Isomerization batch reactors

In this context, the second-stage nitration of 1-mononitronaphthalene was investigated. The isomeric ratio of the two regioisomers, 1,5-dinitro- to 1,8-dinitro-naphthalene, was constant at 1 3.5 for macroscopic batch reactors, whereas it changes to 1 2.8 in micro reactors [166]. 

Figure 4.50 Comparison of isomeric ratios for 1,5- and 1,8-dinitronaphthalene. Reaction was performed in a macroscopic batch reactor and micro reactors of different types and from different suppliers [37],...

For the gas-phase unimolecular isomerization of cyclopropane (A) to propylene (P), values of the observed first-order rate constant, kuni, at various initial pressures, P0, at 470 C in a batch reactor are as follows ... 

At the same time, as a chemist I was disappointed at the lack of serious chemistry and kinetics in reaction engineering texts. AU beat A B o death without much mention that irreversible isomerization reactions are very uncommon and never very interesting. Levenspiel and its progeny do not handle the series reactions A B C or parallel reactions A B, A —y C sufficiently to show students that these are really the prototypes of aU multiple reaction systems. It is typical to introduce rates and kinetics in a reaction engineering course with a section on analysis of data in which log-log and Anlienius plots are emphasized with the only purpose being the determination of rate expressions for single reactions from batch reactor data. It is typically assumed that ary chemistry and most kinetics come from previous physical chemistry courses. 

Industrially relevant consecutive-competitive reaction schemes on metal catalysts were considered hydrogenation of citral, xylose and lactose. The first case study is relevant for perfumery industry, while the latter ones are used for the production of sweeteners. The catalysts deactivate during the process. The yields of the desired products are steered by mass transfer conditions and the concentration fronts move inside the particles due to catalyst deactivation. The reaction-deactivation-diffusion model was solved and the model was used to predict the behaviours of semi-batch reactors. Depending on the hydrogen concentration level on the catalyst surface, the product distribution can be steered towards isomerization or hydrogenation products. The tool developed in this work can be used for simulation and optimization of stirred tanks in laboratory and industrial scale. 

A comparative study of nanocomposites (16% Nafion-silica and commercial SAC-13) has been performed by Hoelderich and co-workers169 in the alkylation of isobutane and Raffinate II. Raffinate II, the remaining C4 cut of a stream cracker effluent after removal of dienes, isobutane, propane, and propene, contains butane, isobutylene, and butenes as main components. High conversion with a selectivity of 62% to isooctane was found for Nafion SAC-13 (batch reactor, 80°C). Both the quality of the product and the activity of the catalysts, however, decrease rapidly due to isomerization and oligomerization. Treating under reflux, the deactivated catalysts in acetone followed by a further treatment with aqueous hydrogen peroxide (80°C, 2 h), however, restores the activity. 

Reaction between 2 -hydroxyacetophenone and benzaldehyde (Claisen-Schmidt condensation) in the absence of a solvent at 423 K giving 2 -hydroxy chalcones and flavanones has been successfully performed with MgO as a solid base catalyst/581 A conversion of 40 % after 1 h with 67 % selectivity to chalcone was achieved. The influence of the solvent and the effects of a substituent on the aromatic ring were investigated by Amiridis et a//59,6"1 The reaction was carried out on MgO at 433 K. Dimethyl sulfoxide (DMSO) showed a strong promoting effect on the reaction, which was attributed to the ability of this dipolar aprotic solvent to weakly solvate anions and stabilize cations so that both become available for reaction. In this case, a conversion of 2-hydroxyacetophenone of 47 % with a selectivity to flavanone of 78 % was achieved after 30 min in a batch reactor. Further investigations1611 showed that DMSO significantly increases the rate of the subsequent isomerization of the 2 -hydroxychalcone intermediate to flavanone. 

In a study of the deactivation by coking of an atmospheric residue HDM catalyst, we have been able to obtain coked catalysts almost free from metal deposits in batch reactor and coked catalysts containing small amounts of metal sulfide deposits in continuous flow reactor using a Safaniya atmospheric residue under similar experimental conditions (30). We report in this paper a study of the deactivating effects of the deposits using toluene hydrogenation, cyclohexane isomerization and thiophene hydrodesulfurization reactions. 

