Continuous CO2 abatement via integrated carbon capture and conversion over Ni-MgO-Al2O3 dual-functional materials

https://doi.org/10.1016/j.seppur.2023.124295Get rights and content

Highlights

  • A flue gas treatment efficiency of 280 L·h−1·kg−1 was achieved.

  • 97 % CO2 can be captured and 95 % converted to CH4 (∼100 % selectivity)

  • Synergy of adsorption and catalytic functionalities is pivotal.

Abstract

Massive emission of CO2 is one of the main contributors to global warming, and CO2 capture, utilization and storage (CCUS) was proposed as an indispensable option for carbon reduction. Recently, integrated carbon capture and conversion (ICCC) was regarded as a potential approach to lower the cost of CCUS, and development of efficient dual-functional materials (DFMs) is among the top priority in the area. Herein, Ni-MgO-Al2O3 DFMs were prepared by calcination of Ni-impregnated Mg-Al layered double hydroxide (MgAl-LDH), as such, the pre-loaded Ni species was actively involved in the decomposition of MgAl-LDH, therefore the synergy and balance of the adsorption and catalytic functionalities for ICCC can be promoted in the resulted DFMs. The optimized sample (20NiMgAl(5 0 0)) showed excellent ICCC performance. At 300 °C, continuous abatement of CO2 from simulated flue gas (15 vol.%CO2/N2) was achieved with an excellent efficiency of 280 L·h−1·kg−1. Composition analysis of the effluent gas demonstrated that over 97 % CO2 in the feed could be captured, and over 95 % of the captured CO2 was converted to CH4 with ∼ 100 % selectivity. Full retention of the adsorption capacity was observed for 10 adsorption-methanation cycles, and the post-reaction characterization of the DFMs indicated little structure change. This work may pave a way to the practical application of the ICCC technology, and also inspire other integration approaches between CO2 capture and the following mitigation technologies.

Introduction

Since the Industrial Revolution, rapid population growth and the burst of fossil energy consumption have led to massive CO2 emissions [1]. For the first time in over 800,000 years, CO2 concentration in the atmosphere rose above 400 ppm. As a result, CO2 reduction is recognized as an unavoidable task among the international community [2], and carbon neutrality is becoming a new benchmark to measure the global ambitions to combat climate change. In this context, CO2 capture, utilization and storage (CCUS) is widely accepted as an indispensable technical pathway to achieve carbon neutrality [3], [4].

The past few years witnessed great development of the CCUS technology, several large-scale demonstrations came on-line, and valuable engineering experiences are established. However, cost of the existing CCUS technology is still very high, this represents one of the major bottlenecks for their wide deployment [5], [6]. In order to further lowering the cost of CCUS, research efforts were devoted to the development of more efficient materials and processes. However, most of the previous practice was focused on single segment of the CCUS chain, e.g. discovering new adsorbents for CO2 capture, novel routes for catalytic CO2 conversion, etc. On the other hand, process integration within the CCUS framework has long been overlooked.

Recently, a new strategy of integrated carbon capture and conversion (ICCC) was proposed [7], [8], [9], [10]. Center to this idea is that CO2 in its captured form is directly converted, therefore the energy requirement for CO2 desorption and activation can be integrated on a molecular level. As a result, overall cost of CO2 mitigation by CCUS can be lowered considerably as the recovery of CO2 from a capture agent (e.g. amine-based absorbent) accounts for more than 60 % energy input in the entire CCUS chain.

Despite that development of ICCC is still in its early infancy, several approaches focusing on different products including methanol [8], [11], [12], [13], [14], methane (CH4) [2], [9], [15], [16], [17], [18], [19], [20], synthesis gas [21], [22], [23], [24], and others [25], [26], [27] have already been verified. Among them, ICCC to CH4 is particularly interesting, this is because that as compared to other CO2 conversion processes, the reaction conditions of methanation are significantly milder (ca. 300 °C and atmospheric pressure). Therefore, when it is applied for the decarbonization of industrial flue gas, less temperature and pressure alteration will be needed, resulting in lower energy consumption. Moreover, the methanation reaction is characterized by high selectivity and conversion rates, and the produced CH4 can be directly used in the existing energy infrastructure [10], [19].

