N2 Desorption Research Articles

Nitrate removal from aqueous solution by glucose-based carbonaceous adsorbent: Batch and fixed-bed column adsorption studies

In the present study, the glucose-based carbonaceous adsorbent was prepared from glucose, melamine and urea by using ZnCl2 activation and heated at 550°C under N2 flow. The sample was treated for the 1st, 2nd and 3rd activation process, and they were characterized by N2 adsorption and desorption isotherms, elemental analysis and X-ray photoelectron spectroscopy (XPS). The results showed that the content of nitrogen increased and that of oxygen decreased with the increasing of the number of activation process. The adsorbent obtained after the 2nd activation showed the best adsorption properties and was used in batch and fixed-bed column adsorption studies. In batch adsorption experiments, we investigated the factors affecting nitrate adsorption such as initial concentration, solution pH, adsorption isotherms and adsorption kinetics. The isotherm data and kinetic data were fitted well to the Langmuir isotherm model and pseudo-second-order model, respectively, and the maximum adsorption capacity calculated by Langmuir model was 1.58 mmol/g at pH 3. The adsorption performance of the adsorbent in industrial application mode was also investigated by fixed-bed column experiments. The breakthrough time of the packed column was 160 min for the initial nitrate concentration of 200 mg/L at pH 3. The saturated column could be regenerated by 1 mol/L HCl and reused for at least 5 adsorption-desorption cycles. The column showed good adsorption performance in both coexisting ions solution and real contamination water.

Boosting hydrogen production of ammonia decomposition via the construction of metal-oxide interfaces

The ammonia decomposition for the production of carbon-free hydrogen has triggered great attention yet still remains challenging due to its sluggish kinetics, posting the importance of precise design of efficient catalysts for ammonia decomposition under low temperatures. Constructing the metal-support interaction and interface is one of the most important strategies for promoting catalysts. In this work, by coating ceria onto the Ni nanoparticles (NPs), we discover that the Ni–CeO2 interfaces create an exceptional effect to enhance the catalytic decomposition of ammonia by over 10 folds, compared with the pristine Ni. The kinetic analysis demonstrates that the recombinative N2 desorption is the rate-determining step (RDS) and the Ni–CeO2 interface greatly increases the RDS. Based on these understandings, a strategy to fabricate the Ni/CeO2 catalyst with abundant Ni–Ce–O interfaces via one-pot sol-gel method was employed (hereafter denoted to s–Ni/CeO2). The s–Ni/CeO2 catalyst shows a high activity for ammonia decomposition, achieving a H2 formation rate of 10.5 mmol gcat−1 min−1 at 550 °C. Combined with a series of characterizations, the relationship between the catalyst structure and the performance was investigated for further understanding the effect of metal-oxide interfaces.

The Effect of Different Diluents and Curing Agents on the Performance of Epoxy Resin-Based Intumescent Flame-Retardant Coatings.

The epoxy resin-based (ESB) intumescent flame-retardant coatings were modified with 1,4-butanediol diglycidyl ether (14BDDE) and butyl glycidyl ether (BGE) as diluents and T403 and 4,4'-diaminodiphenylmethane (DDM) as curing agents, respectively. The effects of different diluents and curing agents on the flame-retardant and mechanical properties, as well as the composition evolution of the coatings, were investigated by using large-plate combustion, the limiting oxygen index (LOI), vertical combustion, a cone calorimeter, X-ray diffraction, FTIR analysis, a N2 adsorption and desorption test, a scanning electron microscope (SEM), a tensile strength test, and a viscosity test. The results showed that the addition of 14BBDE and T403 promoted the oxidation of B4C and the formation of boron-containing glass or ceramics, increased the residual mass of char, densified the surface char layer, and increased the specific surface area of porous residual char. When their dosage was 30%, ESB-1T-3 coating exhibited the most excellent flame-retardant properties. During the 2 h large-plate combustion test, the backside temperature was only 138.72 °C, without any melting pits. In addition, the peak heat release rate (PHRR), total heat release rate (THR), total smoke production (TSP), and peak smoke production (PSPR) were reduced by 13.15%, 13.9%, 5.48%, and 17.45%, respectively, compared to the blank ESB coating. The LOI value reached 33.4%, and the vertical combustion grade was V-0. In addition, the tensile strength of the ESB-1T-3 sample was increased by 10.94% compared to ESB. In contrast, the addition of BGE and DDM promoted the combustion of the coating, affected the ceramic process of the coating, seriously affected the formation of borosilicate glass, and exhibited poor flame retardancy. The backside temperature reached 190.93 °C after 2 h combustion. A unified rule is that as the amount of diluent and curing agent increases, the flame retardancy improves while the mechanical properties decrease. This work provides data support for the preparation and process optimization of resin-based coatings.

