Last updated: June 22, 2019
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Several studies indicated that in presence of an excess of hydrogen peroxide, the oxidation of organic sulfur compounds follows pseudo first order kinetics in carboxylic acid/H2O2 and polyoxometalate/H2O2 systems (Te, et al. 2001; Collins, et al. 1997). In the experiments, conversion of sulfur compounds was calculated using their initial concentration (Co) and after t min reaction (Ci). Conversion X is expressed as Equation AAA:

A number of studies indicate that in presence of an excess amount of hydrogen peroxide, the oxidation of organic sulfur compounds follows pseudo first order kinetics in carboxylic acid/H2O2 and polyoxometalate/H2O2 systems (Te, et al. 2001; Collins, et al. 1997). In the experiments, conversion of sulfur compounds was calculated keeping in focus their initial concentration (Co) and after t min reaction (Ci). Conversion X is illustrated in Equation AAA:

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Assuming that the volume and mass of the reaction mixture were constant, only small amounts of liquid sample were withdrawn during the reaction. If BT and DBT oxidation follows pseudo first order reaction kinetic, then the rate constant and reaction time t can be described using the following equation (Eq. 4.4):

Keeping in practice the assumption that the volume and mass of the reaction mixture remained at a constant level, only small amounts of liquid sample were withdrawn during the reaction. If BT and DBT oxidation follows pseudo first order reaction kinetic, the rate constant and reaction time t can be described with the equation given below (Eq. 4.4):

(Eq. 4.4)

A plot of ln (Ct/C0) versus t should be linear, and the value of the apparent rate constant, k, can be obtained by the slope of the linear relationship.

A plot of ln (Ct/C0) in apposition to t should be linear; and the value of the apparent rate constant, k, can be obtained by the slope of the linear relationship.

In order to study the relative reactivity of organic sulfur compounds under modified UAOD process, the oxidation of representative sulfur compounds, namely T, 2MT, 2ET, BT, 2MBT, DBT and 46-DMDBT, each with sulfur concentration 500 ppm was carried out under protocol condition that discuss at previous section except using “Sulfur” free diesel instead of toluene.

For the purpose of studying the relative reactivity of organic sulfur compounds, under modified UAOD process, the oxidation of representative sulfur compounds, namely T, 2MT, 2ET, BT, 2MBT, DBT and 46-DMDBT, (each with sulfur concentration 500 ppm) was carried out under protocol condition (except using “Sulfur” free diesel instead of toluene) which is discussed in the last section of the paper.

The relationship between the sulfone conversions of model compounds and reaction time with modified UAOD process is showed as Figure 4.15. Since H2O2 was present in excess amount, the reaction data was fitted to a first-order rate equation. A plot of ln(Ct /C0) versus reaction time showed as Figure 4.16. The result displayed a linear relationship that confirmed the pseudo-first-order reaction kinetics. And summery of rate constant (k) is shown on table AVC.

In Figure 4.15 are given the illustrated explanation of the relationship between the sulfone conversions of model compounds and reaction time with modified UAOD process is. Due to the fact that H2O2 was present in abundant amount, the reaction data were adapted to fit to a first-order rate equation. Figure 4.16 illustrates a plot of ln(Ct /C0) versus reaction time. The result displayed a linear relationship that confirmed the pseudo-first-order reaction kinetics. Table AVC manifests the summery of rate constant (k).

Model Sulfur Compound
Rate Constant (min-1)
R2
T
0.0196
0.9972
2MT
0.0199
0.9954
2ET
0.0224
0.9984
BT
0.0276
0.9971
2MBT
0.0223
0.9970
DBT
0.0228
0.9970
46DMDBT
0.0231
0.9792
It is seen clearly that the oxidation reactivities of these organic sulfur compounds decrease in order of BT > 46-DMDBT > DBT > 2MBT > 2ET > 2MT > T. For example, after 200 minutes reaction, the conversion of BT react over 99% while the conversion of Ts are only reach average 97%. Overall, for all the sulfur compounds, under protocol condition, it can all reduce to below 15 ppm.

For the above illustration, it is clearly noticeable that the oxidation reactivities of these organic sulfur compounds decrease in the following order: BT > 46-DMDBT > DBT > 2MBT > 2ET > 2MT > T. For example, after 200 minutes of reaction process, the conversion of BT reacted over 99% while the conversion of the Ts climbed only to an average of 97%. Overall, for all the sulfur compounds, under protocol condition, it can all come to a reduced level which is below 15 ppm.