| abstract |
A catalyst comprising at least one element X selected from Groups 3 to 6 of the periodic table, and at least one element Z selected from Group 14 elements, and an X-ray diffraction spectrum observed using an X-ray diffraction method In the figure, at least one diffraction peak is observed in the low angle range below θ=6°, and the ratio of the peak intensity I of the at least one diffraction peak to the half width H of the diffraction peak, that is, I/H is: 5000 or more. |