Title of Invention

AN IMPROVED PROCESS FOR THE MANUFACTURE OF PAVING BITUMEN.

Abstract

The present invention relates to an improved process for the manufacture of paving bitumen.This invention more specifically relates to bituminous binder used as road paving/construction material. This material provides flexibility and stability to the pavement in the long run. The process is capable of producing paving grade bitumen having improved penetration index value indicating that the product has better rheology/consistency i.e. increased resistance to temperature based deformation/failures. This feedstock on air-blowing in a conventional air-bowling reactor at a temperature ranging between 220-300°C, an air rate of 3-10 lits/min/kg with and without the use of catalyst gave a product having improved characteristics.

Full Text

The present invention relates to an improved process for the manufacture of paving bitumen. This invention more specifically relates to bituminous binder used as road paving/construction material. This material provides flexibility and stability to the pavement in the long run. The invention is very useful for developing paving bitumen of improved quality. The improved quality bitumen is characterized by higher load bearing capacity, increased trouble free service life span and behaves like a softer grade at lower temperature and harder grade at elevated ambient temperature. Improved quality bitumen are most suitable for constructing roads/highways, super highways, speed-corridors to provide smooth driving for any type of vehicle in any season and at any time. All the above applications of binder have to meet basically higher viscosity, higher Marshall Stability values, lower Fraass Breaking Point and higher Penetration Index value (Penetration Index, an empirical value based on penetration and softening point). In the production of high performance bitumen stringent control of penetration index values is to be ensured. Reference may be made to J. Ph. Pfeiffer and P.M. van Doormaal, Journal of Institute of Petroleum Technologists, Vol. 22, p 414, 1936, wherein PI value controls the consistency/rheology of bitumen with variation in ambient temperature and moreover, bitumen associated with low PI values are more susceptible to brittleness of pavement particularly at lower road temperatures. In the prior art it is known that the bitumen is produced by way of air-blowing the petroleum residues with and without the use of catalyst. References may be made to (i) Hoiberg A. J., Proceedings of Association of Asphalt Paving Technologists, 19, 225, 1950. (ii) Stratford R. K. Canadian Patent, 343, 1934, 216, (iii) Allen H. L, US Patent 1935, 466, (iv) Kasten M. L., Ind. Eng. Chem. 40, 548-57, 1948 wherein the bitumen is produced using conventional feedstock, available from indigenous/imported crude, through air blowing operation, with and without the use of catalyst. The bituminous binders thus obtained have poor performance characteristics and reduced life span due to low PI value (range -2.0 to -1.0), low viscosity, high asphaltene content and is associated with high temperature susceptibility. References may be made to Bats F Th de, and Gooswilligen G. Van "Practical Rheological Characterization of Paving Grade Bitumen", Proceedings of Eurobitume 1989,1, 56 wherein the bituminous binders associated with higher temperature susceptibility have reduced life span and ultimately leads to rutting of pavement. Various compounds exhibit catalytic effect in air-blowing operation when present in few percent or less. Recovery of these compounds is not possible since these compounds take part in chemical reactions during air-blowing operation. The use of catalyst produce bitumen of improved characteristics by way of altering the penetration-softening point relationship. Reference may be made to Murayama K., Fukuda Y., and Mamamura W., Japanese Patent 6961, June 1960, wherein the so called catalyst, mostly the compounds of phosphorous e.g., phosphorous sulfide, phosphorous sesqui sulfide, phosphorous penta sulfide, phosphoric acid, phosphorous penta oxide and elemental sulfur have been reported to be used, wherein the use of catalyst has further improved the properties of bitumen. References may be made to Hoiberg A.J., Lion Oil Co., US Patent 2,450, 756, Oct 4, 1948 wherein Phosphorous penta oxide is a very good catalyst but requires special protection during handling as well as is corrosive in nature. Other phosphorous base catalysts have got problem of handling also besides environmental constraints. Elemental sulfur cannot be used due to considerable release of obnoxious smelling sulfur dioxide during bitumen manufacturing process. The required performance of bitumen has a significant bearing on the feedstock composition and processing conditions. The feedstock composition is determined in terms of components like saturate, naphthene aromatic, polar aromatic and asphaltene as per Corbett method (ASTM D 4124-84). References may be made to (i) M. Downes, Shell UK and G. Van Gooswilligen, Shell Research BV, "Future paving bitumen quality requirements", SHRP 1990 United States, (ii) F. Th. De Bats and G. Van Gooswilligen, "Practical rheological characterization of paving bitumen", 4th Eurobitume Symposium, Madrid 1989, wherein the correct balance of all the four components ensure optimum rheological behavior throughout the application range, service temperatures and loading times. Improved quality bitumen need to meet requirement of increased viscosity and Fraass breaking point. Reference may be made to C.P. Valkering, DJL Lancon, E. deHilster and DA Stoker proceedings of American Association of Petroleum Technologists, vol. 59, 1990, p 590-609, wherein the increased viscosity and lower values of Fraass breaking point indicate higher flexibility of binder and resist rutting of pavement. Considering the limitations of hitherto known processes, which produces poor quality bituminous binders and the importance/suitability of improved quality binders for heavily trafficked roads, present invention can meet the challenges. This invention is helpful