Novel polymer supported IBX esters and amides were prepared in two steps, which were the coupling of 2-iodobenzoic acid to a hydroxy or amino polystyrene followed by activation of the intermediate product. These polymer supported reagents were tested as oxidants by the conversion of a series of alcohols to the corresponding aldehydes or ketones. We found that the polymer supported IBX amides displayed excellent oxidative activity, in that they oxidized benzyl alcohol to benzaldehyde completely within 1 h at an oxidant to alcohol ratio of 2 to 1. 相似文献
The reaction of trimethylbenzene (TMB) over alumina-pillared montmorillonite (Al-PM) had been investigated in a fixed-bed flow reactor at 300 °C and atmospheric pressure. Al-PM calcined in the range 300-500 °C exhibited decreased layer distance, surface area and acid amount. The strong acid sites of Al-PM calcined at 500 °C were greatly diminished according to measurements of ammonia temperature-programmed desorption. Under our conditions the reaction proceeded mainly via isomerization and disproportionation with little dealkylation. The conversion of reactant decreased in the order 1,2,3-TMB ≥ 1,2,4-TMB > 1,3,5-TMB and the selectivity of isomerization in the order 1,2,3-TMB > 1,3,5-TMB > 1,2,4-TMB, corresponding to the order of diminishing thermal instability. Both the catalytic activity and the selectivity ratio of disproportionation to isomerization decreased with increased calcined temperature and time-on-stream. o-Xylene content in the total xylene produced from 1,2,4-TMB or 1,2,3-TMB greatly exceeded the composition at thermodynamic equilibrium. These results arc consistent with the decrease of both the strong acid sites and the pore size of Al-PM which exhibits the restricted transition state selectivity. 相似文献
The goal of this study was to assess the effects of surfactant addition on the stability and viscosity of concentrated alumina dispersions. The stabilizing effects of several candidate surfactants were investigated for concentrated dispersions of two different pseudoboehmite aluminas at pH 4 and 7. The stabilities of concentrated alumina dispersions treated by pH adjustment alone and by pH adjustment combined with surfactant addition were compared to assess the degree to which the surfactant enhanced stability. The initial rate of mass removal from a sedimenting alumina dispersion was used as a measure of stability.
The anionic surfactants Surfine WNT-A and DOWFAX 3B2 were identified as effective in enhancing the stability of concentrated alumina dispersions. The optimal doses of these surfactants for stabilizing 15% by weight VERSAL™ 250 alumina dispersions at pH 4 were determined to be about 4.6 × 10−5 mol g−1 for both surfactants. On the basis of the initial rate of mass removal, surfactant-stabilized 15 wt.% suspensions were found to be approximately 2.5 and 10.6 times more stable than similar dispersions stabilized electrostatically by pH adjustment alone. These more stable dispersions exhibited lower viscosities than observed for the alumina dispersions not subjected to surfactant addition. The results indicate that the stability of concentrated alumina dispersions can be enhanced by anionic surfactant addition, and that such surfactants may therefore help to control the rheology of concentrated dispersions of alumina in water. 相似文献
Polyaniline(PAN) supported H6P2W18O62(PW) , H3PMo12O40 (PMo) and H4PMo11VO40(PMoV) catalysts were prepared and their activities for hexanol conversion were tested. IR, XRD, ICP and SEM measurements
proved that the heteropolyacids (HPA) could be supported on this type of polymer. The PAN supported HPA catalysts exhibit
higher redox activities and low acid-base activities for the hexanol conversion. The redox activities increase with increasing
amount of the heteropolyacid. Substitution of Mo ion by V ion results in an increase of redox activities of the catalysts.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献