多壁碳纳米管负载铂的甲苯加氢脱芳催化剂

以多壁碳纳米管(CNTs)为载体制备了负载型Pt催化剂Pt/CNTs并将其用于催化甲苯加氢脱芳(HDA)反应.结果表明,在1.0%Pt/CNTs催化剂上,在0.4MPa,373K,PhCH3/H2摩尔比=6/94和GHSV=120L/(h.g)的反应条件下,甲苯转化率可达100%,比反应速率为0.0523mmol/(s.m2),分别是γ-Al2O3和AC负载各自最佳Pt负载量催化剂1.4%Pt/γ-Al2O3和2.4%Pt/AC上相应值的1.17和1.18倍.甲苯加氢产物全部为甲基环己烷,其他可能的加氢产物均在气相色谱检测限以下.催化剂的表征研究揭示,用CNTs代替γ-Al2O3或AC作为载体并不会引起所负载Pt催化剂上甲苯HDA反应的表观活化能发生明显变化.与γ-Al2O3或AC负载的相应催化剂相比,一方面,CNTs负载的Pt催化剂易于在较低温度下还原活化,并且其工作态催化剂表面催化活性Pt物种(Pt0)所占表面Pt摩尔分率有所提高;另一方面,CNTs负载的Pt催化剂对H2具有较高的吸附/活化和储存能力.这些促进效应对催化剂HDA活性的提高都有重要贡献

上市公司股利政策与股市波动的实证研究

运用事件研究法从实证的角度分析了中国上市公司的年度股利公告对股票价格的影响 ,研究结果表明 ,三种不同的股利分配形式都可以引起股价的异常反应 ,相对于现金股利而言 ,市场更加欢迎股票股利和混合股利 ,而股票股利和现金股利之间的差异并不显著

我国上市公司股利政策与股市波动的实证研究

从实证的角度分析了中国上市公司的年度股利公告对股票价格的影响 ,运用的研究方法是事件研究法。研究结果表明 ,三种不同的股利分配形式都可以引起股价的异常反应 ,相对于现金股利而言 ,市场更加欢迎股票股利和混合股利 ,而股票股利和现金股利之间的差异并不显

Purification of Multiwalled Carbon Nanotubes and Characterization of Their Oxygen-Containing Surface Groups

Corresponding author. Email: [email protected].[中文文摘]用兼具酸性和氧化性的HNO3水溶液可方便地除去残留在原生态多壁碳纳米管(CNT)上的Ni-MgO催化剂组分,同时在其表面产生某些含氧官能团,使原生态多壁碳纳米管的疏水性表面变为亲水性表面.采用Boehm中和滴定法以及X射线衍射(XRD)、热脱附谱(TPD)、傅里叶变换红外(FTIR)光谱和X射线光电子能谱(XPS)等技术对HNO3处理过的多壁碳纳米管的相组成和表面含氧官能团进行测量和表征.结果表明:所生成表面含氧官能团的总量以经7.0mol·L-1硝酸378K处理24h的CNT为最高;3种主要表面含氧官能团的含量高低顺序为,羧基>内酯型羧基>酚型羟基.[英文文摘]We conveniently removed the Ni-MgO catalyst components from an as-grown multiwalled carbon nanotube (CNT) using an aqueous HNO3 solution with strong acidity and oxidizability as a purifying reagent. Some oxygen-containing surface groups were generated at the CNT surface, which converted the hydrophobic surface into a hydrophilic surface. The phase composition and the oxygen-containing surface groups of the CNTs treated by nitric acid were determined and characterized using Boehm′s neutralizing titration method and X-ray powder diffraction (XRD), temperature-programmed desorption (TPD), Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS) techniques. The results indicated that the total content of the formed oxygen-containing surface groups was the highest for the CNTs treated with 7.0 mol·L-1 aqueous HNO3 at 378 K for 24 h. The content of the three major oxygen-containing surface groups was: carboxyl>lactonic carboxyl>phenolic hydroxyl.国家重点基础研究发展规划项目(973)(2009CB939804);福建省重大科技专项专题项目(2009HZ0002-1

氢气在碳纳米管基材料上的吸附-脱附特性

利用高压容积法测定多壁碳纳米管(MWCNTs)及钾盐修饰的相应体系(K+-MWCNTs)的储氢容量,并用程序升温脱附(TPD)方法表征研究氢气在MWCNTs基材料上的吸附-脱附特性.结果表明,在经纯化MWC-NTs上,室温、9.0MPa实验条件下氢的储量可达1.51%(质量分数);K+盐对MWCNTs的修饰对增加其储氢容量并无促进效应,但相应化学吸附氢物种的脱附温度有所升高;K+的修饰也改变了MWCNTs表面原有的疏水性质.在低于723K的温度下,H2/MWCNTs体系的脱附产物几乎全为氢气;773K以上高温脱附产物不仅含H2,也含有CH4、C2H4、C2H2等C1/C2烃混合物;H2/K+-MWCNTs储氢试样的脱附产物除占主体量的H2及少量C1/C2烃混合物外,还含水汽,其量与吸附质H2源水汽含量密切相关.H2在碳纳米管基材料上吸附兼具非解离(即分子态)和解离(即原子态)两种形式

