Electrochemically induced alumina coatings on stainless steel: composition and behaviour at high temperature

Alumina coatings were formed by electrolytic treatment on an Fe-17% Cr stainless steel functionalized by surface conversion treatment to induce a particular surface morphology, suited to anchoring the ceramic layer. As deposited, the coatings appeared amorphous. They were composed of two layers: the superficial layer was constituted only of aluminium compounds while the deep layer had a composition gradient. Heating the coated steel caused interface reactions between the electrochemically-induced deposit and the initial conversion coating compounds. These reactions act to strengthen coat adhesion to the substrate with formation of crystallized mixed oxide such as Fe(Cr,AI)₂O₄. Moreover, Al₂O₃ phases appeared and acted as a barrier which prevented the thermal oxidation of the stainless steel.     

Systematic characterization of petroleum residua based on SFEF

Supercritical fluid extraction and fractionation (SFEF) has been used to separate a variety of petroleum residua and other heavy oils into narrow-cut fractions with total yields up to 75-90%. Any insoluble material, or end-cut, corresponds to the asphaltene fraction in the parent oil. The narrow-cut fractions were analyzed comprehensively and separated into the solubility classes of saturate, aromatic, resin, and asphaltene fractions. The boiling points were measured up to 700 °C and correlations were established with the key factors such as density and molecular weight. This allows extrapolation of boiling points of residue fractions up to 1000 °C. Unlike bulk property measurements, the narrow-cut characterization data show increasing concentrations of key contaminants as the fractions become heavier. The solubility parameter for each narrow-cut fraction was measured using high-pressure fluid phase equilibrium with propane. The corresponding values for the end-cuts were obtained by the conventional precipitation method. The distribution and reactivity of sulfur species were determined by XPS in the bitumen pitch fractions and the corresponding residua produced during thermocracking and hydrocracking. The average structures for the narrow-cuts were constructed from molecular weight and elemental analyses together with FTIR, ¹H-NMR and ¹³C-NMR data. The results were used to develop a generalized feedstock characteristic index, K_R. This index shows good correlation with feedstock hydrocarbon constituents and can be used to assess feedstock reactivity and processability. Downstream refiners can use the narrow-cut data and K_R values for process optimization by either cutting deeper into residua bottoms to increase yield or by selecting the most appropriate process units for the various residue fractions. This information can also be used by upstream operators to determine the economic feasibility of utilizing the end-cut onsite.     

Separation of acidic fraction from the Cold Lake bitumen asphaltenes and its relationship to enhanced oil recovery

Neutral and acidic fractions of cold lake bitumen asphaltene were separated on a KOH treated silica column. It was observed that the neutral fraction can be separated by using CHCl₃ as solvent (eluent) while the acidic fraction can be separated by a CHCl₃ + HCOOH mixture. While the distribution of VO²⁺ ion was approximately the same in the different fractions, the concentration of the radicals may be significantly more in the acidic fraction. The acidic fraction separated has the largest impact on decreasing the interfacial tension (IFT) between asphaltene (in toluene) and 25mM NaOH solution. It was also observed that adsorbed KOH on silica reacted with CHCl₃ when the CHCl₃ + HCOOH mixture was passed through the column.     

Characterization of Algerian Hassi-Messaoud asphaltene structure using Raman spectrometry and X-ray diffraction

Asphaltenes derived from Algerian oil wells were characterized by Raman spectrometry to investigate their molecular structures in solid-state. The aromatic sheet diameter (L_a) was estimated using the integrated intensities of the G and the D1 mode, along with the Tuinstra equation [Tuinstra F, Koenig JL. J Chem Phys 1970;53:1126]. The values obtained for three Algerian Hassi-Messaoud asphaltene samples are on the same order as the literature values and also consistent with the X-ray diffraction results. The Raman spectra corresponding to the G and the D bands can be fitted with Gaussian, Lorentzian, and Gaussian/Lorentzian hybrid functions in a self-consistent manner. A three peak fitting procedure found that the Gaussian/Lorentzian hybrid function with G being Gaussian and D Lorentzian is the best combination. Incorporation of the X-ray data on the height of the crystallite, L_c, gives rise to an estimate of eight asphaltene molecules in each asphaltene aggregate.     

