Process for the preparation of pyridine and substituted pyridines

Process for preparation of compounds of the following general formula (I):

• ##STR5## in which the radicals R.sub.1, which are identical or different, represent a hydrogen atom or a linear or branched alkyl radical having 1 to 4 carbon atoms, by heating, in the vapor phase, at a temperature of 200.degree. C. to 500.degree. C.:
• a compound of the following general formula (II):
• ##STR6##
• in which the radicals R.sub.1 have the same meanings as above or 1. 5-diaminopentane, or
• 1,5-diaminopentane containing, in its hydrocarbon part, from 1 to 3 linear or branched alkyl radicals having from 1 to 4 carbon atoms, or
• a compound of the following general formula (III):
• ##STR7## in which the radicals R.sub.1 have the meanings indicated above, or a mixture of several of the above compounds, the said process being characterized in that the reaction is carried out in the presence of a catalyst comprising palladium, platinum or ruthenium deposited on a macroporous solid support of which the average pore diameter is more than 200 Angstroms and of which the porous volume is between 0.5 and 1.4 cubic centimeters/gram.