Continuous production of biodiesel from low grade feedstock in presence of Zr-SBA-15: Catalyst performance and resistance against deactivation

•Zr-SBA-15 acid catalyst has been tested in methanolysis of low-grade feedstock.•Influence of several catalyst poisons has been assessed.•Metal cations lead to acid sites neutralization by ion exchange.•Unsaponifiables like phospholipids and retinol interact with catalytic acid sites.•Bentonite acts as poison scavenger lengthening the catalyst life.

Zirconium-containing SBA-15 materials have been used in the production of fatty acid methyl esters from low grade oleaginous feedstock. Its resistance against deactivation has been assessed by means of studying the effect of conventional impurities present in lipid wastes over the catalytic performance of this material. Alkaline metal cations like potassium could interact with Brønsted acid sites, causing their neutralization by ion exchange and a limited, but not complete, deactivation of the material. Additionally, organic unsaponifiable compounds like retinoids or phospholipids – being studied in this work as retinol and lecithin, respectively – strongly interact with the catalyst surface, leading to a strong deactivation of the material, though reversible, since they are fully regenerated by calcination in air. Catalytic assays in continuous mode in a fixed bed reactor suggest a higher resistance of Zr-SBA-15/bentonite pellets against catalyst deactivation. Bentonite clay, which has been used as binding agent for the preparation of the particulate catalyst, seems to be responsible for this behavior, acting as poison scavenger and preventing the access of the impurities to the catalytic acid sites and consequently their deactivation.

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