Influence Of Calcination Atmosphere Research Articles

Influence of calcination atmosphere on Fe doped activated carbon for the application of lead removal from water

In the current work, granular activated carbon (GAC) materials doped with 5 and 10 wt% of Fe were prepared via incipient wetness impregnation method utilizing two different solvents (water and ethanol) and calcined in N2 and static air atmosphere. The prepared materials were thoroughly characterized by FE-SEM, EDS, XRD, FT-IR, XPS and BET surface area techniques. The Fe doped materials were examined for adsorptive removal of lead (Pb2+) ions from aqueous solution. According to the adsorption screening experiments, the 5 wt% Fe doped GAC impregnated in ethanol and calcined under nitrogen demonstrated the highest removal of Pb2+ ions (86.6%). The adsorption results were found consistent with the surface and porous properties of the doped GAC. The 5 wt% Fe-GAC/ethanol/nitrogen illustrated the maximum surface area (715 m2/g), the largest pore diameter and volume, and the lowest size of Fe nanoparticles. The adsorption kinetics, isotherm and thermodynamics were evaluated for the remediation of Pb2+ ions by the optimized adsorbent. The kinetic analysis outcomes found well matched with the pseudo-second order model while the isotherm results modelling were well correlated with Redlich-Peterson, Sips and Langmuir models. The Langmuir highest adsorption capacity of Pb2+ ions was 124.3 mg/g at pH 4.7 and room temperature. The process of Pb2+ ions removal by Fe modified GAC was found as endothermic and spontaneous process as confirmed by the analysis of thermodynamic adsorption parameters. It was anticipated that both chemical and physical mechanisms were participated in the adsorption process including electrostatic interactions, complexation, ion exchange and surface adsorption.

Comparative catalytic study on butene/isobutane alkylation over LaX and CeX zeolites: The influence of calcination atmosphere

Lanthanum-containing (LaX) and cerium-containing X zeolites (CeX) were prepared by a double-exchange, double-calcination method. By changing the calcination atmospheres between nitrogen and air, the CeIV contents in CeX zeolites were adjusted and their impacts on physicochemical properties and catalytic performance in isobutane alkylation were established. The crystallinity of CeX zeolite was found to be negatively correlated with the CeIV content. This i s believed to be due to the water formed during the oxidation of CeIII, which facilitates the framework dealumination. As a consequence, calcining in air resulted in a great elimination of strong Brønsted acid sites while under nitrogen protection, this phenomenon was mostly hindered and the sample's acidity was preserved. When tested in a continuously flowed slurry reactor, the catalyst lifetime for isobutane alkylation was found to be linearly related to the strong Brønsted acid concentration. In addition, Ce3+ was found more benefit for the hydride transfer compared with La3+, which is ascribed to the stronger polarization effect on the CH bond of isobutane. Moreover, the decline of hydride transfer activity can be slowed down by the catalytic cracking of the bulky molecules. Based on the product distribution, a new catalytic cycle of dimethylhexanes (DMHs) involving a direct formation of isobutene rather than tert-butyl carbocation was proposed in isobutane alkylation.

Influence of calcination atmosphere and temperature on the fluorescence properties of NH4-form Y-type zeolite

Zeolite of NH4-form Y-type was calcined under different atmospheres and temperatures. The dependence of its fluorescence properties on the calcination conditions was studied to reveal the mechanism of the fluorescence. Whether the atmosphere contained oxygen was significant to determine if oxygen vacancies could be responsible for the fluorescence. It also depended evidently on the temperature and atmosphere and was the strongest on 350 °C calcination in nitrogen atmosphere. The zeolite framework and decomposition of NH4+ might cause this dependence.

Microemulsion based synthesis of promoted Fe–Co/MgO nanocatalyst: Influence of calcination atmosphere on the physicochemical properties, activity and light olefins selectivity for hydrogenation of carbon monoxide

Nanostructured promoted Fe–Co/MgO catalysts were fabricated by microemulsion technique and used for Fischer-Tropsch synthesis, for the first time. Regarding the deficiency of the systematic investigation correlated to the calcination atmosphere on FT catalytic performance, in this study, the effect of different calcination atmospheres on the catalytic activity, product selectivity, and physicochemical properties of promoted Fe–Co/MgO catalyst was investigated. To obtain uniform particle size distribution, the microemulsion technique was used. The prepared nanocatalysts were characterized by XRD, TGA, BET, ICP-OES, FESEM, TEM, FTIR, XPS, and H2-TPR. The higher activity, methane selectivity, and lower C3+ selectivity were obtained for the air-calcined catalyst. Calcination under Ar atmosphere resulted in lower activity, methane selectivity, but higher C3+ selectivity (with high paraffin contents). Characterizations indicated that these performances are related to the metal particle size and reducibility. The air-calcined catalyst with smaller particle size and higher reducibility rather than Ar-calcined one, demonstrated higher activity, oxidized more quickly in the preliminary operation period of Fischer-Tropsch synthesis, and encouraged the formation of CH4 and CO2.

