Esterification of industrial-grade palm fatty acid distillate over modified ZrO2 (with WO3-, SO4 -and TiO2-): Effects of co-solvent adding and water removal

The esterification of palm fatty acid distillate (PFAD), a by-product from palm oil industry, in the presence of three modified zirconia-based catalysts i.e. SO₄-ZrO₂, WO₃-ZrO₂ and TiO₂-ZrO₂ (with several sulfur- and tungsten-loading contents, Ti/Zr molar ratios, and calcination temperatures) was studied. It was found that, among all synthesized catalysts, the reaction in the presence of SO₄-ZrO₂ and WO₃-ZrO₂ (with 1.8%SO₄ calcined at 500 °C and/or 20%WO₃ calcined at 800 °C) enhances relatively high fatty acid methyl ester (FAME) yield (84.9-93.7%), which was proven to relate with the high acid site density and specific surface area as well as the formation of tetragonal phase over these catalysts. The greater benefit of WO₃-ZrO₂ over SO₄-ZrO₂ was its high stability after several reaction cycles, whereas significant deactivation was detected over SO₄-ZrO₂ due to the leaching of sulfur from catalyst. For further improvement, the addition of toluene as co-solvent was found to increase the FAME yield along with reduce the requirement of methanol to PFAD molar ratio (while maintains the FAME yield above 90%). Furthermore, it was observed that the presence of water in the feed considerably lower the FAME yield due to the catalyst surface interfering by water and the further hydrolysis of FAME back to fatty acids. We proposed here that the negative effect can be considerably minimized by adding molecular sieve to remove water from the feed and/or during the reaction.     

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.     

Esterification of palm fatty acid distillate (PFAD) in supercritical methanol: Effect of hydrolysis on reaction reactivity

This study demonstrated the potential use of local palm fatty acid distillate (PFAD) as alternative feedstock for fatty acid methyl esters (FAMEs) production and the possibility to replace the conventional acid-catalyzed esterification process (with H₂SO₄), which was industrially proven to suffer by several corrosion and environmental problems, with non-catalytic process in supercritical methanol. At 300 °C with the PFAD to methanol molar ratio of 1:6 and the reaction time of 30 min, the esterification of PFAD in supercritical methanol gave FAMEs production yield of 95%. Compared with transesterification of purified palm oil (PPO) in supercritical methanol, the production of FAMEs reached the maximum yield of only 80% at 300 °C with higher requirement for methanol (1:45 PPO to methanol molar ratio). Compared with the conventional acid-catalyzed esterification of PFAD, only 75% FAMEs yield was obtained in 5 h. The presence of water in the feed (between 0 and 30% v/v) was found to lower the yield of FAMEs production from PFAD significantly. This negative effect was proven to be due to the further hydrolysis of FAMEs, which nevertheless can be minimized when high content of methanol was used.     

Reactions of C5 and C6-sugars, cellulose, and lignocellulose under hot compressed water (HCW) in the presence of heterogeneous acid catalysts

The benefit of TiO₂, ZrO₂ and SO₄-ZrO₂ on the reactions of C₅-sugar (xylose), C₆-sugar (glucose), cellulose, and lignocellulose was studied in hot compressed water (HCW) at 473-673 K with an aim to produce furfural and 5-hydroxymethylfurfural (HMF). TiO₂ and SO₄-ZrO₂ were found to active for hydrolysis and dehydration reactions producing high furfural and HMF yields with less by-products (i.e. glucose, fructose, xylose, and 1,6-anhydroglucose (AHG)) formation, whereas ZrO₂ was highly active for isomerization reaction; thus significant amount of fructose was observed in the liquid product.Importantly, it was also found that the starting salt precursor, the sulfur-doping content (for SO₄-ZrO₂) and the calcination temperature strongly affected the catalyst reactivity. Catalysts prepared from the chloride-based precursors (i.e. ZrOCl₂ and TiCl₄) gained higher reactivity compared to those prepared from nitrate-based precursors (i.e. ZrO(NO₃)₂ and TiO(NO₃)₂) due to their greater acidity, according to the NH₃- and CO₂-TPD studies. For SO₄-ZrO₂, among the catalyst with sulfur contents of 0.75%, 1.8% and 2.5%, SO₄-ZrO₂ with 1.8% sulfur content presented the highest acidity and reactivity toward hydrolysis and dehydration reactions. It is noted that the suitable calcination temperature for all catalysts was at 773 K; the XRD patterns revealed that different portions of phase formation was observed over catalysts with different calcination temperatures i.e. anatase/rutile for TiO₂ and monoclinic/tetragonal for ZrO₂ and SO₄-ZrO₂; the portion of these phase formations obviously affected the acidity-basicity of catalyst and thus the catalyst reactivity.     

