Effect of SiO2 pore size on catalytic fast pyrolysis of Jatropha residues by using pyrolyzer-GC/MS

Catalytic fast pyrolysis of Jatropha residue was performed over SiO₂ catalysts with different pore sizes (SiO₂-Q3, -Q10, -Q30, and -Q50 with pore diameters of 3, 16, 45, and 68 nm, respectively) at 500 °C using a pyrolyzer-gas chromatography/mass spectrometry system. SiO₂-Q10, which combined weak acidity and medium porosity, was the most effective catalyst in removing oxygenated compounds such as acids, ketones, and aldehydes, which are the principal reason for the polymerization of hydrocarbons from bio-oil, and in inhibiting coke and polycyclic aromatic compound formation. SiO₂-Q10 is also useful for stabilizing bio-oil and has potential for catalytic fast pyrolysis.     

Catalytic depolymerisation and conversion of Kraft lignin into liquid products using near-critical water

A high-pressure pilot plant was developed to study the conversion of LignoBoost Kraft lignin into bio-oil and chemicals in near-critical water (350 °C, 25 MPa). The conversion takes place in a continuous fixed-bed catalytic reactor (500 cm³) filled with ZrO₂ pellets. Lignin (mass fraction of approximately 5.5%) is dispersed in an aqueous solution containing K₂CO₃ (from 0.4% to 2.2%) and phenol (approximately 4.1%). The feed flow rate is 1 kg/h (reactor residence time 11 min) and the reaction mixture is recirculated internally at a rate of approximately 10 kg/h. The products consist of an aqueous phase, containing phenolic chemicals, and a bio-oil, showing an increased heat value (32 MJ/kg) with respect to the lignin feed. The 1-ring aromatic compounds produced in the process are mainly anisoles, alkylphenols, guaiacols and catechols: their overall yield increases from 17% to 27% (dry lignin basis) as K₂CO₃ is increased.     

Characteristics of hemicellulose,cellulose and lignin pyrolysis

The pyrolysis characteristics of three main components (hemicellulose, cellulose and lignin) of biomass were investigated using, respectively, a thermogravimetric analyzer (TGA) with differential scanning calorimetry (DSC) detector and a pack bed. The releasing of main gas products from biomass pyrolysis in TGA was on-line measured using Fourier transform infrared (FTIR) spectroscopy. In thermal analysis, the pyrolysis of hemicellulose and cellulose occurred quickly, with the weight loss of hemicellulose mainly happened at 220–315 °C and that of cellulose at 315–400 °C. However, lignin was more difficult to decompose, as its weight loss happened in a wide temperature range (from 160 to 900 °C) and the generated solid residue was very high (∼40 wt.%). From the viewpoint of energy consumption in the course of pyrolysis, cellulose behaved differently from hemicellulose and lignin; the pyrolysis of the former was endothermic while that of the latter was exothermic. The main gas products from pyrolyzing the three components were similar, including CO₂, CO, CH₄ and some organics. The releasing behaviors of H₂ and the total gas yield were measured using Micro-GC when pyrolyzing the three components in a packed bed. It was observed that hemicellulose had higher CO₂ yield, cellulose generated higher CO yield, and lignin owned higher H₂ and CH₄ yield. A better understanding to the gas products releasing from biomass pyrolysis could be achieved based on this in-depth investigation on three main biomass components.     

Influence of alcohol addition on properties of bio-oil produced from fast pyrolysis of eucalyptus bark in a free-fall reactor

Fast pyrolysis of eucalyptus bark was carried out in a free-fall pyrolysis unit at different temperatures ranging from 400 to 550 °C to produce bio-oil, char and gas. The bio-oil produced at optimum temperature was mixed with alcohols with an aim to improve its properties. The results showed that the maximum bio-oil yield of 64.65 wt% on dry biomass basis could be obtained at the pyrolysis temperature of 500 °C. The addition of a small proportion (2.5–10%) of alcohol into the bio-oil could improve its viscosity, stability and heating value. These effects were further enhanced when increasing the alcohol.     

