Types Of Catalysts Research Articles

Research Progress in Organocatalysts Used in the Synthesis of Medical Polyurethanes and Their Biotoxicity

Medical polyurethanes have emerged as a leading choice for biomedical applications owing to their exceptional biocompatibility and good physical and mechanical properties. Catalysts play a crucial role as additives in the synthesis of medical polyurethanes, enhancing synthesis efficiency and material properties. However, the catalysts used may affect the biocompatibility of polyurethanes and pose potential harm to human health. This review encapsulates the latest findings regarding the catalysts employed in the synthesis of medical polyurethane materials and their biotoxicity. Initially, we reviewed the prevalent types of catalysts used in the synthesis of medical polyurethane materials and described their distinctive characteristics. Subsequently, our focus shifted to exploring the potential biotoxicity associated with these catalysts. Finally, we provided a forward-looking perspective and recommendations for the future trajectory of catalyst selection in the synthesis of medical polyurethane materials. By acquiring a more profound understanding of the properties and biotoxicity of catalysts used in the synthesis of medical polyurethane materials, and by uncovering existing issues and challenges, we can better guide the design of medical polyurethane materials. This, in turn, enables us to chart the course for future development and ultimately enhance the biocompatibility and safety profiles of medical polyurethane materials. Such advancements will promote the continued development and application of medical polyurethane materials in clinical settings.

Preparation of carbon materials by vapor deposition with Fe3+-Modified nickel foam from biomass pyrolysis gas

Biomass carbon materials have attracted attention in various fields due to their excellent properties. In this study, CH4 derived from biomass pyrolysis was utilized as a carbon source gas to synthesize carbon materials by chemical vapor deposition (CVD) in a two-stage reactor with purification system, with Fe3+-loaded nickel foam as the substrate under an argon atmosphere, using a self-designed experimental platform. The reaction process was optimized by examining the effects of the catalyst type, reaction temperature, reaction time, and gas flow rate on the structure and morphology of the carbon materials. The optimal preparation condition was to use FeCl3 ethanol solution as catalyst, with CH4 flow rate of 50 ml/min at 1000 °C for 25 min. The high quality carbon materials with uniform diameters (250–500 nm) were obtained on nickel foam substrate. The carbon materials obtained under optimal conditions were characterized and analyzed to investigate their excellent properties. Surface morphology and structure of as-formed carbon materials were characterized by SEM. The analysis of the XRD spectra and the Raman spectroscopy showed that the graphite diffraction peak (002) at 26.6°, the calculated intensity ratios for ID/IG and I2D/IG were 0.257 and 0.545, respectively, indicated high degree of graphitization and purity of the carbon materials. Furthermore, the growth mechanism of carbon materials on the nickel foam substrate was discussed.

Recent Advances in Electrochemical Water Splitting Electrocatalysts: Categorization by Parameters and Catalyst Types

Recent Advances in Electrochemical Water Splitting Electrocatalysts: Categorization by Parameters and Catalyst Types

Enhancement of gasochromic response to hydrogen of WO3 thin films by post-process modification and catalyst selection

The gasochromic properties of WO3 thin films deposited by electron beam evaporation were investigated, focusing on their structural, morphology and optical changes caused by heat treatment. Moreover, the influence of the thickness and type of catalyst on the gasochromic properties of WO3 was examined. X-ray diffraction measurements revealed that WO3 thin films annealed up to 473 K remained amorphous, whereas annealing at 673 K and above, initiated crystallization into a monoclinic structure. Gasochromic behaviour was observed in response to hydrogen exposure, with the most significant changes occurring in films annealed at 673 K with a thin adlayer of palladium catalyst. A gasochromic response of 1.84 was achieved for H2 concentration as low as 25 ppm. The process of gasochromic colouration was correlated with the changes of free charge carrier concentration calculated based on Drude free electron theory. XPS analysis confirms WO3 reduction under hydrogen exposure, validating proposed colouration mechanisms. These comprehensive findings offer insights into optimizing gasochromic thin films for various sensing applications.

