CO2 Utilization

8/13/2019 CO2 Utilization

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16 CHEMICAL ENGINEERING WWW.CHE.COM JULY 2013

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On May 9, atmospheric carbon di-oxide levels surpassed 400 ppmin Mauna Loa, Hawaii for thefirst time since measurements

began there in 1958. This concentra-

tion is well above the 280 ppm levelsoccurring prior to the Industrial Revo-lution of the 19th century, accordingto the Scripps Institution of Oceanog-raphy, University of California (SanDiego, Calif.; scripps.ucsd.edu). Today’srate of increase of CO2 into the atmo-sphere is more than 100 times fasterthan the increase that occurred whenthe last ice age ended, says Scripps.

Efforts to stem the flow of thisgreenhouse gas (GHG) into the at-mosphere are becoming a priority in

some countries, which are investingconsiderable funding for R&D projectsin carbon capture and storage (CCS;see, for example Chem. Eng., May2008, pp. 28–36). Targeting the mainculprits — combustion of fossil fuelsfor power generation or cement pro-duction — CCS projects over the last20 years have primarily focused oncapturing CO2 from fluegas, and theninjecting the pressurized CO2 under-ground or into wells for enhanced oilrecovery (EOR).

More recently, another branch ofR&D has begun to blossom — car-bon capture and utilization (CCU)— whereby the CO2 captured fromfluegas is used as a feedstock to makechemicals, such as polymers, methanoland even the key chemical buildingblock, CO. Chemists and chemical en-gineers around the world are trying toexploit a variety of technologies fromtheir toolboxes, such as developingnew polymerization catalysts, electro-chemical and photochemical processes,biotechnological methods and others,in order to not only make use of theCO2, but also to reduce the amount of

petroleum-derived feedstock neededto produce products.

In Germany, for example, the FederalMinistry of Education and Research(BMBF; Bonn; www.bmbf.de) has re-

cently earmarked €100 million for“Technologies for Sustainability andClimate Protection — Chemical Pro-cesses and Use of CO2,” with the objec-tives of lowering dependency on crudeoil and natural gas, using CO2 as a rawmaterial, doubling energy productivityby 2020, and reducing CO2 emissionsby up to 40% by 2020. Among the 33funded projects for the 2009–2015timeframe are 11 for CO2 utilizationand seven for making chemicals.

The U.S. Dept. of Energy (DOE;

Washington, D.C.; www.energy.gov), too,has recently added CCU to its pallet oftechnologies receiving funding throughits National Energy Technology Labo-ratory (NETL; Pittsburgh, Pa.; www.netl.doe.gov),. The DOE is also fundingstartup companies struggling to com-mercialize CCU technologies. Some ofthese projects are described below.*

Polymers with CO2 built-inIn February, the world’s first large-scale production of polypropylene

carbonate (PPC) polyol using wasteCO2 as a raw material commenced.Partially funded by a three-year,$25-million grant from the DOE’s Of-fice of Fossil Energy, the PPC run wasconducted by Novomer Inc. (Waltham,Mass.; www.novomer.com) in collabo-ration with Albemarle Corp. (Orange-burg, S.C.; www.albemarle.com), andtested Novomer’s catalyst technology.

The batch run produced seven tonsof finished polymer — a PPC diolwith a molecular weight of 1,000 g/

mol — that is being used to accelerateproduct qualification and adoption ina wide range of polyurethane applica-tions, says Novomer’s executive vicepresident, Peter Shepard. The PPC is

made by the catalytic copolymeriza-tion of CO2 and propylene oxide. Con-taining up to 40 wt.% CO2, the PPCcan be tailored to a range of materialcharacteristics, from solid plastics tosoft, flexible foams, depending on thelength of the polymer chains.

Novomer’s homogeneous, cobalt-based catalyst is 300 times more ac-tive than previous systems developedto synthesize aliphatic polycarbon-ates. This enables the process to op-erate at much milder temperatures

of 35–50°C, says Shepard. Novomer’sprocess takes place in the liquid phaseat 150–300 psi, with the monomer act-ing as a solvent.

