TiO2及金属(Cu、Ni)掺杂催化材料水解制氢反应机理的理论研究

本文研究TiO₂以及金属(Cu、Ni)掺杂TiO₂催化剂水解制氢的两种不同析氢反应机理,计算了不同反应过程催化反应活化能,同时考察了系列催化剂电子激发态的催化活性.结果表明:催化剂电子激发态的催化活性增强,说明光照有助于降低反应的活化能,提高催化剂的活性.金属(Cu、Ni)掺杂TiO₂有助于降低水解制氢反应的活化能,且Cu的掺杂催化效果更明显,这与实验报道的结果一致.     

正丁烷/空气在微反应器内的气相与催化反应

本文通过实验研究了富燃的正丁烷/空气混合物在有、无Pt催化剂蜂窝陶瓷反应器内的气相与表面反应过程。实验结果表明,根据反应温度的不同,正丁烷/空气混合物的催化氧化过程分为三个区域:低温的表面催化反应控制区、高温的气相反应控制区和中温的催化/气相反应共同控制区。在表面催化反应控制区,即使是富燃料混合物,其反应产物也只有完全氧化产物,而不存在CO等不完全氧化产物。在达到气相着火后的气相反应控制区,混合物主要发生部分氧化和热裂解反应过程,表面催化反应的影响很小,反应产物主要是部分氧化产物和裂解产物CO,H_2、CH_4、C_2H_4、C_3H_6等。     

污染物传质作用下的室内光催化空气净化研究

光催化反应是表面反应,污染物必须到达催化剂表面才可被分解去除,同时光催化反应在污染物较高浓度条件下反应速率较高,而污染物较低浓度时则效果不佳.为了提高室内污染物低浓度条件下的催化反应速率,本文将光催化技术与活性炭吸附技术相结合,利用活性炭吸附功能,加强污染物向催化剂表面的传质,在催化剂表面形成污染物局部高浓度,提高室内污染物光催化反应速率,将室内污染物浓度降至国标规定的浓度范围内.     

界面水与催化

水的催化反应在界面进行,对新能源开发和环境保护等领域具有至关重要的作用.理解催化反应中材料界面水分子的结构、物性和分子机制,对于解决清洁能源、污水处理等关系国计民生的重大问题具有关键意义.由于水的复杂性,对于水分子在催化反应中的作用至今仍存在很大争议.界面水分子在催化反应中作为反应物、催化剂、溶剂,或是兼而有之,一直是科学界争论的热点话题.近年来,随着原位实验技术和计算机能力的快速提高,人们已经能够在原子尺度对催化反应中的界面水分子行为进行实时观测和理论模拟,为解析水在催化反应中的作用提供了实验依据和理论基础.本文简述当前催化反应中界面水研究面临的巨大机遇和挑战,以及现有实验和理论方法的最新进展和所遇到的困难,为设计优化与水应用相关的高效催化剂提供可行的思路.     

多功能胶囊催化剂在多相催化中的应用研究进展（英文）

分子筛胶囊催化剂被广泛应用于串联催化反应中.与多步反应相比,串联反应具有更高的化学反应效率,能节约反应时间和原料,并实现反应物到目的产物的一步转化.然而,目前普遍采用的物理混合型催化剂,很难高选择性的生成目的产物.分子筛膜包裹的核-壳型胶囊催化剂由于其特殊的结构形式,在许多串联反应中可以一步高选择性的生成目的产物.如:合成气选择性制异构烷烃,合成气直接制二甲醚,合成气直接制液化石油气等重要多相催化反应.本文综述了分子筛胶囊催化剂的制备方法与应用范围,重点阐述了胶囊催化剂设计,制备及应用方面的最新应用进展,并展望了其研究和发展方向.     

Rh基催化剂上氢甲酰化反应过程的原位高压NMR研究

制备了用于丙烯氢甲酰化反应的Rh/SBA-15 和PPh₃修饰的PPh₃-Rh/SBA-15催化剂. 应用原位变温高压核磁共振技术,对比研究了丙烯在Rh/SBA-15 和PPh₃修饰的多相催化剂PPh₃ Rh/SBA-15上的氢甲酰化反应,实现了高压条件下催化反应的原位固体核磁共振表征. ¹³C MAS NMR研究结果表明：在1.0 MPa的反应压力下,随着反应温度升高丙烯与合成气在Rh/SBA-15催化剂上可转化生成丁醛,而PPh₃配体修饰的PPh₃-Rh/SBA-15催化剂上丁醛产物的正异比显著提高.     

