Athabasca Vacuum Residue Research Articles

Bench-Top Thermal and Steam Catalytic Cracking of Athabasca Residual Fractions: Attainable Upgrading Levels Correlated with Fraction Properties

Thermal cracking (TC) of the Athabasca vacuum residue (ATVR) and its deasphalted product [deasphalted oil (DAO)] was studied. A comparison of conversion and product properties between TC and ultrad...

Hydrocracking of Athabasca Vacuum Residue Using Ni-Mo-Supported Drill Cuttings

Ni-Mo supported drill cuttings were used to catalyze the hydrocracking (HDC) of Athabasca vacuum residue (AVR) in an autoclave. Drill cuttings are a common waste product that are, depending on their origin, plentiful in acidic sites. The catalyst was prepared using the wet impregnation method. HDC was carried out at both low and high H2 pressure at 400 °C. Control thermal cracking (TC) and HDC runs with and without raw drill cuttings were performed to better examine the role of the supported drill cuttings catalyst. The quality in terms of viscosity and °API gravity, and the yield of various fractions making up the product oil were used to gauge the performance of the catalyst. Similar temperature and energy profiles between TC and HDC suggested strong overlap between the two different reactions, despite H2 presence. Nevertheless, supported drill cuttings runs at high H2 pressures promoted H2 consumption to a strong extent. Consequently, the liquid yield was the highest (~75 wt.%) and the coke yield was negligible. High temperature simulated distillation results revealed a residue conversion of ~55% for both low and high pressure HDC catalytic runs. The product oil quality with respect to viscosity and °API gravity was also found to be comparable between the low and high pressure HDC catalytic runs. Accordingly, no trade-off between liquid yield and quality was incurred at high H2 pressure. Effectively the supported drill cuttings drastically reduced coke formation, while maximizing the yield of the desired liquid product.

Hydrocracking of Athabasca VR Using NiO-WO3 Zeolite-Based Catalysts

Hydrocracking of Athabasca vacuum residue (AVR) was carried out in an autoclave using particle and fiber forms of NiO-WO3 zeolite-supported catalyst. AVR hydrocracking was performed at 400 °C at low and high H2 pressure of 70 and 365 psi, together with the corresponding control thermal cracking runs. The yield of the different products and the quality of the upgraded liquid was used to assess the catalyst performance. Similarity among energy consumption for the different samples suggested major thermal cracking endothermic reactions. In general, the catalytic runs provided better quality maltene product, whereas better quality product oil was only attained at high pressure. The catalytic runs at low H2 pressure gave the highest yield of combined asphaltenes and toluene insolubles. This yield, on the other hand, was the lowest for the fiber form at high H2 pressure. Simulated distillation results captured the superior performance of the fiber catalyst at high H2 pressure and showed ∼50% conversion of the r...

Catalytic thermal cracking of Athabasca VR in a closed reactor system

Catalytic thermal cracking of the residue is less common, due to high susceptibility of catalysts to deactivation. In this work, cracking of Athabasca vacuum residue in an autoclave at 400 °C was investigated in presence of in situ prepared and commercial alumina nanoparticles as well as drill cuttings. A high liquid yield of ∼90 wt% was obtained. The nanoparticles and drill cuttings (at 30 wt%) contributed to relatively high coke and gas yields. Nevertheless, the catalytic runs had higher quality maltene product. Reducing drill cuttings concentration to 10 wt% gave the highest liquid yield with high quality maltene. Coke inhibition in presence of optimum drill cuttings concentration is attributed to a balance between the rate of coke precursor formation and adsorption onto the cuttings. Subsequently, at a higher temperature, 420 °C, the higher rate of precursor formation led to similar results between the 10 wt% drill cuttings and the control sample. Both toluene insolubles and produced asphaltenes displayed a lower H/C ratio than asphaltenes in the feed, in line with the thermal cracking activity. Thermogravimetry profiles for the produced asphaltenes was attained at higher temperatures than the toluene insolubles, and was initial-mass sensitive. Accordingly, thermogravimetry profiles should not be indefinitely used to identify the different oil fractions.

