Description:FIELD
The present disclosure relates to a process for removal of sodium from di-sulfide oil.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
Disulfide oil (DSO), consisting of C2 to C4 di-sulfides, is produced during regeneration of spent caustic in Merox process for removal of mercaptans from liquefied petroleum gas (LPG; Scheme 1).
RSH + NaOH ? NaSR + H2O
4NaSR + O2 + 2H2O ? 2RSSR + 4NaOH
Scheme 1- Production of DSO
Generally, total sulfur content in DSO is in the range of 60 % to 65% depending upon its composition. Due to high sulfur content, DSO can be used as a pre-sulfiding agent in steam crackers and for pre-sulfiding of a hydro-treating catalyst. DSO produced from the Merox process contains sodium in the range of 1 ppm to 10 ppm. Sodium content higher than 0.5 ppm in DSO is not desirable for pre-sulfiding of the hydro-treating catalyst. Therefore, DSO is required to be treated with a suitable adsorbent to reduce the sodium content in DSO to less than 0.5 ppm.
Commercially, there are alumina based adsorbents available/ known for the treatment of DSO for reducing its sodium content. However, these adsorbents may be suitable for treatment of a DSO feed having lower sodium concentration in the range of 1 ppm to 2 ppm. The treated DSO showed yellow/pale yellow colour similar to an untreated feed which is not desirable and hence such known adsorbents are not very efficient for the removal of sodium from DSO containing higher sodium concentration in the range of 5 ppm to 30 ppm.
There is, therefore, felt a need to provide a process for removal of sodium from di-sulfide oil that mitigates the drawbacks mentioned hereinabove or at least provides a useful alternative.
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 ameliorate one or more problems of the background or to at least provide a useful alternative.
Another object of the present disclosure is to provide a process for removal of sodium from di-sulfide oil.
Still another object of the present disclosure is to provide a simple and economical process for removal of sodium from di-sulfide oil.
Another object of the present disclosure is to provide a process for removal of sodium from di-sulfide oil to obtain a treated di-sulfide oil having sodium content below 0.5 ppm.
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 relates to a process for removal of sodium from di-sulfide oil. The process comprises passing a stream of di-sulfide oil having sodium level in the range of 5 ppm to 10 ppm through an activated carbon bed packed in a column, at a liquid hourly space velocity (LHSV) ranging from 0.2 h-1 to 6 h-1 at a predetermined temperature for a pre-determined time period and at a predetermined pressure to obtain the treated di-sulfide oil having sodium content below 0.5 ppm.
In accordance with an embodiment of the present disclosure, the liquid hourly space velocity (LHSV) is in the range of 0.2 h-1 to 4 h-1. In accordance with another embodiment of the present disclosure, the liquid hourly space velocity (LHSV) is in the range of 0.3 h-1 to 2 h-1.
In accordance with the present disclosure, the pre-determined temperature is in the range of 20ºC to 40ºC. In accordance with another embodiment of the present disclosure the pre-determined temperature is in the range of 25ºC to 35ºC.
In accordance with the present disclosure, the pre-determined time period is in the range of 5 hours to 500 hours.
In accordance with the present disclosure, the predetermined pressure is in the range of 1 atmosphere to 4 atmospheres.
In accordance with an embodiment of the present disclosure, the treated stream of di-sulfide oil is having sodium level in the range of 0.1 ppm to 0.5 ppm. In another embodiment of the present disclosure, the treated stream of di-sulfide oil having sodium level in the range of 0.1 ppm to 0.3 ppm. In still another embodiment of the present disclosure, the treated stream of di-sulfide oil having sodium level in the range of 0.1 ppm to 0.2 ppm.
In accordance with the present disclosure, an activated carbon of the activated carbon bed is in the form of extrudates, cylindrical, spheres, granules, and a combination thereof.
In accordance with the present disclosure, the activated carbon is having a surface area in the range of 1000 m2/g to 1600 m2/g, a bulk density in the range of 300 kg/ m3 to 450 kg/m3, Na2O and other metallic impurities less than 0.02 wt%.
In accordance with the present disclosure, the activated carbon has a crushing strength in the range of 1.5 kgf to 6 kgf and an attrition loss is less than 0.1%.
The process of the present disclosure is used to treat an upstream process and a downstream process. In accordance with the present disclosure, the treated disulfide stream obtained by the process of the present disclosure is transparent.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
The present disclosure will now be described with the help of the accompanying drawing, in which:
Figure 1 illustrates a removal of sodium from DSO with respect to time in a continuous flow reactor in accordance with the present disclosure; and
Figure 2 illustrates a removal of sodium from DSO with respect to time in a continuous flow reactor by using activated carbon and commercial alumina in accordance with the present disclosure.
DETAILED DESCRIPTION
The present disclosure relates to a process for removal of sodium from di-sulfide oil.
Embodiments of the present disclosure will now be described with reference to the accompanying drawing.
Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.
The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises," "comprising," “including,” and “having,” are open ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.
