CuO-ZnO-ZrO_2催化剂的还原性能及其低温CO催化氧化性能

采用共沉淀法制备得到CuO-ZnO-ZrO2催化剂及对比样品CuO-ZnO,通过XRD、BET、XPS、H2-TIR、H2-TPR等表征,考察了ZrO2的添加对CuO-ZnO-ZrO2催化剂的还原性能及其CO催化氧化性能的影响。与CuO-ZnO相比较,CuO-ZnO-ZrO2催化剂的比表面积增大、CuO和ZnO粒子的平均粒径减小、表面Cu粒子含量增多、还原性能得到显著提高,表明ZrO2的添加有利于提高CuO分散度,存在更多与ZnO相互作用的CuO微粒。TPR的还原动力学研究进一步证实了ZrO2对CuO还原性能的促进作用。在CO催化氧化反应中,CuO-ZnO-ZrO2样品的催化活性最高,并且还原温度对该催化剂的CO催化氧化性能影响显著,在160℃还原活化的催化剂具有77.3%的还原度,表现出较优的CO催化氧化性能。在50℃、3 MPa的反应条件下,CuO-ZnO-ZrO2催化剂可将液相丙烯中体积分数1.0×10-5的CO脱除低至2×10-8,连续反应1 500 min,稳定性能良好。     

沉淀剂对SrCO3/La2O2CO3上低温甲烷氧化偶联反应的影响

利用共沉淀法制备了系列SrCO3/La2O2CO3催化剂,制备中沉淀剂的选择影响催化剂的物理化学性质,并最终决定其在低温甲烷氧化偶联(OCM)中的催化性能,其中以摩尔比2：1的NaOH/Na2CO3 为复合沉淀剂效果最好,对应的催化剂中检测到两种La2O2CO3的组分,分别为四方晶相的(I-)和六方晶相的(II-)La2O2CO3。这两种晶相的共存为OCM的低温反应提供所需要的活性位。助剂SrCO3 抑制了甲烷的过度氧化,提高了C2的选择性。所得到的最佳的催化剂能在100 oC炉温下维持OCM反应至少24 h,使CH4.转化率达到25.6%,C2选择性达到43.4%。伴随OCM的甲烷氧化生成COx的副反应产生的热点效应为OCM温和反应提供了热源。     

制备参数对Au/TiO_2催化剂上CO低温氧化性能的影响

以溶胶-凝胶法制备TiO2载体,用沉积-沉淀法制备出一系列负载型Au/TiO2。系统考察了焙烧温度、金的负载量、反应液pH值、沉淀剂种类以及Cl-存在与否等制备参数对催化剂活性的影响。以室温下CO的催化氧化为探针反应,确定催化剂的最适宜制备参数,并对优化的质量分数为1.0%的Au/TiO2催化剂进行了活性稳定性测试。结果表明：Au/TiO2的最适宜焙烧温度是200～350℃;反应液的最适宜pH值为9;最适宜沉淀剂是NaOH;金的负载量（质量分数,下同）在0.5%～5.0%范围内时,金含量越高,催化剂活性和热稳定性越好。大量Cl-的存在能导致催化剂活性的显著下降。对优化的Au/TiO2催化剂在室温下催化氧化不同浓度的CO进行循环测试,经历3次循环,连续反应2 160 min后,CO的转化率仍为100%。     

纳米Ce0.9Cu0.1O2-δ固溶体的制备、表征和CO低温氧化性能

采用改进的柠檬酸溶胶-凝胶法(即前驱体先在N2气氛下高温预处理)制备了高比表面积纳米Ce0.9Cu0.1O2-δ固溶体。采用XRD、TEM和Raman等对催化剂进行表征,并考察了它们的低温CO氧化性能。研究结果表明,改进的柠檬酸溶胶-凝胶法可以制得晶相比较完整的Ce0.9Cu0.1O2-δ固溶体,晶粒小于10 nm,明显小于常规方法制得的样品。随着样品焙烧温度的提高,表征氧缺位的600 cm-1左右Raman峰的位置向高波数方向迁移。采用改进方法制得的Ce0.9Cu0.1O2-δ固溶体具有更高的CO氧化活性,其原因归结为晶粒的减小,容易形成氧缺位和表面高分散CuO的增加,从而促进了CO的氧化。     

MgO/La2O2CO3催化剂上的低温甲烷氧化偶联

共沉淀法制备的MgO/La2O2CO3催化剂使甲烷氧化偶联(OCM)在炉温460℃时开始反应,且使反应在50℃炉温下至少24 h。助剂Ni的加入降低了起始和最低反应温度,使催化剂在380℃的炉温下开始反应,之后在无热源的情况下可使反应至少24 h。助剂Zn的加入提高了反应活性,使C2的选择性提高了6%,但同时对低温反应不利,反应在炉温100℃下6 h后自动停止。OCM体系中的强放热反应为OCM温和反应提供了热源。催化剂中的La2O2CO3是维持低温甲烷氧化偶联反应的关键H活性组分。     

金掺杂TiO2纳米管的制备及其低温CO氧化催化性能

在NaOH溶液中水热处理TiO2粉末得到高比表面积的TiO2纳米管,通过浸渍-沉积法制备金掺杂TiO2纳米管(Au/TiO2 NTs).通过BET、XRD和TEM等手段对所得材料进行表征,并测定Au/TiO2 Nts对CO氧化的催化性能.载体的形态、制备过程中HAuCl4溶液的pH值、灼烧温度以及气氛、金含量对Au/TiO2 NTs的活性影响极大.     

