(343d) Deactivation of Catalysts in Removal of Hydrogen Sulfide in Coal Gases as Liquid Sulfur

Removal of hydrogen sulfide (H₂S) from coal gas
and sulfur recovery as elemental sulfur are key steps in the development of
advanced power plants that use coal, natural gas, and biomass as feed stocks,
and produce electric power and clean transportation fuels.  The conventional
method of sulfur removal and recovery employing amine scrubbing, Claus, and
tail-gas treatment involves a number of steps and is energy intensive.  A novel
process called Single-Step Sulfur Recovery Process (SSRP) is under development
at various research organizations. In this process, the H₂S in the
coal gas is selectively oxidized in a single step to liquid elemental sulfur
using sulfur dioxide (SO₂) or oxygen (O₂) in the presence
of alumina-or-carbon-based catalyst pellets in a packed/fluidized bed reactor.

This heterogeneous catalytic reaction has gaseous
reactants such as H₂S and SO₂.  However, this
heterogeneous catalytic reaction has heterogeneous products such as liquid
elemental sulfur and steam.  Pellet-type catalysts are used for a fluidized
bubble reactor, whereas monolithic cataltysts are used for a monolithic
catalyst reactor (MCR) for the development of a single-step sulfur recovery
process to remove H₂S from a simulated coal gas in this study.

Sulfur dioxide is used as an oxidizer to convert H₂S
into liquid element sulfur at 125 to 155^oC in this study.  The
monolithic catalyst is wash-coated with gamma alumina oxide, whereas the
pellet-type gamma-alumina catalyst is used for a micro bubble reactor in this
study.  These catalysts are mainly deactivated with the reaction products such
as liquid elemental sulfur and steam.  A special flow regime (Taylor flow) in a
monolithic catalyst channel removes the liquid elemental sulfur formed at the
catalyst surface thereby partially regenerating the catalyst in-situ. Catalyst
pellets surrounded with liquid sulfur in a packed/fluidized beds reactor are
deactivated severely and regenerated periodically.  A performance of the
monolithic catalyst and the pellet catalyst will be presented in terms of
deactivation, H₂S removal capacity, and selectivity of COS with
various catalyst promoters at various reactor operation conditions.