RAW MATERIALS FOR SYNTHETIC RUBBER


approximately 1525 thousand long tons, with the following breakdown: styrene-butadiene, 1170 long tons; neoprene, 120; butyl rubber,90; nitrile, 45; a...
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Commercial Syntheses of Organic Petrochemicals

P E T E R W. SHERWOOD

R A W MATERIALS FOR S Y N T H E T I C R UB B E R Butadiene, chloroprene, isoprene, and aniline n 1962, total U. S. consumption of new rubber (syn-

I thetic and natural) reached its all-time high of 1.69

million long tons. Although the outlook for 1963 is slightly less favorable, the long-term upward trend in rubber consumption is now at an average annual increase rate of approximately 4.3y0. Synthetics presently account for 73y0of new rubber consumption, and may reach 76% by 1965. Total U. S. production of synthetic rubbers in 1962 was approximately 1525 thousand long tons, with the following breakdown : styrene-butadiene, 1170 long tons ; neoprene, 120 ; butyl rubber, 90 ; nitrile, 45 ; and other, 100. Styrene-butadiene production may have passed its peak. Similarly, butyl rubber, neoprene, and nitrile rubbers have only modest growth prospects. Most future growth in synthetic rubber will come from the new classes, notably from ethylene-propylene rubber, as PROCESSES

106 TO 109. n-BUTENE

-H

1,1-Butadiene (CHz=CH-CH=CH*) From n-Butene

BUTADIENE (VAPOR PHASE, ESSENTIALLY ATMOSPHERIC PRESSURE)

Process

Catalyst

106

Fe2O3, promoted by CrzOa and K -X O "? Promoted magnesium-iron oxide Calcium-nickel phosphate Chromia-alumina

107 108 109

well as from synthetic polyisoprene and poly-cis-butadiene. A number of other synthetic rubbers show promise in the specialty classes, notably polyurethanes, chlorosulfonated polyethylenes, halogenated butyl rubbers, ABS terpolymers and, in time polypropylene oxide. The shift toward the newer types of synthetic rubber will mean a change in raw material requirements. However, most of the monomers used in making synthetic rubber have their primary markets elsewhere. The main exceptions are butadiene, chloroprene, and isoprene. This article therefore discusses the technology of manufacturing these monomers and reports on processes used in production of aniline which finds its largest outlet in the synthesis of rubber chemicals.

Temb., . . O C. 500-675 595-675 650

Steam Dilution

1O:l 20: 1 -1O:l

OperationRegeneratiun Cycle, Hr.

Per-Pass Conversion

Selectivity

26-28

75-78

24

25-35 45-55 27

80-85 90-94

>24

VOL

76 55

NO

3

1/2

M A R C H 1963

29

From Butane PROCESS 110. Single-stage conversion of butane. Vapor phase. Catalyst, 18-20% chromia on alumina. Steam dilution damages the catalyst; therefore operation is a t 3 p.s.i.a. to obtain low partial pressure. 600Oto 650° C.; 1 to 2 hr.-1 space velocity. Conversion, 11 % per pass; yield, 56%. Process is carried out adiabatically, using alundum particles in catalyst bed as heat sink. Regeneration by air, using deposited coke as fuel. Operation is cyclical. Total operating cycle in one version of pmcess, 21 minutes. Comments: Recent plant construction is based principally on single-stage conversion of butane as n-butenes are becoming too expensive because of growing demand for polymerization and alkylation purposes. Furthermore, some butadiene is recovered as by-product of ethylene manufacture.

CONSUMMlOII, THOUSANDS OF LOW6 TONS

l6

Chloromne PROCJSSS 111.

2CHsCH

--*

HCI

CH=C-CH=CHz+

CHz==C--CH=CHz

l

a a. Dimerization to monovinyl acetylene (MVA). Liquid phase. Reaction medium is aqueous solution of cuprous chloride and ammonium chloride. 65O to 75O C. 2 to 5 p.s.i.g. 10 to 15 seconds mntact time. Conversion, 20% per pass. Yield, about 60 to 65%.

b. Hydrochlorination of MVA. Liquid phase. Aqueous solution of cuprous chloride and HC1. 25' to 50' C. Conversion, 60 to 80%. Yield, 90 to 93% on MVA. Isopnne

112. Dehydrogenation of isopentene, analogous to production of butadiene. PROCESS 113. One-step dehydrogenation of isopentane, analogous to production of butadiene. Selectivity, 50 to 55 mole %. PROCESS

5

In these two processes, the key problem is in purification of the complex C6 mixture, notably the removal of 1,3pentadiene. PROCESS

114.