Effect of surface modification of Fe/g-C3N4 catalyst on the product distribution in CO hydrogenation

Carbon nitride (g-C3N4) prepared using thermal condensation of urea was pretreated by H2O2/NH3·H2O and used as support to obtain Fe/g-C3N4 catalyst via impregnation method. The catalytic performance of the catalysts both before and after modification was investigated in CO hydrogenation. Combining detailed characterizations, such as XRD, SEM, TEM, FT-IR, TG, CO2-TPD, CO-TPD, H2-TPR, contact angle measurement, and N2 physical adsorption and desorption, we investigated the effects of surface pretreatment on the texture properties of Fe/g-C3N4 catalysts and the product distribution of CO hydrogenation. The results demonstrate that various pretreatment techniques have significant influences on the textural properties and catalytic performance of the catalysts. The prepared g-C3N4 with a typical honeycomb structure has strong interaction with highly dispersed Fe. Both before and after modification, the materials are hydrophilic, and the hydrophilicity is increased after treatment with H2O2 and NH3·H2O. Treatment with H2O2 enhances surface hydroxyl groups. NH3·H2O treatment improves surface amino groups, promotes CO adsorption, and facilitates the formation of Fe(NCN) phase. The surface basicity of all pretreated catalysts is enhanced. The water gas shift (WGS) reaction activity of the two-step modified catalyst Fe/AM-g-C3N4 was lower, and the CO2 selectivity in CO hydrogenation was reduced to 11.61%. Due to the enhanced basicity of Fe/AM-g-C3N4, the secondary hydrogenation ability of olefins was inhibited to obtain higher olefin selectivity with C= 2–C= 4 of 32.37% and an O/P value of 3.23.

Ammonia decomposition mediated at nitrogen vacancies on NaCl-type binary metal nitrides supporting transition metal nanoparticles.

The ability of NaCl-type binary transition metal nitrides (incorporating La, Ce, Y, Zr or Hf) to act as catalytic supports facilitating ammonia decomposition was examined. The effect of nitrogen vacancies formed on nitrides can be understood in terms of the ionic radii of the metal cations. A clear correlation between the N2 desorption temperature and catalytic activity was found.

Study of the adsorption-desorption of Cr (III) on green silica obtained from sodium silicate

Mesoporous silica (MS) is nowadays one of the most widely used materials for the removal of contaminants in water; however, its main disadvantage is its production cost, since it is obtained by the sol-gel process using tetraethyl orthosilicate (TEOS) as silica former, which is not an economical reagent. In this article, we propose the synthesis route of SM from industrial sodium silicate; Na2SiO3 by passing it through an ion exchange column (DOWEX-50WX8-100) to obtain silicic acid (Si(OH)4). The acid fraction is collected from the ion exchange column at pH 1–3 and allowed to age for 24 h. The SM silicate is formed from the gelation of the aged silicic acid and was characterized by infrared spectroscopy. The porosity was determined by N2 desorption adsorption isotherms and scanning electron microscopy. The Cr(3+) removal capacity was evaluated by the effect of the initial Cr(3+) concentration. Obtaining that the maximum removal capacity was 108.7 mg/g for a Cr3+ solution of 2794 ppm

Development of sulfhydryl grafted hierarchical porous geopolymer for highly effective removal of Pb (II) from water

