WO2011070027A1

WO2011070027A1 - Bituminous composition and process for manufacturing the same

Info

Publication number: WO2011070027A1
Application number: PCT/EP2010/069096
Authority: WO
Inventors: David William Britton; Majid Jamshed Chughtai; David Strickland
Original assignee: Shell Internationale Research Maatschappij B.V.
Priority date: 2009-12-08
Filing date: 2010-12-07
Publication date: 2011-06-16
Also published as: AR079309A1

Abstract

The invention provides a bituminous composition comprising a bitumen, sulphur, and a odour suppressant which comprises active components and a diluent, wherein the active components include an ester of salicylic acid and one or more aldehydes having at least 6 carbon atoms. The invention also provides a process for manufacturing the present bituminous composition; a process for manufacturing the bituminous composition; sulphur pellets; an asphalt composition comprising the bituminous composition; a process for manufacturing the asphalt composition; a process for preparing an asphalt pavement; and the asphalt pavement thus prepared.

Description

BITUMINOUS COMPOSITION AND PROCESS FOR MANUFACTURING THE

SAME

Field of the Invention

The invention relates to a bituminous composition; a process for manufacturing the bituminous composition; sulphur pellets; an asphalt composition comprising the bituminous composition; a process for manufacturing the asphalt composition; a process for preparing an asphalt pavement; and the asphalt pavement thus prepared.

Background of the Invention

In the road construction and road paving industry, it is a well-practised procedure to coat aggregate material such as sand, gravel, crushed stone or mixtures thereof with hot fluid bitumen, spread the coated

material as a uniform layer on a road bed or previously built road while it is still hot, and compact the uniform layer by rolling with heavy rollers to form a smooth surfaced road.

The combination of bitumen with aggregate material, such as sand, gravel, crushed stone or mixtures thereof, is referred to as "asphalt". Bitumen, also referred to as "asphalt binder", is usually a liquid binder comprising asphaltenes, resins and oils. Bitumen can for example comprise mixtures derived from petroleum residues such as residual oils or pitch or mixtures thereof.

It is known in the art that sulphur can be mixed with bitumen for applications in the road construction and road paving industry. One of the problems encountered when using sulphur in bitumen is the unwanted formation of hydrogen sulphide, resulting from hydrogenation reactions of sulphur in bitumen at high temperatures, e.g. greater than 145°C.

In view of the substantial amounts of sulphur used, especially in asphalt having high sulphur-bitumen weight ratios, e.g. as high as 2:1, hydrogen sulphide emission is a serious odour nuisance. Therefore, it is desirable to reduce the unwanted formation and emission of hydrogen sulphide from sulphur-comprising asphalt.

One method to reduce hydrogen sulphide emission from hot cast sulphur-asphalt mixtures is described in WO

2005/059016. Incorporating a hydrogen sulphide- suppressant such as ferric chloride into sulphur pellets can reduce hydrogen sulphide emissions during the

manufacture of sulphur-containing asphalt.

In another method which is described in

WO2009/121917 use is made of a paraffin wax to reduce hydrogen sulphide emission. Specific preference is given to the use of wax resulting from a Fischer-Tropsch process .

In WO 2008/046899 it has been disclosed that

reductions in hydrogen sulphide emisions can be achieved when sulphur pellets that are used in the asphalt

manufacturing process contain a monovinyl aromatic compound .

Aim of the present invention is to provide an alternative odour suppressant that can very attractively be used in bituminous composition for use in asphalt manufacturing processes.

Summary of the Invention

The inventors have now discovered that the odour associated with a sulphur asphalt mixture can be abated by addition of a odour abatement additive. This leads to an improved worker experience being associated with use of sulphur asphalt mixes.

Accordingly, a first aspect the present invention is a bituminous composition comprising a bitumen, sulphur, and an odour suppressant which comprises active

components and a diluent, wherein the active components include an ester of salicylic acid and one or more aldehydes having at least 6 carbon atoms.

Suitably, the active components of the odour

suppressant may further include one or more alcohols having at least 6 carbon atoms. The use of such alcohols is optionally not required in the present invention.

Suitably, the active components of the odour

suppressant may further include one or more terpenes and/or one or more ketones. Also the use of such terpenes and/or ketones is optionally not required in the present invention .

