Korean Journal of Chemical Engineering (v.35, #4)

Fuzzy-based nonlinear PID controller and its application to CSTR by Gun-Baek So; Gang-Gyoo Jin (819-825).
This study presents a new design method for a nonlinear variable-gain PID controller, the gains of which are described by a set of fuzzy rules. User-defined parameters are tuned using a genetic algorithm by minimizing the integral of absolute error and the weighted control input deviation index. It was observed in the experimental results on a continuous stirred tank reactor (CSTR) that the proposed controller provided performances: overshoot M p ≤1.25%, 2% settling time t s ≤1.71 s and IAE≤1.26 for set-point tracking, perturbance peak M peak ≤0.05%, 2% recovery time t rcy ≤3.97 s and IAE≤0.10 for disturbance rejection, and M peak ≤0.04%, t rcy ≤2.74 s and IAE≤0.04 for parameter changes. Comparison with those of two other methods revealed that the proposed controller not only led to less overshoot and shorter settling time for set-point tracking and less perturbance peak and shorter recovery time for disturbance rejection, but also showed less sensitivity to parameter changes.
Keywords: PID Controller; Nonlinear Gains; Tagaki-Sugeno Fuzzy Rule; Continuous Stirred Tank Reactor (CSTR)

Intelligent control system for extractive distillation columns by Thiago Gonçalves das Neves; Wagner Brandão Ramos; Gilvan Wanderley de Farias Neto; Romildo Pereira Brito (826-834).
We developed and implemented an intelligent control system to be used in an extractive distillation column that produces anhydrous ethanol using ethylene glycol as solvent. The concept of artificial neural networks (ANN) was used to predict new setpoints after disturbances, and proved to be a fast and feasible solution. The developed control system receives data from temperature, flowrate and composition measurements of the azeotrope feed, and the ANN estimates the new set-points of the controllers to maintain 99.5 mol% of ethanol at the top and less than 0.1mol% at the bottom; feed composition was also estimated using an ANN. All ANN were trained to provide output data corresponding to an optimized operating condition. The results showed that the intelligent control system can predict a new operating condition for any disturbance in the column feed and presented superior performance when compared with the control system without ANN.
Keywords: Ethanol; Extractive Distillation; Artificial Neural Networks; Control; Set-points

Optimization design research of air flow distribution in vertical radial flow adsorbers by Yao Li; Haiqing Si; Bing Wang; Lu Xue; Xiaojun Wu (835-846).
Non-uniform flow distribution usually exists in a vertical radial flow adsorber, which significantly decreases the utilization of adsorbents. We adopted numerical simulation methods based on the ANSYS Fluent 15.0 software to study the flow pattern in vertical radial flow adsorber, where programs of user-defined functions (UDF) were set up to interpret component equation, momentum equation and energy equation. To solve the problem of non-uniform air distribution, the relationship between the radial pressure drop across the bed and the ratio of cross-sectional area of the central pipe to that of the annular channel was studied, and optimization design of the distributor inserted in the central channel was given by parametric method at the same time. Through comparative analysis in the given experimental condition, the uniformity reached about 99.1% and the breakthrough time extended from 564 s to 1,175 s under the present optimized design method.
Keywords: Flow Distribution; Radial Flow Adsorber; Numerical Simulation; Optimization Design; Distributor

With the use of β-cyclodextrin (β-CD), Pickering-type diesel-in-water emulsions were prepared based on the inclusion complex formed between diesel and β-CD which acted as an emulsifier. By using the artificial neural network (ANN), the rheological behavior of the emulsions was characterized using three input variables: diesel-to-water ratio, β-CD concentration, and shear rate and one-output variable as shear stress. Gradient descent (GD), conjugate gradient (CG), and quasi Newton (QN) were used as three different methods in the feed-forward back-propagation algorithm for network training. Hyperbolic tangent sigmoid and pure linear were the transfer functions used for transforming information between input and output through one hidden layer containing ten neurons. By dividing the experimental data into three sets of training, validation, and testing, the QN method in predicting shear stress was found to have performed better than the other two network learning techniques (R2=0.994 and MSE=0.006).
Keywords: β-Cyclodextrin; Diesel-in-water Pickering-type Emulsion; Rheological Behavior of Emulsion; Artificial Neural Network; Feed-forward Back-propagation Learning Algorithm

