Carbon Monoxide

Carbon monoxide (CO) is a colourless, odourless toxic gas that can be produced

naturally or as a result of human activities. It is considered one of the main

contaminants of the air. In Europe, the production and processing of metals is the

source of 16% of CO emissions (European Commission report).

As a raw material, it is mainly used as reducing agent for the production of metals, in

the production of hydrogen (by water-gas shift reaction) and for the synthesis of

organic intermediates. Furthermore, mixtures of hydrogen (H2) and CO known as

synthesis gas: syngas - are used as feedstocks of growing importance for the large-scale

production of several chemicals. Thus, the applications of carbon monoxide can be

classified in: purified CO and CO as a component of Syngas. A summary of some

possible pathways to produce chemicals from both approaches is shown on figure X.

Ca

rbo

n M

on

oxid

e

Purified

Water gas shift Hydrogen

Phosgene synthesis Phosgene

Carbonylation of methanol

Methyl Formate

Acetic Acid

Carbonylation of ethylene

Propionic Acids

As component of Syngas

Fischer-Tropsch synthesis

Waxes

Gasoline/Diesel

Light Olefins

Oxosynthesis Butanal

Methanol synthesis Methanol

Acetogens bacteria fermentation

Ethanol and alcohols

2,3-butanediol

Carboxylic acids

Acetone

CO as a component of syngas

Products obtained through Fischer-Tropsch synthesis

The Fischer-Tropsch (FT) synthesis is a chemical catalytic process that converts syngas -

a mixture of CO and H2 - into hydrocarbons. It includes a large number of consecutive

and parallel transformations which derive on the production of a wide range of

hydrocarbon products of various molecular weights. The product distribution is

influenced by the feed composition (H2-CO ratio), temperature, pressure and catalyst

type, yet this process is usually classified by the applied temperature.

The products related to the Low temperature FT (220-250C) are commonly waxes

and/or diesel fuels, while the ones related to the High temperature (330-350C) synthesis

are gasoline and light olefins such as ethylene, propylene, pentene and hexene -.

Furthermore, for the Low temperature process Cobalt-based catalyst are preferred

whereas Iron-based materials are commonly used for the High temperature FT [1].

Nevertheless, catalyst involving Ruthenium and Nickel are used as well.

The FT process offers a wide variety of economically attractive products to synthesize,

being a technology that has been used at an industrial scale since 1938 [2]. However,

its competitiveness with petroleum processes is usually hindered by the presence of

impurities on the feed stream since compounds as NH3, HCN, H2S and COS have to be

removed to concentrations below 1ppmV in order to avoid severe damage on the

catalyst [3]. Moreover, temperature control of the process due to the large amounts of

heat released during the reaction also represents a technical challenge for its industrial

application.

Considering this, the following products have been taken as the most relevant

examples for further research on the use of the steel mill off-gasses:

FT waxes

Gasoline, Diesel fuels

Ethylene or Propylene

The specific information of each product (estimated market, yield, reaction, etc.) can

be found on Table X.

Oxosynthesis

Butanals (butyraldehydes) are saturated aliphatic C4 aldehydes present in two isomers:

n-butanal - being the straight chain -, and the branched one called isobutyraldehyde.

Due to its high reactivity and availability, butanals are important feedstocks, typically

involved on the production of solvents and plasticizers[4].

They are produced by the oxosynthesis process (also known as hydroformylation). This

involves the reaction of syngas with unsaturated hydrocarbons Alkenes to produce a

mixture of aldehyde isomers. In general, oxosynthesis products range from C3-C15, yet

butanals have the largest produced volume [5]. Currently, butanal production by the

hydroformylation of propene uses Rhodium based catalysts at 70150C and 1.55 MPa.

As in the case of other metallic catalysts, poisoning of the active sites can occur when

in contact with strong acids HCN, H2S, COS, O2 and dienes [5].

Methanol

This alcohol is one of the most important chemical raw materials, one of the top ten

chemicals produced globally. Despite its properties as fuel, about 85% of the methanol

production is used on industry as a starting material or solvent for synthesis[6]. As energy

source, methanol can be used to fire rapid-start combustion turbines and to substitute

for or blend with gasoline to power vehicles. As commodity it is used mainly for the

production of Formaldehyde, Methyl tert-butyl ether, Acetic Acid and Dimethyl Ether

which derive on a wide variety of plastics, coatings, pharmaceutical precursors, etc.

Nowadays, Methanol is produced exclusively by catalytic conversion of synthesis gas

according to the reactions shown on Table X. This exothermic process is carried out at

200-300C and 5-10MPa with catalysts based on CuZnOAl2O3 or Cr2O3 with different

additives and promoters. This materials can actively last from two to five years,

however, deactivation can occur if the operation conditions are not selected properly

and because of the presence of poisons on the streams. It is well known that Sulphur

components usually H2S and COS can block the active sites on metal catalysts.

Hence, sulfur is removed before the methanol synthesis on a gas cleaning stage or in

the watergas shift step.