Pyrolysis of two different biomass samples in a fixed-bed reactor combined with two different catalysts

Pyrolysis of Euphorbia rigida and sesame stalk biomass samples with two selected commercial catalyst, namely DHC-32 and HC-K 1.3Q, have been conducted in a fixed-bed reactor. The effect of different catalysts and their ratio (5, 10 and 20% w/w) and pyrolysis temperature (500 and 750 °C) on the pyrolysis product yields were investigated and the obtained results were compared with similar experiments without catalyst. Bio-oil yield was increased comparing with non-catalytic experiments, at final pyrolysis temperature of 500 °C for both biomass samples and catalysts. In the catalytic experiments; when the temperature reached to 750 °C, although bio-oil product yield was reduced, the gas product yield was increased comparing with non-catalytic experiments.The pyrolysis oils were examined using spectroscopic and chromatographic analyses and then fractioned by column chromatography. Although the aliphatic and aromatic fractions were decreased and polar fraction was increased with catalytic pyrolysis of E. rigida; an opposite trend was observed in the sesame stalk pyrolysis oil, comparing with non-catalytic results.Obtained results were compared with petroleum fractions and determined the possibility of being a potential source of renewable fuels.     

The synthesis of methyl lactate and other methyl oxygenates from cellulose

Light oxygenates, such as methyl lactate (MLA), methyl levulinate (MLE), methyl formate (MFO), methyl acetate (MAC), dimethoxymethane (DMM), and methoxyacetaldehyde dimethyl acetal (MADA) were synthesized from cellulose in the presence of promoted SnX₂ (X = Cl⁻, Br⁻, and I⁻) salt catalysts in methanol. The presence of halides in SnX₂-ML_n (ML_n is metal salt) catalysts was found crucial for methyl lactate formation from sugar. The investigation shows that ZnCl₂ is an efficient promoter for SnX₂ catalyst in converting cellulose to light oxygenates. Up to 52.2% of total one-pass oxygenate yield was obtained in the presence of SnCl₂–ZnCl₂ catalyst.     

TG study on pyrolysis of biomass and its three components under syngas

Pyrolysis of sawdust and its three components (cellulose, hemicellulose and lignin) were performed in a thermogravimetric analyzer (TGA92) under syngas and hydrogen. The effect of different heating rates (5, 10, 15 and 20 °C/min) on the pyrolysis of these samples were examined. The pyrolysis tests of the synthesized samples (a mixture of the three components with different ratios) were also done under syngas. The distributed activation energy model (DAEM) was used to study the pyrolysis kinetics. It is found that syngas could replace hydrogen in hydropyrolysis process of biomass. Among the three components, hemicellulose would be the easiest one to be pyrolyzed and then would be cellulose, while lignin would be the most difficult one. Heating rate could not only affect the temperature at which the highest weight loss rate reached, but also affect the maximum value of weight loss rate. Both lignin and hemicellulose used in the experiments could affect the pyrolysis characteristic of cellulose while they could not affect each other obviously in the pyrolysis process. Values of k₀ (frequency factor) change very greatly with different E (activation energy) values. The E values of sawdust range from 161.9 to 202.3 kJ/mol, which is within the range of activation energy values for cellulose, hemicellulose and lignin.     

