Catalyst Preparation Conditions Research Articles

Modification of Cs/SiO2 with Zr element through sol–gel method for production of methyl methacrylate via one-step aldol condensation

Development of effective cesium-based catalyst is important for methyl methacrylate (MMA) production via one-step aldol reaction. Herein, a kind of Cs/Zr-SiO2 catalyst was prepared by sol–gel method and the acid-base properties and their balance could be controllably regulated. The influence of catalyst preparation conditions including Si/Zr ratio and water content on the structure and acid-base properties of Cs/Zr-SiO2 was demonstrated, which consequentially affected catalytic performance. The formation of Si-O-Zr and Cs-O-Si structure was identified as the dominant Lewis acid and base sites and the acid site density can be enhanced by 1-fold when using sol–gel method. In addition, the MP conversion could reach 37 % with MMA selectivity of 85 % at the optimal condition. Kinetic studies revealed that the activation barrier on the modified 10Cs/Zr-SiO2 exhibited the lowest activation energy of 110.9 kJ/mol. Besides, the initial catalytic activity could still maintain after 800 h recycling, with single-pass life of 160 h.

Unlocking solid waste utilization: Fly ash-supported cobalt catalyzed transformation of 5-hydroxymethylfurfural into biofuel 2,5-dimethylfuran

5-Hydroxymethylfurfural is a crucial platform molecule derived from biomass, and its selective conversion to furan chemicals holds significant importance for the high-value utilization of biomass. In this study, acid-modified coal fly ash was used as a support for non-precious metal cobalt to prepare a novel catalyst (Co/CFA), which demonstrated excellent performance in the selective hydrodeoxygenation of 5-hydroxymethylfurfural to 2,5-dimethylfuran. By investigating the catalyst preparation conditions, it was found that with a 30wt% cobalt loading, the selectivity of 2,5-dimethylfuran can reach 98.1 %, and the conversion of 5-hydroxymethylfurfural is 99.0 %. A series of characterization showed that the acid modification treatment increased the pore structure and specific surface area of the coal fly ash, was conducive to the dispersion of cobalt, and improved the activity of the Co/CFA catalyst. This innovative approach harnesses the potential of waste materials, emphasizing resource efficiency and sustainability in catalyst development.

Influence of Synthesis Conditions on Catalytic Performance of Ni/CeO2 in Aqueous-Phase Hydrogenolysis of Glycerol without External Hydrogen Input.

The aqueous-phase hydrogenolysis of glycerol was studied in Ni/CeO2 catalytic systems prepared by incipient wetness impregnation. The operating conditions were 34 bar, 227 ºC, 5 wt.% of glycerol, and a W/mglycerol = 20 g catalyst min/g glycerol without a hydrogen supply. The effect of the catalyst preparation conditions on the catalytic activity and physicochemical properties of the catalysts was assessed, particularly the calcination temperature of the support, the calcination temperature of the catalyst, and the Ni content. The physicochemical properties of the catalysts were determined by N2 adsorption, H2-TPR, NH3-TPD, and XRD, among other techniques. A relevant increase in acidity was observed when increasing the nickel content up to 20 wt.%. The increase in the calcination temperatures of the supports and catalysts showed a detrimental effect on the specific surface area and acid properties of the catalysts, which were crucial to the selectivity of the reaction. These catalysts notably enhanced the yield of liquid products, achieving global glycerol conversion values ranging from 17.1 to 29.0% and carbon yield to liquids ranging from 12.6 to 24.0%. Acetol and 1,2-propanediol were the most abundant products obtained in the liquid stream.

