CHARACTERISATION OF CYCLIC AND ACYCLIC ALKANES CHARACTERISATION OF CYCLIC AND ACYCLIC ALKANES IN FORTIES AND KUWAIT PETROLEUM CRUDES

Alkane hydrocarbon fractions from Forties (North Sea) and Kuwait petroleum crudes, separated by distillation, solvent extraction and silica-gel column chromatography and sub-fractionated by molecular-sieve adsorption, have been examined by gas chromatography (GC) ¹H and ¹³C ( NMR spectroscopy, GC-mass spectrometry (MS) and field desorption (FD)MS. GC indicates that Forties contains rather more acyclic isoprenoids and cyclic alkanes than Kuwait; FDMS of Kuwait shows molecular-weight ranges for mono-, di-, tri-, tetra- and pentacyclic alkanes. ¹³C NMR spectra provide evidence of higher aromatic carbon, C_A, in Forties than Kuwait and longer T₁ relaxation times.     

Synthesis and Characterization of Mono-Isomeric Alkylbenzene Sulfonates

The synthesis of a series of isomer pure mid-position alkylbenzene sulfonates is described. Three isomers—4-(1-ethyldodecyl)benzene sodium sulfonate, 4-(1-butyldecyl)benzene sodium sulfonate, and 4-(1-hexyloctyl)benzene sodium sulfonate—were synthesized. High performance liquid chromatography (HPLC) indicated that the isomers were of 99.9%, 96.2%, and 97.5% purity, respectively. Their structures were characterized to be correct by electrospray ionization-mass spectrometry (ESI-MS), ¹H NMR, and ¹³C NMR investigations. Furthermore, the purity and structure of the three kinds of intermediates were also determined by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS).     

STRUCTURE REPRESENTATION OF THE SPECIFIC FRACTIONS FROM PINGSHUO COAL

Basic data of four fractions, PM₁, PM₆, PM₇and PM₈, derived from Pingshuo bituminous coal were obtained by ultimate analyses, mean molecular weight measure, GC/MS, ¹³C-NM R, ¹H-NM R and FTIR technigues. A method of calculating the average molecular parameters of the fractions is introduced. Based on the calculated parameters, the molecular structure models of the fractions of PM₆, PM;and PM₈are constructed. Significant structural information about the saturated hydrocarbon and aromatic hydrocarbon with heteroatom groups is given also.     

Thermal Degradation Process of Synthetic Lubricating Oils: Part I—Spectroscopic Study

The characterization of thermal degradation process of synthetic lubricating oils in relation to its spectroscopic properties was evaluated in this work. The fundamental key to understanding synthetic lubricating oxidation is having basic knowledge of the chemistry of lubricants and their degradation. Synthetic lubricants were degraded at different temperatures and times, under air atmosphere. After thermal degradation, lubricant oils were characterized by infrared spectroscopy (IR), nuclear magnetic resonance spectroscopy (NMR) and gas chromatographic/mass spectrometry (GC/MS). IR, NMR, and GC/MS spectra indicated oxidation reaction products.     

STRUCTURE AND REACTIONS OF BEYPAZARJ LIGNITE I. CHARACTERIZATION BY 13C NMR AND IR STUDIES

The solid state ¹³C NMR and infrared spectra of Beypazan lignite were deconvoluied by the least squares curve fitting techniques to resolve the overlapping bands in the 0-220 ppm region of the ¹³C NMR spectra and in the 4000-2700 cm^-1, 1860-900 cm^-1 and 900-400 cm^-1 regions of the infrared spectra to gain information about the structure of the lignite. Measurement of integral absorptivities of some of the functional groups present in the infrared spectra was attempted. Measured values of integral absorptivities are in good agreement with those reported previously.     

INTERACTION OF SUPERCRITICAL METHANOL AND WATER WITH ORGANIC MATERIAL IN GREEN RIVER OIL SHALE

A series of experiments to study the interaction of supercritical methanol and water with Green River oil shale was performed. The volume percentage of methanol (CH₃0H) in water was varied. The temperature was held constant at 400°C. The products were fractionated and characterized with infrared spectroscopy and elemental analyses. A ¹³CH₃0H experiment was carried out and 13C nuclear magnetic resonance (NMR) analysis was used to prove the incorporation of methanol into the products. The methyl esters resulting from the incorporation were isolated and characterized by high resolution mass spectrometry. The experiments on a model compound and gas chromatographic/mass spectral (GC/MS) analysis of the product showed that methanol can react with carboxylic acids found in Green River oil shale to form methyl esters. However, this incorporation of methanol into the product oil from supercritical fluid extraction was found to be not sufficient to account for the increased oil yields, The role of methanol in these experiments on Green River oil shale is discussed.     

