A NEW LOOK AT THE MECHANISMS OF OXIDATIVE SEDIMENT FORMATION IN FUELS

Alkylpyrroles have been known to promote sediment formation and discoloration of petroleum distillates for over thirty years. There has been much effort directed towards understanding the detailed mechanism of alkylpyrrole promoted sediment formation in petroleum distillates. In addition, recent studies have investigated the mechanism of alkylpyrrole sediment formation in shale derived synfuels. It is the intent of this article to critically review some of the postulated mechanisms for alkylpyrrole promoted sediment formation in fuels and then to comment on the significance of these mechanisms to our overall understanding of the field of oxidative fuel stability.     

DEPOSIT FORMATION DUE TO INSTABILITY AND CONTAMINATION OF RAW MATERIALS IN ALKALI-TREATED LIGHT DISTILLATES

ABSTRACT

Alkali treating of petroleum distillates is carried out to obtain the advantages of the product purity and to improve performance. The use and quality of alkaline solutions must be controlled since metal ions present as impurities can catalyze low temperature oxidation and polymerization of olefinic compounds; leading to formation of heavy emulsions which tend to deposit in hydrocarbon phases and eventually to block the handling systems. The effects of the variable factors “time, temperature, antioxidant and anticorrosion additives” were studied. The addition of a small amount of methanol was found to retard the deposit formation. This can be ascribed to ion-molecule reactions of methoxide ions with aryl and heavy thiols present in the light distillates. The promoting effects of light and the surrounding air on the stability of final treated product have been investigated.     

IDENTIFICATION OF NITROGEN COMPOUNDS AND THEIR EVOLUTIONDURINGAGEING NABSENCE ANDPRESENCE OF ADDITIVES EFFICIENCYOFHYDROTREATMENT

Abstract

As established by several previous works, nitrogen compounds play a prominent role in the evolution of middle distillates containing cracked components, particularly regarding sediment formation and color evolution.

In a first part, this paper describes and compares stability properties of fuel blends using both an accelerated ageing method at 120°C (248°F ) and long term storage methods at 43°C(110°F) -ASTM 0 4625 - and at ambient temperature. Effectiveness of stabilizing additives is also evaluated. In mixtures containing LCOs, insoluble products are formed progressively during ageings, more or less rapidly according to the chemical constitution of the mixtures.

Then, it reports the complete identification of nitrogen compounds using gas chromatography equipped with a selective nitrogen detector and mass spectrometry showing that in light cycle oils, alkyl indoles and carbazoles are the main families.

Evolution of these compounds was followed kinetically during ageings in absence and presence of additives and alkyl indoles appeared as the moat evolutionary.

It appeared that some additives avoided evolutions of alkyl indoles without preventing sediment formation and color evolution. Oxidation mechanism involving nitrogen compounds should not be the only one to explain the storage evolutions of middle distillates.

Hydrotreatment converts all the alkyl indoles of LCO and prevents coloration end deposits in the storage of the mixtures of steaight-run distillates and LCOs.     

CHARACTERIZATION OF SEDIMENTS AND ADHERENT GUM FROM CRACKED MIDDLE DISTILLATES

ABSTRACT

ABSTRACT The composition of insoluble sediments and adherent gum obtained from ambient and accelerated oxidation stability tests of different cracked middle distillates (LCO, TCO & Coker Kerosene) were studied using FTIR Spectroscopy. The sediment & gum formed in these fuels after extraction with methanol were also characterized. The differences in the composition of insoluble sediment & adherent gum obtained under different conditions have been observed.     

Characterization and Classification of Some Egyptian Petroleum Crude Waxes Using Different Techniques

Abstract

In order to characterize and identify some crude waxes, derived from various Egyptian petroleum distillates and residues, suitable for production of different types of petroleum waxes, many standard test procedures have been used for measurement the physical characteristics of crude waxes and wax products. Moreover, some analytical techniques such as gas chromatography (GC), Fourier transform infrared (FTIR) spectroscopy, proton nuclear magnetic resonance (H-NMR), urea adducting analysis, and solid-liquid chromatography have been used to characterize the crude waxes. Finally, one stage fractional crystallization has been done to separate the hard waxes from El-Ameria and Suez heavy slack waxes and Alexandria and Suez crude petrolatums using ethyl acetate solvent at an ambient temperature of 20^○C and at fixed dilution and washing solvent ratios of 7:1 and 6:1 by weight, respectively. The resulting wax products are evaluated according to TAPPI-ASTM equation and petroleum wax specifications.     

