Alkylaromatics in Detergents Manufacture: Modeling and Optimizing Linear Alkylbenzene Sulfonation

Linear alkylbenzene sulfonic acid (ASA) is the main ingredient of many commercial formulations for industrial and domestic synthetic detergents. The current industrial ASA production method includes sulfonation of linear alkylbenzene (LAB) with sulfur trioxide in tubular falling‐film reactors. The present study investigates the influence of light alkylaromatics on the efficiency of ASA production. After dealkylation and polymerization, these aromatic compounds form viscous components in the sulfonation reactor. This increases the organic liquid viscosity and disrupts the uniformity of sulfonation. We present the results of IR analysis of the LAB and ASA samples, which indicate that the viscous components are sulfones that are part of the unsulfonated matter. With due consideration of the sulfonation process reaction network, we developed a mathematical model for a sulfonation reactor considering the alkylaromatics content in the feed flow and its effect on the reaction rates. The results allowed the improvement of sulfonation process in terms of increasing the number of days between the reactor washings. The sulfur flow rate increased from 371.7 to 380.9 kg h^?1 at the end of this period for the aromatics content in LAB of 4 wt.% and from 372.1 to 380.1 kg h^?1 for aromatics content in LAB of 6 wt.%. The proposed modifications of the process modes can increase the SO₃ conversion up to 98%.     

Monitoring the linear alkylbenzene sulfonation process using high-temperature gas chromatography

Controlling the linear alkylbenzene sulfonate (LAS) sulfonation process is a critical part of the LAS manufacturing process; this process can be monitored by assaying for LAS content, unsulfonated linear alkylbenzene (LAB), and LAB sulfones. Traditionally, assaying the LAB and LAB sulfone contents has been time consuming and not straightforward. A simple and rapid procedure is described for the isolation and simultaneous capillary gas chromatographic (GC) quantification of LAB and LAB sulfones in LAS. The procedure involves extraction of the unsulfonated LAB and the LAB sulfones into n-heptane; sodium linear alkylbenzenesulfonate or linear alkylbenzenesulfonic acid (reacted to form sodium linear alkylbenzenesulfonate) remains in the aqueous extraction solvent layer. High-temperature capillary GC using a specialty metal capillary column enables both LAB and high molecular weight LAB sulfones to be quantified.     

A contribution to understanding secondary reactions in linear alkylbenzene sulfonation

Modern industrial sulfonation of linear alkylbenzene (LAB) in falling film reactors produces p-alkylbenzene sulfonic acid (HLAS), which is usually neutralized with caustic soda (NaOH) and used in detergent formulations. During the sulfonation process, other products such as anhydrides and sulfones are also formed. Four reactions are proposed to occur during aging and hydrolysis. As a consequences, approximately 25% of sulfones and 75% of unreacted LAB are removed during aging and are transformed into additional active matter. Anhydrides are completely eliminated during hydrolysis. On the other hand, sulfones formed during the process are difficult to remove once formed. The goal of this work was to optimize the various operating conditions of the sulfonation process and to understand the various secondary reactions that occur therein so as to obtain a maximal active ingredient concentration in the final sulfonated product and a minimum of unsulfonated matter. Formation of sulfones can be minimized by using an SO₃/LAB molar ratio slightly lower than the theoretical optimum.     

Extraction rates of amino acids by an emulsion liquid membrane with tri-n-octylmethylammonium chloride

The extraction rates of amino acids from alkaline aqueous solution into an emulsion liquid membrane containing tri-n-octylmethylammonium chloride as a carrier and Paranox 100 as an emulsifier were measured using a stirred transfer cell. The effects of agitation speed (0·33–0·66 rev s⁻¹), amino acid concentrations (0·5–50 mol m⁻³) and temperature (10–45°C) on the extraction rates were examined. The results were analyzed by a double-film model. The mass transfer coefficients of amino acids (0·26–1·58×10⁻⁵ m s⁻¹) and their complexes (0·60–1·72×10⁻⁵ m s⁻¹) were found to correlate well with the hydrophobicities of the amino acids. It was found that the surfactant layer influenced the mass transfer processes of both amino acids in the aqueous film and their complexes in the organic film. The permeation of amino acids with a large hydrophobicity through the emulsion liquid membrane was promoted by both high distribution and larger mass transfer rates. © 1998 Society of Chemical Industry     

