CO Oxidation and Subsequent CO2 Chemisorption on Alkaline

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CO Oxidation and Subsequent CO2 Chemisorption on Alkaline Zirconates: Li2ZrO3 and Na2ZrO3 Brenda Alcántar-Vázquez, Yuhua Duan, and Heriberto Pfeiffer Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.6b02257 • Publication Date (Web): 26 Aug 2016 Downloaded from http://pubs.acs.org on August 29, 2016

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Industrial & Engineering Chemistry Research

CO Oxidation and Subsequent CO2 Chemisorption on Alkaline Zirconates: Li2ZrO3 and Na2ZrO3

Brenda Alcántar-Vázquez,1,* Yuhua Duan2 and Heriberto Pfeiffer3 1

Instituto de Ingeniería, Coordinación de Ingeniería Ambiental, Universidad Nacional

Autónoma de México, Circuito Escolar s/n, Cd. Universitaria, Del. Coyoacán C.P. 04510, Ciudad de México, Mexico. 2

National Energy Technology Laboratory, United States Department of Energy, 626 Cochrans Mill Road, Pittsburgh, Pennsylvania 15236, United States.

3

Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México,

Circuito exterior s/n, Cd. Universitaria, Del. Coyoacán C.P. 04510, Ciudad de México, Mexico. *Corresponding author. Phone; +52 (55) 5622 4627, Fax; +52 (55) 5616 1371 and E-mail; [email protected]

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ABSTRACT: Two different alkaline zirconates (Li2ZrO3 and Na2ZrO3) were studied as possible bifunctional catalytic-captor materials for CO oxidation and the subsequent CO2 chemisorption process. Initially, CO oxidation reactions were analyzed in a catalytic reactor coupled to a gas chromatograph, using Li2ZrO3 and Na2ZrO3, under different O2 partial flows. Results clearly showed that Na2ZrO3 possesses much better catalytic properties than Li2ZrO3. After the CO-O2 oxidation catalytic analysis, CO2 chemisorption process was analyzed by thermogravimetric analysis, only for the Na2ZrO3 ceramic. The results confirmed that Na2ZrO3 is able to work as a bifunctional material (CO oxidation and subsequent CO2 chemisorption), although the kinetic CO2 capture process was not the best one under the physicochemical condition used in this case. For Na2ZrO3, the best CO conversions were found between 445 and 580 ºC (100 %), while Li2ZrO3 only showed a 35 % of efficiency between 460 and 503 °C. However, in the Na2ZrO3 case, at temperatures higher than 580 °C its catalytic activity gradually decreases as a result of CO2 capture process. Finally, all these experiments were compared and supported with theoretical thermodynamic data. Keywords: CO oxidation, sodium zirconate, lithium zirconate, CO2 chemisorption, thermal analysis, ab initio thermodynamics


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INTRODUCTION Excessive greenhouse gas emissions, as one of the most uncontrollable issues in the planet, have attracted widespread attention during the past several decades 1. Global warming caused by the emission of greenhouse gases and the need of alternative energy sources for sustaining the present energy demand, are problems that we must solve. Carbon capture and storage (CCS), the CO2 conversion and utilization, as well as the development of more efficient energy production technologies, provide one of the most promising approaches to alleviate this issue

1,2

. Hydrogen production is considered to be a great candidate for these

energy goals due to low emission of pollutants and more energy per mass. Among the processes for hydrogen production from methane, ethanol, methanol or glycerol as feedstock, are steam reforming (SR), partial oxidation (POX), autothermal reforming (ATR) and sorption enhanced steam reforming (SESR), which are carried out at temperatures of 400-900 °C

2–8

. However, the hydrogen produced via the steam reforming or by the partial oxidation

of hydrocarbons or renewable fuels generally contains carbon monoxide (CO). CO is harmful to proton exchange membrane fuel cells (PEMFC) since it is adsorbed on the surface of the platinum electro- catalysts causing important and fast decrements on the catalytic performance. The catalytic oxidation of CO in H2-rich gas is considered as a promising method and the most cost-effective way to eliminate CO from the reformed fuels

9–12

. A proper catalyst

for the CO oxidation process must ensure high activity, stability and selectivity in a wide temperature range (between 450-900 °C). Noble metals supported on reducible oxides and transition-metal oxides are the best candidates for CO

12–20

. Recently, alkaline ceramics as

sodium cobaltate (NaCoO2), lithium cuprate (Li2CuO2) and sodium zirconate (Na2ZrO3) have been reported as possible bifunctional materials, as catalysts in the CO oxidation and as captors of the subsequent CO2 produced

