Recent progress in the development of solid catalysts for biomass conversion into high value-added chemicals

Abstract

In recent decades, the substitution of non-renewable fossil resources by renewable biomass as a sustainable feedstock has been extensively investigated for the manufacture of high value-added products such as biofuels, commodity chemicals, and new bio-based materials such as bioplastics. Numerous solid catalyst systems for the effective conversion of biomass feedstocks into value-added chemicals and fuels have been developed. Solid catalysts are classified into four main groups with respect to their structures and substrate activation properties: (a) micro- and mesoporous materials, (b) metal oxides, (c) supported metal catalysts, and (d) sulfonated polymers. This review article focuses on the activation of substrates and/or reagents on the basis of groups (a)–(d), and the corresponding reaction mechanisms. In addition, recent progress in chemocatalytic processes for the production of five industrially important products (5-hydroxymethylfurfural, lactic acid, glyceraldehyde, 1,3-dihydroxyacetone, and furan-2,5-dicarboxylic acid) as bio-based plastic monomers and their intermediates is comprehensively summarized.     

固体酸催化生物质制备乙酰丙酸酯的研究进展

综述了用固体酸催化生物质制备乙酰丙酸酯的研究成果和动态,主要阐述了用固体酸作催化剂制备乙酰丙酸酯的3种方法(即乙酰丙酸酯化法,生物质直接醇解法和糠醇醇解法),并对3种方法所涉及的反应路径、反应机理、催化性能进行了比较。最后指出用固体酸取代传统无机酸进行生物质直接醇解生成乙酰丙酸酯的工艺开发较具前景,并对今后的发展方向提出了相关建议。     

层状双氢氧化物析氧催化剂的研究进展

层状双氢氧化物具有制备简单,层间客体可调节,合成成本较低,稳定性较好等优点,因此成为析氧催化剂的研究热点,但仍存在电荷传输速率低,过电位相对较高等问题,因此需要对其改性来加快其大规模应用。首先介绍了层状双氢氧化物的结构特点,简述了其析氧反应的催化机理,然后总结了不同种类的优化改性策略来增强其催化活性。优化改性方法分别包括:与导电基材复合;合成超薄纳米片法;与石墨烯复合法;杂化改性法。重点探讨了层状双氢氧化物析氧催化剂在电解水制氢方面的应用,提出了不同改性方法的优缺点,阐明将其适当结合,有利于制备更高效的析氧催化剂,最后指出了这类催化剂仍面临的问题:回收率较低,催化剂稳定性和可实现的电流密度尚未达到工业化需求,无法实现大规模制备等难点。     

炭材料负载金属催化剂在活化过硫酸盐中的应用进展

近年来,基于硫酸根自由基的高级氧化技术在环境污染治理中的应用受到越来越广泛的关注,而炭材料负载金属催化剂在活化过硫酸盐去除环境污染物方面展示出巨大的优势。全面总结了炭材料负载金属离子、金属单质、金属氧化物等而制备的不同催化剂在活化过硫酸盐中的作用机制以及对污染物的降解效果等方面的研究进展,并指出了该类催化剂在活化过硫酸盐氧化中的应用前景与未来的研究方向。     

支撑液膜分离过程应用研究新进展

简要回顾液膜分离过程的发展史;介绍支撑液膜法的基本原理.在分析支撑液膜所存在问题的基础上重点论述近10年来支撑液膜的应用和发展.     

Histological assessment of follicular delivery of flutamide by solid lipid nanoparticles: potential tool for the treatment of androgenic alopecia

Abstract

Context: Flutamide is a potent anti-androgen with the several unwanted side effects in systemic administration, therefore, it has attracted special interest in the development of topically applied formulations for the treatment of androgenic alopecia.

Objective: The purpose of this study was to prepare and characterize the solid lipid nanoparticles (SLNs) of Flutamide for follicular targeting in the treatment of the androgenic alopecia.

Methods: Flutamide-loaded SLNs, promising drug carriers for topical application were prepared by hot melt homogenization method. Drug permeation and accumulation in the exercised rat skin and histological study on the male hamsters were performed to assess drug delivery efficiency in vitro and in vivo, respectively.

Results: The optimized Flutamide-loaded SLNs (size 198?nm, encapsulation efficiency percentage 65% and loading efficiency percentage 3.27%) exhibited a good stability during the period of at least 2 months. The results of X-ray diffraction showed Flutamide amorphous state confirming uniform drug dispersion in the SLNs structure. Higher skin drug deposition (1.75 times) of SLN formulation compared to Flutamide hydroalcoholic solution represented better localization of the drug in the skin. The in vivo studies showed more new hair follicle growth by utilizing Flutamide-loaded SLNs than Flutamide hydroalcoholic solution which could be due to the higher accumulation of SLNs in the hair follicles as well as slowly and continues release of the Flutamide through the SLNs maximizing hair follicle exposure by antiandrogenic drug.

Conclusion: It was concluded Flutamide-loaded SLN formulation can be used as a promising colloidal drug carriers for topical administration of Flutamide in the treatment of androgenic alopecia.     

