NH3 Temperature-programmed Desorption Research Articles

Low-temperature selective catalytic reduction of NO with NH3 over an FeO x /β-MnO2 composite.

A series of Fe-modified β-MnO2 (FeO x /β-MnO2) composite catalysts were prepared by an impregnation method with β-MnO2 and ferro nitrate as raw materials. The structures and properties of the composites were systematically characterized and analyzed by X-ray diffraction, N2 adsorption-desorption, high-resolution electron microscopy, temperature-programmed reduction of H2, temperature-programmed desorption of NH3, and FTIR infrared spectroscopy. The deNO x activity, water resistance, and sulfur resistance of the composite catalysts were evaluated in a thermally fixed catalytic reaction system. The results indicated that the FeO x /β-MnO2 composite (Fe/Mn molar ratio of 0.3 and calcination temperature of 450 °C) had higher catalytic activity and a wider reaction temperature window compared with β-MnO2. The water resistance and sulfur resistance of the catalyst were enhanced. It reached 100% NO conversion efficiency with an initial NO concentration of 500 ppm, a gas hourly space velocity of 45 000 h-1, and a reaction temperature of 175-325 °C. The appropriate Fe/Mn molar ratio sample had a synergistic effect, affecting the morphology, redox properties, and acidic sites, and helped to improve the low-temperature NH3-SCR activity of the composite catalyst.

Low-temperature NH3-SCR performance of a novel Chlorella@Mn composite denitrification catalyst

The synthesis process of conventional Mn-based denitrification catalysts is relatively complex and expensive. In this paper, a resource application of chlorella was proposed, and a Chlorella@Mn composite denitrification catalyst was innovatively synthesized by electrostatic interaction. The Chlorella@Mn composite denitrification catalyst prepared under the optimal conditions (0.54 g/L Mn2+ concentration, 20 million chlorellas/mL concentration, 450°C calcination temperature) exhibited a well-developed pore structure and large specific surface area (122 m2/g). Compared with MnOx alone, the Chlorella@Mn composite catalyst achieved superior performance, with ∼100% NH3 selective catalytic reduction (NH3-SCR) denitrification activity at 100-225°C. The results of NH3 temperature-programmed desorption (NH3-TPD) and H2 temperature-programmed reduction (H2-TPR) showed that the catalyst had strong acid sites and good redox properties. Zeta potential testing showed that the electronegativity of the chlorella cell surface could be used to enrich with Mn2+. X-ray photoelectron spectroscopy (XPS) confirmed that Chlorella@Mn had a high content of Mn3+ and surface chemisorbed oxygen. In-situ diffuse reflectance infrared Fourier transform spectroscopy (in-situ DRIFTS) experimental results showed that both Langmuir-Hinshelwood (L-H) and Eley-Rideal (E-R) mechanisms play a role in the denitrification process on the surface of the Chlorella@Mn catalyst, where the main intermediate nitrate species is monodentate nitrite. The presence of SO2 promoted the generation and strengthening of Brønsted acid sites, but also generated more sulfate species on the surface, thereby reducing the denitrification activity of the Chlorella@Mn catalyst. The Chlorella@Mn composite catalyst had the characteristics of short preparation time, simple process and low cost, making it promising for industrial application.

Efficient and Stable Rice Husk Bioderived Silica Supported Cu2S-FeS for One Pot Esterification and Transesterification of a Malaysian Palm Fatty Acid Distillate

