\ #LOHEXANE CH2
/
CH~
CH2
The trend is toward hydrogenation and high purity f o r a billion-pound-peryear market H A R R Y
W . HAINES
In many respects cyclohexane is a chemical with a fascinating past and a promising future. T w o major oil companies have been in and out of the business; 20% of the nation’sproduction has been exported to three or more f0rei.p countries; and producers are now faced with the possibility of excess capacity during the next f e w years. But cyclohexane growth, keyed to expanding markets f o r nylon. has promising long-term prospects. Properly called the “benzene of the future” by one trade publication, cyclohexane is well on ils way toward becoming a billion pound-per-year chemical by 1965. big jump in cyclohexane consumption took place in due primarily to large volume exports, estimated a t 20 million gallons. And still anothei sizable increase is anticipated this year, with two new plants on stream manufacturing caprolactam from cyclohexane (Figure 1). Shifting end-uses are obvious by comparing the domestic markets for 1960 and 1962. Although caprolactam is making inroads into the share of the market occupied by Nylon 6 6 , other uses will retain their present position (Figure 2). Exports have remained fairly constant, but the geographical distribution is changing considerably. During 1960, 6 to 7 million gallons went to Europe, mostly to Badische Anilin und Soda Fabrik in Germany; 12 million gallons to Du Pont in Canada; and about 1 to 2 million gallons to Toyo Rayon in .Japan. Next year the Canadian markets will be lost to British American Oil when a new 15 million-gallon benzene hydrogenation unit xoes on stream near Montreal by
A 1960,
the end of 1962. Japanese markets, however, seem to be increasing. Toyo Rayon, for example, has contracted to purchase almost 6 million gallons over a three-year period from Continental Oil, Gulf Oil, and Chemische Werke Huls (Germany). Production
With the loss of certain export markets anticipated, principally in Canada and Germany, American production facilities are now large enough to handle domestic demand for the next several years (Table I). In fact, it can be said that there is hardly room for another producer, because two hydrogenation units can easily be expanded by 15 million gallons or more. Through the years, production has shifted from producer to producer with a trend today toward hydrogenation and high purity materials. Du Pont, for many years, has manufactured a portion of its requirements hy benzene hydrogenation, whereas Chemstrand has always pmchased on the open market. Phillips Petroleum, the first merchant producer, began extracting commercial (85%) cyclohexane in 1946 a t Borger, Tex., from natural gas liquids. I n 1956, Phillips made 98% cyclohexane available to its customers, by superfractionation, and the Sweeny plant went on stream in 1959. Humble Oil and Shell Oil, which formerly recovered commercial (85%) cyclohexane from refinery stocks a t Baytown, Tex., and Wilmington, Calif., are no longer in production. Continental Oil and Gulf Oil became merchant producers in 1960, by benzene hydrogenation. Today, almost 55% of the nation’s plant capacity is based on hydrogenation. lnbrmediales
The most important intermediates manufactured from cyclohexane are adipic acid, caprolactam, and cycloVOL. 5 4
NO. 7
JULY 1 9 5 2
23
IE USE PATTERN
i
24
INDUSTRIAL AND ENGINEERING C H E M I S T R Y
bcxanol(4). Adipic acid, in rum, is used in the production of Nylon 66, complex and noncomplex plasticizers, polyurethane foams and elastomera, synthetic lubricants, and by the food and pharmaceutical industry (Table 11). During the IO-year period from 1950 through 1960, adipic acid consumption leaped from 50 million pounds a year to about 360 million, and is expected to exceed 580 million pounds by 1965. Adipic’s big use (85%) is in Nylon 66 manufacture during which it is reacted with hexamethylmediamine. Chemstrand makes adiponiuile, the common intermediate for hexamethylenediamine, from adipic acid; Du Pont produces its adiponitrile from butadiene (having discontinued the use of furfural). Hence, estimates of