A non-alkoxide sol–gel route to highly active and selective Cu–Cr catalysts for glycerol conversion

Abstract

A non-alkoxide sol-gel route to highly active and selective Cu-Cr catalysts for glycerol conversion is presented. The addition of propylene oxide to ethanol solutions of Cr(NO 3 ) 3 $9H 2 O and Cu(NO 3 ) 2 $3H 2 O resulted in the formation of transparent Cu-Cr gels. The resulting gels were converted to the Cu-Cr catalysts by atmospheric drying and calcination. The Cu-Cr catalysts are characterized by X-ray diffraction (XRD), N 2 physisorption, temperature-programmed reduction (TPR), and transmission electron microscopy (TEM). The results show that the surface area of the Cu-Cr catalyst is adjusted by the hydrolysis conditions, Cu/Cr molar ratio, and treatment conditions (such as gas atmosphere and final temperature). For the sample with Cu/Cr ¼ 0.5, the surface area of Cu-Cr xerogel can reach 94 m 2 /g and decreased to only 31 m 2 /g after calcination at 500 C. The catalysts show significant catalytic activity and selectivity in glycerol conversion, i.e. above 52% conversion of glycerol and above 88% selectivity to 1,2-propanediol at 210 C and 4.15 MPa H 2 pressure. CuCr 2 O 4 supported Cu catalysts are much more active than Cr 2 O 3 supported Cu catalysts. This indicates a strong interaction between Cu and CuCr 2 O 4 that is significantly improving the effectiveness of the catalyst for glycerol conversion.

Hydrogenolysis of glycerol to 1,2-propanediol on copper core-porous silica shell-nanoparticles

“…1,2-propanediol is mainly used as a raw material for producing unsaturated polyester resins, antifreeze fluid, solvent, preservative in food and in tobacco products [7]. C 3 H 5 (OH) 3 + H 2 → CH 3 CH(OH)CH 2 (OH) + H 2 O (1) Copper-based catalysts, including copper chromite [8][9][10][11][12], Cu-ZnO [13][14][15][16][17][18], Cu/SiO 2 [19][20][21], Cu-Al 2 O 3 [22][23][24][25] and Cu/ZnO /Al 2 O 3 [26], are mostly often used for glycerol hydrogenolysis to produce 1,2-propanediol in the presence of high pressure hydrogen. In the literature, Cu/SiO 2 catalysts for glycerol hydrogenolysis were prepared by several different methods, including precipitation-gel [19], homogeneous-precipitation, heterogeneous deposition-precipitation [20], incipient wetness and ion-exchange [21].…”

Magnetism and phase transformation of Cu-Fe composite oxides prepared by the sol-gel route

“…The Cu-Fe composite oxides were synthesized by a sol-gel route [5,6]. The structure and magnetic properties were determined by X-ray diffraction (XRD) [6], Mössbauer spectroscopy and magnetic measurements.…”

Applications and Preparation Methods of Copper Chromite Catalysts: A Review

“…The sol-gel synthesis of mixed oxides from alkoxide mixture usually suffers from the different hydrolysis susceptibilities of the individual components and the benefits of improved homogeneity can be lost during the hydrolysis of the alkoxides, which may ultimately lead to component segregation and mixed phases in the final materials. To achieve homogeneous mixed oxides with predetermined compositions, the difference in reactivity has been minimized by controlled prehydrolysis of the less reactive precursor [365], by chemical modification of the precursors [366], by using single-source , 6 (2), 2011, 97 heterobimetallic alkoxide precursors [367], or by non-hydrolytic sol-gel processes [368].…”

“…The copper chromite (CuCr2O4) is one of the most efficient materials, has wide commercial application as catalysts being used in the unit processes of organic synthesis such as hydrogenation [1], dehydrogenation [2], hydrogenolysis [3], oxidation [4], alkylation [5], cyclization [6], etc. It can be used in the pollution abatement as the catalyst to remove aqueous organic wastes [7], volatile organic compound (VOC) [8] and vehicular primary emissions [9] such as CO, unburned hydrocarbon, NOx and soot.…”