Organoamines-graftedonnano-sizedsilicaforcarbondioxidecapture Miklos Czaun, Alain Goeppert, Ro be rt B. Ma y, Drew Peltier, Hang Zhang, G.K. Surya Prakash *, George A. Olah * LokerHydrocarbonResearchInstituteandDepartmentofChemistry, UniversityofSouthernCalifornia, UniversityParkCampus, LosAngeles,CA90089-1661, USA 1.Introduction Theeverincreasingconsumptionoffossilfuelsbyhumankind hasresultedinarapidincreaseofcarbondioxideconcentrationin theatmospherefrom270ppmatthedawnoftheindustrial revolutiontothepresent395ppm.Itisgenerallyacceptedthatthis higheratmospheric carbondioxideconcentrationisoneofthe majorcontributors toglobalwarming. However, globalwarmingis nottheonlyeffectoftheincreasinganthropogenic emissionofCO 2 . TheoceansofourplanetarenetsinksofCO 2 buttheirabsorption capacityisalsofinite.Furthermore, thedissolutionofCO 2 inthe oceanslowersthepHofseawaterresultinginareductioninthe abundanceand/orsizeofshellfish, coralsandcrustaceans[1].In ordertoavoidfurtherincreaseinCO 2 concentration, the management ofthisgreenhousegashastogainmoreattention andwebelievethatthereductionofanthropogenic CO 2 emission shouldbeamongthehighestprioritiesofthiscentury. Various sequestrationtechniquesthathavebeensuggestedmayprovide onlyatemporary answertoourCO 2 management problem. For examplepumpingCO 2 todeepaquifers, coalbed, depletedoilor naturalgasfieldsarepromisingsolutions[2,3]butthese methods needtobevalidatedonalargescaletoensurethelongtermsafe storageofCO 2 .Asanalternativetosequestration, thecapture, recyclingandutilizationofCO 2 promisesanultimatesolution. An elegantwaytorecycleCO 2 ,forexample, istouseitinreforming reactionssuchasdryreformingorbi-reformingtoproducesyngas, amixtureofcarbonmonoxideandhydrogen[4].Presently, approximately 130milliontonnesperyear[5]ofCO 2 areusedin theenergyandchemicalindustriesandthemajorityisconverted tourea.Thisisstilladropinthebucketconsideringthathumanity nowemitsmorethan30billiontonnesofCO 2 peryear. Fortunately, thereareanincreasingnumberofscientificprojects [5–7]thatconsider CO 2 asavaluableindustrial feedstockrather thanjustagreenhousegasharmfulforthePlanet’secosystem. Asa resultofthepredictedimprovements, theamountofCO 2 utilized intheindustrymaygrowto300milliontonnesperyear[8]inthe shorttermandhigherinthefollowingdecades. Themostwidelyusedpost-combustion capturetechnologies arebasedonthechemisorptionofCO 2 (Scheme1) inaqueous alkanolamine solutionssuchasmonoethanolamine (MEA)[9], diethanolamine (DEA)andmethyldiethanolamine (MDEA). Thecontinuousregenerationofalkanolamine solutions(recov- eryofCO 2 )isaveryenergyintensiveprocessduetohighheating andpumpingcosts.WhileforexampleanaqueoussolutionofDEA/ MDEAhasaheatcapacityofapproximately4.50Jg À1 C À1 ( x H 2 O ¼0:6,x DEA/ x MDEA=0.24/0.16, t=50C)[10],silicabased adsorbents showsignificantlylowerheatcapacities (0.73Jg À1 C À1 ) 1 makingthiskindofadsorbentsmoreenergeti- callyefficientcandidatesforlargescaleCO 2 captureandrecycling. Journal ofCO2 Utilization 1(2013)1–7 ARTICLEINFO Article history: Received2February2013 Re cei ved in re vi sed form 26 Ma rch 2013 Accepted26March2013 Ava ila ble onl ine 24 Apr il 201 3 Keywords: Nanosilica Chemically graftedorganoamines Carbondioxidecapture ABSTRACT Org anoamine– ino rga nic hybrid ads orbent materials wer e syn thesiz ed by cov alent immobilization ofalkylaminotrime thox ysila nes and polyethyl enei minetrimethoxysilane onto fume d silic a (nan osilic a). The obtained si li ca–organ ic hy bri d materi al s were chara ct erized by thermogravimet ry and di ff use refl ecta nce infrared Fourier trans form spe ctroscopy (DRIFT) con firming the successful grafti ng of the amine deriv atives to si lic a an d thei r su rfa ce area measured usingBrun auer –Emme tt–Te ller metho d (BE T). The infl uence of rea cti on con dit ion s on the gra ft den sit y of org ano ami neswas inv est iga ted and it was fo und th at th e sat ura ti on of th e sil ane co upl in g ag ents wit h ca rb on di ox id e pr io r to surf ac e mod ific ation result ed in hig her gra ft densities . Car bon dioxid e uptake of the obtained hybrid mat eri als were det ermine d by thermo gra vimetric analysis at roo m temper atu re as wel l as hig her temper atures result ing in CO 2 adsorpti on capaci ti es from 32.4 to 69.7 mg g À1 adsorbent. ß 2013 El sevi er Ltd. Al l ri ghts reserved. *Corresponding authors. Tel.:+12137405984;fax:+12137406679. E-mailaddresses: [email protected](G.K.SuryaPrakash), [email protected](G.A. Olah). 1 AverageheatcapacityofSil-N2determinedbyDSCinthetemperature range from50to110C. ContentslistsavailableatSciVerseScienceDirect Journal of CO 2 Utilization j ou r nalhome pa ge:www.elsevier.com/locat e/jcou 2212-9820/$ –seefrontmatterß2013Elsevier Ltd.Allrightsreserved. http://dx.doi.org/10.1016/j.jcou.2013.03.007
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Organoamines-Grafted on Nano-sized Silica for Carbon Dioxide Capture
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7/27/2019 Organoamines-Grafted on Nano-sized Silica for Carbon Dioxide Capture
Organoamines-grafted on nano-sized silica for carbon dioxide capture
Miklos Czaun, Alain Goeppert, Robert B. May, Drew Peltier, Hang Zhang, G.K. Surya Prakash *,George A. Olah *
Loker Hydrocarbon Research Institute and Department of Chemistry, University of Southern California, University Park Campus, Los Angeles, CA 90089-1661, USA
1. Introduction
The ever increasing consumption of fossil fuels by humankind
has resulted in a rapid increase of carbon dioxide concentration in
the atmosphere from 270 ppm at the dawn of the industrial
revolution to the present 395 ppm. It is generally accepted that this
higher atmospheric carbon dioxide concentration is one of the
major contributors to global warming. However, global warming is
not the only effect of the increasing anthropogenic emission of CO2.
