A large pore-size mesoporous zirconia supported cobalt catalyst with good performance in Fischer–Tropsch synthesis

Mesoporous zirconias with different pore sizes have been prepared by controlling the synthesis conditions including the pH of the synthesis system and the amount of diglycol added in the initial system. It was found that the F–T catalytic performances strongly depended on the pore sizes of mesoporous zirconias. The cobalt catalyst supported on such a mesoporous zirconia with the pore-size of 9.1 nm showed better catalytic performance in F–T synthesis, especially, displayed higher selectivity to C₁₂–C₁₈ paraffin as the main component of diesel oil fraction as compared to an amorphous SiO₂ with the close pore size. The above result was attributed to the combination of improvement of mass transfer derived from the large pore size and narrow pore size distribution of the mesostructure with the particular reactivity from the zirconia support.     

Ion conductivities and interfacial characteristics of the plasticized polymer electrolytes based on poly(methyl methacrylate-co-Li maleate)

The plasticized polymer electrolytes composed of poly(methyl methacrylate-co-Li maleate), lithium perchlorate, and ethylene carbonate as a plasticizer, were newly prepared. The ion conductivities of the plasticized polymer electrolytes based on the poly(methyl methacrylate-co-Li maleate) were found to be dependent on the ion content of the ionomer, poly(methyl methacrylate-co-Li maleate), in the polymer electrolyte, and the polymer electrolyte based on the ionomer with 8.5 mol% ion content showed the maximum ion conductivity.The interfacial resistance at the polymer electrolyte/lithium interface and the cationic transference number were also investigated as a function of the ion content of the ionomer in the polymer electrolyte. The interfacial resistances as well as the cationic transference numbers of the polymer electrolytes were found to be also dependent on the ion content of the ionomer in the polymer electrolyte. Ion aggregations in the ionomer seemed to significantly influence the electrochemical behavior of the polymer electrolytes based on the ionomer.     

Effect of acidic pretreatment on the chemistry and distribution of lignin in aspen wood and wheat straw substrates

In this work, aspen and wheat straw substrates were pretreated using aqueous dilute acid (DA) and chemimechanical (CM) pretreatment, and the impact of these pretreatments on biomass lignin was investigated. Here DA pretreatment refers to the acidic treatment of biomass powders and CM pretreatment refers to the acidic treatments of chips or stalks followed by disc refining. The resulting substrates were observed using advanced microscopy techniques to determine changes in lignin distribution throughout the fiber cell wall due to the acid treatments. Following acid treatment, lignin within the cell wall was divided into spherical or elongated bundles. The surface of DA and CM pretreated substrates were shown to differ, with CM pretreated aspen exhibited a more cellulose-rich surface. X-ray Photoelectron Spectroscopy data indicated reduced surface lignin on CM pretreated aspen and increased surface lignin on CM pretreated wheat straw. Fourier transform infrared spectroscopy (FT-IR) spectra illustrated changes in bands related to hemicellulose lignin, and surface hydroxyl content suggesting possible differences in lignin chemistry. It was hypothesized that differences in lignin distribution based on biomass type and pretreatment method were due to interactions between the chemical treatment and the mechanical size reductions steps. Particle size prior to chemical treatment could impact the movement of lignin onto sample surface, and chemical treatment prior to size reduction could impact the fracture plane during the downsizing process. It is expected that both these effects could impact lignin distribution within the sample and on the sample surface.     

麦渣与制浆废液共混制备成型颗粒燃料及其燃烧特性分析

为研究麦渣与制浆废液共混制备的成型颗粒燃料的燃烧特性, 通过热重分析法对其燃烧热力学及燃烧动力学进行了研究。结果表明: 制浆废液的添加使颗粒燃料出现固定碳的二次燃烧阶段, 有利于降低成型颗粒燃料的挥发分、固定碳燃烧阶段的点火温度及最大燃烧速率温度, 对颗粒燃料的燃烧有正向协同作用; 制备的颗粒燃料的一阶动力学模型拟合曲线的相关系数在0.95以上, 颗粒燃料在挥发分燃烧和固定碳燃烧阶段的活化能和指前因子均随制浆废液的添加而降低。当废液固形物质量分数为53%时制备的成型颗粒燃料, 其挥发分燃烧阶段和固定碳燃烧阶段的活化能为72.85和83.52kJ/mol, 指前因子为2.82×10⁶和3.73×10⁵min^-1。制浆废液的添加使颗粒燃料更易燃烧, 且燃烧过程稳定不易爆燃。     

