Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C201/00—Preparation of esters of nitric or nitrous acid or of compounds containing nitro or nitroso groups bound to a carbon skeleton
  • C07C201/06—Preparation of nitro compounds
  • C07C201/08—Preparation of nitro compounds by substitution of hydrogen atoms by nitro groups
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
  • B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
  • B01J21/08—Silica
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
  • B01J23/24—Chromium, molybdenum or tungsten
  • B01J23/30—Tungsten
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J29/00—Catalysts comprising molecular sieves
  • B01J29/03—Catalysts comprising molecular sieves not having base-exchange properties
  • B01J29/0308—Mesoporous materials not having base exchange properties, e.g. Si-MCM-41
  • B01J29/0341—Mesoporous materials not having base exchange properties, e.g. Si-MCM-41 containing arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J35/00—Catalysts, in general, characterised by their form or physical properties
  • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
  • B01J35/61—Surface area
  • B01J35/615—100-500 m2/g
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/02—Impregnation, coating or precipitation
  • B01J37/0236—Drying, e.g. preparing a suspension, adding a soluble salt and drying
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/02—Impregnation, coating or precipitation
  • B01J37/03—Precipitation; Co-precipitation
  • B01J37/036—Precipitation; Co-precipitation to form a gel or a cogel
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/04—Mixing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/08—Heat treatment
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07B—GENERAL METHODS OF ORGANIC CHEMISTRY; APPARATUS THEREFOR
  • C07B43/00—Formation or introduction of functional groups containing nitrogen
  • C07B43/02—Formation or introduction of functional groups containing nitrogen of nitro or nitroso groups
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P20/00—Technologies relating to chemical industry
  • Y02P20/50—Improvements relating to the production of bulk chemicals

Definitions

• the present invention relates to an improved process for the liquid phase nitration of aromatic compounds catalysed by W0 3 supported on mesoporous silica support, at low temperature, with high conversion and selectivity.
• Aromatic nitro compounds are an important class of compounds used in industry for the manufacture of dyes, pharmaceuticals and fine chemicals.
• a more common aromatic nitro compound, nitrobenzene is very much used as processing solvents in specific chemical reactions.
• the conventional process of nitrating aromatic compounds includes a nitrating mixture which is concentrated sulphuric acid and fuming nitric acid. During the use of nitrating mixture, a large quantity of dilute sulphuric acid is generated as waste which needs to be concentrated for its reuse which is highly energy intensive process or has to be disposed which poses environmental problems. Thus nitration of aromatic compounds is environmentally hazardous industrial process. Further, selectivity of desired product is low.
• Vapour phase nitration of aromatic compounds, benzene and toluene at temperature ranging from about 275°C to about 310°C and silica gel as catalyst is described in McKee and Wilhelm, Industrial and Engineering Chemistry, 28(6), 662-667 (1936).
• US 2431585 describes vapor phase nitration of aromatic hydrocarbons at temperature from 130°C to 430°C, using metal phosphates of calcium, iron, magnesium and solid supported phosphoric acid catalysts.
• U.S. Pat. No. 4,551 ,568 describes the vapor phase nitration of benzene over solid mixed oxide catalyst comprising WO 3 and M0O 3 , which exhibited a fairly high and stable activity.
• US 3966830, JP-58-157748 and US 4426543 describe the nitration of aromatics using zeolite catalysts.
• EP0092372 disclose a process for the gas -phase nitration of benzene which comprises treating benzene with nitrating agent comprising of an oxide of nitrogen i.e N0 2 or N2O4 in the presence of a solid catalyst composed of an acidic mixed oxide containing at least one of WO3, M0O3 and T1O2 and optionally containing Si0 2 and/or ZnO.
• nitrating agent comprising of an oxide of nitrogen i.e N0 2 or N2O4 in the presence of a solid catalyst composed of an acidic mixed oxide containing at least one of WO3, M0O3 and T1O2 and optionally containing Si0 2 and/or ZnO.
• US6791000 disclose vapor phase nitration of benzene, which comprises nitrating benzene with nitric acid over a molybdenum silica catalyst.
• US6362381 disclose nitration of aromatic hydrocarbon in the liquid phase with an oxide of nitrogen selected from NO, N 2 0 3 , N0 2 and N 2 0 4 and with an oxygen-containing gas stream in the presence of a heterogeneous oxidic catalyst.
• the catalyst is an oxygen compound of one or more elements of groups Ilia, IVa, Illb or IVb of the Periodic Table of the elements.
• CN 101412677 disclose selective nitration of chlorobenzene in liquid phase using nitric acid and in presence of W0 3 /Zr0 2 acid catalyst.
