WO2013038029A1

WO2013038029A1 - Method for producing oxygenated additives from crude glycerine

Info

Publication number: WO2013038029A1
Application number: PCT/ES2011/070637
Authority: WO
Inventors: María DÍAZ MURUAGA; Garikoitz BEOBIDE PACHECO; Ignacio CARVAJO LUCENA; José Manuel BENITEZ FERNANDEZ; Amaia MARTINEZ GOITANDIA; Arrate Marcaide Rodriguez; Ana Aranzabe Garcia
Original assignee: Befesa Gestión De Residuos Industriales S.L.; Fundación Tekniker
Priority date: 2011-09-12
Filing date: 2011-09-12
Publication date: 2013-03-21
Also published as: ES2459865A1; ES2459865B1

Abstract

The present invention relates to a method for preparing oxygenated additives from crude glycerine, such as the two isomers of di-tert-butyl glycerol (DTBG) and tri-tert-butyl glycerol (TTBG), from crude glycerine and tert-butanol. The method includes three essential steps which are defined as: a first step of purification or pretreatment of the crude glycerine; a subsequent step of reaction of the glycerine prepared in the previous step with tert-butanol in a discontinuous, sealed reactor in the presence of a catalyst; and a final step of separating the glycerol ethers prepared as final reaction products. The ethers thus prepared are industrially applicable as oxygenated fuel additives.

Description

PROCEDURE FOR PRODUCTION OF OXYGEN ADDITIVES FROM

CRUDE GLYCERINE

TECHNICAL SECTOR OF THE INVENTION

The present invention relates to a process for obtaining oxygenated additives derived from crude glycerin, by catalytic etherification thereof with tert-butanol in a discontinuous and hermetic reactor. Of the ethers formed, the present invention focuses on obtaining the two isomers of di-tert-butyl glycerol (DTBG) and tri-tert-butyl glycerol (TTBG). The ethers thus obtained find industrial application as oxygenated fuel additives.

BACKGROUND OF THE INVENTION

In the biodiesel manufacturing process, a large quantity of low quality glycerin that is called crude glycerin is generated as the final product of the reaction. The amount of crude glycerin that is generated is approximately 10% by weight of the amount of biofuel produced.

This crude glycerin has a very low economic value, due to the high concentration of impurities it presents. The complete refining of crude glycerin is conditioned by the economy of scale, as well as by the existence of simple purification processes.

However, large-scale biodiesel producers do refine their crude glycerin, in order to target the food, pharmaceutical and cosmetic markets. The refining treatments and processes, to which the crude glycerin is subjected, depend on the required yield or commercial purity. These processes are based on filtration, the addition of chemical substances and the use of vacuum fractional distillation systems. Glycerin used as raw material in cosmetic, pharmaceutical, etc. markets. It must have a very high degree of purity (higher than 99.7%), so that the viability of expensive purification processes is very conditioned by the economy of scale, as well as by the final sales prices of the products obtained at start from it.

Small or moderate scale biodiesel producers cannot cope with the high purification costs of crude glycerin through distillation processes. These glycerins can also be refined using filtration methods that require lower energy intensities. However, these processes reach much lower degrees of purity than those obtained through distillation. Glycerin filtered, it presents a degree of purity much lower than the so-called "chemical purity" grade, required for the listed markets.

The exponential growth in the global production of biodiesel, in the last decade, has been associated with the appearance of large surpluses of crude glycerin, of low economic value. Therefore, in recent years, great interest has emerged in finding new economically viable solutions for the use of crude glycerins from biodiesel production plants.

Recently, studies have been carried out that show the good properties of tert-butyl ethers of glycerin as oxygenated fuel additives, which allow reducing polluting emissions. In the associated literature there is also information on different procedures for obtaining these ethers from glycerin. So far there are several studies that show the usefulness of isobutene as an etherifying agent. These reports allow us to expect good results also using other alcohols as etherifying agents of the process.

In patent application WO 2009/1 17044, Barsa et al. Present a glycerin etherification process using isobutene as the etherifying agent.

In patent application WO 2008/1 12910, Morgan presents a continuous glycerin etherification process by means of a reactive distillation process, in which glycerin reacts with an alcohol to obtain glycerin ether in the presence of a catalyst located in the reaction zone of said distillation column. In this process the reaction temperature is set in the range between 120 and 140 ° C.

Srinivas et al. In patent application WO 2009/1 13079 describe a method for obtaining primary glycerol ethers at temperatures between 60 and 300 ° C and reaction times between 5 and 8 hours in a continuously stirred reactor. For use, the catalyst is activated using sulfuric acid and the final products obtained in the reaction are extracted from the outlet stream by extraction with water.

On the other hand, Essayem et al. In patent application WO 2009/141564 present a method for obtaining ethers at the same stage as the transesterification in which biodiesel is obtained.

