Title of Invention	''A CONTINUOUS PROCESS FOR PRODUCING LOW THIOPHENE CONTENT BENZENE''
Abstract	A continuous process for producing low thiophene content benzene from crude BTX (Benzol), characterised in that crude BTX (Benzol) of composition, such as herein described, is pumped by pump (3) into ball mixers (4) of the modified acid washing system, such as herein described, along with sulphuric acid of 95-98% concentration, injected by acid dozing pump (2) in the pipe line (1) at position (A) in 2.3% V/V of BTX and from mixers (4) partly into reaction vessel (5) at position (B) of pipe line (la) and partly directly through pipe line (la), the output of reaction vessel (5) being mixed with the directly pumped acidic BTX at position (C) of pipe line (la), and then into acid settling tank (6) for separation of acidic BTX from spent acid and sludge decanted at the bottom thereof, which is removed to tank (13) by gravity via pipe line (lb), the acidic BTX containing 40-70 ppm thiophene being transferred from the top thereof into BTX cooler cum buffer tank (7) by gravity via pipe line (1c) and pumped from tank (7) to ball mixers (10) by BTX pump (9) via pipe line (1d) into which 2.3% V/V of said acid is injected at position (G) thereof by pump (8) and then into acid settling tank (12), partly directly through pipe line (1g) and partly via reaction vessel (11) through positions (D and E) of pipe line (1g), the spent acid and sludge decanted at the bottom of tank (12) being allowed to flow into tank (13) by gravity and acidic BTX containing less than 5 ppm thiophene being allowed to flow by gravity into ball mixers (14) via pipe line (1k) into which the required quantity of an alkali solution containing 15% by weight of sodium hydroxide in water, in 5% V/V of BTX, is injected at position (F) thereof and then from ball mixers (14) into alkali settling tank (15) from which completely acid neutralised or partly alkaline BTX is transferred to known fractional distillation plant (16) for collecting benzene of thiophene content less than 5 ppm in tank (17).

Title of Invention

''A CONTINUOUS PROCESS FOR PRODUCING LOW THIOPHENE CONTENT BENZENE''

Abstract

A continuous process for producing low thiophene content benzene from crude BTX (Benzol), characterised in that crude BTX (Benzol) of composition, such as herein described, is pumped by pump (3) into ball mixers (4) of the modified acid washing system, such as herein described, along with sulphuric acid of 95-98% concentration, injected by acid dozing pump (2) in the pipe line (1) at position (A) in 2.3% V/V of BTX and from mixers (4) partly into reaction vessel (5) at position (B) of pipe line (la) and partly directly through pipe line (la), the output of reaction vessel (5) being mixed with the directly pumped acidic BTX at position (C) of pipe line (la), and then into acid settling tank (6) for separation of acidic BTX from spent acid and sludge decanted at the bottom thereof, which is removed to tank (13) by gravity via pipe line (lb), the acidic BTX containing 40-70 ppm thiophene being transferred from the top thereof into BTX cooler cum buffer tank (7) by gravity via pipe line (1c) and pumped from tank (7) to ball mixers (10) by BTX pump (9) via pipe line (1d) into which 2.3% V/V of said acid is injected at position (G) thereof by pump (8) and then into acid settling tank (12), partly directly through pipe line (1g) and partly via reaction vessel (11) through positions (D and E) of pipe line (1g), the spent acid and sludge decanted at the bottom of tank (12) being allowed to flow into tank (13) by gravity and acidic BTX containing less than 5 ppm thiophene being allowed to flow by gravity into ball mixers (14) via pipe line (1k) into which the required quantity of an alkali solution containing 15% by weight of sodium hydroxide in water, in 5% V/V of BTX, is injected at position (F) thereof and then from ball mixers (14) into alkali settling tank (15) from which completely acid neutralised or partly alkaline BTX is transferred to known fractional distillation plant (16) for collecting benzene of thiophene content less than 5 ppm in tank (17).

