WO2008074704A1

WO2008074704A1 - Fuel mixture comprising polyoxymethylene dialkyl ether

Info

Publication number: WO2008074704A1
Application number: PCT/EP2007/063746
Authority: WO
Inventors: Eckhard Stroefer; Rudolf Sinnen; Olaf Schweers; Joachim Thiel; Hans Hasse; Markus Siegert
Original assignee: Basf Se
Priority date: 2006-12-20
Filing date: 2007-12-12
Publication date: 2008-06-26
Also published as: EP2104726A1

Abstract

Fuel mixture comprising (i) diesel oil and (ii) polyoxymethylene dialkyl ether of the general formula 1: R-O-(CH2O)n-R', where R and R' are defined as follows: R: methyl, ethyl, propyl, butyl, R': methyl, ethyl, propyl, butyl, n: 2, 3, 4, 5, 6, 7, 8, where the fuel mixture has sulfur content of < 10 ppm (mg/kg) to EN 590 and the proportion by weight of polyoxymethylene dialkyl ethers of the formula 1 where n is 3 and 4 is between 50% by weight and 99.8% by weight, based on the total weight of the polyoxymethylene dialkyl ethers.

Description

Fuel mixture containing Polyoxymethylendialkylether

description

The invention relates to a fuel mixture comprising (i) diesel oil, preferably of fossil origin, and (ii) polyoxymethylene dialkyl ethers of the general formula 1:

Formula 1: RO- (CH ₂ O) _n -R ', with the following meanings for R, R' and n: R: methyl, ethyl, propyl, butyl, preferably methyl, ethyl, more preferably methyl, R ': methyl , Ethyl, propyl, butyl, preferably methyl, ethyl, more preferably methyl, n: 2, 3, 4, 5, 6, 7, 8,

wherein the fuel mixture has a sulfur content of <10 ppm (mg / kg) according to EN 590 (Diesel fuel "Requirements and test methods" German version EN 590: 1999) and the summed weight fraction of polyoxymethylene dialkyl ethers of formula 1 with n equal to 3 and 4 between 50 wt % and 99.8% by weight, preferably between 98% by weight and 99.8% by weight, based on the total weight of the polyoxymethylene dialkyl ethers Diesel engines having a cylinder displacement of 1 liter or more, in particular as fuel for trucks, locomotives, marine and aircraft engines., In terms of road traffic, the preferred vehicle weight is> 8500 American pounds (lbs.) The sulfur content is expressed as elemental sulfur ("S"). ) measured according to the standards referred to in EN 590: EN ISO 14596: 1998, EN ISO 8745: 1995, EN 24260: 1994).

With a view to the desired substitution of petroleum-based fossil fuels, efforts are being made to replace parts of diesel fuel, for example, with compounds that can be produced from alternative sources. One such approach is the addition of polyoxymethylene dialkyl ethers (POMDAE) to diesel fuel. The

POMDAE can be based on natural gas / synthesis gas / methanol and cause in addition to a substitution of the diesel fuel, a desired increase in the cetane number and a clean combustion of the diesel fuel, in particular a reduced soot formation. The natural gas can originate from geological sources, preferably those referred to as "flared gas" or "stranded gas", or those from which it is produced as co-product in oil production. However, the natural gas / synthesis gas / methanol can also preferably be of biological origin and be obtained from biomass.

Such diesel fuel blends are described in US 5,746,785, WO 86/0351 1 and EP-A 1 070 755. Also on the basis of this state of the art, there are still requirements with regard to an optimized fuel mixture containing diesel. Problems that need to be solved, in particular in an optimized setting of the ignition point of the fuel mixture, the simplest possible leveling of different diesel fuels by ideally an addition, ie the simple and safe adjustment of different diesel fuels on a single profile by possibly only one additive. This includes the refinement of inferior mineral oil fractions to diesel fuel. Other requirements continue to be reducing soot formation, especially in "heavy" diesel engines, which typically can not be equipped with soot filters without sacrificing performance and, in addition, possible additives or substitutes should be compatible with the diesel fuel different property profile should be avoided.

