Piperonyl butoxide distillation process with rectification to obtain high purity PBO

Abstract

The present invention relates to a composition comprising piperonyl butoxide (PBO) in a weight concentration ranging from 94 to 99.9% by weight, dipiperonyl methane (DPM) in a weight concentration ranging from 0.01 to 1% by weight, and dipiperonyl ether (DPE) in a weight concentration ranging from 0 to 0.1% by weight, based on the total weight of the composition, and a distillation method for obtaining the same.

Description

[Technical Field]

[0001] The present invention relates to compositions containing piperonyl butoxide (PBO) and distillation processes for obtaining the same. [Background technology]

[0002] The compound piperonyl butoxide, whose IUPAC name is 5-{[2-(2-butoxyethoxy)ethoxy]methyl}-6-propyl-2H-1,3-benzodioxole and also known by the acronym PBO, is a high-boiling molecule that decomposes rapidly at 300 °C (the boiling point at 278 Pa is 203 °C; the calculated boiling point at 101,300 Pa is 400 °C).

[0003] For this reason, industrial processes for producing PBO involve one or more fractionated evaporations to obtain the final product. The evaporation process can be carried out using a variety of methods, such as vapor stream evaporation, thin film evaporation, or simple batch evaporation.

[0004] Due to the physical properties of the product itself, evaporation methods require harsh conditions such as high vacuum and high temperature, and do not allow for efficient separation of by-products resulting from the synthesis method, which inevitably end up in the final product, especially under essential conditions, thus limiting its quality.

[0005] WO 2021161083 reports a method for producing piperonyl butoxide. Specifically, Example 1c on page 21 describes the separation of the organic layer followed by distillation to obtain PBO. The problem is that the details of the distillation process for PBO are not provided, which concerns the synthesis of various molecules obtained from benzodioxoles, particularly sesamol and DHS, via various catalysts or their mixtures.

[0006] In patent application IND No. 201941007564, in example 3, in relation to step 4, it is stated that after separation of the organic layer and distillation of toluene under vacuum, PBO is distilled by fractional distillation without giving any details regarding the distillation itself.

[0007] A Chinese paper by XU Songlin et al., "Refining Piperonyl Butoxide by Short-Path Distillation," Transactions of the CSAE, Vol. 21, No. 2, February 2005, presents data and graphs showing the results of distilling PBO using two short-path evaporators in series. In the first evaporator, light products are removed, while heavy products move to the second evaporator along with the desired product, PBO. In the second evaporator, cascaded to the first, PBO is collected as the evaporated product, and the heavy by-product is collected as the residue. This paper reports the acquisition of a final PBO product with a purity of up to 96% and a yield exceeding 70%. While the described short-path evaporation is certainly a suitable method for the distillation of high-boiling and thermally unstable molecules, it does not allow for the effective separation of impurities and therefore the acquisition of a high-purity product in high yield.

[0008] Chinese Utility Model Patent No. 212417044, filed in the name of Wujiang Shuguang Chemical, describes a PBO distillation method. Specifically, it describes a continuous vapor flow distillation method using a column with alternating partition walls. Specifically, this document focuses on the energy savings and environmental protection that result from recovering the steam condenser cooling water. Referring to Figure 1 of the model itself, condenser 4 is connected to cylinder 1. This document begins with the assumption that existing rectification methods for producing PBO are inefficient from an energy perspective and have limited rectification efficiency. Referring to line 19 on page 1, it states that the grinding column used to produce PBO has a single function, complex procedures, a relatively low grinding efficiency, and does not allow for the reuse of cooling water.

[0009] The inventors have analyzed the process described in the utility model in detail and found that it involves distillation with rectification in the vapor stream, but does not indicate pressure and temperature conditions. Furthermore, any organic components separated by the feed vapor (18) and carried to the top are completely condensed by the condenser (4) and completely reintroduced into the column through the condensate return (5). Therefore, the inventors realized that, according to the proposed mechanism, any impurities that may be removed at the top (3) are condensed (4) and entirely reintroduced into the process (5) and collected at the bottom with the product (17). The condensed vapor introduced at (18) also renders the process itself unusable at the level of product purification. Therefore, the possible rectification effect introduced by the staggered partition walls described in the specification is nullified by the very arrangement of the equipment in the distillation plant shown in the utility model. The Chinese model reports no data on the purity of the feed material (15) and the resulting product (17), nor any mention of yields, nor any indication of the reflux ratio, temperature, and pressure conditions used in the distillation.

