Hydrogen production from low temperature WGS reaction on co-precipitated Cu–CeO2 catalysts: An optimization of Cu loading

Low temperature water–gas shift (WGS) reaction has been carried out at the gas hourly space velocity of 72,152 h⁻¹ over Cu–CeO₂ catalyst prepared by a co-precipitation method. Cu loading was optimized to obtain highly active co-precipitated Cu–CeO₂ catalysts for low temperature WGS. 80 wt% Cu–CeO₂ exhibited the highest CO conversion as well as the most stable activity (X_CO > 46% at 240 °C for 100 h). The excellent catalytic performance is mainly due to a strong metal to support interaction, resulting in the prevention of Cu sintering.     

Asymmetric Epoxidation of Styrene on the Heterogenized Chiral Salen Complexes Prepared from Organo-Functionalized Mesoporous Materials

Organosilane-modified mesoporous materials have been prepared under mild and acidic conditions by a solvent evaporation method using C₁₆TMABr surfactant as a template. The mesoporous samples synthesized in ethanol solvent by using this evaporation method showed a fully disordered pore system, but those obtained under hydrothermal conditions had highly ordered pores. The chiral salen Mn(III) complexes were immobilized on these organosilane-functionalized mesoporous silicas by a grafting method. The catalysts used in the asymmetric epoxidation of styrene and cis-stilbene and the effect of different mesoporous structures on the reactivity was investigated. Similar enantioselectivities were observed by using these heterogenized salen complexes as compared with reaction under homogeneous conditions.     

Comparative Study on Nano-Sized 1 wt% Pt/Ce<Subscript>0.8</Subscript>Zr<Subscript>0.2</Subscript>O<Subscript>2</Subscript> and 1 wt% Pt/Ce<Subscript>0.2</Subscript>Zr<Subscript>0.8</Subscript>O<Subscript>2</Subscript> Catalysts for a Single Stage Water Gas Shift Reaction

Abstract  

A comparative study on nano-sized Pt/Ce_0.8Zr_0.2O₂ and Pt/Ce_0.2Zr_0.8O₂ catalysts in a single stage water gas shift (WGS) reaction was carried out. These catalysts were prepared by impregnating 1 wt% Pt on nano-sized cubic (Ce_0.8Zr_0.2O₂) and tetragonal (Ce_0.2Zr_0.8O₂) supports. Both catalysts have been applied to WGS under identical conditions to understand beneficial effect of cubic/tetragonal phases of Ce_(1 − x)Zr_(x)O₂. 1 wt% Pt/Ce_0.8Zr_0.2O₂ exhibited higher CO conversion than 1 wt% Pt/Ce_0.2Zr_0.8O₂. In addition, 1 wt% Pt/Ce_0.8Zr_0.2O₂ catalyst showed relatively stable activity with time on stream. The high activity/stability of 1 wt% Pt/Ce_0.8Zr_0.2O₂ catalyst was correlated to its higher Pt dispersion and easier reducibility.     

Synthesis of Highly Active Nano-Sized Pt/CeO<Subscript>2</Subscript> Catalyst via a Cerium Hydroxy Carbonate Precursor for Water Gas Shift Reaction

Abstract  

A novel precipitation/digestion route has been developed to synthesize crystalline cerium hydroxy carbonate (CHC: Ce(OH)CO₃) by using an equimolar quantity of cerium nitrate (Ce(NO₃)₃·6H₂O) and mixed precipitants (KOH + K₂CO₃) at room temperature. Nano-sized CeO₂ supports could be prepared by the pre-calcination of CHC at 400 °C for 4 h. A highly active water gas shift (WGS) catalyst, 1 wt.% Pt/CeO₂ catalyst showed almost equilibrium CO conversion with 100% CO₂ selectivity at 320 °C even at the gas hourly space velocity (GHSV) of 45,625 h⁻¹.     

Discovery of Zr-based metal-organic polygon:Unveiling new design opportunities in reticular chemistry

Metal-based secondary building unit and the shape of organic ligands are the two crucial factors for determining the final topology of metal-organic materials.A careful choice of organic and inorganic structural building units occasionally produces unexpected structures,facilitating deeper fundamental understanding of coordination-driven self-assembly behind metal-organic materials.Here,we have synthesized a triangular metal-organic polygon(MOT-1),assembled from bulky tetramethyl terephthalate and Zr-based secondary building unit.Surprisingly,the Zr-based secondary building unit serves as an unusual ditopic Zr-connector,toform metal-organic polygon MOT-1,proven to be a good candidate for water adsorption with recyclability.This study highlights the interplay of the geometrically frustrated ligand and secondary building unit in controlling the connectivity of metal-organic polygon.Such a strategy can be further used to unveil a new class of metal-organic materials.     

H2 production from high temperature shift of the simulated waste derived synthesis gas over magnetite catalysts prepared by citric acid assisted direct synthesis method

Magnetite (Fe₃O₄) has been prepared directly to avoid the reduction process prior to the H₂ production from the high temperature water gas shift reaction of the simulated waste derived synthesis gas. Citric acid has been employed as a complexing agent for the direct synthesis of magnetite. Notably, without the reduction process, the catalyst prepared at the citric acid molar ratio of 1.0 showed 80% CO conversion at 350 °C at a gas hourly space velocity of 40,057 h⁻¹.     

The catalytic activity of new chiral salen complexes immobilized on MCM-41 in the asymmetric hydrolysis of epoxides to diols

The synthesis of MCM-41 type mesoporous material has been performed by the solvent evaporation method. The chiral salen Co(III)(OAc) complexes are immobilized on a siliceous MCM-41 through the multi-step anchoring and applied as catalysts in the hydrolytic kinetic resolution of racemic epoxides to diols. The incorporation of salen complexes onto the mesoporous material is demonstrated by UV–Vis spectroscopy, and tested with the catalytic hydrolysis reaction. The chiral salen Co(III) complexes catalyze the hydrolysis of epichlorohydine, 1,2-epoxyhexane, epoxystyrene and epoxycyclohexane under very mild conditions. This reaction can proceed in acetonitrile and THF solvents.