Envisioning Catalytic Processes in Chemical Looping Systems: Material and Process Development
| Main Author: | |
|---|---|
| Language: | English |
| Published: |
The Ohio State University / OhioLINK
2020
|
| Subjects: | |
| Online Access: | http://rave.ohiolink.edu/etdc/view?acc_num=osu1586359263610608 |
| id |
ndltd-OhioLink-oai-etd.ohiolink.edu-osu1586359263610608 |
|---|---|
| record_format |
oai_dc |
| collection |
NDLTD |
| language |
English |
| sources |
NDLTD |
| topic |
Chemical Engineering Chemistry Materials Science Chemical looping Material development Process development Oxygen vacancies mechanistic studies Redox reactions Sustainable technology |
| spellingShingle |
Chemical Engineering Chemistry Materials Science Chemical looping Material development Process development Oxygen vacancies mechanistic studies Redox reactions Sustainable technology Baser, Deven Swapneshu Envisioning Catalytic Processes in Chemical Looping Systems: Material and Process Development |
| author |
Baser, Deven Swapneshu |
| author_facet |
Baser, Deven Swapneshu |
| author_sort |
Baser, Deven Swapneshu |
| title |
Envisioning Catalytic Processes in Chemical Looping Systems: Material and Process Development |
| title_short |
Envisioning Catalytic Processes in Chemical Looping Systems: Material and Process Development |
| title_full |
Envisioning Catalytic Processes in Chemical Looping Systems: Material and Process Development |
| title_fullStr |
Envisioning Catalytic Processes in Chemical Looping Systems: Material and Process Development |
| title_full_unstemmed |
Envisioning Catalytic Processes in Chemical Looping Systems: Material and Process Development |
| title_sort |
envisioning catalytic processes in chemical looping systems: material and process development |
| publisher |
The Ohio State University / OhioLINK |
| publishDate |
2020 |
| url |
http://rave.ohiolink.edu/etdc/view?acc_num=osu1586359263610608 |
| work_keys_str_mv |
AT baserdevenswapneshu envisioningcatalyticprocessesinchemicalloopingsystemsmaterialandprocessdevelopment |
| _version_ |
1719456995340189696 |
| spelling |
ndltd-OhioLink-oai-etd.ohiolink.edu-osu15863592636106082021-08-03T07:14:07Z Envisioning Catalytic Processes in Chemical Looping Systems: Material and Process Development Baser, Deven Swapneshu Chemical Engineering Chemistry Materials Science Chemical looping Material development Process development Oxygen vacancies mechanistic studies Redox reactions Sustainable technology <p>The growing strain on natural resources to meet the increasing global demand for energy and chemicals has been a challenge for several decades. This has motivated the emergence of several alternative technologies that provide effective and sustainable solutions while being economically feasible. Chemical looping is one such technology that utilizes the redox gas-solid reaction chemistries to inherently change the reaction mechanism, thus providing new and efficient pathways to produce the desired product. This gives rise to a platform that has higher degrees of freedom as compared to the traditional catalytic systems, which can be leveraged to create economically and environmentally sustainable processes. Several catalytic applications have been investigated as chemical looping alternatives and are given as follows: </p><p><b>Oxidative coupling of methane (OCM): </b></p><p>OCM refers to the reaction where two CH<sub>4</sub> molecules couple to form hydrocarbon products such as ethane/ethylene in the presence of oxygen species. The chemical looping OCM technology uses a catalytic oxygen carrier to provide the oxygen species for CH<sub>4</sub> coupling, consequently reducing the oxygen carrier. The lattice oxygen of this reduced oxygen carrier is replenished by air in a separate reactor which feeds the oxidized oxygen carrier back into the first reactor, thus completing the loop. Traditionally, O<sub>2</sub> is co-fed with CH<sub>4</sub> over a catalyst bed to produce these hydrocarbon products. The use of lattice oxygen as compared to O<sub>2</sub> improves the selectivity of the desired products by eliminating the undesired gas-phase combustion reactions. Additionally, the use of an oxygen carrier expands the product slate up to C<sub>7</sub> hydrocarbons, which has not been reported for the catalytic O<sub>2</sub> co-feed system. However, developing an active oxygen carrier has been challenging due to the tradeoff between product selectivity and CH<sub>4</sub> conversion. Thus, parametric tests have been conducted in a fixed bed reactor with the goal of understanding this tradeoff, investigating the reaction mechanism of OCM and identifying key reaction steps. These tests indicated a direct correlation of the lattice oxygen vacancy generated on the surface of the oxygen carrier and the tradeoff between selectivity and conversion. These insights combined with density functional theory calculations aided in a dopant screening strategy to induce the OCM selective oxygen vacancies on the oxygen carrier. Several doped oxygen carrier particles were synthesized and tested through which the optimal formulation was identified. Thus, a rational design strategy for developing a highly active and stable OCM particle was established.