Makame Mbarawa

Croton megalocarpus oil: a feasible non-edible oil source for biodiesel production.

This study presents the feasibility of converting a non-edible oil source native to the Africa region -croton megalocarpus oil to methyl esters (biodiesel) using sulfated tin oxide enhanced with SiO(2) (SO(4)(2-)/SnO(2)-SiO(2)) as super acid solid catalyst. This study was conducted using design of experiment (DoE), specifically, response surface methodology based on three-variable central composite design (CCD) with alpha (alpha)=2. The reaction parameters studied are: reaction temperature (60-180 degrees C), reaction period (1-3h) and methanol to oil ratio (1:6-1:24). Although the oil was found to contain high free fatty acid, however, yield up to 95% was obtained without any pre-treatment step with the following reaction conditions: 180 degrees C, 2h and 15:1 methanol to oil molar ratio, while keeping constant catalyst concentration and stirring speed at 3 wt.% and 350-360 rpm, respectively.

Effects of Biodiesel Blending with Fossil Fuel on Flow Properties of Biodiesel Produced From Non-Edible Oils

The cold flow properties of biodiesel from various feedstocks have been a challenge in adapting the use of biodiesel in diesel engines, especially in cold regions. The use of cold flow improvers for biodiesel helps using biodiesel in a wide range of temperature conditions. In this study, cold flow properties of biodiesel produced from non-edible feedstocks such as croton megalocarpus, jatropha curcas, and moringa oleifera oils were investigated. The evaluated properties were kinematic viscosity, cloud point, and pour point. Different transesterification methods were used to produce biodiesel from these feedstocks due to their difference in the level of free fatty acids (FFA). Croton and moringa oils were found with FFA levels of 1.68% and 0.6%, respectively; thus, one-step transesterification method was chosen for their methyl esters conversion. Jatropha oil was found with FFA level of 8.14% making a two-step acid-base transesterification method to be employed for its methyl esters conversion. The effect of water in the two-step acid-base transesterification process was also investigated for jatropha biodiesel production. The presence of water after acid pretreatment process of jatropha oil was found to reduce both product and methyl esters yield, the best option was to preheat the pretreated jatropha oil to 110°C for 10 min to evaporate water that remain during gravity separation of methanol–water phase. Blending of biodiesels from these three feedstocks with kerosene improved their cold flow properties. The reduction of cloud and pour points from −4°C and −9°C to −11°C and −15°C, respectively, of croton biodiesel was observed when blended with 20% kerosene while cloud and pour points reduction from 1°C and −2°C to −7°C and −12°C, respectively, of jatropha biodiesel was observed when blended with 20% kerosene. Similarly, the reduction of cloud and pour points from 10°C and 3°C to −3°C and −7°C, respectively, of moringa biodiesel was observed when blended with 20% kerosene.

The use of sulfated tin oxide as solid superacid catalyst for heterogeneous transesterification of Jatropha curcas oil

This work presents the use of sulfated tin oxide enhanced with SiO2 (SO42−/SnO2-SiO2) as a superacid solid catalyst to produce methyl esters from Jatropha curcas oil. The study was conducted using the design of experiment (DoE), specifically a response surface methodology based on a threevariable central composite design (CCD) with α = 2. The reaction parameters in the parametric study were: reaction temperature (60°C to 180°C), reaction period (1 h to 3 h), and methanol to oil mole ratio (1: 6 to 1: 24). Production of the esters was conducted using an autoclave nitrogen pressurized reactor equipped with a thermocouple and a magnetic stirrer. The maximum methyl esters yield of 97 mass % was obtained at the reaction conditions: temperature of 180°C, reaction period of 2 h, and methanol to oil mole ratio of 1: 15. The catalyst amount and agitation speed were fixed to 3 mass % and 350–360 min−1, respectively. Properties of the methyl esters obtained fell within the recommended biodiesel standards such as ASTM D6751 (ASTM, 2003).

Experimental Investigation of the SO2 Abatement Capacity of South African Calcium-Based Materials

One of the most important steps in the wet limestone-gypsum flue gas desulphurization (WFGD) process is CaCO3 dissolution, which provides the dissolved alkalinity necessary for SO2 absorption. Accurately evaluating the CaCO3 dissolution rate is important in the design and efficient operation of WFGD plants. In the present work, the dissolution of limestone from different sources in South Africa has been studied in a pH-stat apparatus under conditions similar to those encountered in wet FGD processes. The influence of various parameters such as the reaction temperature (30 ≤ T ≤ 70°C), CaCO3 particle size (25 ≤ dp ≤ 63μm), solution acidity (4 ≤ pH ≤ 6), and chemical composition were studied in order to determine the kinetics of CaCO3 dissolution. The results obtained indicate that the dissolution rate increased with a decrease in particle size and an increase in temperature. The dissolution curves were evaluated in order to test the shrinking core model for fluid–solid systems. The analysis indicated that the dissolution of CaCO3 was controlled by chemical reaction, i.e. 1 − (1 − X)1/3 = kt.Copyright