I N D U S T R I A L A N D ENGINEERING CHEMISTRY
536
Operation of the unit without recirculation is not recommended, because 2 to 3 liters of material must be passed through the system before it begins t o operate properly. NOTES ON CONSTRUCTION
Standard-taper spherical (ball and socket) joints have been used t o facilitate assembly of equipment and t o eliminate the necessity of making rigid metal-to-glass seals. The open-tapered joint at the column head is connected t o an adjustable shaft in order that fluid flow may be controlled either through an annulus, over a weir, or both. Clearances between walls and coil of the condenser are made as small as practicable, in order t o obtain maximum efficiency of operation. The unit can be constructed of stainless steel; however, provision should be made for internal inspection and cleaning, as entrained material has been found occasionally in the condenser system. The internal diameter of the coil in condenser R is designed t o be large in relation t o the
development
Vol. 43, No. 2
volume of condensate flowing through it, in order to avoid air locks. The seal at the top of the column head, B, is a commercial type normally used in boat propeller-shaft assemblies, and is pressed into a 0.25-inch stainless steel plate. The jacket on column D is held in place by rubber tubing, over which light copper bands are clamped. With the type of manostat used, diffusion of oil vapor from the vacuum pump back into the traps is not a problem. LITERATURE CITED
(1) Carpenter, D. C., and Smith, E. C., IND.ENG.CHEM.,26,449-454 (1934). (2) Cross, J. A., and Gemmill, A. V., Food Inds., 20, 1421-3 (1948). (3) KelIey, E.J., Zbid., 21,1386-90 (1949). (4) Walker, L.H., Nimmo, C. C., and Patterson, D. C., Food Technol., in press. RECEIVED May 29, 1950. ing Act of 1946.
Report of study made under Research & Market-
Vapor-Phase Hydrogenation of light and Heavy Oils M. L. WOLFSON, M. G. PELIPETZ, A. D. DAMICK, AND U.
E. L. CLARK
S. BUREAU OF MINES, BRUCETON, PA,
In order to provide equipment for hydrogenation of light and heavy oils over a fixed catalyst bed, a small plant suitable for operation at 500" C. and 10,000 pounds per square inch gage has been designed. The plant is described and results are presented of an operation designed to test the activity of a German hydrogenation catalyst in producing gasoline from light gas oil derived from coal. The results indicate that the catalyst of chromiummolybdenum-zinc on hydrogen fluoride-activated fuller's earth is suitable for the hydrogenation operation attempted. On a once-through basis at 500' C., a hydrogen pressure of 9,000 pounds per square inch, a space velocity
of 1 kg. of oil per liter of catalyst, the following results are obtained, based on weight per cent of feed: 46.670 gasoline, 4.2qo CI to Ca, and 2.8% hydrogen consumption. The nitrogen, oxygen, and sulfur content are greatly reduced. The gasoline has a high aromatic content and a motor method octane rating of 79.8. The results indicated the suitability of the plant for high pressure catalytic reactions. Good performance and ease of operation characterized the experimental work. The catalyst tested showed good activity in the production of aromatic gasoline from gas oil obtained by the hydrogenation of coal.
