CLIAMS:1. A sulphur additive for the preparation of Sulphur Extended Asphalt, said sulphur additive comprising:
a. sulphur in an amount ranging from 80 to 98 wt% of the sulphur additive; and
b. at least one aluminosilicate in an amount ranging from 2 to 20 wt% of the sulphur additive.
2. The sulphur additive as claimed in claim 1, wherein said aluminosilicate has a highly ordered porous structure with pore size ranging between 4 to 8 Å.
3. The sulphur additive as claimed in claim 1, wherein said aluminosilicate comprises at least one metal ion in its framework selected from the group consisting of alkali metals, alkaline earth metals, rare earth metals and transition metals.
4. The sulphur additive as claimed in claim 1, molded into at least one solid shaped article selected from the group consisting of pastilles, flakes, extrudates and granules.
5. The sulphur additive as claimed in claim 1, wherein said metal ion is inherently present or introduced in the framework of the aluminosilicate.
6. The sulphur additive as claimed in claim 1, wherein the aluminosilicate is at least one selected from the group consisting of virgin aluminosilicate and the aluminosilicate previously used as catalyst.
7. The sulphur additive as claimed in claim 1, wherein said aluminosilicate is modified using at least one of the following processes:
a. treating an aluminosilicate with a metal salt solution containing commercially available adsorbent at ambient temperature for a time period in the range of 1 to 8 hours to obtain a mixture; filtering said mixture to obtain a residue; washing and drying said residue to obtain the modified aluminosilicate; and
b. treating an aluminosilicate contained in a spent catalyst with a caustic aqueous solution to a temperature in the range of 30 to 60 °C for a time period in the range of 10 to 40 hours or sonicating for a time period in the range of 10 to 120 minutes or heating with a caustic powder to a temperature in the range of 400 to 800 °C for a time period in the range of 1 to 4 hours to obtain a mixture; hydrothermally heating said mixture at temperature in the range of 70 to 100 °C under autogenic pressure for a time period in the range of 15 to 40 hours to obtain the modified aluminosilicate.
8. A process for the preparation of a sulphur additive comprising:
a. introducing sulphur in a reactor;
b. heating said sulphur in a reactor to a temperature in the range of 70 to 150 °C to form a molten sulphur;
c. mixing at least one aluminosilicate with said molten sulphur to obtain a slurry; and
d. cooling said slurry to obtain the sulphur additive.

9. The process as claimed in claim 8, wherein the ratio of the amount of said aluminosilicate and the amount of sulphur is in the range of 1: 4 to 1:15.
10. The process as claimed in claim 8, wherein said sulphur and said aluminosilicate are mixed together before introducing in the reactor.
11. A process for the preparation of sulphur extended asphalt using the sulphur additive as claimed in claim 1, wherein said process comprises the following steps:
a. introducing bitumen in a reactor;
b. heating said bitumen to obtain a heated bitumen; and
c. mixing said heated bitumen and said sulphur additive to obtain Sulphur Extended Asphalt.
12. The process as claimed in claim 11, wherein the mixing said heated bitumen and said sulphur additive to obtain sulphur extended asphalt is carried out at a temperature in the range of 110 to 190 °C, preferably 135 to 180 °C, under stirring with a speed of less than 100 rpm, preferably less than 70 rpm. ,TagSPECI:FIELD
The present disclosure relates to a sulphur additive for the preparation of Sulphur Extended Asphalt and a process for preparation thereof.
DEFINITIONS
As used in the present disclosure, the following words and phrases are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used to indicate otherwise.
Pore size: Pore size is defined as the longest dimension per pore.
OSHA (Occupational Safety and Health Administration) standards: OSHA determines the permissible level of H2S in the surrounding which is non-hazardous to human being. As per OSHA standards, H2S emission up to 20 ppm can be considered non-hazardous.
Multi-gas detector apparatus is used for the detection of H2S having detection sensitivity ranging between 1 ppm to 100 ppm (Resolution: 0.1 ppm).
Spent catalyst: A catalyst that has been used and as a result of contamination can no longer serve the purpose for which it was produced.
Highly Ordered Porous Structure: A porous material exhibiting well defined pores arranged in a defined pattern of pores of defined sizes.

