Catalytic Performance Of Catalysts Research Articles

Optically selective catalyst design with minimized thermal emission for facilitating photothermal catalysis

Converting solar energy into fuels is pursued as an attractive route to reduce dependence on fossil fuel. In this context, photothermal catalysis is a very promising approach through converting photons into heat to drive catalytic reactions. There are mainly three key factors that govern the photothermal catalysis performance: maximized solar absorption, minimized thermal emission and excellent catalytic property of catalyst. However, the previous research has focused on improving solar absorption and catalytic performance of catalyst, largely neglected the optimization of thermal emission. Here, we demonstrate an optically selective catalyst based Ti3C2Tx Janus design, that enables minimized thermal emission, maximized solar absorption and good catalytic activity simultaneously, thereby achieving excellent photothermal catalytic performance. When applied to Sabatier reaction and reverse water-gas shift (RWGS) as demonstrations, we obtain an approximately 300% increase in catalytic yield through reducing the thermal emission of catalyst by ~70% under the same irradiation intensity. It is worth noting that the CO2 methanation yield reaches 3317.2 mmol gRu−1 h−1 at light power of 2 W cm−2, setting a performance record among catalysts without active supports. We expect that this design opens up a new pathway for the development of high-performance photothermal catalysts.

High Entropy Alloys as High Performance Catalysts for Electrolytic Water Splitting

Renewable energy driven electrolytic water splitting is a required technology for low-carbon hydrogen production to achieve the goal of net-zero CO2 emission by 2050. This technology also serves as a necessary energy storage route to resolve the intolerable intermittency and unreliability issues of renewable energies. The prevailing of this hydrogen production technology however is restricted by the high cost of electricity. Consequently, developments of cost–effective highly efficient and stable electrocatalysts to drive the electrolytic water splitting reactions are the key. In terms of catalyst developments, mono-component systems are first explored, followed by multi–component systems, taking advantages of possible positive synergy between constituent components. Recently, a new class of multi-component catalyst systems, entropy-stabilized materials, including alloys, oxides, sulfides, phosphides, etc., emerges and is demonstrated promising performances toward electrocatalysis. In light of the variable and flexible element compositions, entropy-stabilized materials provide infinite and enormous potentials for the design of promising electrocatalysts. The key is to maximize the synergy between constituent components. High entropy alloys (HEA), defined as alloys composed of five or more major metallic elements, have been under intensive and extensive development in past fifteen years for their extraordinary mechanical, magnetic, corrosion, and catalytic properties. Herein, an equi–molar FeCoNiCuMo HEA on nickel foam was developed as a breakthrough catalyst for electrocatalytic water splitting, in terms of both activity and stability, in pH-universal media and in severe industrial operation conditions. Furthermore, a new catalytic phenomenon is discovered. Two different catalytic mechanisms function simultaneously on different constituents of the catalyst, and the synergistic interactions between the two categorical domains leads to catalytic kinetics faster than the theoretical limit set by a single rate-limiting step, Tafel step of the Volmer-Tafel route. A new kinetic model is developed to predict a new theoretical lower limit of Tafel slopes of 15 mV/dec based on a synergistic interaction between the two categorical domains of the high entropy alloy catalyst. This new development proves that the theoretical lower limit of Tafel slope of 30 mV/dec posed for the Volmer-Tafel mechanism functioning on a single component catalyst can be further reduced to 15 mV/dec through synergistic interactions between two categorical domains of a multi-component catalyst. It is demonstrated that high entropy materials, composed of five or more atomically/molecularly well-mixed major components, are intrinsically promising candidates for realization of quantum leaps in catalytic performances of catalysts.