• Main objective of the present invention is to provide liquid phase nitration of aromatics using a novel solid acid catalyst that gives higher activity, selectivity, and high stability.
• Another object of the present invention is to develop a process using a solid acid catalyst that can be carried out at low temperature which can control selectivity and avoid the use of sulphuric acid.
• present invention provides a liquid phase nitration of aromatic compounds using solid acid catalyst and the said process comprising the steps of:
• solid acid catalyst used is tungsten oxide (W0 3 ) supported on mesoporous silica having BET surface area in the range of 367 to 397 M 2 /g.
• the aromatic compound is selected from monocyclic or polycyclic aromatic compounds such as benzene, xylene, toluene, naphthalene, phenanthrene, phenols or heteroaryls.
• the aromatic compounds are selected from monocyclic or polycyclic aromatic compounds which may be monosubstituted or polysubstituted by, for example, nitro, nitroso, halogen, hydroxyl, alkoxy, aryloxy, carboxyl, alkylcarbonyloxy, arylcarbonyloxy, acylamino, alkylsulfonyl, arylsulfonyl, alkylsulfoxyl, arylsulfoxyl, sulfo, cyano and/or C I -C I 7 alkyl groups, preferably by nitro, halogen, cyano and/or CI -CI 7 alkyl groups.
• aromatic hydrocarbons are unsubstituted or substituted benzene, xylenes, toluene, naphthalene, phenols, biphenyl, anthracene and phenanthrene, heteroaryls.
• the catalyst is used in the molar ratio of 0.009 to 0.1 per mole of the aromatic compound used.
• the organic solvent is selected from solvents with a boiling point in the range of 80- 1 10°C such as acetonitrile, 1 ,2 dichloroethane or dioxane.
• present invention provides a sol-gel process for preparation of the solid acid catalyst comprising the steps of:
• step (i) adding drop wise aqueous metatungstate salt solution in the solution as obtained in step (i);
• step (iii) stirring the mixture as obtained in step (ii) for a period in the range of 1 to 3 hr followed by addition of 2-10% ammonium hydroxide solution to obtain a white gel;
• step (iii) dryin the gel as obtained in step (iii) for period in the range of 2 to 24 hr followed by calcining for period in the range of 2 to 6 hr at temperature in the range of 450 to 500°C at the rate of 5°C per min to obtain the solid acid catalyst.
• the metatungstate salt is selected from alkali, alkaline earth metals or ammonium meta tungusted salt.
• present invention provides the sol-gel process comprises:
• step (i) reacting the solution of tungstic acid in water with 45 to 55% aq. hydrogen peroxide followed by addition of 20 to 30% ammonia to obtain a solution; ii. Adding drop wise solution of step (i) to a mixture of silica-40 and CI to C6 alcohol, stirring, adding 2-10% ammonia to obtain a white gel; and iii. drying and calcining at about 500 °C to yield the desired product.
• Figure 1 depict XRD patterns of catalysts prepared as given in example a) 1 ; b) 2; c) 3 ; d) 4; e) 5; f) 6; g) 7; h) 8; i) 9.
• the present invention discloses environment friendly, cost effective, liquid phase nitration of aromatic compounds using solid acid catalyst, with high conversion and selectivity.
• the instant liquid phase nitration of the aromatic compound avoids the use of sulphuric acid or the nitrating mixture thus avoiding any hazardous waste, and use of costly material of construction for the process plant.
• the process uses commercial nitric acid of 65-70% concentration as nitrating agent and the nitration is carried out in presence of solid acid catalyst at low temperature, due to which the instant process is cost effective and simple.
• the solid acid catalyst is recyclable, easy to work with high selectivity. It can eliminate the problem associated with the formation of water in nitration reaction. Nitration using Bronsted acid produces water which dilutes the concentration of the acid which lowers the efficiency of the nitrating acid. Thus removal and disposal of large amount of diluted acid left after the reaction is not only tedious but costly as well as not environmental friendly.
• the catalyst used in the process comprises tungsten oxide (WO 3 ) supported on mesoporous silica support.
• the catalyst provides for selective nitration of aromatic compounds and does not degrade during the reaction process.
• the optimum catalytic activity is achieved by controlling the conditions during preparation of catalyst.
• the catalyst used in the instant invention are acidic in nature and have acidity ⁇ 3.
• the present invention provides an improved, industrially feasible, cost effective liquid phase nitration of aromatic compounds characterized in that said process is catalysed by tungsten oxide (WO3) supported on mesoporous silica support, with high conversion and selectivity, comprising;
• the aromatic compounds are selected from monocyclic or polycyclic aromatic compounds which may be monosubstituted or polysubstituted by, for example, nitro, nitroso, halogen, hydroxyl, alkoxy, aryloxy, carboxyl, alkylcarbonyloxy, arylcarbonyloxy, acylamino, alkylsulfonyl, arylsulfonyl, alkylsulfoxyl, arylsulfoxyl, sulfo, cyano and/or Cl-C 17alkyl groups, preferably by nitro, halogen, cyano and/or Cl -C17alkyl groups.
