Abstract. Pt nanoparticles on La-doped sodium tantalum oxide (La0.02Na0.98TaO3), which acts as an active co-catalyst for H2 evolution under UV light irradiation was successfully synthesized by photo-deposition method. The La0.02Na0.98TaO3 photocatalyst was obtained by the reaction of La(NO3)2.3H2O, TaCl5, and NaOH at ambient temperature. The catalyst produced was characterized by a scanning electron microscope (SEM) and a high-resolution transmission electron microscope (HRTEM). SEM images of the La0.02Na0.98TaO3 sample showing that its particles size is ranging between 50-150 nm. The Pt particles are detected from HRTEM images is around 2-4 nm. The Pt/La0.02Na0.98TaO3 samples prepared were applied for photocatalytic H2 production at 30 o C. The photocatalyst performance was evaluated for hydrogen production from water combining with glycerol as an electron donor (sacrificial reagent). The reactions were carried out in a closed reactor with a gas circulation system, illuminated with mercury (Hg) lamp. The experimental results show that the presence of glycerol in the systems can not only improve the efficiency of photocatalytic hydrogen generation but can also be decomposed to hydrogen efficiently. The photocatalytic activity of La0.02Na0.98TaO3 is significantly enhanced when Pt was loaded onto its crystalline surface.

Abstract. Sodium tantalum oxide doping lanthanum (La-NaTaO 3 ) compounds were successfully synthesized by a sol-gel method and calcined at different temperatures. Tantalum chloride (TaCl 5 ) was used as starting material and lanthanum nitrate (La(NO 3 ) 3 .6H 2 O) as lanthanum source. X-ray diffraction (XRD) revealed that the calcination temperature strongly influenced the crystallinity of the prepared samples. The crystallite sizes of the resultant LaNaTaO 3 were in the range of 27-46 nm. The photocatalytic activities of the samples were examined for hydrogen production from an aqueous methanol solution under UV light irradiation. It was found that the photocatalytic activity of the La-NaTaO 3 depended strongly on the calcination temperature. The range of calcination temperatures were 500, 700, and 900°C. The La-NaTaO 3 sample calcined at 900°C showed the highest photocatalytic activity compared to the samples calcined at the other temperatures. The rate of hydrogen production reached a value of 6.16 mmol h -1 g -1 catalyst.

Biodiesel production from palm oil and alcohol has been carried out using a K2O/NbOPO4 solid acid catalyst. NbOPO4 catalyst was synthesized through the sol-gel method, followed by drying and calcination at a temperature of 800°C for 6 hours. The catalyst was further treated using K2CO3 with various concentrations of 15, 25, 35, 45 and 55% through the impregnation technique. Morphology and composition of the catalyst were evaluated by SEM, EDX and XRD instruments. The results showed that the catalyst has non homogeneous particles with size ranging between 1.86 μm to 25 μm, accompanied by the agglomeration. The results of the analysis also confirmed that the prepared catalyst contains potassium, niobium, phosphorus and oxygen with a composition of 10.15; 17.67; 6.11 and 41.83%, respectively. The catalytic activity was tested in the transesterification reaction for 3 hours, at a temperature of 65°C with the molar ratio of palm oil to alcohol of 12:1 and catalyst loading of 6%. The highest yield of 98.87% was obtained on the process using the catalyst impregnated with 35% K2CO3. The overall results show that there is a very promising potential of NbOPO4 catalysts for biodiesel production.

This study reports on the development, preparation, and performance test of NbOPO4 solid acid catalyst for biofuel production from vegetable oil. NbOPO4 catalyst was synthesized by sol-gel method using NbCl5, H2SO4, and citric acid as the precursor solutions and chelating agent, respectively. Dependent variables in the study were calcination time of 5 h; NbOPO4 loading of 2%; transesterification time of 3 h; reaction temperature at 65-70°C and oil mass of 30 g. Whereas, the catalyst pH of 2, 4, 6, 9, and Na impregnation ratio of 20-50% were set as independent variables. The catalyst morphology was analysed by Scanning Electron Microscopy, catalyst elements was detected by Electron Dispersive X-Ray and X-Ray Diffractometer was used to characterize the crystallinity degree of the catalyst. The performance of the catalyst was evaluated from a transesterification reaction for biofuel production. The highest biofuel yield of 98,5% was obtained in the reaction using catalyst with a pH of 4 and Na impregnation ratio of 30%. The density obtained was 0,860 gr/cm3 confirming that the produced biofuel complies with the SNI. It can be concluded that Na-loaded NbOPO4 can be a promising alternative catalyst in biofuel production.