PL222393B1 - Method for preparing propylene glycol out of glycerine - Google Patents

Description

(12) PATENT DESCRIPTION (19) PL (11) 222393 (13) B1 (21) Application number: 403880 ^{(51) Int.Cl.}

C07C 29/60 (2006.01) C07C 29/132 (2006.01) C07C 31/20 (2006.01) (22) Date of notification: 14.05.2013 (54)

Method of obtaining propylene glycol from glycerin

(73) The right holder of the patent: INSTITUTE OF HEAVY ORGANIC SYNTHESIS BLACHOWNIA, Kędzierzyn-Koźle, PL (72) Inventor (s): (43) Application was announced: JÓZEF LACH, Kędzierzyn-Koźle, PL 24/11/2014 BUP 24/14 JANUSZ DULA, Kędzierzyn-Koźle, PL ZBIGNIEW BUDNER, Kędzierzyn-Koźle, PL MAREK WARZAŁA, Łęg Tarnowski, PL ANDRZEJ KRUEGER, Kędzierzyn-Koźle, PL (45) The grant of the patent was announced: GRZEGORZ MATUS, Kędzierzyn-Koźle, PL 29.07.2016 WUP 07/16 JAN WÓJCIK, Zalesie Śląskie, PL DOROTA STAŃCZYK, Kędzierzyn-Koźle, PL SZYMON SKOWRONEK, Wodzisław Śląski, PL (74) Representative: item. stalemate. Renata Fiszer

PL 222 393 B1

Description of the invention

The subject of the invention is a method of obtaining propylene glycol from glycerin, used primarily as a raw material for the production of plastics and as a component of anti-freeze operating fluids.

The development of biodiesel production in recent years has brought hundreds of thousands of tons of by-product glycerin on the market. In the process of fat transesterification with methanol, about 0.1 Mg of glycerol is produced as a side ester per 1 Mg of produced esters. Glycerine finds numerous applications in many areas of the economy, however, the total demand for glycerin in individual industries is limited. As a result of a significant increase in the world production of biodiesel, a large supply of glycerin caused a significant drop in its market price, opening the way to new, previously unprofitable technologies.

One of the most promising directions for the use of glycerin is its hydrogenation to propylene glycol, where both the price and the market demand are much higher than that of glycerin. An additional advantage in favor of this technology is the fact that the use of glycerin in this process will replace the expensive and scarce raw material for the production of propylene glycol of petrochemical origin, i.e. propylene. Propylene glycol from propylene is obtained in industrial practice by means of hydration of the indirectly obtained propylene oxide intermediate.

The theoretical basis and laboratory scale research for various glycerol processing processes began many years ago. The German patent 524101 of 1931 claims a solution in which glycerin vapors (1.5% by volume) were passed through a copper-chromium catalyst doped with phosphoric acid at a temperature of 180-210 ° C placed in a stationary bed. The selectivity of the process towards the production of propylene glycol reached 70%.

In another patent solution from 1932 (DE 541362), it was proposed to hydrogenate glycerin at a temperature of 200-240 ° C, in a tank reactor at a pressure of 10 MPa, in the presence of a nickel catalyst, and a method for separating hydrogenation products by distillation.

According to the methodology used in the American patent 1963997 of 1934, on a nickel-chromium oxide catalyst at a temperature of 275 ° C and a pressure of 21 MPa, the efficiency of the glycerin hydrogenation process to propane-1,2-diol can be obtained at the level of 53%.

Much better results of glycerin hydrogenation were obtained with the use of copper-zinc catalysts according to US patent 5,214,219 of 1993. In a tank reactor, with a glycerin conversion of 91%, 85.1% propylene glycol and 4.9% ethylene glycol were determined in the organic fraction, and in the stationary bed, at the conversion of glycerin 93.2%, the yield was achieved, respectively: 84.0% of propylene glycol and 6.3% of ethylene glycol.

