The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
Achim Stolle - One of the best experts on this subject based on the ideXlab platform.
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influence of reaction parameters on the depolymerization of h2so4 impregnated cellulose in planetary Ball Mills
Powder Technology, 2016Co-Authors: Robert Schmidt, Sindy Fuhrmann, Lothar Wondraczek, Achim StolleAbstract:Abstract The depolymerization of acid-impregnated cellulose in planetary Ball Mills was investigated under the perspective of the influence of reaction parameters. Several process, technological and chemical parameters were examined. It was found that with a higher rotation frequency νrot, smaller milling Balls and a milling Ball filling degree ΦMB of approximately 0.3, the highest solubility could be reached and the milling time could be reduced. The use of milling vessels with larger diameter was beneficial. Variation of the milling Ball material showed huge influence and a linear correlation between solubility and density of the milling Ball material was observed. Kinetic investigations indicate that the degradation of the impregnated cellulose follows a first order model.
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effect of reaction parameters on the synthesis of 5 arylidene barbituric acid derivatives in Ball Mills
Organic Process Research & Development, 2015Co-Authors: Robert Schmidt, Arno Kwade, Christine Friederike Burmeister, Matej Balaž, Achim StolleAbstract:The influence of crucial reaction parameters on Knoevenagel condensation in planetary Ball Mills was investigated. Rotation frequency (νrot), milling Ball diameter (dMB), milling Ball filling degree (ΦMB), and beaker size had obvious influences on yield. It was found that higher νrot, lower dMB, milling beakers with larger diameter, and a ΦMB of ∼0.3 are advantageous for the reaction. Furthermore, the influence of the type of mill was investigated, including reactions performed in different planetary and mixer Ball Mills, in a stirred media mill, and with a mortar mill. Comparisons with the other solvent-free synthetic routes showed that Ball milling is an effective way of performing the reaction with low energy intensity.
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scale up of organic reactions in Ball Mills process intensification with regard to energy efficiency and economy of scale
Faraday Discussions, 2014Co-Authors: Achim Stolle, Robert Schmidt, Katharina JacobAbstract:The scale-up of the Knoevenagel-condensation between vanillin and barbituric acid carried out in planetary Ball Mills is investigated from an engineering perspective. Generally, the reaction proceeded in the solid state without intermediate melting and afforded selectively only one product. The reaction has been used as a model to analyze the influence and relationship of different parameters related to operation in planetary Ball Mills. From the viewpoint of technological parameters the milling Ball diameter, dMB, the filling degree with respect to the milling Balls' packing, ΦMB,packing, and the filling degree of the substrates with respect to the void volume of the milling Balls' packing, ΦGS, have been investigated at different reaction scales. It was found that milling Balls with small dMB lead to higher yields within shorter reaction time, treaction, or lower rotation frequency, rpm. Thus, the lower limit is set considering the technology which is available for the separation of the milling Balls from the product after the reaction. Regarding ΦMB,packing, results indicate that the optimal value is roughly 50% of the total milling beakers' volume, VB,total, independent of the reaction scale or reaction conditions. Thus, 30% of VB,total are taken by the milling Balls. Increase of the initial batch sizes changes ΦGS significantly. However, within the investigated parameter range no negative influence on the yield was observed. Up to 50% of VB,total can be taken over by the substrates in addition to 30% for the total milling Ball volume. Scale-up factors of 15 and 11 were realized considering the amount of substrates and the reactor volume, respectively. Beside technological parameters, variables which influence the process itself, treaction and rpm, were investigated also. Variation of those allowed to fine-tune the reaction conditions in order to maximize the yield and minimize the energy intensity.
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experimental and computational investigation of knoevenagel condensation in planetary Ball Mills
Chemical Engineering & Technology, 2014Co-Authors: Christine Friederike Burmeister, Achim Stolle, Robert Schmidt, Katharina Jacob, Sandra Breitungfaes, Arno KwadeAbstract:The influence of several process parameters like milling time, Ball-to-beaker volume ratio, diameter of milling Balls, and rotation frequency on the Knoevenagel condensation of vanillin and barbituric acid in planetary Ball Mills was investigated. These parameters determine the amount of energy provided for the reaction. Additionally, numerical simulations were carried out to describe the stress conditions in detail and to compute the drive power and energy transfer which cannot be measured directly. The mill and experimental parameters were modeled by the discrete element method with adequate coefficients of friction and restitution required to describe the powder behavior in the system. The coefficients were determined by correlation of experiments and simulations.
