Designing Metal-Organic-Frameworks For Selective Biomass Catalysis

University of Minnesota Ph.D. dissertation. March 2020. Major: Chemical Engineering. Advisor: Michael Tsapatsis. 1 computer file (PDF); xv, 121 pages.Metal-organic frameworks (MOFs) are microporous materials with a wide range of pore sizes and functionalities, making them attractive for a variety of potential applications in catalysis, separations, sensing, and gas storage. Associated with the global demand for clean energy sources to find alternatives to fossil fuels, their use as catalysts for biomass conversion to chemicals finds potential application. The performance of MOFs in these applications is dependent on how stable they are upon modifications to their tunable frameworks. Such modifications include acid treatment, ligand, and cluster functionalization that can be performed by direct synthesis or post-synthesis modification, as desired for optimum performance. This dissertation focuses on using synthetic methods that may enable the tailoring the microstructure of MOFs towards their use for catalysis of biomass. We discuss the use of a method called acid modulation to introduce missing-ligands defects and open Lewis acid sites into the framework of UiO-66 to make it an active and selective catalyst for glucose isomerization to fructose in alcohol media. We demonstrate that upon the alcohol choice, the selectivity of the reaction to fructose can change drastically by favoring other reaction pathways. Furthermore, we investigate the reaction mechanism of glucose isomerization into UiO-66 and identify that glucose reacts via a 1,2-hydride transfer mechanism similar to what was reported for Sn-zeolites. We report the synthesis and installation of phosphonic acid moieties into the ligands of UiO-66 and UiO-67 as a way to introduce Brønsted acidity to these materials by a post-synthesis ligand exchange method. The active sites of P-UiO-66 are elucidated by a combination of solid-state NMR and DFT calculations. P-UiO66 is reported to be active and selective for several acid-catalyzed reactions such as alcohol dehydration and furans dehydra-decyclization with site-time yields approaching that of highly selective phosphoric acid zeolites, holding promise for its use in this and other reactions for the biomass conversion to chemicals. The tunability of MOFs combined with the PSM method and synthesis of phosphonic acids can provide accurate control of the density of active sites with a uniform distribution throughout the framework

Effects of Phosphorus Content on Simultaneous Ultradeep HDS and HDN Reactions over NiMoP/Alumina Catalysts

The effects of phosphorus content on competitive hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT) and hydrodenitrogenation (HDN) of quinoline (Q) over NiMo catalysts were evaluated. Reactions were carried out in a trickle-bed high-pressure flow microreactor. HDS of 4,6-DMDBT was strongly inhibited at Q concentrations of 90 ppmw N, mostly hydrogenation (HYD) route in HDS, suggesting that 4,6-DMDBT and Q compete for the same hydrogenation active sites, which was confirmed by the products’ distribution in HDN reactions. Morphology and nature of active sites promoted by phosphorus addition led to different activity performance on competitive HDS and HDN reactions, as evidenced by TOF values. At low concentrations of Q, promoted catalysts maintained activity for both HDS and HDN. High Q levels (above 90 ppmw N) decreased HDS and HDN activity due to stronger inhibition of catalysts. The addition of 1 wt % of phosphorus showed superior activity, attributed to a combination of better dispersed NiMoS active sites and Brønsted acidity

Xenon Trapping in Metal-Supported Silica Nanocages

Xenon (Xe) is a valuable and scarce noble gas used in various applications, including lighting, electronics, and anesthetics, among many others. It is also a volatile byproduct of the nuclear fission of uranium. A novel material architecture consisting of silicate nanocages in contact with a metal surface and an approach for trapping single Xe atoms in these cages is presented. The trapping is done at low Xe pressures and temperatures between 400 and 600 K, and the process is monitored in situ using synchrotron-based ambient pressure X-ray photoelectron spectroscopy. Release of the Xe from the cages occurs only when heating to temperatures above 750 K. A model that explains the experimental trapping kinetics is proposed and tested using Monte Carlo methods. Density functional theory calculations show activation energies for Xe exiting the cages consistent with experiments. This work can have significant implications in various fields, including Xe production, nuclear power, nuclear waste remediation, and nonproliferation of nuclear weapons. The results are also expected to apply to argon, krypton, and radon, opening an even more comprehensive range of applications.Fil: Xu, Yixin. Brookhaven National Laboratory; Estados Unidos. State University of New York. Stony Brook University; Estados UnidosFil: Dorneles de Mello, Matheus. University Of Delaware; Estados Unidos. Brookhaven National Laboratory; Estados UnidosFil: Zhou, Chen. Brookhaven National Laboratory; Estados Unidos. State University of New York. Stony Brook University; Estados UnidosFil: Sharma, Shruti. State University of New York. Stony Brook University; Estados UnidosFil: Karagoz, Burcu. Brookhaven National Laboratory; Estados UnidosFil: Head, Ashley R.. Brookhaven National Laboratory; Estados UnidosFil: Darbari, Zubin. State University of New York. Stony Brook University; Estados Unidos. Brookhaven National Laboratory; Estados UnidosFil: Waluyo, Iradwikanari. Brookhaven National Laboratory; Estados UnidosFil: Hunt, Adrian. Brookhaven National Laboratory; Estados UnidosFil: Stacchiola, Dario Jose. Brookhaven National Laboratory; Estados UnidosFil: Manzi, Sergio Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich". Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich"; ArgentinaFil: Boscoboinik, Alejandro Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. University of Pennsylvania; Estados UnidosFil: Pereyra, Victor Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi". Universidad Nacional de San Luis. Facultad de Ciencias Físico, Matemáticas y Naturales. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi"; ArgentinaFil: Boscoboinik, J. Anibal. University Of Delaware; Estados Unidos. Brookhaven National Laboratory; Estados Unidos. State University of New York. Stony Brook University; Estados Unido

