Direct synthesis of DME from syngas on hybrid CuZnAl/ZSM-5 catalysts: New insights into the role of zeolite acidity

[EN] A commercial HZSM-5 zeolite (Si/Al = 16) was submitted to mild acid treatment and partial exchange of H+ by Na+ and Co2+ cations in order to produce samples with different amounts and strengths of Brensted and Lewis acid sites. The acid properties of the zeolites were determined by both FTIR of adsorbed pyridine and NH3-TPD. Then, hybrid catalysts comprising a CuO/ZnO/Al2O3 (CZA) methanol synthesis catalyst and the original and treated zeolites were prepared in order to analyze the impact of the zeolite acidity in the efficiency of the hybrids for the direct syngas-to-DME process. Independent methanol dehydration experiments on the bare zeolites and syngas-to-DME runs under methanol dehydration-controlled conditions were performed using hybrids with low zeolite concentration (CZA:zeolite mass ratio of 10:1) prepared by mixing the pre-pelletized CZA and zeolite components. The results revealed that both strong Bronsted and EFAL-related strong Lewis acid sites are the likely zeolite active sites for methanol dehydration at the typical syngas-to-DME temperature of 260 degrees C. Interestingly, we have found that different conclusions regarding the effect of zeolite acidity may be reached depending on the specific method used for preparing the hybrid catalysts when the overall syngas-to-DME process becomes controlled by the methanol synthesis rate on the Cu-based catalyst (i.e. using hybrids with a CZA:zeolite mass ratio of 2:1, that is, with an "excess" of acid sites). Thus, for hybrids prepared by mixing the pre-pelletized components, the same CO conversion and product selectivity (with values approaching those predicted by the thermodynamic equilibrium at the studied conditions) with no signs of deactivation during at least 50h on stream was attained irrespective of the zeolite acidity. By contrast, significant differences in catalyst stability were found for hybrids prepared by grinding the component powders prior to pelletizing. This fact points towards the occurrence of detrimental interactions between the CZA and zeolite components during the grinding preparation stage. The kind and extent of such detrimental interactions are tightly related to the properties (i.e. acidity, chemical composition) of the ZSM-5 zeolite. (C) 2011 Elsevier B.V. All rights reserved.Financial support by the Comisión Interministerial de Ciencia y Tecnología (CICYT) of Spain through the Project CTQ2010- 17988/PPQ is gratefully acknowledged. A. García-Trenco thanks the Ministerio de Ciencia e Innovación (MICINN) of Spain for a predoctoral (FPI) scholarship.García Trenco, A.; Martinez Feliu, A. (2012). Direct synthesis of DME from syngas on hybrid CuZnAl/ZSM-5 catalysts: New insights into the role of zeolite acidity. Applied Catalysis A General. 411:170-179. https://doi.org/10.1016/j.apcata.2011.10.036S17017941

The impact of support surface area on the SMSI decoration effect and catalytic performance for Fischer-Tropsch synthesis of Co-Ru/TiO2-anatase catalysts

