Mo--V--Nb--O-based catalysts for low-temperature selective oxidation of Cα--OH lignin model compounds

Mo–V–Nb tri-component oxide catalysts were prepared and firstly used for the selective oxidation of C_α−OH lignin compounds. The catalytic performance of the composite oxides was obviously enhanced due to the synergistic effects of Mo and V elements. Mo_5−xV_xO₁₄ phase with a variable Mo/V ratio provided suitable active sites for the oxidative dehydrogenation (ODH) of C_α−OH lignin model compound. The optimized Mo–V–Nb molar composition was confirmed as Mo_0.61V_0.31Nb_0.08O_x/TiO₂, which exhibited the prominent catalytic activity with the turnover frequency of 1.04×10⁻³ mmol· g(cat)⁻¹·s⁻¹. Even at room temperature, the catalysts showed highly-efficient ODH reaction activities. The active phase for selective oxidation reaction and the inhibiting effect of α-MoO₃ phase were also discussed in the study.     

Wet electrolytic oxidation of organic sludge

Electrolysis of an aqueous solution at subcritical water conditions, referred here as wet electrolytic oxidation (WEO), results in a completely different reaction product compared to that from usual water electrolysis. Oxygen, hydrogen and chlorine evolution is almost completely suppressed when carrying out the electrolysis of aqueous NaCl solution at temperatures higher than 250 degrees C. Chemical oxygen demand (COD) compounds can be completely mineralized by this electrolytic reaction, but this work focused in partial oxidation of organic sludge and combining with biological process. The treatment of organic sludge by WEO increased the biodegradability of organic sludge due to the formation of organic acids. The electrochemical reaction of WEO suppressed the evolution of color that often appears in subcritical water treatment of organic waste.     

A continuous flow reaction system for producing acetic acid by wet oxidation of biomass waste

A continuous flow reaction system designed for producing acetic acid by wet oxidation (WO) of biomass with the maximum treatment capacity of 1 kg/h of dry biomass was developed. Experimental runs with rice hulls and starch were conducted at reaction temperatures between 300–320°C, for time of 2 and 3 min, with oxygen supplies between 70 and 100%, and at pressures between 10 and 30 MPa. The influence of each of these parameters was evaluated.     

Wet electrolytic oxidation of cationic red X-GRL

Wet electrolytic oxidation (WEO) under mild condition, a relatively less reported process which coupled the advantages of both wet air oxidation (WAO) and electrochemical oxidation (EO) was investigated for the removal of one azo dye, cationic red X-GRL, in a 2L autoclave reactor. It was found that this novel process showed synergistic effect for TOC removal compared with that by the individual WAO and EO, and presented much higher dye removal efficiency. At similar conditions of temperature of 100-180 degrees C, P(N(2))= 0.50 MPa and P(O(2))= 0.14 MPa, a little introduction of current density of 2 mA cm(-2) led to the apparent reaction constants for WEO two times larger than those of WAO. Possible mechanism for the synergistic effect was discussed based on the analysis of free-radical generation and intermediates detected by GC/MS.     

(S)-Nitroxycarnitine nitrate production from (S)-carnitine by using acetic anhydride/nitric acid/acetic acid mixtures: safety assessment

The present work aims at assessing both thermodynamic and kinetic parameters of the esterification process of the (S)-carnitine, using calorimetric techniques. The use of the system acetic anhydride/nitric acid/acetic acid as esterifying agent and the explosive behaviour of nitric esters lead to safety considerations that have been investigated by hypothesizing some common process deviations. In particular, it has been investigated in adiabatic conditions both the batch addition of acetic anhydride and the effect of an initial temperature higher than those required by the process.     

Membrane bioreactor production of lignin and manganese peroxidase

This article is a summary of a talk that was presented during the “Bio- & Hydrometallurgy 02” conference, which was held on 13–15 March 2002, Cape Town, South Africa. It explains the use of the white-rot fungus Phanerochaete chrysosproium for the production of ligninolytic enzymes. The viability of a polysulphone membrane for the cultivation of the fungus, and the continuous production of enzymes was evaluated. The study also examined the effect of operating parameters on biofilm development and enzyme production.     

Wet air oxidation studies of coal gasification wastewaters

The kinetics of wet oxidation of coal gasification wastewater were studied. Experimental studies explored the effect of temperature and residence time on the extent of reaction by conducting constant volume batch tests in a 1-liter high pressure autoclave. The extent of reaction was determined by measuring the chemical oxygen demand (COD) and phenol concentrations of the wastewater at various times.The effect of temperature was studied from 205 to 251°C with residence times from 30 to 90 minutes. The experimental data obtained were used to fit Arrhenius expressions of the reactions. A mathematical model consisted of two first-order reactions in series showing a maximum COD reduction of 60% and a maximum phenol reduction of 95%, both at 251°C and a 90 minute residence time. The activation energies for COD and phenol reduction were both found to be 8.0 kcall.     

