The inner surface of chemical process, Incoloy metallic reactor tubes subject to coking in industrial service were coated with a thin layer of ceramic material formed by chemical vapor deposition (CVD). A non-oxygen containing organosilicon precursor was introduced in the vapor phase and mixed with either an inert or reducing carrier gas. These atmospheres were utilized to minimize the formation of oxide ceramics. CVD was carried out at atmospheric pressure at 750-950 deg C. In laboratory scale studies, control of the movement of the maximum deposition zone, within the tube length from inlet to outlet, was developed through adjusting the flow of carrier gas. One silicon compound suitable for the method is hexamethyldisilazane. Coatings made from this precursor were found to be effective in reducing coke by 80 percent under ethane or butane cracking conditions.
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