These problems and problems have been solved by the fuel mixtures described in the introduction, in particular by fuel mixtures containing (i) diesel oil of fossil origin and (ii) polyoxymethylene dialkyl ethers, the fuel mixture containing between 10 and 95% by weight of (i) diesel oil of fossil origin and between 90 and 5 wt .-% (ii) Polyoxymethylendialkylether, each based on the total weight of the fuel mixture, wherein the fuel mixture has a sulfur content of less than 10 ppm and a content of polycyclic aromatic hydrocarbons of less than 11 mass%, measured according to IP 391/95, component (ii) has a sulfur content of less than 100 ppb and a content of polycyclic aromatic hydrocarbons of less than 100 ppb, measured according to IP 391/95, and also contains component (ii)

between 30 and 70% by weight H ₃ CO- (CH ₂ O) ₃ -CH ₃ , between 30 and 70% by weight H ₃ CO- (CH ₂ O) ₄ -CH ₃ and between 0.1 and 5 Wt% H ₃ CO- (CH ₂ O)> ₄ -CH ₃ ,

in each case based on the total weight of component (ii), and wherein the total weight fraction of H ₃ CO- (CH ₂ O) ₃ -CH ₃ and H ₃ CO- (CH ₂ O) ₄ -CH _{3 is} preferably between 50% by weight. % and 99.8 wt .-%, particularly preferably between 98 wt .-% and 99.8 wt .-% is. The methyl end group can also be replaced by another alkyl radical.

Due to their composition and their reduced freezing point, the preferred mixtures have advantages in storage, handling, in their intended use and in transport at low temperatures. The advantageous properties of the preferred (ii) polyoxymethylene dialkyl ethers according to the invention are also reflected in the fact that a selection of these product mixtures is covered by the chemical-law polymer definition of the European Community. One particular advantage of the mixtures according to the invention is that in addition the flash point of the mixture has been optimized.

More preferably, component (ii) contains more than 30% by weight H 3 C-O- (CH 2 O) _≥ 4-CH 3. In this case, the particularly preferred fuel mixtures comprising (i) diesel oil and this particularly preferred component (ii) have a flash point above 55 ^° C. Such fuel mixtures are particularly suitable for handling in refineries since they comply with the corresponding explosion protection regulations (eg ordinance on systems for storing, filling and transporting flammable liquids by land (Ordinance on Flammable Liquids - VbF)).

As component (i), the fuel mixture according to the invention contains diesel oil of fossil origin. Diesel represents the heavy-boiling fraction of the middle distillates of mineral oil. Typical diesel oil cuts have a boiling point in the range of 150 to 380 ⁰ C, preferably from 200 to 350 ⁰ C and a density of 0.76 to 0.935 g / ml at 15 ⁰ C. In order to achieve the sulfur content in the fuel mixture according to the invention, Either the proportion of the preferred, low-sulfur POMDAE in the fuel mixture can be increased or alternatively a low-sulfur diesel can be used in the fuel mixture.

As component (ii), the fuel mixture according to the invention contains polyoxymethylene dialkyl ethers. Of these, the dimethyl ether and diethyl ether are preferred. Polyoxymethylene dialkyl ethers with n = 3, 4 or 5 oxymethylene units and mixtures thereof are preferred as already indicated by the weight data. Particular preference is given to polyoxymethylene dimethyl ethers having 3, 4 or 5 oxymethylene units and mixtures thereof. Particular preference is given to polyoxymethylene dimethyl ethers having n = 3 or 4 oxymethylene units and mixtures thereof, particularly preferably tetraoxymethylene dimethyl ether (n = 4). Component (ii) preferably contains between 29 and 70% by weight, particularly preferably between 30% by weight and 70% by weight of R-O-

(CH2θ) 3-R \ between 29 wt .-% and 70 wt .-%, more preferably between 30 wt .-% and 70 wt .-% RO- (CH ₂ O) ₄ R ', and between 0.1 and 5% by weight of RO- (CH 2 O)> 4-R 1 in each case based on the total weight of component (ii), where R and R 'have the meanings given at the outset, particularly preferably represent methyl and where the weight fraction of H 3C- O- (CH2θ) _≥ 4-CH 3 in the component (ii) preferably greater than 50 wt .-% is. The sulfur content of component (ii) is preferably less than 100 ppb (parts by weight). The content of polycyclic aromatic hydrocarbons in component (ii) is preferably less than 100 ppb, measured according to IP 391/95.