Influence of calcination atmosphere on structure and electrochemical behavior of LiNi0.6Co0.2Mn0.2O2 cathode material for lithium-ion batteries

Layered Ni-rich LiNi0.6Co0.2Mn0.2O2 (LNCMO) materials are prepared by calcining the mixture of Ni0.6Co0.2Mn0.2(OH)2 precursor (co-precipitation method) and Li salts (Li2CO3). Two different caicination atmosphere (air and oxygen) are adopted to obtain final two samples of LNCMO-A (air) and LNCMO-O (oxygen) to individually investigate the influence of oxygen instead of air atmosphere on the structure and electrochemical behavior of the LNCMO materials. Both two samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and electrochemical charge/discharge tests including cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). XRD and SEM results show the LNCMO-O sample possesses relatively smaller Li+/Ni2+ cation mixing, better layer-structure ordering and smaller primary particle size. The electrochemical charge/discharge test results show the LNCMO-O sample exhibits superior discharge capacity (184.6mAhg−1 at 0.1C), higher cycling retention (91.4% after 100 cycles at 0.5C) and promoted rate performance. Further XPS, CV and EIS analyses on the promotion mechanism demonstrate that the oxygen-atmosphere calcination is important and beneficial to improve the electrochemical performance for Ni-rich LiNi0.6Co0.2Mn0.2O2 material.

ChemInform Abstract: Understanding Co‐Mo Catalyzed Ammonia Decomposition: Influence of Calcination Atmosphere and Identification of Active Phase.

AbstractCo(en)3MoO4 as an NH3 decomposition catalyst precursor is calcined in argon or air (600 °C, 3 h) and then reduced in pure H2 (600 °C, 3 h).

Understanding Co‐Mo Catalyzed Ammonia Decomposition: Influence of Calcination Atmosphere and Identification of Active Phase

AbstractTo elucidate the effect of textural and chemical properties of catalysts and to discriminate the active phase are fundamental issues in heterogeneous catalysis, but they are often complicated by the nature of support adding a new dimension. In this work, metal amine metallate (Co(en)3MoO4) precursor was directly treated by calcination and prenitridation to understand these two issues in Co‐Mo catalyzed ammonia decomposition. The calcination atmosphere (i.e., Ar and Air) is found to remarkably affect the textural and chemical properties of catalysts, and air atmosphere is favorable for higher stable reactivity despite incomplete nitridation of the catalyst. Further prenitridation of the sample from the calcination of Co(en)3MoO4 under air gives rise to higher catalytic activity, and Co3Mo3N is suggested as the dominant active phase of Co‐Mo catalysts. The insights revealed here shed new light on the design of Co‐Mo catalysts for ammonia decomposition.

Influence of calcination atmosphere on adsorptive performance of composite minerals materials

The three composite minerals materials, CMM-1, CMM-2 and CMM-3, which were prepared by four Chinese nonmetallic minerals (sodium bentonite, graphite, metakaolin and rectorite) and calcinated under the atmospheres of air, vacuum and nitrogen respectively, have been studied for the removal of malachite green (MG), a cationic dye, from aqueous solution. The influences of the three calcination atmospheres on the adsorbents' adsorptive performance were evaluated by a batch study in consideration of factors, such as the adsorbent dosage, initial dye concentration, adsorption duration, varied pH and static regeneration. Experimental results suggested that the maximum capacity of CMM to adsorb MG was more than 190mg·g−1, which was calcinated under the atmosphere of vacuum. Their adsorption equilibrium and kinetics confirmed the typical pseudo-first-order, pseudo-second-order, Freundlich and Langmuir adsorption models. The thermodynamic parameters of ΔGƟ, ΔHƟ and ΔSƟ showed that the adsorption was an exothermic and spontaneous process without remarkable change. The spent adsorbents were regenerated five times and probable pathway for the efficient and re-utilizing adsorbent has been proposed. The results indicate that CMM could be employed as porous, low density, and large specific surface area alternatives for the removal of cation dyes from industrial wastewater. The optimum adsorption capacity of the adsorbents was discovered under the calcination condition in vacuum.

