scholarly journals Synthesis of highly stable metal-containing extra-large-pore molecular sieves

2016 ◽  
Vol 374 (2061) ◽  
pp. 20150075 ◽  
Author(s):  
Raquel Martínez-Franco ◽  
Cecilia Paris ◽  
Manuel Moliner ◽  
Avelino Corma
Keyword(s):  
Molecular Sieves ◽  
Chemical Properties ◽  
Aromatic Proton ◽  
Isomorphic Substitution ◽  
X Ray ◽  
Large Pore ◽  
Vis Spectroscopy ◽  
Temperature Programmed ◽  
Proton Sponges ◽  
Large Pore Zeolites

The isomorphic substitution of two different metals (Mg and Co) within the framework of the ITQ-51 zeotype (IFO structure) using bulky aromatic proton sponges as organic structure-directing agents (OSDAs) has allowed the synthesis of different stable metal-containing extra-large-pore zeotypes with high pore accessibility and acidity. These metal-containing extra-large-pore zeolites, named MgITQ-51 and CoITQ-51, have been characterized by different techniques, such as powder X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectrometry, UV–Vis spectroscopy, temperature programmed desorption of ammonia and Fourier transform infrared spectroscopy, to study their physico-chemical properties. The characterization confirms the preferential insertion of Mg and Co atoms within the crystalline structure of the ITQ-51 zeotype, providing high Brønsted acidity, and allowing their use as efficient heterogeneous acid catalysts in industrially relevant reactions involving bulky organic molecules.

Investigating the properties and performance of 3A molecular sieves as an adsorbent to prevent coke formation in olefin dehydration process

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Zoya Moslempour ◽  
Sepehr Sadighi ◽  
Ali Dashti ◽  
Ali Ahmadpour
Keyword(s):  
Molecular Sieves ◽  
Molecular Sieve ◽  
Coke Formation ◽  
Chemical Properties ◽  
X Ray Diffraction ◽  
X Ray ◽  
Na Ions ◽  
Temperature Programmed ◽  
And Performance ◽  
Physical And Chemical

Abstract To study the affinity of 3A aluminosilicate adsorbents to prevent oligomerization of olefin molecules and forming green oil, physical and chemical properties of 3A molecular sieves are measured by using characterization techniques such as temperature-programmed desorption (TPD), nitrogen (N2) and water adsorptions, X-ray diffraction (XRD), X-ray fluorescence (XRF), crushing strength, and carbon dioxide (CO2) adsorption. Moreover, coke formation affinities of the understudy adsorbents are evaluated in a bench-scale system using 1-butene and 1,3-butadiene at temperatures of 220 and 260 °C, and outcomes are validated against the actual data gathered from an industrial scale olefin dehydration plant. Results confirm that the type of binder and the amount of ion exchange affect the performance of a 3A molecular sieve nominated for dehydrating olefinic streams. The binder with the least amount of acidity is preferred, and at least 35% of Na ions of the 4A zeolite should be exchanged with K ions to make it applicable for synthesizing an appropriate 3A molecular sieve. Furthermore, to control the oligomerization and inhibit green oil formation, the CO2 adsorption and acidity of Trisiv shape molecular sieves with the sizes of 1/4 inch should be less than 0.5 wt % and 1.7 mmol NH3/g, respectively. For extrudate shape with the sizes of 1/16 inch CO2 adsorption and acidity should be less than 0.2 wt % and 2.2 mmol NH3/g, respectively.

Catalytic Activity of Bimetallic Cu-Ag/MgO-SiO2 Toward the Conversion of Ethanol to 1,3-Butadiene

2016 ◽  
Vol 14 (5) ◽  
pp. 945-954 ◽  
Author(s):  
Anamol Tripathi ◽  
Kajornsak Faungnawakij ◽  
Apirat Laobuthee ◽  
Suttichai Assabumrungrat ◽  
Navadol Laosiripojna
Keyword(s):  
Chemical Properties ◽  
Catalytic Performance ◽  
X Ray Diffraction ◽  
X Ray ◽  
Monometallic Catalysts ◽  
Reaction Test ◽  
Spent Catalysts ◽  
Temperature Programmed ◽  
Preparation Techniques ◽  
Microwave Assisted Method