BACKGROUND
Use of a viscosity grade bitumen for surface-dressing, spraying, construction and paving of roads is well known. Mixing sulphur with bitumen, to increase the mechanical strength, corrosion resistance, water resistance, Marshall Stability, fatigue, resilient modulus (RM) and the like is known in the art. The mixture of bitumen with sulphur is called as Sulphur Extended Asphalt (SEA). In the process of preparing sulphur extended asphalt or placing SEA on the road surface, H2S is released, which is harmful for human and animal life. OSHA has established a permissible exposure limit (PEL) for emission of H2S (8 hour time-weighted average (TWA) of 10 ppm and acceptable ceiling concentration of 20 ppm).
The preparation of SEA and its application in laying on roads is usually carried out at elevated temperature, wherein the H2S is generated in the amount that would be harmful to human life. The bitumen is melted at higher temperature for preparing a homogeneous mixture of SEA. Therefore, the temperature plays an important factor in the preparation and application of sulphur extended asphalt.
H2S is generated by the reaction of bitumen and sulphur at high temperature (more than 80 °C). Sulphur has condensing effect upon asphalt under heating conditions, resulting in the formation of gaseous hydrogen sulphide as per the reaction given below:
CxHy + S ? CxHy-2 + H2S (g) ?
The dissolved and entrained H2S within the sulphur itself and/or within bitumen is released on melting.
Following four methods are used to suppress H2S generation during the reaction of sulphur with bitumen:
1. By avoiding a H2 donor in asphalt that gives H2S when sulphur is mixed.
2. By adding an additive to sulphur to inhibit H2S evolution/liberation.
3. By adding an additive (metal oxides, and the like) to the sulphur and bitumen mixture to trap H2S from being released.
4. By facilitating reaction of H2S evolved during the process with olefins present in asphalt to arrest H2S emission.
In particular, the technologies used for the suppression of H2S emission during the preparation of sulphur extended asphalt involves using compositions selected from the group of tetraalkylthiuram disulphide, dithiocarbamates, amine compounds, iodine, copper salts, copper oxides, cobalt salts, iron salts and iron oxides. Other available technologies for the suppression of H2S emission include the use of biological sulphur produced by biological conversion of sulphur comprising compounds such as sulphides and/or H2S into elemental sulphur, addition of fillers (including mineral fillers) along with H2S suppressants to the bitumen and the addition of sulphur granules.
However, the known technologies have shown limited success in H2S suppression with increase in temperature during the preparation and application of sulphur extended asphalt. Therefore, there is a long felt need to develop an effective H2S suppressant composition to overcome the drawbacks associated with the prior art.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
An object of the present disclosure is to reduce the emission of hydrogen sulphide (H2S) during the preparation of Sulphur Extended Asphalt.
Another object of the present disclosure is to reduce the emission of hydrogen sulphide (H2S) during the application of Sulphur Extended Asphalt in road pavement.
Still another object of the present disclosure is to reduce the emission of hydrogen sulphide (H2S) during the preparation of Sulphur Extended Asphalt to a temperature greater than 80 ºC.
Yet another object of the present disclosure is to provide a sulphur additive, which on mixing with bitumen during the preparation and application of SEA, reduces the emission of hydrogen sulphide (H2S) to an acceptable safe level.
Still another object of the present disclosure is to provide a simple, economic and safe process for the preparation of a sulphur additive composition.
Yet another object of the present disclosure is to ameliorate one or more problems associated with the conventional methods or at least provide a useful alternative.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure provides a sulphur additive comprising sulphur in an amount ranging from 80 to 98 wt% and at least one aluminosilicate in an amount ranging from 2 to 20 wt% for the preparation of Sulphur Extended Asphalt.
The aluminosilicate is made up of highly ordered porous structure with pore size in the range of 4 to 8 Å.
The aluminosilicate of the present disclosure comprises at least one metal ion in its framework selected from the group consisting of alkali metals, alkaline earth metals, rare earth metals and transition metals.
The metal ion is inherently present or introduced in the framework of the aluminosilicate using known modification methods before adding to sulphur for the preparation of the sulphur additive.
Further, the present disclosure provides a process for the preparation of the sulphur additive and its subsequent use in the preparation of sulphur extended asphalt.
