Atmospheric pressure comparative studies

Comparison Data—Plate Dryers Comparative studies have been done on products under both atmospheric and vacuum drying conditions. See Fig. 12-79. These curves demonstrate (1) the improvement in drying achieved with elevated temperature and (2) the impact to the drying process obtained with vacuum operation. Note that cui ve 4 at 90°C, pressure at 6.7 kPa absolute, is comparable to the atmospheric cui ve at 150°C. Also, the comparative atmospheric cui ve at 90°C requires 90 percent more diying time than the vacuum condition. The dramatic improvement with the use of vacuum is important to note for heat-sensitive materials. 

The influence of electronegative additives on the CO hydrogenation reaction corresponds mainly to a reduction in the overall catalyst activity.131 This is shown for example in Fig. 2.42 which compares the steady-state methanation activities of Ni, Co, Fe and Ru catalysts relative to their fresh, unpoisoned activities as a function of gas phase H2S concentration. The distribution of the reaction products is also affected, leading to an increase in the relative amount of higher unsaturated hydrocarbons at the expense of methane formation.6 Model kinetic studies of the effect of sulfur on the methanation reaction on Ni(lOO)132,135 and Ru(OOl)133,134 at near atmospheric pressure attribute this behavior to the inhibition effect of sulfur to the dissociative adsorption rate of hydrogen but also to the drastic decrease in the... 

This comprehensive article supplies details of a new catalytic process for the degradation of municipal waste plastics in a glass reactor. The degradation of plastics was carried out at atmospheric pressure and 410 degrees C in batch and continuous feed operation. The waste plastics and simulated mixed plastics are composed of polyethylene, polypropylene, polystyrene, polyvinyl chloride, acrylonitrile butadiene styrene, and polyethylene terephthalate. In the study, the degradation rate and yield of fuel oil recovery promoted by the use of silica alumina catalysts are compared with the non-catalytic thermal degradation. 9 refs. lAPAN... 

Subsequently, the problem was investigated by Karpov and Severin [6]. They used closed vessels with a diameter of 10cm and 10, 5, and 2.5cm width, initially at atmospheric pressure. The vessels were filled with different lean hydrogen and methane/air mixtures and rotational speeds in the range of 130-4201/s were employed. They also included data from the study of Babkin et al. [3] in their analysis. Unfortunately, they did not observe the flame itself and measured only the pressure rise in the vessel, which was compared with pressure development in the vessel without rotahon, to draw a conclusion with respect to flame speeds and quenching. 

Here we report only a small selection of experimental results. There are few systematic studies of experimental results of new and conventional techniques for extraction from polymers. Vandenburg et al. [457] have recently compared PFE and MAE with atmospheric pressure methods for extraction of PP/(Irganox 1010, Irganox 1330). 

In this paper, we summarize results from a small scale methane direct oxidation reactor for residence times between lO and lO seconds. For this work, methane oxidation (using air or oxygen) was studied over Pt-10% Rh gauze catalysts and Pt- and Rh-coated foam and extruded monoliths at atmospheric pressure, and the reactor was operated autothermally rather than at thermostatically controlled catalyst temperatures. By comparing the steady-state performance of these different catalysts at such short contact times, tiie direct oxidation of methane to synthesis gas can be examined independent of the slower reforming reactions. 

In the study of atmospheric aerosols several techniques have been used to determine optical constants from measurements on particulate samples. And there have been many such measurements. Yet under pressure from funding agencies and from those waiting at computer terminals for optical constants of the complicated mixture that is the atmospheric aerosol, comparatively little effort has been expended on evaluating these techniques by applying them to particles of solids with known optical constants. 

As seen in Figure 2.2 and from the corresponding discussion, dehydrocyclization is a key reaction in forming aromatic compounds.307 A study comparing dehydrocyclization over mono- and bifiinctional catalysts at atmospheric pressure and high pressure representative of naphtha reforming conditions concludes that primary aromatic products at all pressures are formed by direct six-carbon ring formation.313 Over bifunctional catalysts the acid-catalyzed cyclization is more rapid... 

The Kotsuki group investigated the effect of high-pressure conditions on the direct proline-catalyzed aldol reaction [79a], a process which, interestingly, does not require use of DMSO as co-solvent. Use of high-pressure conditions led to suppression of the formation of undesired dehydrated by-product and enhancement of the yield. Study of the substrate range with a range of aldehydes and ketones revealed that enantioselectivity was usually comparable with that obtained from experiments at atmospheric pressure. Additionally, proline catalyzed aldol reactions in ionic liquids, preferably l-butyl-3-methylimidazolium hexafluorophosphate, have been successfully carried out [79b,c]. 

In an early study by Schery and Gaeddert (1982), an accumulator device was used to measure the effect of atmospheric pressure variations on the flux of Radon (222Rn), an inert radioactive element with a half-life of 3.8 days, from the soil. Fluxes measured by the accumulator were compared with predictions for flow-free diffusion from a model developed by Clements and Wilkening (1974), which applies Fick s law. A mean 222Rn-flux enhancement of about 10%, with a high value of 20%, due to cyclic atmospheric pressure variations was observed. However, the device s effectiveness was limited by back diffusion from the accumulator to the subsurface, leading the authors to view the flux values as semi-quantitative. 

In thermospray interfaces, the column effluent is rapidly heated in a narrow bore capillary to allow partial evaporation of the solvent. Ionisation occurs by ion-evaporation or solvent-mediated chemical ionisation initiated by electrons from a heated filament or discharge electrode. In the particle beam interface the column effluent is pneumatically nebulised in an atmospheric pressure desolvation chamber this is connected to a momentum separator where the analyte is transferred to the MS ion source and solvent molecules are pumped away. Magi and Ianni (1998) used LC-MS with a particle beam interface for the determination of tributyl tin in the marine environment. Florencio et al. (1997) compared a wide range of mass spectrometry techniques including ICP-MS for the identification of arsenic species in estuarine waters. Applications of HPLC-MS for speciation studies are given in Table 4.3. 

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