Synthesis of C4 and C8 Chemicals from Ethanol on MgO-Incorporated Faujasite Catalysts with Balanced Confinement Effects and Basicity.

A new type of catalyst has been designed to adjust the basicity and level of molecular confinement of KNaX faujasites by controlled incorporation of Mg through ion exchange and precipitation of extraframework MgO clusters at varying loadings. The catalytic performance of these catalysts was compared in the conversion of C2 and C4 aldehydes to value-added products. The product distribution depends on both the level of acetaldehyde conversion and the fraction of magnesium as extraframework species. These species form rather uniform and highly dispersed nanostructures that resemble nanopetals. Specifically, the sample containing Mg only in the form of exchangeable Mg(2+) ions has much lower activity than those in which a significant fraction of Mg exists as extraframework MgO. Both the (C6+C8)/C4 and C8/C6 ratios increase with additional extraframework Mg at high acetaldehyde conversion levels. These differences in product distribution can be attributed to 1) higher basicity density on the samples with extraframework species, and 2) enhanced confinement inside the zeolite cages in the presence of these species. Additionally, the formation of linear or aromatic C8 aldehyde compounds depends on the position on the crotonaldehyde molecule from which abstraction of a proton occurs. In addition, catalysts with different confinement effects result in different C8 products.

Selective hydrogenolysis of polyols and cyclic ethers over bifunctional surface sites on rhodium-rhenium catalysts.

A ReO(x)-promoted Rh/C catalyst is shown to be selective in the hydrogenolysis of secondary C-O bonds for a broad range of cyclic ethers and polyols, these being important classes of compounds in biomass-derived feedstocks. Experimentally observed reactivity trends, NH(3) temperature-programmed desorption (TPD) profiles, and results from theoretical calculations based on density functional theory (DFT) are consistent with the hypothesis of a bifunctional catalyst that facilitates selective hydrogenolysis of C-O bonds by acid-catalyzed ring-opening and dehydration reactions coupled with metal-catalyzed hydrogenation. The presence of surface acid sites on 4 wt % Rh-ReO(x)/C (1:0.5) was confirmed by NH(3) TPD, and the estimated acid site density and standard enthalpy of NH(3) adsorption were 40 µmol g(-1) and -100 kJ mol(-1), respectively. Results from DFT calculations suggest that hydroxyl groups on rhenium atoms associated with rhodium are acidic, due to the strong binding of oxygen atoms by rhenium, and these groups are likely responsible for proton donation leading to the formation of carbenium ion transition states. Accordingly, the observed reactivity trends are consistent with the stabilization of resulting carbenium ion structures that form upon ring-opening or dehydration. The presence of hydroxyl groups that reside α to carbon in the C-O bond undergoing scission can form oxocarbenium ion intermediates that significantly stabilize the resulting transition states. The mechanistic insights from this work may be extended to provide a general description of a new class of bifunctional heterogeneous catalysts, based on the combination of a highly reducible metal with an oxophilic metal, for the selective C-O hydrogenolysis of biomass-derived feedstocks.

Hyperbranched ferrocenyl polymer film with high charge transport efficiency.

The electrochemical behaviors of hyperbranched poly(ferrocenyl-methylsilane) (HPFMS) and linear oligo(ferrocenyldimethylsilane) (LOFS) films were studied systematically by cyclic voltammetry and chronocoulometry under different polymer coverage and solvents. Both poly(ferrocenylsilanes) show stable cyclic voltammographs in LiClO 4 solutions. Compared with LOFS films, HPFMS films exhibit higher charge transport efficiency because of their hyperbranched structure: peak current ( i p) and apparent diffusion coefficient ( D app) for HPFMS films are larger than those for LOFS films, especially at high polymer coverage (3.8 x 10 (-11) vs 3.9 x 10 (-12) cm2/s for HPFMS and LOFS film at the coverage of 2.1 x 10 (-6) mol Fc/cm2). The conceptual models of electrode processes for HPFMS and LOFS films were proposed to account for higher charge transport efficiency of HPFMS films. It is also found that a solvent with the appropriate solubility parameter and polarity, lower viscosity, and higher dielectric constant is in favor of charge transport through polymer films, which is consistent with the proposed model of electrode process for HPFMS films. These results imply that hyperbranched ferrocenyl polymers have the potential to be excellent chemical sensor materials with convenient synthesis and high sensitivity.

Study on anion electrochemical recognition based on a novel ferrocenyl compound with multiple binding sites.

A novel ferrocenyl anion receptor N, N, N, N-(dimethyl, ethyl, ferrocenecarboxylic amidodimethylene) ammonium fluoborate 2 with multiple binding sites was synthesized. Its anion recognition behaviors were investigated by CV, 1H NMR and UV-vis spectrum. It was found that the combination of two interactions enforced the anion binding ability and the binding selectivity of 2 to phosphate anion. The effects of scan rate on the CV curves of 2 with phosphate were also investigated. In different scan rate, the CV curves kept stable which indicated the strong binding between 2 and phosphate. According to relationships of peak potential, peak currents and scan rate of 2 binding with phosphate, the kinetic parameters of electrode process such as diffusion coefficient Dapp, surface transfer coefficient alphan alpha, and standard rate constant k0 were calculated.

Preparation of N,N'-bisethoxyethane[12]amideferrocenophane and its application in anion recognition.

Novel N,N'-bisethoxyethane[12]amideferrocenophane has been synthesized by a condensation reaction and characterized by (1)H NMR and mass spectrum. The anion recognition properties of the compound are evaluated via (1)H NMR, FT-IR, and electrochemical measurement. It is found that N,N'-bisethoxyethane[12]amideferrocenophane exhibits remarkable electrochemical response to H(2)PO(4-) anion in CH(2)C(l2) or CH(3)CN solution, and response to anions can also be observed in CH(3)CN solution containing up to 15% water. Binding constants between the compound and HSO(4-) in different solutions have been determined by UV-vis spectrum titration experiments. The results indicate that the compound shows a selective recognition trend of H(2)PO(4-) > HSO(4-) (F(-)) > Br(-).

Study on synthesis and electrochemical properties of a novel ferrocene-based compound and its application in anion recognition.

The novel ferrocene-based compound 2-Fc is synthesized through the reaction of ferrocene carbonate acid and epoxy rosin E-51, and characterized by 1H NMR. The CV behaviors of 2-Fc in different organic solvents are recorded, and the major influential factors, namely, potential scan rate, concentration of electrolyte, and concentration of 2-Fc, and the mechanism of the electrode process are investigated. The CV behaviors of 2-Fc film on electrode in LiClO4 aqueous and organic solutions and the application of 2-Fc in H2PO4- recognition are also studied.