A
unit is only 20 cubic feet per hour, the compressor is only run intermittently and the compressed hydrogen after passing through the oil trap is stored in three accumulators which act as reservoirs. The oil trap and accumulators are of the type described by Clark et aE. (1) and illustrated in their Figure 5 and Figure 6, respectively. The oil feed is drawn from a vessel, which is weighed every half hour, into a piston pump which injects it a t system pressure into the hydrogen stream leaving the accumulators. The combined oil-hydrogen stream passes through a preheater consisting of a coil of 0.25 inch outside diameter by 0.125 inch inside diameter stainless steel tubing embedded in a block of aluminum, heated electrically by strip heaters. The stream then enters the bottom of the reactor, a stainless steel (Type 347) tube 2 inches outside diameter by 0.75 inch inside diameter by 4 feet long (excluding closure assemblies). The type of closure employed, illustrated in Figure 2, utilizes a stainless steel (Type 347) lens ring (Monel metal lens rings were tried originally, but they were attacked by the high sulfur content of the oil feed). The preheated stream of hydrogen and oil flows u p through the catalyst
MONG recent developments in the German synthetic liquid
fuels industry, considerable advantage was found in splitting aromatic oils in the gas-oil range (200" t o 325' C.) by highpressure hydrogenation (about 700 atmospheres of pressure). D a t a in captured German documents indicated promise for this process, which was incorporated into the design of the Bureau of Mines Demonstration Plant a t Louisiana, Mo., as a means of treating aromatic oils obtained from the hydrogenation of coal. To evaluate this process on a small scale and to test the activity of available German catalysts, a small hydrogenation unit suitable for operation a t 10,000 pounds per square inch gage and 500" C. was designed and operated a t the Bruceton laboratories. DESCRIPTIOX O F THE PLANT AND EQUIPMENT
A simplified flow diagram of the unit is illustrated in Figure 1. Commercial cylinder hydrogen is throttled into a 1000-cubic foot gas holder and drawn from there by a Norwalk five-stage compressor. I n order to utilize this available compressor which has a capacity of 600 cubic feet per hour, while the maximum flow in the
537
INDUSTRIAL AND ENGINEERING CHEMISTRY
February 1951
Friction washer Left-hand lhread. End-piece call0
b
to purge
ea cross A Velocity check
N C h e c k volve F3 Tee K Thermocouple POlntS
Figure 1.
Diagram of Unit Figure 2
bed which is held in the middle third of the reactor by spacers. These spacers are tapped so that a threaded bar may be used t o pull them out if coking occurs. From the top of the reactor, the products and excess hydrogen flow through a water-cooled condenser into a high-pressure separator where the liquids and gases disengage. The gases are continuously withdrawn from the top through two throttle valves, sampled, and metered by a wet test meter. At predetermined times, the liquid product is throttled from the bottom of the separator into a low-pressure receiver from which i t is withdrawn into tared sample bottles. During this letdown of product, the gaseous material which is flashed off is measured by a wet test meter, passed into a small gas holder, stored for an hour, sampled, and purged. All high-pressure equipment except the compressor and the pump are in an open-topped stall which has 12-inch thick reinforced concrete walls. When the equipment is in operation, no one is allowed to enter the stall. The valves are operated by means of extension rods leading through the wall, and the pressure gages are
read through slots in the wall covered with bullet-resistant glass. Two fires, resulting from leaking connectiong, and a minor explosion, resulting from the rupture of a Bourdon tube in a pressure gage, caused only minor damage and provided ample justification for these precautions. Two types of cinch connections are used with the 0.25-inch outside diameter, 0.125-hch inside diameter stainless steel tubing which is specified throughout the plant. Both types depend on threads to absorb the stress. With the first type, the cinch is sealed t o thetubing by means of a copper gasket (Figure 3a); with the second type, the seal is made by compression (Figure 3b). Connections of both types are satisfactory for cold service; for heated connections, the compression type was found preferable. The reactor is heated with twelve 500-watt strip heaters mounted on the outside of a Pinch pipe to provide uniform heating around the circumference of the reactor. There are three sets of heaters, one set of four covering the length of the catalyst bed, another set below the bed, and the third set above the bed. By controlling the voltage input to each set with a manually operated variable transformer and by using an automatic temperature
Needle, stop nul Needle slop worher
flon pocking ring
Figure 3
Figure 4.
Types of Valves Used
INDUSTRIAL AND ENGINEERING CHEMISTRY
538
Vol. 43, No. 2
controller for the entire reactor furnace, a uniform temperature is maintained throughout the bed for extended periods with a minimum of attention. The types of valves used are illustrated in Figure 4. Both have the same type of stem and packing arrangement. The block in Figure 4a is designed for straight-through connections; the block in Figure 46 has both connections on one side. A floating needle tip to avoid grinding seat on complete closure or a solid stem may be used in either type. Some of the valves require delicate throttling, and these are equipped with 30 to 1 gear-reduction units (30 turns of the operating handle for 1 turn of the valve stem). The valve-extension rods are connected to the valve
Floof
balance. 2%) and sumption assuming
gask
10
These adjustments have been small (1 or in either direction. The hydrogen conis calculated from the elemental balance, that all nitrogen, sulfur, and oxygen re-
I”
EXPERIMEST4L D A T A
Figure 5.