Biosynthesized Au/TiO2@SBA-15 catalysts for selective oxidation of cyclohexane with O2 by Fang Yao; Lixin Xu; Jili Luo; Xiao Li; Yue An; Chao Wan (853-858).
A variety of TiO2@SBA-15 supporters with various TiO2 loadings were synthesized using a facile sol-gel method. Gold (Au)-based catalysts were prepared with an environmentally benign and economical bioreduction method via Cacumen Platycladi (CP) leaf extract and immobilized on various TiO2@SBA-15 supporters with different TiO2 loadings. The as-prepared biosynthesized Au catalysts were applied in the liquid-phase cyclohexane oxidation. The results showed that the Au nanoparticles were well-dispersed on TiO2@SBA-15, and the Au existed as Au0. These biosynthesized Au catalysts are promising for cyclohexane oxidation, achieving a turnover frequency up to 3,426 h−1 with a 14.1% cyclohexane conversion rate.
Keywords: Cyclohexane Oxidation; Biosynthesis; Nanocomposites; Au/TiO2@SBA-15; Oxygen

Gasification is generally considered as the most effective for low rank coal exploitation, and CO2 gasification offers the advantage of upgrading a greenhouse gas. Herein, the effects of alkali and alkaline earth metals on gasification of char derived from Zhundong low rank coal (R-char) were investigated using a thermo-gravimetric analyzer (TGA). Additionally, the characteristics of chars were analyzed by X-ray fluorescence (XRF) and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). The results show that the carbon conversion increases as the temperature and CO2 concentration increases. The R-char possesses a higher gasification rate and carbon conversion than the acid washing R-char (AR-char). It can be explained that the alkali and alkaline earth metals presence in coal char can remarkably facilitate the compound’s decomposition and make more char surface exposure to react during the gasification process. For the kinetic analysis, the volumetric reaction model reveals a proper description among the three models (VRM, RPM, SCM), and the R-char and AR-char presents a compensation effect in VRM. Besides, the detailed correlation of two chars is ln (k0)=0.10 E A −1.77 (R-char) and ln (k0)=0.10 E A −2.85 (AR-char), respectively.
Keywords: Alkali and Alkaline Earth Metals; CO2 Gasification; Compensation Effect; Catalytic; Zhundong Char

Methanol aromatization over CrZn-modified HZSM-5 catalysts by Bei Liu; Siwu Lu; Enzhou Liu; Xiaoyun Hu; Jun Fan (867-874).
HZSM-5 (HZ) zeolite co-modified with Zn and second promoters (Zr, Ce, Mo and Cr) was synthesized and the aromatization of methanol over the modified HZ in a fixed-bed reactor was investigated. The results of catalytic tests revealed that the methanol conversion and yield of benzene, toluene, and xylene (BTX) over the Cr, Zn comodification HZ (CrZn/HZ) were higher than that over ZrZn/HZ, CeZn/HZ, and MoZn/HZ. The catalysts were characterized by XRD, SEM, TEM, XPS, N2 isothermal adsorption-desorption and NH3-TPD. The results suggest that Zn species exist in two forms in the HZ zeolite. One is ZnO particle, the other one is ZnOH+, which significantly improveds the yield of BTX. Furthermore, the Cr species on the external surface promoted the dispersion of ZnO, increased the amount of ZnOH+, which further improved the yield of BTX. In addition, the optimal Cr2Zn1/HZ catalyst exhibited better catalytic performance and prolonged lifetime of reaction.
Keywords: Methanol to Aromatics; Bimetal-modified; CrZn/HZSM-5; BTX; ZnOH+