[EN] A series of Co-Ru/TiO2 catalysts (10 wt% Co, 0.5 wt% Ru, nominal loadings) were prepared by impregnation of TiO2-anatase supports synthesized with different specific surface areas (Ti-L: 53 m2 /g, Ti-M: 117 m2 /g, and Ti-H: 148 m2 /g) by tuning the conditions of the hydrothermal synthesis and/or the calcination treatments. The most relevant physicochemical properties of supports and catalysts were determined by a set of techniques including ICP-OES, XRD, N2 physisorption, electron microscopy (FESEM, HAADF-STEM, HR-TEM), H2-TPR, H2 chemisorption, and IR-CO. Oxidized precursors were reduced in-reactor under flowing pure H2 at 400 °C for 10 h and evaluated for Fischer-Tropsch synthesis (FTS) in a fixed bed reactor at 220 °C, 2.0 MPa, and H2/CO molar ratio of 2. These catalysts exhibited the well-known strong metal-support interaction (SMSI) effect reported for TiO2 materials by which partially reduced TiOx species formed during the catalyst reduction step migrate and decorate the surface of the supported metal phases. The extent to which the SMSI effect occurred was found to increase with the surface area of the TiO2-anatase carrier, as supported by H2 chemisorption, TEM, and IR-CO surface titration experiments. As a consequence, the activity per total mass of cobalt or cobalt-time-yield (CTY) of the Co-Ru/TiO2 catalysts gradually declined with the increase in support surface area: Co-Ru/Ti-L > Co-Ru/ Ti-M > Co-Ru/Ti-H. The catalysts, however, displayed similar initial TOFs, implying a negligible influence of the SMSI effect on the initial intrinsic activity of the surface Co0 sites. The high surface area Co-Ru/Ti-H catalyst exhibiting the most pronounced SMSI also presented the lowest C5+ selectivity. This behavior was explained by considering the contribution of two effects: the lower resistance to the intraparticle diffusion of ¿-olefins when increasing the support surface area, as inferred from the olefin-to-paraffin ratios and the values of the diffusionrelated parameter ¿, and the reduction in size of the cobalt ensembles on the terraces of Co0 nanoparticles, connected to the extent of SMSI, on which chain growth events are favored.Financial support by the MINECO of Spain through the Severo Ochoa (SEV 2012-0267) and ENE2014-5761-R projects is gratefully acknowledged. The authors also thank the Microscopy Service of the Universitat Politecnica de Valencia for its assistance in microscopy characterization. F. Bertella (Science without Frontiers - Process no. 13705/13-0) thanks CAPES for a predoctoral fellowship.Bertella, F.; Concepción Heydorn, P.; Martinez Feliu, A. (2017). The impact of support surface area on the SMSI decoration effect and catalytic performance for Fischer-Tropsch synthesis of Co-Ru/TiO2-anatase catalysts. Catalysis Today. 296:170-180. https://doi.org/10.1016/j.cattod.2017.05.001S17018029

TiO2 polymorph dependent SMSI effect in Co-Ru/TiO2 catalysts and its relevance to Fischer-Tropsch synthesis

[EN] Pure anatase and rutile TiO2 samples were synthesized by thermal treatment of reverse microemulsions and applied as supports for preparing Ru-promoted Co catalysts (0.5 wt% Ru, 10 wt% Co). The catalysts were characterized by ICP-OES,XRD,Raman spectroscopy, N2 physisorption, H2-TPR, electronmicroscopy (FESEM, HAADF-STEM), H2 chemisorption,XPS, and in situ IR-CO after H2 reduction and reaction with syngas, and their catalytic performance for Fischer-Tropsch synthesis (FTS) studied at industrial conditions (220 ¿C, 2.0 MPa, H2/CO = 2). The two catalysts exhibited comparable mean Co particle sizes (5¿6 nm) as well as high and alike degrees of cobalt reduction (ca. 90%). The SMSI decoration effect arising during H2 reduction was much more pronounced for the anatase-supported catalyst resulting in lower cobalt-timeyield (CTY) compared to that supported on TiO2-rutile. In situ IR-CO under syngas conversion conditions showed equivalent cobalt surface reconstruction and nature of the surface Co0 sites for both catalysts in their working state, and revealed a partial reversibility of the SMSI effect during FTS by which a significant fraction of the decorated Co0 centers in the anatase-based catalyst was uncovered and became available for reaction. The implication of this effect on TOFs is discussed. The C5+ selectivity was higher for the rutile-based catalyst, although a clear impact of the SMSI effect on selectivities was not inferred from our results.Financial support by the MINECO of Spain through the Severo Ochoa project (SEV 2012-0267) is gratefully ackonowledged. The authors also thank the Microscopy Service of the Universitat Politecnica de Valencia for its assistance in microscopy characterization. F. Bertella (Science without Frontiers - Process no. 13705/13-0) thanks CAPES for a predoctoral fellowship.Bertella, F.; Concepción Heydorn, P.; Martinez Feliu, A. (2017). TiO2 polymorph dependent SMSI effect in Co-Ru/TiO2 catalysts and its relevance to Fischer-Tropsch synthesis. Catalysis Today. 289:181-191. https://doi.org/10.1016/j.cattod.2016.08.008S18119128

High-performing Ir- and Pt-containing catalysts based on mesoporous beta zeolite for the selective ring opening of decalin

