Medium Strong Acid Research Articles

The catalytic pathways on niobium-cerium loading catalysts for methylene blue elimination in the Fenton-like system: Roles of oxygen vacancies

The oxidation pathways affected by asymmetric and symmetric Ov sites on catalysts in the Fenton-like process should be illustrated in detail. Based on the experimental and theoretical results, it can be revealed that the asymmetric Ov sites favored nonradical species (1O2) formation by triggering H2O2 and DO to produce surface O2·-, and the migration distance between the species and pollutant was shortened due to the excellent adsorption of methylene blue (MB) on the sites. OH species were liable to be generated on the symmetric Ov sites. Calcination and the amount of medium strong acid sites of the support may be important roles in the formation of asymmetric Ovs for the Nb-Ce loading catalyst prepared by impregnation. This work unravels the different catalytc pathways of asymmetric and symmetric Ovs dominated, and also provides a facile strategy to control the oxidation pathway as desirable in the H2O2-Fenton-like system.

Lignin-MOF hybrid polymetallic composites for selective hydrogenolysis of cellulose derived 5-hydroxymethylfurfural

The development of green, effective and inexpensive catalysts was important for the catalytic transfer hydrogenation of 5-hydroxymethylfurfural (HMF) to prepare 5-methylfurfuryl alcohol (MFA). The assembly of sodium lignosulfonate (LS) with NiCo-MOFs through a simple hydrothermal method was reported, and a series of iron-containing polymetallic hybrid catalysts were investigated. The introduction of iron led to the increase of medium strong acid sites and Lewis acid sites in the catalyst and enhanced the adsorption of furan rings, thus improved the catalytic activity. The effects of calcination temperature, iron content, and reaction parameters (including reaction temperature, pressure, hydrogen donor solvent) were all studied in detail. It was found that HMF could be completely converted over Fe@Ni3Co-MOF-LS, with a MFA yield of 88.75 % under the optimal condition (240 ℃, 2 MPa N2 in 4 h) without the presence of hydrogen. This study provided a new perspective for the utilization of lignin resource as carbon-based catalysts for the production of biomass-derived platform chemicals.

Revisiting Pentazole: An Investigation into the Intriguing Molecule Exhibiting Dual Organic and Inorganic Characteristics.

Pentazole (cyclo-HN5) is a unique heterocycle categorized as both an organic and inorganic compound. However, attempts to synthesize and characterize cyclo-HN5 have been unsuccessful thus far. In this study, we synthesized a cyclo-HN5 solution and investigated the spectra, structure, aromaticity, acidity, and stability of cyclo-HN5. The lone pair of electrons on the protonated N atom of cyclo-HN5 participates in π-electron delocalization, forming two N═N bonds. Further investigations suggest that cyclo-HN5 exhibits significantly decreased π aromaticity and slightly lower σ aromaticity than cyclo-N5-. Experimental results suggest that pure cyclo-HN5 is unstable at ambient temperatures and pressures, but it can be isolated at high pressures or stabilized in solution by abundant hydrogen bonds. The pKa of cyclo-HN5 was determined as 1.63 (H2O, 25 °C) via potentiometric titration, indicating that cyclo-HN5 is a medium-strong acid. This study reveals the fundamental structure and properties of cyclo-HN5, thereby providing important data for advancing cyclo-HN5 chemistry.

Promoted catalytic property of Cu/SSZ-13 by introducing a minority of Mn for NO removal from diesel engine exhaust

The Cu-exchanged SSZ-13 with the small-pore chabazite framework is considered as a highly efficient catalyst for selective catalytic reduction of NO with NH3 (NH3-SCR). In order to further improve the catalytic property, a series of Mn ion-assisted Cu/SSZ-13 powder catalysts were prepared by co-exchange method and stepwise exchange method. It is found that the NH3-SCR activity, N2 selectivity, hydrothermal stability and sulfur resistance of Cu/SSZ-13 are promoted by introducing a minority of Mn (0.15%–0.23%(mass)) through co-exchange method. Characterization results revel that the Cu,Mn co-exchange enables the higher amounts of Cu2+ active sites, the abundant medium strong and strong acid, the optimized ratio of lewis acid to Brønsted acid, etc., which are required for a good NH3-SCR catalytic property over broad temperature range and under harsh working environment. Moreover, a monolithic catalyst was prepared by impregnating a cordierite ceramic support into the coating slurry containing the optimized CuMn/SSZ-13 powder. The diesel engine bench tests show that Cu,Mn co-exchange gives the monolith catalyst a better catalytic property than commercial catalysts. This work provides an important guidance for the rational design of secondary-ion-assisted zeolites applied in NH3-SCR.

