@inbook {47322, title = {Advanced heterogeneous catalysts volume 1: applications at the nano-scale}, volume = {1359}, year = {2020}, publisher = {American Chemical Society}, organization = {American Chemical Society}, doi = {10.1021/bk-2020-1359}, author = {Sudarsanam, Putla and Singh, Lakhveer} } @inbook {47324, title = {Advanced heterogeneous catalysts volume 2: applications at the single-atom scale}, volume = {1360}, year = {2020}, publisher = {American Chemical Society}, organization = {American Chemical Society}, doi = {10.1021/bk-2020-1360}, author = {Sudarsanam, Putla and Singh, Lakhveer} } @inbook {47323, title = {Advances in single-atom catalysts for lignin conversion}, booktitle = {Advanced Heterogeneous Catalysts Volume 2: Applications at the Single-Atom Scale }, volume = {1360}, year = {2020}, pages = {93-125}, publisher = {ACS }, organization = {ACS }, abstract = {

Single-atom catalysts (SACs) have drawn significant attention as promising surfaces for promoting observable reaction processes. As a guideline, SACs should have the proper nanoscale dimensionality to influence their effective and efficient performance, especially during lignin conversion to platform chemicals and other useful products. The development of SACs for functional applications still has many difficulties, such as harnessing and improving low-coordinated metal atoms to have controlled and observable activities per metal atom. Consequently, the need arises to ensure a decrease in the size of the metal particles and their uniform dispersion or coordination on a suitable support material. This has been an industrial target for a long time in the field of catalysis. Supported metal-based catalysts are not dimensionally uniform, thereby reducing their metal-atom efficiency and frequently leading to undesired side reactions that are sometimes difficult to observe. This makes the identification of the active sites responsible for the reaction of interest very difficult or even impossible. To ameliorate this challenge, the ultimate small-size limit for a metal particle is the SAC, which contains isolated metal atoms singly dispersed on any suitable support materials. It is expected that SACs should maximize the metal-atom efficiency with respect to the application, which is particularly significant for supported metal catalysts. Moreover, through uniform single-atom dispersion, SACs offer a great opportunity for achieving high activity and tuning selectivity to the desired product. This chapter provides a comprehensive overview of recent advances in using SACs for the conversion of lignin or lignin model compounds. The different support materials used for SACs, such as zeolites, metal oxides, and carbonaceous and siliceous materials, are discussed. This contribution also covers the catalytic reactions of lignin with an emphasis on cleaving its specific linkages, along with a systematic evaluation of SACs used in the relevant processes. The chapter also addressed key parameters essential for tailoring the particle size and acid{\textendash}base and redox properties of the SACs used in lignin conversion. Special attention is paid to understanding the role of synthesis conditions in tailoring the size of SACs. It is expected that this contribution will provide future directions for practical SAC development and implementation in lignin conversion.

}, doi = {10.1021/bk-2020-1360.ch005}, author = {Halilu, Ahmed and Umar, Ahmad Abulfathi and Balarabe, Yahaya Umar and Haniffa, Mhd. Abd. Cader Mhd. and Munawar, Khadija and Sunku, Kiran and Sudarsanam, Putla} } @article {49931, title = {Additive-free, selective synthesis of N-heteroaromatics using morphology-engineered hollow CeO2 nanocatalyst}, journal = {ACS Sustainable Chemistry \& Engineering}, volume = {13}, year = {2025}, month = {DEC }, pages = {21266-21276}, type = {Article}, abstract = {

We developed a highly efficient, shape-controlled CeO2 nanocatalyst for synthesizing N-heteroaromatics via an aerobic dehydrogenation approach, operating at mild reaction conditions without needing toxic acid/base additives. Different morphologies of CeO2, namely, hollow nanospheres, nanorods, and irregularly shaped nanoparticles, were synthesized, as confirmed by electron microscopy analysis. The CeO2 hollow nanosphere catalyst (CeO2-HNS) exhibited unique features, such as abundant acid-base sites, larger-sized voids, and surface oxygen vacancies. These characteristics are found to be crucial for the additive-free oxidative dehydrogenation of saturated N-heterocycles over the CeO2-HNS catalyst, resulting in 98\% conversion of 1,2,3,4-tetrahydroquinoline with 100\% quinoline product selectivity. The versatility of this approach was further demonstrated by the successful aerobic dehydrogenation of a broad range of saturated N-heterocycles, affording N-heteroaromatics in good to excellent yields. Furthermore, the CeO2-HNS nanocatalyst showed exceptional reusability over six cycles without requiring a regeneration step, such as high-temperature calcination treatment. The structural and morphological stability of the CeO2-HNS catalyst, along with reaction scalability and favorable green chemistry metrics, emphasized the practical viability of the CeO2-HNS catalyst for industrial applications.

}, keywords = {acid-base and defect sites, additive-free aerobicdehydrogenation, CeO2 hollow nanosphere catalyst, N-heteroaromatics, reusability and scalability}, issn = {2168-0485}, doi = {10.1021/acssuschemeng.5c10285}, author = {Singh, Nittan and Swapna, Bhattu and Balu, Alina Mariana and Bhatte, Kushal and Sudarsanam, Putla} }