A Novel Heterogeneous Catalyst Design for Liquid-Liquid and Liquid-Gas Systems Hadi Nur Ibnu Sina Institute for Fundamental Science Studies Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor, Malaysia Tel. +60-7-5576160 ext. 34494 Fax. +60-7-5582893 E-mail: hadi@kimia.fs.utm.my Liquid-liquid and liquid-gas reactions using solid catalysts are often encountered in the chemical process industry, most frequently in hydroprocessing operations and in the oxidation of liquid phase organic. Along this line, we have attempted to make an effective heterogeneous catalytic system for these applications. Recently, a novel concept of "phase-boundary catalysis (PBC)” in order to utilize the immiscible liquid-liquid reaction system with solid catalysts was proposed (see Fig. 1) [1-4]. In the PBC system, it was demonstrated that the bimodal amphiphilic zeolite particles, NaY zeolite loaded with alkylsilane-covered titanium oxide, could be placed at the liquid-liquid phase boundary between aqueous hydrogen peroxide and water-immiscible organic phases and act as efficient catalyst for epoxidation reaction without any mechanical agitation. NaY zeolite was found to be more effective than nonporous silica counterpart as “Phase-boundary catalyst” to promote the epoxidation of alkenes with aqueous 30% H 2 O 2 . The chemical phenomena occurring during gradual addition of 30% H 2 O 2 in epoxidation of 1-octene suggested that the hydrophilic pore system and the hydrophobic/hydrophilic regions on external surface of amphiphilic zeolite particles gave a significant role for supplying the aqueous and the organic substrates to the active sites [4]. In order to elucidate an effective location of the active sites, TS-1 in which the location of the active sites mainly inside the pore system is chosen as model catalyst. Its activity is compared to NaY zeolite loaded with alkylsilane-covered titanium oxide particles, in which the active sites are on their external surface, in epoxidation of 1-octene with 30% H 2 O 2 as model reaction. It was suggested that alkylsilylation on the external surface of zeolite, in which the location of the active site is mainly inside the pore, could not change the mode of the catalytic action; it is still necessary to stir the reaction mixture to drive the mass transfer of substrates and reagents. Thus, the external surface of zeolite is an effective location of the active sites in the PBC system, in which the active site (as well as the catalyst) is placed at