Transesterification of palm oil on KyMg1 − xZn1 + xO3 catalyst: Effect of Mg-Zn interaction

The Mg-Zn interaction effect of K_yMg_1 − xZn_1 + xO₃ heterogeneous type catalyst and its performance on transesterification of palm oil have been studied using the response surface methodology and the factorial design of experiments. The catalyst was synthesized using the co-precipitation method and the activity was assessed by transesterification of palm oil into fatty acid methyl esters. The ratio of the Mg/Zn metal interaction, temperature and time of calcination were found to have positive influence on the conversion of palm oil to fatty acid methyl ester (FAME) with the effect of metal to metal ratio and temperature of calcination being more significant. The catalytic activity was found to decrease at higher calcination temperature and the catalyst type K₂Mg_0.34Zn_1.66O₃ with Mg/Zn ratio of 4.81 gave FAME content of 73% at a catalyst loading of 1.404 wt.% of oil with molar ratio of methanol to oil being 6:1 at temperature of 150 °C in 6 h. A regression model was obtained to predict conversions to methyl esters as a function of metal interaction ratio, temperature of calcination and time. The observed activity of the synthesized catalyst was due to its synergetic structure and composition.     

Hoveyda-Grubbs type metathesis catalyst immobilized on mesoporous molecular sieves—The influence of pore size on the catalyst activity

New hybrid olefin metathesis catalysts were prepared by immobilization of Hoveyda-Grubbs type catalyst (commercially available as Zhan catalyst-1B) on the surface of mesoporous molecular sieves differing in pore size and architecture (MCM-41, MCM-48, and SBA-15) and conventional silica for a comparison. The activity of these catalysts was tested in RCM of (−)-β-citronellene, metathesis of 1-decene, ADMET of 1,9-decadiene, and in ROMP of cyclooctene and was found to increase significantly with the increasing pore size of the supports used. In all reactions, the activity of hybrid catalysts based on mesoporous molecular sieves was higher than that of catalyst using conventional silica as a support. In ROMP of cyclooctene, high molecular weight polymer (M_w = 300,000) in high yield (70-80%) was obtained with catalysts based on mesoporous supports, however, only 40% polymer yield was obtained using catalyst based on conventional silica.     

Inhibition of CoMo/HMS catalyst deactivation in the HDS of 4,6-DMDBT by support modification with phosphate

A series of CoMoS catalysts supported on hexagonal mesoporous silica (HMS) modified with different amounts of phosphate (0.5, 1.0, 1.5 and 2.0 wt.%) were prepared in order to study the influence of phosphate on catalyst deactivation. The catalysts were characterized by a variety of techniques (X-ray fluorescence, N₂ adsorption-desorption at 77 K, FT-IR study of the framework vibration and NO adsorption, NH₃-TPD, H₂-TPR, XPS, ³¹P NMR and TPO/TGA). The sulfided catalysts were tested in the deep hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT) performed in a fixed-bed flow reactor at 598 K, P = 5.0 MPa and WHSV = 46.4 h⁻¹. The catalyst with the largest phosphate content (2.0 wt.%) showed the best catalytic response linked with its low deactivation during on-stream reaction and a larger sulfidation degree of Co species. It was found that coking behavior is closely related with the location of the active sites in the support structure being a lower coke formation on the catalysts having active phases located within support structure. The catalysts modified with a large amount of phosphorous (1.5 and 2.0 wt.% of P₂O₅) were more susceptible to coking and produced a more polymerized coke than P-free sample, as confirmed by TPO/TGA experiments. The presence of P₂O₅ favours the sulfidation degree of Co species and the creation of medium strength acid sites leading to the enhancement of the 4,6-DMDBT HDS reaction toward the isomerization route.     

