不同碱辅助的沉积沉淀法对三效催化剂稳定性的影响

老化处理会导致三效催化剂(TWCs)严重失活,因此提高催化剂的耐久性能是TWCs设计的目标.本工作采用不同碱辅助的沉积沉淀法,即尿素辅助沉积沉淀法和氨水辅助沉积沉淀法制备了Pt/Ce0.4Zr0.5La0.05Pr0.05O2(Pt/CZ)三效催化剂,分析了不同碱对催化剂物理化学性质、催化活性和耐久性的影响.结果表明,...     

羟基锡酸盐载铂复合催化剂Pt/(Co,Zn)Sn(OH)6的合成及其甲醇电催化氧化性能

以羟基锡酸盐CoSn（OH）₆和ZnSn（OH）₆纳米空心立方体为前体,采用抗坏血酸作为弱还原剂,经过超声过程分别合成了羟基锡酸钴载Pt/CoSn（OH）₆和羟基锡酸锌载Pt/ZnSn（OH）₆复合催化剂,并在甲醇氧化反应（MOR）中表现出良好的性能。Pt/CoSn（OH）₆和Pt/ZnSn（OH）₆催化剂的单位质量活性分别为1 095.6 mA/mg和699.5 mA/mg,高于C载Pt（Pt/C）的594.6 mA/mg。利用XRD、SEM、TEM、XPS和电化学测试对催化剂晶体结构和性能间的关系进行了探索。CO溶出实验结果表明,羟基锡酸盐载体有利于Pt表面CO的去除,载体与Pt间的强相互作用和载体表面的大量羟基基团增强了催化剂的催化活性和CO抗毒性。此外,Pt/（Co,Zn）Sn（OH）₆催化剂中单质Pt高的相对含量也有利于提高MOR活性。通过研究载铂羟基锡酸盐电催化氧化甲醇性能,能够揭示载体结构对催化性能的影响,有助于羟基锡酸盐载铂复合催化剂在直接甲醇燃料电池（DMFCs）领域的应用。     

Ti-Zr-V-O复合催化材料的制备及其选择性催化还原NO

采用溶胶凝胶法制备了Ti-Zr-V-O一体化脱硝复合催化材料,研究了锆掺杂对钛钒复合催化材料脱硝活性的影响,采用X 射线衍射（XRD）、扫描电镜（SEM）、能谱分析（EDS）、傅里叶红外光谱（FT-IR）及N₂物理吸附（BET法）等测试手段,分别考察了锆掺杂对钛钒复合氧化物晶型、结晶形貌、组成、官能团结构及比表面积的影响. 实验结果表明,锆掺杂可以稳定锐钛矿晶型,细化晶粒、抑制晶体生长,改变催化剂的结晶形貌,增强固体酸性,从而优化Ti-Zr-V-O复合催化剂的催化性能. 在Ti-Zr-V-O/ATS 陶瓷颗粒整装催化剂存在下,以NH₃为还原剂进行NO的选择性催化还原脱除,锆掺杂明显拓宽了催化活性温度窗口,往高温区偏移100℃;反应温度为300℃时,NO转化率提高了17.3%.     

煅烧温度对钙钛矿复合金属氧化物的结构及其同时催化去除NOx和碳烟的影响

采用简单方便的方法制备了钙钛矿型催化剂La0.8K0.2Cu0.05Mn0.95O3,用程序升温反应的方法评价催化剂同时去除NOx和碳烟的性能,利用XRD、BET和SEM研究煅烧温度对其结构的影响,进而从物理角度分析催化剂性能的影响因素.结果表明,随着煅烧温度的升高,催化剂的晶型更加完美,比表面积和平均孔径都下降,内部的微孔逐渐减少.结合程序升温反应可知,最有利于同时催化去除NOx和碳烟的催化剂的平均孔径为17nm左右.     

