Oxidation of glyoxal to glyoxylic acid by oxygen over V2O5/C catalyst

A novel vanadium oxide catalyst supported on active carbon was prepared by an incipient wetness impregnation method, and the precursor was obtained from oxalic acid aqueous solutions of NH4VO3. The catalyst was applied liquid phase oxidation of glyoxal to glyoxylic acid. It was found that V2O5/C catalyst exhibited obvious activity for glyoxal oxidation. Glyoxylic acid could be obtained without pH regulation during the reaction. By using this catalyst, the conversion of glyoxal and the yield of glyoxalic acid were 29.2% and 13.6%, respectively at 313 K and oxygen flow 0.1 L/rain after reaction for 10 h.     

Preparation of Pt／C Catalyst with a New and Simple Organic Sol Method

It is reported for the first time that the Pt/C catalyst can be prepared with a new and simple organic sol method using SnCl2 as the reductant. It was found that the average size of the Pt particles in the Pt/C catalysts could be controlled with controlling the preparation conditions. The effect of the average sizes of the Pt particles in the Pt/C catalysts obtained with this method on the electrocatalytical activity of the oxidation of methanol was investigated.     

SC-IrO2NR-carbon hybrid: A catalyst with high electrochemical stability for oxygen reduction

The enhanced electrochemical stability of the synthesized hybrid catalyst has been demonstrated by the introduction of the synergistic effect between carbon powder additive and the prepared catalyst.Single crystal IrO 2 nanorod (SC-IrO 2 NR) catalyst was prepared by a sol-gel method.The structure and performance of the catalyst sample were characterized by X-ray diffraction spectroscopy (XRD),scanning electron microscope (SEM),transmission electron microscope (TEM),rotating disk electrode (RDE) and cyclic voltammetry (CV) measurements.XRD patterns and TEM images indicate that the catalyst sample has a rutile IrO 2 single crystal nanorod structure.The onset potential for oxygen reduction reaction (ORR) of the SC-IrO 2 NR-carbon hybrid catalyst specimen is 0.75 V (vs.RHE) in RDE measurement.CV and RDE test results show that the SC-IrO 2 NR-carbon hybrid catalyst has a better electrochemical stability in comparison with the commercial Pt/C catalyst,with attenuation ratios of 17.67% and 44.60% for the SC-IrO 2 NR-carbon hybrid catalyst and the commercial Pt/C catalyst after 1500 cycles,respectively.Therefore,in terms of stability,the SC-IrO 2 NR-carbon hybrid catalyst has a promising potential in the application of the proton exchange membrane fuel cell.     

Production of gasoline range hydrocarbons from methanol on hierarchical ZSM-5 and Zn/ZSM-5 catalyst prepared with soft second template

Nano hierarchical mesoporous ZSM-5 catalysts were prepared with cationic dimethyldiallyl ammonium chloride acrylamide copolymer(PDDA) as a soft second template. Using ZSM-5 catalyst as a matrix,Zn/ZSM-5 catalysts were also obtained by the wet impregnation method. The effect of the PDDA amount and Zn loadings on the properties of the catalysts,including crystallinity,morphology,textural properties,acid nature and catalytic activity in MTG reaction,was investigated by XRD,FESEM,TEM,Nitrogen adsorption–desorption isotherms and NH3-TPD method,respectively. The MTG reaction was performed in a fixed bed reactor,and the result revealed that the nano hierarchical ZSM-5 catalyst prepared with a PDDA/Si molar ratio of 0.070 possesses longer stable phase of 70 h with a liquid hydrocarbon selectivity of 29.8%.Zn/ZSM-5 catalyst with a Zn/ZSM-5 ratio of 0.07 wt.% shows the highest liquid hydrocarbon selectivity,reaching 62.5%.     

