- Email: [email protected]
Reaction: Industrial Perspective on Single-Atom Catalysis
CATALYSIS
Reaction: Industrial Perspective on Single-Atom Catalysis Chuan-Ming Wang,1 Yang-Dong Wang,1,* Jun-Wei Ge,1 and Zai-Ku Xie1,* Chuan-Ming Wang received his PhD degree in chemistry (2008) from Fudan University and now is a professor at Sinopec Shanghai Research Institute of Petrochemical Technology (SRIPT). His research interests include computational catalysis. Yang-Dong Wang received his PhD degree in chemistry (2000) from Nanjing University and now is a professor and director of the R&D management department at SRIPT. His research interests include industrial catalysis and olefin technology. Jun-Wei Ge received his PhD degree in chemistry (2013) from Wuhan University and now is a senior engineer at SRIPT. His research interests include heterogeneous catalysis for fine chemicals. Zai-Ku Xie received his PhD degree in chemical engineering (2000) from East China University of Science and Technology and now is a professor and director of the Science and Technology Department at Sinopec Corporation. His research interests include industrial catalysis and zeolite catalysis. He was elected academician of the Chinese Academy of Sciences in 2017. Catalysis highly relates to every aspect of our daily life and is one of the significant foundations for the sustainable development of human society. Among these, heterogeneous catalysis has strongly promoted the persistent
development of modern chemical industry to supply massive fuels and an immense variety of chemicals. Heterogeneous catalysis is a complex chemical reaction process involving two or more phases, several evolution structures, and multiple time and space scales. It is an eternal subject in the academic and industrial communities to develop optimal catalytic materials and processes with high activity, selectivity, and stability.
each atom constitutes the important component of the active center with high uniform distribution, maximizing the utilization efficiency of metal atoms in heterogeneous catalysis.
The concept of single-atom catalysis or single-atom catalysts (SACs), first proposed by Zhang, Li, Liu, and coworkers in 2011, has opened up a new and exciting research frontier in heterogeneous catalysis.1 This concept not only obviously improves the atomic utilization efficiency of precious metals but also promotes the development of fundamental catalysis theory and provides new application practices of industrial catalysis. A large number of studies have demonstrated that SACs exhibit attracting catalytic performance in thermo-, electro-, and photo-catalytic processes such as ammonia synthesis, alkyne selective hydrogenation, CO oxidation, CO2 hydrogenation, and water gas shift reaction.2,3 Several distinctive benefits of single-atom catalysis over nano-catalysis need to be elaborated in more detail.
Second, single-atom catalysis provides an ideal model and clear picture for the development of fundamental catalysis theory as a result of the definite structure characteristics. The fundamental theory and concept in nanocatalysis has been substantially progressed with the development of advanced characterization techniques and computational chemistry. It is anticipated that single-atom catalysis will further enrich our underlying understanding of heterogeneous catalysis. It has been a significant challenge to identify active sites and address possible reaction mechanisms in nanocatalysis not least because of the diversity in catalyst structures and the complexity in reaction pathways. Great efforts have been devoted to elucidating the influence of catalyst structures and reaction conditions, but the dilemma still remains. Conversely, in single-atom catalysis, the immobilized single active center offers a simple and clear micro-environment, beneficial to the elucidation of the reaction mechanism and rational catalyst design.
First, single-atom catalysis achieves high efficiency of atom utilization in heterogeneous catalysis. The active sites of the widely used nano-catalytic materials are usually coordination-unsaturated surface atoms, and their characteristics strongly depend on the size, morphology, and surface structures of particles, significantly influencing the catalytic performance. The distribution of nanoparticles is usually non-uniform as a result of the limitation of catalyst synthesis methods. The catalytic performance is therefore the apparent average outcome of ensembles of all non-uniform active sites. However, in single-atom catalysis,
Finally, single-atom catalysis offers a heuristic connection between homogeneous catalysis and heterogeneous catalysis. SACs afford a quasi-homogeneous catalytic environment for heterogeneous catalysis by taking advantage of both homogeneous and heterogeneous catalysis. The catalytic performance could be precisely tailored through adjustment of the microscopic geometric structure and electronic structure through the modification of composition and structure of single atom and supports. Heterogeneous SACs exhibit higher reactivity than homogeneous catalysts in some reactions. In addition, the
