Titania-polystyrene textile as phase boundary catalysis

Abstract

In the lights of the trending necessity towards clean and economical technology in chemical industry, heterogeneous catalysts are widely used due to their convenience of effortless separation methodology of catalysts from the products. Thus, this research proposes the establishment of a novel heterogeneous catalytic concept named “Phase-Boundary Catalysis System (PBC)”, utilizing textile as the support of titania active sites and H2O2 as the oxidizing agent. The previous catalyst of PBC was in particulate form, indicating existence of challenges to evenly disperse and immobilize at the liquid-liquid interface for 1-octene oxidation reaction. Therefore, the aim in this study is to design layered catalysts that can immobilize steadily at the interface of liquid-liquid layers and hence, applying the PBC catalyst for potential applications. The layered catalyst was designed using cotton textile as the support and polystyrene (PS) as the binder between titania and cotton textile. It is worth noting that the hydrophobic environment is the main character imposed by layered catalyst, which assists the layered catalyst to be floating and located exactly at the interface of liquid-liquid boundary. The titanium propoxide was chosen as titanium precursor due to the aspect of susceptibility towards cotton textile. The six layered catalysts were prepared by styrene polymerization with varied time (minutes) and denoted as T30, T60, T90, T120, T150 and T180. It was discovered that the cotton textiles bearing titania were gradually covered by PS with time. A series of layered catalysts were investigated in application of oxidation reaction using H2O2 as oxidizing agent. In the oxidation reaction, the conversion of 1-octene increased by approximately 5%, 10% and 25%, for reaction temperatures of 30oC, 60oC and 90oC, respectively. Reaction temperature 90oC showed the highest conversion to products, but the catalysts were low in the selectivity towards 1,2-epoxyoctane. The high selectivity of the oxidation reaction is towards 2-octanone products. It was possibly due to the concentration of H2O2 used (30 mmol) was much higher compared to previous studies (10 mmol), resulting in the process of accelerating 1,2-epoxyoctane to open its oxirane ring, then forming 2-octanone. Amongst all the layered catalyst, layered catalyst T90 gave the highest catalytic activity. It was due to the catalytic active site of layered catalyst T90 that has the optimum condition where the catalytic active site was not surrounded by large amount of polystyrene while attaining the sufficient attachment of titania towards cotton textile. Thus, less energy was needed for the substance to reach the catalyst active site for the reaction. As a comparison from previous study which used particulate catalyst involving variable temperature reaction, layered catalyst improved the catalyst selectivity by giving no side product besides 1,2-epoxyoctane and 2-octanone. However, the conversion activity still remains below 25% as previous study. Despite some limitations, the aim was successfully achieved. Thus, further modification should be carried out to improve the integrity of layered catalyst for potential applications.