adipic acid consumption must be made with a different factor for each Nylon 66 producer. Adipic acid consumption in Nylon 66 production during 1960 was approximately 308 million pounds. Other uses accounted for some 53 million pounds, bringing the total to about 361 million. The key to adipic acid’s future is hidden in the “battle of the nylons.” If Nylon 6 becomes the most important nylon, as some observers predict, adipic acid will suffer. This year, six producers will have 152 million pounds per year of capacity (3). These firms are hoping that Nylon 6 will prosper because of a cost advantage over Nylon 66. However, it appears safe to assume a continued growth of Nylon 66. This will mean a need for 520 million (or more) pounds of adipic acid in 1965. Most of the adipic acid produced in the United States is consumed captively (Figure 3). Sales are now approximately three-fourths of nonnylon markets, but in the future a larger percentage of sales will be diverted into these uses. Five companies manufacture adipic acid from two mutes (phenol and cyclohexane) using three types of processes (Table 111). The Rohm & Haas unit, now under construction, employs air oxidation in both steps of cyclohexane conversion, a recent innovation inmduced by Scientific Design Co. Today, the United States has 50 to 70 million pounds per year of excess adipic acid plant capacity available for nonnylon markets (a 60-million pound market). However, by the end of 1964 this cxcesa will be eliminated as Nylon 66 consumption increases. Although only two producers are engaged in the manufacture of Nylon 66, six wmpanies manufacture Nylon 6 fibers and five firms produce Nylon 6 resins (Table IV). Growth of Nylon 6 resins has been disappointing, hut Nylon 6 fibers have a promking future. More Nylon 6 means more caprolactam manufactured from phenol or cyclohexane (8). This year two new caprolactam plants (Table V) arc going on s w a m using cyclohexane raw material. Almost 40% of the nation’s caprolactam plant capacity will soon be based
enough to meet domestic demand for several years on cyclohexane, and the United States will have ample caprolactam capacity for a t least several years. Cyclohexanol is now potentially cheaper than oxo alcohols and may therefore become a very important plasticizer alcohol, because of recent improvements in cyclohexane oxidation. Some trade observers, however, say that dioctyl phthalate and diisooctyl phthalate will continue to dominate the plasticizer market. Dicylohexyl phthalate has been on the market for several years but, after a fast start, its showing has been disappointing. Output, at 2.3 million pounds in 1956, reached a peak of 6.8 million in 1958, and since then the trend has been downward. Production in 1961 may have slightly exceeded 5.5 million pounds, compared with 5.8 million in 1960. Developed specifically for use in the manufacture of nitrocellulose coating for cellophane, DCHP has lost out, as requirements for moisture-proof cellophane have declined. The reason : introduction of competitive products like Saran. However, in 1960, approximately 1 million pounds of DCHP were consumed in rubber and miscellaneous uses; Howards of Ilford, Ltd., recently completed a 20 million pound-per-year cyclohexanol-cyclohexanone (ex cyclohexane) plant in England to supply the company’s DCHP unit. Du Pont converts some cyclohexane to cyclohexanol and cyclohexanone, for uses other than adipic acid production, estimated a t 3 to 4 million gallons per year of cyclohexane consumption.
TABLE I .
Annual Capacity,
CONTINENTAL OIL Ponca City, Okla.a DU PONT Belle, W. Va. Orange, Tex. GULF OIL Port Arthur, Tex.* PHILLIPS PETROLEUM Borger, Tex. Sweeny, Tex.C Total
Cyclohexane has some growth potential as a solvent in the manufacture of Phillips-type, low-pressure polyethylene. But it is very hard to obtain a good estimate of this market. Phillips supplies commercial (850j0) cyclohexane to its polyethylene licensees and neither group likes to talk freely about the nature of the process solvents. To
30-million-gallun increase rumored. Q
Million
Raw Material
Company
Solvents
TABLE I l l .