In a preferred embodiment of the present invention, the odour suppressant comprises as active components:

A. 20 to 60 wt% of benzylsalicylate or a Ci-Cs alkylsalicylate;

B. 4 to 30 wt% of a C4-C20 alkylaldehyde ;

C. at most 40 wt% of a further aldehyde having 8- 18 carbon atoms;

D. at most 40 wt% of an alcohol having 8-15 carbon atoms ;

E. at most 5 wt% of a terpene; and

F. at most 4 wt% of a ketone; wherein all the weight percentages are based on total weight of the active components.

Preferably, component A of the odour suppressant is benzylsalicylate or methylsalicylate . Benzylsalicylate has a high boiling point, allowing the odour suppressant to be active for a long time.

Preferably, component B of the odour suppressant is heptanal or dodecanal .

Preferably, component C of the odour suppressant is selected from the group consisting of jasmonal(2- Benzylidenheptanal ; Ci₄H_igO) , jasmolan H((2E)-2- Benzylidenoctanal ; Ci₅H₂oO) , lilial(3-(4- tert . butylphenyl ) butanal ; Ci₄H₂oO) , helional(3- benzo ( 1 , 3 ) dioxol-5-yl-2-methyl-propanal ; CnH₁₂0₃) , cyclamenaldehyde ( 3- ( 4-propan-2ylphenyl ) butanal ; Ci₃H₁₈0) , methylundecanal (C₁₂H₂₄O) , and mixtures thereof.

Preferably, component D of the odour suppressant is selected from the group consisting of eugenol ( 2-methoxy- 4-prop-2-enyl-phenol ; CioH₁₂0₂) , linalool (3,7- dimethylocta-1 , 6-dien-3-ol ; Ci₀H₁₈O) , geraniol ((2E)-3,7- dimethylocta-2 , 6-dien-l-ol ; CioH_igO) and mixtures thereof.

Preferably, component E of the odour suppressant is selected from the group consisting of alpha-pinene

( 4 , 7 , 7-trimethylbicyclo ( 3.1.1 ) hept-3-en; CioHi₆) , alpha- terpineol (2-( 4-methyl-l-cyclohex-3-enyl ) propan-2-ol ; CioHigO) , limonene( l-methyl-4-prop-l-en-2-yl-cyclohexene ; C₁0H₁6) and and mixtures thereof.

Preferably, component F of the odour suppressant is selected from the group consisting of benzophenon, butyl- methyl-keton and 1,8-cineol and mixtures thereof.

Suitably, the odour suppressant to be used in accordance with the invention comprises 5 to 50wt%, preferably 10 to 40wt% of the active components and 50 to 95wt%, preferably 60 to 90wt% of the diluent, in each case based on total weight of the odour suppressant.

The odour suppressant comprises active components and a diluent. A wide variety of diluents can be used in accordance with the present invention, as will be clear to the skilled person. Suitable diluents include, for example, mineral oils and vegetable oils such as sunflower oil.

Preferably, the odour suppressant is present in an amount of 10 to 1000 ppm, preferably 50 to 1000 ppm, based on the total weight of the bituminous composition.

The bituminous composition according to the present invention may suitably comprise in addition to the above- mentioned ("present") odour suppressants another odour suppressant .

Preferably, such an additional odour suppressant is added to the bitumen or bituminous composition at the same time as the present odour suppressant of which the active components include an ester of salicylic acid and one or more aldehydes having at least 6 carbon atoms.

Such additional odour suppressants can suitably be selected from the group consisting of paraffin wax, free radical inhibitors, redox catalysts, a monovinyl aromatic compound, a compound of formula I

wherein R and R are independently chosen from C6-C30 alkyl or alkenyl, and mixtures thereof.

The use of such additional odour suppressants further reduces the temperature at which asphalt of desirable strength and durability can be produced.

Suitably, in the bituminous composition according the present invention, the sulphur is present in an amount of from 10 to 200 wt%, based upon the weight of the bitumen.

Preferably, the sulphur used in the preparation of the bituminous composition is in the form of sulphur pellets.

Preferably, the sulphur pellets comprise the odour suppressant of which the active components include an ester of salicylic acid and one or more aldehydes having at least 6 carbon atoms.

