WO2018073835A1

WO2018073835A1 - A process for the preparation of tertiary butyl phenol

Info

Publication number: WO2018073835A1
Application number: PCT/IN2017/050475
Authority: WO
Inventors: Sanjay Pandurang KAMBLE; Arumugam Sudalai
Original assignee: Council Of Scientific & Industrial Research
Priority date: 2016-10-18
Filing date: 2017-10-16
Publication date: 2018-04-26
Also published as: WO2018073835A9

Abstract

The present invention disclosed a process for the preparation of tertiary butyl phenol by reaction of phenol with tertiary butanol using phosphorus pentoxide as catalyst.

Description

A PROCESS FOR THE PREPARATION OF TERTIARY BUTYL PHENOL

FIELD OF THE INVENTION:

The present invention relates to a process for the preparation of tertiary butyl phenol. More particularly, the present invention relates to an environment friendly, cost effective process for the preparation of tertiary butyl phenol by reaction of phenol with tertiary butanol using phosphorus pentoxide as catalyst. BACKGROUND AND PRIOR ART:

Tertiary butyl phenol (TBP) has an important industrial application. TBP is prepared by Friedel-Crafts alkylation of phenol with tert-butyl alcohol (TBA). Alkylation reaction of phenol with tert-butyl alcohol (TBA) is an important reaction both in organic synthesis and chemical manufacturing. The alkylated phenol products are used as raw materials for the manufacture of a variety of resins, durable surface coatings, varnishes, wire enamels, printing inks, surface-active agents, rubber chemicals, antioxidants, fungicides, petroleum additives, ultraviolet absorbers, and heat stabilizers for polymeric materials. The 2-tert-butylphenol (2-TBP) is used as an intermediate for fragrances and pesticides, whereas 4-tert-butylphenol (4-TBP) is used to make oils and phosphate esters. 2,4-DTBP and 2,6-DTBP are useful either as antioxidants for lubricants, or as intermediates for the preparation of antioxidants for lubricants.

Article titled "Ortho-selective alkylation of phenol with 2-propanol without catalyst in supercritical water" by T Sato published in Ind. Eng. Chem. Res., 2002, 41 (13), pp 3064-3070 reports a highly ortho-selective alkylation of phenol with 2-propanol without catalyst in supercritical water at 673 K. The dehydration of 2-propanol gave propene and was followed by the reaction with phenol to produce 2-isopropylphenol as the main alkylphenol product. The ortho/para ratio of alkylphenols was above 20, and the yield of alkylphenols was 83.1%.

GB630487 disclosed a process for alkylation of phenol comprises reacting a phenol with an olefine in the presence of a strongly acid catalyst under substantially anhydrous conditions or in the presence of not more than one gram molecule of water per gram molecule of strongly acid catalyst present, wherein said phenol is selected from phenol, cresols and xylenols and acid catalyst is selected from anhydrous zinc chloride, ferric chloride, aromatic or aliphatic sulphonic acids, phosphoric acid, phosphorous pentoxide and hydrogen halides.

Article titled "tert-Butylation of phenol catalysed by metal exchanged iron pillared montmorillonites" by Kurian et al. published in Catalysis Communications; 2006; 7 (6), pp 417-421 reports the alkylation of phenol by TBA using transition metal exchange pillared montmorillonites as a catalyst. The conversion of phenol is 54% and 96.4% selectivity of p-TBP were obtained at 200°C, 1:3 molar ratio of phenol to TBA and space velocity of 2.6 hr ¹.

Article titled "Effect of different synthesis methods on the structural and catalytic performance of SBA-15 modified by aluminum" by Jing Ma et al. published in J Porous Mater. ;2011; 18; pp 607-614 reports the alkylation of phenol by TBA using aluminium containing mesoporous Al/SBA-15 catalyst which is prepared by post synthesis method and direct synthesis method. The reaction was carried in the tubular reactor at atmosphere pressure. The 89.17% conversion of phenol and 60.77% selectivity of p-TBP were obtained at 5 molar ratio of TBA to phenol, 2.5 hr^"1 space velocity, 0.05 gm catalyst and 190°C temperature. The activity of catalyst remains almost constant up to four runs.

