Claims:
1. A process for preparation of Pivaloyl chloride, the process comprising the steps of:
reacting a stoichiometric amount of pivalic acid with phosphorous trichloride in a reactor to get a crude product mixture, wherein said step of reacting pivalic acid with phosphorous trichloride is carried out in the absence of a solvent and a catalyst; and
effecting separation of Pivaloyl chloride and phosphorous acid from the product mixture.

2. The process as claimed in claim 1, wherein step of reacting pivalic acid with phosphorous trichloride is effected under continuous stirring at a rate ranging from 50 RPM to 200 RPM.

3. The process as claimed in claim 1, wherein said reaction is carried out at a temperature ranging from 50°C to 70°C for a time period ranging from 90 minutes to 150 minutes.

4. The process as claimed in claim 1, wherein the step of the separation of Pivaloyl chloride and phosphorous acid is effected by:
transferring the crude product mixture in a decanter;
allowing settlement of phosphorous acid;
separating the acidic layer containing phosphorous acid from the organic layer containing pivaloyl chloride; and
recovering phosphorous acid from the acidic layer, and Pivaloyl chloride from the organic layer.

5. The process as claimed in claim 3, wherein the step of recovering Pivaloyl chloride from the organic layer comprises subjecting the organic layer to flash distillation to recover Pivaloyl chloride.
, Description:
TECHNICAL FIELD
[0001] The present disclosure pertains to the technical field of chemical synthesis. In particular, the present disclosure pertains to an improved solvent and catalyst free process for preparation of Pivaloyl chloride.

BACKGROUND OF THE INVENTION
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] Pivaloyl chloride is an important synthetic intermediate in the chemical industry. It is widely used in the synthesis of various pharmaceutical products such as antiviral agents, anti-inflammatory agents, and plant-protection products such as herbicides, insecticides etc.
[0004] Various processes for preparation of Pivaloyl chloride are reported in the literature, however, these conventional processes represent complex technologies, on account of the reagents involved and the need to carry out expensive treatments of the products obtained including the effluents, which rule out their industrial production, or at least make them cost prohibitive.
[0005] There is, therefore, an unmet need in the art for a new and an improved process of preparation of Pivaloyl chloride that is cost-effective, easy to implement, and allow easy separation and purification of Pivaloyl chloride and by-products/effluents.
[0006] The present invention satisfies the existing needs, as well as others, and generally overcomes the deficiencies found in the prior art.
[0007] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.

OBJECTS OF THE INVENTION
[0008] It is an object of the present disclosure to provide a process for preparation of Pivaloyl chloride that overcomes one or more limitations associated with the conventional methods.
[0009] It is an object of the present disclosure to provide a process for preparation of Pivaloyl chloride that does not require any solvent or catalyst.
[0010] It is an object of the present disclosure to provide a process for preparation of Pivaloyl chloride that may produce 60% to 80% less by-products/effluents compared to conventional processes.
[0011] It is an object of the present disclosure to provide a process for preparation of Pivaloyl chloride that may allow easy and in-expensive separation of Pivaloyl chloride and by-products/effluents thereof.
[0012] It is an object of the present disclosure to provide a process for preparation of Pivaloyl chloride that is easy to implement and follow.
[0013] It is an object of the present disclosure to provide a process for preparation of Pivaloyl chloride that is economical.
[0014] It is another object of the present disclosure to provide a process for preparation of Pivaloyl chloride that may produce valuable by-products such as phosphorous acid that may be commercially sold or which may act as a reactant in the preparation of other valuable products such as phosphoric acid or diethylphosphite.