Suitably, the sulphur pellets may also comprise the additional odour suppressant.

The present invention also relates a sulphur pellet which comprises the present odour suppressant of which the active components include an ester of salicylic acid and one or more aldehydes having at least 6 carbon atoms.

The present invention also relates to a process for manufacturing the bituminous composition according to the present invention, the process comprising the steps of:

(i) heating bitumen;

(ii) mixing the hot bitumen so obtained with an amount of sulphur in the range of from 10 to 200 wt%, based on the weight of the bitumen; and

wherein the present odour suppressant of which the active components include an ester of salicylic acid and one or more aldehydes having at least 6 carbon atoms is added in at least one of the steps (i) or (ii) .

Suitably, the additional odour suppressant can also added in at least one of the steps (i) or (ii) .

The bituminous composition according to the present invention can advantageously be applied in road and roofing applications, preferably road applications. The present invention further relates to an asphalt composition comprising an aggregate and the bituminous composition according to the present invention.

The present invention also provides a process for manufacturing the asphalt composition according to the present invention, the process comprising the steps of:

(i) heating bitumen;

(ii) heating aggregate;

(iii) mixing the hot bitumen with the hot aggregate in a mixing unit to form an asphalt composition;

wherein from 10 to 200 wt% of sulphur, based on the weight of the bitumen, is added in at least one of steps (i) , (ii) or (iii) ; and

wherein the present odour suppressant of which the active components include an ester of salicylic acid and one or more aldehydes having at least 6 carbon atoms is added in at least one of the steps (i), (ii) or (iii).

Suitably, the additional odour suppressant can suitably also added in at least one of the steps (i), (ii) or (iii) .

Preferably, the sulphur is added in the above processes in the form of a sulphur pellet.

The present invention in addition also provides a process for preparing an asphalt pavement, wherein an asphalt composition is prepared by means of the present asphalt composition manufacturing process, followed by the steps of :

(iv) spreading the asphalt composition into a layer; and

(v) compacting the layer.

The present invention further relates to an asphalt pavement prepared by means of such a process. Detailed Description of the Invention

In step (i) of the processes for manufacturing the present bituminous or asphalt compositions the bitumen is heated, preferably at a temperature of from 60 to 200°C, preferably from 80 to 150°C, more preferably from 100 to

145°C. The bitumen is preferably a paving grade bitumen suitable for road application having a penetration of, for example, from 9 to lOOOdmm, more preferably of from 15 to 450dmm (tested at 25°C according to EN 1426: 1999) and a softening point of from 25 to 100°C, more

preferably of from 25 to 60°C (tested according to EN 1427 : 1999) .

In step (ii) of the process for manufacturing the present asphalt composition the aggregate is heated, preferably at a temperature of from 60 to 200°C,

preferably from 80 to 170°C, more preferably from 100 to 160°C, even more preferably from 100 to 145°C. The aggregate is suitably any aggregate that is suitable for road applications. The aggregate may consist of a mixture of coarse aggregate (retained on a 4mm sieve) , fine aggregate (passes a 4mm sieve but is retained on a 63μηι sieve) and filler (passes a 63μηι sieve) .

In step (iii) of the asphalt manufacturing process, the hot bitumen and hot aggregate are mixed in a mixing unit. Suitably, the mixing takes place at a temperature of from 80 to 200°C, preferably from 90 to 150°C, more preferably from 100 to 145°C. Typically, the mixing time is from 10 to 60 seconds, preferably from 20 to 40 seconds .

The temperatures at which the bitumen and aggregate are heated and subsequently mixed are desirably kept as low as possible in order to reduce hydrogen sulphide emissions when the sulphur is added. However, the temperatures need to be sufficiently high such that the bitumen can effectively coat the aggregate. The present invention allows for bitumen, aggregate and sulphur mixes to be produced with suppression of odour emanating from the asphalt mixture.

The amount of sulphur added to the bitumen,

aggregate or bitumen/aggregate mixture is from 10 to 200 wt%, based upon the weight of the bitumen, preferably from 20wt%, more preferably from 40wt% and preferably to 100wt%, more preferably to 80wt%. The presence of sulphur in the asphalt paving mixture can improve the strength and rutting resistance of the paving mixture and it is important to include sufficient sulphur to realise these advantages. Additionally, incorporating increased amounts of sulphur can decrease the cost of the paving mixture.

