Commercial Syntheses of Organic Petrochemicals.
Part 1
SOLVENTS AND PLASTICIZERS The market is huge: More than 160 dzferent solvents aye produced and over a half billion pounds of plasticizers are consumed annually PETER W. SHERWOOD Y
o set a framework for discussion, two definitions are
TWhat needed Is a Commercial Synthesis? :
0
About 150 chemical conversions account for some 90% of all organic petrochemical production.
This
series of six articles deals with the highlights of these commercial syntheses. It gives special emphasis to newer processes which have recently reached industrial maturity or which are on the verge of doing so.
Peter W . Sherwood is a Chemical Engineer in White Plains, N . Y . This is the first in a series of six articles based in part on lectures given by the author to an industry sympocium at the University of Calafornia in M a y 7962. AUTHOR
Here defined to cover those conversions which are either used commercially or which may be reported as being given serious consideration for commercial purposes. Also included are some of the presently noncommercial processes which, in the author’s judgment, deserve serious consideration for industrial use. Which Organic PerrochemicaL Are Induded? Figure 1 answers this question. Raw material for any patrochemical product is a petroleum fraction or natural gas. This feedstock may be converted directly to carbon black or to first-generation intermediates. Actually, carbon black is a complex substance which is neither clearly organic nor inorganic. Its pocition as a petrochemical is debatable and it is considered outside the scopr of this discussion. All other petrochemical end products are obtained via a first generation of petrochemicals-Le., purified hydrocarbons, synthesis gas, and hydrogen (Figure 1). This group includes those materials which are formed in economically recoverable quantity during petroleum refining. However, quantities recovered from this source are not always sufficient to satisfy market demand, and therefore some are produced in large volumes as main products. This is especially true for ethylene, butylenes, and benzene. This definition of first generation petrochemicals has exceptions, the most notable of which are : -Naphthalene and acetylene. Normally included, although refinery streams do not contain either of these compounds in economically recoverable quantities. -Ethylbenzene. Normally produced by alkylation of benzene, it is considered a second generation derivative, altliough substantial quantities are recovered directly from C, aromatic reformate by superfractionation. Although this first generation of purified hydrocarbons is clearly organic petrochemicals, their manufacture is not within the scope of these articles. During the last few years a number of publications have appeared on their production technology, including several by the author. Processes involved may be summarized as shown in Table I. (Continued on next page) VOL. 5 4
NO. 9 S E P T E M B E R 1 9 6 2 35
Table I .
Methods Used in Producing First Generation Petrochemicals
Comjbound
Method
Lower paraffinic hydrocarbons
Direct recovery”
Ethylene
Recovery from refinery gas. Thermal pyrolysis of hydrocarbon stocks, including use of tubular furnaces, steam cracking, pebble heaters, fluidized sand reactors, and lead bath reactors
Propylene
Recovery from refinery gas or ethylene pyrolysis gas
Butenes
Direct recovery from refinery streams. Catalytic dehydrogenation of corresponding butane-e.g., over potassium-promoted chromium oxide on activated alumina
Isopentenes
Direct recovery from CSfraction
Benzene
Direct recovery from B-T-X fraction Hydrodealkylation of toluene
Toluene
Direct recovery
Xylenes
Direct recovery
Naphthalene
Hydrodealkylation of methylnaphthalenes
Cyclohexane
Direct recovery Hydrogenation of benzene
Acetylene
High temperature pyrolysis of light paraffins. Heat is supplied by partial oxidation, injection of combustion gases, electric discharge methods, or regenerative heat transfer
Synthesis gas
Steam reforming of hydrocarbons. Combined steam reforming and partial oxidation (both thermal and semicatalytic processes are practiced)
Hydrogen
Direct recovery from refinery gas. Catalytic reaction of steam and carbon monoxide in synthesis gas (water gas conversion). Direct (semicatalytic) decomposition of hydrocarbons to hydrogen and carbon
a T h e term “direct recovery” does not imply ease of recovery and purification. I t implies only that no interceding permanent chemical conversions are involved.