Processes for obtaining fuel additives from glycerin have been described, but in all of them, the glycerin from which it is split has a purity greater than 90%, therefore being purified glycerin and not the crude glycerin mixture directly obtained as a byproduct of the biodiesel production process. Therefore, it would be desirable to provide a process for obtaining fuel additives from the crude glycerin mixture, that is, a process adapted to the use as a starting reagent of the crude glycerin obtained directly from the biodiesel production process, this It is, without the need to use glycerin with a degree of purity greater than 90%.

The vast majority of existing processes use isobutene as the glycerin etherifying agent (as for example in WO 2009/1 17044). Methods have also been described in which the etherifying agent is tert-butanol with large molar ratios (as for example in WO 2009/1 13079) whereby the consumption of the etherifying agent is large and therefore, the profitability of the processes industrial is less economical.

Therefore, it would also be desirable to provide a method for obtaining fuel additives in which at the same or similar productive efficiency the etherifying agent was used in a lower molar ratio, thus assuming a saving in the consumption of this agent and in general a superior overall process profitability. In addition, the processes described in the state of the art are carried out at high temperatures (as for example in WO 2008/1 12910) which implies a high energy expenditure. Therefore, it would be desirable to provide a process for obtaining fuel additives that could be carried out at moderate temperatures.

Likewise, the processes described in the prior art are carried out in a time of 5 h (as for example in WO 2009/1 13079). Therefore, it would be desirable to reduce the process time so that it is more profitable at the industrial level.

The processes described in the state of the art are carried out continuously, for example in distillation columns in which a catalyst is located in trays or plates (as for example in WO 2008/1 12910). Methods have also been described in which the reaction is carried out in stirred and continuous reactors (as for example in WO 2009/1 13079) which requires the use of auxiliary equipment to increase the pressure and leads to a decrease in the overall performance of the process, since alcohol losses occur.

Therefore, it would be desirable to provide a procedure in which the losses of alcohol were reduced, to make the process more efficient and profitable at the industrial level. In the prior art, catalyst activation takes place using sulfuric acid (see for example WO 2009/1 13079). Thus, it would be desirable to provide a process whereby activation does not require the use of an acid to reduce the risks associated with its management. Likewise, the process of separating the final product described in the state of the art is carried out by means of water extraction to separate the desired product from the reactor output current (see for example WO 2009/1 13079) which prevents the Unreacted raw material can be reused and the yields of obtaining the final product are good.

Therefore, it would be desirable to provide a process in which the separation stage of the final product allows to establish a zero-residue process and, in turn, improve the overall yield of obtaining the oxygenated additive.

There are procedures described in the state of the art that carry out the production of biodiesel and the etherification of glycerin in a single reaction stage which makes the process poorly controllable (see for example WO 2009/141564).

Therefore, it would be desirable to provide a process in which the etherification of glycerin takes place at a different stage from that of biodiesel production in order to exert a better reaction control.

In short, there is a need in the state of the art, which in turn allows reducing the consumption of reagents and energy, and the amount of waste (or the waste of unreacted raw material or reaction by-products).

OBJECT OF THE INVENTION

The present invention relates to a process for obtaining oxygenated additives derived from crude glycerin, adapted for the selective obtaining of glycerol ethers. Of the ethers formed, the present invention focuses on obtaining the two isomers of di-tert-butyl glycerol (DTBG) and tri-tert-butyl glycerol (TTBG), from crude glycerin and tert-butanol in the presence of a suitable catalyst, which has efficiency and performance advantages superior to those described in the state of the art. The process of the present invention comprises three essential stages defined as: a first stage of purification or pretreatment of the crude glycerin, a subsequent reaction stage, of the purified glycerin obtained in the previous stage with tert-butanol in the presence of a catalyst and a final stage of separation or extraction of the glycerol ethers obtained as final reaction products.

The technical problem solved in the present invention is the provision of a process for obtaining certain glycerol ethers that using raw glycerin as a starting material has important advantages in relation to the efficiency and performance of the process.

These advantages of efficiency and process performance are achieved through the following process characteristics: - Use of lower contents of the etherifying agent, tert-butanol, as a consequence of carrying out the reaction stage in a discontinuous and hermetic reactor, which avoids evaporation losses of the etherifying agent, and recirculation of the unreacted agent. In this way savings of 50% of the necessary etherifying agent are achieved.

- Reuse of the necessary catalyst in the reaction stage, as a consequence of performing a purification of the glycerin as an integral part of the process as well as including a stage of washing the catalyst, which allows the same catalyst to be used for up to 10 consecutive cycles with a yield of obtaining the objective products of the present invention similar to that of the first cycle.

Elimination of the use of sulfuric acid or similar agents for catalyst activation, and

Separation and extraction of the desired glycerol ethers through successive processes of distillation and liquid-liquid extraction that improve the yield of obtaining the objective products of the present invention and allow the reuse of all raw material not converted into the object product of process.

