Pd-Pt-Ce/Al_2O_3催化剂在VOC净化处理中的催化性能

采用浸渍法制备Pd-Pt-Ce/Al_2O_3催化剂,考察贵金属Pd和Pt负载量、助剂种类及负载量、空速对催化甲苯燃烧活性的影响。结果表明,适宜的贵金属负载量和助剂可极大提高Pd-Pt/Al_2O_3催化剂活性,当Pd和Pt质量分数分别为0.05%和0.005%、助剂Ce质量分数为1%时,Pd-Pt-Ce/Al_2O_3催化剂在低温条件下表现出较好的催化性能。空速对催化剂的催化活性影响较为明显,适宜的空速低于20 000 h-1。     

络合-溶剂热法制备钯基催化剂及其催化氧化间二甲苯性能

通过采用络合-溶剂热法、水热法和浸渍法三种方法制备了负载量为0.6%(质量分数)的Pd/Al_2O_3催化剂,重点考察不同制备方法催化氧化间二甲苯作为典型的挥发性有机化合物的能力。结果表明:络合-溶剂热法制备的Pd/Al_2O_3-com催化剂催化氧化间二甲苯的能力最强,间二甲苯体积分数为0.002%时完全转化温度(T_(100))为130℃,低于浸渍法制备催化剂的完全转化温度30℃。对Pd/Al_2O_3催化剂进行了比表面积(BET)、X射线衍射(XRD)、X射线光电子能谱(XPS)、扫描电镜(SEM)等表征分析,发现Pd/Al_2O_3-com中Pd主要以还原态Pd~0高度分散于载体表面,而另两种方法制备的催化剂均有明显的Pd~(2+)存在。结合性能测试及表征分析,表明络合-溶剂热法制备的Pd/Al_2O_3-com催化剂活性组分Pd的高度分散,增强了催化活性,可满足高浓度间二甲苯、宽气体体积空速条件下催化氧化脱除间二甲苯的工业应用要求。     

助剂Ba对Pd/Al_2O_3和Pt/Al_2O_3催化剂的C1-C3烷烃催化燃烧性能的影响

通过浸渍法制备了Al_2O_3负载的Pd和Pt催化剂,考察催化剂的甲烷、乙烷和丙烷催化燃烧活性,以及助剂Ba对催化性能的影响。对于Pd/Al_2O_3催化剂,加入Ba使活性物种PdO颗粒变大和还原温度升高,形成更稳定的PdO活性物种,是Pd-Ba/Al_2O_3催化剂活性提升的主要原因。对于Pt/Al_2O_3催化剂,加入Ba助剂使活性物种Pt0含量降低,PtO_x与Al_2O_3载体相互作用增强,使PtO_x物种更难被还原为Pt~0,导致Pt-Ba/Al_2O_3催化剂活性降低。Pd和Pt催化剂催化烷烃氧化反应活性规律一致:丙烷乙烷甲烷。Pd/Al_2O_3催化剂有利于C—H键活化,Pt/Al_2O_3催化剂有利于C—C键活化。Pt/Al_2O_3催化剂对C1-C3烷烃氧化活性的差别明显大于Pd/Al_2O_3催化剂。Pt/Al_2O_3催化剂对碳比例高的烷烃活性更高。     

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。     

Ni负载量对煤油水重整制氢催化剂性能的影响

采用等体积分步浸渍法,以γ-Al_2O_3为载体制备NiLaLi/Al_2O_3催化剂,并在自制装置研究不同Ni负载量对NiLaLi/Al_2O_3催化剂催化性能的影响。采用SEM及BET对NiLaLi/Al_2O_3催化剂的形貌及结构进行表征。结果表明,NiLaLi/Al_2O_3催化剂对煤油水重整制氢有较好的催化性能,并且NiLaLi/Al_2O_3催化剂的比表面积和孔容随着Ni负载量的增大而减小。当Ni的负载质量分数为10%时,煤油水重整制氢的平均氢产率为12.75mol·mol~(-1)。     

镍基氨分解制氢催化剂的制备及性能

用浸渍法制备Ni/Al_2O_3和Ni/xMo-Al_2O_3催化剂,以氨分解为模型反应,考察Ni负载量、焙烧温度、溶剂和助剂等合成条件对催化剂催化性能的影响,通过XRD和TG-DTG表征方法对催化剂进行表征。结果表明,最佳合成条件:Ni负载质量分数为16%,焙烧温度350℃,采用丙酮为溶剂制备的Ni/Al_2O_3催化剂具有较好的催化活性。500℃添加质量分数3%的助剂Mo可以使Ni/Al_2O_3催化剂的活性显著提高39%,Ni/3%Mo-Al_2O_3催化剂的氨分解率达93.5%。     

