Structured silicalite-1 encapsulated Ni catalyst supported on SiC foam for dry reforming of methane

Structured silicalite-1 zeolite encapsulated Ni catalyst supported on silicon carbide foam (i.e., Ni@S1-SiC) was prepared using a new yet simple one-pot method, showing the significantly improved anti-sintering and anti-coking performance in comparison with the conventional supported and encapsulated Ni catalysts (i.e., Ni/S1, Ni/S1-SiC, and Ni@S1), in catalytic dry reforming of methane (DRM). The developed Ni_0.08@S1-SiC catalyst showed high CO₂/CH₄ conversions of >85% and H₂/CO molar ratio of >0.85 at 700°C, outperforming other control catalysts under investigation. Additionally, the Ni_0.08@S1-SiC catalyst demonstrated high turnover frequency (TOF) values of ~5.6 and ~2.1/s regarding to CO₂/CH₄ conversions at 400°C, exhibiting excellent stability and low pressure-drop during 100 hr on stream evaluation. Post-reaction characterization of the used catalysts demonstrated that the combination of zeolite encapsulated Ni catalysts and SiC foam enabled well-dispersed and ultrafine Ni nanoparticles, low pressure drop and intensified transfer steps, presented excellent anti-sintering and anti-coking abilities.     

The effect of the degree of deacetylation of chitosan on its dispersion of carbon nanotubes

The effect of the degree of deacetylation (DD) of chitosan biopolymer on the noncovalent surface modification of multiwall carbon nanotubes (MWCNTs) is presented. MWCNTs were modified by chitosan having different degree of deacetylation (61%, 71%, 78%, 84%, 90% and 93%) and UV-Visible spectroscopy was used to evaluate their dispersion efficiency as a function of chitosan concentration and degree of deacetylation. Results showed that the dispersion of MWCNTs could be dramatically improved when using chitosan with the lowest degree of deacetylation (61%DD) possibly due to a higher surface coverage of the MWCNTs. Zeta potential measurements were used to confirm that the chitosan surface coverage on the MWCNTs was twice as high when modifying the nanotubes surface with the 61%DD than when using the 93%DD chitosan. These results suggest that the dispersion of MWCNTs with chitosan can be improved when using chitosan having a degree of deacetylation of 61%. These results are of interest in particular for the improved dispersion of MWCNTs in aqueous solutions such as in drug delivery applications.     

Comparative Carbon Footprint of Packaging Systems for Tuna Products

The present study aimed to evaluate and compare the carbon footprint associated with canned tuna meat with a focus on packaging systems used to provide one single‐serve meal. The manufacturing process of retort pouches and cups produced 60% and 70% less greenhouse gas emissions, respectively, than that of metal cans. However, the overall carbon footprint of canned tuna in retort cups was 10% and 22% less than when packaged in metal cans and retort pouches, respectively. Packaging and its associated processing constituted significant fractions of the product's carbon footprint, ranging from 20% to 40%. Hotspots in the life cycle assessment of canned tuna are packaging production and disposal and product sterilization. The improvement of retort operation in terms of capacity and energy utilization and the efficiency of post‐consumption packaging material recovery are the key factors responsible for the reduction of a product's carbon footprint. These issues present a challenge to both the food industry and the local authorities. Copyright © 2011 John Wiley & Sons, Ltd.     

The versatile synthesis method for hierarchical micro‐ and mesoporous zeolite: An embedded nanocarbon cluster approach

In this work, we are reporting for the first time the synthesis of hierarchical micro‐ and mesoporous zeolite using silica–carbon (SiO₂/C) composites prepared by pyrolysis of carbonaceous gases in the presence of silica gel. The pyrolysis effectively yielded carbon deposited onto the raw silica material. The obtained SiO₂/C composites were utilised as a bifunctional material, mesoporous template and silica source, for the zeolite synthesis. Tetrapropylammonium hydroxide (TPAOH) was used as a microporous template. The combination of the obtained composites and the TPAOH for the hydrothermal synthesis resulted in the formation of hierarchical micro‐ and mesoporous ZSM‐5. The results from the SEM, TEM, and N₂ adsorption/desorption isotherms, and ²⁷Al MAS NMR characterisations of the synthesised samples obtained after the removal of the templates confirmed the successful formation of the micro‐ and mesoporous zeolites. The mesoporosity of the zeolites could be controlled by adjusting the carbon content in the SiO₂/C composites while the carbon content could be controlled by varying the deposition time and the concentration of the carbonaceous gases used. This controllable and efficient synthesis method is considered to be a promising method for creating hierarchical micro‐ and mesoporous zeolites. © 2011 Canadian Society for Chemical Engineering     