2736 Chem 5, 2733–2739, November 14, 2019 ª2019 Elsevier Inc.
development of SACs innovates a series of synthetic methodologies of novel catalytic materials in both homogeneous and heterogeneous catalysis. Industrial application is undoubtedly the ultimate goal of catalysis research. Many scientific and technical problems ranging from micro to macro scales have to be tackled for the industrialization of any new catalysts and processes. This research-and-development process is highly demanding because it not only involves a complex chemical reaction itself but also involves the physical process of momentum, quality, and energy transport.4 From the perspective of practical industrial application of SACs, more attention should be paid to technical problems such as the stability of catalysts, space-time yield, and large-scale manufacturing and shaping. Long-period operation with high stability is an important goal of industrial catalysis. Two aspects should be addressed regarding the stability of SACs, namely, the structure stability of single atoms and the resistance to poisoning of the active center. An active single metal atom usually involves strong interaction with supports through covalent bonding to maintain high structure stability. Several ingenious strategies have been systematically explored for the synthesis of stable SACs, for example, the defectengineering strategy, spatial-confinement strategy, and coordinationdesign strategy.5 In industrial catalysis, some impurities such as sulfur- and nitrogen-containing compounds in the feeds of certain reactions can poison the SACs by decreasing the number of active sites or changing their nature. It is therefore essential to address these kinds of poisoning phenomena and mechanisms before industrialization. The space-time yield is a very important index in industrial catalysis. The reactivity of SACs is usually evaluated on
the basis of the turnover frequency (TOF) to emphasize the efficiency of every metal atom. It is, however, the space-time yield (product yield per unit volume of catalyst and per unit time) that is focused on assessing the size of the reactor, capacity of equipment, and economy of the reaction. In most cases, the space-time yield of SACs is still lower than that of nanocatalysis because of the low density of active single atoms on supports. Increasing the loading of metals could boost the density of a single atom but inevitably enhances the tendency of sintering or aggregation of active sites. In addition, two or more distinct active centers are sometimes required for cooperatively catalyzing complex reactions. Therefore, preparing SACs with high density and flexible distribution of single metal atoms is particularly important in industrial application to increase its space-time yield of a variety of reactions. The synthesized catalysts usually need to be shaped for industrial application, and the influence of such a manufacturing process on catalytic performance of SACs is yet to be understood. In addition, other mechanical effects such as catalyst strength, catalyst abrasion, and granularity need to be taken into account as well. To recap, the concept and practice of single-atom catalysis provide distinct strategy and direction for many industrially important reactions. With the progress of in-depth understanding of dynamic structure evolution and complex reaction network and the development of controlled synthesis of high stable SACs in large scale, the important merits of SACs in industrial catalysis are highly anticipated.
ACKNOWLEDGMENTS We gratefully acknowledge the support from the National Natural Science Foundation of China (grant no. 21673295).
1. Qiao, B., Wang, A., Yang, X., Allard, L.F., Jiang, Z., Cui, Y., Liu, J., Li, J., and Zhang, T. (2011). Single-atom catalysis of CO oxidation using Pt1/FeOx. Nat. Chem. 3, 634–641. 2. Kyriakou, G., Boucher, M.B., Jewell, A.D., Lewis, E.A., Lawton, T.J., Baber, A.E., Tierney, H.L., Flytzani-Stephanopoulos, M., and Sykes, E.C.H. (2012). Isolated metal atom geometries as a strategy for selective heterogeneous hydrogenations. Science 335, 1209–1212. 3. Wang, A., Li, J., and Zhang, T. (2018). Heterogeneous single-atom catalysis. Nat. Rev. Chem. 2, 65–81. 4. Hagen, J. (2015). Industrial Catalysis: A Practical Approach (WILEY-VCH). 5. Chen, Y., Ji, S., Chen, C., Peng, Q., Wang, D., and Li, Y. (2018). Single-atom catalysts: synthetic strategies and electrochemical applications. Joule 2, 1242–1264. 1State
Key Laboratory of Green Chemical Engineering and Industrial Catalysis, Sinopec Shanghai Research Institute of Petrochemical Technology, Shanghai 201208, China *Correspondence: [email protected] (Y.W.), [email protected] (Z.X.) https://doi.org/10.1016/j.chempr.2019.10.006
CATALYSIS
Reaction: Open Up the Era of Atomically Precise Catalysis Wei Zhu1,2 and Chen Chen1,* Wei Zhu is an associate professor at Beijing University of Chemical Technology. His research focuses on the development of catalysts and devices for energy-related electrochemical applications. Chen Chen joined the Department of Chemistry at Tsinghua University as an associate professor in 2015. His research focuses on catalyst design and mechanism study at the atomic scale for catalytic activation reactions of small molecules. Just like when the use and manufacture of tools motivated the evolution of human cognition and thus made us different from other species, the development of probe technologies is
