Statistical Optimization of the Biodiesel Production Process Using a Magnetic Core‐Mesoporous Shell KOH/Fe3O4@γ‐Al2O3 Nanocatalyst

A magnetic core‐mesoporous shell KOH/Fe₃O₄@γ‐Al₂O₃ nanocatalyst was synthesized using the Fe₃O₄@γ‐Al₂O₃ core‐shell structure as support and KOH as active component. The prepared samples were characterized by X‐ray diffraction (XRD), field‐emission scanning electron microscopy (FE‐SEM), energy‐dispersive X‐ray spectroscopy (EDS), Fourier transform infrared (FTIR), Brunauer‐Emmett‐Teller (BET), and vibrating sample magnetometry (VSM) techniques. Transesterification of canola oil to methyl esters (biodiesel) in the presence of the magnetic core‐mesoporous shell KOH/Fe₃O₄@γ‐Al₂O₃ nanocatalyst was investigated. Response surface methodology (RSM) based on the Box‐Behnken design (BBD) was employed to optimize the influence of important operating variables on the yield of biodiesel. A biodiesel yield of 97.4 % was achieved under optimum reaction conditions. There was an excellent agreement between experimental and predicted results.     

Fischer‐Tropsch Synthesis Over Co‐Ru/γ‐Al2O3 Catalyst in Supercritical Media

The Fischer‐Tropsch synthesis (FTS) in gaseous and supercritical phases was examined in a continuous, high‐pressure fixed‐bed reactor by employing a cobalt catalyst (Co‐Ru/γ‐Al₂O₃). The kinetic modeling of the FTS was investigated in the reactor over a 60–80 mesh cobalt catalyst. The Langmuir‐Hinshelwood kinetic equation was used for both the Fisher‐Tropsch (FT) and water gas shift (WGS) reactions. The kinetic model was applied for simulation of the reactor with 16–20 mesh cobalt catalyst. The simulation results showed a good agreement with the experimental data. The experimental data showed that higher CO conversion and lower CH₄ and CO₂ selectivities were achieved in supercritical media compared to the gaseous phase. The BET surface area and pore volume enhancement results provided evidence of the higher in situ extraction and greater solubility of heavy hydrocarbons in supercritical media than in gaseous phases. Furthermore, the effects of supercritical solvent such as n‐pentane, n‐hexane, n‐heptane and their mixtures were studied. Moreover, the influence of reaction temperature, H₂/CO ratio, W/F_(CO+H2) and pressure tuning in the supercritical media FT synthesis were investigated, as well as the effect of the supercritical fluid on the heat transfer within the reactor. The product carbon distribution had a similar shape for all types of solvents and shifted to lighter molar mass compounds with increasing temperature, H₂/CO ratio, and W/F_(CO+H2). Finally, the product distribution shifted to higher molar mass hydrocarbons with increasing pressure. As a result, one may conclude that a mixture of hydrocarbon products of the FTS can be used as a solvent for supercritical media in Fischer‐Tropsch synthesis.     

Biolubricant Production of 2‐Ethylhexyl Palmitate by Transesterification Over Unsupported Potassium Carbonate

Owing to the decrease of global oil price, development of downstream value‐added products is important to biodiesel industry. In this study, we used palmitic acid methyl ester (PAME) as a starting material to produce 2‐ethylhexyl palmitate (2‐EHP), an environmentally friendly biolubricant product, which was derived from the transesterification of fatty acid methyl esters and long chain fatty alcohols. Conventional synthetic routes of 2‐EHP have disadvantages, including high catalyst price, low conversion efficiency, and pollution issues. To solve these problems, in situ transesterification of PAME with 2‐ethylhexanol (2‐EH) was conducted over unsupported potassium carbonate as heterogeneous catalyst. The optimal reaction temperature, 2‐EH to PAME molar ratio, and catalyst to PAME mass ratio were 180 °C, 3:1, and 3.0 wt%, respectively. The PAME conversion reached up to 100% within 1 hour under the optimal conditions. In addition, a kinetic model describing the experimental data over a temperature range of 160–180 °C was developed. The dependence of kinetic rate constant (k) on temperature was evaluated, and the activation energy (E_a) for the transesterification of PAME with 2‐EH was calculated to be 57.04 kJ mol^?1.     

