Integration of microwave heating with continuously operated milli-reactors for fine chemical synthesis

Major efforts in the research field of microwave assisted organic synthesis have demonstrated the specific benefits associated with the use of microwave irradiation such as selective and rapid heating of the reaction mixture. In many case studies, these benefits eventually lead to a significant enhancement in the production rates. Therefore, microwave assisted flow synthesis can be an interesting alternative for fine chemical production in conventionally heated batch reactors. However, realization of microwave assisted flow synthesis at kilogram scale requires a proper design of tubular reactors integrated with the microwave heating source, i.e. the cavity. The design of these reactors should primarily be able to overcome the limitations by the penetration depth of the microwaves, i.e. ¿0.013 m. Moreover, operation based on microwave heating should allow accurate temperature control by precise tuning and quantification of the microwave energy distribution. Therefore, being case specific, design efforts are necessary for the microwave setup as well as for the reactor configuration. Heating in monomode microwave equipment is energy efficient and fast in comparison to heating in multimode microwave equipment. State-of-the-art microwave cavities, however, lack in providing important functionalities, such as a predictable electric field pattern, tuning facility, detailed energy distribution and possibilities for modular scale-up. A waveguide type monomode microwave cavity in combination with the short circuit, stub tuners, and isolators can provide the aforementioned functionalities for continuously operated reactors. This type of microwave setup allows an accurate elaboration of energy balances for efficient and uniform heating. Additionally the use of multiple cavities connected to a single microwave generator via a main waveguide permits modular scale-up. The dielectric properties (i.e. dielectric constant and dielectric loss) of a microwave absorbing load (e.g. reaction mixture/solvent) are significantly dependent on temperature. As a consequence, microwave absorption, which involves interaction of the electromagnetic field with the applied load, is a recurring process. Therefore, detailed understanding of the dielectric property change with temperature is a prerequisite for a proper design of the load to be used under stop-flow (batch) and continuous-flow conditions. For stop-flow conditions, the highest heating efficiency (70 %) is observed for a load diameter equal to and larger than half of the wavelength of the microwaves in the liquid medium. For continuous-flow conditions, the heating efficiency increases linearly with the load diameter. However, microwave leakage above the propagation diameter (i.e. half wavelength) limits further increase of the load diameter in continuous operation. The high energy intensity of the focused electromagnetic field in case of waveguide type microwave cavities makes an efficient and controlled continuous operation difficult, especially when a strong microwave absorbing load (e.g. ethanol) is present. In cases, such as the reaction of ethanol and acetic acid to produce ethyl acetate over a strong acid ion-exchange resin, a milli reactor-heat exchanger combination with a co-current flow of a microwave transparent solvent (coolant) can be a solution. Here, rapid volumetric heating to the reaction temperature can be achieved by microwaves before the reaction mixture enters into the catalyst bed. Additionally, the coolant not only limits overheating of the reaction mixture but also permits heat integration, resulting in extended reactor lengths and efficient heating (i.e. 96 %). However, stagnancy in the flow of the microwave absorbing load results in a poor convective heat transport. As a consequence, stagnant layer formation caused either by any insertion (of system components, such as fiber optic sensors) or at the reactor walls, yields higher temperatures and lower microwave energy dissipation regions. One of the promising approaches for scaling microwave assisted flow synthesis is numbering up. The numbering up approach is based on parallelization of tubular structured reactors with a channel diameter in the millimeter range. The performance of such a configuration is evaluated by a multi-tubular milli-reactor/heat exchanger system with a thin Cu film on the inner walls of the reactor tubes. The thin Cu film provides uniform microwave absorption and it improves the production rate by acting as a heated catalytically active surface, as demonstrated in the synthesis of 1,3-diphenyl-2-propynyl-piperidine from benzaldehyde, piperidine, and phenylacetylene. Controlled selective heating of the thin Cu film is achievable by using a counter-current flow of a microwave transparent coolant (toluene). The coolant flow avoids Cu burning and reduces leaching, consequently improving the steady state catalytic performance of the Cu coated reactor tubes. Higher temperatures, i.e. at least 100 K higher than the bulk liquid, are achievable at the locus of the reaction, i.e. the catalyst surface, purely due to selective microwave heating. Another approach to realize higher production rates is utilization of multiple microwave cavities in series. In this approach, the process stream is taken from one cavity to the next where the process efficiency is well optimized over each consecutive cavity. Transient operation through each optimized cavity and utilization of multiple cavities in series increases conversion and consequently results in higher production rate. Additionally, known kinetics allows estimation of the production rate for each additional cavity in the series. This approach of scale-up is possible at minimized grid to applicator losses by connecting multiple cavities to a single microwave generator via a main waveguide. Scale-up approaches based on parallelization of tubular structured reactors as well as on utilization of multiple microwave cavities in series were found to be successful. Application of microwaves as a process intensification tool, especially in the case of organic synthesis, is very attractive for liquid-solid reactions, where the solid is the selectively (microwave) heated catalyst

