Ind. Eng. Chem. Process Des. Dev. 1984, 23, 637-641 637

McNell, D. “High-Temperature Coal Tar” In "Chemistry of Coal Utlilzation”, Elliott, M. A., Ed.; Wky: New Yo&, 1981; p 1003.

Panson, A. G.; Kovach, J. J. “Analytlcai Data-F’roducerlFuli Flow Cleanup System, Run #Q7”, METC, IR No. 1080, July 24, 1981.

Sawada, K. M.S. Thesis, Department of Chemlcal Englnwlng, M.I.T., 1982. Sircar, S.; Kumar, R. ACS Svmp. Ser. 1083, 223, 195-212. sokmon. P. R.; Hamblen. D. 0. EPRI AP-2603, Project 1854-8. Flnal Report,

Swberg, E. M. Sc.D. Thesls, Department of Chmical Engineering, M.I.T.,

Swberg, E. M.; Peters, W. A.; Howard, J. B. 17th International Symposlum

ROSS, c. s.; tienblcks, s. B. us. w. SWV. R O ~ S S . m w IO~L), 2058.

July 1983.

1977.

on Combustion, 1978.

Wilson, S. T.; Lok, B. M.; Messlna, C. A,; Cannan, T. R.; Fianlgen, E. M. Abstracts, 184th National Meetlng of the Amerlcan Chembl Society, Kansas City, MO, INOR-008, 1982.

Received for review March 17, 1983 Revised manuscript received December 1, 1983

Accepted December 21, 1983

The research work was undertaken with a financial report of Morgantown Energy Technology Center, U.S. Department of Energy (Contract No. DE-AC21-80M14385).

Influence of Physical and Chemical Parameters on Wood Pyrolysis

Ollvler Beaumontt and Yvan Schwob’

E W Natbnale SUperiewe des Mines de Paris, Centre Reacteurs et Recessus, Equip de Recherches Ass& au CNRS N o 768, Laboratoke de pvrolve des Blomesses. 60, Bd Saint-Michei, 75272 Paris Cedex 06, France

An original pyrolysis untt has been developed to study the influence of pyrolysis parameters: temperature, heating rate, wood particle size and moisture, gaseous environment, and catalyst impregnation. The effects of these parameters on char yield, dl and gas yield, and composttion are presented and interpreted to assist the industrial application of wood pyrolysis technology.

Introduction The search for alternative energy supplies has renewed

interest in the utilization of agricultural and forest by- products as substitutes for conventional sources of energy. In this area, wood pyrolysis is of special interest as it produces pyrolytic oil as well as energy. Pyrolytic oil differs from natural oil in that valuable chemicals are present in a complex mixture as they are not destroyed by a coarse thermal process. At present, pyrolytic oil, the major product of wood pyrolysis, is seldom processed for chemical recovery. Pyrolytic oil is a very complex mixture; it differs from natural oil that basically contain hydro- carbons. In addition, pyrolytic oil is unstable, leading to considerable difficulties in the separation process.

The scope of this study is the investigation of the py- rolysis phenomena in order to control it better. Experi- mental equipment was developed for testing physical and chemical parameters such as temperature, particle size, gaseous product, extraction, wood moisture, and the in- fluence of catalyst.

Experimental Section Beech wood (Fagus sylvatica) was selected for the study

as the typical European hardwood. The particle size ap- pears to be a determinant parameter; thus the wood saw- dust obtained from the original piece of sound wood was sieved to three different particle sizes: fine, from 0.050 to 0.125 mm (referred to as “F”), medium, from 0.125 to 0.25 mm (referred to as “M”), and course, from 0.25 to 0.5 mm (referred to as “G”).

The chemical composition of beech wood obtained from standard analytical methods (PETROFF and DOAT, 1978) is presented in Table I. Wood moisture is also a relevant parameter. It is de-

termined by oven drying at 105 “C to constant weight.

‘Centre de Recherche Elf-Solaize, Section Proc&l6s-Induatrie, 69360 Saint-Symphorien d‘Ozon, France.

Q79543Q5fa4f 7 ~23-a637$a1.5afQ

Samples of different moisture were prepared by moisturing and/or drying.

Temperature is the most determinant parameter; not only the final temperature of the treatment but also the heating rate is important. An experimental device was developed that allows testing of both parameters.

