Abstract:

In the caprolactam production process, ammonium sulfate grains inevitably entrain a small amount of amide oil, when the grains settle and separate in the gas-liquid-liquid-solid crystallization reactor. Amide oil entrainment causes waste of caprolactam and pollution of ammonium sulfate. By adding surfactants and changing experimental conditions, the entrainment of amide oil was reduced. The influence of surfactant, pH, temperature, and grain size on adsorption behavior of amide oil on the surface of ammonium sulfate crystal was evaluated from the adsorption equilibrium under shaking. The results show that cationic surfactant cetylpyridinium bromide (CPB), dodecyltrimethylammonium bromide (DTAB), non-ionic surfactant Tween 80, and the mixture of non-ionic surfactant Triton X-100 and DTAB reduce the caprolactam adsorption on the surface of ammonium sulfate crystals, while anionic surfactant sodium lauryl sulfate (SDS) and sodium dodecyl benzene sulfonate (SDBS) increase the caprolactam adsorption. In the range of 2—7, pH does not significantly affect the adsorption behavior. Between 50—80℃, amide oil adsorption on the surface of ammonium sulfate increases with temperature. With increasing ammonium sulfate particle size, the adsorption of amide oil decreases.