Aki Hayashi

Adsorption of formaldehyde by polyamine-intercalated α-zirconium phosphate

Gaseous formaldehyde adsorption mechanism of diethylenetriamine- and pentaethylenehexamine-intercalated α-zirconium phosphate was demonstrated to be self oxidation-reduction of formaldehyde, that is, Cannizzaro reaction, in the interlayer space as evidenced by XRD and solid-state NMR. This fact suggests that these intercalation compounds can be used as a reaction field of self oxidation-reduction of formaldehyde, and also as adsorbents of formaldehyde, which causes sick-house syndrome.

Unusual adsorption mechanism for carboxylic acid gases by polyamine-intercalated α-zirconium phosphate

The adsorption mechanism of gaseous carboxylic acid by diethylenetriamine- or pentaethylenehexamine-intercalated α-zirconium phosphate was examined in detail using XRD and solid-state 13C and 31P NMR. The adsorption of acetic acid, propanoic acid, and butyric acid resulted in the co-intercalation of the carboxylic acid molecules into polyamine-intercalated α-zirconium phosphate to expand their interlayer distance by 0.64–0.97 nm. In the case of formic acid, its adsorption induced the rearrangement of the polyamine molecules within the interlayer space.

Adsorption of Carboxylic Acids by Diethylenetriamine Intercalation Compound of α-Zr(HPO4)2 · H2O

Abstract Two kinds of diethylenetriamine (2E3A) intercalation compounds of α-zirconium phosphate with different interlayer distances could be obtained by regulating the reaction time and temperature. Phase I (d = 10.2 Å) slowly transforms to Phase II(d = 15. 8 Å) with transformation enthalpy of 30 kJ-mol−1 in 2E3A aqueous solution. The conformation of 2E3A in Phase I and Phase II were confirmed to be bent and all trans (straight) forms by31P MAS NMR and XRD measurements. Two phases have different adsorption behavior for gaseous carboxylic acids. Phase II can adsorb considerable amount of carboxylic acids whereas Phase I adsorb a little.

Intercalation of α,ω-Alkanediamines in Layered Aluminium Dihydrogen Triphosphate Dihydrate

Intercalation of α,ω-alkanediamines, NH2(CH2)nNH2 (n = 3−10), into layered aluminium dihydrogen triphosphate dihydrate, AlH2(P3(O10.2H2O, was investigated by XRD, DTA-TG, elemental analysis, and solid-state 31P, 13C and 27Al NMR. α,ω-Alkanediamines are intercalated to form a monomolecular layer in the interlayer region, in which the alkanediamines incline at 57 ± 5° to the phosphate layers, whereas n-alkylamines form a bilayer structure with the same inclination angle. Two amino groups in an α,ω-alkanediamine molecule bridge the layered sheets of phosphates.

Mixing Acid Salts and Layered Double Hydroxides in Nanoscale under Solid Condition

The immobilization of potassium sorbate, potassium aspartate and sorbic acid in layered double hydroxide under solid condition was examined. By simply mixing two solids, immobilization of sorbate and aspartate in the interlayer space of nitrate-type layered double hydroxide, so called intercalation reaction, was achieved, and the uptakes, that is, the amount of immobilized salts and the interlayer distances of intercalation compounds were almost the same as those obtained in aqueous solution. However, no intercalation was achieved for sorbic acid. Although intercalation of sorbate and aspartate into chloride-type layered double hydroxide was possible, the uptakes for these intercalation compounds were lower than those obtained using nitrate-type layered double hydroxide. The intercalation under solid condition could be achieved to the same extent as for ion-exchange reaction in aqueous solution, and the reactivity was similar to that observed in aqueous solution. This method will enable the encapsulation of acidic drug in layered double hydroxide as nano level simply by mixing both solids.

The physicochemical properties of ammonium-exchanged aluminum dihydrogen triphosphate dihydrate

Ammonium-exchanged aluminum dihydrogen triphosphate dihydrate (NH4 /AlP) can be obtained by the reaction of layered aluminum dihydrogen triphosphate dihydrate and ammonia solution at 8◦C. NH4 /AlP shows two phases with different interlayer distances (8.9 Å for phase I and 11.9 Å for phase II). Phase II irreversibly transformed to phase I under the relative humidity of 32%. When phase I was kept under the relative humidity of 0%, the interlayer distance decreased to 7.9 Å. 31P MAS NMR spectra and elemental analysis suggested it to be anhydrous NH4 /AlP. 1 Phase I can adsorb considerable amounts of gaseous carboxylic acids and formaldehyde at 40◦C as shown in Figure 1. The amount of adsorption for anhydrous NH4 /AlP was similar as that of phase I and was greater than that of phase II.

Complex Formation with Layered Double Hydroxides for the Remediation of Hygroscopicity

Layered double hydroxides (LDHs) have been used commercially as antacids, to stabilize drugs, to allow the controlled release of incorporated drugs, and to act as drug carriers to reduce drug accumulation within the body. Several types of LDH were investigated: nitrate type (LDH-NO3); chloride type (LDH-Cl); and carbonate type (LDH-CO3). Each type was added to an aqueous or methanol (MeOH) solution containing a drug (pravastatin or nateglinide). With pravastatin sodium, the interlayer distance expanded after reaction with LDH-NO3 and LDH-Cl in aqueous solution. In contrast, the interlayer distance of LDH-CO3 increased in methanol with nateglinide. Each drug was intercalated into the interlayer space of LDH by ion exchange. The hygroscopicity of the drug substances, complexes, and physical mixtures were determined at 70% relative humidity. Increases in weight (%) of the complexes were less than those of the physical mixtures, which demonstrates that hygroscopicity was reduced upon complexation with LDH due to the layer of LDH over the drugs.

Formaldehyde Adsorption Mechanism of Diethylenetriamine Intercalated α-Zirconium Phosphate

In the course of our study on the synthesis of new type of gas adsorbent based on layered phosphate, diethylenetriamine (2E3A) intercalated α-Zr(HPO4)2 ·H2O (α-ZrP) can adsorb considerable amount of carboxylic acid.1 In this work, the adsorption mechanism of formaldehyde gas in 2E3A intercalated α-ZrP was examined by XRD, and solid-state NMR using formaldehyde (13C, 99%) aqueous solution (70%) as a source of formaldehyde vapor. In addition to large signal due to formaldehyde at 70 ppm, other extra signals appear around 40 and 165 ppm. Formaldehyde is known to occur self oxidation-reduction, called Cannizzaro reaction, catalyzed by strong base in aqueous solution as follows,