Showing papers in "Energy & Fuels in 1994"
TL;DR: In this article, X-ray photoelectron spectroscopy (XPS) was used to identify and quantify the organically bound nitrogen forms present in fresh Argonne Premium coals.
Abstract: X-ray photoelectron spectroscopy (XPS) was used to identify and quantify the organically bound nitrogen forms present in fresh Argonne Premium coals. XPS spectra obtained on a wide variety of model compounds were used to establish a curve resolution methodology. Pyrrolic nitrogen is the moat abundant form of organically bound nitrogen, followed by pyridinic types. Quaternary nitrogen species were also identified. An analysis of the sensitivity of XPS for primary amines indicates that these species are not detected at concentrations above 5 mol %. A trend of decreasing level of quaternary nitrogen forms along with increasing levels of pyridinic nitrogen was observed with increasing coal rank. The formation and reactivity of quaternary nitrogen forms in several coals were examined
282 citations
TL;DR: In this article, a thermogravimetric analysis of Avicel cellulose involving prolonged thermal pretreatments of small samples (0.5-3 mg) was performed.
Abstract: The widely accepted Broido-Shafizadeh model describes cellulose pyrolysis kinetics in terms of two parallel (competing) reactions preceded by an initiation step. In spite of the fact that many recent experimental results seem to contradict the predictions of the model, its validity has not been seriously questioned. In this paper we report thermogravimetric analyses of Avicel cellulose involving prolonged thermal pretreatments of small samples (0.5-3 mg). The weight loss curves were simulated by modern numerical techniques using the Broido-Shafizadeh and other related models. Results were not consistent with the presence of an initiation reaction, but they did strongly confirm the role of parallel reactions in the decomposition chemistry. A subsequent, high-temperature (370{degrees}C), pyrolytic degradation of solid intermediates formed below 300{degrees}C was also detected. In the absence of a prolonged thermal pretreatment, only one of the two parallel reactions can be observed. This reaction is first order, irreversible, and manifests a high activation energy (238 kJ/mol). The kinetic parameters of this reaction are not influenced by the large quantity of solid intermediates formed during prolonged, low-temperature thermal pretreatments, indicating that chemical processes are much more significant than the physical structure of the sample during pyrolysis.
229 citations
TL;DR: In this paper, a fluidized sand bed reactor was used to study the production of gases from polyethylene (HDPE) at five nominal temperatures (ranging from 500 to 900°C).
Abstract: A fluidized sand bed reactor was used to study the production of gases from polyethylene (HDPE) at five nominal temperatures (ranging from 500 to 900°C). Both HDPE primary decomposition and wax cracking reactions take place inside the reactor. Yields of 13 pyrolysis products (methane, ethane, ethylene, propane, propylene, acetylene, butane, butylene, pentane, benzene, toluene, xylenes, and styrene) were analyzed as a function of the operating conditions. The results are compared with the data obtained by pyrolysis of HDPE in a Pyroprobe 1000, where secondary wax and tar cracking is small. Correlations between the products analyzed with those of methane are discussed.
174 citations
TL;DR: In this article, surface oxygen complexes formed during carbon gasification with oxygen were studied by combining diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy with transient kinetic (TK) and temperature programmed desorption (TPD) techniques.
Abstract: Surface oxygen complexes formed during carbon gasification with oxygen were studied by combining diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy with transient kinetic (TK) and temperature programmed desorption (TPD) techniques. It was found that lactone (and/or acid anhydride), carbonyl, and ether type complexes are formed on the carbon surface during gasification. The complexes which desorbed during the TK experiment were not detected with DRIFT. However, the complexes which are responsible for the CO 2 and CO evolution in TPD were successfully identified with these combined techniques: CO 2 desorption at around 900 K originates from the decomposition of lactone and/or acid anhydride, whereas CO desorption is mainly from carbonyl and ether type complexes
156 citations
137 citations
131 citations
TL;DR: In this article, a pitch-based active carbon fiber of rather small surface area was found to enhance markedly the activity to allow the conversion of 82% in dry, 65% in 80% relative humidity (rh) and 21% in wet (100% rh) air, respectively, at 25°C by W/F of 1.0 × 10% g min mL −1.
Abstract: Catalytic oxidation of NO (400 ppm) into NO 2 was studied over active carbon fibers at room temperature to trap the unreacted NO as well as the oxidized product in forms of nitric acid or its salts to develop an oxidative removal of NO in the flue gas. The heat treatment of a particular pitch-based active carbon fiber of rather small surface area was found to enhance markedly the activity to allow the conversion of 82% in dry, 65% in 80% relative humidity (rh) and 21% in wet (100% rh) air, respectively, at 25°C by W/F of 1.0 × 10% g min mL −1 . The rate of oxidation was examined by varying humidity to reveal marked decrease of the activity above 80% rh. The strong retardation by humidity of the activity of as-received fiber was moderated by the heat treatment of the fiber at 800°C.