Perovskite materials advance the potent sensor exploration

AbstractPerovskite materials with unique crystal structure have developed rapidly in recent years owing to their special physical and chemical properties, such as high light absorption and extraordinary electrocatalytic properties. Metal halide perovskites are quite attractive in various fields because of their simple manufacturing process, adjustable band gap, good charge transfer performance, and high theoretical photoelectric conversion efficiency. Therefore, perovskite oxides mixed with metal elements become ideal samples for studying the surface and catalytic performance of catalysts. In this review, various metal perovskites are clearly classified and introduced according to the corresponding synthesis methods, including hydrothermal method, sol–gel method, and high‐temperature solid phase, as well as coprecipitation. The excellent properties of perovskite make it extensively used in nanotechnology, chemistry, environmental protection, and material science, especially in solar cells and sensors. In particular, the nanosized perovskite materials are becoming more and more popular in sensors, which was reviewed in detail here. Most importantly, the design of electrochemical sensors using perovskite nanomaterials with low detection limit and high sensitivity will bring new insight into the detection of biomolecules. Both challenges and prospects of metal perovskites were discussed for promoting the development of biosensors in the end.

Revealing the poisoning effect of potassium salts on MnOx catalysts for low-temperature simultaneous removal of NO and CO

Simultaneously elimination of NO and CO in the sintering flue gas is an urgent problem, in which the application of the bifunctional MnOx catalyst has demonstrated its effectiveness in removing NO and CO simultaneously. Potassium salts are frequently found in the sintering flue gas and exert a detrimental influence on the catalytic performance of catalysts. Herein, the primary focus of this study is to investigate different K+ species (K2SO4, KCl, KNO3) poisoning effect on bifunctional MnOx. The findings suggested a deactivation order in the sequence of KNO3 > KCl > K2SO4. Fresh Mn-AC catalyst had finer grains, and poisoning elements were evenly distributed. XPS results revealed an obvious decrease in Mn4+ and Oβ species across all catalysts after K+ species poisoning, hindering redox cycle activation and oxygen species mobility, thus impacting catalytic activity. The in situ DRIFTS results indicated the forbidden of E-R route over KNO3-poisoned catalysts and low reactivity of adsorbed species after poisoning for NO removal. KNO3 severely suppressed surface reaction paths on Mn-AC catalyst and declined the catalytic efficiency, especially in CO activation. Finally, a possible reaction mechanism model for the simultaneous removal of NO and CO was proposed. This study could provide reference for the development of bifunctional catalyst with high resistance to potassium salts.

Exploring the Effects Behind the Outstanding Catalytic Performance of PdAg Catalysts Supported on Almond Shell‐Derived Activated Carbon Towards the Dehydrogenation of Formic Acid

AbstractIn this work, highly efficient carbon‐supported Pd‐based catalysts for formic acid dehydrogenation were synthesized by a straightforward wet impregnation‐reduction method. The carbon support was obtained from a biomass residue (almond shell) prepared via H3PO4‐assisted hydrothermal carbonization (HTC) and thermal activation. This carbon support was doped with nitrogen groups to study the effect on the electronic properties and catalytic performance of the catalysts. Investigating the formation of PdAg alloys with varying Pd : Ag molar ratios resulted in catalysts exhibiting enhanced catalytic activity compared to monometallic Pd counterparts. Notably, the Pd1Ag0.5/NAS catalyst displayed outstanding catalytic performance, achieving an initial TOF of 1716 h−1 (calculated in the first 3 minutes of reaction and expressed per mole of Pd) and maintaining substantial activity over 6 consecutive reaction cycles. This work elucidates the successful synthesis of effective catalysts, emphasizing the influence of nitrogen doping and PdAg alloy composition on catalytic behavior and stability.

Facile Synthesis of Iron Carbide via Pyrolysis of Ferrous Fumarate for Catalytic CO2 Hydrogenation to Lower Olefins.

Hydrogenation of CO2 to olefin catalyzed by iron-based catalysts is a sustainable and important way to achieve carbon neutrality. In this study, iron-based catalysts were facilely prepared by direct pyrolysis of ferric fumarate (FF), which are applied to CO2 hydrogenation to olefin reaction to explore the effects of pyrolysis temperature and atmosphere on catalytic performance of the catalysts. Among them, NaFe-Air-400 catalyst exhibits the highest catalytic activity with 33.7 %, and light olefin selectivity reaches as high as 47.1 %. The catalytic performance of pyrolytic catalysts is better than that the impregnated NaFe catalyst on activated carbon (NaFe/AC). A series of XRD, Raman and SEM characterization results show a suitable pyrolysis temperature would promote the balance between amorphous carbon and graphene, which can affect the formation of FexCy phase, leading the distinctive activity and olefin selectivity. Hence, the presented one-step pyrolysis methodology would provide a facile and quick synthesis of highly-active iron-based catalyst design for CO2 conversion.

