Aftertreatment DeNOx Systems for Future Light Duty Lean-Burned Emission Regulations

Future light duty vehicles in Europe and the United States are required to be certified, owing to progressively more and more stringent regulations [...]This research was funded by the Basque Government (Project IT1297-19)

Simulation-based optimization of cycle timing for CO2 capture and hydrogenation with dual function catalyst

[EN] CO2 methanation could play a significant role in the future energy system. The excess of renewable electric energy can be transformed into storable methane to balance the energy demand when required. Moreover, the CO2 methanation can be performed alternating steps of CO2 storage and reduction, avoiding expensive CO2 purification steps. In this work, we will use a previously developed and validated model to optimize by simulation the CO2 adsorption and hydrogenation cycles timing (t(CO2)/t(H2)). The performance of the catalyst is quantified by the CO2 conversion (X-CO2, %), H-2 conversion (X-H2, %) and CH4 production (Y-CH4, mmol g(-1) cycle(-1)). Long adsorption and hydrogenation times result in high CH4 productions per cycle, however, low CO2 and H-2 conversion. Therefore, adsorption times close to the catalyst saturation (t(CO2)=60 s) and moderate hydrogenation times are preferable. To better select the optimal hydrogenation time, a new catalytic parameter is set, the average formation rate of CH4 (rCH(4), mu mol g(-1) s(-1)). The optimal hydrogenation time is set at 120 s. In addition to having a high average formation rate of CH4, t(CO2)/t(H2)= 60/120 cycle timing would allow to work with three identical beds in parallel, one in adsorption mode and two in regenerating mode. With the optimum cycle timing of 60/120 the production of CH4 results in 148 mu mol g(-1) cycle(-1) (1.2 mu mol CH4 g(-1) s(-1)) and a CO2 and H-2 conversion of 25% and 43%, respectivelyThe financial support from the Economy and Competitiveness Spanish Ministry (CTQ2015-67597-C2-1-R and PID2019-105960RB-C21) and the Basque Government (IT1297-19) is acknowledged. The authors thank for technical and human support provided by SGIker (UPV/EHU Advanced Research Facilities/ ERDF, EU). One of the authors (ABL) also acknowledges the Economy and Competitiveness Spanish Ministry for his PhD grant (BES-2016-077855)

Evaluation of Cu/SAPO-34 Catalysts Prepared by Solid-State and Liquid Ion-Exchange Methods for NOx Removal by NH3-SCR

Cu/SAPO-34 catalysts are prepared using solid-state ion exchange (SSIE) and liquid ion exchange (LIE). SSIE is conducted by calcining a physical mixture of H-SAPO-34 zeolite and CuO nanoparticles at elevated temperatures (500-800 degrees C). The conventional LIE method is conducted by exchanging Na-SAPO-34 with Cu(COOCH3)(2) aqueous solution with a final calcination step at 500 degrees C. Catalysts were fully characterized, focusing on Cu species identification. The NH3-SCR activity is evaluated for NOx removal. Cu/SAPO-34 catalysts synthesized by SSIE at 700 degrees C achieved an optimal reaction rate, which was correlated with a higher proportion of Cu2+ ions. The activation energies of Cu/SAPO-34 catalysts prepared by SSIE and LIE with varying copper loadings are 32-38 and 42-47 kJ mol(-1), respectively. The SSIE catalysts achieve higher turnover frequency than LIE catalysts for a similar copper content, which decreases on increasing the copper loading. These results provide evidence that Cu ions exchanged into the Cu/SAPO-34 catalysts synthesized by SSIE present higher activity than those prepared by LIE for NOx removal by NH3-SCR.The authors wish to acknowledge the financial support provided by the Spanish Economy and Competitiveness Ministry (CTQ2015-67597-2-1-R) and the Basque Government (IT657-013 and IT1297-19). Also, technical support by SGIker (UPV/EHU Advanced Research Facilities) is acknowledged. The assistance of Prof. Luis Lezama during EPR analysis and interpretation is gratefully acknowledged. U.D.-L.T. and M. U. want to acknowledge UPV/EHU and the Spanish Economy and Competitiveness for the postdoc (ESPDOC16/69) and Ph.D. (BFI-2010-330) research grants, respectively

Perovskite-Based Formulations as Rival Platinum Catalysts for NO_x Removal in Diesel Exhaust Aftertreatment

