Transformation of nitrogen-containing compounds in atmospheric residue by hydrotreating

Atmospheric residue from Saudi Arabia light crude oil was subjected to the hydrotreating process in a continuous fixed-bed reactor with hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) catalysts. The detailed molecular composition of the polar heteroatom species in the feedstock and products was determined by electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) combined with other analytical methods. The ESI FT-ICR MS analysis indicates that the N₁ class species have the highest relative abundance. In the hydrotreating process, small neutral N₁ class species with high aromaticity and short side chains showed the highest relative abundance and were defined as easily removable compounds. High aromaticity and small molecule basic N1 compounds exhibited higher catalytic activity towards hydrogenation. The N₁S₁ class species were converted to the N₁ class species, or even hydrocarbons, by the preferential removal of the sulfur atoms. Most of the N₁O₁ class species were difficult to remove, because of their stable chemical structure.     

Identification of acidic species extracted from heavy crude oil by fourier transform ion cyclotron resonance mass spectrometry

Acidic species were extracted from heavy crude oil by alcohol-alkali solution and ion exchange resin. The acidic species in the obtained extracts and extracted crude oil were characterized by negative-ion ESI FT-ICR MS. The analytical results indicated that some class species, O₂, O₁, N₁, N₁O₁, N₁O₂, N₁S₁ and O₂S₁ etc., were identified in the negative-ion spectrum, in which O₂, O₁ and N₁ class showed much higher abundance than others. Compared to O₁ and N₁ class, O₂ class could be extracted from heavy crude oil by using the two methods more efficiently, which means that a great majority of O₂ class can be extracted; meanwhile, almost half of O₁ and N₁ class still remained in residual phase. Detailed analysis demonstrated that alcohol-alkali method was effective for extracting O₂, O₁ and N₁ class with lower molecular weight; ion exchange method, however, was helpful to extract higher molecular weight O₁ and N₁ class and showed almost equal extraction selectivity to all kind of O₂ class.     

ESI FT-ICR mass spectral analysis of coal liquefaction products

We have applied electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to analyze the pyridine soluble fraction of a distillation resid and a further processed liquid product in a coal liquefaction process. The inherent high resolving power (m/Δm_50%>300,000, in which Δm_50% is full mass spectral peak width at half-maximum peak height) and mass accuracy (<1 ppm) of FT-ICR MS makes it possible to resolve and identify polar heteroatomic species. The resid contains more heteroatomic compounds and a higher molecular weight distribution whereas the liquid sample is lower in average mass and more saturated. The data confirms that the liquefaction process produces lower mass, hydrogenated liquid product whereas the resid (highly aromatic and of high heteroatom content) must be recycled to reduce its heteroatom content and increase its degree of saturation.     

Investigation of the tetracarbonatozirconate ion by electrospray mass spectrometry in aqueous media

Reported here is the study of zirconium (IV) aqueous solutions in carbonate media by electrospray ionisation mass spectrometry (ESI–MS). Spectra analysis lead to consider the existence in the spray of the initial pseudomolecular labile species [Zr(CO₃)₄(HCO₃)]⁵⁻, xH⁺, (6−x) K⁺ (or Na⁺). The existence of this species confirms the associative exchange mechanism of carbonate ions with [Zr(CO₃)₄]⁴⁻ ion.     

Generalisation de la theorie de l'electrode dite “electrode a disque-anneau’, dans un fluide d'otswald. Calcul des facteurs de collection

Supposing that in the diffusional boundary layer, the tangential component V_x and radial component V_r of the relative fluid velocity are respectively written in the form V_xS₀x^by and V_ra₀r^by (S₀, a₀ are independent coefficient of the normal coordinate y, tengential coordinate x, radial coordinate r;b is a numerical exponent that is expressed in terms of the behaviour law and of the flow), the authors calculate a analytical expression for the collection factor N defined as the quotient, with the sign inverted, of the limiting diffusional flux on the downstream active surface by the limiting diffusional flux on the upstream active surface. This factor N is dependent only on geometrical characteristics of system and on exponent b.     

Formation Mechanism of Alkyl Nitrites,Valuable Intermediates in C1-Upgrading Chemistry and Oxidation Processes

In this contribution we use computational tools to investigate the reaction of alcohol substrates with reactive nitrogen oxide species such as N₂O₃ and N₂O₄, leading to the formation of alkyl nitrites. These nitrites are interesting intermediates which can be processed to various valuable chemicals such as ketones/aldehydes and dimethyl oxalate while regenerating NO _x . As such, NO _x is used as an oxidation mediator, converting alcohol substrates to more reactive nitrites which can be selectively converted to more desired compounds, closing a catalytic cycle in NO _x species.     

