- Email: [email protected]
Renewable energy and raw materials – The thermodynamic support
Journal of Cleaner Production 241 (2019) 118221
Contents lists available at ScienceDirect
Journal of Cleaner Production journal homepage: www.elsevier.com/locate/jclepro
Renewable energy and raw materials e The thermodynamic support a k, Arp d Bence Palota s, Pe ter Mizsey*, Be la Viskolcz Rachid Hadjadj, Csaba Dea ros, H-3515, Miskolc, Hungary University of Miskolc, Miskolc-Egyetemva
a r t i c l e i n f o
a b s t r a c t
Article history: Received 22 January 2019 Received in revised form 22 August 2019 Accepted 28 August 2019 Available online 4 September 2019
The energy and raw material supplies are crucial issues in our societies. The possible solution of these issues can be coupled with the storage alternatives of renewable energy. The chemical way of energy storage can be quite different but we follow the Supplement of Natural Gas concept since this delivers a high storage capacity solution. The chemical way of energy storage is based on the carbon dioxide hydrogenation. It is in agreement with the theory of the circular economy so that the carbon emission is reduced with the concept of Carbon Capture and Utilization (CCU). In this work the reaction system of the carbon dioxide hydrogenation is studied thermodynamically applying the tool of quantum chemistry. The aim of the study is to support the carbon dioxide transformation alternatives of industrial scale, that is, the CCU. It is determined that the methane production has the highest thermodynamic efficiency where the methanol production is the second in the ranking. These thermodynamic efficiencies are 14.4% for methanol and 44.4% for methane. Both alternatives have, however, advantages since the methane can be introduced directly into the natural gas network and the methanol has the highest volumetric energy content. Both molecules can be transformed into different kind of raw materials, see e.g. methanol economy. At the selection, however, other, practical points of view should be also considered where industrial experiences and circumstances are to be also taken into account. Having recognized the need to deal with the reduction and utilization of carbon dioxide emission (CCU), the University of Miskolc established the “Environmental Carbon Dioxide Partnership”. It has several industrial partners having significant carbon dioxide emission and therefore experience in this issue. The experts of the partnership help to solve emission problems and the carbon dioxide utilization, based on the theoretical and practical results and experiences of the Partnership. This thermodynamic investigation supports the development of the Partnership to carry out the most efficient CCU method. © 2019 Elsevier Ltd. All rights reserved.
Handling editor: Prof. Jiri Jaromir Klemes Keywords: Carbon dioxide hydrogenation Methane Methanol Thermodynamic study Energy storage
1. Introduction The harmful effect of the carbon dioxide emitted into the atmosphere is a well-known issue (Vo et al., 2019). To answer the challenges of environmental protection, University of Miskolc, Hungary, established a network called “Environmental Carbon dioxide Partnership” aiming to contribute to the global warming problem (Chandler, 2018), storage of renewable energies (Banerjee et al., 2019), production of materials on renewable basis (Islam et al., 2018). To complete these goals the carbon dioxide can be the key
* Corresponding author. E-mail address: [email protected] (P. Mizsey). https://doi.org/10.1016/j.jclepro.2019.118221 0959-6526/© 2019 Elsevier Ltd. All rights reserved.
molecule, the so-called platform molecule that is used for the solution of these challenges. The carbon dioxide can be chemically converted into different molecules for the sake of energy storage like formic acid, formic aldehyde, methanol or methane (Leonzio, 2018). These molecules can be used not only for the storage and production of energy but to produce other chemicals on renewable basis (Markewitz et al., 2012). The three goals of the Partnership are associated with the energy and energy production. Energy, the basic element that every nation need, is now a debated subject pushing the scientific world to look for its sustainable forms considering its declining resources combined with the increasing demand as well as the environmental impact (Matthews et al., 2018). It is important to note that the large capacity energy storage is badly needed for the extensive use of renewable electricity. The reason is that the renewable electricity production highly depends
2
R. Hadjadj et al. / Journal of Cleaner Production 241 (2019) 118221
on the weather, that is, its production is fluctuating. Unfortunately, the electricity consumption is also fluctuating but in different frequency. Therefore, the storage of the renewable electricity should be solved (Weitemeyer et al., 2015). The high capacity of energy storage can be completed with the Substitute Natural Gas (SNG) (Specht et al., 2009). Storing energy in chemical bonds by recycling of carbon dioxide via hydrogenative reductions can be the most convenient way of storage for the renewable electrical energy, this will for sure contribute in decreasing the CO2 emission (Olah et al., 2006). The hydrogen is obtained from electrolysis working with renewable electrical energy (Steinlechner and Junge, 2018). The reduction of CO2 could be a key issue to the energy storage while two goals could be reached: namely the reduction of the CO2 emission as well as the long term efficient H2 storage. The two attractive compounds to be produced from CO2 are methanol and methane because of their high energy content and also because of their ability to be reintroduced into other chemical processes as feedstock to produce more advanced chemical compounds (Centi et al., 2013). CO2 has to be collected from several sources such as the industrial flue and other gases, biochemical processes or from the remineralization of organic carbon from groundwater (Pain et al., 2019). To transfer the CO2, hydrogen needed. It can have also many possible sources such as the electrolysis of water, steam reforming of natural gas, or even biological sources (Xia et al., 2019). Between the different methanol production processes CO2 can be reduced directly, or converted first into synthesis gas in a reverse gas shift (RWGS) reaction (Samimi et al., 2019), and methane can be reached by one last step. Last decades the CO2 hydrogenation to methanol has been widely studied, large variety of solid catalysts have been developed and tested (Sheldon, 2017), nevertheless the reduction mechanism is still a debated subject and many alternatives are proposed (Hus et al., 2017). In our paper we investigate all the possible structures involved in the uncatalyzed methanol and methane reactions of a given ratio of CO2 and H2 and compare the thermodynamics of stable species and all the energy barriers using computational chemistry methods which are trusted to be highly accurate nowadays (Varandas, 2018) in order to construct a network of CO2 hydrogenation get a better understanding of the it's reduction possibilities to methanol and methane. Such a thermodynamic analysis can support our Partnership to make the decision which reduced form of the carbon dioxide has the highest efficiency. 2. Theory The reduction of CO2 could be a key issue of the energy storage while two goals could be reached: namely the reduction of the CO2 emission as well as the long term efficient H2 storage obtained from electrolysis using renewable electricity (Kar et al., 2019). In our paper we compare the thermodynamics of stable species of a given combination of CO2 and H2. Fig. 1 shows the possible oxidation states of CO2. To achieve the total reduction of CO2 we create a hypothetical system, with 1:4 M ration of CO2: H2. We address a thermodynamic question: which oxidation state would be the most effective energy storage, that is, the CCU. To answer it, we have created the cyclic molecular reduction mechanism of CO2. The reduction stages of CO2 are constrained by four isolable products, HCOOH, H2CO, CH3OH and CH4(Ruff and Csizmadia, 1994). We aim to know what are all the other possible isolable (stable) products which can build molecular complexes described by the
Fig. 1. RED-OX state of a single carbon atom.
total CH8O2 stoichiometry. The CH8O2 stoichiometry corresponds to CO2 þ 4H2 and/or CH4 þ 2H2O. This elementary stoichiometry is used to characterize all the intermediate species which can play a } ri et al., 2011). role in the CO2 reduction reaction (Szo To compare the relative importance of the structures generated and optimized Using the MOLGEN 5.0 software (Benecke et al., 1997), the relative Gibbs free energy was plotted against the relative entropies. The thermodynamic properties of all the possible intermediate molecular complexes have been calculated using the Gaussian 09 program package (Frisch et al., 2013). The reference state is the starting molecular combination of the reactants (CO2 þ 4 H2), it is defined with a red dot in the Fig. 2. The structures were divided into three clusters: High energy cluster (above the red line; DGor > 300 kJ/mol). Energetically favoured cluster (blow the reference dashed line; DGor < 0 kJ/mol). Energetically available cluster (between the red and the reference line). To construct the molecular network, we considered the middle and low energy cluster of molecules. The [CH4þH2O2þH2] species were not included in the reaction network, while the stability of the peroxide bond leads to OH free radicals. The proposed network summarizes many routes leading to methanol and methane formation considering the molecular complexes (having a relative Gibbs free energy less than 300 kJ/mol only) is shown in Fig. 3. An extended network including all the molecular complexes is provided in the supplementary section. The first intermediate of CO2 hydrogenation is the formic acid (B). After that, four reactions can occur. a) the direct hydrogenation of formic acid leads to formaldehyde and water (D) b) the methanediol H2C(OH)2 (H) produced by H2 addition. c) the water elimination produces CO þ water (C). It is unique, while the ratio of the equilibrium of these products could be increase with the temperature.
