Due to the shortage of oil resources, China increases the oil of high-sulfur content import from Middle East year by year, thus resulting in the higher sulfur content of finished gasoline; therefore, how to reduce the sulfur content of finished gasoline has become a very important issue. China is still lacking in the desulfurization technology currently, domestic catalysts companies have to choose to cooperate with foreign intelligence, which results in a high manufacturing cost of desulfurization catalyst. In addition, since desulfurization transformation launched intensive, the Chinese catalyst market has become mixed, and most of the catalysts have relatively short life which needs to be replaced generally about three years, so the huge amount of waste hydrodesulfurization catalyst produced.

 

Tungsten trioxide and tungsten disulfide are the two main forms in the tungsten-based desulfurization catalyst. Tungsten is a rare metal, widely distributed in various types of rocks in nature, but scattered. Therefore, the recovery of tungsten (mostly tungsten trioxide) from waste desulfurization catalyst is necessary.

 

The specific steps for recycling tungsten disulfide and tungsten trioxide from the waste desulfurization catalyst are as bellows:

1. Load the waste catalyst into the deputy furnace of reflection furnace for roasting at 600~650 °C for 8~10 hours with stirring once every 20~ 30 minutes;

2. Move into the main furnace, continued roasting at 700~750°C for 8 hours, also stirring once every 20~30 minutes;

3. It indicates the end of roasting when the heart of particles turn to black, then discharged and cooled down by nature, crushed to generate the calcined material of waste desulfurization catalyst containing with tungsten trioxide;

4. The calcined material is dissolved in a certain concentration of ammonia, and then gets the ammonium tungstate solution by sedimentation and filtration to remove the residue;

5. The mother liquor is carried out evaporation and crystallization, adjusting pH, cooling down and separating to obtain the ammonium paratungstate crystallization;

6. Calcine by controlling the conditions to obtain tungsten trioxide.