FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION (See section 10 and rule 13)
TITLE OF THE INVENTION
A method of cracking petrochemicals
APPLICANTS
Reliance Industries Limited, 3rd Floor, Maker Chamber IV, 222, Nariman Point, Mumbai 400021, Maharashtra, India, an Indian company
INVENTORS
PATIL Harshad Ramdas, BHAJIWALA Hiren Manojkumar and GUPTA Virendrakumar, all Indian nationals, all of Reliance Industries Limited, Reliance Technology Group, Reliance Corporate Park, Thane Belapur Road, Ghansoli, Navi Mumbai 400701, Maharashtra, India
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes this invention and the manner in which it is to be performed:

FIELD OF THE INVENTION
The present invention relates to a method of cracking petrochemicals. The invention also relates to an antifouling agent to inhibit the formation of fouling materials, and/or to facilitate the dissolution of the fouling materials during pyrolytic cracking of petrochemicals.
BACKGROUND OF THE INVENTION
Pyrolytic cracking of petrochemicals like ethane, propane, butane, naphtha yields olefins along with significant quantities of reactive carbonyl compounds such as aldehydes and ketones and acidic components such as carbon dioxide and hydrogen sulfide. The cracked stream of hydrocarbons is then washed with a basic scrubber to remove the acidic components. The basic scrubbers generally used are amine scrubbers like monoethylamine, diethylamine, butyl amine or isopropyl amine; sodium hydroxide or potassium hydroxide. However, in an alkaline medium the reactive carbonyl compounds like acetaldehyde undergo aldol condensation to form aldol polymers. As the aldol polymers are insoluble in the alkaline medium, they tend to get deposited on the inner surfaces of process equipment which adversely affects flow through the system and reduces process efficiency. The accumulation of such fouling polymers can even lead to premature shutdown of a cracking operation. Therefore, regular maintenance of the equipment is required which in turn increases operating costs.
Also, those reactive carbonyl compounds which inadvertently escape the anti fouling additives and remain unscavenged undergo aldol condensation to form fouling polymers. The same additives are incapable of dissolving the polymers once formed and hence are ineffective in solving the problem completely.
What is needed is an effective common treatment for preventing fouling materials from forming and for dissolving fouling materials once formed.

SUMMARY OF THE INVENTION
According to an embodiment of the invention there is provided a method of cracking petrochemicals which inhibits the formation of fouling materials, and/or facilitates the dissolution of fouling materials comprising:
(a) pyrolytically breaking down large hydrocarbons to yield a cracked
hydrocarbon stream comprising smaller hydrocarbons along with reactive carbonyl compounds and acidic components;
(b) washing the hydrocarbon stream with a basic scrubber to remove the acidic
components; and
(c) contacting the hydrocarbon stream containing the reactive carbonyl
compounds and/or the fouling materials with an antifouling agent of the formula RNH2Si(OY)x(OR')3_x where R is C1 to C8 alkyl group, R' is C1 to C4 alkyl group, Y is an alkali metal or an alkaline earth metal and x is an integer from 1 to 3, wherein the antifouling agent is prepared by reacting an amino silane of the formula RNH2Si(OR')3 where R is C1 to C8 alkyl group, R' is C1 to C4 alkyl, with an alkali metal hydroxide or an alkaline earth metal hydroxide.
According to another embodiment of the invention there is provided a method of cracking petrochemicals which inhibits the formation of fouling materials, and/or facilitates the dissolution of fouling materials comprising:
(a) pyrolytically breaking down large hydrocarbons to yield a cracked
hydrocarbon stream comprising smaller hydrocarbons along with reactive carbonyl compounds and acidic components;
(b) washing the hydrocarbon stream with a basic scrubber to remove the acidic
components; and
(c) adding an amino silane of the formula RNH2Si(OR')3
where R is C1 to C8 alkyl group, R' is C1 to C4 alkyl,
to the hydrocarbon stream containing the reactive carbonyl compounds and/or to the fouling materials.