21–24

. NaCoO2 and Li2CuO2 are able to catalyze the



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conversion of CO to CO2 (following the Mars-van Krevelen mechanism) and subsequently chemisorbs the product. The total CO conversion was achieved between 450 and 700°C and between 420 and 520 °C in NaCoO2 and Li2CuO2, respectively. However, the crystalline structure, microstructure and composition changed, in both materials, as a function of the whole reaction process and the flue gas composition 22–24. Also, in a previous work 21, it was demonstrated that the CO can be oxidized and the CO2 produced chemically trapped on Na2ZrO3. In fact, the CO was totally converted to CO2 between 445 and 580°C. Then, the CO conversion decreased at T ≥ 600 °C, as result of a partial CO2 chemisorption in the Na2ZrO3 bulk, which produces a Na2CO3-ZrO2 external shell 21. On the other hand, in the last years, lithium and sodium zirconates have been proposed as CO2 captors in a wide temperature range since they present interesting kinetic 2,25–34

and cyclability properties

. In addition, due to their excellent properties, Li2ZrO3 and

Na2ZrO3 have been proposed as potential candidates for CO2 removal processes such as SESR, but only a few theoretical works have been performed

2,35–38

. Therefore, the focus of

this paper was to compare the CO oxidation and subsequent CO2 chemisorption between two alkaline zirconates; Li2ZrO3 and Na2ZrO3. Additionally, the experiments were theoretically supported by first-principles density functional theory (DFT) thermodynamic calculations.

EXPERIMENTAL Catalyst-sorbents preparation and characterization Sodium and lithium zirconates were synthesized by solid-state method as it has been previously reported

25,28,31

. Sodium or lithium carbonate (Na2CO3 and Li2CO3, Aldrich) and

zirconium oxide (ZrO2, Aldrich) were mechanically mixed and heated at 850 °C for 6 and 12 h, respectively. 20 wt% excess of sodium or lithium carbonate were added due to sodium and lithium sublimation tendency.


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Later, the calcined powders were characterized structural and microstructurally using X-ray diffraction (XRD) and N2 adsorption-desorption. A diffractometer AXS D8-Advance (Bruker) was used for the XRD characterization, using a copper anode X-ray tube. The N2 adsorption-desorption isotherms were acquired on a Bel−Japan Minisorp II equipment at 77 K. Previously, the samples were degassed at room temperature for 24 hours under vacuum. Finally, temperature-programmed desorption of CO and CO2 (CO-TPD and CO2TPD) analyses were performed in a Belcat-B from Bel Japan equipped with a TCD detector. Samples (50 mg) were previously treated in flowing He at 750 °C for 1 h to clean the surface,

and then CO (Praxair, CO:N2 = 5:95, v/v, certificated standard) or CO2 was adsorbed at 40 °C. After purging CO or CO2 with He for 10 min, the CO-TPD and CO2-TPD were carried out in He flow (30 mL/min) by a dynamic heating process up to 850 °C at a rate of 10 °C/min.

Catalytic activity and CO2 chemisorption measurement CO oxidation tests were carried out in a tubular continuous-flow fixed bed reactor (Bel-Rea, from Bel Japan) at ambient pressure and temperatures between 30 and 850 °C, using a heating rate of 5 °C/min. 200 mg of each catalyst were placed on a thin layer of quartz wool in the middle of the reactor. The feed gas mixture contained 5 vol% of CO and 3 or 5 vol% of O2 (Praxair, grade 2.6), where the total flow rate was 100 cm3/min. The effluent gas analyses were performed by a gas chromatograph (GC-2014, Shimadzu) equipped with a TCD detector and a Carboxen-100 column. The CO conversion efficiency was calculated as follows:

CO conversion (%) =

[஼ை]೔೙ ି[஼ை]೚ೠ೟ [஼ை]೔೙

× 100

(1)

where [CO]in and [CO]out are the CO concentrations in the feed and product gas, respectively. -5ACS Paragon Plus Environment


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After that, only Na2ZrO3-CO oxidation isothermal analyses were performed at different temperatures (400-600 °C) and the catalysts were re-characterized by FTIR and N2 adsorption-desorption. Also, the CO oxidation and subsequent CO2 capture were evaluated thermogravimetrically with a Q500HR equipment (TA Instruments). In both analyses the catalysts were heated in N2 until the desired oven temperature was reached, then the same CO:O2 gas mixture was fed.

Computational calculations To better understand the experimental results, by combining density functional theory (DFT) with lattice phonon dynamics, the ab initio thermodynamics calculations were performed on the CO oxidation and CO2 capture reactions by Na2ZrO3. The detailed descriptions of the calculation method can be found in previous studies.39,40 The Na2ZrO3 reactions with CO2 or CO can be expressed with the following three reactions (for convenience, the reactions were normalized to 1 mole of CO2 or CO): Na2ZrO3 + CO2 → Na2CO3 + ZrO2

(2)

Na2ZrO3 + CO + ½O2 → Na2CO3 + ZrO2

(3)

Na2ZrO3 + CO → Na2CO3 + Zr + 1/2O2

(4)

From the calculations, the thermodynamic properties (∆H(T), ∆G(T), ∆S(T)) and the temperature-gas pressure relationship can be obtained and used for evaluating the CO oxidation and CO2 capture reactions by Na2ZrO3 as discussed in the following sections.

