| dc.description.abstract | Producing and utilising low-carbon fuels are essential to achieving net-zero carbon emission and meeting the requirement of the 2 ℃ scenario. Molecular dynamics simulation can provide an in-depth understanding of the chemical mechanism of fuel production and physiochemical properties of low-carbon fuels, which can be used to guide the production and utilisation of sustainable low-carbon fuels. This study is focused on investigating biomass catalytic gasification for fuel production and two important low-carbon fuels, i.e., polyoxymethylene dimethyl ethers (OMEn) and ammonia. It considers the mechanisms of nickel catalysed gasification of cellulose in supercritical water and key physiochemical properties of OMEn/diesel and coal-ammonia mixtures. Reactive force field molecular dynamic simulation was performed to elucidate the mechanism of Ni-catalysed supercritical water gasification of cellulose. Simulations showed that Ni could decrease the activation energy of C-C and C-O bond cleavage, promoting the depolymerisation and ring-opening process of cellulose. The yields of gaseous products increase with the increasing temperature. H2 yield mainly depends on H free radical number, which can be generated from cellulose dehydrogenation and water-splitting reactions. In the presence of Ni catalyst, water plays a limited role in providing H free radicals to produce H2, while the hydrogen atoms in cellulose are the primary source of H2 generation. Co-firing ammonia, a carbon-free fuel, has been identified as a promising option to reduce CO2 emissions from coal-fired power plants. The effect of ammonia on coal pyrolysis and nitrogen transformation was studied by ReaxFF simulation. The results show that ammonia decomposition products, NH2•, will combine with coal decomposition fragments, preventing char formation. The active site on coal fragments would increase at high temperatures owing to the dehydrogenation reaction of coal, which makes more NH2• interact with carbon in coal, thus increasing the nitrogen content in char. In addition, the transformation and evolution of nitrogen atoms on coal fragments were investigated. Polyoxymethylene dimethyl ethers as an alternative fuel have attracted considerable interest in recent years owing to their much-reduced environmental impact. Since OMEn is often blended with diesel, the miscibility and stability of OMEn/diesel mixtures are essential for engine operation. In this study, the molecular dynamics method was used to investigate the miscibility of OME1-6 and diesel blends. The results suggest that the miscibility of OMEn and diesel blends decreases with the increasing number of oxymethylene units. The aromatics and heteroatomic molecules help maintain the stability of OMEn/diesel blends. The intermolecular interactions between OME1-6 and diesel molecules were investigated, which revealed that the electrostatic interaction plays a significant role in the liquid-liquid equilibrium of OMEn/diesel blends. | en_US |