Full Text	The present invention relates to a continuous process for producing low thiophene content benzene. The invention relates more particularly to a process for producing benzene containing less than 5 ppm thiophene from crude BTX (BENZOL) containing 2000 to 4000 ppm thiophene using a modified continuous acid washing system by injecting sulphuric acid of 95-98% concentration in the pipe line carrying BTX, separating the spent acid and the polymer sludge formed by reaction of acid and BTX, injecting alkali solution to the acid treated BTX for completely acid neutralising the BTX or making the same slightly alkaline, separating the spent alkali from BTX and recovering benzene from acid and alkali-treated BTX of thiophene content less than 5 ppm» by known fractional distillation process. In the prior art process, BTX is treated with acid and alkali in batches instead of using any continuous.acid, washing system. The benzene recovered in the prior art process contains a relatively high proportion of thiophene i.e. around 40-70 ppm. Additional plants for hydrorefining and extractive distillation1 (HRED) are required to be set up for lowering the thiophene content of the benzene produced in the prior art process to a level below 5 ppm. Obviously, the prior art process is relatively slow and involves the setting up of additional HRED plants, and is hence relatively expensive. The object of the present invention is to provide a continuous process for producing benzene of thiophene content less than 5 ppm, using a modified continuous acid washing system from crude BTX containing 2000 to 4000 ppm thiophene. In the invented process, the existing continuous acid washing system has been modified suitably for obtaining BTX of thiophene content below 5 ppm directly i.e. without using any additional HRED plants from crude BTX of thiophene content 2000 to 4000 ppm. Thus the present invention provides a continuous process for producing low thiophene content benzene from crude BTX (Benzol), characterised in that crude BTX (Benzol) of composition, such as herein described, is pumped by pump into ball mixers of the modified acid washing system, such as herein described, along with sulphuric acid of 95-98% concentration, injected by acid dozing pump in the pipe line at position in 2.3% V/V of BTX and from mixers partly into reaction vessel at position of pipe line and partly directly through pipe line, the output of reaction vessel being mixed with the directly pumped acidic BTX at position of pipe line, and then into acid settling tank for separation of acidic BTX from spent acid and sludge decanted at the bottom thereof, which is removed to tank by gravity via pipe line, the acidic BTX containing 40-70 ppm thiophene being transferred from the top thereof into BTX cooler cum buffer tank by gravity via pipe line and pumped from tank to ball mixers by BTX pump via pipe line into which 2.3% V/V of said acid is injected at position thereof by pump and then into acid settling tank, partly directly through pipe line and partly via reaction vessel through positions of pipe line, the spent aoid and sludge decanted at the bottom of tank being allowed to flow into tank by gravity and acidic BTX containing less than 5 ppm thiophene being allowed to flow by gravity into ball mixers via pipe line into which the required quantity of an alkali solution containing 1596 by weight of sodium hydroxide in water, in 5% V/V of BTX, is injected at position thereof and then from ball mixers into alkali settling tank from which completely acid neutralised or partly alkaline BTX is transferred to known fractional distillation plant for collecting benzene of thiophene content less than 5 ppm in tank. The invention is described fully and particularly in an unrestricted manner with reference to the accompanying drawings in which - Figure 1 is a flow diagram of the invented process showing the various steps followed and accessories of the modified acid washing system used in the process. Referring to Fig. 1, crude BTX from which carbon-di-sulphide has been removed by distillation is pumped by means of BTX pump (3) through a-pipe line (1) into which concentrated sulphuric acid of concentration 95-98$ is injected at position (A) in a preferred amount of 2.3% V/V of BTX by means of an acid dozing pump (2). The composition of the crude BTX is given in Table I. The crude BTX is mixed with the injected acid thoroughly by means of ball mixers (4) and a part of the mix is diverted at position (B) into reaction vessel (5) to allow chemical reactions to take place therein between acid and BTX causing (a) polymerisation of unsaturated compounds, (b) copolymerisation of unsaturated compounds with thiophene, (c) additive reaction of sulphuric acid with unsaturated compounds, (d) sulphonation of thiophene, (e) sulphonation of aromatic hydrocarbons, (f) dissolution or oxidation of sulphur compounds and (g) formation of sulphates by nitrogen bases. On completion of chemical reactions, the product of reactions is transferred to pipe line da) from contact vessel (5) at position (C). The combined mix of acidic BTX and acid-reacted BTX is pumped into acid settling tank (6) wherein the spent acid and sludge are separated from acidic BTX by decantation because of the difference in their specific gravities. The thiophene content of the acidic BTX reduces from its initial level of 2000 to 4000 ppm to 40 to 70 ppm in acid settling tank (6). The spent acid and sludge are allowed to flow by gravity from the bottom of acid settling tank (6) to tank (13), and the acidic BTX containing 40 to 70 ppm thiophene is allowed to flow by gravity via line 1c from the top of acid settling tank (6) to BTX cooler cum buffer tank (7) which is introduced in the modified acid washing system in place of the plate heat exchanger used in the existing acid washing system. The BTX cooler cum buffer tank (7) has three cooling sections, each section being provided with its separate cooling arrangement by circulating industrial water through a heat exchanger consisting of a bunch of heat conducting tubes which can be inserted into or removed from outside. In addition, tank (7) has two perforated trays which are cut on one side thereof and suitably disposed inside the tank for providing an extended residence time for the acidic BTX inside the tank. The acidic BTX containing 40 to 70 ppm thiophene is pumped out from the bottom of tank (7) into ball mixers (10) by means of BTX pump (9) via lines (1d and 1f). A measured quantity of sulphuric acid of 95-98% concentration, typically 2.3% v/v of BTX, is injected into line (1d) by means of acid dozing pump (8) at position (G). From ball mixers (10), acidic BTX is pumped into acid settling tank (12) via line (1g). A part of the acidic BTX is diverted at position (D) into reaction vessel (11) and from there is injected into line (ig) at position {(E). The spent acid and sludge separated by decantation at the bottom of tank (12) is allowed to flow by gravity into tank (13) and acidic BTX containing less than 5 ppm thiophene is allowed to flow by gravity into ball mixers (14) from the top of tank (12). An alkali solution, preferably 15% by weight of NaOH in water, is injected into the pipe line (1k) at position (F) in preferred amount of 5%v/v of BTX for either completely neutralising the acidic BTX or making the acidic BTX slightly alkaline. The alkali treated BTX is allowed to flow by gravity from mixers (14) into alkali settling tank (15) in which the spent alkali and BTX are separated by decantation owing to the difference in their specific gravities. Completely acid neutralised or slightly alkaline BTX containing less than 5 ppm thiophene is allowed to flow out from tank (15) to the known fractional distillation plant (16) through pipe line (1n) . Benzene of thiophene content less than 5 ppm obtained from plant (16) is collected in tank (17) via line dp). The modification incorporated in the existing acid washing system comprises the use of accessories (i) BTX cooler cum buffer tank (7), (ii) acid dozing pump (8), (iii) BTX pump (9), (iv) ball mixers (10), (v) reaction vessel (11), (vi) acid settling tank (12) and (vii) pipe lines (1c, 1d, 1e, 1f, 1g, 1h), as enclosed by dashed line in Fig. 1. The particulars of the abovementioned accessories are presented in Table II. Benzene produced in the invented process has been found to be of low thiophene content i.e. below 5 ppm, and of quality on par with petro-benzene and benzene of international standard quality. Table - I Composition of Crude BTX (BENZOL) (Table Removed) Table II Particulars of the Accessories used in the Modified Acid Washing System (Table Removed) Table II (continued) (Table Removed) We Claim :- 1. A continuous process for producing low thiophene content benzene from crude BTX (Benzol), characterised in that crude BTX (Benzol) of composition, such as herein described, is pumped by pump (3) into ball mixers (4) of the modified acid washing system, such as herein described, along with sulphuric acid of 95-9896 concentration, injected by acid dozing pump (2) in the pipe line (1) at position (A) in 2.3% V/V of BTX and from mixers (4) partly into reaction vessel (5) at position (B) of pipe line (la) and partly directly through pipe line (la), the output of reaction vessel (5) being mixed with the directly pumped acidic BTX at position (C) of pipe line (la), and then into acid settling tank (6) for separation of acidic BTX from spent acid and sludge decanted at the bottom thereof, which is removed to tank (13) by gravity via pipe line (1b), the acidic BTX containing 40-70 ppm thiophene being transferred from the top thereof into BTX cooler cum buffer tank (7) by gravity via pipe line (1c) and pumped from tank (7) to ball mixers (10) by BTX pump (9) via pipe line (1d) into which 2.396 V/V of said acid is injected at position (G) thereof by pump (8) and then into acid settling tank (12), partly directly through pipe line (1g) and partly via reaction vessel (11) through positions (D and E) of pipe line (1g), the spent acid and sludge decanted at the bottom of tank (12) being allowed to flow into tank (13) by gravity and acidic BTX containing less than 5 ppm thiophene being allowed to flow by gravity into ball mixers (14) via pipe line (1k) into which the required quantity of an alkali solution containing 15% by weight of sodium hydroxide in water, in 5% V/V of BTX,is injected at position (F) thereof and then from ball mixers (14) into alkali settling tank (15) from which completely acid neutralised or partly alkaline BTX is transferred to known fractional distillation plant (16) for collecting benzene of thiophene content less than 5 ppm in tank (17). 2. The process as claimed in claim 1, wherein the composition of the crude BTX (Benzol) (by weight %) is : Benzene - 65 to 80, toluene - 10 to 16, xylene - 1 to 4, solvents (heavier than xylene) - 4 to 7, thiophene - 0.2 to 0.4, and hydro-carbons - 1 to 2. 3. A continuous process for producing low thiophene content benzene, such as herein described and illustrated in the accompanying drawings.

