Lithium ferrite (LiFe5O8)/polymethyl methacrylate (PMMA) nano-composite used in high dielectric constant capacitor and electromagnetic applications

Poly methyl methacrylate/ Lithium ferrite nano-composites have been prepared by solution mixing process. The electrical conductivity and dielectric properties of these prepared nano-composite have been investigated in the frequency range 10²–10⁶ Hz at different LiFe₅O₈ concentrations from 0 vol% to 25 vol%. The prepared samples are studied by thermal gravimetric analysis (TGA) and X-ray diffraction (XRD). Moreover, the magnetic properties of these nano-composites are investigated through vibrating sample magnetometer studies. XRD spectral investigation revealed that the structural of PMMA and its chemical characterization are appreciably affected by mixed lithium ferrite filler. The thermal stability of the PMMA matrix was found to increase appreciably by LiFe₅O₈ loading. The (I-V) characteristic of these nano-composites are in very good agreement with the non-linearity predicted by Kaiser et al. model. The effective dielectric constant is studied through different proposed models. Saturation magnetization of 10.05 emu/g is achieved for PMMA sample loaded with 25 vol% of LiFe₅O₈ particles.     

Selective nano alumina supported vanadium oxide catalysts for oxidative dehydrogenation of ethylbenzene to styrene using CO2 as soft oxidant

Nano alumina-supported V₂O₅ catalysts with different loadings have been tested for the dehydrogenation of ethylbenzene with CO₂ as an oxidant. High surface area nano-alumina was prepared and used as support for V₂O₅ as the catalyst. The catalysts were synthesized by impregnation techniques followed by calcinations and microwave treatment, denoted as V₂O₅/γ-Al₂O₃-C and V₂O₅/γ-Al₂O₃-MW, respectively. The V₂O₅ loading was varied on nano-alumina from 5 to 30 wt%. The support and catalysts were characterized by X-ray diffraction (XRD), Barett–Joyner–Halenda (BJH) pore-size distribution, N₂-adsorption isotherms, Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and temperature programed desorption (TPD-NH₃). The characterization results indicated that V₂O₅ is highly dispersed on alumina up to 30%-V₂O₅/γ-Al₂O₃-MW prepared by MW method. The TPD studies indicated that there are significant differences in acid amount and strength for V₂O₅/γ-Al₂O₃-C and V₂O₅/γ-Al₂O₃-MW-catalysts. The catalytic activity of the prepared catalysts was evaluated in the temperature range 450–600 °C in relation to the physicochemical properties and surface acidity. The results revealed that optimum catalytic activity and selectivity (～100%) toward styrene production were obtained using 10% V₂O₅/γ-Al₂O₃-MW catalyst treated with microwave.     

The Support Effect on Hydrogenolysis of Thiophene and Gas–Oil

Abstract

Results are reported on the support effect on the catalytic activity in thiophene hydrodesulfurization (HDS) of sulfided Ni-Mo catalysts supported on pure niobia, mixed oxides of Nb₂O₅-TiO₂ prepared by sol-gel method, and Nb₂O₅/TiO₂ and Nb₂O₅/Al₂O₃ prepared by surface deposition. The prepared samples were characterized using N₂ adsorption at ?196°C, X-ray diffraction (XRD), and temperature-programmed reduction (TPR) techniques. This study showed activity variation as a function of support composition. The activity of niobia-rich catalysts was no longer promoted by the synergy between Ni and Mo. The absence of synergy between molybdenum and nickel on niobia can be explained by the strong interaction of each metal with niobia at the expense of interaction with each other. It was found that 5 wt% Nb₂O₅/TiO₂-supported catalyst was the better catalyst for thiophene HDS. It was shown that by means of an adequate support design it is possible to significantly increase the functionalities of HDS catalysts. Semiconducting supports like TiO₂ can improve the HDS activity by exerting electronic effects on the active phase, helping in this way the formation of sulfur vacancies. The 5 wt% Nb₂O₅/TiO₂ was also tested at high pressure with gas oil feedstock. It is observed with the hydrogeolysis of sulfur compounds against time-on-stream that the activity of this catalyst decreases fast with time.     

