PROCESSES FOR CARRYING OUT CHEMICAL REACTIONS IN FLUID PHASE IN THE PRESENCE OF FILMS COMPRISING CATALYST PARTICLES

Abstract

The present invention relates to a process for carrying out a chemical reaction in a chemical reactor, in which at least one starting material, which is an organic chemical compound comprising 1 to 80 carbon atoms, is converted into at least one reaction product in a fluid phase in the presence of a film comprising solid catalyst particles, which catalyze said chemical reaction, and comprising an organic polymer in fibrillated form, wherein the mass fraction of the sum of the starting material and of the reaction product based on the total mass of the fluid phase is in the range from 0.01 to 1.

Claims

1.-9. (canceled)

11. A process for carrying out a chemical reaction in a chemical reactor, in which at least one starting material, which is an organic chemical compound comprising 1 to 80 carbon atoms, is converted into at least one reaction product in a fluid phase in the presence of a film comprising solid catalyst particles, which catalyze said chemical reaction, and comprising an organic polymer in fibrillated form, wherein the film comprises at least one layer comprising solid catalyst particles and the organic polymer in fibrillated form, wherein the mass fraction of the organic polymer in fibrillated form in said layer is in the range from 0.06 to 0.2 and the mass fraction of solid catalyst particles in said layer is in the range from 0.8 to 0.94 based on the total weight of said layer, wherein the organic polymer is a fluoropolymer, and wherein the mass fraction of the sum of the starting material and of the reaction product based on the total mass of the fluid phase is in the range from 0.01 to 1.

12. The process according to claim 11, wherein the chemical reaction is selected from the group of chemical reactions consisting of oxidations, reductions, substitutions, additions, eliminations and rearrangements.

13. The process according to claim 11, wherein the chemical reaction takes place at a temperature in the range from −78° C. to 350° C.

14. The process according to claim 11, wherein the chemical reactor is a fixed-bed reactor selected from the group of reactors consisting of tubular reactors, adiabatic reactors, multitube reactors and microreactors.

15. The process according to claim 11, wherein the fluid phase is a liquid phase.

16. The process according to claim 11, wherein the solid catalyst particles have a particle size d50 in the range from 0.1 to 1000 μm.

17. The process according to claim 11, wherein the film has a thickness in the range from 0.1 μm to 20000 μm.

18. The process according to claim 11 wherein the thickness of the layer comprising solid catalyst particles and the organic polymer in fibrillated form is in the range from 1 μm to 200 μm.

19. The process according to claim 11, wherein the film comprises at least two layers of different compositions, wherein at least one of the two outer layers of the film is the layer comprising solid catalyst particles and the organic polymer in fibrillated form.

20. The process according to claim 11, wherein at least one part of the film provides a porosity of 5 to 70%.

21. A process for carrying out a chemical reaction in a chemical reactor comprising: converting at least one starting material, which is an organic chemical compound comprising 1 to 80 carbon atoms, into at least one reaction product in a fluid phase in the presence of a film comprising solid catalyst particles, which catalyze said chemical reaction, and comprising an organic polymer in fibrillated form, wherein the film comprises at least one layer comprising solid catalyst particles and the organic polymer in fibrillated form, wherein the mass fraction of the organic polymer in fibrillated form in said layer is in the range from 0.06 to 0.2 and the mass fraction of solid catalyst particles in said layer is in the range from 0.8 to 0.94 based on the total weight of said layer, wherein the organic polymer is a fluoropolymer, and wherein the mass fraction of the sum of the starting material and of the reaction product based on the total mass of the fluid phase is in the range from 0.01 to 1.

Description

[0135] The invention is illustrated by the examples which follow, but these do not restrict the invention.

[0136] Figures in percent are each based on % by weight, unless explicitly stated otherwise.

I. Preparation and Characterization of Films Comprising Solid Catalyst Particles and PTFE in Fibrillated Form

[0137] Three catalyst powders (5% Pd on activated carbon) were used as solid catalyst particles. All catalysts were supplied by BASF for hydrogenation of nitrobenzene to aniline. The three powders are here indicated as S1, S2, S3 and they are commercially produced. The three catalysts differ in terms of catalytic activity.

[0138] Films comprising solid catalyst particles and PTFE in fibrillated form were shaped by mixing the catalyst powder with a low amount of PTFE (7.5% PTFE) as fibrillatable organic polymer and processed by a sequence of mechanical treatments (kneading, calendering and conditioning). The resulting films have flexible and porous structure (FIG. 1). For each catalyst, three film thicknesses were prepared: 100, 250 and 400 μm (summary in Table 1). For S3 sandwich films were also produced. With the term sandwich films, it is indicated a film constituted of external layers containing the active metal (Pd) on a support material and an internal layer containing only the support without active metal (active carbon).

