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Abstract: The technologies conventionally used for biodiesel purification imply high consumptions of both energy and water. In the present work, biodiesel was produced by transesterification using a very active calcium glyceroxide catalyst and purified using water-free processes. The study focused on soaps removal that was the main product impurity. The best results were obtained when the crude biodiesel (methyl ester content of 90.2–91.2wt.% and calcium content of 372–393ppm) was pretreated with Na2CO3 and afterward treated by an ion-exchange resin (6wt.%) or a ceramic membrane (0.1μm). The purification was effective using biodiesel produced from both soybean oil and waste frying oil and the quality of the product agreed with the one obtained using the conventional water washing process. The effectiveness of the treatment could be explained by calcium elimination through precipitation as CaCO3 during pretreatment and sodium soaps removal by absorption into the resin or filtration by the ceramic membrane, according to the micelle formation mechanism. The studied process presents a high potential to remove calcium soaps from biodiesel. [Copyright &y& Elsevier]

Modelling the effect of reaction time, catalyst concentration, and oil-to-methanol ratio on the waste cooking oil biodiesel was studied using response surface methodology. Biodiesel was made using three different heterogeneous catalysts. Analysis showed catalysts 2 and 3 to be significant in transesterification. However, all catalysts had second-degree significance for esterification yield. For catalysts 1 and 2 there was a clear interaction between catalyst concentration and oil-to-methanol ratio. Clear interaction was also noticed between reaction time and oil-to-methanol ratio for all catalysts. There was moderate to no interaction between the effects of time and catalyst concentrations for all catalysts. The best yield was found at lower oil-to-methanol ratios (nearly 0.02) and higher catalyst concentrations (at 10%). Reaction times close to 7 hours for catalyst 1 and close to 5 for the other catalysts were the optimum values for best yield and lowest acid value. [ABSTRACT FROM AUTHOR]

• Biodiesel was produced from soybean oil and WFO over Ca catalyst. • Crude biodiesel was purified by dry washing using fumed silica. • Silica behaves as a non-selective sorbent. • Silica its able to remove calcium from produced biodiesel. • Used sorbents are easily regenerated by solvent wash. Aiming the decarbonization of the transport sector, biodiesel, obtained by alcoholysis of oils or animal fats, is currently mixed with conventional fossil diesel. For this purpose, biodiesel has to comply with the established quality standards and, therefore, the production process comprises purification steps, which need huge volumes of water. Thus, the biodiesel purification procedure must be improved in order to provide a greener and low-cost renewable fuel. Biodiesel (FAME) produced by methanolysis of soybean and waste frying oils over a heterogeneous calcium-based catalyst was purified by dry washing, using commercial silica sorbent (Sipernat 22 from Evonik). ATR-FTIR spectra of post-purification sorbents showed that silica was effective to remove unreacted oil species, glycerin and Ca soap from biodiesel and, contrary to the previously reported in the literature, it was also able to remove leached calcium from the biodiesel. For both feedsotcks, the highest purity was reached for the sorption test carried out at 45 ℃ during 60 min. Sorbent regeneration was evaluated using acetone, methanol, and isopropanol alcohols at room temperature during short contact time (5 min for 1 g of sorbent and 20 mL of solvent). All the tested solvents were effective to remove the adsorbed species from silica surface. [ABSTRACT FROM AUTHOR]

The current research proposed the work on the consumption of waste cooking oil (WCO) as a valuable resource for the production of biodiesel. This study focuses on maximizing output yield by employing composite heterogeneous catalysts, namely calcinated calcium oxide with aluminum oxide (CaO/Al2O3) and calcium oxide with titanium oxide (CaO/TiO2). The calcination process was adopted for the catalysts at 600°C for 5 h to improve catalytic activities and to increase surface area. XRD and TGA were implemented to analyze the crystal structure and thermal stability of these heterogeneous catalysts. Experimentation was planned by implementing the response surface methodology (RSM) approach in combination with the BoxBehnken design. The optimum yield of fatty acid methyl esters (FAMEs) was experimentally observed at 96.56%, using CaO/Al2O3 at methanol to oil (m/o) molar ratio of 11.9:1, 3.19% catalyst loading, 53.79°C and 76.86 minutes (min). The maximum experimental yield with CaO/TiO2 was observed at 98.15% with the optimized operating conditions of independent process variables viz. m/o molar ratio 11:99, 2.53 wt.% catalyst loading and 68.14 min at 59.79°C. The research recommends the potential use of WCO and both the heterogeneous catalysts for optimal biodiesel yield; however, CaO/TiO2 exhibits superior performance over CaO/Al2O3, which is also confirmed by the XRD and TGA results. [ABSTRACT FROM AUTHOR]

The catalytic transesterification of vegetable oil over heterogeneous catalysts is an effective approach for biodiesel production. To elucidate the role of MgO in catalyzing this reaction, several CaO-MgO catalysts with various Mg/Ca ratios were synthesized by co-precipitation. The catalysts were characterized by BET, XRD, SEM, HRTEM, FTIR, TGA, CO2-TPD, O2-TPO, and in situ DRIFTS. The catalytic performance in the transesterification of soybean oil with methanol was evaluated in a stirred batch reactor. The results indicated that the synthesized pure MgO had weak basic sites and poor pore structure, showing the lowest activity. The added Mg in the CaO-MgO composites was present in both doped and supported forms. The doped Mg reduced the lattice spacing of CaO, improved the intensity and number of basic sites, and enhanced the activity of catalysts, while the supported Mg hindered the diffusion of reactants to the basic sites. The amount of the doped Mg showed a maximum value due to the solubility nature of CaCO3 and MgCO3. 1Mg3Ca (Mg/Ca=1/3) exhibited the highest activity with a biodiesel yield of 92.28% at 60 °C for 2 h. CaO is sensitive to water and CO2, forming hydroxides and carbonates. The supported MgO with a low porous structure well protected the basic sites from contamination. High-temperature treatment is an effective method to remove the contaminates and the removal temperature increases in the order of H2O < Mg(OH)2 < Ca(OH)2 < CaCO3. [ABSTRACT FROM AUTHOR]