Preparation and characterization of FeNi/Al2O3 catalysts for production of light olefins

The 24%Fe-36%Ni/Al₂O₃ catalyst was prepared using sol-gel method. This research investigated many variable factors for conversion synthesis gas to C₂?CC₄ light olefins by using Fisher-Tropsch synthesis. The effects of calcination atmospheres and calcination heating rates and also operation conditions such as the H₂/CO molar feed ratios, gas hourly space velocity (GHSV), temperatures and total reaction pressure on the catalytic performance of 24%Fe-36%Ni/Al₂O₃ catalyst was investigated. The stability of the catalyst for 240 h has been tested at optimal operating conditions (T = 260°C, H₂/CO = 2/1, GHSV = 3200 h^?1 and P = 3 bar). The results indicated that this catalyst was highly stable for production C₂?CC₄ light olefins. Characterization of precursors and calcined catalysts were carried out by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) specific surface area measurement, temperature program reduction (TPR) and thermal analysis methods such as thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC).     

Catalytic transformations of mixtures of ethers with aliphatic and aromatic nitriles on solid acids under supercritical conditions

The catalytic conversion of mixtures of ethers with aliphatic and aromatic nitriles in supercritical conditions on zeolites (HY, HCaREEY), individual oxides (Al₂O₃, SiO₂, MoO₃, WO₃, TiO₂), and oxide systems (Al₂O₃-SiO₂, H₈[Si(Mo₂O₇)₅], Al₂(WO₄)₃) has been studied. It has been found that acid catalysts, such as zeolites, mixed oxides, and TiO₂ (anatase), are active at 350°C in the direct synthesis of N-acylpyrrolidines from tetrahydrofuran and nitriles (CH₃CN, n-C₄H₉CN, C₆H₅CN): the product yield reaches 40% and the selectivity is 65–94%. The activity and selectivity of TiO₂ samples increase with an increase in the specific surface area (from 37 to 139 m²/g) or with a decrease in the particle size of anatase (from 43 to 13 nm according to XRD data). The character of interaction of the components of the reaction mixture with the TiO₂ surface has been studied by the TG-DTA technique. After oxidative regeneration, TiO₂ exhibits the initial catalytic properties, suggesting the possibility of its repeated use in the direct synthesis of acylpyrrolidines. Replacing THF by other compounds (diethyl ether, 1,4-dioxane, tetrahydropyran) drastically reduces the yield of respective alkylamides.     

Promoted catalysts for hydrogenation of bicyclic aromatic hydrocarbons obtained in situ from molybdenum and tungsten carbonyls

Promoted Мo and W catalysts have been prepared in situ via thermal decomposition of precursors, oil-soluble salts Mo(CO)₆, W(CO)₆, С°C₁₆H₃₀O₄, and NiC₁₆H₃₀O₄. TiO₂, Al₂O₃, and ZrO(NO₃)₂ · 6H₂O have been used as the acidic additives. Also, Mo and W unsupported sulfide catalysts have been prepared in the presence of elemental sulfur as the sulfiding agent. The catalysts have been characterized by transmission electron microscopy and X-ray photoelectron spectroscopy. The activity of the catalysts prepared in situ has been evaluated in the hydrogenation reaction of bicyclic aromatic hydrocarbons by the example of model mixtures of 10% solutions of naphthalenes (unsubstituted naphthalene, 1- and 2-methylnaphthalenes, and 1,5- and 2,3-dimethylnaphthalenes) in n-hexadecane. The effect of the precursor/acidic oxide ratio on the activity of the formed catalyst has been found. Hydrogenation of bicyclic aromatic hydrocarbons has been conducted at a hydrogen pressure of 2 and 5 MPa and a temperature of 380 and 400°C for 2 h. Hydrogenation of the unsubstituted aromatic ring has been preferable due to the absence of steric hindrances. The degree of conversion of n-hexadecane under the reaction conditions has been 1.5–7.5% depending on the reaction temperature. It has been found that the activity of the sulfided catalyst in the conversion of 1- and 2-methylnaphthalenes is inferior to the activity of the unsulfided analogue, while partial replacement of TiO₂ by Al₂O₃ results in a decrease in the conversion of the substrates as opposed to the unsulfided catalysts, in which the use of nanocrystalline Al₂O₃ promotes an increase in the conversion.     