Silica Gel Supported Chlorosulfonic Acid Catalyzed Beckmann Rearrangement of Cyclohexanone Oxime in Liquid Phase

The Beckmann rearrangement of cyclohexanone oxime in the liquid phase using fuming sulfuric acid as a catalyst is a traditional method, which brings many problems, such as environmental pollution, corrosion of equipment, and difficulty in treating the by-product ammonium sulfate. This paper designs and prepares a silica gel-supported chlorosulfonic acid solid acid catalyst for the liquid-phase Beckmann rearrangement of cyclohexanone oxime to caprolactam. The factors affecting the preparation of the catalyst and the optimal reaction conditions for Beckmann rearrangement were investigated. It was found that the best catalyst preparation conditions were as follows: mass ratio of silica gel: chlorosulfonic acid of 1:0.2, room temperature, stirring time of 3 hours, solvent dichloromethane, and silica gel mesh size of 100-200 mesh, and best Beckmann rearrangement conditions were as follows: mass ratio of cyclohexanone oxime: catalyst of 1:1, temperature of 140°C, solvent benzonitrile volume of 40 mL/g cyclohexanone oxime, reaction time of 5 hours. Under the above conditions, the conversion of cyclohexanone oxime is 74%, and the selectivity of caprolactam is 40%.

A novel machine learning framework for designing high-performance catalysts for production of clean liquid fuels through Fischer-Tropsch synthesis

Fischer-Tropsch synthesis (FTS) attracts great interest as a sustainable route for production of sustainable transportation fuels. Catalyst design and operational conditions tune the selectivity of FTS to liquid fuels, which can be predicted with machine learning models (ML). Herein, a comprehensive dataset including 27 key input features related to the catalyst structure (with the focus on carbon supports), preparation, activation, and FTS operating conditions were investigated to predict the CO conversion and C5+ selectivity using three ML algorithms. Feature engineering and selection were implemented to identify the significant catalyst formulation descriptors. Principal component analysis was used to explore the information space and decrease the dimension of the dataset before ML prediction. In addition to the well-known effects of the operational conditions on FTS, roles of physico-chemical properties of the carbon materials were also extensively analyzed. Random forest (RF) including 4 principal components, indicated the highest accuracy for prediction of the CO conversion and C5+ selectivity with R2 of 0.91 and 0.97, respectively. The proposed framework can provide a reliable strategy in designing efficient carbon supported catalysts for FTS and guide experiments by identifying the key descriptors in the catalyst formulation and operating conditions to enhance the selectivity of liquid fuels.

Multiple synergistic roles of Zr modification on ZSM-5 in performant and stable catalyst for ethanol conversion to propene

Bioethanol to propene is a promising avenue to produce propene by non-fossil routes. In this study, the ethanol conversion on metal-modified ZSM-5 catalysts is systematically investigated under catalyst preparation conditions and reaction parameters. Among all metal modified ZSM-5, Zr modification significantly improves the propene selectivity and catalyst durability. On the Zr/ZSM-5 catalyst (Zr/Al molar ratio is 0.4, reaction temperature 500 °C, and contact time 0.005 g⋅min/mL), the maximum yield of propene reaches up to 32.5 %, which can be maintained above 20.0 % within 20 h. Zr modification changes the acidity and electronic structure of the active sites, improves the adsorption stability of the reactant ethanol on Zr/ZSM-5, facilitates easier desorption of the product propene, benefiting propene production. Moreover, Zr modification is found to increase the activation energy of the ethene protonation, inhibit the ethene dimerization reaction, further inhibits the carbon deposition, and extends the lifetime of ZSM-5. In addition to its synergistic and effective role in the conversion of ethanol to propene, the Zr modified catalyst also exhibits high selectivity and stability in the conversion of bioethanol. According to above significant characteristics, Zr modified ZSM-5 will emerge as a promising catalyst for the conversion of bioethanol to propene.

CoZn@N-ALC, highly-efficient magnetic Co nanoparticles anchored by lignin-based Nitrogen-doping carbon for hydrodeoxygenation of vanillin

