WO2024120993A1

WO2024120993A1 - Piperonyl butoxide distillation process with rectification for obtaining high purity pbo

Info

Publication number: WO2024120993A1
Application number: PCT/EP2023/083921
Authority: WO
Inventors: Alberto Guerrini; Carla Marchioro; Stefano BILLI
Original assignee: Endura S.P.A.
Priority date: 2022-12-05
Filing date: 2023-12-01
Publication date: 2024-06-13
Also published as: WO2024121591A1

Abstract

The invention concerns a composition comprising piperonyl butoxide (PBO) at a weight concentration in the range from 94 to 99.9%, dipiperonyl methane (DPM) in the range from 0.01 to 1% by weight and dipiperonyl ether (DPE) in the range from 0 to 0.1% with respect to the total weight of the composition, and a distillation process for obtaining the same.

Description

PIPERONYL BUTOXIDE DISTILLATION PROCESS WITH RECTIFICATION FOR OBTAINING HIGH PURITY PBO

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FIELD OF THE INVENTION

The present invention relates to a composition comprising piperonyl butoxide (PBO) and to a distillation process for obtaining the same.

STATE OF THE ART

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 (the boiling point at 278 Pa is 203°C; the calculated boiling point at 101300 Pa is 400°C) decomposes rapidly at 300°C.

For this reason, the industrial processes for producing PBO provide for one or more fractionated evaporations to obtain the finished product. The evaporation process may be carried out using different methodologies such as vapor stream evaporation, thin film evaporation or simple batch evaporation.

The evaporation process requires drastic conditions, such as high vacuum and high temperatures, due to the physical characteristics of the product itself. The evaporation process does not allow, especially in the required conditions, an efficient separation of the by-products deriving from the synthesis process which inevitably end up in the finished product, thus limiting its quality.

In the international patent application WO2021161083, a process for producing piperonyl butoxide is reported. Specifically, in example 1 c on page 21 , it is stated that, after separation of the organic layer, PBO is obtained by distillation. The question concerns the synthesis of various molecules deriving from benzodioxole, in particular sesamol and DHS, through various catalysts or mixtures thereof, since no details are provided on the part of distillation relating to PBO.

In the patent application IN201941007564, in Example 3, in relation to step 4 it is stated that, following the separation of the organic layer and the distillation of toluene under vacuum, PBO is distilled by fractional distillation without indicating any details relating to the distillation itself.

In the Chinese article by XU Songlin et al, “Refining Piperonyl Butoxide by shorth path distillation”, Transactions of the CSAE, Vol. 21 , No. 2, February 2005, the results obtained by carrying out the distillation of PBO through two short-path evaporations in series are provided through data and graphs. In the first evaporation, the light products are removed, while the heavy products pass along with the product of interest, the PBO, to the second evaporator. In the second evaporator, connected in cascade to the first, the PBO is collected as evaporated product, while the heavy by-products are collected as residue. The article reports the obtainment of a final PBO product with a purity up to 96% and in a yield higher than 70%. The described short-path evaporation is certainly a process suitable for the distillation of high-boiling and thermolabile molecules, but it does not allow an effective separation of the impurities and therefore the obtainment of a highly pure product with high yields.

In the Chinese utility model CN212417044U, in the name of Wujiang Shuguang Chemical, a PBO distillation process is described. Specifically, a continuous vapor stream distillation process on a column with staggered septa is described. Specifically, this document is focused on energy and environmental savings obtainable from the recovery of the vapor condenser cooling water. With reference to Figure 1 of the model itself, the condenser 4 is in communication with the cylinder 1. The document starts from the assumption, and repeatedly reports the concept, according to which the existing rectification processes for producing PBO are inefficient from an energy point of view and have modest rectification effects. With reference to page 1 , line 19, it is stated that the grinding towers used for producing PBO have a single function, a complex procedure, and a relatively poor grinding effect, and cannot recycle cooling water.

