|Title of Invention||
"AN IMPROVED PROCESS FOR THE PREPARATION OF PAVING GRADE BITUMENS FROM WAXY CRUDES."
|Abstract||An improved process for the preparation of paving grade bitumen from waxy crude which comprises blending 10-35% Bombay High Short Residue (BHSR) with middle east region short residue, heating the said blend to 100 - 300°C passing air at the rate of 3 to 6 lit / min / kg for 1-5 hrs in presence of 0.2 to 0.5 [wt.%] FeCl3 as catalyst and recovering the bitumen by any conventional methods.|
|Full Text||This invention relates to an improved process for the preparation of paving grade bitumens from waxy crudes. The objective of the present invention was to assess/evaluate feasibility of blending Bombay High short residue (major Indian offshore crude) in short/vacuum residues of crudes of middle east origin to upgrade with BHSR into quality paving grade bitumens.
Bitumen/Asphalt is a natural constituent of crude oils. This product is of considerable importance since it is widely used in the construction of roads, highways, air fields and several other industrial applications. Bitumens are very complex in their composition and are required to have the right balance in chemical constituents especially with reference to waxes and asphaltene that ensure good service performance.
Bitumens are conventionally derived from asphaltic/naphthenic crudes having a characterization factor (KUOP) of around 11 with economical yields of short residues, sufficient viscosity, low wax content and suitable concentration of asphaltenes. Bitumen production in our country is primarily based on middle-east crudes which usually have a right balance to bitumen constituents i.e. asphaltenes and maltenes. In general bitumen obtained from such crude sources have good balance of rheological and physical properties at low and higher service temperatures. Indian crudes are not acceptable to yield quality bitumen because they are rich in saturates and are considerably low in other hydrocarbon types, particularly the polar aromatics and asphaltenes, both of which have a significant role in imparting acceptable bitumen properties to the residues/feed stocks. This is particularly so in respect of penetration, softening point, ductility and viscosity.
In the bitumen blowing process aromatic compounds present in the feed stock are oxidized with air under controlled conditions to produce hydrocarbons of higher molecular weight (of which those soluble in toluene and insoluble in n-heptane are called asphaltenes), with the simultaneous of water vapour. The main effect of this reaction is that it increase the viscosity of the" blown product. For a given viscosity increase, however, the asphaltene content increases much more rapidly during air blowing than
would be the case if the feed stocks were vacuum distilled, hence the air blown product has different rheological properties. An air blown product is characterized by having a higher softening point than a bitumen of similar penetration value obtained from the same crude source by vacuum reduction. The air blowing thus correct the deficiencies of certain crudes which have low asphaltene contents and can produce paving bitumens suitable for use on the road and or in industrial application. The aim of air blowing process is to generate asphaltenes. This phenomena is characterized by three basic reactions namely : reactions leading to size increase of the molecules through the process of oxygen linkage, formation of cyclic hydrocarbons by means of dehydrogenation and reaction during which the size of the molecules decrease due to dealkylation of side chains. The net effect of all the above reaction is change in colloid-chemical constitution and rheological properties of the bitumen. This is achieved by addition of external agents (catalysts) in air blowing step of bitumen making. Catalyst accelerate the air blowing reactions (reduction in the time cycle), and would produce bitumen of greater flexibility at low temperatures and increased resistance to flow at high temperatures.
The optimum air blowing temperature recommended in these investigation is 250°C. At this temperature the air blowing duration (oxidation time) is relatively short and the bitumen formed is of good quality. The air blowing of cracked residue requires increased temperature of the order of 300°C. This has no adverse effect on bitumen quality and at the same time it raises the oxidation rate considerably.
Historically Ditman's Publication  is perhaps the first to report the attempts on making of bitumen from the waxy crudes of North Africa. Philips Petroleum Refinery at Wood Cross Utah, near Salt Lake City, USA, has such plant for making bitumen from waxy crudes. The available information indicates propane deasphalting is the basic process that is employed for the purpose of lowering the wax content in the asphaltics thereby upgrading its quality to give satisfactory bitumen in subsequent processing depending upon the availability of various fluxing streams in a refinery. IIP [Bahl, J.S.. 1993; Bahl, J.S., 1984; Bahl, J.S., 1983] with this information in view, worked in close
collaboration with Assam Oil Division, Digboi to develop a suitable processing scheme
involving streams available in that refinery which on further processing, blending and air blowing yielded acceptable grade of paving bitumens. Literature [Joe, W., 1988; Eisenmann, J., 1992, Williamson, S.D., 1990] indicates that effect of wax can be reduced by the addition of certain polymeric materials such as styrene-butadiene-styrene (SBS), ethyl vinyl acetate (EVA) etc. Polymer modified bitumen indicated increase in cohesion, adhesion, elastic recovery and decrease in temperature susceptibility. Wax content can also be reduced by the Paratox Process . In this process waxy material is preferentially oxidized to some other products during air blowing operation by the use of some oxidizing catalyst such as FeCl3, P2O5 etc..
