浸渍溶液pH值对Co/SiO2催化剂催化F-T合成反应的影响

 以硅胶为载体,利用硝酸和尿素调节浸渍液的pH值,采用等体积浸渍法制得钴质量分数为10.0%的Co/SiO2 催化剂,结合XRD,TPR和原位IR等表征手段,考察了浸渍溶液pH值对催化剂物化性质和催化性能的影响. 结果表明,浸渍溶液pH值大于硅胶载体的等电点有利于活性组分钴在硅胶表面的吸附和分散,促进了钴与硅的相互作用,降低了催化剂的还原度,使催化活性降低,甲烷选择性增大. 浸渍溶液pH值小于硅胶载体的等电点则减弱了钴在硅胶表面的吸附,降低钴的分散,削弱了钴与硅的相互作用,有利于提高催化剂催化费托合成反应的活性和选择性.     

Co在超细Mo-Co-K催化剂合成低碳醇中的作用

采用BET、XPS和TPD表征手段对超细Mo-Co-K催化剂的织构、表面结构和吸附行为进行了研究，结合催化剂的合成低碳醇性能，论证了Co在超细Mo-Co-K催化剂合成低碳醇中的作用。Co的加入提高了催化剂合成低碳醇的活性和选择性，同时也提高了催化剂的比表面并促进了微孔的形成，催化剂的催化性能与其织构之间呈现出很好的顺变关系。Co对催化剂中可能作为合成低碳醇活性中心的低价Mo物种的电子结合能值影响较小。Co的加入降低了H2和CO在催化剂表面的强吸附中心的吸附强度，从而有利于合成低碳醇反应的发生。研究结果表明，Co仅仅是作为结构助剂，通过调变催化剂的织构和催化剂表面的H2及CO的强吸附中心而影响其合成低碳醇性能的。     

负载型钼系超细催化剂的合成,结构与反应性能研究

负载型钼系催化剂广泛用于加氢脱硫、抗硫甲烷化及部分氧化等,其加氢脱硫活性与低温氧的表面吸附量成正比,活性组分受载体性质的影响。超细粒子是近年来兴起的新型催化材料,由于其表面及体积效应,导致其特殊的表面吸附性能。以超临界法合成NiO/Al_2O_3、Fe_2O_3/SiO_2等超细催化剂已有报道,但该法对MoO_3/Al_2O_3的合成尚未见报道。本文以MoO_3/Al_2O_3超临界法合成超细粒子催化剂,根据超细催化剂分散性与粒径的关系选择了活性与钼表面分散性有依赖关系的临氢重整反应为探针,研究了超细MoO_3/Al_2O_3催化剂的性质。     

多孔活性硅胶的制备及吸附性能的研究

以硅酸钠和氯化铵为原料,通过添加表面活性剂制备高吸附活性的多孔硅胶.采用SEM,IR和XRI)等手段对硅胶样品的结构和形貌进行表征,并利用紫外分光光度法研究硅胶样品对垃圾渗滤液中有机污染物的吸附性能.结果表明,合成的硅胶样品是由纳米量级的无定形二氧化硅颗粒组成的多孔性、疏松状物质,对垃圾渗滤液中的有机物分子具有较强的吸...     

由亲水和疏水硅胶制备的Co/Ru/SiO2催化剂的表征及催化性能研究

以亲水硅胶Degussa A300和疏水硅胶Degussa R106作为催化剂载体，采用等体积浸渍法制备了一系列钴基催化剂。利用MS、XRD、BET、FT-IR、TPR等手段考察了载体热稳定性，催化剂表面物相结构和还原性能等物化性能。结果表明，载体表面有机基团对催化剂中Co3O4尺寸大小有影响，有机基团对载体表面羟基的取代使得金属钴与载体的作用力减弱，有利于金属团聚为较大的颗粒。费-托反应结果表明，亲水硅胶性制得的催化剂通过后处理引入甲基后，造成催化剂活性下降，C18+的选择性下降，但使烃分布集中在C5～C18，这是由于表面甲基的空间位阻作用不利于反应中的吸附过程和链增长过程。由疏水载体制备的催化剂虽然钴颗粒较大，但是由于催化剂制备过程中部分有机基团的烧结，对催化剂活性产生了较大的负面影响，使催化活性降低，重质烃选择性明显降低。     

