改性二氧化钛负载贵金属Ru催化剂催化降解苯胺溶液（英文）

苯胺类废水污染物具有结构复杂、浓度高、不易生物降解、生物毒性大等特点,传统的苯胺降解措施存在着许多弊端,很难达到排放标准.催化湿法氧化技术(CWAO)主要针对降解高浓度难降解的有机废水,表现出降解效率高、反应时间短、对生物毒性物质的废水降解效果良好等优点,越来越受到人们的重视.但催化剂在使用过程中,需要在高温高压下进行,且有机物降解产生了有机酸,使得催化剂的活性组分流失和载体的物理化学性质发生变化,导致其催化活性下降.因此,需要开发出一种降解活性高,性能稳定的催化剂成为此技术在工业中广泛应用的关键.本文采用溶胶凝胶法对二氧化钛进行改性,制备了Ti_(0.9)Zr_(0.1)O_2和Ti_(0.9)Ce_(0.1)O_2载体,采用过量浸渍法将三氯化钌负载到载体表面制备了2%Ru/Ti_(0.9)Zr_(0.1)O_2和2%Ru/Ti_(0.9)Ce_(0.1)O_2催化剂.在高温高压反应条件下,以苯胺为催化湿法氧化污染物,对不同催化剂湿法降解苯胺进行比较研究,系统地探究了催化降解的反应温度和反应压力对苯胺降解的影响.此外,利用HPLC-MS鉴定出催化降解产生的中间产物,确定了催化降解的反应路径图.在改性的催化剂中,2%Ru/Ti_(0.9)Zr_(0.1)O_2催化剂表现出最高的催化降解活性和稳定性.在初始苯胺浓度4 g/L,催化剂浓度4 g/L,反应温度180°C,O_2压力1.5 MPa下,反应时间5 h后,苯胺完全转化,COD转化率达88.3%.并且催化剂进行三次循环试验后,苯胺转化率仍接近100%.X射线衍射和N2物理吸附结果表明,Ce,Zr掺杂到TiO_2晶格中形成了共溶体,其晶格尺寸更小,比表面积和孔体积更大.负载贵金属后,并未出现其他晶相,说明贵金属均匀分散在载体表面.透射电镜结果表明,贵金属负载在改性TiO_2上表现出较好的分散性和较小的颗粒尺寸,为催化降解苯胺提供更多的催化活性位点,而Ru/TiO_2催化剂表面,贵金属发生团聚现象且颗粒尺寸大.X射线光电子能谱结果表明,Ce,Zr的掺杂使得TiO_2表面活性氧和四价Ru的含量增加,更多的表面活性氧成为催化降解苯胺的直接原因.H_2程序升温还原结果表明,在300-400oC处还原峰对应于催化剂载体晶格氧的还原,改性后,其还原峰增至2倍,即使在贫氧环境下,改性催化剂可以及时从载体中释放晶格氧,为催化降解苯胺提供更多的活性氧.     

二氧化钛负载氧化物催化剂上CO的氧化反应

对浸渍法和共沉淀法制备以的各种ＴｉＯ２负载氧化物催化剂进行了活性组分的筛选,结果发现,两种方法得到的ＣｕＯ催化剂均具有优良的ＣＯ氧化催化性能。在此基础上,考察不同ＴｉＯ２载体,活性组分含量以及催化剂焙烧温度对其催化能力的影响。结果表明,具有高比表面、大孔体积的ＴｉＯ２载体负功的ＣｕＯ催化剂具有较好的催化性能,活性组分ＣｕＯ的最佳含量范围在１０％～１５％之间,催化剂最佳焙烧温度为４００℃。     

Co/Bi催化剂催化湿法氧化降解垃圾渗滤液中的氨氮

采用催化湿法氧化(CWAO)技术,以Co/Bi为催化剂,对垃圾渗滤液中氨氮(NH₃-N)进行降解处理,并利用GC-MS检测了垃圾渗滤液中含氮有机物的相对含量.结果表明,随着反应温度的升高,CWAO对NH₃-N的降解能力逐渐增强,在220,240,260和280℃条件下,NH₃-N降解规律符合一级动力学反应(r>0.93,n=6).在升温过程(20～300℃)中,NH₃-N浓度变化经历了先升后降两个阶段,并在220℃时达到最大值.GC-MS检测结果表明,在第一阶段,垃圾渗滤液中几种含氮有机物因催化氧化而生成NH₃-N;第二阶段,NH₃-N逐渐被氧化降解,达到了CWAO技术同时降解有机物和NH₃-N的目的.同时,选取垃圾渗滤液中一种含氮有机物2-巯基苯并噻唑进行含氮有机物氮降解机理的验证实验.     

