NO Oxidation Inhibition by Hydrocarbons over a Diesel Oxidation Catalyst: Reaction Between Surface Nitrates and Hydrocarbons

Abstract  

C₃H₆ oxidation over a Pt/Al₂O₃ catalyst with or without NO _x present was investigated, and the reaction mechanism was studied by diffuse reflectance infrared spectroscopy (DRIFTS). C₃H₆ oxidation is inhibited by the presence of NO, and vice versa, and data indicate that adsorbed NO _x can react with gas phase C₃H₆. DRIFTS results confirm the reaction between C₃H₆ and nitrates, which are formed during NO _x adsorption, with linear nitrites observed as reaction products. Therefore, a reaction route is proposed for C₃H₆ oxidation in the presence of NO _x , namely, nitrates acting as oxidants. Using NO₂ instead of NO, or using a high NO _x /C₃H₆ ratio, which is beneficial for nitrate formation, favors this nitrate reaction pathway.     

甲烷部分氧化反应的磷钨酸催化剂研究

以磷钨酸为催化剂和氧化剂,进行了无氧条件下的甲烷气固相部分氧化的实验研究,考察了磷钨酸催化剂的制备条件、载体影响以及反应温度对甲烷部分氧化反应的影响等.磷钨酸催化剂可有效催化甲烷部分氧化反应,甲烷首先转化生成醋酸甲酯,醋酸甲酯水解生成甲醇.制备的催化剂以SiO2为载体,采用载体质量15%(wt)的磷钨酸水溶液回流浸渍4 h、120℃干燥2 h、300℃焙烧4 h制得.甲烷部分氧化反应在0.10 MPa、267～280℃进行,甲烷转化率为26.61%,目的产物收率25.82%.     

Global Kinetic Model and Parameter Optimization for a Diesel Oxidation Catalyst

This paper describes the development and validation of a global kinetic model for a diesel oxidation catalyst. The model is based on an extension of the classical Voltz model, and incorporates CO, H₂, NO and HC oxidation, and NO reduction by HC. The model is tested against experimental light-off curves for a variety of scenarios. A one dimensional single channel model for the reactor was used. Parameter optimization was performed using a general pattern search algorithm. The model is shown to be able to capture the ignition curves reasonable well.     

Catalytic Hydrogen Production from Methane Partial Oxidation: Mechanism and Kinetic Study

The multifunctional potential of a transition and noble metal catalyst supported on either a single support or combined oxide support in the catalytic partial oxidation of methane (CPOM) is reviewed. The close interaction and interfacial area between the metal, reducible oxide, and acidic support are highlighted, which are crucial for low-temperature CPOM. The effects of the catalyst components and their preparation methods are considered. Their impact on the catalytic performance and stability on the CPOM reaction is evaluated. The two main mechanisms of CPOM, namely, direct partial oxidation and combustion and reforming reaction, are also covered along with the most recent kinetic studies. Finally, the deactivation of the CPOM catalysts is evaluated in terms of coke and carbon deposition along with CO poisoning.     

Methane Oxidation over Alumina and Ceria Supported Platinum

Oxidation of methane over Pt/Al₂O₃ and Pt/CeO₂ catalysts was studied by transient gas-flow reactor and in situ FTIR spectroscopy experiments. The Pt/CeO₂ catalyst is generally more active, indicating more efficient CH₄ dissociation, especially during oxygen pulsing, which likely is connected to the higher oxygen storage capacity/mobility of ceria.     

稀土-Cu-K／Y分子筛催化剂上HCI氧化工艺的研究

制备了以Y分子筛作为载体,铜为活性组分,混合稀土氧化物及钾为助剂的氯化氢氧化催化剂,实验考察了催化剂粒径、HCl和O2体积比、反应温度等对氯化氢氧化反应的影响,进行了催化剂寿命试验.结果表明,采用粒径为0.6 mm的催化剂,在反应温度365 ℃,HCl空速490 L/(kg-cat·h)的条件下,氯化氢单程转化率可达到86%以上.对氧化反应冷凝水中铜含量的等离子体发射光谱(ICP)检测结果显示,催化剂中主要活性组分铜的流失速率为6×10-6 g/h,催化剂具有良好的稳定性.     