A novel heterogeneous catalyst composite (CuS-FeS/SiO2) derived from rice husk silica was engineered following pyrolysis, chemical precipitation, and chemical redox technique. The resulting catalyst was applied to the conversion of palm fatty acid distillate to biodiesel. The presence of CuS and FeS on the catalyst was verified using X-ray diffraction and Fourier transform infrared spectroscopy, nitrogen physisorption, scanning electron microscopy (FESEM) with energy dispersive X-ray (EDS) spectroscopy, and temperature-programmed desorption of NH3 (TPD-NH3), inductively coupled plasma-atomic emission spectrometry (ICP-AES), and TGA; a specific surface area of approximately 40 m2·g−1 was identified. The impact of independent variables, i.e., reaction temperature, reaction duration, methanol:oil ratio and catalyst concentration were evaluated with respect to the efficacy of the esterification reaction. The greatest efficiency of 98% with a high productivity rate of 2639.92 µmol·g−1·min−1 with k of 4.03 × 10−6 mole·S−1 was achieved with the following parameters: temperature, 70 °C; duration, 180 min; catalyst loading, 2 wt.%; and methanol to oil ratio, 15:1. The CuS-FeS/SiO2 catalyst showed relatively high stability indicated by its ability to be reused up to five times.

Study on the Performance of the Zr-Modified Cu-SSZ-13 Catalyst for Low-Temperature NH3-SCR.

Cu-SSZ-13 and Zr-modified Cu-SSZ-13 catalysts with different Zr/Cu mass ratios were prepared by ion-exchange and impregnation methods, respectively. The NH3-SCR performance tests were performed using the catalyst performance evaluation device to investigate the effects of different Zr/Cu mass ratios on the catalyst ammonia-selective catalytic reduction (NH3-SCR) performance. X-ray diffraction, ICP-OES, BET, NH3 temperature-programed desorption (NH3-TPD), H2 temperature-programmed reduction (H2-TPR), X-ray photoelectron spectrometry, and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) were used to characterize the catalysts. The results show that the prepared Cu-SSZ-13 catalyst had good catalytic activity. Zr introduction was carried out on this basis. The results showed that proper Zr doping improved the catalytic activity at low temperatures and widened the high-temperature stage, with an optimal activity stage at a Zr/Cu mass ratio of 0.2. The NO x conversion efficiency was close to 100% at 200 °C and over 80% at 450 °C. The active species were well dispersed on the catalyst surface, and the metal modification did not change the crystal structure of the zeolite. The NH3-TPD results showed that the Zr-modified catalyst had more abundant acid sites, and the H2-TPR results indicated that the Cu species on the catalyst had excellent reducibility at low temperatures. The interaction between Cu and Zr could regulate the Cu+ and Cu2+ proportion on the catalyst surface, which facilitated the increase in the Cu+ for fast SCR reaction at low temperatures. With abundant acid sites and both SCR reactions following the Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) mechanism on the catalyst surface at a low temperature of 150 °C, more abundant acid sites and reaction paths created favorable conditions for NH3-SCR reactions at low temperatures.

WO3-based porous MCM-48 catalysts for renewable acrolein synthesis by the dehydration of glycerol

The gas-phase selective dehydration of glycerol to acrolein was studied over x%W (x: 5, 15, 25, and 35 %, w/w) supported on MCM-48. Microporous silica MCM-48 was synthesized to produce three-dimensional cubic crystals with a high surface area and resistance to hydrolytic pressure. Tungsten oxide (WO3) based solid acid catalysts supported on MCM-48 were prepared by two distinct synthesis methods, namely, oxalic acid added sol–gel (HSG) and nonhydrolytic sol–gel (NHSG) methods. The morphological and textural properties of catalysts were characterized by XRD, BET, SEM, Raman, XPS, and FT-IR techniques. The acidic properties of catalysts were elucidated by FTIR pyridine-adsorption and NH3-Temperature Programmed Desorption (NH3-TPD). The total surface acid sites’ concentration, Brønsted (B) and Lewis (L) acid concentrations, and B/(B+L) ratios were calculated from NH3-TPD and pyridine-FTIR. The steady acrolein yields were obtained with the optimal catalysts (15 %W and 25 %W loaded MCM-48 for HSG and NHSG, respectively). This study demonstrated that the medium-strength surface acidity and B/(B+L) ratios for glycerol dehydration to acrolein were correlated with both the activity and the selectivity of acrolein.

