Plasma-assisted preparation of Fe-Cu bimetal catalyst for higher alcohols synthesis from carbon monoxide hydrogenation

Plasma-assisted Fe-Cu/SiO₂ catalysts were prepared by impregnation technique and characterized by X-ray diffraction (XRD), nitrogen adsorption and desorption isotherms, X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction (H₂-TPR) techniques. Catalytic performances for carbon monoxide hydrogenation to higher alcohols were carried out in a fixed-bed reactor at the conditions of T = 300 °C, P = 5 MPa, H₂/CO = 2, GHSV = 6000 ml/g_cat h. Plasma-promoted Fe-Cu bimetal catalyst (FeCuSi-PC) possessed much better catalytic performances than those of conventional sample in the selective hydrogenation of carbon monoxide. XRD and XPS analysis suggested that the plasma assistance in the catalyst preparation remarkably diminished the particle size, improved the catalyst dispersion, and issued an exposure of more copper and iron species on the catalyst surface. The mechanism of plasma on catalyst crystallize size was also discussed.     

Hydrogen production via catalytic steam reforming of fast pyrolysis bio-oil in a two-stage fixed bed reactor system

Hydrogen production was prepared via catalytic steam reforming of fast pyrolysis bio-oil in a two-stage fixed bed reactor system. Low-cost catalyst dolomite was chosen for the primary steam reforming of bio-oil in consideration of the unavoidable deactivation caused by direct contact of metal catalyst and bio-oil itself. Nickel-based catalyst Ni/MgO was used in the second stage to increase the purity and the yield of desirable gas product further. Influential parameters such as temperature, steam to carbon ratio (S/C, S/CH₄), and material space velocity (W_BHSV, GHSV) both for the first and the second reaction stages on gas product yield, carbon selectivity of gas product, CH₄ conversion as well as purity of desirable gas product were investigated. High temperature (> 850 °C) and high S/C (> 12) are necessary for efficient conversion of bio-oil to desirable gas product in the first steam reforming stage. Low W_BHSV favors the increase of any gas product yield at any selected temperature and the overall conversion of bio-oil to gas product increases accordingly. Nickel-based catalyst Ni/MgO is effective in purification stage and 100% conversion of CH₄ can be obtained under the conditions of S/CH₄ no less than 2 and temperature no less than 800 °C. Low GHSV favors the CH₄ conversion and the maximum CH₄ conversion 100%, desirable gas product purity 100%, and potential hydrogen yield 81.1% can be obtained at 800 °C provided that GHSV is no more than 3600 h^− 1. Carbon deposition behaviors in one-stage reactor prove that the steam reforming of crude bio-oil in a two-stage fixed bed reaction system is necessary and significant.     

Biomass to hydrogen via catalytic steam reforming of bio-oil over Ni-supported alumina catalysts

Production of hydrogen (H₂) from catalytic steam reforming of bio-oil was investigated in a fixed bed tubular flow reactor over nickel/alumina (Ni/Al₂O₃) supported catalysts at different conditions. The features of the steam reforming of bio-oil, including the effects of metal content, reaction temperature, W_bHSV (defined as the mass flow rate of bio-oil per mass of catalyst) and S/C ratio (the molar ratio of steam to carbon fed) on the hydrogen yield were investigated. Carbon conversion (moles of carbon in the outlet gases to moles of the carbon feed) was also studied, and the outlet gas distributions were obtained. It was revealed that the Al₂O₃ with 14.1% Ni content gave the highest yield of hydrogen (73%) among the catalysts tested, and the best carbon conversion was 79% under the steam reforming conditions of S/C = 5, W_bHSV = 13 1/h and temperature = 950 °C. The H₂ yield increased with increasing temperature and decreasing W_bHSV; whereas the effect of the S/C ratio was less pronounced. In the S/C ratio range of 1 to 2, the hydrogen yield was slightly increased, but when the S/C ratio was increased further, it did not have an effect on the H₂ production yield.     

Biofuels from waste fish oil pyrolysis: Continuous production in a pilot plant

Fast pyrolysis of waste fish oil was performed in a continuous pyrolysis pilot plant. The experiment was carried out under steady-state conditions in which 10 kg of biomass was added at a feed rate of 3.2 kg h⁻¹. A bio-oil yield of 72-73% was obtained with a controlled reaction temperature of 525 °C. The bio-oil was distilled to obtain purified products with boiling ranges corresponding to light bio-oil and heavy bio-oil. These biofuels were characterized according to their physico-chemical properties, and compared with the Brazilian-fuel specifications for conventional gasoline and diesel fuels. The results show that the fast pyrolysis process represents an alternative technique for the production of biofuels from waste fish oil with characteristics similar to petroleum fuels.     

