THERMAL DECOMPOSITION OF SAUDI CRUDE OIL ASPHALTENES

Asphaltenes precipitated by the use of pentane, heptane and decane solvents from Saudi Arabian Light (AL) and Saudi Arabian Heavy (AH) crude oils 370^°C + residua have been investigated by thermal gravimetric analysis and pyrolysis - gas chromatographic analysis at 350^°C and 520^°C. Gas chromatographic analysis of the gases evolved during pyrolysis has shown that CO, CO₂ and CH₄ constitute the major portion of the gases evolved at 350^°C from pentane and heptane asphaltenes of AH residue and from pentane asphaltenes of AL residue. Whereas gases evolved from decane asphaltenes are dominated by CO₂ and C₂-C₄ hydrocarbon gases. At 520^°C, hydrogen and methane represent 56-80 vol %of the gases evolved from all the four asphaltenes. The amounts of C₁-C₄ hydrocarbon gases increased with an increase in the carbon number of the precipitating solvent at 350^°C and decreased at 520^°C. The presence of up to C₃₆ normal alkane hydrocarbon has been indicated in the maltenes produced from these asphaltenes. The loss of nitrogen from AH asphaltenes during pyrolysis remained low (1-6 wt %), whereas the losses of oxygen and sulphur ranged from 58 to 74 wt % and 10 to 29 wt %, respectively.     

EFFECT OF PRECIPITATION TEMPERATURE ON THE COMPOSITION OF N-HEPTANE ASPHALTENES Part 2

Petroleum asphaltenes precipitated by n-heptane at temperatures between ambient and 80^°C from two crude oils have been characterized regarding hydrocarbon structures using ¹H and ¹³C nmr, and fluorescence spectroscopy. This indicates a very complex and apparently very small change in structural features except for a molecular weight increase as more material stays in solution at elevated temperature. Aromaticity increase and apparently alkyl chains diminish. The latter trend is however affected by the structural equation used. According to the fluorescence spectroscopy the content of large and complex chromophores increases but a significant effect of the presence of porphyrins on the spectra is also observed. The data is analyzed in combination with previous characterizations of the same asphaltenes presented in the first part of this work (Andersen, 1994). This indicates that as smaller molecules are extracted at elevated temperature the precipitated asphaltenes tend to associate more. This implys that these small molecules block association sites which therefore become available for further association at elevated temperature. For Boscan part of the smaller easy to extract porphyrins may have this behavior.     

ASPHALTENE AND RESID PYROLYSIS: EFFECT OF REACTION ENVIRONMENT

Hondo and Maya vacuum resids and their isolated asphaltenes were pyrolyzed at 400, 425, and 450^°C (752, 797, 842^°F) for batch holding limes ranging from 20 to 180 minutes. Maltene, asphaltene, and coke product fractions were isolated by a solvent extraction sequence; gas yield was determined gravimetrically. Results were summarized in terms of a lumped reaction network. The variation of product yields, kinetics, and apparent activation energies with feedstock and asphaltene environment provided insight into asphaltene structure and thermal reaction pathways.     

CHARACTERIZATION OF COAL CHARS FROM A FLASH PYROLYSIS PROCESS BY CROSS POLARIZATION/MAGIC ANGLE SPINNING 13C NMR

Chars from the Illinois Springfield (No. 5) Coal are prepared by flash pyrolysis at progressively higher charring temperatures. The results of a study of these chars by ¹³C NMR with CP/MAS indicate that the initial stage of heating (300^°C) produces a char with aromatic carbon fraction (f_ar) of 68%, and successive heating gives chars with f_ar of 70% (400^°C), 73% (500^°C), 89% (600^°C), 95% (700^°C), and 96% (800^°C). However, the actual amount of aromatic and aliphatic carbon in the char can be calculated by using the NMR measurements, the organic carbon content of the char, and the weight of the char. The calculated values show that the amount of aromatic carbon in char remains relatively constant at each temperature, but the amount of aliphatic carbon in char is reduced during higher temperature charring. At 600^°C, both a large reduction of the aliphatic carbon content and a maximum weight loss occur. Evidently, the aliphatic-bond carbon in coal is the principal source of volatiles derived from coal. The apparent increase in aromaticity (f_ar) of the char heated to progressively higher temperatures is due to the loss of aliphatic-bond moieties and reduction in volume of materials.     

