Construction of Cu-BTC by carboxylic acid organic ligand and its application in low temperature SCR denitration

Efficient adsorption desulfurization via encapsulation of CeO2 nanoparticles in hierarchical porous HKUST-1

Thiophene-like sulfides present in fuel oil release sulfur oxides (SOx) during combustion, which pose significant risks for both environmental sustainability and public health. Adsorption desulfurization (ADS) has garnered considerable attention because of its mild operating conditions, low production costs, and minimal impact on the octane number of fuels. Metal-organic frameworks used as desulfurizing adsorbents provide several advantages, including a high specific surface area and easily adjustable structures. Here, we synthesized the micro/mesoporous adsorbent CeO2@HP-HKUST-1 (CeO2@Hierarchical Porous-Hong Kong University of Science and Technology-1) through the hybridization of salicylic acid (SA) using a solvothermal method. We assessed the adsorption performance ofCeO2@HP- HKUST-1_1.5for benzothiophene and thiophene through batch and breakthrough adsorption experiments. The adsorption capacities for thiophene and benzothiophene were measured at 21.2 mg S/g and 35.3 mg S/g, respectively. Remarkably, in competitive toluene experiments, the adsorption capacity for benzothiophene remained significant at 28.9 mg S/g, due to enhanced Ce-S bonding interactions and the exposure of unsaturated metal centers of Cu. Additionally, regeneration experiments demonstrated that CeO2@HP-HKUST-1 retained excellent adsorption capacities after four cycles. These findings highlight the potential of CeO2@HP-HKUST-1 as an effective adsorbent for desulfurization applications.

Characterization and evaluation of the adsorption of uremic toxins through the pyrolysis of pineapple leaves and peels and by forming a bio-complex with sodium alginate

This study was performed to develop an optimal process for manufacturing activated carbon (AC) from pineapples' off-cuts (leaves and peels; PL and PP) by pyrolysis and for forming a bio-complex with sodium alginate (CA). In addition, the physicochemical properties were also explored under different preparation conditions, and the effects of adsorbed uremic toxins in three simulated gastrointestinal conditions (in vitro) were evaluated. This study showed that pyrolysis at 800 °C and activation by CO2 (30 min) resulted in satisfactory porous profiles with high specific surface areas of 388.79 and 536.84 m2/g for PLAC and PPAC, respectively. Regarding appearance and microstructures, there are still discernible disparities compared to the AST in regular service, while it exhibits a similar peak shape to that of the AC under the Raman spectrometer. Remarkably, the adsorption capacity of PLAC and PPAC for uremic toxins was best for indole adsorption while providing a consistent effect with AST. Indole-3-acetic acid (3-IAA) and p-cresol (p-C) adsorption capacities were the second highest. Nevertheless, AST also exhibited varying degrees of reduced adsorption capacity under different gastrointestinal simulation conditions. Therefore, this study conditions the development of cost-effective adsorbent products targeting uremic toxins, which could generate novel synergistic systems based on pineapple by-products within the circular economy framework.

Solar radiation-promoted selective photocatalytic degradation of Congo red dye by a novel amorphous Cr-based metal-organic framework serving as sensor for 2,4,6-trinitrophenol explosive detection

Synthesis of novel benzene-1,2,4-tricarboxylic acid-based chromium metal-organic framework (designated as Cr-BTC MOF) by solvothermal method using water:ethanol:dimethylformamide (1:1:2) as solvent media has been undertaken with an aim to exploit its role as photocatalyst in degradation of some anionic dyes along with sensing potential of some explosives. The MOF has been characterized by Fourier transform infra-red, scanning electron microscopy, Brunauer-Emmett Teller and powder X-Ray diffraction techniques and has shown high thermal stability, upto 373 °C. The prepared MOF was utilized as photocatalyst in selective degradation of Congo red (CR) dye. The effects of pH, source of radiation, initiator and concentration of catalyst were monitored and the results have shown that catalyst exhibits maximum efficiency of 93.3% in the presence of sunlight in neutral medium. The stability and reusability of the catalyst, after four cycles of reusability, renders it to be a highly efficient photocatalyst in the treatment of wastewater under the effect of sunlight. Photoluminescence-detection of explosives viz. 2,4,6-trinitrophenol and nitromethane, has been carried out, wherein Stern-Volmer equation was used to assess the quenching efficiency evaluated. The results have shown exceptional efficiency and selectivity of Cr-BTC MOF towards detection of 2,4,6-trinitrophenol (94%). The reusability has shown the synthesized MOF to display excellent recyclability upto 5 cycles. Minimum inhibitory concentration (MIC) method was investigated to establish their antibacterial efficacy against some Gram-positive and Gram-negative strains. The MOF has showed good efficacy towards Bacillus cereus and Staphylococcus aureus, displaying a MIC value of 7.81 µg/mL, and Pseudomonas aeruginosa (15.625 µg/mL) similar to the standard antibacterial drug, chloramphenicol, thereby establishing their biological efficacy.

