The Experts below are selected from a list of 207 Experts worldwide ranked by ideXlab platform
Angeliki A Lemonidou - One of the best experts on this subject based on the ideXlab platform.
-
on the use of an in situ magnetometer to study redox and sintering properties of nio based oxygen carrier materials for chemical looping steam methane reforming
International Journal of Hydrogen Energy, 2019Co-Authors: Dragomir B Bukur, Lishil Silvester, Nico Fischer, Michael Claeys, Angeliki A LemonidouAbstract:Abstract Two NiO based oxygen carrier materials (OCMs) were synthesized and tested for use as potential materials in chemical looping reforming applications. Redox properties of these materials were evaluated in successive methane reduction – air oxidation (redox) cycles in a thermogravimetric analyzer unit (TGA) and an in situ magnetometer. Zirconia supported (Ni–Zr) OCM exhibited excellent redox activity (high degree of reduction and oxidation) and stability during ten CH4 reduction-air oxidation cycles. The degree of reduction of the alumina supported (Ni–Al) OCM increased gradually during cycling experiments, due to the formation of easily reducible NiO from nickel aluminate species with successive reduction/re-oxidation. The Ni–Al OCM exhibited excellent stability with respect to oxidation resulting in nearly complete oxidation of reduced Ni in all cycles. Results from measurements in the magnetometer were in good agreement with those in the TGA for the Ni–Zr OCM (both with regards to the degree of reduction and oxidation) and the degree of oxidation of the Ni–Al OCM. A moderate crystallite growth with cycling was observed for Ni–Al, whereas a decrease in nickel crystallite size was observed for Ni–Zr.
Hiromichi Ohkura - One of the best experts on this subject based on the ideXlab platform.
-
physicochemical properties of a plate type copper based catalyst prepared on an aluminum plate by electroless plating for steam reforming of methanol and co shift reaction
Applied Catalysis A-general, 2008Co-Authors: Choji Fukuhara, Hiromichi OhkuraAbstract:Abstract A plate-type copper-based catalyst was prepared by electroless plating on an aluminum substrate. Its physicochemical properties were measured to examine the relation to methanol reforming and CO shift performances. The catalytic activity of the plated copper-based catalyst was improved more by oxidation treatment in air than by reduction treatment prior to the reaction. In this case, the oxidation treatment caused the zinc located in the bulk layer to migrate to the surface and form a CuZn alloy-like compound. While, the reduction treatment made only a small amount of zinc migration, so the CuZn alloy was barely formed. The surface area of metallic copper component on the catalyst was increased by the reduction treatment, and with the number of reductions; however, there was no relationship between such metallic surface area and CO shift activity. The valence of the copper species at the surface layer was metallic after reduction treatment and cationic after oxidation treatment or reforming reaction. It was found that the presence of metallic copper species on the plated catalyst hardly contributes to the formation of active site. The formate species, which are considered as the intermediate of reforming and CO shift reaction, were adsorbed on the catalyst in the form of a monodentate-type or a bridge-type (and/or bidentate-type). On the surface that experienced oxidation treatment, the proportion of the monodentate-type formate group was higher. It was inferred that the formation of a CuZn alloy-like compound accelerates the increase of monodentate-type formate group and contributes to the improvement of catalytic activity.
Dragomir B Bukur - One of the best experts on this subject based on the ideXlab platform.
-
on the use of an in situ magnetometer to study redox and sintering properties of nio based oxygen carrier materials for chemical looping steam methane reforming
International Journal of Hydrogen Energy, 2019Co-Authors: Dragomir B Bukur, Lishil Silvester, Nico Fischer, Michael Claeys, Angeliki A LemonidouAbstract:Abstract Two NiO based oxygen carrier materials (OCMs) were synthesized and tested for use as potential materials in chemical looping reforming applications. Redox properties of these materials were evaluated in successive methane reduction – air oxidation (redox) cycles in a thermogravimetric analyzer unit (TGA) and an in situ magnetometer. Zirconia supported (Ni–Zr) OCM exhibited excellent redox activity (high degree of reduction and oxidation) and stability during ten CH4 reduction-air oxidation cycles. The degree of reduction of the alumina supported (Ni–Al) OCM increased gradually during cycling experiments, due to the formation of easily reducible NiO from nickel aluminate species with successive reduction/re-oxidation. The Ni–Al OCM exhibited excellent stability with respect to oxidation resulting in nearly complete oxidation of reduced Ni in all cycles. Results from measurements in the magnetometer were in good agreement with those in the TGA for the Ni–Zr OCM (both with regards to the degree of reduction and oxidation) and the degree of oxidation of the Ni–Al OCM. A moderate crystallite growth with cycling was observed for Ni–Al, whereas a decrease in nickel crystallite size was observed for Ni–Zr.
