Catalytic ozonation of volatile organic compounds (ethyl acetate) at normal temperature

Catalytic treatments of VOCs at normal temperature can greatly reduce the cost and temperature of processing, and improve the safety factor in line with the requirements of green chemistry. Activated carbon fiber(ACF) was pretreated with 10% H_2SO_4 by single factor optimization to increase specific surface area and pore volume obviously. The catalytic ozonation performance of ACF loaded with Au, Ag, Pt and Pd noble metals on ethyl acetate was investigated and Pd/ACF was selected as the optimal catalyst which had certain stability. Pd is uniformly distributed on the surface of ACF, and Palladium mainly exists in the form of Pd~0 with a amount of Pd~(+2). The specific surface area of the catalysts gradually decreases as the loading increases. The activation energy of ethyl acetate calculated by Arrhenius equation is 113 kJ·mol~(-1). With 1% Pd loading and the concentration ratio of ozone to ethyl acetate is 3:1, catalytic ozonation performance is maximized and the conversion rate of ethyl acetate reached to 60% in 30–50 ℃ at 15,000–30,000 h~(-1).     

Study on the growth of platinum nanowires as cathode catalysts in proton exchange membrane fuel cells

The platinum nanowires have been verified to be a promising catalyst to promote the performance of proton exchange membrane fuel cells.In this paper,accurately controlled growth of nanowires in a carbon matrix is achieved for reducing Pt loading.The effects of formic acid concentration and reaction temperature on the morphology and size of the Pt nanowires,as well as their electrochemical performances in a single cell,are investigated.The results showed that the increase in the formic acid concentration results in a volcano trend with the length of Pt nanowires.With increasing reduction temperature,the diameter of Pt nanowires increases while Pt particles evolve from one-dimensional to zero-dimensional up to 40°C.A mechanism of the Pt nanowires growth is proposed.The optimized Pt nanowires electrode exhibits a power density(based on electrochemical active surface area)79%higher than conventional Pt/C one.The control strategy obtained contributes to the design and control of novel nanostructures in nano-synthesis and catalyst applications.     

Effects of Supports and Promoter Ag on Pd Catalysts for Selective Hydrogenation of Acetylene

SiO2, a-Al2O3, g-Al2O3, ZrO2 and CeO2 were used as supports and Ag as promoter to study their effects on Pd catalysts for selective hydrogenation of acetylene. The catalysts were prepared by impregnated synthesis and characterized by XRD, BET and TEM. The catalytic reaction was carried out in a fixed-bed reactor. Overall, the low specific surface area supports were better to increase the ethylene selectivity at high conversion rate of acetylene. Among the four Pd catalysts on low specific surface area supports, the catalyst on low specific surface area SiO2 (LSA-SiO2) retained a high ethylene selectivity even at complete conversion, while the other catalysts showed significant decrease in the selectivity at complete conversion. The performance of Pd/LSA-SiO2 was important to decrease the loss of ethylene in selective hydrogenation of trace acetylene in ethylene. Addition of Ag to Pd/LSA-SiO2 significantly decreased the formation of ethane, C4 alkenes and green oil, and improved the ethylene selectivity to 90% when Pd:Ag=1:1 and 1:3(w). When the ratio of Pd to Ag was above 1, the activity of Pd-Ag bimetallic catalyst was similar to that of Pd monometallic catalyst, and the selectivity of ethylene increased with increasing of amount of Ag. When the ratio of Pd to Ag was below 1, the activity of bimetallic catalyst decreased with increasing of amount of Ag, while the selectivity of ethylene was kept unchanged. The optimum temperature was 200~230℃ for 0.02%(w)Pd-0.02%(w)Ag/LSA-SiO2 to give a high ethylene selectivity and low formation of green oil.     