水热法制备氧化铬及其常温低浓度一氧化氮催化性能

以十六烷基三甲基溴化铵(CTAB)为模板剂, 氨水为沉淀剂, 通过水热法并焙烧处理合成氧化铬催化剂。采用X射线衍射分析(XRD)、傅里叶变换红外光谱(FT-IR)、X射线光电子能谱(XPS)和透射电镜(TEM)等技术对催化剂的物化性质进行了表征, 并考察常温不同NO初始浓度下氧化铬催化剂的NO氧化性能。结果表明: 在空速为60000 mL/(g·h)和NO浓度为1×10^-6的条件下, 100℃水热温度制备的Cr-100催化剂表现出最优的性能, 常温下NO消除率高达90%以上并保持120 h, 其优异的常温催化性能与催化剂表面较高的Cr⁶⁺/Cr³⁺摩尔比有关。研究结果表明: 催化剂的失活主要是由于硝酸根在催化剂表面的累积而导致催化剂活性中心被覆盖, 低浓度下能减缓硝酸根的积累。     

多孔莫来石纤维陶瓷负载La 1-x Sr x CoO 3（x ＝0.2~0.8）的NO+CO催化研究

采用真空浸渍法制备了多孔莫来石纤维陶瓷负载La1-xSrxCoO3（x=0.2、0.4、0.6、0.8）钙钛矿型催化剂.利用XRD、SEM、BET等对样品进行了表征.通过XRD发现,所制备的La1-xSrxCoO3催化剂除了存在典型的钙钛矿结构外,图谱中还发现了La（OH）3峰,而且随着x值的减小La（OH）3的衍射峰越来越尖锐.由SEM可以观察到载体具有立体网状结构并且负载在载体上的催化剂颗粒分散性较好.BET表明随着x增加,比表面积相应增加.利用一氧化氮（NO）和一氧化碳（CO）对所制备的La1-xSrxCoO3系列载体催化剂的催化活性进行了测试比较,发现当Sr取代量为x=0.2时,La1-xSrxCoO3整体催化活性较好.     

利用含有模板剂的SAPO-34分子筛制备高效铜基催化剂

氮氧化物污染已经成为一个严重的环境问题。利用分子筛催化剂进行选择性催化还原(SCR)处理氮氧化物是最有效的方法之一。为了降低现有催化剂的制备成本, 本工作直接利用含有模板剂的分子筛浆料为原料, 通过预处理、离子交换及一次焙烧的方法制备Cu-SAPO-34催化剂。采用XRD、BET、TG、ICP、XPS、SEM、TPR、TPD及NH₃-SCR等对制备的Cu-SAPO-34样品进行表征, 并对离子交换过程中的pH条件进行了优化。研究结果表明: 利用含模板剂的分子筛浆料制备得到催化剂含有2.43% Cu、立方晶型完整、酸性较强以及催化还原性能优秀。在200~450℃下, NO转化率超过80%, 并且在300℃时转化率达到最高97.8%。与使用商品化SAPO-34制备的催化剂相比, 两者具有相似的微观结构和SCR性能。SAPO-34分子筛中少量模板剂的存在对最终制备得到的Cu-SAPO-34催化剂的性能影响很小。因此采用含有模板剂的分子筛浆料制备高效Cu-SAPO-34催化剂是可行的。     

陈化体系中醇对Ce0.65Zr0.35O2及其负载的单Pd催化剂性能的影响

采用共沉淀法制备了Ce_0.65Zr_0.35O₂(CZ)储氧材料, 分别以乙醇-水、丙醇-水、乙二醇-水、丙三醇-水体系对沉淀物进行陈化, 研究了醇的种类对CZ及其负载的单Pd催化剂性能的影响。对CZ进行了扫描电镜(SEM), N₂-吸脱附分析, 对Pd/CZ进行了粉末X射线衍射(XRD)、X射线光电子能谱(XPS)、储氧量 (OSC)和程序升温还原( H₂-TPR)的表征, 并考察了三效催化性能。结果表明, 醇的种类对CZ及Pd/CZ的性能有显著影响。在乙醇-水和丙醇-水陈化体系中制备的CZ分散性高, 颗粒堆积松散, 比表面积和孔径大, 孔容高, 且具有优异的热稳定性, 其中丙醇-水陈化体系中制备的CZ老化后比表面积和孔容分别可达28 m²/g和0.1 mL/g, 具有最高的热稳定性, 其负载的单Pd催化剂在老化后对C₃H₈、CO和NO转化显著优于乙二醇-水和丙三醇-水陈化体系中制备的CZ所制备的催化剂。     

