Recent Advances In the Catalysis of HI Decomposition to Give Hydrogen in the SI Cycle.

[NNadir]

Recent Advances In the Catalysis of HI Decomposition to Give Hydrogen in the SI Cycle.

The SI cycle or “sulfur iodine” cycle, about which I have written here and elsewhere before, consists of the following chemical reactions:

I₂ + SO₂ + 2H₂O ↔ 2HI + H₂ SO₄ (a)

2HI ↔ H₂ + I₂

H₂ SO₄ ↔ SO₂ + H₂O + 0.5O₂

It is a thermochemical means of splitting water at lower temperatures, temperatures that are accessible industrially, than would be required for the direct decomposition of water into its elements. These reactions are catalytic and can be utilized to make the direct conversion of industrial grade heat into hydrogen and oxygen, offering the potential for phasing out the dangerous fossil fuel petroleum by providing captive hydrogen to manufacture clean fuels like DME (dimethyl ether). This approach would take place via the direct hydrogenation of carbon oxides including carbon dioxide the dangerous fossil fuel waste that the dangerous fossil fuel industry dumps indiscriminately in Earth’s atmosphere. (The hydrogenation of carbon oxides to give DME is already an industrial process, but regrettably the sources of hydrogen for these applications are the dangerous fossil fuels coal and natural gas.)

Many hundreds of these cycles have been proposed or studied; some are better than others. Without question, the most advanced such cycle, generating a huge number of publications in the last few years, is the SI cycle given above. It is not necessarily the best possible cycle, but it is clearly the one that will go industrial first, probably in China.

The status of the Chinese program can be found in a recent publication in the scientific literature, http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V3F-4WGHJHM-6&_user=10&_coverDate=04%2F30%2F2010&_alid=1352294372&_rdoc=1&_fmt=high&_orig=search&_cdi=5729&_sort=r&_docanchor=&view=c&_ct=2890&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=46d1138d4649bb76dbd59b89d111c8e8">International Journal of Hydrogen Energy Volume 35, Issue 7, April 2010, Pages 2883-2887, in a paper entititled, “Overview of nuclear hydrogen production research through iodine sulfur process at INET.”

China has recently constructed at test nuclear reactor of the “pebble bed” type originally developed in Germany and is using it to explore possible applications for process heat to run chemical reactions including, but not limited to, the SI cycle. According to the paper just cited, China has advanced from the laboratory scale to the bench top scale with the SI cycle and will conduct pilot plant operations about 3 years from now. The HTR-10 test nuclear driven thermochemical hydrogen production pilot is now scheduled for 2019, about a year earlier than was being talked about a few years back, indicating that the Chinese program is quite serious.

This makes the timeline competitive with that being undertaken by KAERI, the Korean Atomic Energy Research Institute, and way more advanced, as I understand it, than the work being done at CEA, the French Nuclear Research Institute and the work being conducted at Sandia, since we don’t have high temperature reactors. (France is working to build one in Central Europe, probably in the Czech Republic, Slovakia or Hungary, as part of its work in an international consortium.)

One of the chemical problems of the reaction series is obtaining appropriate kinetics for the critical step of the decomposition of hydrogen iodide, “hydroiodic acid,” to give free hydrogen. Significant work on catalysis of this reaction is an active area of research. Of considerable interest are ceria based catalysts which include platinum containing systems.

The Chinese have just published a work on the use of a nickel based analogue, which of course would be much cheaper and I think it’s pretty exciting and decided to reference the paper here, even though I’m not necessarily an SI kind of guy, although I’d rather see the SI process used than no thermochemical hydrogen process, since it is a critical task for humanity to present the next generation with a means of phasing out – as quickly as is possible – dangerous oil, no matter what line of horseshit is handed out by dangerous fossil fuel marketers and greenwashers like the ignorant anti-nuke Amory Lovins.

(I would argue that commercialization of these kinds of process should be subject to huge international efforts, fully funded to the maximal extent to dramatically shorten the currently observed timelines. We should have hundreds of thousands of chemists and engineers working full time on this, day and night.)

Whatever.

Here is the paper on the new Ni based CeO₂:


http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V3F-4XB1968-1&_user=10&_coverDate=11%2F30%2F2009&_alid=1352324670&_rdoc=1&_fmt=high&_orig=search&_cdi=5729&_sort=r&_docanchor=&view=c&_ct=248&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=6bf0253a5df40bc96985b316068a797c">International Journal of Hydrogen Energy Volume 34, Issue 21, November 2009, Pages 8792-8798

Some excerpts from the text of this paper follow:

Among the large-scale, cost effective and environmentally attractive thermochemical cycles, the sulfur–iodine (SI or IS) thermochemical cycle is a quite promising one. The potential of the SI process for hydrogen production has been indicated by many researchers <1–14>… The Bunsen reaction (a) is an exothermic SO2 gas-absorbing reaction in an aqueous phase. The hydrogen iodide (HI) solution and the H2SO4 solution are separated by a liquid–liquid phase separation phenomenon that occurs in the presence of an excess I2. The two acids were divided into upper and lower solutions with a clear boundary. The separated HI solution and H2SO4 solution are purified, concentrated, vaporized and decomposed to produce H2 (b) and O2 (c). All chemicals in the cycle are recycled and H2O is decomposed into H2 and O2 in total.
Among these reactions, HI decomposition presents a rather low homogeneous gas-phase conversion even at high operating temperatures. The use of catalyst allows a substantial temperature reduction to achieve workable reaction rates.

