated that the modified samples were catalytically stable in subsequent acetylation runs. The obtained results evidenced the feasibility of using end-of-life tires for the production of effective acid catalysts for glycerol valorization processes.

Effects of Modified Activated Carbon on Microwave-Accelerated Organosolv Fractionation of Rice Husk

Organosolv fractionation is a promising approach for the separation of lignocellulosic components in integrated biorefineries where each component can be fully valorized into valuable platform chemicals and biofuels. In this study, microwave-accelerated organosolv fractionation was developed for the modification of lignocellulosic fractionation of rice husk. The fractionation condition was optimized for 1 h with the microwave irradiation at 300 W using a ternary solvent mixture composed of 24%:32%:44% water/ethanol/methyl isobutyl ketone. The effects of mineral acids (HCl, H₃PO₄, and H₂SO₄) and heterogeneous acid promoters (HCl, H₃PO₄, and H₂SO₄ impregnated over activated carbon) on the efficiency and selectivity of product yields (i.e., glucan, hemicellulose-derived products, and lignin) were also investigated. It was found that the use of H₃PO₄-activated carbon as the promoter showed superior performance on the fractionation of rice husk components, resulting in 88.8% recovery of cellulose, with 63.8% purity in the solid phase, whereas the recovery of hemicellulose (66.4%) with the lowest formation of furan and 5-hydroxymethyl furfural and lignin (81.0%) without sugar cross-contamination was obtained in the aqueous ethanol phase and organic phase, respectively. In addition, the morphology structure of fractionated rice husk presented 2.6-fold higher surface area (5.4 m²/g) of cellulose-enriched fraction in comparison with the native rice husk (2.1 m²/g), indicating the improvement of enzyme accessibility. Besides, the chemical changes of isolated lignin were also investigated by Fourier-transform infrared spectroscopy. This work gives pieces of information into the efficiencies of the microwave strategy as a climate neighborly elective fractionation method for this serious starting material in the biotreatment facility business.

Comparison of hydrochar- and pyrochar-based solid acid catalysts from cornstalk: Physiochemical properties, catalytic activity and deactivation behavior

Biochar made from biowaste provides renewable carbon precursors for catalysts preparation. Here, solid acid catalysts were prepared through functionalizing biochars produced via hydrothermal and pyrolytic carbonization of cornstalk with -SO₃H groups. Hydrochar-based catalysts (HAC) and pyrochar-based catalysts (PAC) exhibited significantly different physiochemical properties, catalytic activities and deactivation behaviors. The test of catalytic effects on cellulose degradation uncovered that HAC had a higher density of -SO₃H but lower surface special area than PAC. Specifically, PAC prepared at 400 °C resulted in the maximum increase of cellulose conversion by 16.00-50.50%. In comparison, the highest yields of glucose (11.14%) and 5-hydroxymethylfurfural (29.54%) were achieved catalyzed via HAC prepared at 240 °C. The results of catalyst deactivation behavior further revealed that used catalysts had an obvious reduction of -SO₃H density. Interestingly, used HAC-240 catalysts showed similar patterns of weight loss to fresh ones due to its high stability.

Sulfonated carbon derived from the residue obtained after recovery of essential oil from the leaves of Cinnamomum longepaniculatum using Brønsted acid ionic liquid, and its use in the preparation of ellagic acid and gallic acid

A Brønsted acid ionic liquid, 3-methyl-1-(4-sulfonylbutyl) imidazolium hydrogensulfate ([HO₃S(CH₂)₄mim]HSO₄), was used for the first time for the preparation of a sulfonated carbon catalyst. The catalyst was prepared from the residue obtained after recovery of the essential oil from the leaves of Cinnamomum longepaniculatum. The sulfonated carbon catalyst with an amorphous structure attained high acidic efficiency at a sulfonation temperature of 200 °C for 2 h of sulfonation time, and was characterised. SEM morphologies revealed that the carbon catalyst consisted of uniform carbon microspores. FTIR analysis, elemental analysis, and X-ray photoelectron spectroscopy revealed that the sulfonic acid group was successfully introduced on the surface of the sulfonated carbon catalyst. The result of TG analysis showed that the obtained sulfonated carbon catalyst has high thermal stability. Good acid and catalytic activity of the obtained sulfonated carbon catalyst were observed for the preparation of ellagic acid and gallic acid, which is comparable to those of diluted sulfuric acid and a sulfonated carbon catalyst that had been prepared with concentrated sulfuric acid. The excellent reusability of the sulfonated carbon catalyst was also confirmed by repeated experimental trials. In summary, the sulfonated catalyst derived from the residue obtained after recovery of essential oil from the leaves of C. longepaniculatum is an economic, eco-benign and promising substitute for traditional mineral acid catalysts for acidic catalysis in industrial applications.

A Brønsted acid ionic liquid, 3-methyl-1-(4-sulfonylbutyl) imidazolium hydrogensulfate ([HO₃S(CH₂)₄mim]HSO₄), was used for the first time for the preparation of a sulfonated carbon catalyst.