ARTICLE pubs.acs.org/IECR
Kinetic Models for Upgrading Athabasca Bitumen Using Unsupported NiWMo Catalysts at Low Severity Conditions Carmen E. Galarraga,* Carlos Scott, Herbert Loria, and Pedro Pereira-Almao Department of Chemical and Petroleum Engineering, Schulich School of Engineering, University of Calgary, Calgary, AB T2N 1N4, Canada ABSTRACT: Typically, the catalytic upgrading of heavy fractions (VGO and VR) has been studied using mostly conventional supported catalysts at temperatures and pressures higher than 400 °C and 6 MPa, respectively. This work focuses on the upgrading of heavy oils at much lower severity conditions using dispersed NiWMo catalysts for processing whole oil with no fractionation. A kinetic study was developed to determine parameters from experimental data obtained at temperatures of 320380 °C and reaction times from 3 to 70 h at a total hydrogen pressure of 3.45 MPa and a stirring speed of 500 rpm in a batch reactor. The conversion, estimated as the reduction of the residue 545 °C+ fraction, was fitted for a first-order reaction with an apparent activation energy of 200 kJ mol1. Two kinetic models are proposed to predict the conversion of the residue fraction and its product distribution. Comparison between experimental data and predictions using the proposed models exhibited good agreement with average absolute errors lower than 5%.
temperatures and high pressures of hydrogen.7,8 Generally speaking, it has been accepted that the upgrading mechanism for heavy feedstocks, such as heavy oils and bitumen, is similar to thermal cracking,7,9 but having hydrogen transfer/hydrogenation superimposed, which helps to improve the quality of the upgraded product while decreasing the coke production.10 It would be very beneficial to find an alternative way of treating these feeds in situ, in the reservoir, to generate an upgraded low-viscosity bitumen that would eliminate the need for addition of diluent when transported. Also, the removal of contaminants and heteroatoms would help to decrease the hydrogen requirements for treatment during the refinement process. Regarding catalysts improvement, heavy oil upgrading technologies have advanced by using dispersed unsupported catalysts.7,9,1113 Dispersed catalysts can be produced from oil soluble precursors11,14 as well as water-in-oil emulsions containing the metallic precursors in the water droplets.15,16 The most used formulations for these developments continue to be those formulations typically used for conventional supported catalysts, such as molybdenum, tungsten, cobalt, nickel, and mixtures thereof.11,1719 Le Perchec and co-workers have indicated that dispersed unsupported catalysts may deactivate slower than typical supported hydroprocessing catalysts due to the higher reaction rates exhibited by unsupported catalysts, which not only can locally generate hydrogen spillover, thus increasing the upgrading of residual feedstocks,20 but also activate the hydrogen required for stabilizing the free radicals normally produced in the thermal cracking of heavy petroleum feeds.9 The interest in dispersed catalysts is mainly that they could be included in the reaction medium to navigate along with the targeted feed as small catalytic particles.15
1. INTRODUCTION According to the Energy Information Administration (EIA), the world marketed energy consumption will continue its tendency to growth; from 500 quadrillion British Thermal Units (BTU) marketed in 2007, the forecast predicts a consumption of 700 quadrillion BTU by 2035.1 Moreover, the International Energy Agency (IEA) has estimated that the oil demand will keep rising from the current 85 million barrels per day (MBBL/d) to 106 MBBL/d by 2030.2,3 Traditionally, these demands have been covered by exploitation of conventional light crude oils due to their easiness of production; however, this practice has generated a depletion in light oils worldwide. Therefore, the production of energy from hydrocarbons is an important issue for Canada because of its large amount of proven oil reserves, which are estimated to be 178.8 billion barrels of crude oil. Nevertheless, most of these reserves (about 174.5 billion barrels) are bitumen contained in oil sands, which are a complex mixture of sand, water, clay, and bitumen.4,5 Bitumen is a type of hydrocarbon, not only very viscous (its transportation inside pipelines usually requires diluent addition), but also with a low American Petroleum Institute (API) gravity value (low marketing value).6 Additionally, bitumen is rich in asphaltenes (1030 wt %), aromatics, and other multiple contaminants, thus requiring intense treatment to produce high valuable cleaner fuels able to comply the recent environmental constraints. One important characteristic of heavy oils and bitumen is their low hydrogen-to-carbon ratio,; thus their processing is preferably performed via hydrogen addition instead of carbon rejection processes. Conventional upgrading of this type of feedstocks has been achieved in petroleum refineries by mildhydrocracking or hydroconversion from moderate to high temperatures under hydrogen pressure aiming to produce light highquality fuels by increasing their low hydrogen-to-carbon ratio and diminishing the undesirable contaminants such as sulfur, nitrogen, aromatics, etc. Thus, such treatment usually requires high r 2011 American Chemical Society
Received: June 5, 2011 Accepted: December 7, 2011 Revised: December 2, 2011 Published: December 07, 2011 140
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The kinetic study of this type of reactions is very important because the assessment of the reaction rate is a key activity for selection of optimum operating parameters, moreover, in this particular case, because not many kinetic studies have been presented at working conditions close to those used for in-reservoir operation. These studies are required to establish sound models for reaction simulation, allowing the prediction of both bitumen upgrading and product quality. When dealing with heavy oils and bitumen upgrading, one important step of research for reactor design is the production of detailed kinetic models that allow for precise estimation of product streams composition. However, because heavy oils and bitumen are complex structures composed by large amounts of resins and asphaltenes, which consist of large molecules of condensed poly aromatic rings, the kinetic study of its reactivity is a complex task. One typical approach to this problem involves the use of grouped lumps of pseudospecies,2124 connected through a reaction scheme by parameter estimation and correlated with process data yield. The larger is the number of lumps, the longer is the time for solving the intricate equations network from the kinetic analysis, because more kinetic parameters need to be estimated and more experimental data need to be gathered. Regarding the reaction order for these type of reactions, there are some discrepancies; while some authors consider this reaction to be second order,25,26 most researchers agree on a power law of a first-order reaction with respect to the hydrocarbon.2731 Reported kinetic models for the catalytic and noncatalytic upgrading of Athabasca bitumen used several levels of complexity for which the lumps include a combination of the separated fractions: heavy ends (coke + asphaltenes + resins), light oils (saturates + aromatics), asphaltics (coke + asphaltenes), maltenes (resins + aromatics + saturates), and gases.27,32,33 The increased number of lumps rendered the best results; however, good approximations were obtained with intermediate numbers (24 lumps).8,34,35 Another way to the traditional lumping technique is modeling based on distillation fractions, such as naphtha, middle distillates, vacuum gas oil (VGO), and residue.28 Also, different reactions schemes have been proposed in the literature, in which it has been concluded that given the complexity of real feedstocks, lumping techniques will continue as useful tools for studying hydroprocessing reaction kinetics.21,36 With respect to the use of ultradispersed catalysts for bitumen and heavy oil upgrading, most of the published work presents kinetic models at typical (high severity) hydroprocessing conditions, which is temperatures from 350 °C and above with minimum reacting pressures of 7 MPa.7,10 One important goal of the present research is to evaluate the performance of these catalysts at operating conditions near those used in-reservoir operation, because typical temperatures and pressures in petroleum reservoirs are lower than those employed in conventional hydroprocessing. Hence, in this Article, we present kinetic models to describe the effects of temperature and reaction time on the extent of conversion of the residue fraction of Athabasca bitumen when hydroprocessed in the presence of unsupported dispersed NiWMo catalysts using a noncomplex stirred batch reactor at low severity operating conditions.
