Showing papers in "Reaction Kinetics, Mechanisms and Catalysis in 2019"
TL;DR: In this paper, several MxOy-supported ZrO2 (MxOY= CuO, CeO2, CuO-CeO2) catalysts were prepared through the direct decomposition of metal organic frameworks UiO-66 in air.
Abstract: In this work, several MxOy-supported ZrO2 (MxOy = CuO, CeO2, CuO-CeO2) catalysts were prepared through the direct decomposition of metal organic frameworks UiO-66 in air. The catalysts were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), N2 adsorption–desorption isotherms and H2-temperature programmed reduction (H2-TPR). The catalytic performance for CO oxidation and toluene oxidation over Zr based catalysts was investigated. Amongst the prepared catalysts, CuCeZr catalyst displayed excellent CO oxidation and toluene oxidation performance. The addition of Cu was favorable to the enhancement of catalytic performance. Importantly, the addition of cerium led to the formation of easily reducible surface copper species, consequently improving the CO oxidation and toluene oxidation performance.
80 citations
TL;DR: In this article, the effect of the support nature (different carbons, aluminum oxide, mixed MgAl oxide) on the activity of palladium catalysts and on the reaction routes of aqueous-phase hydrogenation of furfural at a temperature of 423 K and a pressure of 3 MPa was investigated.
Abstract: The effect of the support nature (different carbons, aluminum oxide, mixed MgAl oxide) on the activity of palladium catalysts and on the reaction routes of aqueous-phase hydrogenation of furfural at a temperature of 423 K and a pressure of 3 MPa was investigated. The carbon-supported catalysts were found to be the most active, and almost complete conversion of furfural is achieved. In the presence of these catalysts, the reaction proceeds predominantly through two parallel water-involved routes depending on the nature of carbon support: catalysts supported on carbon nanoglobules are selective to 4-oxopentanal (selectivity up to about 63%), while catalysts supported on carbon nanotubes give mainly cyclopentanone (selectivity up to 57%). The palladium catalysts based on the oxide supports (γ-Al2O3, MgAlOx) are much less active in the aqueous-phase hydrogenation of furfural compared to carbon-supported catalysts, and complete conversion of furfural does not occur (only up to 55%). In the presence of catalysts prepared using basic support (i.e., MgAl oxide), there are no reactions involving water, and furfuryl alcohol and tetrahydrofurfuryl alcohol are the principal products. According to the results of catalyst characterizations, the revealed differences in performance of palladium catalysts are caused by the effect of the support nature on the formation and dispersion of supported Pd nanoparticles, as well as by the distinctions in the structure and acid–base properties of the supports.
32 citations
TL;DR: In this paper, the authors described catalytic activities of surface active ionic liquids (SAILs) composed of well-known cations 1-butyl-3-methylimidazolium ([bmim+]) and tetra-n-butylammonium ([TBA+]) for cyclic carbonate synthesis.
Abstract: Carbon dioxide (CO2) conversion is an efficient option to mitigate environmental impacts caused by CO2 high concentration in the atmosphere. In this work are described catalytic activities of surface active ionic liquids (SAILs) composed of well-known cations 1-butyl-3-methylimidazolium ([bmim+]) and tetra-n-butylammonium ([TBA+]) and long alkyl chain anions: lauryl sulfate ([C12SO4−]), lauryl ether sulfate ([C12ESO4−]), lauryl benzene sulfonate ([C12BSO3−]) and lauroyl sarcosinate ([C12SAR−]) for cyclic carbonate synthesis. Results evidenced that [TBA+] is more active as a catalyst due to its higher molecular volume increasing the cation–anion distance and weakening the electrostatic interaction resulting in a more electrophilic cation. The [TBA][C12BSO3] SAIL presented better catalytic activity for styrene carbonate (SC) synthesis, reaching 81.4% of conversion and 87.0% of selectivity as well as the high recycle capacity and possible application as catalyst for the syntheses of different cyclic carbonates: glycidyl isopropyl ether carbonate (GC) and epichlorohydrin carbonate (EC).
28 citations
TL;DR: In this article, the authors investigated the catalysts of three different phenolic model compounds, isoeugenol, guaiacol, and vanillin, using Ir/ZrO2 and Ni/ZRO2 as heterogeneous catalysts.
Abstract: The hydrodeoxygenation (HDO) of three different phenolic model compounds, isoeugenol, guaiacol and vanillin was investigated using Ir/ZrO2 and Ni/ZrO2 as heterogeneous catalysts. The catalysts were prepared by incipient wetness impregnation and characterized by transmission electron microscopy, nitrogen adsorption, FTIR pyridine adsorption–desorption. The organic material in the spent catalysts was analyzed by organic elemental analysis and thermogravimetry. The results revealed that in guaiacol HDO at 250 °C under 30 bar total pressure the main product was cyclohexanol with 36% yield over Ni/ZrO2 while the total deoxygenation forming cyclohexane was limited to 2%. Ir/ZrO2 exhibited higher HDO activity compared to Ni/ZrO2 giving 14% yield of cyclohexane. Extensive formation of methane and ethane was also observed in guaiacol HDO. Hydrodeoxygenation of isoeugenol over Ir/ZrO2 resulted in maximally 33% yield of propylcyclohexane due to a low liquid phase mass balance. The main products in vanillin HDO at 100 °C in water was vanillyl alcohol.
