Ce改性Pd基整体式催化剂的结构特征及其甲烷催化燃烧性能

分别以拟薄水铝石和添加Ce的拟薄水铝石制备铝溶胶,经过堇青石（Cord）表面涂覆和Pd溶液浸渍,得到浸渍法和溶胶法Ce改性的Pd/γ-Al₂O₃/Cord整体式催化剂。采用XRD、SEM和XPS等对催化剂进行表征,评价其甲烷催化燃烧反应性能,并考察Ce的不同添加方式对催化剂结构和反应性能的影响。结果表明,适量Ce的添加可提高Pd基整体式催化剂的甲烷催化燃烧性能,溶胶法优于浸渍法。随着Ce添加量的增加,浸渍法改性的Pd基催化剂催化性能有所降低,溶胶法则呈现先升高后降低的趋势。溶胶法中Ce的添加物与γ-Al₂O₃涂层充分融合,提高了涂层的热稳定性和活性组分的分散度,0.5Pd/γ-Al₂O₃(3.0Ce)/Cord催化剂催化性能最优。     

甲烷在Cr改性Pd/Al2O3催化剂上的催化燃烧性能

研究了Cr改性Pd/Al2O3催化剂上低浓度甲烷的催化燃烧反应,考察了载体Cr Al的制备方法和活性组分Pd的负载方法对催化剂催化活性的影响以及添加Ce对催化剂高温稳定性的影响。采用X射线衍射、程序升温还原等表征手段分析了催化剂结构和氧化还原性。结果表明,与采用沉淀法制备的载体P-Cr Al相比,采用浸渍法制备的载体I-Cr Al具有较高的比表面积和反应活性;用Na BH3对Pd负载过程进行还原处理能明显提高催化剂活性,其原因是还原过程加强了催化剂上Pd与载体Cr Al之间的作用,通过H2-TPR证明了其还原能力得到了增加;添加Ce缓解了Al2O3高温条件下的烧结,增强了催化剂的高温稳定性。     

蜂窝陶瓷负载Pd基整体式催化剂制备及催化燃烧性能

以拟薄水铝石和活性氧化铝粉为原料,通过添加胶溶剂、表面活性剂等助剂制备氧化铝涂层浆液,分别对堇青石蜂窝陶瓷载体和预先涂覆氧化硅的蜂窝陶瓷载体涂覆氧化铝涂层,负载活性组分制备Pd基整体式催化剂。考察载体涂层、表面活性剂种类、反应空速对催化剂催化乙烷燃烧活性的影响。结果表明,适宜的表面活性剂及双涂层结构的载体有助于提高催化剂活性。经310 h寿命实验,乙烷脱除率可达99.9%以上,表明制备的Pd基整体式催化剂具有良好的乙烷催化燃烧活性和稳定性。     

合成方法对拟薄水铝石孔结构的影响

重质油加氢催化剂所用的拟薄水铝石要求具有较大的孔容、比表面积和特定的孔结构,工业上通常采用硫酸铝法和碳化法生产。为了提高孔容孔径,本文采用扩孔法制备超大孔拟薄水铝石,同时采用硫酸铝法和碳化法制备常规大孔拟薄水铝石,并将三种拟薄水铝石制备成氧化铝、载体和催化剂,表征分析孔结构,评价催化剂的加氢反应性能。低温N₂吸附-脱附测试表明,扩孔法拟薄水铝石制备的载体孔容孔径最大,硫酸铝法拟薄水铝石制备的载体孔径分布最集中。压汞分析测试表明,三种方法制备的拟薄水铝石主要由晶粒间孔和颗粒间孔组成,经挤压制备成载体后颗粒间的大孔全部消失,只存在晶粒间的孔。XRD分析表明,扩孔法制备的拟薄水铝石晶粒最大,是导致其具有较大孔容孔径的原因之一。SEM和TEM分析显示,硫酸铝法制备的拟薄水铝石呈现纤维状结构,碳化法拟薄水铝石具有较小的片状结构,而扩孔法拟薄水铝石具有更大的片状结构,这也是三种拟薄水铝石呈现不同孔结构的原因。固定床评价结果表明,对于重油加氢处理反应,硫酸铝法、碳化法和扩孔法拟薄水铝石在制备成催化剂以后,活性依次增大,这是由于较大的可几孔径有助于提高重油大分子扩散速率导致的。     