CYCLOHEXANE PRODUCERS
Sales
Benzene
20
hllerchant
Benzene Benzene
15 15
Captive Captive
Benzene
20
Merchant
1::
Merchant Merchant
Natural gas liquids
130
capability.
TABLE I I .
Gal.
b 25-million-gallon
capability.
c
Capactiy
ADIPIC ACID USE PATTERN
(Million pounds) 7959 7960 7967 796.5
Use
NYLON 66
PLASTICIZERS (complex) PLASTICIZERS (noncomplex) FOAMS (urethane) ELASTOMERS (urethane) LUBRICANTS (synthetic) FOOD, PHARMACEUTICALS MISCELLANEOUS Total Nonnylon uses
270
308
326
520a
13
14
15
21
6 8
7 8
7 8
8 5
1
2
3
6
5 4 8
6 8 8
315
361
384
589
45
53
58
69
-.--
6 5 9 1 2 10 12
-
4 If Nylon 66 breaks into the new-car tire maiket, this estimate may reach 580 to 620 million pounds.
ADIPIC ACID PRODUCERS
(Million pounds) Comfiany
ALLIED CHEMICAL Hopewell, Va. CHEMSTRAND Pensacola, Fla. DU PONT Belle, W. Va. Orange, Tex. MONSANTO Luling, La. ROHM & HAAS Louisville, Ky.
Annual Capacity 20
R a w Materials and Intermediates
Phenol Cyclohexanol Cyclohexane
180-200
Cyclohexanol-cyclohexanone
105 105
Cyclohexanol-cyclohexanone
30 20-25
Cyclohexane Phenol Cyclohexanol Cyclohexane Cyclohexanone-cyclohexanol
Conversion Process
Sales
Hydrogenation Nitric acid oxidation Air oxidation Nitric acid oxidation
Captive and merchant
Air oxidation Nitric acid oxidation Hydrogenation Nitric acid oxidation Air oxidation Air oxidation
Captive and merchant
Captive use only
Captive and merchant Captive and merchant
460-485 VOL. 5 4
NO. 7
JULY 1 9 6 2
25
TABLE IV.
cyclohexane with no side reactions, unless elevated temperatures (above 660" F.) are employed; then cracking and rearrangement into other products occurs (2). Benzene may be reduced a t room temperature over platinum, palladium, and similar catalysts, but an acid solvent is usually necessary. I n general, elevated temperatures are required for reduction over such materials as nickel, copper, and cobalt. Although other metals are effective in the hydrogenation of the aromatic nucleus, their activities are generally conceded to be less than that of reduced nickel. Hydrogenation is a relatively simple operation. However, the catalytic reactor must be designed for heat removal because the reaction is esothermic :
NYLON PRODUCERS
(Million pounds) Aylon 6G Company
Fzbers
ALLIED CHEMICAL Chesterfield, Va. Hopewell, Va. Irmo, S. C. AMERICAN ENKA Enka, N. 6. BEAUNIT Elizabethton, Tenn. CHEMSTRAND Greenwood, S. C. Pensacola, Fla. DOW CHEMICAL Williamsburg, Va. DU PONT Chattanooga, Tenn. Martinsville, Va. Parkersburg, UT.Va. Richmond, Va. Seaford, Del. FIRESTONE Hopewell, Va. Pottstown, Pa. FOSTER GRANT Manchester, S.H. ISDUSTRIAL RAYON Covington, Ky. SPENCER CHEMICAL Henderson, Ky. Total a
A)lon 6 Fibers
iQlon 6 Resinr
10 65 20 35
2 15
171 12
0
C
+ 3 Hz-
30.
100 40
1
The free energy change for hydrogenation of benzenc vapor to cyclohexane vapor can be represented in simple mathematical form as
6
-
2 45
AF
I
152
Includes Nylon 66 and 610.
complicate matters further, hcxane can be used in conjunction with cyclohexane, depending on the type of polyolefin desired. As a conservative estimate one gallon of cyclohexaiie is probably required per 100 pounds of polyethylene. Hence, cyclohexane consumption for polyolefin production is in the neighborhood of 3 million gallons per year. Cyclohexane is also used in limited quantities as a paint and varnish remover, and for extraction of essential oils. Hydrogenation Chemistry
Benzene undergoes hydrogenation over a variety of catalysts. The hydrogenation procecds cleanly to TABLE V.
