Fourier transform IR study of NOx adsorption on a CuZSM-5 DeNOx catalyst

The adsorption and coadsorption of selective catalytic reduction (SCR) reactants and reaction products on CuZSM-5-37 containing 11 wt.-% CuO have been studied by FTIR spectroscopy. The catalyst surface is characterized by both weak acidity and weak basicity as revealed by testing with probe molecules (CO₂, NH₃, H₂O). NO₂ adsorption results in formation of different kinds of nitrates. The same species are formed when NO is coadsorbed with oxygen at 180°C. NO adsorption at ambient temperature also leads to formation of nitrates as well as of Cu²⁺NO species. In the presence of oxygen the latter are converted according to the scheme: NO → N₂O₃ → N₂O₄ → NO₂ → NO₃. It is concluded that the surface nitrates are important intermediates in the SCR process. They are thermally stable and resistant towards interaction with CO₂, N₂, O₂, and are only slightly affected by H₂O and NO. However, they posses a high oxidation ability and are fully reduced by propane at 180°C. It is concluded that one of the most important roles of oxygen in SCR by hydrocarbons is to convert NO_x into highly active surface nitrates.     

Recent Advances on TiO2-ZrO2 Mixed Oxides as Catalysts and Catalyst Supports

This is the first review of titanium dioxide-zirconium dioxide (TiO₂-ZrO₂) mixed oxides, which are frequently employed as catalysts and catalyst supports. In this review many details pertaining to the synthesis of these mixed oxides by various conventional and nonconventional methods and their characterization by several techniques, as reported in the literature, are assessed. These mixed oxides have been synthesized by different preparative analogies and were extensively characterized by employing various spectroscopic and nonspectroscopic techniques. The TiO₂-ZrO₂ mixed oxides are also extensively used as supports with metals, nonmetals, and metal oxides for various catalytic applications. These supported catalysts have also been thoroughly investigated by different techniques. The influence of TiO₂-ZrO₂ on the dispersion and surface structure of the supported active components as examined by various techniques in the literature has been contemplated. A variety of reactions catalyzed by TiO₂-ZrO₂ and supported titania-zirconia mixed oxides, namely; dehydrogenation, decomposition of chlorofluoro carbons (CFCs), alcohols from epoxides, synthesis of ε-caprolactam, partial oxidation, deep oxidation, hydrogenation, hydroprocessing, organic transformations, NO_x abatement, and photo catalytic VOC oxidations that have been pursued in the literature are presented with relevant references.     

Synthesis, characterisation and properties of (Ba1 − xSrx) (Nd1/2Nb1/2) O3 ceramics for application as dielectric resonators in microwave circuits

The (Ba_{1 − x}Sr_x) (Nd_1/2Nb_1/2) O₃ ceramics have been prepared by the conventional ceramic route for different values of x. Addition of a small amount of CeO₂ (1 wt%) as a sintering aid increased the density of the samples. The structure and microstructure of the sintered samples are studied by X-ray diffraction and SEM methods. The dielectric properties of the samples are measured in the microwave frequency region as a function of composition. The dielectric constant decreases as x increases. The coefficient of thermal variation of resonant frequency decreases as the Sr content increases and goes to the negative side. The dielectric properties of (Ba_{1 − x}Sr_x) (Nd_1/2Nb_1/2) O₃ are in the range suitable for application as dielectric resonators in microwave circuits.     

A Simple and Cost-Effective Approach to Fabrication of Dense Ceramic Membranes on Porous Substrates

A simple and elegant approach to fabrication of dense ceramic membranes on porous substrates, a traditional dry pressing of foam powders, has been developed to reduce the cost of fabrication. Gd-doped ceria (GDC, Gd_0.1Ce_0.9O_1.95) electrolyte membranes as thin as 8 μm are obtained by dry-pressing highly porous GDC powders. The membrane thickness can be readily controlled by the amount of powder. The electrolyte membranes are studied in a solid-oxide fuel cell (SOFC) with air as oxidant and humidified hydrogen (3% H₂O) as fuel. Open-circuit voltages of about 1.0 V are observed, implying that the permeability of the membranes to molecular gases is insignificant. Power densities of 140 and 380 mW/cm² are demonstrated at 500° and 600°C, respectively, representing a significant progress in developing low-temperature SOFCs.     