Evaluation of CO2 permeation through functional assembled mono-layers: Relationships between structure and transport

CO₂ transport through functional assembled mono-layers was evaluated in relation to H₂O and nonpolar gases such as CH₄, O₂, N₂. Membranes based on Pebax^®2533 were functionalised by incorporating chemical compounds containing free hydroxyl, N-alkyl sulphonamide, bulky benzoate groups. The effects of both the chemical nature and concentration of the modifier on the gas transport were reported, respectively. The permeability coefficients of different penetrating chemical species were compared, evidencing the higher affinity of the layers to water vapour and carbon dioxide, due to favourable interactions between polar moieties and penetrant. The condensability of the penetrant directed the permeability of the species considered and was responsible for the high solubility selectivity between H₂O and CO₂ (i.e. , DH₂O/D₂CO=0.6, SH₂O/S₂CO=11.4 at 25 °C for Pebax/KET 50/50 w/w). An increase in polar moieties resulted in enhanced permeability and selectivity with respect to the pure polymer. In contrast, the functionalised polymer was not capable to discriminate between the smallest penetrants such as O₂ and N₂, with consequent decrease in the ideal selectivity (P₂CO/O₂, P₂CO/N₂). The functional layers exhibited permeability and selectivity covering broad ranges of values.     

Films of hydrogenated silicon oxycarbonitride. Part I. Chemical and phase composition

The method of preparation of hydrogenated silicon oxycarbonitride films with variable composition SiC _x N _y O _z : H by the plasma chemical vapor decomposition of a volatile organosilicon compound, 1,1,1,3,3,3-hexamethyldisilazane (enhanced to IUPAC, bis(trimethylsilyl)amine) in a gas phase containing nitrogen and oxygen in the temperature range of 373–973 K has been developed. It has been shown that nitrogen and oxygen provide the decrease in carbon content in films due to gas-phase reaction giving volatile products (CN)₂, CH₄, CO, and H₂(H). The obtained SiC _x N _y O _z : H films are nanocomposite, in the amorphous part of which the nanocrystals are distributed, which belong to the determined phases of the Si-C-N system, namely, α-Si₃N₄, α-Si_{3 ? x} C _x N₄, and graphite.     

Tantalum (oxy)nitrides prepared using reactive sputtering for new nonplatinum cathodes of polymer electrolyte fuel cell

Tantalum (oxy)nitrides (TaO_xN_y) have been investigated as new cathodes for polymer electrolyte fuel cells without platinum. TaO_xN_y films were prepared using a radio frequency magnetron sputtering under Ar + O₂ + N₂ atmosphere at substrate temperatures from 50 to 800 °C. The effect of the substrate temperature on the catalytic activity for the oxygen reduction reaction (ORR) and properties of the TaO_xN_y films were examined. The catalytic activity of the TaO_xN_y for the ORR increased with the increasing substrate temperature. The ORR current density at 0.4 V vs. RHE on TaO_xN_y prepared at 800 °C was approximately 20 times larger than that on TaO_xN_y prepared at 50 °C. The onset potential of the TaO_xN_y for the ORR was obtained at the ORR current density of −0.2 μA cm⁻². The onset potential of the TaO_xN_y prepared at 800 °C was ca. 0.75 V vs. RHE. The X-ray diffraction patterns revealed that Ta₃N₅ structure grew as the substrate temperature increased. While, the ionization potentials of all specimens were lower than that of Ta₃N₅, and decreased with the increasing substrate temperature. The TaO_xN_y which had Ta₃N₅ structure and lower ionization potential might have a definite catalytic activity for the ORR.     

Effects of oxygen on the thermal stability of silicon nitride fibers

Two types of Si₃N₄ fibers with different oxygen contents were annealed in a nitrogen atmosphere at 1500 °C for 1 h. After annealing, the fiber (SN-L) containing 0.5 wt% oxygen crystallized to α-Si₃N₄ but lost its strength, whereas the fiber (SN-H) containing 4.2 wt% oxygen was amorphous and retained 63.6% of its strength. The phase transition in these fibers was mainly influenced by the oxygen level. The lower oxygen content in the SN-L favored the precipitation of an almost stoichiometric composition of α-Si₃N₄ initially at ~1450 °C with an activation energy (Ea) of 663.357 kJ/mol. Nanopores existing naturally in the fiber promoted crystallization via heterogeneous nucleation. SN-H precipitated as an amorphous SiN_xO_y metaphase preferentially at ~1400 °C with an Ea of 440.434 kJ/mol, owing to the higher oxygen content approaching that of Si₂N₂O. SiN_xO_y inhibited the crystallization of α-Si₃N₄, making SN-H more thermally stable than SN-L at temperatures above 1500 °C.     