The experimental setup allows pyrolysis of wood par- ticles in a gaseous sweeping stream (Figure 1). The gas- eous stream rapidly sweeps the pyrolysis products out of the furnace where they are condensed and cooled. This precaution avoids as much as possible the secondary degradation of the volatile products. An “extractive” wood pyrolysis is thus carried out.

The extractive gas flow can be a permanent gas, such as helium or nitrogen or an superheated solvent vapor. Methanol, 2-methylpropanol, and ethylglycol (C2H60C- H2CH20H) were used because of their efficiency as sol- vents of all the constituents of pyrolytic oil. The solvent is placed in a pressurized tank and flows out through an expansion valve that ensures a steady flow. The solvent is vaporized and superheated in the packing at the bottom of the furnace.

When permanent gas is used for sweeping, a supple- mentary tubing with peristaltic pumping equipment allows one to recirculate part of the gas to obtain high specific flow rate in the furnace without excessive dilution of the pyrolytic products in the sweeping gas. The recirculating gas is taken after recovery of pyrolysis products.

The temperature of the furnace is controlled by a pro- grammed regulator monitored by a chromel-alumel thermocouple placed near the heating coils of the furnace. Another thermocouple of the same type placed in the wood bed measures the effective temperature of the wood. The temperature gradient in the furnace was found to be ho- mogeneous radially but there was a small vertical disper- sion throughout the volume of the wood that could not be reduced to less than 4”.

The condensed pyrolytic oil is collected for analysis in a cold trap and the gaseous products are collected in a tight

0 1984 American Chemical Society

638

Table I. Chemical Composition of Beech Woodu

Ind. Eng. Chem. Process Des. Dev., Vol. 23, No. 4, 1984

constituents % analytical method used ethanol-benzene (1/1) extract 0.9 7 h in a Soxhlet apparatus on extracted sawdust

water extract NaOH extract pentosan

cellulose

lignin ash silica

1.3 7 h refluxing 18.3 7 h refluxing 26.8

40.1

23.2 sulfuric acid method

hydrochloric acid (13.5%) reactant, distillation, of furaldehyde,

3 treatments with nitroalcoholic mixture and correction of the and titration with bromide-bromate

remaining ash and pentosan

constant weight at 425 "C in air 0.5 0.001 nitroperchlorhydric reactant

a Proximate analysis: fixed carbon, 24.5%; volatiles, 75.0%; ash, 0.5%; moisture, given for each experiment.

r -

Figure 1. Experimental setting for sawdust pyrolysis: (1) vibratory device; (2) feedstock (wood); (3) pyrolysis chamber; (4) electric fur- nace; (5) condenser; (6) cold traps; (7) tight gas tank; (8) sweeping gas stream; (9) pressurized solvent tank; (10) gas volume measure; (11) peristaltic pumps; (12) packing materid; (13) thermocouple.

tank where they are homogenized before analysis. The volume of gas produced is then measured by a gasmeter.

Two different experimental procedures are used to study the effect of temperature and heating rate.

(a) Flash Pyrolysis. The furnace is preheated at the desired temperature and the sweeping gas stream is es- tablished. The wood powder is then introduced by a vi- bratory device into the furnace. The rate of introduction is adjusted so that the furnace temperature is not dis- turbed: 10 g of wood is introduced during each experiment at the rate of 0.5 g/min. Afterwards, the temperature is maintained for completion of the processing. (It was found that the char residue underwent no additional transfor- mation after 30 min.) The furnace is then rapidly cooled. The char is collected and weighed. This procedure ap- proximates closely isothermal reaction.

(b) Slow Pyrolysis. Wood powder is placed in the cold furnace and the sweeping gas stream (10 g) is established. The furnace is theh heated a t a definite rate. Gas Analysis

Pyrolytic gas was analyzed by gas solid chromatography for carbon monoxide, carbon dioxide, nitrogen, oxygen and light hydrocarbon determination.

A device made of two analytical columns in series shown in Figure 2 was used with flow of gas through each side of the catharometric detector of a chromatograph Girdel 30 (Jecko and Reynaud, 1967). The first column C1 (2 m, l/g in. stainless steel) is packed with Porapak R and sep- arates carbon dioxide, hydrocarbons, and a mixture of air and CO + methane. The second column (2 m, in. stainlea steel) packed with a 5 A molecular sieve, separates

I

Figure 2. Gas analysis setup for CO, COP, N z , Os, H P , and light hydrocarbons determination: (1) chromatographer oven; (2) sam- pling valve; (3) sampling loop; (4) carrier gas (N2); (5) first column; (6) second column; (7) catharometer.

oxygen, nitrogen, methane, and carbon monoxide; the other components are adsorbed irreversibly. The analytic output is processed by an LTT-ICAP integrator and recorded on a Sefram Servotrace recorder.