The ICCC to CH4 process can be realized by several strategies [28], [29]. For example, Veselovskaya et al. designed a “capture-conversion tandem bed” set-up, namely a fixed-bed adsorber loaded with K2CO3/Al2O3 composites was directly connected with a reactor charged with Ru/Al2O3 methanation catalysts. Regeneration of the CO2 loaded adsorbents was carried out in H2, and the desorbed gas flow going straight from the adsorber outlet to the preheated catalytic reactor, where the CO2 can be converted to CH4 [30]. Alternatively, Miguel and co-workers showed that in a reactor with layered K-based adsorbents and nickel-based catalysts, the ICCC to CH4 process can be proceeded at 300–350 °C [15]. This adsorbent-catalyst mixing strategy was also adopted by Sun et al. [29]. Apart from the above, direct integration of adsorption and catalysis in one material, namely the development of dual-functional materials (DFMs) that are effective for both CO2 adsorption and conversion represents the research frontier for the ICCC to CH4 process [19]. Previously, oxides and carbonates of alkali metals (Na, K) and alkaline earth metals (Ca, Mg) have been widely employed as the adsorption sites in DFMs [9], [30], [31], and metals including Ni, Ru, and Rh were investigated as the catalytic functionalities [16], [32], [33]. For example, Farrauto’s group reported a range of DFMs for the ICCC to CH4 process [9], [31], [33], [34], [35], [36], [37], [38], and the influence of components, compositions, and reaction conditions was comprehensively investigated. It was found that compared with CaO, using K2CO3 and Na2CO3 as the adsorption site resulted in higher CH4 yield [35]. On the other hand, Ni is more vulnerable in oxidative atmosphere, and its activity and stability are slightly lower than that of Ru and Rh [32], [36], [37], [39], [40]. Nevertheless, due to its cost effectiveness, Ni has also received a lot of attention [16], [36]. In the previous work of our group, 2D-Layered Ni-MgO-Al2O3 nano-sheets were prepared by a coprecipitation method, and for the first time, continuous decarbonization of simulated flue gas by the ICCC strategy was demonstrated [41].

Clearly, synergy between the adsorption and catalysis sites in DFMs is crucial to achieve high ICCC efficiency. This is to say that except general factors such as composition, pore structure and crystallinity, considerations on concentration and activity balance between the adsorption and catalytic sites are also needed for the preparation of DFMs [42]. Currently, impregnation and coprecipitation are the major methods for the preparation of DFMs, both of which possesses its pros and cons. For example, DFMs prepared by impregnation of a catalytic component might result in its surface enrichment, but this also led to pore blockage and coverage of adsorption sites, and thus decreasing porosity and CO2 adsorption capacity [16]. At the same time, the DFMs prepared by impregnation are more prone to agglomeration and deactivation due to weak metal-support interaction [43]. On the other hand, coprecipitation favors the formation of a more homogeneous system with stronger metal-support interaction, but a portion of the catalytic sites may be embedded in the skeleton and thus became inaccessible to the reactants [44]. Therefore, preparation protocols to appropriately adjust the adsorption-catalysis synergy of DFMs, which is very important for the smooth operation of ICCC, are urgently needed.

Herein, Ni2+ was directly impregnated on an un-calcined Mg-Al layered double hydroxide (MgAl-LDH), the mixture was then heated to initiate simultaneous decomposition of the MgAl-LDH and Ni(NO3)2, such a protocol enabled active interaction between the pre-loaded species during calcination, leading to the formation of NiO-MgO-Al2O3 DFMs. Characterization results indicated that the obtained samples differ significantly from the sample prepared from either impregnation or coprecipitation, and more importantly, a better balance between adsorption and catalytic properties for ICCC can be achieved. By optimizing the Ni loading and calcination temperature, it was found that 20NiMgAl(5 0 0) has the best performance. In the continuous flue gas decarbonization mode similar to our previous report [41], excellent efficiency of 280 L·h−1·kg−1 can be achieved at 300 °C. Note this is a general requirement to ensure the overall CO2 capture ratio and efficiency are reasonable for industrial operation, while in most previous publications, unacceptable large amounts of CO2 were discharged during the ICCC process. In the current case, over 97 % CO2 in the feed can be captured with over 95 % conversion to CH4 (∼100 % selectivity) and negligible deactivation in 10 cycles. To the best of our knowledge, similar results were rarely reported before, particularly under the consecutive CO2 abatement manner. As such, this study may direct the development of the ICCC technology to practical applications, and inspire other integration approaches between CO2 capture and the following mitigation technologies.

Section snippets

Chemicals and preparation

Chemicals including NaOH (AR, ≥96.0 %), Na2CO3 (AR, ≥99.8 %), Mg(NO3)2·6H2O (AR, ≥99.0 %), Ni(NO3)2·6H2O (AR, ≥98.0 %), Al(NO3)3·9H2O (AR, ≥99.0 %), and ethanol (GR, ≥99.8 %) are purchased from Sinopharm, all of which are directly used without future purification.

The NiO-MgO-Al2O3 DFMs were prepared from a two-step procedure. Firstly, a mixed solution of Mg(NO3)2 and Al(NO3)3 (CMg = CAl = 0.2 M) was coprecipitated with another mixed solution of NaOH and Na2CO3 (CNaOH = CNa2CO3 = 1 M),

Preparation and characterization

Previously, we prepared 2D Ni-MgO-Al2O3 nano-sheets by a coprecipitation method, and continuous abatement of CO2 in simulated flue gas via ICCC was reported [41]. Interestingly, we found that the surface enrichment and relative abundance of the adsorption sites (MgO) and catalysis sites (Ni) dictated the ICCC efficiency. However, their adjustment during the coprecipitation process turned out to be unsuccessful. Therefore, this work aims to develop an alternative preparation method to enhance

Conclusions

Ni-MgO-Al2O3 DFMs for continuous CO2 abatement via integrated carbon capture and conversion (ICCC) were prepared by calcination of Ni-impregnated Mg-Al layered double hydroxide (MgAl-LDH). Systematic characterization indicate that the samples showed distinct structural properties such as higher porosity, medium Ni-Mg interactions, and so on. Taking together, a better balance between adsorption and catalytic behavior can be achieved, which can profoundly affect the ICCC efficiency of the DFMs.