Few-Unit-Cell MFI Zeolite Synthesized using a Simple Di-quaternary Ammonium Structure-Directing Agent.

Synthesis of a pentasil-type zeolite with ultra-small few-unit-cell crystalline domains, which we call FDP (few-unit-cell crystalline domain pentasil), is reported. FDP is made using bis-1,5(tributyl ammonium) pentamethylene cations as structure directing agent (SDA). This di-quaternary ammonium SDA combines butyl ammonium, in place of the one commonly used for MFI synthesis, propyl ammonium, and a five-carbon nitrogen-connecting chain, in place of the six-carbon connecting chain SDAs that are known to fit well within the MFI pores. X-ray diffraction analysis and electron microscopy imaging of FDP indicate ca. 10 nm crystalline domains organized in hierarchical micro-/meso-porous aggregates exhibiting mesoscopic order with an aggregate particle size up to ca. 5 μm. Al and Sn can be incorporated into the FDP zeolite framework to produce active and selective methanol-to-hydrocarbon and glucose isomerization catalysts, respectively

Few-Unit-Cell MFI Zeolite Synthesized using a Simple Di-quaternary Ammonium Structure-Directing Agent.

Synthesis of a pentasil-type zeolite with ultra-small few-unit-cell crystalline domains, which we call FDP (few-unit-cell crystalline domain pentasil), is reported. FDP is made using bis-1,5(tributyl ammonium) pentamethylene cations as structure directing agent (SDA). This di-quaternary ammonium SDA combines butyl ammonium, in place of the one commonly used for MFI synthesis, propyl ammonium, and a five-carbon nitrogen-connecting chain, in place of the six-carbon connecting chain SDAs that are known to fit well within the MFI pores. X-ray diffraction analysis and electron microscopy imaging of FDP indicate ca. 10 nm crystalline domains organized in hierarchical micro-/meso-porous aggregates exhibiting mesoscopic order with an aggregate particle size up to ca. 5 μm. Al and Sn can be incorporated into the FDP zeolite framework to produce active and selective methanol-to-hydrocarbon and glucose isomerization catalysts, respectively

Brazilian Flora 2020: Leveraging the power of a collaborative scientific network

International audienceThe shortage of reliable primary taxonomic data limits the description of biological taxa and the understanding of biodiversity patterns and processes, complicating biogeographical, ecological, and evolutionary studies. This deficit creates a significant taxonomic impediment to biodiversity research and conservation planning. The taxonomic impediment and the biodiversity crisis are widely recognized, highlighting the urgent need for reliable taxonomic data. Over the past decade, numerous countries worldwide have devoted considerable effort to Target 1 of the Global Strategy for Plant Conservation (GSPC), which called for the preparation of a working list of all known plant species by 2010 and an online world Flora by 2020. Brazil is a megadiverse country, home to more of the world's known plant species than any other country. Despite that, Flora Brasiliensis, concluded in 1906, was the last comprehensive treatment of the Brazilian flora. The lack of accurate estimates of the number of species of algae, fungi, and plants occurring in Brazil contributes to the prevailing taxonomic impediment and delays progress towards the GSPC targets. Over the past 12 years, a legion of taxonomists motivated to meet Target 1 of the GSPC, worked together to gather and integrate knowledge on the algal, plant, and fungal diversity of Brazil. Overall, a team of about 980 taxonomists joined efforts in a highly collaborative project that used cybertaxonomy to prepare an updated Flora of Brazil, showing the power of scientific collaboration to reach ambitious goals. This paper presents an overview of the Brazilian Flora 2020 and provides taxonomic and spatial updates on the algae, fungi, and plants found in one of the world's most biodiverse countries. We further identify collection gaps and summarize future goals that extend beyond 2020. Our results show that Brazil is home to 46,975 native species of algae, fungi, and plants, of which 19,669 are endemic to the country. The data compiled to date suggests that the Atlantic Rainforest might be the most diverse Brazilian domain for all plant groups except gymnosperms, which are most diverse in the Amazon. However, scientific knowledge of Brazilian diversity is still unequally distributed, with the Atlantic Rainforest and the Cerrado being the most intensively sampled and studied biomes in the country. In times of “scientific reductionism”, with botanical and mycological sciences suffering pervasive depreciation in recent decades, the first online Flora of Brazil 2020 significantly enhanced the quality and quantity of taxonomic data available for algae, fungi, and plants from Brazil. This project also made all the information freely available online, providing a firm foundation for future research and for the management, conservation, and sustainable use of the Brazilian funga and flora