Title of Invention

"AN IMPROVED PROCESS FOR THE PREPARATION OF NITRO BENZENE"

Abstract The present invention relates to an improved process for preparation of nitrobenzene. More particularly it relates to vapor phase nitration of benzene using dilute nitric acid over beta zeolite catalyst. By the process of present invention nitrobenzene has been prepared in high yield in a continuous process without any byproduct formation making it an environmentally friendly process.
Full Text The present invention relates to an improved process for preparation of nitrobenzene. More particularly it relates to vapor phase nitration of benzene using dilute nitric acid over beta zeolite catalyst. By the process of present invention nitrobenzene has been prepared in high yield in a continuous process without any byproduct formation making it an environmentally friendly process.
Major part of nitrobenzene (95% or more) produced is converted to aniline, which has hundreds of downstream products. Nitrobenzene also is used as a processing solvent in specific chemical reactions. Conventionally nitrobenzene is produced by liquid phase reactions employing mixed acids (Ullmann's Encyclopedia of Industrial Chemistry, 5th edn. Vol.A17, 1991, pp. 415-418). A sulfuric acid/nitric acid mixture is the most commonly used nitrating agent. Generation of large amount of dilute sulfuric acid, organic wastes and products of their neutralization makes the benzene nitration one of the most environmentally harmful processes.
Vapor-phase nitration of benzene to nitrobenzene over zeolite is expected to be a clean process without sulfuric acid waste. A number of heterogeneous catalysts have been proposed for this process.
In the prior art, vapor phase nitration of aromatic compounds, benzene and toluene at temperature ranging from about 275° C to about 310° C is described in McKee and Wilhelm, Industrial and Engineering Chemistry, 28 (6), 662-667 (1936) and U.S. Pat. No. 2,109,873. McKee and Wilhelm catalyzed their reaction with silica gel. Bauxite and alumina were reported to be ineffective as catalyst in the vapor phase nitration of benzene. US. Patent No. 2,431.585 describes vapor phase nitration of aromatic hydrocarbons at temperature from 1300C to 4300C, using metal metalphosphates of calcium, iron, magnesium and solid supported phosphoric acid catalysts.
U.S. patent 4551568 describes the vapor phase nitration of benzene over solid mixed oxide catalyst comprising WO3 and MO3, which exhibited a fairly high and stable activity.
U.S. Pat. No. 3,966,830, Jpn. Pat. No. 58-157748, and U.S. Pat. No. 4, 426, 543 describe the nitration of aromatics using zeolite catalysts. The lower conversion of benzene to nitrobenzene and faster deactivation of zeolite catalysts are the drawbacks of these processes for commercial application.
US patent 5030776 describes a process for nitrating benzene using nitric acid as a nitrating agent under continuous or intermittent feeding of sulfuric acid as a catalyst on a solid carrier. Vapor phase nitration of benzene has been claimed in US patent 5.004,846 wherein nitric acid is used as a nitrating agent and a composite oxide or acidic sheet clay mineral ion exchanged with polyvalent metal as a catalyst.
International patent WO 96/36587 describes a solvent free process for the nitration of aromatic compounds in which the aromatic compound is reacted with nitric acid in presence of an acid anhydride wherein the process is catalyzed by an aluminosilicate catalyst. Nitric acid and acid anhydride react with each other in-situ to form acyl nitrate and this acts as a nitrating agent for aromatic compounds. For example benzene, naphthalene, anthracene, toluene etc. are nitrated to mononitrated compounds. A mixture of orth-meta-para nitrotoluenes is obtained which is then distilled at a pressure of 30 mmHg and a temperature of 300C to remove acetic acid as a byproduct.
These prior art processes for the vapor phase nitration of aromatic hydrocarbons for the preparation of aromatic nitro compounds have the limitations of low conversions low space time yield, low yield, short catalyst life, contamination of the nitrated aromatic hydrocarbon products by undesirable by-products and the
complicated nature of catalysts.
The object of the present invention is to provide a process for the preparation of nitrobenzene in high yield.
Another object is to provide a process high selectivity by vapor phase nitration of benzene using dilute nitric acid and over zeolite catalyst.
Accordingly, the present invention provides an improved process for the
preparation of nitrobenzene which comprises contacting the feed of benzene vapours
and vapours of dilute nitric acid having concentration ranging between 10 to 70%,
characterized in that the molar ratio of nitric acid to benzene ranges between 4:1 to
1:4 over beta zeolite catalyst in an inert atmosphere of nitrogen at a temperature
ranging between 100 to 300°C, at a weight hourly space velocity ranging between 0.1
to 2.0 for a period of at least 4 hours and collecting the desired nitrobenzene in a
receiver maintained at a temperature 0-5°C.
In an embodiment of the present invention the concentration of nitric acid used is 10
to 70%, preferably 20 to 30% nitric acid.
In yet another embodiment the molar ratio of nitric acid to benzene is preferably in
the range of 2:1 -1:2.
In yet another embodiment the reaction temperature used is preferably in the range of 150 to 300°C.
In still another embodiment the Weight hourly space velocity used is preferably
ranging in between 0.1 to 1.
The present invention is described herein below with reference to the examples, which are illustrative only and should not be construed to restrict the scope of the present invention, in any manner.
EXAMPLE 1
Commercially available extrudates of beta zeolite (Si/Al = 30) was procured from United Catalyst India Ltd. 10 g of extrudated zeolite was loaded in tubular glass reactor of 15mm diameter and 25 mm length. The upper part of the reactor is packed with inert ceramic beads as preheating zone.
Feeding vapors of Benzene and vapors of dilute nitric acid over H-beta catalyst carries out nitration. Reaction conditions were as follows. Reaction temperature = 200° C Carrier gas = N2
Benzene/HNO3 = 1.3:1 (molar ratio) WHSV =0.1
The product was condensed at 5° C and collected in a receiver. The product was analyzed by gas chromatography. Results after 25 hours from begiiming of reaction are shown below. No deactivation of the catalyst was seen when the reaction was carried out for 300 hours.
Conversion of benzene (%) 85.56
Yield for nitrobenzene (%) 85.42
Selectivity of nitrobenzene (%) 99.84
EXAMPLE 2
Commercially available beta zeolite (non-formulated) was procured from United Catalyst India Ltd. The catalyst was compacted in the form of pellet and further granulated to -10 + 20 mesh size for using in nitration reaction. 10 g of granulated catalyst was loaded in tubular glass reactor of 15mm diameter and 25 mm length. The upper part of the reactor is packed with inert ceramic beads as preheating zone.
Feeding vapors of Benzene and vapors of dilute nitric acid over H-beta catalyst carries out nitration. Reaction conditions were as follows. Reaction temperature = 200° C Carrier gas = N2
Benzene/HNO3 = 1.3:1 (molar ratio) WHSV =0.1
The product was condensed at 5° C and collected in a receiver. The product was analyzed by gas chromatography. Results after 25 hours from beginning of reaction are shown below.
Conversion of benzene (%) 75.6
Yield for nitrobenzene (%) 75.5
Selectivity of nitrobenzene (%) 99.8
EXAMPLE 3
This example illustrates the effects of benzene/HNO3 ratio on conversion and
selectivity of nitrobenzene. The catalyst H-beta was compacted in the form of pellet and fiirther granulated to -10 + 20 mesh size for using in nitration reaction. 10 g of
granulated catalyst was loaded in tubular glass reactor of 15mm diameter and 25 mm length. The upper part of the reactor is packed with inert ceramic beads as preheating zone.
Feeding vapors of Benzene and vapors of dilute nitric acid over H-beta catalyst carries out nitration. Reaction conditions were as follows. Reaction Temperature = 200 ° C Carrier gas = N2
Benzene/HNO3 = 1.6:1 (molar ratio) WHSV =0.17
The product was condensed at 5° C and collected in a receiver. The product was analyzed by gas chromatography. Results after 25 hours from beginning of reaction are shown below.
Conversion of benzene (%) 56.2
Yield for nitrobenzene (%) 55.75
Selectivity of nitrobenzene (%) 99.2
EXAMPLE 4
This example illustrates the effects of temperature on conversion and selectivity of
nitrobenzene. The catalyst H-beta was compacted in the form of pellet and further granulated to -10 + 20 mesh size for using in nitration reaction. 10 g of granulated catalyst was loaded in tubular glass reactor of 15 mm diameter and 25 mm length. The upper part of the reactor is packed with inert ceramic beads as preheating zone.
Feeding vapors of Benzene and vapors of dilute nitric acid over H-beta catalyst carries out nitration. Reaction conditions were as follows. Reaction temperature = 250° C Carrier gas = N2

