Low Temperature Steam Methane Reforming Over Ni Based Catalytic Membrane Prepared by Electroless Palladium Plating.

A Pd/Ni-YSZ porous membrane with different palladium loadings and hydrazine as a reducing reagent was prepared by electroless plating and evaluated for the steam methane reforming activity. The steam-reforming activity of a Ni-YSZ porous membrane was greatly increased by the deposition of 4 g/L palladium in the low-temperature range (600 °C). With an increasing amount of reducing reagent, the Pd clusters were well dispersed on the Ni-YSZ surface and were uniform in size (∼500 nm). The Pd/Ni-YSZ catalytic porous membrane prepared by 1 of Pd/hydrazine ratio possessed an abundant amount of metallic Pd. The optimal palladium loadings and Pd/hydrazine ratio increased the catalytic activity in both the steam-reforming reaction and the Pd dispersion.

Feasibility study of Aesculus turbinata fruit shell-derived biochar for ammonia removal in wastewater and its subsequent use as nitrogen fertilizer.

In the face of increasing nitrogen demand for crop cultivation driven by population growth, this study presents a sustainable solution to address both the heightened demand and the energy-intensive process of nitrogen removal from wastewater. Our approach involves the removal of nitrogen from wastewater and its subsequent return to the soil as a fertilizer. Using biochar derived from Aesculus turbinata fruit shells (ATFS), a by-product of post-medical use, we investigated the effect of pyrolysis temperature on the NH4-N adsorption capacity of ATFS biochar (ATFS-BC). Notably, the ATFS-BC pyrolyzed at 300 °C (ATFS-BC300) exhibited the highest NH4-N adsorption capacity of 15.61 mg/g. The superior performance of ATFS-BC300 was attributed to its higher number of oxygen functional groups and more negatively charged surface, which contributed to the enhanced NH4-N adsorption. The removal of NH4-N by ATFS-BC300 involved both physical diffusion and chemisorption, with NH4-N forming a robust multilayer adsorption on the biochar. Alkaline conditions favored NH4-N adsorption by ATFS-BC300; however, the presence of trivalent and divalent ions hindered this process. Rice plants were cultivated to assess the potential of NH4-N adsorbed ATFS-BC300 (NH4-ATFS-BC300) as a nitrogen fertilizer. Remarkably, medium doses of NH4-ATFS-BC300 (594.5 kg/ha) exhibited key agronomic traits similar to those of the commercial nitrogen fertilizer in rice seedlings. Furthermore, high doses of NH4-ATFS-BC300 demonstrated superior agronomic traits compared to the commercial fertilizer. This study establishes the viability of utilizing ATFS-BC300 as a dual-purpose solution for wastewater treatment and nitrogen fertilizer supply, presenting a promising avenue for addressing environmental challenges.

Enhancement of performance and sulfur resistance of Si-doped V/W/Ti using sulfation for selective catalytic reduction of NOx with ammonia.

HIGHLIGHTS: The SO2 resistance improvement factor was confirmed to form Si2+(Si-O-Ti) species.In the optimised V/SiW/TiO2 catalyst; the incoming SO2 was converted to Si(SO4).The formation of Si(SO4) increased active sites for adsorbed NH3, in the form of SO4-NH3 to improve denitrification efficiency.

Pore control using the nano structured powders on the fabrication of porous membrane and its application.

In this study, a catalytic membrane with controlled pore size and structure was fabricated with nano sized particles and used in a steam and dry reforming reaction. The catalytic membrane was made using uniaxial-pressing and thermal treatment of the mixed powder. Nano sized yttria stabilized ZrO2 added to the nickel powder was determined to be a key factor in the preparation of the catalytic membrane. The membrane did not show the sintering effect due to the hindering of nickel agglomeration when subjected to heat treatment at high temperature. The optimum yttria stabilized ZrO2 content was below 1 wt% due to its strength and porosity. It was also unnecessary to deposit an additional reforming catalyst on the catalytic membrane, since the surface nickel site displayed excellent catalytic activity. When a mixture of methane and water/carbon dioxide was fed into the YSZ-Ni catalytic membrane reactor, the activity trended exceeded the performance of a conventional catalyst reactor, because of the difference in the flux of the gases.

