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铁助剂对Rh-Mn-Li/SiO2催化剂表面上的CO脱附和CO加氢行为的影响 总被引:3,自引:0,他引:3
采用一氧化碳程序升温脱附(CO-TPD)和吸附的一氧化碳加氢程序升温表面反应(TPSR)考察了Fe助剂对Rh基催化剂上CO的脱附行为及吸附CO的加氢行为的影响.CO-TPD实验表明,在Rh/SiO2催化剂上CO有三个脱附峰.在Rh-Mn-Li/SiO2中加入0.05%Fe后,高温脱附CO比Rh/SiO2催化剂上相应的CO量大.增加Fe的负载量,CO的脱附量减少.TPSR实验中,CO加氢反应的主要产物是甲烷.不同组分的催化剂上甲烷的生成温度有如下顺序:Rh/SiO2(482K)<Rh-Mn-Li/SiO2(489K)<Rh-Fe/SiO2(494K)<Rh-Mn-Li-Fe/SiO2(501K).甲烷峰的产生伴随着CO(s)高温脱附峰的消失,说明甲烷是由强吸附的CO加氢生成的. 相似文献
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本文采用程序升温脱附(TPD)技术研究了光沉积方法制备的Pt/TiO_2催化剂经过氧化、还原后氧、氢的脱附行为.光沉积过程中,Pt/TiO_2表面上可以生成大量的吸咐氢,在TPD中脱附;同时Pt/TiO_2表面上化学吸附的水在TPD过程中也可以分解释氢.氧化处理的Pt/TiO_2在TPD过程中于550~750K温区出现氧脱附峰,随着氧化温度升高,脱附峰位向高温移动,经实验证明,这种可脱附活泼氧物种的生成是由样品前身中留存氢引起的.还原处理的Pt/TiO_2在TPD过程中分别在300~600和大于600K出现两个氢脱附峰,认为是由于表面羟基和钛—氢(Ti~(4+)—H~-)物种的分解释氢引起的Pt/TiO_2上活泼氧物种的存在,增加了样品在室温条件下的吸氢量;在中温(473~573K)这种活泼氧物种则和氢发生反应,减少了TPD过程中的脱氢量;Pt/TiO_2在大于673K温度还原,可以消除活泼氧物种的影响. 相似文献
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研究了氧在Ag/SiO2催化剂上的超高真空程序升温脱附.结果表明,脱附谱中出现了对应于表面分子氧(Tp=340K)、体相氧(Tp=570K)和次表层氧(Tp=700~800K)的脱附峰.由于催化剂在制备过程中经过高温焙烧,因而其表面原子氧浓度低,脱附谱中未出现原子氧的脱附峰.高温焙烧还可使表面缺陷浓度增大,有利于原子氧向体相扩散,形成体相溶解氧,也有利于体相氧向表面扩散,所以对应于体相氧的570K脱附峰较强.体相氧和次表层氧向表面的扩散遵循不同的扩散机理. 相似文献
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通过X射线衍射、N2吸附-脱附、程序升温脱附、程序升温还原和电子顺磁共振方法研究了焙烧温度对MgO-Al2O3载体物化结构和Co-Mo/MgO-Al2O3变换催化剂性能的影响.结果表明,在600~800 ℃范围内焙烧的复合氧化物以MgAl2O4-xMgO-yAl2O3无定形形式存在,载体表面存在较多的中强酸.碱位,相应的负载催化剂具有较高的水煤气变换活性.在氧化态催化剂中存在较多八面体结构的Mo物种,而硫化态催化剂中含有较多氧硫包围的Mo物种.这些钼物种与催化剂的活性紧密相关. 相似文献
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烃在HZSM-5沸石上的程序升温脱附 总被引:2,自引:0,他引:2
本文研究了烃在HZSM-5沸石上的程序升温脱附(TPD).正己烷、环己烷和苯的TPD谱只有一个陡峰,对和间二甲苯的TPD谱均呈现出双峰.实验测得脱附活化能的次序为:正己烷>对二甲苯>苯>环己烷.水汽处理对正己烷的TPD影响不大;但对二甲苯的TPD影响较大.随着吸附量的增大,二甲苯逐渐占据孔道深处的强活性位置. 相似文献
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用程序升温脱附试验考察了LaMn_(1-y)Fe_yO_3型催化剂中B位元素对Co、CH_4氧化活性的影响。发现催化剂的活性与TPD谱上脱氧峰的位置及面积有关,同一催化剂对CO与CH_4的氧化活性中心并不一致。以γ-Al_2O_3为载体制得的锰系ABO_3型催化剂在浸渍微量氧化物助催化剂后,能使CO在130℃完全氧化,CH_4的氧化温度为300~500℃。 相似文献
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甲醇燃料车尾气净化催化剂的研究Ⅲ甲醇深度氧化用Ag-Pd/γ-Al2O3催化剂中Ag与Pd的协同作用 总被引:3,自引:0,他引:3
以银氨络离子和氯钯酸铵为前驱体制备了5%Ag-0.1%Pd/γ-A2lO3催化剂,其低温深度氧化性能明显优于Ag或Pd单组分催化剂;T50和T95(CH3OH)分别为125℃和170℃。且不受O2及CO的阻抑。O2-TPO的结果表明,随着在Ag组分中加入Pd及Pd加入量的增加,O2的低温脱附峰逐渐减弱至消失;中温脱附峰则向低温位移;高温脱附峰峰面积逐渐增大,峰温比单组分钯的氧脱附峰高。Pd与Ag的 相似文献
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利用程序升温技术考察了Ni促进的和未促进的钼基催化剂上进行噻吩加氢脱硫(HDS),苯、环己烯的程序升温加氢反应(TPH),通过对硫化态催化剂的程序升温还原(TPR)、程序升温脱附(TPD)以及程序升温氧化(TPO)等表征,发现添加№之后调变了Mo—S键合行为,使得催化剂在反应过程中易于形成或者维持更多的S配位空位数目,... 相似文献
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氧化铈对氧化锰结构和催化性能的影响 总被引:2,自引:0,他引:2
以共沉淀法制备了铈-锰混合氧化物催化剂,采用X射线衍射分析、程序升温脱附-质谱检测、程度升温还原等手段考察了催化剂的结构还原活性及表面氧脱附性能。结果表明,单组分MN-O催化剂的晶相结构为方铁锰矿型Mn2O3,双组分Mn-Ce-O催化剂为γMn2O3和CeO2。氧化铈的存在不影响氧化锰TPD-O2特征峰的位置,但表面吸附氧量明显增加,并同催化剂对甲醇的完全氧化活性进行了关联,当Mn/Ce原子比为4 相似文献
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The spectral-polarization characteristics of absorption and phosphorescence of molecules of the initial form of nitro-substituted
indolinospirobenzothiopyran were studied in oriented polyethylene films and in solutions with different polarity. An oscillator
model of the electron transitions responsible for the formation of absorption and luminescence spectra was suggested. It was
established that the principal differences in the spectral and photophysical properties of the compound studied and its oxygen-containing
analog are associated with the fact that the electronegativity of the S atom is lower than that of the O atom.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1143–1146, June, 1997. 相似文献
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Two vanilloids, (5E)-8-(4-hydroxy-3-methoxyphenyl)oct-5-en-4-one (1) and 4-[3-hydroxydecyl]-2-methoxyphenol (2), isolated from the dried seeds of Grains of Paradise (Aframomum melegueta), were synthesized; the latter compound was made as the S-enantiomer and the material derived from the seeds was found to be a 1:1.7 mixture of the R and S isomers. The synthetic route used should allow the preparation of analogs having extended alkyl chains and consequently different lipophilicity, and 3, a homolog of 2, was also prepared. 相似文献
