Study On The Application Of Hangjin 2~# Clay In Solid Acid Catalyst

SO₄^2-/M_XO_Y solid superacid has some advantages such as its high acid strength and high activities in many organic reactions,it is easy to separate from the reaction mixture,no corrosive to reactor and friendly to the environment. So it has been extensively used in many organic catalytic reactions of esterification,isomerization of n-alkanes,polymerization,acylation and so on. However,SO₄^2-/M_XO_Y also has some disadvantages,it is small in surface area,hard to adjust its acidity and easy to deactivate,which limited its utilization in some extent.Hangjin 2^# clay from Inner Mongolia is a natural environmental mineral, formated by sedimentation of continental basin. It is abundant, inexpensive and easy to mine, it has a good adsorption property and porous structure, and used in many fields. Currently, Research on hangjin 2^# clay focuses on adsorption of organic or inorganic pollutants and bleaching of colored substances, the research on preparation of catalyst from hangjin 2^# clay is less, Hangjin 2^# clay used in the preparation of solid acid catalyst for the catalytic esterification, hydration reaction has not been reported.In this paper,a naturally abundant hangjin 2^# clay from Inner Mongolia was used as raw material to prepare activated clay by treating with sulfuric acid and chlorhydric acid. SO₄^2-/Hangjin 2^# clay solid acid catalyst was prepared by impregnation method using activated clay as the support. Catalytic activity of the catalyst was evaluated using esterification of acetic acid and n-butyl alcohol as probe reaction. The effects of acid type,Hangjin 2^# clay treatment conditions,catalyst preparation conditions and reaction conditions on the catalyst performance were investigated. SO₄^2-/Hangjin 2^# clay were characterized by means of modern pysical and chemical techniques such as X-ray powder diffraction(XRD),specific surface area(BET),Hammett indicator method,X-ray photoelectron specroscopy(XPS), Fourier transformation infra-red spectra(FT-IR) , Scanning electron microscope(SEM),Thermo gravimetric differential thermo analyzer(TG-DTA). the reasons for influencing its catalytic properties were discussed and the reusability and regeneration method of the catalyst were studied. In order to enhance catalytic stability of the catalyst,SO₄^2-/Hangjin 2^# clay was modified with metal oxide,rare-earth elements and pillared reagent. Furthermore,the terpineol was synthesized by hydration reaction of turpentine,catalyzed by solid superacid of SO₄^2-/Hangjin 2^# clay,the optimum reaction conditions were obtained.Several conclusions from experiments and studies can be drawn as follows:(1) The optimum acid activation conditions of hangjin 2^# clay including that the concentration of sulfuric acid is 25%,solid-liquid ratio of Hangjin 2^# clay and sulfuric acid is 1:2.5,activation temperature is 95℃,activation time is 4h.By treating with sulfuric acid,specific surface area of hangjin 2^# clay was increased,and Layer spacing is expanded, layered structure is more regular。(2) The suitable preparing conditions of SO₄^2-/Hangjin 2^# clay were obtained as follows: liquid-solid ratio of sulfuric acid and activated clay is 5:1,the concentration of sulfuric acid is 2.5mol/L,calcination temperature is 300℃,calcination time is 3h,SO₄^2-/Hangjin 2^# clay prepared under these conditions is solid superacid.The optimum esterification reaction conditions were that the molar ratio of n-butyl alcohol and acetic acid is 2:1,the amount of the catalyst is 0.6g,the reaction temperature is 90℃,reaction time is 2h,under this condition,conversion of ester is over 99%,the conversion of ester was similar in five parallel experimentals,experimental repeatability was excellent.(3) Activated clay prepared by Hangjin 2^# clay with different acid treatment had been used as the carrier to prepare SO₄^2-/Hangjin 2^# clay,it has different catalytic performance for esterification: Comparing that treated by chlorhydric acid,Hangjin 2^# clay treated by sulfuric acid has better stability,the texture structure of Hangjin 2^# clay had been less destroyed and active component SO₄^2- is lost slowly.(4)Deactivation and regeneration of the catalyst were studied,and the results showed that Hangjin 2^# clay exhibited very high catalytic activity but relative lower stability,the main reason of deactivation was loss of SO₄^2- or active centers of catalyst was changed. Modifying with metal oxide,rare-earth elements and pillared reagent produced insignificantly change on the activity of catalyst but increase the stability of catalyst. SO₄^2-/Hangjin 2^# clay modified with Al-pillared reagent had better stability.(5) SO₄^2-/Hangjin 2^# clay exhibited higher catalytic performance in catalysing the synthesis ofα-terpineol by hydration reaction ofα-pinene. Under the optimum conditions,the conversion ofα-pinene is 95.8%,the selectivity ofα-terpineol is 65.8%.