PROCESS FOR THE PRODUCTION OF A COMPOSITION USEFUL AS FUEL

The present invention relates to a new process for the production of a composition useful as diesel fuel or as a component of diesel fuel. In particular, the present invention relates to a process for thp preparation of a composition containing biodiesel, without the problem of the co-production and removal of the glycerin deriving from the transesterification of triglycerides.

The composition obtained is also new and is a further object of the present invention.

The trend and forecasts of the European market in general and the Italian market in particular, relating to products for motor vehicles, are characterized by a constant increase in the request for gasoil and a reduction in the consumption of gasoline. In order to satisfy the market demands, various alternative fuel sources have been taken into consideration, among which those used in the production of biodiesel. Biodiesel

normally consists of esters of fatty acids and is commonly obtained by transesterification with methanol of triglycerides of a vegetable origin. Glycerin is obtained as by-product (about 10% by weight) whose use is an important aspect for improving the production process of biodiesel .

As mentioned above, biodiesel is normally synthesized starting from triglycerides of a vegetable origin and, even if only marginally, of animal origin, which react with methanol, in excess, in the presence of a base or, less frequently, acid catalyst. This is a transesterification reaction that leads i-.r> the formation of fatty acid methyl esters, called FAME, known as biodiesel. The glycerin recovered quantitatively from the reaction, must be disposed of or recovered by means of a subsequent transformation. One of the possible uses of glycerin is the formation of glycerin ethers (mainly di- ter-butyl ethers) , by means of an etherification reaction with olefins, mainly isobutene, catalyzed by acids. In WO 2006/093896, the simultaneous synthesis of FAME and glycerol acetals is described. Among preferred compounds for the formation of acetals, aldehydes, ketones and diethers are claimed. The synthesis envisages a process of two consecutive steps, the first for the formation of FAME and the second for the synthesis of

acetals, without preventive separation and purification of the glycerin. A process which is based on the same type of reactions is also described in FR 2866654.

WO 2005/093015 describes the synthesis of FAME and terbutyl ethers of glycerin. The process takes place in two subsequent steps . The first step comprises the formation of FAME, the methanol in excess is then eliminated, the glycerin is isolated and allow to react with isobutene to give terbutyl ethers of glycerin. This is still a two-step process in which the excess methanol after the first reaction, must be eliminated to avoid to jeopardize the etheri fi ration reaction, because the isobutene can react back with methanol to give MTBE instead of reacting with the glycerin. US 6,174,501 also describes a two-step process: the first step transforms the triglycerides into FAME and the second step consists on the etherification of glycerin with olefins such as isobutene or isoamylenes. The preventive separation of the unreacted glycerin in the first step and complete evaporation of the methanol in excess are necessary also in this case.

US 5,578,090 claims the synthesis of FAME and glycerin ethers starting from fatty acids and olefins, after preparation of the fatty acids from triglycerides by hydrolysis. The resulting mixture is subjected to

partial thermal cracking (catalytic) or hydrocracking to reduce the viscosity which would be too high with respect to the standard diesel parameters .

The above patents mostly describe the possibility of preparing FAME and glycerin ethers from triglycerides in two consecutive processes, possibly without isolating the glycerin, or even in two distinct processes. In both cases it is necessary to evaporate the excess methanol used for the initial synthesis of the FAME. The Applicant has now found a new process for preparing fatty acid methyl esters (FAME) , main constituents of bicdicccl, capable of ccnteiπporaπeously producing FAME and glycerin ethers which, in turn, can be used as oxygenated components for diesel. The present invention therefore eliminates a strongly felt problem, that relating to the co-production of glycerin in the preparation of biodiesel.

As glycerin ethers are used as diesel components, the contemporaneous synthesis of FAME and glycerin ethers allows a mixture to be obtained which can be used directly as diesel fuel or for the preparation of commercial diesels in a single step, rather than two successive synthesis steps.

The process in a single step, object of the invention, uses triglycerides, or mixtures of a

biological origin containing them, and MTBE (methyl- terbutyl-ether) , as starting materials.

The stability of MTBE greatly depends on the temperature (see for example A. Rehfinger, U. Hoffmann Chem. Eng. Sci. (1990) 45,1605-08 or U. Hoffmann, A. Rehfinger Chem. Eng. Techno1. (1990) 13, 150-156) . At a high temperature, the partial decomposition of the MTBE to methanol and isobutene can be observed.

It has now been found, and this is a first object of the present invention, that by causing the decomposition reaction of MTBE to give isobutene and methanol, under suitά.jjα.6 COiIi-IXUJ-OnS, in LHC presence OJ- it is unexpectedly possible to effect the synthesis of FAME and terbutyl ethers of glycerin in a single step: the methanol is in fact available for the transesterification reaction of the triglycerides present to give FAME, whereas the isobutene released is available for the etherification reaction of the glycerin formed as a result of the transesterification reaction. With respect therefore to the known art, the use of MTBE under suitable conditions allows the simultaneous synthesis of FAME and glycerin terbutyl ethers starting from triglycerides, or biological mixtures containing them, and MTBE. A first object of the present invention therefore

relates to a process for the preparation of a composition which can be used as fuel, or as a component of fuels, which comprises reacting a mixture of a biological origin containing one or more fatty acid triglycerides with methyl-terbutyl-ether, in the presence of an acid catalyst, to give a mixture containing one or more fatty acid methyl esters and terbutyl-glycerols .