TABLE-US-00001 TABLE 1 Overview of the films prepared and tested. Thickness of the film comprising Solid Cat-alyst Sample Particles and PTFE in name Solid Catalyst Particles fibrillated form S1 5% Pd on C (high active) — S2 5% Pd on C (middle active) — S3 5% Pd on C (low active) — F1 5% Pd on C (high active) 100 μm F2 5% Pd on C (middle active ) 100 μm F3 5% Pd on C (low active ) 100 μm F4 5% Pd on C (high active ) 250 μm F5 5% Pd on C (middle active) 250 μm F6 5% Pd on C (low active ) 250 μm F7 5% Pd on C (high active ) 400 μm F8 5% Pd on C (middle active ) 400 μm F9 5% Pd on C (low active) 400 μm F10 5% Pd on C (low active) Sandwich Film 25 μm (active layer)/50 μm (inert)/25 μm (active layer) F11 5% Pd on C (low active) Sandwich Film 25 μm (active layer)/60 μm (inert)/25 μm (active layer)

[0139] F10 (Table 1) was produced compressing a 315 μm active-carbon layer between 150 μm Pd/C film in order to obtain a final thickness of 100 μm. In FIG. 4 the profile of a sandwich film measured by SEM produced by higher volume compression is reported.

[0140] FIG. 1: Image of a film prepared according to example I.

[0141] FIG. 2: SEM image of F1. Overview of the film comprising PTFE fibrils and catalyst particles.

[0142] FIG. 3: SEM image of F1. Detail of PTFE nanofibrils keeping together the catalyst particles.

[0143] FIG. 4: SEM images of the vertical profile of the sandwich film F11. For this image the film was cut by FIB (Focused Ion Beam) and measure in backscattering mode. The bright regions contain Pd.

[0144] The physical-chemical characteristics of the used catalyst powders and the films derived from the highest active catalyst S1 are compared in Table 2.

TABLE-US-00002 TABLE 2 Physical and chemical characteristics of the three BASF catalyst samples S1, S2 and S3 and of the films produced from solid catalyst particles S1 (catalyst with the highest activity). S1 S2 S3 F1 F4 F7 Activity high middle low high high high Pd loading [%] 5 5 5 4.63 4.63 4.63 BET surface area [m2/g] 764 758 789 604 654 717 Pore volume [cm3/g] 0.60 0.61 0.63 0.47 0.50 0.55 Grain size Dn10 [μm] 0.754 0.728 0.943 — — — Dn50 [μm] 1.05 1.09 1.44 — — — Dn90 [μm] 2.66 3.07 4.18 — — — Pd dispersion [%] 24 23 30 21 24 24 Pd surface area [m2/g] 5.3 5.1 6.6 4.2 4.9 5.0 Pd particle size (hemi-sphere, 4.7 4.8 3.8 5.5 4.7 4.6 chemisorption) [nm]

[0145] The BET surface area for S1, S2 and S3 is similar, since the same carbon support was used. In case of the films, comprising PTFE in fibrillated form, the porosity and the surface area were dependent on the absolute film thickness, showing a slight decrease in surface area for lower thickness. The effect was limited to maximum of 20% surface area loss for the thinnest catalyst films of 100 μm.

[0146] The Pd dispersion is similar for the S1 and S2 and higher for S3 (see Table 2). In case of F1, F4 and F7, the Pd dispersion was retained independently from the film thickness (considering the margin of the experimental error of the chemisorption measurements).

[0147] The typical structure of the films, comprising PTFE in fibrillated form, was elucidated by SEM (FIG. 3, 4), where PTFE nanofibrils were observed holding together the active carbon grains (solid catalyst particles). The Pd-dispersion was investigated by acquiring SEM images in backscattering mode and by analyzing the catalyst powder by TEM. TEM images did not show remarkable difference in Pd-distribution among the three catalysts.

II. Application and Kinetic Analysis of Films, Comprising PTFE in Fibrillated Form and Pd on C as Solid Catalyst Particles, in Batch Autoclave

[0148] Hydrogenation of nitrobenzene (NB) to aniline was chosen as a test reaction for the catalytic systems.

Method:

[0149] A 60 ml batch reactor was used to evaluate the mass transfer/diffusion phenomena in the original catalyst powders and in the films, comprising PTFE in fibrillated form and solid catalyst particles. The autoclave contained a magnetically coupled stirrer and stream breakers to provide good mixing and minimize gas/liquid mass transport limitations. For kinetic studies the following procedure was developed. The catalyst powder (Pd/C), solvent (methanol) and hydrogen were fed in the autoclave (5 barg), while a solution of nitrobenzene was inserted in the charger. The autoclave was stabilized at the desired temperature. The reaction started at to when the valve of the charger was opened, and nitrobenzene inserted into the reactor (final nitrobenzene concentration 0.03 mol L.sup.−1). The hydrogen consumption of the reaction is calculated by recording the variation of the pressure in the autoclave versus time. Knowing this, the hydrogen moles consumed and the variation in nitrobenzene concentration are calculated. The reaction rate is reported as mol s.sup.−1 of the converted nitrobenzene normalized for the Pd mass. The Arrhenius plot and the effectiveness factor were used to compare the powder and the films, comprising PTFE in fibrillated form and solid catalyst particles, for a temperature range from −8° C. to 20° C. (range where data for the catalyst powders were obtained in the kinetic regime). In this study, the effectiveness factor (η) is defined as the ratio between the reaction rate observed in the films and the reaction rate of the powder.