In another US patent 5276181 of 1994, using a ruthenium catalyst supported on activated carbon in a tank reactor, almost complete conversion of glycerin was achieved in the hydrogenation process. The propane-1,2-diol content in the liquid product was 75%. To achieve high degrees of glycerol conversion, it is necessary to use sodium hydroxide as a promoter (0.23 cg / g), but it cannot be too high as it increases the proportion of lactic acid formed. Under these conditions, the following were adopted as optimal: process temperature 220-280 ° C, pressure 10-15 MPa, amount of catalyst 0.25-1% and water content in the raw material 30-40%.

US Patent 5,616,817 describes a method of converting glycerin containing up to 20% water to propane-1,2-diol over a cobalt-copper-manganese-molybdenum catalyst doped with phosphoric acid. Hydrogenation reactions were carried out both in a tank reactor and in a stationary bed. In the tank reactor, after 6 hours of glycerol hydrogenation at a temperature of 250 ° C and a pressure of 25 MPa, the propane-1,2-diol content was 95.8% in the organic fraction. The only significant by-product was n-propanol, obtained in a yield of 3.2%. The same catalyst was placed in a stationary bed in a long column and reduced with a mixture of hydrogen and nitrogen at a temperature not exceeding 300 ° C. At a temperature of 210-220 ° C and a pressure of 29.5 MPa, the product was obtained with 92% propane-1,2-diol and 4.3% n-propanol in the obtained organic fraction.

In the US patent 6479713 it was proposed to carry out the hydrogenation of glycerin (25% aqueous solution) on a nickel-rhenium catalyst in an alkaline environment. After 4 hours of reaction at the temperature of 230 ° C and the pressure of 7.6-9 MPa, the glycerin conversion was 62%

PL 222 393 B1 and selectivity to propylene glycol of 66%. Better results were obtained on the catalyst (containing 2.5% Ni and 2.5% Rh) placed in the stationary bed, the glycerin conversion was 90%, and the selectivity to propane-1,2-diol depending on the conditions was 60-80%.

Good glycerol hydrogenation results were obtained according to the method described in the US application 2005/0244312 by carrying out the reaction using catalysts in the form of a powder containing various proportions of copper, chromium, manganese, silicon and barium oxides. The one-step process achieved a glycerol conversion of 60% and a selectivity to propane-1,2-diol of 80%. It was assumed that the post-reaction mixture was to be used directly for the production of antifreeze fluids, bypassing the stage of isolating individual reaction products. The optimal parameters for this reaction were the temperature of 200 ° C, with the optimal catalyst content being 5%. Higher catalyst content and longer reaction time increase the amount of propanediol degradation products, such as low-boiling monohydric alcohols and gases. The water content of the reactants, in particular in amounts of 10-20%, is advantageous for a high selectivity of the reaction.

According to the American patent 2008/0242898, a selectivity to propane-1,2-diol of 60% was obtained on a ruthenium catalyst supported on a carbon support within 6 hours at a pressure of 7 MPa and a process temperature of 200 ° C. _{Various basic agents (KOH, K 2} CO ₃ , KHCO ₃ ) were additionally used as additives increasing the selectivity towards propane-1,2-diol and promoting the catalyst.

WO 2008/049470 describes a method for producing propane-1,2-diol in a tank reactor in the presence of a catalyst containing copper oxide and zinc oxide which is activated in a stream of hydrogen before the reaction. The raw material for the process was pure glycerin. At 200 ° C, complete conversion was achieved after 12 hours. The content of propane-1,2-diol in the organic products was 97.7%. In a similar process based on a catalyst additionally containing manganese oxide described in WO 2008/089899, an almost equally high propane-1,2-diol content (97.5%) in the organic fraction of the product was achieved.

