Julio Rodríguez

Synthesis and characterization of a novel layered titanium phosphate

A novel metastable layered titanium phosphate has been synthesized by the treatment of layered titanates (Na 2 Ti 3 O 7 and Na 4 Ti 9 O 2 0) with 1–2 M phosphoric acid solution at 120–150 °C. Based on the data of 31 P MAS NMR and IR spectroscopy, x-ray powder diffraction, and thermal and elemental analysis, the formula Ti 2 O 3 (H 2 PO 4 ) 2 · 2H 2 O was assigned to the novel compound. The layered nature of the compound was confirmed from n -alkylamine intercalation and the ion exchange behavior toward alkali, alkaline earth, and some transition metal ions.

Formation of crystalline titanium(IV) phosphates from titanium(III) solutions

Crystalline phases of titanium (IV) phosphate have been obtained from titanium(III) chloride in phosphoric acid solutions. The {alpha}-titanium phosphate synthesis is possible at low temperature (60--80 C). {gamma}-Titanium phosphate is obtained by reflux with very concentrated phosphoric acid in 3--5 hours by oxidation with O{sub 2}. The influence in these reactions of several factors (concentration of reagents, molar ratio P:Ti in the reaction mixture, temperature and reaction) was studied. The {alpha}-titanium phosphate formation takes place in several steps through the sequential formation of amorphous titanium(IV) phosphate, {gamma}-titanium phosphate and/or a semicrystalline titanium(IV) hydroxophosphate, Ti(OH){sub 2}(HPO{sub 4}){center_dot}H{sub 2}O.

Intercalation of n-alkylamines by lamellar materials of the α-zirconium phosphate type

Abstract n-Alkylamines have been intercalated by α-titanium phosphate by exposing the solid to the vapour of the amines. The formula of the intercalation compounds is Ti(OPO 3 ) 2 .2C n H 2n+1 NH 3 .H 2 O (n=1–9). X-ray diffraction patterns and information on the disposition of the guests within the interlayer region have been derived. The n-alkylamines form a bimolecular film in which the carbon chains incline at roughly 59° to the titanium phosphate layers. The terminal amino groups are protonated by the -POH groups of the host. The results obtained are discussed together with the extracted from literature referring to the n-alkylamines intercalation in α-zirconium phosphate and α-tin phosphate.

Hydrolytic stability of amorphous titanium and zirconium phosphates

Abstract Spherically granulated amorphous titanium and zirconium hydroxophosphates, Ti(OH)P and Zr(OH)P, with different molar P:M(IV) ratio varying in a range of (0.51.1):1, have been synthesized and their hydrolytic behavior has been studied as a function of the chemical composition of the material, type of exchangers sale form, pH and concentration of electrolyte, type of electrolyte, temperature of model solution and some other factors. It was found that the hydrolysis of Ti(OH)P and Zr(OH)P in neutral and alkaline media is a complex process occurring by nucleophilic mechanism of phosphate group substitution. The governing factors are steric hindrances for nucleophilic attack and the value of the effective positive charge on titanium and zirconium atoms.

Synthesis of phosphate–phenylphosphonates of titanium(IV) and their n-butylamine intercalates

Layered compounds of general formula Ti(PhPO3)x(HOPO3)2 –x·yH2O have been synthesized and characterized by X-ray powder diffraction, IR spectroscopy, TG and 31P magic angle spinning NMR spectroscopy. Different sources for the tetravalent metal in the synthetic process have been studied. The overall α-layered structure type is maintained while the ratio of phosphate to phenylphosphonate incorporated into the mixed derivative varies. The intercalation behaviour of mixed derivatives toward n-butylamine was also studied. The synthetic process shows kinetic control as a function of the tetravalent metal source; at low titanium(IV) concentration a mixture of products is obtained (phosphate + phosphonate) rather than a phosphate–phenylphosphonate single phase.

