Catalytic Technology Research Articles

Enhancing blue light excitation in Pb-free double perovskites by decreasing the energy barrier of the self-trapping exciton and prospects for environment-friendly optoelectronic applications

In Pb-free double perovskites (DPs) optoelectronic material systems, the energy barrier ∆Eb suppression between free excitons (FEs) and self-trapped excitons (STEs) makes it difficult to achieve blue-light excitation even as the bandgap narrows, which has become a major challenge in the development of full-colour displays, lighting, optoelectronics and catalytic technologies. Here, Cs2-aKaAg0.6Na0.4In0.8Bi0.2Cl6-x-yBrx(SH)y DPs, prepared by doping with HS- (hydrosulfide ion), Br- and K+, achieve a blue excitation at 468 nm. The octahedral tilt caused by doping with K+, Br- and HS- ions reduces the local crystal dimensions and thus the energy barrier ∆Eb. The aggregation of electrons around the AgX6 octahedron under the action of HS- contributes to the formation of effective STE emission under blue light excitation. Furthermore, the potential impact of blue-light-excited Cs2-aKaAg0.6Na0.4In0.8Bi0.2Cl6-x-yBrx(SH)y DPs on enhancing the power conversion efficiency (PCE) of photovoltaic modules and the photodegradation efficiency of Rhodamine B (RhB) is explored. The study concludes by highlighting the wide-ranging applications in displays, photovoltaics, and photocatalytic degradation that could be realized through the utilization of blue-light-excited Pb-free DPs.

N,S co-doped SnO2 catalysts in gas-liquid interface dielectric barrier discharge for formate formation via CO2 reduction

N,S co-doped SnO2 were deposited on MWNTs/sponge to prepare a series of related N-S-SnO2/MWNTs/sponges for the reduction of CO2 by dielectric barrier discharge (DBD). With optimizing the composition, the N-S-SnO2/MWNTs/sponge (N:S:Sn = 1:0.2:1) achieves higher yields of formate (4791.40 μmol/L) and formaldehyde (66.11 μmol/L) after 60 min. The structural properties and DFT calculations reveal that, the S doped increased oxygen-containing functional groups on catalysts surface, thus the nonmetallic N and S modified Sn based catalysts affected the adsorption sites and reduced the reaction energy barrier of CO2 on the catalyst surface in order to promote energy utilization of DBD system for CO2 catalytic reduction. In addition, different types and concentrations of seawater ions such as K+, Na+, Ca2+, Mg2+, Cl- and SO42- affected on the formation of formic acid and formaldehyde during discharge, which showed that DBD catalysis technology was advanced used for CO2 capture and storage in the ocean.

Deflector device optimization for controlling nitrogen oxide emissions and pressure drop in selective catalytic reduction denitrification system

ABSTRACT Selective catalytic reduction technology effectively controls nitrogen oxide emissions from coal-fired power plants. In denitrification systems, exceeding nitrogen oxide emissions and excessive local pressure drop are common issues. Numerical simulation methods are used in this study to optimize the flow field to enhance denitrification efficiency and reduce pollutant emissions. Specifically, four deflector plate schemes for the variable-section flue duct segment are proposed. In actual retrofitting, the optimization scheme led to a reduction in nitrogen oxide emissions from 97.3 mg/Nm3 to 48.6 mg/Nm3 and an increase in the outlet pressure of the denitrification system from −3000 Pa to −2959 Pa, resulting in a 41 Pa decrease in local pressure drop. This optimization will further reduce pollutant emissions from power plants and the power consumption of induced draft fans.

Catalytic Hydrolysis-Oxidation of Halogenated Methanes over Phase- and Defect-Engineered CePO4: Halogenated Byproduct-Free and Stable Elimination.

