Investigation of Structural Change and Basicity of NaY Zeolite upon Loading KF and Their Application in Henry Nitroaldol Reaction Under Microwave Irradiation Condition

Abstract

Potassium salt modified NaY zeolite along with methanol–water mixture as solvent under microwave irradiation offers an environmentally benign way to synthesize β-nitroalcohols rapidly with excellent yield and selectivities. Here, NaY zeolite was modified with 0.5–20 % KF (w/w) by a wet impregnation method and characterized by X-ray diffraction, FT-IR and Hammett base strength measurement methods. It was observed that framework structure preserved even after 20 % loading of KF while crystallinity decreased from lower to higher loading. The obtained materials showed quite different base strengths with varying percentage of the salt over the support and with change of their activation temperatures. The effects of different reaction parameters such as amount of solvents, nature of solvents, microwave power and microwave irradiation time were studied to minimize the reaction time without compromising the yields. Among the loaded catalysts, 10 wt% KF loaded catalyst was found to be the best catalyst and gave 97 % yield within 2 min under optimized reaction conditions. Recovery of the catalysts was tested for three times and it showed similar conversions in each cycle.