Supercritical water oxidation of nitrogen compounds with multi-injection of oxygen

A supercritical water oxidation (SCWO) process with oxidant multi-injection was studied in a continuous flow system in which the same amount of oxidant feed is split between two points – a first injection at the reactor inlet and a second injection at one of the three different positions along the reactor. Under the same operating conditions, this multi-injection configuration showed advantages over the system with a single oxidant entry. Moreover, oxidant dosage in a SCWO reactor is a key aspect in energy management.In this work, experiments were performed to find the best oxidant dosage to obtain the maximum organic conversion. Experiments were carried out using N,N-dimethylformamide (DMF) as a model compound for nitrogen-containing hydrocarbons in wastewaters. All experiments were carried out at 250 bar with an oxygen coefficient n = 1 and a temperature of 400 °C. Each experiment was carried out at five different residence times (2, 4, 6, 8 and 10 s). Once the best configuration had been determined, the effect of temperature (400–550 °C), initial organic concentration (5–30 mM), oxygen coefficient (0.5–3) and residence time (2–10 s) was investigated in the SCWO process of DMF.     

Polymerization of propylene with Ziegler–Natta catalyst: optimization of operating conditions by response surface methodology (RSM)

Optimization of operational conditions for the polymerization of propylene with Ziegler–Natta catalyst was carried out via RSM. Response surface methodology (RSM) based on a three-level, four-variable Box–Behnken design was used to evaluate the interactive effects of reaction conditions such as reaction temperature (60–80 °C), monomer pressure (5–8 bar), hydrogen volume (130–170 mL), and cocatalyst to catalyst ratio (Al/Ti, 340–500) on the catalyst activity and melt flow rate (MFR). The optimum reaction conditions derived via RSM were: temperature 70 °C, pressure 8 bar, hydrogen volume 151 mL, and cocatalyst to catalyst ratio 390. The experimental catalyst activity and MFR were 8 g polypropylene/mg catalyst and 10.9 g/10 min, respectively, under optimum conditions. Optimum values were determined from process cost point of view and offered better operational conditions.     

Kinetic analysis for decomposition of 2,4-dichlorophenol by supercritical water oxidation

2,4-Dichlorophenol (2,4-DCP), as a halogenated model pollutant, was decomposed by using supercritical water oxidation (SCWO) in a batch reactor made of Hastelloy C-276. SCWO experiments for 2,4-DCP decomposition were performed in the range of 380–420 °C, 230–280 bar and 0.074-0.221 mol/L H₂O₂. The effect of oxidant concentration on decomposition rate and efficiency was significant near the critical temperature of 380 °C. However, the role of the oxidant concentration in the SCWO process decreased with an increase in temperature; also, excess oxidant played a key role in quite significantly decreasing the activation energy of 2,4-DCP oxidation. Variation of the reaction rate by the change of pressure was negligible even at a near critical temperature. The kinetic rate for the decomposition of 2,4-DCP in the SCWO process was well described by a simple first-order kinetic and global reaction rate model. From the SCWO experiments, the various intermediates identified with a GC/MS implied that the first reaction pathway for 2,4-DCP decomposition led to dimers such as dichlorophenoxyphenols, and the second led to single-ring and ring-opening products.     

OPTIMIZATION OF LIPASE-CATALYZED SYNTHESIS OF N-trans-FERULOYLTYRAMINE USING RESPONSE SURFACE METHODOLOGY (RSM)

Enzymatic synthesis of N-trans-feruloyltyramine amide was optimized by response surface methodology (RSM) using 4-hydroxy-3-methoxycinnamic acid and tyramine hydrochloride in a one-step lipase catalyzed reaction using Lipozyme TL IM. Response surface methodology (RSM) based on five-level, four-variable central composite rotatable design (CCRD) was used to evaluate the interaction of synthesis, reaction time (24–96 h), temperature (30°–50°C), amount of enzyme (50–500 mg, 12.5–125.0 IUN), and substrate molar ratio (cinnamic acid:tyramine HCl) 1:1–8:1 mmol on the percentage yield of N-trans-feruloyltyramine amide. The optimum conditions derived via RSM were: reaction time 52 h, temperature 43°C, amount of enzyme 260 mg (65.0 IUN), and substrate molar ratio (cinnamic acid:tyramine HCl) 6.2:1. The actual experimental yield was 96.3% under optimum conditions, which compared well to the maximum predicted value of 97.2%.     