Geopolymers have captured increasing attention in the adsorption of lead ions due to their zeolite-like three-dimensional network structure, and several advantages such as low cost and environmental friendliness. However, their adsorption performance is limited by a small specific surface area and fewer adsorption sites. In this study, a metakaolin-based geopolymer was first pretreated with different concentrations of nitric acid to increase the porosity and surface area. Subsequently, the sulfhydryl functional group was grafted onto the above hierarchical porous geopolymer, which is a inorganic material with multistage pore structure. The result of N2 adsorption and desorption results demonstrated that an increase in specific surface area and number of grafting sites for sulfhydryl groups with increasing acid concentration when the highest nitric acid concentration used is 5 mol/L and acid treatment time is for 5 h. The specific surface area of the fabricated geopolymers was as high as 343.87 m2/g and the concentration of silanol groups reached 4.46 mmol/g at 3 mol/L acid concentration. The maximum Pb2+ adsorption quantities for SH-1HGeo, SH-2HGeo, and SH-3HGeo samples were 173.2 mg/g, 239.8 mg/g, and 386.3 mg/g, respectively. The adsorption processes were in accordance with the pseudo-second-order kinetic model and the Langmuir models, indicating that the Pb2+ adsorption on the sulfhydryl grafted hierarchical porous geopolymer was mainly chemisorption and monolayer adsorption. The contribution of different Pb2+ adsorption mechanism on geopolymer was ion-exchange, while that on SH-3HGeo was functional group complexation.

Surface Characterization of the Adsorbent Derived from Activated East Kalimantan’s Low Rank Coal (LRC) Yuli Patmawati

Adsorption process has several applications today particularly for the treatment of wastewater. Consequently, the creation and enhancement of adsorbent materials is an important subject of research. When a novel adsorbent is offered, adequate material properties is necessary to understand its characteristics, encourage the utilization of it as well as comprehend Its effectiveness in the intended technique. The objective of this inquiry is to figure out the structure and surface area of the adsorbent derived from East Kalimantan’s activated LRC utilizing Brunauer Emmett Teller (BET) analyses. Before conducting BET analysis, the adsorbent is degassed and vacuumed. After that, it gets exposed to N2 gas at constant temperature of 77 Kelvin. From this paper reported an adsorbent derived from East Kalimantan's activated LRC has surface areas of 321.26 m2/g, many micropores with the average pore size of 1.41 nm and 0.23 cm3/g total volume of pore. Furthermore, based upon the isotherms of N2 gas adsorption and desorption, the adsorbent derived from East Kalimantan's activated low rank coal follows a combination of IUPAC types I and IV. It possesses microporous and mesoporous characteristics, as well as monolayer and multilayer adsorption processes. Identifying the surface characteristics of the adsorbent makes it feasible to evaluate the effectiveness of utilizing the adsorbent derived from East Kalimantan’s activated LRC in the adsorption process as compared to different types of adsorbents.

Construction of rGO-Bi2Sn2O7-NiFe2O4 nanoheterojunction system for the enhanced photodegradation of doxycycline: A brief insight on degradation kinetics and toxicological evaluation on Allium cepa

In this study, the rGO-Bi2Sn2O7-NiFe2O4 nanocomposite (RBN NCs) was fabricated using an in-situ hydrothermal method and applied for the effective aqueous degradation of doxycycline (DOX). Various analytical techniques were employed to characterize the physicochemical properties of the fabricated nanoparticles, including TEM, UV–Vis, PL, FE-SEM, ESR, DRS, XPS, XRD, and N2 adsorption and desorption analysis. The efficiency of DOX degradation by the RBN system under different conditions was evaluated. Under optimal conditions (RBN concentration = 50 mg/L and pH = 7.0), the NCs removed 99.1% of DOX (10 mg/L) within 270 min under visible light irradiation. ESR and scavenging tests illustrated that the developed system produced O2⦁- radicals, which played a dominant role in the complete degradation of DOX. The mineralization of DOX was confirmed by total organic carbon results. The RBN system displayed exceptional reusability over six consecutive cycles and could be easily removed from treated water due to its magnetic properties. The toxicity of the end-product after degradation was assessed against Escherichia coli (gram-negative) and Bacillus subtilis (gram-positive). Additionally, GC-MS analysis was conducted to predict the possible photodegradation pathway of DOX, providing a better understanding of the degradation process. Toxicity of intermediate products was also estimated computationally using the ECOSAR software. The fabricated RBN was further investigated for genotoxicity towards Allium cepa. This study provides new insights into the RBN system for environmental remediation.