• aromatic hydrocarbons are unsubstituted or substituted benzene, xylenes, toluene, naphthalene, phenols, biphenyl, anthracene and phenanthrene, heteroaryls.
• the nitrating agent, nitric acid is used in the molar ratio of 2 to 0.35 (cone. 30- 70%) per mole of the aromatic compound used.
• the catalyst is used in the molar ratio of 0.009 to 0.1 per mole of the aromatic compound used.
• the aromatic compound is nitrated in a solution in an organic solvent.
• the organic solvent is selected from solvents with a boiling point in the range of 80-1 10 °C such as acetonitrile, 1 ,2 dichloroethane, dioxane, and the like either alone or in combination thereof.
• the present invention provides a conversion rate of 85-90% with selectivity in the range 30- 60% depending upon the aromatic compound used, molar ratio of catalyst used and molar ratio of nitrating agent.
• the present invention discloses a process for preparation of the solid acid catalyst. Accordingly, solution of metatungstate salt in distilled water is added to a solution of ethyl silicate-40 and C I to C6 alcohol. The mixture is stirred for about 2-4 hrs followed by addition of 5% aqueous NH 3 solution. The solution is stirred further until a gelation started. Once it started slow down the stirring and kept it overnight to form white gel. The gel is air dried and calcined at about 500 °C to obtain desired product.
• the metatungsate salt is selected from alkali or alkaline metals or ammonium salt.
• the process for preparation of solid state catalyst includes oxidizing tungstic acid with aq. H 2 0 2 and neutralizing using ammonia to obtain a mixture. This is followed by adding said solution to a mixture of silica-40 and C I to C6 alcohol, stirring, adding 2-10% ammonia to obtain a white gel. Drying and calcination at about 500 °C to yield the desired catalyst.
• the catalyst W0 3 supported on mesoporous silica support is characterised by XRD as depicted in Fig 1.
• the catalyst used in the instant invention is acidic in nature and have acidity ⁇ 3.
• the BET surface area of the catalyst 367 to 97 M 2 /g.
• the catalyst is stable up to 5 cycles and can be recycled.
• the novelty of the present invention lies in carrying out nitration of aromatics in liquid phase using WO 3 on mesoporous silica support with high conversion and selectivity for the desired product and with no deactivation of the solid acid catalyst. Further, the reaction can be carried out at low temperature using said catalyst.
• tungstic acid was dissolved in 3 mL distilled water and 51 mL 50% aqueous hydrogen peroxide. This was followed by addition of 3 mL 25% aqueous ammonia.
• 40 g ethyl silicate-40 and 30 g of iso-propyl alcohol was stirred for 1 h and to this solution tungstic acid solution was added dropwise. This solution was stirred for 3 h followed by addition of 0.6 mL 10% aqueous ammonia solution. The solution was stirred until a white gel was obtained. This gel was air dried and calcined at 500 °C for 5h.
• Powder X-ray diffraction patterns of the catalysts were recorded on PAN anlytical X'Pert Pro Dual Goniometer diffractometer X'celerator solid state detector was employed for the experiments with CuKa (1.542 A) radiation and a Ni filter ( Figure 1).
• the strength of acid sites on the catalyst was calculated by acid-base titration. Firstly, aqueous NaOH solution (0.01 mol/L, 25 mL) was added to a catalyst (0.022 g). The mixture was then stirred for 2 h at room temperature 27 °C. After centrifugal separation, one drop of phenolphthalein solution was added to the filtrate and this solution was then titrated with HC1 (0.01 mol/L) to neutrality (Table 1 ). The number of acid sites were calculated by subtracting the number of acid sites of Si0 2 from the desired sample. Table 1. Acidity measurements of the catalysts
• the 250 mL three-necked round bottom flask fitted with reverse dean-stark apparatus was charged with 21.21 g o-xylene (0.2 mol), 120 mL 1 ,2 dichloro ethane, and 4.241 g of catalyst as prepared in example 9.
• the flask was flushed with nitrogen.
• the reaction mixture was refluxed at 1 10 °C for 1 h followed by the dropwise addition of 12.8 mL (0.2 mol) 70% HNO 3 .
• the water formed during the reaction was removed using reverse dean-stark apparatus.
• the reaction was carried out for 8 h.
• the reaction was monitored by GC analysis.

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• 2014
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