Microwave Catalyst Research Articles

Enhanced microwave-catalytic performance for CO2 oxidative propane dehydrogenation by acidified and Bi-doped ZnO-based microwave catalysts

The oxidative dehydrogenation of propane by carbon dioxide (CO2-ODHP) has great potential in producing propylene. Resource utilization of CO2 will be the dominant trend in the future to mitigate environmental problems and cope with the growth in energy demand. However, simultaneously achieving high propane conversion, high propylene selectivity, and high CO2 conversion at low temperatures remains challenging. Herein, we report a novel efficient microwave catalyst (1.0-Zn4Bi1/Silicalite-1+SiC) by doping Bi on ZnO/Silicalite-1 and then acid treatment. The (1.0)-Zn4Bi1/Silicalite-1+SiC microwave catalyst exhibited 92 % C3H8 conversion, 84 % C3H6 selectivity, and 45 % CO2 conversion under microwave mode, significantly better than under the thermocatalysis (without microwave: 27 % C3H8 conversion, 92 % C3H6 selectivity, and 14 % CO2 conversion). The CO2 capture capacity was improved by adding Bi to ZnO/Silicalite-1. In addition, acid modification increased the propane and CO2 conversion by 1.9 and 1.3 times, respectively. Notably, acid treatment enriched the pore structure of the catalysts, altered surface acidity and alkalinity, and promoted C3H8 and CO2 activation and C3H6 desorption. In particular, the acid treatment enriches the state of the presence of Zn species in the catalyst. Microwave irradiation reduces the apparent activation energy of the catalytic system and accelerates the removal of coke from the catalyst surface. Microwave catalysis can activate CO2 and propane at lower temperatures than thermocatalysis.

Box-Behnken design optimization of 2D Ti3C2Tx MXene nanosheets as a microwave-absorbing catalyst for methylene blue dye degradation

The 2D MXene Ti3C2Tx was synthesized from the precursor MAX phase Ti3AlC2 by etching the Al layer using hydrofluoric acid. Different Characterization techniques were employed to investigate the properties of the synthesized Ti3C2Tx. The degradation of methylene blue (MB) dye under microwave irradiation in the presence of the prepared 2D MXene was studied. It was found that the synthesized Ti3C2Tx was an excellent microwave catalyst for MB dye degradation, and results obtained were promising. Using this approach, the dye was almost wholly degraded with a degradation efficiency of 99.85 % in only 10 min without adding any oxidant. The degradation was found to follow the pseudo-first-order kinetic model, and the rate constants obtained varied from 0.10 and reached up to 0.67 min−1. The effect of pH, initial MB concentration and catalyst dosage on the MB dye degradation rate has been studied. It was found that carrying out the reaction at pH values ranging from 2 to 10 did not obviously affect its rate. On the other hand, lower initial MB dye concentrations and higher catalyst dosages significantly increased the degradation rate. The high degradation efficiency was found to be maintained for up to five successive catalytic cycles, ensuring the high stability of the synthesized 2D MXene Ti3C2Tx as a catalyst. Optimization of parameters affecting the degradation process was studied using response surface methodology (RSM). According to the Box-Behnken design, the optimal degradation efficiency (99.92 %) could be achieved by adding 21.24 mg of 2D Ti3C2Tx MXene catalyst and using an initial MB dye concentration of 53.06 ppm (mg/L) during a reaction time of 11.93 min.

Highly effective direct conversion of H2S into COx-free H2 and S at low temperature over novel MoxC@ZrO2 microwave catalysts

Direct decomposition of H2S into H2 and S is an attractive alternative to the Claus process, because COx-free H2 and S can be simultaneously recovered from an abundant and toxic waste gas, which has huge social economic and ecological environmental benefits. However, it is still a great challenge to achieve the direct H2S decomposition reaction with high efficiency due to the thermal equilibrium limitation. Herein, a core-shell structured MoxC@ZrO2 was developed as novel microwave catalyst for microwave catalytic H2S decomposition. More specifically, the H2S conversion over MoxC@ZrO2 catalyst is as high as 99.9% at 650 °C, which immensely surpasses the H2S equilibrium conversion (6.1% at 650 °C). This study provides an effective strategy for the design of highly active microwave catalysts, and supplies a strategy for efficiently catalytic decomposition of H2S waste and recovering high-value hydrogen and sulfur at lower reaction temperatures.