固体核磁共振技术在甲醇制烯烃反应中的应用

甲醇制烯烃过程是由非石油路线生成低碳烯烃的重要途径之一.分子筛因具备独特的孔结构和可调变的酸性质,而成为甲醇制烯烃过程的核心催化剂.固体核磁共振(NMR)是鉴定物质结构、阐释催化反应机理的强有力的工具,在甲醇制烯烃的研究中被广泛应用.本文主要总结了近年来利用原位固体NMR、多维多核NMR、脉冲梯度场NMR等固体NMR技术研究甲醇制烯烃反应机理取得的重要进展.原位固体NMR可以在真实反应条件下监测催化反应中反应物、中间体和产物的动态演变过程;多维多核NMR可以在不破坏催化剂结构情况下确定反应中间体结构信息,特别是¹²⁹Xe NMR可以很灵敏探测反应中催化剂的孔道结构变化;脉冲梯度场NMR可用于测定孔道内分子的扩散系数,阐明分子筛的扩散机制.     

表面催化反应对空间预混气体着火影响的研究

催化燃烧中表面反应和空间反应的相互影响是一个非常重要的问题,本文计算了表面有催化剂的高温小球利用催化反应放热点燃空间预混气体的温度和浓度分布情况,从而得到当空间预混气体着火时表面催化小球的温度低于无催化时空间预混气体着火温度,同时得到在利用催化反应放热点燃空间燃烧时,空间预混气体着火的温度却远远高于无催化下的空间预混气体着火温度,该结果与试验相符。     

石墨烯固体酸催化转化葡萄糖为化学品

利用氢化钠和丙磺酸内酯合成出了磺化石墨烯催化剂,采用XPS、FT-IR、TEM等方法对其进行了表征,并且对此催化剂催化葡萄糖的转化反应进行了研究．探究此催化剂在纯水中、没有添加任何有机溶剂下催化转化葡萄糖制备高附加值化学品方面的催化活性,在最优的反应条件下, 5-羟甲基糠醛(HMF)最高产率可达28.8%,产物甲酸、乳酸和HMF的总产率可达51.94%．经过5次催化反应,催化剂仍表现出相对高的催化活性,三种产物的产率依然较高,表明此种固体酸催化剂有很好的热稳定性．     

金属表面催化反应的原位SERS光谱研究

催化表面成分复杂、分子结构不断变化,通过传统的非原位分析手段对其进行表征非常困难。在催化表界面进行原位检测可分析反应物种的变化过程,有望解释催化机理并指导高性能催化剂的制备。表面增强拉曼光谱(SERS)是一种高灵敏度和高特异性的检测方法,并且具有很好的表面选择性,可专注检测表界面物种而不会受到外部组分信号的干扰。我们设计合成了几种双功能纳米粒子,其在催化反应检测中应用表明SERS可以在催化检测中发挥重要的作用,其检测范围有望拓展到SERS模型反应之外的具有实际价值的有机合成催化反应。     

NH_3多相氧化的实验研究

1引言煤燃烧过程中特别是流化床中为了减少SOZ的排放，一般采用向炉内加入石灰石等添加物的方法。这些添加物质的存在，使挥发分含氮物质的氧化机理异于纯单相氧化。因此研究钙基脱硫剂（CaCO。）及其生成物（CaSO。、煤灰）对NH。和HCN的多相氧化有助于了解实际锅炉煤燃烧过程中脱硫对氮氧化物生成的影响。Lin［‘］研究了石灰石和CaSO。对NH。氧化的影响。发现石灰石对NH。氧化生成NO具有相当大的催化作用，可使NH3MNO的转化率达65％，而C3SO4存在和空管时NH3氧化结果一致，表明CaSO。对NHa无氧化作用。IisJ‘」在研究Ca…     

基于DMCC发动机台架的甲醇-SCR催化还原NO_x的研究

为了验证合成气台架上组合式催化剂((Co-Mo)/Al2O3)优异的选择催化甲醇还原NO的性能,试验在一台由增压中冷,废气再循环的电控单体泵柴油机改造的DMCC发动机上实施。结果表明:提高甲醇喷射量和EGR率,推迟柴油喷射时刻均会改善甲醇-SCR的催化效率。甲醇最优喷射量受到HC减活化作用和HC完全氧化反应的控制。各工况下甲醇-SCR对PM排放的影响较小。DMCC发动机耦合甲醇-SCR系统可以实现NOx的超低排放。A25、A75和B75工况点下的NOx体积分数的最低值分别为64×10^-6、66×10^-6和47×10^-6。     

Effect of products of low temperature oxidation reaction on NOx reduction in HC-SCR system

