Determination of the fractional composition of merchantable oil using quantitative <Superscript>1</Superscript>H NMR spectra

A simple method based on quantitative ¹H NMR data has been proposed for determining the fractional composition of merchantable oil.     

Dissociation behavior of （CH4 ＋ C2H4） hydrate in the presence of sodium dodecyl sulfate

Separation of a mixture of CH4+C2H4 gas by forming hydrate in ethylene production has become of interest,and the dissociation behavior of(CH4+C2H4) hydrate is of great importance for this process. The hydrate formation rate could be increased by adding a small amount of sodium dodecyl sulfate(SDS) into water. In this work,the kinetic data of CH4(18.5 mol%) +C2H4(81.5 mol%) hydrate decomposition in the presence of 1000 mg·L-1 SDS at different temperatures and pressures were measured with the depressurizing m...     

A THIRD‐ORDER UNCONFORMITY WITHIN LOWER ORDOVICIAN CARBONATES IN THE TARIM BASIN,NW CHINA: IMPLICATIONS FOR RESERVOIR DEVELOPMENT

This paper presents outcrop, petrographic, geochemical, well log and seismic data which together characterise the third‐order T₇⁸ unconformity located between the carbonate‐dominated Lower Ordovician Penglaiba and Yingshan Formations in the Tarim Basin, NW China. Unconformities in Lower Palaeozoic carbonates in this basin are of increasing interest because major reserves of hydrocarbons have recently been discovered at the North Slope field (> 1000 × 10⁶ brls oil and ～ 3050× 10⁸ m³ gas). The reservoir here consists of karstified Lower Ordovician carbonates bounded by a third‐order unconformity. The T₇⁸ unconformity in Tarim Basin represents a short‐term exposure surface (< 1 Ma) controlled both by sea‐level changes and by palaeogeographic location within the basin, and the intensity of karstification varies laterally. The unconformity has had a major influence on porosity development in the underlying Penglaiba Formation carbonates. At two measured outcrop sections at the NW basin margin (Penglaiba and Shuinichang), dissolution porosity was observed in karstified and dolomitised carbonates below the T₇⁸ unconformity surface. A seismic profile shows the presence of reflection anomalies below the unconformity which are interpreted as karst‐related palaeo‐caverns. Geochemical data indicate that the T₇⁸ unconformity is associated with anomalies in stable isotope ratios and in heavy mineral and trace element profiles. Thus there are negative excursions in δ¹³C and δ¹⁸O ratios within the carbonate rocks immediately below the unconformity surface. Similarly, concentrations of major and trace elements such as Li, K, Ti, Rb, Th, Sr, V and Ni are significantly reduced in the underlying carbonates, while there is an anomalously high content of haematite‐limonite.     

Transformations of tetradecane on La/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> + ZSM catalysts

The behavior of La/Al₂O₃ + ZSM catalysts has been studied in the process of the hydrogen-free conversion of tetradecane. The structure and state of active centers of catalysts have been investigated using a combination of physicochemical and instrumental methods (TPD of ammonia, IR spectroscopy, electron microscopy). It was found that the catalysts are characterized by the presence of acid (Brönsted and Lewis) sites and M⁰ and Mⁿ⁺ metal centers. Lanthanum in different oxidation states can be included in the acid sites. The degree of tetradecane conversion and the product composition are determined by the SiO₂/Al₂O₃ ratio of the zeolite and the conditions of the process. The mechanism of the cracking and transformations of tetradecane on La/Al₂O₃ + ZSM catalysts is discussed.     

Synergism between MC-MA-MCNR<Superscript>2</Superscript> terpolymer and EVA as a cold flow improver in diesel fuel

A novel terpolymer, MC-MA-MCNR², derived from tetradecyl methacrylate (MC), maleic anhydride (MA), and methacrylamide (MCNR²) was synthesized. The ability of MC-MA-MCNR² was evaluated as a cold flow improver in diesel fuel, and the interactions of MC-MA-MCNR² with several kinds of copolymer were studied. To provide a better understanding of the synergistic mechanism, microscopy was used to study the crystal conformation when MC-MA-MCNR² and EVA (ethylene-vinyl acetate) are mixed into a diesel fuel. The results indicate that using blends of MC-MA-MCNR² and EVA, one can obtain a satisfactory cold filter plugging point depression. Based on the microscopy experiment, the synergism mechanism was discussed. Published in Khimiya i Tekhnologiya Topliv i Masel, No. 4, pp. 21–23, 2007.     

