Hydrotreating the bitumen-derived hydrocarbon liquid produced in a fluidized-bed pyrolysis reactor

The pyrolysis of bitumen-impregnated sandstone produces three primary product streams: C₁---C₄ hydrocarbon gases, a C₅⁺ total liquid product, and a carbonaceous residue on the spent sand. The bitumen-derived hydrocarbon liquid was significantly upgraded relative to the native bitumen: it had a higher API gravity, lower Conradson carbon residue, asphaltene content, pour point and viscosity, and a reduced distillation endpoint relative to the native bitumen. The elemental composition was little different from that of the native bitumen except for the hydrogen content, which was lower. Thus, integration of the bitumen-derived liquid into a refinery feedstock slate would require that it be hydrotreated to reduce the nitrogen and sulphur heteratom concentrations and to raise the atomic hydrogen-to-carbon ratio. The bitumen-derived liquid produced in a fluidized-bed reactor (diameter 10.2 cm) from the Whiterocks tar sand deposit has been hydrotreated in a fixed-bed reactor to determine the extent of upgrading as a function of process operating variables. The process variables investigated included total reactor pressure (11.0–17.2 MPa (1600–2500 psig)); reactor temperature (617–680 K; (650–765 °F)) and liquid hourly space velocity (0.18-0.77 h⁻¹). The hydrogen/oil ratio was fixed in all experiments at 890 m³ m⁻³ (5000 scf H₂/bbl). A sulphided Ni-Mo on alumina hydrodenitrogenation catalyst was used in these studies. The extent of denitrogenation and desulphurization of the bitumen-derived liquid was used to monitor catalyst activity as a function of process operating variables and to estimate the extent of catalyst deactivation as a function of time on-stream. The apparent kinetics for the nitrogen and sulphur removal reactions were determined. Product distribution and yield data were also obtained.     

Pyrolysis of oil sand from the Whiterocks deposit in a rotary kiln

A rotary kiln reactor was evaluated for thermal recovery of oil from Utah oil sands. A series of continuous-flow pyrolysis experiments was conducted. Process variables investigated included temperature (748–848 K), solids retention time (10–27 min) and sweep gas flow rate (1.27–2.83 m_s³ h⁻¹). The results indicated that the pyrolysis temperature and the solids retention time were the two most important variables affecting the liquid and gas yields. The liquid yield (C₅⁺]) decreased and the gas yield (C₁–C₄) increased with increasing temperature. The liquid yield increased with decreasing solids retention time, while the gas yield decreased. No significant effect of the sweep gas flow rate on the product distribution and yields was observed. The quality of the bitumen-derived liquids was significantly better than that of the bitumen. A preliminary process kinetics model which conforms to the observed trends was proposed.     

Upgrading coal-derived liquids to diesel fuel

Distilled fractions of a coal-derived liquid from the H-Coal process were upgraded to diesel fuel by catalytic hydrotreatment. The total hydrotreated products were distilled into naphtha (<180°C) and diesel fuel fractions (>180°C) and the diesel fractions were analysed for hydrocarbon-type composition, hydrogen content and some diesel fuel properties. GC—MS-analyses were carried out on the hydrocarbon-type fractions to identify individual chemical compounds. To investigate the effect of different distillation cut points on diesel fuel yield and properties, cut points for one hydrotreated product were varied. The diesel fuel cetane numbers were correlated with percentage hydrogen, total aromatics and saturates. Cetane numbers above 40 were obtained for diesel fuels containing (i) more than 75% saturates, (ii) less than 15% total aromatics and (iii) a hydrogen content above 12.8%. Compounds identified by GC—MS-analyses (in the diesel fractions) were typical aromatic and cycloparaffin compounds. Normal-and iso-paraffin compounds were not detected. By varying the distillation cut point from 135 to 180°C, the cetane number of the residual diesel fraction improved from 37 to 44. This increase is ascribed to the removal of aromatic compounds in the 135–180°C boiling point range.     

