(476ay) Formation of Liquid Element Sulfur and Gaseous Carbonyl Sulfide by Reacting Hydrogen Sulfide in Coal Gases with Sulfur Dioxide

Removal of hydrogen sulfide (H₂S) from coal gases and sulfur
recovery as elemental sulfur are key steps in the development of advanced power
plants that employ coal and natural gas, 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 groups. In this process, the H₂S in the coal gas is
selectively oxidized in a single step to elemental sulfur using sulfur dioxide
(SO₂) or oxygen (O₂) in the presence of
alumina-or-carbon-based catalyst pellets in a packed/fluidized bed.  

A monolithic catalyst reactor (MCR) for the development of a single-step
sulfur recovery process is used 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.  The monolith
catalyst is wash-coated with gamma alumina oxide. A performance of the
monolithic catalyst is presented in terms of H₂S removal capacity,
deactivation, and selectivity of COS with various catalyst promoters at various
reactor operation conditions.

The objectives
of this research are to formulate monolithic catalysts for removal of H₂S from coal gases and
minimum formation of COS with monolithic catalyst supports, gamma-alumina wash,
and catalytic metals, to develop a catalytic regeneration method for a
deactivated monolithic catalyst, to
measure kinetics of both direct oxidation of H₂S to elemental sulfur with SO₂ as an oxidizer and selective formation of COSin the presence of a simulated coal gas mixture containing H₂, CO, CO₂, and moisture, using a monolithic
catalyst 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. The molar
ratio of H₂S to SO₂ in the monolithic
catalyst reactor is maintained at 2 for all the reaction experiment runs.

Experiments on
conversion of hydrogen sulfide into elemental sulfur and selective formation of
COS are carried out for the space time range
of 90 ? 560 seconds at 125 - 155^oC and 40 ? 200 psia to evaluate effects
of reaction temperature, moisture concentration, space time, pressure, and
catalyst age on conversion of hydrogen sulfide into elemental sulfur and selective
formation of COS.