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Metodologia per la produzione di Ossigeno Poliatomico Liquido (OPL)

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Metodologia per la produzione di Ossigeno Poliatomico Liquido

(OPL)

Emilia Bramanti1, Massimo Onor1, Giovanni Barco2
  1. C.N.R. Istituto di Chimica dei Composti Organometallici, UOS di Pisa, via Moruzzi 1, 56124 Pisa, Italy
  2. Barcoline srl

Abstract


  2. We descibe herein an original methodology for the production of a mixture defined as Polyatomic Liquid Oxygen (PLO) and its chemical-physical characterization.
  3. This mixture is succesfully employed in biomedical, biotechnological applications, in zootechnics, agrotechniques, material and chemical sciences.

Introduction


  2. The high electrochemical potential shows ozone's favorable thermodynamics.

  4. The word for ozone (O3) comes from the Greek word "ozein" which means "to smell" since ozone was first noticed because of its characteristic pungent odor (1). The odor is detectable in air at levels of about 0.1 parts per million, and exposure to ozone becomes fatal to humans at around levels of 100 ppm for 10,000 minutes or 10,000 ppm for 30 seconds (2). O3, is a blue-colored gas at ambient temperatures, but this color is not noticed at the low concentrations at which it is usually generated
  5. (2). In the liquid and solid states, ozone is dark blue. Liquid ozone boils at -111.3 °C and solid ozone melts at -192.5 °C (3). Ozone, which is toxic, is an unstable gas and an explosive liquid. The ozone molecule is a bent molecule with an O-O bond length of 1.278 A and a bond angle of 116.8 degree.
  6. Gaseous ozone (O3), formed photochemically in the earth's atmosphere by radiation from the sun, is a normal constituent of the earth's atmosphere which is important in shielding the earth from cancer-causing ultraviolet radiation emitted by the sun. Large scale generation of ozone is extremely important commercially, however, due to its strong oxidizing abilities.
  7. O3(g) + 2H+ + 2e- <====> O2(g) +H2O {Eo = 2.075 V}

  9. Ozone, like oxygen, chlorine, and hydrogen peroxide, is a strong oxidizing agent. The relatively high (+2.075 V) electrochemical potential indicates a very favorable oxidizing agent. Ozone's widespread application is based on its ability to pull electrons from a covalent bond causing it to break, or pulling electrons from an aqueous phase metal (Fe+2 --> Fe+3) causing it to undergo hydrolysis (Fe+3 --> Fe(OH)3(s)) and precipitate from solution.
  10. Second only to fluorine in its oxidizing power, ozone has many uses including but not limited to water purification, bleaching of materials such as paper, synthetic fibers, Teflon, waxes, flour, and other products, treatment of wastes in industry, deodorization and sterilization (3). Previously, chlorine products have been used for these purposes, but recent studies have shown that chlorine products may produce carcinogens such as trihalomethanes and chloramines (4). Ozone is a safe alternative to chlorine products which performs the same functions without the undesirable side effects; it is not harmful to the environment since it is made from oxygen (O2) and decomposes back into O2. Ozone has been used in water treatment (sewage, wastewaters, polluted waters) worldwide for more than 100 years (2).
  11. The oxidative properties of ozone are useful in the removal of soluble iron and manganese, the removal of unwanted colors, tastes, and odors, the decomplexing of bound heavy metals, the destruction of inorganic components such as sulfides, cyanides, and nitrites, and the removal of suspended solids (2). One invention even provides a means for maintaining a degree of residual ozone in the water after treatment so that the water will remain pure during storage (5). It is used to improve the biodegradability of the wastewater (6).
  12. An ozone oxidative process is always based on the effect of direct and indirect reaction mechanisms, e.g. mediated by the disintegration of ozone in water into OH-radicals. These radicals are very shortliving compounds that have an even stronger oxidation mechanism than that of ozone because of their higher oxidation potential (Table 1) (7).

Table 1. Redox potential of oxidizing agents.



  3. Species
  4. Substance Potential (V)
  5. Fluorine (F)
  6. 2.87
  7. Hydroxyradical (OH)
  8. 2,86
  9. Oxygen atom (O)
  10. 2,42
  11. Ozone molecule (O3)
  12. 2,07
  13. Hydrogen peroxide (H2O2)
  14. 1,78
  15. Chlorine (Cl)
  16. 1,36
  17. Chlorine dioxide (ClO2)
  18. 1,27
  19. Oxygen molecule (O2)
  20. 1,23

  22. Direct or indirect oxidative processes dominate, depending on various factors, such as temperature, pH and chemical composition of the water.