R. Hadjadj et al. / Journal of Cleaner Production 241 (2019) 118221
3
Fig. 2. Thermodynamic functions of the CO2 reduction mechanism. Relative free energy DGor as function of the entropy DSor of molecular composition obtained by combinatorial tools. The triplet states are signed by tr.
Fig. 3. Methanol and methane production network through CO2 hydrogenation.
d) a hydrogen shifting in the formic acid molecule can form C(OH)2 (G)e relative stable triplet state, which also can be hydrogenated to methanediol. All these four channels can lead to the formaldehyde formation, however, it can also be formed by CO hydrogenation, hydrogen
shifting in the HCOH molecule, water subtraction in the methandiol. The hydrogenation of formaldehyde (D), methandiol (H) and the HCOH (I) produce methanol (E). The toward hydrogenation (reduction) of methanol is the last step to reach methane (F). The classical combustion of methane can close the thermodynamic cycle.
4
R. Hadjadj et al. / Journal of Cleaner Production 241 (2019) 118221
The longest route to reach methanol and then methane is the following: CO2-TSAB-HCOOH-TSBG-C(OH)2-TSGH-H2C(OH)2-TSHI-HCOH-TSIDH2C]O-TSDE-CH3OH-TSEF-CH4. The shortest route to reach methanol and then methane is the following: CO2-TSAB-HCOOH-TSBD-H2C]O-TSDE-CH3OH-TSEF-CH4.
3. Modelling The overall potential energy surface (PES), was constructed from the individual relative energies of the structures obtained by combinatorial chemistry. All molecular structures of the network were optimized and characterized by first order computation. Thermodynamic functions like internal energy, enthalpy and entropy based on the frequency calculation of every individual structure are listed in Tables 1 and 2. To describe the multidimensional (PES) CO2 þ 4 H2 was selected as a reference for the calculations. The relative Gibbs free energy of an intermediate (X) will be calculated as follows:
DGor ¼ DGðXÞ DGref
Table 2 Gibbs Free Energy, relative enthalpy and entropy of the stable structures and the transition states involved in the network obtained by W1BD level of theory. Code
Particules
DGor
DHor
kJ/mol A B C D E F G H I TSAB TSBC TSCD TSDE TSEF TSBH TSBG TSGH TSHD TSHI TSID TSIE TSHE TSGI TSBD TSGC
CO2þ4H2 HCOOHþ3H2 COþH2Oþ3H2 H2COþH2Oþ2H2 CH3OHþH2OþH2 CH4þ2H2O C(OH)2þ3H2 CH2(OH)2þ2H2 HCOHþH2Oþ2H2 A/B B/C C/D D/E E/F B/H B/G G/H H/D H/I I/D I/E H/E G/I B/D G/C
0 42.14 27.7 58.22 1.62 125.1 214.61 59.9 275.93 334.82 322.64 400.66 379.21 407.18 405.60 359.65 413.22 251.20 357.97 404.19 359.06 447.74 529.02 385.91 355.00
S J/mol K
0 13.65 40.27 39.94 54.49 170.04 186.34 3.47 257.86 306.20 297.84 383.07 324.86 321.41 341.09 331.98 350.92 186.88 297.89 386.36 305.89 353.81 468.55 322.70 327.66
734.73 639.16 776.88 673.41 557.40 583.99 639.89 522.21 674.11 638.74 651.54 675.73 552.42 447.05 518.38 641.89 525.75 519.00 533.21 674.92 556.41 419.67 531.92 522.72 643.04
(1)
The relative enthalpy and entropy were derived analogically.
species.
3.1. Structure generation 3.2. Quantum chemical calculations Considering the nuclei and chemical bonds as the nodes and the edges of a graph, respectively helps to deduct and enumerate all the molecules corresponding to our stoichiometry (CH8O2) from a graph theory (Benecke et al., 1997). A certain number of atoms with a limited number of different valences defines the number of constitutional isomers (Gugisch et al., 2009). All possible stoichiometric isomers of CH8O2 are generated by allowing carbon to form 2 or 4 chemical bonds, hydrogen and oxygen to form 1 and 2 chemical bonds, respectively, except in the case of H2OeO. This graph representation is extended to three dimensions by the means of the atom type specific geometric parameter set obtained from the simplified MM2 force field. By using this procedure, a number of 27 three dimensional molecular configurations can be generated by the Molgen 5.0 program (Benecke et al., 1997). These configurations are used as initial structures in the search for local minima on the multidimensional potential energy surface for all the
All structures generated by graph theory are optimized with the MP2 method (Li and Frisch, 2006) under the aug-cc-pVTZ (Papajak et al., 2011) basis set and then, the outputs are submitted for single point calculations using the CCSD(T) (Bartlett and Purvis, 1978) method under cc-pVTZ, cc-pVQZ, cc-pV5Z (Dunning, 1989) and this in order to calculate all the thermochemistry using the FellerHelgaker extrapolation (Feller, 1992; Helgaker et al., 1998) which is renowned for its accurate results. Additionally, the W1BD (Brueckner Doubles W1) composite method (Barnes et al., 2009) also has been selected to calculate all of the species. The W1BD method is a composite method derived from the W1 (Weizmann-1) (Martin and Oliveira, 1999), it uses the B3LYP density functional theory (DFT) method (Becke, 1993) for geometry optimization (Pulay et al., 1979) and frequencies calculation (Andersson and Uvdal, 2005) and steps further with coupled
Table 1 Heat of formation of 10 optimized structures calculated at CCSD(T)/cc-pV (Q,5)Z//MP2/aug-cc-pVTZ extrapolation, W1BD method and compared to the experimental values from the literature. All enthalpy and deviation values are in kJ/mol. Species
Calculation methods CCSD(T) W1BD
Experiment
Ref.
Absolut Deviation CCSD(T) W1BD
HCOOH CO CH2 CO2 H2CO CH3OH CH4 H2O H2O2 H3COOH
373.62 106.81 430.42 388.14 107.25 202.04 72.65 244.70 137.69 128.07
378.80 110.53 428.80 393.51 108.70 201.00 74.60 241.81 135.77 131.00
McGlashan (2004) (Franck et al., 1990) Ruscic et al. (2005) (Franck et al., 1990) McGlashan (2004) McGlashan (2004) McGlashan (2004) Ruscic et al. (2006) Ruscic et al. (2006) (NIST Chemistry Webbook, n.d.) Average Max. dev.
5.18 3.72 1.62 5.37 1.45 1.04 1.95 2.89 1.92 2.93 2.81 ± 1.53 5.37
381.11 110.17 428.76 394.67 110.59 205.11 76.43 244.31 134.38 130.50
2.31 0.36 0.04 1.16 1.89 4.11 1.83 2.50 1.39 0.50 1.61 ± 1.21 4.10
R. Hadjadj et al. / Journal of Cleaner Production 241 (2019) 118221
cluster calculations for the thermochemistry part. The BD algorithm is employed in the W1BD method which involves macro iterations to update the orbitals, where in each macro iteration involves an integral transformation and a CCD calculation (Barnes et al., 2009). To estimate the accuracy of the theoretical level and to select appropriate method for our system, we calculate the heat of formation of 10 optimized structures by CCSD(T) extrapolated and W1BD methods. Heat of formations are compared to the experimental values from the literature, deviations and references are listed in Table 1. The W1BD method is selected for further calculations. A network involving the optimized species for the uncatalyzed hydrogenation of CO2 to methanol and methane is proposed (Fig. 3). Beside the stable species all transitions states are also characterized by W1BD level of theory, and the potential energy surface (PES) has been constructed (Fig. 4). The transitions states are also verified by normal coordinate analysis and IRC calculations. All the calculations are carried out by Gaussian 09 software package (Frisch et al., 2013).