铜,钾助剂对铁基催化剂吸附—脱附性能的影响

气-固相催化反应活性很大程度上依赖于反应组分在催化剂表面上的吸附与脱附行为,因此,研究反应组分在催化剂表面的吸附与脱附性质对了解催化剂表面活性部位分布、催化活性、反应机理等具有重要意义。本文用程序升温脱附(TPD)及稳态化学吸附研究了具有良好催化活性的F-T合成铁基催化剂对CO和H_2的吸附、脱附特性,并讨论了Cu、K助剂的影响。     

Cu-Mn-Zn/Y直接合成二甲醚催化剂中锌和锰的协同调节作用

通过对Y型分子筛负载Cu-Mn、Cu-Zn和Cu-Mn-Zn催化剂的结构、表面性质及其直接合成二甲醚反应活性的对比,发现Mn和Zn对催化剂还原性能的影响作用相反,对催化剂吸附H₂和CO的影响也不同。Mn和Zn的单独添加或共同添加引起催化剂结构和组分之间相互作用程度的改变,是造成催化剂活性和选择性变化的主要原因。两者的协同作用,能调整催化剂的还原性能和吸附性能达到适合的状态,从而使得催化剂具有高的二甲醚合成活性。     

碱土金属对锆基钙钛矿材料负载钌催化剂氨合成性能的影响

采用柠檬酸络合法制备了含Ca,Sr和Ba的锆基钙钛矿材料,负载Ru后用于催化氨合成反应;研究了碱土金属对催化剂织构性能和载体材料表面碱性的影响,并与催化剂活性相关联.同时,采用程序升温脱附技术对催化剂表面H2脱附性能进行了表征.结果显示,碱土金属对催化剂活性的促进顺序为Ba>Sr>Ca.研究发现,不同锆基碱土金属钙钛矿材料表面均具有较强的碱性位,碱土金属的加入影响了载体碱性强度以及金属-载体的相互作用,其中BaZrO3可有效抑制H2的吸附.因此,Ru/BaZrO3催化剂表现出优异的氨合成活性.     

La促进CuCo催化剂上合成气转化制低碳醇的研究

利用超声辅助的反相共沉淀法制备了合成气选择转化制低碳醇用CuCo基催化剂。研究稀土La助剂对CuCo基复合氧化物催化剂结构的影响和催化性能的促进作用,借助X射线衍射(XRD)、N₂吸附等温线(BET)和程序升温脱附(CO-TPD)等测试技术对催化剂进行表征,并以CO加氢合成低碳醇为模型反应对其催化性能进行评价。结果表明,La助剂的添加使催化剂晶粒细化,显著加大了比表面积,促进了合成醇活性位的形成,提高了催化剂表面较强吸附CO物种的浓度,从而明显提高催化剂的活性与C_2＋醇选择性,有效调节了低碳混合醇中甲醇的含量。     

二甲醚合成催化剂失活原因的研究

采用胶体沉积法制备了Cu-ZnO-ZrO2／HZSM-5二甲醚合成催化剂．对二甲醚合成过程中催化剂的失活原因进行了初步研究．采用BET，NH3TPD，TPD，TP0和N2O脉冲实验对催化剂使用前后比表面积，表面酸性，表面吸附物种，表面积碳和活性组分Cu比表面积的变化进行了研究．发现，在二甲醚合成过程中，催化剂表面酸性，催化剂表面吸附物种和表面积碳变化较小，不是导致催化剂失活的主要原因．而催化剂在使用过程中活性组分Cu烧结使Cu比表面积降低是催化剂失活的主要原因．     

硅胶负载的双高分子-钯催化剂的研究——Ⅰ.硅胶负载的聚[4(2)-乙烯吡啶]-聚[苯乙烯-顺丁烯二酸]-钯催化剂的合成及其催化加氢性能

合成了硅胶负载的聚(4-乙烯吡啶)或聚(2-乙烯吡啶)-聚(苯乙烯-顺丁烯二酸)-钯催化剂(P4VP-PSM-Pd/SiO_2和P2VP-PSM-Pd/SiO_2),研究了合成条件、组成等对其催化性能的影响及对丙烯酸甲酯的催化加氢性能。发现,同时含两种高分子的催化剂比只含一种高分子的催化剂具有较高的催化活性,催化剂在常温常压下对丙烯酸甲酯的氢化反应具有很高的催化活性和选择性,且能重复使用,表现出良好的稳定性。同时还研究了其它因素对催化剂性能的影响。     