112 citations
TL;DR: In this article, the Conradson carbon residue, the standard measure of coking tendency, is a linear function of hydrogen content for petroleum molecules with molecular weights greater than 700 amu and the cumulative properties of the distillable liquid products of the thermal conversion of residua are independent of conversion.
Abstract: Residua macromolecules can be approximated by various combinations of two building blocks that are linked by thermally labile bonds. The pendant building block is volatile when cracked off the rest of the residua molecule while the core building block remains nonvolatile. This simple model explains why the Conradson carbon residue, the standard measure of coking tendency, is a linear function of hydrogen content for petroleum molecules with molecular weights greater than 700 amu and why the cumulative properties of the distillable liquid products of the thermal conversion of residua are independent of conversion. In addition, the model provides a basis for calculating the change in the total Conradson carbon residue with processing of residua, including that it is unaltered by separation, decreased by hydroconversion and increased by thermal conversion.
105 citations
TL;DR: In this article, a high-density polyethylene was thermally cracked in both a closed tubing-bomb reactor at 450-500 °C and an open system using the same reactor at 480 °C.
Abstract: A high-density polyethylene was thermally cracked in both a closed tubing-bomb reactor at 450-500 °C and an open system using the same reactor at 480 °C. In the closed system, distillate yield increased at a higher temperature which also accelerated the formation of gases and coke. Secondary reactions such as saturation, isomerization, cyclization, and aromatization were found at high severity. In contrast, the open system produced less naphtha but more gas oil. Compositionally, the distillates contained more olefins, less saturates, and very little aromatics, compared with those from the closed system. Pyrolytic waxy products from polyethylene were catalytically cracked in a fixed-bed reactor at 470 and 510 °C, respectively. High yields of gasoline of improved quality and liquefied petroleum gas were obtained along with a small amount of low-value products such as dry gas, heavy cycle oil and coke.
97 citations
TL;DR: In this article, the ability of water and water-based metal salt additive systems to upgrade bitumen and determine the chemical mechanisms of observed reactions was examined and the results showed that water had only a minimal effect in preventing formation of insolubles from Peace River bitumen but did result in reduction of the amount produced in similar treatments of Cold Lake bitumen.
Abstract: The objectives of this study were to examine the ability of water and water-based metal salt additive systems to upgrade bitumen and determine the chemical mechanisms of observed reactions. These experiments were conducted on Peace River and Cold Lake bitumens and consisted of thermal treatments (375-415° C) with and without water and with aqueous solutions of iron or ruthenium chlorides in the same temperature range. Little reaction was observed when either bitumen was heated dry or with water at 375° C but significant conversion to insoluble products was observed at higher temperatures. Water had only a minimal effect in preventing formation of insolubles from Peace River bitumen but did result in reduction of the amount of insolubles produced in similar treatments of Cold Lake bitumen
95 citations
TL;DR: In this article, coal-free direct-liquefaction experiments with coal were performed with and without the presence of coal under typical direct liquefaction conditions (420-450°C, 60 min reaction time, 800 psig of H 2 cold).
Abstract: Polyethylene (PE), poly(ethylene terephthalate) (PET), polypropylene (PPE), and actual plastic wastes from such items as milk jugs, soft drink bottles, plastic wraps, plastic flatware, etc., have been successfully converted to oil in direct liquefaction experiments with coal. Comparative experiments were performed with and without the presence of coal under typical direct liquefaction conditions (420-450°C, 60 min reaction time, 800 psig of H 2 cold). Two types of catalysts were used: highly dispersed iron-based catalysts, and an HZSM-5 zeolite catalyst. Using PE, PPE, PET, and a mixed waste plastic with the zeolite catalyst, oil yields of 80-98% and total conversions of 90-100% were obtained at liquefaction temperatures of 420-430°C
TL;DR: A new distributed activation energy model (DAEM) is developed using Weibull distribution to mathematically represent the kinetics of complex thermal transformations and a grid search procedure to estimate the kinetic parameters represented by the DAEM is developed.
