Method for preparing silicon tetrafluoride from quartz sand

The invention discloses a method for preparing silicon tetrafluoride from quartz sand, wherein raw materials comprise metal fluoride and silicon dioxide, and the method comprises the following steps of: 1. calcining and activating the metal fluoride, making the activated metal fluoride react with concentrated sulfuric acid to obtain fluorine hydride gas, washing and cooling the fluorine hydride gas to obtain fluorine hydride liquid, and meanwhile, mixing the silicon dioxide and sulfuric acid into a silicon dioxide premixed slurry; 2. mixing the fluorine hydride liquid, the silicon dioxide premixed slurry and the sulfuric acid and making the mixture react to obtain silicon tetrafluoride gas. The method for preparing the silicon tetrafluoride from the quartz sand has high raw material conversion rate, high product purity, fewer impurities and easy control of reaction processes.