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Adsorption of Athabasca Vacuum Residues and Their Visbroken Products over Macroporous Solids: Influence of Their Molecular Characteristics Francisco Lopez-Linares,*,† Lante Carbognani,† Azfar Hassan,† Pedro Pereira-Almao,† Estrella Rogel,‡ Cesar Ovalles,‡ Ajit Pradhan,‡ and John Zintsmaster‡ †
Alberta Ingenuity Centre for In Situ Energy (AICISE), Department of Chemical and Petroleum Engineering, Schulich School of Engineering, University of Calgary, Calgary, Alberta T2N 1N4, Canada ‡ Petroleum and Material Characterization Unit, Chevron Energy Technology Company, 100 Chevron Way, Richmond, California 94801, United States ABSTRACT: An adsorption study of Athabasca vacuum residue (VR) and its visbroken (VB) products over in-house made macroporous Cakaolin and CaBakaolin adsorbents was carried out at ambient temperatures. Adsorption experiments were performed for 120 min in toluene solution of the adsorbates, monitored via ultravioletvisible (UVvis) 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.
’ INTRODUCTION Nowdays, it is recognized that the world energy consumption has been increasing and the most available energy is provided by petroleum and its derivatives.1 Among them, heavy oil and bitumen reserves are the most available energy source worldwide, and their uses are expected to be increasing in the future.2 Heavy oil and bitumen typically comprise more than 50% (w/w) of distillation residua (500 °C+).3 The production of useful petroleum products from such residua requires already known or new upgrading routes. Some alternatives have been proposed recently, such as a combined “visbreaking adsorptioncatalytic steam gasification” for Athabasca residue, visualized for surface application.4,5 It can be visualized as a sequential process illustrated as follows: (1) thermal cracking of vacuum residua from heavy oils (HOs) and extra heavy oils (XHOs), (2) adsorption step, which may selectively capture at least a fraction of the heaviest hydrocarbon molecules, those most unstable, and (3) low-temperature catalytic steam gasification (CSG) of the adsorbed compounds. The thermally cracked (TC) modified heavy molecules present within the most severely visbroken products proved to be key components for the process.5 They display higher adsorptivity over the solid that act as both adsorbent and catalyst for steam gasification. Another approach that is more oriented to subsurface application is the combination of in situ combustion (ISC)6 with steamassisted gravity drainage (SAGD),7 namely, combined SAGD ISC. In this proposed process scheme, steam preheats and mobilizes the bitumen in place before injecting air.8 In both processes, the interaction of these types of heavy molecules with r 2011 American Chemical Society
solid surfaces is expected. Previous reports have covered this type of interaction with solid sorbents,913 metals,1416 and minerals.1721 Although previous findings highlighted the importance of the textural properties of the solids required for such application, i.e., available surface area, large pore size, and pore volume, less consideration was given to the molecular characteristics of the adsorbates.13,21,22 Focusing on processes for surface applications, the development of adsorbents capable of dealing with large molecules present in heavy oils, such as vacuum residua, and its ability to act as a catalyst for steam gasification is deemed important.4,5 Combining available knowledge of commercial adsorbents23 and a deeper knowledge of the adsorbate characteristics would improve the understanding of the overall adsorption process, designing a more suitable adsorbent catalyst that could enhance the feasibility of novel upgrading schemes. This work aims to combine two of the main aspects mentioned above, providing clues on (1) molecular properties for thermalcracked products, such as asphaltene solubility profile, average molecular mass (MM), aromaticity (fa), total secondary CH2 groups, and N, S, and O contents, and how these characteristics could be correlated with their interaction over a solid surface, such as Camacroporous kaolin developed for adsorption of heavy molecules4,5 and (2) how experiments carried out with modified CaBamacroporous kaolin compare to former (reported) Received: July 18, 2011 Revised: August 15, 2011 Published: August 17, 2011 4049
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Energy & Fuels results.4,5,13 These comparisons help identify important variables governing the interaction of heavy oil compounds over macroporous solids. To achieve these goals, adsorption uptakes were determined by performing a kinetic study in toluene solutions of vacuum residue (VR) and mild thermal-cracked Athabasca vacuum residue products by visbreaking (VB) and calculating the amount of hydrocarbon adsorbed per gram of solid. Characterization of such fractions in terms of recently reported asphaltene solubility profiles,24 1H and 13C nuclear magnetic resonance (NMR) average molecular parameters, and elemental analysis was performed. Trends between those properties versus adsorption uptakes at given times are presented.
