Nickel and vanadyl porphyrins were separated from atmospheric residue of Canadian oil sand bitumen by solvent extraction and column chromatography and then subjected to noncatalytic thermal process under hydrogen. The petroporphyrins before and after thermal process were characterized by UV–vis spectroscopy and positive-ion electrospray ionization FT-ICR mass spectroscopy to probe their structural transformation. Three main vanadyl porphyrins, including N4VO, N4VOS, and N4VO2 and a fraction of N5VO2 are identified in the feed fraction. With time increasing, the relative abundance of CnH2n–28N4VO (DBE = 17) increases initially and then decreases, in contrast with CnH2n–26N4VO (DBE = 18). It suggests the hydrogenation and rapid hydrogenolysis of petroporphyrins. The carbon number shifts to the lower mass range with increased process severity, indicating extensive thermal cracking reactions of petroporphyrins have occurred. N4VOS porphyrins show very similar variation of DBE and carbon number distribution as N4VO. A considerable proportion of new types of N4VO2, N4VO3 and N5VO2 are identified in the product after 30 min by accurate mass measurement and isotopic distribution. Under more severe conditions, these new species gradually diminish. It is inferred that the new species could most possibly derive from disassociation of large molecules in addition to chemical transformation. H2S and high hydrogen pressure could promote the hydrogenation of petroporphyrins. H2S can also enhance their thermal cracking reaction while high hydrogen pressure inhibits it. Nickel porphyrins present almost the same phenomena with vanadyl porphyrins, though with low content. Analysis of the petroporphyrins at the molecular level reveals their behavior and transformation during thermal process under hydrogen and could also benefit the catalysts design in HDM process.

Petroporphyrins were enriched and purified from atmospheric residues of two typical heavy oils, Canadian oil sand bitumen (OSAR: Ni, 80 ppm; V, 190 ppm; S, 3.97 wt %) and Chinese Liaohe heavy oil (LHAR: Ni, 68.7 ppm; V, 1.81 ppm; S, 0.36 wt %) by silica-gel chromatography. The separation and purification were confirmed by atomic absorption spectroscopy (AAS) combined with UV–vis spectroscopy, and the petroporphyrins were characterized by positive-ion electrospray ionization (ESI) Fourier transform–ion cyclotron resonance mass spectrometry (FT-ICR MS). Vanadyl and nickel porphyrins in OSAR are simultaneously identified by mass measurement and isotopic fine structure. Vanadyl porphyrins with structures of N4VO, N4VO2, and N4VOS are all detected as protonated analyte ([M + H]+). Both molecular ion (M+•) and protonated analyte ([M + H]+) as well as their corresponding isotopes are observed for N4Ni porphyrins in OSAR and LHAR with an average mass resolving power of over 400000 (m/Δm50%). This is rarely detected by FT-ICR MS using ESI technique previously. Formation of molecular ion can be attributed to the low oxidation potential of nickel porphyrins, the effect of oil matrix on the solution conductivity, and the relatively low flow rate of solution into the capillary. Three more highly unsaturated types of N4VO porphyrins were identified in addition to the six well-documented structures. Compared to N4VO porphyrins, N4VOS porphyrins present higher DBE ranging from 21 to 27 while N4VO2 porphyrins show lower DBE ranging from 18 to 20 and narrower carbon number distribution, suggesting possible different origins of sulfur (pyrolysis of kerogen) and oxygen (diagenesis of chlorophyills). Ni/V and the ratio of relative abundance of ETIO porphyrins to DPEP porphyrins (∑ETIO/∑DPEP) for nickel porphyrins indicate that Liaohe oil and Canadian oil sand bitumen are continental and marine sediments, respectively, and Liaohe oil has a higher maturity. Enrichment by the simple chromatographic method facilitates the mass spectral identification of nickel porphyrins even for heavy residue with low content of nickel and high content of sulfur.

A wide series of thermal cokes obtained from commercial delayed cokers and a pilot coking plant have been investigated by polarized light microscopy observation, scanning electron microscopy (SEM), and temperature-programmed oxidation (TPO) technology. For discrimination of the characterization of the coke samples, the anisotropy degrees of the cokes are found to be considerably different. According to the series of runs in the pilot plant, the restricted mesophase development in thermal cokes could be ascribed to the increasing severity of coking conditions. A previous proposed signal analysis procedure was then applied to the TPO profiles of the cokes to quantitatively acquire parameters for further correlation. A fairly good linear dependency of optical texture index (OTI) upon the proportion of anisotropic carbon species from TPO (correlation coefficient of 0.984) was observed. All of the results obtained in this and our previous (Chen, K.; Xue, Z.; Liu, H.; Guo, A.; Wang, Z.A temperature-programmed oxidation method for quantitative characterization of the thermal cokes morphology. Fuel 2013, 113, 274−279) studies fall within a 95% confidence interval when the dependence of OTI upon the proportion from TPO is considered, therefore clearly demonstrating the validity and adaptability on the convenient determination of the proportion of anisotropic carbon species from TPO for the coke samples ranging from laboratory sources to pilot and even commercial origins. The distribution map of cokes established in this study could be used for quantitatively characterizing the morphology of various thermal cokes.