Nitrogen compound distributions in hydrotreated shale oil products from commercial-scale refining

The distributions of nitrogen compounds in crude and hydrotreated shale oil products have been determined. About 11600 m³ (73000 bbl) of Paraho retorted shale oil were hydrotreated by The Standard Oil Company of Ohio at their Toledo refinery. A hydrotreated whole product, a jet fuel, a diesel fuel, and a residuum were produced and individually separated into compound-type fractions by adsorption chromatography. The nitrogen compound types in these fractions were characterized by i.r. spectroscopy, differential potentiometric titration, and high-resolution m.s. The distributions of nitrogen compound types and nitrogen base types in the hydrotreated products are compared with those in the Paraho retorted shale oil feedstock used in the hydroprocessing. The nitrogen compound types that were readily hydrodenitrogenated during commercial-scale refining are similar to nitrogen compound types removed during one-pass, bench-scale hydroprocessing.     

A novel method for oxidative desulfurization of liquid hydrocarbon fuels based on catalytic oxidation using molecular oxygen coupled with selective adsorption

The present study explored a novel oxidative desulfurization (ODS) method of liquid hydrocarbon fuels, which combines a catalytic oxidation step of the sulfur compounds directly in the presence of molecular oxygen and an adsorption step of the oxidation-treated fuel over activated carbon. The ODS of a model jet fuel and a real jet fuel (JP-8) was conducted in a batch system at ambient conditions. It was found that the oxidation in the presence of molecular oxygen with Fe(III) salts was able to convert the thiophenic compounds in the fuel to the corresponding sulfone and/or sulfoxide compounds at 25 °C. The oxidation reactivity of the sulfur compounds decreases in the order of 2-methylbenzothiophene > 5-methylbenzothiophene > benzothiophene  dibenzothiophene. The alkyl benzothiophenes with more alkyl substituents have higher oxidation reactivity. In real JP-8 fuel, 2,3-dimethylbenzothiophene was found to be the most refractory sulfur compound to be oxidized. The catalytic oxidation of the sulfur compounds to form the corresponding sulfones and/or sulfoxides improved significantly the adsorptivity of the sulfur compounds on activated carbon, because the activated carbon has higher adsorptive affinity for the sulfones and sulfoxides than thiophenic compounds due to the higher polarity of the former. The remarkable advantages of the developed ODS method are that the ODS can be run in the presence of O₂ at ambient condition without using peroxides and aqueous solvent and thus without involving the biphasic oil–aqueous-solution system.     

Supercritical fluid extraction of a crude oil, bitumen-derived liquid and bitumen by carbon dioxide and propane

Extractions of a crude oil, a bitumen-derived liquid and bitumen were conducted at several temperatures and pressures with carbon dioxide and propane in order to assess the effect of the size and type of compounds in the feedstocks on the extraction process. The pure-solvent density at the extraction conditions was not the only variable governing extraction, and the proximity of the extraction conditions to the pure-solvent critical temperature affected the extraction yields and the compositions of the extract phases. Higher oil yields were obtained at lower solvent reduced densities when the extraction temperatures were in the vicinity of the pure solvent critical temperature. In the crude oil and native bitumen extractions, as the extraction time and/or the extraction pressure increased, heavier compounds were found in the extract phases. This preferential extraction was not observed with the bitumen-derived liquid. The non-discriminatory extraction behaviour of the bitumen-derived liquid was attributed to its thermal history and to the presence of olefins and significant amounts of aromatics. Phase behaviour calculations using the Peng-Robinson equation of state and component lumping procedures provided reasonable agreement between calculated and experimental results for the crude oil and bitumen extractions, but failed to predict the bitumen-derived liquid extractions.     