The inventors analyzed the process described in the utility model in detail and found that it relates to a distillation with rectification in vapor stream without indicating pressure and temperature conditions, and that any organic components separated and carried to the head by the fed vapor (18) are entirely condensed through the condenser (4) and entirely reintroduced into the column through the condensate return (5). The inventors thus realized that, following the proposed scheme, any impurity possibly removed at the top (3) was condensed (4) and entirely reintroduced in the process (5) and collected at the bottom with the product (17) with also the condensed vapor introduced in (18) making the process itself unusable at the level of product purification. Any possible rectification effect introduced by the staggered septa described in the description was therefore nullified by the arrangement of the same devices in the distillation plant shown in the utility model. In the Chinese model, no data concerning the purity of the fed material (15) and of the product obtained (17) are reported, nor any reference to yields is present, being also lacking any suggestion about the used reflux ratios, temperature and pressure conditions for the distillation.

Document CN202131299U in the name of Nanchang Yangpu Natural Essence & Spice Co LTD describes a batch distillation device equipped with a testing device using in the purification process as an on line testing of the purity. As stated in the abstract the device is aimed at inspecting the final purity of PBO.

The document focuses on the fact that the methods commonly used to obtain PBO require sampling from the distillate tank and laborious analyses to understand whether the purity of the obtained PBO is the right one to be used in applications.

According to the reported disclosure there is no example explaining how to conduct the distillation step. There is no disclosure of the impurity contents of starting material PBO, temperature and pressure conditions of the distillation step not even reflux ratios. It is only disclosed the removal of the solvent of the starting material in a separate device and then the compound is fed into the boiler (1 ) of the distillation device. Specifically, the system comprises a boiler (1 ) connected to a pump (2) and recirculating the contents of the boiler through the heater (3). The document reports that passage of the boiler contents via pump (2) through the heater (3) generates high temperatures at low vapor pressure and PBO is evaporated from the liquid phase. According to this document the PBO compound becomes a gas which reaches the head of the column passing through the fractionation column (4) and is condensed back to a liquid form in the condenser (5), that is located at the head of the column. The liquid is then further cooled in a second condenser (6) and from here it passes into the device (7) which controls its quality. If the purity is >95%, a green light on the device display turns on and the liquid is directed towards 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 turns on and the liquid is directed again towards the boiler (1 ) and the above-described steps are repeated. The inventors studied CN202131299U in detail and noted that according to this document piperonyl butoxide could be purified probably by removing the heavy byproduct fraction of the starting material that accumulates in the boiler. It is known the crude PBO as starting material, when heated, develops not only a fraction of heavy degradation byproducts, but also a light degradation byproduct fraction. According to the inspection system described in CN202131299U this light byproduct fraction would inevitably accumulate at the top of the fractionation column (4) after passing through the distillation column (4) itself and once condensed would lower the purity of the collected liquid received by the device (7) after condensation in (5) and (6); This document being aimed at inspecting the final purity of PBO does not teach how to purify PBO with a very low amount of specific impurities and their degradation products.

It is therefore evident that the documents of the prior art do not suggest how to obtain piperonyl butoxide with good purity through a simple distillation with rectification. In fact, up to now, a distillation process with rectification, which would allow impurities to be efficiently removed from the PBO has not been found to be industrially applicable due to the pressure losses inevitably introduced with the use of a rectification column. The expression “pressure losses” refers to the pressure difference between the head of the column and the bottom of the same, which determines the temperature profile in the column itself.

The pressure losses introduced necessarily require higher temperatures for product vaporization with consequent process complications.

As previously mentioned, in fact, high temperatures increase product degradation with formation of further impurities, with the result of low yields and poor purities. Macroscopic degradation processes occur at temperatures around 300°C, however slower but not negligible degradation processes are also observed at temperatures above 240°C if prolonged over time.

The main impurities that are formed from the PBO crude degradation are low-boiling compounds that are generated in the boiler. Among the heavy crude impurities there are dipiperonylmethane (DPM, IIIPAC Name: 5,5'-methanediylbis(6-propyl-1 ,3- benzodioxole)) and dipiperonyl ether (DPE, IIIPAC Name: 5,5'- (oxydimethanediyl)bis(6-propyl-1 ,3-benzodioxole), which in turn tend to degrade at high temperatures, especially at the temperatures known for the evaporation/distillation of PBO itself.

