Cu－ZSM－5分子筛表面铜离子的价态研究

以吸附ＣＯ红外光谱结合ＴＰＲ谱详细表征了经真空自还原及用不同还原剂还原的ＣｕＺＳＭ－５分子筛样品，考察了表面铜离子的价态分布情况及其影响因素。得知铜在Ｃｕ－ＺＳＭ－５表面是分步还原的。用不同方法进行氧化和还原时的难易程度不同。研究了用不同方法进行氧化还原时铜的价态转变条件和铜离子在不同价态间氧化还原循环的可逆性。Ｃｕ２＋与Ｃｕ＋间的氧化还原循环完全可逆，而Ｃｕ０与Ｃｕ＋间的氧化还原循环不完全可逆。Ｃｕ０氧化为Ｃｕ＋比Ｃｕ＋氧化为Ｃｕ２＋容易进行，探讨了Ｃｕ＋在Ｃｕ－ＺＳＭ－５分子筛中不同位置的分布情况及铜在不同条件下的氧化还原机理。     

Cu-ZSM-5型分子筛的合成与结构表征

近年来，杂原子ZSM-5分子筛合成研究发展极为迅速，许多原子例如B、Ge、Fe等取代铝或佳而进入了分子筛骨架[1-4]．特别是1986年Guth等人间报导在弱酸性体系氟离子存在下合成分子筛，为杂原子沸石分子筛的合成开辟了一条新途径．在碱性体系下，Ione等人[6,7]报导过含铜ZSM-5的合成，但铜是否进入分子筛骨架，尚未给出确切的说明．在微酸性介质中合成Cu－ZSM-5还未见报导．本文在弱酸性介质氟离子存在下，应技合成出氨型Cu-ZSM-5分子筛，并运用XRD、IR、SEM、XPS等方法证明了铜进入了分子筛骨架．1实验1．1试剂白炭．t（SIO。，…     

Effects of additional gases on the catalytic decomposition of N2O over Cu-ZSM-5

N₂O decomposition into N₂ and O₂ was investigated in the presence of O₂, NO, CO₂, CO, CH₄, SO₂ and water vapor. Activity inhibition was observed in the presence of water vapor, and oxidant gases, whilst the reductant gases, enhanced the catalytic activity, in the temperature range of 350–550°C.     

NO在Cu－ZSM－5分子筛上程序升温脱附研究

本文用等温动态吸附和程序升温脱附技术研究了ＮＯ与Ｃｕ－ＺＳＭ－５的相互作用，并根据还原预处理样品上ＮＯ吸、脱附循环的研究探讨了全过程样品所经历的氧化还原循环，在２５℃等温吸附时，ＮＯ与Ｃｕ￣＋和／或Ｃｕ￣０反应产生了Ｎ＿２、Ｎ＿２Ｏ和Ｃｕ￣（２＋）以及超晶格氧，同时在Ｃｕ￣＋上有许多可逆吸附的ＮＯ．ＮＯ吸附在Ｃｕ￣（２＋）上是稳定的，升高温度时，ＮＯ分为三种状态脱附，分别位于约１００，１８０和４００℃．后两种可能以Ｃｕ￣（２＋）－ＮＯ＿２和Ｃｕ￣（２＋）－ＮＯ＿３为中间态．第三种ＮＯ脱附同时伴随着Ｏ＿２脱附，对于还原预处理的样品，吸附和脱附的一个循环总体上会使样品部分氧化。     

Characterization of hydrotreated Cu-ZSM-5 catalyst for the selective catalytic reduction of NO by n-decane

The steam treatment of Cu-ZSM-5 prepared by solid ion exchange involves an important decrease of the NO conversion. Characterization of the solids by NO-TPD, H₂-TPR, ²⁷Al MAS NMR shows that the catalyst deactivation is mainly due to change in copper species rather than the collapse of the zeolite framework.This revised version was published online in December 2005 with corrections to the Cover Date.     