Role of metal halides in coke formation during bitumen upgrading

Abstract Metal chlorides are naturally present in bitumen. The concern of such metal chlorides in downstream processing is related to physical processes. However, a previous study revealed that mild bromination of asphaltenes resulted in a product with increased hardness and that was insoluble in both aromatic and paraffinic solvents, like coke. It was then hypothesized that the naturally present metal chlorides could affect solids yield during thermal conversion. The hypothesis was investigated by performing thermal conversion of Athabasca vacuum residue at 400 °C for 1 h in the presence of 1 wt% of different metal bromides (NaBr, CaBr2, MgBr2, CoBr2, and ZnBr2). Metal bromides were chosen instead of metal chlorides because vacuum residue does not contain bromine and it would facilitate analysis. Control experiments were also prepared: i) conversion in the presence of a base (Mg(OH)2) and ii) conversion in the absence of a metal bromide and/or base. The results revealed that the presence of acidic metal bromides during thermal cracking increased solids yield. Formation of a hydrogen halide (irrespective of the type of the halogen composing the metal halide) is a required step for metal halides to contribute to coke formation. It was also observed that acidic metal bromides caused halogen transfer to solid and liquid products and that this transfer was not due to trapped metal bromide salts. Acidic metal bromides increased solid yield during conversion of Athabasca vacuum residue from 2.5 wt% to 4–10 wt%. The increase solids yield and halogen transfer by thermal conversion in the presence of acidic metal bromides was suppressed by the addition of a base, but it was not eliminated. Thermal cracking in the presence of a base, Mg(OH)2, decreased overall solid yield.

Thermal cracking of Athabasca VR and bitumen and their maltene fraction in a closed reactor system

Thermal cracking of Athabasca vacuum residue (AVR) and Athabasca bitumen (AB) and their maltene fraction was investigated at 400°C in a closed system, i.e. autoclave. The effect of the following variables on the product yield and the properties of the liquid fraction and its maltene extract was evaluated: residence time, pressure of the reactor unit, stirring, temperature and asphaltenes content of the feedstock. The yield of the different fractions, the total energy consumption, the pressure buildup in the batch reactor and the °API gravity and viscosity of the liquid fraction and its maltene extract were used to evaluate the impact of a given parameter. In addition, high-temperature simulated distillation (HTSD) analysis of the liquid product and gas chromatography (GC) analysis for gas product were performed. The effect of reaction time, mixing and pressure on the yield of toluene insolubles (TI) depended on the presence of asphaltenes in the feedstock. TI yield increased at the expense of the asphaltenic fraction when reaction time, mixing and pressure increased. There is an inverse relationship between the initial asphaltenes content in the feedstock and the overall asphaltenes yield base on the parent feedstock. Moreover, increasing asphaltenes content of the feedstock did not introduce significant changes in the total energy input to the reactor.

New Pathways for Asphaltenes Upgrading Using the Oxy-Cracking Process

Solvent deasphalting of the bottom of vacuum distillation columns (vacuum residue, VR) is a process practiced worldwide. In Northern Alberta, a solvent deasphalting plant was designed to process up to 4000 tons/day of the asphaltenic pitch. Asphaltenes oxy-cracking in liquid phase could be a new approach to asphaltenes upgrading and conversion into valuable chemicals. Oxy-cracking is a combination of oxidation and cracking in basic aqueous media at moderate temperatures (170–225 °C) and pressures (300–500 psi). This process could act very selectively producing smaller amounts of greenhouse gases like CO2, thus being considered environmentally friendly. In this work, a mild oxy-cracking treatment of C5-asphaltenes solid from Athabasca vacuum residue was investigated. The reaction kinetics and possible reaction mechanism for C5-asphaltenes oxy-cracking in water under alkali conditions were studied. Products solubilized under different severities were characterized using Fourier transform infrared and nuclea...

Dependence of onset time for mesophase formation on operating parameters during catalytic hydroconversion of Athabasca vacuum residue

During the catalytic hydroconversion of vacuum residue fractions of bitumen or petroleum, the formation of mesophase can lead to fouling of reactor internals. In this study we examine the dependence of the onset of mesophase in a batch microreactor designed to enable in situ microscopic observation of the reacting liquid. The following process variables were investigated: temperature, partial pressure of hydrogen, catalyst concentration, agitation speed, and their interactions. Athabasca vacuum residue was converted in the presence of an iron sulfide particulate catalyst, and a statistical model was developed to describe the effects of the process variables on the onset time for mesophase formation. The temperature and catalyst concentration, respectively, had the most effect on mesophase onset time. The time for mesophase formation dropped by 12.1min when the operating temperature increased from 440°C to 450°C. The mesophase onset time increased by 7.4min when 3wt.% of catalyst was added at 440°C, compared to no catalyst addition. Partial pressure of hydrogen was not significant as an independent process variable for the range studied, from 2.4 to 5.2MPa. The combined effects of hydrogen partial pressure and catalyst concentration were significant, as were the combined effects of temperature and catalyst concentration.

