Thermal Decomposition of Methane in Capillary Tubes of Different Materials: Corundum, Titanium, Nickel, and Stainless Steel

The effect of capillary tube material on the process of thermal decomposition of methane at 1100 °C and methane supply at a rate of 2 L/h without the use of catalysts was studied. The materials used were corundum, titanium, nickel, and stainless steel. The reactor was a capillary tube, which was heated from the outside with a propane burner; the length of the heating zone was about 8 cm. It was found that the efficiency of methane decomposition decreases in a number of materials: Al2O3 > Ni > Ti > stainless steel. The highest hydrogen yield (73.35 vol. %) was achieved in the experiment with a corundum tube with an inner diameter of 4 mm, and the lowest (27.75 vol. %) was achieved in the experiment with a stainless steel tube with a diameter of 6 mm. Nickel and titanium showed worse hydrogen yield results than corundum: for nickel, the volume content of hydrogen after pyrolysis was 71.27%, and for titanium, 41.51%.