A high-precision experimental measurement system and method for the parahydrogen concentration and the Ortho-Para hydrogen catalyst's catalytic performance

An experimental system that combines the measurement of parahydrogen concentration with the assessment of ortho-para hydrogen catalyst's catalytic performance was created for this investigation. The concentration of parahydrogen was detected by a thermal conductivity detector integrated into the gas chromatograph. The catalyst sample and the generator of standard gas were integrated into one experimental setup for easier operation. Meanwhile, a new method for catalytic performance evaluation of ortho-para hydrogen catalyst was developed based on this system. This method can decrease test time and yield more valuable test results than the conventional way. Throughout the experiments, the system's dependability was increased by optimizing the utilization of the carrier gas. The deviation analysis and repeatability verification of the relevant test data showed that the relative standard deviation was less than 0.35% and the mean value of the variation coefficient was less than 0.20%, which demonstrated the method had high accuracy, stability, and reliability. Further studies have shown that the catalysts should be densely packed inside the converter and kept out of the air to maximize their catalytic activity. These pertinent findings regarding the application of ortho-parahydrogen catalysts in this study can guide the design of the ortho-parahydrogen converter in actual hydrogen liquefiers. Moreover, the method and the procedure proposed in this study may contribute to the optimization of the ortho-parahydrogen catalyst production process as well as the calibration of the parahydrogen concentration in liquid hydrogen products.

Role of the surface chemistry of carbon xerogel-based supports and Cu catalysts in the oxidation reaction of glycerol

Carbon xerogel with pore size of about 10 nm were obtained using the sol–gel method and applying different thermal treatments. Catalysts were prepared depositing 3 wt% of copper on the xerogel. The catalytic activities of catalysts and supports were evaluated in the selective oxidation of glycerol (GLY). The supports showed good conversion and selectivity to glyceric acid (GA) and lactic acid (LA), with higher preference to GA. For the catalysts, the conversions were slightly higher, and the order of selectivity changed, benefiting the production of LA. Changes in selectivity between supports and catalysts were mainly associated with the different acid-base surface characteristics and the presence of the Cu domains in the catalysts. In the supports, even if the thermal treatment applied modifies the type and content of oxygenated functional groups (OFG) on the surface, predominates a superficial acid character, addressing the selectivity to GA. On the other hand, the basic character of the catalysts due to the Cu presence and the large metallic domain sizes favoured the production of LA. During the recycle test, supports and catalysts showed a decrease in catalytic activity. After three recycles, the catalytic performances of catalysts and supports were similar due to metal leaching.

Highly efficient catalyst of Crednerite CuMnO2 for PMS activation: Synthesis, performance and mechanism

Exploring highly efficient and stable transition metal-based catalysts is significant for the heterogeneous catalysis of peroxymonosulfate (PMS) in contaminants removal during water purification. Herein, we developed a series of Crednerite CuMnO2 catalysts by tuning the hydrothermal synthesis conditions and applied them to catalyze PMS to degrade Orange I (OI). Hydrothermal temperature, hydrothermal reaction time, and NaOH dosage had a great influence on the catalytic performance of catalysts, but different synthetic raw materials had little diversity. Amongst, CMO-160°C-110mmol-24h exhibited the optimal PMS activation effect due to the promoted surface oxygen mobility and electron conduction. Regardless of the wide pH range of 5-9, the coexistence of Inorganic anions and humic acid, the inhibition of OI removal was not significant. Additionally, CMO-160°C-110mmol-24h showed low metal ion leaching and noticeable reusability, implying a great potential application of the CMO-160°C-110mmol-24h/PMS system in practical wastewater engineering. Mechanism studies indicated that surface hydroxyl groups, Cu+/Cu2+ and Mn2+/Mn3+ redox couples were key active sites for PMS activation. Both free radical pathways (•OH, SO4•−, O2•−) and non-free radical pathways (1O2 and electron transfer) were detected in the oxidation reaction, with non-free radical pathways as major contributors. The possible degradation pathway of OI was proposed, and the toxicity of intermediates was assessed. Overall, this study provided an important strategy for the construction of efficient and stable PMS catalysts in wastewater treatment.

