Determination of metals and metalloids in light and heavy crude oil by ICP-MS after digestion by microwave-induced combustion

A method for light and heavy crude oil digestion using microwave-induced combustion (MIC) in closed vessels is described for further determination of Ag, As, Ba, Bi, Ca, Cd, Cr, Fe, K, Mg, Li, Mn, Mo, Ni, Pb, Rb, Se, Sr, Tl, V, and Zn by inductively coupled plasma mass spectrometry (ICP-MS). Conventional microwave-assisted acid digestion (MW-AD) in pressurized vessels and analyte determination by inductively coupled plasma optical emission spectrometry (ICP OES) were also used for results comparison. For MIC procedure, samples were wrapped in polyethylene films and combusted using 20 bar of oxygen and 50 µl of 6 mol l^− 1 ammonium nitrate as aid for ignition. The concentration of nitric acid used as absorbing solution was evaluated (1, 2, 4, 7, 10 and 14 mol l^− 1) using an additional reflux step after combustion. Accuracy was evaluated for As, Ba, Ni, Se V, and Zn using certified reference material (CRM) with similar matrix composition and for Cr, Fe, K, Mg, Mn, and Mo by neutron activation analysis (NAA). Recovery tests were also performed for all the analytes by MIC and they were better than 97% using 2 mol l^− 1 nitric acid as absorbing solution (with reflux step). Agreement with certified values and NAA results was better than 95%. Using MIC it was possible to obtain lower limits of detection (LODs) by ICP-MS and also by ICP OES in comparison with those obtained by MW-AD. In spite of both sample preparation techniques were apparently suitable for crude oil digestion, MIC was preferable in view of the possibility of using diluted nitric acid as absorbing solution that is an important aspect to minimize interferences by ICP-MS and ICP OES. In order to avoid polyatomic interferences on ⁵²Cr and ⁵⁶Fe determinations by ICP-MS, a dynamic reaction cell with ammonia gas was used. Residual carbon content in digests obtained by MW-AD and MIC was 15% and < 1%, respectively. Using MIC the simultaneous digestion of 8 samples was possible in less than 30 min.     

Kinetic analysis of crude oils by a weighted mean activation energy approach

A weighted mean activation energy method was applied to describe the reactivity and combustibility of crude oils via simultaneous TG/DTG. Thermal experiments were conducted with a non-isothermal method at a heating rate of 10C min^–1 with excess air. Reaction rates increased progressively with increasing temperature. The rate data were fitted to an Arrhenius equation; the plots showed three distinct reaction regions. Weighted mean activation energies (E _wm), of the crude oils were calculated and a correlation was established betweenE _wm, API gravity and peak temperatures during high-temperature oxidation.     

Slurries and emulsions of waxy and heavy crude oils for pipeline transportation of crude oil

The high viscosity of many asphaltic crude oils and the high pour points of many waxy crude oils present significant problems in their transportation over long distances by pipeline and tanker. While heating the oils and insulating the pipelines will help alleviate the problem, there is danger associated with an extended shutdown of flow and either congealing or solidification of the oil. A possible solution which we have studied in the laboratory is the emulsification or dispersion of the oil in water or brine so that shear takes place in the continuous aqueous phase rather than the oil droplets or particles.Synthetic waxy crude oils were prepared by dissolving paraffin wax in white mineral oil at slightly elevated temperatures and then measuring the pour point. One containing 30% wax had a pour point of 43°C and was selected for preparations of the dispersions. This was emulsified in water at a temperature higher than the pour point by using a suitable surfactant as an emulsifying agent. Rheological properties were measured at various temperatures and are reported in the paper. The method shows great promise for use in countries such as China which produce significant quantities of waxy crude oil and have seasonal temperatures significantly lower than the pour point of the crude oil.     

Determination of major and trace elements in crude oils by neutron activation and reflection methods

The concentrations of O, Na, Cl, V, Mn and Ni in crude oils of different origins were determined, using sampling (SNAA) and on-stream (ONAA) activation analyses. Samples were irradiated with thermal and fast neutrons produced by a 0.3 mg²⁵²Cf source and a 14 MeV generator. The H-content and the C/H atomic ratio have been determined by thermal neutron reflection method using an 18 GBq Pu−Be source. This work was supported in part by the Hungarian Academy of Sciences.     

Determination and geochemical significance of trace elements in Iraqi crude oils using instrumental neutron activation analysis

The trace-element composition of crude oil was studied using instrumental neutron activation techniques and a large-volume high-resolution Ge(Li) detector. A total of 29 elements were determined in oils representing the various producing formations of the Iraqi oil fields. These were: Al, Ar, As, Au, Br, Ca, Cl, Co, Cr, Cu, Eu, Fe, Ga, Hg, K, La, Mn, Mo, Na, Ni, Re, S, Sb, Sc, Se, Sm, V, W and Zn. The significance of these trace elements in the geochemical investigation of crude oil is discussed.     

