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Synthesis of zeolites in anhydrous glycol systems
H.G. Karge and J. Weitkamp (Eds.) Zeolite Science 1994: Recent Progress and Discussions Studies in Surface Science and Catalysis, Vol. 98 9 1995 Elsevier Science B.V. All rights reserved.
42
SYNTHESIS OF ZEOLITES IN ANHYDROUS GLYCOL SYSTEMS N.B. Milestone', S.M. Hughes and P.J. Stonestreet Industrial Research Limited, PO Box 31-310, Lower Hutt, New Zealand Summary- Sodalite and cancrinite have been synthesized in non aqueous diol systems containing silica, aluminium isopropoxide and sodium hydroxide. Pure sodalite is formed only with 1,2-ethane-diol while other 1,3-diols form predominantly cancrinite. Introduction - Silica sodalite was first synthesized by Bibby and Dalela using a non aqueous route based on alkaline 1,2-ethane-dioi. Later worklb defined the region over which synthesis was possible. Attempts to prepare silica sodalite using other alcohols and diols have not proved successful. Laine et a/. 2 prepared a crystalline potassium trisdiolatosilicate salt in which the silicon was penta-coordinate. The structure of the monomeric sodium salt was determined by Gainsford et al. 3 This penta-coordinated silicon species was shown to be an intermediate in the synthesis route to silica sodalite by Carr eta/. 4 Attempts to prepare other trisdiolato salts directly from silica and alkaline diol solutions have not proved possible except for 1,2-ethane-and 1,2-propane-diol although Kemmitt and Milestone s were able to synthesize several of the other species by ligand exchange of tetraethoxysilane and determine their NMR spectra. Our work has shown that continued heating of the sodium trisdiolatosilicate salt in a minimum amount of 1,2-ethane-diol slowly converts to silica sodalite at temperatures over 150~
Addition of only
a trace of aluminium isopropoxide converts all the salt to sodalite with 24 hours.
Experimental - Pure silica (Aerosil) was heated at 170~ in sealed vessels in a range of anhydrous diols containing sodium hydroxide and varying concentrations of aluminium isopropoxide. The products were examined after 2.5 weeks heating.
Results and Discussion - Pure silica sodalite is formed only with both 1,2-ethane-dioi and 1,2-propanediol provided the Na:Si ratio exceeds 0.5 although Na2Si20s is also formed with the latter. Only a range of different forms of sodium silicates are found with the other diols tested. Additions of small amounts of aluminium as the isopropoxide allows the formation of crystalline aluminosilicates. While 1,2-ethanediol always gives sodalite, 1,3-propane-diol and 1,3-butane-diol consistently produce cancrinite for Si/Ai ratios of 2.5 to 15. At Si/AI ratios of 5 or greater, reactions in 1,2-propane-diol and 2,2-dimethyl-1,3propane-diol tend to produce sodalite while at lower ratios, cancrinite is formed. For all diols other than 1,2-ethane-diol, as the Si/AI is increased, various amounts and forms of sodium silicates are produced. The various crystalline products are presented in Table 1. In pure silica sodalite synthesized in 1,2ethane-diol, one glycol unit per sodalite cage is incorporated. The size of the cage is such that the larger
43
TABLE 1 Crystalline products formed with reactions of glycols with silica and aluminium isopropoxide Si/AI DioI
2.5
1,2-ethane 1,2-propane
sodalite sodalite
1,3-propane
cancrinite sodalite cancrinite sodalite sodalite cancrinite sodalite
1,3-butane 2,3-butane 1,4-butane 2,2-dimethyl 1,3-propane
5
sodalite sodalite cancrinite cancrinite sodalite cancrinite sodalite cancrinite sodalite
10
sodalite cancrinite ~ Na2Si205 sodalite cancrinite cancrinite Na2Si03
~ Na2Si20s
oo
sodalite sodalite ~ Na2Si2Os ,13Na2Si205 ~ Na2SiO3 Na2SiO3 Na2SiO3 J3Na2Si20s
Reaction mixture is 1.5g and SiO2 2.6g NaOH (dry pellet) mixed with lOg of diol and the appropriate amount of Al(OiPr)3 sealed in nitrogen and heated to 170~ for 2.5 weeks.
glycols are unable to pack into the space whereas in the cancrinite structure, the large channel can incorporate the glycol units. Thermogravimetry indicates approximately 1.5 diol per unit cell is retained for the cancrinite products. For the sodalite structures formed with the larger diols, thermogravimetry indicates there is only a small amount of diol present, possibly associated with faults.
It is not
incorporated in the sodalite cages. Only 1,2-ethane- and 1,2-propane-diols are able to initially dissolve the silica to form the penta-coordinated silicon precursor explaining sodalite formation with the pure silica mixtures. Addition of aluminium which readily forms diolato complexes6 is required to allow other glycols to form complexes to provide the nucleation needed for formation of aluminosilicate structures. Clearly the mechanism for formation of these species proceeds by a through solution mechanism via silicon and aluminium complexes. Diethylene and triethylene glycols are unable to form these complexes and do not form crystalline products. REFERENCES
la lb 2
D.M. Bibby and M. Dale, Nature (London) (1985), 37, 157. D.M. Bibby, N.I. Baxter, D. Grant-Taylor and L.M. Parker (1989), ACS Symp Series, p209. R.M. Laine, K.Y. Blohawiak, T.R. Robinson, M.L. Hoppe, P. Nardi, J. Kampf and J. Uhm, Nature (1991), 353, 642. G.J. Gainsford, T. Kemmitt and N.B. Milestone, submitted to Acta Cryst C. B. Heireros, S.W. Carr and J. Klinowski, submitted to Science. T. Kemmitt and N.B. Milestone, submitted to Aust J Chem Soc. T. Kemmitt, unpublished results.