Simultaneous catalytic esterification of carboxylic acids and acetalisation of aldehydes in a fast pyrolysis bio-oil from mallee biomass

This paper reports the simultaneous catalytic esterification and acetalisation of a bio-oil with methanol using a commercial Amberlyst-70 catalyst at temperatures between 70 and 170 °C. The bio-oil was prepared from the pyrolysis of mallee woody biomass in a fluidised-bed pyrolysis reactor under the fast heating rate conditions. Our results show that the conversion of light organic acids and aldehydes to esters and acetals rises significantly with increasing temperature, reaction time and catalysts loading. However, some acetals (e.g. dimethoxymethane) could decompose at higher operating temperatures (>110 °C) and catalyst loadings (>6 wt.%). The medium and heavy fractions of bio-oil also reacted with methanol to result in increases in their volatility (or decreases in boiling points) when their reactive O-containing functional groups were stabilised. The acid-catalysed reactions between bio-oil and methanol also decreased the coking propensity of the bio-oil reaction products.     

Chain walking copolymerization of ethylene with cyclopentene - Effect of ring incorporation on polymer chain topology

Chain walking ethylene copolymerizations with cyclopentene (CPE) as the ring-forming comonomer were carried out in this study to investigate the tuning of polyethylene chain topology via the unique strategy of ring incorporation. Four sets of polymers containing five-membered rings on the polymer backbone at various low contents (in the range of 0-7.5 mol%) were synthesized by controlling CPE feed concentration at four different ethylene pressure/temperature combinations (1 atm/15 °C, 1 atm/25 °C, 1 atm/35 °C, and 6 atm/25 °C, respectively) using a Pd-diimine catalyst, [(ArNC(Me)-(Me)CNAr)Pd(CH₃)(NCMe)]⁺SbF₆⁻ (Ar = 2,6-(iPr)₂C₆H₃). The polymers were characterized extensively using ¹³C nuclear magnetic resonance (NMR) spectroscopy, triple-detection gel permeation chromatography (GPC), and rheometry to elucidate the chain microstructures and study the effect of ring incorporation on polymer chain topology. It was found that CPE was incorporated in the copolymers primarily in the form of isolated cis-1,3 ring units, along with a small fraction in the form of isolated cis-1,2 ring units. Significant linearization of polymer chain topology was achieved with ring incorporation in each of the three sets of polymers synthesized at 1 atm on the basis of the incrementally raised intrinsic viscosity curves in the Mark-Houwink plot and the significantly enhanced zero-shear viscosity of the polymer melts with the increase of ring content despite the decreasing polymer molecular weight. For the set of polymers synthesized at 6 atm/25 °C, the effect of ring incorporation on polymer chain topology was negligible or weaker due to their linear chain topology resulting at this polymerization condition. The results obtained in this study support the proposed blocking effect of backbone-incorporated rings on catalyst chain walking, and demonstrate that effective tuning of polyethylene chain topology from hyperbranched to linear can be conveniently achieved via CPE incorporation while without changing ethylene pressure or polymerization temperature.     

Enhancement of pyrolysis gasoline hydrogenation over Pd-promoted Ni/SiO2-Al2O3 catalysts

Pyrolysis gasoline upgrading by hydrogenation and ring opening was investigated over highly loaded Ni catalysts supported on amorphous silica-alumina and incorporating promoters as Pd, seeking a higher aromatic reduction of this feedstock in order to meet stringent fuel regulations. The effect of Ni loading and Pd component on the activity of those systems was evaluated in a fixed bed reactor under the following operating conditions: T = 573 and 673 K, H₂:PyGas molar ratio = 10, P = 5.0 MPa, WHSV = 4 h⁻¹. The catalyst properties, measured by several characterization techniques (ICP-AES, XRD, N₂ adsorption-desorption isotherms, TPR, H₂-TPD, CO chemisorption, XPS, FTIR spectroscopy of adsorbed pyridine and NH₃-TPD), were related to their catalytic activity and selectivity. Interestingly, the increase in Ni loading from 24.4 to 33.2 Ni wt.% has a negative effect on both hydrogenation and ring opening activities, as it causes a drop in the BET surface area and a decrease in metal-support interaction, with a negative bearing on catalyst stability. On the other hand, the addition of Pd has a positive effect for hydrogenation, linked with the higher electronegativity of Pd⁰ species compared to those of Ni⁰, as well as with a greater stability of Pd-promoted catalysts during on-stream conditions. A linear correlation has been found between the total amount of desorbed H₂, as determined from H₂-TPD experiments on freshly reduced catalysts, and the initial turnover frequency.     