[EN] Selective ring opening (SRO) of naphthenic molecules resulting from the hydrogenation of polyaromatics is a desirable catalytic route for upgrading low-quality diesel fractions such as hydrotreated light cycle oil (LCO) produced in catalytic crackers. In this work, catalysts based on either Ir or Pt (similar to 3 wt%) dispersed on a Cs+-exchanged mesoporous beta zeolite (beta-meso) obtained by controlled desilication of a commercial beta sample (beta-com, Si/Al = 18) with NaOH in the presence of a CTAB surfactant were prepared and evaluated for the SRO of decalin as a model reactant. In comparison to an equivalent Ir catalyst based on the commercial zeolite (Ir/Cs-beta-com), the Ir catalyst based on mesoporous beta (Ir/Cs-beta-meso) attained higher decalin conversions and yields of target ring opening products (C-10-alkylcycloalkanes, ROP, and C-10-alkanes or open chain decanes, OCD). An unprecedented maximum combined yield of ROP + OCD of 72.6 wt% was achieved over the Ir/Cs-beta-meso catalyst at 89.2% decalin conversion. The improved catalytic performance exhibited by the catalyst based on mesoporous beta zeolite can be mainly ascribed to an increased accessibility of decalin molecules to the active sites and to a faster diffusion of ring opening products, retarding their further conversion into unwanted lighter (C9-) hydrocarbons. On the other hand, the catalyst based on Pt dispersed on Cs-beta-meso was less active and achieved a lower maximum combined yield of ROP + OCD (59.6 wt% at 92.7% conversion) than its homologous catalyst based on Ir. However, compared to the Ir catalyst, less branched ROP and OCD isomers (hence, more desirable from the viewpoint of cetane) were formed on the Pt catalyst. The molecular structure of the main ROP and OCD isomers, as assessed by GC x GC, and the carbon number distribution of C9- products indicated that cleavage of C-C bonds on the Ir-based catalysts predominantly occurred at Ir centers via the (non-selective) dicarbene hydrogenolysis mechanism. Differently, both the hydrogenolysis (via the multiplet or selective mechanism) and the bifunctional (via carbocations) pathways contributed to the breaking of C-C bonds on the Pt-based mesoporous catalyst.M. A. Arribas and A. Martinez acknowledge the MINECO of Spain for financial support through the Severo Ochoa project (SEV2016-0683). N. Suarez and A. Moreno acknowledge Colciencias-Ecopetrol (project 1115-559-36523) and Universidad de Antioquia (Colombia) for financial support. N. Suarez acknowledges Colciencia-Ecopetrol and the Instituto de Tecnologia Quimica (ITQ). The authors are indebted to the Microscopy Service of the Universitat Politecnica de Valencia for its assistance in microscopy characterizationSuarez, N.; Arribas Viana, MDLD.; Moreno, A.; Martinez Feliu, A. (2020). High-performing Ir- and Pt-containing catalysts based on mesoporous beta zeolite for the selective ring opening of decalin. Catalysis Science & Technology. 10(4):1073-1085. https://doi.org/10.1039/c9cy01812cS1073108510

Nature of Active Nickel Sites and Initiation Mechanism for Ethylene Oligomerization on Heterogeneous Ni-beta Catalysts

[EN] Higher olefins produced via ethylene oligomerization are versatile commodity chemicals serving a vast range of industries with large global economic impact. Nickel aluminosilicates are promising candidates to replace the homogeneous catalysts employed in industrial ethylene oligomerization processes. The current poor understanding of the true nature of the active nickel centers and the nickel-mediated oligomerization mechanism in these materials, however, hampers the rational design of improved catalysts. Here we applied in situ time- and temperature-resolved FTIR spectroscopy with simultaneous MS analysis of products to disentangle these fundamental issues using nanocrystalline Ni-beta zeolite as catalyst. We elucidate that isolated Ni2+ cations grafted on acidic silanols are the most likely active species in the working catalysts rather than the generally accepted ion-exchanged nickel cations. On the basis of our results, a plausible initiation mechanism involving a nickel vinyl hydride intermediate from which chain propagation proceeds similarly to the Cossee-Arlman pathway is proposed.This work was supported by the MINECO of Spain through the Severo Ochoa Program for Centers of Excellence (SEV 2016-0683) and ENE2014-5761-R project. The authors extend their acknowledgement to the EU project OCMOL ("Oxidative Coupling of Methane followed by Oligomerization to Liquids", 7th Framework Programme, GA no. 228953)Moussa, S.; Concepción Heydorn, P.; Arribas Viana, MDLD.; Martinez Feliu, A. (2018). Nature of Active Nickel Sites and Initiation Mechanism for Ethylene Oligomerization on Heterogeneous Ni-beta Catalysts. ACS Catalysis. 8(5):3903-3912. https://doi.org/10.1021/acscatal.7b03970S390339128

Direct electrocatalytic CO2 reduction in a pressurized tubular protonic membrane reactor

[EN] Power-to-methane technology enables storage of renewable elec-tricity in chemical energy, which can be transported and converted us-ing existing infrastructure. The moderate energy efficiency of this pro-cess is associated with high reactor exothermicity and complex thermal integration. Proton-ceramic electrochemical cells (PCECs) enable ther-mal combination of methanation and electrochemically driven H2 steps via endothermic reactions, boosting energy efficiency and heat man-agement. Here, we report single-step methane production from CO2 in a tubular PCEC at 450 degrees C and less than 30 bar. The H2 reactant is sup-plied by electrochemical pumping of protons from H2 in the external chamber. The electrochemical cell consists of an -25-mm-thick electro-lyte (BaZr0.8Ce0.1Y0.1O3-8) supported on a BaZr0.8Ce0.1Y0.1O3-8/Ni com-posite acting as a methanation catalyst. The reaction was studied as a function of total pressure, H2/CO2 ratio, and current density, reaching CH4 yields greater than 99% above 20 bar. High pressure and a CO2- rich atmosphere ameliorated the electrochemical behavior because of higher electrolyte hydration and boosted electrode kinetics.This study has received European Union Horizon 2020 Research and Innovation funding under grant agreement 838077 (eCOCO2 project) and financial support from the Spanish Government (PID2022-139663OB-I00, PRE2019-090959, and CEX2021-001230-S funded by MCIN/AEI/10.13039/501100011033) and MCIN with funding from NextGenerationEU (PRTR-C17.I1) within the Planes Complementarios con CCAA (Area of Green Hydrogen and Energy) and was carried out in the CSIC Interdisciplinary Thematic Platform (PTI+) Transicion Energetica Sostenible+ (PTI-TRANSENER+). Support from Camilla Vigen (CoorsTek Membrane Sciences) with manufacture of tubular cells is gratefully acknowledged.Quina-García, I.; Almar-Liante, L.; Catalán-Martínez, D.; Dayaghi, AM.; Martinez Feliu, A.; Norby, T.; Escolástico Rozalén, S.... (2023). Direct electrocatalytic CO2 reduction in a pressurized tubular protonic membrane reactor. Chem Catalysis (Online). 3(10):1-17. https://doi.org/10.1016/j.checat.2023.10076611731

Direct conversion of methane to aromatics in a catalytic co-ionic membrane reactor

[EN] Nonoxidative methane dehydroaromatization (MDA: 6CH(4) C6H6 + 9H(2)) using shape-selective Mo/zeolite catalysts is a key technology for exploitation of stranded natural gas reserves by direct conversion into transportable liquids. However, this reaction faces two major issues: The one-pass conversion is limited by thermodynamics, and the catalyst deactivates quickly through kinetically favored formation of coke. We show that integration of an electrochemical BaZrO3-based membrane exhibiting both proton and oxide ion conductivity into an MDA reactor gives rise to high aromatic yields and improved catalyst stability. These effects originate from the simultaneous extraction of hydrogen and distributed injection of oxide ions along the reactor length. Further, we demonstrate that the electrochemical co-ionic membrane reactor enables high carbon efficiencies (up to 80%) that improve the technoeconomic process viability.This work was supported by the Research Council of Norway (grants 195912, 210418, 210765, and 219194) and the Spanish government (grants SEV-2012-0267 and ENE2014-57651). We thank the ALBA Synchrotron Light Laboratory for beam time provision. C.K. and P.K.V. have applied for a patent based on this work (PCT/EP2014/071697). Experimental data are available online at ftp://itqrepositorio.itq.upv.es/pub/.Hernández Morejudo, S.; Zanón González, R.; Escolástico Rozalén, S.; Yuste Tirados, I.; Malerod Fjeld, H.; Vestre, PK.; Coors, WG.... (2016). Direct conversion of methane to aromatics in a catalytic co-ionic membrane reactor. Science. 353(6299):563-566. https://doi.org/10.1126/science.aag0274S563566353629

