PhD, Aristotle University of Thessaloniki (2005), Greece
- Modeling and simulation of process systems
- Coal and Biomass to Poly-generation (Liquids, Chemicals, Power)
- CO2 reduction technologies
- Sulfur reduction in transportation fuels
- Refinery processes
- Hierarchical pore structure zeolites
Member of Clean Energy Engineering Center
Member: Technical Chamber of Greece
Member: Hellenic Chemical Engineering Society
Outreach Activity: Da Vinci Project – Biomass Conversion to Energy (Summer 2013)
Current Research Group
Sulfur reduction in transportation fuels: One of my research interests focuses on the development of new processes and materials for the reduction for the sulfur reduction in transportation fuels, gasoline and diesel. The urgent and significant need to reduce sulfur content in fossil fuels, to almost zero levels, is driven both by mandatory environmental fuel regulations and the stringent tolerance required for their use in fuel cell applications. During the last decade, a lot of scientific effort has been devoted to developing new technologies, which either stand-alone or in combination with the traditional Hydrodesulfurization process HDS, will effectively remove sulfur compounds in transportation fuels. Among the above processes the removal of sulfur compounds using selective adsorption at ambient or mild conditions represents one of the most promising and attractive methods for local stand-alone desulfurization, because it represents a compact, easy-to-handle, economical, and potentially regenerable process. Desulfurization by adsorption is based on the ability of a solid sorbent to selectively adsorb organo-sulfur compounds. Materials containing one or a combination of transition metals are usually used for the selective adsorption of sulfur compounds. The development of zeolite based adsorbents with high sorption capacity, selectivity and regenerability is the focus of my research.
Advanced Coal-Biomass-to-Liquid (CBTL) systems simulation and efficiency analysis:
Strong dependency on crude oil and natural gas and the associated price and supply chain-risk, increase the need for efficient utilization of other existing energy sources, like coal. Nowadays, coal represents about 70% of the world’s proven fossil fuel sources and it has the lowest cost among the different fossil fuels. However, energy production based on coal is characterized by significantly high pollutant emissions, especially carbon dioxide (about 800gr for each kWh of electric energy produced). The growing energy demands of developing countries together with the need of a significant reduction in greenhouse gas (GHG) emissions are the challenging tasks of future energy policies. Thus, the perspective of coal as energy source is based on the success of the emerging “clean coal technologies” (CCT), where good efficiency and thermodynamic performances of the power plant are joined with a control of pollutant emissions (mainly CO2 emissions). The objective of my research is to analyze the perspectives of different emerging technology options for the production of clean liquid fuels and electricity based on coal. The aforementioned technology options include:
- Co-feeding of biomass
- Aggressive CO2 capture technologies
- Replacement of gas turbine power generation system with fuel cell (SOFC)
Novel zeolites and Hierarchical Pore Structure Zeolites for advanced applications
Zeolites are crystalline aluminosilicates that possess uniform micropores (sub-nanometer size) and cavities, with dimensions that are close to those of numerous molecular species of high commercial interest. Accordingly, zeolites are known to exhibit molecular sieve and shape-selective properties, based on the diffusional access of guest species into their sub-nanometer size pores and associated shapes. Moreover, zeolites may incorporate a large number of heteroatoms in four-coordinated sites in the crystalline lattice and may also be used as supports for dispersed metals and metal oxides, conferring these materials with catalytic properties for a large variety of reactions. As a consequence, zeolites are solids with signiﬁcant industrial applications as catalysts, adsorbents, and ion exchangers. Notwithstanding the positive effect of the presence of micropores with respect to shape selectivity, these micropores might impose diffusion limitation diminishing their accessibility to heavier molecules. The key objective of our research is to modify the pore structure architecture within the zeolites in a way that will allow the selective adsorption and/or the reaction of the desired molecules.
As an example, we are currently working on the cracking and reforming of Poly-Aromatic-Hydrocarbons (PAH) derived from biomass gasification. PAH are undesired, carcinogenic, multi-ring hydrocarbons which is essential to be removed or converted. Zeolites could help. However, due their size, PAHs cannot easily diffuse into the zeolite microporous. Our hypothesis is that the introduction of hierarchical pore structure within the zeolite crystals will help on the diffusion of the bulky hydrocarbons in and out of the zeolites, enhancing their conversion. Besides, the incorporation of metals in the pores of the hierarchical zeolites can provide to the zeolites bi-functional activity enhancing also the reforming of hydrocarbons in valuable gases. We are hoping that this idea will help towards the transformation of WASTE TO ENERGY!
