Hydrodeoxygenation of guayacol over platinum modified mesoporous catalysts.

Abstract

Biomass pyrolysis results in fuel bio-oil which can be consider as a renewable petroleum alternative. Bio-oil obtained by this process presents high oxygen content, becoming into a corrosive and unstable fuel. Hydrodeoxygenation (HDO) is a catalytic treatment that improves the bio-oil characteristics. There are more than 400 organic compounds that can be found in bio oil. For that reason we selected guayacol (2-methoxyphenol ó 4-hydroxy-3-methoxybenzyl) as model compound to test the catalytic activity of the developed catalysts. The catalysts tested for hydrodeoxygenation (HDO) of guayacol to produce deoxygenated products such as benzene, toluene, ciclohexene and ciclohexane were platinum modified mesoporous SBA-15 and Ga-SBA 15. The synthetized catalysts were obtained by sol-gel method. Active platinum sites were incorporated by wet impregnation. The system reaction used for HDO is a 600 mL stirred autoclave (Parr Pressure Reactor 4536). Reaction conditions were carried out at 230°C and 12 atm of H2 under 500 rpm. Reactor feed consisted in 50 mL of a 1% w/v solution of guayacol in dodecane. Then, 200 mg of the catalyst was transferred to the reactor. Samples were taken every hour. Products were analysed with HP Series II GC and HP-5 capillary column and identified by GC/MS. Better catalytic results were obtained when Ga was introduced as heteroatom into the SBA-15 siliceous framework. Textural and structural properties of the Pt -supported mesoporous catalysts were determined along with the nature of the active site. The synthetized material were characterized before and after the incorporation of metal active site by XRD, HRTEM, SEM EDX, FTIR, XPS and N2 adsorption-desorption isotherms. Characterization results demonstrated that highly dispersed Pt species are responsible for the high activity in the guayacol conversion. The most active catalyst for HDO of guayacol was Pt/Ga-SBA-15 achieving 99 % of guayacol conversion in a relatively short time (4 h). Gallium atoms incorporated into the support modified the nature of the SBA-15 surface by conferring Bronsted and Lewis acidity. The acid sites are able to interact with the platinum active sites improving the activity of the catalyst. As consequence the gallium modified catalyst showed better dispersion of the Pt sites