Fuel reforming technology using a low temperature oxidation reaction was applied to improvement of NOx reduction efficiency of hydrocarbons selective catalytic reduction (HC-SCR) system, which does not require urea. The low temperature oxidation reaction of hydrocarbons produces oxygenated hydrocarbons which has high NOx reduction ability such as aldehydes. A pre-evaporation and premixing-type fuel reformer was developed in order to generate uniform fuel/air premixed gas. To prevent from hot-flame ignition, the reaction chamber of the fuel reformer has a high surface/volume ratio and the wall temperature of the reaction chamber was controlled. As a fundamental study, NOx reduction experiments and elementary reaction calculation were carried out to investigate the suitable fuel reformer temperature and reforming equivalence ratio for the promotion of NOx reduction on the surface of the catalyst. It was found that the reforming fuel gas has a higher NOx reduction efficiency than the fuel vapor in the catalyst temperature range from 473 to 773 K. The NOx reduction efficiency was highest at the reforming temperature of 673 K. The NOx reduction efficiency at the catalyst temperature of 723 K increases with the increase in the reforming equivalence ratio. It was suggested that alcohols predominantly affect NOx reduction reaction at low catalyst temperatures, and aldehydes at high catalyst temperatures.     

燃煤锅炉燃烧过程与NOx排放的模型与数值计算

本文以一台前墙布置有24只旋流燃烧器的350 MW燃煤电站锅炉为研究对象,对锅炉在100%、95%、85%、70%和50%额定负荷下的流动、燃烧和NOx排放进行了全炉膛数值模拟。模拟结果与锅炉运行和实测数据进行了全面比较并发现,除50%负荷外,其余工况两者符合情况良好。文中提出并采用了NOx模拟中相关的模型参数;对炉内空气量、炉温与NOx生成关系的计算结果表明, NOx的最终排放对温度的敏感性更强。     

In situ DRIFTS研究NO在Cu-ZSM-5上的表面吸附及选择性催化还原

Cu-ZSM-5分子筛催化剂选择性催化还原NO具有较好的低温活性,在613 K时NO还原成N2的转化率达70.6%。原位漫反射红外光谱(In situ DRIFTS)是研究催化剂表面吸附物种及催化机理的重要方法,应用该方法在298～773 K范围原位考察了以C₃H₆为还原剂及富O₂ 条件下,NO在Cu-ZSM-5催化剂上的表面吸附及选择性催化还原。认为NO在Cu-ZSM-5催化剂上还原为N₂的过程中,NO以一系列NO_x吸附态形式与丙稀的活化物种(C_xH_y或C_xH_iyO_z)反应,生成有机中间体,再进一步反应,最终生成N₂。有机中间体存在一个明显的从有机胺物种到腈(或—CN)再到有机氮氧物种(R—NO₂或R—ONO)的过程,催化剂表面形成有机中间物种是关键步骤,Cu的作用是促进NO_x形成,O₂ 的作用是促进C₃H₆活化,并且是有效产生有机-氮氧化物不可缺少的条件。     

Effects of NOx addition on autoignition and detonation development in DME/air under engine-relevant conditions

Exhaust gas recirculation (EGR) technology can be used in internal combustion engines to reduce NOx emission and improve fuel economy. However, it also affects the end-gas autoignition and engine knock since NOx in EGR can promote ignition. In this study, effects of NOx addition on autoignition and detonation development in dimethyl ether (DME)/air mixture under engine-relevant conditions are investigated. Numerical simulation considering both low-temperature and high-temperature chemistry is conducted. First the kinetic effects of NOx addition on the negative temperature coefficient (NTC) regime are assessed and interpreted. It is found that NOx addition greatly promotes both low-temperature and high-temperature ignition stages mainly through increasing OH production. Then the autoignitive reaction front propagation induced by either local NO accumulation or a cold spot within NTC regime with different amounts of NO addition is investigated. For the first time, supersonic autoignition modes including detonation induced by local NO accumulations are identified. This indicates that local accumulation of NOx in end gas might induce super-knock in engines with EGR. A new parameter quantifying the ratio of sound speed to average reaction front propagation speed is introduced to identify the regimes for different autoignition modes. Compared to the traditional counterpart parameter used in previous studies, this new parameter is more suitable since it yields a detonation development regime in a C-shaped curve which is almost unaffected by the initial conditions. The results in this study may provide fundamental insights into knocking mechanism in engines using EGR technology.     

