Ultrasonic-assisted Impregnation Method Research Articles

Catalytic combustion of toluene over cerium modified CuMn/Al2O3/cordierite monolithic catalyst

Catalytic combustion is an effective approach to remove volatile organic compounds, in which the development of highly active and durable catalyst is extremely crucial. Herein, a series of CuMnCex/Al2O3/cordierite monolithic catalysts were synthesized by using the ultrasonic-assisted impregnation method. The physicochemical properties were comprehensively characterized via the BET, XRD, SEM, EDX, H2-TPR, O2-TPD, XPS and EPR techniques. The results showed that the catalytic activity of CuMnCex/Al2O3/Cor for toluene combustion was strongly affected by the Ce content. The CuMnCe2/Al2O3/Cor monolithic catalyst showed the best catalytic activity with toluene conversion of 90% at 263 °C under toluene concentration of 1 g/L and space velocity of 78000 mL/(g·h). Meanwhile, the well-dispersed CeO2 in the CuMn matrix not only improved the content of oxygen vacancies and the mobility of oxygen species, but also enhanced the low-temperature reducibility of the catalyst. Moreover, the CuMnCe2/Al2O3/Cor monolithic catalyst exhibited an excellent stability in the long-term test and cycle ability test.

A comparative study of the catalytic nitration of toluene over bimetallic Ce‐Mn modified Hβ zeolite

AbstractBimetallic cerium‐manganese modified Hβ zeolite sample (Ce/Mn‐Hβ) was prepared by ultrasonic assisted impregnation method and applied in nitration of toluene. The characterization results show that the active components (Ce and Mn) are successfully introduced into the framework of Hβ zeolite. The catalyst shows excellent catalytic activity and reusability for the nitration of toluene, giving high para selectivity. Under optimized conditions, it gives 68.7% selectivity to para‐nitrotoluene at 88.6% conversion over Ce/Mn‐Hβ in the presence of acetic anhydride (Ac2O). The theoretical calculations indicate that the Ce/Mn bimetallic active sites in modified Hβ zeolite can easily activate the nitrification reagent (AcONO2), and the enhancement of para selectivity is owing to the steric hindrance of catalyst. Furthermore, the reaction mechanism was proposed by the combination of experimental results and theoretical calculations.

Highly Active Ni-Ru Bimetallic Catalyst Integrated with MFI Zeolite-Loaded Cerium Zirconium Oxide for Dry Reforming of Methane.

The dry reforming of methane (DRM) is a new potential technology that converts two major greenhouse gases into useful chemical feedstocks. The main challenge faced by this process is maintaining the catalyst with high catalytic activity and long-term stability. Here, a simple and effective preparation route for the synthesis of functional nanomolecular sieve catalysts (NiRuxCZZ5) from kaolinite tailings was developed for dry reforming of methane with CO2. The silica monoliths with flower-like spherical and micropore structures (ZSM-5) were prepared by crystal growth method, and the metal components were loaded by ultrasonic-assisted impregnation method. The NiRu0.5CZZ5 catalyst exhibited excellent catalytic performance (maxmium CO2 and CH4 conversions up to 100 and 95.6%, respectively) and very good stability (up to 100h). The interfacial confinement and the strong support interaction are principally responsible for the excellent catalytic activity of the catalyst. The in situ DRIFTS was used to elucidate the possible carbon conversion steps, and stable surface intermediates were also identified.