Cryo-IR spectroscopy and cryo-kinetics of cluster N2 adsorbate complexes of tantalum cluster cations Ta5-8.

We present an IR-PD study of tantalum cluster adsorbate complexes [Tan(N2)m]+, abbreviated (n,m), n = 5-8. We utilize infrared spectroscopy of isolated and size selected clusters as prepared and characterized by a cryogenic tandem ion trap setup, and we augment our experiments with quantum chemical simulations at the level of density functional theory. The cluster adsorbate complexes (n,m) reveal vibrational bands above 2000cm-1, which indicate end-on coordinated μ1-N2 oscillators, and bands below 2000cm-1, which indicate side-on μ2-κN:κN,N coordinated ones. We observe a general increase in spectral complexity and an inhomogeneous broadening, mainly towards the red, at certain points of N2 loading m, which originates from an increasingly higher amount of double and triple N2 coordination at Ta sites, eventually at all of them. Other than the small tantalum clusters Tan+, n = 2-4, the IR-PD spectra of the initial N2 adsorbate species (n,1), n = 5-8, provide strong evidence for a lack of spontaneous N2 cleavage. Spontaneous N2 cleavage by Tan+, n = 5-8, seems suppressed. Therefore, the ability of a small Ta cluster to cleave dinitrogen disappears with one more tantalum core atom. The study of stepwise N2 adsorption on size selected Tan+, n = 5-8 clusters revealed adsorption limits m(max) of [Tan(N2)m]+ that are independent of cluster size within this size range. Cryo-adsorption kinetics at 26K allowed for kinetic fits to consecutive N2 adsorption steps, and the fits revealed significant N2 desorption rates upon higher N2 loads, and the cluster adsorbate complexes eventually reached equilibrium. Some enhanced N2 desorption rates point towards likely adsorbate shell reorganization, and there is also some evidence for the coexistence of isomeric cluster adsorbate complexes.

Cryo IR spectroscopy and cryo kinetics of dinitrogen activation and cleavage by small tantalum cluster cations.

We investigate small tantalum clusters Tan+, n = 2-4, for their capability to cleave N2 adsorption spontaneously. We utilize infrared photon dissociation (IR-PD) spectroscopy of isolated and size selected clusters under cryogenic conditions within a buffer gas filled ion trap, and we augment our experiments by quantum chemical simulations (at DFT level). All Tan+ clusters, n = 2-4, seem to cleave N2 efficiently. We confirm and extend a previous study under ambient conditions on Ta2+ cluster [Geng et al., Proc. Natl. Acad. Sci. U. S. A. 115, 11680-11687 (2018)]. Our cryo studies and the concomitant DFT simulations of the tantalum trimer Ta3+ suggest cleavage of the first and activation of the second and third N2molecule across surmountable barriers and along much-involved multidimensional reaction paths. We unravel the underlying reaction processes and the intermediates involved. The study of the N2 adsorbate complexes of Ta4+ presented here extends our earlier study and previously published spectra from (4,m), m = 1-5 [Fries et al., Phys. Chem. Chem. Phys. 23(19), 11345-11354 (2021)], up to m = 12. We confirm the priory published double activation and nitride formation, succeeded by single side-on N2 coordination. Significant red shifts of IR-PD bands from these side-on coordinated μ2-κN:κN,N N2 ligands correlate with the degree of tilting towards the second coordinating Ta center. All subsequently attaching N2 adsorbates onto Ta4+ coordinate in an end-on fashion, and we find clear evidence for co-existence of end-on coordination isomers. The study of stepwise N2 adsorption revealed adsorption limits m(max) of [Tan(N2)m]+ which increase with n, and kinetic fits revealed significant N2 desorption rates upon higher N2 loads. The enhanced absolute rate constants of the very first adsorbate steps kabs(n,0) of the small Ta3+ and Ta4+ clusters independently suggest dissociative N2 adsorption and likely N2 cleavage into Ta nitrides.