’ EXPERIMENTAL SECTION Solvents, Samples, and Gases. Toluene (spectrophotometric grade), methylene chloride, n-heptane, methanol, tetrahydrofuran (THF; all high-performance liquid chromatography (HPLC) grade], deuterochloroform (CDCl3; 99.96 atom % D), tetramethylsilane (TMS; ACS reagent, NMR grade), chromium(III) acetylacetonate [Cr(acac)3; 97%], and methyl isobutyl ketone (MIBK) from Sigma-Aldrich were used as received. NH3, H2, O2, and N2 of ultra-high purity (UHP) grade were purchased from Praxair Canada. A VR from Athabasca bitumen provided by Suncor was employed in this work. This feedstock contains 26 wt % distillable fractions (545 °C), as determined by High Temperature Simulated Distillation (SimDist). About 0.7 wt % methylene chloride insoluble materials were determined to be present within this residue. Mild thermal-cracked products obtained by VB were prepared at different conversion levels according to a previous report.5 Kaolin was obtained from Merck (Germany). Ca(CH3COO)2 and Ba(CH3COO)2 of 99% purity were also obtained from Merck (Germany). Asphaltene Solubility Parameter Profiling. Determination of solubility profiles for petroleum samples has been recently described.24 The methodology uses HPLC equipment; however, chromatographic separations are not involved in the procedure. A column packed with inert Teflon particles is sequentially eluted with n-heptane, n-heptanemethylene chloride gradient, and finally methanol. Eluates from the column are quantified with an evaporative light scattering detector (ELSD). Two groups of signals can be determined for each run: (1) maltene peak appearing at the void volume of the packed column (nonprecipitated compounds soluble in n-heptane, which elute with this solvent) and (2) precipitated/redissolved asphaltene signals, which span varying retention times (i.e., different solubility parameter ranges) depending upon their origin and intrinsic properties. Virgin (unprocessed) asphaltenes usually show one single signal, while converted asphaltenes, i.e., materials exposed to thermal cracking, display a bimodal distribution (low- and high-solubility parameters). The most severely cracked asphaltenes are found enriched in the higher solubility parameter peak.25 This is the signal considered in the present paper for further trend with adsorption properties of the studied vacuum residue. Determination of the second peak solubility parameters is described elsewhere.24 NMR Study. The NMR spectra were acquired using a Bruker Avance 500 spectrometer using a 5 mm BBI probe. Each sample was mixed 1:1 (wt/wt) with CDCl3. The 1H NMR was recorded at 500.11 MHz using a 5.4 μs (30°) pulse applied at 4 s intervals with 64 scans coadded for each spectrum. The 13C NMR was recorded at 125.75 MHz using a 15.4 μs pulse and with inverse-gated decoupling, applied at 4 s intervals with 4000 scans co-added for each spectrum. A small amount of 0.1 M Cr(acac)3 was added as a relaxation agent, and TMS was used as an internal standard. The analyses were carried out at 40 °C. Elemental Analysis. Carbon, hydrogen, and nitrogen (CHN) analysis was carried out with a Carlo Erba model 1108 analyzer. Approximately 15 mg of sample is weighed in a tin cup for nonvolatile samples or a piece of indium tubing for volatile samples. The sample is
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combusted with O2 in He carrier gas to produce NOx, CO2, and H2O as combustion products. The nitrogen oxides are reduced to N2 gas, and excess O2 is consumed in a Cu reduction tube, leaving only N2, CO2, and H2O in the carrier gas stream. These combustion products are separated by gas chromatography and quantitatively determined with a thermal conductivity detector. The percentages of oxygen were determined by difference. Metal Analysis. The determination of S, Ni, and V was performed with inductively coupled plasma atomic emission spectrometry (ICPAES). A Thermo Scientific ICPAES model IRIS Intrepid XDL II (Radial) from Thermo Scientific was the instrument used for analysis. Multiple elements can be determined simultaneously using a plasma source and a charge injection device (CID) solid-state detector, which can detect multiple emission lines simultaneously ranging from 175 to 800 nm. The method uses a mixture of o-xylene, surfactant, mineral oil, scandium (internal standard), and MIBK solvent to provide 1:10 (w/w) sample solutions. Size-Exclusion Chromatography (SEC). MM for studied residua were