Ti-Mg-Al复合氧化物催化材料的制备及其加氢脱硫性能

中国石油西南油气田公司天然气研究院(以下简称天研院)申请的"一种天然气井返排压裂液回收再利用系统"实用新型专利获得国家知识产权局授权,专利号为ZL201220050049.4。该实用新型专利是一种应用于气井低分子压裂返排液的回收再利用系统,包括返排液的回收与再利用工艺等方面。气井压裂施工后,大量含有各种     

Fabrication of Hollow Fiber Membrane from Polyarylate–Polyarylate Block Copolymer for Air Separation

A process has been developed for spinning asymmetric hollow fiber membranes from a polyarylate–polyarylate block copolymer having a separation factor for pure gases in the oxygen–nitrogen pair of α(O₂/N₂) = 6.3 and an oxygen permeance coefficient of 2.4 Barrer. The effect of the polymer molecular weight, the composition of the dope solution, and the spinning parameters on the gas transport properties of the hollow fiber membrane and its geometry has been studied. The use of a polymer with a molecular weight of 67 kDa, as well as the introduction of surfactants into the dope solution, has made it possible to prepare samples of defect-free membranes with an oxygen permeance of 120 L(STP)/(m² h bar) and a separation factor of α(O₂/N₂) = 6.5, which correspond to the selective layer thickness of 60 nm.     

CA和EDTA对Co-Mo-P/TiO2-γ-Al2O3选择性加氢脱硫催化剂性能的影响

 制备了添加螯合剂柠檬酸(CA)和乙二胺四乙酸(EDTA)的Co-Mo-P/TiO₂-γ-Al₂O₃加氢脱硫催化剂,并对其进行了BET、SEM和H₂-TPR表征。以FCC汽油重馏分为原料,考察了螯合剂对Co-Mo-P/TiO₂-γ-Al₂O₃催化剂选择性加氢脱硫性能的影响。结果表明,添加CA或EDTA均可不同程度地提高Co-Mo-P/TiO₂-γ-Al₂O₃催化剂的比表面积;适量的加入CA或EDTA可有效改善活性组分在载体上的分散状态,减弱活性组分与载体间的相互作用;加入CA可明显改进催化剂的选择性加氢脱硫性能;而加入EDTA同时提高了催化剂的脱硫活性和加氢活性,没能改善催化剂的选择性加氢脱硫性能。     

A Comparative Study of Surface Characteristics of Nickel Supported on Silica Gel, γ-Alumina,Aluminosilicate

Abstract

Surface characteristics of the prepared nickel catalysts containing 7, 10, and 13 wt% Ni w/w over different supports—silica gel, γ-alumina, and aluminosilicate—were investigated. Surface areas, total pore volumes, and average pore radii were determined for all catalysts. Pore analysis was discussed based on V_l-t plots and pore size distribution. The measured surface areas and pore volumes of pure supports increased in the following order: γ-alumina < aluminosilicate < silica gel. Pore analysis showed that SiO₂ and Al₂O₃-SiO₂ and their supported Ni samples were characterized by presence of narrower mesopores of ink-bottle type. Al₂O₃ was distinguished by presence of two distinct pore types, both showing continual increase in fraction with a shift to larger dimensions upon loading with nickel. Penetration and/or incorporation process of Ni particles took place at the expense of their interaction with Al⁺³. SiO₂ revealed a gradual increase in surface parameters upon loading with nickel. For Al₂O₃-SiO₂—supported samples, the result proposed the interaction of Ni with both alumina and silica contents of the support regardless of the penetration process.     

