Cocation Effects in Rhodium-Exchanged Y Zeolites

1987 ◽  
Vol 111 ◽  
Author(s):  
R. K. Shoemaker ◽  
R. A. Johnson ◽  
T. M. Apple
Keyword(s):  
Room Temperature ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Internuclear Separation ◽  
Y Zeolites ◽  
Yield Information ◽  
Acid Centers ◽  
Angle Spinning ◽  
Metal Electron ◽  
C Nmr

AbstractMagic-angle spinning13C NMR spectra of carbon monoxide adsorbed on rhodium/Y zeolites yield information about the proportioning of CO in the various possible adsorption states; linear, bridged and dicarbonyl. The relative amounts of these adsorbed types, particularly the ratio of bridged to linear CO is influenced by the nature of the majority cations present with the rhodium. Reduced Rh-Na(+) and Rh-Li(+) zeolites form all three CO surface species, while acidic Rh zeolites, formed by the introduction of the co-cations Ca(2+) and H(+), exhibit no bridged carbonyls. The suppression of the bridged moiety results from the withdrawal of electrons from rhodium by the acid centers making the metal electron deficient (more oxidized).Rh(I) dicarbonyl species form on all samples studied, however these species are indistinguishable from the linear monocarbonyls based solely upon the isotropic chemical shift obtained from magic-angle spinning. The number of dicarbonyl species can be quantitatively determined by the Carr- Purcell-Meiboom-Gill sequence, the powder pattern or by selective exchange experiments. At room temperature the two CO molecules in the gemdicarbonyl appear to undergo a mutual hopping exchange. This motion is frozen out at 198K. The carbon-carbon internuclear separation in the gemdicarbonyl is 3.3 Å.Catalysts pre-adsorbed with13CO undergo exchange of the dicarbonyl species upon exposure at 198 K to12CO, however they also react to form13CO2. When exposed to CO at room temperature no CO2formation is detected.

scholarly journals Preparation of Li3PS4–Li3PO4 Solid Electrolytes by Liquid-Phase Shaking for All-Solid-State Batteries

2021 ◽  
Vol 2 (1) ◽  
pp. 39-48
Author(s):  
Nguyen H. H. Phuc ◽  
Takaki Maeda ◽  
Tokoharu Yamamoto ◽  
Hiroyuki Muto ◽  
Atsunori Matsuda
Keyword(s):  
Solid Solution ◽  
Solid State ◽  
Liquid Phase ◽  
Room Temperature ◽  
Reaction Medium ◽  
Magic Angle Spinning ◽  
Resonance Spectroscopy ◽  
Synthesis Methods ◽  
Magic Angle ◽  
Angle Spinning

A solid solution of a 100Li3PS4·xLi3PO4 solid electrolyte was easily prepared by liquid-phase synthesis. Instead of the conventional solid-state synthesis methods, ethyl propionate was used as the reaction medium. The initial stage of the reaction among Li2S, P2S5 and Li3PO4 was proved by ultraviolet-visible spectroscopy. The powder X-ray diffraction (XRD) results showed that the solid solution was formed up to x = 6. At x = 20, XRD peaks of Li3PO4 were detected in the prepared sample after heat treatment at 170 °C. However, the samples obtained at room temperature showed no evidence of Li3PO4 remaining for x = 20. Solid phosphorus-31 magic angle spinning nuclear magnetic resonance spectroscopy results proved the formation of a POS33− unit in the sample with x = 6. Improvements of ionic conductivity at room temperature and activation energy were obtained with the formation of the solid solution. The sample with x = 6 exhibited a better stability against Li metal than that with x = 0. The all-solid-state half-cell employing the sample with x = 6 at the positive electrode exhibited a better charge–discharge capacity than that employing the sample with x = 0.

A 13C and 15N nuclear magnetic resonance study of solid ammonium thiocyanate

1987 ◽  
Vol 65 (5) ◽  
pp. 941-946 ◽  
Author(s):  
Ross M. Dickson ◽  
Michael S. McKinnon ◽  
James F. Britten ◽  
Roderick E. Wasylishen
Keyword(s):  
Ammonium Thiocyanate ◽  
Nuclear Magnetic Resonance Study ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Chemical Shielding ◽  
X Ray ◽  
Shielding Constants ◽  
Angle Spinning ◽  
Good Agreement ◽  
C Nmr