in the hydrocarbon. Conventional hydroprocessing catalysts are bimetallic17 and mainly constituted by CoMo (maximum hydrogenolysis and hydrodesulfurization),37 whereas Ni and W are included when higher hydrogenation activity is desired.18,38 The catalyst for the present study was formulated as a mixture of NiWMo to maximize hydrogenating activity. Thus, 1000 ppmw of metallic species (respect to the bitumen) was added to produce atomic metallic ratios as follows: Ni/Me(atomic) = 0.3 with Me = Ni + W + Mo, and Mo/W(atomic) = 3; additional details regarding this catalytic formulation and its preparation are described elsewhere.12,13 2.2. Feedstock. Athabasca bitumen produced via steamassisted gravity drainage (SAGD) with an API gravity of 9.5°, viscosity of 7890 cP at 40 °C, sulfur of 4.8 wt %, and a residue content of 49 wt % (545 °C+) was used as feedstock for the upgrading experiments. 2.3. Upgrading Experiments. In a typical experiment, about 30 g of catalytic emulsion was placed into a Parr batch autoclave reactor (100 mL), where upgrading reactions are performed at temperatures from 320 to 380 °C, a total hydrogen pressure of 3.45 MPa, for various reaction times (370 h). All experiments were carried out at a stirring speed of 500 rpm to diminish mass transfer limitations. Zero time was taken when the temperature inside the reactor reached the targeted value. Product samples are constituted by hydrocracked products (gases and liquids), catalytic submicrometer particles, and coke (if produced). Gaseous samples are collected in a vacuum-cleaned cylinder and analyzed by gas chromatography (GC) to determine both hydrogen and light hydrocarbons (C1C5) contents; thus, at the sample conditions an average molecular weight can be estimated and used to quantify the sample mass and to calculate the gas yield. Liquid (feedstock or product) samples were analyzed using standard characterization techniques to determine viscosity and sulfur content, whereas boiling point distribution curves were determined by high temperature simulated distillation (HTSD),39 which served to define four pseudocomponents distinguished by boiling points: naphtha (IBP216 °C), distillates (216343 °C), vacuum gasoil, VGO (343545 °C), and residue (545 °C +). Detailed procedures for collection of both samples gases and liquids are described elsewhere.12,13 Coke was defined as the difference between the total solids recovered (nonsoluble matter after contacting the liquid sample with CHCl3 in a ratio 1:50 w/w) minus the nominal mass of catalyst component (0.15 wt %). Equation 1 was used to calculate the conversion of the residue fraction, whereas complete mass balances (average value 97.8 wt %), composition and quantification of gases, as well as coke determination were used to calculate the entire product distribution. The liquid yield then is calculated as 100 minus both gases and coke yield altogether.
2. EXPERIMENTAL SECTION
3.1. Product Composition. The liquid product yield distribution according to the aforementioned fractions together with gases and coke for experiments carried out at temperatures 320380 °C is listed in Table 1. As expected, the higher is the temperature and the longer is the reaction time, the higher is the
conv 545°Cþ ¼
þ mass 545 °Cþ feed mass 545 °Cproduct
mass 545 °Cþ feed
100 ð1Þ
3. RESULTS AND DISCUSSION
2.1. Catalyst Preparation. NiWMo catalysts in the form of submicrometer dispersed species were prepared from aqueous solutions of nickel, tungsten, and molybdenum that were emulsified 141
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Table 1. Product Yield Distribution (wt %) from HCK of Athabasca Bitumen Catalyzed by Submicrometer NiWMo Catalysts at a Total Pressure of 3.45 MPa, Temperatures 320380 °C, and Reaction Times 370 h product distribution, % temperature, °C time, h gases naphtha distillates VGO residue coke feedstock
2.8
15.0
34.5
47.8
320
24
0.6
2.7
15.6
35.8
45.1
0.3
320
38
0.4
3.0
16.1
35.8
44.4
0.3
320
48
0.3
4.2
17.0
35.8
42.6
0.1
320
69
0.1
3.3
17.7
37.7
41.0
0.2
350
6
0.1
4.6
17.0
35.3
42.9
0.2
350 350
7 22
0.3 0.8
3.7 4.7
17.1 20.3
36.1 38.9
42.6 35.0
0.2 0.2
350
30
1.8
5.8
21.8
39.6
30.7
0.3
350
30
1.8
5.8
21.3
39.8
29.5
0.3
350
30
1.8
5.8
21.8
40.2
30.5
0.3
350
48
2.2
7.9
22.7
38.7
28.1
0.4
360
8
1.0
3.3
17.7
35.0
42.8
0.3
360
15
1.8
6.2
19.8
35.4
36.6
0.3
365 365
5 5.5
0.5 0.6
4.8 4.4
19.4 19.2
36.6 37.1
38.7 38.5
0.0 0.3
380
3
2.2
6.7
20.3
38.0
32.6
0.2
380
5.8
2.0
8.8
23.9
39.1
25.9
0.3
380
8
2.0
10.9
27.1
40.2
19.5
0.4
380
14
2.0
14.6
29.4
36.4
16.9
0.8
Figure 1. Rate constant plots for the hydrocracking of whole Athabasca bitumen catalyzed by submicrometer NiWMo catalysts at a total pressure of 3.45 MPa and a stirring speed of 500 rpm.