Hydrotreating of vacuum gas oil on modified Ni–Mo/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts

The effect of the introduction of P₂O₅ into Ni–Mo/Al₂O₃ catalysts on their activity in the hydrotreating of vacuum gas oil has been studied. As the support, γ-Al₂O₃ prepared from aluminum hydroxide AlOOH powder of the TH-100 brand (Sasol) has been used. The catalytic properties of the catalysts obtained have been examined in the hydrotreating of vacuum gas oil in a continuous-flow unit under hydrogen pressure. The amounts of sulfur and polycyclic aromatic hydrocarbons, the hydrocarbon group composition, and the carbon residue of the feedstock and the hydrotreating product have been determined. The catalysts after testing have been studied using differential thermal analysis in combination with thermogravimetry (DTA–TGA); the influence of the amount of the modifier on the catalytic activity and coking of the catalysts has been shown.     

Can Mesoporous TiO<Subscript>2</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-Supported NiMoS OR CoMoS Effectively Perform in Ultra-Deep Desulfurization of Gas Oil?

Waste aluminum foil was used for preparation of mesoporous TiO₂-Al₂O₃ using starch as a textural modifier. The catalytic species, Mo and Ni or Co were loaded onto the mesoporous support, following incipient wetness sequential impregnation. To gain an insight into the pore dimensions effect, Ni and Mo species with the same mass ratio were loaded onto the TiO₂-Al₂O₃, prepared from analytical grade chemicals without templating. TPR spectra, TEM images and BET analysis showed how the promoter (Ni or Co), TiO₂ and the template (starch) affect the ease of reduction of Mo species, the morphology of the active MoS₂ phase and the pore dimensions of the catalysts. The catalysts were employed in hydro-desulfurization process of gas oil using a fixed bed down flow microreactor at varying operating conditions, viz., temperature (320–400°C), Liquid hourly space velocity (0.5–4 h^–1), H₂/oil ratio of 450 v/v, and 6 MPa operating pressure. The results showed that the promotion effect prevails over the textural effect, where Ni promoted catalyst (with lower surface parameters) exhibits higher activity than Co promoted one. The dual layer catalytic bed system achieved the sulfur level less than 10 ppm.     

Effect of binder on the physical stability and bactericidal property of titanium dioxide (TiO2) nanocoatings on food contact surfaces

TiO₂ is a promising photocatalyst for use in food processing environment as an antimicrobial coating. The purpose of this study was to determine the effect of different binding agents on the physical stability and bactericidal property of TiO₂ nanocoatings created on stainless steel surfaces. A total of six different coating suspensions were prepared by mixing TiO₂ (Aeroxide^® P-25) nanoparticles (NPs) with three different types of binders (Shellac (A), polyuretahne (B), and polycrylic (C)) at a 1:4 to 1:16 NP to binder weight ratio. Bactericidal activity of these TiO₂ coatings against Escherichia coli O157:H7 (5-strain) was determined at three different UV-A light intensities (0.25, 0.50 and 0.75 mW/cm²) for 3 h. The type of binder used in the coating had a significant effect on the log reduction of E. coli O157:H7. TiO₂ coatings with binder C showed highest reduction (>4 log CFU/cm²) followed by TiO₂ coating with binder B and A. Increasing the binder concentration in the formulation from a 1:4 to 1:16 weight ratio decreased the log reduction of E. coli O157:H7. Increasing the UV-A light intensity from 0.25 to 0.75 mW/cm² increased the log reduction of bacteria for all the TiO₂ coatings. The physical stability of the TiO₂ coatings was determined using ASTM procedures. TiO₂ coatings with binder B showed highest adhesion strength and scratch hardness when compared to coatings with other binders. However, on repeated use experiments (1, 3, 5, and 10 times), TiO₂ coatings with binder C were found to be physically more stable and able to retain their original bactericidal property. The results of this study showed promise in developing durable TiO₂ coatings with strong photocatalytic bactericidal property on food contact surfaces using appropriate binding agents to help ensure safe food processing environment.     

