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Critical Review
Development Trends in Porous Adsorbents for carbon capture Bolisetty Sreenivasulu, Pathi Suresh, Inkollu Sreedhar, and Kondapuram Vijay Raghavan Environ. Sci. Technol., Just Accepted Manuscript • Publication Date (Web): 30 Sep 2015 Downloaded from http://pubs.acs.org on October 7, 2015
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Environmental Science & Technology
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Development Trends in Porous Adsorbents for Carbon
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Capture
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Mr.Bolisetty Sreenivasulua,
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Dr. Inkollu Sreedhar a,*, a
Department of Chemical Engineering, BITS Pilani Hyderabad Campus, Hyderabad, India
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Mr.Pathi Sureshb
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Granules India Ltd, Gagillapur, Hyderabad, India
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Dr. Kondapuram Vijaya Raghavanc
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Reaction Engineering Laboratory, Indian Institute of Chemical Technology, Hyderabad, India
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*Corresponding author. Tel.: +91 4066303512; fax: +91 4066303998.
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E-mail address:
[email protected] (I. Sreedhar).
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Development Trends in Porous Adsorbents for Carbon Capture
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B. Sreenivasulua, P. Sureshb, I. Sreedhar a,*, K.V. Raghavanc a
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Department of Chemical Engineering, BITS Pilani HyderabadCampus, Hyderabad-78, India b
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Granules India Ltd, Gagillapur, Hyderabad-500043, India
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Reaction Engineering Laboratory, Indian Institute of Chemical Technology, Hyderabad, India
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Abstract: Accumulation of greenhouse gases especially CO2 in the atmosphere leading to global
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warming with undesirable climate changes has been a serious global concern. Major power generation in
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the world is from coal based power plants. Carbon capture through pre- and post- combustion
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technologies with various technical options like adsorption, absorption, membrane separations and
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chemical looping combustion with and without oxygen uncoupling have received considerable attention
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of researchers, environmentalists and the stake holders. Carbon capture from flue gases can be achieved
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with micro and meso porous adsorbents. This review covers carbonaceous (organic and metal organic
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frameworks) and non-carbonaceous (inorganic) porous adsorbents for CO2 adsorption at different process
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conditions and pore sizes. Focus is also given to non-carbonaceous micro and meso porous adsorbents in
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chemical looping combustion involving insitu CO2 capture at high temperature(>400oC). Adsorption
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mechanisms, material characteristics and synthesis methods are discussed. Attention is given to isosteric
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heats and characterization techniques. The options to enhance the techno-economic viability of carbon
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capture techniques by integrating with CO2 utilization to produce industrial important chemicals like
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ammonia and urea are analyzed. From the reader’s perspective, for different classes of materials, each
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section has been summarized in the form of tables or figures to get a quick glance of the developments.
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Keywords: carbon capture, porous adsorbents, micro and mesoporous materials, in-situ ammonia and
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urea synthesis, insitu power generation with carbon capture.
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Contents:
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1. Introduction
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2 Micro- and meso- porous materials
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2.1 Microporous materials
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2.1.1 Inorganics
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2.1.2 Organics
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2.1.3 Metal organic frameworks and their hybrids
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2.1.4 Synthesis and characterization
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2.1.5 Performance related issues in carbon capture
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2.1.6 Challenges and future directions
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2.2 Mesoporous materials
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2.2.1 Inorganics
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2.2.2 Organics
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2.2.3 Metal organic frameworks and their hybrids
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2.2.4 Synthesis and characterization
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2.2.5 Performance related issues in carbon capture
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2.2.6 Challenges and future directions
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3. Conclusions
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*Corresponding author. Tel.: +91 4066303512; fax: +91 4066303998.
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E-mail address:
[email protected] (I. Sreedhar).
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1.Introduction
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The combustion of fossil fuels for power generation is mainly responsible for large scale emission
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of carbon dioxide (CO2) into the environment causing global warming. The alternative option of power
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generation with carbon capture (CC) is commercialized only in few technologies like amine scrubbing but
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yet to be commercialized in many others like membrane separations, cryogenic separations etc. The
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development of a sustainable CC technology is limited by its high energy penalty in pre-combustion,
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post- combustion and oxy-fuel combustion (OFC) methodologies. CC is accomplished by absorption,
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adsorption, membrane separation and chemical looping combustion (CLC) processes. Various methods of
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adsorptions have been reported for CC employing liquids as well as porous solids. They include porous
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solid adsorbent (PSaD) materials, zeolites, ZIF, PPN, MOFs, activated carbons, amine containing
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mesoporous materials, fly ash based porous polymer adsorbents, metal oxide carbonates, perovskites,
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hydrotalcites and clathrate hydrates listed in Fig 1.1-28 Recent reports have also indicated the use of low
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cost materials derived from agricultural and industrial wastes like bio-char from bagasse, coal fly ash and
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biomass based materials.29-33 Among the CC technologies, adsorption has been the simple and economical
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method for CC from flue gases.
