Propanols ULLMANN

� 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Article No : a22_173

Propanols

ANTHONY J. PAPA, Union Carbide Chemicals and Plastics Company, Inc.,

South Charleston, WV 25303, United States

1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . 243

2. Physical Properties . . . . . . . . . . . . . . . . . . . 243

3. Chemical Properties . . . . . . . . . . . . . . . . . . 243

4. Production . . . . . . . . . . . . . . . . . . . . . . . . . . 246

4.1. Production of 1-Propanol. . . . . . . . . . . . . . . 246

4.2. Production of 2-Propanol. . . . . . . . . . . . . . . 247

5. Uses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249

6. Specifications . . . . . . . . . . . . . . . . . . . . . . . . 250

7. Economic Aspects . . . . . . . . . . . . . . . . . . . . 250

8. Storage and Transportation . . . . . . . . . . . . . 251

9. Toxicology and Occupational Health . . . . . . 251

References . . . . . . . . . . . . . . . . . . . . . . . . . . 252

1. Introduction

The propanols C3H7OH,Mr 60.10, comprise twoisomers, 1-propanol [71-23-8] and 2-propanol[67-63-0], also called isopropyl alcohol, of whichthe latter is industrially the more important. Bothare clear, colorless, flammable liquids with aslight odor resembling that of ethanol. Theyoccur in nature in crude fusel oils and as fermen-tation and decomposition products of variousvegetables.

The propanols are used mainly as solvents forcoatings; in antifreeze compositions and house-hold and personal products; and as chemicalintermediates for the production of esters,amines, and other organic derivatives. 2-Propa-nol is produced by hydration of propene, while 1-propanol is manufactured by the hydrogenationof propanal, in turn derived from hydroformyla-tion of ethylene. Annual U.S. production of 1-propanol and 2-propanol is estimated in 1988 tohave been 98 � 103 t and 630 � 103 t, respec-tively [1].

2. Physical Properties

The propanols are completely miscible withwater and readily soluble in a variety of commonorganic solvents (e.g., ethers, esters, acids, ke-tones, and other alcohols). Physical properties ofanhydrous 1- and 2-propanol as well as a

91 vol % azeotropic mixture of 2-propanol withwater are provided in Table 1. Physical proper-ties of the propanols reflect the position of thehydroxyl group. Associative properties in solu-tion cause the propanols to form azeotropes witha variety of compounds, including aromatics,esters, amines, and ketones. Examples of binaryazeotropes of 1- and 2-propanol are given inTable 2.

Freezing points of 1-propanol – water and2-propanol – water mixtures are plotted inFigure 1. These plots show that the advantagesof a substantially lower freezing point for pure 1-propanol relative to 2-propanol are lost in aque-ous solutions of the two alcohols.

3. Chemical Properties

The differences in reactivity between 1-propanoland 2-propanol reflect the influence of the natureof the hydrocarbon radicals in primary and sec-ondary alcohols, respectively. Characteristic re-actions of the hydroxyl group include dehydroge-nation, oxidation, esterification, ammination, anddehydration. The chemical properties of greatestcommercial importance are discussed below.

Dehydrogenation (Oxidation). 2-Propanolcan be readily dehydrogenated to acetone (!Acetone), although the process is being replacedby the cumene – phenol process and by direct

DOI: 10.1002/14356007.a22_173.pub2

oxidation of propene (as developed by Wacker –Hoechst).

Pure dehydrogenation of 2-propanol can beaccomplished in the liquid or gas phase with azinc – copper catalyst at 300 – 500 �C and300 kPa to give ca. 90 % selectivity to acetoneand 98 % 2-propanol conversion. Selectivity canbe increased to 96.8 % by employing a Cu –Zn – Cr catalyst [18]. Dehydrogenation is endo-thermic and requires high temperatures.

Dehydrogenation can also be conducted oxi-datively in the presence of silver or coppercatalysts at 400 – 600 �C [19].

