富氢气体中CO优先氧化催化剂研究进展

介绍了富氢气体中CO优先氧化贵金属与非贵金属催化剂的研究进展,包括Pt催化剂、Au催化剂和Cu催化剂等,综述了载体、助剂、预处理和制备方法等对优先氧化性能的影响,重点评述改善Pt催化剂低温活性的方法.     

CuCe双金属氧化物催化剂催化氧化丙烯腈废气的性能研究

采用溶胶凝胶法制备了CuCe双金属氧化物催化剂,并应用于丙烯腈废气的性能研究中。研究结果表明,CuCe双金属氧化物催化剂均表现出良好的催化活性;在220℃时,所制催化剂的氮气选择性高达60%以上。并对催化剂进行XRD、H₂-TPR、SEM等表征,结果表明,Cu含量的变化会导致CuCe双金属氧化物催化剂微观结构及氧化还原能力的不同。相比Cu₁Ce₁、Cu_0.5Ce₁,Cu₂Ce₁由于拥有较高的比表面积及较好的还原能力,使其丙烯腈催化性能更为突出。     

Pd-Cu/凹凸棒石黏土催化剂催化CO氧化性能

以凹凸棒石黏土(APT)作载体,采用浸渍法制备双金属催化剂Pd-Cu/APT、单金属催化剂Pd/APT和Cu/APT,在连续流动微反装置上考察催化剂的CO催化氧化活性,采用N_2物理吸附/脱附、X射线粉末衍射和程序升温还原/脱附等手段对催化剂进行表征。结果表明,Pd-Cu/APT催化剂中Cu主要以CuCl形式存在,Pd高度分散与Cu之间产生了明显的相互作用,使Cu物种的还原温度大幅降低;经水蒸汽预处理增强了Pd-Cu/APT催化剂表面酸性,促进了催化活性的提高。在CO体积分数为0.5%、水蒸汽体积分数3.3%、空速6 000h^(-1)和常温反应条件下,CO转化率可达90%以上。     

氮掺杂Pd-Cu/Al2O3催化剂富氢气氛下CO优先氧化性能

以Al₂O₃为载体,采用共浸渍法制备Pd-Cu/Al₂O₃和Pd-Cu-N/Al₂O₃催化剂。利用连续流动微反应装置考察氮掺杂对Pd-Cu/Al₂O₃催化剂低温富氢气氛下CO优先氧化性能的影响,结合XRD、FT-IR、H₂-TPR和XPS等手段对催化剂进行表征。结果表明,相较于Pd-Cu/Al₂O₃,Pd-Cu-N/Al₂O₃具有更好的CO优先氧化性能。氮掺杂促进了表面Cu₂Cl(OH)₃的分散,增强了Pd和Cu之间的相互作用,提高了Pd和Cu₂Cl(OH)₃的氧化还原能力。同时,氮掺杂也有利于生成更多的表面活性Cu⁺物种,并且部分进入Pd晶格,抑制了反应过程中PdHx的形成,从而使催化剂催化性能...     

富氢气中优先氧化除去CO催化剂的研究进展

介绍了富氢气中CO的净化技术以及选择性催化氧化CO的必要性,并对各类选择性氧化除去富氢气中CO催化剂的研究进展和性能进行了对比,着重评述了各类金基催化剂的特点、反应机理和失活原因。     

RuO_ 2/MO_x-TiO_2(M=Ce、Mn、La、Zr、Co)催化剂制备及其氯化氢氧化性能

氯化氢催化氧化制氯气具有高效率、低能耗、环境友好等优点,一直是研究的热点。首先采用浸渍法制备RuO_2/TiO_2催化剂,并通过催化活性评价和H_2-TPR表征优化Ru的负载量。然后制备Ce、Mn、La、Zr、Co等氧化物修饰的MO_x-TiO_2(M=Ce、Mn、La、Zr、Co)载体及RuO_2/MOxTiO_2催化剂,考察不同修饰物对催化剂氯化氢氧化性能的影响。结果表明,采用该型号TiO_2载体时最佳负载质量分数为2%~3%;MO_x-TiO_2载体中MOx修饰物均呈高分散状态,La、Zr、Ce等氧化物修饰后,TiO_2晶粒尺寸增大,其中Zr、Mn、Co等氧化物掺杂进入TiO_2晶格。Ce和Zr氧化物修饰可以提高RuO_2/TiO_2催化剂催化活性,Mn、Co、La等氧化物修饰对活性有不利影响。Mn、Co氧化物修饰可以降低反应活化能,所以这两种氧化物修饰的催化剂催化活性较低是由指前因子减小导致的,这意味着进一步提高RuO_2/MO_x-TiO_2(M=Mn、Co)催化剂活性组分分散性才能开发出活性更好的催化剂。     