硅胶负载的双高分子-钯催化剂的研究——Ⅰ.硅胶负载的聚[4(2)-乙烯吡啶]-聚[苯乙烯-顺丁烯二酸]-钯催化剂的合成及其催化加氢性能

 合成了硅胶负载的聚(4-乙烯吡啶)或聚(2-乙烯吡啶)-聚(苯乙烯-顺丁烯二酸)-钯催化剂(P4VP-PSM-Pd/SiO₂和P2VP-PSM-Pd/SiO₂),研究了合成条件、组成等对其催化性能的影响及对丙烯酸甲酯的催化加氢性能。发现,同时含两种高分子的催化剂比只含一种高分子的催化剂具有较高的催化活性,催化剂在常温常压下对丙烯酸甲酯的氢化反应具有很高的催化活性和选择性,且能重复使用,表现出良好的稳定性。同时还研究了其它因素对催化剂性能的影响。     

交联聚4-乙烯基吡啶及其季铵盐负载钯催化剂对丙烯酸甲酯加氢反应的研究

制备了交联聚4-乙烯基吡啶及碘甲烷,溴乙烷季铵化的聚4-乙烯基吡啶负载钯催化剂,考察了它们催化丙烯酸甲酯加氢反应的性能。对碘甲烷季铵化聚4-乙烯基吡啶负载钯催化剂,其催化加氢活性随载体季铵化程度的增加而减小,并且当载体季铵化程度低于80％时,其催化加氢活性比聚4-乙烯基吡啶负载催化剂高。实验结果表明催化剂制备条件对催化性能有很大影响。     

交联聚4-乙烯基吡啶及其季铵盐负载钯催化剂对丙烯酸甲酯加氢反应的研究

 制备了交联聚4-乙烯基吡啶及碘甲烷,溴乙烷季铵化的聚4-乙烯基吡啶负载钯催化剂,考察了它们催化丙烯酸甲酯加氢反应的性能。对碘甲烷季铵化聚4-乙烯基吡啶负载钯催化剂,其催化加氢活性随载体季铵化程度的增加而减小,并且当载体季铵化程度低于80％时,其催化加氢活性比聚4-乙烯基吡啶负载催化剂高。实验结果表明催化剂制备条件对催化性能有很大影响。     

Polymeric amines and their copper(II) complexes: Catalysts for the hydrolysis of organophosphate esters

Catalysis of the solvolysis of organophosphorus esters by polymers of aliphatic amines, imidazole, pyridine, 2,2′-bipyridine, and their copper(II) complexes was studied using diisopropyl fluorophosphate (DEP) as a model substrate. The polymeric catalysts were synthesized either by (1) derivation of available polymers, including polyethylenimine, polyvinyl amine, polyvinyl alcohol, polystyrene, and poly-4-vinylpyridine or (2) by polymerization of functionalized monomers such as 4(5)-vinylimidazole and 4-vinyl-4′-methyl-2,2′-bipyridine. Polymer hydrophilicity was controlled by partial quaternization of amine groups with different alkyl halides. The greatest catalytic activity was exhibited by copper(II) complexes of polymers containing the 2,2′-bipyridine group. At pH 7.6 and 3.7 × 10^?3M, the most active of these catalysts reduced the half-life of DFP from 800 to 9 min. The rate was largely independent of the pH in the range 6.5–8.5 but was limited by the aqueous solubility of the catalyst. Heterogeneous catalysis by some polymers was observed but was less effective. A Lineweaver-Burk plot of V₀^?1 versus [DFP]^?1 for a soluble polymeric 2,2′-bipyridine-copper(II) catalyst was linear. There was no correlation between catalysis of solvolysis of DFP and the carboxylic ester, p-nitrophenyl acetate.     

Bisphenol A analog-imprinted polymers prepared by an immobilized template on a modified silica microsphere matrix.

Bisphenol A (BPA)-recognizing imprinted polymers were synthesized using a template immobilized on silica where the template was grafted to aminopropyl silica. The silica-template conjugate was co-polymerized with a cross-linker (ethylene glycol dimethacrylate) and a functional monomer (4-vinylpyridine or methacrylic acid). The synthesized silica-polymer composites were treated with an aqueous NH4HF2 solution to dissolve the silica matrix. The 4-vinylpyridine-based imprinted polymer showed strong binding affinity to BPA and structurally related compounds having two hydroxyl groups at the 4,4'-position in the bisphenol structure.     