estimated by SEC. An Agilent 1100 series liquid chromatograph equipped with a differential refractive index detector (RID) and auto injector was used. THF was the selected eluent set at a flow rate of 0.4 mL/min. SEC experiments were carried out at 35 °C. A PL-Gel Minimix-E column from Polymer Laboratories (Amherst, MA) provided the SEC separations. Column dimensions were 250 mm length 4.6 mm diameter, packed with 3 μm particles. Sample solutions (2 wt %/vol) were prepared in THF. The injected sample volume was 50 μL. SEC calibration was achieved with real petroleum distillates of known MM. Further details of the method can be found elsewhere.21,26 Adsorbate Uptake Determination. The uptake was determined by following the adsorption kinetics of the VR and VB over the solids. Typically, kinetics experiments were carried out by continuously measuring the change of absorbance for the solution of either the model molecule or asphaltenes in contact with the macroporous solid. The instrument used for these experiments was a Cary 4E dual-beam spectrophotometer from Varian. This procedure was necessary to perform direct light absorption measurements of those solutions. Typically, the procedure was as follows: 3 mL of toluene solution of the corresponding adsorbate (6070 ppm) was placed in a screw-cap cuvette (spectrosil of 3.5 m, rectangular cell quartz, open-top cap, and light path of 10 mm from Sigma-Aldrich), and the initial absorbance was measured (A0). Then, 0.3 g of the solid was added; the system was closed; the cuvette cell was placed in the spectrophotometer; and every 15 min, a spectra was recorded for a total period of 120 min, in a static mode at room temperature. The kinetic plots were obtained by transforming the absorbance A(t) into relative absorbance RA(t) (to make it independent of the initial concentration) as function of time. RA(t) was transformed at solution concentration Cs(t) (mg/L) using eq 1 Cs ðtÞ ¼ RAðtÞC0
ð1Þ
where C0 is the initial concentration. The amount of VR and VB adsorbed at any time Ca(t) per gram of adsorbent (mg/g) was calculated using eq 2 Ca ðtÞ ¼ C0 Cs ðtÞV =m
ð2Þ
where V is the solution volume (L) and m is the mass (g) of the adsorbent. Typical errors in the absorbance scale do not exceed 10% relatively. Details on the methodology have been published previously.13 Adsorbent Preparation. Macroporous adsorbents were prepared using kaolin. A known amount of kaolin was mixed with an aqueous solution of Ca(CH3COO)2 and/or Ba(CH3COO)2. A carbohydrate was then added to kaolin in known amounts. Extrudates were drawn and dried overnight at room temperatures. Dried extrudates of kaolin were then calcined at 650 °C under air in a muffle furnace to form macroporous material. Adsorbents were tailor-made to have significant macropore proportions, with an average pore diameter higher than 4050
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Table 1. Adsorption Uptake of VR and VB Products as a Function of 545 °C+ Conversiona residue
a
Table 2. Average Molecular Properties for Athabasca VR and VB Products as a Function of VB 545 °C+ Conversiona
uptake (mg/g) at 120 min
parameter\residue
VR 8.7% 13.7% 28.5%
VR
0.117
asphaltene solubility parameter, second peak
17.0 17.3
17.7
18.2
VB (8.7%) VB (13.3%)
0.119 0.127
0.33 0.38 aromaticity (fa) by 13C NMR (solution) percent total secondary CH2 carbon (29.7 ppm) 19.5 20.8
0.50 16.4
0.55 14.6
VB (28.5%)
0.139
total naphthenic carbon (TNC)
8.84 8.67
5.70
3.20
H/C atomic ratio
1.42 1.37
1.30
1.21
oxygen (wt %)
2.05 1.61
1.91
2.42
Number in parentheses: VB 545 °C+ conversion of Athabasca VR.
50 nm to allow for the penetration of large molecules and to accommodate them onto the macroporous surface of the solid adsorbents.
Nitrogen Physisorption and Hg Porosimetry Experiments. Surface area, pore volume, and pore diameter for synthesized adsorbents were characterized by N2 physisorption at 77 K, applying the BrunauerEmmettTeller (BET) method, using a Micromeritics Tristar 3020 equipment and experiments conducted at a laboratory facility of Quantachrome Instruments. Before N2 physisorption experiments, the samples were dried at 150 °C overnight under N2 flow. Determined surface areas are 12 m2/g (Cakaolin) and 18 m2/g (CaBakaolin), with pore sizes larger than 50 nm in both cases determined by mercury porosimetry.
a
sulfur (wt %)
5.31 4.94
4.60
4.50
nitrogen (wt %)
0.62 0.68
0.72
0.92
MM (Da)
1459 1107 830
689
VB 545 °C+ conversion of Athabasca VR.
