Modification Of Catalyst Research Articles

Tuning Surface Modification of Potasium Boasted Phosphomolybdic Acid Catalysts for Selective Oxidative Esterification of Benzyl alcohol

Tuning Surface Modification of Potasium Boasted Phosphomolybdic Acid Catalysts for Selective Oxidative Esterification of Benzyl alcohol

Construction of Co9Se8/TiO2 S‐scheme heterojunction photocatalyst for efficient hydrogen production

Construction of S-scheme heterostructure is the focus of catalyst modification in the field of photocatalysis. In this work, the nanosized Co9Se8 and TiO2 particles were fabricated via a simple hydrothermal process. A series of Co9Se8/TiO2 heterojunctions were subsequently constructed through a physical solvent evaporation strategy. The photocatalytic H2 evolution experiment shows that the H2 evolution rate can reach 8282.7 μmol·g−1·h−1 over 15 %-Co9Se8/TiO2 under 300 W Xe lamp irradiation using 20 % triethanolamine (TEOA) as the sacrifice agent, which is 29.9-fold and 95.8-fold higher than that of pristine TiO2 (277.3 μmol·g−1·h−1) and Co9Se8 (86.5 μmol·g−1·h−1), respectively. The enhanced photocatalytic performance is primarily attributed to the improved light absorption ability and the formed S-scheme heterojunctions between TiO2 and Co9Se8, which could efficiently accelerate the separation and migration of photo-induced charges. Furthermore, the powerful electrons and holes are preserved, thereby earned robust redox ability to prompt H2 evolution reaction. This work affords a feasible approach to obtain S-scheme photocatalysts for effectively converting solar energy to H2.

Statistical optimization of ultrasound‐assisted biodiesel production from Moringa oleifera oil – waste cooking oil mixture using modified conch shell catalyst

AbstractBiodiesel is a potential alternative fuel that offers several environmental benefits and can be used in conventional engines. However, high feedstock cost poses a challenge for its commercial viability. This study focuses on producing biodiesel using waste cooking oil (WCO) and Moringa oleifera oil (MOO) as feedstock, with a specific emphasis on the use of modified conch shell as solid catalyst under ultrasonic conditions. Different mixtures of WCO and MOO were evaluated for their suitability in a two‐stage esterification transesterification process, and the acid value of the WCO‐MOO blend was reduced through an ultrasound‐assisted esterification process. Additionally, a calcium oxide‐based catalyst was developed from conch shells (CS) through calcination for 3 h at 900°C and further modified using water and methanol. The characterization studies confirm the successful development and modification of the CS catalyst and also demonstrates excellent catalytic activity. The ultrasound assisted transesterification process parameters were optimized using response surface methodology (RSM) based Box–Behnken design (BBD). By employing a catalyst loading of 5.8 wt%, methanol to esterified oil volumetric ratio of 0.37:1, and an ultrasonication time of 57 min, a maximum predicted methyl ester conversion of 94.7% was achieved. Therefore, this work provides valuable insights into the use of modified conch shell catalyst for biodiesel production from WCO and MOO mixtures thereby contributing to the advancement of cost‐effective and environmentally friendly biodiesel production methods.

Intrinsic kinetics of catalytic hydrogenation of 2-nitro-4-acetylamino anisole to 2-amino-4-acetylamino anisole over Raney nickel catalyst

The catalytic hydrogenation of 2-nitro-4-acetylamino anisole (NMA) is a less-polluting and efficient method to produce 2-amino-4-acetamino anisole (AMA). However, the kinetics of catalytic hydrogenation of NMA to AMA remains obscure. In this work, the kinetic models including power-law model and Langmuir-Hinshelwood-Hougen-Watson (LHHW) model of NMA hydrogenation to AMA catalyzed by Raney nickel catalyst were investigated. All experiments were carried out under the elimination of mass transfer resistance within the temperature range of 70–100 °C and the hydrogen pressure of 0.8–1.5 MPa. The reaction was found to follow 0.52-order kinetics with respect to the NMA concentration and 1.10-order kinetics in terms of hydrogen pressure. Based on the LHHW model, the dual-site dissociation adsorption of hydrogen was analyzed to be the rate determining step. The research of intrinsic kinetics of NMA to AMA provides the guidance for the reactor design and inspires the catalyst modification.

