Carboxylic acids to butyl esters over dealuminated–realuminated beta zeolites for removing organic acids from bio-oils

Abstract

This article describes a novel method to dealuminate and realuminate H-beta zeolites as catalysts for removing organic acids from bio-oils via their esterification reactions with alcohols. Modified H-beta zeolites were prepared by leaching with solutions of oxalic acid, DL-malic acid, and DL-tartaric acid that have different numbers of hydroxyl groups. The results showed that, while all three organic acids can dealuminate the parent H-beta zeolite, with Al(VI) a atoms and Al(IV) c ones being preferentially removed, they show quite different realumination abilities, with tartaric acid with two hydroxyl groups having the highest realumination ability. The concomitance of dealumination and realumination and their dependence on the hydroxyl group numbers of the organic acids provide the possibility of finely tuning the Al and acidity distributions of the resulting zeolites. Among the three acid treated H-beta zeolites, the one obtained from malic acid leaching exhibited the best performance in catalyzing the esterification reaction between acetic acid and sec-butyl alcohol, attributed to its suitable quantity and density of medium and strong Brönsted acid sites and enhanced aluminum gradient. The catalytic results obtained in a fixed-bed microreactor revealed that the malic acid leached H-beta exhibited dramatically enhanced catalytic performance compared to the commercial ion-exchange resin Amberlyst® 15, demonstrating great potential for industrial application.

Comparative Study on the Catalytic Performance of a 13X Zeolite and its Dealuminated Derivative for Biodiesel Production

“…Improvement in the conversion of oleic acid was observed when the modified 13X zeolite was employed, exhibiting a conversion of 73%, the highest conversion achieved in this study (Figure 4 (b)). These results show that zeolites provide better conversions for esterification reactions when they are dealuminated with citric acid [37]. An increased conversion of oleic acid with the modified zeolite could be ascribed to several factors.…”

State of the Art and Perspectives of Hierarchical Zeolites: Practical Overview of Synthesis Methods and Use in Catalysis

“…This was done by several research groups. [335][336][337] Starting with Kowalska-Kuś et al, this group performed an acid treatment with citric acid, which was preceded by an alkaline treatment using a NaOH solution. The outcome was a hierarchical beta zeolite with superior catalytic performance.…”

“…This result was attributed to the quantity and density of medium and strong Brønsted acid sites, and to the enhanced aluminum gradient. [ 336 ] Regarding the realumination, the same research group published a study in which solid AlF 3 was used as realumination agent. [ 337 ] Herein, the structure, texture property, and acidity of the final hierarchical beta zeolite can be adjusted by changing the used amount of AlF 3 .…”

Beneficial use of ultrasound irradiation in synthesis of beta–clinoptilolite composite used in heavy oil upgrading process

“…Peaks at 522 cm À1 and 574 cm À1 are due to the presence of ve-six membered rings and peak around 1087 cm À1 is related to asymmetric O-T-O stretching vibration which is related to Si/Al ratio of the framework. 65 Based on the literature the bands located in 1300-1700 cm À1 region are assigned to unsaturated carbonaceous components deposited on the catalyst. 43,66 Peaks around 1600 cm À1 observed in all the samples, are attributed to the stretching vibrations of C]C band in the aromatic rings.…”