Cu-ZSM-5的NH3选择性催化还原NO性能及其稳态动力学

采用浸渍法制备了一系列不同Cu载量的Cu-ZSM-5整体式催化剂.考察了该系列催化剂的NH3选择性催化还原(SCR)NO的反应特性.结果表明,当Cu质量分数为5%时,Cu-ZSM-5催化剂的SCR活性最高,此时催化剂上NO最高转化率高达96.5%,并且催化剂的活性窗口较宽,催化剂在198-470℃之间NO转化率大于80%.H2O和SO2的添加仅轻微影响Cu-ZSM-5催化剂的SCR活性.当Cu载量大于5%时,Cu-ZSM-5催化剂中出现明显的CuO物相.稳态动力学结果表明,在5%Cu载量的Cu-ZSM-5上的SCR反应中,NO的反应级数接近一级,NH3的反应级数接近零级,O2的反应级数接近1/2级.该反应的表观活化能为47.7kJ·mol-1.     

Cu-ZSM-5分子筛上[Cu-O-Cu]~(2 )物种的原位红外光谱研究

通过原位监测Cu－ZSM－5分子筛的振动红外光谱随温度及不同处理条件的变化情况，观察到［Cu－O－Cu］2＋物种的形成过程，即两个Cu（OH）＋在脱水过程中经二聚形成［Cu－O－Cu］2＋.低交换度样品开始产生［Cu－O－Cu］2＋物种所需脱水温度较高,通过观察不同处理条件对［Cu－O－Cu］2＋的影响，说明Cu2＋是通过脱出［Cu－O－Cu］2＋中的超晶格氧而被还原为Cu＋,较高温度时［Cu－O－Cu］2＋中的超晶格氧能与气相中的氧达到某种平衡.超晶格氧的脱出性能是影响Cu－ZSM－5分子筛上铜价态变化的重要因素．     

垃圾催化燃烧的热重分析研究

采用热重分析,结合机理分析的方法,探讨了不同催化剂对垃圾焚烧过程中着火性能和燃尽性能的影响。结果表明,催化剂对垃圾着火性能的提高主要是催化剂促进了垃圾中挥发性有机物的释放,使着火点提前;催化剂对垃圾燃尽性能的提高,主要作用机理是催化剂充当氧的载体,促进氧转移。提出了表征着火性能和燃尽性能的两个物理参数,并根据两个参数对催化剂进行排序和比较。催化剂影响着火性能大小进行排序：K2CO3> MnO2 > Na2CO3> CuO > MgO > TiO2 > Al2O3 > Fe2O3 > BaCO3> CaO;催化剂影响垃圾燃尽性能大小排序：Na2CO3>MgO> MnO2> K2CO3> BaCO3> CaO> Al2O3> CuO> Fe2O3> TiO2。     

Synthesis of novel hierarchical ZSM-5 monoliths and their application in trichloroethylene removal

A self-supporting ZSM-5 monolith with a hierarchical porosity was prepared using polyurethane foam (PUF) as a structural template and a hydrothermal synthesis procedure. The synthesized monolith was characterized and investigated towards the adsorption and catalytic oxidation of trichloroethylene (TCE). Adsorption of TCE was studied gravimetrically and oxidation of TCE was studied using a vapor-phase down-flow reactor. Monolithic ZSM-5 displayed good sorption properties and completely oxidized TCE. Conversion levels of 50% and 90% were achieved at reduced temperatures (by ~50 ℃) when compared with the conversion temperatures obtained from the powder counterparts. Besides the activity of the monolith towards TCE adsorption and oxidation, it was stable and enhanced diffusion, thereby reducing pressure drops to a great extent owing to its hierarchical porous nature.     

Quantum chemical treatment of active sites in zeolites

A short review on the quantum chemical study of the Bronsted and Lewis acid sites (BAS and LAS) is presented. Various factors that strongly influence the power of BAS in zeolites are considered. Different possible ways of LAS formation in zeolites are dicussed. The probable mechanism of selective oxidation in FeHZSM-5 is considered and the resulting active site structure is calculatedab initio. The initial step of hydrogen peroxide activation in Ti-silicalite is studied and the scale of the energy of structural deformation to proceed during the reaction is evaluated.     