Incorporation of mixed metals into SAPO-34 frameworks by the dry-gel conversion method using mixed templates: investigating catalysts characterisation and performance

The crystallisation of the MeAPSO-34 material was studied under dry-gel conversion conditions and using two and three templates. This study has been focused on the effect of the incorporation of a mixture of Ni and Mn into the SAPO-34 framework. The MeSAPO-34 samples were characterised by X-ray diffraction, energy-dispersive X-ray spectrometer, scanning electron microscope, temperature-programmed desorption and Brunner–Emmett–Teller. The influence of metal incorporation into the framework of SAPO-34 (MeAPSO-34) on methanol conversion was investigated in this study. The performances on methanol conversion for these catalysts were different according to the properties of metals incorporated into the SAPO-34 structure. The catalytic performance demonstrated high activity and light olefins selectivity for the prepared catalysts. Among the light olefin products, Mn and Ni incorporation is helpful for propylene generation, but samples with a mixture of Ni and Mn favour the ethylene production.     

Supported single Au(III) ion catalysts for high performance in the reactions of 1,3-dicarbonyls with alcohols

The high cost and poor atom utilization efficiency of noble metal catalysts have limited their industrial applications. Herein, we designed CeO₂-supported single Au(III) ion catalysts with ultra-low gold loading that can enhance the utilization efficiency of gold atoms and bridge the gap between homogeneous and heterogeneous gold catalysis. These catalysts were highly active and reusable for the reaction of 1,3-dicarbonyls with alcohols. The catalytic turnover number of CeO₂-supported single Au(III) ion catalysts was much higher than that of the homogeneous catalyst NaAuCl₄. In addition, the effects of gold loading and the drying method for the catalysts on the organic reactions were systematically explored. In-depth investigation of the structure–property relationship by highresolution transmission electron microscopy, hydrogen temperature-programmed reduction, X-ray absorption near edge structure analysis, UV–vis diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy revealed that the isolated Au(III) ions were related to the active sites for the synthesis of β-substituted cyclohexenone and that CeO₂ was responsible for yielding ketonic ester.

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Electrode materials: a challenge for the exploitation of protonic solid oxide fuel cells

Abstract

High temperature proton conductor (HTPC) oxides are attracting extensive attention as electrolyte materials alternative to oxygen-ion conductors for use in solid oxide fuel cells (SOFCs) operating at intermediate temperatures (400–700 °C). The need to lower the operating temperature is dictated by cost reduction for SOFC pervasive use. The major stake for the deployment of this technology is the availability of electrodes able to limit polarization losses at the reduced operation temperature. This review aims to comprehensively describe the state-of-the-art anode and cathode materials that have so far been tested with HTPC oxide electrolytes, offering guidelines and possible strategies to speed up the development of protonic SOFCs.     

CO2和环氧化合物共聚负载型催化剂的研究进展

CO2与环氧化合物共聚生成脂肪族聚碳酸酯,其塑料具有生物可降解性,是一类具有发展前景的环境友好型材料。为了实现该过程中催化剂的循环使用,对催化剂进行负载化是一个有效的途径。对CO2和环氧化合物共聚中负载型催化剂的研究进展进行了综述,为该领域负载型催化剂的进一步研究提供指导。     

Effect of Laves phase strengthening on the mechanical properties of high Cr ferritic steels for solid oxide fuel cell interconnect application

Two types of high chromium ferritic steels envisaged as construction materials for SOFC interconnects, were investigated in respect to microstructure and creep in the proposed application temperature range from 700 to 800 °C. The steel compositions mainly differed in the amounts of the Laves phase forming elements Nb, W and Si. The steel containing these alloying additions exhibited substantially higher creep resistance in the temperature range 700-800 °C than the high purity steel. The Laves phase formation occurred trans- as well as intragranular whereby the extent and size of grain boundary precipitates increased with increasing exposure time. Especially at 800 °C the precipitates inside the grains virtually completely vanished after longer exposure times and only intergranular precipitates remained. This change in precipitate morphology resulted especially at 800 °C in a decrease of creep resistance with increasing exposure time, although the Laves phase containing steel still exhibited higher creep strength than the high purity steel.     

Recent progress in the development and properties of novel metal matrix nanocomposites reinforced with carbon nanotubes and graphene nanosheets

One-dimensional carbon nanotubes and two-dimensional graphene nanosheets with unique electrical, mechanical and thermal properties are attractive reinforcements for fabricating light weight, high strength and high performance metal-matrix composites. Rapid advances of nanotechnology in recent years enable the development of advanced metal matrix nanocomposites for structural engineering and functional device applications. This review focuses on the recent development in the synthesis, property characterization and application of aluminum, magnesium, and transition metal-based composites reinforced with carbon nanotubes and graphene nanosheets. These include processing strategies of carbonaceous nanomaterials and their composites, mechanical and tribological responses, corrosion, electrical and thermal properties as well as hydrogen storage and electrocatalytic behaviors. The effects of nanomaterial dispersion in the metal matrix and the formation of interfacial precipitates on these properties are also addressed. Particular attention is paid to the fundamentals and the structure–property relationships of such novel nanocomposites.     