Evaluation of various types of Al-MCM-41 materials as catalysts in biomass pyrolysis for the production of bio-fuels and chemicals

MCM-41, is one of the latest members of the mesoporous family of materials. They possess a hexagonal array of uniform mesopores (1.4–10 nm), high surface areas (>1000 m²/g) and moderate acidity. Due to these properties the MCM-41 materials are currently under study in a variety of processes as catalysts or catalyst supports. The objective of this study was to evaluate different types of MCM-41 materials as potential catalysts in the catalytic biomass pyrolysis process. We expected that the very high pore size and the mild acidity of these materials could be beneficial to reformulate the high molecular weight primary molecules from biomass pyrolysis producing useful chemical (and especially phenolic compounds) and lighter bio-oil with less heavy molecules. Three different samples of Al-MCM-41 materials (with different Si/Al ratio) and three metal containing mesoporous samples (Cu–Al-MCM-41, Fe–Al-MCM-41 and Zn–Al-MCM-41) have been synthesised, characterized and tested as catalysts in the biomass catalytic pyrolysis process using a fixed bed pyrolysis combined with a fixed catalytic reactor and two different types of biomass feeds. Compared to conventional (non-catalytic) pyrolysis, it was found that the presence of the MCM-41 material alters significantly the quality of the pyrolysis products. All catalysts were found to increase the amount of phenolic compounds, which are very important in the chemical (adhesives) industry. A low Si/Al ratio was found to have a positive effect on product yields and composition. Fe–Al-MCM-41 and Cu–Al-MCM-41 are the best metal-containing catalysts in terms of phenols production. The presence of the Al-MCM-41 material was also found to decrease the fraction of undesirable oxygenated compounds in the bio-oil produced, which is an indication that the bio-oil produced is more stable.     

Ag-doped M2O3 nanoflakes as effective catalyst for lignin liquefaction in supercritical methanol medium

Solid biomasses can be exploited as an effective source of energy if they can be converted into liquid and gaseous fuels. In this study, highly crystalline Ag–Mn₂O₃ nanoflakes are introduced as effective catalyst for cracking of lignin into alcohols in supercritical methanol medium. The introduced catalyst was synthesized by a sol–gel process. Typically, mixing of manganese acetate, silver nitrate and citric acid solutions led to form a continuous gel when the pH was kept at 7. Drying, grinding and calcination (at 600 °C) of the obtained gel resulted in producing Ag-Mn₂O₃ nanoflakes. The utilized XRD, SEM, FE-SEM and TEM analyses affirmed the concluded structure and morphology. The introduced inorganic nanostructure could successfully catalyze degradation of lignin into liquid alcohols when the solid biomass was catalytically treated in an autoclave reactor in presence of methanol at 180 °C. The experimental results indicated that maximum lignin dissolution of 42.5 wt% can be obtained when the catalyst content is kept at 17 wt% and treatment time of 2 h. Overall, the present study opens new avenue for the stable ceramic catalysts for solid biowastes conversion into valuable products.     

New members in the [Mn10] supertetrahedron family

Two manganese complexes, [Mn^II₄Mn^III₆Cl₄(CH₃OCH₂CH₂O)₁₂ O₄][Mn^II₃Ti^IVCl₆(CH₃OCH₂CH₂O)₆] (1) and [Mn^II₄Mn^III₆Cl₄(CH₃OCH₂CH₂O)₁₂O₄] [Mn₄^II Cl₁₀(CH₃OCH₂CH₂OH)₄]∙0.5CH₃OCH₂CH₂OH, (2) have been obtained and characterized by single-crystal X-ray diffraction. Both structures consist of the decametallic dicationic [Mn^II₄Mn^III₆Cl₄(CH₃OCH₂CH₂O)₁₂O₄]^2 + core constructed by four vertex-sharing [Mn^III₃Mn^IIO]^9 + tetrahedra. Also, these compounds contain the different tetrametallic dianions: [Mn^II₃Ti^IVCl₆(CH₃OCH₂CH₂O)₆]^2 − (in complex 1) and [Mn₄^IICl₁₀(CH₃OCH₂CH₂OH)₄]^2 − (in complex 2). Magnetic dc and ac susceptibility measurements for compound (1) show that the dicationic decanuclear magnetic cluster possesses an S = 12 ± 1 spin ground-state.     

