不同还原温度制备的石墨烯作为载体对甲酸电催化性能的影响

采用纳米石墨为原料,以3种不同还原温度80,60和40℃分别制得石墨烯GN-1、GN-2和GN-3。用3种不同还原温度制备的石墨烯作为载体制备了Pd催化剂Pd/GN-1、Pd/GN-2和Pd/GN-3。发现这3种钯催化剂Pd/GN-1、Pd/GN-2和Pd/GN-3中,Pd/GN-1具有最大的电化学比表面积,对甲酸的电催化氧化活性也最高,而Pd/GN-2电催化剂对甲酸电催化氧化的稳定性最好。     

Pd-Cu/γ-Al_2O_3双金属催化剂脱除水中硝酸盐

采用分步浸渍法和共浸渍法制备系列Pd负载质量分数为1%的Pd-Cu/γ-Al2O3双金属催化剂,以氢气为还原剂研究其对水中硝酸盐催化脱除的性能。结果表明,催化剂中Cu与Pd物质的量比以及Cu、Pd的浸渍顺序对催化剂性能有重要影响,硝酸根转化率随着Cu与Pd物质的量比的增大而增大;硝酸根转化活性以Cu与Pd物质的量比为5∶1、先浸渍Pd再浸渍Cu所得催化剂较优;从氨氮选择性方面看,以先浸渍Cu后浸渍Pd制备的催化剂选择性较低,在Cu与Pd物质的量比为1∶1、先浸渍Cu再浸渍Pd所得催化剂较优。     

微乳法制备Pd-Cu双金属催化剂

选择Cu为助剂,采用微乳法分别优选具有较好稳定性的Cu和Pd微乳液体系,并将Cu和Pd依次负载于Al_2O_3载体上,经干燥、活化和还原制备了Pd-Cu/Al_2O_3催化剂。采用原位IR、CO化学吸附和HRTEM等对催化剂进行表征,结果表明,与常规溶液负载法制备的Pd-Ag/Al_2O_3催化剂相比,采用微乳法降低了催化剂表面酸性,提高了活性组分Pd分散度,Pd粒径分布更为均匀。在750 mL加氢反应器中,采用C_2后加氢原料对催化剂性能进行评价,结果表明,与常规溶液负载法相比,微乳法制备的催化剂在反应温度低4℃条件下,乙炔转化率相当,选择性高9.9个百分点,绿油生成量较低。微乳法制备Pd-Cu双金属催化剂具有良好的工业应用前景。     

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。     

生物还原法制备负载型Pd-Cu合金催化剂及催化Suzuki反应

以无花果（FL）树叶提取液作为还原剂、稳定剂,以树叶残渣（RFL）为载体,制备了负载型纳米钯铜合金催化剂（Pd Cu/RFL）。采用XRD、FT-IR、TEM、XPS、N₂-吸附脱附等手段对制备的Pd Cu/RFL催化剂进行了表征,并研究了其催化Suzuki偶联反应的性能。Pd4Cu1NPs的粒径分布在2.31～6.62nm之间,平均粒径为3.97nm,均匀地分散在载体RFL表面。Pd与Cu间的电子转移和Pd4Cu1NPs与载体表面上含氧含氮官能团的络合不仅提高了Pd Cu/RFL催化Suzuki偶联反应活性,也改善了催化剂的稳定性。当Pd的加入量为反应底物的0.06mol%时,催化对溴硝基苯和苯硼酸的反应收率可以达到97.00%,催化剂重复使用9次后,收率仍可以保持在93%以上。     

乙醇中硝酸还原工艺条件及Pd-Cu催化剂研究

在间歇反应釜中进行了硝酸催化还原实验,考察了NO体积浓度、气体流量、反应温度和反应时间对硝酸转化率的影响。发现硝酸的转化率随原料气NO的浓度、反应时间及反应温度的增加而增大,气体流量增大,硝酸转化率先增大后趋于稳定。同时采用浸渍法制备了单金属Pd和双金属Pd-Cu催化剂,考察了催化剂焙烧温度及载体类型对催化剂催化性能的影响。结果表明,Cu离子的引入能够增强催化活性,较高的焙烧温度不利于硝酸的还原,以活性炭为载体制备的催化剂催化效果最佳。     

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。     

三氟三氯乙烷加氢脱氯Pd-Cu催化剂失活分析

以活性炭为催化剂载体,采用浸渍法制备Pd、Cu、Pd-Cu三种催化剂,将催化剂应用于三氟三氯乙烷(CFC-113)加氢脱氯制三氟氯乙烯(CTFE)的反应,考察Cu的引入对Pd催化剂性能的影响。对反应前后及再生的Pd-Cu催化剂进行X射线衍射(XRD)、X射线光电子能谱(XPS)、氮气吸附-脱附(BET)、氢气程序升温还原(H₂-TPR)、热重(TG)、氨气程序升温脱附(NH₃-TPD)等表征分析。研究表明,Pd催化剂具有较高的加氢脱氯性能,其主要产物为三氟乙烷,Cu的加入有利于提高CTFE的选择性。这应与Cu、Pd之间存在相互作用并形成合金,抑制了Pd的脱氯性能有关。反应后的催化剂存在表面结焦、反应过程中吸附Cl以及金属Cu价态变化和迁移等现象,其中表面高沸物的形成、卤元素吸附导致的金属迁移和Cu-Pd相互作用的改变是Pd-Cu催化剂失活的主要原因。     

