| 摘要 |
In a process for the concentration of an aqueous formaldehyde solution by pressure distillation the water product discharged from the sump of the distillation column to sewerage is kept practically free from formaldehyde. The process involves bringing water to boil under a pressure of preferably 2 to 6 atmospheres in the sump, and then continually introducing the aqueous solution into the distillation column at between one quarters and four fifths of the way up the column, the solution being distilled off under this pressure at the head of the column and the vapours condensed, and the water product substantially free of formaldehyde being discharged from the sump, the water product containing a maximum of 0.2% by weight of formaldehyde. The concentration of the head product is increased by raising the reflux proportion. The basic aqueous solution introduced may include further constituents, such as methanol, formic acid, and methyl formate. |
