George A. Kraus1

1

Department of Chemistry and Institute

for Physical Research and Technology,

Iowa State University, Ames, IA, USA.

Review

Synthetic Methods for the Preparation of 1,3-

Propanediol

The market for 1,3-propanediol (PDO) is currently over 100 million pounds per year

and is growing rapidly. PDO is a component of industrial polyesters such as Dupont’s

Soronam and CDP Natureworksm or Shell Chemical’s CorterraTM. Markets for the polyester include thermoplastics, textiles, carpets, and upholstery. This paper reviews the

methods for the production of 1,3-propanediol by focusing on four feedstocks: glycerol, ethylene oxide, acrolein, and glucose.

Keywords: Fermentation; Hydroformylation; 1,3-Propanediol; Synthesis;

Received: April 1, 2008; revised: May 8, 2008; accepted: May 15, 2008

DOI: 10.1002/clen.200800084

1 Introduction

PDO is a common abbreviation for 1,3-propanediol. It is a chemical

intermediate used in resins, engine coolants [1], dry-set mortars [2],

water-based inks [3], but mostly in the manufacture of polytrimethylene terephthalate (PTT) [4]. PTT is marketed under trademarks such

as Dupont’s Soronam and CDP Natureworksm or Shell Chemical’s CorterraTM [5]. The structure of PTT is depicted in Fig. 1.

Polymers based on PDO and terephthalic acid exhibit a number of

advantages over polyesters based on ethylene glycol or 1,4-butanediol and terephthalic acid. The advantage stems in part from the difference in molecular structure, with the polymer derived from PDO

and terephthalic acid having a zig-zag or coil-like shape. This coillike shape translates into a polymer having superior stretching and

stretch-recovery characteristics. Additionally, the dyeing temperature is lower than for other commercially available polyesters and a

wider range of colors can be accommodated [4]. The PDO-based polyester is more resistant to stains and has better washfastness. The

PDO-based polyester also resists UV-degradation from sunlight better than other polyesters, making it attractive for sports apparel [4].

The polyester can be injection molded, pressure molded, and blow

molded [6]. Major markets for the Sorona polymers also include textiles, carpets, and upholstery. The huge polymer and terephthalate

plastics industry has an estimated sales volume of over six billion

dollars.

In recent years technological breakthroughs in the preparation of

1,3-propanediol have resulted in lower market prices, currently in

the $0.80 per pound range. This in turn has created an increasing

demand from textile, fabric and carpet manufacturers for PDObased polymers. Increasing PDO demand and expanding product

applications have led to an estimated 100 million pound annual

U.S. demand for 1,3-propanediol.

During the 1990's, Shell Chemical Company developed new catalyst technology for the conversion of ethylene oxide into PDO,

allowing the company to produce PDO at commercially viable pricing levels. This technology led to the Corterra brand of thermoplastic polyesters. Shell produces PDO at an 83,000 ton petroleum-based

manufacturing unit in Geismar, Louisiana. DuPont produces 10,000

tons per year of Sorona brand polymers, using PDO and terphthalate, at its Kinston, North Carolina facility. Dupont has also partnered with Tate & Lyle to produce PDO using corn-based fermentation at its Louden, Tennessee, facility. The fermentation route to

produce PDO from a glucose feedstock is estimated to be price competitive with the petrochemical methods.

The development of new, cost-competitive processes that utilize

renewable resources or by-products from the emerging biorefineries as feedstocks will aid rural revitalization. These processes

also represent important milestones toward the goal of reducing

the United States' dependence on foreign oil. Introduction of such

processes not only avoids the use of more petroleum, but also has

the potential to provide substantial energy savings, and reduce

greenhouse gas emissions.

2 Feedstocks

2.1 Glycerol

Glycerol is the major by-product of biodiesel production from soybean oil or animal fats. This three-carbon triol arises from the transesterification of triglycerides with methanol. For every gallon of biodiesel that is produced, one pound of glycerol is also produced. Most

Correspondence: Dr. G. A. Kraus, Department of Chemistry and Institute

for Physical Research and Technology, Iowa State University, Ames, IA

50011, USA.

E-mail: gakraus@iastate.edu

Abbreviations: PDO, 1,3-Propanediol; PTT, Polytrimethylene terephthalate

i 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.clean-journal.com

Figure 1. Structure of polytrimethylene terephthalate.

