Light fuel gas production from nascent coal volatiles using a natural limonite ore

Basic research on fuel gas production from nascent coal volatiles was conducted in a two-stage fixed-bed reactor. The volatiles from coal carbonization decomposed in the reactor. Indonesian natural limonite ore dramatically promoted coal volatile decomposition at 873–1023 K in ambient pressure and the carbon yields, except in tar, were above 97.8%. We compared these results to experiments without a catalyst. Subsequently, coal tar converted more completely and more than twice the amount of methane-rich product gases were obtained using the limonite catalyst. In addition, catalyst sulphur poisoning was scarcely observed in the H₂S–H₂–N₂ (H₂S/H₂: 0.002–0.004) system at 923 K.     

Improvement and characterization of an impregnated iron-based catalyst for direct coal liquefaction

An impregnation method to prepare an active iron-based catalyst for direct coal liquefaction was improved. With the same catalytic activity, the water usage in the improved method is only 1% of that used in the unmodified method. The improved method not only simplifies the impregnation procedure and reduces cost, but also generates small catalyst particle size on coal surface. Water in the coal promotes thermal liquefaction, but deactivates the impregnated catalyst (possibly due to the adsorption of H₂O molecular on the catalyst surface). Electron probe microanalysis (EPMA), X-ray diffraction (XRD) and extended X-ray absorption fine structure spectroscopy (EXAFS) analyses show that the catalyst precursors prepared by both methods are in nanometer size and highly dispersed on coal surface. The irons deposited on coal surface are not only in sulfide forms, but also coordinate with oxygen from moisture- and oxygen-containing groups of coal. The impregnated iron may be composed of FeOOH and FeS or in the forms of Fe–O–S or Fe–S–O. The iron transforms to crystalline pyrrhotite in coal liquefaction.     

Investigation of the anticorrosion efficiency of ferrites Mg1−xZnxFe2O4 with different particle morphology and chemical composition in epoxy-ester resin-based coatings

Mixed metal oxides with the ferrospinel structure ZnFe₂O₄, Mg_0.2Zn_0.8Fe₂O₄ and MgFe₂O₄ were synthesised by the high-temperature solid-phase process. A series of pigments containing the metals Mg–Zn–Fe was prepared from 4 different starting iron oxides: viz. goethite (FeOOH), hematite (Fe₂O₃), magnetite (FeO·Fe₂O₃) and specularite (Fe₂O₃). The properties of the ferrites as pigments were examined in a solvent-based epoxy-ester resin-based coating material at a pigment volume concentration PVC_ferrite = 10%. The anticorrosion efficiency of the paints with the ferrites was examined by exposing panels coated with the paints to atmospheres with SO₂, NaCl, or condensed moisture. Furthermore, the physico-mechanical properties of paint films containing the pigments were evaluated by standardised tests. Ferrites prepared from the needle-shaped FeOOH or lamellar Fe₂O₃ emerged as pigments with the best anticorrosion properties. From the aspect of chemical composition, the paint films containing Mg_0.2Zn_0.8Fe₂O₄, i.e. combinations of the cations Mg–Zn, were assessed as the best.     

Selective catalytic reduction of nitrogen oxides by ammonia on iron oxide catalysts