CHARACTERIZATION OF HEAVY RESIDUA BY APPLICATION OF A MODIFIED D 2007 AND ASPHALTENE SEPARATION: EFFECT OF SOLVENTS ON PHYSICAL AND CHEMICAL PROPERTIES OF FRACTIONS DERIVED FROM HONDO 850°F RESIDOOM

Hondo 850 ^°F residuum was separated into saturate, aromatic, resin, and asphaltene fractions by a modified D 2007 and asphaltene separation. Two different asphaltene precipitation solvents were used — isooctane and heptane — and differences in selected physical and chemical properties of the derived fractions were compared.

The principal difference in the use of the two solvents was weight recovery after the separation. Isooctane yielded good recovery, while heptane exhibited poor recovery. Isooctane precipitated substantially more asphaltenes, as predicted from the solubility parameters of the two solvents.

The metals concentrations in the fractions were comparable for each solvent — no metals in the saturate and aromatic fractions, approximately 300 and 1500 ppm Ni + V in the resin and asphaltene fractions respectively. The relative distribution was also similar for both solvents, with the highest percentage coming from the asphaltenes.     

HYDROLIQUEFACTION OF TEXAS LIGNITE IN COAL- AND PETROLEUM-DERIVED SLURRY OILS

Hydroliquefaction of Texas lignite (68.5%. C daf) was conducted in a batch autoclave under hydrogen in a coal-derived slurry oil at 90 bar initial pressure for temperatures of 380-460^° C and residence time of 15-60 minutes, or a vacuum distillate from petroleum at 435^° C for 60 minutes and initial H₂-pressure of 60-150 bar, or a vacuum residue from the same petroleum at 435 and 460^° C for 60 minutes and initial H₂-pressure of 90-150 bar or tetralin at 435^°C, 60 minutes and 90 bar initial H₂-pressure. Red mud plus sodium sulfide were added as a catalyst for all experiments. Lignite conversion ranged from 50 to 83%. The products were separated into gases, residue, asphaltenes, oils B,P. above 200^° C, oils B.P. below 200^° C. Total liquid products from coal reached 57% in coal-derived slurry-oil, 56% in vacuum distillate and 64% in vacuum residue at optimum conditions with 32% of product oil B.P. below 200^° C in vacuum distillate and 24% in vacuum residue. When coprocessing lignite with vacuum residue at 120 bar initial pressure, 435^°C and 60 minutes residence time the total mass balance presented an oil yield of 73%. with 32% boiling below 200^°C.     

Phase behavior modeling of asphaltene precipitation utilizing RBF-ANN approach

Precipitation of heavy hydrocarbons, particularly asphaltenes, is the reason for numerous operational and production problems in the petroleum industry. Hence, knowing the amount of asphaltene precipitation is a critical commission for petroleum engineers to overcome its problems. The aim of this study was to predict the amount of asphaltene precipitation as a function of temperature, dilution ratio, and molecular weight of different n-alkanes utilizing radial basis function artificial neural network (RBF-ANN). Additionally, this model has been compared with previous correlations, and its great accuracy was proved to predict the precipitated asphaltene. The values of R-squared and mean squared error obtained were 0.998 and 0.007, respectively. The efforts confirmed brilliant forecasting skill of RBF-ANN for the approximation of the precipitated asphaltene as a function of temperature, dilution ratio, and molecular weight of different n-alkanes.     