Ammonia Temperature-Programmed Desorption Experiments (NH3-TPD). NH3-TPD experiments were performed to measure the total acidity of prepared adsorbents. The amount of NH3 desorbed during heating indicates the total surface acidity of the sample. Quantachrome CHEMBET 3000 was used for this purpose. About 200 mg of sample was introduced in a U-shaped quartz microreactor (2 mm internal diameter). The sample was then dried at 150 °C overnight under N2 flowing at atmospheric pressure. The sample was cooled to 100 °C under He flow. NH3(g) was then used to adsorb NH3 on the surface at 100 °C for 1 h. The flow rate of NH3 was kept at 25 mL/min. Then, He was passed at a flow rate of 15 mL/min for 1 h at 100 °C to desorb physisorbed NH3. The solid was then heated to 900 °C at a heating rate of 10 °C/min to release chemisorbed NH3. The amount of NH3 was determined from the area under the peak using a calibration curve made for this purpose. NH3 uptakes were 520 μmol of NH3/g for macroporous Cakaolin and 286 μmol of NH3/g for CaBakaolin.
’ RESULTS AND DISCUSSION The adsorption experiments of VR and VB products (mild TC process) were performed initially with Cakaolin to determine the extension of the interaction of such products over this solid. Table 1 presents the corresponding adsorption uptake of each product in toluene solution, with an initial concentration of 60 mg/L at 295 K and 120 min, followed via ultravioletvisible (UVvis) spectrophotometry , as described in the Experimental Section. Typical errors in the absorbance scale do not exceed 10% relatively. It is observed that thermal cracking enhances uptake as a function of 545 °C+ conversion. The same behavior has been previously determined for the corresponding thermalcracked asphaltenes while their interactions were studied with reservoir minerals.21,22 These results confirm that adsorption over this solid is feasible and not limited by the molecular characteristics of the adsorbates, owing to the large pore sizes developed within the adsorbent. Table 2 presents the properties of the VR and VB products evaluated in this work. Molecular information gathered from asphaltene solubility profiling, 1H and 13C NMR, MM by SEC, plus elemental analysis help in the understanding of some important aspects that influence adsorption uptakes. From Table 2, it is observed that thermal cracking promotes noticeable molecular changes as a function of conversion. Previous reports
Figure 1. Adsorption uptake (Cakaolin) of Athabasca VR and VB products as a function of the solubility parameter for the second peak in the asphaltene solubility profile. Data points 1, 2, 3, and 4: VB severities 0, 8.7, 13.3, and 28.5%.
dealing with thermal processes suggest that large molecules present in VR are cracked into smaller molecules, depending upon the severity level.2730 Figure 1 presents a trend found between the solubility parameter corresponding to the second asphaltene peak, determined for the studied VR versus uptake. As mentioned in the Experimental Section, the second peak corresponds to the components from the samples that show higher solubility parameters from the distribution. They are normally observed only for thermal-processed materials. Details for asphaltene solubility parameter determination are presented elsewhere.24,25 The trend found between solubility parameters and adsorption uptakes indicates that increasing VB severity leads to the formation of species more difficult to dissolve, more unstable, and prone to interact strongly with the solid surfaces. This indicates that molecular parameters, such as aromaticity, total naphthenic carbon (TNC), and heteroatom content, that may change with VB severity could influence the adsorption processes. Discussion on the influence of these parameters upon adsorption will be addressed in the following sections. Peak MM (apex for SEC distributions) for the studied VR and VB products was determined.21,26 The calculated peak MM values (Da) are as follows: 1459 (feedstock, VR), 1107 (VB 8.7%), 830 (VB 13.3%), and 689 (VB 28.5%). These results clearly support a mass reduction under mild (VB) cracking conditions. The same fact has been observed by other authors for studied asphaltene MM under VB conditions.30 The 4051
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Figure 2. Adsorption uptake (Cakaolin) of Athabasca VR and VB products as a function of log(MM). Data points 1, 2, 3, and 4: VB severities 0, 8.7, 13.3, and 28.5%.