42
SYNTHESIS OF ZEOLITES IN ANHYDROUS GLYCOL SYSTEMS N.B. Milestone', S.M. Hughes and P.J. Stonestreet Industrial Research Limited, PO Box 31-310, Lower Hutt, New Zealand Summary- Sodalite and cancrinite have been synthesized in non aqueous diol systems containing silica, aluminium isopropoxide and sodium hydroxide. Pure sodalite is formed only with 1,2-ethane-diol while other 1,3-diols form predominantly cancrinite. Introduction - Silica sodalite was first synthesized by Bibby and Dalela using a non aqueous route based on alkaline 1,2-ethane-dioi. Later worklb defined the region over which synthesis was possible. Attempts to prepare silica sodalite using other alcohols and diols have not proved successful. Laine et a/. 2 prepared a crystalline potassium trisdiolatosilicate salt in which the silicon was penta-coordinate. The structure of the monomeric sodium salt was determined by Gainsford et al. 3 This penta-coordinated silicon species was shown to be an intermediate in the synthesis route to silica sodalite by Carr eta/. 4 Attempts to prepare other trisdiolato salts directly from silica and alkaline diol solutions have not proved possible except for 1,2-ethane-and 1,2-propane-diol although Kemmitt and Milestone s were able to synthesize several of the other species by ligand exchange of tetraethoxysilane and determine their NMR spectra. Our work has shown that continued heating of the sodium trisdiolatosilicate salt in a minimum amount of 1,2-ethane-diol slowly converts to silica sodalite at temperatures over 150~
Addition of only
a trace of aluminium isopropoxide converts all the salt to sodalite with 24 hours.
Experimental - Pure silica (Aerosil) was heated at 170~ in sealed vessels in a range of anhydrous diols containing sodium hydroxide and varying concentrations of aluminium isopropoxide. The products were examined after 2.5 weeks heating.
Results and Discussion - Pure silica sodalite is formed only with both 1,2-ethane-dioi and 1,2-propanediol provided the Na:Si ratio exceeds 0.5 although Na2Si20s is also formed with the latter. Only a range of different forms of sodium silicates are found with the other diols tested. Additions of small amounts of aluminium as the isopropoxide allows the formation of crystalline aluminosilicates. While 1,2-ethanediol always gives sodalite, 1,3-propane-diol and 1,3-butane-diol consistently produce cancrinite for Si/Ai ratios of 2.5 to 15. At Si/AI ratios of 5 or greater, reactions in 1,2-propane-diol and 2,2-dimethyl-1,3propane-diol tend to produce sodalite while at lower ratios, cancrinite is formed. For all diols other than 1,2-ethane-diol, as the Si/AI is increased, various amounts and forms of sodium silicates are produced. The various crystalline products are presented in Table 1. In pure silica sodalite synthesized in 1,2ethane-diol, one glycol unit per sodalite cage is incorporated. The size of the cage is such that the larger
43
TABLE 1 Crystalline products formed with reactions of glycols with silica and aluminium isopropoxide Si/AI DioI
2.5
1,2-ethane 1,2-propane
sodalite sodalite
1,3-propane
cancrinite sodalite cancrinite sodalite sodalite cancrinite sodalite
1,3-butane 2,3-butane 1,4-butane 2,2-dimethyl 1,3-propane
5
sodalite sodalite cancrinite cancrinite sodalite cancrinite sodalite cancrinite sodalite
10
sodalite cancrinite ~ Na2Si205 sodalite cancrinite cancrinite Na2Si03
~ Na2Si20s
oo
sodalite sodalite ~ Na2Si2Os ,13Na2Si205 ~ Na2SiO3 Na2SiO3 Na2SiO3 J3Na2Si20s
Reaction mixture is 1.5g and SiO2 2.6g NaOH (dry pellet) mixed with lOg of diol and the appropriate amount of Al(OiPr)3 sealed in nitrogen and heated to 170~ for 2.5 weeks.
glycols are unable to pack into the space whereas in the cancrinite structure, the large channel can incorporate the glycol units. Thermogravimetry indicates approximately 1.5 diol per unit cell is retained for the cancrinite products. For the sodalite structures formed with the larger diols, thermogravimetry indicates there is only a small amount of diol present, possibly associated with faults.
It is not
incorporated in the sodalite cages. Only 1,2-ethane- and 1,2-propane-diols are able to initially dissolve the silica to form the penta-coordinated silicon precursor explaining sodalite formation with the pure silica mixtures. Addition of aluminium which readily forms diolato complexes6 is required to allow other glycols to form complexes to provide the nucleation needed for formation of aluminosilicate structures. Clearly the mechanism for formation of these species proceeds by a through solution mechanism via silicon and aluminium complexes. Diethylene and triethylene glycols are unable to form these complexes and do not form crystalline products. REFERENCES
la lb 2
D.M. Bibby and M. Dale, Nature (London) (1985), 37, 157. D.M. Bibby, N.I. Baxter, D. Grant-Taylor and L.M. Parker (1989), ACS Symp Series, p209. R.M. Laine, K.Y. Blohawiak, T.R. Robinson, M.L. Hoppe, P. Nardi, J. Kampf and J. Uhm, Nature (1991), 353, 642. G.J. Gainsford, T. Kemmitt and N.B. Milestone, submitted to Acta Cryst C. B. Heireros, S.W. Carr and J. Klinowski, submitted to Science. T. Kemmitt and N.B. Milestone, submitted to Aust J Chem Soc. T. Kemmitt, unpublished results.