Article titled, "Alkylation of phenol with tert-butyl alcohol catalyzed by zeolite Ηβ" by K Zhang et al. published in Applied Catalysis A: General, 1998, 166; pp 89-95 reports the alkylation of phenol with tert-butyl alcohol over zeolite Ηβ catalyst, the suitable reaction temperature range is from 378-458 K. The reaction was carried out in the tubular down flow stainless steel reactor (i.d.4mm). 95.5% conversion of phenol and 76.38% selectivity of p-TBP were obtained at 418 K, higher space velocity, lower reactant molar ratio and medium acidic site on Zeolite Ηβ. Article titled "Supported 12-tungstophosphoricacid: An efficient and selective solid acid catalyst for tert-butylation of phenol and cresols" by N Bhatt et al. published in Catalysis Communications, 2008, 9; pp 1545-1550 reports that o-cresol, p-cresol and m-cresol gives different results. In case of m-cresol the formation of only one product, o-tertiary butyl phenol (o-isomer) is found. In m-cresol, the 2^nd and 4^th positions are not favourably susceptible to electrophilic attack by tert-butyl cation as they are sterically hindered by the adj acent methyl group; only 6^th position is left for alkylation. In case of p-cresol, 100% selectivity for p-TBP is obtained. U.S. patent no. 2,140,782 disclosed a process for the reaction of phenol and alcohol carried out at lower temperatures and pressures by using acid activated bleaching earths e.g. "Retrol" or "Tonsil" and sulphuric acid as catalysts. The yield of para- tertiary butyl phenol based on the phenol consumed was 85.1% and catalyst is recovered by filtration and re-employed in subsequent reactions. The disadvantage of the process is that the leaching of catalyst is possible; highly acidic water will be formed as side product

Article titled, "Selective alkylation of phenol with tert-butyl alcohol catalyzed by Bronsted acidic imidazolium salts" by J Gui et al. published in Journal of Molecular Catalysis A: Chemical, 2005, 225; pp 27-31 reports that alkylation reaction of phenol with tert-butyl alcohol (TBA) catalyzed by S0₃H-functionalized ionic liquids. The influences of different ionic liquids, reaction time, reaction temperature, reactant ratio (mole ratio of phenol to that of TBA), the amount and the recycle of ionic liquid were studied. The conversion of phenol and the selectivity of 2,4-DTBP were 80.4 and 60.2%, respectively.

Investigation of both homogeneous and heterogeneous catalysts for this typical Friedel-Crafts alkylation reaction results in different selectivity and activities based mainly on the acidity of the catalysts used. Weak acid catalysts mainly lead to an etherified product (phenyl alkyl ether, t-BPE). The presence of phenolic (-OH) group kinetically favors o-alkylation (o-isomer, e.g. 2-TBP); however, due to steric hindrance thermodynamically unfavoured o-isomer (2-TBP) is readily isomerizes into less hindered p-isomer (p-TBP), especially in moderately acidic media. When strongly acidic catalysts are used, 2,4-di-tert-butylpheol (2,4-DTBP) is a dominant product; ortho and para-isomers formed initially are isomerizes to m-TBP at high temperatures or in strongly acid media. At the same time, small amounts of 2,6-di- tert-butylphenol (2,6-DTBP), 2,4,6-tri-tert-butylphenol (2,4,6-TTBP) and 4- (2,2,4- trimethylpenthyl)-phenol are also formed. Catalysts used for this reaction include Lewis acids, such as AICI3 and BF3, Bronsted acids, such as H3PO4, H2SO4, HF, HCIO4, cation-exchange resin, mesoporous materials, zeolites, molecular sieves, and also supercritical and near-supercritical water. Mineral acid catalysts cause equipment corrosion and environmental pollution while solid acids deactivate rapidly due to the build-up of coke.

Although cation-exchange resins show a good performance, thermal stability but fouling of the resins is maj or problems. Ionic liquids gives high conversion of phenol and good selectivity for 2,4-DTBP. The advantages of ionic liquids such as lack of vapor pressure, wide liquid range and thermal stability have made them exceptional reaction media and environmentally benign solvents. They are especially promising solvents for catalysis where activity, selectivity, and stability of catalysts are enhanced. However ionic liquids have many inherent disadvantages such as high cost, not easily available, some ionic liquids are toxic in nature, some cases ionic liquids react with reactants and therefore they cannot be considered as inert solvent, etc.

Therefore there is need to develop eco-friendly, cost effective route for the synthesis of tertiary butyl phenols. Accordingly, the present inventors provide an eco-friendly catalytic process for the synthesis of TBP where phosphorus pentoxide is used as a catalyst, further for isolation of reaction products a viable, simple extraction method has been established.

OBJECTIVE OF THE INVENTION:

The main obj ective of the present invention is to provide an eco-friendly, cost effective process for the preparation of tertiary butyl phenol by reaction of phenol with tertiary butanol using phosphorus pentoxide as catalyst. SUMMARY OF THE INVENTION:

Accordingly, the present invention provides a process for the preparation of tertiary butyl phenol comprises alkylation of phenol with tert-butyl alcohol (TBA) in an autoclave reactor by using phosphorus pentoxide as a catalyst at temperature in the range 80 °C to 230 °C for the period in the range of 6 to 8 hrs to afford tertiary butyl phenol.