The reports on catalytic isomerization using various zeolitic catalysts, in comparison to the conventional catalysts previously used, gives results of reactions carried out discontinuously in a batch reactor in liquid phase, as well as for those carried out continuously in a fixed bed reactor in the vapor phase. The results in the liquid phase over heterogeneous catalysts are summarized in Table 15.2. 

The addition of methanol to alpha-pinene in the presence of the above mentioned beta zeolite as catalyst in the batch reactor results in the cleavage of the cyclobutane ring and yields l-methyl-4-[alpha-methoxy-isopropyl]-l-cyclohexene (alpha-terpinyl methyl ether) as the main reaction product. The most common by-products to be found are isomerization compounds like camphene, limonene and terpinolene, and several bicyclic and double addition products, e.g. endo- or exo-methylbomylether, endo- or exo-methylfenchylether and cis- or trans-1,8-dimethoxy-p-menthane. 

This homogeneous hydroformylation reaction was conducted in a batch reactor, and because of the nature of the catalyst, isomerization reactions of 1-hexene to 2- and 3-hexenes and hydrogenation reactions of hexenes to hexanes and aldehydes to alcohols were minimized. The following data were obtained at 323 K with an initial concentration of 1-hexene at 1 mol/L in toluene and Pco... 

It is known that formic acid is synthesized from H2/CO2 as ester in alcohol solvent using metal complex catalysts such as HM(CO)5 (M W,Cr,Ru) in batch reactor system.[61] However, specific activity (TOF) of these system are relatively low. Recently, Noyori et al. found a significant increase of formic acid in a supercritical mixture of H2/CO2 with N(C2H5)3 using RuH2 P(CH3)3)4 complex at the condition of 20.5 Mpa, 5013 and H2/C02=l/1.4.[62] TOF increased one order of magnitude over that of conventional process because of high miscibdity of H2 with supercritical CO2. It is also noted that methyl formate produced from H2/CO2 is easdy converted to acetic acid by isomerization reaction. 

Roederer et a/. ° investigated an isomeric reaction (alpha- and beta-isophorone) at 388, 423 and 493 K. They experimented in a stirred batch reactor in the form of... 

The isomerization of the glucose syrup thus obtained was originally also employed in batch reactors using the Mg -containing enzyme glucose isomerase in soluble form, but rapidly evolved to the use of an immobilized enzyme... 

Villermaux (1981) has investigated the applicability of the chromatographic batch reactor for isomerizations. The simulation studies show that the conversion within the integrated batch reactor can not exceed the conversion in a fixed bed reactor without separation. Therefore, the integrated batch reactor does not offer any advantages for reactions of type A B compared with a sequential process. 

The preparative Claisen rearrangement was studied in aqueous media at temperatures up to 300 °C. The experiments were conducted in the recently created pressurized microwave batch reactor and in conventional heated autoclaves. It was found that allyl phenyl ether isomerizes in water during 10 min at 240 °C to give the ortho-Claisen rearrangement product in 84% conversion . 

We start the analysis with single reversible reactions. When a reversible reaction takes place, there is only one independent reaction hence, only one design equation should be solved. However, the rates of both forward and backward reactions should be considered. Tbe design procedure is similar to the one discussed in Section 6.2. To illustrate the effect of the reverse reaction, consider the reversible elementary isomerization reaction A B in a constant-volume batch reactor. We treat a reversible reaction as two chemical reactions ... 

Finally, we have established the practical asymmetric isomerization process as follows In a 15-m batch reactor, a mixture of 7 tons of 1 and 6.71 kg of the catalyst 13 (the molar ratio of catalyst to substrate is 1 to 8,000) in THF (3 m ) are charged. The isomerization is completed in 18 h at 100 °C, providing 2 in 99% yield and 98.5% ee [3,11,12]. After the reaction, the whole products (THF, enamine, and catalyst) are subjected for distillation under reduced pressure (initially 400 torr, finally 2 torr) to recover THF and 2. The distillation residue is an... 

