WO2010146117A2

WO2010146117A2 - Method for hydrogenating glycerin into 1,2-propanediol hydrogenating desulfurization in a sacrificial bed

Info

Publication number: WO2010146117A2
Application number: PCT/EP2010/058543
Authority: WO
Inventors: Roman Prochazka; Stephan Maurer; Oliver Bey; Jochen Steiner; Jochem Henkelmann; Gerhard Theis; Peter Wahl
Original assignee: Basf Se
Priority date: 2009-06-19
Filing date: 2010-06-17
Publication date: 2010-12-23
Also published as: WO2010146117A3

Abstract

The present invention relates to a method for producing 1,2-propanediol from glycerin, comprising at least the steps of: (A) providing a glycerin flow G1, (B) desulfurization of the glycerin flow G1 from step (A) by hydrogenating with hydrogen at a pressure of 50 300 bar in the presence of a catalyst in order to obtain a glycerin flow G2, and (C) hydrogenating the glycerin flow G2 from step (B) with hydrogen in the presence of a catalyst, in order to obtain 1,2-propanediol.

Description

Method for the hydrogenation of glycerol to 1,2-propanediol - Hydrogenating desulphurisation in the sacrificial bed

description

The present invention relates to a process for the preparation of 1,2-propanediol from glycerol comprising at least the steps (A) providing a glycerol stream G1, (B) desulfurizing the glycerol stream G1 from step (A) by hydrogenation with hydrogen at a pressure of 50 - 300 bar in the presence of a catalyst to obtain a glycerol stream G2, and (C) hydrogenation of the glycerol stream G2 from step (B) with hydrogen in the presence of a catalyst to obtain 1, 2-propanediol.

Processes for the preparation of 1, 2-propanediol are already known from the prior art.

WO 2007/099161 A1 discloses a process for the preparation of 1, 2-propanediol from glycerol-containing streams by reduction with hydrogen in the presence of a copper-containing, heterogeneous catalyst at a temperature of 100 to 320 ⁰ C and a pressure of 100 to 325 bar. The glycerol used in the hydrogenation can be subjected to catalytic desulfurization before the hydrogenation. For this purpose, the reactant stream is hydrogenated in the presence of a catalyst with hydrogen, wherein this takes place at a temperature of 40 to 200 ⁰ C and a pressure of 1 to 40 bar.

DE 541 362 discloses a process for the hydrogenation of polyoxy compounds, for example glycerol or carbohydrates, at a pressure of 10 to 60 atmospheres or higher pressures such. B. 200 atmospheres or 1000 atmospheres, and a temperature of 200 to 240 ⁰ C. DE 541 362 does not disclose a process for the production of 1, 2-propanediol from glycerol, in which the crude glycerol is first subjected to desulfurization.

DE 524 101 discloses a process for the reduction of polyhydric alcohols. For example, copper, silver, zinc or nickel catalysts from ethyl glycol or of glycerol Propylengly- col and n-propyl alcohol can be obtained at a temperature of 250-260 ⁰ C in the presence of hydrogenation catalysts. DE 524 101 does not disclose a process for the preparation of 1,2-propanediol from glycerol, in which the crude glycerol is first subjected to desulfurization. DE 43 02 464 A1 discloses a process for the preparation of 1, 2-propanediol by hydrogenation of glycerol in the presence of a heterogeneous catalyst at a pressure of 20 to 300 bar and a temperature of 150 to 320 ⁰ C. The use of glycerol-containing streams, which originate from the production of biodiesel and processes for pretreatment of these educt streams are not disclosed in DE 43 02 464 A1.

EP 0 523 015 discloses a process for the catalytic hydrogenation of glycerol for the preparation of 1, 2-propanediol and 1, 2-ethanediol in the presence of a Co / Zn catalyst. According to this document, the starting compound used is an aqueous solution of glycerol having a glycerol content of 20 to 60% by weight.

WO 2005/095536 discloses a process for the preparation of propylene glycol from glycerol, wherein the glycerol-containing stream having a water content of less than 50 wt .-% at a temperature of 150 to 250 ⁰ C and a pressure of 1 to 25 bar catalytically hydrogenated becomes.

The object of the present invention is to provide a process for the preparation of 1,2-propanediol from glycerol, which is distinguished by a particularly long service life of the hydrogenation catalyst used. Furthermore, the activity of the catalyst should be particularly high. The process according to the invention is intended to remove catalyst poisons present in the educt stream in order to increase the service life of the catalyst in the hydrogenation of glycerol to 1,2-propanediol. Furthermore, 1,2-propanediol should be obtainable in high yield and purity by the process according to the invention.

These objects are achieved by the process according to the invention for the preparation of 1,2-propanediol from glycerol, comprising at least the steps:

(A) providing a glycerol stream G1,

(B) desulfurization of the glycerol stream G1 from step (A) by hydrogenation with hydrogen at a pressure of 50 - 300 bar in the presence of a catalyst to obtain a Glycerinstrom G2, and

(C) Hydrogenation of the glycerol stream G2 from step (B) with hydrogen in the presence of a catalyst to obtain 1, 2-propanediol.

