MECHANISMS OF SYNFUEL DEGRADATION. I. EFFECTS OF ORGANIC NITROGEN COMPOUNDS ON THE STABILITY OF A SHALE DERIVED DIESEL FUEL

ABSTRACT

A reliable accelerated fuel stability teat regimen has been developed and applied to the study of the storage stability of a shale derived diesel fuel marine (DFM). The results of a survey of nitrogen compounds as dopants in a stable shale DFM base fuel indicate that 3ome pyrroles and indoles may play significant roles in storage stability. A complete stability test matrix has been developed for the temperatures of 43, 65 and 80°C, for time periods between A and 179 days, and for a ten-fold concentration range of a model dopant, 2,5-dimethylpyrrole (DMP). Stability was defined by the amount of total insoluble material (filterable sediment and adherent gum) produced after stress, and also by the amount of titratable peroxide present in the filtrates of stressed fuel samples. A very regular pattern for insolubles formation was found within the test matrix. Deposit formation rates exhibited a first-order dependence on DMP concentration, with an apparent activation energy of 11-12 kcal/mol. The sediment was found to contain 12% nitrogen and 18-20% oxygen irrespective of the stress conditions employed.     

FUEL INSTABILITY STUDIES: REACTION OF POLAR NITROGEN HETEROCYCLES DERIVED FROM A STABLE SHALE FUEL

Abstract

The degradation of middle distillate fuels with increasing time in storage is a continuing problem. Model systems have defined both the scope and the chemical types of molecules that are Implicated in fuel deterioration. To gain insight into a real fuel system, nitrogen-rich extracts have been isolated from a marginally stable shale derived middle distillate fuel and added as a dopant to a stable base fuel in order to induce instability reactions. Alkyl substituted pyridines, tetrahydro-quinolines, quinolines, and indoles were the prevalent classes of compounds present in the extract. The effects of this added extract were examined in terms of sediment formation and peroxide number under accelerated storage stability test conditions. The activity of the extract in inducing fuel instability was correlated with its nitrogen heterocylic composition.     

Letter to the Editor: Improving the Stability of Diesel Fuel from Heavy Oil Catalytic Cracking

Abstract

Diesel fuel has the potential to form sediment during storage as a result of fuel instability. The cause is due to the presence of unstable components such as unsaturated hydrocarbon compounds and non-hydrocarbon compound. Other effects such as light, oxygen, temperature, and the catalytic action of metals also play a role.

In order to improve the stability of diesel, we have studied the potential for stabilizers to mitigate the formation of the precipitate. Experimental results show that stabilizers can effectively decrease the content of unstable components in diesel fuel, and improve the stability of storing, and have a beneficial effect on the stability of the fuel.     

NITROGEN COMPOUND DISTRIBUTION AND FUEL INCOMPATIBILITY REACTIONS IN A TAR SAND DERIVED MIDDLE DISTILLATE FUEL

A high paraffin, high nitrogen, low sulfur jet fuel derived from Athabasca tar sands was studied. The organo-nitrogen compounds in the fuel were isolated by mild acid extraction followed by silica-gel adsorption. Three extracts were derived from this fuel: a basic nitrogen compounds extract, BNC, in methylene chloride, a non-basic nitrogen compounds extract, NBNC, in methyl alcohol and an NBNC extract in methylene chloride. The major constituents of each extract were identified and quantitated by combined capillary column GC/MS. Alkyl substituted pyrroles, pyridines, indoles, tetrahydro-quinolines, carbazoles, and quinolines were the prevalent organo-nitrogen compounds present. Incompatibility tests were conducted on this fuel using the oxygen overpressure method with both doped and undoped fuel systems. The dopant of choice was cumene hydroperoxide. Practically no sediment formation was observed for the undoped fuel (0.1 mg/100mL fuel). The doped fuel matrix induced incompatibility behavior in proportion to the quantity of dopant present.     

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.     

THE IMPACT OF [60]FULLERENE ON JET FUEL STABILITY

ABSTRACT

The use of Buckminsterfullerene (C₆₀) has been investigated as a jet fuel deposit inhibitor. Based on deposit reductions observed in accelerated storage stability tests of marine diesel fuels, it was hoped that fullerenes would produce similar reductions in thermal deposits. It was found, however, that the most profound impact of the fullerene was to photosensitize the fuel towards formation of high levels of hydroperoxides. Although this may not necessarily be occurring via free radical autoxidation, the rapid formation of hydroperoxides would constitute a likely autoxidation initiator.     

