Ultrasonic-assisted Impregnation Research Articles

Application of ultrasound-assisted cryoprotectant impregnation for improving the storage quality of snakehead fish fillets.

In aquatic products companies, saccharides and phosphates are often used to impregnate products to improve their quality. Insignificant impregnation effect is a main problem met in the impregnation process. The effect of ultrasonic-assisted impregnation on the storage quality of snakehead fish fillets at -18 °C was studied. For all samples, such parameters as water holding capacity, pH value, salt-soluble protein content, whiteness and cooking loss rate were examined periodically. Furthermore, the changes of moisture distribution and migration in snakehead fish fillets during storage were investigated using low-field nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI). The results demonstrated that ultrasonic-assisted impregnation showed better anti-freeze and water holding capacity effects than that of cryoprotectant impregnation alone. Therefore, ultrasonic treatment could be used as an effective way to improve the quality of snakehead fish fillets during the frozen process. This study could provide a broad application prospect in aquatic product processing industry.

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.

Ultrasound-Assisted Synthesis of Nonmetal-Doped Titanium Dioxide Photocatalysts for Simultaneous H2 Production and Chemical Oxygen Demand Removal from Industrial Wastewater.

A series of nonmetal-doped titanium dioxide (Nmx/TiO2, where x is the weight fraction of nonmetal elements) photocatalysts was prepared via ultrasonic-assisted impregnation for simultaneous hydrogen (H2) production and chemical oxygen demand (COD) removal from industrial wastewater. Three types of Nm elements, carbon (C), silicon (Si), and phosphorus (P), were explored. The P1/TiO2 exhibited a higher photocatalytic activity for H2 production and COD removal than the C1/TiO2 and Si1/TiO2 photocatalysts. Approximately 6.43 mmol/g photocatalyst of H2 was produced, and around 26% COD removal was achieved at a P1/TiO2 loading of 4.0 g/L, a light intensity of 5.93 mW/cm2, and a radiation time of 4 h. This is because the P1/TiO2 photocatalyst exhibited lower point of zero charge values and a more appropriate band position compared with other Nmx/TiO2 photocatalysts to produce H+, which can consequently form H2, and reactive oxygen species (HO· and O2·–), which serve as oxidizing agents to degrade the organic pollutants. Increasing the content of the P element doped into the TiO2-based material up to 7.0% by weight enhanced the H2 production and COD removal up to 8.34 mmol/g photocatalyst and 50.6%, respectively. This is attributed to the combined effect of the point of zero charge value and the SBET of the prepared photocatalysts. The photocatalytic activity of the P7/TiO2 photocatalyst was still higher than the TiO2-based material after the fourth use.

Surface modification of g-C3N4-supported iron catalysts for CO hydrogenation: Strategy for product distribution

Surface modified g-C3N4 supported iron catalysts were prepared using ultrasonic-assisted impregnation and employed as model catalysts to investigate the surface modification effects on product distribution in Fischer–Tropsch synthesis. Characterizations evidenced that both hydroxyl and amino groups were grafted on the g-C3N4 surface. Results showed that the selectivity of light olefins in hydrocarbons was increased from 12.3% on pure Fe3O4 to 31.5% on Fe/C3N4 further to 38.4% on Fe/AMC3N4 under same reaction condition as well as elevated activity owing to electron transfer of amino groups. But high CO2 selectivity was inevitable via the enhanced water gas shift reaction. H2O2 treatment increased the hydrophilicity of g-C3N4, resulting in predominance of water-assisted pathway promoted the chain growth. Compared with Fe/C3N4, the CH4 selectivity for Fe/OHC3N4 was significantly reduced from 38.4% to 22.8%. The Fe/OHC3N4 also exhibited lower CO2 selectivity of 11.4% than Fe/AMC3N4 of 24% due to the enrichment of surface hydroxyl. Surface modification played a critical role in tuning the product distribution and promoting the formation of light olefins with low C1 by products (CH4 and CO2).

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.

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.

Tailored activity of Ce–Ni bimetallic modified V2O5/TiO2 catalyst for NH3-SCR with promising wide temperature window

A series of vanadium-based catalysts with different doping amounts of cerium and nickel were prepared by ultrasonic-assisted impregnation. Their catalytic activities were investigated for the selective catalytic reduction of NO with NH3 as the reducing agent (NH3-SCR). XRD, N2 adsorption-desorption, XPS, NH3-TPD, H2-TPR, SEM and HR-TEM were used to probe the physicochemical properties of the catalysts. The characterization results showed that nickel or cerium doping could increase the specific surface area and the concentration of weak acid sites, improve the catalytic activity, and extend the temperature window to some degree. Cerium and nickel co-modification catalyst possesses higher redox ability, and the element is highly dispersed. Besides, the Oα/(Oα+Oβ) ratio and Ce3+/(Ce3++Ce4+) ratio are higher over the co-modification catalyst, and cerium is more active than the redox site of V and plays an essential role in NH3-SCR at low temperatures. In addition, 3.75 V–7Ce-0.1Ni/TiO2 catalyst shows the widest temperature window (200°C–400 °C) and the best catalytic activity (above 90%), and reaches the maximum of 100% at 300 °C.

