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High-throughput preparation and testing of ion-exchanged zeolites
Applied Surface Science 254 (2007) 699–703 www.elsevier.com/locate/apsusc
High-throughput preparation and testing of ion-exchanged zeolites K.P.F. Janssen a,1, J.S. Paul b,*, B.F. Sels a,1, P.A. Jacobs a,1 a
Microbial and Molecular Systems, Katholieke Universiteit Leuven, Kasteelpark Arenberg 23, B-3001 Heverlee, Belgium b Flanders Materials Centre (Flamac), Technologiepark 903, B-9052 Zwijnaarde, Belgium Received 16 January 2007; accepted 14 June 2007 Available online 19 July 2007
Abstract A high-throughput research platform was developed for the preparation and subsequent catalytic liquid-phase screening of ion-exchanged zeolites, for instance with regard to their use as heterogeneous catalysts. In this system aqueous solutions and other liquid as well as solid reagents are employed as starting materials and 24 samples are prepared on a library plate with a 4 6 layout. Volumetric dispensing of metal precursor solutions, weighing of zeolite and subsequent mixing/washing cycles of the starting materials and distributing reaction mixtures to the library plate are automatically performed by liquid and solid handlers controlled by a single common and easy-to-use programming software interface. The thus prepared materials are automatically contacted with reagent solutions, heated, stirred and sampled continuously using a modified liquid handling. The high-throughput platform is highly promising in enhancing synthesis of catalysts and their screening. In this paper the preparation of lanthanum-exchanged NaY zeolites (LaNaY) on the platform is reported, along with their use as catalyst for the conversion of renewables. # 2007 Elsevier B.V. All rights reserved. PACS : 82.65. s (catalysis, heterogeneous); 82.75.Qt (zeolites, catalysis in) Keywords: High-throughput; Zeolite Y; Ion exchange; Catalysis; Renewables
1. Introduction Zeolites modified through ion-exchange procedures have many applications, both in gas-phase [1] and liquid-phase [2] catalysis. However, screening the parameter space involved in their synthesis in order to optimize catalyst performance may prove very difficult and time consuming due to the many unit operations that are typically necessary for their preparation. Therefore it would be highly beneficial if the synthesis and catalytic screening process could be parallellized and automated. Even though numerous accounts exist in literature where heterogeneous solid catalysts have been prepared using high-throughput methodologies [3], be it via sol–gel, precipitation or even wet impregnation techniques [4,5] many technical difficulties remain with these approaches. For instance, minimizing loss of catalyst material while transferring the sample between different synthesis/washing steps or prior
* Corresponding author. Tel.: +32 9 264 58 13; fax: +32 9 264 58 12. E-mail addresses: [email protected] (J.S. Paul), [email protected] (P.A. Jacobs). 1 Tel.: +32 16321468; fax: +32 16321998. 0169-4332/$ – see front matter # 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2007.06.074
to catalytic testing [6] and maintaining overall homogeneity of the sample during the handling and preparation of the catalyst may prove exceedingly difficult. In this work, a high-throughput platform is presented enabling the complete synthesis and liquid-phase screening of ion-exchanged zeolite catalysts. The system is highly flexible, i.e. with regards to the recipients used, and displays high accuracy and reproducibility. As an illustration the platform performance was validated for the exchange of La onto NaY zeolite. These LaNaY materials were evaluated in the acidcatalyzed acetalization of glycerol derived dihydroxy acetone (DHA) (Scheme 1). This reaction is of great importance to pharmaceutical industry and might serve as a useful route for increasing the value of the glycerol byproduct stream in biodiesel production. 2. Platform components The preparation and catalytic testing of ion-exchanged zeolites in the current work is carried out on a per sample basis in 8 ml glass vials charged with a magnetic stir-bar and a phenol cap. These vials are placed in a 24 position library plate with a standard 4 6 layout (Fig. 1a). However, any type of recipient
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K.P.F. Janssen et al. / Applied Surface Science 254 (2007) 699–703
Scheme 1. Conversion of DHA to methyl glyoxal diacetal.
