Volume 16, Issue 1 -

Among the renewable fuels, butanol has become an attractive, economic and sustainable choice because of cost elevation in petroleum fuel, diminishing the oil reserves and an increase of green house effect. Butanol can be derived from renewable sources by using the natural bio-resources and agro-wastes such as orchard wastes, peanut wastes, wheat straw, barley straw and grasses via Acetone Butanol Ethanol (ABE) process. On the other hand, butanol can be directly formed from chemical route involving catalysts also such as from ethanol through aldol condensation. This review presents extensive evaluation for the production of butanol deploying microbial and catalytic routes.

The objective of the current research work is to investigate the performance of batch reactor for saponification of ethyl acetate with sodium hydroxide. Temperature, volume of reaction mixture, rate of agitation, and initial concentration of reactants are the operating conditions considered for analysis. The NaOH concentration decreases from 1.13 × 10 −2  mol/L to 0.57 × 10 −2  mol/L when reaction temperature increases from 293 K to 313 K after the completion of the reaction. The conversion of NaOH increases with increased reaction temperature under the studied range of reaction temperatures until the stable condition is achieved. Reactant concentration declines with increased volume of reaction mixture from 1.2 L to 1.8 L. Sodium acetate concentration and reaction conversion decrease with increased volume of reaction mixture within the studied range. Concentration of sodium acetate decreases with increased rate of agitation. The conversion of sodium hydroxide declines with increased agitation rate from 70 rpm to 150 rpm. Higher initial reactant concentration leads to decreased reaction conversion. The results obtained may be used to optimize the production of ethanol and sodium acetate using saponification reaction.

The aim of this work was to evaluate the photocatalytic activity of two distinct anatase thin films. Films were prepared following the sol-gel procedure from titanium (IV) isopropoxide (TF-1) and from commercial TiO 2 P25 as a starting material (TF-2). The films were compared based on the salicylic acid (2-dihydroxybenzoic acid, 2-HBA) photocatalytic degradation in reactors of different geometry and under different irradiation conditions. Experiments were performed in (i) an annular photoreactors operated under turbulent flow (TAR1 and TAR2) and (ii) semi-annular reactor operated under laminar flow (LFR). The TF-1 and TF-2 were immobilized on the inner side of outer wall of TAR1 and TAR2 and on the bottom of LFR. Experimental study included sorption study and four consecutive photocatalytic runs (t irr = 8 h) using TF-1 and TF-2 in each reactor. Obtained results confirmed the stability and the similar photocatalytic activity of the both films. The 2,5-dihydroxybenzoic acid (2,5-DHBA) and 2,3-dihydroxybenzoic acid (2,3-DHBA) were identified as main 2-HBA degradation by-products. Kinetic models were developed accordingly. Incident photon flux was determined along the inner reactor wall in annular reactors and on the bottom of LFR, i. e. on the thin film surface ( I tf , W m −2 ) using ESSDE radiation emission model. The irradiation factor, i. e. the product of absorption coefficient and incident photon flux at film surface ( μI tf (z)) m was introduced into the kinetic models. Resulting reaction rate constants k i (min −1 W −0.5  m 1.5 ) were independent of reactor geometry, hydrodynamics, irradiation condition and the optical properties of thin films. Efficiencies of TF-1 and TF-2 in studied reactors were given on the basis of quantum yields (QY) for 2-HBA oxidation and overall mineralization toward CO 2 .

The application of nanofiltration membranes to remove sulfate and arsenic from wastewaters was investigated. The influence of operating parameters on the rejection and permeate flux was determined. The nanofiltration experiments carried out with NF90 and NF270 membranes showed a high rejection of sulfate (~90 %) and arsenic (~97 %) under the given set of experimental conditions. Better permeate flux values were obtained by NF270 membrane with a minor drop in rejections, but it proved to be better in water recovery. In FESEM analysis, the sulfate deposition on the membrane surface confirmed its well-known precipitation in desalination types of equipment. The experimental results were successfully predicted by using theoretical framework available in the literature. The simulation was carried out by using Levenberg–Marquardt with Gauss–Newton algorithm in MATLAB and the prime important parameters, viz. membrane resistance(Rm)$({R_m})$, permeability coefficient Pm${{\rm{P}}_{\rm{m}}}$, and mass transfer coefficient (k) were established separately for each membrane. The gel layer thickness was determined to better understand the hydrodynamics over the membrane surface and it validated the assumption of negligible fouling.

Based on the improved computational fluid dynamics and discrete element method (CFD-DEM), heat transfer and two-component flow of biomass and quartz sand have been studied from experiments and numerical simulation in this paper. During experiments, the particle temperature and moving images are respectively recorded by infrared thermal imager and high speed camera. With the increase of the velocity, the mixing index ( MI ) and the cooling rate of the particles are rising. Due to larger heat capacity and mass, the temperature of biomass drops slower than that of quartz sand. Fictitious element method is employed to solve the incompatibility of the traditional CFD-DEM where the cylindrical biomass are considered as an aggregation of numerous fictitious sphere particles arranged in certain sequence. By the comparison of data collected by infrared thermal imager and the simulated results, it can be concluded that experimental data is basically agreement with numerical simulation results. Directly affected by inflow air (25℃), the average temperature of particles in the bed height area ( h >30 mm) is about 3 degrees lower than that of the other heights. When the superficial gas velocity is larger, the fluidization is good, and the gas temperature distribution is more uniform in the whole area. On the contrary, bubbles are not easy to produce and the fluidization is restricted at lower superficial gas velocity. Gas-solid heat transfer mainly exists under the bed height of 10 mm, and decreases rapidly on fluidized bed height. The mixing index (MI) is employed to quantitatively discuss the mixing effectiveness, which first rises accelerate, then rising speed decreases, finally tends to a upper limit.

