scholarly journals Zr-Modified ZnO for the Selective Oxidation of Cinnamaldehyde to Benzaldehyde

Catalysts ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 716 ◽  
Author(s):  
Pengju Du ◽  
Tongming Su ◽  
Xuan Luo ◽  
Xinling Xie ◽  
Zuzeng Qin ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Selective Oxidation ◽  
Active Sites ◽  
Catalyst Surface ◽  
Precipitation Method ◽  
N2 Adsorption ◽  
X Ray ◽  
Temperature Programmed ◽  
Zr Modification ◽  
Adsorption Desorption

ZnO and Zr-modified ZnO were prepared using a precipitation method and used for the selective oxidation of cinnamaldehyde to benzaldehyde in the present study. The results showed that physicochemical properties of ZnO were significantly affected by the calcination temperature, and calcination of ZnO at 400 °C demonstrated the optimum catalytic activity for the selective oxidation of cinnamaldehyde to benzaldehyde. With 0.01 g ZnO calcined at 400 °C for 2 h as a catalyst, 8.0 g ethanol and 2.0 g cinnamaldehyde reacted at an oxygen pressure of 1.0 MPa and 70 °C for 60 min, resulting in benzaldehyde selectivity of 69.2% and cinnamaldehyde conversion of 16.1%. Zr was the optimal modifier for ZnO: when Zr-modified ZnO was used as the catalyst, benzaldehyde selectivity reached 86.2%, and cinnamaldehyde conversion was 17.6%. The X-ray diffractometer and N2 adsorption–desorption characterization indicated that doping with Zr could reduce the crystallite size of ZnO (101) and increase the specific surface area of the catalyst, which provided more active sites for the reaction. X-ray photoelectron spectrometer results showed that Zr-doping could exchange the electrons with ZnO and reduce the electron density in the outer layer of Zn, which would further affect benzaldehyde selectivity. The results of CO2 temperature-programmed desorption showed that Zr-modification enhanced the alkalinity of the catalyst surface, which caused the Zr–ZnO catalyst to exhibit higher catalytic activity.

The Different Morphology of Co3O4 Catalysts and Application in the Abatement of Carbon Monoxide

2021 ◽  
Vol 21 (12) ◽  
pp. 6082-6087
Author(s):  
Chih-Wei Tang ◽  
Hsiang-Yu Shih ◽  
Ruei-Ci Wu ◽  
Chih-Chia Wang ◽  
Chen-Bin Wang
Keyword(s):  
Carbon Monoxide ◽  
Catalytic Activity ◽  
Co Oxidation ◽  
Nitrogen Adsorption ◽  
Catalytic Performance ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Temperature Programmed ◽  
Adsorption Desorption

The increase of harmful carbon monoxide (CO) caused by incomplete combustion can affect human health even lead to suffocation. Therefore reducing the CO discharged by vehicles or factories is urgent to improve the air quality. The spinel cobalt (II, III) oxide (Co3O4) is an active catalyst for CO abatement. In this study, we tried to fabricate dispersing Co3O4 via the dispersion-precipitation method with acetic acid, formic acid, and oxalic acid as the chelating dispersants. Then, the asprepared samples were calcined at 300 ºC for 4 h to obtain active catalysts, and assigned as Co(A), Co(F) and Co(O) respectively, the amount of the dispersants used are labeled as I (0.12 mole), II (0.03 mole) and III (0.01 mole). For comparison, another CoAP sample was prepared via alkaliinduced precipitation and calcined at 300 ºC. All samples were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), scanning electron microscope (SEM), and nitrogen adsorption/desorption system, and the catalytic activity focused on the CO oxidation. The influence of chelating dispersant on the performance of abatement of CO was pursued in this study. Apparently, the results showed that the chelating dispersant can influence the catalytic activity of CO abatement. An optimized ratio of dispersant can improve the performance, while excess dispersant lessens the surface area and catalytic performance. The series of Co(O) samples can easily donate the active oxygen since the labile Co–O bonding and indicated the preferential performance than both Co(A) and Co(F) samples. The nanorod Co(O)-II showed preferential for CO oxidation, T50 and T90 approached 96 and 127 ºC, respectively. Also, the favorable durability of Co(O)-II sample maintains 95% conversion still for 50 h at 130 ºC and does not emerge deactivation.

