P E T E R W. S H E R W O O D
Commercial Syntheses of Organic Petrochemicals
RAW MATERIALS FOR MAN-MADE FIBERS New petrochemical technology supplies a fast-growing market omestic production of man-made fibers for 1961 These fibers fall into three main categories : cellulosics, 1.1 billion pounds ; noncellulosics, 742 million pounds; and textile glass, 180 million pounds. The petrochemical industry is concerned with cellulosics and noncellulosics. For rayon and cellulose acetate, it contributes, above all, acetic anhydride and carbon disulfide. During the last five years, however, total production of these categories has increased little, although acetate surged somewhat during early 1962. For noncellulosics, the sales picture is brighter: from 400 million pounds in 1955, production had risen to 750 million in 1961. Three major categories are involved which, in order of production volume, are polyamides (nylon types), acrylics, and polyesters. The principal petrochemicals which depend on synthetic fibers for primary markets are the monomers, adipic acid, hexamethy-lene diamine, e-caprolactam, acrylonitrile, and terephthalic acid. For making these monomers, $-xylene, cyclohexane, and various other intermediates are used. Other monomers are used, but their primary markets are in other areas-e.g., vinyl chloride, vinylidene chloride, propylene (for polypropylene), vinyl acetate, and ethylene glycol. This article deals with those petrochemical intermediates whose major markets are for synthetic fibers.
D amounted to more than 2 billion pounds.
RAW M A T E R I A L S FOR RAYON AND ACETATES Carbon Disulfide PROCESS
73.
CH4
+ 4s
--+
+ 2HpS
CSZ
Vapor phase. Catalyst: oxides of Si, Al, Mg, by themselves or impregnated with oxides of Zr, Ni, Co, etc. Typical conditions: silica gel; GOO0 C.; 15 to 25 p s i . ; 390 hr.-l; stoichiometric S to CH4 feed ratio (using 98%+ CHI). Conversion: about 90%, almost entirely CSz.
Alternative conditions : catalyst, activated bauxite ; 680' to 700' C.; 15 to 25 p.s.i.; slight excess sulfur in feed; 600 hr.-I. Conversion: 85y0+, almost entirely
csz.
Competitive source : high temperature reaction between sulfur and carbon. Acetic Acid
Routes: a, partial oxidation of acetaldehyde; b , liquid-phase hydrocarbon oxidation ; c, direct oxidation of ethyl alcohol (not commercial) ; d, from methanol and carbon monoxide (probably not commercial). Acetaldehyde (as intermediate for acetic acid and anhydride) PROCESS
74.
Straight dehydrogenation of ethyl alcohol. CzHbOH
--j
CH3-CHO
+ Hz
Vapor-phase. Catalyst: Cu promoted by Co, Cr on support-e.g., asbestos; 275' to 280' C.; 90y0 conversion, 85y0 yield. PROCESS
75.
Oxidation-dehydrogenation
of
ethyl
alcohol (0)
C f H 6 0 H ----+
CH3CHO
+ HzO
Over silver gauze; 550' C . ; 50 to 55y0 conversion; 85 to 95y0 yield. 74 us. 75. Straight dehydrogenation is favored. Its main advantages are ease of temperature control, less product dilution, and formation of by-product Hz. This approach is not feasible for formaldehyde. PROCESS
76. Oxidation of butane-propane. Vapor phase. Noncatalytic. Oxygen now used in lieu of air. Typical operating conditions : hydrocarbon-oxygen ratio, between 5 and 20; pressure, 100 to 300 p.s.i.g.; preheat temperature, 250' to 350' C . ; peak temperaPROCESS
VOL. 5 5
NO
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JANUARY
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37
ture, 430' to 530' C . ; residence time 0.25 to 2 seconds. Quick after-quench required. Typical yield per gallon butane, 1.5 pounds acetaldehyde, 1.6 pounds formaldehyde, 1.O pound methanol, 0.2 pound acetone, plus miscellaneous other oxygenated products. PROCESS 77.