Evaluation of homogeneous and heterogeneous catalytic strategies for furfural production from sugar-derived biomass in a solvent-free green pressurized reaction media (subcritical water-CO2)

A green organic, solvent-free, subcritical water-CO2 (subW-CO2) system was proposed for the production of furfural from the main hemicellulose's sugar, xylose. Despite subW itself showed potential for furfural generation due to its catalytic properties under subcritical conditions; when CO2 was added into the system as pressurization agent, higher yields were reached due to its effect as a Brønsted acid when dissolved in water. Furthermore, its combination with different Lewis acidic catalysts showed a synergistic effect, further improving furfural yield. In a batch configuration, five homogeneous and four heterogeneous catalysts were tested at 180 °C and 5.5 MPa and compared for the first time in a subW-CO2 reaction medium. Different furfural production paths were determined for the two catalysts types, with higher xylose isomerization rates to xylulose when homogeneous trivalent metal catalysts were used. CrCl3 and Nafion NR50 resin were selected as best catalysts from each of the groups due to higher furfural production rates (51.9 ± 0.9 % yield/h) and higher furfural selectivity (60.9 %), respectively. Furthermore, Nafion NR50 catalytic activity remained unchanged after 10 runs at 180 °C. The green subW-CO2 system furfural yields were comparable to water-organic solvent biphasic ones, proving to be a promising green alternative.

Anionic Surfactant-Tailored Interfacial Microenvironment for Boosting Electrochemical CO2 Reduction.

Both the catalyst and electrolyte deeply impact the performance of the carbon dioxide reduction reaction (CO2RR). It remains a challenge to design the electrolyte compositions for promoting the CO2RR. Here, typical anionic surfactants, dodecylphosphonic acid (DDPA) and its analogues, are employed as electrolyte additives to tune the catalysis interface where the CO2RR occurs. Surprisingly, the anionic surfactant-tailored interfacial microenvironment enables a set of typical commercial catalysts for the CO2RR to deliver a significantly enhanced selectivity of carbon products in both neutral and acidic electrolytes. Mechanistic studies disclose that the DDPA addition restructures the interfacial hydrogen-bond environment via increasing the weak H-bonded water, thus promoting the CO2 protonation to CO. Specifically, in an H-type cell, the Faradaic efficiency of CO increases from 70 to 98% at -1.0 V versus the reversible hydrogen electrode. Furthermore, in a flow cell, the DDPA-containing electrolyte maintains over 90% FECO from 50-400 mA cm-2. Additionally, this electrolyte modulation strategy can be extended to acidic CO2RR with a pH of 1.5-3.5.

Recent Progress in Solketal Synthesis from Glycerol and Acetone

AbstractThe extensive use of biodiesel leads to the excess of glycerol as a by‐product. But as a carbon resource, it has been increasingly used in organic synthesis of high value‐added derivatives in recent years. Among them, solketal is one of the most important derivatives of glycerol, which is generated by the reaction of glycerol and acetone. Based on a large number of relevant literatures, this paper systematically summarized the relevant researches in recent ten years. We systematically summary the latest research progress on the synthesis of solketal by glycerol and acetone. We have focused on a systematic study of four different reaction mechanisms for the ketonation reaction of glycerol and acetone. And the types of catalysts were classified into two categories, homogeneous catalysts and non‐homogeneous catalysts, and the non‐homogeneous catalysts were further classified in more details for the study. This review provides a more comprehensive reference for the ketal reaction of glycerol and acetone, and develops some new ideas for the transformation.

Microwave-assisted catalytic rapid pyrolysis of soybean straw for the preparation of high-value indole-rich bio-oils

