Hydroxyapatite (HAP) was synthesized by sol–
gel method. Different ratios of molybdenum oxide
(1–15 % w/w) supported on HAP were prepared by the
impregnation method and calcined at 400 C in a static air
atmosphere. The catalysts were characterized by thermogravimetry,
differential thermal analysis, X-ray diffraction,
FTIR spectroscopy and nitrogen sorption measurements.
The surface acidity of the catalysts was investigated by the
dehydration of isopropyl alcohol and the adsorption of
pyridine (PY) and 2,6-dimethyl pyridine (DMPY). The
gas–phase oxidation of methanol to formaldehyde was
carried out in a conventional fixed-bed flow type reactor
using N2 as a carrier gas. The obtained results clearly
revealed that HAP–MoO3 systems were active and selective
towards the formation of formaldehyde. The maximum
yield of formaldehyde (97 %) was achieved on the catalyst
containing 5 wt% MoO3/HAP. The generation of Mo6?as
Lewis together with Brønsted acid sites play the main role
in the formation of formaldehyde.