Ethylene/1‐octadecene copolymerization using [η5:η1‐C5Me4‐4‐R1‐6‐R‐C6H2O]TiCl2 catalysts

Copolymerization of ethylene with 1‐octadecene was studied using [η⁵:η¹‐C₅Me₄‐4‐R₁‐6‐R‐C₆H₂O]TiCl₂ [R₁ = ^tBu (1), H (2, 3, 4); R = ^tBu (1, 2), Me (3), Ph (4)] as catalysts in the presence of Al(i‐Bu)₃ and [Ph₃C][B(C₆F₅)₄]. The effect of the concentration of comonomer in the feed and Al/Ti molar ratio on the catalytic activity and molecular weight of the resultant copolymer were investigated. The substituents on the phenyl ring of the ligand affect considerably both the catalytic activity and comonomer incorporation. The 1 /Al(i‐Bu)₃/[Ph₃C][B(C₆F₅)₄] catalyst system exhibits the highest catalytic activity and produces copolymers with the highest molecular weight, while the 2 /Al(i‐Bu)₃/[Ph₃C][B(C₆F₅)₄] catalyst system gives copolymers with the highest comonomer incorporation under similar conditions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Cr(III)‐containing Fe3O4/mercaptopropanoic acid‐poly(2‐hydroxyethyl acrylate) nanocomposite: Highly active magnetic catalyst for direct hydroxylation of benzene

In this study, polymer‐grafted magnetic nanoparticles containing chromium(III) ions incorporated onto Fe₃O₄/mercaptopropanoic acid‐poly(2‐hydroxyethyl acrylate) was prepared via a simple and in situ method. The obtained magnetic nanocomposite exhibited high catalytic activity and excellent selectivity in direct hydroxylation of benzene in the presence of hydrogen peroxide under solvent‐free condition. The magnetic catalyst could be also separated by an external magnet and reused seven times without any significant loss of activity/selectivity. Due to the Lewis acidity of the Fe³⁺ groups in the structure of magnetic nanoparticles, the high efficiency of this catalyst is possibly due to the synergetic effect of Cr³⁺ and Fe³⁺ groups in the structure of magnetic nanocomposite. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40383.     

Promoted Fe2O3‐Al2O3‐CuO Chromium‐Free Catalysts for High‐Temperature Water‐Gas Shift Reaction

Promoted Fe₂O₃‐Al₂O₃‐CuO (FAC) chromium‐free catalysts were prepared for high‐temperature water‐gas shift reactions and characterized by X‐ray diffraction (XRD), Brunauer‐Emmett‐Teller method (BET), temperature‐programmed reduction (TPR), and transmission electron microscopy (TEM) techniques. The catalytic results revealed that among the investigated promoted catalysts with Ce, La, Zn, Y, and Mn as promoters, the Mn‐promoted sample showed higher activity compared to the other promoted catalysts. Increasing the Mn content improved the surface area and catalytic activity. The FAC catalyst promoted with a high Mn content exhibited maximum activity and relatively high stability in high‐temperature water‐gas shift reaction.     