Liquid-phase oxidation of ethylene. Oxygen carrier is an aqueous solution of palladium chloride, promoted (for metal reoxidation) by copper chloride. Air or oxygen may be used, with the latter preferred for single-stage oxidation. Operation at p H between - 1 and +2; temperature between 20" and 100' C., depending on details of process. Acetaldehyde yield, about 90%. Minor and Noncommercial Processes a, hydration of acetylene; Liquid phase; HgO catalyst,
80' to 95' C. b , related decomposition of ethylidene diacetate. c, by-product in iron-catalyzed gas synthesis (practiced a t only one plant, in South Africa).
hazardous (explosive) acetaldehyde monoperacetate is involved. An alternative pilot-plant process uses oxygen to oxidize acetaldehyde to peracetic acid in uabor-phase operation. PROCESS
80. Oxidation of butane.
Liquid phase. Acetic acid as solvent: chromium acetate catalyst; 165' to 170' C . ; 815 p.s.i.g.; 100 pounds butane yield a maximum of 104 pounds of acetic acid ; less if by-product methyl acetate is wanted. Alternative: liquid phase; noncatalytic; 80 atm. ; 170" C . ; conversion of 57, per pass. Useful product consists of 63Yc acetic acid, 3.67, formic and propionic acids, 307, esters and ketones (methyl ethyl ketone, acetone, rec-butyl acetate, ethyl acetate, and minor products). I n a similar version, hexane serves as feedstock in lieu of butane.
Acetic Acid PROCESS
78.
CH3CHO
CH3COOH
---+ a i r or
0 2
Air or oxygen as oxidizing agent. Trend is toward ox>-genbecause of easier product recovery ; liquid phase. M n acetate cataly-st: highly exothermic; 50' to 70' C . ; 0 2 absorption is fastest at 25 to 807, acid strength; 70 to SOYc coni7ersion; 95 to 96y0yield. PROCESS
a.
79.
2CHZCHO
(0i )
CHaG,,J O ,, ,, 0-
\c/H 0/ \CH3
Oxidation of acetaldehyde. Liquid phase. Cobalt acetate-copper acetate catalyst ; single-pass coni ersion. Product anhydride: acid ratio, between 0.5 and 0.6: can be raised by use of ethyl acetate as diluent and azeotroping agent. However, this approach slows reaction rate. PROCESSES
82
AUD
83,
Acetaldehyde monoperacetate
0
No
CHaC '0-OH
+ CH3CHO
Peracetic acid
I'
a
CH3C-OH-
1
J
Cat
0 'I CH 3-C-CH3
CHICOOH
CHs=C=OA
-+
h
--CHI
Oxidation to acetaldehyde peracetate by oxygen ; liquid phase (inert diluent). -5" to 0 ' C . Carried out in ultraviolet light; 50-607, conversion; about l O O ~ ,yield.
0 b.
//
CH3-C-O-OH
+ R2C = CR'2
82. Acetic acid cracking to ketene. Vapor phase. Triethyl phosphate catalyst; 740' C.; 120 to 160 mm. of mercury. Product is stabilized by 3" injection and quenched to 0' C. Product ketene is absorbed in a solution of 15 to 357, acetic anhydride in acetic acid. Fractionate. PROCESS
83. Acetone cracking to ketene. Vapor phase. 700' to 850" C. CS2added to suppress carbon formation. lOyc conversion, 860/,yield (70y0 yield at 25yc conversion). Quench product with acetic acid. PROCESS
Liquid phase; 70' C . ; noncatalytic; epoxide yield, 90 to 927,. Here epoxides are produced at very low incremental cost over acetic acid cost. However, very 38
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
RAW MATERIALS FOR ACRYLIC FIBERS Acrylonitrile
Routes: a, from acetylene and hydrogen cyanide; 6 , from propylene, ammonia, and air; c, from propylene and nitrogen oxides. Hydrogen Cyanide as Intermediate PROCESS
84.
CHd
+ + NHz 0 2
--+
HCN
+ H2O
Hydrogen cyanide by partial ammoxidation of methane over rhodium-promoted Pt gauze; 950' to 1000' C.; 60 to 7Oy0 ammonia conversion per pass. Recovery of unconverted ammonia as sulfate or by absorption in regenerable boric acid-pentaerythritol complex.