Developing colorimetric ammonia-sensing nanocomposite films based on potato starch/PVA and ZnCu-BTC nanorods for real-time monitoring food freshness

Smart packaging material capable of real-time monitoring of food freshness is essential for ensuring food safe. At present, colorimetric ammonia-sensing smart film often possesses issues with complicated production, high cost, and inferior long-term colour stability. Herein, Zinc‑copper bimetallic organic framework (ZnCu-BTC, BTC = 1,3,5-benzenetricarboxylate acid) nanorods with colorimetric ammonia-responsiveness were synthesized by adopting facile aqueous solution method, which were then explored as nano inclusions in potato starch/polyvinyl alcohol (PS/PVA) composite film towards developing high-performance smart packaging material. The results demonstrated that the introduction of ZnCu-BTC nanorods within PS/PVA brought about remarkable improvement in blend compatibility, accompanied by a boost in tensile strength to 47.2 MPa, as well as enhanced ultraviolet (UV) blocking efficacy (over 95.0 %). Additionally, the barrier properties of PS/PVA film against water vapor and oxygen were fortified due to the addition of ZnCu-BTC. More importantly, the developed PS/PVA/ZnCu-BTC nanocomposite film displayed satisfactory antibacterial activity (over 99 %) against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), favorable colorimetric ammonia-sensing ability, and long-term colour stability. The ZnCu-BTC incorporated PS/PVA nanocomposite film could grant real-time detection of prawn freshness decline via remarkable colour change, indicating vast promise for smart food packaging applications.

Copper/Nickel/Cobalt modified molybdenum-tungsten-titanium dioxide-based catalysts for multi-pollution control of nitrogen oxide, benzene, and toluene: Enhanced redox capacity and mechanism study

Previous studies have indicated the potential of monometallic-modified TiO2 catalysts in controlling nitrogen oxide (NOx) and volatile organic compounds (VOCs) in coal-fired flue gas. Unfortunately, increasing selective catalytic reduction (SCR) activity under complicated coal-fired flue gas status is tricky. In this study, modified Co-MoWTiO2 catalysts with multiple active sites were synthesized using the wet impregnation method, which exhibited excellent multi-pollution control ability of NO, benzene and toluene under low oxygen and high SO2 concentrations. The modification of Mo and Co achieved high dispersion and electron transfer. The interaction between W5+/W6+ and Co2+/Co3+ promoted gas-phase O2 adsorption on the catalyst surface, forming of reactive oxygen species (Oα). Density functional theory (DFT) calculations informed that the doping of Co effectively enhanced the NH3 and O2 adsorption capacity of the catalyst, and Co possessed the maximum adsorption energy for NH3 and O2. Possible pathways of multi-pollution control of NO, C6H6, and C7H8 were speculated. NH3/NH4+ on the Lewis/Bronsted acid site is reacted with intermediates of NO (e.g., NO2, nitrite, nitrate) via the Langmuir-Hinshelwood and Eley-Rideal mechanism. The introduction of NO and NH3 did not disrupt the oxidation pathways of benzene and toluene. Following the Mars-van Krevelen mechanism, C6H6 and C7H8 were progressively mineralized by Oα into CO2 and H2O.

