Triammonium Hydrogen Disulfate Research Articles

Phase transitions of some sulfur-containing ammonium salts

For the first time high-temperature polymorphic transition of ammonium sulfate (NH4)2SO4 (Tpt∼370°C) was experimentally recorded and characterized by differential scanning calorimetry. Phase transitions parameters of (NH4)2SO4, of ammonium bisulfate NH4HSO4, of triammonium hydrogen disulfate (NH4)3H(SO4)2 and of ammonium sulfamate NH4SO3NH2 were clarified. Method of determining the phase transitions parameters for thermally unstable substances, in particular for the triammonium hydrogen disulfate (NH4)3H(SO4)2, was developed and tested with the help of differential scanning calorimetry.

Proton ordering in (NH4)3H(SO4)2at low-temperature phase transitions

Single-crystal neutron diffraction was used to investigate the H-atom disorder in triammonium hydrogen disulfate (TAHS), (NH4)3H(SO4)2, below room temperature. Crystal structure analysis of the monoclinic phase III shows an increase of proton ordering with decreasing temperature in the (SO4)H(SO4) dimer. Moreover, the NH4(+) groups on a general position begin ordering in this phase. The monoclinic unit cell of TAHS-IV doubles in the b direction and a slight distortion of SO4(2-) and NH4(+) tetrahedra is observed. The order parameter introduced by Landau was determined for the second-order II/III and III/IV phase transitions from the intensities of the superstructure reflections. TAHS-V has a triclinic space group and the crystal structure seems to be completely ordered according to a structure analysis by single-crystal X-ray diffraction measurements. In addition, the decisive role of the dynamical disorder of different ammonium groups on successive phase transitions is discussed. Additional peaks were observed by X-ray powder diffraction measurements at ∼ 70 K on cooling, which refers to the V/VII phase transition. These additional peaks remained up to ∼ 85 K on heating. They were described with a doubling of the unit cell along all three principal crystallographic directions.

Disorder of (NH4)3H(SO4)2 in the high-temperature phase I

The highly disordered crystal structure of triammonium hydrogen disulfate, (NH(4))(3)H(SO(4))(2), in the high-temperature phase I was studied using single-crystal neutron diffraction. It is known that the O atom involved in hydrogen bonding between neighbouring SO(4) tetrahedra is disordered and takes a split-atom position, building a two-dimensional hydrogen-bond network in the (001) plane. The H atoms in these SO(4)-H-SO(4) hydrogen bonds are disordered and hence refined with a split-atom model. Moreover, from the much larger anisotropic mean-square displacements of ammonium protons the NH(4)(+) groups were refined with a reasonable split-atom model, and their motional behaviour was also analysed by rigid-body treatment. Finally, careful consideration was given to show possible supplementary proton migration between the ammonium protons and those of the hydrogen bonds in this high-temperature phase.

Dynamic proton disorder and the II–I structural phase transition in (NH4)3H(SO4)2

X-ray powder diffraction, differential scanning calorimetry (DSC)/thermogravimetry (TG) and single-crystal neutron diffraction methods were used to investigate triammonium hydrogen disulfate (NH(4))(3)H(SO(4))(2) (TAHS) in the temperature range between 293 and 493 K. The temperature-dependent X-ray powder diffraction measurements show a clear hysteresis of the I <-->II phase transition of TAHS with transition temperatures of T(up) = 412.9 (1) K on heating and of T(down) = 402.6 (1) K on cooling. From the existence of hysteresis and from the jump-like changes of the lattice parameters, the I <--> II phase transition of TAHS is considered to be first order. With DSC/TG measurements we confirmed that there is only one phase transition between 293 and 493 K. Through careful investigation on single crystals of TAHS using neutron diffraction, the correct space group (C2/c) of room-temperature TAHS-II phase was confirmed. Crystal structure analysis by single-crystal neutron diffraction showed a strongly elongated displacement ellipsoid of the proton which lies in the middle of the (SO(4))H(SO(4)) dimer with \bar 1 local symmetry. The protons of the NH(4) groups also show strongly enlarged anisotropic mean-square displacements. These findings are interpreted in terms of a characteristic proton disorder in the TAHS-II phase.