Abstract In the present work, the catalytic conversion of ethanol to 1,3-butadiene (1,3-BD) was studied over monometallic of Cu and Ag, and bimetallic Cu-Ag supported on MgO-SiO2 (with MgO/SiO2 ratio of 2.0) under the temperature range from 250 to 325 °C. All catalysts were prepared by 4 different techniques including (i) conventional impregnation, (ii) microwave-assisted method, (iii) polyvinyl alcohol/sodium borohydride (PVA/NaBH4) assisted method, and (iv) benzoxaxine-assisted method to elucidate the effect of catalyst preparation method on their catalytic performance. All fresh and spent catalysts were also characterized by X-ray diffraction (XRD), N2 adsorption and Temperature-programmed reduction (TPR) techniques to understand the relation between their physical/chemical properties and catalytic performance. From the reaction test, it was found that 5 %Ag/MgO-SiO2 showed greater activity towards 1,3-BD production than 5 %Cu/MgO-SiO2; nevertheless, higher deactivation after 6 h of operation was observed from 5 %Ag/MgO-SiO2. Importantly, this study revealed that bimetallic 2.5 %Cu-2.5 %Ag/MgO-SiO2 enhanced significantly higher activity and stability towards the reaction than monometallic catalysts. In addition, 2.5 %Cu-2.5 %Ag/MgO-SiO2 prepared by benzoxaxine-assisted method enhanced significantly higher reaction activity and stability than other preparation techniques, from which 1,3-BD yield of 46.40 % after 6 h of operation can be achieved. From the characterization, the good activity of this catalyst is mainly due to the dispersion improvement of metal over MgO-SiO2 support.

scholarly journals Ni(II) Butylmethyldithiocarbamate: Physico-Chemical Properties, X-Ray Crystallography, DFT and Anti-Corrosion Screening in Different Acids

2021 ◽  
Vol 16 ◽  
pp. 1-11
Author(s):  
Nor Farah Hida Othman ◽  
Noor Syafiqah Habdul Latif ◽  
Sheikh Ahmad Izzadin Sheikh Mohd Ghazali ◽  
Erna Normaya Abdullah ◽  
Nur Nadia Dzulkifli
Keyword(s):  
Fourier Transform ◽  
Chemical Properties ◽  
Attenuated Total Reflection ◽  
X Ray ◽  
Loss Analysis ◽  
X Ray Crystallography ◽  
Industrial Sectors ◽  
Physico Chemical ◽  
Vis Spectroscopy ◽  
Acid Environment

In industrial sectors, pickling and acid cleaning are mutual processes where acid solutions, such as hydrochloric acid (HCl) and sulfuric acid (H2SO4), are used to eliminate the corrosion products yielded on metal surfaces; thus, improving the performance of the machineries. However, the usage of the acid could lead to another metal deterioration. Dithiocarbamate inhibitor is defined as an organic compound that has good corrosion inhibition properties that can work as an inhibitor in an acid environment. Dithiocarbamate (DTC) assists by reducing acid reactiveness which prohibits metal dissolution in the acid. In this study, the Ni(II) N-butylmethyldithiocarbamate (Ni[BuMedtc]2) complex was synthesised by using an in-situ method and characterised by elemental analyser, attenuated total reflection Fourier transform infrared (ATR-FTIR), ultraviolet-visible (UV-Vis) spectroscopy and X-ray crystallographic study, and the chemical properties of the Ni[BuMedtc]2 complex was successfully calculated by the Discrete Fourier Transform (DFT) approach. The experimental results which were obtained through the weight-loss analysis method in two different acids – 1 M HCl and 1 M H2SO4 – indicated that the inhibition efficiency increased as the inhibitor concentration increased. The outcome showed that the Ni[BuMedtc]2 performed better as an inhibitor in 1 M HCl as compared to in1 M H2SO4 to protect the metal exterior because H2SO4 is more corrosive due to the excessive presence of H+.

scholarly journals Supra-molecular assembly of aromatic proton sponges to direct the crystallization of extra-large-pore zeotypes

2014 ◽  
Vol 470 (2166) ◽  
pp. 20140107 ◽  
Author(s):  
Raquel Martínez-Franco ◽  
Junliang Sun ◽  
German Sastre ◽  
Yifeng Yun ◽  
Xiaodong Zou ◽  
...  
Keyword(s):  
Theoretical Calculations ◽  
Aromatic Proton ◽  
Molecular Assembly ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
X Ray Diffraction ◽  
Large Pore ◽  
Proton Sponges ◽  
Angle Spinning

The combination of different experimental techniques, such as solid 13 C and 1 H magic-angle spinning NMR spectroscopy, fluorescence spectroscopy and powder X-ray diffraction, together with theoretical calculations allows the determination of the unique structure directing the role of the bulky aromatic proton sponge 1,8- bis (dimethylamino)naphthalene (DMAN) towards the extra-large-pore ITQ-51 zeolite through supra-molecular assemblies of those organic molecules.

