Dehydration of Castor Oil over NaHSO4/MCM‐41 Catalyst Modified by n‐Dodecyltriethoxysilane

n‐Dodecyltriethoxysilane (DTEOS) modified NaHSO₄/MCM‐41 catalysts (silanized catalysts) were synthesized by different impregnation sequences and evaluated in the liquid‐phase dehydration of castor oil. The samples were evaluated by X‐ray diffraction, nitrogen adsorption‐desorption, SEM, TEM, FT‐IR spectroscopy, XPS, ²⁹Si MAS NMR spectroscopy, contact angle measurements, NH₃‐TPD, and pyridine‐FT‐IR spectroscopy. The analyses demonstrated that silanization enhanced the hydrophobicity of the catalysts, and the impregnation sequence of silanized catalysts had a significant effect on the NaHSO₄ dispersion, surface area, acid distribution, and hydrophobicity of the silanized catalysts. The catalytic activity of the silanized catalysts was much higher than that of NaHSO₄/MCM‐41. Among the silanized catalysts, the catalyst prepared by simultaneous impregnation with DTEOS and NaHSO₄ showed the highest iodine value of 141.8 [g(I₂) per 100 g] and lowest hydroxyl value of 11.3 [mg(KOH) · g^–1].     

Different approaches of impregnation for resolution of enantiomers of atenolol,propranolol and salbutamol using Cu(II)-l-amino acid complexes for ligand exchange on commercial thin layer chromatographic plates

Atenolol and propranolol (the β-blocking agents) and salbutamol (broncho- and vasodilator) were resolved into their enantiomers by adopting different modes of loading/impregnating the Cu(II) complexes of l-proline (l-Pro), l-phenylalanine (l-Phe), l-histidine (l-His), N,N-dimethyl-l-phenylalanine (N,N-Me₂-l-Phe), and l-tryptophan (l-Trp) on commercial precoated normal phase plates. The three different approaches were (A) using the Cu(II)-l-amino acid complex as chiral mobile phase additive, (B) ascending development of plain commercial plates in the solutions of Cu complex, and (C) using a solution of Cu(II) acetate as mobile phase additive for the commercial TLC plates impregnated with ascending development of plates in the solutions of amino acid. Spots were located using iodine vapour. The results obtained for the three methods have been compared for their efficiency and the issue of involvement of the Cu(II) cation for the best performance of the three methods has been discussed with respect to the same mobile phase. The detection limit is 0.18 μg for each enantiomer.     

共溶剂对超临界CO_2注入技术制备聚丙烯/SiO_2纳米复合材料的影响(英文)

采用超临界CO2注入技术制备聚合物-无机纳米粒子复合材料,以乙醇作为共溶剂,在超临界CO2中将正硅酸乙酯(TEOS)注入到聚丙烯(PP)中,重点研究共溶剂乙醇对TEOS在PP中注入率的影响.实验结果表明注入率随着共溶剂加入先增加后减小.同时研究了在共溶剂的存在下其他实验条件对注入率的影响.并采用卢瑟福背散射能谱法(RBS)分析了聚丙烯/SiO2纳米复合材料的注入元素深度分布,发现Si元素在PP中的浓度分布不均匀,随着深度的增加而减小.     

Effect of the order of Ni and Ce addition in SBA-15 on the activity in dry reforming of methane

Dry reforming of methane has been carried out on SBA-15 catalysts containing 5 wt% Ni and 6 wt% Ce. The effect of the order of Ni and Ce impregnation on the catalytic activity has been studied. Both metals were added using the “two-solvent” method that favors metal dispersion inside the pores. Characterizations by XRD (low and high angles), N₂ sorption, SEM and TEM of the materials after metal addition and calcination indicate good preservation of the porosities and high NiO and CeO₂ dispersion inside the porous channels. Reduction was carried out before the catalytic tests and followed by TPR measurements. The most active reduced catalyst was the Ni–Ce/SBA-15 sample prepared by impregnating cerium first, then nickel. All catalysts were highly active and selective towards H₂ and CO at atmospheric pressure. Full CH₄ conversion was obtained below 650 °C. The higher performances compared to those reported in the literature for mesoporous silica with supported Ni and Ce catalysts are discussed.     

Characterization and reactivity of γ-Al_2O_3 supported Pd–Ni bimetallic nanocatalysts for selective hydrogenation of cyclopentadiene

Several g-Al2O3 supported Pd–Ni bimetallic nanocatalysts(Pd–Ni(x:y)/Al2O3; where x and y represent the mass ratio of Pd and Ni, respectively) were prepared by the impregnation method and used for selective hydrogenation of cyclopentadiene to cyclopentene. The Pd–Ni/Al2O3 samples were confirmed to generate Pd–Ni bimetallic nanoparticles by X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS) and transmission electron microscopy(TEM). The catalytic activity was assessed in view of the effects of different mass ratios of Pd and Ni, temperature, pressure, etc. Among all the samples, the Pd–Ni(1:1)/Al2O3(PN-1:1) catalyst showed extremely high catalytic ability. The conversion of cyclopentadiene and selectivity for cyclopentene can be simultaneously more than 90%.     

