Controlled preparation of MOF for performance improvement of vegetable insulating oil

Vegetable insulating oil is a common kind of synthetic liquid insulating medium, which is usually applied in high voltage electrical equipment, such as transformers. At present, some mineral insulating oil has already been replaced by the eco-friendly vegetable insulating oil. Typically, the eco-friendly vegetable insulating oil not only possesses good electrical performances but also owns great biodegradability and high flash point. However, there will be impurities in any kind of vegetable insulating oil inevitably, and those impurities will have a serious influence on the properties of insulating oil. Metal-organic framework (MOF) has potential to be used as adsorbent because of its special micropore structure and large specific surface area. Meanwhile, it is convenient to prepare various of MOFs and control their structures. Nowadays, MOFs are usually used in the field of medicine delivery, chemical catalysis and gas adsorption. Nevertheless, utilizing MOF as a kind of adsorbent in vegetable insulating oil is seldom reported. In this paper, a typical MOF named zeolitic imidazolate framework-67 (ZIF-67) was prepared and used in the research. The microstructure of ZIF-67 was observed under the scanning electron microscope (SEM). The chemical properties of ZIF-67 were characterized by the X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Also, ZIF-67 was used as an adsorbent to treat the aged vegetable insulating oil. Results showed that the dielectric loss of aged vegetable insulating oil can be reduced by 46.7%, and the water and acid value of the aged vegetable insulating oil could be decreased gently at the same time. This approach provides a possible solution to improve the performance of vegetable insulating oil for the high voltage electrical system.