Fresh Catalyst Research Articles

Vapor-phase ethanol carbonylation over Ni supported on activated carbon: Influence of the textural properties and oxygen-containing groups

The performance of ethanol carbonylation for Ni supported on different activated carbons varies considerably. The physicochemical properties of Ni catalysts supported on different activated carbons have been investigated in detail by a series of characterization studies. Catalysts with less oxygen-containing groups and smaller pore size are demonstrated to be more effective for vapor-phase ethanol carbonylation, with higher ethanol conversion and selectivity of propionate and ethyl propionate. However, there is no clear correlation between the carbonylation activity and the initial Ni nanoparticles size of the fresh catalysts due to the re-dispersion of the Ni nanoparticles by the ethane iodide interaction during the reaction. It is also proved that the deactivation of the catalyst may be caused by the loss of the active component Ni and the deposition of oxygen-containing carbon species. ​In situ diffuse reflectance infrared Fourier transform spectroscopy (in-situ DRIFTS) showed that ethane iodide is essential for the ethanol carbonylation reaction and that carbonylation intermediates (C2H5CO-Ni-I) are formed only in the presence of ethane iodide. The mechanism of the ethanol carbonylation reaction was proposed, showing that the carbonylation of CO insertion and the elimination of ethylene production in the intermediate are competing reactions. This work has implications for the design of highly efficient alcohol carbonylation catalysts.

Used Ni/KIT-6 as a sacrificial catalyst for mitigating coking in lower-layer catalyst in steam reforming of acetic acid

Deactivated or coked catalyst from steam reforming may not always be treated as a solid waste, which might be potentially used as a sacrificial or protective layer of catalyst for reducing coke formation of catalyst in the lower bed in the same steam reforming process. In this study, steam reforming of acetic acid over Ni/KIT-6 at 600 °C was conducted with used Ni/KIT-6 in upper layer and freshly reduced Ni/KIT-6 in lower layer (dual-bed system). The results suggested that significantly more coke (3 to 4 times) formed on upper-layer catalyst (used or fresh catalyst) than on lower-layer fresh catalyst. The upper-layer used catalyst was more effectively than counterpart of fresh catalyst for mitigating coking in lower-layer catalysts. The in-situ IR technique suggested that carbonaceous species on the used catalyst impacted or reacted with the intermediates newly formed, generating more oxygen-containing species with functionalities like COC and CO of anhydride or ketones/aldehyde form. These oxygen-containing species could polymerize/condense and pass down to the lower bed, forming more polymeric coke of lower thermal stability. Differently, more unsaturated hydrocarbon species formed on the upper-layer fresh catalyst, making the coke of highly aromatic nature with a higher thermal stability and crystallinity. Additionally, modification of reaction intermediates with the used catalyst in upper layer also formed carbon nanotubes of irregular structures with coarse surface.

Deep insights into the promotion role of Sm doping in the sulfur resistance of Fe2O3 catalyst for NH3-SCR: A combined experimental and DFT study

To investigate the inherent role of Sm doping in metal sulfation over the surface of Fe2O3 catalyst and reveal the reason for the SO2 tolerance enhancement of Sm/Fe2O3 catalyst at low temperatures (<320 °C), sulfated Fe2O3 and Sm/Fe2O3 catalysts were prepared by pretreating fresh catalysts in SO2+O2 atmosphere. Selective catalytic reduction (SCR) of NOx by NH3 activities and physicochemical characteristics of fresh and sulfated catalysts were studied, and the reaction mechanisms on sulfated catalysts analyzed. The minor shift of Fe signal to high value and larger shift of S signal to low value of sulfated Sm/Fe2O3 compared with sulfated Fe2O3 was observed with X-ray photoelectron spectroscopy (XPS), indicating that Sm modification could weaken the sulfation of active Fe sites. Consistent with the XPS results, density functional theory calculations showed that SO2 is more easily adsorbed on the Sm/Fe2O3 catalyst with the adsorption sites located at Sm atom and its neighboring Fe atoms. In-situ DRIFTS results showed that the SCR reaction over the sulfated Fe2O3 catalyst followed both L-H (the adsorbed NH3 species react with adsorbed nitrate species) and E-R (the adsorbed NH3 species react with gaseous NO) mechanisms at 250 °C, with the L-H route much faster, whereas only the L-H pathway occurred over sulfated Sm/Fe2O3 catalyst because of too strong affinity of NH3 on the sulfated sites to inhibit NH3 activation – this was also the reason for its enhanced Lewis and Brønsted acidity. More reactive nitrate species were formed on the sulfated Sm/Fe2O3 catalyst due to the existence of more un-sulfated Fe sites, making the Sm/Fe2O3 catalyst resistant to SO2 poisoning at relatively low temperatures.

