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Heterogeneous Catalysis for Organic Reactions

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This honors thesis is focused on two separate catalysis projects conducted under the mentorship of Dr. Javier Pérez-Ramírez at ETH Zürich. The first project explored ethylene oxychlorination over supported europium oxychloride catalysts. The second project investigated alkyne semihydrogenation over nickel

This honors thesis is focused on two separate catalysis projects conducted under the mentorship of Dr. Javier Pérez-Ramírez at ETH Zürich. The first project explored ethylene oxychlorination over supported europium oxychloride catalysts. The second project investigated alkyne semihydrogenation over nickel phosphide catalysts. This work is the subject of a publication of which I am a co-author, as cited below.

Project 1 Abstract: Ethylene Oxychlorination
The current two-step process for the industrial process of vinyl chloride production involves CuCl2 catalyzed ethylene oxychlorination to ethylene dichloride followed by thermal cracking of the latter to vinyl chloride. To date, no industrial application of a one-step process is available. To close this gap, this work evaluates a wide range of self-prepared supported CeO2 and EuOCl catalysts for one-step production of vinyl chloride from ethylene in a fixed-bed reactor at 623 773 K and 1 bar using feed ratios of C2H4:HCl:O2:Ar:He = 3:3 6:1.5 6:3:82 89.5. Among all studied systems, CeO2/ZrO2 and CeO2/Zeolite MS show the highest activity but suffer from severe combustion of ethylene, forming COx, while 20 wt.% EuOCl/γ-Al2O3 leads to the best vinyl chloride selectivity of 87% at 15.6% C2H4 conversion with complete suppression of CO2 formation and only 4% selectivity to CO conversion for over 100 h on stream. Characterization by XRD and EDX mapping reveals that much of the Eu is present in non-active phases such as Al2Eu or EuAl4, indicating that alternative synthesis methods could be employed to better utilize the metal. A linear relationship between conversion and metal loading is found for this catalyst, indicating that always part of the used Eu is available as EuOCl, while the rest forms inactive europium aluminate species. Zeolite-supported EuOCl slightly outperforms EuOCl/γ Al2O3 in terms of total yield, but is prone to significant coking and is unstable. Even though a lot of Eu seems locked in inactive species on EuOCl/γ Al2O3, these results indicate possible savings of nearly 16,000 USD per kg of catalyst compared to a bulk EuOCl catalyst. These very promising findings constitute a crucial step for process intensification of polyvinyl chloride production and exploring the potential of supported EuOCl catalysts in industrially-relevant reactions.

Project 2 Abstract: Alkyne Semihydrogenation
Despite strongly suffering from poor noble metal utilization and a highly toxic selectivity modifier (Pb), the archetypal catalyst applied for the three-phase alkyne semihydrogenation, the Pb-doped Pd/CaCO3 (Lindlar catalyst), is still being utilized at industrial level. Inspired by the very recent strategies involving the modification of Pd with p-block elements (i.e., S), this work extrapolates the concept by preparing crystalline metal phosphides with controlled stoichiometry. To develop an affordable and environmentally-friendly alternative to traditional hydrogenation catalysts, nickel, a metal belonging to the same group as Pd and capable of splitting molecular hydrogen has been selected. Herein, a simple two-step synthesis procedure involving nontoxic precursors was used to synthesize bulk nickel phosphides with different stoichiometries (Ni2P, Ni5P4, and Ni12P5) by controlling the P:Ni ratios. To uncover structural and surface features, this catalyst family is characterized with an array of methods including X-ray diffraction (XRD), 31P magic-angle nuclear magnetic resonance (MAS-NMR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). Bulk-sensitive techniques prove the successful preparation of pure phases while XPS analysis unravels the facile passivation occurring at the NixPy surface that persists even after reductive treatment. To assess the characteristic surface fingerprints of these materials, Ar sputtering was carried out at different penetration depths, reveling the presence of Ni+ and P-species. Continuous-flow three-phase hydrogenations of short-chain acetylenic compounds display that the oxidized layer covering the surface is reduced under reaction conditions, as evidenced by the induction period before reaching the steady state performance. To assess the impact of the phosphidation treatment on catalytic performance, the catalysts were benchmarked against a commercial Ni/SiO2-Al2O3 sample. While Ni/SiO2-Al2O3 presents very low selectivity to the alkene (the selectivity is about 10% at full conversion) attributed to the well-known tendency of naked nickel nanoparticles to form hydrides, the performance of nickel phosphides is highly selective and independent of P:Ni ratio. In line with previous findings on PdxS, kinetic tests indicate the occurrence of a dual-site mechanism where the alkyne and hydrogen do not compete for the same site.