The terms first, second, third, etc., should not be construed to limit the scope of the present disclosure as the aforementioned terms may be only used to distinguish one element, component, region, layer or section from another component, region, layer or section. Terms such as first, second, third etc., when used herein do not imply a specific sequence or order unless clearly suggested by the present disclosure.
Disulfide oil (DSO), consisting of C2 to C4 di-sulfides, is produced during regeneration of spent caustic in Merox process for removal of mercaptans from liquefied petroleum gas (LPG: Scheme 1).
RSH + NaOH ? NaSR + H2O
4NaSR + O2 + 2H2O ? 2RSSR + 4NaOH
Scheme 1- Production of DSO
Generally, total sulfur content in DSO is in the range of 60 % to 65% depending upon its composition. Due to high sulfur content, DSO can be used as a pre-sulfiding agent in steam crackers and for pre-sulfiding of a hydro-treating catalyst. DSO produced from the Merox process contains sodium in the range of 1 ppm to 10 ppm. Sodium content higher than 0.5 ppm in DSO is not desirable for pre-sulfiding of the hydro-treating catalyst. Therefore, DSO is required to be treated with a suitable adsorbent to reduce the sodium content in DSO to less than 0.5 ppm.
Commercially, there are alumina based adsorbents available/ known for the treatment of DSO for reducing its sodium content. However, these adsorbents may be effective for the treatment of DSO having lower sodium concentration in the range of 1ppm to 2 ppm. The treated DSO stream also showed yellow/pale yellow colour similar to an untreated feed which is not desirable and hence such known adsorbents are not very efficient for the removal of sodium from DSO containing higher sodium concentration in the range of 5 ppm to 30 ppm.
The present disclosure relates to a process for removal of sodium from di-sulfide oil obtaining a treated di-sulfide oil.
In an aspect, the present disclosure provides a process for removal of sodium from di-sulfide oil obtaining a treated di-sulfide oil. The process of the present disclosure provides treated di-sulfide oil having sodium content less than 0.5 ppm from a stream of di-sulfide oil having sodium level in the range of 5 ppm to 10 ppm.
The process of the present disclosure comprises passing a stream comprising di-sulfide oil having sodium level in the range of 5 ppm to 10 ppm through an activated carbon bed packed in a column, at a liquid hourly space velocity (LHSV) ranging from 0.2 h-1 to 6 h-1 at a pre-determined temperature and at a predetermined pressure for a pre-determined period of time to obtain the treated stream of di-sulfide oil having sodium content less than 0.5 ppm.
In accordance with the present disclosure, a ratio of the length of the activated carbon bed to the diameter of the activated carbon bed (L/D ratio) is in the range of 1.5 to 5. In an exemplary embodiment, the ratio of the length of the activated carbon bed to the diameter of the activated carbon bed (L/D ratio) is 2. In another exemplary embodiment of the present disclosure, the ratio of the length of the activated carbon bed to the diameter of the activated carbon bed (L/D ratio) is 4.5.
In accordance with an embodiment of the present disclosure, the liquid hourly space velocity (LHSV) is in the range of 0.2 h-1 to 4 h-1. In another embodiment, the liquid hourly space velocity (LHSV) is in the range of 0.3 h-1 to 2 h-1. In an exemplary embodiment of the present disclosure, the LHSV is 0.42 h-1. In another exemplary embodiment of the present disclosure, the LHSV is 0.31 h-1.
In accordance with the present disclosure, the pre-determined temperature is in the range of 20ºC to 40ºC. In accordance with an embodiment of the present disclosure, the pre-determined temperature is in the range of 25ºC to 35ºC. In an exemplary embodiment, the predetermined temperature is 30ºC.
In accordance with an embodiment of the present disclosure, the predetermined pressure is in the range of 1 atmosphere to 4 atmospheres. In an exemplary embodiment, the pre-determined pressure is 1 atmosphere.
In accordance with an embodiment of the present disclosure, the pre-determined time period is in the range of 5 hrs to 500 hrs. In an exemplary embodiment, the pre-determined time period is 6 hrs. In another exemplary embodiment, the pre-determined time period is 100 hrs. In another exemplary embodiment, the pre-determined time period is 475 hrs.
In accordance with the present disclosure, the treated stream of di-sulfide oil is having sodium content in the range of 0.1 ppm to 0.5 ppm. In another embodiment, the treated stream of di-sulfide oil is having sodium content in the range of 0.1 ppm to 0.3 ppm. In another embodiment, the treated stream of di-sulfide oil is having sodium content in the range of 0.1 ppm to 0.2 ppm.
In accordance with an embodiment of the present disclosure, the activated carbon of the activated carbon bed is in the form of extrudates, cylindrical, spheres, granules, and a combination thereof.
In accordance with the present disclosure, the selection of the activated carbon of the activated carbon bed is very critical as sodium removal from DSO to less than 0.5 ppm should not result in any significant effect on the physico-chemical properties of the treated DSO. Higher surface area with mesopores and absence of metallic impurities in the selected activated carbon are the preferred embodiments of the present disclosure.
In accordance with the present disclosure, the activated carbon is characterized by:
Surface area, pore size and pore volume;
Impurity profile of the activated carbon; and
Crushing strength, attrition loss and bulk density.