1

CH, a.

Dimerization 2CHa-CH=CHz

l

+ CHFG-CHZ-

CHzCHn

b.

Isomerization + CH8-&=CH-CH&H1 CHI

c.

Demethanization

-

I

CHFC-CH=CHZ

C CHI

[Chem. Eng. Prop. (May 1961), p. 43-49] Dimerization of Propylene. Liquid phase; tripropylaluminum as catalyst; 3000 p.s.i.g., 150' to 250' C., 60 to 95% conversion. About 95% efficiency (also, a vapor phase dimerization process has been mentioned.) b. Isomerization. Vapor phase operation over acidtype catalyst. 150' to 300" C. 99% efficiency. c. Pyrolysis. Vapor phase. HBr catalyst and steam dilution. 650' to 800' C.; residence time, 0.05 to 0.3 second. a.

1

I

Other posible routes, not now commercial: from isobutylene and formaldehyde (pilot plant) ; from acetone and acetylene; and from methyl ethyl ketone and formaldehyde.

in White Plains, N. Y. This is thefifth in a series of six articles, based in part on lectures given by the author to an industry Symposium at the University of California in May 1962.

AUTHOR Peter W. Sherwood is a Chic01 Engineu

Higher HzS04 concn. allows lower reduces oxidation reactions.

temperature ;

Commercial continuous process : Several (three) reactors in series; successive units operated at increasing temperature from 35' to 60' C. Thorough agitation and cooling. Despite some reduction in yield, continuous process operates at lower HzS04 content than optimum to reduce formation of waste sulfuric acid. Typical mixed acids composition in feed: 63y0 "03; 19y0 H2SO4; and l8y0 HzO. Some versions recirculate part of the spent acid after fortification with H N 0 3 , or nitrate with continuous overhead removal of H20 as benzene-water azeotrope. Aniline (as Intermediate for Rubber Chemicals)

Reduction of nitrobenzene

PROCESS 116. Hydrogenation in vapor phase. Fixedbed operation using reduced copper carbonate as catalyst. Slightly above atm. press. Temperature from 200' C. at reactor entrance to 350' C. at exit. Cooling by cold hydrogen feed or by heat exchange. Feed, 175 cubic feet H Z per pound nitrobenzene. Nitrobenzene recycle, about 2 to 3%. Aniline yield, 9870, Catalyst regeneration by burning with nitrogendiluted air, followed by hydrogen reduction.

Other catalyst, nickel sulfide on amorphous alumina ; 99% conversion.

Central control panel i n the [email protected] section of GoodrichGulf's polybutadiene plant

PROCESS 117. Hydrogenation in vapor phase. Fluidized-bed operation. Catalyst, copper on silica. Reaction conditions, 270' C.; 20 p.s.i.g.; 98 to conversion and yield. Catalyst regeneration by nitrogendiluted air at 250' C. followed by hydrogen reduction.

Other method of nitrobenzene reduction, reaction with iron filings. Used principally in small plants. Higher raw materials cost; yield, 95%. Nitrobenzene (as Intermediate for Aniline)

Ammonolysis of Chlorobenzene PROCESS

Continuous us. batch process. Batch only for small plants, represents minor portion of production. Nitrating agent is a mixture of nitric and sulfuric acids. Optimum Conditions, Batch 60 Temp. for best yield, ' C. Temp. range allowing yield within 2oj, of optimum, ' C. 35-70 84 Optimum H2S04 concn., wt. yo H2S04 concn. allowing yield within 2y0 of optimum 77-90 HzSOa/aromatic, wt. ratio 1.2 HNOs/aromatic, wt. ratio 1. o Reaction time, min. 40 Max. yield of mononitrobenzene, 7 0 98 [Kobe, K., others, IND.ENG.CHEM.49, 806 (1957)]

118.

0"'

f 2NH3 +

0"'

4- NHkCI

Liquid phase. Integration with chlorine and chlorobenzene required. Liquid phase; 6 to 8 moles ammonia (as 28y0 aqueous solution) per mole chlorobenzene. Catalyst, cuprous oxide in about 0.2 mole yo concentration. 200' to 210' C. 850 to 950 p.s.i. Aniline formation is improved by raising "3-chlorobenzene ratio and by lowering temperature. Estimated per-pass conversion, 50 to 6070. Over-all reported commercial yield, 96y0. By-products, phenol, some diphenylamine. Process 118 is of principal interest for plants integrated with manufacture of chlorine and chlorobenzene. Only one U. S. producer is known to use this method. VOL. 5 5

NO. 3 M A R C H 1 9 6 3

31