</p><p><b>Direct NO<sub>x</sub> decomposition: </b></p><p>Traditionally, NO<sub>x</sub> decomposition from flue gas streams is carried out catalytically by selectively reducing it with NH<sub>3</sub>. The novel chemical looping alternative takes advantage of oxygen vacancies that are available on a specialized metal oxide surface to decompose NO<sub>x</sub> into N<sub>2</sub>, thereby oxidizing the metal oxide. This oxidized metal oxide can release the oxygen in the form of O<sub>2</sub> upon increasing the reaction temperature. This one-of-a-kind technology eliminates the use of NH<sub>3</sub> by directly decomposing NO<sub>x</sub> into N<sub>2</sub> and O<sub>2</sub> which are produced in separate streams. Several metal oxides have been experimentally screened for the activity towards direct NO<sub>x</sub> decomposition and subsequent O<sub>2</sub> evolution. The goal has been to reduce the reaction temperature, which ultimately lowers the parasitic energy requirement of the system. Further, the effect of other components of the flue gas, such as CO<sub>2</sub> and O<sub>2</sub>, on NO<sub>x</sub> decomposition activity was investigated. These components showed a significant loss in NO<sub>x</sub> decomposition activity in a catalytic system. However, the specialized metal oxide has been tailored to show a minimal loss in activity, thus being superior to its catalytic counterpart. Finally, a preliminary techno-economic analysis evaluated the feasibility of the process which indicated significant savings as compared to traditional systems.</p><p><b>Methane to syngas with enhanced CO<sub>2</sub>/H<sub>2</sub>O utilization: </b></p><p>Syngas is an essential intermediate for liquid fuel/chemical production. The lattice oxygen from a metal oxide provides unique gas-solid thermodynamics that improves the syngas production efficiency as compared to traditional reforming systems. This thermodynamic benefit can be capitalized for CH<sub>4</sub> co-fed with CO<sub>2</sub> and H<sub>2</sub>O through reactor design. The effect of these changes can be effectively captured through process simulations done in ASPEN Plus. Several configurations with gas-solid contact including cocurrent, counter-current and cross-current have been investigated at different conditions to improve the CO<sub>2</sub>/H<sub>2</sub>O utilization. These configurations provide a novel approach to take advantage of the differences in gas-solid thermodynamic equilibrium with the change in the solid phase. A systematic study of these process simulations has aided in the design of the actual chemical looping reactor for syngas production. Further, mechanistic studies on the CO<sub>2</sub> utilization has been carried out to understand the effect of oxygen vacancies on CH<sub>4</sub> conversion and CO<sub>2</sub> utilization. </p><p><b>Ammonia decomposition for its use as a hydrogen carrier:</b></p><p>Hydrogen economy is a novel concept that aims to reduce the carbon intensity of the applications pertaining to energy. One of the major hurdles towards adopting such a system lies in the complexity and the cost of storage, transportation, and handling of H<sub>2</sub>. Thus, ammonia has been proposed as a hydrogen carrier to mitigate these drawbacks, however efficient conversion of ammonia back to H<sub>2</sub> can be challenging. A unique chemical looping system has been proposed that uses metal oxides to convert NH<sub>3</sub> into N<sub>2</sub> and H<sub>2</sub>. Due to the peculiar process configuration of this system, the N<sub>2</sub> and H<sub>2</sub> streams can be partially separated in the reactor system itself, providing opportunities for process intensification. </p> 2020-10-05 English text The Ohio State University / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=osu1586359263610608 http://rave.ohiolink.edu/etdc/view?acc_num=osu1586359263610608 restricted--full text unavailable until 2025-05-13 This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws. |