γ-Al2O3催化合成聚甲基膦酸乙二醇酯的适宜活化温度的确定

聚甲基膦酸乙二醇酯(PEMP)作为一种良好的阻燃剂,具有无毒、低烟、含磷量高、阻燃效果好的优点。 γ-Al₂O₃是催化乙二醇(EG)和甲基磷酸二甲酯(DMMP)缩合生成PEMP的良好催化剂。 但是由于γ-Al₂O₃容易吸附CO₂和水分,降低其催化活性,所以使用前需要活化。 活化温度影响着γ-Al₂O₃的催化活性。 本文分别在300、400、500、600、700和800 ℃不同温度下对γ-Al₂O₃进行活化,用X射线粉末衍射(XRD)分析了γ-Al₂O₃晶型变化、用低温氮吸附比表面积测试法(BET法)测量了γ-Al₂O₃比表面积、孔径和孔容积,用傅里叶变换红外光谱(FTIR)分析了红外吸收变化,用吡啶吸附-FTIR测定了γ-Al₂O₃的Brønsted酸位点与Lewis酸位点相对含量。 比较了不同温度下活化的γ-Al₂O₃催化合成PEMP产品的纯度和粘度,找到了γ-Al₂O₃催化合成PEMP的适宜活化温度为400~600 ℃。 此时,γ-Al₂O₃属于典型的γ-Al₂O₃晶型,比表面积较大,孔径较小,所得PEMP产品纯度最高。

Optimal Activation Temperature of γ-Al2O3 for Catalytic Synthesis of Poly(oxy-1,2-ethanediyl)methylphosphonate

Poly(oxy-1,2-ethanediyl)methylphosphonate(PEMP)as a good flame retardant has lots of benefits such as non-toxic,low smoke,high phosphorus content and better flame retardant effects.γ-Al2O3 is a good catalyst for the condensation of ethylene glycol(EG)and dimethyl phosphate(DMMP)to produce PEMP.However,sinceγ-Al2O3 is easy to absorb CO2 and water to reduce its catalytic activity,activation is needed before use.The activation temperature affects the catalytic activity of γ-Al2O3.In this paper,γ-Al2O3 was activated at different temperatures from 300,400,500,600,700 and 800℃.γ-Al2O3 crystal form was analyzed by X-ray difraction(XRD)and its specific surface area,pore diameter and pore volume were measured by Brunauer-Emmett-Teller(BET)method.The change of infrared absorption was analyzed by Fourier transfer infrared(FTIR).The relative contents of Br nsted acid and Lewis acid sites inγ-Al2O3 were determined by pyridine adsorption-FTIR.The purity and viscosity of PEMP catalyzed byγ-Al2O3 were compared,and the optimal activation temperature of γ-Al2O3 was found to be 400,500 and 600℃.At this time,γ-Al2O3 is a typical γ-Al2O3 with large specific surface area and small pore diameter,and the obtained PEMP product has the highest purity.