2中高温固体co2捕集材料研究进展-王强

1、Recent Advances in Inter-mediate and High Temperature CO2 Capture MaterialsProfessor Qiang WangEnvironmental Functional Nanomaterials (EFN) Laboratory, Beijing Forestry University, Beijing, P. R. ChinaIt has been cited for more than 900 timesIt has been cited for nearly 400 timesContents1. Abrief in

2、troduction to CO2 capture, storage, and utilization2. Recent advances in intermediate-temperature CO2 sorbents3. Recent advances in high-temperatureCO2 sorbents4. Conclusions1. A brief introduction to CO2 capture, storage, and utilizationGlobal Warming VS CO2IPCC reports:20th 21thcentury: temperatur

3、e increased 0.74 0.18 oC . century: temperature will increase 1.1 to 6.4 oC.It is critical to reducing CO2 emission to atmosphere now.Reduce CO2Our Earth is burning?Human activities release CO2How to remove CO2?1. CO2storage permanent removal of CO2from atmosphere(a) Underground injection(b) CO2 min

4、eralizationHow to remove CO2?2. CO2utilization converting to value-added products(a) CO2conversion to fuels(b) CO2 conversion to chemicals(c) CO2conversion to polymer(d) Algae cultivationHow important is CO2Capture?For either CO2 storage or CO2 utilization, CO2 capture is an important pre-requisite

5、to provide high concentration CO2.How to capture CO2?(1) pre-combustion capture: to capture CO2 in a synthesis gas after conversion of CO into CO2;(2) post-combustion capture: to capture CO2 in the exhaust gases once the fuel has been fully burned with air;(3) capture in oxy- combustion: consisting

6、of combustion in oxygen with recycling of exhaust gases (therefore, composed mainly of CO2 and water) and purification of the CO2 flow, to eliminate incondensable gases.Q. Wang, et al., book chapter of Encyclopedia of Semiconductor Nanotechnology, American Scientific Publisher, (2014) in press.Solid

7、 CO2 adsorbents/sorbentsFor differentprocesses, a properCO2 adsorbent/sorbent should be selected!Intermediate-temperature andhigh-temperature CO2 sorbents are used for pre-combustion CO2 capture processes and high- temperature post-combustion CO2capture processes.Q. Wang, et al., Energy Environ. Sci

8、. 4 (2011) 4255Pre-combustion CO2 captureSteam reforming: CH4 + H2O CO2 + H2 Hydrocarbon reforming: HC + H2O CO2 + H2 Water gas shift reaction: CO + H2O CO2 + H2Traditional technologyCool down the hot stream from (300-700 oC) to room temperature, then use liquid ammine to absorb CO2 from H2.Complex

9、and high energy consumption.Membrane technologyCO2/H2separationAdvantages of SEHPSorption enhanced processSteam reforming: CH4 (g) + 2H2O (g) + ads (s)4H2 (g) + ads-CO2H2 (g) + ads-CO2 (s)(s)Water-gas shift:CO (g) + H2O (g) + ads (s)CO2CO2CO2CO2CO2CO2sorbentcatalystsorbencatalyst catalyst catalystCO

10、2Ordinary processSorption-enhanced processAdvantages:( ) Shifting the equilibrium to the product side, increasing the conversion of CO (CH4)( ) Producing pure CO2 for the either storage or utilization ( ) Producing pure H2 for direct use( ) Reducing the energy penalty and cost of the processSorption

11、 enhanced reaction (SEWGS)water gas shiftCO (g) + H2O (g) + adsorbent (s) adsorbentCO2 (s) + H2(g)SEWGSBy combining the WGS reaction with CO2 capture, the energy penalty and costs of the process will be dramatically reduced.A suitable CO2 adsorbent is critical for SEWGS.2. Recent advances in interme

12、diate-temperature CO2 sorbentsIntermediate-temperature CO2 sorbentsIntermediate-temperature CO2 sorbents are mainly used for sorption enhanced water gas shift reaction (SEWGS) and sorption enhanced biomass reforming (SEBR).There are mainly two types of intermediate-temperature CO2 sorbents that can

