Preparation of hydrotalcite-supported potassium carbonate catalyst by microwave for removing acids from crude oil by esterification

Potassium carbonate was supported on hydrotalcite by microwave radiation and used as catalyst to remove acids from crude oil. To better understand the influence of the preparation method on the properties and activity of the catalyst, a series of catalysts with the same K2CO3 content were prepared by impregnation, ultrasonic, microwave radiation and mechanical mixing methods, respectively. Their properties were characterized by XRD, N2 adsorption–desorption and Hammett indicator-benzene carboxylic acid titration. Moreover, their catalytic activity was tested by esterification deacidification reaction between high-acid crude oil and glycol. In addition, the effect of microwave radiation time and the K2CO3 content was also investigated. The presence of carboxyl acid in crude oil and ester in deacidified oil was characterized by FT-IR. It was found that the catalyst with high hydrotalcite crystallinity, well-dispersed K2CO3 and more basic sites shows the best deacidification activity. Among the four methods, microwave radiation can provide adequate energy to disperse K2CO3 species on the surface of hydrotalcite homogeneously and rapidly, and thus can greatly reduce the contacting time of hydrotalcite and basic K2CO3 solution to keep the regular layer structure of hydrotalcite. Furthermore, microwave radiation can produce a high temperature instantaneously, which strengthens the interaction of K+ and hydrotalcite to promote the formation of more basic sites. The catalyst loading 15% K2CO3 and radiated by microwave for 5 minutes showed superior activity, which can increase the deacidification ratio from 89.2% to 97.7% and decrease the acid number of Suizhong high-acid crude oil from 3.72 to 0.08 mgKOH/g at 200°C, at a reaction time of 2 h and at catalyst and glycol mass ratios to crude oil of 1% and 2%, respectively.