The conversion of lignin-based platform compounds into valuable biofuels and chemicals through catalytic processes is an attractive approach for the efficient valorization of renewable lignocellulosic biomass. One such process is the hydrodeoxygenation (HDO) of lignin-based vanillin (VL) to produce 2-methoxy-4-methylphenol (MMP), which is a promising liquid fuel and intermediate for fine chemicals. However, the development of a cost-effective catalytic system with high activity and selectivity remains a challenge. In this study, we report the preparation of a highly-efficient magnetic Co nanoparticles catalyst, CoZn@N-ALC, using alkali lignin as an assembly macromolecular ligand, Zn as a sacrificial metal, and dicyandiamide as a nitrogen source before the pyrolysis process. Various characterization techniques, including powder X-ray diffraction (XRD), pyridine adsorption infrared spectroscopy (Py-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), isothermal nitrogen adsorption/desorption, and X-ray photoelectron spectroscopy (XPS), were employed to investigate the role of zinc and nitrogen in the construction process of CoZn@N-ALC and the influence of catalyst preparation conditions. The optimized CoZn@N-ALC catalyst demonstrated nearly 100 % conversion of VL, complete selectivity towards MMP, and easy separation from the aqueous HDO system. Structure-performance investigation and density functional theory (DFT) calculations suggest that the exceptional catalytic performance of this catalyst can be attributed to the selective adsorption of C=O bonds by abundant Co (111) active species and its Lewis acid sites. This work provides valuable insights into the rational design of efficient, non-noble metal nanoparticle catalysts based on alkali lignin for the conversion of lignin-based platform compounds.

A study on the oxidation of toluene to benzaldehyde by air catalyzed by polyoxometalate loaded on activated carbon

At present, benzaldehyde is mainly produced in the way of liquid-phase chlorination of toluene followed by hydrolysis. Such method not only pollutes the environment with the discharge of large amount of waste water, but also limits its application into the field of food and medicine due to the existence of chlorides. In this paper, toluene is oxidized to benzaldehyde by air in acetic acid using polyoxometalate supported on activated carbon as a catalyst. The composition and preparation conditions of the catalyst have been explored. The optimum polyoxometalate composition is determined as Na5.1La0.7CoMn0.3Mo11.7O40·22.05H2O@AC by ICP-OES, FT-IR, XRD and TG. The optimum catalyst preparation conditions are pH1=6.3, pH2=3.8, T1=95°C, T2=85°C, activation temperature 220°C and activation time 4 h. The best experimental results are toluene conversion 13.18 %, benzaldehyde selectivity 40.43 % and benzaldehyde yield 5.33 %.

Valeric Biofuels from Biomass-Derived γ-Valerolactone: A Critical Overview of Production Processes.

This review analyzes critically the production of valeric biofuels from γ-valerolactone, a relevant biomass-derived platform molecule. Initially, the main properties of valeric esters as fuels for spark- and compression-ignition engines are summarized. Then, catalytic routes to valeric esters from γ-valerolactone are meticulously analyzed, describing the acid- and metal-catalyzed reactions taking part in the tandem catalysis. Only works focused on the production of the valeric biofuels were considered, excluding the cases where these esters were observed in minor amounts or as byproducts. The role of the appropriate selection of the support, catalytic species, catalyst preparation and experimental conditions on the valeric ester productivity are thoroughly commented. Finally, some concluding remarks and perspectives are given, mentioning the areas where additional efforts must be done in order to turn the dream of a massive and renewable valeric biofuel production into a reality.

Activation of persulfate by iron‐loaded soybean straw biochar for efficient degradation of dye contaminants: Synthesis, performance, and mechanism

AbstractBiochar loaded with metal ions has been widely used to activate persulfate to degrade organic pollutants. However, the preparation conditions of catalysts are always controversial. In this study, the co‐heating conditions of soybean straw with high carbon and low nitrogen and nano‐iron oxide were systematically discussed by response surface method, and an efficient catalyst (Fe@BC) was obtained. Fe@BC can effectively activate sodium persulfate (PS) and degrade three synthetic azo dyes (Methyl orange (MO), Amino black 10B (AB10B), and Orange II) and rhodamine B (RhB). Under the optimum conditions, the removal rate of total organic carbon of these four dyes reached 41.1%–89.8% and the final degradation rate could reach 100%. The physicochemical properties of Fe@BC were studied by SEM, BET, XRD, XPS and TGA. The results revealed that the specific surface area of Fe@BC was 195.6m2/g. Further, reducing iron oxide by C generated C0.09Fe1.91 and zero‐valent iron. Free radical scavenging experiments and electron paramagnetic resonance (EPR) measurements showed that the main reactive oxide species (ROS) in the Fe@BC/PS system were hydroxyl radicals (•OH) and singlet oxygen (1O2). Finally, Several Fe@BC modification systems were explored, the optimum pH of Fe@BC/PS system was analyzed, and the effects of Fe@BC and PS dosage on degradation performance were also studied. This study provides a scientific basis for the production of efficient catalysts and biochar energy, and an effective treatment scheme for printing and dyeing wastewater.