Effect of the method of preparation on the surface area and porosity of titanium(IV) phenylphosphonate

By using three synthetic procedures we have prepared layered α-titanium phenylphosphonate samples with different degrees of crystallinity and distinct textural parameters. The solids were prepared by reacting phenylphosphonic acid with different titanium compounds used as precursors. The materials obtained have a high thermal stability as shown by TGA measurements.An analysis of nitrogen adsorption-desorption isotherms on the resulting materials allowed determination of the corresponding specific surface area and porous texture. The N2-isotherms correspond to type IV of the BDDT classification with hysteresis loops of the type H-1. The materials are essentially mesoporous and it was not detected any mensurable microporosity. Crystallinity, BET surface areas and porosity are markedly dependent on the preparation procedure.

Textural properties of α-titanium(IV) phenylphosphonate: influence of preparation conditions

Abstract Layered α-titanium(IV) phenylphosphonate can be prepared with a broad variation in surface area and porosity. Several sources for tetravalent titanium ion and different synthetic procedures have been studied. The solids were characterized by powder X-ray diffraction (XRD), thermogravimetric (TG) analysis, IR and 31 P magic angle spinning (MAS) NMR spectroscopies, N 2 adsorption–desorption isotherms, and scanning electron microscopy (SEM). The materials obtained have a high thermal stability as shown by TG analysis. N 2 adsorption–desorption isotherms of the solids correspond to type IV of the BDDT classification and show hysteresis loops of type H-3, characteristic of solids with slit-shaped pores. The materials are essentially mesoporous, and any mensurable microporosity was not detected. BET surface areas, porosity, and crystallinity are markedly dependent on the preparation procedure.

Intercalation ofn-alkylamines into α-titanium phosphate from aqueous solutions

The intercalation reactions betweenn-alkylamines and α-titanium phosphate in aqueous media have been investigated. The compounds with the maximum intercalation have the formula α-Ti(HOPO3)2 · 2 CnH2n+1NH2 · H2O (n=1–10). Defined crystalline phases with lower amine content are described, the general formula being α-Ti(HOPO3)2 ·mCnH2n+1NH2 ·pH2O (m=1.0 1.3, 1.5, 1.7). Whenm=1.0 then-alkylamines form a monomolecular layer. Whenm>1.0 the layer is bimolecular. The inclination angle and the packing density of then-alkylamines in the interlayer space is determined.

Polyhydrated phases in the exchange of H+ and K+ in α-titanium phosphate

The exchange of H+ by K+ in α-titanium phosphate, Ti(HPO4)2·H2O, was studied. The exchange isotherm and the hydrolysis and titration curves were obtained, and the evolution of the material was followed by X-ray diffraction. The existence of partially substituted phases was not detected. Phases saturated in potassium and highly hydrated, Ti(KPO4)2·3H2O (interlayer distance 10.4 A) and Ti(KPO4)2·2H2O (9.6 A), were obtained. The experimental results are explained by taking account of the structures of the materials.

SEPARATION OF COBALT(II) AND NICKEL(II) IONS FROM ACID AQUEOUS SOLUTIONS BY Co IT ION-EXCHANGE INTO γ-TITANIUM PHOSPHATE

ABSTRACT The Co2+-2H+, Ni2+-2H+, and Co2+-Ni2+-2H+ ion exchange processes into γ-Ti(H2PO4)(PO4)2H2O were studied. Exchange isothenns and titration curves were obtained. Monometallic half ion exchange phases were formed by using MC2+HCl (M=Co,Ni) solutions. Equilibrium constants, free energy, enthalpy, and entropy of the Co2+-2H2+ ion exchange reaction were determined. In (Co,Ni)Cl2 solutions, bimetallic a half ion exchange substitution solid solution is detected. Equilibrium constant of the Co2+-Ni2+ substitution process in the γ-Ti(CoxNi0.5−x.HPO4)(PO4)nH2O phase at 85°C was determined. In (Co,Ni)Cl2+HCl solutions, total separation of Co2+ and Ni2+ is obtained.