ITRM960493A1 - PROCEDURE FOR THE PRODUCTION OF DERIVATIVES OF MALEIC DIANTE DIANTE INTEGRATED PROCESS OF ESTERIFICATION AND HYDROGENATION - Google Patents

Description

Description of the industrial invention entitled: PROCEDURE FOR THE PRODUCTION OF DERIVATIVES OF MALE ICA DIOXIDE BY MEANS OF INTEGRATED ESTERIFICATION AND HYDROGENATION PROCESS;

The present invention relates to the production of tetrahydrofuran (THF) and gammabutyrolactone (GBL) by means of an integrated esterification process of maleic anhydride and subsequent hydrogenation of the maleic ester.

In the technical and patent literature various hydrogenation processes of maleic anhydride or esters of maleic anhydride are described, to produce THF and GBL, possibly together with butanediol (BDO).

Maleic anhydride esters, obtained by reacting maleic anhydride with an alcohol having from 1 to 8 carbon atoms, preferably from 1 to 4 carbon atoms (methanol, ethanol, n-propanol, n-butanol), are preferred as they avoid , in the hydrogenation, the presence of organic acids which reduce the selectivity and the life of the catalysts normally used in the hydrogenation itself.

There are various processes, described in the technical and patent literature, for carrying out esterification reactions of organic acids or anhydrides.

As known to experts, the reaction of maleic anhydride (C4H203) with an alcohol (ROH) occurs with the formation of water as indicated by the following reaction:

C4H203 2ROH -> C4H202R2 H20

wherein R is the alkyl radical of the alcohol having from 1 to 8 carbon atoms, preferably from 1 to 4 carbon atoms.

This reaction can be carried out in a plate column in which the maleic anhydride and the alcohol are reacted by coming into contact in countercurrent with vapors of the same alcohol.

The efficiency of the process carried out in the column is increased since, upon contact, the water formed in the reaction passes into the vapor phase, thus favoring the completion of the esterification reaction.

Such a process is known and is described in Groggings "Unit Processes in Organic Synthesis" 5th ed. Mc.Graw Hill pg 705-710.

The esterification reaction takes place in the presence of suitable catalysts, which can be of the homogeneous type, such as sulfuric acid or sulphonic acid, or of the heterogeneous type.

Catalysts of a heterogeneous type, such as ion exchange resins of the sulphonic type, are preferred since they allow to operate with fewer problems of corrosion and effluent treatment.

In any case, as described in the previously cited reference, the esterification reaction requires, in order to be completed, a high consumption of heat to be supplied to the reboiler of the esterification column to vaporize the water produced in reaction together with a fraction of the fed alcohol. in column.

As previously indicated, the production of compounds such as THF, GBL, and possibly BDO, occurs by hydrogenating the ester produced.

In the hydrogenation, the ester of the maleic anhydride initially saturates to the ester of the succinic anhydride, as indicated:

C4H204R2 H2 -> C4H404R2

This hydrogenation is hereinafter referred to as primary hydrogenation.

Subsequently the succinic acid ester is further hydrogenated producing GBL, THF, BDO, in variable proportions depending on the catalysts used and the conditions under which the reaction is carried out. This hydrogenation is hereinafter referred to as secondary hydrogenation. In the present proceeding, operating conditions are considered which favor the production of GBL and THF while minimizing the production of BDO.

A relatively large number of catalysts are available which are capable of effectively carrying out the primary reaction.

Suitable primary hydrogenation catalysts are mentioned in Thomas "Catalytic Processes and Proven Catalysis" 1970, chapter 13 and chapter 15.

The choice of the secondary hydrogenation catalyst and the most suitable reaction conditions is critical for the cost-effectiveness and reliability of the process.

Copper-based catalysts, (preferably copper chromites possibly modified with a stabilizer such as barium and such, for example, the types mentioned by Thomas in chapter 15 of the previous reference) are preferred to other types of catalysts as they are more selective. However, these catalysts tend to be deactivated by organic acids possibly present in the feed or formed by hydrolysis of the ester fed to the secondary hydrogenation in the presence of water.

To limit deactivation, the filler ester must have a minimum content of non-esterified acid and water.

For the same reason, the secondary hydrogenation reaction is preferentially carried out in the vapor phase, with the commitment of high volumes of hydrogen and with a limited degree of conversion of the ester to THF, since the production of THF is accompanied by the production of water. As previously indicated, by activating the hydrolysis reaction of the ester to organic acid, water constitutes an indirect cause of deactivation of the catalyst.

The object of the present invention is a process in which the hydrogenation reactions are integrated with the esterification reaction and are operated in an innovative way in order to overcome the limits of the known processes relating to the production of THF and GBL starting from maleic anhydride.

