Improving Productivity of Multiphase Flow Aerobic Oxidation Using a Tube-in-Tube Membrane Contactor

The application of flow reactors in multiphase catalytic reactions represents a promising approach for enhancing the efficiency of this important class of chemical reactions. We developed a simple approach to improve the reactor productivity of multiphase catalytic reactions performed using a flow chemistry unit with a packed bed reactor. Specifically, a tube-in-tube membrane contactor (sparger) integrated in-line with the flow reactor has been successfully applied to the aerobic oxidation of benzyl alcohol to benzaldehyde utilizing a heterogeneous palladium catalyst in the packed bed. We examined the effect of sparger hydrodynamics on reactor productivity quantified by space time yield (STY). Implementation of the sparger, versus segmented flow achieved with the built in gas dosing module (1) increased reactor productivity 4-fold quantified by space time yield while maintaining high selectivity and (2) improved process safety as demonstrated by lower effective operating pressures

Microwave-assisted synthesis of Pd nanoparticles supported on Fe 3O4, Co3O4, and Ni(OH)2 nanoplates and catalysis application for CO oxidation

In this paper, we report a simple, versatile, and rapid method for the synthesis of Pd nanoparticle catalysts supported on Fe3O4, Co3O4, and Ni (OH)2 nanoplates via microwave irradiation. The important advantage of microwave dielectric heating over convective heating is that the reactants can be added at room temperature (or slightly higher temperatures) without the need for high-temperature injection. Furthermore, the method can be used to synthesize metal nanoparticle catalysts supported on metal oxide nanoparticles in one step. We also demonstrate that the catalyst-support interaction plays an important role in the low temperature oxidation of CO. The current results reveal that the Pd/Co3O4 catalyst has particularly high activity for CO oxidation as a result of the strong interaction between the Pd nanoparticles and the Co 3O4 nanoplates. Optimizations of the size, composition, and shape of these catalysts could provide a new family of efficient nanocatalysts for the low temperature oxidation of CO. © 2014 Springer Science+Business Media

Pd-Fe3O4/RGO: a Highly Active and Magnetically Recyclable Catalyst for Suzuki Cross Coupling Reaction using a Microfluidic Flow Reactor

There are several crucial issues that need to be addressed in the field of applied catalysis. These issues are not only related to harmful environmental impact but also include process safety concerns, mass and heat transfer limitations, selectivity, high pressure, optimizing reaction conditions, scale-up issues, reproducibility, process reliability, and catalyst deactivation and recovery. Many of these issues could be solved by adopting the concept of micro-reaction technology and flow chemistry in the applied catalysis field. A microwave assisted reduction technique has been used to prepare well dispersed, highly active Pd/Fe3O4 nanoparticles supported on reduced graphene oxide nanosheets (Pd-Fe3O4/RGO), which act as a unique catalyst for Suzuki cross coupling reactions due to the uniform dispersion of palladium nanoparticles throughout the surface of the magnetite - RGO support. The Pd-Fe3O4/RGO nanoparticles have been shown to exhibit extremely high catalytic activity for Suzuki cross coupling reactions under both batch and continuous reaction conditions. This paper reported a reliable method for Suzuki cross-coupling reaction of 4-bromobenzaldehyde using magnetically recyclable Pd/Fe3O4 nanoparticles supported on RGO nanosheets in a microfluidic-based high throughput flow reactor. Organic synthesis can be performed under high pressure and temperature by using a stainless steel micro tubular flow reactor under continuous flow reaction conditions. Optimizing the reaction conditions was performed via changing several parameters including temperature, pressure, and flow rate. Generally, a scalable flow technique by optimizing the reaction parameters under high-temperature and continuous reaction conditions could be successfully developed

The Effect Of Graphene On Catalytic Performance Of Palladium Nanoparticles Decorated With Fe3O4, Co3O4, And Ni (OH)2: Potential Efficient Catalysts Used For Suzuki Cross—Coupling

Abstract: In this research, we report a scientific investigation of an efficient method used for the synthesis of highly active Palladium Nanoparticles decorated with Fe3O4, Co3O4, and Ni (OH)2 Supported on Graphene as Potential Efficient Catalysts for Suzuki Cross—Coupling. Pd/Fe3O4 nanoparticles supported on graphene nanosheets (Pd/Fe3O4/G) showed an excellent catalytic activity for Suzuki coupling reactions and recycled for up to four times without loss of catalytic activity. An efficient magnetic catalyst has been successfully synthesized using a simple, reproducible fast and reliable method using microwave irradiation conditions. The prepared catalysts are magnetic as in case of iron and cobalt oxides which is an advantage in the separation process of catalyst from the reaction medium via applying a strong external magnetic field. The synthesis approach is based on the Microwave (MW)-assisted simultaneous reduction of palladium and ferric nitrates in the presence of graphene oxide (GO) nanosheets using hydrazine hydrate as the reducing agent. The results provide a fundamental understanding of the system variables by comparing the catalytic activity and recyclability of different catalysts with different properties. The most active and recyclable catalyst was Pd–Fe3O4—supported on graphene which offers several added advantages including recyclability of up to seven times, mild reaction conditions, and short reaction times in an environmentally benign solvent system. Furthermore, the magnetic properties imparted by the Fe3O4 component of the catalyst enables the catalyst to be easily isolated and recycled, thus greatly simplifying the ability to purify the reaction products and increasing the economic value of the catalyst. The utility of these magnetic catalysts towards Suzuki cross coupling reaction was also demonstrated. The high activity and recyclability of these catalysts are attributed to a strong catalyst-support interaction where the defect sites in the reduced GO nanosheets act as nucleation centers for anchoring the Pd and Fe3O4 nanoparticles thus minimizing the potential of their agglomeration and the subsequent decrease in the catalytic activity. Graphical Abstract: [Figure not available: see fulltext.]