Stereoregularity of poly(2-vinylpyridine) and poly-(4-vinylpyridine)

In order to determine the stereoregularity of poly(4-vinylpyridine), 4-vinylpyridine-β,β-d₂ was synthesized from 4-acetylpyridine. The ¹H-NMR spectra of the deuterated and nondeuterated polymers were measured and analyzed. From the ¹H-NMR spectra of poly(4-vinylpyridine-β,β-d₂), triad tacticity can be obtained, while the ¹H-NMR spectra of nondeuterated poly(4-vinylpyridine) give the fraction of isotactic triad. The ¹³C-NMR spectra of poly(4-vinylpyridine) were also observed, and the spectra of C₄ carbon of polymers were assigned by the pentad tacticities. The fraction of isotactic triad of poly(2-vinylpyridine) and poly(4-vinylpyridine) obtained under various polymerization conditions were determined. The radical polymerization and anionic polymerizations with phenylmagnesium bromide and n-butyllithium as catalysts of 4-vinylpyridine gave atactic polymers.     

Studies on polymers containing functional groups. III. Charge-transfer interaction between quinone and aza polymers

Absorption maxima and equilibrium constants for charge-transfer complexes between quinone and aza polymers, such as poly-2-vinylpyridine, poly-4-vinylpyridine, poly-2-methyl-5-vinylpyridine, and poly-N-dimethylaminomethylacrylamide, were determined spectrophotometrically. For comparison, those for charge-transfer complexes between quinone and aza compounds, such as pyridine, methyl-substituted pyridines, quinoline, triethylamine, and dimethylaniline were also presented. It was found that the equilibrium constants for polymer complexes are always larger than those for the corresponding monomer complexes, while the time required for attaining the equilibrium was longer for polymer complexes than for monomer complexes. In the interaction between quinone and poly-N-dimethylaminomethylacrylamide, two absorption maxima which gradually shifted towards each other were observed. The same phenomenon was found in the interaction between quinone and the corresponding monomer, triethylamine.     

Adsorption of polymers at the solution–solid interface. XIII. Adsorption and steric stabilization with styrene–2-vinylpyridine copolymers

Random and block copolymers of styrene and 2-vinylpyridine, covering the full range of composition, have been synthesized. The adsorption of these polymers from trichloroethylene solution on to precipitated silica has been studied and their ability to impart colloidal stability to the silica dispersions also investigated. Estimates of the layer thickness of adsorbed copolymers have been made. Polystyrene is not adsorbed from trichloroethylene and does not stabilize dispersions of precipitated silica. A random copolymer having 1% 2-vinylpyridine units is adsorbed but shows very little steric stabilization. Random copolymers of 2-vinylpyridine content greater than 10% and AB block copolymers of more than 6% 2-vinylpyridine behave very similarly in respect both of the quantity adsorbed and in their ability to stabilize silica suspensions. Layer thickness does not seem to depend on copolymer composition. Random copolymers with low to intermediate 2-vinylpyridine contents are better steric stabilizers in trichloroethylene than are the corresponding copolymers of methyl methacrylate with styrene: this is attributed in part to the longer sequences of adsorbable units in the vinylpyridine copolymers.     

Anhydrous proton-conducting polymeric electrolytes for fuel cells

The need to design proton-conducting electrolytes for fuel cells operating at temperatures of 120 degrees C and above has prompted the investigation of various "water-free" polymeric materials. The present study investigates the properties of "water-free" proton-conducting membranes prepared from high-molecular-weight polymeric organic amine salts. Specifically, the properties of bisulfates and dihydrogenphosphates of poly-2-vinylpyridine (P2VP), poly-4-vinylpyridine (P4VP), and polyvinylimidazoline (PVI) have been investigated over the temperature range of 25-180 degrees C. Nanocomposites of these polymeric organic amine salts and hydroxylated silica have also been investigated in this study. These polymers are found to be stable and proton-conducting at temperatures up to 200 degrees C. In all the polymer examples studied herein, the phosphates are more conducting than the bisulfates. The activation energy for ionic conduction was found to decrease with increasing temperature, and this is associated with the increased polymer mobility and ionization of the proton. This is confirmed by the high degree of motional narrowing that is observed in proton NMR experiments. The measured values of conductivity and the differences in pKa values of the polymeric organic amine and the mineral acid are clearly correlated. This observation provides the basis for the design of other water-free acid-base polymer systems with enhanced proton conductivity. The results presented here suggest that anhydrous polymer systems based on acid-base polymer salts could be combined with short-range proton conductors such as nanoparticulate silica to achieve acceptable conductivity over the entire temperature range.