Comparing kinetics and mechanism of adsorption and thermo-oxidative decomposition of Athabasca asphaltenes onto TiO2, ZrO2, and CeO2 nanoparticles

In this study, nC7-asphaltenes adsorption and subsequent catalytic oxidation over three transition metal oxide nanoparticles, namely TiO2, ZrO2, and CeO2 were investigated. nC7-asphaltenes studied were obtained from Athabasca vacuum residue using n-heptane. The adsorption equilibrium data of nC7-asphaltenes, dissolved in toluene, fitted very well to the Langmuir adsorption isotherm model. The adsorption behavior of nC7-asphaltenes appeared to change with the type of adsorbent used. It was found that nC7-asphaltenes adsorption at 25°C is metal oxide specific and the adsorption capacities ranked in the following order: CeO2>ZrO2>TiO2. On the other hand the adsorption affinity followed the following order: CeO2>TiO2>ZrO2. Theoretical calculations of the interaction between the Quinolin-65 (Q-65) (a compound used as a model asphaltene molecule) and some of the metal oxides surfaces were carried out to get more insight into its adsorption behavior. Adsorption energies of Q-65 on the surfaces indicated that there are different adsorption sites on each metal oxide. To confirm the catalytic activity of the selected oxide nanoparticles, the nC7-asphaltenes adsorbed onto the transition metal oxide nanoparticles were subjected to oxidation up to 700°C in a thermogravimetric analyzer. All tested nanoparticles showed high catalytic activity for post adsorption oxidation. The oxidation kinetics was studied using the Ozawa–Flyn–Wall (OFW) corrected method. The mechanism function of the nC7-asphaltenes oxidation is strongly dependent on the type of nanoparticles. The kinetic oxidation parameters and the transition state thermodynamic functions for the oxidation process of nC7-asphaltenes in the presence and absence of nanoparticles, to the best of our knowledge, are reported for the first time. Among the selected transition metal oxide nanoparticles, CeO2 appears to have the lowest values of effective activation energy and change in Gibbs free energy of activation (ΔG‡).

Development of a General Modelling Methodology for Vacuum Residue Hydroconversion

This work concerns the development of a methodology for kinetic modelling of refining processes, and more specifically for vacuum residue conversion. The proposed approach allows to overcome the lack of molecular detail of the petroleum fractions and to simulate the transformation of the feedstock molecules into effluent molecules by means of a two-step procedure. In the first step, a synthetic mixture of molecules representing the feedstock for the process is generated via a molecular reconstruction method, termed SR-REM molecular reconstruction. In the second step, a kinetic Monte-Carlo method (kMC) is used to simulate the conversion reactions on this mixture of molecules. The molecular reconstruction was applied to several petroleum residues and is illustrated for an Athabasca (Canada) vacuum residue. The kinetic Monte-Carlo method is then described in detail. In order to validate this stochastic approach, a lumped deterministic model for vacuum residue conversion was simulated using Gillespie’s Stochastic Simulation Algorithm. Despite the fact that both approaches are based on very different hypotheses, the stochastic simulation algorithm simulates the conversion reactions with the same accuracy as the deterministic approach. The full-scale stochastic simulation approach using molecular-level reaction pathways provides high amounts of detail on the effluent composition and is briefly illustrated for Athabasca VR hydrocracking.

Molecule-based kinetic modeling by Monte Carlo methods for heavy petroleum conversion

A methodology for kinetic modeling of conversion processes is presented. The proposed approach allows to overcome the lack of molecular detail of the petroleum fractions and to simulate the reactions of the process by means of a two-step procedure. In the first step, a synthetic mixture of molecules representing the feedstock is generated via a molecular reconstruction method, termed SR-REM molecular reconstruction. In the second step, a kinetic Monte Carlo method, termed stochastic simulation algorithm (SSA), is used to simulate the effect of the conversion reactions on the mixture of molecules. The resulting methodology is applied to the Athabasca vacuum residue hydrocracking. An adequate molecular representation of the vacuum residue is obtained using the SR-REM algorithm. The reaction simulations present a good agreement with the laboratory data for Athabasca vacuum residue conversion. In addition, the proposed methodology provides the molecular detail of the vacuum residue conversion throughout the reactions simulations.