MECHANISMS OF SYNFUEL DEGRADATION. I. EFFECTS OF ORGANIC NITROGEN COMPOUNDS ON THE STABILITY OF A SHALE DERIVED DIESEL FUEL

A reliable accelerated fuel stability teat regimen has been developed and applied to the study of the storage stability of a shale derived diesel fuel marine (DFM). The results of a survey of nitrogen compounds as dopants in a stable shale DFM base fuel indicate that 3ome pyrroles and indoles may play significant roles in storage stability. A complete stability test matrix has been developed for the temperatures of 43, 65 and 80°C, for time periods between A and 179 days, and for a ten-fold concentration range of a model dopant, 2,5-dimethylpyrrole (DMP). Stability was defined by the amount of total insoluble material (filterable sediment and adherent gum) produced after stress, and also by the amount of titratable peroxide present in the filtrates of stressed fuel samples. A very regular pattern for insolubles formation was found within the test matrix. Deposit formation rates exhibited a first-order dependence on DMP concentration, with an apparent activation energy of 11-12 kcal/mol. The sediment was found to contain 12% nitrogen and 18-20% oxygen irrespective of the stress conditions employed.     

CHARACTERIZATION AND STABILITY PROPERTIES OF POLAR EXTRACTS DERIVED FROM A RECENT SHALE LIQUID

ABSTRACT

A shale fuel of marginal stability has been used as a source of nitrogen-rich polar extracts. Polar compounds were isolated by mild acid extraction followed by silica gel adsorption and were identified by GC/HS. Alkyl substituted pyridines were the prevalent class of compounds present in most extracts. The effects of adding these shale derived fractions as dopants to a stable shale diesel fuel (0-11) were examined in terms of sediment formation and peroxide number under accelerated storage stability test conditions. The activities of the extracts in inducing fuel instability were correlated with their composition.     

Analysis and Research on the Cause of Tanker Contaminating Jet Fuel

Abstract

Through a lot of research on the issue that qualified jet fuel became unqualified jet fuel after tanker transportation and a period of storage. By X-ray photoelectron spectroscopy surface analysis of corroded silver strip and silver strip corrosion test, doctor test, determination of mercaptan sulfur, analysis of sulfur and nitrogen content, test of pickling and alkaline wash and laundering, the mercury wash test and silver nitrate experiments of polluted jet fuel, indicated that silver corrosion resulted from sulfide corrosion, H₂S, SO₂, SO₃, sulfuric acid, acid esters, and other corrosive sulfides were not contained in polluted jet fuel, the corrosive substance in jet fuel was sulfur. The tank inner surface of polluted jet fuel was determined according to GB/T14265-93, the sulfur content in the rust of the tanker inner surface was 1.05% by carbon and sulfur analyzer. Adding the rust into qualified jet fuel, the external situation of tanker transportation was simulated, silver strip corrosion level exceeded 3, which demonstrated that elemental sulfur in the rust dissolved in jet fuel slowly to result in unqualified silver strip corrosion.     

FUEL INSTABILITY STUDIES: THE REACTION OF 3-METHYL INDOLE WITH ARYL SULFONIC ACIDS

ABSTRACT

Incompatibility reactions in middle distillate fuels can be ascribed to the presence of specific polar heteroatomic compounds or species containing oxygen, sulfur, and nitrogen. It has been proposed that the observed sediment and/or gum formation results from the interaction of heteroatomic species with the acids contained in fuels. Recent studies have shown that the addition of non-basic nitrogen heterocycles such as indoles to a fuel increases deposit formation dramatically. Therefore, an attempt was made to identify the structure of the sediment. This paper reports on the reaction of 3-methyl indole with aryl sulfonic acids. The results of this study were accomplished by identifying the nature and the structure of the sediments formed using elemental analysis and various instrumental techniques.     

FUEL INSTABILITY 1: ORGANO-SULFUR HYDROPEROXIDE REACTIONS

ABSTRACT

Instability in middle distillate fuels continues to be a problem. Instability is usually defined in terms of sediment formation and increases in peroxide species. There is a growing body of evidence that heteroatomic species, organo-sulfur, nitrogen and oxygen compounds are intimately involved in this deposition process. This is a two part review of the recent literature on middle distillate fuel instability as related to these heteroatomic species.     