These objectives are achieved by means of the innovations which are the subject of the claims of the present invention and which can be more fully appreciated by referring to the diagram of fig. 1 and the detailed description that follows.

DESCRIPTION OF THE PROCEDURE

With reference to this figure 1, the maleic anhydride (line 1) is mixed with an alcohol (line 2 and 18) having from 1 to 8 carbon atoms, preferably from 1 to 4 carbon atoms, which for the purposes of the present description assumed to be n-butanol.

The mixture (line 3) is fed to the upper section of an esterification column A.

The esterification reaction takes place by passing the mixture over layers of catalyst assumed to be, for the purposes of the present description, an ion exchange resin of the sulphonic type.

On each layer, or pack of catalyst, the liquid mixture comes into contact with vapors rich in butanol coming from the bottom of the esterification column A.

Upon contact, the water formed in the esterification reaction passes from the liquid state to the vapor state.

This allows the completion of the esterification reaction with almost total conversion of the maleic anhydride fed to dibutyl maleate (DBM).

Two liquid streams composed of DBM and butanol emerge from a bottom plate of column A.

A first stream feeds (line 4) the shell section of the primary hydrogenation reactor B, in which it partially vaporizes (line 5) at the expense of the heat developed in the hydrogenation of DBM to dibutylsuccinate (DBS).

A second stream (line 6) feeds a heat exchanger (C) in which it partially vaporizes (line 7) exchanging heat with the hot gases produced in the secondary hydrogenation.

As is evident, through this process the heat necessary for esterification is formed by the two subsequent hydrogenations (primary and secondary).

This is made possible by the fact that the esterification takes place at temperatures between 80 and 130 ° C, preferably between 100 and 120 ° C, while the hydrogenations take place at temperatures close to or above 200 ° C, as indicated below.

The advantages of the integration process between esterification and primary and secondary hydrogenation remain unchanged if it is preferred, to increase the degree of flexibility of the system, to generate steam at medium pressure of the shell side of reactor B and of the heat exchanger C.

The advantages of the above mentioned integration process also remain unaltered if it is preferred to use, as esterification catalyst, a homogeneous catalyst such as sulfuric or sulphonic acid.

In this case the esterification column will be flat, as described in the aforementioned reference (Groggings-5a ed.pg.705-710) and the bottom product of the esterification column will have to be subjected to a washing and neutralization treatment before being fed to the primary hydrogenation reactor B.

As shown in the diagram in fig. 1, the bottom product of the esterification column consisting of a mixture of butanol and dibutyl ester of maleic anhydride (line 8) is mixed with a stream of hydrogen (line 9) and fed to reactor B where the DBM is fully converted to DBS.

The reaction takes place at a temperature between 150 and 250 ° C, preferably between 180 and 230 ° C, in the liquid phase, preferably on a palladium or nickel-based catalyst with space velocity measured on the liquid phase between 0.5 and 1.5 hr <-1> 'The effluent of reactor B (line 10) feeds the separator D from which a gas phase rich in hydrogen (line 11) and a liquid phase rich in DBS are separated.

The latter feeds (line 12) the upper section of a secondary reaction column E.

The methodology for carrying out the secondary hydrogenation reaction differs from any previous reference in the patent and technical literature relating to this type of reaction.

In the process object of the present invention THF and GBL are produced by reacting DBS in the liquid phase in countercurrent with a gas rich in hydrogen and alcohol vapors (in the specific case assumed to be nbutanol).

The hydrogenation catalyst is arranged in packs inside the reaction column E, in the same way as described for the esterification column A.

In counter-current contact between the liquid and the hydrogen-rich gas, the light fractions, THF, water and butanol, vaporize and concentrate in the vapor phase.

In this way, in the process object of the present invention, the following advantages are achieved:

- hydrogenation reaction in liquid phase, with the use of limited volumes of hydrogen;

- minimal presence of water in the liquid phase;

- fractionation of the light fractions which are concentrated in the vapor phase;

- high performance of the catalyst in terms of selectivity and duration.

The heat input supplied to the column through the reboiler F is limited as a considerable part of the heat necessary for the vaporization of the light fractions is supplied by the same hydrogenation reactions that take place, with the development of heat, in the same secondary hydrogenation column E .

Vaporization in the reboiler F is favored by feeding to the reboiler itself the hydrogen stream (line 11) coming from separator D which mixes with the liquid (line 13) coming from column E.

The liquid-vapor mixture (line 14) returns to the column from the reboiler.

The separation of light products is facilitated by installing fractionation plates on the bottom and head of the column. Reflux butanol is sent to the upper plate (line 26).

The bottom product of the hydrogenation column E consists of a mixture essentially composed of butanol, GBL, non-converted DBS, with the presence of small quantities of butanediol and organic by-products.