Quantitative gas analysis is performed by internal nor- malization. Individual response factor of each gas is de- termined on a quantity of pure gas precisely injected with a computer-monitored HAMILTON syringe. Pyrolytic Oil Analysis

The pyrolytic oil is analyzed by gas-liquid chromatog- raphy, on a Girdel 3000 chromatograph, with catharometric detector using a 2 m, in. stainless steel column packed with Porapack Q. The same integrator and recorder are used. Only the most important components are isolated by this method but it is enough to test the influence of physical and chemical parameters. Further study of more complete analysis of oil is in progress.

The quantitative determination of the components is performed by internal standard (ethyl acetate). The ac- curacy is satisfactory, except for methanol that is not sufficiently separated from water and formic acid which is difficult to analyze by GLC because of its polarity and tendency to dimerize in the gas phase. Results and Discussion

After weighing, the char, pyrolytic oil, and gas, the total weight obtained was typically 97 to 100.5% of the reacted wood. The intluence of temperature was studied in a series of flash pyrolyses of sawdust at 8% moisture with nitrogen as the sweeping gas. The evolution of yields of char, py- rolytic oil, and gas with the temperature are presented in Figure 3.

Four areas can be established (1) drying area under 220 "C; (2) roasting area from 220 to 330 "C; the solid residue is predominant: it is a roasted wood of dark brown color; (3) pyrolysis area from 330 to 450 O C : a true char is ob-

Ind. Eng. Chem. Process Des. Dev., Vol. 23, No. 4, 1984 630

Table 11. Pyrolytic Oil Composition a

slow pyrolysis

20 to 450 temp, "C 300 3 50 400 450 500 at 8"Imin

flash pyrolysis

water 9.1 13.1 14.9 18.6 16.3 17.3 methanol 0.68 0.86 1.02 0.97 1.54 ethanal 0 0.03 0.07 0.17 0.45 acetone 0.1 0.08 0.03 0.17 formic acid 1.21 0.43 0.17 0.25 acetic acid 5.79 6.91 6.83 7.84 6.87 6.32

1-hydroxy propanone 1.30 2.55 2.86 3.57 2.51 2.66 1-hydroxy-2-butanone 0.51 1.66 1.88 2.49 2.00 1.32 2-furaldehyde 0.76 0.69 0.87 1.04 1.07 0.79 furf urylic alcohol 0.36 0.43 0.44 0.24 <0.02 0.63

propionic acid 0.18 0.14 0.29 0.45 0.55 0.20

a Yields on moisture free wood, with wood moisture 7.5%; particle size, 0.050 to 0.125 mm.

100 0 - I I

C.,. ' Torrefactian Pyrolfs18 Garifi ation 1..

I

4

Drying Zone *, ' Zone zone I z e 9o

( ' \ I I I

150 200 250 300 350 4 C O 450 500 T'C

Figure 3. Flash pyrolysis of beech sawdust (yields on an oven-dry basis). Particle size (mm): (-X-) 0.05 to 0.125; (f) 0.125 to 0.25; (t) 0.25 to 0.5.

tained, more than 50% of pyrolytic oil and a relative low gas yield; (4) gasification area which begins at 500 "C. The gas fraction grows rapidly and becomes predominant around 800 "C as shown by other studies (Knight, 1976). This area was not investigated in our study.

Figure 4 shows the evolution of the gas composition with temperature in the pyrolysis area (flash pyrolysis). At lower temperature, carbon dioxide is predominant; the yield of carbon monoxide increases rapidly only above 450 OC and reaches 13.5% at 500 "C. Yields of ethane and ethylene show an evolution similar to methane. At 500 "C, a small amount of propane was detected. However, hy- drogen was never detected: it seems to appear only above 600 "C (see Rollin, 1981).

With slow pyrolysis of sawdust (moisture 8%) up to 450 "C at the rate of 8 "C/min, a very different result was obtained 26.3% of char, 55.2% of oil, and 18.8% of gas.

Therefore, it is clear that the pyrolytic process is de- pendent on the rate of heating. The char residue that is normally of about 25% in slow pyrolysis can be reduced to 10% by a flash pyrolysis at temperatures as low as 500 "C.

