Types Of Catalysts Research Articles

Identifying N Coordination Types of Single-Atom Catalysts by Spin-Modulated Luminol Cathodic Electrochemiluminescence.

The type of coordinated N atoms in the metal-N coordination structure is of paramount importance to the catalytic property of carbon-based metal single-atom catalysts (SACs). Extended X-ray absorption fine structure (EXAFS) spectroscopy is a powerful tool for analyzing the coordination environments of SACs. Despite its efficacy, the limited availability of synchrotron light sources and the complexity of data analysis have constrained its broader application in identifying metal-N coordination types within SACs. In this work, two kind of CoN4 SACs were prepared by varying the N source. Then their electrochemiluminescence (ECL) behavior in the luminol/dissolved oxygen system during cathodic scanning were investigated. In comparison to CoN4(pyridinic N), for which the spin density displays dz2 orbital characteristics, CoN4(pyrrolic N) exhibits dxz orbital features, which was more conducive to the subsequent cleavage of the O-O bond in O2•- to •OH, resulting in the generation of more active intermediates *OH and the promotion of cathodic ECL emission. This work demonstrates that the ECL technique provides a novel method for the rapid identification of Co-N coordination types and the spin nature of the metal center in CoN4 SACs.

Tackling the Activity Trend of Metal-Loaded Metal Nitride Catalysts for NH3 Synthesis by a First-Principles Microkinetic Study.

Ammonia (NH3) is one of the most widely produced chemicals globally, primarily synthesized through the Haber-Bosch process, which requires high temperatures and pressures. Dual-site catalysts can activate N2 and H2 at spatially separated sites, enabling efficient NH3 synthesis under milder conditions. Despite the rapid experimental progress of the dual-site catalysts (e.g., Ni-LaN), the feasibility and design of dual-site catalysts are challenged recently. Herein, the different metal-loaded metal nitride catalyst models are employed, and their activity map for NH3 synthesis is explored by the first-principles microkinetic simulation. The optimum active region of this type of dual-site catalyst is identified in terms of the formation energy (Ev) of nitrogen vacancy (Nvac) on metal nitride and the adsorption energy (EH) of hydrogen atom on metal cluster, with Ev and EH ideally located around ≈1.50 and ≈-0.30eV, respectively. This offers a framework for designing effective metal-loaded metal nitride catalysts for NH3 synthesis. Importantly, this trend aligns with and rationalizes the current experimental observations of metal-loaded metal nitride reported for NH3 synthesis. This theoretical work provides significant insights into NH3 synthesis on dual-site mechanism, and provides a rational direction for designing metal-loaded metal nitride catalysts.

Enhanced Saccharification Efficiency of Corn Straw by Laccase‐Cu2O Under Light/Dark Cycles

To strengthen the clean utilization of biomass waste, laccase modified cuprous oxide (Cu2O) composite catalyst is synthesized. The effects of catalyst type, catalyst concentration, pH, sunlight exposure time, and lighting method on the reducing sugar yield are investigated. The composite catalyst in combination with sunlight irradiation can effectively enhance the reducing sugar yield of corn straw. The optimum conditions were pretreatment time of 55 min, catalyst concentration of 58 mg L−1, pH of 5.5, enzyme hydrolysis process using a 30 DL (namely 20 min of dark/20 min of light alternating cycle for 30 h) scheme, and enzyme loading of 25 FPU g−1. Validation experiments show that the lignin removal percentage can reach 95.63%, and the reducing sugar yield can reach 124.79 mg g−1 under the optimum condition. The pretreatment and saccharification of straw executed twice are most advantageous for sugar production. Laccase‐Cu2O can be reused three times.