However, too much sulphur can decrease the workability of the paving mixture so it is important not to use more than 200wt% of sulphur pellets, preferably not more than 100wt%.

The sulphur is preferably incorporated in the form of pellets. Reference herein to pellets is to any type of sulphur material that has been cast from the molten state into some kind of regularly sized particle, for example flakes, slates or sphere-shaped sulphur such as prills, granules, nuggets and pastilles or half pea sized

sulphur. The sulphur pellets typically comprise from 50 to 100wt% of sulphur, based upon the weight of the sulphur pellets, preferably from 60wt% and most

preferably from 70wt%; and typically to 99wt%, and preferably to 95wt% or to 100wt%. A more preferred range is from 60 to 100wt%.

Typically, the odour suppressant is distributed homogeneously throughout the sulphur pellet. The present invention also relates to a composition which contains sulphur and an odour suppressant which comprises active components and a diluent, wherein the active components include an ester of salicylic acid and one or more aldehydes having at least 6 carbon atoms.

Suitably, the active components may further include one or more alcohols having at least 6 carbon atoms. The use of such alcohols is optionally not required in the present invention.

Suitably, the active components of the odour

suppressant may further include one or more terpenes and/or one or more ketones. The use of such terpenes and/or ketones is optionally not required in the present invention .

The present invention also provides a sulphur-based composition which contains the present odour suppressant.

Preferably, such a sulphur-based composition

comprises 0.02 to 0.3 wt% of the odour suppressant and at most 8wt% of additives, for instance, at most 5 wt% of a handling agent, and at most 3 wt% of a pigment, all based on total weight of the composition.

The sulphur pellets may comprise other components, for example, they may comprise amyl acetate in a

concentration of at least about 0.08 wt% based upon the weight of the pellet and/or may comprise carbon, such as carbon black, at a concentration of at least 0.25 wt%. As described in WO 03/14231, liquid sulphur can be

plasticized by the addition of carbon, such as carbon black, at a concentration of 0.25 to 5wt% and can be further treated with amyl acetate at a concentration of

0.08 to 2wt% to produce an even more manageable

plasticized sulphur pellet. The sulphur and the present odour suppressant, i.e. the odour suppressant of which the active components include an ester of salicyl acid and one or more

aldehydes having at least 6 carbon atoms are preferably added together, i.e. both in step (i), step (ii) or step

(iii) of the respective processes for manufacturing the present bituminous and asphalt compositions. In a first embodiment, the hot aggregate is mixed with the sulphur and the present odour suppressant. Hot bitumen is then added to the hot aggregate-sulphur mixture. In a second embodiment, hot aggregate is mixed with hot bitumen, and the sulphur and the present odour suppressant are added to the hot bitumen-aggregate mixture. This embodiment offers the advantage of producing a stronger sulphur- asphalt mixture strength. In a third embodiment, hot bitumen is mixed with sulphur and the present odour suppressant and the resulting hot bitumen-sulphur mixture is mixed with hot aggregate to obtain a sulphur- comprising asphalt mixture.

Alternatively, in the asphalt manufacture process the present odour suppressant may be added separately. For example, the present odour suppressant be added to the bitumen in step (i) and the sulphur may be added in step ( iii ) .

In a preferred embodiment of the invention, the sulphur and the present odour suppressant are added together; the sulphur is in the form of pellets and the present odour suppressant is incorporated in the sulphur pellets. The sulphur pellets preferably comprise from 0.01 to 30wt% of the present odour suppressant, based upon the weight the sulphur, more preferably from 0.1 to 12wt%. The sulphur pellets are suitably prepared by a process wherein liquid sulphur is mixed with the odour suppressant and optionally additional components such as carbon or amyl acetate. The mixture is then shaped and/or pelletised .

In one embodiment of the invention sulphur may be added in the form of two types of sulphur pellets; a first type of sulphur pellet that comprises the present odour suppressant and a second type of sulphur pellet that does not comprise the present odour suppressant. This has the advantage that the present odour suppressant is essentially concentrated in the first type of sulphur pellet and conventional sulphur pellets can be used to make up the rest of the sulphur requirement.