The performances of higher alcohol synthesis over nickel modified K2CO3/MoS2 catalyst

Ni modified K₂CO₃/MoS₂ catalyst was prepared and the performance of higher alcohol synthesis catalyst was investigated under the conditions: T = 280–340 °C, H₂/CO (molar radio) = 2.0, GHSV = 3000 h^− 1, and P = 10.0 MPa. Compared with conventional K₂CO₃/MoS₂ catalyst, Ni/K₂CO₃/MoS₂ catalyst showed higher activity and higher selectivity to C₂⁺OH. The optimum temperature range was 320–340 °C and the maximum space-time yield (STY) of alcohol 0.30 g/ml h was obtained at 320 °C. The selectivity to hydrocarbons over Ni/K₂CO₃/MoS₂ was higher, however, it was close to that of K₂CO₃/MoS₂ catalyst as the temperature increased. The results indicated that nickel was an efficient promoter to improve the activity and selectivity of K₂CO₃/MoS₂ catalyst.     

Speciation studies of methyl butanoate ignition

The current work presents the results of an experimental study of the intermediates formed during ignition of methyl butanoate (C₅H₁₀O₂) and air mixtures. A rapid-sampling system and the University of Michigan rapid compression facility were used to acquire gas samples at conditions of P = 10.2 atm and T = 985 K using mixtures of χ_mb = 0.96%, χ_O2 = 20.79%, χ_N2 = 52.89%, and χ_Ar = 25.25% (mole fraction, percent basis); corresponding to ? = 0.30 and an inert gas to O₂ molar ratio of 3.76. The samples were analyzed using gas chromatography. Quantitative measurements of mole fraction time-histories of methane, ethane, propane, ethene, propene, and 1-butene are compared with model predictions based on a reaction mechanism developed in previous work. The methane and ethene time-histories are in excellent agreement (within ∼20%), while propene and ethane are underpredicted by the model. Sensitivity analysis shows ignition is controlled primarily by competition between H₂O₂ and HO₂ kinetics at these conditions. Reaction path analysis shows the methyl butanoate fuel consumption is dominated by H-atom abstraction by OH.     

The porous network in carbon aerogels investigated by small angle neutron scattering

Small angle neutron scattering treated with the Porod approach has been applied to compare the influence of catalysts (C = NaOH, Na₂CO₃ and Ca(OH)₂) on the porous structure of resorcinol-formaldehyde (RF) carbon aerogels. Investigated parameters are the molar ratio (R/C varies from 10 to 800 mol/mol) and the pyrolysis temperature (1050 °C, 1700 °C and 2600 °C).At 1050 °C, carbon aerogels based on NaOH and Na₂CO₃ catalysts provide denser materials than with Ca(OH)₂-based one, due to a three-dimensional network of smaller particles. The density of particles decreases with the amount of catalyst. At 2600 °C the development of an intraparticle microporosity, which is quantified, leads to a slight decrease of the interparticle mesoporosity noticed at 1050 °C. This effect is induced by a stiffness of carbon layers in polyhedral pore walls as illustrated by the feature of the chords length distribution g(r) and TEM micrographs.     

Thermochemical liquefaction characteristics of microalgae in sub- and supercritical ethanol

Thermochemical liquefaction characteristics of Spirulina, a kind of high-protein microalgae, were investigated with the sub- and supercritical ethanol as solvent in a 1000 mL autoclave. The influences of various liquefaction parameters on the yields of products (bio-oil and residue) from the liquefaction of Spirulina were studied, such as the reaction temperature (T), the S/L ratio (R₁, solid: Spirulina, liquid: ethanol), the solvent filling ratio (R₂) and the type and dosage of catalyst. Without catalyst, the bio-oil yields were in the range of 35.4 wt.% and 45.3 wt.% depending on the changes of T, R₁ and R₂. And the bio-oil yields increased generally with increasing T and R₂, while the bio-oil yields reduced with increasing R₁. The FeS catalyst was certified to be an ideal catalyst for the liquefaction of Spirulina microalgae for its advantages on promoting bio-oil production and suppressing the formation of residue. The optimal dosage of catalyst (FeS) was ranging from 5-7 wt.%. The elemental analyses and FT-IR and GC-MS measurements for the bio-oils revealed that the liquid products have much higher heating values than the crude Spirulina sample and fatty acid ethyl ester compounds were dominant in the bio-oils, irrespective of whether catalyst was used.     