Abstract: A new distributed activation energy model (DAEM) is developed using Weibull distribution to mathematically represent the kinetics of complex thermal transformations. Also developed is a grid search procedure to estimate the kinetic parameters represented by the DAEM. This procedure uses approximate analytical solutions to the time-temperature integrals of DAEM. These approximations reduce the computational efforts involved in parameter estimation substantially and allow rapid analysis of the three-dimensional error surface of the objective function over a wide range of kinetic parameters while retaining the true nonlinearity of the model. The existence of multiplicity ― a number of sets of kinetic parameters which describe the observed data, generally within the limits of experimental accuracy ― is also demonstrated using experimental data on kerogen decomposiiton
TL;DR: In this paper, zinc ferrite and zinc titanate were developed as regenerable sorbents capable of removing hydrogen sulfide from hot coal-derived fuel gases, but zinc tends to be reduced to the metallic state under coal gasification conditions resulting in loss of capacity and activity by volatilization of reactive surfaces.
Abstract: In earlier studies, zinc ferrite and zinc titanate were developed as regenerable sorbents capable of removing hydrogen sulfide from hot coal-derived fuel gases. Manganese ore as well as manganese carbonate, precipitated from aqueous solutions, combined with alumina to form indurated pellets is shown to hold promise of being a highly-effective, inexpensive, regenerable sulfur sorbent for hot fuel gases. Although the thermodynamics for sulfur removal by manganese predicts somewhat higher hydrogen sulfide overpressures than can be accomplished with zincbased sorbents, zinc tends to be reduced to the metallic state under coal gasification conditions resulting in loss of capacity and activity by volatilization of reactive surfaces. This volatilization phenomenon limits the temperatures to which desulfurization can be effectively accomplished to less than 550°C for zinc ferrite and 700°C for zinc titanate, whereas, manganese-based sorbents can be utilized at temperatures well in excess of 700°C
TL;DR: In this article, the authors developed molecular representations for Ratawi and ANS asphaltenes using 13 C and H NMR techniques, which differ from the "average structures" given previously in that a molecular weight is not assumed for the ''average molecules''.
Abstract: Asphaltenes are a class of molecules that are defined by the conditions of their insolubility in a particular solvent, such as heptane. A better understanding of the molecular properties of this mixture of molecules is needed in order to understand the mechanisms of coke and sludge formation during refinery upgrading operations. In this work we develop molecular representations for Ratawi and ANS asphaltenes using 13 C and H NMR techniques. These representations differ from the «average structures» given previously in that a molecular weight is not assumed for the «average molecules».
TL;DR: In this article, computer-assisted structure elucidation and molecular simulations presented in this report suggest that the biopolymer is not random but may have an helical structure that is characteristic of many naturally synthesized molecules.
Abstract: The biopolymer lignin, an important constituent of terrestrial plants whine chemistry and reactivity are of great importance in many areas of energy research and industry, is thought to be biosynthesized through a random polymerization. Computer-assisted structure elucidation and molecular simulations presented in this report suggest that the biopolymer is not random but may have an helical structure that is characteristic of many naturally synthesized molecules
TL;DR: The use of the term "kerogen" has been extended to include all nonsoluble solid organic matter in sedimentary rocks as mentioned in this paper, originally defined as the organic component of coal and later extended to oil shale.
Abstract: The use of the term «kerogen», originally described as the organic matter in oil shale, has been extended to include all nonsoluble solid organic matter in sedimentary rocks. Kerogen is divided into «types» based on elemental composition and potential maturation path. «Maceral» nomenclature, originally developed to describe the organic components of coal, has also been extended to source rocks and, later, oil shale. The extension and overlap of these two fields creates problems as attested to by the proliferation of vitrinite terminology and the application of the term vitrinite to organic matter that is not clearly derived from woody tissue. Other problems include the fundamental complex and wide-ranging nature of Type II kerogen which is now acknowledged to be a highly heterogeneous material.
TL;DR: In this article, the thermodynamics of coal swelling are considered in light of various correlations of coal swellability with solvent properties. And it has been found that coal swelling is a strong function of the electron-donating capacity of the solvents, as measured by two very different scales, i.e., the enthalpy of interaction of specific interaction sites in the coal that determine the maximum extent of swelling, though there is the possibility of nonspecific interactions contributing to further swelling, beyond this ''titration end point''.
Abstract: The thermodynamics of the coal swelling process is considered in light of various correlations of swellability with solvent properties. It has been found that the swellability of coals in specifically interacting solvents is a strong function of the electron-donating capacity of the solvents, as measured by two very different scales. The two scales are seen to be closely related. The swelling also correlates with the heat of immersion of coals in solvents, and thus it appears that it is the enthalpy of interaction of specifically interacting solvents with surface functionalities in coal that mainly determines swelling behavior. There is generally a particular number of specific interaction sites in the coal that determine the maximum extent of swelling, though there is the possibility of nonspecific interactions contributing to further swelling, beyond this «titration end point»
TL;DR: In this article, the results of hydrocracking experiments performed on a vacuum residue of Belaym crude in the presence of molybdenum naphthenate (MoN) as hydrogenation catalyst precursor and conducted in batch mode within a wide range of operating conditions and catalyst loading.
