Polish Journal of Chemical Technology (v.11, #2)
New closure method for a simultaneous diazo coupling between 1- and 2-Naphthols and diazotized sulphanilic acid
by Jerzy Bałdyga; Magdalena Jasińska; (pp. 1-5).
This paper presents the effects of mixing on the course of complex chemical reactions in relation to the manufacturing of pure products at high reaction selectivity, and designing mixing strategies using complex, homogeneous test reaction systems. As an example, the competitive-consecutive and parallel reaction test system including a simultaneous diazo-coupling between 1- and 2-naphtols and diazotized sulphanilic acid is considered. The effect of mixing on the reaction selectivity is interpreted using mechanistic modeling and a new closure scheme. The new closure represents an extension of the conditional PDF closure applied before to simple reaction schemes.
Keywords: closure method; diazo-coupling; micromixing; turbulence
Selection and comparison of equipment for deagglomeration processes
by Jerzy Bałdyga; Katarzyna Malik; (pp. 6-12).
The unique properties of nanoparticles and nanoparticle clusters show high potential for nanomaterials to be formulated into numerous products. In this paper, nanosuspensions are formulated by braking up agglomerates in high-shear flows. The flows are generated in the specific equipment, and this paper serves as a guide for equipment selection based on mechanistic modelling. A general model based on the power input to the system is formulated to model agglomerate disintegration in different types of equipment including stirred tanks, the rotor-stator disintegrators, the high-pressure nozzle systems and bead mills. The results of computations based on the rate of energy dissipation are presented in terms of the specific energy input, which is typical of industrial applications. In the considered deagglomeration devices the stresses are generated due to various mechanisms including the effects of hydrodynamic stresses, cavitation and bead collisions. The model includes the effects of agglomerate structure on the suspension viscosity. The results of the simulations are compared with the experimental data.
Keywords: Aggregates; Agglomerates; De-agglomeration; Disintegration; Suspension
A chemical method of the production of "heavy" sodium tripolyphosphate with the high content of Form I or Form II
by Marcin Banach; Zygmunt Kowalski; Zbigniew Wzorek; Katarzyna Gorazda; (pp. 13-20).
Sodium tripolyphosphate STPP is used in laundry detergent as a detergent "builder". The paper presents the chemical method of obtaining "heavy", i.e. with higher bulk density granulated sodium tripolyphosphate. The bulk density of sodium tripolyphosphate was increased by preparing a mixture of the dried sodium phosphates, the recycled subgrain of STPP and water in specific proportions and calcining this mixture for 1 hour at 400°C and 550°C (to obtain a proper STPP form) in the chamber kiln. This method allows producing the granular sodium tripolyphosphate with high bulk density (1.04-1.07 kg/dm3) and a high content of Form I or Form II, respectively.
Keywords: sodium tripolyphosphate; high bulk density; granular product
Technological aspects of the synthesis of 2,4-dichlorophenol
by Arkadiusz Białek; Wiesław Moszczyński; (pp. 21-30).
The main factors influencing the selectivity of chlorophenols synthesis were described. The loss of raw materials and the composition of wastes obtained in a conventional technology of 2,4-D production based on 2,4-dichlorophenol (2,4-DCP) of the 89% purity were presented. The influence of some homogenous catalysts on the selectivity of 2,4-dichlorophenol obtained in phenol and chlorine reaction was examined. Using the combined catalyst enables to chlorinate selectively the monochlorophenols to 2,4-DCP without an undesirable increasing of the 2,6-dichlorophenol and 2,4,6-trichlorophenol contents. The catalyst transformations during the reaction of phenol chlorination were investigated and the method of its elimination after the reaction was elaborated.
Keywords: 2,4-dichlorophenol; chlorination; catalyst; dioxine; 2,4-dichlorophenoxyacetic acid
Transient CFD simulations of turbulent liquid - liquid flow in a Kenics static mixer. Radial and tangential velocities
by Halina Murasiewicz; Zdzislaw Jaworski; (pp. 36-40).
The results of modelling of the two-phase turbulent flow of a two-phase, liquid-liquid mixture in a Kenics static mixer were reported. Advanced transient simulations were performed using the large eddy simulation (LES) approach and a broader analysis of the velocity field was carried out. The two-phase flow was modelled employing the Eulerian approach in the pseudo-homogeneous version of the mixture model. Three cases were again considered, which differed by the density of the two phases and the simulations were performed for Reynolds number of 10,000. The LES results for the tangential and radial components were compared with those obtained in the steady-state RANS approach.
Keywords: LES; liquid-liquid; turbulent flow; Kenics mixer
Application of pervaporation and osmotic membrane distillation to the regeneration of spent solutions from the osmotic food dehydration
by Wojciech Kujawski; Magdalena Gierszewska-Drużyńska; Justyna Warczok; Carme Güell; (pp. 41-45).
Results of pervaporation (PV) of sucrose and calcium chloride spent solutions were presented. Additionally, osmotic membrane distillation (OMD) of sucrose solutions was investigated. It was found that the regeneration of spent sucrose solution for the reuse is possible by using PV or OMD processes. However, OMD process produces another spent stream i.e. CaCl2. Pervaporation membranes showed fluxes in the range of 0.5 - 0.9 kg m-2 h-1 in contact with 40° Brix sucrose solution, whereas OMD water permeate fluxes were in the range of 4 - 5 kg m-2 h-1 for the same feed concentration.