Supported ionic liquid phase-boosted highly active and durable electrocatalysts towards hydrogen evolution reaction in acidic electrolyte

Platinum is generally known as the most effective electrocatalyst for hydrogen evolution reaction because it can greatly lower the overpotential and accelerate the reaction kinetics,while its commercial potential always suffers from scarcity,high cost,low utilization,and poor durability particularly in acidic electrolytes.We herein demonstrate a facile method to improve the hydrogen evolution performance of Pt-based electrocatalysts by simply decorating the-state-of-the-art and commercially available Pt/C with hydrophobic protic([DBU][NTf2])or aprotic([BMIm][NTf2])ionic liquid.The current densities of[BMIm]@Pt/C and[DBU-H]@Pt/C with 10% ionic liquid at an overpotential of 40 mV are 2.81 and 4.15 times,respectively,higher than that of the pristine Pt/C.More importantly,ionic liquid-decoration significantly improves the long-term stability of Pt nanoparticles.After 8 h of chronoamperometric measurements,[DBU-H]@Pt/C and[BMIm]@Pt/C can still retain 83.7% and 78.3% of their original activity,respectively,which is much higher than that of the pristine Pt/C(24.4%).The improved performance of Pt/C decorated with ionic liquid is considered to arise from the improved proton conductivity(particularly for protic ionic liquid)and hydrophobic microenvironment created by the supported ionic liquid phase.The presence of ionic liquid layer not only de-coordinates H+from hydronium ions nearby the Pt nanoparticles,but it also protects Pt nanoparticles from dissolution in the acidic media.     

Characterization and Catalytic Activity of Titanium－containing Aluminum Phosphate Prepared by Sol－gel and Nonuniform Precipitation for O－Alkylation of Catechol with Ethanol

Three titanium-containing aluminum phosphate catalysts with a general formula A10.77Ti0.23PO4 were prepared by the sol-gel method at room temperature(APTS), and a nonuniform precipitation procedure at roomtemperature (APTR) and under reflux(APTF), respectively. The structural features and the surface properties of the three catalysts were determined by means of the physical adsorption of nitrogen at liquid N2 temperature, XRD, UV-Vis, NH3-TPD and IR of adsorbed pyridine. The vapor phase O-alkylation of catechol with ethanol over the prepared catalysts was studied. It was found that the activity and the selectivity of these catalysts are greatly dependent on the preparation method, and catalyst APTF shows the highest activity and selectivity. The characterization evidence indicates that the weak Bronsted acid sites were more effectivo tive for the reaction.     

A Novel Catalyst for Liquid Phase Hydrogenation of m-Dinitrobenzene to m-Phenylenediamine

A novel lanthana-promoted nickel catalyst supported on silica for the liquid phase hydrogenation of m-dinitrobenzene to m-phenylenediamine was prepared by an incipient wetness sequential impregnation method. It was found that Ni-La/SiO2 catalyst exhibited high activity and stability for m-dinitrobenzene hydrogenation. Over this catalyst, the conversion of m-dinitrobenzene and the yield of m-phenylenediamine were up to 97.1% and 93.5%, respectively,at 373 K and 2.6 MPa hydrogen pressure after reaction for 1 h.     

Boosting selectivity and stability on Pt/BN catalysts for propane dehydrogenation via calcination & reduction-mediated strong metal-support interaction

Propane dehydrogenation(PDH) provides an alternative route for producing propylene. Herein, we demonstrates that h-BN is a promising support of Pt-based catalysts for PDH. The Pt catalysts supported on h-BN were prepared by an impregnation method using Pt(NH₃)₄(NO₃)₂ as metal precursors. It has been found that the Pt/BN catalyst undergoing calcination and reduction is highly stable in both PDH reaction and coke-burning regeneration, together with low c...     