VOCs催化燃烧整体式催化剂及涂层材料研究进展

催化燃烧法是当前处理VOCs最具有发展前景的技术之一,其技术的关键在于催化剂。整体式催化剂具有优异的传质、良好的热稳定性、高比表面积、床层压降低、催化效率高、机械性能好、易于装卸和维修等特点,是目前实现工业VOCs治理最佳的催化剂。本文概述了用于VOCs催化燃烧反应的整体式催化剂及其涂层材料的研究现状,并展望了未来的发展趋势。     

Characterization and catalytic activity of unsupported FeV and K-FeV catalysts for diesel soot combustion

A microstructural characterization by XRD, FT-IR and temperature programmed reduction (TPR) of unsupported FeV and K-FeV catalysts, prepared by solid-state synthesis, is reported. The formation of FexVyOz mixed phases of different compositions has been evidenced depending on the V/Fe ratio and calcination temperature. The catalytic activity of the samples in the combustion of diesel soot has been investigated with the aim to understand the role of FexVyOz mixed phases in the title reaction. This revised version was published online in August 2006 with corrections to the Cover Date.     

制备方法对LaMnO3上氯乙烯催化燃烧性能的影响

含氯挥发有机物(CVOCs)广泛用于化工原料以及有机溶剂,由于其毒性大,难降解,直接排放可引起严重的空气污染问题,采用催化燃烧的技术可以实现CVOCs高效净化,其关键在于高活性和高稳定性的催化剂.CVOCs净化催化剂主要有负载型贵金属催化剂、(复合)氧化物催化剂和复合分子筛催化剂.我们以具有高稳定性的LaMnO3钙钛矿为研究对象,主要考察了不同制备方法对于氯乙烯催化燃烧性能的影响;并通过XRD,Raman,N2-吸附脱附,O2-TPD,H2-TPR,ICP-AES,XPS等表征方法研究催化剂的结构和物化性能.性能评价结果表明,MnO2虽具有良好的催化性能,但LaMnO3催化剂则具有更好的循环稳定性.同时,制备方法对LaMnO3催化剂上氯乙烯催化燃烧的性能有显著的影响,其活性高低的顺序为:溶胶凝-胶法(SG)>共沉淀法(CP)>硬模版剂法(HT)>水热法(HM),其中LaMnO3-SG催化剂在182℃时氯乙烯的转化率即可达到90%.XPS结果表明,不同的制备方法导致LaMnO3催化剂表面La和Mn的富集程度不同,并显著影响了催化剂表面Mn离子的价态、分布和氧空穴的数量.其中,LaMnO3-SG催化剂具有最高的表面Mn4+浓度,其对应的氯乙烯催化燃烧活性最高.而对于LaMnO3-HM催化剂,La(OH)3的生成导致其具有最高的表面La/Mn比(2.29)和最低的表面Mn4+浓度.由XPS计算氧空穴浓度可知,LaMnO3-SG催化剂氧空穴浓度(1.03)远高于LaMnO3-HM催化剂表面的氧空穴浓度(0.07),进而LaMnO3-SG在O2-TPD中表现出更高的O2脱附量.进一步分析可知Mn4+离子浓度与氧空穴浓度成正相关的关系,即:Mn4+离子浓度越高,则表面氧空穴浓度越高.而催化剂表面氧空穴浓度越高,则有利于氧在催化剂表面的吸附和活化,从而使得催化剂表面氧物种的浓度增加,这与O2-TPD结果一致.同时,制备方法对催化剂氧化还原性能也有显著的影响,由H2-TPR所得催化剂的耗氢量顺序为:LaMnO3-SG>LaMnO3-CP>LaMnO3-HT>LaMnO3-HM,这与它们催化活性的顺序一致.结合XPS和H2-TPR结果可知,催化剂表面Mn4+/Mn3+比例高,则催化剂的氧化还原能力也越强.以上分析表明,LaMnO3催化剂的催化活性与催化剂表面Mn4+浓度和氧空穴数量相关.具有较高的Mn4+浓度有利于氯乙烯在催化剂表面吸附;而氧空穴数量的增加有利于氧在催化剂表面的吸附和活化,从而提高氯乙烯催化燃烧的反应性能.     