Effects of process and design parameters on heat management in fixed bed Fischer-Tropsch synthesis reactor by Branislav Todic; Milos Mandic; Nikola Nikacevic; Dragomir B. Bukur (875-889).
A two-dimensional pseudo-homogeneous model of wall-cooled fixed bed Fischer-Tropsch synthesis (FTS) reactor with Co/Re/γ-Al2O3 catalyst was developed to study the effect of process and design parameters on heat generation and removal characteristics. The influence of liquid-phase formation on heat transport was accounted for by using two-phase correlations. The effect of intraparticle diffusion on heat generation was considered. Detailed numerical simulations were performed to analyze the effect of process and design parameters on the reactor performance in terms of heat management. Results show that thermal behavior of FTS fixed bed reactors is very sensitive and any large disturbances can lead to temperature runaway. Large tube diameters are shown to be particularly unfavorable, with d t >5 cm resulting in axial and radial gradients greater than 20 K and 13 K, respectively. The importance of detailed reactor modeling when designing and optimizing FTS fixed bed reactors is highlighted.
Keywords: Fischer-Tropsch Synthesis; Fixed Bed Reactor; Cobalt Catalyst; Heat Management

Competitive biosorption of heavy metals from aqueous solutions onto Streptomyces rimosus by Radia Yous; Faroudja Mohellebi; Hakima Cherifi; Abdeltif Amrane (890-899).
The aim of this study is the simultaneous biosorption of Cd+2 and Ni+2 on a dead biomass, Streptomyces rimosus pretreated with NaOH (0,1 M). Kinetic tests were carried out for the binary mixture (cadmium-nickel) during 6 hours contact time to ensure that balance was reached. The amounts adsorbed at equilibrium were 22.8 mg Ni2+/g and 9.86 mg Cd2+/g biomass, respectively. The biosorption depends mainly by some parameters, such as the pH, the initial concentration of metal and the initial concentration of biomass. The isotherm of adsorption according to two models, Langmuir and Freundlich, was carried out in our study. The results of the kinetics of adsorption show that the experimental values are well represented by the kinetic model of pseudo-second order. This enables us to determine the behavior of these adsorbents with respect to a real industrial effluent.
Keywords: Streptomyces rimosus ; Cadmium; Nickel; Wastewater Treatment; Batch Biosorption

Treatment of penicillin with supercritical water oxidation: Experimental study of combined ReaxFF molecular dynamics by Tengzhou Ma; Tingting Hu; Dandan Jiang; Jinli Zhang; Wei Li; You Han; Banu Örmeci (900-908).
Supercritical water oxidation (SCWO) of penicillin (PCN) was investigated under different operating conditions. The chemical oxygen demand (COD) removal rate could reach 99.4% at 400 °C, 24 MPa, 1min and oxidation coefficient (OC) of 2. Experimental results showed that COD removal had no significant dependence on temperature and pressure variations. By contrast, COD removal could be significantly promoted with OC increasing from 0 to 2.0, but the effect was negligible as the OC further increased; similarly, longer residence time than a definite value seemed to contribute little to COD removal. Initial and deeper degradation pathways of penicillin were proposed based on the reactive force field (ReaxFF) molecular dynamics (MD) simulations. By tracing the evolution of intermediates, the migration routes of S and N during the SCWO process were obtained with H2S and NO2 produced as the corresponding products. Simulation results showed that SCW and oxidant not only accelerated the degradation by producing highly reactive radicals or molecules, but also participated in reactions by serving as H and O sources. Moreover, catalysis of water clusters in C-heteroatom bond cleavage was also observed.
Keywords: Penicillin; Supercritical Water Oxidation; ReaxFF; Molecular Dynamics Simulation; Degradation Pathway

This study mainly focuses on a comparative study of electrocoagulation (EC), peroxi-electrocoagulation (PEC) and peroxi-coagulation (PC) processes for the treatment of aqueous solution containing major toxic components of purified terephthalic acid wastewater: benzoic acid (BA), terephthalic acid (TPA), para-toluic acid (p-TA) and phthalic acid (PA). The solution was initially treated by acid treatment method at various pH (2-4) and temperature (15-60 °C). The supernatant was further remediated by EC, PEC and PC methods independently. Process variables such as pH (4-12) and pH (1-5), current density (45.72-228.60 A/m2), electrolyte concentration (0.04-0.08 mol/L), electrode gap (1-3 cm), H2O2 concentration (600-1,000 mg/L) and reaction time (20-100 min) during EC, PEC and PC treatment were effectively optimized through central composite design under Design Expert software. Maximum COD removal of 60.76%, 73.91%, 66.68% with energy consumption (kWh/kg COD removed) of 95.81, 49.58, 69.26 was obtained by EC, PEC and PC treatments, respectively, at optimum conditions. Electrochemical methods were compared by removal capacities, consumption of energy, operating cost, degradation kinetics and sludge characteristics. PEC treatment was found most effective among EC, PEC and PC processes due to its highest removal capacity and lowest energy consumption features.
Keywords: Purified Terephthalic Acid; Electrochemical Treatment; Response Surface Methodology; Optimization; Kinetic Study

