Initial Styrene Concentration Research Articles

Catalytic removal of gaseous styrene using DBD combined with NiO/Pyrite composite

Nickel oxide and pyrite (NiO/Pyr) composites were prepared by impregnation method and employed in the dielectric barrier discharge (DBD) catalytic removal of gaseous styrene. The properties of the NiO/Pyr composites were characterized systematically. The removal efficiencies of styrene and energy yields had been examined as a function of initial concentration of styrene, gas flow rates and input powers. The results showed that the NiO/Pyr composite had excellent catalytic performance in DBD removal of gaseous styrene while mass ratio of NiO and Pyr was 0.2 and calcined temperature was 500 °C. When the initial concentration of styrene was 240 mg m−3, DBD combined with the NiO/Pyr composite could improve the removal and mineralization efficiency from 89.9% to 69%–98.6% and 78.5%, respectively, as compared with bare DBD system. The possible removal pathways were proposed based on the product identification by FTIR and GC-MS.

Degradation of Styrene from Waste Gas Stream by Advanced Oxidation Processes

Waste‐air treatment is experimentally investigated by advanced oxidation processes utilizing UV irradiation combined with ozone and hydrogen peroxide. The effect of operating parameters, such as an initial concentration of styrene and flow rate of gas, on the removal of styrene is studied in a photochemical pilot plant unit. The conversion of styrene decreases with an increasing initial styrene concentration and with a decreasing retention time (higher flow rate) of waste gas. The highest conversion of styrene (87%) is achieved under lower initial styrene concentration (100 ppm) and lower flow rate (42 m3 h−1). The energy per order is also calculated for the advanced oxidation process. Electrical energy per order is calculated for all the experimental conditions and it was found that the energy consumption is of about 0.070 kWh m−3 per order, for the 87% styrene removal at 100 ppm of initial styrene concentration and 42 m3 h−1 flow rate. The combination of UV irradiation and ozone is significantly more efficient with lower electrical energy need per order in comparison with combination of UV irradiation and hydrogen peroxide. Therefore, the advanced oxidation process represents a promising treatment technology for the management of waste‐air, and the pilot plant unit designed for high flow rates of waste‐gas streams is suitable for an industrial use.

Secondary organic aerosol formation from styrene photolysis and photooxidation with hydroxyl radicals

The formation of secondary organic aerosol (SOA) generated by irradiating styrene in the presence and/or absence of OH, NOx, H2O vapour and seed aerosol has been investigated for the first time. Experiments were conducted in a smog chamber at 298 K and atmospheric pressure. Styrene decay was measured by gas chromatography with a mass spectrometric detector (GC-MS), and the temporal evolution of the aerosol was monitored using a fast mobility particle sizer (FMPS). The SOA yield increases as the initial styrene concentration increases, leading to yields ranging from 1.8% to 3.5% for styrene photolysis, and from 2.4% to 5.0% for its photooxidation. In both cases, the organic aerosol formation can be expressed by a one-product gas/particle partitioning absorption model. The particle number concentration, mass and yield decrease in the presence of NOx and seed aerosol but increase at higher relative humidity (RH). The gas phase and SOA composition were analysed offline using a filter/denuder sampling system simultaneously collecting gas- and particle-phase products. Benzaldehyde was confirmed as the main gas-phase product of the reaction. However, although products in the particle phase were detected, they could not be identified. Moreover, the aqueous filter extracts were analysed using UV–Visible spectrophotometry to determine differences in the optical properties of SOA produced in the presence and absence of NOx. The results from this work may be used to discuss the implications of atmospheric SOA generation from styrene degradation.

Purification of Styrene from a Styrene/Ethylbenzene Mixture by Stripping Crystallization

Stripping crystallization (SC) was used to purify styrene (ST) from a liquid mixture of ST and ethylbenzene (EB). This new separation technology combines vaporization and crystallization to yield a crystalline product and a vaporous mixture from a liquid feed via three-phase equilibrium transformations. The three-phase equilibrium conditions for a liquid mixture determined by the thermodynamic calculations were adopted to direct the SC experiments. A unique apparatus was designed for SC experiments at low temperatures and pressures for a series of three-phase equilibrium conditions (from −33 °C and 9.0 Pa to −80 °C and 0.03 Pa). The experiments indicate that SC can be applied to the purification of ST from a liquid mixture of ST and EB with an initial ST concentration of 0.80–0.95.