负载型纳米非贵金属催化剂上CO的氧化

用电弧等离子体法制备了纳米Ｃｕ、Ｃｒ、Ｍｎ、Ｆｅ、Ｎｉ、采用机械方法将其加到Ａｌ２Ｏ３载体上，制成负载型纳米催化剂，用ＴＥＭ、ＳＥＭ、ＸＲＤ、ＨＲＴＥＭ等手段，对纳米粒子和催化剂进行了表征，对ＣＯ催化化的结果表明，铜催化剂的活性最高；铜、铬催化剂的活性高于贵金属钯催化剂；锰催化剂活性与钯相当；铁、镍催化剂活性较差，ＸＲＤ实验表明，催化反应后，纳米金属将变成氧化物。     

负载铱催化剂选择性催化间二硝基苯制间硝基苯胺

用浸渍法制备的负载铱催化剂催化间二硝基苯部分加氢制间硝基苯胺,考察了温度对反应的影响和催化剂循环实验,结果表明,催化剂活性在90℃最佳;间硝基苯胺选择性随温度升高而增加.以甲醇作溶剂,在n(substrate) /n(Ir) =5000, 90℃, 0.8 MPa条件下,反应1 h,间二硝基苯转化率100%,间硝基苯胺选择性96.3%,全部加氢产物间苯二胺很少生成.催化剂经3次循环,活性下降不明显,在第6次循环时延长反应时间至2.5 h,间二硝基苯转化率和间硝基苯胺选择性均能达到100%.催化机理有待进一步研究.     

高活性Ni/HY催化剂加氢催化合成苯胺类化合物的研究

采用浸渍沉淀法制备Ni/HY催化剂,用BET、XRD、TEM、TPR等方法对其进行表征,并将其应用于硝基化合物液相加氢合成苯胺类化合物反应中.结果表明,Ni/HY催化剂具有较高的催化活性,在温和的反应条件下,反应0.5 h后,硝基化合物的转化率和苯胺类化合物的选择性均高达99.0%以上.该催化剂能储存于150℃以下的空气气氛中,活性组分分散度高,且具有良好的磁分离性能.     

碳负载钯催化剂对Heck反应的催化性能

研究了钯碳催化剂对芳基卤和取代芳基卤与丙烯酸和苯乙烯的Heck芳基化反应的催化性能.结果表明:在反应温度为80℃、反应时间为8h、四丁基溴化铵(TBABr)作为溶剂和三丁胺作为碱的条件下,钯碳催化剂对不同取代芳基卤与丙烯酸和苯乙烯的Heck芳基化反应具有良好的催化性能,产物收率在80%以上.     

负载PbO催化剂对苯胺与碳酸二甲酯合成苯氨基甲酸甲酯的催化性能

 考察了几种负载PbO催化剂对苯胺(An)与碳酸二甲酯(DMC)反应合成苯氨基甲酸甲酯(MPC)的催化性能. 结果表明, PbO/SiO2对该反应表现出很高的催化活性. 当w(PbO)=3.6%, n(PbO)/n(An)=1%, n(DMC)/n(An)=5, θ=160 ℃和t=4 h时, MPC收率达到99.5%. PbO/SiO2容易从反应体系中分离,且可重复使用5次,催化活性基本保持不变,使用寿命较长.     

