Catalysis of Organic..

Snåre et al. 417The production of hydrocarbons for diesel fuel via decarboxylation of vegetablebased feeds has been verified in our previous work [6]. The fatty acid, stearic acid,the fatty acid ester, ethyl stearate, and a triglyceride of stearic acid, tristearin, weresuccessfully decarboxylated resulting in the paraffin, n-heptadecane, originatingfrom the stearic acid alkyl chain. The experiments were carried out in a semi-batchreactor over a commercial palladium catalyst. The results showed that ethyl stearatedeoxygenation proceeds over the corresponding fatty acid intermediate which issubsequently deoxygenated to heptadecane and carbon dioxide. In the present studythe continuous deoxygenation of ethyl stearate was investigated in a tubular reactorin order to evaluate the catalyst stability and the industrial applicability.Experimental SectionThe fresh and spent catalysts were characterized with thephysisorption/chemisorption instrument Sorptometer 1900 (Carlo Erba instruments)in order to detect loss of surface area and pore volume. The specific surface area wascalculated based on Dubinin-Radushkevich equation. Furthermorethermogravimetric analysis (TGA) of the fresh and used catalysts were performedwith a Mettler Toledo TGA/SDTA 851e instrument in synthetic air. The meanparticle size and the metal dispersion was measured with a Malvern 2600 particlesize analyzer and Autochem 2910 apparatus (by a CO chemisorption technique) ,respectively.The catalytic deoxygenation experiments were carried out in a tubular fixed bedreactor. The reactor length and the inner diameter were 175 mm and 4.4 mm,respectively. The catalyst powder was placed between a layer of quartz sand andquartz wool. The experiments were typically carried out in an upward two-phasesystem and volumetric flow 0.1 ml/min using a high performance liquidchromatography pump (HPLC). The system was pressurized by adding 10 ml/minpressurizing media (Ar and N 2 ) using a mass controller and a pressure controller,which were placed downstream. The experimental setup is illustrated in Figure 2.Decarboxylation of ethyl stearate in the continuous system is a challenge, due toits high melting point and low solubility in inert solvents. The solvent caused someadditional challenges since the reaction must be carried out in the liquid phase andthe reaction temperature should be sufficiently high for the reaction to occur. Thereaction mixture containing 5 mol% ethyl stearate (Aldrich, >97%) in hexadecane(Fluka >98%) was continuously fed through a fine catalyst powder bed (particlesize