scholarly journals Synthesis of DME by CO2 hydrogenation over La2O3-modified CuO-ZnO-ZrO2/HZSM-5 catalysts

2017 ◽  
Vol 23 (1) ◽  
pp. 49-56 ◽  
Author(s):  
Yajing Zhang ◽  
Yu Zhang ◽  
Fu Ding ◽  
Kangjun Wang ◽  
Wang Xiaolei ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Direct Synthesis ◽  
Catalytic Performance ◽  
Co2 Hydrogenation ◽  
Precipitation Method ◽  
X Ray ◽  
Temperature Programmed ◽  
And Performance ◽  
Co Precipitation ◽  
Adsorption Desorption

A series of La2O3-modified CuO-ZnO-ZrO2/HZSM-5 catalysts were prepared by an oxalate co-precipitation method. The catalysts were fully characterized by X-ray diffraction (XRD), N2 adsorption-desorption, hydrogen temperature pro-grammed reduction (H2-TPR), ammonia temperature programmed desorption (NH3-TPD), and X-ray photoelectron spectroscopy (XPS) techniques. The effect of the La2O3 content on the structure and performance of the catalysts was thoroughly investigated. The catalysts were evaluated for the direct synthesis of dimethyl ether (DME) from CO2 hydrogenation. The results displayed that La2O3 addition enhanced catalytic performance, and the maximal CO2 conversion (34.3%) and DME selectivity (57.3%) were obtained over the catalyst with 1% La2O3, which due to the smaller size of Cu species and a larger ratio of Cu+/Cu.

scholarly journals Catalytic Activity of Mixed Al2O3-ZrO2 Oxides for Glucose Conversion into 5-Hydroxymethylfurfural

Catalysts ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 878 ◽  
Author(s):  
Benjamín Torres-Olea ◽  
Sandra Mérida-Morales ◽  
Cristina García-Sancho ◽  
Juan Antonio Cecilia ◽  
Pedro Maireles-Torres
Keyword(s):  
Catalytic Activity ◽  
Photoelectron Spectroscopy ◽  
Molar Ratio ◽  
X Ray ◽  
Zirconium Oxides ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Secondary Reactions ◽  
Temperature Programmed ◽  
Adsorption Desorption

In the present work, a series of catalysts based on aluminum and zirconium oxides was studied for the transformation of glucose into 5-hydroxymethylfurfural. These catalysts were characterized by using experimental techniques, such as X-ray diffraction, N2 adsorption–desorption at −196 °C, X-ray photoelectron spectroscopy, temperature-programmed desorption of NH3 and CO2, and scanning transmission electron microscopy. The catalytic behavior in glucose dehydration was evaluated in a water-methyl isobutyl ketone biphasic system, in the presence of CaCl2, in order to minimize losses due to unwanted secondary reactions. High glucose conversion and 5-hydroxymethylfurfural (HMF) yield values were obtained in the presence of an Al(Zr)Ox catalyst with an Al:Zr molar ratio of 7:3, reaching 97% and 47%, respectively, at 150 °C after 120 min. Under tested conditions, this catalyst retained most of its catalytic activity for four reuses.

Study of Preparation, Characterization and Temperature-Programmed Reduction of NiO-ZnO Binary Materials

2013 ◽  
Vol 664 ◽  
pp. 515-520
Author(s):  
Chih Wei Tang ◽  
Jiunn Jer Hwang ◽  
Shie Hsiung Lin ◽  
Chin Chun Chung
Keyword(s):  
Weight Percent ◽  
Precipitation Method ◽  
Temperature Programmed Reduction ◽  
X Ray Diffraction ◽  
X Ray ◽  
Surface Areas ◽  
Temperature Programmed ◽  
Co Precipitation ◽  
Adsorption Desorption