TLC separation of some biologically important amino acids on pyridinium tungstoarsenate impregnated layers

Summary A satisfactory TLC separation scheme for 15 important amino acids on silica gel layers impregnated with pyridinium tungstoarsenate using isoamyl alcohol-wateracetic acid (605030) as the solvent system has been worked out. It is found that the Martin relationship is obeyed by similarly constituted amino acids. A plot of R_M vs the concentration of pyridinium ion released shows a scatter suggesting that, besides exchange properties, other factors also strongly influence the movement of amino acids.     

Polymer adsorption on the surface of highly dispersed silica

Attempts at modification of silica surface with a polymer (natural latex) directly in the course of the precipitation process have been made. The effects of temperature, non-ionic surfactants and silane coupling agent in preparation of poly[cis-isoprene]-coated silica on the precipitation of polymer/silica composites initiated by ammonium salts (NH₄Cl, (NH₄)₂SO₄, NH₄HCO₃), have been studied. The influence of the process parameters on the quality of the silicas obtained and the character of the polymer adsorption on the silica surface has been determined along with the effect of the surface impregnation with natural latex on physicochemical parameters of the silicas (bulk density, capacities to absorb water, dibutyl phthalate and paraffin oil) and their surface structure.     

金属含量对Ni-Pd/H-Y上正癸烷加氢异构化反应活性和产物选择性的影响

在Y分子筛上浸渍0.1 wt% Pd和0.1–0.5 wt% Ni,用X射线衍射表征了该催化剂的结晶度,用透射电镜测得平均金属粒径.催化剂中Pd和Ni的化学态用X射线光电子能谱测定,其酸性则用氨-程序升温脱附进行了表征,发现一些酸位被Ni2+离子交换.采用程序升温还原表征了HY分子筛负载的Pd, Ni和Pd-Ni催化剂的还原性能.正癸烷加氢异构化反应在200–450 oC和1 atm条件下进行.结果发现,当0.1 wt% Pd/HY中Ni添加量增至0.3 wt%时,正癸烷转化率和异构化选择性增加.单支链和双支链异构体选择性的增加表明该反应遵循质子化环丙烷中间体机理. Ni添加量超过阈值导致活性和异构化选择性急剧下降.综上可见,双金属催化剂更有利于选择性生成双支链异构体,其辛烷值更高.     

燃料对燃烧法制备Ni-Al_2O_3催化剂结构及浆态床甲烷化催化性能的影响

分别采用浸渍燃烧法和共燃烧法制备了一系列Ni-Al_2O_3催化剂,并对催化剂进行了表征,研究了燃料种类对不同方法制备的催化剂结构及浆态床CO甲烷化性能的影响.结果表明,以尿素、甘氨酸和乙二醇为燃料时,采用浸渍燃烧法制备的Ni-Al_2O_3催化剂织构性质均与载体相近,各催化剂金属Ni分散度和Ni晶粒相差不大,甲烷化性能接近,在260℃反应温度下CO转化率在80.1%~83.5%之间.而共燃烧法制备的Ni-Al_2O_3催化剂受燃烧过程影响明显,以甘氨酸和乙二醇为燃料时制得的催化剂比表面积较小,金属Ni分散度低且Ni晶粒较大,因而甲烷化活性较低;以尿素为燃料制备的催化剂比表面积大且Ni晶粒较小,CO转化率和CH_4选择性分别达到84.7%和91.1%.     

浸渍-裂解工艺对无压烧结制备六方氮化硼陶瓷性能的影响

以硼酸-尿素混合水溶液作为h-BN先驱体,对无压烧结制备的高纯h-BN陶瓷进行了浸渍-裂解-二次无压烧结处理,以提高其致密度和性能.研究了先驱体溶液浓度和循环次数对浸渍-裂解-烧结后h-BN陶瓷的显微结构及性能的影响.结果表明,随着先驱体溶液浓度的增大,h-BN陶瓷的密度、弯曲强度、断裂韧性和热导率均先升高后降低,浓度为68wt;时均达到最大.浓度过高会导致先驱体溶液在浸渍过程中发生析出,反而不利于浸渍.随着循环次数的增加,h-BN陶瓷的致密度、弯曲强度、断裂韧性及热导率均逐渐增大,但趋势逐渐变缓.循环6次得到的h-BN陶瓷的密度、弯曲强度、断裂韧性和热导率分别为1.465 g./cm3、84.1 MPa、1.52 MPa·m1/2、44.36 W·m-1·k-1,相对于未处理的h-BN陶瓷分别提高4.7;、31.6;、63.7;、31.2;.