甲醇在清洁和氧预吸咐Pd（100）面上的吸咐与分解

用高分辨电子能量损失谱（ＨＲＥＥＬＳ），热脱咐谱（ＴＤＳ）在１４０Ｋ—７００Ｋ温度范围内研究了清洁和氧改性Ｐｄ（１００）面上ＣＨ_３ＯＨ的吸咐与分解机理。ＨＲＥＥＬＳ结果表明：在１４０Ｋ吸咐甲醇能形成分子吸咐层；当加热甲醇分子层时，甲醇在１８５Ｋ先分解为ＣＨ_３Ｏ_（ａｄ）和Ｈ_（ａｄ），在２００Ｋ以上温度ＣＨ_３Ｏ_（ａｄ）逐步分解为ＣＯ_（ａｄ）和Ｈ_（ａｄ）；预吸咐氧后表面有甲酸物种生成。ＴＤＳ研究表明；除有少量甲醇在１８５Ｋ脱咐外，甲醇分解的主要脱咐产物为Ｈ_２（３２０Ｋ）和ＣＯ（４４０Ｋ）；次要脱附产物为甲烷（２００Ｋ—２１０Ｋ）。综合ＨＲＥＥＬＳ和ＴＤＳ研究指出，在清洁表面甲醇主要通过Ｏ—Ｈ键断裂，经甲氧基中间物种分解为ＣＯ和Ｈ_２，还有部分甲醇通过Ｃ—Ｏ键断裂分解为甲烷，预吸附氧后甲醇的分解除了存在以上两种方式外，氧的存在一方面能够转移ＣＨ_３Ｏ_（ａｄ）中的氢原子在表面形成一定量的甲酸中间物种，另一方面能够稍许提高少量ＣＨ_３Ｏ_（ａｄ）的热稳定性。     

含手性膦配体的钯（Ⅱ）配合物的二维核磁共振研究

利用一维和二维ＮＭＲ技术，对含有手性膦配体甲基－３脱氧－３（二苯膦基）－４，６－氧－苄叉基－α－Ｄ一吡喃阿卓糖苷（３－ＭＢＰＡ）和甲基－２－脱氧－２－（二苯膦基）－４，６－氧－苄叉基－α－Ｄ－吡喃阿卓糖苷（２－ＭＢＰＡ）的钯配合物ｔｒａｎｓ—［Ｐｄ（３－ＭＢＰＡＨ）２ＣＩ２」（１），ｔｒａｎｓ－［Ｐｄ（２－ＭＢＰＡＨ）２ＣＩ２］（２）和ｃｉｓ－［Ｐｄ（３－ＭＢＰＡ）２］（３），ｃｉｓ－［Ｐｄ（２－ＭＢＰＡ）２］（４）进行~１Ｈ和~（１３）Ｃ ＮＭＲ谱分析，归属了全部的~１Ｈ和~（１３）Ｃ ＮＭＲ谱线，并根据磷的化学位移及Ｒａｍａｎ谱确定化合物（３）和（４）是顺式构型，对实验中的一些现象也做了简单讨论。     

CRYSTAL STRUCTURE OF （Et_4N）_2Pd（i－MNT）_2 AND ITS REACTION WITH （Et_4N）_2WS_4 （i－MNT＝S_2CC（CN）_2~2－）

ＣＲＹＳＴＡＬＳＴＲＵＣＴＵＲＥＯＦ（Ｅｔ_４Ｎ）_２Ｐｄ（ｉ－ＭＮＴ）_２ＡＮＤＩＴＳＲＥＡＣＴＩＯＮＷＩＴＨ（Ｅｔ_４Ｎ）_２ＷＳ_４（ｉ－ＭＮＴ＝Ｓ_２ＣＣ（ＣＮ）_２~２－）￥ＤｅＬｉａｎｇＬＯＮＧ；ＸｉｎＱｕａｎＸＩＮ（ＳｔａｔｅＫｅｙＬａｂｏｒａ?..     