With a view to assess the effect of blending waxy crude Bombay High Short Residue (BHSR) and middle-east short residues on its properties and to determine the acceptable safe percentage of BHSR, blends with increasing percentage of BHSR were prepared. The percentage of BHSR in all feeds were varied from 10-35% because beyond that blend does not meet the physico-chemical characteristics. All feeds so prepared were oxidized at different temperatures and for different duration to quantify the influence of these key operating variables on the bitumen characteristics. Thus the present invention presents a systematic kinetic data and the best mode for the bitumen air blowing process. Several other scientific investigations [Chalton, H.M., 1959] have been concerned with the process conditions for oxidized bitumens. The effect of mechanical agitation in reducing the oxidation time has been studied by Rescorla et al. . Oxidation rate is affected by the degree of dispersion air in the bitumen mass, operating temperature and by the use of various catalyst like FeCl3, P2O5 and mono, di- or hexafluoro phospheric acid [Murayama, K., 1960]
In view of complex reactions involved in bitumen air blowing process all what can be done in kinetic study to choose a representative characteristics indicating conversion level and describe the kinetic behaviour by a suitable model. Actually the
batch air blowing of bitumen, as it commercially practiced, is a semi batch reaction, air being continuously blown while charging batch, as defined by Smith .
The most of the work reported in literature has been carried out on the basis of changes in physical properties of bitumen during blowing. Lockwood  stated that the rate of reaction could be expressed by first order reaction with respect to change in softening point. So far no study has been reported to assess the effect of bitumen composition on end product characteristics. This is important as the relative proportion of these components rather dictates the performance of bitumen under specific conditions.
In the present invention studies have been conducted to quantitatively compare the air blowing process for bitumen oxidation (neat feeds, blends and catalytic bitumen). Effect of temperature and catalysts were quantified on oxidation rate and properties of the bitumen. Apparent activation energies (EJ for first order rate constants for neat feeds, blends and bitumens, both with and without catalyst (Iron based) were deduced. Data has been used to develop a detailed kinetic model for simulating the bitumen blowing process and generate basic design data. Kinetic parameters of the model used to describe the process are presented quantifying the effect of catalyst in accelerating the air blowing reaction. Different mechanism of oxidation has been investigated by the compositional analysis and correlations were developed between physico-chemical properties and compositional parameters.
As such problem of making bitumen from indigenous wax bearing crudes assumes considerable importance in the present context. It is desirable to diversify the production of bitumen from different crudes from the exigency consideration view point and national security reasons. The objective of the present invention is to develop a process for preparation of bitumen of pavement grade by blending waxy short residues in residues of middle-east origin in predetermined proportion upto which they can be added in the blend without suffering loss any of the required bitumen properties.
Study of the chemical compositional changes, i.e. mixing of BHSR with middle east origin residues explains thanhe reactions particularly dehydrogenation of naphthenic aromatic proceed only upto formation of polar aromatics which possibly do not undergo further dehydrogenation and conversion to asphaltenes, due to which there is low built up of asphaltenes, during air blowing process. .
The kinetic studies based on the change in the composition of the bitumen components revealed that the conversion of oils to asphaltenes took place with formation of resins as an intermediate step. The rate constants using saturate component in correlation had low value, it is due to the oily nature of the saturates. The rate equation were characterized by low-frequency factors, thus indicating the occurrence of chain mechanism involving free radicals.
1. It is found that it is feasible to blend 10% and 15% BHSR in middle-east region short
residues. The composite feeds on processing under normal operating conditions are
capable to yield both 80/100 and 60/70 grade bitumen both, with and without catalyst,
meeting all the required specifications.
2. An increase in temperature results in a product more susceptible to temperature and
rise in temperature also reduced the time required to produce bitumen of desired
properties significantly. The temperature of oxidation effects the type of oxygen
containing compounds formed during the air blowing of bitumen. Possible
differences in such chemical reactions accounts for the variation in properties of
3. The use of FeCl3 catalyst (0.5 wt %) enabled the reaction time to be reduced nearly
1/3 and increases rate constant nearly 3 to 4 times for bringing about same changes, in
composition, softening point and penetration of the bitumen. Precised rate equations
for compositional changes, including effect of temperature (250, 265, 280°C) and
catalysts were developed.
4. The correlations developed reveal that key physico-chemical properties can be
described by bitumen composition which significantly contribute to the performance
of bitumen. By controlling the composition of bitumen we can approach to high
5. The developed correlations for bitumen key properties with composition can be
exploited to engineer the proper composition if possible to achieve desired properties.
6. Catalyst response on air blowing process has been quantified as a function of feed
Process of the present invention comprises of the following steps :
On grade bitumens were obtained by air blowing process of 10% and 15% blends of Bombay high short residue, in admixture with both with middle-east short residues and without the use of catalyst at three different temperatures namely, 250, 265 and 280°C.