Photodegradation of polycyclic aromatic hydrocarbons in fossil fuels catalysed by supported TiO2

This paper describes the photodegradation behavior of polycyclic aromatic hydrocarbons present in different types of fossil fuels (commercial diesel, Arabian light crude, heavy fuel oil from the Prestige oil spill and coal from an abandoned coal dump) suspended in artificial seawater or ultrapure water, under irradiation in a stirred photochemical reactor for 14 days. The reactor was continuously fed with air from a compressor at a constant rate of 6 NL h⁻¹, and thin films of TiO₂ (anatase) supported on pyrex glass raschig rings were used as catalyst. Dark control samples were carried out simultaneously for all the experiments, and both phases, aqueous and organic, were analyzed by gas chromatography–mass spectrometry in the experimental and dark control samples, allowing to calculate a photodegradation ratio. The polycyclic aromatic hydrocarbons reached a high degree of photodegradation in the water-soluble fraction of the samples, but the organic fractions remained almost unaffected in most of the experiments. Some photodegradation products have been also identified in the aqueous and organic fractions of the samples.     

Characterization of polynuclear aromatic hydrocarbons in bitumen,heavy oil fractions boiling above 350 °C by g.c.-m.s.

The separation and characterization of polynuclear aromatic hydrocarbons of five fractions of bitumen, heavy oils and synthetic fuels boiling > 350 °C were performed using a combination of Chromatographic techniques. The polynuclear aromatic hydrocarbon fractions were obtained by liquid-solid chromatography and prior to the high performance liquid chromatography and gas chromatography/mass spectrometry techniques, the fractions were subjected to an acid/base extraction procedure to remove polar material. In total, 97 polynuclear aromatic hydrocarbons were tentatively identified by a correlation of their mass spectra and retention indices with those of 25 model polynuclear aromatic compounds.     

The pyrolysis of scrap automotive tyres: The influence of temperature and heating rate on product composition

Shredded automotive tyre waste was pyrolysed in a 200 cm³ static batch reactor in a N₂ atmosphere. The compositions and properties of the derived gases, pyrolytic oils and solid char were determined in relation to pyrolysis temperatures up to 720 °C and at heating rates between 5 and 80 °C min⁻¹. As the pyrolysis temperature was increased the percentage mass of solid char decreased, while gas and oil products increased until 600 °C after which there was a minimal change to product yield, the scrap tyres producing approximately 55% oil, 10% gas and 35% char. There was a small effect of heating rate on the product yield. The gases were identified as H₂, CO, CO₂, C₄H₆, CH₄ and C₂H₆, with lower concentrations of other hydrocarbon gases. Chemical class composition analysis by liquid chromatography showed that an increase in temperature produced a decrease in the proportion of aliphatic fractions and an increase in aromatic fractions for each heating rate. The molecular mass range of the oils, as determined by size exclusion chromatography, was up to 1600 mass units with a peak in the 300–400 range. There was an increase in molecular mass range as the pyrolysis temperature was increased. FT-i.r. analysis of the oils indicated the presence of alkanes, alkenes, ketones or aldehydes, aromatic, polyaromatic and substituted aromatic groups. Surface area determination of the solid chars showed a significant increase with increasing pyrolysis temperature and heating rate.     

The distribution of sulfur compounds in hydrotreated jet fuels: Implications for obtaining low-sulfur petroleum fractions

The mechanism by which jet fuels are hydrotreated to reduce sulfur levels has some important implications in terms of the species and distribution of sulfur compounds remaining in the fuel. The species of sulfur that are most difficult to remove by hydrotreating, such as benzothiophenes and methyl- and dimethyl-benzothiophenes, are concentrated in the higher-boiling fraction of the fuel. Consequently, the lower-boiling fractions of the fuel contain much less sulfur. It may be possible, therefore, to obtain petroleum fractions that contain low levels of sulfur simply by distillation of the jet fuel into low-boiling and high-boiling fractions. A multi-element simulated distillation procedure according to ASTM D-2887, standard test method for boiling range distribution of petroleum fractions by gas chromatography, was coupled with atomic emission detection (GC-AED) and was used to estimate the sulfur concentration in various fractions of jet fuel, namely 20, 50, and 60%. The estimations of sulfur concentration were verified by comparing them to analyzed sulfur concentrations in several fractions of physical distillations of the jet fuels according to a modified ASTM D-86, standard test method for distillation of petroleum products at atmospheric pressure. Sulfur analyses showed that for all fuels analyzed, the initial 20% boiling fraction of the fuel contained no more than approximately 5% of the total sulfur concentration. The initial 50% boiling fraction of the fuel contained no more than 25% of the total sulfur concentration, and in most cases contained significantly less (8-16%). The total concentration of sulfur in the jet fuels tested ranged from 260 to 1380 μg/g, and there did not appear to be a direct relationship between total sulfur concentration and percentage of sulfur in each jet fuel boiling fraction.     