Achieving equilibrium conversions for low-temperature NH3 decomposition: Synergy between catalyst and electric field effects

In the advent of an energy shift towards renewable energy sources, ammonia is considered a promising energy carrier for convenient hydrogen storage and transport. However, ammonia decomposition requires temperatures higher than 500 °C to achieve 100% conversion. Here, we present the facile synthesis and use of nanocluster RuCeO2 catalysts for the low-temperature electric field-assisted ammonia decomposition reaction. The catalysts obtained desirable properties and achieved high conversions for ammonia decomposition under conventional conditions. Interestingly, catalyst activities significantly increased upon exposure to an electric field, achieving 100% conversion at 450 °C and obtaining exceptional conversions of up to 34% at a low temperature of 200 °C and a high GHSV of 30,000 mLNH3/gcath. Optimization of reaction parameters effectively increased NH3 conversions, allowed highly stable long-term activities, and enabled the catalyst to achieve equilibrium conversions at remarkably lower temperatures. Further studies reveal that the electric field essentially reduces apparent activation energies and boosts the ammonia decomposition reaction by promoting the recombinative desorption of N2 and H2, thereby alleviating the rate-determining step and preventing deactivation due to H2 poisoning. The occurrence of surface protonics as a result of N-H bond scission and transport of H+ species to the support, along with increased NH3 activation and oxygen vacancy migration improves charge transfer between the support and the Ru active sites, thereby resulting in increased desorption of N2 and H2 products. Thus, an energy-efficient route toward economical hydrogen production is achieved by combining electric field effects with a highly active RuCeO2 catalyst.

+Development of a modified route for the preparation of BiVO4/ZrO2 composite with tuned heterojunction in it for efficient near-infrared solar reflectance

Recent advancements in pigmentation technology have focused on the development of cost-effective routes to achieve high near-infrared (NIR) reflectivity, offering multifunctional and sustainable applications over conventional methods. Here, we have developed a modified route for the preparation of BiVO4/ZrO2 composite with tuned heterojunction in it. Several advanced techniques were employed to investigate the elemental composition, microstructure, band gap energy, particle size, electronic transition, and color characteristics of the composite. The band gap of BiVO4 was tuned to optimize its suitability for the efficient NIR solar reflections. N2 adsorption and desorption studies indicated that the composite had a typical microporous material behavior, categorized as a type IV isotherm. Thermogravimetric analysis (TGA) and differential thermogravimetry (DTG) revealed excellent thermal stability of the composite up to 800 °C. The equimolar ratio of the composite (1:1 BiVO4/ZrO2) composite demonstrated appreciable NIR solar reflectance, reaching 96%, and exhibited an intense yellow color with excellent color characteristics. Consequently, (1:1 BiVO4/ZrO2) composite holds significant promise as a material for the development of multifunctional, thermally stable, anti-corrosive, and energy-saving exterior cool roof applications.

Efficient synthesis of dimethyl hexane-1,6-dicarbamate via methoxycarbonylation of 1, 6-hexanediamine with methyl carbamate over acid-base enhanced CeO2

The carbonylation of 1,6-hexanediamine (HDA) is an important method for the production of dimethyl hexane-1,6-dicarbamate (HDC), which is of great significance for the non-phosgene synthesis of hexamethylene-diisocyanate. This research focuses on the synthesis of HDC through the methoxycarbonylation of HDA using methyl carbamate as a carbonyl source. The study investigates the utilization of CeO2 catalyst prepared via H2O2assisted precipitation. Various characterization techniques, including N2 physical adsorption and desorption, SEM, TEM, XRD, NH3TPD, CO2TPD, and XPS are employed to analyze the texture and structure of CeO2 catalysts prepared through different methods. In situ FTIR experiments are conducted to monitor the potential process of the carbonylation reaction. The results of the in situ FTIR spectroscopy clearly indicate the formation of polyurea as an intermediate compound, which subsequently converts into HDC. The findings demonstrate that CeO2 prepared using the hydrogen peroxide precipitation method exhibits a larger specific surface area, stronger acid-base properties, and a higher content of surface-adsorbed oxygen. These characteristics are favorable for the carbonylation reaction. Under optimized conditions, the HDC yield reaches 96.0% with complete conversion of HDA. The catalyst's activity essentially maintained throughout ten cycles. Additionally, a substrate versatility study reveals that CeO2 exhibits excellent catalytic properties for synthesizing a range of aliphatic and alicyclic dicarbamates.