What else?

Products obtained through biochemical synthesis

Research on syngas fermentation for the production of multicarbon compounds has

strongly increased since 2006 (Drzyzga paper). Naturally, this recent interest responds to

the environmental and economic requirements to replace petrochemical routes of

production with more sustainable pathways. These researches have demonstrated the

ability of acetogens bacteria to convert C1 mixtures with hydrogen into fuels and

chemicals such as acetate, butyrate, alcohols and fatty acids, among others. Syngas

fermentation can also produce monomers useful for biopolymers synthesis or directly

biopolymers(Kopke, Do YS). Furthermore, genetic engineering techniques have been

and are currently applied to gas fermenting organisms in order to increase the

productivities and to obtain different and more valuable chemicals.

Some of the advantages for the use of biological conversions over the thermochemical

pathways for syngas processing are (Drzyzga paper and Commercial biomass

syngas.):

i. Milder operation conditions: temperature 30-60C and pressures close to

atmospheric;

ii. Exceptional feedstock flexibility since the process is less sensitive to the H2/CO

ratio (one of the main constrains on FT synthesis);

iii. Despite the bacteria usually prefers carbon monoxide as carbon source,

H2/CO2 mixtures can also be used

iv. Bacteria are less susceptible than metal based catalysts to trace contaminants

commonly present on syngas streams - char, tar, ash, chlorine and sulphure ;

v. Biological catalysts are in general more selective than FT catalysts leading to

simplified downstream processing of the product;

Additionally, since only very few microorganisms are capable of living in the presence

of - or using CO, the hazard of microbial contamination is not a problem for this kind

of fermentation.

Currently, a few companies are already applying syngas fermentation for the

production of commodities at pilot or industrial scale. They are mainly focusing on

obtaining alcohols (especially ethanol), however, also fatty acids,

polyhydroxyalkanoates (footnote with what are these) and 2,3-butanediol are being

produced (Drzyzga paper).

A particularly attractive case is the one of Lanzatech Inc., which is currently producing

ethanol and 2,3butanediol (23BD) (http://www.lanzatech.com/23-butanediol-bio-

based-23-bdo-set-for-2014-sales/) through the acetogens fermentation of effluent

waste gases from steel mills and coal producers. Having met the production millestones

at the demonstration facilities built in China (see Table X), Lanzatech has formed a joint

venture with the steel corporations to start the construction of a 50,000 Mton/year

facility at the end of 2015, with the objective to further scale it up to a 100,000

Mton/year plant (http://www.lanzatech.com/china-steel-corporation-approves-

investment-lanzatech-commercial-project/).

Based on this, we consider ethanol and 23BD as the most relevant examples for the

biochemical approach to obtain high value compounds form steel mill off-gasses.

Ethanol

Demand for ethanol is driven primarily by its use as a blending ingredient for gasoline.

Non-fuel consumption in the U.S. was only 269 million gal/yr in 2001 (Davenport et. al. 2002).

2,3-Butanediol (23BD)

is a high value chemical used as a precursor in the manufacture of industrial

solvents such as methyl ethyl ketone (MEK) and 1,3-butadiene. Its downstream products

have a global

market of approximately $43 billion per annum, and it is traditionally

producedpetrochemically

2,3 BDO is currently available as a laboratory chemical and is being sold as a small-

volume intermediate for certain niche applications such as in food flavoring additives.

In the past, 2,3 BDO was used as a feedstock to make butadiene for synthetic rubber,

before it was abandoned in favor of a more costeffective naphtha-based BD.

We think we can separate and convert 2,3 BDO cheaply enough to justify using this as

a bulk intermediate, said Holmgren. Weve done quite a bit of work and if we are

right, since its our same organism and reactor, we could commercialize very, very

quickly, she added. (http://www.lanzatech.com/23-butanediol-bio-based-23-bdo-set-

for-2014-sales/)

1. Dancuart, L.P. and A.P. Steynberg, Fischer-Tropsch based GTL Technology:

a New Process?, in Studies in Surface Science and Catalysis, B.H. Davis and M.L.

Occelli, Editors. 2007, Elsevier. p. 379-399.

2. Dry, M.E., The FischerTropsch process: 19502000. Catalysis Today, 2002. 71(34): p. 227-241.

3. Boerrigter, H. and R. Rauch, Review of applications of gases from biomass

gasification, in Handbook Biomass Gasification, E. Biomassa, Editor. 2005.

4. Raff, D.K., Butanals, in Ullmanns Encyclopedia of Industrial Chemistry. 2012.

5. Spath , L. and C. Dayton, Technical and Economic Assessment of Synthesis

Gas to Fuels and Chemicals with Emphasis on the Potential for Biomass-Derived

Syngas. 2003, National Renewable Energy Laboratory.

6. Ott, J., et al., Methanol, in Ullmanns Encyclopedia of Industrial Chemistry. 2012, John Wiley and Sons.