Electronic structures of CdSe nanocrystals — An X-ray absorption near-edge structure (XANES) investigation

2007 ◽  
Vol 85 (10) ◽  
pp. 756-760 ◽  
Author(s):  
Jigang Zhou ◽  
Xingtai Zhou ◽  
Xuhui Sun ◽  
Michael Murphy ◽  
Franziskus Heigl ◽  
...  
Keyword(s):  
Electronic Structures ◽  
Quantum Confinement Effect ◽  
Chemical Properties ◽  
Trioctylphosphine Oxide ◽  
Cdse Nanocrystals ◽  
Edge Structure ◽  
X Ray ◽  
Vis Spectroscopy ◽  
Capping Ligands ◽  
X Ray Absorption

CdSe nanocrystals (NCs), capped with trioctylphosphine oxide and 1-octadecanamine, have been synthesized with colloidal methods. Both UV–vis absorption and photoluminescence spectra show that the prepared nanostructures exhibit a quantum confinement effect. X-ray absorption near–edge structure (XANES) at Se K-edge recorded in fluorescence yield mode have been carried out on these NCs, with different size and capping ligands to gain insight into how their electronic structures are affected by the NC size and chemical properties of the ligands. The results indicate that XANES are sensitive to both the NC size and the nature of the capping ligands. The whiteline intensity in XANES spectra can be related to the photoluminescence properties of these NCs.Key words: CdSe nanocrystals, capping ligands, X-ray absorption near-edge structure, UV–vis spectroscopy, photoluminescence.

scholarly journals Sol-Gel Synthesized Semiconductor Oxides in Photocatalytic Degradation of Phenol

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Maria K. Cherepivska ◽  
Roman V. Prihod’ko
Keyword(s):  
Photocatalytic Degradation ◽  
Sol Gel ◽  
Chemical Properties ◽  
X Ray Diffraction ◽  
X Ray ◽  
Semiconductor Oxides ◽  
Titanium Dioxide Sample ◽  
Vis Spectroscopy ◽  
Physical And Chemical ◽  
And Chemical Properties

Effectiveness of photocatalytic degradation of phenol in aqueous solution using semiconductor oxides (SO) prepared by a sol-gel method was examined. The physical and chemical properties of synthesized catalysts were investigated by X-ray diffraction (XRD), diffuse reflectance UV-Vis spectroscopy (DRS), and N2-adsorption measurements. The optimal conditions of the photocatalytic degradation of phenol using prepared titanium dioxide sample were defined.

scholarly journals Glycerol Valorization over ZrO2-Supported Copper Nanoparticles Catalysts Prepared by Chemical Reduction Method

Catalysts ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1040
Author(s):  
Juan Garcés ◽  
Ramón Arrué ◽  
Néstor Novoa ◽  
Andreia F. Peixoto ◽  
Ricardo J. Chimentão
Keyword(s):  
Copper Nanoparticles ◽  
Reduction Method ◽  
Chemical Reduction ◽  
X Ray Diffraction ◽  
Chemical Reduction Method ◽  
X Ray ◽  
Transmission Electron ◽  
Vis Spectroscopy ◽  
Region I ◽  
Temperature Programmed

Copper nanoparticles (NPs) and ZrO2-supported copper NPs (Cu NPs/ZrO2) were synthesized via a chemical reduction method applying different pH (4, 7 and 9) and evaluated in a glycerol dehydration reaction. Copper NPs were characterized with transmission electron microscopy (TEM) and UV–vis spectroscopy. Transmission electron microcopy (TEM) results revealed a homogeneous distribution of copper NPs. A hypsochromic shift was identified with UV–vis spectroscopy as the pH of the synthesis increased from pH = 4 to pH = 9. Zirconia-supported copper NPs catalysts were characterized using N2 physisorption, X-ray diffraction (XRD), TEM, X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), temperature-programmed desorption of ammonia (NH3-TPD) and N2O chemisorption. The presence of ZrO2 in the chemical reduction method confirmed the dispersion of the copper nanoparticles. X-ray diffraction indicated only the presence of tetragonal zirconia patterns in the catalysts. XPS identified the Cu/Zr surface atomic ratio of the catalysts. TPR patterns showed two main peaks for the Cu NPS/ZrO2 pH = 9 catalyst; the first peak between 125 and 180 °C (region I) was ascribed to more dispersed copper species, and the second one between 180 and 250 °C (region II) was assigned to bulk CuO. The catalysts prepared at pH = 4 and pH = 7 only revealed reduction at lower temperatures (region I). Copper dispersion was determined by N2O chemisorption. With NH3-TPD it was found that Cu NPs/ZrO2 pH = 9 exhibited the highest total quantity of acidic sites and the highest apparent kinetic constant, with a value of 0.004 min−1. The different pH applied to the synthesis media of the copper nanoparticles determined the resultant copper dispersion on the ZrO2 support, providing active domains for glycerol conversion.

