The zonary model of thermal transformations of alkali metal triphosphates

Prodan, E. A.; Lesnikovich, L. A.

doi:10.1016/0040-6031(92)85202-7

Cited by 4 publications

(2 citation statements)

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“…(5) Carstensen, J. of transition zones are set up perpendicular to the solid surface. 19 Dehydration occurs in a series of steps spread through these zones from the surface to the hexahydrate core, with one step constituting hydrolysis. Then, in the latter stage of the dehydration, pyro-and orthophosphate recondense to yield Form II sodium tripolyphosphate.…”

Section: Introductionmentioning

confidence: 99%

“…The hydrolysis of sodium tripolyphosphate (Na 5 P 3 O 10 = NaTPP) to pyro- and orthophosphate is well-known in the detergent industry and is regularly accounted for in the design of industrial processes. , In the dehydration of the solid sodium tripolyphosphate hexahydrate, a series of transition zones are set up perpendicular to the solid surface . Dehydration occurs in a series of steps spread through these zones from the surface to the hexahydrate core, with one step constituting hydrolysis.…”

Section: Introductionmentioning

confidence: 99%

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Solid-State Hydrolysis of Calcium Tripolyphosphate Scales

and

Carnali

2000

Langmuir

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Precipitation of calcium tripolyphosphate (CaTPP) from strongly supersaturated solution is accompanied by tripolyphosphate hydrolysis if the bulk Ca/TPP mole ratio is in excess of about 2. Along with the tendency for hydrolysis, a change in the crystal habit from crystalline to amorphous is observed beyond this bulk ratio. The composition of the material changes as well from mainly Ca2NaP3O10 at a 2:1 Ca/TPP bulk ratio to Ca5(P3O10)2 at an 8:1 bulk ratio, though the water of hydration contents are similar. The crystallinity change is reflected in the IR and solid-state 31 P NMR spectra, but, beyond these expected differences, the amorphous samples also appear to have a larger fraction of more mobile crystal water. Through a series of sequential experiments, it was identified that hydrolysis of these materials mainly occurs via a mechanism consisting of precipitation of CaTPP followed by hydrolysis of the precipitate. Bulk water does not play a critical role in the hydrolysis nor does surface adsorbed water, to the extent that it can clearly be differentiated from the crystal or bound water. Kinetic studies of the hydrolysis of the 8:1 material showed that its solid-state reaction rate (7.1 × 10 -3 min -1 at 70 °C) is 2 orders of magnitude higher than that of NaTPP. The hydrolysis mechanism is found to lay midway between first order and diffusion controlled, leading us to suspect that loosely bound water within the crystal lattice constitutes the diffusing species. Although the facile hydrolysis at the stronger supersaturation can possibly be explained in terms of the higher Ca/TPP ratio in the precipitate leading to destabilization of the P-O-P bond, the observed trends seem to rather suggest the diffusion of crystal water within the strongly distorted crystal lattice as the dominant factor.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%