The object of the present invention is therefore to obtain piperonyl butoxide in high purity and good yields without using difficult-to-manage plants and thus in the presence of drastic manufacturing conditions.

It is a further object to provide a piperonyl butoxide deprived of heavy and light degradation byproducts that can be generated during the distillation of PBO, that is a high boiling compound.

SUMMARY OF THE INVENTION

These objects have been achieved by the present invention by means of a process for the preparation of piperonyl butoxide (PBO), which allows to obtain a composition comprising PBO at a concentration in the range from 94 to 99.9% by weight, dipiperonylmethane (DPM) in the range from 0.01 to 1 % by weight, and dipiperonyl ether (DPE) in the range from 0 to 1 % with respect to the total weight of the composition.

The invention therefore concerns a composition comprising PBO at a concentration in the range from 94 to 99.9% by weight, dipiperonylmethane (DPM) in the range from 0.01 to 1 % by weight, and dipiperonyl ether (DPE) in the range from 0 to 1 % with respect to the total weight of the composition

The invention therefore allows to obtain high purity PBO with low concentrations of DPM and DPE specific impurities. In fact, when the concentration of PBO has a very high concentration in the mixture, we refer to the percent purity of the same.

Without being bound to any theory, and as opposed to what is reported in the literature, the inventors believe they have succeeded in obtaining PBO of such high purity and having such low amounts of DPE and DPM, thanks to a distillation process with rectification at reduced pressure, that allows the withdrawal of both heavy and light heavy byproducts that generate during the distillation process of PBO and guaranteeing the obtainment of a composition comprising PBO at a concentration in the range from 94 to 99.9% by weight, dipiperonylmethane (DPM) in the range from 0.01 to 1 % by weight, and dipiperonyl ether (DPE) in the range from 0 to 1 % with respect to the total weight of the composition. Contemporaneously, the process of the invention allows a distillation yield greater than 85%.

In fact, as is known in the prior art, when high purities of PBO are obtained from the distillation processes, the use of drastic processing conditions causes, at the same time, a low distillation yield, which makes the process unattractive from an industrial point of view.

In another aspect, therefore, the invention concerns a distillation process distillation process for preparing the composition comprising PBO according to the invention, which comprises one or more distillation steps of a crude product comprising PBO in a distillation device equipped with rectification, said distillation device equipped with rectification comprising at least one distillation column, each at least one independently comprising a number of theoretical stages equal or above 1 and a reflux ratio in the range from 0.5:1 to 15: 1 , wherein said one or more distillation steps is/are carried out under vacuum conditions.

The distillation process of the invention has also allowed to obtain a distillation yield higher than 85%.

Advantageously, the distillation process is carried out under vacuum conditions, preferably at the maximum vacuum degree allowed by the best technical choices available on the market, preferably at a pressure equal or lower than 4000 Pa, more preferably equal or below 2000Pa, still more preferably in the range from 1500 Pa to 10Pa.

The crude product comprising PBO of the process of the invention, i.e. the starting material is preferably a product comprising PBO in a concentration greater than or equal to 75%, preferably greater than or equal to 83%, more preferably greater than or equal to 90%. The crude PBO product starting material as a composition comprising PBO and impurities has a amount of DPM and DPE higher than 1 % with respect to the total amount of total composition. After the distillation process of the invention the final composition comprises PBO at a concentration in the range from 94 to 99.9% by weight, dipiperonylmethane (DPM) in the range from 0.01 to 1 % by weight, and dipiperonyl ether (DPE) in the range from 0 to 1 % with respect to the total weight of the composition.

In a preferred aspect of the invention, the distillation device operates continuously.

In a further advantageous aspect of the invention, one or more distillation columns of the distillation device com prises/com prise an internal condenser which allows to lower the system pressure drops, thus ensuring lower process temperatures which are important for limiting the thermal degradation of the product. Without being tied to any theory, the inventors believe that the presence of the internal condenser allows, through temperature control, to selectively remove and condense only the desired light degradation byproduct portion of the distillate. This advantageously allowed for considerable energy savings, given that the liquid refluxing internally was not “subcooled” and reintroduced with a pump, but remained at the temperature of the distillation phase.