Effect of Protolysis Reactions on the Shape of Chronopotentiograms of a Homogeneous Anion-Exchange Membrane in NaH<Subscript>2</Subscript>PO<Subscript>4</Subscript> Solution

Single-pulse and double-pulse chronopotentiograms of a homogeneous anion-exchange membrane AX in 0.02 M solutions of NaCl (system 1) or NaH₂PO₄ (system 2) have been recorded in underlimiting and overlimiting current modes. It has been found that in the case of exceeding the limiting current (i > i _lim ^Lev ) calculated using the convection–diffusion model, the time required to establish a steady state in system 2 increases by more than an order of magnitude compared to system 1. The slow growth of the potential drop is due to a gradual transition of the membrane from the form in which the main counterion is H₂PO ₄ ^– to the HPO ₄ ^2– form. This transition is due to the deprotonation of a part of H₂PO ₄ ^– ions forming HPO ₄ ^2– and protons as they enter the membrane. The participation of H⁺ in charge transfer in the depleted diffusion layer at a given current density causes a lower value of the potential drop than in system 1 for the same i/i _lim ^Lev ratio. In intense current regimes, chronopotentiograms of system 2 exhibit two inflection points. The first point corresponds to the classical Sand transition time and is due to reaching the limiting current of H₂PO ₄ ^– ions (the main charge carrier for i < i _lim ^Lev ) in the depleted diffusion layer. The second point is associated with a critical current that can be called the second limiting current in the system with NaH₂PO₄ and has no analogue in the system with NaCl. This current, which is approximately 2i _lim ^Lev , corresponds to the state when the membrane is completely transformed into the HPO ₄ ^2– form. Meanwhile, the source of protons due to the transformation of H₂PO ₄ ^– into HPO ₄ ^2– ions as they enter the membrane is exhausted. After reaching this critical value of the potential drop, either the HPO ₄ ^2– deprotonation reaction to give triply charged PO ₄ ^3– ions in the membrane or the water splitting on fixed groups located at the membrane/solution interface may occur.     

GEOCHEMICAL CHARACTERIZATION OF THE PERMIAN–TRIASSIC TRANSITION AT OUTCROP,CENTRAL SAUDI ARABIA

This study presents the results of chemostratigraphic analyses and spectral gamma‐ray logging integrated with sedimentological data across the Permian‐Triassic boundary at a measured outcrop section in central Saudi Arabia. The studied section encompasses the uppermost part of the Midhnab Member and the Lower and Upper Khartam Members of the Khuff Formation. Lithofacies were interpreted to have been deposited in subtidal, tidal to supratidal, lacustrine and meandering fluvial / flood plain, marginal marine and lagoonal depositional environments. Integration of bulk geochemical and carbon isotope (δ¹³C) data allowed the identification of a stratigraphic interval with a negative shift in δ¹³C ratio values, which was interpreted to correspond to the end‐Permian mass extinction event. The end of this “first negative shift in δ¹³C values” is taken to mark the Permian‐Triassic boundary. Above this boundary and just below an interval containing scattered thrombolites, a second negative shift in δ¹³C ratios was observed, and corresponds to an interval with long‐term uranium depletion as indicated by the bulk sediment geochemical and spectral gamma‐ray uranium data. The Permian‐Triassic boundary (PTrB) was placed at the transition between marginal‐marine and subtidal deposits. This stratigraphic position corresponds to the end of the “first negative δ¹³C shift” and the point of greatest uranium depletion. Although previous studies on outcrops of the Khuff Formation in Saudi Arabia identified a major sequence boundary between the Lower and Upper Khartam Members and interpreted it as the P TrB, no evidence is presented in this study for exposure and dissolution at this surface. Accordingly, the Permian‐Triassic transition is placed in the transgressive portion of the Upper Khartam Member, while the sequence boundary below is interpreted to correspond to the end‐Permian extinction. Correlation of Khuff time‐equivalent units in the Arabian Plate is challenging, and this study will contribute to an improved understanding of this important stratigraphic unit, which contains prolific non‐associated gas reservoirs. The identification of the Permian‐Triassic boundary in central Saudi Arabia will help in the construction of a sequence‐stratigraphic scheme for the Khuff, and with the correlation of lithofacies within this heterogeneous reservoir unit.     