RESULTS AND DISCUSSIONS Na2ZrO3 and Li2ZrO3 Characterization Figure 1 shows the XRD patterns of the Na2ZrO3 and Li2ZrO3 samples, which fitted to the JCPDS files 35-0770 and 33-0843, corresponding to the sodium and lithium monoclinic -6ACS Paragon Plus Environment

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crystalline phases, respectively. In addition, the textural properties of both zirconates were determined by N2 adsorption-desorption, where according to the IUPAC classification, both isotherms can be characterized as type II

41

. This behavior corresponds to nonporous

materials frequently obtained by solid state synthesis. The BET surface area was similar for both samples, around 1.5 m2/g. Figure 2 shows the CO-TPD and CO2-TPD profiles of Li2ZrO3 and Na2ZrO3 catalystsorbents. CO-desorption profiles (Figure 2A) show that both zirconates did not adsorb CO, only a well-defined peak was evidenced at 760 to 775 °C, for lithium and sodium zirconates, respectively. These peaks can be attributed to the decomposition of carbonate-like species on zirconates surfaces, which might be superficially produced during the sample handling. On the other hand, the CO2-TPD profiles (Figure 2B) indicate that the Na2ZrO3 has an importantly better affinity for CO2 absorption than Li2ZrO3. In these CO2-TPD curves there are two temperature regions for CO2 desorption. The first region is evidenced at T ≤ 300 °C related to CO2 adsorbed over the alkaline zirconate surfaces, while the second one at T ≥ 600 °C corresponding to CO2 chemisorbed. Initially, Na2ZrO3 profile displayed an intense peak at 232 °C while Li2ZrO3 only shows a narrow peak at 102 °C. At high temperatures, Na2ZrO3 presented two low intensity peaks while the Li2ZrO3 only presented one peak at 763 °C. As it was mentioned, these results agree with the superficial adsorption (first peak) and bulk chemisorption (second peak) processes observed in alkaline ceramics 26,28,29,34.

CO oxidation and subsequent CO2 chemisorption CO oxidation and the consecutive CO2 chemisorption on sodium and lithium zirconates were studied by gas chromatography and thermogravimetric analyses. Initially, the variation of catalytic activity of the materials for CO oxidation, as a function of reaction temperature, were investigated between room temperature and 850 ºC in a catalytic reactor



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connected to a gas chromatograph and the results are shown in Figure 3. As it was previously reported 21, the catalytic activity increased as a function of temperature. CO2 production was detected at 250 ºC or higher temperatures, independently of the alkaline zirconates. However, the highest CO conversion to CO2 was produced by Na2ZrO3, in which a 100 % CO conversion was achieved between 445 and 580 °C, whilst the maximum CO conversion in the Li2ZrO3 was only 35 %, between 460 and 503 °C. At T ≥ 620 ºC, the CO conversion and CO2 production varied differently for both ceramics. Na2ZrO3 sample decreases the CO conversion, and it may be related to the CO2 capture, producing Na2CO3 at the surface, which diminishes the catalytic properties. In the Li2ZrO3 case, the CO2 production seems to increase due to the Li2CO3 desorption. These results show that Na2ZrO3 presents better catalytic activity for CO oxidation than Li2ZrO3, at least under these experimental conditions. Therefore, all subsequent experiments were performed using Na2ZrO3. The calculated thermodynamic properties, heat of reaction (∆H) and Gibbs free (∆G) energies, of CO2 chemisorption as well as CO oxidation and consecutive CO2 chemisorption reactions by Na2ZrO3 are shown in Figure 4. As it can be seen, Na2ZrO3-CO reaction (reaction 4) in absence of oxygen does not occur, because the ∆G is positive. These calculations coincide with the experimental results where CO molecules are not adsorbed on Na2ZrO3 surfaces (see CO-TPD results). However, in the O2 presence (reaction 3), the Na2ZrO3 reacts with CO. In fact, Na2ZrO3 reacting with CO-O2 presents more negative ∆H and ∆G values than in the CO2 case, indicating a more stable process. Different isothermal experiments on Na2ZrO3 converting CO and capturing CO2 were performed at temperatures between 400 and 600 °C (Figure 5), and the products obtained were re-characterized by FTIR and N2 adsorption. Initially, the isotherm at 400 °C presented a decreasing exponential behavior, in which the CO conversion decreased from 26 % to zero after de first two hours. When the isotherm was performed at 450 °C the CO conversion was


