Showing papers in "Preprints-American Chemical Society Division of Petroleum Chemistry in 2004"

Characterization of carbon deposited on Pt/alumina catalyst during reforming of liquid hydrocarbons

Abstract: Abstract Temperature-programmed oxidation (TPO), Raman spectrometry, and X-ray photoelectron spectroscopy (XPS) are used to characterize coke species deposited on a 0.61 wt% Pt/alumina catalyst for three reactions, carried out separately: partial oxidation (POX), steam reforming (SR), and autothermal reforming (ATR). Three individual compounds were used as simulants of liquid fuels in each of these three reactions: tetradecane, decalin, and 1-methylnaphthalene. The TPO profiles of the coke showed that partial oxidation and steam reforming resulted in generally greater coke deposition than autothermal reforming for each of the fuels. 1-Methylnaphthalene produces more coke than the other fuels in each of the reactions. Coke appears to be deposited both on the metal and the support, with the coke on the metal being more easily oxidized by TPO. Raman spectroscopy shows that there is no significant change in the carbon crystallite size on any of the catalysts; all are within the range of 1.45–1.83 nm. XPS analysis of carbon deposited during partial oxidation of tetradecane shows that small amounts of graphitic carbon (C/Al ratio

Composition of Syntroleum S-5 and Conformance to JP-5 Specification

Abstract: : The US Military uses JP-8/JP-5/Jet A-1 fuel. JP-8 is identical to Jet A-1 except that it contains additives required by the military. JP-8 differs from JP-8 only in that it has a slightly higher flash point. A synthetic JP-5 fuel products by Syntroleum Corporation, S-5, differers from petroleum-derived jet fuels in that it has much lower normal paraffin concentration and it does not contain any detectable S, N, or O compounds or aromatics. Despite these compositional differences, S-5 conforms to all JP-5 specification requirements for the chemical and key physical properties evaluated, except the density; S-5 density was slightly lower than the minimum density required. One other key requirement for JP-5 states that, The feed stock from which the fuel is refined shall be crude oils derived from petroleum, tar sands, oil shale, or mixtures thereof. Fuels such as S-5. synthesized from feed stocks other than those allowed, do not conform to the JP-5 specification in this regard.

Methane hydrate formation and dissociation in a partially saturated sand

Abstract: To predict the behavior of hydrate-bearing sediments and the economic extractability of natural gas from reservoirs containing gas hydrates, we need reservoir simulators that properly represent the processes that occur, as well as accurate parameters. Several codes are available that represent some or all of the expected processes, and values for some parameters are available. Where values are unavailable, modelers have used estimation techniques to help with their predictions. Although some of these techniques are well respected, measurements are needed in many cases to verify the parameters. We have performed a series of experiments in a partially water saturated silica sand sample. The series included methane hydrate formation, and dissociation by both thermal stimulation and depressurization. The sample was 7.6 cm in diameter and 25 cm in length. In addition to measuring the system pressure and temperatures at four locations in the sample, we measured local density within the sample using x-ray computed tomography. Our goals in performing the experiment were to gather information for estimating thermal properties of the medium and to examine nonequilibrium processes.

Production and characterization of synthetic jet fuel produced from Fischer-Tropsch hydrocarbons

Abstract: : The U.S. Military has initiated a project to evaluate jet fuel, produced from natural gas by processes developed by Syntroleum Corporation, for use in all military equipment capable of using either diesel fuel or jet fuel. A synthetic Single Battlefield Fuel would need to meet a wide range of specifications and in-use requirements before it would be accepted as a fuel by the military. The Syntroleum process for fuel production includes unique Autothermal Reforming of methane, reaction of the produced synthesis gas over cobalt catalyst to produce linear hydrocarbons of various chain lengths, and conversion of this feedstock into isoparaffinic fuel to meet the physical and chemical requirements per MIL-DTL-5624T for JP-5 Aviation Turbine Fuel. Syntroleum synthetic jet fuel produced for evaluation by DOD has an average carbon number of 13.2 and contains relatively little normal paraffins with proportionally lower normal paraffins at higher carbon numbers.