Structural and Thermal Expansions in Alkali Silicate Binary Glasses

Two volume-changing processes that should be considered in detail are (1) distention of networks by added oxides which may swell glass volumes in proportion to the added oxide volumes and (2) angular change in intertetrahedral bonding which may take place at and above annealing temperatures in proportion to the number of metal ions introduced by the modifications. Accordingly, the partial molar volumes of modifiers, ν _R , are assumed as those of their crystal or liquid states and the partial molar volumes of silica are computed from (1/ν_S) = 2.20 + 0.00057 ( r_m – 0.12) (1723 – t ). Tentative glass volumes are then computed as V_g= S_mν_S+ r_mν_R by use of the mole fractions S_m and r_m for silica and nonsilica, respectively. The excess of computed glass volumes, V₀ , over V as derived from observed densities is taken as a measure of the penetration of modifiers into the network cavities without corresponding distention of the network. By using the computed density of 1.95 for vitron, the value 2.20 for silica glass, and 2.30 as reported for irradiated silica, one can estimate that silica glass consists of 28% vitron and 72% disordered silica in the intervitron tissues. The values of V_g , – V mentioned are found to be in fair accord with expectations computable from the vitron theory.     

Molecular dynamics and dissipative particle dynamics simulations for the miscibility of poly(ethylene oxide)/poly(vinyl chloride) blends

The miscibility of poly(ethylene oxide) (PEO)/poly(vinyl chloride) (PVC) blends are investigated by atomistic molecular dynamics and mesoscale dissipative dynamics simulations. The specific volumes of three PEO/PVC blends (with weight ratio at 70/30, 50/50 and 30/70) as well as pure PEO and PVC are examined as a function of temperature. The glass transition temperatures are estimated to be 251, 268, 280, 313 and 350 K for pure PEO, PEO/PVC 70/30, 50/50, 30/70 and pure PVC. Among different energy contributions, the torsion and van der Waals energies exhibit pronounced kinks versus temperature. The Flory-Huggins parameters determined from the cohesive energy densities and the radial distribution functions of the inter-molecular atoms suggest that PEO/PVC 70/30 and 30/70 blends are more miscible than 50/50 blend. This is further supported by the morphologies of PEO/PVC blends, in which the 50/50 blend exhibits segregated domains implying a weak phase separation. Hydrogen bonds are found to form between O atoms of PEO and H atoms of PVC, with a larger degree in PEO/PVC 70/30 and 30/70 blends than in 50/50 blend. The addition of PVC into PEO suppresses the mobility of PEO chains, which is consistent with the experiment observation of decreased crystallization rate as well as crystallization temperature of PEO.     

PVC／TPU／SBS—g—MMA共混体系研究

制备了ＳＢＳ－ｇ－ＭＭＡ系列接枝共聚物,并对其进行了表征。以ＳＢＳ－ｇ－ＭＭＡ作为ＰＶＣ／ＴＰＵ共混体系的增容剂,对不同配比的ＰＶＣ／ＴＰＵ／ＳＢＳ－ｇ－ＭＭＡ共混体系的物理力学性能、流变性等进行了研究。结果表明,ＳＢＳ－ｇ－ＭＭＡ接枝共聚物对ＰＶＣ／ＴＰＵ共混体系起到了明显的增容作用。     

SOLVATION EFFECTS IN CATALYTIC TRANSFORMATIONS OF OLEFINS IN SULFURIC ACID

Analysis of literature and ab initio quantum chemical calculations indicate that the properties of anhydrous H₂SO₄ as a superacid are determined not by the extent of dissociation of this acid but by the unusually high chemical activity of the weakly solvated protons. In a similar way, the selectivity of the acid-catalyzed transformations of olefins is also determined by solvation of the active intermediates. Depending on the concentration of sulfuric acid, the properties of the active species are changing from almost free carbenium ions in the anhydrous acid to the hydrated oxonium ions in the moderately dilute sulfuric acid. In the later case, similar to zeolites, the carbenium-ion-like alkyl species are formed only as transition states. The subsequent hydrolysis of oxonium ions upon stronger dilution of the acid results in the formation of alcohols. These conclusions are supported by ab initio quantum chemical calculations and by in situ ¹³C-NMR of protonated active intermediates.     