Degradation of cypermethrin,malathion and dichlorovos in water and on tea leaves with O3/UV/TiO2 treatment

The main aims of the present study were to study the efficacy and mechanisms of removing three pesticides (cypermethrin, malathion, dichlorovos) from fresh tea leaves and water by O₃/UV/TiO₂ treatment, and to explore the optimal conditions for the removal. The results indicated that the removal rates of pesticides on tea leaves were not affected by water pH, whereas the removal rates of pesticides from water were affected.Eliminating rates of cypermethrin and malathion from tea leaves by O₃/UV/TiO₂ were significantly higher than that by water rinsing treatment (P < 0.05). The O₃/UV/TiO₂ treatment resulted in an 80% removal rate for cypermethrin (initial residue content 5.8 mg/kg) and 78% for malathion (initial residue content 2.2 mg/kg). It could be concluded that O₃/UV/TiO₂ treatment was especially effective for the removal of insoluble pesticides (e.g. cypermethrin) from tea leaves, with a 250% enhancement over the water rinsing treatment.     

Effects of Modified Co-Mo Catalysts for FCC Gasoline HDS on Catalytic Activity

Abstract

In this article, a series of catalysts with HZSM-5/γ-Al₂O₃, HZSM-5/TiO₂-γ-Al₂O₃ as supports, bearing Co-Mo as active components, were prepared, and the catalysts were modified with alkaline earth and VIII, IB metal oxide. The catalysts were evaluated by hydrodesulfurization for QILU FCC gasoline. The experiment results showed that: (1) the RON (research octane number) of effluents rose with the increase of ZSM-5 mass percent in the support, but the HDS ratio reduced; (2) the catalysts with ZSM-5/TiO₂-Al₂O₃ as support had higher HDS ratio but lower RON of effluent; and (3) the catalysts modified with metal oxide had higher RON of effluent, but lower HDS ratio, compared with the stuff, and as to RON of effluent and hydrodesulfurization ratio for the modified catalysts, it had the following order: Ba-modified > Fe-modified > Cu-modified.     

Amorphous TiO2-supported Keggin-type ionic liquid catalyst catalytic oxidation of dibenzothiophene in diesel

Supported ionic liquid(IL) catalysts [C_nmim]_3PMo_(12)O_(40)/Am TiO_2(amorphous TiO_2) were synthesized through a one-step method for extraction coupled catalytic oxidative desulfurization(ECODS) system. Characterizations such as FTIR, DRS,wide-angle XRD, N_2 adsorption–desorption and XPS were applied to analyze the morphology and Keggin structure of the catalysts. In ECODS with hydrogen peroxide as the oxidant, it was found that ILs with longer alkyl chains in the cationic moiety had a better effect on the removal of dibenzothiophene. The desulfurization could reach 100% under optimal conditions, and GC–MS analysis was employed to detect the oxidized product after the reaction. Factors affecting the desulfurization efficiencies were discussed, and a possible mechanism was proposed. In addition, cyclic experiments were also conducted to investigate the recyclability of the supported catalyst. The catalytic activity of [C_(16)mim]_3 PMo_(12)O_(40)/Am TiO_2 only dropped from 100% to 92.9% after ten cycles, demonstrating the good recycling performance of the catalyst and its potential industrial application.     

Various characteristics of Ni and Pt–Al2O3 nanocatalysts prepared by microwave method to be applied in some petrochemical processes

Alumina-supported metal nanocatalysts were prepared via the microwave method, by loading nano Ni particles (at 1, 3 and 5 wt%) or nano Pt particles (at 0.3, 0.6 and 0.9 wt%). Structural and adsorption features of the nano catalysts were revealed through XRD, DSC-DTA, TEM, H₂-chemisorption and N₂-physisorption. N₂-adsorption–desorption isotherms of type IV were related typically to mesoporous materials with H₂ class of hysteresis loops characterizing ink bottle type of pores. The well dispersed nano-sized metal particles were evidenced in the studied catalytic systems, exhibiting marked thermal stability up to 800 °C. The catalytic performances of different catalyst samples were assessed during cyclohexane, normal hexane and ethanol conversions, using the micro-catalytic pulse technique at different operating conditions. The 5% Ni–γ–Al₂O₃ sample was found to be the most active in dehydration of ethanol to produce ethylene, as well as in n-hexane cracking. However, the 1% Ni–Al₂O₃ sample showed the highest dehydrogenation activity for selective production of benzene from cyclohexane. On the other hand, the 0.9% Pt–γ–Al₂O₃ sample exhibited the highest activity in the dehydration of ethanol and in the dehydrogenation of cyclohexane. The 0.3% Pt–γ–Al₂O₃ sample was the most active in the dehydrocyclization of normal hexane, as compared to the other catalyst samples under study.     

