Showing papers in "Preprints-American Chemical Society Division of Petroleum Chemistry in 2002"

MCM-41-supported CO-MO catalysts for deep hydrodesulfurization of light cycle oil : Sulfur removal from gasoline and distillate streams

Abstract: Abstract Light cycle oil (LCO), a by-product of the fluid catalytic cracking (FCC) process in a petroleum refinery, can be used as a blendstock for the production of diesel and jet fuels. Regulatory and operational issues result in need for new and more active catalysts for the deep hydrodesulfurization (HDS) of diesel feedstocks, such as LCO. This paper reports the activity of a mesoporous molecular sieve MCM-41-supported Co-Mo catalyst in comparison to a commercial γ-alumina (Al2O3)-supported Co-Mo catalyst for the desulfurization of a LCO with a sulfur content of 2.19 wt.%. The HDS of dibenzothiophene, 4-methyldibenzothiophene, and 4,6-dimethyldibenzothiophene—polyaromatic sulfur compounds present in LCO—and their relative reactivities in terms of conversion were examined as a function of time on stream in a fixed-bed flow reactor. The MCM-41-supported catalyst demonstrates consistently higher activity for the HDS of the refractory dibenzothiophenic sulfur compounds, particularly 4,6-dimethyldibenzothiophene. The presence of a large concentration of aromatics in LCO appears to inhibit the HDS of the substituted dibenzothiophenes.

The role of asphaltene solubility and chemistry on asphaltene aggregation : Conversion chemistry of petroleum residua

Abstract: Asphaltenes (n-heptane insolubles and toluene solubles) from a variety of crude oils were fractionated in mixtures of heptane and toluene and analyzed chemically, by vapor pressure osmometry (VPO), and by small angle neutron scattering (SANS). Solubility profiles of the asphaltenes and their sub-fractions indicated strong cooperative asphaltene interactions of a particular sub-fraction that is polar and hydrogen bonding. This sub-fraction had lower H/C ratios and modestly higher N, V, Ni, and Fe contents than the less polar and more soluble sub-fraction of asphaltenes. Number average molar masses by VPO in toluene indicated that the most polar, least soluble sub-fraction was aggregated (>10,000 g/mol) while the more soluble fractions approached monomer dimensions (∼2,000 g/mol) at high dilution. Neutron scattering studies showed that the most polar, least soluble sub-fractions formed aggregates considerably larger than both the whole asphaltenes and their more soluble sub-fractions. Aggregate sizes were calculated using the Guinier method and by fitting the scattering data to Lorentzian lineshapes. The less soluble samples were fit to a Lorentzian lineshape with an additional power law term to account for intense scattering due to flocs in the low wave vector (Q) range. Correlation lengths obtained from the Lorentzian models are quantitatively proportional to the radius of gyration obtained from Guinier analysis by a scale factor of 1.62. Aggregate size of the asphaltenes and their sub-fractions increased with decreasing solvent aromaticity up to the solubility limit, beyond which the aggregate size decreased with heptane addition. The presence of the low Q feature in the scattering curves at 25°C indicated that the individual aggregates were flocculating. The intensity of the low Q feature was diminished upon heating of the samples to 80°C. The asphaltenes were dissociated into even smaller aggregates with the addition of a more polar solvent, such as 1-methylnaphthalene. A detailed picture of SANS information on distributions of asphaltenes in a variety of solvents will be presented.

The short contact time resid test; a novel tool for realistic FCC catalysts evaluations in the laboratory : Cracking chemistry and mechanisms in pretroleum processing

Abstract: With the introduction of zeolites in Fluid Cracking Catalysts the catalyst activity could be substantially increased and more coke selective cracking was obtained. The higher catalyst activity made short contact time cracking possible. Innovations in catalyst assembly technology and functional ingredients to selectively convert very large molecules and increase catalyst activity retention have accelerated the introduction of large quantities of residual hydrocarbon feeds to Fluid Catalytic Cracking Units. Thanks to amongst others above mentioned catalyst innovations short-contact time cracking and the cracking of very heavy resid are nowadays widely applied. Testing of Fluid Cracking Catalysts however was until recently largely done in small -scale test units having catalyst contact time of more than 10 seconds. Obviously, for the further development of improved catalysts, testing should be done at conditions, which closely match the ones found in real commercial applications. In this paper a novel activity and selectivity performance test, developed especially for residual hydrocarbon feed, and having a short injection time of about 1 second is presented.

Complex palladium nickel catalysts: Influence of the nickel on the palladium performance

Abstract: Utilizing an improved method for adding of a non-precious promoter to the precious PdIC in the hydrogenation of benzoic acid, new understanding has been obtained concerning regeneration of deactivation Pd/C catalyst, and an improved process has been completed. The improved process can remove the conventional technical defect for hydrogenation of benzoic acid that the catalyst activity was reduced within a relatively short period of time and the ratio of palladium recovered from the spent catalyst is low. Furthermore, according to this process, cyclohexane carboxylic acid (CCA) can be produced advantageously on a commercial scale at a high selectivity and yields with a prolonged catalyst life.

Modification of the automated flocculation titrimetry (AFT) procedure applied to SHRP asphalts : Separation and characterization of petroleum

Abstract: A modification of the automated flocculation titrimetry test has been developed. In this procedure, which is a modified Heithaus procedure, the entire analysis is performed in a single vial instead of four different vials. Heithaus parameters p., p o , and P obtained by the modified procedure are not identical with those obtained by the classical method. The p, values obtained by the two methods are directly related. For most asphalts, p o and P values also are directly related. In the case of two asphalts, there is no correlation between p o and P values. These two asphalts are not conventional paving materials, one being air-blown and the other having unusually low amounts of asphaltenes. The p a values obtained by the new procedure may prove to be more useful than the p, values obtained by the earlier reported method.

Toward common generalized phase diagrams for asphaltene containing hydrocarbon fluids : Conversion chemistry of petroleum residua

Abstract: Introduction Many hydrocarbon liquids of industrial interest from reservoir fluids to bitumen + diluent mixtures share constituents, from asphaltenes and resins to pentane, and can be classified as asymmetric from a phase behavior perspective. The phase diagrams for these asymmetric fluids are characterized by lenses of four-phase behavior surrounded by three and two regions in both P-x at constant T, and P-T at constant x diagrams. Interest in the phase behavior of reservoir fluids focuses on understanding the impact of phase behavior on flow assurance, risk assessment and other reservoir fluid management issues at temperatures ranging form 270 K to 470 K and pressures ranging from atmospheric to ~ 100 MPa. Until recently, the focus within the heavy oil and bitumen extraction and upgrading sector has been at temperatures greater than 650 K and at pressures ranging from atmospheric to 20 MPa where catalyst coking, line plugging and other refining issues are key applications. Renewed interest in the development of preprocesses for the selective elimination of mineral matter and other undesirable constituents from heavy oil has heightened interest in ROSE like separation processes which have operating conditions and compositions overlapping with those arising in reservoir fluids. Despite this overlap the two literatures remain disparate. Much can be gained by combining achievements from both sectors particularly with respect to the asphaltene deposition issue, a hot topic for both sectors. Qualitative four component phase diagrams can be used to illustrate key features present in the phase diagrams for the entire range of fluids and can provide a sound basis for detailed mathematical model development. This concept will be introduced and discussed using examples drawn from both the reservoir fluids and bitumen + diluent mixtures.