WO 2009/027501 describes the process of hydrogenation of glycerin to propane-1,2-diol running on a fixed bed catalyst containing oxides of copper, aluminum and lanthanum, which was activated with hydrogen prior to the reaction. The reaction was carried out in a cascade of three reactors, obtaining almost complete conversion of glycerin and a selectivity to the desired product of 97%. The reaction was carried out under high hydrogen pressure of 20 MPa and at a temperature of 173-185 ° C.

The US 2009/0126866 describes the process of glycerin hydrogenation in a 40% water-methanol solution, the process was carried out on a copper-cerium-silicon catalyst placed in a fixed bed; conversion of glycerin and selectivity to propane-1,2-diol was 97%.

US 2009/0216050, US 2010/0240934 and US 2010/0312023 describe the process of hydrogenating glycerin to propane-1,2-diol using a series of catalysts containing an active copper with a high surface area as the main ingredient. The hydrogenation reaction was carried out both in a tank reactor and by a continuous method in a cascade of reactors with a stationary bed of the catalyst. A high degree of glycerol conversion was obtained with very good selectivity to propane-1,2-diol (98.5%), but under a hydrogen pressure of 20 MPa.

The patent specification US 7586016 describes a method of obtaining propylene glycol in the glycerin hydrogenation process using a catalyst placed in a fixed bed, based on a system of metal oxides CuO-CeO _{2 -SiO 2} . A high conversion of glycerin (96%) was obtained under mild process conditions (180 ° C, 2.0 MPa), however, with a long process time (100 h).

There are also known processes for the hydrogenation of glycerin to glycol with the use of other oxide catalysts. Application US 2010/0094064 and US 7,868,212 give an example of the use of a CuO / ZnO / MnO2 catalyst.

Application US 2010/0179346 shows the process of hydrogenation of glycerin to propylene glycol carried out in a fluidized bed system in a system of two reactors, where the circulating gas is hydrogen and the catalyst is based on copper or chromium compounds.

Gas-phase hydrogenation processes for glycerin are also known. The application US 2010/0204527 shows a method of hydration of glycerin in gas phase at a temperature of 210-215 ° C and a pressure of 2 MPa on a copper catalyst. Yield of propyl e4 glycol was obtained

At the level of 75%, the rest of the products are water formed according to the reaction chemistry and by-products, which are dominated by low-molecular monohydric alcohols.

US 2010/0256425 and 2011/0040131 describe the process of hydrogenation of glycerin to propylene glycol carried out on a copper-zinc catalyst obtained with the use of an additional support - silica, iron oxides or magnesium. The process was carried out in a stirred tank reactor. After 12 hours of the reaction with the optimal composition of the copper-zinc catalyst deposited on the silica, the yield of propylene glycol was 95.8%.

The analysis of the existing knowledge shows that there are many ways to produce propylene glycol from glycerin, however, as described above, these methods are often characterized by low selectivity to propane-1,2-diol, low conversion, relatively high operating parameters (pressure or operating temperature) or very long reaction times. This results in high operating costs or requires large investment outlays. Moreover, in many known methods there is a rapid deactivation of the catalyst manifested by a decrease in the activity and selectivity of the catalyst. The decrease in the activity of catalysts in the process of hydrogenation of glycerin with hydrogen to propylene glycol is a typical phenomenon and applies in particular to catalysts based on copper or its oxides, for which it is possible to obtain a very high product efficiency in the initial period of catalyst operation. The need to separate an increasing amount of by-products as the catalyst activity decreases is troublesome and increases the running costs of the installation. To some extent, the decrease in catalytic activity can be compensated by a change in the operating parameters of the process being carried out, but in the end there is a need to stop the installation and replace the catalyst.

The object of the invention was to develop an economical method of obtaining propylene glycol from glycerin in the presence of a catalyst with high activity.

It has surprisingly been found that it is possible to develop an economical method of obtaining propylene glycol from glycerin, in view of a highly active heterogeneous catalyst, obtained by precipitation onto amorphous silica and / or on aluminosilicate, deposits from salt solutions containing at least copper, zinc, aluminum and magnesium ions, in the reaction zone in the form of a slurry, partially recycled to the process after separation of the reaction products.