Ethanol steam reforming over Ni/ZnAl 2O 4-CeO 2. Influence of calcination atmosphere and nature of catalytic precursor

The hydrogen production from ethanol steam reforming has been studied over Ni/ZnAl 2O 4-CeO 2 catalysts. The influence of calcination atmosphere and nature of catalytic precursor was analyzed. The impregnation of Ni was carried out from two different nickel salts: nitrate (Nt) and acetate (Ac). The catalysts were obtained from the precursor calcination under reductive and oxidative atmospheres. The catalysts obtained from nitrate salt impregnation were the most carbon resistance measured as mmolC/mol reacted C 2H 5OH, and those obtained under a reductive atmosphere were the most stable, as evidenced by smaller activity losses. The Ni(Nt)/ZnAl 2O 4-CeO 2 obtained under reductive atmosphere was the most active (steady state ethanol conversion = 88%) and stable (activity loss = 14%) under mild reforming conditions (7.8% C 2H 5OH inlet concentration, H 2O:C 2H 5OH molar ratio = 4.9, reaction temperature = 650 °C and W / F = 49 g min mol C 2 H 5 OH − 1 ). The hydrogen selectivity was 49% and the main C-containing products were CO 2, CO and C 2H 4O.

Different Effect of the Atmospheres on the Phase Formation and Performance of Li4Ti5O12 Prepared from Ball-Milling-Assisted Solid-Phase Reaction with Pristine and Carbon-Precoated TiO2 as Starting Materials

Pristine Li4Ti5O12 and Li4Ti5O12/C composite are prepared by high-energy ball-milling (HEBM)-assisted solid-state reaction with TiO2 anatase and Li2CO3 or carbon-precoated TiO2 anatase and Li2CO3 as reactants. The influence of calcination atmosphere on the phase formation and particulate morphology of those two products are systematically investigated by XRD, SEM, TEM, O2-TPO, and TPR techniques. The optimal calcination atmospheres for the synthesis of Li4Ti5O12 and Li4Ti5O12/C are diluted hydrogen and nitrogen atmospheres, respectively. TPR in various atmospheres demonstrates the difference in optimal atmospheres is due to the suppressing effect of hydrogen for Li2CO3 decomposition, the reducing properties of carbon and hydrogen, and the blocking effect of carbon for the reaction between TiO2 and Li2O. Both the pristine and carbon-coated Li4Ti5O12 show good rate and cycling performance. A near theoretical capacity of 175 mA h g−1 is achieved for both samples at 0.5 C rate. After a total cycling number of...

Effect of calcination atmosphere on the catalytic properties of PtSnNaMg/ZSM-5 for propane dehydrogenation

Abstract The influence of calcination atmosphere (flowing air, static air and flowing N 2 ) on the catalytic properties of PtSnNaMg/ZSM-5 catalysts for propane dehydrogenation was investigated. The catalysts were characterized by XRD, BET, TEM, and TPR. Results showed that the calcination atmosphere affected greatly the catalysts in many ways including surface area, the structure of the metallic phase and the interaction between platinum and tin, which are related to their catalytic behaviors. Among the catalysts studied, the PtSnNaMg/ZSM-5 catalyst calcined in flowing air exhibited the best catalytic performance.

Influence of calcination atmosphere on photocatalytic reactivity of K 2La 2Ti 3O 10 for water splitting

The layered perovskite type oxide K 2La 2Ti 3O 10 powders were prepared under air, Ar and H 2 calcination atmospheres by sol-gel method and characterized by X-ray diffractometry, UV-Vis diffuse reflectance and X-ray photoelectron spectroscopy. The influence of the calcination atmosphere on the photocatalytic reactivity of K 2La 2Ti 3O 10 for hydrogen production was investigated. The photocatalytic reactivity of K 2La 2Ti 3O 10 prepared under air, Ar and H 2 atmospheres was compared with that prepared under ultraviolet and visible light radiation using I - as electronic donor. The results show that K 2La 2Ti 3O 10 prepared under Ar and H 2 atmospheres has higher photocatalytic activity for hydrogen production than that prepared under air atmosphere. The hydrogen production rates under ultraviolet irradiation are 127.5, 81.3 and 57.0 μmol/(L·h) and those under visible light irradiation are 40.2, 30.2 and 16.5 μmol/(L·h) respectively when K 2La 2Ti 3O 10 is prepared under Ar, H 2 and air atmospheres.