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Solvent-free reactions of alkynes in Ball Mills: It is definitely more than mixing
Pure and Applied Chemistry, 2011Co-Authors: Achim Stolle, Bernd OndruschkaAbstract:This contribution presents two solvent-free reactions of terminal alkynes in Ball Mills: Pd-catalyzed Sonogashira cross-coupling and Cu-catalyzed homo-coupling (Glaser reaction). The results are compared to other solvent-free reaction protocols, which have been published up to date for those types of reactions. Reactions are assessed on the basis of reac- tion variables like type of catalyst and base or reaction time. Furthermore, performance-based parameters (yield, selectivity, turnover number, TON, and turnover frequency, TOF) are con- sidered and evaluated. Findings from Ball-milling experiments indicate that those processes are comparable to the energy entry by microwave irradiation with respect to reaction time and TOF.
Arno Kwade - One of the best experts on this subject based on the ideXlab platform.
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dry grinding in planetary Ball Mills evaluation of a stressing model
Advanced Powder Technology, 2018Co-Authors: Christine Friederike Burmeister, Sandra Breitungfaes, Larissa Titscher, Arno KwadeAbstract:Abstract Planetary Ball Mills at laboratory scale are widely used for grinding and alloying processes. However, in contrast to other mill types, no applicable mechanistic model exists to describe the stressing conditions and their effect on particle breakage, so that processes are empirically evaluated so far. Within this study, the stressing conditions are determined by simulations based on the discrete element method including the contact model of Hertz and Mindlin. The contact model parameters are carefully calibrated by a series of experiments, so that it is finally possible to validate the simulation results by comparison of measured and calculated power values. The correlation of stressing conditions and breakage rates of alumina powder demonstrates the effect of stressing on breakage kinetics and breakage mechanism. It allows calculating the active mass in dependence on process parameters by an extension of Schonert’s active mass model. Altogether, the presented stressing model features analytical functions for the mill-related stressing conditions and highlights the importance of stressing intensity as process determining parameter, which defines the required number of material-related stressing events and the specific energy.
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effect of reaction parameters on the synthesis of 5 arylidene barbituric acid derivatives in Ball Mills
Organic Process Research & Development, 2015Co-Authors: Robert Schmidt, Arno Kwade, Christine Friederike Burmeister, Matej Balaž, Achim StolleAbstract:The influence of crucial reaction parameters on Knoevenagel condensation in planetary Ball Mills was investigated. Rotation frequency (νrot), milling Ball diameter (dMB), milling Ball filling degree (ΦMB), and beaker size had obvious influences on yield. It was found that higher νrot, lower dMB, milling beakers with larger diameter, and a ΦMB of ∼0.3 are advantageous for the reaction. Furthermore, the influence of the type of mill was investigated, including reactions performed in different planetary and mixer Ball Mills, in a stirred media mill, and with a mortar mill. Comparisons with the other solvent-free synthetic routes showed that Ball milling is an effective way of performing the reaction with low energy intensity.
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experimental and computational investigation of knoevenagel condensation in planetary Ball Mills
Chemical Engineering & Technology, 2014Co-Authors: Christine Friederike Burmeister, Achim Stolle, Robert Schmidt, Katharina Jacob, Sandra Breitungfaes, Arno KwadeAbstract:The influence of several process parameters like milling time, Ball-to-beaker volume ratio, diameter of milling Balls, and rotation frequency on the Knoevenagel condensation of vanillin and barbituric acid in planetary Ball Mills was investigated. These parameters determine the amount of energy provided for the reaction. Additionally, numerical simulations were carried out to describe the stress conditions in detail and to compute the drive power and energy transfer which cannot be measured directly. The mill and experimental parameters were modeled by the discrete element method with adequate coefficients of friction and restitution required to describe the powder behavior in the system. The coefficients were determined by correlation of experiments and simulations.