Recent Advances in the Hydroxylation of Boronic Acids

Hydroxylated compounds represent a significant and diverse class of substances in the field of chemistry. These compounds play critical roles in various chemical reactions and are essential components in numerous industrial applications. Recent years have witnessed remarkable advancements in the synthesis of hydroxylated compounds, especially those derived from boronic acids. The synthesis of hydroxylated compounds from boronic acids typically involves the utilization of various types of catalysts, which are essential for enhancing reaction rates and selectivity, including metal catalysts such as CuFe₂O₄, Cu@C₃N₄, AgNPs, and Ti0.97Ni0.3O1.97, as well as non‐metal catalysts like polycaprolactone (PCL), TFB‐BMTH COF materials, C70, and graphene oxide (GO). These catalytic reactions often require the addition of oxidants such as hydrogen peroxide (H₂O₂) or molecular oxygen, which serve as critical reagents in the hydroxylation process. In certain cases, organic bases act as electron donors to propel the reaction. Furthermore, some studies have reported oxidative hydroxylation reactions that are catalyst‐free.This review aims to summarize the recent advancements and breakthroughs in the synthesis of hydroxylated compounds from boronic acids, with a particular focus on research conducted from 2014 to 2024.

Facilitating the electrooxidation of 5-hydroxymethylfurfural on nickel hydroxide through deintercalation

The electrocatalytic of 5-hydroxymethylfurfural oxidation reaction (HMFOR) is an alternative route for the green production of valuable oxygenated chemicals. Nickel hydroxides, which consist of hydroxide layers and interlayer charge-balancing anions, are a type of promising catalysts for HMFOR. Progresses have been made on elucidating the correlation between the hydroxide layer and HMFOR performance, while the effect of intercalated anions on the activity remains unclear. Herein, two self-supported nickel hydroxide catalysts (i.e., pristine Ni(OH)2/CP-F and deintercalated Ni(OH)2/CP-A) are employed for revealing the relationship between anion-deintercalation and HMFOR activity. Physical characterizations demonstrate that the deintercalation phenomenon can alter the d-band center and increase the electron density of the Ni site. This endows the deintercalated Ni(OH)2/CP-A with improved electrochemical properties (conversion = 99.99 %; FDCA yield > 99 %; FE > 99 %), enhanced adsorption strength for HMF, and increased intrinsic activity, compared to the pristine Ni(OH)2/CP-F. This work not only reports an excellent HMFOR electrocatalyst, but also manifests the crucial effect of deintercalation on the electrochemical oxidation performance of Ni(OH)2.

Synergistically piezocatalytic and Fenton-like activation of H2O2 by a ferroelectric Bi12(Bi0.5Fe0.5)O19.5 catalyst to boost degradation of polyethylene terephthalate microplastic (PET-MPs)

Pollution of microplastics (MPs) has been drastically threating human health, however, whose elimination from the environment by current approaches is inefficient due to their high molecular weight, stronghydrophobicity and stable covalent bonds. Herein, we report a novel and highly-efficient route to degrade MPs contaminants through synergistically piezocatalytic and Fenton-like activation of H2O2 by a ferroelectric Bi12(Bi0.5Fe0.5)O19.5 catalyst under ultrasound treatment. For 10 g/L polyethylene terephthalate microplastics (PET-MPs), the synergistic strategy reached a 28.9 % removal rate in 72 h, which is greatly enhanced in comparison to the individual piezocatalysis and Fenton (Fenton-like) activation. By optimizing the types of oxidants (H2O2, peroxymonosulfate and peroxydisulfate) and bismuth ferrite catalysts (non-piezoelectric Bi2Fe4O9 and piezoelectric BiFeO3/Bi12(Bi0.5Fe0.5)O19.5), it was revealed that H2O2 is the best oxidant, and the piezoelectric Bi12(Bi0.5Fe0.5)O19.5 with a high aspect-ratio morphology showed higher activity than the Bi2Fe4O9 and BiFeO3. The catalyst dosage and H2O2 concentration were further optimized, and the good durability of the catalyst was also demonstrated through multiple uses. Different characterization technologies demonstrated the occurrence of PET-MPs oxidation and fragmentation during the treatment process. The plausible mechanism of synergistically piezocatalytic and Fenton-like H2O2 activation was proposed based on measurements of band structure, piezoelectric property and reactive oxygen species generation. Finally, we detected the intermediates and determined a possible degradation route of PET-MPs. The toxicity assessment indicated that the produced intermediates have low toxicity and potential risks to the environment.

