A novel silver catalyst prepared by using superheated-steam as a heating medium for ethylene oxide production

A high-performance catalyst for the production of ethylene oxide by vapor phase oxidation of ethylene was developed and commercialized. High performance was achieved by the usage of a high surface area carrier with controlled pore distribution and surface acid-base properties, by the adoption of mixed amines to dissolve heat-decomposable silver salt, by the addition of effective additives, and by the introduction of a uniquely developed heat-treatment technology using superheated-steam as the heating medium. The catalyst thus prepared showed high activities because of homogeneously and highly dispersed silver and additive elements within the carrier. As a result, the reaction temperature could be lowered, which led to the improvement of not only the selectivity but also the catalyst life. Heat treatment with superheated-steam proved to have many advantages in producing high-performance catalysts and it is commercially favorable because it needs only a very short processing time.     

Magnetization measurements of Fe1−xCoxSi

Magnetization measurements are made in pulsed magnetic fields up to 200 kOe at 4.2 K and up to 100 kOe at various temperatures on the alloys Fe_1−xCo_xSi. In the paramagnetic region of x<0.05 or x0.7, we expected a metamagnet transition at high field but no remarkable change of magnetization is observed.     

Location of β-emitting12N in V crystal following recoil implantation

Nuclear dipolar broadening in the NMR spectra of β-emitting¹²N implanted in single crystal V was studied as a function of external magnetic field, orientation of the crystal axes relative to the field, and temperature of the sample. The implanted¹²N was located in an interstitial tetrahedral site. The surrounding V atoms nearest to the¹²N were displaced from the regular lattice position; the lattice expansion of large size Δa/a=0.5 was determined.     

Ferromagnetic Dy-Ni and antiferromagnetic Dy-Cu couplings in single-molecule magnets [Dy2Ni] and [Dy2Cu

The exchange couplings in [{Dy(hfac)3}2Cu(dpk)2] and [{Dy(hfac)3}2Ni(dpk)2(py)2] (Hdpk = di-2-pyridyl ketoxime) were precisely evaluated by high-frequency electron paramagnetic resonance and pulsed-field magnetization studies, giving J(Dy-Cu)/kB = -0.126 K and J(Dy-Ni)/kB = +0.031 K.     

A wheel-shaped single-molecule magnet of [MnII 3MnIII 4]: quantum tunneling of magnetization under static and pulse magnetic fields

The reaction of N-(2-hydroxy-5-nitrobenzyl)iminodiethanol (=H3(5-NO2-hbide)) with Mn(OAc)2* 4 H2O in methanol, followed by recrystallization from 1,2-dichloroethane, yielded a wheel-shaped single-molecule magnet (SMM) of [MnII 3MnIII 4(5-NO2-hbide)6].5 C2H4Cl2 (1). In 1, seven manganese ions are linked by six tri-anionic ligands and form the wheel in which the two manganese ions on the rim and the one in the center are MnII and the other four manganese ions are MnIII ions. Powder magnetic susceptibility measurements showed a gradual increase with chimT values as the temperature was lowered, reaching a maximum value of 53.9 emu mol(-1) K. Analyses of magnetic susceptibility data suggested a spin ground state of S=19/2. The zero-field splitting parameters of D and B 0 4 were estimated to be -0.283(1) K and -1.64(1)x10(-5) K, respectively, by high-field EPR measurements (HF-EPR). The anisotropic parameters agreed with those estimated from magnetization and inelastic neutron scattering experiments. AC magnetic susceptibility measurements showed frequency-dependent in- and out-of-phase signals, characteristic data for an SMM, and an Arrhenius plot of the relaxation time gave a re-orientation energy barrier (DeltaE) of 18.1 K and a pre-exponential factor of 1.63x10(-7) s. Magnetization experiments on aligned single crystals below 0.7 K showed a stepped hysteresis loop, confirming the occurrence of quantum tunneling of the on magnetization (QTM). QTM was, on the other hand, suppressed by rapid sweeps of the magnetic field even at 0.5 K. The sweep-rate dependence of the spin flips can be understood by considering the Landau-Zener-Stückelberg (LZS) model.     

Spin-lattice relaxation of 25Al and 28P in Pt

The spin-lattice relaxation times T ₁ for short-lived β emitters ²⁵Al(I?=?5/2, T _1/2?= 7.2 s) and ²⁸P(I?=?3, T _1/2?= 270 ms) in Pt were measured by means of the β-NMR technique. As a result, T ₁[²⁵Al in Pt] = (1.1 $^{+\ 0.7}_{-\ 0.3})$ s and T ₁[²⁸P in Pt] >0.5 s were obtained at temperatures of 17 and 20 K, respectively. The Knight shifts were estimated from the Korringa relation, which were evaluated by comparing to the first principle calculations.     

