Federal Demonstration Partnership (FDP) solid-catalyzed reactions in supercritical reaction mediaEPA Grant Number: R826034
Title: Federal Demonstration Partnership (FDP) solid-catalyzed reactions in supercritical reaction media
Investigators: Subramaniam, Bala
Institution: University of Kansas
EPA Project Officer: Hahn, Intaek
Project Period: October 1, 1998 through September 30, 2001 (Extended to May 20, 2003)
Project Amount: $125,000
RFA: Technology for a Sustainable Environment (1998) RFA Text | Recipients Lists
Research Category: Nanotechnology , Sustainability , Pollution Prevention/Sustainable Development
This research program will rationally exploit supercritical (sc) reaction media to develop new, environmentally-safer and selective processes for such important catalytic reactions as acid catalyzed 1-butene/isobutane alkylation to produce gasoline, skeletal isomerization of n-butane to isobutane and selective functional groups hydrogenations on supported catalysts. The goals include (i) the optimization of the cosolvent-based supercritical solid-acid alkylation process (recently developed in our laboratory) to obtain enhanced alkylate yields at high butene conversions; (ii) the application of the in situ sc decoking concept to extend the life of low-temperature, solid-acid skeletal isomerization catalysts; and (iii) the optimization of solid-catalyzed sc hydrogenation process by pressure-tuning solvent and transport properties in the near-critical region to achieve desired product selectivity and hydrogenation rates.
The following catalytic systems chosen for study offer one or more advantages for operation in sc-media: environmentally-desirable, related to important commercial systems, most catalysts are readily available at reasonable cost, and unusual reactivity.
|Reactions||Catalysts||Application Areas Impacted|
|Alkylation||Solid acids (USY, sulfated zirconia, ZSM-5, zeolite-beta, Nafion, etc.)||1-butene/isobutane alkylation to gasoline|
|Isomerization||Sulfated zirconia, unpromoted and promoted with Fe and Mn||n-butane isomerization to isobutane|
|Hydrogenations||Pd or Ni supported on y-Al2O3 or Deloxan?||Selective hydrogenations of functional groups: cyclicalkenes, ketones, nitriles, alcohols, aldehydes, epoxides, etc.|
The pressure-tunability of the density (i.e., solubilizing power) and transport properties (diffusivity, viscosity) of sc reaction media is exploited to realize unique combinations of these properties which offer several advantages as follows: (i) the desorption of heavy hydrocarbons (i.e., coke precursors) from the catalyst surface and their transport out of the catalyst pores before they can transform to consolidated coke, thus extending catalyst lifetime; (ii) enhanced pore-transport of reactants such as hydrogen to the catalyst surface thereby promoting desired reaction pathways; and (iii) enhanced desorption of primary products preventing secondary reactions that adversely affect product selectivity. Phase behavior measurements will be performed with a variable-volume phase equilibrium analyzer. Supercritical reaction studies, including kinetic measurements, will be performed in flow-reactors, both tubular and stirred (Robinson-Mahoney type) vessels, under well-defined process conditions, using statistical experimental design methods. The reactor contents will be sampled on-line and analyzed using GC/FID.
Besides providing a better fundamental understanding of the physicochemical processes underlying heterogeneous fluid/solid catalysis in sc media, the catalyst systems developed in this research are likely to impact the refining and chemical industries by minimizing chemical waste while optimizing catalyst selectivity, efficiency and lifetime. Specifically, solid-acid catalyzed alkylation and isomerization processes with enhanced activity and product yields could emerge as commercially-viable, environmentally-safer alternatives to liquid-acid based processes. Continuous solid-catalyzed hydrogenation in sc media -- characterized by pressure-tunable selectivities minimizing waste formation, enhanced reaction rates, and inherently safer operation due to decreased holdup of hazardous reagents in the reactor -- could emerge as an attractive process for functional groups' hydrogenations, a subject critical to the fine chemicals, pharmaceutical, and food industries.