Characterization of coal—liquid fractions. Molar enthalpies of quinoline interaction with coal-derived asphaltenes and heavy oils

The toluene-insoluble (Tl), asphaltene (A), and heavy oil (HO) fractions were isolated from three centrifuged SYNTHOIL liquid product (CLP) samples, prepared under different process conditions at 450 °C, 27.6 MPa hydrogen pressure from the same feed coal, Kentucky hvAb, from Homestead Mine. Run FB 53 was made with CoMo catalyst, 11-min preheater residence time, and 3-min reactor residence time. The much higher viscosity of FB 53–59 compared to FB 53-1 correlates with the larger contents of its toluene-insolubles and asphaltene, larger oxygen and sulphur contents of its asphaltene and toluene-insolubles, larger molecular weight and smaller aromaticity of its asphaltene, and the larger enthalpy of interaction (ΔH^o) of its asphaltene with quinoline in benzene. The average molecular weight and percentage of heteroatoms of the heavy oil from FB 53–59 are also greater than that from FB 53-1, and the value of ΔH^o of the heavy oil with quinoline, follows the same order. Run FB 57 was made with glass pellets, 17-min preheater residence time and 6-min reactor residence-time. Since in FB 53–59 the CoMo catalyst has lost part of its activity, a comparison of FB 53–59 with FB 57 yields information on the effect of residence times on the properties. The toluene-insoluble and asphaltene contents, as well as the viscosity, of FB 53–59 is larger, while the heavy oil content of FB 53–59 is smaller than that of FB 57. This comparison indicates that a larger-residence-time preheater and reactor may, to some extent, favour conversion as well as decrease the viscosity of the product oil. The values of ΔH^o for the interaction of quinoline with the heavy oil and asphaltene fractions obtained from the three CLP samples are in the order: FB 53–59 > FB 57-42 > FB 53-1, and they are attributed to the varying degree of hydrogen-bonding effects involving largely aromatic phenols which serve as hydrogen donors to quinoline.     

Preparative gel permeation chromatography of Athabasca asphaltene and the relative polymer-forming propensity of the fractions

Athabasca asphaltene has been separated according to molecular weight on Bio-Beads SX-1 gel. The number-average molecular weights of the five arbitrary fractions obtained by this fractionation range from 1200 to 17000. The chemical, spectral and thermal properties of the fractions are all similar but their polymer-forming propensities are markedly different. The significance of this latter property, which is defined in terms of the amount of CH₂Cl₂-insoluble material produced upon thermolysis at 300 °C, increases rapidly with increasing molecular weight of the fraction. In contrast the whole asphaltene does not form polymer at 300 °C under the same conditions and it is concluded that the chain propagating steps are terminated by a variety of inhibitors that are contained in the asphaltene agglomerate. During gel permeation chromatography separation the clay present in the asphaltene concentrates in the higher-molecular-weight fractions. This affinity to attract the clay is thought to be related to the physical, and not the chemical, properties of these higher-molecular-weight materials. The clay also exerts a catalytic effect on the polymerization of the asphaltene fractions which is most pronounced in the highest-molecular-weight fraction and gradually decreases with decreasing molecular weight.     

Emf measurements in the NaClAlCl3 system—I. Activity of AlCl3 in basic melts at temperatures close to the liquidus line

Emf measurements in the formation cell Al|AlCl₃(l), NaCl(l)|Cl₂ were carried out at different mol fractions of AlCl₃ in the range 0 < x_AlCl3 < 0.5. The activity of AlCl₃ increases strongly as the equimolar composition is approached, indicating the presence of a fairly stable AlCl^?₄ complex ion in such melts. Liquidus temperatures at various melt compositions were determined from emf-temperature curves as well as from cryoscopic measurements.     

