New strategy for coking pathway regulation during n-decane cracking with the additives containing hydroxyl groups

Coking during the endothermic hydrocarbon fuel pyrolysis is a key issue that needs to be solved in the development of regenerative cooling technology for high-speed aircrafts. The compounds containing hydroxyl groups are developed to inhibit coking by regulating coking pathway during the thermal cracking of hydrocarbon fuels. Pyrolytic deposition experiments of n-decane with additives were performed using the method of electrical heating. The anti-coking performance of the additives was characterized by means of gas chromatograph-mass spectrometer (GC-MS), scanning electron microscopy (SEM), temperature programmed oxidation (TPO) and Raman spectroscopy. The results showed that the degree of cracking is reduced at low fuel temperature due to the dilution of the additives, and the additives do not affect the fuel cracking as the fuel temperature increased. With the function of additives, the masses of filamentous and amorphous coke were decreased. A possible mechanism for the additives inhibiting coking has been proposed. The additives containing hydroxyl groups can block the initial coking reaction path to inhibit coking at the source. In general, the hydroxyl radicals released by the additives oxidize the coking precursors to prevent its further growth, and react with the substrate to form particulate matters serving as passivation coating, inhibiting the bulk phase coking and metal catalytic coking simultaneously. This work provides significant ideas for inhibiting coking by regulating coking reaction pathways.