Stabilization of bio-oil over a low cost dolomite catalyst by Hannah Kim; Hoda Shafaghat; Jae-kon Kim; Bo Sung Kang; Jong-Ki Jeon; Sang-Chul Jung; In-Gu Lee; Young-Kwon Park (922-925).
A low cost alkaline catalyst of dolomite (CaMg(CO3)2) was used to stabilize acacia sawdust bio-oil mixed with methanol. The upgrading efficiency was evaluated in terms of the total acid number (TAN) and viscosity. A change in the dolomite calcination temperature from 700 to 900 °C led to a significant change in the TAN and viscosity of the methanol-added bio-oil. Dolomite activated at higher temperatures had larger amounts of active CaO and MgO species due to the enhanced decarboxylation of calcium and magnesium carbonates. An increase in the dolomite content (1-5 wt%) decreased the TAN value of bio-oil remarkably. A thermal aging test of the methanol-added bio-oil upgraded using dolomite (calcined at 900 °C) at 50 °C for 24 h was carried out by storing the bio-oil at 80 °C for one week. Although the TAN value increased after the aging process, it was still lower than the TAN of raw bio-oil. In addition, increasing the methanol content (10-30 wt%) decreased the TAN and viscosity of the bio-oil significantly.
Keywords: Dolomite; CaO/MgO; Bio-oil Stabilization; Bio-oil Aging; TAN; Viscosity

We assessed eight configurations by implementing a dividing wall column (DWC) arrangement and an external heat integration (HI) arrangement for the reduction of energy consumption in the high-purity formic acid (FA) production process. At first, a patented high-purity FA production configuration was adopted and several main process variables were optimized. The optimal configuration was considered the base case for further investigation. The DWC arrangement was applied in the base case configuration to overcome the remixing phenomenon. Next, the external HI arrangement was implemented in those configurations. The simulation results showed that the non-reactive upper DWC between columns C2 and C3 with the HI configuration was the best configuration that provided 46.9% energy saving compared to base case configuration.
Keywords: Reactive Distillation; Dividing Wall Column; External Heat Integration; Energy Efficiency; Formic Acid Production

Energy source diversification through development of coalbed methane (CBM) resources is one of the key strategies to make a country less dependent on simple energy resources (e.g., crude oil, natural gas, nuclear energy etc.). Especially, enhanced coalbed methane (ECBM) technology can be expected to secure the resources as well as environmental benefits. However, the raw CBM gas obtained from CO2 ECBM contains a considerable amount of CO2, and the CO2 content increases depending on the operation time of the facility. Considering the changes of the CBM composition, we developed process simulations of the CBM separation & purification processes based on the amine absorption to meet the design specifications (CH4 purity of product stream: 99%, CH4 recovery rate: 99%) with different CBM feed gas conditions. Using the developed simulation model, we performed an economic evaluation using unit methane production cost (MPC) considering coal-swelling types and facility operation time, and established an operation strategy under different natural gas market scenarios.
Keywords: Energy Diversification; Coal Bed Methane; Gas Separation; Energy System; Economic Evaluation

We propose a new method of resin adsorption (RA) coupled with supercritical fluid elution (SFE) for removal of pesticide residue and recovery of ginsenosides from ginseng extracts. D-101-1 resin was selected as the proper adsorption resin, acetone-n-hexane (4 : 6, v : v) served as the modifier with the flow rate of 1.5 mL/min during supercritical CO2 elution of procymidone at 25 MPa, 55°C for 2 h, and absolute ethanol as the modifier at a flow rate of 1 mL/min for supercritical CO2 elution of ginsenosides at 20 MPa, 60°C and 1 h. The results showed that the content of procymidone in the final products was only 0.0089 mg/kg. Meanwhile, the recovery rate of ginsenosides reached up to 92.5%. RA-SFE procedure provides an efficient approach to remove pesticide residue traces with little loss of active ingredients. The used resin can be recycled without any additional regeneration.
Keywords: Procymidone; Pesticide Residues; Ginsenosides; Supercritical CO2 Extraction; Resin Adsorption

