| Fluid catalytic cracking(FCC)catalysts are important catalysts in the petrochemical industry and are used in large quantities,so a large amount of this spent catalyst is produced each year.The spent catalyst is supported by alumina,and the rare earth is a catalytically active component,and is rich in metal elements such as aluminum,lanthanum and cerium.The rational and comprehensive utilization of such waste catalyst not only enables the recycled metal elements to be recycled,protects the environment,but also conforms to the state’s policy on the scientific treatment of hazardous waste,and has good economic,environmental and social benefits.In this paper,a FCC spent catalyst was used as the research object to carry out the leaching of aluminum and rare earth in waste catalyst;the separation and recovery of aluminum and rare earth in leachate;the rare earth purification and enrichment of sulfuric acid rare earth double salt;and the experimental study of water treatment cycle The optimum process conditions are determined by orthogonal experiments.The detection methods mainly include inductively coupled plasma emission spectroscopy(ICP-OES).Based on the above experimental research,the enterprise process design is carried out.The main contents of this paper are as follows:1.Leaching of FCC spent catalystBecause the rare earth content of the FCC spent catalyst is not high(about 2%),sulfuric acid can also have good leaching effect on aluminum and rare earth like other acids,but it is not volatile like nitric acid and hydrochloric acid,increasing operating cost and wastewater.the amount.The optimum conditions for sulfuric acid leaching of FCC waste catalyst: the molar ratio of actual sulfuric acid to theoretical dosage is 1,concentration 6 mol/L,leaching temperature 90 °C,leaching time 7 h,and the volume ratio of supplementation to sulfuric acid is 0.7 min before the end of leaching.The water is stirred at a constant rate.Under these experimental conditions,the leaching rates of aluminum,lanthanum and cerium in the spent catalyst of FCC were 67.8%,92% and 81.65%,respectively,and most of the activated alumina and rare earth oxide in the spent catalyst were leached.2.Preparation of rare earth and aluminum salts by recycling aluminum and rare earthIn this paper,two methods of potassium hydroxide method and potassium sulfate method were used to recover rare earth and aluminum,and the process conditions of preparing rare earth double salt and potassium alum were prepared.Optimum conditions of potassium hydroxide method: preparation conditions of rare earth double salt,adding 30% potassium hydroxide to the leachate,the final pH value is 1.7,the reaction temperature is 80 ° C,the reaction time is 10 min,vigorous stirring;potassium alum preparation conditions,total hydrogen The amount of potassium oxide is 0.9 times the theoretical amount,the reaction temperature is 80 ° C,and stirring is carried out at a constant speed.At this time,the conversion rate of rare earth is above 99%.3.92 g of rare earth double salt can be prepared from 100 g waste catalyst,the total content of rare earth in the double salt is 22.3%,and the yield of potassium alum is 125.12 g.The optimum conditions of potassium sulfate method: preparation conditions of rare earth double salt,potassium sulfate liquid-solid ratio 10/1,reaction temperature 90 ° C,reaction time 50 min,uniform stirring;potassium alum preparation conditions,total potassium sulfate dosage is 1.3 times theoretical amount The reaction temperature was 90 ° C,the reaction time was 10 min,and stirring was carried out at a constant speed.At this time,the rare earth conversion rate is above 99%.100 g of spent catalyst can prepare 3.309 g of rare earth complex salt sodium,the total content of rare earth in the double salt is 22.31%,and the production of potassium alum is 237.3g.Comparing the two methods,when the rare earth recovery is the same,the potassium alum prepared by the potassium sulfate method is more,and the market price of potassium sulfate is lower than that of potassium hydroxide,so the potassium sulfate method is selected when preparing the rare earth double salt and potassium alum.3.Purification and enrichment of rare earth double salt of sulfuric acidIn this paper,the oxalic acid conversion roasting method and the potassium hydroxide alkali conversion method were used to purify and enrich the rare earth in the rare earth double salt of sulfuric acid.The optimum conditions for oxalic acid conversion roasting method: the amount of oxalic acid is 1.81 times of the amount of lysine,the liquid-solid ratio is 15/1,the reaction time at room temperature is 5 h,and the filter cake is completely oxidized by high temperature calcination.At this time,the total rare earth oxide rare earth oxide content obtained by oxalic acid conversion roasting is 66.83%,of which La40.87% and Ce25.96%.The optimal conditions for the alkali conversion of potassium hydroxide: the amount of potassium hydroxide is 1.6 times the theoretical amount,the liquid-solid ratio is 7.5/1,the reaction time is 10 min,and the reaction temperature is 60 °C.At this time,the total content of rare earth in the basic rare earth obtained by the alkali conversion of potassium hydroxide was 47.6%,wherein La 29.46% and Ce 18.14%.4.water treatment cycleIn the process of waste catalyst utilization and conversion,multiple processes need to be washed with water.During the whole process of research,the effective recycling and treatment of water is the key to measuring the practicability of the process.At the same time,taking into account the optimum process parameters of each section and the overall process material balance,the water is collected by washing the various sections and dilute the sulfuric acid for the purpose of obtaining the best process for the comprehensive utilization of the spent catalyst in the laboratory.Figure.5.Annual process design for processing 3,600 tons of FCC spent catalystAccording to the experimental results,the actual process is determined to determine the sulfuric acid leaching-rare earth complex salt and potassium alum production-water treatment cycle process suitable for the enterprise;material balance calculation and water cycle calculation for each section;process design equipment selection and time schedule;Possible contamination in process design;equipment layout drawings for production workshops;and preliminary production operation standards and specifications. |
