Photo-degradation Effect on Naphtha Octane Number by Using UV Radiation

Abstract

In this work naphtha is exposed to ultraviolet rays under various conditions namely; UV exposure
only, UV exposure with cooling, UV exposure with cooling and catalyst, UV exposure with Cooling,
Catalyst and Oxidant O2 and UV exposure with Catalyst and Oxidant O2 to investigate the bonds
cracking process (Photo-degradation or photolysis reactions) and its effect on naphtha octane number
where several bonds are to be broken due to absorption the high energy of UV radiation. It is expected
that naphtha octane number should be changed as a result of the Photo-degradation effect. Samples are
prepared and treated with various conditions in a UV Reactor unit under prevailing pressure (elevated
pressure). No systematic change in octane number is noticed but the octane number is either decreases
or remains constant. Another technique which the cell unit is used. Samples are prepared and treated in
the cell unit under atmosphere pressure. Three different behaviors of the change in naphtha octane
number are resulted (decreasing, no change and increasing). Maximum decreasing in octane number is
(-11 unit) occurred when naphtha is exposed to UV rays with cooling & TiO2 catalyst in the cell unit ,
while the maximum increasing is (5.6 unit) occurred when naphtha is exposed to UV rays with ZnO
catalyst & (2.1 ml/min) O2 feeding in the cell unit. In order to understand this behavior Gas
chromatography Mass Spectrometry (GCMS) tests are conducted for some samples before and after
UV exposure to study the changes in chemical composition of naphtha specially the changes in
percentage of compounds that affect the octane number such as: Benzene, Toluene, Isooctane and Pxylene.
It is noticed that the percentages of these compounds increased in samples in some tests and
decreased in others. Also Fourier Transform Infrared spectroscopy (FTIR) tests are conducted for these
samples before and after exposure to find the eliminated or created chemical bonds or functional groups
of these bonds.