85. Alternative production of' HCN by nonoxidative reaction of methane and NHa. Thermal or in presence of Pt. PROCESS
Production of Acrylonitrile PROCESS 86.
CHECH
+ HCN
--+
CH2 = CH-CN
Aqueous liquid phase. Catalyst is cuprous chloride solubilized by ammonium chloride. 80' to 90' C.;
Cellulose sheets are reduced to "crumbs," aged, and then converted to cellulase xanthate
15 p.s.i.g. Optimum CzH2:HCN ratio, 8 to 10. Yield, 80 to 85% on acetylene, 90 to 95% on hydrogen cyanide. This process is the source of most acrylonitrile produced today. I t is, however, hard-pressed to compete with the newer, propylene-based methods. Example : Imperial Chemical Industries has discontinued production of acrylonitrile from acetylene. I t is building propylenebased facilities. PROCESS
87.
+
CH2=CH-CH3
0 2 --+
"8
CHz=CH--CHO
CHg=CH-CN
---+
+
H20
of propylene to acrolein (see process 32a). b, conversion of acrolein to acrylonitrile uses dilute acrolein stream from process 87a. a, oxidation
Reaction is carried out in vapor phase using M o o 3 on alkali-modified alumina as catalyst. About 380' C.; 0.4 to 0.5 second contact time. 78y0 yield (carbon basis). PROCESS
88.
CHZ=CH-CH3
+
+
NH3 CHt=CH-CN
1.5 0 2 --+ f 3H20
Catalyst: concentrated (50 to 6OY0) bismuth phosphomolybdate on silica. Fluid bed operation. Air-propylene molar ratio, 1 to 2 ; NH3 to C3H6, 1 to 2.5; steampropylene, 1 ; 425' to 510' C.; 2-3 atm.; 25 seconds contact time. Conversion to acrylonitrile is 50 to 55% (on carbon). By-products : acetonitrile, HCN. Promising among other catalysts: tungstate on silica gel. PROCESS
89.
4C3H6
+ 6N0
--.f
bismuth vanado-
4CHz= CHCN
+ N2
+ 6HzO
Vapor phase. Probable catalyst, Ca-promoted silver on silica; 460' to 500' C . ; 700 hr,-I; per-pass conversion, 10-12%. Yield, up to 90% on NO. PROCESS
8 9 ~ . 1. CHz-CHt
+ HCN
'O/
--$
HO-CH2-CH2CN
-
Production of ethylene cyanhydrin (see process 27). 2.
-nzo CHgsCHCN
HOCHz-CH2-CN
Dehydration: crude ethylene cyanhydrin in 88 to 9070 concentration is converted in liquid phase at about 200' C. MgC03 may be catalyst. PROCESS
89b.
CH3-CHO
f HCN
CH3CH-CN
---t
- HzO ---+ C H Z z C H C N
I
OH
1. Lactonitrile formation. Liquid phase. 20' C., using lactonitrile as reaction medium.
10'
to
2. Dehydration to acrylonitrile: vapor phase. Phosphoric acid as catalyst, flash-heated to 600' to 700' C., 1-2 seconds residence time and quench to 50' C. (Continued on next page) VOL. 5 5
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RAW MATERIALS FOR POLYAMIDES (NYLONS) For Nylon-66, adipic acid, and hexamethylene diamine (HMDA). For Nylon-6, caprolactam. Both adipic acid and caprolactam require cyclohexanone a s intermediate. Cyclohexanone and Cyclohexanol PROCESS
90.
Cyclohexanol by hydrogenation of phenol-e.q., Pd catalyst, liquid phase, 150' C., SO p.s.i.; or vaporphase on supported nickel catall-st. Conversion to cyclohexanone by dehydrogenation. I n vapor phase over supported zinc-iron catalyst or in liquid-phase on Raney nickel catalyst. PROCESS
90a.
Direct conversion of phenol to cyclohexanone. Avoids cyclohexanol formation almost completely. Typical conditions: liquid phase, 57, Pd on charcoal in concentration of 1 part per 1000 parts phenol. Essentially atmospheric pressure; 120' to 128' C.;20 to 40 hours reaction time. Typical performance: at 627, conversion, no cyclohexanol in product; at 99.6y0 conversion, 1.3y0cyclohexanol in product. PROCESSES
91
AND
92.