In accordance with an embodiment of the present disclosure, the activated carbon is having a surface area in the range of 1000 m2/g to 1600 m2/g. In an exemplary embodiment, the activated carbon has a surface area 1200 m2/g.

In accordance with an embodiment of the present disclosure, the bulk density of the activated carbon is in the range of 300 kgs /m3 to 450 kgs/m3. In an exemplary embodiment, the activated carbon has a bulk density 400 kgs/ m3.

In accordance with an embodiment of the present disclosure, Na2O and other metallic impurities in the activated carbon are <0.02 wt.%. In an exemplary embodiment, the activated carbon has other metallic impurities <0.01%.

In accordance with an embodiment of the present disclosure, the crushing strength of the activated carbon is in the range of 1.5 kgf to 6 kgf. In an exemplary embodiment, the activated carbon has the crushing strength is 3 kgf.

In accordance with an embodiment of the present disclosure, the attrition loss of the activated carbon is less than 0.1%. In an exemplary embodiment, the activated carbon has the attrition loss of 0.05%.
In accordance with an embodiment of the present disclosure, the activated carbon is in the cylindrical form and has a diameter in the range of 0.8 mm to 3 mm and a length in the range of 0.5 cm to 2 cm.
In accordance with an embodiment of the present disclosure, the activated carbon is in the form of granules and has a particle size in the range of 1 mm to 3 mm.
In accordance with the present disclosure, the moisture content in the treated DSO is reduced by 40% to 50%.
In accordance with the present disclosure, the color of DSO after treatment with the activated carbon is changed to clear transparent from the yellow colored DSO.
The process of the present disclosure is efficient, simple and economic.
The foregoing description of the embodiments has been provided for purposes of illustration and is not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.
The present disclosure is further described in light of the following experiments which are set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure. The following experiments can be scaled up to industrial/commercial scale and the results obtained can be extrapolated to industrial scale.
EXPERIMENTAL DETAILS
Example 1: Equilibrium studies for screening of activated carbon (adsorbent)
Equilibrium experiments were carried out by using activated carbon (adsorbent) having a surface area in the range of 1000 m2/g to 1600 m2/g. 1g of the activated carbon was pre-heated at 120°C for 4 h and was taken in 30 mL bottle. 5 g disulfide oil (DSO) which contains 5 ppm sodium was added to the bottle containing the activated carbon. Cap of the bottle was closed and stirred manually for 5 minutes to 10 minutes. Then the bottle containing the activated carbon (adsorbent) and DSO was kept at a room temperature for 14 hours. After 14 hours, the treated DSO was separated from the activated carbon (adsorbent) and the separated treated DSO was analyzed for sodium content by inductively coupled plasma mass spectrometry (ICP-MS). The treated DSO was found to have sodium content of 0.23 ppm.
Example 2: Process for removal of sodium from di-sulfide oil, in accordance with the present disclosure
10 g extrudates of activated carbon (3 mm diameter and 0.5 to 1 cm length of extrudates) were charged in a continuous flow glass reactor of 2 cm diameter. DSO containing 5 ppm sodium was fed to the reactor at 26 mL/h flowrate (LHSV = 0.83 h-1). The treated DSO was collected at every 1hour interval for sodium analysis by ICP-MS. The sodium content in the treated DSO was observed in the range of 0.15 to 0.25 ppm in 6 hours of run. The moisture in DSO feed was measured in the range of 800 ppm to 1200 ppm which reduced to 350 ppm to 500 ppm after treatment with the activated carbon (adsorbent). The color of DSO after treatment with the activated carbon changed to clear transparent (no color) from yellow/pale yellow colored DSO as feed.