The individual steps of the method according to the invention are described in detail below. Step (A):

Step (A) of the method according to the invention comprises providing a glycerin stream G1.

In general, all the glycerol streams G1 known to the person skilled in the art can be used in step (A), for example comprising those obtainable from industrial processes. The glycerol streams G1 which can be used according to the invention should have purities which are suitable for the process according to the invention.

In particular, glycerol streams G1 from the treatment of oil and / or fat-containing starting materials, for example, from the soap, fatty acid and fatty acid ester production, etc., are used.

In general, all glycerol-containing streams which are industrially available and have purities suitable for the process according to the invention can be used. In particular, corresponding glycerol-containing streams are used in the processing of oil and / or fat-containing starting materials, e.g. As in the production of soap, or in the production of fatty acids and fatty acid esters, etc. obtained. The glycerol-containing stream preferably provided in step (A) is preferably a glycerol-containing stream obtained in the preparation of the higher fatty acid alkyl esters by transesterification of the fatty acid triglycerides, especially in the production of "biodiesel" In the context of the present invention, "biodiesel" means a mixture of fatty acid alkyl esters obtainable from biogenic oil and / or fat-containing starting materials which can be used as fuel in diesel engines.

In general, all biogenic oil and / or fat-containing starting mixtures known to the person skilled in the art are suitable for the preparation of the glycerol-containing stream. Oils and fats are generally solid, semi-solid or liquid fatty acid triglycerides, particularly from vegetable or animal sources, which in the chemical sense essentially comprise glycerol esters of the higher fatty acids. Suitable higher fatty acids are, for example, the saturated or mono- or polyunsaturated fatty acids, which preferably have 8 to 40, particularly preferably 12 to 30, carbon atoms. These include, for example, n-nonanoic acid, n-decanoic acid, n-undecanoic acid, n-tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, margaric acid, nonadecanoic acid, peanutic acid, behenic acid, lignoic acid, cerotic acid, melissic acid, palmitinoleic acid, oleic acid, linoleic acid, linolenic acid, stearic acid , Elaostearic acid, etc. Vegetable fats and oils are based essentially on fatty acids having an even number of carbon atoms, while animal fats and oils may also comprise fatty acids having an odd number of carbon atoms in the free form or bound as triglyceride esters. The unsaturated fatty acids found in vegetable fats and oils are in the cis configuration, while animal unsaturated fatty acids are often in the trans configuration.

Generally, used or unused, purified or unpurified vegetable, animal or industrial oils or fats or mixtures thereof may be used to provide the glycerol-containing stream in step (A). These can be shares of other ingredients, eg. Free fatty acids. The proportion of free fatty acids is generally from 0 to 50 wt .-%, preferably 0.1 to 20 wt .-%. Optionally, free fatty acids may be removed before or after the transesterification of the fatty acid triglycerides. Salts of these fatty acids, eg. For example, the alkali metal salts may be previously converted to the free acid by reaction with a strong acid, e.g. B. with HCl. The isolation of the free fatty acids takes place z. B. by centrifugation. Preferably, free fatty acids present in the starting mixture of the transesterification are also converted to the corresponding alkyl esters. This can be done before, during or after the transesterification of the fatty acid triglycerides.

Suitable fats and oils which are suitable for providing the glycerol-containing stream according to step (A) of the process according to the invention are generally fatty and / or oleaginous constituents which, after being obtained from the corresponding biogenic starting materials, are initially other purposes, eg. For example, have been used for technical purposes or for food production, and therefore may be chemically modified or unmodified or may contain additional ingredients. These can be at least partially removed.

Not previously used fats and the oils which are suitable for providing the glycerol-containing stream in step (A) are fatty or oleaginous components which, after their recovery from the corresponding biogenic starting materials, have not yet been used for other purposes, e.g. , For example, for technical purposes or for food production have been used, and thus contain only components derived from the starting materials or related to the extraction of the starting materials. Other constituents than fatty acid triglycerides and optionally free fatty acids may optionally be at least partially separated from the starting materials by transesterification before step (A) of the process according to the invention. For cleaning and / or depletion, the fats or oils used or unused may be freed of undesirable components such as lecithins, carbohydrates, proteins, oil sludge, water, etc.

Vegetable oils and fats are those which are generally derived from vegetable source materials such as seeds, roots, leaves or other suitable plant parts. Animal fats or oils are predominantly derived from animal feedstocks such as animal organs, tissues or other body parts or body fluids such as milk. Industrial oils and fats are those obtained in particular from animal or vegetable raw materials and for technical purposes. The used or unused, unrefined or purified oils and / or fats come especially from soap base, brown fat, yellow fat, industrial tallow, industrial lard, frying oil, animal fat, edible tallow, unrefined vegetable oils, unpurified animal oils or mixtures thereof ,

According to the invention, "soap base material" is understood to mean by-products which are obtained in the processing of vegetable oils, in particular in edible oil refineries, for example based on soybean, rapeseed or sunflower oil. "Seefeng round cloth" has a proportion of about 50 up to 80% by weight of free fatty acids. "Brown fat" is understood according to the invention as a waste product containing animal fat, which has a content of free fatty acids 15 to 40 wt .-%. "Yellow fat" comprises about 5 to 15 wt .-% of free fatty acids.

