INFLUENCE OF CATALYST PROPERTIES ON BIODIESEL PRODUCTION FROM SUNFLOWER OIL VIA SULPHATED ZIRCONIA: TOTAL ACIDITY AND SULPHUR IN HIGHEST OXIDATION STATE - ESSENTIAL FACTORS FOR CATALYTIC EFFICIENCY

摘要

Biodiesel is considered to be an environmentally and economically viable fossil fuel alternative. Sulphated zirconia has been suggested as a feasible substitute that would overcome problems connected to the process of biodiesel production by transes-terification of oils with industrially favoured homogenous base catalyst. Activity of sulphated zirconia in the transesterification reaction of sunflower oil and methanol was determined and correlated with the catalyst properties in this paper. Catalysts were synthesised from three different precursors. Catalyst properties evaluated were: calcination temperature, specific surface area, pore volume and diameter, tetragonal/monoclinic crystal phase fraction, sulphates density, Hammett acidity values and Bronsted and Lewis acid sites numbers. Fatty acid methyl ester yields of up to 82.2% (for the commercially sulphated zirconia calcined at 500°C) were obtained. It was determined that the favourable acidic properties of the catalyst, especially the high number of Br?nsted acid sites greatly increase the activity of the catalyst in the test reaction and are probably connected with the increased fraction of catalytically active tetragonal crystal phase, which in turn is a result of a specific activation temperature. Textural properties also influence the activity of the catalyst in the reaction(s), although this influence is somewhat smaller.