scholarly journals Mass Transfer in Hierarchical Silica Monoliths Loaded With Pt in the Continuous-Flow Liquid-Phase Hydrogenation of p-Nitrophenol

2021 ◽  
Vol 3 ◽  
Author(s):  
Haseeb Ullah Khan Jatoi ◽  
Michael Goepel ◽  
David Poppitz ◽  
Richard Kohns ◽  
Dirk Enke ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Flow Rate ◽  
Continuous Flow ◽  
Flow Reactor ◽  
Sol Gel ◽  
Catalyst Support ◽  
Test Reaction ◽  
Silica Monoliths ◽  
Monolithic Catalysts ◽  
Liquid Phase Hydrogenation

Sol-gel-based silica monoliths with hierarchical mesopores/macropores are promising catalyst support and flow reactors. Here, we report the successful preparation of cylindrically shaped Pt-loaded silica monoliths (length: 2 cm, diameter: 0.5 cm) with a variable mean macropore width of 1, 6, 10, or 27 μm at a fixed mean mesopore width of 17 nm. The Pt-loaded monolithic catalysts were housed in a robust cladding made of borosilicate glass for use as a flow reactor. The monolithic reactors exhibit a permeability as high as 2 μm2 with a pressure drop below 9 bars over a flow rate range of 2–20 cm3 min−1 (solvent: water). The aqueous-phase hydrogenation of p-nitrophenol to p-aminophenol with NaBH4 as a reducing agent was used as a test reaction to study the influence of mass transfer on catalytic activity in continuous flow. No influence of flow rate on conversion at a fixed contact time of 2.6 s was observed for monolithic catalysts with mean macropore widths of 1, 10, or 27 µm. As opposed to earlier studies conducted at much lower flow velocities, this strongly indicates the absence of external mass-transfer limitations or stagnant layer formation in the macropores of the monolithic catalysts.

scholarly journals Enantioselective Transamination in Continuous Flow Mode with Transaminase Immobilized in a Macrocellular Silica Monolith

2017 ◽  
Author(s):  
Ludivine van den Biggelaar ◽  
Patrice Soumillion ◽  
Damien P. Debecker
Keyword(s):  
Continuous Flow ◽  
Preferential Flow ◽  
Kinetic Resolution ◽  
Flow Reactor ◽  
Sol Gel ◽  
Flow Mode ◽  
Chiral Amine ◽  
Silica Monoliths ◽  
Covalent Grafting ◽  
Heterogeneous Biocatalysts

ω-Transaminases have been immobilized on macrocellular silica monoliths and used as heterogeneous biocatalysts in a continuous flow mode enantioselective transamination reaction. The support was prepared by a sol-gel method based on emulsion-templating. The enzyme was immobilized on the structured silica monoliths both by adsorption, and by covalent grafting using amino-functionalized silica monoliths and glutaraldehyde as a coupling agent. A simple reactor set-up based on the use of a heat-shrinkable Teflon tube is presented and successfully used for the continuous flow kinetic resolution of a chiral amine, 4-bromo-α-methylbenzylamine. The porous structure of the supports ensures effective mass transfer and the reactor works in the plug flow regime without preferential flow paths. When immobilized in the monolith and used in the flow reactor, transaminases retain their activity and their enantioselectivity. The solid biocatalyst is also shown to be stable both on stream and during storage. These essential features pave the way to the successful development of an environmentally friendly process for chiral amines production.

scholarly journals Enantioselective Transamination in Continuous Flow Mode with Transaminase Immobilized in a Macrocellular Silica Monolith

2017 ◽  
Author(s):  
Ludivine van den Biggelaar ◽  
Patrice Soumillion ◽  
Damien P. Debecker
Keyword(s):  
Continuous Flow ◽  
Preferential Flow ◽  
Kinetic Resolution ◽  
Flow Reactor ◽  
Sol Gel ◽  
Flow Mode ◽  
Chiral Amine ◽  
Silica Monoliths ◽  
Covalent Grafting ◽  
Heterogeneous Biocatalysts

ω-Transaminases have been immobilized on macrocellular silica monoliths and used as heterogeneous biocatalysts in a continuous flow mode enantioselective transamination reaction. The support was prepared by a sol-gel method based on emulsion templating. The enzyme was immobilized on the structured silica monoliths both by adsorption, and by covalent grafting using amino-functionalized silica monoliths and glutaraldehyde as a coupling agent. A simple reactor set-up based on the use of a heat-shrinkable Teflon tube is presented and successfully used for the continuous flow kinetic resolution of a chiral amine, 4-bromo-α-methylbenzylamine. The porous structure of the supports ensures effective mass transfer and the reactor works in the plug flow regime without preferential flow paths. When immobilized in the monolith and used in the flow reactor, transaminases retain their activity and their enantioselectivity. The solid biocatalyst is also shown to be stable both on stream and during storage. These essential features pave the way to the successful development of an environmentally friendly process for chiral amines production.

