| 摘要 |
1,163,428. Preparation of pentaerythritol and/or dipentaerythritol. VYSKUMNY USTAV PRE PETROCHEMIU. 21 Oct., 1966 [19 Nov., 1965], No. 47211/66. Heading C2C. Preparation of pentaerythritol and/or dipentaerythritol by condensing acetaldehyde with a surplus amount of formaldehyde in the presence of a condensing agent, at a temperature up to 70‹ C., optionally in the presence of a substance which retards secondary reactions, wherein a potentiometrio means is used to determine the course of the reaction so that the neutralization is carried out in an interval of from 25 millivolts before reaching the potential reversing point to 10 millivolts after the potential reversing point has been reached, the said point being determined by the two electrodes of the said means, at least one of the said electrodes being metallic. The reaction is carried out in a conventional manner using the starting materials in the form of aqueous solutions. The condensing agents are preferably hydroxides or carbonates of alkali and alkaline earth metals although compounds of amphoteric elements such as aluminium bound to a strongly basic cation may be used. The preferred neutralizing agents are carbon dioxide or sulphuric acid. The process is described using calcium hydroxide optionally containing sodium hydroxide wherein the potential between calomel and platinum electrodes is followed and the reaction is interrupted by neutralizing with carbon dioxide. |