In a preferred embodiment, in fact, one or more distillation columns of the distillation device comprises/comprise an external reboiler which allows to reduce the contact time of the product with the hotter wall portion of the distillation device. This minimizes the product thermal stress with a consequent decrease in degradation. The lower decomposition of the product, coupled with the separation introduced by the distillation device equipped with rectification, leads to obtaining higher product quality and yields. In an even more preferred embodiment, the choice of the external heating (which always operates full) is combined with level control in the device which avoids the formation of potentially dangerous hot spots.

In a preferred and advantageous aspect of the invention, the process of the invention is continuous and allows to have very accurate and reproducible control over the finished product. In fact, given the same productivity, the average residence time at high temperatures in the process is lower compared to a batch process. Furthermore, the continuous distillation process is simpler to operationally manage (fewer unitary operations due to the lack of transients to manage) and, given the same productivity, results to be of smaller size than the batch process and with less equipment (cheaper and with less maintenance), and it is more efficient from an energy point of view (it allows an easy energy recovery through preheating the inlet stream which cools the outlet one). The continuous process also allows for low residence times of the product which lead to minimizing the formation of degradation by-products.

In a further preferred aspect of the invention, the choice of high-efficiency fillings, with the relative liquid distribution system, made it possible to maximize the number of theoretical distillation stages while minimizing pressure drops.

Further characteristics and advantages of the invention will become evident from the following detailed description provided as non-limiting example, with the aid of the figures illustrated in the attached drawings.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to a composition comprising PBO at a concentration in the range from 94 to 99.9% by weight, dipiperonylmethane (DPM) in the range from 0.01 to 1 % by weight, and dipiperonyl ether (DPE) in the range from 0 to 1 % with respect to the total weight of the composition.

The invention therefore allows to obtain high purity PBO with low concentrations of DPM and DPE specific impurities.

The composition comprises PBO at a concentration in the range from 94 to 99.9% by weight, preferably 96 to 99%.

The composition of the invention comprises dipiperonyl methane (DPM) in the range from 0.01 to 1 % by weight, preferably in the range from 0.01 to 0.5, more preferably from 0.01 to 0.1 % with respect to the weight of the composition.

The composition of the invention comprises dipiperonyl ether (DPE) in the range from 0 to 1 %, preferably from 0.01 to 0.5, more preferably from 0.01 to 0.1 % with respect to the total weight of the composition.

In another aspect, therefore, the invention concerns a distillation process for preparing the composition comprising PBO according to the invention, which comprises one or more distillation steps of a crude product comprising PBO in a distillation device equipped with rectification, said distillation device equipped with rectification comprising at least one distillation column, each at least one independently comprising a number of theoretical stages equal or above 1 and a reflux ratio in the range from 0.5:1 to 15: 1 , wherein said one or more distillation steps is/are carried out under vacuum conditions.

In the present invention when using the term:

- “theoretical stage/s” means the number of theoretical plates of one or more columns of the distillation device equipped with rectification calculated according to anyone of the methods known in the art.

- “distillation steps” means the number of steps to be carried out in the distillation device equipped with rectification;

- “crude product comprising PBO” means the starting crude product comprising PBO and comprising a content of the impurities DPE and/or DPM higher than 1 %. Preferably, said crude product comprises PBO in a concentration greater than or equal to 75%, preferably greater than or equal to 83%, more preferably greater than or equal to 90%, more preferably with a DPM and DPE content higher than 1 % and lower than or equal to 4%, still more preferably higher than 1 % and lower than or equal to 3%, even more preferably higher than 1 % lower than or equal to 2%. -“under vacuum condition” means at a pressure below the atmospheric pressure.

- “degradation of the product” or “degradation of crude product” or “degradation of crude impurities” it is meant the degradation of PBO and of the impurities, comprising DMP and DPE.

The distillation process of the invention has also allowed to obtain a distillation yield greater than 85%, preferably a distillation yield in the range from 90% to 98% with respect to the crude product comprising PBO.