N2O and NO2 Formation in the Disproportionation of no over Ion Exchanged Cu-ZSM-5 at Lower Temperature

NO₃-type and NO₂-type adsorbed species are formed on Cu-ZSM-5 together with adsorbed O species at 523 K in the decomposition of NO accompanied by the evolution of N2, N₂O, and NO₂. This revised version was published online in June 2006 with corrections to the Cover Date.     

无定形硅铝负载镍催化剂上乙烯齐聚反应的活性位点结构鉴定

镍(Ni)基催化剂在低碳烯烃聚合领域具有重要的地位,也是该领域研究的热点.自Johnson等报道(J.Am.Chem.Soc.,1995,117,6414–6415)二亚胺配体络合的Ni(Ⅱ)催化剂可有效降低烯烃聚合度,降低产物中非线性烯烃的选择性,甚至可以生成α-烯烃以来,掀起了Ni基催化剂在烯烃聚合领域的研究热潮.从均相到负载型多相Ni基催化剂,从载体类型到配体性质,从Ni纳米粒子的粒径调控到金属表面价态,关于Ni活性中心的研究工作一直存在争论.本课题组之前研究结果表明,曾明确了无定形硅铝(ASA)载体负载的Ni催化剂,经惰性气氛(N2)预处理得到的一价Ni是烯烃齐聚反应的主要活性中心(J.Chem.Soc.Chem.Commun.,1991,126–127).本文进一步深入研究了不同Al2O3含量的ASA载体上Ni活性位点的结构及其在乙烯齐聚反应中的活性.27Al NMR结果表明,催化剂中的铝存在三种配位方式,分别为AlⅣ、AlⅤ和AlⅥ,其中AlⅣ含量随Al2O3含量的增加而增加.载体中铝配位方式的不同,导致其表面金属负载的金属Ni活性位点所处的结构亦不同.原位FTIR-CO和H2-TPR实验结果表明,催化剂表面存在两种不同结构分布的Ni位点,分别是接枝在弱酸性硅醇上的Ni2+阳离子和Si?(OH)?Al桥式羟基离子交换位置的Ni2+阳离子.多数研究者认为,位于离子交换位置处孤立的Ni阳离子是反应的活性中心.然而,近期有研究者提出负载在酸性硅烷醇表面孤立的Ni2+阳离子为反应的活性中心物质.本文研究发现,随着Al2O3负载量的降低,处于离子交换位置处的Ni2+离子含量逐渐减少,而处于硅醇缺陷位点处的Ni2+离子含量则逐渐增多.原位FTIR-CO分析结果表明,处于硅醇缺陷位点处的Ni2+离子物种在惰性气氛中更易于转化为活性中心Ni+.相应的催化反应结果表明,相比于离子交换位置的Ni2+物种,具有与硅醇缺陷位点相连的Ni2+离子结构更有利于表现出更高的乙烯齐聚化活性.由此可知,处于硅醇缺陷位点的Ni2+物种是乙烯齐聚反应的活性中心的前驱体.本文进一步研究了硅醇缺陷位点处的Ni2+离子物种更易于转化为活性中心Ni+的原因.H2-TPR结果表明,相比于离子交换位置的Ni2+物种,处于硅醇缺陷位点的Ni2+物种与载体之间的相互作用力更弱.C2H4-TPD结果进一步表明,具有这种相对较弱的金属载体间作用力结构的催化剂对反应物C2H4分子的吸附作用力相对更强,吸附量也相对增多,因此其乙烯齐聚的催化性能更优.本研究结果对理解活性中心结构和合理设计催化剂提供参考.     