This mixture (line 15) is fractionated in a conventional distillation system G in which a butanol fraction (line 18) is recovered which is used in esterification, gamma butyrolactone produced (line 16) a mixture of unreacted DBS and BDO which is recycled to the hydrogenation column E (line 17) and organic by-products (line 19).

The overhead vapors of the hydrogenation column E (line 20) after having exchanged heat in the exchanger C, are further cooled in the exchanger H.

In the subsequent separator I, a liquid composed mainly of THF, butanol, water, and light organic by-products is separated which is sent (line 21) to a fractionation unit M. The gaseous stream coming from the same unit M is sent (line 22). head of esterification column A.

In the fractionation unit, THF (line 23), the water produced in the reactions (line 24) and finally butanol (line 25) are separated using known techniques: the latter is partially sent (line 2) to the head of the column of esterification A and in part (line 26) to the head of the hydrogenation column E.

A gas rich in hydrogen separates from the head of the separator I which is sent (line 27) to the suction of the compressor L. The compressed hydrogen (line 28), together with the charge hydrogen (line 29) feeds the reactor circuit. primary B and secondary E hydrogenation as previously described.

Typical operating conditions in hydrogenation reactors are indicated below.

PRIMARY HYDROGENATION

Temperature: between 150 ° and 250 ° C, preferably between 180 and 220 ° C.

Pressure: from 2 to 20 ATE, preferably from 10 to 15 ATE

Catalyst: based on nickel, copper or noble metal on support

Space velocity (liquid) from 0.5 to 1.5 h <-1> 'H2 / ester molar ratio: from 5 to 30, preferably from 10 to 20.

SECONDARY HYDROGENATION

Temperature: between 150 ° and 250 ° C, preferably between 190 and 230 ° C.

Pressure: from 2 to 20 ATE, preferably from 10 to 15 ATE

Catalyst: copper-based, preferably stabilized copper chromite Space velocity (liquid) from 0.1 to 0.5 h <-1> '

Molar ratio H2 / ester: from 5 to 30, preferably from 10 to 20.

The process object of the present invention allows to produce THF and GBL in variable proportions with yields higher than 95% molar with respect to the fed maleic anhydride and with a high degree of purity.

A preferred embodiment of the method has been described here by way of non-limiting example. It is evident, however, that numerous modifications and variations can be made by those skilled in the art without departing from the scope of protection of the present industrial patent, as defined by the following claims.

Claims (6)

CLAIMS 1) A process for the production of THF and GBL by esterification of maleic anhydride and subsequent hydrogenation of the alkyl ester of the maleic anhydride, characterized in that the heat of hydrogenation of the ester of the maleic anhydride to the ester of the succinic anhydride (primary hydrogenation) and the heat developed in the subsequent hydrogenation of the succinic anhydride ester to THF and GBL (secondary hydrogenation) are used to directly or indirectly supply the heat necessary to carry out the esterification. 2) A process in which the hydrogenation reaction of the maleic anhydride ester (primary hydrogenation) takes place in the liquid phase in a tubular reactor, operating according to the following parameters: Temperature: between 150 ° and 250 ° C, preferably between 180 and 220 ° C. Pressure: from 2 to 20 ATE, preferably from 10 to 15 ATE Catalyst: based on nickel, copper, or noble metal on support Space velocity (liquid) from 0.5 to 1.5 h <-1> Molar ratio H2 / ester: from 5 to 30, preferably from 10 to 20. 3) A process in which an ester of succinic acid, however produced, is hydrogenated in a hydrogenation column (secondary hydrogenation) in which the hydrogen is fed from below and reacts with the ester to be hydrogenated by countercurrent contact on packs of catalyst in the presence of an alcohol having from 1 to 8 carbon atoms, preferably from 1 to 4 carbon atoms. 4) A process according to claims 1, 2 and 3 in which the ester of the maleic anhydride is obtained by reacting maleic anhydride with an alcohol having from 1 to 8 carbon atoms, preferably from 1 to 4 carbon atoms, preferably the same used in the secondary hydrogenation column as mentioned in claim 3. 5) A process for the hydrogenation of esters of succinic anhydride according to claim 3, operating in accordance with the following parameters: Temperature: from 150 ° to 250 ° C, preferably from 180 to 220 ° C. Pressure: from 2 to 20 ATE, preferably from 10 to 15 ATE Catalyst: based on copper, preferably stabilized copper chromite. Space velocity (liquid): from 0.1 to 0.5 h-1 Molar ratio H2 / ester: from 5 to 30, preferably from 10 to 20. 6) A process for the preparation of THF and GBL starting from maleic anhydride or esters of maleic anhydride or esters of succinic anhydride as described and illustrated in the attached drawing.