Study of the catalytic wet air oxidation of p-hydroxybenzoic acid on a fresh ruthenium catalyst supported by different oxides

The catalytic wet air oxidation (CWAO) of p-hydroxybenzoic acid (p-HBA) was conducted in a batch reactor at 140 °C, and at a total air pressure of 50 bar over Ru-based catalysts. Four materials were selected as supports – TiO2, CeO2–TiO2, ZrO2–TiO2, and La2O3–TiO2 – all of which had mesopores in their texture and pollutant adsorption capacities. The supports were prepared by the sol-gel method, and then impregnated with 3 wt% of Ru precursor. Such characterization techniques as N2-sorption, XRD, XPS, H2–TPR, NH3-TPD, TEM, and HAADF-STEM were used to analyze the different solids. The correlation between catalytic activities and physicochemical properties was discussed. A significant specific surface area (SBET), a large amount of surface-active oxygen, and Lewis acidity sites were observed on cerium-containing catalysts (Ru/CeTi). Fresh Ru catalysts containing cerium showed higher activity than Ru/TiO2, Ru/ZrTi, and Ru/LaTi catalysts. It is assumed that the acidic sites and surface oxygen trap the p-HBA molecule, thus increasing the catalytic properties of the Ru particles which interact with the surface oxygen through the cerium redox process (Ce3+/Ce4+). As the presence of cerium increases surface-active oxygen, it inhibits the deposition of carbon on the surface of the Ru catalyst. The pseudo-second order (PSO) model adequately described the kinetic data of the p-HBA oxidation reaction using Ru catalysts.

Response surface optimization of hydrogen-rich syngas production by the catalytic valorization of greenhouse gases (CH4 and CO2) over Sr-promoted Ni/SBA-15 catalyst

Dry reforming of methane (DRM) which utilizes CO2 and CH4, is a more efficient and environmentally friendly syngas production method. However, since the technique is endothermic, catalyst deactivation from sintering and carbon deposition has prevented its industrial implementation. This study investigated the effect of Strontium (Sr) promoter on Ni-based catalyst synthesized on SBA-15 support via the impregnation method. The incorporation of Sr as a promoter has demonstrated distinct advantages, primarily attributed to its remarkable capability to inhibit carbon formation. This property imparts a notable enhancement in the stability of the catalyst, thereby extending its operational lifespan and maintaining consistent catalytic performance. The physicochemical properties of the fresh catalyst were observed by using various characterization techniques such as X-Ray diffraction (XRD) analysis, N2 physisorption analysis, field emission scanning electron microscopy (FESEM), and temperature programmed reduction using hydrogen as the probing gas (TPR-H2). The catalysts were tested in DRM reaction using a tubular fixed bed reactor at 800 °C with an equimolar feed ratio. Overall, 1% Sr promoted Ni/SBA-15 showed enhanced performance having CO2 and CH4 initial conversions of 88.5% and 96.5%, respectively while remaining stable for 320 min on stream. Furthermore, the predicted optimal condition was 713.73 °C and a feed gas ratio (CH4:CO2) of 1.12, with CO2 and CH4 conversion rates of 69.59% and 84.83%, respectively, resulting in an H2:CO ratio of 1.00. Slight differences from the predicted values were considered insignificant, validating the Srb catalyst at a 95% confidence level with a 5% likelihood of error in the RSM model.

Multi-objective optimization study of hydrothermal aging on NOx-assisted soot catalytic combustion and secondary pollution emission in regeneration of CeO2 catalytic diesel particulate filter