Catalytic methanation reaction over alumina supported cobalt oxide doped noble metal oxides for the purification of simulated natural gas

A series of alumina supported cobalt oxide based catalysts doped with noble metals such as ruthenium and platinum were prepared by wet impregnation method.The variables studied were difference ratio and calcination temperatures.Pt/Co(10∶90)/Al2O3 catalyst calcined at 700 ℃ was found to be the best catalyst which able to convert 70.10% of CO2 into methane with 47% of CH4 formation at maximum temperature studied of 400 ℃.X-ray diffraction analysis showed that this catalyst possessed the active site Co3O4 in face-centered cubic and PtO2 in the orthorhombic phase with Al2O3 existed in the cubic phase.According to the FESEM micrographs,both fresh and spent Pt/Co(10∶90)/Al2O3 catalysts displayed small particle size with undefined shape.Nitrogen Adsorption analysis showed that 5.50% reduction of the total surface area for the spent Pt/Co(10∶90)/Al2O3 catalyst.Meanwhile,Energy Dispersive X-ray analysis(EDX) indicated that Co and Pt were reduced by 0.74% and 0.14% respectively on the spent Pt/Co(10∶90)/Al2O3catalyst.Characterization using FT-IR and TGA-DTA analysis revealed the existence of residual nitrate and hydroxyl compounds on the Pt/Co(10∶90)/Al2O3 catalyst.     

Polystyrene-supported chloroaluminate ionic liquid as a new heterogeneous Lewis acid catalyst for Knoevenagel condensation

Non-hygroscopic polystyrene-supported chloroaluminate ionic liquid was prepared from the reaction of Memfield resin with 1- methylimidazole followed by reaction with aluminum chloride.This Lewis acidic ionic liquid is environmentally friendly heterogeneous catalyst for the Knoevenagel condensation of aromatic and aliphatic aldehydes with ethyl cyanoacetate.The catalyst is stable(as a bench top catalyst) and reusable.     

固相反应制备的Pt/C催化剂对乙醇氧化的电催化活性

用固相反应法制备了Pt/C催化剂(Pt/C(s))，并研究了该催化剂对乙醇氧化的电催化活性. XRD和TEM测量表明， Pt/C(s)中Pt的平均粒径为3.8 nm，结晶度为2.38，远小于用传统的液相还原方法制得的Pt/C催化剂(Pt/C(l))的平均粒径(8.5 nm)和结晶度(5.56).因此, Pt/C(s)对乙醇的电催化氧化性能远好于液相还原法制得的Pt/C(l).     

固相反应法制备Pt-Ru/C催化剂对乙醇氧化的电催化活性研究

0引言近年来,直接甲醇燃料电池(DMFC)由于其燃料来源丰富、价格低廉、甲醇携带和储存安全方便等独特的优越性而越来越受到重视[1]。但是甲醇具有一定的毒性,因此要想实现DMFC在诸如手机、笔记本电脑以及电动车等可移动电源领域的应用,必须探索新的液体燃料以替代有毒性的甲醇。     

Pt单层修饰Pd/C氧还原催化剂

分别利用液相热解法和浸渍还原法制备了碳载钯纳米催化剂（Pd/C）,并研究了其对氧还原反应的电催化活性。与浸渍还原法相比,液相热解法得到的Pd/C催化剂虽然粒径较大,但表现出较好的氧还原反应（ORR）活性和稳定性.在所制备的Pd/C催化剂基础上,通过置换欠电势沉积的Cu原子单层,获得了Pt单层修饰的Pd/C催化剂,其ORR活性较Pd/C催化剂有显著提高,且与纯Pt/C催化剂接近,而其耐久性则较纯Pt/C催化剂有显著提升,显示出Pt单层催化剂的潜在优势.     

甲醇在Pt/C和Pt/WO3/C电极上的电氧化

用液相还原法制备碳载Pt(Pt/C)和碳载Pt/WO3(Pt/WO3/C)催化剂.实验表明该催化剂中加入一定量的WO3后,其对甲醇的催化氧化活性和稳定性都有一定提高,并以Pt、W原子比为1∶1的催化剂性能最好.这是由于Pt催化剂中加入了WO3后,其电化学活性比表面积增大,并且降低了对CO吸附强度.     

