Abstract
With the diminishing storage of fossil fuels and increasingly concerned environmental problems, economically valuable utilization of existing resources, as well as the recycling of waste resources are two efficient ways for sustaining the development of our industrialized society. Fischer-Tropsch (F-T) wax, produced through coal, is seriously overproduced in China. And hydroisomerization of F-T wax to high-quality lubricant oil is an efficient way to achieve the high-value utilization of excessive F-T wax. The core of hydroisomerization is the development of highly efficient bifunctional catalysts with significantly high catalytic activity and selectivity. However, conventional bifunctional catalysts used in hydroisomerization inevitably need the use of noble metals like Pt and Pd which are high cost. Therefore, in the first part, non-noble nickel metal was proposed to replace noble metal for the preparation of bifunctional catalyst, in order to reduce the cost from the perspective of industrial application. Furthermore, to prevent metal agglomeration under high loading capacity of Ni, gamma phased alumina (\gamma-Al2O3) with high surface area was incorporated to enhance Ni dispersion. After physical mixing with SAPO-11, the Ni/Al2O3-S11 catalyst exhibited Ni in extremely smaller size with higher dispersity than the Ni/S11-Al2O3 catalyst (Ni/SAPO-11 physical mixing with \gamma-Al2O3). After precisely adjusting the ratio of Al2O3 to SAPO-11, the Ni/Al2O3-S11(1:1) catalyst demonstrated high isomer yield of 76.5%, which was higher than both the Ni/SAPO-11 (63.64%) and Ni/S11-Al2O3 (66.64%) catalyst, and even comparable to that of Pt/SAPO-11 (78.01%) catalyst when Pt loading capacity is 0.5 wt.%. High catalytic activity combined with low cost makes the Ni/Al2O3-S11 catalyst a perspective candidate for industrial application.Furthermore, conventional bifunctional catalysts were always prepared by an impregnation method, which requires high temperature and consumes a significant energy consumption. And the metals under this preparation process are easily agglomerated resulting in the reduction of catalytic activity. Therefore, in the second part, a low temperature loading method was introduced to address this drawback. This method facilitates the catalysts with reduced particle sizes and higher dispersion as compared to the catalyst prepared by the conventional impregnation method. Specifically, this method produces both single atoms and metal clusters within the catalyst when the loading capacity of metal Pt is 0.3 wt.%. And the catalyst exhibits a balanced metal-acid function once capacity for Pt loading increased to 0.5 wt.%. Furthermore, the electron density of Pt increased after metal loading on graphited carbon nitride (g-C3N4) support, and the turnover frequency (TOF) of each metal site also increased with the rise of nPt/nA. In addition, it is observed that the catalyst prepared by low temperature loading shows significantly increased hydroisomerization activity and selectivity compared to those prepared with the conventional method, with an isomer yield of up to 68.2 %.
In the third part, we focus on the recycling of carbon fiber reinforced polymer (CFRP) composites, who generate significant waste both throughout their manufacturing process and when reaching the end of their service life. A novel hybrid technology, which integrates chemical recycling as pretreatment with pyrolysis, has been proposed. Ethanol was chosen as swelling catalyst during chemical pretreatment, and a comparison was made between the pyrolysis products of cured epoxy resin treated with ethanol and those without pretreatment, and the morphologies before and after pretreatment were also studied. Subsequently, served CFRP as the primary material, surface morphology, Raman spectroscopy and surface element analysis were conducted following the application of various chemicals (ethanol, acetic acid and dimethylformamide) for pretreatment. Ethanol as a pretreated chemical can provide a clean surface of recycled carbon fibre (rCF) to avoid char formation after conventional pyrolysis process, hence preventing the formation of rCF with reduced mechanical properties.
| Date of Award | 15 Mar 2025 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Kok Wong (Supervisor), Nai Yeen Gavin Lai (Supervisor) & Jiusheng Li (Supervisor) |