Deciphering the imperative role of ruthenium in enhancing the performance of Ni/Nd2O3.Gd2O3 in glycerol dry reforming

Glycerol dry reforming (GDR) turns glycerol and CO2 into valuable syngas. The present work aims to decipher the imperative role of Ru metal in enhancing the performance of Ni/Nd2O3.Gd2O3 in GDR. The unpromoted 15%Ni/Nd2O3.Gd2O3 and promoted 3%Ru-Ni/Nd2O3.Gd2O3 catalysts are synthesized via the ultrasonic-assisted impregnation method while XRD, FESEM-EDX, H2-TPR and CO2-TPD analyses are used to characterize the catalysts. In this study, the influence of reaction variables such as temperature and the CO2 to glycerol ratio (CGR) was investigated. In accordance with XRD and FESEM-EDX analyses, the promoted catalyst exhibited a more refined morphology and more uniform Ni dispersion than the unpromoted catalyst. From the reaction study, the promoted 3%Ru-15%Ni/Nd2O3.Gd2O3 gives higher glycerol conversion (91%), H2 yield (65%) and CO yield (80%) at a reaction temperature of 800 °C and CGR of 1. This is due to the higher number of available active sites as well as the excellent diffusion of Ni metal across the surface of the catalyst. However, as Ni metal is susceptible to carbon formation and is easily sintered, the production of carbon is unavoidable for the catalysts. The XRD and TPO analyses shown that the addition of Ru reduces the amount of carbon that accumulates on the site of the catalyst, which in turn reduces the rate of deactivation.

Rationally designed Ti3C2/N, S-TiO2/g-C3N4 ternary heterostructure with spatial charge separation for enhanced photocatalytic hydrogen evolution

The charge separation and transfer are the major issues dominating the under-laying energy conversion mechanism for photocatalytic system. Construction of semiconductor-based heterojunction system considered to be viable option for boosting the spatial charge separation and transfer in the photocatalytic water splitting system. Here, we design a ternary heterojunction of Ti3C2/N, S-TiO2/g-C3N4 by thermal annealing and ultrasonic assisted impregnation method having a well-designed n-n heterojunction and noble metal free Schottky junction for adequate hydrogen evolution. The optimal content of 4 wt% Ti3C2 on N, S-TiO2/g-C3N4 (4-TC/NST/CN) exhibit the highest rate of hydrogen generation 495.06μ mol h−1 which is 3.1, 4.1 and 1.6 fold higher than the pristine N, S doped-TiO2, g-C3N4 and binary hybrid (N, S doped-TiO2/g-C3N4) respectively, with 7% apparent conversion efficiency (ACE). The increment in the activity is described to the robust photogenerated carrier separation and double charge transfer channels because of the formation of dual heterojunction (n-n heterojunction and Schottky junction). XRD and Raman results revealed the occupancy of Ti3C2 in the heterojunction due to the strong interaction between Ti3C2, with N, S doped-TiO2 and g-C3N4. The HRTEM analysis confirmed the formation of close interfacial junction between the Ti3C2, N, S doped-TiO2 and g-C3N4. Moreover, the higher photocurrent, low PL intensity and lower impedance arc suggested the lower charge carrier recombination rate in 4-TC/NST/CN heterojunction. This work represents a significant development to establish a sound foundation for future design of MXene-based ternary hybrid system towards significant charge carrier separation and transfer for H2 production activity.

Experimental Study on the Elemental Mercury Removal Performance and Regeneration Ability of CoOx–FeOx-Modified ZSM-5 Adsorbents

Herein, a series of Co-Fe mixed oxide modified ZSM-5 adsorbents were synthesized using the ultrasonic-assisted impregnation method for the capture of elemental mercury. In comparison with other samples, Co4Fe1-ZSM-5 produced a relatively better performance, with the removal efficiency of around 96.6% Hg0 and the adsorption capacity of around 901.63 ug/mg Hg0 achieved at 120 °C. The interaction between CoOx and FeOx improved the reducibility of oxygen species, thus promoting the oxidation of Hg0. Among a variety of other gas components, O2 and NO exerted a positive effect on Hg0, which improved its removal to a certain extent. By contrast, SO2 caused an adverse effect on the capture of Hg0, which could be reversed to some degree by the introduction of 5% O2. After five cycles, the mercury removal efficiency of Co4Fe1-ZSM-5 remained above 90%, suggesting excellent recyclability. Finally, XPS analysis was conducted to reveal that Mars–Maessen mechanisms are dominant in the process of mercury adsorption.

