An inexpensive apparatus for up to 97% continuous-flow parahydrogen enrichment using liquid helium
An inexpensive apparatus for up to 97% continuous-flow parahydrogen enrichment using liquid helium
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DOI：
10.1016/j.jmr.2020.106869
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发表时间：
2020-12-01
影响因子：
2.2
通讯作者：
Bowers, Clifford R.
中科院分区：
文献类型：
--
作者：
Du, Yong;Zhou, Ronghui;Bowers, Clifford R.
源自仲氢的核自旋超极化可以使核磁共振光谱和成像具有超过四个数量级的灵敏度增强。NMR信号增强与4（xp）-1成比例，其中xp是仲氢摩尔分数。为了方便起见，许多实验室选择在77 K下进行邻-对位转化，其中获得50%的富集。理论上，富集到100%会使NMR信号增强自动增加三倍。本文介绍了一种简单、廉价的高仲富集连续流转化器的结构和试验。在操作过程中，转换器被浸没在运输杜瓦瓶中的液氦中，这种杜瓦瓶通常在NMR实验室中用于填充超导磁体。在4.5 bar和300 mL/min流速下，在30 K下观察到97.3 +/- 1.9%的最大富集。在PdIn/SBA-15催化剂上丙烯非均相加氢制丙烷的反应中，证实了理论预测的信号增强因子增加2.9倍。构建和操作该系统的相对低的成本可以使高仲氢富集以及仲氢衍生的NMR信号的相关增加更广泛地可获得。（C）2020由Elsevier Inc.出版。
Nuclear spin hyperpolarization derived from parahydrogen can enable nuclear magnetic resonance spectroscopy and imaging with sensitivity enhancements exceeding four orders of magnitude. The NMR signal enhancement is proportional to 4(xp)-1, where xp is the parahydrogen mole fraction. For convenience, many labs elect to carry out the ortho-para conversion at 77 K where 50% enrichment is obtained. In theory, enrichment to 100% yields an automatic three-fold increase in the NMR signal enhancement. Herein, construction and testing of a simple and inexpensive continuous-flow converter for high paraenrichment is described. During operation, the converter is immersed in liquid helium contained in a transport dewar of the type commonly found in NMR labs for filling superconducting magnets. A maximum enrichment of 97.3 +/- 1.9% at 30 K was observed at 4.5 bar and 300 mL/min flow rate. The theoretically predicted 2.9-fold increase in the signal enhancement factor was confirmed in the heterogeneous hydrogenation of propene to propane over a PdIn/SBA-15 catalyst. The relatively low-cost to construct and operate this system could make high parahydrogen enrichment, and the associated increase in the parahydrogen-derived NMR signals, more widely accessible. (C)2020 Published by Elsevier Inc.