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complete during the first 30 min, but after that time, a decreasing exponential behavior was again presented and the CO conversion fell down to 40 %. Between 500 and 525 ºC, CO conversion was complete throughout the whole isothermal experiment (5 hours). Even after 24 hours in the 500 °C case (data not show), the catalytic activity remained and the CO was completely converted, which suggests a good thermal stability of the Na2ZrO3. Finally, at higher temperatures (550-600 °C) the CO conversion decreased again and tended to stabilize at 13 and 24 %, respectively. Thus, high Na2ZrO3 carbonation may inhibit CO conversion due to the sintering of the Na2CO3-ZrO2 external shell. Previously, it has been reported that at T > 550 °C the carbonated-Na2ZrO3 external shell tend to sinter, otherwise this core shell presents a porous microstructure 25,27,32,42. All the isothermal products were analyzed by FTIR and N2 adsorption-desorption to probe the Na2ZrO3 carbonation process. The FTIR spectra are shown in Figure 6, which confirm the formation of carbonate species (‫ܱܥ‬ଷଶି ), by the vibration bands located at 1430 and 880 cm-1. FTIR spectra confirm the Na2CO3 formation. Therefore, part of the CO2 generated during CO oxidation is chemisorbed to produce Na2CO3. In fact, the higher intensity peak corresponds to the isotherm performed at 500 °C, which showed complete conversion of CO. Figure 7 presents the N2 adsorption-desorption isotherm of Na2ZrO3 and the Na2ZrO3CO-O2 isothermal product of 500 °C, which clearly show different textural properties. Although, both samples presented a type II isothermal behavior, the sample treated at 500 °C with CO-O2 flow resulted in type H3 hysteresis loop

41

. The surface areas of all isothermal

products increased in comparison to the original Na2ZrO3 sample (̴ 1.5 m2/g). The surface area obtained on the Na2ZrO3-CO-O2 isothermal product at 500 °C was 3.9 m2/g. Therefore, the surface area increments were produced by the Na2CO3 external shell. However when the Na2ZrO3 was treated at temperatures of 550 °C or higher, the hysteresis loops tended to



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disappear, as was observed for the original Na2ZrO3 sample. Also, the surface areas became small due to the sintering process of the carbonate external shell. These results are in agreement with the microstructural properties of the external shell (produced during CO2 chemisorption on Na2ZrO3) as a function of temperature proposed in previous papers 42. Once the CO oxidation and CO2 chemisorption were proved, the effect of O2 concentration on the CO catalytic oxidation was evaluated. Figure 8A shows the Na2ZrO3CO dynamic conversion in the presence of two different O2 amounts; stoichiometric (3% vol) and excess (5% vol, previous results). The CO conversion change dramatically when the O2 concentration was low (3% vol). The CO conversion was similar until the temperature achieved 380 °C, after that, the CO oxidation fell down to 11-15 % between 400 and 600 ºC. Finally, the CO conversion tended to increase again at T ≥ 600°C. When the isothermal behavior was tested at 500 °C (Figure 8B), results evidenced that low O2 concentration diminishes the CO conversion in 50 %. Even, the CO conversion with low O2 concentration was lower than that presented by Li2ZrO3. Therefore, oxygen added in excess is necessary for a total CO conversion on Na2ZrO3. It seems that oxygen adsorption-dissociation is the limiting step of the whole CO oxidation process. Moreover, in other cases

23

, it has been

observed that part of the oxygen atoms present into the crystalline ceramic structure may be released to increase the CO oxidation. In the Na2ZrO3 case, it does not seem to be the case. In order to confirm the CO oxidation and subsequent CO2 chemisorption, different isothermal TG experiments were performed on the Na2ZrO3-CO-O2 system. Figure 9 shows the isotherms at temperatures between 500 and 700 °C in a CO-O2 flow (PCO=0.05). All the isotherms, except the isotherm performed at 700 °C, presented a slow exponential behavior, where none of them reached the plateau even after 14 hours. It must be pointed out that final weight increments did not follow a temperature trend and they were not really high. Na2ZrO3 increases its weight in 8 wt% at 500 and 600 °C, while the highest weight increment was


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obtained at 550 °C (9.2 wt%). In fact, these results are in good agreement with the catalytic results described above and with other Na2ZrO3-CO2 chemisorption reports

25,26,28

. Then, at

650 and 700 °C the gained-weight decreased again, which may be related to the CO conversion drop observed in the catalytic experiments (see Figures 3 and 5). If the Na2ZrO3CO-O2 isotherms are compared with the Na2ZrO3-CO2 (PCO2 =1) isotherm performed at 500 °C26, an important kinetic difference was observed (square inset of Figure 9). It is clearly evident that CO2 chemisorption is faster in the Na2ZrO3-CO2 system than that of the Na2ZrO3-CO-O2 system. This behavior should be attributed to the gas concentration effect, namely, the low CO2 production through the CO oxidation process. Hence, these results show the Na2ZrO3 capacity of CO oxidation and subsequent CO2 chemisorption, even at low CO concentrations.