Impedance analysis of Sr-substituted CePO4 with mixed protonic and p-type electronic conduction

Members of the solid-solution series Ce_1−xSr_xPO_4−δ (x = 0, 0.01, 0.02) with mixed protonic and electronic transport have been synthesized by a nitrate-decomposition method followed by sintering at 1450 °C. Impedance spectroscopy is employed to estimate the bulk electrical conductivity in wet (∼0.03 atm) and dry atmospheres of O₂ and 10%H₂:90%N₂. Conductivity increases with dopant concentration (x), oxygen partial pressure (pO₂) and water vapour partial pressure (pH₂O) reaching ∼3.5 × 10⁻³ S cm⁻¹ at 600 °C for x = 0.02 in wet O₂. Activation energies (E_a) for the bulk conductivity of Ce_0.98Sr_0.02PO_4−δ below 650 °C are 0.44 and 0.78 eV for wet oxidising and wet reducing conditions, respectively. A moderate but positive pO₂⁺ⁿ power-law dependence (n < 1/10) of conductivity is exhibited in the pO₂ range 10^−2.5 to 10⁻¹ atm, consistent with mixed ionic and p-type electronic transport. Thermogravimetric analysis indicates that the Sr-doped materials are stable in a CO₂ atmosphere in the temperature range 25–1200 °C.     

Effect of crystallization temperature on the in situ valorization of physic nut (Jatropha curcus L.) wastes using synthetic HZSM-5 catalyst

Physic nut waste is selected as the biomass feedstock for fast pyrolysis as it is available in large amounts from biodiesel production in Thailand. The volatile matter and fixed carbon contents are 73.8% and 13.6% while ash contents are 5.8%. Carbon is the main element with 49.03 wt%. The oxygen content of 39.0 wt% is considerably high which could directly convert to the oxygenated pyrolysis liquid products. To decrease oxygenated compounds, HZSM-5 was used as a catalyst to upgrade pyrolytic products from fast pyrolysis using analytical pyrolysis–GC/MS method. The HZSM-5 catalyst was successfully synthesized by hydrothermal method at 160–180 °C for 24 h. The particle size, surface area, and pore diameter were 11.25–15.52 μm, 567–582 m²/g, and 21.78–26.11 Å, respectively. The pyrolysis was performed at 500 °C with the Jatropha wastes to catalyst ratio of 1:1–1:10. The presence of HZSM-5 contributed to eliminate the undesirable oxygenated compounds such as acids and ketones which could alleviate problem regarding acidity and instability in bio-oil. In addition, it enhanced significantly the yields of desirable hydrocarbon compounds. The increase in catalyst contents had an effect on the enhancement of hydrocarbons yields, and tended to promote deoxygenation and denitrogenation. At moderate biomass to catalyst ratio (1:5), HZSM-5 synthesized at 170 °C contributed to improve the hydrocarbon yields of 95%, including mainly toluene and xylene, which are valuable products because of their high heating value properties.     

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.     

Comparative study of CO and CO2 hydrogenation over supported Rh–Fe catalysts

The hydrogenation of CO, CO + CO₂, and CO₂ over titania-supported Rh, Rh–Fe, and Fe catalysts was carried out in a fixed-bed micro-reactor system nominally operating at 543 K, 20 atm, 20 cm³ min^− 1 gas flow (corresponding to a weight hourly space velocity (WHSV) of 8000 cm³ g_cat^− 1 h^− 1), with a H₂:(CO + CO₂) ratio of 1:1. A comparative study of CO and CO₂ hydrogenation shows that while Rh and Rh–Fe/TiO₂ catalysts exhibited appreciable selectivity to ethanol during CO hydrogenation, they functioned primarily as methanation catalysts during CO₂ hydrogenation. The Fe/TiO₂ sample was primarily a reverse water gas shift catalyst. Higher reaction temperatures favored methane formation over alcohol synthesis and reverse water gas shift. The effect of pressure was not significant over the range of 10 to 20 atm.     

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.     

