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Title: Investigating the generation and reaction of organoaluminiums in marine container refrigeration systems
Author: Slaughter, Jonathan
ISNI:       0000 0004 7968 4985
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2019
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The unexpected presence of chloromethane in marine container refrigeration systems has led to multiple explosions reported around the world. This is thought to occur due to the generation of methylaluminium chlorides, from the reaction of aluminium with chloromethane, which can then react with the refrigeration oil. This work investigated the generation of organoaluminiums and their subsequent reaction with refrigeration oils. Initial work focused on determining the composition of two industrial refrigeration oils. They analysed as a polyolester (POE) and a polyvinyl ether (PVE). To investigate the reaction of these oils with organoaluminiums, reactions were attempted using simple models of the oils, based on esters and ethers. The reaction of monoesters with organoaluminiums resulted in ester cleavage when reacted with TMA, Me2AlCl or Me1.5AlCl1.5. The products of these reactions revealed that the ester had undergone addition of two methyl groups to form organoaluminium alkoxides. In addition, reactions involving Me2AlCl or Me1.5AlCl1.5 both revealed elimination from the dimethylated species above 60 °C, producing alkenes and methane. To further model the POE oil, two tetraesters were synthesised. Reactions of these tetraesters with organoaluminiums revealed similar reactivity to that seen with monoesters, with ester cleavage observed with TMA, Me2AlCl or Me1.5AlCl1.5. This ester cleavage was also demonstrated with the POE refrigeration oil. Reactions between ethers, models for the PVE oil, and organoaluminiums were then attempted. Whilst most ether-organoaluminium combinations revealed only adduct formation, some led to elimination of the ether to give an organoaluminium alkoxide, an alkene and methane. The PVE oil underwent elimination when reacted with Me2AlCl or MeAlCl2 at elevated temperatures. The reaction of the refrigeration oils with in situ formed organoaluminiums was achieved by combining aluminium, chloromethane and the refrigeration oil in a sealed vessel. Both oils revealed decomposition, with similar reactivity to that seen for the model systems. This oil decomposition is clearly a concern when applied to marine container refrigeration systems as the reaction products cannot provide the same lubrication as the refrigeration oil. Also, the production of alkenes and methane is potentially hazardous due to their flammable nature.
Supervisor: Wheatley, Andrew Sponsor: Cambridge Refrigeration Technology ; Maersk
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
Keywords: Organometallic ; Aluminium ; Organoaluminium ; NMR ; Crystallography ; Refrigeration