Recovery and Purification of Crude Glycerol from Vegetable Oil Transesterification

Abstract

This article reviews the purification techniques involved in producing high-purity glycerol in the biodiesel industry. Utilisation of glycerol byproducts (contains less than 50 wt% of glycerol and the remaining contents are water, salts, unreacted alcohol and catalyst) in biodiesel production affords greener and less costly processes. Research has focussed on several purification steps that are capable of producing high-purity glycerol. Various new techniques for purifying glycerol promise better quality and lower cost and technologies are required to fulfil increasing worldwide demand. Neutralisation, ultrafiltration, the use of ion exchange resins, vacuum distillation and other methods have been utilised in single or multiple stages. Recent studies have demonstrated that the combination of more than one technique produces high-purity glycerol (>99.2%). Purifications cost can be as low as 0.149 USD$/kg. For many applications, high-purity glycerol is more useful. In some cases, it is even necessary, particularly in the fields of hydrogen production, methanol production, pharmaceuticals and food additives.

Understanding the glycerol market

“…Purifying high boiling point glycerol via distillation, however, is much more expensive. Hence, perhaps not surprisingly, a number of bioglycerol leakages from biodiesel plant were soon reported, such as in the case of the Alabama Black Warrior river contaminated in 2007 [16].…”

Solvent‐Aided Crystallization for Biodiesel Purification

“…In Malaysia, few companies such as Malaysian Palm Oil Board, Golden Hope Plantation Sdn Bhd, and Emery Oleochemicals applied transesterification reactions for biodiesel production . However, biodiesel produced through the transesterification process is unsuitable to be used immediately in diesel engines since impurities are formed during the process, which could damage engines.…”

Transesterification of Low FFA Waste Vegetable Oil using Homogeneous Base Catalyst for Biodiesel Production: Optimization, Kinetics and Product Stability

“…The resulting products are then further processed (after using gravity separation). Distillation is applied for both ester layer and glycerol layer to recover unreacted methanol [24,25]. Washing with water is performed to clean biodiesel from impurities such as soap and catalyst traces [26].…”