Impact of Liquid–Vapor to Liquid–Liquid–Vapor Phase Transitions on Asphaltene-Rich Nanoaggregate Behavior in Athabasca Vacuum Residue + Pentane Mixtures

The bulk phase behavior of heavy oil + alkane mixtures and the behavior of the asphaltenes that they contain are topics of importance for the design and optimization of processes for petroleum production, transport, and refining and for performing routine saturates, aromatics, resins, and asphaltenes (SARA) analyses. In prior studies, partial phase diagrams and phase behavior models for Athabasca vacuum residue (AVR) comprising 32 wt % pentane asphaltenes + n-alkanes were reported. For mixtures with pentane, observed phase behaviors included single-phase liquid as well as liquid–liquid, liquid–liquid–vapor, and liquid–liquid–liquid–vapor regions. Dispersed solids were detected under some conditions as well but not quantified. In this work, small-angle X-ray scattering (SAXS) is used to study nanostructured materials in liquid phases present in AVR + n-pentane mixtures from 50 to 170 °C at mixture bubble pressure. The investigation focuses on the impact of the transition from a single AVR-rich liquid to co-existing pentane-rich and AVR-rich liquids on the nanostructure and the nanostructures most resistant to aggregation as the pentane composition axis is approached. Background scattering subtraction was performed using global mixture composition. The robustness of this assumption with respect to values obtained for coefficients appearing in a two level Beaucage unified equation fit is demonstrated. The nanostructured material is shown to arise at two length scales from 1 to 100 wt % AVR. Smaller nanostructures possess mean radii less than 50 Å, while the larger nanostructures possess mean radii greater than 250 Å. The addition of pentane to the AVR causes an increasingly large fraction of the large and small nanostructures to grow in size. Only nanostructures resistant to aggregation remain in the pentane-rich phase as the 0 wt % AVR axis is approached. Step changes in aggregation identified from changes in average radius of gyration, scattering coefficients, and surface/volume ratios arise at the liquid–vapor to liquid–liquid–vapor transition (∼40 wt % pentane) and within the liquid–liquid–vapor region (∼90 wt % pentane). The temperature is shown to have a limited effect on the mean size and structure of the nanostructured material present, irrespective of global composition.

Minimization of Coke in Thermal Cracking of Athabasca Vacuum Residue in a High-Temperature Short-Residence Time Continuous Flow Aerosol Reactor

Yield of coke in thermal cracking of Athabasca vacuum residue in a continuous flow aerosol reactor was minimized by atomization of the feed into submicrometer droplets, which enhanced the vaporization and conversion of the heavy liquid phase with boiling point above 524 °C. The reaction temperature ranged from 700 to 800 °C, and the pressure was atmospheric. The residence time varied from 100 to 115 ms. The yield of coke was found to be insensitive to conversion, with an average value of 6.3 wt %. The average size of the coke particles in the product was less than 190 nm. Alkenes were the dominant components among the gas products, with total yield of ethene and propene ranging from 5 to 18 wt % with conversion. The molar ratio of hydrogen to carbon decreased monotonically with conversion from 1.4 for unconverted feed to 0.98 at 78% conversion, consistent with high yields of hydrogen-rich gas products.

In Situ Observation of Mesophase Formation and Coalescence in Catalytic Hydroconversion of Vacuum Residue Using a Stirred Hot-Stage Reactor

A microreactor equipped with a view window and a stirrer was used to observe mesophase formation in Athabasca vacuum residue with and without catalyst. The effect of stirring on mesophase formation and its growth and coalescence was studied during the cracking of vacuum residue under hydrogen at 4.8 MPa and 440 °C. Stirring can result in a bimodal distribution of size of mesophase domains. The forced coalescence of mesophase droplets by the stirrer led to the formation of very large mesophase regions (bulk mesophase), which coexisted with a large number of small micrometer-sized mesophase domains. The addition of catalyst likely had both chemical and physical effects on the formation and growth of mesophase. The catalyst gave a delay in the onset of mesophase formation as a chemical effect and a decrease in the amount of bulk mesophase regions by suppressing the coalescence of smaller mesophase domains as a physical effect. The analysis of the resulting cokes by scanning electron microscopy (SEM) showed that catalyst particles agglomerated and stuck to the outer surface of the mesophase domains and suppressed their coalescence. The agglomeration of catalyst particles likely decreased their ability to suppress the formation of small mesophase domains, in the range of a few micrometers in size. However, catalyst was effective in suppressing the formation of bulk mesophase domains with areas over 2000 μm2. The results showed that the onset of observable mesophase initially increased with the addition of catalyst, but then decreased at higher catalyst concentrations. SEM observation confirmed that the significant agglomeration of catalyst particles at higher concentrations was likely responsible for the decreased effectiveness of the catalyst in suppressing mesophase formation.