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Cotton cellulose was swollen in a sodium hydroxide solution and carboxymethylated by a two-bath method for different periods of time for each process. The kinetics of acid hydrolysis and the crystallinity of the swollen and carboxymethylated samples were measured. The proportion of broken bonds, rate constants for hydrolysis, and permeability of cellulose to hydrolyzing agents were calculated. The susceptibility of glycosidic linkages to acid hydrolysis was improved by carboxymethylation more than by swelling in alkali. The increased accessibility of carboxymethylcellulose to acid was regarded as a consequence of increased intra-and intercrystalline swelling and of the glycosidic bonds' weakness caused by the electron-attracting carboxymethyl group on the C-6 position. 相似文献
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Stepkowska E. T. Perez-Rodriguez J. L. Jimenez de Haro M. C. Sayagues M. J. 《Journal of Thermal Analysis and Calorimetry》2002,69(1):187-204
Main hydration products of two cement pastes, i.e. CSH-gel, portlandite (P) (and specific surface S) were studied by static heating, and by SEM, TEM and XRD, as a function of cement strength (C-33 and C-43) hydration time (th) and subsequent hydration in water vapour.Total change in mass on hydration and air drying, Mo, increased with strength of cement paste and with hydration time. Content of water escaping at 110 to 220°C, defined as water bound with low energy, mainly interlayer and hydrate water, was independent on cement strength but its content increased with (th). Content of chemically bound (zeolitic) water in CSH-gel, escaping at 220-400°C, was slightly dependent on strength and increased with (th). It was possibly derived from the dehydroxylation of CSH-gel and AFm phase. Portlandite water, escaping at 400-500°C, was independent on cement strength and was higher on longer hydration. Large P crystals were formed in the weaker cement paste C-33. Smaller crystals were formed in C-43 but they increased with (th). Carbonate formated on contact with air (calcite, vaterite and aragonite), decomposed in cement at 600-700oC. It was high in pastes C-33(1 month) and C-43(1 month), i.e. 5.7 and 3.3%, respectively; it was less than 1% after 6 hydration months (low sensitivity to carbonation) in agreement with the XRD study showing carbonates in the air dry paste (1month), and its absence on prolonged hydration (6 months) and on acetone treatment. Water vapour treatment of (6 months) pastes or wetting-drying increased this sensitivity.Nanosized P-crystals, detected by TEM, could contribute to the cement strength; carbonate was observed on the rims of gel clusters.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
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The aim of the presented work was the investigation of thermal oxidation of ilmenite in static air atmosphere. The investigations
were carried out by use of a derivatograph (MOM, Hungary). The changes of crystallographic structure of investigated samples
were identified by X-ray diffractometry on Philips PW-1710 diffractometer. In temperature above 500°C appears structure of
hematite Fe2O3. On the basis of the thermogravimetric measurements, the contracting area and contracting volume models were found as the
best fitting experimental data.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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Cyclopropyl derivative of 2,6-di-tert-butylphenol is synthesized as a probe to investigate the mechanism of base-catalyzed autooxidation of phenol derivatives. Our study indicates that one electron reduction of molecular oxygen from phenolate gives phenoxyl radical 3, a key intermediate of autooxidation. The coupling of phenoxyl radical and superoxide radical gives peroxylate anion 4 and produces the final epoxy alcohol adduct 6. 相似文献
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