等离子体强化贵金属催化净化正葵烷的研究

采用一段式介质阻挡放电催化反应系统,对模拟柴油车发动机尾气中的碳氢化合物(正葵烷,C10)进行处理。研究了C10在不同贵金属催化剂作用下的去除差异性,探讨了催化剂负载量、C10初始浓度、反应温度、能量密度对等离子体贵金属催化去除C10的影响。结果表明:与单独等离子体或热催化相比,等离子体催化能够显著提高C10去除率,等离子体和催化的协同作用显著。Pt/Al_2O_3的催化效果优于Pd/Al_2O_3、Ag/Al_2O_3,其不仅转化率高,而且促进了CO氧化生成CO_2。增加催化剂负载量、能量密度和反应温度都有利于提高C10去除率和CO、CO_2选择性,实验中C10去除率可达91%,CO和CO_2总选择性最大为54.3%,而初始浓度的增加则不利于C10去除。     

自组装低负载量Pd/γ-Al2O3催化剂催化氧化甲苯

以PdCl_2和Pd2(dba)3[三(二亚苄基丙酮)二钯]为前驱体,通过浸渍法、沉积沉淀法和自组装法分别制备了负载量(质量分数,下同)为0.03%的Pd/γ-Al_2O_3-IM、Pd/γ-Al_2O_3-DP和Pd/γ-Al_2O_3-SA催化剂用于催化氧化甲苯。在甲苯体积分数为0.1%、空速(SV)为18000 m L/(g·h)条件下,Pd/γ-Al_2O_3-SA催化剂上甲苯实现98%转化率的温度(T98)为220℃,比Pd/γ-Al_2O_3-DP和Pd/γ-Al_2O_3-IM分别降低了40和75℃。通过N2吸附-脱附、XRD、TEM、XPS和H2-TPR对催化剂进行了表征。结果表明:自组装法制备的Pd/γ-Al_2O_3-SA催化剂的比表面积(345 m2/g)和孔体积(0.52 cm3/g)最大,Pd纳米粒子(Pd NPs)平均粒径最小(5.0 nm),活性物种主要以Pd O的形式高度分散于载体γ-Al_2O_3表面。此外,Pd O与载体γ-Al_2O_3之间的强相互作用(SMSI)促进了其催化氧化甲苯的活性。     

顺丁橡胶尾气净化催化剂的研究与应用

顺丁橡胶尾气排放中主要污染物是正己烷,选择性催化氧化法是处理正己烷的主要技术。以聚乙二醇为助剂,制备Pt/Al_2O_3催化剂,利用侧线测试其催化性能,采用CO化学吸附与透射电子显微镜对催化剂进行表征。侧线测试结果表明,催化剂活性优于进口同类催化剂,250℃时,正己烷被完全氧化;CO化学吸附结果表明,Pt/Al_2O_3催化剂中贵金属分散度为75.9%,进口催化剂只有58.7%;TEM表明,Pt/Al_2O_3催化剂上金属分布更均匀。Pt/Al_2O_3催化剂应用于顺丁橡胶尾气处理,催化活性稳定。     

Pd/HZSM-5催化剂催化加氢丙酮合成甲基异丁基酮

以HZSM-5为载体,采用浸渍法制备系列Pd/HZSM-5催化剂,在高压连续流动固定床反应器中考察Pd/HZSM-5催化剂催化加氢丙酮一步法合成甲基异丁基酮性能,并对工艺条件进行优化。结果表明,当HZSM-5载体上Pd负载质量分数为0.5%时,在反应温度140 ℃、氢压1 MPa、空速0.48 h^-1和氢酮物质的量比为1条件下,Pd/HZSM-5催化剂催化活性较高,丙酮转化率为45.91%,甲基异丁基酮选择性为94.33%。采用XRD、H₂-TPD、SEM、EDS和TGA等对催化剂进行表征,结果表明,负载质量分数0.5%的Pd在HZSM-5分子筛表面分散均匀,且0.5%Pd/HZSM-5催化剂具有较高氢吸附能力,失活的主要原因为催化剂表面积炭,采用流化床反应器取代传统的固定床反应器可以很好的解决催化剂积炭问题。     