STRUCTURAL STUDIES OF SHORT PATH DISTILLATES AND SUPERCRITICAL FLUID EXTRACT OF PETROLEUM SHORT RESIDUE BY NMR SPECTROSCOPY

Abstract

Four short-path distillates obtained at different evaporator temperatures (240, 270, 300, and 330° C) and a supercritical fluid extract (with CO₂ as solvent) of petroleum short residue (North Gujarat Mix) have been separated into saturates and aromatics. Each fraction of all the said samples has been studied by ¹H- and ¹³C-NMR spectrometry and the distributions of various types of hydrogens and carbons are reported. Several reliable average structural parameters have been computed and their relative variation is discussed.     

LIQUEFACTION OF CELLULOSIC WASTE V. WATER FORMATION AND EVALUATION OF PYROLYTIC CHAR AS A BY —PRODUCT OF PYROLYSIS REACTION

ABSTRACT

Liquid hydrocarbon oil and water have been produced from the liquefaction of cellulosic matter present in municipal solid wastes (MSW). Gases and residual char have also been produced as by-products resulting from the pyrolysis reaction of cellulose. Quantities of water and pyrolytic char were estimated at different conditions of the process (temperature pressure of hydrogen, carrier oil medium and concentration of boric acid). From the results obtained, it was suggested that the formation of water seems to be sensitive to the operational conditions which enhance a water-gas shift reaction (in which water molecules are consumed to produce carbon dioxide and hydrogen). Decreasing of the undesired chary by-product could be achieved by increasing the concentration of boric acid that catalyzes the liquefaction reaction. Two petroleum distillates, namely gas oil and residual fuel oil, were used as carrier media of a solid refuse. It was found that fuel oil is more efficient as a buffering medium that prevents cellulose macromolecules from a rapid and complete charing during the liquefaction process. The pyrolytic char was characterized and evaluated by means of different analytical procedures and solvent extraction using petroleum ether 40–60°C and methanol. Calorific value of the pyrolytic char was found to be 4.6 Kcal g^?1 which is quite close to that of a brown coal. Dropping point test of the extracted material by petroleum ether indicated that the extract can be utilized for producing lubricating greases via saponificattion with a salt of sodium or calcium.     

Effect of Sediment on the Biodegradation of Petroleum Contaminants in Natural Water

Abstract

Biodegradation of petroleum contaminants in natural water was studied within an Asian river context where high-suspended sediment content exists. Petroleum contaminant is one of the main pollutants in the Yellow River; at the same time, there is a high sediment content in the river system. This research highlighted the effect of sediment on the biodegradation of petroleum contaminants, as well as the related mechanisms regarding the effect. Biodegradation of petroleum contaminants was studied under different sediment contents. The distribution of petroleum contaminants in water and sediment phases as well as the relevant biodegradation kinetics were also investigated. The results showed that in water system with the sediment content of 0.5 g/L, about 84% of petroleum contaminants with the initial concentration of 11.64 mg/L could be degraded after incubation for 63 days at 20°C. It was also indicated that the presence of sediment exerted significant influences on the biodegradation of petroleum contaminants in water system, and the influences were different from one cultivation stage to another. In the first stage, the biodegradation rate was higher in the water system with sediment than in that without sediment. In the second stage, the biodegradation rate was lower in the former than in the latter. In the last stage, the biodegradation rate was higher in the water system with sediment than in that without sediment. The presence of sediment could stimulate the growth of petroleum contaminant-degrading bacteria. Moreover, about 90% of the contaminants and bacteria were attached on the sediment. The sorbed contaminants on sediment could also be biodegraded by bacteria. The biodegradation of contaminants in water and sediment phases all fit well with the first-order kinetics, and the biodegradation rate constant in water phase was higher than that in sediment phase. However, as the contaminant concentration at the sediment phase was much higher than that in water phase, the biodegradation of petroleum contaminants mainly occurred at the sediment phase.     

SOAKER VISBREAK1NG OF SOME IRAQI RESIDUES

ABSTRACT

An attempt has been made to increase the fuel oil yield of two Iraqi residues using a soaker visbreaking process. This was carried out in a continuous laboratory scale unit at a range of mild conditions, namely, A20–A8O^°C and A3-109 sec. in the coil and 151–379 sec. in the soaker.

Physical properties of the products have been characterized and reported. The fuel oils obtained under the studied conditions remained stable compared with the original feedstocks. Furthermore, data on yield and characteristics of the different distillates from the visbroken products have been obtained. There was an increase in the distillates up to 350^°C (11%) for type A residue and (15%) for type B residue.     