The polyoxymethylene dialkyl ethers can, as described in EP-A 1 070 755, by reacting the corresponding alcohol, preferably methanol, with formaldehyde in Presence of acid catalysts are produced. Processes for the preparation of the polyoxymethylene dimethyl ethers are also shown in WO 2006/045506.

A particularly advantageous process for the preparation of polyoxymethylene dimethyl ethers, especially the polyoxymethylene dimethyl ethers with n = 3 and 4 (trimer, tetrahedron) is based on methylal (n = 1) or dimethyl ether and trioxane. These are preferably fed into a reactor and reacted in the presence of an acidic catalyst, wherein the introduced by methylal, trioxane and / or the catalyst in the reaction mixture amount of water <1 wt .-%, based on the reaction mixture is.

In the reaction of methylal with trioxane to the Polyoxymethylendimethylethern preferably no water is formed as a byproduct. The reaction is generally carried out at a temperature of 50 to 200 ^° C., preferably 90 to 150 ^° C., and a pressure of 1 to 20 bar, preferably 2 to 10 bar. The molar ratio of methylal: trioxane is generally 0.1 to 10, preferably 0.5 to 5.

The acidic catalyst may be a homogeneous or heterogeneous acidic catalyst. Suitable acidic catalysts are mineral acids such as largely anhydrous sulfuric acid, sulfonic acids such as trifluoromethanesulfonic acid and para-toluenesulfonic acid, heteropolyacids, acidic ion exchange resins, zeolites, aluminosilicates, silica, alumina, titanium dioxide and zirconium dioxide. Oxidic catalysts may be doped with sulfate or phosphate groups to increase their acid strength, generally in amounts of from 0.05 to 10% by weight. The reaction can be carried out in a stirred tank reactor (CSTR) or a tube reactor. If a heterogeneous catalyst is used, a fixed bed reactor is preferred. If a fixed catalyst bed is used, the product mixture can then be contacted with an anion exchange resin to obtain a substantially acid-free product mixture.

The amount of water introduced by methylal and trioxane and by the catalyst is preferably in total <1% by weight, more preferably <0.5% by weight, in particular <0.2% by weight and particularly preferably <0.1% by weight. -%, Based on the reaction mixture of methylal, trioxane and the catalyst. For this purpose, practically anhydrous trioxane and methylal are preferably used, and the amount of water optionally introduced by the catalyst is limited. The hemiacetals (monoethers) or polyoxymethylene glycols formed by hydrolysis in the presence of water from already formed polyoxymethylene dimethyl ether have a boiling point comparable to that of the polyoxymethylene dimethyl ethers, thereby making it difficult to separate the polyoxymethylene dimethyl ethers from these by-products. In order to obtain polyoxymethylene dimethyl ether with n = 3 and n = 4 (trimer, tetramer), a fraction comprising the trimer and tetramers is preferably separated from the product mixture of the reaction of methylal with trioxane and unreacted methylal, trioxane and polyoxymethylene dimethyl ethers with n < 3 is preferably attributed to the acid catalyzed conversion. In a further preferred embodiment of the process, the polyoxymethylene dimethyl ethers with n> 4 are additionally recycled to the reaction. Due to the recycling, especially trimer and tetramer are obtained.

In a particularly preferred embodiment, the product mixture of the acid-catalyzed reaction of methylal with trioxane is a first fraction containing methylal, a second fraction containing the dimer (n = 2) and trioxane, a third fraction containing the trimer and tetramers (n = 3, 4) and a fourth fraction containing the pentamer and higher homologs (n> 4). In this case, it is particularly preferred to carry out the separation of the product mixture of the acid-catalyzed reaction of methylal with trioxane in three distillation columns connected in series, the first fraction being separated in a distillation column from the product mixture of the reaction, from the remaining mixture in a second distillation column the second fraction is separated off and the remaining mixture is separated into the third and the fourth fraction in a third distillation column. Here, the first distillation column, for example, at a pressure of 0.5 to 1, 5 bar, the second distillation column, for example, at a pressure of 0.05 to 1 bar and the third distillation column, for example, at a pressure of 0.001 to 0.5 bar operated , Preferably, the first and the second fraction, more preferably additionally also the fourth fraction, are recycled to the reaction.