Microwave driven steam reforming of biomass model tar based on metal organic frameworks (ZIF-67) derived Co/C catalyst

Tar catalytic removal is a key issue in biomass gasification, which is suffering from catalyst coking and sintering. Microwave technology is attractive due to the high activity on polar molecules and ability to lower activation energy. In this study, the Co/C derived from metal-organic frameworks (ZIF-67) was developed as a bifunctional microwave catalyst that can strengthen the interaction between microwave and tar catalytic reforming, and enhance the anti-coking and sintering ability. The effects of the temperature, heating method, tar concentration, and catalyst support on model tar conversion rate were investigated. The operating conditions at 700 °C and tar concentration lower than 20 g/m3 can reach a promising conversion rate over 90.15 % under microwave irradiation. On the one hand, microwave heating groups performed better in conversion rate and coking compared to conventional heating, due to the active species generated from the microwave plasma. On the other hand, Co/C showed better performance in catalytic activity and sintering stability, due to the highly dispersion of cobalt nanoparticles and the confinement effect of carbon nanotubes on the catalyst surface. These findings proposed a novel approach for efficient biomass tar removal under microwave irradiation, and offered a potential tool to further reveal the mechanism in microwave driven tar steam reforming system.

Acid-leaching treated ZnO-based materials as highly efficient microwave catalysts for oxidative dehydrogenation of propane by CO2

The oxidative dehydrogenation of propane by CO2 (CO2-ODHP) reaction has received much attention for its potential to produce high-value propylene from two underutilized reactants and to eliminate CO2. However, it is a great challenge to maintain high propylene selectivity with high propane conversion for CO2-ODHP reaction, especially for non-expensive and environmentally friendly catalysts. Herein, a new and effective ZnO/S-1(1.0)-based microwave catalyst for CO2-ODHP was developed by a simple impregnation method and acid leaching treatment. Interestingly, the acid leaching treatment significantly enhanced the catalytic activity and stability. Importantly, both the conversion of propane and the selectivity of propylene were significantly enhanced in the microwave catalytic reaction mode (MCRM). An amazingly high conversion of ∼60 % and selectivity of ∼92 % is achieved. This method of significantly improving the catalytic activity and stability after a simple acid leaching treatment can provide some inspiration for light alkane dehydrogenation reactions.

Hollow sphere CuCo2O4 as highly efficient catalyst of microwave-assisted Fenton-like reaction for water treatment

In industries with high-value addition, the demand for rapid pollutant breakdown through advanced water treatment techniques is growing. The microwave (MW)-assisted Fenton-like reaction is notable for its exceptionally fast reaction rate, providing enhanced economic benefits, especially in the context of limited factory space. In this research, hollow sphere-shaped CuCo2O4 was synthesized at the various temperature (200 °C, 250 °C, 300 °C, 350 °C, 400 °C, 450 °C, and 500 °C) and used in a MW-assisted Fenton-like reaction to break down the organic model compound, methyl orange (MO). Unlike typical Fenton reactions that are most effective in acidic conditions (around pH 3), the synthesized CuCo2O4 in this study demonstrated its highest efficiency at a circumneutral pH level (pH 6). It was observed that the majority of MO was oxidized by ∙OH within just 3.5 min under the optical condition (10 mg/L MO, 300 mg/L H2O2, 200 mg/L catalyst, pH 6, 20 °C, 200 W, and total volume of 50 mL). Ex-situ analysis confirmed the gradual generation of oxygen vacancies (OV) with each repeated cycle. The formation of OV enhances the catalyst's MW absorption and oxidation potential, resulting in the superior MO decomposition performance even after the 5th cycle. Although there were minor changes in the shell thickness and smoothness, along with some leaching (1.17 mg Cu/L and 0.01 mg Co/L per cycle), the catalyst continued to comply with the US Environmental Protection Agency (EPA) guidelines for drinking and discharge water.