Two-resistance mass transfer models for the adsorption of dyestuffs from aqueous solutions using activated carbon

The adsorption of telon blue (acid blue 25) dye and deorlene yellow (basic yellow) dye on to carbon has been studied. A two-resistance mass transfer model has been developed based on film resistance and homogeneous solid phase diffusion. The model may be applied over a wider range of operating conditions than previous models since it has more extensive analytical components. The variables investigated were initial dye concentration and solid: liquid ratio, and the experimental and theoretical results were in good agreement. The adsorption of telon blue on to carbon has been described using an external mass transfer coefficient of 2.0 × 10⁻³ cm s⁻¹ and a homogeneous solid phase diffusion coefficient of 2.0 × 10⁻⁹ cm² s⁻¹. The adsorption of deorlene yellow has been described using an external mass transfer coefficient of 1.0 × 10⁻³ cm s⁻¹ and a homogeneous solid phase diffusion coefficient of 3.0 × 10⁻¹⁰ cm² s⁻¹.     

气液喷射式磺化反应器的应用研究

用喷射式磺化反应器分别对脂肪酸甲酯、烷基苯、重烷基苯、脂肪醇、脂肪醇聚氧乙烯醚和α 烯烃等原料进行了SO3气相磺化/硫酸化反应,研究了反应器主要结构参数对产品质量的影响,并与膜式反应器作了比较。结果表明:喷射磺化反应器制备的烷基苯磺酸、脂肪酸甲酯磺酸的产品质量与膜式磺化反应器相当,制备的重烷基苯磺酸盐产品质量稳定,降低原油/水界面张力的能力优于膜式磺化器制备的产品,但在磺化α 烯烃、硫酸化脂肪醇和脂肪醇聚氧乙烯醚时转化率低于90%,产品质量明显不及膜式反应器。从两种反应器的传质、传热机理及效率,不同有机原料的SO3磺化机理及反应速度等方面对以上现象进行了分析和讨论,认为喷射式磺化反应器适用于脂肪酸甲酯、烷基苯、重烷基苯的磺化,目前的结构参数不适用于α 烯烃、脂肪醇和脂肪醇聚氧乙烯醚的磺化/硫酸化反应,需要进一步调整,改善传质效率。     

Thermal stability and heat flux investigation of neutron-irradiated nanocrystalline silicon carbide (3C–SiC) using DSC spectroscopy

Nanocrystalline silicon carbide (3C–SiC) particles have been irradiated by neutron flux (2 × 10¹³ n∙cm⁻²s⁻¹) up to 5 h at the TRIGA Mark II type research reactor. At the present work, thermal properties of nanocrystalline 3C–SiC are comparatively investigated before and after neutron irradiation at the 300 K < T < 1300 K ranges. Simultaneously, the DSC (Scanning Calorimetry), TGA (Thermogravimetric Analysis) and DTG (Differential Thermogravimetric Analysis) experiments were conducted from 300 K up to 1300 K. Oxidation mechanism of nanocrystalline 3C–SiC particles have been theoretically and experimentally studied before and after neutron irradiation. The kinetics of mass and heat flux were analysed at the heating and cooling processes using DSC spectroscopy.     

Empirical approach to solid-liquid mass transfer in a three-phase sparged reactor

Solid-liquid mass transfer coefficients were determined in three-phase sparged reactors (TPSRs) using benzoic acid dissolution. Experiments were performed in three acrylic column reactors of internal diameter 0.1, 0.2 and 0.3 m respectively. The superficial gas velocities were varied up to 0.35 m s⁻¹. Using experimental data generated in this work and data reported in the literature for a 0.4-m diameter reactor, the effect of the reactor diameter on the solid-liquid mass transfer coefficient, k_SL, was investigated. It is demonstrated that an empirical approach can be used to determine k_SL from an appropriate mass transfer correlation useful for the design of TPSRs.     

Analytical solution using a pore diffusion model for a pseudoirreversible isotherm for the adsorption of basic dye on silica

An analytical solution for a two resistance mass transfer model explaining the adsorption of Astrazone Blue dye (Basic Blue 69) onto Sorbsil silica has been developed. The model includes a film mass transfer coefficient, k_f1 = 80 × 10⁻⁶cm·s−1, and an internal effective diffusivity, D_eff = 18×10⁻⁹cm²·s⁻¹ which controls the internal mass transport processes based on a pore diffusion mechanism.     

