Performance in continuous

Membrane-based separation techniques constitute nowadays well-established process methods for industrial treatments of fluids. Like SMB, membrane-based separations can be performed in continuous mode. In the field of preparative-scale enan-tiodiscrimination, much effort has been invested in this subject due its high potential [154, 155]. (Chapter 5 of this book is devoted to the subject, and further discusses the advantages and applications of membrane technologies.)... 

Figure 5.4-3 shows the results of a lifetime study for Wilke s catalyst dissolved, activated, and immobilized in the [EMIM][(CF3S02)2N]/compressed CO2 system. Over a period of more than 61 h, the active catalyst showed remarkably stable activity while the enantioselectivity dropped only slightly. These results clearly indicate - at least for the hydrovinylation of styrene with Wilke s catalyst - that an ionic liquid catalyst solution can show excellent catalytic performance in continuous product extraction with compressed CO2. 

Downstream processing compression, coating (not performed in continuous mode)... 

Ortiz, et. al (1999) measured overall mass transfer coefficients for the aqueous dissolution of naphthalene, pyrene, and phenanthrene from oils ranging in viscosities from a light lubricating oil (86 cp) to a high viscosity oil ( 1000cp). These measurements were performed in continuous-flow systems for time periods ranging from several months up to one year. The authors hypothesize that naphthalene, pyrene, and phenanthrene dissolution from a high viscosity oil (1000 cp) results in a depleted zone within the NAPL that increases with dissolution time. 

L. N. Valsamis and E. L. Canedo, Effect of Rotor Geometry and Operating Conditions on Mixing Performance in Continuous Mixers An Experimental Study, SPE ANTEC Tech. Papers, 37, 629-632 (1991). 

With numerous researchers investigating the advantages associated with thermally or biocatalytically controlled asymmetric syntheses, some of which have been performed in continuous flow reactors, few have considered the prospects of photochemical asymmetric synthesis, an idea... 

The basis of the process is to use activated carbon to recover SO2 in a salable form. The process flowsheet and chemistry are summarized in Figure 1. All steps of this dry, cyclic process are performed in continuous, countercurrent, multi-stage fiuidized-bed equipment. In the S02-removal step the carbon catalyzes the reaction of the SO2 with oxygen in the flue gas to form SO3, which is hydrolyzed to sulfuric acid that remains sorbed... 

With numerous researchers investigating the advantages associated with the thermal or biocatalytic control of asymmetric reactions, Ichimura and co-workers [89] considered the potential of photochemical asymmetric syntheses performed in continuous flow reactors. To investigate the hypothesis, the authors employed the asymmetric photochemical addition of MeOH to (R)-( + )-(Z)-limonene (159) as a model reaction, comparing three quartz micro reactors, with a standard laboratory cell as a means of highlighting the synthetic potential of this approach. 

Catalyst Screenins All catalyst screening studies were performed in continuous microreactor units operated in the downflow configuration. For experiments conducted using a two-bed catalyst design, each bed comprised 4 cc of catalyst having the same composition, separated by 4 cc of inert material. Internal... 

Traditionally, the chemical industry has eschewed high-velocity rotational equipment because of maintenance difficulties and poor performance in continuous duty. Advances in equipment design have overcome some of the unreliability problems, and they are becoming more popular despite their high initial cost and power requirements. 

Much of the work designed to elucidate or to improve upon palladium catalysts in the industrial context has naturally been performed in continuous-flow systems, sometimes employing a spinning basket the effect of added ethene has been a recurrent theme. In such work the catalyst is usually allowed to reach its steady level of activity before results are taken, or conditions altered to ascertain their effects. Work of this kind is summarised in Section 9.3. 

Aluminum chloride has been known for a long time to catalyze this reaction. H owever, its high acidity leads to low selectivity for alkylate. Acidic chloroaluminates proved to be interesting alternative catalysts and solvents [28] because it is possible to tune their Lewis acidity by adjusting their composition. The alkylation of ethylene or butene with isobutane has been performed in continuous-flow pilot plant operation at IFF. The feed, a mixture of olefin and isobutane, is pumped continuously into the well-stirred reactor, which contains the IL catalyst In the case of ethylene, which is less reactive than butene, [pyridine, HClj/AlClj (1 2 molar ratio) IL proved to be the best candidate. The reaction can be run at room temperature and provides good quality alkylate (2,3-dimethylbutanes is the major product) over a period of 300 h (MON = 90-94 RON = 98-101). 

Limitations Volumetric precision of the described dosing process strongly depends on the uniformity of the droplet distance and transport velocity of the target droplet sequence. Therefore, this approach can be employed for assays, which are performed in continuous flow mode and strictly serial droplet transport regime. 

Proton-NMR is usually performed in continuous-wave instruments on relatively concentrated solution... 

Raman spectroscopy has been used to monitor a variety of industrial processes to improve product quality and process understanding [18,19]. The same features that make Raman spectroscopy a useftd technique for traditional process monitoring, such as the short analysis time and ease of optical sampling, mean that it can also be a useful tool for analyzing and understanding chemical reactions performed in continuous microreactors. 

All of the pyrolysis reactions described herein were performed in continuous flow, isothermal reactor systems. One such laboratory reactor system is schematically depicted in Figure 1. Usually, these systems incorporated separate preheat zones, for hydrocarbon and diluent. Catalysts or promoters used were added along with the diluent stream. The heated portions of the preheat and reactor systems were constructed from 316 stainless steel in most cases. 

A two-step enantioselective synthesis of 2-amino-l,3.4-butanetriol 12 was performed in continuous mode using two serial capillary microreactors with HiSg-tagged transketolase (TK) /oo-transaminase (TAM) bound to the wall via immobihzed Ni-nitrilotriacetic add (Ni-NTA) complex [78]. The TK-catalyzed conversion of hydroxypyruvate 8 and glycolaldehyde 9 to L-erythrulose 10 followed by the TAM-catalyzed amination resulted in the formation of the product This work demonstrated the implementation of a dual enzyme microreactor system for the evaluation of a de novo pathway for an enzyme-catalyzed synthesis. 

Numerous hydrolaseotalyzed KRs of various secondary alcohols were performed in continuous-flow mode (Figure 9.8 and Table 9.6). The bioimprinting effect in sol-gel immobilization of various lipases (Lipase AK, Lipase PS, CaLB, and CrL) was studied (116]. The performance of the immobilized biocatalysts were characterized by enantiomer selective acylation of various racemic secondary alcohols in two different multisubstrate systems (mix A rac-23a,c-e and mix B rac-23b and roc-23i) in batch and continuous-flow mode. The synthetic usefiilness of the best biocatalysts was demonstrated by the KR of racemic l-(thiophen-2-yl)ethanol (rac-23j) in batch and continuous-flow systems [116]. 

Shamez, R. andD. Sammons, Strate esfor Enhancing Performance in Continuous-Flow Electrophoresis, I Selective Manipulation of Particle Trajectories, Preprints of First Separations Division Topical Conference on Separation Technolo es New Developments and Opportunities, Miami Beach, FL, Nov. 2-6 (1992), pp. 264-270. 

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