Production of ethyl ester from crude palm oil by two-step reaction with a microwave system

The production of ethyl esters of fatty acids from a feed material of crude palm oil (CPO) with a high free fatty acid (FFA) content under microwave assistance has been investigated. Parametric studies have been carried out to investigate the optimum conditions for the esterification process (amount of ethanol, amount of catalyst, reaction time, and microwave power). As a result, a molar ratio of FFA to ethanol of 1:24 with 4% wt./wt. of H₂SO₄/FFA, a microwave power of 70 W, and a reaction time of 60 min have been identified as optimum reaction parameters for the esterification process aided by microwave heating. At the end of the esterification process, the amount of FFA had been reduced from 7.5 wt.% to less than 2 wt.%. Similar results were obtained following conventional heating at 70 °C, but only after a reaction time of 240 min. Transesterification of the esterified palm oil has been accomplished with a molar ratio of CPO to ethanol of 1:4, 1.5 wt.% KOH as a catalyst, a microwave power of 70 W, and a reaction time of 5 min. This two-step esterification and transesterification process provided a yield of 80 wt.% with an ester content of 97.4 wt.%. The final ethyl ester product met with the specifications stipulated by ASTM D6751-02.     

Reduction of high content of free fatty acid in sludge palm oil via acid catalyst for biodiesel production

In this study, sulphuric acid (H₂SO₄) was used in the pretreatment of sludge palm oil for biodiesel production by an esterification process, followed by the basic catalyzed transesterification process. The purpose of the pretreatment process was to reduce the free fatty acids (FFA) content from high content FFA (> 23%) of sludge palm oil (SPO) to a minimum level for biodiesel production (> 2%). An acid catalyzed esterification process was carried out to evaluate the low content of FFA in the treated SPO with the effects of other parameters such as molar ratio of methanol to SPO (6:1-14:1), temperature (40-80 °C), reaction time (30-120 min) and stirrer speed (200-800 rpm). The results showed that the FFA of SPO was reduced from 23.2% to less than 2% FFA using 0.75% wt/wt of sulphuric acid with the molar ratio of methanol to oil of 8:1 for 60 min reaction time at 60 °C. The results on the transesterification with esterified SPO showed that the yield (ester) of biodiesel was 83.72% with the process conditions of molar ratio of methanol to SPO 10:1, reaction temperature 60 °C, reaction time 60 min, stirrer speed 400 rpm and KOH 1% (wt/wt). The biodiesel produced from the SPO was favorable as compared to the EN 14214 and ASTM D 6751 standard.     

Synthesis of CeO2-ZrO2 solid solution by glycothermal method and its oxygen release capacity

The glycothermal (GT) reaction of Ce acetate and Zr alkoxide directly yielded CeO₂-ZrO₂ solid solutions in a region of low Ce content ≤40 mol%. Of the CeO₂-ZrO₂ solid solutions obtained by the GT method and subsequent calcination at 500 or 800 °C, the sample with 20 mol% Ce content had the largest BET surface area. This sample exhibited the highest Ce-based oxygen release capacity in the whole Ce/Zr composition range. The oxygen release capacities of CeO₂-ZrO₂ solid solutions synthesized by the GT method were much larger than those of the samples prepared by a coprecipitation (CP) method. The Reitveld analysis and the repetitive reduction-oxidation experiment indicated that the CeO₂-ZrO₂ solid solution synthesized by the GT method has a homogeneous structure as compared with that prepared by the CP method.     

