Preparation of Novel Oxygen Carriers Supported by Ti, Zr-Shelled γ-Alumina for Chemical Looping Combustion of Methane

Abstract

Highly stabilized mesoporous core−shell-structured oxygen carriers (OCs) were fabricated by a repetitive coating process of alumina supports using the mesopore-forming surfactant assembly method. The wet coating strategy, along with the sol− gel process, was used for the synthesis of mesoporous material-shelled OCs with various shell compositions (i.e., zirconia, titania). The cyclic performance of the synthesized OCs during chemical looping combustion (CLC) was investigated in a thermogravimetric analyzer (TGA). The mesoporous-shelled OCs demonstrated significantly better performance compared to the OCs without mesoporous shells. The synthesized OCs with a mesoporous zirconia/titania shell reveal a unique oxygen capacity of 100% based on active metal oxide for supported NiO and Fe 2 O 3 . Also, the synthesized OCs showed no activity loss after 10 cycles. This was attributed to the exceptional core−shell coating strategy, in which the thermally stable mesoporous Zr/Ti layers prevent the sintering and over-reaction of the active metal oxide crystals with the alumina support.

Recent Advances and Development of Various Oxygen Carriers for the Chemical Looping Combustion Process: A Review

“…Furthermore, it prevented spinel (NiAl 2 O 4 ) formation and decreased attrition and hence no activity loss occurred even after 10 redox cycles. The OTC of the OC was 9.3 wt % reported for the combustion of methane gas . Thus, the coating with a core–shell structure promoter can stabilize the reactivity (OTC) of OC in repeating reduction and oxidation cycles.…”

Comparative Study on Ni/γ-Al2O3 Prepared via Ultrasonic Irradiation and Impregnation Approaches as an Oxygen Carrier in Chemical Looping Combustion

“…Though these metal oxides exhibited great potential in CLC, their performances and reactivities decreased after several cycles. 19 The efficiency of OCs can be increased by combining them with certain supports such as SiO 2 , TiO 2 , ZrO 2 , and Al 2 O 3 to preserve cyclic stability and improve the kinetics. 20 Utilization of metal oxides without the aid of support would cause the material to lose the ability to transfer oxygen over many cycles and be subject to quick agglomeration.…”

“…Transition metals such as Cu, Mn, Fe, Co, and Ni are the potential candidates and have been tested in CLC as OCs. Though these metal oxides exhibited great potential in CLC, their performances and reactivities decreased after several cycles . The efficiency of OCs can be increased by combining them with certain supports such as SiO 2 , TiO 2 , ZrO 2 , and Al 2 O 3 to preserve cyclic stability and improve the kinetics .…”

Preparation of Metal Oxide‐based Oxygen Carriers Supported with CeO2 and γ‐Al2O3 for Chemical Looping Combustion

“…Several preparation methods such as sol‐gel 25, freeze granulation 26, ball milling 27, and coprecipitation 28 have been adopted for OCs formation. However, wet impregnation is known to be a more suitable method, which could successfully improve stability, number of metal oxides, CO 2 sequestering, chemical reactivity without attrition, and agglomeration of OCs 29, 30.…”