Biodegradation kinetics and interactions of styrene and ethylbenzene as single and dual substrates for a mixed bacterial culture.

This study examined biodegradation kinetics of styrene and ethylbenzene as representatives of alkenylbenzenes and mono-alkylbenzenes, respectively. The compounds were studied independently and as binary mixtures using a series of aerobic batch degradation experiments introduced by acclimatized mix culture. Initial concentration of styrene and ethylbenzene in the liquid phase vacillated from 0 to 220 mg/l. The Andrew model was applied for the biodegradation of individual substrates and the estimated constants of the equation for styrene and ethylbenzene were μmax = 0.1581, 0.2090 (1/h), KS =25.91, 37.77 (mg/L), KI =13.15, 62.62 (mg/L), respectively. The accomplished parameters from single substrate degradation tests were used to predict possible interaction factors achieved from dual substrate experiments. The Sum Kinetics with Interaction Parameters (SKIP) model and the purely competitive enzyme kinetics model were employed to evaluate any interactions. The SKIP model was found to accurately describe these interactions. Moreover, it was revealed that ethylbenzene plays an influential role on styrene consumption (e.g. IE,S = 1.64) compared to styrene which has insignificant inhibitory effect on ethylbenzene usage (e.g. IS,E =0.4) . The active site differences for styrene and ethylbenzene biodegradation and the pathway variations for biodegradation are among the major potential reasons for failure of the estimation that occurred in purely competitive kinetics model. This study is the first to calculate the interactions between styrene and ethylbenzene.

Application of response surface methodology for optimization of operational variables in photodegradation of aqueous styrene under visible light

In this study, the center composite design in response surface methodology was firstly applied to optimize the photocatalytic degradation of aqueous styrene under visible light. Twenty experiments were done by adjusting three parameters (initial concentration of styrene, concentration of catalyst and initial pH of reaction mixture) at five levels by the method of multiple variable analyses. Based on the experimental design, an empirical expression was firstly established and subsequently applied to predict the photocatalytic degradation efficiency of aqueous styrene under visible light. The results showed that the experimental photocatalytic degradation efficiencies are in accordance with the theoretically predicted values very well with a high correlation. The strongest interaction between the parameters assessed was concentration of catalyst /initial pH of mixture. Optimal experimental conditions for arbitrary aqueous styrene concentration of 115 mg L−1 were found initial pH 6.8 and catalyst loading 2 g L−1. The photocatalytic degradation efficiency of aqueous styrene under this condition reached to about 84%. Furthermore, the main degradation intermediate produced in this process was identified by GC/MS technique. The photocatalytic mineralization of styrene in aqueous solution has been studied by TOC.

Dispersion polymerization of styrene using a polystyrene/poly(l-glutamic acid) block copolymer as a stabilizer

A block copolymer (PS-b-poly(l-Glu)) composed of polystyrene and poly(l-glutamic acid) was used as a stabilizer for dispersion polymerization of styrene. When dispersion polymerization of styrene was conducted at 70°C in 80% dimethylformamide–water with 0.5wt% PS-b-poly(l-Glu), spherical polystyrene particles with Dn=0.72μm and narrow size distribution were obtained. Whereas AIBN concentration did not have any effects on particle size, molecular weight of the polystyrene particles was strongly dependent on the initiator concentration. As concentration of the PS-b-poly(l-Glu) increased from 0.2 to 1.0wt%, particle size decreased from Dn=0.91 to 0.69μm with keeping surface area occupied by one poly(l-glutamic acid) chain about S=50nm2. On the other hand, an increase in initial concentration of styrene from 2 to 20wt% caused an increase in particle size from Dn=0.48 to 1.36μm and a decrease in surface area per poly(l-glutamic acid) block from S=91 to 45nm2. Colloidal stability of the polystyrene particles in aqueous solution was responsive to pH due to the surface-grafted poly(l-glutamic acid). For dispersion polymerization of styrene, the PS-b-poly(l-Glu) functions as both a stabilizer and a surface modifier.

Styrene photocatalytic degradation reaction kinetics

The aqueous styrene photocatalytic degradation reaction was evaluated using TiO2 P-25 (Degussa) as a catalyst. These experiments were accomplished in a batch slurry reactor with temperature control and a UV lamp. The effects of the initial styrene concentration, the catalyst concentration, the hydrogen peroxide addition and the initial pH of the solution on the reaction were evaluated. The experimental results showed that in 90 min, 95% of the initial styrene was degraded by photocatalysis. It was verified that the styrene degradation rate fits a pseudo-first-order kinetics for initial styrene concentrations between 15.27 and 57.25 ppm, at 30oC. The chromatographic analysis of the samples collected during the photocatalytic degradation revealed benzaldehyde as one of the intermediates. The addition of H2O2 accelerated the degradation reaction until the system reached a certain optimum peroxide concentration in the reactor. Further H2O2 additions resulted in a reaction rate reduction.