Excess-Flow Check \’alves
stems with close-fitting tapered pins to eliminate all slack between valve stem and valve-extension rod. The rods must be very carefully aligned to prevent any trace of binding which could wear the packing and result in a leak. Teflon packing proved t o be more satisfactory than any other packing tried in maintaining a seal under this severe throttling service. All gages not subject to rapid pressure fluctuation are preceded by excess-flow check valves (Figure sa). Gentle pressure changes are transmitted through the clearance between the float and the housing without lifting the float appreciably, but if the Bourdon tube should leak or burst, the rapid flow should lift the float forcing the Teflon gasket against the tubing above and safely sealing the system. The check valve is normally housed vertically in a standard Bureau of Mines straight connector used to join 0.25inch outside diameter tubing. Whwe possible surges are likely to seal the gasket and to prove a n operational nuisance, the excessflow check valve can be installed in a valve body (Figure 5 b ) . Normally, the valve is closed, but, when the check is inadvertently sealed, the valve can be opened slowly to equalize the pressure, allowing the check to drop down to its normal open position. The valve is then closed again. OPERATIKG PROCEDURE
Data are recorded every half hour and include the pressures in the accumulators, reactor, pump, and separator; the temperatures of the preheater, heating jacket (3, one a t each level), external wall of the reactor, and a t three levels within the catalyst bed; the weight of the feed oil vessel to check the oil feed rate; the number of cubic feet of tail gas bled off, which is read on the wet test meter to give a n approximation of the hydrogen flow rate accurate enough for operational purposes. Constant reactor pressure is very important, not so much for its own sake, but because small fluctuations in pressure affect the pumping rate markedly, and this upsets the temperature equilib-
The first plant operation was carried out using a blend of light oils obtained by the liquid-phase hydrogenation of various coals in the Bureau of ?rIines pilot plant a t Pittsburgh. The blend was distilled in a 100-gallon packed column, and t h a t portion boding below 325’ C. was taken as the feed stock. The characteristics of the oil are tabulated in Table 11. The oil was quite aromatic in character
TABLE
I. TYPICAL ELEMEXTAL BALAXCE Total 100
Feed oil Products
Oil
Hydrocarbon gases HzO
NE8 HzS Totals H2 absorbed
H
C
8.60
89.59
N S 0 . 3 2 0.17
90.70 9.57 80.36 0 . 0 3 1 1 . 2 3 2.00 9.23 . . . 0.71 0.08 . . . . . . . . . 0.29 0.35 0.06 0 . 1 3 0.01 103.12 11.72 89:59 0132 .... 3.12 . . . . . .
0.05
0,969
Refractive index
1.5560
ASTM distillation, O C. Initial boiling point 5% 10%
20%
%E
60% 70 %
80 9% 90 CZ
95% End ooint Recovery
75 169 182 202 214 22 1 232 242 257 275 293 308 331 99.5%
0.69
. . . . . .
. . . 0.63 . . . . . .
0.12 0.17
1:32
. . . . . .
011, TABLE 11. CHARACTERISTICS O F FEED
Specific gravity
0 1.32
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INDUSTRIAL AND ENGINEERING CHEMISTRY
February 1951
as evidenced by the low hydrogen content and the high refractive index. While this oil is in the same boiling range as the "middle oil" product from the liquid phase hydrogenation of cod, i t is not entirely typical, being of lower oxygen and hydrogen con.o tent.
360m 35 30 25 20
04 OS 08 12 14 SPACE VELOCITY, KILOGRAMS OF FEED PER LITER OF CATALYST
'502
PER HOUR
Figure 7
2
500 500
3
500
5
475
I
I 40
I
40
0
20
.32 I 60
I
80
100
I n Figure 7, the hydrocarbon gas production (C, t o Cs), the per cent gasoline in the product oil, and the hydrogen consumption based on feed are plotted against hourly space velocity (catalyst charge 100 cc.) for both temperatures.
