Activation of Mg–Al hydrotalcite catalysts for transesterification of rape oil

Mg–Al hydrotalcites with different Mg/Al molar ratios were prepared and characterized by powder X-ray diffraction (XRD), Fourier-transform infrared spectra (FTIR), thermogravimetric apparatus and differential thermal analysis (TGA-DTA) and scanning electron micrograph (SEM). It was confirmed by XRD that the materials had hydrotalcite structure. The hydrotalcite catalyst calcined at 773 K with Mg/Al molar ratio of 3.0 exhibited the highest catalytic activity in the transesterification. In addition, a study for optimizing the transesterification reaction conditions such as molar ratio of the methanol to oil, the reaction temperature, the reaction time, the stirring speed and the amount of catalyst, was performed. The optimized parameters, 6:1 methanol/oil molar ratio with 1.5% catalyst (w/w of oil) reacted under stirring speed 300 rpm at 65 °C for 4 h reaction, gave a maximum ester conversion of 90.5%. Moreover, the solid catalyst could be easily separated and possibly reused.     

Optimization of flocculation conditions for the separation of TiO2 particles in coagulation-photocatalysis hybrid water treatment

TiO₂ mediated photocatalysis can decompose organic micropollutants (e.g., 1,4-dioxane) in water, but the removal of used TiO₂ particles is challenging. Although retrofitting enhances the particle separation efficiency, optimizing a coagulation/flocculation process should be most suitable for existing treatment plants. Therefore, the present study investigated the separation characteristics of TiO₂ particles added to drinking water treatment processes along with a polyaluminum coagulant. TiO₂ photocatalysts were able to achieve significant degradation of 1,4-dioxane (∼100% within 50 min) as well as dissolved organic matter (∼75% within 150 min) at a TiO₂ dose of 1.0 g/L under UV irradiation. Although the TiO₂ particle separation efficiency was sensitive to G values, maximal removal occurred at a G value of <34 s⁻¹ with a coagulant concentration of >8 mg/L as Al₂O₃. Sand filters had the capability to remove residual turbid materials and thus, the turbidity of the final product water dropped to as low as 0.1 NTU when the coagulation/flocculation process was preceded. The final effluent quality was comparable to that of a 0.45-μm membrane filter. The post separation of the TiO₂ photocatalysts dispersed for emergency water treatment to degrade 1,4-dixoane was successfully achieved with an optimal coagulant dose, proper flocculation, and sand filtration.     

Optimization of coagulation–flocculation process for papermaking-reconstituted tobacco slice wastewater treatment using response surface methodology

A coagulation–flocculation process was used to treat papermaking-reconstituted tobacco slice wastewater with polyaluminium chloride (PAC) as coagulant and a cationic polyacrylamide (CPAM) as flocculant. To maximize the reduction of chemical oxygen demand (COD) and color, the jar tests were carried out in the experiments and response surface methodology (RSM) was applied to optimize the process. A central composite design, i.e., a standard approach in RSM, was used to evaluate the effects and interactions of three factors, i.e. PAC dosage, CPAM dosage and pH on the treatment efficiency. Results revealed that the maximum reduction of COD and color could be achieved at an optimal conditions, i.e., PAC = 715 mg/L, CPAM = 4.8 mg/L and pH = 6.6, from which the reduction of COD and color were 67.8% and 77.7%, respectively. The study also showed that the regression equations could be used as the theoretical basis for coagulation–flocculation process of papermaking-reconstituted tobacco slice wastewater. They will be very helpful to flexibly select the appropriate process parameters in the engineering applications     

Removal of turbidity from drinking water using natural coagulants

The ability of three plant materials, seeds such as Moringa oleifera, Strychnos potatorum and Phaseolus vulgaris, to act as natural coagulants was tested using synthetic turbid water formulated to resemble the drinking water. An improved and alternative method for the extraction of the active coagulant agent M. oleifera, S. potatorum, P. vulgaris seeds was developed and compared with the conventional water extraction method. In the new method the seeds were extracted using different solvents of NaCl and NaOH to extract the active coagulant agent from natural coagulants. In addition, ultrasound was investigated as a potential method to assist the extraction process. Batch coagulation experiments were conducted to evaluate the performance of the extracted coagulant achieved through various schemes. The optimum turbidity removal at different values of initial synthetic wastewater turbidity from 100 to 500 NTU was investigated. Sodium chloride at 0.5 M was found to provide a high turbidity removal of >99% compared to NaOH and distilled water extract. Among these three coagulant M. oleifera seed extracts is the highest performance in turbidity removal. The optimum coagulant dosage showed the coagulation with blended coagulant M. oleifera, S. potatorum and P. vulgaris. The study was carried out for initial turbidity of the sample such as 100 NTU (low), 250 NTU (medium) and 500 NTU (high). For the natural coagulant dosage was found to be 250–1000 mg/L respectively. It was found that the percentage of removal is highest in M. oleifera.     