THE INCREASE OF EFFICIENCY OP PINE OIL BY HEATING AND USAGE IN THE FLOTATION OF OXIDIZED AHASRA COAL

The effect of heating temperature and time on the efficiency of pine oil was examined in the flotation of oxidized Amasra Coal in this work. Samples were taken from waste heap Amasra Coal which were collected in 1973-1978 and stored in atmospheric conditions. The optimized impeller speed was 1000 rpm, aeration rate was 35 ml/s and solid content of the pulp was 20% in the flotation tests. Motorin was added to the pulp as a collector. The pine oil was heated to 50^°C, 75^°C, 106^°C, 125^°C, 150^°C, 175^°C, 200^°C and used as a frother. The flotation resulta indicated that 125^°C was suitable temperature for heating. Increasing the heating time increased the efficiency of pine oil. The recovery of combustibles also Increased depending on the increase in the amount of oil heated for 5 hours at 125^°C.     

KINETICS OF CORN COB CHAR GASIFICATION IN CARBON DIOXIDE

The Reactivity of corn cob char in CO₂ has been studied on a thermogravimetric balance to develop a rate equation for the design of biomass gasifiers operating on corn cob char. Experiments in the range of 650-1000^°C were conducted with cylindrical shaped pellets of 1 cm diameter having L/D=l. The average porosity of the pellets was 0.5. It was observed that the rate of the CO₂/char reaction decreased with increase in temperature from 650-750^°C and then increased with temperature upto 1000^°C.

The data obtained at temperatures 750^°C and above has been used to determine a rate equation for char gasification. It has been found that the reaction proceeds according to the Sharp Interface Model (SIM) with a first order chemical reaction as the rate controlling step. The activation energy is found to be 40 Kcal/mole with frequency factor being 1.2 × 10⁷ mm/sec. Analysis of the data obtained for the decreasing reaction rate regime (650-750^°C) indicates that the change in the ash structure result in this kind of behavior.     

COKE CHARACTERISTICS IN RELATION TO THE COLLOIDAL. MATTER OF PETROLEUM FOR THERMAL. PROCESSES

The purpose of this work is to research the characteristics of the production of coke in thermal and hydrothermal cracking from residual oils and their deasphalted oils Using ethyl acetate, because it allows the elimination of both resins and asphaltenes (colloidal matter) from the parent oil in only one step. This improves the deasphalted oil as coke precursors and basic nitrogen compounds present in the resin fraction are practically eliminated.

A 104 ml batch autoclave reactor with a cooling system was used for the thermal and hydrothermal cracking experiments. This reactor can withstand temperatures of up to 500^°C, pressures of 500 bar and a rocking velocity of 1 Hz. The influence of the temperature was investigated at 400, 425 and 450^°C and at 0, 20, 40, 80,     

COPROCESSING OF COAL WITH HEAVY PETROLEUM CRUDES AND RESIDUA

This work investigates the coprocessing of coal in six different heavy petroleum crudes and residua. Coprocessing reactions of coal and the petroleum solvents are performed under three sets of constant reaction conditions, yielding informative comparative data for processing applications. Definitive comparisons of coal reactivity and solvolysis in the petroleum solvents have been obtained using solvent fractionation which provides a measure of the degree of upgrading achieved by the liquefied coal. Regressive reactions and low coal conversions are observed in coprocessing reactions in N₂ at 400^°C. Higher conversions and a reduction in regressive reactions are observed in H₂ at 400^°C. Catalytic hydrotreatment and higher temperature, 425^°C, result in increased coal conversion and a net production of pentane soluble materials. The amount of product fractions obtained from the upgrading of the coal alone is calculated. The effect of reaction temperature using different solvents and reaction conditions on the product slate is also examined.     

SOLUBILITY STUDIES OF PARAFFIN WAXES IN SELECTED PETROLEUM FRACTIONS AND TOLUENE

Solubility studies of paraffin waxes with melting point range of 43^°C to 57^°C in two undefined petroleum fractions and Toluene have been carried out. An Attempt was made to develop a correlation for predicting the solubility of the waxes in these solvents. The one parameter ideal solubility law expression has been successfully used to represent the experimental data.     

