Hiroyuki Nariai

Formation and catalytic characterization of various rare earth phosphates

Various rare earth phosphates [rare earth elements: R = La, Ce, Pr, Nd, Sm, Yb, and Y; phosphates: Monazite-type, Xenotime-type, Rhabdophane-type, and Weinshenkite-type orthophosphates RPO4, polyphosphate R(PO3)3, and ultraphosphate RP5O14] were synthesized by heating the mixtures of each rare earth oxide and diammonium hydrogenphosphate or phosphoric acid. The compositions of rare earth phosphates were determined by XRD, FT-IR, and TG–DTA. Catalytic properties were studied as one of properties of various rare earth phosphates. Specific surface areas of samples were measured by the BET method. Acid strengths and amounts of acidic sites were measured using several indicators by n-butylamine titration. Acidic properties were also confirmed by adsorption of ammonia. Various rare earth phosphates were characterized by catalytic activities on dehydration reaction of 2-propanol, cracking/dehydrogenation reaction of cumene, and isomerization reaction of butene. The characterization of catalysts was discussed with regard to type of rare earth elements, type of phosphates, and type of phosphorus resources.

Syntheses of various rare earth phosphates from some rare earth compounds

Abstract Each rare earth compound (rare earth element; R=La, Ce, and Nd, anion; oxide, carbonate, chloride, nitrate, sulfate, oxalate, and fluoride) was mixed with (NH4)2HPO4 or H3PO4 in P/R=1, 3, and 5, and heated in air. The resulting salts were analyzed by TG-DTA, XRD and FT-IR. CePO4·nH2O was not formed in the system of CeO2–H3PO4. However, this phosphate was synthesized in the systems of Ce(NO3)3·6H2O–(NH4)2HPO4, Ce2(CO3)3·8H2O–, CeCl3·7H2O–, and Ce(NO3)3·6H2O–H3PO4. The crystallinity of CePO4·nH2O was high in the systems of CeCl3·7H2O–, and Ce(NO3)3·6H2O–H3PO4. In P/Ce=1, formation of CeO2 was observed in the systems of Ce2(CO3)3·8H2O–, CeCl3·7H2O–, and Ce2(C2O4)3·9H2O–(NH4)2HPO4.

Determination of average chain length of linear polyphosphates by isotachophoresis

Abstract The relationship between the logarithm of the corrected average chain length, n c, of linear polyphosphates and the corrected zone length, Cc, obtained by isotachophoresis was found to be linear; however, an inflection was discernible at n c near 7 and the slope in the range of nc > 7 was higher than that for n c

Addition of Urea or Biuret on Synthesis of Rhabdophane-Type Neodymium and Cerium Phosphates

Urea or biuret was added to the thermal synthetic system of Rhabdophane-type neodymium and cerium phosphates. The mixture of a rare earth compound, a phosphorus compound, and an additive [CO(NH2)2 or NH(CONH2)2] was heated at 150°C or 300°C for 20 hr, and the thermal products were analyzed by the XRD, FT-IR, and BET methods. H3PO4 and (NH4)2HPO4 were used for phosphorus compounds, and for rare earth compounds, Nd2O3, Nd(NO3)3 · 6H2O, NdCl3 · 6H2O, Nd2(CO3)3 · 8H2O, CeO2, Ce(NO3)3 · 6H2O, CeCl3 · 7H2O, and Ce2(CO3)3 · 8H2O were used. Urea and biuret worked not only as a dispersing agent but also as a reactant. By the addition of biuret, the thermal products changed from cerium oxide to Rhabdophane-type cerium phosphate in the system using CeCl3 · 7H2O and (NH4)2HPO4. Addition of urea or biuret influenced the specific surface area of Rhabdophane-type neodymium and cerium phosphates. Furthermore, to increase the reactivity of the raw solid materials, mechanical treatment was performed. The mixture of diammonium hydrogenphosphate and a rare earth compound was ground with water and then heated. The influence of the addition of urea or biuret was also studied in these systems.

Separation and quantificaton of various phosphorous oxoacids containing two phosphorus atoms by isotachophoresis

Abstract The separation and determination of various phosphorus oxoacids containing two phosphorus atoms, such as 5 P—O—5 5 P, 3 P—O— 5 P and 3 P—O— 3 P salts, by capillary isotachopheresis was investigated. The potential unit (PU) values, which are indicators in quantitative analysis, increased in the order 3 P—O— 3 P 3 P—O— 5 P 5 P—O— 5 P. The calibration graphs for these ocoacids were linear in the range 0–10 −7 mole as phosphorus oxoacids. Separation times were approximately 20 min. The procedure was applied to the analysis of some crude products and to the study of the hydrolyticdegradation of some condensed phosphates. The amount f each phosphorus oxoacid could be determined rapidly and easly, and the results were in good agreement with those obtained by ion-exchange chromatography.