Influence of preparation conditions to structure property, NOx and SO2 sorption behavior of the BaFeO3 − x perovskite catalyst

A series of the BaFeO_3 − x perovskite catalysts was synthesized by a sol-gel method using citric acid and/or EDTA as complexants with a purpose to improve their sulfur-resistance by forming a uniform perovskite structure at a low calcination temperature, i.e. 750 °C. The thermogravimetry results show that almost no carbonate was formed after calcination of the xerogel precursor with the complexants' molar ratio of CA/EDTA ≤ 1.5, which was convinced by the in situ DRIFT spectra results of the Ba-Fe-1 catalyst during the SO₂/O₂ sorption. It indicates that, after adding EDTA into the complexants, the metal ions of the raw material could be mixed homogeneously and react stoichiometrically by calcination at 750 °C to form a uniform perovskite structure. Accordingly, the obtained Ba-Fe-1 perovskite presented a performed sulfur-resistance. Moreover, the seriously damaged structure of the BaFeO_3 − x perovskite by reduction could be in situ regenerated by calcination under lean conditions at 400 °C, which is within the operating temperature zone of the aftertreatment system of diesel to meet the real commercial demands.     

SO2 removal from flue gas by activated semi-cokes: 1. The preparation of catalysts and determination of operating conditions

The objective of this work was to use waste semi-coke as the raw material to prepare catalysts of industrial-scale size for SO₂ removal from flue gas and to find the optimal preparation methods. Results showed that lignite semi-coke was a suitable raw material, and that the catalyst, prepared by pre-activating in an autoclave, oxidizing with HNO₃, loading with CuSO₄ and finally calcining at 700 °C, exhibited the best desulfurizing property with a sulfur retention of about 9.6% SO₂/100 gC at a reaction temperature of 90 °C. Also, the effects of H₂O content in the flue gas, reaction temperature and space velocity on the desulfurizing property were investigated to determine optimum operating conditions. An H₂O content of 7% was appropriate for catalysts in this work. In the temperature range 80-120 °C, the catalyst showed good performance for SO₂ removal and was gradually deactivated at temperatures above 120 °C. Space velocity exhibited an optimal value of 830 h⁻¹. The kinetic behavior varied with space velocity and the desulfurizing property was controlled by diffusion at space velocities below 830 h⁻¹, and controlled by adsorption or catalytic reaction at space velocities above 830 h⁻¹.     

Optimal process conditions for the isomerization-cracking of long-chain n-paraffins to high octane isomerizate gasoline over Pt/SO4-ZrO2 catalysts

An assessment of the process conditions for the isomerization-cracking of long-chain n-paraffins over commercial Pt/SO₄^2--ZrO₂ catalysts was made. Pretreatment and reaction conditions were optimized with a focus on the maximization of the yield of short, high octane branched paraffins for the gasoline pool. While selectivity was an important issue attention was also paid to the reduction of the yield to gases (C_1-C₄). Therefore cracking had to be modulated to produce the correct molecular size adjustment without scission to too much smaller fragments. Skeletal isomerization was to be maximized. The activity in both acid-catalyzed reactions had to be tuned while keeping a stable activity level.The only pretreatment condition assessed was the calcination temperature (screened in the 600-800 °C range). Calcination at 600 °C produced the highest activity level while 700 °C was convenient from the point of view of selectivity. The optimum temperature coincided with the production of the highest concentration of Brönsted acid sites.Regarding the reaction conditions, increasing temperature values augmented the conversion but also increased the cracking. Therefore optimum values were found at a moderate temperature, 225 °C, given the high reactivity of the feed. Space velocity values were analyzed with attention to the liquid C₅₊ yield, the selectivity to branched isomers and the stability of the catalysts. Best yields to branched naphtha products were obtained at WHSV = 18 h^- 1. The H₂/hydrocarbon molar ratio was a function of the catalyst coking rate. A value of 10 was enough to attain a stable conversion value. The values of liquid yield as a function of pressure displayed a volcano pattern that was rationalized in terms of a non-classical bifunctional mechanism of reaction. High pressure values increased the concentration of Brönsted acid sites and hence the activity while high pressures enhanced hydrocracking and decreased the liquid yield. The optimal pressure value was 20 atm.     