Molecular characterization of organically-bound sulfur in crude oils. A feasibility study for the application of Raney Ni desulfurization as a new method to characterize crude oils

Five crude oils with varying sulfur contents (0.1 – 4.7%) were characterized on a molecular level for organically-bound sulfur. Aromatic fractions were analyzed by GC-(MS) and asphaltene and polar fractions were analyzed by flash pyrolysis-GC-(MS). The polar fractions were also desulfurized with Raney Ni and the hydrocarbons formed were analyzed by GC-MS. Major sulfur compounds in the aromatic fractions were identified as alkylbenzo- and alkyldiben-zothiophenes. The flash pyrolyzates of the asphaltene contained alkylthiophenes and alkylbenzothiophenes as major compounds, depending on the thermal maturity of the oil. Generally, the sulfur-rich crude oils contained relatively more sulfur compounds. The flash pyrolyzates of polar fractions contained a variety of sulfur compounds (alkylthiolanes, alkylthianes, terpenoid sulfides, alkylbenzothiophenes) with substantial differences between different crude oils. Raney Ni desulfurization of the polar fraction yielded hydrocarbons dominated by n-alkanes, but isoprenoid alkanes, n-alkylcyclohexanes, mid-chain methylalkanes, tricyclic terpanes, hopanes and steranes were also present. These hydrocarbons show a potential to fingerprint crude oils since their distribution patterns are more characteristic than those of the hydrocarbons present in the saturated hydrocarbon fraction.     

Electron spin resonance and electronic structure of vanadyl-porphyrin in heavy crude oils

A study of vanadyl-porphyrin by electron spin resonance (ESR) was carried out looking for answers about the role that the central V=O ion plays when these kinds of molecules are present in heavy crude oils. The eigenvalues of the linear combination of atomic orbitals (LCAO) were obtained from the experimental values of g and parameters (ESR). The contributions to the molecular orbitals that describe the various energy levels of vanadyl ion were also obtained for the porphyrin species. The trends of the degree of covalent character of the metal-ligand bonds and the length of the vanadium-oxygen chemical bond are discussed. It is interesting to note that the Fermi contact term, K(eff), is essentially constant for all samples investigated, and it was found to be independent of the calculated electron delocalization (1 - delta(2)) and shows only little variation among the three different samples of oil. The orbital energies derived from our ESR study qualitatively agree with those predicted from MO theory for synthetic vanadyl-porphyrins.     

Determination of mercury in SRM crude oils and refined products by isotope dilution cold vapor ICP-MS using closed-system combustion

Mercury was determined by isotope dilution cold-vapor inductively coupled plasma mass spectrometry (ID-CV-ICP-MS) in four different liquid petroleum SRMs. Samples of approximately 0.3 g were spiked with stable (201)Hg and wet ashed in a closed system (Carius tube) using 6 g of high-purity nitric acid. Three different types of commercial oils were measured: two Texas crude oils, SRM 2721 (41.7+/-5.7 pg g(-1)) and SRM 2722 (129+/-13 pg g(-1)), a low-sulfur diesel fuel, SRM 2724b (34+/-26 pg g(-1)), and a low-sulfur residual fuel oil, SRM 1619b (3.5+/-0.74 ng g(-1)) (mean value and 95% CI). The Hg values for the crude oils and the diesel fuel are the lowest values ever reported for these matrices. The method detection limit, which is ultimately limited by method blank uncertainty, is approximately 10 pg g(-1) for a 0.3 g sample. Accurate Hg measurements in petroleum products are needed to assess the contribution to the global Hg cycle and may be needed in the near future to comply with reporting regulations for toxic elements.     

Fe/SiO_2纳米复合物上合成气制低碳烯烃催化性能研究

分别采用一步合成法和常规共沉淀法制备了Fe/SiO2催化剂,通过N2物理吸附、X射线衍射、透射电镜、傅里叶变换红外光谱和程序升温还原等方法对催化剂进行了表征,并在固定床反应器中对其费托合成制低碳烯烃的催化性能进行了评价。结果表明,与共沉淀铁基催化剂不同,采用一步合成法制备的纳米复合物主要由Fe3O4相构成,形貌呈规则球形,平均粒径为30 nm,尺寸分布窄,更容易还原。一步合成法制得的Fe/SiO2催化剂对费托合成反应具有较高的活性和低碳烯烃选择性、较低的甲烷选择性和良好的稳定性。     

原油中微量金属元素的测定及风化条件下元素的变化规律

建立了微波消解-电感耦舍等离子体质谱(ICP.MS)法同时测定原油及自然风化后原油中的V、Cr、Mn、Fe、Ni、zn、Mo、Ba等11种微量金属元素的方法.结果表明,11种微量金属元素的检出限为0.0056～0.8729μg/g,线性关系良好,相关系数r≥0.9995;相对标准偏差(RSD)<5.0%.经过30d风化...     

