CrO_x/ZrO_2催化剂上甲烷催化燃烧性能

采用沉淀法制备了CrO_x/ZrO_2催化剂,考察800℃高温焙烧的CrO_x/ZrO_2催化剂对CH_4燃烧的催化性能。采用X射线衍射和拉曼光谱等技术对催化剂进行物相结构表征。结果表明,Cr物种以Cr_2O_3形式存在,随着焙烧温度升高,催化剂中ZrO_2和Cr_2O_3的晶粒明显增大。CrO_x/ZrO_2催化剂的比表面积大于相应的纯Cr_2O_3和ZrO_2。催化剂的CH_4燃烧活性随着Cr含量的增加而提高,Cr质量分数20%时活性最高,CH_4完全燃烧温度为450℃。     

甲烷催化燃烧催化剂催化理论与应用研究进展

概述了甲烷催化燃烧催化剂的研究现状,从组成甲烷燃烧催化剂的3个部分（基体、活性组分、氧化物载体）分别加以论述。通过掺杂一些金属和金属氧化物,不但可以提高高活性贵金属催化剂的热分解温度,还可以提高高温催化剂（如钙钛矿和六铝酸盐材料等）的催化活性。最后简要综述了甲烷催化燃烧反应机理。     

低温CO催化氧化负载型Pd催化剂研究进展

综述了低温CO催化氧化负载型Pd催化剂在制备方法、载体的选用和催化机理等方面的研究进展,并介绍了该类催化剂的最新进展.在文章末对该催化剂领域尚待深入研究的问题进行了探讨.     

硫化处理对负载钯催化剂甲烷低温催化燃烧性能的影响

采用浸渍法制备氧化硅负载钯催化剂,考察硫化气氛和硫化时间对催化剂性能的影响,并采用XRD对催化剂进行表征。结果表明,硫化后形成的Pd4S物种可以提高催化剂抗硫中毒性能,同时催化剂表面的SPd4S/SPd对催化活性有重要影响,改变硫化气氛和硫化时间可以调节Pd4S物种的形成和SPd4S/SPd。     

制备抗硫性负载钯甲烷低温氧化催化剂的研究进展

介绍了耐硫性负载钯甲烷氧化催化剂的研究现状,比较了3种不同的提高催化剂耐硫性的方法。其中,重点介绍了钯硫化物催化剂。该方法是对传统抗硫方法的一次突破,通过以Pd_xS_y组分取代PdO活性相使催化剂具备真正意义上的抗硫性。重点对气相、液相硫化方法进行了概述,并对该领域的研究前景进行了展望。     

负载型Ni基CO甲烷化催化剂研究进展

负载型Ni基催化剂是应用于CO甲烷化反应的重要催化剂,其金属分散度、活性位结构和化学组成是决定催化剂活性与稳定性的关键因素。综述了金属Ni活性中心结构、载体与助剂对负载型Ni基催化剂甲烷化反应活性和稳定性的影响,在提高催化剂活性的基础上,为开发低成本的负载型Ni基催化剂具有重要意义。     

多孔材料负载型催化剂催化氧化VOCs的研究进展

从不同类型催化剂的设计和结构出发,重点介绍了由多孔材料设计制备VOCs催化氧化催化剂的研究进展,包括金属有机框架（MOF）、沸石分子筛、多孔碳等载体及其衍生物在VOCs催化降解上的性能及相关比较,并阐述了该类催化剂增强氧化机理。最后,阐述了VOCs催化氧化技术面临的问题和未来发展方向。     

甲烷催化部分氧化制合成气催化剂的研究进展

叙述了甲烷催化部分氧化制合成气催化剂的最新研究进展,包括含钴的钙钛矿、碳化钼、碳化、Ｎｉ／α－Ａｌ２Ｏ３,Ｐｔ－Ｎｉ／α－Ａｌ２Ｏ３、ｌａＯ３＿ＮｉＯ／Ａｌ２Ｏ３等。     