负载型纳米非贵金属催化剂上CO的氧化行为Ⅱ.纳米铜的制备、结构及催化性能

用惰性气体蒸发法和电弧等离子体法制备了纳米铜粒子，用物理干法将其担载到载体上，并用于催化ＣＯ氧化反应。用ＴＥＭ，ＸＲＤ，ＳＥＭ对纳米粒子和催化剂进行了表征。结果表明，载体，氧化气氛及制备工艺均影响催化剂的活性，稀土元素铈的存在能提高铜的催化活性，纳米铜在催化过程中将转变为氧化物。     

苯胺自催化聚合反应的混合电位

在苯胺自催化聚合反应的开路电位实验中,Pt、Pd和聚苯胺膜具有远正于其它金属的开路电位.该实验结果可以根据混合电位理论来解释.由于苯胺自催化聚合反应具有电化学机理,因此该反应的基底材料将具有同时对应于阳极半反应和阴极半反应的混合电极电位.混合电位在实验上表现为开路电位,其数值大小可以看作是苯胺自催化聚合反应能否进行的标志.有关开路电位的实验结果进一步证明了苯胺自催化聚合反应的电化学机理.     

Catalytic wet air oxidation of 2-nitrotoluidine and 2,4-dinitrotoluene

The rates of wet air oxidation of 2-nitrotoluidine and 2,4-dinitrotoluene in the presence of excess oxygen and at different temperatures and oxygen pressures was investigated. Oxidation experiments were carried out at temperatures between 180 and 225^oC and oxygen partial pressures of 1,0-3,0 MPa, in a 280 mL glass vessel-inserted stainless steel reactor. Copper sulfate (CuSO₄ .5H₂O) was used as a catalyst, and the effect of catalyst loading was studied by varying the concentration: 0.75, 2.5 and 25 mg/L as Cu²⁺. Addition of Cu²⁺ ions in the reaction media accelerated 2-nitrotoluidine oxidation nearly ten times even if it exists in trace amount in the reaction medium (0.75 ppm Cu²⁺). Unfortunately copper did not show catalytic effect for the oxidation of 2,4-dinitrotoluene. This revised version was published online in August 2006 with corrections to the Cover Date.     

Reduction behavior of Ru/CeO2 catalysts and their activity for wet oxidation

Three kinds of Ru/CeO₂ catalysts were prepared. The mobility of the oxygen on Ru and their catalytic activity in the wet oxidation of acetic acid was investigated. Ru was present in the form of RuO₂, and TPR experiment showed that the reaction, RuO₂ + 2H₂ Ru + 2H₂O, took place in different temperature ranges depending upon the kind of the catalysts. The catalyst with easily reducible oxygen on Ru had high activity in wet oxidation, and the importance of the release of oxygen from Ru to the reactant was suggested.     

Lactose oxidation over palladium catalysts supported on active carbons and on carbon nanofibres

Liquid-phase lactose oxidation was investigated over supported Pd/C and Pd-carbon nanofibre catalysts, which were characterized by several methods. A complex relationship between catalyst activity and catalyst acidity was established, i.e. optimum catalyst acidity resulted in the highest activity in lactose oxidation. In-situ catalyst potential measurements during lactose oxidation gave information about the extent of accumulation of oxygen on the metal surface. These results could be correlated with catalyst deactivation, which was extensive over the most acidic catalysts at low reaction temperatures. Selectivity for the desired product, lactobionic acid, was a maximum of approximately 83% at 93% conversion. The main side-product was lactulose formed via isomerisation of lactose. Lower selectivity toward lactobionic acid was obtained when the rate of oxidation of lactose was low.     

Ru/Mn-Ce/TiO2催化剂催化湿式氧化丁二酸的反应活性和动力学研究

在二氧化钛载体中通过掺杂Ru，Mn，Ce制备了一系列用于催化湿式氧化的催化剂，利用XRD，TEM，BET等手段对催化剂进行了表征．在反应温度T=210～270℃，氧分压Po2=2．1MPa条件下，在间歇式高压反应釜中对丁二酸进行了降解实验．催化剂在反应中有很高的催化活性．催化剂在30min内对丁二酸降解的COD去除率为54．4～98．3％．Ru及Mn，Ce的氧化物对催化活性都有促进作用．建立了丁二酸催化湿式氧化的一级分段动力学模型．基于COD的一段及二段反应的活化能分别为43．74kJ／mol和54．28kJ／mol．     

Catalytic and electrocatalytic oxidation of aniline to nitrobenzene over vanadium silicate molecular sieves: VS-1 usingt-butyl hydroperoxide (TBHP) as oxidant