NOx removal is still a technological challenge in diesel engines. NOx storage and reduction (NSR), selective catalytic reduction (SCR), and combined NSR-SCR systems are the efficient approaches for diesel exhaust aftertreatment control. However, NSR and combined NSR-SCR technologies require high noble metal loadings, with low thermal stability and high cost. Recently, perovskites have gained special attention as an efficient alternative to substituting noble metals in heterogeneous catalysis. Up to date, few studies analyzed the application of perovskites in automobile catalytic converters. This chapter overviews recent research on development of novel perovskite-based catalysts as a component of single-NSR and hybrid NSR-SCR systems for NOx removal from diesel engine exhaust gases. Results in our laboratory are compared with similar work reported in the literature by other authors. Under realistic conditions, 0.5% Pd–30% La0.5Ba0.5CoO3/Al2O3 catalyst achieves NOx-to-N2 conversion higher than 92% when is coupled with an SCR catalyst placed downstream. The results show promise for a considerably higher thermal stability and lower cost diesel exhaust treatment system

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

[EN] The performance of nickel supported on lanthana-modified hydroxyapatite (HAP) catalysts is investigated in the CO2 methanation. The addition of La (1-6.6 wt%) leads to a surface enrichment following a sequential multilayer deposition model. Moreover, La addition systematically improves the dispersion of Ni particles and their reducibility, which in turn increases spectacularly the amounts of basic sites and their thermal stability. Such physicochemical changes impact positively on the activity of the catalysts in CO2 methanation. The estimated turnover frequency (TOF) suggest that the small Ni particles are the most efficient. The latter seem to provide a large density of very active defects on Ni-La2O3 interface. The optimized catalyst proves to be highly resistant to deactivation during 100 h time-on-stream (TOS). The samples were also assayed as dual function materials (DFMs) for CO2 adsorption and methanation. A scheme is proposed to describe the different steps involved in a CO2 adsorption/hydrogenation cycle.The financial support from the Science and Innovation Spanish Ministry (PID2019-105960RB-C21) and the Basque Government (IT1297-19) is acknowledged. The authors also acknowledge the technical support provided by SGIker (UPV/EHU Advanced Research Facilities/ERDF, EU)

Role of the different copper species on the activity of Cu/zeolite catalysts for SCR of NOx with NH3

The SCR of NOx with NH3 has been studied by using different Cu zeolite catalysts, prepared both with ZSM5 and BETA zeolite supports by ionic exchange or by impregnation. The catalysts were characterized by ICP-AES, N2 adsorption at −196 °C, XRD, TEM, XPS and H2-TPR. The catalysts characterization confirmed the presence of different Cu(II) species on all catalyst (CuO and Cu(II) exchanged on tetrahedral and octahedral positions of the zeolites framework). Clear evidences of Cu(I) or Cu(0) species were not obtained. CuO was more abundant in high copper-content catalysts and in ZSM5 catalysts, due to its lower ionic exchange capacity, while isolated Cu(II) ions are more abundant in low copper-content catalysts and in BETA catalysts. It was concluded that CuO catalyzes the oxidation of NO to NO2, and this favors the reduction of NOx at lower temperature (the NH3-NO2 reaction is faster than the NH3-NO reaction because NO2 is much more oxidizing than NO), whereas isolated Cu(II) ions maintain high NOx conversion at high temperatures.Financial support provided by the Spanish Ministry of Economy and Competitiveness (CTQ2012-30703), the Basque Government (IT-657-13) and the UPV/EHU (UFI11/39). One of the authors (UDLT) wants to acknowledge to the Basque Government for the PhD Research Grant (BFI-2010-330)

Tuning basicity of dual function materials widens operation temperature window for efficient CO2 adsorption and hydrogenation to CH4

Mitigation of CO2 emissions by integrated CO2 capture and utilization (ICCU) is challenging. This work focuses on widening operation temperature window of the hydrogenation of adsorbed CO2 to CH4. For this, a set of dual function materials (DFMs) 4%Ru-x%Na2CO3-y%CaO/gamma-Al2O3 are prepared. DFMs are deeply characterized by N-2 adsorption-desorption, XRD, H-2 chemisorption, TEM, H2-TPR and CO2-TPD. The catalytic behavior, in cycles of CO2 adsorption and hydrogenation to CH4, is evaluated and the temporal evolution of the concentration of re-actants and products is analyzed. The presence of both adsorbents in the DFMs improves ruthenium dispersion and the basicity is modulated with the Na2CO3/CaO ratio. Ru-8Na/8Ca improves methane production over the whole temperature window compared to DFMs based only on a unique adsorbent. The best results are assigned to the promotion of contact between the carbonates of medium strength with the metallic sites, which boost the CO2 adsorption and hydrogenation to CH4.The financial support from the Science and Innovation Spanish Ministry (PID2019–105960RB-C21) and the Basque Government (IT1297–19) is acknowledged. The authors thank for technical and human support provided by SGIker (UPV/EHU Advanced Research Facilities/ ERDF, EU)