PERCENT DISTILLED
Figure 6
One hundred cubic centimeters of catalyst, Type K536, were used. It was available in 0.5-inch cylindrical pellets, which were crushed to 4- to 6-mesh irregular shapes, According to German microfilm data, the catalyst consisted of 60 parts of AD5 paste (crude fuller's earth) to 40 parts of Terrana (activated fuller's earth), both treated with hydrogen fluoride, and small amounts of zinc, chromium, molybdenum, and sulfur which were found by analysis to be as follows: Zinc Chromium Molybdenum Sulfur
*.
2.76% 1.27% 0.44%
2.32%
Five tests were made a t a pressure of 9000 pounds per square inch gage, three a t 500" C. and hourly space velocities of about 0.7, 1.0, and 1.3, and two a t 475" C. and hourly space velocities of about 0.3 and 0.5. The unit was in continuous operation for 306.6 hours. The product oils were distilled according to A.S.T.M. D 285-41, and the fraction boiling below 200" C. is referred to as gasoline. This method does not provide too good a separation and the gasoline thus produced has a slightly higher end point than commercial gasoline. I n addition, sufficient C i s and Ce's are flashed off on discharge to lower the low boiling content below that found in commercial gasolines. The hydrocarbon gas breakdown is given in Table 111and the Cj's and Ce)s have been included in the per cent yield of gasoline. Analytical values for both the gasoline fraction and the residue are given in Table 111. The properties given for gasoline in Tables 111, IV, and V are for gasoline as obtained from the liquid product. The product oils and the fractions above 200" C. were distilled according t o A.S.T.M. D 158-41 aad the gasoline fractions according to A.S.T.M. D 86-46. The A.S.T.M. distillations are given in Table IV, and the curves for the whole product oils are in Figure 6. Results of group analyses on the gasolines and additional tests on the gasoline produced in test 2 are given in Table V.
CONDITIONS AND PRODUCT TABLE 111. OPERATING CHARACTERISTICS (Pressure, 9000 pounds per square inch gage' hydrogen flow, 3 cubic meters per kg. oil feed) 1 2 3 4 5 Test No. Temp., ' C. 500 500 500 475 475 Space velocity, g. oil/cc. catalyst/hr. 0.72 1.02 1.28 0.317 0.507 Ht consumed Wt. % feed 3 12 2.80 2.48 2.89 2.12 1000 CU. ft. per bbl. 2.01 . 1.80 1.59 1.86 1.36 feed Hydrocarbon gases, wt. % feed CI to Ca inclusive 6.00 4.14 3.84 2.52 1.99 C4 3.58 2.62 2.39 0.90 0.67 c5 1.31 0.82 0.65 0.24 0.05 c6 0.35 0.21 0.19 0.06 Total product oil Vol. % feed 99.31 101.5 99.89 105.97 102.97 Specific gravity 0.885 0,895 0.916 0.893 0.923 Refractive index 1.5075 1.5136 1.5219 1.5045 1.5220 Ultimate composition,
... .
c
07
'O
H N
S OQ
Gasoline (Oo to 200' C. cut) b ' Vol. % feed Wt. 70feed Specific gravity Refractive index Ultimate composition, C% H N
S
0" Residue (above 200' C.) Specific gravit Refractive in&x Ultimate composition,
c
88.75 10.54 0.05 0.04 0.62
88.70 10.29 0.10 0.03 0.88
88.68 10.93 0.04 0.06 0.29
89.02 10.28 0.09 0.04 0.57
63.0 54.3 0.835 1.4853
52.8 45.8 0,840 1.4837
44.3 38.8 0,849 1.4825
60.1 51.7 0.834 1.4690
42.7 37.6 0.853 1.4781
87.62 11.53 0.03 0.01 0.81
88.13 11.30 0.09 0.02 0.46
87.99 11.08 0.14 0.01 0.78
88.33 11.55 0.03 0.05 0.04
87.52 11.30 0.09 0.04 1.05
0.960 1.5403
0.966 1.5442
0.968 1.5457
0.950 1.5312
1.5387
w.