Esterification of Renewable Levulinic Acid to n‐Butyl Levulinate over Modified H‐ZSM‐5

The synthesis of n‐butyl levulinate, one of the most important biodiesel additives, by catalytic esterification of biomass‐derived levulinic acid (LA) with n‐butanol over modified H‐ZSM‐5 (micro/meso‐HZ‐5) in a closed‐batch system is reported for the first time. The optimization of the reaction conditions such as the reactant molar ratio, the catalyst loading, the reaction time and the temperature was performed in view to maximize the yield of n‐butyl levulinate. Micro/meso‐HZ‐5 was found to be the most efficient catalyst, with 98 % yield of n‐butyl levulinate and a reusability for six cycles, which is higher than reported in the literature. A possible catalytic mechanism for the esterification reaction is also proposed. A second‐order pseudo‐homogeneous model with R² > 0.97 confirmed that the esterification reaction is performed in the kinetic regime due to the high activation energy of 23.84 kJ mol^?1.     

Synthesis of Nano‐γ‐Ferric Oxide by Thermolysis of the 2‐Mercapto‐5‐Methylpyridine‐N‐Oxide‐Iron(III) Complex via Factorial Design

2‐Mercapto‐5‐methylpyridine‐N‐oxide (MMPNO) and its sodium salt (NaMMPNO) were synthesized. The reaction of the latter with Fe³⁺ generates Fe(MMPNO)₃ chelate. The thermolysis of this chelate at 350 °C yielded highly pure reddish‐brown γ‐Fe₂O₃ nanocrystallites with an average particle size of 6.2 nm, a particle size range of 4.2 to 14.8 nm, and a specific surface area of 51.5 m²g^–1. The thermolysis process was optimized using the 2² fractional design. Quantitative tests and characterization of products were carried out by UV‐vis spectroscopy, XRD, LLS, SEM, TGA, BET, TEM, FT‐IR, elemental microanalysis, and classical analytical measurements.     

Mechanistic insights into methanol‐to‐olefin reaction on an α‐Mn2O3 nanocrystal catalyst

The synthesis and utilization of an α‐Mn₂O₃ nanocrystal catalyst for methanol‐to‐olefin reaction is described. A methanol conversion of 35% and a maximum selectivity of 80% toward ethylene were obtained at 250^°C. In particular, formaldehyde, a primary intermediate for the reaction, was used to produce ethylene via a coupling reaction. A conversion of 45% and a selectivity of 66% to ethylene were achieved at 150^°C in a formaldehyde stream. In situ diffuse reflectance infrared Fourier transform spectra reveal the formation of the surface CH₂‐containing species during reaction, which implies that the main pathway for formaldehyde coupling is probably through interactions of those intermediates. In addition, the weakly adsorbed oxygen on the α‐Mn₂O₃ nanocrystal surface was found to play an important role in this reaction. © 2012 American Institute of Chemical Engineers AIChE J, 2012     

Nano‐engineered nickel catalysts supported on 4‐channel α‐Al2O3 hollow fibers for dry reforming of methane

A nickel (Ni) nanoparticle catalyst, supported on 4‐channel α‐Al₂O₃ hollow fibers, was synthesized by atomic layer deposition (ALD). Highly dispersed Ni nanoparticles were successfully deposited on the outside surfaces and the inside porous structures of hollow fibers. The catalyst was employed to catalyze the dry reforming of methane (DRM) reaction and showed a methane reforming rate of 2040 Lh^?1gNi^?1 at 800°C. NiAl₂O₄ spinel was formed when Ni nanoparticles were deposited on alpha‐alumina substrates by ALD, which enhanced the Ni‐support interaction. Different cycles (two, five, and ten) of Al₂O₃ ALD films were applied on the Ni/hollow fiber catalysts to further improve the interaction between the Ni nanoparticles and the hollow fiber support. Both the catalyst activity and stability were improved with the deposition of Al₂O₃ ALD films. Among the Al₂O₃ ALD coated catalysts, the catalyst with five cycles of Al₂O₃ ALD showed the best performance. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2625–2631, 2018     

