An aldolisation-dehydration process is disclosed for converting an aldehyde, e.g. n-valeraldehyde, to a substituted acrolein, e.g. propyl butyl acrolein (2-propylhept-2-enal). Aldolisation and dehydration are effected in a stirred tank reactor (16;111) using an alkali catalyst, such as sodium hydroxide. A reaction product stream (23;113) containing both organic and aqueous phases is supplied to an intermediate section of a distillation zone (25;123) which further includes a higher temperature section below the intermediate section and a lower temperature distillation section. Decomposition aldols and "heaving" to regenerate aldehyde or aldehydes occurs in the higher temperature section of the distillation column so that aldehyde or aldehydes are recoverable from the top of the distillation section in a heterogeneous azeotrope containing water and aldehyde. On condensation and phase separation the lower water layer (34;150) can be discharged from the plant without the need for neutralisation. From the bottom of the distillation zone a mixture (36;157) of substituted acrolein and alkali catalyst solution is obtained. The substituted acrolein is recovered as product (45;173), while the catalyst solution (47;175) is recycled to the aldolisation reactor. Part (49;181) of the catalyst solution is purged to control the level of Cannizzaro reaction products.
本发明公开了一种醛化脱
水工艺,用于将醛(如
正戊醛)转化为取代的
丙烯醛(如丙基丁基
丙烯醛(2-丙基庚-2-烯醛))。醛化和脱
水在搅拌罐反应器 (16;111) 中使用碱催化剂(如
氢氧化钠)进行。含有有机相和
水相的反应产物流(23;113)被输送到蒸馏区(25;123)的中间段,该蒸馏区还包括中间段以下的高温段和低温蒸馏段。醛醇分解和 "翻腾 "再生醛或醛的过程发生在蒸馏塔的高温段,因此醛或醛可以从蒸馏段顶部的含
水和醛的异质共沸物中回收。冷凝和相分离后,下部
水层(34;150)无需中和即可排出设备。从蒸馏区底部可以得到取代
丙烯醛和碱催化剂溶液的混合物(36;157)。取代的
丙烯醛作为产品 (45;173) 被回收,而催化剂溶液 (47;175) 则被回收至醛化反应器。部分 (49;181) 催化剂溶液被净化,以控制坎尼扎罗反应产物的含量。