The static 13C nmr powder pattern for solid ammonium thiocyanate is analyzed to obtain the 13C chemical shielding anisotropy, 321 ± 7 ppm, and the 13C–14N dipolar splitting, 1295 ± 25 Hz. Slow magic angle spinning 15N nmr experiments are analyzed to obtain a nitrogen chemical shielding anisotropy of 415 ± 15 ppm. The 13C–14N dipolar splitting leads to an effective C—N bond length of 1.19 ± 0.01 Å, in good agreement with the value of 1.176 Å reported from accurate X-ray and neutron crystallographic studies. In solid NH4NCS absolute values of the average shielding constants [Formula: see text] and ct[Formula: see text] are 52 and 34 ppm, respectively. Comparison of calculated and observed [Formula: see text] values indicates that intermolecular interactions decrease the 13C and 15N shielding constants by approximately 10 and 30 ppm, respectively.

scholarly journals Room-Temperature Reduction of Graphene Oxide in Water by Metal Chloride Hydrates: A Cleaner Approach for the Preparation of Graphene@Metal Hybrids

Nanomaterials ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 1255
Author(s):  
Patrick. P. Brisebois ◽  
Ricardo Izquierdo ◽  
Mohamed Siaj
Keyword(s):  
Graphene Oxide ◽  
Metal Oxide ◽  
Room Temperature ◽  
Structural Integrity ◽  
Metal Oxide Nanoparticles ◽  
Particle Diameter ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Angle Spinning ◽  
Metal Hybrids

Headed for developing minimalistic strategies to produce graphene@metal hybrids for electronics on a larger scale, we discovered that graphene oxide (GO)-metal oxide (MO) hybrids are formed spontaneously in water at room temperature in the presence of nothing else than graphene oxide itself and metal ions. Our observations show metal oxide nanoparticles decorating the surface of graphene oxide with particle diameter in the range of 10–40 nm after only 1 h of mixing. Their load ranged from 0.2% to 6.3% depending on the nature of the selected metal. To show the generality of the reactivity of GO with different ions in standard conditions, we prepared common hybrids with GO and tin, iron, zinc, aluminum and magnesium. By means of carbon-13 solid-state nuclear magnetic resonance using magic angle spinning, we have found that graphene oxide is also moderately reduced at the same time. Our method is powerful and unique because it avoids the use of chemicals and heat to promote the coprecipitation and the reduction of GO. This advantage allows synthesizing GO@MO hybrids with higher structural integrity and purity with a tunable level of oxidization, in a faster and greener way.

Carbon-13 CP/MAS NMR and DR-FTIR spectroscopic studies of sugarcane distillery waste

1998 ◽  
Vol 78 (1) ◽  
pp. 227-236 ◽  
Author(s):  
M. B. Benke ◽  
A. R. Mermut ◽  
B. Chatson
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Fourier Transform ◽  
Organic Carbon ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Cross Polarization ◽  
Distillery Waste ◽  
Angle Spinning ◽  
Cp Mas Nmr ◽  
C Nmr

The application of a sugarcane distillery waste known as vinasse to agricultural land has become a common practice in Brazil. The vinasse samples used in this study were collected from several sugarcane distilleries in Northeastern Brazil. These samples were fractionated into dissolved organic carbon (DOC) and particulate organic carbon (POC) fractions. Unfractionated and fractionated vinasse were studied using 13C cross-polarization and magic-angle spinning nuclear magnetic resonance (CP/MAS NMR) spectroscopy as well as diffuse reflectance Fourier-transform infrared (DR-FTIR) spectroscopy. Approximately 79 to 92% of the total unfractionated vinasse dry matter was in the form of DOC fraction. O-alkyl C (42–53% of the total C) and carboxyl C (12–25% of the total C) comprised a significant portion of the 13C NMR spectra of the DOC fraction. The presence of carbohydrates and COOH/COO− was suggested by the DR-FTIR as well. Both 13C NMR and DR-FTIR spectra of this fraction were generally similar to the spectra of the fulvic acid (FA) fraction of soil and sewage sludge. The spectra of DOC differed from the FA fraction in that they showed smaller amounts of aromatic C and had an absence of amide group (bands at 1650 cm−1 and 1540 cm−1). In the POC fraction, O-alkyl (17–52% of the total C) and alkyl C (15–41% of the total C) were the major contributors. The peaks at 62 ppm, 72 ppm, 84 ppm and 105 ppm in the O-alkyl region indicate the presence of cellulose and/or hemicellulose. The alkyl group was comprised mainly of long-chain structures. The total N content in this fraction is ~3–7 times as much as in the DOC fraction. The presence of amino acids in the POC fraction was suggested by both 13C NMR and DR-FTIR spectra. Key words:13C cross-polarization and magic-angle spinning nuclear magnetic resonance, dissolved organic carbon, Fourier-transform infrared, particulate organic carbon, vinasse

Intercalation of molecular species into the interstitial sites of fullerene

1992 ◽  
Vol 7 (8) ◽  
pp. 2136-2143 ◽  
Author(s):  
Roger A. Assink ◽  
James E. Schirber ◽  
Douglas A. Loy ◽  
Bruno Morosin ◽  
Gary A. Carlson
Keyword(s):  
Molecular Species ◽  
Room Temperature ◽  
Primary Resonance ◽  
Magic Angle Spinning ◽  
Hydrogen Gas ◽  
Magic Angle ◽  
Hydrogen Molecules ◽  
Fcc Lattice ◽  
Angle Spinning ◽  
A Minor

