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- All Subjects: urban planning
- Creators: School of Sustainability
- Member of: Theses and Dissertations
- Status: Published
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
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.
There are unfortunately very few curricular guides that focus on community engagement within the higher education of landscape architecture. A Beginner’s Guide to Community Engagement in the Curriculum of Landscape Architecture and Urban Planning to Improve Social Justice and Sustainability helps resolve this issue and serves as a resource to students, educators, designers, and more. The guide centralizes a diverse collection of resources, guides students through learning materials, shares insight, and proposes potential community engagement methods. The booklet aims to help readers understand the importance of community engagement in design and shares different curricular approaches to introduce the work to students.