Boreskov Institute of Catalysis of the Siberian Branch of Russian ...

OP-V-4KINETICS OF CATALYTIC DEOXYGENATION OF STEARIC ACIDOVER Pd CATALYSTS: EFFECT OF METAL DISPERSION1. IntroductionI. Simakova 1 , O. Simakova 1 , P. Mäki-Arvela 2 , D.Yu. Murzin 21 Boreskov Institute of Catalysis, Novosibirisk, Russia2 Åbo Akademi University, Turku/Åbo, FinlandCatalytic deoxygenation of triglycerides is of great interest for production of biodiesel inorder to decrease the dependence of fossil fuels. Deoxygenation of fatty acids and theirderivatives was successfully demonstrated in a semibatch [1, 2] and continuous reactor [3]with one of the most promising catalyst being Pd/C. Several parameters, like pressure,temperature and reaction atmosphere have been optimized previously. The effect of metalparticle size has not, however, been systematically studied earlier. In this work a series of Pdcatalysts supported on synthetic carbon, Sibunit, were studied with the main emphasis onelucidation of the influence of metal dispersion. Additionally temperature dependence wasstudied for the most promising catalyst.2. ExperimentalThe catalytic deoxygenation of stearic acid was performed in a 300 ml semi-batch reactor.The reaction temperature was kept constant during reaction in the range of temperatures from260 to 300°C and the reaction pressure was 17 bar. The stirring speed of 1100 rpm was usedto prevent external mass transfer limitation. Four different Pd/C catalyst supported on Sibunitwere prepared by deposition of palladium hydroxide yielded by hydrolysis of palladiumchloride at pH 8-10 [4]. The catalysts were reduced in-situ by hydrogen for 1h prior to thecatalytic tests at constant temperature and pressure being 60°C and 3.5 bar, respectively. In atypical reaction, the following catalysts and substrate amounts were used: 0.5–1.0 g ofcatalyst; 0.1 M stearic acid in 50 ml of dodecane. The reaction temperature was adjusted witha heating ramp 10°C/min to the desired reaction temperature and the reaction commenced.Both gas- and liquid phase samples were analyzed by GC [2]. The catalysts werecharacterized by CO-chemisorption, SEM and nitrogen adsorption.3. Results and discussionThe kinetics of the catalytic deoxygenation of stearic acid over four different Pd/Ccatalyst revealed (Fig. 1a) that there is an optimum Pd dispersion (D=47%, corresponding tothe Pd particle size of 2.3 nm), giving the highest reaction rate and conversion. Both withsmaller and higher metal dispersions lower reaction rates and conversions were achieved.173