The 10th International Conference on CO2 Utilization

14 October 2009

1. CO2 Capture and Separation

Present utilization techniques cannot handle flue gas or other CO₂-containing gas mixtures directly - capture, separation or purification needs to be performed first.

 Jun Liu, Fellow of Pacific Northwest National Laboratory,  US indicated that CO₂ capture and separation is a materials science problem. It is more efficient to use solid sorbents than conventional liquid amine scrubbing processes. In this regard, various adsorbents have been developed. For example, Chunshan Song, Penn State University, US has developed a "CO₂ molecular basket sorbent".  Yuhan Sun, Shanxi Institute of Coal Chemistry, Chian reported organic-inorganic composites (amine grafted mesoporous material) and inorganic-inorganic composites (mixed oxides with nanostructure) for low-temperature and high-temperature CO₂ capture.  Wha-Seung Ahn, Inha University,  South Korea, Honglai Liu, East China University of Science & Technology and others reported similar adsorbents but the super activated carbon was applied too in Liu's work.

Process intensification becomes more and more important for CO₂Capture and separation. Membrane technology is a typical example for this aspect. Inorganic membranes have the capabilities to operate at high temperatures and improve the process efficiency, as addressed by J. C. Diniz da Costa at the University of Queensland. How to put it in a large-scale application is the major challenge to the membrane scientists. Much work to combine the membrane separation with catalytic reactions (like CO₂ reforming) has been carried out. This combination has a very good potential for future utilization of carbon dioxide if large-scale membrane technologies become commercially available.  Jian-feng Chen, Beijing University of Chemical Technology, China, presented a high gravity technology enhanced CO₂ capture method. Suojiang Zhang reported applications of ionic liquids in CO₂ capture, which has the potential to be developed as a new process for CO₂ conversion to chemicals immediately after capture.

2. General uses and catalytic conversion

Philip Jessop, Queen's University, Canada introduced his excellent work on CO₂ as a trigger for switchable chemistry. Marc Schaefer at Technische Universität Berlin reported on evaluation of strategies for the subsequent uses of CO₂. Many others summarized recent advances, problems to be solved and future developments in catalytic conversion of carbon dioxide. 

Several groups reported their results in molecular modeling or thermodynamic analyses of catalytic CO₂ conversion . Qingfeng Ge, Southern Illinois University, US, has studied many catalyst systems. He has found a significant effect of surface hydroxyl on CO₂ adsorption and activation. Dr. Uwe Burghaus, North Dakota State University, US, presented his surface science studies using carbon dioxide as the probe molecule. Few studies on it have been reported before. Surface science research will be helpful to understand the following fundamental issues:
1) What are the differences in the catalysis of metal and metal oxide surfaces for CO₂ adsorption and activation?
2) How do the adsorption kinetics and dynamics change when we go from a metal surface to a related metal oxide?
3) Is adsorption kinetics correlated in a simple way to the adsorption dynamics (gas-surface energy transfer processes)?
4) How is the catalytic activity affected by the defects on the oxide surfaces? Can we tune the reactivity of metal oxide surfaces by varying the defect density? Can these defects serve to better understand powder catalysts or nanoparticles that have a large defect density?
5) How does the oxidation state of a system such as FeOx affect the kinetics/dynamics of surface reactions?
6) How does the size (and shape) of supported metal (metal oxide) clusters relate to chemical activity? We can expect that more investigations will be conducted to answer these questions in the future with various catalysts. Scanning Probe Microscopy (SPM) will have a very important application in this aspect.

In addition to the theoretical studies, we were delighted to see some significant progresses in the development of catalysts on CO₂ activation at mild conditions. Yugen Zhang, Institute of Bioengineering and Nanotechnology, Singapore, reported the first CO₂ reduction reaction catalysed by N-heterocyclic carbene (NHC) organocatalysts with silanes under ambient conditions. The NHCs present superior efficiency and allow for the use of milder and more flexible reaction conditions for CO₂ activation. A highly selective methoxide end-product in excess of 90% hydrogen transferring yield with carbon dioxide gas or dry air as feedstock. This is very promising since this kind of catalysts can be applied towards the direct conversion of CO₂ in air to methanol.