  24. Direct reactions. The direct oxidation of organic matter by ozone is a selective reaction mechanism, during which ozone reacts quickly with organic matter that contains double bonds, activated aromatic groups or amines.

  26. Cyclo addition (Criegee mechanism)

  28. Consequentially to is dipolar structure, an ozone molecule can undergo a 1-3 dipolar cyclo addition with saturized compounds (double or tripple bonds). This leads to the formation of a compound called ‘ozonide’ (A):

image
image

  2. A B

  4. In a protonic solution, such as water and more in acid solutions, primary ozonide disintegrates into an aldehyde, a keton or hydrogen peroxide and carboxyl compounds (B).
  5. Electrophilic reactions

  7. Electrophilic reactions occur mainly in aromatic compounds. Ozone reacts fast with aromatic compounds substituted by electron donors (such as OH and NH2), which have a high electronic density on the carbon compounds in ortho and para position (e.g. phenol).

image


  3. Nucleophilic reactions

  5. Nucleophilic reactions of ozone occur with carbon compounds that contain electron-retreating groups, such as –COOH and -NO2.
  6. Indirect reactions

  8. OH-radical reactions are, instead, very complex and not selective. The following steps occur: 1. Initiation; 2. Radical chain-reaction; 3. Termination.

  10. Initiation. It is accelerated by an initiator (e.g. OH-):

  12. O3 + OH- -> O2• - + HO2•

  14. This radical has an acid/ base equilibrium of pKa = 4,8. Above this value, this radical no longer splits, because it forms a superoxide radical (reaction 2):
  15. HO2• -> O2•- + H+ (pKa = 4,8)

  17. Radical chain-reactions. They involve the superoxyde anion and OH radicals: O3 + O2•- -> O3•- + O2
O3•- + H+ -> HO3• (pH < ≈ 8)
OH• + O3 -> HO4• HO4• -> O2 + HO2•
HO2• radicals can continue the reaction.
Promotors are fundamental in order to transform OH-radicals to superoxide radicals (Table 2).
Initiator
Promotor
Radical catcher (inhibitor)
OH-
Humic acid
HCO3-/CO3=
H2O2
Aryl-R
PO34-
Fe2+
P r i m a r y a n d s e c o n d a r y
alcohols
Humic acids, aryl-R, Tert-butyl
alchol (TBA)
Advanced oxidation processes (indirect oxidation)
The Advanced Oxidation Process (AOP) mainly involves OH-radicals. These radicals have a very short half-life (10 µS at a 10-4 M concentration) and are unselective. AOP often includes the use of ozone AND hydrogen peroxide (H2O2), or ozone and UV-light, or hydrgen peroxide and UV-light. Ozone reacts with hydrogen peroxide according to the following reactions:
H2O2  HO2- + H+
2 O3 + H2O2 -> 2 OH• + 3 O2
Direct an indirect oxidation reactions with ozone and OH- radicals can be considered second-order. The reaction speed of OH-radicals (108 -1010 L mol-1 s-1) is much higher than that of ozone (1 -103 L mol-1 s-1). However, OH-radicals are consumed by radical catchers in water much faster that ozone, in particular by carbonate and bicarbonate. Ozone oxidation is efficient for aromatic compounds, and for compounds with amino groups, double bonds, sulphide groups. Protein (amino) groups react with ozone very slowly.
The decay of ozone in OH-radicals in waters depends on temperature, pH, water composition. Around pH 6-8,5 at 20°C its half life is about 20 min. Basic media favourite the decomposition of ozone in OH radicals and superoxide anion.
Industry holds several patents on environmentally improved methods of bleaching pulp with ozone. Among these patents are US Patent #5,164,043, US Patent #5,520,783, US Patent #5,174,861, and US Patent #5,451,296. Ozone is such a powerful oxidizing agent that in pulp bleaching processes, it not only bleaches the lignin portion of the pulp, but also degrades the cellulose in the pulp (8). Wood is made up of two main components, a cellulosic portion and lignin (8). The lignin portion of wood is ideally destroyed in pulp bleaching processes, but the cellulosic portion of wood gives pulp its strength, and therefore should not be attacked by the bleaching agent (9). In order to prevent the problem of ozone attacking the cellulosic portion of pulp, the processes outlined in some patents involve using ozone as a third step in the bleaching treatment under selectively defined and carefully controlled parameters (pH control, use of chelating agents for metal ion control, pulp consistency) so that the ozone minimally degrades the cellulosic portion of the pulp (8).
Because of its relatively short half-life, ozone is always generated on-site by an ozone generator.
Although many methods exist for producing ozone, there are three main categories of methods of ozone production:
-corona discharge methods utilizing:
2020-12-22 09:56 Научный