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

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     

氧化铈对Pd／Al2O3表面上CO氧化性能的影响

采用ＴＰＤ－ＭＳ及ＴＰＳＲ－ＭＳ技术研究了添加ＣｅＯ２对Ｐｄ／Ａｌ２Ｏ３催化剂上ＣＯ脱附、表面反应及表面氧脱附等性能的影响，考察了不同含氧量的气氛下ＣＯ的氧化活性，结果表明，Ｐｄ－Ｃｅ间的相互作用有利于各自原子上表面氧的吸脱附及ＣＯ的表面反应，并发现ＣＯ２脱附量大小及峰温次序与对ＣＯ的催化氧化活性有一致的对应关系。     

两个异亚砂基乙酰丙酮—N—芳基亚胺Pd（Ⅱ）配合物的合成 …

合成了两个异亚硝基乙酰丙酮－Ｎ－芳基亚胺的Ｐｄ（Ⅱ）配合物,ＰｄＣｌ（Ｃ６Ｈ５－ＩＡＩ）（Ｃ６Ｈ５ＮＨ２）（１）和ＰｄＣｌ（ｐ－ＣＨ３Ｃ６Ｈ４－ＩＡＩ）（ｐ－ＣＨ３Ｃ６Ｈ４ＮＨ２）（２）,并测定了配合物１的晶体结构。配合物１晶体属正交晶系,空间群为Ｐｃａ２１,晶胞参数ａ＝１．８５８７（４）ｎｍ,ｂ＝０．９３８０（２）ｎｍ,ｃ＝２．１２３７（４）ｎｍ,Ｚ＝８,Ｆ（０００）＝１７６０,μ＝１．１６０ｍ     

稀土铕与2—[（取代苯胺基）羰基]苯甲酸配合物的研究

报道了配合物Ｅｕ（ＸｎＰ）３．３Ｈ２Ｏ「其中Ｘ＝Ｈ，２－Ｃｌ，３－ＯＨ，４－Ｂｒ，３－ＮＯ２，２－ＯＣＨ３，２－ＣＨ３，２，４－二氯；Ｐ＝２－（ＣＯＯ）Ｃ６Ｈ４ＣＯＮＨＣ６Ｈ５－＾－，ｎ＝１，２」的制备，并用元素分析，红外光谱，电子反射光谱，热重分析进行了表征。     

CO2部分氧化乙烷制乙烯Pd—Cu／MoO3—SiO2催化剂的研究

用化学吸附－红外光谱、化学吸附－程序升温脱附（ＴＰＤ）和微型反应技术研究了Ｐｄ－Ｃｕ／ＭｏＯ３－ＳｉＯ２（ＭｏＳＯ）催化剂对ＣＯ２和乙烷的吸附活化和部分氧化反应性能．结果表明，乙烷以Ｃ—Ｈ键中的Ｈ吸附于ＭｏＳＯ载体表面ＭｏＯ键的端基氧上；Ｐｄ－Ｃｕ／ＭｏＳＯ催化剂对ＣＯ２有良好的化学吸附活化性能，ＣＯ２的吸附除有线式吸附态和剪式吸附态外，还有一种新的卧式吸附态；Ｐｄ－Ｃｕ／ＭｏＳＯ催化剂的晶格氧参与了化学反应．探讨了在Ｐｄ－Ｃｕ／ＭｏＳＯ催化剂上ＣＯ２的部分氧化乙烷反应机理     

Pt／Al_2O_3，Pd／Al_2O_3催化剂上CO氧化与表面氧脱出－恢复性能

Ｐｔ／Ａｌ_２Ｏ_３，Ｐｄ／Ａｌ_２Ｏ_３催化剂上ＣＯ氧化与表面氧脱出－恢复性能周仁贤，郑小明（杭州大学催化研究所，杭州３１００２８）关键词铂，钯，氧化铝，氧化锆，负载型催化剂，一氧化碳，氧化，氧脱附ＡＩ。Ｏ。负载的贵金属（Ｐｔ，Ｐｄ或Ｒｈ等）催化剂对有...     