Al_2(SO_4)_3-NH_3·H_2O法大孔拟薄水铝石的制备及其应用

在Al3+浓度0.6 mol·L-1、反应温度60℃和p H=9条件下,研究了硫酸铝滴定氨水(酸滴碱法)、氨水滴定硫酸铝(碱滴酸法)、p H摆动法和并流法成胶方式对共沉淀法制得的拟薄水铝石物化性能的影响。采用X射线衍射、N2吸附-脱附和扫描电镜等对拟薄水铝石进行表征。结果表明,成胶方式对拟薄水铝石物理性能影响显著,采用并流法成胶方式制得的拟薄水铝石比表面积374 m2·g-1,孔容0.89 cm3·g-1,孔径6.4 nm且分布集中,结晶度高,纯度好,能够满足加氢催化剂载体所用拟薄水铝石的物化性能要求。以并流法成胶方式得到的拟薄水铝石制备的Pd/Al2O3催化剂用于裂解汽油双烯烃选择加氢时表现出优异的加氢性能。     

EISA表面修饰法制备抗烧结催化剂

通过催化剂表面修饰控制催化剂表面活性组分颗粒的表面迁移能力,可以提高催化剂的抗烧结性能。通过蒸发诱导自组装(EISA)法修饰催化剂表面制备抗烧结催化剂,并对其性能进行研究。将经过验证的可形成二维有序介孔薄膜的EISA起始溶液沉积在Pd@Si O_2模型催化剂表面,采用TEM表征m Si O_2@Pd@Si O_2催化剂结构,证明了EISA表面修饰法的可行性。将EISA表面修饰法用于修饰Pd/Al2O3催化剂,通过表面涂覆的次数控制修饰层的厚度。XRD和甲烷燃烧活性结果表明,经过修饰的m Si O_2@Pd/Al2O3催化剂耐高温性能提高,其中,涂覆两次后的催化剂表面Pd O纳米颗粒晶粒尺寸增大程度最小,甲烷燃烧活性最好。EISA表面修饰法制备抗烧结催化剂是一种提高催化剂高温稳定性的有效方法。     

Pd/C催化Suzuki偶联反应合成啶酰菌胺中间体

采用过氧化氢改性活性炭,并将其作为载体制备Pd/C催化剂。结果表明,通过不同温度处理,活性炭织构和表面性质被选择性地修饰,载体表面官能团影响钯纳米颗粒的分散度和化学状态。与其他处理温度相比,250℃处理的活性炭表面含有更多的酸性含氧基团,所制得Pd/C分散度最高。在催化Suzuki偶联反应合成啶酰菌胺中间体4′-氯-2-硝基联苯中活性显著提高,反应收率增加。酸性含氧基团为钯纳米颗粒在活性炭表面的分散提供了有效的锚定位点,促进了载体与钯纳米颗粒之间的电子转移,形成了相对缺电子的钯纳米颗粒,从而提高了Pd/C催化剂的活性。     

载体及活性组分对甲烷低温燃烧催化性能的影响

以一定浓度的Pd为活性组分,-γA l2O3为载体,用浸渍法制备了甲烷低温燃烧催化剂,运用固定床反应装置着重研究载体对甲烷低温燃烧反应的催化性能的影响。同时采用同一种载体条件下,重点考察不同浓度的单一活性组分Pd或Pt和(Pt-Pd)双活性组分催化剂对甲烷低温燃烧反应的催化性能的影响。结果表明,由不同载体,负载同一浓度活性组份制备出的催化剂活性有较大差异。(Pt-Pd)/A l2O3双组分燃烧催化剂,性能优于单一组分的Pd/A l2O3或Pt/A l2O3催化剂,(Pd-Pt)/A l2O3体系具有较高的甲烷催化燃烧活性,催化燃烧的起燃温度最低。相比当(Pd 0.2%-Pt 0.1%)/A l2O3时催化剂活性最高,CH4转化率50%的温度为345℃,完全转化温度为405℃。通过1 000 h稳定性试验,显示出甲烷完全氧化温度为405℃左右,具有较好的低温活性及热稳定性。     