Membrane fouling is a universal problem for conventional membrane filtration that usually causes a deterioration in membrane performance. We used electro-assisted carbon nanotubes hollow fiber membranes (CNTs-HFMs) to investigate the anti-fouling properties using natural organic pollutants. Benefiting from the electro-assistance, the permeation flux of humic acid solution using CNTs-HFMs was 190.20 L/(m2·h·bar), which was about 1.5- and 4.4-times higher than those of CNTs-HFMs without electro-assistance and traditional polyvinylidene fluoride hollow-fiber membranes (PVDF-HFMs). And the permeation fluxes of bovine serum albumin, sodium alginate and supernatant of anaerobic bioreactor also presented similar results. The average COD removal rate of CNTs-HFMs (66.8%) at −1.0 V was higher than that of CNTs-HFMs without electro-assistance and PVDF-HFMs, which can be attributed to the formation of electrostatic repulsive force. It could reduce the deposition of pollutants on membrane surface under electroassistance.
Keywords: Carbon Nanotubes Hollow Fiber Membranes; Membrane Fouling; Natural Organic Pollutants; Electrochemical Effects; COD Removal

The electrochemical route is a promising and environmentally friendly technique for fabrication of metal organic frameworks (MOFs) due to mild synthesis condition, short time for crystal growth and ease of scale up. A microstructure Cu3(BTC)2 MOF was synthesized through electrochemical path and successfully employed for CO2 and CH4 adsorption. Characterization and structural investigation of the MOF was carried out by XRD, FE-SEM, TGA, FTIR and BET analyses. The highest amount of carbon dioxide and methane sorption was 26.89 and 6.63 wt%, respectively, at 298 K. The heat of adsorption for CO2 decreased monotonically, while an opposite trend was observed for CH4. The results also revealed that the selectivity of the developed MOF towards CO2 over CH4 enhanced with increase of pressure and composition of carbon dioxide component as predicted by the ideal adsorption solution theory (IAST). The regeneration of as-synthesized MOF was also studied in six consecutive cycles and no considerable reduction in CO2 adsorption capacity was observed.
Keywords: MOF; Cu3(BTC)2 ; Electrochemical Synthesis; CO2/CH4 Adsorption; IAST

Agomelatine co-crystals with resorcinol and hydroquinone: Preparation and characterization by Min-Jeong Lee; Nan-Hee Chun; Hyo-Cheol Kim; Moon-Jip Kim; Paul Kim; Min-Yong Cho; Guang Jin Choi (984-993).
We prepared and characterized co-crystals of the antidepressant drug agomelatine with pharmaceutically acceptable coformers for enhanced solubility. A novel agomelatine-resorcinol (AGO-RES, 2 : 1) co-crystal was synthesized and its crystal structure was confirmed via single crystal X-ray diffraction. The AGO-RES co-crystal structure was created through the O-H∙∙∙O and N-H∙∙∙O hydrogen bonding between the phenolic OH of RES and the amide group of AGO. The chemical structure of two AGO co-crystals was characterized by FT-IR and Raman spectroscopies, whereas the solution behavior was determined by the intrinsic dissolution rate. When tested in water, both AGORES and AGO-HYQ form-I co-crystals showed higher apparent solubility than pure AGO. But the resulting AGO solution in a supersaturated state partially precipitated into specific crystal forms of AGO. As anticipated, the intrinsic dissolution rate of AGO was substantially enhanced by the co-crystal forms, which signifies that the bioavailability of AGO can be increased via co-crystal formulation approach.
Keywords: Co-crystal; Agomelatine; Resorcinol; Hydroquinone; Solubility