34 GHz e.p.r. study of vanadyl complexes in various asphaltenes: Statistical correlative model of the coordinating ligands

High precision 34 GHz e.p.r. measurements were performed to study the coordination of vanadyl complexes in various asphaltenes. The spin-Hamiltonian parameter analysis indicates that the asphaltenes can be classified into those which have g- and A-parameters nearly identical to those for the vanadyl tetraphenyl porphyrins doped in carbonaceous materials and those for which these parameters are nearly identical to those for the vanadyl etioporphyrins. Quantitative statistical analysis of the parameters for model compounds with coordination N₄, N₂S₂, NS₃, S₄, S₂O₂, N₂O₂ and O₄ shows that these parameters cannot be used to predict the coordination for various asphaltenes. It is found that g₀ is a better parameter than A₀ to predict the coordination, although it cannot resolve the N₄, S₄ and S₂O₂ coordinations. However, the spin-Hamiltonian parameter resolution was sufficient to distinguish between those vanadyl complexes present in porphyrins, humates and minerals. The importance of high precision e.p.r. measurement at 34 GH_z or higher frequencies for model compounds and chromatographically-separated fractions is discussed.     

Novel S,N co-doped Ba2In2-xCrxO5+y oxides: Synthesis and optical properties

The (S, N) co-doped Ba₂In_2-xCr_xO_5+y (0 ≤ x ≤ 0.5) oxides are successfully obtained by mixing the Ba₂In_2-xCr_xO_5+y oxides and thiourea through a simple ball milling method followed by sintering at 400 °C for 3 h. The colors of the compounds change from orange-brown to yellow-green after reacting with thiourea. When Cr amount is small (x = 0.1), the crystal structure of (S, N) co-doped Ba₂In_2-xCr_xO_5+y is orthorhombic Ba₂In₂O₅ phase. When x ≥ 0.3, the crystal structure of the sample is cubic BaInO_2.5 phase. And this phase transition is the same as Ba₂In_2-xCr_xO_5+y. XPS results reveal that Cr⁶⁺ in Ba₂In_2-xCr_xO_5+y (0 ≤ x ≤ 0.5) oxides are reduced to Cr³⁺ after sintering. S exists in both cation and anion forms, and N exists in substitutional forms. UV–Vis analysis indicates that the yellow-green hue comes from the d-d transition of Cr³⁺, and the doping of S, N ions leads to a red shift of the absorption edge of the samples.     

Detailed compositional comparison of acidic NSO compounds in biodegraded reservoir and surface crude oils by negative ion electrospray Fourier transform ion cyclotron resonance mass spectrometry

Traditional hydrocarbon biomarker analyses determined the degree of biodegradation in two reservoir and two surface oils. These data were then correlated to the distribution and type (rings plus double bonds) of acidic NSO species selectively ionized and mass resolved by negative ion electrospray Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) to determine if oxygenated polars could be used to estimate the degree of biodegradation in crude-oil contaminated soil (surface) samples. Since the histories of the surface samples were unknown (as it often the case for environmental samples), non-degraded and severely degraded reservoir oils were used as compositional benchmarks. The biodegraded reservoir crude oil exhibited an increase in relative abundance of O₂-species, a decrease in acyclic fatty acids, an increase in multi-ring naphthenic acids and a decrease in C₃₂ hopanoic acids compared to the non-biodegraded reservoir crude oil. The surface oils exhibited trends similar to the biodegraded reservoir oil, indicating that the surface oils were biodegraded in the reservoir, the environment or both. However, one surface sample also exhibited biomarker signatures indicative of a non-degraded oil. This evidence, in combination with the ESI FT-ICR MS data, suggests that the sample was contaminated with a mixture of biodegraded and non-degraded oils and demonstrates how analysis of hydrocarbon and polar fractions can reveal complex histories of surface contamination. This work is the first detailed compositional analysis of acidic NSO species in crude oil soil extracts and lays the foundation for our understanding of how surface biodegradation effects the composition of polars.     