MESOPOROUS SILICOALUMINATE MATERIALS (MCM-41, SBA-15 AND MCF) BY ATRANE ROUTE FOR COBALT CATALYST

In this work, the synthesis of mesoporous silicoaluminum supports synthesized by the atrane route was performed. The obtained supports presented high homogeneity of the aluminum dispersion, high surface area and narrow pore size distribution. The synthesized mesoporous supports were: MCM-41, SBA-15 and MCF with 10% of Al2 O3 in the matrix of SiO2 . Twelve percent of cobalt was added to these supports by the incipient wetness impregnation method. These materials were characterized by adsorption of Nitrogen (BET-BJH), Scanning Microscopy Electron (SEM), X-Ray Diffraction (XDR), H2 Temperature-Programmed Reduction (TPR) and NH3 Temperature-Programmed Desorption (TPD). According to their structural properties of these catalysts, a promising application in the Fischer- Tropsch syntheses (FTS) is identified.

Destructive and Protective Effects of NH3 on the Low-Temperature Hydrothermal Stability of SAPO-34 and Cu-SAPO-34.

The influences of gaseous, weakly adsorbed, and strongly adsorbed NH3 on the low-temperature (<100 °C) hydrothermal stability of SAPO-34 and Cu-SAPO-34 were investigated. NH3 temperature-programmed desorption (NH3-TPD), 1H magic angle spinning nuclear magnetic resonance (MAS NMR), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) were adopted to characterize the adsorption states of NH3 and H2O in SAPO-34, and the destruction of the SAPO-34 framework was revealed by direct and cross-polarization 29Si, 27Al, and 31P MAS NMR. Gaseous NH3 coadsorbed with H2O inside SAPO-34 micropores and induced the hydrolysis of framework P-O-Al and Si-O(H)-Al bonds. Weakly adsorbed NH3 was released during aging and played a similar negative role to gaseous NH3. When being combined with hydrolyzed Al species from the framework, active Cu ions transformed to inactive CuAl2O4-like species, leading to deactivation in low-temperature SCR of Cu-SAPO-34. Strongly adsorbed NH4+ via 200 °C preadsorption protected the framework integrity of SAPO-34 and the SCR activity of Cu-SAPO-34.

One-pot synthesis of CNT-SAPO-34 composite supported copper and cerium catalysts with excellent surface resistance to SO2 and H2O in NH3-SCR

CuCe/CNTx-SAPO-34 (x = 0, 0.5, 1, 2) with various CNT doping quantities were synthesized through the one-pot hydrothermal synthesis method using CNT and SAPO-34 as composite supporters. The selected CuCe/CNT1-SAPO-34 catalyst exhibits remarkable SCR activity and high H2O/SO2 resistance in a wide temperature range of 200–450 °C. X-ray diffraction (XRD), N2 adsorption–desorption, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), H2-temperature programmed reduction (H2-TPR), and NH3-temperature programmed desorption (NH3-TPD) were used to characterize the physiochemical structure, surface state of active sites reducibility, and surface acidity of the catalysts. The characterization results reveal that CuCe/CNT1-SAPO-34 possesses a hierarchical structure, small particle size, high levels of surface Cu2+, Ce3+ and chemisorbed oxygen, enhanced reducibility, and suitable surface acidity. For comparison, CuCe/CNT1-SAPO-34 (P) mixed mechanically with CuCe/CNT0-SAPO-34 and CNT was investigated through the NH3-SCR with and without H2O/SO2, it also displays lower resistance of H2O and SO2 than CuCe/CNT1-SAPO-34. The catalytic performance made CuCe/CNT1-SAPO-34 a promising catalyst for the NOx emission control from diesel vehicles.

