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- All Subjects: Agriculture
- Creators: School of Sustainability
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
Is there a mismatch between urban farmers’ perceptions of their farm’s environmental sustainability and its actual environmental impact? Focusing on the use of water and nutrients on each farm as described by the farmers through interviews, it is evident that there is some level of disconnect between ideals and practices. This project may aid in bridging the gap between the two in regard to the farmers’ sustainability goals. This project will move forward by continuing interviews with farmers as well as collecting soil and water from the farms in order to more accurately quantify the sustainability of the farms’ practices. This project demonstrates that there is some degree of misalignment between perception and reality. Two farms claimed they were sustainable when their practices did not reflect that, while 2 farms said they were not sure if they were sustainable when their practices indicated otherwise. Samples from two farms showed high concentrations of nutrients and salts, supporting the idea that there may be a mismatch between perceived and actual sustainability.
As technology has evolved over time and the U.S. population increases each year, this thesis focuses on the ways in which food production has shifted from the original farm to table to industrialized, processed food systems. Through a rationalization perspective, this research looks to the history and repercussions of industrial agriculture as it has shifted over time. The term over-industrialization is used to operationalize the state of our current production methods. These methods focus extensively on the least expensive and most rapid methods to produce large yields of food products and pay no mind to ethics, respect of culture, land, or quality of products. Today, there is a shroud the corporations have placed over food production to ensure a “what we can’t see doesn’t affect us” belief system. In this way, the thesis provides insight on past, current, and future methods of manufacturing. I conclude that although plausible alternatives are present, continued research and substantial producer and consumer changes must be our main priority.
Animal agriculture is a growing industry worldwide as the global demand for animal products increases. This has resulted in many harmful unintended consequences for human health, the environment, and animal welfare. This paper aims to uncover the hidden costs of negative externalities by answering the question: What types of subsidies is the US government distributing to the animal agriculture industry and in what amount? This paper will begin with some background on a few of the externalities created by the animal agriculture industry focusing specifically on environmental issues of water, air, and deforestation. Once this background is established, this will show that animal agriculture is in fact a negative-externality-generating industry. Next, subsidies will be defined and the principal findings of the research will reveal the different forms of support that the US government provides to animal agriculture. Lastly, these subsidies, both direct and indirect, will be quantified.
In the Southwestern United States, climate change poses challenges to reliable water access due to droughts, wildfires, and urban development. Arizonan farmers are faced with unpredictable precipitation, muddled legal water rights, and outdated equipment to irrigate their land. Located in Northern Arizona, Verde Valley residents and stakeholders are challenging the way the Verde River water is managed through collaboration, partnerships, and technical changes to water infrastructure. Through interviews conducted with various stakeholders involved in the Verde River ditch irrigation system, ranging from water users to nonprofit organizations, this paper identifies sociotechnical tinkering as an important aspect of maintaining agricultural operations along the river amid political tensions, social relations, and climate change. Through interviews and analysis, this paper further contributes to the relatively new discourse on the concept of sociotechnical tinkering by proving its existence and its subsequent effectiveness in the Verde Valley. Using statements made by respondents, the paper argues that sociotechnical tinkering helps manage resources through political and social relations.
Most urban agriculture sites experience challenges related to sustainability, but in the Sonoran Desert, even more challenges arise as a result of a unique climate, soil conditions, intense storms, and water scarcity. The objective of this project was to obtain information on common barriers to urban agriculture in the Sonoran Desert, as well as ways to overcome these barriers that will be made public for the purpose of improving sustainability of similar agriculture projects. I used interviews with gardeners and farm staff as my primary research method to gain insight to these barriers and solutions, and I coded their responses relating to challenges according to frequency mentioned. Using my findings, I compiled a thorough list of recommendations that urban agriculture projects in the Sonoran Desert or in similar climatic areas can use to achieve greater success and sustainable outcomes.