I
A. W. LANGER, JOSEPH STEWART, C. E. THOMPSON, H. T. WHITE, and R. M. HILL Esso Research and Engineering Co., Linden, N. J.
Thermal Hydrogenation of Crude Residua Partially hydrogenated refinery process streams are efficient, practical hydrogen donor diluents. Complete conversion of residual stocks is possible, and either gasoline or distillate fuel can be maximized
T i I E COXVERSION of crude residua to lo\\-er boiling products b!. mild cracking in the presence of a hydrogen donor diluent (HDDC) \vas described in a previous publication ( I ) . I n this early work-spring. 1952--tetcahydronaphthalene \vas used as the thermal hydrogen transfer agent! and high ultimate conversion of residua to more valuable loLver boiling products ivith very low yields of coke and dry gas was demonstrated. L-arga and coworkers ( 3 ) independentl! initiated \rery similar \vork in 1952. \vhich evolved into the "I-arga Hydrocracking Process" using iron oxide catalysts. T h e present \vork is concerned \vith studies of other hydrogen donor diluents for use in noncatalytic cracking of residua. Tetralin, which is a condensed ring aromatic-naphthene compound. is a relatively expensive material derived from naphthalene by partial hydrogenation. Accordingly, immediately folloming the successful thermal hydrogenation experiments \vith Tetralin. a search \vas made for more practical donor diluents. T h e development of effective. lo\v-cost hydrogen donor diluents has completely eliminated the need for catalysts in the residuum hydrocracking stage ( I ) . T h e distillate products may be catalytically hydrofinished or reformed in conventional manner \vithout exposure to residuum poisons. T h e residuum conversion process is flexible in that either gasoline or distillate fuel production can be maximized. T h e %asoil produced can be catalytically
Table I. Boiling Range, O F. SCF Hz added per bbl." Carbon, wt. % Hydrogen, wt. % H/C atomic ratio Sulfur, wt. 7' Specific gravity, 60,!60
cracked to yield high antiknock quality gasoline, and the naphtha produced can be catalytically reformed to yield high quality gasoline. Yumerous fractions available in refinery process streams are relatively rich in condensed ring aromatic compounds such as alk? lated naphthalenes. alkylated anthracenes. and phenanthrenes. Partial hydrogenation of these fractions should +ld products Ivhich ivould readily transfer hydrogen to cracked residua in the same manner as Tetralin. For these studies. the thermal tar obtained from thermal cracking of clarified oilfrom catalytic cracking of \Vest Texas gas oil--was selected as the source of condensed ring aromatic compounds for partial hydrogenation to condensed ring aromatic-naphthenic compounds. Previous workers (2) have shown that the 430' to 700' F. aromatic fraction of various refinery streams contains ovcr 709; of naphthalenic ring compounds and about 12ycof higher condensed ring aromatic structures. I n addition, the aromatic fraction of a 700' to 1000" F. clarified oil contained 73.67, condensed ring aromatics of which 7.07, were t\voring. 26.07, three-ring, and 39.77, were four-ring and higher. Thermal craLking of clarified oil concentrates these aromatics such that the resulting thermal tars contain over 90Yc aromatic compounds which are predominantly condensed ring types. T h e thermal tar was distilled into a number of fractions of different boiling ranges and each partially hydrogenated
Thermal Tar Inspections
43S650 500-600 500-550 550-600 600-650 650-700 590* 400 400 400 400 400 88.25 87.96 11.50 11.49 1.55 1.56 0.45 0.30 0.916 0.906 0.909 0.894 0.934 0.961 Batch hydrogenations in a rocking bomb, using nickel-tungsten sulfide or molybdenum sulfide catalyst at 60C&7OO0 F . The amount of hydrogen added was determined by pressure drop. Determined from hydrogen analyses by Beta-Ray H/C Meter on thermal tar before and after hydrogenation. 0 88.54 10.25 1.38 1.04 0.942
(Tables I and 11). T h e hydrogenation was carried out both in conventional rocking bomb equipment, and in continuous hydrosenation equipment using a nickel tungsten sulfide h)-drogenation catalyst. T h e hydrogen donor diluent cracking experiments were carried out in a continuous coil unit (see p. 28). A number of crude residua and asphalts were investigated, and the properties of these feed stocks are given in Table 111. I n general, one half or one volume of the hydrogen donor diluent was premixed with one volume of the residuum, and the mixture was preheated and pumped through the coil maintained at the desired temperature. T h e recovery S ~ S rem consisted of a liquid product receiver. \vet ice, and dry ice traps. S o n condensible gas \\;as measured by means of a dry test meter. Follo\ving cornpletion of a n experiment. the coil reactor
Table II. Continuous Hydrogenation of 700-900" F. Thermal Tar Nickel tungsten sulfide
Catalyst Pressure, p.s.i.g. Temperature, F. Feed rate, V/V/hr. Hydrogen rate, CF/B Hydrogen consumption, CF/B Inspections Carbon, wt. To Hydrogen, wt. H/C atomic ratio Sulfur, wt. 70 Gravity, OA.P.1.