The Continuous Synthesis Of Pd Supported On Fe3O4 Nanoparticles: A Highly Effective And Magnetic Catalyst For CO Oxidation

We report a facile approach used for the simultaneous reduction and synthesis of a well dispersed magnetically separable palladium nanoparticle supported on magnetite (Pd/Fe3O4 nanoparticles) via continuous flow synthesis under microwave irradiation conditions, using a Wave Craft\u27s microwave flow reactor commercially known as Arrhenius One, which can act as a unique process for the synthesis of highly active catalysts for carbon monoxide (CO) oxidation catalysis. The prepared catalysts are magnetic, which is an advantage in the separation process of the catalyst from the reaction medium. The separation process is achieved by applying a strong external magnetic field which makes the separation process easy, reliable, and environmentally friendly. Hydrazine hydrate was used as the reducing agent under continuous flow reaction conditions. The investigated catalysis data revealed that palladium supported on iron oxide catalyst synthesized by continuous flow microwave irradiation conditions showed remarkable high catalytic activity towards CO oxidation compared to the ones that were prepared by batch reaction conditions under the same experimental conditions. This could be attributed to the high degree of dispersion and concentration ratio of the Pd nanoparticles dispersed on the surface of magnetite (Fe3O4) with a small particle size of 5-8 nm due to the effective microwave-Assisted reduction method under continuous flow conditions. These nanoparticles were further characterized by a variety of spectroscopic techniques including X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and transmission electron microscopy (TEM)

The Growth Cone Cytoskeleton in Axon Outgrowth and Guidance

Axon outgrowth and guidance to the proper target requires the coordination of filamentous (F)-actin and microtubules (MTs), the dynamic cytoskeletal polymers that promote shape change and locomotion. Over the past two decades, our knowledge of the many guidance cues, receptors, and downstream signaling cascades involved in neuronal outgrowth and guidance has increased dramatically. Less is known, however, about how those cascades of information converge and direct appropriate remodeling and interaction of cytoskeletal polymers, the ultimate effectors of movement and guidance. During development, much of the communication that occurs between environmental guidance cues and the cytoskeleton takes place at the growing tip of the axon, the neuronal growth cone. Several articles on this topic focus on the “input” to the growth cone, the myriad of receptor types, and their corresponding cognate ligands. Others investigate the signaling cascades initiated by receptors and propagated by second messenger pathways (i.e., kinases, phosphatases, GTPases). Ultimately, this plethora of information converges on proteins that associate directly with the actin and microtubule cytoskeletons. The role of these cytoskeletal-associated proteins, as well as the cytoskeleton itself in axon outgrowth and guidance, is the subject of this article

Integrin Signaling Switches the Cytoskeletal and Exocytic Machinery that Drives Neuritogenesis

Neurons establish their unique morphology by elaborating multiple neurites that subsequently form axons and dendrites. Neurite initiation entails significant surface area expansion, necessitating addition to the plasma membrane. We report that regulated membrane delivery coordinated with the actin cytoskeleton is crucial for neuritogenesis, and identify two independent pathways that use distinct exocytic and cytoskeletal machinery to drive neuritogenesis. One pathway employs Ena/VASP-regulated actin dynamics coordinated with VAMP2-mediated exocytosis, and involves a novel role for Ena/VASP in exocytosis. A second mechanism occurs in the presence of laminin through integrin-dependent activation of FAK and src, and utilizes coordinated activity of the Arp2/3 complex and VAMP7-mediated exocytosis. We conclude that neuritogenesis can be driven by two distinct pathways that differentially coordinate cytoskeletal dynamics and exocytosis. These regulated changes and coordination of cytoskeletal and exocytic machinery may be utilized in other physiological contexts involving cell motility and morphogenesis.Jane Coffin Childs Memorial Fund for Medical ResearchNational Institutes of Health (U.S.) (NIH grant GM68678)Stanley Medical Research Institut

5′-Inositol phosphatase SHIP2 recruits Mena to stabilize invadopodia for cancer cell invasion

Invadopodia are specialized membrane protrusions that support degradation of extracellular matrix (ECM) by cancer cells, allowing invasion and metastatic spread. Although early stages of invadopodia assembly have been elucidated, little is known about maturation of invadopodia into structures competent for ECM proteolysis. The localized conversion of phosphatidylinositol(3,4,5)-triphosphate and accumulation of phosphatidylinositol(3,4)-bisphosphate at invadopodia is a key determinant for invadopodia maturation. Here we investigate the role of the 5′-inositol phosphatase, SHIP2, and reveal an unexpected scaffold function of SHIP2 as a prerequisite for invadopodia-mediated ECM degradation. Through biochemical and structure-function analyses, we identify specific interactions between SHIP2 and Mena, an Ena/VASP-family actin regulatory protein. We demonstrate that SHIP2 recruits Mena, but not VASP, to invadopodia and that disruption of SHIP2–Mena interaction in cancer cells leads to attenuated capacity for ECM degradation and invasion in vitro, as well as reduced metastasis in vivo. Together, these findings identify SHIP2 as a key modulator of carcinoma invasiveness and a target for metastatic disease