| Taking Hainan kaolin as raw material,the AICl3 solvent was obtained by leaching method with hydrochloric acid.The special aluminas(high purity alumina,metallurgical grade alumina and pseudo boehmite)were prepared with above AICl3 solvent.The process for preparing the special alumina was investigated and optimized.Taking one of the special aluminas,the pseudo boehmite,as matrix of cracking catalyst,the effect of pseudo boehmite on the catalytic performance was invested.The research work was showed as follow:(1)The process of acid leaching was optimized by uniform design method,the optimal leaching conditions were obtained as follow:the grain size of kaolin was 20 mesh,calcining temperature was 550? the roasting time was 10 min,leaching temperature was 105?,the leaching time was 225 min,Cl/Al ratio(atomic ratio in leaching solution)was 4,liquid to solid ratio was 9.5 mL/g.The leaching solution was AICl3 solvent with strong acidity.Under these condition,the alumina leaching rate was 98%.(2)The process of extracting iron from AICl3 solvent was investigated,the optimal conditions were obtained as follow:The phase ratio O/A(volume ratio)was 2:1,the concentration of tri-butyl phosphate in organic phase was 40%,extracting time was 20 min,extracting temperature was 25?30?.Under those condition,the extraction rate of iron was 99.82%,the separation coefficient of Fe/Al was 1.386x104.(3)Taking the AICl3 solvent as raw material,the process of preparing high purity special alumina with large particles was investigated.With the method of salting out,the effect of salting out temperature,stirring speed and acid supplement speed on particle size and bulk density of high purity alumina was investigated.The results showed that:Taking the largest median diameter of product as target,the optimal conditions were obtained as follow:salting out temperature was 40? stirring speed was 90 r/min,acid supplement speed was 130 drop/mim.Under those condition,the median diameter of product was more than 26um,the bulk density was relatively small(about 0.44g/mL).The effect of salting to remove impurities was investigated in detailedly.The results showed that:After three times of salting out,the contents of potassium and sodium impurities were reduced to 1.2 mg/kg and 2.9 mg/kg,the content of total metallic impurities was reduced to 50.5 mg/kg,the content of total impurities was reduced to 56.9 mg/kg,the purity of alumina was more than 99.99%.(4)The process of complete pyrolysis of crystalline aluminum chloride to remove the chloride ions was investigated.The results shower that:The crystalline aluminum chloride was complete pyrolysised to aluminum after being calcined in 400? for 1 hour.The chloride escaped from the calcining systems in the form of HC;gas.(5)The preparation of metallurgical grade alumina from AICl3 solvent with Spray granulation method was explored.The metallurgical grade alumina which coming up to the requirement of Grade No.3 product was obtained.(6)The preparation of pseudo boehmite from AICl3 solvent with the acid and alkali combination method was explored.The pseudo boehmite which having a relative degree of crystallinity of 65.5%and a grain size of 5.841nm was obtained.(7)The application of pseudo boehmite in cracking catalyst was investigated.The results showed that:The microreactor activity of catalyst improved 4.1 units when the introducing quantity of pseudo boehmite was 15wt%.The catalyst was modified by phosphorus to improve the on this basis.The results show that:The effect of pseudoboehmite addition to the microreactor activity of pseudo boehmite-modified catalyst had a best value.The catalytic performance was unable to improved well when the content of phosphorus was too little or too much.When the content of phosphorus reached 1%,the comprehensive performance of catalyst achieved the best:the microreactor activity increased 8.8 units,the coke reduced 0.39 units,the ability of resistancing to heavy metal pollution increased significantly. |
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