The anti-coking effect of TiN and TiC coatings during pyrolysis of hydrocarbon fuel

In order to inhibit the metal catalytic coking, the TiN and TiC coatings were made on the inner surface of stainless steel 304 tubes by chemical vapor deposition (CVD) method. The coatings were characterized by means of scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), metalloscopy and thermal shock. The results show that the thickness of TiN and TiC coatings is about 7.24 μm and 11.52 μm, respectively. And the two kinds of coatings are uniform and dense, which have a good adhesive strength. To evaluate the anti-coking effect of TiN and TiC coatings, the supercritical cracking of hydrocarbon fuel (A) was employed in the temperature programmed mode and the experiment was terminated when the pressure drop of reaction tube is more than 1 MPa. The results show that the experiment with the 304 blank tube is terminated in 180 s at the reaction temperature of 650 ℃, while the experiments with the TiN and TiC coated tubes are terminated in 275 s and 1 560 s only at 780 ℃, respectively. At the same time, the anti-coking effect of the coatings is evaluated by analyzing the pressure drop, gas composition and morphology of coke. It is indicated that the two kinds of coatings could inhibit coking effectively, and TiN is better than TiC.