36
INDUSTRIAL AND E N G I N E E R I N G CHEMISTRY
Second Generation Derivatives. Among these, Figure 1 shows a group of inorganics. Actually, only two major products are involved here-ammonia and sulfur which are not discussed in these articles. The group of products which will be discussed is the organic petrochemicals shown in color in Figure 1. Further, only the major products are discussed which, in general, means those having an annual domestic production of more than 10 million pounds. A striking aspect of this group of chemicals is that they have a small number of primary outlets. I t is true that many petrochemicals have a host of miscellaneous usese.g., glycerol has as many as 2500 to 3000 end applications. However, as here defined, “primary” refers to markets which represent the largest single outlet. For any one product, such a market may account for 30 to 90% of total demand. These primary markets provide the framework for this report which covers processes employed to manufacture organic hydrocarbon derivatives for the industry’s main market, namely : -Solvents and plasticizers -Intermediates for plastics and resins -Intermediates for synthetic fibers -Intermediates for synthetic rubbers -Miscellaneous products, notably intermediates for surfactants and automotive chemicals Each chemical is discussed within the framework which constitutes its largest single market. Thus, phthalic anhydride is classed here as an intermediate for alkyd and polyester resins, its largest market area. However, about 40% of production is consumed for plasticizers. In addition, there are a number of other significant outlets. Operating conditions reported are either typical or optimum. Details of process technology, economics, or commercial implications are not discussed. These aspects must be left to individual evaluation.
SOLVENTS AND PLASTICIZERS Solvents have been defined as substances which can bring solids to a fluid state (Durrans, T. H., “Solvents” Van Nostrand, A-ew York, 1950). Plasticizers are substances of low volatility which increase flexibility, workability, or distensibility of polymers. Within these broad definitions, required product characteristics limit severely the number of widely consumed solvents and plasticizers. For solvents: the most important characteristics are solvent power, volatility, stability, toxicity, inflammability, and color. For plasticizers, efficiency, low temperature flexibility, speed of fusion, electrical and viscosity properties, volatility, water and chemical resistance, extent of migration, and toxicitj- are mostim portant. An estimated 60y0 of total solvent requirements is accounted for by three industries-surface coating,
Figure 1. The scope of this sm’es of articles is indicatsd in blue
textiles, and adhesives. Other markets are widespread and range from cleaning--e.g., metals, or textile products-to syntheses and purification processes in the chemical and pharmaceutical industry to extraction in refining petroleum and recovery of edible oils, pyrethrins, and vitamins from natural sources. A number of other uses are also included-for example, denaturants, and oreflotation agents. In 1953,about 160 solvents (Dwlittle, A. K., “Technology of Solvents and Plasticizers” Wiley, New York, 1954) were offered commercially and since then the list has certainly grown. However, only a few of these compounds make up the bulk of the market. Other than hydrocarbon solvents and turpentine, the following categories are predominant: CrCl alcohols C A Sacetates Carbon disulfide Chlorinated methanes and ethanes Chlorinated ethylenes
In almost all instances, esters are employed for plasticizing purposes. The principal group is phthalates followed by phosphates, adipates, sebacates, stearates, azeleates, oleates, plus various others of minor sales volume. The following organic petrochemicals find significant markets in the plasticizers field: Acids and Anhydrides
Alcoholr and Phenols
Phthalic Adipic
Phenol and cresols n-Butanol Ethyl alcohol CBand Clo oxo alcohols 2-Ethyl hexyl alcohol
SYNTHESIS FOR SOLVENTS, PLASTICIZERS AND THEIR INTERMEDIATES
ALCOHOLS For plasticizers, the market is more clearly defined. Consumption figures in 1961 have been estimated as follows :
US$
Poly(viny1 chloride) and copolymers Other vinyl resins Cellulosic resins Synthetic rubber Gasoline additives Functional fluids Synthetic lubricants Other Total
Millionr of POd
437 33 43 23 27 10 19 25
_ .
617
Ethyl, isopropyl, and sa- and fcrt-butyl alcohols Principal methods in their manufacture involve hydration of olefins (processes 1 and 2). Substitution occurs in the order, tertiary > secondary, > primary. Although the principal use of ethyl alcohol is in making acetaldehyde, it is included here for convenience of discussion. PROCESS 1. Liquid phase hydration:
RCH=CH,
+ HSO,
RCH-CHz
I
(plus dialkyl sulfate)
OSOxH
HI0 ----t R
--*
CH4Hx
I
+ HSOI
OH VOL 5 4
NO. 9
SEPTEMBER 1962
37
Higher strength acid is required to react with the lower olefins : Acid Str~ngtli,5; Absorbing 1)ilute
OIejn
96-99 75-80 70-75 60-65
CZH4 C3H6 n-C4H8 Isobutene
-
50 30-40 25 25
Operating conditions vary widely. For the absorption stage, typical conditions are 60" to 70" C. and 225 to 350 p.s.i.g; in the hydrolysis stage, up to atmospheric boiling point. Typical yields on olefin: 86 to 88YG ethyl alcohol, and 93 to 9570 isopropyl alcohol. PROCESS
2.