Recent Advances of Triglyceride Catalytic Pyrolysis via Heterogenous Dolomite Catalyst for Upgrading Biofuel Quality: A Review.

This review provides the recent advances in triglyceride catalytic pyrolysis using heterogeneous dolomite catalysts for upgrading biofuel quality. The production of high-quality renewable biofuels through catalytic cracking pyrolysis has gained significant attention due to their high hydrocarbon and volatile matter content. Unlike conventional applications that require high operational costs, long process times, hazardous material pollution, and enormous energy demand, catalytic cracking pyrolysis has overcome these challenges. The use of CaO, MgO, and activated dolomite catalysts has greatly improved the yield and quality of biofuel, reducing the acid value of bio-oil. Modifications of the activated dolomite surface through bifunctional acid-base properties also positively influenced bio-oil production and quality. Dolomite catalysts have been found to be effective in catalyzing the pyrolysis of triglycerides, which are a major component of vegetable oils and animal fats, to produce biofuels. Recent advances in the field include the use of modified dolomite catalysts to improve the activity and selectivity of the catalytic pyrolysis process. Moreover, there is also research enhancement of the synthesis and modification of dolomite catalysts in improving the performance of biofuel yield conversion. Interestingly, this synergy contribution has significantly improved the physicochemical properties of the catalysts such as the structure, surface area, porosity, stability, and bifunctional acid-base properties, which contribute to the catalytic reaction's performance.

Identification of reversible and irreversible deactivation of MDA catalysts: A key to design a viable process

We report a detailed kinetic study of methane dehydroaromatization on three bifunctional Mo/HZSM-5 catalysts (0.9 wt%, 2.7 wt%, and 17.2 wt% Mo). Two main deactivation modes are present: (i) irreversible damage by zeolite amorphization during the isothermal pre-treatment in an inert atmosphere and (ii) reversible deactivation by coke deposition (“soft”, “hard” and carbide species). The former occurs at high Mo loading (>4.0 w%) and provides low activity catalysts. Catalysts with a lower and well-balanced molybdenum loading (<4 w%) suffer mainly from the second deactivation mode. The catalyst decay is modelled by semi-empirical laws including time on stream and coke level. The latter initiates textural and structural catalyst modifications leading to an activity loss. Three deactivation descriptors, 1: coke level on the spent samples, 2: loss of micropore volume, and 3: monoclinic/orthorhombic phase transition of the zeolite are identified. Further characterization indicates that both molybdenum and carbon species are responsible for the catalytic deactivation of well-balanced catalysts. At least 50% of the initially dispersed molybdenum migrates to the external surface of the zeolite to form large clusters of molybdenum carbide. The coke extracted from the zeolite micropores are confirmed to be mainly unsubstituted polyaromatics.

Synthesestrategien für die Funktionalisierung homogener Katalysatoren zur Verbesserung ihrer Abtrennbarkeit

AbstractDas Recycling von homogenen Katalysatoren unter Beibehaltung einphasiger Bedingungen ist eine ständige Herausforderung, der sich viele Reaktionen stellen müssen, wenn sie den Schritt in die industrielle Anwendung schaffen sollen. Zwar gibt es eine Fülle von verschiedenen synthetischen Ansätzen für bessere, wiederverwendbare homogene Katalysatoren, doch der Literatur fehlt bisher ein knapper Überblick über die verschiedenen Katalysatormodifikationen. Dieser Übersichtsbeitrag soll diese Lücke schließen, indem die bestehenden Synthesewege zu polaren, unpolaren, fluorhaltigen und molekulargewichtsvergrößerten Katalysatoren zusammengefasst und die jeweiligen Syntheserouten mit Schwerpunkt auf modularen und Late‐Stage‐Ansätzen untersucht werden. Darüber hinaus zeigen wir das Potenzial für eine allgemein anwendbare Bibliothek auf, die es ermöglicht, Katalysatoren durch einfache Modifikationen auf die jeweils gewünschte Recyclingstrategie abzustimmen.