Figure 3. Correlation of the adsorption uptake (Cakaolin) of Athabasca VR and VB products with total secondary methylene groups. Data points 1, 2, 3, and 4: VB severities 0, 8.7, 13.3, and 28.5%.
corresponding MM values were correlated with the uptakes and presented in Figure 2. As observed, the reduction of average VR MM increases the uptake. Because product MM was observed to impact adsorption, total secondary methylene groups by 13C NMR were determined because they can provide indication of chain lengths. It is expected that, during thermal cracking, alkyl appendages are removed mostly by β-scission.27 Therefore, size reduction can positively affect the uptake by exposing aromatic moieties to a greater level. The trend between this parameter and uptake was determined, and the results are presented in Figure 3. The results from Figure 3 clearly indicate that, during thermal cracking, chain lengths are indeed reduced, leading to species having less steric hindrance, which preferentially adsorb on the studied Cakaolin solid. Concomitant with this observation, a plot between MM and total secondary CH2 (data not shown) was carried out. A straight line with a regression factor of 0.9978 indicates that both parameters are operating in the same direction. The preceding findings on MM and chain-length reduction suggest two possible reasons for the generation of products with higher adsorptive capacity; i.e., their decrease sizes facilitate their diffusion into adsorbent porous spaces. Further molecular information that can help with the understanding of the studied phenomena will be addressed in the ensuing paragraphs. The aromatic character of the feedstock and VB residua was evaluated by determining the residua aromaticity (fa) by 13C
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Figure 4. Adsorption uptakes (Cakaolin) of Athabasca VR and VB products as a function of carbon aromaticity (fa). Data points 1, 2, 3, and 4: VB severities 0, 8.7, 13.3, and 28.5%.
Figure 5. Adsorption uptakes (Cakaolin) of Athabasca VR and VB products versus TNC. MMs used for obtaining TNC were presented within the Results and Discussion (and their logarithms were presented in Figure 2). Data points 1, 2, 3, and 4: VB severities 0, 8.7, 13.3, and 28.5%. Tie lines were drawn to indicate trends.
NMR. This parameter was further correlated with adsorption uptake. Figure 4 presents the results from this trend. VB leads to an increase in the aromatic character for the products that facilitates their adsorption over Cakaolin. The results agree with previous findings determined for adsorption studies of VR and converted asphaltenes over different surfaces5,13,21,22 and aromatic nitrogen compounds, such as anilines, over kaolin surfaces.31 Furthermore, from 13C NMR analysis, the information about the naphthenic character of the products can be gathered. Figure 5 presents trends between the total naphthenic carbons present on each sample versus adsorption uptakes. It is clear that products with less naphthenic character seem to be more prone to be adsorbed on the studied solid. These results confirm that, particularly for this solid, the presence of more exposed aromatic cores in the molecules enhances their adsorption. This could be associated with the possibility of interaction via π-bonding through the aromatic electrons to silicon atoms present on the kaolin surface.3234 Figure 6 presents H/C atomic ratios for the residua, correlated with adsorption uptakes. The results from these trends complement the previous findings; i.e., the more the aromatic character (lower H/C ratio), the better the adsorptive behavior. 4052
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Figure 6. H/C atomic ratios for Athabasca VR and VB products correlated with adsorption uptake (Cakaolin). Data points 1, 2, 3, and 4: VB severities 0, 8.7, 13.3, and 28.5%. Tie lines were drawn to indicate trends.
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Figure 8. Correlation of asphaltene (second peaks) average solubility parameter for Athabasca VR having 0, 13.3, and 28.5% VB conversion, with adsorption uptakes over Cakaolin and CaBakaolin. Tie lines were drawn to indicate trends.
Figure 7. Correlation of VB severity with heteroatom contents (N, S, and O; wt %) and adsorption uptakes (Cakaolin) of Athabasca VR. Tie lines were drawn to indicate trends.
Considering that the studied thermal-cracked residua have varying heteroatom abundances (N, S, and O), their determined contents could also be important for addressing this investigation. It has been reported that, during thermal cracking, the heteroatom content varies according to the VB severity.30 Figure 7 presents heteroatom contents (left y axis) versus adsorption uptake (right y axis) for Athabasca VR and VB products as a function of VB conversion. Nitrogen is determined to increase as a function of thermal-cracking severity, and the oxygen content increases notably particularly at the highest severity achieved in this work. Linking these findings with the previous ones13,21,22 indicates that more severely VB products are mainly an aromatic nucleus with shorter alkyl chains and higher contents of N and O heteroatomic species present in their structures, which probably facilitates the interaction of these atomic moieties with solid sorbent surfaces. The sulfur content appears to decrease as thermal-cracking severity increases. It could be because alkyl moieties linked to molecular cores through S linkages (sulfide or disulfide bridges) are fragments being easily removed by thermal cracking, leading to a decrease in the S content with an increase in cracking severity and also leaving an exposed nucleus that interacts better with solid surfaces. Adsorption of Athabasca VR and VB Products over Macroporous CaBaKaolin. To determine if the observed trends
Figure 9. Adsorption uptakes on CaBakaolin for Athabasca VR with 0, 13.3, and 28.5% VB conversion as function of aromaticity and N contents.