复合催化材料纳米氧化铜颗粒(CuO NPs)@纤维素纳米纤丝(CNF)-Si-N(OH)2的制备及其对4-硝基苯酚的催化还原性能

针对目前降解工业废水中4-硝基苯酚(4-NP)的催化剂效率低,催化活性差等问题,以桉木漂白化学浆为原料,通过超微粒研磨机和高压均质机处理制备得到直径50～100 nm和长度1 500～2 000 nm的纤维素纳米纤丝(CNF),在其表面原位负载纳米氧化铜颗粒(CuO NPs),并通过3-氯丙基三甲氧基硅烷(CPTES)与二乙醇胺(DEA)进行接枝反应制备得到复合催化材料-CuO NPs@CNF-Si-N(OH)2。探讨了DEA添加量对CuO NPs@CNF–Si–N(OH)₂的性能影响,采用Zeta电位、FTIR、XRD、XPS、热重分析和形貌分析等方法对复合材料进行了表征。结果表明,CuO NPs被原位还原并成功负载在CNF表面,其直径约为3.84 nm,负载量为3.83wt%,通过硅烷化改性及接枝胺基可提高CuO NPs在复合材料表面的分散性及稳定性,进而增强了其催化活性。CNF基复合催化材料对4-NP的催化还原结果显示,DEA添加量为20wt%下的CuO NPs@CNF-SiN(OH)₂对4-NP催化还原性能最佳,在180 s内可催化还...     

微晶纤维素基复合材料的制备及其对亚甲基蓝的催化降解性能

以微晶纤维素(MCC)为原料,通过在其表面负载纳米氧化铜颗粒(CuO NPs),添加3-氯丙基三甲氧基硅烷(CPTES)与二乙醇胺(DEA)进行接枝反应制备CuO NPs@MCC–Si–N(OH)₂复合材料。探讨了DEA添加量对CuO NPs@MCC–Si–N(OH)₂性能的影响,表征并分析了改性微晶纤维素红外光谱、晶体结构、表面形貌和热稳定性。结果表明,CuO NPs可成功负载在MCC表面,硅烷偶联剂可提高复合材料的分散性与接枝胺基的能力,进而增强其催化活性,使硼氢化钠(NaBH₄)与亚甲基蓝(MB)氧化还原反应效率增加,快速降解MB染色剂。通过优化发现DEA用量为20wt%时制得的CuO NPs@MCC–Si–N(OH)₂催化效果最佳,CuO NPs@MCC–Si–N(OH)₂和NaBH₄的用量分别为30 mg和10 mg,处理30 mL 3 mmol/L MB溶液5 min后,MB去除率可达99.71%,五次循环性测试后,去除率为93.24%。      

Comparative study of the hydrogen isotopes yield from Ti,Zr, Ni,Pd, Pt during thermal,electric current and radiation heating

The results of studying the hydrogen isotopes (H, D) yield of Ni, Pd, Pt, Ti, Zr metals with linear heating: a) by the accelerated electrons beam with energy up to 35 KeV, b) by joule heat of AC (50 Hz) through samples, c) by external coaxial furnace samples in metal (stainless steel) and d) quartz vacuum cells are presented. The highest temperature of the position of the maximum intensity hydrogen isotopes release at the linear heating corresponds to the samples heating in a metal vacuum cell, an external coaxial furnace. The lowest temperature position of the maximum intensity hydrogen isotopes release corresponds to the heating by accelerated electrons beam. The difference in these positions of the maximum is ΔТ ≈ 350°С. Difference in maxima position of the hydrogen and deuterium release into the low-temperature region is significant (ΔТ ≈ 50–100°С) for the Ni, Pd, Pt samples, and insignificant (ΔТ <10°С) for the Ti and Zr samples was found, when metals are heated by electric current or in a quartz vacuum cell compared to their heating in a metal vacuum cell.Possible mechanisms of non-equilibrium stimulation of the hydrogen isotopes release from metals, due to the accumulation of external energy by the hydrogen subsystem of crystals considered theoretically. The notions used wherein are in agreement with the obtained experimental results.     