Table 1. Physical properties of propanols [2–15]

1-Propanol 2-Propanol (anhydrous) 2-Propanol (91 vol % in water)

Mr 60.096 60.096 60.096

Critical temperature, �C 263.63 235.15

Critical pressure, kPa 5175 4762

fp, �C �126.1 �88.5 �50

bp, �C

101.325 kPa 97.15 82.26 80.40

39.997 kPa 74.479 60.66

2.0 kPa 20.04

1.3333 kPa 2.49

Vapor pressure at 20 �C, kPa 4.4136 4.5

Refractive index at 25 �C 1.3837 1.3752 1.3769

Liquid density at 20 �C, kg/m3 803.78 785.39

Liquid viscosity at 20 �C, mPa � s (cP) 2.21 2.37 2.1 (25 �C)

Surface tension at 20 �C, mN/m (dyn/cm) 23.7 21.32 21.40

Flash point (closed cup), �C 15 11.85 18.3

Flash point (Tag open cup), �C 27 17.2 21.7

Autoignition temperature, �C 370.85 398.85

Lower flammability limit in air, vol % 2.1 2.5

Upper flammability limit in air, vol % 13.5 12

Solubility in water at 20 �C, wt % miscible miscible miscible

Table 2. Binary azeotropic mixtures with 1-propanol and 2-propanol [2], [16]

Component 1-Propanol 2-Propanol

bp at 101.3 kPa, �C Alcohol, wt % bp at 101.3 kPa, �C Alcohol, wt %

Water 88.1 71.8 80.4 87.8

Ethyl acetate nonazeotrope 75.9 25

Cyclohexane 74.3 20 69.4 32

2-Butanone nonazeotrope 77.9 32

3-Pentanone 96.0 63 nonazeotrope

Benzene 77.12 16.9 71.9 33.3

Propyl formate 80.6 9.8 75.5 � 36

Hexane 65.65 4 62.7 23

Dioxane 95.3 55 nonazeotrope

Propyl ether 85.8 32.2 78.2 52

Figure 1. Freezing points of 1- and 2-propanol – watermixtures [2], [17]

244 Propanols Vol. 30

Patents describe a 2-propanol dehydrogena-tion process for the production of a mixture ofacetone, methyl isobutyl ketone, and higherketones [20], [21]. For example, vapor-phasedehydrogenation of an azeotropic mixture of 2-propanol and water over a copper-based catalystat 220 �C yields a product mixture containingacetone (52.4 %), 2-propanol (11.4 %), methylisobutyl ketone (21.6 %), diisobutyl ketone(6.5 %), and 4-methyl-2-pentanol (2.2 %) [20].

Partial oxidation of 1-propanol can beachieved with air in the presence of catalysts toform propanal and propionic acid [79-09-4] [22].Strong oxidizing agents such as nitric acid reactexothermically with both alcohols, giving a com-plex mixture of products.

Esterification. The propanols can be con-verted into propyl esters by reaction with organicand inorganic acids using the conventional meth-od for esterification in the presence of mineral-acid catalysts. The commercially important n-propyl acetate [109-60-4] and isopropyl acetate[108-21-4] are produced by direct esterificationof the corresponding alcohols with acetic acid inthe presence of sulfuric acid, p-toluenesulfonicacid, methanesulfonic acid [23], [24], or a strongcationic resin [25] as catalyst. A higher-pressure(170 – 310 kPa) continuous process at 110 –160 �C with continuous removal of product esterand water has been described, which should offerhigher production rates [26]. 1-Propanol can alsoundergo ester interchange with methyl or ethylacetate in the presence of a strong cationic ex-change resin to give n-propyl acetate [27].

Reaction of 2-propanol with CS2 in alkalinesolution produces xanthate esters. The methodsimply involves refluxing the alcohol with alkali-metal hydroxide in trichlorofluoromethane sol-vent while adding CS2 [28], [29]. Sodium iso-propyl xanthate, (CH3)2CHOCSSNa [140-93-2],is a herbicide used for weed control.

Reaction of 2-propanol with phosphorus ha-lides proceeds readily to form phosphite esters.Generally, reaction is conducted in a solventcontaining an acid scavenger, but a new solvent-less spray method could have merit [30].

Titanium(IV) isopropoxide [546-68-9] andtitanium(IV) propoxide [3087-37-4] are madeby reaction of the corresponding alcohol withTiCl4 in refluxing heptane with removal of HClcoproduct [31]. These esters are especially useful

as polymerization and transesterificationcatalysts.

The propanols also form esters upon reactionwith active metals. For example, aluminum iso-propoxide [555-31-7] and aluminum propoxidecan be prepared by contacting aluminum withalcohol vapor [32], [33]. These materials find useas catalysts, in the preparation of aluminumsoaps, as dispersants in paint formulations, andas starting materials for ceramics.

