Ana S. Reis Machado

High-pressure delignification of Eucalyptus Wood by 1,4-Dioxane-CO2 Mixtures☆

Abstract High-pressure reactive extraction of Eucalyptus globulus wood was undertaken. Extractions were carried out with CO 2 + 1,4-dioxane mixtures at 170 bar pressure at temperatures of 160–180 °C. The influence of temperature, extraction time, composition of the fluid mixture, and flow rate on the extraction were investigated. In the range of temperatures studied, only a small increase in lignin and hemicellulose extraction is observed when temperature is increased. At 180 °C, the degradative extraction of cellulose starts, but at lower temperatures, cellulose losses are small. The selectivity of the extraction depends upon the composition of the extracting mixture. CO 2 -rich fluid mixtures extract hemicellulose preferentially and total hemicellulose removal can be achieved. Maximum delignification was obtained by extraction with pure dioxane with 75% of the lignin initially present in wood being removed. Selectivity towards lignin vs. hemicellulose extraction increases with increasing flow rate until a plateau is reached.

High Pressure Carbon Dioxide Extraction from Coriander Plants. Headspace Analysis

ABSTRACT Dried coriander plants were examined by headspace gas chromatographic analysis. Volatile concentrates of the same plants were obtained by three different methods: steam distillation, extraction with liquid CO2 (at 20°C, 5.7 MPa) and extraction with supercritical CO2 (at 34.5°C, 16 MPa). Yields between 0.6–1.0% were obtained in the extraction by liquid CO2 and yields of 0.3% were obtained by steam distillation. Headspace GC analysis of the volatile concentrates was also performed and the results were compared to those obtained directly from the plants. The difference in aroma of the CO2 extracts and of the steam distillate is quite noticeable, and can be attributed to quantitative differences in the proportions of the components. Within experimental error, CO2 extracts reproduce the natural headspace of the plants.

High Pressure CO2 Extraction from Geranium Plants

ABSTRACT The headspace of fresh and dried geranium plants were compared with those of extracts obtained by three different methods: liquid extraction (21°C, 56.5 bar), supercritical (34.5°C, 160 bar) CO2 extraction, and steam distillation. The difference in aroma of the CO2 extracts and of the steam distillate is due to quantitative differences in the composition of these two. A trend of increasing capability to extract the less volatiles is observed from the steam distillate to liquid to supercritical CO2, the first being richer in rose oxides, the second in isomenthone and the third extract in citronellyl formate and citronellol.

High - pressure extraction of cork with CO2 and 1,4-dioxane

Abstract The extraction of cork from cork-oak ( Quercus suber L.) by high-pressure dioxane and supercritical CO 2 mixtures was studied at 170 bar and in the temperature range of 160°C - 180°C. Suberin is preferably extracted, but extraction percentages were lower than 46%. Lignin extraction percentages are lower than 11%. Extraction selectivity did not change significantly with extracting fluid composition. The results so far obtained support the idea of the existence of an extensive polymeric system across the cell wall and the concept of a close interaction of suberin and lignin, which hinders lignin depolymerization and solubilization in the high-pressure fluid. Fourier transform infrared spectra of cork, extraction residues and extracts are also presented.

Characterisation of residues and extracts of high-pressure extraction of eucalyptus wood by 1,4-dioxane-CO2 mixtures. Part I. Characterisation by FTIR, UV and HPLC

In this work residues and extracts resulting from high-pressure extractions of Eucalyptus globulus Labill. by 1,4-dioxane and 1,4-dioxane-CO 2 mixtures, in the temperature range 160°C-180°C at 170 bar and 250 bar pressures were characterised by spectroscopic and chromatographic techniques. Spectral data of extraction residues showed that thermal degradation starts to occur at 180°C. At lower temperatures cellulose is neither degraded nor extracted and changes in intensity of FTIR absorption bands indicate lignin and hemicellulose extraction. Hemicellulose removal is an essentially degradative process. The FTIR spectra of lignins recovered from extraction liquors show absorption bands with very well defined peaks. They are very similar to literature data obtained for hardwood lignins extracted in mild conditions. Namely, all the absorption bands observed in milled wood lignins of GS3-GS4 types are visible. Acid soluble residual lignins appear to be rich in guaiacyl units, while UV and FTIR spectra show that extracted lignins are rich in syringyl units.

A signalling theory of excessive technological adoption.

Technology adoption has been identified as one of the main elements behind the growth of health care expenditures. It has been argued that the health insurance arrangements in the US justify, to a certain extent, the technology‐driven rise in costs. Moreover, it eases the adoption of less cost‐effective procedures and devices. This paper presents an additional argument by which excessive technology investments may occur: providers of care invest in technology as a way to “signal” their intrinsic (and unobservable) quality. Providers face the option of adopting a new technology. The decision of adoption in itself may convey information about his/her quality: for example, patients conjecture that providers who display newer technology are of higher quality. Providers, being aware of this, may invest in technology to reveal themselves as high quality. Thus, technology adoption could result only from the desire to attract patients. The investment is self‐defeating in the sense that if all providers invest, no information about quality is transmitted to patients. We evaluate the argument in a context of demand for health care services where patients have initially no information about the quality of different providers. We show that an incentive to invest as a way to signal quality may or may not lead to overinvestment. It is also possible that only some providers invest. They reveal themselves as high quality providers. The analysis suggests that the argument is more important for some services than for others. Overall, an additional argument for overinvestment in technology in some circumstances is provided.

Characterisation of residues and extracts of high-pressure extraction of eucalyptus wood with 1,4-dioxane-CO2 mixtures : Part II. Determination of macromolecular parameters of lignins extracted with high-pressure 1,4-dioxane

In this work, lignins extracted from Eucalyptus globulus Labill. with 1,4-dioxane at high-pressure under different conditions were characterised and several macromolecular parameters were calculated according to the Molecular Theory of Degelation model. Lignins extracted by this process show unimodal mass distributions. Lignins recovered from the extraction liquor of extractions carried out at 160°C. 170°C at 170 bar possess average molecular weights in the following ranges: M n = 600-1000 and M w = 1600-2200, and show a polydispersity of about 2, characteristic of a random depolymerization process. Lignins extracted at 250 bar and obtained in traps have higher molecular weights (M w of about 3000) and higher polydispersities. The calculated average degrees of polymerisation of primary chains (y) and branched chains (x) are in the following ranges: y n = 3-6, y w = 5-11, x n = 4-6, x w = 8-21. Branching densities (p) and branching probabilities (α 1 ) were extremely low (p<0.1 and α 1 < 0.2). Thus, lignin extracted by this process is obtained in the form of essentially linear oligomers.