Development of the technology for detoxification of Freons by using oxidative and reductive methods

研究了PO_4/ZrO_2催化剂对模型化合物氟里昂12的催化分解。以硝酸氧锆为原料，采用沉淀法和浸渍法制备了Hammett酸度系数小于-12.14的PO_4/ZrO_2超强酸。氟利昂12在该催化剂上在低至300 ° C的温度下完全分解。虽然这种催化剂对反应过程中产生的无机氟相对稳定，但在长期使用过程中会失活。为了延长该催化剂的寿命，在反应混合物中加入水（1%，4%）。水对PO_4/ZrO_2催化剂的活性有很大的促进作用，30 h后仍有60%以上的氟里昂12被分解，水中的氢以HF的形式将沉积在催化剂表面的无机氟除去。还原法以二氢化萘锂和二氢化萘钠为还原剂，以氟里昂113为模型化合物。卤素原子以氯化钠和氟化物的形式被有效地去除。在紫外光照射下，脱硝速率显著加快，室温下脱硝反应在100 min内完成。对反应中间体的分析表明，主要中间体是二氢萘与氟利昂113的二碳单元偶联生成的。由于锂的还原能力低于钠，因此锂的加入提高了脱氯率。通过使用二乙醚作为溶剂也增加了该比率。这些结果表明了将使用过的氟里昂转化为有用的氟化化合物的可能性。

Catalytic decomposition of Freon 12 (a model compound) on PO_4/ZrO_2 was carried out. Superacid PO_4/ZrO_2 whose Hammett acidity coefficient was lower than -12.14 was prepared by precipitation from zirconium (IV) oxynitrate followed by impregnation of PO_4 anion. Freon 12 was completely decomposed on this catalyst at a temperature as low as 300 ﾟC. Although this catalyst was comparatively robust against inorganic fluorine produced during the reaction, it deactivated during prolonged use. In order to prolong the lifetime of this catalyst, water (1%, 4%) was added in the reaction mixture. Water helped maintain the activity of PO_4/ZrO_2, and more than 60% of Freon 12 was decomposed even after 30 h; inorganic fluorine accumulated on the surface of the catalyst was removed by hydrogen from water as HF. This result suggested the possibility of developing practical catalytic decomposition process for Freons.Reductive method employed sodium and lithium dihydronaphthylides as reducing agents and Freon 113 as a model compound for Freons. Halogen atoms were effectively removed as sodium chloride and fluoride. The rate of defluorination was accelerated remarkably under UV irradiation, thus the defluorination was completed at a room temperature within 100 min. Analysis of the reaction intermediates suggested that the major intermediates were produced by the coupling between dihydronaphthylide and two-carbon unit of Freon 113. As the reducing ability of lithium is lower than that of sodium, ratio of dechlorination to defluorination increased by using lithium. This ratio was also increased by using diethyl ether as a solvent. These results suggested the possibility of transforming used Freons to useful fluorinated compounds.