Catalytic elimination of halogenated volatile organic compound (HVOC) emissions was still a huge challenge through conventional catalytic combustion technology, such as the formation of halogenated byproducts and the destruction of the catalyst structure; hence, more efficient catalysts or a new route was eagerly desired. In this work, crystal phase- and defect-engineered CePO4 was rationally designed and presented abundant acid sites, moderate redox ability, and superior thermal/chemical stability; the halogenated byproduct-free and stable elimination of HVOCs was achieved especially in the presence of H2O. Hexagonal and defective CePO4 with more structural H2O and Brønsted/Lewis acid sites was more reactive and durable compared with monoclinic CePO4. Based on the phase and defect engineering of CePO4, in situ diffuse reflectance infrared Fourier transform spectra (DRIFTS), and kinetic isotope effect experiments, a hydrolysis-oxidation pathway characterized by the direct involvement of H2O was proposed. Initiatively, an external electric field (5 mA) significantly accelerated the elimination of HVOCs and even 90% conversion of dichloromethane could be obtained at 170 °C over hexagonal CePO4. The structure-performance-dependent relationships of the engineered CePO4 contributed to the rational design of efficient catalysts for HVOC elimination, and this pioneering work on external electric field-assisted catalytic hydrolysis-oxidation established an innovative HVOC elimination route.

Study of Pt-modified chromium-manganese oxide alloys to improve the performance of toluene abatement

This research is dedicated to solving the environmental problems of volatile organic compounds (VOCs), particularly aromatic chemicals in industrial emissions. The research aims to explore low-temperature, effective catalytic degradation technologies, specifically involving metal oxide and noble metal oxide catalysts, especially the Cr-Mn-Pt series catalysts. The Cr-Mn-Pt catalysts synthesized by the co-precipitation method showed efficient catalytic degradation of VOCs in low-temperature environments. The results of the experiment show that the Cr-Mn-Pt catalysts achieved 90 % toluene conversion at 198 °C, a 1000 ppm toluene concentration, and GHSV=15,000 mL/g·h, which is superior to single MnOx and Cr-Mn catalysts. The catalysts are characterized in depth using X-ray diffraction, specific surface area analysis and Fourier transform infrared spectroscopy. The result shows that the high specific surface area and large volume of pores of the Cr-Mn-Pt catalyst are advantageous for enhancing their catalytic activity and stability. The catalytic mechanism analysis shows that the degradation mechanism of toluene follows the Mars-van Krevelen mechanism with the final conversion of the intermediate product benzoate to CO2 and H2O. In summary, the Cr-Mn-Pt catalyst shows great potential in the technical treatment of VOCs due to their excellent low-temperature catalytic efficiency and stability, and it has enormous practical implications for protecting the environment in the industry.

Physical Strategies for Geometric Control of Transition Metal Dichalcogenide Atomic Layers by Chemical Vapor Deposition

AbstractThe diverse morphologies of 2D transition metal dichalcogenides (2D TMDs) motivate their broad potential applications in the next generation of electronic, optical, and catalytic technologies. It is advantageous to develop controllable growth techniques that afford versatility through direct manipulation of the growth parameters. A fundamental understanding of the physical mechanisms driving various growth modes is crucial for achieving the process precision necessary for obtaining reproducible morphologies in 2D TMDs. Thermodynamic and kinetic considerations are two key physical strategies. Thermodynamic strategies mainly involve the manipulation of parameters like temperature and the chemical potential of precursors to ensure the thermostability of various morphologies. Conversely, kinetic strategies, focusing on the factors, like precursor diffusion, adsorption, and desorption during the growth, also enable atomic‐level kinetics control of the resulting morphologies. Often, an interplay of both mechanisms drives the growth of a particular morphology. This review aims to provide an updated guidance for exploiting these physical strategies in the versatile technique of chemical vapor deposition. The opportunities for further exploring the control of these physical mechanisms are discussed through recent examples with an eye on unlocking the untapped potential of 2D TMDs in areas such as phase engineering and shape control for advanced applications.

