Enhanced thermal stability of biomedical thermoplastic polyurethane with the addition of cellulose nanocrystals

Freeze‐dried cellulose nanocrystals (CNCs) were dispersed in the thermoplastic polyurethane [Pellethane 2363‐55D (P55D)] by a solvent casting method to fabricate CNC‐reinforced nanocomposites. This study demonstrated that the addition of small amounts (1–5 wt %) of CNCs to P55D increased the thermal degradation temperature while maintaining a similar stiffness, strength, and elongation of the neat P55D. CNC additions to P55D did not alter the glass‐transition temperature, but the onset decomposition temperature was shifted from 286 to 327°C when 1 wt % CNCs was dispersed in the matrix. The higher onset decomposition temperature was attributed to the formation of hydrogen bonds between the hydroxyl groups on the CNC surface and urethane groups in the hard block of P55D. The ultimate tensile strength and strain to failure (ε_f) of the nanocomposites were minimally affected by additions up to 5 wt % CNCs, whereas the elastic modulus was increased by about 70%. The observation that ε_f was unchanged with the addition of up to 5 wt % CNCs suggested that the flow/sliding of the hard blocks and chains were not hindered by the presence of the CNCs during plastic deformation. The ramifications of this study was that CNC additions resulted in wider processing temperatures of P55D for various biomedical devices while maintaining a similar stiffness, strength, and elongation. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41970.     

Deep oxidation of VOC mixtures with platinum supported on Al2O3/Al monoliths

Pt impregnated metallic monoliths prepared from anodised aluminium foils were tested to study their catalytic activity in complete oxidation of volatile organic compound (VOC) mixtures. The VOCs oxidised were 2-propanol, toluene, methyl ethyl ketone (MEK), acetone and their mixtures. Complete oxidation was obtained in all cases except for the case of 2-propanol, where acetone was found as an oxidation intermediate. Even if the adsorption of the VOC on the Al₂O₃ is governed by its polarity, the reactivity is mainly affected by the competition of the oxygen atoms chemisorbed on the Pt particles.     

Structure,texture and surface acidity studies of a series of mixed zinc–aluminum (60–90 molar % Al) phosphate catalysts

A series of mixed zinc–aluminum phosphate (ZnAlP) catalysts containing 40–90 aluminum molar % were synthesized by a coprecipitation method and characterized by nitrogen adsorption–desorption, X‐ray diffraction, FTIR spectroscopy, thermogravimetric analysis (TGA), differential thermal analysis (DTA), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and temperature programmed desorption (TPD) of ammonia. The presence of aluminum greatly affected the surface properties of Zn₃(PO₄)₂ by delaying the crystallization process of Zn₃(PO₄)₂. All amorphous samples were shown to be mesoporous and they contained two types of aluminum surface hydroxyl groups and one type of phosphorus hydroxyl group, as shown by DRIFT spectra. The specific surface area and the acidity of ZnAlP increased on increasing the aluminum content. On the other hand, a great difference in the texture and the concentration of surface acid sites was found by changing the precipitating agent and calcination temperature. Thus these factors also play an important role in the final properties of these catalysts. © 2001 Society of Chemical Industry     

FAME Production and Fatty Acid Profiles from Moist Chlorella sp. and Nannochloropsis oculata Biomass

In the present study, we investigated the production of fatty acid methyl esters (FAME) from moist Chlorella sp. and Nannochloropsis oculata biomass using a hydrolysis–esterification process. Additionally, we evaluated for the first time the fatty acid profile before and after this process. Hydrolysis of the lipid fraction was performed on a moist biomass in the presence of differing amounts of an acid catalyst in both 50 and 100 % w/w water relative to the biomass. The esterification of the crude extracts of the free fatty acids (FFA) was then investigated. The experiments show that in the presence of 50 % w/w water relative to the biomass, the hydrolysis–esterification process results in higher FFA and FAME yields. The analysis of the fatty ester profiles did not reveal any degradation of the FFA from the microalgae biomass under the hydrolysis–esterification conditions. The results were compared with both extraction–transesterification and direct transesterification processes using dry biomass. The extraction–transesterification and hydrolysis–esterification processes resulted in similar FAME yields and similar profiles of the fatty esters from dry and moist biomass materials, respectively.     

FLOCCULATION/COAGULATION OF NATURAL ORGANIC MATTER FOR PRETREATMENT OF WATER AND WASTE WATER

Characterization of water, waste water and natural organic matter are involved in this paper, and as well as the features of flocculation and coagulation for removing natural organic matter from water and waste water Novel flocculant and coagualant is strongly asked for improving removal efficiency and environment friendly. Enhanced coagulation is introduced to meet the experimental and practical requirement.     

Effect of the reducing agent on the hydrodechlorination of dioxins over 2 wt.% Pd/γ-Al2O3

2-Propanol and molecular H₂ (in methanol (MeOH) and MeOH–water) were examined as reducing agents for the liquid phase hydrodechlorination (HDC) of dioxins over 2 wt.% Pd/γ-Al₂O₃. Different amounts of NaOH were added to the reaction mixtures. The 2-propanol and H₂(g)/MeOH systems presented similar HDC activity. Notwithstanding, Pd sintering and graphitic carbon directly bonded to Pd on catalyst surface was observed on samples used with H₂(g)/MeOH. The addition of water to H₂(g)/MeOH decreased Pd sintering and favored dissolution of sodium compounds. However, dioxin degradation efficiency diminished. By contrast, 2-propanol acting both as reducing agent and solvent provided hydrogen to the HDC reaction, avoided metal sintering and Pd–C formation. Besides, almost complete dioxin degradation under mild reaction conditions was obtained. Kinetic experiments of dioxin HDC with 2-propanol showed a maximum net reaction rate and turnover frequency (TOF) for a given initial concentration of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). After that value, both reaction rate and TOF decreased. On the other hand, reaction rates and TOFs of dioxin-like polychlorinated biphenyls (DL-PCBs) linearly increased with concentration.     

Use of different mesostructured materials based on silica as cobalt supports for the Fischer–Tropsch synthesis

To obtain a novel, active and selective to diesel catalytic material for syngas processing via Fischer–Tropsch synthesis (FTS), a series of 20 wt.% cobalt catalysts has been prepared by impregnation of a mesoporous molecular sieve based on silica (SBA-15, Al-MCM-41, INT-MM1), and a commercial amorphous silica for comparison purposes. All materials were characterized by several physico-chemical techniques: AAS, BET surface area, XRD, TPR, and H₂ chemisorption with pulse reoxidation and finally their reactivity on the FTS reaction was evaluated at 523 K, 10 bar, and H₂/CO = 2. Catalytic and characterization results show a great influence of mesoporous support porosity on the structure, reducibility, and FTS catalytic behavior of cobalt oxide species supported over these ordered materials. It was found that the size of supported cobalt oxide species formed during the calcination step increased with the average pore size (D_p) of the mesoporous support. Thus, the catalyst with larger Co oxide species located in wide pore silica showed to be easily reducible, more active and very selective toward the diesel fraction. It seems to be the case of the Co/SBA-15 solid, which showed to be the most active solid (XCO 63%) when the same mass of catalyst was used. Under CO iso-conversion conditions (XCO 40%), Co/SBA-15 was more selective toward the formation of C₅₊ hydrocarbons (80%, α = 0.76) and less selective to CH₄ (15%). On the contrary, when Al-MCM-41 and INT-MM1 were used as supports, a lower selectivity to C₅₊ and CO conversion and higher CH₄ selectivity (20%) were observed due to the decrease of D_p, of the cobalt oxide species size and the reducibility degree of such species.