SUMMARY OF INVENTION
[0015] The present disclosure pertains to the technical field of chemical synthesis. In particular, the present disclosure pertains to an improved solvent and catalyst free process for preparation of Pivaloyl chloride.
[0016] An aspect of the present disclosure relates to a process for preparation of Pivaloyl chloride, the process including the steps of: (a) reacting a stoichiometric amount of pivalic acid with phosphorous trichloride in a reactor at a temperature ranging from 50°C to 70°C preferably 55°C to 65°C for a time period ranging from 90 minutes to 150 minutes to get a crude product mixture, said step of reacting pivalic acid with phosphorous trichloride being done in absence of any of a solvent and a catalyst; and effecting separation of Pivaloyl chloride and phosphorous acid from the crude product mixture. In an embodiment, the step of reacting pivalic acid with phosphorous trichloride is effected under continuous stirring at a rate ranging from 50 RPM to 200 RPM. In an embodiment, the step of the separation of Pivaloyl chloride and phosphorous acid is effected by: (a) transferring the crude product mixture in a decanter; (b) allowing settlement of crude product mixture; (c) separating a bottom acidic layer containing phosphorous acid from a top organic layer containing Pivaloyl chloride; and (d) recovering phosphorous acid from the bottom acidic layer, and Pivaloyl chloride from the top organic layer. In an embodiment, the step of recovering Pivaloyl chloride from the top organic layer includes subjecting the top organic layer to flash distillation to recover Pivaloyl chloride. In an embodiment, the recovered Pivaloyl chloride is of purity greater than 98%, when determined using Gas Chromatography.
[0017] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.
[0019] FIG. 1 is a schematic illustrating a process for preparation of Pivaloyl chloride, in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION
[0020] The following is a detailed description of embodiments of the present invention. The embodiments are in such detail as to clearly communicate the invention. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention as defined by the appended claims.
[0021] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the “invention” may in some cases refer to certain specific embodiments only. In other cases it will be recognized that references to the “invention” will refer to subject matter recited in one or more, but not necessarily all, of the claims.
[0022] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability.
[0023] Unless the context requires otherwise, throughout the specification which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense that is as “including, but not limited to.”
[0024] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
[0025] Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing. The expression “reacting pivalic acid with phosphorous trichloride in absence of any of a solvent and a catalyst”, “solvent and catalyst free process for preparation of Pivaloyl chloride” and the likes as used herein synonymously and interchangeably throughout the present disclosure denotes the meaning that the step of reacting pivalic acid with phosphorous trichloride, at process parameters (like temperature, stirring, reaction time etc.) laid down in embodiments of the present disclosure, does not necessitate utilization of solvent and/or catalyst. However, it should be appreciated that, if desired, one may use any of the conventionally known solvent and/or catalyst in advantageous process of the instant disclosure in such amounts that does not materially alter the character of the reaction schematic and/or does not materially alter progress of the reaction without departing from spirit of the present invention. For example, one may use any of the conventionally known inert solvent(s) in an amount of less than 5% by weight of the reaction mixture while reacting pivalic acid with phosphorous trichloride. Preferably, as explained below in detail, it would be advantageous to preclude utilization of solvent and catalyst while reacting pivalic acid with phosphorous trichloride.
[0026] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0027] In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable.
[0028] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein.
[0029] The headings and abstract of the invention provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.
[0030] All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[0031] The following discussion provides many example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed.
[0032] The present disclosure pertains to the technical field of chemical synthesis. In particular, the present disclosure pertains to an improved solvent and catalyst free process for preparation of Pivaloyl chloride.
[0033] The present disclosure is on the premise of surprising discovery of inventors of the present disclosure that reacting pivalic acid with phosphorous trichloride at a temperature ranging from 55°C to 65°C over a period of time ranging from 90 minutes to 150 minutes could produce a crude reaction mixture that allows easy and cost-effective separation of Pivaloyl chloride and phosphorous acid without need of utilization of any of a solvent and a catalyst. The process can be easily implemented at an industrial scale and is significantly cost-effective in comparison to the conventional processes. Since, usage of solvent and/or catalyst is not necessary in the advantageous process of the instant disclosure, the instant process circumvents several shortcomings of the conventional processes like difficulty in separation and/or purification of the desired products from the crude reaction mixture, apart from accruing significant cost reduction.
[0034] Accordingly, an aspect of the present disclosure relates to a process for preparation of Pivaloyl chloride, the process including the steps of: (a) reacting a stoichiometric amount of pivalic acid with phosphorous trichloride in a reactor at a temperature ranging from 55°C to 65°C for a time period ranging from 90 minutes to 150 minutes to get a crude product mixture, said step of reacting pivalic acid with phosphorous trichloride being done in absence of any of a solvent and a catalyst; and effecting separation of Pivaloyl chloride and phosphorous acid from the crude product mixture.