26 citations
TL;DR: In this article, a hybrid plasma catalytic process for CO2 methanation is presented, based on the combination of a DBD plasma and Ni/CeZrO2 catalyst.
Abstract: The present study focuses on the hybrid plasma catalytic process for CO2 methanation. This plasma-catalytic process, based on the combination of a DBD plasma and Ni/CeZrO2 catalyst, has several advantages over conventional catalysis: it operates at ambient conditions and requires no external heating. An optimization of the process considering the effect of the different operational parameters such as voltage, GHSV, catalyst mass, flow rate, discharge length, is herein presented. Moreover, a spectroscopic study, aiming to understand the mechanism of the reaction, is also showed. At temperatures around 270 °C and under adiabatic conditions, CO2 conversion rates of about 80% were measured, with a CH4 selectivity greater than 95%.
25 citations
TL;DR: In this paper, FeNi3 nanoparticles were coated by silica and applied for green, inexpensive, selective and efficient epoxidation of alkenes as well as oxidation of sulfides to the corresponding sulfoxides.
Abstract: In this article, FeNi3 nanoparticles were coated by silica and applied for green, inexpensive, selective and efficient epoxidation of alkenes as well as oxidation of sulfides to the corresponding sulfoxides. The oxidation was performed over FeNi3@SiO2 nanoparticles in the presence of meta-chloroperoxybenzoic acid as an oxygen source in dichloromethane at room temperature. High reaction conversion as well as oxidation product selectivity were obtained for both sulfoxide or epoxide compounds. The properties of the catalyst were studied by transmission electron microscopy, powder X-ray diffraction, Fourier transform infrared spectroscopy and vibrating sample magnetometer instruments. The heterogeneous nanocatalyst was magnetically recovered and could be reused in at least five consecutive runs without noticeable reactivity loss.
22 citations
TL;DR: In this article, the catalysts were tested in parallel hydrodeoxygenation (HDO) and hydrodesulfurization (HDS) of 1-benzothiophene.
Abstract: Mo, CoMo and NiMo sulfide catalysts were prepared using MgO, Al2O3, ZrO2, TiO2, MCM-41 and activated carbon supports. The catalysts were tested in parallel hydrodeoxygenation (HDO) of octanoic acid and hydrodesulfurization (HDS) of 1-benzothiophene. For all supports, NiMo catalysts were more active in both HDO and HDS than Mo and CoMo catalysts. HDO activity of NiMo catalysts decreased with type of support in the following order TiO2 > C > ZrO2 > Al2O3 > MCM-41 > MgO. The products of HDO were linear C7 and C8 hydrocarbons. Some isomerization and cracking activity was observed only with MCM-41 support. HDS activity of NiMo catalysts decreased in the following order C > ZrO2 > TiO2 > Al2O3 > MgO > MCM-41. HDO/HDS selectivity was influenced by the active phase and the support type and it was the highest over the NiMo/TiO2 catalyst.
21 citations
TL;DR: In this article, a simple and low-cost method was used to synthesize MgO nanoparticles in the size range of 2.5-11.3 nm from X-ray diffraction peaks.
Abstract: Methylene blue is the main component of several stains such as Wright–Giemsa and Leishman stain that are used in histology and hematology laboratories. 97.8% of methylene blue from medical laboratory wastewater were photodegraded with the aid of MgO nanoparticles as photocatalysts and direct solar irradiation as a renewable source. The rate of photodegradation was 0.0184 min−1. The direct precipitation method was used as a simple and low cost method to synthesize MgO nanoparticles in the size range of 2.5–11.3 nm as estimated from X–ray diffraction peaks. The optical band gap energy was reduced to 4.25 eV. The photoluminescence spectra of MgO nanoparticles show four bands corresponding to F and F+ oxygen vacancy defects. The effects of the operational parameters (MgO dose, initial pH, irradiation source energy, initial concentration of the dye and temperature) were evaluated on the efficiency and rate of the photodegradation. The efficiency of the synthesized MgO nanoparticles was compared with TiO2 and ZnO nanoparticles as well.
21 citations
TL;DR: Covalently linked sulfonic acid (SO3H)-modified ordered mesoporous silicas were synthesized, characterized and their catalytic activities were evaluated in the transesterification reaction of triacetin with methanol as mentioned in this paper.