=
-94.700
Company
DO!$'-BADISCHE Freeport, Tex. DU PONT Beaumont, Tex.
26
+ 94.6T B.t.u.,/lb.-mole
where T = O R., from which A F = 0 at about 1000" K. (540' F.), but there will be little difference in free energy change far these hydrocarbons in the liquid phase (5). At commercial hydrogenation pressures (300 to 550 p.s.i.g.) and temperatures (300' to 550' F.), conditions can be maintained where equilibrium benzene content in the product is about 0.01%. At the turn of the century, chemiss thought beiizene could be hydrogenated only when the vapors came into contact with the catalyst. but this theory was disproved in 1906 by the Russian chemist Ipatieff. Today, commercial cyclohexane plants are designed for liquidphase and mixed-phase reaction. Kinetically, benzene hydrogenation is generally first order with respect to hydrogen pressure and zero order with respect to benzene concentration. However, it has been noted that, over a nickel catalyst, the order uith
READER PLEASE NOTE:
CAPROLACTAM PRODUCERS
(Million pounds)
ALLIED Hopewell, Va.
c
CH:,
AH (77' F.) = -88,650 B.t.u./lb.-mole
2
466
(Vapor phase)
HzC
Hz
12
--
HzcoCHz Hz
90 50
After half of this article
Annual Capact4
Raw M a t e d
130
Phenol Hydroxylamine
Cyclohexanol Cyclohexanone Cyclohexanone oxime
error was noted in the
Cyclohexane Hydroxylamine Cyclohexane Sitric acid
Cyclohexanone-cyclohexanol
three final paragraphsof
44
50 224
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
Intermedaates
Cyclohexanone oxime Nitrocyclohexane
had gone to press, an process descriptions. The the UOP process, page
28, refer to the Scientific Design process, page 29.
respect to hydrogen changes from zero order (below 230" F.) to first order (above 390' F.) as the temperature is increased. This change in order is probably evidence that the benzene molecule is more strongly adsorbed than hydrogen at low temperatures (below 350" to 360" F.), but this relationship is reversed at higher temperatures. Russian studies on benzene hydrogenation in the vapor phase over nickel show a maximum reaction rate around 300" to 340' F. ; and in regions of high benzene vapor pressure (0.5 to 0.8 atm.) the reaction rate is directly proportional to hydrogen pressure and independent of benzene pressure. For low benzene pressures, the kinetic orders are reversed. Hydrogenation rates reported in the literature indicate that benzene reacts faster than polyalkyi benzenes, with the suggestion that an accumulation of methyl groups hinder hydrogenation (Table VI). The rate can be approximated by the formula
Vn
= 2-
V
where n is the number of substituents and V velocity of benzene hydrogenation. There are, however, several exceptions to this rule (p-xylene with two substituents undergoes hydrogenation more rapidly than toluene with only one; mesitylene with three substituents is reduced more rapidly than either o-xylene or m-xylene, each with two methyl groups; and durene is hydrogenated more rapidly than hemimellitene) . Symmetry of substitution apparently has an additional effect and for any given number of substituents, the isomer which is most symmetrically substituted shows the greatest hydrogenation velocity. But this is a question of symmetry of substitution and not molecular symmetry itself. I t is difficult to distinguish between two possibilities for the mechanism of benzene hydrogenation. According to one mechanism, known as the adjacent interaction mechanism, two reacting molecules are adsorbed on adjacent sites in a chemisorbed monolayer and, after interaction on the monolayer, the product is desorbed. The second possibility is that one reacting species is chemisorbed on the catalyst surface and molecules of the other species react with it from the gas phase or van der Waals layer. (This mechanism has been called the van der Waals chemisorbed-layer interaction.) Commercially, the reaction mechanism does not make a lot of difference; space velocities in the reactor are always adjusted to obtain essentially equilibrium conversions, which are almost stoichiometric. Manufacturing Technology