A reversible liquid-phase isomerization A B is carried out hoihei-msecond order in both the forward and reverse directions. The liquid enters ai the top of the reactor and exits at the bottom. Experimental data taken in a batch reactor shows the CSTR conversion to be 40%. The reaction is reversible with A (- =. 3.0 at 300 K. and... 

Simple diols have been subjected to the pinacol rearrangement in the presence of Amberlyst 15, a polystyrene sulfonic resin with a high concentration of acidic centers. When excess catalyst is used (g catalyst/g diol = 1.25) pinacol gives 3,3-dimethyl-2-butanone in near quantitative yield (batch reactor, 373 K, 2 h) [33]. Of the two isomeric ketones 3,3-diphenyl-2-butanone (10), formed with phenyl migration, is the sole product when 2,3-diphenyl-2,3-butanediol (9) is reacted (Scheme 6). This feature is very similar to that observed under homogeneous conditions in the presence of sulfuric acid [2]. An arylsulfonic silica catalyst prepared by grafting and sulfonation proved to be less selective [33]. 

Consider the irreversible, liquid-phase isomerization reaction carried out in a solvent containing dissolved catalyst at 25 C in a batch reactor... 

Isomerization of 1-acetyl-2-methoxynaphthalene was investigated over HFAU, HBEA and HMFI zeolites (batch reactor, T=120°C). Due to its pore size, HMFI was inactive for isomerization while HFAU is about 3 times more active than HBEA. This can be attributed to the easier desorption of the isomers from the HFAU pores. However, the selectivity of 2-acetyl-6-methoxynaphthalene (the desired isomer) is favoured over HBEA. Analysis of the compounds retained in the zeolite pores show that the reaction occurs inside the micropores of the zeolites. Indeed, the desired isomer was found to be retained in the pores of HMFI showing that even for this zeolite, isomerization occurs in its micropores and that the desorption of the reaction products appears to be the limiting step. 

In conclusion, the use of zeolites as catalysts in the isomerization of isophorone oxide (1), yields up to 86% keto aldehyde. The formation of (4) by decarbonyla-tion of (2) could be reduced by increasing the catalyst loading in a liquid phase batch reactor or by conducting the reaction under short contact time in the gas phase. The heterogeneously-catalysed isomerization of teipene epoxides over zeolites is a suitable, non-polluting method of preparing relevant and useful aldehydes for the synthesis of perfumes and synthetic flavours. 

Reactions in the Batch Reactor - Methanol reacts with limonene over acidic catalysts in a batch reactor to l-methyl-4-[a-methoxyisopropyl]-l-cyclohexene (a-terpinyl methyl ether) as the main reaction product (see Figure 8 R = Me). Besides the desired methoxylation, isomerization reactions leading to terpinolene and traces of a- and y-terpinene can be observed. Furthermore, the addition of methanol to the terpinyl methyl ether leads to the undesired cis- or fra/w-1,8-dimethoxy-p-menthane. The amount of unidentified products does not exceed 1%. At high temperatures and long reaction times the reverse reaction of the a-terpinyl methyl ether and the other addition products to limonene and its isomers can be observed. The reaction scheme of the alkoxylation of limonene is illustrated in Figure 10... 

For these reasons, the outcome of the reaction will be very different depending on which thermodynamic or kinetic factor will be favored. In the presence of excess hydrocarbon in equilibrium with the catalytic phase and long contact times, the thermodynamic hydrocarbon isomer distribution is attained. However, in the presence of a large excess of acid, the product will reflect the thermodynamic stability of the intermediate carbenium ions (which, of course, is different from that of hydrocarbons) if rapid hydride transfer or quenching can be achieved. Torek and coworkershave shown that the limiting step, in the isomerization of n-hexane and n-pentane with the HF SbF5 acid catalyst, is the hydride transfer with sufficient contact in a batch reactor, as indicated by the thermodynamic isomer distribution of Cg isomers. 

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