Removal of C.I. Basic Blue 41 from aqueous solution by supercritical water oxidation in continuous-flow reactor

Oxidation of aqueous solution of C.I. Basic Blue 41 (BB41), which is model azo dye pollutants, was studied in a continuous-flow reactor that was operated between 400 and 650 °C at a fixed pressure of 25 MPa. The total organic carbon (TOC) concentration of BB41 was in the range of 30.60 and 152.97 mmol/L in the feed stock solution. Hydrogen peroxide (H₂O₂) was used as an oxygen source and the oxidant concentrations were between 73.53 and 489.64 mmol/L in the feed stock solution. The results demonstrated that supercritical water oxidation (SCWO) process decreases the TOC up to 99.87% in very short reaction times (at residence times of 9–19 s). According to the wastewater and oxidant concentrations, the global rate expression was regressed from the complete set of data for each dye solution. As a result of regression analysis, the reaction rate expression for the oxidation of BB41 was determined with the activation energy of 18.88 (±0.9) kJ/mol and the pre-exponential factor of 2.8 (±0.5) mmol^?0.16 L^0.16 s^?1; and the reaction orders for BB41 (based on TOC) and the oxidant were 0.84 (±0.03) and 0.32 (±0.05) in a 95% confidence level.     

Catalytic oxidation of isophorone to ketoisophorone over ruthenium supported MgAl-hydrotalcite

Selective oxidation of α-isophorone to ketoisophorone was carried out over Ruthenium supported MgAl-hydrotalcite in the temperature range 40–100 °C using acetonitrile as a solvent and tert-butyl hydroperoxide as an oxidant. The influence of various reaction parameters, such as reaction temperature, reaction time, substrate: catalyst mass ratio, substrate:oxidant mole ratio, and nature of solvent was studied. A maximum conversion of 60% KIP with 100% selectivity in 48 h was observed with a substrate: catalyst mass ratio of 10:1 at 60 °C.     

Preparation of a composite coagulant: Polymeric aluminum ferric sulfate (PAFS) for wastewater treatment

A new composite coagulant polymeric aluminum ferric was synthesized and parameters affecting the coagulant performance such as reaction temperature and time, and OH/Fe, P/Fe and Al/Fe molar ratios in this study, were examined. In addition, to obtain the optimum synthetic conditions resulting in the maximum turbidity removal efficiency, response surface methodology (RSM) was used to assess their interactive effects on coagulation–flocculation performance. The results showed that reaction temperature (60–80 °C) and time (30–50 min), and OH/Fe (0.1–0.3), P/Fe (0.2–0.3) and Al/Fe (1:9–1:10) molar ratios were favorable to the preparation process. The optimum synthesis conditions were reaction temperature and time, and OH/Fe, P/Fe and Al/Fe molar ratios of 80 °C, 40 min, 0.1, 0.25 and 1:10, respectively. Evaluation of the coagulation–flocculation process showed that COD (chemical oxygen demand) and turbidity removal efficiency of 82.8% and 98.2%, respectively, were achieved at coagulant dosage of 45 mg/L, wastewater initial pH of 8.5, and rapid agitation speed of 250 rpm. In addition, charge neutralization and adsorption/bridging coagulation–flocculation mechanisms played an important role in reducing the surface charge of colloids.     

含乙醇废水的超临界水氧化反应动力学及反应机理

研究了等温平推流反应器中乙醇的超临界水氧化反应（SCWO）,反应温度475～550 ℃、压力22～30 MPa、停留时间0.6～63.7 s、氧气与乙醇摩尔浓度比4.56～9.09.一氧化碳和二氧化碳分别是反应中间产物和最终产物.随停留时间增大、温度升高,乙醇去除率增大,压力和氧气浓度变化对过程无显著影响.以幂指数方程描述乙醇SCWO动力学,乙醇和氧气的反应级数分别为1和0,计算值和实验值相差基本在10%以内.超临界条件下分别以过氧化氢和氧气为氧化剂时乙醇的氧化反应无明显差别,亚临界条件下过氧化氢氧化速率大于氧气.基于对此现象的分析,作者推测：无论以过氧化氢或氧气作为氧化剂,在超临界水中,它们之间可以通过一系列自由基反应迅速达到平衡,且各物种的平衡分布与初始分布无关,体系的主要氧化过程在平衡分布下进行.     

