Description:FIELD OF INVENTION
The present disclosure relates to a process for preparing 3-pentadecyl phenol.
BACKGROUND
The known process for producing 3-pentadecyl phenol from cardanol in the presence of a suitable catalyst makes use of solvents such as methanol, toluene, ethyl acetate, etc. These solvents are associated with various hazards, such as VOCs, flammability, toxicity, environmental pollution, and limited fossil fuel sources. Although it is desirable to develop new processes and eliminate the requirement for said solvents, the elimination of solvents will cause an increase in the viscosity of the reaction mass, making it difficult to mix the reaction mass efficiently, and hence limit the scalability of the process.
In view of the scalability issues, the existing process for producing 3-penatdecyl phenol from cardanol continues to use organic solvents.
SUMMARY
A process for preparing 3-pentadecyl phenol is disclosed. Said process comprises hydrogenating cardanol in the presence of a heterogeneous catalyst at a reaction temperature in the range of 70 to 140°C, in a high-pressure reactor under a hydrogen pressure in the range of 5 to 15 bar, for a residence time in the range of about 1 to 8 hours. The hydrogenation is carried out without the addition of an organic solvent.
BRIEF DESCRIPTION OF DRAWINGS
Fig. 1 shows high-performance liquid chromatography (HPLC) chromatogram of 3-pentadecyl phenol obtained by process in accordance with an exemplary embodiment (Example 1) of the present disclosure;
Fig. 2 shows the HPLC chromatogram of 3-pentadecyl phenol obtained in Comparative example 1 by conventional process using organic solvent; and
Fig.3 shows the HPLC chromatogram of the reference 3-pentadecyl phenol obtained from commercial source of cardanol.
DETAILED DESCRIPTION
To promote an understanding of the principles of the disclosure, reference will now be made to embodiments and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended, such alterations and further modifications in the disclosed composition and method, and such further applications of the principles of the disclosure therein being contemplated as would normally occur to one skilled in the art to which the disclosure relates.
It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the disclosure and are not intended to be restrictive thereof.
Reference throughout this specification to “one embodiment” “an embodiment” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, appearances of the phrase “in one embodiment”, “in an embodiment” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.
Also, any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of "1 to 10" is intended to include any and all subranges between and including the recited minimum value of 1 and the recited maximum value of 10, that is, all subranges beginning with a minimum value equal to or greater than 1 and ending with a maximum value equal to or less than 10, and all subranges in between.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the disclosure, the preferred methods, and materials are now described. All publications mentioned herein are incorporated herein by reference.

The term “cardanol” refers to the phenolic lipid synthesized from anacardic acid, and represented by Formula 1:

Formula 1
wherein n=0, 2, 4, or 6.