For the purposes of the present invention, "crude glycerin" is understood as the glycerin obtained as a byproduct of industrial biodiesel production processes. It is therefore an unpurified glycerol by-product that has a glycerol content greater than 75% and also contains water in an amount not exceeding 10%, ashes in an amount less than 10% and dissolved ions in concentrations between 5,000 and 30,000 ppm of Na ⁺ and K ^{+ in} addition to particles of oily substance not miscible in suspension. The term "purified glycerin" refers to the product of purified glycerin through the first stage of purification of the crude glycerin according to the present invention, which has a glycerin content of between 80 and 95% with a concentration in Na ⁺ and K ⁺ ions of less than 3000 ppm, and a moisture content of less than 6% and which does not have oily matter in perceptible suspension.

The term "hermetic discontinuous reactor" refers to a reactor in which an amount of feed is charged and allowed to react during the reaction time. Once that time has elapsed, another amount of power is reloaded. This operation is repeated successively. It also includes an impermeable closure or any system (such as a cooling column) that prevents the leakage of reagents in the liquid phase or in the vapor phase inside. An example of this reactor would be a cylindrical container with conical bottom that facilitates its emptying, with top lid with airtight seal which prevents losses of etherifying agent and reaction intermediates and a stirrer. Another example would be a reactor with the same geometric characteristics and with an agitator with a cooling column located on top of it through which a coolant circulates (for example water) at a temperature that prevents leakage by evaporation of the agent etherifier and reaction intermediates.

The term "acid catalyst" refers to a homogeneous or heterogeneous catalyst whose active sites have a protic acid nature. In particular, it refers to an "ion exchange resin". Examples include, among others, Zeolite BEA-CP814E, Amberlyst 15, Amberlyst 35, Sulfuric acid, Zeolite ZSM-5, Zeolite CBV-2314, Montmorillonite KSF and Montmorillonite KP10.

It is therefore an object of the present invention a process for obtaining ethers of glycerol di-tert-butyl glycerol (DTBG) and tri-tert-butyl glycerol (TTBG) from crude glycerin and tert-butanol comprising a step of purification of glycerin, followed by reaction between glycerin and tert-butanol in the presence of a catalyst and separation and recovery of glycerol ethers.

An object of the present invention is also a process for obtaining, in particular, ethers of glycerol di-tert-butyl glycerol (DTBG) and tri-tert-butyl glycerol (TTBG) from crude glycerin and tert-butanol whose Purification stage comprises a centrifugation stage of the crude glycerin to separate non-miscible impurities (composed mainly of non-glycerinic organic matter or MONG) and a second stage of treatment with an ion exchange resin to remove the alkaline ions from the glycerin.

It is also a further object of the present invention a process for obtaining, in particular, ethers of glycerol di-tert-butyl glycerol (DTBG) and tri-tert-butyl glycerol (TTBG) from crude glycerin and tert-butanol in which the catalyst used in both the purification and reaction stage is an ion exchange resin that is activated prior to use through a wash with methanol or ethanol and subsequent drying.

A further object of the present invention is also a process for obtaining in particular ethers of glycerol di-tert-butyl glycerol (DTBG) and tri-tert-butyl glycerol (TTBG) from crude glycerin and tert-butanol in which the ion exchange resin used is regenerated by washing with, preferably, hydrochloric acid after the purification step.

A further object of the present invention is also a process for obtaining in particular ethers of glycerol di-tert-butyl glycerol (DTBG) and tri-tert-butyl glycerol (TTBG) from crude glycerin and tert-butanol whose separation stage It comprises a first vacuum distillation followed by a first extraction with pentane or heptane solvent, followed by a second liquid-liquid extraction with water and a second distillation that allows the final reaction products, DTBG and TTBG, to be recovered and reused.

A further object of the present invention is also a process for obtaining in particular ethers of glycerol di-tert-butyl glycerol (DTBG) and tri-tert-butyl glycerol (TTBG) from crude glycerin and tert-butanol which additionally allows the catalyst to be recovered through a stage of filtering, washing and drying.

A further object of the present invention is also a process for obtaining in particular ethers of glycerol di-tert-butyl glycerol (DTBG) and tri-tert-butyl glycerol (TTBG) from crude glycerin and tert-butanol which allows recovering the tert-butanol for later use in the process of the invention through the addition of preferably calcium oxide (CaO) to the tert-butanol-water solution and subsequent distillation.

A further object of the present invention is also a process for obtaining in particular ethers of glycerol di-tert-butyl glycerol (DTBG) and tri-tert-butyl glycerol (TTBG) from crude glycerin and tert-butanol in which the yield of obtaining DTBG is between 1 1 and 13%.

Finally, it is an object of the present invention to use glycerol ethers obtained from glycerin and tert-butanol according to the process of the present invention as oxygenated additives for diesel fuels.