Investigation on hybrid nanofluids based on carbon nanotubes filled with metal nanoparticles: Stability, thermal conductivity, and viscosity

In recent years, nanofluids as heat transfer fluids have shown huge potential in heat exchange systems. However it is still needed to discover new types of nanofluids with excellent thermal conductivity, dispersion stability and low viscosity to expand its applications. In the present work metal nanoparticles (copper or silver)-filled carbon nanotubes (Cu@CNT, Ag@CNT) have been synthesized by a simple ultrasonic-assisted impregnation combined with chemical reduction. The morphology, phase structure, and degree of crystallization of the prepared nanocomposites have been characterized in detail. Two kinds of nanofluids, including water-based and ethylene glycol-based, have been prepared employing the nanocomposites without adding any surfactant. The dispersion stability, thermal conductivity, and viscosity of the hybrid nanofluids with different mass fraction are studied systematically. The results show that the hybrid nanofluids process good dispersion stability and high thermal conductivity. No obvious delamination can be observed in all nanofluids (0.01–0.05 wt%) after standing for 6 months. The maximum enhancement in thermal conductivity for water-based and ethylene glycol-based Ag@CNT nanofluids with mass fraction of 0.05 wt% reach 52.37% and 40.42% respectively at 65 °C, compared to the base fluid. And the Cu@CNT and Ag@CNT hybrid nanofluids exhibit higher thermal conductivity and lower viscosity than functionalized CNT nanofluids. These results indicate that the metal nanoparticles-filled CNTs composites can be used to improve the thermal conductivity of nanofluids and promote the development of new thermal conductive agents.

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.

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.

Preparation and evaluation of highly dispersed HHSS supported Cu-Fe bimetallic catalysts for higher alcohols synthesis from syngas

Porous carriers play an important role in the catalytic transformation of syngas into higher alcohols, which promises higher sustainability in C1 chemistry. In this work, a series of hierarchical hollow silica spheres (HHSS) supported Cu-Fe bimetal catalysts were successfully prepared through ultrasonic-assisted impregnation for higher alcohols synthesis from syngas. Structural characterization results indicate that the hierarchical hollow structure of HHSS support can be maintained and the Cu-Fe bimetallic nanoparticles are highly dispersed on HHSS surface. The catalytic performances of samples in the test of CO hydrogenation for higher alcohols synthesis were investigated. The results revealed that the conversion rate of CO and the selectivity of C2+OH alcohol increased first and then decreased with the decrease of the amount of Cu content in the CuxFey@HHSS catalyst. The highest CO conversion, alcohol selectivity and STYROH over Cu-Fe@HHSS catalyst are 65.1 %, 46.6 %, and 118.1 gkg−1 h−1, respectively. It was found that a large number of CuFe2O4 were formed in Cu-Fe@HHSS catalyst and also confirmed that the CuFe2O4 spinel and CuO-CuFe2O4 were converted to Cu-Fe5C2 composite in the spent Cu-Fe@HHSS catalyst, which can enhance the synergy between Cu-Fe bimetals. Furthermore, copper and iron are highly dispersed on HHSS after the reaction, which enhances the structural stability of the catalyst. Based on the development and utilization of low-cost catalysts and the production of clean liquid fuels, HHSS has a great prospect of catalyst support in the energy field.

Effect of Na+ on catalytic performance of CoCe/ZSM-5 catalysts for oxidation of toluene

A CoCe/ZSM-5 catalyst was prepared by ultrasonic-assisted impregnation for the catalytic combustion of toluene. To study the effect of Na+ on catalytic performance of CoCe/ZSM-5 catalysts, a series of different Si/Al ZSM-5 zeolites and catalysts doped with Na were synthesized. The experimental results show that 0.71 wt% Na+ can inhibit active growth, generate more active small crystal grains, and promote improvement of the catalytic activity by the grain boundary segregation block mechanism, and the catalyst with 0.71 wt% of Na shows toluene conversion of 90 vol% at 250 °C. Over 0.71 wt% of Na+ content will neutralize the acid centre of the catalyst, lowering the specific surface area of the catalyst and resulting in a gradual decrease in the catalytic activity.

