Javier Pozueta Romero

Identification of residual lignin markers in eucalypt kraft pulps by Py–GC/MS

Abstract Pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS) has been used to characterize the residual lignin in eucalypt ( Eucalypt globulus ) kraft pulp during the pulping and bleaching processes. The composition and structure of eucalypt wood lignin and kraft lignin have also been studied by Py–GC/MS and 13 C-nuclear magnetic resonance (NMR). Pulp samples were collected at different stages of the pulping process (after cooking, oxygen delignification, and bleaching with chlorine dioxide or hydrogen peroxide). By comparison with lignin pyrolysis products obtained from Py–GC/MS of eucalypt wood and kraft lignin, characteristic features of lignin in the different pulps have been established. The main lignin-derived markers detected in pulps were guaiacol, 4-methylguaiacol, 4-ethylguaiacol, 4-vinylguaiacol, syringol, 4-methylsyringol, 4-ethylsyringol, 4-vinylsyringol and trans -4-propenylsyringol, all of them in very low amounts. Analytical pyrolysis was also used to characterize the changes in the residual lignin after kraft pulping of eucalypt wood pretreated with two lignin-degrading fungi ( Bjerkandera adusta and Poria subvermispora ) in wood ‘biopulping’ experiments. In general, Py–GC/MS has shown to be valuable in the characterization of residual lignin markers in kraft pulps due to the sensitivity of the technique when individual-ion chromatographic profiles for selected lignin markers are used.

Characterization of organic deposits produced in the kraft pulping of Eucalyptus globulus wood

The composition of the organic deposits (the so-called pitch deposits) accumulated in different parts of the mills during the kraft pulping of Eucalyptus globulus wood using an ECF (elementary chlorine free) bleaching sequence has been studied. Three pitch deposits were selected in the bleaching sequence. The first one was taken just after the kraft pulping and the oxygen prebleaching step, while the other two were taken from different parts of the mill after the chlorine dioxide bleaching step. The pitch deposits were Soxhlet extracted with acetone, and the extracts were redissolved in chloroform and subsequently analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). The composition of E. globulus wood extractives was also analyzed for comparison. High temperature short capillary columns were used for the GC and GC-MS analyses, which enabled the elution and separation of compounds with a wide range of molecular mass, with no prior derivatization nor fractionation. Sterols and sterol esters were major compounds in the lipidic extractives of E. globulus wood, and hence, contribute to pitch deposition during pulping. The composition of the pitch deposits varied along the bleaching sequence. The kraft cooking and oxygen prebleaching had a minor influence on the composition of the extract of the pitch deposits. These extracts were very similar to those of E. globulus wood extractives, but with a higher content of waxes. No structural changes of sterols and sterol esters were observed. In contrast, after chlorine dioxide bleaching (ECF), the deposits were composed of saturated sterols and sterol esters, with the remarkable absence of unsaturated sterols and sterol esters, mainly the b-sitosterol and b-sitosterol esters, which were completely degraded. The insoluble residues left after acetone extraction of the pitch deposits were analyzed by Curie-point flash pyrolysis-GC-MS and by pyrolysis-methylation-GC-MS. Whereas conventional pyrolysis released series ofn-alkanes / n- alkenes, a series of fatty acid methyl esters were released after pyrolysis-methylation, suggesting that the residues left after acetone extraction might be made up of fatty acids salts. Very minor amounts of ellagic acid were also found in all the pitch deposits, probably deposited as magnesium complex.

Ease of delignification assessment of wood from different Eucalyptus species by pyrolysis (TMAH)-GC/MS and CP/MAS 13C-NMR spectrometry

Abstract Flash-pyrolysis in the presence of tetramethylammonium hydroxide (TMAH) of woods from different species of Eucalyptus yields series of guaiacyl-type (G) and syringyl-type (S) units in slightly but characteristically different relative proportions. Such differences have been used to suggest a fine and appropriate index of the ease of delignification of the different Eucalyptus species when pulped by the Kraft process. The pyrolytic data were in agreement with those obtained from CP/MAS 13C-NMR spectra of the woods. On the other hand, the various eucalypt woods showed additional differences in their pyrolytic patterns regarding the relative amounts and structure of the high molecular weight aromatic compounds arising from the pyrolysis of polyphenolic wood constituents, which might be used as a basis for chemotaxonomic differentiation of the origin of the woods

Analysis of pitch deposits produced in Kraft pulp mills using a totally chlorine free bleaching sequence.

