Energy and operating cost analysis of the smart-scaled flow route directly to adipic acid

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Beckmann rearrangement of cyclohexanone oxime to ε-caprolactam in a microreactor

The selectivity and conversion of the sulfuric acid-catalyzed Beckmann rearrangement of cyclohexanone oxime, dissolved in cyclooctane, to ¿-caprolactam are determined in a microreactor for conditions with a high concentration of ¿-caprolactam. The microreactor consists of a low-temperature mixing zone followed by a high-temperature reaction zone. The mixing is conducted in a split-and-recombine micromixer and a microchannel at 65¿°C, followed immediately by a second microchannel at 100–127¿°C to obtain complete conversion. Under these conditions a selectivity of 99¿% is achieved. The residence time of the reactants in the microreactor setup is about 10¿s. In literature, a selectivity of about 95¿% for the same reaction in a similar setup is reported, but at a uniform temperature of 120–130¿°C for mixing and reaction. So, suppressing the reaction during mixing is a major tool to enhance the selectivity to ¿-caprolactam

Beckmann rearrangement of cyclohexanone oxime in microreactor setup with internal recirculation

Beckmann rearrangement of cyclohexanone oxime dissolved in cyclooctane with oleum to ¿-caprolactam was demonstrated in a microreactor setup with internal recirculation operated in continuous mode. The core of the setup comprised a 316 stainless-steel micromixer consisting of 17 split-and-recombine units connected to a delay loop, a 316 stainless-steel microchannel reactor with an internal diameter of 0.250¿mm and a length of 0.50¿m. At 100¿°C, the conversion of cyclohexanone oxime was complete and the selectivity towards ¿-caprolactam was approximately 99¿%. The solvent cyclooctane reduces the observed purity of the produced oleum/¿-caprolactam. This reduction in purity might be a severe hurdle for usage of a solvent on the industrial scale in the Beckmann rearrangement of cyclohexanone oxime in oleum to ¿-caprolactam

Density, viscosity and surface tension of liquid phase Beckmann rearrangement mixtures

We have determined the density, dynamic viscosity, and surface tension of liquid phase Beckmann rearrangement mixtures, consisting of e-caprolactam and fuming oleum. These important properties have been measured in wide ranges of both temperature and molar ratios of acid and e-caprolactam, covering conditions that are of relevance for industrial production of e-caprolactam from cyclohexanone oxime, i.e., T = (293 to 393) K and ([H2SO4] + [SO3])/[e-caprolactam] = (1.4 to 2.6). The results were correlated as functions of temperature and composition. The density of oleum/e-caprolactam mixtures shows a linear relationship with both temperature and composition. A modification of the traditional Reynolds model proved to be the most suitable way to represent the dynamic viscosity of these Beckmann rearrangement mixtures. The reduction of the surface tension with temperature is described with a power law expression, while the decrease of the surface tension with increasing molar ratios of acid over e-caprolactam is described with a linear relationship. These results can be applied to design liquid phase Beckmann rearrangement processes on both large scale and microscale

Beckmann rearrangement of cyclohexanone oxime to ε-caprolactam in a microreactor

The selectivity and conversion of the sulfuric acid-catalyzed Beckmann rearrangement of cyclohexanone oxime, dissolved in cyclooctane, to ¿-caprolactam are determined in a microreactor for conditions with a high concentration of ¿-caprolactam. The microreactor consists of a low-temperature mixing zone followed by a high-temperature reaction zone. The mixing is conducted in a split-and-recombine micromixer and a microchannel at 65¿°C, followed immediately by a second microchannel at 100–127¿°C to obtain complete conversion. Under these conditions a selectivity of 99¿% is achieved. The residence time of the reactants in the microreactor setup is about 10¿s. In literature, a selectivity of about 95¿% for the same reaction in a similar setup is reported, but at a uniform temperature of 120–130¿°C for mixing and reaction. So, suppressing the reaction during mixing is a major tool to enhance the selectivity to ¿-caprolactam

The absorption of propane and ethene in slurries of activated carbon in water—II

The results of a study are given on batchwise absorption of a binary gas mixture (propane and ethene) in activated carbon—water slurries in a stirred cell. It has been studied how the initial composition of the gas phase, the carbon concentration in the slurry and the particle diameter affect the absorption curves. It was found that the selectivity of absorption is quite different in slurries under non-equilibrium and equilibrium conditions. The experimental absorption curves of ethene pass through a maximum, because in the liquid phase ethane is absorbed faster than propane, whereas on the solid surface ethene is absorbed less strongly than propane. The data were successfully simulated by a model based on gas—liquid and liquid—solid mass transfer resistances and sorption capacities of both component

Influence of elevated pressure and particle lyophobicity on hydrodynamics and gas-liquid mass transfer in slurry bubble columns

This article reports on the influence of elevated pressure and catalyst particle lyophobicity at particle concentrations up to 3 vol % on the hydrodynamics and the gas-to-liquid mass transfer in a slurry bubble column. The study was done with demineralized water (aqueous phase) and Isopar-M oil (organic phase) slurries in a 0.15 m internal diameter bubble column operated at pressures ranging from 0.1 to 1.3 MPa. The overall gas hold-up, the flow regime transition point, the average large bubble diameter, and the centerline liquid velocity were measured along with the gas-liquid mass transfer coefficient. The gas hold-up and the flow regime transition point are not influenced by the presence of lyophilic particles. Lyophobic particles shift the regime transition to a higher gas velocity and cause foam formation. Increasing operating pressure significantly increases the gas hold-up and the regime transition velocity, irrespective of the particle lyophobicity. The gas-liquid mass transfer coefficient is proportional to the gas hold-up for all investigated slurries and is not affected by the particle lyophobicity, the particle concentration, and the operating pressure. A correlation is presented to estimate the gas-liquid mass transfer coefficient as a function of the measured gas hold-up: k1a1/ eg = 3.0v(Du¿ /d¿) s-

Effect of particle lyophobicity in slurry bubble columns at elevated pressures

The influence of particle lyophobicity on gas hold-up, homogeneous to churn-turbulent regime transition, and gas–liquid mass transfer is investigated in a 0.15 m diameter slurry bubble column at pressures from 0.1 to 1.3 MPa. An air/nitrogen mixture is bubbled through 0–3 vol% slurries of activated carbon particles or silica particles suspended in demineralized water or organic oil Isopar M. The gas hold-up and flow regime transition point are not influenced by the presence of lyophilic particles. Lyophobic particles shift the regime transition to a higher gas velocity and cause foam formation. The gas–liquid mass transfer coefficient is proportional to the gas hold-up for all investigated slurries and is not affected by the particle lyophobicity and the operating pressure. A correlation is presented to estimate the gas–liquid mass transfer coefficient