GRIP Seminar

Graduate Research Initiative Program, Sponsored by the Chemical Engineering Graduate Council

Sourabh Nadgouda

Upgrading Methane to Olefins Using Oxidative Coupling of Methane in a Chemical Looping

Abstract

Methane is viewed as a fuel or an energy source, with limited applications in its direct use as a feedstock for chemicals manufacturing. The high molecular stability of methane requires an indirect approach where it is first converted to an intermediate chemical like syngas, which can then be used for producing commodity chemicals. This method of methane conversion requires multiple processing steps that are highly energy intensive. The direct approach for methane conversion to value-added products, on the other hand, allows for process intensification, which makes it competitive both in terms of cost and energy. Oxidative Coupling of Methane (OCM) has the highest per pass yields towards products among all existing direct methane conversion technologies. It also provides a one-step process towards manufacturing olefins (C2+hydrocarbons) from methane. Traditionally, methane oxidation in OCM has been carried out by co-feeding molecular oxygen with methane over an activated catalyst. The chemical looping method, however, utilizes the lattice oxygen in a catalytic oxygen carrier for methane oxidation, which results in a higher selectivity towards C2+as compared to the results from the traditional co-feed process. The chemical looping approach for OCM has been studied mechanistically for the first time with a Mn-Mg based catalytic oxygen carrier (COC). The COC delivered stable performance in a fixed bed for 100 cycles for more than 50 hrs. with a 63.2% C2 selectivity and 23.2% yield. These experimental results and original process simulations of an OCM chemical looping system for olefins or liquid fuel production with electricity co-generation present a direct method for methane utilization. The intended use of the olefinic product stream could be to separate it into different components and integrate it with existing refinery operations. In another approach the product stream can be sent to an oligomerization reactor to convert the unsaturated hydrocarbons to gasoline over a ZSM-5 catalyst. Such a process shows flexibility in its utilization as a commercial technology.

 

Aamena Parulkar

High Yield Stoichiometric Synthesis of ZIF-8 Nanoparticles Using Novel Reactor

 

Abstract

Zeolitic imidazolate Frameworks (ZIFs) are chemical and thermally stable sub-class of metal organic frameworks. The desirable molecular sieving properties of ZIFs make these materials an interesting candidate for energy-efficient separation techniques, mainly membrane and adsorption techniques. The particle size becomes an important criterion for membrane applications as bigger particles can pose diffusion limitations. The main challenge for greater utilization of ZIFs is the difficulty to synthesize material with uniform particle size and high surface areas at large scales, while achieving high yields.

In this work, a scalable, solution phase synthesis is demonstrated for ZIF-8 nanoparticles with uniform diameters in the range of 40-80 nm. ZIF-8 is synthesized with 89% yield using stoichiometric precursor concentrations using a novel reactor. Turbulence created by the reactor provides homogeneous conditions in the reaction volume resulting in improved yield. The surface area and micropore volume of the synthesized materials confirm the high quality of products. The reactor was studied to determine the effect of different synthesis parameters including ligand to metal ratio, base concentration, and mixing intensity. The base concentration has the most effect on the product size, morphology, and yield. The versatility of the reactor is shown by synthesizing ZIF-67 with 79% yield. Further, a larger reactor was constructed and tested, demonstrating that the method can be scaled to increase productivity. Overall, this work presents a versatile and scalable route for nanoparticle synthesis.

 

Abhilasha Dehankar

Iron Oxide Nanoparticle-Graphene Patterned Interfaces

Abhilasha Dehankar1, Justin Young2, Josh Goldberger3, Ezekiel Johnston-Halperin2, Jessica O. Winter1,4

1William G. Lowrie Department of Chemical and Biomolecular Engineering, 2Department of Physics, 3Department of Chemistry and Biochemistry, 4Department of Biomedical Engineering

Abstract

Nanoparticles, such as superparamagnetic iron oxide nanoparticles (SPIONs), exhibit unique properties because of their small size; and therefore, have significant potential to improve optical, electronic, and magnetic devices. Significant research has occurred in the synthesis of these particles; however, integration of these particles with higher order constructs, as required for device development, remains a challenge. Further, such integration could lead to the development of synergistic structures with novel properties. To harness the full potential of these composites, nanoparticles should be capable of being assembled in a specific, user-defined, and scalable manner on larger film-based materials. Therefore, the broad aim of this research is to develop facile and controlled techniques for generation of nanoparticle-film composites and to study the emergent properties of their interfaces. 

 

As a model system, we are investigating graphene-SPION interfaces. Graphene is a diamagnetic single layer of carbon with excellent electronic properties. However, it lacks intrinsic magnetic ordering, which could be exploited for magneto electronic or spintronic functionality. Existing strategies for generating magnetism in graphene have disrupted native electronic properties. However, recent investigations have shown induced magnetism in graphene without impairing its electronic properties when magnetic materials are placed in close proximity with graphene films[1], [2].  Thus, we deposited SPIONs, which can locally modify the magnetic field felt by charge carriers in the graphene, with the goal of creating ordered assemblies with emergent magnetic properties. As a first approach, we deposited materials through direct deposition and determined that solvent properties significantly influence aggregation state. To create ordered structures, we first encapsulated SPIONs in micelles, that can in turn self-assemble on thin films following Langmuir-Blodgett[3] and spin coating deposition[4]. These materials were characterized using Atomic Force Microscopy (AFM) to evaluate composite surface topography. Magnetic and electronic properties of these composites would be evaluated. Knowledge gained from this research could enable novel 0D-2D interfaces. Similar techniques could be applied to a broad array of nanoparticles and surfaces to generate novel emergent behaviors.