Class Of Bifunctional Catalysts Research Articles

A novel alkylation process of benzene with CO2 and H2 over bifunctional ZnxCeyZrzO/Z5 catalyst

The synergy between the two active sites in Zn 3 Ce 1 Zr 3 O that the active hydrogen atoms provided by ZnO species hydrogenated the adsorbed CO 2 at adjacent oxygen vacancy of cerium zirconium solid solution effectively improved the CO 2 hydrogenation selectivity. While the HZSM-5 zeolite with moderate acidity was beneficial to the rapidly alkylation of methoxy intermediate with benzene. Coupling Zn x Ce y Zr z O with HZSM-5 could contribute to the well kinetic matching between CO 2 activation and alkylation, thus affording an effective bifunctional catalyst Zn x Ce y Zr z O/Z5 for highly selective conversion of benzene with CO 2 and H 2 into toluene and xylene. • In situ alkylation process of benzene with CO 2 and H 2 to produce TX is proposed. • The synergy in Zn x Ce y Zr z O promoted the CO 2 hydrogenation kinetics. • Zn x Ce y Zr z O/Z5 contribute to the well matching of CO 2 activation and alkylation. • The mechanism of the alkylation of benzene with CO 2 and H 2 is proposed. Alkylation of benzene using CO 2 and H 2 to toluene and xylene (TX) can not only give value-added chemical products but also alleviate the greenhouse effect. The key to achieving this goal is to develop a highly efficient catalyst. Herein, a class of bifunctional catalysts containing series of Zn x Ce y Zr z O metal oxide and HZSM-5 was prepared and studied for the catalytic properties. Higher CO 2 conversion and alkylation utilization were achieved using the Zn x Ce y O coupling with HZSM-5 compared to its counterpart ZnO and CeO 2 , revealing synergy between the ZnO and CeO 2 . More strikingly, the Zn x Ce y Zr z O, synthesized by insertion of Zirconia (Zr) atoms into CeO 2 , can not only improve the concentration of oxygen vacancy but also facilitate CO 2 adsorption. After coupling with HZSM-5, the alkylation utilization of CO 2 was significantly improved and the unwanted CO selectivity was obviously reduced by hindering the RWGS reaction. The optimal bifunctional catalyst Zn 3 Ce 1 Zr 3 O/Z5 showed alkylation utilization of 24%, unwanted CO selectivity of only 64% and the TX selectivity as high as 82%. In situ DRIFTS results confirmed that the methanol generated on the Zn x Ce y Zr z O metal oxide via the formate-methoxy intermediates mechanism was rapidly alkylated on HZSM-5 with benzene to produce TX.

Development of Chiral, Bifunctional Thiosquaramides: Enantioselective Michael Additions of Barbituric Acids to Nitroalkenes.

We report a general method for the synthesis of chiral thiosquaramides, a class of bifunctional catalysts not previously described in the literature. Thiosquaramides are found to be more acidic and significantly more soluble in nonpolar solvents than their oxosquaramide counterparts, and they are excellent catalysts for the unreported, enantioselective conjugate addition reaction of the barbituric acid pharmacaphore to nitroalkenes, delivering the chiral barbiturate derivatives in high yields and high enantioselectivities, even with catalyst loadings as low as 0.05 mol%.

ChemInform Abstract: Metal@Silica Yolk‐Shell Nanostructures as Versatile Bifunctional Nanocatalysts

AbstractReview: 59 refs.

Metal@Silica yolk-shell nanostructures as versatile bifunctional nanocatalysts

Recent developments in nanochemistry offer precise morphology control of nanomaterials, which has significant impacts in the field of heterogeneous catalysis. Rational design of bifunctional catalysts can influence various aspects of catalytic properties. In this review, a new class of bifunctional catalysts with a metal@silica yolk-shell nanostructure is introduced. This structure has many advantages as a heterogeneous catalyst since it ensures a homogeneous environment around each metal core, and particle sintering is effectively eliminated during high temperature reactions. The catalysts exhibit high activity and recyclability in gas- and solution-phase reactions. It is anticipated that appropriate selection of bifunctional components and optimal structural control will significantly further enhance the catalytic properties, and enable target reaction-oriented development of new catalysts.

ChemInform Abstract: Chiral (o‐Hydroxyaryl)oxazaphospholidine Oxides: A New Class of Bifunctional Catalysts in the Enantioselective Borane Reduction of Ketones.

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Chiral (o-Hydroxyaryl)oxazaphospholidine Oxides: A New Class of Bifunctional Catalysts in the Enantioselective Borane Reduction of Ketones

The synthesis of a new class of bifunctional organophosphorus catalysts for the asymmetric borane reduction of prochiral ketones has been investigated. Keys to the architecture of effective catalysts are an oxazaphospholidine structural unit and a hydroxyaryl moiety. These (o-hydroxyaryl)oxazaphospholidine oxides have been successfully applied to the catalytic (2 mol-%) asymmetric borane reduction of numerous prochiral ketones with enantiomeric excesses up to 84% ee.

Tungsten carbides modified by chemisorbed oxygen. A new class of bifunctional catalysts

Tungsten carbides modified by chemisorbed oxygen. A new class of bifunctional catalysts