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Multitasking mesoporous nanomaterials for biorefinery applications (open access)

Multitasking mesoporous nanomaterials for biorefinery applications

Mesoporous silica nanoparticles (MSNs) have attracted great interest for last two decades due to their unique and advantageous structural properties, such as high surface area, pore volume, stable mesostructure, tunable pore size and controllable particle morphology. The robust silica framework provides sites for organic modifications, making MSNs ideal platforms for adsorbents and supported organocatalysts. In addition, the pores of MSNs provide cavities/ channels for incorporation of metal and metal oxide nanoparticle catalysts. These supported metal nanoparticle catalysts benefit from confined local environments to enhance their activity and selectivity for various reactions. Biomass is considered as a sustainable feedstock with potential to replace diminishing fossil fuels for the production of biofuels. Among several strategies, one of the promising methods of biofuel production from biomass is to reduce the oxygen content of the feedstock in order to improve the energy density. This can be achieved by creating C-C bonds between biomass derived intermediates to increase the molecular weight of the final hydrocarbon molecules. In this context, pore size and organic functionality of MSNs are varied to obtain the ideal catalyst for a C-C bond forming reaction: the aldol condensation. The mechanistic aspects of this reaction in supported heterogeneous catalysts are explored. The …
Date: May 2, 2013
Creator: Kandel, Kapil
System: The UNT Digital Library
Synthesis of main group, rare-earth, and d{sup 0} metal complexes containing beta-hydrogen (open access)

Synthesis of main group, rare-earth, and d{sup 0} metal complexes containing beta-hydrogen

A series of organometallic compounds containing the tris(dimethylsilyl)methyl ligand are described. The potassium carbanions KC(SiHMe{sub 2}){sub 3} and KC(SiHMe{sub 2}){sub 3}TMEDA are synthesized by deprotonation of the hydrocarbon HC(SiHMe{sub 2}){sub 3} with potassium benzyl. KC(SiHMe{sub 2}){sub 3}TMEDA crystallizes as a dimer with two types of three-center-two-electron KH- Si interactions. Homoleptic Ln(III) tris(silylalkyl) complexes containing β-SiH groups M{C(SiHMe{sub 2}){sub 3}}{sub 3} (Ln = Y, Lu, La) are synthesized from salt elimination of the corresponding lanthanide halide and 3 equiv. of KC(SiHMe{sub 2}){sub 3}. The related reactions with Sc yield bis(silylalkyl) ate-complexes containing either LiCl or KCl. The divalent calcium and ytterbium compounds M{C(SiHMe{sub 2}){sub 3}}{sub 2}L (M = Ca, Yb; L = THF{sub 2} or TMEDA) are prepared from MI{sub 2} and 2 equiv of KC(SiHMe{sub 2}){sub 3}. The compounds M{C(SiHMe{sub 2}){sub 3}}{sub 2}L (M = Ca, Yb; L = THF{sub 2} or TMEDA) and La{C(SiHMe{sub 2}){sub 3}}{sub 3} react with 1 equiv of B(C{sub 6}F{sub 5}){sub 3} to give 1,3- disilacyclobutane {Me2Si-C(SiHMe2)2}2 and MC(SiHMe2)3HB(C6F5)3L, and La{C(SiHMe{sub 2}){sub 3}}{sub 2}HB(C{sub 6}F{sub 5}){sub 3}, respectively. The corresponding reactions of Ln{C(SiHMe{sub 2}){sub 3}}{sub 3} (Ln = Y, Lu) give the β-SiH abstraction product [{(Me{sub 2}HSi){sub 3}C}{sub 2}LnC(SiHMe{sub 2}){sub 2}SiMe{sub 2}][HB(C{sub 6}F{sub 5}){sub 3}] …
Date: May 2, 2013
Creator: Yan, Ka King
System: The UNT Digital Library
A cross section measurement of charm hyperons {Xi}{sub c}{sup +} and {Xi}{sub c}{sup 0} in 250 GeV p/K/{pi}-nucleon interactions (open access)

A cross section measurement of charm hyperons {Xi}{sub c}{sup +} and {Xi}{sub c}{sup 0} in 250 GeV p/K/{pi}-nucleon interactions

Fermilab Experiment 769 used a charge-selected, hadron beam of mean energy 250 GeV/c, composed of pions, kaons, and protons, impinging on beryllium, aluminum, copper and tungsten targets. Using a sample of approximately 4000 {Xi}{sub s}{sup {minus}} {yields} {Lambda}{sup 0}{pi}{sup {minus}} decays, measurements of the charm baryon forward cross sections times branching ratio {pi}{sup {+-}}N {yields} {Xi}{sub c}{sup +}X and {pi}{sup {+-}}N {yields} {Xi}{sub c}{sup 0}X are presented. Upper limits on {alpha} x BR are also determined for the states {Xi}{sub c}{sup +} {yields} {Xi}{sub s}{sup {minus}}{pi}{sup +}{pi}{sup +} and {Xi}{sub c}{sup 0} {yields} {Xi}{sub s}{sup {minus}}{pi}{sup +} produced in (p, {pi}{sup +}, {pi}{sup {minus}}, K{sup +}, K{sup {minus}})-nucleon interactions.
Date: May 2, 1995
Creator: Francisco, J. & Vergara, A.
System: The UNT Digital Library