If a homogeneous catalyst, for example a mineral acid or a sulfonic acid, is used, it preferably remains in the fourth fraction and is recycled with it to the acid-catalyzed reaction.

The novel fuel mixture may contain components (i) and (ii) preferably in the following proportions by weight:

From 10 to 95% by weight of (i) diesel oil, usually of fossil origin,

From 90 to 5% by weight of (ii) polyoxymethylene dialkyl ethers,

each based on the total weight of the fuel mixture.

In the fuel mixtures according to the invention, 0 to 5 wt .-%, preferably 0 to 1 wt .-% further additives may be included. Usual further additives are z. B. conventional, known Cetanzahlerhöher which in amounts of usually up to 1 Wt .-% may be included or z. B. compounds that increase the flow and lubricating properties of the diesel fuel. The content of polycyclic aromatic hydrocarbons in the fuel mixture according to the invention is preferably less than 1 1 mass%, measured according to IP 391/95. The fuel mixtures according to the invention preferably have a cetane number of> 41, particularly preferably> 51, in particular between 51 and 98.6.

The preparation of the fuel mixtures according to the invention can preferably be carried out by mixing (i) and (ii) in a continuous process. Particularly preferably, the preparation can be carried out such that (i) mineral oil fractions or diesel oil, preferably of fossil origin, and component (ii), d. H. the polyoxymethylenedialkyl ethers continuously withdrawn from their storage tanks, the components (i) and (ii) in the desired mixing ratio continuously merges in a mixing apparatus, the resulting mixture continuously removed and for further use.

The mixtures obtained can be transposed into transport containers, such as tank trucks, containers or barrels, or temporarily stored in product storage tanks.

Static mixers may preferably be used as mixing apparatuses. Such apparatuses are generally known to the person skilled in the art. Such an apparatus for mixing liquids is described, for example, in EP 0 097 458. Static mixers are usually tubular apparatuses with fixed internals, which serve to mix the individual substance flows over the pipe cross-section. Static mixers can be used in continuous processes to perform various process engineering operations, such as mixing, mass transfer between two phases, chemical reactions, or heat transfer. The homogenization of the starting materials is preferably effected by a pressure gradient generated by means of a pump. Depending on the type of flow in the static mixer, two basic mixing principles can be distinguished. In laminar flow-through mixers is homogenized by division and rearrangement of the flow of the individual components. By continuously doubling the number of layers, the layer thicknesses are reduced so far until a complete macro-mixing is achieved. The micro-mixing by diffusion processes depends on the residence time. For mixing tasks with laminar flow, spiral mixers or cross channel mixers are used. The laminar flow resembles a normal pipe flow with low shear forces and a narrow residence time distribution. Vortexes are generated in turbulent flow-through mixers in order to homogenize the individual material flows in this way. For this purpose, cross-channel mixers and special turbulence mixers are suitable. Both types of mixers can be used for the preferred method. The internals used usually consist of flow dividing ends and -derlenkenden, three-dimensional geometric bodies that lead to a rearrangement, mixing and reuniting of the individual components. Static mixers are commercially available mixing apparatuses and are offered for example by the company Fluitec Georg AG, Neftenbach, Switzerland for various fields of application.

Example:

According to the manufacturing process described above, a mixture of 49.8%

POMDME 4 (H ₃ CO- (CH ₂ O) ₄ -CH ₃ ), 49.8% POMDME 3 (H ₃ CO- (CH ₂ O) ₃ -CH ₃ ) and 0.4% POMDME 5 (H ₃ CO - (CH ₂ O) ₅ -CH ₃ ). The S content was below 50 ppb. The corresponding flash point of the compound was measured according to DIN EN ISO 13736, and amounted to 61 ⁰ C. The corresponding blend had a filterability (CFPP) according to EN 1 16 of less than - 54 ⁰ C. The Cloud Point according to EN 23015 was - 53 ⁰ C. The cetane number of the mixture could not be determined in a MWM test engine: For the measurement of blends with 30% / 50% / 70% kerosene could however borderline cetane number of 98.6 can be determined , The blends were made via a static mixing system as described in the text. In the following, a mixture of the POMDME mixture (10%) with diesel fuel (90%) was produced by a static mixing system and tested on a Daimler Chrysler OM646 DE 22LA engine test bench. This resulted in a reduction in soot emissions compared to the operation of pure diesel fuel by up to 60%.