The essence of the method according to the invention consists in the fact that • an aqueous solution of purified glycerin obtained as a by-product as a result of transesterification of vegetable or animal fats with low molecular weight alcohol C ₁ -C ₆ is hydrogenated at a pressure of 4-18 MPa and a temperature of 190-260 ° C at a flow reactor in the presence of a heterogeneous catalyst kept in suspension by hydrogen flowing at a rate that provides at least three times the excess in the amount required stoichiometrically, using a heterogeneous catalyst obtained by precipitation on amorphous silica and / or on aluminosilicate sediments from salt solutions containing at least copper and zinc ions , aluminum and magnesium with an alkaline agent, subjecting the obtained sediments to the process of filtration and calcination in a furnace, products, are returned to the hydrogenation process along with a new portion of the reactants, the spent catalyst outside the system is separated from the reaction mixture and subjected to regeneration.

Preferably, a catalyst with a grain size in the range of 0.1-100 µm containing at least 10 cg / g copper, based on the elemental component, is used.

It is preferred that the hydrogenation is carried out in the presence of a cocatalyst.

Preferably, alkali metal hydroxides and / or salts of strong bases and weak acids in solution form are used as cocatalyst.

Preferably, the hydrogenation is carried out in a neutral or moderately basic medium using the weight ratio glycerin: water: catalyst: basic cocatalyst: 1000: (25-500): (1-150): (0-15).

Preferably, the continuous process employs a volumetric flow rate of liquid raw materials in the range of 0.05-2 h ^- .

Preferably, a portion of the catalyst slurry carried outside the reaction system is separated by standing and / or centrifugation and / or product distillation and / or membrane separation.

PL 222 393 B1

Preferably, the catalyst suspension is returned to the reactor in a solution consisting of a mixture of raw materials and part of the products.

Preferably, the losses of the catalyst are made up with fresh portions of the catalyst.

Preferably, propylene glycol, separated from the catalyst and gaseous substances, is separated and purified by distillation.

Preferably, the unreacted glycerin and the by-products after the isolation of propylene glycol are returned to the hydrogenation process.

In the proposed solution, the hydrogenation of glycerin to propylene glycol takes place in a reaction system enabling the reaction to be carried out in a continuous manner. A high selectivity catalyst based on reduced oxides of transition metals, mainly copper, is kept in the reaction zone in the form of a suspension. This catalyst is active in the reaction zone by reducing it to nanocrystalline copper. The separation of the glycerol hydrogenation products from the heterogeneous catalyst is carried out outside the reaction system. The isolation of the catalyst can be carried out in many ways, such as: distilling the products under reduced pressure, filtration or separation on membranes. After the separation of the solid phase, the filtrate or distillate is subjected to further separation and purification processes leading to the final product - propylene glycol of high purity.

Part of the catalyst carried outside the reaction system can be returned to the hydrogenation process in the form of a thickened suspension. The loss of the catalyst, which is discharged outside the system, can be continuously supplemented with fresh portions of the catalyst. The activity of the catalyst is achieved in the reaction medium by reduction with hydrogen. This solution simplifies the method of preparing the catalyst for the process. Conducting the reduction of the catalyst in the environment of liquid reactants with high thermal inertia and intensive mixing provide favorable conditions for this highly exothermic process without fear of excessive temperature increase and local overheating of the catalyst. At the moment of starting the hydrogenation plant until the catalyst is reduced and full catalytic activity is obtained, the degree of conversion of glycerin to glycol is lower, however, the high selectivity of the process allows for complete or partial use of the stream leaving the reactor and return to the process.