Effect of annealing on quality enhancement of micro-machining green alumina ceramics by laser ablation

The natural characteristics of sintered ceramics limit the micromachining of functional surface textures in terms of tool wear, processing quality and economic effectiveness. So, the micro-machining of green ceramics before completely sintering is introduced. In this paper, micro-channels are fabricated on the surfaces of green ceramics pretreated by different annealing temperatures. The effect of parametric combination of annealing temperature and laser parameters on the response of processing quality, channel dimension and material removal rate (MRR) are studied by single fact experiments and multi-objective optimization by the response surface method (RSM). The mathematical models of the interaction between different factor combinations are developed based on RSM. Results show that the annealing temperature has significant influence on the aspect ratio under different laser parameters. Continuous channels with few recast layers are always formed at the annealing temperatures of 500–800 °C and a higher annealing temperature always contributes to a larger aspect ratio. Based on the responses of RSM, the optimal parameters of laser ablation and annealing temperature are chosen as laser power of 6 W, scanning speed of 350 mm/s, laser frequency of 40 KHz, and the pretreatment annealing temperature of 750 °C. The experiments validate good agreement of proposed model.     

Low-temperature hot-press sintering of AlN ceramics with MgO–CaO–Al2O3–SiO2 glass additives for ceramic heater applications

Aluminum nitride (AlN) is used a ceramic heater material for the semiconductor industry. Because extremely high temperatures are required to achieve dense AlN components, sintering aids such as Y₂O₃ are typically added to reduce the sintering temperature and time. To further reduce the sintering temperature, in this study, a low-melting-temperature glass (MgO–CaO–Al₂O₃–SiO₂; MCAS) was used as a sintering additive for AlN. With MCAS addition, fully dense AlN was obtained by hot-press sintering at 1500 °C for 3 h at 30 MPa. The mechanical properties, thermal conductivity, and volume resistance of the sintered AlN–MCAS sample were evaluated and compared with those of a reference sample (AlN prepared with 5 wt% Y2O3 sintering aid sintered at 1750 °C for 8 h at 10 MPa). The thermal conductivity of AlN prepared with 0.5 wt% MCAS was 91.2 W/m?K, which was 84.8 W/m?K lower than that of the reference sample at 25 °C; however, the difference in thermal conductivity between the samples was only 14.2 W/m?K at the ceramic-heater operating temperature of 500 °C. The flexural strength of AlN–MCAS was 550 MPa, which was higher than that of the reference sample (425 MPa); this was attributed to the smaller grain size achieved by low-temperature sintering. The volume resistance of AlN–MCAS was lower than that of the reference sample in the range of 200–400 °C. However, the resistivity of the proposed AlN–MCAS sample was higher than that of the reference sample (500 °C) owing to grain-boundary scattering of phonons. In summary, the proposed sintering strategy produces AlN materials for heater applications with low production cost, while achieving the properties required by the semiconductor industry.     

Product Selectivity and Optimization of Lipase-Catalyzed 1,3-Propylene Glycol Esters by Mixture Design and RSM

Propylene glycol mono- (PGM) and diesters (PGD) are widely used as emulsifiers in food and pharmaceutical industry. Solvent engineering was applied to determine the optimum solvent mixtures for the lipase-catalyzed synthesis of 1,3-PGM and 1,3-PGD. After 24 h reaction, the results showed that the molar production of 1,3-PGM was 75% under pure 2M2B (2-methyl-2-butanol) system, whereas 1,3-PGD was preferred to produce in binary mixture system (n-hexane: octane 1:1) with 55% of molar production. Furthermore, the reaction parameters that affect esterification of 1,3-PGD using oleic acid as acyl donor in optimum cosolvent environment were evaluated by response surface methodology (RSM). The reaction temperature and reaction time were the most important parameters. Based on a ridge max analysis, the optimum conditions for 1,3-PGD synthesis were predicted to consist of a reaction time of 40.6 min, a temperature of 59 °C, an enzyme amount of 70.4%, a substrate molar ratio (1,3-propylene glycol/oleic acid) of 1:2.7 and an enzyme pretreatment pH of 6.4 on percentage of molar production of 1,3-PGD of 43.3 ± 4.2%.     