Synthesis Strategies towards Tagged Homogeneous Catalysts to Improve Their Separation.

The recycling of homogeneous catalysts while keeping them in the homogeneous matrix is an ongoing challenge many reactions face if they are to take the step into industrial application. While a plethora of different synthetic approaches towards better, recyclable homogeneous catalysts exist, the literature shows a gap when one searches for a concise overview of the different catalyst modifications. This review is designed to close that gap by summarising the existing synthesis pathways towards polar, non-polar, fluorous, and molecular-weight-enlarged catalysts and examining their respective synthesis routes with a focus on modular and late-stage approaches. Furthermore, we map out the potential for a generally applicable tag library that allows straightforward catalyst modifications to tune them for each desired recycling strategy.

Enhancing ammonia production rates from electrochemical nitrogen reduction by engineering three-phase boundary with phosphorus-activated Cu catalysts

Electrochemical N2 reduction reaction (eNRR) over Cu-based catalysts suffers from an intrinsically low activity of Cu for activation of stable N2 molecules and the limited supply of N2 to the catalyst due to its low solubility in aqueous electrolytes. Herein, we propose phosphorus-activated Cu electrocatalysts to generate electron-deficient Cu sites on the catalyst surface to promote the adsorption of N2 molecules. The eNRR system is further modified using a gas diffusion electrode (GDE) coated with polytetrafluoroethylene (PTFE) to form an effective three-phase boundary of liquid water - gas N2 - solid catalyst to facilitate easy access of N2 to the catalytic sites. As a result, the new catalyst in the flow-type cell records a Faradaic efficiency of 13.15% and an NH3 production rate of 7.69 μg h−1 cm−2 at −0.2 VRHE, which represent 3.56 and 59.2 times increases from those obtained with a pristine Cu electrode in a typical electrolytic cell. This work represents a successful demonstration of dual modification strategies; catalyst modification and N2 supplying system engineering, and the results would provide a useful platform for further developments of electrocatalysts and reaction systems.

Catalytic Oxidation of Acetone on SmMn2O5: Effect of Acid Etching and Loading Treatment.

The key of catalytic oxidation technology is to develop a stable catalyst with high activity. It is still a serious challenge to achieve high conversion efficiency of acetone with an integral catalyst at low temperature. In this study, the SmMn2O5 catalyst after acid etching was used as the support, and the manganese mullite composite catalyst was prepared by loading Ag and CeO2 nanoparticles on its surface. By means of SEM, TEM, XRD, N2-BET, XPS, EPR, H2-TPR, O2-TPD, NH3-TPD, DRIFT, and other characterization methods, the related factors and mechanism analysis of acetone degradation activity of the composite catalyst were discussed. Among them, the CeO2-SmMn2O5-H catalyst has the best catalytic activity at 123 and 185 °C for T50 and T100, respectively, and shows excellent water and thermal resistance and stability. In essence, the surface and lattice defects of highly exposed Mn sites were formed by acid etching, and the dispersibility of Ag and CeO2 nanoparticles was optimized. Highly dispersed Ag and CeO2 nanoparticles have a highly synergistic effect with the support SmMn2O5, and the reactive oxygen species provided by CeO2 and the electron transfer brought by Ag further promote the decomposition of acetone on the carrier SMO-H. In the field of catalytic degradation of acetone, a new catalyst modification method of high-quality active noble metals and transition metal oxides supported by acid-etched SmMn2O5 has been developed.

The Ru−Ni bimetallic catalyst activated by high-voltage atmospheric cold plasma (HVACP) and application in the isomerization of grape seed oil

