Alkylation of α-pinene with isobutene/isobutane over Hβ zeolite†

Abstract

α-Pinene and isobutene/isobutane can undergo hybrid alkylation under acid catalysis, resulting in C₁₄ and C₂₀ product fractions with favorable bio-based high-energy-density fuel properties after hydrogenation. In this study, the catalytic performance of zeolite molecular sieves, such as Hβ, HY, HZSM-5, HZSM-35, HSAPO-11, was investigated for the alkylation of α-pinene and Isobut-5 (a mixture of isobutene/isobutane with a mass ratio of 1 : 5) given the acidic sites and specific pore structures with shape-selective abilities of zeolite catalysts. Various characterization techniques, including temperature-programmed desorption of ammonia (NH₃-TPD), Fourier transform infrared spectroscopy with pyridine adsorption (Py-IR), N₂ adsorption/desorption, X-ray fluorescence spectrum (XRF), and particle size analysis, were conducted to analyze the acidic properties, pore characteristics, silica–aluminum ratio, and grain size of the zeolites, and their influence on the alkylation of α-pinene and Isobut-5. Moreover, the recycling performance of the favorite Hβ-25n catalyst and an effective regeneration method were investigated using temperature-programmed oxidation (TPO) analysis. This study provides essential research data for the preparation of α-pinene-based high-energy-density fuels.