The PBO crude product is obtained according to any of the methods known in the art.

According to the invention, the crude product comprising PBO comprises PBO in a concentration greater than or equal to 75%, preferably greater than or equal to 83%, more preferably greater than or equal to 90%. The crude PBO product starting material as a composition comprising PBO and impurities has an amount of DPM and DPE higher than 1 % with respect to the total amount of total composition. After the distillation process of the invention the final composition comprises PBO at a concentration in the range from 94 to 99.9% by weight, dipiperonylmethane (DPM) in the range from 0.01 to 1 % by weight, and dipiperonyl ether (DPE) in the range from 0 to 1 % with respect to the total weight of the composition.

According to the invention, the process is carried out by means of a distillation device equipped with rectification comprising at least one distillation column, preferably from one to three distillation columns comprising in turn, independently from each other, a number of theoretical stages of at least one, preferably from 1 to 30 and a reflux ratio in the range from 0.5:1 to 15:1 .

According to a preferred embodiment, said rectification device is a rectification column or a series of rectification columns, preferably from 2 to 3 columns, which can operate in series or continuously, i.e. operating simultaneously in a cascade.

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

For instance the raw product can be fed into the first column from which the light byproducts can exit. The compound PBO with the heavy byproducts exit from the bottom of the boiler and the compound PBO is then fed into the second column. The light degradation byproducts come out from the second column at the top and the high purity PBO comes out from the side withdrawal and the heavy byproducts come out of the bottom of the column.

The same scheme with two columns, for example, by changing the process parameters, could provide for the heavy byproducts to come out from the bottom of the first column and the PBO with the light products and part of the DPM at the top. The PBO with the light substances and part of the DPM could then be fed to the second column where the light/degradation byproducts would come out at the top, the high purity PBO from the side withdrawal and the DPM from the bottom.

Therefore, the process according to the invention in the embodiment with more than one column provides for at least one distillation step under vacuum condition.

In a preferred and advantageous embodiment, the distillation process takes place in a distillation device equipped with rectification which comprises a single distillation column.

Said rectification device comprises a number of theoretical stages of at least one, preferably from 1 to 30, and a reflux ratio of the same distillation device in the range from 0.5:1 to 15:1 .

Said number of theoretical stages is preferably in the range from 5 to 25, more preferably from 9 to 20.

Without being bound to any theory, the inventors believe that a distillation device equipped with rectification having a number of stages greater than 30 would allow to obtain high purity PBO, but in a too low yield; while a number lower than one would not allow to sufficiently purify the product from one or both of the DPE and DPM impurities:

According to the preferred invention, when the number of theoretical stages is almost or equal to 30, to avoid pressure drops which raise the boiling point and cause PBO degradation, the distillation process involves multiple distillation phases, preferably 2 or 3 distillation phases.

In the process of the invention, the distillation device equipped with rectification comprises at least one distillation column, preferably one to three distillation columns comprising in turn, independently from each other, a reflux ratio in the range from 0.5:1 to 15:1. Preferably said reflux ratio is in the range from 3:1 to 10:1 , more preferably from 4:1 to 8:1 .

The distillation device comprises a boiler, preferably in the form of a reactor heating system with diathermic oil or a boiler external to the at least one distillation column. Said boiler is at a temperature in the range from 170°C to 270°C, preferably from 190°C to 260°C, more preferably from 200°C to 250°C to allow PBO distillation.

According to the invention and advantageously, when the number of stages of one or more columns of the distillation device equipped with rectification is greater than 9, the distillation of the crude PBO can preferably take place in a single phase, if conversely the number of stages is less than nine, advantageously the distillation process takes place envisaging more than one distillation phase, in which the product of the previous distillation is used as starting material for the subsequent distillation.

In a preferred aspect of the invention the distillation device operates continuously. The distillation process also preferably provides for the use of a condenser and/or reboiler for each distillation column, both internal and external.