"Industrial tallow" and "industrial lard" are understood according to the invention as animal fats, which are produced for industrial purposes and obtained after drying or wet-melting process, for. B. from slaughterhouse waste. Industrial tallow is added according to the acid number, i. H. the content of free fatty acids, evaluated, the z. B. 1 to 20 wt .-% is.

In particular, the "animal fats" include the fat-containing waste products obtained in the use of poultry, livestock, pigs, fish and marine mammals as a solid residue.

The stream containing glycerol provided in step (A) of the process according to the invention is preferably obtained from unpurified vegetable oils as starting material. This can be based on liquid or of the solid compositions obtained from vegetable starting materials, for. By subjecting them to settling, centrifuging or filtering, in which only mechanical forces, such as gravity, centrifugal force or pressure, for the separation of the oil are responsible for the solid components. Such unrefined vegetable oils may also be vegetable oils obtained by extraction. The proportion of free fatty acids in the unrefined vegetable fats and oils and is z. B. 0 to 20 wt .-%.

Before the vegetable oils are supplied to the transesterification, the vegetable oils can be subjected to one or more treatment steps. Thus, purified vegetable oils, eg. As raffinates or semiraffinates of the above-mentioned vegetable oils can be used as starting materials.

According to the invention, particular preference is given to using a vegetable oil or a fat selected from the group consisting of rapeseed oil, palm oil, soybean oil, sunflower oil, corn oil, cottonseed oil, palm kernel oil, coconut fat and mixtures thereof, particular preference is given to rapeseed oil or a mixture containing rapeseed oil. Tiered oils or fats are selected from the group consisting of milk fat, wool fat, beef tallow, pork fat, fish oils, Tran, etc., and mixtures thereof.

The production of the glycerol-comprising stream for step (A) of the process according to the invention particularly preferably comprises the following steps:

a1) providing a starting mixture containing biogenic fats and / or oils,

a2) transesterification of the fatty acid triglycerides containing in the starting mixture with at least one C 1 -C ₉ monoalcohol and optionally esterification of the free fatty acids present in the mixture to form an esterification mixture,

a3) separation of the esterification mixture to obtain at least one biodiesel-enriched fraction and at least one glycerol-enriched fraction,

a4) if appropriate, workup of the at least one glycerol-enriched

Fraction.

Step a1):

In a preferred embodiment, provision of a starting mixture containing biogenic fats and / or oils according to step a1) comprises at least one purification step. For cleaning, the fat and / or oil-containing starting mixture may be at least be subjected to a purification process suitable for fats and oils, such as clarification, filtration, treatment with bleaching earth or working up with acids or bases, for the separation of impurities such as proteins, phosphatides and sludges. Also possible is a combination of the mentioned methods.

Step a2):

At least one d-Cg monoalcohol, in particular at least one dC ₄ monoalcohol, is preferably used for the transesterification of the fatty acid triglycerides. The use of methanol or ethanol is particularly preferred. The transesterification of the fatty acid triglycerides can be carried out by acidic or preferably basic catalysis. Suitable acids are, for. For example, mineral acids such as HCl, H ₂ SO ₄ or H ₃ PO ₄ . At least one base is preferably used as the catalyst. Preferred bases are alkali metal hydroxides such as NaOH, KOH, alkaline earth metal hydroxides such as Ca (OH) ₂ , alkali metal and alkaline earth metal d-Ce alkoxides such as NaOCH ₃ , KOCH ₃ , Na (OCH ₂ CH ₂ ) and Ca (OCH ₂ CH ₂ ) ₂ and mixtures thereof. NaOH, KOH or NaOCH ₃ are particularly preferably used.

The amount of the base used is generally in the range of 0.1 to 10 wt%, preferably 0.2 to 5 wt%, based on the amount of the fatty acid triglycerides used.

The base is preferably used in the form of an aqueous or an alcoholic, more preferably an alcoholic, solution. A solution of NaOCH ₃ in methanol is preferably used for the transesterification.

The transesterification is preferably carried out at a temperature of 20 to 150 ⁰ C, more preferably 30 to 95 ⁰ C.

The transesterification takes place in conventional apparatus known to those skilled in the art, preferably continuously, more preferably in a column. A high-boiling phase enriched with the basic catalyst, with unreacted monoalcohol and glycerol, which is formed in the transesterification, and a low-boiling phase, which is enriched with the transesterification product, is generally obtained in this case. If the transesterification product still contains triglycerides which have not been transesterified, these may be separated or subjected to a further transesterification stage.