Assembly of polyelectrolyte multilayers on nylon fibers

Non‐woven nylon fibers were investigated as a new type of substrate for the deposition of polyelectrolyte multilayers (PEM) thin films. PEM assembled from cationic poly(diallyldimethylammonium chloride) PDADMAC, and anionic Scarlet dye (λ_max absorbance = 510 nm) were deposited directly on Nylon fibers and characterized using a reflectometer spectrophotometer. Evidences of the film assembly are presented as well as a study of the factors controlling the growth of the PDAMAC/dye PEM film on the fiber. The relation between the sorption coefficient (K) and the scattering (S) extracted from the reflectance data is commonly used to represent the dye fixation or the dye content of a given textile fiber. The increase in K/S value at 510 nm was correlated with the dye deposition and was found to increase linearly with the number of layers. The effect of increasing number of layers, ionic strength of the solutions, concentration of chemicals, and dipping time on the film growth was investigated. Our results show that while increase in dye and PDADMAC concentrations from 0 to 1 mM enhance the deposition process, further increase in PDADMAC concentration to 50 mM led to a decrease in K/S value. The optimum salt concentration for the PDAMAC/dye film growth was found to be 0.5M and dipping times as short as 15 s were found to be sufficient for the deposition of the PEM. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3286–3290, 2006     

Simple method for the layer-by-layer surface modification of multiwall carbon nanotubes

A simplified method for the surface modification of multiwall carbon nanotubes (MWCNTs) using the layer-by-layer (LbL) technique is proposed. In this approach, the minimum polyelectrolyte content was added to the solution in order to eliminate the tedious centrifugation step. The one pot LbL deposition of poly (diallyldimethylammonium chloride) (PDADMAC), and poly (sodium 4-styrenesulfonate), (PSS) is presented. UV–Vis spectroscopy and zeta potential measurements were used to determine the minimum PDADMAC and PSS concentration needed for the deposition of each polyelectrolyte layer. The deposition cycle was repeated until six layers of PDADMAC/PSS were deposited. The film growth was confirmed by transmission electron microcopy and was found to increase as a function of the number of deposited layers with a final thickness of 18 nm. Evidence of the alternate deposition of oppositely charged polyelectrolytes was further investigated by measurement of the zeta potential values which were found to reverse from positive to negative as a function of the number of deposited layers thus confirming the overcompensation of the surface charge at each adsorption step. This simple method could be useful for the fast preparation of large volumes of MWCNTs solutions in a single batch without the need for centrifugation step.     

Impact of Production and Conversion Processes on the Carbon Footprint of Flexible Plastic Films

The present study aimed to identify and compare the carbon footprint associated with polyolefin films (linear low‐density polyethylene, high‐density polyethylene and polypropylene), with the idea of developing a simple and affordable empirical method to assist the flexible packaging industry, notably small and medium‐sized enterprises, in estimating the carbon footprint of different products or of new products at the early stage of development. It was found that the total global warming potential (GWP) of the studied films increased 19–67% during processing when compared with the GWP embodied in plastic resins. This indicated that film production processes greatly contribute to the carbon footprint of plastic films. The relative impact of the film‐making process on the total GWP of films is largely a function of plastic type, in particular, its melting point. Printing and lamination processes also contribute significantly to the total GWP of films, with the major factor being electricity use. The constant k was derived to indicate the influences of plastic types and manufacturing processes on the total GWP of films and to help calculate the carbon footprint of polyolefin films for which the production process and weight are known. Moreover, the GWP of each studied film was normalized with respect to film thickness and area. This information would be useful for packaging manufacturers and users to calculate the carbon footprint of multilayer films. The proposed empirical model showed satisfactory results, as the difference was less than 10% when compared with the results obtained from life cycle assessment studies. Copyright © 2014 John Wiley & Sons, Ltd.     

Structure-Activity Relationships of Pt-WOx/Al2O3 Prepared with Different W Contents and Pretreatment Conditions for Glycerol Conversion to 1,3-Propanediol

Topics in Catalysis - Turning waste glycerol into a fundamental chemical used in the petrochemical industry offers an opportunity to reduce not only waste from biodiesel production but also the...