'u
H N
S
OQ a b
88.60 10.55 0.03 0.05 0.77
B difference
89.80 9.66 0.04 0.01 0.49
89.94 9.61 0.05 0.01 0.39
90.05 9.61 0.04 0.03 0.27
89.73 10.21 0.02 0.02 0.02
89.99 9.85 0.04 0.01 0.11
d e i g h t and volume per cents include C5's and Ce's found in hydrocarbon gases. Analytical data, are for gasoline as obtained from liquid product.
'
INDUSTRIAL AND ENGINEERING CHEMISTRY
540 T.4BLE
Feed
1
Initial boiling point 5 10 20 30 40 50 60 70 80 90 95 E n d point
Total % distilled
TABLE v. GROUPANALYSES ON GASOLINES~
IT. A.S.T.M. DISTILLATIONS
% Distilled
99 5
98.5
Test h-0. 2 3 4 Whole Product Oils, ' C. 65 101 117 145 171 193 207 218 23 1 249 276 298 326 97 5
65 108 127 157 183 201 212 223 236 253 277 298 328 98 0
Kot run Not run Not run s o t run h o t run Not run Not run Not run S o t run Not run Not run Not run S o t run
5
80 I
.
.
125 167 192 208 218 228 240 259 276
...
61 85 91 100 112 124 137
1.54
169 183 197 210 216 96.0
97.0
73
..
97 105 113 122 131 154 171 185 198 2i7' 98.0
66 91 98 108 120 133 151 166 179 189 199 206 215 98.0
66 86 94 103 114 128 142 159 172 183 194 202 210 98.0
68 93 100 110 121 132 149 166 180 190 Excessive foaming
...
Residues (over 200° C , ) , O C . Initial boiling point 5 10 20 30 40 50 60 70 80 90 95 E n d point Reoovery,
205
...
226 234 241 248 266 266 278 289
.... ..
92
300 89.0
190 208 211 218 221 226 231 239 251 266 288 307 316 97.5
198 212 215 220 225 230 236 244 256 271 292 308 325 98.5
199 213 216 222 225 232 239 248 260 275 293 307 349 9Q
Not able to run, excessive foaming
Test 1 2 3 4 5 Temp., C. 500 500 500 475 473 Space velocity 0.72 1.02 1.28 0.32 0.81 Paraffin, olefin, naphthene, 70 40 31 39 35 34 Aromatic, % 48 49 48 45 47 Tests on Test 2 Gasoline Octane S o . , motor method (F-2) 79.8 Existent gum in gasoline, A.S.T.11. D 381-46 mg. of residue per 100-ml. sample 30.4 Free a n d corrosive sulfur in gasoline Passing Lamp sulfur, 70 0.026 a The sample was absorbed from petroleum ether a t - l o o C. on a silica gel column similar to one described b y Mair (41, and developed with ethyl alcohol. The separation was determined b y refractive index of successive 1-ml. samples.