Abstract: Covalently linked sulfonic acid (–SO3H)-modified ordered mesoporous silicas MCM-48, MCM-41, and SBA-15 were synthesized, characterized and their catalytic activities were evaluated in the transesterification reaction of triacetin with methanol Acid modified materials were prepared by oxidative transformation of immobilized functionalized unit, 3-mercaptopropyltriethoxysilane (MPTES) as a precursor The mesophase and porosity of the catalysts were determined by means of X-ray diffraction and N2 adsorption techniques No degradation of structure was observed in the preparation process The acid concentrations were calculated using TG–DTA and NH3–TPD analysis The acid modified materials were found to be active catalysts for the transesterification of triacetin with methanol Especially, three-dimensional-MCM-48-SO3H showed better catalytic activity compared to its two-dimensional counterparts MCM-41 and SBA-15
20 citations
TL;DR: In this article, the photocatalytic activity of immobilized Fe2O3/TiO2 on carbon fiber cloth as a chemically stable and flexible supporting material toward degradation of textile dye [Basic Blue 41 (BB 41)] under visible light.
Abstract: This work focuses on the photocatalytic activity of immobilized Fe2O3/TiO2 on carbon fiber cloth as a chemically stable and flexible supporting material toward degradation of textile dye [Basic Blue 41 (BB 41)] under visible light. The photocatalysts were characterized by SEM, XRD, diffuse reflectance UV–Vis, photoluminescence spectroscopy, and FTIR. The photocatalytic activities of immobilized Fe2O3/TiO2 samples with different contents of Fe2O3 (5–25 wt%) were studied for degradation of BB 41 solution (100 ml, 10 ppm) under visible light irradiation for 240 min. The optimum amount of Fe2O3 was found to be 20 wt% from experimental results that indicated 97.54% photoactivity. In order to further investigate the photocatalytic degradation, chemical oxygen demand experiments were carried out that showed the degradation of dye solution was about 84% utilizing the optimum photocatalyst. The reusability of the optimum photocatalyst was studied in 7 reaction cycles (28 h) which revealed only 13% loss of photoactivity.
19 citations
SIDI1
TL;DR: In this article, the authors presented an efficient, easy and green method for the benzimidazoles and benzothiazoles synthesis by a condensation reaction of 1,2-diamino benzene and 2-amino thiophenol with various aromatic aldehydes using SnP2O7 as a new heterogeneous catalyst.
Abstract: This work presents an efficient, easy and green method for the benzimidazoles and benzothiazoles synthesis by a condensation reaction of 1,2-diamino benzene and 2-amino thiophenol with various aromatic aldehydes using SnP2O7 as a new heterogeneous catalyst. This catalyst was prepared by adding MAP to the solution of SnCl2 and characterized by microscopic and spectroscopic methods namely X-ray diffraction, scanning electron microscopy and infrared which proved that the chemical structure of MAP has been modified when SnCl2 was added leading to the formation of SnP2O7. On the other hand, the reaction conditions were optimized namely the nature of the solvent and the mass of the catalyst. The high yields (85–97%) and very short reaction times (5–40 min) obtained for various benzimidazoles and benzothiazoles derivatives synthesis show that the new catalyst is very interesting because of its good catalytic activity and its reusability for at least five cycles without any degradation of its activity.
TL;DR: In this article, a series of Ce-Cu-SSZ-13 catalysts were synthesized by the ion exchange method based on the CuSSZ13 prepared via a one-pot method and investigated for the selective catalytic reduction by NH3.
Abstract: A series of Ce-Cu-SSZ-13 catalysts were synthesized by the ion exchange method based on the Cu-SSZ-13 prepared via a one-pot method and investigated for the selective catalytic reduction by NH3. Compared with Cu-SSZ-13, the catalytic activity and sulfur resistance of Ce-Cu-SSZ-13 were enhanced by modifying with cerium. XRD, N2-BET, MP-AES, XPS, H2-TPR and in situ DRIFTS were carried out to characterize the catalysts. XPS results suggested that more active sites on the surface of Ce-Cu-SSZ-13 catalysts. H2-TPR showed that the redox capacity of the Cu-SSZ-13 catalyst was enhanced after doping with Ce. In situ DRIFTS results demonstrated that the synergistic effect existing between copper and cerium species enhanced the adsorption performance of NH3 and NO + O2 on the catalyst surface. All of the above factors played important roles for achieving the high NH3-SCR performance.
TL;DR: In this article, a co-precipitation method was used to synthesize pure CeO2 and CeO 2-MOx (M: Mn, Zr and Ni) catalysts for the oxidation of toluene.