WO3添加方式对V2O5/TiO2催化剂性能影响

以TiO2为载体,采用挤压成型法制备了钒系蜂窝整体式SCR脱硝催化剂,通过N2吸附-脱附(BET)、X射线衍射(XRD)、扫描电镜(SEM)、FT-Ra-man光谱等表征手段和催化活性测试对混合练泥工序中助催化剂WO3不同引入方式制备的催化剂进行了对比研究。实验结果表明,由钛钨粉制备的催化剂具有较大的比表面积及孔容积;而由偏钨酸铵制备的催化剂具有较均匀的微观结构形貌,活性物种分散性好,拥有更多的VO6八面体结构,且出现了WOx四面体结构,表现出良好的NH3-SCR活性和较宽的活性温度窗口,在空速为10000h-1,氨氮比为1.0时,活性温度范围内NO脱除率达到了93%。     

负载型MoO3／β分子筛催化剂的丙烷氧化脱氢性能

以β分子筛为载体,采用浸渍法负载钼制备了MoO3／β筛催化剂,通过XRD、FTIR、BET、NH3-TPD进行表征,结果表明,样品中有活性组分氧化钼存在,也有不同酸性质的活性位存在,负载量对催化剂的表面积和孔径有影响;考察了催化剂对丙烷氧化脱氢制丙烯的催化性能,结果表明,单纯β分子筛载体有催化活性,不同钼负载量对催化性能有影响,考察负载量区间内反应转化率出现极值。     

A comparative study of catalytic partial oxidation of methane over CeO2 supported metallic catalysts

In the present study, the catalytic partial oxidation of methane (CPOM) over various active metals supported on CeO2 (M/CeO2, M = Ir, Ni, Pd, Pt, Rh and Ru) has been investigated. The catalysts were characterized by X-ray diffraction (XRD), BET surface area, H2-temperature programmed reduction (H2-TPR), CO chemisorption and transmission electron microscope (TEM) analysis. Ir/CeO2 catalysts showed higher BET surface area, higher metal dispersion, small active metal nano-particles (approximately 3 nm) than compared to other M/CeO2 catalysts. The catalytic tests were carried out in a fixed R(mix) ratio of 2 (CH4/O2) in a fixed-bed reactor, operating isothermally at atmospheric pressure. From time-on-stream analysis at 700 degrees C for 12 h, a high and stable catalytic activity has been observed for Ir/CeO2 catalysts. TEM analysis of the spent catalysts showed that the decrease in the catalytic activity of Ni/CeO2 and Pd/CeO2 catalysts is due to carbon formation whereas no carbon formation has been observed for Ir/CeO2 catalysts.     

Synthesis and characterization of catalysts produced from paper mill sludge. I. Determination Of NOx removal capability

Characteristics and catalytic properties of a series of carbon-based catalysts (CBCs) produced from paper mill sludge were evaluated. The major processes involved in the production of the catalysts were chemical activation, impregnation, pyrolysis, and post pyrolysis rinsing. The porous structure, catalytic activity and thermostability of the catalysts were tailored during the production stage by introducing hetero-atoms (zinc chloride, and ferric nitrate) in the carbon structure. Characterization of the produced CBCs included determination of the surface area, pore size, and pore size distribution (PSD) from standard N₂-adsorption isotherm data. The extent of graphitization and the presence of metal crystals were identified from X-ray diffraction (XRD). The limit of the catalyst gasification was estimated from thermogravimetric analysis (TGA) conducted in an oxidized environment. The NO_x reduction capability of the produced catalysts was evaluated in the presence of carbon monoxide using a fixed bed reactor. The reaction temperature ranged from 300 to 500°C. It was shown that paper mill sludge is an excellent precursor for the production of CBCs with NO_x removal capability of 66–94%. The catalytic capability of the produced CBCs varied according to the method of production, catalyst surface properties (surface area, pore structure, PSD), metal composition and reaction temperature. The highest NO_x removal capacity was observed for the catalytic reactions carried out at 400°C. The mesoporous catalyst produced with a Zn:Fe molar ratio of 1:0.5 exhibited the maximum NO_x removal catalytic activity of 94%.     