CONCLUSIONS Lithium and sodium zirconates (Li2ZrO3 and Na2ZrO3) were evaluated as possible catalytic and captor materials for the CO oxidation and subsequent CO2 chemisorption processes. Although both alkaline ceramics are able to perform the CO oxidation, Na2ZrO3 presented importantly better CO oxidation conditions than Li2ZrO3. In fact, while Na2ZrO3 is able to completely catalyze this reaction between 500 and 580 ºC. However, at higher temperatures the CO2 capture products decrease the catalytic properties of Na2ZrO3. Li2ZrO3 did not complete the catalytic process at any temperature. The best Li2ZrO3 catalytic efficiency was 35 %. In addition, the CO2 chemisorption results showed that Na2ZrO3 is able to trap only part of the CO previously converted to CO2 due to the low CO2 concentration and CO oxidation kinetic properties. In this case, the CO2 chemisorption process was lower than those usually reported for Na2ZrO3-CO2 systems. All these results were in very good agreement with different theoretical thermodynamic calculations.



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ACKNOWLEDGEMENTS This work was financially supported by PAPIIT-UNAM project (IN-101916). Authors thank to Adriana Tejeda for technical assistance.

REFERENCES (1)

Lu, X.; Jin, D.; Wei, S.; Wang, Z.; An, C.; Guo, W. Strategies to Enhance CO2 Capture and Separation Based on Engineering Absorbent Materials. J. Mater. Chem. A 2015, 3, 12118.

(2)

Yancheshmeh, M. S.; Radfarnia, H. R.; Iliuta, M. C. High Temperature CO2 Sorbents and their Application for Hydrogen Production by Sorption Enhanced Steam Reforming Process. Chem. Eng. J. 2016, 283, 420.

(3)

Radfarnia, H. R.; Iliuta, M. C. Development of Al-Stabilized CaO–nickel Hybrid Sorbent–catalyst for Sorption-Enhanced Steam Methane Reforming. Chem. Eng. Sci. 2014, 109, 212.

(4)

Nematollahi, B.; Rezaei, M.; Khajenoori, M. Combined Dry Reforming and Partial Oxidation of Methane to Synthesis Gas on Noble Metal Catalysts. Int. J. Hydrogen Energy 2011, 36, 2969.

(5)

Halabi, M. H.; de Croon, M. H. J. M.; van der Schaaf, J.; Cobden, P. D.; Schouten, J. C. Modeling and Analysis of Autothermal Reforming of Methane to Hydrogen in a Fixed Bed Reformer. Chem. Eng. J. 2008, 137, 568.

(6)

Lima da Silva, A.; Müller, I. L. Hydrogen Production by Sorption Enhanced Steam Reforming of Oxygenated Hydrocarbons (ethanol, Glycerol, N-Butanol and Methanol): Thermodynamic Modelling. Int. J. Hydrogen Energy 2011, 36, 2057.

(7)

Hufton, J. R.; Mayorga, S.; Sircar, S. Sorption-Enhanced Reaction Process for


Page 12 of 27

Page 13 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Hydrogen Production. AIChE J. 1999, 45, 248. (8)

Li, Z.; Gao, D.; Chang, L.; Liu, P.; Pistikopoulos, E. N. Hydrogen Infrastructure Design and Optimization: A Case Study of China. Int. J. Hydrogen Energy 2008, 33, 5275.

(9)

Alihoseinzadeh, A.; Khodadadi, A. A.; Mortazavi, Y. Enhanced Catalytic Performance of Au/CuO-ZnO Catalysts Containing Low CuO Content for Preferential Oxidation of Carbon Monoxide in Hydrogen-Rich Streams for PEMFC. Int. J. Hydrogen Energy 2014, 39, 2056.

(10)

Di Benedetto, A.; Landi, G.; Lisi, L.; Russo, G. Role of CO2 on CO Preferential Oxidation over CuO/CeO2 Catalyst. Appl. Catal. B Environ. 2013, 142-143, 169.

(11)

Biabani-Ravandi, A.; Rezaei, M.; Fattah, Z. Catalytic Performance of Ag/Fe2O3 for the Low Temperature Oxidation of Carbon Monoxide. Chem. Eng. J. 2013, 219, 124.