According to another embodiment of the invention there is provided an antifouling agent of the formula
RNH2Si(OY)x(OR')3.x where R is C1 to C8 alkyl group, R' is C1to C4 alkyl group, Y is an alkali metal or an alkaline earth metal and x is an integer from 1 to 3, to inhibit the formation of fouling materials, and/or to facilitate the dissolution of the fouling materials during pyrolytic cracking of petrochemicals, wherein the antifouling agent is formed by reacting an amino silane of the formula RNH2Si(OR')3 where R is C1 to C8 alkyl group, R' is C1 to C4 alkyl, with an alkali metal hydroxide or an alkaline earth metal hydroxide.
It is to be understood that both the foregoing general description and the following detailed description of the present embodiments of the invention are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying graphical representations are included to substantiate the invention and are incorporated into and constitute a part of this specification.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
For simplicity and illustrative purposes, the present invention is described by referring mainly to exemplary embodiments thereof. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one of ordinary skill in the art that the present invention may be practiced without limitation to these specific details. In other instances, well known methods and structures have not been described in detail so as not to unnecessarily obscure the present invention.
In the context of the invention, the term "fouling materials" as used in the specification refers to products of aldol condensation of reactive carbonyl compounds produced from the pyrolysis of petrochemicals. The petrochemicals can be ethane, propane, butane, naphtha or mixtures thereof.

The antifouling agent is present in an amount effective for preventing aldol fouling and/or for dissolving the fouling polymers, as the case may be. In one embodiment, an excess may be added. In another embodiment, the antifouling agent may be in solution form such as in an aqueous solution. In one embodiment, the antifouling agent can be prepared in situ by reacting an amino silane with an alkali metal hydroxide or an alkaline earth metal hydroxide wherein the amino silane is of the formula RNH2Si(OR')3 where R is C1 to C8 alkyl group, R' is C1 to C4 alkyl group.
The antifouling agent is preferably sodium salt of 3-aminopropyl triethoxy silane of the formula C3H6 NH2Si(ONa)(OC2Hs)2 or sodium salt of 3-aminopropyl trimethoxy silane of the formula C3H6 NH2Si(ONa)(OCH3)2.
In one embodiment, the antifouling agent, when used for preventing the formation of fouling materials, is used in a mole ratio of the antifouling agent to reactive carbonyl compounds in an amount of from 1:1 to 1:8. In one embodiment, the antifouling agent is formed in situ by adding an amino silane, having the formula RNH2Si(OR')3 where R is C1 to C8 alkyl group, R' is C, to C4 alkyl group, to the hydrocarbon stream and basic scrubber which may be a caustic scrubber. The scrubber reacts with the amino silane in situ yielding the antifouling agent. In another embodiment, the antifouling agent is prepared prior to its addition into the hydrocarbon stream being washed with the basic scrubber. In another embodiment, the antifouling agent may be added to the hydrocarbon stream simultaneously with the basic scrubber. In another embodiment, the antifouling agent may be added to the basic scrubber before contacting the hydrocarbon stream. The hydrocarbon stream is obtained from the pyrolysis of hydrocarbons, such as petrochemicals. In one embodiment, the petrochemicals may be pyrolytically cracked at a temperature of up to about 800°C. In another embodiment, the petrochemicals may be pyrolytically cracked at a temperature in the range of from about 700°C to about 900°C. In one embodiment, the cracked hydrocarbon stream may be from the pyrolysis of ethane, propane, butane, naphtha or mixtures thereof. In another embodiment, the hydrocarbon stream includes olefins. In another embodiment, the olefinic compounds include, but are not limited to, ethylene, propylene, butadiene, or mixtures thereof. The hydrocarbon stream may contain any amount of reactive

carbonyl compounds and any amount of reactive carbonyl compounds may be treated. In one embodiment, the concentration of reactive carbonyl compounds in the hydrocarbon stream will range from 50 ppm to 500 ppm.
The hydrocarbon stream is washed with a basic scrubber. The basic scrubber may be any alkaline wash having a pH of greater than 7.0. In one embodiment, the basic scrubber is a caustic scrubber. In another embodiment, the basic scrubber includes, but is not limited to, sodium hydroxide or potassium hydroxide or both.
The hydrocarbon stream may be scrubbed by any suitable method or means for contacting with a basic solution. In one embodiment, the hydrocarbon stream may be contacted with a basic scrubber in trayed or packed columns utilizing any of the various types of packing elements; or spray type contactors. The mode of flow within a basic scrubber can be either cross-flow or countercurrent flow, or both.
In one embodiment, a basic stream may be introduced into an upper portion of a basic wash system and the hydrocarbon stream may be introduced into a lower portion. The basic scrubber introduced into the basic wash system flows downward through the vessel while the hydrocarbon stream flows upwards through the basic wash system, whereby the hydrocarbon stream comes into intimate contact with the basic stream.
In one embodiment, the antifouling agent, when used for facilitating the dissolution of fouling materials, is used in a mole ratio of the antifouling agent to fouling materials in an amount of from 1:1 to 5:1. In one embodiment, the antifouling agent is formed in situ by adding an amino silane, having the formula RNH2Si(OR')3 where R is Ci to C8 alkyl group, R' is d to C4 alkyl group, to the fouling materials in a caustic solution as an alkaline medium. In another embodiment, the caustic solution includes, but is not limited to, sodium hydroxide or potassium hydroxide. The caustic solution reacts with the amino silane in situ yielding the antifouling agent. In another embodiment, the antifouling agent is prepared prior to its addition to the fouling materials. In another embodiment, the antifouling agent may be added to the fouling materials simultaneously with the

