Search

The chemical structures of four alkali lignins isolated from poplar, fir, straw, and bagasse were investigated. To explore the relationship between the structural units and the thermal decomposition behavior, the system was tested by elemental analysis, Fourier transform infrared spectrometry, thermogravimetric analysis (TGA), and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The results indicated that the carbon content of poplar lignin (PL) was higher than that of others. Fir lignin (FL) exhibited the highest guaiacol units, while the other three lignins were abundant in syringol units. The thermal decomposition characteristics and pyrolysis products of the four lignins were influenced by the material structural and composition. The DTG curves showed that the initial temperatures and major degradation temperatures of woody lignins(FL and PL) with complex inherent structures were shifted to the high temperature zoom compared with that of non-woody (BL and SL) lignins. Py-GC/MS analysis showed that guaiacol-type phenolic compounds were predominant pyrolysis products derived from the four lignins. The yield of guaiacol-type phenols could reach 82.87%. Moreover, the BL had selectively on phenol-type compounds with yield of 27.89%. [ABSTRACT FROM AUTHOR]

Catalytic fast pyrolysis of Alcell lignin with various additive ratios (5%, 10%, and 15%, mass ratio) of nano-NiO was investigated using a horizontal pyrolyzer. Characterization methods, including Fourier transform infrared spectroscopy (FTIR), gas chromatography (GC), gas chromatography coupled with mass spectrometry (GC/MS), and elemental analysis, were utilized to identify the catalytic fast pyrolysis products. The results indicated that the nano-NiO catalyst had remarkable effects on the yield and quality of these products. The formation of gases, especially CO, CO2, and CH4, were greatly promoted when the additive ratio increased, while the formation of bio-char was clearly inhibited. However, when the additive ratio was 10%, the maximum yield of bio-oil (53.09 wt.%) was obtained, and the corresponding maximum higher heating value (HHV) was 25.33 MJ/kg. Furthermore, nano-NiO caused a large variation in the species of the compounds in bio-oil. Operating with the optimal nano-NiO additive ratio (10%), the carbon conversion rate was 65.50%, and the energy conversion rate was 74.53%. [ABSTRACT FROM AUTHOR]

In the present work, enzymatic/mild acidolysis lignin (EMAL) was isolated from the raw material Cunninghamia lanceolata, and hydrothermal depolymerization was carried out in subcritical water (from 250 to 350℃) using a cylindrical autoclave. The results revealed that the lowest yield of solid residue and highest liquid product yield were achieved at 325℃. The liquid products were primarily composed of phenolic monomers and oligomers. As the reaction temperature increased, repolymerization of the liquid products and dehydrogenation and deoxidation of the solid residues occurred. The high heating value (HHV) of the residues was larger than that of the EMAL, and it reached a maximal level at 275℃. Hydrothermal depolymerization and condensation reactions took place simultaneously even under mild conditions (250℃). Carbonization of the EMAL was remarkable when the reaction temperature reached 325℃. [ABSTRACT FROM AUTHOR]

In this study, two purified mild acidolysis lignins (MAL) extracted from triploid poplar, i.e., Alcell MAL and Alkali MAL, were compared. Some properties, including elemental contents, higher heating value (HHV), functional hydroxyl group compositions, and molecular weights, were tested to characterize the structure of these two MALs. The releasing laws of gases and the distribution of products were also investigated through the use of thermogravimetric Fourier transform infrared (TGFTIR) and pyrolysis-gas chromatography combined with mass spectrometry (Py-GC/MS). The results showed that both MALs had pyrolytic advantages, largely because of their unique chemical structures. However, although the species of volatiles from Alkali MAL were similar to those from Alcell MAL, the releasing temperature range for Alcell MAL was relatively narrow and the volatiles from it were concentrated. Among the fast pyrolytic products, phenols were the most abundant. The yield of 2,6-dimethoxy-4-(2-propenyl)phenol, which was the dominant product, was 25.66% for Alcell MAL and 20.77% for Alkali MAL, respectively. Overall, pyrolytic products from Alcell MAL were more enriched. [ABSTRACT FROM AUTHOR]