The process for the preparation of SEA comprises mixing of the sulphur additive and bitumen at a temperature in the range of 110 to 190 °C, preferably between 135 to 180 °C, under stirring with a speed of less than 100 rpm, preferably less than 70 rpm.
DETAILED DESCRIPTION
The inventors of the present disclosure envisage a sulphur additive for reducing the emission of H2S during the preparation and application of Sulphur Extended Asphalt (SEA). The sulphur additive of the present disclosure suppresses H2S emission up to an acceptable safe limit during the preparation and application of the SEA at an elevated temperature.
In accordance with one aspect of the present disclosure, there is provided a sulphur additive for the preparation of Sulphur Extended Asphalt, wherein the sulphur additive comprises:
• sulphur in an amount ranging from 80 to 98 wt% of the sulphur additive; and
• at least one aluminosilicate in an amount ranging from 2 to 20 wt% of the sulphur additive.
In accordance with the present disclosure, the aluminosilicate has a highly ordered porous structure with pore size ranging between 4 to 8 Å.
In accordance with one embodiment of the present disclosure, the aluminosilicate comprises at least one metal ion in its framework selected from the group consisting of alkali metals, alkaline earth metals, rare earth metals and transition metals.
The metal ion is inherently present or introduced in the framework of the aluminosilicate using known modification methods, before adding to sulphur for the preparation of the sulphur additive.
In accordance with another aspect of the present disclosure, there is provided a process for the preparation of a sulphur additive, wherein the process comprises the following steps:
In the first step, sulphur is introduced into a reactor.
In the second step, the sulphur is heated to form a molten sulphur.
In the third step, the aluminosilicate and the molten sulphur are mixed to obtain a slurry.
In the fourth step, the slurry is cooled to obtain the sulphur additive.
In accordance with one embodiment of the present disclosure, the sulphur introduced into the reactor is raw sulphur.
In accordance with one embodiment of the present disclosure, the sulphur is in molten form.
In accordance with another embodiment of the present disclosure, the sulphur is in solid form and is mixed with the aluminosilicate before heating to obtain a mixture and the mixture is heated to form a molten slurry.
The sulphur additive is molded into at least one solid shaped article selected from the group consisting of pastilles, flakes, extrudates and granules.
The molding unit is selected from the group consisting of, but is not limited to, a pastillation unit, an extruder unit, a nodulizer unit, a granulator and the like to obtain at least one solid shaped article of the sulphur additive.
The heating of sulphur to obtain the molten sulphur is carried out in the temperature range of 70 to 150 °C.
In accordance with one embodiment of the present disclosure, sulphur is heated to 150 °C to obtain molten sulphur.
The ratio of the amount of the aluminosilicate and the amount of sulphur is in the range of 1: 4 to 1:15.
In accordance with one embodiment of the present disclosure, the ratio of the amount of the aluminosilicate and the amount of sulphur is 1:12.
In accordance with still another aspect of the present disclosure, there is provided a process for the modification of an aluminosilicate. The aluminosilicate is modified using at least one of the following processes:
In accordance with one embodiment of the present disclosure, the modification of the aluminosilicate can be carried out by treating the aluminosilicate with a metal salt solution containing a commercially available adsorbents at ambient temperature for a time period in the range of 1 to 8 hours to obtain a mixture; the mixture is filtered to obtain a first residue; the first residue is washed and dried to obtain the modified aluminosilicate.
In accordance with one embodiment of the present disclosure, the modification of the aluminosilicate can be carried out alternatively by treating an aluminosilicate contained in a spent catalyst wherein the process comprises the following steps: contacting aluminosilicate with caustic aqueous solution to a temperature in the range of 30 to 60 °C for a time period in the range of 10 to 40 hours or sonication is carried out for a time period in the range of 10 to 120 minutes or heating with a caustic powder to a temperature in the range of 400 to 800 °C for a time period in the range of 1 to 4 hours to obtain a mixture; the mixture is hydrothermally heated to a temperature in the range of 70 to 100 °C under autogenic pressure for a time period in the range of 15 to 40 hours to obtain the modified aluminosilicate.
In accordance with one embodiment of the present disclosure, the aluminosilicate is at least one selected from the group consisting of virgin aluminosilicate and an aluminosilicate previously used as catalyst.
The spent catalyst is modified using one of the modification processes for aluminosilicate.