•The effect of the fraction oils recycle on the stability of blends has been studied.•The stability could be reflected by heterogeneity in coke texture and coke yield.•It was strongly suggested that AGO was not conducive to the stability of blends.•Appropriate selection of recycled fraction favors the stability of feedstocks.Thermal treatment and pyrolysis of vacuum residue/fraction oil blends have been conducted to quantitatively study the effect of the fraction oils recycle (i.e. the composition and the ratio of recycled fraction oils) on the stability of blends. The thermal treatment was completed in a static autoclave and the pyrolysis was run at 500 °C according to a standard test (i.e. the MCR test, ASTM D4530). The pyrolysis coupled with the polarized light microscopic observation of the coke products provided a quantitative and convenient method for predictive assessment of the stability of a given feed. It was strongly suggested that atmospheric gas oil distillate (AGO) was not conducive to the stability of blends. The recycle ratio of AGO and light vacuum gas oil distillate (LVGO) had better be confined to around 0.1 and the valid upper limitation of recycle ratio for heavy vacuum gas oil distillate (HVGO) could be increased up to 0.6 for the purpose of digesting ill-processable vacuum gas oil fraction (VGO). It was concluded that appropriate selection of recycled fraction and ratio might not only favor the improvement of coking products distribution and the process capacity debottleneck, but also be beneficial for maintaining the stability of coking feedstock, suppressing asphaltenes-involved phase separation in the exchanger sections at high temperature, and consequentially favor the operation period extending of coking plants.

Removing solid impurities inside slurry oil from residual fluidized catalytic cracking (RFCC) is critical for efficient use of its aromatic hydrocarbons, and selective separation of the solid components is also an important issue of recycling valuable resources for catalyst and carbon material. Different separation methods were employed to isolate the solids and their components in the slurry oil from a RFCC unit, and the resultant solids and components were comprehensively characterized by elemental analysis, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electronic microscopy (SEM), and energy-dispersive X-ray (EDX) analysis, etc. Results show that the content of toluene-insoluble solids in the slurry oil varies from separation methods employed. The solid components, i.e., catalyst particles and coke powders, can be sequentially separated, and the choice of an appropriate separation method is critical for accurate determination of the solid content in a RFCC slurry oil. When an aliphatic solvent is used for dilution and, after filtering, an aromatic solvent is employed for extraction, the solids can be completely separated and the total content of toluene-insoluble solids is thus obtained. Also, selective separation of the two major components of the solid has also been established. When the slurry oil is digested with hot toluene, followed by filtration and extraction with hot toluene, catalyst particles can be separated at a selectivity of 71.0 wt %. Afterward, when the filtrate is digested with a substantially aliphatic solvent, followed by filtration and extraction with hot toluene, fine coke powders are separated at a selectivity of 96.9 wt %. This selective separation opens a possible way to recover catalyst and obtain fine coke powders as valuable resources from a single RFCC slurry oil. At the same time, the slurry oil may thus be highly clarified, which might find a variety of flexible applications. Finally, the mechanism for particle aggregation and clustering for the efficient separation of solids from heavy oils, such as slurry oil from a fluidized catalytic cracking (FCC)/RFCC unit, has been postulated, where upon adding an aliphatic solvent, heavy asphaltenes precipitate to be adsorbed on the surfaces of fine particles and function as natural binders to aggregate and cluster the fine particles, rendering separation of nanosized coke fines possible.

Selected characteristics and molecular structural parameters of a wide range of heavy oils originating from paraffinic, naphthenic, and intermediate crude oils were estimated, and carbonization was then performed in the form of delayed coking or the Conradson carbon residue (CCR) test to elucidate the aromatization fate of naphthenic ring structures and thus the feed composition, coke formation relationships during heavy oil carbonization. The results show that the heavy oils have very different characteristics such as density, viscosity, CCR content, asphaltene content, etc. Heavy oil may be rich in naphthenic ring structures found in molecules such as naphthenes of varying sizes; its aromaticity increases upon delayed coking, during which solid, liquid, and gaseous products are obtained. Further CCR tests of the heavy liquid products from delayed coking and the other heavy oils show that any single structural parameter such as aromaticity, aromatic ring size, or naphthenic ring size fail to account for coke product formation when heavy oils are carbonized under atmospheric pressure. However, the condensed ring (including aromatic and naphthenic) structures with no fewer than four rings fundamentally end in the coke product, showing essential aromatization and coke formation of the naphthenic structures. Because of the higher concentration of naphthenic structures, heavy oils from the naphthenic or intermediate crude oils tend to form more coke than those from the paraffinic ones.