In the present work, three different kinds of lignin fractions (L1, L2, and L3) were isolated from the alkali black liquor of Cunninghamia lanceolata by selective precipitation at the pH values of 8 (fraction L1), 5 (fraction L2), and 2 (fraction L3). Elemental analysis, gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FT-IR), 31P nuclear magnetic resonance (31P-NMR), thermal gravimetric analysis (TG), and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) were used to characterize the chemical structure and thermochemical properties of the three lignin fractions. The results showed that L1 presented higher heating value (HHV) and molecular weight compared with L2 and L3. The structures and functional group types were similar for the three lignin grades. However, there was more hydroxyl group in L1 than that in L2 and L3, and the L3 contained a higher amount of carboxylic hydroxyl. L1 exhibited the lowest weight loss value (47.8%) at 200 to 600 oC and the highest amount of charred residue (45.1%), which was exactly the opposite for L3. Phenols, the dominant pyrolysis products, constituted 92.17% of all the pyrolysis products for L1, 93.93% for L2, and 88.09% for L3. [ABSTRACT FROM AUTHOR]

Enzymatic/Mild Acidolysis Lignin (EMAL) was isolated from Cunninghamia lanceolata and eucalyptus woods. The chemical structure and thermochemical properties were characterized by means of elemental analysis, Fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analysis (TG), and pyrolysis-gas chromatography combined with mass spectrometry (Py-GC/MS). The EMAL isolated from Cunninghamia lanceolata (C-EMAL) had larger HHV (higher heat value) in comparison to the EMAL isolated from eucalyptus (E-EMAL) due to the greater carbon content of the C-EMAL. The E-EMAL had more syringyl units, whereas the C-EMAL contained more guaiacyl units. It was observed that thermal decomposition occurred over a wide temperature range, and that at a given starting temperature, within the same sample, a higher heating rate produced a higher temperature at which maximum weight loss peaked. The pyrolysis products were mainly composed of carboxylic acids, alcohols, ketones, aldehydes, olefins, alkanes, esters, ethers, and phenols. At all pyrolysis temperatures, the largest components of the pyrolysis products obtained from C-EMAL were the phenols. [ABSTRACT FROM AUTHOR]

Pyrolysis characteristics and mechanism of tobacco stem were studied by pyrolysis coupled with gas chromatography/mass spectrometry (Py-GC/MS), thermogravimetric analyzer coupled with Fourier transform infrared spectrometry, and mass spectrometry (TG-FTIR and TG-MS) techniques. The composition of evolved volatiles from fast pyrolysis of tobacco stem was determined by Py-GC/MS analysis, and the evolution patterns of the major products were investigated by TG-FTIR and TG-MS. Py-GC/MS data indicated that furfural and phenol were the major products in low temperature pyrolysis, and these were generated from depolymerization of cellulose. Indene and naphthalene were the major products in high temperature pyrolysis. TG-FTIR and TG-MS results showed that CO, CO2, phenols, aldehydes, and ketones were released between 167°C and 500°C; at temperatures >500°C, CO and CO2 were the main gaseous products. [ABSTRACT FROM AUTHOR]

Microstickies in whitewater have caused serious deterioration of paper quality and low efficiency of paper machine runnability. To solve this problem it is necessary to master the characteristics of various aspects of microstickies. In this study, the physicochemical properties and size distribution of microstickies in whitewater of three typical kinds of waste papers, old newspaper (ONP), old book paper (OBP), and mixed office wastepaper (MOW), were investigated by conventional methods and a modified Flow Cytometry Method (FCM). The results showed that white water microstickies in different kinds of waste paper have different characteristics. This is a premise for analyzing stickies problems. Furthermore, in a certain kind of waste paper, the physicochemical properties and the direct determination of size and number of microstickies particle in whitewater can be combined together and taken as a whole to account for more phenomena or deduce more mechanisms, such as agglomeration and deposition, etc. [ABSTRACT FROM AUTHOR]