合成氯甲烷的负载型ZnCl2/γ-Al2O3催化剂的研制

采用Ｘ射线光电子能谱分析（ＸＰＳ）及宽角Ｘ射线衍射（ＸＲＤ）等技术对不同条件制备、自理的催化剂性能、组成结构进行研究及评价,实验结果表明,浸沛时间是影响活性组分分布均匀程度的主要因素ＺｎＣｌ２渍淮质量分数决定着载体γ－Ａｌ２Ｏ３上ＺｎＣｌ２负载量。催化剂的活性与直 分在载体表面的分布主相互作用有关,取决于载体、ＺｎＣｌ２负载量及热处理的条件。ＺｎＣｌ２与载体相互作用,形成了复杂的多相体系。包括过量     

甲烷高温燃烧催化剂研究进展

催化燃烧具有环保、高效、节能等诸多优点.综述了甲烷高温催化燃烧的研究现状,对甲烷燃烧催化剂材料的研究进展做了较详细的介绍,并阐述了甲烷高温催化燃烧反应器的研究进展.     

硫化处理对钯锆纤维催化剂甲烷低温催化燃烧性能的影响

采用胶体喷吹成型法制备钯锆-γ-氧化铝纤维催化剂。将催化剂在不同硫化气氛进行硫化处理,置于扩散式催化燃烧取暖器。考察硫化气氛、热负荷和耐久试验时间对燃烧取暖器的烟气浓度、起燃温度和燃烧板面平均温度的影响。使用烟气分析仪和红外热成像仪对取暖器的烟气浓度和板面平均温度进行分析。结果表明,纤维催化剂经10%H₂S-H₂气氛硫化120 min,可以制得初始活性良好、稳定性较好且完全符合燃气取暖器CE标准指标的催化剂。     

Remarkable activity enhancement in the catalytic combustion of methane on supported palladium catalysts

The activity of supported palladium catalysts for the combustion of methane has been determined. It has been observed that the activity increases with time on stream irrespective of whether the catalysts are pre-calcined or pre-reduced. Careful re-reduction experiments have shown that the enhanced activity is maintained. It is concluded that the increase in activity with time on stream is not attributable to slow variations in the chemical state of the palladium particles, but to changes in the morphology of the palladium crystallites under reaction conditions. The possible role of dissolved carbon in stabilising the reconstructed crystallites against reduction is discussed.     

整装式铝泡沫负载Pd催化剂Pd/AlOOH/Al-foam及其催化甲烷燃烧性能

以三维网络结构的铝泡沫板作为骨架基体和铝源,利用水热氧化法制备整装式拟薄水铝石(Al OOH/Al-foam)纳米阵列,随后通过丙酮辅助-初湿浸渍法,制备出整装式铝泡沫负载Pd催化剂Pd/Al OOH/Al-foam,用于低浓度甲烷催化燃烧反应。在制备条件优化过程中,发现催化剂性能受到纳米阵列的形貌特征、物相组成以及焙烧温度等因素的影响。其中,表面富含羟基的拟薄水铝石可促进Pd颗粒的均匀分散,也增强载体和Pd之间的相互作用,进而提高甲烷燃烧的低温活性。稳定性测试初期活性下降较快,主要原因是表层Al_2O_3纳米阵列载体和Pd纳米颗粒自身的不稳定性导致的Pd颗粒烧结。     

MnOx/Mg-Al2O3催化甲烷燃烧反应的研究

在Al2O3上浸渍Mg（NO3）2溶液,焙烧后制得Mg改性Al2O3（Mg-Al2O3）。以Mg-Al2O3为载体,制备了MnOx/Mg-Al2O3系列催化剂,测试了这些催化剂对甲烷燃烧反应的催化活性。结果表明：Mg的加入有效抑制了Al2O3在高温焙烧时发生γ相变,提高了Al2O3的热稳定性,MnOx/10%Mg-Al2O3对甲烷燃烧的催化活性较高,Mg的适宜加入量为10%。     

Effect of support on the apparent activity of palladium oxide in catalytic methane combustion

