1,721,032 research outputs found
PLLA Depolimerization Kinetics: A Preliminary Study
No full textPoly(L-lactide) (PLLA) which is produced from renewable plant resources, is recently increasingly utilized as an alternative to petroleum-based polymers in order to reduce their impact on the environments. The monomer of PLLA is mainly produced from corn, which can also be utilized for food or to produce bioethanol or biofuels. Because of these reasons, the recycling of PLLA after its utilization, like other plastic material (PE, PP, or PET), must be carried out. For plastic material it is possible to carry out both a mechanical and chemical recycling: in the first case, the material is mechanically processed to obtain polymer pellets, while, in the second case, it is possible to obtain the monomer directly from the material depolymerization in order to reduce the consumption of renewable resources for the monomer synthesis. One of the most important processes used to produce lactic acid (LA) from PLLA is based on hydro-depolymerization of PLLA at high temperature and under pressure. In the present paper the hydrolytic depolymerization of pellets of PLLA in batch reactor at temperature near the melting temperature of the solid PLLA has been investigated and some preliminary experimental data are presented. Considering a residence time lesser than 120 minutes, a yield of lactic acid higher than 95% has been obtained at temperature equal to about 170-180 degrees C, at pressure equal to water vapour pressure and with a water/PLLA ratio equal to about 20
Lactic Acid Production by Hydrolysis of Poly(Lactic Acid) in Aqueous Solutions: An Experimental and Kinetic Study
No full textPoly(lactic acid) (PLA) is increasingly utilized as an alternative to petroleum-based polymers in order to reduce their impact on the environment. The monomer of PLA is mainly produced from corn, which, in addition to its food utilization, can be also used for the production of bioethanol or biofuels. In this work the depolymerization (chemical recycling) of PLA pellets in a batch reactor at temperatures near the melting temperature of solid PLA has been investigated to produce lactic acid. New experimental data are presented and a kinetic model is provided for a first analysis. With a residence time less than 120 min, a yield of lactic acid greater than 95 % has been obtained at temperatures of 160 and 180 A degrees C for pressure equal to water vapour pressure and a water/PLA ratio by weight equal similar to 10
Life Cycle Assessment of Polylactic Acid and Polyethylene Terephthalate Bottles for Drinking Water
No full textThe biodegradable plastics were introduced in the 1980s to detect possible renewable feedstock to produce nonpetroleum-based plastics as well as to reduce the environmental problems due to the increase of landfill volume. Furthermore, the biodegradable plastics have been used to reduce the environmental impact (in terms of energy requirement from nonrenewable resources and CO(2) gas emissions) derived from production, utilization, and disposal of petroleum-based plastics, like polyethylene terephthalate (PET). To this end, in the last years, different typologies of bioplastics were introduced (both biodegradable plastics and plastics made from renewable resources) like Mater-Bi (made from starch), poly-3-hydroxybuyrate, polycaprolactone, and polylactic acid (PLA). Nowadays, the most important tool to evaluate the environmental impact of a bioplastic and/or of a petroleum-based plastic (conventional plastic) is the life cycle assessment (LCA) that determines the overall impact of a plastic on the environment by defining and analyzing several impact indices directly related to production, utilization, and disposal of the considered plastics. In this work the LA (cradle to grave) of PLA bottles for drinking water was developed and compared to the LA of PET bottles for the same use. The obtained results highlighted that the true advantage of the PLA bottles with respect to the PET bottles arises from the use of renewable resources, but this benefit is paid in environmental terms due to the higher impact on human health and ecosystem quality (due to the use of pesticides, consumption of land, and consumption of water for the production of raw materials). (C) 2010 American Institute of Chemical Engineers Environ Prog, 30: 459-468, 201
A Triethylene Glycol-Water System: A Study of the TEG Regeneration Processes in Natural Gas Dehydration Plants
No full textNatural gas pipeline transportation requires very low water content in the gas stream in order to avoid condensation or hydrate formation. To reach this goal, when triethylene glycol is used to dehydrate natural gas, after the absorption step, triethylene glycol must be regenerated to levels substantially above 98.5-99.0% by weight available from atmospheric distillation of glycol-water mixtures. In order to regenerate triethylene glycol to higher purity levels, some of the methods used require a stripping gas, a solvent, or to perform the distillation under vacuum. Another method to perform a further dehydration of triethylene glycol is the use of a water exhauster, known as Coldfinger, where the vapor in equilibrium with the liquid to be dehydrated is continuously condensed and removed. In the first part of this work, measurements of boiling temperatures are reported for binary mixtures of triethylene glycol and water at pressures of 50, 100, 200, and 400 mmHg. The experimental data obtained were correlated by employing the NRTL model, with temperature-dependent parameters, to express activities in the liquid phase. The fitted NRTL parameters were then used in the Hysys process simulator to perform a process simulation of a natural gas dehydration plant, provided both with a Coldfinger water exhauster and a conventional stripping column for triethylene glycol regeneration
Chemical Recycling of PLA: A Great Opportunity Towards the Sustainable Development?