As indicated before, an additional odour suppressant can be used in addition to the present odour suppressant. Such an additional odour suppressant can be added to the hot bitumen, hot aggregate-sulphur mixture or the hot bitumen-aggregate mixture in the same way as the present odour suppressant. When use is made of two types of sulphur pellets, as discussed hereabove, a first type of sulphur pellet may comprise the additional odour

suppressant and a second type of sulphur pellet may not comprise the additional odour suppressant. In such embodiment the first type of sulphur pellet comprises both the present and additional odour suppressants, whereas the second type of sulphur pellet does not comprise odour suppressant.

Preferably, the present odour suppressant and, if applicable, the additional odour suppressant are added at the same time to the hot bitumen, hot aggregate-sulphur mixture or the hot bitumen-aggregate mixture.

When the additional odour suppressant is a paraffin wax, preferably a slack wax, de-oiled slack wax or

Fischer-Tropsch wax, the amount of wax that is added to the bitumen, aggregate or bitumen/aggregate mixture is from 0.1 to 20 wt%, preferably from 0.5 to 20wt%, more preferably from 1 to 8wt%, based upon the weight of the bitumen. Preferably the slack wax comprises at most

50%wt. of oil, more preferably from 0.5 to 40%wt. of oil; even more preferably from 1 to 25%wt. of oil. The de- oiled slack wax preferably comprises at most 15%wt. of oil, more preferably from 0.5 to 10 wt%, even more preferably from 0.5 to 5 %wt . of oil. Preferably the melting point of the paraffin wax is from 80 to 110°C.

When the additional odour suppressant is a free radical inhibitor or a redox catalyst, suitable odour suppressants are compounds selected from the class of free radical inhibitors and redox catalysts.

Preferred odour suppressants are selected from the group of tetra-alkyl-thiuram disulfide, dithiocarbamates , especially zinc dialkyl dithiocarbamates, amine

compounds, iodine, copper salts, copper oxides, cobalt salts, cobalt oxides, iron oxides and iron salts.

Preferred iron salts are iron chloride compounds, in particular those iron chloride compounds selected from the group of ferric chloride, hydrated ferric chloride, ferrous chloride and hydrated ferrous chloride. Hydrated ferrous chloride is the most preferred, because of its greater effectiveness as an odour suppressant and because of its non-corrosivity .

In that case, the sulphur pellet typically comprises such an odour suppressant in amounts in the range of from 0.02% to 10% (w/w) , preferably from 0.05% to 6.5%, more preferably from 0.1% to 2.0%, based on the weight of the sulphur pellet. When the additional odour suppressant is a monovinyl aromatic compound, the monovinyl aromatic compound typically has the following general formula II:

wherein Ar is an aromatic group and R¹, R² and R³ are independently chosen from hydrogen and C1-C10 alkyl . Ar is typically phenyl, Ci-Cio alkyl-subst ituted phenyl, naphthalene or Ci-Cio alkyl-subst ituted naphthalene, and is preferably phenyl, tolyl or xylyl . R¹, R² and R³ are preferably hydrogen or methyl and are most preferably all hydrogen such that the monovinyl aromatic compound contains a terminal alkene. Preferred monovinyl aromatic compounds include styrene, vinyl toluene, vinyl xylene, ethyl vinyl benzene and vinyl naphthalene, and the most preferred monovinyl aromatic compounds are styrene and vinyl toluene.

In that case, the sulphur pellet typically comprises from 1 to 50wt% of a monovinyl aromatic compound, based upon the weight of the sulphur pellet, typically from 2wt%, preferably from 5wt% and most preferably from 8wt%; and typically to 40wt%, preferably to 30wt% and most preferably to 20wt%. A preferred range is from 5 to 30wt% and a most preferred range is from 8 to 20wt%.

When the the additional odour suppressant is a compound of formula I

wherein R¹ and R^z are independently chosen from C6-C30 alkyl or alkenyl, the compound of formula I is

essentially the condensation product of ethylene diamine and one or more fatty acids. R¹ and R² are independently chosen from C6-C30 alkyl or alkenyl, but preferably R¹ and R² are the same. Preferably R¹ and R² are C₁₀-C2₀ alkyl or alkenyl; more preferably R¹ and R² are C₁2-C18 alkyl or alkenyl. Most preferably R¹ and R² are (¾((¾) 16 such that compound of formula I is ethylene bis stearamide.