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process engineering with planetary Ball Mills
Chemical Society Reviews, 2013Co-Authors: Christine Friederike Burmeister, Arno KwadeAbstract:Planetary Ball Mills are well known and used for particle size reduction on laboratory and pilot scales for decades while during the last few years the application of planetary Ball Mills has extended to mechanochemical approaches. Processes inside planetary Ball Mills are complex and strongly depend on the processed material and synthesis and, thus, the optimum milling conditions have to be assessed for each individual system. The present review focuses on the insight into several parameters like properties of grinding Balls, the filling ratio or revolution speed. It gives examples of the aspects of grinding and illustrates some general guidelines to follow for modelling processes in planetary Ball Mills in terms of refinement, synthesis' yield and contamination from wear. The amount of energy transferred from the milling tools to the powder is significant and hardly measurable for processes in planetary Ball Mills. Thus numerical simulations based on a discrete-element-method are used to describe the energy transfer to give an adequate description of the process by correlation with experiments. The simulations illustrate the effect of the geometry of planetary Ball Mills on the energy entry. In addition the imaging of motion patterns inside a planetary Ball mill from simulations and video recordings is shown.
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experimental investigations and modelling of the Ball motion in planetary Ball Mills
Powder Technology, 2011Co-Authors: S Rosenkranz, Sandra Breitungfaes, Arno KwadeAbstract:Abstract Planetary Ball Mills feature attractive properties, like the possibility of dry or wet operation, straightforward handling, cleanability and moderate costs. Consequently they are very well suited for lab scale process development in diverse industries, including pharmaceuticals and new materials. A number of questions still remain unanswered regarding this mill type. These include the stress conditions as well as transfer of the grinding results to other types of Mills with free moving Balls, such as stirred media Mills, which can be built in large scales and operated continuously. In order to measure the Ball motion and, thus, the stress conditions, a planetary Ball mill was equipped with a high speed video camera, so that the grinding Ball motion during the comminution process can be recorded and analysed. The influence of important process parameters on the Ball motion pattern was assessed in this study, namely speed ratio, Ball filling ratio and friction conditions, the latter by applying different mill feeds. The experimental results show considerable influences of the Ball filling ratio and friction conditions. The measured Ball motion patterns differ significantly from Ball trajectories which were calculated using kinetic equations proposed in older publications. In addition to the measurements the Ball motion was simulated using a three dimensional Discrete Element Model (DEM). An attempt was made to account for mill feed via altered friction coefficients. Correlations of the DEM results and experimental findings at different operating conditions show a good agreement. Based on simulation data the frequency distribution of the stress energies in the mill could be calculated and compared for different operating conditions.
Robert Schmidt - One of the best experts on this subject based on the ideXlab platform.
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influence of reaction parameters on the depolymerization of h2so4 impregnated cellulose in planetary Ball Mills
Powder Technology, 2016Co-Authors: Robert Schmidt, Sindy Fuhrmann, Lothar Wondraczek, Achim StolleAbstract:Abstract The depolymerization of acid-impregnated cellulose in planetary Ball Mills was investigated under the perspective of the influence of reaction parameters. Several process, technological and chemical parameters were examined. It was found that with a higher rotation frequency νrot, smaller milling Balls and a milling Ball filling degree ΦMB of approximately 0.3, the highest solubility could be reached and the milling time could be reduced. The use of milling vessels with larger diameter was beneficial. Variation of the milling Ball material showed huge influence and a linear correlation between solubility and density of the milling Ball material was observed. Kinetic investigations indicate that the degradation of the impregnated cellulose follows a first order model.
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effect of reaction parameters on the synthesis of 5 arylidene barbituric acid derivatives in Ball Mills
Organic Process Research & Development, 2015Co-Authors: Robert Schmidt, Arno Kwade, Christine Friederike Burmeister, Matej Balaž, Achim StolleAbstract:The influence of crucial reaction parameters on Knoevenagel condensation in planetary Ball Mills was investigated. Rotation frequency (νrot), milling Ball diameter (dMB), milling Ball filling degree (ΦMB), and beaker size had obvious influences on yield. It was found that higher νrot, lower dMB, milling beakers with larger diameter, and a ΦMB of ∼0.3 are advantageous for the reaction. Furthermore, the influence of the type of mill was investigated, including reactions performed in different planetary and mixer Ball Mills, in a stirred media mill, and with a mortar mill. Comparisons with the other solvent-free synthetic routes showed that Ball milling is an effective way of performing the reaction with low energy intensity.