The mixture obtained from the transesterification is then preferably fed to a drying unit in order to remove residual amounts of water. After drying lies the preferred desired end product "biodiesel" in purified form, and can be used directly.

The optionally present free fatty acids are preferably esterified with the same d-Cg monoalcohol which is used for the transesterification of the fatty acid triglycerides. The esterification of the free fatty acids can take place before, during or after the transesterification of the fatty acid triglycerides. In a preferred embodiment, the esterification of the free fatty acids takes place before the transesterification of the fatty acid triglycerides. The esterification of the free fatty acids can be carried out by basic or preferably acid catalysis. Suitable acids are the above-mentioned mineral acids, such as HCl, H ₂ SO ₄ or H ₃ PO ₄ , para-toluene-sulfonic acid, etc. The esterification is preferably carried out at a temperature of 20 to 95 ⁰ C, especially 40 to 80 ⁰ C. The esterification takes place in customary and known to the expert devices, such as a column.

Step a3):

During or after transesterification and / or esterification, the esterification mixture is separated to obtain at least one biodiesel-enriched fraction and at least one glycerol-enriched fraction. This separation is preferably carried out by the conventional distillation methods known to those skilled in the art. Suitable distillation apparatuses are those mentioned above.

Step a4):

The at least one glycerol-enriched fraction obtained in step a3) may optionally be subjected to at least one work-up step. This includes z. For example, the removal of undesirable components such as salts and components that adversely affect the catalytic hydrogenation or the removal of water or, if present, the organic solvent. With regard to the possible methods in step a4), reference is made to the above.

The glycerol stream G1 used in step (A) optionally contains water. The glycerol stream G1 preferably has a water content of less than 30% by weight, more preferably less than 20% by weight, for example 8 to 12% by weight, in particular 10% by weight. Methods for determining the water content are known in the art, for example Karl Fischer titration. The use of a glycerol stream G1 having a water content in the range of less than 30 wt .-%, preferably less than 20 wt .-%, allows the production of 1, 2-propanediol with high yields and high selectivity in the temperature and pressure range of the method according to the invention (step (C)). The hydrogenation of glycerol streams G1, which are essentially not anhydrous, in particular of streams which have a higher water content than glycerol monohydrate, but according to the invention is also possible with high yields and high selectivity. The use of glycerol streams G1 which contain more water than described, for example more than 20% by weight, is however economically less advantageous owing to the reduced space-time yield. Apart from that, a water content in the range of 3 to 30 wt .-% may be advantageous for the rheological properties during the hydrogenation.

In a preferred embodiment, therefore, a glycerol stream G1 is used in step (A) of the process according to the invention, which has a water content of 3 to 30 wt .-%, preferably 5 to 20 wt .-%, each based on the total current G1, for example to lower the viscosity of the reaction mixture during hydrogenation.

The glycerol stream G1 can generally contain at least one further, preferably a glycerol-miscible, and therefore also water-miscible, organic solvent instead of or in combination with water. The glycerol stream G1 used in step (A) of the process according to the invention generally has a total solvent content of less than 20% by weight, preferably less than 15% by weight, very preferably less than 10% by weight and in particular preferably less than 5% by weight, in each case based on the total glycerol flow G1.

If according to the invention solvent mixtures which comprise water and at least one further glycerol or water-miscible organic solvent are used, the proportion of the organic solvent is preferably less than 50% by weight, more preferably less than 20% by weight, in each case on the total amount of solvent.

Suitable glycerol-miscible organic solvents are C 1 -C ₄ -alcohols, for example methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, polyols, and mono- and dialkyl ethers thereof, cyclic ethers For example, dioxane and tetrahydrofuran, etc. Other suitable solvents are aromatic hydrocarbons, for example benzene, toluene or the xylene. Preferred organic solvents are CrC ₄ -AlkOhOIe, preferably methanol and / or ethanol, and mixtures thereof with water. A particularly preferred glycerol stream G1 used in step (A) of the process according to the invention contains no organic solvents, ie in the glycerol stream G1 used according to the invention the content of organic solvents is more preferably less than 4% by weight, preferably less as 2% by weight, more preferably less than 1% by weight. Analytical methods for determining the content of organic solvents are known to the person skilled in the art, for example gas chromatography GC or high performance liquid chromatography to HPLC.

The glycerol stream G1 provided in step (A) of the process according to the invention generally has a sulfur content of 0.1 to 20 ppm, preferably 0.1 to 5 ppm. In the glycerol stream G1, the said amount of sulfur is preferably present in sulfur-containing compounds, for example as organic sulfur-containing compounds, for example sulfur-containing amino acids such as cysteine and / or methionine, or as inorganic sulfur-containing compounds, for example sulfates or sulfides.

The glycerol stream G1 provided in step (A) of the process according to the invention may, in addition to sulfur, optionally contain further substances as impurity, for example inorganic salts, for example NaCl, KCl. These are for example in amounts of 0 to 5 wt .-%, based on the current G1, before.