重油催化裂解汽柴油二次裂解性能研究

This paper investigated the secondary cracking of gasoline and diesel from the catalytic pyrolysis of Daqing atmospheric residue on catalyst CEP-1 in a fluidized bed reactor.The results show that the secondary cracking reactivity of gasoline and diesel is poor,and the yield of total light olefins is only about 10%（by mass）.As reaction temperature increases,ethylene yield increases,butylene yield decreases,and propylene yield shows a maximum.The optimal reaction temperature is about 670℃for the production of light olefins.With the enhance- ment of catalyst-to-oil mass ratio and steam-to-oil mass ratio,the yields of light olefins increase to some extent. About 6.30%of the mass of total aromatic rings is converted by secondary cracking,indicating that aromatic hy- drocarbons are not easy to undergo ring-opening reactions under the present experimental conditions.     

非均相羰基氧化一步合成碳酸二苯酯的研究(Ⅴ)筛选催化剂及优化合成条件

Pd/LaxPbyMnOz, Pd/C, Pd/molecular sieve and Pd-heteropoly acid catalysts for direct synthesis of diphenyl carbonate (DPC) by heterogeneous catalytic reaction were compared and the results of DPC synthesis indicated that the catalyst Pd/LaxPbyMnOz had higher activity. The Pd/LaxPbyMnOz catalyst and the support was characterized by XRD, SEM and TEM, the main phase was Lao.szPbo.asMnOa and the average diameter could be about 25.4nm. The optimuna conditions for synthesis of DPC with Pd/LasPbyMnOz were determined by orthogonal experiments and the experimental results showed that reaction temperature was the first factor of effect on the selectivity and yield of DPC, and the concentration of O2 in gas phase also had significant effect on selectivity of DPC. The optimum reaction conditions were catalyst/phenol mass ratio l to 50, pressure 4.5MPa, volume concentration of O2 25%, reaction temperature 60℃ and reaction time 4 h. The maximum yield and average selectivity could reach 13% and 97% respectively in the     

用过氧化氢和乙酸对未经氢化处理的煤油进行直接氧化脱硫

The oxidative desulfurization of a real refinery feedstock (i.e., non-hydrotreated kerosene with total sulfur mass content of 0.16%) with a mixture of hydrogen peroxide and acetic acid was studied. The influences of various operating parameters including reaction temperature (T), acid to sulfur molar ratio (nacid/nS), and oxidant to sulfur molar ratio (nO/nS) on the sulfur removal of kerosene were investigated. The results revealed that an increase in the reaction temperature (T) and nacid/nS enhances the sulfur removal. Moreover, there is an optimum nO/nS related to the reaction temperature and the best sulfur removal could be obtained at nO/nS 8 and 23 for the reaction temperatures of 25 and 60C, respectively. The maximum observed sulfur removal in the present oxidative desulfurization system was 83.3%.     

蒸发鼓泡塔反应器的轴向分散模型

Evaporating bubble column reactor (EBCR) is a kind of aerated reactor in which the reaction heat is removed by the evaporation of volatile reaction mixture. In this paper, a mathematical model that accounts for the gas-liquid exothermic reaction and axial dispersions of both gas and liquid phase is employed to study the performance of EBCR for the process of p-xylene(PX) oxidation. The computational results show that there are remarkable concentration and temperature gradients in EBCR for high ratio of height to diameter (H/DT). The temperature is lower at the bottom of column and higher at the top, due to rapid evaporation induced by the feed gas near the bottom. The concentration profiles in the gas phase are more nonuniform than those (except PX) in the liquid phase, which causes more solvent burning consumption at high H/DT ratio. For p-xylene oxidation, theo ptimal H/DT is around 5.     