In this study, new Fe₂O₃ based materials are developed for the selective catalytic reduction (SCR) of NO_x by NH₃ in diesel exhaust. As a result of the catalyst screening, performed in a synthetic model exhaust, ZrO₂ is considered to be the most effective carrier for Fe₂O₃. The modification of the Fe₂O₃/ZrO₂ system with tungsten leads to drastic increase of SCR performance as well as pronounced thermal stability. These results show that tungsten acts as bifunctional component. The highest catalytic activity is observed for ZrO₂ that is coated with 1.4 mol% Fe₂O₃ and 7.0 mol% WO₃ (1.4Fe/7.0W/Zr). By the use of this catalyst quantitative conversion of NO_x is obtained between 285 and 430 °C with selective formation of N₂. Here, the turnover frequency of NO_x per Fe atom is found to be 35 × 10⁻⁵ s⁻¹ that indicates a high catalytic performance. The SCR activity of the 1.4Fe/7.0W/Zr material is decreased in the presence of H₂O and CO₂, whereas it is increased by NO₂.Temperature programmed reduction by H₂ (HTPR) analyses show that the Fe sites of the 1.4Fe/7.0W/Zr catalyst are mainly in the form of crystalline Fe₂O₃, whereby relatively small oxide entities are also present. The strongly aggregated Fe₂O₃ species are associated with the presence of the promoter tungsten. Based upon stationary catalytic examinations as well as diffuse reflectance infrared fourier transform spectroscopy (DRIFTS) studies we postulate an Eley Rideal type mechanism for SCR on 1.4Fe/7.0W/Zr catalyst. The mechanistic model includes a redox cycle of the active Fe sites. As first reaction step, we assume dissociative adsorption of NH₃ that leads to partial reduction of the iron as well as to production of very reactive amide surface species. These amide intermediates are supposed to react with gaseous NO to form N₂ and H₂O. In the final step, the reduced Fe sites be regenerated by oxidation with O₂. As a side reaction of SCR, imide species, originated from decomposition of amide, are oxidized by NO₂ or O₂ into NO.     

Synthesis of carbon-supported binary FeCo–N non-noble metal electrocatalysts for the oxygen reduction reaction

In this paper, a carbon-supported binary FeCo–N/C catalyst using tripyridyl triazine (TPTZ) as the complex ligand was successfully synthesized. The FeCo–TPTZ complex was then heat-treated at 600 °C, 700 °C, 800 °C, and 900 °C to optimize its oxygen reduction reaction (ORR) activity. It was found that the 700 °C heat-treatment yielded the most active FeCo–N/C catalyst for the ORR. XRD, EDX, TEM, XPS, and cyclic voltammetry techniques were used to characterize the structural changes in these catalysts after heat-treatment, including the total metal loading and the mole ratio of Fe to Co in the catalyst, the possible structures of the surface active sites, and the electrochemical activity. XPS analysis revealed that Co–N_x, Fe–N_x, and C–N were present on the catalyst particle surface. To assess catalyst ORR activity, quantitative evaluations using both RDE and RRDE techniques were carried out, and several kinetic parameters were obtained, including overall ORR electron transfer number, electron transfer coefficient in the rate-determining step (RDS), electron transfer rate constant in the RDS, exchange current density, and mole percentage of H₂O₂ produced in the catalyzed ORR. The overall electron transfer number for the catalyzed ORR was ～3.88, with H₂O₂ production under 10%, suggesting that the ORR catalyzed by FeCo–N/C catalyst is dominated by a 4-electron transfer pathway that produces H₂O. The stability of the binary FeCo–N/C catalyst was also tested using single Fe–N/C and Co–N/C catalysts as baselines. The experimental results clearly indicated that the binary FeCo–N/C catalyst had enhanced activity and stability towards the ORR. Based on the experimental results, a possible mechanism for ORR performance enhancement using a binary FeCo–N/C catalyst is proposed and discussed.     

Coal liquefaction with in situ impregnated Fe2(MoS4)3 bimetallic catalyst

Daliuta subbituminous coal (DL), loaded with Fe₂(MoS₄)₃ bimetallic catalyst, was liquefied in a 50 ml micro-autoclave with tetralin as solvent at 440 °C, initial hydrogen of 6.0 MPa, soaking time of 30 min in attempt to produce one to four ring aromatic chemicals. The catalytic effects of in situ impregnated Fe₂(MoS₄)₃ in water solution with and without surfactant were investigated in terms of coal conversion, oil+gas yield and the yields of aromatic, aliphatic and polar compound fractions in the oil. The conversion, oil+gas, aromatics and polar compound yields of DL coal, loaded with 1 wt% daf FeMo of Fe₂(MoS₄)₃ bimetallic catalyst, were 78.2, 70.5, 20.8 and 16.7 wt% daf, respectively, which were higher than those with 1.0 wt% Fe (based on daf coal) of Fe₂S₃ (62.6, 54.2, 13.4, 13.2 wt% daf, respectively) or 1.0 wt% Mo of ammonium tetrathiomolybdate (70.8, 63.2, 16.7, 14.1 wt% daf, respectively) alone under the same conditions. When the catalyst was impregnated on coal in surfactant solution, the coal conversion and product yields were further increased.     