RECOVERY OF ORGANIC MATTER FROM GREEN RIVER OIL SHALE AT TEMPERATURES OF 400°C AND BELOW

Experiments to recover organic matter from Green River oil shale in high yields at temperatures of 400^°C and below are described. Three different recovery procedures are discussed: 1) experiments wherein liquid organic materials were extracted at atmospheric pressure and temperatures below 75^°C by solvents of different strengths, 2) autoclave experiments where liquid organics were recovered by heating the shale with a variety of solvents at temperatures between 300 and 400^°C and pressures between 5 and 32 MPa, and 3) an autoclave experiment where liquid organics were recovered by heating shale in an argon atmosphere for 1 hour at 400^°C. The liquid organic materials recovered in these experiments represent from four to 90 weight percent of the total organic material in the shale. The liquid organic materials have an average molecular weight of between 500 and 600 amu as compared to a typical shale oil that has an average molecular weight of 300 to 350 amu. Elemental analyses show that the liquid organic materials contain high percentages of hydrogen and nitrogen, as does shale oil. Moreover, the liquid organic materials also contain much larger concentrations of oxygen-containing compounds than shale oil. The experimental results suggest the possibility of developing a new process for recovering both organic and inorganic material from Green River shale.     

FREE RADICALS FORMED IN HYDROTREATED COAL LIQUID AND INFLUENCE OF OXYGEN

The behavior of radicals formed in hydrotreated coal liquid with heat treatment and the influence of oxygen have been investigated by electron spin resonance (e.s.r.) spectroscopy. A set of e.s.r. spectral lines identified as phenalenyl radical appears from 50^°C as the oil is heated in argon atmosphere. The radical concentration is enhanced with temperature, reaches a maximum between 130 and 150^°C and then decreases at higher temperatures. The radical is very stable even at 200^°C for the sample hydrotreated under mild condition, whereas the radical in the sample treated under severe conditions disappears drastically from 150^°C. When oxygen is introduced in the oil, the radical is converted into semiquinone and/or aryloxy radicals and stable molecules. The treatment in the presence of oxygen at higher temperatures is considered to accompany the formation of other aryloxy radicals by the reaction of aromatic hydrocarbons and oxygen.     

THERMAL CRACKING (VISBREAKING) STUDIES ON QUYARAH RESIDUES

Visbreaking experiments on Quyarah long residue have been conducted in a continuous laboratory-scale visbreaking unit at different temperatures from 435^°C to 490^°C at one pressure (7 bar) and constant residence time (90 sec.). Data on yield of different products have been reported. Further, thermal cracking experiments on visbroken vacuum gas oil under relatively high severity were also given in the same unit in order to reduce the residual yield of Quyarah crude.     

CHARACTERIZATION OF KUWAITI CRUDE TBF-FRACTIONS WITH EMPHASIS ON KINEMATIC VISCOSITY - TEMPERATURE BEHAVIOR

Characterization of Kuwaiti crude oil, has been carried out in terms o API gravity, debutanized gravity, total sulfur content, Reid Vapor pressure ash content, heating value, salt content, viscosity SUS, vanadium content a: V2 O5, pour point and analysis of various metals. The true boiling poinl (TBP) fractions of this crude (IBP - 95^° C, 95 - 205^°C, 205 - 260^° C, 260 - 345^° C and 455^° C⁺;) were also characterized in terms of API gravity, total sulfui content, H₂S content, mercaptans content, molecular weight and elementa analyses for total carbon, hydrogen and nitrogen. The kinematic viscosity temperature data have been obtained for 95^°C⁺; TBP fractions for a wide range of temperatures.     