In a preferred embodiment, before it is provided in step (A) of the process according to the invention, the glycerol stream G1 is first fed to at least one work-up step. This pretreatment step (s) includes, for example, at least one purification step to remove unwanted components. Further, this pretreatment step (s) also includes lowering the level of water and / or, if present, organic solvents, for example, to achieve the preferred levels specified above. Depending on the origin of the glycerol stream G1, this may contain, in addition to the sulfur-containing compounds, inorganic salts as undesired components. These can be removed from the glycerol stream G1, for example by appropriate work-up steps, for example thermal work-up, for example with a Sambay evaporator.

Preferably, the stream G1 is treated by distillation to obtain a stream G1 which contains substantially no inorganic salts. Further pretreatment steps to which the glycerol stream G1 may be subjected are, for example, distillation, adsorption, ion exchange, membrane separation, crystallization or extraction, or a combination of two or more of these methods, to obtain a glycerol stream G1 satisfying the requirements of the present invention Method corresponds. These methods are known to the person skilled in the art and are described, for example, in WO 2007/099161 A1.

The glycerol stream G1 preferably used according to the invention may also contain acidic compounds. A measure of the content of acidic compounds is the Versei- number, which can be determined by methods known in the art. In general, the glycerol stream G1 used in step (A) of the process according to the invention has a saponification number of 0.1 to 10 mg KOH / g, preferably 0.1 to 5 mg KOH / g, particularly preferably 0.1 to 3 mg KOH / g , on.

Step (B):

Step (B) of the process according to the invention comprises the desulfurization of the glycerol stream G1 from step (A) by hydrogenation with hydrogen at a pressure of 50 to 300 bar in the presence of a catalyst in order to obtain a glycerol stream G2.

The desulfurization according to step (B) of the process according to the invention serves to lower the content of sulfur-containing compounds. The reduction of the sulfur content is advantageous because the catalyst used in the hydrogenation to 1, 2-propanediol is damaged by the presence of sulfur, and thus has a limited activity. The separation of sulfur from the reactant stream thus contributes to increasing the activity and the service life of the hydrogenation catalyst.

Suitable catalysts which can be used in step (B) of the process according to the invention generally comprise metal components known to the person skilled in the art, which are selected, for example, from groups 6, 7, 8, 9, 10, 11 and 12 of the Periodic Table of the Elements ( new IUPAC nominee).

Therefore, in a preferred embodiment, the present invention relates to the process according to the invention, wherein in step (B) a catalyst is used comprising at least one metal component selected from the groups 6, 7, 8, 9, 10, 11 and / or 12 of the Periodic Table of the Elements (new IUPAC nomenclature). In particular, the metals present in the catalyst used in step (B) of the process according to the invention are selected from the group consisting of Mo, Ni, Cu, Ag, Zn and mixtures thereof.

The catalyst in step (B) can be used in oxidized, reduced form or in the form of a mixture comprising oxidized and reduced fractions. The active element of the catalyst according to step (B) can be used on a support material or unsupported.

Suitable support materials are for example selected from the group consisting of activated carbon, graphite, carbon black, Al ₂ O ₃ , SiO ₂ , TiO ₂ , ZrO ₂ , SiC, silicates, zeolites, clay-like earth, z. B. bentonite, and mixtures thereof.

The application of the at least one metal component and optionally further components to the support material can be carried out by methods known to the person skilled in the art, for example by co-precipitation or impregnation.

The catalyst used in step (B) of the process according to the invention can generally be used in any form known to those skilled in the art, for example as spheres, rings, cylinders, cuboids and / or other geometric bodies. Unsupported catalysts may be formed by shaping processes known to those skilled in the art, e.g. Extrusion, tableting, etc. The shape of the supported catalysts of step (B) is generally dictated by the shape of the support material.

In a particularly preferred embodiment, a copper-containing catalyst is used in step (B) of the process according to the invention. This may be supported or not supported. The catalyst can be used in the form of a uniform composition, as impregnated catalyst, coated catalyst or precipitated catalyst.

In general, a large number of copper-containing catalysts which may additionally contain at least one further element from groups 1 to 15 of the periodic table and lanthanides (new IUPAC nomenclature) are suitable for step (B) of the process according to the invention. Particularly preferred further elements are selected from the group consisting of Ca, Mg, Al, La, Ti, Zr, Cr, Mo, W, Mn, Ni, Co, Zn and mixtures thereof.

In a preferred embodiment, a skeletal catalyst or a metal sponge catalyst is used in step (B) of the process according to the invention, for example, known as "Raney catalysts." Preferred Raney catalysts include, in particular, Raney copper and copper-containing metal alloys in the form of a Raney catalyst.

Raney catalysts containing at least 95%, more preferably at least 99%, copper as the metal component are preferred. Processes for the preparation of Raney catalysts are known to the person skilled in the art and are described, for example, in DE-A-43 35 360, DE-A-43 45 265, DE-A-44 46 907 and EP-A-842-699.