[0010] China Utility Model No. 202131299, filed in the name of Nanchang Yangpu Natural Essence & Spice Co., Ltd., describes a batch distillation apparatus equipped with a test device for use in a purification process as an in-process purity test. As stated in the abstract, the apparatus is intended to test the final purity of PBO.

[0011] This paper highlights the fact that commonly used methods for obtaining PBO require sampling and laborious analysis from distillation tanks to determine whether the resulting PBO is of suitable purity for use in its intended application.

[0012] The reported disclosure does not provide any examples explaining how the distillation process is carried out. There is no disclosure of the impurity content of the starting material, the temperature and pressure conditions of the distillation process, or even the reflux ratio. The only disclosure is that the starting solvent is removed in a separate device, and then the compound is fed to the boiler (1) of the distillation system. Specifically, the system includes a boiler (1), connected to a pump (2) that recirculates the boiler contents via a heater (3). The document reports that passing the boiler contents through the heater (3) via the pump (2) generates high temperatures with low vapor pressure, causing the PBO to evaporate from the liquid phase. According to the document, the PBO compound passes through a fractionation column (4) to become a gas that reaches the top of the column, where it condenses back into liquid form in a condenser (5) located at the top of the column. The liquid is then further cooled in a second condenser (6) and enters a device (7) that controls its quality. If the purity is greater than 95%, a green light on the device display will illuminate and the liquid will be sent to the collection tank (8). If the purity of the liquid in the device (7) is less than 95%, a red light on the device display will illuminate and the liquid will be sent back to the boiler (1) and the above process will be repeated.

[0013] The present inventors have studied Chinese Utility Model No. 202131299 in detail and found that, according to this document, piperonyl butoxide can be almost reliably purified by removing the heavy by-product portion of the starting material that accumulates in the boiler. It is known that when crude PBO as a starting material is heated, it generates not only heavy decomposition by-products but also light decomposition by-products. According to the inspection system described in Chinese Utility Model No. 202131299, these light by-products inevitably accumulate at the top of the fractionation column (4) after passing through the distillation column (4) itself, and when condensed, they reduce the purity of the collected liquid received by the device (7) after condensation in (5) and (6). This document, which aims to inspect the final purity of PBO, does not teach how to purify PBO containing very small amounts of specific impurities and their decomposition products.

[0014] It is therefore clear that the prior art does not suggest a method for obtaining piperonyl butoxide in good purity by simple distillation followed by rectification. In fact, to date, no distillation method followed by rectification that allows for the efficient removal of impurities from PBO has found industrial applicability due to the pressure loss inevitably introduced by the use of a rectification column. The expression "pressure loss" refers to the pressure difference between the top and bottom of the column, which has a strong influence on the temperature profile of the column itself.

[0015] The pressure loss introduced necessarily requires higher temperatures for vaporization of the product, which complicates the process.

[0016] As mentioned above, high temperatures actually increase the decomposition of the product with the formation of additional impurities, resulting in lower yields and lower purity. Macroscopic decomposition processes occur at temperatures of about 300°C, but slower but significant decomposition processes are observed at temperatures above 240°C over long periods of time.

[0017] The main impurities formed from the decomposition of PBO crude are low-boiling compounds produced in the boiler. Among the heavy crude impurities are dipiperonyl methane (DPM, IUPAC name: 5,5'-methanediylbis(6-propyl-1,3-benzodioxole)) and dipiperonyl ether (DPE, IUPAC name: 5,5'-(oxydimethanediyl)bis(6-propyl-1,3-benzodioxole)), which in turn tend to decompose at high temperatures, especially at temperatures known for the evaporation / distillation of PBO itself.

[0018] The object of the present invention is therefore to obtain piperonyl butoxide in high purity and good yield without using a plant that is difficult to manage and therefore in the presence of harsh production conditions.

[0019] A further object is to provide piperonyl butoxide free of heavy and light decomposition by-products that may be produced during the distillation of PBO, a high boiling compound. Summary of the Invention

[0020] These objects have been achieved according to the invention by a process for the preparation of piperonyl butoxide (PBO), which makes it possible to obtain compositions containing PBO in concentrations ranging from 94 to 99.9% by weight, dipiperonyl methane (DPM) ranging from 0.01 to 1% by weight, and dipiperonyl ether (DPE) ranging from 0 to 1% by weight, relative to the total weight of the composition.