Diesel-like hydrocarbons obtained by direct hydrodeoxygenation of sunflower oil over Pd/Al-SBA-15 catalysts

Hydrodeoxygenation of sunflower oil was performed in an autoclave over 5.0 wt.% Pd/Al-SBA-15 (Si/Al molar ratios from 22 to 300) and Pd/HZSM-5(22). The effects of acidity of the catalysts and the reaction temperatures on the activity of the catalysts were investigated. Pd/Al-SBA-15(Si/Al = 300) showed a high activity as 74.4% liquid yield and 72.9% C15–C18 diesel-like hydrocarbons yield at 250 °C. At 300 °C, the higher activity over Pd/Al-SBA-15(Si/Al = 50, 100 and 300) catalysts compared with that over Pd/Al-SBA-15(22) and Pd/HZSM-5(22) indicated that strong acidity of the catalysts was not favorable for converting sunflower oil into C15–C18 diesel-like hydrocarbons at a high temperature.     

Effects of Fe addition on the structure and catalytic performance of mesoporous Mn/Al–SBA-15 catalysts for the reduction of NO with ammonia

Mesoporous Al–SBA-15 has been synthesized by a hydrothermal method and used as a support for Mn/Al–SBA-15, Fe/Al–SBA-15, and Mn–Fe/Al–SBA-15 catalysts. XRD, N₂ sorption, XPS, H₂-TPR and activity tests have been used to assess the properties of catalysts. The Mn–Fe/Al–SBA-15 catalyst exhibited a higher SCR activity than Mn/Al–SBA-15 or Fe/Al–SBA-15 due to a synergistic effect between Mn and Fe. After the addition of Fe, the binding energy of Mn 2p_3/2 on Mn–Fe/Al–SBA-15(573) decreased by about 0.4 eV and the Mn^4 +/Mn^3 + ratio decreased to 1.10. The appropriate Mn^4 +/Mn^3 + ratio may have a great effect on the reduction of NO over Mn–Fe/Al–SBA-15(573) catalyst.     

Continuous synthesis of fine MgFe2O4 nanoparticles by supercritical hydrothermal reaction

We produced magnesium ferrite (MgFe₂O₄) nanoparticles by hydrothermal synthesis in supercritical water. Suspensions containing varying ratios of Mg(OH)₂ and Fe(OH)₃ at room temperature were pressurized to 30 MPa, fed into a tubular reactor by high-pressure pump, and rapidly heated to reaction temperature by mixing with supercritical water. The MgFe₂O₄ phase forms at 460 °C. The Mg/Fe molar ratio was varied from 0.5 to 1.5 with the goal of obtaining single-phase MgFe₂O₄. At the stoichiometric ratio for MgFe₂O₄, Mg/Fe = 0.5, the product contains both MgFe₂O₄ and α-Fe₂O₃. At Mg/Fe = 1.0 and 1.5, the product is the desired single-phase MgFe₂O₄. The synthesized MgFe₂O₄ nanoparticles, with particle size of about 20 nm, exhibit superparamagnetic behavior.     

Morphology of cubic boron nitride crystals synthesized using (Fe,Co, Ni)–(Cr,Mo)–Al alloy solvents under pressure

The growth region of the cubic boron nitride (cBN) using (Fe, Ni)–Cr–Al and Co–(Cr, Mo)–Al solvents were presented in the pressure range of about 4–6 GPa and the temperature range between 1200 and 1700 °C. The minimum pressure for cBN formation was confirmed at about 4–4.1 GPa for both (Fe, Ni)–Cr–Al and Co–(Cr, Mo)–Al solvents. Based upon this pressure–temperature condition of the cBN growth region, the morphology of cubic boron nitride crystals was examined under various compositions of the solvents. The morphology of cBN crystals was affected by not only the reaction pressure and but also the composition of the solvents. It was found that the variation of alloy composition provides various morphologies and grain sizes of cBN crystals.     

