Solid-state 13C NMR Research Articles

Solid–Liquid Phase Transitions of Triglycerides in Griebenschmalz, Smalec, and Fedt Studied Using 13C Solid-State NMR with Dynamics-Based Spectral Filtering

The consumer satisfaction of lard-based bread spreads depends on a delicate balance between a liquid fat phase, allowing the spread to flow, and solid fat crystals, providing the product with substance sometimes further enhanced by crispy pork cracklings. Here we apply 13C solid-state NMR with dynamics-based spectral filtering to characterize and follow the temperature dependence of the co-existing solid and liquid triglyceride phases in commercial German Griebenschmalz and Polish smalec, both containing cracklings, as well as home-made Danish fedt and, as a chemically more pure reference, German Schweineschmalz intended for baking. The NMR method allows detection of carbon atoms representative of saturated, unsaturated, and polyunsaturated acyl chains in both solid and liquid states. The results show that the solid comprises multiple crystal forms with different melting temperatures, while the liquid is at low temperature enriched in triglycerides with shorter acyl chains and higher degree of unsaturation, which become diluted with long-chain saturated triglycerides as the solids are melting. The obtained deeper understanding of the concomitant aspects of the phase transitions may pave the way for future efforts of rational optimization of fat blend composition to extend the temperature range over which the product contains sufficient amounts of both solids and liquids to give texture properties appealing to consumers.

Lithium Promotes Acetylide Formation on MgO During Methane Coupling Under Non-Oxidative Conditions.

A prototypical material for the oxidative coupling of methane (OCM) is Li/MgO, for which Li is known to be essential as a dopant to obtain high C2 selectivities. Herein, Li/MgO is demonstrated to be an effective catalyst for non-oxidative coupling of methane (NOCM). Moreover, the presence of Li is shown to favor the formation of magnesium acetylide (MgC2 ), while pure MgO promotes coke formation as evidenced by solid-state 13 C NMR, thus indicating that Li promotes C-C bond formation. Metadynamic simulations of the carbon mobility in MgC2 and Li2 C2 at the density functional theory (DFT) level show that carbon easily diffuses as a C2 unit at 1000 °C. These insights suggest that the enhanced C2 selectivity for Li-doped MgO is related to the formation of Li and Mg acetylides.

Efficient and regulable extraction of keratin from yak hair using imidazolium-based ionic liquids

Yak hair is very difficult to dissolve in most conventional solvents due to the stable three-dimensional structure of keratin, which limits its application. In this study, a series of imidazole-based ionic liquids (ILs) were screened out and used to extract keratin from yak hair. The results indicated that the time of 8 wt% yak hair completely dissolved in five ILs at 130 °C was in the sequence of 1-allyl-3-methylimidazolium chloride ([Amim]Cl) > 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) > 1-ethyl-3-methylimidazolium chloride ([Emim]Cl) > 1-ethyl-3-methylimidazolium diethylphosphate ([Emim]DEP) > 1-ethyl-3-methylimidazolium acetate ([Emim]OAc), and the anion played an essential role in the dissolution process. However, the XRD and the solid-state 13C NMR results showed that the secondary structure of regenerated yak hair keratin changed from β-sheet and random coil conformation to α-helix for [Emim]DEP, [Bmim]Cl, [Emim]Cl, while the regenerated yak hair keratin from [Emim]OAc was damaged greatly. The regenerated yak hair keratin using [Emim]DEP had the highest disulfide bond content and relatively complete structure. Furthermore, [Emim]DEP has an excellent performance in dissolving human hair and goat wool, and the secondary structure of the regenerated keratins was also maintained. Meanwhile, the dissolution performance of the fifth recycled [Emim]DEP remained steady, suggesting that [Emim]DEP is a potentially efficient solvent for the extraction keratin from hairs.

