The synthesis route of 10Al2O3·2B2O3 (10A2B) and effect of additives were studied to use this compound as a thermally stable support material for Pd catalysts. The preparation by reverse coprecipitation was found to have a beneficial effect on the BET surface area of 10A2B and thus Pd metal dispersion, compared to other preparation routes via solid-state reaction and hydrolysis of metal alkoxides. The addition of 3 wt % BaO suppressed the sintering of 10A2B and Pd during thermal aging at 900 °C in a stream of air containing 10% H2O. Although direct interactions between Pd and the support material were not detected by EXAFS, the catalytic performance for NO–CO–C3H6–O2–H2O reactions under modulated air-to-fuel ratio (A/F) conditions was strongly influenced by the Ba additive. The activity for NO and C3H6 in a rich region (A/F < 14.6) was especially enhanced in the presence of Ba because of accelerated elemental reactions including NO–CO and NO–C3H6. In situ FT-IR of CO suggested that the Pd electronic state changed by electrostatic effect of Ba additives would activate NO and weaken the self-poisoning effect of C3H6.
High reactivity of trimethoxyphenyl (TMP)iodonium(III) acetate for phenol O-arylation was achieved. It was first determined that the TMP ligand and acetate anion cooperatively enhance the electrophilic reactivity toward phenol oxygen atoms. The proposed method provides access to various diaryl ethers in significantly higher yields than the previously reported techniques. Various functional groups, including aliphatic alcohol, boronic ester, and sterically hindered groups, were tolerated during O-arylation, verifying the applicability of this ligand-and counterion-assisted strategy.
h i g h l i g h t s• Enzymes were immobilized on magnetic nanoparticles by a methioninetag system.• Methionine-tagged immobilized enzymes showed 98% residual specific activity.• The system provided orientational immobilization via the formation of Au-S bonds.
g r a p h i c a l a b s t r a c t a b s t r a c tWe developed a novel technique for immobilizing enzymes on magnetic nanoparticle surfaces by using a methionine-tag system. Au/Fe-oxide composite nanoparticles synthesized through a radiochemical process were used as magnetic nanocarriers. The C-terminus of Tk-subtilisin, a model enzyme, was modified with a methionine tag and mixed with Au/Fe-oxide composite nanoparticles for immobilization via Au-S bonding. Methionine-tagged immobilized enzymes showed 98% residual specific activity, while the untagged enzymes showed 78%. The methionine-tagged immobilized enzymes retained their activities in a wide temperature range of 30-70 • C. Thus, the methionine-tag system provided orientational immobilization via the formation of Au-S bonds, which resulted in structural stability of the immobilized enzymes.
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