Role of Nano Catalysts In Green Chemistry

Abstract This study explores the role of nano catalysts in enhancing catalytic performance through their unique properties and applications in sustainable chemistry. Nano catalysts, defined as materials operating at the nanometer scale, typically between 1 and 100 nanometers, exhibit significantly increased surface area and altered electronic properties, leading to improved reaction rates and efficiencies. The investigation highlights the critical properties of nano catalysts, such as their high surface area-to-volume ratio, controlled shapes, and tunable surface functionalities, which contribute to their effectiveness in various catalytic processes. Different types of nano catalysts, including metal nanoparticles, metal oxides, and carbon-based nano materials, are examined for their distinct advantages and applications. Metal nanoparticles, like gold and platinum, offer enhanced catalytic activity due to their unique electronic behaviors, while metal oxides, such as titanium dioxide, provide stability in photocatalytic applications. Additionally, carbon-based nano materials, including carbon nanotubes and graphene, are recognized for their exceptional electrical conductivity and surface area, making them suitable for energy conversion and environmental remediation.

Production of phenol-rich bio-oil from Arundo donax via catalytic pyrolysis over SAPO-31

Herein, the SAPO-31 produced phenol-rich bio-oil from Arundo donax (AD) via catalytic fast pyrolysis (CFP) in a fixed bed. Effective variables including type of catalyst, temperature, weight hourly space velocity (WHSV) and N2 flow rate (Nfr) were evaluated to enhance the CFP. The results showed that SAPO-31 demonstrated selectivity of 80.28 % towards naphtha-range compounds and 33.57 % towards phenolic compounds (PCs) within the naphtha range at 500 °C, Nfr of 300 mL min−1 and WHSV of 1 h−1, contrasting sharply with those of control groups (50.82 % and 14.40 %, respectively), HZSM-5 (67.66 % and 5.51 %, respectively) and Hβ (61.10 % and 25.50 %, respectively). Moreover, SAPO-31 gave the highest bio-oil yielded (26.97 wt%) compared to that of the control group (22.45 wt%), Hβ (22.21 wt%) and HZSM-5 (21.42 wt%). These results indicate that the SAPO-31 self-synthesized exhibits promising capabilities in producing phenol-rich naphtha-range compounds via the CFP of AD.

Hydrogen-rich gas generation from enhanced catalytic cracking of biomass tar and related model compounds on Ni-Fe/ASA@HZSM-5 catalyst: Pathways and mechanisms

This study focused on the design of complex tar model compounds (CTMC) and synthesized a highly efficient aluminum dross (ASA) combined with HZSM-5 molecular sieve co-loaded bimetallic Ni-Fe catalyst (Ni-Fe/ASA@HZSM-5), comprehensively evaluated the catalytic cracking of real tar and its model compound by adjusting the injection amount and injection state of tar, and catalyst types to obtain hydrogen-rich gas with high H2 and low CO2 content. The results showed under the conditions of the injection amount of 0.6 mL/min, pyrolysis temperature of 600 °C, reforming temperature of 800 °C in the liquid phase, Ni-Fe/ASA@HZSM-5 displays excellent catalytic cracking performance with CTMC conversion efficiency of 87.80 % (79.46 % of gas yield and 34.20 vol% of H2 yield). The possible cracking paths between different components of CTMC in the Ni-Fe catalytic system were summarized by the experimental data and product distribution, the catalytic mechanism of Ni–Fe based catalysts can be attributed to the formation of a Ni-Fe alloy and the synergistic effect of ASA and HZSM-5 co-carrier. Further, the catalytic cracking pathway of CTMC was enhanced in the gas phase, the higher CTMC conversion efficiency of 93.68 %, gas yield (a mass fraction of 82.51 %) and H2 (a volume fraction of 33.59 %) were obtained from catalytic cracking of CTMC, the liquid yield decreased by 12.39 %, significantly improved the cracking degree and gas production capacity of CTMC. The real tar showed the same catalytic pyrolysis path and product distribution. Under the same cracking conditions, the yields of gas, liquid and char were 84.85 %, 12.00 % and 3.15 % respectively, and obtained the hydrogen yield of 55.29 mL/g. The CTMC simplifies the cracking process and reduces polymerization, provides insights into the cracking mechanisms of heavy components in biomass tar. Furthermore, the synergy of Ni and Fe contributed to greater activity for CTMC and real tar cracking, ASA combined with HZSM-5 molecular sieve co-loaded bimetallic Ni-Fe catalysts have a promising application potential as highly efficient catalysts for tar removal and reutilization.