The present study aimed to explore the effect of hydrothermal aging on the heterogeneous catalytic combustion process of soot in CeO2 catalytic diesel particular filter and the formation of secondary pollutants (N2O and CO).The present study was based on a fixed-bed experimental bench for NOx-assisted soot catalytic oxidation in CeO2-CDPF with different soot loading and catalyst coating amounts. A non-linear regression surrogate model and a multi-objective optimization decision approach were used to analyze the trade-off relationship between the design variables and the optimization objectives. The results showed that lower levels of soot loading (2.5 g/L), CeO2 catalyst coating amount (2.5 g/L) and higher NOx concentration (1000 ppm) in fresh catalysts were favorable for improving the performance of soot-assisted catalytic combustion and minimizing the formation of N2O and CO. However, it was observed that higher levels of catalyst coating amount (10 g/L) resulted in better soot catalytic combustion performance with lower N2O and CO emissions. Global sensitivity analysis showed a positive correlation between N2O and CO peak concentrations and peak temperatures with soot loading, but a negative correlation with catalyst loading. Over time, hydrothermal aging of CDPF caused the inhibitory effect of CeO2 catalyst on N2O to shift from negative to positive correlation, while also decreasing the synergistic performance of NOx in soot catalytic combustion.

The Investigation of Zeolite to Matrix Ratio Effect on the Performance of FCC Catalysts during Catalytic Cracking of Hydrotreated VGO

Fluidized catalytic cracking of vacuum gas oil is considered a promising factor in enhancing the gasoline yield to fulfill global energy demands. In this study, a series of FCC catalysts with a zeolite to matrix ratio varying from 18 to 50 was prepared using USY zeolite and amorphous matrix. The matrix was composed of amorphous silica-alumina, kaolin, and silica sol binder. All fresh catalysts were subjected to hydrothermal deactivation treatment at 750 °C for 5 h. The performance evaluation of FCC catalysts was conducted in a fixed bed microactivity test unit, with vacuum gas oil as feed at 550 °C. Comparing a steamed CAT01 sample with a fresh CAT01, the surface area of the steamed sample was 23.3% less. Similarly, the fresh sample CAT05 acidity increased by 102% when compared with the fresh CAT01 sample. As the zeolite to matrix ratio increased, the selectivity of dry gas, LPG, and coke increased, associated with a consistent decrease in gasoline and heavy ends (LCO and HCO). The combined selectivity of product gasoline and LCO with low-zeolite steamed catalyst (CAT01) was 82%, and that of high-zeolite steamed catalyst (CAT05) was 76%. Furthermore, coke selectivity for the steamed CAT01 was 2.1%, whereas 3.7% was observed for the steamed CAT05 sample. The effect of the zeolite to matrix ratio was less pronounced in steamed catalysts as compared with fresh catalysts.

Boosting the low-temperature activity of fast-synthesized Cu-SAPO-18 for NH3-SCR by hydrothermal treatment

Cu-SAPO-18 catalysts attracts increasing attention in the reaction of selective catalytic reduction (SCR) of nitrogen oxides (NOx), but the catalyst synthesis process is complicated and time-consuming. Also, it is urgent to enhance the low-temperature catalytic conversion of NOx for practical applications. Herein, we reported a fast-synthesis method to prepare the Cu-SAPO-18 catalysts in 32–80 h, and the catalysts showed an excellent catalytic performance of over 80 % NO conversion at 260–480 °C. The crystalline of the catalysts was improved in short crystallization time and high crystallization temperature, accelerating the NH3-SCR reaction. The low-temperature activity of all catalysts was improved after hydrothermal treatment, and the temperature range of over 80 % NO conversion was extended to 190–515 °C for the optimized catalyst, which was due to the increasing active Cu2+ species (ZCuOH and Z2Cu, where Z represents an anionic site on the zeolite framework). The redox cycle of Cu2+/Cu+ was accelerated and more Lewis acid sites on the catalyst enhanced the NO/NH3 adsorption and activation, promoting the low-temperature catalytic activity. Furthermore, after hydrothermal treatment, part of Z2Cu species converted to ZCuOH species, which exhibited stronger NO adsorption energies (−2.06 eV) than that of Z2Cu (−1.38 eV) based on theoretical calculation. Both fresh and aged catalysts showed remarkable SO2/H2O resistance. This work reveals the effects of hydrothermal treatment on the Z2Cu and ZCuOH species, which is helpful to prepare the fast-synthesized zeolite catalysts with excellent low-temperature SCR performance.