DESCRIPTION OF THE FIGURES

Figure 1: DTBG isomers and TTBG molecule

Figure 2. Formation reactions of MTBG, DTBG and TTBG

Figure 3. Diagram of the reaction process

DETAILED DESCRIPTION OF THE INVENTION

As described above, the present invention relates to a process for obtaining oxygenated additives derived from crude glycerin, adapted for the selective obtaining of glycerol ethers selected from the group consisting of the two isomers of di-tert-butyl glycerol (DTBG) and tri-tert-butyl glycerol (TTBG), (Figure 1), from crude glycerin and tert-butanol.

The process of the present invention is divided into three main stages: pretreatment or purification phase, reaction phase and separation phase. A schematic of the process of the present invention is illustrated in Figure 3. In the first phase the purification of the crude glycerin is carried out. This glycerin comes directly from the biodiesel manufacturing process (transesterification). It contains moisture, non-glycerinic organic matter (MONG), oily matter of lower density than glycerin and dissolved ions (mainly Na ⁺ and K ⁺ from the previous transesterification process). These impurities must be removed as they directly and negatively affect the etherification reaction of the glycerin that will take place.

In the second phase the etherification reaction develops. In it, glycerin, in the presence of a catalyst, such as, for example, Amberlyst 15, reacts with the etherifying agent, tert-butanol to give, in serial reactions, mono-ethers, di-ethers and glycerine tri- ethers, preferably di-ethers, in particular, DTBG.

In the third phase, the objective products of the process, di-ethers and tri-ethers of glycerol, are isolated by successive processes of distillation and liquid-liquid extraction. In addition, the streams composed of unreacted raw material (tert-butanol, glycerin) and by-products (MTBG isomers) can be recovered successively for later reuse in the reaction stage.

Purification Phase:

First, a centrifugation of the crude glycerin is carried out in which the less dense oily substance particles are removed from the glycerin. This centrifugation is carried out in a centrifuge (eg Digicen model of the Orto Alresa commercial house) at a glycerin temperature of between 45 and 75 ° C, preferably between 50 and 70 ° C to facilitate the separation of the phases by viscosity reduction of glycerin.

From this centrifuge two streams are obtained, one formed by the clean centrifuged glycerin and another formed by the separated oily matter that is discarded.

Subsequently, adsorption of the alkaline ions takes place through the use of an ion exchange resin through which the clean centrifuged glycerin stream is passed. The resin used that has provided better results is Amberlyst 15 (Rohm and Haas), although other options have been tested, such as: Zeolite BEA (H-Form), commercial molecular sieve, hydrotalcite, sepiolite 60/120, sepiolite 15/30 , alumina, cobalt oxalate and combinations of several of them.

The contact between the glycerin and the resin can be carried out in filler columns or in a stirred tank with subsequent filtration. The optimum ratio between the amount of glycerin and resin for exchange is 1: 3 to 1: 12 Amberlyst 15: Glycerin preferably, 1: 3 by weight (1 kg of resin for every 3 kg of glycerin to be treated). In case of stirring, the stirring time should be 60 minutes to 120 minutes, preferably 90 minutes. The agitation tank can be a cylindrical tank with a lower drain valve with an agitator inside. The filling column can be cylindrical with upper or lower feed and with product outlet on the opposite side that should consist of a filter to avoid losses of ion exchange resin.

For filtering the mixture (either after stirring or at the bottom of the filler column), the filter should have a mesh light of less than 600 microns, preferably 500 microns (0.5 mm). Any mesh or commercial filter with mesh light less than indicated can serve this purpose. By way of example, in the present process the mixture has been filtered on a laboratory glass funnel on which metallic mesh of 500 microns of mesh light has been placed. It has been proven that this initial purification of crude glycerin improves the results obtained in the subsequent reaction in several aspects:

- It allows the reuse of the reaction catalyst in successive reactions without breaking and deactivating it, maintaining glycerin conversion values and DTBG performance at least until the tenth cycle of reuse.

It allows to increase the selectivity of the reaction towards the DTBG.

The ion exchange resin used in this stage must be activated prior to use and regenerated after use in order to be reused. This reuse is possible as many times as necessary whenever the process of reactivation of the active sites of the resin is carried out.

The activation of the resin consists in washing it with methanol or ethanol for a time of approximately 5 to 30 minutes, preferably 15 minutes (with stirring or recirculation through the filler column) and subsequent drying of the same at a temperature of between 100 and 130 ° C, preferably 100 ° C, for a period of time between 6 and 48 hours, preferably, 12 hours (in an oven or by circulating hot air current through the filler column ).

The reactivation of the active sites of the resin is carried out by washing it with 1-6M HCI, preferably 4M, for a period of 2 to 4 hours, preferably 2 hours (under stirring or by recirculation in the column of filling). This reactivation of the active sites must be followed by the washing (activation) process described, prior to its use as an ion exchange resin. In substitution of HCI, any other acid capable of reactivating the active sites of the catalyst can be used, that is to say that it gives protons to the exchange resin and captures the alkaline ions retained therein, such as: HN0 ₃ , H ₂ S0 _{4 ,} HCI0 ₄ , HCI0 ₃ .