The support effect on the low temperature catalytic oxidation of methane over palladium catalysts was studied by comparing a series of metal oxides as the support. Samples of 0.010 g/g Pd catalysts supported on different grades and/or phases of TiO₂, Al₂O₃, and ZrO₂ were prepared via incipient impregnation and their catalytic activity was evaluated using a laboratory plug-flow reactor. The specific surface area of the supports determined by nitrogen adsorption varied from about 13-220 m²/g. Initial experiments conducted with titania (anatase) as a support showed a low apparent activity and a poor thermal stability. Focusing on anatase, we have successfully improved its thermal stability by additions of Al₂O₃ or by doping with CeO₂, or La₂O₃. However, contrary to expectations based on some information in the literature, we have found that the activity decreased in the sequence of Al₂O₃ > ZrO₂ > TiO₂, and was not a direct function of specific surface area. This was especially evident in the case of titania. The surface structure of the support and the nature of its interaction with the active component PdO seem to play a far more important role in activity than the apparent specific surface area. Moreover, anatase-supported catalysts present a very rapid deactivation, whereas rutile-supported catalysts are relatively stable. The observed phenomena could potentially be related to the interaction between support and the active phase of palladium. Several models have been proposed to describe the strong metal-support interaction, but either charge transfer or encapsulation seems to be the most probable.     

Deactivation of palladium catalyst in catalytic combustion of methane

Catalytic combustion of natural gas, for applications such as gas turbines, can reduce NO_x emissions. Palladium-on-stabilised alumina has been found to be the most efficient catalyst for the complete oxidation of methane to carbon dioxide and water. However, its poor durability is considered to be an obstruction for the development of catalytic combustion. This work was aimed at identifying the origin of this deactivation: metal sintering, support sintering, transformation or coking.

Catalytic combustion of methane was studied in a 15 mm i.d. and 50 mm length lab reactor and in a 25 mm i.d. pilot test rig on monolithic honeycomb substrates. Experiments were performed at GHSV of 50 000 h⁻¹ in lab test and 500 000 h⁻¹ in pilot test. The catalysts used were palladium on different supports on cordierite substrate. The catalysts were characterised by XRD, STEM, ATG and XPS.

In steady-state conditions, deactivation has been found to be dependent on the air/methane ratio, the palladium content on the washcoat and the amount of washcoat on the substrate. An oscillating behaviour of the methane conversion was even observed under specific conditions, due to the reducibility of palladium oxide PdO to Pd. The influence of the nature of the support on the catalyst deactivation was also investigated. It has been shown that some supports can surprisingly eliminate this oscillating behaviour. However, in pilot test, deactivation was found to be very rapid, even with stabilised alumina supports. Furthermore, successive tests performed on the same catalyst revealed that the activity (light-off temperature, conversion) falls strongly from one test to another.

Then, the stabilised alumina support was calcined at 1230°C for 16 h prior to its impregnation by palladium, in order to rule out its sintering. Experiments carried out on precalcined catalysts point out that deactivation is mostly correlated to the metal transformation under reaction conditions: activity decreases gradually as PdO sinters, but it dropped much more steeply in relation to appearance of metallic palladium.     

Catalytic combustion of methane over palladium exchanged zeolites

Palladium cation exchanged zeolites (ZSM-5, mordenite and ferrierite) were studied as catalysts for methane combustion. Pd-zeolites showed much higher activities than PdO/Al₂O₃. For comparable palladium loadings, PdO/Al₂O₃ requires a reaction temperature of ca. 70–80°C higher than Pd-ZSM-5 for conversions between 50–100%. The catalytic activity of Pd-ZSM-5 seems to be related to its reducibility. Temperature-programmed reduction experiments with carbon monoxide showed a lower reduction temperature (ca. 157°C) for Pd-ZSM-5 than for PdO/Al₂O₃ (225°C). Further, the positioning of the palladium by ion exchange offers a highly dispersed form of Pd^II supported on the high surface area zeolite.     

甲烷催化燃烧用LaMn/Al_2O_3催化剂研究

为获得具有优良低温活性的甲烷燃烧用催化剂,采用稀土La作为助剂制备了系列Mn基催化剂,借助X射线衍射(XRD)、X射线光电子能谱(XPS)和程序升温还原(TPR)技术对催化剂的结构进行了表征,并评价了其对甲烷燃烧的低温催化性能。结果表明,La助剂的添加显著促进了活性组分MnO2的分散,使其更易于还原,且使Mn4+和晶格氧富集于催化剂表面,因而显著提高了催化剂对甲烷催化燃烧的低温活性。当La质量分数为5%时,催化活性最高,甲烷50%转化率对应的温度较未加助剂时降低了70℃,且完全转化的温度低至480℃。