Electrochemical oxidative dehydrogenation of ethane to ethylene in a solid oxide electrolysis cell with in situ grown metal-oxide interface active electrodes

The shale gas revolution bolsters ethane supply, thereby enhancing the economic viability of ethylene production from ethane. Presently, catalytic ethane dehydrogenation technology exhibits immense potential in the realm of ethylene production. This study achieves the electrochemical oxidative dehydrogenation conversion of ethane to ethylene via a solid oxide electrolysis cell (SOEC), effectively circumventing the issue of excessive oxidation during the ethane oxidative dehydrogenation process. An active electrode with an in situ grown metal-oxide interface significantly promotes the activation of the ethane C–H bond, leading to efficient ethylene production. Under the co-electrolysis mode of ethane with CO2, the Co@CeO2 electrode demonstrates exceptional performance, achieving an ethane conversion rate of 33.1% and an ethylene selectivity of 88.9% at an applied voltage of 1.0 V. Moreover, the metal-oxide interface constructed via an in situ exsolved method effectively prevents the agglomeration of nanoparticles at high temperatures, thus enhancing the catalyst's resistance to coking and stability. Notably, the electrode's performance does not exhibit significant degradation even after 100 h of electrochemical reaction.

Global Trends in the Research and Development of Petrochemical Waste Gas from 1981 to 2022

As a highly energy-intensive and carbon-emitting industry with significant emissions of volatile organic compounds (VOCs), the petroleum and chemical industry is a major contributor to the global greenhouse effect and ozone layer destruction. Improper treatment of petrochemical waste gas (PWG) seriously harms human health and the natural environment. This study uses CiteSpace and VOSviewer to conduct a scientometric analysis of 1384 scholarly works on PWG and carbon sequestration published between 1981 and 2022, revealing the basic characteristics, knowledge base, research topic evolution, and research hotspots of the field. The results show the following: (1) In the early stages of the petrochemical industry, it was processed tail gas, plant leakage waste gas, and combustion flue gas that were investigated in PWG research. (2) Later, green environmental protection technology was widely studied in the field of PWG treatment, such as biotechnology, catalytic oxidation technology, membrane separation technology, etc., in order to achieve efficient, low energy consumption and low emissions of waste gas treatment, and the number of publications related to this topic has increased rapidly. In addition, researchers studied the internet of things and technology integration, such as the introduction of artificial intelligence, big data analysis, and other technologies, to improve the accuracy and efficiency of exhaust gas monitoring, control, and management. (3) The department has focused on how to reduce emissions by optimizing petrochemical process lines or improving energy efficiency. Emission reduction and low-carbon transition in the petrochemical industry will become the main trend in the future. Switching from renewable carbon to feedstock carbon derived from captured carbon dioxide, biomass, or recycled chemicals has become an attractive strategy to help curb emissions from the chemical industry. The results of our analysis can provide funding agencies and research groups with information to better understand the global trends and directions that have emerged in this field from 1981 to 2022 and serve as a reference for future research.

Micro-nano H2 bubbles enhanced hydrodehalogenation of 3-chloro-4-fluoroaniline: Mass transfer and action mechanism

3-chloro-4-fluoraniline (FCA) is an important intermediate for the synthesis of antibiotics, herbicides and insecticides, and has significant environmental health hazards. Catalytic hydrogenation technology is widely used in pretreatment of halogenated organics due to its simple process and excellent performance. However, compared with the research of high activity hydrogenation catalyst, the research of efficient utilization of hydrogen source under mild conditions is not sufficient. In this work, micro-nano H2 bubbles are produced in situ by electrolytic water and active metal replacement, and their apparent properties are studied. The result show that the H2 bubbles have a size distribution in the range of 150–900 nm, which can rapidly reduce the REDOX potential of the water and maintain it in a hydrogen-rich state for a long time. Under the action of Pd/C catalyst, atomic hydrogen (H•) produced by dissociative adsorption can sequentially hydrogenate FCA to aniline. The H• utilization ratios of the above two hydrogen supply pathways reach 6.20% and 4.94% respectively, and H2 consumption is reduced by tens of times (≥50 → ≈1.0 mL/min). The research provides technical support for the efficient removal of halogenated refractory pollutants in water and the development of hydrogen economy.

