Selective oxidation of ammonia to nitrogen on transition metal containing mixed metal oxides

The selective catalytic oxidation of ammonia to nitrogen (NH₃-SCO) has been studied over hydrotalcite derived mixed metal oxides containing Cu, Co, Fe or Ni. XRD, BET, NH₃-TPD and TPR techniques were used for catalysts characterization. Results of NH₃-SCO were compared with those of selective catalytic reduction of NO with NH₃ (NO-SCR). Reaction mechanism was studied by temperature-programmed surface reaction (TPSR) and activity tests with a various contact time. Catalytic performance of the studied samples depends on both kind and loading of transition metals in the mixed metal oxide system. The Cu-containing samples have been found to be the most active catalysts of the NH₃-SCO process. Transition metal loading strongly influences distribution of ammonia oxidation products. The highest selectivity to N₂ was measured for the catalysts with the lowest transition metal content.     

非晶态NiB配位催化2-亚丁基环己酮的选择加氢动力学研究

以超细非晶态NiB为催化剂、乙醇为溶剂 ,研究了常压条件下 2 -亚丁基环己酮的选择催化氢化反应。确定了反应对 2 -亚丁基环己酮的反应级数n =1,80℃下准一级反应的速率常数为k =3.4× 10 -3 min-1。同时考察了氢化过程中外扩散的影响以及温度、催化剂用量对反应的影响。求得反应的活化能Ea =16 .391kJ/mol。     

A molecular level mechanism ofn-butane oxidation to maleic anhydride over vanadyl pyrophosphate

A molecular level mechanism is proposed for the highly selective 14-e^– oxidative transformation ofn-butane to maleic anhydride on the surface of vanadyl pyrophosphate. The mechanism suggests that the dimeric active sites assume at any given time, one of four possible interconvertible states which differ from each other in the number of available oxygen atoms and the formal oxidation states of the individual vanadium atoms. The relative ratios of active sites in each of the four possible states are dictated by the reaction conditions, the redox properties of the reacting gases and the structure of the vanadyl pyrophosphate active surface. A crucial feature of the mechanism is a pseudo-ozonide surface species formed by the interaction of a chemisorbed dioxygen molecule and an adjacent metal-oxo group. This unusual species is responsible for the initial activation of then-butane, which occurs when the chemisorbed dioxygen abstracts an H-atom from the alkane and the adjacent metal-oxo group reacts with the incipient alkyl radical to form an alkoxy group. The proposed mechanism is entirely consistent with literature reports describing the behaviour of (VO)₂P₂O₇ in flow, pulse and TAP reactors.     

便携式瓦斯检测仪管理系统的设计与实现

针对以人工登记为主的矿山便携式瓦斯检测仪发放和回收工作存在效率低下、工作流程繁琐及不利于管理和统计的问题,设计一种便携式瓦斯检测仪自动收发系统.该系统包括收发装置、服务器和Web客户端三部分,采用C-S和B-S共存的复合结构,以PHP作为开发语言,选用MySQL数据库.实际应用结果表明,该系统能够很好地完成仪表发放回收工作,便于科学的管理仪表,加快了矿山信息化和智能化的建设.     

在线红外检测仪在头孢噻肟酸合成中的应用

利用在线红外检测仪ReactIRTM4000在线监测以7-氨基头孢烷酸(7-ACA)与2-甲氧亚氨基-2-(2-氨基-4-噻唑基)-硫代乙酸苯并噻唑酯(MEAM)为原料,用二甲基乙酰胺(DMA)作催化剂,一步合成头孢噻肟酸的实验过程,主要考察了反应时间对反应的影响。在最佳反应条件下(催化剂用量、反应物用量、结晶pH已经优化)头孢噻肟酸的合成摩尔收率超过98%。     

基于VB6.0的红外甲烷检测仪串行通信的实现

针对煤矿安全生产中存在的瓦斯爆炸问题,该文以MSP430系列单片机为核心,设计了红外甲烷检测仪.其中着重介绍了检测仪的串行通信,编写了串行通信程序,使检测仪能实现与PC机的数据通信功能,并使用VB6.0编写了人机交互界面,以方便用户及时观察和处理数据,实现对检测仪的校准、复位和阈值设置等操作功能.实验结果表明,编写的串行通信程序能实现检测仪与PC的数据通信功能,检测仪能快速、准确地检测出甲烷气体的浓度,具有较高的实用价值.     

The removal of NOx from a lean exhaust gas using storage and reduction on H3PW12O40·6H2O

NO_x sorption and reduction capacities of 12-tungstophosphoric acid hexahydrate (H₃PW₁₂O₄₀·6H₂O, HPW) were measured under representative alternating conditions of lean and rich exhaust-type gas mixture. Under lean conditions, the sorption of NO_x is large and is equivalent to 37 mg of NO_x/g_HPW. Although a part of these NO_x remains unreduced, HPW is able to reduce some of the NO_x to produce N₂ by a reaction between the sorbed NO₂ and hydrocarbon (HC), but this process is slow. The addition of 1% Pt affects strongly the chemical behaviour occurring during the course of a rich operation. The NO desorption observed at the beginning of the rich phase is strongly accelerated. The direct correlation between NO₂ consumption and CO₂ production shows that the principal pathway is the reaction CO+NO₂→CO₂+NO. In a mixture of reducing gas (CO, HC, H₂), the competition is strongly in favour of CO though in its absence the reaction observed was the hydrogenation of propene to propane.     

Performance of solvothermally prepared Ga2O3-Al2O3 catalysts for SCR of NO with methane

The solvothermal reaction of mixtures of aluminum isopropoxide (AIP) and gallium acetylacetonate (Ga(acac)₃) directly yielded the mixed oxides of γ-Ga₂O₃-Al₂O₃. In the solvothermal synthesis, the crystal structure of mixed oxides was controlled by the initial formation of γ-Ga₂O₃ nuclei. The mixed oxides prepared in diethylenetriamine have extremely high activities for selective catalytic reduction (SCR) of NO with methane as a reducing agent. With increasing crystallite size of the spinel structure, the catalytic activity increased. The ratio of the amount of methane consumed by combustion to total methane conversion was proportional to the density of acid sites on the surface of the mixed oxides. The mixed oxide catalysts prepared in diethylenetriamine had lower densities of acid sites and showed a higher methane-efficiency for CH₄-SCR than those prepared in other solvents. These catalysts maintained their high activity even when the reaction was carried out under the severe conditions (i.e., high space velocity and low NO concentration).     

NDN-1型氮氧化物脱除催化剂的评价及应用

对NDN-1型氮氧化物脱除催化剂进行了实验室性能评价,并与进口催化剂A及国产催化剂B进行了比较,结果表明,NDN-1型催化剂的化学组成、结构、性能均优于进口催化剂A。介绍了该催化剂在南京帝斯曼东方化工有限公司工业应用的情况。     

Methanol Selective Oxidation to Formaldehyde over Iron-Molybdate Catalysts

This review deals with the important industrial reaction of formaldehyde manufacture by methanol oxidation over iron molybdate catalysts. Detailed reference is made to the used catalyst, preparation techniques (coprecipitation, sol-gel like, mechanical mixing, etc.) including unsupported and supported catalysts, promoters and characterization methods. The controversial active phase assignment (stoichiometric versus Mo rich iron molybdate) is discussed. The proposed reaction mechanisms and kinetic laws for the main and side reactions are examined. The catalyst deactivation processes are reviewed and the role of Mo excess on these processes is underlined. Finally conclusions and perspectives are presented.