Microwave-Assisted Synthesis of Nitrogen-Doped Carbon Catalysts for Oxygen Reduction Reaction with Tunable Selectivity

The oxygen reduction reaction (ORR) is the core reaction in electrocatalysis systems such as fuel cells, metal-air batteries and hydrogen peroxide (H2O2) electro-generation. The ORR reaction mechanism has two possible pathways, namely, two-electron (2e−) or four-electron (4e−) processes that enable a reduction of oxygen into H2O2 or water (H2O), respectively. Both paths are useful where the former can provide on-site direct production of H2O2 and the latter is desired in fuel cells and batteries since it enables higher energy efficiency. Optimal ORR electrocatalyst should exhibit high activity, selectivity, stability, and low cost. Carbon materials modified with heteroatoms (e.g. nitrogen (N)) are considered potential alternatives for costly noble metal catalysts including Pt for ORR in fuel cells, and Au for the ORR to H2O2 (1,2). The typical synthesis procedure for the porous nitrogen-doped carbons (N–C) is based on the single or multiple pyrolysis steps of nitrogen-rich carbon precursor. The reactions required a pyrolysis step at the temperature range of 500-1200 °C and timing of one to tens of hours. Such processes showed a highly negative environmental impact due to high energy consumption. The production of 1 ton of activated carbon from lignocellulosic biomass feedstock requires 669.83 kWh (equivalent to an emission of 62.78 tons of CO2) (3). The synthesis of the N–C by microwave (MW) irradiation can reduce energy usage and ensure a more environmentally sustainable and economically viable approach. This procedure necessitates non-transparent materials to electromagnetic waves that can convert MW energy into heat and simultaneously enable the carbonization of the starting material.This work investigated the electrocatalytic activity towards ORR for N–C–MW catalysts derived from polyaniline (PANI) prepared in a one-step MW carbonization approach. PANI was selected due to two reasons: (i) N–C made by thermal pyrolysis of PANI showed improved electrocatalytic activity toward ORR where both the 4e− and the 2e− electron transfer pathways are feasible depending on the nature of active sides (4), (ii) PANI displayed good MW adsorption properties (5). The work aimed to identify the influence of the MW reaction condition on the resulting structure of the N–C–MW and the direction of the ORR. The N–C–MW samples were prepared under MW power of 450 and 800 W and time of 70, 140 and 210 s. The ORR activity of N–C–MW samples was investigated by cyclic voltammetry in the alkaline media (O2-saturated 0.1 M KOH). The experiment was performed in a three-electrode configuration composed of a rotating ring (Pt)–disk (glassy carbon) electrode (RRDE), a graphite rod as the counter electrode and a reversible hydrogen electrode (RHE) as the reference electrode. An influence of catalyst loading on disk electrode (0.05, 0.1 and 0.2 mg/cm2) was analyzed. All investigated MW reaction conditions resulted in the formation of porous disordered carbon structures with nitrogen and oxygen functionalities confirmed by X-ray photon-electron spectroscopy. The shorter time (70 s) and lower power (450 W) of MW treatment resulted in the formation of structures with a low carbonization rate and simultaneously a relatively poor catalytic activity for ORR (an onset potential of ∼0.65 V vs RHE). The samples carbonized under moderate (power of 450 W and 800 W, time of 140 s) and severe (power of 450 W, time of 210 s) reaction conditions showed higher selectivity to H2O2 or water H2O, respectively. The selectivity of 80 % to H2O2 was achieved for the N–C–MW-800W-140s sample at the potential of 0.6 V vs RHE at the catalyst loading of 0.05 mg/cm2. The results showcase the potential of MW carbonization in producing ORR electrocatalysts with diverse functionalization, leading to modified reaction selectivity that can be utilized in various electrocatalytic applications. Acknowledgments The research leading to these results was supported by the Johannes Amos Comenius Programme, European Structural and Investment Funds, project 'CHEMFELLS V‘ (No. CZ.02.01.01/00/22_010/0003004). References Yang, S. et al., Toward the decentralized electrochemical production of H2O2: A focus on the catalysis. ACS Catalysis, 2018.Bouleau, L. et al., Best practices for ORR performance evaluation of metal-free porous carbon electrocatalysts. Carbon, 2022.Wang, YX. et al., Quantifying environmental and economic impacts of highly porous activated carbon from lignocellulosic biomass for high-performance supercapacitors. Energies, 2022.Silva, R. et al., Efficient metal-free electrocatalysts for oxygen reduction: Polyaniline-derived N- and O-doped mesoporous carbons. Journal of the American Chemical Society, 2013.Oyharçabal, M. et al., Influence of the morphology of polyaniline on the microwave absorption properties of epoxy polyaniline composites. Composites Science and Technology, 2013. Figure 1

