Catalytic Activity For Decomposition Research Articles

Europium barium titanate perovskite nano-photocatalysts: Mechanistic analysis of a chloro-dialkyl sulfide decomposition/detoxification

Mixed europium-barium titanate perovskites, EuxBa1-xTiO3, were investigated as nanocatalysts for the photodetoxification of a mustard gas surrogate, 2-chloroethylethyl sulfide, CEES. EuxBa1-xTiO3 nanoparticles were prepared using an enhanced sol–gel method, resulting in 10–25 nm particles. A lanthanide valence and nanostructure was altered by applying a heat treatment in either oxidizing or reducing atmospheres. The results demonstrated a high adsorption capacity and improved catalytic decomposition activity in comparison to a set of previously explored transition metal oxide photocatalysts, including barium titanate. Analysis of the decomposition products indicated hydrolysis as the predominant reactive detoxification mechanism in the dark. Upon light irradiation, radicals were formed and contributed to the degradation and oxidation of CEES, especially in the sample rich in Eu(III) and oxygen, with a more developed porosity. The results suggested photogenerated electrons and holes, influenced by the presence of Eu, contributed to the free radical formation and oxidation reactions, respectively, increasing both the weight uptake and efficiency of catalytic decomposition.

Typing of cancer cells by microswimmer based on Co-Fe-MOF for one-step simultaneously detect multiple biomarkers

Capturing, identifying, and counting CTCs cancer cells that have escaped from the tumor and wandered into the bloodstream is a major challenge. We proposed a noval microswimmer dual-mode aptamer (electrochemical and fluorescent)-(Mapt-EF) homogeneous sensor with active capture/controlled release double signaling molecule/separation and release cell based on the Co-Fe-MOF nanomaterial for simultaneous one-step detection of multiple biomarkers protein tyrosine kinase-7 (PTK7), Epithelial cell adhesion molecule (EpCAM), and mucin-1 (MUC1) for diagnosis of multiple cancer cell types. The Co-Fe-MOF is a nano-enzyme capable of catalyzing the decomposition of hydrogen peroxide to release bubbles of oxygen, producing a driving force to conduct hydrogen peroxide through the liquid, and has the capacity to self-decompose during the catalytic process. Phosphoric acid is present in the aptamer chains of PTK7, EpCAM, and MUC1, and the aptamer chains are adsorbed to the surface of the Mapt-EF homogeneous sensor in the form of a gated switch to inhibit the catalytic decomposition activity of hydrogen peroxide. The Mapt-EF homogeneous sensor has the capability to actively target biomarkers that can be entrained by oxygen bubbles without being degraded. The detection time of the sensor was 20 min, the detection limits were 9.6 fg/mL, 8.4 fg/mL and 7.7 fg/mL with the linear range was 0–20 pg/mL, respectively. The Mapt-EF homogeneous sensor has high detection sensitivity, and its detection limit can reach the level of single cell at the lowest. The Mapt-EF homogeneous sensor has great application potential in clinical detection and analysis of tumor cells.

Catalytic removal of 2-butanone with ozone over porous spent fluid catalytic cracking catalyst

To remove harmful volatile organic compounds (VOCs) including 2-butanone (methyl ethyl ketone, MEK) emitted from various industrial plants is very important for the clean air. Also, it is worthwhile to recycle porous spent fluid catalytic cracking (SFCC) catalysts from various petroleum refineries in terms of reducing industrial waste and the reuse of discharged resources. Therefore, Mn and Mn–Cu added SFCC (Mn/SFCC and Mn–Cu/SFCC) catalysts were prepared to compare their catalytic efficiencies together with the SFCC catalyst in the ozonation of 2-butanone. Since the SFCC-based catalysts have a structure similar to that of zeolite Y (Y), the Mn-loaded zeolite Y catalyst (Mn/Y) was also prepared to compare its activity for the removal of 2-butanone and ozone to that of the SFCC-based ones at room temperature. Among the five catalysts of this study (Y, Mn/Y, SFCC, Mn/SFCC, and Mn–Cu/SFCC), the Mn–Cu/SFCC and Mn/SFCC catalysts showed the better catalytic decomposition activity than the others. The increased distributions of the Mn3+ species and the Ovacancy sites in Mn/SFCC and Mn–Cu/SFCC catalysts which could supply more available active sites for the 2-butanone and ozone removal would enhance the catalytic activity of them.

