Research on Chemical Intermediates最新文献

This work reports the preparation, characterization, and application of silver salt derivatives of HPW (Ag_xHPW) in ethanol dehydration. The materials were fully characterized by elemental EDXRF analysis, XRD, SAXS, SEM, FT-IR, ³¹P MAS NMR, thermal analysis (TG/DTG), N₂ sorption at low temperature (− 196 °C), and pyridine adsorption acidity. The results of the characterization demonstrated that the Keggin structure was preserved in all the synthesized materials. Using the ethanol dehydration model reaction, it was possible to select the most active catalyst in the series: Ag₂HPW. Activation of this salt at 200 and 300 °C revealed that the degree of hydration is an important parameter for catalytic activity. In addition, a dependence on the BET specific surface area was detected for both conversion and selectivity towards ethylene in the salt series. The conversion of ethanol was significantly enhanced after loading 20 wt.% of Ag₂HPW onto ordered mesoporous silica type SBA-15. The reaction conditions were optimized, and the best catalyst (20%Ag₂HPW/SBA-15, calcined at 300 °C) achieved complete ethanol conversion with about 100% selectivity towards ethylene at a temperature of 400 °C.

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This research explored the process of acetone steam reforming using Ni/Al₂O₃ catalysts. Different contents of nickel, ranging from 5 to 20% by weight, were applied to a commercial alumina support with a surface area of 158 m²/g. It was observed that increasing the nickel concentration from 5 to 20% resulted in a reduction of the catalyst's specific surface area from 146 to 127 m²/g, alongside an increase in the crystallite size from 4.9 to 6 nm. The amount of nickel was found to significantly influence the catalyst's performance, its durability, and the formation of carbon deposits on its surface. The catalyst containing 20% weight of nickel on alumina, achieving an 86% rate of acetone conversion and a 74% yield of hydrogen at a temperature of 550 °C, was identified as the most effective. Experiments to determine optimal processing conditions were conducted with this catalyst, varying the temperatures of reduction and calcination, gas hourly space velocity (GHSV), and the steam-to-acetone ratio. The calcination temperature was varied at 600, 700, and 800 °C, revealing that calcination at 600 °C provided the best acetone conversion rate of 100% at 550 °C, correlating with a decrease in specific surface area as calcination temperature increased. Reduction temperatures tested were 500, 600, and 700 °C for a duration of 2 h, where the sample reduced at 700 °C exhibited superior performance with an 86% conversion rate of acetone at 550°C. Evaluating the catalyst's efficacy at steam-to-carbon molar ratios of 4, 6, and 8 demonstrated the highest efficiency at a ratio of 8, achieving complete conversion at 550 °C. Moreover, catalyst activity was tested at GHSVs of 12,000, 18,000, and 24,000 (ml/h.g_cat), finding the highest conversion rate of 90% at the lowest GHSV of 12,000 at 550 °C.

Photocatalytic technology has received widespread attention as an effective means of treating organic pollutants in wastewater, but the development of effective and sustainable photocatalysts remains a serious challenge. In this study, a novel Mn_0.2Cd_0.8S (MCS)/Bi₄O₅Br₂ (BOB) heterojunction photocatalyst was successfully prepared by a two-step solvothermal method. The photocatalytic activity of the MCS/BOB heterojunction photocatalyst for degrading Rhodamine B (RhB) is significantly enhanced relative to Mn_0.2Cd_0.8S and Bi₄O₅Br₂. When the molar content of Mn_0.2Cd_0.8S was 15% of Bi₄O₅Br₂, the prepared 15% MCS/BOB had the best photocatalytic performance toward RhB with the degradation rate of 91.7% under 60 min of visible light irradiation. The apparent rate constant of 15% MCS/BOB is 10 and 7 times higher than that of Mn_0.2Cd_0.8S and Bi₄O₅Br₂, respectively. The excellent photocatalytic performance is associated with the increased specific surface area, extended light absorption range, and proper construction of Z-scheme heterojunction that facilitate effective charge separation and excellent redox capacity. In addition, the heterojunction photocatalyst shows remarkable photocatalytic stability. This study constructs a novel and effective Z-scheme heterojunction photocatalyst and promotes the exploration of photocatalyst in the purification of organic wastewater.