in any layout could be used without problem in order to accommodate any type of synthesis or catalytic experiment. At maximum capacity, the high-throughput platform presented here can process up to six library plates simultaneously. The platform, developed by Symyx1 Discovery Tools Inc., consists of a number of specialized components to accommodate the many manipulations of solid and liquid precursors and reagents typically involved in catalyst synthesis and screening. A first workflow element is the Powdernium1 solid handling robot (Fig. 1b). This robot makes use of a gravimetric dispensing technology using a balance to determine the exact weight of a dispense. Each single dispense is weighed and electronically recorded. No segregation of the powder into different particles sizes occurs (vide supra) and no mechanical stress is put on the particles. A very interesting feature of the Powdernium1 is the way in which it can handle low initial charges (100 mg) and dispense them very accurately in almost any kind of receptacle. A very wide range of materials with different physical properties, e.g. density, can be readily processed with typical dispense times ranging from 20 to 100 s, per dispense depending on the desired amount and the nature of the solid. The supplied control software is self-regulating,
which allows for automatic selection of the optimal dispense parameters; so no special calibration of the unit is necessary to allow accuracies of up to 1 mg with an R.S.D. of only 1–5% depending on the flow properties of the dispensed powders. A second element of the workflow is a modified Tecan Cavro1 liquid handling station with integrated heating and magnetic stirring (Fig. 1c). This liquid handling unit is equipped with two X–Y–Z moveable arms which can be fitted with different tools, according to the experimental requirements. For catalyst preparation and washing one of these arms is mounted with a pickup for 200 or 1000 ml disposable pipettes or specially modified pipettes equipped with a filter plug. The volumetric liquid handling system is furthermore equipped with several pulse-motor driven syringes of different sizes to allow accurate and fast processing of liquids over a wide volume range. Aspiration and dispense speeds, as well as airgaps are all freely configurable and in combination with an automated weighing station (Fig. 1d) a special protocol allows for automated calibration of the volumetric system to ensure maximal accuracy. Liquid surface levels can be detected by the device through capacitance measurements with the disposable tips which are made of a conducting material. This further minimizes errors by preventing liquid runoff of residual droplets on the outside of the dispensing head. Finally, reaction mixtures from catalytic experiments can be directly analyzed by gas chromatography. For this purpose the GC is equipped with a state-of-the-art autosampler which can be adapted to the layout of the libraries used (Fig. 1e). This eliminates the need for further sample transfer. The entire workflow is operated through a complete suite of software tools for experimental design, equipment control, data storage, and data retrieval and analysis (Fig. 1f). Using this
Fig. 1. High-throughput synthesis and screening platform components.
K.P.F. Janssen et al. / Applied Surface Science 254 (2007) 699–703
software suite, custom scripts were developed in order to accommodate all of the operational requirements for conducting the experimental methods described in the presented work. 3. Platform operation 3.1. Workflow overview In Fig. 2 an overview is given of the different unit operations that make up the presented workflow. The starting NaY zeolite material is first dispensed to the 24 position library plates containing the 8 ml glass vials using the powder handler. Once this is done, the sample library is manually transferred to the liquid handling station after which the precursor solutions for ion exchange can be added (for further details on the exact exchange procedure see Section 3.2). After this initial dispense phase all samples are thoroughly mixed using the magnetic stirrer of the liquid handling platform. In a second phase the exchanged zeolite samples are separated from the exchange solution by the liquid handler using a modified disposable 1000 ml tip equipped with a filter
701
and liquid level detection. This way, all samples can be washed by consecutive cycles of supernatant removal and addition of distilled water. Using this approach the need for cumbersome centrifugation or even filtration procedures is eliminated, further reducing the risk of possible sample loss. After catalyst washing the libraries are once again transferred in their entirety to an oven for drying and thermal activation of all samples. Finally, the liquid handler is once again used to add the reagent mixture to all sample vials of the library followed by reaction at the desired temperature using the liquid handlers built-in heating and magnetic stirring capabilities. 3.2. Catalyst preparation For ion exchange, standard NaY (Si/Al, Zeocat) with a CEC of 3.29 mequiv./gequilib was used. The zeolite was kept in a controlled atmosphere over saturated NH4Cl solution. In order to study the influence of the ion-exchange degree on the catalytic performance, 0.2 g of this NaYequilib was exchanged with different amounts of a 0.132 equiv./l stock solution such
Fig. 2. Unit operations in the automated preparation and catalytic screening of ion-exchanged Y zeolites.