Kinetic study of CO hydrogenation on the MgO supported Fe–Co–Mn sol–gel catalyst

The kinetic of the Fischer–Tropsch synthesis over the MgO supported Fe–Co–Mn catalyst prepared using sol–gel procedure, was investigated in a fixed bed micro-reactor. Experimental conditions were varied as follow: reaction pressure 5–20 bar, reaction temperature 220–250 °C, H₂/CO feed molar ratio of 0.67–2 and space velocity range of 2400–3600 h^?1. 18 models according to the Langmuir–Hinshelwood–Hougen–Watson (LHHW) type rate equation were derived, and the reaction rate is fitted fairly well by one kinetic expressions based on LHWW mechanism. The kinetic parameters were estimated with non-linear regression method. The activation energy was obtained 110.9 kJ/mol for the best-fitted model.     

Boron-doped mullite derived from single-phase gels

Mullite with low dielectric constant and high transparency in infrared and microwave range has potential applications in communication industry. To improve the above properties of mullite, boron-doped mullite single-phase gels with a constant molar ratio of Al/Si = 3/1 and various B/Al ratios (B/Al = 0–0.4/3) were prepared in this study by slow hydrolysis of aluminum nitrate, boric acid and tetraethoxysilane. It was found that boron reduces the mullite formation temperature and suppresses spinel formation. The cell unit lattice parameters and cell volume in boron-doped mullite generally decrease with the increase of boron amount. The SEM observation shows that a small amount of boron reduces the grain sizes of mullite sintered bodies while a large amount of boron facilitates the formation of elongated grains and the amorphous glass phase. Boron decreases the transmittance of mullite ceramic and produces additional intensive absorption bond at 3.9 μm and also reduces the dielectric constants in the frequent range of 1 M–1 GHz.     

Characterisation of Diclofenac,Ketoprofen or Chloramphenicol Succinate encapsulated in layered double hydroxides with the hydrotalcite-type structure

Three series of hybrid organic–inorganic layered double hydroxide samples containing Zn^2 + and/or Mg^2 + and Al^3 + in the brucite-like layers (nominal M^2 +/Al molar ratio 2:1) and Diclofenac, Ketoprofen or Chloramphenicol Succinate as counter-anions, were synthesized by coprecipitation using drug/Al molar ratios of 2:1 to prepare the starting solutions. All samples have been characterised by element chemical analysis, powder X-ray diffraction, FT-IR spectroscopy, thermal analysis and morphology analysis (Scanning Electron Microscopy). The nanohybrids here prepared show a rather high crystallinity degree and the drug molecules are strongly interacting with the brucite-like layers.     

High-pressure synthesis of cubic BN using Fe–Mo–Al and Co–Mo–Al alloy solvents

The pressure and temperature regions of cubic BN formation were determined using Fe–Mo–Al and Co–Mo–Al ternary alloys as synthetic solvents of cubic BN. The alloy compositions employed in the present study were (in weight percent) Fe60.14–Mo36.86–Al3 and Co57.6–Mo38.4–Al4. The cubic BN was successfully synthesized at minimum pressure of about 4.4 GPa and temperature of about 1250 °C. Pressure and temperature of cubic BN synthesis were decreased drastically by small amount of Al addition into Fe–Mo or Co–Mo alloy solvents. The growth of cubic BN was started at the interface between the molten alloy and the source hexagonal BN. In the present study, we proposed that Fe–Mo and Co–Mo work as solvent of B and N atoms and Al acts as a nucleation agent of cubic BN.     