Hydrogen desorption/absorption properties of the extensively cold rolled β Ti–40Nb alloy

β Ti–Nb BCC alloys are potential materials for hydrogen storage in the solid state. Since these alloys present exceptional formability, they can be processed by extensive cold rolling (ECR), which can improve hydrogen sorption properties. This work investigated the effects of ECR accomplished under an inert atmosphere on H₂ sorption properties of the arc melted and rapidly solidified β Ti40Nb alloy. Samples were crushed in a rolling mill producing slightly deformed pieces within the millimeter range size, which were processed by ECR with 40 or 80 passes. Part of undeformed fragments was used for comparison purposes. All samples were characterized by scanning electron microscopy, x-ray diffractometry, energy-dispersive spectroscopy, hydrogen volumetry, and differential scanning calorimetry. After ECR, samples deformed with 40 passes were formed by thick sheets, while several thin layers composed the specimens after 80 passages. Furthermore, deformation of β Ti–40Nb alloys synthesized samples containing a high density of crystalline defects, cracks, and stored strain energy that increased with the deformation amount and proportionally helped to overcome the diffusion's control mechanisms, thus improving kinetic behaviors at low temperature. Such an improvement was also correlated to the synergetic effect of resulting features after deformation and thickness of stacked layers in the different deformation conditions. At the room temperature, samples deformed with 80 passes absorbed ∼2.0 wt% of H₂ after 15 min, while samples deformed with 40 passes absorbed ∼1.8 wt% during 2 h, excellent results if compared with undeformed samples hydrogenated at 300 °C that acquired a capacity of ∼1.7 wt% after 2 h. The hydrogen desorption evolved in the same way as for absorption regarding the deformation amount, which also influenced desorption temperatures that were reduced from ∼270 °C, observed for the undeformed and samples deformed with 40 passes, to ∼220 °C, for specimens rolled with 80 passes. No significant loss in hydrogen capacity was observed in the cold rolled samples.     

Synthesis of multi-walled carbon nanotube bundles with uniform diameter

A new method is used to grow macroscopic multi-walled carbon nanotube (MWNT) bundles with uniform diameter in bulk quantities. The diameter of the bundles are about 15–25 μm and their length is over 500 μm. The CNTs in each bundle are closely compact and parallel to each other along the direction of the bundle axis, which have potential applications as a composite enhancer or a high-strength nanostructure. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman analysis have been used to evaluate the morphological and structural features of such nanotube-based material. The formation mechanism of the bundles is discussed.     

Tween 80 enhancing cellulase recyclability during activation of dissolving pulp

Abstract

Enhancing cellulase recyclability is a promising approach to reducing the high enzyme cost for activation of dissolving pulp. For this purpose, Tween 80, an amphiphilic surfactant, was employed to facilitate cellulase recovery from fibers. Results indicated that the Cellulase–Tween complex was formed (with a particle size increase of 140%) through a hydrophobic interaction. A much lower maximum binding capacity and affinity (i.e., absorption ability) of cellulase onto fibers (6.03 versus 24.3?mg protein/g cellulose and 7.45 versus 13.8?ml/mg protein) were achieved for the complex in comparison with the control. The recovered cellulase activity was increased up to 65.7% from the control one in five consecutive recycle rounds with Tween 80 addition. As a result, the recovered cellulase efficiency was improved in terms of viscosity and reactivity. Other properties, such as α-cellulose content, alkaline solubility, molecular weight distribution, morphology, and crystalline structure, were all supported by the positive effect of Tween 80 in cellulase recycling.