Search

The aim of this work was to evaluate biomethane production by anaerobic digestion using aqueous phase from Fast Pyrolysis of Douglas Fir Wood as substrate. The effect of biomass acid treatment and condensation temperature on the bio-oil chemical composition and aqueous phase separation with a fractional condensation system coupled to Auger reactor during pyrolysis at 500 °C was reported. As the first condenser temperature was augmented from 40 and 80 °C, the bio-oil yield obtained decreased from 30 to 16 wt% and the aqueous phase yield in the second condenser (kept at 25 °C) increased from 27 till 37 wt%. When the untreated biomass was pyrolyzed, the aqueous phase collected in the second condenser (at the first condenser operated at 80 °C) was anaerobically digested at 100 ppm for 400 h results in 31.3 NmL of CH4/batch. However, the best result was attained after washed biomass with acetic acid (10%) previously to fast pyrolysis, obtaining 86.8 NmL of CH4/batch using just 10 ppm, perhaps due to halved of formed hydroxyacetaldehyde and estimated levoglucosan content increases by more than three times at this condition. Thus, the attained results confirmed the viability of the adopted strategy to improve the anaerobic digestion of the aqueous phase obtained by fractional condensation systems for biomethane production. [ABSTRACT FROM AUTHOR]

In this study, acid-catalyzed conversions of three typical C6 sugar monomers/oligomers (glucose, maltose, and beta-cyclodextrins) to levulinic acid in water, tetrahydrofuran (THF) and toluene have been investigated over a solid acid catalyst Amberlyst 70 (A70), aiming to understand behaviors of the sugars in the solvents with distinct polarities. Molecular sizes of the sugars do not affect both insoluble polymer and levulinic acid formation in the same solvent, but levulinic acid yields vary significantly in the different solvents: In water > in THF with wet A70 > in THF with dried A70 ∼ in toluene. This is due to the different ways of dispersion of the sugars, catalyst and products in the solvents. Sugars are well dispersed in water. Instead, in THF or toluene sugars dissolve in wet A70 that contains water (55 wt.%), which facilitates conversion of the sugars but promotes polymerization as well. In addition, the formation of insoluble polymer, soluble polymer and other products also varied a lot due to distinct polarities of the solvents. [ABSTRACT FROM AUTHOR]

Thisstudy reports changes in solid phase composition when samplesof Avicel cellulose (crystallinity: 60.5%) and ball-milled microcrystallinecellulose (crystallinity: 6.5%) were subjected to pyrolysis in a spoonreactor. Solid state chemistry evolution was examined by hydrolysis-ionexchange chromatography, scanning electron miscroscopy (SEM), Fouriertransform infrared (FTIR), and 13C nuclear magnetic resonance(NMR). The liquid reaction intermediate was found to cause particleagglomeration at temperatures below 300 °C. At higher temperatures,the ball-milled cellulose melted completely but the more crystallinecellulose conserved its fibrous structure. The formation of COand CC groups was accelerated by the presence of liquid intermediatesderived from the amorphous cellulose. The content of cross-linkedcellulose was quantified by the combined use of acid hydrolysis and 13C NMR. A new reaction mechanism to describe the changes inthe solid residue composition at different reaction conditions isproposed. [ABSTRACT FROM AUTHOR]

Abstract: The effect of cellulose crystallinity on the formation of a liquid intermediate and on its thermal degradation was studied thermogravimetrically and by Py-GC/MS using a control cellulose (Avicel, crystallinity at 60.5%) and ball-milled Avicel (low cellulose crystallinity at 6.5%). The crystallinity of the materials studied was quantified by XRD and FTIR. Thermogravimetric analyses (TGA) show the samples with lower crystallinity start to degrade at lower temperatures, exhibiting sharper DTG curves and lower thermal degradation activation energies. Scanning electron microscopy (SEM) studies of the solid residues formed in TGA tests showed that, while the conversion of the ball-milled cellulose (mostly amorphous cellulose) occurs through the formation of a liquid intermediate, in the conversion of the control the fibrous structure is conserved. Py-GC/MS studies showed major differences in the thermal behavior of the samples studied. At 300°C, amorphous cellulose yielded more levoglucosan. At temperatures between 350 and 450°C, higher yields of mono-anhydrosugars (levoglucosan and levoglucosenone) were obtained with the samples with higher crystallinity (control). The ball-milled cellulose produced more 5-(hydroxymethyl) furfural, 5-methylfurfural and furfural. The higher yields of these compounds are due to the acceleration of dehydration reactions when a liquid phase intermediate was formed. Fragmentation reactions responsible for the formation of light compounds (glycoaldehyde, acetic acid, methyl-vinyl-ketone and acetol) and the reactions responsible for the formation of cyclopentane do not seem to be affected by cellulose crystallinity and by the formation of a liquid intermediate. [Copyright &y& Elsevier]