SYNTHESIS OF 4－（2，3－DIMETHOXY－4－ISOPROPYLBENZYL）－3－ETHOXYCARBONYLMETHYL－2－CYCLOHEXENONE

ＳＹＮＴＨＥＳＩＳ　ＯＦ　４－（２，３－ＤＩＭＥＴＨＯＸＹ－４－ＩＳＯＰＲＯＰＹＬＢＥＮＺＹＬ）－３－ＥＴＨＯＸＹＣＡＲＢＯＮＹＬＭＥＴＨＹＬ－２－ＣＹＣＬＯＨＥＸＥＮＯＮＥＳＹＮＴＨＥＳＩＳＯＦ４－（２，３－ＤＩＭＥＴＨＯＸＹ－４－ＩＳＯＰＲＯＰＹ...     

The Adsorption,Thermal Desorption and Photochemistry of Methyl Iodide on an Ag‐Covered TiO2(110) Surface

The thermal reactions and photochemistry of monolayer methyl iodide (CH₃I) on a silver covered TiO₂(110) surface have been studied using combinative techniques of temperature programmed desorption (TPD) and x‐ray photoelectron spectroscopy (XPS). About ? 60% of CH₃I at monolayer coverage on Ag/TiO₂(110) dissociates between 130 and 200 K yield adsorbed CH₃ and I, with the rest desorbing molecularly at a peak temperature of 200 K in a TPD study. Photochemistry of CH₃I on Ag/TiO₂(110) is wavelength dependent. Irradiation of monolayer CH₃I by 404 nm photon causes C‐I bond dissociation and CH₃ desorption. Upon 290 nm, UV irradiation, the depletion of CH₃I_(a) is dominated by photodesorption of molecular CH₃I.     

Chemisorption and reaction characteristics of methyl radicals on Cu(110)

Methyl radicals are generated by pyrolysis of azomethane, and the condition for achieving neat adsorption on Cu(110) is described for studying their chemisorption and reaction characteristics. The radical-surface system is examined by X-ray photoemission spectroscopy, ultraviolet photoemission spectroscopy, temperature-programmed desorption, low-energy electron diffraction (LEED), and high-resolution electron energy loss spectroscopy under ultrahigh vacuum conditions. It is observed that a small fraction of impinging CH3 radicals decompose into methylene possibly on surface defect sites. This type of CH2 radical has no apparent effect on CH3(ads) surface chemistry initiated by dehydrogenation to form active CH2(ads) followed by chain reactions to yield high-mass alkyl products. All thermal desorption products, such as H2, CH4, C2H4, C2H6, and C3H6, are detected with a single desorption peak near 475 K. The product yields increase with surface coverage until saturation corresponding to 0.50 monolayer of CH3(ads). The mass distribution is, however, invariant with initial CH3(ads) coverage, and all desorbed species exhibit first-order reaction kinetics. LEED measurement reveals a c(2 x 2) adsorbate structure independent of the amount of gaseous exposure. This strongly suggests that the radicals aggregate into close-packed two-dimensional islands at any exposure. The islanding behavior can be correlated with the reaction kinetics and is deemed to be essential for the chain propagation reactions. Some relevant aspects of the CH3/Cu(111) system are also presented. The new results are compared with those of prior studies employing methyl halides as radical sources. Major differences are found in the product distribution and desorption kinetics, and these are attributed to the influence of surface halogen atoms present in those earlier investigations.     

预吸附氧对NO在Pt(110)表面吸附和分解的影响

 利用程序升温反应谱、X射线光电子能谱和高分辨电子能量损失谱研究了NO在清洁和预吸附氧的Pt(110)表面的吸附和分解. 在清洁的Pt(110)表面,室温下低覆盖度时NO以桥式吸附为主,高覆盖度时NO以线式吸附为主. 加热过程中部分NO(主要是桥式吸附物种)分解,生成N2和N2O. 室温下O2在Pt(110)表面发生解离吸附. Pt(110)表面预吸附氧会抑制桥式吸附NO的生成,并导致其脱附温度降低40 K. 降低脱附温度有利于桥式吸附NO的分子脱附,从而抑制分解反应. 这些结果从表面化学的角度合理地解释了铂催化剂在富氧条件下对NO分解能力的降低.     