Table I1 shows the compn. of pyrolytic oil for different temperatures of flash pyrolysis and slow pyrolysis. The water yield indicated results from the pyrolytic process, initial moisture of wood being substracted.

The organic fraction contains the expected products of wood pyrolysis: methanol, acids, furaldehyde, and acetone

300 350 400 450 500 T'C

Figure 4. Composition of beech wood pyrolytic gas. Particle size (mm): (-X-) 0.05 to 0.125; (-O-) 0.25 to 0.5.

Table 111. Wood-Moisture Effectsa moisture, %

0 7.63 26.2 char pyrolytic oil gas gas composition

3 CH,

oil composition water methanol ethanal acetone formic acid acetic acid propionic acid 1-hy droxypropanone 1-hydroxy-2-butanone 2-furaldehyde furfurylic alcohol

24.6 27.4 64.1 6.13 11.3 11.2

8.3 8.2 2.8 2.9 0.05

15.5 13.4 1.09 0.85 0.04 0.09 0.14 0.06 0.51 0.33 6.64 6.33 0.23 0.14 2.11 2.28 1.07 0.97 0.71 0.63 0.51 0.32

27.7 60.3 12.0

8.7 3.1 0.08

13.9 0.76

0.28 6.06 0.13 1.72 0.65 0.70 0.43

Yields on moisture-free wood. Flash pyrolysis at 350 "C; particle size, 0.050 to 0.125 mm.

(Schwenker and Beck, 1963), but it is also interesting to note the high yields of chemicals such as hydroxy-l- propanone, hydroxy-1-butanone-2, and furfurylic alcohol. Yields are temperature dependent and most of them show

640

Table IV. Influence of Catalyst a

Ind. Eng. Chem. Process Des. Dev., Vol. 23, No. 4, 1984

+5% +5% wood FeCl, NaOH

char 27.4 34.7 36.6 pyrolytic oil 61:3 54.7 44.3 gas 11.2 9.8 19.7 gas composition

8.2 6.0 14.0 2.9 3.7 5.6

CO, co CH, 0.06 0.08

water 13.4 24.9 22.1 me than ol 0.85 0.66 1.24 ethanal 0.09 0.10 0.05 acetone 0.06 0.53 0.09 formic acid 0.33 0.35 0.11 acetic acid 6.33 5.40 5.50 propionic acid 0.14 0.09 0.50 1-hydroxypropanone 2.28 0.59 3.31 1-hydroxy-2-butanone 0.97 0.07 0.73 2-furaldehyde 0.63 2.28 0.26 furfurylic alcohol 0.32 0.08 0.21

oil composition

a Flash pyrolysis at 350 "C; particle size, 0.05 to 0.125 mm; dry wood.

Table V. Influence of the Sweeping Gas Flowa sweeping gas flow, L/min

0 0.5 1 2 char 16.7 15.1 16.3 15.6 pyrolytic oil 64.7 64.2 65.6 66.6 gas 18.7 18.7 17.9 17.8 gas composition

10.36 9.0 10.8 7.52 8.6 6.58 0.48 0.56 0.53

3 CH,

oil composition water 16.2 16.8 13.6 11.2 methanol 1.03 1.08 0.97 0.76 ethanal 0.24 0.39 0.20 acetone 0.47 0.46 formic acid acetic acid 5.73 5.62 5.55 5.77 propionic acid 0.30 0.30 0.23 0.23 1-hydroxypropanone 3.44 3.19 3.19 3.52 1-hydroxy-2-butanone 2.04 1.84 1.81 2.45 2-furaldehyde 0.74 0.61 0.52 0.85 furfurylic alcohol 0.16 0.06 0.10 0.35

a Flash pyrolysis at 450 "C; particle size, 0.05 to 0.125 mm; wood moisture, 6%.

Table VI. Influence of the Sweeping Gas Naturea

a maximum in the pyrolysis area. However, the yield of acetaldehyde grows with rising temperature although formic acid and acetone exhibit a rapid decrease. Slow pyrolysis yields more methanol than flash pyrolysis.

Influence of Particle Size. The comparison of the curves of Figure 3 illustrates the effect of particle size on flash pyrolysis. Coarser particles yield more char and gas, and less oil. Gas composition (Figure 4) is also modified by particle size, although the oil composition does not vary qualitatively. These results can be interpreted by the effort of particle size on heat transfer: the coarser the particles, the slower is the heating, and pyrolysis is per- formed on average at a lower temperature. Flash pyrolysis is thus not completely isothermal in spite of the precaution taken to ensure an isothermal process. With slow pyrolysis, particle size did not show any influence.