The carbon extrudates of 0.8 mm and 2 mm diameter also showed sodium in treated DSO in the range of 0.15 ppm to 0.25 ppm with clear transparent color of the treated DSO.
Examples 3-8: Process for removal of sodium from di-sulfide oil, in accordance with the present disclosure
The same experimental procedure was followed as described in example 2 except that the amount of sodium in the feed and the flow rate (LHSV) of the untreated DSO was varied as indicated in Table 1.
Table 1: Sodium in feed DSO (ppm), flow rate of untreated DSO (LHSV), and sodium content in the treated DSO (ppm)
Example No Sodium in Feed DSO (ppm) LHSV (h-1)
Sodium content in the treated DSO (ppm)
3 5 0.22 0.14
4 5 0.31 0.2
5 5 0.42 0.22
6 5 0.83 0.25
7 5 1.66 0.95
8 15 0.83 1.01
9 30 0.83 1.74

From Table 1, it is evident that on increasing the LHSV (ratio of volumetric flow rate of the untreated DSO to adsorbent volume), sodium in the treated DSO was increased due to lower contact time between adsorbent and feed. Further, on increasing sodium concentration in the untreated DSO feed, sodium in the treated DSO also increased.
Figure 1 illustrates the removal of sodium from DSO with respect to time in a continuous flow reactor. It is observed that upto 100 hours sodium in the treated DSO was observed to be less than 0.2 ppm, which is increased in the range of 0.23 to 0.41 ppm on further increasing the run length upto around 500 hours. The increase in the sodium content in the treated DSO on increasing the run length may be attributed to the decrease in the adsorbent capacity for adsorption of sodium from DSO over the period of time.
Example 9
13.6 gm extrudates of activated carbon (3 mm diameter and 0.5 to 1 cm length of extrudates) were charged in a continuous flow glass reactor of 2.94 cm diameter. DSO containing 5 ppm sodium was fed to the reactor at 13 mL/h flowrate (LHSV = 0.31 h-1). The treated DSO was collected at every 1 hour’s interval for sodium analysis by ICP-MS. Initially 0.16 to 0.25 ppm sodium was observed in the treated DSO upto 150 hours which subsequently increased to the range of 0.3 to 0.52 ppm in 475 hours time on stream run. On increasing the run length (hours on stream), the available sites for the adsorption of sodium in the adsorbent decrease. The moisture in DSO feed was measured in the range of 800 ppm to 1200 ppm which reduced to 350 ppm to 500 ppm after treatment with the activated carbon. The color of the DSO after treatment with the activated carbon changed to clear transparent (no color) from yellow/pale yellow colored DSO as feed.
Comparative Example: Process for removal of sodium from di-sulfide oil by using the commercial alumina adsorbent
For comparison of the data, removal of sodium was also carried out by using commercial alumina as a reference adsorbent under similar experimental conditions as given in Example 9. Sodium content in the treated DSO was obtained in the range of 0.2 to 0.9 ppm using commercial alumina adsorbent, 5 ppm sodium in feed DSO, with the LHSV being 0.31 h-1.
Comparative data for the sodium in the treated DSO by using commercial alumina adsorbent and activated carbon is shown in Figure 2. Alumina based adsorbent showed higher sodium content in the treated DSO than the sodium content when treated with activated carbon under similar adsorption conditions. The sodium in the treated DSO was observed to increase from 0.2 to 0.9 ppm on increasing the run time to 475 hours by using alumina based adsorbent, whereas, the activated carbon showed 0.16 to 0.52 ppm sodium in the treated DSO. This data confirmed the activated carbon of the present disclosure has higher sodium removal capacity than that of the commercial alumina adsorbent. The color of DSO after treatment with the activated carbon changed to clear transparent as compared to pale yellow color of treated DSO using commercial alumina adsorbent.