(12)

Royer, S.; Duprez, D. Catalytic Oxidation of Carbon Monoxide over Transition Metal Oxides. ChemCatChem 2011, 3, 24.

(13)

Biabani-Ravandi, A.; Rezaei, M.; Fattah, Z. Low-Temperature CO Oxidation over Nanosized Fe-Co Mixed Oxide Catalysts: Effect of Calcination Temperature and Operational Conditions. Chem. Eng. Sci. 2013, 94, 237.

(14)

Singh, S. A.; Madras, G. Detailed Mechanism and Kinetic Study of CO Oxidation on Cobalt Oxide Surfaces. Appl. Catal. A Gen. 2015, 504, 463.

(15)

Amini, E.; Rezaei, M. Preparation of Mesoporous Fe-Cu Mixed Metal Oxide Nanopowder as Active and Stable Catalyst for Low-Temperature CO Oxidation. Chinese J. Catal. 2015, 36, 1711.

(16)

Qwabe, L. Q.; Dasireddy, V. D. B. C.; Singh, S.; Friedrich, H. B. Preferential CO Oxidation in a Hydrogen-Rich Stream over Gold Supported on Ni–Fe Mixed Metal Oxides for Fuel Cell Applications. Int. J. Hydrogen Energy 2016, 41, 2144.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(17)

Laguna, O. H.; Domínguez, M. I.; Oraá, S.; Navajas, A.; Arzamendi, G.; Gandía, L. M.; Centeno, M. A.; Montes, M.; Odriozola, J. A. Influence of the O2/CO Ratio and the Presence of H2O and CO2 in the Feed-Stream during the Preferential Oxidation of CO (PROX) over a CuOx/CeO2-Coated Microchannel Reactor. Catal. Today 2013, 203, 182.

(18)

Bokhimi, X.; Zanella, R.; Maturano, V.; Morales, A. Nanocrystalline Ag, and Au-Ag Alloys Supported on Titania for CO Oxidation Reaction. Mater. Chem. Phys. 2013, 138, 490.

(19)

Méndez-Cruz, M.; Ramírez-Solís, J.; Zanella, R. CO Oxidation on Gold Nanoparticles Supported over Titanium Oxide Nanotubes. Catal. Today 2011, 166, 172.

(20)

Mariño, F.; Descorme, C.; Duprez, D. Supported Base Metal Catalysts for the Preferential Oxidation of Carbon Monoxide in the Presence of Excess Hydrogen (PROX). Appl. Catal. B Environ. 2005, 58, 175.

(21)

Alcántar-Vázquez, B.; Vera, E.; Buitron-Cabrera, F.; Lara-García, H. A.; Pfeiffer, H. Evidence of CO Oxidation–Chemisorption Process on Sodium Zirconate (Na2ZrO3). Chem. Lett. 2015, 44, 480.

(22)

Vera, E.; Alcántar-Vázquez, B.; Pfeiffer, H. CO2 Chemisorption and Evidence of the CO Oxidation–chemisorption Mechanisms on Sodium Cobaltate. Chem. Eng. J. 2015, 271, 106.

(23)

Lara-García, H. A.; Alcántar-Vázquez, B.; Duan, Y.; Pfeiffer, H. CO Chemical Capture on Lithium Cuprate, through a Consecutive CO Oxidation and Chemisorption Bifunctional Process. J. Phys. Chem. C 2016, acs.jpcc.5b11147.

(24)

Vera, E.; Alcántar-Vázquez, B.; Duan, Y.; Pfeiffer, H. Bifunctional Application of Sodium Cobaltate as a Catalyst and Captor through CO Oxidation and Subsequent CO2 Chemisorption Processes. RSC Adv. 2016, 6, 2162.


Page 14 of 27

Page 15 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(25)

Martínez-dlCruz, L.; Pfeiffer, H. Cyclic CO2 Chemisorption–desorption Behavior of Na2ZrO3: Structural, Microstructural and Kinetic Variations Produced as a Function of Temperature. J. Solid State Chem. 2013, 204, 298.

(26)

Alcántar-Vázquez, B.; Diaz, C.; Romero-Ibarra, I. C.; Lima, E.; Pfeiffer, H. Structural and CO2 Chemisorption Analyses on Na2(Zr1−xAlx)O3 Solid Solutions. J. Phys. Chem. C 2013, 2, 16483.

(27)

Alcántar-Vázquez, B.; Gómez-García, J. F.; Tavizón, G.; Ibarra, I. A.; Díaz, C.; Lima, E.; Pfeiffer, H. Structural and Ionic Conduction Analyses of the Na2(Zr1−xAlx)O3−x/2 Solid Solution, During the CO2 Chemisorption Process. J. Phys. Chem. C 2014, 2, 26212.