A surface mechanism for O3 production with N2 addition in dielectric barrier discharges

Ozone, O3, is a strong oxidizing agent often used for water purification. O3 is typically produced in dielectric barrier discharges (DBDs) by electron-impact dissociation of O2, followed by three-body association reactions between O and O2. Previous studies on O3 formation in low-temperature plasma DBDs have shown that O3 concentrations can drop to nearly zero after continued operation, termed the ozone-zero phenomenon (OZP). Including small (<4%) admixtures of N2 can suppress this phenomenon and increase the O3 production relative to using pure O2 in spite of power deposition being diverted from O2 to N2 and the production of nitrogen oxides, N x O y . The OZP is hypothesized to occur because O3 is destroyed on the surfaces in contact with the plasma. Including N2 in the gas mixture enables N atoms to occupy surface sites that would otherwise participate in O3 destruction. The effect of N2 in ozone-producing DBDs was computationally investigated using a global plasma chemistry model. A general surface reaction mechanism is proposed to explain the increase in O3 production with N2 admixtures. The mechanism includes O3 formation and destruction on the surfaces, adsorption and recombination of O and N, desorption of O2 and N2, and NO x reactions. Without these reactions on the surface, the density of O3 monotonically decreases with increasing N2 admixture due to power absorption by N2 leading to the formation of nitrogen oxides. With N-based surface chemistry, the concentrations of O3 are maximum with a few tenths of percent of N2 depending on the O3 destruction probability on the surface. The consequences of the surface chemistry on ozone production are less than the effect of gas temperature without surface processes. An increase in the O3 density with N-based surface chemistry occurs when the surface destruction probability of O3 or the surface roughness was decreased.

Unraveling the promoter role of Ba in Co–Ce catalysts for ammonia decomposition using microkinetic modeling

Ammonia decomposition is an attractive process for decarbonized hydrogen production. Alkalis are known to promote the reaction, which is especially important to enable non-noble metal catalysts to achieve similar performances to the benchmark Ru catalyst. Herein, we evaluate the kinetic contribution of Ba as a promoter in Co–Ce catalysts, using a microkinetic approach to investigate the influence of the promoter on the elementary steps of ammonia decomposition. For this purpose, we performed experiments over a wide range of conditions with two Co–Ce catalysts, with and without Ba. The results were used to fit microkinetic models with enthalpy–entropy constraints for parameters such as prefactors, activation energies, and sticking coefficients. Based on the differences in these parameters, we compared surface coverages and partial equilibrium indices to show how Ba enhances the rate of N2 desorption, one of the two kinetically relevant steps, along with the NH2 dehydrogenation.

Catalytic formic acid dehydrogenation via hexagonal-boron nitride supported palladium

Formic acid dehydrogenation is an effective pathway for hydrogen storage, transportation, and in situ supply; however, the problems of catalyst sintering and agglomeration remain challenging. In this regard, this study aims at modulating hexagonal boron nitride-supported Pd catalyst with strong metal support interactions, thereby promoting its long-term stability. Effects of particle sizes of h-BN (500 nm, 1–2 μm, 5–10 μm) and dehydrogenation temperatures on formic acid conversion, hydrogen yield, CO concentration, and product distribution are investigated. The nano-scaled h-BN supported Pd nanoparticles show the best performance of 24.25 mmol H2 mL-1 HCOOH with a H2 concentration of 44.7 vol%. Characterizations such as N2 adsorption and desorption, XRD, TEM-EDX mapping, and XPS are used to study the physicochemical properties of the as-synthesized and reacted catalysts. Specifically, the diffraction peaks of Pd cannot be detected from XRD, possibly attributing to the homogeneous dispersion of its nanoparticles, as confirmed by the TEM-EDX mapping results. The durability tests indicate that the Pd/h-BN (500 nm) catalyst remains long-term stability under a temperature as high as 160 °C. Moreover, results from XPS reveal that there is a strong interaction between the Pd nanoparticles and the hexagonal BN support, as proved by the electronic transformation from Pd to N by XPS, thereby enhancing the stability of the Pd/h-BN catalyst.