Microwave-assisted catalysed rapid pyrolysis of soybean straw to prepare high-value bio-oils rich in indoles achieved value-added use of biomass. The effects of different urea doping ratios, two typical Al-based catalysts (γ-Al2O3, HZSM-5), and different HZSM-5 doping ratios on the preparation of N-rich bio-oils (NCBs) from soybean straw by microwave-assisted pyrolysis were investigated. It was shown that the yield of the liquid product at 40 % urea addition was 39.63 %, in which pyridine compounds were enriched to the extent of 20.86 %. On this basis, the effects of γ-Al2O3 and HZSM-5 on N-containing compounds (NCCs) in bio-oil were analyzed in detail. The yield of NCCs increased significantly with the addition of HZSM-5. The best parameter combinations were obtained through orthogonal experiments: urea addition of 50 %, HZSM-5 catalyst type, and catalyst doping ratio of 200 %. At this point, the bio-oil yield reached 29.575 wt%. Among them, indole yield reached 41.66 wt% and exhibited high selectivity of 68.92 % in NCCs. The formation mechanism of indoles during microwave-assisted N-rich pyrolysis was further investigated on the basis of experimental studies. In addition, the inhibitory effect of the HZSM-5 catalyst on the formation of pyridine compounds during pyrolysis process and the enhancement mechanism of the formation of indole compounds were deeply investigated. This provided a green pathway for the preparation of indoles by microwave-assisted fast pyrolysis directional catalytic conversion of biomass.

MgO Modified by X2, HX, or Alkyl Halide (X = Cl, Br, or I) Catalytic Systems and Their Activity in Chemoselective Transfer Hydrogenation of Acrolein into Allyl Alcohol.

A new type of catalyst containing magnesium oxide modified with various modifiers ranging from bromine and iodine, to interhalogen compounds, hydrohalogenic acids, and alkyl halides have been prepared using chemical vapor deposition (CVD) and wet impregnation methods. The obtained systems were characterized using a number of methods: determination of the concentration of X- ions, surface area determination, powder X-ray diffraction (PXRD), surface acid-base strength measurements, TPD of probe molecules (acetonitrile, pivalonitrile, triethylamine, and n-butylamine), TPD-MS of reaction products of methyl iodide with MgO, and Fourier transform infrared spectroscopy (FTIR). The catalysts' activity and chemoselectivity during transfer hydrogenation from ethanol to acrolein to allyl alcohol was measured. A significant increase in the activity of modified MgO (up to 80% conversion) in the transfer hydrogenation of acrolein was found, while maintaining high chemoselectivity (>90%) to allyl alcohol. As a general conclusion, it was shown that the modification of MgO results in the suppression of strong basic sites of the oxide, with a simultaneous appearance of Brønsted acidic sites on its surface. Independently, extensive research on the reaction progress of thirty alkyl halides with MgO was also performed in order to determine its ability to neutralize chlorinated wastes.

Degradation of bisphenol A by using perovskite LaCO3 as heterogeneous catalyst for activating peroxymonosulfate

Perovskite has attracted a lot of attention in the area of present-day environmental catalysis because of its cheap cost, excellent stability, great catalytic activity, varied structure, and significant transformation flexibility. In order to remove organic contaminants from wastewater, researchers have been experimenting with combining perovskite catalysts with advanced oxidation processes (AOPs). Herein present study, LaCoO3 was synthesized and calcined at 450, 650, and 850 °C (LC450, LC650, and LC850), and the connections between their surface features and crystalline assembly to catalytic performance were thoroughly explored to activate peroxymonosulfate (PMS) in order to degrade aqueous organic contaminants. Further, the catalysts were characterized by XRD, FTIR, FSEM, and TEM, and their catalytic efficiency was investigated. The Co-O bond length is recommended as a biomarker for PMS activation because it strongly influences the Co2+/Co3+ redox capability, regulating the total PMS activation. LC850/PMS has demonstrated the highest degradation efficiency (79%), with kapp value 0.102 min−1. Further modification of these types of perovskite catalysts might be very feasible and promising to degrading organic pollutants.

Modulating the Electrolyte Microenvironment in Electrical Double Layer for Boosting Electrocatalytic Nitrate Reduction to Ammonia.