Chem 5, 2733–2739, November 14, 2019 ª2019 Elsevier Inc. 2737
Reaction: Industrial Perspective on Single-Atom Catalysis Chuan-Ming Wang,1 Yang-Dong Wang,1,* Jun-Wei Ge,1 and Zai-Ku Xie1,* Chuan-Ming Wang received his PhD degree in chemistry (2008) from Fudan University and now is a professor at Sinopec Shanghai Research Institute of Petrochemical Technology (SRIPT). His research interests include computational catalysis. Yang-Dong Wang received his PhD degree in chemistry (2000) from Nanjing University and now is a professor and director of the R&D management department at SRIPT. His research interests include industrial catalysis and olefin technology. Jun-Wei Ge received his PhD degree in chemistry (2013) from Wuhan University and now is a senior engineer at SRIPT. His research interests include heterogeneous catalysis for fine chemicals. Zai-Ku Xie received his PhD degree in chemical engineering (2000) from East China University of Science and Technology and now is a professor and director of the Science and Technology Department at Sinopec Corporation. His research interests include industrial catalysis and zeolite catalysis. He was elected academician of the Chinese Academy of Sciences in 2017. Catalysis highly relates to every aspect of our daily life and is one of the significant foundations for the sustainable development of human society. Among these, heterogeneous catalysis has strongly promoted the persistent
development of modern chemical industry to supply massive fuels and an immense variety of chemicals. Heterogeneous catalysis is a complex chemical reaction process involving two or more phases, several evolution structures, and multiple time and space scales. It is an eternal subject in the academic and industrial communities to develop optimal catalytic materials and processes with high activity, selectivity, and stability.
each atom constitutes the important component of the active center with high uniform distribution, maximizing the utilization efficiency of metal atoms in heterogeneous catalysis.
The concept of single-atom catalysis or single-atom catalysts (SACs), first proposed by Zhang, Li, Liu, and coworkers in 2011, has opened up a new and exciting research frontier in heterogeneous catalysis.1 This concept not only obviously improves the atomic utilization efficiency of precious metals but also promotes the development of fundamental catalysis theory and provides new application practices of industrial catalysis. A large number of studies have demonstrated that SACs exhibit attracting catalytic performance in thermo-, electro-, and photo-catalytic processes such as ammonia synthesis, alkyne selective hydrogenation, CO oxidation, CO2 hydrogenation, and water gas shift reaction.2,3 Several distinctive benefits of single-atom catalysis over nano-catalysis need to be elaborated in more detail.
Second, single-atom catalysis provides an ideal model and clear picture for the development of fundamental catalysis theory as a result of the definite structure characteristics. The fundamental theory and concept in nanocatalysis has been substantially progressed with the development of advanced characterization techniques and computational chemistry. It is anticipated that single-atom catalysis will further enrich our underlying understanding of heterogeneous catalysis. It has been a significant challenge to identify active sites and address possible reaction mechanisms in nanocatalysis not least because of the diversity in catalyst structures and the complexity in reaction pathways. Great efforts have been devoted to elucidating the influence of catalyst structures and reaction conditions, but the dilemma still remains. Conversely, in single-atom catalysis, the immobilized single active center offers a simple and clear micro-environment, beneficial to the elucidation of the reaction mechanism and rational catalyst design.
First, single-atom catalysis achieves high efficiency of atom utilization in heterogeneous catalysis. The active sites of the widely used nano-catalytic materials are usually coordination-unsaturated surface atoms, and their characteristics strongly depend on the size, morphology, and surface structures of particles, significantly influencing the catalytic performance. The distribution of nanoparticles is usually non-uniform as a result of the limitation of catalyst synthesis methods. The catalytic performance is therefore the apparent average outcome of ensembles of all non-uniform active sites. However, in single-atom catalysis,
Finally, single-atom catalysis offers a heuristic connection between homogeneous catalysis and heterogeneous catalysis. SACs afford a quasi-homogeneous catalytic environment for heterogeneous catalysis by taking advantage of both homogeneous and heterogeneous catalysis. The catalytic performance could be precisely tailored through adjustment of the microscopic geometric structure and electronic structure through the modification of composition and structure of single atom and supports. Heterogeneous SACs exhibit higher reactivity than homogeneous catalysts in some reactions. In addition, the