稀土-Cu-K/Y分子筛催化剂上HCl氧化工艺的研究

制备了以Y分子筛作为载体,铜为活性组分,混合稀土氧化物及钾为助剂的氯化氢氧化催化剂,实验考察了催化剂粒径、HCl和O2体积比、反应温度等对氯化氢氧化反应的影响,进行了催化剂寿命试验.结果表明,采用粒径为0.6 mm的催化剂,在反应温度365 ℃,HCl空速490 L/(kg-cat·h)的条件下,氯化氢单程转化率可达到86%以上.对氧化反应冷凝水中铜含量的等离子体发射光谱(ICP)检测结果显示,催化剂中主要活性组分铜的流失速率为6×10-6 g/h,催化剂具有良好的稳定性.     

Kinetic Study of Nickel Oxide Reduction by Methane

The reduction of the nickel oxide, NiO, by methane was investigated in this work. The thermogravimetric technique was used for the determination of kinetic parameters for the reaction. The reaction was carried out in the temperature range of 600–725 °C, at atmospheric pressure with porous pellets prepared from nickel oxide powder with a mean particle size of 0.026 μm. The conversion‐time data have been interpreted by using the grain model. Complete conversion can be achieved in 11 min at 725 °C, which is shorter than the time required by carbon, i.e., ca. 120 min at 1000 °C. This faster reduction in comparison with carbonthermal reduction is attributed to the high carbon activity in methane. For the first order reaction with respect to methane concentration, the activation energy is found to be 63.9 kcal/g mol.     

V-Mg-O催化剂上丁烷氧化脱氢动力学研究

制备了V－Mg-O催化剂,并测定了在该催化剂上进行丁烷氧化脱氢的反应动力学。应用BET和X射线衍射技术对催化剂进行了表征,在反应温度793－873K范围内,改变接触时间（W／F）和丁烷与氧气的分压进行了动力学实验。在所有的实验条件下,产物主要有脱氢产物（丁烯、丁二烯）、CO和CO2。提出了一个包括C4烯烃、COx生成反应的反应网络;从所测量的动力学数据中得到了合适的幂率型动力学方程。因为氧化脱氧反应的表观活化能比深度氧化反应的表观活化能大,在相同转化率时,C4烯烃选择性随着反应温度的提高而增加。     

甲烷非催化部分氧化制乙炔和合成气过程的实验研究

通过探头取样和四极杆质谱在线测量甲烷、氧气和乙炔等组分的浓度分布,考察了氧气/甲烷(甲烷+乙烷/丙烷)摩尔比、气体预热温度及原料气中添加乙烷和丙烷对甲烷非催化部分氧化制乙炔和合成气的影响. 结果表明,随轴向距离增加,乙炔浓度先增大后减小,存在最大值;随氧气/甲烷(甲烷+乙烷/丙烷)摩尔比增加,乙炔选择性下降;升高混合气体预热温度产物中乙炔浓度增大,620℃时最大乙炔浓度为4.52%;添加乙烷和丙烷时产物中乙炔浓度基本不变,但甲烷消耗量下降. 在实验条件下,生成最大乙炔浓度的激冷位置距烧嘴出口的距离约为80 mm.     

钒催化剂上二氧化硫氧化过程的本征动力学模型

在二段反应器内,模拟工业条件下,测定了细颗粒S101型钒催化剂上二氧化硫氧化过程的数据,并首次将序贯法应用于二氧化硫氧化过程动力学的研究.将基本实验测定的数据,用非线型最小二乘法回归,算出模型的参数估算值,利用离散度最大原理选择补充实验条件,从十一个竞争模型中筛选出适定的最佳模型.应用最小联合置信容积准则精估了模型参数.推荐S101型钒催化剂上二氧化硫氧化过程的本征动力学速率方程是     

Kinetic Model for Oxidative Dehydrogenation of n-Butanol over Copper-Barium Catalyst

Kinetics for oxidative dehydrogenation of n-butanol over copper-barium catalyst was investigated in a fixed-bed reactor. The effects of oxygen addition, temperature, initial partial pressure, and time factor on the conversion were studied. The results show that the catalyst is quite active and selective for the dehydrogenation of n-butanol and will become more active when a small amount of oxygen is added in the feed stream. A partial redox model including a pair of redox reaction steps parallel with a direct dehydrogenation reaction step was developed. The rate constants for the three reaction steps were evaluated. The model can predict the experimental data quite well, with a standard deviation less than ±5%.     