caustic solution. In another embodiment, the antifouling agent may be added to the caustic solution before contacting the fouling materials.
In order that those skilled in the art will be better able to practice the present disclosure, the following examples are given by way of illustration and not by way of limitation.
Example 1
0.03 mole of 3-aminopropyl trimethoxy silane (APTMS) and 0.12 mole of caustic soda (in 48% solution) were stirred and heated to 40°C for one hour. The water content in the reaction mixture was then removed by evaporation to get a dry salt. The salt was studied by proton Nuclear magnetic resonance spectroscopy (NMR) to ascertain the conversion of APTMS to Na salt of APTMS.
Separately, 0.03 mole of 3-aminopropyl triethoxy silane (APTES) and 0.12 mole of caustic soda (in 48% solution) were stirred and heated to 40°C for one hour. The water content in the reaction mixture was then removed by evaporation to get a dry salt. The salt was studied by proton Nuclear magnetic resonance spectroscopy (NMR) to ascertain the conversion of APTES to Na salt of APTES.
Tabid: Proton NMR study of synthesized sodium salt of APTMS and sodium salt of APTES

Proton NMR study indicated that four and seven proton is replaced in APTMS and APTES which indicated formation predominantly of mono substituted salt of APTMS and monosubstituted salt of APTES.

Fig 1 of the accompanying drawings is a graphical representation of 'H NMR of
APTMS.
Fig 2 of the accompanying drawings is a graphical representation of 'H NMR of
APTMS+NaOH.
Fig 3 of the accompanying drawings is a graphical representation of 'H NMR of
APTES.
Fig 4 of the accompanying drawings is a graphical representation of 'H NMR of
APTES+NaOH.
Example 2
In order to determine whether the APTMS or APTES alone are responsible for dissolution of fouling materials, the following experiment was conducted. 1.9 g (0.021 mole) vinyl acetate was added in 40 ml of 10 % caustic soda solution. The mixture was shaken vigorously at 350rpm at 40°C. After a few minutes, the solution turned from colorless to yellow. Yellowish orange precipitates were formed after 2 hours. Solid polymer was separated by filtration followed by multiple water wash to remove excess caustic soda. The solid polymer was then transferred into two containers each holding 40 ml water and APTMS was added into one container while APTES was added in the other. The efficiency of APTMS and APTES alone to dissolve the solid polymer was measured by evaluating transmittance of each of the solutions by UV visible spectroscopy at 800nm. A blank was also run simultaneously to compare the efficiencies of the additives and the transmittance of blank solution was measured after 2 hours by UV Visible spectroscopy at 800nrn. The % Transmittance (%T) was measured and is recorded below in Table 2:


Example 3
Sodium salt of 3-aminopropyl trimethoxy silane prepared by Example 1, sodium salt of 3-aminopropyl triethoxy silane prepared by Example 1, commercially available ethanolamine and sodium salt of 6-amino hexanoic acid were separately added in the amounts mentioned in Table 3 below into four containers each having 40 ml of 10% caustic solution. The ethanolamine and sodium salt of 6-amino hexanoic acid were used for a comparative study. In order to simulate conditions prevailing during basic scrubbing of the hydrocarbon stream, 0.021moles of vinyl acetate was added into each container as vinyl acetate on hydrolysis in alkaline media yields acetaldehyde. The solutions in each of the containers were stirred at 350 rpm at 40°C for 2 hours. The efficiency of additives to act as antifouling agents were measured by evaluating transmittance of each of the solutions by UV visible spectroscopy at 800nm. A blank containing 40ml of 10%caustic and 0.021 moles of vinyl acetate was also run simultaneously to compare the efficiencies of the additives, and the transmittance of blank solution was also measured after 2 hours by UV Visible spectroscopy at 800nm. The % Transmittance (%T) was measured and is recorded below in Table 3:


Example 4
The procedure followed in Example 3 was repeated except that mixtures of the additives were used in various proportions and then the % T was recorded as shown below in Table 4.


