Disclosed is a method for jointly producing (i) formic acid (III); (ii) a
carboxylic acid comprising at least two carbon atoms (II) and/or the
derivatives thereof; and (iii) a carboxylic acid anhydride (VII).
According to said method, (a) a formic acid ester (I) is transesterfied
to formic acid (III) and the corresponding carboxylic acid ester (IV) by
means of a carboxylic acid comprising at least two carbon atoms (II); (b)
at least one portion of the carboxylic acid ester (IV) formed in step (a)
is carbonylated in order to obtain the carboxylic acid anhydride (V); and
(c) at least one portion of the carboxylic acid anhydride (V) formed in
step (b) is further dehydrated by means of a carboxylic acid (VI) so as
to form a carboxylic acid anhydride (VII) and the carboxylic acid (II).