Sustainable Bio-Oil Production from Sugarcane Bagasse: Modified Natural Clinoptilolite as a High-Performance, Low-Cost Alternative to ZSM-5 Zeolite

Abstract

In Colombia, annual sugarcane bagasse (SCB) generation reaches 10.86 Mt, and the residue has a higher heating value (HHV) of approximately 13.0 MJ kg−1. This study evaluated SCB catalytic pyrolysis using natural clinoptilolite (CLI) modified by sulfuric acid (CLI-SA), phosphoric acid (CLI-PA), or ammonium chloride exchange (CLI-AC), with commercial ZSM-5 as a benchmark. A mild 2 vol.% H2O2 treatment was applied for 12 h at 25 °C primarily for biological stabilization and as a gentle oxidative wash; no quantitative delignification is claimed. Pyrolysis was conducted at 475 °C for 5 min under N2 (60 mL min−1) with 5 wt.% catalyst. CLI-PA achieved the highest bio-oil yield (65.1%) and estimated HHV (20.5 MJ kg−1), compared with 46.5% and 16.8 MJ kg−1 for ZSM-5 and approximately 16.4 MJ kg−1 for the thermal liquid. Targeted GC-MS/SIM profiles, interpreted semi-quantitatively, showed a toluene-normalized area of 28.989% for CLI-PA versus 7.287% for thermal pyrolysis; oxygenated products nevertheless remained substantial. A cradle-to-gate screening LCA (1 kg catalyst, OpenLCA/CML Baseline) showed ZSM-5/CLI-PA ratios of 6.00–6.50 across nine impact categories (mean 6.19), while the estimated catalyst-related cost was 42.95-fold higher for ZSM-5. These findings identify CLI-PA as a promising low-cost catalyst under the tested conditions, while catalyst structure, acid-site distribution, reuse, gas-phase products, and effluent treatment remain priorities for further validation.