Influence of alumina on the performance of Ag/ZnO based catalysts for carbon dioxide hydrogenation

We study silver-zinc oxide type catalysts with and without the addition of alumina and perform structural analysis and activity tests for the hydrogenation of carbon dioxide. Adding alumina has a dispersing effect on the zinc oxide without structurally altering the silver phase. An alumina-surface enriched ZnO/Al2O3 phase is observed with an increased surface reducibility. Ag/ZnO has a high selectivity towards carbon monoxide (63 ± 12 %) and methane (24 ± 3 %) and low selectivity towards methanol (13 ± 0.5 %). Operando infrared (SSITKA-FTIR) and mass spectrometric product detection indicate methane formation via an adsorbed carbon monoxide (COads) intermediate. The selectivity changes gradually with increasing alumina content, up to 80 ± 3 % toward methanol, and 20 ± 4 % carbon monoxide without methane detection, combined with a tripling of the space time yield to 0.65 ± 0.02mmolMeOH*gcat-1*h−1 at 250 °C and 30 bar. Kinetic analysis suggests that the selectivity change originates from hindering the CO-pathway, while the formate pathway leading to methanol remains active.

Visible-Light-Driven (NSNO)Nickel complex catalyzed (Z)-Selective semi-hydrogenation of alkynes

We reported that a new type of nickel catalysts, in combination with use of as a 2,4,5,6-tetra(9H-carbazol-9-yl)isophthalonitrile (4CzIPN) as a photoinitiator, are capable of affecting (Z)-selective semi-hydrogenation of alkynes utilizing carbonic acid, in-situ generation by the reaction of carbon dioxide and water, and Et3N as a hydrogen source under mild photochemical conditions. This catalytic system allows wide scopes of alkynes, including aryl internal alkynes, mono-alkylacetylene, and aryl terminal alkynes, affording (Z)-alkenes as major product in good to excellent yields. It is noteworthy that N-heteroaromatic internal alkynes, such as 2-pyridyl arylenyne, yield (E)-alkenes. The cooperative catalysis between nickel complexes and 4CzIPN was revealed by in situ infrared spectroscopy, high-resolution mass spectrometry (HRMS), and control experiments.

FeCo Alloy-Decorated Proton-Conducting Perovskite Oxide as an Efficient and Low-Cost Ammonia Decomposition Catalyst

Ammonia is known as an alternative hydrogen supplier because of its high hydrogen content and convenient storage and transport. Hydrogen production from ammonia decomposition also provides a source of hydrogen for fuel cells. While catalysts composed of ruthenium metal atop various support materials have proven to be effective for ammonia decomposition, non-precious-metal-based catalysts are attracting more attention due to desires to reduce costs. We prepared a series of Fe, Co, Ni, Mn, and Cu monometallic catalysts and their alloys as catalysts over proton-conducting ceramics via the impregnation method as precious-metal-free ammonia decomposition catalysts. While Co and Ni showed superior performance compared to Fe, Mn, and Cu on a BaZr0.1Ce0.7Y0.1Yb0.1O3−б (BZCYYb) support as an ammonia decomposition catalyst, the cost of Fe is much lower than that of other metals. Alloying Fe with Co can significantly increase the conversion and stability and lower the overall cost of materials. The measured ammonia decomposition rate of FeCo/BZCYYb reached 100% at 600 °C, and the ammonia decomposition rate was almost unchanged during the long-term test of 200 h, which reveals its good catalytic activity for ammonia decomposition and thermal stability. When the metallic catalyst remained unchanged, BZCYYb also exhibited better performance compared to other commonly used oxide supports. Finally, when ammonia cracked using our alloy catalyst was fed to solid oxide fuel cells (SOFCs), the peak power densities were very close to that achieved with a simulated fully cracked gas stream, i.e., 75% H2 + 25% N2, thus proving the effectiveness of this new type of ammonia decomposition catalyst.

Generative Pretrained Transformer for Heterogeneous Catalysts.