13、be used over the temperature range of 200-500 oC.1. Layered double hydroxides derived CO2 sorbents2. MgO-based CO2 sorbentsLayered double hydroxides (LDHs)Formulation:M2+1-xM3+x(OH)2An-x/nZH2O,x: 0.2 0.4M2+: Mg2+, Co2+, Ni2+, Cu2+, Zn2+, Ca2+, etc.M3+: Al3+, Fe3+, Ga3+, Mn3+, Cr3+, etc.Anions: CO32-

14、, NO3-, Cl-, SO42-, etc.Thermal structure evolution of LDHs1.High surface area2.More active Mg-O sitesThis stage shows the highest CO2 adsorption capacity!Adsorption site:Mg-O + CO2 Mg-OCO2 (ad)LDHs derived CO2sorbents4. Controlling of the morphology of LHDs6. Preparation of LDHs-based hybrid materi

15、als (LDH/CNT, LDH/graphene oxide, etc)5. Alkali carbonates doping (K2CO3, Na2CO3, Li2CO3, etc)Effect of anions (CO32, HCO3, SO42, Cl, NO)3HTsBET, fresh(m2/g) 4.95.9BET, calcined(m2/g) 239.0114.941.9136.5135.6Molecular formulad003 (nm)CO2 capture capacity(mmol/g) 0.580.187.808.

16、808.858.047.85Mg3Al1CO3Mg3Al1NO3 Mg3Al1SO4 Mg3Al1Cl Mg3Al1HCO3Mg3Al1(OH)8(CO3)0.52H2OMg3Al1(OH)8NO32H2O Mg3Al1(OH)8(SO4)0.52H2O Mg3Al1(OH)8Cl2H2O Mg3Al1(OH)8HCO32H2O(1)The inter-layer anions influence the thermal stability, morphology, as well as on the surface area of LDHs, consequently influencing

17、 the CO2 adsorption capacity.Among various LDHs, Mg3Al1-CO3 showed the highest CO2 adsorption capacity of 0.51 mmol/g.(2)Q. Wang, et al., Catalysis Today, 164 (2011) 198203.CO2 adsorbent from organic anions intercalated LDHGeneral idea: organic anions may lead to a much more disorderedmicrostructure

18、 of the mixed oxide.Stearic acid (CH3(CH2)16 CO2) was intercalated into Mg3Al LDHs.During thermal treatment:( ) More CO2 gas will be produced ( ) More water vapor will be producued( ) The textile of formed mixed metal oxide might be more disordered.Q. Wang, et al., Energy and Environmental Science,

19、5 (2012) 7526Mg3Al-stearate LDHs The inter-layer distance was enlarged:from 0.78 nm to 3.54 nm. Much more weight loss: 79.8% VS 43.2% Much weaker memory effort: rema amorphous phase even after 15 days.itsMg3Al-stearate LDHsMg3Al-stearateMg3Al-CO3The CO2 capture capacity is markedly increased from 0.

20、5 to 1.24 mmol/g!Q. Wang, et al, Energy and Environmental Science, 5 (2012) 7526Mechanism of CO2 derived sorbentscapture on LDHsSix-coordinated Al.Four-coordinated Al.With the increase in calcination temperature, certain Al3+ cations migrates out from the MgO lattice to the surfaceQ. Wang et al. J M

21、ater. Chem. A, 2013, 1, 12782Mechanism of CO2 derived sorbentscapture on LDHs If the calcination temperature is toolow, it remain hydroxide phase,and the CO2 capture capacity is low. If the calcination temperature is too high, it transforms into spinel (MgAl2O4), and the CO2 capture capacity becomes

22、 low as well. The substitution of Mg2+ by Al3+ creates active Mg-O sites The migration of Al3+ from Mg2+ sites also creates active Mg-O sitesQ. Wang et al. J Mater. Chem. A, 2013, 1, 12782MgO-based CO2sorbentsMechanism:MgO + CO2 MgCO3Adsorption temperature: 200-400 oC, Regeneration temperature: ca.