Abstract: Pure CeO2 and CeO2–MOx (M: Mn, Zr and Ni) catalysts were synthesized by the co-precipitation method and evaluated for the oxidation of toluene. The characterization showed that the specific surface area and the porous texture of catalysts were improved due to the doping of transition metal. Besides, the doping of MOx into ceria contributed to the generation of structural defects, which could contribute to the easier storage and release of surface oxygen. Furthermore, the CeO2–MOx (M: Mn, Zr and Ni) catalysts exhibited higher concentration of Ce3+ and surface adsorbed oxygen than pure CeO2, which could correlate with the generation of oxygen vacancies, resulting in the enhancement of redox properties. Hence, CeO2–MnOx exhibited the best apparent catalytic activity of toluene due to its more Ce3+, structural defects and active oxygen species.
TL;DR: In this paper, the Fischer-Tropsch synthesis (FTS) was performed using a nanostructure catalyst of Co-Ru/CNTs and a set of catalytic experiments were designed and conducted for the FTS using the synthesized catalyst in a fixed bed reactor.
Abstract: In this work, the nanostructure catalyst of Co–Ru/CNTs is prepared by chemical reduction technique. Then, a set of catalytic experiments are designed and conducted for the Fischer–Tropsch synthesis (FTS) using the synthesized catalyst in a fixed bed reactor. The physical and chemical properties of the support and the synthesized catalyst were determined using the BET, XRD, H2–TPR, TEM, and H2-chemisorption characterization techniques. Based on the alkyl mechanism and using the Langmuir–Hinshelwood–Hougen–Watson (LHHW) isotherm, a kinetic model is developed for FTS. In most of the previous kinetic models, the primary reactions have merely been used, but in the current derivation of the developed kinetic model, the secondary reactions (adsorption, hydrogenation and chain-growth) and re-adsorption of primary olefins at the secondary active sites are considered. The present comprehensive kinetic model is applied for the product distribution such that the rate equations parameters are acquired via optimization. To estimate the kinetic model parameters, FTS was accomplished via a series of tests under the operating conditions as pressure (P): 10–20 bar, temperature (T): 483–513 K, gas hourly space velocity (GHSV): 1400–2400 h−1 and the H2/CO ratio of 1–2. The rationality and significance of the suggested model were checked through the statistical and correlation tests. The obtained results indicated that the outcomes of the current kinetic model were in good agreement with the experimental data. Using the present kinetic model, the average absolute deviations (AAD%) for the prediction of methane, ethylene and heavier hydrocarbons (C5+) formation rates are obtained as 7.06%, 11.57% and 14.74%.
TL;DR: In this article, a mixture of catalysts based on Cu-Ca-Al derived from hydrocalumite were synthesized by continuous coprecipitation and evaluated in ethanol dehydrogenation and showed high ethanol conversions and high selectivity for acetaldehyde, either as oxide or metallic phase.
Abstract: Catalysts based on Cu–Ca–Al derived from hydrocalumite were synthesized by continuous coprecipitation and evaluated in ethanol dehydrogenation. Samples were characterized by surface area measurements, XRD, TG/DTA, H2-TPR, NH3-TPD and TPO. The catalytic runs were performed at temperature range of 250–350 °C. For reduced samples, the activation was carried out in situ at 300 °C. The catalysts showed high ethanol conversions and high selectivity for acetaldehyde, either as oxide or metallic phase. The high selectivity for dehydrogenation promoted the reduction of CuO phase to Cu° of unreduced samples during the reaction. The catalysts with high Cu content were deactivated by sintering whereas the catalysts with lower Cu content deactivated mainly by carbon deposition. Acetone is favored by catalysts in the oxide form and with higher Cu content.
TL;DR: In this paper, a modification of the Langmuir rate equation, referred to as Diffusion-Controlled LK (DCLK), was proposed, assuming that the macroscopic forward rate of adsorption is inversely related to the square root of time.
Abstract: It is widely agreed that the classical Langmuir rate equation cannot be applied for describing the kinetics of adsorption processes whose rate is controlled by diffusive transport phenomena. To overcome this limit, we propose a modification of the Langmuir rate equation, referred to as Diffusion-Controlled Langmuir Kinetics (DCLK), assuming that the macroscopic forward rate of adsorption is inversely related to the square root of time. We tested the DCLK model on experimental adsorption kinetic data. The results indicate that the DCLK model describes the kinetic data better than the traditional pseudo-second order model. Consistently with the intraparticle adsorption/diffusion theory, the adsorption amount predicted by the DCLK model proportionally increases with the square root of time at the beginning of the process. The effect of temperature on the adsorption rate and the relative role played by kinetics and thermodynamics are discussed.
TL;DR: The immobilized on silica rPichia/lip was found to have sufficiently wide specificity toward saturated fatty acids and aliphatic alcohols, and the catalytic activity was completely retained for several tens of reaction cycles in a periodic batch process of low-temperature synthesis of various fatty acid esters.