Acid Properties of the Surface of Zn–B–P/γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/Al Catalysts and Their Activity in Microwave-Stimulated Reaction of Diethylamine Acylation with <Emphasis Type="Italic">m</Emphasis>-Toluic Acid

The acid–base properties of Zn–B–P/γ-Al₂O₃/Al catalysts for the direct acylation of diethylamine with m-toluic acid have been studied using ammonia temperature-programmed desorption, probe adsorption, and IR spectroscopy techniques, the catalysts having been synthesized and tested under conditions of microwave-assisted thermal treatment. A correlation between the activity of the microwave-absorbing catalysts in the target N,N-diethyl-m-toluamide formation reaction and the concentration of acid sites of medium strength on the surface of the samples has been revealed. It has been shown that the main reason behind the higher activity of Zn–B–P/γ-Al₂O₃/Al catalysts prepared under conditions of the thermal action of microwave field is the formation of a more developed active surface characterized by a prevalence of medium acid sites.     

The effect of packaging conditions on the quality of minimally processed celeriac flakes

The aim of the study was to select packaging conditions of minimally processed celeriac to preserve their quality during storage for 12 days at 4 and 15 °C. The quality of the product was determined on the basis of colour measured in the CIE L¹a¹b¹ system, sensory quality and total counts of mesophilic and psychrophilic bacteria, counts of moulds and yeasts, coliform counts, counts of Pseudomonas bacteria and the presence of bacteria from the genus Clostridium perfringens. Moreover, changes were determined in oxygen and carbon dioxide contents in the atmosphere within the packs, in which the product was stored. Celeriac flakes were packaged in the atmosphere with varying CO₂ contents (0%, 5%, 10%, 20%, 30%, 50% plus 2% O₂ and with balance N₂). After 12 days at 4 °C, it was found that celeriac flakes packaged in atmosphere containing 5% or 10% CO₂, 2% O₂ and balance N₂ were characterized by better quality than samples packaged in air atmosphere or in the atmosphere with CO₂ contents of 0% or higher than 10%. Modified atmosphere with the content of 5% or 10% CO₂, 2% O₂ and balance N₂, applied in the packaging of celeriac flakes, resulted in the inhibition of growth of mesophilic, psychrophilic and coliform bacteria in the tested minimally processed product.     

微量TiO2对Ni/SiO2催化剂催化顺酐加氢制γ-丁内酯的促进作用

 采用等体积浸渍法分别制备了Ni/SiO₂和含TiO₂的Ni/SiO₂催化剂,采用XRD、TPR、XPS、N₂吸附-脱附技术对催化剂进行了表征,并将催化剂应用于顺酐液相加氢制γ-丁内酯反应中,考察了Ni含量、TiO₂添加量、催化剂还原温度对催化剂活性的影响。结果表明,Ni/SiO₂催化剂对顺酐液相加氢制γ-丁内酯反应具有很高的催化活性, γ-丁内酯选择性很高;Ni/SiO₂添加微量助剂TiO₂,可以提高该反应的γ-丁内酯选择性。推测可能是由于TiO₂促进了催化剂的还原,产生更多的活性中心,并且在400℃还原时,Ni和TiO₂之间产生了强金属-载体相互作用（SMSI效应）,TiO₂富集到Ni的表面,将电子转移到Ni上,产生了更多有利于吸附羰基的活性中心,从而提高了γ-丁内酯选择性。