PROCESS FOR THE PREPARATION OF ISOPRENE FROM ISOBUTENE AND FORMALDEHYDE

摘要

Process for the production of isoprene, by reaction of isobutene with formaldehyde in aqueous solution in the presence of an acid catalyst to form 4,4-dimethyl-m-dioxane, and by cleavage of the latter in the presence of a second catalyst system at a temperature elevated, characterized in that in a first step isobutene is reacted, respectively a mixture of hydrocarbons of 4 carbon atoms containing isobutene, with an aqueous solution of formaldehyde in the molar ratio of 1: 1-2 in the presence of 0.01 to 1.5% by weight of ortho-phosphoric acid, calculated on the amount of aqueous formaldehyde, within the temperature range of 90 to 180º c; the reaction mixture formed is separated into an organic phase containing 4,4-dimethyl-m-dioxane and an aqueous phase and the aqueous phase is evaporated for the separation of the phosphoric acid and the by-products therein dissolved; subsequently, the 4,4-dimethyl-m-dioxane formed together with the phosphoric acid-containing by-products obtained in the evaporation of the aqueous phase is introduced in a liquid state in a fluidized bed reactor operating at 200-400ºC and returned to the first reaction stage the formaldehyde solution formed in the cleavage and containing phosphoric acid. (Machine-translation by Google Translate, not legally binding)