Simulation of the phase behaviour of Athabasca vacuum residue + n-alkane mixtures

Phase behaviour measurement and prediction for ill-defined hydrocarbons such as vacuum residue + light hydrocarbons present significant challenges, from view-cell design and operation, to thermolysis reactions at high temperature to fluid speciation and phase stability analysis during equilibrium calculations. In a prior contribution, simulated phase behaviour results for Athabasca vacuum residue + n-decane mixtures based on the Peng–Robinson equation of state were presented. In that work, Athabasca vacuum residue pseudo components that were identified exogenously and parameters for the model were computed from these pseudo components using the Marrero and Gani group contribution method. Here, this thermodynamic model is extended to include Athabasca vacuum residue + n-alkanes from n-pentane to n-dodecane. Only binary interaction coefficient values between residue pseudo components and n-alkanes were tuned. Densities of co-existing liquid phases present in the three-phase regions are calculated and compared to the experimental data for AVR + n-decane. The simulations are in qualitative and quantitative agreement with measurements over a broad ranges of temperature, pressure, and composition. The results presented in this contribution illustrate the reliability of the proposed thermodynamic modeling approach and its potential use as a universal heavy oil modeling tool for the simulation of paraffinic deasphalting, separation and refining processes for ill-defined hydrocarbon mixtures.

Iron oxide nanoparticles for rapid adsorption and enhanced catalytic oxidation of thermally cracked asphaltenes

Thermally cracked asphaltenes from Athabasca vacuum residue produced at four different process severities were investigated for adsorption and subsequent catalytic oxidation. Fe3O4 nanoparticles were used for the removal of these four different thermally cracked asphaltenes from toluene solutions by a batch-adsorption technique followed by subsequent catalytic oxidation. Asphaltene adsorption kinetics and isotherms are presented. Further, the catalytic effect of nanoparticles on asphaltene oxidation has been addressed. Adsorption was rapid as equilibrium was achieved within 10min. The equilibrium adsorption data fit well to the Langmuir model. It was found that the adsorption rate, affinity and capacity depend on the molecular weight (MW) of the asphaltenes. Adsorption rate and capacity were highest for the lower MW molecules while adsorption affinity was strongest for the larger MW molecules. In addition, in the absence of nanoparticles, the four thermally cracked asphaltenes oxidized differently. However, when adsorbed onto Fe3O4 nanoparticles their oxidation behavior became similar, showing the enhanced catalytic effect of nanoparticles.

Adsorption of Athabasca Vacuum Residues and Their Visbroken Products over Macroporous Solids: Influence of Their Molecular Characteristics

An adsorption study of Athabasca vacuum residue (VR) and its visbroken (VB) products over in-house made macroporous Ca–kaolin and Ca–Ba–kaolin adsorbents was carried out at ambient temperatures. Adsorption experiments were performed for 120 min in toluene solution of the adsorbates, monitored via ultraviolet–visible (UV–vis) spectrophotometry to determine the corresponding uptake. The extent of the uptake was correlated with molecular parameters obtained from 1H and 13C nuclear magnetic resonance (NMR) spectroscopy, elemental analysis, and solubility profiles to determine which properties may enhance the adsorption. It was found that the severity of thermal cracking induced noticeable changes in solubility profiles, aromaticity (fa), total naphthenic carbon (TNC), and secondary methylene groups on the corresponding products. Furthermore, heteroatom content also changed with 545 °C+ conversions, leading to products with decreased sulfur contents and enhanced in nitrogen and oxygen as the severity increases. Higher uptakes were observed in adsorbates with more aromaticity, higher solubility profile, and higher nitrogen and oxygen contents. Trends between these molecular properties with uptakes allowed for the prediction of the potential adsorption capacity of the thermal-cracked products over this type of adsorbent.