In an aspect, a process for preparing 3-pentadecyl phenol is described. Said process comprises hydrogenating cardanol in the presence of a heterogeneous catalyst at a reaction temperature in the range of 70 to 140°C, in a high-pressure reactor under a hydrogen pressure in the range of 5 to 15 bar, for a residence time in the range of about 1 to 8 hours. The hydrogenation is carried out without the addition of an organic solvent.
In the disclosed process, the organic solvent used in the conventional methods of preparing 3-pentadecyl phenol has been replaced with cardanol. The present inventors found that if the organic solvent used in the conventional methods of preparing 3-pentadecyl phenol is replaced with cardanol such that cardanol is added in the amount of 35-80% of the volume of the high-pressure reactor, the process results in >98% conversion of cardanol into 3-pentadecyl phenol without the requirement of the organic solvent. In some embodiments, cardanol is added in the amount of about 60-70% of the volume of the high-pressure reactor. Cardanol used in the disclosed process was obtained from commercial sources, such as- Zantye Agro, Maharashtra.
In an embodiment, the hydrogenation of cardanol is carried out at the reaction temperature of 70-140°C. In some embodiments, the hydrogenation of cardanol is carried out at the reaction temperature of 90 to 110°C.
In an embodiment, the hydrogenation of cardanol is initiated at the hydrogen pressure of 9 to 11 bar. In some embodiments, the hydrogenation of cardanol is initiated at the hydrogen pressure of 10 bar. In an embodiment, the hydrogen pressure is maintained at a specific pressure till the completion of the reaction to form 3-pentadecyl phenol. In some embodiments, the hydrogen pressure is maintained at 10 bar till the completion of the reaction to form 3-pentadecyl phenol.
In an embodiment, the heterogeneous catalyst is selected from the group consisting of Palladium on Carbon (Pd/C), Platinum (Pt), and Raney nickel (Raney Ni). In an embodiment, the heterogeneous catalyst is Pd/C and the amount of catalyst is in the range of 0.5-2.0 % by weight of cardanol. In some embodiments, the heterogenous catalyst is Pd/C (5%Pd) added to cardanol in the amount of 1% by weight of cardanol. In an embodiment, the heterogeneous catalyst is Raney Ni and the amount of catalyst is in the range of 5-15% by weight of cardanol. In some embodiments, Raney Ni is added to cardanol in the amount of 10 % by weight of cardanol.
In an embodiment, the hydrogenation is carried out under vigorous mixing in the high-pressure reactor at a stirring frequency of 300-800 rpm. In some embodiments, the hydrogenation is carried out at the stirring frequency of 500-600 rpm.
The high-pressure reactor used in the disclosed process is any reactor known to a person skilled in the art for carrying out the process of hydrogenation. In an embodiment, the high-pressure reactor include but is not limited to SS304, SS316, SS316L, Hastelloy, Inconel and Glass line SS.
In an embodiment, the residence time is in the range of 1-8 hours. In some embodiments, the residence time is 2.5-4 hours.
It will be apparent to those skilled in the art that various modifications and variations can be made to the method/process of the present disclosure without departing from the scope of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the method/process disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalent.
Examples:
Example 1: Synthesis of 3-pentadecyl phenol in accordance with an exemplary embodiment of the present disclosure
600 grams cardanol, and 6 grams of Pd/C (5%Pd) on dry basis were charged in a 1.0 L high-pressure reactor. The reaction temperature was brought to 90°C and hydrogen flow was started at 10 bar pressure. The reaction mixture was subjected to vigorous mixing and hydrogen pressure till >98 % conversion of cardanol, measured by HPLC, was obtained. The reaction mixture was subjected to standard filtration techniques to separate the catalyst and reaction mass comprising of 600 grams of 3-pentadecyl phenol. Fig. 1 shows HPLC chromatogram of the obtained 3-pentadecyl phenol.
Comparative Example 1: Synthesis of 3-pentadecyl phenol using organic solvent
150 grams cardanol, 450 mL methanol and 1.5 grams Pd/C (5%Pd) on dry basis were charged in a 1.0 L high-pressure reactor. The reaction temperature was brought to 90°C and hydrogen flow was started at 10 bar pressure. The reaction mixture was subjected to vigorous mixing and hydrogen pressure till >98 % conversion of cardanol, measured by HPLC, was obtained. The reaction mixture was subjected to standard filtration techniques to separate the catalyst and reaction mass from the reaction mixture. This reaction mass was distilled to distil out methanol and obtain 150 grams of 3-pentadecyl phenol. Fig.2 shows the HPLC chromatogram of the obtained 3-pentadecyl phenol.
The HPLC chromatogram of the 3-pentadecyl phenol obtained in Example 1 and that obtained in Comparable Example 1 were found to be equivalent, suggesting that elimination of external organic solvent methanol, and replacement with cardanol does not adversely affect the purity of obtained 3-pentadecyl phenol. Also, the HPLC chromatogram of the 3-pentadecyl phenol obtained in Example 1 was found to be comparable to that of 3-pentadecyl phenol (shown in Fig. 3) obtained from commercial sources.
Comparative Example 2: Synthesis of 3-pentadecyl phenol using organic solvent
200 grams cardanol, 400 mL methanol and 2.0 grams Pd/C (5%Pd) on dry basis were charged in a 1.0 L high-pressure reactor. The reaction temperature was brought to 90°C and hydrogen flow was started at 10 bar pressure. The reaction mixture was subjected to vigorous mixing and hydrogen pressure till >98 % conversion of cardanol, measured by HPLC, was obtained. The reaction mixture was subjected to standard filtration techniques to separate the catalyst and reaction mass from the reaction mixture. This reaction mass was distilled to distil out methanol and obtain 200 grams of 3-pentadecyl phenol.
Comparative Example 3: Synthesis of 3-pentadecyl phenol using conventional method
300 grams cardanol, 300 mL methanol and 3.0 grams Pd/C (5%Pd) on dry basis were charged in a 1.0 L high-pressure reactor. The reaction temperature was brought to 90?C and hydrogen flow was started at 10 bar pressure. The reaction mixture was subjected to vigorous mixing and hydrogen pressure till >98 % conversion of cardanol, measured by HPLC, was obtained. The reaction mixture was subjected to standard filtration techniques to separate the catalyst and reaction mass from the reaction mixture. This reaction mass was distilled to distil out methanol and obtain 300 grams of 3-pentadecyl phenol.