Effect of thermal treatment on phase composition and ethanol oxidation activity of a carbon supported Pt50Sn50 alloy catalyst

A carbon supported Pt–Sn electrocatalyst in the Pt/Sn atomic ratio 50:50 was prepared by the reduction of Pt and Sn precursors with formic acid and thermally treated at 200 °C (i.e., in the presence of solid tin) and 500 °C (in the presence of molten tin) in flowing hydrogen. In the absence of thermal treatment, X-ray diffraction (XRD) analysis showed a solid solution of Sn in the face centered cubic (fcc) Pt and SnO₂. After thermal treatment, the formation of a main phase of hexagonal PtSn (niggliite) and a secondary phase of cubic Pt₃Sn was observed in the Pt50Sn50 catalyst. The relative amount of the PtSn phase increased with increasing thermal treatment temperature. The presence of molten tin gave rise to the formation of some big particles during annealing at 500 °C. The activity for the ethanol oxidation reaction (EOR) of the as-prepared catalyst was higher than that of both thermally treated catalysts and Pt75Sn25/C and Pt50Ru50/C by E-TEK. The higher activity for the EOR of the as-prepared Pt–Sn catalysts was ascribed to the presence of a large amount of SnO₂. Dedicated to Teresa Iwasita’s 65th birthday.     

无机胶体法制备Pt/C催化剂及其性能表征

采用无机胶体法制备用于质子交换膜燃料电池(PEMFC)的Pt/C催化剂。研究了影响PtO₂胶体生成和稳定性的因素(溶液的pH值、浓度和温度条件等)以及不同还原剂浓度对Pt/C催化剂性能的影响。透射电子显微镜测试结果表明，采用经优化的工艺条件所制备的Pt/C催化剂平均粒径为3 nm，且分散性好、粒度均匀。X-射线衍射分析表明，催化剂中Pt(111)晶面的相对含量较高，有利于加速氧还原反应。单体PEMFC的电压/电流密度曲线测试表明，所制备的Pt/C催化剂具有良好的电化学性能。     

Pt纳米催化剂在质子交换膜燃料电池催化层中的尺寸效应研究

以XC-72碳黑为载体, H2[PtCl6]为前驱体, 采用浸渍还原法并结合后续高温处理, 制备出不同尺寸Pt颗粒(3～8 nm)的Pt/C催化剂. 在基于质子交换膜燃料电池(PEMFC)单电池的电化学电解池中, 对实际PEMFC催化层中燃料电池反应的Pt催化剂尺寸效应进行了研究. 结果表明, 在PEMFC催化层环境中, Pt/C纳米催化剂对氢氧化和氧还原反应均有显著的粒度尺寸效应. 随着Pt粒度减小, 氢氧化和氧还原反应的表面积活性均降低.     

有序介孔碳材料负载铂纳米粒子：用于硝基苯及其衍生物液相催化氢化的高效催化剂

介孔碳材料由于具有规整的孔道结构、表面疏水性、化学惰性、大的比表面积和大的孔体积等特点,在催化领域的应用备受关注,不仅可以直接用作催化剂,还可以作为催化剂载体负载金属活性中心并用于催化反应.介孔碳材料作为载体用于加氢反应已有报道,并且其催化活性明显优于活性炭材料.有序介孔碳材料的代表之一CMK-3可以经过SBA-15翻模合成.采用浸渍法将氯铂酸负载到CMK-3载体上,经过甲酸钠还原制得质量分数为5%的Pt/CMK-3催化剂.小角XRD谱表明CMK-3保留了p6mm对称性,介孔结构完好;从广角XRD谱可以看出,金属铂粒子的衍射峰比较宽,说明铂纳米粒子分散比较均匀. CO化学吸附和透射电镜(TEM)的表征结果进一步证明铂纳米粒子分散得比较均匀,平均粒子大小约为2.5 nm (CO化学吸附), EDX结果表明铂的实际担载量为4.7%.将Pt/CMK-3催化剂用于硝基苯及其衍生物的液相加氢反应中,发现溶剂对反应结果具有很大的影响.首先参考以前的工作,选用水和乙醇体积比9：1的混合溶液为溶剂.在298 K和4 MPa氢气条件下,50 mg催化剂可以将21 mmol硝基苯在10 min内转化98.4%,产物苯胺的选择性高于99%;活性明显高于商品化Pt/C催化剂(相同条件下转化率为88.7%).在此基础上,把Pt/CMK-3催化剂用于含有不同取代基的硝基苯衍生物的液相催化加氢反应,含有吸电子基团如氯取代的硝基苯衍生物转化率为(21.4%–77.7%);苯环上含有给电子基团如甲基时,硝基甲苯加氢反应的转化率为(83.3%–98.0%);而给电子能力更大的基团如甲氧基取代的硝基苯衍生物的转化率却并不高.一方面是由于电子效应导致氯取代的硝基苯衍生物活性偏低,另一方面是由于空间位阻导致邻位取代的硝基苯衍生物活性相对其它位置取代的衍生物转化率偏低.考虑到部分反应物在混合溶剂中溶解度较低,可能导致加氢反应过程受到影响,从而影响反应结果,所以又选用无水乙醇溶剂进行了比较.首先仍用50 mg催化剂于硝基苯催化加氢反应,发现在乙醇溶剂中,21 mmol硝基苯在5 min内可以完全转化;当把硝基苯的量增加到5倍时,转化率为22.2%,苯胺选择性高于99%.因此,在乙醇溶剂中将催化剂用量减半,结果在5 min内21 mmol硝基苯衍生物均完全转化为对应的芳香胺化合物;除了硝基氯苯发生脱氯副反应外,其它衍生物选择性都很高.为了更好地区分不同取代基硝基苯衍生物的加氢活性,将2-氯硝基苯和2-甲基硝基苯的用量增大至105 mmol,反应过程中保持氢气压力恒为4 MPa,并使反应在5 min后中止,此时测得2-氯硝基苯催化加氢的TOF值为28.3 s–1,而2-甲基硝基苯的TOF值高达43.8 s–1. X射线光电子能谱(XPS)显示Pt/CMK-3表面含有带一定正电的铂物种,推测此物种有助于吸附硝基的氧原子,从而活化底物,促进加氢反应的顺利进行.最后还考察了Pt/CMK-3催化剂在硝基苯加氢中的循环使用性能,发现催化剂可以循环使用至少14次,活性没有任何下降.对反应滤液进行ICP分析,发现滤液中并没有铂离子流失;对使用过的催化剂进行透射电镜表征也没有观察到铂粒子聚集现象,说明催化剂的稳定性良好.     

氢水液相交换反应用高分散度Pt/C/FN疏水催化剂制备及Pt粒径效应研究

以乙二醇代替常规的异丙醇为分散溶剂, H₂PtCl₆为前驱体溶剂, 甲醛为还原剂, 采用改进浸渍还原法制备Pt/C催化剂, 用XRD, TEM和XPS对其进行表征. 改进浸渍还原法容易制备高分散度Pt/C催化剂, 催化剂Pt粒径大小可通过改变溶液pH值控制, pH值从1.6增加至11.3, 铂纳米粒子的平均粒径由3.3 nm减小到1.8 nm. pH值11.3时催化剂中Pt(0), Pt(II)和Pt(IV)的含量分别为43.3%, 30.8%和25.9%. 选择不同Pt粒径大小的Pt/C催化剂与聚四氟乙烯(PTFE)一起负载于泡沫镍(FN), 得到Pt/C/FN疏水催化剂, 考查其对氢水液相交换反应的催化活性, Pt粒径越小, 催化剂活性越高.     

应用于氧还原反应的石墨烯-无定形碳核壳结构复合材料载铂催化剂(英文)

采用氯化法制备石墨烯-无定型碳复合材料(GNS@a-C),并用作质子交换膜燃料电池(PEMFC)氧还原反应Pt催化剂的载体.结果显示,所制Pt/GNS@a-C催化剂与传统商业催化剂Pt/C相比,有较好的活性和较高的稳定性:质量活性(0.121 A/mg)几乎是Pt/C(0.064 A/mg)的两倍.更重要的是,该新型催化剂加速4000圈后其电化学活性面积保留了最初的51%,与Pt/C的33%相比,前者有更好的电化学稳定性,显示它在PEMFC中将具有较好的应用潜力.