An open framework microporous rare-earth silicate ion exchange composition comprised of [SiO4/2] tetrahedra, [MO6/y]z− octahedra, and [M′O6/y]z− octahedral units having one of two novel frameworks, depending on the choice of the rare-earth cation, identified by their empirical formulas on an anhydrous basis of:
- Ar+pMs+1-xM′t+xSinOm
- where A is an exchangeable cation selected from the group consisting of alkali metals, alkaline earth metals, hydronium ion, ammonium ion, and mixtures thereof, “r” is the weighted average valence of A and varies from 1 to 2, “p” is the mole ratio of A to total metal (total metal=M+M′) and varies from about 2 to about 5, M is at least one element selected from the group of rare-earth elements, “'s” is the weighted average valence of M and varies from 3 to 4, “(1-x)” is the mole fraction of total metal that is M and varies from 0.01 to 1, M′ is a framework metal having a valence of +2, +3, +4, or +5, “t” is the weighted average valence of M′ and varies from 2 to 5, “x” is the mole fraction of total metal that is M′ and varies from 0 to 0.99, “n” is the mole ratio of Si to total metal and has a value of about 5 to about 10, and “m” is the mole ratio of O to total metal and is given by
- m
- =
- [
- (
- r
- ·
- p
- )
- +
- (
- s
- ·
- (
- 1
- -
- x
- )
- )
- +
- (
- t
- ·
- x
- )
- +
- (
- 4
- ·
- n
- )
- ]
- 2
- and when M is Ho, Er, Tm, Yb, Lu, Y or Sc, the material is characterized by the X-ray diffraction pattern having at least the d-spacings and relative intensities set forth in Table A:
- TABLE A
- 2-Θ
- d(Å)
- I/I0%
- 6.85-6.60
- 12.89-13.39
- vs
- 12.99-12.75
- 6.81-6.94
- m
- 13.74-13.51
- 6.44-6.55
- m
- 15.13-14.85
- 5.85-5.96
- w-m
- 18.87-18.47
- 4.70-4.80
- w-m
- 19.24-18.83
- 4.61-4.71
- w-m
- 19.67-19.36
- 4.51-4.58
- w-m
- 23.97-23.71
- 3.71-3.75
- w
- 24.92-24.64
- 3.57-3.61
- w-m
- 25.88-25.58
- 3.44-3.48
- w
- 27.08-26.67
- 3.29-3.34
- w
- 28.22-27.86
- 3.16-3.20
- w
- 29.26-28.97
- 3.05-3.08
- w
- 29.76-29.55
- 3.00-3.02
- w-m
- 30.38-30.06
- 2.94-2.97
- w-m
- 30.92-30.48
- 2.89-2.93
- w-s
- 31.59-31.36
- 2.83-2.85
- w
- 33.67-33.41
- 2.66-2.68
- w-m
- 49.50-49.21
- 1.84-1.85
- w-m
- 52.88-52.55
- 1.73-1.74
- w-m
- and when M is La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, or Dy, and the material is characterized by the X-ray diffraction pattern having at least the d-spacings and relative intensities set forth in Table B:
- TABLE B
- 2-Θ
- d(Å)
- I/I0%
- 11.71-11.45
- 7.55-7.72
- m
- 12.56-12.30
- 7.04-7.19
- w-m
- 13.53-13.26
- 6.54-6.67
- m-vs
- 13.83-13.59
- 6.40-6.51
- m-vs
- 17.14-16.87
- 5.17-5.25
- m-vs
- 21.03-20.79
- 4.22-4.27
- w-m
- 21.39-21.14
- 4.15-4.20
- m
- 23.39-23.21
- 3.80-3.83
- w-m
- 24.78-24.57
- 3.59-3.62
- w-m
- 26.59-26.35
- 3.35-3.38
- vs
- 27.00-26.83
- 3.30-3.32
- w-s
- 27.77-27.51
- 3.21-3.24
- m-vs
- 28.04-27.86
- 3.18-3.20
- w-m
- 28.49-28.31
- 3.13-3.15
- w-m
- 29.86-29.66
- 2.99-3.01
- w-m
- 34.60-34.06
- 2.59-2.63
- m
- 35.31-34.88
- 2.54-2.57
- m
- 36.34-36.04
- 2.47-2.49
- w-m
- 39.67-38.61
- 2.27-2.33
- w
- 45.31-44.83
- 2.00-2.02
- m.
- wherein the ion exchange composition is obtained using a process where a rare-earth metal precursor is first dissolved in an acidic solution prior to addition of a basic silicate solution.