Process for preparing monodispersed emulsions

A process for preparing an emulsion is disclosed comprising: injecting a first liquid as dispersed phase liquid through a central inlet of a microchannel (15) system with a cross junction geometry chip and injecting a second liquid as continuous phase liquid through the outer cross inlet (16), which continuous phase liquid does not instantly mix with said injected first liquid prior to the cross junction, wherein the flow rate Qc of the continuous phase in cubic meters per second is given by (I) where A is the exit area of the microchannel (17) in square meters, y the interfacial tension between the first liquid and the second liquid in Newtons per meter and [mu]d the viscosity of the dispersed phase in Pascal-seconds, characterized in that f is in the range from 0.04 to 0.25

Process for preparing monodispersed emulsions

A process for preparing an emulsion is disclosed comprising: injecting a first liquid as dispersed phase liquid through a central inlet of a microchannel (15) system with a cross junction geometry chip and injecting a second liquid as continuous phase liquid through the outer cross inlet (16), which continuous phase liquid does not instantly mix with said injected first liquid prior to the cross junction, wherein the flow rate Qc of the continuous phase in cubic meters per second is given by (I) where A is the exit area of the microchannel (17) in square meters, y the interfacial tension between the first liquid and the second liquid in Newtons per meter and [mu]d the viscosity of the dispersed phase in Pascal-seconds, characterized in that f is in the range from 0.04 to 0.25

Magnetic Ordering and Superconductivity in the RE2_2Ir3_3Ge5_5 (RE = Y, La-Tm, Lu) System

We find that the compounds for RE = Y, La-Dy, crystallize in the tetragonal Ibam (U$_2$Co$_3$Si$_5$ type) structure whereas the compounds for RE = Er-Lu, crystallize in a new orthorhombic structure with a space group Pmmn. Samples of Ho$_2$Ir$_3$Ge$_5$ were always found to be multiphase. The compounds for RE = Y to Dy which adopt the Ibam type structure show a metallic resistivity whereas the compounds with RE = Er, Tm and Lu show an anomalous behavior in the resistivity with a semiconducting increase in $\rho$ as we go down in temperature from 300K. Interestingly we had earlier found a positive temperature coefficient of resistivity for the Yb sample in the same temperature range. We will compare this behavior with similar observations in the compounds RE$_3$Ru$_4$Ge$_{13}$ and REBiPt. La$_2$Ir$_3$Ge$_5$ and Y$_2$Ir$_3$Ge$_5$ show bulk superconductivity below 1.8K and 2.5K respectively. Our results confirm that Ce$_2$Ir$_3$Ge$_5$ shows a Kondo lattice behavior and undergoes antiferromagnetic ordering below 8.5K. Most of the other compounds containing magnetic rare-earth elements undergo a single antiferromagnetic transition at low temperatures (T$\leq$12K) while Gd$_2$Ir$_3$Ge$_5$, Dy$_2$Ir$_3$Ge$_5$ and Nd$_2$Ir$_3$Ge$_5$ show multiple transitions. The T$_N$'s for most of the compounds roughly scale with the de Gennes factor. which suggests that the chief mechanism of interaction leading to the magnetic ordering of the magnetic moments may be the RKKY interaction.Comment: 25 pages, 16 figure