23、500 oC;Adsorption sites: low coordinated Mg2+-O2-sitesMajor issues: Low CO2 sorption capacity Relative slow sorption kinetics Easy to lose its surface areaResearch activities on MgO-based sorbentsIn order to further increase the CO2 capture performance of MgO-based sorbents, four types of works have

24、 been carried out:( )decreasing the particle size and synthesis of porous MgO;( )dispersing MgO nanoparticles on porous supports;( )modifying MgO with alkali carbonates;( )preparation of MgO-based mixed oxides.However, due to its relatively low CO2 capture capacity, its practical application is quit

25、e limited.Molten salt promoted MgOThe paper reported molten alkali metal nitrates on CO2 uptake by MgOparticles and the adsorption can reached 10.2 mmol/g at moderate temperatures ( 300 oC) under ambient pressure.A big breakthrough(Li-Na-K)NO3/MgO10.2 mmol/gMgO 800 oCAdvantages: CO2 uptake is high (

26、theoretical value 78.6 wt%) Low cost of raw materialsMajor issuesSintering during CO2 sorption/desorptioncycles Attrition during CO2 sorption/desorption cycles SO2 poisoningSintering of CaO-based CO2sorbentsCycle number The particle size recarbonationbecomes incomplete (only outer layer can be utili

27、zed)A. I. Lysikov, A. N. Salanov, and A. G. Okunev, Ind. Eng. Chem. Res. 2007, 46, 4633.Research activities on CaO-basedCO2 sorbentsAttrition resistanceModification of pure CaO Smaller particle size(1) Use different synthesis methods including precipitation, sol gel, bubble templating, interfacial r

28、eaction, ion liquid-assisted hydrothermal and solvothermal processes, etc.(2) Use different Ca precursors including CaCl2 and Ca(NO3)2, etc. Novel structuresFortance, mesoscopic hollow sphere of CaO/Ca12Al14O33 with tunable cavitysize, etc.F.-Q. Liu, W.-H. Li, B.-C. Liu and R.-X. Li, J. Mate. Chem.

29、A, 2013, 1, 8037.Modification of neat CaO Creating porosityTreat limestone with organic acids (acetic acid, formic acid, oxalic acid, etc) or mineral acids (HCl, HBr, HI, and HNO3), etc.For pure CaO sorbent, although its CO2 capture capacity can besomehow improved by utilizing different synthesis me

30、thods, alerting the morphologies, crystal structures and porosities, or pretreatment with organic acids etc, the enhancement is still too marginal in most cases.CaO-based mixed oxidesPure CaOCaO based mixed oxidesMany inert materials which acts as structural supports or matrices including Al2O3, MgO

31、, TiO2, KMnO4, SiO2, CexZryOz, La2O3, LaAlxMgyO3, CaZrO3, etc have been studied.Scheme 1Scheme 2Advantages:The CaO particles can be separated by the inert materials, which prevents the sintering CaO. This has been regarded as one of the most efficient method for improving the performance of CaO-base

32、d CO2 sorbents.C.-C. Li, U.-T. Wu and H.-P. Lin, J. Mater. Chem. A, 2014, 2, 8252.Increasing attrition resistanceThe limestone is quite fragile, particles have been shown to break up upon calcination.To increase the attrition resistance, one reported method is to make CaO pellets with aluminate ceme

33、nt.The attrition resistance of particles is likely to become a key issue since the current pilot plants will be scaled up to full size in the next few years and much more works are demanded.Reactivation of degraded sorbentAfter long-term operation, CaO sorbent will degrade severally due to sintering

34、, the best reactivation method is using steam hydration.Mechanism:The hydration causes the formation of cracks in the CaO particles, creating channels extending to the interior of the particles and, thus, improving CO2 capture.hydrationDegraded CaOReactivated CaOThe effect of SO2MechanismCaO (s) + S

