About half of the product from iron-based high-temperature Fischer–Tropsch synthesis is an aqueous product containing dissolved oxygenates. Volatile oxygenates can be recovered by distillation, but the bulk of the carboxylic acids remain in the water, which is called acid water. Fractional freezing was explored as a process for producing a more concentrated carboxylic acid solution from which the carboxylic acids could be recovered as petrochemical products, while concomitantly producing a cleaner wastewater. Solid–liquid equilibrium data were collected for aqueous solutions of acetic acid, propionic acid, and butyric acid. A synthetic Fischer–Tropsch acid water mixture (0.70 wt% acetic acid, 0.15 wt% propionic acid, and 0.15 wt% butyric acid) was prepared and the liquid phase concentrations of the acid species at solid–liquid equilibrium were determined. Control experiments with material balance closure on each of the carboxylic acid species were performed at selected conditions. Having more than one carboxylic acid species present in the mixture meaningfully changed the solid–liquid equilibrium versus temperature of the system. The carboxylic acids partitioned between the solid phase and the liquid phase and a practical design would require multiple duty-controlled solid–liquid equilibrium stages, with most of the separation taking place in the temperature range 0 to − 5 °C.

铁基高温费托合成中大约一半的产品是含有溶解的含氧化合物的水性产品。挥发性的含氧化合物可通过蒸馏回收，但大部分羧酸保留在水中，称为酸性水。研究了部分冷冻作为生产更高浓度的羧酸溶液的方法，可以从中回收羧酸作为石油化学产品，同时产生更清洁的废水。收集了乙酸，丙酸和丁酸水溶液的固液平衡数据。合成的费-托酸水混合物（0.70 wt％的乙酸，0.15 wt％的丙酸和0。制备了15 wt％的丁酸），并测定了固液平衡时酸种类的液相浓度。在选定的条件下对每种羧酸物质进行了物质平衡封闭的对照实验。混合物中存在一种以上的羧酸物质会显着改变固液平衡与系统温度的关系。羧酸在固相和液相之间分配，根据实际设计，需要多个占空比控制的固液平衡阶段，其中大多数分离过程均在0至-5°C的温度范围内进行。混合物中存在一种以上的羧酸物质会显着改变固液平衡与系统温度的关系。羧酸在固相和液相之间分配，根据实际设计，需要多个占空比控制的固液平衡阶段，其中大多数分离过程均在0至-5°C的温度范围内进行。混合物中存在一种以上的羧酸物质会显着改变固液平衡与系统温度的关系。羧酸在固相和液相之间分配，根据实际设计，需要多个占空比控制的固液平衡阶段，其中大多数分离过程均在0至-5°C的温度范围内进行。