Insights into the enhanced activity and SO2 resistance of air oxidation treated Mn-Fe doped biochar catalyst in the low-temperature catalytic reduction of NOx with NH3

In this study, a sustainable two-stage air oxidation (TAO) was employed to prepare Fe modified MnOx-biochar catalyst (C-O2-MF-O2) instead of high temperature treatment and/or chemical activation for selective catalytic reduction of NO with NH3 (NH3-SCR). The collaborative effect of Fe modification and TAO on the physicochemical properties and catalytic performance of catalysts was systematically studied. Compared with counterpart catalysts treated with two-stage N2 (C-N2-MF-N2) or one-stage O2 (C-O2-MF-N2, C-N2-MF-O2), C-O2-MF-O2 showed obvious enhanced physicochemical properties (SBET, pore properties, high-valance metal ratio, chemisorption oxygen (Oα) content), superior catalytic performance, achieving 91.3% NO conversion with nearly 100% N2 selectivity at 150 °C, and much better H2O and SO2 resistance. It is worth noting that TAO facilitated the redox performance of MnOx after Fe modification to generate more dispersed high-valance metal (Mn4+ and Fe3+), thereby favoring the low-temperature SCR activity of the catalyst. Further, the in situ DRIFTS studies revealed TAO produced remarkable effects on the adsorption behaviors of NH3, NO and SO2, and the corresponding mechanisms of catalyst activity enhancement and SO2 resistance were proposed. Generally, TAO could be a favorable avenue to prepare catalysts with binary active metals for improving performance of NH3-SCR.

Selectivity and catalytic performance of Pdx@Pty/C nanoparticles for methanol electrooxidation

The catalytic performance of catalysts in specific oxidation reactions strongly depends on their composition and structure. In this study, we synthesized and evaluated the catalytic activity of Pdx@Pty/C core-shell nanoparticles (with x:y molar ratios of 0.2:0.8, 0.3:0.7, and 0.4:0.6) for methanol electrooxidation, aiming to investigate the influence of Pd incorporation in the core of the structure. XRD measurements revealed minor distortions in the Pt lattice parameters of all core-shell catalysts compared to Pt/C catalysts. The nanoparticles exhibited good dispersion on the carbon support, with spherical shapes and small particle sizes (3–3.5 nm). The core-shell nanoparticles are formed by a Pd-Pt-rich core and a Pt shell. Electrochemical characterizations revealed that core-shell catalysts displayed improved catalytic properties compared to Pt/C catalysts, which is due to electronic and geometric effects in the Pt structure resulting from the core-shell morphology. The Pd0.3@Pt0.7/C catalyst achieved the highest catalytic activity, presenting the lowest onset potential and the highest current densities for methanol oxidation. In situ FTIR data revealed that core-shell catalysts start CO2 production at significantly lower potentials than the Pt/C catalyst (about 500 mV lower) and achieved the highest production of this product across the potential range. Among the core-shell catalysts, Pd0.4@Pt0.6/C is the most selective material for CO2 production. These findings indicate enhanced selectivity of the catalysts, likely resulting from synergistic modifications facilitated by a higher Pd content, enabling the conversion of methanol and intermediate species on the catalyst surface.