Determination of trace vanadium in petroleum oils by oxygen flask combustion and a catalytic method

The petroleum oil sample is combusted in an improved oxygen flask and vanadium (?0.1 ppm) is then determined by a catalytic method based on spectrophotometric monitoring of the gallic acid-bromate reaction. For most samples, there is no interference from other elements normally present, but an ion-exchange separation prior to catalytic determination is recommended in order to achieve reliable analyses of a wide variety of real petroleum samples.     

Molecular weights in polymerization as a function of conversion

A relatively novel method of calculating molecular weight changes and broadening during a polymerization is proposed. It differs from others in that the distribution is considered implicitly rather than explicitly. This allows direct use of kinetic rate equations in the derivation of weight-average and number-average degree of polymerization etc.; the mathematics simplifies to simple integration rather than sums of complicated series. The method is illustrated by applying it to several cases. These range from various models where only monomer concentration changes, to where both monomer and initiator or monomer and chain transfer agent are changing. Cases previously unsolvable can now be handled.     

A comprehensive analysis of the properties of light crude oil in oxidation experimental studies

The analysis of light crude oil for oxidation reaction experiments is a kind of important technological for evaluating an air injection project in a reservoir. In this study, the paper comprehensively analyzes the variations of Jilin crude oil composition comparing crude oil component’s variations before and after oxidation, and investigates the effluent gas composition and hydrocarbon, analyzes the mechanism of low temperature oxidation reaction (LTO), and rebuilds the light crude oil cracking reaction of intermediate component in a new pattern. In the early stage of the oxidation reaction, firstly, oxygen is captured by forming chemical bond in liquid hydrocarbon. And then oxygen takes part in the free radical chain reaction by forming hyperoxide and decomposes to ketones, aldehydes, alcohols, and so on. Meanwhile, chain scission reaction comes up. Research result shows that the intermediate components (C_7–17) of crude oil make great contribution to crude oil cracking. The experimental result shows that Jilin reservoir has the potential of implementing air injection project.     

Photocatalysis: Light energy conversion for the oxidation,disinfection, and decomposition of water

The results of many-year studies of the relationship between the physical properties and photocatalytic activity of TiO₂ and Pt/TiO₂ in photocatalytic purification and disinfection of air and water and water photodecomposition with oxygen evolution are presented. Recommendations are given as to finding the optimal method for platinum supporting on TiO₂ to achieve the highest possible catalytic activity. Multisite kinetic models of the gas-phase oxidation of simple organic substances are considered. Methods for regenerating the photocatalyst after its deactivation in the oxidation of sulfur-containing organic substances are suggested. New data are discussed on the acceleration of air purification by the combination of photocatalytic oxidation with atmospheric electric discharges, the addition of gaseous hydrogen peroxide, and oxidation on photocatalysts existing in the aerosol state. As compared to pure TiO₂, platinated titanium dioxide has a higher capability for disinfection and complete mineralization of microorganisms. Two promising methods for production of hydrogen from water using solar light are presented.     

Ligand oxidation as a method for intramolecular activation of metal complexes

The results of investigations of organometallic and coordination compounds whose ligands contain redox fragments based on 2,6-di-tert-butylphenol and linked to the metal by various coordinating groups are summarized. The redox properties of -aryl, - and -allyl complexes, -diketonates, hydrazides, hydroxamates, glyoximates, and metalloporphyrins and metallophthalocyanines are considered. The possibility of changing the reactivity of organometallic and coordination compounds by changing the magnetic state due to oxidation of the redox-active phenolic group in the ligand is demonstrated. It is proposed to use ligand oxidation as a method for intramolecular activation of metal complexes.     

Importance of quality control in a gas chromatographic method to characterize crude oils

A quality control scheme has been developed to achieve reproducible capillary GC characterization of crude oils and petroleum condensates. The method uses an internal standard to quantify the amount of non-eluted material in the crude oil sample. Correlation between the gas chromatographic results and actual distillation was 2 %. After repeated use, however, weekly analysis of the same standard crude oil did not give the correct composition. This was a result of discrimination, which worsened with time, as a result of leaks in the septum or the graphite ferrules. More reproducible results were obtained by performing frequent analyses of quality control samples to ensure that the gas chromatographic system was operating properly. The use of quality control charts was a convenient way of ensuring correct operation and identifying the need for corrective action on the gas chromatographic system.