炭负载Pd/Sm双金属催化剂对Heck反应催化性能研究

通过简便的一步法制备了炭负载Pd/Sm双金属催化剂(C-Pd/Sm),利用Pd/Sm双金属催化剂的协同效应提高对Heck反应的催化效率。利用所制备的C-Pd/Sm催化碘苯与丙烯酸的Heck反应,结果显示,在温度为120℃、三丁胺为碱,DMF为溶剂,时间为5 h的反应条件下,催化剂对Heck反应具有较高的催化效率。另外,CPd/Sm能够催化反应活性较低的溴苯和氯苯与丙烯酸的Heck芳基化反应。     

炭负载Pd/Sm双金属催化剂对Heck反应催化性能研究

通过简便的一步法制备了炭负载Pd/Sm双金属催化剂(C-Pd/Sm),利用Pd/Sm双金属催化剂的协同效应提高对Heck反应的催化效率。利用所制备的C-Pd/Sm催化碘苯与丙烯酸的Heck反应,结果显示,在温度为120℃、三丁胺为碱,DMF为溶剂,时间为5 h的反应条件下,催化剂对Heck反应具有较高的催化效率。另外,CPd/Sm能够催化反应活性较低的溴苯和氯苯与丙烯酸的Heck芳基化反应。     

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。     

Preparation,characterization and kinetic behavior of supported copper oxide catalysts on almond shell-based activated carbon for oxidation of toluene in air

Dispersed copper oxide nano-catalysts supported on almond shell-based activated carbon were prepared for catalytic oxidation of toluene in air. The response surface methodology was used to express the catalyst removal efficiency in terms of catalyst metal loading and calcination temperature. Catalyst activity increased with both increasing calcination temperature and metal loading. Calcination temperature had a significant effect on the catalyst activity only at high metal loadings. Two different catalyst preparation methods were employed to investigate the effect of impregnation technique on the deposition–precipitation method. Well-dispersed nano catalysts with higher efficiency towards oxidation of toluene were prepared by the heterogeneous deposition–precipitation (HDP) as compared with the combined impregnation and deposition–precipitation method. The support and catalyst properties were determined by X-ray diffraction, Transmission electron microscopy, field-emission scanning electron microscope, Boehm test, Brunauer–Emmett–Teller surface area measurements, and energy-dispersive X-ray spectroscopy. Characterization analyses and reaction experiments indicated the antonym effect of impregnation method on the deposition–precipitation method for catalyst preparation. Two types of crystallite (large and small) were formed on the support as a consequence of using the combined catalyst preparation method. Kinetic models were proposed for oxidation of toluene using copper oxide catalysts prepared by the HDP method. The kinetic study indicated that an Eley–Rideal mechanism could adequately describe the kinetic behavior of toluene oxidation.     

Catalytic enhancement of platinum supported on zeolite beta for toluene hydrogenation by addition of palladium

This work focused on the preparation, characterization and catalytic performance of a bimetallic platinum–palladium catalyst for toluene hydrogenation. A catalyst with 3 wt% loading of each metal was prepared by co-impregnation on zeolite beta in proton form and denoted as 3Pt3Pd/HBEA. The structure of HBEA was retained after catalyst preparation and the metal occupied strong acidic sites of the zeolite. Compared to monometallic 3Pt/HBEA, the 3Pt3Pd/HBEA exhibited smaller Pt particle size due to better dispersion on the support. The catalytic performance of the bimetallic catalyst at various temperatures indicated that the presence of Pd enhanced toluene hydrogenation of Pt catalyst at high temperature. The most suitable temperature for toluene hydrogenation on 3Pt3Pd/HBEA was 150 °C for which a complete toluene conversion was obtained with methylcyclohexane as the only product.     

CFC-115加氢脱氯制HFC-125 Pd/C催化剂制备研究

以商品化活性炭为载体、贵金属Pd为活性组分,采用浸渍法制备了一系列Pd/C催化剂.在常压固定床微型反应器中,以CFC-115加氢脱氯生产臭氧消耗物质(ODS)替代品HFC-125为目标反应,评价了催化剂的性能.详细考察了载体预处理硝酸浓度、载体粒径、Pd源前驱体及溶剂等制备条件对其催化性能的影响.在研究的范围内,采用粉末活性炭为载体,Pd(NO_3)_2为Pd源,甲醇为溶剂制备的催化剂具有最好的催化性能.     

