Two-dimensional ¹H magnetic resonance imaging and spatially-resolved ¹H 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 °C and 29 bara, respectively, with continuous downflow of ethene at a flowrate of 0.78 L h⁻¹. During conversion the accumulation of ¹H-containing species within the catalyst pellets was imaged, and spatially-resolved ¹H 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.

在固定床反应器中记录二维¹ H磁共振成像以及空间分辨的¹ H磁共振波谱学和扩散测量值与运行时间的关系，以提供对非均相催化齐聚反应进展的直接测量。在1重量％的Ni-Al ₂ O ₃ -SiO ₂催化剂上产生乙烯。催化剂床的内径为2cm。在5.5厘米的床长上记录磁共振测量结果。实验分别在110°C和29 bara的温度和压力下进行，乙烯以0.78 L h ^-1的流量连续向下流动。转换过程中累积¹对催化剂颗粒中的含H物质进行成像，并进行空间分辨¹沿反应器的长度以1 mm的间隔记录1 H NMR光谱。扩散过滤的一维化学位移成像用于以1 mm的间隔沿反应器的长度区分气相和液相物质。最后，使用分子扩散的光谱编码脉冲场梯度测量方法来推断气相和液相的分子组成，并确定催化剂颗粒孔隙空间内部和外部的这些相的种群。这些测量值沿反应堆的长度在空间上解析，数据在4 mm高的区域内取平均值。结果与碳原子数为C 20的低聚物和存在于催化剂粒料的孔中的更大的低聚物一致，该低聚物起堵塞孔空间的作用，从而使催化剂失活。