Carbon cloth@SnS2 nanosheet array catalysts for efficient microwave induced catalytic reduction of Cr(VI): Experiment and DFT study

Aqueous hexavalent chromium (Cr(VI)) is an environmental safety problem that seriously threatens ecosystems and human health. Herein, SnS2 nanosheet array catalysts on carbon cloth (CC) for microwave-induced catalytic reduction of Cr(VI) were prepared by a simple hydrothermal method. Benefiting from the unique interfacial and the improved electron transfer effect between the SnS2 nanosheet arrays and the CC substrate, the reduction ratio of the CC@SnS2 nanosheet array catalysts reached 100 % for a Cr(VI) solution (50 mg/L) under 35 min-microwave treatment at a frequency of 2.45 GHz and a power of 300 W. Density functional theory (DFT) calculations reveal that Cr2O72− ions were more easily adsorbed on S atoms than HCrO4– ions in an acidic solution, indicating that the activity of S atoms was evidently superior to that of Sn atoms in CC@SnS2 nanosheet arrays. This work provides an in-depth understanding of the mechanism of microwave-catalyzed removal of Cr(VI) and paves a new avenue for designing highly efficient microwave catalysts for wastewater treatment.

Hydrogen production via steam reforming of glycerol over Ce-La-Cu-O ternary oxide catalyst: An experimental and DFT study

In this study, Ce-La-xCu-O catalysts with distinct Cu contents were fabricated through two different microwave methods; conventional microwave (MW) method and enhanced microwave method, where air cooling (AC) during heating was applied and studied for glycerol steam reforming. The characterization of catalysts reveals that the synthesis methods (MW and AC) influence mainly on the degree of Cu incorporation into the Ce-La-O fluorite lattice, thus leading to one or two phases system. In glycerol steam reforming, MW catalysts showed improvement in glycerol conversion (X) and glycerol conversion to gaseous products (Xgas) with an increase of temperature from 400 to 750 °C; a higher tradeoff between total conversion X (93–94%) and Xgas (89–93%) was attained at 750 °C. The H2 yield over MW catalysts was attained in the range of 3.8–5.0 mol/mole of glycerol. Interestingly, Ce-La-10Cu-O (AC) catalyst exhibits higher glycerol conversion, conversion to gaseous products and higher yield of H2 (5.3 mol/mole of glycerol) as compared to MW catalyst. Moreover, the Ce-La-10Cu-O (AC) catalyst exhibited high stability and deactivated at slower rate. The improved performance of AC catalyst can correlate to a more homogeneous Cu incorporation into Ce-La-O mixed oxide thus forming more accessible active sites to reactants which overall impact on the catalytic performance. DFT calculations showed that doping ceria (111) surface greatly facilitates the adsorption of glycerol compared to the undoped ceria surface by tuning the adsorption energy and the surface-glycerol distance, to −1.42 eV and 1.09 Å, respectively, and by shifting the Fermi level into the valence band (p-type doping), enhancing with the latter the glycerol chemisorption.

Highly effective microwave catalytic oxidative dehydrogenation of propane by CO2 over V-La-doped dendritic mesoporous silica-based microwave catalysts

The great potential of the oxidative dehydrogenation of propane by CO2 (CO2-ODHP) reaction in facilitating propylene production from propane and elimination of CO2 has attracted much attention. However, the challenge of the oxidative dehydrogenation of propane by CO2 (CO2-ODHP) reaction is the high thermodynamic stability of CO2, which requires high temperature for activation but the predominance of propane cracking reactions at high temperatures leads to difficulties in maintaining high selectivity for propylene at high conversion rates. Herein, a new and effective method for CO2-ODHP by microwave catalysis has been developed. Meanwhile, a novel vanadium-lanthanum-doped three-dimensional dendritic mesoporous silica nanospheres (V-La-MSNS) based microwave catalyst is synthesized by the in situ growth approach. Importantly, the propane conversion increases from 2% in conventional reaction mode (CRM) to 13% in microwave catalytic reaction mode (MCRM) at 500 °C, with the propylene selectivity still remained at a high level. The catalyst exhibits good stability and reproducibility in microwave catalytic reaction mode. Besides, the doping of La in V-MSNS can dramatically increase the catalytic activity. More importantly, the apparent activation energy of the V-La-MSNS + SiC microwave catalyst drops from 132.7 kJ/mol in the CRM to 71.4 kJ/mol in the MCRM, indicating a significant microwave direct catalytic effect. This work presents a new method for high-efficient catalytic CO2-ODHP reaction under microwave irradiation.

Rapid and Efficient Microwave Catalytic Oxidation Degradation of Chlorotetracycline Over Mno2-Coo/Ac Microwave Catalyst

Rapid and Efficient Microwave Catalytic Oxidation Degradation of Chlorotetracycline Over Mno2-Coo/Ac Microwave Catalyst

Atomic sheets of silver ferrite with universal microwave catalytic behavior

Prompt degradation of organic pollutants renders microwave (MW) catalysis technology extremely lucrative; ideal microwave catalysts are therefore being hunted with an unprecedented urgency. Ideal functional microwave catalyst should be highly crystalline, room temperature ferromagnetic (for magnetic retrieval), highly dielectric (for sufficient microwave absorption) apart from being structurally stable at high temperature. The potential of silver ferrite 2D sheets (2D AFO) synthesized using a novel microwave technique as a microwave catalyst for the degradation of a variety of organic dyes and antibiotics was investigated in this article. While organic dyes like malachite green (MG), brilliant green (BG) and nile blue A (NB) achieved 99.2%, 98.8% and 95.2%, respectively; antibiotic tetracycline hydrochloride (TCH) molecule resulted in 75.8% degradation efficiency. Total organic carbon (TOC) measurements yielded 76%, 59.1%, 49.1% and 47.6% of carbon content for MG, BG, NB and TCH, respectively. The reaction pathway via intermediates and subsequent degradation to CO2 and H2O is revealed by liquid chromatography-mass spectrometry (LCMS). Both superoxide and hydroxyl radicals are participating in the process, according to scavenger tests. The evolution of silver ferrite as a new 2D material and its demonstration as an ideal microwave catalyst will lead to a new beginning in catalysis science and technology.

Coke-Resistant Ni–Co/ZrO2–CaO-Based Microwave Catalyst for Highly Effective Dry Reforming of Methane by Microwave Catalysis

The dry reforming of methane (DRM) reaction is an attractive approach to convert two greenhouse gases into valuable syngas. However, the DRM reaction remains a great challenge due to catalyst deact...

Highly efficient H2 and S production from H2S decomposition via microwave catalysis over a family of TiO2 modified MoxC microwave catalysts

Highly efficient H2 and S production from copious waste H2S is beneficial from both environmental and energy. Whereas, the highly effective direct decomposition of H2S reaction faces a gigantic obstacle, that is, there is the severe thermal equilibrium limitation. Herein, a family of TiO2 modified MoxC as novel microwave catalysts have been developed. This work demonstrates that Mo2C, Mo2C-TiO2 and MoC@TiO2 microwave catalysts display excellent catalytic performance to recover both valuable H2 and elemental S from the direct decomposition of H2S under microwave irradiation. The optimal H2S conversion of MoC@TiO2 can be as high as 99.9% (almost complete conversion) at 700 °C, which greatly outpaces the corresponding H2S equilibrium conversion under microwave irradiation. This result of the chemical equilibrium limitation being broken shows an interesting phenomenon, namely a significant microwave selective catalytic effect by microwave catalysis in H2S decomposition reaction. In addition, the apparent activation energy of the Mo2C, Mo2C-TiO2 and MoC@TiO2 microwave catalysts reduced to 18.2 kJ/mol, 16.8 kJ/mol and 15.6 kJ/mol under microwave irradiation. The work supplies a strategy for highly effective valuable H2 and S production from H2S decomposition reaction, and paves a path to high-value utilization of hazardous waste H2S resources with energy-saving heating method.

Microwave synthesized strontium hexaferrite 2D sheets as versatile and efficient microwave catalysts for degradation of organic dyes and antibiotics

Microwave catalysis is extremely lucrative due to prompt mineralization and superior efficiency. Ideal microwave catalysts should possess crystalline nature, large surface area, room temperature ferromagnetic, high dielectric properties apart from structural stability at elevated temperature. In the present article, the candidature of microwave synthesized strontium hexaferrite 2D sheets (2D SFO) has been explored as microwave catalysts for the degradation of a host of organic dyes and antibiotics. Malachite green (MG) and nile blue A (NB) in particular exhibited 99.8% and 97.6% degradation, respectively. Degradation reaction is established to follow pseudo-second-order kinetics. Total organic carbon (TOC) measurements hint at 52% and 60% mineralization for MG and NB, respectively. Liquid chromatography-mass spectroscopy (LCMS) measurements indicate the reaction pathways via intermediates and eventual mineralization to CO2 and H2O. Mott-Schottky measurements along with scavenger tests hint that both hydroxyl and superoxide radicals participate in the reaction. Having superior efficiency apart from the versatile nature of the 2D SFO microwave catalyst, the present research will guide to the emergence of microwave catalysis as a new technology.

Production of Methyl ester from Coconut Oil using Heterogeneous K/Al2O3 under Microwave Irradiation

Methyl esters derived from coconut oil are very interesting to study because they contain free fatty acids with a medium carbon chain structure (C12-C14), so most methyl esters (70%) can be bio-kerosene and the rest can be biodiesel. The process of preparing methyl ester by reaction of Trans-esterification triglyceride generally using a homogeneous KOH catalyst but this process requires a long catalyst separation process through washing and drying process. The use of heterogeneous catalysts in the production of methyl esters can remove the washing and drying processes, but trans-esterification reactions with heterogeneous catalysts require severe conditions (high pressure and high temperature), whereas at low temperatures and atmospheric conditions, the methyl ester yield is relatively low. Using microwave-irradiated trans-esterification reactions with heterogeneous catalysts, it is expected to be much faster and can obtained higher yields. Therefore, in this study we prepare a heterogeneous catalyst K/Al2O3 using solution KOH that impregnated in catalyst support Al2O3, and catalyst obtained are caracterized by XRD, BET dan SEM. Our objective was to compare the yield of methyl esters obtained through the trans-esterification process of coconut oil assisted by microwave using a heterogeneous K / Al2O3 catalyst with yield obtained using a homogeneous KOH catalyst. Experimental equipment consists of a batch reactor placed in a microwave oven equipped with a condenser, agitator and temperature controller. The batch process was carried out at atmospheric pressure with variation of K/Al2O3 catalyst concentration (0.5, 1.0, 1.5, 2.0, 2.5%) and microwave power (100, 264 and 400 W). In general, the process of producing methyl esters by heterogeneous catalysts will get three layers, wherein the first layer is the product of methyl ester, the second layer is glycerol and the third layer is the catalyst. The experimental results show that the methyl ester yield increases with increasing of microwave power, catalyst concentration and reaction time. The results obtained with K /Al2O3 catalysts are generally slightly lower than those obtained using a homogeneous KOH catalyst. However, the yield of methyl esters obtained by the K / Al2O3 heterogeneous catalyst process are relatively easy to separate rather than using a homogeneous KOH catalyst.

Highly Effective Direct Dehydrogenation of Propane to Propylene by Microwave Catalysis at Low Temperature over Co−Sn/NC Microwave Catalyst

AbstractThe direct catalytic dehydrogenation of propane (C3H8) to value‐added propylene (C3H6) has attracted much attention. However, direct dehydrogenation of C3H8 to C3H6 with outstanding catalytic performance at low temperature is a great challenge. Herein, we report a new approach for the direct dehydrogenation of C3H8 to C3H6 at low temperature by microwave catalysis over non‐precious Co−Sn/NC microwave catalyst. It is found that the microwave direct catalytic dehydrogenation of C3H8 over Co−Sn/NC microwave catalyst at low temperature (450 °C) is highly efficient. The C3H8 conversion is 15 % and the C3H6 selectivity is 75 % at 450 °C. Comparatively, the C3H8 conversion and C3H6 selectivity were respectively only 3.2 % and 67.8 % for Co−Sn/NC catalyst at 450 °C in the conventional reaction mode under identical conditions. Furthermore, the microwave catalyst does not show visible change after tested for 180 min. Importantly, the apparent activation energy of Co−Sn/NC catalyst drop from 59.58 kJ/mol in the conventional reaction mode to 20.98 kJ/mol in microwave catalytic reaction mode, which suggests a significant microwave direct catalytic effect. This work provides a novel approach for highly effective direct dehydrogenation of C3H8 to C3H6 by microwave irradiation at low temperature.

Development of composite microwave catalysts (ABSx/CNTs, A = Co, B = Ni, Mo) for the highly effective direct decomposition of H2S into H2 and S

The direct decomposition of hydrogen sulfide into hydrogen and sulfur has attracted plenty of attention due to its capability of recovering hydrogen and sulfur from a hazardous waste gas simultaneously. Nevertheless, it remains a tough challenge to achieve the direct decomposition of hydrogen sulfide at high conversion. In this work, we report the highly effective direct decomposition of hydrogen sulfide by microwave catalysis over the CoNi2S4/CNTs and CoMoS3.13/CNTs composite microwave catalysts. CoMoS3.13/CNTs exhibits excellent catalytic activity under microwave irradiation. The best H2S conversion of CoNi2S4/CNTs and CoMoS3.13/CNTs are respectively up to 58.15% and 71.77% at 750 °C under microwave irradiation, which far exceed the corresponding equilibrium conversion under conventional heating mode. Moreover, the apparent activation energies of CoNi2S4/CNTs and CoMoS3.13/CNTs are reduced to 17.88 and 15.83 kJ/mol, respectively, indicating an excellent microwave selective catalytic effect. Our finding is believed to provide a novel method to achieve direct H2S decomposition reaction.

Synthesis and application of magnetic materials-barium ferrite nanomaterial as an effective microwave catalyst for degradation of brilliant green

In this work, magnetic separably barium ferrite nanomaterial (BaFeO) was synthesized via citrate acid assisted sol–gel combustion method. Subsequently, X–ray diffraction (XRD), scanning electron microscopy–energy dispersion spectroscopy (SEM–EDS), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) were applied for its structural, morphological, and electromagnetic characterization. In addition, microwave (MW) absorption and thermal conversion test results indicated the BaFeO had electrothermal rather than magnetothermal conversion capacity. Meanwhile, the synthesized BaFeO showed satisfactory performance in both eliminating and mineralization of a typical triphenylmethane dye, brilliant green (BG), in MW–induced catalytic oxidation (MICO) process without extra oxidant addition. Besides, changes in element valence and content of BaFeO before and after MICO process investigated with XRD, Fourier transform infrared spectroscopy (FTIR) and X–ray photoelectron spectroscopy (XPS) showed its relatively stable properties. Furthermore, transition oxygen species involved in MICO process was deduced as lattice oxygen species. Then, the possible degradation pathway of BG was proposed as demethylation, open–loop of triphenylmethane, releasing one ring, formation of the benzene ring and the ultimate mineralization based on the degradation intermediates tentatively identified by gas chromatography mass spectrometry (GC/MS) and liquid chromatography mass spectrometry (LC/MS), respectively. Finally, ecotoxicity analysis by ecological structure activity relationships (ECOSAR) showed that both the acute and chronic toxicity of these intermediates were lower than that of parent BG. These findings are important regarding the development of efficient catalysts in MICO process for degradation of BG analogues in wastewater.

Microwave Assisted Co/SiO2 preparation for Fischer-Tropsch synthesis

Cobalt catalyst has been widely used for Fischer-Tropsch (FT) Synthesis in Industry. The most common method to prepare cobalt catalyst is impregnations. Metal is deposited on porous support by contacting dry support with solution containing dissolved cobalt precursor. This step will follow by drying, calcination and reduction. The heating step used in this conventional method, however, may lead to the formation of metal silicate which is inactive site for catalysis. In this study, author explore the use of microwave to prepare catalyst compared to conventional drying method. Cobalt catalyst with SiO2 support was prepared and characterized. Particle size, surface area, and cobalt content were investigated. Crystallite size of 3-8 nm was formed which was reported to be the optimum size for cobalt catalyst in FT Synthesis. Scanning Electron Microscope (SEM) and Transmission Electron Microscopy (TEM) image revealed that microwave catalyst showed better uniformity and cobalt dispersion on silica support. Thermo-Gravimetric Analysis (TGA) study also indicated that this catalyst has good stability at Low Temperature Fischer-Tropsch Synthesis. The catalysts were then applied plasma assisted FT process over a range of power plasma (20-60W) to investigate the effect on the conversion and selectivity. The results showed that microwave catalyst exhibit lower CO conversion at 42.06% compared to conventional method at 68.32%. However, microwave catalyst is more favourable for long chain hydrocarbon selectivity.