Sodium silicate as heterogeneous base catalysts is more environmentally friendly and easily separated by filtration. The objective of this research was to evaluate the activated sodium silicate as catalyst for synthesis of monoacylglycerol (MAG) and diacylglycerol (DAG)-rich structured lipids (SLs) from a palm olein-stearin blend. Sodium silicate was activated and functional group was characterized. Reaction was performed using 5% catalyst (w/w) at various reaction temperature (70–120 °C) for 3 h in a batch stirred tank reactor. Physical properties of SLs, such as melting point, slip melting point, and hardness of SLs were determined. Reaction kinetics were also evaluated. The results show that Si−O bending was reduced and shifted to a Si−O−Na and Si−O−Si functional groups after sodium silicate activation. Temperature had a significant effect on SLs composition at higher than 90 °C. An increase in temperature produced more MAG, resulting in better product physical properties. The best reaction condition was at 110 °C. Rate constants and the Arrhenius equation were also obtained for each reaction step. In summary, the activated sodium silicate catalyzed glycerolysis-interesterification reaction, which produced MAG and DAG at temperature higher than 90 °C. Therefore, the physical properties of SLs were improved. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

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Rice husk biochar was added to modify ureic fertilizer in order to control nitrogen release in two methods: (1) mixed-granule and (2) as a coating. The mixed-granule fertilizer was made of varied compositions of rice husk biochar, ureic fertilizer, and clay as a binder, whereas the coating model was formulated from ureic fertilizer, biogas sludge, and clay as a core and coated with various compositions of biochar and clay. All of the samples were leached by 100 mL of water once every three days, and the leachate was analyzed for its nitrogen content. Of all samples, coated fertilizer with a composition of 20% biochar and 80% clay showed the slowest nutrient diffusion with an effective diffusivity (De) number of 2.85×10 -8 cm/s 2 . The results show that both models increase fertilizer's ability to hold nitrogen longer than pure fertilizer. Both methods, mixed-granule and coated, showed slow release rate patterns, particularly at the beginning of the leaching process, and held the nitrogen content longer. Both models' release rates enable the modification of nitrogen release to meet the need for nitrogen in certain plantations.

The deactivation of solid catalyst is one of the catalyst parameters that has to be known to predict how long catalyst can be used to catalyze a reaction. In this research, the catalyst was applied to catalyze the transesterification of corn oil with methanol. Sodium silicate was produced from NaOH and silica was extracted by gelation method from Dieng Geothermal Power Plant solid sludge which had 55% of silica content. Sodium silicate catalyst was activated by calcination process at 400oC, with heating rate of 20ºC/min, and holding time of 3 hours. The transesterification was run at 60oC, methanol and corn oil mole ratio of 9:1 and 5% (w/w) catalyst for 60 minutes. The sample was taken at 0, 5, 10, 20, 40 and 60 minutes after corn oil was poured into the flask. The used catalyst was separated from the reactant and product, was then washed with methanol and was heated at 120 oC in the oven for 2 hours until it dried. The catalyst was then used for catalyzing the next experiment run for the next four cycle. This research showed that the conversion of the reaction decreased with every reaction cycle. The most fitting reaction kinetics was modeled with second order kinetics. The highest conversion obtained using fresh catalyst was 91,67%.

The objective of this research was to investigate the effect of temperature on the glycerolysis-interesterification reaction kinetics of immiscible and high viscous reactants at relatively low temperatures in a high shear reactor (HSR), and their physical product properties. The reaction was performed at various temperatures (80-120°C) and a mixing rate of 2000 rpm for 5 h. Results showed that the reaction rate constant increased and followed the Arrhenius equation as temperature increased. TAG conversion was 2.5 fold greater at 110 and 120°C compared to lower reaction temperatures. MAG and DAG increased by about 18.3% and 13.4%, respectively, as the reaction temperature increased from 80 to 120°C. The product’s melting point, hardness, and color were also improved by increasing temperature. In summary, structured lipids (SLs) synthesis containing high MAG and DAG could be produced at a relatively low temperature (110°C) using HSR, and followed the glycerolysis-interesterification kinetic and Arrhenius model.