I/EC A
COSTS
W O R K B O O K
F E A T U R E
by Walter L. Hardy, Foster D. Snell, Inc.
Phenol Manufacture Comparative costs are given for three commercial processes, and a fourth is discussed
A
RÉCENT column in this series
[IND.
E N G . C H E M . 4 8 , N o . 9, 45 A
(1956)] discussed t h e economics of phenolformaldehyde resin manufacture. Sales of phenolic resins in the U n i t e d States m a y exceed 600,000,000 pounds per year by 1960. As at least 0.6 pound of phenol is consumed per p o u n d of phenolic resin, sales of phenol for this purpose alone will exceed 360,000,000 pounds per year. F r o m 60 to 7 0 % of t h e total production of phenol is consumed by the phenolic resin industry. T h e r e m a i n d e r is used in a wide variety of applications, including the m a n u facture of aspirin, 2-4-D, wood preservatives, insecticides, a n d medicinals. A b o u t 500,000,000 p o u n d s per year are sold by 17 manufacturers located largely in t h e northeastern region of the United States, with scattered plants in California and Texas. Less t h a n 1 0 % of all phenol produced is obtained from coal t a r a n d petroleum. T h e greater portion is synthesized from benzene by a n y one of several processes. Installed phenol manufacturers' capacity in the United States appears a d e q u a t e to satisfy anticipated d e m a n d for at least 5 years. I n m a n y other parts of the world, however, t h e lack of domestically produced phenol is a
serious h a n d i c a p to the development of a local plastics industry as well as the manufacture of essential insecticides and pharmaceuticals. Four commercial processes for the synthesis of phenol are in use. 1. Sulfonation System. Benzene is sulfonated with oleum a n d m a d e to react with sodium sulfite to form sodium benzenesulfonate. Sulfur dioxide gas is evolved and sodium sulfate formed by reaction of sodium sulfite with free excess sulfuric acid. T h e sodium benzenesulfonate is freed from sodium sulfate, neutralized, a n d m a d e to react with molten caustic soda a t a b o u t 300° C . to form sodium phenate a n d sodium sulfite. After separation of sodium sulfite, the sodium phenate is treated with sulfur dioxide a n d water to form phenol a n d sodium sulfite. T h e phenol is isolated a n d purified. Reactions a r e : C,H 6 + H 2 S0 4 — C 6 H 5 S0 3 H + H 2 0 2C 6 H 6 S0 3 H + Na 2 S0 3 — aCeHeSOsNa + S 0 2 + H 2 0 (Na 2 S0 3 + excess H 2 S0 4 -* Na 2 S0 4 -I- S 0 2 + HjO) C 6 H 6 S0 3 Na + 2NaOH — C,H 6 ONa + Na 2 S0 3 + H 2 0 2C«H6ONa + S 0 2 + H 2 0 -~ 2C 6 H 5 OH + Na2SOa
2.
Chlorobenzene
CAUSTIC
SODA
Process.
HYDROLYSIS.
Ben-
zene is chlorinated by conventional chlorination procedures to produce monochlorobenzene. Chlorobenzene, a certain a m o u n t of recycled diphenyl ether, and caustic soda solution react at about 360° C. a n d 4000 p.s.i. pressure. After discharge from the pressure vessel, diphenyl ether and other alkali-insoluble material is extracted with chlorobenzene. T h e extracted mass is acidified with hydrochloric acid to neutralize excess caustic a n d liberate phenol. T h e acidified mass separates into aqueous and phenol layers. Phenol is distilled from the phenol layer a n d separated from t h e aqueous layer by steaming out. Reactions a r e : 2C6H6 + 2C12 — 2C6H5C1 + 2HC1 C«H5C1 + 2NaOH - * C e H s ONa + NaCl + H 2 0 C«H6ONa + C6H6C1 — CeH5—O—CeH5 + NaCl CeH6ONa + HC1 — CeH^OH + NaCl 3.
Chlorobenzene
Process.
REGENERATIVE V A P O R PHASE.
Ben-
zene vapor is heated to 300° C. a n d mixed with air a t 150° C. a n d hydroVOL. 4 9 , N O . 5
·
MAY 1957
47 A
I/EC
COSTS
Table I.