Branched‐Chain Fatty Acid Methyl Esters as Cold Flow Improvers for Biodiesel

Biodiesel is an alternative diesel fuel derived mainly from the transesterification of plant oils with methanol or ethanol. This fuel is generally made from commodity oils such as canola, palm or soybean and has a number of properties that make it compatible in compression‐ignition engines. Despite its many advantages, biodiesel has poor cold flow properties that may impact its deployment during cooler months in moderate temperature climates. This work is a study on the use of skeletally branched‐chain‐fatty acid methyl esters (BC‐FAME) as additives and diluents to decrease the cloud point (CP) and pour point (PP) of biodiesel. Two BC‐FAME, methyl iso‐oleate and methyl iso‐stearate isomers (Me iso‐C_18:1 and Me iso‐C_18:0), were tested in mixtures with fatty acid methyl esters (FAME) of canola, palm and soybean oil (CaME, PME and SME). Results showed that mixing linear FAME with up to 2 mass% BC‐FAME did not greatly affect CP, PP or kinematic viscosity (ν) relative to the unmixed biodiesel fuels. In contrast, higher concentrations of BC‐FAME, namely between 17 and 39 mass%, significantly improved CP and PP without raising ν in excess of limits in the biodiesel fuel standard specification ASTM D 6751. Furthermore, it is shown that biodiesel/Me iso‐C_18:0 mixtures matched or exceeded the performance of biodiesel/Me iso‐C_18:1 mixtures in terms of decreasing CP and PP under certain conditions. This was taken as evidence that additives or diluents with chemical structures based on long‐chain saturated chains may be more effective at reducing the cold flow properties of mixtures with biodiesel than structures based on long‐chain unsaturated chains.     

Synthesis and properties of novel benzobisthiazole‐containing hyperbranched polyamides derived from 2,6‐diaminobenzo[1,2‐d:4,5‐d']bisthiazole

In this article, two novel benzobisthiazole‐containing hyperbranched polyamides with different end groups were synthesized, by adjusting the feed molar ratio of the reaction monomers, using 1,3,5‐benzenetricarboxylic acid and 2,6‐diaminobenzo[1,2‐d:4,5‐d']bisthiazole as monomers, polyphosphoric acid as solvent, and catalyst. The molecular structure of the synthesized hyperbranched polymers were speculated by ¹H‐nuclear magnetic resonance (NMR) analysis, ¹³C‐NMR analysis, and Fourier transform infrared analysis. The M_n, M_w, and DB of the carboxyl terminated polymer HB‐COOH are 3264 g/mol, 3350 g/mol, and 44.1%, respectively, with a polydispersity of 1.03. The M_n, M_w, and DB of amino terminated polymer HB‐NH₂ are 3340 g/mol, 3420 g/mol, and 41.7%, respectively, with a polydispersity of 1.02. The thermal stability of HB‐NH₂ was higher than HB‐COOH in the range of 30 °C–800 °C.These two benzobisthiazole‐containing hyperbranched polyamides were completely amorphous and soluble in DMSO. Their DMSO solutions exhibited strong blue fluorescence. The fluorescent intensity of HB‐NH₂ was higher than HB‐COOH. The prepared polymers were potential useful in the area of blue light emitting and display. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43453.     

Response surface modeling and optimization of biodiesel production from Cynara cardunculus oil

Cardoon (Cynara cardunculus L.) is a perennial spontaneous thistle grown in Mediterranean countries and well adapted to marginal lands, recently considered as a non‐food energy crop. Their seeds contain 24% of oil (dry basis). In this study, modeling and optimization of the production of fatty acid methyl esters (FAME) from cardoon oil for biodiesel uses was performed at laboratory scale, via response surface methodology, following a central composite rotatable design. FAME were obtained by transesterification of crude cardoon oil with methanol in the presence of a catalyst (sodium methoxide) for 120 min. The temperature ranged from 26 to 94 °C, the amount of sodium methoxide varied between 0.12 and 2.5 wt‐% and the molar ratio methanol/oil from 0.95 : 1 to 11 : 1. The estimated yield of FAME (97%) was obtained after 30 min, at 52 °C, for a molar ratio of 6.4 : 1 and 1.4 wt‐% of catalyst. In laboratory‐scale model validation experiments, 94% of FAME yield was obtained after 30 min of reaction. Transesterification was performed in a 30‐L reactor, under previously optimized conditions: A yield of 88% FAME was obtained after 90 min of reaction time, due to mass transfer limitations. After purification, the biodiesel showed high quality according to DIN EN 14214 standard specifications.     