Two different hybrid processes were suggested: i) pretreatment followed by OMD reconcentration of spent sucrose solution and independently PV for CaCl2 regeneration; ii) membrane pretreatment (MP) followed by PV of sucrose solution. Based on the experimental results, the membrane areas for both systems were calculated and compared. MP-PV system seems to be a better solution for the spent mixtures management.
Keywords: food processing; spent solution management; pervaporation; osmotic membrane distillation
Carbon modified TiO2 photocatalysts for water purification
by Antoni W. Morawski; Magdalena Janus; Beata Tryba; Masahiro Toyoda; Tomoki Tsumura; Michio Inagaki; (pp. 46-50).
Carbon can form different structures with TiO2: carbon-doped TiO2, carbon coated TiO2 and composites of TiO2 and carbon. The presence of carbon layer on the surface of TiO2 as well as the presence of porous carbon in the composites with TiO2 can increase the concentration of organic pollutants on the surface of TiO2, facilitating the contact of the reactive species with the organic molecules. Carbon-doped TiO2 can extend the absorption of the light to the visible region by the narrowing of the band gap and makes the photocatalysts active under visible light irradiation. TiO2 loaded carbon can also work as a photocatalyst, on which the molecules are adsorbed in the pores of carbon and then they undergo the photocatalytic decomposition with UV irradiation. Enhanced photocatalytic activity for the destruction of some organic compounds in water was noticed on the carbon coated TiO2 and TiO2 loaded activated carbon, mostly because of the adsorptive role of carbon. However, in carbon-doped TiO2, the role of carbon is somewhat different, the replacement of carbon atom with Ti or oxygen and formation of oxygen vacancies are responsible for extending its photocatalytic activity towards the visible range.
Keywords: TiO2/AC; carbon-doped TiO2carbon-coated TiO2photocatalysis
Preparation of cobalt titanates via co-precipitation while using industrial intermediates as titanium precursors
by Aleksander Przepiera; Justyna Płaska; Krystyna Przepiera; Maciej Jabłoński; Aleksandra Konratowska; (pp. 51-54).
This paper reports on the results of cobalt titanates preparation by calcination of green bodies obtained by a co-precipitation method. For the investigations were used: as titanium sources, acidic solutions of titanyl sulfate and hydrous titanium dioxide, originating from the production process of titanium dioxide by sulfate method. The composition of the obtained materials was determined using titration methods. The calcined powders were characterized by X-ray diffraction method. It has been found that the obtained products are composed of cobalt methatitanate CoTiO3 or cobalt orthotitanate Co2TiO4 occurring as single phases, and also as cobalt titanates and titanium dioxide phase mixtures. The proposed method of proceeding can be used for the preparation of series of transition metals titanates, such as nickel, iron, zinc, copper and also aluminium titanates.
Keywords: titanium compounds; cobalt titanates preparation; titanyl sulfate; hydrous titanium dioxide
The effect of hydrotropes on the solubility and mass transfer coefficient of 2-nitrobenzoic acid
by S. Thenesh-Kumar; D. Gnana-Prakash; N. Nagendra-Gandhi; (pp. 55-59).
A comprehensive investigation on the solubility and mass transfer coefficient enhancement of 2-nitrobenzoic acid through hydrotropy, has been undertaken. The solubility and mass transfer coefficient studies were carried out using hydrotropes such as sodium acetate, citric acid and nicotinamide under a wide range of hydrotrope concentrations (0 to 3.0 mol/L) and different system temperatures (303 to 333 K). It was found that the solubility and mass transfer coefficient of 2-nitrobenzoic acid increases with an increase in hydrotrope concentration and also with system temperature. All hydrotropes used in this work showed an enhancement in the solubility and mass transfer coefficient to different degrees. The maximum enhancement factor value has been determined for both the solubility and mass transfer coefficient. The effectiveness of hydrotropes was measured in terms of Setschnew constant Ks and reported for all the hydrotropes used in this study.
Keywords: hydrotropy; solubilization; mass transfer coefficient; separation
Scaling diminution by heterogeneous crystallization in a filtration element integrated with membrane distillation module
by Marek Gryta; (pp. 60-65).
Water desalination by membrane distillation is restricted by calcium carbonate precipitation on the membrane surface, what resulted in a progressive decline of the permeate flux. The module rinsing by HCl solution removed this deposit, however, such operation could cause the membrane wettability, associated with lowering of the permeate flux. This phenomenon was inhibited when the membrane modules with prefiltration element, assembled directly at the inlet to module, were used. The salt deposits were formed mainly on the surface of the filtration element (nets area constituted over 10% of the membranes area), what protected the membranes assembled inside the module. The filter efficiency decreased when the deposit layer covered the entire surface of pre-filter element, and after a few hours (period of 10-20 h) the formation of crystallite on the membrane surface was also observed. Therefore, the formed deposit was systematically removed (at every 5 h) from this pre-filter by 3 wt.% HCl solutions. The periodical rinsing of nets by acid did not have a negative influence on the membrane
Keywords: membrane distillation; capillary module; scaling; water desalination