纳米片Ga-MFI分子筛合成及其对航空燃油催化裂解反应中低碳烯烃选择性的影响

在纳米片Al-MFI分子筛合成的基础上，以镓源Ga(NO₃)₃·xH₂O]替换铝源Al₂(SO₄)₃·18H₂O]，合成出类质同象纳米片Ga-MFI分子筛，采用X射线衍射、扫描电镜、BET比表面积分析和NH₃程序升温脱附法等技术对其进行了表征，并考察了普通ZSM-5分子筛、纳米片Al-MFI分子筛和纳米片Ga-MFI分子筛对航空燃油裂解反应的催化性能。结果表明，合成的分子筛是具有MFI骨架拓扑结构的纳米片状分子筛，具有较大的比表面积（482m²/g）和中孔孔容；与铝原子相比，镓原子与硅、氧原子形成的酸性位点的酸性减弱。在高温下（600℃），它抑制了氢转移反应的进行，减少了低碳烯烃的二次反应和结焦前体（芳香烃）在酸性位点上的吸附，使其具有更高催化活性和低碳烯烃选择性，从而获得了比纳米片Al-MFI分子筛高14.47%的热沉。该研究为高超音速飞行器的主动热防护提供了技术支撑。

Synthesis of nanosheets Ga-MFI zeolites and its effect on selectivity of low carbon olefin in aviation fuel catalytic cracking reaction

Based on the synthesis of nanosheets Al-MFI zeolite, isomorphous MFI nanosheets zeolite was synthesized by replacing aluminum source with gallium source. The obtained samples were characterized by XRD, SEM, BET and NH₃-TPD. The catalytic performances of ordinary ZSM-5 zeolite, nanosheets Al-MFI zeolite and nanosheets Ga-MFI zeolite were tested with aviation fuel. The results showed that it was indeed a kind of nanosheets zeolite with an MFI skeleton topology, with a large specific surface area (482m²/g) and mesoporous volume. Compared with aluminum atoms, gallium atoms became less acidic at the acidic site formed by silicon and oxygen atoms. This made nanosheets Ga-MFI zeolite inhibit the hydrogen transfer reaction at high temperature (600℃), reducing the secondary reaction of low olefins and the adsorption of coking precursors (aromatic hydrocarbons) on acidic sites. This led to higher catalytic activity and light olefin selectivity, resulting in heat sink 14.47% higher than that of nanosheets Al-MFI zeolite. The study provided technical support for the active thermal protection of hypersonic vehicles.