Search

In hydrocarbon reforming processes, coke formation on the catalyst usually reduces reaction rates. We show that when subjected to thermal treatment, a commercial nickel catalyst, overcoated with alumina, ALD exhibited both higher activity per g Ni and higher carbon formation rates than an uncoated catalyst. During the temperature‐programmed reaction in a CH4+CO2 atmosphere, the uncoated catalyst deactivated rapidly from carbon buildup, but the overcoated catalyst displayed an increase in catalytic activity per g Ni, despite generating two times the surface carbon. The unexpected phenomenon was investigated via TEM/EDS, TGA/DSC, SEM, XRD and Raman spectroscopy. We hypothesize that this may be due to (a) formation of a thicker than expected 'quasi‐ALD' overcoat of amorphous alumina, (b) crystallization of ALD overcoat into nanofibers that act as secondary supports for migrating Ni, and (c) the ability of ALD overcoat to isolate carbon as carbon nano‐onions (CNOs). [ABSTRACT FROM AUTHOR]

• Ni/Al 2 O 3 stability for CH 4 dry reforming (DRM) higher with alumina ALD overcoats. • Rates of Ni sintering and C deposition lower on overcoated than uncoated catalyst. • Nickel aluminate phase unstable under DRM conditions used. • Slow reduction of NiAl 2 O 4 cause of gradual catalyst activity increase. • Proposed to stabilise alumina overcoated Ni based catalysts by avoiding NiAl 2 O 4. A catalyst consisting of 2 wt% Ni supported on a commercially available transition alumina is modified using TMA-H 2 O ALD cycles to deposit thin alumina overcoats on the catalyst, and it is then investigated for the catalytic dry reforming of methane (DRM) at 700 °C. Highly dispersed Ni rapidly sinters to form bulk Ni particles on the uncoated catalyst. In contrast, deposition of an alumina overcoat by ALD significantly lowers the rate of Ni sintering, and also lowers the propensity towards carbon deposition during DRM. Additionally, it is experimentally demonstrated that the Ni aluminate (NiAl 2 O 4) spinel phase is unstable under the present DRM conditions and slowly undergoes reduction to metallic Ni and Al 2 O 3. Slow reduction of the Ni2+ from NiAl 2 O 4 is proposed as the origin of the large increase in DRM activity observed for the alumina-overcoated Ni catalysts. [ABSTRACT FROM AUTHOR]

In this work we present chemical looping and simulated chemical looping as a new reactor concept for the oxidative coupling of methane over Na 2 WO 4 /Mn/SiO 2 . As a consequences of an alternating feed of oxygen and methane to the catalyst bed side reactions are avoided and the selectivity of the coupling reaction is greatly increased. By variation of methane pulse contact time and temperature a maximum yield of 0.25 is obtained. Although this does not exceed the often discussed yield limitation of OCM, it is achieved from a substantially lower amount of converted methane. A time on stream experiment were carried out at 775 and 800 °C for 150 min and showed stable performance and C2 yield. [ABSTRACT FROM AUTHOR]

Self-supported nickel-manganese-based catalysts were synthesized from heterobimetallic nickel manganese oxalate precursors via a versatile reverse micelle approach. The precursors were subjected to thermal degradation (400 °C) in the presence of synthetic air to form respective metal oxides, which were treated under hydrogen (500 °C) to form Ni2MnO4-O2-H2, Ni6MnO8-O2-H2 and NiO-O2-H2. Similarly, the precursors were also treated directly under hydrogen at the same temperature to form Ni2MnO4-H2 and Ni6MnO8-H2. The catalysts were extensively investigated by PXRD, SEM, TEM, XPS and BET analyses. The resulting catalysts were applied for dry reforming of methane (DRM) and exhibit better stability and resistance to coking than coprecipitated catalysts. Further, we show that addition of manganese, which is not an active catalyst for DRM alone, to nickel has a significant promotion effect on both the activity and stability of DRM catalysts, and a Ni/Mn ratio lower than 6:1 enables optimized activity for this system. [ABSTRACT FROM AUTHOR]

Supported NiO nanoparticles (NPs) were prepared by impregnation of mesoporous silica SBA-15 with a molecular, metalorganic [Ni4O4] cubane cluster as precursor. By using this ligand-stabilized Ni cluster, deposition of four Ni ions in close proximity on the silica support was achieved; this resulted in the formation of small and highly dispersed NiO NPs after heat treatment. These clusters were shown to have a significant influence on the formation of NiO NPs compared to a conventional Ni(OAc)2 precursor. After a further reduction step, the materials were used as catalysts for the dry reforming of methane, which showed that preorganization of the Ni atoms on the support surface had a beneficial effect on the methane conversion rate. [ABSTRACT FROM AUTHOR]

