高活性Pd-Fe催化剂对CO的低温氧化性能研究

用共沉淀法制得Pd-Fe催化剂,考察了煅烧温度、载体、金属担载量对CO低温催化氧化反应活性的影响。结果表明,负载在炭黑上的Pd-Fe催化剂经200℃和300℃煅烧,性能最佳,在室温下可将CO完全转化。采用透射电镜(TEM)、X射线光电子能谱(XPS)、X射线粉末衍射(XRD)和CO化学吸附表征发现,催化剂的高活性是由于Pd与Fe之间具有强相互作用,导致Pd向界面Fe3+(Fe2O3)进行电子转移,形成还原态的Fex+物种。Pd O和还原态的Fex+物种分别是吸附CO和O2的活性中心,成为CO氧化高活性的主要原因。     

Ce改性ZSM-5分子筛载Pd催化剂的CeO2-Pd协同作用研究

采用XRF、XRD、SEM和CH4-TPR表征手段,研究了Ce改性ZSM-5分子筛载Pd催化剂在CO、CH4氧化过程中的CeO2-Pd协同作用。结果表明,经Ce改性后ZSM-5分子筛的载Pd量提高;Pd/Ce-ZSM-5催化剂对 CH4的起始吸附温度降低;Pd/Ce-ZSM-5催化剂中 Ce 主要以 CeO2形态存在。Pd是CO的催化氧化活性物种,CeO2-Pd协同作用可促进CO的氧化。Pd和PdO均是CH4的催化氧化活性物种,CeO2的供氧-储氧特性有助于Pd→PdO的转化,CeO2与Pd的相互作用使Pd/Ce-ZSM-5催化剂具有高的CO和CH4催化氧化活性。     

La助剂对Pd-AL2O3催化C3H8氧化性能的研究

采用不同稀土La前驱体浸渍掺杂改性Pd/γ-Al2O3催化剂,利用多功能催化性能评价装置测试不同催化剂的C3H8催化氧化性能,并通过H2-TPR、XRD、XPS等手段对催化材料进行结构表征,结果表明：La能促进贵金属钯分散,增强钯与载体相互作用,稳定高活性Pd2+物种,从而提高了催化剂的C3H8催化氧化性能。在选用不同La前驱体改性的Pd/γ-Al2O3催化剂中,硝酸镧改性效果最佳,能更好地促进活性金属钯的分散和Pd2+高活性物种的稳定。相比Pd/γ-Al2O3,La改性催化剂均降低了C3H8和NO的反应转化温度。选用不同La前驱体对催化活性影响存在差异的主要原因是La前驱体添加而引起的金属-载体相互作用和活性贵金属钯的分散状态变化。     

La、Ba的添加对Pd/Y2O3-ZrO2催化氧化CH4性能的影响

以浸渍法制备了1.0%Pd/Y2O3-ZrO2催化剂,考察了Pd负载过程中La和Ba的添加对Pd/Y-ZrO2催化氧化CH4性能的影响,用BET、XRD、CO脉冲、TEM和H2-TPR等方法对所制备的催化剂进行表征。结果表明,La和Ba的添加降低了Pd/Y2O3-ZrO2催化剂氧化CH4的活性。催化剂中活性金属的分散度及体相PdO的还原性影响催化剂对CH4的氧化活性,La、Ba的添加降低了Pd/Y2O3-ZrO2催化剂中活性金属Pd的分散性,使Pd在高温老化后更容易团聚,同时增强了PdO与载体的相互作用,使PdO不容易被还原。     

Ce/Zr比对PdO/Ce_xZr_(1-x)O_2催化剂三效催化性能的影响

采用溶胶-凝胶法制备一系列CexZr1-xO2(x=0～1)复合氧化物,并以该复合氧化物为载体制备负载贵金属的PdO/CexZr1-xO2(x=0～1)催化剂,选择NO-CO反应和CO以及CH4氧化反应为模型反应对催化剂的三效催化性能进行评价,并通过XRD、H2-TPR等手段对载体和催化剂进行初步表征。结果表明:Ce/Zr比对CexZr1-xO2载体及负载PdO催化剂三效催化性能均存在重要影响,不同Ce/Zr比的CexZr1-xO2复合氧化物载体具有不同的晶相结构及还原性能,由其负载的PdO催化剂的三效催化性能也各不相同。同时,催化剂的NO还原活性与CO氧化活性与α还原峰存在一定的对应关系。     