Poly-dimethylsiloxane (PDMS) based micro-reactors for steam reforming of methanol

A miniaturized methanol steam reformer with a serpentine type of micro-channels was developed based on poly-dimethylsiloxane (PDMS) material. This way of fabricating micro-hydrogen generator is very simple and inexpensive. The volume of a PDMS micro-reformer is less than 10 cm³. The catalyst used was a commercial Cu/ZnO/Al₂O₃ reforming catalyst from Johnson Matthey. The Cu/ZnO/Al₂O₃ reforming catalyst particles of mean diameter 50-70 μm was packed into the micro-channels by injecting water based suspension of catalyst particles at the inlet point. The miniaturized PDMS micro-reformer was operated successfully in the operating temperatures of 180-240 °C and 15%-75% molar methanol conversion was achieved in this temperature range for WHSV of 2.1-4.2 h⁻¹. It was not possible to operate the micro-reformer made by pure PDMS at temperature beyond 240 °C. Hybrid type of micro-reformer was fabricated by mixing PDMS and silica powder which allowed the operating temperature around 300 °C. The complete conversion (99.5%) of methanol was achieved at 280 °C in this case. The maximum reformate gas flow rate was 30 ml/min which can produce 1 W power at 0.6 V assuming hydrogen utilization of 60%.     

Heterogeneous catalyzed biodiesel production from Moringa oleifera oil

In this study, biodiesel was produced from Moringa oleifera oil using sulfated tin oxide enhanced with SiO₂ (SO₄²⁻/SnO₂-SiO₂) as super acid solid catalyst. The experimental design was done using design of experiment (DoE), specifically, response surface methodology based on three-variable central composite design (CCD) with alpha (α) = 2. The reaction parameters studied were reaction temperature (60 °C to 180 °C), reaction period (1 h to 3 h) and methanol to oil ratio (1:6 to 1:24). It was observed that the yield up to 84 wt.% of Moringa oleifera methyl esters can be obtained with reaction conditions of 150 °C temperature, 150 min reaction time and 1:19.5 methanol to oil ratio, while catalyst concentration and agitation speed are kept at 3 wt.% and 350-360 rpm respectively. Therefore this study presents the possibility of converting a relatively new oil feedstock, Moringa oleifera oil to biodiesel and thus reducing the world's dependency on existing edible oil as biodiesel feedstock.     

Facile synthesis of bimodal porous silica and multimodal porous carbon as an anode catalyst support in proton exchange membrane fuel cell

A simple and easy sol-gel approach has been developed to directly synthesize in situ three-dimensionally interconnected uniform ordered bimodal porous silica (BPS) incorporating both the macroporosity and mesoporosity in the lattice without extra synthesis process performed in previous work. Multimodal porous carbon (MPC) was fabricated through the inverse replication of the BPS. The unique structural characteristics such as well-developed 3-D interconnected ordered macropore framework with open mesopores embedded in the macropore walls, large surface area (1120 m² g⁻¹) and mesopore volume (1.95 cm³ g⁻¹) make MPC very attractive as an anode catalyst support in polymer exchange membrane fuel cell. The MPC-supported Pt-Ru alloy catalyst has demonstrated much higher power density toward hydrogen oxidation than the commercial carbon black Vulcan XC-72-supported ones.     

Hydrodearomatization of petroleum fuel fractions on silica supported Ni-W sulphide with increased stacking number of the WS2 phase

Ni-W catalysts supported on commercial γ-alumina and silica displayed similar activity in dibenzothiophene hydrodesulfurization (DBT HDS), while the activity of the Ni-W/SiO₂ catalyst in toluene hydrogenation (HYD) was 6 times higher compared with Ni-W/Al₂O₃. The dearomatization performance of Ni-W/SiO₂ catalyst was tested over a wide range of operation conditions with naphtha and middle distillates. 90% saturation of aromatics in FCC naphtha (340 °C, LHSV of 1 h⁻¹) and 50% in Light cyclic oil (LCO) (360 °C, LHSV of 1 h⁻¹) was achieved at 5.4 MPa. In a two stage process with the same Ni-W/SiO₂ and intermediate separation of hydrogen sulphide 90% saturation of aromatics in LCO was achieved at 320 °C and total LHSV of 0.5 h⁻¹. At equal conditions, Ni-W/Al₂O₃ catalyst yielded 1.5-4 times lower total aromatics saturation.     