Preferred catalysts which can be used in step (B) of the process according to the invention include the following metals or combinations of metals in oxidic form, reduced form (elementary form) or a combination thereof. Metals which are stable in more than one oxidation state can be used as a whole in an oxidation state or in a combination of different oxidation states.

1. Cu

2. Cu, Ti

3. Cu, Zr

4. Cu, Mn

5. Cu, AI

6. Cu, Ni, Mn

7. Cu, Al, at least one further metal selected from La, W, Mo, Mn, Zn, Ti, Zr,

Sn, Ni, Co

8. Cu, Zn, Zr

9. Cu, Zr, Ca

10. Cu, Cr, C

1 1. Cu, Al, Mn, optionally Zr.

In general, all support materials known to those skilled in the art can be used, for example silica (quartz), porcelain, magnesium oxide, tin oxide, silicon carbide, TiC> ₂ (rutile and / or anatase), ZrC> ₂ , Al ₂ O ₃ , aluminum silicate, Steatite (magnesium silicate), zirconium silicate, cersilicate or mixtures thereof. Particularly preferred support materials are alumina and silica. Silica materials of different origin or production process, for example pyrogenically or wet-chemically produced silica, such as silica gels, aerogels or precipitated silica, can be used as silica support material for the catalyst used in step (B) of the process according to the invention be used. As a further particularly preferred embodiment, in step (B) of the process according to the invention a catalyst can be used which comprises copper in oxidic form and optionally additionally in elemental form. In this embodiment, the catalyst used in step (B) of the process according to the invention preferably contains at least 23% by weight, particularly preferably at least 35% by weight, of copper in oxidic and / or elemental form, based on the total weight of the catalyst.

Methods for producing such catalysts are known to the person skilled in the art, in particular impregnation of the support material with solutions of the catalyst components, which are then converted into the catalytically active form by thermal treatment, decomposition and / or reduction. Suitable processes for preparing such catalysts are disclosed, for example, in WO 2007/099161.

In a particularly preferred embodiment, a catalyst is used in step (B) of the process according to the invention, preferably containing, in addition to copper, another metal selected from the group consisting of Al, La, W, Mo, Ti, Zr and mixtures thereof, more preferably in oxidic Shape.

The composition of the catalyst according to step (B) of the process according to the invention is generally such that the proportion of copper oxide in the range of 40 to 90 wt .-%, the content of the oxides of La, W, Mo, Ti and / or Zr in the range of 0 to 50 wt .-% and the content of alumina up to 50 wt .-%, each based on the total weight of the catalyst. The total mass of said metal oxides is at least 80 wt .-% of the catalyst, the missing wt .-% of materials that do not fall under the above-mentioned oxidic compounds, for example, elemental copper in an amount of up to 15 wt .-% ,

In a particularly preferred embodiment, a catalyst is used in step (B) of the process according to the invention comprising an oxidic material containing

(a) copper oxide in an amount of 50 <x <80% by weight, preferably 55 <x <75% by weight,

(b) alumina in an amount of 15 <y <35% by weight, preferably 20 <y <30% by weight, and (c) at least one of the oxides of La, W, Mo, Ti or Zr, preferably of La and / or W, in an amount of 3 <z <20% by weight, preferably 3 <z <15% by weight , in each case based on the total weight of the oxidic material after calcination, wherein 80 ≦ x + y + z <100 wt .-%, preferably 95 <x + y + z <100 wt .-% applies.

In a particularly preferred embodiment of the process according to the invention, a catalyst is used in step (B), which corresponds to the following general formula CuOm (Al ₂ Os) _n (La ₂ O ₃ ) O, where

m 0.55 to 0.85, preferably 0.60 to 0.75, particularly preferably 0.60 to 0.70, n 0.15 to 0.30, preferably 0.18 to 0.28, particularly preferably 0, 20 to 0.25 and 0.01 to 0.10, preferably 0.02 to 0.08, particularly preferably 0.03 to 0.06

mean, where the sum of m, n and o is 1 each.

Before the start of the desulfurization according to step (B) of the process according to the invention, the catalyst used is preferably reduced in situ by treatment with hydrogen. This is preferably done under the conditions that are also present in step (B).

The catalyst which is preferably used in step (B) can generally be arranged in the reactor in a manner known per se in the art, for example as a fixed bed.

Step (B) of the process according to the invention can generally be carried out in any reactor known to the person skilled in the art for carrying out such a reaction, for example a shaft reactor which can be operated in trickle or bottom mode.

The desulfurization according to step (B) of the process according to the invention is carried out at a pressure of 50 to 200 bar, preferably 100 to 250 bar, particularly preferably 150 to 220 bar. By this compared to the prior art high pressure, it is possible to almost completely free the Glycerinstrom G1 in a short time of sulfur-containing compounds.