乙醇在Mn薄膜／Rh（100）上吸附和分解的研究

应用高分辨电子能量损失谱（HREELS）和热脱附谱（TDS）,研究了Mn薄膜／Rh(100)上乙醇的吸附和分解,提出了表面吸附和分解的反应工,在300K时,蒸镀的Mn在清洁Rh(100)表面上以层层模式生长;在130－300K间,在25mLMn/Rh(100)表面上吸附20L乙醇的TDS结果与乙醇在Rh(100)表面上的结果一致在155K处,脱附出多层凝聚态吸附的乙醇;升温到255K,脱附出H2和CH4,继续升温,出现了与乙醇在R (100)表面上不一致的现象,在470K,同时出现了第2个H2和CH4的脱附峰,在500K,脱附极少量的CO;在950K附近,脱附出大量CO。     

Nondissociative chemisorption of methanethiol on Ag(110): a critical result for self-assembled monolayers

Three definitive experiments have been performed to investigate the possibility of dissociative adsorption of methanethiol (CH3SH) on clean Ag(110). On the clean Ag(110) surface, the adsorption in the first layer occurs to 0.5 ML, producing a (2 x 1) low-energy electron diffraction (LEED) structure. The undissociated molecule desorbs starting at approximately 140 K, and only tiny quantities of other gaseous products are desorbed, and only tiny quantities of S-containing species remain. Using a 50:50% mixture of CH3SD and CD3SH, we find no evidence of S-H or S-D bond scission between these molecules upon desorption. And finally, when the CH3SH molecule is incident on the clean Ag(110) surface in the temperature range of 230-400 K, less than 1% of the incident molecules dissociate to produce adsorbed sulfur-containing species. The results influence our thinking about the surface bonding of alkanethiol-based self-assembled monolayers (SAMs) on noble metals.     

Two-dimensional superstructures and softened C-H stretching vibrations of cyclohexane on Rh(111): effects of preadsorbed hydrogen

Adsorption structures and interaction of cyclohexane molecules on the clean and hydrogen-preadsorbed Rh(111) surfaces were investigated using scanning tunneling microscopy, spot-profile-analysis low-energy electron diffraction, temperature-programmed desorption, and infrared reflection absorption spectroscopy (IRAS). Various ordered structures of adsorbed cyclohexane were observed as a function of hydrogen and cyclohexane coverages. When the fractional coverage (θ(H)) of preadsorbed hydrogen was below 0.8, four different commensurate or higher-order commensurate superstructures were found as a function of θ(H); whereas more densely packed incommensurate overlayers became dominant at higher θ(H). IRAS measurements showed sharp softened C-H vibrational peaks at 20 K, which originate from the electronic interaction between adsorbed cyclohexane and the Rh surface. The multiple softened C-H stretching peaks in each phase are due to the variation in the adsorption distance from the substrate. At high hydrogen coverages they became attenuated in intensity and eventually diminished at θ(H) = 1. The gradual disappearance of the soft mode correlates well with the structural phase transition from commensurate structures to incommensurate structures with increasing hydrogen coverage. The superstructure of adsorbed cyclohexane is controlled by the delicate balance between adsorbate-adsorbate and adsorbate-substrate interactions which are affected by preadsorbed hydrogen.     

Surface chemistry of CN bond formation from carbon and nitrogen atoms on Pt(111)

The mechanism of CN bond formation from CH3 and NH3 fragments adsorbed on Pt(111) was investigated with reflection absorption infrared spectroscopy (RAIRS), temperature-programmed desorption (TPD), and X-ray photoelectron spectroscopy (XPS). The surface chemistry of carbon-nitrogen coupling is of fundamental importance to catalytic processes such as the industrial-scale synthesis of HCN from CH4 and NH3 over Pt. Since neither CH4 nor NH3 thermally dissociate on Pt(111) under ultrahigh vacuum (UHV) conditions, the relevant surface intermediates were generated through the thermal decomposition of CH3I and the electron-induced dissociation of NH3. The presence of surface CN is detected with TPD through HCN desorption as well as with RAIRS through the appearance of the vibrational features characteristic of the aminocarbyne (CNH2) species, which is formed upon hydrogenation of surface CN at 300 K. The RAIRS results show that HCN desorption at approximately 500 K is kinetically limited by the formation of the CN bond at this temperature. High coverages of Cads suppress CN formation, but the results are not influenced by the coadsorbed I atoms. Cyanide formation is also observed from the reaction of adsorbed N atoms and carbon produced from the dissociation of ethylene.     