J A Pena - One of the best experts on this subject based on the ideXlab platform.
-
Production and purification of hydrogen by biogas combined reforming and steam-iron process
International Journal of Hydrogen Energy, 2018Co-Authors: J. Lachén, Javier Herguido, J A PenaAbstract:Cobalt ferrite and hematite with minor additives have been tested for production and purification of high purity hydrogen from a synthetic biogas by steam-iron process (SIP) in a fixed bed reactor. A catalyst based in nickel aluminate has been included in the bed of solids to enhance the rate of the reaction of methane dry reforming (MDR). The reductants resulting from MDR are responsible for reducing the oxides based on iron that will, in the following stage, be oxidized by steam to release hydrogen with less than 50 ppm of CO. Coke minimization along reduction stages forces to operate such reactors above 700 °C for reductions, and as low as 500 °C for oxidations to avoid coke gasification. To avoid problems such as reactor clogging by coke in reductions and/or contamination of hydrogen by gasification of coke along oxidations, steam in small proportions has been included in the feed with the aim of minimizing or even avoiding formation of carbonaceous depositions along the reduction stage of SIP. Since steam is an oxidant, it exerts an inhibiting effect upon reduction of the oxide, that slows down the efficiency of the process. It has been proved that co-feeding low proportions of steam with an equimolar mixture of CH4 and CO2 (simulating a poor heating value desulphurized biogas) is able to avoid coke deposition, allowing the operation of both, reductions and oxidations, in isothermal regime (700 °C). Empirical results have been contrasted with data found in literature for similar processes based in MDR and combined (or mixed) reforming process (CMR), concluding that the combination of MDR + SIP proposed in this work, taking apart economic aspects and complex engineering, shows similar yields towards hydrogen, but with the advantage of not requiring a subsequent purification process.
Choji Fukuhara - One of the best experts on this subject based on the ideXlab platform.
-
physicochemical properties of a plate type copper based catalyst prepared on an aluminum plate by electroless plating for steam reforming of methanol and co shift reaction
Applied Catalysis A-general, 2008Co-Authors: Choji Fukuhara, Hiromichi OhkuraAbstract:Abstract A plate-type copper-based catalyst was prepared by electroless plating on an aluminum substrate. Its physicochemical properties were measured to examine the relation to methanol reforming and CO shift performances. The catalytic activity of the plated copper-based catalyst was improved more by oxidation treatment in air than by reduction treatment prior to the reaction. In this case, the oxidation treatment caused the zinc located in the bulk layer to migrate to the surface and form a CuZn alloy-like compound. While, the reduction treatment made only a small amount of zinc migration, so the CuZn alloy was barely formed. The surface area of metallic copper component on the catalyst was increased by the reduction treatment, and with the number of reductions; however, there was no relationship between such metallic surface area and CO shift activity. The valence of the copper species at the surface layer was metallic after reduction treatment and cationic after oxidation treatment or reforming reaction. It was found that the presence of metallic copper species on the plated catalyst hardly contributes to the formation of active site. The formate species, which are considered as the intermediate of reforming and CO shift reaction, were adsorbed on the catalyst in the form of a monodentate-type or a bridge-type (and/or bidentate-type). On the surface that experienced oxidation treatment, the proportion of the monodentate-type formate group was higher. It was inferred that the formation of a CuZn alloy-like compound accelerates the increase of monodentate-type formate group and contributes to the improvement of catalytic activity.