To investigate the effect of organic bound Na groups on pyrolysis and gasification behaviors of alkali lignin, an experimental study was carried out by Thermogravimetric Analyzer coupled with Fourier Transform Infrared Spectrometry (TG-FTIR). Acid precipitated lignin (APL) and Alkali soluble lignin (ASL) were selected as the testing samples, and physiochemical properties were studied by FTIR, ¹H NMR, and SEM analyses. The research results showed that the pyrolysis and gasification characteristics of alkali lignin depended on phenolic sodium (-CONa) and carboxylate sodium (-COONa) groups (PCSG). In pyrolysis stage, PCSG improved the yields of alcohols and hydrocarbons but inhibited benzenes. During gasification stage, in the present of PCSG, the peak value of gasification rate increased, yet the initial gasification temperature decreased. Meanwhile, CO releasing was relatively concentrated and intensively increased from 37 min (740 °C) to 42 min (840 °C). [ABSTRACT FROM AUTHOR]

Catalytic fast pyrolysis of Alcell lignin with various additive ratios (5%, 10%, and 15%, mass ratio) of nano-NiO was investigated using a horizontal pyrolyzer. Characterization methods, including Fourier transform infrared spectroscopy (FTIR), gas chromatography (GC), gas chromatography coupled with mass spectrometry (GC/MS), and elemental analysis, were utilized to identify the catalytic fast pyrolysis products. The results indicated that the nano-NiO catalyst had remarkable effects on the yield and quality of these products. The formation of gases, especially CO, CO2, and CH4, were greatly promoted when the additive ratio increased, while the formation of bio-char was clearly inhibited. However, when the additive ratio was 10%, the maximum yield of bio-oil (53.09 wt.%) was obtained, and the corresponding maximum higher heating value (HHV) was 25.33 MJ/kg. Furthermore, nano-NiO caused a large variation in the species of the compounds in bio-oil. Operating with the optimal nano-NiO additive ratio (10%), the carbon conversion rate was 65.50%, and the energy conversion rate was 74.53%.

In the present work, enzymatic/mild acidolysis lignin (EMAL) was isolated from the raw material Cunninghamia lanceolata, and hydrothermal depolymerization was carried out in subcritical water (from 250 to 350 °C) using a cylindrical autoclave. The results revealed that the lowest yield of solid residue and highest liquid product yield were achieved at 325 °C. The liquid products were primarily composed of phenolic monomers and oligomers. As the reaction temperature increased, repolymerization of the liquid products and dehydrogenation and deoxidation of the solid residues occurred. The high heating value (HHV) of the residues was larger than that of the EMAL, and it reached a maximal level at 275 °C. Hydrothermal depolymerization and condensation reactions took place simultaneously even under mild conditions (250 °C). Carbonization of the EMAL was remarkable when the reaction temperature reached 325 °C.

In this study, two purified mild acidolysis lignins (MAL) extracted from triploid poplar, i.e., Alcell MAL and Alkali MAL, were compared. Some properties, including elemental contents, higher heating value (HHV), functional hydroxyl group compositions, and molecular weights, were tested to characterize the structure of these two MALs. The releasing laws of gases and the distribution of products were also investigated through the use of thermogravimetric Fourier transform infrared (TG-FTIR) and pyrolysis-gas chromatography combined with mass spectrometry (Py-GC/MS). The results showed that both MALs had pyrolytic advantages, largely because of their unique chemical structures. However, although the species of volatiles from Alkali MAL were similar to those from Alcell MAL, the releasing temperature range for Alcell MAL was relatively narrow and the volatiles from it were concentrated. Among the fast pyrolytic products, phenols were the most abundant. The yield of 2,6-dimethoxy-4-(2-propenyl)phenol, which was the dominant product, was 25.66% for Alcell MAL and 20.77% for Alkali MAL, respectively. Overall, pyrolytic products from Alcell MAL were more enriched.