Kinetics of asphaltenes conversion during hydrotreating of Maya crude

The kinetics of asphaltene conversion was studied during the hydrotreating of Maya heavy crude oil. Experimental tests were conducted in a pilot plant at the following reaction conditions: total pressure of 70–100 kg/cm², liquid hourly space-velocity (LHSV) of 0.33–1.5 h⁻¹, and reaction temperature of 380–420 °C at a constant hydrogen-to-oil ratio of 5000 ft³/bbl. A commercial NiMo/Al₂O₃ catalyst was used in all experiments. Asphaltenes were precipitated from Maya crude and from hydrotreated products in a Parr Batch Reactor at 25 kg/cm² and 60 °C with n-heptane as solvent. Asphaltene hydrocracking data were used to estimate reaction orders and activation energy using a power-law model, and the average absolute error between experimental and calculated concentrations of asphaltenes was found to be less than 5%.     

Hydrotreating coal-derived liquid distillation fractions. 1. Study of single-stage treated products for transport fuel use

A coal-derived liquid distillate obtained from catalytic hydrogenation of Wandoan coal at Australian Coal Industry Research Laboratories has been fractionated into three main distillation fractions: naphtha, kerosine, and diesel. Compositional properties of each fraction are reported, particularly elemental, ¹H and ¹³C n.m.r. and h.p.l.c. results. Hydrorefining of each fraction was undertaken in a trickle-bed reactor at various conditions using commercial nickel-molybdenum hydrotreating catalysts. The hydrotreated liquid products were assessed for transport fuel use or as feedstocks for further processing.     

Effect of hydrotreating conditions on Maya asphaltenes composition and structural parameters

Hydrotreating of Maya crude was carried out in a pilot plant at different pressure, temperature and space-velocity, keeping constant the hydrogen-to-oil ratio. Pressure was varied in the range of 70–100 kg/cm², temperature between 380 and 420 °C, and space-velocity between 0.33 and 1.5 h⁻¹. Asphaltenes were precipitated from the feed and from hydrotreated products by using a batch reactor with n-heptane as solvent. Asphaltenes were characterized by elemental analysis, metals content, VPO aggregate molecular weight and NMR measurements. The effects of reaction conditions on asphaltene properties during hydrotreating are discussed in terms of changes in heteroatom contents and structural parameters.     

Characterization of phenols and indanols in coal-derived liquids: Use of Curie-point vaporization gas chromato-graphy/mass spectrometry

A combination of liquid chromatography, gas chromatography and mass spectrometry techniques was used to characterize (alkyl)hydroxyaromatic compounds in several coal liquefaction process fractions, including Exxon Donor Solvent (EDS) atmospheric bottoms and hydrotreated atmospheric bottoms. Solvent extraction failed to provide representative subfractions independent of overall sample composition. Satisfactory subfractionation was achieved by liquid chromatography with increasingly polar solvents on a silica gel column. Subfractions as well as parent samples were analysed by g.c.-m.s. using a Curie-point flash vaporization technique for splitless injection onto glass SCOT columns. C₀-C₆ alkylphenols and C₀-C₃ alkylindanols were almost completely recovered in the benzene/ether subfractions and were found to be the dominant hydroxyaromatic series in both liquids. Whereas phenol distributions were virtually identical in both samples, indanol distributions differed markedly, indicating strong differences in reactivity towards hydrotreatment. The possible role and origin of indanols, the only major class of hydroxyhydroaromatic compounds in these coal-derived liquids, is discussed.     