Ni-Na/Zr02-Mn02-Zn0催化合成甲基异丙基酮和二乙基酮（英文）

ZrO2-MnO2-ZnO supports were prepared by the co-precipitation method,and then Ni-Na/ZrO2-MnO2-ZnO catalysts were prepared by the impregnation method.In this paper,the reactions to synthesize methyl isopropyl ketone and diethyl ketone by the one-step synthesis method over this catalyst were studied,and meanwhile,the impact of the catalyst preparation conditions and the reaction conditions on catalyst performance was also investigated.It was observed that under the conditions when Ni loading was 25%,calcination temperature was 400℃ and reduction temperature was 410℃,this catalyst had good catalytic performance on the reaction.The suitable reaction conditions were achieved:reaction temperature was 400℃;reaction at atmospheric pressure;liquid hourly space velocity of raw material of 0.5 h 1 ;and the molar ratio of(methanol)/(methyl ethyl ketone)/(water) was equal to 1/1/1.Under such conditions,the conversion of methyl ethyl ketone could achieve 41.7%,and the overall selectivity of methyl isopropyl ketone and diethyl ketone could achieve 83.3%,which was comparable to the conversion of 38.1% and the selectivity of 82.2% achieved by using palladium as the active material.The good stability made this catalyst have good prospects for industrial application.     

五氯酚在低转速短时间内球磨脱氯（英文）

In order to apply grinding method for degradation of pentachlorophenol (PCP) to an industrial scale, the propor-tion of different materials [CaO, SiO2 and CO(NH2)2] and the size of grinding balls were examined. For saving en-ergy and increasing dechlorination efficiency, the rotation speed and grinding time were maintained at relatively low values. At a mass ratio of grinding bal s to materials (40:1), PCP was added into a big steel jar (300 ml) with other materials to grind at 300 r·min?1 for 5 h. The results indicated that when PCP was mixed with CaO and SiO2 in a molar ratio of 1:60:60, the best dechlorination of 58.4%was achieved. CO(NH2)2 could not be used as hydro-gen donor in the dehalogenation by mechanochemical reaction, since it restrained the dechlorination process. The size of grinding balls has significant effect on the reaction. The experiment with 5 mm steel balls indicates that the weight is too light to provide appropriate energy for the reaction, while steel balls of 10 and 15 mm could give better dechlorination reaction. It indicates that dechlorination depends on the mass of balls and fill rate.     

Experimental Study on Hydrogenation of SiCl_4 to SiHCl_3 in a Stirred Bed Reactor

The hydrogenation of SiCl_4 to SiHCl_3 was studied in a stirred bed reactor with CuCl catalyst.The properties of the CuCl catalysts and silicon particles before and after the reaction were characterized by SEM,XRD and XPS.The XRD showed that the active component of Cu3Si was formed during the reaction,and the EDX proved the molar ratio of Cu and Si on the region of apertures.The valent of Cu was discussed by XPS before and after the hydrogen reaction.Then the effects of the reaction temperature,pressure,molar ratio of H2 to SiC l4,weight hourly space velocity(WHSV),and catalyst loading were studied.The results showed that the conversion rate of Si Cl4 was about 38%at WHSV of 190 Nm3/(t·h),temperature of 540℃,pressure of 1.8 MPa,catalyst loading of 0.9%(ω),and molar ratio of H2 to Si Cl4 1.7:1.Based on the experemental results,a reaction mechanism was proposed,which involved the continuous consumption of silicon(many apertures was showed on SEM image)and formation of new Cu3Si active component during the hydrogenation reaction.     

Pd/Fe双金属对水中m-二氯苯的催化脱氯

引　言氯代芳烃及其衍生物化学性质稳定 ,易在生物体内累积 ,大多被列为美国EPA环境优先控制污染物 ,一旦进入环境将对人类及其生态环境造成长期威胁 .因此 ,氯代芳烃的治理技术日益引起全球的关注[1] .自 2 0世纪 80年代末提出金属铁屑用于地下水的原位修复以来[2 ,3] ,用Fe0 还原脱氯已成为一个非常活跃的研究领域 ,特别是应用于地下水修复方面的研究 .Fernando等[4～ 7] 将双金属催化剂用于有机氯的催化还原脱氯 ,Fe0 表面的Pd或Ni等金属加速了还原脱氯反应 ,脱氯速率比Fe0 体系快得多 .本研究利用Pd/Fe双金属对m DCB进行了催化还…     