[0021] Thus, the present invention relates to a composition comprising a PBO in a concentration ranging from 94 to 99.9% by weight, dipiperonyl methane (DPM) in a concentration ranging from 0.01 to 1% by weight, and dipiperonyl ether (DPE) in a concentration ranging from 0 to 1% by weight, relative to the total weight of the composition.

[0022] Therefore, the present invention makes it possible to obtain a highly pure PBO with low concentrations of specific impurities of DPM and DPE. In fact, when we say that the concentration of PBO is very high in a mixture, we are referring to its percent purity.

[0023] Without being bound by any theory, the inventors believe that, in contrast to what has been reported in the literature, they have succeeded in obtaining such high purity PBO and having such low amounts of DPE and DPM thanks to a distillation method involving rectification under reduced pressure, which allows for the recovery of both heavy and light by-products formed during the distillation of PBO, ensuring the obtaining of a composition containing PBO in a concentration ranging from 94 to 99.9% by weight, dipiperonyl methane (DPM) ranging from 0.01 to 1% by weight, and dipiperonyl ether (DPE) ranging from 0 to 1% by weight, relative to the total weight of the composition. At the same time, the method of the present invention allows for a distillation yield of more than 85%.

[0024] In fact, as is known in the prior art, if high purity PBO is obtained from a distillation process, the use of harsh processing conditions simultaneously leads to low distillation yields, which makes the process unattractive from an industrial point of view.

[0025] Thus, in another aspect, the present invention relates to a distillation method for preparing a composition comprising a PBO according to the present invention, comprising one or more distillation steps of a crude product comprising a PBO in a distillation apparatus comprising a rectification apparatus, the distillation apparatus comprising at least one distillation column, each independently having one or more theoretical stages and a reflux ratio in the range of 0.5:1 to 15:1, wherein the one or more distillation steps are carried out under vacuum conditions.

[0026] The distillation process of the present invention also makes it possible to obtain distillation yields of over 85%.

[0027] Advantageously, the distillation process is carried out under vacuum conditions, preferably at the maximum vacuum possible with the best technical options available on the market, preferably at a pressure of less than or equal to 4000 Pa, more preferably less than or equal to 2000 Pa, even more preferably in the range of from 1500 Pa to 10 Pa.

[0028] The PBO-containing crude product, i.e., the starting material, of the process of the present invention is preferably a product containing PBO at a concentration of 75% or more, preferably 83% or more, and more preferably 90% or more. The crude PBO product starting material, as a composition containing PBO and impurities, has DPM and DPE in amounts greater than 1% by weight based on the total weight of the entire composition. After the distillation process of the present invention, the final composition contains PBO at a concentration ranging from 94 to 99.9% by weight, dipiperonyl methane (DPM) ranging from 0.01 to 1% by weight, and dipiperonyl ether (DPE) ranging from 0 to 1% by weight based on the total weight of the composition.

[0029] In a preferred embodiment of the invention, the distillation apparatus operates continuously.

[0030] In a further advantageous embodiment of the present invention, one or more distillation columns of the distillation apparatus include an internal condenser, which allows for a reduction in the system pressure drop and therefore ensures lower processing temperatures, which is important for limiting the thermal decomposition of the product. Without being bound by any theory, the inventors believe that the presence of the internal condenser allows for the selective removal and condensation of only the desired light cracking by-product portion of the distillate through temperature control. This advantageously allows for significant energy savings, given that the internal reflux liquid is not "subcooled" and is not reintroduced by pumping, remaining at the temperature of the distillation phase.

[0031] In a preferred embodiment, one or more distillation columns of the distillation apparatus actually contain an external reboiler, which allows the product to have a shorter contact time with the hotter wall sections of the distillation apparatus. This minimizes the thermal stress on the product, resulting in less decomposition. The reduced product decomposition, combined with the separation provided by the distillation apparatus with rectification equipment, leads to higher product quality and yield. In an even more preferred embodiment, the option of external heating (which always operates at full capacity) is combined with level control within the apparatus, which avoids the formation of potentially dangerous hot spots.

[0032] In a preferred and advantageous embodiment of the present invention, the process of the present invention is continuous, allowing for very precise and reproducible control over the final product. In fact, the average residence time at high temperatures during the process is less than that of a batch process, given the same productivity. Furthermore, a continuous distillation process is easier to manage operationally (fewer single operations due to the absence of transient events to manage), smaller in size and less equipment (cheaper and less maintenance) than a batch process, given the same productivity, and more efficient from an energy standpoint (allowing for easy energy recovery by preheating the inlet stream to cool the outlet stream). A continuous process also allows for a shorter residence time of the product, which minimizes the formation of decomposition by-products.