The nucleation, crystallization and dispersion behavior of PET-monodisperse SiO2 composites

To more accurately investigate the nucleation, crystallization and dispersion behaviors of silica particles in polymers, the composites of PET with monodisperse SiO₂-PS core-shell structured particles were prepared with SiO₂ size from 380 nm to 35 nm.For these SNPET samples, DSC results showed that the nucleation rate of silica particles increased as their size decreased, in which 35 nm SiO₂ particles produced the most obvious nucleation effect. At 2.0 wt.% load of 35 nm silica, Avrami equation proved that the isothermal crystallization rate G of SNPET was ca. 30% higher than that of pure PET and the crystallization activation energy for SNPET was −218.7 kJ mol⁻¹ lower than −196.1 kJ mol⁻¹ for PET. While, the non-isothermal crystallization ΔE for SNPET was −199.8 kJ mol⁻¹ lower than −185.5 for PET.On non-isothermal crystallization, Jeziorny equation presented the primary and secondary crystallization stages in PET and SNPET, in which nano SiO₂ accelerated the crystallization rate. Their Ozawa number m was from 2.1 to 2.7, which was smaller than that of Avrami number n.The nucleation and dispersion behaviors of SiO₂ particles were directly observed. POM results demonstrated that SNPET samples crystallized more quickly from melt and their crystallization rate increased as silica load increases but accelerated at 2-3 wt.%. The spherulites grew well in PET but their size was smaller in SNPET due to the silica barrier on their growth. SEM and TEM observed the homogeneous silica dispersion morphology and the vivid ordered patterns formed in SNPET. The monodisperse particles are highly expected to give more accurate and valuable references than multi-scale ones in obtaining novel advanced PET composites.     

Transesterification of castor oil assisted by microwave irradiation

Microwave assisted transesterification of castor bean oil was carried out in the presence of methanol or ethanol, using a molar ratio alcohol/castor bean oil of 6:1, and 10% w/w of acidic silica gel or basic alumina (in relation to the oil mass) as catalyst. Under acid catalysis, the reaction occurred with satisfactory yields using H₂SO₄ immobilized in SiO₂, methanol under conventional conditions (60 °C for 3 h) as well as using microwave irradiation for 30 min. The best results were obtained under basic conditions (Al₂O₃/50% KOH) using methanol and conventional (60 °C, stirring, 1 h) or microwave conditions (5 min). In comparison with conventional heating, the catalyzed alcoholysis assisted by microwaves is much faster and leads to higher yields of the desired fatty esters.     

Highly efficient procedure for the synthesis of biodiesel from soybean oil using chloroaluminate ionic liquid as catalyst

The novel efficient procedure has been developed for the synthesis of biodiesel. The chloroaluminate ionic liquid has been selected for the synthesis of biodiesel. The catalyst was very efficient for the reaction with the yield of 98.5% when the reaction was carried out under the conditions of [Et₃NH]Cl-AlCl₃ (x(AlCl₃) = 0.7), soybean oil 5 g, methanol 2.33 g, 9 h, 70 °C. Operational simplicity, low cost of the catalyst used, high yields, no saponification and reusability are the key features of this methodology.     

Preparation of CuY catalyst using CuCl2 as precursor for vapor phase oxidative carbonylation of methanol to dimethyl carbonate

Cu^IY catalyst was prepared by heating the mixture of CuCl₂ and acidic Y zeolite under flowing nitrogen and characterized by TG/DTG, XRD and elementary analysis techniques. The experimental result indicate that when the heating temperature was from 350 °C to 500 °C, the CuCl₂ of the CuCl₂ and acidic Y zeolite mixture sample decompose to CuCl and Cl₂ gas, then the produced CuCl reacted with the Brønsted acid center H⁺ of Y zeolite to form Cu^IY catalyst by the solid-state ion-exchanged reaction. The amount of ion-exchanged Cu^I in the Cu^IY catalyst reached the maximum of 0.1 mol/g when the heating temperature was 650 °C, and the catalyst exhibited the best catalytic activity, the conversion of methanol (C_MeOH), the selectivity and the space-time yield of dimethyl carbonate (S_DMC and STY) reached 4.36%, 74.55% and 97.32 mg/(g h), respectively.     