Terbutyl glycerols refer to a mixture of mono-, di- and tri-terbutyl ethers of glycerin, preferably 1-mono- terbutyl ether, 1,3- and 1, 2-di-terbutyl ethers and 1, 2, 3-triterbutyl ether of glycerin.

The mixtures of a biological origin used in the process of the present invention, containing one or more triglycerides of fatty acids, possibly with quantities of free fatty acids, can be mixtures of a vegetable or animal origin. The portion of free fatty acids can range, for example, from 2 to 20% by weight with respect to the total mixture of a biological origin. Typical fatty acid triglycerides contained in these mixtures are triglycerides of fatty acids wherein the hydrocarbon chain of the fatty acid can contain from 12 to 24 carbon atoms and can be mono- or poly-unsaturated. The mixtures of a biological origin can be selected from vegetable oils, animal fats, fish oils or mixtures thereof. The vegetable oils or fats can be sunflower, rape, canola,

palm, soybean, hemp, olive, linseed, peanut, castor, mustard, coconut oils or oils contained in the pulp of pine-trees (tall oil), or mixtures thereof. Animal oils or fats can be selected from bacon- fat, lard, tallow, milk fats, and mixtures thereof. Recycled oils or fats from the food industry, of either an animal or vegetable origin can also be used. The vegetable oils or fats can also derive from plants selected by means of genetic manipulation . The oils and fats are directly used in the process of the present invention as feeding, or the triglycerides can be isolated before bp-ing used, by rr.εanc of any of the methods described in the known art, for example as described in "Bailey's Industrial Oil and Fat Products, Edible Oil and Fat Products: Products and Application Technology", Hui Y. H., editor, Wiley-Interscience ; 5 edition (December 1995) .

The process can be carried out at a temperature ranging from 80 to 150 ⁰ C ad a pressure ranging from 5 to 30 bar.

According to a particularly preferred aspect of the invention, the process is carried out in two moments or subsequent phases which differ in the reaction temperature: in particular the first phase is carried out at a higher temperature than the second.

In the first phase, according to a preferred aspect, it is preferable to operate for a time ranging from 1 to 5 hours, preferably from 2 to 3 hours, at a temperature ranging from 80 to 15O ⁰ C, preferably from 120 to 150 ⁰ C, at a pressure ranging from 5 to 30 bar.

The second phase is preferably carried out for a time ranging from 3 to 10 hours, even more preferably from 5 to 6 hours, at a temperature ranging from 50 to

100 ⁰ C, even more preferably from 60 to 80 ⁰ C, at a pressure ranging from 10 to 30 bar.

The reaction is catalyzed by an acid catalyst.

CatalvRts suitable for the purpose are all acid catalysts, organic or inorganic, solid or liquid.

Sulfuric acid, methanesulfonic acid or toluenesulfonic acid, for example, can be conveniently used.

Solid acids which can be well used as heterogeneous catalysts can be polymers with acid groups, resins with acid groups, acid zeolites and polymeric materials with superacid groups. Superacids are preferably used, such as, for example, trifluoromethanesulfonic acid, which allow to obtain higher yields .

Examples of polymers or resins with acid groups are

Amberlyst 15, Amberlyst 35 and Amberlyst 39. These resins are commercial products which can be supplied for example

by Rohm and Haas Co . , USA .

Acid zeolites which can be conveniently used are for example Y zeolite, beta zeolite and X zeolite. Y zeolite is described for example in US 3,130,007, X zeolite in US 2,882,244, beta zeolite is described in US 3,308,069.

A polymeric material with superacid groups which can be conveniently used is Nafion SAC- 13, a silica with trifluoromethanesulfonic groups. Nafion SAC-13 is a product of Engelhart, Italy or commercialized by Sigma- Aldrich.

It is preferable to operate at an acid concentration ranging frcrr. 0.02 rr.illicquivalents/litre (nϊeq/1) Lu i.O meq/1.

The quantity of MTBE is preferably that corresponding to a molar ratio, with respect to the triglycerides contained in the mixture of biological origin used, ranging from 4:1 to 15:1. The reaction can be carried out in a closed reactor under stirring (CSTR) .

The reagents can be introduced into the reactor in any sequence.

The reaction can also be carried out in continuous.

In this case, according to a preferred aspect of the invention, the process is composed by two closed reactors in series, the first reactor operating at a higher temperature with respect to the second reactor, and

preferably under the conditions previously indicated with respect to the embodiment in two phases .

At the end of the reaction MTBE, methanol and isobutene are evaporated and the non-reacted glycerin can be easily removed and separated as independent phase on the bottom of the reactor (less than 1%) .

The final mixture can be used directly for the preparation of biofuels, i.e. compositions containing biodiesel. The final mixture thus obtained, in fact, also contains oxygenated additives synthesized starting from the glycerin coming from the same biological source.

