| Vinyl acetate is one of the most output of organic chemical industry materials over the world. Producing vinyl acetate is mainly adopted by means of synthesizing acetylene, and Zn(Ac)2/C is used as catalyst of vinyl acetate produced. In the course of production, the active of the catalyst is quickly lost and then the longevity of catalyst is shortened. As a result, there is a lot of spent activated catalyst produced, which severely pollutes the environment, as well as the resource is waste seriously. Therefore, researching and utilizing the spent activated catalyst synthetically is one of the focuses. At present, some people have researched utilizing it, but the leaching rate of zinc is not high. As the result of it, the spent activated catalyst is not widely used. A novel technology of preparation of nanometer zinc oxide from spent activated catalyst was researched in this paper. Entire process of preparation of nanometer zinc oxide and pilot testing was accomplished and then achieved a recycle economical type with feedback of resource- product-waste-renewable resources. The main research results are as follows:1. Experimental researches on leaching spent activated catalyst pre-treated with microwave irradiation by hydrochloric acid or ammonia water have been accomplished. Effects of the concentration of hydrochloric acid or ammonia water, leaching temperature, the ratio of liquor to solid on the zinc leaching rate were discussed in this paper. Through experiment, the right condition of microwave irradiation has been acquired, and mechanism of spent activated catalyst by microwave irradiation has been discussed. The experimental results show that the leaching rate of zinc exceeds 92% under the leaching conditions: leaching dose hydrochloric acid, microwave irradiation 30 min, the ratios of liquor to solid 4:1,leaching temperature 50℃, leaching time lh,the adding concentration of hydrochloric acid 30g/L;the leaching rate of zinc exceeds 94% under the leaching conditions: leaching dose ammonia, leaching temperature room temperature, microwave irradiation 30 min, leaching time 4.5 h, the ratios of liquor to solid 3:1, the adding concentration of ammonia 28.6g/L,ammonium carbonate 24.2g/L, it is indicated that the leaching of spent activated catalyst pre-treated with microwave irradiation by hydrochloric acid or ammonia water ispractical.2. Experiments on preparation of precursor of nanometer zinc oxide have been researched. Preparation of nanometer zinc oxide by direct precipitation has been adopted. The optimum conditions are obtained as follows: the adding concentration of zinc chloride 1.5mol/L,the concentration ratio of ammonium carbonate to zinc chloride: 1.5:1, sodium dodecyl benzene sulfate(SDBS) as surfactant, filtrating and washing zinc hydroxide carbonate, drying 2~3h under 100-120 °C. Zinc hydroxide carbonate has been gained under above conditions. Experimental results indicate that granularity of Zinc hydroxide carbonate was uniform and narrow-sized.3. Calcining technology of zinc hydroxide carbonate has been determined. Nanometer zinc oxide can be obtained at the condition of adopting traditional heating for 3 h at 350 "C. TEM has been used to characterize the product. Results indicate that uniformly sized, narrow-sized, dispersed, high specific surface, nanometer-sized zinc oxide has been obtained by using this method.4. Lixivium has been heated and ammonia vaporized. After that, the dispersed nanometer-sized zinc oxide has been gained, and the reclaimed ammonia recycled, which have supplied with evidence to the later experiments. At last, clean production with whole process has been achieved and an environmentally friendly approach has been found for comprehensive utilization of spent activated catalyst.In conclusion, the paper has brought forward an environmentally friendly technology for comprehensive utilization of spent activated catalyst. The technology adopts ammonia to lixiviate the spent activated catalyst which has been pre-treated with microwave irradiation, which makes the whole preparation achieved closed circuit. Therefore, this technology achieves the effective utilization of spent activated catalyst, which has important researching significance of comprehensive utilization of spent activated catalyst and sustainable development of economy. |
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