Preparation of nano-structured catalysts

gold catalysts have been found to be effective for many oxidation reactions and it is known that the performance of these catalysts depends strongly on the particle size of Au nanoparticles. However, other factors have strong influence on the catalytic activity such as the preparation methods, choice of support, the structure and morphology of supports. The effect of support morphology and structure on the activity of Au catalysts was investigated using two hydrothermally prepared supports, CeO2 and MnO2. Ceria foams as a support for nano-clusters of gold were synthesised hydrothermally at 160 °C by the reaction of L-Asparagine and CeCl3.7H2O at different crystallisation times. The effect of the reaction time on the morphology of prepared CeO2 was investigated. The morphology varied remarkably and it was found to change from spherical particles to foam and eventually to a collapsed foam as the crystallisation time increased. Gold catalysts were prepared by sol-immobilisation, supported on the foam ceria and examined for solvent free oxidation of benzyl alcohol using molecular O2 as an oxidant and the effect of the support was compared with commercial ceria. Au/CeO2 foam catalysts were more active than the Au/commercialCeO2 although the Au nanoparticles were larger in ceria foam supports. This was due to the greater lability of surface oxygen in the foam support compared with commercial CeO2 materials. The Au/CeO2 foam catalyst was found to be reusable over three experiments. The effect of catalyst loading, oxygen pressure and reaction time-online were also studied. It was found that there was no mass transfer limitation when the mass of catalyst varied from 5 to 40 mg under the reaction conditions. The conversion of benzyl alcohol decreased as the oxygen pressure decreased which shows that oxygen was involved in the oxidation process. For time-online study, the conversion increased as the reaction time increased with slightly increase. MnO2 supports were synthesised by reacting MnSO4.H2O with (NH4)2S2O8 hydrothermally at 160 °C. Two different phases and morphologies of MnO2 were formed and as the reaction time increased the morphology changed from microspheres to nanowires and the MnO2 phase changed from α- to β-. Gold was deposited on all prepared MnO2 materials and the catalysts were examined for solvent free benzyl alcohol and CO oxidation. The influence of the preparation method on the catalytic activity was studied and sol-immobilisation was found to be the best for benzyl alcohol VII oxidation whereas the deposition-precipitation was found to be the best for CO oxidation. Impregnation method exhibited poor activity for both reactions. The effect of the morphology and phase on the catalyst activity for both reactions was researched and Au/α-MnO2 microspheres catalysts were best for benzyl alcohol oxidation while Au/β- MnO2 nanowires catalysts exhibited better performance for CO oxidation due to their smaller Au nanoparticles and easier surface reduction. The catalysts reusability, timeonline and the effect of catalyst loading were also studied of an Au/MnO2 microsphere catalyst for benzyl alcohol oxidation reaction. Vanadium phosphate catalysts have been extensively studied for the selective oxidation of butane to maleic anhydride. The catalytic activity of vanadium phosphates is greatly dependant on the preparation method of the catalyst precursor VOHPO4·0.5H2O. Poly (acrylic acid-co-maleic acid) copolymer, PAAMA, was employed as a structure directing agent in the preparation of VOHPO4.0.5H2O via two routes. The effect of PAAMA concentration on the structure morphology of VOHPO4·0.5H2O was studied in both preparation routes. As the concentration of PAAMA increased the morphology changed from rosette like for the standard precursors to rosette-like agglomerates with isolated rhomboidal platelets and eventually to isolated rhomboidal platelets at highest concentration of PAAMA. The XRD confirmed that all precursors were VOHPO4·0.5H2O but as the concentration of PAAMA increased the (001) reflection increased and the (220) reflection decreased. When these precursors were tested for butane selective oxidation, the standard precursors that contain rosettes VPO0 and VPD0 activated to the active phase ((VO)2P2O7) over typically observed time (> 100 h). While the precursors that had rosette-like agglomerates with isolated rhomboidal platelets and a relative intensity ratio of the (001)/(220) reflections of around 1.4, VPO5 and VPD15, activated much faster, less than 20 h with a comparable conversion and selectivity. The isolated rhomboidal platelets precursors which had a high relative intensity ratio of the (001)/(220) reflections, VPO15, VPO25 and VPD25, displayed very poor activity because the thin platelets were rapidly oxidised to αII-VOPO4 phase as confirmed by the XRD and Laser Raman Spectroscopy

Highly crystalline vanadium phosphate catalysts synthesized using poly(acrylic acid-co-maleic acid) as a structure directing agent