Quantitative characterization of coal properties using bidirectional diffuse reflectance spectroscopy

The 0.3–26 μm (33,000–385 cm⁻¹) reflectance spectra of the <45 μm fractions of a series of coal samples ranging from lignite to anthracite were analyzed in conjunction with compositional information to derive spectral–compositional–structural relationships. The reflectance spectra, particularly in the 1.8–4 μm (5500–2500 cm⁻¹) region exhibit a number of absorption features attributable to both the organic and inorganic components. Quantitative spectral–compositional relationships were found which permit the derivation of properties such as aromaticity, total aliphatic, aromatic content, moisture content, volatile content, fixed carbon abundance, fuel ratio, carbon content, nitrogen abundance, H/C ratio, and vitrinite reflectance. In general, all absorption bands become less intense, and overall reflectance decreases with increasing rank.     

Upgrading of middle distillate fractions of a syncrude from Athabasca oil sands

Current processes for upgrading bitumen from Athabasca oil sands produce synthetic crudes which are high in aromatics and deficient in hydrogen. As a consequence, middle distillate fractions derived from these syncrudes produce diesel fuels of low cetane number and jet fuels which are hydrogen deficient. Results obtained from bench-scale hydrotreating experiments indicate that quality fuels may be produced from Athabasca syncrudes. Middle distillate fractions from this source were subjected to high-severity hydroprocessing in a continuous-flow reactor unit using conventional hydrotreating catalysts which were pre-sulphided by a mixture of $\text{H}{}_2\text{H}{}_2\text{S}$. Aromatic hydrogenation at high temperatures and pressures was affected by the approach to thermodynamic equilibrium, however, at lower temperatures, in some cases virtually 100% saturation was achieved and treated fractions were found to meet cetane number and jet fuel smoke point requirements. Data treatment in the present study includes a model for the hydrogenation kinetics and correlations between aromatic carbon and fuel combustion properties.     

Compositional and structural variations of bitumen and its interactions with mineral matters during Huadian oil shale pyrolysis

Thermal bitumen is an important intermediate derived from kerogen decomposition during oil shale pyrolysis. In this study, free bitumen (FB) and bound bitumen (BB) were obtained by extracting oil shale chars (300–550 °C) before and after demineralization, and then analyzed by liquid chromatography fractionation, Fourier transform infrared spectroscopy, and gas chromatography/mass spectrometry. The FB yield first increased and then decreased with increasing temperature, and the maximum value was 2.10% at 400 °C. The decarboxylation of acids and decomposition of esters at 350–450 °C decreased the content of these compounds. Meanwhile, the intense cracking reactions of aliphatic compounds and alkyl chains at 400–450 °C decreased the carbon chain lengths and molecular weights of these compounds. From the analytical results obtained for the BB fractions, we suggest that some carboxylic acids or carboxyl group-containing compounds may be trapped on carbonate particles by the formation of Ca₂₊COO_? bonds, whereas other oxygenated compounds (e.g., esters and phenols) can be adsorbed preferentially by clay minerals through Lewis acid-base interactions.     

Production of gasoline range hydrocarbons from catalytic reaction of methane in the presence of ethylene over W/HZSM-5

The catalytic conversion of a methane and ethylene mixture to gasoline range hydrocarbons has been studied over W/HZSM-5 catalyst. The effect of process variables, such as temperature, percentage of volume of ethylene in the methane stream and catalyst loading on the distribution of hydrocarbons was studied. The reaction was conducted in a fixed-bed quartz-micro reactor in the temperature range of 300–500 °C using percentage of volume of ethylene in methane stream between 25 and 75% and catalyst loading of 0.2–0.4 g. The catalyst showed good catalytic performance yielding hydrocarbons consisting of gaseous products along with gasoline range liquid products. The mixed feed stream can be converted to higher hydrocarbons containing a high-liquid gasoline product selectivity (>42%). Non-aromatics C₅–C₁₀ hydrocarbons selectivity in the range of 12–53% was observed at the operating conditions studied. Design of experiment was employed to determine the optimum conditions for maximum liquid hydrocarbon products. The distribution of the gasoline range hydrocarbons (C₅–C₁₀ non-aromatics and aromatics hydrocarbons) was also determined for the optimum conditions.     

