High temperature membrane reactors for clean productions

 The coupling of reaction and separation in the same device (membrane reactor) has been demonstrated to be an interesting way to enhance the performance of several reactions. In particular, by-products can be separated, side-reactions can be avoided and higher yields and conversions can be achieved. This means that the same conversions of traditional reactors can be obtained at more mild conditions (e.g. lower temperatures and pressures) with consequent energy saving and, thus, environmental benefits. Low temperatures are preferred also because they increase the life-time of the catalyst (it can be used for much longer time before it has to be regenerated) and reduce the tendency of both products and reactants to degrade (to avoid undesired side-reactions), which might lead to a loss of yield. Membrane reactors, then, seem to constitute a possible means for reducing waste production. In this paper the potential role of high temperature membrane reactors in clean productions is presented and discussed. Received: 20 April 2000 / Accepted: 12 June 2000     

Methodology for estimating saving of primary energy with membrane operations in industrial processes

Membrane separation processes can realize significant savings of direct energy (e.g., oil, gas, coal) and indirect energy (intrinsically contained in the materials recovered and/or recycled). The methodology of the energy analysis in various industrial cycles is described, and the benefits of these operations, based principally on electrical energy consumption, are evaluated using the definition of “substitution coefficient” (primary energy saved vs. 1 kWh of electrical energy consumed). The industrial sectors where this methodology has been applied are: textile (recycle of water, dyes and chemicals); polymer manufacturing (recycle of caprolactame and water); the tanning industry (recycle of sulfides and protein recovery), the dairy industry (saving of thermal energy and recovery of fat substances); and tomato and orange juice concentration (saving of thermal energy). The analyses show very interesting values for the substitution coefficients confirming the convenience of membrane operations from an energetic viewpoint.     

Pervaporation separation of methanol/methyl tert‐butyl ether with poly(lactic acid) membranes

Poly(lactic acid), as a natural source polymer, was used to prepare pervaporation dense membranes. The performance of these membranes for the separation of the methanol (MeOH)/methyl tert‐butyl ether (MTBE) mixtures was investigated. The effects of different operating conditions, including the feed concentration of MeOH, temperature, and flow rate, were examined. Several characterization tests were performed as well. The swelling results, scanning electron microscopy images, contact angles, and mechanical strength measurements are presented. These membranes were found to be selective to MeOH, particularly for traces of MeOH in MTBE with a separation factor of more than 30. There was a small decrease in the separation factor when the feed temperature was increased; meanwhile, the total flux increased to some extent. This could be explained with respect to the thermal motions of the polymer chains and the permeating molecules. With an increase in the feed flow rate, both the selectivity and total flux increased because the concentration and temperature polarizations decreased. At higher flow rates, the feed components were homogeneously distributed over the membrane surface, whereas there may have been a concentration or temperature gradient at lower flow rates. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Experimental and numerical modeling of attenuated total reflectance method in the process of hazard substances contact detection

Investigations about hazardous substances traces detection by using absorption infrared spectroscopy are described in this work. Method of numerical modeling of hazardous substances tracesradiation interaction based on attenuated total reflectance effect is calculated. Results of researches were used in explosives traces detection device elaboration. As a substance carrier fingerprints, paper etc. can be used. Diffracting array is used as a spectral analyzer.     

Nonionic surfactants. Regioselective synthesis of fatty acid esters of α- and β-glucopyranose

Lipophilic esters of saccharides belong to the family of nonionic surfactants widely employed in pharmaceutical and cosmetics formulations. A very simple method is presented whereby 6-O-esters of α- and β-glucose can be prepared and isolated. Good results have been obtained in the synthesis of 6-O-oleyl derivatives by simple acylation with appropriate oleyl chloride. The condensing agent bis(2-oxo-3-oxazolidinyl) phosphinic chloride (BOP-Cl) allows the preparations of the same esters with better regioselectivity but with yields strongly dependent on the aliphatic chain length of the carboxylic acids employed.     

The Determination of Stress Distribution and Elastic Properties for Heterogeneous Materials with Hybrid Finite Element

This paper describes a numerical method for evaluating the micro and macromechanical response of two-dimensional heterogeneous materials with both periodic and random distribution of the second phase. The proposed method uses two different numerical programs, based on the Voronoi Cell Finite Element Method, developed by the authors. Various numerical examples are executed for validating the effectiveness of the proposed method in evaluating the overall elastic constants of heterogeneous materials, and different comparison with analytical models and experimental results are shown. In order to validate the accuracy of the programs for predicting the stress micro-fields around the inclusion, some comparisons with a FEM commercial numerical code are performed.     

Preparation and characterization of calcium phosphate biomaterials

Calcium phosphate cement (CPC) samples have been prepared with a mixture of monocalciumphosphate monohydrate (MCPM) and calcium carbonate (CC) powders, in stechiometric moles ratio 1:2.5 to obtain a Ca/P ratio of about 1.67 typical of hydroxyapatite (HAp), with or without addition of HAp. All specimens are incubated at 30 °C in a steam saturated air environment for 3, 6 and 15 days respectively, afterwards dried and stored under nitrogen. The calcium phosphate samples have been characterized by X-ray diffraction (XRD), Vickers hardness test (HV), diametral compression (d.c.), strength compression, and porosity evaluation. MCPM/CC mixture has a 30% HAp final concentration and is characterized by higher porosity (amount 78%) and mechanical properties useful as filler in bone segments without high mechanical stress.     

Metal ions removal from wastewater or washing water from contaminated soil by ultrafiltration-complexation

In the present paper a process for removal of ions from wastewater or from washing water of contaminated soil by using the weakly basic water-soluble polymer polyethylenimine (PEI) as chelating agent and the Cu(2+) ion as model in combination with an ultrafiltration process was investigated. The complexing agent was preliminarily tested to establish the best operative conditions of the process. Next, ultrafiltration tests by using five different membranes were realised to check membrane performance like flux and rejection. Finally, the possibility for recovering and recycling the polymer was tested in order to obtain an economically sustainable process. Obtained results showed that complexation conditions depends on pH: indeed, at a pH>6 PEI-Cu(2+) complexes are formed, while at pH<3 the decomplexation reaction takes place. Saturation condition is 0.333 mg Cu(2+)/mg PEI, meaning a ratio PEI/Cu(2+)=3(w/w). UF tests showed good results using the PAN 40 kDa membrane reaching an average copper concentration in the permeate of 2 mg/l and a flux of 135.4 and 156.5l/h.m(2) at 2 and 4 bar, respectively. Metal rejection, permeate flow rate, and possibility to regenerating and recycling the polymer makes the polymer-assisted ultrafiltration process (PAUF) very interesting for metal ion removal from waters.