Example 5
0.021 moles of vinyl acetate was added each in 40 ml of 10 % caustic solution contained in four separate containers. The solutions in the four containers were stirred at 350 rpm on a magnetic stirrer at 40°C. After a few minutes, the colorless solutions

turned yellow. Yellowish precipitates formed after 15 minutes. 0.042 moles of Na salt of APTMS was added into the solution contained in one container, 0.042 moles of Na salt of APTES in another and 0.042 moles of Na salt of 6-aminohexanoic acid was added into the solution of the third container. The solution in the fourth container served as a blank (no additive was added therein) for comparison. This was repeated for 0.063 moles, 0.084 moles and 0.105 moles of the additives. In each case, transmittance of the solutions was measured after 30 minutes by UV-Visible spectroscopy at 800 nm. The observations are shown in Table 5 below.



Example 6
The procedure followed in Example 5 was repeated except that mixtures of the additives were used in various proportions and the total amount of additives was fixed at 0.084moles in all cases. The % T was recorded after 30 minutes and the results are shown below in Table 6.


*Used individually/not with any other additive
Fig 1 indicates that APTMS having nine protons of -OCH3 group attached to Si shows signals between 3.0- 3.4 ppm while Fig 2 indicates that there is a replacement of nearly four protons indicating that synthesized salt is predominantly monosubstituted sodium salt.
Fig 3 indicates that APTES having nine protons of -CH3 group shows signals between 0.80-0.87ppm and six protons of-OCH2 group show two signals at 3.4 and

3.2 ppm. Fig 4 indicates that there is a replacement of approximately four proton from the -CH3 groups and replacement of approximately three protons from -OCH2 groups indicating the formation of predominantly monosubstituted sodium salt. Results indicate that addition of disclosed antipolymerant and its mixtures increase transmittance indicating dissolution of solid formed due to aldol condensation.
From Table 2 it is evident that APTMS and APTES alone are not effective in dissolving fouling materials.
It is clear from Table 3 that the Na salt of APTMS and Na salt of APTES showed better efficiency in inhibiting the formation of fouling materials than conventional antifouling materials like ethanolamine and comparable to Na salt of 6-aminohexanoic acid.
As can be inferred from Table 4, the efficiency of ethanolamine in inhibiting aldol condensation appears to have greatly increased due to mixing it with Na salt of APTMS and Na salt of APTES respectively. Also, the mixture of Na salt of 6-aminohexanoic acid with Na salt of APTMS and Na salt of APTES respectively indicated a slightly better inhibition efficiency than Na salt of 6-aminohexanoic acid. alone.
From Table 5, it is clear that Na salt of APTES shows better efficiency for dissolution of fouling materials at a mole ratio of 1:1 to 5:1 of antifouling agent to fouling materials than Na salt of 6-aminohexanoic acid.
It is clear from Table 6 that a mixture of Na salt of 6-aminohexanoic acid and Na salt of APTMS or APTES in a molar ratio of 75:25 to 90:10 is effective in dissolving fouling materials. Also, a mixture of Na salt of 6-aminohexanoic acid and Na salt of APTES in a molar ratio of 75:25 to 90:10 is effective in dissolving fouling materials.
It is possible that the presence of the amine group in Na salt of APTMS and Na salt of APTES helps in conversion of aldehyde to imine. Unlike aldehyde, imine does not undergo polymerization in alkaline media. Hence, the amine group appears to prevent aldol condensation. On the other hand, the Si-O-Na moiety of Na salt of APTMS and

Na salt of APTES probably forms an adduct with the solid aldol polymers which facilitates dissolution of the aldol polymers in the alkaline medium. It is possible that Si-O-Na is more effective than the Si-O-alkyl moiety of pure APTES or pure APTMS on account of the higher bond forming characteristics of Si-O-Na due to its ionic nature.
What has been described and illustrated herein is a preferred embodiment of the invention along with some of its variations. The terms, descriptions and figures used herein are set forth by way of illustration only and are not meant as limitations. Those skilled in the art will recognize that many variations are possible within the spirit and scope of the invention, which is intended to be defined by the following claims—and their equivalents—in which all terms are meant in their broadest reasonable sense unless otherwise indicated.