High-Temperature Reaction of Kaolin with Ammonium Sulfate

Reactions between kaolin and inorganic salts, such as sodium hydrogen sulfate and ammonium sulfate, or inorganic acids, such as hydrochloric acid and sulfuric acid, can be focused either on the production of Al or on the adjustment of the silica-to-alumina ratio of the kaolin. On the basis of adjusting the silica-to-alumina ratio, kaolin and ammonium sulfate [(NH4)2SO4] are mixed and heated in a furnace at temperatures between 200 and 1000 °C. The parameters studied were the reaction temperature and time, the proton-to-alumina molar ratio, the calcination temperature and time, and the reaction atmosphere. The products of the reaction between kaolin and (NH4)2SO4 were characterized by means of X-ray diffraction (XRD). The Al reaction yield grew until reaching a maximum at 600 °C and started to decrease sharply beyond this temperature. The Ti reaction yield values were lower than the Al reaction yield values, showing a maximum at 600 °C and decreasing smoothly as the reaction temperature was increased. The Fe reaction yield exhibited the same tendencies as the Al reaction yield. With regard to the proton-to-alumina molar ratio, a maximum in Al, Ti, and Fe reaction yields was observed at rH = 3. Precalcination of kaolin produced only slight decreases in the Al and Ti reaction yields and a slight increase in the Fe reaction yield. The products of the reaction were triammonium hydrogen disulfate [(NH4)3H(SO4)2], ammonium aluminum sulfate [NH4Al(SO4)2], aluminum sulfate [Al2(SO4)3], and alumina [Al2O3]. Brunauer−Emmett−Teller (BET) specific surface area tests indicated an increase of the BET specific surface area for short reaction times, reaching values above 200 m2/g.

H-bonding dependent structures of (NH4+)3H+(SO4 2-)2. Mechanisms of phase transitions.

The role of different H-bonds in phases II, III, IV, and V of triammonium hydrogen disulfate, (NH(4)(+))(3)H(+)(SO(4)(2)(-))(2), has been studied by X-ray diffraction and (1)H solid-state MAS NMR. The proper space group for phase II is C2/c, for phases III and IV is P2/n, and for phase V is P onemacr;. The structures of phases III and IV seem to be the same. The hydrogen atom participating in the O(-)-H(+).O(-) H-bond in phase II of (NH(4)(+))(3)H(+)(SO(4)(2)(-))(2) at room temperature is split at two positions around the center of the crucial O(-)-H(+).O(-) H-bonding, joining two SO(4)(2)(-) tetrahedra. With decreasing temperature, it becomes localized at one of the oxygen atoms. Further cooling causes additional differentiation of possibly equivalent sulfate dimers. The NH(4)(+) ions participate mainly in bifurcated H-bonds with two oxygen atoms from sulfate anions. On cooling, the major contribution of the bifurcated H-bond becomes stronger, whereas the minor one becomes weaker. This is coupled with rotation of sulfate ions. In all the phases of (NH(4)(+))(3)H(+)(SO(4)(2)(-))(2), some additional, weak but significant, reflections are observed. They are located between the layers of the reciprocal lattice, suggesting possible modulation of the host (NH(4)(+))(3)H(+)(SO(4)(2)(-))(2) structure(s). According to (1)H MAS NMR obtained for phases II and III, the nature of the acidic proton disorder is dynamic, and localization of the proton takes place in a broader range of temperatures, as can be expected from the X-ray diffraction data.

Crystal Structure of (NH 4) 3H(SO 4) 2 in Phase I

The crystal structure of triammonium hydrogen disulfate (NH4)3H(SO4)2 in phase I has been studied by single-crystal X-ray diffraction. The space group is assigned as trigonal R\\overline3, and the structure parameters are determined. The difference in the structural changes of (NH4)3H(SO4)2 and (NH4)3H(SeO4)2 at the ferroelastic-superionic phase transition is discussed.