A S T l I Distillation, Vol. % IBP 5 10
20 30 40 50 60 70 80 90 95
VOL. 53, NO. 1
550 650-700 0.5 6000 400
Feed
Product
88.25 8.60 1.17 1.81 4.2
90.24 9.46 1.25 0.81 8.0
F. Corr. t o 760 m r n .
~.
550 650 690 713 722 735 749 765 780 798 840 875
455 590 625 663 684 701 718 730
750 770 805 840
JANUARY 1961
27
was flushed with nitrogen to remove remaining volatile hydrocarbons after which air was introduced to burn out the carbon deposits in the system. Coke formation during cracking was determined by measurement and analysis of the gases produced in the oxidation step.
ing \cas investigated by distilling a thermal tar into 50" F. boiling range fractions. hydrogenating each fraction with about 400 cubic feet per barrel of hydrogen, and determining product distribution from cracking a 2 to 1 rrsiduum-diluent blend to 507, conversion. A 12.97, vacuum LYest Texas residuum was used in these studies. Data. given in Table IV, are compared Ivith tivo wide boiling range dilurnts--430" to 650" F. and 700" to
Experimental Results
The effect of diluent boiling range on product distribution in residuum crack-
P A M L L E L MITY-MITE CONTROL V A L V E S
T1
FEED RESERVOIR
HAND CONTROL KNOCK OUT
LIQUID PRODUCT RECEIVER
I
R--
v
GAS SAMPLE BALLOON
L I G H T ENDS TRAPS
The hydrogen donor diluent cracking experiments were carried out in a continuous coil unit
Table Ill.
Feed Stock Inspections
12.976 27% West Texa? Hawkins Residuum Residuum
Carbon, wt. % Hydrogen, wt. 76 Sulfur, wt. % Specific gravity, 60'60 Conradson carbon, wt. % Softening point, O F.
Table IV.
85.28 10.77 3.32 1.017 21.4 134
84.87 9.91 4.54 1.046 24.6 155
29y0 Hawkins Residuuni
Hawkins Asphalt
9000 F.+ Bachaquero Residuum
84.25 9.44 4.27 1.023 23.6 130
83.94 9.30 4.03 1.080 29.4 189
84.81 10.44 3.36 1.032 20.3 116
Comparison of Hydrogenated Thermal Tar Fractions as Hydrogen Donors
Thermal tar Boiling range, O F." SCF H 2 added/bbl. tar Cracking temp., O F. Pressure, p.s.i.g. Feed rate, V/V,'hr. Conversion of residuum to 1000a F., vol.
430-650 590 853 380 3.59 45.2
400 830 350 2.60
Tetralin 1850b 804 450 1.98
63Sd
52.66
500-550 550-600 600-650 650-700 700-900 400 860 400 3.52
400 860 400 3.42
400 860 400 3.49
400 860 400 3.43
61.2
59.1
49.9
64.6
Yields on residuum, corr. to 50% conv. to 1000° F.f Coke, wt. % c3, wt. % c4, vol. % Cs-430' F.,V O ~ . 70 43O0-10OO0F. exdiluent, vol. 70
0.07 2.7 1.0 19.0