Table 2. Kinetic Constants for a First-Order HCK Reaction of Whole Athabasca Bitumen Using Submicrometer NiWMo Catalysts temperature, °C kinetic constant, h1 regression coefficient, r2 AAE, %
conversion of the residue fraction into lighter products. At the lowest temperature (320 °C), the production of gases and coke is almost negligible. At the highest temperature (380 °C), the scattered pattern observed for gases yield is probably due to experimental error, because one would expected that the gases yield increases with temperature.40 A similar behavior has been reported for the conversion of Maya heavy oil.28 The content of residue 545 °C+ decreased with both temperature and reaction time even at the lowest temperature of 320 °C. At moderate to high temperatures (350380 °C), the majority of the residue fraction produces VGO, distillates, naphtha, and gases. The production of coke increases with severity, as expected; however, because of the mild conditions used in this work, selected to be near those of the in-reservoir operation, this undesired product was kept at a minimum. In a previous work, it was demonstrated that including these catalytic species at 380 °C and 8 h the coke amount was decreased from 8 to 0.2 wt %.12 Reproducibility of these experiments was evaluated by performing three different runs at 350 °C, 3.45 MPa for 30 h. These results are also included in Table 1. A good reproducibility was found with an average absolute error less than 3 wt % for all of the fractions. 3.2. Kinetic Models. As already mentioned, the cracking reaction of bitumen and its fractions is considered to be first order with respect to hydrocarbons28 and zero order with respect to hydrogen.25 Also, it is reported that the cracking of hydrocarbons is a bimolecular reaction taking place on the catalytic surface,25 in which both reactants should adsorbed on adjacent surface sites. Thus, given the complexity of the reacting system, the mathematical model for this work adopted a power law simple model.
320
0.0022
0.98
0.53
350
0.0127
0.95
1.56
360
0.0178
0.99
0.08
365
0.0418
0.99
0.44
380
0.1108
0.99
2.32
average AAE for all data, %
1.21
The first approach in this kinetic evaluation, so-called model A, considers the conversion of the residue fraction into lighter products as an irreversible first-order reaction, as follows: residue 545 °Cþ ðbitumenÞ þ H2 f lighter products
ð2Þ
with the following rate equation: dCR ¼ kCR dt
ð3Þ
where CR is the concentration of fraction 545 °C+, t is the reaction time (h), and k is the rate constant (h1). The linear form of eq 3 (using values from Table 1) is plotted in Figure 1. The linearity of these plots allows one to conclude that a first-order reaction describes quite well the conversion of the residue fraction of Athabasca bitumen when hydroprocessing it in the presence of the catalysts prepared from catalytic emulsions. The calculated rate constants are included in Table 2 along with the data correlation indexes, r2, and the average absolute errors (AAE), which were obtained from eq 4 by comparing the experimental value, CR exp (listed in Table 1), with the calculated concentration of residue, CR cal (estimated using the kinetic constant, slope of the fitting line, at each temperature) at the ith reaction time for n total number of concentrations. As expected for a cracking reaction, the kinetic parameter, k, increased with temperature. The AAE for the calculated kinetic constants resulted as less than 3%. These results agree with previous literature data obtained for supported catalysts and operating conditions typical of commercial reactors.25,28 142
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Figure 2. Arrhenius plot for model A.
Figure 3. Fractional conversion of the residue fraction 545 °C+ as a function of reaction time at temperatures 320380 °C. Symbols, experimental data; lines, calculated data from model A.