Full Text

The present invention relates to a continuous process for producing low thiophene content benzene.
The invention relates more particularly to a process for producing benzene containing less than 5 ppm thiophene from crude BTX (BENZOL) containing 2000 to 4000 ppm thiophene using a modified continuous acid washing system by injecting sulphuric acid of 95-98% concentration in the pipe line carrying BTX, separating the spent acid and the polymer sludge formed by reaction of acid and BTX, injecting alkali solution to the acid treated BTX for completely acid neutralising the BTX or making the same slightly alkaline, separating the spent alkali from BTX and recovering benzene from acid and alkali-treated BTX of thiophene content less than 5 ppm» by known fractional distillation process.
In the prior art process, BTX is treated with acid

and alkali in batches instead of using any continuous.acid, washing system. The benzene recovered in the prior art process contains a relatively high proportion of thiophene i.e. around 40-70 ppm. Additional plants for hydrorefining and extractive distillation1 (HRED) are required to be set up for lowering the thiophene content of the benzene produced in the prior art process to a level below 5 ppm. Obviously, the prior art process is relatively slow and involves the setting up of additional HRED plants, and is hence relatively expensive.

The object of the present invention is to provide a continuous process for producing benzene of thiophene content less than 5 ppm, using a modified continuous acid washing system from crude BTX containing 2000 to 4000 ppm thiophene.
In the invented process, the existing continuous acid washing system has been modified suitably for obtaining BTX of thiophene content below 5 ppm directly i.e. without using any additional HRED plants from crude BTX of thiophene content 2000 to 4000 ppm.
Thus the present invention provides a continuous process
for producing low thiophene content benzene from crude BTX (Benzol),
characterised in that crude BTX (Benzol) of composition, such as
herein described, is pumped by pump into ball mixers of the
modified acid washing system, such as herein described, along with
sulphuric acid of 95-98% concentration, injected by acid dozing
pump in the pipe line at position in 2.3% V/V of BTX and from
mixers partly into reaction vessel at position of pipe line and partly directly through pipe line, the output of reaction vessel being mixed with the directly pumped acidic BTX at position of pipe line, and then into acid settling tank for separation of acidic BTX from spent acid and sludge decanted at the bottom thereof, which is removed to tank by gravity via pipe line, the acidic BTX containing 40-70 ppm thiophene being transferred from the top thereof into BTX cooler cum buffer tank by gravity via pipe line and pumped from tank to ball mixers by BTX pump via pipe line into which 2.3% V/V of said acid is injected at position thereof by pump and then into acid settling tank, partly directly through pipe line and partly via reaction vessel through positions