[0035] In an embodiment, the step of reacting pivalic acid with phosphorous trichloride is effected under continuous stirring at a rate ranging from 50 RPM to 200 RPM (rotation per minutes). In an embodiment, the step of reacting pivalic acid with phosphorous trichloride is effected under continuous stirring at a rate ranging from 80 RPM to 120 RPM. In an embodiment, the step of reacting pivalic acid with phosphorous trichloride is effected under continuous stirring at a rate of 100 RPM.
[0036] In an embodiment, the step of the separation of Pivaloyl chloride and phosphorous acid is effected by: (a) transferring the crude product mixture in a decanter; (b) allowing settlement of crude product mixture; (c) separating a bottom acidic layer containing phosphorous acid from a top organic layer containing Pivaloyl chloride; and (d) recovering phosphorous acid from the bottom acidic layer, and Pivaloyl chloride from the top organic layer.
[0037] In an embodiment, the step of recovering Pivaloyl chloride from the top organic layer includes subjecting the top organic layer to flash distillation to recover Pivaloyl chloride. In an embodiment, the recovered Pivaloyl chloride is of purity greater than 98%, when determined using Gas Chromatography. In an embodiment, the recovered Pivaloyl chloride is of purity greater than 99%, when determined using Gas Chromatography.
[0038] The recovered phosphorous acid (or the bottom acidic layer containing phosphorous acid) may further be converted to phosphoric acid by: mixing the bottom acidic layer with chilled water and FeSO4; raising temperature of the reaction mass to a temperature ranging from 40°C to 60°C; effecting addition of H2O2 to the reaction mass over a time period of 2 hours to 4 hours while maintaining a temperature ranging from 50°C to 100°C; and allowing completion of the reaction by maintaining the reaction mixture at a temperature ranging from 50°C to 100°C for a time period of 4 hours to 6 hours to obtain a crude product mass containing phosphoric acid. If required or desired, the crude product mass may further be subjected to separation and/or purification to recover phosphoric acid of desired purity and/or strength. For example, the crude product mass containing phosphoric acid may be subjected to evaporation to increase strength to about 70-75%. Phosphoric acid so obtained as byproduct may be sold as a value-added product. Alternatively, Phosphoric acid may be converted into phosphorous acid and also used for preparation of Diethyl phosphite (DEP). Advantageously the overall process of present invention is cost-effective and industrially viable.
[0039] FIG. 1 is a schematic illustrating a process for preparation of Pivaloyl chloride, in accordance with an embodiment of the present disclosure. As can be seen from FIG. 1, a stoichiometric amount of pivalic acid is reacted with phosphorous trichloride in a reactor 110 defining one or more feeding lines 102 (through which one or more reactants may be introduced in the reactor), a stirrer 104 or such other mechanism that affords stirring of the reaction mass, one or more outlets 106 (through which crude product mixture may be taken out from the reactor), and one or more outlets for the gas(es) 108 generated during the course of reaction. Any conventional reactor known to persons skilled in the art may be used, for example, glass lined reactor (e.g. MSGL reactor).
[0040] As can also be seen from FIG. 1, one or more scrubbers 120, 130 may be connected to the reactor 110 affording scrubbing of the gas(es) generated during the course of reaction. Preferably, the gas(es), primarily containing HCl gas, generated during the reaction due to moisture present in the system is removed from the reactor 110 and it is passed through condenser 140 to scrubbers 120 and 130. In scrubber 120, the gas may be scrubbed using water, and in scrubber 130, the gas may be scrubbed using caustic solution i.e. NaOH solution of appropriate strength, for example, using 10% NaOH solution. Scrubbing of the gas(es) in the scrubbers 120 number of times affords aqueous HCl of requisite purity.
[0041] As described above in detail, pivalic acid is reacted with phosphorous trichloride under appropriate reaction conditions to get the crude product mixture containing pivaloyl chloride and phosphorous acid. The crude product mixture may be taken out from the reactor 110 using outlet 106 for separation of pivaloyl chloride and phosphorous acid from the crude product mixture.
[0042] As can also be seen from FIG. 1, the crude product mixture is fed (transferred) to a decanter 150 and kept stationery for a suitable period allowing settlement of phosphorous acid, affording separation of bottom acidic layer containing phosphorous acid and top organic layer containing pivaloyl chloride. Top organic layer containing pivaloyl chloride can be taken out from the decanter 150 and subjected to further processing to recover pivaloyl chloride therefrom.
[0043] As can also be seen from FIG. 1, top organic layer containing pivaloyl chloride, obtained from the decanter 150 is fed to a flash distillation column 160 to obtain pivaloyl chloride of requisite purity. The flash distillation unit 160 may be operated at a temperature ranging from 110°C to 150°C and at atmospheric pressure. Alternatively, flash distillation column may be operated at other suitable operating conditions as known to or appreciated by a person skilled in the art for obtaining/recovering pivaloyl chloride of desired purity. It should also be appreciated that in place of flash distillation, any other conventional separation and/or purification technique(s) may be used for obtaining/recovering pivaloyl chloride of desired purity from the top organic layer.
[0044] Bottom acidic layer containing phosphorous acid may be used as such for production of phosphoric acid or such other valuable products for example diethyl phosphite. Alternatively, the bottom acidic layer may be subjected to separation and/or purification process(es), as known in the art, to get phosphorous acid of requisite purity and/or strength.
[0045] While the foregoing description discloses various embodiments of the disclosure, other and further embodiments of the invention may be devised without departing from the basic scope of the disclosure. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