Vanadium phosphate catalysts have been widely studied for the selective oxidation of alkanes to a variety of products, including maleic and phthalic anhydride. More recently they are starting to find use as low temperature liquid phase oxidation catalysts. For all these applications the synthesis of the precursor is key to the performance of the final catalyst. Changes in the preparation procedure can alter the morphology, surface area, crystallinity, oxidation state and the phases present in the final catalyst which can all affect the selectivity and/or activity of the catalyst. Adding a diblock copolymer, poly(acrylic acid-co-maleic acid) (PAAMA), during the synthesis was found to influence the crystallinity and morphology of the VOHPO4·0.5H2O precursors obtained. An optimal level of copolymer was found to form precursors that showed a faster, more efficient, activation to the active catalyst, whereas high amounts of copolymer formed thin platelets, which were prone to oxidise to undesirable V5+ phases under reaction conditions, reducing the selectivity to maleic anhydride

Multicenter, real-life experience with checkpoint inhibitors and targeted therapy agents in advanced melanoma patients in Switzerland.

Metastatic melanoma is a highly aggressive disease. Recent progress in immunotherapy (IT) and targeted therapy (TT) has led to significant improvements in response and survival rates in metastatic melanoma patients. The current project aims to determine the benefit of the introduction of these new therapies in advanced melanoma across several regions of Switzerland. This is a retrospective multicenter analysis of 395 advanced melanoma patients treated with standard chemotherapy, checkpoint inhibitors, and kinase inhibitors from January 2008 until December 2014. The 1-year survival was 69% (n=121) in patients treated with checkpoint inhibitors (IT), 50% in patients treated with TTs (n=113), 85% in the IT+TT group (n=66), and 38% in patients treated with standard chemotherapy (n=95). The median overall survival (mOS) from first systemic treatment in the entire study cohort was 16.9 months. mOS of patients treated either with checkpoint or kinase inhibitors (n=300, 14.6 months) between 2008 and 2014 was significantly improved (P<0.0001) compared with patients treated with standard chemotherapy in 2008-2009 (n=95, 7.4 months). mOS of 61 patients with brain metastases at stage IV was 8.1 versus 12.5 months for patients without at stage IV (n=334), therefore being significantly different (P=0.00065). Furthermore, a significant reduction in hospitalization duration compared with chemotherapy was noted. Treatment with checkpoint and kinase inhibitors beyond clinical trials significantly improves the mOS in real life and the results are consistent with published prospective trial data

Oxidation of benzyl alcohol and carbon monoxide using gold nanoparticles supported on MnO2 nanowire microspheres

MnO2 was synthesised as a catalyst support material using a hydrothermal method. This involved reacting MnSO4⋅H2O and (NH4)2S2O8 at 120 °C for a range of crystallisation times, which affords control over the morphology and phase composition of the MnO2 formed. Gold was deposited on these supports using sol-immobilisation, impregnation and deposition precipitation methods, and the resultant materials were used for the oxidation of benzyl alcohol and carbon monoxide. The effect of the support morphology on the dispersion of the gold nanoparticles and the consequent effect on the catalytic performance is described and discussed

Nickel Nanoparticles Decorated on Glucose-Derived Carbon Spheres as a Novel, Non-Palladium Catalyst for Epoxidation of Olefin

Carbon spheres supporting nickel nanoparticles (NPs), generated by the integration of hydrothermal and microwave irradiation techniques, catalyzed the epoxidation of 1-octene, cyclooctene, styrene, allyl alcohol, and cyclohexene. The average particle sizes of the carbon spheres (CSs) and nickel oxide species immobilized on the CSs were 240 nm and 26 nm, respectively. The fabricated composites incorporating nickel NPs showed higher activity in the cyclohexene epoxidation process. The cyclohexene conversion was enhanced by raising the Ni loading to 10%. Within 14 h, the cyclohexene conversion had grown to 98%. This robust catalytic activity can be attributed to the efficient distribution of Ni species on the CSs, the facile lowering of the surface, and the development of uniformly nanosized species. The composite exhibited good recyclability across at least five cycles (which is not a simple task involving nickel-nanoparticle-based catalysts that are employed in water), and no nickel species leached into the solution, making the total system environmentally benign and cost-effective

Catalytic activity of bimetallic AuPd alloys supported MgO and MnO2 nanostructures and their role in selective aerobic oxidation of alcohols