648 Clean 2008, 36 (8), 648 – 651
Clean 2008, 36 (8), 648 – 651 Preparation of 1,3-Propanediol 649

industry experts predict that the U.S. biodiesel industry will generate approximately 1.8 billion pounds of glycerol per year by the end

of 2009. This is in addition to approximately 560 million pounds of

glycerol produced annually from non-biodiesel sources [7]. While

there was enough need for glycerol in past years, the recent

increases in biodiesel production make it necessary to create new

applications for glycerol. Some reports indicate that at a $0.03 per

pound price level for glycerol, it may actually be useful to burn glycerol as a fuel. Inefficient use of this by-product weakens the overall

profitability of biodiesel plants in the biodiesel industry. The utilization of a by-product from the biodiesel industry to produce PDO

would add value, thereby benefiting the emerging biodiesel industry in the United States.

Early studies to produce PDO from glycerol involved the fermentation studies reported by Bock [8], Zeng [9, 10], and Wang [11]. These

early studies demonstrated that 1,3-propanediol could be generated

from glycerol using microorganisms such as Citrobacter freundii, Klebsiella pheumoniae, or Clostridium pasteurianum. The reaction is catalyzed by an enzyme that effects dehydration (a coenzyme B12

dependent glycerol dehydratase) followed by an enzyme that effects

reduction of the aldehyde (a 1,3-propanediol oxidoreductase).

Although concentrations of approximately 70 g/L of 1,3-propanediol have been reported, this concentration may be close to the

amount that inhibits growth of the microorganisms. In 2007, Zang

reported that 1,3-propanediol could be generated from glycerol

using a recombinant form of Escherichia coli that expressed glycerol

dehydratase, 1,3-propanediol oxidoreductase and the reactivating

factor for glycerol dehydratase [12]. In 2008, Papanikolaou and coworkers reported that crude glycerol directly from the biodiesel plant

could be used as a substrate with Clostridium butyricum [13]. They

showed that 47.1 g/L of propanediol could be produced from batch

anaerobic cultures.

Glycerol could also be used to make 1,3-propanediol (PDO) by

selective deoxygenation of the secondary alcohol using organometallic catalysts. This deoxygenation might occur via a dehydration/

hydrogenation pathway or by way of the reduction of a cationic

intermediate. Several strategies focusing on selective deoxygenation reactions have been reported. Drent and coworkers reported

one of the first strategies for the deoxygenation of glycerol using

organometallic catalysts [14]. They utilized heterogeneous palladium or platinum catalysts. Although they obtained acrolein as the

major product of the reaction, they also produced 1,3-propanediol

as a minor product.

Bullock has reported an innovative reduction of 1,2-diols to primary alcohols. An example is illustrated below in Fig. 2. While this

chemistry works well for the deoxygenation of certain 1,2-diols, preliminary experiments suggest that this technology does not work

well with glycerol [15].

The hydrogenation method of Schlaf is illustrated below in Fig. 3

for the reduction of 1,2-propanediol. He has reduced glycerol to generate both PDO and 1-propanol [16]. The boiling points of PDO and

tetramethylenesulfone, the solvent used in the Schlaf reduction,

are within thirty degrees of each other, making purification a challenge on a large scale. In the case of the glycerol reduction, the conversion was modest, but the reaction conditions had not yet been

optimized. The authors indicated that the reduction of glycerol can

be complicated by the acid-catalyzed formation of acetals derived

from 3-hydroxy propionaldehyde.

In 2008 Kurosaka and coworkers reported the reduction of glycerol using a heterogeneous organometallic catalyst composed of

platinum, tungsten trioxide on a zirconium dioxide support as

shown in Fig. 4 [17]. The reaction was conducted at 1708C and elevated pressures of hydrogen to provide a 24% yield of 1,3-propanediol with 12% 1,2-propanediol and 28% 1-propanol. The use of alumina or silica supports gave lower yields of 1.3-propanediol.

2.2 Ethylene Oxide

The hydroformylation of ethylene oxide to produce 1,3-propanediol

involves a two-stage process. This approach to the synthesis of PDO

has been studied extensively by scientists at Shell Chemical Company. In the first-stage, ethylene oxide reacts with carbon monoxide

and an organometallic catalyst to produce a hydroxy aldehyde. In

the second stage, the hydroxy aldehyde is reduced to a diol by hydrogenation. One of the successful organometallic catalysts is a homogeneous cobalt catalyst that effects ring opening of ethylene oxide

followed by insertion of carbon monoxide to form the three-carbon

hydroxy aldehyde. Heterogeneous organometallic catalysts can also

be employed. The aldehyde reduction stage can use a copper chromite catalyst with synthesis gas (hydrogen and carbon monoxide) as

the hydrogen source [18].

