Highly Selective Production of “Jadeite Hydrogen” from the Catalytic Decomposition of Diesel

Ammonia is one of the syngas contaminants that must be removed before using the syngas downstream applications. The most promising hot-gas clean-up techniques of ammonia are selective catalytic oxidation (SCO) and catalytic decomposition. In this study, the catalytic activities over Zeolite Hβ supported iron catalyst (Fe/HZβ) were compared both for the two catalytic routes. For SCO experiments; temperature (300-550 °C), O 2 (2000-6000 ppmv) and (0-10%) H 2 concentrations were investigated with the presence of 800 ppm NH 3 in each of the final gas mixture. In the second route, catalytic ammonia decomposition experiments were carried out with H 2 in balance N 2 (0-30%) containing 800 ppm NH 3 at 700°C and 800°C. In the SCO, NH 3 conversions were increased with increasing reaction temperatures with the absence of H 2 in the reaction mixture. With 10% H 2 , it was shown that NH 3 conversions increased with decreasing the reaction temperature. This was interpreted as the competing H 2 and NH 3 oxidations over the catalyst. On the other hand, in the catalytic decomposition, thermodynamic equilibrium conversion of almost 100% was attained at both 700 and 800 °C. Upon H 2 addition, all conversions decreased. The decrease in conversion seemed to be linear with inlet hydrogen concentration. Hydrogen was seen to inhibit ammonia decomposition reaction. It was shown that Fe/HZβ catalyst is better to use for catalytic decomposition of NH 3 in syngas rather than SCO of NH 3 in spite of higher reaction temperatures needed in the decomposition reaction.

Ozone (O3) is a powerful oxidant and a significant atmospheric pollutant that poses serious risks to human health and the environment. Various technologies such as activated carbon filtration, solution adsorption, and catalytic decomposition have been employed to mitigate ozone pollution. Among these, room‐temperature catalytic ozone decomposition has gained attention due to its high efficiency, low energy requirements, and the absence of harmful by‐products. This review comprehensively summarizes the recent progress in ozone decomposition catalysts, categorizing and evaluating their properties and mechanisms of action. The discussion also includes the catalytic degradation and deactivation mechanisms, with proposed synergistic processes for the simultaneous removal of ozone and volatile organic compounds, and the mechanism for catalytic ozonation for wastewater treatment. Additionally, primary pathways for catalyst deactivation are identified along with protocols for catalyst reactivation. Finally, this review addresses the challenges of catalytic ozone decomposition and offers recommendations for future catalyst designs to improve performance and durability.

The catalytic thermal decomposition of water and the production of hydrogen

I NTERESTS in rocket-grade hydrogen peroxide have been renewed in recent years as a new demand for a nontoxic alternative to rocket propellants arises. The use of high-concentrated hydrogen peroxide as a propellant in propulsion dates back to the 1940s. After the SecondWorldWar, it was used as amonopropellant and as an oxidizer in a bipropellant system for thrusters. Hydrogen peroxide was eventually replaced by higher-performing propellants such as hydrazine and N2O4. In the middle of the 1990s, there was renewed interest in hydrogen peroxide due to low toxicity, clean products, and enhanced versatility [1,2]. The performance of the catalyst is crucial in the design of the propulsion devices that use the decomposition of hydrogen peroxide. Silver has been the most widely used catalyst despite many shortcomings, including low melting point, nonuniform flow path, high-pressure loss, and need of preheating [2]. In addition, silver cannot withstand the high decomposition temperatures of hydrogen peroxide at concentration levels higher than 92% [3]. Alternative catalysts including manganese oxides [3– 6] and perovskites [7] have been tested with varying degree of effectiveness. Perovskite material such as La0:8Sr0:2CoO3 (hereafter referred to as LSC) had superior characteristics at elevated temperature but displayed very slow reactivity at room temperature [8]. On the other hand, permanganate-based catalysts displayed very high reactivity at room temperature but were not stable at elevated temperature [9]. In the gas generator proposed in the present study (Fig. 1), hydrogen peroxide goes through two distinct reaction phases: catalytic and thermal decomposition [10]. In the inlet region, the liquid-phase hydrogen peroxide decomposes mainly by catalytic decomposition upon contact with the catalyst surface. In this region, unreacted hydrogen peroxide vaporizes by the heat of the decomposition process. The vapor content of the partially decomposed hydrogen peroxide increases along the axial direction of the reactor bed. Down the reactor bed, the unreacted hydrogen peroxide in vapor state decomposes by further catalytic reaction. Good startup performance and catalytic reactivity are required in the inlet region, and high catalytic reactivity and thermal stability at high temperature are required in the outlet region. The LSC catalyst has good thermal stability and high reactivity at high temperature, but is hard to start up at room temperature [8]. To use the LSC catalyst for the high-temperature region, various catalysts for a vaporizer catalyst bed were selected and evaluated using a constant volume reactor and gas generator. Finally, the gas generator with a dual catalytic bedwas tested and evaluated.