4. Results 4.1. Analysis of the optimization results The Fig. 2 shows well separated species regarding to the number of molecules constituting the complex. All thermodynamic information and structural data are available in the Supplementary Table 1. The reference level of the CO2 þ 4H2 is selected. We decide to consider the complexes having a relative Gibbs free energy inferior to 300 kJ/mol. Only the methanol and methane complexes have lower free energy compared to the reference. Both
5
complex has significant lower entropy compared to the reference. This total entropy lowering could be hindered by the positive influence of the temperature on the equilibrium. It is important to note that CO formation (third most stable complex) has an entropy increasing by 40 kJ/mol K. It would be a preferred way of reduction by increasing the temperature. This complex without water could be referred to the classical syngas and can open different catalytical reduction way. Complexes of all other stable oxidation state (from Fig. 1) of carbon atom can be find in 60 kJ/mol relative free energy range. The thermodynamic properties of the optimized structures and the transition states between local minima are summarized in Table 2. The letter code of the elements of molecular network also listed in Table 2. The relative Gibbs free energy, relative enthalpy and entropy values are listed in the Table 2. Table 2 is divided into two parts, the first part shows the thermodynamic properties of the stable intermediate molecular complexes related with the energetically available cluster. The second part contains the activation free energy, activation enthalpies as well as the absolute entropy of the transition states (TSab), were a and b refers to the reactants and the products corresponding to the Fig. 3. Storing energy would be possible only in exothermic reactions, in other words, in the case of products having a negative reaction enthalpy. Although the methanediol (H) corresponds to a local minima in the potential energy surface (PES) in Fig. 4, it is a nonisolable product with an almost thermoneutral properties. Only two products for energy storage are available: methanol (E) and methane (F), with respectively, 55 and 170 kJ/mol. The CO2 reduction can lead in many different routes to E and F as shown in Fig. 3. The most energy efficient route is highlighted in red in the Fig. 4. To take place, the complete energy storage content of
Fig. 4. Potential Energy Surface (PES) of the uncatalyzed hydrogenation of CO2 to methanol and methane calculated under W1BD level of theory plotted against the reaction coordinates with a highlighted energetically favored route.
6
R. Hadjadj et al. / Journal of Cleaner Production 241 (2019) 118221
the reactants should reach the highest energy of the most energy efficient route. This is corresponding to the highest activation energy of the reaction path DH max TS ; the system needs to achieve this energy to overcome the product site. The theoretical efficiency can be defined by the ratio of the stored enthalpy DHor and the invested enthalpy.
h¼
o D H r
DHmax TS
(2)
5. Discussion The DGor values of every single transition state and optimized structure of the methanol and methane production network shown in the Fig. 3 are plotted in Fig. 4. The Fig. 4 shows the Potential Energy Surface (PES) of the uncatalyzed hydrogenation of CO2 to methanol and methane calculated under W1BD level of theory were all the reaction steps and energy barriers to overcome in order to transform CO2 to methanol and methane are visible. The goal of this plot is to select the lowest reaction path leading to the products (shown in red in the Figure), and the highest energy barrier will correspond to the energy needed to cross over all the barriers to store energy. The highest activation enthalpy is TSCD¼383.07 kJ/mol. All free energy values of the transition states are in the range of [250e530] kJ/mol, and the lowest reaction pathway for methanol and methane production is: Carbon dioxide (A) - formic acid (B) e carbon monoxide (C) e formaldehyde (D) e methanol (E) e methane (F). The relative Gibbs free energies of the latter pathway are reported in the Table 2. We assume the theoretical efficiency of the energy storage can be estimated based on the computed thermodynamic functions (eq. (2)). The stored heat (DH or ) is compared with the highest enthalpy of the corresponding reaction path. We can conclude that the theoretical efficiencies of methanol and methane formation are hðEÞ ¼ 14.4% (enthalpy of methanol (E) and TSCD) and hðFÞ ¼ 44.4% (enthalpy of methane (F) and TSCD), respectively. We also conclude from the Fig. 4 that in order to increase the efficiency of the energy storage, catalytic reactions are needed. Nevertheless, the case of CO production (C) can be the key intermediate: while its formation can be slightly increased with temperature. On the other hand, it allows a different entrance to the network, namely the classical syngas reaction (Neto et al., 2019). 6. Conclusions The high capacity storage of the renewable electrical energy can be completed with the Substitute Natural Gas (SNG) alternative. Actually, the SNG alternative is the chemical bounding of hydrogen obtained from electrolysis using renewable electricity and the reduction of the carbon dioxide emission. However, the reduction of carbon dioxide has several reaction steps and intermediate products, and it is not clear witch reduction step, that is, hydrogenated form of carbon dioxide has the highest efficiency. The theoretical efficiencies of methanol and methane formation are 14.4% (enthalpy of methanol (E) and TSCD) and 44.4% (enthalpy of methane (F) and TSCD), respectively. The result indicates that the conversion of carbon dioxide to methane has the highest thermodynamic efficiency. The efficiencies can be and should be increased with catalysis and the selection of the proper catalyst has a paramount importance. Our thermodynamic analysis and modelling prove that the
methane production has the highest thermodynamic efficiency whereas the methanol is the second in the row. At the selection of the right degree of hydrogenation, that is, which molecule should be used for the electrical energy storage, other points of views have to be also considered, e.g. the methane can be introduced directly into the existing natural gas grid but the methanol has higher volumetric energy content. On the other hand, the transport of the liquid product is cheaper and easier. The chemical transformation of both possible energy carriers can be transformed into different raw materials originated from renewables. Our “Environmental Carbon Dioxide Partnership” with several industrial partners definitely needs such theoretical support but the final decision can be made with the consideration of local industrial economic issues, as well. Acknowledgments This research was supported by the OTKA112169, OTKA128543 projects and the European Union and the Hungarian State, cofinanced by the European Regional Development Fund in the framework of the GINOP-2.3.4-15-2016-00004 project, aimed to promote the cooperation between the higher education and the industry. Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi.org/10.1016/j.jclepro.2019.118221. References Andersson, M.P., Uvdal, P., 2005. New scale factors for harmonic vibrational frequencies using the B3LYP density functional method with the triple-z basis set 6-311þG(d,p). J. Phys. Chem. A 109, 2937e2941. https://doi.org/10.1021/ jp045733a. Banerjee, J., Dutta, K., Rana, D., 2019. Carbon Nanomaterials in Renewable Energy Production and Storage Applications. Springer, Cham, pp. 51e104. https://doi. org/10.1007/978-3-030-04474-9_2. Barnes, E.C., Petersson, G.A., Montgomery, J.A., Frisch, M.J., Martin, J.M.L., 2009. Unrestricted coupled cluster and Brueckner Doubles variations of W1 theory. J. Chem. Theory Comput. 