Study On The Preparation Of Aluminum-pillared Montmorillonite From Natural Bentonit

A natural bentonite resource from Yanshan county in Yunnan province was used as raw materials to prepare Na-montmorillonite by purification and sodium modification in this paper.The swelling capacity of modified montmorillonite was used as evaluated index in the experiment of single factor and orthogonal,and the optimum conditions of sodium modification were obtained.The alumina-pillared montmorillonite(Al-PILM)was synthesized with the Na-montmorillonite as the matrices and aluminium polyhydroxocation as pillaring precursor.The phase,pore structure and thermal stability of the Na-montmorillonite and Al-PILM were characterized by X-ray diffraction(XRD),N2 adsorption/desorption and thermogravimetry-differential scanning calorimetry(TG-DSC)respectively.In order to study catalytic properties of the Al-PILM,it was used as solid acid catalyst over a-pinene isomerization reaction,and with Au(en)2Cl3 as precursor was supported on Al-PILM(Au/Al-PILM),whose catalyst activity was investigated by CO oxidation reaction.The results showed that:(1)The large amount of impurities were removed from the Ca-montmorillonite by traditional wet sedimentation separation process for a natural bentonite resource from Yanshan county in Yunnan province,and the content of montmorillonite was improved notably.But the characteristic diffraction peaks of cristobalite was still existed strongly,which indicated that the cristobalite could not be removed from Ca-montmorillonite structure by the traditional physical purified method.(2)The swelling capacity of modified montmorillonite was used as evaluated index in the experiment of single factor and orthogonal,and the optimum conditions of sodium modification was obtained.The basal spacing of the purified montmorillonite and sodium-modified montmorillonite were characterized respectively by X-ray diffraction.The results showed that NaF was better than the traditional modification reagents NaCl on the sodium modification.The Na-Montmorillonite catalytic support with 1.28 nm of basal spacing and 87.3 mmol/l00g of the cation exchange capacity was obtained by using 6%NaF as modification reagents to modify the purified Ca-montmorillonite at 60℃ for 3h,with 10%of the concentration suspension of purified clay.(3)The Al-PILM was synthesized with the Na-montmorillonite as the matrices,and the basal spacing of the Na-montmorillonite and Al-PILM were characterized respectively by X-ray diffraction.The results showed the basal spacing of d001 reflection of the Na-montmorillonitewas shifted from 1.28nm to 1.83nm of the Al-PILM,which confirmed the successful modification of Na-montmorillonite by pillaring.(4)The Al-PILM was characterized by N2 adsorption/desorption,the results showed that the specific surface area and micropore volume of Al-PILM increased largely by pillaring,and the value of specific surface area and micropore volume increased from 56.15m2/g and 0.00163cm3/g of Na-montmorillonite to 275.76m2/g and 0.07149cm3/g of Al-PILM respectively.The Al-PILM was characterized by TG-DSC the results showed that the thermal stability of Al-PILM was better than Namontmorillonite,the 2:1 layered model structure of Al-PILM could be steady existed before 917℃.It showed that Al-PILM was formed with abundant specific surface area and micropore volume,the high thermal stability material by pillaring,which was met the all quality indexs of catalyst or catalytic support.(5)The liquid phase catalytic isomerization of α-pinene over alumina-pillared montmorillonite was investigated,and the influence of reaction temperature,reaction time and amount of the catalyst on the conversion of α-pinene were discussed systematically,and the optimum reaction conditions for isomerization of α-pinene over alumina-pillared montmorillonite were obtained:reaction temperature was 100℃,reaction time was 3h,and the mass ratio of catalyst to α-pinene was 1/10.The result showed that alumina-pillared montmorillonite exhibited a high catalytic activity for the isomerization of α-pinene,under these optimum conditions,the conversion ofα-pinene and selectivities for camphene and limonene could reach to 97.4%,33.1%and 30.3%respectively.(6)Au/Al-PILM was prepared using Au(en)2Cl3 as precursor was supported on Al-PILM,whose catalyst activity was investigated by CO oxidation reaction,and the influence of calcination temperature,supported temperature and different support on the conversion of CO were discussed.The results showed that Au/Al-PILM exhibited a high catalytic activity for the oxidation reaction of CO,and 100%conversion of CO was achieved at reaction temperature 250℃ using the Al-PILM as carrier at supported temperature was 60℃,and at the calcination temperature 450℃ for 1h.