«
A Workbook Feature
Estimated Production Cost Comparison f o r Synthetic Phenol
(Based on data of Messing and Kearny and 1957 costs. pounds per year)
Sulfonation $4,200,000
Plant investment
Plant capacity 15 million Chlorobenzene Vapor phase (diphenyl oxide Caustic hydrolysis recycled) $4,900,000 $4,350,000
Cost per Pound 0.77 0.77 Labor, average $2.20/hr. 0.91 1.48 1.55 utilities 1.31 1.63 1.45 Maintenance 2.24 1.62 1.45 Taxes, insurance, and fixed charges 1.40 0.38 0.39 Overhead and supervision 0.45 3.25 2.90 Depreciation at 10%/yr. 2.80 Production cost 9.11 9.13 8.51 Estimated net material cost (1957 prices 4.33° less by-product credits) 4.92" 4.52" Total production cost 14.03 13.65 12.84 Current sales price. Phenol, USP, synthetic, drums, c.l. and l.c.l., wks , freight allowed, 0.20-0.22/lb. ° Net material costs vary with chemical prices and marketing conditions for by-products. These figures are based on estimated material balances in absence of practical data.
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gen chloride before passing over a catalyst in a first stage converter. T h e reacted mixture consists of ben zene, chlorobenzene, some dichlorobenzenes, excess hydrochloric acid, oxygen, and nitrogen. Pure chloro benzene is produced by partial con densation a n d distillation. Chlorobenzene vapor a n d steam are passed over a catalyst at about 500° C. in a second stage converter. T h e gases leaving this unit consist of chlorobenzene, phenol, hydrochloric acid, a n d water. Hydrochloric acid is removed from this stream by passage through a water scrubbing tower. Tower overheads consist of water-chlorobenzene azeotrope a n d phenol. Bottoms a r e dilute hydro chloric acid a n d some phenol, which is recovered by benzene extraction. T h e overhead stream is separated by a second scrubbing with hot water, which results in isolation of phenol as a water solution. Phenol is re covered by extraction with benzene, followed by distillation. Reactions are: G,H6 + HC1 + Ο
Free Bulletin
C 6 H 6 C1 + H2O
Edwin L. Wiegand Company 7511 Thomas Boulevard · Pittsburgh 8, Pa C-2II6-A
^ catalyst C 6 H 5 O H + HC1
4. Cumene Process. Benzene is alkylated with propylene to produce cumene. T h e cumene is oxidized with air to form cumene hydroper oxide. Phenol a n d acetone a r e o b tained by treatment of cumene by
Circle No. 48 A on Readers' Service Card, page 115 A
48 A
>catalyst C 6 H 5 C1 + H 2 0
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INDUSTRIAL AND ENGINEERING CHEMISTRY
hydroperoxide with sulfuric acid under conditions of heat a n d pres sure. This is the newest of the cur rently used phenol processes a n d t h e least documented in the literature. Its economic success is very much dependent upon available markets for t h e by-product acetone. Reac tions a r e : C6H6CH(CH3)2 — C0H5C(CH3)2OOH Cumene air Cumene hydro peroxide CeH6C(CH3)2OOH
>• H 2 SO, CiHjOH + (CH3)2CO Acetone
Processes 1, 2, and 3 are covered in some detail by P. H . Groggins ( " U n i t Processes in O r g a n i c Synthesis," 4th éd., p p . 693-701, McGraw-Hill, N e w York). A tabular comparison of plant investment a n d operating costs for t h e three processes b y Messing a n d K e a r n y , which originally a p p e a r e d in Chemical Industries in 1948, is reprinted on page 700. T a b l e I gives essentially t h e same data, scaled u p to 1957 costs. Process selection will frequently be tied into other activities of t h e investing firm. A sulfonator having captive sulfuric acid production a n d know-how in sulfonation techniques will select the older process. O n e of the chlorobenzene processes m a y be preferred by a manufacturer with a n excess of by-product chlorine or hydrochloric acid, both of which m a terials are notoriously difficult to dispose of.