The desulfurization according to step (B) of the process according to the invention is carried out at a temperature of 100 to 300 ^° C., preferably 120 to 250 ^° C., particularly preferably 160 to 220 ^° C. The desulfurization by hydrogenation according to step (B) of the process according to the invention is carried out in the presence of hydrogen as a reducing agent.

The hydrogen used according to the invention generally has a purity of> 99.8% by volume, preferably 99.9% by volume, particularly preferably ≥99.95% by volume.

In general, the weight ratio of glycerol stream G1 to hydrogen in step (B) of the process according to the invention is 40,000: 1 to 1,000: 1, preferably 38,000: 1 to 5,000: 1, more preferably 37,000: 1 to 15,000: 1, very particularly preferably 36,000: 1 to 25,000: 1, more preferably 35,000: 1 to 30,000: 1.

Step (B) of the process according to the invention can be carried out continuously or batchwise, preferably continuously.

After step (B) of the process according to the invention, a glycerol stream G2 is obtained which differs from glycerol stream G1 by a reduced sulfur content.

According to the invention, in step (B) of the process according to the invention, the sulfur-containing compounds are preferably removed from the stream G1 by being bound to the catalyst used by reductive chemisorption.

In step (B) of the process according to the invention, the glycerol contained in glycerol stream G1 is at least partially reduced to 1,2-propanediol.

The glycerol stream G2 obtained in step (B) is converted in a preferred embodiment directly into step (C) of the process according to the invention. In a particularly preferred embodiment, steps (B) and (C) are carried out in a reactor so that the stream obtained in step (B) is transferred directly to step (C).

In a preferred embodiment, steps (B) and (C) are carried out in at least two spatially separate reactors.

Step (C):

Step (C) of the process according to the invention comprises the hydrogenation of the glycerol stream G2 from step (B) with hydrogen in the presence of a catalyst in order to obtain 1,2-propanediol. Methods for the hydrogenation of glycerol-containing streams are known per se to those skilled in the art. By virtue of the hydrogenation step (C) being preceded by a desulfurization step (B) according to the invention, it is possible to separate sulfur-containing compounds which would act as catalyst poisons in step (C), so that the catalyst used in step (C) produces a longer life and higher activity.

In step (C) of the process according to the invention, it is generally possible to use all catalysts which have been mentioned with regard to step (B). Therefore, what has been said about the catalyst used in step (B) also applies correspondingly to step (C).

In a preferred embodiment, the same catalyst as in step (B) is used in step (C). Thus, in a preferred embodiment, in step (C) of the process according to the invention, a catalyst is used comprising an oxidic material containing

(a) copper oxide in an amount of 50 ≦ x ≦ 80 wt%, preferably 55 <x <75 wt%,

(b) alumina in an amount of 15 <y <35% by weight, preferably 20 <y <30% by weight, and

(c) at least one of the oxides of La, W, Mo, Ti or Zr, preferably of La and / or W, in an amount of 3 <z <20% by weight, preferably 3 ≦ z <15% by weight , in each case based on the total weight of the oxidic material after calcination, wherein 80 ≦ x + y + z <100 wt .-%, preferably 95 <x + y + z <100 wt .-% applies.

In a particularly preferred embodiment of the process according to the invention, a catalyst is used in step (C), which corresponds to the following general formula CuOm (Al ₂ Os) _n (La ₂ O ₃ ) O, where

mean, where the sum of m, n and o is 1 each. The catalysts used in step (C) of the process according to the invention can, for. B. in a fixed bed or as a suspension. The hydrogenation may, for. B. in the trickle bed, in the upflow mode or in the liquid phase. For the liquid phase hydrogenation, the catalysts are preferably in finely divided form, for. As a powder used. In the hydrogenation in trickle bed process, the catalysts are preferably used as moldings, for. In the form of pressed cylinders, tablets, lozenges, strands, rings, stars or extrudates, for example solid extrudates, polylobal extrudates, hollow extrudates and honeycombs.

Excess hydrogen is preferably recycled, so that it is preferably possible to separate off a portion of the hydrogen so as to discharge inert materials.

It is possible to use in step (C) of the process according to the invention a reactor or a plurality of reactors arranged in series or in parallel.

The temperature in the hydrogenation in step (C) of the process according to the invention is generally from 100 to 325 ⁰ C, preferably 150 to 300 C °, particularly preferably 175 to 250 ⁰ C.

Step (C) of the process according to the invention is generally carried out at a pressure of 100 to 325 bar, preferably 140 to 250 bar.

Therefore, the present invention also relates to the process according to the invention, wherein the hydrogenation in step (C) is carried out at a temperature of 100 to 325 ⁰ C and a pressure of 100 to 325 bar.

The molar ratio of hydrogens to glycerol in step (C) is preferably 2: 1 to 500: 1, more preferably 3: 1 to 100: 1.

The catalyst space velocity in the continuous procedure is preferably 0.1 to 1, particularly preferably 0.2 to 0.6 and very particularly preferably 0.3 to 0.6, kg of glycerol to be hydrogenated per kg of catalyst per hour.