The catalytic properties of tungstated zirconia in <Emphasis Type="Italic">n</Emphasis>-heptane isomerization

The catalytic properties of zirconia modified with different amounts of tungstate anions in the hydroisomerization of n-heptane and its mixtures with benzene or toluene have been studied. It has been found that at a low temperature of 170°C, the yield of isoheptanes reaches 62.8% with a fairly high selectivity of 87.6% on the Pt/WO₄²⁻/ZrO₂ catalyst prepared by impregnation to contain 17.6 mol % tungstate anions. Under the same conditions, the yield of isoheptanes on a sulfated Pt/SO₄²⁻/ZrO₂ catalyst is as low as 14.0% with a selectivity of 20.3%. The hydroisomerization process effectively occurs on the tungstated catalyst in the presence of benzene or toluene.     

Conversions of mixtures of propane and benzene on Pt,Re/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> + H-zeolite systems

The conversion of C₆H₆: C₃H₈C mixtures on mixed catalysts composed of the metal catalysts Pt,ReOx/Al₂O₃ and zeolites Y, M, and ZSM-5 in the H form was studied. The products of benzene dehydroalkylation by propane and propane dehydrogenation products are formed at 180–350°C. It has been shown that propane is activated on the metal catalysts and C₆H₆ interacts with the zeolites yielding the C₆H₇ ⁺ intermediate, which acts as an agent of proton transfer from a zeolite to a metal catalyst, and another intermediate C₉H₁₃⁺ (I). Cumene, alkylbenzenes, and propene are formed as a result of the conversion of I. A comparison of the results of the conversion of these mixtures on the composite catalysts with different zeolites shows that the formation of cumene and propene is thermally controlled and the formation of the other products is kinetically controlled. It has been concluded that the coupling of the redox properties of the metal catalysts with the acid-base properties of the zeolite catalysts facilitates the low-temperature transformations of the mixtures.     

CONSTRAINING THE TIMING AND DEPOSITIONAL CONDITIONS OF THE MAIKOP FORMATION WITHIN THE KURA BASIN,EASTERN AZERBAIJAN,THROUGH THE APPLICATION OF RE‐OS GEOCHRONOLOGY AND CHEMOSTRATIGRAPHY

The Oligocene – Miocene Maikop Formation is the key source rock in the South Caspian and Kura Basins. The Maikop is composed of a thick (up to 3 km) succession of clay‐rich mudstones containing up to 15% total organic carbon (TOC). Despite decades of study, the mudstones often lack precise age control – Maikop strata rarely contain diagnostic microfaunal assemblages which can be used for dating, stratigraphic correlation, or constraining the depositional setting. Using rhenium‐osmium geochronology, this study adds important numerical age data for the Maikop Formation. Of five sample suites analysed from the Kura Basin, eastern Azerbaijan, one Re‐Os data‐set produced a significant range in ¹⁸⁷Re/¹⁸⁸Os versus ¹⁸⁷Os/¹⁸⁸Os space to yield an isochron of 17.2 ± 3.2 Ma (Early Miocene). Other sample suites yielded imprecise Re‐Os age constraints as a result of variable initial ¹⁸⁷Os/¹⁸⁸Os values and a limited range in ¹⁸⁷Re/¹⁸⁸Os versus ¹⁸⁷Os/¹⁸⁸Os space. The initial ¹⁸⁷Os/¹⁸⁸Os values of these data‐sets were compared with the known ¹⁸⁷Os/¹⁸⁸Os values of seawater for the past 70 Ma to provide more qualitative age constraints. Pre‐Maikopian strata from the Perikeshkul locality were found to coincide in ¹⁸⁷Os/¹⁸⁸Os values with an isotope excursion at the Eocene – Oligocene Transition (EOT), therefore indicating that deposition of Maikopian strata began around the EOT. While values such as this match well with global values, there are several ¹⁸⁷Os/¹⁸⁸Os values that are not easily explained by global ratios. Intervals with initial ¹⁸⁷Os/¹⁸⁸Os values that deviate significantly from global ¹⁸⁷Os/¹⁸⁸Os values suggest periodic basin restriction and the development of anoxia at discrete times as the basin transitioned towards a closed system. High Os abundances outside of expected global values are often coupled with enrichment in detrital elements (Al, Ti, Ga, Sc and La) and changes in basin circulation, suggesting changing basinal conditions and sediment routing dynamics related to the initial uplift of the Greater Caucasus Mountains, changes in sediment provenance, or changing proximity to the sediment source. Through generation of isochron age dates and imprecise Re‐Os age constraints from the Maikop Formation, we gain a better understanding of the timing and nature of the evolution of the South Caspian Basin during this critical time period. Better age constrains will also help to better constrain the wealth of geochemical information already gathered within this petroleum‐rich basin.     