5, 2687e2693. https://doi.org/10.1021/ct900260g. Bartlett, R.J., Purvis, G.D., 1978. Many-body perturbation theory, coupled-pair manyelectron theory, and the importance of quadruple excitations for the correlation problem. Int. J. Quantum Chem. 14, 561e581. https://doi.org/10.1002/qua. 560140504. Becke, A.D., 1993. Density-functional thermochemistry. III. The role of exact exchange. J. Chem. Phys. 98, 5648e5652. https://doi.org/10.1063/1.464913. Benecke, C., Gruer, T., Kerber, A., Laue, $ R., Wieland, T., 1997. MOLecular structure GENeration with MOLGEN, new features and future developments. Fresenius J. Anal. Chem. 359, 23e32. Centi, G., Quadrelli, E.A., Perathoner, S., 2013. Catalysis for CO2 conversion: a key technology for rapid introduction of renewable energy in the value chain of chemical industries. Energy Environ. Sci. 6, 1711. https://doi.org/10.1039/ c3ee00056g. Chandler, W., 2018. Energy and Environment in the Transition Economies. Routledge. https://doi.org/10.4324/9780429500817. Dunning, T.H., 1989. Gaussian basis sets for use in correlated molecular calculations. I. The atoms boron through neon and hydrogen. J. Chem. Phys. 90, 1007e1023. https://doi.org/10.1063/1.456153. Feller, D., 1992. Application of systematic sequences of wave functions to the water dimer. J. Chem. Phys. 96, 6104e6114. https://doi.org/10.1063/1.462652. Franck, E.U., Cox, J.D., Wagman, D.D., Medvedev, V.A., 1990. Codata - key Values for Thermodynamics, aus der Reihe: CODATA, Series on Thermodynamic Properties. Hemisphere Publishing Corporation, New York, Washington, Philadelphia, London 1989. Berichte der Bunsengesellschaft für physikalische Chemie 94, 93e93. https://doi.org/10.1002/bbpc.19900940121. Frisch, M.J., Trucks, G.W., Schlegel, H.B., Scuseria, G.E., Robb, M.A., Cheeseman, J.R., Scalmani, G., Barone, V., Petersson, G.A., Nakatsuji, H., Li, X., Caricato, M., Marenich, A.,V., Bloino, J., Janesko, B.G., Gomperts, R., Mennucci, B., Hratchian, H.P., Ortiz, J.V., Izmaylov, A.F., Sonnenberg, J.L., Williams-Young, D., Ding, F., Lipparini, F., Egidi, F., Goings, J., Peng, B., Petrone, A., Henderson, T., Ranasinghe, D., Zakrzewski, V.G., Gao, J., Rega, N., Zheng, G., Liang, W., Hada, M., Ehara, M., Toyota, K., Fukuda, R., Hasegawa, J., Ishida, M., Nakajima, T., Honda, Y., Kitao, O., Nakai, H., Vreven, T., Throssell, K., Montgomery Jr., J.A., Peralta, J.E.,
R. Hadjadj et al. / Journal of Cleaner Production 241 (2019) 118221 Ogliaro, F., Bearpark, M.J., Heyd, J.J., Brothers, E.N., Kudin, K.N., Staroverov, V.N., Keith, T.A., Kobayashi, R., Normand, J., Raghavachari, K., Rendell, A.P., Burant, J.C., Iyengar, S.S., Tomasi, J., Cossi, M., Millam, J.M., Klene, M., Adamo, C., Cammi, R., Ochterski, J.W., Martin, R.L., Morokuma, K., Farkas, O., Foresman, J.B., Fox, D.J., 2013. Gaussian 09, Revision E.01. Gaussian Inc., Wallingford CT. Gugisch, R., Kerber, A., Kohnert, A., Laue, R., Meringer, M., Rucker, C., Wassermann, A., 2009. MOLGEN 5.0 reference guide. https://doi.org/10.13140/ RG.2.2.11192.96007. Helgaker, T., Klopper, W., Koch, H., Noga, J., 1998. Basis-set convergence of correlated calculations on water. J. Chem. Phys. 106, 9639. https://doi.org/10.1063/1. 473863. Hus, M., Dasireddy, V.D.B.C., Strah Stefan ci c, N., Likozar, B., 2017. Mechanism, kinetics and thermodynamics of carbon dioxide hydrogenation to methanol on Cu/ZnAl2O4 spinel-type heterogeneous catalysts. Appl. Catal. B Environ. 207, 267e278. https://doi.org/10.1016/J.APCATB.2017.01.077. Islam, M.T., Huda, N., Abdullah, A.B., Saidur, R., 2018. A comprehensive review of state-of-the-art concentrating solar power (CSP) technologies: current status and research trends. Renew. Sustain. Energy Rev. 91, 987e1018. https://doi.org/ 10.1016/j.rser.2018.04.097. Kar, S., Sen, R., Kothandaraman, J., Goeppert, A., Chowdhury, R., Munoz, S.B., Haiges, R., Prakash, G.K.S., 2019. Mechanistic insights into Ruthenium-Pincercatalyzed amine-assisted homogeneous hydrogenation of CO 2 to methanol. J. Am. Chem. Soc. 141, 3160e3170. https://doi.org/10.1021/jacs.8b12763. Leonzio, G., 2018. State of art and perspectives about the production of methanol, dimethyl ether and syngas by carbon dioxide hydrogenation. J. CO2 Util. 27, 326e354. https://doi.org/10.1016/j.jcou.2018.08.005. Li, X., Frisch, M.J., 2006. Energy-represented direct inversion in the iterative subspace within a hybrid geometry optimization method. J. Chem. Theory Comput. 2, 835e839. https://doi.org/10.1021/ct050275a. Martin, J.M.L., Oliveira, G. de, 1999. Towards standard methods for benchmark quality ab initio thermochemistrydW1 and W2 theory. J. Chem. Phys. 111, 1843. https://doi.org/10.1063/1.479454. Matthews, H.D., Zickfeld, K., Knutti, R., Allen, M.R., 2018. Focus on cumulative emissions, global carbon budgets and the implications for climate mitigation targets. Environ. Res. Lett. 13, 010201. https://doi.org/10.1088/1748-9326/ aa98c9. Markewitz, P., Kuckshinrichs, W., Leitner, W., Linssen, J., Zapp, P., Bongartz, R., Schreiber, A., Müller, T., 2012. Worldwide innovations in the development of carbon capture technologies and the utilization of CO2. Energy Environ. Sci. 5, 7281e7305. McGlashan, M., 2004. Thermodynamic properties of individual substances. J. Chem. Thermodyn. Hemisphere Pub. Corp, New York https://doi.org/10.1016/00219614(80)90157-3. Neto, A.F.G., Marques, F.C., Amador, A.T., Ferreira, A.D.S., Neto, A.M.J.C., 2019. DFT and canonical ensemble investigations on the thermodynamic properties of Syngas and natural gas/Syngas mixtures. Renew. Energy 130, 495e509. https:// doi.org/10.1016/j.renene.2018.06.091. NIST Chemistry Webbook [WWW Document], n.d. https://doi.org/10.18434/ T4D303. Olah, G.A., Goeppert, A., Prakash, G.K.S., 2006. Beyond Oil and Gas: the Methanol
7
Economy, Focus on Catalysts. WILEY-VCH. https://doi.org/10.1016/S13514180(06)71901-8. Pain, A.J., Martin, J.B., Young, C.R., 2019. Sources and sinks of CO 2 and CH 4 in siliciclastic subterranean estuaries. Limnol. Oceanogr. https://doi.org/10.1002/lno. 11131. Papajak, E., Zheng, J., Xu, X., Leverentz, H.R., Truhlar, D.G., 2011. Perspectives on basis sets beautiful: seasonal plantings of diffuse basis functions. J. Chem. Theory Comput. 7, 3027e3034. https://doi.org/10.1021/ct200106a. Pulay, P., Fogarasi, G., Pang, F., Boggs, J.E., 1979. Systematic ab initio gradient calculation of molecular geometries, force constants, and dipole moment derivatives. J. Am. Chem. Soc. 101, 2550e2560. https://doi.org/10.1021/ ja00504a009. Ruff, F., Csizmadia, I.G., 1994. Organic Reactions: Equilibria, Kinetics, and Mechanism. Elsevier, Amsterdam. sza r, A.G., Demaison, J., Janoschek, R., Ruscic, B., Boggs, J.E., Burcat, A., Csa Martin, J.M.L., Morton, M.L., Rossi, M.J., Stanton, J.F., Szalay, P.G., rces, T., 2005. IUPAC critical evaluation of Westmoreland, P.R., Zabel, F., Be thermochemical properties of selected radicals. part I. J. Phys. Chem. Ref. Data 34, 573e656. https://doi.org/10.1063/1.1724828. Ruscic, B., Pinzon, R.E., Morton, M.L., Srinivasan, N.K., Su, M.-C., James, W., Sutherland, A., Michael, J.V., 2006. Active thermochemical tables: accurate enthalpy of formation of hydroperoxyl radical, HO2y. https://doi.org/10.1021/ JP056311J. Samimi, F., Hamedi, N., Rahimpour, M.R., 2019. Green methanol production process from indirect CO2 conversion: RWGS reactor versus RWGS membrane reactor. J. Environ. Chem. Eng. 7, 102813. https://doi.org/10.1016/j.jece.2018.102813. Sheldon, D., 2017. Methanol production - a technical history. Johnson Matthey Technol. Rev. 61, 172e182. https://doi.org/10.1595/205651317X695622. Specht, M., Brellochs, J., Frick, V., Stürmer, B., Zuberbühler, U., Sterner, M., Waldstein, G., 2009. Storage of Renewable Energy in the Natural Gas Grid. FVEE/ AEE Topics, pp. 69e78 (2009). Steinlechner, C., Junge, H., 2018. Renewable methane generation from carbon dioxide and sunlight. Angew. Chem. Int. Ed. 57, 44e45. https://doi.org/10.1002/ anie.201709032. } ri, M., Jo j } ri, K., Csizmadia, I.G., Viskolcz, B., 2011. Chemical Szo art, B., Izs ak, R., Szo evolution of biomolecule building blocks. Can thermodynamics explain the accumulation of glycine in the prebiotic ocean? Phys. Chem. Chem. Phys. 13, 7449. https://doi.org/10.1039/c0cp02687e. Varandas, A.J.C., 2018. Straightening the hierarchical staircase for basis set extrapolations: a low-cost approach to high-accuracy computational chemistry. Annu. Rev. Phys. Chem. 69, 177e203. https://doi.org/10.1146/annurev-physchem050317-021148. Vo, D.H., Nguyen, H.M., Vo, A.T., McAleer, M., 2019. CO2 emissions, energy consumption and economic growth. Econom. Inst. Res. Pap. Weitemeyer, S., Kleinhans, D., Vogt, T., Agert, C., 2015. Integration of Renewable Energy Sources in future power systems: the role of storage. Renew. Energy 75, 14e20. https://doi.org/10.1016/j.renene.2014.09.028. Xia, A., Zhu, X., Liao, Q., 2019. Hydrogen production from biological sources. In: Fuel Cells and Hydrogen Production. Springer New York, New York, NY, pp. 833e863. https://doi.org/10.1007/978-1-4939-7789-5_955.