scholarly journals A Solvothermal Synthesis of TiO2 Nanoparticles in a Non-Polar Medium to Prepare Highly Stable Nanofluids with Improved Thermal Properties

Nanomaterials ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 816 ◽  
Author(s):  
Teresa Aguilar ◽  
Ivan Carrillo-Berdugo ◽  
Roberto Gómez-Villarejo ◽  
Juan Gallardo ◽  
Paloma Martínez-Merino ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Properties ◽  
Tio2 Nanoparticles ◽  
Photoelectron Spectroscopy ◽  
High Stability ◽  
Chemical Properties ◽  
Heat Transfer Fluid ◽  
Promising Alternative ◽  
X Ray ◽  
Vis Spectroscopy

Nanofluids are systems with several interesting heat transfer applications, but it can be a challenge to obtain highly stable suspensions. One way to overcome this challenge is to create the appropriate conditions to disperse the nanomaterial in the fluid. However, when the heat transfer fluid used is a non-polar organic oil, there are complications due to the low polarity of this solvent. Therefore, this study introduces a method to synthesize TiO2 nanoparticles inside a non-polar fluid typically used in heat transfer applications. Nanoparticles produced were characterized for their structural and chemical properties using techniques such as X-ray Diffraction (XRD), Raman spectroscopy, Transmission Electron Microscopy (TEM), Fourier Transform Infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The nanofluid showed a high stability, which was analyzed by means of UV-vis spectroscopy and by measuring its particle size and ζ potential. So, this nanofluid will have many possible applications. In this work, the use as heat transfer fluid was tested. In this sense, nanofluid also presented enhanced isobaric specific heat and thermal conductivity values with regard to the base fluid, which led to the heat transfer coefficient increasing by 14.4%. Thus, the nanofluid prepared could be a promising alternative to typical HTFs thanks to its improved thermal properties and high stability resulting from the synthesis procedure.

scholarly journals Effects of Surface Oxygen-Containing Groups of the Flowerlike Carbon Nanosheets on Palladium Dispersion, Catalytic Activity and Stability in Hydrogenolytic Debenzylation of Tetraacetyldibenzylhexaazaisowurtzitane

Catalysts ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 441
Author(s):  
Yun Chen ◽  
Xinlei Ding ◽  
Wenge Qiu ◽  
Jianwei Song ◽  
Junping Nan ◽  
...  
Keyword(s):  
Chemical Properties ◽  
Carbon Support ◽  
Chemical Oxidation ◽  
Photoelectron Spectra ◽  
Surface Oxygen ◽  
Carbon Supports ◽  
Element Analysis ◽  
Carbon Nanosheets ◽  
X Ray ◽  
Temperature Programmed

The influence of the surface chemical properties of the carbon support on the Pd dispersion, activity and stability of Pd(OH)2/C catalyst for the hydrogenolytic debenzylation of tetraacetyldibenzylhexaazaisowurtzitane (TADB) was studied in detail. The flowerlike nanosheet carbon material (NSC) was chosen as the pristine support, meanwhile chemical oxidation with nitric acid and physical calcination at 600 °C treatments were used to modify its surface properties, which were denoted as NSCox-2 (treated with 20 wt% HNO3) and NSC-600, respectively. The three carbon supports and the corresponding catalysts of Pd/NSC, Pd/NSC-600, and Pd/NSCox-2 were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), nitrogen sorption isotherm measurement (BET), powder X-ray diffraction (XRD), Raman spectra, X-ray photoelectron spectra (XPS), temperature-programmed desorption (TPD), temperature-programmed reduction (H2-TPR), thermogravimetric analysis (TG), and element analysis. The debenzylation activities of Pd/NSC, Pd/NSC-600, and Pd/NSCox-2, as well as the three catalysts after pre-reduction treatment were also evaluated. It was found that the activity and stability of the Pd(OH)2/C catalysts in the debenzylation reaction highly depended on the content of surface oxygen-containing groups of the carbon support.

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