TiN、Al_2O_3涂层对燃料裂解结焦的抑制效果研究

Inhibition Effect of TiN and Al_2O_3 Coating on Fuel Pyrolysis Coking

为抑制镍基不锈钢油道本身对吸热型碳氢燃料裂解的金属催化结焦积碳作用,采用化学气相沉积法在Ф3 mmφ0.5 mm,800 mm长的3128型不锈钢基体管道内表面分别沉积了TiN和Al2O3涂层,沉积温度分别为950和1050℃,沉积时间为3 h。通过SEM、EDS和XRD分析了涂层的形貌特征和组织结构。SEM结果表明,CVD法制备的TiN、Al2O3涂层结构均匀致密;EDS结果显示,实验制得的氮化钛涂层的组成为非化学计量比的TiN0.67,氧化铝涂层的Al和O原子比为1:3;XRD结果表明,实验所得到的TiN为立方晶相结构,Al2O3为惰性的α-Al2O3。以二甲苯为原料采用自制的超临界裂解装置对TiN、Al2O3涂层的钝化效果进行了评价。二甲苯超临界裂解实验结果表明,TiN涂层钝化效果不明显,而Al2O3涂层的钝化效果十分显著,达到2倍的钝化效果。

In order to avoid the coke forming in the catalytic cracking process of the endothermic hydrocarbon fuels in the stainless steel oil tube, a TiN coating and a Al2O3 coating were deposited on the inner surface of the stainless steel tube with the diameter of Ф3 mm×0.5 mm and the length of 800 mm by a chemical vapor deposition method. The deposition temperature was 950 and 1050 ℃ for TiN and Al2O3 , respectively, and the deposition time was 3 h. The coatings＇ morphological features and textures were characterized by SEM, EDS and XRD. The results from SEM indicate that both the TiN coating and the Al2O3 coating have uniform structure. According to the observation of EDS, the titanium nitride in the coating is the TIN0.67 stoichiometrically, and AI and O atomic ratio in the alumina coating is 1：3. As shown in the XRD patterns, the TiN in the coating has cubic phase and the Al2O3 is the inert α-Al2O3. By adopting the self-made supercritical cracking device, the passivation effect of the TiN coating and the Al2O3 coating was assessed with the fuel of dimethylbenzene. The results of supercritical cracking experiment reveal that the passivation effect is unconspicuous for the TiN coating, while the Al2O3 coating can effectively inhibit coking, of which the passivation effect is about twice than that in blank tube.