Novomer is talking to other tollmanufacturers for larger-scale pro-duction runs, and is positioning itspolymer technology to compete withconventional petroleum-based mate-rials for applications such as flexible,rigid and microcellular packagingfoams, thermoplastics, polyurethaneadhesives and sealants, and coating

resins for food-and-beverage cans.CO2-derived polyols are also being

developed at Bayer MaterialScience AG (BMS; Leverkusen, Germany; www.bayermaterialscience.com), as part ofthe three-year Dream Production proj-ect, launched in 2010 with funding fromthe BMBF, and with partners RWE AG(Essen; www.rwe.com), RWTH AachenUniversity (www.rwth-aachen.de) andthe CAT Catalytic Center (a researchfacility jointly run by the universityand Bayer). A new zinc-based catalystwas developed as part of a forerunnerproject, Dream Reactions, to enable theefficient reaction of CO2.

Newsfront

Researchers are developing new

technologies for using CO2 as a feedstock

to make a variety of chemicals

CO2 UTILIZATION

FIGURE 1. This miniplant in Leverkusen, Germanyis being used to develop CO2-containing polymers formaking polyurethane foam used in cars and furniture

* A longer version of this article, as well as atable of more R&D projects, can be found onlineat www.che.com



CHEMICAL ENGINEERING WWW.CHE.COM JULY 2013 17

Since the beginning of 2011, thecompany has been running its DreamProduction Miniplant (Figure 1),which is now operating continuously

and producing sample amounts (kilo-grams) for internal testing of the newmaterial, says project leader ChristophGürtler. The miniplant uses CO2 thathas been captured from the fluegas ofa lignite-fired power plant operated byRWE in nearby Cologne.

BMS is now testing the polymers forpotential applications. By mixing theCO2-based polyether polycarbonatepolyol with isocyanates, the companyis producing samples of polyurethanefoam for testing. Initial results show

that the material containing CO2 match those made the conventionalway. If the new process continues toproduce good results, Bayer intends tostart industrial production of polyolswith CO2 from 2015.

Meanwhile, a lifecycle analysis(LCA) has been performed by RWTH

Aachen University, and the resultswere reported last month at the In-ternational Conference on CO2 Utili-zation (June 23–27; Alexandria, Va).

The LCA analysis shows that the newmaterials do have a better carbon foot-print than those made by conventionalmethods. “This is mainly due to thesavings of fossil materials and replac-ing them by CO2, says Gürtler.

Another “dream” reaction is the di-rect synthesis of acrylate from CO2 and alkenes, says Michael Limbach,a chemist working at the Synthesisand Homogeneous Catalyst Dept. ofBASF SE (Ludwigshafen; www.basf.com) and the Catalyst Research Labo-

ratory of the University of Heidel-berg (CaRLa; both Germany; www.carla-hd.com). Metal-catalyzed oxida-tive coupling of CO2 with alkenes oralkynes is one of the most attractiveroutes to acrylates, but finding a suit-able catalyst has eluded researchersfor over 30 years, he says.

Until now. Last year, Limbach andhis colleagues from BASF, CaRLa,and hte AG (Heidelberg; www.hte-company.com) reported the first syn-

thesis of sodium acrylate from CO2,ethylene and a base. The group devel-oped a homogeneous organometalliccatalyst based on nickel as part of thethree-year, €2.2-million ACER projectfunded by BMBF, with BASF and hteadding an additional €1.7-million forthe next few years. Sodium acrylate isa key ingredient for high-performancepolymers, such as superabsorbentpolymers used in diapers. The projectaims to further develop the direct routeto acrylates as an economical alterna-

tive to current production methods,which use fossil-fuel-derived propyl-ene or propane in a two-step oxidationprocess, says Limbach. He estimatesthe current global-market volume foracrylic acid at approximately 4 millionton/yr. Although CO2 is a cheap sourceof carbon, a great deal of expensive

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energy is needed for thermodynamicreasons, to make it usable. Productionprocesses would therefore only trulyconsume CO2 if this energy were gen-

erated “CO2-neutrally,” he says.