Preparation of easily-stripped and high-purity carbon nanotubes from various waste plastics

The conversion of waste plastics to carbon nanotubes (CNTs) through catalytic pyrolysis technology marks a significant advancement in environmental sustainability. This process not only mitigates environmental pollution but promotes the effective use of solid waste. However, the use of powder particle catalysts still faces a separation challenge after carbon deposition. To address this, a carbon paper-based catalyst has been introduced in this study, which possesses a milk thistle-like structure. The results shows that this catalyst facilitated the generation of easily-stripped CNTs on the surface of carbon paper. Around 9 wt% CNTs was collected from 1 g of polyethylene (PE), followed by polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC). Thermogravimetric analysis revealed that CNTs constituted over 95 % of carbon deposition. The harvested CNTs-PE exhibited a more uniform diameter of around 15 nm, which is smaller compared to that of CNTs-PP, CNTs-PS, and CNTs-PVC. Further cyclic experiments confirmed the reusability of carbon paper as a catalyst support, with the yield of CNTs remaining nearly constant over five cycles. This innovative approach paves the way for recycling plastic waste into high-valued CNTs that can be easily-stripped from the support materials with simple physical operations such as pickling.

Thermal reactivity and gas–solid product evolution during coal catalytic combustion: An experimental study

To achieve efficient and clean coal combustion, catalytic combustion technology has received widespread attention. This paper systematically studied the influence of calcium-based compounds on the thermal reactivity and gas–solid two-phase product evolution behavior of different coal using TG-MS and FTIR analysis, combining kinetics and thermodynamics methods, the catalytic coal mechanism was discussed. Results demonstrated that both catalysts improved the combustion reactivity, the burnout temperatures of lignite, bituminous coal and anthracite were reduced by 30.75 °C, 53 °C and 25.5 °C respectively with CaO, as well as decreased by 24.75 °C, 55.5 °C and 29 °C respectively with CaCl2. Meanwhile, it was worth noting that the activation energy of three coals was also reduced. CaCl2 was more likely to bind with the C = O functional group on the surface of coal, forming CO-Ca2+ complexes, resulting in a decrease in the content of C = O and C-O. While CaO tended to absorb volatile matter, causing local overheating and promoting the breakage of side chains and bridge bonds. Besides, the calcium-based compounds advanced the gas evolution peak of combustion and the emissions of CO2, NO2 and SO2 were effectively controlled. These results aimed at providing a new reference direction for further industrial development of clean coal combustion technology.

Solar-powered flow-through catalytic evaporator for high-performance water desalination and synergistic pollutant degradation

Solar interfacial evaporation has been considered one of the most promising strategies to address freshwater scarcity. It is of great interest to explore means of expanding the utilization of solar interfacial evaporation for organic wastewater treatment to capture freshwater. To this end, it is proposed herein that a unidirectional flow-type solar-powered catalytic evaporator is fabricated as a unique integrated device with efficient vapor generation and organics degradation capability, giving rise to simultaneously achieving collection of freshwater and treatment of organics. Benefitting from the flow-through interfacial evaporation and the rational design of the high-performance array-type catalytic evaporative material composed of polydopamine (PDA)-coated CdS photocatalysts on carbon cloth (CC) substrate, the as-built solar-powered catalytic evaporator demonstrates excellent evaporation rate and organic treatment efficiency of 1.93 kg m−2 h−1 and 90.7 %, respectively, well exceeding those of the initial, un-designed evaporator (1.63 kg m−2 h−1 and 60.3 %). This work may provide a new strategy for the treatment of organic wastewater with versatility based on solar interfacial catalytic evaporation technology.

High-efficient removal of oxygen (O2) impurity from hydrogen (H2) flow on nickel-based oxide: effect of metal dopants

Hydrogen is considered as a green energy source, which has attracted widespread attention. Electrocatalytic hydrogen production is a promising technology for generating clean hydrogen. However, the by-product oxygen in this process would lead to a risk of explosion that should be removed before using. In this work, nickel-based oxides doped with variable proportions of Mn, Co, and Cu were used for oxygen removal through catalytic oxidation technology. The catalytic test results show that the optimized catalysts, including 4NiMn, 2Ni1.5Co, and NiCu exhibit better performance. Among all the catalysts, 4NiMn catalyst has the best catalytic performance, achieving a 90% oxygen removal rate below 100 °C. According to the results of H2-TPR, O2-TPD and H2-TPD, the catalysts with better deoxidation effect (4NiMn, 2Ni1.5Co and NiCu) exhibit a stronger oxidation-reduction ability. 4NiMn has higher amounts of adsorption surface oxygen species and overflow hydrogen, which are key factors of the promoting deoxidation effect. Overall, it can be concluded that the optimal catalytic performance of 4NiMn can be attributed to its ability to better adsorb oxygen on its surface, promote the release of overflow hydrogen and participate in oxidation-reduction reactions.

