Gypsum-derived CaO catalytic pyrolysis of palm oil in a continuously packed bed reactor

Abstract

This study employed a Gypsum-derived CaO catalyst with 10 wt% MgCO3 to convert palm oil into biofuel via pyrolysis in a continuous packed-bed reactor at atmospheric pressure without purge gas. The reaction occurred within the 500–550 °C temperature range, with varying catalyst calcination temperatures. ASTM D86 distillation to separate the pyrolytic oil into biogasoline (75–150 °C), biokerosene (150–250 °C), and biodiesel (250–330 °C) was conducted. The physical and chemical properties of products and catalysts using various techniques were determined. Notably, calcination temperature changes minimally affected the final oxygen content in the product but significantly influenced the textural properties of the catalyst. At a reaction temperature of 525 °C, the 10% MgCO3 catalyst calcined at 850 °C yielded the highest volume of distilled product distilled from pyrolytic oil, accounting for 100% of pyrolytic oil (equivalent to 66.44 vol% of palm oil). It implies that 100% of pyrolytic oil could be converted to distilled oil completely by the distillation process. The primary constituents of the pyrolytic oil were aliphatic and olefinic compounds, with a notable presence of ketones, mainly in the C5 to C33 range. C17 ketones were prominent, constituting approximately 5 wt% of the pyrolytic oil (equivalent to 2.92 wt% of palm oil). These ketones likely resulted from the decarboxylation of carboxylic acids and aldol condensation reactions facilitated by CaO or MgO catalysts. CaO decarboxylation was confirmed by the presence of CaCO3 in the spent catalyst. Additionally, the pyrolytic oil exhibited an acidity of approximately 5.72 mg KOH/g, primarily attributed to phenolic compounds, confirmed through GCxGC-FID, GCxGC-TOFMS, and 1H NMR spectroscopy.