One of the most important commercial considerations is to avoid poisoning of the catalyst with sulfur compounds when nickel is employed. Room-temperature
Harry W . Haines, Jr., is a consulting chemical engineer, and owner o f Haines @ Associates in Houston, Texas. He has had extensive experience in research, development, process and blant design, in sulfur, pelroleurn refining, and petrochemicals. During the period 7953-56, Mr. Haines was Associate Editor in charge of the ACS Applied Publicafions ofice in Houston. AUTHOR
TABLE VI. HYDROGENATION RATES OF POLYALKYLBENZENES
Compound
Absolute
Benzene Toluene o-Xylene m-Xylene $-Xylene
Relative Rates Nickel- Calculated alumina Vn = 2-"V
Ratea
Platinum catalystb
4 61
100
100
100
3.01
62
50
50
1.47
32
24
25
2.27
49
23
25
2.98
65
31
25
a Cu. ft./Ib./min. of Pt catalyst with acetic acid solvent.
b With acetic acid solvent.
laboratory studies on this subject indicate that 0.0002 pound of thiophene per pound of nickel decreases the rate of hydrogenation 5001,. Apparently the size of the nickel crystals (hence, the number of active centers) determines sulfur tolerance, but complete inactivity will occur when sulfur contamination reaches a level of 0.0005 to 0.0030 pound per pound of nickel. Furthermore, high levels of sulfur contamination (0.0033 pound of thiophene per pound of nickel) cause permanent retention of sulfur after catalyst reactivation (up to 0.0003 pound of thiophene per pound of nickel). And 0.01% thiophene in benzene is sufficient to poison the catalyst during vapor phase hydrogenation a t 350" F . ; subsequent treatment with hydrogen does not restore its activity. Commercial hydrogenation catalysts are now available, containing up to 33 weight per cent nickel on a refractory oxide support. Fixed bed reactors are preferred and two engineering firms- Universal Oil Products Go. (Figure 4) and Scientific Design Go. (Figure 5)-offer proprietary processes (9, 70). T o date Universal Oil Products and Procon have designed and built all of the hydrogenation units in the United States with the exception of the Du Pont facilities. One of the basic differences in the two process schemes seems to be the method of removing heat from the reactor. Scientific Design employs indirect water cooling for steam generation; U O P uses direct vaporization of the feed-benzene and recycle cyclohexane. Chemetron Corp. ( 7 ) has published data on vapor phase hydrogenation, although units in the United States do not appear to use this principle. I n this method, cyclohexane with a purity of 99.5 volume per cent was obtained by hydrogenation over a nickel catalyst at 300" to 400" F. and atmospheric pressure, with a hydrogen vapor space velocity of 1000, benzene liquid space velocity of 0.4, and a hydrogen-to-benzene molar ratio of 9.0 to 9.5. Results in an isothermal reactor a t 1 to 35 atm. indicated that hydrogen space velocity is somewhat critical at 300" F. with a liquid benzene space velocity of 0.4 to 0.9. Increasing the pressure from 1 to 35 atm. does not improve conversion at 300' F., but it does permit use of higher reaction temperatures which in turn improves conversion and space-time yields. Mixed phase hydrogenation studies by Chemetron VOL 54
NO. 7 J U L Y 1 9 6 2
27
are similar to the UOP process scheme, even though different catalysts (platinum) are employed by UOP. The use of recycle wherein a substantial portion of liquid product i s added concurrently with the reactants provides an effective method of temperature control. Heat of reaction i s removed by vaporization o f the liquid phase leaving a n appreciable portion of the p i d u c t in the vapor phase at the reactor outlet. A cooler at the outlet to separate liquid product from the gaseous product can be of comparatively simple design. Recycle totally eliminates water jackets, coolers and heat exchange apparatus within the reactor, and the need for preheat and vaporizing equipment. Tests in an adiabatic reactor at 500 p.s.i.g., a t 515" to 550" F., produced pure cyclohexane (99.5% or better). T h e feed stock, a mixture of cyclohexane and benzene