[0046] EXAMPLES
[0047] EXAMPLE 1
[0048] About 845 kg of pivalic acid and 511 kg of phosphorous trichloride (PCl3) was fed to the reactor (MS glass lined reactor available commercially from PMM pfaudler and heated to a temperature of about 60°C for about 120 minutes, with continuous stirring at around 100 RPM to obtain a crude product mixture. The progress of reaction was monitored by analysing the reaction mass using a gas chromatography. Completion of the reaction was noted when the concentration of the unreacted pivalic acid left in the reaction mixture was less than 2%.
3(CH3)3CCOOH + PCl3 ? 3(CH3)3CCOCl + H3PO3
[0049] After completion of the reaction, the crude product mixture was transferred to a decanter, wherein crude product mixture was kept stationery for about 30 minutes, affording separation of crude product mixture into a top organic layer and a bottom acidic layer. 982 kg top organic layer containing Pivaloyl chloride was obtained from the decanter, and 230 kg of bottom acidic layer containing phosphorous acid was obtained from the decanter.
[0050] 982 kg top organic layer containing Pivaloyl chloride was subjected to flash distillation at temp 110 to 150 °C and atmospheric pressure with Vapor temperature of about 105-110 °C for 3 hours to 4 hours in a flash distillation unit to obtain 940 kg of Pivaloyl chloride with purity of 99% (measured by gas chromatography).
[0051] 230 kg bottom acidic layer containing phosphorous acid was mixed with 340 kg of chilled water and 17 kg of FeSO4. Temperature of the reaction mass was slowly raised to about 50°C. About 825 Kg of 50% H2O2 was slowly added to the above mixture in a time period of about 3 to 4 hrs. The reaction was allowed to complete by maintaining temperature between 50°C to 100°C for about 5 hrs to 6 hrs to get 875 Kg of crude product mass including phosphoric acid having strength of 28% to 30% with yield of about 90%.
[0052] Gases liberated during the reaction (primarily containing HCl) were sent to a scrubber through a condenser (maintained at room temperature). In the first scrubber, about 60 Kg of HCl gas was scrubbed with about 1000 litres of water, and the resultant gas was scrubbed in a second scrubber using 500 kg 10% NaOH solution.