Calculation of mass emissions, oxygen mass fraction and thermal capacity of the inducted charge in SI and diesel engines from exhaust and intake gas analysis

New computational procedures are proposed for experimentally evaluating air-fuel ratio and mass fractions of exhaust emissions as well as EGR rate, oxygen mass fraction and thermal capacity of the inducted charge in IC engines running with diesel oil, gasoline or any alternative liquid or gaseous fuel, such as LPG or CNG. Starting from the chemical reaction of fuel with air, from gaseous and smoke level measurements in the raw gases, the procedures calculate the volume fractions of oxygen in the combustion air and of compounds in the exhaust gases, including those that are not usually measured, such as water, nitrogen and hydrogen. The methods also take the effects of various fuel and combustion air compositions into account, as well as to the presence of water vapor, CO₂, Ar and He in the combustion air.The algorithms are applied to four different automotive engines under wide ranges of steady-state operating conditions: three turbocharged diesel engines featuring high-pressure cooled EGR systems, and an SI naturally aspirated bi-fuel engine running on either gasoline or CNG. The computed air-fuel ratios are compared to those obtained from directly measured air and fuel mass-flow rates as well as from more conventional UEGO sensor data. The mass emissions are worked out in terms of both brake specific mass emissions and emission indexes of each pollutant species, and the results are compared to those obtained by applying SAE and ISO recommended practices. The computed oxygen mass fraction of the inducted charge was then compared to that derived from direct measurement of O₂ concentration in inlet manifold. Finally, the sensitivity of results to the main engine working parameters, the influence of environmental conditions (in particular the effect of air humidity on NO_x formation) and the experimental uncertainties are determined.     

Inhibition of catalytic oxidation of carbon/carbon composites by phosphorus

The inhibition effectiveness of thermally deposited phosphorus (P) compounds on the carbon oxidation catalyzed by potassium or calcium acetate has been investigated. The P deposit was formed by impregnating carbon/carbon composite samples with methanol solution of methyl-phosphoric acid or phosphorus oxychloride and heating at ca. 600 °C. An amorphous layer formed by a relatively large amount of P deposit functioned as a barrier for the access of the catalyst to the carbon surface even though it had almost no barrier effect for O₂ access. The catalytic effect of calcium was almost completely suppressed by such deposit, but the effect of potassium was only partially suppressed due to the superior wetting ability and mobility of potassium species. Small amounts of P deposit showed similar inhibition effects on non-catalyzed oxidation, while their effects on catalytic oxidation were not as good. Characterization of P-deposited carbon samples by XPS, XRD, SEM and TPD, as well as ab initio MO calculations, suggested that the inhibition effect mainly resulted from the formation of oxygen-containing P groups which may include metaphosphates, C-O-PO₃ groups and C-PO₃ groups. Those groups are suggested to act as a physical barrier against carbon/catalyst interfacial contact as well as to block the active carbon sites. The presence of bridge oxygen bonded to a carbon site and a P group appears to be a critical factor for maintaining the inhibition effect. Indeed, the loss of such oxygen or connecting bond seems to result in loss of inhibition.     

Hydroliquefaction of Yallourn coal catalysed by organotin compounds

The hydroliquefaction of Yallourn coal was investigated in a batch micro autoclave, using halogen free organotin compounds as a catalyst precursor. The catalytic activities of tin compounds were compared as a function of reaction time, initial hydrogen pressure and catalyst concentration. All the organotin compounds studied showed moderate to good catalytic activity in the liquefaction of Yallourn coal. In the presence of 1 wt% of tetra-n-butyl tin (n-Bu₄Sn) as Sn, at 698 K under an initial hydrogen pressure of 5.0 MPa in a non-hydrogen donating solvent, 1-methyl-naphthalene, coal conversion was increased from 36.7% to 78.6% with catalyst. An amount of hydrogen transferred to coal from the gas phase also increased from 0.8 to 1.6 wt% of d.a.f. coal with the 1 wt% of n-Bu₄Sn. An increase in the catalyst concentration of more than 2 wt% did not show any remarkable change in coal conversion or the amount of hydrogen absorbed. After the reaction time of 20 min, coal conversion, yield of asphaltene and yield of oil fraction levelled off. An increase in the initial hydrogen pressure substantially affected the catalytic activity of n-Bu₄Sn. Catalytically active species derived from n-Bu₄Sn seem to activate molecular hydrogen and may transfer hydrogen directly to coal fragment radicals to stabilize them.     

