Sr–Mg Mixed Oxides as Biodiesel Production Catalysts

Abstract

The Sr–Mg basic catalysts were developed for biodiesel production through transesterification of palm oil with methanol. The evidence for synergistic effects between active Sr and Mg species was clearly demonstrated by transesterification tests over a series of Sr–Mg catalysts with varied Sr‐to‐Mg molar ratios. The catalyst properties were characterised by means of temperature‐programmed desorption of CO2 (CO2‐TPD), N2 sorption, XRD, SEM and TEM experiments. The super strong basic site was formed in Sr–Mg catalysts through a partial solid state reaction induced by thermal treatment at 600 °C. The new basic site, together with the original basic site from SrO (average basic site density=757 μmol m−2), effectively catalysed a transesterification reaction at mild conditions. Biodiesel containing 96 % methyl esters was obtained at reaction conditions of 75 min, 60 °C, 0.1 MPa, 3 wt. % catalyst loading and a methanol‐to‐oil ratio of 6:1, and the catalyst exhibited good reusability. Improved surface areas and porosities were also achieved compared to the unsupported SrO. Density functional theory (DFT) calculations of methylpropanoate adsorption on SrO, MgO and Sr/MgO showed that the adsorption energies of all adsorbate–surface complexes corresponded well with the experimental catalytic activity, which increased in the order MgO<SrO<Sr/MgO.

Montmorillonite-supported KF/CaO: a new solid base catalyst for biodiesel production

“…7b, which were 49.47 kJ mol -1 and 2.58 9 10 6 L min -1 mol -1 , respectively. The activation energy was similar to those reported in the literature (54.74 kJ mol -1 [38]; 49.3 kJ mol -1 [52]; 75.94 kJ mol -1 [53]); it was within the range of 33.5-83.7 kJ mol -1 reported by Freedman [54] in transesterification of soybean oil, and hence the rate is truly governed by a chemical step.…”

“…Two desorption peaks between 470-610°C and 610-730°C were observed for Ca/MMT and KCa/MMT-10, the former is due to the interaction of CO 2 with the moderate basic sites [31][32][33]; the latter ascribes to decomposition of the structural carbonate [36,37]. The structural carbonate might be generated during a long time period or impregnation process [37], whereas only one desorption peak between 550 and 700°C was found from that of KCa/MMT-20, 30 and 40, which is attributable to strong basic sites [38]. And a maximum desorption temperature of 650°C was obtained from that of KCa/MMT-30.…”

On the relationship between the basicity of a surface and its ability to catalyze transesterification in liquid and gas phases: the case of MgO

“…1 However, this reaction can also be used through gas or liquid phase processes for the production of other molecules of industrial interest: different kinds of organic carbonates, 2 levulinate by the way of the opening of lactones, 3 some polyesters from polyols and organic carbonates 4 or from lactones. [6][7][8][9] Nevertheless, in most of these publications, the basicity of the catalyst is investigated by means of the desorption of a Lewis acid (CO 2 ) followed by TPD 10,11 or IR spectroscopy. [6][7][8][9] Nevertheless, in most of these publications, the basicity of the catalyst is investigated by means of the desorption of a Lewis acid (CO 2 ) followed by TPD 10,11 or IR spectroscopy.…”

“…Other publications still find a correlation between the reactivity in the transesterification reaction and the Brønsted basicity, measured with the adsorption of methanol followed by IR spectroscopy, 17 with Hammett indicators, 11,18 or probed with DFT modeling. 19 However, Hattori et al have shown that the order of reactivity of various oxides in transesterification catalysis depends on the nature of the alcohol and not only on basicity of the catalyst.…”

Characterization of Dolomite Promoted by NaAlO2 and Application as Catalyst in Transesterification by Response Surface Methodology

“…Besides, biodiesel possesses the similar physicochemical properties with the petroleum diesel and could be used directly without the mechanical modification . Biodiesel, which mainly consists of fatty acids monoalkyl esters, is normally obtained through transesterification of triglycerides, the main components of vegetable oils, animal fats or waste cooking oils (WCOs), with methanol under the catalytic effect . The homogeneous base catalysts of KOH, NaOH and CH 3 ONa are effective but their application in esterification is restricted by the severe equipment corrosion and high recycle cost .…”