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Table 1 Summary of the results of a typical zeolite powder dosing experiment Row
Column
Target dispense weight (mg)
Actual dispense weight (mg)
1 1 1 1 1 1 2 2 2 2 2 2 3 3 3 3 3 3 4 4 4 4 4 4
1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6
200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200
199.2 199.4 199.8 200.3 200.4 200.0 200.0 200.2 200.9 200.2 199.1 199.3 199.7 200.2 199.5 200.6 200.0 199.3 200.9 199.3 199.6 199.3 201.0 199.7
small scale. After 15 h all samples were washed three times in an automated fashion with distilled water to remove excess salt and the samples were subsequently dried at 353 K for 6 h and calcined according to the following standard procedure (5 K/ min to 723 K for 1.5 h). After calcination all samples were kept at 373 K up to the moment of reaction. 3.3. Reaction mixture preparation In a typical experiment, 5 ml of an ethanol-based mixture containing the DHA substrate (0.4 M) and 1,4-dioxane (internal standard) was added to each sample of the library plate containing 24 samples with 0.2 g of catalyst per sample. 3.4. Catalytic screening and analysis After reaction at 90 8C for a well defined period individual samples or the entire library are taken from the liquid handler heating bay and left to cool after which a small sample of the reactant mixture for each sample is transferred to a fresh library. All sample vials are closed with a septum cap and the libraries are placed directly on the GC (Thermo Finnigan TraceGC, RTX-5 column, 30 m, 0.32 i.d., 25 mm) with a programmable CTC autosampler for analysis.
Mean (mg) = 199.9; S.D. (mg) = 0.57; S.D. (%) = 0.29.
4. Platform evaluation
that 500 ml of this solution theoretically corresponds to 10% of the total CEC. After addition of the stock solution, distilled water was added to obtain a constant volume of 5 ml in order to allow proper stirring during the exchange procedure on such a
As the ability to generate large numbers of experiments has accelerated, it becomes increasingly important to ensure that the quality of each process step and each individual sample is as high as possible. Therefore, to achieve a reasonable level of
Table 2 Summary of the results of a typical liquid dosing experiment for water Row
Column
Target dispense volume (ml)
Dispensed volume (ml)
Average dispensed volume (ml)
S.D. (ml)
S.D. (%)
1 1 1 1 1 1 2 2 2 2 2 2 3 3 3 3 3 3 4 4 4 4 4 4
1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6
320 320 320 320 320 320 320 320 650 650 650 650 650 650 650 650 950 950 950 950 950 950 950 950
316 317 317 315 316 314 316 316 647 641 641 638 646 646 645 647 936 934 923 935 935 936 935 937
316
0.912
0.289
644
3.074
0.477
934
4.45
0.476
K.P.F. Janssen et al. / Applied Surface Science 254 (2007) 699–703
703
individual workflow components is clearly retained when they are combined in the full catalyst synthesis and screening procedure (Fig. 3). The presented high-throughput setup can thus be used to obtain meaningful data about the catalytic system. For instance it becomes possible to evaluate the effect of different exchange degrees on the catalyst performance kinetic, as is illustrated in Fig. 4. Such a task, when carried out conventionally, requires a lot of work since each experimental point is usually obtained from a separate sample. 5. Conclusion
Fig. 3. % Conversion of DHA to methyl glyoxal by LaY (90% La) after 6 h.
Fig. 4. Conversion of DHA in function of time for various zeolite Y-based catalysts: (^) 30% La, (&) 50% La, (~) 90% La (two repetitions).
