Batch catalysis

Application of the largest dendritic catalyst 8 (Figure 4.15) in a continuous process showed activity over 15 exchanged reactor volumes (Figure 4.16). The decrease in activity caused by wash out was calculated to be only 25% (retention of ligand 98.1%). The drop in activity was therefore ascribed to the decomposition of the palladium catalyst. Addition of membrane material to batch catalysis experiments did not change the conversion showing that this was not the cause of decomposition. 

A hst of polyol producers is shown in Table 6. Each producer has a varied line of PPO and EOPO copolymers for polyurethane use. Polyols are usually produced in a semibatch mode in stainless steel autoclaves using basic catalysis. Autoclaves in use range from one gallon (3.785 L) size in research faciUties to 20,000 gallon (75.7 m ) commercial vessels. In semibatch operation, starter and catalyst are charged to the reactor and the water formed is removed under vacuum. Sometimes an intermediate is made and stored because a 30—100 dilution of starter with PO would require an extraordinary reactor to provide adequate stirring. PO and/or EO are added continuously until the desired OH No. is reached the reaction is stopped and the catalyst is removed. A uniform addition rate and temperature profile is required to keep unsaturation the same from batch to batch. The KOH catalyst can be removed by absorbent treatment (140), extraction into water (141), neutralization and/or crystallization of the salt (142—147), and ion exchange (148—150). 

As far as industrial applications are concerned, the easy scale-up of two-phase catalysis can be illustrated by the first oxo aqeous biphasic commercial unit with an initial annual capacity of 100,000 tons extrapolated by a factor of 1 24,000 (batch-wise laboratory development production reactor) after a development period of 2 years [4]. 

Battelle has developed an efficient process for the thermo-catalytic conversion of succinate into pyrrolidones, especially N-methyl-2-pyrrolidone. The process uses both novel Rh based catalysts and novel aqueous process conditions and results in high selectivities and yields of pyrrolidone compounds. The process also includes novel methodology for enhancing yields by recycling and converting non-useful side products of the catalysis into additional pyrrolidone. The process has been demonstrated in both batch and continuous reactors. Additionally, stability of the unique Rh-based catalyst has been demonstrated. 

A literature procedure whereby bromopyrimidine is oxidised by excess peroxy-acetic acid in acetone, with sulfuric acid catalysis, was being scaled up. The crude product from the fourth batch at two molar scale was filtered out and allowed to dry to dry in the sintered glass funnel over the weekend. An explosion occurred when it was scraped out to complete purification on the Monday. This was considered due to acetone peroxides, which had probably concentrated locally by wicking or sublimation. 

A set of core-functionalized dendrimers was synthesized by Van Leeuwen et al. and one compound was applied in continuous catalysis. [45] The dendritic dppf, Xantphos and triphenylphosphine derivatives (Figures 4.22, 4.30 and 4.31) were active in rhodium-catalyzed hydroformylation and hydrogenation reactions (performed batch-wise). Dendritic effects were observed which are discussed in paragraph 4.5. The dendritic rhodium-dppf complex was applied in a continuous hydrogenation reaction of dimethyl itaconate. 

The catalysis was performed batch-wise (Figure 4.36). After reaching ca. 90% conversion, the bulk phase was replaced and similar turnover frequencies (TOF) of about 25 h"1 were obtained in the following three runs 2, 3 and 4. When the catalyst capsule was removed, no further activity was detected. Furthermore, the Ru content in the bulk phase was always below the detection limit of AAS, which shows good catalyst retention by the membranes used. 

The kinetics results of the batch reactor runs lead to the following qualitative observations At low CO pressures (less than about 1 atm) the catalysis appears to be first order in ruthenium over the range 0.018 M to 0.072 M and also in Pco as illustrated by the log Pco vs time plots of Fig. 2 and also shown by the method of initial rates. Changes in the sulfuric acid and water concentrations over the respective ranges 0.25 M to 2.0 M and 4 M to 12 M have relatively small effects on the catalysis rates, although the functionalities are complicated and show concave rate vs concentration curves with maximum rates... 