Investigation of Molecular Weight and Aggregation of Asphaltenes in Organic Solvents Using Surface Tension Measurements

Abstract

The physico-chemical behavior of asphaltene is very useful to assist prediction and control the mechanisms of asphaltene deposition during the production of petroleum fluids. It has been realized that the first step in the formation of precipitated asphaltene particles is the self-aggregation mechanism to form colloidal particles or pseudo-micelles in several solvents. In this work, the critical micelle concentration (CMC) of two asphaltene fractions extracted from vacuum residues (VR) were obtained by surface tension measurements, using aromatic solvents. The molecular weight (1094-565 g/mol), calculated from average radii of the asphaltene molecules adsorbed at the air–solvent interface, are also in agreement with the values for small aggregates reported using small angle X-ray scattering.     

Formation Damage through Aqueous Phase Trapping: A Review of the Evaluating Methods

Abstract

Aqueous-phase trapping (APT) in many petroleum reservoirs is a significant mechanism of formation damage during drilling and production operations. Evaluating a reservoir's potential for APT is of great importance where the reservoir is susceptible to APT, because well productivity can be improved through proper evaluation and consequent attempts to reduce associated formation damage. During the last 15 years, a number of formulas have been proposed to evaluate APT. In this article, the first effective parameters on APT are presented. Then formulas for evaluating APT are reviewed. To demonstrate practical application of formulas, check the validity of each formula, and compare predictions made by different formulas, some reservoirs are considered.     

Behavior and Role of Asphaltenes in a Two-stage Fixed Bed Hydrotreating Process

Abstract

Residue upgrading processes are very important for the production of distillates and low sulfur fuel oils. Among those, fixed bed technologies are very efficient for deep desulfurization of petroleum residue heavy oils, even for highly asphaltenic feeds. This work analyzes the effects of the operating conditions on the evolution of asphaltenes and on their inhibition effect during the hydrodesulfurization reactions. Residue hydrotreating experiments were performed on a pilot plant and asphaltene fractions were investigated using size exclusion chromatography (SEC), ¹³C nuclear magnetic resonance (NMR), liquid chromatography, and elemental analyses. Besides the overall decrease in asphaltenes yield, significant changes in the average structure of the asphaltenes were also observed.     

DEPOSIT FORMATION DUE TO INSTABILITY AND CONTAMINATION OF RAW MATERIALS IN ALKALI-TREATED LIGHT DISTILLATES

Alkali treating of petroleum distillates is carried out to obtain the advantages of the product purity and to improve performance. The use and quality of alkaline solutions must be controlled since metal ions present as impurities can catalyze low temperature oxidation and polymerization of olefinic compounds; leading to formation of heavy emulsions which tend to deposit in hydrocarbon phases and eventually to block the handling systems. The effects of the variable factors “time, temperature, antioxidant and anticorrosion additives” were studied. The addition of a small amount of methanol was found to retard the deposit formation. This can be ascribed to ion-molecule reactions of methoxide ions with aryl and heavy thiols present in the light distillates. The promoting effects of light and the surrounding air on the stability of final treated product have been investigated.     

DETERMINATION OF ORGANIC SULFUR COMPOUND TYPES IN VACUUM GAS OILS USING GC-FID-SCD METHOD

ABSTRACT

The analyses of individual organic sulfur compounds in petroleum distillates are the key to understanding the kinetics of the chemistry involved in hydrodesulfurization, HDS. A sample of vacuum gas oil (VGO) produced commercially by distillation of treated atmospheric residue was analyzed by GC-FID-SCD method for individual organic sulfur compounds characterization and quantification. Dibenzothiophene and benzonaphthothiophene and their alkyl derivatives were found to constitute almost the entire organic sulfur compound range present in the VGO. Using a relationship between the total sulfur determined by “X-ray” and “Coulomax” methods and the composition of individual sulfur compounds determined by SCD, the quantity of those organic sulfur compounds present in VGO was estimated. Despite the limit in temperature raise (325°C) in the capillary column and that the range studied (346-555°C) is higher than those limits, optimum conditions were chosen to overcome those obstacles. From the analyses the behavior of refractory and unrefractory sulfur compounds in the VGO region can now be followed easily.     

