Commercial Sythneses of Organic Petrochemicals
PETER W. SHERWOOD
RAW MATERIALS F O R P L A S T I C S A N D RESINS Vinyls, po&yrene,PolyoleJins, and polyurethanes are the fastest-growing mgjor groups of plastics and resins, in turn the fastest-growing of all
chloride---e.g., on alumina. Fluid-bed and movingbed catalyst systems have been proposed. I n one fluidbed version (U. s. Patent 2,644,846), the feed contains oxygen, HCl, and C2H4 in the mole ratio 1 to 3.3 to 1.65. Operating a t 285" C. and atmospheric pressure, over-all EDC yield is 9O.?y0based on ethylene.
Vinyl Chloride
industrial chemicals
PROCESS
52. CH2Cl-CH&l+
CHFCHCl
+ HC1
Conversion of ethylene dichloride (Kosterhon, K. J., Erdol u. Kohle, June 1958, p. 391). his article continues the highlight discussion of
Tmonomers for plastics and resins, including surface coatings, which appeared in the October issue of I&EC. RAW MATERIALS FOR V I N Y L RESINS There are two competitive routes, based on ethylene and acetylene, respectively. At present, the acetylenebased synthesis accounts for about 6OY0 of production. Ethylene-based synthesis involves production of ethylene dichloride as an intermediate. Its manufacture involves two practicable routes. Ethylene Dichloride PROCESS
50.
CH-CH2
c11
+CH&l-CH&l
As described by Vlugter (Chim. Ind. 67, No. 2, p. 8?), the direct chlorination of ethylene is carried out in the presence of FeC13 catalyst suspended in liquid ethylene dichloride at 75 p.s.i.g. Reactants enter the converter coils at 30" and leave at 46" C. Thc feed should be a narrow C 2fraction, freed of acetylene. O n a oncethrough basis, 98y0 conversion is obtained to yield a chlorination product containing 96y0 of 1,2-dichloroethane. PROCESS
51.
CH2=CH2
+ 2HC1 + O2
Purified ethylene dichloride is pyrolized in a pipestill at about 500" C. and 7 to 15 p.s.i.g. Per-pass conversion is limited to Toy0. Local overheating must be avoided to minimize breakdown reactions. Reactor product is quenched to 70" to 80" C. by injection of liquid ethylene dichloride. I n related work, yield in excess of 90% has been reported [Chim. Ind. (Paris) 30,269-71 ; 33,61341. Acetylene PROCESS 53.
Acetylene
+ HC1 -+
vinyl chloride
Vapor phase. Typical conditions : catalyst, 10% mercuric chloride on charcoal. Reaction temperature, from initial 100' to eventual 180" C. as catalyst ages. Slight excess (10%) HCl in feed. Slightly superatmospheric pressure. Conversion about 25y0 per pass. Reactor yield, 96y0 based on acetylene. Purification losses reduce yield to 92 to 94oj,. Key to choice of process 52 us. 53 rests in HC1 value us. hydrocarbon cost [Sherwood, P. W., PetrolChem. Eng., pp. 39-46 (October 1961)]. Acetylene-based plants have lower capital investment than ethylene-based facilities, assuming that acetylene is purchased. (Continued on next page)
-+
CHpCl--CH&l
+ 2H20
Oxychlorination of ethylene by HCl and air is carried out in the vapor phase. Catalyst is supported cuprous
Peter W. Sherwood is a Chemical Engineer in White Plains, N . Y. This is the third in a series of six articles based in part on lectures given by the author t o an industry symposium at the University of California in M a y 1962. AUTHOR
VOL. 5 4
NO. 1 2
DECEMBER 1962
29
Air Reduction Co.'s vinyl acetate production facilities Vinyl Acetate
Vinylidene Chloride
0 'I
CH3COOH
+ CHeCH
PROCESS
1,
+
54. Liquid phase. 60" to 80" C. Catalyst is acid-promoted mercuric acetate; 75 to 80% yield. No longer commercial, mainly because of diKicult mzrcury recovery, cumbersome character of the operation, and lower yield than in process 54a.
54a. Vapor phase.
Catalyst is zinc acetate on activated charcoal. Reactor temperature : 170" to 200" C. Exothermic reaction. Acetylene must be specially purified for removal of H2S and phosphorus compounds. Conversion: 60 to 70YG per pass. Yield 97 to 99y0based on acetic acid; 92 to 95y0on acetylene. PROCESS 55. CHaCHO $- (CH&O)2O ---f
0 I1
/I
CH,CH(OC-- CHH) z
0
+ CHaC-OCH=CH:!
Formation of ethylidene diacetate. Best performance reported for reaction of 11 parts paraldehyde with 20 parts acetic anhydride at 110" to 120" C. in presence of sulfuric acid catalyst. Other proposed catalysts include BF3. a.
b . Decomposition of EDA is carried out in liquid phase. Acetic anhydride is the solvent and benzene sulfonic acid is catalyst. This process is practiced at only one plant. For a discussion of techniques, see Sherwood, P. W., W o r l d Petrol., p. 52 (August 1957). New possibilities are offered by the availability of a low-cost new route to acetaldehyde from ethylene (process 77). 30
NaOH
HC1-
CH2=CClL
+
+ NaCl
1,1,2-TrichIoroethane by chlorination of 1,2-dichloroethane or of vinyl chloride [Sherwood, P. W.,Petrol. Process, p. 1810 (December 1952)]. Dehl-drochlorination by lime or caustic used in slight excess (2 to 10%). Liquid phase conversion. In continuous operation at 98"-99" C . ; yield is approximately 90%. Performance with caustic is somewhat better than with lime. In dehydrochlorination by caustic, by-product HC1 is, of course, destroyed. Attempts to effect the conversion by catalytic pyrolysis-e.g., over alumina at 350" C.have led to extensiv: formation of undesired symdichloroethvlene.
--t
Ethylidene diacerate
CHaCOOH
CIS
CHPCI--CH2C1 --3 CHzCl - CHClz
CHaCO---CH=CH*
PROCESS
PROCESS
56.
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
RAW MATERIALS FOR POLYSTYRENES Ethyl Benzene
57. Direct recovery from CB reformate by superfractionation. Carried out in conjunction with xylenes production. O n this basis, EB output by process 57 is limited to 500 million pounds per )-ear (20% of 1962 requirements). PROCESS
PROCESSES
58 and 59.
