Synthesis of MOFs for carbon capture application

The work in this thesis focuses on the synthesis of metal organic frameworks (MOFs) both in batch and continuous work. Improvements are made in both, compared to the previous research. Furthermore, post-modification experiments are conducted to advance the characteristics of end product. Also, their application as solid sorbents in carbon capture is investigated. In Chapter 1, the background of greenhouse gas emissions is reviewed and discussed, followed by the development of carbon capture technologies and different adsorbents used in post-combustion carbon capture. An introduction to metal organic frameworks is then presented, including a literature review of the research to date, and various synthesis methods including batch and continuous routes. The last part of this chapter presents a literature review on how pre-synthetic design and post-synthetic modification synthesis of MOFs can be achieved. The theories and introductions of the characterization techniques used in this thesis are discussed in detail in Chapter 2. Chapter 3 discusses a new batch method for the efficient synthesis of micro-sized HKUST-1 with high yield (84%) under mild conditions. Different activation methods are conducted in the washing process. Both ethanol and methanol are tested to remove the impurities in pores of the samples. Finally, the optimal sample of HKUST-1 achieved is shown to produce a relatively high surface area (1615 m2/g) with a CO2 adsorption of 8.1% (measured by TGA at 1 atm and 27 oC). A step increase in the surface area is made by immersing the powders into a solution consisting of NaCl, water and methanol. Nano scale HKUST-1 is synthesized by adding trimethylamine (TEA) solution with the organic ligand precursor. The reaction rate is accelerated with this case because TEA solution is able to deprotonate the trimesic acid (the organic ligand). The method for nano scale HKUST-1 synthesis is the focus of Chapter 4. Chapter 5 reports the continuous synthesis process of HKUST-1 and ZIF-8. This work builds on previous work at Nottingham. A counter-current Nozzle reactor is used in this work. The products were compared with commercial equivalents. Post-synthetic modification of HKUST-1 was made to improve the hydrophobicity of HKUST-1 to extend its resilience to breakdown in the presence of moisture. In Chapter 6, a hybrid material TiO2@ZIF-8 is synthesized using the same reactor. Different reactor configurations were also used to generate a range of different products that are then compared. To conclude, a summary of the work conducted in this thesis is presented in Chapter 7, followed by a discussion on potential future work

Optimized synthesis of nano-scale high quality HKUST-1 under mild conditions and its application in CO2 capture

This study was focused on the development of an optimized method for the rapid synthesis of nano-scale HKUST-1 with high yield, high surface area and high CO2 uptake capacity but under mild conditions. A series of HKUST-1 were synthesized under different conditions, such as preparation time, temperature, activation method, etc. It was found that the nano-scale HKUST-1 MOFs (T85-3-Pm4-120) was successfully synthesized at a high yield (87%) under low temperature (85 °C) using a mixture of Triethylamine (TEA), Cu2+ and trimesic acid (TMA) with a molar ratio of 6:3:2. The highest porosity was achieved via this pristine HKUST-1 being activated (powder activation, drying at 120 °C) four times using methanol to remove impurities trapped in the pores. The best HKUST-1 MOFs (T85-3-Pm4-120) hereby prepared was then tested in CO2 adsorption and exhibited an adsorption capacity of 2.5 mmol/g. It is therefore demonstrated that the new approach proposed in this study is a rapid and effective way to synthesize highly porous HKUST-1 MOFs under mild conditions, which is of comparable surface area and CO2 uptake capacity with those MOFs prepared under harsh conditions

Production of H2-rich syngas from lignocellulosic biomass using microwave-assisted pyrolysis coupled with activated carbon enabled reforming

This study focuses on the use of a microwave reactor that combines biomass pyrolysis, at mild temperature, with catalytic reforming of the pyrolytic gas, using activated carbon, for generating hydrogen-rich synthesis gas. The traditional pyrolysis of biomass coupled with the reforming of its pyrolytic yields were also conducted using an electrically heated reactor. The bio-oil attained from conventional pyrolysis was higher in comparison to the yield from microwave pyrolysis. The reforming of the pyrolytic gas fraction led to reductions in bio-oil yield to <3.0 wt%, with a simultaneous increase in gaseous yields. An increase in the syngas and H2 selectivity was discovered with the reforming process such that the use of microwave pyrolysis with activated carbon reforming produced 85 vol% synthesis gas fraction containing 55 vol% H2 in comparison to the 74 vol% syngas fraction with 30 vol% H2 obtained without the reforming. Cracking reactions were improved with microwave heating, while deoxidation and dehydrogenation reactions were enhanced by activated carbon, which creates a reduction environment. Consequently, these reactions generated H2-rich syngas formation. The approach implemented in this study revealed higher H2, syngas yield and that the overall LHV of products has huge potential in the transformation of biomass into high-value synthesis gas

High efficiency synthesis of HKUST-1 under mild conditions with high BET surface area and CO2 uptake capacity