In preferred embodiment, the mole ratio of phenol to tert-butyl alcohol (TBA) is in the range of 1:1 to 1:4.

In another preferred embodiment, the catalyst loading is in the range of 1 to 6 w/w% (based on weight of phenol). In yet another preferred embodiment, the conversion of phenol is in the range of 50 to 74%.

In yet still another preferred embodiment, wherein selectivity of said reaction towards p-tert-butyl phenol (4-DTBP) is in the range 40 to 70 %.

BRIEF DESCRIPTION OF THE DRAWINGS:

Fig 1: 1H NMR of tertiary butyl phenols.

Fig 2: Formation of 2-TBP confirmed by GC/MS

Fig 3: Formation of 4-TBP confirmed by GC/MS

Fig 4: Formation of 2,4-DTBP confirmed by GC/MS

Fig 5: Formation of 2,6-DTBP confirmed by GC/MS

DETAILED DESCRIPTION OF THE INVENTION:

The invention will now be described in detail in connection with certain preferred and optional embodiments, so that various aspects thereof may be more fully understood and appreciated. In line with the above obj ectives, the present invention provides an eco-friendly, cost effective catalytic process for the preparation of tertiary butyl phenol by reaction of phenol with tertiary butanol using phosphorus pentoxide as catalyst. In an embodiment, the present invention provides a process for the preparation of tertiary butyl phenol comprises alkylation of phenol with tert-butyl alcohol (TBA) in an autoclave reactor by using phosphorus pentoxide catalyst at temperature in the range 80 °C to 230 °C for the period in the range of 6 to 8 hrs to afford tertiary butyl phenol.

In another preferred embodiment, the catalyst loading is in the range of 1 to 6 w/w% (based on weight of phenol).

In yet another preferred embodiment, the conversion of phenol is in the range of 50 to

74%.

In yet still another preferred embodiment, the separation of reaction mixture was done via simple extraction technique.

The process for the preparation of tertiary butyl phenol is as depicted in scheme 1:

Phenol TBA O-TBP P-TBP 2,4-DTBP 2,6-DTBP Water

Scheme: 1 Nuclear magnetic resonance (NMR) spectroscopy is used to confirm the formation of TBP molecule in the reaction. The product sample is dissolved in CDC1₃ and ¾ (200 MHz) process is used for the detection of the molecule as shown in Figure 1. So each molecule shows duplet, triplet and multiple peaks according to their proton resonance with their respective chemical shift. This helps to identify the number of molecules present in the structure and the nature of bonds with which they are attached. Thus, NMR confirm the structure of compound which is present the solution.

The GC/MS (Agilent Technologies 7890B, having HP-5 non-polar column of length 30 m and 0.25 μπι i.d.) analysis was used for identification of products in this alkylation reaction of phenol with tertiary butyl alcohol. GC-MS determines mass-to- charge ratio of the structure of the compounds by fragmenting the product structure into ions. The formation of 2-TBP, 4-TBP, 2,4-DTBP and 2,6-DTBP was confirmed by GC/MS as shown in Figure 2, 3, 4 and 5 respectively.

During the alkylation of phenol with tertiary butyl alcohol water is formed as a byproduct which further reacts with catalyst to give phosphoric acid as aqueous layer. The resultant reaction is taken separating funnel where organic layer is easily separated from aqueous layer. Further organic layer subjected for the separation of reaction products by vacuum distillation. Phosphoric acid being a chemical reagent has wide variety of uses, including as a rust inhibitor, food additive, etc.

The following examples, which include preferred embodiments, will serve to illustrate the practice of this invention, it being understood that the particulars shown are by way of example and for purpose of illustrative discussion of preferred embodiments of the invention.

Examples:

Example 1: Synthesis of tertiary butyl phenol:

Alkylation reaction of phenol with tert-butyl alcohol (TBA) was carried out in an autoclave reactor by using phosphorus pentoxide catalyst. Autoclave was charged with 47 grams phenol and 74 grams TBA (mole ratio Phenol:TBA=l:2). Then 2% (w/w of phenol) phosphorus pentoxide catalyst was added into it. Afterwards the reaction solution was at stirring speed 300 rpm. Reaction temperature was maintained at 230 °C for 6 hours. Auto generated pressure was continuously monitored. The concentration of tertiary butyl phenols in the sample was confirmed by GC, GC-MS and NMR technique. The concentration of 2-TBP, 4-TBP, 2,4-DTBP and 2,6-DTBP were 26.34%, 32.34%, 15.49% and 0.83% respectively after 6 hr reaction time. During the alkylation of phenol with tertiary butyl alcohol water is formed as a byproduct which further reacts with catalyst to give phosphoric acid as aqueous layer. The resultant reaction is taken separating funnel where organic layer is easily separated from aqueous layer. Further organic layer subjected for the separation of reaction products by vacuum distillation to afford phosphoric acid.