Influence of NOx chemistry on the prediction of natural gas end-gas autoignition in CFD engine simulations

Natural gas (NG) represents a promising low-cost/low-emission alternative to diesel fuel when used in high-efficiency internal combustion engines. Advanced combustion strategies utilizing high EGR rates and controlled end-gas autoignition can be implemented with NG to achieve diesel-like efficiencies; however, to support the design of these next-generation NG ICEs, computational tools, including single- and multi-dimensional simulation packages will need to account for the complex chemistry that can occur between the reactive species found in EGR (including NOx) and the fuel. Research has shown that NOx plays an important role in the promotion/inhibition of large hydrocarbon autoignition and when accounted for in CFD engine simulations, can significantly improve the prediction of end-gas autoignition for these fuels. However, reduced NOx-enabled NG mechanisms for use in CFD engine simulations are lacking, and as a result, the influence of NOx chemistry on NG engine operation remains unknown. Here, we analyze the effects of NOx chemistry on the prediction of NG/oxidizer/EGR autoignition and generate a reduced mechanism of a suitable size to be used in engine simulations. Results indicate that NG ignition is sensitive to NOx chemistry, where it was observed that the addition of EGR, which included NOx, promoted NG autoignition. The modified mechanism captured well all trends and closely matched experimentally measured ignition delay times for a wide range of EGR rates and NG compositions. The importance of C2-C3 chemistry is noted, especially for wet NG compositions containing high fractions of ethane and propane. Finally, when utilized in CFD simulations of a Cooperative Fuels Research (CFR) engine, the new reduced mechanism was able to predict the knock onset crank angle (KOCA) to within one crank angle degree of experimental data, a significant improvement compared to previous simulations without NOx chemistry.     

Numerical study on effects of hydrothermal aging to composite regeneration in CeO2-based catalyzed diesel particulate filter

The effects of hydrothermal aging on the performance of CeO₂-based catalyzed diesel particulate filter (CDPF) was numerically investigated in this study based on a zero-dimensional model using the plug flow reactor in which a chemical reaction kinetic mechanism was established and validated by the simulated gas environment experiment. The effects of regeneration temperature, O₂ concentration in the ultimate emission conditions, the ratio of NO₂ in NOx (α) and the ratio of NOx to soot (β) on catalyst deactivation temperature and soot oxidation rate were investigated with fresh and hydrothermal aging CeO₂-based CDPF. The results show that hydrothermal aging of CeO₂-based catalysts raises the regeneration temperature from 613 to 783 K and shifts the soot catalytic combustion reaction path from complete to incomplete oxidation. Soot oxidation rate of fresh catalyst first increases rapidly at 516 K and then starts to slow down gradually at 633 K, but for hydrothermal aging catalysts, are 601 K and 789 K, respectively. With O₂ concentration increased from 1.5 mol/m³ to 5.5 mol/m³, the catalyst deactivation of fresh and hydrothermal aging catalyst increased from 609 K to 602 K, 791 K to 818 K, respectively. The increase in α and β leads to an increase in soot oxidation rate and a decrease in regeneration temperature. The deactivation temperature of catalyst is increased in higher α (1.0) and lower β (0.1), which the highest is 821 K. Synergistic mechanisms of NOx, regeneration temperature, and hydrothermal aging effects on soot catalytic combustion in CeO₂-based CDPF are revealed deeply with the help of zero-dimensional model.     

不同制备工艺钒系SCR催化剂理化及催化性能研究

本文研究了制备工艺对 TiO2-WO3-V2O5- 载体型催化剂理化特性及其在 NH3-SCR 反应中催化性能的影响.通过 XRD、TG/DTA 等分析方法考察了煅烧温度等对催化剂中各组分晶体结构的影响,确定了制备负载型催化剂的最佳煅烧温度为 500℃.不同制备工艺催化剂理化性能的对比表明,多步浸渍法不仅提高了锐钛矿型 TiO2 向金红石型 TiO2 的转变温度,而且使更多的钒氧化物处于较低的价态,有利于提高还原反应的催化性能;催化活性评价试验也表明使用多步浸渍法制备的 SCR 催化剂具有较高的催化活性和更宽的高活性反应温度窗口.最后考察了反应空速对多步浸渍法所制备催化剂 NOx 转化效率的影响,结果表明:随空速的增加,NOx 转化效率逐渐降低.     

发动机采用柴油／甲醇组合燃烧的性能研究

分别在增压和自然吸气式高速直喷柴油机上采用柴油/甲醇组合燃烧方式进行研究.试验结果表明,采用组合燃烧后发动机和纯柴油燃烧发动机相比,尾气中NOx和碳烟排放显著减少,消耗燃料的比能耗降低,组合燃烧用燃料的使用经济性优予原机;仅未燃碳氢和一氧化碳较原机有所增加,但是由于排气温度高于催化转换器起燃温度,可以通过催化转换器将其转化.