Comparative study of hydrodeoxygenation performance over Ni and Ni2P catalysts for upgrading of lignin-derived phenolic compound

To deeply understand the different hydrodeoxygenation (HDO) behavior of the monometallic Ni and Ni2P catalysts in HDO processes, the Ni/SiO2 and Ni2P/SiO2 catalysts were prepared, respectively. The as-prepared catalysts were characterized by X-ray diffraction (XRD), N2 adsorption–desorption, X-ray photoelectron spectra (XPS), H2 temperature-programmed reduction (H2-TPR), transmission electron microscope (TEM), NH3 temperature-programmed desorption (NH3-TPD), and CO uptakes. Taking the lignin-derived phenolic compound as raw material, the HDO performance and reaction route of the monometallic Ni and Ni2P catalysts were compared. The results showed that the phosphorization contributed to highly dispersion of active sites, formation of smaller active sites and significantly enhanced acid sites, showing Ni2P/SiO2 catalyst is a bifunctional metal–acid catalyst. For both of the Ni/SiO2 and Ni2P/SiO2 catalysts, the HDO of m-cresol mainly proceeded by the hydrogenation (HYD) step. However, the acid sites on Ni2P/SiO2 catalyst can significantly promote the conversion of oxygenated 3-methylcyclohexanol (MCHnol) to deoxygenated methylcyclohexane (MCH) owing to its strong hydrogenolysis of C–OH bond originated from the bifunctional metal–acid sites. In addition, the unique electron structure of Ni2P phase involved in two different types of sites (tetrahedral Ni(I) and square pyramidal Ni(II)) and the highly dispersed smaller Ni2P particles also contributed to the outstanding HDO performance. Density functional calculation (DFT) calculations clarified that the Ni2P active phase possessed prior ability to cleavage of C–OH bond in comparison with the metallic Ni species. As a result, Ni2P/SiO2 catalyst showed a significantly higher selectivity to MCH (96.3 %) than that of Ni/SiO2 (14.1 %) catalyst at the conditions of 250 ℃ for 240 min.

An Efficient Zr-ZSM-5-st Solid Acid Catalyst for the Polyol Esterification Reaction

In this study, Zr active species were implanted into a ZSM-5 zeolite framework to form a solid acid catalyst through steam treatment and the liquid-solid isomorphous substitution process. The as-synthesized Zr-ZSM-5-st catalyst ensured excellent esterification of trimethylolpropane and fatty acids (FAs) to achieve a polyol ester production yield of 94.41%. Combined with N2 physisorption, X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, transmission electron microscopy mapping, X-ray photoelectron spectroscopy, NH3 temperature-programmed desorption, and inductively coupled mass plasma spectroscopy were conducted. The results revealed that the excellent performance of Zr-ZSM-5-st catalyst could be attributed to the enhanced acidity and the developed surface area and pore structure.

Doping effect of rare earth metal ions Sm3+, Nd3+ and Ce4+ on denitration performance of MnOx catalyst in low temperature NH3-SCR reaction

The MnXOx catalysts (i.e., MnSmOx, MnNdOx, MnCeOx) were prepared by reverse co-precipitation method and used for NH3-SCR reaction. It is found that MnCeOx catalyst presents the best low temperature catalytic activity (higher than 90% NOx conversion in the temperature range from 125 to 225 °C) and excellent H2O + SO2 resistance. In order to explore the reason for this result, the characterization of X-ray diffraction (XRD), Raman spectroscopy, Brunauer–Emmett–Teller (BET), H2-temperature programmed reduction (H2-TPR), NH3-temperature programmed desorption (NH3-TPD), X-ray photoelectron spectroscopy (XPS) and in situ diffuse reflaxions infrared Fourier transformations spectroscopy (DRIFTS) were conducted. The obtained results suggest that MnCeOx catalyst shows the largest amount of acid sites and the best reducibility among these MnXOx catalysts. Besides, Ce4+ doping inhibits the crystallization of MnOx catalyst and shows the largest specific surface area. Finally, in situ DRIFTS experiments reveal that NH3-SCR reaction over MnCeOx catalyst follows both Langmuir–Hinshelwood (L-H) and Eley-Rideal (E-R) mechanisms, which is through “fast SCR” reaction.