A new ternary copper (Ⅱ) complex of 2,4-dihydroxybenzoic acid: Synthesis, crystal structure and its catalytic decomposition effect on AP and RDX

In order to solve the unclear problems of structure and composition for 2,4-dihydroxybenzoic acid (2,4-DHBA) copper salt (β-Cu), a new insoluble ternary copper (Ⅱ) complex of 2,4-DHBA ([Cu(C12H8N2)2(C7H5O4)](C7H5O4)) was designed and synthesized in water. The ternary complex crystallizes in the monoclinic system with the space group P21/n. The central Cu2+ is coordinated with four nitrogen atoms from two 1,10-phenanthroline ligands and one carboxyl oxygen atom from a 2,4-DHBA anion. The other 2,4-DHBA anion does not participate in coordination and only provides the action of balance charge. In addition, compared with β-Cu, no water molecules exist in the ternary complex. The thermal stability of the ternary complex was investigated, as well as its catalytic decomposition activity on AP and RDX. With the addition of the ternary complex, the exothermic decomposition peak temperatures of AP and RDX were reduced from 406.5 to 353.9 ​°C, and 242.3 to 181.4 ​°C respectively, and the apparent activation energies were reduced from 293.1 to 207.4 ​kJ ​mol−1, and 239.6 to 177.5 ​kJ ​mol−1, respectively. Moreover, the addition of the ternary complex has greatly improved the heat release of AP and RDX. The catalytic decomposition performance of the new ternary complex on AP and RDX is much better than that of the traditional β-Cu. Moreover, the new copper (Ⅱ) complex completely changed the thermal decomposition process of RDX from melting decomposition to direct solid phase decomposition, and such catalytic effect is uncommon. Therefore, the new ternary copper (Ⅱ) complex presents a better potential application for modified double-base propellant of RDX.

Fabrication of Copper-Cerium Oxide Hollow Spheres with Carbon Template and Their Catalytic Activity for Decomposition of Nitrous Oxide

Fabrication of Copper-Cerium Oxide Hollow Spheres with Carbon Template and Their Catalytic Activity for Decomposition of Nitrous Oxide

Site-Selective Nitrogen-Doped α-MnO2 for Catalytic Oxidation of Carcinogenic HCHO in Indoor Air

Developing high-efficiency formaldehyde (HCHO) catalytic oxidation catalysts is of significance and practicability for indoor air decontamination. It is generally considered that anionic doping is a traditional strategy to regulate the reaction activity of catalyst materials. However, one of the concerns worth exploring is the recognition of doping sites and their impact on catalytic performance. Herein, nitrogen atoms are successfully introduced into the MnO2 structure by high-temperature calcination with urea as the nitrogen source for the first time. By regulating the usage of urea, nitrogen atoms are selectively and successfully doped into the interstitial sites and substitutional sites. Furthermore, the effect of nitrogen-doped MnO2 on the catalytic oxidation of HCHO is studied in detail. Results indicate that nitrogen doping can promote the formation of oxygen vacancies, strengthen the activation of adsorbed O2, and enhance the adsorption of HCHO, which is conducive to catalytic decomposition of HCHO. Importantly, nitrogen doping at various doping sites has a considerable effect on catalytic decomposition activity. Although both interstitial and substitutional nitrogen doping can boost the decomposition performance of HCHO, the interstitial sites are the most suitable doping sites in the α-MnO2 lattice. The chemical environment around the interstitial sites is favorable for the creation of oxygen vacancies, as well as the adsorption/activation of HCHO and O2. Interstitial nitrogen doping can dramatically increase the HCHO catalytic activity of α-MnO2, and the complete catalytic decomposition temperature is reduced from 130 to 90 °C at the condition of GHSV = 90 L/gcat·h. This study provides a facile and effective method for site-selective nitrogen-doping and an in-depth understanding of its effect on catalytic activity.