Kinetics of styrene biodegradation by Pseudomonas sp. E-93486

The research into kinetics of styrene biodegradation by bacterial strain Pseudomonas sp. E-93486 coming from VTT Culture Collection (Finland) was presented in this work. Microbial growth tests in the presence of styrene as the sole carbon and energy source were performed both in batch and continuous cultures. Batch experiments were conducted for initial concentration of styrene in the liquid phase changed in the range of 5–90 g m−3. The Haldane model was found to be the best to fit the kinetic data, and the estimated constants of the equation were: μ m = 0.1188 h−1, K S = 5.984 mg l−1, and K i = 156.6 mg l−1. The yield coefficient mean value Y_{text{xs}}^{text{app}} for the batch culture was 0.72 gdry cells weight (gsubstrate)−1. The experiments conducted in a chemostat at various dilution rates (D = 0.035–0.1 h−1) made it possible to determine the value of the coefficient for maintenance metabolism m d = 0.0165 h−1 and the maximum yield coefficient value Y_{text{xs}}^{text{M}} = 0.913 . Chemostat experiments confirmed the high value of yield coefficient Y_{text{xs}}^{text{app}} observed in the batch culture. The conducted experiments showed high activity of the examined strain in the styrene biodegradation process and a relatively low sensitivity to inhibition of its growth at higher concentrations of styrene in the solution. Such exceptional features of Pseudomonas sp. E-93486 make this bacterial strain the perfect candidate for technical applications.

Admicellar Polymerization of Polystyrene on Natural Rubber Particles

Admicellar polymerization is a reaction for coating a thin-film of polymer on a surface. The process consists of the polymerization of the adsolubilized monomer in the hydrophobic regions of the surfactant bilayers that adsorbed on the substrate surface. In this research, the admicellar polymerization of polystyrene was carried out using micron to submicron size natural rubber particles as substrates. Cetyl trimethyl ammonium bromide (CTAB) was used to form the surfactant template. The adsorption isotherm of CTAB was determined in the absence and presence of salt. Styrene adsolubilization was found to increase with initial styrene concentration and in the presence of salt. The synthesized polystyrene in the molecular bilayer of micelles surrounding the natural rubber particles was characterized by optical microscope, Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The observed morphology of the rubber particles after reaction was clearly two phases, a core-shell structure having the natural rubber core covered by the polystyrene shell. These core-shell particles were spheres and aggregated strongly in the emulsion. Effect of initiator type was investigated. The synthesized products showed core-shell morphology, which was still obtained after heating but after cooling phase inversion occurred and showed polystyrene-rich core and natural rubber-rich shell. Thin lamellar of both components was found in both polystyrene-rich core and natural rubber-rich shell making unique morphology and extended single transition of thermal decomposition. FTIR results show characteristic peaks of natural rubber and polystyrene and the absorbance of styrene increases with increasing styrene content. The TGA result showed that the decomposition temperatures of the products were altered by the amount of polystyrene.

Dispersion polymerization of styrene in supercritical CO 2 stabilized by random copolymers of 1 H,1 H-perfluorooctyl methacrylate and 2-dimethylaminoethyl methacrylate

The dispersion polymerizations of styrene in supercritical CO 2 employing random copolymers composed of 1,1-dihydroperfluorooctyl methacrylate (FOMA) and 2-dimethylaminoethyl methacrylate (DMAEMA) (poly(FOMA- co-DMAEMA)) as stabilizers were investigated with two different compositions. It was demonstrated that micron-sized, free-flowing, spherical polystyrene (PS) particles could be obtained in high yields by poly(FOMA- co-DMAEMA) containing as low as 50% (w/w) FOMA. Results indicate that DMAEMA units in the stabilizer, as an anchor group with its special characteristics, can be adsorbed on PS particles to provide an enough colloidal stability. The initial concentration of styrene and the stabilizer affected the molecular mass, polymerization yield, and the morphology of PS particles. The PS particles could be redispersed in buffered water (pH 2.1) by an ionic stabilization mechanism provided by DMAEMA units on the surface. Dynamic light scattering (DLS) measurements of aqueous latexes gave similar particle sizes as those from SEM analysis.