The use of metal oxides as supports for gold and palladium (Au-Pd) nano alloys constitutes new horizons to improve catalysts materials for very important reactions. From the literatures, Pd-based bimetallic nanostructures have great properties and active catalytic performance. In this study, nanostructures of magnesium oxide (MgO) and manganese dioxide (MnO₂) were synthesised and utilized as supports for Au-Pd nanoparticle catalysts. Gold and palladium were deposited on these supports using sol-immobilisation method. The MgO and MnO2 supported Au-Pd catalysts were evaluated for the oxidation of benzyl alcohol and 1-octanol, respectively. These catalysts were found to be more selective, active and reusable than the corresponding monometallic Au and Pd catalysts. The effect of base supports on the disproportionation reaction during the oxidation process was investigated. The results show that MgO stopped the disproportionation reaction for both aromatic and aliphatic alcohols while MnO₂ stopped it in the case of benzyl alcohol only. The outcomes of this work shed light on the selective aerobic oxidation of alcohols using bimetallic Au-Pd nanoalloys and pave the way to a complete investigation of more basic metal oxides for various aliphatic alcohols

Selective oxidation of benzyl alcohol using in situ generated H 2O2 over hierarchical Au-Pd titanium silicalite catalysts

Benzyl alcohol was oxidized by an in situ generated hydrogen peroxy species, formed from a dilute mixture of hydrogen and oxygen, under mild conditions at a high rate over gold, palladium and gold-palladium nanoparticles supported on hierarchical titanium silicate materials. Hierarchical TS-1 supports were obtained from the crystallization of silanized protozeolitic units, being characterized by having a secondary porous system within supermicro/mesopore range and an enhanced surface area over a standard reference TS-1 material. The presence of the secondary porosity not only improves the accessibility to the active sites of the relatively large reactant molecules but also enhances the metal dispersion, leading to an improved catalytic performance for alcohol oxidation. The catalytic activity of metal loaded hierarchical TS-1 materials was found to be higher in reactions conducted in the presence of diluted hydrogen and oxygen, resulting in a 5-fold increase in the yield of benzaldehyde at 30 °C with an AuPd catalyst with secondary porosity. The improvement in rate observed is due to the oxidizing efficacy of in situ generated hydroperoxy species as compared to molecular oxygen alone as the terminal oxidant

Biogenic-Mediated Synthesis of Mesoporous Cu2O/CuO Nano-Architectures of Superior Catalytic Reductive towards Nitroaromatics

Cu2O/CuO nano-architectures were prepared by biogenic-mediated synthesis using pomegranate seeds extract as the reducing/stabilizing mediator during an aqueous solution combustion process of the Cu2+ precursor. The fabricated Cu2O/CuO nanocomposite were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and nitrogen sorption. Nitrobenzene (NB) was applied a probe to test the catalytic activities of the fabricated Cu2O/CuO nanocomposite. The results indicated that pomegranate seeds extract (PSE) manifest Cu2O/CuO NPs of tiny particle size, larger pore volume and greater surface area compared to the bulky CuO synthesized in the absence of PSE. The surface area and total pore volume of Cu2O/CuO NPs were 20.1 m2 g−1 and 0.0362 cm3 g−1, respectively. The FESEM image shows the formation of broccoli-like architecture. The fabricated Cu2O/CuO nanocomposite possesses surprising activity towards the reduction of nitro compounds in the presence of NaBH4 into amino compounds with high conversion (94%). The reduction process was performed in water as a green solvent. Over four consecutive cycles the resulting nanocomposite also exhibits outstanding stability. In addition, the resulting Cu2O/CuO nanocomposite suggested herein may encourage scientists to start preparing more cost-effective catalysts for marketing instead of complicated catalysts

Chitosan Polymer Functionalized-Activated Carbon/Montmorillonite Composite for the Potential Removal of Lead Ions from Wastewater

A simple approach for synthesizing a highly adsorbent composite was described for the uptake of heavy metal ions from wastewater. A simple approach for synthesizing a highly adsorbent composite was also described for the elimination of heavy metal ions from contaminated water. The nanocomposite was synthesized via a polymer grafting of chitosan on the activated carbon surface, followed by a stacking process with the layers of montmorillonite clay. The spectroscopic analyses were exploited to confirm the composite structure of the prepared materials. Various adsorption parameters, such as pH, initial concentration, and adsorption time, were assessed. The results showed that the adsorption capacity of the composite for Pb2+ ions increased as the pH increased until it reached pH 5.5. The maximum adsorption capacity was observed at an initial Pb2+ level of 20 mg/L and a contact time of 150 min. Kinetic models were evaluated, and the pseudo second-order model showed the best match. The adsorption isotherm data were processed by fitting the model with different isotherm behaviors, and the Langmuir isotherm was found to be the most suitable for the system. The maximum adsorption capacity for Pb2+ ion on the MMT/CS/AC composite was found to be 50 mg/g at pH 5.5. Furthermore, the composite maintained a high adsorption capability of 85% for five adsorption–desorption cycles. Overall, this composite is envisioned as an addition to the market of wastewater remediation technology due to its chemical structure, which provides influential functional groups for wastewater treatment