Conversion of dimethyl ether into C<Subscript>2</Subscript>-C<Subscript>4</Subscript> olefins on zeolite catalysts

The effect of the nature of the metal introduced into HZSM-5 on the properties of the catalysts for the synthesis of olefins from dimethyl ether was studied. By means of the ammonia temperature-programmed desorption technique, it was shown that a decrease in the total amount of acid sites increases the selectivity for lower olefins. As the ratio of the medium to strong acid sites increases, the yield of olefins increases. The effect of the nature of gaseous additives in the feedstock on the selectivity for lower olefins was studied at T = 340°C, p = 0.1 MPa, and ν ₀ = 2000 h^?1.     

Hygiene and good practices in school meal services: Organic matter on surfaces,microorganisms and health risks

The aim of this study was to evaluate and classify the sanitation and hygiene conditions in Porto Alegre/Rio Grande do Sul (RS) public schools using an analysis of surfaces that come in contact with food and a food safety checklist validated for the school environment. The following mesophilic heterotrophic bacteria count medians were observed on each piece of equipment or utensil studied: countertops, 27.3 Colony-Forming Units (CFU)/cm²; cutting boards, 15 CFU/cm²; blenders, 14.5 CFU/cm²; dishes, 2 CFU/cm²; and refrigerators, 1 CFU/cm². The median of the surface measurements analyzed by adenosine triphosphate (ATP) bioluminescence was less than 40 Relative Light Units (RLU)/100 cm² for all equipment and utensils, except for the countertop surface, which had a median of 52.5 RLU/100 cm². The data from 120 schools showed that 33, 64 and 3% were classified as high, regular and low health risk, respectively. The results showed that most schools were exposed to cross-contamination with failures especially with regard to environmental hygiene and procedures. Failures related to both factors potentially raise the risk of outbreaks in this environment. The scores used enabled the classification of school meal services and the identification of the points that need more attention. Intervention strategies that target different aspects of food handling, not only knowledge, may be promising in this scenario, which may address problems that mainly involve the food handler and promote changes in food handling practices.     

Photochemical oxidation of thiophene by O<Subscript>2</Subscript> in an organic two-phase liquid-liquid extraction system

Photochemical oxidation products and the kinetics of thiophene in an n-octane/acetonitrile extraction system using O₂ as an oxidant was studied. The results could be used as a reference for the oxidative desulfurization of gasoline because thiophene is one of the main components containing sulfur in a fluid catalytic cracking (FCC) gasoline. Thiophene dissolved in n-octane was photodecomposed and removed into the water phase at an ambient temperature and atmospheric pressure. A 500-W high-pressure mercury lamp (main wavelength 365 nm, 0.22 kW m⁻²) was used as the light source for irradiation and air was introduced by a gas pump to supply O₂. Thiophene could be photooxidized to SO₄ ²⁻ and CO₂. The desulfurization yield of thiophene in n-octane is 65.2% for a 5-h photoirradiation under the conditions of air flow at 150 m min⁻¹ and V(n-octane): V(acetonitrile) = 1:1. It can be improved to 96.5% by adding 1.5 g L⁻¹ artificial zeolite, which is an absorbent for O₂. Under such conditions, the photooxidation kinetics of thiophene with O₂ is of the first order with an apparent rate constant of 0.6297 h⁻¹ and a half time of 1.10 h. The sulfur content can be depressed from 800 to 28 ppm. The text was submitted by the authors in English.     

