BackgroundLignocellulose is the most abundant biomass on earth. However, biomass recalcitrance has become a major factor affecting biofuel production. Although cellulose crystallinity significantly influences biomass saccharification, little is known about the impact of three major wall polymers on cellulose crystallization. In this study, we selected six typical pairs of Miscanthus samples that presented different cell wall compositions, and then compared their cellulose crystallinity and biomass digestibility after various chemical pretreatments.ResultsA Miscanthus sample with a high hemicelluloses level was determined to have a relatively low cellulose crystallinity index (CrI) and enhanced biomass digestibility at similar rates after pretreatments of NaOH and H2SO4 with three concentrations. By contrast, a Miscanthus sample with a high cellulose or lignin level showed increased CrI and low biomass saccharification, particularly after H2SO4 pretreatment. Correlation analysis revealed that the cellulose CrI negatively affected biomass digestion. Increased hemicelluloses level by 25% or decreased cellulose and lignin contents by 31% and 37% were also found to result in increased hexose yields by 1.3-times to 2.2-times released from enzymatic hydrolysis after NaOH or H2SO4 pretreatments. The findings indicated that hemicelluloses were the dominant and positive factor, whereas cellulose and lignin had synergistic and negative effects on biomass digestibility.ConclusionsUsing six pairs of Miscanthus samples with different cell wall compositions, hemicelluloses were revealed to be the dominant factor that positively determined biomass digestibility after pretreatments with NaOH or H2SO4 by negatively affecting cellulose crystallinity. The results suggested potential approaches to the genetic modifications of bioenergy crops.

We report the use of a simple complex assembled from Ni(II) salt and 2-mecaptoethanol in one step in water as the efficient catalyst in a molecular hydrogen system which can be sensitized by a low-cost xanthene dye, Erythrosin B. An excellent quantum efficiency of 24.5% is attained at 460 nm. This simple system is expected to contribute toward the development of economical and environmentally benign solar hydrogen production systems.

No abstract

A novel nanostructured Pd 2 Ga intermetallic catalyst is presented and compared to elemental Pd and a macroscopic bulk Pd 2 Ga material concerning physical and chemical properties. The new material was prepared by controlled coprecipitation from a single phase layered double hydroxide precursor or hydrotalcite-like compound, of the composition Pd 0.025 Mg 0.675 Ga 0.3 (OH) 2 (CO 3 ) 0.15 • mH 2 O. Upon thermal reduction in hydrogen, bimetallic nanoparticles of an average size less than 10 nm and a porous MgO/MgGa 2 O 4 support were formed. HRTEM images confirmed the presence of the intermetallic compound Pd 2 Ga and are corroborated by XPS investigations which revealed an interaction between Pd and Ga. Due to the relatively high dispersion of the intermetallic compound, the catalytic activity of the sample in the semihydrogenation of acetylene was more than 5000 times higher than observed for a bulk Pd 2 Ga model catalyst. Interestingly, the high selectivity of the model catalyst toward the semihydrogenated product of 74% was only slightly lowered to 70% for the nanostructured catalyst, while an elemental Pd reference catalyst showed only a selectivity of around 20% under these testing conditions. This result indicates the structural integrity of the intermetallic compound and the absence of elemental Pd in the nanosized particles. Thus, this work serves as an example of how the unique properties of an intermetallic compound, well-studied as a model catalyst, can be made accessible as real high-performing material allowing establishment of structure-performance relationships and other application-related investigations. The general synthesis approach is assumed to be applicable to several Pd-X intermetallic catalysts, with X being elements forming hydrotalcite-like precursors in their ionic form.