In-situ Infrared Study on Surface Species in Selective Catalytic Reduction of NO with Hydrocarbon over Copper ZSM-5 Zeolite

Ｉｎ┐ｓｉｔｕＩｎｆｒａｒｅｄＳｔｕｄｙｏｎＳｕｒｆａｃｅＳｐｅｃｉｅｓｉｎＳｅｌｅｃｔｉｖｅＣａｔａｌｙｔｉｃＲｅｄｕｃｔｉｏｎｏｆＮＯｗｉｔｈＨｙｄｒｏｃａｒｂｏｎｏｖｅｒＣｏｐｐｅｒＺＳＭ┐５ＺｅｏｌｉｔｅＺＨＡＮＧＷｅｎ－ｘｉａｎｇ＊,ＪＩＡ...     

Hydrocarbon specificity in the selective catalytic reduction of NOx over Cu-ZSM-5 and Co-ZSM-5 catalysts

Transformation of surface nitrates under CH₄ (CH₄+O₂) was found to ensure steady-state activity of Co-ZSM-5 in the selective catalytic reduction of nitrogen oxides by methane (CH₄-SCR). For Cu-ZSM-5, such species are mainly converted into NO. Relaxation of the coordination sphere due to oxygen and NO adsorption, stability of C,N-containing intermediates and activation routes of hydrocarbons (methane, propane) were analyzed as factors determining catalytic properties of Cu and Co cations.     

Activity promotion of anti-sintering AuMgGa2O4 using ceria in the water gas shift reaction and catalytic combustion reactions

Heterogeneous gold nanocatalysts have both inspired researchers with their unique catalytic performance and frustrated them due to the contradictions observed in their activities and stabilities. A recent breakthrough has shown that gold nanoparticles (NPs) can retain their catalytically active size over a MgGa₂O₄ spinel support upon sintering at high temperatures. Herein, we report the catalytic activity of anti-sintering Au

MgGa₂O₄ for use in water gas shift reaction (WGSR) and catalytic combustion reactions, and the promoting effect of ceria. Upon adding ceria to 800°C-aged Au

MgGa₂O₄, the CO conversion in the WGSR was increased from ～1.5% to ～34.0% at 450°C, and the “light-off” temperatures (T₅₀) for methane combustion and CO oxidation were decreased by ～80 and ～100°C, respectively. Characterizations using XRD, HAADF-STEM, EDS mapping, H₂-TPR, XPS, and DRIFTs confirmed the proximate contact of Au with ceria and their significant synergistic effect, which thereby combined the benefits of ceria toward the dissociation of H₂O or O₂ and the Au NPs toward activating CO or CH₄. These results show that this stepwise stabilization-activation strategy is efficient for rationally constructing stable and active gold nanocatalysts, which may open up possibilities for the wide application of gold nanocatalysts at elevated temperatures.     

Ni-Nb2O5和Ni-Cu-Nb2O5催化甲烷燃烧活性研究

在微型固定床反应器中考察了新型甲烷催化燃烧催化剂Ni-Nb2O5和Ni-Cu-Nb2O5的活性．实验结果表明，含Nb2O5的Ni及Ni-Cu双金属催化剂具有好的催化甲烷低温燃烧性能，其甲烷转化率与反应温度、活性组分含量和空速有关．70％Ni担载量的Ni-Nb2O5催化剂可使甲烷在500℃时完全转化，并具有稳定的催化活性．Ni-Cu-Nb2O5体系催化剂中，Ni／Cu比为65／25时催化剂具有最佳的活性；该催化剂中Nb2O5可以在一个比较宽的范围内调节，并在此调节范围内可使甲烷在550℃温度下完全转化．     

Nanostructured perovskite oxides as promising substitutes of noble metals catalysts for catalytic combustion of methane

In this review, we summarize the recent development of nanostructured perovskite oxide catalysts for methane combustion, and shed some light on the rational design of high efficient nanostructured perovskite catalysts via lattice oxygen activation, lattice oxygen mobility and materials morphology engineering.