Reaction with Ammonia and Amines.Both 1- and 2-propanol can be reductively ami-nated by reaction with ammonia or lower aminesto give propylated amine derivatives. The reac-tions are normally conducted at 1.0 – 10.0 MPaand 190 –250 �C using catalysts consisting ofnickel, aluminum, cobalt, molybdenum, and/orchromium. Alcohol conversions are usually ca.90 % [34]. For example, H2 – NH3 – 2-propa-nol (12: 8: 1 mole ratio) was passed over anickel-based catalyst at 110 �C in the vaporphase at a liquid hourly space velocity (LHSV)of 1 h�1 to give a mixture of 93.5 % isopropylamine [75-31-0] and 6.3 % diisopropyl amine[108-18-9] with a 2-propanol conversion of93 % [35].

Etherification and Dehydration. 1-Propa-nol and 2-propanol can be reacted with one, two,or three moles of ethylene oxide, propyleneoxide, or both to give a family of glycol ethershaving broad utility as solvents. Reaction isgenerally catalyzed by alkali hydroxide.

Diisopropyl ether [108-20-3] can be preparedby liquid-phase dehydration of 2-propanol at130 – 190 �C and 1.96 – 7.85 MPa over acidiccatalysts containing aluminum [36], [37]. Dehy-dration of 1-propanol to di-n-propylether [111-43-3] can be accomplished with a cation-exchangeable layered-clay catalyst containingtitanium or zirconium at 180 �C [38].

The dehydration of 1- or 2-propanol to givepropene has no practical value. Nevertheless,dehydration is most facile with 2-propanol in thepresence of mineral acid catalysts at room tem-perature or higher, conditions that should other-wise be avoided in most instances.

Others. The propanols give hemiacetaladducts readily on addition to aldehydes. Theproducts can in turn be converted to acetals with a

Vol. 30 Propanols 245

second mole of alcohol under dehydration con-ditions in the presence of an acidic catalyst [39].Acetals find use as intermediates in the prepara-tion of pharmaceuticals.

2-Propanol can be condensed with such aro-matic compounds as toluene and phenol to pro-duce isopropoxylated derivatives.

4. Production

1-Propanol and 2-propanol are produced by verydifferent processes starting from ethylene andpropene, respectively.

4.1. Production of 1-Propanol

Propanal, obtained by hydroformylation of eth-ylene (! Propanal), is the primary commercialsource of 1-propanol. In a second step the pro-panal is hydrogenated to 1-propanol.

Hydroformylation of Ethylene. UnionCarbide Chemicals and Plastics Company, Inc.[40], and Hoechst Celanese practice the two-stepoxo process based on rhodium-substituted phos-phine-catalyzed low-pressure hydroformylationtechnology (! Oxo Synthesis, Section 3.1.),while Eastman Kodak Company uses a higher-pressure cobalt-based process for production ofthe intermediate propanal [1]. Typical oxo con-ditions employed in the low-pressure rhodium-catalyzed oxo process are 90 – 130 �C, <2.8MPa total pressure, with CO at <380 kPa, H2

at <1.4 MPa, and <500 ppm rhodium [41].Conditions of the cobalt oxo process are 110 –180 �C, 20 – 30 MPa (200 – 300 atm), 1: 1 to1: 2 H2: CO ratios, and 0.1 – 1.0 wt % cobaltbased on ethylene [42]. The crude propanal isremoved by vapor stripping with excess synthe-sis gas, and the rhodium – triphenylphosphinecatalyst is recycled [40]. Traces of CO are re-moved in a stripping column from the crude,condensed propanal before hydrogenation toprevent poisoning of the hydrogenation catalyst

in the second step. The higher selectivity andmilder conditions of the rhodium-catalyzed pro-cess provide crude 1-propanol for hydrogenationcontaining fewer impurities, such as higher al-dol-condensation products and aldehyde trimers(Tischenko esters).

Hydrogenation of Propanal is convention-ally carried out as a heterogeneous process ineither the vapor or liquid phase over a variety ofmetal catalysts. Heterogeneous vapor-phase pro-cesses are effective at ca. 110 – 150 �C, and0.14 –1.0 MPa at a 20: 1 mole ratio of hydrogento propanal [43–45]. Reductions are accom-plished in excess hydrogen, and the heat ofreaction is removed by circulating the vaporthrough external heat exchangers or by coolingthe reactor internally [46].

