Graft copolymerization of acrylic acid onto cellulose: Effects of pretreatments and crosslinking agent

The graft copolymerization of acrylic acid (AA) and 2-acrylamido 2-methylpropane sulfonic acid (AASO(3)H) onto cellulose, in the presence or absence of crosslinking agent N,N'-methylene bisacrylamide (NMBA), by using different concentrations of eerie ammonium nitrate (CAN) initiator in aqueous nitric acid solution at either 5 or 30 degreesC was investigated. To investigate the effect of pretreatment of cellulose on the copolymerization, before some grafting reactions cellulose was pretreated with either 2 or 20 wt % NaOH solutions or heated in distilled water/aqueous nitric acid (2.5 x 10(-3) M) at 55 degreesC. To determine how the excess of initiator affects the grafting and homopolymerization, separate reactions were carried out by removing the excess of eerie ions by filtration of the mixture of initiator solution and cellulose before the monomer addition. Extraction-purified products were characterized by grafting percentage and equilibrium swelling capacity. Pretreatment of cellulose with NaOH solutions decreased the grafting percentage of copolymers. In the case of AA-AASO(3)H mixtures, nonpretreated cellulose gave a higher grafting percentage than NaOH-pretreated cellulose. Filtration also lowered the grafting of AA on the cellulose in the cases of pretreatment with either water or nitric acid. Copolymers with the highest grafting percentage (64.8%) and equilibrium swelling value (105 g H2O/g copolymer) were obtained in grafting reactions carried out in the presence of NMBA at 5 degreesC. (C) 2001 John Wiley & Sons, Inc

Room temperature carbon monoxide oxidation over Pt/Co2SnO4 and Pt/(Co3O4+SnO2) catalysts

Catalytic activities of Pt/Co2SnO4, Pt/(Co3O4+SnO2), Pt/SnO2, and Pt/Co3O4 catalysts for CO oxidation were investigated by varying CO concentration at room temperature. Reaction rates over Pt/Co2SnO4 and Pt/Co3O4 catalysts were not affected from increase in CO concentration

The oxidative dehydrogenation of propane over potassium-promoted molybdenum oxide/sol-gel zirconia catalysts

The effect of potassium loading on the structural and catalytic properties of MoOx/ZrO2 catalysts for oxidative dehydrogenation of propane was investigated. Catalysts have been prepared by modified sol-gel method, and they were characterized by nitrogen physisorption, XRD, FT-Raman spectroscopy, XPS and temperature-programmed reduction (TPR). Catalytic activity measurements have been carried out between 400 and 530degreesC under atmospheric pressure. It was observed that potassium addition prevented crystalline Zr(MoO4)(2) formation, suppressing the interaction of molybdenum oxide and zirconia phases, and it also favored the formation of three-dimensional molybdenum oxide and two-dimensional polymolybdates. Both propylene selectivity and yield were enhanced with a certain amount of potassium addition. (C) 2004 Elsevier B.V. All rights reserved

Synthesis, characterization and magnetic properties of Fe3O4 doped chitosan polymer

Fe3O4 nanoparticles doped into chitosan films were prepared by the solution casting technique. Various samples were synthesized in atmospheric medium and in vacuum. The morphological properties of the samples were characterized by high resolution transmission electron microscopy (HR-TEM) and Scanning Electron Microscopy (SEM). The structural, magnetic, and microwave absorption properties of magnetic chitosan films have been carried out using the Vibrating Sample Magnetometer (VSM) and Ferromagnetic Resonance (FMR). It is shown that the composite polymer behaves like a superparamagnetic material with high blocking temperature. The effective magnetization shows gradual increments with the concentration of dopant Fe3O4 nanoparticles. The microwave absorption characteristic of superparamagnetic composite polymer shows low reflection loss. (C) 2014 Elsevier B.V. All rights reserved