Professional Education

  • Bachelor of Science, University of Wisconsin Madison, Chemical Engineering (2006)
  • Doctor of Philosophy, University of California Berkeley, Chemical Engineering (2015)
  • Bachelor of Science, University of Wisconsin Madison, Chemistry (2006)
  • Certificate, University of Wisconsin Madison, Business (2006)

Stanford Advisors

All Publications

  • Theoretical Analysis of the Influence of Pore Geometry on Monomolecular Cracking and Dehydrogenation of n-Butane in Brønsted Acidic Zeolites ACS Catalysis Van der Mynsbrugge, J., Janda, A., Mallikarjun Sharada, S., Lin, L., Van Speybroeck, V., Head-Gordon, M., Bell, A. T. 2017; 7 (4): 2685-2697

    View details for DOI 10.1021/acscatal.6b03646

  • Effects of Zeolite Structural Confinement on Adsorption Thermodynamics and Reaction Kinetics for Monomolecular Cracking and Dehydrogenation of n-Butane JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Janda, A., Vlaisavljevich, B., Lin, L., Smit, B., Bell, A. T. 2016; 138 (14): 4739-4756


    The effects of zeolite structure on the kinetics of n-butane monomolecular cracking and dehydrogenation are investigated for eight zeolites differing in the topology of channels and cages. Monte Carlo simulations are used to calculate enthalpy and entropy changes for adsorption (ΔHads-H+ and ΔSads-H+) of gas-phase alkanes onto Brønsted protons. These parameters are used to extract intrinsic activation enthalpies (ΔHint‡), entropies (ΔSint‡), and rate coefficients (kint) from measured data. As ΔSads-H+ decreases (i.e., as confinement increases), ΔHint‡ and ΔSint‡ for terminal cracking and dehydrogenation decrease for a given channel topology. These results, together with positive values observed for ΔSint‡, indicate that the transition states for these reactions resemble products. For central cracking (an earlier transition state), ΔHint‡ is relatively constant, while ΔSint‡ increases as ΔSads-H+ decreases because less entropy is lost upon protonation of the alkane. Concurrently, selectivities to terminal cracking and dehydrogenation decrease relative to central cracking because ΔSint‡ decreases for the former reactions. Depending on channel topology, changes in the measured rate coefficients (kapp) with confinement are driven by changes in kint or by changes in the adsorption equilibrium constant (Kads-H+). Values of ΔSint‡ and ΔHint‡ are positively correlated, consistent with weaker interactions between the zeolite and transition state and with the greater freedom of movement of product fragments within more spacious pores. These results differ from earlier reports that ΔHint‡ and ΔSint‡ are structure-insensitive and that kapp is dominated by Kads-H+. They also suggest that ΔSads-H+ is a meaningful descriptor of confinement for zeolites having similar channel topologies.

    View details for DOI 10.1021/jacs.5b11355

    View details for Web of Science ID 000374274100009

    View details for PubMedID 26909765

  • Effects of Pore and Cage Topology on Thermodynamics of n-Alkane Adsorption at Brønsted Protons in Zeolites at High Temperature Journal of Physical Chemistry C Janda, A., Vlaisavljevich, B., Smit, B., Lin, L., Bell, A. T. 2016

    View details for DOI 10.1021/acs.jpcc.6b09703

  • Adsorption Thermodynamics and Intrinsic Activation Parameters for Monomolecular Cracking of n-Alkanes on Bronsted Acid Sites in Zeolites JOURNAL OF PHYSICAL CHEMISTRY C Janda, A., Vlaisavljevich, B., Lin, L., Sharada, S. M., Smit, B., Head-Gordon, M., Bell, A. T. 2015; 119 (19): 10427-10438
  • Effects of Si/Al Ratio on the Distribution of Framework Al and on the Rates of Alkane Monomolecular Cracking and Dehydrogenation in H-MFI JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Janda, A., Bell, A. T. 2013; 135 (51): 19193-19207


    The aim of this study was to investigate the influence of Si/Al ratio on the locations of exchangeable cations in H-MFI and on the monomolecular cracking and dehydrogenation reactions of n-butane. On the basis of UV-visible spectroscopic analysis of Co(II) exchanged into MFI, it was inferred that the fraction of Co(II) (and, by extension, Brønsted protons) located at channel intersections relative to straight and sinusoidal channels increases with increasing Al content. Concurrently, turnover frequencies for all monomolecular reactions, and the selectivities to dehydrogenation versus cracking and to terminal cracking versus central cracking, generally increased. The changes in selectivity with Al content are consistent with the finding that the transition-state geometry for dehydrogenation is bulky and resembles a product state, and should therefore exhibit a stronger preference to occur at channel intersections relative to cracking. Increases in turnover frequencies are attributed partly to increases in intrinsic activation entropies that compensate for concurrent increases in intrinsic activation energies, most strongly for dehydrogenation and terminal cracking, resulting in increased selectivity to these reactions at higher Al content. This interpretation contrasts with the view that intrinsic activation barriers are constant. It is also observed that isobutene inhibits the rate of n-butane dehydrogenation. Theoretical calculations indicate that this effect originates from adsorption of isobutene at the channel intersections. Because cracking reaction rates are not affected by the presence of isobutene, this result suggests that the preference of dehydrogenation to occur at channel intersections is much stronger than the preference for cracking to occur at these locations.

    View details for DOI 10.1021/ja4081937

    View details for Web of Science ID 000329137300031

    View details for PubMedID 24237304