Metal hydrated-salts as efficient and reusable catalysts for pre-treating waste cooking oils and animal fats for an effective production of biodiesel

Luigi di Bitonto and Carlo Pastore

Renewable Energy, 2019, vol. 143, issue C, 1193-1200

Abstract: A very efficient chemical pre-treatment method that uses cheap and safe hydrated-salts as catalysts for the conversion of waste cooking oils and animal fats having a high Free Fatty Acids (FFAs) content into an oily feedstock convertible into biodiesel through a conventional route (basic catalysis) was investigated. These hydrated-salts allow FFAs to be efficiently (>99%) esterified with alcohols under very mild conditions (343 K, 2 h). At the end of this treatment, a very convenient separation of products was verified. Two different phases were eventually obtained: an upper alcoholic phase, which contains most of the unreacted alcohol, water obtained by direct-esterification (>95%), and the salt that was used as catalyst (recovery >99%); and a lower oily-phase mainly composed of glycerides, methyl-esters derived from direct-esterification of FFAs (residual acidity of about 0.8 mg KOH/g), and part of unreacted alcohol (7–10%wt). Such a separation was convenient because the oily-phase could be directly trans-esterified through conventional base-catalysis, without any further pre-treatments, thus avoiding production of salty-waste. Also, the alcoholic phase could be recovered and directly re-used for new pre-treatments cycles of fresh waste-oils. A final scheme of the proposed process was discussed and the relevant advantages with respect to conventional routes were highlighted.

Keywords: Esterification process; Free fatty acids; Oils pre-treatment; Biodiesel production; Green technology; Waste oil/grease valorization (search for similar items in EconPapers)
Date: 2019
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Citations: View citations in EconPapers (6)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:renene:v:143:y:2019:i:c:p:1193-1200

DOI: 10.1016/j.renene.2019.05.100

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