The influence of zeolite surface-aluminum species on the deactivationof CuZnAl/zeolite hybrid catalysts for the direct DME synthesis

[EN] The influence of the nature and amount of zeolite-surface Al species on the deactivation behavior ofbifunctional CZA/zeolite hybrid catalysts during the direct DME synthesis (260◦C, 4.0 MPa) from syn-gas (66% H2, 30% CO, 4% CO2) has been studied. To this aim, a series of delaminated ITQ-2 zeolites hasbeen prepared by acid treatment and steaming of an Al-ITQ-2 (Si/Al = 12) sample as well as by impreg-nation of an all-silica Si-ITQ-2 sample with Al(NO3)3(aq.) and calcination, and used as the methanoldehydration function of the hybrids. When prepared by grinding, all the hybrid catalysts experienced aloss of activity with time during the syngas-to-DME reaction under conditions where the synthesis ofmethanol on the copper catalyst (CZA) controlled the overall DME synthesis rate. The decay was neitherrelated to changes in the properties of the Cu species (dispersion, Cu0surface area) nor to depositionof carbon species on the metallic function (as ascertained by TPO) but to a particular mode of deacti-vation of the CZA catalyst due to adverse interactions between the copper component and the zeolite.Interestingly, the extent of the deactivation was seen to increase linearly with a parameter ˇ, arbitrarilydefined as ˇ = Sext× [Al/(Si + Al)]surf× %EFAL/100, where Sextis the external surface area of the zeolite,[Al/(Si + Al)]surfis the relative Al surface concentration (from XPS), and %EFAL is the percentage of penta-and hexacoordinated extraframework Al species with respect to the total Al detected by27Al MAS NMR.The correlation suggests that EFAL species located at the surface contact between the CZA and zeoliteparticles were primarily responsible for this particular mode of deactivation of the copper catalyst. Wehypothesize that EFAL species could migrate to the CZA catalyst during DME synthesis through a water-assisted mechanism, modifying the interaction between Cu and ZnOxat the Cu ZnOxinterface where theactive copper sites are likely locatedFinancial support by the Comisión Interministerial de Ciencia y Tecnología (CICYT) of Spain through the Project CTQ2010-17988/PPQ is gratefully acknowledged. A. García-Trenco thanks the Ministerio de Economía y Competitividad (former Ministerio de Ciencia e Innovación) of Spain for a predoctoral (FPI) scholarship.García Trenco, A.; Martinez Feliu, A. (2014). The influence of zeolite surface-aluminum species on the deactivationof CuZnAl/zeolite hybrid catalysts for the direct DME synthesis. Catalysis Today. 227:144-153. https://doi.org/10.1016/j.cattod.2013.09.051S14415322

A simple an efficient approach to confine Cu/ZnO methanol synthesis catalysts in the ordered mesoporous SBA-15 silica