沼气水洗净化制取压缩生物质甲烷试验研究

为了提高沼气热值,设计沼气水洗净化制取压缩生物质甲烷试验,并对工艺参数和设备进行合理的设计和选型。首先,利用脱硫塔和过滤器,去除沼气中硫化氢和粉尘等杂质;然后,将沼气加压输送至水洗塔进行净化处理,去除二氧化碳;最后,把净化后获得的生物质甲烷加压灌装入气瓶。经检验,产品气中甲烷浓度达到88.1%,热值得到极大提高。     

甲烷部分氧化制合成气膜反应实验与模拟

采用钙钛矿型致密透氧膜对甲烷部分氧化制合成气进行了膜反应实验研究,并建立了该膜反应的数学模型。模拟计算结果与实验结果吻合较好：通过该模型考察了绝热条件下的反应床层温度分布,以及恒温反应体系中温度、流量、反应器长度等因素对膜反应结果的影响。     

Oxidation of Ethylene over Silver: Adsorption,Kinetics, Catalyst

Abstract

Selective oxidation of ethylene to ethylene oxide over supported silver catalysts is not only one of the very few uses of that element as n catalyst of industrial importance, it also has been the basis for the manufacture of an important chemical intermediate that underlies the large glycol industry as well as the manufacture of a varied array of solvents and related chemical materials, The chemical reactions offer a classical example of selectivity for partial oxidation to ethylene oxide versus complete combustion to carbon dioxide and water.     

Oxidation of Ethylene over Silver: Adsorption, Kinetics, Catalyst

Selective oxidation of ethylene to ethylene oxide over supported silver catalysts is not only one of the very few uses of that element as n catalyst of industrial importance, it also has been the basis for the manufacture of an important chemical intermediate that underlies the large glycol industry as well as the manufacture of a varied array of solvents and related chemical materials, The chemical reactions offer a classical example of selectivity for partial oxidation to ethylene oxide versus complete combustion to carbon dioxide and water.     

煤层气耐硫脱氧催化剂的研究开发

介绍了一种煤层气耐硫脱氧催化剂的制备方法,该催化剂是以非贵金属及活性助剂的可溶性盐为活性组分,采用浸渍沉淀法,将活性物负载于特种载体上制成。该催化剂经模拟煤层气耐硫脱氧测试表明,在410℃~580℃、空速2 000 h-1~10 000 h-1、压力0.1 MPa~0.5 MPa,进口氧体积分数1.5%~5.5%的实验条件下,可将模拟煤层气中的氧脱除至体积分数小于0.05%,转化率大于97%,满足了工业应用对氧含量的要求。对催化剂进行的500 h活性稳定性实验和高温老化实验表明,该催化剂稳定性好,能耐高温冲击。     

低压静电用于循环冷却水阻垢的实验研究

对低压静电处理循环冷却水的阻垢性能进行了实验研究与机理分析。采用动态监测污垢热阻的方法进行了结垢与阻垢实验,并对溶液的水质进行了分析。结果表明,低压静电处理循环冷却水对换热表面的结垢起到很好的抑制作用,实验中仅需2.2W功率就可达到100%的阻垢率。低压静电水处理不同与其它物理水处理技术,它可降低溶液的硬度、碱度、电导率及pH值,是一种主动的抗垢技术。被处理溶液中发生的微电解反应使更多的污垢晶体在处理器中聚集并生长,而不是沉积在换热表面,从而起到阻垢作用。     

Experimental and Modelling Study of a Dual-Layer NH3 Slip Monolith Catalyst for Automotive SCR Aftertreatment Systems

The approach to the development of a chemically and physically consistent mathematical model of ASC dual-layer (SCR + PGM) washcoated monolith converters is herein presented. Steady-state and transient kinetic runs were performed over each one of the two ASC components (SCR and PGM) in the form of powders and also over the two mixed powdered catalysts, thus acquiring information on the interactions between the SCR and the PGM catalytic chemistries. Global kinetic models were fitted to the SCR and to the PGM catalyst data, and validated against experiments performed over both washcoated single-layered SCR and PGM monoliths and over a full dual-layer ASC honeycomb catalyst (SCR layer on top). It was found that the dual-layer (SCR + PGM) ASC architecture grants increased N₂ selectivities compared to a PGM-only washcoat.