Increasing energy demand, especially in the transportation sector, and soaring CO2 emissions necessitate the exploitation of renewable sources of energy. Despite the large variety of new energy carriers, liquid hydrocarbon still appears to be the most attractive and feasible form of transportation fuel taking into account the energy density, stability and existing infrastructure. Biomass is an abundant, renewable source of energy; however, utilizing it in a cost-effective way is still a substantial challenge. Lignocellulose is composed of three major biopolymers, namely cellulose, hemicellulose and lignin. Fast pyrolysis of biomass is recognized as an efficient and feasible process to selectively convert lignocellulose into a liquid fuel-bio-oil. However bio-oil from fast pyrolysis contains a large amount of oxygen, distributed in hundreds of oxygenates. These oxygenates are the cause of many negative properties, such as low heating value, high corrosiveness, high viscosity, and instability; they also greatly limit the application of bio-oil particularly as transportation fuel. Hydrocarbons derived from biomass are most attractive because of their high energy density and compatibility with the existing infrastructure. Thus, converting lignocellulose into transportation fuels via catalytic fast pyrolysis has attracted much attention. Many studies related to catalytic fast pyrolysis of biomass have been published. The main challenge of this process is the development of active and stable catalysts that can deal with a large variety of decomposition intermediates from lignocellulose. This review starts with the current understanding of the chemistry in fast pyrolysis of lignocellulose and focuses on the development of catalysts in catalytic fast pyrolysis. Recent progress in the experimental studies on catalytic fast pyrolysis of biomass is also summarized with the emphasis on bio-oil yields and quality.
Cyclohexanone is an important intermediate in the manufacture of polyamides in chemical industry, but direct selective hydrogenation of phenol to cyclohexanone under mild conditions is a challenge. We report here a catalyst made of Pd nanoparticles supported on a mesoporous graphitic carbon nitride, Pd@mpg-C(3)N(4), which was shown to be highly active and promoted the selective formation of cyclohexanone under atmospheric pressure of hydrogen in aqueous media without additives. Conversion of 99% and a selectivity higher than 99% were achieved within 2 h at 65 °C. The reaction can be accelerated at higher temperature, but even at room temperature, 99% conversion and 96% selectivity could still be obtained. The generality of the Pd@mpg-C(3)N(4) catalyst for this reaction was demonstrated by selective hydrogenation of other hydroxylated aromatic compounds with similar performance.
We report a catalyst made of Pd nanoparticles (NPs) supported on mesoporous N-doped carbon, Pd@CN(0132), which was shown to be highly active in promoting biomass refining. The use of a task-specific ionic liquid (3-methyl-1-butylpyridine dicyanamide) as a precursor and silica NPs as a hard template afforded a high-nitrogen-content (12 wt %) mesoporous carbon material that showed high activity in stabilizing Pd NPs. The resulting Pd@CN(0.132) catalyst showed very high catalytic activity in hydrodeoxygenation of vanillin (a typical model compound of lignin) at low H(2) pressure under mild conditions in aqueous media. Excellent catalytic results (100% conversion of vanillin and 100% selectivity for 2-methoxy-4-methylphenol) were achieved, and no loss of catalytic activity was observed after six recycles.