Photocatalytic removal of NOx over immobilized BiFeO3 nanoparticles and effect of operational parameters by Taher Rahimi Aghdam; Habib Mehrizadeh; Dariush Salari; Hui-Hsin Tseng; Aligholi Niaei; Azam Amini (994-999).
Perovskite type BiFeO3 (BFO) was synthesized by sol-gel auto-combustion method. Synthesized BFO was immobilized on the micro slides glass plates by sol-gel dip-coating method. The sample was characterized by XRD, FESEM, UV-Vis DRS, and BET techniques. The XRD pattern confirmed the perovskite structure, and from the Debye-Scherrer equation the average crystalline size was calculated as 19 nm. The FE-SEM images of prepared BFO showed porous structure with low agglomeration. The band gap energy was calculated about 2.13 eV, and the specific surface area (SSA) of prepared BFO nanostructure was obtained 55.1m2 g−1. The photocatalytic activity of prepared pure and immobilized BFO was investigated in the removal of NOx under UV irradiation, in the batch photoreactor. The effects of operational parameters such as initial concentration of NOx, light intensity and amount of coated photocatalyst, under identical conditions, were investigated. The results showed that the highest conversion of NOx was obtained as 35.83% in the 5 ppm of NOx with 1.2 g immobilized BFO and under 15 W illumination lamp.
Keywords: Air Pollution; Photocatalysis; Perovskite; Nanostructure; Bismuth Ferrite

Application of ZnO and TiO2 nanoparticles coated onto montmorillonite in the presence of H2O2 for efficient removal of cephalexin from aqueous solutions by Rasoul Khosravi; Ahmad Zarei; Mohsen Heidari; Ali Ahmadfazeli; Mehdi Vosughi; Mehdi Fazlzadeh (1000-1008).
This study considers the feasibility of uptake of cephalexin, an emerging contaminant, from aqueous solutions by using green local montmorillonite (GLM), montmorillonite coated with ZnO (ZnO/GLM) and montmorillonite coated with TiO2 (TiO2/GLM) in the presence of H2O2. Batch adsorption experiments were carried out as a function of pH, initial concentration of the cephalexin, adsorbent dosage, contact time, and temperature. Finally, the adsorbents were characterized by XRD, SEM and FTIR analyses. XRD patterns showed dramatic changes in the adsorbents after loading with the nanoparticles, confirming successful placing of the nanoparticles onto GLM. The GLM mineral surface after nanoparticle loading appears to be fully exposed and more porous with irregular shapes in particles diameters of 1-50 microns. FTIR analyses also confirmed dramatic changes in surface functional groups after modification with these nanoparticles. The results showed that the removal efficiency of cephalexin was better at lower pH values. Totally, the removal efficiency increased with increase in adsorbent dosage and contact time and decreased with concentration and temperature increase. The thermodynamics values of ΔG o and ΔH o revealed that the adsorption process was spontaneous and exothermic. In isotherm study, the maximum adsorption capacities (qm) were obtained to be 7.82, 17.09 and 49.26 mg/g for GLM, ZnO/GLM and TiO2/GLM, respectively. Temkin constant (B T ) showed that adsorption of cephalexin from solution was exothermic for all three adsorbents.
Keywords: Adsorption; Cephalexin; Montmorillonite; Nanoparticles

This study attempted to obtain various products from carbon dioxide photoreduction using TiO2 catalysts doped with different transition metals of Mn, Fe, Co, Ni, Cu, and Zn (MTiO2). The band-gaps of MTiO2 catalysts decreased compared to pure TiO2, except for ZnTiO2. The intensities in photoluminescence curves, which can predict the recombination of excited electrons and holes, were weaker in MTiO2 catalysts than that of pure TiO2. The products obtained from carbon dioxide photoreduction were strongly related to the redox potential of carbon dioxide and the locations of band-gaps of MTiO2 catalysts. Methane was predominantly obtained in pure TiO2, FeTiO2, and NiTiO2 catalysts, and methanol and carbon monoxide were selectively produced in the CuTiO2 and ZnTiO2 catalysts, respectively. This result suggests that the desired product from carbon dioxide photoreduction can be selectively synthesized by doping certain metals.
Keywords: MTiO2 ; 3d-Transition Metal; Carbon Dioxide Photoreduction; Methane; Carbon Monoxide; Methanol