Suitable Density Determination for Heavy Hydrocarbons by Solution Pycnometry: Virgin and Thermal Cracked Athabasca Vacuum Residue Fractions

Density is an important parameter for understanding molecular packing, stability, and reactivity of petroleum fractions. The determination of density for extremely viscous residual fractions measured at high temperature (reduced viscosity) is difficult and prone to error if results are extrapolated to lower temperature ranges. This problem is addressed in the present study with fractions derived from virgin and visbroken Athabasca vacuum residua. Solution pycnometry (toluene solvent) was studied and demonstrated a feasible, fast, simple, and reliable technique, applicable to a wide variety of petroleum materials, including asphaltenes and vacuum residua. Reported densities were affected to the third decimal position [American Petroleum Institute (API) gravities found reliable to ±0.15° API]. The density for mixtures of residual oil fractions was determined to be an additive property. Athabasca vacuum residue solvent deasphalting and thermal cracked fractions are studied. Thermal cracking was observed to i...

On the phase behaviour of Athabasca vacuum residue + n-decane

Phase behaviour measurement and prediction for ill-defined hydrocarbon mixtures, such as vacuum residues, are subject to significant experimental and theoretical challenges. Consequently, despite the industrial importance of such fluids, experimental data sets are sparse with respect to the composition, pressure, and temperature ranges available and computational results are typically of poor quality. There are typically large differences between measured and predicted pressure–temperature and pressure–composition phase boundaries, and the numbers and natures of phases present are misidentified in many cases. Athabasca vacuum residue + n-decane mixtures exemplify these challenges. In the present work, computed phase behaviour results are based on the Peng–Robinson Equation of State. Parameters are identified using the Marrero and Gani group contribution method (J. Marrero, R. Gani, Fluid Phase Equilibria 183–184 (2001) 183–208 [13]) applied to pseudo components identified by Sheramata (J.M. Sheremata, Ph.D. Thesis, University of Alberta, 2008 [7]). Binary interaction parameters are estimated using the PPR78 method (J.-N. Jaubert, F. Mutelet, Fluid Phase Equilibria 224 (2004) 285–304 [15]) and a predictive correlation developed by Gao et al. (G.H. Gao, J.L. Daridon, H. Saintguirons, P. Xans, and F. Montel, Fluid Phase Equilibria 74 (1992) 85–93 [18]). At temperatures above 267 °C there is quantitative agreement between the measured and the predicted phase behaviour. L1V to L1 and L1L2V to L1L2 phase transitions are identified to within 5 °C and 5 bar and L-points (L1 = L2 + V) on the LV–LLV boundary are also predicted. At temperatures less than 267 °C, the breadth of the experimental LLV region shrinks dramatically with respect to composition. This change is not picked up in the calculations and there is a mismatch between the measured and the predicted phase behaviour over the composition range 35–65 wt.% vacuum residue, where the predicted phase behaviour includes L1L2V and L1L2 phase behaviours not observed experimentally. Even with this limitation, these proof of concept computational results provide a significant advance over current practice for ill-defined hydrocarbons, in general, and provide an accurate phase behaviour model for key deasphalting and other refining processes not previously available for Athabasca vacuum residue in particular.

Sorption of Athabasca Vacuum Residue Constituents on Synthetic Mineral and Process Equipment Surfaces from Mixtures with Pentane

Deposition of organic material on mineral and process equipment surfaces poses production, transport, and refining challenges for the petroleum industry. For high-asphaltene content hydrocarbon resources, such as bitumen, deposits are frequently assumed to be asphaltene rich. In this work, deposits formed from Athabasca vacuum residue (AVR) comprising 32 wt % asphaltenes + pentane mixtures on acidic (FeS, SiO2) and basic (Fe2O3/FeOOH/FeO, Ni/NiO/NiOH) substrates are analyzed using X-ray photoelectron spectroscopy. Control experiments with pure compounds are used to confirm experimental protocols and to address substrate contamination, which interferes with deposit composition measurements, if the organic deposit is thin or surface coverage is partial. Substrate properties are found to affect both deposit thickness and deposit composition. On basic substrates, deposits are thinner and are enriched in sulfur relative to AVR. On acidic substrates, deposits are thicker and are sulfur deficient relative to AVR, even though asphaltenes, which are rich in sulfur, sorb more strongly on acidic substrates in the absence of competition from other species. Deposit composition was also found to be invariant with the composition and phase behavior of the AVR + pentane mixtures. These results were not expected.