The feasibility of using combined Fenton-SBR for antibiotic wastewater treatment

The first part of this study examined the effect of operating conditions on Fenton pretreatment of an antibiotic wastewater containing amoxicillin and cloxacillin. The optimum H₂O₂/COD and H₂O₂/Fe²⁺ molar ratios were 2.5 and 20, respectively. Under the optimum operating conditions, complete degradation of the antibiotics occurred in 1 min. In the second part of this study, a bench-scale SBR was operated for 239 days and fed with Fenton-treated wastewater under different operating conditions. BOD₅/COD ratio below 0.40 of the Fenton-treated wastewater had negative effect on the SBR performance. Hydraulic retention time (HRT) of 12 h was found suitable for the SBR and increasing HRT to 24 and 48 h did not significantly improve the SBR efficiency. Statistical analysis (two-way ANOVA) was made on the results to optimize the H₂O₂/Fe²⁺ molar ratio and Fenton reaction time and it was found possible to reduce the Fe²⁺ dose and increase the Fenton reaction time. Under the best operating conditions (H₂O₂/COD molar ratio 2.5, H₂O₂/Fe²⁺ molar ratio 150, Fenton reaction time 120 min and HRT 12 h), the combined Fenton-SBR process efficiency was 89% for sCOD removal and the SBR effluent met the discharge standards. Combined Fenton-SBR is a feasible process for antibiotic wastewater treatment.     

Michael reaction of β-ketoesters with vinyl ketones by iron(III)-exchanged fluorotetrasilicic mica: catalytic and spectroscopic studies

Michael reaction of β-ketoesters with vinylketones at room temperature under solvent-free condition is investigated with various Fe³⁺ catalysts, including FeCl₃ ⋅ 6H₂O supported on various supports (Fe–mica, Fe–mont, Fe–SiO₂, Fe–Al₂O₃, Fe–NaY) and homogeneous catalysts, FeCl₃ ⋅ 6H₂O and Fe(NO₃)₃ ⋅ 9H₂O. Fe³⁺-exchanged fluorotetrasilicic mica (Fe–mica) shows highest activity. Fe–mica exhibits almost quantitative yields of Michael adducts, high turnover numbers (TON = 1000), and a low level of Fe leaching. After simple work-up procedures, Fe–mica can be recycled without a loss in activity. The relationship between catalytic activity and the catalyst structure determined by XRD, UV–vis, and Fe K-edge XANES/EXAFS is discussed in terms of the effect of clay support on the structure and reactivity of Fe³⁺ species. The Fe³⁺ cation, highly dispersed in the interlayer of clay (mica or mont) or on SiO₂, is more active than the cluster-like Fe³⁺ oxide or hydroxide species in Fe–NaY and Fe–Al₂O₃. UV–vis and XAFS results for the catalysts treated with reactants suggest that, during the reaction, the FeCl₂(O)₄ octahedral species in FeCl₃ ⋅ 6H₂O or those on Fe–SiO₂ are converted to the β-diketonato complexes with two β-diketonato ligands, whereas in Fe–mica β-diketonato complexes with one β-diketonato ligand are formed. The formation of β-diketonato complexes results in a slight lowering of the Fe oxidation number from 3+, probably as a result of the electron donation from the β-diketonato ligand to Fe³⁺ as a Lewis acid site. The lower numbers of β-diketonato ligand coordinated with Fe³⁺ in Fe–mica should result in a larger coordination strength for β-diketonato ligand than that in Fe–SiO₂, which was confirmed by acetylacetone-TPD. Thus, the central carbon atom of the β-diketonato ligand in Fe–mica is more reactive toward nucleophilic attack by the coordinated enone, leading to higher activity for the Michael reaction.     