First-Principles Investigation of Graphene and Fe2O3 Catalytic Activity for Decomposition of Ammonium Perchlorate.

The employment of catalysts is an effective way to improve ammonium perchlorate (AP) decomposition performance during the combustion of composite solid propellants. Understanding the micromechanism of catalysts at the atomic level, which is hard to be observed by experiments, can help attain more excellent decomposition properties of AP. In this study, first-principles simulations based on density functional theory were used to explore the effect of the graphene catalyst and iron oxide (Fe2O3) catalyst on AP decomposition. Considering the transfer of a H atom during AP decomposition, the most stable adsorption sites for aforementioned catalysts were found: the top of the C atom of the graphene surface with the adsorption energy of -0.378 eV and the top of the Fe atom of the Fe2O3 surface with the adsorption energy of -1.596 eV. On the basis of adsorption results, our transition state calculations indicate that, in comparison to control groups, graphene and Fe2O3 can reduce the activation energy barrier by ∼19 and ∼37%, respectively, to promote AP decomposition with a transfer process of a H atom on the catalyst surface. Our calculations provide a way for explaining the micromechanism of the catalytic activity of graphene and Fe2O3 nanocomposites in AP decomposition and guide experimental applications of graphene and Fe2O3 for catalytic reactions.

Rapid and green combustion synthesis of nanocomposites based on Zn–Co–O nanostructures as photocatalysts for enhanced degradation of acid brown 14 contaminant under sunlight

It is highly favorable to introduce an efficacious magnetic separable structure as visible light photocatalyst for practical usages to eliminate organic contaminants. Herein, magnetic separable zinc–cobalt mixed-metal oxides as visible light photocatalysts were successfully fabricated utilizing diverse saccharides as eco-friendly kinds of capping agents and fuels, for the first time. The influence of saccharide kind and its dosage was explored to achieve the circumstances for creating the sample with more favorable morphology, catalytic capability, and size. The features of the nanostructured zinc–cobalt mixed-metal oxides were investigated, and its creation corroborated with several techniques. In the following, the catalytic decomposition activity of varied ZnCo2O4/Co3O4 micro/nanostructures for acid brown 14 as a water contaminant was explored, for the first time. The outcomes reveal that the nanostructured zinc–cobalt mixed-metal oxides as visible light photocatalysts could denote superb yield. The use of the binary composite nanostructures (ZnCo2O4-Co3O4) resulted in quick decomposition, with almost 94.3% of acid brown 14 being decomposed within 75 min. This work offers a feasible and eco-friendly way to create magnetic separable zinc–cobalt mixed-metal oxides as high potential visible light photocatalysts that can be apposite for environmental remediation.

Optimizing chemical and mechanical stability of catalytic nanofiber web for development of efficient detoxification cloths against CWAs

N–Cl functional groups have been widely utilized for antimicrobial and detoxification purpose. However, along with the high reactivity of N–Cl moiety, long term stability of N–Cl moiety under ambient condition is of special interest for final applications. Diverse organic moieties have been developed to enhance N–Cl stability, and hydantoin N–Cl groups are generally accepted as a promising candidate. Here, N–Cl functionalized electrospun nanofibers are prepared via surface functionalization method for fabrication of catalytic nanofiber mat against chemical warfare agent. Thermoplastic polyurethane (TPU) containing abundant pandent azide moiety is firstly synthesized, and nanofiber web is prepared via electrospinning. Hydantoin functional groups that are well-known moiety to stabilize N–Cl functional groups are introduced via surface click reaction. The storage stability of N–Cl groups from surface reaction is superior than that of bulk reaction with maintaining their catalytic activity for decomposition of chemical warfare agents. In order to increase mechanical properties of nanofiber web, amount of hydantoin groups on surfaces has been controlled by blending of normal TPU with azide TPU, and blended nanofiber web maintains their inherent flexibility after hydantoin functionalization and N-chlorination. Optimized blending conditions to achieve both of high N–Cl stability and enhanced catalytic activity have been traced. Surface rich N–Cl groups show better stability with maintaining their inherent catalytic activities.

