Abstract
Abstract : The use of adavanced chemicals (i.e. fine and speciality), forms an intergral part of our daily life in the consumer end-user products formulation for the industries such as flavor and fragrance, aroma food additives, aromatherapy, and pharmaceutical. These kinds of chemical derivatives boast high manufacturing costs and are mostly produced in limited or small volumes. In the present work, the focus is on developing the catalytic process the for production of some aroma bearing chemicals, i.e. pinene oxide, verbenol and verbenone from the pinene platform chemical. Unfortunately, these fine chemicals cannot be produced from fossil carbon resources, thus this has been a motivation in the growth of the biorefinery related research work within the frame-work of the South African government Department of Science and Technology (DST) bioeconomy strategy in addition to the CSIR Industrialisation Synapse intiations. In the paper and pulping industry, the product yield efficiency based on material balancing is barely 50% of the process wood. As a result, millions of rand one spent on waste management issues. Most of the waste end up as saw dust, wood sludge or wood chips. This current work attempts to provide solutions pertaining to the possible commercial process of interest that can beneficiate the tons of waste material generated from the pulp and paper industry. The wood biomass-derived turpentine, a mixture of hydrocarbons such as carene, camphene and pinene, offers attractive commercial advantages for catalytic upgrading of its extractives into renewable and green produced fine chemicals. The main aim in this study is to design active magnetic bimetal copper ferrite (CuFe2O4) oxide catalyst for application in the liquid-phase oxidation of pinene using tertiary butyl hydroperoxide (TBHP) as terminal oxidant to produce various aroma oxygenates such as pinene oxide, verbennol and verbenone. Despite significance success shown by noble metals in various reactions, this study aim to develop new strategies on nano-heterostructuring cheap and less toxic catalyst based on copper and iron. The proposed catalyst design strategy involves studying the effect of mixing different volume ratio of solvents such as ethylene glycol and water in nano- structuring the CuFe oxide catalysts using Cu(NO3)2.3H2O and Fe(NO3)2.9H2O as metal precusor salts in the presence of surfactants, polyvinylpyrrolodie (PVP) and F127 Pluronic. The aim is to induce the controlled varying structural morphologies, textural, electronic and redox properties of the catalyst that are crucial for driving the free- radical oxidation reactions. The structural characteristics of the calcined catalysts were assessed using powder X-ray diffraction (PXRD), laser Raman spectroscopy (LRS), N2 physisorption (BET), field emission scanning electron microscopy (FESEM) coupled to energy dispersive X-ray (EDX), high-resolution transition electron microscopy (HRTEM), and hydrogen- temperature programmed reduction (H2-TPR). PXRD measurements and Rietveld analysis revealed that the catalysts possessed different CuFe2O4 phases. It was also found that the varying the compositional ratio of the solvent induced the formation of CuFe2O4, such as CuO and Cu(OH)2. The LRS results were in good agreement with the PXRD in terms of phase selectivity, with the strong vibration band being associated with the CuFe2O4 phase. FESEM and BET surface area showed that the synthesized nano-CuFe catalysts possessed the bimetal oxides hybrid, reaffirmed by the textural combination of macro and mesopores morphology. In addition, bimetallic CuFe SEM micrograph images showed two distinctive morphologies spherical and rods-like shapes. HR-TEM, fast fourier transform (FFT) and electron diffraction pattern (EDP) simulations confirmed that the structure of CuFe2O4 has a simple cubic crystal symmetry defined by the normal spinel with formula AB2O4. The TPR profiles of the analysed catalysts exhibited more than one step reduction which are in accordance with the profound of Cu and Fe oxides redox surface oxygen reactivity. The catalytic perfomance of the CuFe catalysts were evaluated in the oxidation of pinene in a high-pressure autoclave and glassflask reactors. The catalytic experimental results revealed that the CuFe catalyst selectivity and activity were than the perfomance of the individual CuO and Fe2O3 catalysts. CuFe displayed greater selectivity towards verbenone compared to verbenol. The high-pressure autoclave reactor showed better oxidation rates in terms of productivity space time yield at comparable conditions when compared to the glass flask reactor. In particular, the high-pressure autoclave reaction afforded a pinene conversion of 78.5% at state selectivity towards verbenol and verbenone separately. the synthesized nano-CuFe catalysts possessed the bimetal oxides hybrid, reaffirmed by the textural combination of macro and mesopores morphology. In addition, bimetallic CuFe SEM micrograph images showed two distinctive morphologies spherical and rods-like shapes. HR-TEM, fast fourier transform (FFT) and electron diffraction pattern (EDP) simulations confirmed that the structure of CuFe2O4 has a simple cubic crystal symmetry defined by the normal spinel with formula AB2O4. The TPR profiles of the analysed catalysts exhibited more than one step reduction which are in accordance with the profound of Cu and Fe oxides redox surface oxygen reactivity. The catalytic perfomance of the CuFe catalysts were evaluated in the oxidation of pinene in a high-pressure autoclave and glassflask reactors. The catalytic experimental results revealed that the CuFe catalyst selectivity and activity were than the perfomance of the individual CuO and Fe2O3 catalysts. CuFe displayed greater selectivity towards verbenone compared to verbenol. The high-pressure autoclave reactor showed better oxidation rates in terms of productivity space time yield at comparable conditions when compared to the glass flask reactor. In particular, the high-pressure autoclave reaction afforded a pinene conversion of 78.5% at state selectivity towards verbenol and verbenone separately.
M.Sc. (Chemistry)