富氢气体中CO优先氧化催化剂研究进展

以高纯氢为燃料的质子交换膜燃料电池广泛应用于电动汽车,但其阳极容易被富氢气体中含有的少量CO毒化,造成电池性能严重降低。富氢气体在进入燃料电池前,必须进行CO净化处理。优先氧化法是除去富氢气体中少量CO最简单经济有效的方法,常用催化剂主要有Pt系、Au系和Cu系催化剂。着重阐述负载Au催化剂的制备方法、载体调变、助剂改性以及其他因素（如反应气氛中CO与O₂浓度比、水蒸汽和CO₂等）对Au催化剂CO优先氧化反应催化性能的影响。介绍以CuO/CeO₂催化剂为典型的非贵金属氧化物催化剂用于CO优先氧化反应的研究成果以及制备方法、载体和助剂改性等对催化性能的影响和反相结构CeO₂/CuO的催化性能。考虑利用催化剂活性组分,尤其是Au与Cu之间的协同作用,选用合适的载体,进行催化剂组分的设计仍然是今后研究的热点。突破常规无定形金属氧化物作载体,通过设计合成具有特定形貌的载体,研究不同晶面和不同价态等因素对催化剂CO优先氧化催化性能的影响,也是一项很有意义的研究。     

双金属RhAux/γ - Al203催化剂的CO催化氧化反应活性

采用超声辅助膜扩散法制备了双金属RhAu/γ- Al2O3催化剂(x=0、0.25、0.5、1.0、2.0和4.0),研究了该系列催化剂的CO催化氧化反应活性.采用程序升温还原(TPR)、X射线衍射(XRD)、原位DRIFTS和电子透射显微镜(TEM)等技术对催化剂的结构、形貌和物化性能进行了表征.结果表明,双金属Rh...     

Au/LaCo_(1-x)Ce_xO_3催化剂的制备及其对CO催化氧化性能的研究

为进一步提高催化剂活性,用Ce对LaCoO3载体进行改性,并采用溶胶-凝胶法制备系列LaCo1-xCexO3(x=0~0.5)载体。其中,x=0.1和0.2时,载体为钙钛矿结构。采用沉积-沉淀法制备Au/LaCo1-xCexO3(x=0.1、0.2)催化剂,通过XRD、BET和H2-TPR等方法对催化剂进行催化活性评价及稳定性表征测试。结果表明,Au/LaCo0.9Ce0.1O3和Au/LaCo0.8Ce0.2O3催化剂能够在90℃将CO完全转化,在此温度进行的连续20h和30h的寿命实验中,CO转化率保持100%,催化活性和稳定性均优于Au/LaCoO3催化剂。表明掺杂Ce改性载体,能够提高催化剂活性和稳定性。     

富H2中优先氧化CO的CeO2/CuO催化剂的研究进展

逆负载型CeO2/CuO催化剂是富H2中优先氧化CO的一种新型催化剂,其活性较传统CuO-CeO2催化剂高.本文综述了CeO2/CuO催化剂的制备方法,着重介绍了逆微乳液法和浸渍法,对CeO2/CuO催化剂的尺寸效应和界面效应对催化剂性能的影响作了大胆的猜测,对未来CeO2/CuO催化剂的研究趋势提出了建议,旨在找到C...     

富氢原料气脱一氧化碳催化剂C-846A的开发

开发了一种富氢原料气中CO选择性氧化脱除催化剂C-846A。该催化剂贵金属用量少,使用空速高（8 500 h^-1）,在温度不高于133 ℃的条件下,可将富氢原料气中含0.13%的CO氧化脱除至100×10^-6以下。近700 h寿命试验结果表明,催化剂低温活性好,脱除精度高,性能稳定,应用前景广阔。     

Ge-modified Pt/SiO2 catalysts used in preferential CO oxidation (CO-PROX)

A bimetallic PtGe catalyst was prepared by a controlled surface reaction and studied for the PROX reaction. The good activity of the bimetallic catalyst can be assigned to the presence of a “noble metal-oxidized metal promoter” ensemble site in close contact, the noble metal (Pt) being the CO adsorption site and the oxidized metal promoter (Ge) the O₂ adsorption site. The stability of the PtGe clusters is confirmed by the EXAFS spectra and activity measurements in the preferential oxidation reaction that show similar values for samples subjected to different oxidation–reduction cycles.     

Gd-Bi-M-Ce-O (M = Cu,Zr, Ni,Co, Mn) ceria-based solid solutions for low temperature CO oxidation

Ceria based solid solutions doped by Gd, Bi, and the third dopant were synthesized by the co-precipitation method with ultrasonic treatment, followed by calcination at the temperature of 500°С. Characterization of the synthesized nanosystems by XRD, TEM, TG, Raman spectroscopy, FTIR, XPS was carried out. It is shown that all obtained powders of solid solutions crystallized into a cubic structure of the fluorite type, with an average particle size of 5–15 nm. The samples had a mesoporous structure of the pore diameter of 2–5 nm. The catalytic activity of Gd-Bi-M-Ce-O (M = Cu, Zr, Ni, Co, Mn) solid solutions was carried out. The catalyst Gd_0.05Bi_0.15Mn_0.20Ce_0.60O₂ has the lowest oxidation temperature.     

