Mechanisms of gasoline deposit formation in engine induction systems. Characterization of reaction product between benzothiophene oxides on hot metallic surfaces

To understand the nature and mechanisms of deposit formation in engine induction systems, reactions among benzothiophene oxides were carried out in an induction system deposit (i.s.d.) apparatus at five different temperatures: 100, 150, 200, 250 and 300°C, respectively. Deposits formed on the metallic surface of the apparants were analyzed by mass spectrometry (m.s.) and identification of compounds of interest was carried out by m.s.–m.s. experiments. Compounds at m/z: 234 and 248 Da were detected at 100°C, and were assigned to naphthobenzothiophenes. At higher temperatures new higher molecular weight sulphur aromatic compounds m/z 368, 406, 408, 446, 462, 524, 538, 544, 552, 566, 578, 590, 616 were detected. M.s.–m.s. experiments were carried out on several of these products to elucidate their structure.