Conventional carbon capture and sequestration (CCS) in aqueous alkanolamine solutions is an energy-intensive process for power plant flue gas CO2 treatment. We report a laboratory parametric study on the utilization of CO2 from simulated natural gas postcombustion effluent by cyclic adsorption and methanation using a single dual functional material (DFM). The DFM is composed of nanodispersed CaO and Ru metal supported on an γ-Al2O3 carrier (5% Ru, 10% CaO/Al2O3), respectively functioning as the CO2 adsorbent and methanation catalyst. The stored H2 used for methanation is assumed to be produced by water electrolysis using excess alternative wind or solar energy. The effects of DFM preparation methods, Al2O3 carrier materials (with different shapes and properties), and adsorption and methanation conditions (feed compositions, flow rates, and reaction temperatures) were examined. The DFM samples, prepared using chloride precursor salts, showed stable performance under cyclic operating conditions. Reaction conditions were explored for the optimized CO2 utilization efficiency.

Abstract:The Pd component in the automotive three way catalyst (TWC) experiences deactivation during fuel shutoff, a process employed by automobile companies for enhancing fuel economy when the vehicle is coasting downhill. The process exposes the TWC to a severe oxidative aging environment with the flow of hot (800 °C-1050 °C) air. Simulated fuel shutoff aging at 1050 °C leads to Pd metal sintering, the main cause of irreversible deactivation of 3% Pd/Al2O3 and 3% Pd/CexOy-ZrO2 (CZO) as model catalysts. The effect on the Rh component was presented in our companion paper Part I. Moderate support sintering and Pd-CexOy interactions were also experienced upon aging, but had a minimal effect on the catalyst activity losses. Cooling in air, following aging, was not able to reverse the metallic Pd sintering by re-dispersing to PdO. Unlike the aged Rh-TWCs (Part I), reduction via in situ steam reforming (SR) of exhaust HCs was not effective in reversing the deactivation of aged Pd/Al2O3, but did show a slight recovery of the Pd activity when CZO was the carrier. The Pd couples in Pd/CZO are reported to promote the catalytic SR by improving the redox efficiency during the regeneration, while no such promoting effect was observed for Pd/Al2O3. A suggestion is made for improving the catalyst performance. OPEN ACCESSCatalysts 2015, 5 1798 Keywords: automotive three way catalysts (TWC); Pd/Al2O3; Pd/CexOy-ZrO2; fuel shutoff aging; catalyst deactivation; fuel rich regeneration; metal sintering; metal-support interaction

No abstract

The rhodium (Rh) component in automotive three way catalysts (TWC) experiences severe thermal deactivation during fuel shutoff, an engine mode (e.g., at downhill coasting) used for enhancing fuel economy. In a subsequent switch to a slightly fuel rich condition, in situ catalyst regeneration is accomplished by reduction with H2 generated through steam reforming catalyzed by Rh 0 sites. The present work reports the effects of the two processes on the activity and properties of 0.5% Rh/Al2O3 and 0.5% Rh/CexOy-ZrO2 (CZO) as model catalysts for Rh-TWC. A very brief introduction of three way catalysts and system considerations is also given. During simulated fuel shutoff, catalyst deactivation is accelerated with increasing aging temperature from 800 °C to 1050 °C. Rh on a CZO support experiences less deactivation and faster regeneration than Rh on Al2O3. Catalyst characterization techniques including BET surface area, CO chemisorption, TPR, and XPS measurements were applied to examine the roles of metal-support interactions in each catalyst system. For Rh/Al2O3, strong metal-support interactions with the formation of stable rhodium aluminate (Rh(AlO2)y) complex dominates in fuel shutoff, leading to more difficult catalyst regeneration. For Rh/CZO, Rh sites were partially oxidized to Rh2O3 and were relatively easy to be reduced to active Rh 0 during regeneration.

Typical allowable O 2 concentration in recovered CO 2 for certain applications including Enhanced Oil Recovery (EOR) is as low as 100 ppmv. The removal of high content O 2 (3−5%) in oxy-combustion flue gas requires additional compression work in the conventional downstream CO 2 purification process. RTI hereby proposes to develop a novel technology for flue gas O 2 removal based on catalytic oxidation of natural gas. Preliminary catalytic tests were performed over various supported Pd and Pt catalysts under simulated oxy-combustion flue gas conditions, with the addition of a stoichiometric amount of CH 4 as a model compound for natural gas. Among the studied catalysts, Pd supported on zeolite H-ZSM-5 showed the highest oxygen conversion at relevant conditions. Compared to Pt catalysts, Pd catalysts generally showed higher oxidation reaction kinetics. The catalytic oxidation activity can be further increased by optimizing reaction gas hourly space velocity (GHSV) and total reaction pressure.