搅拌速率对Pd/Al_2O_3催化剂CH_4催化燃烧性能的影响

为了考察搅拌速率在Pd/Al2O3催化剂制备过程中的作用,通过对不同搅拌速率制备的Pd/Al2O3催化剂进行XRD、H2-TPR和XPS表征及CH4催化燃烧活性测试,研究搅拌速率对Pd/Al2O3催化剂活性的影响。结果表明,低搅拌速率[(200~300)r·min-1]条件制备的催化剂,Pd O粒径较大,Pd分散度高,表面Pd与Pd O物质的量比=0.55~0.56,催化剂的CH4催化反应活化能与无搅拌时相比降低,在200 r·min-1达到最低;随着搅拌速率增加,高搅拌速率[(400~600)r·min-1]抑制了Pd O晶粒的生长,导致Pd O粒径变小,Pd分散度降低,并使表面Pd O含量增大,Pd与Pd O物质的量比=0.41~0.52,提高了CH4催化燃烧反应的活化能。     

热活化提升Pd/C催化剂甲酸电氧化性能的研究

通过微波辅助多元醇方法以XC-72碳黑作为基体材料制备了Pd/C材料,对其进行惰性气氛下热活化处理,制备了热活化Pd/C催化剂,并对不同温度制备的Pd/C催化剂的电催化甲酸氧化反应的性能进行了探究。在电化学测试中,热活化后的Pd/C催化剂的电催化活性和长时间运行稳定性都得到了显著提升。此外,在对热活化温度优化后,发现当热活化温度达到500℃时,所制备的Pd/C-500℃催化剂的甲酸电氧化活性和稳定性达到最佳水平。分析认为,催化性能的提升来源于Pd纳米颗粒的结晶性的提高,以及更强的金属载体的相互作用。     

An excellent support of Pd catalyst for methane combustion: Thermal-stable Si-doped alumina

Thermal-stable Si-doped alumina was prepared by the reverse microemulsion method and was used as the support of Pd catalyst for the methane combustion. The physicochemical properties of Si-alumina and catalytic performance of Pd/Si-Al₂O₃ were characterized by XRD, N₂ adsorption, FT-IR, XPS and methane catalytic combustion. The results indicate that the presence of Si can increase the thermal stability of alumina and promote the coordination state of aluminum from tetrahedral to octahedral, but its content added should be controlled appropriately to 5–6 wt%. Si-doped alumina prepared by the reverse microemulsion method is an excellent support of Pd catalyst for the methane combustion, which can increase both the catalytic activity and thermal stability of the Pd catalyst. The studies also show that the calcination temperature of support affects remarkably the performance of catalyst, and the high thermal stability of support is very important to increase the performance of Pd catalyst for the methane combustion.     

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.     

Complete oxidation of methane on Pd/YSZ and Pd/CeO2/YSZ by electrochemical promotion

In this work, methane combustion over Pd/YSZ and Pd/CeO₂/YSZ catalyst was investigated at a temperature range of 470–600 °C. For the first time, the feasibility of electrochemical promotion on palladium films prepared by wet impregnation was reported. The catalytic activity of palladium was found to increase over 160% via transference of oxygen ions from the solid electrolyte to the catalyst film. In addition, palladium supported over ceria and yttria-stabilized zirconia showed the highest activity. As expected, the presence of ceria allowed improving the oxygen storage capacity of the catalyst system.     

