On the textural and morphological properties of crystalline and amorphous α-tin phosphate

Abstract

The synthesis as well as the textural and morphological properties of microporous amorphous and crystalline tin(IV) phosphate, Sn(HPO 4 ) 2 Á H 2 O (a-SnP), prepared by the sol-gel technique are presented. Tin tetra-tertamyloxide, Sn(OAm t ) 4, is first synthesized and a solution of this reactant in tert-amyl alcohol reacts with orthophosphoric acid to obtain in due course both the amorphous and the crystalline a-SnP forms. The N 2 sorption isotherm of the crystalline powder attains a hysteresis cycle proper of lamellar void structures over a long interval of relative pressures. The differential t-plot of this isotherm reveals the presence of two kinds of supermicropores: (i) a group of narrow slit-like pores with interlamellar void maxima arising at 0.712 nm, 0.774 nm, and 0.828 nm (these values suggest that the primary micropore filling of the interlayer space occurs with at most two layers of N 2 indicating likewise the non-rigid character of the plates that are delimiting each slit-like pore), (ii) a second microporous contribution that involves the cooperative micropore filling of wider slit-like pores having widths in the interval 1.01-1.57 nm. The narrow supermicropores are formed by the interlamellar spacing between a pair of elementary a-Sn-P sheets, while the wider micropores are delimited by solid plates that may be built by the parallel stacking of several elementary sheets of a-Sn-P. BET and t surface areas of the a-SnP specimen both correspond to 20.2 m 2 g À1 , therefore confirming adsorption on flat surfaces and the absence of voids other than supermicropores. Application of Bragg's equation to the X-ray diffraction pattern of the a-SnP sample renders an elementary interlayer distance of 0.80 nm that compares well with the theoretical 0.78 nm value. NMR spectra depict sharp crystalline peaks at À11.9 and À12.1 ppm for the amorphous and crystalline forms, respectively. SAXS measurements render crystallite sizes between 4 and 32 nm for the amorphous and crystalline forms. Crystalline a-SnP also depicts a wide-ranging fractal structure; this fact is confirmed by the consistent values of the surface fractal dimension obtained from application of the Neimark-Kiselev sorption approach over a long range of relative pressures.

Influence of hydrothermal, microwave and mechanochemical treatment of tin phosphate on porous structure and catalytic properties

“…Only HTT of the gel at 300 °C leads to the formation of crystalline tin phosphate. Thereby, reflexes at 2θ = 20.79 (0.427 nm), 26.40 (0.337 nm), 33.70 (0.266 nm) and 51.65°(0.177 nm) are attributed to tin hydrophosphate Sn (HPO 4 ) 2 •H 2 O [2,8,[41][42][43].…”

Layered microporous tin(iv) bisphosphonates

“…Thus, substitution of one hydrogen by tin(IV) in the local coordination of the phosphorus tetrahedron causes a shift in the 31 P spectrum of ca. 6-7 ppm, for tin(IV) phosphate, 29 and 8 ppm for tin(IV) phenylphosphonates. 30 On this basis, the weak resonance at ∼18 ppm is assigned to diprotonated phosphonate groups with only a weak, if any, Sn • • • OP interaction.…”

Simple and green route for preparation of tin phosphate catalysts by solid-state grinding for dehydration of glucose to 5-hydroxymethylfurfural (HMF)

“…35,39 As reported by Chen et al, the formation of a-Sn(HPO 4 ) 2 $H 2 O was conrmed by solid state reaction of SnCl 4 $5H 2 O and P 2 O 5 at lower temperatures.…”

“…34 A broad IR band appeared between 3300-3700 cm À1 is attributed to the asymmetric stretching vibrations of O-H groups, arising from the interlayer water and P-OH groups. 35,36 As such, it is expected that the intensity of the band at 3500 cm À1 increases with increasing the P/Sn mole ratio from 0.5 to 1. While further increasing P/Sn mole ratio from 1 to 1.5 and 2, however, there is a slight decrease in intensity of the peak of asymmetric stretching vibrations of O-H (the interlayer water and P-OH groups), which might be caused by the increase in crystallinity of the catalysts forming Sn-O-P structure with the increase of P/ Sn mole ratio, as evidenced by the XRD results (Fig.…”