Improving the activity of Mn/TiO2 catalysts through control of the pH and valence state of Mn during their preparation.

In this study, the authors investigated the influence of the valence state of Mn on the efficacy of selective catalytic reduction using a Mn-based catalyst. The nitrogen oxides (NOx) conversion rate of the catalyst was found to be dependent on the type of TiO2 support employed and on the temperature, as the catalyst showed an excellent conversion of > 80% at a space velocity of 60,000 hr(-1) when the temperature was above 200 degrees C. Brunauer-Emmett-Teller, X-ray diffraction, and X-ray photoelectron spectroscopy analyses confirmed that catalyst displaying the highest activity contained the Mn4+ species and that its valence state was highly dependent on the pH during the catalyst preparation.

Effect of the Mn oxidation state and lattice oxygen in Mn-based TiO2 catalysts on the low-temperature selective catalytic reduction of NO by NH3.

UNLABELLED: TiO2-supported manganese oxide catalysts formed using different calcination temperatures were prepared by using the wet-impregnation method and were investigated for their activity in the low-temperature selective catalytic reduction (SCR) of NO by NH3 with respect to the Mn valence and lattice oxygen behavior. The surface and bulk properties of these catalysts were examined using Brunauer-Emmett-Teller (BET) surface area, X-ray diffraction (XRD), temperature-programmed reduction (TPR), and temperature-programmed desorption (TPD). Catalysts prepared using lower calcination temperatures, which contained Mn4+ displayed high SCR activity at low temperatures and possessed several acid sites and active oxygen. The TPD analysis determined that the Brönsted and Lewis acid sites in the Mn/TiO2 catalysts were important for the low-temperature SCR at 80-160 and 200-350 degrees C, respectively. In addition, the available lattice oxygen was important for attaining high NO to NO2 oxidation at low temperatures. IMPLICATIONS: Recently, various Mn catalysts have been evaluated as SCR catalysts. However, there have been no studies on the relationship of adsorption and desorption properties and behavior of lattice oxygen according to the valence state for manganese oxides (MnO(x)). Therefore, in this study, the catalysts were prepared by the wet-impregnation method at different calcination temperatures in order to show the difference of manganese oxidation state. These catalysts were then characterized using various physicochemical techniques, including BET, XRD, TPR, and TPD, to understand the structure, oxidation state, redox properties, and adsorption and desorption properties of the Mn/TiO2 catalysts.

Physicochemical properties of chars at different treatment temperatures.

In this study, the physicochemical properties of the char of Indonesian SM coal following heat treatment at various temperatures were evaluated using X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and morphological and specific surface area analysis. Based on these analyses, heat treatment of coal was determined to be the most effective in increasing the coal rank. In the XPS analysis, the C-O and C-O-C groups and quaternary-N species were found to be of a lower grade coal when the pretreatment temperature decreased, meanwhile the C-C group and pyridinic species increased. In the FT-IR analysis, the collapse of the C-O and C-O-C group was observed due to the collapse of the ether group. In SEM and Brunauer-Emmett-Teller (BET) analysis, a decrease in the ether group was shown to be accompanied with the formation of micropores.

A study on the reaction characteristics of vanadium-impregnated natural manganese oxide in ammonia selective catalytic reduction.

This study investigated the effect of adding vanadium (V) to natural manganese oxide (NMO) in ammonia (NH3) selective catalytic reduction (SCR). The addition of V to NMO decreased the catalytic activity at low temperatures by blocking the active site. However, the enhancement of catalytic activity was achieved by controlling NH3 oxidation at high temperatures. From the NH3 temperature programmed desorption and oxygen on/off test, it was confirmed that the amount of Lewis acid site and active lattice oxygen of the catalyst affects the catalytic performance at low temperature.

Characteristics of fundamental combustion and NOx emission using various rank coals.

