Gas-Dependent Active Sites on Cu/ZnO Clusters for CH3OH Synthesis.

This study describes an instantaneously gas-induced dynamic transition of an industrial Cu/ZnO/Al2O3 catalyst. Cu/ZnO clusters become "alive" and lead to a promotion in reaction rate by almost one magnitude, in response to the variation of the reactant components. The promotional changes are functions of either CO2-to-CO or H2O-to-H2 ratio which determines the oxygen chemical potential thus drives Cu/ZnO clusters to undergo reconstruction and allows the maximum formation of Cu-Zn2+ sites for CH3OH synthesis.

Polyvinylamine-graft-TEMPO adsorbs onto, oxidizes, and covalently bonds to wet cellulose.

Described is a new, greener approach to increasing adhesion between wet cellulose surfaces. Polyvinylamine (PVAm) with grafted TEMPO spontaneously adsorbs onto cellulose and oxidizes the C6 hydroxyl to aldehyde groups that react to form covalent bonds with primary amines on PVAm. Grafted TEMPO offers two important advantages over solutions of low-molecular-weight water-soluble TEMPO derivatives. First, the oxidation of porous cellulose wood fibers is restricted to the exterior surfaces accessible to high-molecular-weight PVAm. Thus, fibers are not weakened by excessive oxidation of the interior fiber wall surfaces. The second advantage of tethered TEMPO is that the total dose of TEMPO required to oxidize dilute fiber suspensions is much less than that required by water-soluble TEMPO derivatives. PVAm-TEMPO is stable under oxidizing conditions. The oxidation activity of the immobilized TEMPO was demonstrated by the conversion of methylglyoxal to pyruvic acid.