In accordance with yet another aspect of the present disclosure, there is provided a process for the preparation of Sulphur Extended Asphalt, wherein said process comprises the following steps:
In the first step, bitumen is introduced in a reactor.
In the second step, the bitumen is heated to obtain a heated bitumen.
In the third step, the heated bitumen and the sulphur additive are mixed to obtain the Sulphur Extended Asphalt.
The heating of bitumen is carried out to a temperature range within 70 to 180 °C.
In accordance with one embodiment of the present disclosure, the bitumen is heated to 165 °C.
The weight ratio of the sulphur additive and the bitumen is in the range of 1:1 to 1:10.
The Sulphur Extended Asphalt prepared using the sulphur additive of the present disclosure shows the suppressed H2S emission to a temperature in the range of 80 to 180 °C.
The process for the preparation of Sulphur Extended Asphalt comprising mixing the sulphur additive and the bitumen is carried out at a temperature in the range of 110 to 190 °C, preferably between 135 to 180 °C, under stirring with a speed of less than 100 rpm, preferably less than 70 rpm.
In one of the embodiment the solid bitumen and the sulphur additive are mixed together before heating.
The present disclosure is further illustrated herein below with the help of the following experiments. The experiments used herein are intended merely to facilitate an understanding of the ways in which the embodiments herein may be practiced and to further enable those of skilled in the art to practice the embodiments herein. Accordingly, the experiments should not be construed as limiting the scope of the embodiments herein.
Experiment 1: Process for the preparation of a sulphur additive
A reactor was charged with 30 g of sulphur. The sulphur was heated to 150 °C to obtain molten sulphur. 2.5 g of aluminosilicate was added to the molten sulphur to obtain a slurry. The slurry was continuously stirred to make a homogeneous mixture. The homogeneous mixture was cooled at 80 °C to obtain the sulphur additive.
Experiment 2A: Preparation of sulphur extended asphalt using a sulphur additive (containing aluminosilicate with alkali/alkaline earth metal ions)
A flask was charged with 70 g of bitumen. The bitumen was then heated at 165 °C to obtain heated bitumen. 30 g of sulphur additive was added to the heated bitumen to obtain a homogeneous mixture. The homogeneous mixture is stirred at a speed of 100 rpm. The emission of hydrogen sulphide (H2S) from the flask was detected in the temperature range of 120 °C to 180 °C using the multi-gas detector.
Table 2A: H2S emission at increasing mixing temperature
Sulphur additive
(wt%) Bitumen
(wt%) Stirring rate
(rpm) Temperature
(°C) H2S emission on detector (ppm)
30 70 70 120 0 (not-detectable)
30 70 70 140 0 (not-detectable)
30 70 70 160 0 (not-detectable)
30 70 70 170 2
30 70 70 180 4

It was observed that the emission of hydrogen sulphide (H2S) and sulphur dioxide (SO2) during the preparation of sulphur extended asphalt at 160 °C was 0 ppm on multi-gas detector. The temperature of the sulphur extended asphalt was further raised to 180 °C, and it was observed that the emission of hydrogen sulphide (H2S) was 4 ppm on multi-gas detector.
Experiment 2B: H2S emission from Sulphur Extended Asphalt (SEA) with increasing temperature
The sulphur extended asphalt samples prepared in Experiments 2A were cooled to room temperature. The cooled samples were further cut into pieces. The pieces were heated at 80 °C and the emission of hydrogen sulphide (H2S) was detected at different levels using multi-gas detector. It was observed that there was no emission of hydrogen sulphide (H2S) and sulphur dioxide (SO2) emission detected on multi-gas detector till 80 °C.
Table 2B: H2S emission with increasing temperature
SEA (wt %) Temperature (°C) H2S emission (ppm)
100 40 0 (non-detectable)
100 60 0 (non-detectable)
100 80 0 (non-detectable)

Experiment 3A: Preparation of sulphur extended asphalt using a sulphur additive (containing aluminosilicate with rare earth/transition metal ions)
The experimental procedure was followed as given in Experiment 2A. The results are demonstrated in Table 3A.

