Construction of a Phosphoric Acid-Based Catalytic System for Efficient Conversion of Mevalonolactone to Isoprene

Abstract

Isoprene is an important feedstock for the production of synthetic rubber, pharmaceutical intermediates, and fine chemicals. Developing sustainable routes for isoprene production from biomass-derived feedstocks is therefore of considerable interest. In this study, mevalonolactone (MVL) was used as the substrate, and phosphoric-acid-modified Si/Al solid acids were employed as catalysts. The effects of acid type, acid concentration, reaction temperature, reaction time, catalyst dosage, and Si/Al ratio on the catalytic conversion of MVL were systematically investigated. Pyridine-adsorbed infrared spectroscopy (Py-IR) was further employed to characterize the Brønsted and Lewis acid sites on the catalyst surface. The results showed that the H₃PO₄-modified catalysts exhibited substantially higher isoprene selectivity than the H₂SO₄-modified catalyst. Under the optimized reaction conditions, an MVL conversion of 95.9% and an isoprene selectivity of 62.0% were achieved, exceeding the values reported in related studies. The phosphoric acid-based catalytic system also exhibited good recyclability, with an isoprene yield of 61.0% in the first cycle and yields stabilizing at approximately 40% in subsequent cycles. Mechanistic analysis suggested that appropriate regulation of the surface acidity and the Brønsted/Lewis acid sites played an important role in improving isoprene selectivity. This study provides an experimental basis for the chemical production of isoprene from mevalonolactone.

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