Molecular species were found to diffuse readily into the octahedral interstitial sites of the fcc lattice of C60. The 13C NMR spectrum of C60 under magic angle spinning (MAS) conditions consisted of a primary resonance at 143.7 ppm and a minor peak shifted 0.7 ppm downfield. The downfield shift obeys Curie's law and is attributed to the Fermi-contact interaction between paramagnetic oxygen molecules and all 60 carbon atoms of rapidly rotating adjacent C60 molecules. Exposure of C60 to 1 kbar oxygen for 1.75 h at room temperature resulted in a spectrum of seven evenly spaced resonances corresponding to the filling of 0 to 6 of the adjacent octahedral interstitial sites with oxygen molecules. The distribution of site occupancies about a C60 molecule provided evidence that the intercalation process is controlled by diffusion kinetics. Exposure to 0.14 kbar hydrogen gas at room temperature for 16 h filled a substantial fraction of the interstitial sites of C60 and C70 with hydrogen molecules.

scholarly journals Cellulose of Salicornia brachiata

2010 ◽  
Vol 5 (4) ◽  
pp. 1934578X1000500 ◽  
Author(s):  
Naresh D Sanandiya ◽  
Kamalesh Prasad ◽  
Ramavatar Meena ◽  
Arup K Siddhanta
Keyword(s):  
Thermo Gravimetric Analysis ◽  
Magic Angle Spinning ◽  
Resonance Spectroscopy ◽  
Magic Angle ◽  
Gravimetric Analysis ◽  
X Ray Diffraction ◽  
Salicornia Brachiata ◽  
Whatman Filter Paper ◽  
Angle Spinning ◽  
C Nmr

Cellulose was extracted from the roots, stems and stem tips of Salicornia brachiata Roxb. Each crude cellulose sample obtained was fractionated into α- and β-celluloses. The yields of crude cellulose from the stems and stem tips were greatest and lowest, respectively, while the yields of α- and β-celluloses were in the order, roots > stems > stem tips. The cellulose samples were characterized by Fourier transform infrared spectroscopy (FTIR), solid state cross polarisation magic angle spinning carbon-13 nuclear magnetic resonance spectroscopy (CP/MAS 13C NMR), X-ray diffraction pattern (XRD), thermo gravimetric analysis (TGA) and scanning electron microscopy (SEM). The data were compared with those of the celluloses (predominantly α-cellulose) isolated from Whatman filter paper No. 4 (WFP).

Analysis of lignin and extractives in the oak wood of the 17th century warship Vasa

Holzforschung ◽  
2014 ◽  
Vol 68 (4) ◽  
pp. 419-425 ◽  
Author(s):  
Dina Dedic ◽  
Teresia Sandberg ◽  
Tommy Iversen ◽  
Tomas Larsson ◽  
Monica Ek
Keyword(s):  
Oxidative Degradation ◽  
Magic Angle Spinning ◽  
Chemical Degradation ◽  
Gas Chromatography Mass Spectrometry ◽  
Magic Angle ◽  
Chemical Mechanisms ◽  
Wood Extracts ◽  
Cellulose Depolymerization ◽  
Angle Spinning ◽  
C Nmr

Abstract The wood in the 17th century Swedish warship Vasa is weak. A depolymerization of the wood’s cellulose has been linked to the weakening, but the chemical mechanisms are yet unclear. The objective of this study was to analyze the lignin and tannin moieties of the wood to clarify whether the depolymerization of cellulose via ongoing oxidative mechanisms is indeed the main reason for weakening the wood in the Vasa. Lignin was analyzed by solid-state nuclear magnetic resonance [cross-polarization/magic-angle spinning (CP/MAS) 13C NMR] and by means of wet chemical degradation (thioacidolysis) followed by gas chromatography-mass spectrometry (GC-MS) of the products. No differences could be observed between the Vasa samples and the reference samples that could have been ascribed to extensive lignin degradation. Wood extracts (tannins) were analyzed by matrix-assisted laser desorption ionization (MALDI) combined with time-of-flight (TOF) MS and 13C NMR spectroscopy. The wood of the Vasa contained no discernible amounts of tannins, whereas still-waterlogged Vasa wood contained ellagic acid and traces of castalagin/vescalagin and grandinin. The results indicate that the condition of lignin in the Vasa wood is similar to fresh oak and that potentially harmful tannins are not present in high amounts. Thus, oxidative degradation mechanisms are not supported as a primary route to cellulose depolymerization.

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