Polyethylenes produced with zirconocene immobilized on MAO-modified silicas

The effect of Al content on MAO-modified silicas was evaluated on catalyst activity, on polymer properties and on residual metal content in the resulting polyethylenes. MAO-modified silicas were prepared by impregnating MAO toluene solutions in concentration range between 0.5 and 20.0 wt% Al/SiO₂. Commercial MAO-modified silica (Witco) containing 24.4 wt% Al/SiO₂ was used for comparative reasons. The resulting modified-silicas were employed as supports for grafting (nBuCp)₂ZrCl₂. Using external MAO as cocatalyst (Al/Zr=2000) no difference in catalyst activity was observed. Nevertheless, for Al/Zr=500, catalyst activities were shown to be higher for supported zirconocene systems containing 0.0-2.0 wt% Al/SiO₂ range. According to DSC analysis, one T_m peak was detected for polymer obtained with catalyst prepared with 0.5 wt% Al/SiO₂ (135 °C), but two T_m peaks were observed for polymers obtained with catalysts prepared with 10.0 wt% Al/SiO₂ (136 and 141 °C) and 20.0 wt% Al/SiO₂ (133 and 141 °C).     

Transesterification of vegetable oils over a phosphazenium hydroxide catalyst incorporated onto silica

The catalytic activity of a phosphazenium hydroxide (PzOH) catalyst incorporated onto silica (PzOH/SiO₂) was investigated in the transesterification of vegetable oils with methanol. The PzOH stably incorporated onto silica (SiO₂) maintained its basicity and converted methanol molecules to methoxide ions. The PzOH/SiO₂ catalyst exhibited high activity in the transesterification of palm, corn, grape seed, and soybean oils (S-oil) with methanol, achieving ~ 90% conversion at 75 °C with a catalyst loading of 0.2 g per 4.8 ml of S-oil. Although the accumulation of organic materials on PzOH/SiO₂ reduced its activity, this accumulation was effectively removed by washing with methanol. The high activity of PzOH/SiO₂ was responsible for its strong basicity and for the free mobility of the PzOH moiety.     

Catalytic ammonia decomposition over CMK-3 supported Ru catalysts: Effects of surface treatments of supports

CMK-3 carbon was used as a catalyst support for Ru catalyst for ammonia decomposition. The supports were treated with acid, and the effects of treatment on the properties of CMK-3 supports were studied by N₂ adsorption, XRD, XPS and mass titration. The chemical treatment of carbon support cause significant changes in carbon surface chemistry and in turn had significant effects on both catalyst dispersion and catalytic activity. It is found that the as-synthesized CMK-3 carbon is not a good catalyst support for this reaction. However, surface functional groups produced by acid treatments led to larger Ru catalyst particles, while alkali treatments made the Ru catalyst dispersion even worse due to the residue alkali or earth alkali metals. Interestingly, relatively larger Ru catalyst particles but still well dispersed in the channel of the mesoporous structures of the carbon improves NH₃ conversion into H₂. This is determined by the chemical reaction rate-limiting step of ammonia decomposition. The catalytic activity follows the order: Ru-K/CMK-3 > Ru-Na/CMK-3 > Ru-Ca/CMK-3 > Ru-Cl/CMK-3 > Ru-SO₄/CMK-3 > Ru-PO₄/CMK-3 > Ru/CMK-3 > Ru-Li/CMK-3. CMK-3 is not a good carbon catalyst support due to its amorphous structure resulting in the poor electron conductivity.     