Two organic deposits accumulated in a Kraft pulp mill during pulping of Eucalyptus globulus wood and throughout a TCF (totally chlorine free) bleaching sequence were characterized. One deposit was collected after cooking and an oxygen delignification stage while the other was collected after bleaching with hydrogen peroxide. The deposits were Soxhlet extracted with acetone, and the extracts redissolved in chloroform and subsequently analyzed by gas chromatography (GC) and GC-mass spectrometry (MS) using short and medium length high temperature capillary columns, respectively. On the other hand, the insoluble residues left after the acetone extraction were analyzed by Curie-point flash pyrolysis-GC-MS and by pyrolysis-methylation-GC-MS. The compounds identified in the deposits arise from the E. globulus wood lipophilic extractives that survive the pulping and bleaching processes. Triglycerides were completely hydrolyzed during the Kraft cooking and the fatty acids dissolved. Steroids (alcohols, hydrocarbons, ketones and esters) and waxes were the main components in the deposit collected after the oxygen delignification stage. After the bleaching with hydrogen peroxide, content of the waxes were reduced and fatty acids appeared. High amounts of fatty acids salts were also identified in the deposit collected after the oxygen stage, and in minor amounts in the deposit collected after hydrogen peroxide bleaching. In contrast, this deposit was mainly made up of high amounts of lignin-derived phenolic moieties.

Structural modification of eucalypt pulp lignin in a totally chlorine-free bleaching sequence including a laccase-mediator stage

Abstract Structural modification of eucalypt pulp lignin was investigated in a totally chlorine-free (TCF) bleaching sequence including a laccase-mediator stage. This stage was applied after two oxygen delignification stages, and was followed by an alkaline peroxide stage. After two oxygen delignification stages, two more stages with a laccase mediator and alkaline peroxide were applied. The residual lignins were enzymatically isolated from the different pulps and analyzed by spectroscopic techniques and analytical pyrolysis. The latter revealed high amounts of syringyl units (>70%) in the lignins. 13C-1H heteronuclear single quantum correlation (HSQC) NMR indicated high amounts of β-O-4′ inter-unit linkages (>75% side-chains). Changes in lignin composition and inter-unit linkages were demonstrated in the course of the bleaching sequence. Moreover, oxidative modification of the major syringyl units was shown by C2,6-H2,6 HSQC correlations and by the presence of oxidized pyrolysis markers in pyrograms. The existence of both Cα keto and carboxyl groups in the residual lignin, together with normal (Cα-hydroxylated) units, was revealed by heteronuclear multiple bond correlation (HMBC) between aromatic H2,6 and side-chain carbons. These Cα-oxidized structures represent nearly 60% of total units in the lignin isolated from the enzymatically treated pulp. Analysis of residual lignin after the final peroxide stage compared with a simple alkaline treatment revealed that most of the oxidatively altered lignin was removed by the alkali used in the peroxide stage. Thus, the kappa number decreased and the final residual lignin was more structurally related to that found before the oxidative stages, although it contained less resinols and more carboxyl group-bearing units. However, the action of peroxide is necessary to attain the high brightness required (>90% ISO).

Towards industrially-feasible delignification and pitch removal by treating paper pulp with Myceliophthora thermophila laccase and a phenolic mediator

The ability of two natural phenols to act as mediators of the recombinant Myceliophthora thermophila laccase (MtL) in eucalypt-pulp delignification was investigated. After alkaline peroxide extraction, the properties of the enzymatically-treated pulps improved with respect to the control. The pulp brightness increased (3.1 points) after the enzymatic treatment with MtL alone, but the highest improvements were obtained after the MtL treatment using syringaldehyde (4.7 points) and especially methyl syringate (8.3 points) as mediators. Likewise, a decrease in kappa number up to 2.7 points was obtained after the MtL-methyl syringate treatment, followed by decreases of 1.4 and 0.9 points after the treatments with MtL-syringaldehyde and MtL alone, respectively. On the other hand, removal of the main lipophilic extractives present in eucalypt pulp was observed after the above laccase-mediator treatments. Finally, the doses of both MtL and methyl syringate were reduced, and results compatible with industrial implementation were obtained.