Spinel cobalt(II) ferrite-chromites as catalysts for H2O2 decomposition: Synthesis, morphology, cation distribution and antistructure model of active centers formation

Cobalt (II) ferrite-chromites CoCr2-xFexO4 (x = 0.0 ÷ 2.0, step is 0.2) with spinel structure have been synthesized using sol-gel method with citrate metal-polymer precursor. The relations between structural, morphological and catalytic properties of the mixed spinels have been studied. The CoCr2-xFexO4 powders were analyzed using X-ray diffraction analysis, Mössbauer spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy, energy-dispersive analysis and Brunauer–Emmett–Teller (BET) methods. The average crystallite size was calculated using the Williamson-Hall and size-strain plot methods. Increase of Fe content resulted in increase of the crystallite size from 10 nm (CoCr2O4) to 35 nm (CoFe2O4). Chromium ions were located mainly in octahedral sites, whereas the cobalt and ferric ions were distributed between the octahedral and tetrahedral sites. The lattice parameter was dependent mostly on the octahedral site radius. Superparamagnetic properties of the nanoparticles were described by two-level relaxation model. The samples with a high content of chromium (III) have highly porous structure. Porosity of the samples was decreased with increasing the Fe content. IR spectra contain two peaks corresponding to two characteristic sites in the cubic spinel structure. The mixed ferrite-chromite spinels have catalytic activity in decomposition of hydrogen peroxide. Rate of H2O2 decomposition in the presence of cobalt (II) ferrite-chromite NPs corresponds to the first-order kinetic model. Within 25 min, the decomposition degree is 76.6% with the most active CoFe2O4 sample. Catalytic activity of the samples depends on two factors: the specific surface area and the surface active sites. Antistructure modeling revealed that the tetrahedral Fe(III) sites have electron acceptor properties. The formed Fe(II) ions are active centers in the Fenton-like processes. Probably, the red-ox pairs Co2+/Co3+ in the spinel lattice promote catalytic activity due to acceleration of electron transfer. The spinel cobalt (II) ferrite-chromites are promising catalysts for oxidation of toxic organic impurities in wastewaters with using H2O2.

Promoting effects of Fe-Ni alloy on co-production of H2 and carbon nanotubes during steam reforming of biomass tar over Ni-Fe/α-Al2O3

Fe-modified Ni/Al2O3 catalysts with Fe/Ni molar ratios of 0, 0.5, 1 and 2 were prepared to promote the co-production of H2 and carbon nanotubes (CNTs) during steam reforming of toluene as a tar model compound. After the addition of Fe, toluene conversion increased from 55.1% of Ni/Al2O3 to 73.6% of F1N1A (Fe/Ni ratio of 1), and H2 yield over F1N1A reached the maximum of more than 2000 mmol/(g-cata). Multi-walled carbon nanotubes with average diameter of 10–30 nm were generated and follow tip-growth mechanism. Compared with Ni/Al2O3, the addition of Fe remarkably increased the amount and quality of CNTs which had longer length and less tortuosity. These dual promoting effects on H2 and CNTs after the addition of Fe were attributed to the strong interaction between Ni and Fe in Fe-Ni alloy. Fe-Ni alloy had the high activity for the decomposition performance of toluene and H2O to generate more H2 and intermediates for improving the reforming reaction. Meanwhile, the high catalytic decomposition activity supplied more carbon species and the formation of Fe-Ni alloy enhanced the generation of metal carbide for promoting CNTs growth. Besides, the deposition of amorphous carbon was suppressed and the interaction between Ni particle and catalyst support was weakened after the addition of Fe, which kept the activity of catalyst and promoted the tip-growth of CNTs.