This research evaluates the use of metal nanoparticles, produced from the pyrolysis of metal–organic frameworks, as catalysts for breaking down organic pollutants. The study specifically examines CoC and CoC/Zn nano-catalysts, which were synthesized, characterized, and tested against pollutants like p-nitrophenol (PNP) and methyl orange (MO) using sodium borohydride. SEM analysis showed that the nanoparticles ranged in size from 50 to 200 nm, while TEM revealed smaller sizes from 20 to 100 nm. EDX analysis confirmed zinc’s presence in CoC/Zn, and XPS analysis detected various elements, including C, N, O, Cl, Co, and Zn in CoC/Zn, with the absence of Zn and presence of K in CoC. Additional tests like EDAX and XRD confirmed the presence of Co and Zn in the samples. During the pyrolysis, graphite was formed, as indicated by Raman spectroscopy. BET analysis showed that Co/C had a surface area of 100 m²/g, which was significantly higher than CoC/Zn, attributed to the use of K₂EDTA during Co/C’s synthesis. In degradation tests, CoC outperformed CoC/Zn, with first-order rate constants of 0.128 min⁻¹ for PNP and 0.425 min⁻¹ for MO, showing higher catalytic efficiency and durability—lasting 18 cycles for PNP and 34 cycles for MO. Although CoC/Zn had lower performance, it was noted for its efficiency. In terms of energy storage, CoC/Zn and CoC displayed specific capacitance values of 470 F/g and 560 F/g, respectively, and showed high durability by retaining about 93.46% of their original capacitance after 2300 cycles. These findings underscore the potential of CoC as an effective, durable catalyst for environmental cleanup and both materials as viable, cost-effective options for energy storage.

The use of bifunctional catalysts, combining methanol synthesis and zeolite components, has been cleverly expanding to the hydrogenation of CO₂ into liquefied petroleum gas (LPG). However, such catalysts in this reaction displayed low catalytic efficiency due to the mismatch of the two components. In this study, an efficient strategy was realized via physically coating β zeolite onto the CuZnAl methanol catalyst, resulting in a shell thickness controllable core–shell encapsulated catalyst, denoted as CuZnAl@β. Sufficient characterization proves that the micro-coupling structure between methanol active sites and zeolite acid sites is designed reasonably and successfully, as consequently, the zeolite capsule catalysts embody a significant improvement toward LPG selectivity. Hence, the CuZnAl@β catalyst reached a high selectivity to LPG at 77.9% with 21.3% CO₂ conversion, under a reaction pressure of 2.0 MPa and a temperature of 320 °C. The strategy employed in this study could offer valuable insights into guiding catalyst design.

Catalyst deactivation due to coke formation is a key issue in dimethyl ether to gasoline (DTG) process, and it is significant to investigate the change of catalyst properties during reaction to inhibit the rapid deactivation of catalyst. Here, the nanocrystalline H[Fe,Al]ZSM-5 zeolite synthesized hydrothermally was evaluated as catalyst for DTG process in different reaction time. The detailed characterizations of fresh and spent catalysts were carried out, such as UV-Vis, XRD, SEM, N₂ adsorption-desorption and NH₃-TPD, and the coke formation and its location in catalyst were studied. The results indicated that DTG reaction mainly occurred at strong acid sites of nanocrystalline H[Fe,Al]ZSM-5, and Brønsted acid sites were the most active. Furthermore, the catalysts even with small amount of B acid still possessed the higher catalytic activity during stable period of DTG reaction. The coke deposition was produced in DTG reaction, and at the initial stage, coke precursors including alkylbenzenes retained inside the micropores. These precursors grow gradually to form polycyclic aromatic hydrocarbons, which overflow on the outer surface with increasing reaction time, and then mainly accumulates on the external surface of catalyst. The coke occludes the active sites and hampers the molecular diffusion, eventually causing activity loss. The catalyst deactivation was mainly caused by the blockage of micropores and coverage of B acid sites due to coke deposition. And the deactivated catalysts could be oxidized and regenerated in air at 550–650 °C.

A novel nanomaterial namely Si-propyl-functionalized 4,4′-bipyridine-1,1ʹ-diium bisulfate tetrachloroferrate anchored to rice husk-derived nano-silica (PBBTRS) was fabricated, and analyses involving EDS (energy-dispersive X-ray spectroscopy), elemental mapping, FE-SEM (field emission scanning electron microscopy), XRD (X-ray diffraction), FT-IR, Raman and inductively coupled plasma-optical emission spectroscopy (ICP-OES) were utilized to corroborate its structure. Thereafter, PBBTRS was applied as a highly efficacious, recoverable and dual-functional catalyst for the construction of N,N′-alkylidene bisamides from aryl aldehydes and primary amides under solvent-free conditions. A valuable improvement in this methodology is performing the reaction under mild conditions (60 °C).