Vapor phase hydration :
R C H = CHz
+ HzO
--+
RCH-CH3
of hydrocarbon (for heptenes) ; typical system prcssurc, 1500 to 4000 p.s.i; exothermic reaction (50,000 to 62,500 B.t.u. per pound-mole olefin converted). Product must be freed of cobalt which is recoverable. The higher (>C5) oxo aldehydes cannot he purified suitably Xvithout excessive product loss. The crude mixture is therefore hydrogenated to the corresponding alcohols which constitute the bulk of oxo product sales (Sherwood, P. I$'., Rejning Engr, (February--March 1958). n-Butanol, 2-Ethyl Hexanol, Methyl Isobutyl Carbinol
By Condensation. Notably n-butanol from acetaldchyde, 2-ethyl hexanol from n-butraldehyde, and inethyl isobutyl carbinol from acetone. PROCESS 5 . For example,
I
OH
I
OH
Catalysts: supported phosphoric acid or promoted tungsten oxide on silica gel. Steam concentration in reactor feed is just below saturation point. PROCESS 2 COMPARED WITH PROCESS 1. Advantages: no sulfuric acid fortification required : single step operation : simpler reaction equipment ; less corrosive conditions. Disadvantages: high purity (97y0 +) olefin needed; low conversion per pass (about 4-57, for ethylene) and therefore dilute reactor product: high pressure and temperature (1000 p.s.i. and 300" C. for hydration of ethylene). NONCOMMERCIAL. Liquid phase hydration of olefins over cation-exchange resins. For isobutylene: 100' C. and 150 p.s.i.g.; 20 to 50yoconversion. For propylene: 160' to 170" C . where available resins are unstable. Selectivity reported high. Amyl Alcohols PROCESS
3.
Practiced for amyl alcohols only. TaOH
CaHlz
+ Clz + CBHllCl + HC1 -+
CbHiiOH
C3 to Cia Alcohols
Oxo process, practiced in U. S. for Cq, PROCESS 4. C5, C8, ( 2 1 0 , and C13 alcohols:
0
//
R = CHz
--
/
R-CH-CH3 0
// R-CH2-CHZ-C-H
and Hz
-+
R-CH-CH:,
and
CHzOH R C H 2-C H 2- CHzOH Liquid phase reaction. Catalyst is cobalt hydrocarbonyl, usually formed in situ from oil-soluble cobalt salt. For higher hydrocarbon conversion, 160" to 175" C. and for propylene, 140" to 160" C. CO to H Z ratio, 1 : 1 ; gas rate, 6500 standardc ubic feet per barrel 38
-+
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
Hz0
CH3--CH-CHz-CHO
-----)
nz
CH3-CH=CH-CHO
+
CH 3CH zC H zC2H 2 0 1 - I Reaction conditions: aldolization, aqueous caustic, 5 to 25" C . ; dehydration, 30 to 35% sodium acid pliosphate solution, 95" C . ; hydrogenation, copper on pumice, vapor phase, 200" C. (nickel catalyst, liquid phase for butyraldehyde). Straight-Chain Primary Alcohols.
See process 127 in a
subsequent article
KETONES Acetone PROCESS 6. Vapor-phase, endothermic, equilibriuiii reaction. Catalyst is ZnO on pumice (alteriiari\.e possibilities: Cu, Xi); 380' C . ; presence of H:! rcquired ; atmospheric pressure; 80 to 98y0 conversion per pass. By-product, some diisopropyl ether and propylene. PROCESS 7. Liquid-phase dehydrogenation of isopropanol; 150" C., pressure. Raney nickel catalyst suspended in high-boiling solvent. IVear-quantitati\e acetone yield. Frequent catalyst regeneration is neccssary. Reaction for processes 6 and 7 :
OH I CH3-CH-CH3
C-H
CO+HP
2 CH3-CHO
- H?
0
il
CH3-C---C€13
PROCESS 8. Co-product in reduction of acrolein -+ allyl alcohol (see process 32b). PROCESS 9. Co-product in oxidation of isopropanol .+ Hz02 (see process 138). PROCESS 10. From cuinene : co-product or phenol (see process 45). PROCESS 11. From CZ-CA oxidation : co-product of acetaldehyde, etc. (see process 76). Other possibilities: liquid-phase oxidation of propylene (see process 77), apparently not yet cornmercial. HBr-directed vapor-phase oxidation of propane, not commercial.
Methyl Ethyl Ketone
Analogous to dehydrogenation of isopropanol (processes 6 and 7). Liquid-phase oxidation of n-butenes (see process 77). By-product of acetic acid in process 80. Methyl Isobutyl Ketone
Acrtone + diacetone alcohol (aqueous phase, catalyzed by lime; 2o-23yO conversion per pass) ; - H20
-+
mesityl oxide (100 "-1 20 " C. catalyzed by weak acid)
H P
methyl isobutyl ketone. (see process 5 for -analogous conversion of acetaldehyde).