This contribution shows an integrated robotic solid–liquid handling platform, which is extremely suitable for the manipulation of aqueous precursor solutions and other wet and solid reagents that are typically used in the preparation of heterogeneous catalysts and their subsequent screening. Using this hardware platform and its control software a methodology can be devised which enables almost full automation of the preparation steps and catalytic screening for ion-exchanged materials. By allowing the entire process to be carried out in the same recipients no material is lost while transporting the samples between the different workflow components and no manual handling of the solid materials is necessary, this not only eliminates one of the major bottlenecks in high-throughput catalyst research efforts [4] but also minimizes exposure of the experimentalist to harmful compounds. The employed methods were successfully verified for the acid-catalyzed acetalization of glycerol derived dihydroxy acetone to methyl glyoxal diacetals as a model system. It could be shown that the individual high accuracy and reproducibility of the separate workflow components is maintained during the entire operation of the overall process. Acknowledgements
quality in the information obtained from a high-throughput experimental system, some evaluation of the performance in the different process steps is crucial. In principle, since the variance of the whole workflow is a function of the variances of the different subsystems within the workflow. When looking first at the performance of the solid handler for the dispensing of the NaY zeolite used in the present work we can see that very high accuracies and reproducibilities can be attained judging by the very small standard deviation (Table 1). The same holds true for the performance of the liquid handler (Table 2). When the platform is used for the synthesis of 24 identical LaNaY catalyst samples, the high reproducibility of the
KJ wishes to thank Flamac (Flanders Materials Centre) and IWT Vlaanderen for financial support. References [1] D. Best, B.W. Wojciechowski, J. Catal. 47 (1977) 11. [2] B. Thomas, S. Prathapan, S. Sugunan, Micropor. Mesopor. Mater. 80 (2005) 65. [3] B. Jandeleit, D.J. Schaefer, T.S. Powers, H.W. Turner, W.H. Weinberg, Angew. Chem. Int. Ed. 38 (1999) 2494. [4] S. Senkan, Angew. Chem. Int. Ed. 40 (2001) 312. [5] F. Schu¨th, D. Demuth, Chem. Eng. Technol. 78 (2006) 851. [6] C. Hoffmann, H.W. Schmidt, F. Schu¨th, J. Catal. 198 (2001) 348.
High-throughput preparation and testing of ion-exchanged zeolites K.P.F. Janssen a,1, J.S. Paul b,*, B.F. Sels a,1, P.A. Jacobs a,1 a
Microbial and Molecular Systems, Katholieke Universiteit Leuven, Kasteelpark Arenberg 23, B-3001 Heverlee, Belgium b Flanders Materials Centre (Flamac), Technologiepark 903, B-9052 Zwijnaarde, Belgium Received 16 January 2007; accepted 14 June 2007 Available online 19 July 2007
Abstract A high-throughput research platform was developed for the preparation and subsequent catalytic liquid-phase screening of ion-exchanged zeolites, for instance with regard to their use as heterogeneous catalysts. In this system aqueous solutions and other liquid as well as solid reagents are employed as starting materials and 24 samples are prepared on a library plate with a 4 6 layout. Volumetric dispensing of metal precursor solutions, weighing of zeolite and subsequent mixing/washing cycles of the starting materials and distributing reaction mixtures to the library plate are automatically performed by liquid and solid handlers controlled by a single common and easy-to-use programming software interface. The thus prepared materials are automatically contacted with reagent solutions, heated, stirred and sampled continuously using a modified liquid handling. The high-throughput platform is highly promising in enhancing synthesis of catalysts and their screening. In this paper the preparation of lanthanum-exchanged NaY zeolites (LaNaY) on the platform is reported, along with their use as catalyst for the conversion of renewables. # 2007 Elsevier B.V. All rights reserved. PACS : 82.65. s (catalysis, heterogeneous); 82.75.Qt (zeolites, catalysis in) Keywords: High-throughput; Zeolite Y; Ion exchange; Catalysis; Renewables
1. Introduction Zeolites modified through ion-exchange procedures have many applications, both in gas-phase [1] and liquid-phase [2] catalysis. However, screening the parameter space involved in their synthesis in order to optimize catalyst performance may prove very difficult and time consuming due to the many unit operations that are typically necessary for their preparation. Therefore it would be highly beneficial if the synthesis and catalytic screening process could be parallellized and automated. Even though numerous accounts exist in literature where heterogeneous solid catalysts have been prepared using high-throughput methodologies [3], be it via sol–gel, precipitation or even wet impregnation techniques [4,5] many technical difficulties remain with these approaches. For instance, minimizing loss of catalyst material while transferring the sample between different synthesis/washing steps or prior