Impact of the presence of common polymer additives in thermal and catalytic polyethylene decomposition

Catalytic decomposition of biomass tars with iron oxide catalysts

This study was to grasp the change of materiality of natural material through decomposition techniques after the raw material are extracted from natural material. In addition, it is to analyze examples to achieve the purpose that is to apply expressive possibility of new material into the space design. The results of the research are as in the following. First, the development of technology could allow use in various directions on nature material which has not been applied on architectural and spatial until now. In particular, material properties and surface design are shown differently by 'decomposition techniques'. Second, decomposition techniques fall into two categories. One can be subdivided into 'thermal decomposition, catalytic decomposition and electrolysis' that is the technology to decompose nature material with the chemical combination. Other is 'cutting, grinding, crushing and pressing' that is to dissolve nature material with physical power. Third, 'thermal decomposition' and 'catalytic decomposition' technology changed into natural ingredients which are to complement properties than raw material by removing harmful or unnecessary ingredients of nature material and 'cutting' technology changed color, form, and patterns etc hidden in natural material into the ways to express outwards. In addition, 'grinding' and 'crushing' technology confirm characteristics that are unlike earlier by vanishing most of existing properties. Forth, surface design is appeared as realistically, metaphorically, concretely, timely and autonomically. Therefore, decomposition techniques expand the area of expression by leading (inducing) differences between the change of materiality and surface design. Also it will serve as a foundation that excellent properties of natural resources appear in a positive qualities and will have a great influence on various use as an advanced material.

Water-dispersible Fe3O4 nanoparticles with diameters of 4.2 ± 0.6, 6.1 ± 0.8, 8.1 ± 1, and 10.4 ± 1 nm were prepared through the polyol method and employed as the precursors of Fe3O4/Al2O3 catalysts to study the size-dependent activity. We identified that the activity of the catalysts in NH3 decomposition (driven by both thermal and dielectric barrier discharge plasma) increased with increasing Fe3O4 particle size. The turnover frequencies (TOFs) were increased from 0.9 to 5.8 s–1 with an increasing Fe3O4 precursor size from 4.2 to 10.4 nm during the thermocatalytic decomposition. A quite similar “particle size effect” was also observed for the plasma catalytic decomposition, although lower TOF was observed. Additionally, reaction-induced catalyst reconstruction was identified during the early-stage of the catalytic decomposition and can be attributed to the nitridation of FeOx to FexN. Our results provide new evidence for the “structure-sensitivity” of the catalytic NH3 decomposition.

Nitrous oxide (N2O) is a significant greenhouse gas and its emissions from fluidized bed combustion systems can be controlled using catalytic conversion and decomposition. The catalytic decomposition of N2O was studied in a quartz fixed‐bed reactor at 450–700 °C. The low‐cost catalyst was prepared from fly ash and iron oxides, and was characterized in terms of the BET specific surface area and XRD. This study showed that both the Fe content on the catalyst surface and the calcination temperature during the preparation of the catalyst should be optimized in order to significantly improve the catalyst performance when used for N2O decomposition. The influences of O2, H2O, CO2 and SO2 on the N2O decomposition were investigated at the most reactive temperature. Experimental results showed that O2 had a small negative effect on the catalytic activity, while CO2 had no obvious effect on the N2O decomposition. The N2O conversion was still high even when H2O was present. However, the N2O conversion dropped sharply when H2O and O2 were both present. The catalytic activity was reduced by SO2 because of its reaction with the catalyst. The difference between the N2O conversion with H2O present and with both H2O and O2 present was analyzed in order to determine the N2O decomposition mechanism. Two mechanisms for the N2O catalytic decomposition mechanism have been considered, of which the one with formation of oxygen atoms at two sites with migration and recombination shows better agreement with our experimental results. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.

<div class="section abstract"><div class="htmlview paragraph">In order to rapidly achieve the goal of global net-zero carbon emissions, ammonia (NH<sub>3</sub>) has been deemed as a potential alternative fuel, and reforming partial ammonia to hydrogen using engine exhaust waste heat is a promising technology which can improve the combustion performance and reduce the emission of ammonia-fueled engines. However, so far, comprehensive research on the correlation between the reforming characteristic for accessible engineering applications of ammonia catalytic decomposition is not abundant. Moreover, relevant experimental studies are far from sufficient. In this paper, we conducted the experiments of catalytic decomposition of ammonia into hydrogen based on a fixed-bed reactor with Ru-Al<sub>2</sub>O<sub>3</sub> catalysts to study the effects of reaction temperature, gas hour space velocity (GHSV) and reaction pressure on the decomposition characteristics. At the same time, energy flow analysis was carried out to explore the effects of various reaction conditions on system efficiency. The results show that both the ammonia catalytic conversion and decomposition efficiency increase with the reaction temperature increasing. However, these two parameters decrease with the increases of GHSV and reaction pressure, the former due to the reduction of ammonia retention time in the reactor as GHSV accelerates, and the latter due to the high-pressure environment inhibiting the overall reaction towards ammonia decomposition. In addition, the maximum conversion rate of 86% and a peak decomposition efficiency of 112% were achieved at 853 K, 2000 h<sup>-1</sup>, and 0.1 MPa. The energy flow analysis shows that increasing the reaction temperature increases the decomposition losses, but the total calorific value of the reformate increases, which is expected to improve the combustion efficiency of ammonia fueled engines and reduce the unburned ammonia emissions. Furthermore, GHSV has a negligible impact on decomposition losses. This paper contributes to the database of hydrogen production from the ammonia thermo-catalytic decomposition, analyze the energy flow distribution of the catalytic decomposition process, and provides important information for development of zero-carbon ammonia-hydrogen fueled engines.</div></div>

