Singh Kaman, Gupta Satya Prakash, Kumar Ashok, Kumar Ajay
Ultrasonic Laboratory, Department of Chemistry, Babasaheb Bhimrao Ambedkar University (A Central University), Lucknow 226025, India.
Ultrasonic Laboratory, Department of Chemistry, Babasaheb Bhimrao Ambedkar University (A Central University), Lucknow 226025, India.
Ultrason Sonochem. 2019 Apr;52:19-24. doi: 10.1016/j.ultsonch.2018.05.030. Epub 2018 May 26.
The application of a technique to eliminate the latent period during crystallization of sucrose by high intensity ultrasound (HIU) was investigated in this paper. Employing HIU (20 kHz, 750 W) to crystallization of sucrose, latent period was eliminated and it was found to obey first order kinetics (K ∼10s) in the temperature range of 30-50 °C. Employing Arrhenius equation, the average energy of activation (E) estimated as 5.0 kcal mol. Traditional knowledge indicates that crystallization is sufficiently spontaneous; however, the magnitude of "K" and other thermodynamic quantities of the process indicate that crystallization is actually a slow process. Generally, chemical reactions which posses low rate constants, need the high energy of activation. On the contrary, the energy of activation is appreciably less. The energy of activation with a rate constant of the order of 10s could be predicted of the order of 20 kcal mol at 27 °C. The low energy of activation for crystallization of sucrose is of interest. A very interesting elucidation can be had from neutron diffraction data and transport property of the sucrose which is discussed in details in this paper.
本文研究了一种利用高强度超声（HIU）消除蔗糖结晶潜伏期的技术应用。采用HIU（20kHz，750W）对蔗糖进行结晶，消除了潜伏期，发现在30 - 50°C温度范围内其遵循一级动力学（K ∼10s）。利用阿伦尼乌斯方程，估计平均活化能（E）为5.0 kcal mol。传统知识表明结晶是充分自发的；然而，该过程的“K”值大小和其他热力学量表明结晶实际上是一个缓慢的过程。一般来说，具有低速率常数的化学反应需要高活化能。相反，这里的活化能明显较低。在27°C时，速率常数为10s量级的反应，其活化能预计为20 kcal mol量级。蔗糖结晶的低活化能很有意思。本文将详细讨论从中子衍射数据和蔗糖的输运性质中可以得到的非常有趣的解释。