Hydrogen production by autothermal reforming of sulfur-containing hydrocarbons over re-modified Ni/Sr/ZrO2 catalysts

The catalytic autothermal reforming (ATR) of liquid hydrocarbons to provide hydrogen for mobile or stationary fuel cells was carried out over a Ni/Sr/ZrO₂ catalyst that is active for steam reforming (SR). The catalyst system was found to be active for the ATR reaction, although the hydrogen concentration obtained by ATR, under the conditions employed, was a little lower than that for SR. Addition of sulfur, introduced in the form of thiophene, reduced the catalytic stability of Ni/Sr/ZrO₂, even at 1073 K. The catalyst lifetime decreased with increasing sulfur concentration between 0 and 100 ppm. Additives for improving the sulfur-tolerance of Ni/Sr/ZrO₂ were examined, and additions of Re or La were found to be effective in improving the stability of the catalysts. The best catalyst was 5 wt.% Re–Sr/Ni/ZrO₂. This catalyst was used in the ATR of liquid hydrocarbon fuels such as commercial premium gasoline, hydrotreated FCC gasoline, reagent mixtures, and methylcyclohexane. For premium gasoline, the activity remained unchanged during 30 h, but then diminished rapidly. With the other fuels, however, the catalyst showed a much improved performance, indicating that the presence of sulfur could be associated with catalyst stability. ATR coupled with the water–gas shift reaction led to a reduction in the CO concentration by up to 2800 ppm. The catalyst's activity remained constant even after cold-start runs with 853–423–853 K temperature cycles under H₂O/O₂/N₂ conditions. Thus, the Re–Sr/Ni/ZrO₂ catalyst is effective for ATR of liquid hydrocarbon fuels. Further work is currently under way to extend the catalyst life.     

Desulfurization of commercial fuels by π-complexation: Monolayer CuCl/γ-Al2O3

Monolayer CuCl/γ-Al₂O₃ sorbent was studied for desulfurization of a commercial jet fuel (364.3 ppmw S) and a commercial diesel (140 ppmw S). The sorbent was prepared by means of spontaneous monolayer dispersion methods. Deep desulfurization (sulfur levels of <1 ppmw) was accomplished with this sorbent using a fixed-bed adsorber. The CuCl/γ-Al₂O₃ sorbent was capable of removing 6.4 and 11.2 mg of sulfur per gram for jet fuel at breakthrough (at <1 ppmw S) and saturation, respectively. The same sorbent was capable of removing 0.94 and 1.8 mg of sulfur per gram for BP diesel at breakthrough and saturation, respectively. The difference in sulfur capacities for jet fuel and diesel was apparently caused by the difference in concentrations of strongly binding compounds, such as nitrogen heterocycles, heavy (polynuclear) aromatics and fuel additives. In comparison with CuCl/γ-Al₂O₃, Cu(I)Y zeolite has higher sulfur capacities but is less stable and can be easily oxidized to Cu(II)Y by fuel additives (such as oxygenates) and moisture and consequently loses π-complexation ability. However, all these cuprous π-complexation sorbents selectively adsorb thiophenic compounds over aromatics and olefins (as predicted by the high separation factors), which resulted in the observed desulfurization capability. A feasibility study is shown for efficient regeneration of CuCl/γ-Al₂O₃ using ultrasound at ambient temperature. Possible problems associated with desulfurization using π-complexation sorbents for commercial fuels are discussed.