On the various Cu-redox pathways and O2-mediated Bronsted-to-Lewis adsorbed-NH3 redistribution under SCR half-cycle conditions

The Standard SCR reaction on Cu-SSZ-13 is a complex redox process facilitated by a reduction half cycle (RHC) and an oxidation half cycle (OHC). It is generally accepted that RHC requires the simultaneous presence of NO and NH3, while OHC requires both NO and O2; however understanding of how these individual reactants impact the Cu redox cycle is limited. In this study, we provide experimental investigation of NO-only, NH3-only and NO+NH3 RHC, and their relative rates. Simple kinetic models were developed to understand the dependance of NO-only and NH3-only RHC on Cu speciation. Various OHC routes including NO+O2 and O2-only OHC, and a previously unreported H2O-mediated OHC pathway were also investigated. Detailed NH3 temperature-programmed desorption studies showed that RHC selectively consumes NH3 adsorbed on Lewis-acid sites, and that part of the remaining Bronsted-bound NH3 moves to the Lewis-acid sites during subsequent OHC, thereby resulting in a repartitioning of adsorbed NH3.

Effect of different doping elements on performance of Ce–Mn/TiO2 catalyst for low temperature denitration

Sm and Ho were doped in Ce–Mn/TiO2 catalyst respectively to enhance its denitration performance at low temperature. X-ray diffraction (XRD), N2 adsorption–desorption, X-ray photoelectron spectroscopy (XPS), NH3-temperature programmed desorption (NH3-TPD), H2-temperature programmed reduction (H2-TPR) and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) techniques were used to analyze the structure and performance of catalysts. The results demonstrate that Ho doping increases the amount of acid sites and improves low temperature redox property of Ce–Mn/TiO2, which lead to excellent DeNOx performance of Ho-Ce-Mn/TiO2 in the whole reaction temperature range. Sm doping results in decline of redox property, but it is beneficial to increasing the acid sites of Ce–Mn/TiO2. The increased surface acid sites and moderate oxidative ability impart Sm-Ce-Mn/TiO2 higher denitration activity and N2 selectivity at temperature above 150 °C. Lewis acid sites and redox property are the main factors affecting the activity of catalysts. Doping of Ho and Sm both improves sulfur resistance performance of Ce–Mn/TiO2 by inhibiting the adsorption of SO2 and formation of sulfate. Ce–Mn/TiO2 modified by Ho shows better sulfur resistance than that doped with Sm because of its more surface acid sites.

Low-Temperature NH3-SCR on Cex-Mn-Tiy Mixed Oxide Catalysts: Improved Performance by the Mutual Effect between Ce and Ti

A series of Cex-Mn-Tiy catalysts were synthesized using the coprecipitation method, and sodium carbonate solution was used as a precipitant. The various catalysts were assessed by selective catalytic reduction of NOx with NH3, and characterized by X-ray diffraction, Raman spectroscopy, H2 temperature-programmed reduction, NH3 temperature-programmed desorption, and X-ray photoelectron spectroscopy to investigate the physicochemical properties, surface acidity, and redox abilities of the Cex-Mn-Tiy catalysts. The Ce0.1-Mn-Ti0.1 catalyst exhibited the best catalytic performance (more than 90% NOx conversion in the range of 75 to 225 °C), as a result of proper redox ability, abundant acid sites, high content of Mn4+ and Ce3+, and surface-adsorbed oxygen (OS). The results of in situ DRIFT spectroscopy showed that the NH3-SCR reaction followed both the E-R and L-H paths over the Ce0.1-Mn-Ti0.1 catalyst, and it occurred faster and more sharply when it mainly abided by the E-R mechanism.

Selective Hydrodeoxygenation of Lignin and Its Derivatives without Initial Reaction Pressure Using MOF-Derived Carbon-Supported Nickel Composites

In this study, Ni-metal–organic frameworks (MOFs) were used as precursors to obtain carbon-supported nickel composites (Ni@C) after calcination. The hydrodeoxygenation properties of the model compound and corncob lignin were investigated without an external hydrogenation source and initial pressure. Additionally, the effect of Ni@C on degradation of model compounds, corncob lignin, and benzyl phenyl ether (BPE) under different conditions was examined. The results showed that with isopropanol as the in situ hydrogen source, the conversion percentage of BPE was 90.2% and the yield of phenol was 88.3 wt % at 150 °C. The catalysts were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), NH3 temperature-programmed desorption (NH3-TPD), X-ray photoelectron spectroscopy (XPS), and thermogravimetry (TG), and the lignin and bio-oil were characterized by gas chromatography–mass spectrometry (GC–MS) and two-dimensional heteronuclear single quantum coherence (2D-HSQC). It was found that the Ni@C catalyst with well dispersion, high support rate, and rich acid sites was successfully synthesized. In the process of degradation, the C–O ether bond in the structure of lignin was successfully broken to generate the phenolic monomer, and the high-efficiency hydrodeoxygenation of lignin was realized under mild conditions.

Catalytic oxidation of soot by CeO2–ZrO2 catalysts: Role of Zr

Human health has been adversely affected by the soot particles in the exhaust of diesel engines. In this study, ceria-zirconia supported 1, 3, and 5 wt% zirconium (Zr) catalysts were prepared using the co-precipitation method and tested for soot combustion. The chemical and physical properties of catalysts were evaluated through NH3-temperature-programmed desorption (NH3-TPD), scanning electron microscopy (SEM), physisorption analysis, Raman spectroscopy, H2-temperature programmed reduction (H2-TPR), and X-ray diffraction (XRD). The catalytic activity of the catalysts for soot combustion was tested in loose contact through thermo-gravimetric analysis (TGA). Nitrogen and air atmosphere were used for the combustion of model soot. 3 and 5 wt% Zr/CeO2–ZrO2 showed higher soot oxidation than 1 wt% Zr/CeO2–ZrO2 in the nitrogen atmosphere, whereas percentage weight loss of model soot was high with 1 wt% Zr/CeO2–ZrO2 than 3 and 5 wt% Zr/CeO2–ZrO2.

Effect of Physicochemical Properties of Co and Mo Modified Natural Sourced Hierarchical ZSM-5 Zeolite Catalysts on Vanillin and Phenol Production from Diphenyl Ether

The conversion of lignocellulose biomass to value-added chemicals is challenging. In this paper, the conversion process of diphenyl ether (DPE) as a model lignin compound to phenol and vanillin compounds involved a bifunctional catalyst in reaching the simultaneous one-pot reaction in mild conditions with a high yield product. The catalysts used in this conversion are hierarchical ZSM-5 zeolites and their cobalt oxide and molybdenum oxide impregnated derivate. The ZSM-5 zeolites were synthesized using alternative precursors from natural resources, i.e., Indonesian natural zeolite and kaolin. The physicochemical properties of the catalysts were determined with various characterization methods, such as: X-ray Diffraction (XRD), Fourier Transform Infra Red (FT-IR), Scanning Electron Microscope - Energy Dispersive X-ray (SEM-EDX), X-ray Fluorescence (XRF), Surface Area Analyzer (SAA), and NH3-Temperature Programmed Desorption (NH3-TPD). The catalytic activity on conversion of DPE substrates showed that the MoOx/HZSM-5 produced the highest %yield for phenol and vanillin products; 31.96% at 250 °C and 7.63% at 200 °C, respectively. The correlation study between the physicochemical properties and the catalytic activity shows that the dominance of weak acid (&gt;40%) and mesoporosity contribution (pore size of ~ 9 nm) play roles in giving the best catalytic activity at low temperatures. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Synthesis and characterization of mesoporous-HZSM-5 as a catalyst for ethanol dehydration to ethylene

In this work, mesoporous HZSM-5 (M-HZSM-5) was synthesized with γ-(2,3-epoxypropoxy) propyltrimethoxysilane as pore-expanding agent through one-pot method and was studied for its catalytic activity and stability in ethanol dehydration. The resultant samples were characterized by various techniques, including Brunauer-Emmett-Teller, Scanning electron microscopy, Fourier transform infrared spectroscopy, the temperature-programmed desorption of NH3, and Thermogravimetric. Based on the analysis of the results, M-HZSM-5 with the typical MFI structure displays a specific surface area of 450 m2 g−1. Furthermore, the improvement of the activity and anti-coking ability of the catalyst for ethanol dehydration to ethylene is attributed to the existence of mesopores in HZSM-5, which can provide the reaction space and acid sites.

Dispersion and Stabilization of Supported Layered Double Hydroxide-Based Nanocomposites on V-Based Catalysts for Nonoxidative Dehydrogenation of Isobutane to Isobutene

Nonoxidative dehydrogenation of isobutane is one of the sustainable strategies for producing high value added isobutene. As alternatives for the commercial Pt- and Cr-based dehydrogenation catalysts, supported V-based catalysts are worthy of study. In this work, a series of VOx/mMgAlO-R catalysts (m = 10, 15, 20, 25 and 30) were designed and prepared by loading VOx on mMgAlO composite oxide supports derived from mesoporous Al2O3-supported layered double hydroxide (LDH) nanocomposites. The calcined and reduced catalysts were characterized by X-ray diffraction (XRD), Raman spectra, Ultraviolet-visible diffuse reflectance (UV-Vis) spectra, NH3 temperature-programmed desorption (NH3-TPD), Temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TG) and low temperature N2 adsorption–desorption isotherms. The as-synthesized VOx/20MgAlO-R with appropriate Mg addition exhibits superior activity (43–56% conversion and 77–81% selectivity), excellent stability and coking-resistance for the isobutane dehydrogenation. The structure–performance relationship reveals that the formation of VOx species confined in the reconstructed LDH interlayer and porous MgO facilitates dispersing and stabilizing the VOx species. The low polymerization degree and higher proportion of V4+ ion for VOx species, strong acidity of medium acid sites and low concentration of strong acid sites are responsible for the excellent anti-coking and catalytic performance. The strong VOx–support interaction is beneficial for enhancing the stability of the catalysts.

Micro-meso structure NaP zeolite @TiO2 nanocomposite: eco-friendly photocatalyst for simultaneous removal COD and degradation of methylene blue under solar irradiation.

A low-cost NaP zeolite@TiO2 nanocomposite catalyst with zeolite Si/Al ratio lower than three were synthesized for the first time under hydrothermal condition. The nanocomposites were characterized by different methods such as Fourier transform infrared (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS), N2 physisorption, NH3 temperature-programmed desorption (NH3-TPD), fluorescence microscopy, thermal analysis (TGA/DTA) and zeta potential analysis. The results showed that a micro-meso structure NaP zeolite with higher surface area and acidity with respect to pure zeolite was prepared. TiO2 nanoparticle was dispersed over the whole of zeolite without aggregation. A reduction of the TiO2 bandgap nanoparticle was observed from DRS spectra. The photocatalytic activity of low-cost NaP zeolite@TiO2 nanocomposite was tested for simultaneous methylene blue dye (MB) and chemical oxygen demand (COD) under solar and ultraviolet light. The result showed that the nanocomposite catalyst has great potential (above 90%) for COD removal discolouring of MB (about 99.6%) at room temperature. The optimum amount of some parameters such as the loaded amount of TiO2 (0.36g), catalyst dosage (0.1g), time (2h), initial dye concentration (100mg/L), solution pH value (about 7) under solar light were considered. In addition, present negative charge in the surface that show in zeta potential confirm the high activity of catalyst to interaction with cationic dye. As a further advantage, the NaP zeolite@TiO2 nanocomposite was easier to be separated in aqueous media than the pure TiO2 powders, making possible the reuse several times (over five runs) without using oxidant. Finally, the NaP zeolite@TiO2 nanocomposite was used for COD abatement in wastewater from two real industrial streams. The MB degradation kinetics were fitted by a pseudo-first-order model with K = 0.534h-1.