238
Ind. Eng. Chem. Process Des. Dev. 1983, 22, 236-242
L = liquid
Literature Cited Bemer, G. G.; Kalis, G. A. J. Trans. Ind. C h m . Eng. 1978, 56, 200. Billet. R. Chem. €ng. Frog. 1087, 63(4), 53. BoHes. W. L.; Fak. J. R. “Performance and Deslgn of Packed Dlstlllatlon Columns”, Ind. Chem. Eng. Symposlum Serbs, No. 56; I. Chem. E. ServIces: Rugby, 1979; pp 33-35.
Cornell, D.;Knapp, W. G.: Close, H. J.; Fair, J. R. Chem. Eng. Prog. 1960, 56(8), 48. Sawkowskl, H. Personal communlcatlon, Imperial College, London SW7, 1980.
Received f o r reuiew September 22, 1981 Accepted September 1, 1982
.‘
Asphaltene Cracking in Catalytic Hydrotreating of Heavy Oils. 1 Processing of Heavy Oils by Catalytic Hydroprocessing and Solvent Deasphatting Chlrato lakeuchl, Yoshlo Fukui, Munekaru Nakamura, and Yoshiml Shiroto +
Chiyoda Chemical Engineering B Construction Co., Ltd., 3- 13, Moriye-cho, Kanagawa-ku, Yokohama 221, Japan
A new catalytic hydrotreating process, the Asphaltenlc Bottom Cracking (ABC) process, for heavy residual oils has been Investigated in the relation between catalysis and chemical structure. A proprietary catalyst has been developed which is capable of hydrocracking asphaltenes into heptane-soluble materials and decreasing the vanadium content of heavy crudes and residues at a lower hydrogen consumptlon than a commercial hydrodesulfurization(HDS) catalyst and wlthout change In activity In a six-month test. Various heavy feedstocks were tested in a catalytic reactor (ABC sectlon) and a solvent deasphaltlng unit (SDA). Precipitated asphaltenes were recycled. Reactivities of various residues and a proposed mechanism are dlscussed. This ABC process will be most useful as a step preceding an existing hydrocrackii process In the upgrading of resMues with h$h asphaltenes and metals contents. In addition, the appllcation of this technology Is described.
Introduction The primary energy source today and in the near future must be sought in petroleum, although substitute energy sources are being actively developed worldwide as a result of warnings of a foreseen shortage of petroleum resources. Particularly, the demands of transportation fuels and light fractions as the feedstock for the hydrocarbon chemistry are expected to increase steadily, and their significance must be enhanced because those needs are not easily replaced by other resources. It is certain that in the many years of history refineries have been endeavoring to produce light and heavy oil products according to their demands from the available barrels of various crude oils. Those efforts, however, were directed mainly to the distillate oil where, for example, gas oil was converted to FCC gasoline. The new upgrading technologies which are sought for refining engineers today are aimed at the conversion of the bottom of the barrel to distillate oils. These are also useful for the development of fossil fuels such as tar sand bitumen and Orinoco belt crude expected to be hydrocarbonaceous resources. Most of the conversion schemes for processing heavy residual oils are based on two basic approaches, i.e., carbon rejection and hydrogen input. Heavy residual oils are usudy characterized by the very large content of so-called asphaltenes, which consist of large molecules of condensed polyaromatic rings, associated with each other as micelles. Consequently, the technology of upgrading heavy residual ‘This work was presented in part at the ACS/CSJ Joint Meeting, Division of Petroleum Chemistry, Symposium on Advances in Petroleum Processing, Honolulu, April 1979. It also was presented in part in the Symposium on Upgrading for Heavy Oils, Japan Petroleum Institute, Tokyo, Nov 6, 1981. 0196-4305/83/ 1 122-0236$0 1.50/0