In brief, the blends/feeds to be air blown (around 1.0 kg/batch) were charged and melted to the reaction kettle (Laboratory air blowing set-up). Controlled heating of the blends/ feeds was commenced with the heating rate of ~2°C/min when the blends/feeds temperature reached about 120°C, air was switched on and the rate gradually controlled to 6 lit/min/kg. In the case of experiments involving catalyst » 50-60 ml of aqueous solution containing 0.5% FeCl3 was added at this stage to the blends/feeds about 20-25°C prior to the actual air blowing temperature of 250 to 280°C reached. The mass was then allowed to attain the air blowing temperatures (250, to 280°C). The final air blowing temperatures were maintained within +2°C by controlling the energy input to the reaction kettle. Air blowing of the feed under derived operating conditions was continued upto maximum 5 hrs. Probe samples were withdrawn after definite time intervals to assess the progress of oxidation by measuring penetration and softening point of the samples. Complete product was withdrawn at the end of the blowing duration by the use of gate valve provided at the bottom of reactor.
Using our developed oxidation kinetics model a first-order kinetic analysis describe the behaviour of the air blowing reaction. This type of kinetic analysis provides acceptable correlations for plant design and control of operations. The use of FeCl3 catalyst enabled the reaction time to be reduced nearly by one-thirds due to increase in rate constant nearly three to four times for brining about some changes, in composition, softening point, and penetration of the bitumen.
Bitumens are usually obtained by suitable air blowing process at temperatures ranging between 250 to 300°C, the severity of air blowing depends upon the quality of the end product desired.
Accordingly the present invention provides an improved process for the
preparation of hgaving grade bitumens from waxy crudes which comprises blending 10-35%
Bombay High Short Residue (BHSR) with middle east region short residue heating the
said blend to 100-300°C passing air at the rate of 3 to 6 lit/min/kg for 1 to 5 hrs optionally
in presence of 0.2 to 0.5 [wt%] FeCl3 as catalyst and recovering bitumen by any conventional method.
An embodiment of the present invention 10 to 15% o BHSR may be mixed with middle east origin residue selected from Iran mix, Arab mix, Dubai mix.
Another embodiment of the invention the FeCl3 used ranges from 0.2 to 0.5 (wt%).
Still another embodiment is that the mix residue is heated at the rate of 3 to 6 lit/kg to the temperature ranging from 100 to 300°C prior to blowing the air.
Air may be blown at 3 to 6 lit/min/kg for 1 to 5 hours at 100 to 300°C.
The following examples are given as an illustration. However, this should not construed to limit the scope of the invention.
1. It is feasible to blend 10% and 15% BHSR in middle-east origin short residues. The composite feeds on processing under normal operating conditions are capable to yield both 80/100 and 60/70- grade bitumen both, with and without catalyst, meeting all the required specifications.
Feed taken = 1.0/batch
Yield = 99.9-100%
Reaction velocity constants (Rate constants) of different feeds at different temperatures
R2= Regression constant, K = Reaction velocity constant
Reaction velocity constant (K) of different blends in presence of 0.5 wt % FeCl3 catlayst at different temperatures
2. A first order kinetic analysis describe the behaviour of the air blowing reaction. This
type of kinetic analysis provides acceptable correlation for plant design and control of
3. The use of catalyst enabled the reaction time to be reduced nearly 1/3 and increases
rate constants nearly 3 to 4 time without affecting the properties of final product.
. Yield = 99.9-100%
5. The key physico-chemical properties of bitumen can be well correlated with bitumen composition which significantly contribute to the performance of bitumen. By controlling the composition of bitumen we can approach to desired performance characteristics of bitumen.
1. An improved process for the preparation of paving grade bitumen from waxy
crude which comprises blending 10-35% Bombay High Short Residue (BHSR)
with middle east region short residue, heating the said blend to 100 - 300°C
passing air at the rate of 3 to 6 lit / min / kg for 1-5 hrs in presence of 0.2 to 0.5
[wt.%] FeCl3 as catalyst and recovering the bitumen by any conventional
2. An improved process as claimed in claim 1, wherein 10-15% of BHSR is blended
with Middle East region residue selected from Iran mix, Arab mix and Dubai mix.
3. An improved process as claimed in any preceding claims, wherein the blend is
heated at the rate of 3 to 6 lit/min/kg to 250-280°C prior to blowing of air.
4. An improved process as claimed in any preceding claims, wherein air is blown at
6/lit/kg for 1 to 5 hrs.
5. An improved process for the preparation of paving grade bitumen from waxy
crude substantially as herein described with reference to the examples.
|Indian Patent Application Number||1118/DEL/1998|
|PG Journal Number||12/2008|
|Date of Filing||27-Apr-1998|
|Name of Patentee||COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH|
|Applicant Address||RAFI MARG, NEW DELHI-110001, INDIA.|
|PCT International Classification Number||C10C 3/00|
|PCT International Application Number||N/A|
|PCT International Filing date|