of pipe line, the spent aoid and sludge decanted at the bottom of tank being allowed to flow into tank by gravity and acidic BTX containing less than 5 ppm thiophene being allowed to flow by gravity into ball mixers via pipe line into which the required quantity of an alkali solution containing 1596 by weight of sodium hydroxide in water, in 5% V/V of BTX, is injected at position thereof and then from ball mixers into alkali settling tank from which completely acid neutralised or partly alkaline BTX is transferred to known fractional distillation plant for collecting benzene of thiophene content less than 5 ppm in tank.
The invention is described fully and particularly in an unrestricted manner with reference to the accompanying drawings in which -
Figure 1 is a flow diagram of the invented process showing the various steps followed and accessories of the modified acid washing system used in the process.
Referring to Fig. 1, crude BTX from which carbon-di-sulphide has been removed by distillation is pumped by means of BTX pump (3) through a-pipe line (1) into which concentrated sulphuric acid of concentration 95-98$ is injected at position (A) in a preferred amount of 2.3% V/V of BTX by means of an acid dozing pump (2). The composition of the crude BTX is given in Table I. The crude BTX is mixed with the injected acid thoroughly by means of ball mixers (4) and a part of the mix is diverted at position (B) into reaction vessel (5) to

allow chemical reactions to take place therein between acid and BTX causing (a) polymerisation of unsaturated compounds,
(b) copolymerisation of unsaturated compounds with thiophene,
(c) additive reaction of sulphuric acid with unsaturated
compounds, (d) sulphonation of thiophene, (e) sulphonation of
aromatic hydrocarbons, (f) dissolution or oxidation of sulphur
compounds and (g) formation of sulphates by nitrogen bases.
On completion of chemical reactions, the product of reactions is transferred to pipe line da) from contact vessel (5) at position (C). The combined mix of acidic BTX and acid-reacted BTX is pumped into acid settling tank (6) wherein the spent acid and sludge are separated from acidic BTX by decantation because of the difference in their specific gravities. The thiophene content of the acidic BTX reduces from its initial level of 2000 to 4000 ppm to 40 to 70 ppm in acid settling tank (6). The spent acid and sludge are allowed to flow by gravity from the bottom of acid settling tank (6) to tank (13), and the acidic BTX containing 40 to 70 ppm thiophene is allowed to flow by gravity via line 1c from the top of acid settling tank (6) to BTX cooler cum buffer tank (7) which is introduced in the modified acid washing system in place of the plate heat exchanger used in the existing acid washing system. The BTX cooler cum buffer tank (7) has three cooling sections, each section being provided with its separate cooling arrangement by circulating industrial water through a heat exchanger consisting of a bunch of heat conducting tubes which can be inserted into or removed from outside. In addition, tank (7)

has two perforated trays which are cut on one side thereof and suitably disposed inside the tank for providing an extended residence time for the acidic BTX inside the tank.
The acidic BTX containing 40 to 70 ppm thiophene is pumped out from the bottom of tank (7) into ball mixers (10) by means of BTX pump (9) via lines (1d and 1f). A measured quantity of sulphuric acid of 95-98% concentration, typically 2.3% v/v of BTX, is injected into line (1d) by means of acid dozing pump (8) at position (G). From ball mixers (10), acidic BTX is pumped into acid settling tank (12) via line (1g). A part of the acidic BTX is diverted at position (D) into reaction vessel (11) and from there is injected into line (ig) at position {(E).
The spent acid and sludge separated by decantation at the bottom of tank (12) is allowed to flow by gravity into tank (13) and acidic BTX containing less than 5 ppm thiophene is allowed to flow by gravity into ball mixers (14) from the top of tank (12). An alkali solution, preferably 15% by weight of NaOH in water, is injected into the pipe line (1k) at position (F) in preferred amount of 5%v/v of BTX for either completely neutralising the acidic BTX or making the acidic BTX slightly alkaline. The alkali treated BTX is allowed to flow by gravity from mixers (14) into alkali settling tank (15) in which the spent alkali and BTX are separated by decantation owing to the difference in their specific gravities. Completely acid neutralised or slightly alkaline BTX containing less than 5 ppm thiophene is allowed

to flow out from tank (15) to the known fractional distillation plant (16) through pipe line (1n) . Benzene of thiophene content less than 5 ppm obtained from plant (16) is collected in tank (17) via line dp).
The modification incorporated in the existing acid washing system comprises the use of accessories (i) BTX cooler cum buffer tank (7), (ii) acid dozing pump (8), (iii) BTX pump (9), (iv) ball mixers (10), (v) reaction vessel (11), (vi) acid settling tank (12) and (vii) pipe lines (1c, 1d, 1e, 1f, 1g, 1h), as enclosed by dashed line in Fig. 1. The particulars of the abovementioned accessories are presented in Table II.
Benzene produced in the invented process has been found to be of low thiophene content i.e. below 5 ppm, and of quality on par with petro-benzene and benzene of international standard quality.