Abstract: Immobilization of recombinant Thermomyces lanuginosus lipase (designated as rPichia/lip) was carried out by moisture capacity impregnation of mesoporous silica granules followed by drying, and forcible adsorption of enzyme occurred. Eventually prepared lipase-active heterogeneous biocatalysts were systematically studied for enzymatic esterification performed at ambient conditions (20 ± 2 °C, 1 bar) in unconventional anhydrous media of organic solvents such as hexane and diethyl ether. The saturated fatty acids differing in the number of carbon atoms (C2–C10, C18), and aliphatic alcohols differing in the structure of the molecules, namely both the number of carbon atoms (C2–12, C16), and the isomerism of the carbon skeleton (n- and iso-), and OH-group position (prim-, sec-, tert-) were studied as substrates for enzymatic esterification. The specificity of the heterogeneous enzymatic esterification was determined by comparing the reaction rates for various pairs of substrates; and the matrix of relative units of activities was composed. The immobilized on silica rPichia/lip was found to have sufficiently wide specificity toward saturated fatty acids and aliphatic alcohols. High reaction rates were measured in esterification of fatty acids and primary n- and iso-aliphatic alcohols possessing more than four carbon atoms in the molecules. The enanthic acid (heptanoic, C7:0) reacted with butanol (C4) with the highest rate; and the kinetic parameters such as Michaelis constant (KM) for acid and maximal reaction rate (Vmax) were determined under the studied conditions of esterification. Substrates containing aromatic residues did not participate in esterification. The lipase-active heterogeneous biocatalysts possessed considerably high operational stability, and the catalytic activity was completely retained for several tens of reaction cycles in a periodic batch process of low-temperature synthesis of various fatty acid esters.
TL;DR: In this article, a ceria-supported Au-Pt catalyst with metal ratio 3:2 was prepared using a single-source precursor, and the double complex salt [AuEn2]2[Pt(NO2)4]3·6H2O was used as such precursor.
Abstract: In the present work, ceria-supported Au–Pt catalyst with metal ratio 3:2 was prepared using a “single-source precursor” concept. The double complex salt [AuEn2]2[Pt(NO2)4]3·6H2O was used as such precursor. CeO2 of unique morphology with developed surface area (120 m2/g) obtained by urea precipitation technique was used as a support. According to XRD data, size of the alloyed Au–Pt particles was estimated to be less than 3 nm. It was shown that bimetallic Au–Pt system intensifies release of oxygen from the CeO2 lattice. The 0.5%Au2Pt3/CeO2 catalyst was comparatively studied in low temperature CO oxidation (simplified model reaction mixture) and under prompt thermal aging conditions (complex reaction mixture) with regard to monometallic reference samples 0.2%Au/CeO2 and 0.3%Pt/CeO2. The catalytic performance of the samples was found to be significantly dependent on the reaction and pre-treatment conditions. In the case of the bimetallic catalyst, reversible redistribution and enrichment of the nanoparticle surface with Pt or Au were shown to be the key factor defining the activity.
TL;DR: In this paper, the best fitting of PSO kinetics and isotherm modeling was established using the nonlinear and linear regression analyses using the statistical functions such as R2, χ2 and RMSE were used to determine the bestfitting of the adsorption modeling.
Abstract: For the present study, activated carbon–epoxidized natural rubber–poly(vinyl)chloride composite was fabricated on the glass plates to remove phenol from the aqueous solution. The best fitting of kinetics and isotherm modeling was established using the nonlinear and linear regression analyses. The statistical functions such as R2, χ2 and RMSE were used to determine the best-fitting of the adsorption modeling. It was found that the adsorption data best-fitted the PSO kinetics model for both nonlinear and linear regression analyses. The best-fitting isotherm models for both analyses was the Freundlich model with the highest R2 and lowest χ2 and RMSE values among all models. The intraparticle diffusion was the sole rate-controlling step during the phenol uptake onto the immobilized AC composite. The plot exhibited multilinear portions, which corresponded to three stages of adsorption. The nonlinear regression modeling for kinetics and isotherm achieved higher R2 with lower χ2 and RMSE values as compared to the linear regression showing that the former analysis is more robust, accurate and consistent than the latter approach. Based on the results of the analysis, it is highly recommended to use nonlinear regression when dealing with the adsorption data for the specific and accurate fitting of kinetics and isotherm models.
TL;DR: In this paper, the catalytic properties of synthesized materials were compared for the HDO of rendering fat into hydrocarbons and the liquid products were analyzed by simulated distillation, C, H, N, S elemental analysis, ATR and density.