Photocatalytic water splitting technologies are currently being considered for alternative energy sources. However, the strong demand for a high H2 production rate will present conflicting requirements of excellent photoactivity and low-cost photocatalysts. The first alternative may be abundant nanostructured titanate-related materials as a photocatalyst. Here, we report highly dispersed Na2Ti3O7 nanotubes synthesized via a facile hydrothermal route for photocatalytic degradation of Rhodamine B (RhB) and the water splitting under UV-visible light irradiation. Compared with commercial TiO2, the nanostructured Na2Ti3O7 demonstrated excellent photodegradation and water splitting performance, thus addressing the need for low-cost photocatalysts. The as-synthesized Na2Ti3O7 nanotubes exhibited desirable photodegradation, and rate of H2 production was 1,755 μmol·g−1·h−1 and 1,130 μmol·g−1·h−1 under UV and simulated solar light irradiation, respectively; the resulting as-synthesized Na2Ti3O7 nanotubes are active in UV light than that of visible light response.
Keywords: Photocatalysts; Na2Ti3O7 ; Hydrogen Evolution; Pollutants; Renewable Energy

Effect of MAO-modified nanoporous silica supports with single-site titanocene catalyst on ethylene polymerization by Farideh Azimfar; Alireza Badiei; Seyed Mehdi Ghafelebashi; Majid Daftari-Besheli; Abbas Rezaee Shirin-Abadi (1026-1032).
Three types of nanoporous silica support were modified by methylaluminoxane MAO and characterized by using BET, SEM, XRD and TGA. Dimethylsilyl (N-tert-butylamido)(tetramethylcyclopentadienyl) titanium dichlride was synthesized and immobilized on modified support. The prepared complex was then used as a reactive catalyst for ethylene polymerization. The effect of immobilization conditions on catalyst performance was studied. The results revealed elevated temperature grafting, decrease in precatalyst loading. Also, increasing of immobilization reaction time showed an increase in activity to 130 Kg poly/mol Ti.h.bar. The effects of polymerization temperature and [Al]/[Ti] ratio on the catalyst behavior, namely activity and bulk density, were investigated. According to the results, the activity of single-site catalyst depends on condition of immobilization and structure of nanoporous silica support.
Keywords: Nanoporous Silica; Titanocene; Immobilization; Polymerization; Polyethylene (PE)

A novel system dynamics model for forecasting naphtha price by Byeonggil Lyu; Hweeung Kwon; Il Moon (1033-1044).
Fluctuations in naphtha price are directly related to the profit of petrochemical companies. Thus, forecasting of naphtha price is becoming increasingly important. To respond to this need, a naphtha crack (the price gap between naphtha and crude oil) forecasting model is developed herein. The objective of this study was to design a reasonable forecasting model that is immediately available and can be used to develop various naphtha supply strategies. However, it is very difficult to forecast a price value with a high accuracy. Therefore, the proposed model focuses not on the price value but on the direction of the crack. These considerations are vital to a company’s decision-making process. In addition, a system dynamics model that considers causal relations is proposed. It was developed based on heuristics, statistical analysis, seasonal effects, and relationships between factors that affect naphtha price, and it exhibits an accuracy rate of 84%-95% in forecasting of the naphtha crack three months in advance.
Keywords: Naphtha Crack; Causal Loop; Seasonal Effect; System Dynamics; Forecasting

Polyurethane foam is widely used for automobile compartments as sound absorption materials due to its excellent noise dissipation characteristics. This sound absorption property is strongly dependent on the cavity and pore structures of the foams, and the cell morphology can be modulated by controlling experimental parameters. Two types of gelling catalysts were demonstrated in fabrications of polyurethane foams to control the cell morphology. The cell morphology of the free-rising polyurethane foams was investigated using dibutyltin-dilaurate and triethylenediamnine gelling catalysts, and the cell structures were analyzed from the free-rising samples obtained in various sampling heights and flow directions. The finer cell morphology was obtained with the organotin type catalyst by the faster gelling reactivity, compared with the amine type catalyst. In addition, the spherical small cavities in the samples obtained from horizontal planes of the free-rising foams revealed higher sound absorption coefficient and physical toughness than the elliptical irregular cavities from vertical planes, due to the higher homogeneity of cavity distributions in the horizontal planes.
Keywords: Polyurethane Foams; Flow Direction; Catalysts; Sound Absorption Coefficient