Treatment of dyehouse waste‐water by supercritical water oxidation: a case study

BACKGROUND: Supercritical water oxidation (SCWO) of dyehouse waste‐water containing several organic pollutants has been studied. The removal of these organic components with unknown proportions is considered in terms of total organic carbon concentration (TOC), with an initial value of 856.9 mg L^?1. Oxidation reactions were performed using diluted hydrogen peroxide. The reaction conditions ranged between temperatures of 400–600 °C and residence times of 8–16 s under 25 MPa of pressure. RESULTS: TOC removal efficiencies using SCWO and hydrothermal decomposition were between 92.0 and 100% and 6.6 and 93.8%, respectively. An overall reaction rate, which consists of hydrothermal decomposition and the oxidation reaction, was determined for the hydrothermal decomposition of the waste‐water with an activation energy of 104.12 ( ± 2.6) kJ mol^?1 and a pre‐exponential factor of 1.59( ± 0.5) × 10⁵ s^?1. The oxidation reaction rate orders for the TOC and the oxidant were 1.169 ( ± 0.3) and 0.075 ( ± 0.04) with activation energies of 18.194 ( ± 1.09) kJ mol^?1, and pre‐exponential factor of 5.181 ( ± 1.3) L^0.244 mmol^?0.244 s^?1 at the 95% confidence level. CONCLUSION: Results demonstrate that the SCWO process decreased TOC content by up to 100% in residence times between 8 and 16 s under various reaction conditions. The treatment efficiency increased remarkably with increasing temperature and the presence of excess oxygen in the reaction medium. Color of the waste‐water was removed completely at temperatures of 450 °C and above. Copyright © 2010 Society of Chemical Industry     

Supercritical water oxidation of coal: Investigation of operating parameters' effects, reaction kinetics and mechanism

Supercritical water oxidation (SCWO) of coal was conducted in a continuous tubular reactor under various reaction conditions. Our experimental results show that the removal rate of chemical oxygen demand (COD) had no significant dependence on the temperature variations. Effect of residence time was less significant as exceeded fixed values. Free radical mechanism of SCWO reaction may be a possible explanation for the relative low conversion rate of coal at the range of tested oxygen excess. Compared with other parameters, effect of pressure was less significant. A global power-law rate expression was regressed from experimental data. The reaction orders for coal slurry and oxidant were 1.79 and 0.28 respectively. The reaction activation energy E_a was determined to be 112.3 kJ mol⁻¹, and the pre-exponential factor k₀ was 412 (mol/L)^−1.07 s⁻¹. The deviation between the model and experimental data was within ± 9%. Free radical mechanism, oxidation and hydrolysis mechanisms and phenolic hydroxyl oxidation mechanism were considered to be the possible mechanisms for the SCWO process of coal.     

Lipase-Catalyzed Irreversible Transesterification of <Emphasis Type="Italic">Jatropha Curcas</Emphasis> L. Seed Oil to Fatty Acid Esters: An Optimization Study

In this work, fatty acid ethyl esters were produced from the lipase-catalyzed irreversible transesterification reaction between Jatropha oil and diethyl carbonate (DEC). Response surface methodology (RSM) based on central composite design (CCD) was used to optimize the five important reaction variables for the irreversible transesterification of Jatropha oil in a solvent-free system. The optimum conditions for the transesterification were a reaction time of 13.3 h, a temperature of 44.5 °C, a lipase amount of 13.7% (w/w), a DEC to Jatropha oil molar ratio of 3.75:1 and no need for adding water. The optimal predicted yield of fatty acid esters was 97.7% and the actual value was 96.2%. The results showed that the RSM based on CCD was adaptable for a fatty acid esters yield study for the current transesterification system.     