Discovery of novel and promising materials is a critical challenge in the field of chemistry and material science, traditionally approached through methodologies ranging from trial-and-error to machine-learning-driven inverse design. Recent studies suggest that transformer-based language models can be utilized as material generative models to expand the chemical space and explore materials with desired properties. In this work, we introduce the catalyst generative pretrained transformer (CatGPT), trained to generate string representations of inorganic catalyst structures from a vast chemical space. CatGPT not only demonstrates high performance in generating valid and accurate catalyst structures but also serves as a foundation model for generating the desired types of catalysts by text-conditioning and fine-tuning. As an example, we fine-tuned the pretrained CatGPT using a binary alloy catalyst data set designed for screening two-electron oxygen reduction reaction (2e-ORR) catalyst and generated catalyst structures specialized for 2e-ORR. Our work demonstrates the potential of generative language models as generative tools for catalyst discovery.

A Green Chemistry Approach to Catalytic Synthesis of Ethyl Levulinate

Esterification of levulinic acid with ethanol was investigated using deep eutectic systems based on choline chloride and oxalic or p-toluenesulfonic acid as catalysts under conventional heating and alternative energy inputs, namely microwave, ultrasound, and mechanochemical treatment. The experiments were performed under varying operating conditions such as catalyst type and loading, alcohol to carboxylic acid molar ratio, temperature, or time. The obtained results demonstrate the overall better catalytic performance of the p-toluenesulfonic acid-based deep eutectic mixture in comparison with the oxalic acid-based analogue. The best results: levulinic acid conversion of 76% and 58%, for p-toluenesulfonic and oxalic acid containing deep eutectic systems, respectively, with 100% selectivity for both cases, were achieved for microwave-assisted synthesis with 5 wt.% of catalyst and excess alcohol to acid (molar ratio 5), at 413.15 K and for 10 min. The main advantage of all of the alternative activation methods studied (microwaves, ultrasounds, and ball mill processing) was the significant reduction in the reaction time.

Effects of base catalyst on the physicochemical properties and surface reactivity of silica nanoparticles

The surface reactivity of silica particles is a key property that enhances their versatility in various industries. Therefore, it is imperative to investigate the effects of different base catalysts on the surface reactivity of silica nanoparticles. Silica nanoparticles were synthesised using potassium hydroxide (KOH) and sodium hydroxide (NaOH) as strong base catalysts, as well as ammonia (NH3) and lysine amino acid as weak base catalysts. The particle size was observed to increase with the pH of the reaction mixture. Additionally, X-ray photoelectron spectroscopy (XPS) revealed that the catalyst molecules adsorb onto the particle surface, thereby enhancing their surface reactivity. Sodium and potassium ions were found to significantly improve surface reactivity during silanisation, with KOH- and NaOH-sil-C8 samples exhibiting high silane grafting density (> 2.58 alkyl chains/nm2). These findings indicate that the type of base catalyst plays a crucial role in tailoring the properties and surface reactivity of silica nanoparticles.

Optimization of microwave-assisted biodiesel production using response surface methodology

Energy stands as the fuel of the human activities, and with finite fossil fuels, biodiesel has become a promising, eco-friendly alternative. Microwave technology is emerging as one of the most efficient biodiesel production methods. The primary goal of this work is to optimize the microwave-assisted production of biodiesel and improve its productivity using response surface methodology. A modified microwave oven with built-in stirring system and temperature measurement significantly reduces the reaction time compared to traditional thermoelectric heating. Numerous factors impact microwave-assisted biodiesel production, encompassing catalyst type and concentration, microwave power, reaction temperature, alcohol type, alcohol-to-oil molar ratio, water content, and stirring rate. Hence, acquiring a comprehensive understanding of how these variables affect the biodiesel production becomes imperative. Response surface methodology was utilized to improve the biodiesel microwave-assisted production yield of sunflower oil involving ethanol as alcohol and NaOH as catalyst. The impact of the ethanol-to-oil ratio, the catalyst amount and the reaction temperature on biodiesel production yield was investigated. Results demonstrated that the temperature had the most significant impact on biodiesel production, with an optimal temperature of 70 °C. The highest biodiesel yield, of 98.4%, was obtained at an alcohol-to-oil ratio of 6:1 and 2% by mass of sodium hydroxide.