Fermentation methods A demonstration plant for the pro-duction of acetic acid from the CO2 in industrial offgases will be built atan operating plant of Petronas (KualaLumpur; www.petronas.com.my), Ma-laysia’s national oil company, under anagreement with LanzaTech (Roselle,Ill.; www.lanzatech.com), developer ofthe process. Scheduled for startup inlate 2013, the plant will be similar in

size to a demonstration unit for a Lan-zaTech process that produces ethanoland 2,3 butanediol (2,3-BD) from theCO in offgases, says Mike Schultz, thecompany’s vice-president of engineer-ing. That plant started up last April ata Bao Steel (Shanghai) steel mill andproduces 100,000 gal/yr (300 ton/yr)of ethanol (see Chem. Eng., December2010, p. 12).

The CO2 process is similar to theCO technology in that it uses fermen-tation media containing naturally oc-

curring bacteria that have been opti-mized to obtain a product (acetic acidin the case of CO2). Raw offgases aresparged into the solution, and the CO2 reacts with H2 at 35–40°C to yieldacetic acid, plus water. The rest of thecomponents in the gases are inert andpass through the reactor.

Schultz says that, unlike CO, CO2 isreadily soluble in water, which makesthe CO2 process more effective. Lan-zaTech plans to recover the acid fromthe solution by counter-current solvent

extraction (the CO process uses dis-tillation to obtain ethanol). He notesthat CO2 is present in the offgasesfrom many industrial processes andcan account for as much as 50–60%of raw natural gas. H2 for the processcan be provided from various low-valuesources, such as coke oven gas, hydro-gen plant offgas, and refinery fuel gas.

Meanwhile, biotechnology is alsobeing tapped as a method for mak-ing acetone, a widely used solventthat is also a key ingredient for mak-ing methyl methacrylate, isophoroneand bisphenol A. Today, acetone isproduced from fossil-based resources,

reacting propylene andbenzene into acetone andphenol. The goal of theBMBF-funded COOPAF

project (CO2-based ac-etone fermentation) isto develop a laboratory-scale, gas-fermentationprocess in which bacte-ria produce acetone di-rectly from CO2 and H2.Natural acetogenic bac-teria strains normallymetabolize CO2 and H2 into ethanol and acetate.In cooperation with uni-

versities of Ulm and

Rostock, metabolic engineered aceto-genic bacteria strains that are able toproduce acetone using CO2 are beingdeveloped. In contrast to other R&Defforts, this project uses only CO2 asthe carbon source, says Jörg-JoachimNitz, group leader, reactor technol-ogy, at Evonik Industries AG’s (Essen,Germany: www.evonik.com) Coatingsand Additives — BL Crosslinkersbusiness unit in Marl, Germany.

Already the group has confirmedthat it is able to produce acetone from

CO2 and H2.One advantage of this biotechnologi-

cal gas-fermentation approach is thatpurified gases are not required as rawmaterials. “We can use CO2- and H2-rich waste gas streams,” says Nitz, suchas synthesis gas (syngas) from biomass,and offgases from steel processing.

ElectrochemistryOver the last four years, Det Norske

Veritas (DNV; Oslo, Norway; www.dnv.com) has been developing its electro-

chemical process (ECFORM; Electro-chemical Reduction of CO2 to Formate)for making formic acid from CO2. Inthe process (Figure 2), dissolved CO2 iselectrochemically reduced at the cath-ode into formate ions (along with smallamounts of H2 and CO) by a two-step,catalytic reaction, explains EdwardRode, principle researcher at DNV’sResearch and Innovation Group in Co-lumbus, Ohio. At the anode, hydroxideions are oxidized into O2.

DNV has developed a highly selec-tive cathode catalyst, based on tin ortin alloys, and a mixed-metal-oxidesanode catalyst, which combine to re-

duce the total cell voltage by almost 1 V compared to other electrochemicalroutes. The electrochemical cell reac-tor has also been designed to reducethe resistive losses by another 2 V.

As a result, the total cell voltage isdecreased by about 60%, says Rode.The lifetime of the cathode catalysthas also been increased by at least 20times over literature values, he says.

The ECFORM process has beentested in a semi-pilot-sized reactorwith a superficial area of 600 cm2,

which is capable of reducing about 1kg/d of CO2. This unit was assembledinto a solar-powered trailer to demon-strate the operation using completelyrenewable power. The reactor was mod-eled using gPROMS, a model-basedflowsheet simulator from Process Sys-tems Enterprises (PSE; London, U.K.;www.psenterprise.com). The model de-

veloped by DNV is also being used forscaleup assessment, says Rode. Thenext step will be a demonstration unitfor converting 1-ton/d of CO2, which

Rode estimates will emerge in thenext couple of years. Once developedat that scale, the process will be easyto move to commercial productionscale by simply increasing the numberof cells, he says.

