Microwave Catalysis 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.

Suppressed Active Site Loss by Y-Doped ZnO/Silicalite-1 for Superior CO2 Oxidative Propane Dehydrogenation Performance by Microwave Catalysis

Suppressed Active Site Loss by Y-Doped ZnO/Silicalite-1 for Superior CO₂ Oxidative Propane Dehydrogenation Performance by Microwave Catalysis

Oxygen vacancy formation strengthened microwave catalysis of Zn-Zr solid solution for antibiotic-free therapy strategies of bacteria-infected osteomyelitis

Osteomyelitis, a grave deep tissue infection primarily caused by Staphylococcus aureus, results in serious complications such as abscesses and sepsis. With the incidence from open fractures exceeding 30 % and prevalent antibiotic resistance due to extensive treatment regimens, there's an urgent need for innovative, antibiotic-free strategies. Photothermal therapy (PTT) and photodynamic therapy (PDT) renowned for generating localized reactive oxygen species (ROS), face limitations in penetration depth. To overcome this, our method combines the deep penetration attributes of medical microwaves (MW) with the synergistic effects of the ZnO/ZrO2 solid solution. Comprehensive in vitro and in vivo evaluations showcased the solid-solution's potent antibacterial efficacy and biocompatibility. The ZnO/ZrO2 solid solution, especially in a 7:3 M ratio, manifests superior microstructural characteristics, optimizing MW-assisted therapy. Our findings highlight the potential of this integrated strategy as a promising avenue in osteomyelitis management.

Cobalt-promoted Zn encapsulation within silicalite-1 for oxidative propane dehydrogenation with CO2 by microwave catalysis at low temperature

CO2-ODHP is an attractive process that can simultaneously produce propylene and reduce CO2. Microwave catalysis significantly improves propane dehydrogenation performance at low temperatures with high conversion and excellent selectivity.

Direct microwave energy input on a single cation for outstanding selective catalysis.

Microwave (MW)-driven catalytic systems are attracting attention not only as an aggressive electrification strategy of the chemical industry but also as creating a unique catalytic reaction field that conventional equilibrium heating cannot achieve. This study unlocked direct and selective heating of single alkali metal cations in the pores of aluminosilicate zeolites under MW. Selectively heated Cs+ cations in FAU zeolite exhibited selective CH4 combustion performance, that is, COx generation at the heated Cs+ cations selectively occurred while side reactions in the low-temperature gas phase were suppressed. The Cs-O pair distribution function revealed by synchrotron-based in situ x-ray total scattering gave us direct evidence of peculiar displacement induced by MW, which was consistent with the results of molecular dynamics simulation mimicking MW heating. The concept of selective monoatomic heating by MW is expected to open a next stage in "microwave catalysis" science by providing physicochemical insights into "microwave effects."

Order-of-magnitude increase in rate of methane dry reforming over Ni/CeO2-SiC catalysts by microwave catalysis

Methane dry reforming (MDR) produces syngas from CH4 and CO2. The endothermic character of the reaction forces the lower surface catalyst temperature than targeted furnace temperature in thermal catalysis, which decreases carbon gasification ability and prones to deactivate catalyst. Increasing catalyst surface temperature is a way to enhance the gasification ability. In this work, we designed Ni/CeO2-SiC catalysts for MDR under microwave irradiation. The microwave adsorption by Ni and SiC increased the surface temperature of catalyst, significantly enhancing MDR performance and considerably reducing carbon deposition compared with those in thermal catalysis. CH4 and CO2 rates reached 16.5 mmol/(gNi·s) and 18.6 mmol/(gNi s), respectively, on the 1Ni/CeO2-SiC. The rates were one order-of-magnitude increased when be compared in literatures. Carbon deposits were as 1.4 wt% by microwave catalysis in comparison to 5.0 wt% by thermal catalysis on the used 1Ni/CeO2-SiC catalyst. The work explores a more effective microwave catalysis of Ni/CeO2-SiC catalyst for high-performance MDR.

CuCeO Bimetallic Oxide Rapidly Treats Staphylococcus aureus-Infected Osteomyelitis through Microwave Strengthened Microwave Catalysis and Fenton-Therapy.

Osteomyelitis caused by bacteria is a deep-seated lesion and is often treated clinically with antibiotics. Long-term use of antibiotics may predispose bacteria to develop resistance. Here, CuCeOx material is applied to treat infectious bacterial osteomyelitis using microwave (MW)-assisted bacterial killing. Heat generation occurs as a result of the dielectric properties of the material under MW irradiation, and the material generates reactive oxygen species (ROS) under MW irradiation. Heat and ROS increase the thermal sensitivity and permeability of bacterial cell membranes, and the released copper ions easily penetrate the bacterial membrane and react with H2 O2 to produce a toxic hydroxyl group inside the bacteria, leading to the bacteria's eventual death. This is due to the synergistic effect of the MW thermal effect, ROS, and the breaking of the equilibrium within the bacteria. CuCeOx can effectively treat osteomyelitis caused by Staphylococcus aureususing MW irradiation. This study can safely and effectively address the challenge of deep tissue infections by shedding light on non-invasive antimicrobial systems and using MW thermal therapy and MW dynamics to achieve therapeutic results.

Developing a microwave-driven reactor for ammonia synthesis: insights into the unique challenges of microwave catalysis

Reactor requirements grow with scale as new phenomena can become more and more relevant, creating trends that we've observed in the development of microwave-driven ammonia synthesis – a technique with a unique combination of high output and energy efficiency.

Synergistic Effect of Fe Single-Atom Catalyst for Highly Efficient Microwave-Stimulated Remediation of Chloramphenicol-Contaminated Soil.

Chloramphenicol (CAP) has long been used extensively in agriculture and is severely toxic to the biological environment. Microwave catalysis appears a promising method for soil remediation due to its fast and effective heat transfer, but it is challenging to prepare catalysts with good electromagnetic wave absorption and robust catalytic activity. In this study, atomically dispersed Fe on three-dimensional N-doped carbon supports (3D Fe-NC) is firstly used for microwave remediation of soil. Thanks to the synergistic effect of microwave "hot spots" and reactive oxygen species (•OH, •O2 - ), 3D Fe-NC can completely remove 99.9% of CAP in 5min. The removal rate constant is nearly twice that of commercial activated carbon. Significantly, the germination rate of lettuce seeds in microwave-repaired soil contaminated by CAP reaches 70%. This work demonstrates the application of Fe single-atom catalyst in microwave remediation of contaminated soil, providing a novel insight for agricultural soil remediation.

Enhanced removal of elemental mercury using MnO2-modified molecular sieve under microwave irradiation

Developing efficient catalysis-adsorption method for elemental mercury (Hg0) removal with wide temperature window and good sulfur/water resistance is a hot topic. In this study, a novel method of microwave (MW) catalysis of MnO2 modified molecular sieve (Mn@MOS) composite for Hg0 removal was developed. Results indicated that Hg0 removal efficiency of MOS was poor, only 18% at 150 °C, while the efficiency was significantly increased to 97.8% when MW/Mn@MOS was used. Compared with thermo-catalysis way, MW irradiation method achieved better Hg0 removal efficiency (97.8% vs 86.4%) under a wider temperature window (150–450 °C), and sulfur/water resistance were greatly strengthened under MW irradiation. The dynamical adsorption capacity of Hg0 was calculated as 1.52 mg/g when the efficiency was below 80%. Kinetic analysis indicated that MW field significantly increased the rate constant and reduced the activation energy. The fate of Hg0 was unfolded: almost 96% of Hg0 was chemisorbed as HgO, less than 4% was converted to gaseous Hg2+. The mechanism was speculated as followed: (i) excited active site of *MnO2 was first generated under MW irradiation; (ii) then the oxidizing species including Mn(IV)/Mn(III), Oads, Olatt and O* dominated the Hg0 removal process; (iii) the reactive oxygen species of Oads, Olatt and O* were replenished by the interaction between oxygen vacancies and free O2. This study first demonstrates the superiority of MW catalysis towards Hg0 removal, and provides a new thought on the development of the novel Hg0 removal technologies.

Interface Polarization Strengthened Microwave Catalysis of MoS2/FeS/Rhein for the Therapy of Bacteria‐Infected Osteomyelitis

AbstractStaphylococcus aureus (S. aureus)‐induced osteomyelitis is fatal to patients, even leading to death without timely debridement processing, which is difficult to be treated by antibiotics or phototherapy due to deep infections. Herein, a microwave (MW) assisted bacteria‐killing strategy for treating S. aureus‐induced osteomyelitis by using MW‐responsive molybdenum disulfide (MoS2)/ferrous sulfide (FeS) heterojunction with anti‐inflammatory herb of rhein (Rhe) is reported. Under medical MW irradiation, MoS2/FeS/Rhe effectively eradicates S. aureus‐infected rat tibial osteomyelitis. The robust therapeutic effects of MoS2/FeS/Rhe are ascribed to the anti‐inflammatory effect of Rhe, the enhanced MW thermal and dynamic effects of MoS2/FeS. MoS2/FeS is composed of S‐Mo‐S‐Fe‐S stacked layers sandwiched in between by weak Van Der Waals interactions, which means that ions or molecules can be retained in the space between the layers. Under MW irradiation, dipoles or ions are aligned in an oscillating electric field, which cause dipolar polarization and ionic conduction, leading to molecular friction and dielectric loss to generate MW heat. In addition, the dipole orientation polarization caused by the interfacial polarization of MoS2/FeS is the main factor for microwave catalysis. This kind of MW responsive nanocomposite comprising inorganics and herbs may solve the challenge of how to effectively treat deep tissue infections.

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.

SELF-CONDENSATION OF ACETOPHENONE TO DYPNONE: SYNERGISM OF MICROWAVE AND SOLID ACID CATALYSIS

SELF-CONDENSATION OF ACETOPHENONE TO DYPNONE: SYNERGISM OF MICROWAVE AND SOLID ACID CATALYSIS

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...

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.

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-assisted catalytic pyrolysis of corn cobs with Fe-modified Choerospondias axillaris seed-based biochar catalyst for phenol-rich bio-oil

In order to develop a more economical and easy-to-recover catalyst, this study prepared Fe-modified biochar catalyst by microwave pyrolysis carbonization and impregnation, and applied it to microwave catalysis pyrolysis of corn cobs to prepare phenol-rich bio-oil. The results showed that H3PO4 can greatly increase the specific surface area of the biochar catalyst. The Fe-modified biochar catalyst promoted the conversion of aldehydes and ketones in corn cobs bio-oil, thereby greatly increasing the content of phenolic compounds. Among them, Fe0.4@biochar had the best selectivity to phenol, approximately 16.45 area%. Fe0.2@biochar had the best selectivity to furfural, which was 10.68 area%. After repeated use for 5 times, the catalytic effect was still selective to phenolic compounds.

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.

Continuous Biodiesel Production from Waste Soybean Oil Using a Nano-Fe3O4 Microwave Catalysis

In this study, we conducted an efficient microwave-assisted transesterification process combining homogeneous and heterogeneous catalytic phases to produce biodiesel from waste soybean oil. A cylindrical quartz reactor packed with nanoparticles of Fe3O4 as a co-catalyst was applied to improve the reaction. The process was carried out with a methanol-to-oil molar ratio of 6:1, power of 560 W, and residence time of 30 s. The specifications of the biodiesel produced in this study were compared with two standards, i.e., ASTM D6751 and EN 14214. We found that the continuous conversion of waste soybean oil to methyl ester was approximately 95%. The biodiesel showed a higher flash point and a higher carbon residue content than that of both standards, and the viscosity (5.356 mm2/s) and density (898.1 kg/m3) were both at a high level. Compared to a conventional heating plate, the energy consumption was significantly reduced by nearly 93%. It is expected that these findings will provide useful information for green and sustainable processes for the regeneration and reuse of oil.

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.