明清江西萧公、晏公信仰入黔考

本文以贵州地方志为基本资料,考察了明清时期江西地方性神祇萧公、晏公信仰在贵州的分布、传播情况;进而探讨了它们由乡土之神转变为他乡之神的动力问题;认为萧公、晏公信仰的广泛传播,与明清时期移民社会的大背景相关。江西移民、商人进入贵州的同时也移植了自己的信仰,成为推动萧公、晏公信仰在贵州广泛分布的主要力量;同时,国家的支持也起到了推动作用。江西省社科规划青年项目“江西水神萧公信仰的建构与传播研究”(项目编号:13LS14)阶段性成

Catalytic Epoxidation of Propylene Using Nitrous Oxide or Oxygen as Oxidant

丙烯环氧化制环氧丙烷是催化领域的最关键的挑战之一.本文对作者等近年来开展的以一氧化二氮为氧化剂的铁催化体系和以氧气为氧化剂的铜催化体系的研究进展进行了综述.在这两类催化体系中,碱金属离子(特别是K+)的修饰作用均是获得较高环氧丙烷选择性的关键.碱金属离子通过调变催化剂中铁或铜物种的分散度、配位环境和酸碱性等,实现了对反应途径的调控,使反应朝着有利于环氧丙烷生成的方向进行.活性金属组分(铁或铜)与氧化剂(一氧化二氮或氧气)间的特定的组合对丙烯环氧化反应的发生也起着重要作用.推测在两类催化体系中,氧化剂均在具有特定结构和价态的铁或铜活性位上活化,产生导致丙烯环氧化反应发生的亲电性活性氧物种.The epoxidation of propylene to propylene oxide is one of the most challenging research targets in catalysis.This review highlights our recent studies on the epoxidation of propylene by nitrous oxide and oxygen catalyzed by iron-and copper-based heterogeneous catalysts.For both iron-and copper-based catalysts,the modification with an alkali metal ion(especially K+) plays pivotal roles in obtaining high selectivity to propylene oxide.Alkali metal ions may enhance the dispersion of iron and copper species,change their coordination environments,and regulate the surface acid and base properties,and thus contribute to the selective formation of propylene oxide.The unique combination of active metal component(iron or copper) and oxidant(nitrous oxide or oxygen) is also crucial for the epoxidation of propylene.We propose that the oxidant is activated on active iron or copper sites with peculiar structures and oxidation states,forming active oxygen species responsible for the epoxidation of propylene.国家自然科学基金(20625310,20773099,20433030);; 国家重点基础研究发展计划(973计划,2003CB615803,2005CB221408

Selective activation of the C–O bonds in lignocellulosic biomass for the efficient production of chemicals

高效转化来源丰富且可再生的木质纤维素制备化学品和燃料对建立可持续发展社会具有重要意义.木质纤维素利用的一条理想途径是将其主要成分纤维素、半纤维素和木质素在温和条件下高选择性地催化转化为关键平台化学品.本文综述了近年报道的有关纤维素、半纤维素和木质素或其模型分子中C–O键选择性活化生成葡萄糖、葡萄糖衍生物(包括葡萄糖苷、六元醇和葡萄糖酸)、木糖、阿拉伯糖和芳香化合物的新催化剂和新策略,阐述了决定催化性能的关键因素.本文还讨论了相关反应机理以深入理解C–O键选择性活化.纤维素由葡萄糖单元通过β-1,4-糖苷键连接而成,通过水解反应,选择性切断这些糖苷键可以获得葡萄糖或其低聚物.鉴于葡萄糖在水热条件下不稳定,发展纤维素温和条件下水解的酸催化剂至关重要.众多研究表明,均相酸催化剂(如无机酸,杂多酸等)具有强br？nSTEd酸,在该水解反应中显示高的催化活性.另一方面,拥有强酸性基团-SO3H的固体酸也表现出优异的水解糖苷键性能,但是-SO3H官能团易于流失,限制了这类固体酸催化剂的循环使用.最近研究显示,一些催化剂尤其是碳材料上引入能够与纤维素形成氢键的官能团时,其催化纤维素水解性能显著增强.设计合成这类具备酸性位和氢键位协同效应的稳定固体酸催化剂是纤维素水解转化的一个颇具前景的研究方向.以醇替代水为溶剂实施纤维素醇解制葡萄糖苷是高效活化糖苷键的有效策略.杂多酸被证实为该醇解反应的高性能催化剂.在相同反应条件下,醇解产物葡萄糖苷较水解产物葡萄糖更为稳定,因此可以获得高的葡萄糖苷收率.开发稳定可重复利用的固体酸催化剂是纤维素醇解的关键.耦合水解与加氢或氧化反应可以直接将纤维素转化为相对稳定且具有广泛用途的多元醇或有机酸.目前已有一系列双功能催化剂被报道,这些催化剂通常组合了具备水解功能的液体酸或固体酸和具备加氢或氧化功能的贵金属或过渡金属(譬如ru,PT,nI和Au).其中杂多酸盐或含有磺酸官能团的固体酸负载ru或Au双功能催化剂显示出优异的生成六元醇或葡萄糖酸的催化性能.半纤维素由葡萄糖、甘露糖、木糖、阿拉伯糖、半乳糖等单糖单元通过糖苷键连接而成,糖苷键选择性活化可生成各种单糖混合物.硫酸可以有效水解半纤维素,但是同时也易于催化所生成的单糖深度转化为呋喃及其衍生物.较之硫酸,酸性较弱的有机酸特别是二元羧酸(例如马来酸、草酸等)具有较高的单糖选择性.固体酸如酸性树脂,分子筛等亦可催化半纤维素水解反应,但树脂类催化剂中官能团的流失问题有待解决.木质素是由含甲氧基等取代基的苯丙烷单元通过一系列化学键连接而成的复杂大分子,其芳香单元间包括β-O-4,α-O-4和4-O-5等三种主要连接方式,选择性切断这些C–O键可获得高附加值的芳香化合物.水解和氢解是两类普遍用以活化木质素及其模型化合物C–O键的反应.酸和碱均可催化木质素及其模型化合物水解,但是通常需要苛刻条件获取高转化率.近期研究显示,通过对木质素Cα-OH预氧化,再以HCOOH/HCOOnA实施水解反应,可以成功实现温和条件下有机溶剂提取木质素及其模型化合物的高效转化.另一方面,均相金属络合物(如nI,fE和ru)或多相负载型金属催化剂(如nI,Cu,MO,PT,ru,Pd或ru等)均可有效催化木质素及其模型化合物中C–O键氢解,获得芳烃化合物.在部分多相催化剂体系中,除C–O键活化断裂外,还伴随芳环深度加氢反应,产生较多环己烷衍生物.因此,设计合成具备氢解功能同时抑制过度加氢功能的催化剂是获得芳烃化合物的关键.The efficient transformation of abundant and renewable lignocellulosic biomass for the production of chemicals and fuels is of considerable importance for establishing a sustainable society.The selective catalytic conversion of the major components of lignocellulosic biomass, including cellulose, hemicellulose and lignin, into key platform chemicals under mild conditions represents an ideal route for the utilization of this abundant resource.Cellulose is composed of multiple glucose units, which are linked together through β-1,4-glycosidic bonds, and the selective cleavage of these glycosidic bonds would therefore provide access to glucose and glucose derivatives.Hemicellulose is a heteropolysaccharide composed of different sugar units such as glucose, mannose, xylose, arabinose and galactose.The selective cleavage of the glycosidic bonds in hemicelluloses would therefore provide a mixture of different sugars.In contrast to cellulose and hemicellulose, lignin is a complex macropolymer consisting of methoxylated phenylpropane structures.Furthermore, lignin contains a variety of different C–O bond types, including β-O-4, α-O-4 and 4-O-5 bonds, which connect the primary aromatic units in lignin.The selective cleavage of these C–O bonds would therefore lead to the formation of high-value aromatic compounds.In this review article, we have provided a detailed summary of recent advances towards the development of new catalysts and novel strategies for the selective cleavage of the C–O bonds in cellulose, hemicellulose and lignin, as well as closely related model systems, for the production of glucose, glucose derivatives(including alkyl glucosides, hexitols and gluconic acid), xylose, arabinose and aromatic compounds.The key factors determining catalytic performances have been described in detail.The reaction mechanisms have also been discussed to provide the reader with a deeper understanding of the processes involved in the selective activation of C–O bonds.supportedbyNationalNaturalScienceFoundationofChina(21173172;21473141); theResearchFundfortheDoctorialProgramofHigherEducation(20130121130001); theProgramforInnovativeResearchTeaminUniversity(IRT_14R31)~

Hydrogenation of carbon dioxide to light olefins over non-supported iron catalyst

研究了非负载型铁催化剂上CO2加氢制低碳烯烃反应.结果显示,添加碱金属可显著提高铁催化剂上的CO2转化率和烯烃选择性.在经k和rb修饰的fE催化剂上,CO2转化率可达约40%,烯烃选择性达到50%以上,其中C2~C4烯烃收率超过10%.催化剂表征结果表明,碱金属促进了催化剂中碳化铁的生成,这可能是催化剂性能提高的一个关键原因.随着k含量由1WT%增加至5WT%,CO2转化率及烯烃选择性均升高.但k含量过高时,催化剂活性降低.这可能是由于催化剂比表面积和CO2化学吸附量降低所致.当k含量为5%~10%时,k-fE催化剂上烯烃收率较高;进一步添加适量的硼可进一步提高烯烃选择性,且CO2转化率下降不大.The hydrogenation of CO2 to light olefins was investigated over non-supported Fe catalysts.It was found that the addition of alkali metal ions to the Fe catalyst led to significant increases in both the CO2 conversion and the selectivity for olefins.Over K-or Rb-modified catalysts, about 40% CO2 conversion and more than 50% olefin selectivity were obtained.The yield of C2–C4 olefins exceeded 10% over these modified catalysts.Catalyst characterization suggested that the formation of iron carbide species was accelerated by the modification of the Fe catalyst with alkali metal ions, and this enhancement may be one of the key reasons for the enhanced catalytic performance.For the K-modified Fe catalysts, K content has a major influence on the catalyst behavior.An increase in the K content from 1 to 5 wt% increased both CO2 conversion and olefin selectivity.However, too high a K content led to a decrease in the activity, probably because of decreases in the surface area and CO2 chemisorption capacity of the catalyst.The presence of an appropriate amount of B in the K-modified Fe catalyst was found to be beneficial to the olefin selectivity, without significantly de-creasing the conversion of CO2 .supportedbytheNationalBasicResearchProgramofChina(973Program;2013CB933100); theNationalNaturalScienceFoundationofChina(21173174;20923004;21033006;and21161130522); theSpecializedResearchFundfortheDoctoralProgramofHigherEducation(20090121110007); thePro

Oxidative dehydrogenation of ethane to ethylene in the presence of HCl over CeO_2-based catalysts

报道了一种HCl存在时温和条件下的乙烷氧化脱氢制乙烯催化转化新途径.研究发现,在多种金属氧化物催化剂中,CEO2呈现最佳乙烯生成的催化性能.与纳米粒子相比,具有棒状和立方体状形貌的CEO2纳米晶具有较高的乙烷转化率和乙烯选择性.以MnOX修饰CEO2可进一步提高催化性能.在8 WT%MnOX-CEO2催化剂上,723 k反应2 H时乙烷转化率和乙烯选择性分别为94%和69%.该催化剂性能稳定,反应100 H乙烯收率可保持在65%–70%.HCl的存在对乙烯的选择性生成起着至关重要的作用,一部分乙烯来自于氯乙烷的脱HCl反应.This article reports a new catalytic route for the oxidative dehydrogenation of ethane to ethylene in the presence of HCl at moderate temperatures.CeO2 was found to be the most efficient catalyst for the production of ethylene from the variety of metal oxides examined in this work.CeO2 nanocrys‐tals with rod and cube morphologies showed higher ethane conversions and ethylene selectivities than CeO2 nanoparticles.The modification of CeO2 by MnOx further enhanced the catalytic perfor‐mance.Ethane conversion of 94% and ethylene selectivity of 69% were obtained after 2 h of reac‐tion at 723 K over an 8 wt% MnOx-CeO2 catalyst.This catalyst was stable and the ethylene yield could be sustained at 65%–70% over 100 h of reaction.The presence of HCl played a key role in the selective production of C2H4, and some of the C2H4 was probably formed from chloroethane by de‐hydrochlorination.supportedbytheNationalBasicResearchProgramofChina(973Program;2010CB732303); theNationalNaturalScienceFoundationofChina(21033006); theProgramforChangjiangScholarsandInnovativeResearchTeaminUniversity(IRT1036)~

应用微乳法制备二氧化硅包裹钯纳米粒子

以氯钯酸为钯源 ,正硅酸乙酯 (TEOS)为硅源 ,利用十六烷基三甲基溴化铵 (CTAB) /正己醇 /水构成的微乳体系制备了二氧化硅包裹纳米金属Pd粒子 .其中Pd的粒径可在 5～ 3 0nm调变 ,外部SiO2 层的厚度可在 5～ 3 5nm调变 .详细考察了氯钯酸和正硅酸乙酯的浓度、微乳体系中水和正己醇的量等参数对制备的Pd/SiO2 粒子的大小及形态的影响

Characterization and Catalytic Performance of Co-MCM-41 for Styrene Epoxidation

分别采用模板剂离子交换法(TIE法)、水热合成法(DHT法)及浸渍法合成了Co-MCM-41,此催化剂能够在无共还原剂存在条件下催化以氧气为氧化剂的烯烃环氧化反应.另外考察了催化剂的结构特别是钴的存在状态与催化性能之间的关系,以期能够弄清催化环氧化反应中催化剂活性位的本质.X射线衍射及N2吸附-脱附等结果证实,当导入分子筛中的钴的量在2.2%以下时,所有的Co-MCM-41均具有规整排列的六方孔道结构.漫反射光谱和H2程序升温还原等结果表明,通过TIE法合成的样品中钴主要以孤立态钴离子(single-site Co(Ⅱ))形式存在,而以DHT法合成的样品中钴主要以微晶态Co2SiO4形式存在,浸渍法合成的样品中则存在大量颗粒状氧化钴.催化反应结果表明,当钴含量均接近1.0%时,采用TIE法合成的样品的苯乙烯转化率为45%,而用DHT法和浸渍法合成的样品的苯乙烯转化率均低于30%.考虑到氧化钴和Co2SiO4的低活性以及DHT法和浸渍法合成样品中可能存在一小部分孤立态钴离子,我们推测MCM-41中的孤立态钴离子是催化活化分子氧发生环氧化反应的高效活性位.The cobalt-containing MCM-41 can be used as the catalyst for the liquid-phase epoxidation of styrene with molecular oxygen.The correlations between its structures,especially the states of Co in it,and its catalytic performance were studied.It may be helpful to make clear the nature of active sites for the epoxidation.(Co-MCM-41) samples synthesized by a template-ion exchange(TIE) method, a direct hydrothermal(DHT) method and a conventional impregnation method have been characterized in detail.The X-ray diffraction and(N_2-adsorption) results indicate that the hexagonal array of mesopores in these samples is sustained as the cobalt contents are lower than 2.2%.The results of diffuse reflectance UV-Vis spectroscopy and H_2 temperature-programmed-reduction suggest that the cobalt introduced into Co-MCM-41 by the TIE method exists mainly as single-site(Co(Ⅱ)) ions,whereas the cobalt in the sample synthesized by the DHT method exists mainly as Co_2SiO_4 in a microcrystalline form and the samples prepared by the impregnation method contain a large proportion of cobalt oxide.With a similar cobalt content(ca 1.0%),the sample prepared by the TIE method gave a conversion of 45% in the epoxidation of styrene with molecular oxygen,however,the sample prepared by the DHT method or impregnation method gave a conversion lower than 30%.Since cobalt oxide and Co_2SiO_4 show a lower activity for the epoxidation reaction and there may also exist a small part of single-site Co(Ⅱ) ions in the samples prepared by the DHT method or impregnation method,we thus suggest that the single-site Co(Ⅱ) ions in MCM-41 are the real active sites for the epoxidation with molecular oxygen.国家自然科学基金资助项目(20273054,20373055

