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US-Israeli Symposium on C1 Chemistry :
08:00am - 09:30am USA / Canada - Eastern - August 22, 2021 | Room: B216 - B217
Aditya Bhan, Organizer, Univ of Minnesota; Oz M Gazit, Organizer, Technion; Prof. Dmitri Gelman, Organizer, The Hebrew University of Jerusalem; Daniel Resasco, Organizer, University of Oklahoma; Daniel Resasco, Presider, University of Oklahoma; Aditya Bhan, Presider, Univ of Minnesota
Division: [CATL] Division of Catalysis Science & Technology
Session Type: Oral - Hybrid
Division/Committee: [CATL] Division of Catalysis Science & Technology

This symposium explores the topic of C1 conversion in context of the broader chemical enterprise. Presentations will feature research at the state-of-the-art in electrochemical and thermochemical upgrading of C1 species to fuels and chemicals.

Sunday
Catalytic activation of light alkanes on promoted molybdenum oxide catalysts: Coupling of catalytic rates and their mechanistic implications
08:00am - 08:30am USA / Canada - Eastern - August 22, 2021 | Room: B216 - B217
Division: [CATL] Division of Catalysis Science & Technology
Session Type: Oral - Hybrid
Catalytic conversions of light alkanes to their corresponding olefins are attractive routes for utilizing natural gas feedstocks. Starting with ethane, its reaction produces ethylene as the platform molecule for sequential synthesis of a wide variety of commodity chemicals, including polyethylene, styrene, ethylene oxide, and ethylene glycol. Its catalytic turnovers occur either without a co-oxidant via dehydrogenation or with O2 or CO2 via oxidative dehydrogenation reactions. Herein, we will unravel the mechanistic similarities and differences among the various ethane conversion reactions, on two-dimensional MoOx dispersed on Al2O3 catalysts promoted by Fe, Co, or Ni catalysts. These reactions, irrespective of the presence of or the chemical identity of the co-reactant, occur via the common step, that the initial C-H bond activation of ethane limits rates. The ethane activation cycle is catalytically coupled with the oxidant activation cycle, the latter generates reactive oxygen species that scavenge the surface carbon debris and therefore retain the catalytic reactivity and stability. We will discuss these catalytic cycles among the different ethane conversion catalysis, the key catalytic events, and their periodic reactivity trends, when incorporating the earth abundant Fe, Co, and Ni transition metal into the dispersed MoOx structures. More specifically, we will discuss how these metal cations could alter the catalytic rates of the various, concomitant catalytic cycles, interjecting deactivation, leading to the observed rates and selectivities. We attempt to provide consolidate mechanistic framework, accounting for both the rates as well as the time-dependent rate decay for ethane reactions for the series of catalyst materials.
Sunday
Multi-phase catalysts for stable methane cracking and reforming
08:30am - 09:00am USA / Canada - Eastern - August 22, 2021 | Room: B216 - B217
Prof. Brian A. Rosen, Presenter, Tel Aviv University
Division: [CATL] Division of Catalysis Science & Technology
Session Type: Oral - Hybrid
Defective solid-catalysts and multi-phase catalysts are intriguing materials which would pave the way towards stable methane cracking and reforming. While point defects have been well studied in energy conversion ceramics by exploiting non-isovalent lattice substitutions and non-stoichiometric compounds, the impact of multidimensional defects on catalytic activity and stability is far less studied. During activation, energy conversion catalysts often go through solid-state phase transitions. These transitions can either be beneficial or detrimental to performance. We observe that extended defects critically impacts the temperature at which such phase transitions can occur, the pathway of the phase transition, and resulting catalytic activity and stability of the catalyst. Extended defects such as stacking faults in substituted lanthanum nickelates and lanthanum ferrates can be exploited to significantly extend catalyst lifetimes and lower apparent activation energy for critical reactions such as methane and carbon monoxide oxidation. Furthermore, multi-phase catalysts involving solid-liquid equilibrium are also exploited to imbue stable methane cracking with increased performance.
Sunday
Elucidating and controlling the selective electrocatalytic reduction of CO2 to C1 chemical intermediates
09:00am - 09:30am USA / Canada - Eastern - August 22, 2021 | Room: B216 - B217
Matthew Neurock, Presenter
Division: [CATL] Division of Catalysis Science & Technology
Session Type: Oral - Hybrid
The development of sustainable strategies to meet the world’s increasing energy demands will require the use of renewable energy sources together with carbon-neutral and energy efficient processes that can significantly reduce CO2 emissions. The sustainable catalytic conversion of CO2 to carbon monoxide as well as formic acid and their subsequent transformation to fuels and chemical intermediates offer attractive routes to carbon-neutral fuels. Nature readily carries out these reactions out with very high selectivities by co-locating the active metal centers within highly reactive reaction cavities. Recent experimental results show that the CO2 can be efficiently reduced over various late transition metals within ionic liquid as well as within alkaline media. The metal-electrolyte-solvent interface plays a critical role in enhanced the CO2 reduction and selectively forming either CO or formic acid produces.
Novel potential-dependent ab initio molecular dynamics simulations are carried out herein to help unravel the elementary steps and the mechanisms that govern these transformations and to show how changes in the solvent, electrolyte, pH and potential drive the activity as well as the selectivity in these systems. We show how changes in the potential and the reaction conditions can drive the formation of unique electrolyte, solvent, reactant environments that readily facilitate the rate controlling electron transfer reaction and selectively guide the subsequent proton addition to exclusively form CO or formic acid products. The simulations combined with experiments show that subtle changes in the electrolyte and the solvent can be used to dictate the formation of CO or formic acid with Faradaic Efficiencies of > 97 %. The simulations are used to help identify important electrolyte and metal catalysts systems as well as mixed electrolyte systems that will drive the active and selective formation to C1 products.

US-Israeli Symposium on C1 Chemistry :
10:30am - 12:00pm USA / Canada - Eastern - August 22, 2021 | Room: B216 - B217
Aditya Bhan, Organizer, Univ of Minnesota; Oz M Gazit, Organizer, Technion; Prof. Dmitri Gelman, Organizer, The Hebrew University of Jerusalem; Daniel Resasco, Organizer, University of Oklahoma; Aditya Bhan, Presider, Univ of Minnesota
Division: [CATL] Division of Catalysis Science & Technology
Session Type: Oral - Hybrid
Division/Committee: [CATL] Division of Catalysis Science & Technology

This symposium explores the topic of C1 conversion in context of the broader chemical enterprise. Presentations will feature research at the state-of-the-art in electrochemical and thermochemical upgrading of C1 species to fuels and chemicals.

Sunday
Effect of surface phase oxides on Ni catalyzed methane dry reforming
10:30am - 11:00am USA / Canada - Eastern - August 22, 2021 | Room: B216 - B217
Anup Tathod; Jin Wang; Oz M Gazit, Presenter, Technion
Division: [CATL] Division of Catalysis Science & Technology
Session Type: Oral - Hybrid
Under reducing conditions, a strongly interacting reducible support can hinder the sintering of a nickel (Ni) nano-particle but, may also lead to severely reduced catalyst activity due to overcoating of the Ni by the support (i.e. SMSI). In contrast, Ni supported on a weakly interacting non-reducible support will have lower thermal stability but, can show higher activity. We find that the level of these metal support interactions (MSI) can be balanced using a mediating layer of surface phase thin oxides (SPO) in the form of MgAl mixed oxide nano-platelets (MO). We show that this approach can be practically implemented to balance between the benefits of the strong MSI of the SPO and the weak MSI of the underlying support (SiO2, ZrO2). Testing this approach for methane dry reforming (MDR) we found that the presence of 0.5-2.5 %wt Ni on the SPO, which is dispersed on an underlying ZrO2 surface, enhances the catalytic activity by ~15 fold, as compared to Ni supported on bulk MO. To better understand and control the nature of these interaction we performed extensive HAADF-STEM-EDS and XPS analyses. Planer model catalysts are analyzed using atomic force microscopy (AFM) to study the effect of the underlying support on the Ni and on the exposed surface of the SPO. Obtained information related to surface adhesion, surface potential and surface friction forces of the MO-NSs are correlated to catalyst performance and the mechanism by which the Ni is promoted by the presence of the SPO.
Sunday
Mechanism and surface species for formic acid decomposition on dispersed copper nanoparticles
11:00am - 11:30am USA / Canada - Eastern - August 22, 2021 | Room: B216 - B217
Division: [CATL] Division of Catalysis Science & Technology
Session Type: Oral - Hybrid
Mechanistic details of HCOOH dehydrogenation routes on Cu nanoparticles are relevant to C1 chemistries that involve formate-type species as intermediates or spectators, such as water-gas shift and methanol synthesis. It has been widely accepted that HCOOH decomposes unimolecularly on transition metal surfaces via bidentate formate (*HCOO*) intermediate, with its C-H activation kinetically limiting the overall rates. Although such route is relevant during temperature-programmed surface reactions (TPSR) of pre-adsorbed *HCOO* species, bimolecular routes may be prevalent at catalytic conditions when HCOOH(g) coexists with *HCOO*. This study seeks to clarify and update our understanding of HCOOH dehydrogenation routes on Cu nanoparticles by combining kinetic, isotopic, and spectroscopic experiments with density functional theory (DFT) calculations.