Rearrangement of α-terpineol by using PTA/TiO2 catalyst synthesized by ultrasonic-assisted impregnation method

1,8-cineole was synthesized via α-terpineol rearrangement over SiO2- and TiO2-supported phosphotungstic acid (PTA) catalysts prepared by ultrasonic impregnation. The structures of the catalysts were analyze using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared (FT-IR) spectroscopy. The effects of reaction conditions on α-terpineol conversation and 1,8-cineole selectivity were investigated and the optimal reaction conditions are PTA loading of 20 wt%, mass fraction of 0.02, reaction temperature of 50 °C, and reaction time of 6 h. Under these conditions, the α-terpineol conversion and 1,8-cineole selectivity over PTA/TiO2 were 98.96% and 48.77%, respectively, which were better than that over PTA/SiO2.

Highly dispersed Ru anchored on nanosheet N-doped carbon for efficient and chemoselective hydrogenation of nitroaromatics to aromatic amines under mild conditions

An efficient catalyst for chemoselective hydrogenation of nitroaromatics to produce aromatic amines under mild conditions is highly desirable. In this work, a series of N-doped carbon (NC-x) with high nitrogen contents were firstly synthesized by pyrolysis of 1-butyl-3-vinylimidazolium bromide-co-acrylonitrile with a template of g-C3N4. Furthermore, Ru/NC-x catalysts were successfully prepared by ultrasonic-assisted impregnation method. The catalysts were characterized by various methods in detail, e.g.X-ray diffraction, N2 physical adsorption-desorption, Transmission electron microscopy, Raman spectra, Scanning electron microscopy and H2 temperature programmed reduction. Characterization results revealed that N-doping on carbon contributed to the high dispersion of Ru nanoparticles and resulted in the forming of the electron-deficient of Ru species. Nanosheet Ru/NC-2 with high N-doping content of 28 wt% exhibited superior performance under room temperature, i.e., nitrobenzene conversion >99.0% and aniline selectivity 98.4%. Kinetic study indicated that the hydrogenation of nitrobenzene over Ru/NC-2 was the first-order kinetics with an intrinsic activation energy of 43.7 kJ/mol. Density functional theory calculation results suggested that Ru-Nx species, especially, Ru-pyrrolic-N facilitated nitrobenzene adsorption and H2 dissociation, resulting in enhanced catalytic performance. In addition, the excellent stability of Ru/NC-2 made it essentially reserved for 410 h in the fixed-bed reactor. Moreover, Ru/NC-2 exhibited superior performance for the hydrogenation of various nitroaromatics to corresponding aromatic amines. This work could provide meaningful guidance on designing effective and stable catalyst for chemoselective hydrogenation of nitroaromatics to aromatic amines under mild conditions.

Palladium-halloysite nanocomposites as an efficient heterogeneous catalyst for acetylene hydrochlorination

Halloysite nanotubes (HNTs) were employed to design and synthesize palladium-based heterogeneous catalysts with the purpose of exploring an efficient non-mercuric catalyst for acetylene hydrochlorination. Various Pd/UHNTs catalysts with urea modification were prepared using ultrasonic-assisted impregnation method and the Pd/9UHNTs catalyst exhibited the best catalytic performance, with 90% acetylene conversion and above 94% vinyl chloride selectivity under the reaction conditions of T = 160 °C, a C2H2 gas hourly space velocity (GHSV) = 150 h−1 and V(HCl): V(C2H2) = 1.25. The results demonstrated that the urea additive (mainly nitrogen species) significantly immobilized Pd species and inhibited the carbon deposition on the catalyst surface, thus contributing to enhance the catalytic performance of Pd/HNTs catalysts during the reaction.