Impact of nanoclay on physicomechanical and thermal analysis of polyvinyl alcohol/fumed silica/clay nanocomposites

Polyvinyl alcohol (PVA)/fumed silica/clay nanocomposites are prepared via solution intercalation by exploiting phase separation based on the bridging of particles by polymer chains. PVA/fumed silica/clay nanocomposites are characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy, and thermogravimetric analysis. Mechanical properties are determined by universal testing machine. From FTIR results, it indicates that IR spectrum for PVA/fumed silica/clay nanocomposites, especially PVA/fumed silica/clay (1.30E) nanocomposites, is much broader than pure PVA and other clay nanocomposites. The better interfacial bonding between PVA/fumed silica/clay (1.30E) nanocomposites are reflected in the improvement of the mechanical properties as well as thermal stability. The surface area analysis result proves that the PVA/fumed silica/clay (1.30E) nanocomposites have higher surface area and pore volume with less pore size. With the addition of 1.30E clay to the composite system, the tensile strength and modulus had shown the highest values as well as higher activation energy for thermal decomposition. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41843.     

Epoxy-Polysulfone Networks as Advanced Matrices for Composite Materials

Compatibility between polysulfone (PSF) and epoxy oligomers in the melt state as well as the morphology and properties of alloys obtained were studied as a function of composition. The compatibility depends on the length and structure of epoxy molecules, and is best in the case of epoxysulfone oligomers (ESO).

The properties of hybrid matrices are determined by their composition and morphology. The most pronounced effects are observed in the regions of small concentrations of either component. A small quantity of PSF significantly improves thermal stability and heat resistance of the epoxy resin as well as its impact strength. On the other hand, on addition to PSF of small amounts of epoxysulfone oligomers, the processability of the matrix can be substantially improved. In particular, the melt viscosity decreases, and wetting and impregnation of fibrous reinforcement is facilitated. Besides, the matrix adhesion to fibers is increased.

Powdered PSF/ESO/curing agent mixtures are good for application in solvent-free technological processes of fibrous composites production, e.g. in electrostatic deposition of matrix particles onto a reinforcing fabric. Plastics based on hybrid matrices are distinguished by improved strength.     

Polymeric membrane formation by wet-phase separation; turbidity and shrinkage phenomena as evidence for the elementary processes

The direct accumulation of polymer, the nucleation and growth of the polymer lean as well as the polymer rich phase and the spinodal phase separation are postulated as four elementary processes of the mechanisms of the polymeric membrane formation by wet-phase separation. With the study of five different polymer/solvent:water systems they are discriminated by the investigation of the turbidity and the shrinkage phenomena taking place during (proto)membrane formation, as well as by the measurement of the pure water permeability and by the inspection of the membranes’ cross-section morphology. The general scheme of membrane formation mechanisms is arranged by gathering the groups of different modes of mass transport and the group of nonsolvent/solvent/polymer forms of solidification as elementary processes; by forming combinations of the so postulated elementary processes in time and space particular mechanisms are established.     

Interpretation and kinetic modeling of product distributions of cobalt catalyzed Fischer–Tropsch synthesis

Carbon number distributions of Fischer–Tropsch products on iron and cobalt catalysts show deviations from the ideal Anderson–Schulz–Flory (ASF) distribution. For products obtained on cobalt catalysts these deviations are traced back by many authors to re-adsorption and incorporation of 1-alkenes followed by subsequent chain growth. In the present work, it could be shown by means of model calculations and based on experiments with co-feeding of ethene and 1-alkenes that such subsequent chain growth cannot be regarded as the main reason of observed deviations of the carbon number distribution from the ideal ASF distribution. The co-feeding experiments suggest that these deviations are the consequence of two different mechanisms of chain growth causing a superposition of two ASF distributions.