Abstract: Acid-modified phonolite material, Al2O3/foam zeolite and foam zeolite were used as supports for NiW catalysts. The zeolite type materials were prepared by a novel procedure from natural clinoptilolite. Phonolite materials were loaded with 5, 7.5 and 10 wt% of Ni containing 10, 7.5 and 5 wt% of W. Al2O3/foam zeolite contained 4 and 13 wt% of Ni and W and pure foamed zeolite was effectively loaded with 5 and 16 wt% of Ni and W. NiW/Al2O3 catalyst (3 wt% Ni and 11 wt% of W) was used for comparison of catalytic properties of synthesized materials. Catalytic tests were carried out in an autoclave pressurized at 7 MPa (H2) at room temperature and then heated to 365 °C for 1 h. Catalysts were characterized by N2 physisorption, XRD, XRF, NH3-TPD, CO2-TPD and H2-TPR. Catalyst properties were compared for the HDO of rendering fat into hydrocarbons. The liquid products were analyzed by simulated distillation, C, H, N, S elemental analysis, ATR and density (15 °C). Gaseous products were characterized by RGA-GC. Used catalysts were also analyzed by N2-TGA and O2-TGA. Novel phonolite modified solids and NiW/foam zeolite type materials were tested for the first time as catalysts being in some cases more active than NiW/Al2O3 material. Ni(5%)W(10%)/Acid phonolite and NiW/Foamed Zeolite resulted to be the most active materials for the HDO and hydrocracking reactions. The lowest amount of carbonaceous species on the surface of tested catalyst was found for the Ni(5%)W(10%)/Acid phonolite solid.
TL;DR: In this article, a facile method was developed for the synthesis of highly crystallized nano-sized HZSM-5 via adding sodium alginate into zeolite precursor solution.
Abstract: A facile method was developed for the synthesis of highly crystallized nano-sized HZSM-5 via adding sodium alginate into zeolite precursor solution. The effects of addition order and dosage of sodium alginate on the physicochemical properties of the catalysts were systematically studied by XRD, FT-IR, TEM, N2 adsorption–desorption, ICP-OES, 27Al MAS-NMR and NH3-TPD. It was found that the addition order and dosage of sodium alginate have strong influences on the crystal sizes and acidic properties of the obtained catalysts. About 100 nm crystals were generated in S-HZSM-5-0.75-p through adding the sodium alginate prior to TEOS, which were smaller than the crystal size of conventional HZSM-5 (200–350 nm). However, this method was unfavorable for the incorporation of Al into the framework of HZSM-5. The low content of framework Al could cause a decrease in acidity and the amount of acid sites was only 0.38 mmol g−1 in S-HZSM-5-0.75-p, which was slightly lower than conventional HZSM-5 (0.42 mmol g−1). In contrast, smaller crystals (50 nm) and more acid amounts (1.24 mmol g−1) could be obtained for the S-HZSM-5-0.75 synthesized by adding the sodium alginate after TEOS. Nevertheless, the crystals could be easily aggregated to a dandelion-like particles and possessed fewer acid sites when the sodium alginate was added excessively. Under the conditions of 0.1 MPa, 400 °C and a WHSV of 0.96 h−1, a desired 35.06% BTX yield with 8.5 h service lifetime in glycerol aromatization was obtained over S-HZSM-5-0.75 comparing with conventional HZSM-5 (22.19% BTX yield and 3.5 h service lifetime). The remarkable improvement in catalytic performance of nano-sized HZSM-5 zeolite was mainly attributed to the more acid amounts and smaller crystal size, which could increase the accessibility to the acid sites and shorten the diffusion path length.
TL;DR: In this article, hierarchical ZSM-5 (HZ) zeolites with different SiO2/Al2O3 ratios were synthesized using a two-step hydrothermal treatment method, and the Al and Si were obtained from fly ash by the alkali melting and acid leaching method.
Abstract: Hierarchical ZSM-5 (HZ) zeolites with different SiO2/Al2O3 ratios (SiO2/Al2O3 = 50, 100, 150, 200, 250 and 300) were synthesized using a two-step hydrothermal treatment method, and the Al and Si were obtained from fly ash by the alkali melting and acid leaching method. On this basis, the 10 wt% LaMnO3/HZ catalysts were prepared by impregnation. The all the synthesized catalysts were investigated for the low-temperature (200 °C) catalytic oxidation of pentanal, which was selected as a typical odorous volatile organic compound (VOC) in cooking fumes. In addition, the physicochemical properties of HZ zeolites were characterized by several techniques (XRD, N2 physical adsorption–desorption, ICP-OES, SEM,TEM,NH3-TPD and 27Al MAS-NMR). The results showed that the HZ zeolite, which was micro-mesoporous material and had high specific surface area, provided a higher diffuser efficiency for long-chain VOC gas. The catalytic performance of HZ zeolite was better than that of the traditional ZSM-5 zeolite. Compared with the dry atmosphere, HZ-100 zeolite, which possessed more proper medium strong acid sites and the appropriate amount of acid sites, had the higher pentanal catalytic combustion conversion of above 92% and the relatively superior stability with 2 V% water steam in air, indicating that the suitable acid sites can form the best synergistic catalytic effect with water molecules for purifying long-chainVOC gas. In addition, the catalytic conversion of pentanal on 10 wt% LaMnO3/HZ-100 was 100% with no deactivation, and compared with HZ under a dry atmosphere, the average CO2 yields of 10 wt% LaMnO3/HZ catalysts in the steady catalytic oxidation stage under a dry atmosphere and 2 V% water steam in air were improved by 6–18% and 13–20%.
