γ-Al_(2)O_(3)颗粒溶液浸润过程的原位磁共振成像  

In situ Magnetic Resonance Imaging of Solvent Infiltration onγ-Al_(2)O_(3) Particles

作　　者：徐若韬 王强 鲍庆嘉 王伟宇 张志 刘朝阳 徐君 邓风 XU Ruotao;WANG Qiang;BAO Qingjia;WANG Weiyu;ZHANG Zhi;LIU Zhaoyang;XU Jun;DENG Feng(National Center for Magnetic Resonance in Wuhan,State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics,Innovation Academy for Precision Measurement Science and Technology,Chinese Academy of Sciences,Wuhan 430071,China;Wuhan National Laboratory for Optoelectronics,Huazhong University of Science and Technology,Wuhan 430074,China)

机构地区：[1]中国科学院精密测量科学与技术创新研究院,波谱与原子分子物理国家重点实验室,武汉磁共振中心,武汉430071 [2]华中科技大学武汉光电国家研究中心,武汉430074

出　　处：《高等学校化学学报》2023年第4期35-44,共10页Chemical Journal of Chinese Universities

基　　金：国家自然科学基金(批准号:22127801,U1932218,22172177,22225205);湖北省自然科学基金(批准号:S22H120101);中国科学院青年创新促进会项目(批准号:2019326)资助。

摘　　要：在催化剂的制备过程中,常采用浸渍法将金属或活性相负载到多孔固体载体上以获得高性能的负载型催化剂;在浸渍过程中溶剂对载体的浸润能力和效果对负载活性组分的分布和状态至关重要,进而会影响催化剂的催化性能.本文利用磁共振成像(MRI)技术开展了溶剂对γ-Al_(2)O_(3)颗粒浸润过程的原位研究.评估了自旋回波(SE)、梯度回波(GRE)和超短时间回波(UTE)3种不同MRI序列的成像效果,发现UTE序列在观测短横向弛豫时间(T_(2))值的1H MRI信号方面展现出优越的性能,应用小激发角和短恢复时间(TR)可以获得比SE和GRE序列更高时间分辨率(<1 min)的动态图像.利用UTE序列对γ-Al_(2)O_(3)在不同极性溶剂中的浸渍过程进行了原位监测,发现极性溶剂水和甲醇均表现出典型的自由扩散过程,即溶剂从颗粒的外缘逐渐扩散到其中心直至饱和;非极性溶剂环己烷展现了不同的浸润行为,γ-Al_(2)O_(3)颗粒的整体1H MRI信号分布呈现出颗粒中心信号强、边缘信号低的特点,并在γ-Al_(2)O_(3)颗粒的外层形成了强1H MRI信号的“液膜”.Impregnation method is commonly used to prepare high-performance catalyst via loading metal or active phase on porous solid support.Solvent infiltration on the support during the impregnation process is essential for the distribution and state of the supported active components,which impact the catalytic property of the supported catalyst.In this study,magnetic resonance imaging(MRI)is implemented for in situ investigation of the solvent infil⁃tration process onγ-Al_(2)O_(3)particles.MRI ofγ-Al_(2)O_(3)particles infiltrated with sufficient water was evaluated by three different MRI sequences,i.e.,spin-echo(SE),gradient-echo(GRE)and ultra-short time of echo(UTE).It is found that the UTE sequence is superior in the acquisition of 1H MRI signals with short T_(2) values.The selection of very short time of echo(TE)values can significantly alleviate the differences in signal intensity caused by protons with different mobility.Particularly,the signals from the motion-restricted protons that diffuse into interior ofγ-Al_(2)O_(3)particles can be observed by using the UTE sequence.Meanwhile,the use of small excitation angle and short time of recovery(TR)in UTE allows to obtain the dynamic images with higher time resolution(<1 min)than that of SE and GRE sequences.The UTE sequence is employed to in situ monitor the infiltration process ofγ-Al_(2)O_(3)particles in solvent with distinct polarities.For polar solvent water and methanol,both show a typical free diffusion process that the solvent gradually diffuses from the outer edge of the particle to its center up to saturation.Interestingly,there is a different infiltration behavior for the non-polar solvent cyclohexane,and the overall 1H MRI exhibits strong central signal and low edge signal in theγ-Al_(2)O_(3)particles after immersed for a certain time.The"liquid film"with a strong signal intensity is formed around the particle,which probably prevents the infiltration of outer cyclohexane into particles,thus affecting the subsequent molecular diffusion and redistribu

关 键 词：磁共振成像 Γ-氧化铝 浸渍过程 原位表征 固体催化剂 

分 类 号：O657.61[理学—分析化学]