Solid-state 13C NMR, X-ray diffraction and structural study of methyl 4-O-methyl β-D-glucopyranosides with all eight possible methyl-substitution patterns

Cellulose model compounds that mimic the building blocks of modified cellulose and cellulose derivatives are widely used in cellulose research to infer the properties of the polymer from the monomer. Based on the well-established model compound methyl 4-O-methyl β-d-glucopyranoside, in which the methyl groups represent the truncated side chains of the cellulose, the corresponding O-methyl-substituted derivatives with all eight different substitution patterns (mono-, di- and trisubstituted at O-2, O-3, O-6) were synthesized. Crystallization of the products in sufficient quality for solid-state structure determination by single-crystal X-ray diffraction succeeded in all cases, and the results are reported. Two of the compounds showed more than one independent molecule per unit cell. Solid-state 13C NMR showed a significant down-field shift (5–10 ppm) of the OMe-substituted carbons relative to the OH-substituted counterparts and generally confirmed the important influence of solid-state packing on the chemical shifts as seen by comparison to the solution NMR data.Graphical abstract

Enhancing the metal ion binding characteristics and reversal of selectivity of crosslinked chitosan sorbents through functionalisation for targeted applications

In this study, we report optimised synthesis of N-carboxymethylated chitosan (CM-Cts) and its crosslinking to obtain, for the first time, glutaraldehyde crosslinked N-carboxymethylated chitosan (CM-Cts-Glu) as a metal ion sorbent. CM-Cts and CM-Cts-Glu were characterised using FTIR and solid state 13C NMR techniques. As compared to epichlorohydrin, glutaraldehyde was found to be better suited for efficient synthesis of the crosslinked functionalised sorbent. CM-Cts-Glu showed better metal ion uptake properties compared to the crosslinked chitosan (Cts-Glu). Metal ion removal by CM-Cts-Glu was studied in detail under different conditions such as different initial solution concentrations, pH, presence of complexants and competing ions. Further, sorption-desorption kinetics was studied and it was shown that complete desorption and multiple cycles of reuse without any loss in capacity was feasible. The maximum Co(II) uptake obtained for CM-Cts-Glu was found to be 265 μmol/g, while for Cts-Glu it was 10 μmol/g. Metal ion sorption by CM-Cts-Glu was found to be through chelation by the carboxylic acid functional groups present over the chitosan backbone. Utility of the CM-Cts-Glu under complexing decontamination formulations used in nuclear industry was ascertained. While Cts-Glu generally preferred iron over cobalt under complexing conditions, it was shown that the selectivity was reversed in favour of Co(II) in the functionalised sorbent, CM-Cts-Glu. N-carboxylation followed by crosslinking with glutaraldehyde was found to be a feasible approach for the generation of superior chitosan-based sorbents.

Engineering of Adhesion at Metal-Poly(lactic acid) Interfaces by Poly(dopamine): The Effect of the Annealing Temperature.

Control over adhesion at interfaces from strong bonding to release between thermoplastic polymers (TPs) and metal oxides is highly significant for polymer composites. In this work, we showcase a simple and inexpensive method to tune adhesion between a TP of growing interest, poly(lactic acid) (PLA), and two commercial metal alloys, based on titanium and stainless steel. This is realized by coating titanium and stainless steel wires with polydopamine (PDA), thermally treating them under vacuum at temperatures ranging from 25 to 250 °C, and then comolding them with PLA to form pullout specimens for adhesion tests. Pullout results indicate that PDA coatings treated at low temperatures up to a given threshold significantly improve adhesion between PLA and the metals. Conversely, at higher PDA annealing temperatures beyond the threshold, interfacial bonding gradually declines. The excellent control over interfacial adhesion is attributed to the thermally induced transformation of PDA. In this work, we show using thermogravimetric analysis, X-ray photoelectron spectroscopy, Fourier transform infrared, and 13C solid-state NMR that the extent of the thermal transformation is dependent on the annealing temperature. By selecting the annealing temperature, we vary the concentration of primary amine and hydroxyl groups in PDA, which influences adhesion at the metal/PLA interface. We believe that these findings contribute to optimizing and broadening the applications of PDA in composite materials.

Elucidation of the CH4 coupling mechanism to C2H4 over GaN catalysts under non-oxidative conditions

The second C−H bond cleavage in methane to form methylene (CH2*) from methyl (CH3*) is the rate-limiting step for the direct non-oxidative methane coupling to ethylene over gallium-nitride catalysts. Herein, we use isotope labelled experiments, in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), 13C solid state-NMR, as well as kinetic modelling to elucidate the reaction mechanism. Our experiments showed that supported GaN/SBA-15 had more aliphatic surface intermediates (CH3* and CH2*) than unsupported GaN catalysts, which had higher amounts of aromatics intermediates and coke deposition. Isotope labelling experiments and the kinetic study confirmed that the most likely pathway is via the fast abstraction of the first H from CH4 to form methyl (CH3*) surface intermediates, followed by the slow second C−H bond cleavage to form methylene (CH2*) and subsequent coupling to ethylene. The intrinsic activation energy predicted by kinetic modelling was rather low at around 20 kJ mol−1.