ATRP poly(acrylate) star formation: A comparative study between MALDI and ESI mass spectrometry

Optimised matrix-assisted laser desorption/ionisation (MALDI) and electrospray ionisation (ESI) mass spectrometry (MS) methodologies were systematically compared in terms of their relative abilities to identify distinct chemical species present in samples associated with a polymer mechanistic study. In order to perform the investigation, formation processes involved in atom transfer radical polymerisation (ATRP) mediated methyl acrylate (MA) star polymerisations were studied. In addition to the 4-armed ATRP initiator employed in the polymerisations, initiator side-products were found to generate oligomeric chains. At a relatively high monomer to polymer conversion, terminal Br loss was observed in these oligomers; this Br loss was hypothesised to occur via degradative transfer reactions involving the radicals (CH₃)₂?OH, ?H₃ and ?H₂COCH₃, which were derived from the acetone used as a solvent in the polymerisations, as well as hydrogen radicals donated by the ligand N,N′,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA). In performing these studies, ESI was found to identify a greater number of distinct chemical species in the samples under investigation when compared to the employed MALDI technique, suggesting that the utilisation of ESI must be strongly considered in polymer mechanistic investigations if the maximum number of end-group functionalities within a given polymer sample are to be identified.     

Presulfidation and activation mechanism of Mo/Al2O3 catalyst sulfided by ammonium thiosulfate

Mo/Al₂O₃ catalyst was presulfided with (NH₄)₂S₂O₃ to elucidate presulfidation and activation mechanism. It is illustrated that the Mo oxide is firstly partially sulfided during presulfidation and then in situ reduced into MoS_2?x in activation, and finally sulfided to active state during hydrodesulfurization (HDS). A synergistic effect between the S^2? and S⁶⁺ ions in (NH₄)₂S₂O₃ produces a positive influence on the HDS performance. The S^2? ions contribute to the sulfidation of Mo ions, while the S⁶⁺ species interact with Al₂O₃ support, weakening the interaction of active species with support.     

Compositional analysis of deasphalted oil before and after hydrocracking over zeolite catalyst by Fourier transform ion cyclotron resonance mass spectrometry

Elemental compositions of components in feed and catalytically processed deasphalted oils were characterized by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The processed oils which were hydrocracked over a zeolite catalyst at three different reaction temperatures (370, 380, and 390 °C) were analyzed. Species of the deasphalted oils were ionized either by electrospray ionization (ESI) or by in-beam electron ionization (EI). The ESI mass spectra were obtained from every feed and processed deasphalted oil. Over 550 chemically different compounds were observed in the feed oil mass spectra. Molecular formulas for the detected peaks were calculated by using accurate mass. The compounds with one N atom as well as one N and S atoms were detected as major and minor component, respectively, in every mass spectrum. The number of the detected species in processed deasphalted oil decreases as the reaction temperature increases. However, the carbon distribution of NS-containing species shifts to high number as the reaction temperature increases. Molecular formulas distribution against Z-value (Z-value is defined as C_nH_2n + ZN_mS_sO_o) and C-number were investigated for the ESI mass spectra. Z-value distribution of the peaks assigned to N-compounds was convergent in its compounds with Z = − 25 as increasing the reaction temperature. Detailed mass spectrum analysis reveals that compounds which were not detected in the feed oil were observed in the mass spectra of processed oils; N, S, and O-containing compounds. For the in-beam EI only the processed oil at 390 °C yields approximately 700 resolved peaks at adopted probe temperature (300 °C) of EI. Molecular formula analysis for the observed peaks was conducted as well as ESI. It reveals that the molecular formulas having Z-value (− 30 < Z < 2) and carbon number ranged from 8 to 31 except for (− 18 < Z < − 12, 15 < C-number < 22) were contained in the processed deasphalted oil. Using complementary ionization techniques to characterize the feed and catalytic reacted deasphalted oils provide better understanding of fuel processing conditions.     

