Catalysis of Organic..

424 Production of Biodieselproduct selectivity patterns were noticed for all three catalyst masses. The selectivityto the desired product, heptadecane, was above 75% and in all three cases minorconcentrations of ethyl stearate dehydrogenation products were present. Complexityof relationship between liquid phase composition and catalyst deactivation calls for,further investigations of the impact of the gas-phase reactions, which result inproducts, strongly influencing catalyst deactivation. . The initial conversion and theinitial selectivities towards the desired C17-products in the deoxygenationexperiments are summarized in Table 4.The influence of the reaction temperature on the decarboxylation rate wasstudied in the temperature range of 270-360˚C. The pressure was adjusted dependingon the vapor pressure of the solvent, hexadecane, at specific temperatures in order tokeep the reaction in the liquid phase. As expected the conversion of ethyl stearateincreased with increasing reaction temperature (Figure 8). The complete conversionof ethyl stearate was achieved at 360˚C. Furthermore the catalyst was very stable atthese temperatures, hence loosing not more than 10% of ethyl stearate conversionduring 5 h of time-on-stream. The surface areas of the spent catalysts at differenttemperatures were approximately 300 m 2 /g for all four temperatures, which is equalto a 75% decrease of the initial surface area and moreover is an indication of a heavycoke formation on the catalyst surface. Based on the Arrhenius equation, theapparent activation energy was calculated to 69 kJ/mole in a temperature range of270-330˚C, applying zero order kinetics.100-1Conversion of ethyl stearate (%)80604020360˚C330˚C300˚C270˚C-2ln(k)-300 60 120 180 240 300Time-on-stream (min)-40.0016 0.0017 0.0018 0.00191/TFigure 8. The effect of reaction temperature on ethyl stearate conversion as afunction of time-on-stream and Arrhenius plot (based on zero order kinetics)Reaction conditions: 5 mol% ethyl stearate in hexadecane, m cat =0.4 g, p 270˚C =1 bar,p 300˚C =3 bar, p 330˚C =5 bar, p 360˚C =7 bar and V’=0.1 ml/min.The effect that temperature had on selectivity is minor, thus formation ofheptadecane was maintained stable over 90% as a function of temperature, while an