Making Hydrogen from Hydrogen Sulfide

Hydrogen sulfide (H₂S) is a waste gas produced at natural gas plants and at oil refineries. It is highly toxic and has an intense odor. For this reason it is converted to non-toxic elemental sulfur by the Claus Process at most locations that produce it.

The hydrogen in H₂S is quite loosely bound compared to many other simple compounds that contain hydrogen such as water (H₂O) and methane (CH₄). Many researchers around the world have been working on ways to win the hydrogen from H₂S.

Hydrogen is a desirable fuel because it burns cleanly. Today it is important for refining oil and for making methanol and ammonia. Current methods to manufacture it are considered rather expensive. Because of the low energy of the H-S bond, it is possible that lower cost processes could be devised by making hydrogen from H₂S.

Converting Waste to Value!

Dissociating H₂S into its elements is sometimes called H₂S cracking or splitting.

Many experimental processes have been devised to make hydrogen from hydrogen sulfide. The different processes are quite diverse, and many of them are interesting. A summary of the processes follows.

• In the early '80s, the I.V. Kurchatov Institute in Moscow began experiments to convert H₂S to hydrogen using microwave radiation. Within a short time they had installed a large scale pilot plant at a gas plant at Orenburg, Russia. Follow-up work took place in North America at Argonne National Laboratory and in a joint Canadian study (Alberta Energy/Shell Canada/Atomic Energy of Canada).
• Several laboratories are working on electrolysis of H₂S, either as a gas or as liquefied H₂S or as an aqueous solution. Major projects have been conducted at Georgia Tech, CANMET, Texas A&M and elsewhere.
• Some novel processes use electrical discharges. Again there are several variants. Thus "hot" electric arcs or the cooler discharges from ozonizers can be used.
• Other processes that are being looked at use thermal decomposition -- basically strong heating. Alberta Sulphur Research Ltd. is piloting a thermal process in which heat from a Claus reaction furnace is used as the source of energy. The economics of thermal processes have been studied at the University of Calgary.
• Ingenious and elaborate thermal cycles have been investigated. In most of these, at least one step does not give good yields, and economic separation of the products is an issue.
• An oxidation-reduction cycle using anthraquinone derivatives is being pursued by Marathon Oil. It is quite advanced and is heading for the pilot stage.
• There are processes that use light energy. Some of these use the sun's thermal energy, while others use photochemical principles. Research in the latter is focused (!) on finding better photo catalysts and on ways to obtain sulfur in a salable form.

Considering the intensity of research in this field, a commercial H₂S splitting process could emerge soon. Such a process could be practiced anywhere there is a source of H₂S. However, transporting hydrogen is costly. Hydrogen should preferably be consumed at the site. Therefore the most suitable locations would be refineries or heavy oil upgraders, including the Alberta oil sands.

For imaginative solutions to chemical process issues, contact

Ed Luinstra, Ph.D.
Chemical Process Consultant
Sulfotech Research
Calgary, Alberta, Canada
phone: 403-686-1562

With 25 years experience in oil and gas research.

Visit Sulfotech's Home Page!

Supported by Alberta Hydrogen Research Program, Hydrogen Industry Council, Natural Resources Canada, PanCanadian Petroleum Limited, Shell Canada Limited, Suncor Inc. Oil Sands Group, Syncrude Canada Ltd., and Industrial Hydrogen Chair, University of Calgary.