CONTINUOUS PROCESS FOR PREPARATION OF UREA-FORMALDEHYDE CONCENTRATE Russian patent published in 2005 - IPC

FIELD: polymer production.

SUBSTANCE: in a continuous process, formaldehyde is chemically sorbed between by 45-65% aqueous urea solution in neutral or alkaline medium (pH 6.5-9.0) created by contact gases from the process of catalytic dehydrogenation of methanol to form urea-formaldehyde preconcentrate and aqueous condensate. Before chemisorption stage, contact gases are preliminarily routed to absorption stage, wherein part of formaldehyde is isolated in the form of concentrates formalin. The latter is mixed with preconcentrate obtained in the chemisorption stage at formaldehyde-to-urea molar ratio (4.5-5.2):1. Aqueous condensate is divided into process streams, one of them being used for preparation of urea solution and the other for diluting initial methanol supplied into catalytic dehydrogenation stage, whereas the rest of aqueous condensate is mixed with part of concentrated formalin to form process formalin.

EFFECT: increased stability of concentrate on storage during at least 6 months (lack of reaction product precipitates) and achieved chemical stability of formaldehyde concentrate.

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