an investigation of antioxidant properties of zinc and molybdenum dithiocarbamates in hydrocarbons

The oxidation and degradation of hydrocarbons at high temperature and pressure in the presenceof oxygen is one of the common oil product problems. there are many antioxidants to prevent orinhibit oxidation processes; molybdenum and zinc dithiocarbamates are known as powerfulantioxidants. in this paper, the oxidation inhibition time of cumene has been investigated using zincand molybdenum dithiocarbamate substituted with different alkyl groups as antioxidants andazobisisobutyronitrile (aibn) as the initiator. the best result obtained for molybdenumdibutyldithiocarbamate was about 210 min, while zinc dialkyldithiophosphate (zddp), a well knowncommercial antioxidant, showed an oxidation inhibition time of about 14 min under the sameconditions. it was shown that antioxidancy properties decreased with increasing the chain length ofthe substituted alkyl groups. this can be explained by the fact that alkyl groups participate in theoxidation process and thus increasing the alkyl chain length reduces antioxidancy effect. thesynergism effect of molybdenum dibenzyl dithiocarbamate on zddp was also investigated and theoxidation inhibition time of about 110 min was obtained, which was greater than that of anyindividual antioxidant.