Uniformity of stationary phase films in dynamically coated glass capillary columns for gas chromatography

Blomberg, Lars G.

doi:10.1007/bf02350795

Cited by 19 publications

(2 citation statements)

References 8 publications

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“…It is clear from Figure that after introduction of a back pressure regulator at the microchannel outlet to control the linear velocity of the displacing plug, the coating thickness uniformity is dramatically improved in comparison to that shown in Figure ; nevertheless, the coating thickness is still not ideally uniform. In addition to the coating procedure itself, the drying step is also often a source of irregularity in thickness of the deposited film if not performed carefully. , Namely, temperature fluctuations along the capillary length might cause some of the evaporated solvent to condense in the downsteam, cooler parts of capillaries, creating a restriction to the gas flow used to dry the capillary . Restrictions create a pressure difference leading to the transport of some of the liquid film toward the outlet.…”

Section: Resultsmentioning

confidence: 99%

Catalyst Coating on Prefabricated Capillary Microchannels for the Direct Synthesis of Hydrogen Peroxide

Paunovic

d’Angelo

Schouten

et al. 2015

Ind. Eng. Chem. Res.

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The geometric surface area of capillary microchannels is insufficient for the direct deposition of a catalyst active phase to reach a sufficient level of microreactor activity. For this reason it is necessary to coat a porous layer of a catalyst support on the channel wall prior to the deposition of the active metallic species. This work addresses the challenges related to the preparation of well-adhered and uniform silica coatings inside closed capillary channels suitable for catalyst deposition for the direct synthesis of hydrogen peroxide. The method used to deposit a layer of coating suspension, which upon solvent evaporation and heating is transformed into a solid film, is known as dynamic gas displacement. Variation of coating parameters and properties of the coating solution could be used to produce microreactors coated with different silica loadings. The most critical aspect of coating is maintaining the film regularity during and after displacement of the coating fluid. The uniformity of the coating thickness is greatly affected not only by the ability to maintain the coating parameters constant, such as the coating velocity, temperature, and solvent evaporation rate during and after displacement of the coating solution, but also by the rheological properties of the coating fluid. Advantages and disadvantages of different coating techniques such as colloidal coating, sol–gel, and slurry coating are discussed in detail. Finally, we demonstrate that silica wall-coated layers with embedded Au–Pd colloidal alloy nanoparticles are active in catalyzing the direct synthesis of hydrogen peroxide.

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Section: Resultsmentioning

confidence: 99%

Catalyst Coating on Prefabricated Capillary Microchannels for the Direct Synthesis of Hydrogen Peroxide

Paunovic

d’Angelo

Schouten

et al. 2015

Ind. Eng. Chem. Res.

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“…Fast column flow rates, normally between 4-10 ml/min, are preferred for drying as this minimizes the column preparation time but will usually result in the formation of thicker films [215,216]. Orienting the coil of the column horizontally when coating and drying can minimize the influence of drainage of the coating solution to the lowest parts of the coil.…”

Section: Procedures For Coating Open Tubular Columnsmentioning

confidence: 99%