Once the glycerin has undergone this purification process it is called purified glycerin, and is apt to be introduced into the reaction phase. The characteristics of this purified glycerin are as follows: it has a glycerin content of between 80 and 95% with a concentration of Na ⁺ / K ⁺ ions of less than 3000 ppm, and a moisture content of less than 6% and not it presents oily matter in perceptible suspension

Reaction Phase

The purified glycerin is fed to the reactor. It is a hermetic agitated discontinuous reactor or with a cooling column, as described above. The objective is to prevent the leakage of etherifying agent and reaction intermediates (eg isobutene) that favor the development and selectivity of the reaction towards the target products (therefore any type of reactor that serves this purpose could be used). The purified glycerin, the etherifying agent (tert-butanol) in a ratio of 1: 3 to 1: 8, preferably 1: 4 molar versus glycerin (4 moles of tert-butanol for each mole of fed glycerin) and preferably the catalyst (Amberlyst 15) in an amount of between 3 and 20%, preferably 8% to 16%, more preferably 8% by weight versus the purified glycerin fed.

The reaction conditions are a reaction temperature between 50 and 120 ° C, preferably 80 ° C and a reaction time between 30 minutes and 8 hours, preferably 120 minutes, which maximize glycerin conversion and yield in obtaining DTBG and TTBG.

In the reaction, serial etherification reactions occur, as shown in Figure 2. First, from the reaction between glycerin and tert-butanol, mono-tert-butyl glycerol (MTBG) is obtained in its two isomers . Next, the MTBG molecule reacts again with tert-butanol to obtain di-tert-butyl glycerol (DTBG) in its two isomers. Finally, the DTBG molecule reacts with tert-butanol to obtain tri-tert-butyl glycerol (TTBG).

Once the reaction is finished, the resulting mixture, called the synthesis mixture, is filtered through two successive grid filters, the first one with a mesh light of less than 600 microns, preferably 500 microns and the second one with a mesh light. less than 100 microns, preferably 50 microns. The filtering systems set forth above may be used for this purpose.

After filtration, the synthesis mixture is stored to pass the separation or isolation phase of the target reaction products.

The catalyst used in the reaction must be previously activated by washing it with methanol or ethanol, during a stirring period of between 5 and 30 minutes, preferably 15 minutes and subsequent drying at a temperature between 100 and 130 ° C, preferably 100 ° C for a period of between 6 and 48 hours, preferably 12 hours.

The catalyst collected in the first grid filter, thanks to the initial purification of the glycerin made, can be reused in the reaction. It is necessary to apply a catalyst wash with methanol or ethanol and a drying under the same conditions as in the initial activation. In this way, the catalyst can be reused in up to ten reactions without decreasing the conversion of glycerin obtained or the yield of obtaining DTBG and TTBG.

Separation Phase

The filtered synthesis mixture is introduced in the separation phase to isolate the target additive (DTBG and TTBG) from the rest of the components of the reactor output current to recover and recirculate the unreacted raw material.

For this, a first vacuum distillation is performed (60 ° C and the absolute pressure OOmbar) in which the unreacted tert-butanol (mixed with water) is recovered. By way of example, the present invention has carried out the distillation in vacuum systems composed as main equipment by a column, a heated vessel into which the fresh feed is introduced, a refrigeration system for the condensate collection of the most volatile compound and a commercial vacuum pump capable of reach up to 100 mbar of absolute pressure. The product stream passes to the first liquid-liquid extraction.

In this extraction a solvent (pentane or heptane) is added in volumetric ratio between 5: 1 and 2: 1, preferably 2: 1 (2 volumes of solvent for each volume of feed stream). The mixture is stirred for a period of 10 to 120 minutes, preferably 30 minutes and allowed to stand. Two phases are formed. The densest phase is formed by unreacted glycerin and MTBG mainly, in addition to traces of DTBG. This current is recirculated to the reactor. The recirculation of this current improves the results obtained in the reaction.

The less dense phase is formed by DTBG, TTBG and solvent and is fed to a second decanter in which a new liquid-liquid extraction is carried out. The solvent used in this case is water. The mixture is also stirred for a period of 10 to 120 minutes, preferably 30 minutes and allowed to decant.

The densest phase of this extraction consists mainly of water and contains some traces of MTBG and glycerin. The objective of this extraction is to eliminate these traces of glycerin and MTBG that would contaminate the product additive stream (DTBG and TTBG). This denser stream is stored waiting to be reused again in the extraction, since it is mostly water.

The less dense phase, formed by the solvent of the first extraction (pentane or heptane) and DTBG and TTBG, is introduced into a second distillation column (which operates under the same conditions as the first). In this distillation, the solvent is separated from the additives (DTBG and TTBG) targeted by the process.

Extractions with chloroform, pentane, octane, heptane or ethyl ether have been tested in order to assess the suitability of each solvent in the separation process. As an example, the compositions of the exit streams are presented after successive extractions with the indicated solvents in the tables and the proportions (ratios) indicated.