Response surface methodology as a tool to study the lipase‐catalyzed synthesis of betulinic acid ester

BACKGROUND: The synthesis of betulinic acid ester using betulinic acid and oleyl alcohol catalyzed by Novozym 435 (immobilized Candida antarctica lipase) was carried out. Response surface methodology (RSM) based on a five‐level, three‐variable, central composite rotatable design (CCRD) was employed to evaluate the interactive effects of various parameters. The parameters were reaction time (8–16 h), temperature (20–60 °C) and enzyme amount (120–160 mg). RESULTS: Simultaneously increasing reaction time, temperature and amount of enzyme increased the yields of betulinic acid ester produced. CONCLUSION: The optimum conditions derived via RSM for the reaction were reaction time of 10.2 h, temperature of 53.1 °C and enzyme amount of 138 mg. The actual experimental yield was 48.5% under optimum conditions, which compared well with the maximum predicted value of 47.6%. Copyright © 2008 Society of Chemical Industry     

Effect of calcination temperature on structural,vibrational, optical,and rheological properties of zirconia nanoparticles

ZrO₂ nanoparticles (NPs) were prepared by a simple, versatile, and an efficient methodology based on microwave. The synthesized NPs were calcined at temperatures ranging from 100 °C to 600 °C. The samples were characterized by X-ray powder diffraction (XRD), transmission electron microscope (TEM), FT-IR spectroscopy, Far-IR spectroscopy, Raman spectroscopy, and UV-vis absorption spectroscopy. The results clearly showed the presence of purely monoclinic phase of zirconia when the calcination temperature exceeds 400 °C. The experimental results showed that the viscosity of zirconia NPs in ethylene glycol (EG) increases with increasing the particle volume fraction and decreases with increasing temperature.     

Optimization of mesoporous K/SBA-15 catalyzed transesterification of palm oil using response surface methodology

K/SBA 15 was investigated for the transesterification of palm oil. The influence of temperature, reactants' ratio, catalyst loading and reaction time on the biodiesel yield was studied using a Central Composite Design (CCD). The process optimization using Response Surface Methodology (RSM) was performed and the interactions between the operational variables were elucidated. The optimum conditions were found to be 70 °C for the reaction temperature, 11.6 mol/mol for methanol to oil ratio, 3.91 wt.% for the catalyst loading and 5 h for the reaction time to achieve 93% of biodiesel yield. High catalytic activity was attributed to high surface area of the catalyst and the relatively easy diffusion of reactants in the mesopores. The effect of catalyst loading and reaction time was relatively more dominant in affecting the biodiesel yield. High potential of SBA-15 as catalyst for biodiesel production was demonstrated.     

Green synthesis and biomedical behavior of Mg-doped ZnO nanoparticle using leaf extract of Ficus religiosa

Eco-friendly synthesis of Mg doped ZnO NPs was prepared by Ficus religiosa leaf extract. XRD confirmed the crystalline structure of the prepared Mg-doped ZnO. The functional groups and Zn and O bonding were realized from FTIR and Raman analyses. The surface plasma resonance absorption peak at 363 nm affirmed the formation of Mg–ZnO nanoparticles. The 3.32eV bandgap value of Mg–ZnO NPs was calculated by using Tauc's plot. The photoluminescence spectrum showed the emission behavior and point defect arising from zinc, oxygen vacancies. The hexagonal wurtzite structure of the prepared nanoparticles was observed from FESEM images. From the EDAX study, the elemental compositions have confirmed.The Thermal studies(TG/DTA)study,the Mg doped ZnO Material become thermally stable at 600 °C In XPS spectrum shows good formation of Mg doped ZnO nano materialThe facile synthesized Mg–ZnO NPs using Ficus religiosa leaves showed better antimicrobial properties on gram-positive bacterium, Staphylococcus aureus and fungus, Aspergillus niger. The biomedical behavior of prepared Mg–ZnO NPs was clearly understood from antioxidant(500 μg/mL-87), anti-inflammatory(500 μg/mL-89) and anti-diabetic assays(500μg/mL-82)     

Sulfur transformations during supercritical water oxidation of a Chinese coal

The oxidation of coal in supercritical water was explored by using H₂O₂ as the oxidant. The sulfur-containing components in the effluents were identified. The experiments, which were conducted in a bench scale semi-continuous Supercritical Water Oxidation (SCWO) installation, indicated that the sulfur contained in coal could be gradually oxidized to sulfate in supercritical water medium. The main species containing sulfur in the effluents of coal SCWO were determined as sulfide, thiosulfate, sulfite and sulfate, in which thiosulfate and sulfate were predominant. The effects of the reaction temperature and time on the sulfur transformations during SCWO of coal were also investigated.