Pt/CrCeAlO催化剂对二氯甲烷的催化氧化性能

催化氧化是消除挥发性有机废气的有效手段,而二氯甲烷是含氯有机废气的代表性化合物。采用沉淀法制备了不同CrO_x含量的CrCeAlO催化剂,并用浸渍法制备了Pt/CrCeAlO催化剂,将其用于二氯甲烷催化氧化。结果表明,催化剂均表现出较好的活性,Cr_0.03Ce_0.05Al_0.95O₂催化剂在390 ℃时即可完全氧化二氯甲烷。而负载Pt后的催化剂活性明显提高,2.0Pt/Cr_0.03Ce_0.05Al₀.₉₅O₂催化剂表现出最好的活性,在340 ℃条件下,转化率即达100%。采用XRD、SEM、TEM、H₂-TPR和NH3-TPD对催化剂进行表征,表明催化剂的活性主要受其表面酸性和氧化还原性的影响,表面酸性位提供二氯甲烷化学吸附位,而催化剂表面氧化还原性则有利于反应中氧物种的活化。催化剂中添加Pt后,由于Pt、CeO₂ 和 CrO_x物种间的相互作用而增强了催化剂的氧化还原性,从而进一步促进了反应活性的提高。     

Preferential oxidation of CO in rich H2 over CuO/CeO2: Details of selectivity and deactivation under the reactant stream

A CuO/CeO₂ catalyst is examined with respect to its performance for preferential oxidation of CO in H₂-rich streams. Catalytic activity results are explained on the basis of characterization by operando-DRIFTS and complemented with the analysis of redox properties by electron paramagnetic resonance (EPR) and X-ray photoelectron spectra (XPS). General catalytic activity features are accounted for by comparative analysis of the activities for individual CO and H₂ oxidation, for which similar CuO and CeO₂ interfacial active sites appear to be involved. An interesting particularity is related to observation of a low temperature hydrogen oxidation process in which CO apparently acts as gaseous promoter. A deactivation process taking place rapidly under the reactant stream is evidenced and attributed to accumulation of hydroxyls on the interfacial active sites and/or to copper sintering in the course of the run.     

MnOx/Pt/Al2O3 catalysts for CO oxidation in H2-rich streams

The catalytic activity of Pt on alumina catalysts, with and without MnO_x incorporated to the catalyst formulation, for CO oxidation in H₂-free as well as in H₂-rich stream (PROX) has been studied in the temperature range of 25–250 °C. The effect of catalyst preparation (by successive impregnation or by co-impregnation of Mn and Pt) and Mn content in the catalyst performance has been studied. A low Mn content (2 wt.%) has been found not to improve the catalyst activity compared to the base catalyst. However, catalysts prepared by successive impregnation with 8 and 15 wt.% Mn have shown a lower operation temperature for maximum CO conversion than the base catalyst with an enhanced catalyst activity at low temperatures with respect to Pt/Al₂O₃. A maximum CO conversion of 89.8%, with selectivity of 44.9% and CO yield of 40.3% could be reached over a catalyst with 15 wt.% Mn operating at 139 °C and λ = 2. The effect of the presence of 5 vol.% CO₂ and 5 vol.% H₂O in the feedstream on catalysts performance has also been studied and discussed. The presence of CO₂ in the feedstream enhances the catalytic performance of all the studied catalysts at high temperature, whereas the presence of steam inhibits catalysts with higher MnO_x content.     

碳纳米管负载CuO-CeO_2催化剂用于CO选择性氧化

分别以碳纳米管(CNTs)和68%浓HNO3处理的CNTs为载体,采用超声辅助的浸渍法制备负载型Cu O-CeO_2复合氧化物催化剂,用于富氢气中CO选择氧化。采用XPS和LRS对预处理前后CNTs管的结构与表面性质进行研究。采用XRD和H2-TPR对催化剂结构进行表征。结果表明,经浓HNO3处理的CNTs载体表面含氧官能团—COOH相对含量提高了约68%,且表面缺陷增多,有助于催化剂活性组分的沉积和分散。以此负载的Cu O-CeO_2催化剂上Cu O物种具有较好的分散性,晶粒尺寸较小,催化剂表现出强的低温氧化还原能力,且表面CO氧化活性位增多,对CO选择性氧化具有低温高活性,T50低至90℃,反应温度低于140℃保持高选择性,且CO完全转化反应温度窗口拓宽宽至30℃。