Contents lists available at ScienceDirect
Journal of Cleaner Production journal homepage: www.elsevier.com/locate/jclepro
Renewable energy and raw materials e The thermodynamic support a k, Arp d Bence Palota s, Pe ter Mizsey*, Be la Viskolcz Rachid Hadjadj, Csaba Dea ros, H-3515, Miskolc, Hungary University of Miskolc, Miskolc-Egyetemva
a r t i c l e i n f o
a b s t r a c t
Article history: Received 22 January 2019 Received in revised form 22 August 2019 Accepted 28 August 2019 Available online 4 September 2019
The energy and raw material supplies are crucial issues in our societies. The possible solution of these issues can be coupled with the storage alternatives of renewable energy. The chemical way of energy storage can be quite different but we follow the Supplement of Natural Gas concept since this delivers a high storage capacity solution. The chemical way of energy storage is based on the carbon dioxide hydrogenation. It is in agreement with the theory of the circular economy so that the carbon emission is reduced with the concept of Carbon Capture and Utilization (CCU). In this work the reaction system of the carbon dioxide hydrogenation is studied thermodynamically applying the tool of quantum chemistry. The aim of the study is to support the carbon dioxide transformation alternatives of industrial scale, that is, the CCU. It is determined that the methane production has the highest thermodynamic efficiency where the methanol production is the second in the ranking. These thermodynamic efficiencies are 14.4% for methanol and 44.4% for methane. Both alternatives have, however, advantages since the methane can be introduced directly into the natural gas network and the methanol has the highest volumetric energy content. Both molecules can be transformed into different kind of raw materials, see e.g. methanol economy. At the selection, however, other, practical points of view should be also considered where industrial experiences and circumstances are to be also taken into account. Having recognized the need to deal with the reduction and utilization of carbon dioxide emission (CCU), the University of Miskolc established the “Environmental Carbon Dioxide Partnership”. It has several industrial partners having significant carbon dioxide emission and therefore experience in this issue. The experts of the partnership help to solve emission problems and the carbon dioxide utilization, based on the theoretical and practical results and experiences of the Partnership. This thermodynamic investigation supports the development of the Partnership to carry out the most efficient CCU method. © 2019 Elsevier Ltd. All rights reserved.
Handling editor: Prof. Jiri Jaromir Klemes Keywords: Carbon dioxide hydrogenation Methane Methanol Thermodynamic study Energy storage
1. Introduction The harmful effect of the carbon dioxide emitted into the atmosphere is a well-known issue (Vo et al., 2019). To answer the challenges of environmental protection, University of Miskolc, Hungary, established a network called “Environmental Carbon dioxide Partnership” aiming to contribute to the global warming problem (Chandler, 2018), storage of renewable energies (Banerjee et al., 2019), production of materials on renewable basis (Islam et al., 2018). To complete these goals the carbon dioxide can be the key
* Corresponding author. E-mail address: [email protected] (P. Mizsey). https://doi.org/10.1016/j.jclepro.2019.118221 0959-6526/© 2019 Elsevier Ltd. All rights reserved.
molecule, the so-called platform molecule that is used for the solution of these challenges. The carbon dioxide can be chemically converted into different molecules for the sake of energy storage like formic acid, formic aldehyde, methanol or methane (Leonzio, 2018). These molecules can be used not only for the storage and production of energy but to produce other chemicals on renewable basis (Markewitz et al., 2012). The three goals of the Partnership are associated with the energy and energy production. Energy, the basic element that every nation need, is now a debated subject pushing the scientific world to look for its sustainable forms considering its declining resources combined with the increasing demand as well as the environmental impact (Matthews et al., 2018). It is important to note that the large capacity energy storage is badly needed for the extensive use of renewable electricity. The reason is that the renewable electricity production highly depends
2
R. Hadjadj et al. / Journal of Cleaner Production 241 (2019) 118221
on the weather, that is, its production is fluctuating. Unfortunately, the electricity consumption is also fluctuating but in different frequency. Therefore, the storage of the renewable electricity should be solved (Weitemeyer et al., 2015). The high capacity of energy storage can be completed with the Substitute Natural Gas (SNG) (Specht et al., 2009). Storing energy in chemical bonds by recycling of carbon dioxide via hydrogenative reductions can be the most convenient way of storage for the renewable electrical energy, this will for sure contribute in decreasing the CO2 emission (Olah et al., 2006). The hydrogen is obtained from electrolysis working with renewable electrical energy (Steinlechner and Junge, 2018). The reduction of CO2 could be a key issue to the energy storage while two goals could be reached: namely the reduction of the CO2 emission as well as the long term efficient H2 storage. The two attractive compounds to be produced from CO2 are methanol and methane because of their high energy content and also because of their ability to be reintroduced into other chemical processes as feedstock to produce more advanced chemical compounds (Centi et al., 2013). CO2 has to be collected from several sources such as the industrial flue and other gases, biochemical processes or from the remineralization of organic carbon from groundwater (Pain et al., 2019). To transfer the CO2, hydrogen needed. It can have also many possible sources such as the electrolysis of water, steam reforming of natural gas, or even biological sources (Xia et al., 2019). Between the different methanol production processes CO2 can be reduced directly, or converted first into synthesis gas in a reverse gas shift (RWGS) reaction (Samimi et al., 2019), and methane can be reached by one last step. Last decades the CO2 hydrogenation to methanol has been widely studied, large variety of solid catalysts have been developed and tested (Sheldon, 2017), nevertheless the reduction mechanism is still a debated subject and many alternatives are proposed (Hus et al., 2017). In our paper we investigate all the possible structures involved in the uncatalyzed methanol and methane reactions of a given ratio of CO2 and H2 and compare the thermodynamics of stable species and all the energy barriers using computational chemistry methods which are trusted to be highly accurate nowadays (Varandas, 2018) in order to construct a network of CO2 hydrogenation get a better understanding of the it's reduction possibilities to methanol and methane. Such a thermodynamic analysis can support our Partnership to make the decision which reduced form of the carbon dioxide has the highest efficiency. 2. Theory The reduction of CO2 could be a key issue of the energy storage while two goals could be reached: namely the reduction of the CO2 emission as well as the long term efficient H2 storage obtained from electrolysis using renewable electricity (Kar et al., 2019). In our paper we compare the thermodynamics of stable species of a given combination of CO2 and H2. Fig. 1 shows the possible oxidation states of CO2. To achieve the total reduction of CO2 we create a hypothetical system, with 1:4 M ration of CO2: H2. We address a thermodynamic question: which oxidation state would be the most effective energy storage, that is, the CCU. To answer it, we have created the cyclic molecular reduction mechanism of CO2. The reduction stages of CO2 are constrained by four isolable products, HCOOH, H2CO, CH3OH and CH4(Ruff and Csizmadia, 1994). We aim to know what are all the other possible isolable (stable) products which can build molecular complexes described by the
Fig. 1. RED-OX state of a single carbon atom.
total CH8O2 stoichiometry. The CH8O2 stoichiometry corresponds to CO2 þ 4H2 and/or CH4 þ 2H2O. This elementary stoichiometry is used to characterize all the intermediate species which can play a } ri et al., 2011). role in the CO2 reduction reaction (Szo To compare the relative importance of the structures generated and optimized Using the MOLGEN 5.0 software (Benecke et al., 1997), the relative Gibbs free energy was plotted against the relative entropies. The thermodynamic properties of all the possible intermediate molecular complexes have been calculated using the Gaussian 09 program package (Frisch et al., 2013). The reference state is the starting molecular combination of the reactants (CO2 þ 4 H2), it is defined with a red dot in the Fig. 2. The structures were divided into three clusters: High energy cluster (above the red line; DGor > 300 kJ/mol). Energetically favoured cluster (blow the reference dashed line; DGor < 0 kJ/mol). Energetically available cluster (between the red and the reference line). To construct the molecular network, we considered the middle and low energy cluster of molecules. The [CH4þH2O2þH2] species were not included in the reaction network, while the stability of the peroxide bond leads to OH free radicals. The proposed network summarizes many routes leading to methanol and methane formation considering the molecular complexes (having a relative Gibbs free energy less than 300 kJ/mol only) is shown in Fig. 3. An extended network including all the molecular complexes is provided in the supplementary section. The first intermediate of CO2 hydrogenation is the formic acid (B). After that, four reactions can occur. a) the direct hydrogenation of formic acid leads to formaldehyde and water (D) b) the methanediol H2C(OH)2 (H) produced by H2 addition. c) the water elimination produces CO þ water (C). It is unique, while the ratio of the equilibrium of these products could be increase with the temperature.