In that case, the amount of compound of formula I that is added to the bitumen, aggregate or

bitumen/aggregate mixture is from 0.1 to 20wt%,

preferably from 0.5 to 20wt%, more preferably from 1 to 8wt%, based upon the weight of the bitumen.

The invention further provides asphalt prepared by a process according to the invention. Typically, the asphalt comprises at least 1 wt% of bitumen, based on the weight of the asphalt. Asphalt comprising from about 1 weight% to about 10 weight% of bitumen is preferred, with a special preference for asphalt comprising from about 3 weight % (%wt.) to about 7 weight % of bitumen based on the weight of the asphalt.

The invention further provides a process for

preparing an asphalt pavement, wherein asphalt is prepared by a process according to the invention, and further comprising steps of:

(iv) spreading the asphalt into a layer; and (v) compacting the layer. The invention further provides an asphalt pavement prepared by the processes according to the invention.

The compaction in step (v) suitably takes place at a temperature of from 80 to 200°C, preferably from 90 to

150°C, more preferably from 100 to 145°C. The temperature of compaction is desirably kept as low as possible in order to reduce hydrogen sulphide emissions. However, the temperature of compaction needs to be sufficiently high such that the voids content of the resulting asphalt is sufficiently low for the asphalt to be durable and water resistant .

The invention will now be described by reference to examples which are illustrated by means of the following Examples, which are not intended to limit the invention.

Example 1

An odour suppressant was prepared by mixing the following active components: 40wt% of benzoylsalicylate ; 18wt% of dodecanal ; 7wt% of jasmonal H; 3wt% of

cyclamenaldehyde ; 9wt% of jasmonal; 10wt% of linalool;

9wt% of eugenol; lwt% of limonene; 2wt% of alpha- terpineol; and lwt% of alpha- pinene.

30wt% of the odour suppressant so obtained was mixed with 70wt% of CATENEX (a commercial oil available from Shell) to obtain the odour suppressant in liquid form.

Sulphur pellets were then prepared by mixing 0.1 wt% of odour suppressant in liquid form, 3 wt% of

ethylenebisstearylamide and 1 wt% of carbon black with 100 wt% of liquid sulphur, and forming pellets from the mixture so obtained. The sulphur pellets so obtained were then mixed with a liquid bitumen (30wt% pellets/ 70wt% bitumen) . The use of these pellets established much less formation of hydrogen sulphide and sulphur dioxide. It was further noted that the sulphur pellets reduced the odour nuisance considerably when the mixture of the pellets and bitumen was applied in road and roofing applications .

Example 2

An odour suppressant was prepared by mixing the following active components: 43wt% of methylsalicylate ; llwt% of heptanal; 10wt% of jasmonal H; 5wt% of lilial; 7wt% of jasmonal; 5wt% of 2-methylundecanal ; 2wt% of helional; llwt% of linalool; and 6wt% of geraniol.

Sulphur pellets were then prepared by mixing 0.12wt% of odour suppressant in liquid form and 3.5wt% of ethylenebisstearylamide with 100wt% of liquid sulphur, and forming pellets from the mixture so obtained. The sulphur pellets so obtained were then mixed with a liquid bitumen (30wt% pellets/ 70wt% bitumen) . The use of these pellets established much less formation of hydrogen sulphide and sulphur dioxide. It was further noted that the sulphur pellets reduced the odour nuisance

considerably when the mixture of the pellets and bitumen was applied in road and roofing applications.

Claims

C L A I M S

1. A bituminous composition comprising a bitumen, sulphur, and an odour suppressant which comprises active components and a diluent, wherein the active components include an ester of salicylic acid and one or more aldehydes having at least 6 carbon atoms.

2. A composition according to claim 1, wherein the active components of the odour suppressant further include one or more alcohols having at least 6 carbon atoms .

3. A composition according to claim 1 or 2, wherein the active components of the odour suppressant further include one or more terpenes and/or one or more ketones.