Infrared Spectrum and Principal Component Analysis of Heavy Tar Cut by Different Fractions from Tar-Rich Coal

The composition and content of heavy tar vary significantly depending on the pyrolysis conditions and separation methods. This study aimed to effectively identify the main components and content of heavy coal tar and provide a theoretical basis for its subsequent utilization. To achieve this, simulated distillation and infrared spectrum analysis of heavy coal tar were conducted with a focus on understanding the impact of simulated distillation on the composition and structure of tar. The results showed that the fraction content in the tar underwent significant changes after simulated distillation at different temperatures. Specifically, the content of light oil decreased from 4.3 to 0.1%, while the asphalt content increased from 77.6 to 90.6%. Infrared spectrum and peak fitting revealed that the distilled coal tars exhibited similar characteristic peaks in regions associated with hydroxyl, aliphatic hydrocarbon, oxygen-containing functional group, and aromatic hydrocarbon structure. Based on the infrared spectrum of heavy coal tar, principal component analysis was conducted on different fractions. When using two principal components, the cumulative value reached 96.93%. It was found that PC1 displayed strong peak signals around 749 and 687 cm-1, while PC2 exhibited strong peak signals near 2356 and 1143 cm-1.

Purification of Quinoline Insolubles in Heavy Coal Tar and Preparation of Meso-Carbon Microbeads by Catalytic Polycondensation

The quinoline-insoluble (QI) matter in coal tar and coal tar pitch is an important factor affecting the properties of subsequent carbon materials. In this paper, catalytic polycondensation was used to remove QI from heavy coal tar, and meso-carbon microbeads could be formed during the purification process. The results showed that AlCl3 had superior catalytic performance to CuCl2, and the content of QI and heavy components, including pitch, in the coal tar was lower after AlCl3 catalytic polycondensation. Under the condition of catalytic polycondensation (AlCl3 0.9 g, temperature 200 °C, and time 9 h), AlCl3 could reduce the QI content in heavy coal tar. The formed small particles could be filtered and removed, and good carbon materials could be obtained under the condition of catalytic polycondensation (AlCl3 0.9 g, temperature 260 °C, and time 3 h).

Multi-objective prediction for denitration systems in cement: an approach combining process analysis and bi-directional long short-term memory network

Selective Non-Catalytic Reduction (SNCR) can improve the denitration process and reduce NOx emissions by accurizing prediction of NOx concentration and ammonia escape. However, there are inevitable time delays and nonlinearity problems in the prediction of NOx emission. To reduce NOx concentration quickly in SNCR, excessive ammonia spraying often causes a large amount of ammonia to escape, resulting in secondary pollution. Therefore, it is particularly important to monitor ammonia escape. To solve the above problems, this paper proposes a framework by specifically analyzing the cement denitration process and combining a multi-objective time series bi-directional long short-term memory network (MT-BiLSTM). Among them, the model achieves multi-objective prediction of NOx emission concentration and ammonia escape simultaneously. In addition, time series containing delay information are introduced in the input layer to eliminate the influence of delay. Based on the bi-directional LSTM model, the dropout strategy is adopted to improve the generalization of the model and the Adam optimizer is applied to improve the network performance. Besides, through the multi-step prediction of NOx emission at 3 time points, the dynamic nature of the data is preserved, which provides dynamic information support for realizing the automation of denitration system. The prediction performance of the MT-BiLSTM model is experimentally validated, and the results demonstrate that it can reliably predict both NOx and ammonia escape. The model achieves more accurate and reliable results for the prediction of flue gas concentrations compared with other methods such as SVR, DTR and LSTM. Therefore, the MT-BiLSTM model provides a basis for achieving NOx emission reduction and accurate ammonia injection.

Revealing the crystal facet effect on N2O formation during the NH3-SCR over α-MnO2 catalysts

The detailed atomic-level mechanism of the effect induced by engineering the crystal facet of α-MnO₂ catalysts on N₂O formation during ammonia-selective catalytic reduction (NH₃-SCR) was ascertained by combining density functional theory (DFT) calculations and thermodynamics/kinetic analysis. The surface energies of α-MnO₂ with specific (100), (110), and (310) exposed planes were calculated, and the adsorptions of NH₃, NO, and O₂ on three surfaces were analyzed. The adsorption energies showed that NH₃ and NO molecules could be strongly adsorbed on the surface of the α-MnO₂ catalyst, while the adsorption of O₂ was weak. Moreover, the key steps in the oxidative dehydrogenation of NH₃ and the formation of NH₂NO as well as dissociation of NH₂ were studied to evaluate the catalytic ability of NH₃-SCR reaction and N₂ selectivity. The results revealed that the α-MnO₂ catalyst exposed with the (310) plane exhibited the best NH₃-SCR catalytic performance and highest N₂ selectivity, mainly due to its low energy barriers in NH₃ dehydrogenation and NH₂NO generation, and difficulty in NH₂ dissociation. This study deepens the comprehension of the facet-engineering of α-MnO₂ on inhibiting N₂O formation during the NH₃-SCR, and points out a strategy to improve their catalytic ability and N₂ selectivity for the low-temperature NH₃-SCR process.