Benzene/HNO3 = 1.3:1 (molar ratio) WHSV =0.17
The product was condensed at 5° C and collected in a receiver. The product was analyzed by gas chromatography. Results after 25 hours from beginning of reaction are shown below. No deactivation of the catalyst was seen during this period.
Conversion of benzene (%) 48.56
Yield for nitrobenzene (%) 47.8
Selectivity of nitrobenzene (%) 98.5
EXAMPLE 5
This example illustrates the effects of temperature on conversion and selectivity of
nitrobenzene. The catalyst H-beta was compacted in the form of pellet and further granulated to -10 + 20 mesh size for using in nitration reaction. 10 g of granulated catalyst was loaded in tubular glass reactor of 15 mm diameter and 25 mm length. The upper part of the reactor is packed with inert ceramic beads as preheating zone.
Feeding vapors of Benzene and vapors of dilute nitric acid over H-beta catalyst carries out nitration. Reaction conditions were as follows. Reaction Temperature = 1800 C Carrier gas = N2
Benzene/HNO3 = 1.3:1 (molar ratio) WHSV =0.17
The product was condensed at 5° C and collected in a receiver. The product was analyzed by gas chromatography. Results after 25 hours from beginning of reaction are shown below.
Conversion of benzene (%) 50.2
Yield for nitrobenzene (%) 49.7
Selectivity of nitrobenzene (%) 99.0
EXAMPLE 6
This example illustrates the effects of WHSV on conversion and selectivity of
nitrobenzene. The catalyst H-beta was compacted in the form of pellet and further granulated to -10 + 20 mesh size for using in nitration reaction. 10 g of granulated catalyst was loaded in tubular glass reactor of 15mm diameter and 25 mm length. The upper part of the reactor is packed with inert ceramic beads as preheating zone.
Feeding vapors of Benzene and vapors of dilute nitric acid over H-beta catalyst carries out nitration. Reaction conditions were as follows. Reaction temperature = 200° C Carrier gas = N2
Benzene/HNOs = 1.3:1 (molar ratio) WHSV = 0.25
The product was condensed at 5° C and collected in a receiver. The product was analyzed by gas chromatography. Results after 25 hours from beginning of reaction are shown below. No deactivation of the catalyst was seen during this period.
Conversion of benzene (%) 53.06
Yield for nitrobenzene (%) 52.75
Selectivity of nitrobenzene (%) 99.42
Advantages of the invention:
1. No use of sulfuric acid for nitration and hence no formation of dilute sulfuric acid waste which makes process environmentally friendly.
2. Use of dilute nitric acid is cost effective.
3. Higher selectivity for nitrobenzene.
4. Use of solid catalyst, which makes the process easy for operation.
5. Present process is clean compared to the conventional process.





