Matching Items (6)
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- All Subjects: Carbon Sequestration
- All Subjects: Direct Air Capture
- All Subjects: Bipyridine
- Creators: Lackner, Klaus S
- Resource Type: Text
- Status: Published
Description
Increasing concentrations of carbon dioxide in the atmosphere will inevitably lead to long-term changes in climate that can have serious consequences. Controlling anthropogenic emission of carbon dioxide into the atmosphere, however, represents a significant technological challenge. Various chemical approaches have been suggested, perhaps the most promising of these is based on electrochemical trapping of carbon dioxide using pyridine and derivatives. Optimization of this process requires a detailed understanding of the mechanisms of the reactions of reduced pyridines with carbon dioxide, which are not currently well known. This thesis describes a detailed mechanistic study of the nucleophilic and Bronsted basic properties of the radical anion of bipyridine as a model pyridine derivative, formed by one-electron reduction, with particular emphasis on the reactions with carbon dioxide. A time-resolved spectroscopic method was used to characterize the key intermediates and determine the kinetics of the reactions of the radical anion and its protonated radical form. Using a pulsed nanosecond laser, the bipyridine radical anion could be generated in-situ in less than 100 ns, which allows fast reactions to be monitored in real time. The bipyridine radical anion was found to be a very powerful one-electron donor, Bronsted base and nucleophile. It reacts by addition to the C=O bonds of ketones with a bimolecular rate constant around 1* 107 M-1 s-1. These are among the fastest nucleophilic additions that have been reported in literature. Temperature dependence studies demonstrate very low activation energies and large Arrhenius pre-exponential parameters, consistent with very high reactivity. The kinetics of E2 elimination, where the radical anion acts as a base, and SN2 substitution, where the radical anion acts as a nucleophile, are also characterized by large bimolecular rate constants in the range ca. 106 - 107 M-1 s-1. The pKa of the bipyridine radical anion was measured using a kinetic method and analysis of the data using a Marcus theory model for proton transfer. The bipyridine radical anion is found to have a pKa of 40±5 in DMSO. The reorganization energy for the proton transfer reaction was found to be 70±5 kJ/mol. The bipyridine radical anion was found to react very rapidly with carbon dioxide, with a bimolecular rate constant of 1* 108 M-1 s-1 and a small activation energy, whereas the protonated radical reacted with carbon dioxide with a rate constant that was too small to measure. The kinetic and thermodynamic data obtained in this work can be used to understand the mechanisms of the reactions of pyridines with carbon dioxide under reducing conditions.
ContributorsRanjan, Rajeev (Author) / Gould, Ian R (Thesis advisor) / Buttry, Daniel A (Thesis advisor) / Yarger, Jeff (Committee member) / Seo, Dong-Kyun (Committee member) / Arizona State University (Publisher)
Created2015
Description
Carbon dioxide (CO2) is one of the most dangerous greenhouse gas. Its concentration in the atmosphere has increased to very high levels since the industrial revolution. This continues to be a threat due to increasing energy demands. 60% of the worlds global emissions come from automobiles and other such moving sources. Hence, to stay within safe limits, it is extremely important to curb current emissions and remove those which have already been emitted. Out of many available technologies, one such technology is the moisture swing based air capture technology that makes use of resin material that absorbs CO2 when it is dry and releases it when it is wet. A mathematical model was developed to better understand the mechanism of this process. In order to validate this model, numerical simulation and experimentation was done. Once the mechanism was proved, it was seen that there are many factors and parameters that govern this process. Some of these do not have definite value. To find the best fit value for these parameters, an optimized fitting routine needs to be developed that can minimize the standard deviation of the error. This thesis looks into ways in which the optimization of parameters can be done and the possible future work by using substantial data.
ContributorsChopra, Vinuta (Author) / Lackner, Klaus S (Thesis advisor) / Fox, Peter (Committee member) / Wright, Allen (Committee member) / Arizona State University (Publisher)
Created2016
Description
This paper will explore the existing relationship between direct air capture (DAC)technology and energy justice (EJ) principles. As DAC is a nascent technology that is
transitioning from the R&D phase to the deployment phase, a standard for typical scaling
practices has not yet been established. Additionally, since the industry of DAC aims to
capture at least 10 gigatonnes of carbon dioxide per year by 2050, and at least 20 Gt/yr by
2100, the scaling practices of this technology will have a significant impact on
communities around the world. Therefore, in this thesis I argue that if DAC is not scaled
equitably, it will negatively impact the communities hosting the technology, and would
develop a negative reputation which could slow down the overall scaling process. On the
flip side, if DAC is scaled equitably, then it could create a positive effect by being
deployed in underserved and marginalized communities and providing an economic
benefit. This could result in DAC having a positive reputation and scaling more rapidly.