The hydrogenation according to step (C) of the process according to the invention is generally carried out up to a conversion with respect to glycerol of at least 90%, preferably at least 95%. The selectivity with respect to 1,2-propanediol is according to According to the invention, preferably at least 85%, particularly preferably at least 90%, very particularly preferably at least 95%.

The hydrogenation is preferably carried out continuously. The product obtained after step (C) of the process according to the invention contains essentially 1,2-propanediol. Further constituents are, if appropriate, inter alia methanol, ethanol, n-propanol, isopropanol, 1,3-propanediol, glycerol, ethylene glycol and / or water.

The product obtained after the hydrogenation according to step (C) can be worked up by methods known to the person skilled in the art, for example thermal treatment, preferably distillation, adsorption, ion exchange, membrane separation, crystallization or extraction or a combination of two or more of these processes, wherein distillative workup is preferred. According to the invention, distillation processes known to those skilled in the art can be used. Suitable devices for the workup by distillation are also known to the person skilled in the art.

The glycerol separated off in the work-up of the product from step (C) of the process according to the invention can in a preferred embodiment be recycled to the hydrogenation stage.

The invention is further illustrated by the following examples:

Examples

As starting material for the following experiments, glycerine of the qualities pharmaceutical grade and pure glycerine of the company JCM Biodiesel Neckermann GmbH is used. Table 1 shows the analysis data of the glycerol used.

Table 1: Analysis of the Pharmaglycerin

Details on GC analysis for the hydrogenation of glycerol

The analysis of the starting material glycerol and the reaction is carried out by gas chromatography GC, which is known in the art. Device: HP 5890-2 with sample sampler

Range: 2

Column: 30 m DBWax; Film thickness: 0.25 μm Sample volume: 1 μl

Carrier gas: helium

Flow rate: 100 ml / min

Injector temperature: 240 ⁰ C Detector: FID Detector temperature: 250 ⁰ C

Temperature program: 5 min at 40 ⁰ C, 10 ° C / min to 240 ° C / 15 min,

Total running time 45 min.

Example desulfurization

For the glycerol hydrogenation, a fluid circulation reactor is used. In the first reactor 1000 ml of a catalyst containing Cu, La and Al are filled in oxidic form. The catalyst is reduced in situ with hydrogen. A glycidyl cerin-water mixture having a water content of 10 wt .-% and hydrogen advertising the introduced into the first reactor and brought bar at a temperature of 175-215 ⁰ C and a pressure of 200 with the catalyst in contact.

The reactor is followed by a second reactor (control reactor), which is filled under identical operating conditions with the same catalyst. When the process according to the invention is actually carried out, this reactor corresponds to the reactor in which, according to step (C), the glycerol stream G2 is reduced to 1,2-propanediol.

The catalyst in the second reactor is also assayed for traces of sulfur after 8000 hours to determine the efficiency of the first reactor. The reactor effluent is collected and analyzed. After 8000 hours of operation, the catalyst is removed in portions and analyzed for sulfur content. Based on the measured data, a sulfur profile is created over the catalyst bed. The designation of the samples corresponds to the position in the reactor (sample 1 = inlet and sample 4 = outlet, sample 5 = inlet after reactor).

Table 2

Claims

claims

1. A process for the preparation of 1, 2-propanediol from glycerol, comprising at least the steps:

(A) providing a glycerol stream G1,

(B) desulfurizing the Glycerinstromes G1 from step (A) by hydrogenation with hydrogen at a pressure of 50 - 300 bar in the presence of a catalyst to obtain a Glycerinstrom G2, and (C) hydrogenation of the Glycerinstromes G2 from step (B) Hydrogen in the presence of a catalyst to obtain 1, 2-propanediol.

2. The method according to claim 1, characterized in that the steps (B) and

(C) are carried out in at least two separate reactors.

3. The method according to claim 1 or 2, characterized in that in steps (B) and (C), the same catalyst is used.

4. The method according to any one of claims 1 to 3, characterized in that in step (A) provided Glycerinstrom G1 has a sulfur content of 0.1 to 5 ppm.

5. The method according to any one of claims 1 to 4, characterized in that the hydrogenation in step (C) at a temperature of 100 to 325 ⁰ C and a pressure of 100 to 325 bar.

6. The method according to any one of claims 1 to 5, characterized in that the provided in step (A) glycerol flow G1 has a water content of at most 30 wt .-%.

7. The method according to any one of claims 1 to 6, characterized in that a Glycerinstrom G1 is used, which is obtained in the production of alkyl esters of higher fatty acids by transesterification of the corresponding fatty acid triglycerides.

8. The method according to any one of claims 1 to 7, characterized in that in step (B), a catalyst is used, comprising at least one metal component selected from the groups 6, 7, 8, 9, 10, 11 and / or 12 of Periodic Table of the Elements (new IUPAC nomenclature).