oils will be influenced by how these asphaltenes are treated. The carbon rejection processes are achieved by removing hydrocarbons with the lowest hydrogen to carbon ratio (such as asphaltenes and Conradson carbon residue) from heavy residual oils in the form of coke matter and obtaining cracked distillates from which part of the sulfur and nitrogen compounds and most of the organometallic compounds of nickel and vanadium are removed. Examples of this approach include coking, catalytic cracking of residuum, etc. The hydrogen input processes are hydrocracking and hydrotreating, Le., hydrocracking heavy fractions including asphaltene and the precursor of carbon residue to lighter oil products, removing metals contained in the oil by deposition on the catalyst, and removing sulfur and nitrogen compounds in the forms of H2S and NH3, respectively. Both approaches, however, appear still to require improvements in various aspects such that the former is unavoidable from rejection of lower-value byproducts such as coke and the latter from excessive consumption of catalyst. In the viewpoint described above, the R & D Center of Chiyoda Chemical Engineering & Construction Co. has been engaged actively in the research of hydrotreating. During the course of catalyst development, a particular group of catalysts was found to exhibit demetallation closely malted to conversion of asphaltenes to lighter hydrocarbon oii by the reduction of molecular weights. The upgrading technology employing these new catalysts is the Asphaltenic Bottom Cracking (ABC) process. As shown in Figure 1, by recycling the unreacted asphaltenes separated by solvent extraction, it has become possible to convert the asphaltenic residue completely to deasphalted oil. This paper is presented for the upgrading technology of heavy residual oils based on the conversion of as0 1983 Amerlcan Chemical Society
Ind. Eng. Chem. Process Des. Dev., Vol. 22, No. 2, 1983 237 Table I. Reactivity of Various Heavy Oils with ABC Catalyst Khafji VR
Gach Saran VR
Basrah heavy VR
conversion, % wt asphaltenes conversion demetallation desulfurization chemical H, consumption, scf/bbl
49 71 40 500-530
properties specific gravity, d1S/4 asphaltenes, wt % CCR, wt % pour point, "C sulfur, wt % vanadium, wt ppm nickel, wt ppm
47 80 32 400-440
66
88 56 900-940
feed
product
feed
product
feed
product
1.036 13.5 23.6 > 46 5.27
0.989 6.9 16.8 11 3.17 42 26
0.131 10.9 23.0 >46 3.83 282 91
0.989 5.8 16.5 12 2.61 46 28
1.051 16.1 25.6 > 46 6.14 211 71
0.979 5.39 13.6 -4.5 2.72 19 16
181 55
Boscan crude
Orinoco AR conversion, % wt
70 90 51 400-460
69 82 42 500-540
asphaltenes conversion demetallation desulfurization chemical H, consumption, scf/bbl
78
80 59 550-590
feed
product
feed
product
feed
product
0.998 11.5 15.9 4.5 5.18 1.130 106
0.950 3.5 9.3 -9.0 2.53 100 27
1.002 14.1 17.9 32 3.92 478 107
0.975 4.4 11.2 -6.0 2.28 77 30
1.006 9.0 13.5 9.5 4.40 177 77
0.957 2.0 7.3 -22.5 1.80 36 16
properties specific gravity, d'5/, asphaltenes, & % CCR, wt % pour point, "C sulfur, wt % vanadium, wt ppm nickel, wt ppm
Athabasca bitumen
~~
~~
Temperature, 405 "C; pressure, 140 kg/cmz. Product Oil
\Inmaaim Qae;An,a
ction
Recovery
Deosphalting
Figure 1. Schematic representation of ABC process.
phaltenes in with regard to product oil properties, reactivities of various heavy residues, and applications of this new process. Experimental Section Feedstock. Various kinds of heavy residues have been inveatigated in the present experiments, i.e., Khafji vacuum residue (VR),Gach Saran vacuum residue, Basrah heavy vacuum residue, Orinoco atmcepheric residue (AR),Boscan crude, Athabasca bitumen, etc. The properties of these feedstocks are shown in Table I (in comparison with those of typical product oils). Some feedstocks were used after proper pretreating; e.g., Khafji VR which has been used in long runs was sufficiently desalted prior to use. Orinoco belt crude was blended with a distillate to remove mud water and then was desalted and distilled to separate atmospheric distillate oils, for feed preparation. Equipment and Operation. The experimental units consist of a fixed-bed, high-pressure catalytic reaction unit and a solvent deasphalting (SDA) unit. A simplified flow diagram of the test plant for the ABC is shown in Figure 2, in which both units are connected for the residue conversion process development. Nominal capacity of the unit is 1 L/h. The reaction unit consists of two catalytic reactors, connected in series, with a catalyst bed volume of 750 mL within each reactor tube of 31.1 mm inner diameter and 2200 mm long. The SDA column consists of the
I L
Figure 2. Simplified diagram of pilot plant.