Structure,stability and permeation properties of NaA zeolite membranes for H2O/H2 and CH3OH/H2 separations

NaA zeolite membranes were synthesised in the secondary growth hydrothermal method based on the seeding of the inner surface of a ceramic α-alumina tube. The impacts of crystallisation time and zeolite precursor concentration (in H₂O) were investigated. The structure and stability of the prepared NaA zeolite membranes were also investigated with operating temperatures, times and pressures. The results indicate that the optimal synthesis gel molar composition was 3Na₂O: 2SiO₂: Al₂O₃: 200H₂O. This led to cubic-shaped NaA zeolite which showed good stability. The optimal NaA zeolite membrane had H₂O and CH₃OH fluxes of 2.77 and 0.19 kg/m²h, with H₂O/H₂ and CH₃OH/H₂ separation factors of ∞ and 0.09 at a temperature of 30 °C. The NaA zeolite membrane had high thermal stability, but poor separation performance at high temperature (240 °C). The results suggested that the H₂ permeation flux is significantly influenced by preferential adsorption of vapour in the NaA zeolite membrane.     

Influence of particle size on the analytical and chemical properties of two energy crops

Two energy crops (switchgrass and reed canary grass) have been processed using ball mills and divided into two size fractions (<90 μm and 90–600 μm) and analysed using an array of analytical techniques including proximate and ultimate analysis, metal analysis, calorific value determination, and plant component analysis (cellulose, lignin and hemicellulose contents). The results indicate that smaller particles of the two grasses have a significantly higher concentration of inorganic matter and moisture content than larger particles. In contrast the larger size fractions had a higher carbon content, and lower nitrogen content, with a resulting higher calorific value. The volatile content was also higher in the larger size fraction. The composition of the organic content varied between the two size fractions, most noticeable was the difference in cellulose concentration which was approximately 50% higher in the >90 μm sample. Two laboratory scale techniques, thermogravimetric analysis (TGA) and pyrolysis–GC–MS (py–GC–MS), were used to study the significance of these differences in thermal conversion. In py–GC–MS of reed canary grass, and switchgrass to a lesser extent, the amounts of cellulose and lignin decomposition products were higher for the larger particle size fraction. The differences in cellulose contents were also apparent from the TGA studies, where different mass losses were seen in the cellulose decomposition region of the two size fractions. From the results of these two techniques it was concluded that the differences in ash, and therefore catalytic metal contents, between the two size fractions, resulted in lower pyrolysis temperatures, lower char combustion temperatures, and higher yields of catalytic pyrolysis decomposition products for the smaller size fractions. The implications of the results are discussed in terms of the bio-oil quality in fast pyrolysis and the predicted behaviour of the ash in combustion. It is suggested that pre-treatment by milling is one route that might be used routinely as a feedstock quality improvement strategy in integrated biomass conversion processes.     

Heavy oil upgrading in the presence of high density water: Basic study

Heavy oil (Canada oil sand bitumen) upgrading in high density water (100 and 200 kg/m³) at 723 K was performed by a batch reactor. Yields of asphaltene, maltene, and coke were evaluated. With increasing water density, the rate of coke formation was promoted. To get some hints of coke formation mechanism, the formed coke was observed by scanning electron microscope (SEM). The most part of the coke formed st neat pyrolysis (pyrolysis in the absence of high density water) was coalescent structure of some small coke particles, while that at pyrolysis in the presence of water (200 kg/m³ of water density) was porous structure that indicated occurrence of phase inversion of coke precursors. Based on the results, the reaction mechanism of the heavy oil upgrading was considered: lighter oil was extracted in high density water and the concentration of light hydrocarbon decreased in a heavier oil phase, while the concentration of heavier oil in the oil phase increased. Thus, the lighter oil decomposed further in high density water phase and the heavier oil in the oil phase combined together to form coke due to its higher concentration.     