In order to understand how the field viewed the integration of EJ principles into the
scaling process, I interviewed representatives from DAC companies, experts in energy
justice from NGOs and academia, and local government officials. These interviews were
semi-structured, open-ended and conducted anonymously. Through these interviews I
was able to refine my arguments and put forward a set of guidelines that the industry
could use to scale DAC with equity and justice as core principles.
ContributorsSriramprasad, Vishrudh (Author) / Lackner, Klaus S (Thesis advisor) / Miller, Clark (Committee member) / Green, Matt (Committee member) / Hanemann, Michael (Committee member) / Arizona State University (Publisher)
Created2023
Description
A brief describing how certificates of carbon sequestration ought to work, their meaning, and their requirements.
ContributorsArcusa, Stéphanie (Author) / Lackner, Klaus S (Author)
Created2021
Description
As the global community raises concerns regarding the ever-increasing urgency of climate change, efforts to explore innovative strategies in the fight against this anthropogenic threat is growing. Along with other greenhouse gas mitigation technologies, Direct Air Capture (DAC) or the technology of removing carbon dioxide directly from the air has received considerable attention. As an emerging technology, the cost of DAC has been the prime focus not only in scientific society but also between entrepreneurs and policymakers. While skeptics are concerned about the high cost and impact of DAC implementation at scales comparable to the magnitude of climate change, industrial practitioners have demonstrated a pragmatic path to cost reduction. Based on the latest advancements in the field, this dissertation investigates the economic feasibility of DAC and its role in future energy systems. With a focus on the economics of carbon capture, this work compares DAC with other carbon capture technologies from a systemic perspective. Moreover, DAC’s major expenses are investigated to highlight critical improvements necessary for commercialization. In this dissertation, DAC is treated as a backstop mitigation technology that can address carbon dioxide emissions regardless of the source of emission. DAC determines the price of carbon dioxide removal when other mitigation technologies fall short in meeting their goals. The results indicate that DAC, even at its current price, is a reliable backup and is competitive with more mature technologies such as post-combustion capture. To reduce the cost, the most crucial component of a DAC design, i.e., the sorbent material, must be the centerpiece of innovation. In conclusion, DAC demonstrates the potential for not only negative emissions (carbon dioxide removal with the purpose of addressing past emissions), but also for addressing today’s emissions. The results emphasize that by choosing an effective scale-up strategy, DAC can become sufficiently cheap to play a crucial role in decarbonizing the energy system in the near future. Compared to other large-scale decarbonization strategies, DAC can achieve this goal with the least impact on our existing energy infrastructure.
ContributorsAzarabadi, Habib (Author) / Lackner, Klaus S (Thesis advisor) / Allenby, Braden R. (Committee member) / Dirks, Gary W (Committee member) / Reddy, Agami (Committee member) / Arizona State University (Publisher)
Created2020
Description
Global emissions of carbon dioxide are reaching new heights every year since the Industrial Revolution. A major contributor to this is fossil fuel consumption. The consumption trend has indicated all this. It has also strengthened the argument for the need to cut down emissions and sweep out historical emissions through the implementation of Carbon Capture, Utilization, and Storage (CCUS) and Carbon Dioxide Removal (CDR) technologies respectively. This is required to control global warming. Direct Air Capture (DAC) is one of the CDR technologies. Extensive research and projections have suggested that DAC has tremendous potential to achieve global climate change mitigation goals. The feasibility of DAC is proven but work is required to bridge gaps in DAC research to make it affordable and scalable. Process modelling is an approach used to address these concerns. Current DAC research in system design and modelling is discrete and existing models have limited use cases. This work is focused on the development of a generalized process mass transfer model for the capture stage of solid sorbent DAC contactors. It provides flexibility for defining contactor geometry, selection of ambient conditions, and versatility to plug different sorbents in it for CO2 capture. The modelling procedure is explained, and a robustness check is performed to ensure model integrity. The results of the robustness check and sensitivity analysis are then explained. This research is part of a long-term effort to create a complete modelling package for the DAC community to boost research and development to large-scale deployments.
ContributorsPatel, Kshitij Mukeshbhai (Author) / Green, Matthew D (Thesis advisor) / Lackner, Klaus S (Committee member) / Cirucci, John (Committee member) / Arizona State University (Publisher)
Created2023