Zeolite synthesis in unstirred batch reactors I. Nuclear magnetic resonance imaging of non-uniform pre-mixing

The application of nuclear magnetic resonance (NMR) imaging to the study of the design and performance of chemical reactors is introduced. NMR imaging is a non-invasive technique which can be utilized for the investigation of physical processes such as the mixing of reagents within a sealed reactor. A series of experiments is described on the mixing of aluminate solutions with silicate solutions or silica slurries within zeolite crystal growth reactors. Mixing was followed by the imaging of protons present in triethanolamine (a nucleation suppressant) or tetraethylammonium bromide (a structure-directing agent) in sodium aluminosilicate mixtures which were otherwise fully deuterated. Compositions suitable for the crystallization of zeolites A, X and mordenite, in four reactor designs, were studied. The reactors were designed specifically for the growth of large zeolite crystals in microgravity aboard the space shuttle. NMR imaging was shown to be a reliable indicator of the mixing process, provided the organic was present in sufficient concentration and that its distribution was representative of the distribution of the other reagents. The possibility of utilizing NMR imaging to study a wide range of reactors, where other (invasive) techniques are unsuitable, is realized.