H. Pakdel

Separation of phenols from Eucalyptus wood tar

Isolation of phenols from Eucalyptus wood pyrolysis tar was carried out with the objective of recovering valuable pure phenols, such as phenol, cresols, guaiacol, 4-methylguaiacol, catechol and syringol. The approach included a primary conversion of the raw wood tar into a lighter oil. Phenolic compounds were further separated from the oil by liquid-liquid extraction using alkali and organic solvents. GC/MS analysis of acetyl-derivatized phenolic compounds was used to evaluate the separation method. The primary conversion allowed the isolation of a lighter oil containing the desirable compounds without causing major chemical changes in the distilled oil. Liquid-liquid extraction by alkali and organic solvents essentially yielded a phenolic fraction. Removal of phenols was more efficient under highly alkaline conditions. An evaluation of the analytical procedure for the determination of phenols was also undertaken.

Production of dl-limonene by vacuum pyrolysis of used tires

Abstract Various samples of used car and truck tires were pyrolyzed in a batch mode under vacuum and in a continuous feed reactor. The pyrolysis temperature varied in the range of 440–570°C. dl -limonene is a major product formed during the thermal decomposition of rubber under reduced pressure conditions. The pyrolysis oils were distilled to obtain a dl -limonene-rich fraction. The difficulty of obtaining a pure dl -limonene fraction is discussed. A high pyrolysis temperature decreases the dl -limonene yield due to the cracking of the pyrolysis oil. Several secondary organic compounds produced by cracking were identified by gas chromatography/mass spectrometry (GC/MS) analysis. These compounds had a boiling point similar to dl -limonene. The dl -limonene yield decreases with an increase of the pyrolysis reactor pressure. The mechanism of the thermal degradation of tires leading to the formation of dl -limonene is discussed. A dl -limonene-rich fraction was obtained following a series of distillation. Sulfur-containing compounds in the dl -limonene-rich fractions were analyzed by GC using a sulfur specific detector. Several thiophene-derivatives were identified. Quantitative analysis of the sulfur compounds in the dl -limonene rich fractions was made. An olfactometry test was performed on a standard thiophene sample in d - and dl -limonene solutions to establish an approximate threshold value to detect the thiophene odor.

Step-wise and one-step vacuum pyrolysis of birch-derived biomass to monitor the evolution of phenols

Abstract One-step and stepwise laboratory batch vacuum pyrolysis of a mixture of birch bark (ca. 46%) and birch sapwood (ca. 54%) was carried out in the temperature range 25–550°C. The pyrolysis oil (defined as the total condensates, including water and organics) was analyzed by GC–MSD and the quantity of phenols (referred to monolignols in this paper) was determined as a function of temperature. The active zone of decomposition and the maximum recovery of phenols were found to be in the temperature range 275–350°C. Distribution of phenols, charcoal and water as a function of temperature was investigated. Stepwise and one-step pyrolysis yielded total phenols of 4.43 and 2.51 wt.% (anhydrous feed basis), respectively. The yields of pyrolysis oil (62.39 wt.%), wood charcoal (23.25 wt.%) and gas ( 14.36 wt.%) produced by both methods were approximately similar, on an anhydrous feed basis.

Seperation of syringol from birch wood-derived vacuum pyrolysis oil

A birch wood sample (Betula papyrifera) composed of 54% sapwood and 46% bark was pyrolyzed in a pilot plant reactor. The products were 53.9% condensates (pyrolysis oil including 8% reaction water), 24.0% gas and 22.1% wood charcoal (anhydrous initial feed basis). The pyrolysis oil was steam distilled and the recovery of phenols at various steam pyrolysis oil ratios was studied. A 14.9% by wt. of volatile pyrolysis oil fraction (based on the total feed oil) was recovered at a steam:oil ratio of 27. The distillate was analyzed by GC/MS after acetylation and showed 21.3% by wt. of phenolic compounds on the pyrolysis oil basis. The distillate was further distilled under a total pressure of 0.7 kPa. About 16 sub-fractions were recovered. The steam-distilled fractions were found to be chemically and thermally stable when subjected to further purification processes. The 2,6-dimethoxyphenol (syringol)-rich fraction was separated and purified. Syringol with a purity of 92.3% was obtained.

Characterization of used tire vacuum pyrolysis oil: Nitrogenous compounds from the naphtha fraction

Abstract Vacuum pyrolysis of used tires yielded 61% by weight hydrocarbon type oil from which 18% by weight naphtha fraction can be distilled off. The pyrolysis oil consisted of (i) the processing oil as part of the tire formulation, (ii) organic additives, and (iii) tire pyrolysis products. A procedure was developed for the separation and identification of nitrogenous compounds in used tire-derived oil, which were partially produced by pyrolysis of tire accelerants. The analytical separation technique involved liquid—solid chromatography on a dual packed silica gel and alumina column. n-Pentane and ethylacetate eluted the hydrocarbons. The nitrogenous compounds were eluted with methanol. Thirty-one nitrogenous compounds were identified by gas chromatography/mass spectrometry and gas chromatography/ atomic emission detection.

