of c 2 was 9 u02dc 19 at a temperature of 650 u00b0 u02dc 700 u00b0 c using the pb substituted hydroxyapatite catalyst ca 9 5 pb 0 5 po 4 6 oh 2 prepared in example 1 the catalytic activity was measured at a lower contact time in the same way as in example 1 table 2 shows the result of using 0 24 g of the catalyst the result was that the methane conversion was 36 u02dc 40 and the yield of c 2 was 20 u02dc 22 at a temperature of 725 u00b0 u02dc 800 u00b0 c although the contact time was lower an activation effect identical to that in example 1 was obtained using the pb substituted hydroxyapatite catalyst ca 9 pb po 4 6 oh 2 prepared in example 1 the reaction experiment was carried out in accordance with an increase in the contact time in the same way as in example 1 table 2 shows the result of using 0 60 g of the catalyst the result was that the methane conversion was 40 u02dc 44 and the yield of c 2 was 21 u02dc 24 at a temperature of 725 u00b0 u02dc 800 u00b0 c compared with example 3 although the conversion was increased the c 2 selectivity was maintained at a similar level resulting in obtaining the c 2 compound at a high yield the activity and stability at high temperature of the catalyst ca 9 pb po 4 6 oh 2 prepared per example 1 and of the conventional pb substituted hydroxyapatite prepared by an ion exchange y matsumura.