R. Hadjadj et al. / Journal of Cleaner Production 241 (2019) 118221
3
Fig. 2. Thermodynamic functions of the CO2 reduction mechanism. Relative free energy DGor as function of the entropy DSor of molecular composition obtained by combinatorial tools. The triplet states are signed by tr.
Fig. 3. Methanol and methane production network through CO2 hydrogenation.
d) a hydrogen shifting in the formic acid molecule can form C(OH)2 (G)e relative stable triplet state, which also can be hydrogenated to methanediol. All these four channels can lead to the formaldehyde formation, however, it can also be formed by CO hydrogenation, hydrogen
shifting in the HCOH molecule, water subtraction in the methandiol. The hydrogenation of formaldehyde (D), methandiol (H) and the HCOH (I) produce methanol (E). The toward hydrogenation (reduction) of methanol is the last step to reach methane (F). The classical combustion of methane can close the thermodynamic cycle.
4
R. Hadjadj et al. / Journal of Cleaner Production 241 (2019) 118221
The longest route to reach methanol and then methane is the following: CO2-TSAB-HCOOH-TSBG-C(OH)2-TSGH-H2C(OH)2-TSHI-HCOH-TSIDH2C]O-TSDE-CH3OH-TSEF-CH4. The shortest route to reach methanol and then methane is the following: CO2-TSAB-HCOOH-TSBD-H2C]O-TSDE-CH3OH-TSEF-CH4.
3. Modelling The overall potential energy surface (PES), was constructed from the individual relative energies of the structures obtained by combinatorial chemistry. All molecular structures of the network were optimized and characterized by first order computation. Thermodynamic functions like internal energy, enthalpy and entropy based on the frequency calculation of every individual structure are listed in Tables 1 and 2. To describe the multidimensional (PES) CO2 þ 4 H2 was selected as a reference for the calculations. The relative Gibbs free energy of an intermediate (X) will be calculated as follows:
DGor ¼ DGðXÞ DGref
Table 2 Gibbs Free Energy, relative enthalpy and entropy of the stable structures and the transition states involved in the network obtained by W1BD level of theory. Code
Particules
DGor
DHor
kJ/mol A B C D E F G H I TSAB TSBC TSCD TSDE TSEF TSBH TSBG TSGH TSHD TSHI TSID TSIE TSHE TSGI TSBD TSGC
CO2þ4H2 HCOOHþ3H2 COþH2Oþ3H2 H2COþH2Oþ2H2 CH3OHþH2OþH2 CH4þ2H2O C(OH)2þ3H2 CH2(OH)2þ2H2 HCOHþH2Oþ2H2 A/B B/C C/D D/E E/F B/H B/G G/H H/D H/I I/D I/E H/E G/I B/D G/C
0 42.14 27.7 58.22 1.62 125.1 214.61 59.9 275.93 334.82 322.64 400.66 379.21 407.18 405.60 359.65 413.22 251.20 357.97 404.19 359.06 447.74 529.02 385.91 355.00
S J/mol K
0 13.65 40.27 39.94 54.49 170.04 186.34 3.47 257.86 306.20 297.84 383.07 324.86 321.41 341.09 331.98 350.92 186.88 297.89 386.36 305.89 353.81 468.55 322.70 327.66
734.73 639.16 776.88 673.41 557.40 583.99 639.89 522.21 674.11 638.74 651.54 675.73 552.42 447.05 518.38 641.89 525.75 519.00 533.21 674.92 556.41 419.67 531.92 522.72 643.04
(1)
The relative enthalpy and entropy were derived analogically.
species.
3.1. Structure generation 3.2. Quantum chemical calculations Considering the nuclei and chemical bonds as the nodes and the edges of a graph, respectively helps to deduct and enumerate all the molecules corresponding to our stoichiometry (CH8O2) from a graph theory (Benecke et al., 1997). A certain number of atoms with a limited number of different valences defines the number of constitutional isomers (Gugisch et al., 2009). All possible stoichiometric isomers of CH8O2 are generated by allowing carbon to form 2 or 4 chemical bonds, hydrogen and oxygen to form 1 and 2 chemical bonds, respectively, except in the case of H2OeO. This graph representation is extended to three dimensions by the means of the atom type specific geometric parameter set obtained from the simplified MM2 force field. By using this procedure, a number of 27 three dimensional molecular configurations can be generated by the Molgen 5.0 program (Benecke et al., 1997). These configurations are used as initial structures in the search for local minima on the multidimensional potential energy surface for all the
All structures generated by graph theory are optimized with the MP2 method (Li and Frisch, 2006) under the aug-cc-pVTZ (Papajak et al., 2011) basis set and then, the outputs are submitted for single point calculations using the CCSD(T) (Bartlett and Purvis, 1978) method under cc-pVTZ, cc-pVQZ, cc-pV5Z (Dunning, 1989) and this in order to calculate all the thermochemistry using the FellerHelgaker extrapolation (Feller, 1992; Helgaker et al., 1998) which is renowned for its accurate results. Additionally, the W1BD (Brueckner Doubles W1) composite method (Barnes et al., 2009) also has been selected to calculate all of the species. The W1BD method is a composite method derived from the W1 (Weizmann-1) (Martin and Oliveira, 1999), it uses the B3LYP density functional theory (DFT) method (Becke, 1993) for geometry optimization (Pulay et al., 1979) and frequencies calculation (Andersson and Uvdal, 2005) and steps further with coupled
Table 1 Heat of formation of 10 optimized structures calculated at CCSD(T)/cc-pV (Q,5)Z//MP2/aug-cc-pVTZ extrapolation, W1BD method and compared to the experimental values from the literature. All enthalpy and deviation values are in kJ/mol. Species
Calculation methods CCSD(T) W1BD
Experiment
Ref.
Absolut Deviation CCSD(T) W1BD
HCOOH CO CH2 CO2 H2CO CH3OH CH4 H2O H2O2 H3COOH
373.62 106.81 430.42 388.14 107.25 202.04 72.65 244.70 137.69 128.07
378.80 110.53 428.80 393.51 108.70 201.00 74.60 241.81 135.77 131.00
McGlashan (2004) (Franck et al., 1990) Ruscic et al. (2005) (Franck et al., 1990) McGlashan (2004) McGlashan (2004) McGlashan (2004) Ruscic et al. (2006) Ruscic et al. (2006) (NIST Chemistry Webbook, n.d.) Average Max. dev.
5.18 3.72 1.62 5.37 1.45 1.04 1.95 2.89 1.92 2.93 2.81 ± 1.53 5.37
381.11 110.17 428.76 394.67 110.59 205.11 76.43 244.31 134.38 130.50
2.31 0.36 0.04 1.16 1.89 4.11 1.83 2.50 1.39 0.50 1.61 ± 1.21 4.10
R. Hadjadj et al. / Journal of Cleaner Production 241 (2019) 118221
cluster calculations for the thermochemistry part. The BD algorithm is employed in the W1BD method which involves macro iterations to update the orbitals, where in each macro iteration involves an integral transformation and a CCD calculation (Barnes et al., 2009). To estimate the accuracy of the theoretical level and to select appropriate method for our system, we calculate the heat of formation of 10 optimized structures by CCSD(T) extrapolated and W1BD methods. Heat of formations are compared to the experimental values from the literature, deviations and references are listed in Table 1. The W1BD method is selected for further calculations. A network involving the optimized species for the uncatalyzed hydrogenation of CO2 to methanol and methane is proposed (Fig. 3). Beside the stable species all transitions states are also characterized by W1BD level of theory, and the potential energy surface (PES) has been constructed (Fig. 4). The transitions states are also verified by normal coordinate analysis and IRC calculations. All the calculations are carried out by Gaussian 09 software package (Frisch et al., 2013).