At practical conditions (0.1-3.5 kPa HCOOH; 473-503 K), Cu surfaces are covered with *HCOO* species, which reach their saturation at 0.25 monolayer (ML) (*HCOO*/Cusurface=0.25) because of strong repulsion among bound *HCOO* species. HCOOH(g) binds molecularly at the interstices (denoted as ' sites; HCOOH') within such saturated *HCOO* adlayers; such interstices become saturated with HCOOH' upon formation of another 0.25 ML adlayer, with HCOOH' species forming strong H-bonds with vicinal *HCOO*. Measured rates reflect the bimolecular decomposition of the HCOOH'-*HCOO* complex, in which either HCOOH' or *HCOO* can lead to the formation of the CO2 product, while the other one re-forms the *HCOO* adlayer. These two bimolecular routes cannot be distinguished from kinetic data, isotopic effects, or infrared spectra or accessible to TPSR studies. DFT-derived barriers are slightly larger for the route that forms CO2 from HCOOH' than for the one forming CO2 from *HCOO* (ΔHact = 83 vs. 68 kJ mol-1).

These bimolecular routes are consistent with all experimental and theoretical data. This work, in turn, provides a compelling example of how repulsive interactions among bound species restricts their coverages to < 1 ML, thus allowing residual interstices in such “passivated” surfaces to bind intermediates less strongly, thus allowing them to react or to increase the reactivity of the bound species in the more refractory template.

Sunday
Multifunctional pincer complexes possessing a secondary coordination sphere as catalysts for CO2 hydrogenation
11:30am - 12:00pm USA / Canada - Eastern - August 22, 2021 | Room: B216 - B217
Prof. Dmitri Gelman, Presenter, The Hebrew University of Jerusalem
Division: [CATL] Division of Catalysis Science & Technology
Session Type: Oral - Hybrid
Burning fossil fuels worldwide has led to an increasing CO2 concentration in the atmosphere to such a large extent that global climate change caused by greenhouse gases has become a major ecological challenge. At present, its amount can be reduced by either capture and storage or by chemical conversion and utilization. There is no doubt that carbon dioxide storage is a cheaper solution and that it is useful for reducing CO2 emissions quickly. Unfortunately, it does not solve the accumulation problem in the long term, whereas converting CO2 into carbon-containing value-added products and feedstock does.
The catalytic conversion of CO2/H2/CO to methanol is already being performed on an industrial scale. Other products, such as formic acid and its derivatives, can be synthesized by carbon dioxide hydrogenation. However, despite this progress, we are still far from the point where carbon dioxide becomes a concrete player in the sustainable chemistry/energy market. Significant steps should be taken toward developing more efficient catalysts for CO2 conversion processes, as well as developing new reaction schemes that allow for more efficient utilization of carbon dioxide in fine and bulk synthesis.
The talk is devoted to designing ligand-metal cooperative catalytic systems for the dehydrogenation of formic acid and hydrogenation of CO2. Our studies revolve around a family of 3-dimensional PC(sp3)P pincer complexes developed by our group. The synthetic approach leading to all these examples is straightforward and represents a modular and divergent approach to a variety of 3-dimensional platforms equipped with custom-tailored primary and secondary coordination spheres. In particular, we address the cooperative activation and functionalization of carbon dioxide by bifunctional catalysts possessing transition metals in the primary coordination sphere and a pendant Lewis acidic functionality in the secondary sphere.

