1,721,014 research outputs found
Continuous countercurrent deterpenation of lemon essential oil by means of supercritical carbon dioxide: Experimental data and process modelling
No full textA thermodynamic model based on the Peng-Robinson equation of state was developed in order to perform high-pressure phase equilibria calculations for the system carbon dioxide-lemon essential oil. The multicomponent natural oil was simulated by a mixture of three key components, one for each relevant class of compounds (monoterpenes, monoterpene oxygenated derivatives and sesquiterpenes). Firstly the proposed model was validated on semi-batch experimental data and then it was used to simulate the behaviour of a continuously operated countercurrent column. Experiments on deterpenation process on a packed column, operating as a stripping section, were carried out in the temperature range 50-70 °C and pressure range 8.7-11.2 MPa. The comparison between experimental results and process simulation demonstrated that the proposed model is capable of reliable predictions on the behaviour of the countercurrent continuous deterpenation process. Furthermore, an average height equivalent to a theoretical plate of about 40 cm was estimated, for the stated packing and operating conditions. A case study for the production of 10-fold high quality oil, with strict specifications for the recovery of oxygenated compounds (99%), was investigated by simulations of a continuous countercurrent process with an external reflux. The linkage between the number of theoretical stages, the reflux ratio and the solvent to feed ratio was investigated throughout the above-mentioned pressure and temperature ranges. Operating conditions at higher pressure and temperature proved to be more favourable. As an example, operating a 20 theoretical stage column at 70 °C and 11.2 MPa, it is possible to attain process specifications with a solvent to feed ratio of about 63. © 2007 Elsevier Ltd. All rights reserved
Bioplastics and GHGs Saving: The Land Use Change (LUC) Emissions Issue
No full textMost life-cycle studies have found that a reduction of greenhouse gas emissions can be achievable by replacing petroleum-based plastics with bioplastics made from renewable feedstock, but these analyses have failed to count the carbon emissions that occur as farmers worldwide convert forest and grassland to new cropland to replace the corn diverted to bioplastics. By excluding emissions from land use change, most previous accountings were one-sided because they counted the carbon benefits of using land for bioplastics but not the carbon costs, the carbon storage, and sequestration sacrificed by diverting land from its existing uses. The accounting for the land use change emissions can limit the attractiveness of bioplastics for the displacement of petroleum-based plastics, at least from an environmental point of view. The use of agricultural by-products as bioplastic feedstock is a valid solution to the problem. Alternatively, recycling of bioplastic wastes could contribute to reducing the land use change emissions. From this point of view, it is clear that the incineration or the landfilling of the bioplastic products are not a valid alternative for a real solution of the problem. © 2012 Copyright Taylor and Francis Group, LLC
High Pressure equilibrium data for k-benzylpenicillin(1)+water(2)+carbon dioxide (3) system
No full text
Kinetics of Hydrolytic Degradation of PLA
No full textThe chemical recycling of poly(lactic acid) (PLA) to its monomer is crucial to reduce both the consumption of renewable resources for the monomer synthesis and the environmental impact related to its production and disposal. In particular, the production of lactic acid from PLA wastes, rather than from virgin raw materials, it is also possible to achieve considerable primary energy savings. The focus of this work is to analyse deeply the PLA hydrolytic decomposition by means of a kinetic model based on two reactions mechanism. To this end, new experimental data have been gathered in order to investigate a wider temperature range (from 140 to 180 A degrees C) and to extend the water/PLA ratio up to 50 % of PLA by weight. The reported results clearly highlight that more than 95 % of PLA is hydrolyzed to water-soluble lactic acid within 120 min, when it is hydrolyzed within 160-180 A degrees C. Furthermore, the kinetic constant is highly influenced by reaction temperature. The proposed "two reactions" kinetic mechanism complies satisfactorily with the experimental data under analysis.The chemical recycling of poly(lactic acid)
(PLA) to its monomer is crucial to reduce both the consumption
of renewable resources for the monomer synthesis
and the environmental impact related to its
production and disposal. In particular, the production of
lactic acid from PLA wastes, rather than from virgin raw
materials, it is also possible to achieve considerable primary
energy savings. The focus of this work is to analyse
deeply the PLA hydrolytic decomposition by means of a
kinetic model based on two reactions mechanism. To this
end, new experimental data have been gathered in order to
investigate a wider temperature range (from 140 to 180 C)
and to extend the water/PLA ratio up to 50 % of PLA by
weight. The reported results clearly highlight that more
than 95 % of PLA is hydrolyzed to water-soluble lactic
acid within 120 min, when it is hydrolyzed within
160–180 C. Furthermore, the kinetic constant is highly
influenced by reaction temperature. The proposed ‘‘two
reactions’’ k
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