(28)

Alcérreca-Corte, I.; Fregoso-israel, E.; Pfeiffer, H. CO2 Absorption on Na2ZrO3: A Kinetic Analysis of the Chemisorption and Diffusion Processes. J. Phys. Chem. C 2008, 112, 6520.

(29)

Wang, S.; An, C.; Zhang, Q.-H. Syntheses and Structures of Lithium Zirconates for High-Temperature CO2 Absorption. J. Mater. Chem. A 2013, 1, 3540.

(30)

Khokhani, M.; Khomane, R. B.; Kulkarni, B. D. Sodium-Doped Lithium Zirconate Nano Squares: Synthesis, Characterization and Applications for CO2 Sequestration. J. Sol-Gel Sci. Technol. 2012, 61, 316.

(31)

Martínez-Dlcruz, L.; Pfeiffer, H. Effect of Oxygen Addition on the Thermokinetic Properties of CO2 Chemisorption on Li2ZrO3. Ind. Eng. Chem. Res. 2010, 49, 9038.

(32)

Ortiz-Landeros, J.; Ávalos-Rendón, T. L.; Gómez-Yánez, C.; Pfeiffer, H. Analysis and Perspectives Concerning CO2 Chemisorption on Lithium Ceramics Using Thermal Analysis. J. Therm. Anal. Calorim. 2012, 108, 647.

(33)

Pfeiffer, H.; Va, C.; Lara, H.; Bosch, P. Thermal Behavior and CO2 Absorption of Li2XNaXZrO3

Solid Solutions. 2007, 3, 922.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(34)

Xiao, Q.; Liu, Y.; Zhong, Y.; Zhu, W. A Citrate Sol–gel Method to Synthesize Li2ZrO3 Nanocrystals with Improved CO2 Capture Properties. J. Mater. Chem. 2011, 21, 3838.

(35)

Jakobsen, J. P.; Halmøy, E. Reactor Modeling of Sorption Enhanced Steam Methane Reforming. Energy Procedia 2009, 1, 725.

(36)

Ochoa-Fernández, E.; Rusten, H. K.; Jakobsen, H. A.; Rønning, M.; Holmen, A.; Chen, D. Sorption Enhanced Hydrogen Production by Steam Methane Reforming Using Li2ZrO3 as Sorbent: Sorption Kinetics and Reactor Simulation. Catal. Today 2005, 106, 41.

(37)

Ochoa-Fernandez, E.; Zhao, T.; Ronning, M.; Chen, D. Effects of Steam Addition on the Properties of High Temperature Ceramic CO2 Acceptors. J. Environ. Eng. 2009, 135, 397.

(38)

Aceves Olivas, D. Y.; Baray Guerrero, M. R.; Escobedo Bretado, M. a.; Marques da Silva Paula, M.; Salinas Gutiérrez, J.; Guzmán Velderrain, V.; López Ortiz, A.; Collins-Martínez, V. Enhanced Ethanol Steam Reforming by CO2 Absorption Using CaO, CaO*MgO or Na2ZrO3. Int. J. Hydrogen Energy 2014, 39, 16595.

(39)

Duan, Y.; Pfeiffer, H.; Li, B.; Romero-Ibarra, I. C.; Sorescu, D. C.; Luebke, D. R.; Halley, J. W. CO2 Capture Properties of Lithium Silicates with Different Ratios of Li2O/SiO2: An Ab Initio Thermodynamic and Experimental Approach. Phys. Chem. Chem. Phys. 2013, 15, 13538.

(40)

Duan, Y.; Sorescu, D. C. CO2 Capture Properties of Alkaline Earth Metal Oxides and Hydroxides: A Combined Density Functional Theory and Lattice Phonon Dynamics Study. J. Chem. Phys. 2010, 133, 074508.

(41)

Lowell, S.; Shields, J. E.; Thomas, M. A.; Thommes, M. Characterization of Porous Solids and Powders: Surface Area, Pore Size and Density; Particle Technology Series, Kluwer Academic Publishers: London, 2004.


Page 16 of 27

Page 17 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(42)

Martínez-dlCruz, L.; Pfeiffer, H. Microstructural Thermal Evolution of the Na2CO3 Phase Produced during a Na2ZrO3−CO2 Chemisorption Process. J. Phys. Chem. C 2012, 116, 9675.