This study focuses on the development of a hydrothermal method for the rapid synthesis of good quality copper benzene-1,3,5-tricarboxylate (referred to as HKUST-1) with high yield under mild preparation conditions to address the issues associated with reported methods. Different synthesis conditions and activation methods were studied to understand their influence on the properties of HKUST-1. It was found that mixing the precursors at 50 °C for 3 h followed by activation via methanol refluxing led to the formation of a product with the highest BET specific surface area of 1615 m2/g and a high yield of 84.1%. The XRD and SEM data illustrated that the product was highly crystalline. The sample was also tested on its capacity in CO2 adsorption. The results showed strong correlation between surface area of the sample and its CO2 uptake at 1 bar and 27 °C. The HKUST-1 prepared in this study demonstrated a high CO2 uptake capacity of 4.2 mmol/g. It is therefore concluded that this novel and efficient method can be used in the rapid preparation of HKUST-1 with high surface area and CO2 uptake capacity

Synthesis of MOFs for carbon capture application

The work in this thesis focuses on the synthesis of metal organic frameworks (MOFs) both in batch and continuous work. Improvements are made in both, compared to the previous research. Furthermore, post-modification experiments are conducted to advance the characteristics of end product. Also, their application as solid sorbents in carbon capture is investigated. In Chapter 1, the background of greenhouse gas emissions is reviewed and discussed, followed by the development of carbon capture technologies and different adsorbents used in post-combustion carbon capture. An introduction to metal organic frameworks is then presented, including a literature review of the research to date, and various synthesis methods including batch and continuous routes. The last part of this chapter presents a literature review on how pre-synthetic design and post-synthetic modification synthesis of MOFs can be achieved. The theories and introductions of the characterization techniques used in this thesis are discussed in detail in Chapter 2. Chapter 3 discusses a new batch method for the efficient synthesis of micro-sized HKUST-1 with high yield (84%) under mild conditions. Different activation methods are conducted in the washing process. Both ethanol and methanol are tested to remove the impurities in pores of the samples. Finally, the optimal sample of HKUST-1 achieved is shown to produce a relatively high surface area (1615 m2/g) with a CO2 adsorption of 8.1% (measured by TGA at 1 atm and 27 oC). A step increase in the surface area is made by immersing the powders into a solution consisting of NaCl, water and methanol. Nano scale HKUST-1 is synthesized by adding trimethylamine (TEA) solution with the organic ligand precursor. The reaction rate is accelerated with this case because TEA solution is able to deprotonate the trimesic acid (the organic ligand). The method for nano scale HKUST-1 synthesis is the focus of Chapter 4. Chapter 5 reports the continuous synthesis process of HKUST-1 and ZIF-8. This work builds on previous work at Nottingham. A counter-current Nozzle reactor is used in this work. The products were compared with commercial equivalents. Post-synthetic modification of HKUST-1 was made to improve the hydrophobicity of HKUST-1 to extend its resilience to breakdown in the presence of moisture. In Chapter 6, a hybrid material TiO2@ZIF-8 is synthesized using the same reactor. Different reactor configurations were also used to generate a range of different products that are then compared. To conclude, a summary of the work conducted in this thesis is presented in Chapter 7, followed by a discussion on potential future work

Translating intercultural experiences into pedagogic insights : shifts in language teachers' perceptions of English as a language for intercultural communication

These days, many pre-service and in-service language English language teachers now complete at least part of their professional training overseas. There is, thus, an important question concerning the impact of intercultural encounters on teachers’ perspectives towards the English language and the teaching of English. This paper reports on a study of how a small group of in-service teachers interpreted their experiences of intercultural communication in the UK whilst completing an MA TESOL degree, illuminating the nature of teachers’ perceptions of language and culture and how teachers translated insights derived from reflection on experience into pedagogic insights for the teaching of English as a global language. The findings reveal that participants’ views shifted away from highly normative conceptions of English language use as they recognised the variability and fluidity of communication in real-life intercultural encounters. Based on critical moments in their communication experiences, teachers articulate the importance of broadening their own learners’ perspectives on diversity within the English language and helping them develop cognitive and attitudinal tools to interact appropriately with diverse others. The paper contributes to understanding of the facilitative potential of teachers’ reflections on their own experiences of linguistic and cultural diversity in coming to formulate pedagogical ideals and concrete methodological possibilities

Predicting information popularity: A study of sina weibo

In this paper, we explore if information characteristics, including accuracy, familiarity, fluency, importance, informativeneΒ and relevance, can predict the popularity of a meΒage posted and reposted on Sina Weibo, the most popular social media platform in mainland China. Based on past literature, we propose that the factors mentioned above can determine the likelihood that information is spread through various social media venues. But, it is under explored if the relationships between these factors and information popularity would remain in the context of Sina Weibo. In an experiment, we use actual Weibo posts to test the effects of these characteristics on information popularity, operationalized as reposting likelihood. The results show that a short meΒage perceived as familiar, objective, and relevant to oneself would be more likely to be forwarded. Subjects also indicate that boring, implausible, and useleΒ information would be leΒ popular while interesting information would be more viral online. Finally, we provide theoretical and practical implications