Enhanced Catalyst Activity of WO₃ Using Polypyrrole as Support for Acidic Esterification of Glycerol with Acetic Acid

Abstract

A series of polypyrrole supported WO3were fabricated and characterized by FT-IR, XRD, XPS, BET, TGA, and FESEM-EDX. The activity of the catalysts was tested in glycerol esterification with acetic acid, and it found that WO3-Ppy-20 (nanocomposite with 20% WO3loaded) showed the maximum catalyst activity with 98% and selectivity of 70% to triacetin at 110°C with a reaction duration of 10 h and also recorded the highest selectivity (75%) for acetylation of glycerol to monoacetin with about 59% conversion only. The highest acidity of WO3-Ppy-20 is also confirmed using TPD-NH3analysis. The activity and selectivity to triacetin of the catalyst were enhanced by increasing WO3loading amount, resulting in 82% conversion for WO3-Ppy-5 with about 32 and 50% selectivity to monoacetin and diacetin and about 18% selectivity to triacetin; in case of WO3-Ppy-20, these amounts were changed to 5, 25, and 70% selectivity to monoacetin, diacetin, and triacetin, respectively with the conversion of 98%. TPD-NH3analysis found that polypyrrole supported WO3increases the catalyst acidity of WO3. BET and FESEM analyses revealed that WO3particles were well dispersed with the smallest average size in nanocomposite compared to pure WO3, which could contribute to the high activity of WO3-Ppy catalyst for esterification of glycerol.

Review on recent progress in catalytic carboxylation and acetylation of glycerol as a byproduct of biodiesel production

“…Therefore, TAG selectivity in glycerol esterification with acetic acid is temperature dependent because only 7% of TAG was produced at temperatures below 90°C compared with 55% selectivity at 110°C. Similarly, Mufrodi et al [107] reported that increase in reaction temperature from 50°C to 110°C increased glycerol conversion from 58.8% to 98% and TAG selectivity from 5% to 70%; however, MAG selectivity decreased from 75% to 10% by using heterogeneous tungstic oxide catalyst WO 3 supported on polypyrrole (polymer material). The optimum temperature should be selected based on the material used for catalyst synthesis.…”

“…Ghoreishi et al [107] reported a linear relationship between the increase in time and glycerol conversion rate in a 10-h reaction; they observed 70% TAG selectivity within 10 h and a corresponding reduction in MAG formation. Consequently, DAG selectivity increased from 25% to 50% within 6 h of reaction and then decreased.…”

“…Similarly, the influence of catalyst loading from 0.1 g to 0.4 g was investigated using the silicotungtic acid catalyst supported on zirconia and showed that a slight increase in catalyst loading from 0.1 g to 0.2 g slightly increased glycerol conversion from 97.7% to 100%; further increase in catalyst loading up to 0.3 g promoted higher selectivity of DAG and TAG, although catalyst loading over 0.3 g showed no significant effect on selectivity or conversion [29]. Ghoreishi et al [107] investigated the influence of catalyst loading by using polypyrrole-supported WO 3 under catalyst loading from 0.1 g to 0.5 g while all other reaction conditions constant (temperature of 110°C, molar ratio of acetic acid: glycerol¼6, and reaction time of 10 h); the results showed that the selectivity of MAG decreased from 45% to 5%, whereas that of TAG increased from 15% to 70% with a slight increase in glycerol conversion. The slight increase in glycerol conversion reported by Zhu et al [29] and Ghoreishi et al [107] suggests that the conversion during acetylation is not largely dependent on catalyst; hence, MAG production can equally proceed without a catalyst.…”

“…Ghoreishi et al [107] investigated the influence of catalyst loading by using polypyrrole-supported WO 3 under catalyst loading from 0.1 g to 0.5 g while all other reaction conditions constant (temperature of 110°C, molar ratio of acetic acid: glycerol¼6, and reaction time of 10 h); the results showed that the selectivity of MAG decreased from 45% to 5%, whereas that of TAG increased from 15% to 70% with a slight increase in glycerol conversion. The slight increase in glycerol conversion reported by Zhu et al [29] and Ghoreishi et al [107] suggests that the conversion during acetylation is not largely dependent on catalyst; hence, MAG production can equally proceed without a catalyst. This finding was supported by a blank experiment without catalyst performed by Zhou et al [46]; in this study, 73.5% glycerol and 84.7% MAG were obtained.…”

Polyaniline-Titanium dioxide composite as humidity sensor at room temperature

“…Thus, reliable fabrication of devices using these materials by cost effective methods is a major concern of many researchers. One such method is the incorporation of metal/metal oxides into the conducting polymers via a chemical or electrochemical route [6][7][8][9][10][11][12].…”