Innovative TiO2-doped polyvinyl alcohol sponge for efficient oil–water separation and dye degradation in wastewater treatment

Regular problems faced due to oil spills and soluble contaminants have increasingly caused serious water pollution. Therefore, there is an urgent need to develop efficient strategies to purify wastewater. This study aims to formulate a synergistic treatment technology of sorption and ultraviolet light catalysis for oil–water separation and degradation of dyes in wastewater. In this study, TiO2 doped PVF sponge (DTMS-TiO2@PVF) was prepared with a water contact angle of 151.5° and a removal rate of 98.86 % of MB in 120 min. Meanwhile, DTMS-TiO2@PVF sponge could easily realize the selective separation of oil–water mixtures. Its saturated sorption capacity for oil and organic solvent was 4.13–10.05 g/g. In addition, DTMS-TiO2@PVF sponge had better environmental stability, which could withstand chemical corrosion (acid, alkaline, and salt solutions). Therefore, DTMS-TiO2@PVF sponge showed great potential for application as an efficient oil–water separation and photocatalytic material, especially in the field of treating oil wastewater and water purification.

Piezocatalysts and Piezo‐Photocatalysts: From Material Design to Diverse Applications

AbstractPiezocatalysis and piezo‐photocatalysis technology is a continuously developing catalytic technology based on the piezoelectric effect of catalysts, which breaks the barrier between mechanical and chemical energy. The piezoelectric polarization field formed by the mechanical deformation of piezoelectric materials is proven to effectively manipulate band structures, improve the separation of electron‐hole pairs and enhance the catalytic activity, thus alleviating energy crises and environmental issues. Herein, this review first introduces the technology of piezocatalysis and piezo‐photocatalysis, comprehensively summarizes the synthesis methods of piezo(photo)catalysis materials, and analyzes and discusses the measures to optimize the performance of piezo(photo)catalysts. The following systematically summarizes the characteristics and development of the current main piezo(photo)catalytic systems, and discusses the application of first principles calculations in piezo(photo)catalysis in combination with practical researches. Subsequently, the main application progress of piezo(photo)catalysis in environmental remediation, energy conversion, and biomedical therapy fields is presented. In the end, the current challenges, development direction, and future prospects are prospected.

Insight into Ca-based compounds on different coal devolatilization behavior by TG-MS

Catalytic pyrolysis, as an indispensable technology, can efficiently achieve clean coal conversion. In this work, the effect of calcium-based compounds (CaO and CaCl2) on devolatilization characteristics and gas evolution behavior of three coals were investigated by thermogravimetry-mass spectrometry (TG-MS). The catalytic mechanism was further explored in combination with the bond cleavage and gas kinetics. The results showed that both catalysts increased the weight loss rate and pyrolysis characteristic index, which also promoted the early release of CH4, H2, CO2 and C6H6, leading to an increase on the amount of CH4 and H2 production. CaO had a better catalytic effect than that of CaCl2. In addition, the kinetic results indicated that both compounds significantly reduced the activation energy of the methane I and IV stages, by 21.33%–34.66 % and 0.8%–18.60 %, respectively. And the activation energy of hydrogen III stage evolution was also reduced by 2%–18.98 % with catalysts. The calcium-based compounds tended to act on the Cal-O, Cal-Car and Car-H structures, improved the coal devolatilization behavior. The results aim to provide theoretical understanding for the practical application of catalytic pyrolysis technology.

