Additional Hydrogen Source Research Articles

Photodegradation mechanism and rate improvement of chlorinated aromatic dye in non-ionic surfactant solutions

A typical insoluble chlorinated aromatic dye (CAD), disperse red (DR), was used to explore the reaction mechanism and kinetics of photodegradation in non-ionic surfactant solutions. The use of an additional hydrogen source and photosensitizer is also studied to improve the decay rates. The decay rate of dye in surfactants depends on the K m of surfactants and their ability to offering an effective hydrogen source. The photodegradation of CAD can be divided into three stages: the initial lag stage, the fast degradation stage and the final retardation stage. The lag stage will vanish and the decay rates of dye can be greatly improved by 2.5–3.6 times after adding an additional hydrogen source (NaBH 4) or photosensitizer (acetone) to the surfactant micellar solution. However, the use of an additional hydrogen source or photosensitizer has dosage limitations in such applications. The photoreduction of DR is the main reaction mechanism, in which photodechlorination is observed first with the generation of HCl as the final product, then followed by photodecolorization by breaking the azo bond of the chromophore.

High-Pressure Synthesis of Hydrides in Ca-Mg-Ni Systems

The high-pressure synthesis of new hydrides of the Ca-Mg-Ni system and crystal structural and thermal analyses have been conducted. The high-pressure synthesis was carried out at 1073 K for 2 h at 5 GPa using a cubic-anvil-type apparatus. An additional hydrogen source was used to stabilize the hydride phases. A series of (Ca 1-x Mg x ) 2 NiH δ was found to form solid solutions in the range of x = 0-0.4. The crystal structure of the (Ca 1- xMgx)2NiHδ solid solutions was of the CsCl-type. The lattice constant of the CsCl-type phase decreased from 0.35542(2) nm (x = 0) to 0.35478(2) nm (x = 0.4) with increasing Mg content. For the samples with a Ni-rich composition, in addition to the CsCl-type phase, a Mg 2 Ni 3 H 3,4 phase was also present at high pressures. The CsCl-type phases were thermally stable at less than 646 ±2 K, regardless of Mg content.

High-Pressure Synthesis of Hydrides of Ca-TM Systems (<B>TM</B>=<B>Mn</B>, Fe, Co and Ni)

New hydrides of Ca-TM-H systems (TM = Mn, Fe, Co and Ni) have been explored by using a high-pressure technique. The high-pressure of up to 5 GPa was yielded by cubic-anvil-type apparatus. All the samples of Ca-TM-H systems (TM = Mn, Fe and Co) prepared at 1073 K under 5 GPa were found to be mixtures of the raw materials. However, for the Ca-Ni-H system, a new hydride with a chemical composition of CaH 2 -33 at%Ni was prepared at 1223 K under 5 GPa. The color of the hydride was reddish brown. As an additional hydrogen source was used during the synthesis, the color changed into black. The new hydride prepared with additional hydrogen was found to have the CsCl-type structure. The lattice parameter was a = 0.35542(2) nm.

Thermal Stability of Hydrides of Magnesium-Transition Metal System Prepared under a High Pressure

Phases present and thermal stability of synthesized hydrides of Mg - TM - H systems (TM = Co and Ni) by preparing under a high pressure of 5 GPa using an anvil-type apparatus were studied. The MgNi 2 phase with a novel crystal structure was formed at 1073 K under 5 GPa. In addition, for MgH 2 - Ni system, two novel phases with a new composition of Mg- 64 at% Ni, and Mg - 55 at% Ni were formed. Using an additional hydrogen source to supply enough hydrogen, the volume fraction of the new phase with a composition of Mg- 55 at%Ni increased, and the other phase vanished. This Mg-Ni-H compound was thermally stable up to 498K under an Ar atmosphere of 0.5 MPa.

Interplanetary Neutral Particle Fluxes Influencing the Earth's Atmosphere and the Terrestrial Environment

It is well known that the Solar System is swept over by neutral interstellar gases, primarily hydrogen and helium, entering the heliosphere from the upwind side and penetrating inward, even up to the orbit of the Earth. The Earth on its orbit is thus moving through this density field and is intercepting time-variable hydrogen and helium fluxes. Quantitatively, this is associated with a sensitive reaction of the density fields to time-dependent conditions of the solar radiation pressure and the ionizing solar radiations during the solar activity cycle. As we shall show, the density distribution of interstellar hydrogen along the orbit of the Earth is strongly varying during the solar cycle. In connection with the variation of the mean relative velocity of this gas with respect to the orbiting Earth a highly variable hydrogen inflow into the Earth's atmosphere will be induced. There is also an additional source of hydrogen influencing the Earth's environment due to the fact that neutral interstellar hydrogen and helium are neutralizing solar wind protons by charge exchange inside the orbit of the Earth, thereby producing an antisolar flux of keV-energetic hydrogen atoms impinging onto the Earth's atmosphere. These time-variable fluxes could be directly monitored by gas detectors of an advanced technology. They might also be indicated by indirect terrestrial effects. We are investigating the question of whether and how these time-variable inflows could be recognized by careful studies of relevant upper atmospheric reactions. We study particle-induced energy inputs and ionization rates in the upper atmosphere and analyze influences on the hydrogen geocorona. We also study the process of relaxation of the inflowing hydrogen within the terrestrial atmosphere and investigate the reaction of atmospheric hydrogen densities to these variable inflows. While it is shown that the induced short-period variation of upper atmospheric hydrogen densities is of negligible amplitude at the present epoch, long-periodic variations of the hydrogen inflow like those connected with the entrance of the Solar System into a region of increased interstellar density at earlier or later eons clearly give their imprints even at lower heights and could even be reflected in ozone depletions induced by increased hydrogen densities at heights of around 50 km. At present anomalous variations of the geocoronal H-1216 A and He-584 A glows uncorrelated with the solar resonance line illumination indicate a breathing of the geocorona under variable interplanetary gas inflows.

The mechanism of the acetaldehyde pyrolysis

Previous work on the acetaldehyde pyrolysis is shown to be vitiated by the presence, in the acetaldehyde, of impurities, mainly ethanol and crotonaldehyde. The reaction has been reinvestigated with the use of acetaldehyde, prepared from paraldehyde, which is free from these and other impurities. On the basis of a study of the kinetics of formation of the major products (methane and carbon monoxide) and of a number of minor products (hydrogen, acetone, propionaldehyde, ethane and ethylene) a reaction mechanism is proposed. This includes all of the reactions in the original Rice-Herzfeld scheme, together with a number of other elementary processes, in particular CH 3 + CH 3 CHO → CH 4 + CH 2 CHO. The decomposition of the radical CH 2 CHO into CH 2 CO and H provides an additional source of hydrogen, the rate of production of which is therefore not a measure of the rate of the initiation process. Acetone is believed to arise mainly by the reaction CH 3 + CH 3 CHO → CH 3 COCH 3 + H, and only to a negligible extent by the combination of CH 3 and CH 3 CO. The main chain-ending step is concluded to be CH 3 + CH 3 → C 2 H 6 , with a small contribution from CH 3 + CH 2 CHO → CH 3 CH 2 CHO. The work provides further evidence for the falling off, at low pressures, of the second order coefficient for the combination of methyl radicals. Rate constants for various elementary processes are deduced from the rates of formation of the various products, and are shown to be consistent with values obtained directly.