Sustainable biodiesel production via transesterification of vegetable oils and waste frying oil over reusable magnetic Ca2Fe2O5/CaO@MgFe2O4-Fe2O3 catalyst

ABSTRACT The leaching and reusability problem of the catalyst in the catalytic transesterification for biodiesel production led to the poor sustainability and high posttreatment cost. Herein, a reusable magnetic Ca2Fe2O5/CaO@MgFe2O4-Fe2O3 catalyst with high textural stability and good catalytic activity was prepared in this study, and its catalytic performance toward transesterification of five different oil feedstocks was evaluated. Catalyst preparation conditions were optimized and characterizations including scanning electron microscope (SEM), X-ray diffraction analysis (XRD), and so on, were also conducted to investigate the catalytic behaviors. The results demonstrated that the catalyst has good ferromagnetism for magnetic separation, and the presence of synergistic interaction enhanced catalytic activity with all of > 90% biodiesel yield and improved the reusability with > 75% biodiesel yields at the 10th cycle. In addition, the biodiesel yield reached the maximum under the transesterification reaction parameters were optimized, and at the 15/1 methanol/oil molar ratio, 2.5 wt% catalyst dosage, 70°C for 120 min. Further, for biodiesel from five different oil feedstocks, the same composition, all of > 90% yield and the quality that met the American Society of Testing Materials (ASTM) standards demonstrated the strong oil feedstocks applicability and application potential of catalysts.

Prediction and interpretation of photocatalytic NO removal on g-C3N4-based catalysts using machine learning

Predictive modeling of photocatalytic NO removal is highly desirable for efficient air pollution abatement. However, great challenges remain in precisely predicting photocatalytic performance and understanding interactions of diverse features in the catalytic systems. Herein, a dataset of g-C3N4-based catalysts with 255 data points was collected from peer-reviewed publications and machine learning (ML) model was proposed to predict the NO removal rate. The result shows that the Gradient Boosting Decision Tree (GBDT) demonstrated the greatest prediction accuracy with R2 of 0.999 and 0.907 on the training and test data, respectively. The SHAP value and feature importance analysis revealed that the empirical categories for NO removal rate, in the order of importance, were catalyst characteristics > reaction process > preparation conditions. Moreover, the partial dependence plots broke the ML black box to further quantify the marginal contributions of the input features (e.g., doping ratio, flow rate, and pore volume) to the model output outcomes. This ML approach presents a pure data-driven, interpretable framework, which provides new insights into the influence of catalyst characteristics, reaction process, and preparation conditions on NO removal.

Study on Treatment of Basic Yellow 28 dye Wastewater by Micro-nano Bubble Ozone Catalytic Oxidation

Mn loaded AC (Mn/AC), Cu loaded AC (Cu/AC), and Fe loaded AC (Fe/AC) catalysts were prepared by the impregnation-calcination method, which can be used to degrade Basic Yellow 28 dyes in simulated printing and dyeing wastewater for catalytic ozonation. The catalyst preparation and reaction conditions were optimized with the degradation efficiency of chemical oxygen demand (COD) and the absorbance of some organic compounds under 254 nm UV light (UV254) as indicators. The surface structure, specific surface area, and active component distribution of the catalysts were analyzed by scanning electron microscopy (SEM), nitrogen adsorption, and X-ray diffraction (XRD) characterization. Results indicated that Mn was the best active component, and a catalyst dosage of 3.5 g/L, an initial pH of 9.4, and an initial temperature of 31.7°C were the best reaction parameters to degrade Basic Yellow 28 dyes. After five recycling experiments, the catalysts could retain a relatively stable catalytic effect. Furthermore, this study can be informative for the sustainable development of future catalysts.