We claim
1. A method of cracking petrochemicals which inhibits the formation of fouling materials, and/or facilitates the dissolution of fouling materials comprising:
(a) pyrolytically breaking down large hydrocarbons to yield a cracked
hydrocarbon stream comprising smaller hydrocarbons along with reactive carbonyl compounds and acidic components;
(b) washing the hydrocarbon stream with a basic scrubber to remove the acidic
components; and
(c) contacting the hydrocarbon stream containing the reactive carbonyl
compounds and/or the fouling materials with an antifouling agent of the formula
RNH2Si(OY)x(OR')3-x where R is C1 to C8 alkyl group, R' is C1to C4 alkyl group, Y is an alkali metal or an alkaline earth metal and x is an integer from 1 to 3, wherein the antifouling agent is prepared by reacting an amino silane of the formula RNH2Si(OR')3where R is C1 to C8 alkyl group, R' is C1 to C4 alkyl, with an alkali metal hydroxide or an alkaline earth metal hydroxide.
2. The method as claimed in claim 1. wherein the antifouling agent is sodium salt of 3-aminopropyl trimethoxy silane of the formula C3H6 NH2Si(ONa)(OCH3)2
3. The method as claimed in claim 1, wherein the antifouling agent is sodium salt of 3-aminopropyl triethoxy silane of the formula C3H6 NH2Si(ONa)(OC2H5)2
4. The method as claimed in claim 1, wherein the antifouling agent is added in a mole ratio of 1:1 to 1:8 of the antifouling agent to the reactive carbonyl compounds to inhibit the formation of fouling materials.
5. The method as claimed claim 1, wherein the antifouling agent is added in a mole ratio of 1:1 to 5:1 of the antifouling agent to the fouling materials to facilitate the dissolution of fouling materials.

6. The method as claimed in claim 1, wherein the antifouling agent is added to the hydrocarbon stream simultaneously with the basic scrubber.
7. The method as claimed in claim 1, wherein the cracked hydrocarbon stream is obtained from the pyrolysis of ethane, propane, butane, naphtha or mixtures thereof.
8. The method as claimed in claim 1, wherein the basic scrubber comprises sodium hydroxide or potassium hydroxide or both.
9. A method of cracking petrochemicals which inhibits the formation of fouling materials, and/or facilitates the dissolution of fouling materials comprising:
(a) pyrolytically breaking down large hydrocarbons to yield a cracked
hydrocarbon stream comprising smaller hydrocarbons along with reactive carbonyl compounds and acidic components;
(b) washing the hydrocarbon stream with a basic scrubber to remove the acidic
components; and
(c) adding an amino silane of the formula RNH2Si(OR')3
where R is C1 to C8 alkyl group, R' is C1 to C4 alkyl,
to the hydrocarbon stream containing the reactive carbonyl compounds and/or to the fouling materials.
10. The method as claimed in claim 9, wherein the amino silane is added simultaneously with the basic scrubber.
11. The method as claimed in claim 9, wherein the amino silane is added in a mole ratio of 1:1 to 1:8 of the amino silane to the reactive carbonyl compounds to inhibit the formation of fouling materials.
12. The method as claimed claim 9, wherein the amino silane is added in a mole ratio of 1:1 to 5:1 of the amino silane to the fouling materials to facilitate the dissolution of fouling materials.

13. The method as claimed in claim 9, wherein the cracked hydrocarbon stream is obtained from the pyrolysis of ethane, propane, butane, naphtha or mixtures thereof.
14. The method as claimed in claim 9, wherein the basic scrubber comprises sodium hydroxide or potassium hydroxide or both.
15. An antifouling agent of the formula
RNH2Si(OY)x(OR')3-x where R is C1 to C8 alkyl group, R' is C1 to C4 alkyl group, Y is an alkali metal or an alkaline earth metal and x is an integer from 1 to 3, to inhibit the formation of fouling materials, and/or to facilitate the dissolution of the fouling materials during pyrolytic cracking of petrochemicals, wherein the antifouling agent is formed by reacting an amino silane of the formula RNH2Si(OR')3 where R is C1 to C8 alkyl group, R' is C1 to C4 alkyl, with an alkali metal hydroxide or an alkaline earth metal hydroxide.
16. The antifouling agent as claimed in claim 15 being sodium salt of 3-aminopropyl trimethoxy silane of the formula C3H6 NH2Si(ONa)(OCH3)2.
17. The antifouling agent as claimed in claim 15 being sodium salt of 3-aminopropyl triethoxy silane of the formula C3H6 NH2Si(ONa)(OC2H5)2.