Grape seed oil, as a high-linoleic acid type, can be used for the production of conjugated linoleic acid, which cannot be synthesized by the human body, through isomerization under the action of catalysts. Improving the activity of the catalyst is an effective way to obtain conjugated linoleic acid-rich edible oils. In this study, the Ru−Ni bimetallic catalyst was activated by high-voltage atmospheric cold plasma (HVACP) catalyst modification. The results showed that the specific surface area, pore size distribution, and average particle size of the Ru−Ni bimetallic catalyst were enhanced when the treatment condition was 180 s, the power at both ends of the plate was 150 W, and the gas composition was 5% H2/95% He. The catalyst characterization showed that the dispersion of the HVACP-treated Ru−Ni bimetallic catalyst was enhanced, which elevated the catalytic performance of the catalyst. Linoleic acid in grape seed oil was isomerized by the HVACP-treated Ru−Ni bimetallic catalyst, and grape seed oil rich in conjugated linoleic acid was obtained. The conjugated linoleic acid content, trans oleic acid content, peroxide value, and p-anisidine value were 42.52%, 0.63%, 5.01 mmol kg−1, and 12.41, respectively. Quantum chemical analysis further predicted the reaction sites and clarified the rationality of the isomerization reaction. This method provided a scientific basis for producing high-quality functional oils.

Degradation of tetracycline by activated peroxodisulfate using a sulfur-modified iron-based material.

The activation of persulfate by an iron-based catalyst presents a promising approach for the degradation of antibiotics; however, the activation efficiency remains a challenge. Herein, a sulfur-modified iron-based catalyst (S-Fe) by co-precipitation of sodium thiosulfate and ferrous sulfate in a molar ratio of 1:2 was prepared and the efficacy of the S-Fe/PDS system for the removal of tetracycline (TCH) was studied, where a higher removal efficiency was observed compared to the Fe/PDS system. Moreover, the effects of TCH concentration, PDS concentration, initial pH, and catalyst dosage on TCH removal were evaluated, and the highest efficiency was about 92.6% within a 30 min reaction time using a catalyst dosage of 1.0 g/L, a PDS dosage of 2.0 g/L, and a solution pH value of 7. The products and degradation pathways of TCH were analyzed by LC-MS. The free-radical-quenching experiments revealed that both SO4- • and •OH radicals contributed to the degradation of TCH in the S-Fe/PDS system, with the former playing a more significant role. The S-Fe catalyst also showed good stability and reusability for the removal of organic pollutants. Our findings suggest that the modification of an iron-based catalyst offers an effective approach to activate persulfate for removal of tetracycline antibiotics.

Enhanced Electrochemical Nitrate-to-Ammonia Performance of Cobalt Oxide by Protic Ionic Liquid Modification.

Electrochemical conversion of nitrate to ammonia is an appealing way for small-scale and decentralized ammonia synthesis and waste nitrate treatment. Currently, strategies to enhance the reaction performance through elaborate catalyst design have been well developed, but it is still of challenge to realize the promotion of reactivity and selectivity at the same time. Instead, a facile method of catalyst modification with ionic liquid to modulate the electrode surface microenvironment that mimic the role of the natural MoFe protein environment is found effective for the simultaneous improvement of NH3 yield rate and Faradaic efficiency (FE) at a low NaNO3 concentration of 500 ppm. Protic ionic liquid (PIL) N-butylimidazolium bis(trifluoromethylsulfonyl)imide ([Bim]NTf2) modified Co3O4-x is fabricated and affords the NH3 yield rate and FE of 30.23 ± 4.97 mg h-1 mgcat.-1 and 84.74 ± 3.43% at -1.71 and -1.41 V vs. Ag/AgCl, respectively, outperforming the pristine Co3O4-x. Mechanistic and theoretical studies reveal that the PIL modification facilitates the adsorption and activation of NO3- as well as the NO3--to-NH3 conversion and inhibits hydrogen evolution reaction competition via enhancing the Lewis acidity of the Co center, shuttling protons, and constructing a hydrogen bonded and hydrophobic electrode surface microenvironment.