TECHNICAL ADVANCEMENTS
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of a process for removal of sodium from di-sulfide oil, obtaining treated di-sulfide oil that:
is simple and economical;
is environment-friendly;
yields clear transparent color of treated DSO
reduces sodium level below 0.5 ppm; and
has the potential to replace imported dimethyl disulphide (DMDS) for a steam cracker and a hydrotreater application.

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 example only, and are not intended to limit the scope of the inventions. Variations or modifications to the formulation 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. , Claims:WE CLAIM:

1. A process for removal of sodium from di-sulfide oil for obtaining a treated di-sulfide oil having sodium content below 0.5 ppm, said process comprising passing a stream of di-sulfide oil having sodium content in the range of 5 ppm to 10 ppm through an activated carbon bed packed in a column, at a liquid hourly space velocity (LHSV) ranging from 0.2h-1 to 6 h-1 at a predetermined temperature for a predetermined time period and at a predetermined pressure to obtain the treated di-sulfide oil stream having sodium content below 0.5 ppm.
2. The process as claimed in claim 1, wherein said liquid hourly space velocity (LHSV) is in the range of 0.2 h-1 to 4 h-1.
3. The process as claimed in claim 1, wherein said liquid hourly space velocity (LHSV) is in the range of 0.3 h-1 to 2 h-1.
4. The process as claimed in claim 1, wherein said pre-determined temperature is in the range of 20ºC to 40ºC.
5. The process as claimed in claim 1, wherein said pre-determined temperature is in the range of 25 ºC to 35 ºC.
6. The process as claimed in claim 1, wherein said pre-determined time period is in the range of 5 hrs to 500 hrs.
7. The process as claimed in claim 1, wherein said predetermined pressure is in the range of 1 atmosphere to 4 atmospheres.
8. The process as claimed in claim 1, wherein said treated stream of di-sulfide oil is having sodium level in the range of 0.1 ppm to 0.5 ppm.
9. The process as claimed in claim 1, wherein said treated stream of di-sulfide oil is having sodium content in the range of 0.1 ppm to 0.3 ppm.
10. The process as claimed in claim 1, wherein said treated stream of di-sulfide oil is having sodium content in the range of 0.1 ppm to 0.2 ppm.
11. The process as claimed in claim 1, wherein an activated carbon of the activated carbon bed is in the form of extrudates, cylindrical, spheres, granules, and a combination thereof.
12. The process as claimed in claim 11, wherein the activated carbon is having a surface area in the range of 1000 m2/g to 1600 m2/g;
13. The process as claimed in claim 11, wherein the activated carbon has a bulk density in the range of 300 kgs/ m3 to 450 kgs/m3.
14. The process as claimed in claim 11, wherein the activated carbon is having Na2O and other metallic impurities less than 0.02 wt%.
15. The process as claimed in claim 11, wherein the activated carbon has a crushing strength in the range of 1.5 kgf to 6 kgf.
16. The process as claimed in claim 11, wherein the activated carbon has an attrition loss less than 0.1%.
17. The process as claimed in claim 1, wherein said treated disulfide stream is transparent.

Dated this 28th day of December, 2023

_______________________________
MOHAN RAJKUMAR DEWAN, IN/PA – 25
of R.K.DEWAN & CO.
Authorized Agent of Applicant

TO,
THE CONTROLLER OF PATENTS
THE PATENT OFFICE, AT MUMBAI