Highlights • The maximum yield of oil phase organics (OPO) in CFP never exceeded the corresponding oil yield of thermal pyrolysis. • A path forward to obtain higher oil yields is not expected to come from process improvements. • For higher OPO yields, catalysts being able to convert the sugar fraction into OPO are required. Abstract Catalytic pyrolysis of woody biomass and cellulosic materials has been investigated by analyzing the effect of catalysts on aqueous phase (sugar rich) and oil phase (lignin rich) organics produced by the preceding thermal pyrolysis. Tests were done in a downer reactor using ZSM-5 and Na 2 O/γ-Al 2 O 3 as typical commercially available catalysts. Both catalysts converted the aqueous phase organics to coke, water and gas, and deoxygenated and cracked the oil phase organics. The maximum yield of oil phase organics when applying the catalysts never exceeded the corresponding oil yield of thermal pyrolysis (∼22% on carbon basis). Analysis of new results of ex-situ with in-situ catalysis, in combination with earlier reported data, indicates that a path forward to obtain higher oil yields is not expected to come from process improvements. The development of catalysts that can convert the aqueous phase organics (potentially ∼35% on carbon basis) into organic phase ones, instead of cracking and polymerizing them to respectively gas and char, should be considered. [ABSTRACT FROM AUTHOR]

The interactions between lignin and cellulose during the slow pyrolysis of their blends were studied by means of Thermogravimetric Analysis (TGA) and Scanning Electron Microscopy (SEM). Fast pyrolysis was studied using Pyrolysis-Gas Chromatography/Mass Spectroscopy (Py–GC/MS). Crystalline cellulose (Avicel), amorphous cellulose, organosolv lignin, and their blends containing 20, 50, and 80 wt.% of lignin were used for the experiments. Differential thermogravimetry (DTG) revealed that the interaction between crystalline cellulose and lignin resulted in a shift toward higher decomposition temperatures, but for lignin/amorphous cellulose mixtures this effect was small. No effect of adding lignin to cellulose was observed on the yields of bio-char. Cellulose-lignin interactions during fast pyrolysis in Py–GC/MS did occur. Products from cellulose fragmentation reactions (hydroxyl-acetaldehyde and acetol) were not influenced by the presence of lignin. In general, production of lignin derived phenolics remains quite similar at 500 °C, but the yield of many methoxylated monophenols increases at 350 °C in the presence of both types of cellulose. Importantly, it was found that the presence of lignin enhanced the yield of levoglucosan, but decreased the yield of some of their dehydration products (e.g., levoglucosenone, 5-Hydrosymethylfurfural, Furfural). This result could be explained by the reduction of residence time of cellulose products in liquid intermediates, a phase where most of the dehydration reactions occur. Lignin seems to enhance micro-explosions, decreasing in this way the residence time of cellulose derived products in the liquid intermediates. [ABSTRACT FROM AUTHOR]

Highlights: [•] Pyrolysis of beech wood particles (0.3 and 14mm). [•] The yield of pyrolytic lignin decreased as particle size increased. [•] Two different pyrolysis regimes were confirmed between 0.3 and 14mm. [•] Secondary reactions and mass transfer limitations lead to more char. [Copyright &y& Elsevier]

• The effect of recycle gas atmosphere on biomass fast pyrolysis was investigated. • Recycle gas atmosphere did not have a notable effect on the product yields. • Recycle gas atmosphere did not lead to a bio-oil with improved quality. It has been reported that a deoxygenated bio-oil (ca. 0.12 kg kg−1 O on bio-oil basis) can be obtained simply by recycling the non-condensable gases (NCG) of biomass fast pyrolysis to a fluidized-bed reactor operated at atmospheric pressure [Mullen et al., 2013, Energy Fuels, 27, 3867–3874]. Such an unprecedented effect would (i) complicate the use of lab-scale research results obtained typically under inert gas (N 2 , He, Ar) atmosphere for the design of commercial scale pyrolysis units projected to utilize a recycle gas atmosphere (ii) obviate the need for catalytic pyrolysis or mild hydrotreatment processes. Considering these implications, further validation or refutation of the claimed deoxygenation effect of recycle gas atmosphere is needed. Therefore, fast pyrolysis experiments with pine wood were performed in a bench-scale fluidized bed reactor under N 2 atmosphere, recycle gas atmospheres (75 % and 90 % recycle gas volume fraction) at reactor temperatures of 430 °C and 500 °C. Mass balances were obtained and the bio-oils were analyzed using GC/MS, GPC, elemental analysis and Karl Fischer titration. No significant differences were observed in product yield and bio-oil composition (e.g. oxygen content) when going from a nitrogen gas atmosphere to a recycle gas atmosphere for both pyrolysis temperatures. [ABSTRACT FROM AUTHOR]

This study investigated the pyrolysis of lignin pyrolysis in a temperature region from 200 to 800 °C, aiming to understand influence of pyrolysis temperature on evolution of structures of the resulting char. The results showed that fusion of the ring structure initiated at 200 °C, where the C/H ratio in the char was equal to that in naphthalene (two fused rings). The C/H ratio in the char obtained at 350 °C corresponded to that in pyrene (four fused rings), while the char produced at 550 °C was equivalent to 20 fused benzene rings in terms of C/H ratio. The increasing pyrolysis temperature also shifted the oxygen-containing functionalities such as the carbonyl, esters, ketones in the bio-oil to the ether functionality that had a higher thermal stability. The DRIFTS study of pyrolysis of lignin showed that drastic changes of the functionalities and the internal structure of the char occurred in a narrow temperature region from 520 to 530 °C. The carbonyl functionality and the aliphatic structure were eliminated, and new conjugated π-bond systems formed. • C/H ratio in different char is equivalent to that in fused rings of varied size. • Increasing pyrolysis temperature shifted ketones, esters in bio-oil to ethers. • Tar obtained above 550 °C had a higher oxygen content but better thermal stability. • DRIFTS study shows the drastic structural changes of char occurred at 520 to 530 °C. [ABSTRACT FROM AUTHOR]