[0033] In a further preferred embodiment of the present invention, the selection of a highly efficient packing with a relative liquid distribution system allowed for maximizing the number of theoretical distillation stages while minimizing pressure drop.

[0034] Further characteristics and advantages of the invention will become apparent from the following detailed description, given by way of non-limiting example with the aid of the figures shown in the accompanying drawings, in which: DETAILED DESCRIPTION OF THE INVENTION

[0035] The present invention relates to a composition comprising a PBO in a concentration ranging from 94 to 99.9% by weight, dipiperonyl methane (DPM) in a concentration ranging from 0.01 to 1% by weight, and dipiperonyl ether (DPE) in a concentration ranging from 0 to 1% by weight, based on the total weight of the composition.

[0036] Thus, the present invention makes it possible to obtain a highly pure PBO with low concentrations of specific impurities of DPM and DPE.

[0037] The composition contains PBO in a concentration ranging from 94 to 99.9% by weight, preferably from 96 to 99%.

[0038] The compositions of the present invention comprise dipiperonyl methane (DPM) in the range of 0.01 to 1%, preferably in the range of 0.01 to 0.5%, more preferably 0.01 to 0.1% by weight relative to the weight of the composition.

[0039] The composition of the present invention comprises dipiperonyl ether (DPE) in the range of 0 to 1%, preferably 0.01 to 0.5, more preferably 0.01 to 0.1%, by weight of the total composition.

[0040] Thus, in another aspect, the present invention relates to a distillation method for preparing a composition comprising a PBO according to the present invention, comprising one or more distillation steps of a crude product comprising a PBO in a distillation apparatus comprising a rectification apparatus, the distillation apparatus comprising at least one distillation column, each independently having one or more theoretical stages and a reflux ratio in the range of 0.5:1 to 15:1, wherein the one or more distillation steps are carried out under vacuum conditions.

[0041] When the following terms are used in the present invention: "Theoretical stage" means the number of theoretical stages in one or more columns of a distillation apparatus comprising a rectification apparatus, calculated according to any of the methods known in the art. "Distillation steps" means the number of steps carried out in a distillation apparatus equipped with rectification equipment. "Unpurified product containing PBO" means a starting unpurified product containing PBO and having a content of the impurities DPE and / or DPM of more than 1%. Preferably, the unpurified product contains PBO at a concentration of 75% or more, preferably 83% or more, more preferably 90% or more, and more preferably has a DPM and DPE content of more than 1% to 4%, even more preferably 1% to 3%, even more preferably 1% to 2%. "Under vacuum conditions" means a pressure below atmospheric pressure. "Product degradation" or "crude product degradation" or "crude impurity degradation" means degradation of PBO and impurities including DMP and DPE.

[0042] The distillation process of the present invention also makes it possible to obtain a distillation yield of more than 85%, preferably in the range of 90% to 98%, of the crude product containing PBO.

[0043] The PBO crude product can be obtained according to any of the methods known in the art.

[0044] According to the present invention, the crude PBO-containing product contains PBO at a concentration of 75% or more, preferably 83% or more, and more preferably 90% or more. The crude PBO product starting material as a composition containing PBO and impurities has DPM and DPE in amounts greater than 1% by weight based on the total weight of the entire composition. After the distillation process of the present invention, the final composition contains PBO at a concentration ranging from 94 to 99.9% by weight, dipiperonyl methane (DPM) ranging from 0.01 to 1% by weight, and dipiperonyl ether (DPE) ranging from 0 to 1% by weight based on the total weight of the composition.

[0045] Advantageously, the distillation process is carried out under vacuum conditions, preferably at the maximum vacuum possible with the best technical options available on the market, preferably at a pressure of less than or equal to 4000 Pa, more preferably less than or equal to 2000 Pa, even more preferably in the range of from 1500 Pa to 10 Pa.

[0046] According to the invention, the process is carried out in a distillation apparatus equipped with a rectification apparatus comprising at least one distillation column, preferably one to three distillation columns, which likewise have, independently of one another, at least one, preferably several, from 1 to 30, theoretical stages and a reflux ratio in the range of 0.5:1 to 15:1.

[0047] According to a preferred embodiment, said rectification unit is a rectification column or a series of rectification columns, preferably two to three columns, which can be operated in series or succession, i.e. simultaneously in a cascade.