Preparation and thermal decomposition of hexa-ammonium tetraphosphate dihydrate(NH4)6P4O13·2H2O

Hexa-ammonium tetraphosphate dihydrate, (NH4)6P4O13·2H2O (HATP), was prepared by the hydrolysis of sodium cyclo-tetraphosphate with sodium hydroxide solution, followed by ion-exchange with ammonium. Thermal decomposition in static air was first carried out dynamically, at a heating rate of 5 K min-1 as used in thermal analysis (thermogravimetric-differential thermal analysis), and also isothermally. To examine the effect of humidity on the thermal decomposition, HATP was heated isothermally in streams of dry and humid air. The products were characterized by X-ray diffraction analysis and high-performance liquid chromatography–flow injection analysis. At 100°C, HATP was decomposed to mono- and triphosphates and to 2 mol diphosphate, and this was accelerated by humidity. Further degradation of the triphosphate to mono- and diphosphates took place slowly. The 2 mol diphosphate also decomposed slowly to 4 mol monophosphate. At temperatures above 150°C, the form I of ammonium polyphosphate (I-APP) was produced. I-APP was further hydrolysed by humidity to shorter-chain phosphates, such as mono-, di- and triphosphates.

Mechanochemical Decomposition of Dipotassium Peroxodisulfate by Dry Grinding

The mechanochemical decomposition of dipotassium peroxodisulfate by dry grinding was investigated by X-ray diffractometry, infrared spectrophotometry, electron spin resonance (ESR) spectrometry, and thermal and volumetric analyses. When dipotassium peroxodisulfate (K2S2O8) was ground, type I of K2S2O8 was transformed into type II and then into type III. With prolonged grinding, the O–O linkage in K2S2O8 was severed to produce KSO4· radicals, which reacted with a little moisture to give KHSO4.The mechanochemical decomposition of dipotassium peroxodisulfate by dry grinding was investigated by X-ray diffractometry, infrared spectrophotometry, electron spin resonance (ESR) spectrometry, and thermal and volumetric analyses. When dipotassium peroxodisulfate (K2S2O8) was ground, type I of K2S2O8 was transformed into type II and then into type III. With prolonged grinding, the O–O linkage in K2S2O8 was severed to produce KSO4· radicals, which reacted with a little moisture to give KHSO4.

On the Protonation Behavior of Several Simple Thiophosphate Anions

Stepwise protonation constants of several thiomonophosphate anions, that is, PSnO(4-n)3− (n= 1–4), have been determined (Table I). Since the rate of substitution of sulfur in thiomonophosphate anions for oxygen atom belonging to water molecule is fast, it is difficult to measure the protonation constants of these anions with conventional methods, so 31P NMR has been employed in this study. The successive protonation constants decrease with an increase in the number of sulfur atoms bound to center phosphorus atom. It has been revealed that the logarithms of the stabilities of the proton complexes of thiomonophosphate anions decreases “linearly” with an increase in the number of sulfur atoms which constitute the anions.

Novel reaction of linear phosphates with cyclo-phosphate in coacervate

Phosphorus pentaoxide, and various organic phosphorus compounds have been used as phosphorylating agents for organic and bioorganic compounds. Feldmann reported that phosphorylation of alkylamines1 and alcohols2 can be effected by the use of cyclo-triphosphate (P3m). Rabinowitz reported that amino acids (glycine and alanine) condense to form oligopeptides in the presence of polyphosphate or P3m. Recently, we found that some linear phosphates were characteristically formed through the decomposition processes of P3m in coacervate. The contents of various linear phosphates formed were affected by coexistent metal ions, the fraction of water/organic solvent, standing time, and so on. As a part of our developmental work on the application of P3m as a phosphorylating agent, the present authors investigated the reaction of P3m or other cyclo-phosphates with a metal ion and phosphate in coacervate. The formation mechanisms were also discussed from the viewpoint of ring-opening of cyclo-triphosphate and stability of the resulting product in coacervate. The favorable metal ions to ring-opening were Mg2+, Co2+, and Ni2+ ions. However, Mg2+ ion acted as a hydrolysis agent of cyclo-triphosphate and linear phosphates, resulted in the disappearance of selective formation of linear phosphates. The proposal reaction mechanisms in coacervate were shown as follows:

Inconsistency in the stability constants of inorganic polyphosphate anions determined by potentiometry and spectroscopy

Compared with cyclo -triphosphate anions, cyclo -tri- w -imidotriphosphate anions (Figure 1), cP 3 (NH) 3 3 m , form stable complexes with transition metal ions. Two experimental procedures, potentiometry and spectroscopy, have been applied to determine the stability constants of the complexes with Co 2+ , Ni 2+ , and Cu 2+ ions at 25;C and at I = 0.10 (NaClO 4 ). One-to-one (ML) complex formation has been assumed for the analyses. In the presence of sufficiently high concentration of metal ions, the log g 1 values determined by both methods are consistent with each other, whereas the log g 1 value determined by spectroscopy decreases with the decrease in metal ion concentration. This peculiar phenomenon cannot be explained by the presence of additional complexes, that is, ML 2 or M 2 L. One possible reasoning is agglomeration formation of ligand molecules mediated by countercations in aqueous solution.