Synthesis and characterization of novel block copolymer from trans‐4‐hydroxy‐L‐proline and poly(ethylene glycol)

A series of novel ABA‐type block copolymers were synthesized by polymerization of trans‐4‐hydroxy‐L ‐proline (HyP) in the presence of various molecular weight poly(ethylene glycol)s (PEGs), a bifunctional OH‐terminated PEG using stannous octoate as catalyst. The optimal reaction conditions for the synthesis of the copolymers were obtained with 5 wt % stannous octoate at 140°C under vacuum (20 mmHg) for 24 h. The synthesized copolymers were characterized by IR spectroohotometry, proton nuclear magnetic resonance, differential scanning calorimetry, and Ubbelohde viscometer. The glass transition temperature (T_g) of the copolymers shifted to significantly higher temperature with increasing the number average degree of polymerization and HyP/PEO molar ratio. In contrast, the melting temperature (T_m) decreased with increasing the HyP/PEO molar ratio. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1581–1587, 2001     

Optimization of Process Variables for Biodiesel Production Using the Nanomagnetic Catalyst CaO/NaY‐Fe3O4

Due to decreasing oil resources, alternative fuels such as biodiesel are required. The nanomagnetic catalyst CaO/NaY‐Fe₃O₄ was synthesized and used for biodiesel production from canola oil. The structure of the catalysts was characterized by X‐ray diffraction, field emission scanning electron microscopy, Brunauer‐Emmett‐Teller method, Fourier transform infrared spectroscopy, and vibrating sample magnetometer method. To optimize the influence of the operating variables, such as the methanol/canola oil molar ratio, the amount of catalyst, and the reaction time, on the yield of transesterification reaction, an experimental design was applied based on the Box‐Behnken method. The optimum values of these variables were predicted by the cubic model and were in excellent agreement with the experimental results.     

RAFT polymerization of N‐vinyl pyrrolidone using prop‐2‐ynyl morpholine‐4‐carbodithioate as a new chain transfer agent

RAFT polymerization of N‐vinyl pyrrolidone (NVP) has been investigated in the presence of chain transfer agent (CTA), i.e., prop‐2‐ynyl morpholine‐4‐carbodithioate (PMDC). The influence of reaction parameters such as monomer concentration [NVP], molar ratio of [CTA]/[AIBN, i.e., 2,2′‐azobis (2‐methylpropionitrile)] and [NVP]/[CTA], and temperature have been studied with regard to time and conversion limit. This study evidences the parameters leading to an excellent control of molecular weight and molar mass dispersity. NVP has been polymerized by maintaining molar ratio [NVP]: [PMDC]: [AIBN] = 100 : 1 : 0.2. Kinetics of the reaction was strongly influenced by both temperature and [CTA]/[AIBN] ratio and to a lesser extent by monomer concentration. The activation energy (E_a = 31.02 kJ mol^?1) and enthalpy of activation (ΔH^?= 28.29 kJ mol^?1) was in a good agreement to each other. The negative entropy of activation (ΔS^? = ?210.16 J mol^‐1K^‐1) shows that the movement of reactants are highly restricted at transition state during polymerization. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Hydrogenation of cis‐1,4‐poly(isoprene) catalyzed by OsHCl(CO)(O2)(PCy3)2

