Heavy oil and vacuum residue were used to obtain road bitumen 50/70 using two different methods of steam distillation at 323–362 °C and by oxidation, a method using packed column at temperature of 211–220 °C. The obtained residues using two methods steam distillation and oxidation are known as non-oxidized bitumen and oxidized bitumen, respectively. The products were evaluated using different standards including GOST 33133-2014, GOST 22245-90, and ASTM D5. The results showed that the yield of oxidized bitumen reached a maximal rate of 89.59% wt., while that of non-oxidized bitumen is 55% wt. The softening point of oxidized bitumen is 49–57 °C compared to non-oxidized bitumen (46–49 °C). Remarkably, the previous softening point and penetrability of 47–71 points of oxidized bitumen are consistent with norms to 50/70 bitumen, according standard. The non-oxidized bitumen has a relatively low softening point and a higher penetration value of 71–275, which refers to 200/300 bitumen. Comparatively, the use of a packed column is beneficial than the steam distillation, due to high capability of the nozzles to strengthens contact between feedstock and compressed air in the reaction zone and decreases the reaction time to 4.15 h.
Daily needs, due to the worldwide economic growth, increase road transport activities destroying the roads1. However, the necessity to improve the building and reconstructing of new roads became the main challenge of bitumen producers. Given the gradual disappearance of conventional oil added to that, the petroleum industries are faced with a major challenge which is to develop new but less expensive techniques that facilitate bitumen production in order to remedy road infrastructure problems.
Nowadays, unconventional hydrocarbons sources such as heavy oil, natural bitumen, shale oil were discovered in many countries as Canada, Venezuela, Brasilia, Russia, Chad, and Madagascar. The discovery of these resources will promote the growth of production in order to balance the energy deficit and that of bitumen in the world market By definition, heavy oil and natural bitumen are characterized by high viscosity and low API density with a very low concentration of volatile distillate fractions, such as gasoil and kerosene, as well as high amount of resins and asphaltenes.
Generally, the road bitumen is essentially assessed by the technology of production, the relative concentration of resins, and asphaltene. The respective components in the road bitumen play a particular role giving a synergistic performance to the bitumen. Asphaltene is the heaviest and responsible components for a non-newtonian character of bitumen, and they have a direct influence on the softening point and the rigidity of the bitumen. The resins promote good adhesion of bitumen to the surface of the minerals and of ductility (elasticity). Saturates and aromatics are responsible for the rheological property of the bitumen, such as viscosity.
To meet the challenges associated with the demands and requirements of the quality of road bitumen on the market, the development of new efficient techniques is necessary. Among the methods already known are vacuum distillation of oil, air oxidation, a compound of heavy residues after vacuum distillation, selective extraction, and the residue from the tar deasphalting process. Several series of works on the production of road bitumen have been carried out to obtain a better quality of bitumen adaptable to practical requirements as well as to point out the mechanism of the reactions which can occur during the oxidation of the vacuum residue and the upgrading of heavy oil. Abdullin et al. studied the thermal-oxidative stability of petroleum bitumen using «over-oxidation» from 240 to 260 °C with the oxidation time from 4 to 8 h. They reported that the softening temperature increased from 30.5–36 °C as a function of the oxidation time. The properties such as viscosity-temperature and the ductility at 0 °C have decreased. Hilde Soenen et al. experimented the oxidation process of two different residues from the visbreaking process and cracking process using the laboratory air-blowing vessel at 260 °C, and airflow of 1 l/min, under atmospheric pressure. They concluded the needle penetration of bitumen is 187–190 points and the softening point 36.9 °C and 39.2 °C according to EN 1426 and EN 1427. Chaala et al. carried out vacuum pyrolysis of automobile shredder residues using the pyrolytic oil as a modifier for road bitumen, and they indicated that the needle penetration of bitumens is 113 and 204, the softening point was 45 °C and 45.8 °C and Fraass point were − 7 °C and − 8.5 °C. They also concluded that, mixing the vacuum bitumen and the pyrolytic residue can decrease the penetrability and increase the softening point due to the compositional change of bitumen then these bitumen can behave as non-Newtonian fluids with high viscosity. On the side of non-oxidized bitumens, few works and literature were presented, except Chaale et al. according to its physicochemical and rheological analyzes of residue from vacuum pyrolysis, they declared that the pyrolytic residue is considered to be petroleum bitumen.
In the above mentioned studies, authors proposed different methods of producing road bitumen taking into account all parameters such as temperature, airflow, pressure, time, and raw materials except to improve equipment performances including column and accessory, to reduce the cost of production. Secondly, no comparison was done on the obtained products by different methods in the mentioned works. However, this work focuses on using a specially packed oxidation column to increase the contact surface between the feedstock and the injected compressed air to reduce the production cost, followed by comparison of the oxidized with non-oxidized bitumen obtained by the steam distillation. For evaluation the performance of obtained products various method such as penetration of the needle into the bitumen to determine the mark and rigidity of the bitumen by the penetrometer are essential. In addition, the softening temperature measured by the ball and ring method to determine the maximum bitumen operating temperature, ductility is determined by a ductilometer set at 0 °C, brittleness temperature is obtained by the Fraass method the rheological measurements (viscosity and adhesion capability of bitumen) as well as determining the composition of the bitumen by SARA (saturates, aromatics, resins, and asphaltenes) analysis.
Results and discussions
Steam distillation process (production of non-oxidized bitumen)
Tables 1 and 2 show the results of the obtained products after steam distillation of heavy oil. The results reveal that the increase of temperature of the bottom (302–340 °C ± 2 °C) and top (150–201 °C ± 1 °C) of the column decreases the yield of bitumen from 55% ± 0.3 to 47% ± 0.2 respectively. On the other hand, this rise in temperatures decreases the penetration of bitumen from 275 to 71 units. A decrease in bitumen yield occurred due to reactions as evaporation and condensation of high molecular components (resins and asphaltenes). The yield of bitumen and its properties are mostly promoted by the bottom temperature of the column and determined by the temperature of the superheated water steam. Remarkably, when the temperature at the bottom part of the column is around 300 °C, the bottom collected product (non-oxidized bitumen) seems to be as viscous plastic whiles with an increasing temperature to 340 °C and more, the non-oxidized bitumen residue presents a low penetration until 71 units. Thus, varying the bottom temperature of the column helps obtain the required bitumen residue with different penetration. Therefore, it should be mentioned that the expected bitumen properties depend mostly on the temperature of the bottom part of column, preferably above 300 °C. The temperature remains a key factor for the process of steam distillation of heavy oil for the production of the non-oxidized bitumen. Parallelly, the light hydrocarbons (synthetic oils) are the resulting condensation of the steam of light hydrocarbons; they have been obtained by the side of the column. The result showed that the yield of the light synthetic oil I increased in samples 1 and 2 from 34 to 37% and decreased to 23% in sample 3. The synthetic oil II exponentially increased from 11 to 14% and up to 30% respectively in samples 1, 2, and 3, with an increase in temperature. This explains why the rate of light fractions in the heavy oil is less than the middle fractions. The top temperature of the column allows controlling the amount of the top products while the bottom temperature of the column ensures the control of the amount and quality of the non-oxidized bitumen.