[0150] The reaction rate decreased for high film thickness and consequently with it the effectiveness factor for the respective films (Table 3). For definition, the effectiveness factor of the catalyst powder in kinetic regime is 100%. In Table 3, the highest active catalyst powder S1 shows an effectiveness factor less than 8%, which means that less than 8% of the porous body is effectively used, showing therefore mass transfer limitations. For the middle (F2, F5, F8) and low active (F3, F6, F9) catalysts the effectivity factor is higher (40-47% for the 100 μm film, Table 3), but still far from 100%.

[0151] Sandwich films were considered as approaches to increase the effectivity of monolayer films. The 100 μm sandwich film (low activity catalyst) had an enhanced activity, comparable to the powder, demonstrating therefore that using this geometry the noble metal can be fully exploited and no mass transfer limitation were present.

TABLE-US-00003 TABLE 3 Effectiveness factor (η) calculated for the reaction nitrobenzene to aniline over films comprising solid catalyst particles (S1, S2, S3) and PTFE in fibrillated form. Film η at −8° C. η at 0° C. η at 10° C. η at 20° C. F1  7.3%  6.2%  5.0%  4.2% F4  3.1%  2.6%  2.2%  1.9% F7  3.2%  2.8%  2.4%  2.1% F2 47.3% 36.5% 26.9% 20.2% F5 16.6% 16.7% 16.7% 16.8% F8 13.3% 13.3% 13.3% 13.3% F3 40.9% 35.8% 30.7% 26.5% F6 13.7% 13.4% 13.0% 12.6% F9 10.6% 10.2%  9.9%  9.5% F10  100%  100% 90.8% 76.3%

III. Films, Comprising PTFE in Fibrillated Form and Pd on C as Solid Catalyst Particles, Application and Kinetic Analysis of Films, in Microreactor as Flow Chemistry Application

[0152] Films, comprising PTFE in fibrillated form and Pd on C as solid catalyst particles as described above, were immobilized on the microchannels of a 100 μl microreactor and tested in continuous mode. The film F1 was inserted in the microstructures by pressing it gently and going to constitute one of the wall of the channel (FIG. 5). Hydrogenation of nitrobenzene was used as test reaction to monitor the catalyst performance over time.

[0153] FIG. 5: Microchannels used in the conversion of nitrobenzene to aniline. On the left, PTFE microchannels, on the center PTFE microchannel with immobilized films, comprising PTFE in fibrillated form and Pd on C as solid catalyst particles, on the right stainless steel microchannels with said film and with Taylor flow applied.

[0154] Method: The nitrobenzene solution (0.03 mol/l in methanol, liquid flow 2 ml/min) was supplied by a syringe pump. This was mixed with hydrogen (approximative volume ratio liquid/gas 1:5) by a T junction and insert consequently in the microreactor. The reaction was carried out at 20° C. at atmospheric pressure with an approximate residence time of circa 5 s.

[0155] In FIG. 5, the microchannels are shown: on the left empty microchannel, on the center with the immobilized film, comprising PTFE in fibrillated form and Pd on C as solid catalyst particles, and on the right Taylor flow was applied on said film. The residence time was chosen to hit a conversion a value lower than 100% in order to monitor eventual deactivation. The conversion was approximatively stable at around 50% during a TOS (time on stream) of 5 hours (see Table 4).

[0156] The selectivity toward aniline was also high (near 100%), as observed by UV-Vis spectrometry and confirmed also by GC-MS. The linear combination of UV-Vis spectra of nitrobenzene and aniline could fit properly the product spectrum, being therefore able to determine the aniline concentration. In conclusion, films, comprising PTFE in fibrillated form and Pd on C as solid catalyst particles, were suitable also for a) continuous operation and b) operation in microreactors.