The NiO-ZnO binary materials had been prepared by co-precipitation method. The weight percent of nickel of NiO-ZnO materials were 5, 10 and 20; they were pretreated under air at temperature of 300, 500 and 700°C, respectively. The characterization of NiO-ZnO materials were the thermal gravity analysis(TGA), X-ray diffraction(XRD), N2 adsorption-desorption at 77K, scaning electron microscope(SEM) and temperature-programmed reduction(TPR). The results revealed that surface areas of NiO-ZnO materials order from large to small were 20NiZn(OH)x(66 m2·g-1) > 10NiZn(OH)x(34 m2·g-1) > 5NiZn(OH)x(9 m2·g-1) after being calcined at the temperature of 500°C. Further, NiO-ZnO materials had two main reductive peaks at 390-415°C and 560-657°C, respectively. In all NiO-ZnO materials, 20NiZn(OH)x-C500 material had the highest surface area and the best interaction between NiO and ZnO.

scholarly journals Palladium-doped hierarchical ZSM-5 for catalytic selective oxidation of allylic and benzylic alcohols

2021 ◽  
Vol 8 (10) ◽  
Author(s):  
Shengzhe Ding ◽  
Muhammad Ganesh ◽  
Yilai Jiao ◽  
Xiaoxia Ou ◽  
Mark A. Isaacs ◽  
...  
Keyword(s):  
Selective Oxidation ◽  
Active Site ◽  
Photoelectron Spectroscopy ◽  
Active Sites ◽  
Hierarchical Zeolites ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Temperature Programmed ◽  
Alcohol Conversion

Hierarchical zeolites have the potential to provide a breakthrough in transport limitation, which hinders pristine microporous zeolites and thus may broaden their range of applications. We have explored the use of Pd-doped hierarchical ZSM-5 zeolites for aerobic selective oxidation (selox) of cinnamyl alcohol and benzyl alcohol to their corresponding aldehydes. Hierarchical ZSM-5 with differing acidity (H-form and Na-form) were employed and compared with two microporous ZSM-5 equivalents. Characterization of the four catalysts by X-ray diffraction, nitrogen porosimetry, NH 3 temperature-programmed desorption, CO chemisorption, high-resolution scanning transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray absorption spectroscopy allowed investigation of their porosity, acidity, as well as Pd active sites. The incorporation of complementary mesoporosity, within the hierarchical zeolites, enhances both active site dispersion and PdO active site generation. Likewise, alcohol conversion was also improved with the presence of secondary mesoporosity, while strong Brønsted acidity, present solely within the H-form systems, negatively impacted overall selectivity through undesirable self-etherification. Therefore, tuning support porosity and acidity alongside active site dispersion is paramount for optimal aldehyde production.

scholarly journals Effect of aluminum precursor on physicochemical properties of Al2O3 by hydrolysis/precipitation method

Nova Scientia ◽  
2018 ◽  
Vol 10 (20) ◽  
pp. 83-99 ◽  
Author(s):  
Rafael Romero Toledo ◽  
Víctor Ruiz Santoyo ◽  
Cristina D. Moncada Sánchez ◽  
Merced Martínes Rosales
Keyword(s):  
Aluminum Sulfate ◽  
Structural Defects ◽  
Precipitation Method ◽  
Lower Percentage ◽  
N2 Adsorption ◽  
Oh Groups ◽  
X Ray ◽  
Transmission Electron ◽  
Analytical Reagent ◽  
Adsorption Desorption

This study reports the synthesis of mesoporous nano-fibrillar alumina prepared by hydrolysis-precipitation route from aqueous solution of aluminum sulfate analytical reagent (AR) compared to aluminum sulfate technical grade (TG) of low purity under similar conditions using ammonia as the precipitating agent. The phisicochemical properties of these samples was studied with the assistance of characterization techniques such as Thermogravimetric and differential thermal analysis (TG/DTGA–DTA), X-ray diffraction (XRD), N2 adsorption-desorption isotherms, Fourier transform infrared (FTIR) spectroscopy, particles size and Transmission electron microscopy with energy-dispersive X-ray analysis (TEM/EDAX). The TG-DTA and XRD results show greater stability and a slightly greater crystallinity in Al2O3-TG sample than Al2O3-AR. N2 adsorption-desorption results show for both materials greatly surface area of 311 m2/g for Al2O3-TG and 272 m2/g for Al2O3-AR exhibiting characteristics of mesoporous materials. The FTIR results show a lower percentage of surface OH groups for Al2O3-TG showing a lower acidity due to the lower concentration of Al-OH species (AlIV). TEM measurements confirmed fibers size ranged from 20 to 100 nm for Al2O3-TG and 20-80 nm for Al2O3-AR. EDAX shows the presence of 0.20 % atomic of Mg as an impurity in Al2O3-TG, is attributed that this amount is sufficient to generate structural defects and decrease slightly acidity, likewise, extended the fibrillar chain of the alumina.