Enhanced Electrochemical Nitrate‐to‐Ammonia Performance of Cobalt Oxide by Protic Ionic Liquid Modification

AbstractElectrochemical conversion of nitrate to ammonia is an appealing way for small‐scale and decentralized ammonia synthesis and waste nitrate treatment. Currently, strategies to enhance the reaction performance through elaborate catalyst design have been well developed, but it is still of challenge to realize the promotion of reactivity and selectivity at the same time. Instead, a facile method of catalyst modification with ionic liquid to modulate the electrode surface microenvironment that mimic the role of the natural MoFe protein environment is found effective for the simultaneous improvement of NH3 yield rate and Faradaic efficiency (FE) at a low NaNO3 concentration of 500 ppm. Protic ionic liquid (PIL) N‐butylimidazolium bis(trifluoromethylsulfonyl)imide ([Bim]NTf2) modified Co3O4−x is fabricated and affords the NH3 yield rate and FE of 30.23±4.97 mg h−1 mgcat.−1 and 84.74±3.43 % at −1.71 and −1.41 V vs. Ag/AgCl, respectively, outperforming the pristine Co3O4−x. Mechanistic and theoretical studies reveal that the PIL modification facilitates the adsorption and activation of NO3− as well as the NO3−‐to‐NH3 conversion and inhibits hydrogen evolution reaction competition via enhancing the Lewis acidity of the Co center, shuttling protons, and constructing a hydrogen bonded and hydrophobic electrode surface microenvironment.

Modification of Copper-Ceria Catalyst via Reverse Microemulsion Method and Study of the Effects of Surfactant on WGS Catalyst Activity

Some major drawbacks encountered in the synthesis of copper-ceria (Cu-CeO2)-based Water Gas Shift (WGS) catalyst via the conventional Impregnation (IMP) method are aggregate formation and nanoparticles’ instability. These lead to the poor interaction between Copper and Ceria, thereby impeding the catalytic activity with the inefficient utilization of active sites. To overcome these drawbacks, in this study, we described the synthesis of the Cu-CeO2 catalyst via the Reverse Microemulsion (RME) method with the help of the organic surfactant. This development of insights and strategies resulted in the preparation of porous particles with uniform size distribution and improved interaction within the composites, which were evident through XRD, XPS, BET Surface area, TPR, TEM and SEM analysis results. Remarkably, the optimum 20% Cu-CeO2 catalyst prepared by RME method was found to have superior Water Gas Shift (WGS) catalytic activity than the conventionally Impregnated catalyst when their CO conversion efficiencies were tested in WGS reaction at different feed gas compositions with and without CO2. Moreover, the 20% Cu-CeO2 sample prepared by RME method exhibited sustained catalytic activity throughout the entire 48 h period without any signs of deactivation. This observation highlights RME method as the potential pathway for developing more effective nanoparticle catalysts for hydrogen production, contributing to the growing demand for clean and sustainable energy sources.

Boosting Hydrogen Peroxide Electrosynthesis via Modulating the Interfacial Hydrogen-Bond Environment.

Designing highly efficient and stable electrode-electrolyte interface for hydrogen peroxide (H2O2) electrosynthesis remains highly challenging. Inhibition of the side reaction of competitive 4e- oxygen reduction to H2O is essential to obtain highly selective H2O2 electrosynthesis. Instead of catalyst modification to hinder excessive hydrogenation of H2O2, we propose that the addition of a hydrogen-bond acceptor, dimethyl sulfoxide (DMSO) to the KOH electrolyte enables the improvement of the selectivity and activity of H2O2 electrosynthesis simultaneously. Spectral characterization and molecular simulation confirm that the formation of hydrogen bonds between DMSO and water molecules at the electrode-electrolyte interface can reduce the activity of water dissociation into active H* species. The suitable H* supply environment hinders excessive hydrogenation for the oxygen reduction reaction (ORR), thus improving the selectivity of 2e- ORR and achieving over 90% selectivity of H2O2. This work highlights the importance of regulating the interfacial hydrogen-bond environment by organic molecules as a means of boosting electrochemical performance in aqueous electrosynthesis and beyond.