TABLE-US-00004 TABLE 4 Conversion of nitrobenzene to aniline in a microreactor (reaction conditions: 20° C., 1 atm H.sub.2, 0.03M nitrobenzene, residence time 5 s). Time on stream [h] Conversion [%] 0.5 57.2% 1.0 56.0% 1.5 57.9% 2.0 47.4% 2.5 50.1% 3.0 44.1% 3.5 51.9% 4.0 53.7% 4.5 53.9% 5.0 49.6% 5.5 51.3%

IV. Additional Investigative Experiments

[0157] Additional experiments were carried out in the autoclave to assess: [0158] Resistance of the film to high temperatures (180° C.) and leaching of Pd [0159] Influence of the binder amount on catalytic performance [0160] Reusability of the films comprising solid catalyst particles in sequential batch reactions

[0161] After the film (low activity catalyst, 100 μm) was exposed at 180° C. for 3 h in methanol, the autoclave was cooled down and a reaction was performed at 20° C. Same procedure was applied for a powder catalyst sample, treated in the identical way.

[0162] Both resulted catalytically not active materials (powder catalyst and catalyst film) after the thermal treatment at 180° C. We assume that the powder catalyst was deactivated during the treatment procedure. However, the film looked macroscopically intact by visual inspection and SEM, indicating that the fibrils were intact and mechanically stable. Therefore, the deactivation processes seem to have only affected the catalytic function and not the mechanical stability. In conclusion, deactivation processes are only dependent on the nature of the catalyst and not on the fibrillation process. As well, leaching at different temperatures up to 180° C. was investigated. No leaching could be observed. The content of Palladium in the solution was under the detection limit of the instrument.

[0163] Films with a different amount of fibrillated PTFE (20% instead 7.5% of PTFE) were tested and no significant differences could be seen in the catalytic activity. This result constitutes an advantage in term of flexibility in tuning the catalyst surface property, varying the polarity of the film (larger amounts of PTFE as binder will result in a less polar catalyst film).

[0164] A sequence of repeated reactions was performed using the same film F3 (low activity catalyst, 100 μm). The activity for a set of four experiments decrease compared to the first experiment to 90% for the second, 75% for the third and 59% for the fourth experiment. Preliminary experiments with the powder suggested that also the powder is affected by deactivation. In conclusion, deactivation processes are attributed to the nature of the catalytical powder and not to the specific immobilization in the films, comprising PTFE in fibrillated form and Pd on C as solid catalyst particles.

V. Mechanical Stability Experiments

[0165] Additional experiments were carried out investigating the mechanical stability of catalytic fibrillated films at the example of transition metal carbonate particles with a d50 of 9 μm and a BET surface 3.3 m.sup.2/g (90%) and PTFE particles with a d50 of 400 μm (10%).

[0166] To investigate the effect of multiple layers to the film stability, the film samples were folded like described in the following:

[0167] The initial films all were single layered with a thickness of 360 μm. Those films were produced as described above. First the catalyst particles (transition metal carbonate) were mixed with PTFE particles. Second the particle mixture was pre-fibrillated for 10 min via ball mill (1-liter container on rolling bench, 15 g particles, 1 kg of 2.7 mm zirconium oxide milling balls). The resulting particle/PTFE flakes were finally calendered between two rollers and a fixed gap of 360 μm. 2-layer films were achieved by folding the single-layer films before compacting them again to 360 μm via calendering rolls. Accordingly, 4-layer films were achieved by folding 360 μm thick 2-layer films before compacting them again to 360 μm thickness. 8-layer films were achieved similar, starting with 360 μm thick 4-layer films.

[0168] For investigating the effect of further compaction to the film stability, the multiple layered films were further compacted, starting from their common thickness of 360 μm.

[0169] For measuring the mechanical stability of the films, a minimum of three samples, each 10×50 mm.sup.2, were measured for tensile strength applying a force testing machine BTC-FR2.5TN.D09 from Zwick GmbH. [0170] FIG. 6: SEM-cross-section view of a 160 μm thick, 4-layered film comprising transition metal carbonate particles (90%) and PTFE (10%). [0171] FIG. 7: Plot of tensile strength measurements for various layered and compacted films comprising transition metal carbonate particles (90%) and PTFE (10%). The square (.square-solid.) represents the initial 1-layered film at 360 μm without any compaction or folding. The diamonds (.box-tangle-solidup.) represent the tensile strength of compacted 2-layer films, the triangles (.diamond-solid.) represent the tensile strength of compacted 4-layer films, while the circles (.circle-solid.) represent the tensile strength of compacted 8-layer films.

[0172] In FIG. 6 a SEM-cross-section view of a 160 μm thick, 4-layered film is shown. In the picture there is no layered structure visible. Hence, the layered processing of the films vanishes during further compaction which promotes further fibrillation between the layers.

[0173] In FIG. 7 the results of the tensile strength measurements are plotted. Two overall trends are obvious. First, the tensile strength for all amounts of layers increases when the films get compacted from 360 μm to 85 μm. Second, the tensile strength increases with an even higher impact when the number of layers is increased from 2 to 8. This is due to fact that the layering is achieved by a folding and a subsequent compaction to the initial thickness.