Genetic mechanisms of secondary pore development zones of Es<Stack><Subscript>4</Subscript><Superscript>x</Superscript></Stack> in the north zone of the Minfeng Sag in the Dongying Depression,East China

The genetic mechanisms of the secondary pore development zones in the lower part of the fourth member of the Shahejie Formation (Es4 x) were studied based on core observations, petrographic analysis, ?uid inclusion analysis, and petrophysical measurements along with knowledge of the tectonic evolution history, organic matter thermal evolution, and hydrocarbon accumulation history. Two secondary pore development zones exist in Es4 x, the depths of which range from 4200 to 4500 m and from 4700 to 4900 m, respectively. The reservoirs in these zones mainly consist of conglomerate in the middle fan braided channels of nearshore subaqueous fans, and the secondary pores in these reservoirs primarily originated from the dissolution of feldspars and carbonate cements. The reservoirs experienced ‘‘alkaline–acidic–alkaline–acidic–weak acidic’’, ‘‘normal pressure–overpressure–normal pressure’’, and ‘‘formation temperature increasing–decreasing–increasing’’ diagenetic environments. The diagenetic evolution sequences were ‘‘compaction/gypsum cementation/halite cementation/pyrite cementation/siderite cementation–feldspar dissolution/quartz overgrowth–carbonate cementation/ quartz dissolution/feldspar overgrowth–carbonate dissolution/feldspar dissolution/quartz overgrowth–pyrite cementation and asphalt ?lling’’. Many secondary pores (fewer than the number of primary pores) were formed by feldspar dissolution during early acidic geochemical systems with organic acid when the burial depth of the reservoirs was relatively shallow. Subsequently, the pore spaces were slightly changed because of protection from early hydrocarbon charging and ?uid overpressure during deep burial. Finally, the present secondary pore development zones were formed when many primary pores were ?lled by asphalt and pyrite from oil cracking in deeply buried paleoreservoirs.     

Effect of temperature and concentration of solutions on the position of <Superscript>13</Superscript>C NMR signals for fractions of saturated hydrocarbons forming urea adducts

An empirical equation was proposed for calculating the chemical shifts of ¹³C NMR signals from monomethylated alkanes and mono-n-alkyl-substituted cyclopentanes and cyclohexanes in the spectra of isoparaffin and naphthene fractions that form adducts with urea, depending on the analyte concentration in deuterochloroform C and the spectrum recording temperature T _rec. Deviations of the calculated chemical shifts from the measured values did not exceed 5 × 10^?3 ppm while varying T _rec from 303 to 323 K and C from 200 to 600 mg/ml. It was shown that such an accuracy is sufficient for the unequivocal identification of components by means of ¹³C NMR technique; ignoring this dependence leads to errors in signal assignment in the spectra of petroleum fractions. The use of the chemical shift of certain signals as internal standards for determination of T _rec and C was proposed. It was assumed that numerical values of the temperature and concentration coefficients that describe the dependence of the chemical shift on T _rec and C would be useful for the ¹³C NMR detection of new groups of compounds in petroleum hydrocarbons.     

Use of natural geochemical tracers to improve reservoir simulation models

This article introduces a methodology for integrating geochemical data in reservoir simulations to improve hydrocarbon reservoir models. The method exploits routine measurements of naturally existing inorganic ion concentration in hydrocarbon reservoir production wells, and uses the ions as non-partitioning water tracers. The methodology is demonstrated on a North Sea field case, using the field's reservoir model, together with geochemical information (SO₄²⁻, Mg²⁺, K⁺, Ba²⁺, Sr²⁺, Ca²⁺ and Cl⁻ concentrations) from the field's producers. Based on the dataset, some of the ions are shown to behave almost as ideal seawater tracers, i.e. without sorption to the matrix, ion exchange with the matrix or scale formation with other ions in the formation water. Moreover, the dataset shows that ion concentrations in pure formation water vary according to formation. This information can be used to allocate produced water to specific water-producing zones in commingled production. Based on an evaluation of the available data, one inorganic component, SO₄²⁻, is used as a natural seawater tracer. Introducing SO₄²⁻ as a natural tracer in a tracer simulation has revealed a potential for improvements of the reservoir model. By tracking the injected seawater it was possible to identify underestimated fault lengths in the reservoir model. The demonstration confirms that geochemical data are valuable additional information for reservoir characterization, and shows that integration of geochemical data into reservoir simulation procedures can improve reservoir simulation models.     