Hydrogen efficiencies are >90 %, with alde-hyde conversions as high as 99.9 % and alcoholyields >99 %. The commonly used commercialhydrogenation catalysts include combinationsof copper, zinc, nickel, and chromium com-pounds. Major impurities at vapor-phase pro-cess temperatures are dipropyl ether, ethane,and propyl propionate. In addition to reducedzinc oxide and copper oxide catalysts, selectivi-ty enhancers such as alkali and transition metalscan be added to significantly reduce the forma-tion of esters (by Tischenko reaction of thestarting aldehyde) and ethers [44]. Addition of1 – 10 % water to the reactor feed also sup-presses ether formation [47].

The propyl propionate byproduct formed inthe catalytic hydrogenation can be separated andhydrogenolyzed in the presence of reducedCuO – ZnO catalyst at 75 – 300 �C and9.8 kPa –9.8 MPa to give 1-propanol as the ma-jor product [48].

Liquid-phase heterogeneous processes areconducted at higher pressures. For example,hydrogenation at 95 – 120 �C and 3.5 MPa ofhydrogen gives 1-propanol with >99.9 % purity.Nickel- and copper-based catalysts containingmolybdenum, manganese, and sodium promotersare preferred [49]. The catalysts are usuallysupported on alumina.

Other Processes have been described forthe preparation of 1-propanol; for example, intwo steps by isomerization and hydrogenation ofpropylene oxide [50]; from synthesis gas [51],


[53]; from methanol [67-56-1] and synthesis gas[53]; and by the Guerbet reaction [54].

4.2. Production of 2-Propanol

There are two major commercial processes forthe production of 2-propanol: indirect and directhydration of propene. Smaller quantities areproduced by hydrogenation of acetone.

Indirect Hydration involves two steps. Inthe first, a mixture of mono- and diisopropylsulfate esters is formed from reaction of propenewith sulfuric acid. The reaction is exothermic,yielding about 50 kJ/mol.

3 CH3CH ¼ CH2þ2 H2SO4�ðCH3Þ2CHOSO3H

þ½ðCH3Þ2CHO�2SO2

The sulfate esters are then hydrolyzed toproduct 2-propanol in a second step.

A major byproduct in the indirect process isdiisopropyl ether, which is formed from reactionof the sulfate esters with product 2-propanol.

Other impurities include hydrocarbons, char,polymeric residues (oils), propanal, acetone, andodorous sulfur-containing compounds. Isopropylsulfate esters are particularly unstable, decom-posing at temperatures as low as 50 – 100 �C[55]. Mono- and disulfate esters can be thermallydesulfonated to give SO2, SO3, and a mixture ofpropene and acetone.

The indirect hydration process can be con-ducted with either strong or weak acid. A sche-matic for an indirect weak-acid hydration isshown in Figure 2.

Propene-containing feed gas (propene content� 60 %) is reacted with ca. 60 % H2SO4 in aseries of absorption columns (a) at 75 – 85 �Cand 0.59 – 1.0 MPa. Production rates and effi-ciencies are linked to a balance of initial sulfuricacid concentration, temperature, total pressure,and propene partial pressure. High absorber tem-peratures favor ether formation. The propene issparged into the lower portion of the absorberswhile the H2SO4 is fed to the top to establish acountercurrent flow pattern. The ‘‘sulfates’’product stream is taken from the bottom of theabsorbers and fed to vacuum strippers (b) whereit is hydrolyzed with steam and the resulting 2-propanol is flashed as overhead product. Product-free acid bottoms (recycle acid) from the strip-pers are concentrated to about 60 % and recycledto the absorbers. The required reconcentration ofacid in this process is less costly than in thestrong-acid process, where reconcentration to>90 % is required. Vaporized stripper productis neutralized by scrubbing with caustic (c), anduncondensed vapors (vent gas) are combinedwith the blow-off gas from the scrubbers andrecycled to the reaction.

Crude 2-propanol is fed to a multicolumnrefining system where a constant-boiling mixture(CBM) of 2-propanol is obtained. Byproductdiisopropyl ether is recovered as a lights streamfrom the first column in the refining train andrecycled to the reaction absorbers, where it ishydrolyzed back to product, thus preventingether accumulation in the process:

Figure 2. 2-Propanol production by indirect, weak-acidprocess a) Absorbers; b) Strippers; c) Caustic scrubber;d) Scrubber; e) Liquifier


Heavy-end concentrated oils are also collect-ed and discarded.