Boosting Hydrogen Peroxide Electrosynthesis via Modulating the Interfacial Hydrogen‐Bond Environment

AbstractDesigning highly efficient and stable electrode‐electrolyte interface for hydrogen peroxide (H2O2) electrosynthesis remains challenging. Inhibiting the competitive side reaction, 4 e− oxygen reduction to H2O, is essential for highly selective H2O2 electrosynthesis. Instead of hindering excessive hydrogenation of H2O2 via catalyst modification, we discover that adding a hydrogen‐bond acceptor, dimethyl sulfoxide (DMSO), to the KOH electrolyte enables simultaneous improvement of the selectivity and activity of H2O2 electrosynthesis. Spectral characterization and molecular simulation confirm that the formation of hydrogen bonds between DMSO and water molecules at the electrode‐electrolyte interface can reduce the activity of water dissociation into active H* species. The suitable H* supply environment hinders excessive hydrogenation of the oxygen reduction reaction (ORR), thus improving the selectivity of 2 e− ORR and achieving over 90 % selectivity of H2O2. This work highlights the importance of regulating the interfacial hydrogen‐bond environment by organic molecules as a means of boosting electrochemical performance in aqueous electrosynthesis and beyond.

Waste-derived chars as methanation catalyst support: Role of inorganics in the char and its guide to catalyst design

The municipal solid waste-derived biochar (MSWC) can be applied as a catalyst support for low-cost syngas methanation. However, the mechanism of the char support as a catalyst in methanation process remains unclear. Based on the similarity between the intrinsic inorganics present in the chars and the promoters used for methanation catalyst modification, the impacts of the inorganics in different waste-derived chars on the methanation reaction were investigated. The results showed that the acid-soluble inorganics in the MSWC significantly improved the methanation activity of the MSWC-supported Ni catalysts. The acid-soluble inorganics were proved to have the role of promoting the formation of suitable Ni/support interactions, improving the dispersion of the Ni species, and increasing the concentration of the basic sites on the catalyst’s surface. Compared with the MSWC, the biochar contained much more water-soluble alkali metal salts (up to 15–57% of ash), which may be detrimental to the methanation activity of the biochar-supported Ni catalysts by leading to increases in Ni particle size and the concentration of the strong basic sites on the catalyst’s surface, especially when existing alone. A new alkali–carbon index was created to evaluate the effect of the inorganics in the waste-derived char on the methanation activity of the char-supported catalyst. A higher alkali–carbon index reflects improved methanation activity. Thus, the findings of this study can provide quantitative guidance for designing suitable waste-derived char as methanation catalyst supports.

Design and modification of metal sulfide-based catalysts for lithium-sulfur batteries

Metal sulfide (MS) have good conductivity, strong adsorption ability, and excellent catalytic activity for the conversion of sulfur species, and thus, show great promise as the catalysts in Li–S batteries. However, the relationship between their properties and electrochemical performance is still unclear. Thus, further in-depth discussions are required to improve their design in Li–S batteries. This review systematically summarizes the basic structural and electrochemical properties of MSs and highlights the advantages that guarantee them as high-performance catalysts in Li–S batteries. Then, various modification strategies for MSs to enhance the catalytic activity, efficiency, and stability are also reviewed. At last, future opportunities for MS catalysts in Li–S batteries are proposed.

Plasma-modified Ni foam-supported CuCo2S4 nanowires as bifunctional electrocatalysts for high-performance overall water splitting

To solve the current energy and environmental dilemma, hydrogen energy is considered to be the best clean energy source to replace traditional fossil fuels. Water electrolysis as the main technology for hydrogen production has been affected by two half-reactions, making it difficult to improve the yield. To solve this problem, the development of inexpensive and efficient bifunctional electrocatalysts is the focus of current research. CuCo2S4/NF(Ni foam) nanowires are synthesized using a mild hydrothermal process and were later placed in a plasma reactor. Application of the voltage triggers a chemical reaction between the microdischarge wires and the sample. This leads to a change in the physical morphology of the catalyst and an improvement in its catalytic performance. The morphological characterization results show that the catalyst modification generates a distinct flower-like nanowire structure, which helps in the solid attachment of the catalyst to the nickel foam surface. The plasma-modified CuCo2S4/Ni foam (PA@CuCo2S4/NF) exhibits low overpotentials of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline solutions. Additionally, the Tafel slopes of the HER and OER are 85.9 mVdec−1 and 142.7 mVdec−1, respectively, indicating optimal reaction kinetics. A cell voltage of only 1.55 V is required to provide a 10 mA cm−2 current during water splitting. This study validates the feasibility of using plasma technology to create high-performance electrocatalysts.