Efficient selective combustion of n-butylamine on hierarchical Cu-Mn/SAPO-34 catalysts: The effect of mesoporosity and acidity

The efficient catalytic oxidation of nitrogen-containing volatile organic compounds remains a big challenge due to unmanaged production of harmful byproducts. Herein, a series of Cu-Mn modified hierarchical SAPO-34 zeolite catalysts with different pore structures were synthesized for n-butylamine oxidation. The physicochemical properties and catalytic performance of catalysts were investigated and analyzed in detail. Among them, CuMn/S-1 shows the highest activity (T90 = 279 °C, GHSV = 12,000 h−1), which is attributed to its higher porosity, higher surface acidity and superior reducibility. Meanwhile, it is found that the hierarchical structure and mesopore play an important role in improvement of N2 selectivity. Meanwhile, CuMn/S-1 also exhibits high stability and water resistance. The catalytic mechanism of n-butylamine on CuMn/SAPO-34 was investigated by in situ DRIFTS, showing that propanol, methanol and acetate are the main intermediates.

Analysis on the catalytic performance of catalysts and cost-effectiveness and selectivity of methanol carbonylation

Methanol is an essential raw chemical that is also a source of environmentally friendly energy for use in automobiles and other uses. It is one of the most important organic raw materials that is used in the manufacturing of a wide variety of organic compounds, such as chloromethane, methylamine, and dimethyl sulfate, among many others. It is one of the raw materials used in the production of dimethyl terephthalate, methyl methacrylate, and methyl acrylate, in addition to being a raw material for pesticides (insecticides, acaricides), pharmaceuticals (sulphonamides, co-trimoxazole, etc.), and other chemicals (such as sulfonamides and co-trimoxazole, for example). This paper investigates the catalytic performance of various catalysts for methanol carbonylation through a method of literature review. The purpose of the study is to determine which catalyst offers the most value for the price. In addition to that, the research investigates the efficiency in terms of cost and the selectivity of the methanol carbonylation process.

Study on the performance and sulfur tolerance mechanism of Pd/beta zeolite in catalytic combustion of toluene

Based on the method of quantitative pyrolysis of ammonium sulfate, sulfur tolerance of Pd/beta zeolite in catalytic conversion of toluene was explored in this paper. Changes in pore structure, valence, acidity, oxidation, and adsorption/desorption behavior were investigated in detail through XRD, N2 adsorption, HRTEM-EDS, XPS, H2-TPR, and NH3-TPD before and after sulfur poisoning. The results proved the structural stability of Pd/beta zeolite in the process of sulfur poisoning. Combined with FT-IR and ICP characterization results, the possible sulfur poisoning process and the intrinsic sulfur tolerance mechanism of Pd/beta zeolite were revealed: Active PdO/Pd reacted with sulfur species to produce inactive PdSO4 was regarded as a major cause of partial deactivation of Pd/beta zeolite. AlO4 units in beta zeolite were likely to combine with sulfur species to obtain Al2(SO4)3 and generate more acidic sites, and SiO4 units in beta zeolite were structurally stable enough to resist sulfur corrosion, guaranteeing the stability of the catalyst. The catalyst catalytic performance was not seriously affected after deep sulfur poisoning, exhibiting good resistance to sulfur poisoning.

La–Ce binary oxide catalysts for low-temperature dry reforming

A series of Ni-based catalysts supported by La–Ce binary oxide were synthesized by a one-pot microwave-assisted hydrothermal method. With fine-tuning of the La/Ce ratio and synthesis process, fabricated Ni/La–Ce catalysts showed comparable catalytic performance in low-temperature dry reforming of methane (DRM). With a La/Ce ratio of 1:4, the synthesized catalyst had optimal conversions of reactants but severe coke formation. When La/Ce ratio increased to 1:1, with declined DRM reactivity Ni/La–Ce catalyst showed great coke resistance. Different characterizations had been performed on the fresh and spent Ni/La–Ce catalyst to evaluate the correlations between structures and surface properties with the catalytic performance of catalysts. It was found that synthesis and carbonate species formed on the surface of La–Ce binary oxide played important roles in the DRM reaction. The La–Ce binary oxide had its intrinsic lattice configuration with La inserting into the CeO2 phases and proved its efficiency in low-temperature DRM reactions.