Claims

claims

1. A fuel mixture comprising (i) diesel oil and (ii) polyoxymethylene dialkyl ethers of the general formula 1:

RO- (CH ₂ O) _n -R ', with the following meanings for R, R' and n: R: methyl, ethyl, propyl, butyl, R ': methyl, ethyl, propyl, butyl, n: 2, 3 , 4, 5, 6, 7, 8,

characterized in that the fuel mixture has a sulfur content of <10 ppm (mg / kg) according to EN 590 and the weight proportion of polyoxymethylene dialkyl ethers according to formula 1 with n equal to 3 and 4 between 50 wt .-% and 99.8 wt. %, based on the total weight of the polyoxymethylene dialkyl ethers.

2. A fuel mixture according to claim 1, characterized in that the component (ii) contains between 30 and 70 wt .-% RO- (CH ₂ O) ₃ -R ', between 30 and 70 wt .-% RO- (CH ₂ O) ₄ -R 'and between 0.1 and 5 wt.% RO- (CH ₂ O)> ₄ -

R ', in each case based on the total weight of component (ii).

3. Fuel mixture according to claim 1, characterized in that component (ii) has a sulfur content of less than 100 ppb.

4. Fuel mixture according to claim 1, characterized in that component (ii) has a content of polycyclic aromatic hydrocarbons of less than 100 ppb, measured according to IP 391/95.

5. Fuel mixture according to claim 1, characterized in that the fuel mixture contains

10 to 95% by weight of (i) diesel oil of fossil origin

5 to 90 wt .-% (ii) Polyoxymethylendialkylether, each based on the total weight of the fuel mixture.

6. Fuel mixture according to claim 1, characterized in that the fuel mixture has a cetane number> 41.

7. Fuel mixture according to claim 1, characterized in that the fuel mixture has a content of polycyclic aromatic hydrocarbons of less than 1 1 mass%, measured according to IP 391/95.

8. A fuel mixture comprising (i) diesel oil of fossil origin and (ii) polyoxymethylene dialkyl ether, characterized in that the fuel mixture contains between 10 and 95% by weight of (i) diesel oil of fossil origin and between 5 and 90% by weight (ii) Polyoxymethylendialkylether, each based on the total weight of the fuel mixture, wherein the fuel mixture has a sulfur content of less than 10 ppm and a content of polycyclic aromatic hydrocarbons of less than 11 mass%, measured according to IP 391/95, the component (ii) has a sulfur content of less than 100 ppb and a content of polycyclic aromatic hydrocarbons of less than 100 ppb, measured according to IP 391/95, and also contains component (ii)

in each case based on the total weight of component (ii).

9. A fuel mixture according to claim 8, characterized in that the total weight percentage of H ₃ CO- (CH ₂ O) ₃ -CH ₃ and H ₃ CO- (CH ₂ O) ₄ -CH ₃ in the

Component (ii) is between 50% and 99.8% by weight.

10. A fuel mixture according to claim 1 or 8, characterized in that the component (ii) contains more than 50 wt .-% H ₃ CO- (CH ₂ O) _≥4 -CH ₃ .

1 1. Use of fuel mixtures according to one of claims 1 to 10 as fuel for diesel engines with a cylinder displacement of> 1 liter.

12. Use of fuel mixtures according to one of claims 1 to 10 as fuel for trucks, locomotives, marine and aircraft engines.

13. A process for the preparation of a fuel mixture according to claim 1 or 8, characterized in that (i) diesel oil and the Konponente (ii) continuously removed from their storage tanks, the components (i) and (ii) in the desired mixing ratio continuously in a mixing apparatus and the resulting mixture continuously removed