Consequently, the carbon number distributions are represented by this superposition. In order to describe distributions as a function of reaction conditions the model parameter, the growth probabilities ₁ and ₂ as well as μ₁, the fraction of distribution (₁) are presented as function of the partial pressures of hydrogen and carbon monoxide. Finally, the typical model parameters of products formed on cobalt and iron are compared.     

Polyamide 6 and polyamide 66 blends with functionalized polyolefins: Effect of phenomenal increase in viscosity and melt strength of polyamide 66-based materials

The effect of adding blends of linear low-density polyethylene (LLDPE) and ethylene-octene copolymer (EOC) functionalized by grafting (in the course of reactive extrusion) of trans-ethylene-1,2-dicarboxylic acid (TEDA) onto polyamide 6 (PA6) and polyamide 66 (PA66) on rheological and elastic properties of their melts, structural morphology, and mechanical properties has been studied. It is shown that PA66/functionalized polyolefins (fPO) blends are characterized by more significant changes in the characteristics being analyzed as compared to PA6/fPO blends. A phenomenally sharp increase (by more than two decimal orders of magnitudes) in the melt viscosity of PA66/fPO blend as compared to the initial PA66 was established. At the same time, the melt strength may increase more than 50-fold. The degree of TEDA grafting (β) onto PO macromolecules is the most important parameter determining the level of the values of property indices, as well as the structural features of PA/fPO blends. Only when particular β values (varying in a relatively narrow range) are reached, a quasi-homogeneous morphology is formed in PA/fPO blends and their deformation capacity as well as the impact strength of materials increase dramatically. The observed effects are caused by the influence of TEDA grafting on interphase interactions in PA/fPO and PA66/fPO blends.     

Oxidation Kinetics of Single-Crystal SrTiO3

The oxidation kinetics were determined for single-crystal SrTiO₃ by measuring the time and temperature dependence of the weight gain of reduced crystals. The oxidation can be described as a diffusion-controlled process. The calculated diffusion coefficients between 850° and 1460°C are represented by D = 0.33 exp (-22.5 ± 5.0 kcal/ RT ) cm²/sec. Directly measured oxygen ion diffusion coefficients in the same temperature interval reported earlier are interpreted as being extrinsic and can be represented by D = 5.2 × 10⁻⁶ exp (-26.1 ± 5.0 kcal/ RT ) cm²/sec, where the activation energy is for mobility only. Assuming that the calculated diffusion coefficients are for vacancy diffusion and the two activation energies are equivalent within experimental error, a vacancy concentration (fraction of vacant lattice sites), [O□], fixed by impurities in the fully oxidized crystal is calculated to be 1.6 × 10⁻⁵ by virtue of the relation between the oxygen self-diffusion coefficient, D_02-, and the oxygen vacancy diffusion coefficient, D_o□ ; D _o2-= [O□] D _o□ where the oxygen ion concentration [O^2-] is taken as unity.     

黑曲霉作为分泌蛋白细胞工厂的研究进展

黑曲霉具有极强的分泌蛋白的能力,其分泌的木质纤维素降解酶、淀粉酶、蛋白酶、脂肪酶等广泛应用于食品、饲料和生物技术等相关工业中。本文围绕黑曲霉生产同源和异源分泌蛋白,阐述黑曲霉作为分泌蛋白细胞工厂的巨大潜力。首先,通过总结黑曲霉表达系统的优越性,确定了黑曲霉作为分泌蛋白细胞工厂的开发前景。随后,介绍了初步构建黑曲霉分泌蛋白细胞工厂的一般流程。接着,总结了近十年来黑曲霉作为同源分泌酶细胞工厂的研究进展,提出在黑曲霉中定向表达分泌酶是深入研究黑曲霉自身分泌酶性质、功能和结构的理想策略。最后,总结了近年来黑曲霉作为异源分泌蛋白细胞工厂的研究进展,并从异源蛋白表达中遇到的难点出发介绍了完善黑曲霉细胞工厂来提高异源蛋白产量的对策。     

