Solvent continued short-contact-time

Continuous Bench-Scale Experimentation With encouraging results obtained from microautoclave tests, experimentation emphasis moved to the bench-scale unit Here the concept of adding Light SRC to the recycle solvent on a continuous basis was tested Earlier work (j>) performed on short contact time coal liquefaction showed Indiana V coal to be out-of-solvent balance Also the operability of the continuous bench-scale SRT unit was highly dependent upon the quality of the solvent ... 

There are few reports of successful one-step synthesis of primary diamines, and the examples are limited to amines with a special structure. Amination of 1,4-cy-clohexanediol in supercritical ammonia (135 bar) over a Co-Fe catalyst alforded 67 % 1,4-diaminocyclohexane [21]. Excess ammonia, as both supercritical solvent and reactant, and short contact time in the continuous fixed-bed reactor favored the desired reactions. In the best example the cumulative selectivity for the diamine and the intermediate amino alcohol was 97 % at 76 % conversion. Recycling of the unreacted diol and amino alcohol can provide an alternative to the eurrent process, the hydrogenation of pnra-phenylenediamine. The high seleetivity was because of the rigid structure and the relative positions of OH functionality in the substrate. For comparison, amination of 1,4-butanediol under similar conditions yielded pyiTolidine as the major product 1,4-diaminobutane was barely detectable. When 1,3-cyclohexanediol was aminated with the same catalyst in the continuous system, the yield of 1,3-diaminoeyclohexane dropped below 5%, mainly because elimination of water led to undesired monofunctional products via a,/9-unsaturated alcohol, ketone, and/or amine intermediates [22]. 

Upon continuing vaporization, the stage of bubbles in the liquid transforms to liquid droplets in a vapour. The temperature measured at the vaporizer tube wall over the length of the capillary is also shown in Figure 2. When complete solvent evaporation inside the tube would be achieved, a sharp increase of the capillary wall temperature would be observed, where the vapour is heated. However, optimum ionization conditions are achieved at nearly complete inside-tube vaporization. From this description of the nebulization process, it may be concluded that the contact time between the liquid and the analyte molecules dissolved in the liquid and the hot surface of the capillary is relatively short. This limits the extent of thermal decomposition of labile analytes. 

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