Mild Hydrocracking—A Review of the Process,Catalysts, Reactions,Kinetics, and Advantages

Abstract

The demand for high quality middle distillates is increasing world wide while the demand for residue and fuel oil is decreasing. Hydrocracking is the major conversion process that meets the twin objectives of producing more middle distillates of very high quality. Since hydrocracking is a capital-intensive process, many refiners consider the option of converting their existing vacuum gas oil hydrotreating units into mild hydrocracking units. The use of mild hydrocracker bottom as FCC feedstock can improve the quality of FCC products. In view of the advantages of mild hydrocracking process, it is essential to understand the process, catalysts used, reactions, kinetics, and advantages. This article reviews recent literature on MHC process, various catalysts used, reactions involved and advantages of mild hydrocracking process in terms of improved product qualities and increased distillates. The kinetics of the mild hydrocracking process and kinetic challenges with respect to aromatic saturation have been summarized. The limitations of the process and future scope of work in this area are also discussed briefly.     

Aromatization Reaction of Liquefied Petroleum Gas

Abstract

The aromatization reaction of liquefied petroleum gas has been studied by using Huabei liquefied petroleum gas as raw material and LBO-A as catalyst, and the four lumped kinetics models network have been put up forward on the basis of lumped theory and the aromatization reaction mechanism. In the network, the aromatization reaction species were firstly lumped into C₄, propylene, low-molecular hydrocarbon, liquid, and coke. A mathematical method is first introduced to study on the product distribution of liquefied petroleum gas aromatization reaction. The results from experimental data are in accordance with the quantitatively analytical conclusions drawn from the calculated data.     

INVESTIGATION OF NITROGEN COMPOUND TYPES IN HIGH-BOILING PETROLEUM DISTILLATES FROM SAUDI ARABIAN CRUDE OILS

ABSTRACT

Acids, bases and neutral nitrogen compounds from high-boiling petroleum distillates were separated and further fractionated into fractions containing nitrogen compound types by HPLC on neutral alumina. Acids and bases were separated with anion and cation exchange resins respectively while the neutral nitrogen compounds were removed by complexation with ferric chloride supported on Attapulgus clay. The HPLC fractions were characterized by potentiometric titration for their basic and nonbasic nitrogen contents while infrared spectroscopy was used for the quantitative determination of major compound types present which are pyridines, pyrroles, amides, phenols and carboxylic acids. Characterization of individual nitrogen compounds was accomplished using gas chromatography and gas chromatography -mass spectrometry. The nitrogen compounds identified belong to three compound types which are pyridine, pyrrole and amide.     

Stability of Water-in-Crude Oil Emulsions: Effect of Oil Aromaticity,Resins to Asphaltene Ratio,and pH of Water

Abstract

The formation of tight water-in-oil emulsions during production and transport of crude oils is a great problem challenging the petroleum industry. Tremendous research works are directed to understanding the mechanism of formation, stabilization, and controlling of oil field emulsions. This article presents experimental results of some of the factors controlling the formation and stabilization of water-in-crude oil emulsions. In this study, asphaltenes and resins separated from emulsion samples collected from Burgan oil field in Kuwait have been used to study emulsion stability. Model oils of resin to asphaltene ratio of 5:1 and toluene-heptane mixtures have been used to study the effect of oil aromaticity on emulsion stability. Results indicate that at low toluene content (below 20%) or high content (above 40%) less stable emulsions are formed. At a threshold value of 30% toluene, a very tight model oil emulsion is formed. The effect of resins to asphaltene (R/A) ratio on stability of model oil has also been investigated. Results reported in this paper show that as the R/A increases the emulsions become less stable. The effect of pH on stability of model oil emulsion made of 50/50 heptane-toluene mixture having R/A ratio of 5:1 have been studied. Experimental results revealed that as the pH of the aqueous phase of model oil increased from 2 to 10, the emulsion became less stable. At high pH, the asphaltene particles are subjected to complete ionization leading to destruction of the water-oil interface and eventually breakdown of the emulsion.     

THE PRELIMINARY STUDY ABOUT THE COMPOSITION OF DAQING HEAVY FRACTION OIL

ABSTRACT

The family composition of Daqing heavy fraction oil and the latent content of lubricating oil by mass spectrography and slovent dewaxing methods were determined, and then compared with document data.The change of Daqing heavy distillate is discussed.The results show Daqing crude oil and its distillates have the trend to be heavier,but its heavy distillates are still suitable for catalytic stocks of heavy catalytic cracking and its residuum can be also used for the feed stocks and other wide uses. We hope the analysis results can provide scientific basis for refineries.     

KINETIC PARAMETERS OF HYDROPROCESSING REACTIONS IN A FLOW REACTOR

ABSTRACT

The change in distillation properties of a blend of light and heavy distillates over a commercial hydrotreating catalyst was studied using a small packed bed reactor. The results were interpreted assuming a pseudo-component model that took into account the physical and chemical complexity of the system. A first order series-parallel reaction mechanism was found to be valid for the operating conditions involved. Pore diffusion effects were also taken into consideration.