The expense of platinum is noted and described as a motivation for the current work.

The majority of work to identify active catalysts for this reaction was performed in the late 1970s and early 1980s <15– 18> and is best summarized by O’Keefe et al. <15>. Different catalytic systems were found effective, in particular the platinum group metals supported on activated carbon or g-Al₂O₃ showed very good performance. Recent work explored platinum– ceria catalysts for the hydrogen production reaction <19,20>. The limited availability of noble metal makes it necessary to develop less expensive catalysts based on nonprecious metals and supports. Some authors proposed activated carbon <21> and Ni-supported catalysts <15,22,23> for HI catalytic decomposition. The cost savings resulting from the use of non-precious metals may be an advantage in the design of a plant of large size.

For the record, the Ni/CeO₂ catalyst is very versatile, and widely investigated in a number of important reactions.

Nickel is a cogener of platinum and palladium. The latter element is available in huge quantities from used nuclear fuels and its recovery from these sources is an active area of nuclear chemistry research.

Here is a brief review of the experimental procedure used in the Chinese laboratory to investigate the catalyst:

2.2. Catalysts characterization

The thermokinetics characteristic of the Ni/CeO2 gel was investigated on a thermo-gravimetric apparatus (air atmosphere, 30 ml/min and 30 _C/min) with an online infrared spectrum analyzed (TG-FTIR). The specific surface area, average pore diameter and pore olume were determined by Brunauer–Emmett–Teller (BET) method with a Quantachrome NOVA instrument using N2 as adsorbent. The X-ray diffraction analysis (XRD) was performed on a D/max 2550PC. The X-ray tube was operated at 40 kV and 200 mA. The -ray powder diffractogram was recorded at 0.02_ intervals in the range 20_ _ 2q _ 90_ with 0.3 s count accumulation per step. The
High Resolution Transmission Electron Microscopy (HRTEM) picture was performed on a JEM-2010 (HR). Temperature programmed reduction (TPR) experiment was carried out on a TPR catalytic surfaces analyzer. The samples were heated under flowing H2 (5% in N2, 20 ml/min) from room temperature to 800 _C (10 _C/min).

2.3. Activity measurement

The catalytic decomposition of HI was performed at 300–550 ^oC in a quartz tube with the diameter of 18 mm. The mixture composed of 1 g catalyst powder and appropriate volume of coarse quartz particles was loaded in the tube. As shown in Fig. 1, the 55 wt.% hydriodic acid (HI solution) was pumped using a BT00-50Mperistaltic pump into an evaporator where the acid vaporized and mixed with nitrogen gas and then the mixture was introduced into the quartz tube. Flow rate of the nitrogen gas and HI was maintained at 60 ml/min and 0.7 ml/min. The reaction was carried out at atmospheric pressure. All the gases from the quartz tube, except hydrogen and nitrogen gas, were trapped in a spiral condenser and few residual HI and I2 were sequentially trapped in two scrubbers.
Hydrogen was analyzed by a gas chromatograph.

Some remarks from the conclusion.

4. Conclusions.

In this study, the Ni/CeO2 catalysts with different calcinations temperatures have been tested to evaluate their effect on HI decomposition in sulfur–iodine cycle. TG-FTIR, BET, XRD, HRTEM and TPR were performed for catalyst characterization. It was found that the Ni2þ ions could be inserted into the ceria lattice. This brought about the strong interaction between Ni and CeO2, especially at high calcination temperature and the generation of oxygen vacancies. Oxygen vacancy and the surface site played the important role in catalytic surface reaction. The two active sites were well-balanced on Ni/Ce700 catalyst, which resulted in the best activity as well as good stability. All the results provided this material with a potentialto be used in sulfur–iodine cycle for hydrogen production

This is certainly not the only approach to improving this reaction by the way, an interestingly another interesting approach involves the use of nickel via decomposition of a nickel iodide intermediate.

Have a wonderful Memorial Day Weekend, and try to do some memorializing.

http://www.rmi.org/rmi/Amory+B.+Lovins">Famous Anti-nuke Amory Lovins describes his revenue sources:

Mr. Lovins’s other clients have included Accenture, Allstate, AMD, Anglo American, Anheuser-Busch, Bank of America, Baxter, Borg-Warner, BP, HP Bulmer, Carrier, Chevron, Ciba-Geigy, CLSA, ConocoPhillips, Corning, Dow, Equitable, GM, HP, Invensys, Lockheed Martin, Mitsubishi, Monsanto, Motorola, Norsk Hydro, Petrobras, Prudential, Rio Tinto, Royal Dutch/Shell, Shearson Lehman Amex, STMicroelectronics, Sun Oil, Suncor, Texas Instruments, UBS, Unilever, Westinghouse, Xerox, major developers, and over 100 energy utilities. His public-sector clients have included the OECD, the UN, and RFF; the Australian, Canadian, Dutch, German, and Italian governments; 13 states; Congress, and the U.S. Energy and Defense Departments.