In a further advantageous aspect of the invention, one or more distillation columns of the distillation device com prises/com prise an internal condenser which allows to lower the system pressure drops ensuring lower process temperatures which are important for limiting the thermal degradation of the product/crude impurities. Without being tied to any theory, the inventors believe that the presence of the internal condenser allows, through temperature control, to selectively remove and condense only the desired light portion of the distillate. This advantageously allowed for considerable energy savings, given that the liquid refluxing internally was not “subcooled” and reintroduced with a pump, but remained at the temperature of the distillation phase.

In a preferred embodiment, in fact, one or more distillation columns of the distillation device comprises/comprise an external reboiler which allows to reduce the contact time of the product with the hotter wall portion of the distillation device. This minimizes the product/crude impurities thermal stress with a consequent decrease in degradation. The reduced product decomposition, coupled with the separation introduced by the distillation device equipped with rectification, leads to obtaining higher product quality and yields. In an even more preferred embodiment, the selection of the external heating (which always works full) is combined with level control in the device which avoids the formation of potentially dangerous hot spots. The distillation device equipped with rectification may comprise at least 1 to three or more distillation columns which are sized to have the optimum reflux under the process conditions.

The internal reflux may preferably be varied within the indicated range, by varying the temperature of the outlet vapors, the feed rate, the feed temperature and the amount of heat supplied to the external reboiler, if present.

In fact, in a preferred embodiment, the distillation device of the invention comprises at least one distillation column, preferably from one to three distillation columns comprising, independently from each other, an external reboiler which allows to reduce the contact time of the product with the hotter wall portion of the distillation device. This minimizes the product/crude impurities thermal stress with a consequent decrease in degradation. The decreased product/crude-impurities decomposition, coupled with the separation introduced by the distillation device equipped with rectification, leads to obtaining higher product quality and yields. In an even more preferred embodiment, the choice of the external heating (which always operates full) is combined with level control in the device which avoids the formation of potentially dangerous hot spots.

Without being tied to any theory, the inventors believe that the use of an internal condenser and/or external reboiler is an advantageous aspect since it allows to lower the pressure drops and to reduce product/crude impurities degradation.

In a preferred and advantageous aspect of the invention, the process of the invention is continuous and allows to have very accurate and reproducible control over the finished product. In fact, given the same productivity, the average residence time at high temperatures in the process results to be lower compared to a batch process. Furthermore, the continuous distillation process is simpler to operationally manage (fewer unitary operations due to the lack of transients to manage) and, given the same productivity, results to be of smaller size than the batch process and with less equipment (cheaper and with less maintenance), and it is more efficient from an energy point of view (it allows an easy energy recovery through preheating the inlet stream which cools the outlet one). The continuous process also allows low residence times of the product/crude impurities which lead to minimizing the formation of degradation by-products.

In a further preferred aspect of the invention, the distillation device comprises at least one distillation column, preferably from one to three columns with high efficiency fillings, with the relative liquid distribution system, thus advantageously minimizing the load losses.

Also in this case, the reduction of the pressure drops allowed to have lower process temperatures which limited product/crude impurities degradation.

According to the invention the distillation process of the invention the distillation device, preferably the at least one distillation column, can comprise preferably a withdrawal system of the heavy and light degradation impurities, said withdrawal system comprising- a finished product withdrawal pump, a bottom products withdrawal pump, connected respectively to preferably a bottom products collection tank and a head products collection tank.

In a further aspect, therefore, the invention relates to the composition of the invention obtainable from the distillation process of the invention.

The invention will be further described in the following experimental part, to be intended for illustrative and non-limiting purposes, which reports examples of use of the method of the invention on different raw materials and the effect of the method on the final product. EXPERIMENTAL PART

Example 1

Obtainment of 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 a 86% w/w titer were placed in a 4-neck, 1 liter flask.

The flask was equipped with a rectification column, h 50mm x d 25mm, equipped with 10 cm of Sulzer EX fillings, connected to the column head and set up for high vacuum distillation with an oil pump. The system was equipped with vacuum and temperature measurement points in the head and in the boiler.

The system was heated through an aluminum mantle using a heating plate.

The stirring of the boiler was carried out with a magnetic stir bar.

The vacuum was measured with a capacitance cell and digital reader.