TL;DR: In this article, three-component Ru-Ba-Cs/C catalysts supported on the graphite-like carbonaceous composite material Sibunit were synthesized and the effects of the graphitization procedure of the support (thermal treatment at 1900°C) on the phase composition and the distribution of the components were studied.
Abstract: Three-component Ru-Ba-Cs/C catalysts supported on the graphite-like carbonaceous composite material Sibunit were synthesized. The effects of the graphitization procedure of the support (thermal treatment at 1900 °C) on the phase composition and the distribution of the components were studied. The catalytic activity in the ammonia decomposition reaction and the thermal stability of the samples were examined in comparison with the untreated support. The samples were characterized by Raman spectroscopy, XAFS, TEM, and XRD methods. It was found that in the case of untreated support, Ru presents in the form of both the metallic and partially oxidized fine particles. The graphitization of the carbon support facilitates the formation of large, well-crystallized metal particles. Barium in both samples was found to be unevenly distributed and presented mainly as large particles of carbonate. Cesium-containing species were not detected. The effect of the support graphitization on the thermal stability is comparable with catalyst modification by Ba and Cs. At the same time, combination of these effects noticeably increases the efficiency of the catalyst. Thus, the non-promoted Ru catalyst deposited on the untreated support decomposes 107 g of NH3 per 1 g of the lost carbon. Modification of the catalyst with Ba and Cs allows one to increase this value up to 498 g of NH3, while graphitization of the support and application of the combined approach were shown to give 910 and 1577 g, correspondingly.
TL;DR: In this paper, the effect of the addition of different promoters, such as, Ce, Zn and Co (0.3, 0.5 and 0.7 wt%) to the trimetallic Pt-Sn-K/Al2O3 catalyst in order to enhance performance of propane dehydrogenation was investigated and characterized.
Abstract: The effect of the addition of different promoters, such as, Ce, Zn and Co (0.3, 0.5 and 0.7 wt%) to the trimetallic Pt–Sn–K/Al2O3 catalyst in order to enhance performance of propane dehydrogenation was investigated and characterized with several analytic techniques, including, TPR, XRF, UV analysis, SEM and TGA–DTA. The catalysts were prepared by sequential impregnation of γ-Al2O3 technique. It was found that suitable addition of Zn (0.7 wt%), Ce (0.5 wt%) and Co (0.3 wt%) to the Pt–Sn–K/γ-Al2O3 catalyst can improve the catalytic performance more than the commercial Pt–Sn/γ-Al2O3 catalyst. The best results on Sn reduction was obtained by adding Zn (0.7 wt%) and Co (0.3 wt%) to the trimetallic Pt–Sn–K/Al2O3 catalyst. Ce (0.5 wt%) due to its ability on Pt reduction peak temperature was able to reveal better result. The performance of Pt–Sn–K–Ce0.5–Zn0.7/γ-Al2O3 and Pt–Sn–K–Co0.3–Zn0.7/γ-Al2O3 catalysts were improved by a suitable amount of Ce, Zn and Co Pt–Sn–K–Co0.3–Zn0.7/γ-Al2O3 showed better performance in terms of conversion and propylene selectivity. The synergic effect of Co and Zn can enlarge the Pt reduction peak areas than Pt–Sn–K–Co0.3/γ-Al2O3 and Pt–Sn–K–Zn0.7/γ-Al2O3, so can suppress the coke formation and improve the catalyst performance.
TL;DR: In this article, in situ FTIR spectroscopy (with ethanol and acetone as probe molecules) has shown the main reason for a decrease in activity of the catalyst to be H2O adsorption on active sites of aldol condensation of acetaldehyde and, to a lesser extent, ethanol dehydrogenation.
Abstract: Zn–La–Zr–Si oxide composition has been investigated in the ethanol-to-butadiene process using ethanol–water mixtures with different water content. An increase of H2O content in the initial reaction mixture decreases ethanol conversion, 1,3-butadiene selectivity, yield and productivity. The results of in situ FTIR spectroscopy (with ethanol and acetone as probe molecules) have shown the main reason for a decrease in activity of the catalyst to be H2O adsorption on active sites of aldol condensation of acetaldehyde and, to a lesser extent, ethanol dehydrogenation. Zn–La–Zr–Si oxide composition is a highly active and selective catalyst for the ethanol-to-butadiene process when ethanol–water mixture of 80 vol% ethanol and 20 vol% H2O is used, 60% 1,3-butadiene yield is achieved.