* Corresponding author. Tel.: +32 9 264 58 13; fax: +32 9 264 58 12. E-mail addresses: [email protected] (J.S. Paul), [email protected] (P.A. Jacobs). 1 Tel.: +32 16321468; fax: +32 16321998. 0169-4332/$ – see front matter # 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2007.06.074
to catalytic testing [6] and maintaining overall homogeneity of the sample during the handling and preparation of the catalyst may prove exceedingly difficult. In this work, a high-throughput platform is presented enabling the complete synthesis and liquid-phase screening of ion-exchanged zeolite catalysts. The system is highly flexible, i.e. with regards to the recipients used, and displays high accuracy and reproducibility. As an illustration the platform performance was validated for the exchange of La onto NaY zeolite. These LaNaY materials were evaluated in the acidcatalyzed acetalization of glycerol derived dihydroxy acetone (DHA) (Scheme 1). This reaction is of great importance to pharmaceutical industry and might serve as a useful route for increasing the value of the glycerol byproduct stream in biodiesel production. 2. Platform components The preparation and catalytic testing of ion-exchanged zeolites in the current work is carried out on a per sample basis in 8 ml glass vials charged with a magnetic stir-bar and a phenol cap. These vials are placed in a 24 position library plate with a standard 4 6 layout (Fig. 1a). However, any type of recipient
700
K.P.F. Janssen et al. / Applied Surface Science 254 (2007) 699–703
Scheme 1. Conversion of DHA to methyl glyoxal diacetal.
in any layout could be used without problem in order to accommodate any type of synthesis or catalytic experiment. At maximum capacity, the high-throughput platform presented here can process up to six library plates simultaneously. The platform, developed by Symyx1 Discovery Tools Inc., consists of a number of specialized components to accommodate the many manipulations of solid and liquid precursors and reagents typically involved in catalyst synthesis and screening. A first workflow element is the Powdernium1 solid handling robot (Fig. 1b). This robot makes use of a gravimetric dispensing technology using a balance to determine the exact weight of a dispense. Each single dispense is weighed and electronically recorded. No segregation of the powder into different particles sizes occurs (vide supra) and no mechanical stress is put on the particles. A very interesting feature of the Powdernium1 is the way in which it can handle low initial charges (100 mg) and dispense them very accurately in almost any kind of receptacle. A very wide range of materials with different physical properties, e.g. density, can be readily processed with typical dispense times ranging from 20 to 100 s, per dispense depending on the desired amount and the nature of the solid. The supplied control software is self-regulating,
which allows for automatic selection of the optimal dispense parameters; so no special calibration of the unit is necessary to allow accuracies of up to 1 mg with an R.S.D. of only 1–5% depending on the flow properties of the dispensed powders. A second element of the workflow is a modified Tecan Cavro1 liquid handling station with integrated heating and magnetic stirring (Fig. 1c). This liquid handling unit is equipped with two X–Y–Z moveable arms which can be fitted with different tools, according to the experimental requirements. For catalyst preparation and washing one of these arms is mounted with a pickup for 200 or 1000 ml disposable pipettes or specially modified pipettes equipped with a filter plug. The volumetric liquid handling system is furthermore equipped with several pulse-motor driven syringes of different sizes to allow accurate and fast processing of liquids over a wide volume range. Aspiration and dispense speeds, as well as airgaps are all freely configurable and in combination with an automated weighing station (Fig. 1d) a special protocol allows for automated calibration of the volumetric system to ensure maximal accuracy. Liquid surface levels can be detected by the device through capacitance measurements with the disposable tips which are made of a conducting material. This further minimizes errors by preventing liquid runoff of residual droplets on the outside of the dispensing head. Finally, reaction mixtures from catalytic experiments can be directly analyzed by gas chromatography. For this purpose the GC is equipped with a state-of-the-art autosampler which can be adapted to the layout of the libraries used (Fig. 1e). This eliminates the need for further sample transfer. The entire workflow is operated through a complete suite of software tools for experimental design, equipment control, data storage, and data retrieval and analysis (Fig. 1f). Using this
Fig. 1. High-throughput synthesis and screening platform components.