Preparation and characterization of Cu–Mn composite oxides in N2O decomposition

A series of CuxMn composite oxide catalysts with different Cu/Mn molar ratios (x = 1, 1.5 and 2) was synthesized by the co-precipitation method. The catalytic performance of CuxMn in N2O decomposition has been studied with a continuous flowing microreactor system. The obtained catalysts were characterized by XRD, BET, Raman, FT-IR, ICP-AES and H2-TPR. The catalytic tests show that the CuxMn catalysts exhibit more excellent N2O catalytic decomposition activity compared with the pure CuO and Mn2O3 catalysts, and the Cu1.5Mn shows the highest catalytic activity under the reaction conditions of N2O 0.1%, GHSV 10000 h−1. The characterizations results suggest that bulk CuO and Mn2O3 existed in pure CuO and Mn2O3 catalysts, respectively. In the CuxMn catalysts, with the decreasing of x, the amount of bulk CuO gradually decreases until it disappears, while the amount of newly formed CuMn2O4 gradually increases. However, the amount of small crystal CuO increases first and then decreases, which might be considered as an important active phase that contributes to the excellent catalytic performance of CuxMn in N2O decomposition.

Decomposition of Nitrous Oxide over Cu/TiO2 Catalysts: The Effect of Cu Loading, TiO2 Structure, and Reaction Conditions

Decomposition of nitrous oxide (N2O) over titania (TiO2) supported copper (Cu) catalyst was investigated with the existence of oxygen and water vapor. The catalytic activity of TiO2 was promoted by copper loading. It was found that there are optimum levels of copper loading on TiO2, and these values are correlated to the specific surface area of TiO2 support being used. The relationship between the catalytic activity for decomposition of N2O and the crystal structure of TiO2 was also investigated. The result revealed that Cu/TiO2 catalysts with the rutile structure has a higher activity toward N2O decomposition than those with the anatase structure. In this research, Cu(5wt%)/TiO2 prepared from TiO2 JRC-TIO-4 (reference catalyst provided by Catalysis Society of Japan) which was mainly constituted of rutile showed the highest activity for N2O decomposition and it could decompose N2O completely at 650℃. The catalytic activity was inhibited by the existence of oxygen. However, there was no influence of water vapor to the catalytic activity of Cu/TiO2 for N2O decomposition.

Activity and stability of biochar in hydrogen peroxide based oxidation system for degradation of naphthenic acid

This study investigated the stability and catalytic activity of wheat straw biochar (WS), hardwood biochar (HW) and commercial activated carbon (AC) in hydrogen peroxide (H2O2) based oxidation system for degradation of model naphthenic acids compound, 1-methyl-1- cyclohexane carboxylic acid (MCCA). WS showed excellent catalytic activity for decomposition of H2O2 and MCCA degradation as demonstrated by high H2O2 decomposition rate (2.0*10−4 M−1s−1), amount of hydroxyl (OH) radicals generated (182 mg/L) and degradation efficiency of MCCA (100% at Co – 100 mg/L). 2-Methyl pentatonic acid was identified as reaction intermediate and 99% mineralization of MCCA was obtained within 4 h. The real wastewater conditions were simulated by addition of chloride (Cl−) and bicarbonate ions (HCO3−) and found that lower concentrations of Cl− and HCO3− have minimal influence on MCCA removal. Overall, biochar catalyzed H2O2 based oxidation process has great potential and can be applied for degradation of NAs in oil-sand processed water.

