Mineral oil regeneration using selective molecular sieves as sorbents
Résumé
Microporous molecular sieves are investigated as effective, environmentally safe and cost effective materials for purification of lubricants in late stages of oxidation and also as an alternative to traditional antioxidant additives. Molecular sieve crystals with LTL- and BEA-type structures with variable morphology and silica content are used to trap oxidation by-products. It has been found that the aluminum content and the type of charge balancing cations in the molecular sieves play an important role on the amount of organic adsorbed due to a higher affinity of strong Bronsted acid sites and surface cations to hydrocarbons and carbonyl moieties. High selectivity of the molecular sieves towards oxidation products was achieved without influencing additive compounds in the oxidized oil, and thus results in high degrees in oil purification Lip to 90% depending on the oil formulation. The influence of treatment factors such as temperature, treatment time, solid content and type of oil were investigated. The sorption properties of two different molecular sieves capable of removing selectively the oxidation products, and thus effectively leading to purification in the early and late stages of oxidation, but also to slow down the oxidation process of oils are demonstrated. The considered molecular sieve materials are environmentally safe, cost effective, and due to their high thermal stability are adequate for recovery and multi-cycle reuse. (C) 2009 Elsevier Ltd. All rights reserved.