An ideal feedstock, kusum (Schleichera triguga) for preparation of biodiesel: Optimization of parameters

Kusum (Schleichera triguga), a non-edible oil bearing plant has been used as an ideal feedstock for biodiesel development in the present study. Various physical and chemical parameters of the raw oil and the fatty acid methyl esters derived have been tested to confirm its suitability as a biodiesel fuel. The fatty acid component of the oil was tested by gas chromatography. The acid value of the oil was determined by titration and was found to 21.30 mg KOH/g which required two step transesterification. Acid value was brought down by esterification using sulfuric acid (H₂SO₄) as a catalyst. Thereafter, alkaline transesterification was carried out using potassium hydroxide (KOH) as catalyst for conversion of kusum oil to its methyl esters. Various parameters such as molar ratio, amount of catalyst and reaction time were optimized and a high yield (95%) of biodiesel was achieved. The high conversion of the feedstock into esters was confirmed by analysis of the product on gas chromatograph-mass spectrometer (GC-MS). Viscosity and acid value of the product biodiesel were determined and found to be within the limits of ASTM D 6751 specifications. Elemental analysis of biodiesel showed presence of carbon, hydrogen, oxygen and absence of nitrogen and sulfur after purification. Molar ratio of methanol to oil was optimized and found to be 10:1 for acid esterification, and 8:1 for alkaline transesterification. The amounts of H₂SO₄ and KOH, 1% (v/v) and 0.7% (w/w), respectively, were found to be optimum for the reactions. The time duration of 1 h for acid esterification followed by another 1 h for alkaline transesterification at 50 ± 0.5 °C was optimum for synthesis of biodiesel.     

Preparation, characterization and dielectric properties of CaCu3Ti4O12 ceramics

CaCu₃Ti₄O₁₂ nano-sized powders were successfully prepared by sol-gel technique and calcination at 600-900 °C. The thermal decomposition process, phase structures and morphology of synthesized powders were characterized by IR, DSC-TG, XRD, TEM, respectively. It was found that the main weight-loss and decomposition of precursors occurred below 450 °C and the complex perovskite phase appeared when the calcination temperature was higher than 700 °C. Using above synthesized powders as starting materials, CCTO-based ceramics with excellent dielectric properties (?₂₅ = 5.9 × 10⁴, tan δ = 0.06 at 1.0 kHz) were prepared by sintering at 1125 °C. According to the results, a conduction mechanism was proposed to explain the origin of giant dielectric constant in CCTO system.     

Selective catalytic reduction of NOX with ammonia over Mn-Ce-OX/TiO2-carbon nanotube composites

Mn-Ce-O_X catalysts loaded on TiO₂-carbonaceous materials were prepared by sol-gel method. Selective catalytic reduction of NO_X was conducted in a fixed-bed flow-reactor over catalysts coated on aluminum plates. A de-NO_X efficiency of more than 90% was obtained over the Mn-Ce-O_X/TiO₂-carbon nanotubes (CNTs) catalyst between 75 °C and 225 °C under a gas hourly space velocity (GHSV) of ~ 36,000 h⁻¹. This activity improvement is attributed to the increase of the BET surface area, and the occurrence of reaction between adsorbed NO_X and NH₃. Moreover, the de-NO_X efficiency was increased to 99.6% by adding 250 ppm SO₂ between 100 °C and 250 °C.     