A novel hydrotreating (HT) catalyst of Mo−W−Ni−P supported on γ-Al2O3 modified by a Group IVA element and a hydroisomerizing (HI) catalyst of W−Ni supported on modified zeolite β with mesopores were prepared by the impregnation method. An integrated process using HT and HI catalysts was designed, and its advantages were well-investigated for directly producing clean diesel from various feedstocks. An industrial application shows that the integrated catalysts have flexible operating modes and are suitable for a wide range of feedstocks. For the HT operating mode, the integrated catalysts showed better hydrodesulfurization (HDS) performance for upgrading the poor quality diesel with a sulfur content of 1000 ppmw and a nitrogen content of 1131 ppmw. The sulfur content of diesel product is less than 40 ppmw, coupled with a hydrodenitrogenation (HDN) rate of 85.76% and an HDS rate of 96.3%. The cetane index increases by 7 units, and the diesel yield is more than 98.0 wt %. For the hydro-dewaxing operating mode, the integrated catalysts showed excellent catalytic performance for upgrading the feeds, with a sulfur content of 990 ppmw and a nitrogen content of 805 ppmw. The HDN rate of 99.42% and HDS rate of 99.99% were also achieved. More importantly, while retaining the cetane index, the diesel yield was as high as 88.72 wt % and the sulfur content and solidifying point of diesel were less than 10 ppmw and −29.3 °C, respectively. The higher HDS and HDN activities of the integrated catalysts are associated primarily with enhanced hydrogenation activity and increased acidity of the HI catalyst.

Anthracene was used as a chemical probe to evaluate hydrogen donating abilities (HDAs) of two petroleum vacuum residues and their SARA fractions (i.e., saturates, aromatics, resins, and asphaltenes), and hydrogen donating kinetics of aromatics and resins were then analyzed. Also, 9,10-dihydroanthracene was used as a chemical probe to evaluate hydrogen accepting abilities of the asphaltenes of the residues. Coking propensities of both residues under thermal processing at 400 °C were evaluated by their coke induction periods. Results show that HDA of either residue proceeds to increase at first and then tends to decline under thermal processing, forming a maximum in the middle. The HDA peak value increases progressively with temperature increasing; the two residues may exhibit either different or similar HDAs at certain test conditions. When the four SARA fractions coexist in the form of a residue for further thermal processing, there exhibits synergism in HDA among the four SARA fractions. Hydrogen donating of aromatics and resins can be treated by first-order kinetics, and both rate constant and initial rate in hydrogen donating for resins show much higher values than those for aromatics. Asphaltenes accept substantially more hydrogens than the amounts they donate. A comprehensive analysis of the data thus obtained shows hydrogen transfer among the SARA fractions is essentially related to coking propensity of residue under thermal processing, where asphaltenes accept hydrogens from resins in the immediate neighborhood that are then supplemented by aromatics. Donatable hydrogens in asphaltenes alone appear insufficient to prevent asphaltenic radicals from combining to form coke. A residue whose asphaltenes accept more hydrogens with resins and aromatics releasing fewer hydrogens exhibits a higher coking propensity under thermal processing. Hydrogen donor/acceptor additives may serve to suppress/promote coke formation by influencing the coking rates of asphaltenes in the center by supplementing/depleting donatable hydrogens of the surrounding medium constituents, that is, resins and aromatics.

Using 4 inferior residual oils as raw materials, the effect of feedstock properties on the characteristics of coke formation during initial thermal conversion process was studied. The results show that the influence for coke induction period of different oils affected by temperature can be measured with the sensitivity parameters. The shorter the coke induction period of the residue, the bigger the sensitivity parameter. The coke induction period has a higher decrease rate with the reaction temperature rising. The coke formation property generally depends on feedstock's basic properties, and the influence of various properties of inferior residual oils on coke formation is different under the same reaction conditions. Carbon residue, ash, relative molecular mass, asphaltene precipitation onset point and stability parameter have strong correlations with the coke induction period, especially for the colloidal stability of oil reflected by asphaltene precipitation onset point and stability parameter. The colloidal stability of the inferior residual oils is related to the coke formation characteristics. The worse the stability of the residue, the more likely the coke is to form. The coke forming process is a gradual destruction of the colloid system during thermal reaction.