Pd/Fe双金属对1,2,4-三氯苯的催化脱氯

采用Pd/Fe双金属体系对1,2,4-三氯苯（1,2,4-TCB）进行了快速催化还原脱氯的研究.结果表明,在钯的催化作用下,零价铁对1,2,4-TCB有较好的还原脱氯效率.当Pd/Fe双金属的钯化氯为0.06%时,催化剂用量为1g/40mL,反应1h后TCB的脱氯率可达99%.反应速率随钯化氯的提高而增加.反应在Pd/Fe表面进行,符合准一级反应,反应速率常数为0.0837min-1.TCB在催化脱氯的过程中先脱氯成为DCB,再依次脱氯为氯苯和苯.     

Electrocatalytic Dechlorination of Chloroform in Aqueous Solution on Palladium/Titanium Electrode

Electrochemical dechlorination of chloroform in aqueous solution was investigated on a palladium‐loaded meshed titanium electrode at ambient temperature. The palladium/titanium (Pd/Ti) electrode, which provided a catalytic surface for reductive dechlorination of chloroform in aqueous solution, was prepared with an electrodepositing method. Scanning electron microscope (SEM) micrographs show that Pd microparticles uniformly disperse on the meshed Ti electrode with spheroidal structure. Dechlorination experimental results indicate that, in aqueous solution with the high current efficiency of 33 %, the removal efficiency of chloroform on the Pd/Ti electrode was 37 %, under the conditions of a dechlorination current of 0.1 mA and dechlorination time of 180 min.     

纳米级Co/Fe双金属催化剂对废水脱氯的研究

采用化学还原法制备了纳米级Co/Fe双金属催化剂,对其催化水溶液中四氯化碳还原脱氯性能进行了考察,并与废铁屑催化性能进行了对比。同时,考察了反应条件对脱氯性能的影响。结果表明,采用化学还原法制备的纳米级Co/Fe双金属催化剂具有较高的比表面积和表面反应活性,对四氯化碳的脱氯效果优于废铁屑。搅拌转速、反应温度和脱氯时间对脱氯效率有促进作用。     

纳米钯金铁三金属催化剂的制备及其对三氯乙烯的降解

在乙醇-水体系中利用硼氢化物液相还原法合成纳米铁颗粒,通过化学沉淀法将钯金粒子负载于纳米铁表面,得到纳米钯金铁(Pd-Au@Fe)三金属催化剂复合材料,采用TEM, EDS和XPS对其进行表征. 结果表明,与纳米单金属Fe0及双金属Pd@Fe相比,三金属催化剂对三氯乙烯(TCE)具有更高的降解能力. 保持催化剂加量1.4 g/L, Pd/Fe为0.35%(w), Au/Fe为1.0%(w)时,其降解15 mg/L TCE的速度最快,5 min时去除率为88.21%,表观速率常数为0.311 min-1,是相同Pd含量下Pd@Fe双金属催化剂的3.6倍. 随降解反应持续,Pd-Au@Fe的乙烯乙烷生成率及乙烯加氢转换乙烷速率均远高于双金属Pd@Fe.     

Catalytic dechlorination of 1-chlorooctadecane in supercritical carbon dioxide

Palladium catalyzed hydrodechlorination of 1-chlorooctadecane in supercritical carbon dioxide (SC–CO₂) was performed and compared to dechlorination in isopropanol at atmospheric pressure (liquid isopropanol). The reaction utilized isopropanol as a hydrogen donor and its rate in SC–CO₂ was significantly faster than in isopropanol at atmospheric pressure. The dechlorination yield in liquid isopropanol was increased by addition of NaOH, while the presence of either NaOH or triethylamine in SC–CO₂ lowered the dechlorination yield significantly. Experimental parameters such as pressure, temperature, and the concentrations of reagents (isopropanol and palladium) in the absence of base were optimized in SC–CO₂ to obtain complete dechlorination. Kinetic studies of the reaction were then performed to deduce the reaction mechanism. The apparent activation energies of the reaction were 43±5 kJ mol⁻¹ in SC–CO₂ and 35±3 kJ mol⁻¹ in liquid isopropanol. The rate determining step of the reaction was deduced to be adsorption of 1-chlorooctadecane on the palladium surface.     