Effects of magnesium loading on ammonia capacity and thermal stability of activated carbons

Mg-loaded activated carbons were prepared by adding various amounts of Mg (1 to 20 wt%) via ultrasonic-assisted impregnation to investigate the effects on the adsorption and desorption characteristics of ammonia. Mg-loaded activated carbons were characterized by TGA, BET, SEM, EDS mapping, and NH3-TPD analysis. Mg was homogeneously dispersed on the activated carbon and NH3-TPD analysis confirmed improved desorption and thermal stability for the 10 wt% Mg sample, named AC-Mg(10). AC-Mg(10) retained the highest desorption for five cycles and showed average desorption amount of 0.788 mmol NH3/g. During the breakthrough analysis, the AC-Mg(10) showed an initial ammonia adsorption capacity of 0.81 mmol NH3/g and average adsorption capacity of 0.69 mmol NH3/g over 30 adsorption and desorption cycles.

Induced high selectivity methanol formation during CO2 hydrogenation over a CuBr2-modified CuZnZr catalyst

Developing catalysts with high activity and high selectivity toward methanol, and elucidating the structure-activity relationship, are important in the area of CO2 hydrogenation. Herein, a simple ultrasonic-assisted impregnation modification method, which modifies a CuZnZr catalyst for methanol synthesis from CO2, is reported. The results show high methanol selectivity (97.1%) and a CO2 conversion of 10.7%, in the presence of the catalyst modified with CuBr2 (CuZnZr/CuBr2). Furthermore, detailed investigations of the structure-activity relationship demonstrate that the CuBr2 modification influences both the catalyst surface properties and catalyst morphology. In particular, residual Br, as a CuBr phase, is stabilized on the catalyst surface and is able to significantly passivate the reverse water-gas shift activity on the Cu surface; therefore, CO formation on the Cu surface is almost completely suppressed. The catalytic evaluation and IR data support the formate pathway mechanism in the presence of the CuZnZr/CuBr2 catalyst to synthesize methanol from CO2.

Pd/SAPO-41 Bifunctional Catalysts with Enhanced Pd Dispersion Prepared by Ultrasonic-Assisted Impregnation: High Selectivity for n-Hexadecane Hydroisomerization

The preparation of bifunctional catalysts with high catalytic selectivity for the n-alkanes hydroisomerization still remains challenging for the production of bio-diesel. Herein, two series of Pd/SAPO-41 bifunctional catalysts are prepared by the ultrasonic-assisted impregnation (xPd/S41-U) with different treating time and conventional incipient wetness impregnation methods (0.30Pd/S41-I) on the SAPO-41 molecular sieve, respectively. The physico-chemical property of the synthesized SAPO-41 and prepared catalysts were studied by XRD, SEM, ICP, N2 physical adsorption, H2 chemisorption and Py-IR measurements. The catalytic performance for the n-hexadecane hydroisomerization over all catalysts is also studied. The characteristic results indicate that the xPd/S41-U catalysts show stronger Bronsted acidity compared with the 0.30Pd/S41-I catalyst. In addition, the Pd dispersion of the xPd/S41-U catalysts is almost two times higher than that of the 0.30Pd/S41-I catalyst, which leads more Pd cluster to enter into the micropores of the SAPO-41 molecular sieve. Furthermore, the 0.30Pd/S41-U catalyst with 0.30 wt % Pd loading shows promoted catalytic performance than that of the 0.30Pd/S41-I catalyst with the same Pd loading because of the stronger metal function and more favourable metal-acid balance caused by the larger CPd/CH+ ratio. Therefore, the ultrasonic-assisted impregnation prepared Pd/SAPO-41 catalysts are potential to be widely employed for the n-alkane hydroisomerization.

Ultrasonic-assisted preparation of highly active Co3O4/MCM-41 adsorbent and its desulfurization performance for low H2S concentration gas.

Co3O4/MCM-41 adsorbents were successfully prepared by ultrasonic assisted impregnation (UAI) and traditional mechanical stirring impregnation (TMI) technologies and characterized by X-ray diffraction (XRD), N2 adsorption desorption, Fourier transform infrared spectra (FT-IR), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and thermogravimetry-differential thermal analysis (TG-DTA). The H2S removal performances for a simulated low H2S concentration gas were investigated in a fixed-bed. The effect of preparation and adsorption conditions on the H2S removal over Co3O4/MCM-41 were systematically examined. The results showed that UAI promotes more and well defined highly dispersed active Co3O4 phase on MCM-41. As compared to the Co3O4/MCM-41-T prepared via TMI, the saturated H2S capacity of Co3O4/MCM-41-U prepared via UAI improved by 33.2%. The desulfurization performance of adsorbents decreased in the order of Co3O4/MCM-41-U > Co3O4/MCM-41-T > MCM-41. The Co3O4/MCM-41-U prepared using Co(NO3)2 concentration of 10%, ultrasonic time of 2 h, calcination temperature of 550 °C and calcination time of 3 h exhibited the best H2S removal efficiency. At adsorption temperature of 25 °C with model gas flowrate of 20 mL min−1, the breakthrough time of Co3O4/MCM-41-U was 10 min, and the saturated H2S capacity and H2S removal rate was 52.6 mg g−1 and 47.8%, respectively.

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.