K.P.F. Janssen et al. / Applied Surface Science 254 (2007) 699–703
software suite, custom scripts were developed in order to accommodate all of the operational requirements for conducting the experimental methods described in the presented work. 3. Platform operation 3.1. Workflow overview In Fig. 2 an overview is given of the different unit operations that make up the presented workflow. The starting NaY zeolite material is first dispensed to the 24 position library plates containing the 8 ml glass vials using the powder handler. Once this is done, the sample library is manually transferred to the liquid handling station after which the precursor solutions for ion exchange can be added (for further details on the exact exchange procedure see Section 3.2). After this initial dispense phase all samples are thoroughly mixed using the magnetic stirrer of the liquid handling platform. In a second phase the exchanged zeolite samples are separated from the exchange solution by the liquid handler using a modified disposable 1000 ml tip equipped with a filter
701
and liquid level detection. This way, all samples can be washed by consecutive cycles of supernatant removal and addition of distilled water. Using this approach the need for cumbersome centrifugation or even filtration procedures is eliminated, further reducing the risk of possible sample loss. After catalyst washing the libraries are once again transferred in their entirety to an oven for drying and thermal activation of all samples. Finally, the liquid handler is once again used to add the reagent mixture to all sample vials of the library followed by reaction at the desired temperature using the liquid handlers built-in heating and magnetic stirring capabilities. 3.2. Catalyst preparation For ion exchange, standard NaY (Si/Al, Zeocat) with a CEC of 3.29 mequiv./gequilib was used. The zeolite was kept in a controlled atmosphere over saturated NH4Cl solution. In order to study the influence of the ion-exchange degree on the catalytic performance, 0.2 g of this NaYequilib was exchanged with different amounts of a 0.132 equiv./l stock solution such
Fig. 2. Unit operations in the automated preparation and catalytic screening of ion-exchanged Y zeolites.
702
K.P.F. Janssen et al. / Applied Surface Science 254 (2007) 699–703
Table 1 Summary of the results of a typical zeolite powder dosing experiment Row
Column
Target dispense weight (mg)
Actual dispense weight (mg)
1 1 1 1 1 1 2 2 2 2 2 2 3 3 3 3 3 3 4 4 4 4 4 4
1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6
200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200
199.2 199.4 199.8 200.3 200.4 200.0 200.0 200.2 200.9 200.2 199.1 199.3 199.7 200.2 199.5 200.6 200.0 199.3 200.9 199.3 199.6 199.3 201.0 199.7
small scale. After 15 h all samples were washed three times in an automated fashion with distilled water to remove excess salt and the samples were subsequently dried at 353 K for 6 h and calcined according to the following standard procedure (5 K/ min to 723 K for 1.5 h). After calcination all samples were kept at 373 K up to the moment of reaction. 3.3. Reaction mixture preparation In a typical experiment, 5 ml of an ethanol-based mixture containing the DHA substrate (0.4 M) and 1,4-dioxane (internal standard) was added to each sample of the library plate containing 24 samples with 0.2 g of catalyst per sample. 3.4. Catalytic screening and analysis After reaction at 90 8C for a well defined period individual samples or the entire library are taken from the liquid handler heating bay and left to cool after which a small sample of the reactant mixture for each sample is transferred to a fresh library. All sample vials are closed with a septum cap and the libraries are placed directly on the GC (Thermo Finnigan TraceGC, RTX-5 column, 30 m, 0.32 i.d., 25 mm) with a programmable CTC autosampler for analysis.
Mean (mg) = 199.9; S.D. (mg) = 0.57; S.D. (%) = 0.29.