4. Results 4.1. Analysis of the optimization results The Fig. 2 shows well separated species regarding to the number of molecules constituting the complex. All thermodynamic information and structural data are available in the Supplementary Table 1. The reference level of the CO2 þ 4H2 is selected. We decide to consider the complexes having a relative Gibbs free energy inferior to 300 kJ/mol. Only the methanol and methane complexes have lower free energy compared to the reference. Both
5
complex has significant lower entropy compared to the reference. This total entropy lowering could be hindered by the positive influence of the temperature on the equilibrium. It is important to note that CO formation (third most stable complex) has an entropy increasing by 40 kJ/mol K. It would be a preferred way of reduction by increasing the temperature. This complex without water could be referred to the classical syngas and can open different catalytical reduction way. Complexes of all other stable oxidation state (from Fig. 1) of carbon atom can be find in 60 kJ/mol relative free energy range. The thermodynamic properties of the optimized structures and the transition states between local minima are summarized in Table 2. The letter code of the elements of molecular network also listed in Table 2. The relative Gibbs free energy, relative enthalpy and entropy values are listed in the Table 2. Table 2 is divided into two parts, the first part shows the thermodynamic properties of the stable intermediate molecular complexes related with the energetically available cluster. The second part contains the activation free energy, activation enthalpies as well as the absolute entropy of the transition states (TSab), were a and b refers to the reactants and the products corresponding to the Fig. 3. Storing energy would be possible only in exothermic reactions, in other words, in the case of products having a negative reaction enthalpy. Although the methanediol (H) corresponds to a local minima in the potential energy surface (PES) in Fig. 4, it is a nonisolable product with an almost thermoneutral properties. Only two products for energy storage are available: methanol (E) and methane (F), with respectively, 55 and 170 kJ/mol. The CO2 reduction can lead in many different routes to E and F as shown in Fig. 3. The most energy efficient route is highlighted in red in the Fig. 4. To take place, the complete energy storage content of
Fig. 4. Potential Energy Surface (PES) of the uncatalyzed hydrogenation of CO2 to methanol and methane calculated under W1BD level of theory plotted against the reaction coordinates with a highlighted energetically favored route.
6
R. Hadjadj et al. / Journal of Cleaner Production 241 (2019) 118221
the reactants should reach the highest energy of the most energy efficient route. This is corresponding to the highest activation energy of the reaction path DH max TS ; the system needs to achieve this energy to overcome the product site. The theoretical efficiency can be defined by the ratio of the stored enthalpy DHor and the invested enthalpy.
h¼
o D H r
DHmax TS
(2)
5. Discussion The DGor values of every single transition state and optimized structure of the methanol and methane production network shown in the Fig. 3 are plotted in Fig. 4. The Fig. 4 shows the Potential Energy Surface (PES) of the uncatalyzed hydrogenation of CO2 to methanol and methane calculated under W1BD level of theory were all the reaction steps and energy barriers to overcome in order to transform CO2 to methanol and methane are visible. The goal of this plot is to select the lowest reaction path leading to the products (shown in red in the Figure), and the highest energy barrier will correspond to the energy needed to cross over all the barriers to store energy. The highest activation enthalpy is TSCD¼383.07 kJ/mol. All free energy values of the transition states are in the range of [250e530] kJ/mol, and the lowest reaction pathway for methanol and methane production is: Carbon dioxide (A) - formic acid (B) e carbon monoxide (C) e formaldehyde (D) e methanol (E) e methane (F). The relative Gibbs free energies of the latter pathway are reported in the Table 2. We assume the theoretical efficiency of the energy storage can be estimated based on the computed thermodynamic functions (eq. (2)). The stored heat (DH or ) is compared with the highest enthalpy of the corresponding reaction path. We can conclude that the theoretical efficiencies of methanol and methane formation are hðEÞ ¼ 14.4% (enthalpy of methanol (E) and TSCD) and hðFÞ ¼ 44.4% (enthalpy of methane (F) and TSCD), respectively. We also conclude from the Fig. 4 that in order to increase the efficiency of the energy storage, catalytic reactions are needed. Nevertheless, the case of CO production (C) can be the key intermediate: while its formation can be slightly increased with temperature. On the other hand, it allows a different entrance to the network, namely the classical syngas reaction (Neto et al., 2019). 6. Conclusions The high capacity storage of the renewable electrical energy can be completed with the Substitute Natural Gas (SNG) alternative. Actually, the SNG alternative is the chemical bounding of hydrogen obtained from electrolysis using renewable electricity and the reduction of the carbon dioxide emission. However, the reduction of carbon dioxide has several reaction steps and intermediate products, and it is not clear witch reduction step, that is, hydrogenated form of carbon dioxide has the highest efficiency. The theoretical efficiencies of methanol and methane formation are 14.4% (enthalpy of methanol (E) and TSCD) and 44.4% (enthalpy of methane (F) and TSCD), respectively. The result indicates that the conversion of carbon dioxide to methane has the highest thermodynamic efficiency. The efficiencies can be and should be increased with catalysis and the selection of the proper catalyst has a paramount importance. Our thermodynamic analysis and modelling prove that the
methane production has the highest thermodynamic efficiency whereas the methanol is the second in the row. At the selection of the right degree of hydrogenation, that is, which molecule should be used for the electrical energy storage, other points of views have to be also considered, e.g. the methane can be introduced directly into the existing natural gas grid but the methanol has higher volumetric energy content. On the other hand, the transport of the liquid product is cheaper and easier. The chemical transformation of both possible energy carriers can be transformed into different raw materials originated from renewables. Our “Environmental Carbon Dioxide Partnership” with several industrial partners definitely needs such theoretical support but the final decision can be made with the consideration of local industrial economic issues, as well. Acknowledgments This research was supported by the OTKA112169, OTKA128543 projects and the European Union and the Hungarian State, cofinanced by the European Regional Development Fund in the framework of the GINOP-2.3.4-15-2016-00004 project, aimed to promote the cooperation between the higher education and the industry. Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi.org/10.1016/j.jclepro.2019.118221. References Andersson, M.P., Uvdal, P., 2005. New scale factors for harmonic vibrational frequencies using the B3LYP density functional method with the triple-z basis set 6-311þG(d,p). J. Phys. Chem. A 109, 2937e2941. https://doi.org/10.1021/ jp045733a. Banerjee, J., Dutta, K., Rana, D., 2019. Carbon Nanomaterials in Renewable Energy Production and Storage Applications. Springer, Cham, pp. 51e104. https://doi. org/10.1007/978-3-030-04474-9_2. Barnes, E.C., Petersson, G.A., Montgomery, J.A., Frisch, M.J., Martin, J.M.L., 2009. Unrestricted coupled cluster and Brueckner Doubles variations of W1 theory. J. Chem. Theory Comput. 