FIGURE CAPTIONS Figure 1. XRD patterns of the Na2ZrO3 and Li2ZrO3 samples. Figure 2. CO-TPD (A) and CO2-TPD (B) profiles of Li2ZrO3 and Na2ZrO3 catalyst-sorbents. Figure 3. Dynamic thermal evolution of CO and CO2 using Li2ZrO3 and Na2ZrO3 as a catalyst-sorbents. Figure 4. The calculated heat of reactions (A) and free energy change (B) versus temperatures for the following reaction systems: Na2ZrO3-CO2, Na2ZrO3-CO, and Na2ZrO3CO-O2. Figure 5. CO conversion isothermal analyses using 200 mg of Na2ZrO3 as catalysts at different temperatures. Figure 6. FTIR spectra of different Na2ZrO3-CO-O2 oxidation isothermal products. Figure 7. N2 adsorption-desorption isotherm of pristine Na2ZrO3 and the Na2ZrO3-CO-O2 isothermal product obtained at 500 °C. Figure 8. Na2ZrO3-CO conversion in the presence of stoichiometric (3% vol) and excess (5% vol) O2 flow: dynamic (A) and isothermal analyses at 500 °C (B). Figure 9. CO–O2 thermogravimetric isothermal analyses of Na2ZrO3 at different temperatures and the Na2ZrO3–CO2 isotherm performed at 500 °C taken from Ref. 26 (square inset).



Graphical Abstract

100

Na2ZrO3 60

40

CO2 chemisorption

80

Li2ZrO3

Na2ZrO3 + CO2 → Na2CO3 + ZrO2

Na2ZrO3 + CO + ½O2→ Na2CO3 + ZrO2

CO conversion (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

20

0 100

200

300

400

500

600

700

Temperature (°C)


800

Page 18 of 27

Page 19 of 27

(260)

(110)

(531) (060)

(531)

Na2ZrO3

(331)

(020) (011)

(131) (400) (131)

(200)

(331)

Figure 1

Intensity (a. u.) 10

20

30

40

60

(151) (202)

(150) (240) (-223)

(221)

(041)

50

(112)

(130) (200) (-221) (040) (022)

(111)

(-111)

(131)

(021)

Li2ZrO3

(020)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


70

2

ACS Paragon Plus Environment

80


Figure 2

(A)

Li2ZrO3

CO intensity (a. u.)

Na2ZrO3

100

200

300

400

500

600

700

800

Temperature (°C)

(B) Na2ZrO3 Li2ZrO3

CO2 intensity (a. u.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 27

100

200

300

400

500

600

Temperature (°C)


700

800

Page 21 of 27

Figure 3

Na2ZrO3

7 6

Concentration (sccm)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


5

CO2

CO

Li2ZrO3

CO

4 3

CO2

2 1 0 100

200

300

400

500

600

700

Temperature (°C)


800


Figure 4

800

(A) 600

600

400

400

Na2ZrO3 + CO + ½O2 Na2CO3 + ZrO2

200

Na2ZrO3 + CO2  Na2CO3 + ZrO2

0 -200

(B) Na2ZrO3 + CO + ½O2 Na2CO3 + ZrO2 Na2ZrO3 + CO Na2CO3 + Zr + ½O2

Na2ZrO3 + CO Na2CO3 + Zr + ½O2

G (kJ/mol)

H (kJ/mol)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 27

200

Na2ZrO3 + CO2  Na2CO3 + ZrO2

0

-200

-400

-400 -600 300

600

900

1200

1500

300

600

Temperature (K)


900

1200

Temperature (K)

1500

Page 23 of 27

Figure 5

100

500 °C

525 °C 80

CO Conversion (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


450 °C 60

40

600 °C 20

550 °C 400 °C

0 0

50

100

150

200

250

Time (min)


300


Figure 6

 Na2CO3 

600 °C

Transmittance (a. u.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

 

550 °C



500 °C

 



450 °C

 400 °C 2000





1800

1600

1400

1200

1000

800

-1

Wavenumber [cm ]


600

Page 24 of 27

Page 25 of 27

Figure 7

4.5 4.0 3.5

3 -1

Vad[cm g (STP)]

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


3.0

Na2ZrO3-CO-O2

2.5

500 °C

2.0 1.5 1.0

Na2ZrO3

0.5 0.0 0.0

0.2

0.4

0.6

0.8

p/p0


1.0


Figure 8

100

(A)

CO Conversion (%)

80

60

3% vol 5% vol

40

20

0 100

200

300

400

500

600

700

800

Temperature (°C)

100

(B)

Na2ZrO3-5% vol

80

CO Conversion (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

60 Li2ZrO3-5% vol 40 Na2ZrO3-3% vol

20

0 0

50

100

150

200

250

Time (min)


300

Page 26 of 27

Page 27 of 27

Figure 9

114 114

Weight %

112 110

500 °C

111 108 105 102

Weight %

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


108

550 °C 0

50

100

150

200

Time (min)

500 °C

106 104

600 °C 650 °C

102

700 °C 100 0

100

200

300

400

500

600

700

Time (min)


800

CO Oxidation and Subsequent CO2 Chemisorption on Alkaline

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