Spectroscopic and DFT study of tris(β-diketonato)cobalt(III) complexes

Nuclear magnetic resonance measurements confirm that, as expected, the mer isomer of tris(β-diketonato) cobalt(III) complexes is more stable ( mer isomers are more stable because they are less affected by steric hindrance and they have lower dipoles). An excess of the mer isomer or only the mer isomer is experimentally observed. The existence of both fac and mer isomers is predicted by density functional theory calculations. At room temperature, the nuclear magnetic resonance peaks of phenyl-containing mer complexes are broad due to the intermediate rotation of bulky phenyl groups resulting in only the average orientation of the non-equivalent protons in the mer complexes. However, upon heating to 55 °C (thus speeding up the rotation) or cooling to −50 °C (slowing down the rotation), this broad peak is resolved into three sets of carbon peaks appearing in the 13C NMR spectrum, as well as splitting of the 1H NMR peaks for the non-equivalent protons in the mer isomer. In solid-state 13C NMR the aromatic rings do not rotate, resulting in the splitting of all the 13C NMR peaks. Two sets of well-defined peaks are observed for the fluorine-containing compound [Co(CF3COCHCOCPh)3] in both the 13C and 19F NMR spectra, indicating that both the fac and mer isomers are present with a ratio of fac:mer = 0.1:1. The X-ray photoelectron spectroscopy measured binding energy of the Co 2p3/2 photoelectron lines are influenced by the subtle electronic (electron-donating or electron-withdrawing) properties of the R groups on the β-diketonato ligands. Various relationships are established between the binding energy of Co 2p3/2 and several physical and density functional theory–calculated properties, confirming good electronic communication (the measurable electronic effect that a molecular fragment has on the physical properties of another molecular fragment in the molecule) of the substituent groups through the pseudo aromatic system of the β-diketonato backbones to the metal.

Molecular organization and molecular order of two rod-like smectogens in mesophases

ABSTRACT Structurally simple two rod-like mesogens with a three-ring core consisting of biphenyl and phenyl rings are synthesised to investigate the mesophase properties, molecular organisation and the orientational order parameter. In mesogen-1, a dodecyloxy terminal chain is present on the biphenyl ring while the phenyl ring is free from substituent. For mesogen-2, in addition to the dodecyloxy chain, the butyl chain is placed on the phenyl ring. The Hot-stage optical polarising microscopy (HOPM) and differential scanning calorimetry (DSC) measurements show smectic A (SmA), smectic B (SmB), and crystal E (CryE) phases for mesogen-1 and SmA, smectic C (SmC) and smectic F (SmF) phases for mesogen-2. The presence of smectic mesophases is established by X-ray Diffraction (XRD). 1D and 2D 13C solid-state NMR experiments are performed in smectic mesophases to find the orientational order parameters of the phenyl rings of the core. The main order parameter (Szz) of the mesogens in the SmB and SmF phase is in the range of 0.87–0.93. The excellent spectral resolution noticed in 13C NMR spectra in the SmB mesophase (mesogen-1) indicates that the internal rotations of the molecules along the long axis are primarily unhindered.

Metal- and Peroxide-Free Silicone Rubbers with Antibacterial Properties Obtained at Room Temperature

Metal- and peroxide-free silicone rubbers were obtained via a reaction between amino-containing poly(dimethylsiloxanes) (amino-terminated (APDMS-1) or a copolymer with pendant amino groups (APDMS-2)) and iodine-containing polysiloxanes (PIMSs) (Menshutkin reaction). Simple mixing of functional polymers at room temperature resulted in forming silicone materials. The formation of ammonium cross-links was confirmed using solid-state 1H and 13C NMR spectroscopy. The equimolar ratio of NH2 groups to the I-containing moiety (1:1) was the most optimal among other ratios (2:1 and 1:2) to carry out cross-linking and led to the highest cross-linking density according to the swelling measurements. PIMS/APDMS-1 (1:1) rubbers had the lowest average molecular weight of segments between cross-links Mc = 250 compared to PIMSs/APDMS-1 (1:2) and (2:1) with Mc = 1110 and 390, respectively. The obtained silicone rubbers showed antibacterial activity against Escherichia coli and Staphylococcus aureus and thereby could be applied in biomedicine and the food industry as antibacterial coatings and materials.