Heterogeneous basic catalysts, namely calcium oxide, are referred to as promising catalysts for biodiesel (FAME, fatty acid methyl esters) production since they can be easily separated from the reaction medium allowing them to operate in a continuous mode. Despite the relatively high catalytic activity of calcium catalysts, they present slower alcoholysis rates than homogeneous conventional catalysts (sodium or potassium methanoate). In order to improve the catalytic activity, CaO-based catalysts, modified with alkali elements (Li, Cs, Sr, and Mg) were prepared. Dopant element contents of 10% and 30%, as weight basis (5–50% molar), were introduced by wet impregnation using aqueous solutions of nitrate salts. The effect of calcination temperature (575°C and 800°C) on both activity and stability was studied. All the prepared catalysts, raw and alkali modified, showed pKa<15.0 when characterized by Hammett indicators in methanolic solution. Such basicity is characteristic of Ca hydroxide, thus indicating that the catalysts surfaces were covered with Ca-OH species. FAME yield, in soybean oil methanolysis, higher than 96% was obtained for the first batch reaction for all the tested catalysts showing that alkali dopants have an almost nihil effect on the catalysts performances. The deactivation tests performed with catalysts without intermediate reactivation showed that calcination temperature plays a major role in stability as it enhances the formation of calcium diglyceroxide. The presence of Ca hydroxide in fresh catalysts appears to be responsible for fast deactivation. The dopant elements prompt the catalysts deactivation. Catalysts calcined at higher temperatures showed slower deactivation, which can be due to the formation of larger particles, thus reducing the contact with the formed glycerin. Alkali dopants enhanced the CaO sintering for the highest calcination temperature. Calcium diglyceroxide formed during the reaction is responsible for deactivating the catalyst, due to leaching, and such effect is prompted by alkali dopants. [ABSTRACT FROM AUTHOR]

Different catalysts containing CaO particles dispersed in commercial activated carbon were prepared by wet impregnation followed by heat treatments. The catalytic efficiency of the prepared materials was investigated by evaluating their performance in biodiesel production by the transesterification reaction of soybean oil with methanol. The catalysts were prepared by three different routes; the first two routes involved the use of co-precipitation, with Ca(NO 3) 2 ·4H 2 O as the source of calcium and either NaOH (route 1) or NH 4 OH (route 2) as the precipitating agent, which were mixed with the activated carbon in aqueous suspension; in the third method (route 3), NaOH and CaO were directly mixed with the activated carbon in aqueous suspension. In all cases, the as-prepared materials were heat-treated at 800 °C for 3 h under argon flow. The best catalytic efficiency was achieved for the Na,Ca-based catalyst prepared by route 3, which was mainly composed of a mixture of CaO and Na 2 CO 3 crystals dispersed in the porous carbon network. Catalytic recycling tests were also performed to evaluate the possibility of catalyst reuse, which revealed a drop in efficiency after 3 cycles; however the reused catalysts still showed significant activity, attributed to the permanence of Na+ ions within the porous carbon structure. Analysis of the Ca and Na contents in biodiesel samples synthesized in the three reaction cycles revealed low concentrations of metals; in the case of Ca, the concentration leached into the biodiesel after the 3rd cycle was 9 times lower than that of a biodiesel sample synthesized using pure CaO. The results obtained showed that the chosen methodology is a promising route for the development of heterogeneous carbon-supported Na,Ca-based catalysts with considerable surface area and good catalytic efficiency in the transesterification reaction for biodiesel production. Image 1 • Carbon-supported Na,Ca-based catalysts with high surface areas were prepared. • Different preparation routes followed by heat treatments were investigated. • The catalysts were tested in biodiesel production from soybean oil. • The best efficiency was achieved for the catalyst containing Na and Ca species. • Reused catalysts still showed good activity due to the permanence of Na+ ions. [ABSTRACT FROM AUTHOR]

The dwindling of global petroleum deposits and worsening environmental issues have triggered researchers to find an alternative energy such as biodiesel. Biodiesel can be produced via transesterification of vegetable oil or animal fat with alcohol in the presence of a catalyst. A heterogeneous catalyst at an economical price has been studied widely for biodiesel production. It was noted that various types of natural waste shell are a potential calcium resource for generation of bio-based CaO, with comparable chemical characteristics, that greatly enhance the transesterification activity. However, CaO catalyzed transesterification is limited in its stability and studies have shown deterioration of catalytic reactivity when the catalyst is reused for several cycles. For this reason, different approaches are reviewed in the present study, which focuses on modification of waste-shell derived CaO based catalyst with the aim of better transesterification reactivity and high reusability of the catalyst for biodiesel production. The catalyst stability and leaching profile of the modified waste shell derived CaO is discussed. In addition, a critical discussion of the structure, composition of the waste shell, mechanism of CaO catalyzed reaction, recent progress in biodiesel reactor systems and challenges in the industrial sector are also included in this review. [ABSTRACT FROM AUTHOR]