The explosive growth of energy consumption hungers for highly efficient energy conversion and storage devices, whose innovation greatly depends on the development of advanced electrode materials and catalysts. Among those advanced materials explored, carbon materials have drawn much attention due to their excellent properties, such as high specific surface area and tunable porous structures. Challenges also come from global warming and environmental pollution, which require sustainable carbon-rich precursors for carbon materials. Hence, the use of biomass for carbon materials features the concept of Green Chemistry. This review has summarized the most advanced progress in biomass-derived carbon for the use of fuel cells, eletrocatalytic water splitting devices, supercapacitors and lithium-ion battery. Several synthetic strategies for synthesizing biomass-derived carbon, including direct pyrolysis, hydrothermal carbonization, and ionothermal carbonization, have been reviewed, and the corresponding formation mechanisms and prospects are also discussed. This provides fundamental insight and offers an important guideline for future design of biomass-derived carbon on specific energy application.Please do not adjust margins Please do not adjust margins process, the activators make great effects on the properties of the final products. Among those activators, KOH is very promising due to its lower activation temperature, hence leading to high yields, and well-defined micropore size distribution with ultrahigh SSA (up to 3000 m 2 /g). Through KOH activation, micropores and small mesopores can be introduced into the framework of various structured carbons. 33 The high SSA and increased micropore and mesopore volume demonstrate excellent properties in energy storage and conversion. Although, the activation mechanism of KOH is complex and it is not understood clearly, three main activation processes for KOH activation of carbon are accepted: 13 1) Potassium compounds, including KOH and some compounds (K 2 CO 3 and K 2 O) formed during the calcination process, react with carbon, generating the pore network; 2) the intermediate products (H 2 O and CO 2 ) contribute to the further development of the porosity via the gasification of carbon; 3) the as-prepared metallic K intercalate into the carbon lattices of carbon matrix effectively, leading to the expansion of the carbon lattices. The porous structure is created, after the metallic K and other K compounds are removed. Fig. 1 (a) Schematic diagram of the formation of HPCs: mixing the biomass with the "leavening" agents followed by pyrolysis under an inert gas, 34 (b) the SEM images with different mass ratio of cellulose, hemicellulose, and lignin. 35 Reproduced with permission from ref. 34, 35. Copyright©Fig. 20 (a) schemiatic mechanism of the synthesis of nanostructured silicon/porous carbon spheres; the charge-discharge curves and schematic diagram of the lithiationdelithiation process (inset) of (a) Si NPs and (c) N-SPC, and (d) their cycling performance at constant densi...
Two-dimensional vibrational spectroscopy is applied to investigate the dilution process of 1-ethyl-3-methyl-imidazolium tetrafluoroborate ([Emim][BF4]) in water. With increasing water content in ionic liquid (IL)/water mixtures, the C-H stretching vibration of the imidazolium cation showed systematic blue-shifts, which reflect the weakening of the cohesion between the cation and anion of ILs. The two-dimensional IR results reveal that the ILs sense quite different environments during the whole dilution process. First, the three-dimensional network structure of pure ILs was destroyed gradually into ionic clusters, then the clusters were further dissociated into ionic pairs surrounded by water molecules, and finally the latter became the dominant form in bulk water. Within the concentration range we investigated (0.02
Developing novel and efficient catalysts is always an important theme for heterogeneous catalysis from fundamental and applied research points of view. In the past, carbon materials were used as supports for numerous heterogeneous catalysts because of their fascinating properties including high surface areas, tunable porosity, and functionality. Recently, the newly emerging N-doped carbon-supported metal catalysts have arguably experienced great progress and brought the most attention over the last decades in view of the fact that nitrogen doping can tailor the properties of carbon for various applications of interest. Compared with pristine carbon-supported metal catalysts, these catalysts normally show superior catalytic performance in many heterogeneous catalytic reactions because of the introduced various metal–support interactions from N doping. In this Perspective, we focus on the fabrication methods for N-doped carbon-supported metal catalysts and the catalytic application of these fascinating catalysts in several industrially relevant reactions, including hydrogenation, dehydrogenation, oxidation, and coupling. Notably, we try to elucidate the structure–activity correlations obtained from theoretical calculation, extensive characterization, and observed catalytic performances, thereby providing guidance for the rational design of advanced catalysts for heterogeneous catalysis.
Quantum chemical calculations have been used to investigate the interaction between water molecules and ionic liquids based on the imidazolium cation with the anions [Cl(-)], [Br(-)], [BF(4)(-)], and [PF(6)(-)]. The predicted geometries and interaction energies implied that the water molecules interact with the Cl(-), Br(-), and BF(4)(-0 anions to form X(-)...W (X = Cl or Br, W = H(2)O), 2X-...2W, BF(4)(-)...W, and W...BF(4)(-)...W complexes. The hydrophobic PF(6)(-) anion could not form a stable complex with the water molecules at the density functional theory (DFT) level. Further studies indicate that the cation could also form a strong interaction with the water molecules. The 1-ethyl-3-methylimidazolium cation (Emim(+)) has been used as a model cation to investigate the interaction between a water molecule and a cation. In addition, the interaction between the ion pairs and the water was studied by using 1-ethyl-3-methylimidazolium chloride (Emim x Cl) as a model ionic liquid. The strengths of the interactions in these categories follow the trend anion-W > cation-W > ion pair-W.
The layered Fe-doped alpha-type cobalt hydroxide (α-Co4Fe(OH)x) nanosheet exhibited superior activity towards the oxygen evolution reaction and the correlation between the Fe content and activity could be plotted as a volcano curve.
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