Selective hydrocracking of 1-methylnaphthalene to benzene/toluene/xylenes (BTX) over NiW/Beta bifunctional catalyst: Effects of metal–acid balance

The hydrocracking catalyst is characteristic of bifunctional catalyst mainly requiring metal–acid balance, which includes metal–acid ratio and metal–acid proximity. Here, we screened and clarified the optimal metal–acid balance on 1-methylnaphthalene (1-MN) hydrocracking by adjusting metal–acid ratio (nM/nA) via physically mixing the γ-Al2O3 supported NiW samples and Beta zeolite with different acidity (denoted as NiW/AB(x) and x presents the molar ratio of SiO2/Al2O3 for Beta zeolite). NiW/AB(60) catalyst with a nM/nA of 0.40 showed the highest BTX selectivity (14.4 %) at a 1-MN conversion of 76.6 %, suggesting an optimal site balance between the metal sulfide site and medium-strong acid sites (ca. 1:2.5). Also, four different metal–acid proximities with centimeter, millimeter, micrometer and nanoscale distances were compared. The nanoscale proximity enabled the highest BTX selectivity (19.6 %) as compared to the microscale (14.4 %), millimeter scale (12.4 %) and centimeter scale (7.1 %) catalysts, confirming that the selectivity of BTX benefited from the fast diffusion for transporting reaction intermediates between metal and acid sites. Thus, we realized a nM/nA of 0.40 and a nanoscale site proximity for improving the reactivity and selectivity of 1-MN hydrocracking. This work not only presents an elegant showcase of achieving the synergistic effects of bifunctional catalyst, but also provides a rational approach for enhancing the catalytic performance of hydrocracking and beyond.

The influence of H2O or/and O2 introduction during the low-temperature gas-phase sulfation of organic COS + CS2 on the conversion and deposition of sulfur-containing species in the sulfated CeO2-OS catalyst for NH3-SCR.

Herein, the typical components of blast furnace gas, including H2O and O2, were introduced to improve the NH3-SCR activity of the sulfated CeO2-OS catalyst during the gas-phase sulfation of organic COS + CS2 at 50 °C. The characterization results demonstrate that the introduction of O2 or H2O during gas-phase sulfation enhances the conversion of organic COS + CS2 on a cubic fluorite CeO2 surface and reduces the formation of sulfur and sulfates in the catalyst, but decreases the BET surface area and pore volume of the sulfated CeO2-OS catalyst. However, the introduction of O2 or H2O during the gas-phase sulfation increases the molar ratios of Ce3+/(Ce3+ + Ce4+) and Oβ/(Oα + Oβ + Oγ) on the sulfated CeO2-OS catalyst surface, thus promoting the formation of surface oxygen vacancies and chemisorbed oxygen, and these properties of the catalyst are further enhanced by the co-existence of O2 and H2O. Furthermore, the reduction of sulfates formed under the action of O2 or H2O decreases the weak acid sites of the sulfated CeO2-OS catalyst, but the few and highly dispersive sulfates present stronger reducibility, and the proportion of medium-strong acid sites of the catalyst increases. These factors help to improve the NH3-SCR activity of the sulfated CeO2-OS catalyst. Thus, there exists a synergistic effect of H2O and O2 introduction during gas-phase sulfation on the physical-chemical properties and catalytic performance of the sulfated CeO2-OS catalyst by organic COS + CS2 at 50 °C.