4. A composition according to any one of claims 1-3, wherein the odour suppressant comprises as active components :

A. 20 to 60 wt% of benzylsalicylate or a Ci-Cs alkylsalicylate;

B. 4 to 30 wt% of a C4-C20 alkylaldehyde ;

C. at most 40 wt% of a further aldehyde having 8 to 18 carbon atoms;

D. at most 40 wt% of an alcohol having 8-15 carbon atoms ;

E. at most 5 wt% of a terpene; and

5. A composition according to claim 4, wherein

component A of the odour suppressant is benzylsalicylate or methylsalicylate .

6. A composition according to claim 4, wherein

component B of the odour suppressant is heptanal or dodecanal .

7. A composition according to claim 4, wherein

component C of the odour suppressant is selected from the group consisting of jasmonal, jasmolan H, lillial, helional, cyclamenaldehyde, methylundecanal and mixtures thereof .

8. A composition according to claim 4, wherein

component D of the odour suppressant is selected from the group consisting of eugenol, linalool, geraniol and mixtures thereof.

9. A composition according to claim 4, wherein

component E of the odour suppressant is selected from the group consisting of alpha-pinene, alpha-terpineol , limonene and and mixtures thereof.

10. A composition according to claim 4, wherein

component F of the odour suppressant is selected from the group consisting of benzophenon, butyl-methyl-keton and 1 , 8-cineol .

11. A composition according to any one of claims 1-10, wherein the odour suppressant comprises 5 to 50 wt% of the active components and 50 to 95 wt% of the diluent, based on total weight of the odour suppressant.

12. A composition according to any one of claims 1-11, wherein the odour suppressant is present in an amount of 10 to 1000 ppm, based on the total weight of the

bituminous composition.

13. A composition according to any one of claims 1-12, wherein the composition comprises an additional odour suppressant selected from the group consisting of

paraffin wax, free radical inhibitors, redox catalysts, a monovinyl aromatic compound, a compound of formula I

14. A composition according to claim 13, wherein the paraffin wax is a slack wax, a de-oiled slack wax or a Fischer-Tropsch wax.

15. A composition according to any one of claims 1-14, wherein the sulphur is present in an amount of from 10 to 200 wt%, based upon the weight of the bitumen.

16. A composition according to any one of claims 1-13, wherein the sulphur that is used in the preparation of the bituminous composition is in the form of sulphur pellets .

17. A composition according to claim 16, wherein the sulphur pellets comprise the odour suppressant as defined in any one of claims 1-12, and optionally also the additional odour suppressant as defined in claims 13 and 14.

18. A composition according to claim 16 or 17, wherein the sulphur pellets are plasticized sulphur pellets that also comprise amyl acetate and carbon.

19. A process for manufacturing a bituminous composition according to any one of claims 1-18, the process

comprising the steps of:

(i) heating bitumen;

(ii) mixing the hot bitumen so obtained with an amount of sulphur in the range of from 10 to 200 wt%, based on the weight of the bitumen; and wherein the odour suppressant as defined in any one of claims 1-11 is added in at least one of the steps (i) or (ii) .

20. A process according to claim 19, wherein the

additional odour suppressant as defined in claims 12 and

13 is also added in at least one of the steps (i) or (ii) .

21. A sulphur pellet as described in claim 17 or 18.

22. An asphalt composition comprising an aggregate and the bituminous composition according to any one of claims

1-18.

23. A process for manufacturing the asphalt composition according to claim 21, the process comprising the steps of:

(i) heating bitumen;

(ii) heating aggregate;

wherein from 10 to 200 wt% of sulphur, based on the weight of the bitumen, is added in at least one of steps

(i) , (ii) or (iii) ; and

wherein the odour suppressant as defined in any one of claims 1-12 is added in at least one of the steps (i),

(ii) or (iii) .

24. A process according to claim 21, wherein the

additional odour suppressant as defined in claims 13 and

14 is also added in at least one of the steps (i), (ii) or (iii) .

25. A process according to any one of claims 19, 20, 23 and 24, wherein the sulphur is in the form of a sulphur pellet as described in claim 21.

26. A process for preparing an asphalt pavement, wherein an asphalt composition is prepared by a process according to any one of claims 23-25, and further comprising steps of:

(iv) spreading the asphalt composition into a layer; and

(v) compacting the layer.

27. An asphalt pavement prepared by a process according to claim 26.