(17.5 volume per cent benzene), was treated at a hydrogen space velocity of 5800 and a liquid benzene space velocity o f 2.0. Recently the Institut Francais du Petrole developed a liquid phase hydrogenation process which uses liquid pump-around to cool the reactor (7). This unit operates a t pressures up to 40 atm. and produces 99.8 weight per cent cyclohexane containing less than 0.1 weight per cent benzene, and having a freezing point of 42.8' F. (based on high purity benzene feed with a 41.7' F. solidification point). Claims are made that cyclohexane is produced at a n over-all operating cost of 2.34 cents per gallon. Where hydrogenation i s employed, cyclohexane purity and price (Table VII) are keyed to the purity and cost o f benzene. Most merchant producers sell cyclohexane at
Operating conditions are moderate, allowing the use of carbon steel throughout the plant. Two Hydrar unitsare presently in operation by Continental Oil and Gulf Oil in the United States. Several others either are licensed for construction or are under construction. The following cost figures apply to a Mx) barrels-perstream-day unit lapproximutely 8.33 million gallons per year):
LWILM
Figure 4
UOP's Hydror process charges benzene and a hydrogencontaining gas for the catalytic hydrogenation of benzene to produce high-purity cyclohexane. It i s also capable of converting toluene and higher aromatics to their respective cycloparaffins. Purity of the cyclohexane product i s a function of the purity of the benzene feed. If the benzene i s 99.8+% pure, as is the case when it is produced by a Udex unit, the cyclohexane will have a freezing point of 42.6' F., indicating less than 0.2 weight per cent impurities. Benzene feed, recycle cyclohexane, and fresh and recycle hydrogen are brought to reaction temperature and charged to the reactor. Conversion of benzene to cyclohexane is stoichiometric. The reactor effluent, after exchanging heat with the feed, is charged to the separator and gas from the separator i s recycled to the reactor, with a small net gas stream being removed. A portion of the cyclohexane from the Separator i s recycled to assist in the control of the reaction temperature. Product cyclohexane i s flashed and/or stabilized to remove light hydrocarbons. 28
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
Steam 1450 psig.), Ib./hr. Fuel gos consumed, B.t.u./hr. Cooling woter, gal./rnin. Electric power, kw.-hr. Catalyst and chemicals, $/stream day Operating labor lper shift), no. men Maintenance iertimotedl, %/yr. of unit cos! Investment cost iestimatedl, $ Materials, labor, catalyst charge Design, engineering, construction fees
Total process unit cost
1500
2 x 108 750 230
40 1 to 2 3
572.000 130,ooo _ _
702,000
Benzene feedstock i s mixed with fresh hydrogen makeup and recycled hydrogen, then passed through a feed-product exchanger into the hydrogenation reactor. The reactor i s cooled by vaporizing water, thus producing intermediate pressure steam which may be used to furnish requirements in the process area. Reactor product, comprising hydrogen and cyclohexane with practically no benzene (benzene concentration may be controlled as desiredl, i s portiolly cooled in the feedproduct exchanger and further cooled and condensed in o water-cooled exchanger. The cold product passes to o first separator from which the major port of the hydrogen i s removed and recycled to the reactor. Liquid cyclohexane product i s passed to o second separator in which inerts are vented from the system. Cyclohexane of exceptionally high purity i s removed from the second separator as product from the plant.
