• Journal of the Korean Chemical Society
• /
• v.16 no.3
• /
• pp.157-165
• /
• 1972

Thermal decomposition of ammonium metavanadate has been investigated by using the quartz spring balance and differential thermal analysis. It showed that the decomposition of ammonium metavanadate is proceeded at two stages which correspond to $180^{\circ}C-220^{\circ}C$ and $310^{\circ}C-330^{\circ}C$ decomposition temperatures, respectively. Evolved ammonia gas in thermal decomposition has been analyzed quantitatively by titration. And the constituents of gases evolved have been evaluated by gas chromatography and omegatron spectrometer. From these results, it was concluded that the gases evolved in the first step decomposition were $NH_3$ and $H_2O$ with 2:1 ratio and the second step decomposition corresponded to the formation of $NH_3$, $H_2O$ and $N_2O$ which was produced in oxidation of $NH_3$ by $V_2O_5$. The decomposition products were identified by means of X-ray diffraction method. The decomposition product in air was V_2O_5 and the product in vacuum $V_3O_7.$ The kinetics of the thermal decomposition was studied, giving the values of the activation energy of 41.4 kcal/mole and 64.4 (kcal/mole) respectively.

• Journal of the Korean Ceramic Society
• /
• v.21 no.1
• /
• pp.67-73
• /
• 1984

A stable intercalation complex was formed by adsorption of alcanol (ROH, R; $C_{10}H_2$, $C_{12}H_{25}$, $C_{14}H_{29}$) on the surfaces of Yongil bentonite in which the interlayer cation had been exchanged by n-decylammonium ion $(C_{10}H_{21}NH_3^+)$ The layer charge density calculated from the increaments of basal spacings was 0.34 per unit chemical formula. Thermochemical properties of synthesized $C_{10}H_{21}NH_3^+$ montmorillonite were studied by means of DSC, TGA, DTG, Thermal analysis showed two steps of desoption behavior of $C_{10}H_{21}NH_3^+$ ion namely nonyl $(CH_3(CH_2)_8$ decomposition reaction of 40$0^{\circ}C$ and methyleneammonium decomposition reaction of 78$0^{\circ}C$ The activation energy of nonyl decomposition reaction of $C_{10}H_{21}NH_3^+$ -montmorillonite respectively.

• Journal of Korean Society for Atmospheric Environment
• /
• v.33 no.6
• /
• pp.605-615
• /
• 2017

Efficient simultaneous reduction conditions for $NO_x$ and $NH_3$-slip was investigated in SCR (Selective Catalytic Reduction) process with load variation by applying dual catalysts (SCR catalyst, $NH_3$ decomposition catalyst) system. $N_2O$ formation characteristics were analyzed to look into possible undesirable reaction pathways. In the experiments of catalyst characteristics, various operational variables were tested for the combined catalytic system, such as $NH_3/NO_x$ ratio, temperature, oxygen concentration and $H_2O$. The reaction characteristics of $NO_x$, $NH_3$ and $N_2O$ were analyzed and optimal conditions could be evaluated for the combustion facility with varied load. In terms of $NO_x/NH_3$ simultaneous reduction and $N_2O$ formation suppression, optimal condition was considered NSR 1.2 and temperature $300^{\circ}C$. At this operational condition, $NO_x$ conversion was 98%, $NH_3$ reduction efficiency was 95%, generated $N_2O$ concentration 9.5 ppm with inlet $NO_x$ concentration of 100 ppm. In $NH_3-SCR$ process with $NH_3$ decomposition catalyst, $NO_x$ and $NH_3$ can be considered to be reduced simultaneously at limited conditions. The results of this study may be utilized as basic data at facilities requiring simultaneous $NO_x$ and $NH_3$ reduction for facilities with load variation.