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Reverse micellar templated nickel carbonate nanospheres are employed to prepare a double-phase inversion Pickering emulsion. Nickel carbonate nanospheres are synthesized within the core of reverse micelles, composed of Span 80/1-butanol/toluene/water. The evaluation of nanospheres within the core of reverse micelles was conducted using TEM and FESEM instrumentations. Micromorphological analysis of the results indicated a two-phase formation process for the nanospheres: nucleation phase (5–15 min) followed by a growth phase (15–60 min). At neutral pH (⁓ 6.16), the synthesized nanospheres are positively charged (+ 5.342 mV). Due to their extreme hydrophilic properties, they alone cannot provide the desired stability to O/W Pickering emulsions. With the assistance of negatively charged head groups, anionic surfactants like SDS and nickel carbonate nanospheres are involved in in situ hydrophobization through the electrostatic adsorption of surfactant molecules onto their surfaces. It eventually provides stability to the toluene–water Pickering emulsions, and an intriguing double-phase inversion is detected. The first-phase inversion (O/W to W/O) occurred due to the increased hydrophobicity of modified nickel carbonate nanospheres where SDS (≤ 7 mM) molecules formed a monolayer on the nickel carbonate surface. The second-phase inversion (W/O to O/W) is detected due to the bilayer adsorption (through tail-to-tail interaction) of SDS (> 7 mM) on nickel carbonate nanospheres, thereby converting the hydrophobic nickel carbonate nanocomposites to hydrophilic again. Consequently, the wettability of nickel carbonate-SDS nanocomposites can shift from hydrophilic to hydrophobic and back again to hydrophilic, triggering the evaluation of double-phase inversion Pickering emulsions.

The simple extrusion method used to combine metakaolin (MK) with aminoethyl-3-aminopropyltriethoxysilane (AEAPTES) to create composite (MK/AEAPTES) is described in this article. Owing to amine group inherent on MK, it exhibited a basic nature. The novel basic catalyst is used for the synthesis of pyrazolyl phosphonates by Michael-addition reaction. Significant product yields, environmental friendliness, rapid reaction durations, broad range of substrate compatibility, and lack of hazardous solvent requirement make these reactions remarkable. Furthermore, there is no appreciable decrease in activity subsequently five recycles of the catalyst and catalyst separation using a straightforward filtration technique without any extraction. The synthesized derivatives were characterized by ¹H, ¹³C NMR, and ³¹P NMR & FT-IR analysis. Synthesized composite is analyzed by FT-IR, XRD, and SEM–EDX, investigation is compared with MK. The recycled catalyst is also checked by FT-IR, XRD, and SEM–EDX analysis.

Enhancing photocatalytic selectivity is essential for the effective and efficient utilization of catalysts. In this study, a molecularly imprinted polymer POPD/Bi₂O₃/CeO₂, designated as MIP-POPD/Bi₂O₃/CeO₂, was successfully synthesized via photopolymerization using pyridine as a template. The resulting MIP-POPD/Bi₂O₃/CeO₂ was characterized through Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, N₂ adsorption–desorption isotherms, and UV–vis diffuse reflectance spectroscopy. MIP-POPD/Bi₂O₃/CeO₂ exhibited enhanced charge transfer and efficient separation of photogenerated carriers, as confirmed by photoluminescence measurements, electrochemical impedance spectroscopy analysis, and photocurrent response (I–t) curve evaluations. When the concentration of pyridine in simulated oil reached 80 µg/g, with an amount of 1.6 g/L for MIP-POPD/Bi₂O₃/CeO₂ and an illumination time of 120 min, the degradation rate of pyridine achieved 80%, which is 1.57 times greater than that observed using NMIP-POPD/Bi₂O₃/CeO₂. After an adsorption for 30 min, MIP-POPD/Bi₂O₃/CeO₂ exhibited the adsorption capacity of 5 mg/g, attributed to the large number of molecularly imprinted pores on its surface. In various mixed systems, the selectivity coefficients for pyridine using MIP-POPD/Bi₂O₃/CeO₂ consistently exceeded 1.5, which can be attributed to the selective adsorption properties of the imprinted pores within the polymers that preferentially recognize and remove pyridine. Furthermore, after five cycles, the photocatalytic degradation rate of pyridine by MIP-POPD/Bi₂O₃/CeO₂ can still reach 77%, indicating that MIP-POPD/Bi₂O₃/CeO₂ possesses good stability. Trapping experiments demonstrated that superoxide radicals (·O₂⁻) and holes (h⁺) were the predominant active species in photocatalytic reactions. Additionally, a proposed mechanism for photocatalytic denitrification utilizing MIP-POPD/Bi₂O₃/CeO₂ was presented. This study provides a promising strategy for designing Bi-based molecular imprinting photocatalysts aimed at efficiently removing low-concentration, highly toxic target pollutants from mixed samples.