Electrochemical nitrate reduction reaction (NO3RR) is a promising approach to achieve remediation of nitrate-polluted wastewater and sustainable production of ammonia. However, it is still restricted by the low activity, selectivity and Faraday efficiency for ammonia synthesis. Herein, we propose an effective strategy to modulate the electrolyte microenvironment in electrical double layer (EDL) by mediating alkali metal cations in the electrolyte to enhance the NO3RR performance. Taking bulk Cu as a model catalyst, the experimental study reveals that the NO3 --to-NH3 performance in different electrolytes follows the trend Li+<Cs+<Na+<K+. Theoretical studies illustrate that the proton transport rate in NO3RR and the activity of the rate-determining step (NO3 - to NO2 -) increase in the order Li+<Cs+<Na+<K+. The cation effects are also general for two typical nanostructured catalysts including copper/cuprous oxide and nickel phosphides, achieving near-100 % Faradaic efficiency and over 99 % conversion of NO3 - to NH3. Furthermore, we demonstrate that NO3 - can be converted to high-purity NH4Cl by copper/cuprous oxide catalyst in K+-containing electrolyte.

Modulating the Electrolyte Microenvironment in Electrical Double Layer for Boosting Electrocatalytic Nitrate Reduction to Ammonia

AbstractElectrochemical nitrate reduction reaction (NO3RR) is a promising approach to achieve remediation of nitrate‐polluted wastewater and sustainable production of ammonia. However, it is still restricted by the low activity, selectivity and Faraday efficiency for ammonia synthesis. Herein, we propose an effective strategy to modulate the electrolyte microenvironment in electrical double layer (EDL) by mediating alkali metal cations in the electrolyte to enhance the NO3RR performance. Taking bulk Cu as a model catalyst, the experimental study reveals that the NO3−‐to‐NH3 performance in different electrolytes follows the trend Li+&lt;Cs+&lt;Na+&lt;K+. Theoretical studies illustrate that the proton transport rate in NO3RR and the activity of the rate‐determining step (NO3− to NO2−) increase in the order Li+&lt;Cs+&lt;Na+&lt;K+. The cation effects are also general for two typical nanostructured catalysts including copper/cuprous oxide and nickel phosphides, achieving near‐100 % Faradaic efficiency and over 99 % conversion of NO3− to NH3. Furthermore, we demonstrate that NO3− can be converted to high‐purity NH4Cl by copper/cuprous oxide catalyst in K+‐containing electrolyte.

MOF-derived In2O3/TiO2 S-scheme heterojunction for efficient photocatalytic degradation of tetracycline

It is challenging to engineer a photocatalyst that can degrade antibiotics efficiently. We have successfully developed a series of photocatalysts by annealing In-MOF (BUT-205) with TiO2, namely (a) In2O3/TiO2-I, (b) In2O3/TiO2-II, and (c) In2O3/TiO2-III. These catalysts, particularly In2O3/TiO2-III, exhibited superior efficiency in degrading tetracycline (TC) under visible light. The enhanced photocatalytic performance of In2O3/TiO2-III can be attributed to the formed S-scheme heterojunction, which promoting the separation of electron-hole pairs. The S-scheme heterojunction was confirmed by XPS, in-situ XPS, UV–vis diffuse reflectance spectroscopy, and Mott-Schottky plot, etc. Compared to pure TiO2 and In2O3, the In2O3/TiO2-III demonstrated an 18-fold and 3-fold higher degradation rate constant (k). Various factors affecting the degradation of TC were investigated, including pollutant concentration, catalyst type, solution pH, catalyst dosage, inorganic anions, inorganic cations, and radical species. Photoluminescence (PL) and transient photocurrent density evaluate the separation rate of electron-hole pairs, and EPR experiments (active species trapping) studies confirmed •O2− and h+ as the primary entities in TC photodegradation by In2O3/TiO2-III. HPLC/MS analysis revealed the photocatalytic degradation pathway. The MOF-derived photocatalysts efficiency in TC photoreduction results from the formed S-scheme heterojunction, making it a promising candidate for environmental remediation.

Bimetal Oxides Anchored on Carbon Nanotubes/Nanosheets as High-Efficiency and Durable Bifunctional Oxygen Catalyst for Advanced Zn-Air Battery: Experiments and DFT Calculations.