Table 3A:
sulphur additive
(wt %) Bitumen
(wt %) Stirring rate
(rpm) Temperature
(°C) H2S emission on detector (ppm)
30 70 70 120 0 (not-detectable)
30 70 70 140 0 (not-detectable)
30 70 70 160 0 (not-detectable)
30 70 70 170 0 (not-detectable)
30 70 70 180 2

Experiment 3B: H2S emission from Sulphur Extended Asphalt with increasing temperature
Sulphur Extended Asphalt samples prepared in Experiments 3A were cooled to room temperature. The solid mass obtained was cut into pieces and heated 80 °C to check H2S emission. H2S emission was checked at different levels using the multi-gas detector. At 80 °C, no H2S emission was observed at the zero inch level of the beaker brim.
Table 3B: H2S emission from Sulphur Extended Asphalt (SEA) with increasing temperature

SEA (wt %) Temperature (°C) H2S emission on detector (ppm)
100 40 0 (non-detectable)
100 60 0 (non-detectable)
100 80 0 (non-detectable)
(The H2S detection experiments are conducted up to 80 °C on the basis of the fact that the maximum temperature of road surface raised up to 60 °C in the Indian climate.)
Experiment 4A: Preparation of Sulphur Extended Asphalt using sulphur additive (containing aluminosilicate with Caustic/ultrasonic treatment)
Experimental procedure was followed as given in Experiment 2A. The results are shown in Table 4A.
Table 4A: H2S emission with increasing mixing temperature
sulphur additive
(wt %) Bitumen
(wt %) Stirring rate
(rpm) Temperature
(°C) H2S emission on detector (ppm)
30 70 70 120 0 (not-detectable)
30 70 70 140 0 (not-detectable)
30 70 70 160 0 (not-detectable)
30 70 70 170 0 (not-detectable)
30 70 70 180 4

No emission of hydrogen sulphide (H2S) and sulphur dioxide (SO2) was observed till 170 °C. However 4 ppm H2S was observed at 180 °C.
Experiment 4B: H2S emission from Sulphur Extended Asphalt with increasing temperature
The experimental procedure was followed as given in Experiment 2B using sulphur extended asphalt of Experiment 4A.
Table 4B: H2S emission with increasing temperature
SEA (wt%) Temperature (°C) H2S emission on detector (ppm)
100 40 0 (non-detectable)
100 60 0 (non-detectable)
100 80 0 (non-detectable)
(The H2S detection experiments are conducted up to 80 °C on the basis of the fact that the maximum temperature of road surface raised up to 60 °C in the Indian climate.)
No emission of hydrogen sulphide (H2S) and Sulphur dioxide (SO2) was observed throughout the experiment indicating efficacy assurance during field application.
Experiment 5: Compaction Test
A flask was charged with 14 g of bitumen and heated at 165 °C to obtain a heated bitumen. 380 g of gravel (aggregates as per mix design, preheated at 170 °C) was added to the heated bitumen to obtain a slurry. The slurry was continuously stirred to get a homogeneous mixture. 6 g of sulphur additive was added to the homogeneous mixture and stirred to a speed of 100 rpm. The homogeneous mixture was aged at 135 °C for 4 hours followed by aging at 150 °C for 30 minutes. Further, the homogeneous mixture was pressed at 150 °C and 600 kPa. Emission of hydrogen sulphide (H2S) and sulphur dioxide (SO2) was detected using multi-gas detector. No emission of hydrogen sulphide (H2S) and sulphur dioxide (SO2) was observed throughout the experiment.
TECHNICAL ADVANCEMENT
The present disclosure relates to the sulphur additive for making sulphur extended asphalt and the process for preparation thereof. The Sulphur additive has several technical advancements such as:
• hydrogen sulphide (H2S) emission during the preparation of Sulphur Extended Asphalt to a temperature greater than 100 ºC is mitigated;
• The spent catalyst containing aluminosilicate is reused, as the spent catalyst containing aluminosilicate is modified and mixed with sulphur to form a sulphur additive; and
• the process for the preparation of the sulphur additive is economically viable.
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results. While certain embodiments of the inventions have been described, these embodiments have been presented by way of experiment only, and are not intended to limit the scope of the inventions. Variations or modifications to the composition of this invention, within the scope of the invention, may occur to those skilled in the art upon reviewing the disclosure herein. Such variations or modifications are well within the spirit of this invention.
The numerical values given for various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the invention unless there is a statement in the specification to the contrary.
While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the disclosure. These and other changes in the preferred embodiment of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.