Calcium phosphate fouling on TiN-coated stainless steel surfaces: Role of ions and particles

Modifying the surface properties of the stainless steel used in heat exchangers to decrease its tendency for the building-up of milk deposits seems to be a promising strategy to reduce fouling during heat treatment in the dairy industry. In this work, several modified stainless steel surfaces, obtained by reactive magnetic sputtering, were used as fouling supports for a milk-simulating mineral solution under constant conditions of temperature, pH and calcium concentration. The aim of the work was to quantify deposition and removal parameters, based on the influence of surface energy properties on the type of deposit. The fouling process was characterized by the surface reaction coefficient of the ions present in solution, as well as the adhesion coefficients of the particles formed in the bulk. An insight on the mechanisms of deposition and removal processes was achieved, as well as by the dependence between those two processes and the electron-donor component (γ^-) of the surface energy of the stainless steel-based materials. The surfaces with lower γ^- were found to have lower amounts of deposit, and this deposit could be more easily cleaned than for the other surfaces (including the non-modified stainless steel).     

Study of the products of coal hydrogenation and deuteration by electron paramagnetic resonance

Products of Loveridge Mine high-volatile bituminous coal (81.8% C daf) after treating with H₂, D₂, H₂-tetralin-d₁₂, were separated into oils (hexane-soluble), asphaltenes (benzene-soluble), benzene) methanol-soluble, and insoluble fractions. The fractions were then studied by electron paramagnetic resonance at 9.5 GHz in which the g-factors, linewidths, and unpaired electron concentrations were measured. The unpaired electron concentrations decreased in the sequence: insoluble fraction > benzene-methanol fraction > asphaltene > oil, while the g-factor decreased in the opposite sequence. Results of these measurements also show that the number of unpaired electrons in the total product is approximately the same as that of the starting coal, although 90% or more remains the insoluble residue, and hydrogenation or hydrogen exchange is largely associated with high unpaired electron content. Measurements at 35 GHz on solids as well as 9.5 GHz on dissolved samples show that the greatest contributions to the homogeneous lineshape arise from both isotropic g-factors and hyperfine splittings. Manganese (II) is also found in the H₂ treated insoluble fraction in larger amounts than in the tetralin treated fraction or the initial coal suggesting that H₂ diffusion into the solid can cause reduction of the mineral components in the initial coal.     

Distribution of vanadium and vanadyl porphyrins in petroleum distillates of different chemical types

• 1.1. The greater part of atomic vanadium and vanadyl porphyrin molecules present in crude oils from all producing layers of the Samotlor deposit is concentrated in the petroleum resin, although the absolute concentration of V is maximum in asphaltene fractions. Vanadium atoms associate mainly with hetero-aromatic fragments of crude oil resin-asphalt substances. Up to 98% vanadium is contained in asphaltenes and almost all V atoms in petroleum fractions are contained in non-porphyric compounds.
• 2.2. Using Samotlor crude oils a clear is observed with: a) a reduction in overall vanadium concentration in all fractions, b) in the content of vanadyl porphyrins in malthene fractions, c) according to the paraffinicity of crude oils, particularly in relation to intensification of catagenic transformations with increasing depth and age of the surrounding deposits.