• Applied Chemistry for Engineering
• /
• v.5 no.4
• /
• pp.588-596
• /
• 1994

A decomposition reaction of bauxite ore with $(NH_4)_2SO_4$ was investigated to prepare Al component pregnant solution for the direct product of high purity $Al_2O_3$ from low grade bauxite ore. Al component in the bauxite was sulfatized to $NH_4Al(SO_4)_2$ or $Al_2(SO_4)_3$ in this decomposition. The optimum conditions of the decomposition for bauxite ore were reaction temperature of $425^{\circ}C$, reaction time of 40min, $(NH_4)_2SO_4$ weight ratio to bauxite of 7.0 and particle size of bauxite ore of -200mesh. The optimum leaching conditions of sulfated bauxite ore were leaching temperature of $100^{\circ}C$, leaching time of 1hr and pulp density of 200ml $H_2O$ to sulfated ore of 1.0g bauxite. Under the above mentioned decomposition and leaching conditions, 94% of Al component in the bauxite ore was extracted.

• Bulletin of the Korean Chemical Society
• /
• v.15 no.5
• /
• pp.341-346
• /
• 1994

The frameworks of $(Cu(NH_3)_3OH^+)_x(NH_4^+)_{12-x}-A{\cdot} zH_2O$ which were prepared by the ion-exchange of zeolite A with ammoniac cupric nitrate solution are more stable than those of $Cu_xNa_{12-2x} -A$ obtained by the ion exchange with aqueous cupric nitrate solution are more stable than those of $Cu_xNa_{12-2x} -A$ obtained by the ion exchange with aqueous cupric nitrate solution. An energetic calculation was made on the relatively stable $(CuOH^+)_2(NH_4^+)_{10}-A{\cdot} 2H_2O$ prepared by the partial evacuation of $(Cu(NH_3)_3OH^+)_2(NH_4^+)_{10}-A{\cdot} zH_2O$. The mean stabilization energies of water, OH-, and $NH_4^+$ ions are -30.23 kcal/mol, -60.24 kcal/mol, and -16.65 kcal/mol, respectively. The results of calculation were discussed in terms of framework stability. The $(Cu(NH_3)_3OH^+)_2(NH_4^+)_{10}-A{\cdot} zH_2O$ zeolite shows two step deammoniation reactions. The first deammoniation around 210 $^{\circ}$C (third DSC peak) was attributed to the decomposition of $[Cu(NH_3)_3OH^+]$ ion and the second one around 380 $^{\circ}$C (fourth DSC peak) was ascribed to the decomposition of $NH_4^+$ ion. The activation energies of the first and second deammoniation reactions were 99.75 kJ/mol and 176.57 kJ/mol, respectively.

• Korean Chemical Engineering Research
• /
• v.51 no.3
• /
• pp.358-363
• /
• 2013

Lithium-ammonia (Li-$NH_3$) solutions are possible to be successfully made under the vacuum condition but there still remains a problem of undergoing stable and reliable decomposition in vacuum for high-efficiency thermoelectric power generation. This paper describes a new method for improving the thermoelectric conversion efficiency of Li-$NH_3$ solutions in vacuum. The proposed method uses a 'U'-shaped Pyrex vacuum tube for the preparation and decomposition of pure fluid Li-$NH_3$ solutions. The tube is shaped so that a gas passageway ('U') connecting both legs of the 'U' helps to balance pressure inside both ends of the tube (due to $NH_3$ gasification) during decomposition on the hot side. Thermoelectric experimental results show that solution reaction in the 'U'-shaped tube proceeds more stably and efficiently than in the 'U'-shaped tube, and consequently, thermoelectric conversion efficiency is improved. It is also proved that the proposed method can provide a reversible reaction, which can rotate between synthesis and decomposition in the tube, for deriving the long-time, high-efficiency thermoelectric power.