聚苯胺/乙炔炭黑多孔类棒状复合材料的制备及电化学性质

以纳米乙炔炭黑在盐酸掺杂的反应体系中的聚集体为硬模板,原位吸附化学氧化法制备了聚苯胺/炭黑复合材料。实验结果显示,聚苯胺复合物为表面附着大量纳米颗粒的类棒状结构,且棒与棒间富有孔隙。复合材料分解温度在350℃左右。循环伏安曲线表现出该复合材料法拉第准(赝)电容有良好的电极可逆性,在5,10 mA/cm2电流密度下,单电极比电容高达376 F/g和311 F/g。     

聚甲氧基二甲醚合成工艺及产业化述评

聚甲氧基二甲醚（DMM_n）作为一种新型绿色环保柴油添加剂,因其具有较高的十六烷值和含氧量,能有效减轻燃烧后的污染物排放,同时完善以煤基甲醇为源头的煤化工产业结构,这使得其合成工艺及产业化进程受到国内外学者的广泛关注。本文对国内外DMM_n合成工艺、国内工业化布局以及未来发展前景进行综述。在现有工艺基础上,归纳总结了由甲醇出发经不同中间产物合成DMM_n的各类合成路线的特点。通过分析制约DMM_n工业化进程的关键因素,特别是结合当前全球性新冠肺炎疫情导致的石油价格断崖式下跌,给煤化工产业带来巨大的冲击,认为反应精馏工艺将成为未来DMM_n产品推广和工业应用最具有竞争潜力的工艺技术路线。     

Structure and dynamics of water in TiO2 nano slits: The influence of interfacial interactions and pore sizes

The interaction of water with TiO₂ surfaces is of enduring interest because of wide applications of the TiO₂ materials in aqueous environments. The structure and dynamic properties of water molecules in TiO₂ nanopores are crucial as increasingly TiO₂ materials are synthesized into nanoporous structures. In this work, the structural and dynamic properties of water molecules in nanoscale slit pores of TiO₂ are investigated, by using three sets of force field models for the water- TiO₂ interaction, as well as four TiO₂ slit pore widths. It is concluded that the water- TiO₂ interaction dominates the interfacial structure of water molecules, while the dynamic properties of water molecules are primarily influenced by the slit width in both interfacial and central regions. These findings indicate that both of the fluid properties and the interactions of fluids with pore wall will determine the transport properties of fluid in nanopores. If the pore size is large enough, e.g. 1.0 nm or larger in this work, the transport properties will be determined most by the fluids themselves. For the cases of pores whose sizes are in the range of interfacial region, the influences of pore size and interfacial interaction will interfere each other.     

Mechanical properties of Al2O3/ZrO2 composites

In the present study, both t-phase zirconia and m-phase zirconia particles are incorporated into an alumina matrix. Dense Al₂O₃/(t-ZrO₂+m-ZrO₂) composites were prepared by sintering pressurelessly at 1600 °C. The microstructure of the composites are characterized, the elastic modulus, strength and toughness determined. Because the ZrO₂ inclusions are close to each other in the Al₂O₃ matrix, the yttrium ion originally in t-ZrO₂ particles can diffuse to nearby m-ZrO₂ particles during sintering, and the m-phase zirconia is thus stabilized after sintering. The strength of the Al₂O₃/(t-ZrO₂+m-ZrO₂) composites after surface grinding can reach values as high as 940 MPa, which is roughly three times that of Al₂O₃ alone. The strengthening effect is contributed by microstructural refinement together with the surface compressive stresses induced by grinding. The toughness of alumina is also enhanced by adding both t-phase and m-phase zirconia, which can reach values as high as two times that of Al₂O₃ alone. The toughening effect is attributed mainly to the zirconia t–m phase transformation.     

气相色谱-质谱联用检测环境水体中的三嗪类除草剂

研究了用气相色谱-质谱联用技术检测环境水中三嗪类除草剂的分析方法,被测物质包括阿特拉津、西玛津、氰草津及阿特拉津的两种代谢产物去乙基阿特拉津和去异丙基阿特拉津。外标法定量,液–液萃取分析500mL水样,加标浓度分别为0.2,0.5,1.0μg/L时,回收率在51.75%～125.05%之间,两种代谢物的回收率相对较低。理论方法检出限为0.01～0.06μg/L,线性范围为0.01μg/mL～1.0μg/mL。用该方法可实现对环境水体中痕量三嗪类除草剂的检测。