锌/银二元金属体系中五氯吡啶的电催化还原脱氯

研究了Zn/Ag二元金属体系对五氯吡啶的催化还原脱氯性能。实验考察了初始pH值、催化剂的投加量、反应温度等参数对反应的影响,在此基础上探讨了其脱氯机理。实验结果表明：反应温度为60℃时,单一锌粉能够对五氯吡啶进行还原脱氯生成四氯吡啶,但是收率不高,只有20%左右,在银的催化作用下,四氯吡啶收率得到了很大提高。当反应初始pH控制在弱酸条件下（5左右）,硝酸银浓度为10 g·L^-1时,反应3h后四氯吡啶收率可达到60%以上。在Zn/Ag双金属表面,五氯吡啶的脱氯反应符合一级反应,速率常数为0.0097 min^-1。     

Dechlorination kinetics of monochlorobiphenyls by Fe/Pd: Effects of solvent, temperature, and PCB concentration

Well-known, yet undefined, changes in the conditions and activity of palladized zerovalent iron (Fe/Pd) over an extended period of time hindered a careful study of dechlorination kinetics in long-term experiments. A short-term experimental method was, therefore, developed to study the effects of temperature and solvent on the dechlorination of monochlorobiphenyls (MCBs), 2-chlorobiphenyl (2-ClBP), in particular by Fe/Pd. The experiments started with specified initial conditions and lasted only for 10 min. The average value (k) of the first-order rate constant for the dechlorination of 2-ClBP was 0.13 ± 0.03 L m⁻² h⁻¹, not significantly different from the average values for 3-chlorobiphenyl and 4-chlorobiphenyl. The apparent activation energy was 20 ± 4 kJ mol⁻¹ and 17 ± 7 kJ mol⁻¹, in a temperature range between 4 °C and 60 °C, for the dechlorination of 2-ClBP using two batches of Fe/Pd catalyst. The k values decreased significantly in mixtures with a methanol concentration higher than 10%. The values of the rate constant were slightly influenced by the initial concentrations in the experiments at a low temperature and in a solution with a high methanol concentration. The concentration dependence was described with a Langmuir equation, based on the Langmuir–Hinshelwood mechanism that includes an adsorption step of a single species preceding a rate-determining catalytic reaction.     

Pd/Fe催化剂脱氯的稳定性研究

以1,2,4-TCB为材料,研究了不同的处理方式对Pd／Fe催化剂脱氯稳定性的影响。结果显示:干燥处理会显著降低 Pd／Fe催化剂的活力,失活后的Pd／Fe经酸洗可恢复部分活力,保存在水中的Pd／Fe其催化活力也会逐渐降低,2d后会降至最初的1/5。     

Gas-phase hydrodechlorination of pentachlorophenol over supported nickel catalysts

The gas-phase hydrodechlorination of pentachlorophenol (PCP) over nickel/silica and nickel/Y zeolite catalysts at 573 K has been studied. Each catalyst was 100% selective in cleaving the C–Cl bonds, leaving the hydroxyl substituent and benzene ring intact. The variation of catalytic activity and selectivity (in terms of partial and full dechlorination) with time-on-stream is illustrated and catalyst deactivation is addressed. Dechlorination efficiency is quantified in terms of dechlorination rate constants, phenol selectivity/yield and the ultimate partitioning of chlorine in the parent organic and product inorganic host. Increasing the nickel loading on silica was found to raise the overall level of dechlorination while the use of a zeolite support introduced spatial constraints that severely limited the extent of dechlorination. Product composition was largely determined by steric effects where resonance stabilisation had little effect. The reaction pathways, with associated pseudo-first-order rate constants, are also presented. This revised version was published online in November 2006 with corrections to the Cover Date.