Schiff base stabilized palladium nanoparticles: Synthesis, characterization, catalytic degradation of organophosphorus pesticides, and fluorometric detection of Cr6+ in aqueous media

As a stabilizing and reducing agent, the Schiff base (2-(4-(trifluoromethoxy)phenylimino)methyl)-6-methoxyphenol) was used to synthesize palladium nanoparticles (PdNPs) with an average particle size (12 ± 2 nm) and a spherical shape. The numerous methods, including UV–vis absorption spectroscopy, photoluminescence (PL), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and thermal gravimetric analysis (TGA) were used to characterize the PdNPs. The Schiff base capped PdNPs have FCC structure with 10 ± 3 nm particle size was estimated from XRD and TEM analysis. The catalytic, sensing, antibacterial, and antioxidant abilities of the created PdNPs were assessed. The findings demonstrated that PdNPs followed pseudo-first-order kinetics and had superior catalytic activity in the degradation of pesticides (monocrotophos (MCP), 99.9%) and chlorpyrifos (CLP), 98.2%) using NaBH4 as a reducing agent in 1 h reaction. PdNPs were still stable and exhibited a high catalytic activity with only a marginal decrease from maximum degradation (99.9% of MCP and 98.2% of CLP) using the fresh catalyst to 92.6% (MCP) and 90.1% (CLP) of the used catalyst (recycled after 5 times) was observed. Additionally, at a concentration range of 10–100 µM, the PdNPs demonstrated selective fluorescence sensing for Cr6+ metal ions in aqueous media. The significant antimicrobial action was also shown by the PdNPs against pathogens such S. aureus, B. subtilis, E. coli, P. aeruginosa, A. niger, and C. albicans. The PdNPs also demonstrated antioxidant activity in the DPPH free radical scavenging assay, with a 78.06% scavenging efficiency. This technique is efficient and cost-effective, and it may be used as an effective biological agent, sensor, and catalyst for a variety of environmental applications.

Effect of Different Zinc Species on Mn-Ce/CuX Catalyst for Low-Temperature NH3-SCR Reaction: Comparison of ZnCl2, Zn(NO3)2, ZnSO4 and ZnCO3

The effects of four distinct zinc species (ZnCl2, Zn(NO3)2, ZnSO4, and ZnCO3) on a Mn-Ce co-doped CuX (MCCX)catalyst were investigated and contrasted in the low-temperature NH3-SCR process. Aqueous solutions of ZnCl2, Zn(NO3)2, ZnSO4, and ZnCO3 were used to poison the catalysts. The catalytic activity of all catalysts was assessed, and their physicochemical properties were studied. There was a notable drop trend in catalytic activity in the low temperature range (200 °C) after zinc species poisoning on MCCX catalyst. Interestingly, ZnSO4 and ZnCO3 on MCCX catalyst had more serious effect on catalytic activity than Zn(NO3)2 and ZnCl2 from 150 °C to 225 °C, in which NO conversion of the MCCX-Zn-S and MCCX-Zn-C catalysts dropped about 20–30% below 200 °C compared with the fresh MCCX catalyst. The zeolite X structure was impacted by Zn species doping on the MCCX catalyst, and the Zn-poisoned catalysts had less acidic and lower redox ability than fresh Mn-Ce/CuX catalysts. Through the results of in situ DRIFTS spectroscopy experiments, all catalysts were governed by both Langmuir–Hinshelwood (L–H) and Eley–Rideal (E–R) mechanisms, and the possible mechanism for poisoning the Mn-Ce/CuX catalyst using various zinc species was revealed.

Promoting effect of N2 calcination on FeCeOx for selective catalytic reduction of NOx with NH3

AbstractBACKGROUNDSelective catalytic reduction of NOx with NH3 (NH3‐SCR) technology is effective for NOx removal. Acidity and redox ability are two significant characteristics for NH3‐SCR catalysts. This study investigated the effects of N2 calcination on the NH3‐SCR performance of FeCeOx, inspired by the promotion of active oxygen species with inert atmosphere calcination. The structure‐activity relationship and reaction mechanism of the two catalysts (Fe9CeOx‐N2 and Fe9CeOx‐air) were concluded based on the results of characterization.RESULTSFe9CeOx‐N2 showed better NOx conversion and SO2 resistance than Fe9CeOx‐air, especially in low and medium temperature range. For fresh catalysts, a higher amount of Oα, Fe3+ and Ce3+ promoted the redox ability of Fe9CeOx‐N2, and further improved the NOx adsorption and activation. Additionally, the greater number of acid sites of Fe9CeOx‐N2 was another reason for its competitive performance. For SO2‐poisoned catalysts, the primary reaction pathway was the reaction between pre‐adsorbed NH3 species and NOx. The higher amount of acidity from metal sulfate contributed to its better SO2 tolerance of Fe9CeOx‐N2.CONCLUSIONHigher redox ability and acidity led to better NH3‐SCR activity and SO2 tolerance of Fe9CeOx‐N2. This study provides a feasible preparation method for enhancing the NOx conversion and SO2 tolerance of NH3‐SCR catalysts. © 2023 Society of Chemical Industry.

