Research
Our research goal is to develop creative solutions for sustainable energy and synthetic materials to deal with the pressing environmental sustainability, climate resilience and clean water challenges. We integrate innovative catalyst, thermal and/or electrocatalysis, membrane science and technology, and reaction engineering to significantly improve a low-carbon and circular economy by generating energy and materials from renewable and waste sources, using renewable energy (e.g., electricity and solar) as driving forces, increasing energy efficiency and decreasing waste generation in conversions. The pursuit of this research goal is supported by our current research activities in the following four interrelated areas: (1) Innovating catalyst materials and reactor systems to promote non-oxidative methane coupling; (2) Developing catalysts and membrane reactors for light alkane dehydrogenation; (3) Synthesizing high-performance catalysts by low cost and high throughout methods; and (4) Broadening research to improve the environmental and water sustainability.
Area 1. Innovating catalyst materials and reactor systems to promote non-oxidative methane coupling.
Direct non-oxidative methane coupling (NMC) is an important one-step process for upcycling of methane to value-added larger hydrocarbons and COx-free hydrogen. Unfortunately, its operation under conventional catalyst and reactor solutions often suffers from low conversion, low hydrocarbon selectivity along with catalyst deactivation by coking due to the high dissociation energy of C-H bond in CH4 and subsequent promotion of heavy hydrocarbons and coke-forming reactions at high temperature. Our research group in this area focuses on catalyst, reactor and process heating innovations to modulate methane activation and the following reaction network to overcome barriers in NMC. We have advanced hierarchical lamellar zeolite supported metal catalysts with tunable textural properties for NMC. The correlations among the synthesis, textural and acidity properties, and catalytic functions of the as-designed catalysts in NMC reaction formed the basis for the studies of a suite of alkane activation catalysts in our group. In parallel with catalyst development, we innovated novel reactor technologies for manipulating kinetics or thermodynamics to achieve high methane conversion and low coke formation in NMC. For instance, we have been innovatively exploiting millisecond catalytic wall reactor that manipulates CH4 conversion and product selectivity to realize its technoeconomic viability.
Area 2. Developing catalysts and membrane reactors for light alkane dehydrogenation.
Membrane reactors hold the promise to circumvent thermodynamic equilibrium limitations by in-situ removal of product species, resulting in improved product yields. The continuous hydrogen co-productremoval in light alkane dehydrogenation reactions leads to high alkane conversion and hydrocarbon yield. We have been exploring dense metal oxide and porous ceramic materials as H2 separation membranes for C1-C4 dehydrogenation reactions at lower temperatures.For example, in NMC reaction, significant improvement in CH4 conversion was achieved upon H2 removal from the membrane reactor compared to that in a fixed-bed reactor. The selectivity towards C2 or benzene was manipulated purposely by adding H2 into or removing H2 from the membrane reactor. When CO2 was used in the sweep gas, permeated hydrogen (driving the NMC reaction) reacts with CO2 sweep to form CO and water via the reverse water gas shift reaction. The single hydrogen-permeable membrane reactor simultaneously addresses both reduction of greenhouse gas (CO2 and CH4) emissions as well as production of value-added hydrocarbon products with in-situ gas separation. The coupling of chemical reaction and the separation process in the same membrane reactor device fulfills the criteria of process intensification, and thus minimizes environmental, economical and social impacts
Area 3. Synthesizing high-performance catalysts by low cost and high throughout methods.
Our research lab has been working on innovative catalysts and supported metal catalysts for a variety of reactions. For instance, we innovated a vapor phase pillarization (VPP) process to produce pillared zeolites from 2D layered zeolite structures. The VPP process has ~100% efficiency of alkoxide usage in the intercalation step, requires less (and, in some cases, zero) water addition in the hydrolysis step, does not require separation for product recovery, and generates no liquid waste. Furthermore, synthesis of pillared zeolites via the VPP process can be accomplished within a single apparatus with one-time operation. We worked towards the tuning of precise structures of formed mesopore by pillaring of the lamellar zeolite materials, together with various structural characterization and reaction test with biomass, waste plastics, food waste conversion to prove the improvement of catalyst durability and selectivity to value-added products.
Area 4. Broadening research to improve the environmental and water sustainability.
Our group expands the material synthesis, catalysis, membrane, and reaction engineering research into other exciting yet challenging applications such as desalination, hydrofracking water treatment, and environmental remediation fields. For example, in recent years, significant progress has been made in the development of water purifications and photocatalytic environmental remediation. As the core component of a membrane reactor technology, catalysts, and membranes function as chemical and physical filters to remove toxic compounds and wastes while retaining clean water and environment in nature. Through collaborations with colleagues in different disciplines, we synthesized zeolite/polymer composite membranes to drastically increase the hemocompatibility and fouling resistance of the water purification membranes. To improve the efficiency in adsorption and degradation of toxic industrial chemicals and disposal of chemical warfare agents, we synthesized conformal titania-zeolite microporous films supported on a light absorber by an atomic layer deposition. The as-developed devices can also efficiently convert CO2 into alcohols by using solar energy.