Eight types of coals of different rank were selected and their fundamental combustion characteristics were examined along with the conversion of volatile nitrogen (N) to nitrogen oxides (NOx)/fuel N to NOx. The activation energy, onset temperature, and burnout temperature were obtained from the differential thermogravimetry curve and Arrhenius plot, which were derived through thermo-gravimetric analysis. In addition, to derive the combustion of volatile N to NOx/fuel N to NOx, the coal sample, which was pretreated at various temperatures, was burned, and the results were compared with previously derived fundamental combustion characteristics. The authors' experimental results confirmed that coal rank was highly correlated with the combustion of volatile N to NOx/fuel N to NOx.

Promotional effect of antimony on the selective catalytic reduction NO with NH3 over V-Sb/Ti catalyst.

The effect of antimony on the selective catalytic reduction (SCR) performance and SO2 durability of V-Sb/Ti was investigated. The physicochemical characteristics of catalyst were characterized by various techniques, including Brunauer-Emmett-Teller (BET) surface area analysis, X-ray diffraction (XRD), NH3/SO2-temperature programmed desorption (TPD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTs), X-ray photoelectron spectroscopy (XPS), and H2-temperature programmed reduction (H2-TPR). The V-Sb/Ti catalyst showed excellent activity in the range 200-300°C (compared with V/Ti), with an optimum achieved for 2 wt.% antimony. The total amount of acidic sites and NH3 adsorption characteristics did not affect the catalytic efficiency. The Sb5+ fraction was highest for V-2.0Sb/Ti and exhibited a positive correlation with the V4+ fraction. This phenomenon is related to the effect of synergistic between vanadium and antimony, promoting the conversion of V5+ to V4+ by Sb5+. Increasing the V4+ fraction in V-Sb/Ti increased the catalytic activity, which was mainly attributed to enhanced catalyst re-oxidation capability due to the addition of antimony. Furthermore, the addition of antimony delayed the adsorption of SO2 onto the V-Sb/Ti catalyst surface, improving the resistance to this gas. Therefore, the addition of antimony to V/Ti improved NOx conversion and SO2 durability.

Influence of the addition of vanadium to Pt/TiO2 catalyst on the selective catalytic oxidation of NH3 to N2.

In this work, the effect of the addition of vanadium to the Pt/TiO2 catalyst on the selective catalytic oxidation (SCO) of NH3 to N2 was investigated. It was found that the addition of vanadium significantly enhanced catalytic activity at all tested temperatures. The Pt/V/TiO2 catalyst exhibited the highest NH3 conversion (∼100%) and NH3 to N2 conversion (∼81%) at 250°C. The physicochemical characteristics of the catalysts were investigated via Brunauer-Emmett-Teller (BET) analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), NH3 temperature-programmed desorption (TPD), NH3 temperature-programmed oxidation (TPO), and in situ Fourier-transform infrared (FTIR) spectroscopy. It was found that the addition of V to the catalyst enhanced the conversion of NH3 as a result of the formation of new acid sites. The increase in the number of acid sites resulted in increased NH3 to N2 conversion via the internal selective catalytic reduction (i-SCR) mechanism. This mechanism involves the SCR of NOx, which are formed by the oxidation of NH3. Based on experimental results and analyses of the catalysts modified by the addition of V, it was shown that there was a close relation between reaction selectivity and the surface oxygen species of the catalyst and N2 yield. Furthermore, the addition of V increased the durability of SO2 by inhibiting the formation of ammonium bisulfate (ABS).

Catalytic Performance of Ce0.6Y0.4O2-Supported Platinum Catalyst for Low-Temperature Water-Gas Shift Reaction.

In this study, Pt/Ce0.6Y0.4O2 catalyst was prepared using a citric sol-gel method and was used as a catalyst for a water-gas shift (WGS) reaction. Compared to 1 wt % Pt/CeO2 and Pt/Y2O3 catalysts, the Pt/Ce0.6Y0.4O2 catalyst showed a much higher WGS catalytic activity. At 250 °C, the conversion of carbon monoxide was 86.35% at a weight hourly space velocity of 30 000 cm3 gcat -1 h-1. The physicochemical properties of the catalysts were investigated via X-ray diffraction, transmission electron microscopy, chemisorption, H2 and CO temperature-programmed reduction, and in situ diffuse reflection infrared Fourier transform spectroscopy. These results confirmed that the catalytic activity did not depend on the dispersion and particle size of platinum. The high reducibility of the Ce0.6Y0.4O2 support plays a crucial role in improving the activity of the Pt/Ce0.6Y0.4O2 catalyst, and this improvement can also be explained by the reduction in CO adsorption strength.

