Core‐shell structured CaO‐based pellets protected by mesoporous ceramics shells for high‐temperature CO 2 capture

Karami

et al. 2017

Ind. Eng. Chem. Res.

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Calcium oxide (CaO) has been investigated as a high-temperature performance sorption material for carbon capture due to its high carbon dioxide (CO 2 ) capacity, low cost, and environmental benignity. Unfortunately, commercialized application of CaO materials has been hindered by severe capacity loss during cycling operations. In an attempt to overcome these problems, this study investigated the effects of adding zirconia-based ceramic dopants and coating sorbents with highly crystalline zirconium dioxide (ZrO 2 ) layers derived from the hydrolysis of zirconium butoxide to control the growth of ZrO 2 crystals. Uncoated natural Cadomin delivered a high CO 2 capture capacity of more than 13 mole CO 2 / kg, while the zirconia-coated sorbents showed excellent cycling stability corresponding to a maximum capacity of retention of 79% after 21 cycles at high temperatures. More importantly, the highly crystalline ZrO 2 -coated sorbents doped by zirconia-based sorbents exhibited a significantly lower decay capacity compared to the uncoated sorbents, which could be attributed to the formation of a perovskite structure that is resistant at high temperatures and a high-temperature-resistant ceramic layer through the solidstate reaction of the highly mesoporous crystalline ZrO 2 layer with CaO. These results shed light on the development of sorbents with special structures and superior chemical and mechanical properties for high-performance calcium looping or regenerative calcium cycle processes.

Section: -Results and Discussionmentioning

confidence: 99%

Pelletizing and Coating of Synthetic Zirconia Stabilized Calcium-Based Sorbents for Application in Calcium Looping CO₂ Capture

Soleimanisalim

Karami

et al. 2017

Ind. Eng. Chem. Res.

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“…The formation of the spinel layer reduces the activity and oxygen capacities of Ni/Al 2 O 3 , which can be avoided by introducing an inert layer between the Ni and Al 2 O 3 surface. Alumina has been proved as a suitable support for elevated-temperature applications and is commercially abundant. ,, However, its application in CLC has been hindered due to the above-mentioned problems. Mesoporous zirconia and titania act as inert and thermally stable shells on the alumina surface, stabilizing the alumina particles by an isolation effect attributed to the exclusive coating technique.…”

Section: Resultsmentioning

confidence: 99%

“…In the core–shell method, the soaking solutions were prepared according to the mole ratios of components mentioned below: − …”

Section: Experimental Sectionmentioning

confidence: 99%

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

Karami

Soleimanisalim

et al. 2020

Ind. Eng. Chem. Res.

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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.

“…Non‐catalytic gas‐solid reactions are numerous and involved in many industrial applications such as sulphation of lime, waste gas desulphurization, and chemical‐looping combustion (CLC) . The reaction between carbon dioxide (CO 2 ) and a calcium‐based solid sorbent (Equation ) as a heterogeneous non‐catalytic gas‐solid reaction has gained recognition for the calcium‐looping CO 2 capture process:

C a O (normals) + {C O}_{2} (normalg) \leftrightarrow C a {C O}_{3} (normals)

…”

Section: Introductionmentioning

confidence: 99%

A modified grain size distributed model for kinetic study of non‐catalytic gas‐solid reactions in presence of solid structural changes

Mahinpey²

2019

Can J Chem Eng

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This study investigated the carbonation behaviour of a calcium-based sorbent in the calcium-looping CO 2 capture process as a non-catalytic gassolid reaction using a modified grain size distributed (GSD) model. In GSD model, the calcium-based particle consisted of numerous spherical grains with variable size distribution. The GSD model was modified by considering a variable diffusion coefficient of the gaseous reactant through the development of the product layer. The overall conversion over the reaction time was calculated by a mathematical modelling. The overall sorbent conversion obtained by using the modified GSD model showed better agreement with the experimental data with the average absolute deviation of 4.2 % than the results obtained using the grain model with the average absolute deviation 9.4 %. In the modified GSD model, the physical microstructure of the sorbent particle changes due to the molar volume expansion during the carbonation reaction. The model also predicted accurately the change of particle structural properties such as porosity, molar density, and specific surface area during the carbonation reaction.