The perplexing pH and concentration-dependent hydrogen production from formic acid catalyzed by iridium complexes in aqueous solutions

Iridium based catalysts exhibit promising potential for large-scaled hydrogen production from formic acid due to their high activity and stability in base-free aqueous solutions. However, the performance of many of them is highly pH and catalyst concentration dependent, diminishing substantially at high catalyst concentrations, imposing grand challenges for fundamental understanding and scaling up and practical applications at large volume densities. In this work, we conduct a kinetic analysis to quantitatively examine the correlations between the turnover frequency (TOF) of a typical Iridium-based catalyst and its pH and concentration. The study reveals the intrinsic mechanism for the long-standing perplexing pH and concentration dependences of hydrogen production rates. Inspired by the mechanism, a new catalyst is developed. The hydrogen production rate of this catalyst increases linearly with concentration, thereby facilitating successful scale-up of formic acid dehydrogenation. These results not only address difficulties in practical applications but also offer valuable insights for future catalyst design.

Optimization of process parameters of catalytic pyrolysis using natural zeolite and synthetic zeolites on yield of plastic oil through response surface methodology

This study aims to reach a sustainable solution for waste management of medical plastics through value-added product extraction. It uses the DOE technique to examine the effect of natural zeolite and synthetic Al2O3 and SiO2 as catalysts. A small lab-scale pyrolysis setup was used for medical plastic waste management treatment. Pyrolysis of medical plastics with temperature range (350–450 °C), three catalysts, and wt.% are examined. This process is designed for 3 factors and 3 levels, such as type of catalyst, catalyst wt.%, and temperature, to create an L9 orthogonal array. At the same time, the heating rate and residence time are maintained constant at 5 °C/min and 75 minutes, respectively. Furthermore, this study analyzed the input variables in catalytic pyrolysis using response surface methodology. As a result of the study, generating the regression equation for oil yield, F and P values assure the model is significant. Optimization result shows the type of catalyst, temperature, and catalyst concentration values are found as aluminum oxide, 376 °C, and 6.6 wt.%, respectively. HDPE and LDPE oil yield a value of 58.3648 and 61.2051 wt%, respectively, under the optimum variables condition. For oil yield prediction, HDPE and LDPE’s correlation coefficient (R2) were 0.9949 and 0.9943, respectively. Authentication of the model response using a regression equation validated with the experimental result shows good agreement. The produced medical plastic oil has a density, viscosity, flash & fire point, carbon residue, and cetane number 904 kg/m3, 2.3 cSt, 42 & 45 °C, 7.1 wt.% and 51 respectively. Finally, this study concludes that plastic oil extraction from medical waste through catalytic pyrolysis can be a potential source of alternative fuels in IC engines. Priority to optimization and low-cost catalysts highlights medical plastics waste management under the socio-economic model.

SILP Type Catalyst Based on H3PMo12O40: Composition of Heteropolyanions According to Mass Spectrometry Data and Activity in Oxidation of Sulfur-Containing Substrates

SILP Type Catalyst Based on H3PMo12O40: Composition of Heteropolyanions According to Mass Spectrometry Data and Activity in Oxidation of Sulfur-Containing Substrates

Guidance for targeted degradation analysis of OER kinetics of low-loading iridium-based catalysts in PEM water electrolysis cells

This paper critically evaluates three methods for determining metrics of the oxygen evolution reaction (OER) describing the performance and stability of low-loading iridium-based anode catalyst layers (CLs) in proton exchange membrane water electrolysis (PEMWE) cells. The methods applied are OER mass activity, voltage breakdown analysis (VBA), and constant Tafel slope VBA (CT-VBA). They are used to assess the OER metrics as a function of anode CL configurations, potential cycling, and level of degradation. Therefore, various accelerated stress tests (ASTs) are carried out for a targeted degradation of different anode CLs based on Ir black or Ir oxide. It turns out that the OER mass activity method is robust, straightforward and an ideal method for e.g., in-house screening tasks. On the other hand, the VBA method is suitable for comparative analysis across laboratories by distinguishing between the three main overpotentials. The CT-VBA method, however, offers improved accuracy, as it accounts for mass transport overpotential at low current density, and is particularly suitable for determining apparent exchange current density values further used in modelling approaches. This benefit comes with a drawback, as commonly accepted reference Tafel slopes for respective catalyst type and PTL configurations would be required within the PEMWE community. This guidance therefore helps to choose the right method for determining OER metrics depending on the research question.