双膜式和多管式磺化反应器传质系数的比较

通过对双膜和多管膜式磺化反应器传质系数的计算与分析比较，表明传质系数的决定性因素是三氧化硫的扩散距离，其传质系数与实际情况较接近。又根据传质系数建立了反应高度与反应率的关系，分析了产品质量差异的原因，以及多管膜式磺化反应器和双膜式磺化反应器差异的原因。     

两种不同链长烷基苯的磺化工艺比较

讨论了三氧化硫膜式磺化工艺生产长链(C20~24)烷基苯磺酸盐的可行性,并根据长链烷基苯的物理『生质,从反应原理、工艺条件、产能及设备选型等方面对比了十二烷基苯和长链烷基苯磺酸盐的生产工艺。     

Mass Transfer of Ozone Using a Microporous Diffuser Reactor System

An ozone reactor was constructed using a tubular gas diffuser made of microporous stainless steel to significantly reduce gas bubble size and increase overall mass transfer area. Overall mass transfer coefficient, K_La [s ^?1], was correlated with gas (G) and liquid (L) flow rates using K_La = AL^αG^β , with A = 3.96 × 10 ⁸ [s^?1], α = 1.53, and β = 0.40, with L and G in [m ³s^?1]. The reactor is essentially plug flow at high G or L. This system achieves one of the highest ozone mass transfer rates observed in the literature.     

Electrocombustion of humic acid and removal of algae from aqueous solutions

This paper reports experiments involving the electrochemical combustion of humic acid (HA) and removal of algae from pond water. An electrochemical flow reactor with a boron-doped diamond film anode was used and constant current experiments were conducted in batch recirculation mode. The mass transfer characteristics of the electrochemical device were determined by voltammetric experiments in the potential region of water stability, followed by a controlled current experiment in the potential region of oxygen evolution. The average mass transfer coefficient was 5.2 × 10⁻⁵ m s⁻¹. The pond water was then processed to remove HA and algae in the conditions in which the reaction combustion occurred under mass transfer control. To this end, the mass transfer coefficient was used to estimate the initial limiting current density applied in the electrolytic experiments. As expected, all the parameters analyzed here—solution absorbance at 270 nm, total phenol concentration and total organic carbon concentration—decayed according to first-order kinetics. Since the diamond film anode successfully incinerated organic matter, the electrochemical system proved to be predictable and programmable.     

Understanding the oxygen barrier property of highly transparent poly(lactic acid)/benzoxazine composite film by analyzing the UV-shielding performance

This work reports a new composite film from poly(lactic acid) (PLA) and benzoxazine (BOZ). Introduction of BOZ to PLA simultaneously improves the ultraviolet (UV)-shielding and oxygen barrier properties, which show strong dependence on the content of BOZ. The PLA film demonstrates almost no UV-shielding capacity, but the PLA/BOZ composite film can reach UV-shielding capacity of 98.3% at 350 nm. The corresponding average oxygen permeability coefficient of the composite film is as low as 1.168 × 10⁻¹⁸ m³ m m⁻² s⁻¹ Pa⁻¹, which is significantly lower than that of PLA (5.540 × 10⁻¹⁷ m³ m m⁻² s⁻¹ Pa⁻¹). Meanwhile, the composite film retains visible transparency ≥90.0% at 550 nm. The relationship and its implication between the oxygen barrier performance and UV-shielding capacity are discussed, which propose new guidelines for the development of high barrier PLA film. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47510.     