CHARACTERIZATION of ARAB MEDIUM CRUDE FRACTIONS WITH EMPHASIS ON KINEMATIC VISCOSITY - TEMPERATURE BEHAVIOR

Characterization of Arab medium Crude Oil, has been carried out in terms of API gravity, debutanized crude gravity, total sulfur content, Reid vapour pressure ash content, heating value, salt content, viscosity SUS, vanadium content as V₂O₅, pour point and analysis of various metals. Further, six true boiling point (TBP) fractions (IBP-95^°C, 95-205^°C, 205-260^°C, 260-345^°C, 345-455^°C and 455^°C+) of this crude were characterized in terms of API gravity, total sulfur contents H2S content, mercaptons content, molecular weight, elemental analyse; for total carbon, hydrogen and nitrogen, analyses of various metals and paraffin, aromatic and naphthene contents of lighter fractions. The kinematic viscosity-temperature data have been obtained for 95^°C+ TBP fractions for a wide range of temperatures.     

CHARACTERIZATION OF ASPHALTENE PARTICLES BY LIGHT SCATTERING AND ELECTROPHORESIS

The solubility of asphaltenes in heptane/toluene mixtures was studied at several temperatures. A significant increment in asphaltene solubility was observed when the temperature increases from 0°C to 20°C and a moderate increase when the temperature rose from 20°C to 50°C. These results indicate that asphaltenes behave as a higher consulate temperature system, similar to nonpolar waxes. Examined by photon correlation spectroscopy, diameters from the particles formed a range between 125 and 400 nm, depending on the amount of non-solvent (n-heptane) used for the precipitation process and the initial concentration of asphaltenes. The particles presented a small positive surface potential that was not altered by the addition of resins.     

Variation in Composition of Subfractions of Petroleum Asphaltenes

Boscan asphaltenes were precipitated from the crude oil using mixtures of toluene and heptane at temperatures of 24, 50, and 80°C. Another process of extracting solid n-heptane asphaltenes (24°C) using the same solvent systems and temperatures was also investigated. Asphaltene yield is different by the two processes at similar conditions although both increases in temperature or toluene content lead to lower solid yield. This way the asphaltene continuum was investigated from incipient flocculation to total n-heptane precipitated asphaltenes. The asphaltenes were analyzed using elemental analysis, fluorescence spectroscopy, vapor pressure osmometry, and HPLC size exclusion chromatography. The distribution of porphyrins was also measured using absor-bance spectroscopy. The asphaltenes were found to follow a regular trend in elemental ratios, H/C and N/C, indicating increased aromaticity and nitrogen content as the solid yield decreases. Also the molecular weight was seen to increase. Size exclusion chro-matograms and fluorescence spectra were found to be different comparing solids from the two separation processes. This indicates that the asphaltene fractions obtained by extraction of solid asphaltenes are altered relative to asphaltenes obtained by ordinary precipitation. The porphyrin concentration was found to diminish rapidly with solid yield decrease in both precipitation and extraction experiments, the latter fractions, however, containing significantly less asphaltenes indicating an adsorption step in the coprecipitation of porphyrins. Soluble fractions were found to exhibit relatively low molecular weights and an apparent lack of indications of association up to a point of solubles exceeding 50 % of the total asphaltenes. The-latter have implications for the further understanding and experimental investigation. of the associating nature of asphaltenes such as concentration effects during analytical characterization.     

PYROLYSIS STUDIES OF ORGANIC OXYGENATES. IV. NAPHTHALENE METHYL ETHER PYROLYSIS UNDER BATCH AUTOCLAVE CONDITIONS

Aryl alkyl ethers undergo two major kinds of thermal reactions at temperatures of about 450^°C. They cleave homolytically at the C-H alkyl bond to produce phenols and they cleave homolytically at the C-H alkyl bond, and rearrange to an aryloxy radical leading to carbonyl compounds and ultimately to other products. Results obtained with the methyl ethers of 1- and 2-naphthol and with anisole show clearly that relative kinetics for these pathways differ for different substrates. Unimolecular decomposition rates at 400^°C and at 450^°C show that 1-methoxy naphthalene decomposes faster than 2-methoxy naphthalene which in turn is more thermally reactive than anisole.