|2010 – 2013||Assistant Research Professor at Chemical & Biomolecular Engineering, University of Connecticut|
|2007 – 2010||Project Leader/Research Scientist, Rive Technology Inc., Cambridge, MA|
|2006 – 2007||Research Assistant, Aerosol and Particle Technology Laboratory (APTL), Chemical Process Engineering Research Institute (CPERI), Thessaloniki, Greece|
|2000 – 2005||Doctoral Research Assistant, Laboratory of Environmental Hydrocarbons and Fuels (LEFH) Chemical Process Engineering Research Institute (CPERI), Thessaloniki, Greece|
|1999 – 2000||Research Assistant, Laboratory of Environmental Hydrocarbons and Fuels (LEFH), Chemical Process Engineering Research Institute (CPERI), Thessaloniki, Greece|
Awards & Honors
|2012||Precision Combustion, Inc Award: 13X Zeolite as Potential Molecular Sieve for Gas Phase Impurities Removal|
|2012||NSF Award: Turning Tars into Energy: Zeolites with Hierarchical Pore Structure for the Catalytic Removal of Tars|
|2000||European Program Recovery and Utilization of Carbon Dixoide (RUCADI) Project Award for study: Better Use Of Carbon Dioxide.Topic: CO as raw material for the synthesis of products of the chemical and energy industry.|
Kunhao Li, Julia Valla, Javier Garcia Martinez “Realizing the Commercial Potential of Hierarchical Zeolites: New Opportunities in Catalytic Cracking” Chem Cat Chem Review, ChemCatChem, 2014, 6 (1), 46-66.
Shoucheng Du, Julia A. Valla and George M. Bollas, “Characteristics and origin of char and coke from fast and slow, catalytic and thermal pyrolysis of biomass and relevant model compounds” Green Chem., 2013, 15, 3214 – 3229.
Javier Garcia-Martinez, Marvin Johnson, Julia Valla, Kunhao Li and Jackie Y. Ying, “Mesostructured zeolite Y-high hydrothermal stability and superior FCC catalytic performance” Catalysis Science and Technology, 2 (2012) 987-994.
Javier Garcia Martinez, Marvin M. Johnson, Ioulia Valla, “Introduction of mesoporosity in low Si/Al USY zeolite and the effect of drying conditions on mesoporosity introduction”, US Provisional Patent Application Number 61145724.
Lawrence B. Dight, Javier Garcia Martinez, Ioulia Valla, Marvin M. Johnson, “ Methods of improving the hydrothermal stability of mesostructured zeolites by rare earth ion exchange” US Provision Patent Application Number 61145723.
Athanasios G. Konstadopoulos, Jean-Christophe Hoguet, George Karagiannakis, Julia Valla, Christos Agrafiotis “Gas and liquid desulphurization for hydrogen production via reforming processes” International Journal of Hydrogen Energy, 3(11) (2009) 4953-4962.
J. A. Valla, E. Mouriki, A.A Lappas, I.A. Vasalos “The effect of heavy aromatic sulfur compounds on sulfur in cracked naphtha” Catal. Today, 127 (2007) 92-98.
J.A. Valla, A. A. Lappas, I. A. Vasalos “Catalytic Cracking of thiophene and benzothiophene: Mechanism and Kinetics” Applied Catalysis A:General, 297 (2006) 90-101.
J.A. Valla, A. A. Lappas, I. A. Vasalos, C. Kuehler, N. J. Gudde “Feed and Process effects on the in situ reduction of sulfur in FCC gasoline” Applied Catalysis A: General, 276 (2004) 75-87.
Α. Α. Lappas, J. A. Valla, I. A. Vasalos, C. Kuehler, J. Francis, P. O’ Connor, N. J. Gudde “The effect of catalysts properties on the in situ reduction of sulfur in FCC gasoline” Applied Catalysis A: General, 262 (2004) 31-41.
A.A. Lemonidou, J.A. Valla and I.A. Vasalos, “Methanol production from natural gas-Assessment of CO2 utilization in natural gas reforming” in Carbon Dioxide Recovery and Utilisation, Edited by M. Aresta, Kluwer Academic Publishers (2003) p. 379-394.
A. A. Lappas, J. A. Valla, I. A. Vasalos, C. W. Kuehler, J. Francis, P. O’ Connor, N.J. Gudde “Sulfur Reduction in FCC Gasoline” Preprints Division of Petroleum Chemistry, American Chemical Society, Orlando, Florida, April 7-11, 2002.