(Hive Bee)
10-05-03 05:58
No 462663
(Rated as: good read)
Here is another articel i picked up at the libraby and finally got around to posting. I think that someone might be able to figure something out from this articel like maybe a possible photo-production of amphetamine from acetic acid and phenalanine with a powdered semiconductor catalyst. Good luck to all those that try!
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J. Phys. Chem. 1984, 88, 2344-2350
Hetrogenous Photocatalytic Reactions of Organic Acids and Water. New Reaction Paths besides the Photo-Kolbe Reaction
Tadayoshi Sakata, * Tomojii Kawai, {dagger} and Kazuhito Hashimoto
...
The hetrogenous photocatalytic reactions of acetic, proponic, and butyric acids were studied on several kinds of powdered semiconductors, mainly TiO2. The influence of Ag+ as an electron acceptor, and the dependence of the reactions on the kind of semiconductor and pH, were investigated. ... At neutral or alkiline pH, hydrocarbon stops being evolved and only hydrogen is evolved. ...
Introduction
... Other photocatalytic reactions such as oxidation of cyanide, [3,4] sulfite, [4] aceate, [5] hydrocarbons, [6-9] and other substances [10] have been investigated. Recent studies from this laboratory have shown photocatalytic hydrogen production from the reactions of water with various organic compounds such as alcohols, [11, 12] carbohydrates, [13] hydrocarbons, ... with powdered semiconductor photocatalysts. IN these ractions, organic molecules are oxidized and water is reduced to produce hydrogen. In several caeses hydrogen production is very efficient [11, 12]. ... Recenbtly, Yoneyama et al. investigated the factors influencing product distrubition in the photocatalytic decoompositon of aqueous acetic acid on platinized TiO2 [24]. The found that the relative yield of ethane to methane produced was high when the decomposition rate was high and that the amount of CO2 produced exceeded that of the methyl radical comsumed in the formation formation of methane and ethane. They also found that the ratio of ethane to methane increased linearly with illumination intensity. IN these reactions organic acids are decomposed into hydrocarbons and CO2. Water was not thought to be involved in the main reactions. HOwever, we found that these reactions depend strongly on pH. IN alkaline medium organic acids produce only hydrogen. ...
...
Results and Discussion
Hydrogen and Hydrocarbon Production from Organic acids. Bard et al. investigated the photocatalytic reactions of organic acids with powdered TiO2/Pt [5, 17-22]. They confirmed the following reaction and called it the photo-Kolbe reaction:
RCOOH --> RH + CO2 (1)
ONe of the characteristic features of this reaction with powdered semiconductors si that RH is the main product and R-R, the dimer *R, is a byproduct [18]. This seems to be a result of the large surface area of the powdered semiconductor, which causes the surface concentration of *R to be so small that RH is formed more easily than R-R.
...
TABLE I: Production Rate of Hydrogen and Hydrocarbon by the Photocatalytic Decomposition of Organic acids [a]
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reactant pH H2 RH
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CH3COOH 1.4 160 156
C2H5COOH 1.6 154 1470
n-C3H7COOH 1.6 334 996
n-C4H9COOH 1.9 523 1018
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[a] 30 mL of a water-orgainc acid (6:1) mixture with 300 mg of TiO2 (rutile, doped)/Pt was irradiated with a 500-W Xe lamp.
TABLE II: Dependence of Hydrogen and Methane Production Rate on pH for the Photocatalytic Decomposotion of Acetic acid on Aqueous Medium [a]
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pH H2 CH4 H2/CH4
--------------Micromol/h--------------mi
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2.1 23 119 0.19
5.4 23 28 0.82
6.2 25 10 2.5
7.5 51 3.3 15
8.8 57 0.5 110
11.8 43 <0.08 >500
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[a] 30 mL of a water-acetic acid mixture (6:1 in volume) with 300 mg TiO2 (rutile, doped)/Pt was irradiated with a 1-kW Xe lamp (operated at 500-W. The pH of each solution, which was controlled by adding NaOH or H2SO4, hardly changed after each experimental run (1-h irradition).
...
As seen in this table, the hydrogen production rate is high and cannot be neglected even compared with the production rate of RH. This suggests that reactions other than reaction 1 are taking place. ... At pH 14, almost pure hydrogen is eveolved, and methane was hardly produced. Interestly, hydrogen is also evolved in pure acetic acid. Bard et al. propsed the follwoing reactions for acetic acid [5, 17-22]:
CH3COOH --> CH4 CO2 (2)
2 CH3COOH --> C2H6 + 2 CO2 + H2 (3)
The main reaction is reaction 2, and reaction 3 is a minor one. Actually ethana formation is minor compared with that of methane. For instance, C2H6/CH4 is 0.21 at pH 2.1. ...