Near-infrared hyperspectral imaging for detecting Aflatoxin B1 of maize kernels

The feasibility of detecting the Aflatoxin B₁ in maize kernels inoculated with Aspergillus flavus conidia in the field was assessed using near-infrared hyperspectral imaging technique. After pixel-level calibration, wavelength dependent offset, the masking method was adopted to reduce the noise and extract region of interest (ROI's) of spectral image, then an explanatory principal component analysis (PCA) followed by inverse PCA and secondary PCA was conducted to enhance the signal to noise ratio (SNR), reduce the dimensionality, and extract valuable information of spectral data. By interactive analysis between score image, score plot and load line plot, the first two PCs were found to indicate the spectral characteristics of healthy and infected maize kernels respectively. And the wavelengths of 1729 and 2344 nm were also identified to indicate AFB₁ exclusively. The n-dimensional visualization method based on PC₃ to PC₇ was adapted to select the two classes of end members as the input data of the spectral angle mapper (SAM) classifier to separate the aflatoxin infection and clean kernels. The result was compared with chemical analysis of Aflatest^®. And the verification accuracy of pixel level reached 100% except the tip parts of some healthy kernels were falsely identified as aflatoxin contamination. Furthermore, another 26 maize kernels were selected as an independent data set to verify the reproducibility of the method proposed, and the detection accuracy attained to 92.3%, which demonstrated that hyperspectral imaging technique can be used to detect aflatoxin in artificially inoculated maize kernels in the field.     

Degradation of phenylethyl hydroperoxide in the presence of styrene epoxide and <Emphasis Type="Italic">p</Emphasis>-toluenesulfonic acid in an acetonitrile solution

It was shown that phenylethyl (ethylbenzene) hydroperoxide (EBHP) decomposes in an acetonitrile solution in an argon atmosphere in the presence of a styrene epoxide (SE)-p-toluenesulfonic acid (TSA) binary system yielding acetophenone and methylphenylcarbinol in a molar ratio of 1: 1. The expression for the EBHP degradation rate v = k _p[TSA]¹[SE]⁰[EBHP]⁰ is equivalent to the relationships obtained earlier for the rates of oxygen uptake by the binary system and the buildup of the oxidation product. The temperature dependence of the specific rate of degradation is given by k _p = 1 × 10¹⁴exp (?111.8 kJ mol^?1/RT) s^?1 (333–348 K).     

Effect of CO<Subscript>2</Subscript> on the oxidation of cyclohexene by H<Subscript>2</Subscript>O<Subscript>2</Subscript> using Co<Subscript>1.5</Subscript>PW<Subscript>12</Subscript>O<Subscript>40</Subscript> catalyst

Oxidation of cyclohexene by cheap and environmentally friendly oxidants, namely H₂O₂ and CO₂ has been catalyzed by Co_1.5PW₁₂O₄₀. It has been found that the main products of the oxidation are 2-cyclohexen-l-one (enone), 2-cyclohexen-l-ol (enol) and 1, 2-cyclohexanediol (diol) with the enone as the major product. Oxidation by CO₂ along with H₂O₂ remarkably increased the conversion compared to that by CO₂ and H₂O₂ separately. This might be due to the fact that CO₂ increases the percarbonate species (HCO₄ ^?) responsible of the oxidation by oxygen transfer, which indicated that the CO₂/H₂O₂ mixture is a useful reagent system. The decrease of both the selectivity of the enone and epoxide in favor of that of diol at higher conversions indicated that the diol was formed from the epoxide by consecutive reaction and/or directly from cyclohexene.