~
4 to 5 cents a gallon more than they pay for benzene, in order to obtain a fair return o n investment. But both of the new hydrogenation u n i t s will soon be paid out-a fact to remember if the market becomes highly competitive. T h e prospects for new plants are n o t good without product contracts. Cyclohexane by hydrogenation meets the minimum specifications established by Phillips Petroleum (Table VIII) for cyclohexane recovered from natural gas liquids (6). Capital costs of hydrogenation units (Figure 6) may vary as much as SO%, depending o n whether the reaction is conducted in the liquid or mixed phase, and whether the hydrogenator i s charged with a nickel or platinum catalyst. Although platinum may cost more, it has a m u c h longer life than nickel and can be reprocessed. Hmce, operating economics require careful
TABLE Vll.
PRODUCT AND INTERMEDIATES PRICES
Adipic Acia
cyclohexanal'
@clahexanan@
1955
35
27
32
1956
32-35
24-27
29-32
1957
32-32'],
24
29
1958
32'/4
24-26
29-31
32'/4
26
31
~dohcxane,
Yam
D
98%"
1959
36
1960
36-40
32'/1
26
31
1961
36
29-32'14
26-28
31
1962
30
28
31
Ccncl pa
pound, barn carload, dclivned. mnka works. B &am k -Arks, f m i g h f a b d & s t .
c Cenmprm o d ,t
29
VENT FOR IMPURITIES IN Hz EED RED
EXCHANGER
CYCLOHEXANE
HYDROGEN
SEPARATORS
BENZENE
Figure 5 Scientific Design's cyclohexane process i s characterized by extreme simplicity. Featuring o single reactor and no fractionating columns, it yields cyclohexane of very high purity at high conversion levels and generates only moderate temperatures and pressures during operation. Existing commercial grades of benzene are fully utilizable in the process. In addition, the process is readily adaptable to hydrogen feed streams of many different purities and concentrations such as are usually found in the petrochemical industry. The process may be used to produce cyclohexane for any commercial application. It has also been specifically designed to produce suitable feedstock for use in processes involving Scientific Design's latest advances in cyclohexane technology Icyclohexanol, cyclohexanone, caprolactam, adipic acid, and anilinel. On a toluene feedstock, the same plant may be used in analogous Scientific Design technologies to produce methylcyclohexanols and other related compounds. Raw Materials. Benzene requirements are essentially theoretical. Hydrogen requirements may be essentially
COMPIt€~b!
theoretical if highly pure, but actual consumption depends upon the level of impurities in the feed.
UHIHIer. These costs are negligible, becouse credit may be taken for the steam produced in the reaction t o balance other utility requirements. labor. Partial attention of one operator i s a11 that is necerxlry.
Maintenance.
This plant i s in the very lowest category of maintenance cost-about 1 to 2% per year of capital investment, depending on plant size and the manufacturer's maintenance organization.
Capital Investment. Because of its extreme simplicity, this process has the lowest capital cost of any conceivable route to cyclohexane, according to claims by Scientific Design. Actual investment costs, they say, will depend upon plant size, location, site conditions, construction labor costs, hydrogen feed purity and pressure, and the nature of available utilities. Investment for any size plant will therefore vary according to the specific situation of the proposed manufacturer. VOL 5 4
NO. 7 J U L Y 1 9 6 2
29
TABLE V I I I .
TYPICAL CYCLOHEXANE SPEC1FICATIONSa
Specgcation
98% Commercial
70
Test Method
98 min.
85 min.
IBP
1 7 5 . 1 min.
172 min.
ASTM D1078
DP
1 7 9 . 6 max.
182 max.
ASTM D1078
0.765-0.775
ASTM D1298
Purity, wt.
Specific gravity, 60”/60’ F. Vapor pressure, p.s.i.a. 100’ F.
3 . 5 max.
Color (Saybolt) Sulfur content, wt.
Infrared
F.
Distillation Range,
+30 min.
%
Corrosion
ASTM D156
0.02 max.
ASTM D1266
1 max.
1 max.