Analysis of Reaction Products in Aqueous Medium in the Presence of Ag+. ... The Photocatalytic reactions were carried out by adding Ag+ (AgNO3) as a strong electron acceptor [25, 26]. In the Presence of Ag+, the reactions proceed very easily with TiO2 alone. Since electrons in the conduction band are consumed to reduce Ag+, hydrogen was not evolved under these conditions. ... For acetic acid, CO2 is produced by reaction 2 and the following reaction, which is a modification of reaction 3:
2 CH3COOH + 2 Ag+ --> C2H6 + 2 CO2 + 2 Ag + 2 H+ (4)
From reactions 2 and 4, the total quantity of CO2 is expected to be equal to the quantity of CH4 + 2 C2H6. HOwever, as is calcuated from the results in Table IV, the ratio of CO2 to CH4 + 2 C2H6 is 2.2 for the photocatalytic reaction of acetic acid. ... This result indicates the existence of other reactions in which water is involved. ... For instance, the formation of CH3OH from C3HCOOH... can be explained by the following reaction [29]:
*R + *OH --> ROH (5)
TABLE IV: Reaction Products of the Photocatalytic Reactions of Acetic... Acids in the Presence of Ag+ [a]
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run reactant pH of soln irradn time, gaseous products ...
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1 CH3COOH 2.0 21.8 CH4 491
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...
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[a] Aqueous solutions of each organic acid and AgNO3 (2 mL of organic acid and 1.0 g of AgNO3 in 30 mL of distilled water) with 300 mg of powdered TiO2 (rutile, undoped) were irradiated with a 500-W Xe lamp. ...
...
The production of C2H5COOH from CH3COOH would be explained by the following reactions:
*CH3 + CH3COOH --> CH4 + *CH2CH2COOH (17)
or
*OH + CH3COOH --> H2O + *CH2COOH (18)
*CH2COOH + *CH3 --> C2H5COOH (19)
...
Two Reaction Paths for Methane Formation. As is shown in Table IV, methane is produced even in the presence of Ag+. Since the concentration of hydrogen atoms would be negligibly small under these conditions, methane formation by combination of a hydrogen atom and a methyl radical would be unlikely. The photocatalytic decompostion of acetic acid in heavy water (CH3COOH:D2O = 1:20 in volume, pH 2.1) uin the presence of Ag+ showed that the main component of the produced methane does was not CH3D but CH4. The ratio of CH3D to CH4 was 1:13 [36]. This resulte demonstrates clearly that the hydrogen in methane does not come prodominantly from water, but from the methyl group in acetic acid by the hydrogen abstration reaction 17.
On the other hand, in the absence of a strong electron acceptor such as Ag+ or O2, the main reaction path for methane formation is thought to be the reaction of a methyl radical with a hydrogen atom produced on Pt [19]:
*H + *CH3 --> CH4 (26)
Actually, mainly CH3D is produced from CH3COOH in heavy water. The ratio of CH3 to CH4 was 14:1. This result shows that the main reaction path for methane formation is reation 28 in the absnce of a strong electron acceptor [36]. IN the absnce of Ag+, the ratio of C2H6 to CH4 is 0.1 - 0.2 with TiO2(r)/Pt, while the ratio is increased to 0.83 in the presence of Ag+ (See Table IV), indicating that C2H6 is formed comparably with CH4. This result suggests that the reaction rate of hydrogen abstration (eq. 17) is slower than that of reaction 26. ...
...
TABLE VII: Dependence of Phtocatalytic Reactions of Acetic Acid on the Kind of Semiconductor [a]
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gaseous products Products in aq. medium
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compd / amt, micromol compd / amt, micromol
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CH4 / 225-------------------------------------
C2H6 / 187-------------------------------------
CO2 / 1350
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CH4 / 62--------------------------------------
C2H6 / 133-------------------------------------
CO2 / 570
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CH4 / 73--------------------------------------
C2H6 / 96--------------------------------------
CO2 / 617
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CH4 / 33--------------------------------------
C2H6 / 47--------------------------------------
CO2 / 299
---------------------------------------F
CH4 / 2.7-------------------------------------
CO2 / 3.0
minor products: C2H5OH, (CH3)2CO, CH3COOCH3
[a] Aqueous solution of acetic acid (2.0 mL in 30 mL of distilled water) containing 1.0 g of AgNO3 with various kinds of semiconductors was irradiated fro 10 h with a 500-W Xe lamp. [b] TiO2 (a, u) = anatase, undoped.
...
PLEASE DO NOT ATTEMPT ANYTHING ILLEGAL! I HAVE NOT AND NOR SHOULD YOU!