n（Zn）/n（Zr）对催化剂CuO-ZnO-ZrO2的结构及其合成甲醇性能的影响

采用并流沉淀法制备了一系列不同n(Zn)/n(Zr)时的CuO-ZnO-ZrO2甲醇合成催化剂,运用X射线衍射仪(XRD)、N2物理吸附(BET)和H2程序升温还原(H2-TPR)等手段对催化剂进行了表征分析。在固定床反应器中进行CO2加H2合成甲醇的活性评价研究,考察了n(Zn)/n(Zr)在催化剂中的作用。结果表明,当n(Zn)/n(Zr)=4/1时,CO2转化率最高;当n(Zn)/n(Zr)=1/4时,甲醇的选择性最好;当n(Zn)/n(Zr)=4/1或1/4时,有效降低了副产物CO的含量,此时的甲醇催化活性最好。     

Aqueous phase reforming of glycerol over the Pd loaded Ni/Al2O3 catalysts

Bifunctional catalysts containing (0.5-1.5 wt%) palladium and 15 wt% of Nickel supported on gamma-Al2O3 were prepared via an impregnation technique and catalysts were characterzed by XRD BET surface area and SEM, respectively. The aqueous phase reforming of glycerol (APR) was conducted over alumina-supported catalysts at different reaction conditions for catalytic activity. Finally, we concluded that the 1.0 wt% Pd 15 wt% Ni/gamma-Al2O3 catalyst evidences higher conversion, hydrogen selectivity, lower alkane selectivity and CO production. This indicate that Pd loaded Ni/gamma-Al2O3 could be a potential catalyst for the APR of glycerol.     

Electrochemical EDTA recycling after soil washing of Pb, Zn and Cd contaminated soil

Recycling of chelant decreases the cost of EDTA-based soil washing. Current methods, however, are not effective when the spent soil washing solution contains more than one contaminating metal. In this study, we applied electrochemical treatment of the washing solution obtained after EDTA extraction of Pb, Zn and Cd contaminated soil. A sacrificial Al anode and stainless steel cathode in a conventional electrolytic cell at pH 10 efficiently removed Pb from the solution. The method efficiency, specific electricity and Al consumption were significantly higher for solutions with a higher initial metal concentration. Partial replacement of NaCl with KNO₃ as an electrolyte (aggressive Cl⁻ are required to prevent passivisation of the Al anode) prevented EDTA degradation during the electrolysis. The addition of FeCl₃ to the acidified washing solution prior to electrolysis improved Zn removal. Using the novel method 98, 73 and 66% of Pb, Zn and Cd, respectively, were removed, while 88% of EDTA was preserved in the treated washing solution. The recycled EDTA retained 86, 84 and 85% of Pb, Zn and Cd extraction potential from contaminated soil, respectively.     

Pd-ZrO2/Al2O3催化剂对丙烯选择性催化还原NO的催化活性研究

采用浸渍法制备了具有高比表面积的氧化铝负载的Pd-ZrO2复合物催化剂(Pd-ZrO2/Al2O3),利用BET、XRD、TEM等手段研究了该复合物催化剂的物理特性,并重点研究了该复合物催化剂对以C3H6为还原剂选择性催化还原(SCR)NO的催化反应活性,分别讨论了反应温度、组分、焙烧温度、原料气组分、空速等因素对该催化反应的影响.结果发现,少量的Pd纳米粒子均匀分散于载体氧化铝上,添加适量ZrO2后,所制备的低负载量的Pd(1wt%)-ZrO2(2wt%)/Al2O3复合物催化剂具有较高的NO选择性催化还原反应活性,在240～250℃可使NO的转化率达到50%～70%.其活性提高的机制在于适量ZrO2的添加增强了反应物中NO和C3H6在催化剂表面的吸附,同时与Pd催化剂形成一种协同催化作用.     