CuO-ZnO-ZrO_2催化剂低温深度脱除液相丙烯中微量一氧化碳的性能

采用共沉淀法制备了CuO-ZnO-ZrO2催化剂,并研究其在低温脱除液相丙烯中微量CO的应用情况。通过XRD、BET、SEM等测试表明,CuO-ZnO-ZrO2催化剂中的ZrO2以无定形状态存在,可以显著增大比表面积和孔容积,促进CuO和ZnO的分散。在CO脱除应用中,还原预处理对于催化剂是必不可少的一步,并且还原温度显著影响催化剂的CO脱除性能。160℃还原活化的催化剂具有77.3%的还原度,在50℃、3.0 MPa的反应条件下,可将液相丙烯中体积分数1.0×10-5的CO脱除低至2×10-8,达到聚合级烯烃对CO脱除深度的要求,并且稳定性能良好。CO2杂质的引入降低了CuO-ZnO-ZrO2催化剂对CO的脱除深度,表明CO2气氛对CO的脱除起到一定的抑制作用。     

CuO-ZnO-ZrO2催化剂低温深度脱除液相丙烯中微量CO性能的研究

本文采用共沉淀法、在较优的条件下制备得到CuO-ZnO-ZrO2催化剂,并研究其在低温脱除液相丙烯中微量CO的应用情况。通过XRD、BET、SEM等测试表明,CuO-ZnO-ZrO2催化剂中的ZrO2以无定型状态存在,可以显著增大比表面积和孔容积,促进了CuO和ZnO的分散。在CO脱除应用中,还原预处理对于催化剂是必不可少的一步,并且还原温度显著影响催化剂的CO脱除性能。160 ℃还原活化的催化剂具有77.3 %的还原度,在50 ℃、3.0 MPa的反应条件下,可将液相丙烯中10 ppm含量的CO脱除低至0.02 ppm,达到聚合级烯烃对CO脱除深度的要求,并且稳定性能良好。CO2杂质的引入降低了CuO-ZnO-ZrO2催化剂对CO的脱除深度,表明CO2气氛对CO的脱除起到一定的抑制作用。     

改进柠檬酸络合法制备CuO-CeO2及其CO低温氧化催化性能

采用改进的柠檬酸络合法即以乙醇代替水作溶剂制备CuO-CeO₂催化剂，应用N₂物理吸附、XRD和H₂-TPR等技术对催化剂进行了表征，并采用微反-色谱装置考察了其对CO低温氧化反应的催化活性。结果表明，常规柠檬酸络合法所制备的CuO-CeO₂催化剂中仅存在一种与CeO₂相互作用较弱、粒子较大的CuO，而采用改进的柠檬酸络合法所制备的催化剂中除此之外还存在与CeO₂相互作用较强、粒子较小的高度分散的CuO，从而具有更高的CO低温氧化活性。     

还原温度对CuO-ZnO-ZrO2催化剂的还原度及其低温CO氧化反应性能的影响

采用还原热力学计算、H2-TIR、H2-TPR及活性评价等手段,考察了还原温度对CuO-ZnO-ZrO2催化剂的还原度和低温CO氧化反应性能的影响。研究发现,在CuO-ZnO体系中添加ZrO2,提高了CuO的分散度,使得活性组分CuO更容易还原,在相同还原条件下, 比 更容易进行。H2-TIR结果表明,随着还原活化温度的升高,还原耗氢量增大、还原峰出峰时间前移。通过H2的消耗量计算得到,随着还原温度的升高,还原度依次增大：0 %（100 ℃）< 45.7 %（140 ℃）< 77.3 %（160 ℃）< 86.2 %（200 ℃）。低温CO脱除性能评价表明,较优还原温度（160 ℃）下活化的催化剂具有较高的CO催化氧化活性,在100℃反应温度下,CO转化率达100 %;可将液相丙烯中微量的CO（10ppm）脱除低至0.02ppm,连续反应1500min,稳定性能良好。     

Temporal analysis of products (TAP) study on low temperature carbon monoxide oxidation on supported Au catalysts

TAP (temporal analysis of products) technique was used to clarify the controversial mechanism for low-temperature CO oxidation on supported Au catalysts involving unidentified moisture effects on the performances. The unique TAP transient technique, along the use of a specially prepared, highly active Au/Ti(OH) ₄ ^* catalyst, provided the information and characterization of each elementary step involving weak and reversible CO adsorption, strong and molecular O₂ adsorption, and their surface reaction, which are suppressed by the coexistence of water vapor.     