Hydrogen production by partial oxidation of methanol over bimetallic Au–Ru/Fe2O3 catalysts

Hydrogen production by partial oxidation of methanol (POM) was investigated over Au–Ru/Fe₂O₃ catalyst, prepared by deposition–precipitation. The activity of Au–Ru/Fe₂O₃ catalyst was compared with bulk Fe₂O₃, Au/Fe₂O₃ and Ru/Fe₂O₃ catalysts. The reaction parameters, such as O₂/CH₃OH molar ratio, calcination temperature and reaction temperature were optimized. The catalysts were characterized by ICP, XRD, TEM and TPR analyses. The catalytic activity towards hydrogen formation is found to be higher over the bimetallic Au–Ru/Fe₂O₃ catalyst compared to the monometallic Au/Fe₂O₃ and Ru/Fe₂O₃ catalysts. Bulk Fe₂O₃ showed negligible activity towards hydrogen formation. The enhanced activity and stability of the bimetallic Au–Ru/Fe₂O₃ catalyst has been explained in terms of strong metal–metal and metal–support interactions. The catalytic activity was found to depend on the partial pressure of oxygen, which also plays an important role in determining the product distribution. The catalytic behavior at various calcination temperatures suggests that chemical state of the support and particle size of Au and Ru plays an important role. The optimum calcination temperature for hydrogen selectivity is 673 K. The catalytic performance at various reaction temperatures, between 433 and 553 K shows that complete consumption of oxygen is observed at 493 K. Methanol conversion increases with rise in temperature and attains 100% at 523 K; hydrogen selectivity also increases with rise in temperature and reaches 92% at 553 K. The overall reactions involved are suggested as consecutive methanol combustion, partial oxidation, steam reforming and decomposition. CO produced by methanol decomposition is subsequently transformed into CO₂ by the water gas shift and CO oxidation reactions.     

Modeling and operating conditions optimization of Fischer–Tropsch synthesis in a fixed-bed reactor

The effect of a range of operation variables such as pressure, low temperature and H₂/CO molar feed ration the catalytic performance of 80%Co/20%Ni/30 wt% La₂O₃/1 wt% Cs catalyst was investigated. It was found that the optimum operating conditions is a H₂/CO = 2/1 molar feed ratio at 260 °C temperature and 2 bar pressure. Reaction rate equations were derived on the basis of the Langmuir–Hinshelwood–Hougen–Watson (LHHW) type models for the Fischer–Tropsch reactions. The activation energy obtained was 59.69 kJ/mol for optimal kinetic model.     

Hierarchically porous N-doped carbon nanoflakes: Large-scale facile synthesis and application as an oxygen reduction reaction electrocatalyst with high activity

Hierarchically porous N-doped carbon nanoflakes (HPNCNFs) were facilely synthesized on a large scale via pyrolysis of 1,8-diaminonaphthalene (DAN)/FeCl₃·6H₂O mixture under Ar followed by acid leaching. Both pyrolysis temperature and the amount of Fe species have strong influence on catalyst activity. It suggests that the presence of large excess Fe species not only is key to nanoflake formation but also serves as a mesopore-forming agent. The HPNCNF-900 catalyst, obtained at 900 °C with a mass ratio 1:5 of DAN to FeCl₃·6H₂O, was found to exhibit superhigh oxygen reduction reaction activity and excellent durability in alkaline media outperforming the state-of-the-art Pt/C catalyst at a moderate loading.     

