Control Synthesis Of Mesoporous SBA-1 Molecular Sieve In A Moderate Condition

SBA-1 refers to a mesoporous silica molecular sieve with 3D cubic space group structure,synthesis in strongly acidic?p H < 0?medium at low temperature?0 ??under static condition,using large head-group cationic quaternary ammonium salt surfactants like cetyltriethylammonium bromide?CTEAB?as the template agent,and tetraethyl orthosilicate?TEOS?as silica source.Compared to SBA-3 with 2D hexagonal p6 mm and MCM-41 molecular sieve with one-dimensional channels,SBA-1 with unique three-dimensional cage-type channel structure will be more conducive to diffusion and transmission of guest molecules which make them suitable for wide applications in heterogeneous catalysis,macromolecular adsorption and separation.Strongly acidic medium during the synthesis process,however,not only to a great extent,restricts the efficient doped in situ of various active metal,has become one of the main obstacle of large-scale preparation of the materials.This work synthesizes for the first time high quality and high-hydrothermal stability of mesoporous molecular sieve SBA-1 in mild acid system by using weak acid provided hydrolysis of aluminum salt instead of replace strong acid to induce the hydrolysis of TEOS,and using XRD,N2 adsorption,TEM and SEM characterization techniques to do research the influence of various synthetic parameters and preparation conditions.At the same time,SBA-1 can also control synthesis by this synthetic thought to expand to other inorganic salt system such as nickel salt,iron and copper salt,and its formation mechanism has carried on the preliminary discussion.The main findings are as follows:1.For the first time,high-quality SBA-1 has been successful synthesized in the system of TEOS-CTEAB-AlX-H₂O system(X = Cl^-,SO₄^2-and NO₃^-)at room temperature?18? to 28??by adjusting the type,concentration of aluminium salt and the ratio of components,without the introduction of strong acid only using mild acidity provided hydrolysis of aluminum salt,the specific surface area,pore volume and pore size amounts to 1342.34 m2/g,0.59cm3/g and 2.2nm,respectively.Research found that SBA-1 in a wide range component concentration can be synthesized by using of Al Cl₃ or Al₂?SO₄?₃ as catalyst,while 2D hexagonal p6 mm mesoporous materials can be only synthesized by using Al?NO₃?₃,and induction period in the synthesis process shorten in accordance with SO₄^2-<Cl^-<NO₃^-,comply with the order of Hofmeister anionic effect.SBA-1 molecular sieve by using the preparation method can be not only resistant to water washing operations,and thermal stability of SBA-1 up to 900?,but too high concentration of template agent,synthetic temperature and stirring reaction operation are not conducive to the formation of high-quality SBA-1.2.The above ideas of synthesis expand to other typical inorganic salt system such as nickel salt,iron salt,copper salt,zinc salt and cobalt salt,etc.,the study found that in a moderate system SBA-1 phase can be synthesized through appropriate adjustment of synthetic parameters in most inorganic salt system.However,may be due to the acidic differences result from the different salt hydrolyzed or with different metal cation surfactant micelle structure and accumulation way,3D hexagonal p63/mmc mesoporous materials can be only synthesized in ferric sulfate system,and the poor order of 2D hexagonal p6 mm phase structure can be synthesized in nickel sulfate,ferric chloride and zinc sulfate system.By introducing proper phosphate can obviously improve the order of the final mesoporous phase structure,at present,the inner reason of the phase structure transformation is still not very clear,further research is still in progress.High quality and high-hydrothermal stability of mesoporous SBA-1 molecular sieve can be prepared by using the inorganic salt induced,its new ideas proposed firstly not only reduces the synthesis difficulty and preparation cost of the materials,synthetic process more concise,efficient and environmentally friendly,meanwhile also confirmed that mesoporous silica materials in the strong acidic system can be completely synthesized in a more modest system.Fully hydrolysis of TEOS in mild acidic conditions can be only realized,further condensation self-assembly process between the hydrolysis species and surfactant micelle template is more depending on the type and concentration of the anion instead of H+ ions provided strong acid.This method will be more conducive to synchronization in situ modification of different functional groups and the active metal in the skeleton mesoporous SBA-1,more in-depth research is still in progress.