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- All Subjects: Nanoparticles
- Creators: Chemical Engineering Program
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
Scaled Formulations of Succinate based Polymeric particles for Eventual Testing in Clinical Settings
With an estimated 19.3 million cases and nearly 10 million deaths from cancer in a year worldwide, immunotherapies, which stimulate the immune system so that it can attack and kill cancer cells, are of interest. Tumors are produced from the uncontrolled and rapid proliferation of cells in the body. Cancer cells rely heavily on glutamine for proliferation due to its contribution of nitrogen for nucleotides and amino acids. Glutamine enters the tricarboxylic acid (TCA) cycle as α-ketoglutarate via glutaminolysis, in which glutamine is converted into glutamate by the enzyme glutaminase (GLS). Cancer cell proliferation may be limited by using glutaminase inhibitor CB-839. However, immune cells also rely on these metabolic pathways. Thus, a method for restarting the metabolic pathways in the presence of inhibitors is attractive. Succinate, a key metabolite in the TCA cycle, has been shown to stimulate the immune system despite the presence of metabolic inhibitors, such as CB-839. A delivery method of succinate is through microparticles (MPs) or nanoparticles (NPs) which may be coated in polyethylene glycol (PEG) for improved hydrophilicity. Polyethylene glycol succinate (PEGS) MPs were generated and tested in vivo and were shown to reduce tumor growth and prolong mouse survival. With the success in stimulating the immune system with MPs, NPs were investigated for an improved immune response due to their smaller size. These PES NPs were generated in this study. For clinical settings, it is necessary to scale-up the production of particles. Two methods of scale-up were proposed: (1) a combination of multiple small batches into a mixed batch, and (2) a singular, big batch. Size and release properties were compared to a small batch of PES NPs, and it was concluded that the big batch more closely resembled the small batch compared to the mixed batch. Thus, it was concluded that batch-to-batch variability plays a larger role than volume changes when scaling-up. In clinical settings, it is recommended to produce the particles in a big batch rather than a mixed batch.