Chemical Engineering & Technology

Hydrotropes are water-soluble surface-active compounds that at higher concentration enhance the solubilities of organic reactants in aqueous phases. Besides being cheap, nontoxic, and environmentally friendly, aqueous hydrotropic solutions possess physicochemical characteristics required to be an alternative reaction media. Applications of hydrotropy and its mechanism are reviewed and discussed.

The relevance of photocatalysis pretreatment prior to biological treatment was examined for various pollutants, based on the monitoring of some specific parameters like target compounds or that of global parameters like TOC, COD, BOD₅, and toxicity. Since criteria evolution is highly compound-dependent, integration of photocatalysis and biological treatment can only be applied to specific wastewaters.

The solid dissolution rate in liquid has been the subject of intense and profitable scientific developments over recent years. This work studies the influence of hydrodynamics on the dissolution rate of solid in water. The impact of the mixing system design is also investigated. The dissolution process can be followed through several parameters.

A pretreatment process using alcohol for the removal of chlorophyll a, b and β-carotene from Chlorella vulgaris was developed to improve the yield and selectivity of lutein in the extract obtained by supercritical carbon dioxide extraction. Ethanol and methanol were selected as elution solvents, of which ethanol was found most suitable for the elution or pretreatment process.

The optimal control structure and the optimal controller parameters are determined simultaneously using mixed-integer dynamic optimization (MIDO) under uncertainty. Application of the sigma point method is proposed in order to approximate the expectation and the variance of a chosen performance index with a minimum number of points to solve the MIDO problem under uncertainty.

The adsorption of atrazine (ATZ) from aqueous solution by granular activated carbon and carbon nanotubes was studied at different initial concentrations of ATZ and at different temperatures. The adsorption kinetics and thermodynamic parameters ΔH⁰, ΔS⁰, and ΔG⁰ were estimated using the van't Hoff equation.

Shannon's entropy theory is introduced for the first time to the petrochemical engineering area. Its effectiveness is demonstrated in two applications for determining the unknown parameters required for the simulation of the naphtha pyrolysis process. Compared with other methods, this approach can be extrapolated and provides more accurate results. Furthermore, it requires much less experimental data.

Rotating-drum bioreactors provide excellent gas-liquid mass transfer, low power consumption, and potential for bleaching processes. The critical particle collision intensity is calculated by simulating the collision process of the individual solid particles with each other. Its maximum collision intensity in the rotating-drum bioreactor is ∼1/10 of that in the conventional stirred-tank bioreactor.

A 2D model for a packed-bed membrane reactor to describe ethylene production via oxidative coupling of methane was developed. Radial concentration gradients can occur for the fast reaction, emphasizing the need for precise prediction of temperature and conversion patterns. It is demonstrated that a significant improvement in prediction of experimental data is achieved when the 2D model is applied.

Various Ni-Co bimetallic catalysts were prepared and applied in a laboratory-scale fixed-bed reactor to investigate their effects on hydrogen production from steam reforming of bio-oil. When compared to commercial Ni-based catalysts, the self-developed 3Ni9Co/Ce-Zr-O catalyst provided the maximum hydrogen yield and lowest coke formation rate and presented a better stability.

An approach to high value conversion of black liquor acid precipitated lignin from corn straw pulping by phosphoric acid activation is reported. The mathematical modeling at high pressure is established. Low and high pressure adsorption of N₂, CO₂ and CH₄ on the produced activated carbon is extensively explored.

A turbidimetric method using spectroscopic data was applied to determine the nanoparticle size distribution in a matrix. The method, based on the scattering and absorption of light by the particles, uses not only a few wavelengths but a whole spectral range for evaluation. It can serve as an accurate and easy-to-use analysis instrument for the characterization of nanosuspensions, emulsions, and aerosols.

Additional criteria for improved oilfield separator design are proposed by efficient combination of two suitable multiphase models of a commercial computational fluid dynamics (CFD) simulator. The CFD simulation results indicate that the most important affecting parameters are vapor density and oil viscosity. A systematic method for estimation of realistic separation velocities is developed.

The two-phase flow in the narrow channels of corrugated packing was determined by computational fluid dynamics (CFD) simulations. On this basis, the Zigzag-pak as a new type of corrugated packing was developed. Considering its prominent advantages in vapor-liquid intensification and high efficiency in mass transfer, the Zigzag-pak could replace common corrugated packing in chemical engineering.

A new method for separation of hydrogen sulfide (H₂S) from highly saline wastewaters originating from an oil-gas field by emulsion liquid membranes (ELMs) is presented. The ELM technique offers the advantages of high diffusion rate, large mass transfer area, separation and stripping in one system, wide adaptability, and high separation efficiency.

Some salts of H₃PW₁₂O₄₀-M_x/nH_3–xPW₁₂O₄₀ were prepared and used as acid catalysts for transesterification and esterification reactions. These catalysts have both Lewis and Brønsted acid properties that are suitable for the conversion of waste cooking oil into biodiesel. The relationship between the acidic properties and the catalytic activity is discussed in detail.

Central composite rotatable design (CCRD) was applied for analysis and optimization of the effects of impeller rotational speed, gas flow rate, probe location, and tracer injection point on the gas-liquid two-phase mixing time in an agitated vessel with a dual six-blade Rushton turbine. CCRD requires fewer experimental runs and provides sufficient information as compared to a factorial design.

Emodin-polyethylene glycol (PEG) composite microparticles were generated from a mixture of dichloromethane and methanol via the solution-enhanced dispersion by supercritical fluids through prefilming atomization process. The effects of experimental variables on morphologies and sizes of emodin-PEG composite microparticles were determined. Emodin could be successfully encapsulated with PEG by this process.

Detailed simulation of the influence of the catalyst particle size on the behavior of a multitubular Fischer-Tropsch reactor with regard to syngas conversion and production rate of hydrocarbons per tube in a wall-cooled single tube with cobalt as catalyst indicates that the reactor performance is improved by enlarging the catalyst particle diameter. Reasons for this unexpected behavior are evaluated.

With cobalt as catalyst, the optimal combination of particle size and tube size for simulation of a single tube of a wall-cooled multitubular Fischer-Tropsch reactor was established. The maximum size of the tubes, realized without temperature runaway, is improved with increasing particle size until an optimal value is reached, thereby improving the production rate of liquid fuels per tube.

Polyelectrolyte-enhanced ultrafiltration was originally used to achieve the recovery of rhenium from aqueous solutions with the help of polyquaternium-6. The effects of various operating parameters on the permeate flux and the rhenium rejection coefficient were investigated. The integration of four experiments including concentration, decomplexation, diafiltration and reuse of the regenerated polymer was carried out.