On Properties of ®-Sumudu Transform and Applications

The ®-Sumudu transform is defined and its properties areproved. ®-Sumudu transform of convolution product and composition offunctions is obtained. The ®-Sumudu transform of Riemann-Liouvilleintegral and derivatives of fractional order are determined. As an application,the solution of Initial Value Problems with Riemann-Liouville derivativeof fractional order is obtained. .AMS (MOS) Subject Classification Codes: 34A12; 26A33;44A35Key Words: Riemann-Liouville derivative, Sumudu transform, Initial value problems,Mittag-Leffler functions

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Not AvailableCurrent status of land/soil resources of the IndoGangetic Plains (IGP) is analysed to highlight the issues that need to be tackled in near future for sustained agricultural productivity. There are intraregional variations in soil properties, cropping systems; status of land usage, groundwater utilization and irrigation development which vary across the subregions besides demographies. Framework for land use policy is suggested that includes acquisition of farm-level data, detailing capability of each unit to support a chosen land use, assess infrastructural support required to meet the projected challenges and finally develop skilled manpower to effectively monitor the dynamics of land use changes.Not Availabl

Evaluation of Water Retention Functions and Computer Program “Rosetta” in Predicting Soil Water Characteristics of Seasonally Impounded Shrink–Swell Soils

Not AvailableSoil water retention is a critical factor influencing irrigation decisions and hence agricultural crop yields. However, information on soil water retention characteristics (SWRC) is seldom available for irrigation planning, crop yield modeling, or hydrological simulations, especially for problematic soils, such as seasonally impounded shrink-swell soils. As large scale direct measurement of SWRC is not viable due to a number of reasons, researchers have developed pedotransfer functions (PTFs) to estimate SWRC from easily measured soil properties, such as texture, organic matter content, bulk density, etc. However, PTF applicability in locations other than those of data collection has been rarely reported. One of the most recent PTFs that has shown overall reasonable predictions in evaluation studies is Rosetta, a numerical code for estimating soil hydraulic parameters with hierarchical pedotransfer functions. Relatively, the development of large databases makes it one of the widely used PTFs. If validated for spatial application, it has immense use potential in countries like India, where data on soil hydraulic properties are seldom available, a deficiency that hampers better simulations in processes, like partitioning runoff and infiltration, assessing evapotranspiration, irrigation scheduling, etc. Rosetta is also relatively flexible allowing estimation of hydraulic properties from easily available minimum input of textural fractions. This study was conducted to evaluate (1) an applicability of four widely used soil water retention functions to describe SWRC; and (2) the computer program Rosetta for its validity. Statistical indices, i.e., root mean square error (RMSE), mean absolute error, maximum absolute error, and degree of agreement (d) were computed to evaluate “goodness-of-fit” of the four functions to the measured SWRC data. These indices were also used to compare measured SWRC with estimates of SWRC by Rosetta. For soil samples collected from 41 profiles, 175 SWRC were measured in the laboratory. The van Genuchten function fitted relatively better (RMSE=0.052m3m−3) to SWRC of clay soils, whereas the Brooks–Corey (BC) function was better in expressing SWRC of clay loam and sandy clay loam soils with RMSE=0.06 and 0.07m3m−3, respectively. Campbell and Cass–Hutson (CH) functions were of intermediate value. Worst performing functions were BC (clay soils), Campbell (clay loam), and CH (sandy clay loam) with corresponding RMSE=0.059, 0.065, and 0.077m3m−3. Estimates of two important points on the SWRC curve, i.e., field capacity and permanent wilting point were predicted with relatively better accuracy for clay and sandy clay loam soils by all the four functions. RMSE and d ranged from 0.027to0.043m3m−3 and from 0.73 to 0.88 for clay soils. Corresponding values for sandy clay loam soils were 0.008–0.019m3m−3, and 0.92–0.98. However, in clay loam soils, only two functions were found suitable. Estimates of SWRC obtained by applying hierarchical rules in Rosetta were reliable (RMSE<0.05m3m−3). Magnitude of average RMSE increased progressively in clay loam, clay and sandy clay loam soils (0.028<0.035<0.042m3m−3). The study established that SWRC of the “Haveli” soils could be estimated using generic PTF and thus information that is prerequisite in simulating hydrological processes occurring in seasonally impounded soils could be acquired.Not Availabl