TL;DR: In this paper, a simple and effective method to synthesize nickel phosphide nanoparticles with target phases was reported, in which pure-phase nickel nanoparticles were obtained in different crystalline states (Ni2P and Ni12P5).
Abstract: The controlled synthesis of transition metal phosphides has been pursued to obtain excellent performances in application. Herein, we report a simple and effective method to synthesize nickel phosphide nanoparticles with target phases. Pure-phase nickel phosphide nanoparticles were obtained in different crystalline states (Ni2P and Ni12P5), and the crystalline phase of nickel phosphide could be controlled by varying the reaction conditions such as the temperature and duration of thermal treatment or the ratio between Ni and P. In addition, the nickel phosphide particles after thermal treatment maintained their sizes without serious agglomeration. In the hydrogenation of nitrobenzene, the phosphides with pure-phase (Ni2P or Ni12P5) and high crystallinity showed high catalytic activities. This proves that the crystalline phase of nickel phosphide plays an important role in the catalytic activity.
TL;DR: In this paper, the authors used the solvothermal method to synthesize VPO catalysts supported on silicon carbide, which reduced the reaction temperature by 70°C and increased the productivity of maleic anhydride.
Abstract: VPO catalysts supported on silicon carbide were prepared using the solvothermal method. A decrease the reaction temperature by 70 °C under application of SiC, prepared from sucrose and fumed silica, as a support for an active VPO phase compared to a bulk VPO catalyst prepared under similar synthesis conditions was demonstrated. A twofold increase of the productivity towards maleic anhydride was reached. The higher specific reaction rate of n-butane oxidation over prepared supported VPO-SiC systems compared to the bulk VPO catalyst was shown. Use of an environmentally safe support allowed to reduce an amount of active vanadium-containing phase, and an application of the solvothermal method decreased the synthesis duration and an amount of organic solvent compared to the traditional approaches to the synthesis of VPO systems.
TL;DR: In this article, a series of hierarchical ZSM-5 aggregates with a relatively low SiO2/Al2O3 ratio was successfully synthesized using Cetyltrimethylammonium bromide (CTAB) as mesogenous template.
Abstract: A series of hierarchical ZSM-5 aggregates with a relatively low SiO2/Al2O3 ratio (~ 50) were successfully synthesized using alkali-treated commercial ZSM-5 as seeds and cetyltrimethylammonium bromide (CTAB) as mesogenous template. The effect of the amounts of CTAB on the physicochemical and catalytic properties of the synthesized catalysts was characterized by XRD, FE-SEM, FE-TEM, N2 physical adsorption, ICP-OES, NH3-TPD, Py-IR and TGA. Moreover, the possible formation mechanism of the hierarchical ZSM-5 aggregates was studied. The results indicated that the mesoporosity of the hierarchical ZSM-5 aggregates was greatly enhanced with the addition of CTAB. The primary crystal size of the ZSM-5 aggregates significantly decreased owing to the protective effect of CTAB, which inhibits the further crystal growth. The hierarchical ZSM-5 aggregates prepared with addition of a suitable amount of CTAB showed large specific surface areas and large external surface areas, abundant intercrystalline mesopores and appropriate concentration of acid sites, which resulted in excellent catalytic performance in the methanol to gasoline reaction. The stability of the catalyst was remarkably improved and the gasoline yield was given a rise of 10% compared with the catalyst prepared in the absence of CTAB.
TL;DR: In this paper, the influence of copper content in the monometallic catalysts supported on the CeO2·Al2O3 binary oxide system on their catalytic activity and physicochemical properties in oxy-steam reforming of methanol was investigated.
Abstract: The influence of copper content in the monometallic catalysts supported on the CeO2·Al2O3 binary oxide system on their catalytic activity and physicochemical properties in oxy-steam reforming of methanol was investigated. It was shown that activity and selectivity depends on the content of copper, its dispersion on the catalysts surface. It was confirmed that optimal copper content was 20 wt% of Cu. Copper catalysts with 20 wt% of Cu exhibited the highest methanol conversion and reaction rate value compared to the rest of the investigated catalysts systems. The kinetic measurements performed in oxy-steam reforming of methanol on 20%Cu/CeO2·Al2O3 catalysts, showed an activation energy for this system equal Ea (OSRM) = 66.56 kJ/mol.
TL;DR: The scope of the field and its main thematic features and trends are discussed for the period 1990–2017 and the findings match up expert opinion on catalysis as the core area of nanotechnology and nanoscience.
Abstract: Catalysis by nanoparticles is an important segment of contemporary nanotechnology. Abundant relevant information is scattered an over enormously big number of sources, only a part of which formally regards to catalysis and/or nanotechnology and nanoscience. With the CAPlus database, the scope of the field and its main thematic features and trends are discussed for the period 1990–2017. The findings match up expert opinion on catalysis as the core area of nanotechnology and nanoscience.