Development of phosphotungstic acid immobilized amine-grafted graphene oxide as heterogeneous catalyst for synthesis of bis(indolyl)methane derivatives

Phosphotungstic acid was immobilized hydrothermally on the surface of 3-aminopropyltriethoxysilane-grafted graphene oxide (GO-N-PTA) and used as a heterogeneous solid acid catalyst for the synthesis of bis(indolyl)methane derivatives. X-ray diffraction (XRD), fourier transform infrared (FTIR) spectroscopy, BET isotherm, FESEM with EDS and elemental mapping, FETEM, X-Ray photoelectron spectroscopy (XPS), Raman spectroscopy techniques were used to characterize the synthesized catalyst. The catalyst was found to be highly effective for the synthesis of bis(indolyl)methane derivative compounds with yields in the ranges of 94–96.5 % under the optimized reaction conditions. The catalyst was recycled upto 3rd cycle for a specific reaction, that produced 94.5% yield with marginal loss in yield compared to the fresh catalyst (96.5%) depicting the hetreogneiety and sustainability of the present GO-N-PTA catalyst. This study provides the development of sustainable heterogeneous GO-N-PTA catalyst towards the synthesis of highly pharmaceutically important bis(indolyl)methanes derivative compounds.

Upgrading the catalytic activity recovery capacity of a Ni–Mo/γ–Al2O3 catalyst via a modified remanufacturing process for residue hydrodesulfurization: Effect of acid leaching conditions and process sequence

In this study, the improvement of catalytic activity recovery capacity of a modified catalyst remanufacturing process for Ni–Mo/γ–Al2O3 catalysts in residue hydrodesulfurization (RHDS) is evaluated by comparing it with our previous study. The enhancement of catalytic activity recovery is achieved by modifying the sequence and conditions of the acid leaching process in the catalyst remanufacturing process. The proposed improved process successfully restored the collapsed pore structure caused by contaminant deposition, a major deactivation factor identified in our previous study. The selective leaching of vanadium through the addition of ferric nitrate in the acid leaching process effectively addresses the issue of simultaneous removal of active species caused by excessive leaching. Consequently, the remanufactured catalyst exhibited an impressive catalytic activity recovery of 99% compared to the fresh catalyst at a reaction temperature of 395 °C, approaching a near-perfect state. Notably, the reducibility of the catalyst emerges as a key factor influencing catalytic activity recovery. The restored pore structure and selective removal of vanadium using ferric nitrate application increase the contact area between reactants and active precursors, enhancing reducibility and leading to a higher number of active sites. Additionally, a threshold effect is observed in the recovery of catalytic activity through improved specific surface area, where the enhancement of pore diameter resulting from vanadium removal on the exterior of catalyst surface becomes crucial. These findings contribute to advancing catalyst remanufacturing processes and understanding the factors influencing catalytic activity recovery.

Boosting Fenton's Oxidation Reaction by a Food Waste-Derived Catalyst for Oxidizing Organic Dyes: Synergistic Effect of Complex Iron Oxides and the Layer Carbon Structure.

The constant increase in the human population drives the demand for food supply and thereby increasing the food wastage dramatically all over the world. Especially, around 60% of banana biomass has been generated as inedible domestic waste. Herein, we successfully employed banana waste as a catalyst for Fenton's oxidation reaction. The biomass-derived catalysts were subjected to various characterization techniques such as XRD, ATR-FTIR, confocal Raman spectroscopy, and XPS, XRF, BET, SEM, and TEM analyses. The XRD results revealed that, after carbonization of the dried banana bract material, a perloffite-like metal oxide phase was formed due to the aerial oxidation reaction. Characterization results of Raman and ATR-FTIR confirm that the carbonized catalyst possesses a layer-like structure with different types of functional groups. The calcium, magnesium, potassium, sodium, and iron are the dominating metal species in the resultant material, which was evident from the XRF and EDAX analyses. The carbonized banana bract catalyst is successfully utilized for the Fenton's oxidation reaction at neutral pH. The experimental results showed that the degradation efficiency of the fresh catalyst was 95% in 4 h of reaction time, and the stability of the catalyst was retained up to nine consecutive cycles. The high activity of MB, methylene blue, is mainly attributed to the strong interaction between oxy functional groups of the catalyst and MB molecule as compared to RhB. Further, the calculated efficiency of the hydrogen peroxide was found to be 99% and the self-decomposition of hydrogen peroxide by the formed metal oxides was highly limited.