Abstract: This paper discusses the results of hydrocracking experiments performed on a vacuum residue of Belaym crude in the presence of molybdenum naphthenate (MoN) as hydrogenation catalyst precursor and conducted in batch mode within a wide range of operating conditions and catalyst loading. The influence of severity on product distribution and quality is described as well as a kinetic analysis of the data. Results of this work demonstrate that the in-situ decomposition of MoN generates micrometer-sized particles of very active hydrogenation catalysts molybdenum disulfide utilizing the sulfur present in the feedstock.
Journal Article•
TL;DR: In this paper, a probabilistic method for the representation of the molecular components of heavy resid feedstocks is introduced, which describes resid molecule attributes in terms of quantitative probability density functions, optimized by comparison of the properties of Monte Carlo-constructed molecules with experimental measurements.
Abstract: A novel probabilistic method for the representation of the molecular components of heavy resid feedstocks is introduced. The method describes resid molecule «attributes» in terms of quantitative probability density functions, optimized by comparison of the properties of Monte Carlo-constructed molecules with experimental measurements. Both molecular distributions and averages are provided.
TL;DR: In this paper, SO 2 was adsorbed, oxidized, hydrated, and recovered continuously as aqueous H 2 SO 4 at 30-100°C on a poly(acrylonitrile)-based active carbon fiber (PAN-ACF-FE-300) SO 2 of 1000 ppm in a model flue gas was removed completely for longer than 60 h at 30 and 50°C.
Abstract: SO 2 was adsorbed, oxidized, hydrated, and recovered continuously as aqueous H 2 SO 4 at 30-100°C on a poly(acrylonitrile)-based active carbon fiber (PAN-ACF-FE-300) SO 2 of 1000 ppm in a model flue gas was removed completely for longer than 60 h at 30 and 50°C by W/F = 50 × 10 −3 g min mL −1 by supplying sufficient humidity of 10 and 20 vol%, respectively The heat treatment of the ACF at 800°C was found very effective to enhance the catalytic activity, the temperature appearing very best between 30 and 1000°C A pitch-based activated carbon fiber exhibited less activity than PAN-ACF
TL;DR: In this article, the authors used biomarkers, organic petrography, and characterization of the source rock facies to determine the most likely candidate source rock for the Paleozoic oils of Saudi Arabia.
Abstract: The Paleozoic petroleum system of the Central and Northern Provinces of Saudi Arabia contains one of the most prolific oil-prone source rocks of Silurian age worldwide, the Qusaiba shale of the Qalibah Formation. This source rock is responsible for charging the large, gentle structures of the Central Province with billions of barrels of light, sweet, crude oil. Organic geochemical methods such as biomarkers, organic petrography, and characterization of the source rock facies have been used to determine the most likely candidate source rock for the Paleozoic oils of Saudi Arabia. By using detailed extract and oil characterizations, the basal «hot» shales of the Qusaiba Member of the Silurian Qalibah Formation have been correlated to the oils reservoired in the Permian sands of the Central Province of Saudi Arabia.
TL;DR: In this article, the authors describe gasification tests with wood in a continuous bench scale fluidized bed reactor but with no added air or oxygen in the region of 500-700°C and at short gas contact times, using a crystalline nickel aluminate catalyst.
Abstract: Various kinds of catalysts are being developed and tested for the pyrolytic gasification of biomass using the Waterloo Fast Pyrolysis Process (WFPP) technology. The present report describes gasification tests with wood in a continuous bench scale fluidized bed reactor but with no added air or oxygen in the region of 500-700°C and at short gas contact times, using a crystalline nickel aluminate catalyst. The objective was to determine the most appropriate operating conditions for this catalyst and its performance for the production of a synthesis gas in high yields. Experiments were carried out with this catalyst in both inert and reactive gasification media, but without any oxygen or air addition. The results show the influence of the catalyst on the nature of the gasification products and the effect of operating variables
TL;DR: In this article, the results of a study carried out on a suite of samples from the Silurian Qusaiba Member of the Qalibah Formation in Saudi Arabia were evaluated in order to determine how the vitrinite-like reflectance of graptolites and chitinozoans (zooclasts) relates to other organic geochemical data.
