Hydrogen peak temperature

The results of a similar experiment with adsorbed hydrogen is shown in Fig. 2.3b. Only one desorption peak was observed in the temperature range studied [50], The desorption peak temperature lies at 420 K for the experiment with 0.8 L and is shifted to lower temperatures as the H2 concentration increases indicating second order desorption kinetics. Surface states with desorption temperatures at 165 K, 220 K, 280 K and 350 K were reported for the adsorption of H2 and D2 at 120 K [51]. Thermal desorption experiments after H2 adsorption at 350 K show only one desorption state at ca. 450 K [52],... 

A 90% reduction in activation energy, not an unreasonable expectation for catalysts in general, reduces the peak temperature below 0 C. Clearly, only a small amount of catalytic action is required to make dramatic reductions in the release temperature. This implies that, with careful control of the invented process, it should be possible to dial-in the desorption temperature for hydrogen desorption. This allows us to assess how this hydrogen storage media can be applied. 

The results of these studies are tabulated in Table IV. This table lists the surfaces studied, the intermediates observed, the products, the adsorption temperature (T ds). the initial sticking probability of HCOOH (Sq), the peak temperature for product evolution (7J,), and the activation energy (E i) and the preexponential factor (v) determined by methods discussed earlier (see Section I,D). Data for HCOOD is given where available in order to distinguish the two hydrogens in the acid. 

Metal-Oxygen and Metal-Hydrogen Surface Bond Strengths Compared to TPRS Peak Temperature for Formic Acid Decomposition"... 

Fig. 2.30 Changes of DSC hydrogen desorption temperatures from Fig. 2.29 as a function of the particle size (BCD) of (a) miUed (HES57 mode) and (b) cycled ABCR powder. Numbers beside each data point indicate the grain size of P-MgH. (a) Onset temperature (T ) and (b) peak temperatures Standard deviations for the mean particle size (BCD) from Table 2.14 are omitted...

Fig. 2.33 DSC hydrogen desorption temperatures vs. particle size for as-received and ball-milled Tego Magnan powder, (a) Onset temperature (T ) and (b) low-temperature (LT) and high-temperature (HT) DSC peaks. Numbers beside data points indicate grain (crystallite) size of the P-MgH phase. Standard deviation bars for the particle size (BCD) are omitted for clarity [6]...

The corresponding DSC curves of Mg powders milled in hydrogen atmosphere after various milling times under the HES mode are shown in Fig. 2.40. The 5 h milled sample has only one small peak at 410.5°C, but the others show double peaks (peak doublets). Desorption peak temperatures of the doublet peak first decrease as... 

Mg(BH4)2) at the temperatures up to 700°C and hydrogen pressures up 10 atm. [177, 178]. The thermal deeomposition of NaBH (and KBH as well) is very simple. The microstructure of as-received NaBH and its DSC trace obtained in our laboratory are shown in Fig. 3.17. The first endothermic peak centered at 498°C is due to melting. Its peak temperature is in an excellent agreement with 505°C reported in [177, 178]. The second endothermic peak is due to the decomposition in a molten state of NaBH according to the reaction put forward by Stasinevich and Egorenko [177, 178]... 

DSC and DTA measurements show melting of ADN, NH4N(N02)2, at 328 K, the onset of decomposition at 421 K, and an exothermic peak at 457 K.l l Gasification of 30% of the mass of ADN occurs helow the exothermic peak temperature, and the remaining 70% decomposes after the peak temperature. The decomposition is initiated by dissociation into ammonia and hydrogen dinitramide. The hydrogen dinitramide further decomposes to ammonium nitrate and NjO. The final decomposition products in the temperature range 400-500 K are NH3, HjO, NO,... 

This hypothesis has been confirmed by the greatly improved thermal stability of PVC as a result of the formation of a graft copolymer of d -l,4-polybutadiene onto poly (vinyl chloride). The improved thermal stability is demonstrated by the almost total absence of discoloration on molding the graft copolymer into a film at 200°C in air, the reduced rate of dehydrochlorination on heating in an inert atmosphere at 180°C, and higher onset and peak temperatures for hydrogen chloride evolution as determined by differential thermal analysis. 

Sulfur models Peak temperature of hydrogen sulfide during PTP Peak temperature of sulfur dioxide during PTO... 

Session 4 focused on recent advances in the thermochemical copper chloride and calcium bromide cycles. Much of the current research on thermochemical cycles for hydrogen production involves the sulphur cycles (sulphur-iodine, hybrid sulphur), however, these cycles require very high temperatures ( 800-900°C) to drive the acid decomposition step. The interest in the Cu-Cl and Ca-Br cycles is due to the lower peak temperature requirements of these cycles. The peak temperature requirement for the Cu-Cl cycle is about 550°C, which would allow this cycle to be used with lower temperature reactors, such as sodium- or lead-cooled reactors, or possibly supercritical water reactors. Ca-Br requires peak temperatures of about 760°C. Both of these cycles are projected to have good efficiencies, in the range of 40%. Work on Cu-Cl is ongoing in France, Canada and the United States. Work on Ca-Br has been done primarily in Japan and the US, with the more recent work being done in the US at ANL. The papers presented in this session summarised the recent advances in these cycles. 

A modelling and experimental effort has identified a new uranium thermochemical cycle (UTC) for the production of hydrogen from water. The peak temperature within the cycle is below 700°C - a temperature achievable with existing high temperature nuclear reactors and some solar systems using commercially auailable materials. This paper describes the new process and some of the experimental work. It is an early report of chemical feasibility. Much work will be required to determine engineering and economic viability. 

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