Carbon Dioxide Sequestration by Triboelectric Charging of Tumbling Quartz Sand

Mechanical activation (i.e., tumbling) of quartz sand in a carbon dioxide (CO2) atmosphere leads to triboelectric charging of the sand grains, driving a process that ultimately sequesters and removes CO2 from the ambient atmosphere. Supported by diffuse reflectance FTIR and 13C solid-state NMR experiments and density functional theory (DFT) calculations, we propose that CO2 is inserted into the quartz lattice to form an anchored CO3 species, a process that otherwise requires high temperature and pressure to proceed synthetically. The products of the reaction are stable for at least 6 months at ambient temperature and pressure, but CO2 is liberated at temperatures above 150 °C. The prospect of using this method to remove CO2 from the atmosphere and, ultimately, to help mitigate the adverse effects of greenhouse gases and global warming is briefly discussed.

Chemical Structure of Organic Matter of Agrochernozems of Different Alocalization on the Slope

The chemical structure of organic matter (OM) pools in agrochernozems confined to different zones of denudation-accumulation has been studied by solid-state 13C-NMR spectroscopy. It was revealed that in the erosion zone there are two competing processes occurring simultaneously: the decomposition of the “old” OM of the earlier underlying horizon and the stabilization of the fresh OM that has arrived with plant remains of cultivated plants (dynamic replacement of OM). Analytical data allow us to assert that the processes of dynamic replacement of eroded OM in the erosive zone quite effectively compensate for the processes of OM decomposition, as evidenced by the highest C/N ratio of all the studied OM pools in the eroding agrochernozem, along with the absence of significant differences in the integral indicators of their chemical structure. However, the constant removal of the upper soil layer from the eroding agrochernozem during each erosion event does not allow one to fully compensate for the OM quantitative losses in it. During the transportation of eroded material to the accumulative zone, the most labile part of OM can be mineralized. Accordingly, the OM again entering the accumulative zone is more transformed than that of the eroding agrochernozem. Nevertheless, the alluvial agrochernozem is characterized by an increased level of C accumulation in the soil as a whole and in all the studied OM pools. Accordingly, it can be stated that the constant OM inputs from the eroding position with its subsequent burial with each subsequent erosion event, as well as the repacking/aggregation of newly deposited OM, very effectively contribute to the deposition of C in the accumulative zone.

Experimental and DFT study on the relationships between the evolution mechanism of PAHs and NOx precursors during coal pyrolysis

The evolution mechanism of coal carbon skeleton to polycyclic aromatic hydrocarbons (PAHs) with temperature has been researched by in-situ Raman and solid-state 13C NMR. A theoretical exploration with density functional theory at M06-2X/6-31G(d,p)//def-TZVP level was performed, in order to investigate the mutual conversion pathways among different functional nitrogen, and the relationships between their evolution to NOx precursors and PAHs. The aromatic nucleus radicals produced by homolysis reaction of aliphatic side chains can be connected by carbon-carbon single bonds to form PAHs remaining in char at medium pyrolysis temperature. The participation of olefin compounds cracked from aliphatic side chains is favorable to the conversion of pyrrolic and pyridinic (N-6) nitrogen to NOx precursors and PAHs, and the cyclopentadiene and butadiene obtained by the cleavage of different functional nitrogen in coal skeleton are important intermediates for the formation of PAHs. The conversion of pyridine oxide and quaternary nitrogen (N-Q) to N-6 around 440 °C can compensate for the own thermal decomposition of N-6, while the conversion of N-Q to N-6 is gradually dominated by the reverse reaction from around 690 °C.

Organic-inorganic building block of phytic acid intercalated graphene oxide for performance enhancement of plant-derived adhesives