thus far can be extended to other solids, a macroporous kaolin containing Ba with Ca within the kaolin matrix was prepared. The incorporation of Ba leads to a solid with a higher surface area (18 m2/g, as compared to 12 m2/g) but one-half of the total acidity compared to Cakaolin, as determined by NH3-TPD (NH3 uptakes were 520 μmol of NH3/g for macroporous Cakaolin and 286 μmol of NH3/g for CaBakaolin). Adsorption experiments of VR as well as VB with 13.3 and 28.5% conversion were performed with this new solid. Figure 8 presents trends of their second asphaltene peak solubility parameters versus uptakes for both solids Cakaolin and CaBakaolin. Initially, it is observed that all samples display more adsorptivity on the new CaBa-containing kaolin. The fact that the total acidity is reduced in the new solid indicates that this surface is more basic and may point out that functional groups that are acidic in nature could interact effectively with this new surface, thus enhancing the adsorption. Second, the trend observed in Cakaolin with the solubility parameter is more pronounced in the new solid. Therefore, the results found here suggest that samples with a high solubility parameter would interact in more extension with basic surfaces. Experiments to validate this assumption are in progress and will be presented elsewhere. 4053
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Energy & Fuels Then, two parameters, such as aromaticity and nitrogen content, were selected for further trends with uptakes over CaBakaolin. Figure 9 presents the results. Again, a reasonable trend of both parameters with adsorption uptake was observed, indicating that the more basic nature of the more adsorptive Bamodified solid did not change the adsorption trends determined for the VR and VB Athabasca residua. Trends between molecular parameters of their corresponding asphaltene fractions with this type of solid surface are in progress, and the results will be published in our future work.
’ CONCLUSION The results from the present study indicate that knowledge on molecular properties of heavy oil adsorbates could help to predict their potential adsorption capacity on solids, such as macroporous Cakaolin. Products with higher aromaticity, lower contents of naphthenic carbon, lower alkyl appendage lengths, lower H/C atomic ratios, and lower sulfur and higher nitrogen and oxygen contents were produced after thermal cracking. It was found that adsorbates with high values of second-peak asphaltene solubility parameters, aromaticity, and nitrogen and oxygen contents display higher adsorption capacities over the studied macroporous kaolins. Findings with Ba-modified macroporous kaolin (CaBa kaolin) indicate that this is a more adsorptive material; however, it gives the same adsorption trends previously determined with a Ca analogue. The results suggest that the molecular parameters studied can be extended to different solids as feasible predictors for adsorption processes. ’ AUTHOR INFORMATION Corresponding Author
*Telephone: (403) 220-9806. Fax: (403) 210-3973. E-mail: fl
[email protected].
’ ACKNOWLEDGMENT The authors acknowledge funding from the Alberta Ingenuity Centre for In Situ Energy (AICISE), Carbon Management Canada, Inc. (CMC), and the facilities provided by the Schulich School of Engineering, University of Calgary, Canada. E. Rogel, C. Ovalles, A. Pradhan, and J. Zintsmaster thank Chevron ETC for permission to publish this work. M. Moir (Chevron ETC) is acknowledged for his support and valuable comments on this manuscript. Lina Diaz is acknowledged for providing VR SEC data. ’ REFERENCES (1) Lee, S.; Speight, J. G.; Loyalka, S. K. Handbook of Alternative Fuel Technologies; CRC Press (Taylor and Francis Group): Boca Raton, FL, 2007. (2) Roberts, P. The End of Oil: On the Edge of a Perilous New World, 1st ed.; Houghton Mifflin: Boston, MA, 2005. (3) Altgelt, K. H.; Boduszynski, M. M. Composition and Analysis of Heavy Petroleum Fractions; Marcel Dekker: New York, 1994. (4) Sosa, C.; Gonzalez, M. F.; Carbognani, L.; Perez Zurita, M. J.; Lopez-Linares, F.; Pereira-Almao, P.; Moore, R. G.; Hussein, M. Visbreaking based combined process for bitumen upgrading and hydrogen production. Proceedings of the Canadian International Petroleum Conference (57th Annual Technical Meeting); Calgary, Alberta, Canada, June 1315, 2006; Paper CICP 2006-074.
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