STRUCTURAL STUDIES OF PINSHUO COAL EXTRACTS USING 1H- AND 13C-NMR SPECTROSCOPY

The pyridine extracts of Pingshuo coal were fractionated by silica gel chromatography. Several fractions have been characterized in terms of their average molecular structures using a combination of ¹H- and ¹³C-NMR spectroscopy. The ¹H- and ¹³C-NMR spectra of the fractions revealed distributions of hydrogen as well as carbon in the fractions. From the NMR data, average molecular weight and elemental analysis of the fractions, the average molecular structure parameters were calculated, and their structure models were represented based on these average parameters. Some significant structural differences were found which have provided reliable information in detail for Pingshuo coal bulk structure.     

Changes in Asphaltenes Properties Modified with Fe in Hydrotreating Reactions

The properties of the Hamaca of asphaltenes extra-heavy crude oil (AsfH) of Petroliferous Orinoco Belt can be modified for evaluating the changes produced with hydrotreating (HDT). One characterized the solid modified by means of UV-visible spectroscopy and nuclear magnetic proton resonance (NMR ¹H). The samples were put under hydrotreating to 200°C to avoid thermal cracking, atmospheric pressure, and a flow of feeding of 10.5 mL/hr in a fixed-bed reactor in the presence of H₂S generated in situ. The reactivity was followed by gas chromatography (GC). All the samples were evaluated before and after being hydrotreated by ¹H NMR, total sulfur analysis, and determination of molecular weight average by vapor pressure osmometry (VPO). The obtained results suggest the iron possibly is inserted in the structure of the asphaltene forming a new active phase catalytically, presumably a mixed sulfide (pyrrotite type) of iron-metal of transition (V and Ni) present in the asphaltene.     

Enhanced Oil Recovery: The Synthesis of Anthraquinone [1, 2-C] Alkylisoxazole

Anthraquinone [1, 2-C] methylisoxazole is synthesized from 2-ethylanthraquinone through nitration and treating with oleum. The different methods of 2-ethylanthraquinone nitrated were discussed. The optimum conditions were determined. The structure of the product was confirmed by MS and ¹H NMR.     

Group Type Analysis of Asphalt by Column Liquid Chromatography

An improved analysis method for characterization of asphalt was established. The method is based on column chromatography technique. The asphalts were separated into four groups: saturates, aromatics, resins, and asphaltenes, quantitatively. About 0.1 g of sample was required in each analysis. About 20 mL of n-heptanes was used to separate out saturates first. Then about 35 mL of n-heptanes/dichloromethane (1/2.5, v/v) mixture was used to separate out aromatics. About 30 mL of dichloromethane/tetrahydrofuran (1/3, v/v) mixture was used to separate out resin. The quality of the separation was confirmed by infrared spectra (IR) and ¹H NMR analysis. The model compounds, tetracosan for saturates, dibenz(ah)anthracen for aromatics, and acetanilide for resins were used for verification. The IR and ¹H NMR analysis of the prepared fractions from the column liquid chromatography were in good agreement that of pure reagents.     

USE OF NMR SPECTROSCOPY TO STUDY THE EFFECT OF HYDROCRACKING ON THE CHEMISTRY OF HYDROCARBONS

The use of hydrocracking technology provides an opportunity to modify the chemistry of hydrocarbons and improve the properties of mineral base stocks. The ¹H NMR spectra of the nonaromatic fractions separated from different hydrocracked base stocks showed no significant difference in the chemistry of hydrocarbons. The ¹³C NMR spectra showed also the same hydrocarbon chemistry, except for some differences in the degree of branching. Some of the most important components of the hydrocarbon structure including branch-ethyl, terminal-methyl, branch-methyl and bulk methylene peaks were identified. The methyl-branching, calculated with respect to the bulk methylene (-CH₂-) signal, was found to vary from 205 to 255 per 1000 bulk (-CH₂-). The ethyl-branching was significantly lower and varied from 60 to 80 per 1000 bulk (-CH₂-). The effectiveness of the polymethacrylate pour point depressant to depress the dewaxed pour points of hydrocracked base stocks was studied. The results indicated that an increase in the methyl- and ethyl-branching of hydrocracked base stocks leads to an improvement in their response to pour point depressant. The ¹³C NMR data were found useful in assessing the extent of hydrocracking and degree of branching in hydrocracked base stocks. Low depressed pour points are required to assure good flow properties of formulated lubricating oils.     