The main problem encountered in purificationof 2-propanol is its separation from water. En-richment of the CBM to >99 % or absolute 2-propanol is accomplished by use of an azeotrop-ing agent, which forms a ternary constant-boilingmixture. Diisopropyl ether and cyclohexane arecommon entraining agents for 2-propanol enrich-ment [56]. Undesirable intense odors inevitablyarise from sulfur-containing compounds, and thiscan cause difficulties in such commercial uses ascosmetic products, spray products, and medicinalformulations. Odor is generally removed by con-tacting the 2-propanol with ion-exchange resins,activated carbon, activated alumina, or metals(e.g., copper, nickel) [57–59].

The weak-acid indirect hydration process suf-fers from high corrosion rates and disposal pro-blems with water, acid, caustic, and off-gaswastes. A major advantage is the ability to uselow-purity propene feed. Advances in wasteminimization include replacement of the lead-lined absorbers with corrosion-resistant ceramicsand synthetics.

Indirect hydration is still the primary processconducted in the United States by Exxon, ShellOil, and Union Carbide Chemicals and Plastics[60], while Lyondell Petrochemical produces asmaller amount by hydrogenation of acetone[60]. There are indications that a few companiesin Europe and Japan may also be employing thisolder technology [19].

In the strong-acid process reaction is con-ducted with a high sulfuric acid concentration(> 90 wt %), while the pressure and temperatureare low compared to the weak-acid process (1.0 –1.2 MPa and 20 – 30 �C, respectively). Hydro-lysis is accomplished in a separate second stage.Both processes offer 2-propanol selectivities of>90 wt %.

It is reported that for 1 t of 2-propanol pro-duced, 0.8 t propene, 0.35 t H2SO4, 3.5 t steam,and 40 – 50 kW � h of electricity are required inan optimized process [61]. It is believed that thestrong acid process is not employed as a majorcommercial source of 2-propanol in the worldtoday because of the requirement for high-puritypropene feedstock and waste-disposal problems.

Direct Hydration. The direct hydration ofpropene has been in commercial use since 1951.

High pressures and low temperatures over anacidic fixed-bed catalyst characterize this pro-cess, causing the exothermic equilibrium reac-tion to be displaced to the right. Three versions ofthe direct hydration process are practiced com-mercially today.

1. Low-temperature (130 – 160 �C), high-pres-sure (8.0 – 10.0 MPa) vapor – liquid phasehydration over a sulfonated polystyrene ion-exchange resin catalyst was pioneered byDeutsche Texaco [62–69]. The feed, consist-ing of propene gas and liquid water, is fed in asupercritical state to the top of a fixed-bedreactor and allowed to trickle downward.Feed containing about 92 % propene can beused, resulting in propene conversions ofabout 75 % per pass. About 5 % diisopropylether and about 1.5 % oxygenates (alcohols)of propene oligomers (hexenes) are formed asbyproducts. This technique requires high-pressure equipment, and could suffer fromproblems of short catalyst life. This technolo-gy and plants based on it are licensed outsideEurope [70].

2. High-temperature, high-pressure (270 –300 �C, 20 MPa) vapor – liquid hydration ofpropene over a reduced tungsten oxide cata-lyst was developed by Tokuyama Soda[71–73]. This process utilizes a molar ratioof water to propene of about 2.5: 1. Water ispresent in both the gas and liquid phases,which increases conversion (because equilib-rium is shifted farther to the right due to thesolubility of 2-propanol in water). This tech-nology requires high-pressure equipment, butfeatures high propene conversions of 60 –70 % per pass and 2-propanol selectivities of98 – 99 % based on converted propene. Thecatalyst must be durable (stable in the pres-ence of water). The process has low gas-recycle requirements, so propene of only95 % purity can be used.

3. ICI developed technology for vapor-phasehydration of propene involving medium to


high pressures. This process uses a WO3 –SiO2 catalyst at 250 �C and 25 MPa [19],[74], and it gives yields of about 95 %. InGermany, VEBA developed a similar hydra-tion process based on a phosphoric acid cata-lyst supported on SiO2 and operated at 180 –260 �C and 2.5 – 6.5 MPa [75–77]. Typical-ly, these processes require high propene recy-cle (less than 10 % conversion per pass) andutility costs are probably high. High-puritypropene (� 99 %) is required. The phosphoricacid process is commercial in Germany, theNetherlands,the United Kingdom,and Japan.