Abstract: Petrographic and geochemical results of a study carried out on a suite of samples from the Silurian Qusaiba Member of the Qalibah Formation in Saudi Arabia were evaluated in order to determine how the vitrinite-like reflectance of graptolites and chitinozoans (zooclasts) relates to other organic geochemical data. The sample set includes a range of maturities from immature (≤ 0.5% VRe) to post-oil-expulsion mature (0.9-1.0% VRe) as determined from pyrolytic data (T max from Rock-Eval pyrolysis), thermal alteration index (TAI), and liptinite fluorescence. Data compiled in this study indicate that the reflectance values measured on graptolite and chitinozoan fragments were higher than equivalent vitrinite reflectance based on other geochemical maturity indicators.
TL;DR: In this article, the effect of experimental conditions on the deep hydroconversion (up to 90 %) of an heavy oil residue (Safaniya) in the presence of dispersed catalysts is reported.
Abstract: A comparative study of the effect of experimental conditions on the deep hydroconversion (up to 90 %) of an heavy oil residue (Safaniya) in the presence of dispersed catalysts is reported. Severe thermal conditions are required to obtain a high conversion level. With molybdenum naphthenate as catalyst precursor, a low metal concentration (0.02 wt %) and a moderate hydrogen pressure level (7.5 MPa at cold) are efficient to maintain a low coke yield (2 wt %). In contrast to molybdenum naphthenate, a higher amount of phosphomolybdic acid is needed to achieve the same result. The reason for its weaker catalytic activity was attributed to a lower sulfidation state of the Mo catalyst, as outlined by physical characterization of the catalyst (XRD, HREM, STEM-EDX).
TL;DR: Kerogen has been isolated from Green River oil shale by dissolving the minerals in HF and HCI and also by using aqueous ammonium sulfate as mentioned in this paper, and the resulting kerogen samples were swollen in 28 different solvents.
Abstract: Kerogen has been isolated from Green River oil shale by dissolving the minerals in HF and HCI and also by using aqueous ammonium sulfate. The resulting kerogen samples were swollen in 28 different solvents. The volumetric solvent swelling of the kerogen roughly follows the predictions of regular solution theory for almost all of the solvents including good hydrogen bond acceptors. The solubility parameter from the swelling studies is close to that calculated from Siskin's structure. Hydrogen bonding does not seem to be an important factor because good hydrogen bonders show swellings similar to non-hydrogen bonders of similar solubility parameter. The inorganic content of the isolated kerogen does not have a large effect on solvent swelling. Samples containing 42% inorganics generally swell somewhat more than samples containing 5% inorganics. The cross-link density of this kerogen is high.
TL;DR: In this paper, a statistical approach to predict petroleum resid structure composition using Monte Carlo method is presented, and a comparison between experimental and analytical data give very good results with very good performance.
Abstract: This paper presents a statistical approach to predict petroleum resid structure composition using Monte Carlo method. A comparison between experimental and analytical data give very good results
TL;DR: In this article, the phase transformation of multicomponent aluminosilicates on liquidus curves becomes an important parameter in the prediction of the slag behavior upon cooling, and three major factors are taken into consideration: (1) thermodynamic driving forces for a selection of stable phases, such as free energies of components at various temperatures, (2) the effect of free energy of mixing on the tendency to phase segregation in liquid solution, and (3) free energy change at the solid-melt interface and entropy of fusion and their effects on the morphology of the crystalline phase
Abstract: The phase transformation of multicomponent aluminosilicates on liquidus curves becomes an important parameter in the prediction of the slag behavior upon cooling. Three major factors are taken into consideration: (1) thermodynamic driving forces for a selection of stable phases on liquidus curves, such as free energies of components at various temperatures, (2) the effect of free energy of mixing on the tendency to phase segregation in liquid solution on cooling, and (3) free energy change at the solid-melt interface and entropy of fusion and their effects on the morphology of the crystalline phase(s). In order to identify the solid phase(s) crystallized from ash slag it is proposed, first, to calculate major binary free energy composition diagrams based on major oxides in ash and, second, to select phase(s) with the free energy and composition constrained by free energy diagrams.
TL;DR: In this paper, a kinetic model was developed to represent the catalytic cracking of heavy oil from waste plastics by rare-earth metal exchanged Y-type (REY) zeolite to produce gasoline.
Abstract: A kinetic model was developed to represent the catalytic cracking of heavy oil from waste plastics by rare-earth metal exchanged Y-type (REY) zeolite to produce gasoline. The influences of reaction conditions on the product distributions were previously reported by us. On the basis of these results, a reaction pathway was proposed and a set of differential equations was developed. The kinetic parameters were determined by nonlinear least-squares regression of the experimental data. These parameters were found to be proportional to the amount of strong acid sites of the used catalysts. The calculated values of the product distribution were found to be in good agreement with the experimental data