Mass transfer limitations on fixed-bed reactor for Fischer-Tropsch synthesis

Mass transfer limitations on fixed-bed for Fischer-Tropsch synthesis were investigated by changing synthesis gas superficial velocity, catalyst pellet size, and catalyst amount. To study external mass transfer limitation, synthesis gas superficial velocity was changed from 8.47 × 10^− 4 m s^− 1 to 3.39 × 10^− 3 m s^− 1. As a result, the synthesis gas superficial velocity of 3.39 × 10^− 3 m s^− 1 was most suitable for hydrocarbon chain growth resulting to liquid hydrocarbon formation. In case of internal mass transfer limitations, the effects of catalyst pellet size and catalyst amount (W_cat/F) were discussed. The large catalyst pellet showed higher C₅₊ selectivity and a lower α value compared to the small pellet because of more severe internal mass transfer limitations of α-olefin and long-chained hydrocarbons in the large pellet, respectively. Catalyst amount (W_cat/F) was inversely proportional to the internal mass transfer limitation because increased catalyst amount gave more time for liquid hydrocarbon products to diffuse from the catalyst pellet and, therefore, the catalyst amount of 4.5 g (W_cat/F = 45 g_cat min L^− 1) was most appropriate for liquid hydrocarbon formation.     

Catalytic pyrolysis of biomass in inert and steam atmospheres

The objective of this study was to investigate thermal conversion of a perennial shrub, Euphorbia rigida biomass sample with catalyst in inert (N₂) and steam atmospheres. Experimental studies were conducted in a well swept fixed bed reactor with a heating rate of 7 °C/min to a final pyrolysis temperature of 550 °C and with a mean particle size of 0.55 mm in order to determine the effect of different atmospheres with various catalyst ratios on pyrolysis yields and characteristics. The catalyst ratios were 5%, 10% and 20% (w/w) under nitrogen atmosphere with flow rates of 50, 100, 200 and 400 cm³/min and steam atmosphere with well-swept velocities of 12, 25 and 52 cm³/min. The optimum oil yield was obtained as 32.1% at the nitrogen flow rate of 200 cm³/min, while it was obtained as 38.6% at steam flow rate of 25 cm³/min when a 10% catalyst by weight according to the biomass was used. Higher oil yields were observed when biomass sample was treated in steam atmosphere than in inert (N₂) atmosphere. The oil composition was then analysed by elemental analyses techniques such as IR and GC-MS. The oil products were also fractionated by column chromatography. The bio-oils obtained at both atmospheres contain mainly n-alkanes and alkenes, aromatic compounds; mainly benzene and derivatives and PAHs, nitrogenated compounds and ketones, carboxylic acids, aldehydes, phenols and triterpenoid compounds. More oxygenated compounds and less substituted alkanes and alkenes were obtained in catalytic pyrolysis of E. rigida in the steam atmosphere. The experimental and chemical characterisation results showed that the oil obtained from perennial shrub, E. rigida can be used as a potential source of renewable fuel and chemical feedstock.     

A new approach to catalytic hydrolysis of ester-bound biphenyl cyclooctene lignans from the fruit of Schisandra chinensis Baill by ion exchange resin

In this study, a novel approach was developed to hydrolyze ester-bound biphenyl cyclooctene lignans (EBBCL) from the fruits of Schisandra chinensis Baill into free-state biphenyl cyclooctene lignans (FSBCL) using ion exchange resin. The results of static hydrolysis tests showed that SK1B (H-type strongly acidic cation exchange resin) was the best acidic hydrolysis catalyst and 201 × 7 (OH-type strongly basic anion exchange resin) was the best basic hydrolysis catalyst. According to the underlying mechanism for hydrolytic degradation, the hydrolysis effect of basic catalyst is more obviously. The dynamic hydrolysis efficiency of 201 × 7 (146.7 ± 5.0%) was higher than that of SK1B (131.5 ± 4.7%). Compared with the purity of FSBCL (3.52 ± 0.06%) catalytic hydrolysis by traditional catalyst NaOH, the purity of FSBCL (5.85 ± 0.04%) hydrolysis by 201 × 7 resin was much higher, increased 2.94-fold under the optimization hydrolysis conditions.     