Emission modeling of styrene from vinyl ester resins

The use of vinyl ester (VE) resins in the composites industry has increased in the last decade, and the trend is projected to continue. Styrene is a commonly used co-monomer in VE resins, which acts as a reactive diluent and is required in many liquid molding methods to reduce viscosity and increase gel time. The emission rate of styrene from VE resins is affected by various parameters, including styrene content, temperature, and resin surface-to-volume ratio. This study experimentally measured the effect of these parameters on styrene emission rates from VE resins. It was observed that the emission rate and amount of styrene decreased with decreasing surface-to-volume ratio, temperature, and styrene content. It is also shown that diffusion coefficient and evaporation coefficient of styrene have an exponential relationship with temperature, while they remained constant with initial styrene concentration and aspect ratio. Emission rate and amount decreased with increasing resin initial depth to radius ratio. The emission profiles were self-similar for different aspect ratios and were scaled by the ratio of the instantaneous sample depth to radius. Overall, the effect of these various parameters on the emission profile can be accurately modeled using a modification of a simple one-dimensional diffusion model based on the Crank solution to diffusion through a planar sheet.

Kinetics of polymerization and particle stabilization mechanism on dispersion copolymerization of styrene and divinylbenzene

AbstractMonodisperse highly crosslinked microspheres were prepared by dispersion copolymerization of styrene and divinylbenzene in an ethanol/water medium using poly(N‐vinylpyrrolidone) (PVP) as the stabilizer. The locus of polymerization and growth of particles were investigated. The polymerization kinetics, average particle diameter (Dn), polydispersity index (PDI), and numbers of particles (Np) were presented. When the initial styrene concentration is below 20%, the results indicate that the polymerization occurs in the particles, and the particles grow to their final size by the diffusion of monomer and oligomer into the existing particles. The polymerization rate can be described by the equation Rp = k[l]0.87 ([St]1.91 + [DVB]0.09) (1 + [PVP]0.01) exp(− 45.35/RT). The data from infrared spectroscopy demonstrated that the graft stabilizer was present. The dissolution experiments show that the crosslinking reaction occurred irregularly in batch dispersion polymerization. Using the postaddition approach, up to 3% divenylbenzene (DVB) was successfully incorporated in the synthesis of coagulum‐free substance, and monodisperse crosslinked 5 μ m microspheres with a superior resistance to solvents have been prepared. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2230–2238, 2002

Dispersion polymerization of styrene in ethanol-water media: Monomer partitioning behavior and locus of polymerization

A simulation model has been developed to predict the partitioning behavior of styrene in dispersion polymerization in ethanol–water mixtures. The composition of both the continuous phase and the dispersed phase are quantitatively estimated throughout the polymerization process. The presence of water in the system causes a considerable increase of the styrene partitioning in favor of the particles. Thus, at 70°C and for an initial composition of ethanol/water/styrene = 63.3/26.9/9.8, the concentration of styrene in the particles is about 4.8 times higher than that in the serum instead of about one in pure ethanol. The higher the polymerization temperature, the lower the styrene concentration in the particles; the higher the initial styrene concentration, the higher the styrene concentration in the particles, whereas the partition coefficient is not largely effected. In contrast, neither the interfacial tension nor the final particle size do significantly alter the simulation results. The predicted data from this model have been successfully applied to clarify the mechanisms involved in dispersion polymerization, in terms of stabilization and of kinetic events. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 325–335, 1998

Dispersion polymerization of styrene in ethanol–water media: Monomer partitioning behavior and locus of polymerization

A simulation model has been developed to predict the partitioning behavior of styrene in dispersion polymerization in ethanol–water mixtures. The composition of both the continuous phase and the dispersed phase are quantitatively estimated throughout the polymerization process. The presence of water in the system causes a considerable increase of the styrene partitioning in favor of the particles. Thus, at 70°C and for an initial composition of ethanol/water/styrene = 63.3/26.9/9.8, the concentration of styrene in the particles is about 4.8 times higher than that in the serum instead of about one in pure ethanol. The higher the polymerization temperature, the lower the styrene concentration in the particles; the higher the initial styrene concentration, the higher the styrene concentration in the particles, whereas the partition coefficient is not largely effected. In contrast, neither the interfacial tension nor the final particle size do significantly alter the simulation results. The predicted data from this model have been successfully applied to clarify the mechanisms involved in dispersion polymerization, in terms of stabilization and of kinetic events. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 325–335, 1998