The magnetic stirring was turned on, the system was brought to maximum pump vacuum and heating was started by setting the plate temperature to 250°C. Fraction collection was initiated under the conditions shown in the following Table 1. The distillation step was carried out under vacuum conditions.

Table 1

Once the collection of Fraction 2 was completed, the distillation was stopped.

83.5 g of heavy by-products remained in the flask.

The system operated with the distillate collection valve partially open in order to have a 10:1 reflux ratio. There were 2 separation stages.

Table 5 below shows the compositions of the input crude and the compositions of the output product. The distillation step was carried out under vacuum conditions. Table 2

The distillation yield based on PBO was 91.5%.

Example 2

Obtainment of 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 a 86% w/w titer were placed in a 4-neck, 1 liter flask.

The flask was equipped with a rectification column, h 50mm x d 25mm, equipped with 15 cm of Sulzer EX fillings, connected to the column head and set up for high vacuum distillation with an oil pump. The system was equipped with vacuum and temperature measurement points in the head and in the boiler.

The system was heated through an aluminum mantle with using a heating plate.

The stirring of the boiler was carried out with a magnetic stir bar.

The vacuum was measured with a capacitance cell and digital reader.

The magnetic stirring was turned on, the system was brought to maximum pump vacuum and heating was started by setting the plate temperature to 250°C. The distillation step was carried out under vacuum conditions.

Fraction collection was initiated under the conditions shown in the following Table 4.

Table 3

Once the collection of Fraction 2 was completed, the distillation was stopped.

88 g of heavy by-products remained in the flask. The system operated with the distillate collection valve partially open in order to have a 10:1 reflux ratio. There were 3 separation stages.

The following Table 5 shows the compositions of the input crude and the compositions of the output product.

Table 4

The distillation yield based on PBO was 89.7%.

Example 3

Obtainment of 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 a 83% w/w titer were placed in a 4-neck, 1 liter flask.

The flask was equipped with a rectification column, h 50mm x d 25mm, equipped with 20 cm of Sulzer EX fillings, connected to the column head and set up for high vacuum distillation with an oil pump. The system was equipped with vacuum and temperature measurement points in the head and in the boiler.

The system was heated through an aluminum mantle using a heating plate.

The stirring of the boiler was carried out with a magnetic stir bar.

The vacuum was measured with a capacitance cell and digital reader. The distillation step was carried out under vacuum conditions.

The magnetic stirring was turned on, the system was brought to maximum pump vacuum and heating was started by setting the plate temperature to 250°C. Fraction collection was initiated under the conditions indicated in the following Table 4.

Table 5

Once the collection of Fraction 2 was completed, the distillation was stopped.

87.5 g of heavy by-products remained in the flask.

The system operated with the distillate collection valve partially open in order to have a 10:1 reflux ratio. There were 5 separation stages.

Table 6

The distillation yield based on PBO was 88.5%.

The laboratory tests have shown that it is possible to obtain the desired product under the described conditions.

Example 4

Obtainment of 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 94.9% w/w titer were placed in a 4-neck, 2 liter flask.

The flask was equipped with a rectification column, h 55 mm x d 43 mm, equipped with 50 cm of Sulzer type DX fillings, connected to the column head and set up for high vacuum distillation with oil pump. The system was equipped with vacuum and temperature measurement points in the head and in the boiler.

At the head there was a reflux management system with a timed valve which allowed to adjust collection time and reflux time.

The system was heated through a heating mantle connected to a potentiometer to control the power supplied.

The vacuum was measured with a capacitance cell and digital reader. The system was brought to the maximum vacuum allowed by the oil pump, and heating was started by acting on the potentiometer.

The collection of the fractions was carried out with a 2:1 reflux: collection ratio (Reflux 10”: Collection 5”) under the conditions indicated in the following Table 7.

Table 7

Once the collection of Fraction 2 was completed, the distillation was stopped.

99 g of heavy by-products remained in the flask.

The system operated with a 2:1 reflux ratio. There were 10 separation stages.

The following Table 8 shows the compositions of the input crude and the compositions of the output product.

Table 8

The distillation yield was 89.2%.