X-ray study on the phase transitions in triammonium hydrogen disulfate crystals and deuterated crystals

Abstract The structural phase transitions in triammonium hydrogen disulfate crystals and deuterated crystals below room temperature have been studied by X-ray diffraction. Three phases are observed in the temperature range from 25°C down to — 160°C. The space groups in three different phases are identified as C2/c, P2/n (or Pn), and C2 for (NH4)3H(SO4)2 and (ND4)3D(SO4)2 crystals. No isotope effect on the structural phase transitions in these crystals could be detected by these studies. The occurrence of structural phase transitions caused by the reorientation of SO4 groups and/or the shift of oxygen atoms from the sulfate atom in the SO4 group are suggested from the diffraction photographs.

II → III Phase transitions in triammonium hydrogen disulfate (NH4)3H(SO4)2

Abstract The second-order phase transition at 265 K in the triammonium hydrogen disulfate compound (NH4)3H(SO4)2 has been observed by X-ray diffractometry. The space group below 265 K is identified to be P2/b. The recorded X-ray diagrams show a doubling of the primitive unit cell. The observed symmetry change has been described by the Landau theory of continuous phase transitions. The implied high-symmetry point of the corresponding first Brillouin zone shows other possible space groups for the low-temperature structure which are in agreement with Landau and Lifshitz criteria. All the theoretical results are discussed and compared with the obtained space group.

Structure of deuterated triammonium hydrogendisulfate, (ND4)3D(SO4)2. Phases (III') and (VI)

Structure of deuterated triammonium hydrogendisulfate, (ND₄)₃D(SO₄)₂. Phases (III') and (VI)

Optical and VO2+EPR studies of the twin structure in triammonium hydrogen disulfate and rubidium hydrogen sulfate crystals

Abstract The domain structure in ferroelastic triammonium hydrogen disulfate and rubidium hydrogen sulfate crystals has been studied comparatively by optical and VO2+ EPR methods. The results indicate that two types of domains are related with a mirror reflection plane (0,1,0), suggesting that left and right orientational orderings of sulfate ions are the mechanism leading to the order parameter for the ferroelastic transitions in these crystals.

Pressure-Temperature Phase Diagram of Triammonium Hydrogen Disulfate (NH4)3H(SO4)2

The pressure-temperature phase diagram of (NH 4 ) 3 H(SO 4 ) 2 was studied by means of dielectric and differential thermal analysis measurements in a range of \(p{\lesssim}8.5\) kbar, –100°C \({\lesssim}T{\lesssim}\)150°C. The I-II transition point (140°C at 1 atm) linearly decreases with increasing hydrostatic pressure with a slope of -5.76 deg kbar -1 . The pressure dependence of the II-III transition point is expressed by a quadratic equatuon T c = T 0 c + K p +γ p 2 with parameters of T 0 c =-8.1^° C , K =-3.7 deg kbar -1 , and γ=-0.13 deg kbar -2 . Two pressure-induced ferroelectric phases (Phases VI, VII) are found above about 5 kbar. The II-III-VI triple point is found at p =7.0 kbar, T =-40.5^° C .

Dielectric study on the phase transitions in triammonium hydrogen disulfate (NH4)3H(SO4)2

Phase transitions in triammonium hydrogen disulfate (NH4)3H(SO4)2 were studied by means of dielectric measurements and differential thermal analysis. Below room temperature three phase transitions were observed at −8, −132, and −140°C. The dielectric constant along the c*-direction shows breaks at the −8 and −132°C transitions, while it shows a discontinuous change accompanied with a thermal hysteresis at the −140°C transition. In addition to the above-mentioned transitions, a broad maximum of the dielectric constant was found at about −28°C along the c*-direction. However, no thermal anomalies were observed around −28°C. Mit Hilfe dielektrischer Messungen und differentieller Thermoanalyse wurden die Phasenubergange in Triammoniumhydrogendisulfat (NH4)3H(SO4)2 untersucht. Unterhalb der Raumtemperatur wurden drei Phasenubergange bei −8, −132 und −140°C gefunden. Die entlang der c*-Richtung gemessene Dielektrizitatskonstante zeigt bei den −8 und −132°C-Ubergangen stufenformige Anderungen, beim −140°C-Ubergang andert sie sich, begleitet von thermischen Hystereseerscheinungen, diskontinuierlich. Zusatzlich zu den o. g. Ubergangen wurden bei Messung in c*-Richtung ein breites Maximum der Dielektrizitatskonstanten bei etwa −28°C, aber keine thermischen Anomalien gefunden.