The effect of Nd on the properties of ceria-zirconia solid solution and the catalytic performance of its supported Pd-only three-way catalyst for gasoline engine exhaust reduction

A series of ceria-zirconia-neodymia mixed oxides with different contents of neodymia and the supported Pd-only three-way catalysts before and after aging have been prepared and characterized. The influence of Nd doping on the structural/textural properties of ceria-zirconia (CZ) and the effect on the three-way catalytic performance are also investigated. The results demonstrate that the addition of neodymia results in the formation of ceria-zirconia-neodymia ternary solid solution (CZN) with better textural and structural properties as well as improved reducibility and redox behavior, leading to the promoted three-way catalytic activity and enlarged air/fuel operation window. The modified solid solution with 5 wt.% neodymia shows the preferable textural/structural properties considering that the capacity of foreign cation is limited in the crystal lattice of ceria-zirconia solid solution, and Pd/CZN5 shows the optimum three-way catalytic performance and wider air/fuel operation window, especially for the corresponding aged one.     

In-situ synthesis and characterizations of Bi2(O,S)3/Zn(O,S) composites for visible light hexavalent chromium reduction

Heterojunction construction with low band gap materials is an effective way of utilizing UV light active materials under visible light irradiation. Here, we report the synthesis of Bi₂(O,S)₃/Zn(O,S) heterostructure using simple solvothermal method without surfactant. The catalysts were investigated with different characterization techniques. All the composite catalysts showed high light absorption capacity in the whole visible light spectrum. The catalytic activity of the catalysts was evaluated by Cr(VI) reduction. While pure Zn(O,S) catalyst showed no significant Cr(VI) reduction, higher photocatalytic activity than individual components were exhibited after heterojunction construction with Bi₂(O,S)₃. 20-BiZnOS catalyst with Bi/Zn molar percentage of 20% showed the best photocatalytic activity among the composites with 99.5% Cr(VI) reduction within 12 min under visible light irradiation. Heterojunction formation between Bi₂(O,S)₃ and Zn(O,S) nanoparticle, and selective adsorption of Cr(VI) and desorption of Cr(III) on the surface of 20-BiZnOS composite catalyst were ascribed to the enhanced photocatalytic activity of the composite catalyst.     

球形活性炭担载MnOx-CeO2和三聚氰胺的低温脱硝行为研究

以MnO_x-CeO₂为活性组分, 以三聚氰胺为还原剂, 制备了球形活性炭(SAC)担载MnO_x-CeO₂和三聚氰胺的复合催化剂, 并考察了该催化剂在低温下(120~180℃)对NO的选择性催化还原(SCR)反应行为。实验还利用扫描电子显微镜-能谱仪(SEM-EDS)、X射线衍射(XRD)和低温N₂吸附法等技术对催化剂进行了表征。结果表明, 当反应温度为180℃、空速为6000 h^-1、NO和O₂浓度分别为0.1%和8%时, 担载8% Mn(摩尔比Mn:Ce固定为1:1)和10%三聚氰胺的催化剂可在8.8 h内实现99%的NO_x转化率。煅烧温度高于400℃将促使MnO_x-CeO₂形成更大的晶体颗粒和更加规整的晶型结构, 从而降低其melamine-SCR活性。三聚氰胺担载量高于15%将造成催化剂比表面积和孔容的急剧减小, 最终导致其稳态NO_x转化率的下降。而金属氧化物担载量的增加和反应温度的升高都有利于Melamine-SCR反应, 且在较宽的NO和O₂浓度范围内, 催化剂的稳态NO_x转化率都能维持在99%左右。     

K2MnAl11O19六铝酸盐催化剂的制备及其催化甲烷燃烧性能的研究

采用共沉淀法、溶胶-凝胶法和反相微乳液法制备六铝酸盐催化剂K2MnAl11O19,利用XRD、BET和TG-DTA技术及甲烷燃烧活性对催化剂进行了表征和活性验证。结果表明,3种方法所制备催化剂经1200℃焙烧4h后均可以形成完整的六铝酸盐晶型,同时都具有高的催化性能和高温稳定性,其中反相微乳液法制备的K2MnAl11O19催化剂具有较高的比表面积和甲烷催化燃烧活性,起燃温度T10%=458℃,至676℃(T90%)甲烷完全转化。