Process for preparing concentrated formaldehyde solutions

Claim 1

CONTINUOUS PROCESS FOR THE DIRECT RECOVERY OF FORMALDEHYDE, IN THE FORM OF A CONCENTRATED AQUEOUS-ALCOHOL SOLUTION, FROM FORMALDEHYDE SYNTHESIS GAS, WHICH PROCESS CONSISTS ESSENTIALLY IN (A) INTORUDCIING A SUPPLY OF FORMALDEHYDE SYNTHESIS GAS INTO A FIRST ABSORPTION STAGE OF AN ABSORPTION SYSTEM, SCRUBBING SAID GAS IN SAID FIRST STAGE WITH A CONTINUOUSLY CIRCULATING COUNTERCURRENT FLOW OF A FIRST LIQUID MIXTURE OF FORMALDEHYDE AND ALCOHOL, AND A MINOR AMOUNT OF WATER, WHEREBY AT LEAST A MAJOR PORTION OF THE FORMALDEHYDE CONTENT OF SAID SYNTHESIS GAS IS ABSORBED IN SAID FIRST LIQUID, (B)THEREAFTER INTRODUCING AT LEAST A PORTION OF THE REMAINDER OF SAID SYNTHESIS GAS FROM WHICH SAID FORMALDEHYDE HAS BEEN REMOVED IN SAID FIRST STAGE INTO A FINAL ABSORPTION STAGE OF SAID ABSORPTION SYSTEM, SCRUBBING SAID PORTION OF SAID SYNTHESIS GAS THEREIN WITH A COUNTERCURRENT-FLOWING SECOND LIQUID, CONTAINING ALCOHOL, WHEREBY SUBSTANTIALLY ALL REMAINING PORTIONS OF THE FORMALDEHYDE CONTENT OF SAID GAS ARE ABSORBED IN SAID SECOND LIQUID, AND (C) INTRODUCING AN ADDED AMOUNT OF ALCOHOL, AND DELIVERING SAID SECOND LIQUID, CONTAINING ABSORBED FORMALDEHYDE FROM SAID FINAL STAGE, TO SAID CIRCULATING FIRST LIQUID MIXTURE OF SAID FIRST ABSORPTION STAGE, WHILE WITHDRAWING PORTIONS OF SAID FIRST LIQUID MIXTURE CIRCULATING IN SAID FIRST ABSORPTION STAGE AS THE DESIRED CONCENTRATED AQUEOUS SOLUTION OF FORMALDEHYDE, AT A RATE AND IN AN AMOUNT SUCH THAT THE SOLUION THUS DISCHARGES REMOVES THE FORMALDEHYDE AND ALCOHOL FROM SAID SYSTEM AT SUBSTANTIALLY THE SAME RATE THE FORMALDEHYDE AND ALCOHOL ARE INTRODUCED THEREINTO, AND WHILE BALANCING THE AMOUNT OF WATER, ALCOHOL AND FORMALDEHYDE SUPPLIED TO THE SYSTEM, SO THAT SAID FIRST AQUEOUS LIQUID MIXTURE CIRCULATING IN SAID FIRST ABSORPTION STAGE IS MAINTAINED AT A COMPOSITION CONTAINING FROM 5% TO 40% BY WEIGHT OF WATER WITH FROM AOUT 0.5 MOLS TO AT MOST ABOUT 5 MOLS OF FORMALDEHYDE PER MOL OF ALCOHOL.