To increase the conversion of hydrogenation of carbobenzoxy phenylalanine in the gas-liquid-liquid-solid four-phase trickle-bed reactor, Teflon powder was deposited on the surface of the catalyst. Teflon powder was expected to break the water film on the catalyst, Pd/Al2O3, surface since it has hydrophobic property. Then organic solution, in which the reactant was dissolved, could easily contact the catalyst surface; thus, mass transfer was promoted. Three kinds of Teflon powder were tested and Fussoseparate increased the conversion. A rotary evaporator was used to control the amount of the Teflon powder deposition on the catalyst surface. Conversion was increased with an increase of the amount of Teflon powder. But excessive Teflon powder decreased the catalyst activity because it covered the active site of the catalyst. The highest activity was achieved by 0.064 wt % of Teflon powder.