Catalytic wet peroxide oxidation with in-situ generated H2O2: An efficient strategy for improving the stability of metal-organic framework catalysts

Although catalytic wet peroxide oxidation (CWPO) may offer an efficient method for wastewater treatment, the use of metal-organic framework (MOF) catalysts for the CWPO reaction in the presence of H2O2 is challenging because the MOF structure is highly vulnerable to water and/or oxidizing agents. Herein, a range of M-1,3,5-benzenetricarboxylate (BTCs) (M = Fe, Co, Mn, and Cu) were prepared, and their catalytic activities in the CWPO of methyl orange (MO) were evaluated. To examine the stability of the M-BTCs under different reaction conditions, the CWPO reaction was performed with ready-made H2O2 (CWPO-I) or in-situ generated H2O2 using H2 and O2 (CWPO-II). In the latter, Pd was supported onto an M-BTC (Pd/M-BTC). The CWPO-I reaction rate was significantly affected by the metal nodes of the M-BTC, with the Fe-BTC catalyst showing the fastest MO degradation rate. However, regardless of the type of metal node, the M-BTC catalysts underwent significant decomposition during the CWPO-I reaction, leading to a considerable decrease in their textural properties. This result suggests that the M-BTC structure collapsed due to attack by the hydroxyl radicals generated during the reaction. Therefore, the activity of the regenerated Fe-BTC catalyst significantly decreased to 40% of that of the fresh catalyst. In contrast, the catalyst stability in CWPO-II outperformed that in CWPO-I. The Pd/Fe-BTC catalyst exhibited a moderate decrease in activity owing to the gradually reduced surface area of the catalyst during the recycling runs, and the crystallinity of Fe-BTC was preserved. Moreover, the content, particle size, and electronic properties of Pd supported on Fe-BTC showed little change after the reaction. These results demonstrate that the use of in-situ generated H2O2 is superior for impeding the catalyst deactivation caused by structural deformation of the MOF.

A modelling approach to investigate the performance of slurry bubble column reactors implementing Fischer–Tropsch synthesis

AbstractA reliable estimation of the reactor performance is a crucial aspect of slurry bubble column reactor design. Hydrodynamics, mass transfer, and reaction rate are the main parameters influencing the overall performance. A new hydrodynamic model was adopted in this study to properly predict the effect of solids loading, particle size, pressure, and temperature on the gas holdup, bubble size distribution, and mass transfer coefficient. The reactor was divided into small cells with individual hydrodynamic parameters. The results were compared with the experimental data and showed that the model can acceptably predict the hydrodynamic and mass transfer parameters in various process situations. A parametric study was accomplished to understand the effect of catalyst loading, superficial gas velocity, H2/CO ratio, L/D ratio, pressure, temperature, and catalyst attrition on the conversion rate, catalyst productivity, and space–time yield. A cobalt/silica catalyst was adopted in this study. Based on the obtained results, the syngas conversion increases by catalyst loading, L/D, and temperature, while it decreases by Ug and pressure. The H2/CO ratio results in a maximum conversion somewhere between 2 and 2.5. Three different scenarios were determined to study the effect of catalyst attrition on the reactor performance. The results show that the attrition decreases the syngas conversion due to the decrease in the catalyst size and the catalyst loss. Also, the performance remains constant if a sufficient amount of fresh catalyst is added to the system continuously.

