Facile, One-Pot, Two-Step, Strategy for the Production of Potential Bio-Diesel Candidates from Fructose

The production of bio-diesel fuels from carbohydrates is a promising alternative to fossil fuels with regard to the growing severity of the environmental problem and energy crisis. Potential bio-diesel candidates or additives, such as 5-(hydroxymethyl)-2-(dimethoxymethyl) furan (HDMF), 2-(dimethoxymethyl)-5-(methoxymethyl) furan (DMMF), and 5-(methoxymethyl)-2-furaldehyde (MMF) could be produced from the alcoholic solutions of both 5-HMF and fructose in the presence of solid acid catalysts. In the present study, a readily prepared, silica, gel-supported nitric acid (SiO2-HNO3) catalyst was found to be exceptionally reactive for the production of HDMF from fructose. A DMSO-methanol biphasic solvent system was developed and HDMF, DMMF, and MMF were observed at 150 °C, with maximum yields of 34%, 34%, and 25%, respectively. Meanwhile, a maximum HDMF yield of 77% was obtained from 5-HMF in methanol. Moreover, a sequential, one-pot, two-step dehydration/acetalization process, involving the dehydration of fructose to 5-HMF in dimethylsulfoxide (DMSO) at 150 °C, and followed by adding a certain amount of methanol to react with the formed 5-HMF to HDMF at 100 °C, was developed to promote the yield of HDMF. The optimum yield of HDMF reached 70% with the complete conversion of fructose. The reaction mechanisms of dehydration and acetalization have been proposed for the conversion of 5-HMF to HDMF. The two-step design allows for facile catalyst recycling while supplying as a promising method for the production of biodiesel from complex carbohydrates

The Distribution and Strength of Brönsted Acid Sites on the Multi-Aluminum Model of FER Zeolite: A Theoretical Study

One of the fundamental issues in catalysis is to identify the catalytic active site. Due to its prominent pore topology and acidity, ferrierite (FER) zeolite has attracted extensive interest in various catalytic reactions such as isomerization of butenes. However knowledge on the active Brönsted acid site is still absent. In the present study, we perform extensive density functional theory calculations to explore the distribution and strength of the Brönsted acid sites and their potential catalytic activity for the double-bond isomerization of 1-butene to 2-butene. We employ a two-layered ONIOM scheme (our Own N-layered Integrated molecular Orbital + molecular Mechanics) to describe the structure and energetic properties of FER zeolite. We find that the hydrogen bond could improve the stability of Brönsted acid sites effectively, and, as a result, Al4-O6-Si2 and Al4-O-(SiO)2-Al4 are the most stable sites for 1-Al substitution and 2-Al substitution, respectively. We further find that the Brönsted acid strength tends to decrease with the increase of Al contents and increase when the distance between the Al atoms is increased in 2-Al substitution. Finally it is demonstrated that the strength of acid sites determines the catalytic activity for the double bond isomerization of 1-butene to 2-butene

Recent Modification Strategies of MoS₂ towards Electrocatalytic Hydrogen Evolution

Hydrogen production by the electrolysis of water is a green and efficient method, which is of great significance for achieving sustainable development. Molybdenum disulfide (MoS2) is a promising electrocatalyst for hydrogen evolution reaction (HER) due to its high electrochemical activity, low cost, and abundant reserves. In comparison to the noble metal Pt, MoS2 has poorer hydrogen evolution performance in water electrolysis. Therefore, further modifications of MoS2 need to be developed aiming at improving its catalytic performance. The present work summarizes the modification strategies that have been developed in the past three years on hydrogen evolution from water electrolysis by utilizing MoS2 as the electrocatalyst and following the two aspects of internal and external modifications. The former includes the strategies of interlayer spacing, sulfur vacancy, phase transition, and element doping, while the latter includes the heterostructure and conductive substrate. If the current gap in this paper’s focus on modification strategies for electrocatalytic hydrogen evolution in water electrolysis is addressed, MoS2 will perform best in acidic or alkaline media. In addition to that, the present work also discusses the challenges and future development directions of MoS2 catalysts

Morphology-Dependent Properties of Cu/CeO2 Catalysts for the Water-Gas Shift Reaction

CeO2 nanooctahedrons, nanorods, and nanocubes were prepared by the hydrothermal method and were then used as supports of Cu-based catalysts for the water-gas shift (WGS) reaction. The chemical and physical properties of these catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption/desorption, UV-Vis spectroscopy, X-ray photoelectron spectroscopy (XPS), hydrogen temperature-programmed reduction (H2-TPR) and in situ diffuse reflectance infra-red fourier transform spectroscopy (DRIFTS) techniques. Characterization results indicate that the morphology of the CeO2 supports, originating from the selective exposure of different crystal planes, has a distinct impact on the dispersion of Cu and the catalytic properties. The nanooctahedron CeO2 catalyst (Cu-CeO2-O) showed the best dispersion of Cu, the largest amount of moderate copper oxide, and the strongest Cu-support interaction. Consequently, the Cu-CeO2-O catalyst exhibited the highest CO conversion at the temperature range of 150–250 °C when compared with the nanocube and nanorod Cu-CeO2 catalysts. The optimized Cu content of the Cu-CeO2-O catalysts is 10 wt % and the CO conversion reaches 91.3% at 300 °C. A distinctive profile assigned to the evolution of different types of carbonate species was observed in the 1000–1800 cm−1 region of the in situ DRIFTS spectra and a particular type of carbonate species was identified as a potential key reaction intermediate at low temperature