Activation of peroxymonosulfate into amoxicillin degradation using cobalt ferrite nanoparticles anchored on graphene (CoFe2O4@Gr)

The study focused on the catalytic activation of peroxymonosulfate (PMS) using cobalt ferrite nanoparticles decorated on graphene (CoFe2O4@Gr) into amoxicillin (AMX) degradation-based on sulfate radicals. Oxidation experiments were performed at different experimental variables such as PMS dosages, pH, reaction time and various concentrations of catalyst and AMX. CoFe2O4@Gr has a good magnetic response and rapidly separated from aquatic media. It also showed a significant catalytic activity in decomposition of PMS molecules. At optimum conditions, 99.27, 83.1 and 61.11% of AMX, chemical oxygen demand and total organic carbon were removed during 60 min reaction, respectively.

Label-free fluorometric assay for cytochrome c in apoptotic cells based on near infrared Ag2S quantum dots

As an important biomarker, cytochrome c (Cyt c) plays a crucial role in mitochondrial electron transport chain and cell apoptosis. Herein, a label-free near-infrared (NIR) Ag2S quantum dots (QDs)-based fluorescent strategy was constructed for the sensitive and selective detection of Cyt c. In this system, Cyt c was hydrolyzed by trypsin, and the resulting heme-peptide fragment exhibited peroxidase-like activity for catalytic decomposition of H2O2 into hydroxyl radical (·OH). The presence of caffeic acid in this system resulted into the formation of caffeic acid-quinone due to the strong oxidizing ability of ·OH. The production of caffeic acid-quinone led to the fluorescence quenching of Ag2S QDs through electron transfer mechanism. Based on the cascade reaction, we successfully developed a label-free approach to detect Cyt c using Ag2S QDs as nanoprobes. Under the optimized conditions, the fluorescence intensity of Ag2S QDs was linearly relative to the concentration of Cyt c over the range from 2.0 to 150 nM with a detection limit of 1.7 nM. In addition, this strategy was successfully applied for quantitative detection of Cyt c in cell lysates of H2O2 or etoposide (anticancer drug)-induced apoptotic cells, providing great potential application for cell-based oxidation pressure determination and screening of anticancer drugs.

Effect of La, Ce and Nd oxides addition on the activity and stability of Co/MgO catalyst for methane decomposition into COx-free H2 production and carbon nanotubes

ABSTRACTThe influence of lanthanide metals (La, Ce or Nd) addition as a promoter to Co/MgO catalyst was investigated for the “COx-free” hydrogen production via catalytic decomposition of methane (CDM). The catalysts were prepared using impregnation or co-impregnation method with a total metal content of 40 wt%. The characterizations of fresh and used catalysts were carried out by XRD, Raman spectroscopy, BET, TPR, TEM and TGA techniques. It was found that the incorporation of 10% La to 30% Co/MgO has improved the catalytic decomposition activity (∼ 82% hydrogen yield) and stability (220 min) compared to the un-promoted 40% Co/MgO catalyst. On the contrary, the addition of 10% Ce has induced a remarkable inhibition in the catalytic performance (25% at 210 min), where no significant change was observed upon addition of 10% Nd to 30% Co/MgO. The results revealed that the incorporation of La as a promoter induced a suitable strong interaction between MgO support and CoO active metal, enhancing the catalytic activity and stability of the catalyst for methane decomposition reaction. From XRD and TPR analysis, the presence of LaCoO3 phase facilitates the reduction of Co oxide so enhanced the production of Co metallic form which can be referred to its highest activity. TEM images illustrated that the accumulated carbon over all catalysts is multi-walled carbon nanotubes.