Example 2: Effect of different operating parameters:

Alkylation reaction of phenol with tert-butyl alcohol (TBA) was carried out in an autoclave reactor by using phosphorus pentoxide catalyst. Autoclave was charged with different quantities of phenol and TBA. The reaction solution was stirred at 300 rpm and subsequently solution was heated at desired temperature for 6-8 hrs. Effect of different operating parameters such as reactants mole ratios (PhenokTBA), reaction temperature and effect of catalyst loading w/w % (based on phenol) was investigated in detail.

A. Effect of Phenol: TBA molar ratios on butylation of phenol over phosphorus pentoxide:

The effect of mole ratio on alkylation of phenol with tertiary butyl alcohol was studied at reaction temperature of 230 °C, reaction time of 6 hours and catalyst loading of 2% (w/w of phenol). It was found that the maximum conversion of phenol was observed at 1:2 molar ratio of reactant. The effect of Phenol: TBA molar ratios on phenol tertiary butylation reaction are as summarized in Table 1: Table: 1: Effect of Phenol: TBA molar ratios butylation of phenol

Reaction conditions: Reaction temperature = 230°C, catalyst loading = 2% (w/w of phenol); Reaction time = 6 hours; Stirrer speed = 300 rpm

B. Effect of catalyst loading on butylation of phenol over phosphorus pentoxide:

The effect of catalyst loading on alkylation of phenol with tertiary butyl alcohol was studied at reactant molar ratios 1:2, reaction temperature of 230 °C, reaction time of 6 hours. The catalyst loading was varied from 1% to 6% (w/w of phenol). The effect of catalyst loading on phenol tertiary butylation reaction is as summarized in Table 2:

Table: 2: Effect of catalyst loading on butylation of phenol

Reaction conditions: Reaction temperature = 230 °C; Reaction time = 6 hours; Stirrer speed=300 rpm; Molar ratios Phenol: t-butyl alcohol (TBA) = 1: 2 [47 grams Phenol and 74 grams TBA]

C. Effect of temperature on butylation of phenol over phosphorus pentoxide:

The effect of temperature on alkylation of phenol with tertiary butyl alcohol was studied at 1:2 molar ratios of reactants, reaction time of 6 hours, catalyst loading of 2% (w/w of phenol). The temperature of the reaction was varied from 100 °C to 250 °C in order to understand its effect on product formation. The effect of temperature on phenol tertiary butylation reaction is as summarized in Table 3:

Table: 3: Effect of temperature on butylation of phenol

Reaction conditions: catalyst loading = 2% (w/w of phenol); Reaction time = 6 hours; Stirrer speed = 300 rpm D. Effect of reaction time on phenol tertiary butylation reaction over phosphorus pentoxide:

The effect of reaction time on alkylation of phenol with tertiary butyl alcohol was studied at 1:2 molar ratios of reactants, catalyst loading of 2% (w/w of phenol), and temperature of 230 °C and by varying the reaction time from 1 hour to 7 hours. The Effect of reaction time on phenol tertiary butylation reaction is as summarized in Table 4:

Table: 4: Effect of reaction time butylation of phenol

Reaction conditions: catalyst loading = 2% (w/w of phenol); Reaction temperature = 230 °C; Stirrer speed = 300 rpm

Advantages of invention:

1. One step, eco-friendly process for the synthesis of tertiary butyl phenols from phenol and tert. butanol using phosphorus pentoxide as dehydrating agent.

2. Organic layer is easily separated from aqueous layer by simple extraction process.

3. Side product water react with phosphorus pentoxide gives phosphoric acid as byproduct which has good commercial value.

4. The conversion of phenol is in the range of 60 to70% and selectivity for p- tert- butyl phenol (4-DTBP) is more than 60%.

Claims

WE CLAIM:

1. A process for preparation of tertiary butyl phenol, said process comprising alkylation of phenol with tert-butyl alcohol (TBA) in an autoclave reactor by using phosphorus pentoxide as a catalyst at temperature in the range 80 °C to 230 °C for the period in the range of 6 to 8 hrs to afford tertiary butyl phenol.

2. The process as claimed in claim 1, wherein the mole ratio of phenol to tert-butyl alcohol (TBA) is in the range of 1:1 to 1:4.

3. The process as claimed in claim 1, wherein said catalyst loading is in the range of 1 to 6 w/w% (based on weight of phenol).

4. The process as claimed in claim 1, wherein conversion of phenol is in the range of 50 to 74%.

5. The process as claimed in claim 1, wherein selectivity of said reaction towards p- tert-butyl phenol (4-DTBP) is in the range 40 to 70 %.