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scale up of organic reactions in Ball Mills process intensification with regard to energy efficiency and economy of scale
Faraday Discussions, 2014Co-Authors: Achim Stolle, Robert Schmidt, Katharina JacobAbstract:The scale-up of the Knoevenagel-condensation between vanillin and barbituric acid carried out in planetary Ball Mills is investigated from an engineering perspective. Generally, the reaction proceeded in the solid state without intermediate melting and afforded selectively only one product. The reaction has been used as a model to analyze the influence and relationship of different parameters related to operation in planetary Ball Mills. From the viewpoint of technological parameters the milling Ball diameter, dMB, the filling degree with respect to the milling Balls' packing, ΦMB,packing, and the filling degree of the substrates with respect to the void volume of the milling Balls' packing, ΦGS, have been investigated at different reaction scales. It was found that milling Balls with small dMB lead to higher yields within shorter reaction time, treaction, or lower rotation frequency, rpm. Thus, the lower limit is set considering the technology which is available for the separation of the milling Balls from the product after the reaction. Regarding ΦMB,packing, results indicate that the optimal value is roughly 50% of the total milling beakers' volume, VB,total, independent of the reaction scale or reaction conditions. Thus, 30% of VB,total are taken by the milling Balls. Increase of the initial batch sizes changes ΦGS significantly. However, within the investigated parameter range no negative influence on the yield was observed. Up to 50% of VB,total can be taken over by the substrates in addition to 30% for the total milling Ball volume. Scale-up factors of 15 and 11 were realized considering the amount of substrates and the reactor volume, respectively. Beside technological parameters, variables which influence the process itself, treaction and rpm, were investigated also. Variation of those allowed to fine-tune the reaction conditions in order to maximize the yield and minimize the energy intensity.
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experimental and computational investigation of knoevenagel condensation in planetary Ball Mills
Chemical Engineering & Technology, 2014Co-Authors: Christine Friederike Burmeister, Achim Stolle, Robert Schmidt, Katharina Jacob, Sandra Breitungfaes, Arno KwadeAbstract:The influence of several process parameters like milling time, Ball-to-beaker volume ratio, diameter of milling Balls, and rotation frequency on the Knoevenagel condensation of vanillin and barbituric acid in planetary Ball Mills was investigated. These parameters determine the amount of energy provided for the reaction. Additionally, numerical simulations were carried out to describe the stress conditions in detail and to compute the drive power and energy transfer which cannot be measured directly. The mill and experimental parameters were modeled by the discrete element method with adequate coefficients of friction and restitution required to describe the powder behavior in the system. The coefficients were determined by correlation of experiments and simulations.
Christine Friederike Burmeister - One of the best experts on this subject based on the ideXlab platform.
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dry grinding in planetary Ball Mills evaluation of a stressing model
Advanced Powder Technology, 2018Co-Authors: Christine Friederike Burmeister, Sandra Breitungfaes, Larissa Titscher, Arno KwadeAbstract:Abstract Planetary Ball Mills at laboratory scale are widely used for grinding and alloying processes. However, in contrast to other mill types, no applicable mechanistic model exists to describe the stressing conditions and their effect on particle breakage, so that processes are empirically evaluated so far. Within this study, the stressing conditions are determined by simulations based on the discrete element method including the contact model of Hertz and Mindlin. The contact model parameters are carefully calibrated by a series of experiments, so that it is finally possible to validate the simulation results by comparison of measured and calculated power values. The correlation of stressing conditions and breakage rates of alumina powder demonstrates the effect of stressing on breakage kinetics and breakage mechanism. It allows calculating the active mass in dependence on process parameters by an extension of Schonert’s active mass model. Altogether, the presented stressing model features analytical functions for the mill-related stressing conditions and highlights the importance of stressing intensity as process determining parameter, which defines the required number of material-related stressing events and the specific energy.