La改性Pd基催化剂催化甲烷氧化的抗水热性能研究

甲烷是第二大温室气体,其年度增温潜能是CO2的26～28倍。天然气车排放尾气中的主要成分为未燃烧完全的甲烷和高浓度的水(高达20%),目前已有大量研究表明水会严重影响Pd活性组分的催化活性及氧化铝载体的催化稳定性,因此如何在高含水废气中处理这些甲烷一直是天然气车后处理催化剂的研究热点。本研究采用等体积浸渍法制备了改性载体(AlLa5、AlLa10和AlLa15),并用过量浸渍法将0.5%Pd负载到改性载体Al2O3-La和未改性载体γ-Al2O3上,同时考察了La的引入比例对催化剂催化甲烷氧化中的耐水热性能影响,用N2物理吸脱附、CO脉冲吸附、XPS和XRD等方法对所制备催化剂进行表征。结果表明,La的加入明显提高催化剂在催化甲烷氧化中的耐水热性能,其中Pd/AlLa5表现出最优异的耐水热稳定性。     

超临界CO2沉积技术制备负载钌炭催化剂

以氯化钌为活性前驱体,活性炭为载体,采用超临界CO2沉积技术制备了负载钌/炭催化剂,以葡萄糖催化加氢反应考察了催化剂的活性,研究了助溶剂种类,助溶剂用量,超临界压力对催化剂活性的影响,并用SEM、XRD、XPS对催化剂表面的形貌、晶形及钌分布情况进行了表征.结果表明:超临界CO2沉积技术可有效提高负载钌炭催化剂的活性,在实验范围内,当助溶剂为甲醇,用量为2 ml,超临界CO2压力为12.0 MPa时制得催化剂的活性最佳,其催化活性是传统水浸渍方法制得样品的1.48倍;钌在催化剂中以无定型的非晶形式存在,钌在活性炭表面均匀分布,超临界沉积技术进一步增强了活性组分钌和载体间的相互作用.     

纳米Pd/C催化剂的制备及其催化氧化乙二醛生成乙醛酸的研究

利用化学还原法分别以PdCl2和Pd(OAc)2为前体制备了胶体Pd纳米粒子,然后采用胶体负载法获得2种Pd/C催化剂并应用于催化乙二醛氧化生成乙醛酸的反应。研究了催化反应条件如温度、乙二醛初始浓度以及在催化剂制备中Pd负载量、使用的前体对催化反应的影响,从而在最佳催化条件下得到乙醛酸产率为31.07%,选择性为67.06%的反应结果;利用XPS技术对Pd/C催化剂使用前后Pd的表面化学状态进行了表征,简要探讨了Pd/C催化剂的选择性和催化剂失活机理。     

贵金属和载体对催化剂催化脱氧裂化性能的影响

采用浸渍法制备了一系列分别负载活性组分Pt,Pd,Ru的γ-Al2O3载体催化剂和分别以固体酸γ-Al2O3,Si O2-Al2O3,USY-Al2O3为载体的Pd催化剂。通过XRD、HRTEM、H2-TPR、NH3-TPD、BET等分析表征技术和以油酸甲酯为模型化合物的反应体系,考察了贵金属及载体性质对催化剂催化加氢脱氧性能和催化裂化性能的影响。结果表明:贵金属及其粒子大小是影响催化剂催化加氢脱氧活性的主要因素;载体的酸强度、酸量是影响催化剂催化裂化性能的主要因素。同时,该性能也受比表面积和孔结构特征的影响;Pd/USY-Al2O3在系列催化剂中表现出了良好的催化加氢脱氧活性和最佳的催化裂化活性。     

金属蜂窝负载Pd催化甲烷部分氧化制合成气

采用浸渍法制备负载金属Pd(其中金属Pd含量0.6g/L)活性组分的金属蜂窝载体催化剂,应用于甲烷部分氧化制合成气。实验表明,焙烧温度为950℃的催化剂较600℃的催化剂甲烷转化率、CO和H2的选择性更高,焙烧温度为950℃的催化剂在反应温度800℃,GHSV=1×105ml/g·h条件下,甲烷转化率为91%,CO和H2的选择性分别达到90%和89%。用SEM与XPS对催化剂进行表征,结果表明,950℃焙烧催化剂并没有出现明显的烧结现象,且可能由于更多零价Pd的出现,使得该催化剂的性能更好。由于金属蜂窝载体优良的导热性,对950℃焙烧温度制备的金属蜂窝催化剂,催化剂床层的飞温点温度小于880℃,可以解决其它类型催化剂在甲烷部分氧化反应中出现的飞温问题,具有一定的工业化意义。     

