气提脱酚制备聚碳级双酚A工艺研究

针对传统的精馏法、结晶法及刮膜蒸发法脱酚工艺存在的诸多弊端,有必要对新的脱酚工艺进行研究,以制备超低游离酚质量分数的聚碳级双酚A。鉴于双酚A-苯酚物系高沸点、热敏性特性,文中以降膜蒸发脱除大部分苯酚、获得的粗双酚A为原料,采用向真空填料塔通入过热水蒸气进行气提的方法,研究制备超低游离酚质量分数聚碳级双酚A的脱酚工艺。研究结果表明:气提塔的操作压力、水蒸气温度和流量对脱酚效果有很大的影响。操作压力越低,组分间相对挥发度增大,脱酚效果越好。但过低的压力对脱酚效果的改善将不明显,带来的负面影响是设备投资的增加;水蒸气温度越高,塔内物料温度也随之升高,苯酚的饱和蒸汽压增大,脱酚效果越好;水蒸气流量越大,在操作压力不变的情况下,苯酚的气相分压就越低,脱酚效果越好。适宜的工艺条件是:操作压力为4.0—5.0 kPa;气提水蒸气温度185—190℃,流量为处理量的2%。

Preparation of polycarbonate grade bisphenol A by gas-stripping dephenolization

Due to many defects existing in the traditional dephenolization process,such as distillation,crystallization,and wiped film evaporation,it is necessary to study the new dephenolization process by using stripping steam to obtain polycarbonate grade bisphenol A(BPA) with ultra-lower free phenol mass fraction.In the new process,the raw material of crude BPA was obtained by falling-film evaporation with removal of most phenol.In view of BPA-phenol system with high boiling point,and heat-sensitivity,overheated steam was injected into the vacuum packed tower.The results show that the operating pressure of phenol stripping column,the temperature and the flowrate of stripping steam have great influences on the free phenol mass fraction in BPA product.The lower the pressure is,the higher the relative volatility is,and the better the dephenolization effect is;while too low pressure results in the increase of the equipment investment.The higher the temperature of stripping steam is,the higher the temperature of the materials in the tower is,thus the higher the saturated vapor pressure of phenol is and the better the dephenolization effect is.In the condition of constant operating pressure,the larger the flowrate of stripping steam is,the lower the partial pressure of phenol is,thus the better the dephenolization effect is.The suitable process parameters are as follows: the pressure is 4.0-5.0 kPa,the stripping steam temperature is 185-190 ℃,and the stripping steam flowrate is 2% of handling capacity.