• Bulletin of the Korean Chemical Society
• /
• v.22 no.2
• /
• pp.154-158
• /
• 2001

The steps for the generation of very thin GaN films on ultrathin AlN/6H-SiC surface by alternating a pulsative supply (APS) of trimethyl gallium and NH3 gases have been examined by ASED-MO calculations. We postulate that the gallium cul ster was formed with the evaporation of CH4 gases via the decomposition of trimethyl gallium (TMG), dimethyl gallium (DMG), and monomethyl galluim (MMG). During the injection of NH3 gas into the reactor, the atomic hydrogens were produced from the thermal decomposition of NH3 molecule. These hydrogen gases activated the Ga-C bond cleavage. An energetically stable GaN nucleation site was formed via nitrogen incorporation into the layer of gallium cluster. The nitrogen atoms produced from the thermal degradation of NH3 were expected to incorporate into the edge of the gallium cluster since the galliums bind weakly to each other (0.19 eV). The structure was stabilized by 2.08 eV, as an adsorbed N atom incorporated into a tetrahedral site of the Ga cluster. This suggests that the adhesion of the initial layer can be reinforced by the incorporation of nitrogen atom through the formation of large grain boundary GaN crystals at the early stage of GaN film growth.

• Bulletin of the Korean Chemical Society
• /
• v.17 no.8
• /
• pp.730-735
• /
• 1996

The layered perovskite oxide, KSr2Nb3O10, was synthesized. The interlayer potassium cations were readily exchanged by protons in hydrochloric acid solution to give the protonation compound, HSr2Nb3O10·0.5H2O. The intercalation compounds, [NH3(CH2)nNH3]xSr2Nb3O10, were also obtained by acid-base reactions between the protonation compound and organic bases, 1,n-alkyldiamines. The interlayer distances in the intercalation compounds were linearly increased with the increase of the number of carbon (Δc/Δn=1.05 Å) in 1,n-alkyldiamines. The intercalated alkyldiammonium ions formed a paraffin-like monolayer with average tilting angle (θ) of ca. 56°. The intercalation reactions occurred stoichiometrically. The thermal decomposition process of the intercalation compounds showed distinct three steps due to the desorption of hydrated water, the decomposition of organic moiety, and the decomposition of Sr-related compounds.

• Journal of Korean Society of Environmental Engineers
• /
• v.35 no.5
• /
• pp.356-362
• /
• 2013

An attempt has been made to optimize elongated rotating arc plasma $NH_3$ scrubber. Among diverse semiconductor processes, diffusion and implantation process inevitably produce $NH_3$ as byproduct and efficient dry process for the decomposition of $NH_3$ is required. Plasma process does not produce NOx that is commonly produced in combustion process and there is no problem of deactivation, usually experienced in catalyst process. However, plasma process uses electrical energy and needs to be optimized to achieve feasibility of application. In this work, mode control of rotating arc is presented as tentative solution for the possible optimization of the process. Based on existing rotating arc, scale-up and following mode mapping was tried. Proposed reactor design was evaluated in the $NH_3$ decomposition process and revealed that optimization scheme is at hand. In the experiment of full scale scrubber including heat exchanger, the process gave more stable and efficient process of $NH_3$ decomposition.

• Journal of the Korean Ceramic Society
• /
• v.39 no.2
• /
• pp.204-209
• /
• 2002

In this study, $UO_4{\cdot}2NH_4F$, the precipitates which has low solubility, was obtained by chemical precipitation method to recover and reuse the trace uranium from the liquid waste producing in AUC process and for this compound it was characterized by means of chemical analysis, TG-DTA, XRD and FT-IR analyses. This compound was analyzed as $UO_4{\cdot}2NH_4F$ and shape of this precipitate was hexagonal type, having the size of 2∼3 ${\mu}m$. Also, the intermediates were obtained as $UO_4F,\;UO_4,\;UO_3,\;and\;U_3O_8$ by the thermal decomposition over the temperature of 220, 310, 515 and 640$^{\circ}C$, respectively. It is concluded that under the condition of a constant heating rate of 5$^{\circ}C$/min in air atmosphere range of between room temperature and 800$^{\circ}C$, thermal decomposition reaction mechanism of $UO_4{\cdot}2NH_4F$ is as follow; $UO_4{\cdot}2NH_4F{\rightarrow}UO_4F{\rightarrow}UO_4{\rightarrow}UO_3{\rightarrow}U_3O_8$.