Simultaneous gas chromatographic—Fourier transform infrared spectroscopic—mass spectrometric analysis of synthetic fuel derived from used tire vacuum pyrolysis oil, naphtha fraction

Abstract Used tires were pyrolysed in a process development unit under vacuum at about 510°C and yielded 45% oil from which 27% (w/w) of a naphtha fraction (initial boiling point, IBP: 204°C) was separated. A new gas chromatographic configuration by combining infrared, mass spectrometric and flame photometric detectors to simultaneously analyze the effluent from a single capillary column injection was tested. Over 150 compounds were identified and quantified. Sulfur compounds distribution was established by sulfur-specific detection and selected ion GC—MS. Unlike petroleum, tire-derived pyrolytic naphtha is composed of highly branched chain isomeric hydrocarbons. Infrared spectroscopy as an extremely sensitive isomer-specific probe of molecular structures is described. Over 50 compounds were positively characterized by combining MS and IR data. It is shown that mass spectrometry provides superior quantitative capabilities, while infrared spectroscopy is an excellent complementary technique for simultaneous qualitative analysis of pyrolysis oils. Some of the difficulties encountered in the present application are discussed.

Production and characterization of carboxylic acids from wood. Part I: low molecular weight carboxylic acids.

Abstract Pyrolysis oil from wood has been fractionated directly at the outlets of a multiple hearth reactor using six heat exchangers in parallel. A large portion of the organic liquid phase was recovered in the heat exchangers, and the bulk of the aqueous phase was condensed in a series of cooling traps (secondary condensing unit). The C1 to C7 carboxylic acids in the wood pyrolysis oils were analysed using gas chromatography following conversion into benzyl esters via tetrabutylammonium salts, purification by solvent extraction and silica-gel elution chromatography. The technique of benzylation and purification is an improved carboxylic acid determination method and is more accurate than the other techniques particularly for the quantifications of C3 to C7 carboxylic acids. The method of C1−C7 acid production of vacuum pyrolysis of wood and the reactor overall separation efficiency are also discussed.

Quantification of urea formaldehyde resin in wood fibers using X-ray photoelectron spectroscopy and confocal laser scanning microscopy

The potential merits of X-ray photoelectron spectroscopy (XPS) technique for the quantification of nitrogen on the wood fiber surface before and after resination with UF resin was investigated and the resin content was calculated. The bulk nitrogen content of the fibers obtained by XPS after grinding was compared with those obtained by combustion and Kjeldahl methods. Four different fluorescence staining agents were tested by UV spectroscopy. Their λmax shifted to longer wavelengths when reacted with UF resin. Appropriate analysis conditions were tested for a satisfactory analysis of wood fibers by the confocal laser scanning microscopy (CLSM). The result obtained by CLSM was compared with that obtained by XPS.

Vacuum pyrolysis of lignin derived from steam-exploded wood

Vacuum pyrolysis of 100 g of lignin derived from steam explosion of wood yielded 42.7% oil, 38.0% charcoal, 10.0% gas and 9.3% pyrolytic water (wt. %, moisture and ash-free basis) at 465°C and below 2 kPa absolute pressure. The pyrolysis oil was fractionated into eight fractions, F1–F8. F1 and F2 were mainly hydrocarbons and accounted for 3.4% of the anhydrous oil. F3 to F7 were mainly mono and diphenols and represented 41.6% of the anhydrous oil. F8 had very low GC/MS response due to its low volatility and/or high polarity. It may be possible to use directly fractions F3 to F7 in phenolic resin formulation.

Production and Characterization of Carboxylic Acids From Wood. Part Ii: High Molecular Weight Fatty and Resin Acids

Abstract Various waste wood species including primary sludges from spruce wood debarking stage, spruce bark, aspen poplar wood and a mixture of spruce wood and aspen bark were pyrolysed under vacuum in a bench scale reactor and a Process Development Unit. The low water content pyrolysis oils were recovered and derivatized by diazomethane to methyl esters. The oils were then fractionated on a silica gel column into three fractions. High molecular weight carboxylic acid methyl esters and resin acid methyl esters were recovered in the second fraction. The methyl ester fractions were analyzed by capillary gas chromatography-mass spectrometry. Fatty acid and resin acid methyl esters in the range of C 4 -C 28 were identified and quantified. The acid distribution in the pyrolysis oils was studied regardless of the initial wood sample location, age, and storage time before pyrolysis. Free acid methyl ester and other ester (e.g. triglycerides) contents of the pyrolysis oils were determined. The primary sludges and softwood bark were Soxhlet extracted with acetone and their acid contents were determined and compared with the pyrolysis oils. The production of high molecular weight acids under varying pyrolysis conditions is discussed.