to over come the problems in hitherto known processes by making use of better starting feedstock (in terms of balanced chemical composition), operating condition which ultimately lead to the development of a product having improved performance characteristics. To over come the above mentioned problems of producing improved quality bituminous binders, present invention involves the use of better quality feedstock i.e. more balanced feedstock in terms of composition and air blowing operation in presence of ferric chloride as a catalyst. The use of ferric chloride as catalyst in air blowing operation does not pose any problem of safety, handling, environmental constraints, corrosion and has further shown improvement in the above mentioned performance characteristics. One of the objectives of this process is to develop paving bitumen of improved characteristics using available feedstock and air blowing along with use of ferric chloride as catalyst. The main objective of this process is to develop paving bitumen of improved quality by way of using a feedstock of balanced chemical composition, which obviates the drawbacks observed in the use of convention paving bitumen. The use of Ferric Chloride (FeCb) as a catalyst has further improved the desired characteristics. This process leads to the development of a bitumen of superior quality than the conventional bitumen. This improved product has required characteristics like higher viscosity, better PI values but with very less amount of asphaltene content. The reduced temperature Susceptibility increased load-bearing capacity and increased resistance to deformation is reflected in the resulting bituminous binder obviously due to higher stiffness at high service temperature as compared to conventional binders. The catalyst used is also a cheap material and easily available. Accordingly the present invention provides an improved process for the manufacture of paving bitumen which comprises; heating feedstock comprising short residue having boiling point 490°C+ containing saturates 15 to 25% wt, naphthene aromatics 35 to 40% wt, polar aromatics 40 to 45% wt as herein described and asphaltenes 0 to 1% wt at a temperature in the range of 220 to 300°C, blowing compressed air at the rate 3 to 10 lit/min/kg through the said feedstock, optionally in presence of FeCl3 catalyst in the range of 0.1 to 0.2 wt% to get paving bitumen. In an embodiment of the present invention the process is capable of producing paving grade bitumen having improved penetration index clue indicating that the product has better rheology/consistency i.e. increased resistance to temperature based deformation/failures. This feedstock on air-blowing in a conventional air-bowling reactor at a temperature ranging between 220-300°C, an air rate of 3-10 lits/min/kg with and without the use of catalyst gave a product having improved characteristics in terms of viscosity at 135°C (510 to 925 cSt), penetration index (-0.14 to +0.65), Marshall Stability (800-lOOOKg), Fraass Breaking point (-6.0 to 8.5°C), retained penetration after RTFOT (77 to 89%) and penetration ratio (42 to 51.5), the catalyst is FeCl3 dose level varies from 0.1 to 0.2% wt and air-blowing reactor requires minor modification that too in case of catalytic operation, the product of comparable grade but having improved characteristics is obtained in considerably less duration, the feedstock used is different in composition since having low asphaltene. In another embodiment of the present invention the product obtained has higher Marshall stability list values indicating that the pavement is cable of handling higher loads e.g. of commercial goods vehicles. In yet another embodiment of the present invention the product has higher kinematic viscosity indicating improved behavior of pavement at higher ambient temperatures. In still another embodiment of the present invention the product has lower values of Fraass breaking point indicating more flexibility of pavement at lower ambient temperatures thereby minimizing the brittleness of pavement/roads at lower ambient temperatures. In still another embodiment of the present invention the product has higher percentage of retained penetration after RTFO test indicating longer durability of pavement. The air blowing set basically comprises of three sections namely: compressed air drying, airflow metering and finally the air blowing. The laboratory air blowing set up consists of a 3-litre capacity, mild steel cylindrical reaction vessel, with an external heating arrangement. The design of air blowing assembly includes an arrangement for bubbling air into the feed and to provide thorough mixing and dispersion of air. The operating temperature is measured with the help of a thermocouple. An automatic pyrometer controller controls the energy input. The airflow is measured by a pre-calibrated manometer and continuously monitored by a wet gas meter. The probe samples can be taken out after different interval through a half inch gate wall provided at the bottom of the reaction vessel. The flux to be air blown (about 1.0 kg/batch) is melted and charged to the reaction kettle and controlled heating is started. When the feedstock attains the desired temperature, blowing of air is switched on and catalyst in the form of an aliquot is added with minimum amount of water. The flux is then allowed to attain the actual air-blowing temperature. Counting of air-blowing duration begins when flux temperature reaches to a required value, as at this temperature measurable oxidation of the flux commences. Air blowing temperature is maintained within ± 2 °C by controlling the energy input to the reaction system. The airflow rate is maintained through the manometer limb difference with a counter check by the reading of wet gas meter within 2-3%. Air blowing operation of flux is continued under defined conditions for fixed reaction duration. Probe samples are withdrawn at definite time intervals to assess the progress of oxidation, by measuring their penetration and softening point. The reaction products (non-condensable) along with the excess air are allowed