High-Performance Materials from Bio-based Feedstocks. Группа авторов
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Название: High-Performance Materials from Bio-based Feedstocks

Автор: Группа авторов

Издательство: John Wiley & Sons Limited

Жанр: Химия

Серия:

isbn: 9781119655626

isbn:

СКАЧАТЬ in 2004 and presents astonishing properties. Its appearance is like a soft film, and it has a high Young’s modulus and excellent thermal and electrical properties. Previous research reveals that graphene has a very high surface area of over 2000 m2 g−1 and can be easily chemically modified [67]. Within the past decade, numerous investigations have used graphene in various applications along with exploring the practical synthesis procedures of graphene from biomass [68, 69]. Graphene can be synthesized through several methods including micromechanical exfoliation of graphite, chemical vapor deposition (CVD) of graphite, epitaxial graphene growth on silicon carbide, chemical graphitization of graphene oxide, and carbonization of biomass and waste materials [70–74]. Micromechanical exfoliation and CVD of graphite produced good‐quality graphene. The transformation of biomass into graphene can be accomplished via the carbonization of biomass under specific conditions. For example, pyrolysis of camphor leaves at an ultra‐high temperature of 1200 °C under nitrogen or argon atmosphere produced a biochar, which was subsequently reacted with D‐tyrosine as a bio‐based dispersion agent under sonication to obtain graphene [75]. The graphene derived from biomass contained many impurities, whereas the graphene synthesized from graphite is usually purer. To avoid contamination, some researchers used pure lignin to produce fine graphene through a stepwise pyrolysis process [76]. The biomass type may affect the properties of graphene as well. Populus wood was mixed with KOH before carbonization under nitrogen. Surprisingly, the graphene‐like carbon material was found on the structure of the obtained biochar [20]. Sucrose, xylitol, and glucose were also used as starting materials for graphene synthesis. The carbonization of sugar mixed with FeCl3 generated graphene‐like carbon materials, which presented excellent catalytic activity in the hydrogenation of nitrobenzene [77]. Even though graphene is one of the beneficial carbon materials, the production of graphene from biomass without any impurities remains a challenge.

Bio‐based carbon materials Surface area (m2 g−1) Pore volume (cm3 g−1) Functional groups
Biochar 100–500 0.03–0.25 –COOH, –OH, C–H, C=C, C=O
Hydrochar 1–43 0.007–0.2 –OH, C=C, C=O, C–C, –CH2, –CH3
Activated carbon (chemical treatment) 400–2700 0.3–1.53 –OH, C–H, C=C, C–O
Activated carbon (physical treatment) 300–1000 0.1–0.99 –OH, C=O, C–O
Graphene 800–1800 0.3–0.9 C–H, C–OH, C=C
Sugar‐derived carbon 1–5
Carbon nanotube 300–600 2.5 –COOH, –OH

      Over 90% of chemical industries (e.g. petroleum, renewable energy, fine chemicals, polymers, and food and pharmaceutical industries) are associated with catalytic processes. In 2019, approximately 72% of industrial catalytic processes used heterogeneous (solid) catalysts [1]. In order to develop more industrially friendly catalysts, many investigations have advanced the use of different bio‐based carbon materials for a wide range of catalytic applications. The studied bio‐based carbon catalysts and supports initially started with biochar, activated carbon, carbon nanotubes (CNTs), mesoporous carbons, and sugar catalysts, but have now been extended to include graphene and its derivatives. The crucial target for these developments is the upgrading of bio‐based carbon materials into direct catalysts or as catalyst supports to maximize catalytic efficiency. A simple process for the preparation of bio‐based carbon materials as well as achieving high conversion and highly desired product yield under mild reaction conditions are aimed for.

      An understanding of the mechanisms of heterogeneous catalysis could address the appropriate characteristics of bio‐based carbonaceous catalysts. Generally, a heterogeneous catalytic reaction takes place through the following steps: (1) dispersion of the substrate from the bulk fluid to the pore entrance on the external catalyst surface; (2) diffusion of the substrate from the pore entrance into the internal catalyst pore; (3) adsorption of the substrate on the active catalyst site; (4) reaction of the substrate on the active site to generate a product; (5) desorption of the product from the active site; (6) diffusion of the product from the internal catalyst pore to the external surface of the catalyst; and (7) dispersion of the product from the external surface of catalyst into the bulk fluid [78].