Ca doping effect on the performance of La1−xCaxNiO3/CeO2-derived dual function materials for CO2 capture and hydrogenation to methane

CO2 valorization in form of synthetic natural gas is a convenient way to store large amounts of intermittent energy produced from renewable sources for long periods of time. Here reported research addresses the development of novel dual function materials (DFMs) for the utilization of CO2 from simulated post-combustion effluent by cyclic adsorption and in-situ methanation. These DFMs, obtained after the controlled reduction of 20% La1−xCaxNiO3/CeO2-type precursors (with x = 0–0.5), are widely characterized before and after catalytic tests. XRD diffractograms, H2-TPD experiments and STEM-EDS images denote that Ca-doping shows low influence on materials composition, slight detrimental effect on textural properties and no influence on Ni, La and Ce distribution. Meanwhile, the concentration of Ca-based species increases as long as La3+ substitution by Ca2+ increases, which leads to a progressively promotion of medium and, especially, strong basic sites concentration (CO2-TPD). As a result, the 20% La0.5Ca0.5NiO3/CeO2-derived DFM almost doubles (188.8 µmol g−1) the CH4 production of the 20% LaNiO3/CeO2-derived DFM (96.5 µmol g−1) at high temperatures. Indeed, this novel DFM enhances the methanation capacity of the conventional 15% Ni-15% CaO/Al2O3 DFM (143.0 µmol CH4 g−1), with higher stability during long-term experiments and adaptability under variable feed compositions, which further support the applicability of these novel DFMs. Thus, Ca doping emerges as an effective way of tailoring CO2 adsorption and in-situ hydrogenation to CH4 efficiency of 20% LaNiO3/CeO2-derived DFMs.Support for this study was provided by Proyecto PID2019-105960RB-C21 by MCIN/AEI /10.13039/501100011033 and the Basque Government (Project IT1509-2022). One of the authors (JAOC) acknowledges the Post-doctoral Research Grant (DOCREC20/49) provided by the University of the Basque Country (UPV/EHU)

How the presence of O2 and NOx influences the alternate cycles of CO2 adsorption and hydrogenation to CH4 on Ru-Na-Ca/Al2O3 dual function material

The Integrated Carbon Capture and Utilization-Methanation (ICCU-Methanation) requires a Dual Function Material (DFM), which firsts captures CO2 and then converts it into CH4, working in alternating adsorption and hydrogenation periods. The ICCU technology can be applied directly to a flue gas leaving a combustion chamber, which usually contains oxidizing species such as oxygen and nitrogen oxides. In this work, the stability of a DFM with composition 4%Ru-8%Na2CO3-8%CaO/Al2O3 is studied for the CO2 adsorption and hydrogenation in alternate cycles including O2 (0–10%) and NOx (0–2000 ppm) during the adsorption period. The variation of CO2 concentration in the usual range of flue gases (5–15%) has little influence on the global performance of the ICCU technology. However, the incorporation of O2 during the adsorption period decreases the production of CH4, and this decrease is even accentuated with increasing the oxygen concentration. This fact is mainly attributed to the oxidation of metal sites that limits the reduction behavior. On the other hand, the addition of NOx competes with CO2 for the basic adsorption sites, which slightly limits the amount of CO2 stored, and consequently the production of CH4. Helpfully, the proposed DFM presents high stability during the 207 cycles here performed, which corresponds to 34 h of time-on-stream, including different CO2 concentrations, and in the presence or absence of O2 and/or NOx. It is concluded that the proposed DFM formulation is competent for long-term operation in the presence of O2 and NOx during the CO2 adsorption period.The financial support from the Science and Innovation Spanish Ministry (PID2019-105960RB-C21) and the Basque Government (IT1509-22) is acknowledged. The authors thank for technical and human support provided by SGIker (UPV/EHU Advanced Research Facilities/ ERDF, EU)