A comparison of the results of catalytic and electrocatalytic oxidation of aniline using VS-1 in the presence of H₂O₂ and TBHP indicates remarkable differences in conversion and selectivity. VS-1 catalyzes the oxidation of aniline selectively to nitrobenzene (73%) in the presence oft-butyl hydroperoxide (TBHP), while azoxybenzene (95.2%) is formed selectively when H₂O₂ is used. Cyclic voltammetric studies show a three-step oxidation of aniline to nitrobenzene in H₂O₂ but in the presence of TBHP only one step is observed. Electrocatalytic oxidation of aniline to nitrobenzene occurs at a potential 700 mV less than that corresponding to H₂O₂ as oxidant along with a selectivity of 91.8%. The enhancement of electrocatalytic rate is attributed to the stabilization of electron deficient transition state.     

Catalytic wet peroxide oxidation of phenol over AlFe-pillared montmorillonite

Catalytic wet peroxide oxidation of phenol over AlFe-pillared montmorillonite was carried out at room temperature, in a glass batch reactor, under constant airflow at day and UV light, alternatively. At higher concentration of phenol in water solution the efficiency of heterogeneous pillared clay catalyst was significantly lower than the efficiency of homogeneous iron catalyst. This revised version was published online in June 2006 with corrections to the Cover Date.     

湿式催化氧化技术研究进展

现代化学工业的迅速发展促进了经济的快速发展,但与此同时进入水体的化学物质的种类和数量也急剧增加,给环境带来了很大的危害.因此,发展高浓度、有毒、有害的有机工业废水的高效处理技术,就显得日趋紧迫和十分重要,得到了人们的广泛关注.     

Catalytic wet air oxidation of oleic acid on ceria-supported platinum catalyst.effect of pH

Summary Catalytic wet air oxidation (CWAO) of oleic acid was carried out in a batch reactor on platinum supported ceria catalyst (Pt/CeO₂). Oleic acid is a water insoluble linear unsaturated fatty acid of 18 carbon atoms. To increase the homogeneity of the solution by saponification, the influence of NaOH additions in oleic acid CWAO mechanism and catalyst performances have been investigated. The oxidation of such molecule occurs by two types of mechanisms: successive carboxy-decarboxylation which leads essentially to CO₂and/or C-C bonds splitting in the alkyl chain inducing a high formation of acetic acid. With or without NaOH, the 5%Pt/CeO₂catalyst is active in the conversion of oleic acid and selective to carbon dioxide. In alkaline medium, oleic acid is initially saponified which increases the solubility of the reactant before it to be oxidized. Finally the oxidation is slightly delayed by the presence of NaOH. The catalyst characterizations show no significant difference before and after reaction.</o:p>     

Kinetics of wet air oxidation of sodium sulfide over heterogeneous iron catalyst

Wet air oxidation (WAO) is an established technique for reducing the chemical oxygen demand (COD) of refinery sulfidic spent caustic waste. In the present work, the heterogeneous form of the cheap and abundant catalyst ferrous sulfate (FeSO₄) was employed for WAO of sodium sulfide. The performance of this catalyst in the oxidative destruction of this model compound is thus far unfamiliar. Kinetic data for the non-catalytic and catalytic oxidation processes was collected in a batch reactor. For the catalytic process, temperature (T), oxygen partial pressure () and catalyst concentration (ω) were varied in the ranges 80-150°C, 0.69-2.06 MPa and 0.8-2.4 g/L respectively. Around 94% COD was destroyed within 1 h when feed containing 8 g/L of sulfide was oxidized at T = 100°C, = 0.69 MPa, and ω = 0.8 g/L. First, the data on disappearance of COD were fitted to a power law model and reaction rate constants were determined. The activation energy for the non-catalytic (91 kJ/mol) and catalytic (50 kJ/mol) oxidation process was found from the temperature dependence of the rate constants. Second, hyperbolic models based on Langmuir-Hinshelwood (L-H) and Eley-Rideal (E-L) kinetics were used for fitting kinetic data. It was found that the L-H model suggesting dissociative adsorption of oxygen provided the best fit. In this way, a deep insight into oxidation kinetics of sodium sulfide was provided.