PROCESS91. Noncatalytic: 35 atm.; 180' C., 10 minutes contact time; 7 to 87@per-pass conversion. Addition of some water (5% on hydrocarbon). Primary product: 3570 cyclohexanone, 657@ cyclohexanol. By-product formation estimated at 10 to lSyG. PROCESS 92. Catalytic (main commercial process), using oil-soluble cobalt salt; multistage operation. 155' to 160' C., 8-9 atm.; 1 2 to 157, per-pass convercyclohexanone about sion. Yield of cyclohexanol 70y0. Total products convertible to adipic acid in 80 to 857, of theory.
+
Creeling and beaming acetate yarn
derived cyclohexanone. Liquid phase. Catalyst: 257, Cu, 0.17, V; 60' to 80' C. Low nitric acid concentration at all points of reaction system. Two-stage operation, with increased temperature in second stage, raises yield. Typical yield, 90 to 937,. PROCESS 94. Air oxidation of crude cyclohexanolcyclohexanone. For best over-all yield, feed is produced by carrying out process 92 at low temperature (125' to 135' C . ) , Resulting cyclohexanone, -01 mixture, freed of cyclohexane, is oxidized in liquid phase. Acetates of manganese and copper serve as catalyst and acetic acid as solvent. 80' to 85' C.;several hours' reaction time. Indicated yield : about 76 weight on liquid feed.
Adiponitrile a s Intermediate for HMDA Cln
PROCESS
95.
a.
CHg=CH-CH==CH2 --+ Cl-CHz-CH=CH-CH
2'21
Adipic Acid (0)
Crude mixture of cyclohexanol and cyclohexanone -+ HOOC--(CHz)d C O O H PROCESS 93. Nitric acid oxidation of crude cyclohexanol-cyclohexanone, or, less commonly, phenol-
40
INDUSTRIAL A N D ENGINEERING CHEMISTRY
AUTHOR Peter W . Sherwood is a Chemical Engineer in W h i t e Plains, N . Y . T h i s is the fourth i n a series of six articles, based in part on lectures given by the author t o an industry symposium at the b'niwrsity of California in M a y 7962.
Noncatalytic. Vapor-phase. 65' to 75' C . ; Clz to C4Hs ratio, 1.1; 78 to 80% yield. Liquid-phase chlorination is also feasible.
Caprolactam
0 II
C H 2 -C H2-C
ClCH2-CH=CH-CKzCl-+
PROCESS
C H 2-CH=CH-CH&N CN Conversion to 1,4-dicyanobutene-2 by reaction of dichlorobutene-2 with HCN. Liquid phase. Noncatalytic or (preferred) catalytic, using cuprous chloride, HC1 (plus potassium chloride). Diluent is used-e.g. water; 80' C., eventually raised to 95' C. Yield, about 95y0,. Ha
C.
CHz--CH=CH-CHzCN
98.
I
CN
a. Formation of cyclohexanone oxime. React cyclohexanone with aqueous hydroxylamine sulfate. Slight (5y0) excess cyclohexanone; 20' C. Neutralize product by ammonia.
b. Beckmann rearrangement of oxime to caprolactam. Liquid phase. 32 parts 97.8y0 HzS04 and 20 parts cyclohexanone oxime; 140' C. Product quickly cooled to 75' C. Yield, 90 to 937' on oxime.
N-OH
0
2-CH2-CN
I
+
CN
HOOC-(CH2),-cOOH
75'
--+
+ 2NH3
4
NC-(CHz)*CN
Vapor phase. Boron phosphate catalyst in fixed bed operation. Reactor temperature: 360' C. at entrance, 310' C. at exit. NH3 to adipic acid feed ratio, 20 to 1. Typical yield, 85 to 90%.
In an alternative process, silico-phosphoric acid serves as catalyst. Alternative: adiponitrile from furfural. Has been employed commercially but seems to be on way out. New possibility, not yet commercial : electrolytic reduction of acrylonitrile : (H)
CNCHz-CH2-CH2-CHz-CN
Hexamethylene Diamine (HMDA) Ha
97.