Table - I Composition of Crude BTX (BENZOL)

(Table Removed)

Table II
Particulars of the Accessories used in the Modified
Acid Washing System
(Table Removed)

Table II (continued)

(Table Removed)

We Claim :-
1. A continuous process for producing low thiophene content benzene from crude BTX (Benzol), characterised in that crude BTX (Benzol) of composition, such as herein described, is pumped by pump (3) into ball mixers (4) of the modified acid washing system, such as herein described, along with sulphuric acid of 95-9896 concentration, injected by acid dozing pump (2) in the pipe line (1) at position (A) in 2.3% V/V of BTX and from mixers (4) partly into reaction vessel (5) at position (B) of pipe line (la) and partly directly through pipe line (la), the output of reaction vessel (5) being mixed with the directly pumped acidic BTX at position (C) of pipe line (la), and then into acid settling tank (6) for separation of acidic BTX from spent acid and sludge decanted at the bottom thereof, which is removed to tank (13) by gravity via pipe line (1b), the acidic BTX containing 40-70 ppm thiophene being transferred from the top thereof into BTX cooler cum buffer tank (7) by gravity via pipe line (1c) and pumped from tank (7) to ball mixers (10) by BTX pump (9) via pipe line (1d) into which 2.396 V/V of said acid is injected at position (G) thereof by pump (8) and then into acid settling tank (12), partly directly through pipe line (1g) and partly via reaction vessel (11) through positions (D and E) of pipe line (1g), the spent acid and sludge decanted at the bottom of tank (12) being allowed to flow into tank (13) by gravity and acidic BTX containing less than 5 ppm thiophene being allowed to flow by gravity into ball mixers (14) via pipe line (1k) into which the required quantity of an alkali solution containing 15%

by weight of sodium hydroxide in water, in 5% V/V of BTX,is injected at position (F) thereof and then from ball mixers (14) into alkali settling tank (15) from which completely acid neutralised or partly alkaline BTX is transferred to known fractional distillation plant (16) for collecting benzene of thiophene content less than 5 ppm in tank (17).
2. The process as claimed in claim 1, wherein the
composition of the crude BTX (Benzol) (by weight %) is :
Benzene - 65 to 80, toluene - 10 to 16, xylene - 1 to 4, solvents
(heavier than xylene) - 4 to 7, thiophene - 0.2 to 0.4, and
hydro-carbons - 1 to 2.
3. A continuous process for producing low thiophene
content benzene, such as herein described and
illustrated in the accompanying drawings.

Documents:

3800-del-1997-abstract.pdf

3800-del-1997-claims.pdf

3800-del-1997-correspondence-others.pdf

3800-del-1997-correspondence-po.pdf

3800-del-1997-description (complete).pdf

3800-del-1997-drawings.pdf

3800-del-1997-form-1.pdf

3800-del-1997-form-19.pdf

3800-del-1997-form-2.pdf

3800-del-1997-form-4.pdf

3800-del-1997-gpa.pdf

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Patent Number

232037

Indian Patent Application Number

3800/DEL/1997

PG Journal Number

13/2009

Publication Date

27-Mar-2009

Grant Date

15-Mar-2009

Date of Filing

29-Dec-1997

Name of Patentee

STEEL AUTHORITY OF INDIA LIMITED,

Applicant Address

ISPAT BHAWAN, LODHI ROAD, NEW DELHI-110 003

Inventors:

#	Inventor's Name	Inventor's Address
1	JAYANTI VENKATA SITARAMA MURTY	RDCIS, SAIL, RANCHI-834002
2	HARSHARAJ KRISHNARAO CHATI	RDCIS, SAIL, RANCH-834002

PCT International Classification Number

C07C 143/20

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA