等离子体引入方式对强化制备二氧化碳重整甲烷反应的Ni/γ-Al2O3催化剂的影响

采用等离子体技术强化制备了Ni/γ-Al2O3催化剂, 以CO2重整CH4为模型反应考察了等离子体引入方式对催化剂性能的影响, 并采用H2-TPR, BET, CO2-TPD, XRD, CO2-TPSR, TGA及XPS技术对催化剂进行了表征. 研究结果表明, 与常规焙烧的催化剂相比, 在氢气还原过程前引入氮气等离子体处理能有效提高催化剂的低温反应活性. N2气等离子体处理使前驱体中的硝酸盐能在温和条件下分解, 并使催化剂具有较强的还原能力和较大的比表面积. 先进行N2气等离子体处理再进行H2气还原的催化剂, 其活性组分的分散度显著提高, 对CO2的吸附量也明显增加, 并且反应后催化剂上的积炭量比常规催化剂上的显著降低, 形成比较单一的碳物种.     

采用等离子体强化制备CO2甲烷化用镍基催化剂

采用等离子体技术强化制备了-γAl2O3担载的镍基催化剂,以CO2甲烷化为模型反应考察了等离子体引入方式对催化剂性能的影响,并采用程序升温还原和脱附、氧滴定、N2吸附、X射线衍射、X射线光电子能谱和热重分析对催化剂进行了表征.反应结果表明,经等离子体处理再还原活化的催化剂具有较高的低温催化活性,在101.325 kPa,13 500 h-1,H2/CO=2.5和250℃的条件下,CO2转化率为84.6%,比常规催化剂提高了27.2%.表征结果表明,等离子体处理有利于前驱体在温和条件下分解形成活性相,促使催化剂的活性组分晶粒细化并在表面富集,有效提高了活性组分的分散度,从而提高了催化剂的催化活性.     

射频等离子体技术制备合成低碳醇用铜钴基催化剂

采用射频等离子体技术制备了CO加氢合成低碳醇用新型CuCo/ZrO2催化剂, 研究了等离子体气氛氮气、氢气和先氮气后氢气处理对催化剂结构和性能的影响, 并应用BET、XRD、XPS、TG和TPR技术对催化剂进行了表征. 与常规焙烧制得的样品相比, 射频等离子体技术制备的催化剂可有效抑制烃类生成, 提高总醇选择性, 大幅提高反应活性和低碳醇的时空收率. 表征结果显示, 等离子体技术使催化剂前驱体在低温下分解形成活性相, 显著提高了催化剂比表面积, 促进催化剂活性组分晶粒细化并提高其分散度, 催化剂表面的铜含量增加.     

射频等离子体对合成低碳醇用CuCoAl催化剂的改性作用

采用共浸渍法制备了CuCo/γ-Al₂O₃催化剂,应用射频等离子体技术对催化剂进行改性处理。以CO加氢合成低碳醇为模型反应对催化剂进行活性评价,通过X射线物相分析(XRD)、氢氧滴定(HOT)、CO程序升温脱附(CO-TPD)和程序升温还原(TPR)等技术对催化剂进行表征,研究了射频等离子体技术强化处理对催化剂结构、吸附性能和还原性能的影响。结果表明,等离子体技术改性处理提高了催化剂活性组分的分散度,细化了铜物种的晶粒尺寸,增加反应活性位并调变了活性位对吸附物种的吸附强度,改进了催化剂的还原性能,等离子体改性处理的催化剂比未处理的样品CO加氢反应活性和低碳醇的时空产率显著提高。     

常压高频冷等离子体炬制备的CH4/CO2重整用Ni/γ-Al2O3催化剂的表征

 分别采用常规焙烧还原 (C)、常规焙烧与常压高频冷等离子体炬还原相结合 (PR), 以及常压高频冷等离子体炬直接焙烧还原 (PC&;R) 制备了 Ni/γ-Al2O3 催化剂. 通过 X 射线衍射、H2-程序升温脱附、CO2-程序升温脱附、N2 吸附-脱附实验、透射电镜和热重分析等方法对催化剂进行了表征. 并考察了其 CH4/CO2 重整反应活性. 结果表明, 催化剂经等离子体处理后低温活性明显增加. 在得到相同 CH4 和 CO2 转化率情况下, PC&;R 法制备的催化剂与常规催化剂相比, 反应所需温度可以降低 50 oC. PC&;R 催化剂上 Ni 分散度提高了 100%, Ni 粒子粒径降低了 70%, 达到 5 nm, 催化剂的抗积炭性能显著增强. 所得催化剂较高的低温活性和抗积炭性能得益于常压高频冷等离子体炬对催化剂前驱体还原速率快, 处理时间大为缩短, 避免了由于长时间高温焙烧和还原所引起的对载体的烧结和金属 Ni 的团聚.     

等离子体技术对CO2甲烷化用Ni/SiO2催化剂的改性作用

采用浸渍法制备了Ni/SiO₂催化剂,应用等离子体技术对催化剂进行改性处理。以CO₂甲烷化为模型反应对催化剂进行活性评价,通过H₂程序升温还原(H₂-TPR)和CO₂程序升温脱附(CO₂-TPD)技术对催化剂进行表征。研究了等离子体技术强化处理对催化剂吸附性能和还原性能的影响。结果表明,与常规焙烧的催化剂相比,等离子体技术改性处理提高了催化剂活性组分的分散度,增加反应活性位并调变了活性位对吸附物种的吸附强度,改进了催化剂的还原性能,CO₂甲烷化反应活性和甲烷的时空产率显著提高。     

光辐照驱动CH4-CO2重整中Ni/MgO-Al2O3催化活性吸收体的活性

将等离子体还原法和常规焙烧还原法制备的Ni基催化剂用于制备太阳能催化活性吸收体,在氙灯模拟的太阳光聚光反应系统中,考察了其催化CH4-CO2重整反应活性.结果表明,等离子体还原法制备的Ni/MgO-A12O3催化活性吸收体的低温活性最高,在光辐照平均能流密度为61 kW/m2,空速36 dm3/(g·h),CH4和CO...     

常压低温等离子体有效去除催化CO氧化的金原子团簇的保护剂（英文）

采用介质阻挡放电等离子体技术可以在低温、常压下实现对纳米金催化剂中保护基团的有效去除.本文通过对不同保护基团(聚乙烯吡咯烷酮和半胱氨酸)保护的金催化剂进行等离子体预处理,发现采用该技术能有效去除载体中的层间阴离子,还可能将金原子与保护基团之间的化学键打断.通过X射线粉末衍射对等离子体处理后的样品和未经处理的样品进行表征,发现经等离子体处理后的样品,载体从水滑石结构变为复合氧化物结构,这说明等离子体处理可将载体中的羟基和羰基除去,从而引起载体结构变化.热重分析结果显示,经等离子体处理后的样品失重量(19%-23%)与未处理样品的失重量(31%)相比差10%左右,这说明采用该方法可以在一定程度上去除纳米金表面保护基团和载体的层间阴离子.用紫外-可见光谱和高角环形暗场像-扫描透射电子显微镜对催化剂中金颗粒的尺寸分布和平均粒径进行分析,发现金颗粒在等离子体处理过后其粒径没有发生严重聚集,平均粒径由未处理时的1.4-1.7 nm轻微长大至2.4-3.7 nm.以含硫醇化合物(半胱氨酸)保护的金原子团簇催化剂为例考察了等离子体不同处理时间的影响,发现随着处理时间从25 min延长至150 min,样品的颜色从浅紫色变为暗紫色.结合XRD和TGA等结果可知,随着处理时间的延长,催化剂中保护基团的去除度逐渐提高.CO氧化反应活性评价结果显示,与未经处理的样品相比,经等离子体处理后的样品催化CO氧化反应活性有明显提高,且随预处理时间延长,活性有提高的趋势.动力学测试结果表明,经等离子体处理后的样品催化CO氧化的表观活化能低至1.2-2.9 k J/mol,接近于文献中报道的Au/TiO_2催化剂.这说明作为一种催化剂处理方法,介质阻挡放电等离子体技术可以有效去除催化剂中的保护剂,且因其处理条件相对温和,可在一定程度上保持金颗粒尺寸的稳定,这对于控制合成负载型小尺寸的金催化剂具有重要意义.     

等离子体处理制备对甲烷重整Ni基催化剂抗积炭性能的改进

对于甲烷重整反应,Ni基催化剂具有与贵金属催化剂相当的活性,但其易于积炭失活.本文总结了辉光放电等离子体处理制备CO2甲烷重整Ni催化剂以提高催化剂抗积炭性能的研究进展.比较表明,辉光放电等离子体处理制备的Ni催化剂,Ni颗粒较小,分散性更好,密集平面增加,且Ni活性组分与载体相互作用加强.这些变化导致Ni催化剂抗积炭性能改善.     

等离子体还原催化剂在CO2甲烷化反应中的活性

采用浸渍法和原位生长水滑石法制备了Ni-Ce/γ-Al₂O₃和Ni-Ce-LDHs/γ-Al₂O₃ 2种不同类型的催化剂前驱体, 考察了2种前驱体分别经氩-氢等离子体和常规氢热方法还原所得催化剂在CO₂甲烷化反应中的活性. 结果表明, 等离子体还原催化剂的低温活性明显高于常规氢热还原催化剂, 主要表现为前者反应启动的临界温度点比后者低20~30 ℃. 采用X射线衍射(XRD)分析、 透射电子显微镜(TEM)、 CO₂程序升温脱附(CO₂-TPD)以及X射线光电子能谱(XPS)对所得催化剂的形貌和结构进行了表征. 结果表明, 等离子体还原催化剂具有较小的活性组分粒径、 较高的活性组分分散度以及较高的表面碱性, 这些特性有利于催化剂活性位对CO₂的化学吸附, 使其在甲烷化反应中表现出较好的低温活性.     

Molybdenum Phosphosulfide: An Active,Acid‐Stable,Earth‐Abundant Catalyst for the Hydrogen Evolution Reaction

Introducing sulfur into the surface of molybdenum phosphide (MoP) produces a molybdenum phosphosulfide (MoP|S) catalyst with superb activity and stability for the hydrogen evolution reaction (HER) in acidic environments. The MoP|S catalyst reported herein exhibits one of the highest HER activities of any non‐noble‐metal electrocatalyst investigated in strong acid, while remaining perfectly stable in accelerated durability testing. Whereas mixed‐metal alloy catalysts are well‐known, MoP|S represents a more uncommon mixed‐anion catalyst where synergistic effects between sulfur and phosphorus produce a high‐surface‐area electrode that is more active than those based on either the pure sulfide or the pure phosphide. The extraordinarily high activity and stability of this catalyst open up avenues to replace platinum in technologies relevant to renewable energies, such as proton exchange membrane (PEM) electrolyzers and solar photoelectrochemical (PEC) water‐splitting cells.     

Molybdenum Phosphosulfide: An Active,Acid‐Stable,Earth‐Abundant Catalyst for the Hydrogen Evolution Reaction

Introducing sulfur into the surface of molybdenum phosphide (MoP) produces a molybdenum phosphosulfide (MoP|S) catalyst with superb activity and stability for the hydrogen evolution reaction (HER) in acidic environments. The MoP|S catalyst reported herein exhibits one of the highest HER activities of any non‐noble‐metal electrocatalyst investigated in strong acid, while remaining perfectly stable in accelerated durability testing. Whereas mixed‐metal alloy catalysts are well‐known, MoP|S represents a more uncommon mixed‐anion catalyst where synergistic effects between sulfur and phosphorus produce a high‐surface‐area electrode that is more active than those based on either the pure sulfide or the pure phosphide. The extraordinarily high activity and stability of this catalyst open up avenues to replace platinum in technologies relevant to renewable energies, such as proton exchange membrane (PEM) electrolyzers and solar photoelectrochemical (PEC) water‐splitting cells.     

Plasma Decomposition and Reduction in Supported Metal Catalyst Preparation

Supported metal catalysts are of importance in chemical engineering. But some disadvantage exists in the conventional method for their preparation. In this review, we summarized our recent works about plasma treatment of catalyst and clarified the phenomena of plasma decomposition and reduction. According to the present research, a criterion is proposed whether the catalyst can be reduced by plasma or not. The plasma reduction has great potential in catalyst preparation.     

掺氮碳化钨的制备及其电催化性能的研究

碳化钨是一种具有应用前景的电催化剂,本文尝试对碳化钨的非金属位进行氮掺杂,以钨酸钠为钨源,经由中间体氮化钨（WN）,并在一氧化碳气体中进行渗碳后合成掺氮的碳化钨纳米片（WN|WC）. 通过扫描电镜（SEM）和透射电镜（TEM）观测发现,WN|WC纳米片尺寸均匀,碳原子进入WN晶格中形成具有密排六方结构的WC晶相,并和WN的晶格条纹紧密联结而形成异质结构. X射线衍射（XRD）结果显示碳化后的样品中含有WN和WC两种晶型,XPS结果进一步表明WN|WC表面形成了WN和WC的异质结构. 为讨论氮元素掺杂对电催化性能的影响,本文通过微波辅助加热法负载少量铂制备Pt/WN|WC催化剂,并以甲醇氧化为指针反应,纯相碳化钨和商用铂碳材料（Pt/C）等为对比样,评价了Pt/WN|WC催化剂的电化学性能. 电化学测试表明,该催化剂甲醇氧化的电流密度是商业Pt/C的3倍,具有较高的交换电流密度和速率常数,且经过200周的循环伏安扫描后,正扫峰电位（Ep_f）和负扫峰电位（Ep_b）仍保持稳定,结果表明氮的掺杂改变了碳化钨表面的电子状态,形成了WN和WC的异质界面,有利于催化性能的提高.     

Plasma Treatment of Ni Catalyst for Partial Oxidation of Methane

The 10%Ni/Al2O3 catalyst for partial oxidation of methane was treated by DBD (dielectric barrier discharge) plasma in a continuous system under atmospheric pressure and room temperature by flowing He. It was found that 10%Ni/Al2O3 catalyst treated by plasma presents a higher catalytic activity and an enhanced stability than the catalysts prepared without plasma treatment. The methane conversion over the catalyst treated by plasma is 3%-5% higher than the catalysts untreated by plasma. Moreover,the enhanced dispersion of the catalyst can be achieved by plasma treatment, which can improve the interaction between active species and supports, catalytic activity and the resistance to carbon deposition.     

等离子体与催化剂协同催化CH4选择性还原脱硝反应

研究了在低温等离子体和催化剂共同作用下,CH4选择催化还原(SCR)NO的反应.在所考察的金属氧化物催化剂中,γ-Al2O3表现出最高的催化活性.当等离子体放电功率为4.5 W,反应温度为300℃时,NO转化率为56.5％;该条件下单纯等离子体反应和以γ-Al2O3为催化剂时NO转化率分别为28.9％和0,表明等离子体...     

The Preparation and Characterization of Highly Dispersed PdO over Alumina for Low‐temperature Combustion of Methane

PdO/Al₂O₃ catalysts prepared by glow discharge plasma treatment followed by thermal calcination show a much higher dispersion and a better catalytic activity for methane combustion at relatively low temperatures. The dispersion of palladium active species by such plasma prepared catalysts is 29.7%, 5.4 times higher than that of conventional catalysts. XPS analysis indicates that a surface enrichment of Pd active species (PdO) has been achieved after plasma treatment. The surface atomic composition of PdO of plasma prepared catalysts reaches 10.5%. XRD characterization also confirms a wellcrystallized PdO phase present on the plasma prepared catalyst. The lightoff temperature of the plasma prepared catalyst is 370°C, 50°C lower than that obtained from the conventional catalyst.     

Impact of ageing on the distribution of platinum group elements and catalyst poisoning elements in automobile catalysts

The distribution of platinum group elements (PGEs) and catalyst poisoning elements (Pb, Zn, P and S) on the surface of gasoline and diesel automobile catalysts was investigated within this study. Laser ablation–inductively coupled plasma mass spectrometry (LA–ICPMS) provides both the sensitivity and the spatial resolution required for the surface analysis of sectioned automobile catalysts, and scanning along channels reveals the distribution of longitudinal changes in PGE and catalyst poisoning elements. Changes in catalyst surface features were studied for fresh catalysts and after ageing of the catalyst up to 80 000 km for both types of catalysts studied. The PGEs in the gasoline catalyst were found to decrease at the front of the catalyst after ageing, whereas the diesel catalyst presented a more constant loss along the catalyst. The fraction of poisoning elements (Pb, P and Zn for the gasoline catalyst and P and Zn for the diesel catalyst) retained by the catalyst is distributed non‐uniformly over the length of the catalyst. This could indicate different ageing mechanisms for gasoline and diesel catalysts. Copyright © 2003 John Wiley & Sons, Ltd.