Water-gas shift reaction over Cu–Zn,Cu–Fe,and Cu–Zn–Fe composite-oxide catalysts prepared by urea-nitrate combustion

Water-gas shift reaction was investigated over Cu–Zn, Cu–Fe and Cu–Zn–Fe composite-oxide catalysts at atmospheric pressure from 200 to 375 °C in terms of reducing the CO content with maximal H₂ yield. The Cu_0.15ZnFe₂ spinel catalyst expressed a higher CO conversion level and H₂ yield at a lower temperature compared to the Cu_0.15Zn and Cu_0.15Fe catalysts. Adding H₂O to the feed up to 30% (v/v), but not above, increased the CO reduction level, presumably by increasing the hydroxyl species to react with the adsorbed CO. Increasing the W/F ratio to 0.24 g s cm^?3 increased the CO conversion level to 0.76 at 275 °C with the Cu_0.15ZnFe₂ catalyst, and could be further increased to 0.86 at 350 °C by increasing the Cu molar ratio to 0.30 (Cu_0.30ZnFe₂). Nevertheless, increasing the Cu molar content to 0.50 reduced the CO conversion level. No requirement for adding O₂ when using the Cu_0.30ZnFe₂ catalyst at >260 °C was observed. Increasing the CO content in the reactant decreased its conversion level. The performance of the Cu_0.30ZnFe₂ catalyst was stable over a test period in a CO-rich condition. No undesired product was detected, suggesting a higher selectivity for hydrogen production with a low CO content.     

Hydrogenation of CO2 to dimethyl ether on La-, Ce-modified Cu-Fe/HZSM-5 catalysts

Cu–Fe–La/HZSM-5 and Cu–Fe–Ce/HZSM-5 bifunctional catalysts were prepared and applied for the direct synthesis of dimethyl ether (DME) from CO₂ and H₂. The catalysts were characterized by X-ray diffraction (XRD), N₂ adsorption–desorption, H₂-temperature programmed reduction (H₂-TPR), and X-ray photoelectron spectroscopy (XPS). The results showed that La and Ce significantly decreased the outer-shell electron density of Cu and improved the reduction ability of the Cu–Fe catalyst in comparison to the Cu–Fe–Zr catalyst, which may increase the selectivity for DME. The Cu–Fe–Ce catalyst had a greater specific surface area than the Cu–Fe–La catalyst. This promoted CuO dispersion and decreased CuO crystallite size, which increased both the DME selectivity and the CO₂ conversion. The catalysts were stable for 15 h.     

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%.     

Polyoxometalate as effective catalyst for the deep desulfurization of diesel oil

Aiming at the deep desulfurization of the diesel oil, a comparison of the catalytic effects of several Keggin type POMs, including H₃PW_xMo_12?xO₄₀ (x = 1, 3, 6), Cs_2.5H_0.5PW₁₂O₄₀, and H₃PW₁₂O₄₀, was made, using the solution of DBT in normal octane as simulated diesel oil, H₂O₂ as oxidant, and acetonitrile as extractant. H₃PW₆Mo₆O₄₀ was found to be the best catalyst, with a desulfurization efficiency of 99.79% or higher. Hence, it is promising for the deep desulfurization of actual ODS process. The role of the main factors affecting the process including temperature, O/S molar ratio, initial sulfur concentration, and catalyst dosage, was investigated, whereby the favourable operating conditions were recommended as T = 60 °C, O/S = 15, and a catalyst dosage of 6.93 g (H₃PW₆Mo₆O₄₀)/L (simulated diesel). With the aid of GC–MS analysis, sulfone species was confirmed to be the only product after reaction for 150 min. Furthermore, macro-kinetics of the process catalyzed by H₃PW₆Mo₆O₄₀ was studied, from which the reaction orders were found to be 1.02 to DBT and 0.38 to H₂O₂, and the activation energy of the reaction was found to be 43.3 kJ/mol. Moreover, the catalyst recovered demonstrated almost the same activity as the fresh.     

Effect of variation Mn/W molar ratios on phase composition,morphology and optical properties of MnWO4

Manganese tungstate (MnWO₄) particles were successfully synthesized by a microwave hydrothermal method using MnCl₂·4H₂O and Na₂WO₄·2H₂O as the starting materials. The products were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy and UV–vis absorption spectra. Results show that pure MnWO₄ particles can be fabricated in the Mn/W molar ratio range from 1:2 to 2:1. The crystallinity of MnWO₄ increases first and then decreases with increasing Mn/W molar ratio. MnWO₄ morphology transforms from nanorods to aggregated spheres. UV–vis absorption spectra of these two morphologies exhibit a distinct redshift compared with bulk MnWO₄. The band gaps of the nanorods and aggregated spheres-like MnWO₄ particles are 2.75 eV and 2.65 eV, respectively.     

