Modified Clinoptilolite Zeolites as Heterogeneous Catalysts for Bio‐oil Upgrading via Esterification of Acetic Acid with n‐butanol

ABSTRACT In this study, natural zeolite‐clinoptilolite was treated with hydrochloric acid (HCl) and sulfuric acid (H 2 SO 4 ) at varying concentrations (0.1, 0.5, and 1.0 M) at a temperature of 80°C for 2 h. The catalytic activity of the acid‐treated clinoptilolite samples was evaluated in the esterification of acetic acid with n‐butanol for bio‐oil upgrading, conducted at 80°C with a 1:1 molar ratio and a catalyst loading of 3 wt.% over a reaction time of 4 h. Following this, the clinoptilolite treated with 0.1 M H 2 SO 4 , which demonstrated the highest catalytic activity (22% conversion) was loaded with tungstophosphoric acid (TPA). TPA loadings on the support zeolite varied from 10% to 40% w/w using the wet impregnation method, and the supported catalysts underwent calcination treatment. The properties of the zeolite samples were analyzed using techniques including X‐ray diffraction (XRD), X‐ray fluorescence (XRF), scanning electron microscopy with energy dispersive X‐ray spectroscopy (SEM‐EDX), nitrogen adsorption/desorption isotherms, and Fourier transform infrared spectroscopy (FTIR). The results indicate that 30 wt.% TPA supported on the clinoptilolite zeolite modified with a 0.1 M H 2 SO 4 solution exhibited the highest catalytic performance, achieving 56% conversion under the specified conditions compared to the other prepared catalysts.