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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.

With the aim to reduce the negative impacts caused by the widespread of water hyacinth to the environment, this paper reports the utilization of water hyacinth as a source of biomass to fabricate a heterogeneous catalyst. The catalyst was prepared by calcinating the grounded hyacinth biomass at 600°C, and K2CO3 was then introduced as a co-catalyst through impregnation method. The properties of biodiesel were also evaluated in terms of yield and density. To better understand the impregnation effects, surface topography, particle size, and atom composition of water hyacinth catalyst with K2CO3 impregnation were analysed. The performance of the synthesized catalyst was studied for the transesterification reaction of palm oil into biodiesel. The reaction was carried out in a batch mode for 3 hours with stirring at 65°C. The molar ratio of methanol to the oil of 12:1, and the catalyst loading was 15 wt. %. The highest yield (97.57%) was obtained from the process using 15% of the hyacinth-based catalyst which impregnated with 10% of K2CO3. The biodiesel produced was in the range of the SNI standard. The water hyacinth can be a promising heterogeneous catalyst for biodiesel production at an industrial scale.

Abstract. This paper reports the evaluation of La-NaTaO3 photocatalyst performance in producing hydrogen from water-glucose solution. The main goal of the studies is to investigate the influence of glucose as a sacrificial reagent on the photocatalytic efficiency in water splitting reactions under ultraviolet (UV) irradiation. Photocatalyst has been fabricated via solgel method and being confirmed using x-ray diffraction (XRD) and scanning electron microscopy (SEM). Nickel loaded La-NaTaO3 photocatalyst are prepared by impregnation method. It was observed that the prepared photocatalysts displayed particle sizes in the 30-250 nm range with orthorhombic structure. Their photocatalytic activity for hydrogen production via water splitting was conducted in a Pyrex glass reactor under UV light irradiation. The aqueous solution contained glucose employed as a renewable organic scavenger. A significant improvement in hydrogen production was observed in glucose-water mixtures and NiO loaded photocatalyst. The prepared La-NaTaO3 showed that the highest activity for hydrogen generation of 35.1 mmol h -1 .g -1 was obtained at 0.10 mol.L -1 glucose and 0.3 wt.% NiO. This suggests the important role played by the glucose as electron donor and loading nickel on LaNaTaO3 as a cocatalyst increasing electron storage and suppressing electron-hole recombination.

Catalytic biodiesel production from vegetable oil and methanol using K2O/C has been studied. The aim of this research was to investigate the performance of a K2O/C catalyst for biodiesel production at varied of K2CO3 loading. The activated carbon-based from rice husk were fabricated via pyrolysis route. The catalyst were formed by depositing active phase K2CO3 (10%; 20%; 30%; 40%; 50%) on the carbon surface for comparative purposes. To better understand of the impregnation effects, particle size, surface topography, and atom composition, the catalysts were analyzed by Scanning Electron Miscroscopy (SEM) and Energy Dispersive X-Ray (EDX). Biodiesel was produced via transesterification reaction. The reaction was carried out during 90 minutes at 65°C using 4wt% of the catalyst and methanol to oil molar ratio 10:1. The highest yield of biodiesel was reached of 96.62% at K2O loading of 50% on carbon-based rice husk. The use of K2O/C as catalysts enhance the purity of the product (carbon-based effect). The characterization of biodiosel, such as viscosity, density, and acid number were evaluated to confirm the purpose of catalyst function. The biodiesel characterization showed in the range with SNI standard.