Effect of CO on NO oxidation over platinum based catalysts for hybrid fast SCR process.

The oxidation characteristics of NO over Pt/TiO2 (anatase, rutile) catalysts have been determined in a fixed bed reactor as a function of O2, CO and SO2 concentrations in the presence of 8% water. The conversion of NO to NO2 increases with increasing O2 concentration up to 12% and it levels off. This saturation effect is more pronounced over rutile-Pt/TiO2 (r-Pt/TiO2) than that of anatase-Pt/TiO2 (a-Pt/TiO2). The presence of CO increases NO oxidation significantly and this enhanced effect is more pronounced on a-Pt/TiO2 than that on r-Pt/TiO2 with increasing CO concentration at lower temperatures. The same effect is also observed on the catalysts with different Pt and tungsten oxide (WO3) loadings. With increasing Pt and WO3 loadings on TiO2 support (Pt-WO3/TiO2), formation of NO2 is high even at lower temperatures. The presence of SO2 significantly suppresses the oxidation of NO over both r-Pt/TiO2 and a-Pt/TiO2 catalysts but it is less pronounced due to low stability of sulfate on a-Pt/TiO2.

Effects of NO2 and SO2 on selective catalytic reduction of nitrogen oxides by ammonia.

The selective catalytic reduction (SCR) characteristics of NO and NO(2) over V(2)O(5)-WO(3)-MnO(2)/TiO(2) catalyst using ammonia as a reducing agent have been determined in a fixed-bed reactor at 200-400 degrees C. The presence of NO(2) enhances the SCR activity at lower temperatures and the optimum ratio of NO(2)/NO(x) is found to be 0.5. During the SCR reactions, there are some side reactions occurred such as ammonia oxidation and N(2)O formation. At higher temperatures, the selective catalytic oxidation of ammonia and the nitrous oxide formation compete with the SCR reactions. The denitrification (DeNO(x)) conversion decreases at lower temperatures but it increases at higher temperatures with increasing SO(2) concentration. The presence of SO(2) in the feeds inhibits N(2)O formation.

Influence of Mn valence state and characteristic of TiO2 on the performance of Mn-Ti catalysts in ozone decomposition.

The effects of physicochemical properties of Mn-Ti catalysts on O3 conversion were examined. The catalysts were prepared by a wet impregnation method that gave manganese supported on various commercial sources of TiO2. The properties of the catalysts were studied using physicochemical techniques, including Brunauer-Emmett-Teller (BET) surface area analysis, X-ray diffraction (XRD), H2 temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), and thermal gravimetric analysis (TGA). The O3 decomposition tests of Mn-Ti catalysts with various manganese loadings revealed that the 10 wt% manganese catalyst exhibited optimal, excellent activity. The O3 conversion and Mn valence state of the Mn-Ti catalysts were different, depending on the structure of the TiO2 source. Increasing the O/Ti surface atomic ratio in TiO2 increased the Mn3+ ratio. The Mn3+ ratio directly affected the O3 decomposition activity of the Mn-Ti catalyst. When the Mn3+ ratio was the largest, the catalyst showed the highest activity in O3 decomposition. The valence state of Mn exposed to the surface was a critical factor in O3 decomposition by Mn-Ti catalysts.

Characterization and reactivity of natural manganese ore catalysts in the selective catalytic oxidation of ammonia to nitrogen.