低温一氧化碳催化氧化研究进展

综述了贵金属 (Au、Pd、Pt)与非贵金属催化剂 (Co、Cu氧化物 )在低温CO氧化反应中的催化机理 ;阐述了催化剂的制备方法 (共沉淀法、细菌还原法、光沉积法、沉积沉淀法、化学气相沉积法、浸渍法等 )、制备条件 (pH值、焙烧温度、焙烧时间、沉淀剂种类等 )及载体种类 (金属氧化物、金属氢氧化物、沸石 )等对催化剂催化活性及稳定性的影响。指出了寻找一种活性、稳定性好且价廉的催化剂 ,以及通过助剂、载体的选择降低贵金属催化剂活性组分的含量 ,提高非贵金属的活性、稳定性的研究工作是今后的重要目标     

催化CO氧化的铜系催化剂的研究进展

综述了近年来铜催化剂体系催化CO氧化反应的研究进展。阐述了催化剂的制备方法、制备条件及载体种类等对催化剂催化活性及稳定性的影响。通过加入添加剂、合适的制备方法和处理条件等手段是提高催化剂活性和选择性有效的途径。     

Ambient temperature oxidation of carbon monoxide using a Cu2Ag2O3 catalyst

The mixed copper–silver oxide, Cu₂Ag₂O₃, has been prepared by co-precipitation and tested for ambient temperature carbon monoxide oxidation. The catalyst demonstrated appreciable low temperature oxidation activity and the catalyst aged for 4 h was the most active. Carbon monoxide conversion increased with time-on-stream, reaching steady state after ca. 1000 min. Acomparison of the catalytic activity has been made with a representative sample of a high activity hopcalite, mixed copper/manganese oxide catalyst. On the basis of CO oxidation rate data corrected for the effect of catalyst surface area the Cu₂Ag₂O₃, aged for 4 h was at least as active as the hopcalite.     

A novel catalyst for CO oxidation at low temperature

Supported catalysts of palladium over ceria–titania mixed oxides (Pd/CeO₂–TiO₂) were prepared and tested for carbon monoxide oxidation. The catalysts exhibited high catalytic activity at room temperature. The Pd/CeO₂–TiO₂ catalyst was more active than Pd/CeO₂, Pd/SnO₂–TiO₂, Pd/ZrO₂–TiO₂, Pd/Al₂O₂–TiO₂ and Pd/TiO₂ catalysts under the same conditions examined. The effects of preparation methods of the support, the mole ratio of ceria and titania in mixed supports as well as Pd loading upon the catalytic activity of CO oxidation were investigated. Among the Pd/CeO₂–TiO₂ catalysts, the best one corresponds to the Pd loading of 1.0 wt% or above, and the mole ratio of ceria and titania ranging from 1 : 7 to 1 : 5. The steady-state catalytic performance of such catalyst was recorded without any deactivation over 8 h time-on-stream in the present study. This revised version was published online in July 2006 with corrections to the Cover Date.     

CO低温氧化霍加拉特催化剂的研究

综述了CO低温氧化霍加拉特（Hopcalite）催化剂的活性影响因素、催化机理、催化剂失活原因以及最新研究进展,并展望了以后的发展方向。     

Mechanism for the formation of carbon dioxide in the catalytic oxidation of carbon monoxide and methane on silica

The oxidation of carbon monoxide to carbon dioxide is shown to be catalyzed at 850 K or above over almost all lattice oxygen atoms on the surface of silica prepared by the sol-gel method from ethyl orthosilicate under conditions which yield high selectivity to carbon dioxide in the oxidation of methane.     

Nitric oxide reduction and carbon monoxide oxidation over carbon-supported copper-chromium catalysts

Carbon supported copper-chromium catalysts are shown to be very active for both the reduction of nitric oxide with carbon monoxide and the oxidation of carbon monoxide with oxygen. Mixed copper-chromium oxide active phases have good activity in the simultaneous removal of nitric oxide and carbon monoxide from exhaust gases. The influence of several catalyst variables has been investigated. The activity per volume of catalyst increases with increasing loading, while the intrinsic activity shows a maximum around C/M=100−50. An optimum catalyst for nitric oxide reduction and carbon monoxide oxidation has a copper/chromium ratio of 2/1. The apparent activation energy for the carbon monoxide oxidation over carbon supported copper-chromium catalysts is 77 kJ/mol, suggesting that the Cu---O bond rupture is the rate-limiting process. The reduction of nitric oxide takes place at higher temperatures. Since all catalysts have a low selectivity for molecular nitrogen formation at lower temperatures, the dissociation of nitric oxide is probably rate determining, resulting in a slightly reduced catalyst system. In an excess of carbon monoxide the reaction is first-order in nitric oxide and zero-order in carbon monoxide. Moisture inhibits the reaction by reversible competitive adsorption, whereas carbon dioxide does not. Oxygen completely inhibits the reduction of nitric oxide due to the more rapid reoxidation of the catalytic sites compared to nitric oxide. Therefore, the reduction of nitric oxide takes place only when all oxygen has been converted and, hence, is shifted to higher temperatures. As a possible consequence, the production of nitrous oxide is reduced. Nitric oxide and molecular oxygen react preferentially with carbon monoxide, so, in an excess of oxidizing component, gasification of the carbon support occurs at higher temperatures after carbon monoxide has been completely consumed.