285 95.0
Gasolines (0" to 200' C. cut),' C. Initial boiling point 5 10 20 30 40 50 60 70 80 90 95 E n d point Total % distilled
Vol. 43, No. 2
Not able to run, excessive foaming
Table I11 indicates the refining properties of this catalyst. Nitrogen is reduced from 0.32% in the feed to 0.10% or less in the product, sulfur from 0.17 to 0.06% or less, and oxygen from 1.32 t o 0.88% or less. This reduction is not as marked as that predicted by German sources. Thus, Frese ( 2 ) , in an operation with middle oil from low-temperature carbonization of bituminous coal, reports a reduction of nitrogen bases from 2 to 3% in the feed to 0,015y0 and a reduction of phenols from 4.5% to 0.1 to 0.2%. (Assuming a n average molecular weight for nitrogen bases and oxygen compounds of about 175, this refinement corresponds to a reduction in nitrogen from about 0.20 to 0.01% and a reduction in oxygen from 0.41 to about 0.014%.) Because of the different nitrogen and oxygen contents of the two feeds and the different types of feed material, the reductions are not strictly comparable. From Figure 7, it can be seen that in the range covered, the percentage of gasoline in the product is virtual11 a linear function of the space velocity. However, if the space velocity were decreased to a very low value, the gas production would probably increase greatly and result in a decrease in gasoline. It is apparent t h a t temperature has a very marked effect on the gasoline production. Thus, to produce a material containing 50% gasofine by weight, based on feed, the hourly space velocity can be increased from 0.34 a t 475' C. to 0.88 a t 500" C. Of course, this advantage is offset by the higher gas production (C, to C,) a t the higher temperature, 2.4% a t 475" C. and 0.34 space velocity as against 4.8% a t 500" C. and 0.88 space velocity. It may also be seen from Figure 7 that, a t 500" C. and a space velocity of 1.0, a product containing 46.6% by weight Cp-free gasoline based on feed was obtained, and the hydrogen consump-
tion was 2.8%. These are in good agreement with the values estimated by Hirst et al. (3) of 47% stabilized gasoline production and a hydrogen consumption of 3.0 to 3.2 weight % based on the feed. The gasolines for all tests are very similar in ultimate composition except for the oxygen content, a value which is not too reliable as it is obtained by difference and hence reflects the errors in all other determinations. The group analyses on the gasoline fractions (Table V) show the excellent retention of the aromatic quality of the oil in this process, a characteristic t h a t is not significantly affected by different test conditions. SUMMARY
A unit for the high-pressure hydrogenation of oils has been described. In the first operation, an aromatic light oil produced by hydrogenation of coal was treated over a hydrogenation-splitting catalyst a t 475' and 500' C. and 9000 pounds per square inch gage pressure. I n this operation, the oil was refined by the reduction of the nitrogen, oxygen, and sulfur content. At 500' C. and a space velocity of 1 kg. of oil per liter of catalyst per hour, a product containing 46.6% gasoline was obtained; the gasification (C, to C,) n-as 4.2%, and 2.8% hydrogen was consumed (all percentages on feed). The gasoline product showed a high retention of the aromatic quality of the feed and good antiknock characteristics. ACKNOWLEDGMENT
The authors wish to express their grateful appreciation t o P. L. Golden and R. JV. Hiteshue and their groups for invaluable assistance in erecting the unit, to J. Lederer for the analyses, to R. Friedel for mass spectrometer analyses of the gases, to H. .J. Kandiner and A. M. Whitehouse for help in design of the unit, to H. H. Ginsberg, A. P. Bishel, and A . Burick €or operation of the unit, and to IT.Kama for help in erection and operation of the unit. LITERATURE CITED
(1) Clark, E. L., Golden, P. L., Whitehouse, A. hI., and Storch, H. H..
IND. ENG.CHEX, 39, 1555 (1947). ( 2 ) Frese, Erioh, "Status of Recent Research Work on Hydrogenation
with a Fixed Bed Catalyst a t 700 Atmospheres, Hydrogenation of Middle Oil," Bureau of Mines Special Communication, Xovember 1946. (3) Hirst, L. L., Rlarkovits, J. A., Skinner, L. C . , Dougherty, R. W., and Donath, E. E., U. S. Bur. Mines, Rept. Invest. 4564 (1949). (4) Mair, B. J., N a t l . Bur. Standards Research Paper 1652 (1945). RECEIVEDJune 29, 1950. Presented before the Division of Industrial a n d Engineering Chemistry a t the 118th 1\Ieeting of the AMIERICAN C H E a f I C a L SOCIETY, Chicago, Ill.
Correction I n the I.&E.C. Report on 'Wercurial Metallurgy" [IND. ENG. CHEW,42, 20 A ( M a y 1950)], the reference t o the work of Hohn fihould have been [Hohn, H., Research (London), 3,16-23 (1950)l.
