Sapphire tubes

Another interesting application of high-pressure tubes is the in-situ investigation of reactions in supercritical solvents such as carbon dioxide. For example, the iridium-catalyzed enantioselective hydrogenation of imines was investigated in a sapphire tube at 313 K [32]. 

Despite the advantages and ease of use of sapphire tubes, great care must be taken. It is very important that protective measurements are put in place when a pressurized tube is handled outside the spectrometer, because the tube s abil-... 

Figure 2.13 Schematic drawing of Roe s titanium-alloy valve glued to a 5 mm outer diameter sapphire tube.

Schematic drawing of the sapphire tube/Ti-valve assembly (expanded) and the safety...

High-pressure NMR studies for catalysis and with supercritical fluids will lead to a much broader application of sapphire NMR cells and to special applications of toroidal probes. The sapphire tube technique can today be considered as a standard, cheap and easily applicable technique to study samples under medium gas pressures, up to 100 MPa. 

Figure 5.6 H HP NMR data (sapphire tube) for carbonylation of MeOAc catalysed by Rh/Mel (i) aqueous and (ii) anhydrous, measured by H NMR at 180°C and 35 bar (initial) in AcOH/ Mel/[QAS]I.

Figure 5.7 H HP NMR spectra (sapphire tube) showing formation of Acl and MeOAc after heating Mel/Ac20/AcOH/Nal to 180°C.

Figure S.9 H HP NMR data (sapphire tube) of extent ofincorporation in MeOAc at 160 °C in ACOH/H2O starting from C-MeOAc and C-Mel.

Figure 7.2 Fast spinning, high pressure NMR sapphire tube with safety and charging device (constructed at ICCOM-CNR, 2003).

Figure 7.7 Selected P H NMR spectra recorded during a CO/ethene copolymerization assisted by [Pd TFA)2(Na2DPPPDS)] in the presence of 20 equiv of TsOH and a 1 1 CO/C2H4 pressure of 600 psi (10 mm sapphire tube, D2O, 20—85°C,...

Figure 7.8 Variable-temperature P H NMR study (sapphire tube, MeOH-t/4, 81.01 MHz) of the carbo-nylation reaction of ethene catalyzed by (3) (a) Dissolving (3) in MeOH-d4 under nitrogen at room temperature (b) after the tube was pressurized with 40 bar of CO/C2H4 (1 1) at room temperature (c) after 10 min at 50 °C (d) after 10 min at 70 °C ...

Figure 7.10 P H NMR study (sapphire tube, CD2CI2, 81.01 MHz) of CO/C2H4 copolymerization ...

Long and Sloan (1996) performed a series of measurements to investigate the site of nucleation for natural gas and carbon dioxide hydrate initiation in a sapphire tube. 

A hydrate nucleating agent (precipitated amorphous silica) and a quiescent surface inhibitor (sodium dodecyl sulfate) were used in an attempt to initiate hydrates in the bulk phase. While the induction time (for detectable hydrate formation) was not predictable, in every case hydrate was initiated at a surface—usually at the vapor-water interface, but infrequently along the sides of the sapphire tube in the gas phase, and at the metal end-plate below the liquid phase. 

We have measured emission and absorption spectra of an HPS sodium discharge within a sapphire tube. The tube has an inside diameter of 7.6 mm, is terminated... 

Sapphire tubes are susceptible to unpredictable, catastrophic failure. 

Sapphire tubes require protection from chips and scratches. 

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