Operation of iron-based monolithic catalyst packing ozonation for industry wastewater advanced treatment: The importance of gas–liquid flow patterns and wastewater flow regimes

In this study, from the feasibility verification of the lab-scale test to the working condition study of the pilot-scale test the large-scale engineering application of the display manufacturing industry wastewater advanced treatment by ozonation with iron (Fe)-based monolithic catalyst packing was finally realized. Different from chemical packings, the catalyst packing has large porosity and specific surface area, while the pore size is small, which meets the requirements of •OH reaction, and these characteristics are necessary for engineering applications. Under the three scales, the reaction procedure and the corresponding reactor structure were introduced in detail. The importance of gas–liquid flow patterns and gas distribution device on treatment effect were proved in pilot-scale test. The treatment effect under gas–liquid counter-current flow was better than that of co-current flow. Through the analysis of the working conditions, the working parameters for high wastewater quantity and high organic loading were obtained. The large-scale test achieved the same excellent treatment effect as the lab/pilot-scale test, after 5 years of operation, the average chemical oxygen demand (COD) removal was about 72.0 %, and the COD concentrations after treatment were all lower than 30 mg/L. The biochemical oxygen demand (BOD5) decreased from 10.22 to 2.50 mg/L on average. Under the short-circuiting phenomenon, the wastewater through the catalyst area unevenly and the organic pollutants were not effectively oxidized and decomposed. This also proved the importance of Fe-based monolithic catalyst packing in advanced treatment. This work proved the importance of gas–liquid flow patterns and wastewater flow regimes in the reactor, which can provide reference for other catalytic ozonation technology in large-scale engineering applications.

Influence of anionic species on the low temperature pyrolysis performance of heated tobacco sheets catalyzed by sodium salts.

Development of low temperature catalytic pyrolysis technology for heated tobacco sheets is expected to increase the aroma of heated tobacco products and improve their overall smoking quality. In this study, the low temperature pyrolysis performances of heated tobacco sheets catalyzed by various anionic sodium salts were investigated using TG-DTG, Py-GC-MS technology and smoke routine chemical composition analysis. The results showed that the total weight loss between 100°C and 300°C increased by 7.8%-13.15% after adding various anionic sodium salts, among which, sodium acetate and sodium tartrate showed a relatively higher weight loss. The relative content of free hydroxyacetone, furfuryl alcohol, butyrolactone and megastigmatrienone in the pyrolysis gas increased, while the relative content of free nicotine decreased. With the change of anionic species, the catalytic decomposition ability of cellulose, lignin, and other substances may change, resulting in the distribution alteration of compounds in the pyrolysis gas. After adding sodium acetate and sodium citrate, the release of total particulate matter (TPM), glycerol, and nicotine in flue gas increased. Overall, the addition of sodium acetate and sodium citrate showed a higher low temperature pyrolysis performance of heated tobacco sheets. The research results in this paper provide data support for changing the low temperature catalytic pyrolysis performance of heated tobacco sheets by adjusting the type of anions in sodium salts.

Application of catalytic technology based on the piezoelectric effect in wastewater purification

The demands of human life and industrial activities result in a significant influx of toxic contaminants into aquatic ecosystems. In particular, organic pollutants such as antibiotics and dye molecules, bacteria, and heavy metal ions are represented, posing a severe risk to the health and continued existence of living organisms. The method of removing pollutants from water bodies by utilizing the principle of the piezoelectric effect in combination with chemical catalytic processes is superior to other wastewater purification technologies because it can collect water energy, mechanical energy, etc. to achieve cleanliness and high removal efficiency. Herein, we briefly introduced the piezoelectric mechanisms and then reviewed the latest advances in the design and synthesis of piezoelectric materials, followed by a summary of applications based on the principle of piezoelectric effect to degrade pollutants in water for wastewater purification. Moreover, water purification technologies incorporating the piezoelectric effect, including piezoelectric effect-assisted membrane filtration, activation of persulfate, and battery electrocatalysis are elaborated. Finally, future challenges and research directions for the piezoelectric effect are proposed.

New catalytic technology driving tetrahydrofuran market to $5.1 bn by 2034

New catalytic technology driving tetrahydrofuran market to $5.1 bn by 2034