Fluid Phase Endocytic Uptake of Artificial Nano-Spheres and Fluorescent Quantum Dots by Sycamore Cultured Cells

Fluid phase endocytic uptake of external solutes in plant cells was further substantiated using artificial polystyrene nano-spheres (40 nm) and CdSe/ZnS quantum dots (20 nm). Both types of artificial nano particles were taken up by sycamore cultured cells. However, whereas polystyrene nano-spheres were delivered to the central vacuole, CdSe/ZnS nano-dots were sequestered into cytoplasmic vesicular structures. Using dextran Texas Red (m.w. 3,000; d-TR) as additional marker, confocal micrographs confirmed the distinct topographic distribution of CdSe/ZnS quantum dots within the cell. Initially, d-TR and CdSe/ZnS quantum dots co-localized within cytoplasmic vesicles. After 18 h incubation, d-TR was distinctly localized in the vacuole whereas CdSe/ZnS quantum dots remained sequestered in cytoplasmic membranous compartments. The data provide a first evidence for the rapid distribution of solutes taken up by endocytosis to distinct intracellular compartments.

Extracting value from Eucalyptus wood before kraft pulping: Effects of hemicelluloses solubilization on pulp properties

Eucalyptus globulus wood samples were subjected to autohydrolysis for extracting hemicelluloses, and the resulting solids were assayed as substrates for kraft pulping and further Totally Chlorine Free (TCF) bleaching. The susceptibility of treated solids to kraft processing was assessed under selected experiments covering the optimum experimental range. In order to establish a basis for comparison, samples of untreated wood were also subjected to kraft delignification. The best kraft pulps obtained from autohydrolyzed solids were subjected to an optimized TCF bleaching sequence involving double alkaline oxygen and pressurized H(2)O(2) processing, and characterized using standard methods. The suitability of the final product obtained by autohydrolysis-kraft delignification-TCF bleaching for specific purposes is discussed on the basis of the experimental results.

Lipophilic extractives in process waters during manufacturing of totally chlorine free kraft pulp from eucalypt wood.

The chemical composition of lipophilic extractives from process waters throughout a totally chlorine free (TCF) bleaching sequence after kraft pulping of eucalypt wood has been studied. These compounds are among the most problematic wood constituents for both TCF and zero liquid effluent (ZLE) processes, since they tend to accumulate in circuits resulting in the formation of the so-called pitch deposits causing serious problems in the pulp and paper industry. Pitch deposits collected at different parts of the pulp mill were also characterized and their composition compared with that of lipophilic compounds in process waters and Eucalyptus globulus wood. The identification of these compounds from process waters, wood and pitch deposits was performed by gas chromatography and gas chromatography-mass spectrometry using short- and medium-length high temperature capillary columns. Sterols, sterol esters, steroid ketones and steroid hydrocarbons were the main compounds identified. These chemical species arise from eucalypt wood extractives that survive the pulping and are released from pulp into the process waters during the bleaching process. Finally, they can deposit in pulp and on different parts of the mill or remain suspended in process waters being discharged in effluents.

Variation in the composition of wood extractives from Eucalyptus globulus during seasoning

The variation in the content of extractives from Eucalyptus globulus wood has been studied during a three-month seasoning experiment. The decrease in the total acetone extract (by over 56%) after seasoning is well correlated to a parallel reduction on the colloidal pitch measured in black liquors. The composition of lipophilic extractives during the seasoning period has been studied by gas chromatography and gas chromatography-mass spectrometry. Sterols, sterol esters, triglycerides, fatty acids and steroid ketones were the main lipophilic compounds among E. globulus wood extractives. Significative variations in the content of these compounds were observed during seasoning.