Preparation of ZrO2/Na-β and ZrO2/H-β catalysts and their catalytic performance for the Meerwein–Ponndorf–Verley reaction of cyclohexanone and isopropanol

ZrO2/Na-β and ZrO2/H-β catalysts are prepared by the reflux impregnation method and are applied to the Meerwein–Ponndorf–Verley reduction of cyclohexanone and isopropanol. The catalysts are characterized by X-ray diffraction, scanning electron microscopy-energy dispersive spectrum, temperature-programmed desorption of ammonia, N2 isothermal adsorption and desorption, and inductively coupled plasma mass spectrometry. The products are identified by gas chromatography‒mass spectrometry and analyzed by gas chromatography. The experimental results showed that ZrO2/H-β exhibits higher catalytic activity for the above Meerwein–Ponndorf–Verley reduction because ZrO2/H-β has both Zr4+ and Al3+ ion acid centers, which provide the moderately strong acid needed for the reaction. Under optimized conditions, ZrO2/H-β(6) is used as the catalyst, and the conversion rate of cyclohexanone was 92.0% as determined by the area-normalized calculation based on cyclohexanone. The catalyst can be regenerated by programmed heating calcination. The conversion rate of cyclohexanone decreased to 79.4% after five recycling cycles, and its service life needs further study to be improved.

Plasma-catalytic synthesis of ammonia over Ru/BaTiO3-based bimetallic catalysts: Synergistic effect from dual-metal active sites

Plasma-catalytic synthesis of ammonia (NH3) was carried out using BaTiO3 supported Ru-M bimetallic catalysts (Ru-M/BaTiO3, M = Fe, Co and Ni) in a dielectric barrier discharge (DBD) reactor. The NH3 synthesis performance followed the order of Ru-Ni/BaTiO3 > Ru/BaTiO3 > Ru-Co/BaTiO3 > Ru-Fe/BaTiO3, with the highest NH3 concentration (3895 ppm) and energy yield (0.39 g kWh−1) achieved over Ru-Ni/BaTiO3 at 25 W and 10 W, respectively. To gain insights into the physio-chemical properties of the Ru-M/BaTiO3 catalysts, comprehensive catalyst characterizations were performed, including X-ray diffraction, N2 physisorption measurements, X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), energy dispersive spectroscopy (EDS), and temperature-programmed desorption of CO2 and N2 (CO2 and N2-TPD). The results indicated that the loading of Ni enhanced the basicity and N2 adsorption capacity of the catalyst, as well as the density of oxygen vacancy (OV) on the BaTiO3 surface, which facilitated the adsorption and activation of N2 on catalyst surface. These effects led to the enhanced NH3 synthesis, as excited N2 could be adsorbed on Ru-Ni/BaTiO3 from plasma region and stepwise hydrogenated to form NHx species and ultimately NH3.

Green synthesis of photocatalytic TiO2/Ag nanoparticles for an efficient water remediation

This work reports a green method to produce efficient photocatalytic nanopowders. Titanium dioxide nanoparticles were easily synthetized by an extract of Thymus vulgaris, and then decorated with commercial silver nanoparticles. A detailed morphological, structural, and chemical characterization was performed by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) adsorption–desorption of N2, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), Raman spectroscopy, transmission electron microscopy (TEM), and UV–Vis spectroscopy. The synthetized TiO2 nanoparticles showed a mean size of 10–15 nm, and had the anatase crystallographic phase. The photocatalytic efficiency of the TiO2 nanoparticles was demonstrated by the photo-degradation under UV-light irradiation of different pollutants in aqueous solution (methylene blue, diclofenac, and sodium dodecyl sulfate). TiO2 was coupled to Ag nanoparticles with different percentage in weight (from 0.25 to 3%), to investigate an eventual improvement of its photocatalytic efficiency. The best photocatalytic composite among the tested compositions was the one with the lowest Ag percentage (0.25%). Zebrafish embryo toxicity tests ruled out the toxicity of the synthetized nanoparticles. The present results offer a new, green, and easy method to prepare TiO2/Ag nanoparticles with high photocatalytic efficiency. The proposed materials are therefore promising for applications in photocatalysis, especially for wastewater remediation and reuse.