The single particle acts as a batch reactor in which conditions change with respect to time, This unsteady-state behavior for a reacting particle differs from the steady-state behavior of a catalyst particle in heterogeneous catalysis (Chapter 8). The treatment of it leads to the development of an integrated rate law in which, say, the fraction of B converted, /B, is a function oft, or the inverse. 

Fig. 12. Electroenzymatic oxidation of p-cresol under catalysis by PCMH in. long-time batch electrolysis under formation of p-hydroxy benzylalcohol (alcohol) and p-b. .roxy benzaldehyde (aldehyde) (PCMH 16 U = 5.6 nmol PEG-20000 ferrocene 3 0.51 mmr - 9.45 pmol ferrocene starting concentration of p-cresol 41.25 mM = 0.66 mmol additions o. substrate after 4140 min (0,0925 mmol), 5590 min (0.0784 mmol), 6630 min (0.184 mmol), 11253 min (0.371 mmol), in 10 ml tris/HCl-buffer of pH 7.6 divided cell Sigraflex-anode 26 cm2)...

Ford et al.60 also made a significant contribution to the metal carbonyl catalyzed shift reaction in acidic medium. A solution of Ru3(CO)i2 (0.006-0.024 M with 0.25-2.0 M H2S04 4.0-12.0 M H20) in 5 ml of diglyme had good catalytic activity at 100 °C. They used a batch reactor with Pqo = 0-9 atm. Typical H2 turnover activity was reported to be about 50 turnovers per day. Their in situ spectroscopic studies show that the principal component was HRu2(CO)8-. They found that, at low CO partial pressures (< 1 atm), the catalysis was first order in Ru. However, at high CO partial pressures, the rate was inhibited. On the basis of their studies, they proposed the catalytic cycle outlined in Scheme 15. 

Like the monomers, the co-monomers are diols or diacids, and according to their functional groups, their reactions with TPA and EG follow the principal mechanisms outlined above. Very few data have been published on reactions with co-monomers, and it may be assumed that the same mechanisms and catalysis concepts should hold. Nevertheless, it has been observed that co-monomers influence the overall reaction rates significantly. In a typical batch process, the polycondensation time needed to prepare a polymer with an IV of 0.64 dL/g increases by about one third with co-monomer IPA and by about two thirds with co-monomer CHDM, in comparison to homo-PET. This may in part be due to the differing correlations between Pn and IV, but additionally a reduced reactivity due to steric and electronic effects or the influence of co-monomers on the mobility of functional groups seems probable. 

Research in this field started in the wake of the reports of SL-PC. Consisting of a catalyst-containing supported liquid layer for CF reactions in the gas phase, the concept was transferred to batch reactions, using a catalyst dissolved in a supported aqueous phase. This was first referred to as supported aqueous-phase catalysis (SAPC) by Davis in an article published in Nature in 1989. Later, the concept was extended, using a variety of names, but the essence has remained the same a supported catalyst-philic phase. 

The first results of the batch hydrogenation of prenal and citral to geran-iol and nerol provided evidence for the use of aqueous biphasic catalysis to increase the selectivity of the conversion of the substrates the accumiilation of byproducts can be nearly suppressed by the fast extraction of the product from the catalyst phase. For this reason, the distribution of the product between extraction and catalyst phase had been studied in detail. 

Fig. 1 Organometallic cartridge catalysis. A selection from a variety of transition metal complex catalysed conversions of substrates S,- with different reagents to the desired product Pix is possible using a single catalyst batch with the same apparatus and separation techniques...

One of the most attractive features of the IL/CO2 approach to homogeneous catalysis is the development of continuous processes [7]. Consequently it needs to be demonstrated that the combination of a suitable IL and compressed CO2 can offer more potential for process optimisation than just a simple protocol for batch-wise catalyst recycling. As an example we were able to activate, tune and immobilise Ni catalyst 13 in a continuous-flow system for the hydroviny-lation of styrene (Scheme 3). Styrene is co-dimerised with ethene yielding 3-substituted 1-butenes [26,27]. We could show that this powerful carbon-carbon bond-forming reaction can be achieved with high enantioselectivity in batch-wise operation and in continuous-flow systems. 

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