35、O2 (g) + 1/2 O2 (g) CaSO4 (s), Hr,298K = 502 kJ/molCaCO3(s) + SO2(g) + 1/2 O2(g) CaSO4(s) + CO2 (g),Hr,298K= 324 kJ/mol1.2.3.CaO is preferable to react with SO2 first; Even CaCO3 could react with SO2 ;The formed CaSO4 is more thermally stable than CaCO3.It is suggested that the best way to avoid the

36、 effect of SO2 is to desulfurize the flue gases in a separate reactor.Molten salt promoted CaOWe demonstrated that the moltentemperature of the doped salts greatly effects the CO2 capture performance of CaO;Lower molten temperature gives higher CO2 capture capacityDoping alkali carbonate molten salt

37、 cansignificantly improve the CO2 capture capacity and kinetics of CaO;(LiK)2CO3 showed the best performance.Molten salt promoted CaOThe promoting effect by molten salt is moresignificant at lower sorption temperaturesThe optimal molten salt loading is 7.5 mol%Liang Huang, Yu Zhang, Wanlin Gao, Taku

38、ya Harada, Qingqing Qin, Qianwen Zheng, T. Alan Hatton, and Qiang Wang*, Alkali carbonate molten salt-coated CaO with highly improved CO2capture capacity, Energy Technology, 5 (2017) 1328-1336. (ide back cover page).Alkali silicate-based CO2 sorbentsMechanism:Li4SiO4+ CO2 Li2SiO3+ Li2CO3Optimal adso

39、rption temperature:550-600oCAdvantages: Lower regeneration temperature (ca. 750 oC) Lower cost of raw materials Steam has promoting effectSO2has to beremoved for this systemResearch activities on alkali silicatesIn order to further improve the performance of alkali silicates, four types of work have

40、 been carried out:Alkali silicates are very promising but more works are needed.SchemesMaterialsCO2 uptakesMicrostructure modificationLi4SiO46.3 mmol g1 at 500 oC, 20% CO2Li4SiO4 pellet6.3 mmol g1 at 600 oC, 15% CO2Li4SiO46.6 mmol g1 at 525 oC, 10% CO2Li4SiO4 pellet6.8 mmol g1 at 550 oC, 14.7% CO2Li

41、4SiO46.3 mmol g1 after 16 cycles, sorption: 700 oC, desorption: 700 oC, 50% CO2Li4SiO43.5 mmol g1 after 10 cycles, sorption: 550 oC, desorption: 550 oC, 100% CO2Alkali promotionsL i 4 S i O 4 + K2CO3/Na2CO35 mmol g1 after 20 cycles, sorption: 580 oC, desorption: 700 oC, 4% CO2Li4SiO4+ K2CO3 + Li2TiO

42、35.7 mmol g1 at 650 oC, 15% CO2Transition metal dopingAl and Fe doped Li4SiO45 mmol g1 at 650 oC, 100% CO2Li4+x(Si1xAlx)O43.9 mmol g1 at 700 oC, 100% CO2Li substitutionLi4xNaxSiO44.4 mmol g1 at 680 oC, 100% CO2Li8SiO611.6 mmol g1 at 650 oC, 100% CO2Li8SiO67.0 mmol g1 at 600 oC, 100% CO2CaSiO33.5 mmo

43、l g1 after 10 cycles, sorption: 700 oC, desorption: 800 oC, 15% CO2Synthesis of Li4SiO4 from SBA-15SBA-15High specific surface area Ordered mesoporous channel Thin channel wallGood precursor for the synthesis of Li4SiO4BASBA-15 was successfully synthesized:- mesoporous structure- pore size：5.6 nm- s

44、pecific surface area: 907m2/gDCSynthesis of Li4SiO4from SBA-15-The Li4SiO4 synthesized from SBA-15 was much better than that from commercial SiO2, 36.3 wt% VS 23.5 wt%.Comparing to literature reports, the CO2 capture capacity of 36.3 wt% represents the highest value, which accounts for 99% of theoretical capacity.The cycling performance is very good.-Synthesis of Li4SiO4 from vermiculiteSynthesis of Li4SiO4from vermiculiteMultiple cycles of CO2 sorption (650 C in 100 vol% CO2, for 30 min) and desorption (650 C in 100 vol