Synthesis Of Y Zeolites From Natural Aluminosilicate Clay Cinerals And Their Catalytic In Isobutane Alkylation

With the continuous improvement of clean motor gasoline standards in the world and China,the alkylate has no sulfur,olefins and aromatics,it is also the most ideal blend component of clean gasoline.the alkylation of butene and isobutane plays an increasingly important role in the petroleum refining industry.In isobutane alkylation industrial plants,sulfuric acid and hydrogen fluoride are often used as isobutane alkylation catalysts.Although sulfuric acid alkylation has the disadvantages of high acid consumption and strong corrosion.Due to the high toxicity of hydrofluoric acid and its ability to form aerosols,hydrofluoric acid has become an extremely dangerous catalyst and its industrial application has been greatly limited.Solid acid and acidic ionic liquid are new green catalysts for carbon tetraalkylation.Molecular sieve,as a kind of solid acid catalyst,has the advantages of adjustable acidity,easy regeneration,and green environmental protection,and has been widely concerned,and Y zeolites because of a large three-dimensional pore structure so the space hindrance is weak,relatively strong acidity.So it is an ideal alkylation catalyst.Y zeolites are generally synthesized from inorganic salts,and most of these chemical reagents come from natural aluminosilicate clay minerals,which involve complex reaction and separation steps.Our research group has developed a green synthesis technique of zeolites directly synthesized from natural aluminosilicate clay minerals.In this paper,Y zeolites was synthesized from kaolin and diatomite.on the basis of previous research work in our laboratory.Investigated The effects of different activation methods and conditions of synthesis on the phy-chemical properties of Y zeolites.The Y zeolites were modified with rare earth elements,and evaluate the catalytic performance of the Y zeolites.Finally,the process of isobutane alkylation by Y zeolites was optimized.The main results obtained are:Kaolin was respectively activated by thermally activated（TA）,alkali fused（AF）,Sub-molten salt（SMS）and Quasi-solid-phase（QSP）.Y zeolite was synthesized by using the activated products as partial silicon and aluminum sources,In addition to thermally activated diatomite as supplementary silicon sources.The results show that TA-Y synthesized from thermally activated kaolin has the highest relative crystallinity 91%and the highest acidity,while SMS-Y and QSP-Y have smaller size and more mesoporous structures.SMS-Y has the largest mesoporous volume,reaching 0.26 cm²·g^-1.The size of QSP-Y is uniformly distributed at about 200 nm.Crystal dynamics analysis showed that some kaolin fragments existed in the synthesis of zeolites from thermal activated kaolin,which acted as"seed"in the reaction system,promoted the nucleation of zeolites and improved the crystallinity of zeolites.The catalytic performance of four kinds of Y zeolites for isobutane alkylation reaction was evaluated.The results showed that TA-Y synthesized from thermally activated kaolin showed a longer life and higher selectivity of trimethylpentane（TMPs）,the selectivity of initial reaction TMPs was 61.7 wt%.SMS-Y synthesized by activated kaolin with meltolytic salts maintained a relatively high C8selectivity（60%）within 60 min,The research octane number of alkylated oil is 88.The effects of Molar ratio of Na₂O/Al₂O₃ and Si O₂/Al₂O₃ on the physicochemical properties of Y zeolites were investigated using SMS-Kaolin as material.The final results display that the crystallinity of Y zeolites increases gradually with the decrease of the basicity of the synthesized system.When the molar ratio of Na₂O/Al₂O₃ is 6.0,the relative crystallinity of Y obtained is the highest（71%）,the specific surface area is the largest,and it has the most abundant mesoporous structure and the highest acid content.It showed a long reaction life（20min）and selectivity of TMPs（47.6%）when used to catalyze carbon tetralkylation.The Molar ratio of Si O₂/Al₂O₃ make a great different of the acidity of the synthesized Y zeolite.When Si O₂/Al₂O₃ is 11,the synthesized 11Si-SMS-Y is the most acidic.However,the 12Si-SMS-Y obtained when the Si O₂/Al₂O₃ ratio is 12 has rich mesoporous structure,which shows a long life and selectivity of target products in catalytic carbon tetraalkylation reaction.The SMS-Y was synthesized under the condition of Na₂O/Al₂O₃ molar ratio of 6.0and Si O₂/Al₂O₃ molar ratio of 12 as a parent modified with lanthanum metal,and get the product La-SMS-Y.The La-SMS-Y Compared with H-SMS-Y,the framework of La-SMS-Y is more stable,and used for isobutane alkylation.When the I/O ratio is 150,At the optimum reaction temperature of 80 ^oC and space velocity of 0.3 h^-1,Its research octane number can reach 95.