The quantitative hydrogenation of cis‐1,4‐poly(isoprene) (CPIP) provides an easy entry to the alternating copolymer of ethylene–propylene, which is difficult to prepare by conventional polymerization. The homogeneous hydrogenation of CPIP, in the presence of OsHCl(CO)(O₂)(PCy₃)₂ as catalyst, has been studied by monitoring the amount of hydrogen consumed during the reaction. The final degree of olefin conversion measured by computer‐controlled gas uptake apparatus was confirmed by infrared spectroscopy and ¹H nuclear magnetic resonance analysis. Kinetic experiments for CPIP hydrogenation in toluene solvent indicate that the hydrogenation rate is first order with respect to catalyst and carbon–carbon double bond concentration. A second‐order dependence on hydrogen concentration for low values and a zero‐order dependence for higher values of the hydrogen concentration was observed. The apparent activation energy for the hydrogenation of CPIP over the temperature range of 115–140°C was 109.3 kJ/mole. Mechanistic aspects of this catalytic process are discussed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 142–152, 2003     

Photo‐Induced atom transfer radical polymerization with nanosized α‐Fe2O3 as photoinitiator

Photo‐induced atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) was achieved in poly(ethylene glycol)‐400 with nanosized α‐Fe₂O₃ as photoinitiator. Well‐defined poly(methyl methacrylate) (PMMA) was synthesized in conjunction with ethyl 2‐bromoisobutyrate (EBiB) as ATRP initiator and FeCl₃·6H₂O/Triphenylphosphine (PPh₃) as complex catalyst. The photo‐induced polymerization of MMA proceeded in a controlled/living fashion. The polymerization followed first‐order kinetics. The obtained PMMA had moderately controlled number‐average molecular weights in accordance with the theoretical number‐average molecular weights, as well as narrow molecular weight distributions (M_w/M_n). In addition, the polymerization could be well controlled by periodic light‐on–off processes. The resulting PMMA was characterized by ¹H nuclear magnetic resonance and gel permeation chromatography. The brominated PMMA was used further as macroinitiator in the chain‐extension with MMA to verify the living nature of photo‐induced ATRP of MMA. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42389.     

Controlled Reversible Anchoring of η6‐Arene/TsDPEN‐ Ruthenium(II) Complex onto Magnetic Nanoparticles: A New Strategy for Catalyst Separation and Recycling

A new catalyst separation and recycling protocol combining magnetic nanoparticles and host‐guest assembly was developed. The catalyst, (η⁶‐arene)[N‐(para‐toluenesulfonyl)‐1,2‐diphenylethylenediamine]ruthenium trifluoromethanesulfonate [Ru(OTf)(TsDPEN)(η⁶‐arene)] bearing a dialkylammonium salt tag, was easily separated from the reaction mixtures by magnet‐assisted decantation, on basis of the formation of a pseudorotaxane complex by using dibenzo[24]crown‐8‐modified Fe₃O₄ nanoparticles. The ruthenium catalyst has been successfully reused at least 5 times with the retention of enantioselectivity but at the expense of relatively low catalytic activities in the asymmetric hydrogenation of 2‐methylquinoline.     

Electrochemical Performance of MnO2‐based Air Cathodes for Zinc‐air Batteries

This paper compares the oxygen reduction on four MnO₂‐based air cathodes assembled in home‐made electrochemical cells, with some particular observations on α‐MnO₂ cathode. The results show that the catalytic activity decreases in the following order: electrolytic MnO₂ (EMD) > natural MnO₂ (NMD) > β‐MnO₂ > α‐MnO₂. The maximum power density of the zinc‐air battery with EMD as the catalyst reaches up to 141.8 mW cm⁻² at the current density of 222.5 mA cm⁻², which is about 60%, 20% and 10% higher than that of α‐MnO₂ (90.0 mW cm⁻² at 120.3 mA cm⁻²), β‐MnO₂ (121.5 mW cm⁻² at 150.4 mA cm⁻²) and NMD (128.2 mW cm⁻² at 207.8 mA cm⁻²), respectively. It is believed that its unique crystal structure and biggest BET surface area make EMD have the smallest charge transfer resistance (R_ct), thus EMD has the highest activity.