2736 Chem 5, 2733–2739, November 14, 2019 ª2019 Elsevier Inc.
development of SACs innovates a series of synthetic methodologies of novel catalytic materials in both homogeneous and heterogeneous catalysis. Industrial application is undoubtedly the ultimate goal of catalysis research. Many scientific and technical problems ranging from micro to macro scales have to be tackled for the industrialization of any new catalysts and processes. This research-and-development process is highly demanding because it not only involves a complex chemical reaction itself but also involves the physical process of momentum, quality, and energy transport.4 From the perspective of practical industrial application of SACs, more attention should be paid to technical problems such as the stability of catalysts, space-time yield, and large-scale manufacturing and shaping. Long-period operation with high stability is an important goal of industrial catalysis. Two aspects should be addressed regarding the stability of SACs, namely, the structure stability of single atoms and the resistance to poisoning of the active center. An active single metal atom usually involves strong interaction with supports through covalent bonding to maintain high structure stability. Several ingenious strategies have been systematically explored for the synthesis of stable SACs, for example, the defectengineering strategy, spatial-confinement strategy, and coordinationdesign strategy.5 In industrial catalysis, some impurities such as sulfur- and nitrogen-containing compounds in the feeds of certain reactions can poison the SACs by decreasing the number of active sites or changing their nature. It is therefore essential to address these kinds of poisoning phenomena and mechanisms before industrialization. The space-time yield is a very important index in industrial catalysis. The reactivity of SACs is usually evaluated on
the basis of the turnover frequency (TOF) to emphasize the efficiency of every metal atom. It is, however, the space-time yield (product yield per unit volume of catalyst and per unit time) that is focused on assessing the size of the reactor, capacity of equipment, and economy of the reaction. In most cases, the space-time yield of SACs is still lower than that of nanocatalysis because of the low density of active single atoms on supports. Increasing the loading of metals could boost the density of a single atom but inevitably enhances the tendency of sintering or aggregation of active sites. In addition, two or more distinct active centers are sometimes required for cooperatively catalyzing complex reactions. Therefore, preparing SACs with high density and flexible distribution of single metal atoms is particularly important in industrial application to increase its space-time yield of a variety of reactions. The synthesized catalysts usually need to be shaped for industrial application, and the influence of such a manufacturing process on catalytic performance of SACs is yet to be understood. In addition, other mechanical effects such as catalyst strength, catalyst abrasion, and granularity need to be taken into account as well. To recap, the concept and practice of single-atom catalysis provide distinct strategy and direction for many industrially important reactions. With the progress of in-depth understanding of dynamic structure evolution and complex reaction network and the development of controlled synthesis of high stable SACs in large scale, the important merits of SACs in industrial catalysis are highly anticipated.
ACKNOWLEDGMENTS We gratefully acknowledge the support from the National Natural Science Foundation of China (grant no. 21673295).
1. Qiao, B., Wang, A., Yang, X., Allard, L.F., Jiang, Z., Cui, Y., Liu, J., Li, J., and Zhang, T. (2011). Single-atom catalysis of CO oxidation using Pt1/FeOx. Nat. Chem. 3, 634–641. 2. Kyriakou, G., Boucher, M.B., Jewell, A.D., Lewis, E.A., Lawton, T.J., Baber, A.E., Tierney, H.L., Flytzani-Stephanopoulos, M., and Sykes, E.C.H. (2012). Isolated metal atom geometries as a strategy for selective heterogeneous hydrogenations. Science 335, 1209–1212. 3. Wang, A., Li, J., and Zhang, T. (2018). Heterogeneous single-atom catalysis. Nat. Rev. Chem. 2, 65–81. 4. Hagen, J. (2015). Industrial Catalysis: A Practical Approach (WILEY-VCH). 5. Chen, Y., Ji, S., Chen, C., Peng, Q., Wang, D., and Li, Y. (2018). Single-atom catalysts: synthetic strategies and electrochemical applications. Joule 2, 1242–1264. 1State
Key Laboratory of Green Chemical Engineering and Industrial Catalysis, Sinopec Shanghai Research Institute of Petrochemical Technology, Shanghai 201208, China *Correspondence: [email protected] (Y.W.), [email protected] (Z.X.) https://doi.org/10.1016/j.chempr.2019.10.006
CATALYSIS
Reaction: Open Up the Era of Atomically Precise Catalysis Wei Zhu1,2 and Chen Chen1,* Wei Zhu is an associate professor at Beijing University of Chemical Technology. His research focuses on the development of catalysts and devices for energy-related electrochemical applications. Chen Chen joined the Department of Chemistry at Tsinghua University as an associate professor in 2015. His research focuses on catalyst design and mechanism study at the atomic scale for catalytic activation reactions of small molecules. Just like when the use and manufacture of tools motivated the evolution of human cognition and thus made us different from other species, the development of probe technologies is
Chem 5, 2733–2739, November 14, 2019 ª2019 Elsevier Inc. 2737