extractor part, which is 28 mm in inner diameter and 690 mm in height and separated into compartments by 102 pieces of a starter ring (20.5 mm diameter) and disk (18 mm diameter) and a settler part which is 53.5 mm in diameter and 515 mm in height. In the once-through reaction test, only feed and reactor sections were used, and in the complete conversion test to bottomless the whole unit was put into operation and all of the bottom from SDA was recycled to the reaction unit. In the ABC and SDA combination operation, the first 500 h were in once-through operation and thereafter the extinction recycle operation of SDA asphalt was conducted. Fresh feed is supplied to the level-controlled flash vessel of SDA asphalt, and the feed rate is measured by weight change of feed drum. Fresh feed and SDA asphalt are completely mixed in an oil mixing vessel, supplied at a constant rate to the preheat section of the reactor bottom
238 Ind. Eng. Chem. Process Des. Dev., Voi. 22, No. 2, 1983 Feedstock Temp Pres
.
VR 405.C 140kglrd-G
Feedstock
KhOlji
VR
0
Khafji
0
Gach Saran VR
AR
Orinoco
'0
500 loo0
IKX) 2000
25O03cO3 3&2 4oO34500 5.cx3055CO 6cO365oO7ccO Process Time ( H r l
Figure 3. Catalyst activity and stability.
with compressed make-up hydrogen. The reactor effluent separates hydrogen in the high-pressure separator, dry gas and H2S in the low-pressure separator, and then is fed to the SDA section. SDA feed, after being mixed with solvent in the solvent mixing vessel, is injected to the middle of extractor column for the separation of asphaltenes. Deasphalted oil (DAO) and solvent mixture from the top of extractor is separated in a DAO flash vessel; DAO is measured by weight and obtained as the product outside of the system. Recovered solvent is recycled to the solvent vessel. Separated SDA asphalt is recycled to the reactor section again and is run down to an SDA asphalt flash vessel where the fresh feed is supplied. The investigated ranges of process variables of the experimental units are as follows. For the reaction section: pressure, 90 to 180 kg/cm2; temperature, 360 to 430 "C; LHSV, 0.2 to 1.5 h-l; hydrogen to liquid ratio in volume, 600 to 2000 NL/L. For the SDA section: pressure, 40 kg/cm2 g; extraction temperature, up to 190 "C; solvent to oil ratio, 3 to 7 (vol/vol); solvent, butane and pentane. Catalysts. The ABC catalyst, which has been selected after many tests for the purpose of the present investigation, has proprietary properties in chemical composition and physicochemicalstructure. It is a cylindrical extrudate of 0.8 mm diameter and ca. 5 mm length. The HDS catalyst used for comparison is of the cobalt-molybdenum type, supported on an alumina carrier designed in physicochemical structure for direct HDS. The size and the shape are similar to the ABC catalyst. Both have been prepared in Chiyoda's R & D center. Analyses. Gas streams were analyzed by an on-line process gas chromatograph for hydrogen, hydrogen sulfide, and C5- hydrocarbon gases. Receiver product oils as obtained and sample oils from streams in an SDA processing were analyzed for the following items: elemental analysis, specifc gravity, viscosity, asphaltenes (heptane-insolubles), content, Conradson carbon residue (CCR), pour point, softening point, gel permeation chromatography (GPC), and average molecular weight.
Results and Discussion Catalyst Stability and Selectivity. The catalyst activity for asphaltene cracking and demetallation was proved in this study to have excellent resistance against the carbon deposition and the metal poisoning and was subjected to long continuous tests at a constant temperature. Figures 3 and 4 show the ABC catalyst activity and stability in asphaltene cracking and vanadium removal. In Figure 4 the changes of the relative rate constants, based on the values of 10 w t % metals deposition for asphaltene cracking and vanadium removal, are shown against the metals deposition on the fresh ABC catalyst in comparison with the HDS catalyst. The activity of catalyst is expected to continue for at least six months to keep asphaltenes content constant without the temperature rising. The ABC catalyst selectivity for demetallation and asphaltene cracking in comparison with the HDS catalyst is illustrated in Figure 5.
1
Lb
~ 0 1 11 0 IO
1
l
1
l
l
I
I
!
I
l
60 70
80 90 100 110 120 I 3 0 140 Metals Deposition ( W t % on Fresh Catalyst I
20 30 40 50
Vanadium Removal
d -HDS
\ 7
,
-" c
01:
10
L
20
i
Catalyst
for Khafji VR
$0
io
Metals Deposition
A A
A (W
,io
iio
i~o!,
t X an Fresh Catalyst 1
Figure 4. Catalyst stability.
0
0
] ]
Asphaltene Cracking Catalyst H O S Catalyst Asphaltene Cracking Catalyst H D S Catalyst
Desulfurization IYd
for Orinoco A R VR
for Khofji
l%I
Desulfurization
Figure 5. Catalyst selectivity. 151
\ y ,
,
,
Khafji V R
Feedstock
,
'
1
1
0
0
m
400
Chemical Hydrogen
600 Consumption
800
1,000
lSCF/ B E L )
Figure 6. Asphaltenes content of product oil.
Feature of Asphaltene Cracking and Proposed Mechanism. The ABC catalyst activity and the feature of the ABC reaction were investigated in the comparison with the behavior of the commercial direct HDS catalyst. Under various reaction conditions, the asphaltenes and vanadium contents of product oils are related to the chemical hydrogen consumption, as shown in Figures 6 and 7. One of the features of ABC catalyst is that it possesses higher activities in the asphaltenes conversion and the demetallation than the direct HDS catalyst at the same chemical hydrogen consumption. This fact suggests that
Ind. Eng. Chem. Process Des. Dev., Vol. 22, No. 2, 1983 239 2001,
Feedstock '
'
I
I
'
I
K h a f j i VR '
Asphdttnc Cracking
3l
-
itji VR 1
\
$ 2
-
00 I
200
403
Boo
Mx)
1,000
1
-~
OL
'
2bO
Chemical
'
400
'
& I ' 8&
Hydrogen Consumption
'
I.&
IS C F / B B L I
Chemical Hydrogen Consumption
Feedstock
= 2.000
Khat11 VR
Khafji VR
Feedstock
Figure 7. Vanadium content of product oil.
6.000
iSCFlBBLl
Figure 10. Sulfur content of asphaltenes.
-I 7 80 at
Asphaltene Cracking Cotapst
H D S Catalyst
L
D
Asphollene
2
20
'0 Chemical Hydropen Consumption
100
aX,
300
400
xx)
800
700
ISCFlBBLI
Figure 8. Average molecular weight of asphaltenes.
Chemical Hydrogen Consumplion (
900
800
1,ooO IJM)
SCF / BBL 1
Figure 11. Sulfur removal vs. chemical hydrogen consumption.
Feedstock Khofji V R
ob
"400'
\I
&'ebo'I.doo
Chemical Hydrogen Consumption i SCFlBBL I
Figure 9. Vanadium content of asphaltenes.
asphaltene molecules could be converted to heptane-soluble materials in the state such that hydrogenation and dealkylation of condensed polyaromatic rings were suppressed extremely. Also, the progress of demetallation is considered to be closely related to the action which converts asphaltenes to heptane-soluble materials. The changes of average molecular weight and vanadium content of remaining asphaltenes in product oil were illustrated in Figures 8 and 9, respectively. The average molecular weight of asphaltenes in the feedstock, Khafji vacuum residue, is approximately 5000, but it becomes smaller rapidly in the progress of the reaction and down to approximately 1500. At the same time, the vanadium content reduces from ca. 660 wt-ppm to 300 wt-ppm. These reductions should be observed as clear differences from the performances of the direct HDS catalyst. Indicated in Figure 10 are the sulfur contents in asphaltenes. The direct HDS usually requires extremely severe conditions for deep desulfurization because of low reactivity of asphaltenic sulfur, but the ABC catalyst removes it comparatively well. As described above, the reaction by this catalyat provides higher rates in asphaltene cracking, demetallation, and reduction of molecular weight than those by the direct HDS catalyat at the same chemical hydrogen consumption. Furthermore, to investigate the role of hydrogen in the reaction, the sulfur content is shown in relation with hy-
I o""lo3
'
'
"
""I
10'
Average Molecular Weight
Figure 12. Conversion VB. average molecular weight of asphaltenee.
drogen consumption in Figure 11. In the HDS,hydrogen consumption is known to increase proportionally at low rates of desulfurization, and hydrogen consumption of this reaction quite agrees with that of direct HDS. In other words, it is considered that hydrogen in the asphaltene cracking reaction is used mainly to convert sulfur compounds to hydrogen sulfide and hydrogenate the fragment where sulfur is combined. The other characteristics of the reaction became obvious when the asphaltenes having broad distribution of molecular weight were separated into fractions and the change of fractions was investigated before and after the reaction. As an example, Khafji VR in which asphaltenes are with molecular weight from 1500 up to 22 300 is divided into eleven fractions, conversions of which were measured making use of gel permeation chromatography, as indicated in Figure 12. Reaction rates of larger asphaltenes are more rapid than those of smaller asphaltenes. This leads to a promising suggestion that the separation and recycling of remaining asphaltenes from once-through product to the reaction makes it possible to produce asphaltene-free oil. Furthermore, the reduction of viscosity in the ABC reaction is significant as illustrated in Figure 13. To summarize the above, the fact common to all characteristics of the reaction is to activate the heavier as-
240
Ind. Eng. Chem. Process Des. Dev., Vol. 22, No. 2, 1983 Feedstock b Athabasco Bitumen 0
Boscon Crude
A Gach Saran VR A Khafji V A
I
'
"
"'
'
' ' I " ' ' /
'
'
I
~~
\
Product
',
\
IO 0
40
20
60
80
1
100
AsphOltene Conversion (XI
\
-'I
"Bosroh " " " ' Heavy VR
""""
Figure 13. Visbreaking effect of asphaltene cracking catalyst. o b
- M - Metal - Aromatic
Destruction of Asphaltene Depolymerization
Miceile
due to Hetero -atoms Removal
Sheet
IL
102
wwm Aliphatic
Product
\',
103
io*
104
Equivalent Molecular Weight (Colibroted by Polystyrene)
Weak Link
io'
103 Equivalent Molecular Weight
IColibroted by Polystyrene)
Figure 15. Molecular weight distributions of feed and product. Feedstock Property-
0Aspholtenes
- 20 E
Metols
Figure 14. Proposed mechanism of asphaltene cracking.
phaltene molecules. Conversion of key components which determine the physical properties of heavy residue naturally plays the roles of reducing specific gravity, viscosity, and pour point, etc. If the physical structures of asphaltene molecules are visualized according to Dickie and Yen (1967), the mechanism of the reaction is considered to be as shown in Figure 14. It is expected that metals such as vanadium and nickel contained in asphaltene micelles play the important role of bonding to constitute large molecules, and the removal of these metals destroys the association of asphaltene micelles. Further progress of molecular weight reduction will require partial rupture of bonds called weak links. Reactivity of Various Heavy Oils. The above characteristics of asphaltene cracking are common to most heavy oils for which the upgrading is challenged. The extinction of high molecular asphaltenes by the ABC reaction was revealed by gel permeation chromatography as shown in Figure 15. Asphaltenes which have molecular weight of 1O00 to 20 O00 contained in feedstocks of Khafji VR, Gach Saran VR, Basrah heavy VR, Orinoco AR, Boscan crude, and Athabasca bitumen are changed by once-through reaction to oil whose properties are similar to those of solvent deaephalted oils. Table I shows properties of product oils as well as those of feedstocks. Common phenomena for all heavy oils are that contents of asphaltenes and metals and pour point are reduced markedly, but contents of CCR and sulfur content are moderately reduced. The relative reactivities of typical heavy oils are shown in Figure 16 with reference to asphaltenes and metals
"
3
Reoctivitg;
e
0 E
VR'
VR
H&VR
AR
Crude
Reaction Condition Temp 405°C Press 140 kg/cm*-G Figure 16. Reactivity and content of asphaltenes and metals.
contents. It is considered that the reactivity of asphaltene cracking is approximately proportional to the metals contents. The details of the phenomena and the mechanism seem to require further studies. Complete Conversion to Bottomless. As explained clearly by the characteristics of the ABC reaction, the ABC catalyst selectively attacks asphaltene molecules. Therefore, the concept shown in Figure 1 and the flow scheme of Figure 2 make it poasible that all of asphaltenes in heavy oils are cracked by the extinction recycle mode of SDA asphalt. Indicated in Table I1 are the analyses of various streams at steady state when the recycle rate becomes
Ind. Eng. Chem. Process Des. Dev., Vol. 22, No. 2, 1983 241
Table 11. Yields and Qualities of DAO from SDA Combination Test for Khafji VR
SDA solvent
-
DAO
-
ABCISDA ABCISDA (once-through) (ext recycle) butane yield, wt % on fresh feed
SDA
Khafji VR
38.1 61.9
75.8 21.8
94.1 0
1.025 1549 (at 100 "C) 20.1 4.90 0.33
0.9513 982 3.9 3.39 0.13
0.9346 123 4.3 1.36 0.24
0.9405 155 4.6 1.63 0.26
11.1
trace
trace
trace
128 43
3.2 1.1
0.2 0.3
0.2 0.3
SDA asphalt
Oil Inspections specific gravity, d1Sl4 viscosity, at 50 "C, CP
CCR, wt
%
sulfur, wt %
nitrogen, wt % asphaltene, wt % vanadium, wt ppm nickel, wt ppm
Nophlho
Asptaltene Cracking Condition Temperature
r
4 0 5 C'
-_I Almorpheric Residue
1
1
,Feedstock
1
1
E
Cycle Oil DAO
Figure 18. Production of gasoline and middle distillate. Y
-
f 20
Vacuum Residue
d
OO
500
1,000 1,500 2,000 Process Time lhrl
2,503
LSFO
ABC
3,000
Figure 17. Operation resulta of ABC/SDA test for Khafji VR. constant for Khafji VR. DAO obtained is very low in asphaltene and metals contents and desirable feedstock if it is treated further by processes such as hydrotreating, hydrocracking, and catalytic cracking. An SDA asphalt is concentrated with asphaltenes and CCR and inferior heavy oil. Figure 17 shows the results of more than 3000 h of operation, including the test for the complete conversion of asphaltenes b flow rate in relation to hours on stream. In Figure 17, andOindicate the results of the tests in which butane and pentane were used as the deasphalting solvent, and all of the SDA asphalt was recycled for the complete conversion of asphaltenes. It is noted that in both cases the reaction reached a steady level. The resulh of the repeated operation shown a a a n d a n d i c a t e that the activity of the catalyst did not show any appreciable degradation despite the extinction recycling of the SDA asphalt. Application of ABC Technology. The field where ABC technology is utilized most effectively will be the processing of vacuum residue which contains large quantities of asphaltenes and metals; i.e., vacuum residue is upgraded to gasoline and middle distillates according to the demand of light products. Figure 18 shows the combination of ABC with existing hydrocracking and FCC processes. By this arrangement, a refinery can be configured so as to maximize higher added value distillate oils from gasoline, naphtha, jet fuel, and middle distillates to ultralow sulfur fuel oil. In case clean fuel is required to prevent emissions of sulfur and nitrogen oxides in combustion, the selection of hydrotreating catalyst and reaction conditions in Figure 18 makes it possible to produce ultralow sulfur fuel oil with moderate hydrogen consumption.
Figure 19. Direct HDS of vacuum residue.
6
100 I
1
1
I
1
I
I
1
i
I
I
I
I
I
1
I
1
I
I
1
I
I
I
I
I
I
I
I
1
L
%
Z!
V
1,200 1
Process Time
lhrl
Figure 20. ABC/HDS long run test results.
Also, as shown in Figure 19, the ABC combined with direct HDS will be used for more economic HDS of vac-
Ind. Eng. Chem. Process Des. Dev. 1983, 22, 242-248
242
Table 111. Properties of Khafji VR and ABC/HDS Treated Oil Khafji VR C5+yield, wt % properties specific gravity, dI5, viscosity, at 50 "C, CP sulfur, wt % nitrogen, wt % CCR, wt % vanadium, wt ppm nickel, wt ppm distillation C,-375 OF, V O ~% 375-450 OF,V O ~7% 450-650 O F , VOI % 650-1050 OF, V O ~% 1 0 5 0 "F +, vol % chemical hydrogen consumption, scf/bbl
ABC/HDS treated oil 94.9
1.023 5.1 X l o 5 4.96 0.40 21.2 130 41
27.5 72.5
0.9470 153 0.97 0.29 9.8 13 12 2 3 9.5 49.5 36 1000
uum residue, and the combination of ABC and HDS catalysts for some heavy residual oils will make it possible to produce feedstock for residual catalytic cracking. Figure 20 shows the results of ABC followed by HDS test during 5000 h, and some typical properties of the product oil therefrom are shown in Table 111. The effects of the
combined ABC/HDS process compared with HDS to be expected are summarized as follows: longer catalyst life; higher qualities on metals in the product oil; more distillate in the product oil due to ABC reaction effect. (It is possible in the HDS section t~ operate at higher temperature.) In view of effective uses of petroleum resources and a long-range stable supply of primary energy, ABC technology seems to be extremely adequate for the upgrading of tar sand bitumen and Orinoco belt crude, because these represent a kind of oils which contain asphaltenes and metals in high concentrations and are of high residue yields.
Acknowledgment Grateful appreciation is expressed to the memory of Dr. Akiyoshi Tamaki, the former president of Chiyoda Chemical Engineering Construction Co., Ltd.,deceased in June 1981. We are indebted to him for his leadership and assistance on the present work.
Literature Cited Fukui, Y.; Shhoto, Y.; Ando, M.;Homma, Y.; U.S. Patent 4 191 636, 1980. Dlckle, J. P.; Yen, T. F. Anal. Cbem. 1987 39, 1847.
Received for review March 12, 1982 Revised manuscript received August 26, 1982 Accepted September 20, 1982
Asphaltene Cracking in Catalytic Hydrotreating of Heavy Oils. 2.' Study of Changes in Asphaltene Structure during Catalytic Hydroprocessing Sachlo Asaoka,' SMnkhl Nrkata, Yoshiml Shlroto, and Chbato Takeuchl Chiyo& Chemical Engineering & Constructlon Co., LM.,3-13, Mor&a-cho, Kanagawa-ku, Yokohama 221, Japan
Characteristics in catalytic conversion of aspheltenes in petroleum heavy residues were studii in the hydrotreating process. A Boscan crude, an Athabasca bitumen, and a Khafji vacuum residue were tested as typical feedstocks. Various analyses were made to obtain the properties of asphaltenes before and aftsr the reaction, e.g., changes of heteroatoms such as sulfur and metals, and decreases of molecular weight. The characteristic changes of asphattene molecules were also investlgated by electron spin resonance (E=) and X-ray analyses. The association and coordination of vanadyl in asphaltenes were studied by the temperature dependence on the ESR spectra, and the sizes of the stacked crystallites and the aggregated asphaltene mlcelles were measured with X-ray diffraction and smalkngle scattering. In the asphaltene cracking mechanism, it was clarified that the main reactions were the destruction of asphaltene micelles caused by vanadium removal and the depolymerization of asphaltene molecules by removal of heteroatoms such as sulfur.
Introduction Some heavy oils contain a large amount of asphaltenes formed by association of molecules, including condensed polyaromatic rings. Since the asphaltenes make catalytic hydrotreating very difficult, a better understanding of the properties and these changes is important for the development of upgrading technology for asphaltene-containing heavy oils. This work was presented a t the 181st National Meeting of the American Chemical Society, Division of Petroleum Chemistry, Symposium on Residuum Upgrading and Coking, Atlanta, Apr 1, 1981. 0198-4305/83/1722-0242$07.50/0
The authors of this work have previously reported a hydrotreating process (Asphaltenic Bottom Cracking (ABC) process) (Takeuchi et al., 1979a,b) with the focus on the conversion of asphaltenes. A catalyst employed shows a high activity for the decomposition of asphaltenes, in which molecular weight reduction proceeds with low hydrogen consumption and without any excessive hydrocracking reaction. Therefore, the characteristics of the catalytic conversion of asphaltenes during the processing were investigated based on the physical and chemical properties of asphaltenes. A Boscan crude, an Athabasca bitumen, and a Khafji vacuum residue were chosen as typical asphaltenic feedstocks for this study, since they contain many asphaltenes as well as sulfur, and their metal 0 1983 American Chemical Society