多壁碳纳米管及其对H_2吸附体系的Raman光谱

利用原位和非原位紫外 Raman谱法 ,对以 CH4 为碳源 ,由催化法制备的多壁碳纳米管( MWCNTs) ,K+-修饰的该类 MWCNTs,以及它们对 H2 的吸附体系进行了 Raman谱表征 ,观测到可分别归属于类石墨结构的基频模 D和 G以及它们的三阶组合频 ,表面 C-H3基和 C-H2 基等的特征Raman峰 ;H2 在这类碳纳米管上的吸附态包括解离吸附生成表面 C-H3和非解离吸附分子氢 H2 ( a) ;在相同实验条件下 ,K+-修饰体系上这两类氢吸附物种的表面浓度都比未经 K+-修饰的相应体系高

碳纳米管及其H_2吸附体系的Raman光谱

利用紫外Raman光谱技术 ,对分别以CO和CH4为碳源、由化学催化法制备的两种多壁碳纳米管以及它们的H2 吸附体系进行Raman光谱表征 ,观测到可分别归属于类石墨结构的基频模G (1 5 80cm- 1 )和D (1 41 6cm- 1 ,缺陷诱导 ) ,以及它们的二阶和三阶组合频 2D(2 83 2cm- 1 ) ,D +G (2 996cm- 1 ) ,2G (3 1 6 0cm- 1 )和 2D +G (441 2cm- 1 )的Raman峰 ;H2在这些多壁碳纳米管上吸附有两种形式 :非解离吸附分子氢H2 (a)和解离吸附生成含氢表面物种CHX(x =3 ,2 ,1 ) ,所观测在 2 85 0 ,2 96 7和 3 95 0cm- 1 处的Raman谱峰可分别归属于表面CH2 基的对称C -H伸缩模 ,CH3基的不对称C -H伸缩模 ,以及吸附态分子氢H2 (a)的H -H伸缩

Pt catalyst supported on multiwalled carbon nanotubes for hydrogenation-dearomatization of toluene

Using home-made multiwalled carbon nanotubes (CNTs) as the support, the Pt/CNTs catalyst was prepared by an incipient wetness method. Performance of the catalyst for hydrogenation-dearomatization (HDA) of toluene was evaluated and compared with the reference catalysts supported on gamma-Al2O3 and activated carbon (AC). Over the 1.0 % Pt/CNTs catalyst under the reaction conditions of 0.4 MPa, 373 K, PhCH3/H-2 = 6/94 (mol/mol) and GHSV = 120 L/(h center dot g), the observed conversion of toluene HDA reached 100 %, and the corresponding specific reaction rate was 0.052 3 mmol/(s center dot m(2)). This value was 1.17 and 1.18 times that of the 1.4 % Pt/gamma-Al2O3 and 2.4 % Pt/AC catalysts with the respective optimal Pt loading, respectively. It was experimentally found that using CNTs in place of gamma-Al2O3 or AC as the support of the catalyst did not cause a significant change in the apparent activation energy for the toluene HDA reaction but led to a slight increase in concentration of catalytically active Pt species (Pt-0) at the surface of the functioning catalyst. In addition, the Pt/CNTs catalyst could reversibly adsorb a greater amount of hydrogen under atmospheric pressure at temperatures from room temperature to 573 K. This unique feature would help to generate a microenvironment with higher stationary state concentration of active hydrogen-adspecies at the surface of the functioning catalyst. These effects favored the toluene HDA reaction

甲烷在流态化催化剂床裂解生长多壁碳纳米管

在常压、823～873K、流化床反应条件下,用自行研制的Ni0.5Mg0.5O催化剂,催化甲烷分解生长碳纳 米管(CNTs),考察催化剂床层由固定床过渡到流化床状态的条件及其对制管过程的影响。结果表明,在 Φ32mm管式反应器及相应供热工况条件下,其流化床操作条件以管壁温度控制在约853K、原料气CH4线速 v为18～22cm/s、空速GHSV为3×104～6×104mL(STP) CH4/(h·g)为宜;反应1.0h,最高产率达 10g CNTs/g,这相当于固定床将制管反应时间延长至4～5h的产率水平。所得CNTs产物经TEM、SEM、 TPH、XRD和LRS等测试技术表征。结果表明,其为多壁碳纳米管(MWCNTs),外管径在10～50nm范围;纯 化后的CNTs产物含碳量≥99.5%,石墨状碳含量≥90%

H_2在K~0-MWCNTs上储存和吸附/脱附特性研究

利用高压容积法辅以卸压升温脱附排水法,测定金属K修饰多壁碳纳米管对H2的吸附储存容量.结果表明,在室温(25℃),7.25MPa实验条件下,x%K0-MWCNTs(x%=30%～35%,质量百分数)对H2的吸附储存容量可达3.80wt%(质量百分数),是相同条件下单纯MWCNTs氢吸附储量的2.5倍;室温下卸至常压的脱附氢量为3.36wt%(占总吸附氢量的～88%),后续升温至673K的脱附氢量为0.41wt%(占总吸附氢量的～11%).利用LRS和H2-TPD-GC/MS等谱学方法对H2/K0-MWCNTs吸附体系的表征研究表明,H2在K0-MWCNTs上吸附存在非解离(即分子态)和解离(即原子态)两种吸附态;在≤723K温度下,H2/K0-MWCNTs体系的脱附产物几乎全为H2气;723K以上高温脱附产物不仅含H2,也含有CH4,C2H4和C2H2等C1/C2-烃