scholarly journals Effect of High Pressure on the Reducibility and Dispersion of the Active Phase of Fischer–Tropsch Catalysts

Materials ◽  
2019 ◽  
Vol 12 (12) ◽  
pp. 1915 ◽  
Author(s):  
Simón Yunes ◽  
Miguel Ángel Vicente ◽  
Sophia A. Korili ◽  
Antonio Gil
Keyword(s):  
High Pressure ◽  
Physicochemical Characterization ◽  
Active Phase ◽  
Incipient Wetness Impregnation ◽  
X Ray Diffraction ◽  
N2 Adsorption ◽  
X Ray ◽  
Temperature Programmed ◽  
Adsorption Desorption

The effect of high pressure on the reducibility and dispersion of oxides of Co and Fe supported on γ-Al2O3, SiO2, and TiO2 has been studied. The catalysts, having a nominal metal content of 10 wt.%, were prepared by incipient wetness impregnation of previously calcined supports. After drying at 60 °C for 6 h and calcination at 500 °C for 4 h, the catalysts were reduced by hydrogen at two pressures, 1 and 25 bar. The metal reduction was studied by temperature-programmed reduction up to 750 °C at the two pressures, and the metal dispersion was measured by CO chemisorption at 25 °C, obtaining values between 1% and 8%. The physicochemical characterization of these materials was completed by means of chemical analysis, X-ray diffraction, N2 adsorption-desorption at −196 °C and scanning electron microscopy. The high pressure lowered the reduction temperature of the metal oxides, improving their reducibility and dispersion. The metal reducibility increased from 42%, in the case of Fe/Al2O3 (1 bar), to 100%, in the case of Fe/TiO2 (25 bar).

scholarly journals K-Modified Co–Mn–Al Mixed Oxide—Effect of Calcination Temperature on N2O Conversion in the Presence of H2O and NOx

Catalysts ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1134
Author(s):  
Kateřina Karásková ◽  
Kateřina Pacultová ◽  
Květuše Jirátová ◽  
Dagmar Fridrichová ◽  
Martin Koštejn ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Calcination Temperature ◽  
Mixed Oxide ◽  
Active Sites ◽  
N2o Decomposition ◽  
Temperature Programmed Desorption ◽  
X Ray ◽  
Surface Basicity ◽  
Unit Surface ◽  
Temperature Programmed

The effect of calcination temperature (500–700 °C) on physico-chemical properties and catalytic activity of 2 wt. % K/Co-Mn-Al mixed oxide for N2O decomposition was investigated. Catalysts were characterized by inductively coupled plasma spectroscopy (ICP), X-ray powder diffraction (XRD), temperature-programmed reduction by hydrogen (TPR-H2), temperature-programmed desorption of CO2 (TPD-CO2), temperature-programmed desorption of NO (TPD-NO), X-ray photoelectron spectrometry (XPS) and N2 physisorption. It was found that the increase in calcination temperature caused gradual crystallization of Co-Mn-Al mixed oxide, which manifested itself in the decrease in Co2+/Co3+ and Mn3+/Mn4+ surface molar ratio, the increase in mean crystallite size leading to lowering of specific surface area and poorer reducibility. Higher surface K content normalized per unit surface led to the increase in surface basicity and adsorbed NO per unit surface. The effect of calcination temperature on catalytic activity was significant mainly in the presence of NOx, as the optimal calcination temperature of 500 °C is necessary to ensure sufficient low surface basicity, leading to the highest catalytic activity. Observed NO inhibition was caused by the formation of surface mononitrosyl species bonded to tetrahedral metal sites or nitrite species, which are stable at reaction temperatures up to 450 °C and block active sites for N2O decomposition.