Structural properties and sensing performances of CoNxOy ceramic films for EGFET pH sensors

This paper describes the impact of both Ar/N₂ flow rate and rapid thermal annealing (RTA) on the structural properties and sensing characteristics of CoN_xO_y ceramic films formed through reactive sputtering and then used in extended-gate field-effect transistor (EGFET) pH sensors. The CoN_xO_y ceramic films were prepared under three different Ar/N₂ flow rates (20/5, 20/10, and 20/15) and then annealed at three different RTA temperatures (200, 300, and 400 °C). X-ray diffraction revealed that all of the CoN_xO_y ceramic films featured amorphous structures. X-ray photoelectron spectroscopy demonstrated that the Co³⁺ content of the CoN_xO_y film prepared at the 20/10 flow rate was higher than those of the films prepared at the other flow rates. Atomic force microscopy indicated that the surface roughnesses of the CoN_xO_y films obtained at flow rates of 20/10 and 20/15 were higher than that of the film prepared at 20/5. High pH-sensitivity (64.36 mV/pH), a small drift rate (0.27 mV/h), and a low hysteresis voltage (1.4 mV) were achieved for the CoN_xO_y EGFET sensor that had been fabricated at a flow rate of 20/10 with subsequent RTA at 300 °C. This high performance was due to its CoN_xO_y film having a rough surface, a high Co³⁺ ion content, and a low number of oxygen vacancies or defects.     

Structural and electrical characterization of Sr- and Al- doped apatite type lanthanum silicates prepared by the pechini method

The subject of this work regards the synthesis of La_9.83−xSr_xSi_6−yAl_yO_26+δ (0≤x,y≤0.5) via a modified Pechini method. The compounds where characterized by XRD and SEM. Pure La_9.83Si₆O_26+δ, La_9.38Sr_0.45Si₆O_26+δ and La_9.38Sr_0.45Si_5.70Al_0.30O_26+δ were prepared after sintering at 1400 °C for 20 h while La_9.38Sr_0.45Si_5.55Al_0.45O_26+δ and La_9.38Sr_0.45Si_5.50Al_0.50O_26+δ contained traces (<8%) of La₂SiO₅ as secondary phase. Rietveld analysis showed that La_9.83−xSr_xSi_6−yAl_yO_26+δ (0≤x,y≤0.5) compounds crystallize in the P6₃/m space group. Al doping on Si site exhibits more pronounced effect upon structural parameters in comparison to Sr doping on La site. Interstitial oxygen accommodates a position at the periphery of the hexagonal channels in the vicinity of the SiO₄ groups. Ion conduction is close related with the size of the hexagonal channels and the interstitial oxygen content. The ion conductivity is promoted when an optimum balance between the aforementioned magnitudes is reached. The LS and LsSa4530 compounds exhibit the highest values of ionic conductivity at 700 °C with 11 and 14 mS/cm and activation energy of 0.47 and 0.46 eV, respectively.     

Persistent deNOx Ability of CaAl2O4:(Eu, Nd)/TiO2-x N y Luminescent Photocatalyst

Abstract  

CaAl₂O₄:(Eu, Nd)/TiO_2-x N _y composite luminescent photocatalyst was successfully synthesized by a simple planetary ball milling process. Improvement of photocatalytic deNOx ability of TiO_2-x N _y , together with the persistent photocatalytic activity for the decomposition of NO after turning off the light were realized, by coupling TiO_2-x N _y with long afterglow phosphor, CaAl₂O₄:(Eu, Nd). The novel persistent photocatalytic behavior was related to the overlap between the absorption wavelength of TiO_2-x N _y and the emission wavelength of the CaAl₂O₄:(Eu, Nd). It was found that CaAl₂O₄:(Eu, Nd)/TiO_2-x N _y composites provided the luminescence to persist photocatalytic reaction for more than 3 h after turning off the light.     

The electronic and optical properties of quaternary GaAs1-x-y N x Bi y alloy lattice-matched to GaAs: a first-principles study

First-principles calculations based on density functional theory have been performed for the quaternary GaAs_1-x-y N _x Bi _y alloy lattice-matched to GaAs. Using the state-of-the-art computational method with the Heyd-Scuseria-Ernzerhof (HSE) hybrid functional, electronic, and optical properties were obtained, including band structures, density of states (DOSs), dielectric function, absorption coefficient, refractive index, energy loss function, and reflectivity. It is found that the lattice constant of GaAs_1-x-y N _x Bi _y alloy with y/x =1.718 can match to GaAs. With the incorporation of N and Bi into GaAs, the band gap of GaAs_1-x-y N _x Bi _y becomes small and remains direct. The calculated optical properties indicate that GaAs_1-x-y N _x Bi _y has higher optical efficiency as it has less energy loss than GaAs. In addition, it is also found that the electronic and optical properties of GaAs_1-x-y N _x Bi _y alloy can be further controlled by tuning the N and Bi compositions in this alloy. These results suggest promising applications of GaAs_1-x-y N _x Bi _y quaternary alloys in optoelectronic devices.