Water-assisted assembly of (E)-arylvinylpyridine hydrochlorides: effective substrates for solid-state [2+2] photodimerization

Water molecules assist the assembly of (E)-arylvinylpyridine hydrochlorides in a head-to-tail and face-to-face fashion by way of N-HO hydrogen bonds in combination with cation-π interactions between the pyridinium and aromatic rings. Photolysis of the pyridinium salt hydrates provided synHT dimers in high yields.     

Single-molecule magnet behavior enhanced by magnetic coupling between 4f and 3d spins

We synthesized and characterized a new compound [{Dy(hfac)₃}₂Pd(dpk)₂] ([Dy₂Pd]; Hdpk = di-2-pyridyl ketoxime), which is isostructural with the known [Dy₂Cu] and [Dy₂Ni]. The study of the [Dy₂Pd] compound containing diamagnetic Pd ion is indispensable to clarify a contribution of the exchange coupling for a 4f-3d single-molecule magnet behavior. From the ac susceptibility measurements on [Dy₂Pd], we obtained Δ/k_B = 28.6(11) K and T_B = 1.1 K. In accordance with the blocking behavior, the pulsed-field magnetization showed the hysteresis behavior below 1.1 K. These parameters on [Dy₂Pd] having S_Pd = 0 was compared with those of the derivatives having S_Cu = 1/2 (Δ/k_B = 47 K and T_B = 1.8 K) and S_Ni = 1 (Δ/k_B = 62(4) K and T_B = 2.5 K). The T_B and Δ steadily increase with the increasing 3d(4d) spin quantum number.     

Molecular magnetism of M6 hexagon ring in D(3d) symmetric [(MCl)6(XW9O33)2](12-) (M = Cu(II) and Mn(II), X = Sb(III) and As(III))

Ferromagnetic [n-BuNH(3)](12)[(CuCl)(6)(SbW(9)O(33))(2)]·6H(2)O (1) and antiferromagnetic [n-BuNH(3)](12)[(MnCl)(6)(AsW(9)O(33))(2)]·6H(2)O (4) have been synthesized and structurally and magnetically characterized. Two complexes are structural analogues of [n-BuNH(3)](12)[(CuCl)(6)(AsW(9)O(33))(2)]·6H(2)O (2) and [n-BuNH(3)](12)[(MnCl)(6)(SbW(9)O(33))(2)]·6H(2)O (3) with their ferromagnetic interactions, first reported by us in 2006. (1) When variable temperature (T) direct current (dc) magnetic susceptibility (χ(M)) data are analyzed with the isotropic exchange Hamiltonian for the magnetic exchange interactions, χ(M)T vs T curves fitted by a full matrix diagonalization (for 1) and by the Kambe vector coupling method/Van Vleck's approximation (for 4) yield J = +29.5 and -0.09 cm(-1) and g = 2.3 and 1.9, respectively. These J values were significantly distinguished from +61.0 and +0.14 cm(-1) for 2 and 3, respectively. The magnetization under the pulsed field (up to 10(3) T/s) at 0.5 K exhibits hysteresis loops in the adiabatic process, and the differential magnetization (dM/dB) plots against the pulsed field display peaks characteristic of resonant quantum tunneling of magnetization (QTM) at Zeeman crossed fields, indicating single-molecule magnets for 1-3. High-frequency ESR (HFESR) spectroscopy on polycrystalline samples provides g(∥) = 2.30, g(⊥) = 2.19, and D = -0.147 cm(-1) for 1 (S = 3 ground state), g(∥) = 2.29, g(⊥) = 2.20, and D = -0.145 cm(-1) for 2 (S = 3), and g(∥) = 2.03 and D = -0.007 cm(-1) for 3 (S = 15). An attempt to rationalize the magnetostructural correlation among 1-4, the structurally and magnetically modified D(3d)-symmetric M (=Cu(II) and Mn(II))(6) hexagons sandwiched by two diamagnetic α-B-[XW(9)O(33)](9-) (X = Sb(III) and As(III)) ligands through M-(μ(3)-O)-W linkages, is made. The strongest ferromagnetic coupling for the Cu(6) hexagon of 2, the structure of which approximately provides the Cu(6)(μ(3)-O)(12) cylindrical geometry, is demonstrated by the polarization mechanism based on the point-dipole approximation, which provides a decrease of the ferromagnetic interaction due to the out-of-cylinder deviation of the Cu atoms for 1. The different nature of the magnetic exchange interaction in 3 and 4 is understood by the combined effect of the out-of plane deviation (the largest for 4) of the Mn atoms from the Mn(μ(3)-O)(2)Mn least-squares plane and the antiferromagnetic contribution arising from the large Mn-O-Mn bond angle. The primary contribution to D is discussed in terms of the magnetic dipole-dipole interaction between the electrons located on the magnetic sites in the M(6) hexagon.