Space Time, advantage

Application of this system in the continuous transfer-hydrogenation reaction of acetophenone gave a stable conversion of about 87%, an ee of 94%, and a space-time yield of 255 g L"1 d"1. A continuous dosage of isopropoxide was necessary in order to compensate for deactivation caused by traces of water in the feed stream. Under these circumstances a TTON of 2360 was reached. Comparison of this system with an enzymatic process showed that both approaches offer different advantages and are therefore complementary. 

Another example in which a biocatalytic transformation has replaced a chemo-catalytic one, in a very simple reaction, is the Mitsubishi Rayon process for the production of acrylamide by hydration of acrylonitrile (Fig. 1.42). Whole cells of Rhodococcus rhodocrous, containing a nitrile hydratase, produced acrylamide in >99.9% purity at >99.9% conversion, and in high volumetric and space time yields [121]. The process (Fig. 1.42) currently accounts for more than 100000 tons annual production of acrylamide and replaced an existing process which employed a copper catalyst. A major advantage of the biocatalytic process is the high product purity, which is important for the main application of acrylamide as a specialty monomer. 

Conversion and coke formation during catalytic ethene oligomerization catalyzed by HZSM-5 have been investigated in the TEOM and in a conventional gravimetric microbalance under similar conditions (2). The results show that the TEOM is a powerful tool for determination of the kinetics of deactivation of catalysts, with a design that makes determination of the true space velocity (or space time) easy. The TEOM combines the advantages of the conventional microbalance with those of a fixed-bed reactor, and the same criteria can be used to check for plug flow and differential operation. 

For the first type of reactions (A n > 0) the PFR and the CSTR operated at the permeate-side pressure perform better than the CMR or the PBIMR. The performance of the CMR is slightly belter than that of PBIMR with catalysts on the feed side when the pressure drop across the membrane is low. For the second type of reactions (A n s 0), both CMR and PBIMR perform better than the conventional PFR and the CSTR due to the equilibrium displacement induced by selective removal of a product The PBIMR is preferred over the CMR at a longer space time. For the third type (A n < 0), the PBIMR outperforms any other reactors at a longer diffusional space time. The CMR in this case does not provide advantages due to the undesirable equilibrium effect induced by the pressure variation in the membrane. 

Summary The newly developed continuous process [1] realized in the pilot plant shown is superior to the state-of-the-art batch process currently in use. The main advantages are a higher space time yield and a simplified work-up resulting in a more cost efficient production of primary aminoalkyl silanes. 

The study by Hitzler et al. has illustrated the broad scope of potential hydrogenation reactions in SC-Some of the substrates investigated included m-cresol, benzaldehyde, acetophenone, 1-octene, and cyclohexene. Reactions were performed in 5 and 10 ml packed bed reactors and space times of up to 300 hr were achieved. Residence times of this magnitude render the issue of scale-up largely irrelevant for small (kilogram) quantities of product in a continuous process. This is advantageous for the commercialization of SCF reaction processes because it minimizes development and capital costs. 

An advantage of an extrusion device as a reactor is the combination of several chemical process operations into one piece of equipment with accompanying high space-time yields of product. An extruder reactor is ideally suited for continuous production of material after equilibrium is established in the extruder barrel for the desired chemical processes. 

A one-stage process for the manufacture of PO from propane instead of propene would have substantial economical advantages. In one patent, a catalyst composed of Ag/Cl/NaN03/La/Cr/BaC03 is claimed that gives 10% propane conversion with a PO selectivity of 8% at 480 °C, resulting in a PO space-time-yield of0.002 gpo gcat h however, this catalyst deactivates very rapidly [45a]. 

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