As can be seen in Tables 1 and 2, the extraction with pentane followed by an extraction with water makes it possible to obtain an MTBG free output current and with a DTBG amount greater than 95%. It should be noted that with heptane similar values have been obtained, as with octane, but the lower boiling point of these solvents (pentane and heptane) facilitates separation in the subsequent stage.

Table 1

Amberlyst Catalyst 15

DTBG MTBG glycerin ratio

Initial sample 10.41 48.76 40.84

Extraction with 1: 2

15.81 72.45 1 1.74 chloroform synthesis: chloroform

1 ^a Extraction with 1: 2

55.37 43.42 1.21 water chloroform: water

2 ^a Extraction with 1: 2

93.41 4.42 2.18 water chloroform: water Table 2

DTBG MTBG GCL Ratio

Initial sample 46,98065 42,75523 10,2641

1: 2

Pentane extraction 85.45 1 1, 71 2.83

synthesis: pentane

1: 2

Cleaning with water 96.01 0 3.99

synthesis: pentane

Comparing both tables it is clear that the extraction with pentane (or heptane) is more advantageous since wealth is reached in DTBG in the major outflows with less number of extractions and in addition there are no traces of MTBG in the output stream.

The separated solvent can be reused in the first liquid-liquid extraction, since the separation is practically total.

The tert-butanol that has not reacted and that was separated in the first distillation can also be reused in the reaction. For this it is necessary to separate the water it contains (which forms azeotrope with tert-butanol) from the alcohol. This is achieved by mixing said stream with a drying agent, selected from the group consisting of: sodium sulfate heptahydrate, magnesium sulfate heptahydrate, hydrated calcium carbonate, potassium acetate and CaO, preferably CaO, in a proportion of between 5 and 30%, preferably 22% by weight compared to the water-alcohol mixture fed. It is kept under stirring for a period of 2 to 9 hours, preferably 7 hours and subsequently distilled at 120-150 ° C, preferably at 135 ° C the resulting paste. The vapor formed is condensed and collected as tert-butanol without water content. The remaining paste formed by calcium hydroxide can be distilled again to recover the CaO and reuse it in the process. This distillation takes place at between 80 and 100 ° C, 100 mbar of absolute pressure and a time of 1 hour.

The DTBG yields and conversion of the purified glycerin according to the process of the present invention are illustrated in Table 3. It can be concluded that according to the process described above, the catalyst can be reused for up to 10 cycles while maintaining the conversion and obtaining yields of DTBG obtained in the first cycle.

Table 3 . Reuse of AM15 using pre-treated Bionet GCL.

Activation Cycle AM15 Time (gr) Conversion Performance

DTBG reaction (%)

1 EtOH, 12h 100 ° C 120 min 1.00 45.69 7.41

2 EtOH, 12h 100 ° C 120 min 0.99 52.09 9.96

3 EtOH, 12h 100 ° C 120 min 0.99 52.72 8.64

4 EtOH, 12h 100 ° C 120 min 0.98 45.52 6.20

5 EtOH, 12h 100 ° C 120 min 0.97 47.2 7.65

6 EtOH, 12h 100 ° C 120 min 0.97 50.01 7.80

7 EtOH, 12h 100 ° C 120 min 0.71 39.75 6.08

8 EtOH, 12h 100 ° C 120 min 0.65 35.04 4.15

9 EtOH, 12h 100 ° C 120 min 0.61 36.44 4.68

10 EtOH, 12h 100 ° C 120 min 0.56 46.12 6.05

EXAMPLE

Purification Phase:

10 gr is available. of crude glycerin with a moisture content of 3% and alkaline ion concentrations of 14,300 ppm of K ⁺ ions and 300 ppm of Na ⁺ ions in the Digicen model centrifuge of the Orto Alresa house, at a glycerin temperature of 65 ° C to facilitate the separation of the phases by reducing the viscosity of glycerin.

Subsequently, adsorption of the alkaline ions takes place through the use of an ion exchange resin through which the clean centrifuged glycerin stream is passed. The resin used is Amberlyst 15 (Rohm and Haas).

The contact between the glycerin and the resin is carried out in an agitated tank consisting of a cylindrical vessel with a lower emptying system and an agitator inside with subsequent filtration. The ratio between the amount of glycerin and resin for exchange is 1: 3 by weight, and the stirring time 90 minutes.

For filtering the mixture, after stirring, the filter has a mesh light of less than 600 microns (0.6 mm). For filtering, a 500 micron mesh metal grid is placed on the glass funnel and the mixture from the previous stirred tank is passed through it. The ion exchange resin used in this stage is activated prior to use and regenerated after use to be reused. This reuse is possible as many times as necessary whenever the process of reactivation of the active sites of the resin is carried out. The resin is activated by washing it with methanol for 15 minutes while stirring and drying it at a temperature of 100 ° C, for 12 hours in an oven with forced air convection Binder brand model FD1 15 Reactivation of the active sites of the resin is carried out by washing it with 4M HCI for 2 hours with stirring. This reactivation of the active sites is followed by the washing (activation) process described above.