Thermal decomposition of acetic anhydride-nitric acid mixtures

The adoption of Ac2O/HNO3 mixtures for the nitration of organics or the preparation of nitric esters is not free from some risks of explosion. The behaviour of these mixtures at varying Ac2O/HNO3 molar ratios is studied by means of adiabatic and scanning calorimetry. A simplified kinetic model, based on two lumped reactions (one of which leads to the formation of tetranitromethane) is developed to simulate the thermal decomposition of the investigated system under adiabatic conditions. The use of this model allows satisfactory prediction of the temperature profiles in the reactor whereas calculated pressures are generally overestimated due to some model inadequacies to account for the absorption of gaseous decomposition products into the reacting solution.     

Wet peroxide oxidation and catalytic wet oxidation of stripped sour water produced during oil shale refining

Catalytic wet oxidation (CWO) and wet peroxide oxidation (WPO) of stripped sour water (SSW) from an oil shale refinery was investigated. Greater than 70% total organic carbon (TOC) removal from SSW was achieved using Cu(NO(3))(2) catalysed WO under the following conditions using a glass lined reaction vessel: 200 degrees C, pO(2)=0.5MPa, 3h, [Cu(NO(3))(2)]=67mmol/L. Significant TOC removal ( approximately 31%) also occurred in the system without added oxygen. It is proposed that this is predominantly due to copper catalysed oxidative decarboxylation of organics in SSW based on observed changes in copper oxidation state. Greater than 80% TOC removal was achieved using WPO under the following conditions: 150 degrees C, t=1.5h, [H(2)O(2)]=64g/L. Significantly more TOC could be removed from SSW by adding H(2)O(2) in small doses as opposed to adding the same total amount in one single dose. It was concluded that WPO was a far more effective process for removing odorous compounds from SSW.     

Hydrothermal conversion of biomass into acetic acid

Hydrothermal process is one of the most promising processes for the conversion of biomass waste into resources among the several biomass conversion processes, because water of high temperature and high pressure has remarkable properties as a reaction medium. This paper described advances in our research involving overall reaction pathways for acetic acid production from biomass, mainly including (1) acetic acid production by controlling pathways of hydrothermal reaction, (2) acid-base behavior of water in the subcritical region and (3) effect of lignin on the acetic acid production in WO of lignocellulosic biomass.     

Wet oxidation of acid brown dye by hydrogen peroxide using heterogeneous catalyst Mn-salen-Y zeolite: a potential catalyst

Catalytic wet hydrogen peroxide oxidation of acid dye has been explored in this study. Manganese(III) complex of N,N'-ethylene bis(salicylidene-aminato) (salenH(2)) has been encapsulated in super cages of zeolite-Y by flexible ligand method. The catalyst has been characterized by FT-IR, XRD, TG/DTA and nitrogen adsorption studies. The effects of various parameters such as pH, catalyst and hydrogen peroxide concentration on the oxidation of dye were studied. The results indicate that after 20 min at 30 degrees C, 0.175 M H(2)O(2) and 3g/L catalyst, about 90% dye removal was obtained. These studies indicate that manganese-salen complex immobilized on zeolite framework can act as a good heterogeneous catalyst for removal of dye from wastewaters.     

2-噻吩乙酸的HPLC分析测定

建立了一种2-噻吩乙酸的反相高效液相色谱-紫外检测法.研究了流动相的组成、流速及色谱柱温度等因素对测定的影响.采用色谱柱为VARIAN C18(250 mm×4.6 mm,5μm)反相色谱柱,流动相为甲醇-水(V∶V=70∶30),流速1.0 mL/min,柱温为室温,紫外检测波长235 nm,在6 min内可完成分析.该方法的回收率为98.4%~99.8%,RSD<1%.其优点为2-噻吩乙酸与其同分异构体3-噻吩乙酸得到较好的分离,明显不重叠,且操作简单、快速和准确可靠,用于2-噻吩乙酸产品的纯度测定,结果令人满意.     

Ozonation of trichloroethylene in acetic acid solution with soluble and solid humic acid

The combined flushing and oxidation process using acetic acid and ozone has been used successfully to remove trichloroethylene (TCE) completely from contaminated soil. In this study, the effects of humic acid, a fraction of the organic matter in soil, over the performance of TCE decomposition was evaluated. TCE decomposition by ozone was enhanced by the presence of humic acid at concentrations lower than 8mgCL(-1) and then inhibited at higher concentrations. It is possible that the presence of the soluble humic acid fraction during the ozonation of TCE in acetic acid solutions produces hydroxyl radicals during the TCE ozonation which appears to be the reason for the enhanced TCE decomposition rate. Solid humic acid reduced TCE decomposition rate by acting as an ozone scavenger. Similarly, sorbed TCE reduced the amount of TCE available for decomposition by ozone in solution.     