Example 5

Obtainment of 99% PBO with 0.03% DPM and 0% DPE (Continuous industrial column; 4:1 reflux ratio; 20 stages)

The continuous distillation system consisted of:

- crude feed tank

- dosing pump for feeding crude into column

- crude feed pre-heating system

- rectification column with 20 theoretical stages equipped with internal condenser, side feed inlet, light products withdrawal, heavy products withdrawal and product side withdrawal

- head products post-condenser

- external bottom reboiler heated with diathermic oil

- column bottom/external reboiler recirculation pump

- finished product withdrawal pump

- finished product collection tank

- bottom products withdrawal pump

- bottom products collection tank

- head products collection tank

- pressure and temperature sensors located at the column bottom, feed, product withdrawal, and column head.

- high efficiency vacuum pumps and boosters

- diathermic oil circuit

1200 kg of crude PBO at 91.9% by weight were loaded into the column bottom, the system was brought to the maximum degree of vacuum allowed by the pumps and the system started to run, setting the boiler temperature to 240°C and the internal head condenser at 120°C.

Once the stationary conditions were reached, the crude was fed with a pump at a flow rate of 180 kg/h (200°C); at the same time, through the respective pumps, the product began to be collected from the side withdrawal with a flow rate of 163 kg/h (side withdrawal from the column at 190°C) and the residues from the bottom with a flow rate of 12 kg/h (221 °C).

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

The system operated with a reflux ratio of 4:1 and with 20 stages.

The system was used continuously for 7.5 h, and 1222.5 kg of high purity product, 37.5 kg of head by-products and 90 kg of bottom by-products were obtained.

The following Table 9 shows the compositions of the crude input and the compositions of the product output from the column side drawing. Table 9

The distillation yield was 97.4%.

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

Claims

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

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

3. The composition according to claim 1 or 2, wherein dipiperonyl methane (DPM) is in the range from 0.01 to 0.5, preferably from 0.01 to 0.1 % with respect to the weight of the composition.

4. The composition according to any one of claims 1 to 3, wherein dipiperonyl ether (DPE) is in the range from 0.01 to 0.5, preferably from 0.01 to 0.1 % with respect to the total weight of the composition.

5. A distillation process for preparing the composition comprising PBO according to anyone of claims 1 to 4, which comprises one or more distillation steps of a crude product comprising PBO in a distillation device equipped with rectification, said distillation device equipped with rectification comprising at least one distillation column, each at least one distillation column independently comprising a number of theoretical stages equal or above 1 and a reflux ratio in the range from 0.5:1 to 15:1 , wherein said one or more distillation steps is/are carried out under vacuum conditions.

6. The process according to claim 5, wherein the final distillation yield is greater or equal than 85%, preferably in the range from 90% to 98% with respect to the crude product comprising PBO.

7. The process according to claim 5 or claim 6, wherein one or more distillation steps of the distillation process is/are carried out, independently each other, at a vacuum degree equal or lower than 4000 Pa, preferably equal or below 2000Pa, more preferably in the range from 1500 Pa to 10Pa.

8. The process according to anyone of claims 5 to 7, wherein said rectification device comprises a single distillation column.

9. The process according to anyone of claims 5 to 7, wherein said rectification device comprises from 2 to 3 distillation columns, which operate in series or continuously.

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

11 . The process according to anyone of claims 5 to 10, wherein the distillation device equipped with rectification comprises at least one distillation column, each at least one independently comprising a reflux ratio in the range from 3:1 to 10:1 , preferably from 4:1 to 8:1.

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

13. The process according to anyone of claims 5 to 12, wherein the distillation device operates continuously.

14. The process according to anyone of claims 5 to 13, wherein the distillation process also provides for the use of an internal condenser and/or external reboiler for each distillation column.

15. The process according to anyone of claims 5 to 14, wherein the distillation device, preferably the at least one distillation column, can comprise a withdrawal system of the heavy and light degradation impurities, said withdrawal system comprising a finished product withdrawal pump, a bottom products withdrawal pump, connected respectively to preferably a bottom products collection tank and a head products collection tank.

16. A composition comprising PBO according to anyone of claims 1 to 4 obtainable from the distillation process according to claims 5 to 15.