-4STM D130
Nonvolatile matter, g./100 ml.
0 , 0 0 1 max.
Benzene content, wt.
0 . 1 max.
70
3-30 min.
ASTM D323
0 . 0 1 max. Xegative
Doctor test
3 . 5 max.
Negative
0.002 max.
...
ASTM D484
ASTM D1353 Ultraviolet
a For material extracted from natural gas liquids; hydrogenation units are designed to produce a comparable or better quality product.
analysis. In general a plant which costs more than 3 cents per gallon to operate is probably poorly designed. AI though never commercialized, Ashland Oil and Eastern States Petroleum are reported to have developed their own hydrogenation processes. A l o o k Into the Future
Aside from the fast-growing nylon markets, which promise to push cyclohexane into the billion-pound class at an early date, cyclohexane has other attractive outlets. Complex plasticizers, manufactured from adipic acid esters, continue to grow at a healthy rate; urethane elastomers appear to be virgin territory. Additional uses are being developed, such as Union Carbide’s relatively new epoxy resin, based on cyclohexanone, And no one seems io know exactly what may happen to cyclohexanol (by cyclohexane oxidation) as the price of benzene decreases. In fact, a lot of speculation has circulated about the possibility of making phenol by cyclohexanol dehydrogenation. But the economics of this route may also face competition from new methods of toluene oxidation.
Overseas, the probpects for new hydrogenation units appear attractive, as caprolactam-from-cyclohexane units make new inroads. I F P says its first commercial hydrogenation unit has been engineered and others are at the desiyn stage. Unconfirmed reports indicate that East Germany’s VEB Leuna Werke is exploring benzene hydro yenation as a route to cyclohexanone. They apparently are hydrogenating benzene at 20 to 24 atm. and 500” F. over a Ni-TVSn catalyst to give a 99y0 yield of cyclohexane. The latter is washed with a caustic solution to remove hydrogen sulfide, then pumped in liquid form to a column where countercurrent contact with air oxidizes i t to cyclohexanone. The effecl of Toy-o Rayon Co.‘s new photochemical process for manufacturing caprolactam from cyclohexane is yet to come. This method is reported to be very economical, with a cyclohexane consumption below 0.8 pound per pound of caprolactam. Toyo spokesmen say they have received inquiries from more than 20 companies, many in the United States and Europe, interested in licensing the process. If the process has production costs around 20 cents per pound, as claimed, it could create an upsurge in cyclohexane demand. SUGGESTED READING
PLANT CAPACITY, MILLION GAL./YR.
Figure 6. Capital costs of h),drogenatl’on ~ n i l sf
l q
u q as much as
50% 30
INDUSTRIAL A N D ENGINEERING CHEMISTRY
(1) Chemetron Corp., Chemical Products Div., Louisville, Icy., Girdler Catalysts Data: G-33>G-52, Bull. G-33-52-5189. (2) Emmett, Paul H., “Catalysis,” Vol. 5, pp. 175-98, Reinhold, New York, 1937. (3) Fedor, W. S., Chem. Erig. ;l’ews 39, 116-34 (March 20, 1961). (4) Zbid., 39, 118-38 (Nov. 13, 1961). (5) Goldstein, Richard Frank, “The Petroleum Chemicals Industry:” 2nd ed., p. 218, Wiley, New York, 1958. (6) Phillips Petroleum Co., Special Products Div., Bartlesville, Okla., “Phillips 66 Hydrocarbons,” p. 39, 1958. (7) Ponder, Thomas C., Petrol. Re-ner 40, 233 (November 1961). (8) Sherwood, P. W., Oil in Canada 14,40-4 (April 19, 1962). (9) Sturchio, Joseph, Scientific Design Co., Inc., New York, N. Y . ,private communication, Dec. 14, 1961. (10) Thorton, D. P., Jr., Universal Oil Products Co., Des Plaines, 111.. private communication, Dec. 11, 1961.