Properties of TiO2 support and the performance of Au/TiO2 Catalyst for CO oxidation reaction

Gold catalysts were prepared on TiO₂ supports of different phase structures (i.e., anatase, rutile and biphasic), TiO₂ crystal size (i.e., 9–23 nm), surface and textural properties (i.e., hydration and surface area). The CO oxidation on the gold catalysts was carried out in an operando-DRIFTS set-up equipped with DRIFTS reactor cell connected on-line to CO gas analyser and gas chromatograph enabling real time monitoring of surface reaction and simultaneous reaction rate measurements. Gold catalysts supported on pure anatase TiO₂ were more resistant to sintering compared to catalysts supported on rutile and bi-phasic TiO₂. Besides catalyst sintering, deposition of surface carbonates is an important cause of catalyst deactivation. The best gold catalyst was prepared on 13 nm anatase TiO₂. It displays both increased activity and stability for CO oxidation reaction at room temperature. Surface and textural properties of TiO₂ also play a role on the performance of the Au/TiO₂ catalyst.     

Promotion of Pt-Ru/C catalysts driven by heat treated induced surface segregation for methanol oxidation reaction

Carbon supported Pt-Ru/C (1:1) alloy catalysts supplied by E-TEK are widely used for fuel cell research. Heat treatments in various atmospheres are conducted for the promotion of the methanol oxidation reaction (MOR) and the investigation of the structure-activity relationship (SAR) of the catalysts. The alloy structures, surface compositions, surface species, and electro-catalytic activities of the alloy catalysts are characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV), respectively. The as-received Pt-Ru/C catalysts have a Ru rich in the inner core and Pt rich on the outer shell structure. Thermal treatments on the catalysts induce Ru surface segregation in different extents and thereby lead to their alteration of the alloying degrees. O₂ treatment results in obvious Ru segregation and formation of RuO₂. Catalysts treated in H₂ have the highest I_f/I_b value in the CV scans among all samples, indicating the catalysts have the excellent CO de-poisoning ability as evidenced by anodic CO stripping experiments. N₂ treatment may serve as an adjustment process for the surface composition and structure of the catalysts, which can suppress the surface Pt depletion (∼60% Pt on the surface), make the components stable and hence promote the MOR significantly.     

Catalytic properties of metallic fibers fabricated by tempering of melt on a rotating heat-receiver

Metallic fibers fabricated by the method of directly suspended melt-droplet extraction are promising for application in catalysis as carriers of catalytically active compounds and as catalytic systems themselves due to their physicochemical properties, structure, surface defects, and low hydrodynamic resistance of porous permeable materials formed from them. The catalytic activity of fibers based on copper, nickel, iron, aluminum, and titanium, also containing noble, transition, refractory, and rare-earth metals, in the reaction of CO oxidation has been estimated. Among the studied samples, fibers based on copper, copper–nickel alloy, and Nichrome with addition of noble metals have been found promising to perform further studies for their application as catalysts of oxidation–reduction reactions.     

Comparative studies of adsorbed CO and methanol electrooxidation on carbon supported Pt and PtRu catalysts in acid solution

1. Introduction Direct methanol fuel cells (DMFCs) have con-siderable advantages compared to gas feed (H2/air) polymer electrolyte membrane (PEM) fuel cells [1-2]. The hydrogen PEM fuel cells use gaseous hy-drogen as fuel. But there is no source and infra-structure established yet for hydrogen distribution and storage, neither as a liquid nor as a gas. How-ever, the DMFC, similar to a proton exchange membrane fuel cell (PEMFC), uses methanol fuel directly for electric power generation …     

Preparation and catalytic behavior of reduced graphene oxide supported cobalt oxide hybrid nanocatalysts for CO oxidation

The reduced graphene oxide (rGO) supported cobalt oxide nanocatalysts were prepared by the conventional precipitation and hydrothermal method. The as-prepared rGO-Co₃O₄ was characterized by the XRD, Raman spectrum, SEM, TEM, N₂-sorption, UV-Vis, XPS and H₂-TPR measurements. The results show that the spinel cobalt oxide nanoparticles are highly fragmented on the rGO support and possess uniform particle size, and the as-prepared catalysts possess high specific surface area and narrow pore size distribution. The catalytic properties of the as-prepared rGO-Co₃O₄ catalysts for CO oxidation were evaluated through a continuous-flow fixed-bed microreactor-gas chromatograph system. The catalyst with 30% (mass fraction) reduced graphene oxide exhibits the highest activity for CO complete oxidation at 100 °C.     