[0048] Distillation can be carried out in many different ways, and the possible combinations increase as the number of columns increases.

[0049] For example, raw product can be fed to a first column from which light by-products exit. Compound PBO with heavy by-products exits the bottom of the boiler, and then compound PBO is fed to a second column. Light cracked by-products exit the top of the second column, high-purity PBO exits through a side strip, and heavy by-products exit the bottom of the column.

[0050] For example, by changing the process parameters, the same setup with two columns can result in PBO with heavy by-products coming out the bottom of the first column and light products and a portion of the DPM on top. The PBO with the lights and a portion of the DPM can then be fed to a second column where the light / cracked by-products come out at the top, high purity PBO comes out the side strip, and DPM comes out the bottom.

[0051] Thus, the process according to the invention in embodiments having two or more columns provides at least one distillation step under vacuum conditions.

[0052] In a preferred advantageous embodiment, the distillation process is carried out in a distillation apparatus equipped with a rectification apparatus comprising a single distillation column.

[0053] The rectification unit has at least one, preferably several theoretical stages ranging from 1 to 30, and a reflux ratio of a similar distillation unit ranging from 0.5:1 to 15:1.

[0054] The number of theoretical stages preferably ranges from 5 to 25, more preferably from 9 to 20.

[0055] Without being bound by any theory, the inventors believe that a distillation apparatus with a rectification apparatus having a number of stages greater than 30 makes it possible to obtain highly pure PBO, but at a yield that is too low, while a number less than 1 does not allow the product to be sufficiently purified from one or both of the DPE and DPM impurities.

[0056] According to a preferred invention, when the number of theoretical stages is approximately or equal to 30, the distillation process includes multiple distillation phases, preferably two or three distillation phases, to avoid pressure drops that would increase the boiling point and cause PBO decomposition.

[0057] In the process of the present invention, the distillation apparatus equipped with rectification equipment comprises at least one distillation column, preferably one to three distillation columns, each of which independently has a reflux ratio in the range of 0.5:1 to 15:1. Preferably, the reflux ratio is in the range of 3:1 to 10:1, more preferably 4:1 to 8:1.

[0058] The distillation apparatus preferably includes a boiler in the form of a reactor heating system with diathermic oil or a boiler external to at least one distillation column, said boiler being at a temperature in the range of 170°C to 270°C, preferably 190°C to 260°C, more preferably 200°C to 250°C to enable PBO distillation.

[0059] According to the invention, advantageously, if the number of stages in one or more columns of the distillation apparatus equipped with rectification equipment exceeds 9, the distillation of the crude PBO can be carried out preferably in a single phase, whereas if the number of stages is less than 9, the distillation process is advantageously carried out in two or more distillation phases, in which the product of the previous distillation is used as starting material for the subsequent distillation.

[0060] In a preferred embodiment of the invention, the distillation apparatus operates continuously.

[0061] The distillation process also preferably provides for the use of condensers and / or reboilers for each distillation column, both internal and external.

[0062] In a further advantageous embodiment of the present invention, one or more distillation columns of the distillation apparatus include an internal condenser, which allows for a reduced system pressure drop, ensuring lower processing temperatures, which is important for limiting thermal decomposition of the product / crude impurities. Without being bound by any theory, the inventors believe that the presence of the internal condenser allows for selective removal and condensation of only the desired light fraction of the distillate through temperature control. This advantageously allows for significant energy savings, given that the internal reflux liquid is not "subcooled" and is not reintroduced by pumping, remaining at the temperature of the distillation phase.

[0063] In a preferred embodiment, one or more distillation columns of the distillation apparatus actually contain an external reboiler, which allows for a shorter contact time of the product with the hotter wall sections of the distillation apparatus. This minimizes the thermal stress of the product / crude impurities, resulting in less decomposition. Combined with the separation provided by the distillation apparatus with rectification equipment, reduced product decomposition leads to higher product quality and yield. In an even more preferred embodiment, the option of external heating (which always operates at full capacity) is combined with level control within the apparatus, which avoids the formation of potentially dangerous hot spots.

[0064] The distillation apparatus comprising the rectification apparatus may include at least one to three or more distillation columns sized to have optimum reflux under process conditions.

[0065] The internal reflux can preferably be varied within the ranges indicated by varying the outlet steam temperature, feed rate, feed temperature, and the amount of heat supplied to the external reboiler, if present.

