The hydrogen peroxide presoaking prior to ammonia fiber expansion (H-AFEX) pretreatment is an effective and promising method for agricultural residues to decrease biomass recalcitrance and enhance enzyme accessibility. To illuminate the structural changes of lignin after the H-AFEX process, ball-milled wood lignins were isolated from raw material and H-AFEX-treated corn stover. The features and structures of the obtained lignins were characterized by elemental analysis, gel permeation chromatography, Fourier transform infrared spectroscopy, and nuclear magnetic resonance spectroscopy. The results demonstrated that the H-AFEX-treated lignins had higher oxygen and nitrogen contents while lower carbon and hydrogen contents when compared to those of untreated lignin. A remarkable decrease in molecular weight of H-AFEX-treated lignin was observed. Ammonolysis, hydrolysis, and oxidation reactions were major chemical modifications to lignin, and the cleavages of ferulate and p-coumarate ester bonds, alkyl ether bonds, and aryl ether bonds were observed during the H-AFEX process. G unit lignin was more easily degraded through demethoxylation, while the interunit linkages of resinol and phenylcoumaran were relatively stable. The study on lignin structural changes during the H-AFEX process could reveal the pretreatment mechanism and develop of a new pretreatment method, with a perspective of reducing biomass recalcitrance and improving the bioconversion of biomass to biofuels or biomaterials.

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To illuminate the lignin evolution after hydrogen peroxide presoaking prior to ammonia fiber expansion (H-AFEX) pretreatment and enzymatic hydrolysis, ball-milled wood lignins were separated from untreated corn stover, H-AFEX-treated corn stover, and enzymatic hydrolyzed residue, labeled as UN-L, HA-L, and EH-L, respectively. The structural features of EH-L were compared with HA-L and UN-L by elemental analysis, GPC, FT-IR, and NMR. The inhibition deriving from lignin loading and the structure were assessed by adding UN-L/HA-L in enzymatic hydrolysis. The thermogravimetric analysis and thermal degradation kinetics analysis of EH-L were performed to evaluate its industrial utilization. The results showed that a significant decline in molecular weight was observed in EH-L, while the polydispersity index was almost unchanged. The decrease of the G unit and the increase of the S unit were shown in EH-L when comparing to UN-L. The G unit had the strongest inhibition to enzymatic hydrolysis, and the increasing relative proportion of S/G in lignin was beneficial for enzymatic hydrolysis. The resinol structure in lignin was relatively stable after pretreatment and enzymatic hydrolysis. The thermogravimetry analysis indicated that the EH-L exhibited better thermal stability than that of UN-L, offering potential to prepare lignin-based heat-resistant epoxy resin and new flame-resistant materials.

Rapid depletion in fossil fuels, inflation in petroleum prices, and rising energy demand have forced towards alternative transport fuels. Among these alternative fuels, diesel-ethanol and diesel-biodiesel blends gain the most attention due to their quality characteristics and environmentally friendly nature. The viscosity and density of these biodiesel blends are slightly higher than diesel, which is a significant barrier to the commercialization of biodiesel. In this study, the density and viscosity of 30 different ternary biodiesel blends was investigated at 15 °С and 40 °С, respectively. Different density and viscosity models were developed and tested on biodiesel blends soured from different feedstock’s including palm, coconut, soybean, mustard, and calophyllum oils. The prognostic ability and precisions of these developed models was assessed statistically using Absolute Percentage Error (APE) and Mean Absolute Percentage Error (MAPE). The MAPE of 0.045% and 0.085% for density model and 1.85%, 1.41%, 3.48% and 2.27%, 1.85%, 3.50% for viscosity models were obtained on % volume and % mass basis. These developed correlations are useful for ternary biodiesel blends where alcohols are the part of biodiesel blends. The modeled values of densities and viscosities of ternary blends were significantly comparable with the measured densities and viscosities, which are feasible to avoid the harm of vehicles’ operability.

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