Application of the Shvo catalyst in homogeneous hydrogenation of bio-oil obtained from pyrolysis of white poplar: New mild upgrading conditions

Upgrading of bio-oils obtained from the fast pyrolysis of biomasses requires the development of efficient catalysts able to work under mild conditions and to cope with the complex chemical nature of the reactant. The present work focuses on the use of the ruthenium based Shvo homogeneous catalyst for the hydrogenation of model mixtures (vanillin, cinnamaldehyde, methylacetophenone, glycolaldehyde, acetol, acetic acid) and of a real bio-oil. The hydrogenation of model compounds has been investigated both in mono- and biphasic mixtures under a P(H₂) = 10 atm in the temperature range of 90-145 °C varying the substrate to catalyst molar ratio from 2000:1 to 200:1. Employing the most active reaction conditions (substrate/catalyst 200:1, T = 145 °C, P(H₂) = 10 atm) the Shvo catalyst maintains its performances under acidic “bio-oil conditions” leading to the almost quantitative conversion of the polar double bonds within 1 h. The activity of the Shvo catalyst was also investigated for the hydrogenation of a bio-oil from poplar in solvent free conditions. Hydrogenation deeply changed the chemical nature of the pyrolysis oil. Aldehydes, ketones and non-aromatic double bonds were almost totally hydrogenated. The catalytic system also promoted the hydrolysis of sugar oligomers into monomers.     

Deep desulfurization of diesel oil oxidized by Fe (VI) systems

Fe (VI) compound, such as K₂FeO₄, is a powerful oxidizing agent. Its oxidative potential is higher than KMnO₄, O₃ and Cl₂. Oxidation activity of Fe (VI) compounds can be adjusted by modifying their structure and pH value of media. The reduction of Fe (VI), differing from Cr and Mn, results in a relatively non-toxic by-product Fe (III) compounds, which suggests that Fe (VI) compound is an environmentally friendly oxidant. Oxidation of model sulfur compound and diesel oil by K₂FeO₄ in water-phase, in organic acid and in the presence of phase-transfer catalysts is investigated, respectively. The results show that the activity of oxidation of benzothiophene (BT) and dibenzothiophene (DBT) is low in water-phase, even adding phase-transfer catalyst to the system, because K₂FeO₄ reacts rapidly with water to form brown Fe(OH)₃ to lose ability of oxidation of organic sulfur compounds. The activity of oxidation of the BT and DBT increases markedly in acetic acid. Moreover, the addition of the solid catalyst to the acetic acid medium promotes very remarkably oxidation of organic sulfur compounds. Conversions of the DBT and BT are 98.4% and 70.1%, respectively, under the condition of room temperature, atmospheric pressure, acetic acid/oil (v/v) = 1.0, K₂FeO₄/S (mol/mol) = 1.0 and catalyst/K₂FeO₄ (mol/mol) = 1.0. Under the same condition, diesel oil is oxidized, followed by furfural extraction, the results display sulfur removal rate is 96.7% and sulfur content in diesel oil reduces from 457 ppm to 15.1 ppm.     

Thermal decomposition of 2-methylpyridine N-oxide: Effect of temperature and influence of phosphotungstic acid as the catalyst

The thermal decomposition of 2-methylpyridine N-oxide was studied at temperatures between 190 °C and 220 °C using an Automatic Pressure Tracking Adiabatic Calorimeter. The effect of the catalyst on the decomposition was evaluated using different amounts of phosphotungstic acid. It was determined that 2-methylpyridine N-oxide decomposes faster with low amounts of catalyst and temperatures above 200 °C. Below 200 °C, the decomposition is very slow. For the cases presented here, the decomposition reaction was accompanied by substantial production of non-condensable gasses, and 2-methylpyridine and pyridine were identified as the main decomposition products.