No full textThis work aims at analyzing the energy efficiency of the chemical recycling process of polylactic acid (PLA) and its sustainability from an environmental point of view. The results show that the production of lactic acid from chemical depolymerization of PLA is preferable, from an energy point of view, to the production of lactic acid by glucose fermentation. The study also shows that the environmental footprint of the analyzed process is larger than that of the PLA mechanical recycling.This work aims at analyzing the energy efficiency of the chemical recycling process of polylactic acid (PLA) and its sustainability from an environmental point of view. The results show that the production of lactic acid from chemical depolymerization of PLA is preferable, from an energy point of view, to the production of lactic acid by glucose fermentation. The study also shows that the environmental footprint of the analyzed process is larger than that of the PLA mechanical recycling
Tannins Extraction from Walnuts Residues
No full textTannins are natural water-soluble products, characterized by a phenolic structure and by the ability to bind and precipitate proteins. They are widely found in natural products, and their "historical" utilization was to convert animal hides into leather. Nowadays tannins are extensively used in food and beverage industry and in pharmaceutical and nutraceutical industry for their positive effects on human health. In conventional processes tannins are extracted from vegetable material by using water as solvent in a temperature range from 40 to 90 degrees C; other polyphenols are always extracted and are classified as non tannins. Scope of this work is to characterize residue (in particular the woody septum) of walnut core in terms of total extractable tannins. To this aim chemical analytic methods, reported in the literature, for the quantitative determination of these compounds in aqueous solution of unknown composition have been assessed. Total extractable tannins in woody septum have been determined by means of an experimental procedure developed in previous works focused on tannins extraction from chestnut wood. The evaluation of extractable tannins is very important to determine the feasibility of a process to extract tannins from this type of residue. Furthermore experimental data on equilibrium distribution of tannins between solid (woody septum) and liquid (water) at temperature of 80 degrees C have been collected. The obtained equilibrium data have been correlated by means of a linear adsorption isotherm
Bioplastics and Petroleum-based Plastics: Strengths and Weaknesses
No full textthe eutrophication; the abioticdepletion; and many others directly related tothe production, utilization, and disposal of the considered plastics. The aim of thiswork is to present a comparison between bioplastics and conventional plastics throughthe use of the “Life Cycle Assessment” methodology. In particular, the life cycleassessment’s Cradle to Grave of shoppers made from Mater-Bi (starch-based plastic)an polyethylene were reported and compared as a case study in order to highlightthe strengths and weaknesses of the bioplastics and the conventional plastics.; the acidification; the human toxicity; The application of biomass, such as starch, cellulose, wood, and sugar,used to substitute fossil resources for the production of plastics, is a widely acceptedstrategy towards sustainable development. In fact, this way a significant reductionof non renewable energy consumption and carbon dioxide emission is accomplished.In recent years, several typologies of bioplastics were introduced and the most importantare those based on cellulosic esters, starch derivatives, polyhydroxybutyrate,polylactic acid, and polycaprolactone. Nowadays, the most important tool to evaluatethe environmental impact of a (bio)plastic is the life cycle assessment that determinesthe overall impact of a plastic on the environment by defining and analyzing severalimpact categories index like the global warmin
Equilibrium and extraction kinetics of tannins from chestnut tree wood in water solutions
No full textTannins are natural water-soluble products, characterized by a phenolic structure and the ability to bind and precipitate proteins. They are widely found in natural products, and their 'historical' utilization was in tanning animal hides into leather. Nowadays, tannins are extensively used in the food and beverage industry and in pharmaceutical and nutraceutical industries for their positive effects on human health. In conventional processes, tannins are extracted from vegetable material by using water as a solvent in a temperature range of 40-90 degrees C; other polyphenols are always extracted and classified as nontannins. The scope of this work is to characterize chestnut tree wood in terms of the total extractable tannins. To this aim, analytic methods, reported in the literature, for the quantitative determination of these compounds in aqueous solution of unknown composition have been assessed. Experimental data on equilibrium distribution of tannins between solid (wood) and liquid (water) at a temperature of 80 degrees C are presented. The obtained results have been correlated by means of the Freundlich isotherm. Experimental data are also reported on the extraction kinetics of tannins from the solid phase. Experimental extraction curves were simulated by a plug flow model, and an overall mass transfer coefficient was evaluated. (C) 2010 Curtin University of Technology and John Wiley & Sons, Ltd
Adsorption of albumin-bound toxins on anion exchange resin: An equilibrium study
No full textBilirubin and tryptophan are among the albumin-bound toxins that must be removed from blood during liver-failure therapy. Artificial liver support devices currently used in clinical practice remove these types of toxins by means of different processes, that are mainly based on adsorption. In this paper, bilirubin and tryptophan adsorption isotherms on anion exchange resin with different albumin concentrations are presented. The results show that the adsorbed amount of toxin decreases with increasing albumin concentration in the solution. This behaviour has been analyzed by means of an original semi-empirical adsorption model that takes in to account the effect of albumin on toxins adsorption equilibrium. The model highlights that this phenomenon is principally because of the competitive binding of toxin between albumin and sorbent, but, in the case of bilirubin, the reduction in the adsorbed amount of toxin was higher than what can be predicted by considering only this phenomenon. From a different point of view, the experimental results show that the anion exchange resin tested is a suitable sorbent for bilirubin removal, while its adsorption capacity for tryptophan is very low and, therefore, different sorptive media should be considered to remove this compound. Copyright © 2011 Curtin University of Technology and John Wiley & Sons, Ltd
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