The oceans of our planet are net sinks of CO2 but their absorption
capacity is also finite. Furthermore, the dissolution of CO2 in the
oceans lowers the pH of seawater resulting in a reduction in the
abundance and/or size of shellfish, corals and crustaceans [1]. In
order to avoid further increase in CO2 concentration, the
management of this greenhouse gas has to gain more attention
and we believe that the reduction of anthropogenic CO2 emission
should be among the highest priorities of this century. Various
sequestration techniques that have been suggested may provideonly a temporary answer to our CO2 management problem. For
example pumping CO2 to deep aquifers, coal bed, depleted oil or
natural gas fields are promising solutions [2,3] but these methods
need to be validated on a large scale to ensure the long term safe
storage of CO2. As an alternative to sequestration, the capture,
recycling and utilization of CO2 promises an ultimate solution. An
elegant way to recycle CO2, for example, is to use it in reforming
reactions such as dry reforming or bi-reforming to produce syngas,
a mixture of carbon monoxide and hydrogen [4]. Presently,
approximately 130 million tonnes per year [5] of CO2 are used in
the energy and chemical industries and the majority is converted
to urea. This is still a drop in the bucket considering that humanity
now emits more than 30 billion tonnes of CO2 per year.
Fortunately, there are an increasing number of scientific projects
[5–7] that consider CO2 as a valuable industrial feedstock rather
than just a greenhouse gas harmful for the Planet’s ecosystem. As a
result of the predicted improvements, the amount of CO2 utilized
in the industry may grow to 300 million tonnes per year [8] in the
short term and higher in the following decades.
The most widely used post-combustion capture technologies
are based on the chemisorption of CO2 (Scheme 1) in aqueous
alkanolamine solutions such as monoethanolamine (MEA) [9],
diethanolamine (DEA) and methyldiethanolamine (MDEA).
The continuous regeneration of alkanolamine solutions (recov-ery of CO2) is a very energy intensive process due to high heating
and pumping costs. While for example an aqueous solution of DEA/
MDEA has a heat capacity of approximately 4.50 J gÀ1 8CÀ1
( xH2O ¼ 0:6, xDEA / xMDEA = 0.24/0.16, t = 50 8C) [10], silica based
adsorbents show significantly lower heat capacities
(0.73 J gÀ1 8CÀ1)1 making this kind of adsorbents more energeti-
cally efficient candidates for large scale CO2 capture and recycling.
Journal of CO2 Utilization 1 (2013) 1–7
A R T I C L E I N F O
Article history:
Received 2 February 2013
Received in revised form 26 March 2013Accepted 26 March 2013
Available online 24 April 2013
Keywords:
Nanosilica
Chemically grafted organoamines
Carbon dioxide capture
A B S T R A C T
Organoamine–inorganic hybrid adsorbent materials were synthesized by covalent immobilization of
alkylaminotrimethoxysilanes and polyethyleneiminetrimethoxysilane onto fumed silica (nanosilica).
The obtained silica–organic hybrid materials were characterized by thermogravimetry and diffusereflectance infrared Fourier transform spectroscopy (DRIFT) confirming the successful grafting of the
amine derivatives to silica and their surface area measured using Brunauer–Emmett–Teller method
(BET). The influenceof reaction conditions on the graft density of organoamineswas investigatedand it
was found that the saturation of the silane coupling agents with carbon dioxide prior to surface
modification resulted in higher graft densities. Carbon dioxide uptake of the obtained hybridmaterials
were determined by thermogravimetric analysis at room temperature as well as higher temperatures
resulting in CO2 adsorption capacities from 32.4 to 69.7mggÀ1 adsorbent.
In order to further increase the adsorption capacities of the
hybrid materials, we attempted to achieve higher graft densities byfollowing a different grafting procedure. It was shown that H-
Fig. 4. Adsorption capacities of functionalized silica particles at 25/55/85 8C followed by 10 cycles of adsorption/desorption at 85 8C.
Fig. 5. Adsorption capacity of Sil-N1 and Sil-PEI in repeated adsorption and desorption cycles at 85 8C. Inset: Adsorbent weight versus time diagram for Sil-PEI.
M. Czaun et al. / Journal of CO 2 Utilization 1 (2013) 1–7 5
7/27/2019 Organoamines-Grafted on Nano-sized Silica for Carbon Dioxide Capture
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