Treatment of paint manufacturing wastewater by electrocoagulation

Treatability of paint manufacturing wastewater (PMW) by electrocoagulation (EC) process was investigated. Effects of operating parameters for the EC process such as electrode type (Al or Fe), initial pH (2–10), current density (5–80 A/m²) and operating time (0–50 min) were evaluated for optimum operating conditions. The highest removal efficiencies for COD and TOC in PMW were obtained with 93% and 88% for Fe and 94% and 89% for Al electrodes at the optimum conditions (35 A/m², 15 min and pH 6.95). Operating costs for removal of PMW at the optimum conditions were calculated for Fe and Al electrodes as 0.187 €/m³ and 0.129 €/m³. Toxicity test was carried out to obtain information about toxic effect of the raw and treated wastewaters at optimum operating conditions. The samples measured by respirometric method contained hardly toxicities. Performance of Al electrode was better than that of Fe electrode in terms of removal efficiency and operating cost.     

A kinetic study on hydrochloric acid leaching of nickel from Ni–Al2O3 spent catalyst

Hydrochloric acid leaching of nickel from spent Ni–Al₂O₃ catalyst (12.7% Ni, 39.2% Al and 0.68% Fe) has been investigated at a range of conditions by varying particle size (50–180 μm), acid concentration (0.025–2 M), pulp density (0.2–0.4%, w/v) and temperature (293–353 K). Nickel was selectively leached from the catalyst, irrespective of the different conditions. Under the most suitable conditions (1 M HCl, 323 K, stirring at 500 rpm, 50–71 μm particle size), the extent of leaching of Ni and Al after 2 h was 99.9% and 1%, respectively. The XRD pattern of the spent catalyst corresponded to crystalline α-Al₂O₃ along with elemental Ni. The peak due to elemental Ni was absent in the residue sample produced at the optimum leaching conditions, confirming the complete dissolution of Ni from the spent catalyst. The leaching results were well fitted with the shrinking core model with apparent activation energy of 17 kJ/mol in the temperature range of 293–353 K indicating a diffusion controlled reaction.     

Synthesis of Li/Al LDH using aluminum and LiOH

The synthesis of Li/Al layered double hydroxide (LDH) within the ternary system of LiOH–Al–H₂O was investigated to determine the feasibility of a one-step synthetic process and the optimal yield composition for the process. The dissolution of Al metal in LiOH solutions was spontaneous and resulted in the generation of H₂ gas and heat. Pure Li/Al LDH precipitate was obtained when the Al/Li molar ratio was between 0.1 and 2 and was independent of the LiOH concentration. The yield of Li/Al LDH was correlated with the initial amounts of LiOH and Al in the system and inversely correlated to the quantity of water. However, the Al metal could not be completely dissolved if there was not enough water content due to its consumption in the reaction. The optimal yield of Li/Al LDH, as defined by the efficient conversion from Al and LiOH to Li/Al LDH, was obtained with a LiOH concentration = 3 mol kg^− 1 and an Al/Li molar ratio = 2. The reaction mechanism involves the dissolution of the Al metal in LiOH and the formation of aluminate ions in solution. The aluminate ion and the hydrated Li⁺ ion subsequently form an ion pair, and the polarizing effect of the Li⁺ on the water in its hydration shell leads to the acid hydrolysis of the aluminate ion and the formation of Li/Al LDH. This study demonstrated a synthetic process for Li/Al LDH with a high anion exchange capacity. This synthetic process will have additional economical and environmental benefits if recycled Al metal can be used in the synthesis and the evolved hydrogen gas and heat from the process can be further utilized.     

Palladium nanoparticles supported on amino functionalized metal-organic frameworks as highly active catalysts for the Suzuki–Miyaura cross-coupling reaction

Well dispersed Pd nanoparticles supported on amino functionalized metal-organic frameworks MIL-53(Al)-NH₂ (Al(OH)[H₂N-BDC], H₂N-BDC = 2-aminoterephthalic acid, MIL = Materials of Institut Lavoisier) were prepared using a direct anionic exchange approach and subsequent reduction with NaBH₄. The Pd/MIL-53(Al)-NH₂ catalyst exhibitted high activity and good stability for Suzuki–Miyaura cross-coupling reaction.     