This work is the subject of a publication of which I am a co-author, as cited below.

D. Albani; K. Karajovic; B. Tata; Q. Li; S. Mitchell; N. López; J. Pérez-Ramírez. Ensemble Design in Nickel Phosphide Catalysts for Alkyne Semi-Hydrogenation. ChemCatChem 2019. doi.org/10.1002/cctc.201801430

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2019-05

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An Evaluation of Bicycle Friendly Rating Schemes for Cities and the Implications for Tempe, AZ

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City planners often use bicycle friendly rating schemes as tools to guide them in their efforts to establish a bicycle community. However, the criteria and methodologies used vary from program to program and often do not encapsulate all of the

City planners often use bicycle friendly rating schemes as tools to guide them in their efforts to establish a bicycle community. However, the criteria and methodologies used vary from program to program and often do not encapsulate all of the necessary elements that comprise true bicycle friendliness. This report documents the important elements, strategies, and best practices that well-established Dutch, Danish, and German bike friendly cities exhibit to create a baseline standard for bicycle friendliness. Not all rating programs' criteria and methodologies align perfectly within this understanding of bicycle friendliness. City planners should use these programs as tools while keeping their limitations in consideration. The City of Tempe currently uses the League of American Bicyclists Bicycle Friendly Community program and BikeScore.com. By understanding the limitations associated with these programs, Tempe should move forward in their pursuit of bicycle friendliness by using multiple rating programs simultaneously and by looking at top-rated cities' strategies to enhance their infrastructure, network, urban form, and biking culture.

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2014-05

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Lessons in Arcology: An Overview of Two Experimental Urban Projects and Their Viability in Phoenix's Sustainable Urban Development

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Defines the concept of the arcology as conceived by architect Paolo Soleri. Arcology combines "architecture" and "ecology" and explores a visionary notion of a self-contained urban community that has agricultural, commercial, and residential facilities under one roof. Two real-world examples

Defines the concept of the arcology as conceived by architect Paolo Soleri. Arcology combines "architecture" and "ecology" and explores a visionary notion of a self-contained urban community that has agricultural, commercial, and residential facilities under one roof. Two real-world examples of these projects are explored: Arcosanti, AZ and Masdar City, Abu Dhabi, UAE. Key aspects of the arcology that could be applied to an existing urban fabric are identified, such as urban design fostering social interaction, reduction of automobile dependency, and a development pattern that combats sprawl. Through interviews with local representatives, a holistic approach to applying arcology concepts to the Phoenix Metro Area is devised.

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2015-05

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Women and Bicycling: Exploring the Connections Between an Improved Infrastructure and the Perception of Safety Among Women Cyclists in Tempe

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This paper explores women and bicycling, with the focus of looking at how to get more women onto the bicycle in Tempe, Arizona. The main areas of interest for this study are improvements to bicycling infrastructure and an increase in

This paper explores women and bicycling, with the focus of looking at how to get more women onto the bicycle in Tempe, Arizona. The main areas of interest for this study are improvements to bicycling infrastructure and an increase in the safety and the perception of safety of women cyclists in the Tempe area. In order to explore this topic, an online survey of 75 Arizona State students was conducted. From the results women were primarily concerned with their safety due to the condition of the overall infrastructure and the lack of bicycle related improvements. Research such as this that examines women and cycling is significant due to the current underrepresentation of women in the cycling community and has the potential to improve safety and increase bicycle ridership.