scholarly journals Novel Nano-Fe2O3-Co3O4 Modified Dolomite and Its Use as Highly Efficient Catalyst in the Ozonation of Ammonium Solution

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Manh B. Nguyen ◽  
Giang H. Le ◽  
Trang T. T. Pham ◽  
Giang T. T. Pham ◽  
Trang T. T. Quan ◽  
...  
Keyword(s):  
Catalytic Performance ◽  
Catalytic Ozonation ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
Kcal Mole ◽  
Efficient Catalyst ◽  
X Ray ◽  
Sem Image ◽  
Temperature Programmed ◽  
Adsorption Desorption

Catalytic ozonation is a new method used for removal of NH4OH solution. Therefore, high catalytic performance (activity and selectivity) should be achieved. In this work, we report the synthesis and catalytic performance of Fe2O3-Co3O4 modified dolomite in the catalytic ozonation of NH4OH solution. Dolomite was successfully activated and modified with Fe2O3 and Co3O4. Firstly, dolomite was activated by heating at 800°C for 3 h and followed by KOH treatment. Activated dolomite was modified with Fe2O3 by the atomic implantation method using FeCl3 as Fe source. Fe2O3 modified dolomite was further modified with Co3O4 by precipitation method. The obtained catalysts were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), N2 adsorption–desorption (BET), and temperature-programmed reduction (H2-TPR). From SEM image, it was revealed that nano-Fe2O3 and Co3O4 particles with the size of 80–120 nm. Catalytic performance of activated dolomite, Fe2O3 modified dolomite, and Fe2O3-Co3O4 modified dolomite in catalytic ozonation of NH4+ solution was investigated and evaluated. Among 3 tested catalysts, Fe2O3-Co3O4 modified dolomite has the highest NH4+ conversion (96%) and N2 selectivity (77.82%). Selectivity toward N2 over the catalyst was explained on the basis of bond strength M-O in oxides through the standard enthalpy ΔH°f of oxide. Catalyst with lower ΔH°f value has higher N2 selectivity and the order is the following: Co3O4 (ΔH°f of 60 kcal (mole O)) > Fe2O3 (ΔH°f of 70 kcal (mole O)) > MgO (ΔH°f of 170 kcal (mole O)). Moreover, high reduction ability of Fe2O3-Co3O4 modified dolomite could improve the N2 selectivity by the reduction of NO3- to N2 gas.

Basicity and Crystal Phase of Mesoporous K2O-MgO/ZrO2-La2O3 Catalyst

2014 ◽  
Vol 924 ◽  
pp. 269-274
Author(s):  
Yu Su ◽  
Guo Jun Dong ◽  
Cheng Yuan Wang ◽  
Jin Sheng Gao ◽  
Dong Sheng Ma ◽  
...  
Keyword(s):  
High Temperature ◽  
Monoclinic Phase ◽  
Dimethyl Carbonate ◽  
Catalyst Surface ◽  
Temperature Programmed Desorption ◽  
Solid Base ◽  
X Ray Diffraction ◽  
X Ray ◽  
Temperature Programmed ◽  
Adsorption Desorption

A new solid base, mesoporous K2O-MgO/ZrO2-La2O3, was prepared by hydrothermal and immersion process using a cationic surfactant C16H33(CH3)3NBr (CTAB) as template．The samples were characterized by N2 adsorption-desorption, X-ray diffraction(XRD), Raman spectroscope and CO2 temperature programmed desorption(CO2-TPD). XRD and Raman spectra indicated that the catalyst calcined at 600°C and 700 °C remained surface and bulk tetragonal phase and good mesoporous characteristics when the content of K2O is less than 0.5. While the monoclinic phase is appeared on catalyst surface when the content of K2O is more than 0.5 calcined at 700 °C. CO2-TPD proves that there are two adsorption states at high temperature corresponding to super alkaline sites of K2O and undecomposed KNO3. The catalyst with 0.4 mol ratio of K2O to ZrO2 calcined at 700 °C showed higher activity in the synthesis of di-2-ethylhexyl carbonate (DEHC) from dimethyl carbonate (DMC) and 2-ethylhexanol (EHOH).

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