不同pH对焦磷酸铵水解的影响

以主成分为焦磷酸铵的水溶性聚磷酸铵为实验原料，设置8.2、6.0、4.0、3.5、3.0、2.5、2.0等7组pH梯度，系统研究了酸度对焦磷酸铵水解的影响。结合一级反应动力学方程与阿累尼乌斯方程进行焦磷酸铵的水解动力学计算，结果表明：经过310 d（第二批260 d）的放置，pH从8.2降低到2.0时焦磷酸铵质量分数从初始态的92.6%依次减少为85.4%、51.2%、50.6%、50.2%、24.3%、12.9%和6.0%。焦磷酸铵在自然温度下的水解速率随着pH的降低而不同程度地加快，服从一级反应机理。pH从8.2降低到2.0时焦磷酸铵的水解速率常数从2.92×10-4~3.43×10-4增加至3.41×10-3~1.47×10-2，二者相差10~40余倍，对应半衰期为50~2 000 d。秋冬与春夏两时段的水解速率差异很大，二者水解速率常数相差1.17~4.32倍，焦磷酸铵的水解活化能为7.5~68.5 kJ/mol。

Effect of different pH on hydrolysis of ammonium pyrophosphate

Water soluble ammonium polyphosphate mainly containing ammonium pyrophosphate was used as the experimen tal raw material.Seven groups of pH gradients（8.2，6.0，4.0，3.5，3.0，2.5 and 2.0） were set up to systematically research theinfluence of pH on the hydrolysis of ammonium pyrophosphate.Combining the first order reaction kinetic equation andArrhenius equation to calculate the hydrolysis kinetics of ammonium pyrophosphate.The results showed that the mass fraction of ammonium pyrophosphate successively decreased from initial 92.6% to 85.4%，51.2%，50.6%，50.2%，24.3%，12.9%and 6.0% after hydrolyzing 310 d（second batch of 260 d）.The hydrolysis rate of ammonium pyrophosphate under natural temperature conditions increases by varying degrees with the decrease of pH and it obeys the first order reaction.Thehydrolysis rate constant of ammonium pyrophosphate increased from 2.92×10-4~3.43×10-4 to 3.41×10-3~1.47×10-2 whenpH decreased from 8.2 to 2.0.The difference of both of them were 10~40 times，the corresponding half-life was 50~2 000 d. The hydrolysis rates of autumn winter and spring summer were very different.The hydrolysis rate constants of the twoperiods differ by 1.17~4.32 times，and the hydrolysis activation energy of ammonium pyrophosphate was in the range of 7.5~68.5 kJ/mol.