The introduction of 2D graphene into the soybean protein (SP) adhesive is expected to enhance its mechanical performance. However, insufficient binding of the two materials inevitably leads to the resulting composite having limited mechanical strength. Using phytic acid (PA) and a supramolecular self-assembly strategy, hard graphene oxide (GO) was first assembled with PA to form a supramolecular polymer, PA-co-GO, that has a “bricks and mortar” structure as a result of strong non-covalent interactions. PA-co-GO was then further combined with SP in the presence of the long-chain epoxy compound neopentyl glycol diglycidyl ether (NG) to produce a novel biopolymer-based adhesive PA-co-GO/NG/SP. The prepared adhesive has a moisture-insensitive interface as a result of non-covalent/covalent bonds and a “bricks and mortar” microstructure that allows the dissipation of energy, resulting in an enhancement in the water-resistant bonding strength of the material, with a 345% increase in its wet bonding strength compared with the unmodified SP adhesive. Additionally, the combination of the heat shielding of the GO and catalytic carbonization of PA resulted in the adhesive having excellent flame retardant properties. The structure and morphology of the materials were characterized using atomic force microscopy (AFM), dynamic light scattering (DLS), Fourier-transform infrared (FTIR), X-ray photoelectron spectra (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and solid-state 13C NMR. Overall, a new clean route for preparing green high-performance biopolymer-based adhesives is described, with potential applications for sustainable agricultural byproducts.

Combined liquid hot water and sulfonation pretreatment of sugarcane bagasse to maximize fermentable sugars production

Sugarcane bagasse (SCB) is a widely available biomass feedstock currently used for ethanol production in various parts of the world. Here, we carried out a combined liquid hot water and neutral/alkaline sulfonation pretreatments of SCB at relatively low temperatures to maximize enzymatic hydrolysis yields. To describe multi-step pretreatments severities, analytical equations for modified combind severity factors (CSF´m) were introduced. Although the chemical composition of SCB after the liquid hot water pretreatment alone has not been significantly changed under tested conditions, this pretreatment led to an increase in the efficiency of its enzymatic hydrolysis. Furthermore, a combination of liquid hot water pretreatment (at 120 °C for 1 h) and sulfonation of SCB (at 120 °C for 2 h) resulted in excellent enzymatic hydrolysis yields. After alkaline sulfonation, glucose yields reached 99.6 ± 0.21% for autoclaved and alkaline sulfonated bagasse (AASB) and 97.47 ± 0.75% for boiled and alkaline sulfonated bagasse (BASB), whereas xylose yields were 86.9 ± 1.9% and 88.0 ± 1.8% for AASB and BASB, respectively. High enzymatic hydrolysis yields are in line with elevated CSF´m of the latter pretreatments. X-ray diffraction, confocal laser scanning microscopy, and solid-state 13C NMR spectroscopy analyses showed that the structural desorganization of bagasse after liquid hot water pretreatment associated to chemical modifications of lignin and its massive removal promoted by alkaline sulfonation led to efficient separation of carbohydrates and lignin, revealing underlying structural reasons of the observed efficient enzymatic hydrolysis.

Synthesis of N-Unprotected Diaryl Ketimines and Alkyl Ketimines from Ketones and Ammonia Using Porous Solid Acids with Analysis of Their Adsorption Behavior

Abstract The most atom-efficient synthetic method for N-unprotected ketimines (N-H ketimines) from ketones is the dehydration condensation reaction with ammonia (NH3). However, until now, few synthetic methods for N-H ketimines with high versatility have been known. In this study, we examined various solid acids and found that N-H diaryl ketimines with various functional groups on the aryl groups could be synthesized in high yields from diaryl ketones and NH3 under solvent-free conditions using silica-alumina (SiO2-Al2O3) or proton-exchanged Y-type zeolite (H-Y). Solid-state 13C and 15N NMR measurements indicated that the N-H ketimine formed in the pores of acidic zeolite was coordinated to NH4+ species on the pore surface. By quantum chemical calculations we also discussed the reason why the dehydration-condensation reaction between ketone and NH3, which is an endothermic reaction in a vacuum, was biased toward the product side in the actual experiment. In addition, this synthetic method can be applied to synthesize N-H alkyl ketimines with α-acidic hydrogens, which are less stable and more sensitive to hydrolysis and oligomerization than diaryl ketimines.

A facile approach to undecylenic acid-functionalized stationary phases for per aqueous liquid chromatography

Green chromatography techniques using low-toxic mobile phase are getting increasingly attention in recent years. The core is developing stationary phases that possess adequate retention and separation under the mobile phase of high content water. Using thiol-ene click chemistry, an undecylenic acid-bonded silica stationary phase (UAS) was prepared in a facile manner. Elemental analysis (EA), solid-state 13C NMR spectroscopy and Fourier transform infrared spectrometry (FT-IR) confirmed the successful preparation of UAS. The synthesized UAS was employed for per aqueous liquid chromatography (PALC), which uses little organic solvent during separation. Due to the hydrophilic carboxy, thioether group and hydrophobic alkyl chains of the UAS, various categories of compounds (including nucleobases, nucleosides, organic acids and basic compounds) with different properties can achieve enhanced separation under the mobile phase of high content water compared with commercial C18 and silica stationary phases. Overall, our present UAS stationary phase shows excellent separation ability toward highly polar compounds and meets the requirements of green chromatography.