This purified glycerin contains 1.4% moisture and an alkali ion concentration of 1,600 ppm K ⁺ ions and 90 ppm Na ⁺ ions.

Reaction Phase

In the stirred reactor, purified glycerin (10 grams), the etherifying agent (tert-butanol) is introduced in a ratio of 1: 4 molar to glycerin (4 moles of tert-butanol for each mole of glycerin fed, equivalent to 32.1 grams of tert-butanol) and the catalyst (Amberlyst 15) in an amount of 8% by weight against the fed glycerin (800 milligrams).

The reaction conditions are a reaction temperature 80 ° C and a reaction time of 120 minutes, which maximize glycerin conversion and yield in obtaining DTBG.

In the reaction, serial etherification reactions occur. First, from the reaction between glycerin and tert-butanol, mono-tert-butyl glycerol (MTBG) is obtained in its two isomers. Next, the MTBG molecule reacts again with tert-butanol to obtain di-tert-butyl glycerol (DTBG) in its two isomers. Finally, the DTBG molecule reacts with tert-butanol to obtain tri-tert-butyl glycerol (TTBG).

Once the reaction is finished, the synthesis mixture is filtered through two successive grid filters, the first one with a 500 micron mesh light and the second one with a 50 micron mesh light. This filtration is carried out as in the previous stage on glass funnels as previously mentioned.

The catalyst used in the reaction is previously activated by washing it with methanol, during a stirring period of 15 minutes and then drying at a temperature of 100 ° C for a period of 12 hours.

The catalyst collected in the first grid filter is reused in the reaction. A catalyst wash with methanol and drying under the same conditions as in the initial activation is applied. In this way, the catalyst can be reused in up to ten reactions without decreasing the conversion of glycerin obtained or the yield of obtaining DTBG and TTBG. It should be noted that the tri-tert-butyl glycerol (TTBG) obtained as a product of the reaction taking place is not quantifiable. Thanks to analysis techniques applied in the development of the process, the existence of this product in the reactor output current is known, but due to the lack of commercial patterns of the product and the detection limits of the equipment currently available, it is not possible Determine the exact amount of this component. However, its contribution as a fuel additive is proven in literature given the chemical properties of the molecule of this ether. Separation Phase

A first vacuum distillation is carried out on the type equipment described above at 60 ° C and 100mbar of absolute pressure and the unreacted tert-butanol is recovered (mixed with water). The product stream passes to the first liquid-liquid extraction.

In this extraction a solvent (heptane) is added in a 2: 1 volumetric ratio (2 volumes of solvent for each volume of feed stream). The mixture is stirred for 30 minutes and allowed to stand. Two phases are formed. The densest phase is formed by unreacted glycerin and MTBG mainly, in addition to traces of DTBG. This current is recirculated to the reactor.

The less dense phase is formed by DTBG, TTBG and solvent and is fed to a second decanter in which a new liquid-liquid extraction is carried out. The solvent used in this case is also water in a 2: 1 ratio to the fed mixture. The mixture is also stirred for 30 minutes and allowed to decant.

The densest current is stored waiting to be reused again in the extraction, since it is mostly water.

The less dense phase, formed by the solvent of the first extraction (heptane) and DTBG and TTBG, is introduced into a second distillation column (which operates under the same conditions as the first). In this distillation, the solvent is separated from the additives (DTBG and TTBG) targeted by the process.

The separated solvent is reused in the first liquid-liquid extraction, since the separation is practically total.

The tert-butanol that has not reacted and separated in the first distillation is also reused in the reaction. For this it is necessary to separate the water it contains (which forms azeotrope with tert-butanol) from the alcohol. This is achieved by mixing said stream with CaO 22% by weight versus the water-alcohol mixture fed. It is kept under stirring for a period of 7 hours and subsequently distilled at 120-150 ° C, preferably at 135 ° C the resulting paste. The vapor formed is condensed and collected as tert-butanol without water content. The remaining paste formed by hydroxide of Calcium can be distilled again to recover the CaO and reuse it in the process. This distillation takes place at between 80 and 100 ° C, 100 mbar of absolute pressure and a time of 1 hour.

Claims

one . Process for obtaining ethers of glycerol di-tert-butyl-glycerol (DTBG) and tri- tert-butyl-glycerol (TTBG) from crude glycerin and tert-butanol characterized in that it comprises the following steps:

a) Purification of glycerin.

b) Reaction between glycerin and tert-butanol in the presence of a catalyst, c) Separation and recovery of glycerol ethers

characterized in that the reaction stage b) is carried out by catalysis in a discontinuous and hermetic reactor.

2. Procedure for obtaining glycerol ethers from glycerin and tert-butanol according to claim 1, characterized in that crude glycerin is used, with a glycerol content greater than 75% and also containing water in an amount not exceeding 10%, ashes in quantity less than 10% and ions in solution at concentrations between 5,000 and 30,000 ppm of Na ⁺ and K ^{+ in} addition to particles of oily miscible substance in suspension.