We present a facile synthesis of bioinspired manganese oxides for chemical and photocatalytic water oxidation, starting from a reliable and versatile manganese(II) oxalate single-source precursor (SSP) accessible through an inverse micellar molecular approach. Strikingly, thermal decomposition of the latter precursor in various environments (air, nitrogen, and vacuum) led to the three different mineral phases of bixbyite (Mn2O3), hausmannite (Mn3O4), and manganosite (MnO). Initial chemical water oxidation experiments using ceric ammonium nitrate (CAN) gave the maximum catalytic activity for Mn2O3 and MnO whereas Mn3O4 had a limited activity. The substantial increase in the catalytic activity of MnO in chemical water oxidation was demonstrated by the fact that a phase transformation occurs at the surface from nanocrystalline MnO into an amorphous MnO x (1< x<2) upon treatment with CAN, which acted as an oxidizing agent. Photocatalytic water oxidation in the presence of [Ru(bpy)3]2+ (bpy=2,2 ′-bipyridine) as a sensitizer and peroxodisulfate as an electron acceptor was carried out for all three manganese oxides including the newly formed amorphous MnO x. Both Mn2O3 and the amorphous MnO x exhibit tremendous enhancement in oxygen evolution during photocatalysis and are much higher in comparison to so far known bioinspired manganese oxides and calcium-manganese oxides. Also, for the first time, a new approach for the representation of activities of water oxidation catalysts has been proposed by determining the amount of accessible manganese centers. [ABSTRACT FROM AUTHOR]

Atomic layer deposition, deactivation, carbon nano onions, alumina nanofibers, DRM Keywords: Atomic layer deposition; deactivation; carbon nano onions; alumina nanofibers; DRM EN Atomic layer deposition deactivation carbon nano onions alumina nanofibers DRM 2959 2959 1 07/21/21 20210707 NES 210707 B The Front Cover b shows an alumina-overcoated Ni/Al SB 2 sb O SB 3 sb catalyst undergoing disintegration during dry methane reforming due to carbon buildup under the overcoat. [Extracted from the article]

Energy supply for clean cooking is a priority for Sub-Saharan Africa (SSA). Liquefied petroleum gas (LPG, i.e., propane or butane or a mixture of both) is an economically efficient, cooking energy solution used by over 2.5 billion people worldwide and scaled up in numerous low- and middle-income countries (LMICs). Investigation of the technical, policy, economic and physical requirements of producing LPG from renewable feedstocks (bioLPG) finds feasibility at scale in Africa. Biogas and syngas from the circular economic repurposing of municipal solid waste and agricultural waste can be used in two groundbreaking new chemical processes (Cool LPG or Integrated Hydropyrolysis and Hydroconversion (IH2)) to selectively produce bioLPG. Evidence about the nature and scale potential of bioLPG presented in this study justifies further investment in the development of bioLPG as a fuel that can make a major contribution toward enabling an SSA green economy and universal energy access. Techno-economic assessments of five potential projects from Ghana, Kenya and Rwanda illustrate what might be possible. BioLPG technology is in the early days of development, so normal technology piloting and de-risking need to be undertaken. However, fully developed bioLPG production could greatly reduce the public and private sector investment required to significantly increase SSA clean cooking capacity. [ABSTRACT FROM AUTHOR]

The Caustic Aqueous Phase Electrochemical Reforming (CAPER) process can convert aqueous-phase ethanol to high-pressure and high-purity hydrogen (H 2) at lower cell operating temperatures and voltages than traditional methods. Additionally, any carbon dioxide (CO 2) produced by the ethanol electrochemical oxidation is captured by the caustic electrolyte solution. Without using a membrane, the only gas-phase species is H 2. The CAPER process achieves process intensification for compressed and pure H 2 production by eliminating the need for downstream separation and external compression steps. All the compression is performed on the liquid-phase reactants to circumvent less efficient gas-phase compression. This study uses a high-pressure batch electrochemical reactor to demonstrate the capability of the CAPER reforming process and investigates catalytic behavior under operating conditions. Our Tafel analysis showed that both palladium and platinum nanoparticles on carbon supports have high activity for ethanol electrooxidation under the caustic electrolyte condition (exchange current density (i 0) > 1 × 10−5 A cm−2), while non-noble nanoparticles on carbon supports showed poor activity. The only gas phase product was pressurized H 2 and its faraday efficiency was determined as 100%. The exchange current density was not affected by high-pressure operation. The carbon selectivity toward unwanted byproduct acetate on the anode increased from 17% to 63% as the applied anode potential increased from −500 mV to −200 mV vs. Ag/AgCl. [Display omitted] • CAPER achieves process intensified hydrogen production from ethanol. • High-pressure H 2 is electrochemically produced at low temperatures and voltages. • CO 2 is captured within the caustic electrolyte for a carbon-neutral process. • 100% Faraday efficiency and pure H 2 in the gas phase is achieved. [ABSTRACT FROM AUTHOR]