Study on catalytic performance of Co-Ni-B/SBA-15 for hydroformylation of 1-octene

SBA-15 zeolite supported amorphous ternary Co-Ni-B was prepared by the ultrasonic-assisted impregnation method for catalyzing the hydroformylation of 1-octene to nonanal. Supporting on SBA-15 increased the dispersion of nano amorphous Co-Ni-B. The crystallization temperature of amorphous Co-Ni-B was elevated by 280°C that improves the thermal stability of Co-Ni-B. Using Co-Ni-B/SBA-15 with Co loading of 7.22% and the ratio of n(Ni)/n(Co) of 0.157 and n(B)/n(Co+Ni) of 0.434, the conversion of 1-octene and the selectivity of nonanal reached 100% and 91.24%, respectively, in the hydroformylation reaction at 120°C and 5 MPa. The selectivity of side-product was reduced by 1 time compared with that of Co-Ni-B. The Co-Ni-B/SBA-15 is stable after repeated used for 5 times.

Enhancement of catalytic activity in NH3-SCR reaction by promoting dispersibility of CuCe/TiO2-ZrO2 with ultrasonic treatment

A series of CuCe-modified TiO2-ZrO2 catalysts synthesized by stepwise impregnation method and ultrasonic-assisted impregnation method were investigated to research the removal of NO in the simulated flue gas. Results showed that the CuCe/TiO2-ZrO2 catalyst prepared by ultrasonic-assisted impregnation method exhibited the superior NO conversion, in which higher than 85% NO was degraded at the temperature range of 250–400 °C and the highest NO conversion of 94% at 350 °C. It proves that ultrasonic treatment can markedly improve the performance of catalysts. The effect of ultrasonic enhancement on CuCe/TiO2-ZrO2 was comprehensively studied through being characterized by physicochemical characterization. Results reveal that the ultrasonic cavitation effect improves the distribution of active species and the synergistic interaction between Cu with Ce components (Cu+ + Ce4+ ↔ Cu2+ + Ce3+) on the catalysts significantly, thus resulting in better dispersibility as well as a higher ratio of Cu2+ and Ce3+ of the catalysts. Moreover, it was found that the CuCe/TiO2-ZrO2 catalyst prepared by the ultrasonic-assisted impregnation method represented a higher degree of ultrafine metal particles and evenness. The above results were described with the generalized dimension and singularity spectra in multifractal analysis and validated by the comparative test. Therefore, it can be concluded that ultrasonic treatment facilitates the particle size and distribution of active sites on the catalysts.

Design of new activated carbon based adsorbents for improved desulfurization of heavy gas oil: experiments and kinetic modeling

Abstract In this work, adsorption desulfurization is considered for making cleaner fuel. New efficient adsorbents have been designed by using two active metal oxides mainly potassium permanganate (KMnO4) and potassium phosphate (KPO4·3H2O) on Activated Carbon (AC). Ultrasonic assisted impregnation method (IWI) is used in designing the adsorbents offering high pore volume, pore size, surface chemistry, and high surface area. Use of ultrasonic method increases the dispersion of the active material (groups) on AC leading to increased number of collisions between O-atom on AC-support resulting in high sulfur removal from fuel. KMnO4 on AC shows higher adsorption capacity towards sulfur than KPO4·3H2O at the same operating conditions. New results with respect to sulfur removal has obtained compared with those obtained by previous studies. Finally, the adsorption kinetic parameters of such process are developed. Thomas and Yoon–Nelson models and the experimental data are used for this purpose using linear and non-linear regression analysis. Yoon–Nelson kinetic model fits well with the experiments data better than Thomas kinetic model in the entire adsorption column system.

Non-mercury catalytic acetylene hydrochlorination over Bi/CNTs catalysts for vinyl chloride monomer production

The serial Bi/CNTs catalysts were prepared by ultrasonic-assisted impregnation method with bismuth chloride and carbon nanotubes. During acetylene hydrochlorination reaction, the Bi/CNTs catalyst with 20 wt% Bi loading exhibited an excellent catalytic performance with 91.7% acetylene conversion and 97.3% vinyl chloride selectivity in 10 h at T = 160 °C, GHSV(C2H2) = 120 h−1 and V(HCl): V(C2H2) = 1.29. It is proposed that the BiOCl with a stable Bi3+ species existed on the catalyst surface, which can be considered as the major active site in the Bi-based catalysts. Bi species loss and the carbon deposition formation are the main deactivation reasons for Bi/CNTs catalysts.