Catalytic oxidative desulfurization of diesel utilizing hydrogen peroxide and functionalized-activated carbon in a biphasic diesel-acetonitrile system

This paper presents the development of granular functionalized-activated carbon as catalysts in the catalytic oxidative desulfurization (Cat-ODS) of commercial Malaysian diesel using hydrogen peroxide as oxidant. Granular functionalized-activated carbon was prepared from oil palm shell using phosphoric acid activation method and carbonized at 500 °C and 700 °C for 1 h. The activated carbons were characterized using various analytical techniques to study the chemistry underlying the preparation and calcination treatment. Nitrogen adsorption/desorption isotherms exhibited the characteristic of microporous structure with some contribution of mesopore property. The Fourier Transform Infrared Spectroscopy results showed that higher activation temperature leads to fewer surface functional groups due to thermal decomposition. Micrograph from Field Emission Scanning Electron Microscope showed that activation at 700 °C creates orderly and well developed pores. Furthermore, X-ray Diffraction patterns revealed that pyrolysis has converted crystalline cellulose structure of oil palm shell to amorphous carbon structure. The influence of the reaction temperature, the oxidation duration, the solvent, and the oxidant/sulfur molar ratio were examined. The rates of the catalytic oxidative desulfurization reaction were found to increase with the temperature, and H₂O₂/S molar ratio. Under the best operating condition for the catalytic oxidative desulfurization: temperature 50 °C, atmospheric pressure, 0.5 g activated carbon, 3 mol ratio of hydrogen peroxide to sulfur, 2 mol ratio of acetic acid to sulfur, 3 oxidation cycles with 1 h for each cycle using acetonitrile as extraction solvent, the sulfur content in diesel was reduced from 2189 ppm to 190 ppm with 91.3% of total sulfur removed.     

High-temperature close coupled catalysts Pd/Ce-Zr-M/Al2O3 (M = Y, Ca or Ba) used for the total oxidation of propane

A series of high-temperature close coupled catalysts Pd/Ce-Zr-M/Al₂O₃ (M = Y, Ca or Ba) were prepared by ultrasonic-assisted successive impregnation. The catalysts were subjected to a series of characterization measurements. The results of activity evaluation show that Y is the best promoter for propane total oxidation, especially at the calcination temperature of 1100 °C. It is interesting that although the BET specific surface areas and the dispersion of Pd species decrease, the Y-promoted catalyst calcined at 1100 °C shows higher catalytic activity than the corresponding one calcined at 900 °C and better sulfur-resisting performance. The results of TEM, TPHD and CO chemisorption indicate that Y can remarkably increase the dispersion of Pd species. However, the dispersion is hard to be connected with the activity increase as the calcination temperature is elevated from 900 to 1100 °C. The change of active phases and the interaction between Pd species and the supports may account for the activity enhancement. Combined with XRD, H₂-TPR and O₂-TPD results, it is deduced that the coexistence of metallic Pd and PdO species in the catalysts calcined at 1100 °C may be also favorable to C₃H₈ oxidation. In a word, Pd/Ce-Zr-Y/Al₂O₃ is indeed a promising high-temperature close coupled catalyst applicable to high temperature.     

