Preparation Of Biomass - Based Porous Carbon Materials And Its Application In Adsorption, Separation And Catalysis

Owing to high specific surface area, large pore volume, good electronic conductivity and thermal conductivity, well controlled pore size and surface properties, porous carbon materials (PCMs) have significances in science and great potential applications in many areas, such as adsorption, catalysis, separation, electrochemistry, sensor and gas storage. Performance of PCMs can be effectively improved by doping and modifying, especially for nitrogen doping usually could alter the electronic and crystalline structures of the carbon materials, enhancing the surface polarity and affecting basic active sites. Now, PCMs were fabricated by hard template, soft template methods or activation of carbon and so on. Ordered or disordered PCMs with different pore structures can be obtained by different preparation methods, these different pore structures have different properties and different applications. The present fabrication methods suffer from high costs, complicated preparation technology, pure reagents and strict reaction conditions, which significantly hinder their wide applications. Thus it could be seen that the fabrication methods of PCMs are still requirement of high degrees of innovation and breakthrough, and the applications of PCMs research are still reinforce. Study results showed that the choice of the precursor of carbon materials obviously influenced the porous structure, feature and functionality of PCMs. In terms of the precursor of PCMs, thus far, most of works were mainly focus on the conventional chemicals, such as phenol formaldehyde resin, glucose, and phenol, etc. Carbon-based nanomaterials fabricated from biomass resources as the alternative to conventional chemicals will possess a prosperous future, but there is still no general and satisfactory process for the production of valuable carbon materials from crude biomass to date. Preparation method, structure control and potential application for PCMs were investigated for enriching the content of the PCMs and promoting the practical application in many fields.Carbon-based solid acid catalyst is a new class of solid acid catalyst. It has been reported as promising catalysts with unique catalytic activity in a variety of catalytic reaction, especially for biodiesel production. It has the characteristics of high catalytic efficiency, relatively easy separated, no corrosion of equipment and easily recycled in the process of biodiesel production. Compared with magnetic solid acid catalyst, non-magnetic carbon-based solid acid can not be easily separated in highly viscous or solid reaction mixtures, which still is an intractable problem. Considering from production costs and fabrication methods, a low-cost raw material and simple rout are used for fabricating magnetic carbonaceous solid acid, which has positive significance for the development of biodiesel.This thesis presents a systematic study regarding the following well-connected aspects of PCMs, including develop a novel, simple and low cost preparation method for nitrogen doped hierarchically PCMs by chelate-assisted multi-component co-assembly and solvent evaporation induced self-assembly (EISA) processes respectively, solving the issues of production cost, controllable and large-scale fabrication of PCMs in an integrated manner. Meanwhile, the as-obtained carbon materials were further used for investigating their performances in organic pollutant remove, carbon dioxide capture, bilirubin adsorption, and size-selective separation protein. Additionally, this thesis also explores a fabrication method of low-cost magnetic carbon-based solid acid catalysts. The catalytic activities of as-made magnetic carbon-based solid acid catalysts were also systematically studied by esterification of oleic acid with methanol. Specifically, the main research works as followed:In Chapter 2, banana peel-derived highly porous functional carbon material (HPFCM) fabricated via using a chelate-assisted multi-component co-assembly route for efficient removal of methylene blue. Briefly, the HPFCMs were fabricated by using A1 (â…¢) ions as central ion, Pluronic F127 as a microstructure-directing agent and banana peel as precursor or chelating agent-like. Several critical variables for fabrication including doses of Al (III) and F127, carbonization temperature had been optimized and the adsorption behavior of PCMs was examined by using methylene blue as dye model compound. The optimal adsorbent was validated as HPFCMs-5-1-800, and its equilibrium data were well fitted to the Langmuir isotherm model with a monolayer adsorption capacity of 385.12 mg/g at ambient temperature. The surface physical properties of HPFCMs-5-1-800 were also exemplarily characterized.In Chapter 3, nitrogen-doped hierarchically porous carbons were fabricated by a hybrid dual-template route for CO2 capture and bilirubin removal. Based on a general EISA strategy, nitrogen-doped hierarchically PCMs were fabricated by using Al-based composite and triblock copolymer F127 as co-templates, and banana peel as precursor. This versatile strategy allows to easily achieve tunable surface area (699-2086 m2/g), pore volume (0.38-1.65 cm3/g) and a narrow average mesoporous size of ca.2.72-4.03 nm by simply varying the dosages of Al3+ and F127, and to attain high N content (4.54 wt%) in a large-scale fabrication system (2 L). X-ray photoelectron spectroscope characterization of the as-prepared sample reveals nitrogen atoms are mainly in the form of pyridinic nitrogen, quaternary nitrogen and pyridine-N-oxide. Importantly, these as-obtained carbon materials showed excellent performance in CO2 capture and bilirubin removel with high adsorption capacities and selectivities. The present fabrication strategy is also applicable to the design of porous carbons doped with other elements by choosing appropriate precursors.In Chapter 4, fabrication of intestine-like mesoporous carbon (ILMC) for size-selective separation of proteins. An ILMC was fabricated by a hybrid dual-template route and banana peel with some modifications, and used for size-selective separation of proteins. The as-made ILMC has been exemplarily characterized by FTIR, XRD, SEM, TEM, and N2 adsorption measurements. The adsorption character of ILMC was also evaluated with three typical proteins, cytochrome c (Cyt c), bovine serum albumin (BSA) and lysozyme (Lyz), with different molecular sizes. The adsorption of binary mixtures of Cyt c and BSA, Cyt c and Lyz, and a ternary mixture of Cyt c, BSA and Lyz showed that the ILMC is effective and highly selective adsorbent for Cyt c. This simple and procurable ILMC may be utilized as potential and promising supports for immobilizing bio-macromolecules, and drug delivery and separation.In Chapter 5, bottom-up fabrication of magnetic carbonaceous solid acids with excellent catalytic activities for esterification reaction. A kind of biomass-derived magnetic carbonaceous solid acids (MCSAs) were synthesized by using a bottom-up strategy, i.e., integrated fast pyrolysis of Fe(III)-based complexes and vapor-phase sulfonation from banana peel. This versatile strategy enables large-scale preparation (1.8 L) of MCSAs with easily tunable surface areas (156-1097 m2/g) and pore volumes (0.17-0.74 cm3/g), and relatively large average mesoporous sizes of ca. 6.1-11.4 nm, by simply varying the dosage of Fe(III) ions. The MCSAs have excellent catalytic activities in the esterification of oleic acid with methanol, far higher than those of Amberlyst 15, sulfonated activated carbon, and niobic acid. In particular, the catalytic activities of the obtained MCSAs rival that of a H2SO4 catalyst. An investigation of the kinetics of the esterification reaction further showed that the present catalysts are promising candidates for green and efficient esterification of free fatty acids to produce biodiesel. The present work provides an inexpensive and large-scale method to synthesize MCSAs from waste banana peel and may contribute to a holistic approach for biomass conversion.