Graphene-like wrapped Ni@C catalyst with magnetic recyclability for selective hydrogenation of nitro-aromatics

The graphene-like wrapped Ni@C catalysts were facilely synthesized by a modified sol–gel method. Nickel nitrate and citric acid (CA) were adopted as the raw materials to form sol–gel mixture. Under the circumstances, the additive CA were employed not only as a complexing agent but also as a carbon source. It is found that the calcination temperature and the mole ratios between Ni and CA are the key factors affecting the physical property and the catalytic performance of catalysts in the conversion of nitroarenes into corresponding anilines. The results show that the Ni@C-500(1:1) catalyst exhibited the best performance in the hydrogenation of o-chloronitrobenzenes (o-CNB) to o-chloroanilines (o-CAN). The yield of o-CAN was achieved at 100% when o-CNB was completely converted at 40.0 °C under 2.0 MPa H2 for 2.0 h. Furthermore, the Ni@C-500(1:1) catalyst could be separated and recovered easily after reaction by an external magnetic field. The investigated results indicate that the Ni@C-500(1:1) catalyst remained higher activity after using twelve times. More importantly, this kind of catalyst is also active for the selective hydrogenation of other nitroarenes into the corresponding anilines. This new synthetic method may pave a way for producing low-cost Ni@C catalysts on a large scale, which is attractive for industrial anilines applications.

ABATEMENT OF HARMFUL CARBON MONOXIDE OVER THE NICKLE DOPED CO3 O4 CATALYST

This work aimed at evaluating the effect of nickle (Ni) dopant on the catalytic performance of Co3 O4 catalyst for abatement of harmful carbon monoxide (CO), a resistance toward sintering and durability of catalytic activity were also pursued. Choose the Co(NO3 )2 ×6H2 O(aq) as precursor and NaOH as precipitant to prepare cobalt oxide (Co3 O4 ) with precipitation method, then calcined at 300 and 500 °C, separately (named as C3 and C5). The Ni dopant (0.1 ~ 5 wt%) was added by deposited precipitation through Ni(NO3)2 ×6H2 O(aq) with drop wisely added NaOH(aq) into suspended Co3 O4 solution, then put the NaOCl for oxidation to obtain series 0.1%Ni-Co3 O4 , 0.2%Ni-Co3 O4 , 1%Ni-Co3 O4 and 5%Ni-Co3 O4 catalysts. All catalysts were characterized through BET, XRD, TEM/SEM, Raman, ICP and TPR instruments, and evaluated the catalytic performance of CO oxidation with a self-devised fluidized micro-reactor. It was observed that the calcination temperature and loading of dopant remarkably influenced the physicochemical characteristics and catalytic performance of the catalysts. Preferential catalyst was obtained for calcination at 300 °C and loading of Ni dopant below 1%. The doping of Ni on the surface of Co3 O4 enhanced the performance due to the inducing of synergistic effect between Co3 O4 and NiO, while the excessive NiO incorporated to the surface constrained the activity due to the abundant NiO on the surface, overlaying the active sites caused the decreasing of surface area and reducible capacity. Among these series Ni-Co3 O4 catalysts, the 0.2%Ni-Co3 O4 (C3) catalyst behaved an eminent activity with T50 of 98 °C and durability without apparent deactivation for 50 hr reaction at 125 °C. The excellent performance is primarily attributed to the synergistic effect and formation of NiCo2 O4 composite oxide.

Electronic control of catalytic activity of ZnO for higher alcohols synthesis via tailoring Fermi level

