Synthesis of high surface area supported copper based-bimetallic catalysts for hydrogenation of fatty alcohols to fatty amines / Normazuin Abdul Rahman

Normazuin, Abdul Rahman (2011) Synthesis of high surface area supported copper based-bimetallic catalysts for hydrogenation of fatty alcohols to fatty amines / Normazuin Abdul Rahman. Masters thesis, University of Malaya.

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Abstract

Over the past few decades it has been observed that copper (Cu) ‘supported on’ or ‘incorporated into’ solid matrices are widely used as catalysts for various types of reactions. It was reported that the high activity of supported Cu catalyst is generated by properties of the clusters and nanoparticles including high dispersion and uniform distribution of nanoparticle Cu on the support material. All these factors exert a direct effect on the formation of active surface of Cu and their catalytic properties accordingly. In this study, Cu based catalysts supported on silica, SiO2 were prepared by incipient wetness impregnation of SiO2 with aqueous metal citrate salt solution. A chelated precursor was chosen because previous work has shown that catalyst prepared in the presence of some specific chelated metal-complexes resulted in catalysts with high dispersion of small metal (oxide) particles with a narrow particle size distribution. The Cu based catalysts consisting of a second metal (Zn and Ni) were also prepared and examined for their influence on surface and structural properties of the final catalysts. Characterization of the catalysts was carried out by Xray Diffraction (XRD), Scanning Electron Microscope (SEM) and Energy Dispersive X-ray (EDX), Ultraviolet Visible (UV-Vis) Spectroscopy, Fourier Transform Infrared (FTIR) and X-ray Fluorescence (XRF), Thermal Gravimetric Analysis-Mass Spectrometer (TGA-MS), Differential Scanning Calorimetric (DSC) and Temperature Programme Reduction (TPR). The catalysts were later screened for their performance in process of hydrogenation of fatty alcohol to fatty amines using high throughput reactor. The results from the characterization indicate that second metal influences the final. catalysts produced with different characteristics. The morphology and BET surface area of SiO2 as a support was not preserved in Cu-Zn and Cu-Ni catalysts. This is due to agglomeration that changes the basic structural units (BSU) through precipitation of active metal oxide particles, and/or through modification of the support oxide surface occurring from their contact with the impregnated liquid and also the thermal treatment during drying and calcination. The XRD analysis shows the formation of amorphous nano-structured Cu supported on SiO2 in the calcined catalysts. The Nitrogen physisorption measurement (BET) analysis shows that higher surface area (191.84 m2/g) was obtained in Cu-Ni catalyst and this gives the best Cu metal dispersion on support. This study shows that the choice of appropriate synthesis parameters and thermal treatment for Cu-Zn/SiO2 and Cu-Ni/SiO2 are extremely important to obtain superior surface area of nanocrystallites active Cu metals for the target reaction. Similarly, from this study, undesirable conditions of catalysts preparation and activation parameter that gave rise to catalysts with poor structure and thermal characteristics are identified. The two catalysts, Cu-Zn and Cu-Ni, were studied for their catalytic behaviour in hydrogenation of fatty alcohol. Upon in situ activation, the catalysts were then screened in a high-throughput Oleobed reactor, conducted at a 30 bar pressure and over a temperature range of 443-523 K. In the screening, Cu-Ni supported catalysts show significant selectivity towards hydrogenation of fatty alcohols compared with Cu-Zn.

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