Hydroxypropyl cellulose (HPC)‐stabilized dispersion polymerization of styrene in polar solvents: Effect of reaction parameters

AbstractDispersion polymerization of styrene in polar solvents in the presence of hydroxypropyl cellulose (HPC) produces latex particles from ca. 1 to 26 μm depending on reaction parameters. Increasing the initiator concentration or temperature decreases the molecular weight, but increases the particle size and breadth of the size distribution. The decrease in molecular weight with increasing Ri, caused by larger initiator concentration or higher temperature, is expected based of fundamental kinetic relationships. The inverse correlation between size and rate of initiation is rationalized by polarity (stabilizing ability) of the grafted HPC‐polystyrene formed in situ. High polar HPC‐g‐PS, which contains shorter graft polystyrene chain, stabilizes particles less effectively and this leads to larger particles. The primary influence of initial styrene concentration is a solvent effect: larger particles are obtained at high styrene concentration due to high solubility of polystyrene during the initial part of the reaction. The influence of the molecular weight of HPC is to change the polarity of the HPC‐g‐PS stabilizer. Comparison of particle growth of three critical polymerization systems suggests that the favorable continuous‐phase solubility parameter for dispersion polymerization of styrene is around 11.6 (cal/mL)1/2. Too high or too low polarity generates particles with broad size distribution because large particles are formed during the initial stage and nucleation continues as the polymerization proceeds. © 1992 John Wiley & Sons, Inc.

Kinetics of oxidation of tetralin over supported NiO catalyst

Nickel oxide and pyrite (NiO/Pyr) composites were prepared by impregnation method and employed in the dielectric barrier discharge (DBD) catalytic removal of gaseous styrene. The properties of the NiO/Pyr composites were characterized systematically. The removal efficiencies of styrene and energy yields had been examined as a function of initial concentration of styrene, gas flow rates and input powers. The results showed that the NiO/Pyr composite had excellent catalytic performance in DBD removal of gaseous styrene while mass ratio of NiO and Pyr was 0.2 and calcined temperature was 500 °C. When the initial concentration of styrene was 240 mg m−3, DBD combined with the NiO/Pyr composite could improve the removal and mineralization efficiency from 89.9% to 69%–98.6% and 78.5%, respectively, as compared with bare DBD system. The possible removal pathways were proposed based on the product identification by FTIR and GC-MS.

Radiation‐induced grafting of styrene vapor to polyethylene

AbstractThe radiation‐induced grafting of styrene vapor to low‐density polyethylene film of 0.063 mm thickness was studied at 23°C at a dose rate of 1.98 × 104 rad/hr. The concentration C of monomer in the film was measured as a function of pre‐irradiation exposure time to monomer vapor. The concentration‐dependent diffusion coefficient of styrene in polyethylene was calculated to be 4.9 × 10−9 exp {2.0C/C0} cm2/sec, where C0 is the saturation concentration of styrene in the film, and a linear boundary diffusion coefficient for styrene vapor into polyethylene film was found to be 2.0 × 10−7 cm/sec. The rate of grafting was determined as a function of the concentration of styrene absorbed in the film. The maximum graft yield was obtained with an initial styrene concentration in the film of 4 wt‐%. Under conditions of low initial monomer concentration, the grafting rate increases with irradiation time. The results are compared with previously published data on grafting of polyethylene from methanol–styrene solutions. They are explained in terms of the viscosity of the amorphous region as a function of styrene content and the resistance to the diffusion of monomer at the film–vapor interface.

Kinetics of the polymerization of styrene by Friedel-Crafts catalysts.

ALTHOUGH the mechanisms and kinetics of the free-radical catalysed polymerization of styrene have been fairly extensively investigated1,2, the polymerization employing Friedel Crafts catalysts has received much less attention. Williams3 has investigated the stannic chloride catalysed polymerization of styrene in carbon tetrachloride solution and shown that the overall rate of monomer consumption can be represented by the expression: where m is initial styrene concentration, x is styrene consumed in time t, b is initial catalyst concentration. He has also shown that induction periods are present. We are studying the aluminium chloride catalysed polymerization of styrene in carbon tetrachloride solution from a kinetic point of view, and it is proposed to summarize here the principal conclusions reached to date.