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Inorganic porous adsorbents have been receiving industrial attention for their use in both CLC
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and in CC from flue gases with negligible environmental impact. At the same time, carbonaceous
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adsorbents based on organic and MOFs (hybrid materials) are also capable of CC from flue gases at
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ambient conditions. But, they cannot be used at the combustion temperatures used in CLC. The limitation
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of additional energy penalty of the various adsorbents can be resolved by the integration of CC with insitu
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manufacture of value added products like NH3 and urea from byproducts (H2, N2, CO2 and steam) with
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the Integration of IGCC with CLC.34 Employing inorganic adsorbents with appropriate porosity and
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strength is another option in CC.35 Dry reforming of coal and CH4 with CO2 could be used to increase the
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production of CO+H2 gas mixture.36 CaO or limestone based adsorbents with coal flyash (CFA) as
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support could be used for CC in calcination-carbonation cycle and CaSO4 for oxidation - reduction cycle
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of coal combustion. Around 25% CFA is utilized from 750 million tons of coal fly ash produced globally
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and it has adverse environmental impact in terms of polluting ground water with nano sized heavy metal
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particles.37 The main drawback of CaO (limestone) based adsorbents in CC is their poor recyclability. The
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spent CaO in combination with CFA could be reused in cement manufacture to minimize its
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environmental hazard. The energy penalty and economic viability are critical parameters of CC and its
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commercialization potential. The profitability depends on CO2 concentration in flue gas, its pressure and
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temperature, flue gas type, possible value added products and byproducts that could be derived along with
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CC.
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The economics of CCS greatly depends on the tax structure adopted by energy markets. The cost of electricity (COE) in $/MWh is obtained by: ( )
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=
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The annual power plant operational cost (TCPP) and CC cost (TCcapture) are related to electricity
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generation (E). TCPP is the sum of the annual capital, operation, maintenance and fuel costs. The energy
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penalty is calculated as a difference in COE with and without CC in electricity generation.38- 40 The COE
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could be reduced by using chemical looping with oxygen uncoupling (CLOU) with 10-15% energy
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penalty. The best option looks to minimize the energy penalty of CC by making use of its byproducts
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(CO2, N2 and H2). The energy penalty could also be reduced by utilizing solar thermal energy for CC.41
(1)
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In this review, recent advances made in the development of micro and mesoporous inorganic
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adsorbents and carbonaceous porous adsorbents are discussed. The carbonaceous adsorbents have been
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classified into organic adsorbents and MOFs in both micro and meso porous forms. Their synthesis,
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characterization and adsorption mechanisms are covered. The inorganic adsorbents are also examined as
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oxygen carriers (OC) in CLC. Future directions for achieving sustainable carbon capture have also
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received attention.
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2. Micro and mesoporous materials as adsorbents
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Adsorbents can be classified as microporous (500Ǻ). They exist in carbonaceous and non-
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carbonaceous forms. Adsorption is gaining industrial importance due to the limitations of absorption
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with respect to stability, corrosion and energy penalty issues.42 Traditional applications of porous
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materials are in ion-exchange, catalysis, physical and chemical adsorption. Their effectiveness is
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governed by their composition and the structural attributes like poresize (PS), shape, void space, volume
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and surface area (SA).
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The macroporous materials are larger than the mean free path length of typical fluid molecules
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which are controlled by viscous flow and bulk diffusion. Their porosity is achieved due to cavities,
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channels, interstices and the pores that are deeper than wider. The mesoporous materials are still smaller
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than the mean free path but are controlled by Knudsen diffusion (KDif), surface diffusion (SDif),
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multilayer adsorption and capillary condensation. Porous materials are used for controlling combustion
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flames and in solar and thermal energy storage applications.41,43,44 Various types of adsorbents with
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transport mechanisms viz., viscous flow, bulk diffusion, KDif, SDif and capillary condensation have
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been reported.45
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2.1 Microporous materials
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Microporous materials are classified as ultra microporous (