Promotional effect of H2O introduction on the NH3-SCR activity of the gas-phase sulfated CeO2 catalyst by organic CS2+COS: Influence of H2O concentration

Herein, as an indispensable key reactant for the hydrolysis of organic sulfur, H2O was firstly introduced to optimize the NH3-SCR activity of CeO2 by providing the adsorption and reaction spots of catalysis for organic CS2+COS during the low-temperature gas-phase sulfation. The results demonstrate that the introduction of 0.33 vol% H2O is beneficial to enhance the interaction between organic CS2+COS and cube fluorite CeO2, which not only increases the concentrations of Ce3+ ions, chemisorbed oxygen (Oβ) and oxygen vacancies on CeO2-CS2+COS surface, but also effectively enhances the redox cycle of Ce4+/Ce3+ ion pairs and the medium-strong acid sites of catalyst. These all help enhance the promotional effect of organic sulfur low-temperature gas-phase sulfation on the NH3-SCR activity of CeO2 and further improve NOx reduction over the CeO2-CS2+COS catalyst. However, the introduction of 5.0 vol% H2O shows a certain inhibitory effect due to the competitive adsorption of excess water and CS2+COS on the cube fluorite CeO2 surface, which weakens their interaction during the low-temperature gas-phase sulfation, thereby decreases the promotional effect of low concentration water introduction on the NH3-SCR activity of the CeO2-CS2+COS catalyst. Therefore, the results of this research provide a scientific reference for developing the NH3-SCR CeO2-based catalyst in practical applications.

Synthesis of mordenite by solvent-free method and its application in the dimethyl ether carbonylation reaction

Mordenite with different Si/Al ratios were synthesized by solvent-free method and used for dimethyl ether (DME) carbonylation reaction. The influence of Si/Al ratio in the feedstock on the structure, porosity and acid sites were systematically investigated. The characterization results showed that with the increase of Si/Al ratio in the feedstock, part of silicon species fail to enter the skeleton and the specific surface area and pore volume of the samples decreased. The amount of weak acid and medium strong acid decreased alongside with the increasing Si/Al ratio, and the amount of strong acid slightly increased. The Al atoms preferentially enter the strong acid sites in the 8 MR channel during the crystallization process. The high Si/Al ratio sample had more acid sites located in the 8 MR channel, leading to more active sites for carbonylation reaction and higher catalytic performance. Appropriately increasing the Si/Al ratio was beneficial for the improvement of carbonylation reaction activity over the MOR catalyst.

Isolated CuO and medium strong acid on CuO/Nb2O5-H catalyst for efficient enhancement of triethylamine selective catalytic oxidation

The selective catalytic oxidation (SCO) of triethylamine (TEA) to harmless N2, CO2, and H2O is an appropriate elimination technology. It is necessary to develop the catalysts capable of working under mild condition and with excellent N2 selectivity for this reaction. In this article, the CuO/Nb2O5-H catalysts with various loadings were characterized and employed for the SCO of TEA. The 15 %CuO/Nb2O5-H demonstrated the most noticeable catalytic performance. At 220 °C, the conversion of TEA reached 100.0 %, and the selectivity of N2 was 96.0 %. XPS, UV–vis results demonstrated the presence of isolated CuO species in the catalyst and auger electron energy spectra proved the content of Cu2+ species over 85 %. Pyridine-IR and NH3-TPD demonstrated the presence of a substantial number of acidic sites in Nb2O5-H. Based on the in-situ DRIFTs results, the adsorption of TEA on the acidic sites of Nb2O5-H at low temperature is considered as the initial step in the process, followed by C-N bond activation, cleavage, and adsorption of the -NH* intermediates. The -NH* was oxidized to N2 by highly dispersed copper oxide species on the catalyst surface at 220 °C.

The catalytic characteristics of 2-methylnaphthalene acylation with AlCl3 immobilized on Hβ as Lewis acid catalyst

Abstract The heterogeneous supported Lewis acid catalyst prepared by immobilization technology has high reaction activity. It is an environment-friendly catalyst. Using Lewis acid immobilized as the catalyst, 2-methyl-6-propionyl naphthalene is synthesized by Friedel–Crafts reaction with 2-methylnaphthalene and propionic anhydride, which has a good development prospect. A variety of AlCl3 catalysts supported by H-zeolite molecular sieves are prepared using the solvent reflux method in the paper. It is found that AlCl3/Hβ has better catalytic performance. The results showed that AlCl3/Hβ catalyst is mainly composed of L acid. The acid content of B acid and the specific surface area increase, and the pore volume and pore size decreases. With the increase in AlCl3 concentration, the acid content of strong acid, medium strong acid, and weak acid increases, but the solubility of AlCl3 in CHCl3 is limited. When the concentration of AlCl3 is too high, too much AlCl3 is deposited on the surface of the molecular sieve, which is useless to its binding with Si–OH. AlCl3/Hβ’s activity is higher when the concentration of AlCl3 is 3 g·L−1, and the solvent is refluxed for 8 h and calcined at 550°C for 3 h. Under these conditions, the conversion of 2-methylnaphthalene is 85.86%, and the yield of β,β-methyl propyl naphthalene is increased to 81.19%.

Effective synthesis of limonene over mild alkali-modified 13X catalysts in α-pinene isomerization

The mild alkali-treated 13X was employed in the liquid phase isomerization reaction of α-pinene to increase the yield of limonene. A maximum α-pinene conversion of 100% and limonene yield of 59.1% could be achieved. Crystallinity could be well retained, and the amounts of medium-strong acid sites and the distribution of Brønsted and Lewis acid sites could be changed after the mild alkali treatment for 13X zeolite. Samples with higher micropore specific surface area were easier to obtain higher yields of limonene due to shape-selectivity. A proper amount of the medium-strong acid and the synergistic effect of Brønsted and Lewis acid sites were beneficial to enhance the catalytic activity and the yield of monocyclic product limonene. The main reason for catalyst deactivation could be the decrease in the active sites due to soft coke deposition. For the regeneration process, the conversions of α-pinene were between 95% and 99% during the first seven cycles and the conversion dropped to 90.6% after the eighth cycle, which demonstrated that the ethanol flushing and calcination could be an effective regeneration method for the 13X catalyst used in the α-pinene isomerization reaction.

In situ oxygen-induced zigzag graphene as metal-free catalyst for hydrogen activation in nitroarenes hydrogenation

Metal-free catalysts for hydrogenation reactions using molecular hydrogen (H2) are a major challenge in the field of catalysis. The Frustrated Lewis Pairs (FLPs) systems and heteroatom-doped carbon materials as metal-free catalysts are currently the mainstream research in hydrogenation reactions. Here, a series of oxygen-induced zigzag graphene (OZG) was constructed over thermal treatment of reduced graphene oxide (rGO) and applied as metal-free catalysts in nitrobenzene hydrogenation. The OZG-800 (thermal treatment at 800 °C) shows promising performance activity with 99.7% nitrobenzene conversion and 94.4% selectivity to aniline. The experimental results indicate that the zigzag edge and medium-strong acid sites formed by oxygen species may be the active centers in nitrobenzene hydrogenation. The density functional theory (DFT) calculations are in accord with experimental results that the zigzag edge and oxygen species play a critical role in H2 activation and dissociation. This work provides a promising route for the rational design of metal-free catalysts for hydrogenation.

Preparation of ZrO2/TiO2/Al2O3 Nanofiltration Lab-Scale Membrane for Filtering Heavy Metal Ions

ZrO2 is an excellent ceramic preparation material that can maintain chemical stability in medium–strong acid and alkali environments. The sintering impregnation method was used to prepare the ZrO2/TiO2/Al2O3 composite nanofiltration membrane (ZTA membrane). Nano-ZrO2, submicron TiO2, and microporous Al2O3 were used as the surface layer, the transition layer, and the support layer, respectively. The structure and phase of the membrane were measured by scanning electron microscopy (SEM) and X-ray diffractometer (XRD). The composite membrane’s retention, hydrophilic and hydrophobic properties were characterized and evaluated using a UV–Vis spectrophotometer, a water contact angle tester (WCA), and a dead-end filtration device. With the increase in separation layer deposition time, the retention rate of methyl blue increased, and the water flux decreased. At a deposition time of 75 min, the retention rate of methyl blue was more than 80%, and the water flux reached 337.5 L·m−2 h−1 bar−1 at −1 bar transmembrane pressure. The membranes are hydrophilic and have different interception abilities for metal ions, and the order of retention effect is Ag+ > Cu2+ > Mg2+ > Na+, and Ag+ and Cu2+ reached 65.3% and 50.5%, respectively. The prepared ZTA composite nanofiltration membrane has potential application value in heavy metal ion filtration.

CeO2-doped WO3 composite catalyst based on acid site enhancement for diesel exhaust gas denitration

Based on the complicated preparation of current diesel vehicle exhaust gas denitration catalysts, an in-situ deposited composite oxide catalyst, CeO2-WO3 mixed oxide catalyst, was prepared by electrodeposition and hydrothermal methods, which was loaded on the titanium mesh and applied to the selective catalytic reduction denitration of diesel vehicle exhaust. Denitration performance of the catalysts was tested by a fixed bed reactor, and the influence of different electrodeposition time of CeO2 was investigated. The results demonstrate that 20 min is the best electrodeposition time of CeO2 (100% NOx conversion at 250–350 °C). The high dispersion of active CeO2 on WO3 promotes the synergistic effects among different components. The as-prepared catalysts were characterized by SEM, XRD, XPS, H2-TPR, NH3-TPD and in-situ DRIFTS. It is evident that Ce3+ is successfully introduced by loading CeO2, which enhances the chemisorption of oxygen. Meanwhile, the increased acidity including both weak acid and medium-strong acid sites of CeO2-WO3 composite catalyst is observed, which improves the co-adsorption of NH3 on Lewis acid and Brønsted acid simultaneously and facilitates the denitration process. Through the characterization by in-situ DRIFTS, it is elucidated that the NH3-SCR reactions are mainly carried out following the Eley-Rideal (E-R) pathway in a medium-temperature range (250–350 °C).

Efficiently reducing olefin content of FCC gasoline over ZSM-5 zeolite based catalyst via hydro-upgrading

The reduction of olefin content in FCC gasoline is challenging for clean gasoline production, owing to the tightened regulations at 15% (vol%) olefin content of clean vehicle fuels with China VI standard. The best route for olefin reduction has been proposed by selective converting olefins to aromatics or iso-alkanes with a high-octane number. Here, ZSM-5 zeolite supported metal catalysts have been developed for hydro-upgrading FCC gasoline. ZSM-5 zeolite blended with alumina was firstly treated by hydrothermal treatment at 450 °C, 500 °C and 550 °C, respectively, and the effect of Zn, Ni-Zn and La-Ni-Zn deposition on hydro-upgrading was also investigated. The hydrothermal modification effectively reduced acidity of ZSM-5 zeolite with the increase of B/L ratio and the decrease of L acid sites. The introduction of Zn, Ni and La to the zeolite supports increases the proportion of medium-strong acid from 42% to 48%, and the resulting catalyst shows excellent olefin reduction performance in FCC gasoline hydro-upgrading. The content of aromatics increases 5% (1.2 vol%); iso-alkane content increases 16% (5.5 vol%) and the research octane number (RON) increases 4.6. These findings show the ZSM-5 supported Zn-Ni-La catalyst can be served as a potential industrial catalyst for FCC gasoline hydro-upgrading.

Construction of a dual catalytic mechanism controlled by multiple active sites in Cu-Al catalysts to facilitate gas-phase hydrogenation of diethyl oxalate to ethyl ethoxyacetate

The hydrogenation of diethyl oxalate (DEO) to synthesize ethanol, ethylene glycol (EG), and ethyl glycolate (Egly) is always a hot topic in the field of carbon catalytic conversion, but its catalytic hydrogenation to synthesize ethyl ethoxyacetate (EEA) has received significantly insufficient attention. Here, a series of bifunctional Cu-Al catalysts with different Lewis acid distributions were synthesized using a self-assembly method and employed to interpret the effect of the dependence of Cu-Al multisite on the hydrogenation of DEO to EEA. A trend of volcano shape is observed between the reactivity of the catalyst and the increasing amount of Cu loading, indicating that the active Cu site determines the hydrogenation of DEO. The highest conversion of about 40% is obtained for the Cu10Al100 catalyst over a reaction time of 56 h. Meanwhile, the specific relationship between the selectivity of EEA and the content of the medium-strong Lewis acid site (LAS) on the catalyst surface is indicative of the decisive role of the amount of the medium-strong acid on the production of EEA. The highest EEA selectivity of ∼55% is achieved over the Cu1Al100 catalyst. The results show (e.g·NH3-TPD, 27Al MAS-NMR, H2-TPR) that EEA is the product of synergistic catalysis between the Cu site and the medium-strength LAS in the CuxAl100 catalyst. It is demonstrated that EEA synthesis involves two reaction pathways: dehydration of ethyl 2-hydroxy-2-ethoxyacetate intermediate at LAS and etherification of Egly and ethanol at LAS. The multi-reactivity pathway driven by this Cu-Al double site can be extended to the gas-phase hydrogenation of dialkyl oxalate for the synthesis of a variety of Alcohol-Ethers-Esters (AEE) compounds.

Synergistic effect of low valence manganese ions in manganese-based catalysts for non-oxidative dehydrogenation of isobutane

A series of manganese-based catalysts supported on γ-Al2O3 with low loading amount of manganese from 0.5% to 2.0% were prepared by incipient impregnating method. All catalysts were tested on non-oxidative dehydrogenation of isobutane at 600 °C. In order to explore physicochemical properties of all catalysts, various characterizations including XRD, H2-TPR, XPS, UV-vis, NH3-TPD and TG were carried out on manganese-based catalysts. The experimental results indicated that MnOx species were highly dispersed on γ-Al2O3 support, and both Mn2+ and Mn3+ ions are main active species for isobutane dehydrogenation. The reduced catalyst 1.5%Mn/γ-Al2O3 exhibited the most optimal dehydrogenation performance among all catalysts, reaching at isobutane conversion of 36% and isobutene selectivity of 79%. The main reasons for the excellent activity and selectivity of 1.5%Mn/γ-Al2O3 were related to the high proportion of low valence manganese ions including Mn2+ and Mn3+ as well as the high concentration of medium strong acid sites and weak strong acid strength.

Direct Conversion Syngas to Isobutanol over Ce/ZC Catalysts: Effect of Ce Promoter on the Catalytic Performance

AbstractThe fuel‐efficient production of isobutanol via CO hydrogenation is a meaningful path, but still remains large challenges. Here, varied contents Ce promoter were introduced to optimize the catalytic performance of ZnCr‐based catalysts. The evaluation results displayed that 2.5‐Ce/ZC catalyst obtained optimum total alcohols yield and isobutanol selectivity. A combination of XPS, TPD, and in‐situ FTIR measurements was performed to probe into the enhancing effect of Ce promoter. The XPS characterization results disclosed the evident changes in the oxygen vacancy concentration and electron structure derived from Ce doping. Furthermore, this unique structure promoted the formation of HCOO species, and modulated the HCOO binding with proper strength to enable further carbon chain growth. According to the acid‐base properties tests, the doping of Ce introduced meaningful medium strong acid and base sites. The facilitated C−C coupling activity was a forthright result that led to the production of C2+ products, especially isobutanol.

Promotional catalytic activity and reaction mechanism of Ag-modified Ce0.6Zr0.4O2 catalyst for catalytic oxidation of ammonia

Ce1-xZrxO2 composite oxides (molar, x = 0-1.0, interval of 0.2) were prepared by a cetyltrimethylammonium bromide-assisted precipitation method. The enhancement of silver-species modification and catalytic mechanism of adsorption-transformation-desorption process were investigated over the Ag-impregnated catalysts for low-temperature selective catalytic oxidation of ammonia (NH3-SCO). The optimal 5 wt.% Ag/Ce0.6Zr0.4O2 catalyst presented good NH3-SCO performance with >90% NH3 conversion at temperature (T) ≥ 250°C and 89% N2 selectivity. Despite the irregular block shape and underdeveloped specific surface area (∼60 m2/g), the naked and Ag-modified Ce0.6Zr0.4O2 solid solution still obtained highly dispersed distribution of surface elements analyzed by scanning electron microscope-energy dispersive spectrometer (SEM-EDS) (mapping), N2 adsorption-desorption test and X-ray diffraction (XRD). H2 temperature programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS) results indicated that Ag-modification enhanced the mobility and activation of oxygen-species leading to a promotion on CeO2 reducibility and synergistic Ag0/Ag+ and Ce4+/Ce3+ redox cycles. Besides, Ag+/Ag2O clusters could facilitate the formation of surface oxygen vacancies that was beneficial to the adsorption and activation of ammonia. NH3-temperature programmed desorption (NH3-TPD) showed more adsorption-desorption capacity to ammonia were provided by physical, weak- and medium-strong acid sites. Diffused reflectance infrared Fourier transform spectroscopy (DRIFTS) experiments revealed the activation of ammonia might be the control step of NH3-SCO procedure, during which NH3 dehydrogenation derived from NHx-species and also internal selective catalytic reduction (i-SCR) reactions were proposed.

Isolated Cuo and Medium Strong Acid on Cuo/Nb2o5-H Catalyst for Efficient Enhancement of Triethylamine Selective Catalytic Oxidation

Isolated Cuo and Medium Strong Acid on Cuo/Nb2o5-H Catalyst for Efficient Enhancement of Triethylamine Selective Catalytic Oxidation