醋酸分子印迹电化学传感器的制备

基于循环伏安电化学聚合方法,以30mmol/L醋酸作为模板分子,5mmol/L苯酚作为功能单体,0.1mol/L氯化钾和0.05mol/L磷酸盐缓冲溶液(pH=5.4)作为聚合底液,聚合电位为-0.8~1.2V,扫描圈数为20,以0.1mol/L碳酸氢钠溶液作为洗脱液进行洗脱20min,最终制得性能较佳的醋酸分子印迹电化学传感器。对该传感器进行循环伏安(CV)表征、阻抗表征、扫描电镜的形貌表征、差分脉冲表征,探索了不同pH磷酸盐缓冲溶液作为聚合底液、不同浓度洗脱液和不同洗脱时间对该传感器性能的影响。发现在以0.05mol/L磷酸盐缓冲溶液(pH=5.4)作为最佳底液条件下,醋酸分子印迹电化学传感器与0~45×10^-9 mol/L浓度范围内醋酸分子二者呈现出良好的线性关系,其检出限为2.85×10^-9 mol/L,同时研究了该传感器的重现性和稳定性。     

Effective abatement of VOC and CO from acrylic acid and related production waste gas by catalytic oxidation

Waste gasses containing volatile organic compounds (VOC) are arising mainly form industrial production in which organic materials are processed. These VOC must be treated to levels so that they meet the local applicable legislation limits. Momentive specialty chemicals is a company which produces acrylic acid, acrylic acid esters, and acrylate polymers in Sokolov (Czech Republic). A mixed waste stream which contains 6,000–10,000 mg TOC/Nm³ of VOC is treated. The management would like to lower the operating costs of the thermal incineration unit used. It seems suitable in this case to replace the existing incinerator with a catalytic oxidation unit with use of a Pt–Pd/Al₂O₃ catalyst for VOC abatement. A full-scale unit was designed according to the waste gas composition and flow. Mass and energy balances were carried out, and it was discovered that the catalytic bed must be divided into two parts to prevent the reactor overheating and irreversible damage to the catalyst. A pilot plant was designed and implemented due to the potential threat of catalyst fouling by solid impurities and to confirm the expected conversion of VOC and CO. It also proves the long-term reliability of the catalytic reactor. The performed pilot tests confirmed that catalytic oxidation is suitable for the disposal of waste gas from acrylic acid and acrylates production (for this application and treated inlet concentration of VOC). VOC and CO removal efficiencies during pilot trials were 98.3 and 98.5 %, respectively.     

The oxidation resistance and hardness of some intermetallic compounds

Thirty-nine intermetallic compounds have been oxidation-tested in air. These include all the known compounds in the Al-V, Al-Ni and Al-La systems, three compounds each from the Al-Mn and Cu-Zn systems, four zinc-rich transition-metal phases, six intertransition metal Laves phases, and the equiatomic compounds of antimony with aluminium, indium and nickel respectively. From the oxidation results the temperature corresponding to a weight change of 1 mg cm⁻² (4h)⁻¹ was determined by interpolation. An attempt is made to classify the compounds in terms of the ratio of this temperature to the melting point of the appropriate compound or its oxidation product. The hardness of the compounds and of additional Al-3d compounds has been estimated, and in conjunction with the oxidation data forms the basis for some observations on the nature and incidence of binary intermetallic compounds of high atomic ratio.     

Facile and rapid exfoliation of black phosphorus assisted by acetic acid

Journal of Materials Science: Materials in Electronics - Rapid and facile exfoliation of phosphorene sheets from freshly crystallized black phosphorus on silicon substrates, is achieved using...     

两相电解电渗技术浓缩回收乙酸的研究

在两相电泳的基础上,针对含乙酸稀溶液的处理提出了两相电解电渗的技术．利用饱和水的正丁醇为有机相,以AM203阴离子交换膜为介质,开展普通电解电渗和两相电解电渗的研究工作,考察了浓度、电流密度等因素对电流效率、浓缩比以及水的电渗量的影响、结果发现较普通的电解电渗技术和两相电解电渗技术在浓缩比、水的电渗量的控制方面具有明显的优势,在本实验范围内,在两相电解电渗过程中基本没有发现水的电渗现象的发生,同样乙酸的回收率也可以达到100％．由此可以说明新的两相电解电渗技术对于环境稀溶液的处理是一种较为理想的方法．     

Hydrogen peroxide and oxygen-hydrogen oxidation of aromatic compounds in catalytic systems containing heteropoly compounds

Hydrogen peroxide and Pt activated mixture of gaseous O(2) and H(2) have been applied to oxidation of aromatic compounds in the presence of redox active heteropoly compounds in the form of acid H(4)PMo(11)VO(40) and tetrabuthylammonium (TBA) salts TBA(4)PMo(11)VO(40) and TBA(4)HPW(11)Fe(OH)O(39). Benzene, toluene and phenol were subjected to hydroxylation of the ring, which was accompanied by secondary oxidation in the reaction with hydrogen peroxide. Oxygenation of toluene was equally directed to the ring and to methyl group. The total reactivity of substrates was increased in the order of benzene相似文献