Sensitivity of methyl thiolate desulfurization selectivity to reaction temperature and hydroxyl coverage

The adsorption and reaction of methanethiol (CH3SH) and dimethyl disulfide (CH3SSCH3) on Mo(110)-(1 x 6)-O have been studied using temperature-programmed reaction spectroscopy and reflection-absorption infrared spectroscopy over the temperature range of 110-550 K. The S-H bond is broken upon adsorption to form adsorbed OH, water, and methyl thiolate (CH3S-) at low temperature. Water is evolved at 210 and 310 K via molecular desorption and disproportionation of OH, respectively. Some hydroxyl remains on the surface up to 350 K. Methyl thiolate is also formed from CH3SSCH3 on Mo(110)-(1 x 6)-O. Methyl thiolate undergoes C-S cleavage above 300 K, yielding methane and methyl radicals. There is also a minor amount of nonselective decomposition leading to the formation of carbon and hydrogen. Methane production is promoted by adsorbed hydroxyl. As the hydroxyl coverage increases, the yield of methyl radicals relative to methane diminishes. Accordingly, there is more methane produced from methanethiol reaction than from dimethyl disulfide, since S-H dissociation in CH3SH produces OH. The maximum coverage of the thiolate is approximately 0.5 monolayers, based on the amount of sulfur remaining after reaction measured by Auger electron spectroscopy. In contrast to cyclopropylmethanethiol (c-C3H5CH2SH), for which alkyl transfer from sulfur to oxygen is observed, there is no evidence for transfer of the methyl group of methyl thiolate to oxygen on the surface. Specifically, there is no evidence for methoxy (CH3O-) in infrared spectroscopy or temperature-programmed reaction experiments.     

An EELS study of CO2 and CO3 adsorbed on oxygen covered Ag(110)

The vibrational spectra of CO₂ and CO₃ adsorbed on Ag(110) was studied with high-resolution electron energy-loss spectroscopy (EELS). CO₂ does not adsorb on the clean surface at 100 K. EELS results show that preadsorbed atomic oxygen can induce adsorption and reaction with CO₂ to form a stable surface carbonate as well as a molecular CO₂ binding state at 100 K. The latter desorbs at 130 K while CO₃ decomposes to CO_2(g) and O_(a) at 480 K as shown by both EELS and thermal desorption. The vibrational spectrum of CO_2(a) bears remarkable similarities with CO₂ gas; both the strong asymmetric stretch at 2350 cm^? and the Fermi resonance are seen. EELS measurements performed as a function of annealing temperature indicate that the carbonate species binds with one oxygen down and the other two up with respect to the surface. Additionally, an irreversible conversion between this form and that with two oxygens down does not occur.     

Surface Chemistry of Ga(CH3)3 on Pd(111) and Effect of Pre-covered H and O

The adsorption and decomposition of trimethylgallium (Ga(CH₃)₃, TMG) on Pd(111) and the effect of pre-covered H and O were studied by temperature programmed desorption spectroscopy and X-ray photoelectron spectroscopy. TMG adsorbs dissociatively at 140 K and the surface is covered by a mixture of Ga(CH₃)_x (x=1, 2 or 3) and CHx(a) (x=1, 2 or 3) species. During the heating process, the decomposition of Ga(CH₃)₃ on clean Pd(111) follows a progressive Ga-C bond cleavage process with CH₄ and H₂ as the desorption products. The desorption of Ga-containing molecules (probably GaCH₃) is also identi ed in the temperature range of 275-325 K. At higher annealing temperature, carbon deposits and metallic Ga are left on the surface and start to di use into the bulk of the substrate. The presence of precovered H(a) and O(a) has a signi cant effect on the adsorption and decomposition behavior of TMG. When the surface is pre-covered by saturated H₂, CH₄, and H₂ desorptions are mainly observed at 315 K, which is ascribed to the dissociation of GaCH₃ intermediate. In the case of O-precovered surface, the dissociation mostly occurs at 258 K, of which a Pd-O-Ga(CH₃)₂ structure is assumed to be the precusor. The presented results may provide some insights into the mechanism of surface reaction during the lm deposition by using trimethylgallium as precursor.