5, 2687e2693. https://doi.org/10.1021/ct900260g. Bartlett, R.J., Purvis, G.D., 1978. Many-body perturbation theory, coupled-pair manyelectron theory, and the importance of quadruple excitations for the correlation problem. Int. J. Quantum Chem. 14, 561e581. https://doi.org/10.1002/qua. 560140504. Becke, A.D., 1993. Density-functional thermochemistry. III. The role of exact exchange. J. Chem. Phys. 98, 5648e5652. https://doi.org/10.1063/1.464913. Benecke, C., Gruer, T., Kerber, A., Laue, $ R., Wieland, T., 1997. MOLecular structure GENeration with MOLGEN, new features and future developments. Fresenius J. Anal. Chem. 359, 23e32. Centi, G., Quadrelli, E.A., Perathoner, S., 2013. Catalysis for CO2 conversion: a key technology for rapid introduction of renewable energy in the value chain of chemical industries. Energy Environ. Sci. 6, 1711. https://doi.org/10.1039/ c3ee00056g. Chandler, W., 2018. Energy and Environment in the Transition Economies. Routledge. https://doi.org/10.4324/9780429500817. Dunning, T.H., 1989. Gaussian basis sets for use in correlated molecular calculations. I. The atoms boron through neon and hydrogen. J. Chem. Phys. 90, 1007e1023. https://doi.org/10.1063/1.456153. Feller, D., 1992. Application of systematic sequences of wave functions to the water dimer. J. Chem. Phys. 96, 6104e6114. https://doi.org/10.1063/1.462652. Franck, E.U., Cox, J.D., Wagman, D.D., Medvedev, V.A., 1990. Codata - key Values for Thermodynamics, aus der Reihe: CODATA, Series on Thermodynamic Properties. Hemisphere Publishing Corporation, New York, Washington, Philadelphia, London 1989. Berichte der Bunsengesellschaft für physikalische Chemie 94, 93e93. https://doi.org/10.1002/bbpc.19900940121. Frisch, M.J., Trucks, G.W., Schlegel, H.B., Scuseria, G.E., Robb, M.A., Cheeseman, J.R., Scalmani, G., Barone, V., Petersson, G.A., Nakatsuji, H., Li, X., Caricato, M., Marenich, A.,V., Bloino, J., Janesko, B.G., Gomperts, R., Mennucci, B., Hratchian, H.P., Ortiz, J.V., Izmaylov, A.F., Sonnenberg, J.L., Williams-Young, D., Ding, F., Lipparini, F., Egidi, F., Goings, J., Peng, B., Petrone, A., Henderson, T., Ranasinghe, D., Zakrzewski, V.G., Gao, J., Rega, N., Zheng, G., Liang, W., Hada, M., Ehara, M., Toyota, K., Fukuda, R., Hasegawa, J., Ishida, M., Nakajima, T., Honda, Y., Kitao, O., Nakai, H., Vreven, T., Throssell, K., Montgomery Jr., J.A., Peralta, J.E.,
R. Hadjadj et al. / Journal of Cleaner Production 241 (2019) 118221 Ogliaro, F., Bearpark, M.J., Heyd, J.J., Brothers, E.N., Kudin, K.N., Staroverov, V.N., Keith, T.A., Kobayashi, R., Normand, J., Raghavachari, K., Rendell, A.P., Burant, J.C., Iyengar, S.S., Tomasi, J., Cossi, M., Millam, J.M., Klene, M., Adamo, C., Cammi, R., Ochterski, J.W., Martin, R.L., Morokuma, K., Farkas, O., Foresman, J.B., Fox, D.J., 2013. Gaussian 09, Revision E.01. Gaussian Inc., Wallingford CT. Gugisch, R., Kerber, A., Kohnert, A., Laue, R., Meringer, M., Rucker, C., Wassermann, A., 2009. MOLGEN 5.0 reference guide. https://doi.org/10.13140/ RG.2.2.11192.96007. Helgaker, T., Klopper, W., Koch, H., Noga, J., 1998. Basis-set convergence of correlated calculations on water. J. Chem. Phys. 106, 9639. https://doi.org/10.1063/1. 473863. Hus, M., Dasireddy, V.D.B.C., Strah Stefan ci c, N., Likozar, B., 2017. Mechanism, kinetics and thermodynamics of carbon dioxide hydrogenation to methanol on Cu/ZnAl2O4 spinel-type heterogeneous catalysts. Appl. Catal. B Environ. 207, 267e278. https://doi.org/10.1016/J.APCATB.2017.01.077. Islam, M.T., Huda, N., Abdullah, A.B., Saidur, R., 2018. A comprehensive review of state-of-the-art concentrating solar power (CSP) technologies: current status and research trends. Renew. Sustain. Energy Rev. 91, 987e1018. https://doi.org/ 10.1016/j.rser.2018.04.097. Kar, S., Sen, R., Kothandaraman, J., Goeppert, A., Chowdhury, R., Munoz, S.B., Haiges, R., Prakash, G.K.S., 2019. Mechanistic insights into Ruthenium-Pincercatalyzed amine-assisted homogeneous hydrogenation of CO 2 to methanol. J. Am. Chem. Soc. 141, 3160e3170. https://doi.org/10.1021/jacs.8b12763. Leonzio, G., 2018. State of art and perspectives about the production of methanol, dimethyl ether and syngas by carbon dioxide hydrogenation. J. CO2 Util. 27, 326e354. https://doi.org/10.1016/j.jcou.2018.08.005. Li, X., Frisch, M.J., 2006. Energy-represented direct inversion in the iterative subspace within a hybrid geometry optimization method. J. Chem. Theory Comput. 2, 835e839. https://doi.org/10.1021/ct050275a. Martin, J.M.L., Oliveira, G. de, 1999. Towards standard methods for benchmark quality ab initio thermochemistrydW1 and W2 theory. J. Chem. Phys. 111, 1843. https://doi.org/10.1063/1.479454. Matthews, H.D., Zickfeld, K., Knutti, R., Allen, M.R., 2018. Focus on cumulative emissions, global carbon budgets and the implications for climate mitigation targets. Environ. Res. Lett. 13, 010201. https://doi.org/10.1088/1748-9326/ aa98c9. Markewitz, P., Kuckshinrichs, W., Leitner, W., Linssen, J., Zapp, P., Bongartz, R., Schreiber, A., Müller, T., 2012. Worldwide innovations in the development of carbon capture technologies and the utilization of CO2. Energy Environ. Sci. 5, 7281e7305. McGlashan, M., 2004. Thermodynamic properties of individual substances. J. Chem. Thermodyn. Hemisphere Pub. Corp, New York https://doi.org/10.1016/00219614(80)90157-3. Neto, A.F.G., Marques, F.C., Amador, A.T., Ferreira, A.D.S., Neto, A.M.J.C., 2019. DFT and canonical ensemble investigations on the thermodynamic properties of Syngas and natural gas/Syngas mixtures. Renew. Energy 130, 495e509. https:// doi.org/10.1016/j.renene.2018.06.091. NIST Chemistry Webbook [WWW Document], n.d. https://doi.org/10.18434/ T4D303. Olah, G.A., Goeppert, A., Prakash, G.K.S., 2006. Beyond Oil and Gas: the Methanol
7
Economy, Focus on Catalysts. WILEY-VCH. https://doi.org/10.1016/S13514180(06)71901-8. Pain, A.J., Martin, J.B., Young, C.R., 2019. Sources and sinks of CO 2 and CH 4 in siliciclastic subterranean estuaries. Limnol. Oceanogr. https://doi.org/10.1002/lno. 11131. Papajak, E., Zheng, J., Xu, X., Leverentz, H.R., Truhlar, D.G., 2011. Perspectives on basis sets beautiful: seasonal plantings of diffuse basis functions. J. Chem. Theory Comput. 7, 3027e3034. https://doi.org/10.1021/ct200106a. Pulay, P., Fogarasi, G., Pang, F., Boggs, J.E., 1979. Systematic ab initio gradient calculation of molecular geometries, force constants, and dipole moment derivatives. J. Am. Chem. Soc. 101, 2550e2560. https://doi.org/10.1021/ ja00504a009. Ruff, F., Csizmadia, I.G., 1994. Organic Reactions: Equilibria, Kinetics, and Mechanism. Elsevier, Amsterdam. sza r, A.G., Demaison, J., Janoschek, R., Ruscic, B., Boggs, J.E., Burcat, A., Csa Martin, J.M.L., Morton, M.L., Rossi, M.J., Stanton, J.F., Szalay, P.G., rces, T., 2005. IUPAC critical evaluation of Westmoreland, P.R., Zabel, F., Be thermochemical properties of selected radicals. part I. J. Phys. Chem. Ref. Data 34, 573e656. https://doi.org/10.1063/1.1724828. Ruscic, B., Pinzon, R.E., Morton, M.L., Srinivasan, N.K., Su, M.-C., James, W., Sutherland, A., Michael, J.V., 2006. Active thermochemical tables: accurate enthalpy of formation of hydroperoxyl radical, HO2y. https://doi.org/10.1021/ JP056311J. Samimi, F., Hamedi, N., Rahimpour, M.R., 2019. Green methanol production process from indirect CO2 conversion: RWGS reactor versus RWGS membrane reactor. J. Environ. Chem. Eng. 7, 102813. https://doi.org/10.1016/j.jece.2018.102813. Sheldon, D., 2017. Methanol production - a technical history. Johnson Matthey Technol. Rev. 61, 172e182. https://doi.org/10.1595/205651317X695622. Specht, M., Brellochs, J., Frick, V., Stürmer, B., Zuberbühler, U., Sterner, M., Waldstein, G., 2009. Storage of Renewable Energy in the Natural Gas Grid. FVEE/ AEE Topics, pp. 69e78 (2009). Steinlechner, C., Junge, H., 2018. Renewable methane generation from carbon dioxide and sunlight. Angew. Chem. Int. Ed. 57, 44e45. https://doi.org/10.1002/ anie.201709032. } ri, M., Jo j } ri, K., Csizmadia, I.G., Viskolcz, B., 2011. Chemical Szo art, B., Izs ak, R., Szo evolution of biomolecule building blocks. Can thermodynamics explain the accumulation of glycine in the prebiotic ocean? Phys. Chem. Chem. Phys. 13, 7449. https://doi.org/10.1039/c0cp02687e. Varandas, A.J.C., 2018. Straightening the hierarchical staircase for basis set extrapolations: a low-cost approach to high-accuracy computational chemistry. Annu. Rev. Phys. Chem. 69, 177e203. https://doi.org/10.1146/annurev-physchem050317-021148. Vo, D.H., Nguyen, H.M., Vo, A.T., McAleer, M., 2019. CO2 emissions, energy consumption and economic growth. Econom. Inst. Res. Pap. Weitemeyer, S., Kleinhans, D., Vogt, T., Agert, C., 2015. Integration of Renewable Energy Sources in future power systems: the role of storage. Renew. Energy 75, 14e20. https://doi.org/10.1016/j.renene.2014.09.028. Xia, A., Zhu, X., Liao, Q., 2019. Hydrogen production from biological sources. In: Fuel Cells and Hydrogen Production. Springer New York, New York, NY, pp. 833e863. https://doi.org/10.1007/978-1-4939-7789-5_955.