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D. Wang et al., Simultaneously efficient adsorption and photocatalytic degradation of tetracycline by Fe-based MOFs. J. Colloid Interface Sci. 519, 273–284 (2018) A step increase in the CO 2 conversion and CH 4 selectivity was observed after the addition of the CaO basic promoter and the Ru second metal. Catalysts stable at 550 °C for 109 h due to the confinement effect. Ni and Ru synergy could reduce the activation energy for CO 2 methanation. This view has been adapted to work with screen readers and braille display, and is keyboard operated. ESC Switch, Steering Angle Sensor, ICM Relay Box (Sub Start Relay), Driver/Passenger Seat Warmer Control Module, Multifunction Switch (Remote Control) MIJANGOS F, VARONA F, VILLOTA N. Changes in solution color during phenol oxidation by Fenton reagent[J]. Environmental Science & Technology, 2006, 40(17): 5538-5543.
SANCHEZ C M, EXPOSITO E, CASADO J, et al. Goethite as a more effective iron dosage source for mineralization of organic pollutants by electro-Fenton process[J]. Electrochemistry Communications, 2007, 9(1): 19-24. doi: 10.1016/j.elecom.2006.08.023 D. Jiang et al., Facile synthesis of metal-organic framework films via in situ seeding of nanoparticles. Chem. Commun. 48(41), 4965–4967 (2012)K. Yang et al., Adsorption of volatile organic compounds by metal–organic frameworks MIL-101: influence of molecular size and shape. J. Hazard. Mater. 195, 124–131 (2011) Among all metals, Fe is by far the most studied element in bimetallic Ni-based catalysts for CO 2 methanation, since it is quite cheap and highly available and it exhibits a high solubility into the Ni lattice, favouring the formation of NiFe alloys [ 25]. It has been suggested, based on computational screening and catalytic experiments, that alumina supported and Ni-rich NiFe catalysts can improve the rate of CO 2 conversion, with the optimal Ni/(Ni + Fe) ratio being around 0.7–0.9 [ 40, 41]. Many more works have focused on NiFe alloys prepared with different methods and supported on various metal oxides [ 42]. Generally, the Ni/Fe ratio in the alloy and the reducibility of the metal-oxide support appear to be the most critical parameters that determine whether Fe will promote or suppress the catalyst’s CO 2 methanation activity.
Y. Zhang et al., Synthesis, characterization and photocatalytic properties of MIL-53 (Fe)–graphene hybrid materials. RSC Adv. 4(15), 7594–7600 (2014) H. Yamauchi et al., Performance of VOC abatement by thermal swing honeycomb rotor adsorbers. Ind. Eng. Chem. Res. 46(12), 4316–4322 (2007) You can also choose which timetables you would like to synchronise with your smartphone, tablet or calendar application.F. Wu et al., Copper nanoparticles embedded in metal–organic framework MIL-101 (Cr) as a high performance catalyst for reduction of aromatic nitro compounds. Inorg. Chem. Commun. 32, 5–8 (2013) There are many works that use a transition metal additive to enhance the activity of Ni-based catalysts [ 24]. These additives may include: V, Cr, Mn, Fe, Co, Y and Zr. Y and Zr, for example, are mostly used as dopants to modify the lattice of the metal oxide support and enhance its defect chemistry. Zr is used to stabilize the CeO 2 structure and enhance its oxygen vacancies population (i.e., oxygen storage capacity, OSC) [ 19], while Y can generate oxygen vacancies in ZrO 2-based supports [ 34, 35]. Mn mostly forms MnO x phases that increase the catalyst basicity and favour CO 2 chemisorption. All these modifications on the support’s properties can lead to an increase in CO 2 activation and, thus, Mn, Ce, Zr and Y are often regarded as efficient promoters in CO 2 methanation [ 19, 34, 35, 36]. The Grunwaldt group have been amongst the pioneers in the development of NiFe-based methanation catalysts and the elucidation of the role of Fe in the overall catalytic performance. Mutz et al. [ 26] prepared Ni 3Fe catalysts supported on Al 2O 3 via deposition–precipitation. The formed alloy nanoparticles exhibited a small size and high dispersion, and the NiFe-based catalyst proved to be more active and stable at lower temperatures compared to the monometallic Ni-based catalyst. The alloy catalyst was also proven to have a quite stable and robust performance after a 45 h time-on-stream operation under industrially oriented conditions [ 26]. No carbon deposition could be observed under various gas feeds for such catalysts using operando Raman spectroscopy [ 46]. Farsi et al. [ 47] investigated the CO 2 methanation kinetics on such Ni 3Fe methanation catalysts under technical operation conditions. CO selectivity over CH 4 was found to increase over shorter residence times and higher temperatures, while water concentration was indicated as the main inhibiting factor. The transition metals Fe and Co offer the obvious advantage of being cheap like Ni and their similar size and electronic properties allow for their intricate interaction with the Ni primary phase and their easy dissolution into the Ni lattice, forming NiFe and NiCo alloys, respectively. The composition of the formed alloy is of great importance, since only specific bimetallic combinations can lead to an optimal CO 2 methanation performance, especially in the case of NiFe alloys. The combined bimetallic catalysts can also offer additional advantages, such as higher stability, as well as resistance towards oxidation and sulphur poisoning.
Z.-Y. Gu et al., Adsorption and separation of xylene isomers and ethylbenzene on two Zn–terephthalate metal–organic frameworks. J. Phys. Chem. C 114(1), 311–316 (2009)Contrasting the results discussed until now [ 115, 117], there are a number of works that observe a deactivating effect of Rh presence in Ni-based catalysts. Mutz et al. [ 46] reported that a NiRh 0.1 catalyst supported on Al 2O 3 showed inferior CO 2 conversion to a similar monometallic Ni catalyst over the entire temperature range tested. Moreover, Mihet et al. [ 119] and Renda et al. [ 33] both showed that 0.5% Rh addition on a 10% Ni catalyst supported on Al 2O 3 and CeO 2, respectively, led to a drop in the CO 2 conversion and the overall CH 4 yield. A NiRh combined catalyst supported on Al 2O 3 and prepared Heyl et al. [ 120] was also less active for CO 2 methanation compared to a monometallic Rh catalyst. Y.-Y. Liu et al., Improved hydrogen storage in the modified metal-organic frameworks by hydrogen spillover effect. Int. J. Hydrog. Energy 32(16), 4005–4010 (2007)
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