The effect of methanol additive on n-decane cracking and coking over TiN coating

Investigation on cracking and coking of hydrocarbon fuel is of great significance to regenerative cooling technology. In this work, the cracking and coking experiments of pure methanol and n-decane/methanol mixture were carried out in TiN coated tube and blank 304 stainless steel tube, respectively. The purpose is to explore the effect of TiN coating on methanol cracking, and the inhibition effect of methanol on n-decane coking. The gas and liquid phase products were analyzed by gas chromatography. The coke characteristics were analyzed by SEM, EDS and carbon burn-off techniques. The results show that the active sites on the surface of the metal tube will catalyze methanol cracking and coking, and the coking phenomenon is very serious. However, the TiN coating can effectively inhibit the carbon deposition during methanol cracking and ensure methanol cracking in high temperature channels. In the blended cracking experiment of n-decane and methanol in coated tube, methanol can inhibit the cracking and coking of n-decane, and will not reduce the heat sink. When the amount of methanol added is 5 wt%, the inhibition effect on coking is the best. When the outlet temperature is 730celcius, the coking inhibition rate is 63.40%. Methanol as a hydrogen donor can inhibit the chain transfer and the formation of coking precursor of the n-decane cracking process, thereby achieve the effect of inhibiting coking.