Sasol Slurry Phase Distillate semi-synthetic aviation turbine fuel

Abstract: Semi-synthetic aviation turbine fuel was approved in 1999 under British Aviation Turbine Fuel Defence Standard 91-91 (DEF STAN 91-91) specifications with certain limitations including that the synthetic kerosene should be derived solely from products of the (high temperature) Fischer-Tropsch process. With Sasol Slurry Phase Distillate (SPD) fuel, a low temperature Fischer-Tropsch derived fuel composed only of normal and iso-paraffins, the objective of this study was to evaluate the utilization of a light Sasol SPD kerosene fraction as a semi-synthetic aviation turbine fuel blending component like its high temperature Fischer-Tropsch counterpart. Sasol SPD diesel fuel was fractionated targeting the freezing point requirement for Jet A-1. With Sasol SPD fuel containing no aromatics, the Sasol SPD kerosene fraction was blended with sweetened and severely hydrotreated crude derived kerosene to demonstrate a semi-synthetic aviation turbine fuel conforming to Jet A-1 requirements. The compositional properties, volatility, fluidity, combustion, lubricity and thermal stability requirements for semi-synthetic aviation turbine fuel were met with up to 50 vol-% Sasol SPD kerosene blends.

Organic matter models of oil shale revisited

Abstract: This work revisits the chemical structure models of the organic material in Rundle Ramsey Crossing and Green River oil shale reported by Siskin et al. [1] by comparing them with recently obtained direct characterization data from solid state 13 C NMR, XPS and sulfur XANES methods. The results presented herein quantitatively confirm many of the chemical structural features for hydrocarbon, nitrogen, oxygen and sulfur chemical structures in the organic matter models. Minor differences were found in the average aromatic ring size and heteroatom structures.

Physical and chemical properties of fully synthetic aviation turbine fuel from coal

Abstract: Semi-Synthetic aviation turbine fuel has been in use now for 5 years in South Africa as commercially approved aviation turbine fuel. The approval of synthetic hydrocarbons in aviation turbine fuel is currently limited by Defence Standard 91-91 to a mixture of 50 volume% maximum, with petroleum derived aviation turbine fuel making up the balance. The production of a fully synthetic aviation turbine fuel at the Sasol Synfuels plant in Secunda, South Africa was investigated. Four synthetic kerosene component streams produced by the Sasol plant can be blended to produce an aviation turbine fuel that meets the specification requirements for Jet A1 as given by ASTM D1655 and Defence Standard 91-91. The streams originate form High Temperature Fischer-Tropsch synthesis and hydrocracked tar liquid. Four synthetic kerosene blends were blended to represent a range of possible aviation turbine fuels that meets the specification requirements for Jet Al. The synthetic blends were compared with petroleum derived aviation turbine fuel, demonstrating close resemblance to typical Jet A1.

State-of-the-art monitoring of fuel acidity

Abstract: Development of a novel Iridium oxide based acidity sensor for off-line monitoring of the acidity of fuel is described. The sensor works in the potentiometric mode using an IrO x electrode as an indicating electrode and a Ag/Ag + electrode as a reference electrode. The data show that the IrO x sensor responds to compounds present in fuel that have acid-base character. An off-line IrO x sensor would allow the determination of the acidity of different fuels and the discrimination between neat and thermally stressed fuels. Experimental results also indicate that the low conductance of fuel and / or the material used for sensor encapsulation may influence the response time of the IrOx sensor.