Tuning the catalytic properties of La-Mn perovskite catalyst via variation of A- and B-sites: effect of Ce and Cu substitution on selective catalytic reduction of NO with NH3

Perovskites with flexible structures and excellent redox properties have attracted considerable attention in industry, and their denitration activities can be further improved with metal substitution. In order to investigate the effect of Ce and Cu substitution on the physicochemical properties of perovskite in NH3-SCR system, a series of La1-x Ce x Mn1-y Cu y O3 (x = 0, 0.1, y = 0, 0.05, 0.1, 0.2, 0.4) catalysts were prepared by citrate sol-gel method and employed for NO removal in the simulated flue gas, and the physical and chemical properties of the catalysts were studied using XRD, SEM, BET, XPS, DRIFT characterizations. The Ce substitution on A-site cation of LaMnO3 can improve the denitration activity of the perovskite catalyst, and La0.9Ce0.1MnO3 displays NO conversion of 86.7% at 350 °C. The characterization results indicate that the high denitration activity of La0.9Ce0.1MnO3 is mainly attributed to the larger surface area, which contributes to the adsorption of NH3 and NO. Besides, the appropriate Cu substitution on B-site cation of La0.9Ce0.1MnO3 can further improve the denitration activity of perovskite catalyst, and La0.9Ce0.1Mn0.8Cu0.2O3 displays the NO conversion of 91.8% at 350 °C. Although the specific surface area of La0.9Ce0.1Mn0.8Cu0.2O3 is lower than La0.9Ce0.1MnO3, the Cu active sites and the Ce3+ contents are more developed, making many reaction units formed on the catalyst surface and redox properties of catalyst improved. In addition, strong metal interaction (Ce4+ + Mn2+ + Cu2+ ↔ Ce3+ + Mn3+/Mn4+ + Cu+) and high concentrations of chemical adsorbed oxygen and lattice oxygen both strengthen the redox reaction on catalyst surface, thus contributing to the better denitration activity of La0.9Ce0.1Mn0.8Cu0.2O3. Therefore, appropriate cerium and copper substitution will markedly improve the denitration activity of La-Mn perovskite catalyst. We also reasonably conclude a multiple reaction mechanism during NH3-SCR denitration process basing on DRIFT results, which includes the Eley-Rideal mechanism and Langmuir-Hinshelwood mechanism.

Cu-Y2O3 Catalyst Derived from Cu2Y2O5 Perovskite for Water Gas Shift Reaction: The Effect of Reduction Temperature

Cu2Y2O5 perovskite was reduced at different temperatures under H2 atmosphere to prepare two Cu-Y2O3 catalysts. The results of the activity test indicated that the Cu-Y2O3 catalyst after H2-reduction at 500 °C (RCYO-500) exhibited the best performance in the temperature range from 100 to 180 °C for water gas shift (WGS) reaction, with a CO conversion of 57.30% and H2 production of 30.67 μmol·gcat−1·min−1 at 160 °C and a gas hourly space velocity (GHSV) of 6000 mL·gcat−1·h−1. The catalyst reduced at 320 °C (RCYO-320) performed best at the temperature range from 180 to 250 °C, which achieved 86.44% CO conversion and 54.73 μmol·gcat−1·min−1 H2 production at 250 °C. Both of the Cu-Y2O3 catalysts had similar structures including Cu°, Cu+, oxygen vacancies (Vo) on the Cu°-Cu+ interface and Y2O3 support. RCYO-500, with a mainly exposed Cu° (100) facet, was active in the low-temperature WGS reaction, while the WGS activity of RCYO-320, which mainly exposed the Cu° (111) facet, was greatly enhanced above 180 °C. Different Cu° facets have different abilities to absorb H2O and then dissociate it to form hydroxyl groups, which is the main step affecting the catalytic rate of the WGS reaction.