3. Procedure for obtaining glycerol ethers from glycerin and tert-butanol according to claims 1-2, characterized in that step (a) comprises a step of centrifuging the crude glycerin to separate the non-glycerol organic material Not miscible and a second stage of treatment with an ion exchange resin to remove alkaline ions from glycerin.

4. Process for obtaining glycerol ethers from glycerin and tert-butanol according to claims 1-3, characterized in that the ion exchange resin used in (a) is an Amberlyst resin.

5. Procedure for obtaining glycerol ethers from glycerin and tert-butanol according to claims 1-4, characterized in that the ratio between glycerin and resin is 1: 3 by weight.

6. Procedure for obtaining glycerol ethers according to claims 1-5, characterized in that the ion exchange resin used in (a) is activated prior to use through a wash with methanol or ethanol and subsequent drying.

7. Procedure for obtaining glycerol ethers from glycerin and tert-butanol according to claims 1-6, characterized in that the ion exchange resin used in (a) is regenerated by washing with hydrochloric acid and subsequent washing with methanol or ethanol and dried.

8. Procedure for obtaining glycerol ethers from glycerin and tert-butanol according to claims 1-7, characterized in that the reaction step (b) is carried out between the tert-butanol and the purified glycerin obtained of the

REPLACEMENT SHEET (Rule 26) step a) in a molar ratio between 1: 3 and 1: 8, and in the presence of a catalyst in an amount of 3 to 20% by weight with respect to the purified glycerin fed.

9. Process for obtaining glycerol ethers from glycerin and tert-butanol according to claims 1-8, characterized in that the catalyst is an ion exchange resin, a zeolite or an acid catalyst.

1 0. Process for obtaining glycerol ethers from glycerin and tert-butanol according to claim 9, characterized in that the catalyst is an ion exchange resin, Amberlyst 1 5 with a grain diameter between 600 and 850 μηι .

eleven . Process for obtaining glycerol ethers from glycerin and tert-butanol according to claims 1-10, characterized in that the ion exchange resin used in (b) is activated prior to use or reuse through washing with methanol or ethanol and subsequent drying.

1 2. Process for obtaining glycerol ethers from glycerin and tert-butanol according to claims 1 -1 1, characterized in that the separation step (c) comprises:

- a first vacuum distillation to remove alcohol that has not reacted in step b),

- a first liquid-liquid extraction, to remove reagents that have not reacted in step b) of the product stream

- a second liquid-liquid extraction to remove traces of glycerin and MTBG from the product stream and

- second distillation for the recovery of glycerol, DTBG and TTBG ethers.

1 3. Process for obtaining glycerol ethers from glycerin and tert-butanol according to claim 12, characterized in that both vacuum distillations are carried out at a temperature of 50-90 ⁵ C, and at an absolute pressure between 100 - 200mbar.

14. Procedure for obtaining glycerol ethers from glycerin and tert-butanol according to claims 1 and 13, characterized in that the first liquid-liquid extraction is carried out with the solvent pentane or heptane.

1 5. Process for obtaining glycerol ethers from glycerin and tert-butanol according to claims 1 to 14, characterized in that it additionally comprises the recirculation of the glycerin and MTBG reagent stream recovered in the first liquid extraction - liquid to the reactor for reuse in stage b).

REPLACEMENT SHEET (Rule 26)

16. Process for obtaining glycerol ethers from glycerin and tert-butanol according to claims 12-15, characterized in that the second extraction is carried out with the water solvent.

17. Method according to any of the preceding claims, characterized in that it additionally comprises a catalyst recovery stage after step b).

18. Method according to claim 17, characterized in that the catalyst recovery step comprises:

a first stage of grid filtration that collects the majority fraction of the catalyst that has not lost its structure,

- a second stage of washing the majority fraction of the catalyst that has not lost its structure with methanol or ethanol, and

a third oven drying stage of the catalyst recovered in the previous stage.

19. Method according to any of the preceding claims, characterized in that it additionally comprises a stage of recovery of tert-butanol after step c).

20. Method according to claim 19, characterized in that the recovery step of tert-butanol comprises the addition of calcium oxide (CaO) to the tert-butanol-water solution in a stirred tank and column distillation of the product of the previous stage for the extraction of tert-butanol in the volatile fraction.

twenty-one . Process according to claims 19 and 20, characterized in that it additionally comprises the recirculation of the tert-butanol stream recovered after step c) to the reactor for reuse in step b).

22. Process for obtaining glycerol ethers from glycerin and tert-butanol according to any of the preceding claims, characterized in that the yield of the glycerol ethers obtained is between 1 and 13% di- tert-butyl glycerol (DTBG)

23. Use of the glycerol ethers obtained from glycerin and tert-butanol according to claims 1-22, as oxygenated additives for diesel fuels.

REPLACEMENT SHEET (Rule 26)