FUEL INSEVHELETY 2: ORGANO-SUIHJR HYEKDEERDXIDE REACTIONS

Abstract

Instability in middle distillate fuels continues to be a problem. Instability is usually defined in terms of sediment formation and increases in peroxide species. There is a growing body of evidence that heteroatomic species, organo-sulfur, nitrogen and oxygen compounds are intimately involved in this deposition process. This is a two part review of the recent literature on middle distillate fuel instability as related to these heteroatomic species.     

Removing Organic Nitrogen Compounds From Middle Distillate Fuels with a Catalyst Used as a Filtering Media

Abstract

Fuel storage instability reactions of middle distillate fuel continue to be of great interest to the Department of Defense. Unlike civilian fuel, military fuel typically remains in storage tanks for one or more years. As fuel is removed from these tanks, the tanks are subsequently filled with more recently purchased fuel. In many cases, the mixed fuel is not compatible, resulting in chemical sediment and sludge formation. This fuel incompatibility can result in chemical degradation reactions that form solids that will plug nozzles and filters and render the entire contents of the storage tank unusable. Previous research has shown that polar organic nitrogen functional groups are involved in fuel instability reactions. These organo-nitrogen compounds are difficult and expensive to completely remove during the refining process; hence, this investigation involved the removal of these compounds employing three heterogeneous catalyst systems and combinations of these systems as filtering media. An unstable fuel was treated separately with Sc₂O₃, Cu/Sc₂O₃, fullerene (F), a 1:1 ratio of Sc₂O₃:(F), and a 1:1 ratio of Cu/Sc₂O₃:(F). The composition of the filtrates after filtering with the different catalytic systems was analyzed by combined gas chromatography/mass spectrometry (GC/MS). The results of this study showed that after treating the fuel with the catalyst systems, the organic nitrogen compounds detected in the extract were 0.29% carbazoles, 18.2% indoles, and 1.0% for both pyrroles and tetrahydroquinolines, and neither pyridines nor quinolines were detected. This investigation showed that scandium oxide, which is a recycled catalyst, is capable of removing organic nitrogen compounds from fuels.     

Examination of Liquid-Phase Oxidation of Jet Fuel at Operational Temperatures

Abstract

To gain a more complete understanding of the relevance of laboratory testing to predict fuel stability in advanced jet engine designs, the Navy single tube reactor (STR) was employed to examine the impact of copper contamination on fuel oxidation at fuel temperatures closer to operational limits. Oxygen consumption during autoxidation, in the presence of dissolved copper, was similar in both the STR and the standard jet fuel oxidation test at higher temperatures, although differences in flow rates and residence times were evident. By contrast, copper was innocuous in promoting the formation of thermal deposits at lower temperatures in the STR, up to approximately 170°C, after which rapid deposition occurred. This deposition was accompanied by depletion of copper in the fuel, except in the presence of selected additives. In addition to suppressing oxidation, limiting available oxygen also suppressed copper depletion. The findings of this study indicate that as bulk fuel design temperatures continue to increase, copper contamination may begin to be a greater factor in contributing to the accumulation of deleterious thermal deposits within advanced jet engine fuel systems. However, the results also indicate that additives containing metal deactivators could play a useful role in mediating the impact of copper contamination on thermal deposition within fuel system components.     

CHARACTERIZATION OF POLAR EXTRACTS FROM TWO PETROLEUM-DERIVED FUELS

Abstract

Petroleum fuels of marginal stability have been used as a source of nitrogen-rich polar extracts. Polar compounds were isolated by mild acid extraction followed by silica gel adsorption. The extracts were characterized and identified by combined capillary column GC/MS. Both fuels were studied by two methods under accelerated storage conditions, bottle tests and oxygen overpressure. Bottle tests were conducted at 80°C for 14 days and the oxygen overpressure at both 65 and 43°C for 6 days and 4 weeks respectively. Filterable insolubles and adherent gum were measured for both methods. Peroxide numbers were determined by ASTM D3703-85 for both stressed and original fuel samples.     

CHEMICAL BASIS OF MIDDLE DISTILLATE FUEL INSTABILITY: Interactive Effects of Selected Nitrogen Heterocycles with Organic Bases in a Shale-Derived Diesel Fuel.

ABSTRACT

Fuel instability reactions are defined in terms of the formation of deleterious products such as filterable sediments and peroxides. Gravimetric stability tests have been carried out at 80^°C using two model nitrogen heterocycles: 2,5-dimethy1pyrrole, DMP, and 3-methylindole, 3-MI, in an otherwise stable shale derived middle distillate fuel. Potential interactive effects for these model nitrogen heterocycles have been described by the presence of organic base co-dopants. Organic bases employed included: tri-n-butylamine, N, N-dimethyl-aniline, and 4-dimethylaminopyridine. Simple organic amines exerted only minor interactive effects, usually an increase in filterable sediment in the range of 5–15%. However, the diamine species, 4-dimethylaminopyridine, interacted in a strong positive fashion to generate increased amounts, 22–44%, of sediment.     