Natural manganese ore (NMO) catalysts were characterized and tested in the selective catalytic oxidation of ammonia to nitrogen oxides under dilute conditions. Also, the oxidation of ammonia (NH(3)) was carried out using pure MnO(2), Mn(2)O(3) for comparing with the activity. It is found that the activity of NMO was similar to that of MnO(2) at low temperature below 150 degrees C but above this temperature, the activity of these catalysts showed the difference. In the course of NH(3) oxidation, N(2), NO, N(2)O and H(2)O were produced. But the quantity of NO(2) produced in this experiment was negligible. At temperature below 250 degrees C, selectivity into N(2) from NH(3) oxidation was in the order, NMO > MnO(2) > Mn(2)O(3). This is the reverse of activity of these manganese oxides. Also the characterization of NH(3) oxidation was proposed and supported by the effect of space velocity, inlet O(2) and NH(3) concentration. The increase of space velocity remarkably influenced not only the conversion but also selectivity into N(2). The higher the reaction temperature was, the higher the effect of inlet O(2) and NH(3) concentration on the reaction rate was. By introducing NO during NH(3) oxidation reaction, the possibility of NMO as selective catalytic reduction catalyst at low temperature was studied and showed positive results.

Photocatalytic degradation of volatile organic compounds at the gas-solid interface of a TiO2 photocatalyst.

In the present work, photocatalytic degradation of volatile organic compounds including gas-phase trichloroethylene (TCE), acetone, methanol and toluene over illuminated TiO2 was closely examined in a batch photoreactor as a function of water vapor, molecular oxygen and reaction temperature. Water vapor enhanced the photocatalytic degradation rate of toluene, but was inhibitive for acetone, and, there was an optimum water vapor concentration in the TCE and methanol removal. In a nitrogen atmosphere, it showed lower photocatalytic degradation rate than in air and pure oxygen. Thus, it could be concluded that oxygen is an essential component in photocatalytic reactions by trapping photogenerated electrons on the semiconductor surface and by decreasing the recombination of electrons and holes. As for the influence of reaction temperature, it was found that photocatalytic degradation was more effective at a moderate temperature than at an elevated temperature for each compound.

A study on the characteristics of CO oxidation at room temperature by metallic Pt.

Various experiments and analysis were conducted in order to manufacture a catalyst that could very efficiently oxidize carbon monoxide at room temperature and also to identify the relevant factors influencing the oxidation reaction. Pt/TiO(2) catalyst can increase the oxidizing capability of CO at low temperature and room temperature by reduction. In FT-IR experiments, the catalyst that displayed excellent activity was capable of efficiently oxidizing CO to CO(2) using atmospheric oxygen. Based on the results of XPS analysis, we found that the reduced catalyst changed the platinum's oxidation value to Pt(+2) and Pt(+0). Through the O(2)-reoxidation experiments, the catalyst, which consisted of non-stoichiometric platinum oxidized species, displayed an excellent ability to accept oxygen. In this study, the Pt/TiO(2) catalyst was able to very efficiently oxidize CO at low temperature and room temperature even with a minute quantity of platinum.

Degradation of gas-phase trichloroethylene over thin-film TiO2 photocatalyst in multi-modules reactor.

The present paper examined the photocatalytic degradation (PCD) of gas-phase trichloroethylene (TCE) over thin-film TiO2. A large-scale treatment of TCE was carried out using scale-up continuous flow photo-reactor in which nine reactors were arranged in parallel and series. The parallel or serial arrangement is a significant factor to determine the special arrangement of whole reactor module as well as to compact the multi-modules in a continuous flow reactor. The conversion of TCE according to the space time was nearly same for parallel and serial connection of the reactors.

The control of valence state: how V/TiO2 catalyst is hindering the deactivation using the mechanochemical method.

Various experiments were conducted to improve durability against SO(2) by impregnating the same amount of vanadium in TiO(2) which had the various physical properties. According to those catalysts, the degree of deactivation by SO(2) had various results, and it was found that the production of unreacted NH(3) in selective catalytic reduction reaction should be low. Based on X-ray photoelectron spectroscopy analysis, O(2) on-off test, O(2) reoxidation test and H(2)-temperature programmed reduction experiment, the redox capacity of catalyst was improved due to increasing of non-stoichiometric compounds. Such a non-stoichiometric oxide and redox capacity of catalyst can be enhanced by the ball-milling process, and the production of ammonium sulfate salt can be more easily inhibited by the superior oxidation-reduction capacity of catalyst. We found that this result is caused by producing and increasing of V(x+) (x