Hydrogenation of Acetone. Hydrogena-tion can be conducted in the liquid phase overa fixed catalyst bed of a Raney-nickel catalyst togive 99.9 % selectivity and 99.9 % conversion ofthe acetone [78], [79]. Hydrogenation over cop-per oxide – chromium oxide at 120 �C and196 kPa gives lower selectivities and conver-sions (98 % and 94 %, respectively) [80]. It isnot essential that the acetone be pure. This pro-cess is particularly advantageous where excessacetone is available as a byproduct from anotherprocess (e.g., the cumene – phenol process).

Other Processes. Patents have been issueddescribing the manufacture of 2-propanol fromcellulosic materials (e.g., cotton, corn, and wood)[81], [82].

5. Uses

Uses of the two propanols are dictated by theirsolvent properties, their high water miscibility,and by their potential for introducing the propylgroup into chemical intermediates.

1-Propanol. In 1988 over 75 % of the 1-propanol in the United States was employed insolvent applications, either directly or in the formof acetate ester or glycol ether derivatives [1]:

Solvent uses 24 900 t

1-Propyl acetate 19 500 t

n-Propylamines 11 300 t

Glycol ethers 5 400 t

Others 2 300 t

Total 63 400 t

As a solvent, 1-propanol is used principally inprinting inks, paint, cosmetics, pesticides, andinsecticides [83].

The EC used about 100 000 t of 1-propanol in1988 [84]. In Germany, BASF converts most ofits propanal into 1-propanol for printing inks,cosmetics, solvents, and intermediates for pro-pylamines used in pharmaceuticals and pesti-cides [1]. In Japan, 1000 – 2000 t of 1-propanolwas consumed in 1988 for printing inks andpaints, all of which was imported [1].

1-Propanol is used commercially to produceglycol ethers. These are characterized by dualfunctionality, which imparts high solvency,chemical stability, and water compatibility. Gly-col ethers such as ethylene glycol monopropylether (from 1-propanol and 1 mol of ethyleneoxide), diethylene glycol monopropyl ether(from 1-propanol and 2 mol of ethylene oxide),propylene glycol monopropyl ether (from 1-propanol and 1 mol of propylene oxide) anddipropylene glycol monopropyl ether (from 1-propanol and 2 mol of propylene oxide) aremarketed by Union Carbide Chemicals and Plas-tics [85] and Eastman Chemical Products [86].

n-Propyl propionate [106-36-5] is a new sol-vent available from Union Carbide Chemicalsand Plastics and developed for use in automotiverefinishing, appliance coatings, and high-solidscoating systems [85]. n-Propyl propionate istouted as a replacement for the isomeric n-butylacetate in coatings, where improved odor char-acteristics are desirable.

2-Propanol. 2-Propanol is used primarily asa solvent in inks and surfactants [70]. Otherapplications include its role as an antisepticalcohol, as a reaction solvent for cellulose car-boxymethyl ether [9000-11-7] (CMC), in theproduction of cosmetic base materials and pesti-cide carriers, as a source of material for organicsynthesis, for washing of a flux used in solderingelectrical circuits, and for removal of water fromgasoline tanks in cars [70]. Table 3 shows ap-proximate consumption data for 2-propanol inboth 1986 and 1990 in the United States.

The coatings use of 2-propanol has reached aplateau due to a shift toward waterborne andhigh-solids coatings. Its use as an electronicssolvent is growing, but the market is small[89]. 2-Propanol is a particularly versatilesolvent for producing high-performance (e.g.,


gelation-resistant and polyamide-containing)printing inks [90]. In the pharmaceutical indus-try, 2-propanol enjoys favor as a processingsolvent during manufacture of drugs.

Use of 2-propanol for the production of ace-tone has decreased dramatically. There remainsonly one acetone plant in the United States (com-pared to four in 1985), and the market is stilloversupplied [91]. However, since the cumeneroute to phenol provides equal amounts of phenoland acetone (! Acetone), a strong demand foracetone relative to phenol can increase the needfor acetone production from 2-propanol [88].