To meet increasing requirement for innovative energy storage and conversion technology, it is urgent to prepare effective, affordable, and long-term stable oxygen electrocatalysts to replace precious metal-based counterparts. Herein, a two-step pyrolysis strategy is developed for controlled synthesis of Fe2O3 and Mn3O4 anchored on carbon nanotubes/nanosheets (Fe2O3-Mn3O4-CNTs/NSs). The typical catalyst has a high half-wave potential (E1/2 = 0.87V) for oxygen reduction reaction (ORR), accompanied with a smaller overpotential (η10 = 290mV) for oxygen evolution reaction (OER), showing substantial improvement in the ORR and OER performances. As well, density functional theory calculations are performed to illustrate the catalytic mechanism, where the in situ generated Fe2O3 directly correlates to the reduced energy barrier, rather than Mn3O4. The Fe2O3-Mn3O4-CNTs/NSs-based Zn-air battery exhibits a high-power density (153mW cm-2) and satisfyingly long durability (1650 charge/discharge cycles/550h). This work provides a new reference for preparation of highly reversible oxygen conversion catalysts.

Talc: A natural mineral base catalyst for the one pot synthesis of bis(pyrazolyl)methane derivatives under thermal and solvent-free conditions

In this work, we were decontaminated the ore to extract the talc, directly. Then, we used talc as a heterogeneous basic catalyst for one pot synthesis of bis(pyrazolyl)methane derivatives via the condensation of ethylacetoacetate, hydrazine hydrate and aromatic aldehyde derivatives under thermal and solvent-free conditions. This solid type of catalyst was identified by fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), energy-dispersive X-ray spectroscopy (EDS), EDS mapping and Brunauer–Emmett–Teller (BET) theory. Heterogeneous and solvent-free conditions, catalyst recyclability, high yields of the products and short reaction times are some advantages of this method. The reusability of the catalyst was examined for five times and it was successfully used in each run without any significant decreasing in its activity.

[formula omitted] -catalyzed trans-esterification of brassica carinata seed oil for biodiesel production

Brassica carinata seed is a non-edible oil containing crop grown for oil-based product development like biodiesel synthesis. However, recently technical challenges such as availability of feedstock, type of catalyst, cost, and quality of biodiesel hindered the feasibility and utilization of biodiesel. Thus, this study addressed those problems under the production of fatty acid methyl ester through trans-esterification reaction in the presence of heterogeneous catalyst (CaO), and methanol alcohol from Ethiopian brassica carinata seed oil. The synergetic and antagonistic effects of selected parameters (temperature, methanol to oil molar ratio, and amount of catalyst) on the yield of FAME were analyzed. Box-Behnken response surface methodology statistical analysis was applied to examine the parametric interaction effect, and optimization of reaction conditions. Accordingly, 90 % of fatty acid methyl ester (FAME) yield was achieved at the optimum value of 65 °C temperature, 14.85: 1 methanol to oil molar ratio, and 13.77 % catalyst load. The fuel properties of the resulted biodiesel were determined following standard procedures, and the results were within the standard limits (ASTM D6751). This implies that brassica carinata oil over heterogeneous catalyzed reaction medium under optimum reaction conditions provides higher biodiesel yield.

λ−carrageenan based ammonium-tagged Hoveyda-Grubbs type catalyst: Novel heterogeneous system for olefin metathesis

An ammonium tagged Hoveyda-Grubbs-type catalyst, i.e., FixCat, was non-covalently heterogenized for the first time in a λ−carrageenan xerogel via ion-exchange, which was confirmed by FTIR, SEM-EDS and TGA analyses. The new heterogeneous catalyst, i.e., λ−FixCat, was successfully employed in ring-closing metathesis using representative olefins in several solvents without leaching of the complex. The best catalytic performances were detected in the nonpolar solvents hexane and toluene. The activity of λ−FixCat was shown to be superior in toluene in terms of catalyst reusability, as it was easily separated from the reaction mixture, and it was successfully recycled five times. This study is part of our ongoing efforts to demonstrate the applicability of natural polysaccharides as supports for various catalysts.

Experimental and Quantum Chemical Calculations on the High-Efficiency Transesterification of Dimethyl Carbonate with Alcohol Catalyzed by Calcium Oxide.