Influence of Wood Moisture. Wood samples of dif- ferent moistures were pyrolyzed in the same way (flash pyrolysis 350 "C, using nitrogen as sweeping gas). The results are given in Table 111.

Increased moisture promotes charring and lowers oil yield. Qualitative composition of oil remains unchanged. However, quantitative shifts are observed.

The amount of water due to the thermal degradation is dependent on the moisture: more water is formed by the pyrolysis of dry wood. The moisture also causes a decrease in the yields of the organic products, especially methanol, formic and propionic acids, and hydroxy-l- acetones.

These results can be explained by the effect of moisture on heat transfer. Heating of the particles is hindered by the heat requirement of moisture evaporation. On the average, pyrolysis takes place at lower temperatures. According to the known evolution of the phenomena with temperature (Figure 5 and Table N) this shift corresponds to the observed effect: increasing yield of char, decreasing yields of oil and organics.

Influence of a Catalyst. Two samples of wood saw- dust were impregnated respectively with a basic (5% NaOH) and an acidic (5% FeC1,) catalyst and submitted to flash pyrolysis at 350 OC under nitrogen. Significant effects on the pyrolysis process are observed (Table IV: the char yield is increased along with gas yield in the case of the basic catalyst. Catalysts promote water formation, especially FeC13. Organic component yields vary by large amounts; FeC13 leads to a drastic increase in furaldehyde

ethylglycol methanol 350 "C 350 "C

char 29.9 30.9 pyrolytic oil 60.2 59.6 gas 8.11 9.5 gas composition

co, 5.0 6.5 co 3 .O 2.9 CH, 0.06 0.06

water 14.35 methanol 1.55 ethanal 0.36 formic acid acetic acid 5.9 6.8 1-hy droxy propanone 0.22 1-hydroxy-a-butanone 3.49 3.3

2-f uraldehyde 0.74 0.80

oil composition

hydroxy-2-butanone 1.93

furfurylic alcohol 0.31 0.39

a Flash pyrolysis; particle size, 0.25 to 0.5 mm; wood moisture

nature of sweeping gas

nitrogen helium methanol nitrogen 350 "C 350 "C 450 "C 450 "C 31.6 31.3 15.2 14.2 56.8 57.0 68.7 67.5 11.6 11.2 16.1 17.9

8.8 2.8 0.13

13.9 14.2 0.81 0.75

8.1 8.8 6.9 7.7 0.9 1.1

16.2 1.07

0.19 7.05 7.0 5.5 7.34 0.18 0.17 0.25 0.24 2.58 3.06 2.9 2.5 1.63 1.4 2.4 2.03 0.86 0.85 0.95 0.93 0.49 0.40 0.22 0.22

,7%.

I d . Eng. Chem. Process Des. Dev. 1984, 23, 641-640 841

and lowering of hydroxypropanone and furfurylic alcohol; caustic soda gives more hydroxypropanone and less fur- aldehyde.

These results do agree with the ionic mechanism of pyrolytic reactions proposed for cellulose by Byrne et al. (1966). An acid catalyst promotes dehydration and fur- aldehyde formation (Shafizadeh, 1968). Basic catalyst favors gasification and charring.

Influence of the Sweeping Gas Flow. The flow of nitrogen affects the residence time of the vapor phase produced by pyrolysis. Different flow values were used under similar conditions of operation (flash pyrolysis at 350 “C) so that the residence time would vary from a few seconds to more than 1 min (Table V).

The overall yields of char, oil, and gas are not signifi- cantly affected, but the amount of water increases con- siderably when the sweeping flow is decreased. Unstable organics undergo secondary dehydration when the rapid extraction and dilution by sweeping is not achieved. This is of particular relevance for process design of extractive pyrolysis for chemicals recovery.

Influence of Chemical Nature of the Sweeping Gas. The experimental setting makes sweeping possible not only by a permanent gas, but also by condensable vapor of a solvent.

methanol, 2-methyl- propanol, and ethylglycol (C2HSOCH2CH20H). All three are good solvents of the prolytic oil. When using this procedure, the solvent is collected and condensed with the pyrolytic oil. The considerable complication of oil analysis explains why these experiments could not be performed extensively.