This work introduces a simple and versatile method for researching the concentration gradient generator (CGG) which can present the arbitrary approximate linear and quadratic concentration gradient curves output. The concentration gradients of arbitrary approximate linear curves with two inlets and arbitrary quadratic curves in the CGG with three inlets are obtained with the corresponding flow velocities. The CGG was simulated basing on the finite element method (FEM). The fluid-dynamic and mass-transport about the CGG was studied. Moreover, the feasibility of simulation was clearly verified by an experiment which two microfluidic chips of CGG on the PMMA substrate were processed using CNC engraving and milling machine. The paper successfully demonstrates the controllability of concentration gradient profiles in CGG with two inlets and three inlets. The study on the CGG can help the trends study of cell and molecule in different samples in the biochemical engineering.

An investigation on the catalytic performance of various transition-metal ions-exchanged clinoptilolite zeolites in the propane selective catalytic reduction process of NO x (NO+NO 2 ) is reported for the first time. The metallic ions include Zn 2+ , Fe 2+ , Cu 2+ and Mn 2+ . The catalytic performance of these materials was compared with the proton form and natural clinoptilolite zeolites. Compared with the raw and H-form clinoptilolite, the ion-exchanged zeolites shift the temperature corresponding to the maximum conversion around 50 °C towards lower temperatures, irrespective of the type of used transition-metal used. The maximum conversion is substantially enhanced especially in the case of Cu 2+ and Mn 2+ -exchanged zeolite. The enhanced activity is attributed to the creation of strong acidic sites, redox centers, enhanced specific surface area and residual extra framework Fe species. Ion-exchange with transition metals results in a distinct effect on the reduction of the CO concentration in the product gas stream. Cu 2+ exchanged clinoptilolite resulted in the smallest outlet concentration of CO, i. e. about 81 % reduction with respect to the protonated zeolite form.

In this study, the sorption of Congo red (CR), as a toxic dye, from aqueous media was investigated using montmorillonite (MMT) as a low-cost adsorbent. The influence of several factors such as contact time, pH, adsorbent dosage, dye content, and ionic strength was investigated on the dye removal. MMT was characterized by Fourier transformed infrared (FTIR) spectroscopy and X-ray diffractometer (XRD). Different kinetic and isotherm models including pseudo-first and pseudo-second order kinetic and Langmuir and Freundlich were applied to analyze experimental data, respectively. The results showed that the data were well fitted by pseudo-second-order kinetic and Freundlich isotherm models. The optimum conditions for the sorption of CR were achieved over 40 min and at pH=2. According to the results of the present study, MMT can be used as a low-cost, eco-friendly and effective option for the adsorption of CR from aqueous solutions.

Hydrocracking is a significant process in a refinery which is commonly used for converting heavy fractions such as vacuum gas oil (VGO) to the valuable products such as naphtha and diesel. In this research, VGO hydrocracking process was studied in a pilot scale plant in the presence of a zeolite and two amorphous based commercial catalysts called RK-NiY, RK-MNi and KF-101, respectively. In order to study the effect of support on the yield of the process, a discrete 4-lump kinetic model, including feed (vacuum gas oil and unconverted materials), distillate (diesel and kerosene), naphtha and gas was proposed for each catalyst. At first, each network had six reaction paths and twelve kinetic coefficients, and then by using the model reduction methodology, only four main routes for RK-MNi and RK-NiY, and three ones for KF-101 were designated. Results showed that the absolute average deviation (AAD%) of reduced models decreased from 5.11 %, 10.1 % and 21.8 % to 4.54 %, 8.9 % and 19.67 % for RK-MNi, KF-101 and RK-NiY, respectively. Moreover, it was confirmed that amorphous and zeolite catalysts could be selected for producing middle distillate and naphtha products, respectively.

The hybrid bioreactor heated by microwave or conventional by hot water jacket is presented. The reactor consisted of two functional sections. The upper section was constituted by an unsinkable anaerobic biological bed, whereas the bottom section – by suspended anaerobic activated sludge. Both sections were closed in one casing. The study was conducted in mesophilic (35 °C) and thermophilic (55 °C) conditions. Depending on the method of heating, the homogeneity of the temperature field in both functional parts of the reactor was determined. In mesophilic conditions only at measurement points located directly under the wave-guide the temperatures were significantly higher than in the other zones inside the reactor. This implies that it is possible to homogenous heat of the bioreactor in semi-technical scale by microwave irradiation. Under thermophilic conditions a homogenous field of temperature was obtained in the upper and in the bottom section of the bioreactor, however, significant differences were found in values of the temperature between the particular sections of the bioreactor.