Additionally, in the present case, it is important to mention that at low severity conditions, that is, reaction temperature e 365 °C, the AAE was smaller than 1%. The highest error (>2%) was observed for the highest temperature (380 °C); this increased error might be due to the high level of conversion achieved at long reaction times for this temperature, which in consequence might produce a higher amount of coke and gases. Also, it has been reported that at higher severity conditions a second-order reaction seems to fit better than the first-order typically assumed for this reaction.26 n
AAE% ¼
∑
i¼1
jCR i exp CR i calj 100 CR i exp
! ð4Þ
n
The Arrhenius plot (ln k vs 1/T) to determine the apparent activation energy (Ea) for the data included in Table 2 is displayed in Figure 2. As a general result, the average activation energy for this range of temperatures was found to be 204 kJ mol1 with a correlation index, r2 = 0.98, which is in close agreement with values already reported in the literature for this type of reacting system.7,9 It has been mentioned that in these processes, the catalysts do not have catalytic activity toward the cracking reactions.9 Thus, it can be assumed that the apparent activation energy observed in these experiments is related to a noncatalytic hydrocracking reaction, that is, thermal cracking with excess of hydrogen. It is worth mentioning that as the temperature decreases the thermal cracking of the CC bond reaction may be inhibited, but the hydrogenating reactions will get promoted because they require lower energy as compared to the thermal cracking ones.41 In this case, the dispersed catalysts are effectively catalyzing the hydrogenating reactions, and therefore helping to synthesize a product with a better quality exhibiting not only an improved viscosity and API gravity but also a lesser amount of solids, as previously reported.12 These improved product characteristics not only would help to decrease the amount of solvent required for bitumen transportation (from remote areas to refining facilities) but also would promote product stability. The apparent kinetic parameters from model A were then used to estimate the theoretical conversion at temperatures from 320 to 380 °C as a function of reaction time and compared to the conversion from the experimental data (Table 1). The results are displayed in Figure 3. As it can be observed,
Figure 4. Proposed lumped kinetic model for the hydrocracking reaction of Athabasca bitumen using ultradispersed catalysts at conditions near in-reservoir operation.
the model represents very well the experimental residue conversion in the interval of operational conditions here explored. This model, however, is not sufficient to further predict the composition and quality of the obtained products. Therefore, a more complex approach is required, and thus the lumped technique (based on Sanchez et al.28 ) was adopted to propose a second model, model B, which is exhibited in Figure 4. The base for model B includes 10 kinetic parameters (k1, ..., k10). Considering the same assumptions as for model A, eq 3 is adapted for each pseudo component j, with j = residue, VGO, distillates, naphtha, and gases, and thus the following equations can be written: R residue : r R ¼ ðk1 þ k2 þ k3 þ k4 ÞC 143
ð5Þ
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Table 3. Kinetic Parameters for Hydrocracking of Athabasca Bitumen Using Submicronic NiWMo Catalysts As Described by Model B temperature 1
kinetic constant (h )
320 °C
350 °C
k1
1.18 103 4
380 °C
r2
activation energy Ea (kcal/mol)
6.81 103
4.48 102
3
0.983
172.1
k2
1.51 10
4.49 10
2.68 102
0.978
276.7
k3 k4
1.79 104 3.62 105
2.49 103 5.09 104
2.87 102 1.06 102
1.000 0.995
271.7 303.1
k5
9.78 104
2.10 103
1.78 102
0.916
157.0
6
4
0.965
342.9
0.928
242.0
k6
3.81 10
3.13 10
2.26 103
k7
3.62 108
5.19 104
0
k8
3.19 106
5.86 104
2.86 103
4
k9
1.54 10
0
0
k10
1.24 104
2.02 103
0
VGO R ðk5 þ k6 þ k7 ÞC VGO : r VGO ¼ k1 C
ð6Þ
D R þ k5 C VGO ðk8 þ k9 ÞC distillates : r D ¼ k2 C
ð7Þ
R þ k6 C VGO þ k8 C D k10 C N naphtha : r N ¼ k3 C
ð8Þ
R þ k7 C VGO þ k9 C D þ k10 C N gases : r G ¼ k4 C
ð9Þ
j ¼ C
Cj ¼ 1 xj Coj
were controlled by the inclusion of the hydrogenating phases via the catalytic emulsion. (b) The first four kinetic rate constants (k1k4) represent the global (apparent) kinetic rate constant (k from model A); therefore, the sum of these rate constants was set to be equal to the global k already found from model A at each temperature (k1 + k2 + k3 + k4 = k). (c) The kinetic rate constants must follow the Arrhenius temperature dependence; then the values of the kinetic rate constants at a specific temperature were set to be higher than those from lower temperatures (kn at T2 > kn at T1, where T2 > T1). Results of these calculations are shown in Table 3, which also includes the activation energies determined from Arrhenius law as well as the corresponding correlation indexes. It should be mentioned that it was not possible to calculate the activation energies for reactions 7, 9, and 10 because the estimation gave scattered values for these parameters, some of them resulting in zero value. A similar trend was observed before.28 Because reactions 7, 9, and 10 are for gases production, the reason for this uncertainty might be either some experimental error in the gases quantification or that those reactions do not proceed in the same extent as the temperature changes. Additional experiments will be required to clarify this uncertainty. All of the regression indexes were found to be higher than 0.9, thus indicating good confidence for this set of data. The activation energies range from 157 to 342 kJ mol1. The least energy-demanding reactions were found to be VGO to distillates and residue to VGO, which indicates that these reactions are feasible at the lowest temperatures here evaluated. It also confirms that naphtha and middle distillates are essentially nonreactive at the present conditions.8 Figure 5 shows the parity plots for calculated and experimental compositions for products collected at 380, 350, and 320 °C. As observed, the data fit very well with a correlation index higher than 0.999. At these temperatures, the scattered pattern of the residuals (calculated as the difference between the experimental and the calculated composition) plotted in Figure 6 against the experimental composition permits one to conclude that any error in these calculations may be of experimental nature and not of the model. The so-developed model B along with empirical correlations (conversion-quality) already proposed12 for the liquids products whose characterization produced the set of data presented in Table 1 can be used as a valuable tool to predict not only the extent of residue conversion but also the product distribution and the quality of the converted product at any operating condition within the range here evaluated: 320380 °C and 370 h of reacting time.
ð10Þ
j is the dimensionless concenwhere rj is the rate of reaction; C tration relating the initial and actual concentration of component j at any reaction time t; xj is the fractional conversion of component j; and k1,...,10 is the kinetic constant for each reaction, as depicted in Figure 4. Kinetic rate constants, k1k10, were calculated by means of a semilinearization method. The first step was to represent reaction rate equations by integral equations defined in time intervals corresponding to different residence times; these integrals were solved numerically for each time interval employing the trapezoidal rule. The integral equations produced an overdetermined system of equations where the variables were represented by the kinetic rate constants. The integral equations system was implemented in Microsoft EXCEL, and initial guesses for the kinetic rate constants were selected randomly. The kinetic rate constants were calculated employing the tool SOLVER from Microsoft EXCEL; the objective of this tool was to obtain the group of kinetic rate constants that provided the lower performance index (PI). The lower is the PI, the closest are the experimental (Cj,iexp) and model (Cj,imod) products concentrations. The performance index is defined as: PI ¼
m
∑i j∑¼ 1 jCj, i exp Cj, i mod j2
ð11Þ
where Cj,i represents the concentration of the product j at the ith evaluated residence time and m is the total number of evaluated residence times. The best fit from the tool SOLVER from EXCEL was subjected to the following constraints: (a) Only irreversible reactions are taken into account; thus all kinetic rate constants were set to be positive (kn > 0). From previous results,12,13 it was confirmed that condensation reactions (which may produce coke) 144
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4. CONCLUSIONS A kinetic study to describe the extent of upgrading and the product distribution obtained during the hydrocracking reaction of Athabasca bitumen in the presence of ultradispersed submicrometer catalysts at conditions similar to those used in-reservoir operation was successfully performed. A model based on the boiling points lumps and including five pseudo components, residue, vacuum gas oil, distillates, naphtha, and gases, serves to predict the product composition with less than 5% error. At moderate to low severity conditions (temperatures lower than 380 °C), the average apparent activation energy was found to be 200 kJ mol1. ’ AUTHOR INFORMATION Corresponding Author Figure 5. Parity plots for experimental and calculated values of each component produced by the hydrocracking reaction of Athabasca bitumen using ultradispersed catalysts at conditions near in-reservoir operation (T = 320380 °C).
*Tel.: (403) 210-9590. Fax: (403) 210-3973. E-mail: cegalarr@ ucalgary.ca.
’ ACKNOWLEDGMENT We would like to thank the Alberta Ingenuity Centre for In Situ Energy (AICISE) funded by the Alberta Ingenuity Fund and the industrial sponsors Shell International, Conoco-Phillips, Nexen Inc., Total Canada, and Repsol-YPF for financial support. Valuable comments from three anonymous referees are acknowledged. C.E.G. appreciates the economical support granted by The Schulich School of Engineering at the University of Calgary, Canada. ’ REFERENCES (1) U.S. Energy Information Administration. International Energy Outlook 2010. World Energy Demand and Economic Outlook, Report # DOE/EIA 0484 (2010); retrieved August 25, 2010; http://www.eia.doe. gov/oiaf/ieo/world.html. (2) U.S. Energy Information Administration. World Proved Reserves of Oil and Natural Gas 2009; retrieved February 15, 2010; http://www. eia.doe.gov/emeu/international/reserves.html. (3) Shah, A.; Fishwick, R.; Wood, J.; Leeke, G.; Rigby, S.; Greaves, M. A review of novel techniques for heavy oil and bitumen extraction and upgrading. Energy Environ. Sci. 2010, 3, 700. (4) Patel, S. Canadian oil sands: Opportunities, technologies and challenges. Hydrocarbon Process. 2007, 65–73. (5) Stelmach, E. Speech at the II World Heavy Oil Congress Edmonton, Alberta 2008; available via the Internet at http://www.premier.alberta. ca/speeches/speeches-2008-mar-10-World_Oil.cfm (accessed March 2009). (6) Strausz, O. P.; Lown, E. M. The Chemistry of Alberta Oil Sands, Bitumens, and Heavy Oils; Alberta Energy Research Institute: Calgary, 2003. (7) Del Bianco, A.; Panariti, N.; Anelli, M.; Beltrame, P. L.; Carniti, P. Thermal cracking of petroleum residues 1. Kinetic analysis of the reaction. Fuel 1993, 72, 75. (8) Ayasse, A. R.; Nagaishi, H.; Chan, E. W.; Gray, M. R. Lumped kinetics of hydrocracking of bitumen. Fuel 1997, 76, 1025. (9) Del Bianco, A.; Panariti, N.; Di Carlo, S.; Beltrame, P. L.; Carniti, P. New developments in deep hydroconversion of heavy oil residues with dispersed catalysts. Part 2: Kinetic aspects of the reaction. Energy Fuels 1994, 8, 593. (10) Mohanty, S.; Kunzru, D.; Saraf, D. N. Hydrocracking a review. Fuel 1990, 69, 1467. (11) Panariti, N.; Del Bianco, A.; del Piero, G.; Marchionna, M.; Carniti, P. Petroleum residue upgrading with dispersed catalysts Part 2. Effect of operating conditions. Appl. Catal., A 2000, 204, 215.
Figure 6. Residual values from comparison in Figure 5.
Additional contributions from this research group will address the scaling up of the present kinetic study but approaching a plug flow model (bench scale evaluation) in which mass transfer limitations may be considered. Also, research at temperatures lower than those explored in this work is required to further evidence the hydrogenating catalytic effect of the dispersed NiWMo particles here employed. Estimating the extent of dispersion (or aggregation) of these unsupported catalytic species during reaction is a paramount activity mainly due to (a) the lack of transparency of the oil medium (bitumen); (b) the change of properties (viscosity and density) of the oil where the particles are dispersed; and (c) the sample recovery methodology after reaction, which requires additional manipulation techniques, such as filtration, centrifugation, etc., and may alter the initial aggregation state of these unsupported particles. Nevertheless, future work attempting to study the effect of dispersion will be addressed by contrasting the use of the catalytic emulsions alone versus the use of a mixture containing sand particles along with the catalytic emulsion as to simulate the catalytic behavior inside a porous medium. 145
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dx.doi.org/10.1021/ie201202b |Ind. Eng. Chem. Res. 2012, 51, 140–146