Solid Acid Catalyst Derived from Cotton for Conversion of Xylose and Corn Cob to Furfural

AbstractCarbon‐based solid acid catalysts (CS−SO3H) were prepared by one‐pot carbonization‐sulfonation method with concentrated sulfuric acid using cotton as raw material, which was used to transformation of xylose and corn cob to furfural. The catalyst preparation conditions were optimized to be that the cotton mass/sulfuric acid volume ratio is 1 : 20 (g/mL), and the reaction is carried out at 160 °C for 10 h. The morphology, functional groups and surface chemical state were investigated. The yield of furfural can reach 87.3 % from xylose under the optimal reaction condition of 0.1 g xylose, 0.05 g catalyst, 180 °C for 90 min in 5.0 mL γ‐valerolactone‐water solvent. The yield of furfural can reach 63.2 % by the direct one‐pot conversion of corn cob over the CS−SO3H under the optimal reaction condition of 0.1 g corn cob, 0.1 g catalyst, 190 °C for 90 min in 5.0 mL γ‐valerolactone‐water solvent. The catalytic activity gradually declined when it was cycled for four times. The reason was determined to be the partial shedding of the sulfonic acid groups grafted on the catalyst during the reaction and insoluble humus accumulated on the catalyst surface. After regeneration, the catalytic activity can be restored.

Synthesis of CuO/GO-DE Catalyst and Its Catalytic Properties and Mechanism on Ciprofloxacin Degradation

A new catalyst, copper oxide/graphene oxide-diatomaceous earth (CuO/GO-DE), was prepared by the ultrasonic impregnation method. The optimal conditions for catalyst preparation were explored, and its structure and morphology were characterized by BET, XRD, SEM, TEM, FTIR, Raman and XPS. By taking ciprofloxacin as the target pollutant, the performance and reusability of CuO/GO-DE to degrade antibiotic wastewater was evaluated, and the optimal operating conditions were obtained. The main oxidizing substances in the catalytic system under different pH conditions were analyzed, as well as the synergistic catalytic oxidation mechanism. The intermediate products of ciprofloxacin degradation were identified by LC-MS, and the possible degradation process of ciprofloxacin was proposed.

Magnetic reusable acid-base bifunctional Co doped Fe2O3–CaO nanocatalysts for biodiesel production from soybean oil and waste frying oil

Biodiesel is a promising renewable liquid fuel, but the poor reusability and low FFA resistance of the transesterification catalyst is hindering its development. In this work, acid-base bi-functional Co doped Fe2O3–CaO nanocatalysts were prepared by one-pot hydrothermal followed by calcination method for biodiesel production from soybean oil and waste frying oil (WFO). The catalyst was characterized by XRD, XPS, TPD technologies and so on. The results showed that the doping of Co into the Fe2O3 lattice makes α-Fe2O3 crystal transform into γ-Fe2O3 thus the catalyst has stronger magnetic strength for magnetic separation. And the catalyst preparation conditions and reaction parameters were optimized, the results showed that under the 16:1 methanol to oil molar ratio, 3 wt% catalyst dosage, and 70 °C for 150 min, the enhanced catalytic activity and improved FFA resistance with the 98.2% and 91.5% biodiesel yield from soybean oil and WFO can be obtained, respectively. In addition, stability and reusability of the catalysts were improved and no distinct activity drop after 5 consecutive transesterification recycles. Furthermore, the functional group and composition of biodiesel were analyzed using GC-MS, ATR-FTIR and NMR techniques. And combustion dynamic characteristics were analyzed by TG, and the results demonstrate that the produced biodiesel has good combustion ability and potential application in industrial production.