US-Israeli Symposium on C1 Chemistry :
02:00pm - 04:00pm USA / Canada - Eastern - August 22, 2021 | Room: Zoom Room 27
Aditya Bhan, Organizer, Univ of Minnesota; Oz M Gazit, Organizer, Technion; Prof. Dmitri Gelman, Organizer, The Hebrew University of Jerusalem; Daniel Resasco, Organizer, University of Oklahoma; Aditya Bhan, Presider, Univ of Minnesota; Prof. Dmitri Gelman, Presider, The Hebrew University of Jerusalem
Division: [CATL] Division of Catalysis Science & Technology
Session Type: Oral - Virtual
Division/Committee: [CATL] Division of Catalysis Science & Technology

This symposium explores the topic of C1 conversion in context of the broader chemical enterprise. Presentations will feature research at the state-of-the-art in electrochemical and thermochemical upgrading of C1 species to fuels and chemicals.

Sunday
New mechanistic and reaction pathway insitings into oxidative coupling of methane reaction over supported Na2WO4/SiO2 catalysts
02:00pm - 02:30pm USA / Canada - Eastern - August 22, 2021 | Room: Zoom Room 27
Division: [CATL] Division of Catalysis Science & Technology
Session Type: Oral - Virtual
Oxidative coupling of methane (OCM) over supported the Na2WO4/SiO2 catalyst (prepared by incipient-wetness impregnation) was studied to identify the catalyst structure, roles of various oxide phases and catalytic active sites using in-situ Raman spectroscopic technique, along with transient kinetic analysis and steady-state (SS) OCM reaction performance. The in-situ Raman spectra of this catalyst under dehydrated conditions (400 °C, 10% O2/Ar) reveal the presence of surface Na-WOx species along with the crystalline Na2WO4 phase and the β-cristobalite phase of SiO2 support. Stability analysis of above metal oxide phases under OCM reaction conditions (900 °C, CH4+O2+N2 3.3:1:4), through in-situ Raman spectroscopy (see Figure 1 (left)), established that only surface Na-WOx sites, anchored to the SiO2 support, are thermally stable under OCM environment; whereas the crystalline Na2WO4 phase is unstable and melts.
To further understand the nature and types of oxygen species associated with two different types of metal oxide phases (surface Na-WOx and molten Na2WO4), 16O2-18O2 pump-probe experiments were conducted in a Temporal Analysis of Products (TAP) reactor (see Figure 1 (Right)). The evolution of molecular 16O2* species (after 18O2 introduction) from the lattice of the supported 5%Na2WO4/SiO2 catalyst was observed at 800 °C. At lower temperature (650 °C) where the Na2WO4 phase crystallizes or when only dispersed Na-WOx sites are present (0.5%Na-5%WOx/SiO2 catalyst), the evolution of molecular 16O2* does not occur. This suggests that the evolved O2* species are associated with the molten Na2WO4 phase. Additional CH4 series pulsing experiment in the TAP reactor studies revealed the presence of an O* type species during anaerobic OCM.
To determine the roles of these two oxygen species towards the catalytic OCM reaction, experimental protocols were undertaken with transient O2-CH4, O2-C2H6 and O2-C2H4 pump-probe experiments in the TAP reactor and SS-OCM reaction in a flow reactor. These studies showed that (i) the O2* species are mostly involved in the over-oxidation of CH4 to CO2 and in the catalytic dehydrogenation of C2H6 to C2H4 and (ii) the O* species selectively activate CH4 to form C2H6 and oxidize CHx to form CO.

Sunday
Electrooxidation catalysis of dimethyl ether (DME) in new fuel cells
02:30pm - 03:00pm USA / Canada - Eastern - August 22, 2021 | Room: Zoom Room 27
Alex Schechter, Presenter
Division: [CATL] Division of Catalysis Science & Technology
Session Type: Oral - Virtual
Dimethyl ether (DME) was recently proposed as an alternative fuel for fuel cells due to its high energy density (8 kWh kg−1) and low boiling point (-24 °C), which enables to supply it as ambient pressure gas instead of liquid solution. Yet, most metallic DME oxidation catalysts, such as PtRu, exhibit low oxidation kinetics or limited stability. Fuel cells utilizing Pt-based catalysts require high anode loading (above 2-4 mg of Pt) and relatively high pressure and temperature (1.4 - 3.0 bar and 80 C) to produce power outputs of 60- 200 mW/cm2.

We present herein a study of a new approach utilizing our patented ternary PtPdSn\C catalyst, which combines C-H and CO activation. The catalyst was optimized in terms of synthesis conditions and composition for DME oxidation in liquid electrolytes. Comparison with Pt\C, Pd\C and PtPd\C catalysts was made to explore the role of the different metals in the oxidation process over PtPdSn. Analytical analysis of the DME oxidation product formed under selected anode operation conditions was carried out by online mass spectrometry exhibiting the signal of methanol, formic acid and methyl formate at anodic potential range. Online FTIR showed formic acid as the main partial oxidation product at water: DME molar ratio lower than 3.

In contrast, at full hydration above 3 moles of water per mole of DME, the main product other than CO2 was methanol resulting from the ether bond's hydrolysis reaction. Polymer electrolyte fuel cell implementing PtPdSn/C catalyst produced a peak power density of 210 mW/cm2 with the loading of only 1.2 mg/cm2 of active platinum group metal (PGM) at 70 C and ambient pressure. The high electrto-activity in DME oxidation was retained after prolonged cycling at 0.5 M H2SO4, contrary to the state of the art commercial PtRu methanol oxidation catalyst. This power output is significantly higher than reported power density values with PtRu under more demanding conditions and anode catalysts loading. The results mentioned above suggest that DME feed directly as gas to an acidic polymer electrolyte membrane fuel cell (PEMFC) device has the potential of becoming a viable alternative to compressed hydrogen FC systems in a broad spectrum of applications.

Sunday
Factors influencing the activity and selectivity of Cu for the electrochemical reduction of CO2
03:00pm - 03:30pm USA / Canada - Eastern - August 22, 2021 | Room: Zoom Room 27
Alexis Bell, Presenter
Division: [CATL] Division of Catalysis Science & Technology
Session Type: Oral - Virtual
The electrochemical reduction of CO2 driven by renewable sources of electricity (wind and solar) offers a potentially attractive means for producing fuels and chemicals from CO2 taken from stationary sources or the atmosphere. The desired products of the CO2 reduction reaction (CO2RR) are ethene and ethanol, since these compounds can be readily converted to higher molecular weight compounds by conventional catalysis. Extensive research has shown that the only electrocatalyst capable of producing ethene and ethanol with high faradaic yield is metallic copper (Cu) and that many other factors influence the yield of these products, as well. These include the roughness of the Cu surface and the microenvironment of the electrolyte in contact with the Cu surface, i.e., the strength of electrostatic field in the Helmholtz double layer present at the catalyst-electrolyte interface, the pH, and the concentrations of H2O and CO2 at the Cu surface. This talk will discuss how these variables can be controlled through the choice of electrolyte (liquid vs solid) and the manner in which the cathode voltage is applied (static vs pulsed) in order achieve maximum production of C2+ products.
Sunday
C1 catalysis considerations for on-board hydrogen production in autothermalmembrane reactors
03:30pm - 04:00pm USA / Canada - Eastern - August 22, 2021 | Room: Zoom Room 27
Michael Patrascu, Presenter, Technion - Israel Institute of Technology
Division: [CATL] Division of Catalysis Science & Technology
Session Type: Oral - Virtual
The production of electrical power in proton exchange membrane fuel cells (PEMFC) for small scale stationary or portable applications (such as electric vehicles) is currently limited by the complex and expensive infrastructure and equipment requirements for transport and storage of hydrogen. Previous work has demonstrated an intensified scaled-down system for on-board hydrogen production; an autothermal membrane reactor (ATMR) fed by various hydrocarbons including methane, ethanol and glycerol [1,2]. The ATMR is constructed as a shell and tube architecture – steam reforming of the hydrocarbon over Ni based catalyst is carried out in the shell-side and the by-products are recycled to the tube-side to undergo oxidation on a Pt based catalyst to generate the heat required for the reforming.
In this work we study the use of methanol as feed for an ATMR. Methanol, as opposed to other hydrocarbons, does not yield methane as a significant product of reforming or decomposition. The oxidation reaction is then limited to oxidation of CO and H2 which have a much lower activation energy compared to CH4. Consequently, this system can operate at much lower temperatures, lowering the heat loss to the surroundings. Furthermore, the hydrogen partial pressure obtained in the case of methanol reforming is much higher compared to reforming of other fuels, which increases the driving force for hydrogen transport through the membrane. The combination of these phenomena leads to a more efficient intensified system.
In this talk we will share details of the rigorous analysis considering methanol as feed and compare it to validated results of a system fed by methane.