Pyrolysis of rapeseed in a free fall reactor for production of bio-oil

Pyrolysis experiments of rapeseed (Brassica napus L.) were performed in a free fall reactor at atmospheric pressure under nitrogen atmosphere. The effects of final pyrolysis temperature, particle size and sweep gas flow rate on the yields of products were investigated. The temperature of pyrolysis, particle size and sweep gas flow rate were varied in the ranges of 400—700 °C, −0.224 to 1.8 mm and 50–400 cm³ min⁻¹, respectively. The elemental analysis and calorific value of the bio-oil were determined, and compared with diesel fuel and then the chemical composition of the bio-oil was investigated using chromatographic and spectroscopic techniques (¹H NMR, IR, column chromatography and GC/MS). The chemical characterization has shown that the bio-oil obtained from rapeseed could be use as diesel fuel and chemical feeedstock.     

Direct synthesis of isoparaffin from synthesis gas under supercritical conditions

To produce isoparaffins from synthesis gas directly, modified Fischer–Tropsch (FT) synthesis was carried out under supercritical conditions using n-butane as a medium. One-step FT synthesis using a hybrid catalyst consisting of Co/SiO₂, HZSM-5 and Pd/SiO₂ was carried out. Introduction of supercritical-phase n-butane increased light isoparaffins significantly and suppressed the formation of the by-product, methane. Under supercritical-phase butane, hydrogenolysis and isomerization reactions were promoted. Due to the fact that the optimum temperatures for FT and HZSM-5 catalysts are different, 513 K and over 573 K, respectively, two-step FT synthesis was also carried out to optimize the reaction temperatures. The first-step reaction used Co/SiO₂ catalyst containing small amount of HZSM-5 for FT synthesis at 513 K, and the second-step reaction used a hybrid catalyst containing Pd/SiO₂ and zeolite for hydrogenolysis and isomerization of hydrocarbons at 573 K. Introduction of supercritical n-butane increased the isoparaffin selectivity, and decreased the methane selectivity significantly. The production of heavy hydrocarbons C₉+ was inhibited in both gas and supercritical phase. The isoparaffin selectivity in the gas phase decreased with time-on-stream, but very stable for the supercritical-phase reaction. Because water and heavy hydrocarbons were removed from active sites on zeolite and the zeolite acidity was promoted in the supercritical medium, the selectivity of isoparaffin was considered stable. Among zeolites added to the hybrid catalyst in the second-step reactor, HZSM-5 and H-beta zeolite were suitable for producing light isoparaffins. These results indicated that two-step FT synthesis under supercritical n-butane was superior for producing light isoparaffins from synthesis gas directly.     

Bio-oil production from oil palm biomass via subcritical and supercritical hydrothermal liquefaction

This paper presents the studies on the liquefaction of three types of oil palm biomass; empty fruit bunch (EFB), palm mesocarp fiber (PMF) and palm kernel shell (PKS) using water at subcritical and supercritical conditions. The effect of temperature (330, 360, 390 °C) and pressure (25, 30, 35 MPa) on bio-oil yields were investigated in the liquefaction process using a Inconel batch reactor. The optimum liquefaction condition of the three types of biomass was found to be at supercritical condition of water i.e. at 390 °C and 25 MPa, with PKS yielding the maximum bio-oil yield of 38.53 wt%, followed by EFB and PMF, with optimum yields of 37.39 wt% and 34.32 wt%, respectively. The chemical compositions of the bio-oils produced at optimum condition were analyzed using GC–MS and phenolic compounds constituted the major portion of the bio-oils, with other minor compounds present such as alcohols, ketones, aromatic hydrocarbons and esters.     