     

Use of pyrogenic silicas for petroleum oil polar fraction characterisation. Fourier transform infrared spectroscopy and microelectrophoresis studies

In the power transformer, the presence of polar or charged species in the insulating oil can cause failure and electric discharges. Solid substrates such as silica can be used to extract the polar species and to refine the oil in order to prevent future failure in the power transformer. However, the use of silica for petroleum oil separation and refining will depend on the silica characteristics such as surface charge, surface composition, specific surface area and particle size.Various pyrogenic silicas having various specific surface areas (49-200 m² g⁻¹) and particle sizes (207-500 nm) were used to extract the polar fractions from the neat transformer insulating oils (a new, NO, and used, UO2, oils). The oil covered silica samples were investigated by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy in the range 4000-600 cm⁻¹. The bare silica surfaces present two main hydroxyl components, a sharper peak at 3745 cm⁻¹, I₃₇₄₅, due to isolated silanols and a second broad, which spreads over 3745-3000 cm⁻¹, I_3745-3000, due to H-bonded silanols. The relative intensities of the two components, I₃₇₄₅/I_3745-3000, varied for the bare and the oil covered silicas depending on the solid surface characteristics. The adsorption of the NO polar fraction onto silica leads to strong reduction in intensity of the sharper peak in favour of the broad one. However, the adsorption of the UO2 polar fraction onto silica leads in all cases to the decrease in the intensity of the both silica OH components. Further, the UO2 adsorption on the silica leads to the apparition of a broad peak at low frequency in the region 3250-3300 cm⁻¹ which, is due to the associated phenolic groups of UO2 oil polar fraction. The analysis of the DRIFT spectra for various samples indicates that the oil polar fraction resembles to asphaltenes compounds.The microelectrophoresis method used to investigate the surface charge at the water/oil polar fraction covered silica interface, indicates negatively charged particles. Further, the negative charge increased with the pH, as resulting from the increase of the ionisation and/or the amount of the oil polar carboxylic and phenolic groups. The oil polar fraction, i.e. the asphaltene components, in contact with both the silica surface and water at high pH values rearrange, due to their amphiphilic character.Finally, the use of the silica substrates seems to be suited to extract and analyse polar species present in petroleum oil. A correlation is found between the nature of the oil, its functionalities, and the magnitude of its zeta potential value at the water/oil covered silica interface.     

Semiquantitative analysis of thiophenic compounds in light cycle oil (LCO) using C NMR spectroscopy

S-methyltetrafluoroborate salts of the thiophenic compounds (CH₃-S⁺:BF₄⁻) present in LCO petroleum fractions were obtained and analyzed by ¹H and ¹³C NMR spectroscopy. The methylation of the samples was carried out using 99.5% ¹³C enriched methyl iodine, to improve the sensitivity of the technique. The amount of the methylated derivatives was determined by the internal standard method; using dioxane as a reference, 37 sulphur compounds were detected. Among them, benzo[b]thiophene, dibenzo[b,d]thiophene, and several isomers of methyl, dimethyl and trimethyl[b]benzothiophenes were the most abundant. With this research, it was demonstrated that NMR spectroscopy can be used to analyze thiophenic compounds from petroleum medium fractions.     

Extraction of sage (Salvia officinalis L.) by supercritical CO2: Kinetic data, chemical composition and selectivity of diterpenes

The supercritical carbon dioxide (SFE) extraction of Dalmatian sage (Salvia officinalis L.) was investigated and compared to extraction performed by Soxhlet ethanol-water (70:30) mixture extraction (SE) and hydrodistillation (HD). The supercritical extraction allowed isolation of wide spectrum of phytochemicals, while other applied methods were limited to either volatiles (HD) or high molecular compounds isolation (SE). The kinetics of the supercritical extraction and fractionation within the pressure range of 10-30 MPa at 50 °C were also analyzed as well as the chemical compositions of total extract and partial or differential fractions isolated at different CO₂ consumption. Volatile fraction could be isolated at low pressure and low CO₂ consumption, whereby the pressures between 10 and 15 MPa followed by increased CO₂ consumption were favourable for obtaining desired selectivity of diterpenes which contain compounds with expressed antioxidative characteristics.     