Mass transfer with chemical reaction in liquid foam reactors

Mass transfer studies were conducted in a stable liquid foam reactor under various operating conditions to evaluate gas holdup, effective interfacial area, liquid-phase mass transfer coefficient and a modified interfacial mass transfer coefficient to include the surface-active agents employed. Gas holdup and effective interfacial area were evaluated experimentally. The interfacial mass transfer coefficient was evaluated semitheoretically, by considering the interfacial region as a separate phase and using the experimental data developed for mass transfer accompanied by a fast first-order chemical reaction. The liquid-phase mass transfer coefficient was also evaluated semitheoretically, using Danckwert's theory for the liquid phase and the experimental data on mass transfer accompanied by a slow pseudofirst-order chemical reaction. An experimental unit was set up to provide a stable flowing foam column, simulating the foam reactor. Mass transfer rates were studied for superfacial gas velocities in the range from 1.5 × 10⁻² m/s to 5 × 10⁻² m/s, giving gas residence times in the range from 20 to 55 seconds. A cationic and nonionic surface-active agent and three different wire mesh sizes, giving bubble size distributions in the range from 2.2 to 5.4 mm Sauter mean diameters, were employed. It is observed that gas holdup is insensitive to the type of surface-active agent; it is however, dependent on wire mesh size and gas velocity. The bubble diameter and, hence, the interfacial area are found to be insensitive to gas velocity in the range studied; they are, however, strong functions of wire mesh size. The liquid-phase mass transfer coefficient increases with increase in gas velocity. The surface-active agent introduces additional resistance to mass transfer in both reaction cases, this being the controlling one in the case of the fast reaction. A comparison with conventional packed bed contactors indicates the mass transfer rates to be about 8 times lower for the foam reactor, for the fast reaction case; for slow reactions, the foam reactor has mass transfer rates approximately 2-4 times higher than those for conventional packed bed contactors.     

烷基苯生产工艺对烷基苯磺酸钠物化性能的影响

介绍了烷基苯生产工艺的发展动向以及几种已工业化的烷基苯工艺生产的烷基苯组成及相应的烷基苯磺酸盐的物化性能，认为固定床烷基化工艺是今后研究和发展的方向。     

The influence of liquid-side mass transfer on heat transfer and selectivity during surface and nucleate boiling of liquid mixtures in a falling film

Experimental studies using a falling film apparatus and a theoretical analysis of heat and mass transfer for mixtures lead to the following results.During nucleate boiling the separation effect, that is, the selectivity, and the heat transfer are influenced to a great extent by liquid-side mass transfer resistances. The selectivity diminishes significantly with increasing heat flux. The heat transfer coefficients for boiling mixtures can be much lower than for pure substances. For the calculations liquid-side mass transfer resistances were assumed to be the only reason for the reduction of both the selectivity and the heat transfer coefficients. No further physical explanations were needed.During surface boiling the reduction of the heat transfer coefficients is negligible for practical applications. The selectivity is mainly controlled by the thermodynamic equilibrium. The liquid-side mass transfer coefficients are of the same order of magnitude as found in physical absorption and absorption with chemical reactions, i.e. (2–5) × 10⁻⁴ ms⁻¹.The effect if liquid-side mass transfer resistances on heat transfer and selectivity during partial evaporation of the binary refrigerant mixture R11–R113 in a falling film apparatus was investigated by varying the heat flux, the film Reynolds number and the liquid composition. During surface boiling the reduction of the heat transfer coefficients in negligible for technical applications, because of the minor deviations from evaporation which are mainly controlled by thermodynamic equilibrium. Nevertheless, the liquid-side mass transfer coefficients, which can be determined by the measured vapour and liquid mole fractions, are of the same order of magnitude as in physical absorption and absorption with chemical reactions, i.e. β_ℓ = (2–5) × 10⁻⁴ m s⁻¹. The coupled heat and mass transfer during falling film evaporatation of mixtures, condensation and absorption [17,19] can be calculated with the same relationships as for the hydrodynamics of falling films.During nucleate boiling the selectivity diminishes significantly and heat transfer is influenced to a great extent by liquid-side mass transfer resistances. There is considerable deviation form evaporation controlled exclusively by thermodynamic equilibrium. The heat transfer coefficients α for the R11–R113 mixture as well as for ten other binary and two ternary mixtures could be calculated assuming the mass transfer resistances to be the only reason for the reduction of the heat transfer coefficient α during boiling of mixtures. No other physical explanations were needed. The calculation method is easily extendable to multicomponent mixtures, if the corresponding vapour-liquid equilibria are available.     