The Catalyst of Ruthenium Nanoparticles Decorated Silicalite-1 Zeolite for Boosting Catalytic Soot Oxidation

Herein, the Ruthenium nanoparticles (NPs) with the size of 12 nm were decorated on the hexagonal prism silicalite-1 (Ru/S-1) by the gas bubbling-assisted membrane reduction method (GBMR). The adsorption/activation properties are improved for reactant molecules due to the formation of an interfacial structure that enhances the interaction between the Ru NPs and S-1. The Ru/S-1 catalyst displays the highest catalytic activity (T50 = 356 °C) and CO2 selectivity (SCO2m = 99.9%). Moreover, no obvious deactivation was observed over the Ru/S-1 catalyst even after five cycles, and the values of T50 and SCO2m after cycling five times are similar to the fresh catalyst. The Ru/S-1 catalyst with excellent catalytic performance can be compared with a series of noble metal catalysts for soot oxidation. The catalytic mechanism of the Ru/S-1 catalyst was revealed by in situ characterization for soot oxidation. The interfacial effect between Ru NPs and S-1 plays an important role in the conversion of NO to NO2 during soot oxidation. Preparation of Ru/S-1 catalyst provides a hopeful way to obtain considerably low-cost and highly stable auto-exhaust treatment catalysts.

Sintering resistance of Pt-based oxidation catalyst via constructing Pt/MnOx interface

It is a challenge to improve the catalytic activity and hydrothermal stability of platinum-based catalyst in concurrently oxidizing CO/C3H6/NO. The construction of Pt/MnOx interface over Pt-based diesel oxidation catalyst via overlayer deposition to form partial-embedded structure, inhibiting the aggregation of platinum nanoparticles in Ostwald Ripening process. Even after hydrothermal aging, the average platinum particle size is equal to that of the fresh catalyst via traditional impregnation method. The electronic-transferring from platinum to manganese results in a weaker CO adsorption ability on Pt species and an improved oxygen activation ability with the help of the redox cycle of Pt and MnOx, as well as the formation of more active nitrate species via in situ DRIFTs. Measurement on the activity shows the lower apparent activation energy, so that the light-off temperature of CO/C3H6/NO on the partial-embedded catalyst via overlayer deposition method decreases by around 20 °C and 40% NO maximum conversion still keeps after severely aging comparing with the traditional catalyst. The work enlightens us the importance of interface sites in stabilizing platinum atoms and creating oxidize active sites.

Revealing Active Sites and Reaction Pathways in Methane Non-Oxidative Coupling over Iron-Containing Zeolites.

Non-oxidative coupling of methane is a promising route to obtain ethylene directly from natural gas. We synthesized siliceous [Fe]zeolites with MFI and CHA topologies and found that they display high selectivity (>90 % for MFI and >99 % for CHA) to ethylene and ethane among gas-phase products. Deactivated [Fe]zeolites can be regenerated by burning coke in air. In situ X-ray absorption spectroscopy demonstrates that the isolated Fe3+ centers in zeolite framework of fresh catalysts are reduced during the reaction to the active sites, including Fe2+ species and Fe (oxy)carbides dispersed in zeolite pores. Photoelectron photoion coincidence spectroscopy results show that methyl radicals are the reaction intermediates formed upon methane activation. Ethane is formed by methyl radical coupling, followed by its dehydrogenation to ethylene. Based on the observation of intermediates including allene, vinylacetylene, 1,3-butadiene, 2-butyne, and cyclopentadiene over [Fe]MFI, a reaction network is proposed leading to polyaromatic species. Such reaction intermediates are not observed over the small-pore [Fe]CHA, where ethylene and ethane are the only gas-phase products.

Revealing Active Sites and Reaction Pathways in Methane Non‐Oxidative Coupling over Iron‐Containing Zeolites

AbstractNon‐oxidative coupling of methane is a promising route to obtain ethylene directly from natural gas. We synthesized siliceous [Fe]zeolites with MFI and CHA topologies and found that they display high selectivity (&gt;90 % for MFI and &gt;99 % for CHA) to ethylene and ethane among gas‐phase products. Deactivated [Fe]zeolites can be regenerated by burning coke in air. In situ X‐ray absorption spectroscopy demonstrates that the isolated Fe3+ centers in zeolite framework of fresh catalysts are reduced during the reaction to the active sites, including Fe2+ species and Fe (oxy)carbides dispersed in zeolite pores. Photoelectron photoion coincidence spectroscopy results show that methyl radicals are the reaction intermediates formed upon methane activation. Ethane is formed by methyl radical coupling, followed by its dehydrogenation to ethylene. Based on the observation of intermediates including allene, vinylacetylene, 1,3‐butadiene, 2‐butyne, and cyclopentadiene over [Fe]MFI, a reaction network is proposed leading to polyaromatic species. Such reaction intermediates are not observed over the small‐pore [Fe]CHA, where ethylene and ethane are the only gas‐phase products.