SOLVENT EXTRACTION OF PAKISTANI COALS (ii): EXTRACTION AND CHARACTERIZATION OF METHANOL-BENZENE EXTRACTS

Structural characterization of the solvent extracts from four different Pakistani lignitic coals has been carried out by their proximate, elemental analysis and FT-Infrared and ¹H n.m.r. spectra. The yield of each extracts was greater with 1:1 benzene-methanol mixture in comparison to the total yield obtained by separate extractions with benzene and methanol. The extracts contained significantly less amount of ash and fixed carbon along with an increase in the percentage of volatile matter. The FTIR and ¹H n.m.r. spectra indicated that basically all the extracts contained less condensed aromatic rings in comparison to the coal. The FTIR spectra showed sharp well resolved peaks which have been assigned to various functional groups.

The ¹H n.m.r. spectra were used to obtain average structural parameters for all the extracts. A detailed analysis of the FTIR and n.m.r. spectra of the coal and their extracts provided an important in-sight into the differences between various extracts and also between various coals and their corresponding extracts.     

Composition and Properties of Some Petroleum Waxes

Structural composition of paraffin waxes and soft wax fraction derived from microcrystalline wax were determined. Waxes were fractionated by multistage solvent crystallization at different temperatures. The n-alkane components of the waxes were separated by urea adduction. The average structural parameters of parent waxes, their fractions, and urea adductables were estimated by ¹h and ¹³C NMR spectroscopy. The thermal parameters viz. phase transition temperature and the associated energy during phase transitions were determined by using DSC and correlated with the penetration temperature behavior of waxes. The carbon number distribution determined by GC for these waxes and their n-alkane components were also correlated with physical properties and thermal parameters.     

Structural Characterization of VGOs from Western Region Crudes by NMR Spectrometry

Vacuum gas oils from western region crudes were analyzed by ¹H and ¹³C NMR and several structural parameters were estimated. In addition, analytical data was generated by separation techniques. The combination of analytical data with average structural parameter accounted for certain distinctive features of composition of these feed stocks.     

Structural Aspects of Crude Oil Derived Asphaltenes by NMR and XRD and Spectroscopic Techniques

Asphaltene samples obtained from crude processed at two Indian refineries were characterized for chemical composition and structure by nuclear magnetic resonance (NMR), X-ray diffractometry (XRD), fluorescence spectroscopic techniques, and chromatographic (column and GPC) techniques. Estimation of NMR average structural parameters were obtained by combined ¹H, NMR ¹³C, NMR DEPT-45, and QUAT pulse sequence spectral editing techniques. The macrostructure and crystalline parameters of these samples were obtained by XRD. The nature of the functional groups have been obtained by IR technique. A combined NMR and XRD parameters were used to estimate the size of average aromatic structural units. Asphaltenes from one of the crudes (ASP-A) was found to be highly pericondensed, highly substituted, and higher molecular size compared to ASP-B asphaltene molecules. The number of aromatic sheets per unit sheets are 3.7 and 2.5 in the sample ASP-A and ASP-B, respectively. Both the asphaltene molecules in the samples have periodically and systematic arrangement of aromatic sheets in the unit sheet. The number of aromatic rings per unit sheet in ASP-A and ASP-B are 6.0 and 5.0, respectively. The fluorescence spectral studies has also exhibited λ_max (the wavelength of maximum intensity) at 505 and 509 nm confirming to pericondensed higher polycondensed aromatic ring system in both the samples. The analysis of liquid chromatographic fractions of these samples show that each sample is composed of several polycondensed aromatic systems where unit sheet of ring sizes vary from 1.8 to 6.3 with varying molecular sizes. These structural parameters allowed a model structure of the asphaltenes to be constructed.     