Carbon nanotubes supported N-promoted Pd-based catalysts for acetylene hydrochlorination

A novel N-promoted carbon nanotubes (CNT) supported Pd catalyst (PANI/CNT-Pd) was prepared by the ultrasonic-assisted impregnation method and applied in the acetylene hydrochlorination reaction successfully. Compared with the Pd-CNT catalyst, the PANI/CNT-Pd catalyst exhibited the enhanced catalytic performance with more than 91.6% acetylene conversion and 99.6% vinyl chloride selectivity during 20 h at T = 160 °C, GHSV(C2H2) = 120 h-1 and V(HCl) : V(C2H2) = 1.5. It is suggested that PANI species contained N elements have been deposited on the CNT surface and they display the critical role on the enhanced catalytic performance of PANI/CNT-Pd catalysts correlated with the less palladium loss and the carbon deposition.

Synthesis of bi-functionalized ionic liquid — mesoporous alumina composite material and its CO2 capture capacity

Bi-functionalized ionic liquid (IL) — mesoporous alumina (MA) composite material was synthesized and used for CO2 capture. Ordered mesoporous alumina was synthesized by self-assembly method with aluminum isopropoxide as aluminum source. Then bi-functionalized ionic liquid 1-methoxyethyl-3-methyl imidazole glycinate ([MOEmim][Gly]) was immobilized on mesoporous alumina by ultrasonic-assisted impregnation method. Ordered mesostructure of alumina keeps well in the composite material. Compared with bi-functionalized ionic liquid, thermal stability of the composite material greatly improved. Finally, CO2 capture capacity of IL-MA composite material was studied under different temperatures. On the basis of both capture capacity and capture rate, 40 ·C is the optimal temperature. The capture capacity is 1.42 mol·mol IL−1 — equivalent to 144 mg·g sorben−1, which is higher than IL or MA alone. Furthermore, the capture capacity of composite material almost maintains constant after eight capture-regeneration cycles.

Mercury removal from flue gas by magnetic iron-copper oxide modified porous char derived from biomass materials

In this work, a magnetic iron-copper oxide modified porous char derived from biomass materials was prepared by microwave activation and ultrasonic-assisted impregnation method to remove Hg0 from flue gas. The effects of operating parameters and flue gas components on Hg0 removal performance as well as physicochemical properties of samples were studied. The reaction mechanism and the regeneration performance of samples were also investigated. The experimental results display that the biomass-based porous char derived from microwave and steam activation exhibits a larger pore volume, higher surface area and well-developed pore structure. The ultrasonic treatment promotes the dispersion of active components on the surface of samples. The CuFe0.3/WSWU10(500) sample exhibits good Hg0 removal performance, and about 90.58% of Hg0 is captured from flue gas at 130 °C. Increasing SO2 concentration inhibits Hg0 removal. The presence of O2 and NO promotes the removal of Hg0. Low concentration of water vapor (>4%) improves Hg0 removal performance, while excessive water vapor plays an opposite role. The presence of copper/iron active components, chemisorbed oxygen and lattice oxygen over the surface of adsorbent is conducive to the removal of Hg0. The modified sample exhibits a good regeneration performance.