[0066] Indeed, in a preferred embodiment, the distillation apparatus of the present invention comprises at least one distillation column, preferably one to three, each containing an external reboiler, which allows for a reduction in the contact time of the product with the hotter walls of the distillation apparatus, independently of one another. This minimizes the thermal stress on the product / crude impurities, resulting in less decomposition. Combined with the separation provided by the distillation apparatus with rectification equipment, the reduced decomposition of the product / crude impurities leads to higher product quality and yield. In an even more preferred embodiment, the option of external heating (which always operates at full capacity) is combined with level control within the apparatus, which avoids the formation of potentially dangerous hot spots.

[0067] Without being bound by any theory, the inventors believe that the use of an internal condenser and / or an external reboiler is an advantageous aspect as it allows for a reduced pressure drop and reduced cracking of the product / crude impurities.

[0068] In a preferred and advantageous embodiment of the present invention, the process of the present invention is continuous, allowing for very precise and reproducible control over the final product. In fact, for the same productivity, the average residence time at high temperatures during the process is reduced compared to batch processes. Furthermore, continuous distillation processes are easier to manage operationally (fewer single operations due to the absence of transients to manage), require smaller equipment (cheaper and less maintenance) than batch processes for the same productivity, and are more efficient from an energy standpoint (enabling easy energy recovery by preheating the inlet stream to cool the outlet stream). Continuous processes also allow for shorter residence times of the product / raw impurities, which minimizes the formation of decomposition by-products.

[0069] In a further preferred embodiment of the invention, the distillation apparatus comprises at least one distillation column, preferably one to three columns, using a relative liquid distribution system and therefore advantageously with high efficiency packing to minimize loading losses.

[0070] Again, the reduced pressure drop allowed for lower processing temperatures which limited product / crude impurity decomposition.

[0071] According to the present invention, the distillation method, distillation apparatus, preferably at least one distillation column of the present invention may preferably comprise a recovery system for heavy and light cracked impurities, said recovery system preferably comprising a final product recovery pump and a bottom product recovery pump connected to the bottom product collection tank and the top product collection tank, respectively.

[0072] Therefore, in a further aspect, the present invention relates to the composition of the present invention obtainable from the distillation process of the present invention.

[0073] The present invention is further described, for illustrative and non-limiting purposes, in the following experimental section, which reports examples of the use of the method of the present invention on various raw materials and the effect of the method on the final product.

[0074] Experimental section Example 1 Obtaining 97% PBO with 0.7% DPM and 0.1% DPE (laboratory batch, 10:1 reflux ratio, 2 stages) 499 g of PBO crude product with 86% w / w titre was placed in a 4-neck 1 litre flask.

[0075] The flask was equipped with a rectification column (h 50 mm × d 25 mm) equipped with 10 cm of Sulzer EX packing, the flask was connected to the top of the column and prepared for high vacuum distillation using an oil pump. The system was equipped with vacuum and temperature measuring points at the top and in the boiler.

[0076] A heating plate was used to heat the system through the aluminum enclosure.

[0077] Agitation of the boiler was achieved using a magnetic stir bar.

[0078] The vacuum was measured using a capacitance cell and a digital reader.

[0079] Magnetic stirring was started, the system was brought to maximum pump vacuum, and heating was initiated by setting the plate temperature at 250° C. Distillate collection was started under the conditions shown in Table 1 below. The distillation process was carried out under vacuum conditions.

[0080] [Table 1] Once collection of fraction 2 was complete, the distillation was stopped. 83.5 g of heavy by-product remained in the flask. The system was operated with the distillate collection valve partially open to give a reflux ratio of 10:1. There were two separation stages. Table 5 below shows the composition of the input crude and the composition of the output product. The distillation process was carried out under vacuum conditions.

[0081] [Table 2] The distillation yield based on PBO was 91.5%.

[0082] Example 2 Obtaining 97% PBO with 0.5% DPM and 0.05% DPE (laboratory batch, 10:1 reflux ratio, 3 stages) 500 g of PBO crude product with 86% w / w titre was placed in a 4-neck 1 litre flask.

[0083] The flask was equipped with a rectification column (h 50 mm × d 25 mm) equipped with 15 cm of Sulzer EX packing, the flask was connected to the top of the column and prepared for high vacuum distillation using an oil pump. The system was equipped with vacuum and temperature measuring points at the top and in the boiler.

[0084] A heating plate was used to heat the system through the aluminum enclosure.

[0085] Agitation of the boiler was achieved using a magnetic stir bar.