Effects of ZrO2/Al2O3 properties on the catalytic activity of Pd catalysts for methane combustion and CO oxidation

Zirconia supported on alumina was prepared and characterized by BET surface area, X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), temperature programmed desorption (TPD), and pulse reaction. 0.2% Pd/ZrO₂/Al₂O₃ catalyst were prepared by incipient wetness impregnation of supports with aqueous solution of Pd(NO₃)₂. The effects of support properties on catalytic activity for methane combustion and CO oxidation were investigated. The results show that ZrO₂ is highly dispersed on the surface of Al₂O₃ up to 10 wt.% ZrO₂, beyond this value tetragonal ZrO₂ is formed. The presence of a small amount of ZrO₂ can increase the surface area, pore volume and acidity of support. CO–TPD results show that the increase of CO adsorption capacity and the activation of CO bond after the presence of ZrO₂ lead to the increase of catalytic activity of Pd catalyst for CO oxidation. CO pulse reaction results indicate that the lattice oxygen of support can be activated at lower temperature following the presence of ZrO₂, but it does not accelerate the activity of 0.2% Pd/ZrO₂/Al₂O₃ for methane combustion. 0.2% Pd/ZrO₂/Al₂O₃ dried at 120 °C shows highest activity for CH₄ combustion, and the activity can be further enhanced following the repeat run. The increase of treatment temperature and pre-reduction can decrease the activity of catalyst for CH₄ combustion.     

Pd/Ce基催化剂催化氧化氯苯的性能

采用等体积浸渍法制备Pd/Al₂O₃系列催化剂,考察不同Pd负载量对催化剂催化氯苯活性的影响,结果表明0.75%Pd/Al₂O₃催化剂活性最优,采用BET、H₂-TPR、SEM等对催化剂进行表征分析,表明添加Ce后氧化能力增强,催化氧化效率提高。对催化产物进行分析,使用离子色谱分析了无机Cl^-生成情况及其选择性,使用GC-MS定性分析了有机副产物,发现350℃时有少量苯生成。同时考察了焙烧温度、氯苯浓度、空速对催化活性的影响,结果表明焙烧温度过高或过低都会影响催化剂的活性,在550℃焙烧的催化剂活性更优,400℃时氯苯转化率为96%;氯苯入口处质量浓度在1500～6000mg/m³时,浓度升高,催化氯苯活性降低;空速在15000～30000h^-1时,空速对氯苯催化活性影响不大,但继续提高空速会明显降低催化活性。     

贵金属催化剂用于低浓度甲烷的去除

制备不同负载量的Pd基和Pt基催化剂,建立催化剂活性评价装置,考察贵金属Pd和Pt负载量对甲烷转化率的影响,结果表明,甲烷转化率最高的Pd和Pt负载质量分数分别为1.25%和2%,相同负载质量分数0.1%时,Pd基催化剂的甲烷转化率优于Pt基催化剂。催化剂的BET比表面积大小不能反映催化剂的催化活性,二者之间无线性关系。     

Characterization and catalytic activity of Pd/V2O5/Al2O3 catalysts on benzene total oxidation

The role of vanadium oxide and palladium on the benzene oxidation reaction over Pd/V₂O₅/Al₂O₃ catalysts was investigated. The Pd/V₂O₅/Al₂O₃ catalysts were more active than V₂O₅/Al₂O₃ and Pd/Al₂O₃ catalysts. The increase of vanadium oxide content decreased the Pd dispersion and increased the benzene conversion. A strong Pd particle size effect on benzene oxidation reaction was observed. Although the catalysts containing high amount of V⁴⁺ species were more active, the Pd particle size effect was responsible for the higher activity.     

Pt/Pt-Ce/γ-Al2O3催化氧化甲苯研究

通过等体积浸渍法制备单贵金属Pt/γ-Al₂O₃和双金属Pt-Ce/γ-Al₂O₃催化剂,考察Ce对催化剂活性的影响,确定催化剂最优配比。结果表明,当Pt的负载量为质量分数0.5%时,Pt/γ-Al₂O₃催化活性最高;当Pt的负载量为质量分数0.2%,Ce的负载量为质量分数1.0%时,Pt-Ce/γ-Al₂O₃催化剂的催化活性最高。Pt-Ce/γ-Al₂O₃催化剂的甲苯转化率高于Pt/γ-Al₂O₃催化剂。随着Pt负载量增大,催化剂孔容、孔径减小。粉体式催化剂性能优于整体式催化剂,但差别不大;Ce的添加有助于催化剂活性的提升。     