Magnetic separation of iron catalysts from Fischer-Tropsch wax

Abstract: This paper describes recent work in magnetic separation of precipitated iron catalysts particles from Fischer-Tropsch wax at 260 °C in fields up to 0.2 Tesla employing a novel magnetic micro-particle separator (MM-PS patent pending) adapted from an earlier continuously operating magnetic particle separator (CO-MPS) described elsewhere. The MM-PS is scaled up by a factor of 29 from the bench scale CO-MPS. In processing nominal 20-25 wt% catalyst slurries, it has operated at a product rate of 7950 liters per day (Lpd) while producing concentrations as low as 0.35 wt% solids with filtration rates up to 250 kg/min/m 2 . The upper limit of the filtration rate is not known. The MM-PS is designed to achieve isobaric and isothermal separation of the bulk of the catalyst for immediate return to the Fischer-Tropsch reactor. Catalyst concentrations of 100 ppm were obtained employing a second stage batch operated HGMS. While the feed to the first stage exhibited strongly magnetic behavior, the product of HGMS was diamagnetic.

Regeneration of cobalt-based slurry catalysts for Fischer-Tropsch synthesis

Abstract: During Fischer-Tropsch synthesis the cobalt catalyst deactivates with time-n-stream. In commercial-scale plants, catalyst cost can be a considerable proportion of the overall operating cost. A regeneration method specifically for cobalt-based Fischer-Tropsch slurry catalyst has been developed at Syntroleum that successfully recovers the catalyst activity. In most cases, the catalyst activity following regeneration is higher than that of the fresh catalyst, even after several consecutive regeneration cycles. Starting from the first cycle regeneration, the irrecoverable cyst activity loss through sequential regeneration is marginal, typically less than 2% per cycle when demonstrated in lab scale fixed-bed reactors. The regeneration method involves the oxidation of the spent catalyst to remove carbonaceous deposits through combustion while converting the catalyst to the oxide form, followed by hydrogen reduction. The introduction of a catalyst regeneration capability substantially improves the economic competitiveness of a Fischer-Tropsch process.

Catalytic decarboxylation for naphthenic acid removal from crude oils: A theoretical and experimental study

Abstract: A combined effort of theoretical and experimental study to develop a catalytic decarboxylation process to remove naphthenic acids from crude oils is presented. Among the various solid catalysts tested, MgO exhibits the high reactivity towards the decarboxylation reaction of both saturated and aromatic model naphthenic acid compounds at temperature range from 150 to 250 °C for a 4-hour reaction duration. In the presence of Ag 2 O, the CO 2 yield well matches the acid conversion and the decarboxylation product, naphthalene, was also detected. This identified the occurrence of a direct catalytic decarboxylation. Theoretical DFT calculations predict the attacking of the hydroxy group on the ortho- position of the aromatic ring is a key step with a transition barrier of ∼30kcal/mol and this is in consistent with our experimental observations.

Reduction of NOx emissions from FCCU regenerators with additives

Abstract: Environmental emissions, particularly NO x emissions, have been a growing concern for refiners in recent years. NO x emissions from the regenerator are primarily derived from nitrogen in the coke. This work describes the development of active oxides as catalysts for reduction of NO x . Chemisorption of NO was used as a screening tool to measure and rank performance of metal oxides. The fresh capacity, and more importantly the hydrothermal stability of the chemisorption capacity, of the oxides were considered. Performance of these active oxides formulations were also evaluated during regeneration of spent FCC catalyst in a fluid bed. The resulting materials reduced FCCU NO x in full burn regeneration by as much as 30–70%.

The effectiveness of deasphalted oil in the stability of visbroken Athabasca bitumen

Abstract: The production of heavy oils and bitumen in Alberta is increasing and a significant portion of these materials will be transported to the United States by pipeline. However, the pipeline transportation of these extra-heavy oils is difficult because of their high viscosities (>100,000 cPs). Partial upgrading of bitumen by thermal processes such as visbreaking results in improvements in viscosity and other properties. Product stability is also an important issue during pipeline transportation. Thermal processing of bitumen, such as by visbreaking, forms less soluble asphaltenes that may precipitate to form solid sediments. In this paper we present the results on the effectiveness of virgin deasphalted oil (C 5 -DAD) derived from Athabasca bitumen on the stability of Athabasca visbroken products. We demonstrate that DAO is not a very good stabilizing agent, especially at low concentrations, for stabilization of asphaltenes.