Preparation of MFI type tubular membranes by steam-assisted crystallization

Zeolite MFI membranes were successfully prepared on both alumina and stainless steel tubular supports by crystallization of previously deposited silicate layers under a steam atmosphere. The resultant membranes were able to separate n/isobutane mixtures at relatively high temperatures, displaying separation selectivities of 11.3, 8.9 and 2.5 at 100, 230 and 330 °C, respectively.     

Optimization by lumped control of reactors with langmuir-hinshelwood catalyst deactivation

A method is proposed for solving the problem of temperature optimal control in tubular fixed-bed reactors with reaction systems described by Langmuir-Hinshelwood-Hougen-Watson kinetic equations. The optimization problem is formulated by N state differential equations corresponding to the N differential fixed-bed reactors in which the integral reactor is divided. It is solved using the control vector parameterization computational technique. The proposed method when applied to a simple reaction system reported previously in the literature gives analogous results, and thus validates the theory. This theory is applied to the dehydrogenation of benzyl alcohol to benzaldehyde. An analysis of optimality problem shows a strong influence of the temperature dependence of the ratio of reaction rate to deactivation reaction rate on the optimal policy.     

Alternative Method for Determining O2 and CO2 Transmission Rates Through Microperforated Films for Modified Atmosphere Packs

Most experimental systems for measuring the permeability of microperforated polymeric films are static, mainly because in dynamic systems the small differences in pressure on both sides of the perforation may result in serious errors in the measurements. The O₂ and CO₂ transmission rate through microperforations of different sizes (from 40 × 30 to 350 × 110 µm) were determined in a static and in a dynamic system. In the latter case, rather than the diffusive flow, the hydrodynamic flow generated by the difference in pressure was measured (between 5 and 90 mbar). This was determined by applying Bernouilli's theorem and an experimental equation potentially relating the area of the microperforation with the transmission rate. A comparison of the transmission rates obtained in both cases gives coefficients of determination close to one (>0.993). This means that measuring the hydrodynamic flow can be considered as an alternative for the quantification of the diffusive flow through a microperforation. This is a simple and quick methodology that does not require expensive equipment. Furthermore, this feature enables commercial leak detection equipment to be used to quantify diffusive transmission rates through microperforations. Copyright © 2012 John Wiley & Sons, Ltd.     

Image Analysis Techniques for Automated Hazelnut Peeling Determination

According to FAO statistics, in 2000, Italy was the second largest hazelnut (Corylus avellana, L. 1753) producer in the world. The price of the stock depends on the nut quality (kernel/nut ratio, nut and seed defect, percentage of peeling, and taste panel scores). The evaluation of peeling efficiency after toasting is generally conducted by trained operators in sight on 100 kernels. This work tests two alternative objective methods of after toasting peeling evaluation based on image analysis. Eleven hazelnut cultivars were analyzed and results were compared with the ones assessed by trained operators. Images were analyzed with two statistical approaches: fixed values of RGB thresholding and trained K Nearest Neighbors (KNN). Root mean squared error (RMSE), estimating the comparison between operators and the two image analysis-based techniques, shows better results for KNN (6.6) with respect to fixed threshold (15.9).     

Electrodeposition of Co-Ni and Co-Ni-Cu systems in sulphate-citrate medium

Electrodeposition of Co-Ni and Co-Ni-Cu alloys was performed in a sulphate-citrate medium. Experimental electrodeposition parameters (pH, cobalt(II), nickel(II) and citrate concentrations) were varied in order to analyse their influence on the deposition. Anomalous Co-Ni codeposition occured in the citrate medium. High [Ni(II)]/[Co(II)] ratios (above 5) were suitable for the preparation of homogeneous magnetic Co-rich Co-Ni deposits of hexagonal close-packed (hcp) structure or face centred cubic (fcc) structure as a function of the deposition potential.The presence of very low copper(II) concentrations (<10⁻² mol dm⁻³) in the nickel-cobalt bath makes it possible to incorporate copper in the deposits in amounts ranging from 5 to 60% Cu, although uniform deposits are obtained only for low copper percentages. These ternary deposits are solid solutions with fcc structure and magnetic behaviour both dependent on the deposition potential.     

Reduced strength degradation of alumina–aluminium titanate composite subjected to low-velocity impact loading

The impact behaviour of monophase alumina and alumina–aluminium titanate monolithic composite ceramics that present flaw tolerant behaviour was studied. Low-velocity impact loading tests were performed on bending bars and the residual strength after the impact was evaluated by four-point bending tests. The impact tests were monitored using an instrumented drop-weight machine. During impact, the composites absorbed higher energy than the monophase material. The strength retention, in percentage, after the impact was significantly higher for the composite that presented damage tolerance for impact energy levels higher than monophase alumina. These results are discussed and fractographic analysis was used to identify the mechanisms responsible for the lower strength degradation of the composite.     

Monitoring a mixed starter of Hanseniaspora vineae-Saccharomyces cerevisiae in natural must: impact on 2-phenylethyl acetate production

The effect of simultaneous or sequential inoculation of Hanseniaspora vineae CECT 1471 and Saccharomyces cerevisiae T73 in non-sterile must on 2-phenylethyl acetate production has been examined. In both treatments tested, no significant differences in Saccharomyces yeast growth were found, whereas non-Saccharomyces yeast growth was significantly different during all days of fermentation. Independently of the type of inoculation, S. cerevisiae was the predominant species from day 3 till the end of the fermentation. The dynamics of indigenous and inoculated yeast populations showed H. vineae to be the predominant non-Saccharomyces species at the beginning of fermentation in sequentially inoculated wines, whereas the simultaneous inoculation of S. cerevisiae did not permit any non-Saccharomyces species to become predominant. Differences found in non-Saccharomyces yeast growth in both fermentations influenced the analytical profiles of final wines and specifically 2-phenylethyl acetate concentration which was two-fold increased in sequentially inoculated wines in comparison to those co-inoculated. In conclusion we have shown that H. vineae inoculated as part of a sequential mixed starter is able to compete with native yeasts present in non-sterile must and modify the wine aroma profile.