to escape through a long slanting tube fixed at the outlet of the reactor vessel. Air rate adjustments are made after each withdrawal of probe sample. Complete product is drained out at the end of the reaction duration. Air blowing is a conversion process accompanied by dehydrogenation, oxidation and polymerization type reactions. During air blowing operation oxygen not only chemically combines with bitumen but dehydrogenate the molecules also. Most of the oxygen that reacts with the bitumen forms water vapors. Very small amount is bound in the form of esters, acids, ketones, aldehydes etc. The amount of oxygen in product increases with the increase in aromaticity of feedstock, extent of blowing operation and decreased blowing temperature. The incorporation of oxygen leads to the formation of oxygenates, the oxygenates particularly esters through intermolecular association with other polar species tend to form bigger structural units. This mechanism results in the formation of asphaltene and a change in the colloid-chemical constitution as well as Theological properties of bitumen. It is also stipulated that excessive structuring leads to brittle bituminous binder which tends to crack, while too little structuring leads to material, which deform under stress. Typical compositional changes that take place during air blowing operation is oil → resin→ asphaltene Considering the compositional fractions (based on ASTM D 4124-82) from bitumen analysis, some of the resins are converted to additional asphaltene and some oil part, principally more aromatic constituents, is converted into resins. The amount of resins remain more or less the same but a careful look at the resins fractions suggest that the H/C ratios of resin fraction in product are higher than those of resin in starting material. This suggests that new resins formed are similar in nature and properties to original one except more aliphatic (higher H/C ratios). The changed properties of oil, resin and asphaltene and the modified tendencies of these fractions produce elastic gel type colloidal structure with characteristic of air blown bitumen. The use of catalyst alters the penetration-softening point relationship i.e., for same penetration a product of higher softening point is obtained, besides there is a considerable reduction in air blowing duration. As mentioned above during air blowing operation the formation of oxygenates take place which on further intermolecular associations produced species of higher molecular weight. It appears that the use of FeCl3 as a catalyst during air blowing operation acts in two ways: • Helps in promoting saturate to take part in the reaction by way of dehydrogenating them. • Besides formation of oxygenates, there is an increased tendency of molecules to polymerize thus giving rise to bigger molecules having higher molecular weight. This aspect particularly changes the penetration-softening point relationship. And the product so obtained behave in a flexible manner at lower ambient temperature and more viscous at high temperatures. The following examples are given by way of illustrations and therefore should not be construed to limit the scope of the present invention. Example 1 Short residue (490°C+) with a yield of 51.5% wt is the starting feedstock.. This feedstock on air blowing at a temperature in the range of 220 to 300°C and an air rate in the range of 3 to 10 lit/min/kg without the use of catalyst gave a product having improved characteristics. Example 2 Short residue (490°C+) after air blowing operation at a temperature range of 225 to 300°C and air rate in the range of 3 to 10 lit/min/kg produced bitumen in 1.75 hours duration having penetration 92 (80-100 grade) and penetration index-0.14. Example 3 Short residue (490°C+) after air blowing operation on same conditions as in example 2 but after 3.0 hours duration produced bitumen of penetration 70 (60-70 grade) and penetration index + 0.5. Example 4 Short residue (490°C+) after air blowing on same conditions as in examples 1 to 3 but with the use of catalyst (dose level in the range of 0.1 to 0.2% wt) gave a product having further improved characteristics. Example 5 Short residue (490°C+) after air blowing as mentioned in example 4 but with catalyst produced bitumen in 1.60 hours duration having penetration 97 (80-100 grade) and penetration index 0.12. Example 6 Short residue (490°C +) after air blowing operation as in example 4 and 5 but with catalyst produced bitumen in 2.25 hours duration having penetration 65 (60-70 grade) and penetration index +0.65. The main advantages of the present invention are: 1. The process is capable of producing quality paving bitumen from a non-bituminous bearing feedstock. 2. Bitumen produced through this process possess high value of viscosity, PI, Fraass breaking point etc. besides meeting the BIS specification IS 73-1992. 3. The bitumen thus produced is most suitable for making high quality roads like highways/expressways etc. to provide smooth driving of any type of vehicle in extreme weather conditions. 4. This material can provide flexibility and increased stability to the pavement. 5. The catalyst used during the process is cheap and commercially available. We Claim: 1. An improved process for the manufacture of paving bitumen which comprises; heating feedstock comprising short residue having boiling point 490°C+ containing saturates 15 to 25% wt, naphthene aromatics 35 to 40% wt, polar aromatics 40 to 45% wt as herein described and asphaltenes 0 to 1% wt at a temperature in the range of 220 to 300°C, blowing compressed air at the rate 3 to 10 lit/min/kg through the said feedstock, optionally in presence of FeCl3 catalyst in the range of 0.1 to 0.2 wt% to get paving bitumen. 2. An improved process for the manufacture of paving bitumen substantialy as herein described with reference to the examples.

Documents:

240-del-2000-abstract.pdf

240-del-2000-claims.pdf

240-del-2000-correspondence-others.pdf

240-del-2000-correspondence-po.pdf

240-del-2000-description (complete).pdf

240-del-2000-form-1.pdf

240-del-2000-form-19.pdf

240-del-2000-form-2.pdf