Ir-Catalysed Nitrous oxide (N2O) Decomposition: Effect of Ir Particle Size and Metal–Support Interactions

The effect of the morphology of Ir particles supported on γ-Al2O3, 8 mol%Y2O3-stabilized ZrO2 (YSZ), 10 mol%Gd2O3-doped CeO2 (GDC) and 80 wt%Al2O3–10 wt%CeO2–10 wt%ZrO2 (ACZ) on their stability on oxidative conditions, the associated metal–support interactions and activity for catalytic decomposition of N2O has been studied. Supports with intermediate or high oxygen ion lability (GDC and ACZ) effectively stabilized Ir nanoparticles against sintering, in striking contrast to supports offering negligible or low oxygen ion lability (γ-Al2O3 and YSZ). Turnover frequency studies using size-controlled Ir particles showed strong structure sensitivity, de-N2O catalysis being favoured on large catalyst particles. Although metallic Ir showed some de-N2O activity, IrO2 was more active, possibly present as a superficial overlayer on the iridium particles under reaction conditions. Support-induced turnover rate modifications, resulted from an effective double layer [Oδ−–δ+](Ir) on the surface of iridium nanoparticles, via O2− backspillover from the support, were significant in the case of GDC and ACZ.

Effect of precipitants on the catalytic activity of Co–Ce composite oxide for N2O catalytic decomposition

Co–Ce composite oxide catalysts have been prepared by the co-precipitation method using K2CO3 (Co–Ce–A), KOH (Co–Ce–B) and NH3·H2O (Co–Ce–C) as precipitants. The effect of different precipitants on the catalytic activity for N2O catalytic decomposition was investigated in a fixed-bed continuous flow reactor. The structure and properties of the catalysts were characterized by XRD, TEM, FT-IR, Raman, XRF, BET, EC, H2-TPR and O2-TPD. The results show that under the reaction conditions of N2O 0.1% and GHSV 10,000 h−1, the catalyst prepared by using K2CO3 as precipitant exhibits better N2O catalytic decomposition activity than that prepared by using KOH or NH3·H2O as precipitant. The XRD, TEM and BET results reveal that all the samples exist as a Co3O4 phase with the spinel structure though the precipitated precursors are different, while Co–Ce–A shows higher specific surface area and smaller crystalline size. Further characterizations results suggest that compared with Co–Ce–B and Co–Ce–C, Co–Ce–A possesses not only stronger interaction between Co and Ce species, but also higher electrical conductivity resulting from the more amount of residual K, which improves the reduction of Co3+–Co2+ and facilitates the desorption of surface oxygen species. Therefore, Co–Ce–A exhibits enhanced N2O catalytic decomposition activity.

Chemical looping combustion of biomass using metal ferrites as oxygen carriers

The evaluation of chemical looping combustion (CLC) for CO2 capture was conducted via a thermogravimetric analyzer (TGA) and a laboratory-scale fluidized bed using pine sawdust (PS) as fuel and metal ferrites, MFe2O4 (M=Cu, Ni and Co), as oxygen carriers. Metal ferrites were prepared by sol-gel method. The fresh, reduced and after five redox cycles oxygen carriers were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and accelerated surface area porosimetry. Thermodynamic simulation was performed using software HSC Chemistry 6.0. The TGA results indicated that CuFe2O4 shows a lower initial reaction temperature, and CoFe2O4 has a faster oxygen uptake rate. Both carbon conversion (xc) and carbon capture efficiency (ηCO2) increased with temperature. The maximum values of xc and ηCO2 were 96.86% and 95.48%, 95.45% and 94.25%, and 95.17% and 94.04% for CuFe2O4, CoFe2O4, and NiFe2O4 at 900°C, respectively. The CuFe2O4 shows higher reaction reactivity, while NiFe2O4 has a higher catalytic activity for decomposition of tar in fluidized bed tests. The XRD results show CoFe2O4 is more readily reduced to FeO, which agreed with the results of thermodynamic simulation, and three metal ferrites can be regenerated completely after five cycles. The values of xc and ηCO2 remained high for both CuFe2O4 and CoFe2O4, while a significant decrease in xc and ηCO2 for NiFe2O4 was observed after five cycles due to significant sintering. Both CuFe2O4 and CoFe2O4 are more applicable as oxygen carriers in biomass CLC compared with NiFe2O4.