过渡金属Ni对Pd/Al_2O_3催化剂甲烷催化燃烧性能的影响

考察过渡金属Ni对Pd/Al_2O_3催化剂甲烷催化燃烧活性的影响以及过渡金属负载量及循环条件对甲烷降解性能的影响,采用扫描电镜、N_2吸附-脱附以及H_2程序升温还原技术对催化剂进行表征。结果表明,过渡金属Ni的添加对催化剂在(375~475)℃下的甲烷催化燃烧活性产生影响。催化剂经多次重复使用后,催化燃烧活性提高。分析原因为经过渡金属Ni改性后,可与载体形成NiAl_2O_4尖晶石,促进活性组分形成较小晶粒,并改善活性组分分散度,提高催化剂催化活性。     

Low temperature oxidation of methane over Pd/SnO2 catalyst

Catalytic activities of supported Pd were investigated for low temperature oxidation of methane. Pd/SnO₂ catalysts demonstrated excellent activity for methane oxidation in spite of their low surface area. The catalytic activity of Pd/SnO₂ was strongly affected by the preparation procedure. Impregnation of Pd on SnO₂ using aqueous solution of Pd(CH₃COO)₂ was most effective in enhancing the catalytic activity. The catalytic activity was also improved when well-crystallized SnO₂ was employed as a support material. TEM observations revealed that catalytic activity is strongly influenced by the dispersion state of Pd. For the active catalysts, strong interaction between Pd and SnO₂ support was observed in the adsorption of oxygen.     

Na改性Pt/AlOOH对甲醛催化氧化反应活性的影响

具有晶面取向的阳极氧化AlOOH因其低温甲醛催化性能而被用于催化氧化甲醛体系。为丰富AlOOH表面羟基含量,采用Na₂CO₃为Na前体浸渍法改性载体,制备不同Na含量（0.13%、0.19%、0.30%、0.41%,质量分数）的Pt/Na_x/AlOOH催化剂。通过BET、FTIR、XPS、HRTEM等表征分析,发现加入Na后,Na/AlOOH的表面羟基更加丰富,Pt/Na_x/AlOOH催化剂的比表面积增大,拥有更小的Pt颗粒尺寸,表面Pt颗粒分散度提高,Pt0元素价态含量增加。当Na含量为0.41%时,催化剂Pt/0.41Na/AlOOH的Pt分散度高达56%。实验结果证明,Pt/0.41Na/AlOOH展现出最优的HCHO催化活性,60℃时HCHO转化率达100%。     

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。     

Methane combustion over Pd/ZrO2/SiC,Pd/CeO2/SiC,and Pd/Zr0.5Ce0.5O2/SiC catalysts

The performances of different promoters (CeO₂, ZrO₂ and Ce_0.5Zr_0.5O₂ solid solution) modified Pd/SiC catalysts for methane combustion are studied. XRD and XPS results showed that Zr⁴⁺ could be incorporated into the CeO₂ lattice to form Zr_0.5Ce_0.5O₂ solid solution. The catalytic activities of Pd/CeO₂/SiC and Pd/ZrO₂/SiC are lower than that of Pd/Zr_0.5Ce_0.5O₂/SiC. The Pd/Zr_0.5Ce_0.5O₂/SiC catalyst can ignite the reaction at 240 °C and obtain a methane conversion of 100% at 340 °C, and keep 100% methane conversion after 10 reaction cycles. These results indicate that active metallic nanoparticles are well stabilized on the SiC surface while the promoters serve as oxygen reservoir and retain good redox properties.     

Development of a catalytic burner with Pd/NiO catalysts

A catalytic burner was studied which can be used as a heater operated at medium temperature. The catalytic combustion was initiated by an igniter which was placed on the exit surface of the catalyst layer. Noble metal catalysts (Pd/NiO) which were supported on alumina washcoated honeycomb were used, whose maximum heat-resisting temperature is about 900°C. The optimal operating conditions for stable catalytic combustion were obtained by means of analyzing the catalytic combustion region, the temperature distribution, and the combustion efficiency.