99.
From Nitrocyclohexane
a. Production of nitrocyclohexane.
Adiponitrile from Adipic Acid and Ammonia
PROCESS
caprolactam
to
- Hv0
-+
(Beckmann rearr.)
HZto PROCESS
Liquid phase. About 2y0 Pd on charcoal; 150' C., 0.3-0.5 hr.-I; yield, 95 to 97%.
2CH2=CHCN
+
( H !
Vapor phase. Palladium on carrier (charcoal). dicyanobutene molar ratio, 1 0 ; 250' to 300' C.
96.
(acid)
NHzOH.HzS04
Hydrogenation to adiponitrile.
PROCESS
From Cyclohexanone
By-product: 2.8 to 3 pounds ammonium sulfate per pound caprolactam.
--+
CH2-CHz-CH
C H 2 - C Hz- C
-NH
HCN
b.
H 2-
Adiponitrile --+ H2N-(CH2)4-NHz HMDA
Liquid phase nitration of cyclohexane by nitric acid. Relatively early work (1950) calls for use of 35Y0 nitric acid a t 120' to 125' C. and 60 to 75 p.s.i.g.; 3-minute reaction time. Yield, 63y0 nitrocyclohexane, 35% adipic acid.
I n more recent (1957) related work, optimum conditions for nitration of isopropyl cyclohexane were found to be : 48% " 0 3 ; mole ratio hydrocarbon to " 0 3 , 1 :2.5; 80' to 85' C . ; 15-hour reaction time; 57y0 conversion. Yield of mononitroisopropyl cyclohexane, 78.8y0 on converted hydrocarbon. Other nitrating agents have also been proposed, particularly nitrous oxides.
b . Nitrocyclohexane to cyclohexanone oxime. By mild hydrogenation in liquid (aqueous) phase. Catalyst is palladium on acetylene black, promoted by about 10% lead oxide or carbonate. Catalyst concentration, about 1% on hydrocarbon. 140' C., 500 p.s.i.g. Conversion to oxime and yield, 75 to 797'. Other methods of hydrogenation included liquid phase reaction with C O in the presence of methanol, and liquid phase reaction with ethylene, yielding ethylene oxide as co-product. c. Cyclohexanone oxime to caprolactam. man rearrangement. See process 98b. PROCESS
Liquid phase. Supported cobalt catalyst (may be promoted by copper) in fixed bed arrangement. 100' to 135' C.; 10,000 p.s.i., 0.5 hr.-I Yield about 90% in single pass. Can be raised by recycle.
By Beck-
100.
(Continued on next page) VOL. 5 5
NO. 1
JANUARY
1963
41
J. A. CABLE
FOR VISCOUS FLUIDS To performnce data given f o r water,
appb correctionfactors, and derive performance of the pump when handling a more viscous liquid
to estimate how a centrifugal I pump ' oftenwill necessary alter in performance with a change in the t IS
'
viscosity of the fluid pumped. T h e estimation procedure is simple. Charts available from the Hydraulic Institute provide a rapid method, accurate enough for all but borderline cases. However, the correction factors are so often misapplied that it seems worthwhile to go through the correct procedure. When the properties of the fluid pumped are changed: -No density correction is required, if discharge pressure is measured in height of fluid pumped -Viscosity change affects pump performance and requires correction. A sketch of the chart from the Hydraulic Institute Standards, giving the corrections, appears on the right -Net positive suction head is affected by viscosity. A more viscous fluid requires a higher suction head -Both fluid density and fluid viscosity affect driver requirements The engineer must know how to apply the correction factors to derive value from them. It is important to rewgniee that these factors apply to the pump and not to the rating required. Once this is realized, the application of thecorrections fallsintoa workable pattern. The correction factors are applicable to any pump. They are based on its water performance and are given in terms of its point of maximum efficiency. If it were always possible to use a pump at the capacity a t which it gives maximum efficiency, all corrections would be alike. However, by nature of their application, centrifugal pumps are used over a fairly broad range. An example will show how to correct performance data for any point in this range.
F
z
CAPACIW IN 100 CPM VOL 5 5
NO. 1 J A N U A R Y 1 9 6 3
43