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2014-12

Debunking Common Landscaping Misconceptions in Phoenix, Arizona

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This project was inspired by Dr. Kelli L. Larson’s research which disproved three common landscaping misconceptions in the Phoenix Valley. The first misconception states that newcomers, not long-time Phoenicians more often have and prefer grassy lawns instead of xeric, desert-adapted

This project was inspired by Dr. Kelli L. Larson’s research which disproved three common landscaping misconceptions in the Phoenix Valley. The first misconception states that newcomers, not long-time Phoenicians more often have and prefer grassy lawns instead of xeric, desert-adapted landscapes when actually the opposite is true. Secondly, the rise in xeric landscapes is not due to personal choice but rather a variety of other factors such as developer decisions. Finally, Dr. Larson’s research also disproves the assumption that people who possess pro-environmental attitudes correspondingly demonstrate sustainable landscaping behavior, and finds that people with those attitudes actually tend to irrigate more frequently in the winter months. Debunking these misconceptions is important because the long-term impacts of global climate change could have effects on water use in the desert southwest, and promoting water conservation in urban residential landscaping is an important step in the creation of sustainable water use policy. <br/><br/>The goal of my project was to make this information more accessible to broader public audiences who may not have access to it outside of research circles. I decided to create a zine, a small batch, hand-made mini-magazine, centered around disproving these myths so that the information could be distributed to broader audiences. I conducted informal stakeholder interviews to inform my design in order to appeal to those audiences, and constructed a 16-page booklet which debunked the myths and encouraged critical thinking about individual water use and urban landscaping habits. The zine included hand-painted illustrations and was constructed as a physical copy with the intention of eventually copying and distributing both a physical and digital version. The purpose of this project is to create a way of accessing reliable information about urban landscaping for residents of the Phoenix Valley, where the climate and geography necessitate water conservation.

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2021-05

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Evaluating the Meaning of Community in Community Land Trusts

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This thesis explores the role and meaning of community in the community land trust (CLT) model, and uses a single embedded case study to examine the mission, organizational structure, and governance model of Newtown CDC, a CLT based in Phoenix,

This thesis explores the role and meaning of community in the community land trust (CLT) model, and uses a single embedded case study to examine the mission, organizational structure, and governance model of Newtown CDC, a CLT based in Phoenix, Arizona. The thesis seeks to answer the questions, “What does community participation and empowerment mean to Newtown CDC”, and “how does the organization satisfy the competing needs of community participation and affordable housing production?” Historical documents of Newtown CDC, interviews with CLT staff, board members, and national policy representatives, as well as a survey of current and former CLT residents, reveal the perceived meaning and role of community, its evolution, and successes and failures in engaging the community. The data finds that a change in political and cultural dynamics has contributed to more resources focused on developing affordable housing, and less focus on community engagement. CLTs have adapted to this change, and the role and execution of community engagement has also evolved.

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2020-05

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The Politics Behind the Spatial Planning of Green Infrastructure in U.S. Cities

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This research project is part of a larger study of green infrastructure in urban planning and sustainability initiatives in cities across the U.S. Within the past few decades, the topic of sustainability has been at the forefront of city planners’

This research project is part of a larger study of green infrastructure in urban planning and sustainability initiatives in cities across the U.S. Within the past few decades, the topic of sustainability has been at the forefront of city planners’ minds as cities grow, there is new or redevelopment, and the threat of climate change and future climate variability increases. Green infrastructure is one increasingly popular urban sustainability strategy, which is widely promoted for its ability to provide multiple benefits. This multi-functionality translates into ecosystem services and possible disservices for a local community and the city as a whole. This research project examines 120 planning documents from 19 U.S. cities to examine whether the services cities say they expect green infrastructure to provide, or the rationale, match with the criteria used to determine where green infrastructure is sited. For this project, we ask: what are the rationales that cities provide for developing green infrastructure and what are the criteria cities are using to determine where to site it? We find that certain rationales, or benefits, are claimed without corresponding and specific siting criteria to substantiate how these benefits will be achieved, while other benefits, like those related to stormwater management, are prioritized over other potentially important benefits.

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2020-12