Catalytic conversion of CO,NO and SO2 on the supported sulfide catalyst: I. Catalytic reduction of SO2 by CO

Catalytic reduction of SO₂ to elemental sulfur by CO has been systematically investigated over γ-Al₂O₃-supported sulfide catalysts of transition metals including Co, Mo, Fe, CoMo and FeMo with different loadings of the metals. The sulfided CoMo/Al₂O₃ exhibited outstanding activity: a complete conversion of SO₂ was achieved at a temperature of 300°C. The reaction proceeds catalytically and consistently over time and most efficiently at a molar feed ratio CO/SO₂ = 2. A precursor CoMo/Al₂O₃ oxide which experienced sulfurization through the CO–SO₂ reaction yielded a working sulfide catalyst having a yet lower activity than the CoMo catalyst sulfided before reaction (pre-sulfiding). The catalytic activity of various metal sulfides decreased in order of 4% Co 16% Mo > 4% Fe15% Mo > 16% Mo ≥ 25% Mo > 14% Co ≥ 4% Co > 4% Fe. A DRIFT study showed that CO adsorbs exclusively on CoMo phase and that SO₂ predominantly on γ-Al₂O₃. It is suggested that the Co–Mo–S structure is more adequate than the other metal-sulfur structures for the formation of a carbonyl sulfide (COS) intermediate because of the proper strength of metal–sulfur bond, and catalytically works with γ-Al₂O₃ for the COS–SO₂ reaction.     

Effects of coal blending on the reduction of PM10 during high-temperature combustion 1. Mineral transformations

Two coals with comparable mineral particle distributions, but different contents of Ca were blended and combusted. Mineral transformations and their effects on particulate matter smaller than 10 μm (PM₁₀) emissions were investigated during the combustion of single and blended coals. Combustion experiments were carried out at 1450 °C in air atmosphere using a lab-scale drop tube furnace (DTF). The particle size distributions (PSD), morphologies, elemental compositions, and chemical composition of minerals in coal and PM were analyzed. The results indicate that emissions of PM smaller than 1 μm (PM₁) and particulate matter sized between 1 and 10 μm (PM_1–10) are reduced compared to their calculated linear results during combustion. The transformation of P, S, Al, and Si from submicron particles to PM larger than 1 μm (PM₁₊) reduces PM₁ emissions. The transformation of Ca, Fe, Al, and Si from PM₁₀ to particles larger than 10 μm (PM₁₀₊) reduce PM_1–10 emissions. The high concentration of Ca in coal blends enhances the liquid phase percentage produced during combustion, and as a result, improves both the adhesion of volatilized P, S, Al, and Si on the sticky surface of large particles to be transformed to PM₁₊, and the probability of collision and coalescence of particles to form larger particles of Ca–Fe–Al–Si, Ca–Al–Si, or Fe–Al–Si. Thus, as Ca, Fe, Al, and Si are transformed into PM₁₀₊. PM₁ and PM_1–10 emissions are reduced accordingly.     

Biodiesel production from waste cooking oil in a microtube reactor

Waste cooking oil (WCO) was used to produce biodiesel in a microtube reactor. First, the acid value of the WCO was reduced from 3.96 mg KOH/g to less than 1 mg KOH/g via acid catalyzed esterification. The effects of the methanol-to-WCO molar ratio (4.5:1–18:1), the H₂SO₄ concentration (0.5–2 wt.%), reaction temperature (55–70 °C), and reaction time (5–20 s) were studied. The optimal conditions were 9:1 methanol-to-WCO molar ratio, 1 wt.% H₂SO₄, 65 °C and 5 s of reaction time. Triglycerides in the product from the first step were transesterified with methanol and alkaline catalyst. Methyl ester content of the biodiesel was 91.76%.     

High Li-ion conductivity of Al-doped Li7La3Zr2O12 synthesized by solid-state reaction

Li₇La₃Zr₂O₁₂ (LLZO) has cubic garnet type structure and is a promising solid electrolyte for next-generation Li-ion batteries. In this work, Al-doped LLZO was prepared via conventional solid-state reaction. The effects of sintering temperature and Al doping content on the structure and Li-ion conductivity of LLZO were investigated. The phase composition of the products was confirmed to be cubic LLZO via XRD. The morphology and chemical composition of calcined powders were investigated with SEM, EDS, and TEM. The Li-ion conductivity was measured by AC impedance. The results indicated the optimum sintering temperature range is 800–950 °C, the appropriate molar ratio of LiOH·H₂O, La(OH)₃, ZrO₂ and Al₂O₃ is 7.7:3:2:(0.2–0.4), and the Li-ion conductivity of LLZO sintered at 900 °C with 0.3 mol of Al-doped was 2.11×10⁻⁴ S cm⁻¹ at 25 °C.