Meanwhile, Dioxide Materials(Champaign, Ill.; www.dioxidemate-rials.com) is working on two aspectsof CO2 electrochemical conversion tofuels and chemicals: lowering the en-ergy requirement for the primary con-

version of CO2 into CO or HCOOH andO2; and expanding the market for thesubsequent products to large-volumechemicals. One of the main thrusts

Catholyte

+

Formate/formic acid

(aqueous product)

+

H2 + CO

(gas by-products)

+

CO2 (unreacted)

Anolyte

+

O2 (gas)

Positive ions

Cathode reactionsCO2(aq) + H+ + 2e- ➞HCOO- (aq)

2H+ + 2e- ➞H2(g)

CO2(aq) + 2H+ + 2e- ➞CO(g) + H2O

Anode reactions4OH- ➞2H2O + O2 + 4e-

Catholyte+

CO2

Anolyte

Cathodecatalyst

Anodecatalyst

Ionexchangemembrane

FIGURE 2. Electrochemistry is one way toreduce CO2 into chemicals. The process shownhere makes formate or formic acid, depending on the pH

Source: DNV



CHEMICAL ENGINEERING WWW.CHE.COM JULY 2013 19

is the use of bifunctional catalysts to

lower the voltage needed to convertCO2 to CO or HCOOH. Bifunctionalcatalysts are quite well known in in-dustry, but they usually involve twodifferent metals or a metal and a metaloxide. Dioxide Materials’ advance wasto develop novel bifunctional catalyststhat combined a metal and an organicspecies (ionic liquids) to lower theoverpotential for the reaction (thatis, reducing the energy barrier for theformation of the CO2

– intermediate).Dioxide Materials’ technology cre-

ates a new reaction pathway for the re-action, that does not require the high-energy intermediate so the wastedenergy is much less. Research (pub-lished in Science) showed that CO2 can be converted to CO and O2 at 80%energy efficiency and 98% selectivity.

The initial work was done in a 1-cm2

cell, but Dioxide Materials recently won

a $5 million DOE Advanced ResearchProjects Agency (ARPA-E) award andis collaborating on the project with3M (St. Paul, Minn.; www.3m.com), asub-recipient of the ARPA-E award,and is currently evaluating the tech-nology. Since the ARPA-E funded workstarted in February 2013, the teamhas already increased the CO outputof the cell by three orders of magnitude(from microliters per minute to milli-liters per minute). The final goal ofthe ARPA-E project is to increase the

output to liters per minute, in a designthat is scalable to the industrial (thou-sands of tons per day) scale.

Meanwhile, the BMBF-funded Sun-fire project was started in May 2012with the aim to produce Fischer-Trop-sch (F-T) liquids from CO2 and H2Ousing renewable energy. The three-year

project is lead by Sunfire GmbH (Dres-den, Germany; www.sunfire.de), withseven partners from German researchinstitutes and companies. The idea is to

produce syngas by the reverse water-gas shift (RWGS) reaction (CO2 + H2 —> H2O + CO) using H2 generated byhigh-temperature steam electrolysis.The syngas is then converted to liquids(gasoline, diesel, kerosene, methanol)and methane via F-T synthesis.

What makes the project unique is theuse of a 10-MW prototype, solid-oxidefuel cell (SOFC) electrolyzer operatingunder pressure. Using electricity gen-erated from renewable sources (solaror wind power), and by utilizing steam

generated from the downstream RWGSand F-T reactions, the HT electrolyzerhas an efficiency of over 90%, accordingto Sunfire. An integrated 159-L/d testfacility will be constructed and used for

validating the process under realisticoperating conditions. ■

Gerald Ondrey

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CONFERENCE NOTE:

For the latest on CO2 utilization, readers may consider attending the 2nd Confer-ence on CO2 as Feedstock for Chemistry and Polymers, which takes place October7–9 at the Haus der Technik, in Essen, Germany. Organized by nova-institut GmbH

(Hürth, Germany; www.nova-institut.de), the event is expected to draw more than 300participants from leading industrial and academic players in CO2 utilization. ❏

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