CRediT authorship contribution statement

Xingbo Wang: Methodology, Investigation, Formal analysis, Data curation, Visualization, Writing – original draft. Deng Hu: Methodology, Formal analysis, Visualization, Writing – review & editing. Yingdong Hao: Formal analysis, Visualization. Lina Zhang: Formal analysis. Nannan Sun: Writing – review & editing, Conceptualization, Supervision. Wei Wei: Conceptualization, Supervision.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This work was supported by the National Key R&D Program of China (No. 2022YFE0208100), “CAS Photon Science Research Center for Carbon Dioxide” and Shanghai Science and Technology Committee (No. 21DZ1207000).

References (59)

  • A. Al-Mamoori et al.

    Oxidative dehydrogenation of ethane to ethylene in an integrated CO2 capture-utilization process

    Appl Catal B

    (2020)
  • R. Han et al.

    Two birds with one stone: MgO promoted Ni-CaO as stable and coke-resistant bifunctional materials for integrated CO2 capture and conversion

    Sep. Purif. Technol.

    (2023)
  • H. Sun et al.

    Direct and highly selective conversion of captured CO2 into methane through integrated carbon capture and utilization over dual functional materials

    Journal of CO2 Utilization

    (2020)
  • J.V. Veselovskaya et al.

    Catalytic methanation of carbon dioxide captured from ambient air

    Energy

    (2018)
  • S. Wang et al.

    Parametric, cyclic aging and characterization studies for CO2 capture from flue gas and catalytic conversion to synthetic natural gas using a dual functional material (DFM)

    Journal of CO2 Utilization

    (2018)
  • A. Porta et al.

    Ru-Ba synergistic effect in dual functioning materials for cyclic CO2 capture and methanation

    Appl Catal B

    (2021)
  • L. Proaño et al.

    In-situ DRIFTS study of two-step CO2 capture and catalytic methanation over Ru, “Na2O”/Al2O3 Dual Functional Material

    Appl. Surf. Sci.

    (2019)
  • M.S. Duyar et al.

    CO2 utilization with a novel dual function material (DFM) for capture and catalytic conversion to synthetic natural gas: An update

    Journal of CO2 Utilization

    (2016)
  • M.A. Arellano-Treviño et al.

    Catalysts and adsorbents for CO2 capture and conversion with dual function materials: Limitations of Ni-containing DFMs for flue gas applications

    Journal of CO2 Utilization

    (2019)
  • M.A. Arellano-Treviño et al.

    Bimetallic catalysts for CO2 capture and hydrogenation at simulated flue gas conditions

    Chem. Eng. J.

    (2019)
  • S. Wang et al.

    The Role of Ruthenium in CO2 Capture and Catalytic Conversion to Fuel by Dual Function Materials (DFM)

    Catalysts

    (2017)
  • L. Proano et al.

    Mechanistic assessment of dual function materials, composed of Ru-Ni, Na2O/Al2O3 and Pt-Ni, Na2O/Al2O3, for CO2 capture and methanation by in-situ DRIFTS

    Appl. Surf. Sci.

    (2020)
  • F. Kosaka et al.

    Direct and continuous conversion of flue gas CO2 into green fuels using dual function materials in a circulating fluidized bed system

    Chem. Eng. J.

    (2022)
  • Z. Boukha et al.

    Study on the promotional effect of lanthana addition on the performance of hydroxyapatite-supported Ni catalysts for the CO2 methanation reaction

    Appl Catal B

    (2022)
  • Y. Liu et al.

    Dynamic performance of CO2 adsorption with tetraethylenepentamine-loaded KIT-6

    Microporous Mesoporous Mat.

    (2010)
  • A. Zhao et al.

    Ni–Al2O3 catalysts prepared by solution combustion method for syngas methanation

    Catal. Commun.

    (2012)
  • L. Zhang et al.

    La-promoted Ni/Mg-Al catalysts with highly enhanced low-temperature CO2 methanation performance

    Int. J. Hydrogen Energy

    (2018)
  • X. Zou et al.

    Development of highly effective supported nickel catalysts for pre-reforming of liquefied petroleum gas under low steam to carbon molar ratios

    Int. J. Hydrogen Energy

    (2010)
  • W. Kim et al.

    Effect of grinding on synthesis of MgAl2O4 spinel from a powder mixture of Mg(OH)2 and Al(OH)3

    Powder Technol.

    (2000)
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