Surfactant free RGO/Pd nanocomposites as highly active heterogeneous catalysts for the hydrolytic dehydrogenation of ammonia borane for chemical hydrogen storage

In this study, monodisperse palladium (Pd) nanoparticles on reduced graphene oxide (RGO) surfaces were successfully prepared by a "wet" and "clean" method in aqueous solution. Without any surface treatment, Pd nanoparticles are firmly attached to the RGO sheets. These RGO/Pd nanocomposites exhibited catalytic activity in hydrogen generation from the hydrolysis of ammonia borane (AB). Their hydrolysis completion time and activation energy were 12.5 min and 51 ± 1 kJ mol(-1), respectively, which were comparable to the best Pd-based catalyst reported. The TOF values (mol of H(2)× (mol of catalyst × min)(-1)) of RGO/Pd is 6.25, which appears to be one of the best catalysts reported so far. We also obtained a (11)B NMR spectrum to investigate the mechanism of this catalytic hydrolysis process. This simple and straightforward method is of significance for the facile preparation of metal nanocatalysts with high catalytic activity on proper supporting materials.     

A Facile Diethylene Glycol Reduction Method for the Synthesis of Ultrafine Pd/C Electrocatalyst with High Electrocatalytic Activity for Methanol Oxidation

The high‐quality carbon supported Pd nanoparticles (Pd/C) composites have wide applications in catalysis. In this work, we demonstrate an efficient diethylene glycol (DEG) reduction method for the synthesis of a Pd/C catalyst with high dispersion and small particle size. During the synthesis, no surfactants and halogen ions are introduced in the reaction system, and DEG efficiently acts as solvent and reducing agent, which results in a “clean” Pd surface. Meanwhile, compared to the classic ethylene glycol (EG) reduction method, the present DEG reduction method can produce the high‐quality Pd/C composites. As a result, the as‐prepared Pd/C electrocatalyst exhibits a large electrochemical active surface area and good electrocatalytic performance for the methanol oxidation reaction in an alkaline media, due to the high dispersion and small particle size. This result indicates the as‐prepared Pd/C electrocatalyst has potential applications in alkaline direct methanol fuel cells.     

助剂对莫西沙星侧链合成用钯炭催化剂性能的影响

采用浸渍法制备不同助剂的钯炭催化剂,考察不同金属硝酸盐、酸根离子和甲酸镍用量对莫西沙星侧链合成用钯炭催化剂的影响。结果表明,助剂镍能够提高催化剂催化活性,助剂甲酸镍用量为钯物质的量的15%时,产物收率达96%。不同酸根离子对催化剂催化活性产生一定影响。     

Enhanced electrocatalytic reduction of aqueous nitrate by modified copper catalyst through electrochemical deposition and annealing treatment

Copper has been intensively investigated as an electrocatalyst for electrochemical reduction of aqueous nitrate. Here we report preparation of Cu electrocatalyst by electrochemical deposition of Cu on Ni foils, annealing treatment to produce nanograins of Cu oxides and electroreduction to form metallic Cu nanograins to enhance the catalytic activities of nitrate reduction. The prepared Cu electrocatalysts were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. The electrochemical deposition of Cu on Ni substrates produced different sizes and sharp-edged microcrystal of Cu, and the annealing treatment at 300°C transformed these microcrystals into uniform spheroids of Cu oxides in sizes of 150–350?nm. The potentiostatic electrolysis of aqueous nitrate showed that the annealing treatment improved nitrate reduction efficiency by 4.5 times and 20% at ?0.8 and ?1.4?V versus the saturated calomel electrode, respectively. The rate and Faradaic efficiency for nitrate reduction by modified Cu electrode remained constant within a testing time of 48?h. The results demonstrate that electrochemical deposition on Ni foils and subsequent annealing treatment provide a simple and cost-effective approach to enhance the catalytic activity and stability of a transition metal catalyst.     

The synergic effects of highly selective bimetallic Pt-Pd/SAPO-41 catalysts for the n-hexadecane hydroisomerization

The hydroisomerization of n-hexadecane over Pt-Pd bimetallic catalysts is an effective way to produce clean fuel oil. This work reports a useful preparation method of bimetallic bifunctional catalysts by a co-impregnation or sequential impregnation process. Furthermore, monometallic catalysts with loading either Pt or Pd are also prepared for comparison. The effects of the metal species and impregnation order on the characteristics and catalytic performance of the catalysts are investigated. The catalytic test results indicate that the maximum iso-hexadecane yield over different catalysts increases as follows: Pt/silicoaluminophosphate SAPO-41iso-hexadecane yield of 89.4% when the n-hexadecane conversion is 96.3%. Additionally, the Pt-Pd/SAPO-41 catalyst also presents the highest catalytic activity and best stability even after 150 h long-term tests.