[0053] EXAMPLE 2
[0054] About 500 kg of pivalic acid and 305 kg of phosphorous trichloride (PCl3) was fed to the reactor and heated to a temperature of about 60°C for about 120 minutes, with continuous stirring at around 100 RPM to obtain a crude product mixture. Progress of the reaction was monitored by analysing the reaction mass in a gas chromatography. The reaction was marked completed when concentration of the unreacted pivalic acid left in the reaction mixture was not greater than 2%.
[0055] After completion of the reaction, the crude product mixture was transferred to a decanter, wherein crude product mixture was kept stationery and allowed to settle for about 30 minutes, resulting in separation of crude product mixture into a top organic layer of 585 kg containing Pivaloyl chloride and a bottom acidic layer of 135 kg containing phosphorous acid.
[0056] The top organic layer of 585 kg containing Pivaloyl chloride was subjected to flash distillation in a flash distillation unit at temp 110 to 150°C and atmospheric pressure with Vapor temperature of about 105 to 110°C for 3 hours to 4 hours to get 545 kg of Pivaloyl chloride with purity of 99% (measured by gas chromatography).

[0057] COMPARATIVE COST BENEFIT STUDIES
[0058] Numerous experiments were conducted wherein Pivaloyl Chloride was produced using conventional process viz. (i) reacting Pivalic acid with Thionyl Chloride, (ii) reacting Pivalic acid with Oxalyl Chloride, and (iii) reacting Pivalic acid with Phosgene. In such conventional processes, the byproduct is HCl gas along with SO2 and/or CO2 gases. It could be noted that in conventional processes, the amount of HCl liberated during the process is almost 5 times as compared to the process as detailed in Example 1. These gases require treatment with caustic solution which generates effluent like Sodium Bisulfite. Consequently, it could be concluded that the cost of production of Pivaloyl Chloride using the process of the instant disclosure (Example 1) is in the range of INR 10 to 12 per Kg of Pivaloyl Chloride versus the cost of production of Pivaloyl Chloride using the conventional processes which are in the range of INR 22 to 25 per Kg of Pivaloyl Chloride. Thus, the present process is very cost-effective and commercially viable process.
[0059] From the experimental data, it could be concluded that in the advantageous process for preparation of Pivaloyl chloride, as detailed herein, one need not necessarily use solvent or catalyst. Further, the advantageous process of the present disclosure affords easy and cost-effective separation of Pivaloyl chloride and by-products/effluents such as phosphorous acid, overcoming the problems associated with conventional processes for preparation of Pivaloyl chloride. Notably, the process of the instant disclosure is capable of implementation at an industrial scale and is significantly cost effective as compared to conventional processes.

ADVANTAGES OF THE PRESENT INVENTION
[0060] The present disclosure is simple and provides high yield product and reduces the cost of the process.
[0061] The present disclosure provides a process for preparation of Pivaloyl chloride that overcomes one or more limitations associated with the conventional methods.
[0062] The present disclosure provides a process for preparation of Pivaloyl chloride that does not require any solvent or catalyst.
[0063] The present disclosure provides a process for preparation of Pivaloyl chloride that produces 60% to 80% less by-products/effluents compared to conventional processes.
[0064] The present disclosure provides a process for preparation of Pivaloyl chloride that allow easy and in-expensive separation of Pivaloyl chloride and by-products/effluents thereof.
[0065] The present disclosure provides a process for preparation of Pivaloyl chloride that is easy to implement.
[0066] The present disclosure provides a process for preparation of Pivaloyl chloride that is economical.
[0067] The present disclosure provides a process for preparation of Pivaloyl chloride that produces valuable by-products such as phosphorous acid that may be commercially sold or which can be used as a reactant in the preparation of other valuable products such as phosphoric acid or diethylphosphite. Further present invention is valuable for preparing precursor intermediate compounds that are useful for the manufacture of Clomazone.