Catalysis by Gold Nanoparticles

Gold catalysts have superior activity in CO and other oxidations at low temperatures. Both a small (~ 5nm) particle size and the presence of a partly reducible oxide (ceria or a transition metal oxide) have a beneficial effect on the catalyst performance. The present paper reviews our recent studies focused on understanding the specific role of the Au particle size and that of the oxide (MO). Our personal viewpoint on gold catalysis is outlined. The effects of Au particle size and of the oxidic additive are distinguished by using several alumina-supported gold catalysts having different gold particle sizes and various oxidic additives. The most active catalyst in CO oxidation is the multicomponent catalyst Au/MgO/MnOx/Al2O3 with MgO being a stabilizer for the Au particle size and MnOx being the cocatalyst. This catalyst also exhibits good performance in selective oxidation of CO in a hydrogen atmosphere, a reaction relevant for the development of polymer electrolyte fuel cell technology.     

A Novel internally heated Au/TiO2 carbon-carbon composite structured reactor for low-temperature CO oxidation

A compact, internally heated, catalytic reactor is demonstrated for the low-temperature oxidation of carbon monoxide. Carbon nanofibres were grown on carbon felt and used as a support material for Au/TiO₂ catalysts. The carbon composite plays two roles; as a support material for the catalyst and for providing heat to the reaction by the Joule effect. The internal heating offers a stable reactor system with quick temperature response at relatively low energy input. Comparison between external and internal heating shows higher conversion of CO in the low-temperature range when using internal heating. The Au/TiO₂ catalyst supported on the carbon-carbon composite shows good stability at 250°C.     

喷雾干燥法制备碳载铂钴镍合金催化剂及其甲醇催化氧化性能研究

本文以氯铂酸、氯化镍和硝酸钴为原料,XC-72炭黑为载体,通过雾化干燥法结合煅烧还原制备碳载铂基（PtCo Ni）分散性好的多元合金纳米粒子催化剂。重点研究表面经过改性的炭黑对合金纳米粒子形成和分散的影响规律,研究碳载PtCoNi（原子比为1:1:1）合金纳米粒子的甲醇催化氧化活性、抗CO中毒能力和耐久性,以及不同原子比对催化氧化甲醇活性和抗CO中毒能力的影响规律。研究结果表明,采用表面改性后的炭黑作为载体,制备的碳载铂基（PtCoNi）催化剂为合金纳米粒子,且纳米粒子在炭黑表面分散均匀,粒径分布在1-4nm,平均粒径为2.3nm;与商用的Pt/C催化剂相比,PtCoNi/C（原子比为1:1:1）催化剂具有更高的甲醇催化氧化活性、耐久性和抗CO中毒性;不同原子比铂基多元催化剂在催化氧化甲醇活性上的顺序为：PtCoNi/C>Pt3CoNi/C>Pt5CoNi/C,抗CO中毒性顺序为：PtCoNi/C>Pt3CoNi/C>Pt5CoNi/C。     

The effect of dopant Cu, Fe, Ni or La on the structures and properties of mesoporous Co-Ce-O compound catalysts

A series of Co-Ce-O mesoporous catalysts doped with Cu, Fe, Ni or La and the undoped one were synthesized by using tri-block copolymer P-123 as the template. These catalysts show wormhole-like structures, high surface areas (144–167 m²/g) and uniform meso-pore size distributions (4.0–4.8 nm) after calcination at 500 °C. The activity for low-temperature CO oxidation and the thermal stability of the mesoporous Co-Ce-O catalyst are largely modified by the dopant Cu, Fe, Ni or La in different ways. It is revealed by in situ diffuse reflectance infrared spectroscopy that CO oxidation over all the samples except the Ni-doped one undergoes carbonates pathway. In this case, the oxidation activities of the catalysts are mainly determined by the mobility of surface lattice oxygen species, which is indicated by the temperature-programmed reduction and desorption results. Doping with Cu greatly enhances the oxidation activity of Co-Ce-O catalyst at the calcination temperatures of 500 °C and 650 °C, and doping with La significantly improves its activity at the calcination temperature of 800 °C. However, doping with Fe always decreases the activity of Co-Ce-O catalyst regardless of the calcination temperature. Largely different from other dopants, the addition of Ni induces a change of the mechanism for CO oxidation and results in a remarkable decrease in the activity.