Photocatalytic conversion of carbon dioxide has also made some good progress. For example, Qing-hui Zhang, East China University of Science and Technology, Dong Liu, University of Nottingham, UK and Jun Fan reported photocatalytic reduction of CO₂ with H₂O over TiO₂ supported catalysts. Jeffrey Wu, National Taiwan University, reported an optical-fiber photoreactor, comprised of near 200 catalyst (Cu/TiO₂ and Ag/TiO₂) coated fibers. With this reactor, carbon dioxide and water can be effectively converted into methanol under UV irradiation. Bao-lian Su, University of Namur, Belgium, reported his work on the design of the "artificial leaf" to target a novel photosynthetic reaction center, by entrapping within a silica network active thylakoids, the part of a chloroplast that harnesses solar energy and converts water into oxygen. This biological structure is very efficient, according to Su, since the quantum yield of the primary process of photochemical reaction is close to 100%. His work on the immobilization of whole cells (vegetable cells, cynobacteria or algae), which have the total function to convert CO₂ and water under sunlight to oxygen and carbohydrates by photosynthesis, has attracted much attention from industry and academia.  

Ionic liquids as catalysts for CO₂ conversion were reported by several groups, including Buxing Han, Institute of Chemistry, Chinese Academy of Science,  Suojiang Zhang, Institute of Process Engineering, Chinese Academy of Science and Daw-won Park, Pusan National University, South Korea. Further development in this area could lead to some large scale industrial applications.

Carbon dioxide reforming of methane and other hydrocarbons has been considered as another potential way to utilize carbon dioxide in a large scale. A problem that has to be dealt with is the carbon deposition and sintering of active metal species during the reaction. Novel catalyst design and new catalyst preparation technologies were reported to solve these problems. For example, Susan Stagg-Williams, University of Kansas, US and Wanqin Jin, Nanjing University of Technology, China, reported membrane enhanced CO₂ reforming. Wei Chu, Sichuan University, China and Chang-jun Liu, Tianjin University, China, applied a plasma treatment to enhance the interaction between the support and metal species and to improve the dispersion of the catalyst. A significant improvement in catalyst stability has been achieved. Yun Hang Hu presented his work on solid solution catalyst for CO₂ reforming. He found that the reduction of NiO in the NiO/MgO solid solution is much more difficult than that of pure NiO, which contributes to the formation of very small Ni particles to inhibit carbon deposition. Hu indicated that a critical factor to control NiO reduction in the solid solution is the isolation effect instead of the stronger O-metal bonding. 

3. Utilization of supercritical CO2

Utilization of supercritical CO₂ is a very important aspect of CO₂ utilization. Masahiko Arai, Hokkaido University, Japan summarized the important aspects, including possible roles and actions of dense phase carbon dioxide, phase behavior, molecular interactions of CO₂ with reacting species, modification of catalytically active metal particles and so on. E. Dinjus, ITC-CPV, Germany, Liang-nian He, Nankai University, China, Fengyu Zhao, Changchun Institute of Applied Chemistry, Chinese Academy of Science, Roger Glaeser, University of Leipzip, Germany, Tao Jiang, Institute of Chemistry, Chinese Academy of Science and others reported their work on the use of supercritical CO₂ as solvent or feedstock for the organic syntheses. The combination of supercritical CO₂ with ionic liquids is very promising for many future applications.

4. Industrial Involvement

ICCDU-X also had a lot of industrial involvement. Scientists from SINOPEC, China Petroleum, ENN Group, Saudi Aramco, Siemens AG, Eni S.p.A. and others attended the conference and there were several speakers from industry. For example, Junfeng Rong from SINOPEC reported their work on bio-fixation of carbon dioxide. We are delighted to see that more and more industries are interested in the utilization of carbon dioxide.

5. Post-workshop on CO2 Chemistry for training and education purposes

After ICCDU-X,  a Post-workshop on CO₂ Chemistry for training and education purposes was held. Most of the attendees at this workshop were post-docs and graduate students from Japan, Germany and China.  Chunshan Song,  Dae-won Park and Liang-nian He gave lectures on properties of carbon dioxide, catalyst design and reaction of carbon dioxide, experimental skills and paper writing skills. Some of attendees told the organizers and the speakers that the lectures in this workshop were honestly the best lectures they ever attended. They learned a lot about CO₂  Chemistry and CO₂  utilization. They also learned even more on how to structure their research and how to pave the way for the future. They appreciated this great experience!