Petroleum Radiation Processing

289

4

Complex Radiation-

Thermal Treatment and

Radiation Ozonolysis of

Petroleum Feedstock

4.1 APPLICATION OF THE IONIZED AIR AND

OZONE-CONTAINING AIR MIXTURES FOR ENHANCED

THERMAL AND RADIATION-THERMAL CRACKING

Changes in the composition and properties of crude oils and oil fractions caused by

ozonolysis and decomposition of their primary conversion products due to subse-

quent thermal treatment are described in the works by Kamyanov et al. (1997). The

ability of ozone to selectively interact with saturated suldes, arene derivatives of

thiophene, pyrrole, and furan (with the exception of dibenzo-derivatives and poly-

cycloaromatic hydrocarbons) was used in the development of the methods for oil

distillate cleaning from sulfur and polyarene compounds.

The ozonides of oil polyarenes, as well as other organic peroxides, undergo

homolytic decomposition at temperatures above 110°C–120°C (Kamyanov et al.

1997). Sulfoxides formed as a result of interactions of oil suldes with ozone have

sill lower thermal resistance and decompose even at temperatures below 100°C. Both

ozonides and sulfoxides can play the role of initiators in radical chain reactions.

The initiating properties of these compounds can be used for the intensication of

thermo-destruction of the heavy components in crude oils and bitumen. In particular,

it provides increase in the yields of distillate fractions and reduction in the yields of

heavy residues in the distillation process.

For the maximal accumulation of ozonides and for preventing their decomposi-

tion, the ozonation process was carried out in the ow reactor at a short-time (less

than 3 min) contact of feedstock with the ozone-containing mixture. The temperature

in the reactor was kept at the level of 20°C when low-viscous West Siberian oils were

ozonized and was increased to 70°C–80°C in the case of high-viscous oils and bitu-

men treatment. In all the cases, the estimations were made for the amount of ozone

being rapidly (by electrophilic mechanism) bound with the feedstock components.

One of the test subjects was a commodity mixture of West Siberian crude oils

having a density of 0.865 g/cm

3

and containing 1.28 mass% sulfur, 11.5% pitches,

1.24% asphaltenes, and 6.6% parafns. Concentrations of the fractions boiling below

200°C, 350°C, and 490°C were 24.0, 54.0, and 77.8 mass%, respectively (Kamyanov

et al. 1997). Ozone consumption was 26 g/kg. The ozonized oil was subjected to

290 Petroleum Radiation Processing

thermolysis at the temperature of 350°C during 1 h. The changes in oil fractional

contents after ozonation and thermal processing are shown in Figure 4.1.

The analyses of the products treated indicated decomposition of big polyarene

nuclei with parallel decomposition of the sulfuric compounds and the presence of

10–16 mass% olens, the direct products of C–C bond breaks in the saturated frag-

ments of oil components in the distillates of ozonized and thermolized oil. Thus,

the thermolysis of ozonized oil was accompanied with intense initiated cracking at

temperatures lower by about 150°C than those of the conventional thermal cracking

(TC) at practically atmospheric pressure instead of 45–50 atm.

The effects of initiating thermo-destruction reactions of oil components by radi-

cals formed due to sulfoxide decomposition at relatively low temperatures become

more pronounced when ozonized oil is rich in sulfur compounds. This phenomenon

was studied on the example of the blended crude oil having a density of 0.9266 g-cm

3

at 20°C and viscosity of 384 cSt at 20°C and 34.4 cSt at 50°C (Kamyanov et al.

1997). Sulfur concentration in oil was 4.6 mass%. It contained 17.4 mass% pitches

and asphaltenes, 5.1 mass% solid parafns, 13.5 mass% gasoline fraction, and about

33% light fuel distillates.

The experiments have shown that this type of oil is capable of a rapid electrophilic

addition up to 58 g ozone per 1 kg of feedstock; however, the optimal ozone expense

in oil processing was about 12 g/kg. The ozonized oil was subjected to thermal

processing at the temperature of 350°C during 20–60 min. As a result of initiated

cracking of ozonized oil, the yield of the gasoline distillate SB-350°C increased by

2.6 mass%, the yield of diesel fraction 200°C–350°C increased by 8.2 mass%, and

the total yield of motor fuels increased by 10.8%.

The total increase in the yield of a wide distillate SB-400°C was 14.5 mass% and

79.14 mass% of fraction was distilled at the temperature of 480°C (by 20.2 mass%

0

10

20

30

40

50

<150°C 150°C–200°C 200°C–250°C 250°C–300°C300°C–350°C >350°C

Yield, mass%

1

2

3

Fractions

FIGURE 4.1 Distillation curves of West Siberian crude oil before and after ozonation.

1—Crude oil; 2—Ozonized oil; 3—Ozonized oil after thermal processing.