---t
s
ESTERS Ethyl and amyl acetate, and octyl and decyl phthalates, adipates, and sebacates. PROCESS 15. Alcohol acid ester HzO. Reaction carried out near boiling point of system. Different methods for removing excess water, depending on boiling point of ester. Yield, 98y0+. (Groggins, P., "Unit Processes in Organic Synthesis," McGrawHill, New York, 1958). PROCESS 16. Ethyl acetate is also produced from acetaldehyde (Tschitschenko synthesis).
sa +
+
0
2CHaCHO
/I
-+
CH~C-OCH~CHS
CHLORINATED HYDROCARBONS Chlorinated Methanes
+
PROCESS 17. C H 4 Clz [CHdC1,CHzC12,CHC13, CC14] n HC1 Vapor-phase reaction ; noncatalytic. Typical conditions: mixed chlorine and methane fed at 280'300 " C . Product distribution depends on chlorinemethane ratio as shown below, whereby it is critical to avoid local overconcentrations of chlorine at mixing point. This is a highly exothermic reaction (43,000 B.t.u./lb.mole chlorine reacted) and average reactor temperature depends on chlorine-methane ratio. Typical ranges have been reported as 370°-410" C. and 500"-520" C. ---f
Reaction a: iron catalyst, 30" C. Product CC14 is separated from SzClz by distillation. Reaction b: 60" C.; product is distilled and air-blown for removal of unconverted SZC12. PROCESS 19. C H 4 4 HC1 2 0 z + CC1, 4Hz0. Along with other chlorinated methanes ; HC1 consumer. Vapor phase : Catalyst is probably supported copper chloride; one set of pilot plant data indicates formation of 4070 CC14, 4070 CHC13, 15Oj, CHzC12, 5yo CH3C1, but considerable variation should be possible at different conditions.
+
+
+
+
PROCESS 20. CHs-CH=CHz 7 c l p -+ CClzCClz CC14 6 HC1. High-temperature chlorination of C 3 hydrocarbons is illustrated by thermal conversion of propane at 400"-500" C. Mole ratio Clz to C3H8, 12.3. Product composition: 44 weight yo cc14, 46% CzC14, 10% higher chlorinated hydrocarbons. PROCESS 21. CHz=CHz f 4 clz + cc1,=cc12 4 HC1. Chlorine reacts with ethylene in water-jacketed burner. Flame temperature : 600"-650" C., followed by residual reaction at 480" C. ; reported yield in single passage, 70 to 85%. PROCESSES 22-24. Dehydrochlorination of acetylenederived pentachloroethane ; thermal decomposition of carbon tetrachloride ; and high temperature chlorinolysis of propane. Other chlorinated solvents of interest: trichloroethylene and trichloroethanes.
+
+
+
MISCELLANEOUS SOLVENTS Nitroparaffins
lo0
PROCESS 25. By thermal vapor-phase nitration of propane a t 400" to 425" C. Typical product: 2570 1-nitropropane, 4Oy0 2-nitropropane, 10% nitroethane, and 25y0 nitromethane. Can be shifted toward more extensive formation of lower nitroparaffins by adding oxygen, or toward more extensive formation of nitropropanes by adding chlorine.
s 280
s
=' 60 4 S4O
'
+ + g, 6.CS2 + S2Clz+ 6 S + CC1,
Tetra c hIo ro et hy Iene (Per c Ie ne)
Catalyst: aluminum ethoxide promoted by A1C13 and ZnO; 0" C.; liquid phase; 97y0yield.
+
Furthermore, chlorine in feed gas must be diluted to prevent explosion. This objective and temperature control may be achieved by recycling a large portion of the reactor effluent. Furthermore, explosion danger can be reduced by use of a high-velocity jet at the mix point. Formation of higher chlorinated products can be boosted by further chlorination of lighter products. This may be accomplished by recycle as above, or by a second chlorination step in which nitrogen serves as diluent . Economics are significantly influenced by ability to use or sell by-product hydrochloric acid. PROCESS 18 (for carbon tetrachloride only). a. cs2 3 c1z-t SZClZ cc14
6
am
Ethers 0.4
Or8
1.2 1.6 2.0 2.4 2.8 VOLUMETRIC RATIO, Clz:CH4
3.2
3.6
4.0
(Diethyl, diisopropy1)-mainly sponding alcohols. VOL. 5 4
NO. 9
by-product of corre-
SEPTEMBER 1962
39
