Showing papers in "Industrial & Engineering Chemistry Process Design and Development in 1983"

A versatile phase equilibrium equation of state

Abstract: The Soave modification of the Redlich-Kwong equation has been very effective for correlating the phase equilibrium of systems containing nonpolar and slightly polar substances. In this work further modifications are introduced which retain the simplicity and robustness of the Soave equation but extend its application to systems containing highly polar substances such as water. Applications shown in the work include systems of interest in coal processing and some common systems containing water.

Effects of potassium promotion on the activity and selectivity of iron Fischer-Tropsch catalysts

Abstract: A systematic study has been carried out of the effects of potassium promotion on the performance of alumina supported iron catalysts for Fischer-Tropsch synthesis. The results show that potassium promotion causes a decrease in Fe dispersion, an increase in the strength of CO chemisorption on reduced Fe, a decrease in the turnover frequency for total CO consumption, an increase in the average molecular weight and olefi to paraffin ratio of the products, and an increase in the water-gas-shift activity. The addition of potassium is also found to increase the rate of catalyst carburization. This process occurs more rapidly in a mixture of CO and H/sub 2/ than in CO alone.

Asphaltene cracking in catalytic hydrotreating of heavy oils. 2. Study of changes in asphaltene structure during catalytic hydroprocessing

Abstract: Characteristics in catalytic conversion of asphaltenes in petroleum heavy residues were studied in the hydrotreating process. A Boscan crude, an Athabasca bitumen, and a Khafji vacuum residue were tested as typical feedstocks. Various analyses were made to obtain the properties of asphaltenes before and after the reaction, e.g., changes of heteroatoms such as sulfur and metals, and decreases of molecular weight. The characteristic changes of asphaltene molecules were also investigated by electron spin resonance (ESR) and X-ray analyses. The association and coordination of vanadyl in asphaltenes were studied by the temperature dependence on the ESR spectra, and the sizes of the stacked crystallites and the aggregated asphaltene micelles were measured with X-ray diffraction and small-angle scattering. In the asphaltene cracking mechanism, it was clarified that the main reactions were the destruction of asphaltene micelles caused by vanadium removal and the depolymerization of asphaltene molecules by removal of heteroatoms such as sulfur.

Correlation and prediction of solid-supercritical fluid phase equilibriums

Abstract: A semiempirical correlation has been developed to describe quantitatively the solubility of heavy nonpolar solids in slightly subcritical and supercritical solvents using only one temperature-independent pure component parameter for each component. The method, based partly on regular solution theory and the van der Waals equation of state, correlates available solubility data for 24 binary solid-fluid systems within an average standard deviation of 25% with ethylene, ethane, and carbon dioxide as solvents. The range of solubility correlated was 10/sup -6/ to 10/sup -2/ mole fraction, 20-80 /sup 0/C, and 80-500 bar. Pure-component parameters for solutes are presented for naphthalene, anthracene, triphenylmethane, phenanthrene, fluorene, pyrene, 2,3- and 2,6-dimethylnaphthalene, biphenyl, hexamethylbenzene, and hexachloroethane along with solvent parameters for ethylene, ethane, and carbon dioxide.

Asphaltene cracking in catalytic hydrotreating of heavy oils. 1. Processing of heavy oils by catalytic hydroprocessing and solvent deasphalting

Abstract: A new catalytic hydrotreating process, the Asphaltenic Bottom Cracking (ABC) process, for heavy residual oils has been investigated in the relation between catalysis and chemical structure. A proprietary catalyst has been developed which is capable of hydrocracking asphaltenes into heptane-soluble materials and decreasing the vanadium content of heavy crudes and residues at a lower hydrogen consumption than a commercial hydrodesulfurization (HDS) catalyst and without change in activity in a six-month test. Various heavy feedstocks were tested in a catalytic reactor (ABC section) and a solvent deasphalting unit (SDA). Precipitated asphaltenes were recycled. Reactivities of various residues and a proposed mechanism are discussed. This ABC proces will be most useful as a step preceding an existing hydrocracking process in the upgrading of residues wit high asphaltenes and metals contents. In addition, the application of this technology is described.

Thermogravimetric determination of the coking kinetics of Arab heavy vacuum residuum

Abstract: The progressively heavier nature of available feedstocks has put a premium on efficient, low-cost refinery processes to convert residuum to lighter products. One such process is fluid coking, and the present study was undertaken to provide information on the coking kinetics of Arab Heavy vacuum residuum-a feed of commercial interest. The feed was first separated by solvent deasphalting and liquid-solid absorption techniques into four fractions asphaltenes, polar aromatics, aromatics, and saturates. Each of these fractions and the whole residuum were then subjected to nonisothermal kinetic analysis using thermogravimetry. Both weight loss and its first derivative were monitored as a function of temperature at heating rates ranging from 1 degree C/min to 20 degrees C/min. Activation energies and frequency factors were obtained at various conversion levels and in all cases were shown to increase with conversion. This strongly suggests the use of an activation energy distribution for future coking kinetic modeling.

