Operando magnetic resonance studies of phase behaviour and oligomer accumulation within catalyst pores during heterogeneous catalytic ethene oligomerization
Operando magnetic resonance studies of phase behaviour and oligomer accumulation within catalyst pores during heterogeneous catalytic ethene oligomerization
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DOI：
10.1016/j.apcata.2018.03.011
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发表时间：
2018-05-05
影响因子：
5.5
通讯作者：
Gladden, L. F.
中科院分区：
文献类型：
--
作者：
Baker, L.;Renshaw, M. P.;Gladden, L. F.
二维 H-1 磁共振成像、空间分辨 H-1 磁共振光谱和扩散测量被记录为固定床反应器内运行时间的函数，以直接测量在 1 wt% Ni-Al2O3-SiO2 催化剂上发生的乙烯非均相催化低聚反应的进展情况。催化剂床内径2cm；磁共振测量是在 5.5 cm 的床长上记录的。实验在温度和压力分别为110℃和29bara的条件下进行，乙烯以0.78L·h(-1)的流量连续下降。在转化过程中，对催化剂颗粒内含 H-1 物质的积累进行成像，并沿反应器长度以 1 毫米间隔记录空间分辨 H-1 NMR 光谱。扩散过滤一维化学位移成像用于沿反应器长度以 1 毫米间隔区分气相和液相物质。最后，采用分子扩散的光谱编码脉冲场梯度测量来推断气相和液相的分子组成，并识别催化剂颗粒孔隙空间内部和外部的这些相的数量；这些测量沿着反应器的长度进行空间解析，数据在高度为 4 毫米的部分上取平均值。结果与催化剂颗粒的孔内存在碳数C20和更大的低聚物一致，其起到堵塞孔空间的作用，从而使催化剂失活。
Two-dimensional H-1 magnetic resonance imaging and spatially-resolved H-1 magnetic resonance spectroscopy and diffusion measurements were recorded as a function of time-on-stream within a fixed-bed reactor to provide direct measurements of the progress of the heterogeneous catalytic oligomerization of ethene occurring over a 1 wt% Ni-Al2O3-SiO2 catalyst. The catalyst bed was of internal diameter 2 cm; magnetic resonance measurements were recorded over a bed length of 5.5 cm. Experiments were conducted at a temperature and pressure of 110 degrees C and 29 bara, respectively, with continuous downflow of ethene at a flowrate of 0.78 L h(-1). During conversion the accumulation of H-1-containing species within the catalyst pellets was imaged, and spatially-resolved H-1 NMR spectra were recorded at 1 mm intervals along the length of the reactor. Diffusion-filtered 1D chemical shift imaging was used to discriminate between gas- and liquid-phase species along the length of the reactor at 1 mm intervals. Finally, spectrally-encoded pulsed field gradient measurements of molecular diffusion were employed to infer the molecular composition of the gas and liquid phases and to identify populations of these phases inside and external to the pore space of the catalyst pellets; these measurements were spatially-resolved along the length of the reactor, with data being averaged over sections of height 4 mm. The results are consistent with oligomers of carbon number C20 and greater existing within the pores of the catalyst pellets which act to block the pore space, thereby deactivating the catalyst.