The final omposition of the mixture thus obtained is the following: 92-93% FAME, 6.5-7.5% glycerin terbutyl ethers; £0.5 % mixed glycerin ethers wherein glycerin terbutyl ethers refer to a mixture of mono-, di- and tri- terbutyl ethers of glycerin, and mixed glycerin ethers refer to glycerin methyl-terbutyl ethers. This composition is new and is a further object of the present invention. The following examples are provided for the sole purpose of illustrating the invention more clearly without limiting its contents in any way.

Example 1 40 g of MTBE (0.45 moles) and 0.5 g (0.0052 moleq)

of methanesulfonic acid, as catalyst, were added to 29 g of olive oil (about 0.032 moles of triglycerides). The reaction was carried out at 14O ⁰ C for 2 hours (pressure 20 bar) and, after cooling, for 6 hours at 7O ⁰ C (pressure 8 bar) . After evaporating the excess MTBE, the non- reacted isobutene and methanol under reduced pressure, the final composition in w/w % of the reaction mixture obtained by gas chromatographic analysis, excluding the unreacted glycerin, was the following:

The conversion of the glycerin to ethers is 60% in moles (mol/mol) . The unreacted glycerin (0.2-0.5 g) is separated as independent phase on the bottom of the reactor and can be easily removed. Example 2

61 g of MTBE (0.76 moles) and 0.78 g (0.0081 moleq) of methanesulfonic acid, as catalyst, were added to 47 g of sunflower oil. The reaction was carried out at 140 ⁰ C for 2.5 hours (pressure 20 bar) and, after cooling, for 6

hours at 70 ⁰ C (pressure 8 bar) . After evaporating the excess MTBE, the non-reacted isobutene and methanol under reduced pressure, the final composition in w/w % of the reaction mixture obtained by gas chromatographic analysis, excluding the unreacted glycerin, was the following:

The conversion of the glycerin to ethers is 71 % in moles (mol/mol) . The unreacted glycerin (0.1-0.5 g) is separated as independent phase on the bottom of the reactor and can be easily removed. Example 3

68 g of MTBE (0.77 moles) and 0.79 g (0.0082 moleq) of methanesulfonic acid, as catalyst, were added to 48 g of soybean oil. The reaction was carried out at 140 ⁰ C for 2 hours (pressure 20 bar) and, after cooling, for 5.5 hours at 7O ⁰ C (pressure 8 bar) . After evaporating the excess MTBE, the non-reacted isobutene and methanol under reduced pressure, the final composition in w/w % of the

reaction mixture obtained by gas chromatographic analysis, excluding the unreacted glycerin, was the following:

The conversion of ths glycerin tu cthciia io 55% in moles (mol/mol) . The unreacted glycerin (0.1-0.5 g) is separated as independent phase on the bottom of the reactor and can be easily removed. Example 4

68 g of MTBE (0.77 moles) and 0.79 g (0.0082 moleq) of methanesulfonic acid, as catalyst, were added to 48 g of rape oil. The reaction was carried out at 140 ⁰ C for 2.5 hours (pressure 20 bar) and, after cooling, for 5.5 hours at 70 ⁰ C (pressure 8 bar) . After evaporating the excess MTBE, the non-reacted isobutene and methanol under reduced pressure, the final composition in w/w % of the reaction mixture obtained by gas chromatographic analysis, excluding the unreacted glycerin, was the

following:

The conversion of the glycerin to ethers is 61% in moles (mol/mol) . The unreacted glycerin (0.1-0.5 g) is separated as independent phase on the bottom of the reactor and can be easily removed. Example 5

69 g of MTBE (0.79 moles) and 0.8 g (0.0083 moleq) of methanesulfonic acid, as catalyst, were added to 50 g of palm oil. The reaction was carried out at 14O ⁰ C for 2.5 hours (pressure 20 bar) and, after cooling, for 6 hours at 7O ⁰ C (pressure 8 bar) . After evaporating the excess MTBE, the non-reacted isobutene and methanol under reduced pressure, the final composition in w/w % of the reaction mixture obtained by gas chromatographic analysis, excluding the non-reacted glycerin, was the following:

The conversion of the glycerin to ethers is 65% in moles (mol/mol) . The unreacted glycerin (0.1-0.5 g) is separated as independent phase on the bottom of the reactor and ran v>e easily relieved. Example 6 Use of a superacid catalyst

As in example 4, 70 g of MTBE (0.79 moles) and 1.23 g (0.0082 moleq) of trifluoromethanesulfonic acid, as catalyst, were added to 50 g of rape oil. The reaction was carried out at 140 ⁰ C for 2.5 hours (pressure 20 bar) and, after cooling, for 5.5 hours at 7O ⁰ C (pressure 8 bar) . After evaporating the excess MTBE, the non-reacted isobutene and methanol under reduced pressure, the final composition in w/w % of the reaction mixture obtained by gas chromatographic analysis, excluding the non-reacted glycerin, was the following:

The conversion of the glycerin to ethers is 79% in moles (mol/mol) . The unreacted glycerin (0.1-0.5 g) is separated as independent phase on the bottom of the reactor and can be easily removed.