Synthesis Of Highly Stable And Strongly Acidic Mesoporous Aluminosilicates Under Neutral Conditions

While much attention was being paid to the mesoporous aluminosilicates（MAs）since it was reported by Mobile Oil Company in 1992.However,this new material suffers from low acidity and poor hydrothermal stability.To solve this problem,our group introduced the primary/secondary structural units of zeolite Y into the mesophase wall,improving significantly its hydrothermal stability.In spite of this,how to decrease raw material consumption（acid and templates）is still a great challenge for the application of MAs.In addition,the acidic synthesis medium makes it difficult for Al species to enter the framework of the MAs,leading to the weak acidity of them.Therefore,the synthesis of MAs with high aluminum content by low acid consumption and low templates is still a great challenge.In this paper,a novel strategy was employed by using sodium persulfate（Na₂S₂O₈）as a hydroxyl radical（·OH）initiator.In this process,the depolymerization of silicon species and the polymerization of silicon/aluminum species can be catalyzed by Na₂S₂O₈under neutral conditions.MAs with a large content of aluminum species will be obtained.At the same time,the stability and acidity of MAs have been improved.Based on this idea,this paper has carried out the following research:（1）Ordered MAs were synthesized under near-neutral conditions with reagent P123(EO₂₀PO₇₀EO₂₀)as a template and Na₂S₂O₈as·OH initiator.The characterization results of XRF showed that the n（Si O₂）/n（Al₂O₃）of Al-SBA-15 was 13.71 and the acid consumption was 0.48 g H₂SO₄/g product.As for comparison,the n（Si O₂）/n（Al₂O₃）of MAs synthesized by the traditional acid method was 21.74,and the acid consumption was as high as1.12 g H₂SO₄/g product.（2）Based on the high price of reagent P123,MAs were synthesized by using cheap industrial polyether(EO₈₀PO₃₀EO₈₀)instead of P123 as a template,which reduced the synthesis cost of the system.The acid consumption was0.47 g H₂SO₄/g product,and template consumption was 0.70 g template/g product.At the same time,the product had great order,with the specific surface area of 864.6 m²·g^-1and the pore volume of 0.88 cm³·g^-1.（3）MAs with high aluminum content were prepared in·OH/aluminum sulfate/industrial polyether system.The n（Si O₂）/n（Al₂O₃）of the product can reach 14.63.The acid consumption was 0.36g H₂SO₄/g product,and the water consumption was 9.71g H₂O/g product.For further comparison,three samples were obtained by direct synthesis method,post-treatment method,and hydroxyl radical method with a similar Al content.BET studies showed that the specific surface areas of 578.1 m²·g^-1,546.4 m²·g^-1,and 624.7 m²·g^-1by three methods,and the pore volumes of 0.67 cm³·g^-1,0.65 cm³·g^-1,and 0.71cm³·g^-1respectively.These results suggested the advantages of the Na₂S₂O₈strategy in obtaining aluminum-containing MAs.In addition,the scale-up synthesis was conducted by·OH/aluminum sulfate/industrial polyether in a 10L crystallization kettle.The characterization results indicated good repeatability,which sheds a light on the industrial application of MAs.