螺吡喃及其衍生物用作金属离子传感材料的研究进展

利用螺吡喃(Spiropyran,SP)-部花青(Merocyanine,MC)的光致异构特性,赋予金属离子光纤传感敏感材料可逆性,近年来已成为研究热点.综述了螺吡喃及其衍生物用作金属离子传感材料的研究进展,分析了SP类金属离子敏感材料在可逆性、检测灵敏度和选择性方面的优势与不足,并展望了其研究前景.     

The biharmonic problem and progress in the development of analytical methods for the solution of boundary-value problems

A comparative analysis of harmonic and biharmonic boundary-value problems for 2D problems on a rectangle is given. Some common features of two types of problems are emphasized and special attention is given to the basic distinction between them. This distinction was thoroughly studied for the first time by L. N. G. Filon with respect to some plane problems in the theory of elasticity. The analysis permits to introduce an important aspect of the general solution of boundary-value problems. The procedure for solving the biharmonic problem involves both the method of homogenous solutions and the method of superposition. For some cases involving self-equilibrated loadings on one pair of sides of the rectangle, the complete solution, including calculation of the quantitative characteristics of the displacements and stresses, is given. The efficiency of the numerical implementation of the general solutions is shown. The analysis of the quantitative data allows to elucidate some main points of the Saint-Venant principle.     

Mechanical milling to foster the solid solution formation and densification in Cr-W-Si for hot-pressing of PVD target materials

Based on the significantly different melting points and high oxygen affinities, the fabrication of chromium-based tungsten silicides is restricted to powder metallurgical production routes. To foster particle contacts and diffusion processes between chromium and tungsten, which are known to necessitate long sintering times, mechanical alloying or milling processes prior to sintering are established. Nonetheless, due to spinodal decomposition of Cr and W, the solid solution formation is complex and yet little understood. For this reason, the influence of the mechanical milling time (0–24 h) on the crystal structure and the microstructural properties of hot-pressed 60Cr30W10Si (wt.–%) is examined. In this context, two different powders containing a different tungsten particle size (0.8 and 3 µm) were mechanically alloyed to analyze the impact on the phase formation and the particle distribution in the microstructure. It was shown that mechanical milling supported the mechanical clamping between the particles. However, the increased milling times significantly decreased the crystallite sizes of the particles and fostered the tungsten solubility in the Cr-rich (Cr, W) solid solution formed during sintering, thus supporting the densification.     

Recent advances in very high frequency plasma enhanced CVD process for the fabrication of thin film silicon solar cells

We have deposited amorphous silicon (a-Si) and nanocrystalline silicon (nc-Si) materials and the total p-i-n configurations for solar cells in a high vacuum multichamber system ASTER using very high frequency plasma enhanced chemical vapour deposition (VHF PECVD) process. The deposition process is monitored and controlled by in-situ diagnostic tools to maintain reproducibility of the material quality. In this paper we show our recent results on single junction (amorphous silicon) and tandem (a-Si/nc-Si) cells on plastic foil using the Helianthos concept. The tandem cell efficiency on Asahi U-type SnO₂:F coated glass is ~ 12% and this is achieved by employing nc-Si deposited at high pressure (p) conditions of 5 mbar and a small inter-electrode distance (d) of 5 mm. The deposition scheme of this cell on glass was adapted for the SnO₂:F coated Al foil substrates from Helianthos b.v., especially taking into account the expansion of the foil during deposition. The inter-electrode distance d was one of the variables for this optimisation process. Depositions at four inter-electrode distances of 6 mm, 8 mm, 10 mm and 12 mm (keeping the pressure-distance product constant) revealed that the deposition rate increases at higher distances, reaching 0.6 nm/s at a d of 10 mm and pressure p of 3.0 mbar. The Raman crystalline ratio showed a monotonic increase with the combination of higher d and lower p. Tandem cells with an area of 2.5 cm² on plastic foil fabricated by the Helianthos concept and employing the above mentioned nc-Si made at 0.6 nm/s in the bottom cell and a-Si in the top cell, showed an efficiency of 8.12%, with a short circuit current density of 10 mA/cm². The combined deposition time of the photoactive silicon layers of the top and bottom cells amounted to only 85 min.     

Texture development of Ca3Co4O9 thermoelectric oxide by high temperature plastic deformation and its contribution to the improvement in electric conductivity

High temperature uniaxial compression is conducted on Ca₃Co₄O₉ layered cobaltite, in order to achieve a thermoelectric oxide with low resistivity by the development of (0 0 1) texture. It is found that flow stress varies depending on deformation temperature and strain rate. Development of a sharp texture having the maximum (0 0 1) pole density of about 33 times as high as the random level is achieved. It is found that the high temperature compression process is quite effective for the simultaneous achievement of densification and (0 0 1) texture development. It is experimentally confirmed that resistivity decreases drastically by the construction of a sharp (0 0 1) texture.