Granulated Carbon Nanotubes as the Catalyst Support for Pt for the Hydrogenation of Nitrobenzene

2010 ◽  
Vol 63 (1) ◽  
pp. 131 ◽  
Author(s):  
Shao Jin ◽  
Weizhong Qian ◽  
Yi Liu ◽  
Fei Wei ◽  
Dezeng Wang ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Mass Transfer ◽  
Catalytic Activity ◽  
Activated Carbon ◽  
Liquid Phase ◽  
Transfer Rate ◽  
High Selectivity ◽  
Mass Transfer Rate ◽  
Catalyst Support ◽  
Liquid Phase Hydrogenation

Granulated Pt/carbon nanotubes (CNTs) were found to have a much better catalytic activity in the liquid phase hydrogenation of nitrobenzene than Pt/activated carbon (AC). The granulated CNTs had much larger pores than the AC particles, which gave a faster mass transfer rate of H2 that helped produce aniline with high selectivity.

Continuous Flow Mode Biocatalytic Transamination Using Macrocellular Silica Monoliths: Optimizing Support Functionalisation and Enzyme Grafting

2019 ◽  
Author(s):  
Ludivine van den Biggelaar ◽  
Patrice Soumillion ◽  
Damien Debecker
Keyword(s):  
Enzyme Immobilization ◽  
Continuous Flow ◽  
Sol Gel ◽  
Fold Increase ◽  
Covalent Attachment ◽  
Flow Mode ◽  
Active Materials ◽  
Silica Monoliths ◽  
Transamination Reaction ◽  
Reported Data

<div>Transaminases are immobilized onto macrocellular silica monoliths and used for carrying a continuous flow mode transamination reaction. Monoliths were prepared via an emulsion-templated sol-gel method and functionalized by amino-moieties (APTES) in order to covalently immobilize the enzymes, using glutaraldehyde as a cross-linking agent. In order to obtain higher performance and improved reproducibility, we investigate the key parameters of APTES functionalization and of enzyme grafting. Four functionalization protocols were studied. It is shown that controlling the moisture levels in monolith and in the functionalisation solution led to a 3-fold increase in activity as compared to the previously reported data, and greatly improved the reproducibility. Additionally, we report a strong beneficial effect of running the enzyme immobilization at room temperature instead of 4°C, further enhancing the obtained activity. Finally, the popular method which consists in stabilizing the covalent attachment of the enzyme by reducing the imine bonds formed between the enzyme and the functionalized surface was investigated. We highlight a strong enzyme deactivation caused by cyanoborohydride, making this strategy irrelevant in this case. All in all, the improvements presented here for enzyme immobilization in macrocellular silica monoliths, lead to the preparation of more active materials for continuous flow mode biocatalysis.<br></div>

scholarly journals Continuous Flow Friedel–Crafts Alkylation Catalyzed by Silica Supported Phosphotungstic Acid: An Environmentally Benign Process

2021 ◽  
Author(s):  
Zsófia Császár ◽  
Tatjána Juzsakova ◽  
Miklós Jakab ◽  
Szabolcs Balogh ◽  
Ágnes Szegedi ◽  
...  
Keyword(s):  
Flow Rate ◽  
Continuous Flow ◽  
Phosphotungstic Acid ◽  
Flow Reactor ◽  
Analytical Techniques ◽  
Catalyst System ◽  
Molar Ratio ◽  
Flow Mode ◽  
Reaction Conditions ◽  
Composite Catalysts

AbstractSix silica-supported phosphotungstic acid catalysts (PTA/SiO2) of different composition (20–70 wt% PTA content) have been synthesized and characterized by elemental analysis, BET, BJH, NH3-TPD methods, FT-IR spectroscopy of adsorbed pyridine and 1H MAS NMR techniques. The new composite catalysts were first applied in the Friedel–Crafts alkylation of toluene with 1-octene as a benchmark process under batch conditions in order to screen their activity and recyclability. The combined analytical techniques together with the catalytic studies enabled the identification of the main factors affecting the activity of the catalysts. Based on these preliminary experiments, the best performing catalyst system (50 wt% PTA/SiO2) was investigated in continuous flow mode using an in-house-made flow reactor. The thorough screening of the reaction conditions (temperature, toluene/1-octene molar ratio and flow rate) provided firm evidence that the 50 wt% PTA/SiO2 composite is highly active, selective and stable catalyst under mild reaction conditions even at elevated flow rate. Additionally, the catalyst used in the flow mode could successfully be regenerated and reused in the alkylation process.