Comparison of product selectivity during hydroprocessing of bitumen derived gas oil in the presence of NiMo/Al2O3 catalyst containing boron and phosphorus

A detailed experimental study was performed in a trickle-bed reactor using bitumen derived gas oil. The objective of this work was to compare the activity of NiMo/Al₂O₃ catalyst containing boron or phosphorus for the hydrotreating and mild hydrocracking of bitumen derived gas oil. Experiments were performed at the temperature and LHSV of 340-420 °C and 0.5-2 h⁻¹, respectively, using NiMo/Al₂O₃ catalysts containing 1.7 wt% boron or 2.7 wt% phosphorus. In the temperature range of 340-390 °C, higher nitrogen conversion was observed from boron containing catalyst than that from phosphorus containing catalyst whereas in the same temperature range, phosphorus containing catalyst gave higher relative removal of sulfur than boron containing catalyst. Phosphorus containing catalyst showed excellent hydrocracking and mild hydrocracking activities at all operating conditions. Higher naphtha yield and selectivity were obtained using phosphorus containing catalyst at all operating conditions. Maximum gasoline selectivity of ∼45 wt% was obtained at the temperature, pressure, and LHSV of 400 °C, 9.4 MPa and 0.5 h⁻¹, respectively, using catalyst containing 2.7 wt% phosphorus.     

Synthesis and diffused phase transition of Ba0.7Sr0.3TiO3 ceramics by a reaction-sintering process

Ba_0.7Sr_0.3TiO₃ (BST) ceramics prepared by a reaction-sintering process were investigated. BST ceramics could be obtained after 2–6 h sintering at 1330–1370 °C without any calcination involved. BST with density 5.68 g/cm³ (99.8% of the theoretic value) was obtained at 1350 °C for 6 h sintering. Grains of 2–15 μm were formed after 2–6 h sintering at 1330–1370 °C. A diffused ferroelectric–paraelectric transition was observed in pellets sintered at 1330 °C for 2 h and disappeared at a longer soak time or a higher sintering temperature.     

Formation of TiO2 nano fibers on a micro-channeled Al2O3-ZrO2/TiO2 porous composite membrane for photocatalytic filtration

In this study, needle-shape TiO₂ fibers were successfully fabricated inside a micro-channeled Al₂O₃-ZrO₂ composite porous membrane system using sol-gel method. The micro-channeled Al₂O₃-ZrO₂ composite was fabricated using the fibrous monolithic (FM) process. Pure anatase phase TiO₂ was crystallized from the as-coated amorphous phase during calcination at 510 °C. The TiO₂ fibers grew on the surface frame of the micro-channeled Al₂O₃-ZrO₂ composite membrane and fully covered the inside of the micro-channeled pores. The specific surface area of the TiO₂ coated membrane system was dramatically increased by over 100 fold compared to that of the non-coated system. The photocatalytic activity of the membrane was also assessed and was shown to very effectively convert organic materials. Thus, this novel membrane holds promise for use as an advanced filtration system.     

Insights on the SO2 poisoning of Pt3Co/VC and Pt/VC fuel cell catalysts

SO₂ poisoning of carbon-supported Pt₃Co (Pt₃Co/VC) catalyst is performed at the cathode of proton exchange membrane fuel cells (PEMFCs) in order to link previously reported results at the electrode/solution interface to the FC environment.First, the surface area of Pt₃Co/VC catalyst is rigorously characterized by hydrogen adsorption, CO stripping voltammetry and underpotential deposition (upd) of copper adatoms. Then the performance of PEMFC cathodes employing 30 wt.% Pt₃Co/VC and 50 wt.% Pt/VC catalysts is compared after exposure to 1 ppm SO₂ in air for 3 h at constant cell voltage of 0.6 V. In agreement with results reported for the electrode/solution interface, the Pt₃Co/VC is more susceptive to SO₂ poisoning than Pt/VC at a given platinum loading.Both catalysts can be recovered from adsorbed sulfur species by running successive polarization curves in air or cyclic voltammetry (CV) in inert atmosphere. However, the activity of Pt₃Co/VC having ∼3 times higher sulfur coverage is recovered more easily than Pt/VC. To understand the difference between the two catalysts in terms of activity recovery, platinum-sulfur interaction is probed by thermal programmed desorption at the catalyst/inert gas interface and CV at the electrode/solution interface and in the FC environment.