WE CLAIM:
1. An improved process for the preparation of nitrobenzene which comprises contacting the feed of benzene vapours and vapours of dilute nitric acid having concentration ranging between 10 to 70%, characterized in that the molar ratio of nitric acid to benzene ranges between 4:1 to 1:4 over beta zeolite catalyst in an inert atmosphere of nitrogen at a temperature ranging between 100 to 300°C, at a weight hourly space velocity ranging between 0.1 to 2.0 for a period of at least 4 hours and collecting the desired nitrobenzene in a receiver maintained at a temperature 0-5°C.
2. An improved process as claimed in claim 1 wherein the concentration of nitric acid used is preferably ranging between 20 to 30% nitric acid.
3. An improved process as claimed in claims 1-2 wherein the molar ratio of nitric acid to benzene is preferably in the range of 2:1 -1:2.
4. An improved process as claimed in claims 1-3 wherein the reaction temperature used is preferably in the range of 150 to 3000C.
5. An improved process as claimed in claims 1-4 wherein the Weight hourly space velocity used is preferably ranging inbetween 0.1 to 1.
7. An improved process for the preparation of nitrobenzene substantially as
herein described with reference to examples.

Documents:

810-del-2001-abstract.pdf

810-del-2001-claims.pdf

810-del-2001-complete specification(granted).pdf

810-del-2001-correspondence-others.pdf

810-del-2001-correspondence-po.pdf

810-del-2001-description (complete).pdf

810-del-2001-form-1.pdf

810-del-2001-form-18.pdf

810-del-2001-form-2.pdf


Patent Number 242407
Indian Patent Application Number 810/DEL/2001
PG Journal Number 35/2010
Publication Date 27-Aug-2010
Grant Date 25-Aug-2010
Date of Filing 30-Jul-2001
Name of Patentee COUNCIL OF SCIENTIFIC & INDUSTRIAL RESEARCH,
Applicant Address RAFI MARG, NEW DELHI-110 001, INDIA
Inventors:
# Inventor's Name Inventor's Address
1 DONGARE MOHAN KERABA, NETIONAL CHEMICAL LABORATORY, PUNE-411 008, INDIA
2 DAGADE SHARDA PRABHAKAR NETIONAL CHEMICAL LABORATORY, PUNE-411 008, INDIA
3 KADAM VIJAY SHIVAJI NETIONAL CHEMICAL LABORATORY, PUNE-411 008, INDIA
4 PAUL RAT NASAMY NETIONAL CHEMICAL LABORATORY, PUNE-411 008, INDIA
PCT International Classification Number C07C 205/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA