甲烷部分氧化制合成气Ni/MgO和Ni-MgO/MgO催化剂的研究

甲烷氧化偶联制乙烷、乙烯以及甲烷选择氧化制甲醇、甲醛等反应 ,因其转化率和收率低 ,故短期内无法实现工业化 .目前 ,工业上应用甲烷蒸汽转化制合成气 ,进而合成氨等化工产品 .甲烷蒸汽转化制的合成气 ,其 H2 /CO≥ 3,不适用于甲醇合成和 F- T合成 .而甲烷部分氧化制的合成气 ,其H2 /CO≤ 2 ,因而最适合用于甲醇合成和 F- T合成 ,故近 1 0年来倍受科学家的关注[1 ,2 ] .在 CH4部分氧化制合成气中 ,钌、铑、钯、铂等贵金属催化剂的活性高、选择性好、稳定性好[1 ] ,但价格昂贵 (负载量以 1 2 %～ 4 0 %为佳 ) ,因而难以实现商品化 .N…     

添加贵金属的Ni/α-Al2O3催化剂甲烷部分氧化制合成气的研究

甲烷部分氧化制合成气因其高空速、高转化率、低H2/CO比而引起人们的重视[1～5].本文研究了在Ni/α-Al2O3催化剂中添加的Rh、Ru、Pt和Pd等贵金属在甲烷部分氧化制合成气反应中的催化作用,重点研究了添加Pt对Ni/α-Al2O3催化剂反应性能的影响.     

氧化锆担载镍甲烷干重整催化剂的载体形貌效应（英文）

煤层气是储量十分丰富的煤炭伴生资源,也是煤炭开采中最大的安全隐患之一,同时还是重要的温室气体.研究煤层气的高效、清洁资源化利用具有资源和环境双重意义.因此,世界主要产煤国均十分重视煤层气的开发和利用.煤层气的主要成分是甲烷,目前主要通过两种方式实现其资源化利用:(1)直接转化,主要通过氧化偶联、催化氧化官能团化或脱氢芳构化等途径将其转化为高碳烃、含氧化合物及芳烃等;(2)间接转化,甲烷首先经催化重整反应制取合成气,而后再经Fischer-Tropsch合成、甲醇化和氢甲酰化等过程来合成饱和烃、烯烃、甲醇及其他含氧化物.对于前者,由于热力学限制,反应收率很低,应用前景较差,而经由合成气这一平台产物的间接转化路线被认为是一条甲烷资源化利用颇具工业前景的转化路线.因此,甲烷催化重整制合成气备受关注.研究表明,贵金属具有较好的甲烷重整催化性能,但其储量有限、价格昂贵的内在缺陷不利于甲烷大规模转化和资源化利用.Ni基催化剂具有与贵金属可比的催化活性和选择性,且其储量丰富,价格低廉,因此在甲烷重整反应中备受青睐.但是,相对于贵金属,Ni基催化剂易于积碳和烧结失活,这已成为制约其大规模工业化应用的瓶颈.迄今,大量文献报道关注如何提高Ni基催化剂的催化稳定性.而载体形貌调控是调节负载型催化剂的有效途径.本文开展了用作载Ni催化剂的氧化锆载体的形貌调控研究,以期可以有效调节载Ni催化剂的物化性质,进而调控载Ni催化剂的甲烷重整催化性能.采用水热法成功制备了松球状和鹅卵石状的单斜相氧化锆载体,进一步负载镍,制备了载镍催化剂,用于甲烷重整制合成气反应.具有分级结构的松球状氧化锆载Ni催化剂(Ni/ZrO_2-ipch)展示出比鹅卵石状氧化锆和常规氧化锆纳米粒子载Ni催化剂显著好的催化活性和稳定性.采用XRD、N_2吸附、TEM、H_2-TPR、CO化学吸附、CO_2-TPD、XPS和TGA等手段研究了松球状氧化锆载Ni催化剂高催化活性和稳定性的原因和机制.发现,其较高的催化活性主要归因于高的Ni分散度、改善的可还原性、促进的氧流动性以及较多的碱性位和较强的碱性,这些物化性质依赖于氧化锆载体的独特形貌.分级结构的松球状氧化锆载Ni催化剂高的甲烷重整催化稳定性主要源于催化剂的高抗烧结、抗积碳性能.加强的金属载体效应和介孔限域效应可以阻止金属Ni的高温烧结,而优良的抗积碳稳定性主要源于催化剂良好的氧流动性、较多的碱性位、较强的碱性以及小的Ni粒子尺寸.鉴于分级结构松球状氧化锆载Ni催化剂高的催化活性和优良的抗积碳、抗烧结稳定性,该催化剂用于甲烷重整制合成气具有广阔前景.而所制备的分级结构松球状氧化锆由于具有独特的结构和优良的热稳定性,可以作为性能优良的载体用于其他反应,尤其对于高温转化过程可望表现出明显优势.     

在Li-Nd-Zn-Mg氧化物上甲烷氧化偶联

天然气资源丰富,其中主要成分为甲烷.以甲烷为原料开发化工产品一直引起人们的重视.1982年Keller首先提出甲烷氧化偶联制乙烯、乙烷的催化过程,为开拓廉价乙烯原料路线提供了新的可能途径,从而引起各国催化工作者的重视.近年来,此催化过程的乙烯及乙烷的收率(y_(02))已提高到10—30%之间.各国都在努力开发活性高及选择性好的催化剂,促使此催化过程工业化。本文研究了Li-Nd-Zn-Mg氧化物甲烷氧化偶联催化剂,对反应条件进行了初步考察,乙烯及乙烷的收率y_(02)达到30.8%。     

氧化锆担载镍甲烷干重整催化剂的载体形貌效应

煤层气是储量十分丰富的煤炭伴生资源,也是煤炭开采中最大的安全隐患之一,同时还是重要的温室气体.研究煤层气的高效、清洁资源化利用具有资源和环境双重意义.因此,世界主要产煤国均十分重视煤层气的开发和利用.煤层气的主要成分是甲烷,目前主要通过两种方式实现其资源化利用:(1)直接转化,主要通过氧化偶联、催化氧化官能团化或脱氢芳构化等途径将其转化为高碳烃、含氧化合物及芳烃等;(2)间接转化,甲烷首先经催化重整反应制取合成气,而后再经Fischer-Tropsch合成、甲醇化和氢甲酰化等过程来合成饱和烃、烯烃、甲醇及其他含氧化物.对于前者,由于热力学限制,反应收率很低,应用前景较差,而经由合成气这一平台产物的间接转化路线被认为是一条甲烷资源化利用颇具工业前景的转化路线.因此,甲烷催化重整制合成气备受关注.研究表明,贵金属具有较好的甲烷重整催化性能,但其储量有限、价格昂贵的内在缺陷不利于甲烷大规模转化和资源化利用.Ni基催化剂具有与贵金属可比的催化活性和选择性,且其储量丰富,价格低廉,因此在甲烷重整反应中备受青睐.但是,相对于贵金属,Ni基催化剂易于积碳和烧结失活,这已成为制约其大规模工业化应用的瓶颈.迄今,大量文献报道关注如何提高Ni基催化剂的催化稳定性.而载体形貌调控是调节负载型催化剂的有效途径.本文开展了用作载Ni催化剂的氧化锆载体的形貌调控研究,以期可以有效调节载Ni催化剂的物化性质,进而调控载Ni催化剂的甲烷重整催化性能.采用水热法成功制备了松球状和鹅卵石状的单斜相氧化锆载体,进一步负载镍,制备了载镍催化剂,用于甲烷重整制合成气反应.具有分级结构的松球状氧化锆载Ni催化剂(Ni/ZrO2-ipch)展示出比鹅卵石状氧化锆和常规氧化锆纳米粒子载Ni催化剂显著好的催化活性和稳定性.采用XRD、N2吸附、TEM、H2-TPR、CO化学吸附、CO2-TPD、XPS和TGA等手段研究了松球状氧化锆载Ni催化剂高催化活性和稳定性的原因和机制.发现,其较高的催化活性主要归因于高的Ni分散度、改善的可还原性、促进的氧流动性以及较多的碱性位和较强的碱性,这些物化性质依赖于氧化锆载体的独特形貌.分级结构的松球状氧化锆载Ni催化剂高的甲烷重整催化稳定性主要源于催化剂的高抗烧结、抗积碳性能.加强的金属载体效应和介孔限域效应可以阻止金属Ni的高温烧结,而优良的抗积碳稳定性主要源于催化剂良好的氧流动性、较多的碱性位、较强的碱性以及小的Ni粒子尺寸.鉴于分级结构松球状氧化锆载Ni催化剂高的催化活性和优良的抗积碳、抗烧结稳定性,该催化剂用于甲烷重整制合成气具有广阔前景.而所制备的分级结构松球状氧化锆由于具有独特的结构和优良的热稳定性,可以作为性能优良的载体用于其他反应,尤其对于高温转化过程可望表现出明显优势.     

微波辐照引发甲烷部分氧化制合成气Ⅰ.反应条件对Ni/La2O3催化剂催化活性的影响

甲烷部分氧化可直接制得H2/CO比为2的合成气,该反应具有高活性、高选择性、高时空收率和反应温度较低等特点,有可能替代水煤气变换反应制取F-T合成和甲醇合成原料.因此,近年来甲烷部分氧化(POM)制合成气受到了人们的极大关注[1～7].我们的研究结果[4]表明,在微波场中进行的POM反应与常规加热条件下相比较,前者具有反应速率加快、催化床层温度降低、反应物的转化率和产物的选择性均得到改善等优点.在实验中我们还注意到,当原料气的空速增大到某一值后,一旦用微波辐照将反应引发,即可停止辐照,仅靠反应自身放出的热量就能维持反应的继续进行.显然,这对于降低能耗、节约能源大有益处.为此,本文以Ni/La2O3作催化剂,考察了微波辐照引发甲烷部分氧化制合成气的反应行为.     

甲烷在Ni/TiO2催化剂表面的活化

考察了Ni/TiO2催化剂甲烷部分氧化和二氧化碳重整制合成气的反应活性,实验表明,以TiO2为载体的镍系催化剂对于甲烷部分氧化制合成气反应具有较好的活性,尤其对H2的选择性较高,对二氧化碳重整制合成气反应具有较好的低温反应活性.采用脉冲-质谱在线分析等技术,在无气相氧条件下向Ni/TiO2催化剂脉冲CH4,发现甲烷在催化剂表面的活化（转化）及其氧化产物的选择性与金属催化剂表面氧的浓度密切相关.CH4与Ni/TiO2催化剂作用过程中存在明显的氢溢流和氧溢流现象,可能是这种溢流效应使得Ni/TiO2催化剂具有良好的反应活性和抗积碳性能.     

抗积炭CH_4/CO_2重整用Ni/Al_2O_3催化剂

甲烷转化制备的合成气是合成液体燃料和含氧有机化合物的原料 .甲烷转化制合成气的方法有甲烷蒸汽重整、甲烷部分氧化和甲烷、二氧化碳重整 3种 [1～ 3] .对于 CH4/CO2 重整反应 ,调节进料比可制备出 H2 /CO≤ 1、富含 CO的合成气 ,它适于羰基合成和 F- T合成 .这种方法一方面充分利用碳资源 ,缓解能源危机 ;一方面可减少温室气体的排放 ,改善人类的居住环境 .目前倍受关注 .CH4/CO2 重整制合成气 ,Rh、Ru、Pd、Ir等贵金属有很高的活性和稳定性 [4] .但其价格昂贵 ,高温易流失 ,商业化困难 .Ni基催化剂的活性与贵金属相当 ,但它易积…     

甲烷氧化偶联催化剂的研究：氯化锂在第一过渡金属氧化物中的添加效果

甲烷大量存在于自然界中,是石油气、天然气和沼气的主要成分.近年来,化学工作者进行了甲烷氧化偶联制乙烯的研究.其特点是可以不经过合成气的过程,直接由甲烷转化成乙烯或乙烷.本文介绍了氯化锂对甲烷直接氧化偶联成乙烯的创催化作用,可以明显地提高乙烯的选择性和收率. 本实验使用的是常压固定床流动体系反应装置.反应条件为750℃,W/F=0.233g     

氧载体的氧物种直接氧化甲烷制合成气

甲烷部分氧化制合成气由于合成气中n(H2)/n(CO)接近2,可直接用于甲醇合成或烃类F-T合成等后续工业过程而在国内外受到了广泛的关注。利用氧载体的氧物种在无气相氧下直接选择氧化甲烷制合成气是天然气化工利用的新方法,本文介绍了该方法的基本原理、概念工艺和对氧载体的性能要求,对应用于该方法的铈基复合氧化物的掺杂和助剂对选择氧化甲烷性能的影响、钙钛矿氧化物氧载体的氧缺陷、氧物种迁移、结构稳定性及其氧物种氧化甲烷的性能进行了阐述和分析,提出了控制氧载体表面状态是获得高合成气选择性的关键,并对该技术今后的研究重点进行了展望。     

碳纳米管的激光溅射产生

碳纳米管的激光溅射产生程大典,余荣清,刘朝阳,张强,王育煌,黄荣彬,詹梦熊,郑兰荪（固体表面物理化学国家重点实验室,厦门大学化学系,厦门,３６１００５）关键词碳纳米管,激光溅射,碳球Ｓｍａｌｌｅｙ等［１］曾以脉冲激光束在超声分子束喷口的喉道处蒸发石墨...     

Effect of surface structure on the charge storage capacity of carbon black electrodes

In this work we study the effect of surface structure on the charge storage capacity of carbon black electrodes with various changes in surface chemistry, morphology, and doping species. Cyclic voltammetry and chronopotentiometry studies, performed under alkaline conditions with carbon paste electrodes, indicate the importance of surface structure and grain size on the faradic and capacitive charge contributions of these materials. Among the various carbon blacks studied, the lithiated material shows superior charge storage capacity, suggesting the importance of alkaline metals and oxygenated groups on the carbon surface. For the graphitic carbon, the appearance of a reversible redox process with cycling resembles the electrochemical behavior reported for hydrogen storage in carbon nanotubes. Electronic Publication     

交流放电法合成多种形态的碳纳米管

碳纳米管的发现［１］引起了科学界的广泛重视,人们对于这种新型材料在纳米导线、高强纤维、超导等方面的应用寄予厚望．目前,合成碳纳米管的方法主要是采用不等径石墨棒直流放电,在阴极上得到含有碳纳米管的沉积物［２］．对于碳纳米管的应用,有关的理论研究［３］及...     

Modern Strategies for Carbon Isotope Exchange

In contrast to stable and natural abundant carbon-12, the synthesis of organic molecules with carbon (radio)isotopes must be conceived and optimized in order to navigate through the hurdles of radiochemical requirements, such as high costs of the starting materials, harsh conditions and radioactive waste generation. In addition, it must initiate from the small cohort of available C-labeled building blocks. For long time, multi-step approaches have represented the sole available patterns. On the other side, the development of chemical reactions based on the reversible cleavage of C−C bonds might offer new opportunities and reshape retrosynthetic analysis in radiosynthesis. This review aims to provide a short survey on the recently emerged carbon isotope exchange technologies that provide effective opportunity for late-stage labeling. At present, such strategies have relied on the use of primary and easily accessible radiolabeled C1-building blocks, such as carbon dioxide, carbon monoxide and cyanides, while the activation principles have been based on thermal, photocatalytic, metal-catalyzed and biocatalytic processes.     

非晶碳纳米球的低温石墨化(英文)

The investigation by SEM/TEM, porosity, and X-ray diffraction measurements of the graphitization process starting from amorphous carbon nanospheres, prepared by glucose carbonization, is reported. Aspects studied are the annealing temperature in the 750–1000 °C range, the type of inert carrier gas, and time of treatment in the 2–6 h range. It is investigated how these parameters influence the structural and morphological characteristics of the carbon materials obtained as well as their nanostructure. It is shown that it is possible to maintain after graphitization the round-shaped macro morphology, a high surface area and porosity, and especially a large structural disorder in the graphitic layers stacking, with the presence of rather small ordered domains. These are characteristics interesting for various catalytic applications. The key in obtaining these characteristics is the thermal treatment in a flow of N2. It was demonstrated that the use of He rather than N2 does not allow obtaining the same results. The effect is attributed to the presence of traces of oxygen, enough to create the presence of oxygen functional groups on the surface temperatures higher than 750 °C, when graphitization occurs. These oxygen functional groups favor the graphitization process.     

Electrochemical storage of hydrogen in nanocarbon materials: electrochemical characterization of carbon black matrices

In this work, various types of carbon black are electrochemically characterized to study their possible use in the electrochemical evaluation of fullerene materials as hydrogen storage candidates. The cyclic voltammetry and chronopotentiometry studies were performed in alkaline media, 6 M KOH, with carbon paste electrodes. Differences in the electrodes' electrochemical response and their correlation with the various surface chemistries, morphology and doping species of carbon blacks suggest a stronger dependency on the presence of doping agents (foreign metals) and on the surface structure than on the carbon black surface area. The study allows the selection of appropriate carbon black materials to be used as matrixes in future fullerene composite studies. Electronic Publication     

析因设计结合响应面法分析甲烷干重整过程中通过形成碳纳米管进行二氧化碳减排(英文)

A factorial experimental design was combined with response surface methodology(RSM) to opti-mize the catalyzed CO2 consumption by coke deposition and syngas production during the dry re-forming of CH4. The CH4 /CO2 feed ratio and the reaction temperature were chosen as the variables, and the selected responses were CH4 and CO2 conversion, the H2 /CO ratio, and coke deposition. The optimal reaction conditions were found to be a CH4 /CO2 feed ratio of approximately 3 at 700 °C, producing a large quantity of coke and realizing high CO2 conversion. Furthermore, Raman results showed that the CH4 /CO2 ratio and reaction temperature affect the system's response, particularly the characteristics of the coke produced, which indicates the formation of carbon nanotubes and amorphous carbon.     

Photocatalytic carbon dioxide reduction by photocatalyst innovation

The photocatalytic conversion of carbon dioxide into sustainable fuel methanol using carbon quantum dots is highlighted in this paper. The multifaceted roles of carbon quantum dots in photocatalytic reactions and future directions of CQD materials are outlined.     

Pt-CNTs 修饰玻碳电极(Pt-CNTs/GC)电氧化活性的研究

采用透射电镜(TEM)和选区电子衍射(SAED)技术, 分别表征了Pt-CNTs/GC电极的表面形貌和所负载铂纳米原子簇的结构. 以CO和CH3OH为探针分子, 用循环伏安和计时电流等常规电化学方法检测了CO和CH3OH在Pt-CNTs/GC电极上的氧化行为. 研究结果表明, CO在Pt-CNTs/GC电极上有3个氧化电流峰(Ⅰ, Ⅱ, Ⅲ), 其中峰Ⅰ为CO桥式吸附的氧化峰, 而峰Ⅱ和Ⅲ则分别为CO线形吸附在碳纳米管负载的不同粒径的Pt纳米原子簇以及Pt原子薄膜上所分裂的氧化峰; CH3OH在Pt-CNTs/GC电极上也能自发解离吸附强吸附中间体CO; Pt-CNTs/GC电极对CH3OH的氧化峰电流不总是随CNTs上载铂量的增加而增大, 表明在制备直接甲醇燃料电池阳极时, 应选择合适的载铂量.     

Synthetic Approaches toward Molecular and Polymeric Carbon Allotropes

Life on earth is based on compounds that have carbon frames and backbones. Today, chemists have added to the world of biomolecules and biopolymers approximately 10⁷ different synthetic molecules and polymers, the structures of which also depend on the formation of strong, stable carbon–carbon bonds. Although the stability of carbon–carbon bonds has been recognized for more than a century, the two natural modifications graphite and diamond were, until recently, the only allotropic forms of carbon on earth that were available in macroscopic quantities and were structurally well characterized. With the synthesis of macroscopic quantities of buckminsterfullerene (C₆₀) and the higher fullerenes (C₇₀, C₇₆, C₇₈, etc.) and the exploration of the fascinating properties of these all-carbon spheres, this situation has completely changed. In the coming decades, the design, preparation, and study of novel molecular and polymeric allotropic forms of carbon will be a central topic in chemistry. Research in this area will dramatically advance the fundamental knowledge on carbon-based matter and, as already illustrated by the ongoing work on C₆₀, generate unprecedented technological perspectives. This review surveys synthetic organic-chemical approaches toward the preparation and study of all-carbon molecules and polymers that differ from the familiar networks of graphite and diamond as well as from the fullerenes. We will also discuss the ongoing research on fullerenes with a particular focus on the synthetic approaches to these all-carbon spheres and their transition metal complexes.