Molten waste plastic pyrolysis in a vertical falling film reactor and the influence of temperature on the pyrolysis products

Molten plastics are characterised with high viscosity and low thermal conductivity. Applying falling film pyrolysis reactor to deal with waste plastics can not only improve heat transfer efficiency, but also solve the flow problem.In this work, the pyrolysis process of molten polypropylene(PP) in a vertical falling film reactor is experimentally studied, and the influence of heating temperature on pyrolysis products is discussed. It has been found that with the temperature increases from 550 ℃ to 625 ℃, the yield of pyrolysis oil decreases from 74.4 wt%(± 2.2 wt%) to53.5 wt%(±1.3 wt%). The major compositions of the pyrolysis oil are C_9, C_(12) and C_(18), and β-scission reactions are predominant. The content of the light fraction C_6-C_(12) of pyrolysis oil is 69.7 wt%. Compared with other pyrolysis reactors, the yield of oil from vertical falling film pyrolysis reactor is slightly higher than that from tubular reactor,equal to that from rotary kiln reactor, and slightly lower than that in medium fluidised-bed reactor.     

The synthesis of hydrocarbons and oxygenates during CO hydrogenation on CoCuZnO catalysts: Analysis at the site level using multiproduct SSITKA

This paper addresses the effect of component interaction in CoCuZnO catalysts on oxygenate synthesis during CO hydrogenation. Formation of the various products was investigated for the first time using in-situ multiproduct SSITKA. CO hydrogenation was carried out in a fixed-bed differential reactor at 250 °C and 1.8 atm. Reaction results indicate that the activities for all products decrease with the combination of Co with Cu, possibly, based on SSITKA results, due to partial blockage of the Co surface by Cu. ZnO alone, on the other hand, seems to serve primarily as a support for Co but may increase slightly the intrinsic activities for higher oxygenates. The effects of Cu and ZnO on Co, however, were not additive. The Co–Cu–ZnO combination resulted in a synergy that greatly increased selectivities for higher oxygenates by significantly decreasing the ability for hydrocarbon formation. Interestingly, the rate of synthesis for C₂ oxygenates on Co/CuZnO was identical to that on Co/Al₂O₃ (considered by most to be only a hydrocarbon synthesis catalyst)—but without the high production rate of hydrocarbons.     

Promoting effect of Pd on H2 production from cellulose pyrolysis over mesocellular-foam-supported Ni catalysts

Noble-metal promoters have been added to catalysts for reactions such as steam-methane reforming, but have rarely been applied to systems that produce H₂ from larger, biomass-derived molecules, such as polyols or cellulose. We have previously found that nickel catalysts supported on mesocellular-foam-(MCF)-type silica catalyze H₂ formation during cellulose pyrolysis, and sought to increase their activity. Thus, palladium-promoted nickel catalysts supported on MCF were prepared, and their activities were tested in cellulose pyrolysis (RT → 800 °C, 40 °C/min) under dry argon. A thermogravimetric analyzer–mass spectrometer (TG–MS) was used to semi-quantitatively monitor the gases, especially H₂, that were released during pyrolysis over catalysts with and without Pd promoters. Although the Pd promoters had little impact on the fraction of H₂ in the product gas, adding ≥ 0.4 wt.% Pd enhanced the H₂ yield from cellulose pyrolysis by increasing the total gas yield from the reaction. Thus the promoter improved H₂ yield by enhancing the tar-cracking activity of the catalyst. A 5%Ni/MCF catalyst that was doped with 0.7 wt.% Pd yielded 85 cm³ H₂/g cellulose, which was 15% more H₂ than was obtained when the catalyst was 5%Ni/MCF.     

The first complex of the pentameric phosphazane macrocycle [{P(μ-NtBu)}2(μ-NH)]5 with a neutral molecular guest: Synthesis and structure of [{P(μ-NtBu)}2(μ-NH)]5(CH2Cl2)2

The reaction of [{P(μ-N^tBu)}₂(μ-NH)}₅I]⁻[Li(thf)₄]⁺([1 · I]⁻[Li(thf)₄]⁺) with NaOMe in CH₂Cl₂ gives the title compound [{P(μ-N^tBu)}₂(μ-NH)]₅(CH₂Cl₂)₂ [1 · (CH₂Cl₂)₂] the first adduct containing this type of macrocyclic phosph(III)azane host and a neutral guest.