4. Platform evaluation
that 500 ml of this solution theoretically corresponds to 10% of the total CEC. After addition of the stock solution, distilled water was added to obtain a constant volume of 5 ml in order to allow proper stirring during the exchange procedure on such a
As the ability to generate large numbers of experiments has accelerated, it becomes increasingly important to ensure that the quality of each process step and each individual sample is as high as possible. Therefore, to achieve a reasonable level of
Table 2 Summary of the results of a typical liquid dosing experiment for water Row
Column
Target dispense volume (ml)
Dispensed volume (ml)
Average dispensed volume (ml)
S.D. (ml)
S.D. (%)
1 1 1 1 1 1 2 2 2 2 2 2 3 3 3 3 3 3 4 4 4 4 4 4
1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6
320 320 320 320 320 320 320 320 650 650 650 650 650 650 650 650 950 950 950 950 950 950 950 950
316 317 317 315 316 314 316 316 647 641 641 638 646 646 645 647 936 934 923 935 935 936 935 937
316
0.912
0.289
644
3.074
0.477
934
4.45
0.476
K.P.F. Janssen et al. / Applied Surface Science 254 (2007) 699–703
703
individual workflow components is clearly retained when they are combined in the full catalyst synthesis and screening procedure (Fig. 3). The presented high-throughput setup can thus be used to obtain meaningful data about the catalytic system. For instance it becomes possible to evaluate the effect of different exchange degrees on the catalyst performance kinetic, as is illustrated in Fig. 4. Such a task, when carried out conventionally, requires a lot of work since each experimental point is usually obtained from a separate sample. 5. Conclusion
Fig. 3. % Conversion of DHA to methyl glyoxal by LaY (90% La) after 6 h.
Fig. 4. Conversion of DHA in function of time for various zeolite Y-based catalysts: (^) 30% La, (&) 50% La, (~) 90% La (two repetitions).
This contribution shows an integrated robotic solid–liquid handling platform, which is extremely suitable for the manipulation of aqueous precursor solutions and other wet and solid reagents that are typically used in the preparation of heterogeneous catalysts and their subsequent screening. Using this hardware platform and its control software a methodology can be devised which enables almost full automation of the preparation steps and catalytic screening for ion-exchanged materials. By allowing the entire process to be carried out in the same recipients no material is lost while transporting the samples between the different workflow components and no manual handling of the solid materials is necessary, this not only eliminates one of the major bottlenecks in high-throughput catalyst research efforts [4] but also minimizes exposure of the experimentalist to harmful compounds. The employed methods were successfully verified for the acid-catalyzed acetalization of glycerol derived dihydroxy acetone to methyl glyoxal diacetals as a model system. It could be shown that the individual high accuracy and reproducibility of the separate workflow components is maintained during the entire operation of the overall process. Acknowledgements
quality in the information obtained from a high-throughput experimental system, some evaluation of the performance in the different process steps is crucial. In principle, since the variance of the whole workflow is a function of the variances of the different subsystems within the workflow. When looking first at the performance of the solid handler for the dispensing of the NaY zeolite used in the present work we can see that very high accuracies and reproducibilities can be attained judging by the very small standard deviation (Table 1). The same holds true for the performance of the liquid handler (Table 2). When the platform is used for the synthesis of 24 identical LaNaY catalyst samples, the high reproducibility of the
KJ wishes to thank Flamac (Flanders Materials Centre) and IWT Vlaanderen for financial support. References [1] D. Best, B.W. Wojciechowski, J. Catal. 47 (1977) 11. [2] B. Thomas, S. Prathapan, S. Sugunan, Micropor. Mesopor. Mater. 80 (2005) 65. [3] B. Jandeleit, D.J. Schaefer, T.S. Powers, H.W. Turner, W.H. Weinberg, Angew. Chem. Int. Ed. 38 (1999) 2494. [4] S. Senkan, Angew. Chem. Int. Ed. 40 (2001) 312. [5] F. Schu¨th, D. Demuth, Chem. Eng. Technol. 78 (2006) 851. [6] C. Hoffmann, H.W. Schmidt, F. Schu¨th, J. Catal. 198 (2001) 348.