Effects of cations on the rapid pyrolysis of a Wyodak subbituminous coal

Abstract: The effects of cations on product compositions from rapid pyrolysis of a Wyodak sub-bituminous coal were examined. Raw coal and demineralized coal in acid, Ca, Na and K forms were heated in helium at 1000 K/s to temperature of up to 1400 K, and yields of char, tar and individual gaseous volatile products were determined as a function of time-temperature history. Metal-ion form coals gave lower yields of tar and gaseous hydrocarbon volatiles than did the acid-form coal. CO/sub 2/ yields from acid-form coal reflected stoichiometric decomposition of carboxyl groups, while cation-form coals gave CO/sub 2/ yields that were considerably larger than those from demineralized coal, probably reflecting non-carboxyl coal oxygen decomposition via a metal carbonate intermediate. In all cases, Na and K ions had larger effects than did Ca ions.

Pyrite catalysis of coal liquefaction, hydrogenation and intermolecular hydrogen transfer reactions

Abstract: This work explores the effect of pyrite as a mineral catalyst on several types of reactions occurring in coal liquefaction. Both coal and model compound experiments were carried out. The effect of pyrite on the conversion of coal to preasphaltenes, asphaltenes, oils and gases was determined. Model compound experiments were used to investigate the role of pyrite in catalysing direct hydrogenation with molecular hydrogen. Pyrite was found to exert an influence on all of the reaction processes.

Recovery of ethanol from fermentation broths by catalytic conversion to gasoline

Abstract: The technical and economic feasibility of recovering ethanol from fermentation broths by catalytic conversion to gasoline was investigated Reactions of diethyl ether, ethanol, and aqueous 95 wt % ethanol over a shape-selective zeolite catalyst were studied in terms of product distributions, and the effects of pressure, temperature, and space velocity were established Higher pressure was found to decrease the amount of gaseous hydrocarbon produced, while increasing the space velocity had the opposite effect An optimum temperature of 623 K was found to maximize the amount of liquid paraffins and aromatics with a corresponding minimum in gaseous hydrocarbons No significant effect of the presence of water in the feed stream was observed A preliminary analysis revealed that the proposed process could offer significant economic advantages over traditional processes o ethanol recovery

Hydrocracking polycyclic hydrocarbons over a dual-functional zeolite (faujasite)-based catalyst

Abstract: Mixtures of two-, three-, and four-ring (naphthalene, phenanthrene, and pyrene) structures were hydrocracked over a nickel-tungsten sulfide ultrastable zeolite Y catalyst. The hydrocracking of tetralin and phenanthrene proceeds by elimination of butanes to form C/sub 6/ and C/sub 10/ hydrocarbons primarily. Isomerization of saturated six-member rings to methyl-substituted five-member rings is also prominent. The presence of 1-cyclohexyl-2-phenylethane in the products from phenanthrene hydrocracking suggests an alternative reaction path for the hydrocracking of structures containing adjacent saturated rings. Pyrene hydrocracking proceeds primarily by elimination of propane followed by butanes elimination, i.e., C/sub 16/ ..-->.. C/sub 13/ ..-->.. C/sub 10/ ..-->.. C/sub 6/. The C/sub 13/ intermediates are mostly hydrogenated phenalenes. The zeolite-based catalyst was very active in hydrocracking pyrene (critical diameter = 9 A) and smaller molecules. The perhydropyrene component of the feed mixture was relatively inert, but it could not be established whether this was due to a molecular sleve effect or intrinsic chemical kinetics factors.

Effect of catalyst properties and operating conditions on hydroprocessing of high-metals feeds.

Abstract: Catalytic hydroprocessing of high metals heavy oils, containing over 480 ppm Ni + V, was carried out in trickle bed pilot units. The analyses of the used catalysts (coke, metals content, and vanadium distribution) were correlated with the deactivation runs. The deactivation by coke is very much dependent on the catalyst physical properties (mean pore diameter), rather than on the chemical properties, and on the nature of the feed. As metals removal is a diffusion-controlled reaction, catalysts and operating conditions that increase the Thiele modulus, e.g., high activity and small pore catalysts, high hydrogen pressures and temperatures, show a stronger deactivation by feed metals. In this case, most of the vanadium was deposited in the outer edge of the catalyst particle. Unconventional vanadium profiles along the reactor length were obtained under certain conditions. Based on these data, a kinetic model was proposed which considers that demetallization is a complex reaction that occurs through a series of consecutive and parallel reactions.

Formation of clathrate hydrates in hydrogen-rich gases

Abstract: A hydrogen-rich gas obtained from the high-pressure separator system of the SRC-II process development unit was contacted with liquid water at pressures up to 975 psia and at temperatures below 48/sup 0/F. Test results showed that clathrate hydrates readily formed at these conditions and that the potential exists for the formation of clathrate hydrates in many coal conversion processes where high-pressure gas must be cooled to temperatures below approximately 72/sup 0/-80/sup 0/F. The currently used predictive model significantly underpredicts the experimental dissociation pressures, indicating that further studies of hydrate formation from hydrogen-rich gases are needed. This sensitivity to hydrate formation is strongly dependent upon composition; however, kinetic limitations do exist - for example, appropriate nucleation sites must be available - and in practice a gas stream must be subcooled before hydrate formation is initiated.