[0086] The vacuum was measured using a capacitance cell and a digital reader.

[0087] Magnetic stirring was started, the system was brought to maximum pump vacuum, and heating was initiated by setting the plate temperature to 250° C. The distillation process was carried out under vacuum conditions.

[0088] Fraction collection was started under the conditions shown in Table 4 below.

[0089] [Table 3] Once collection of fraction 2 was complete, the distillation was stopped. 88 g of heavy by-product remained in the flask. The system was operated with the distillate collection valve partially open to give a reflux ratio of 10:1. There were three separation stages. Table 5 below shows the composition of the input crude and the composition of the output product.

[0090] [Table 4] The distillation yield based on PBO was 89.7%.

[0091] Example 3 Obtaining 96.4% PBO with 0.35% DPM and 0% DPE (laboratory batch, 10:1 reflux ratio, 5 stages) 505.2 g of PBO crude product with 83% w / w titre was placed in a 4-neck 1 litre flask.

[0092] The flask was equipped with a rectification column (h 50 mm × d 25 mm) equipped with 20 cm of Sulzer EX packing, the flask was connected to the top of the column and prepared for high vacuum distillation using an oil pump. The system was equipped with vacuum and temperature measuring points at the top and in the boiler.

[0093] A heating plate was used to heat the system through the aluminum enclosure.

[0094] Agitation of the boiler was achieved using a magnetic stir bar.

[0095] The vacuum was measured using a capacitance cell and a digital reader. The distillation process was carried out under vacuum conditions.

[0096] Magnetic stirring was started, the system was brought to maximum pump vacuum, and heating was initiated by setting the plate temperature to 250° C. Distillate collection was started at the conditions shown in Table 4 below.

[0097] [Table 5] Once collection of fraction 2 was complete, the distillation was stopped. 87.5 g of heavy by-product remained in the flask. The system was operated with the distillate collection valve partially open to give a reflux ratio of 10:1. There were five separation stages. Table 5 below shows the composition of the input crude and the composition of the output product.

[0098] [Table 6] The distillation yield based on PBO was 88.5%. Laboratory tests have shown that it is possible to obtain the desired product under the conditions described.

[0099] Example 4 Obtaining 97.6% PBO with 0.09% DPM and 0% DPE (laboratory batch, 2:1 reflux ratio, 10 stages) 1205 g of PBO crude product with a titer of 94.9% w / w was placed in a 4-neck 2 liter flask.

[0100] The flask was equipped with a rectification column (h 55 mm × d 43 mm) equipped with 50 cm of Sulzer type DX packing, the flask was connected to the top of the column and prepared for high vacuum distillation using an oil pump. The system was equipped with vacuum and temperature measuring points at the top and in the boiler.

[0101] At the top was a reflux control system with timed valves that allowed adjustment of collection and reflux times.

[0102] The system was heated through a heating enclosure connected to a potentiometer that controlled the power supplied.

[0103] The vacuum was measured using a capacitance cell and a digital reader.

[0104] The system was brought to the maximum possible vacuum by means of an oil pump and heating was initiated by acting on a potentiometer.

[0105] Distillate collection was carried out under the conditions shown in Table 7 below, with a reflux:collection ratio of 2:1 (10 inches reflux: 5 inches collection).

[0106] [Table 7] Once collection of fraction 2 was complete, the distillation was stopped. 99 g of heavy by-product remained in the flask. The system was operated at a reflux ratio of 2:1. There were 10 separation stages. Table 8 below shows the composition of the input crude and the composition of the output product.

[0107] [Table 8] The distillation yield was 89.2%.

[0108] Example 5 Obtaining 99% PBO with 0.03% DPM and 0% DPE (continuous industrial column, 4:1 reflux ratio, 20 stages) The continuous distillation system consisted of: -Raw feed tank - a dosing pump for feeding the crude into the column - Raw feed preheating system - a rectification column having 20 theoretical stages with an internal condenser, a side feed inlet, a light product withdrawal section, a heavy product withdrawal section and a product side withdrawal -Condenser after the overhead product - External bottom reboiler heated with diathermic oil -Tower bottom / external reboiler recirculation pump -Final product recovery pump -Final product collection tank -Bottom product recovery pump -Bottom product collection tank -Top product collection tank Pressure and temperature sensors located at the bottom, feed, product withdrawal, and top of the column. -High efficiency vacuum pumps and boosters -Diathermic oil circuit

[0109] 1200 kg of crude PBO, 91.9% by weight, was charged to the bottom of the column, the system was pumped to the maximum possible vacuum, the system was started, the boiler temperature was set to 240°C, and the internal top condenser was set to 120°C.