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effect of reaction parameters on the synthesis of 5 arylidene barbituric acid derivatives in Ball Mills
Organic Process Research & Development, 2015Co-Authors: Robert Schmidt, Arno Kwade, Christine Friederike Burmeister, Matej Balaž, Achim StolleAbstract:The influence of crucial reaction parameters on Knoevenagel condensation in planetary Ball Mills was investigated. Rotation frequency (νrot), milling Ball diameter (dMB), milling Ball filling degree (ΦMB), and beaker size had obvious influences on yield. It was found that higher νrot, lower dMB, milling beakers with larger diameter, and a ΦMB of ∼0.3 are advantageous for the reaction. Furthermore, the influence of the type of mill was investigated, including reactions performed in different planetary and mixer Ball Mills, in a stirred media mill, and with a mortar mill. Comparisons with the other solvent-free synthetic routes showed that Ball milling is an effective way of performing the reaction with low energy intensity.
-
experimental and computational investigation of knoevenagel condensation in planetary Ball Mills
Chemical Engineering & Technology, 2014Co-Authors: Christine Friederike Burmeister, Achim Stolle, Robert Schmidt, Katharina Jacob, Sandra Breitungfaes, Arno KwadeAbstract:The influence of several process parameters like milling time, Ball-to-beaker volume ratio, diameter of milling Balls, and rotation frequency on the Knoevenagel condensation of vanillin and barbituric acid in planetary Ball Mills was investigated. These parameters determine the amount of energy provided for the reaction. Additionally, numerical simulations were carried out to describe the stress conditions in detail and to compute the drive power and energy transfer which cannot be measured directly. The mill and experimental parameters were modeled by the discrete element method with adequate coefficients of friction and restitution required to describe the powder behavior in the system. The coefficients were determined by correlation of experiments and simulations.
-
process engineering with planetary Ball Mills
Chemical Society Reviews, 2013Co-Authors: Christine Friederike Burmeister, Arno KwadeAbstract:Planetary Ball Mills are well known and used for particle size reduction on laboratory and pilot scales for decades while during the last few years the application of planetary Ball Mills has extended to mechanochemical approaches. Processes inside planetary Ball Mills are complex and strongly depend on the processed material and synthesis and, thus, the optimum milling conditions have to be assessed for each individual system. The present review focuses on the insight into several parameters like properties of grinding Balls, the filling ratio or revolution speed. It gives examples of the aspects of grinding and illustrates some general guidelines to follow for modelling processes in planetary Ball Mills in terms of refinement, synthesis' yield and contamination from wear. The amount of energy transferred from the milling tools to the powder is significant and hardly measurable for processes in planetary Ball Mills. Thus numerical simulations based on a discrete-element-method are used to describe the energy transfer to give an adequate description of the process by correlation with experiments. The simulations illustrate the effect of the geometry of planetary Ball Mills on the energy entry. In addition the imaging of motion patterns inside a planetary Ball mill from simulations and video recordings is shown.
Bernd Ondruschka - One of the best experts on this subject based on the ideXlab platform.
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Solvent-free reactions of alkynes in Ball Mills: It is definitely more than mixing
Pure and Applied Chemistry, 2011Co-Authors: Achim Stolle, Bernd OndruschkaAbstract:This contribution presents two solvent-free reactions of terminal alkynes in Ball Mills: Pd-catalyzed Sonogashira cross-coupling and Cu-catalyzed homo-coupling (Glaser reaction). The results are compared to other solvent-free reaction protocols, which have been published up to date for those types of reactions. Reactions are assessed on the basis of reac- tion variables like type of catalyst and base or reaction time. Furthermore, performance-based parameters (yield, selectivity, turnover number, TON, and turnover frequency, TOF) are con- sidered and evaluated. Findings from Ball-milling experiments indicate that those processes are comparable to the energy entry by microwave irradiation with respect to reaction time and TOF.
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studies on the solvent free and waste free knoevenagel condensation
Green Chemistry, 2008Co-Authors: Ronald Trotzki, Markus M Hoffmann, Bernd OndruschkaAbstract:The mechanochemical reaction of malononitrile with various aldehydes was studied with the goal to achieve quantitative stoichiometric conversion of the reactants to their corresponding benzylidene-malononitriles in absence of any solvents and catalysts. Besides already known reactions in the solid state, reactions with liquid aldehydes were also attempted. These reactions were carried out in vibration and planetary Ball Mills as well as, for comparison, in a melt under microwave irradiation. A successful quantitative conversion depended strongly on the choice of the aldehyde, precluding a generalization of the reaction scheme. Furthermore, the results obtained from the various approaches for non-classical heating (Ball Mills, microwaves) were compared.
