Study On Preparation Of Nano-pseudo-boehmite By Continuous High-gravity Carbonation Method

Pseudo-boehmite?AlOOH·nH₂O,n=0.08⁰.62?is a kind of partially crystallized hydrated alumina,which is widely used in petrochemical industry as a catalyst carrier in catalytic cracking,catalytic hydrogenation and other processes.With the tendency of heavy and poor quality of raw oil,the preparation of large pore volume and high specific surface area of pseudo-boehmite has become a hot research topic.At present,there are many production processes of pseudo-boehmite.In this project,the carbonation production process with the lowest cost in actual production is adopted.Relying on the alumina process,the intermediate product sodium aluminate solution and CO₂ in flue gas are used as reaction raw materials to solve the traditional carbonation problems such as uneven pore size distribution,large crystal particles,and many impurities in the split process.?1?The feasibility of the preparation of pseudo-boehmite using high-rgravity continuous carbonation method is theoretically analyzed.The new method for preparing pseudo-boehmite is proposed by combining high-gravity technology with continuous carbonation process.The raw materials and the cross-flow rotating packed bed using the traditional carbonation method are continuously prepared by strengthening micro-mixing under high-gravity environment to obtain pseudo-boehmite.?2?The effects of the concentration of NaAlO₂ solution,gas-liquid ratio and high-gravity factor on the pore properties of pseudo-boehmite were investigated.With the increase of the concentration of NaAlO₂ solution,gas-liquid ratio and high-gravity factor,the specific surface area and pore volume of pseudo-boehmite tend to increase first and then decrease.The best preparation condition is that the concentration of NaAlO₂ solution is 0.1mol/L,the gas-liquid ratio is 3:1,and the high-gravity factor is 54.The specific surface area and pore volume of the pseudo-boehmite product obtained based on this condition are 505m²/g,1.102 cc/g.?3?The pore properties were analyzed by Fourier infrared spectrometer?FT-IR?,X-ray diffractometer?XRD?,scanning electron microscope?SEM?specific surface area analyzer?BET?,and transmission electron microscope?TEM?.The experiments showed that nano-sized pseudo-boehmite with fibrous pores can be prepared by high-gravity continuous carbonation methods.?4?In the preparation process,polyethylene glycol 400?PEG?was introduced to conduct pore reaming modification.Through BET,XRD,SEM and other characterization methods,it was found that the impurities in the modified pseudo-boehmite were reduced,and the pore channels were rich and uniform.The specific surface area and pore volume of the large-hole pseudo-boehmite were 495m²/g and 2.125cc/g,respectively.After roasting at 550?,the specific surface area and pore volume of nano-scaled large-hole fibrous?-Al₂O₃ were 322m²/g and 1.826 cc/g respectively.?5?The high-gravity continuous carbonation method was used for the amplification experiment.The reaction solution was sodium aluminate solution,which was used as the raw material in the actual production process of the factory,and carbonation reaction occurred with CO₂ in the cross-flow rotating packed bed.In this experiment,diluted 20L solution was used for continuous production.Finally,the prepared pseudo-boehmite sample was compared with the sample actually produced by the factory.The results showed that the products obtained by high-gravity continuous carbonation have outstanding advantages in specific surface area,pore volume and particle size.Two kinds of pseudo-boehmite were evaluated by ACE,and the evaluation results showed that the pseduo-boehmite prepared by high-gravity continuous carbonation method was applied to catalyst support,and was improved in C5gasoline,light and total liquid,which provided a foundation for industrial application.