The N2O concentration was measured in a circulating fluidized bed boiler of commercial size. Kinetics for N2O reduction by char and catalytic reduction and decomposition over bed material from the combustor were determined in a laboratory fixed bed reactor. The destruction rate of N2O in the combustion chamber and the cyclone was calculated taking three mechanisms into account: reduction by char, catalytic decomposition over bed material, and thermal decomposition. The calculated destruction rate was in good agreement with the measured destruction of N2O injected at different levels in the boiler. The conclusion is that in the bottom part of the combustor, where the solids concentration is about 1000 kg/m3 (voidage 0.6) and the char content in solids 2 wt %, heterogeneous reactions were the most important N2O destruction mechanisms. Reduction by char accounted for 80% of the N2O destruction, 20% was due to catalytic decomposition over bed material, and homogeneous thermal decomposition was negligible. However, at higher levels in the combustor, the solids concentration is lower: at the top 60% of the N2O destruction was due to thermal decomposition and in the cyclone heterogeneous destruction of N2O was insignificant. It was estimated that more than one-half of the formation of N2O in the combustion chamber takes place above the secondary air inlet.

The NO oxidation process has been applied to improve a removal efficiency of NO included in exhaust gas. In this study, to produce a dry oxidant for the NO oxidation process, the catalytic H2O2 decomposition method was proposed. A variety of the heterogeneous solid-acidic Mn-based catalysts were prepared for the catalytic H2O2 decomposition and the effect of their physico-chemical properties on the catalytic H2O2 decomposition was investigated. The results of this study showed that the acidic sites of the Mn-based catalysts have an influence on the catalytic H2O2 decomposition. The Mn-based catalyst having the abundant acidic sites within the wide temperature range in NH3-TPD shows the best performance for the catalytic H2O2 decomposition. Therefore, the NO oxidation efficiency, using the dry oxidant produced by the H2O2 decomposition over the Mn-based catalyst having the abundant acidic properties under the wide temperature range, was higher than the others. As a remarkable result, the best performances in the catalytic H2O2 decomposition and NO oxidation were shown when the Mn-based Fe2O3 support catalyst containing K component was used for the catalytic H2O2 decomposition.

Exploring the efficient catalytic decomposition behavior of AsH3 over HZSM-5 molecular sieve based on in situ DRIFTS characterization

The NO oxidation process has been applied to improve a removal efficiency of NO included in exhaust gas. In this study, to produce a dry oxidant for the NO oxidation process, the catalytic H2O2 decomposition method was proposed. A variety of the heterogeneous solid-acidic Mn-based catalysts were prepared for the catalytic H2O2 decomposition and the effect of their physico-chemical properties on the catalytic H2O2 decomposition were investigated. The results of this study showed that the acidic sites of the Mn-based catalysts has an influence on the catalytic H2O2 decomposition. The Mn-based catalyst having the abundant acidic sites within the wide temperature range in NH3-TPD shows the best performance for the catalytic H2O2 decom- position. Therefore, the NO oxidation efficiency, using the dry oxidant produced by the H2O2 decomposition over the Mn-based catalyst having the abundant acidic properties under the wide temperature range, was higher than the others. As a remarkable result, the best performances in the catalytic H2O2 decomposition and NO oxidation was shown when the Mn-based Fe2O3 support catalyst containing K component was used for the catalytic H2O2 decomposition.

N2O is a stratospheric ozone-depleting greenhouse gas with a global warming potential. The catalytic decomposition of N2O is one of the most promising and economical techniques to reduce the amount of the gas in the atmosphere. In the present study, the effects of support materials and Ir loading on the catalytic N2O decomposition properties were comprehensively investigated. The decomposition activity is closely associated with the Ir dispersion which is estimated using pulsed CO chemisorption. In addition, NO-TPD profiles and in situ FTIR spectra revealed a correlation between the adsorption properties of N2O/NOx and the catalytic N2O decomposition activity.