Oxidative Dehydrogenation of Ethylbenzene over Cu1-x Co x Fe2O4 Catalyst System: Influence of Acid–Base Property

A series of Cu–Co ferrites with the general formula Cu_1-x Co _x Fe₂O₄ (x = 0, 0.25, 0.50, 0.75 and 1.0) was prepared by a low-temperature hydroxide coprecipitation route. The catalyst systems were characterized by adopting various physicochemical techniques. The acid–base properties were studied in detail, and the catalytic activity as well as the selectivity for oxidative dehydrogenation of ethylbenzene was compared for various compositions. FTIR adsorption of pyridine is carried out to understand the relative acidity of various compositions of the systems. IR studies of spinel surface with adsorbed CO₂ and adsorption studies of electron acceptors such as 7,7,8,8-tetracyanoquinodimethane, 2,3,5,6-tetrachloro-1-4-benzoquinone and p-dinitrobenzene are carried out to evaluate the nature of basic sites and the strength and distribution of electron donor sites present on the spinel surface. It is found that acidity (basicity) of the Cu_1-x Co _x Fe₂O₄ spinel system increases (decreases) from x = 0 to 1. A good correlation was found between the activity for this reaction and the surface acid–base properties of the catalysts. Intermediate compositions show better catalytic performance, among which x = 0.50 is superior and demonstrates an intermediate acid–base character. It was observed that dehydrogenation of ethylbenzene to styrene proceeds mainly on an acid–base pair site.     

Hydrogenolysis reaction of coal-derived asphaltene using molten salt catalysts

Hydrogenolysis of benzene-soluble, hexane-insoluble material (asphaltene) derived from Chinese Tatung coal was carried out using molten metal halide catalysts. Molten salts such as SnCl₂-containing mixtures, showing low ratios of iso-butane to normal butane in the gaseous products, were found to accelerate the conversion of asphaltene to hexane solubles (HS) and suppress the production of gases. The conversion reaction of asphaltene to oil with this catalyst system is always accompanied by the elimination of phenolic hydroxyl groups bonded to aromatic rings. The ZnCl₂CuCl system, of strong acidity as indicated by a high ratio of iso-butane to normal butane, exhibited a high activity in hydrogenolysis, the degradation proceeding to gasification. The systems containing KCl, giving relatively low ratios of iso-butane to normal butane, allowed high yields of HS with large amounts of hydroxyl groups. The reactions involved in the conversion are discussed.     

Initial stages of asphaltene aggregation in dilute crude oil solutions: studies of viscosity and NMR relaxation

In crude oil-toluene solutions dynamic viscosity η and spin-spin relaxation time T₂ were measured as functions of asphaltene concentration C in the range of 10-300 mg/l. The results were supplemented by studies of optical absorption. Extrema in the measured concentration dependencies are attributed to a transient predominance of specific asphaltene aggregates—from dimers to stacked molecular nanoclusters (MNCs) of four monomers. The strikingly non-ideal properties of solutions with C below 150-170 mg/l are attributed to the strong interactions between asphaltene species. At higher C the solution properties are evidently determined by the weaker interacting MNCs and the concentration effects are closer to those in ideal fluid mixtures. The observed re-entrant η(T₂) behaviour in asphaltene solutions hypothetically has the same origin as in supercooled or demixing molecular systems, where anomalous structural and dynamical features are often explained by emerging heterogeneity due to transient spontaneous clustering.     

Novel Imidazolium-Based Gemini Surfactants: Synthesis, Surface Properties, Corrosion Inhibition and Biocidal Activity Against Sulfate-Reducing Bacteria

Three novel imidazolium-based gemini surfactants had been synthesized and characterized using different spectroscopic techniques. The surface properties of the synthesized surfactants were determined using surface tension measurements at 20 °C. The surface parameters including critical micelle concentration (CMC), π _CMC, Pc₂₀, Γ_max and A _min were determined. The synthesized compounds were evaluated as corrosion inhibitors for carbon steel in 0.5 M HCl solution using the weight loss and polarization techniques. The biological activity of these surfactants was evaluated against sulfate reducing bacteria using most probable number method. The results indicate that the synthesized compounds have good surface properties and are proper corrosion inhibitors for low carbon steel, with a high inhibition efficiency observed around their CMC. These compounds exhibit a significant biocidal activity against sulfate reducing bacteria.