Typical catalysts used in dimethyl carbonate (DMC) transesterification encounter challenges in terms of environmental sustainability and economic viability. Calcium oxide (CaO), being an environmentally friendly and cost-effective catalyst, exhibits favorable compatibility with the criteria above. It has been conclusively demonstrated that CaO performs high efficiency as a catalyst for the transesterification between alcohols and DMC. The optimal conditions for the CaO-catalyzed transesterification of DMC and 1-octanol were determined (90 °C, 17 h, and CaO/1-octanol/DMC molar ratio = 0.3:1.0:40.0), under which the conversion of 1-octanol reaches 98.3%, while the yield and selectivity of methyl octyl carbonate are 98.1 and 99.9%, and CaO has been proven to have the efficient ability to be recycled three times. Meanwhile, the CaO-catalyzed reaction mechanism of the transesterification of DMC with alcohol is illustrated in the quantum chemical method based on the M06-2X functional, and the structures of the corresponding transition states are simultaneously derived. The activation energy barrier is proven to be effectively decreased by the catalytic effect of CaO. In addition, the electrostatic potential diagram verifies the proposed reaction sites. This research constructs the theoretical basis for CaO-based DMC chemistry and expands the green catalysts available for the synthesis of dialkyl carbonates.

Ni-Ag Catalysts for Hydrogen Production through Dry Reforming of Methane: Characterization and Performance Evaluation

To investigate the influence of Ag and the loading of Ni species, Ni-Ag type catalysts were synthesized with varying Ni/Ag ratios (1, 1.5 and 2) using the coprecipitation method. The catalysts were extensively characterized using various techniques such as TG-DSC-SM, XRD, ICP, BET, SEM-EDX and TPR and subsequently tested in the CH4/CO2 reaction without any pretreatment. Regardless of the ratio employed, a phase mixture containing NiO and Ag was observed after calcination under air between 600 °C and 1200 °C. SEM analysis confirmed the presence of a close interface between Ag and NiO. The specific surface area was found to be significantly higher for the catalyst with lower Ni content (R = 1). TPR analysis demonstrated that the inclusion of Ag facilitated the reduction of Ni at lower temperatures. XRD analyses of the spent catalyst confirmed catalyst reduction during the reaction. Among the samples, a catalyst with Ni/Ag = 1 exhibited superior catalytic activity without any pretreatment under a reduction atmosphere, in which case the conversions of methane and CO2 at 650 °C amounted to 38 and 45 mol%, respectively, with H2/CO = 0.7 and 71 mol% of H2. The presence of Ag species enhances the stability of the Ni catalyst and improves catalytic performance in the dry reforming of methane.

Synthesis of a water‐soluble high hydroxymethyl content phenolic resin crosslinker and the associated polyacrylamide weak gel property investigation

AbstractAs an in‐depth profile control agent, water‐soluble phenolic resin crosslinking polyacrylamide weak gel has been widely used in the middle and high water cut stage of water flooding reservoir. In this study, the phenolic resin was synthesized by two‐step alkali catalysis. Factors influencing the synthesis of phenolic resin, including the molar ratio of phenol and formaldehyde, catalyst types, reaction time, were investigated with hydroxylmethyl and aldehyde content as the criterion. When the molar ratio of phenolic resin was 1:2 and NaOH was catalyst, at 80°C for 4 h, the phenolic resin had the highest hydroxymethyl content (49.37%) and the lowest free aldehyde content (2.95%). Weak gel was formed by the reaction of LT002‐polyacrylamide with phenolic resin. Taking the gelation time and strength as criteria, the factors influencing the crosslinking property, including hydroxymethyl content, crosslinker addition, and polyacrylamide concentration were investigated respectively. Under optimal formulation, the property investigation shows that the hydroxymethyl group in the phenolic resin can be crosslinked with the amide group in polyacrylamide, the gelation time is long (50–60 h), and the gelation strength is larger than 5 × 104 mPa s, which is conductive to the plugging of deep oil layers. When the permeability was 5061 × 10−3 μm2, the plugging rate was 72.73%.