Continuous Flow Mode Biocatalytic Transamination Using Macrocellular Silica Monoliths: Optimizing Support Functionalisation and Enzyme Grafting

2019 ◽  
Author(s):  
Ludivine van den Biggelaar ◽  
Patrice Soumillion ◽  
Damien Debecker
Keyword(s):  
Enzyme Immobilization ◽  
Continuous Flow ◽  
Sol Gel ◽  
Fold Increase ◽  
Covalent Attachment ◽  
Flow Mode ◽  
Active Materials ◽  
Silica Monoliths ◽  
Transamination Reaction ◽  
Reported Data

<div>Transaminases are immobilized onto macrocellular silica monoliths and used for carrying a continuous flow mode transamination reaction. Monoliths were prepared via an emulsion-templated sol-gel method and functionalized by amino-moieties (APTES) in order to covalently immobilize the enzymes, using glutaraldehyde as a cross-linking agent. In order to obtain higher performance and improved reproducibility, we investigate the key parameters of APTES functionalization and of enzyme grafting. Four functionalization protocols were studied. It is shown that controlling the moisture levels in monolith and in the functionalisation solution led to a 3-fold increase in activity as compared to the previously reported data, and greatly improved the reproducibility. Additionally, we report a strong beneficial effect of running the enzyme immobilization at room temperature instead of 4°C, further enhancing the obtained activity. Finally, the popular method which consists in stabilizing the covalent attachment of the enzyme by reducing the imine bonds formed between the enzyme and the functionalized surface was investigated. We highlight a strong enzyme deactivation caused by cyanoborohydride, making this strategy irrelevant in this case. All in all, the improvements presented here for enzyme immobilization in macrocellular silica monoliths, lead to the preparation of more active materials for continuous flow mode biocatalysis.<br></div>

scholarly journals Self-immobilized Pd nanowires as an excellent platform for a continuous flow reactor: efficiency, stability and regeneration

Nanoscale ◽  
2018 ◽  
Vol 10 (45) ◽  
pp. 21396-21405 ◽  
Author(s):  
Lipipuspa Sahoo ◽  
Moumita Rana ◽  
Sanjit Mondal ◽  
Neeru Mittal ◽  
Pronoy Nandi ◽  
...  
Keyword(s):  
Continuous Flow ◽  
Precious Metal ◽  
Flow Reactor ◽  
Catalyst Surface ◽  
Catalyst Support ◽  
Regeneration Strategy ◽  
Continuous Flow Reactor ◽  
Pd Nanowires ◽  
Metal Nanowire

The first precious-metal nanowire-based catalytic flow-reactor involving no catalyst-support, maximized catalyst surface, usability across different filtration platforms, and its in situ regeneration strategy are presented.

scholarly journals Performances of Homogeneous and Heterogenized Methylene Blue on Silica Under Red Light in Batch and Continuous Flow Photochemical Reactors

2021 ◽  
Vol 3 ◽  
Author(s):  
Maxime Lancel ◽  
Catherine Gomez ◽  
Marc Port ◽  
Zacharias Amara
Keyword(s):  
Mass Transfer ◽  
Methylene Blue ◽  
Continuous Flow ◽  
Electrostatic Interactions ◽  
Flow Reactor ◽  
Red Light ◽  
Model Reaction ◽  
Catalytic Systems ◽  
Transfer Properties

Methylene blue was efficiently immobilized on silica micro- and nanoparticles by electrostatic interactions and the performances of the heterogenized photocatalysts were compared against the homogeneous conditions using the photooxidation of citronellol as a model reaction under red light, in a batch and a continuous flow photochemical reactor. In batch, the heterogeneous photocatalyst outperforms the homogeneous one, presumably due to kinetic and stability effects. The two catalytic systems are also compared in a flow reactor displaying improved mass transfer properties. We demonstrate that this results in a dramatic enhancement in photocatalyst stability, reactivity and productivity. This study highlights the importance of photocatalyst stability under homogeneous versus heterogenized conditions and in batch versus flow photochemistry.

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