2-Propanol is widely used as a chemical in-termediate, for example in reductive amination toproduce monoisopropyl amine (for herbicide andpesticide production), and as a source of isopro-pyl acetate. Some diisopropyl amine is utilized asan intermediate in the synthesis of diisopropy-lammonium nitrate, a corrosion inhibitor [91].

Nippon Petrochemical has begun marketingpure 2-propanol (99.99 %) for use in high-puritylarge-scale integration (LSI) and silicon wafersfor the electronics industry [92]. Another attrac-

tive new application is as an octane enhancer,carburetor anti-icing additive, and methanol co-solvent in motor gasoline blends [93].

2-Propanol is useful in extraction processes;thus, aqueous solutions are utilized in liquid –liquid extractions of fatty acids from vegetableoil at temperatures as low as �2 �C [94].

6. Specifications

ASTM standard specifications for propanol aregiven in Table 4.

Product purity is generally determined bycapillary gas chromatography. Typical puritiesspecified by manufactures for 1- and 2-propanolare 99.7 – 99.9 wt % and 99.8 wt %, respective-ly. Because of its use in packaging, 1-propanolmay sometimes be required to pass a specific odortest conducted for consumers by an odor panel.Occasionally, alkalinity and propanal content areincluded in the requirements for 1-propanol.

7. Economic Aspects

Manufacture of 2-propanol in major industrialcountries is summarized in Table 5.

Since 2-propanol is no longer the primaryfeedstock for acetone growth stagnated in theUnited States until recently. In 1989 productionunits there were currently operating at about60 – 80 % of capacity [96]. United States outputof 2-propanol was 649�103 t in 1989 [97], and669� 103 t by the year 1999. Demand fell by4.4 %/a in 1977 – 1986 to 578�103 t in 1986 dueto the decrease in use for acetone production [99]In 2003, the production capacity rose to

Table 3. 2-Propanol consumption in the United States (103 t) [87],

[88]

Year

1986 1990

Coating solvents 8.2 9.1

Processing solvents 6.4 6.8

Household/personal 6.4 5.4

Pharmaceuticals 6.4 5.4

Acetone 4.5 3.6

Miscellaneous solvent

applications and

chemical intermediates

4.5 3.2

Exports 9.1 11.8

Total 45.5 45.0

Table 4. ASTM Specifications for propanols

1-Propanol 2-Propanol

Specification

method

ASTM standard D 3622–90 D 770–90

d2020 0.804 – 0.807 0.785 – 0.7870

d2525 0.801 – 0.804 0.782 – 0.784 D 268 or D 4052

Color, Pt-Co (ASTM) 10 10 D 1209

Distillation range, 101.3 kPa distill within a 2 �C

range that includes

97.2 �C

distill within a 1.5 �C

range that includes 82.3 �C

D 1078

Nonvolatile matter, mg/100 mL 5 5 D 1353

Water, max, wt % 0.1 0.2 D 1364 or D 1476

Acidity, acetic acid, max, wt % 0.003 0.002 D 1613


870� 103 t. The capacity for 2-propanol in West-ern Europe is roughly comparable to that in theUnited States. It was estimated based on U.S.import/export data that Western Europe in 1991operated at or near full 2-propanol capacity.

2-Propanol production in Japan has been risingby about 5 %/a. Demand in Japan reached130 � 103 t in 1989 [100], with steady growth(3 – 4 %) in paints and solvents and rapid growth(15 – 20 %) in detergent applications [101]. In1990 there was a shortage in Japan [100]. Pro-duction capacity in 2000 was 180� 103 t.

Worldwide in 2003, 22 production units for 2-propanol had a total capacity of 2350� 103 t/a.12 of these units use the direct hydration processwith a capacity accounting for 47.1% of theworld total.

8. Storage and Transportation

The propanols are flammable liquids, and shouldbe considered dangerous fire risks when exposedto heat or flame. Explosive limits for propanols inair are 2 – 12 %. Some important data for the safehandling of propanols are given in Table 6.

Care should be taken during heating (e.g.,distillation) of old samples of 2-propanol. Sev-

eral violent explosions have been reported duringattempts to concentrate old samples to smallvolume, suggesting that this compound shouldbe classed as peroxidizable (via autoxidation ofthe tertiary hydrogen) [103].