[0110] Once a steady state was reached, the crude was pumped in at a rate of 180 kg / h (200°C), while the collection of product from the side draw at a rate of 163 kg / h (side draw from the column at 190°C) and the collection of residue from the bottom at a rate of 12 kg / h (221°C) were started via respective pumps.

[0111] The removal rate of the top fraction leaving the condenser was 5 kg / h at a temperature of 120° C. The top pressure was equal to 280 Pa and the bottom pressure was equal to 900 Pa.

[0112] The system was operated at a reflux ratio of 4:1 and 20 stages.

[0113] The system was run continuously for 7.5 hours, yielding 1222.5 kg of high purity product, 37.5 kg of overhead by-product and 90 kg of bottom by-product.

[0114] Table 9 below shows the composition of the crude feed and the product discharged from the column side draw.

[0115] [Table 9] The distillation yield was 97.4%.

[0116] The creation of a designed distillation system with continuous rectification and the adopted technical solutions made it possible to obtain the desired results.

Claims

1. A composition comprising PBO in a concentration ranging from 94 to 99.9% by weight, dipiperonyl methane (DPM) in a concentration ranging from 0.01 to 1% by weight, and dipiperonyl ether (DPE) in a concentration ranging from 0 to 1% by weight, based on the total weight of the composition.

2. 2. The composition of claim 1, wherein the composition comprises PBO at a concentration ranging from 94 to 99.9% by weight, preferably from 96 to 99%.

3. 3. The composition according to claim 1 or 2, wherein dipiperonyl methane (DPM) is present in an amount ranging from 0.01 to 0.5%, preferably from 0.01 to 0.1%, by weight of the composition.

4. 4. The composition according to claim 1, wherein dipiperonyl ether (DPE) is present in an amount ranging from 0.01 to 0.5%, preferably from 0.01 to 0.1%, relative to the total weight of the composition.

5. 5. A distillation process for preparing the composition comprising PBO of any one of claims 1 to 4, comprising one or more distillation steps of a crude product comprising PBO in a distillation apparatus comprising a rectification apparatus, the distillation apparatus comprising at least one distillation column, each at least one distillation column independently having one or more theoretical stages and a reflux ratio in the range of 0.5:1 to 15:1, and wherein the one or more distillation steps are conducted under vacuum conditions.

6. 6. The process according to claim 5, wherein the final distillation yield is 85% or more, preferably in the range of 90% to 98%, based on the crude product containing PBO.

7. 7. The method according to claim 5 or 6, wherein one or more distillation steps of the distillation method are carried out independently of one another at a vacuum of 4000 Pa or less, preferably 2000 Pa or less, more preferably in the range of 1500 Pa to 10 Pa.

8. 8. The process of any one of claims 5 to 7, wherein the rectification apparatus comprises a single distillation column.

9. 8. The process of any one of claims 5 to 7, wherein the rectification apparatus comprises two to three distillation columns operating in series or continuously.

10. 10. The process of any one of claims 5 to 9, wherein the rectification apparatus comprises at least one distillation column, each at least one distillation column independently comprising a number of theoretical stages from 5 to 25, preferably from 9 to 20.

11. 11. The process of any one of claims 5 to 10, wherein the distillation apparatus with rectification equipment comprises at least one distillation column, each at least one distillation column independently having a reflux ratio in the range of from 3:1 to 10:1, preferably from 4:1 to 8:

1.

12. 12. The method according to any one of claims 5 to 11, wherein the distillation apparatus comprises a boiler at a temperature in the range of 170°C to 270°C, preferably 190°C to 260°C, more preferably 200°C to 250°C to allow the PBO to be distilled.

13. 13. The method of any one of claims 5 to 12, wherein the distillation apparatus operates continuously.

14. 14. The method according to any one of claims 5 to 13, wherein the distillation method also presents the use of an internal condenser and / or an external reboiler for each distillation column.

15. 15. The method according to any one of claims 5 to 14, wherein the distillation apparatus, preferably the at least one distillation column, can include a recovery system for heavy and light cracked impurities, the recovery system preferably including a final product recovery pump and a bottom product recovery pump connected to a bottom product collection tank and a top product collection tank, respectively.

16. 16. A composition comprising the PBO of any one of claims 1 to 4 obtained from the distillation process of any one of claims 5 to 15.

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