Effect of Silicone Modifier on the Physical Properties of Flexible Silica Aerogels.

Research on the development of flexible silica aerogels (FSAs) has been ongoing due to their excellent thermal insulation, low density, and high elasticity. However, the physical properties of FSAs, such as density, thermal conductivity, mechanical strength, and surface wettability, are highly dependent on the preparation conditions. To achieve the desired properties of FSAs for various applications, it is necessary to develop a method to fine-tune their physical properties. In this paper, two modifiers of methyltrimethoxysilane (MTMS)/trimethylethoxysilane (TMES) were employed to fine-tune the bulk density of a series of flexible silica aerogels (FSAs), reflecting a series of FSAs with fine-tunable physical properties. First, the precursor was synthesized by a click reaction between vinyltrimethoxysilane (VTMS) and 2,2' (ethylenedioxy) diethanethiol (EDDET). The VTMS, EDDET, and the as-prepared precursor were characterized by FT-IR and NMR spectroscopy. Subsequently, the precursor was converted into a series of FSAs (denoted by FSA, FSA-M, and FSA-T) through conventional sol-gel reactions with/without MTMS/TMES. Chemical structures of synthesized FSAs were confirmed by 13C and 29Si solid-state NMR spectroscopy. The porous structure of FSAs was identified by BET and SEM, respectively. Physical properties, such as thermal conductivity, mechanical strength, and surface wettability of FSAs were determined by a Hot Disk, durometer/DMA in compression mode, and contact angle measurements, respectively. This study found FSAs containing none, 1 wt%, 5 wt%, and 10 wt% of MTMS increase the density of FSAs from 0.419 g/cm3 (FSA), 0.423 g/cm3 (FSA-M1), 0.448 g/cm3 (FSA-M5), and 0.456 g/cm3 (FSA-M10). It should be noted that the thermal conductivity, surface hardness, bulk mechanical strength, and hydrophobicity of FSA-Ms of increasing MTMS loading were all found to show a rising trend, while FSA-Ts exhibited lower density. FSA-T10 exhibited lower thermal conductivity, surface hardness, and bulk mechanical strength as compared to FSA. However, it was found to show higher hydrophobicity as compared to that of FSA.

Elucidating the chemical structures of petroleum resin using solid-state 13C NMR

In this study, a new method to perform the solid-state 13C NMR analysis of oil resin has been proposed and the 3D molecular model of oil resin has been established for the first time. This method is not only suitable for petroleum resin, but also can be used in the structural detection of all colloidal component of fossil fuel. In this research, both liquid- and solid-state 13C NMR based on CP-TOSS/MAS method have been carried out to detect the chemical structural of petroleum resin. Solid-state 13C NMR showed less influence from solvent peaks and achieved a more accurate identification of aromatic carbon and oxygen-containing functional groups than liquid-state 13C NMR, and the FT-IR was used to verify this; thus, it is more suitable for resin structure detection. Based on the results of the two types of NMR, the petroleum resin structure was found to consist of aromatic clusters at the core, with short aliphatic chains and cycloalkanes connected in the periphery. In addition, two new parameters were established to evaluate the length of aliphatic chains (CnR) and oxygen-containing in resins (OINMR: NMR oxygen index of resin). Combined with elemental analysis, the average 3D resin molecular model was established in this research. In general, this study underscored a suitable method for detecting chemical structures in the field of fossil fuel and energy engineering, and successfully introduced solid-state 13C NMR for the analysis of colloidal component of fuel. At the same time, the most stable structural model of petroleum resin in three-dimensional space was established; this provides a basic model for the molecular simulation research of the constituents of petroleum. Considering the important influence of resin on the properties of petroleum, this research has a great significance to migration and exploitation of heavy oil.

Resolving the discrepancies in reported 13C solid state NMR chemical shifts for native celluloses

Resolving the discrepancies in reported 13C solid state NMR chemical shifts for native celluloses