The yields of vanillin and syringaldehyde obtained by the alkaline nitrobenzene oxidation of aspen wood meal have been determined at various temperatures for various times. The maximum yield of each of these aldehydes, ca. 15 and 36% respectively, was obtained under the same conditions. Similar maximum yields result at 130 ± 5 °C. as at 170 ± 5 °C. if the reaction time is markedly increased. Treatment of the wood meal with sodium hydroxide at 160 °C. for two and one half hours prior to the addition of nitrobenzene and subsequent heating under the same conditions decreases, by over 30%, the yields of aldehydes. Samples of 3,4,5-trimethoxybenzaldehyde, β-D-glucovanillin, and β-D-glucosyringaldehyde were oxidized by alkaline nitrobenzene at 160 °C. for two and one half hours and yields of the corresponding phenolic aldehydes of 10.7, 69.6, and 71.9% respectively were obtained. These results are discussed with respect to the chemistry of aspen lignin.
1H-NMR spectra of the following lignin model substances have been analyzed: cinnamaldehyde, 2-methoxycinnamaldehyde, 3-methoxycinnamaldehyde, 4-methoxycinnamaldehyde, 3,4-dimethoxycinnamaldehyde, 3-methoxy-4-hydroxycinnamaldehyde and 3,4,5-trimethoxycinnamaldehyde. From the NMR spectra analysis it follows that the studied compounds exist in solutions as trans isomers. Theoretical (PCILO) calculations in agreement with the NMR data have shown that the more stable conformer has trans orientation of C=O group with respect to the double bond of the conjugated side chain.
Removal of colloidal particle and lignin from pre-hydrolysis liquor (PHL) is important for the subsequent processing and utilization of the saccharides in the PHL. Cationic polymers treatment is a common method for the purpose, and pectinase pre-treatment of PHL can improve the efficiency of the treatment with cationic polymers. To investigate the mechanism of pectinase pre-treatment for improvement of the cationic polymer efficiency, polygalacturonic acid (PGA) was added in the colloidal lignin and dissolved lignin model substances systems, respectively, and the effects of polygalacturonic acid (PGA) and its pectinase pre-treatment on the removal of colloidal and dissolved lignin in the following cationic polymer treatment process were studied. The results showed that the presence of PGA caused the increase of negative charge density of the colloidal lignin and dissolved lignin systems, which lowered the efficiency of the cationic polymers and negatively affected the removal of both the colloidal lignin and the dissolved lignin. After pectinase treatment, the PGA present in the colloidal and dissolved lignin system was degraded and the negative effects on the cationic polymers were eliminated, and the efficiency of the cationic polymers was improved. Compared to the colloidal lignin and dissolved lignin systems with PGA, less cationic polymers were needed for the same systems with pectinase treatment to obtain the similar lignin removal level.
A series of aroyl methyl ketones (ArCOCOCH3 in which Ar was phenyl, p-hydroxyphenyl, p-methoxy phenyl, 4-hydroxy-3-methoxyphenyl, 3,4-dimethoxyphenyl, 4-hydroxy-3,5-dimethoxyphenyl, and 3,4,5-trimethoxyphenyl) has been prepared by the oxidation, using selenium dioxide, of the correspondingly substituted benzyl methyl ketones.
Microbial purification capacity is an important factor in natural self-regulation in water. Evaluating the fate of biodegradable organic pollution downstream from the discharge seems an appropriate way to follow the effect of pollution and its hazard assessment, which dictates the needed sanitation measures. We suggest a simple test for such monitoring. A modification of the additional oxygen demand test, standardised in Ausgewählte Methoden der Wasseruntersuchung, was applied in two river case studies. The additional oxygen demand is a measure of the capability and rate of biodegradation of known organic substance as well as of the amount and activity of heterotrophic organisms in the river. The original test using peptone and glucose as additional feedings of BOD samples was modified by the use of other organic biodegradable model substances characteristic for individual industrial pollutants. The test was found to be an excellent indicator of adapted microorganisms, which are essential for the biodegradation of the appointed organic substances downstream of their discharge into the receiving stream.
Background:
There is a developing demand for innovation in petroleum systems replacements. Towards this aim, lignocellulosic biomass suggested as a possible sustainable source for the manufacturing of fuels and produced chemicals. The aims of this paper are to investigate different kinds of β-O-4 lignin model compounds for the production of value-added chemicals in presence of ionic liquids. Especially, a cheap β-O-4 lignin model Guaiacol glycerol ether (GGE) (Guaifenesin) is introduced to produce valuable chemicals and novel products.
Methods:
Research related to chemical depolymerization of lignocellulosic biomass activity is reviewed, the notes from different methods such as thermal and microwave collected during at least 10 years. So, this collection provides a good source for academic research and it gives an efficient strategy for the manufacturing of novel value-added chemicals at an industrial scale.
Results:
This research presented that ionic liquid microwave-assisted is a power saving, cost efficient, fast reaction, and clean way with high selectively and purity for production of high value chemicals rather that conversional heating. Guaiacol and catechol are some of these valuable chemicals that is produced from β-O-4 lignin model compounds with high word demands that are capable to produce in industry scale.
Conclusion:
The β-O-4 lignin model compounds such as Guaiacol glycerol ether (GGE) (Guaifenesin) are good platform for developing food materials, perfumery, biorefinery, and pharmaceutical industry by ionic liquids-assisted lignin depolymerization method.
Methyl 4-O-(3-methoxy-4-hydroxybenzyl) and methyl 4-O-(3,5-dimethoxy-4-hydroxybenzyl)-α-D-glucopyranoside and their 6-O-isomers were prepared as model substances for the ether lignin-saccharide bond by reductive cleavage of corresponding 4,6-O-benzylidene derivatives. Kinetic study of acid-catalyzed hydrolysis of the compounds prepared was carried out by spectrophotometric determination of the benzyl alcoholic groups set free, after their reaction with quinonemonochloroimide, and it showed the low stability of the p-hydroxybenzyl ether bond.
Enhancement of colloidal particle and lignin removal from pre-hydrolysis liquor by pectinase pre-treatment – Study on model substances