The ammonia-driving deposition-precipitation (ADP) method has been applied with the purpose of confining active Cu/ZnO methanol synthesis phases inside the pores of the ordered mesoporous SBA-15 silica. Thus, a series of CuZnx/SBA-15 catalysts with total (Cu + Zn) metal loading of 35 wt% and Cu/Zn mass ratios (x) of 0.5, 1, 2, 4, and 6, as well as a Zn-free Cu/SBA-15 sample, have been prepared. Additionally, a CuZn2/SBA-15 sample (Cu + Zn = 35 wt%, Cu/Zn = 2) prepared by impregnation and a coprecipitated Cu-ZnO-Al2O3 (CZA) catalyst have been prepared as reference. The materials have been characterized by ICP-OES, N2 physisorption, XRD, in situ H2-XRD, TEM, H2-TPR, and N2O chemisorption, and their methanol synthesis activities determined, after in situ H2 reduction, under realistic conditions (533 K, 4.0 MPa, syngas: 66%/30%CO/4%CO2). Copper NPs in CuZnx/SBA-15 (ADP) catalysts with Cu/Zn mass ratios up to 2 were effectively confined within the SBA-15 pores (dCu 2-XRD experiments. A. Garcia-Trenco thanks the Ministerio de Economia y Competitividad (former Ministerio de Ciencia e Innovacion) of Spain for a predoctoral (FPI) scholarship.García Trenco, A.; Martinez Feliu, A. (2013). A simple an efficient approach to confine Cu/ZnO methanol synthesis catalysts in the ordered mesoporous SBA-15 silica. Catalysis Today. 215:152-161. https://doi.org/10.1016/j.cattod.2013.03.005S15216121

Direct hydrogenation of CO2 to aromatics via Fischer-Tropsch route over tandem K-Fe/Al2O3+H-ZSM-5 catalysts: Influence of zeolite properties

[EN] Direct hydrogenation of CO2 to valuable aromatics using multifunctional catalysts is an attractive technology to produce low-carbon footprint chemicals. In this work, the relevant zeolite parameters driving the formation of total and BTEX aromatics from CO2 and H2 on tandem K-Fe/gamma-Al2O3+H-ZSM-5 catalysts following the FischerTropsch (FT)-mediated route were investigated. To this end, a set of H-ZSM-5 zeolites covering a wide range of physicochemical properties (density of Br phi nsted and Lewis acid sites, external acidity, crystallite size, and mesoporosity) was used, characterized by different techniques (ICP-OES, XRD, N2 physisorption, FTIR-pyridine, FTIR-2,6,-di-tert-butyl pyridine, XPS, 27Al MAS NMR, and electron microscopy), and evaluated in CO2 hydrogenation at 400 degrees C, 30 bar, H2/CO2 = 3.1, and GHSV of 4700 mL/(gFe-cat & sdot;h). At these conditions, high and stable CO2 conversions of 50 - 55% and low CO selectivity of ca. 10% were obtained for the Fe-based and tandem catalysts. The density and, to a certain extent, the strength of Br phi nsted acid sites were found the main parameters determining the selectivity of aromatics, reaching initial (TOS = 1.5 h) values of about 79% and 40% in liquid (C5+) and total hydrocarbons, respectively, for the catalyst based on the most acidic zeolite. Lewis acid sites associated to extraframework Al species (EFAL), by contrast, did not appear to play a relevant role in our conditions. Moreover, although a positive effect of the total amount and strength of Br phi nsted acid sites on the selectivity to the most valuable BTEX aromatics was inferred from our results, the external Br phi nsted acidity was the most influential factor in this case. Hence, a remarkable BTEX selectivity of 75% in aromatics was achieved for the zeolite previously submitted to a surface-passivation treatment by silylation.This work has received European Union's Horizon 2020 Research and Innovation funding under grant agreement No 838077 (eCOCO 2 project) . Funding by the Generalitat Valenciana through the Prometeo CIPROM/2022/10 project is also acknowledged. This study was supported by MICIN with funding from European NextGenerationEU (PRTR-C17. I1) within the Green Hydrogen and Energy Program-CSIC and CSIC Interdisciplinary Thematic Platform (PTI +) Transicion Energetica Sostenible + (PTI-TRANSENER +) . We are grateful to Dr. S. Escorihuela, Dr. M. Navarro, and Dr. J.A. Vidal-Moya for their assistance in part of the experimental work. The authors are also thankful to the Microscopy Service of the Universitat Polite cnica de Valencia (UPV) .Murciano Martínez, R.; Serra Alfaro, JM.; Martinez Feliu, A. (2024). Direct hydrogenation of CO2 to aromatics via Fischer-Tropsch route over tandem K-Fe/Al2O3+H-ZSM-5 catalysts: Influence of zeolite properties. Catalysis Today. 427. https://doi.org/10.1016/j.cattod.2023.11440442