Investigation on the catalytic roles of silver species in the selective catalytic reduction of NOx with methane

Silver impregnated H-ZSM-5 zeolite catalysts with silver loading from 3 to 15 wt.% were investigated for the selective catalytic reduction (SCR) of NOx with CH4 in the excess of oxygen. X-ray diffraction (XRD) and UV-Vis measurements established the structure of silver catalysts. A relationship between the structure of silver catalysts and their catalytic functions for the SCR of NOx by CH4 was clarified. The NO conversion to N-2 showed a S-shape dependence on the increase of Ag loading. No linear dependence of catalytic activity on the amount of silver ions in the zeolite cation sites was observed. Contrastively, the activity was significantly enhanced by the nano-sized silver particles formed on the higher Ag loading samples (greater than or equal to7 wt.%). Temperature programmed desorption (TPD) and temperature programmed reduction (TPR) studies showed that nano-silver particles provided much stronger adsorption centers for active intermediates NO3-(s) on which adsorbed NO3-(s) could be effectively reduced by the activated methane. Silver ions in the zeolite cation sites might catalyze the reaction through activation of CH4 at lower temperatures. Activated CH4 reacted with NO3-(s) adsorbed on nano-silver particles to produce N-2 and CO2. (C) 2003 Elsevier B.V. All rights reserved.

Effect of addition of Zn on the catalytic activity of a Co/HZSM-5 catalyst for the SCR of NOx with CH4

The selective catalytic reduction (SCR) of NOx by methane in the presence of excess oxygen was studied on a Zn-Co/HZSM-5 catalyst. It was found that the addition of Zn could improve effectively the selectivity of methane towards NOx reduction. When prepared by a coimpregnation method, the Zn-Co/HZSM-5 catalyst showed much higher catalytic activity than the two catalysts of a Zn/Co/HZSM-5 and Co/Zn/HZSM-5 prepared by the successive impregnation method. It is considered that there exists a cooperative effect among the Zn, Co and zeolite, which enhances the reduction of NO to NO2 reaction and the activation of methane. (C) 2002 Elsevier Science B.V. All rights reserved.

城市NOx人体健康风险评估的GIS应用研究

城市大气污染是人类目前及未来面临的主要健康威胁之一,而随着交通的发展NOx对人体健康的影响越来越受到重视。基于GIS技术进行健康风险评估的研究是目前城市环境健康问题研究的热点。论文采用环境健康风险评估的基本框架(浓度、暴露、剂量、效应4个环节),应用GIS栅格数据模型和域面分析技术构建城市空气质量健康风险空间量化评估模型,模拟了主要大气污染物NOx的剂量—效应函数关系;并根据污染物的分布进行城市局地尺度NOx健康风险评估。

用于低温脱除烟气NOx的催化剂及制备方法和应用

一种用于低温脱除烟气ＮＯｘ的催化剂各组分重量百分比为：活性炭纤维９０．０％～９９．９％，Ｖ↓［２］Ｏ↓［５］０．１％～１０．０％。按催化剂组成将活性炭纤维浸渍在含有Ｖ↓［２］Ｏ↓［５］浓度为０．００００８８７３５－０．００８８７３５ｇ／ｍｌ的草酸与偏钒酸铵所配成的混合溶液中，然后室温放置２－５ｈ，４０－６０℃干燥２－１２ｈ，１００－１２０℃干燥２－６ｈ，然后在４００－５００℃氩气气氛下煅烧２－８ｈ和２００－２６０℃空气中煅烧２－５ｈ，得到催化剂。本发明具有操作简单，很好的抗Ｈ↓［２］Ｏ和ＳＯ↓［２］的毒化能力，提高了选择催化还原ＮＯｘ的活性的优点。

一种脱除烟气NOx的催化剂及其应用

一种脱除烟气ＮＯｘ的催化剂以硫酸为活性组分，活性焦为载体，各组份重量百分比为：活性焦８０－９５％、硫酸５－２０％。具有制备方法简单、成本低、高的催化活性和长的寿命。

催化还原NOx的钛基催化剂的制备方法

一种催化还原ＮＯｘ的钛基催化剂的制备方法，取一定量的ＴｉＣｌ↓［４］溶液溶解在少量浓ＨＮＯ↓［３］（６９．２％）［ＴｉＣｌ↓［４］∶ＨＮＯ↓［３］（摩尔比）＝１∶６］中，加入一定量的脲素［ＴｉＣｌ↓［４］∶脲素（摩尔比）＝０．１－０．２］，再加入相应活性组份的胺盐或硝酸盐，搅拌成糊状物，置于温度控制在５００℃的马弗炉中焙烧１０分钟后取出，即得所需产品。此法简单快捷，能随意添加各种组分。

以水滑石为前体的Mg-Al-M复合氧化物对催化消除NOx的活性

通过H2-TPR，XRD，TG-DTA及比表面积测定等对ＭｇＡｌ水滑石化合物进行了表征，研究了焙烧温度对水滑石物理性质的影响．在此基础上，研究了ＭｇＡｌ水滑石中加入过渡金属（Ｍ）离子后对ＮＯ＋ＣＯ反应的催化活性．结果发现，含有Ｃｕ离子的样品对ＮＯ＋ＣＯ反应有较高的催化活性，并与ＣｏＡｌＭ的催化性能进行了比较

In situ preparation of Ir/ZSM-5/cordierite honeycombs and their application for NOx abatement

ZSM-5 zeolites were synthesized in situ onto cordierite honeycombs by vapor phase transport (VPT) for the first time. The as-synthesized ZSM-5/cordierite honeycombs were impregnated with IrCl3 and tested for NOx reduction with a simulated exhaust gas as the reducing agent. Under the conditions of excess oxygen, the Ir/ZSM-S/cordierite monolith catalyst exhibited NO reduction of 73% at a temperature of 573 K and a space velocity of 20,000 h(-1).

On the selectively catalytic reduction of NOx with methane over Ag-ZSM-5 catalysts

The catalytic performance of silver-modified ZSM-5 catalysts in the selectively catalytic reduction (SCR) of NOx with methane was investigated. NO was selectively reduced by CH4 to N-2 in the presence of excess O-2, and the catalytic activity depended on both the activation of CH4 and the adsorption properties of NOx. Silver incorporated in ZSM-5 zeolite activated CH4 at low temperatures and lowered the "light-off" temperature for the CH4-SCR of NOx. Temperature-programmed (TP) spectroscopy studies depicted that surface nitrosyl species directly decomposed to N-2 in the absence of O-2. CH4 could not effectively reduce surface nitrosyl species, but might facilitate the direct decomposition of NO through the removal of surface oxygen. Surface nitrates were formed in NO and O-2 coexisting system and could be effectively reduced by CR4 to nitrogen. The priority of surface nitrates to O-2 in the reaction with CH4 clearly demonstrated that CH4 selectively and preferentially reduced the surface nitrate species to N-2 in the excess of oxygen. (C) 2002 Elsevier Science B.V. All rights reserved.