FUEL INSTABILITY STUDIES: REACTION OF POLAR NITROGEN HETEROCYCLES DERIVED FROM A STABLE SHALE FUEL

The degradation of middle distillate fuels with increasing time in storage is a continuing problem. Model systems have defined both the scope and the chemical types of molecules that are Implicated in fuel deterioration. To gain insight into a real fuel system, nitrogen-rich extracts have been isolated from a marginally stable shale derived middle distillate fuel and added as a dopant to a stable base fuel in order to induce instability reactions. Alkyl substituted pyridines, tetrahydro-quinolines, quinolines, and indoles were the prevalent classes of compounds present in the extract. The effects of this added extract were examined in terms of sediment formation and peroxide number under accelerated storage stability test conditions. The activity of the extract in inducing fuel instability was correlated with its nitrogen heterocylic composition.     

Letter to the Editor: Improving the Stability of Diesel Fuel from Heavy Oil Catalytic Cracking

Diesel fuel has the potential to form sediment during storage as a result of fuel instability. The cause is due to the presence of unstable components such as unsaturated hydrocarbon compounds and non-hydrocarbon compound. Other effects such as light, oxygen, temperature, and the catalytic action of metals also play a role.

In order to improve the stability of diesel, we have studied the potential for stabilizers to mitigate the formation of the precipitate. Experimental results show that stabilizers can effectively decrease the content of unstable components in diesel fuel, and improve the stability of storing, and have a beneficial effect on the stability of the fuel.     

EFFECT OF CLAYS AND ADSORBENTS ON THE NITROGEN CONTENT AND THE STABILITY OF JET FUELS

The effect of composition, surface area and pH of different clays and alumina adsorbents on the stability of jet fuel was studied. The stability of jet fuel was tested following the ASTMD 3241 procedure. Under the batch adsorption conditions, clays and adsorbents were not effective in adsorbing polar molecules and improving the stability of jet fuels. Under the column adsorption conditions, the effectiveness of clays and adsorbents in improving the stability of jet fuel was found to vary. Clays having a high surface area and an acidic pH were found to be more effective in adsorbing polar molecules and improving the stability of jet fuel. High surface area alumina adsorbents were found effective in adsorbing basic nitrogen molecules and improving the stability of jet fuel despite having a basic pH. The basic type nitrogen compounds, pyridines and quinolines, were found to affect the stability of jet fuel. The initial effluent jet fuel passed through fresh clays was found to have no N compounds and a good stability. However, the analysis of effluent jet fuel showed a gradual increase in N content reaching the level of N content in untreated jet fuel. The effluent jet fuel reaching 9-10 ppm of N content failed the stability test indicating that clays need to adsorb and retain N compounds. The adsorbent capacity of different clays was studied but no significant difference in retaining N molecules was observed.     

EFFECT OF CLAYS AND ADSORBENTS ON THE NITROGEN CONTENT AND THE STABILITY OF JET FUELS

The effect of composition, surface area and pH of different clays and alumina adsorbents on the stability of jet fuel was studied. The stability of jet fuel was tested following the ASTMD 3241 procedure. Under the batch adsorption conditions, clays and adsorbents were not effective in adsorbing polar molecules and improving the stability of jet fuels. Under the column adsorption conditions, the effectiveness of clays and adsorbents in improving the stability of jet fuel was found to vary. Clays having a high surface area and an acidic pH were found to be more effective in adsorbing polar molecules and improving the stability of jet fuel. High surface area alumina adsorbents were found effective in adsorbing basic nitrogen molecules and improving the stability of jet fuel despite having a basic pH. The basic type nitrogen compounds, pyridines and quinolines, were found to affect the stability of jet fuel. The initial effluent jet fuel passed through fresh clays was found to have no N compounds and a good stability. However, the analysis of effluent jet fuel showed a gradual increase in N content reaching the level of N content in untreated jet fuel. The effluent jet fuel reaching 9–10 ppm of N content failed the stability test indicating that clays need to adsorb and retain N compounds. The adsorbent capacity of different clays was studied but no significant difference in retaining N molecules was observed.