The two-stage process can be combined in a single reaction as

depicted in Fig. 5. A patent by scientists from Shell Chemical Company describes a homogeneous bimetallic catalyst formed from a

cobalt compound and a ruthenium compound in a 1:1 ratio with a

1,2-diphospholanoethane ligand. This catalyst reacts with ethylene

oxide in the presence of synthesis gas in methyl tert-butyl ether at

elevated temperatures and pressures to generate 1,3-propanediol in

approximately 90% yield in a single pot reaction [19].

Although this method employs a catalyst, the need for methyl

tert-butyl ether as a solvent and the petroleum-based starting material are counter to the principles of green chemistry. Recently,

Powell and Weider reported that the hydroformylation of ethylene

oxide could be successfully conducted in expanded solvents [20]. A

practical disadvantage is that PDO generated by the hydroformylation route contains almost ten times the level of impurities than

PDO derived from fermentation [5].

i 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.clean-journal.com

Figure 2. Selective reduction of 1,2-propanediol.

Figure 3. Reduction of 1,2-propanediol.

Figure 4. Reduction of glycerol.
650 G. A. Kraus Clean 2008, 36 (8), 648 – 651

2.3 Acrolein

Acrolein is a third major feedstock for the production of 1,3-propanediol. The acrolein approach has been rigorously evaluated by

researchers at Degussa and DuPont. The two-step process is shown

in Fig. 6 and involves the addition of water to acrolein to form 3-

hydroxy propionaldehyde followed by catalytic hydrogenation to

generate PDO. The addition of water to acrolein is generally mediated by acid catalysts. The selectivity of the addition is only around

70 to 80% when zeolites or ion exchange resins are used. Recently,

Tsunoda and Nomura reported that a silicoaluminophosphate

based molecular sieve afforded a selectivity of 96% when the reaction was conducted in aqueous solution at 608C [21].

Although acrolein is currently generated from the oxidation of

propylene, recent studies have demonstrated that glycerol can be

efficiently converted into acrolein using catalytic quantities of sulfuric acid in hot compressed water [22, 23]. The acrolein can be produced at 80% selectivity at 90% glycerol conversion [23].

The reduction of 3-hydroxypropionaldehyde has been studied

with a number of catalysts and supports. One problem is the plugging of the nickel catalysts by impurities in the feedstock. Gallezot

and coworkers reported that a ruthenium catalyst on a macroporous titanium dioxide support was not subject to fouling by oligomeric organic impurities. However, the same catalyst on a microporous or mesoporous support was deactivated [24]. Using the ruthenium catalyst on a macroporous support, Gallezot and coworkers

achieved yields of 98% in the reduction of 3-hydroxypropionaldehyde to 1,3-propanediol.

2.4 Glucose

The pathways based on ethylene oxide or acrolein both have the disadvantage that the starting materials are derived from petroleum. A

pathway based on the fermentation of renewable resources is

expected to be more environmentally benign and have fewer greenhouse gas emissions than its petroleum counterpart [25]. Now that

the cost of oil routinely exceeds $100 a barrel, it might also be more

cost effective, provided that high titers and good separation procedures are available.

DuPont has recently developed a commercial process for the production of 1,3-propanediol from D-glucose using genetically engineered E. coli [26]. The recombinant E. coli expressed a group of genes

that encoded dehydratase activity, dehydratase reactivation factor,

glycerol-3-phosphate dehydrogenase and glycerol-3-phosphatase.

The group of genes in their original study also contained a 1,3-propanediol oxidoreductase; however, they found that removal of that

enzyme resulted in a higher titer of 1,3-propanediol. This result was

unexpected. Apparently E. coli is capable of converting 3-hydroxypropionaldehyde into 1,3-propanediol by an endogenous enzyme.

The authors speculated that the higher titer of 1,3-propanediol

might be due to increased cell viability during the fermentation

[26]. This process has been commercialized. It has been reported

that PDO produced by the fermentation process has fewer impurities than the PDO produced using petroleum-based feedstocks [5].

Chinese researchers have recently reported the development of a

recombinant Saccharomyces cerevisiae strain that can convert D-glucose into 1,3-propanediol in a one-pot reaction [27]. Further research

into this promising area will be necessary before a commercial process can be envisioned.

3 Concluding Remarks

In summary, polyesters derived from 1,3-propanediol have

improved properties compared to other polyesters and are now

used in thermoplastics, textiles, carpets, and upholstery. The

expanding uses have stimulated considerable research into cost

effective preparations of 1,3-propanediol. Both fermentation-based

routes and organometallic catalyst-based routes have been commercialized.

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