Abstract

Levulinic acid (LA; 4-oxopentanoic acid, C<inf>5</inf>H<inf>8</inf>O<inf>3</inf>) is a useful platform chemical for making diverse other commercial products. This work developed a novel catalytic system for efficient production of LA from oil palm empty fruit bunch (EFB), a widely available lignocellulosic waste. First, the EFB was pretreated with tetrahydrofuran to obtain a cellulose-rich solid substrate that was subsequently converted to LA in a stirred batch reactor using solid acid catalysts. The catalysts were sulfated tin oxide (SO<inf>4</inf>²⁻/SnO<inf>2</inf>) and a newly developed iron-doped variant, sulfated iron–tin oxide (SO<inf>4</inf>²⁻/Fe–SnO<inf>2</inf>). Iron doping significantly increased both the specific surface area (from 145.9 to 168.7 m² g⁻¹) and the number of acid sites. The effects of reaction temperature (180–220 °C), reaction time (1–6 h), and the catalyst loading (0–4 % w w⁻¹) on the yield of LA and the other useful byproducts are reported. The sulfated iron-tin oxide catalyst was more active than the sulfated tin oxide under certain reaction conditions. Notably, it achieved a maximum LA yield of 31.2 % w w⁻¹ based on the pretreated EFB, or 39.9 % w w⁻¹ based on available cellulose, surpassing many metal oxide catalysts reported in the literature. The optimum reaction conditions were 200 °C, 1 h, and a SO<inf>4</inf>²⁻/Fe-SnO<inf>2</inf> catalyst loading of 2 % w w⁻¹. The promising heterogeneous catalytic approach used here for upgrading lignocellulosic waste to higher value chemicals offers environmental and economic benefits.