Abstract
A series of Cu or Ni monometallic and Cu-Ni bimetallic catalysts supported on γ-Al2O3 were synthesized by incipient wetness impregnation method. X-ray diffraction results exhibited the formation of bimetallic Cu-Ni phase in the reduced Cu-Ni(1:1)/γ-Al2O3 catalyst. Among the catalyst examined for hydrogenolysis of glycerol, bimetallic catalysts exhibited higher catalytic activity than monometallic catalysts due to synergetic effect of Cu-Ni bimetal. Cu-Ni(1:1)/γ-Al2O3 catalyst displayed a maximum glycerol conversion of 71.6% with 92.8% selectivity to 1,2-propanediol at 210 °C and 4.5 MPa hydrogen pressure. The superior performance of Cu-Ni(1:1)/γ-Al2O3 catalyst was attributed to the formation of bimetallic Cu-Ni phase, high active metal surface area, small Cu-Ni particle size, and high acidic strength of the catalyst. Stability and reusability of Cu-Ni(1:1)/γ-Al2O3 catalyst was performed and detailed characterization results of fresh and used catalysts suggested that bimetallic Cu-Ni phase remained stable after reuses.
Highlights
Biodiesel has received considerable attention due to scarcity of fossil fuel reserves and global warming problems
To optimize glycerol conversion and 1,2-PDO selectivity, the effect of reaction temperature, hydrogen pressure, reaction time, glycerol concentration, catalyst amount, and metal loading on hydrogenolysis of glycerol is examined in the presence of Cu-Ni(1:1)/γ-Al2O3 catalyst
Turnover frequency (TOF) values are observed in the range of 15.4-64.2 h−1, as the temperature increases from 190 to 230 °C. These results suggest that at higher temperature (> 210 °C), 1,2-PDO undergoes further hydrogenolysis that lead to C−C bond cleavage and produce 1-propanol and low molecular alcohols such as ethylene glycol, ethanol, and methanol.[6,8,25]
Summary
Biodiesel has received considerable attention due to scarcity of fossil fuel reserves and global warming problems. For the reduced catalysts except for Cu-Ni (1:1), the size of the Cu particle increases due to the particle agglomeration resulted by change of surface electronic properties of Cu particles, which indicates less metal support interaction.[22,23] In case of Cu-Ni(1:1)/γ-Al2O3 catalyst, the size of the Cu particle estimated from line width of the peaks corresponding to (111), (200) and (220) crystal planes is decreased from 56 to 33 nm after the reduction.
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