The results, presented in Table VI, show very little difference between nitrogen and helium. Use of a vapor slightly modifies yields expecially on acetic acid, but no modification in qualitative composition is noted so that a chemical reaction with the solvent is excluded and the thermal nature of pyrolysis is confirmed. Conclusions

The comprehensive results of this study lead to an evaluation of the significance of each parameter of wood pyrolysis. The major influence of temperature and rate

Three solvents were tested:

of heating is clearly established. The particle size has an influence on the overall yield

of char, oil, and gas, but does not modify the qualitative Composition of oil. In addition, this influence is explained by the relation between particle size and heat transfer.

Influence of moisture is interpreted in the same way: effective pyrolysis temperature is shifted by the heat re- quirement of moisture vaporization. Pyrolysis carried out with different sweeping gases shows that pyrolysis reac- tions are not changed. Wood pyrolysis appears as a thermal phenomenon only. Variations of sweeping gas rate have, on the contrary, great significance; they modify the residence time of vapors in the hot zone and their evolution after the pyrolysis. Finally, the significant influence of catalysts confirms the ionic nature of pyrolytic mecha- nisms.

The results also show the influence of the reactor design on the pyrolysis reactions. The extraction procedure used here characterized by the flash effect and the rapid with- drawing of pyrolytic vapors out of the hot zone leads to original results. In the perspective of an industrial ap- plication, reactor design and operating conditions should be adapted to the desired product of pyrolysis charcoal, gas, or instable chemicals. The study presented here provides some of the necessary information.

Registry No. FeClS, 7705-08-0; NaOH, 1310-73-2; methanol, 67-56-1; ethyl glycol, 110-80-5; 2-methylpropanol, 78-83-1; acet- aldehyde, 75-07-0; acetone, 67-64-1; formic acid, 64-18-6; acetic acid, 64-19-7; propionic acid, 79-09-4; 1-hydroxypropane, 116-09-6; l-hydroxy-2-butanone, 5077-67-8; 2-furaldehyde, 98-01-1; furfuryl

Literature Cited Byne, 0. A.; Gardlner, D.; Holmes, F. H. J . Appl. Chsm. 1988, 76, 81. Jecko, G.; Reynaud. B. Association Technique de la SWrurgle Francgise

(Commission des Ing6nleurs de Laboratolre), Paris, France, 1967. Knight J. A. Symposium on “Thermal Uses and Properles of Carbohydrates

and Llgnlns”; Shafizadeh, Ed.. Academlc Press: New York, 1976. Petroff, G.; Doat, J. Bois Fw. Trop. 1978, 177, 51. Rollln T h h CNAM, Unlversk6 de Nancy I , Nancy, France, 1981. Shadzadeh. F. A&. Carbohydr. Chem. 1968, 23, 419. Shwenker, R. F.; Beck, L. R. J . Powm. Sci., Pari C 1983, 2 331.

alcohol, 98-00-0.

Received for review March 4, 1982 Revised manuscript received August 4, 1983

Accepted September 23,1983

Upgrading of Heavy Oils by Asphaltenic Bottom Cracking

Jlro Sudoh,’ Yorhlmi Shlroto, Yoshlo Fukul, and Chlsato Takeuchl C h w h Chemlcai Engineering & Construction Co., Ltd., 3-13, Moriya-cho, Kanagawa-ku, Yokohema 221, Japan

Asphaltenk Bottom Cracking (ABC) is a catalytic hydrotreating process for heavy asphaitenic petroleum ends. ABC in combination with solvent deasphalting (SDA) is an effective way to completely convert and upgrade asphaltenic bottoms. This paper presents various correlations in SDA operations for yleids and properties of deasphaked oils (DAO) and asphalts obtained from KhafJi vacuum residua under different hydrotreating conditions. By using a mathematical model of the combined process of ABC and SDA, the quantitative reiatlonship between the recycle rate of SDA asphatt and the ABC conditlons in the extinction and partial recycle operations is discussed.

Introduction Technologies such as upgrading of heavy petroleum ends

and converting them into high quality lighter stocks have become more desirable due to the recent growing demand for lighter oil products. On the other hand, since the supply of crude is likely to consist more of heavy oils,

research and development of conversion technologies have been actively carried out worldwide. The Asphaltenic Bottom Cracking (ABC) process under development by Chiyoda is a catalytic hydrotreating process for residua containing large quantities of metals and asphaltenes. This process upgrades the residua by selectively cracking as-

0196-4305/8411123-0641$01.50/0 @ 1984 American Chemical Society