Effect of Catalyst Preparation Conditions on Activity and Selectivity of Pt-Sn/Sio2 Catalysts in Citral Hydrogenation

Effect of Catalyst Preparation Conditions on Activity and Selectivity of Pt-Sn/Sio2 Catalysts in Citral Hydrogenation

Application of converter slag as an effective and low-cost solid base catalyst for the transesterification process

ABSTRACT Calcium oxide is a suitable and valuable catalyst for producing biodiesel. In this research, the feasibility of producing biodiesel from waste frying oil with a new environmentally friendly and low cost heterogeneous solid-base catalyst from waste slag was evaluated. The composition, texture, structure, and chemical characteristics of the converter slag were examined by thermogravimetric analysis (TGA), X-ray fluorescence (XRF), Brunauer–Emmett–Teller (BET), Field Emission Scanning Electron Microscopy (FE-SEM), and X-ray diffraction (XRD). Moreover, the catalyst reusability, reaction conditions, and the effects of catalyst preparation conditions were studied in this experiment. The converter slag was calcined at 1100°C for 8 hours. Gas chromatography (GC) was used to analyse and evaluate the produced biodiesel. The biodiesel characteristics were compared with the ASTM D 6751 standard. It was found that the maximum efficiency of using converter slag for producing biodiesel was 77.8 ± 1.5% under the reaction time 6 hours, catalyst amount 10 wt.%, and reaction conditions of methanol to oil molar ratio 15:1. The converter slag as a catalyst was recovered and reused for three cycles. This study demonstrated how a low-cost catalyst could be used in the production of a value-added product (i.e. biodiesel) from waste oil.

Efficient removal of carbonyl sulfur and hydrogen sulfide from blast furnace gas by one-step catalytic process with modified activated carbon

The performance of modified activated carbon (AC) and the reaction mechanism for the one-step removal of COS and H2S from blast furnace gas were investigated by improving the catalyst preparation conditions. Optimal performance was achieved when the reaction temperature was 60 °C, the oxygen concentration was 0.1 vol%, and the catalyst was prepared by drying at 110 °C. A combined sulfur capacity of 218.21 mg/g was achieved, and the desulfurization mechanism was revealed through a series of characterization methods. The COS in the inlet gas was captured on the catalyst surface under the action of alkaline sites and was subsequently hydrolyzed to H2S. The generated H2S and the original H2S dissociated within the water film on the catalyst to generate HS- and H+. The lattice oxygen of CuO and Cu2O was activated, and the active oxygen oxidized most of the HS- to elemental S. Meanwhile, some of the HS- combined with metal ions to form sulfides, and CoPcS acted as an auxiliary to facilitate this oxidation process. The elemental S was further oxidized by reacting with H2O to form sulfuric acid, which interacted with the active components to form sulfate. This process eventually led to the deactivation of the catalyst.

Enhanced removal of ibuprofen by heterogeneous photo-Fenton-like process over sludge-based Fe3O4-MnO2 catalysts

Abstract Heterogeneous photo-Fenton-like catalysts with low cost, little hazard, high effectiveness and facile separation from aqueous solution were highly desirable. In this study, sludge-based catalysts combining nano Fe3O4-MnO2 and sludge activated carbon were successfully synthesized by high-temperature calcination method and then characterized. These synthetic materials were applied to remove ibuprofen in the heterogeneous photo-Fenton process. The preparation conditions of sludge-based catalysts optimized by orthogonal experiments were 2.0 M of ZnCl2, a temperature of 500 °C, a pyrolysis time of 60 min, and a sludge ratio: Fe3O4-MnO2 of 25:2. In batch experiments, the optimal experimental conditions were determined as catalyst dosage of 0.4 g·L−1, hydrogen peroxide concentration of 3.0 mL·L−1, pH value of 3.3, and contact time of 2.5 h. The degradation rate sludge/Fe3O4-MnO2 catalyst to ibuprofen is up to 95%. The removal process of ibuprofen fitted the pseudo-second-order kinetic model, and the photocatalytic degradation process was the main factor controlling the reaction rate. The catalytic mechanism was proposed according to the Fourier transform infrared analysis and mass spectrometry product analysis; it was mainly attributed to the interaction between hydroxyl groups and benzene rings.