Search Results (3)

In this work, a dense and acid-resistant beta zeolite membrane was applied to improve the esterification of citric acid and n-butanol, for the first time. Through the continuous removal of the by-product water via pervaporation (PV), the conversion of citric acid was significantly enhanced from 71.7% to 99.2% using p-Toluenesulfonic acid (PTSA) as catalyst. PTSA was a well-known strong acid, and the membrane kept almost no change after PV-esterification, indicating the superior acid resistance of beta zeolite membrane. Compared to the use of acid-resistant MOR zeolite membrane by PV-esterification, a consistently higher conversion of citric acid was obtained using a high-flux beta zeolite membrane. The results showed that high water permeation on the beta zeolite membrane, with good acid resistance, had a strong promoting effect on esterification, leading to an improved conversion. In addition, the citric acid conversion of 97.7% could still be achieved by PV-esterification at a low reaction temperature of 388 K. Full article

This research aims at developing an efficient and reusable catalyst to improve biodiesel production processes. To achieve this, a vanadium-substituted polyoxometalate (POM) acid, namely H₆PV₃MoW₈O₄₀, was firstly prepared, and then the heterogenzation of the homogeneous Keggin-type heteropoly acids was performed by the partial proton substitution by monovalent large cesium cations with the formation of solid Cs₂H₄PV₃MoW₈O₄₀ catalysts. Several techniques, such as X-ray diffractometer, Fourier transform infrared, coupled plasma–atomic emission spectrometry, Diffuse reflectance ultraviolet–visible spectrum, thermal gravimetric analysis and N₂ adsorption–desorption techniques, were employed to characterize the as-prepared solid catalyst. The solid acid catalyst had the capacity to catalyze both the transesterification of soybean oil and esterification of free fatty acids (FFAs) simultaneously, providing an efficient production process for the production of biodiesel from low-quality oils. Under the operational conditions of a methanol/oil molar ratio of 30:1, a catalyst dosage of 5 wt.%, a reaction temperature of 140 °C, and a reaction duration of 8 h, an oil conversion of 92.2% was attained with the total FFA transformation to biodiesel. Furthermore, the catalyst could be reutilized for several cycles with no significant drop in its activity, thus having great potential for application with a bright perspective in the production of biodiesel, especially from low-quality oil feedstocks. Full article

Aspirin eugenol ester (AEE) is a novel compound that is formed from the esterification of aspirin (acetylsalicylic acid (ASA)) and eugenol. This study aimed to investigate the effects of AEE on blood stasis in rats and to characterize the underlying mechanisms using a plasma metabolomic study. The results indicate that AEE and ASA could modulate whole blood viscosity (WBV), plasma viscosity (PV), blood coagulation parameters, platelet count, platelet aggregation, lactate dehydrogenase (LDH), creatinine (CR) and the levels of thromboxane A2 (TXA₂) and 6-keto prostaglandin F1α (6-keto-PGF_1α). The metabolic profiles of the plasma samples from all groups were clearly separated in the score plots. Nineteen potential metabolites were selected and identified, and disordered levels of these metabolites could be regulated by AEE and ASA. Pathway analysis showed that the mechanism of action of AEE on blood stasis might be principally related to the metabolism of amino acid, fatty acid, energy and glycerophospholipid. The above results indicate that AEE protected the rats against blood stasis, and that this effect might have been caused by the anticoagulation activity of AEE and its abilities to maintain a balance between TXA₂ and PGI₂, reduce blood viscosity, inhibit platelet aggregation and normalize the plasma metabolic profile. Full article