Hydroxyphenyl (H-type) and guaiacyl (G-type) lignin model polymers composed of the β–O–4 structure without gamma–hydroxymethyl groups were synthesized. The chemical structures of the H- and G-type lignin models were characterized by 1H- and 13C-NMR, as well as MALDI-TOF/MS. The pyrolysis response was analyzed by means of TG-DTG, Py-GC/MS, and a tube furnace technique. 1H-, 13C-NMR, and MALDI-TOF/MS showed that the lignin models were linear polymers. The polymers included the β–O–4 linkage, as in natural lignin. Pyrolytic products from H-type lignin model only possessed p-hydroxyphenyl structure without methoxyl groups, and the pyrolytic products from G-type lignin model only possessed guaiacyl structure with methoxyl groups. Pyrolysis products from H- and G- type lignin models were classified into char, gas, and liquid (bio-oil), and the gaseous products of two model compounds mainly consisted of H2, CO, CH4, CO2, and C2H4.

Pyrolysis characteristics of corn stalk hemicellulose were investigated in a tubular reactor at different temperatures, with focus mainly on the releasing profiles and forming behaviors of pyrolysis products (gas, char, and tar). The products obtained were further identified using various approaches (including GC, SEM, and GC-MS) to understand the influence of temperature on product properties and compositions. It was found that the devolatilization of hemicellulose mainly occurred at low temperatures

A pyrolysis tube furnace system was designed to assess the impact of different components on pyrolysis characteristics under nitrogen atmosphere, and pyrolysis temperature (400 to 900oC) as important factors acting on the samples during pyrolysis. The obtained pyrolysate was classified into three groups, i.e. the condensed liquid product (bio-oil), solid product (bio-char), and light gas. Gas chromatography (GC) was used to analyze ingredients of the light gas released during pyrolysis, and a gas chromatography/mass spectrometer (GC/MS) was used to analyze bio-oil. The results revealed that the volatiles from rice straw pyrolysis exceeded that from lignin at temperatures below 700oC as a result of the higher char generation from lignin pyrolysis. With an increase of pyrolysis temperature, the yield of char decreased and light gas persistently increased, and the yield of bio-tar was maximized at 500oC. In the gas product, H2, CO, CO2 and some light hydrocarbons (CH4, C2H4 and C2H6) could be found, and H2 and CO were abundant. Compounds of bio-oil derived from lignin were simple and consisted of aromatic hydrocarbons, chain hydrocarbon, monoaromatics, and a minor amount of ketones. Phenolic compounds, which comprised 50 to 60%, can be converted easily to obtain high-value chemicals and high quality biofuels.

In order to study the thermal decomposition characteristics of hemicellulose, a highly efficient procedure was carried out to extract hemicellulose from corn stalk. Several different sugar units were observed by 13C NMR spectra to show the presence and species of hemicellulose. Following isolation of the hemicellulose, experimental research on its thermal behavior were carried out with a thermogravimetric analyzer under inert atmosphere at heating rates ranging from 10 to 50°C/min, and the kinetic parameters were calculated by the Kissinger and Ozawa methods, respectively. It was found that the thermal degradation of hemicellulose mainly occurred in the temperature range 180-340°C with a final residue yield of 24% at 700°C. An increase of the heating rate could slightly increase both the temperatures at which the peak weight loss rate was observed and the maximum value of weight loss rate. The activation energy (E) and the pre-exponential factor (lnA) obtained by the Kissinger and Ozawa methods were 213.3kJ mol-1, 211.6kJ mol-1 and 46.2min-1, 45.9min-1, respectively. Even though the data showed little difference, the fitting degree of the Ozawa method was better than that of the Kissinger method. The experimental results and kinetic parameters may provide useful data for effective design and improvement of thermochemical conversion units.