络合-溶剂热法制备钯基催化剂及其催化氧化间二甲苯性能

通过采用络合-溶剂热法、水热法和浸渍法三种方法制备了负载量为0.6%（质量分数）的Pd/Al₂O₃催化剂，重点考察不同制备方法催化氧化间二甲苯作为典型的挥发性有机化合物的能力。结果表明：络合-溶剂热法制备的Pd/Al₂O₃-com催化剂催化氧化间二甲苯的能力最强，间二甲苯体积分数为0.002%时完全转化温度（T₁₀₀）为130℃，低于浸渍法制备催化剂的完全转化温度30℃。对Pd/Al₂O₃催化剂进行了比表面积（BET）、X射线衍射（XRD）、X射线光电子能谱（XPS）、扫描电镜（SEM）等表征分析，发现Pd/Al₂O₃-com中Pd主要以还原态Pd⁰高度分散于载体表面，而另两种方法制备的催化剂均有明显的Pd²⁺存在。结合性能测试及表征分析，表明络合-溶剂热法制备的Pd/Al₂O₃-com催化剂活性组分Pd的高度分散，增强了催化活性，可满足高浓度间二甲苯、宽气体体积空速条件下催化氧化脱除间二甲苯的工业应用要求。     

Comparison of catalytic activity and selectivity of Pd/(OSC + Al2O3) and (Pd + OSC)/Al2O3 catalysts

The effect of the Pd addition method into the fresh Pd/(OSC + Al₂O₃) and (Pd + OSC)/Al₂O₃ catalysts (OSC material = Ce_xZr_1−xO₂ mixed oxides) was investigated in this study. The CO + NO and CO + NO + O₂ model reactions were studied over fresh and aged catalysts. The differences in the fresh catalysts were insignificant compared to the aged catalysts. During the CO + NO reaction, only small differences were observed in the behaviour of the fresh catalysts. The light-off temperature of CO was about 20 °C lower for the fresh Pd/(OSC + Al₂O₃) catalyst than for the fresh (Pd + OSC)/Al₂O₃ catalyst during the CO + NO + O₂ reaction. For the aged catalysts lower NO reduction and CO oxidation activities were observed, as expected. Pd on OSC-containing alumina was more active than Pd on OSC material after the agings. The activity decline is due to a decrease in the number of active sites on the surface, which was observed as a larger Pd particle size for aged catalysts than for fresh catalysts. In addition, the oxygen storage capacity of the aged Pd/(OSC + Al₂O₃) catalyst was higher than that of the (Pd + OSC)/Al₂O₃ catalyst.     

The role of lanthana loading on the catalytic properties of Pd/Al2O3-La2O3 in the NO reduction with H2

The role of La₂O₃ loading in Pd/Al₂O₃-La₂O₃ prepared by sol–gel on the catalytic properties in the NO reduction with H₂ was studied. The catalysts were characterized by N₂ physisorption, temperature-programmed reduction, differential thermal analysis, temperature-programmed oxidation and temperature-programmed desorption of NO.

The physicochemical properties of Pd catalysts as well as the catalytic activity and selectivity are modified by La₂O₃ inclusion. The selectivity depends on the NO/H₂ molar ratio (GHSV = 72,000 h⁻¹) and the extent of interaction between Pd and La₂O₃. At NO/H₂ = 0.5, the catalysts show high N₂ selectivity (60–75%) at temperatures lower than 250 °C. For NO/H₂ = 1, the N₂ selectivity is almost 100% mainly for high temperatures, and even in the presence of 10% H₂O vapor. The high N₂ selectivity indicates a high capability of the catalysts to dissociate NO upon adsorption. This property is attributed to the creation of new adsorption sites through the formation of a surface PdO_x phase interacting with La₂O₃. The formation of this phase is favored by the spreading of PdO promoted by La₂O₃. DTA shows that the phase transformation takes place at temperatures of 280–350 °C, while TPO indicates that this phase transformation is related to the oxidation process of PdO: in the case of Pd/Al₂O₃ the O₂ uptake is consistent with the oxidation of PdO to PdO₂, and when La₂O₃ is present the O₂ uptake exceeds that amount (1.5 times). La₂O₃ in Pd catalysts promotes also the oxidation of Pd and dissociative adsorption of NO mainly at low temperatures (<250 °C) favoring the formation of N₂.