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Suitable Catalyst (suitable + catalyst)
Selected AbstractsCellulose Acetate- graft -Poly(hydroxyalkanoate)s: Synthesis and Dependence of the Thermal Properties on Copolymer CompositionMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 14 2004Yoshikuni Teramoto Abstract Summary: Several different series of cellulose acetate- graft -poly(hydroxyalkanoate)s (CA- g -PHAs) were synthesized over a wide range of compositions by the graft copolymerization of lactic acid, L -lactide, (R,S)- , -butyrolactone, , -valerolactone and , -caprolactone onto the residual hydroxyl positions of CA, by virtue of a suitable catalyst, solvent and procedure for each individual case. To achieve a diversity of molecular architectures of the respective graft copolymer series, the degree of acetyl substitution (acetyl DS) of the CA starting material was also varied, resulting in different levels of the intramolecular density of grafts. The CA- g -PHAs thus obtained were subjected to differential scanning calorimetric measurements and the relationship between their molecular structure and thermal transition behavior was estimated, in comparison with some semi-empirical equations available for polymer blends or comb-like polymers. In particular, the composition dependence of the Tgs of the graft copolymers was represented well in terms of a formula proposed by Reimschuessel for comb-like polymers, when CAs of acetyl DS ,2 were employed as a trunk polymer. The deviation of the glass transition data from the model function was discussed in connection with the manner of graft modification. [source] Steam reforming of propane in a zirconia membrane reactor with a Rh-supported Ce0.15Zr0.85O2 catalystASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2009K. Kusakabe Abstract The steam reforming (SR) of propane for hydrogen production at 400,600 °C in a porous yttria-stabilized zirconia (YSZ) membrane reactor was investigated. The YSZ membrane was used as a hydrogen selective membrane. A Rh-supported Ce0.15Zr0.85O2 catalyst was packed in the membrane reactor because the catalyst was found to be the most suitable catalyst for the low-temperature SR of propane on the basis of the results obtained using a packed bed reactor. The conversion of propane in the membrane reactor was higher than that in a packed bed reactor due to the shift of equilibrium toward the hydrogen-producing side. In spite of relatively low permeation selectivity (ideal H2/CO selectivity = 9 at 100 °C), hydrogen permeation through the membrane caused an increase in the CO2 fraction and a decrease in the CO fraction in reformed gas. This indicates that the water-gas shift reaction was an important contributor in the product distribution in the membrane reactor. Meanwhile, the methane fraction remained largely unchanged, regardless of selective hydrogen permeation. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Synthesis of a Bioxazoline-Derived Ru Metathesis CatalystCHEMCATCHEM, Issue 7 2010Kati Vehlow As ligand has it, A new class of ruthenium catalyst based on a bioxazoline-derived N-heterocyclic carbene (IBioxNHC) ligand has been synthesized that exhibits high stability at elevated temperatures and is a suitable catalyst for olefin metathesis. A slow initiation rate, owing to the steric hindrance of the NHC ligand, may be of interest for certain metathesis applications. [source] Simultaneous Catalytic Removal of Nitrogen Oxides and Soot from Diesel Exhaust Gas over Potassium Modified Iron OxideCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 9 2003S. Kureti Abstract Iron oxide modified by potassium, i.e. Fe1.9K0.1O3, exhibits high catalytic performance for the simultaneous conversion of soot and NOx into CO2 and N2. The present study shows that long-time treatment of the catalyst leads to a drastic decrease in the activity, whereas even the aged catalyst maintains considerable activity. On the other hand, long-time treatment causes selective N2 formation, i.e. no more formation of the byproduct N2O. This alteration of catalytic performance is likely due to agglomeration of the promoter potassium being present at the surface of catalyst. Detailed experiments were carried out with a more realistic diesel model exhaust gas to confirm that Fe1.9K0.1O3 is a suitable catalyst for the simultaneous removal of soot and NOx between 350 and 480 °C. It was assumed that (CO) intermediates, formed by the catalytic reaction of NOx and oxygen with the soot surface, are the reactive species in NOx -soot conversion. [source] Synthesis of Chiral 2-Phospha[3]ferrocenophanes and their Behaviour as Organocatalysts in [3+2],Cyclization ReactionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2009Arnaud Voituriez Abstract Planar chiral 2-phospha[3]ferrocenophanes have been prepared via a stereoselective three-step synthesis. The key step is the lithiation of the 1,1,-disubstituted ferrocene 11 bearing (S)-2-(methoxymethyl)pyrrolidines as the chiral ortho -directing groups. The diastereoselectivity of these reactions has been mastered by an appropriate choice of the metallating agent, so as to afford a suitable access to C2 -symmetrical, tetrasubstituted ferrocenes. These compounds have been converted into the enantiomerically pure 2-phospha[3]-ferrocenophanes 16, via the corresponding acetates and their reactions with primary phosphines. Phosphines 16 have been used as nucleophilic catalysts in model cyclization reactions. Unlike 2-phospha[3]-ferrocenophanes with stereogenic ,-carbons, the planar chiral derivatives 16 proved to be suitable catalysts for these processes. Thus, for instance, phosphine 16c successfully promotes the enantioselective [3+2],annulations of allenes and enones into functionalized cyclopentenes (ees up to 96%). Among others, spirocyclic derivatives have been obtained in good yields and ees in the range 77,85%. The robustness of this catalyst has been demonstrated by recycling experiments. [source] Oxidation of Benzene to Maleic Anhydride in a Fluidized Bed ReactorCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 12 2007C. Uraz Abstract In this project, the selective oxidation of benzene to maleic anhydride (MAN) was studied. Gas phase catalytic oxidation of benzene was carried out in a laboratory scale fluidized bed reactor on six different types of catalysts, which have different compositions. Effects of temperature, flow rates of benzene and air and catalyst type on the reaction selectivity were investigated at atmospheric pressure. The experiments were performed over a temperature range of 325 to 400,°C, a space-time (W/FA0) range from 11.28,×,105 to 31.9,×,105 g,s,mol,1, and benzene/air mole ratio changes between 0.0109 and 0.0477. It was seen that conversion of benzene to MAN increased with increasing temperature for the catalysts supported by silica gel, aluminum oxide and titanium oxide. From the results it was found that conversion increased with increasing flow rate of air. When the comparison of the catalysts were made, it could be said that catalysts supported by silica gel showed higher MAN conversions. So it can be concluded that catalysts supported by silica gel were more suitable catalysts for benzene oxidation to MAN in a fluidized bed reactor. [source] | ||||||||||