Baked phenolic-lined steel or stainless steeltanks are recommended for storage and ship-ping of the propanols in order to maintain highquality. Mild steel tanks are also adequateproviding a filtering system is installed to re-move rust [104]. Storage and transport underdry nitrogen is also recommended to protectagainst moisture pickup and to minimize flam-mability hazards. Aluminum is not recom-mended. The flash points of the propanols arelow enough so that the compounds can be storedunderground under a nitrogen atmosphere.Pipes and pumps can be constructed from thesame metals as the storage facility. Centrifugalpumps with explosion-proof electric motors aresuitable [104].

9. Toxicology and OccupationalHealth

The propanols are considered to have generallylow toxicity in humans [102]. Ingestion of

Table 5. 1-propanol and 2-propanol manufacture in major producing countries (103 t)

Country Capacities of 2-propanol Production of 2-propanol

2000 2003 1995 1997 1999

United States 650 870 646 670 669

Japan 180 470a 132 133 149

Western Europe 760 846 587 490 510

a Japan and Asian Countries.

Table 6. Safety data and transport regulations for propanols [102]


Flash point (open cup), �C 15.0 11.7

Flammability limits in air, vol % 2.0 – 12.0 2.0 – 12.0

Autoignition temperature, �C 371.11 398.89

Vapor pressure at 20 �C, kPa 1.9854 4.4053

Percent in saturated air, 25 �C 2.7 5.8

Density in saturated air,

(air ¼ 1), 25 �C 1.028 1.06

Heat of combustion, MJ/kg �33.60 �33.35

U.N. No. 1274 1219

RID/ADR Class 3, number 3 b Class 3, number 3 b

IMDG Code Class 3.2 Class 3.2

CFR 49 172.101 flammable liquid 172.101 flammable liquid


excessive dosages of 2-propanol by alcoholicsand suicidals has been reported to cause poison-ing due to depression of the CNS and respiratoryirritation. Repeated or prolonged contact withpropanols may cause drying of the skin. Thepropanols display an exposure warning becausethey can cause mild to severe irritation to theeyes, nose, and throat. However, adverse effectsare rare in light of widespread use by the generalpublic and considerable industrial exposure[102], [105].

Animal studies reveal irritation to the eyes,low acute oral toxicity, and low irritation to theskin, as shown by the data in Table 7.

The mean exposure limits for 1- and 2-pro-panol in air at the workplace by ACGIH (TLV)and OSHA (PEL) are 200 ppm and 400 ppm,respectively. The MAK value for 2-propanol is400 ppm. Odor threshold data are provided inTable 8.

The propanols are registered in the ToxicSubstance Control Act (TSCA) and the EuropeanInventory of Existing Commercial Substances(EINECS).

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LD50 rat (oral), mg/kg 1 870a 5 045b

LD50 rabbit

(intravenous), mg/kg

483a 1 184a

LCLo rat (inhalation),

ppm/4 h

4 000a 12 000a, ppm/8 h

Eye injury, rabbit 20 mg/24 h, moderate 10 mg, moderate

4 mg, open severe

LD50 rabbit

(cutaneous), mg/kg

5 040a 12 800a

aNo description of toxic effects.bBehavioral (altered sleep time).

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Absolute odor

threshold a,

ppm

50 % Odor

recognitionb,

ppm

100 % Odor

recognitionb,

ppm

1-Propanol <0.03 0.08 0.13

2-Propanol

(anhyd.)

3.20 7.50 28.2

aThis is the concentration at which 50 % of an odor panel observed

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Further Reading

G. P. Chiusoli, P. M. Maitlis (eds.): Metal-Catalysis in

Industrial Organic Processes, Royal Society of Chemis-

try, Cambridge, UK 2006.

E. Klabunovskii, G. V. Smith, A. Zsigmond: Heterogeneous

EnantioselectiveHydrogenation,Springer,Dordrecht2006.

W. L. Luyben, I.-L. Chien:Design andControl of Distillation

Systems for Separating Azeotropes, Wiley, Hoboken, NJ

2010.

S. D. Minteer (ed.): Alcoholic Fuels, CRC Taylor & Francis,

Boca Raton, FL 2006.

J. D. Unruh, D. Pearson: n-Propyl Alcohol, ‘‘Kirk Othmer

Encyclopedia of Chemical Technology’’, 5th edition,

John Wiley & Sons, Hoboken, NJ, online DOI:

10.1002/0471238961.1618151621141821.a01.


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