PROCESS FOR THE PRODUCTION OF AQUEOUS UREA/FORMALDEHYDE SOLUTION OF HIGH FORMALDEHYDE CONCENTRATION

摘要

1421263 Formaldehyde BADISCHE ANILIN- & SODA-FABRIK AG 17 May 1973 [18 May 1972] 23479/73 Heading C2 An aqueous urea/formaldehyde solution havng a concentration of free and combined formaldehyde of more than 42% by weight is obtained by oxidative dehydrogenation of methanol with air in the presence of a silver catalyst followed by absorption of the formaldehyde formed in an aqueous solution of formaldehyde and urea and/or a urea/formaldehyde precondensate at a pH of less than 7, at least part of the solution obtained being treated with air which is then used for the dehydrogenation. In a preferred embodiment, the product stream is first passed through a plurality of absorbers containing urea-formaldehyde precondensates passing through the successive absorbers in the opposite sense to the product stream, and then through an absorber containing aqueous urea, the bottoms from which is mixed with some of the bottoms from the first absorber and mixed with acid to form the precondensates which are fed to the penultimate absorber. The air stream is passed through bottoms from the first absorber to concentrate the solution to give the required product.