Hydroxyl-promoter on hydrated Ni-(Mg, Si) attapulgite with high metal sintering resistance for biomass derived gas reforming

As hydrated magnesium-aluminum-silicate crystals, attapulgite and HNO3/NaOH pretreated attapulgite were used as support to prepare nickel-based catalysts via ultrasonic-assisted impregnation method. The as-prepared catalysts were employed in the biomass derived gas (especially CO2 and CH4) reforming with a considerable catalytic performance achieved (CH4 conversion: 75.26%, CO2 conversion: 85.75%) over HNO3-attapulgite (10% Ni) at 700 °C and GHSV of 36000 mL/g.h during 600 min, demonstrating the potential of modified attapulgite as support applied in catalytic reforming. According to the characterization results obtained from BET/FT-IR/H2-TPR/XRD/SEM/TPO, it was found that the formation of (Ni, Mg) containing phyllosilicate improved metal sintering resistance by the confinement effect. Besides, FT-IR results illustrated the existence of hydroxyl in the catalyst structure, which was beneficial for inhibiting the Boudouard side reaction, further enhancing the carbon resistance of catalysts. Moreover, TPO results showed that the deposited carbon on modified attapulgite was mainly fibrous carbon which can be removed easily, thus maintaining the catalytic performance. Due to its unique structure and high metal sintering resistance, it is believed that the attapulgite supported catalyst can be used in any other catalytic reforming process such as steam reforming of methane.

A novel and effective Zn/PEI-MCM catalyst for the acetylene hydration to acetaldehyde

MCM-41 material was modified by polyethyleneimine (PEI) using ultrasonic assisted impregnation method with different PEI loading (P-MCM-x, x = 0–15 wt%). The synthesised P-MCM-x materials and corresponding Zn/P-MCM-x catalysts were characterised by FTIR, XRD, TEM, BET, XPS, TG and H2-TPR, as well as their catalytic performance in the hydration of acetylene was investigated. The results showed that the modified materials retained the mesoporous structure with good thermostability, and the corresponding Zn/P-MCM-x displayed the higher catalytic performance than that of Zn/MCM-41 catalyst, especially for the Zn/P-MCM-12 catalyst with about 88% C2H2 conversion and 85% selectivity, and the optimal content of PEI is 12 wt%. More importantly, the introduction of PEI enhanced metal-support interaction to make the better metal dispersion and more active sites, and the charge transfer from N atom to Zn species. These all would be responsible for the high activity of the modified Zn catalysts in the acetylene hydration.

Promotion Effect of SiO2 on the Catalytic Performance of Ni/CF for Biomass Derived Gas Reforming

A series of nickel-based carbon fiber prepared via ultrasonic-assisted impregnation method, were applied for biomass derived gas (CH4 and CO2) reforming. Results illustrated that parts of the carriers were consumed by CO2, followed by the deactivation of catalysts. In order to improve the catalytic activity and stability of the catalyst, a certain amount of silica was introduced into the 15%Ni/CF by hydrothermal synthesis method. The results demonstrated that the presence of silica species plays positive roles by inhibiting the reaction of carbon fiber and improving the metal support interaction. Additionally, hydrogen temperature-programmed reduction (H2-TPR), carbon dioxide temperature-programmed surface reaction (CO2-TPSR), scanning electron microscope (SEM) and X-ray diffraction (XRD) were used to characterize the morphology of the catalysts for the sake of illustrating the promotion mechanism of silica. At last, a process of carbon dioxide reforming methane on the Ni/SiO2–CF catalyst was proposed.

Palladium supported on low-surface-area fiber-based materials for catalytic oxidation of volatile organic compounds

Fiber-based palladium catalysts were synthesized via an ultrasonic-assisted impregnation method on ceramic and glass fiber supports pretreated by leaching with water, sulfuric acid and nitric acid, respectively. The as-prepared catalysts were next tested for the catalytic combustion of benzene. The Pd-Ceramic fiber exhibited better activity than Pd-glass fiber in terms of benzene conversion and carbon dioxide yield, and 0.8 wt% Pd loading was the optimum loading amount. The prepared catalysts were characterized by FE-SEM, BET, XRD, XPS, TEM, in situ DRIFTS and TPD. The results indicated that a relatively large surface area, strong support acidity, well-dispersed Pd particles, and suitable redox and desorption properties all contributed to the good performance of ceramic-fiber-based catalysts. Our findings demonstrate that the Pd-Ceramic fiber catalyst is an effective candidate for application in elimination of volatile organic compounds.