The time required for completion of reaction, the conversion % and product output were assessed for each of the processes followed in above examples, and summarized in table 1 below.
Example Cardanol (Litre) Solvent (Litre) Reaction time
(hr) Conversion %
(assessed by HPLC) Product output per batch, Kg
Comparative Example 1 0.150 0.450 3.0 99.26 0.15
Comparative Example 2 0.200 0.400 3.5 99.28 0.20
Comparative Example 3 0.300 0.300 4.0 99.45 0.30
Example 1 0.600 Nil 2.5 99.30 0.60
Table 1: Effect of solvent on time for completion of reaction, conversion % and product output
It was observed that replacement of solvent with equivalent volume of raw material (cardanol) reduces the time required for completion of reaction, and product output as shown above in table 1. This directly reduces the energy consumption per Kg of product, while eliminating the requirement of distillation process and reducing the cost of production.
Example 2: Synthesis of 3-pentadecyl phenol in accordance with an exemplary embodiment of the present disclosure
400 grams cardanol, and 40.0 grams Raney nickel on dry basis were charged in a 1.0 Lit high-pressure reactor. The reaction temperature was brought to 110°C and hydrogen flow was started at 10 bar pressure. The reaction mixture was subjected to vigorous mixing and hydrogen pressure till >98 % conversion of cardanol, measured by HPLC, was obtained. The reaction mixture was subjected to standard filtration techniques to separate the catalyst and reaction mass comprising of 400 grams of 3-pentadecyl phenol.
Example 3: Effect of catalysts on reaction
The process of Example 1 was carried out with varying percentages of catalysts- Pd/C (5%Pd) catalyst, Raney nickel, as summarized in table 2 below. Table 2 also summarises the effect of different catalysts and their % loading on conversion and productivity of the reaction.
Sr. No. Cardanol
(Kg) Catalyst % Catalyst loading w.r.t. Cardanol Time(hr) Conversion % (assessed by HPLC) Product output per batch, Kg
1 0.600 Pd/C 0.5 12 70.0 0.420
2 0.600 Pd/C 1.0 2.5 99.30 0.600
3 0.600 Raney Ni 5.0 14 55 0.330
4 0.600 Raney Ni 10 12 99.23 0.600
Table 2: Effect of catalyst and their amount on time required for completion of reaction, the conversion % and product output.
It was observed that Pd/C catalyst achieved >98% conversion using only 1% loading at lower reaction time i.e. ~2.5 hr, while Raney Ni catalyst required higher catalyst loading i.e. 10% and higher reaction time~12 hr for achieving >98% conversion.
Example 4: Effect of hydrogen pressure on reaction
500 grams cardanol, and 5.0 grams Pd/C (5%Pd) on dry basis were charged in a 1.0 L high-pressure reactor. The reaction temperature was brought to 90°C and hydrogen flow was started at 10 bar. The reaction mixture was subjected to vigorous mixing and varying hydrogen pressures, as stated in table 3 below, till >98% conversion of cardanol, measured by HPLC, was obtained. The reaction mixture was subjected to standard filtration techniques to separate the catalyst and reaction mass comprising of 500 grams of 3-pentadecyl phenol. Table 3 summarises effect of hydrogen pressure on the reaction time.
Sr. No Cardanol
(Kg) RPM Hydrogen pressure
(bar) Time (hr) Conversion, %
(assessed by HPLC) Product output per batch, Kg
1 0.500 500 5-6 5.0 99.16 0.500
2 0.500 500 10-11 2.5 99.12 0.500
3 0.500 500 15-16 2.5 99.00 0.500
Table 3: Effect of hydrogen pressure on the reaction time
It was observed that maintaining continuous hydrogen pressure during reaction at 10-11 bar substantially reduces (~50%) reaction time as against process carried under condition in which hydrogen is pressurized to 10 bar and allowed to react until pressure drops to 5 bar and then again brought up to 10 bar in a cyclic manner till completion of reaction.
Example 5: Effect of reaction temperature on reaction
The process of Example 1 was repeated using varying amounts of cardanol and reaction temperature, as summarized in table 4 below. Table 4 also summarises the effect of reaction temperature on reaction time, % conversion and product output.
Sr. No Cardanol (Kg) RPM Reaction temp
(oC) Time (hr) Conversion, % (assessed by HPLC) Product output per batch, Kg
1 0.500 500 60 12 82 0.410
2 0.400 500 70 6.0 99.24 0.400
3 0.400 500 80 4.5 99.18 0.400
2 0.500 500 90 2.5 99.12 0.500
3 0.500 500 120 2.5 99.08 0.500
4 0.500 500 140 2.5 99.00 0.500
Table 4: Effect of reaction temperature on reaction time and percentage conversion
It was observed that at reaction temperatures lower than 70oC, reaction proceeds at a very slow rate with low conversion. Further, at temperature >90oC, complete conversion was achieved in less than 3 hrs consistently.
Example 6: Effect of stirring frequency on reaction
The process of Example 1 was repeated using 500 grams of cardanol and at varying stirring frequencies, as summarized in table 5 below. Table 5 also summarises the effect of stirring frequency on reaction time, % conversion and product output.
Sr. No Cardanol
(Kg) Stirring frequency (RPM) Reaction time
(hr) Conversion, % (assessed by HPLC) Product output per batch, Kg
1. 0.500 300 11 99.02 0.500
2. 0.500 500 2.5 99.12 0.500
3. 0.500 800 1.5 99.10 0.500
Table 5: Effect of stirring frequency on reaction time
It was observed that at low stirring frequencies (300 rpm and below), the reaction proceeds at a slow rate. Further, at high stirring frequencies (= 500 rpm), complete conversion was achieved within 1 to 3 hours.
INDUSTRIAL APPLICABILITY
The disclosed process finds application in the industrial production of 3-penatdecyl phenol. The disclosed process results in >98% conversion of cardanol to 3-pentadecyl phenol without the requirement of organic solvent such as methanol, toluene, ethyl acetate, etc.
The disclosed process allows eliminating the use of solvents such as methanol, dichloromethane, ethyl acetate, toluene, hexane etc. Thus, the disclosed process is a VOC-free and effluent-free process. The disclosed process reduces the cost of production of the product, exhibits lower energy demand, and eliminates down streaming steps (distillation). Elimination of solvent recovery and distillation unit operation results in increased product output per batch while achieving reduction in energy consumption, process time, and cost.
The disclosed process allows recycling, reuse, and regeneration of the reaction catalyst, thus reducing waste generation. Also, safety and health hazards associated with the handling and usage of solvents are eliminated.
Thus, the disclosed process not only has economic advantages over the known processes but is also environment friendly.
3-penatdecyl phenol obtained using the disclosed process finds application as precursor for bio-based surfactant, such as for use in powder detergent formulations.
, Claims:We Claim:

1. A process for preparing 3-pentadecyl phenol, the process comprising:
hydrogenating cardanol in the presence of a heterogeneous catalyst at a reaction temperature in the range of 70 to 140°C, in a high-pressure reactor under a hydrogen pressure in the range of 5 to 15 bar, for a residence time in the range of 1 to 8 hours;
wherein the hydrogenation is carried out without the addition of an organic solvent.

2. The process as claimed in claim 1, wherein cardanol is added in an amount of around 35 to 80% of volume of the high-pressure reactor.

3. The process as claimed in claim 1, wherein the hydrogenation of cardanol is carried out at the reaction temperature of 70 to 140°C.

4. The process as claimed in claim 1, wherein the hydrogenation of cardanol is carried out under the hydrogen pressure of 5 to 15 bar.

5. The process as claimed in claim 1 or 4, wherein the hydrogen pressure is maintained at a specific pressure till the completion of the reaction to form 3-pentadecyl phenol.

6. The process as claimed in claim 1, wherein the heterogeneous catalyst is selected from the group consisting of Palladium on Carbon (Pd/C), and Raney nickel (Raney Ni).

7. The process as claimed in claim 6, wherein the heterogeneous catalyst is Pd/C comprising 5% Pd loading, and the amount of catalyst is in the range of 0.5 to 2.0% by weight of cardanol.
8. The process as claimed in claim 6, wherein the heterogeneous catalyst is Raney Ni and the amount of catalyst is in the range of 5 to 15% by weight of cardanol.

9. The process as claimed in claim 1, wherein the hydrogenation of cardanol is carried out under vigorous mixing in the high-pressure reactor at a stirring frequency of 300 to 800 rpm.