Metal doping are essential for electronic modulation of semiconductors, leading to different Fermi level, which determined the surface chemisorption and catalytic properties. Here, ZnO doping with 4 mol% Cu were synthesized by four preparation routes, which tuned Cu existing states and Fermi level appearing remarkable impacts on the catalytic performance of catalysts. It shows a negative correlation between synthesis of higher alcohols and Fermi level over electronically modified ZnO catalysts, and the lower Fermi level exerted better facilitation for the carbon chain growth. Copper was incorporated into ZnO lattice and existed in the form of isolated Cu2+, which regulated the electronic structure of ZnO with lower Fermi level and boosted the process of catalysts obtaining electrons. Thus, the lower Fermi level promoted the dissociation CO bond and p-type reaction of forming surface alkyl species, and a higher proportion of straight chain higher alcohols can be achieved via CO or CHxO* inserting into alkyl species. Especially the catalyst prepared by urea hydrolysis with the lowest Fermi level significantly increased the higher alcohols fraction in total alcohol products to 69.9%. For comparison, the higher Fermi level are unfavorable for p-type reaction, leading to high methanol selectivity. This work provides a new viewpoint for promoting catalytic performance from the perspective of electronic modification of ZnO.

Preparation of Novel Triangular Prism e -Zn(OH)2 by the Facile Precipitation Route for the Photocatalysis Under Visible Light

Objective: This study aims to decompose antibiotic of tetracycline hydrochloride (TCH) in aqueous medium by photocatalysis under the visible light irradiation. Method: Photocatalyst e -Zn(OH)2 was synthesized by facile precipitation method from an aqueous containing zinc nitrate, using trisodium citrate dihydrate. The characterization of as-prepared material was confirmed by XRD, SEM, FI-IR, and UV-Vis-DR. The catalytic performance of catalyst was evaluated by batch reaction. Finding: e -Zn(OH)2 has an orthorhombic structure with a length prism of 5-7 mm and triangle angles of 56.92, 69.46, and 66.71o e -Zn(OH)2 has been shown to efficiently degrade tetracycline hydrochloride. The degradation efficiency (DE) and reaction rate at the TCH concentration of 5 mg/L were the highest, exhibiting 89.51% and 0.120 min-1, respectively. The alkaline medium was an appropriate condition for degradation of TCH on catalyst. Application/Improvement: e -Zn(OH)2 was synthesized by the facile precipitation method, it has relatively strong photocatalytic ability for applying in treatment of medical wastewater. Novelty: Novel triangular prism e -Zn(OH)2 was prepared for photocatalysis. The relationship between structure and catalytic efficiency was investigated in detail. In addition, the photocatalytic mechanism of TCH on e -Zn(OH)2 has been proposed. Keywords: Photocatalyst; Zn(OH) 2; Tetracycline hydrochloride; Degradation; Kinetic

Catalytic Performance of Alumina-Supported Cobalt Carbide Catalysts for Low-Temperature Fischer–Tropsch Synthesis

The determination of the catalyst’s active phase helps improve the catalytic performance of the Fischer–Tropsch (FT) synthesis. Different phases of cobalt, including cobalt oxide, carbide, and metal, exist during the reaction. The content of each phase can affect the catalytic performance and product distribution. In this study, a series of cobalt carbide catalysts were synthesized by exposure of Co/Al2O3 catalyst to CH4 at different temperatures from 300 °C to 800 °C. The physicochemical properties of the carbide catalysts (CoCx/Al2O3) were evaluated by different characterization methods. The catalytic performances of the catalysts were investigated in an autoclave reactor to determine the role of cobalt carbides on the CO conversion and product distribution during the reaction. XRD and XPS analysis confirmed the presence of Co2C in the prepared catalysts. The higher carbidation temperature resulted in the decomposition of methane into hydrogen and carbon, and the presence of graphitic carbon was confirmed by XRD, XPS, SEM, and Raman analysis. The Co2C also decomposed to metallic cobalt and carbon, and the content of cobalt carbide decreased at higher carbidation temperatures. Higher content of Co2C resulted in a lower CO conversion and higher selectivity to light alkanes, mainly methane. The higher carbidation temperature resulted in the decomposition of Co2C to metallic cobalt with higher activity in the FT reaction. The CO conversion increased by increasing the carbidation temperature from 300 °C to 800 °C, due to the higher content of metallic cobalt. In the presence of pure hydrogen, the Co2C could be converted mainly into hexagonal, close-packed (hcp) Co with higher activity for dissociative adsorption of CO, which resulted in higher catalyst activity and selectivity to heavier hydrocarbons.