An indispensable feature of the catalyst used in the suspension of glycerol hydrogenation reaction is the possibility of easy separation of it from the post-reaction mixture after it has been transferred outside the reaction system. In the simplest embodiment, this can be done by distilling off the glycerol hydrogenation products from the mixture containing the catalyst slurry. However, it is more energetically beneficial to carry out this process as a result of the filtration process. In order for the filtration process to take place quickly enough, it is necessary to obtain a catalyst with an appropriate grain size so that, on the one hand, it is entirely retained on the filter surface with a suitably selected pore diameter, and on the other hand, the formed filter deposit does not create large flow resistance. This effect is achieved by applying the precipitated metal oxides to a high-surface amorphous silica or aluminosilicate. The catalyst obtained in this way is characterized by low agglomeration tendency and is mechanically stable.

The method according to the invention is more energy-efficient than the previously known solutions and is characterized by a better use of the apparatus.

From the catalyst discharged from the reaction system, the metals used for its preparation can be recovered by dissolving it in nitric acid into the appropriate salts, which can then be reused in the preparation of new catalyst batches.

As a raw material for the hydrogenation process, glycerin can be pre-purified by simple distillation and removal of compounds that may poison the catalyst, such as sulfur or phosphorus compounds.

As a raw material for the hydrogenation process, an aqueous glycerol solution obtained by purification of the glycerol fraction obtained by way of the transesterification of fats of both vegetable and animal origin is preferred.

P r z k ł a d 1

A liquid feed containing 83.7% of distilled glycerin obtained from the glycerin fraction obtained from biodiesel production, 9.3% distilled water, 7% of the catalyst prepared as follows is fed to the continuously operating bubble reactor, with a volume of 0.6 dm. way:

An aqueous mixture containing 15% by weight of copper, zinc, aluminum and magnesium nitrates and 5% of amorphous silica with an average grain size of 19 μm and a purity based on dry weight of at least 99% SiO _{2 is} intensively stirred at a temperature of 20 ° C to achieving homogeneity of the mixture. The suspension thus obtained is metered into the Na ₂ CO ₃ carbonate solution with vigorous stirring and kept at a temperature of 20 ° C. The precipitated catalyst precipitate is filtered and washed with distilled water and then calcined at 200-300 ° C in a muffle furnace for 4 hours. The catalyst thus obtained contains oxygen compounds of copper (in the amount of 18 cg / g in terms of the elemental component) in a mixture of oxides and hydroxides of zinc and magnesium, applied to the surface of the silica.

The liquid feed flow is kept at 230 g / hour at a temperature inside the reactor of 235 ° C. To the reactor is metered into hydrogen, which at the same time used to present mixed ₃ (bubbling) of the mixture in the reactor. The hydrogen flow is kept at 12 Ndm / minute. The pressure in the reactor is kept at 9 MPa. The reaction product is subjected to a recovery filtration to recover the catalyst which is recycled directly to the process in the next batch of raw material. The filtrate is separated by distillation. The components are volatile and the water is distilled off under normal pressure. Part of the obtained distillate containing water and easily volatile components is used to prepare the next batch of raw material. The glycol is separated from the filtrate and purified by fractional distillation at 50 mbar. The exhaust liquid resulting from the distillation containing, especially during start-up, large amounts of glycerol is also recycled to the process. After 70 hours of the process, process stability and complete conversion of glycerol in the process are achieved.

The product contains water and the following organic ingredients

Ingredient Component content Methanol 0.59 Isopropanol 0.12 Ethanol 0.30 Propanol 0.37 2,3-butandiol 0.38 1-Methoxy-2-butanol 0.13 Propylene glycol 96.36 Ethylene glycol 1.06 others 0.69

As a result of purification of the product thus obtained on a rectifying column with the number of theoretical plates> 10, propylene glycol with a purity of more than 99% is obtained.

P r z k ł a d 2

A liquid feed containing 83.5% distilled glycerin obtained from the glycerin fraction obtained from biodiesel production by-product, 9.3% distilled water, 0.2% Na ₂ CO is fed to a continuously operating bubble reactor, with a volume of 0.6 dm. _3, 7% of the catalyst prepared according to the method described in example 1.