Catalytic conversion of methyl chloride to lower olefins over modified H-ZSM-34

比较了几种典型的沸石分子筛在氯甲烷转化制乙烯、丙烯和丁烯等低碳烯烃反应中的催化性能,发现H-zSM-34具有较佳的催化活性和选择性.经乙二胺四乙酸二钠(nA2H2EdTA)水溶液处理,并经离子交换及焙烧后,H-zSM-34上氯甲烷转化制低碳烯烃的催化性能显著改善.当nA2H2EdTA浓度为0.1 MOl/l,反应温度为673 k,CH3Cl分压9.2 kPA时,C2–C4烯烃选择性和收率分别达82%和61%.研究还发现,CE修饰H-zSM-34催化剂同样可改善氯甲烷制低碳烯烃的选择性和收率.表征结果表明,nA2H2EdTA处理和CE修饰均降低了H-zSM-34的酸性.酸性的降低可抑制低碳烯烃的氢转移反应,继而避免了其进一步转化为低碳烷烃.Among several typical zeolites,H-ZSM-34 was found to be an efficient catalyst for the conversion of methyl chloride to lower olefins,i.e.,ethylene,propylene,and butenes.Treatment of H-ZSM-34 with a Na2 H2 EDTA(EDTA = ethylenediaminetetraacetate) aqueous solution followed by ion exchange and calcination enhanced the catalytic performance significantly.The selectivity to lower olefins increased significantly for certain Na2 H2 EDTA aqueous solution concentrations;when the H-ZSM-34 catalyst was treated with a 0.1 mol/L Na2 H2 EDTA solution,the selectivity and yield of C2 –C4 olefins reached 82% and 61%,respectively,at 673 K and a CH3 Cl partial pressure of 9.2 kPa.The modifica- tion of H-ZSM-34 with Ce ions improved C2 –C4 olefin selectivity and yield.Catalyst characterization suggests that treatment with Na2 H2 EDTA or modification by Ce decreases the acidity of H-ZSM-34.The weakened acidity of the treated or modified H-ZSM-34 may suppress the hydrogen transfer reaction and prevent lower olefins from further transformation to paraffins.supportedbytheNationalBasicResearchProgramofChina(2010CB732303); theNationalNaturalScienceFoundationofChina(21173174;20923004;21033006;and21161130522); theProgramforChangjiangScholarsandInnovativeResearchTeaminUniversity(IRT1036)~

Effect of size of catalytically active phases in the dehydrogenation of alcohols and the challenging selective oxidation of hydrocarbons

The size of the active phase is one of the most important factors in determining the catalytic behaviour of a heterogeneous catalyst. This Feature Article focuses on the size effects in two types of reactions, i.e., the metal nanoparticle-catalysed dehydrogenation of alcohols and the metal oxide nanocluster-catalysed selective oxidation of hydrocarbons (including the selective oxidation of methane and ethane and the epoxidation of propylene). For Pd or Au nanoparticle-catalysed oxidative or non-oxidative dehydrogenation of alcohols, the size of metal nanoparticles mainly controls the catalytic activity by affecting the activation of reactants (either alcohol or O(2)). The size of oxidic molybdenum species loaded on SBA-15 determines not only the activity but also the selectivity of oxygenates in the selective oxidation of ethane; highly dispersed molybdenum species are suitable for acetaldehyde formation, while molybdenum oxide nanoparticles exhibit higher formaldehyde selectivity. Cu(II) and Fe(III) isolated on mesoporous silica are highly efficient for the selective oxidation of methane to formaldehyde, while the corresponding oxide clusters mainly catalyse the complete oxidation of methane. The lattice oxygen in iron or copper oxide clusters is responsible for the complete oxidation, while the isolated Cu(I) or Fe(II) generated during the reaction can activate molecular oxygen forming active oxygen species for the selective oxidation of methane. Highly dispersed Cu(I) and Fe(II) species also function for the epoxidation of propylene by O(2) and N(2)O, respectively. Alkali metal ions work as promoters for the epoxidation of propylene by enhancing the dispersion of copper or iron species and weakening the acidity.National Natural Science Foundation of China[20625310, 20773099, 20873110, 20923004, 21033006]; National Basic Research Program of China[2010CB732303

纳米Co_3O_4的制备及其在富氢气氛下CO选择氧化反应中的催化性能

过渡金属氧化物四氧化三钴(Co3O4)在CO氧化反应中展示了较好的低温活性.Co3O4催化剂用于富氢气氛下CO选择氧化反应已引起了人们极大的关注,具有潜在的应用前景.采用液相沉淀-热解氧化方法制备了2种不同形貌的纳米Co3O4.用X射线衍射(XRD)、扫描电子显微镜(SEM)等技术考察了包括沉淀剂种类、老化时间、焙烧温度等合成条件对生成Co3O4形貌、晶粒尺度的影响.制备的Co3O4的外形与沉淀前驱物外形直接相关.焙烧温度越高,Co3O4的颗粒越大.研究了制得的Co3O4在富氢气氛下CO选择氧化反应中的催化性能.对比以上方法制备的Co3O4的催化性能发现,催化剂的粒径和比表面积与催化剂的活性存在关联.使用尿素沉淀法并经250~300℃空气热解氧化制得的Co3O4具有较好的催化活性