二苯硫脲的常温常压合成与相关分析

研究了在常温常压和密闭条件下用升华AlCl3催化苯胺和CS2 反应制二苯硫脲的方法。对反应产物用乙醇重结晶获得白色片状晶体 ,选择性和收率分别达到 99.7%和 80 .1%。经熔点测定 ,HPLC/MS/MS ,FTIR ,UV及1 HNMR等分析确定为二苯硫脲。但用GC/MS分析该晶体为异硫氰酸苯酯 ,这可能是在GC/MS分析过程中二苯硫脲发生了中性丢失苯胺的缘故。     

EFFECT OF ABIETIC ACID DERIVATIVE SURFACTANTS ON CALORIFIC VALUE AND FLOW OF CRUDE OIL AND SOME DISTILLATES

A series of abietic monoester and amide have been prepared by esterification of abietic acid with long chain alcohol blend (Nafol 20⁺), polyethylene glycol (PEG 400, 600, 1000 and 4000) and hexadecylamine. The abietic diester derivatives were prepared by esterification of abietic-maleic anhydride adduct with Nafol 20⁺ only or polyethylene glycol-1000 and Nafol 20⁺. These reactions were carried out to prepare eight abietic acid derivatives. The products were purified and characterized by FTIR and ¹H NMR analyses. The surface-active properties of these compounds were correlated with their effect on pour point and calorific values of crude oil. From the results, it has been found that the compound EA23-MN, which has the more negative value of ΔG_ad, exhibited maximum pour point depression and increases the calorific values of crude oil and some distillates.     

Structural Characterization of Different Asphaltenes of Kuwaiti Origin

Asphaltenes obtained by precipitation from crude Kuwaiti oils have been analyzed by proton magnetic resonance (¹H-NMR), carbon-13 nuclear magnetic resonance (¹³C-NMR) and Infrared (IR) spectral techniques. The molecular weight and elemental analysis were also determined. These combined analytical data were used for the characterization of these Kuwaiti oils. The asphaltenes molecular weights range from approximately 4200-6500 with an H/C ratio of 0.91-1.1 with an average 45-71% aromatic carbons. The average side chain length was of 4-6 carbons. It can also be concluded that the asphaltenes under investigation contain 5-9 sets of condensed aromatic rings joined together by bridges of alkyl chains or other hetero atoms and the average number of each of these sets of condensed aromatic rings is nearly 7. There are a number of alicyclic rings and condensed alicyclic rings in asphaltene. The IR spectra showed main molecular groups including OH, NH, SH, C=O and aliphatic and aromatic C-H's.     

Structural Studies on Residual Fuel Oil Asphaltenes by RICO Method

Structural characterization of asphaltenes isolated from Saudi Arabian heavy and medium crude oils was undertaken by using ruthenium ion catalyzed oxidation (RICO) method. The RICO method was capable to convert aromatic carbons selectively into carbon dioxide and carboxylic acids and esters group while leaving aliphatic and naphthenic structures of asphaltenes essentially unaffected. Detailed analyses of RICO products of both Arab heavy and Arab medium asphaltenes were conducted using FT-IR, ¹³C-NMR, IC, GPC, and GC-MS techniques. These analyses indicate that the aqueous phase fraction (water-soluble products) obtained from RICO reaction of asphaltenes consists of aliphatic dicarboxylic acids and aromatic poly carboxylic acids with longer alkyl chains. The ¹³C-NMR and GC-MS analyses of organic phase products of asphaltenes indicate that this fraction contains large amount of aliphatic carboxylic acids with longer alkyl groups. The oxidation products of both Arab heavy and Arab medium asphaltenes were found to be dominated by a homologous series of straight chain monocarboxylic acids suggesting that the normal alkyl chains are major and important constituents of the chemical structure of both asphaltenes.     

STUDY OF SATURATED COMPONENTS IN ASPHALT

The saturated fractions separated from blown and straight run asphalts of the same penetration grade have been investigated by using GC, MS and ¹³ The saturated components in asphalt represent complex mixture of polyalkyl structures in which straight chain paraffins prevail. The content of saturates in asphalt and their molecular composition were found to be affected by the chemical nature of crude oil as well as by the method of its processing into asphalt. Saturated fractions from blown asphalt are richer in long chain paraffins than those from straight run asphalts. The structural examination of saturated components separated from the products of asphalt pyrolysis has confirmed die presence of long straight-chain units in the asphalt-forming micelles. The structural differences between the saturated fractions obtained from asphalts of different origin (Uralian and Brent-blend) suggest, that the distribution of straigh-chain hydrocarbons in asphalts is dependent on the aliphatic network already existing in the raw material.