The liquid feed flow is maintained at 280 g / hour at a temperature inside the reactor of 235 ° C. To the reactor is metered into hydrogen, which at the same time used to present mixed ₃ (bubbling) of the mixture in the reactor. The hydrogen flow is kept at 12 Ndm / minute. The pressure in the reactor is kept at 9 MPa. The reaction product is filtered to recover the catalyst, which is recycled directly to the process in the next batch of raw material. The filtrate is separated by distillation. The components are volatile and the water is distilled off under normal pressure. Part of the obtained distillate containing water and easily volatile components is used to prepare the next batch of raw material. The glycol is separated from the filtrate and purified by fractional distillation at 50 mbar. The exhaust liquid coming from the distillation containing especially

During start-up, large amounts of glycerin are also recycled to the process. After 60 hours of the process, process stability and complete conversion of glycerin in the process are achieved.

The product contains water and organic constituents, wherein propylene glycol is 96%, and slightly increased the alcohol content _of C ₁ -C ₃ compared to example 1.

As a result of purification of the product thus obtained on a rectifying column with the number of theoretical plates> 10, propylene glycol with a purity of more than 99% is obtained.

Claims (11)

Patent claims 1. The method of obtaining propylene glycol from glycerin, characterized in that • an aqueous solution of purified glycerin obtained as a by-product as a result of transesterification of vegetable or animal fats with low molecular weight C ₁ -C ₆ alcohol is hydrogenated at a pressure of 4-18 MPa and a temperature of 190- 260 ° C in a flow reactor in the presence of a heterogeneous catalyst kept in suspension by hydrogen flowing at a rate that provides at least three times the excess amount of the stoichiometric required, using a heterogeneous catalyst obtained by precipitation on amorphous silica and / or on aluminum silicate sediments from salt solutions containing carbon the least ions of copper, zinc, aluminum and magnesium are an alkaline agent, subjecting the obtained sediments to the process of filtration and calcination in the furnace, • the catalyst suspension is led outside the reaction system together with the mixture of products, and part of the catalyst suspension is led outside the reaction system After separating some of the products, the feedstock is returned to the hydrogenation process along with a new portion of the reactants, the spent catalyst outside the system being separated from the reaction mixture and subjected to regeneration. 2. The method according to p. The process of claim 1, wherein the catalyst is used with a particle size in the range of 0.1-100 µm containing at least 10 cg / g of copper, based on the elemental component. 3. The method according to p. The process of claim 1, wherein the hydrogenation is carried out in the presence of a cocatalyst. 4. The method according to p. The process of claim 1, wherein the cocatalyst is metal hydroxides and / or salts of strong bases and weak acids in the form of a solution. 5. The method according to p. A process as claimed in claim 1, characterized in that the hydrogenation is carried out in a neutral or moderately alkaline medium using the weight ratio glycerin: water: catalyst: alkaline catalyst: 1000: (25-500): (1-150): (0-15). 6. The method according to p. The process of claim 1, characterized in that the continuous process uses a volumetric flow rate of liquid raw materials in the range of 0.05-2 h ^- . 7. The method according to p. A process as claimed in claim 1, characterized in that a portion of the catalyst slurry carried outside the reaction system is separated by standing and / or centrifugation and / or product distillation and / or membrane separation. 8. The method according to p. The process of claim 1, wherein the catalyst slurry is returned to the reactor in a solution consisting of a mixture of raw materials and a portion of products. 9. The method according to p. The process of claim 1, wherein the losses in the catalyst are made up with fresh portions of the catalyst. 10. The method according to p. A process as claimed in claim 1, characterized in that propylene glycol separated from the catalyst and gaseous substances is separated and purified by distillation. 11. The method according to p. The process of claim 1, characterized in that unreacted glycerin and by-products after the isolation of propylene glycol are returned to the hydrogenation process.