Experimental investigation of role of steam in entrained flow coal gasification

Experimental investigations of the influence of excess oxygen coefficient, H₂O/coal mass ratio using high-temperature steam, mean mass diameter of pulverized coal and coal size fraction on basic characteristics of coal gasification were performed. Experiments were carried out on a laboratory scale (0.09 m i.d. × 1.5 m high) coal gasification apparatus with lignite type of coal. Influence of steam was realized through comparison of results obtained from experiments with (H₂O/coal = 0.287 kg kg⁻¹) and without steam addition (H₂O/coal = 0.024 kg kg⁻¹). High values of carbon conversion, obtained both for finely ground and for coarse pulverized coal points to the easiness of lignite gasification, i.e. to its high suitability for gasification.     

Synthesis of AlOOH slurry catalyst and catalytic activity for methanol dehydration to dimethyl ether

AlOOH slurry catalysts were prepared by complete liquid-phase technology from aluminum iso-propoxide (AIP). Dehydration of methanol to dimethyl ether (DME) over these catalysts was investigated in slurry reactor. The catalysts were characterized by X-ray diffraction (XRD), nitrogen adsorption, temperature-programmed desorption of ammonia (NH₃–TPD). The results showed that the slurry catalysts had high specific surface area and pore volume, and the specific surface area and the strength of weak acidic sites were influenced considerably by the molar ratio of H₂O/AIP and HNO₃/AIP. Activity tests indicated that AlOOH slurry catalysts had excellent catalytic activity and stability in slurry reactor for the dehydration of methanol to dimethyl ether, and the activity correlated well with the strength of weak acidic sites of catalysts, which can be controlled by changing the H₂O/AIP and HNO₃/AIP molar ratios. The average methanol conversion at even stage reaches nearly 80% and DME selectivity almost 100% over CAT-P1 catalyst. No deactivation was found during the reaction of 500 h. It is also expected that CAT-P1 becomes a promising methanol dehydration catalyst for the STD process based on CuZuAl methanol synthesis catalyst.     

Kinetics of coal liquefaction during heating-up and isothermal stages

Direct liquefaction of Shenhua bituminous coal was carried out in a 500 ml autoclave with iron catalyst and coal liquefaction cycle-oil as solvent at initial hydrogen of 8.0 MPa, residence time of 0–90 min. To investigate the liquefaction kinetics, a model for heating-up and isothermal stages was developed to estimate the rate constants of both stages. In the model, the coal was divided into three parts, easy reactive part, hard reactive part and unreactive part, and four kinetic constants were used to describe the reaction mechanism. The results showed that the model is valid for both heating-up and isothermal stages of liquefaction perfectly. The rate-controlled process for coal liquefaction is the reaction of preasphaltene plus asphaltene (PAA) to oil plus gas (O + G). The upper-limiting conversion of isothermal stage was estimated by the kinetic calculation.     

Synthesis of Ag promoted porous Fe3O4 microspheres with tunable pore size as catalysts for Fischer–Tropsch production of lower olefins

Ag promoted porous Fe₃O₄ microspheres with tunable pore size were synthesized via one-pot solvothermal method and employed as catalysts for Fischer–Tropsch synthesis. The introduction of Ag played an important role in regulating the pore size of catalysts and the dispersion of Fe. Comparable to unmodified catalyst in this system, Ag promoted Fe-based catalysts displayed excellent selectivity to lower olefins, particularly for Fe–0.9Ag with smaller pore size of 1.33 nm and Fe dispersion of 10.1%. The maximum selectivity to C₂ through C₄ olefins was 43.0 wt.%, and the selectivity to CH₄ was low to 14.8 wt.%.