The interaction effects of dehydration function on catalytic performance and properties of hybrid catalysts upon LPDME process

Three bi-functional catalysts have been prepared by physical mixing of a commercial methanol synthesis catalyst (CuO–ZnO–Al₂O₃) with three different methanol dehydration catalysts including: H-MFI90, γ-Al₂O₃ and H-Mordenite in order to investigate the role of interaction effects of dehydration component on characteristic properties and performance of these admixed catalysts. The bi-functional catalysts have been characterized by XRD, N₂ adsorption, H₂-TPR, NH₃-TPD and XRF techniques and tested in a mixed slurry bed reactor at the same operating conditions (T = 240 °C, P = 50 bar, H₂/CO = 2, SV = 1100 ml g-cat^− 1 h^− 1) for 60 h time on stream. Among the examined bi-functional catalysts, the physical mixture of KMT + HMFI-90, which had lower reducing peak temperature (T = 200 °C), higher S_Cu (39.1 m² g-cat^− 1) and Cu Dispersion (11.6%), showed higher X_CO (84 mol%), yield of DME (Y_DME = 55.5 mol%), DME selectivity (Select_DME = 66.7 mol%) and also good stability over 60 h time on stream as compared to the other catalysts. This could be assigned, from NH₃-TPD results, to more middle strength acidic sites of H-MFI90 zeolite (SiO₂/Al₂O₃ = 90, total acid site density = 476 µmol/g-cat) which inhibits detrimental interactions with methanol synthesis catalyst and deep dehydration of methanol.     

Influence of temperature and alumina catalyst on pyrolysis of corncob

Corncob has been investigated as an alternative feedstock to obtain fuels and chemicals via pyrolysis in fixed-bed reactor. The influence of pyrolysis temperature in the range 300-800 °C as well as the catalyst effects on the products was investigated in detail and the obtained results were compared. The results indicated that a maximum oil yield of 22.2% was obtained at a moderate temperature of 600 °C. The oil yield was reduced when the temperature was increased from 600 to 800 °C, whereas the gas yield increased.Pyrolysis oils were examined by using instrumental analysis, ¹H NMR spectroscopy and GC/MS. This analysis revealed that the pyrolysis oils were chemically very heterogeneous at all temperatures. It was determined that the most abundant compounds composing the bio-oil were phenolics.It was observed that the catalyst decreased the reaction temperature. Most of the components obtained using a catalyst at moderate temperatures was close to those obtained at high temperatures without using a catalyst. Moreover, the use of a catalyst and the high temperatures of the reactions also decreased the amount of oxygenated compounds produced.According to these results, corncob bio-oils can be used as fuel and constitute a valuable source of chemical raw materials.     

Enhancement of pyrolysis gasoline hydrogenation over Zn- and Mo-promoted Ni/γ-Al2O3 catalysts

Alumina-supported nickel catalysts modified by Zn and/or Mo were prepared and characterized using several techniques (XRF, BET, XRD, XPS, and TPR). The effect of Zn and Mo on catalytic hydrogenation activity was evaluated in hydrogenation of pyrolysis gasoline (PyGas) using styrene conversion for monitoring the activity trend in a fixed-bed reactor under the following conditions: temperature of 70–120 °C, H₂:PyGas volume ratio of 200:1, pressure of 2.8 MPa, and volume space velocity of 3.0 h^− 1. The promoted Ni-based catalysts exhibited excellent catalytic activity for the hydrogenation of PyGas. The styrene conversion doubled after the introduction of Zn and Mo.     

Characterization of gases and solid residues from closed system pyrolysis of peat and coals at two heating rates

Closed system gold-tube pyrolysis experiments were performed on a peat and two coals (TY: R_o = 0.51%; SX: R_o = 0.94%) at temperatures ranging from 337 to 600 °C and a pressure of 50 MPa with heating rates of 2 and/or 20 °C/h. Solid reaction residues were analyzed microscopically. Yields and chemical and isotopic compositions of the generated gases were also determined. All three samples had similar thermal evolution pathways. With increasing heating temperature, vitrinite reflectances (VR_r) of the residues increased linearly from 0.72% to 4.50%. This increase was lesser for the sample with a higher hydrocarbon generation potential and at faster heating rates. Gas compositions are dominated by CO₂ and CH₄ throughout the experimental process. Total gas and CH₄ yields gradually increase with pyrolysis temperature for all samples. The carbon isotopic compositions of CH₄ generated from the peat are lighter than those from the coals. The δ¹³C_CH4 values exhibit a generic evolution pattern which the initial CH₄ is isotopically heavy, then becomes lighter at moderate temperatures, and finally becomes heavier again. Methane produced from the samples at low heating rate has higher transformation ratio than that at high heating rate under the same temperature, so tends to be isotopically heavy after pyrolysis temperature of more than 408 °C.