Influence of different reactor types on Nannochloropsis oculata microalgae culture for lipids and fatty acid production

Greenhouse gases emitted into the atmosphere by burning of fossil fuels cause global warming. One option is obtaining biodiesel. Nannochloropsis oculata was cultured under different light intensities and reactors at 25°C for 21 days with f/2 medium to assess their effects on cell density, lipid, and fatty acids (FAs). N. oculata improved cell density on fed-batch glass tubular reactor (7 L) at 200 μmol E m⁻² s⁻¹, yielding 3.5 × 10⁸ cells ml⁻¹, followed by fed-batch Erlenmeyer flask (1 L) at 650 μmol E m⁻² s⁻¹ with 1.7 × 10⁸ cells ml⁻¹. The highest total lipid contents (% g lipid × g dry biomass⁻¹) were 44.4 ± 0.8% for the reactor (1 L) at 650 μmol E m⁻² s⁻¹ and 35.2 ± 0.2% for the tubular reactor (7 L) at 200 μmol E m⁻² s⁻¹, until twice as high compared with the control culture (Erlenmeyer flask 1 L, 80 μmol E m⁻² s⁻¹) with 21.2 ± 1%. Comparing the total lipid content at 200 μmol E m⁻² s⁻¹, tubular reactor (7 L) and reactor 1 L achieved 35.2 ± 0.2% and 28.3 ± 1%, respectively, indicating the effect of shape reactor. The FAs were affected by high light intensity, decreasing SFAs to 2.5%, and increased monounsaturated fatty acids + polyunsaturated fatty acids to 2.5%. PUFAs (20:5n-3) and (20:4n-3) were affected by reactor shape, decreasing by half in the tubular reactor. In the best culture, fed-batch tubular reactor (7 L) at 200 μmol E m⁻² s⁻¹ contains major FAs (16:0; 38.06 ± 0.16%), (16:1n-7; 30.74 ± 0.58%), and (18:1n-9; 17.15 ± 0.91%).     

Removal of H2S and volatile organic sulfur compounds by silicone membrane extraction

BACKGROUND: This study explores an alternative process for the abatement and/or desulfurization of H₂S and volatile organic sulfur compounds (VOSC) containing waste streams, which employs a silicone‐based membrane to simultaneously remove H₂S and VOSC. An extractive membrane reactor allows the selective withdrawal of VOSC and H₂S simultaneously from the waste stream, while preventing direct contact between the waste stream and the absorbing solution and/or the biological treatment system. The influence of the sulfur compounds, membrane characteristics, extractant and pH was studied. RESULTS: Sulfide and the VOCS studied, i.e. methanethiol (MT), ethanethiol (ET) and dimethylsulfide (DMS) were removed from the synthetic wastewater using a silicone rubber membrane. Methanethiol showed the highest (8.72 × 10^?6 m s^?1) overall mass transfer coefficient (k_ov) and sulfide the lowest k_ov value (1.23 × 10^?6 m s^?1). Adsorption of the VOCS into the silicone membrane reduced the overall mass transfer coefficient. The k_ov when using Fe(III)EDTA^? as extractant (5.81 × 10^?7 m s^?1) for sulfide extraction was one order of magnitude lower than with anaerobic water (2.54 × 10^?6 m s^?1). On the other hand, the sulfide removal efficiency with Fe(III)EDTA^? was higher (84%) compared with anaerobic water (60%) as extractant. An additional mass transfer resistance was formed by elemental sulfur which remained attached to the membrane surface. CONCLUSIONS: Extraction of sulfide and VOCS from a synthetic wastewater solution through a silicone rubber membrane is a feasible process as alternative to the techniques developed to treat VOSC emissions. Optimizing the aqueous absorption liquid can increase the efficiency of extraction based processes. Copyright © 2008 Society of Chemical Industry     

Chemistry and kinetics of LAS acid thermal decomposition

The emission of sulfur dioxide (SO₂) from linear alkylbenzene sulfonate (LAS) acid (LASH) at high temperatures has been studied. Rate constants and Arrhenius parameters have been determined, enabling estimation of the amount of SO₂ evolved under any time/temperature combination for risk assessment purposes. Further analysis of the kinetic data and comparison with earlier molecular modeling work on the mechanism of sulfonation of linear alkyl benzene (LAB) to make LASH provide insight into the reaction pathway of SO₂ formation by thermal decomposition of LASH. For risk assessment purposes, the calculation is as follows: Estimate k from k=3.9×10⁷·e^{−13,000/(273+T)}, where T is in degrees C and k is in s⁻¹. Estimate N(SO₂,t), the number of moles of SO₂ evolved when N(LASH₀) moles of LASH are heated for t s at T ^oC, from: N(SO₂,t)=N(LASH₀)×(1−e^−kt ).