WO2010102361A1

WO2010102361A1 - Method for producing propyleneglycol from biodiesel glycerol

Info

Publication number: WO2010102361A1
Application number: PCT/BR2010/000029
Authority: WO
Inventors: Junior Marlito Gomes; Carlos Rene Klotz Rabello; Bernardo GALVÃO SIQUEIRA; Raphael Bezerra De Menezes
Original assignee: Petróleo Brasileiro S.A. - Petrobras
Priority date: 2009-03-09
Filing date: 2010-02-24
Publication date: 2010-09-16
Also published as: BRPI0902818A2; AR077531A1

Abstract

The present invention describes a method for producing propyleneglycol from glycerol obtained during a biodiesel production process, wherein purified glycerol is converted into propyleneglycol by a hydrogenolysis reaction in the liquid phase, in two successive steps in a single, fixed-bed reactor (1) in predetermined temperature and pressure conditions, and the effluent from the fixed-bed reactor (1) is led to subsequent method steps, including separation and purification.

Description

PROPYLENGLYCOL PRODUCTION PROCESS FROM

BIODIESEL GLYCERIN

FIELD OF INVENTION

The present invention is in the field of processes for producing propylene glycol from glycerin. Specifically, the invention relates to the production of propylene glycol from glycerine resulting from the process of obtaining biodiesel.

BACKGROUND OF THE INVENTION

Currently, there is a significant increase in the supply of glycerine in the market, largely due to the worldwide expansion of biodiesel production. Within the biodiesel production process, glycerin is a byproduct generated at a mass ratio of 10/1 (biodiesel / glycerin).

However, this excess supply of glycerine directly implies the drop in its commercial value making other applications viable.

Several studies have been started with the purpose of harnessing this excess glycerin by turning it into new products or employing glycerin as a raw material for the production of new products that have greater commercial value.

Technical publications on the subject are increasing as solutions are devised for the use of this excess glycerin.

One of the products of interest is propylene glycol and its production from glycerin.

RELATED TECHNIQUE

Within the state of the art that has been forming in this regard, some very exemplary documents on the development of related processes can be highlighted.

WO 2008/051540 A2 (Archer-Daniels-Midland Company) discloses a process for the production of propylene glycol from from glycerin using a fluidized bed reactor operating at temperatures in the range 178 ° C to 205 ° C, pressures in the range 1200 psi to 1600 psi, with hydrogen / glycerine molar ratio in the range 1: 1 to 10: 1 and a space velocity in the range between 0,5 h ^"1 and 10 h ^{" 1} . The reactor charge is a predominantly aqueous solution containing at least 30% by weight of glycerine in alkaline medium selected from metal hydroxides, alkoxides, basic salts and metal oxides.

WO 2007/053705 A2 (University of Missouri Board of Curators) discloses a process for producing a mixture of acetol and propylene glycol in any proportion from vapor phase glycerine. Glycerin partial pressure is in the range 0.01 bar to 0.5 bar and the temperature in the range 80 ° C to 300 ° C. The hydrogen partial pressure within the process is in the range 0.01 bar to 25 bar. A heterogeneous catalyst having at least one group I or VIII element from the periodic table, ruthenium, copper, chromium or a combination of these elements is used.

US 2005/0244312 and PI 0507874-1 (Galen J. Suppes, William Rusty Sutterlin and Mohanprasad Dasari) disclose processes for the production of acetol, propylene glycol or a mixture of glycerine and propylene glycol, primarily used as an antifreeze fluid. from glycerin as raw material. For the production of propylene glycol, the emphasis is on a two-step process, in which the first step is production of acetol by reactive distillation where glycerin is dehydrated to acetol with the aid of a catalyst, which is immediately distilled from the medium. reaction with the aid of a catalyst. In this first step, batch or semi-batch reactors are employed, temperature in the range 170 ° C to 270 ° C, pressure in the range 0.2 bar to 25 bar, the glycerine in the charge must contain a range between 0% and 15% by weight of water with a heterogeneous catalyst which may have an element chosen from palladium, nickel, rhodium, chromium, copper or a combination thereof, preferably a catalyst based on a combination of copper and chromium. In a second step, the acetol produced, when mixed with hydrogen, undergoes hydrogenation to propylene glycol with catalyst aid. In this second step the reaction time is in the range of 0 to 24 hours, temperatures are in the range of 50 ° C to 250 ° C, preferably 150 ° C to 220 ° C, pressure 1 bar to 25 bar, preferably between 10 bar and 20 bar, the acetol filler contains at most 50% by weight of water, preferably between 0% and 35%, with a catalyst which can be chosen in the same way as the catalyst chosen for the first step, a catalyst based on a combination of copper and chromium being preferred.

WO 2008/049470 A1 (Clariant International Ltd.) discloses an autoclaving process for the production of propylene glycol from glycerin, where glycerine must be at least 95% pure under hydrogen pressure in the range of 20 bar to 100 bar. bar in the range 180 ° C to 240 ° C and in the presence of a catalyst comprising 20% to 0% copper oxide, 30% to 70% zinc oxide and 1% to 10% oxide of manganese.

WO 2007/010299 (Davy Process Technology Ltd.) discloses a process of producing propylene glycol from glycerine, carried out in vapor phase in the presence of a copper based catalyst. The process temperature is in the range between 160 ° C and 260 ° C and the pressure in the range between 10 bar and 30 bar. The ratio of hydrogen to glycerine is in the range 400: 1 to 600: 1 with spatial velocity between 0.01 h ^" and 2.5 h ^{" 1} .

WO 2008/012244 (Davy Process Technology Ltd.) discloses process modifications of the above mentioned document by adding various stages to the process emphasizing the reduction in the amount of hydrogen required by the process when operated under this stage regime.

WO 03/035582 (Battelle Memorial Institute & Michigan State University) discloses a hydrogenolysis process of sugars containing six carbon atoms and polyols, including glycerin, using a rhenium-containing multimetal solid catalyst. The process is conducted under temperature in the range of 120 ° C to 250 ° C, with a net charge pH value in the range of 8 to 13 and a hydrogen pressure during the glycerine hydrogenolysis reaction in the range of 600 psi to 1800 psi

WO 2008/133939 (Archer-Daniels-Midland Company) discloses a glycerine catalytic hydrogenolysis process wherein the spatial charge velocity is in the range of 0.5 h- ^{1 to} 2.5 h- ¹ . The filler is made up of a solution containing 25 to 40% USP glycerine, alkalized with sodium or potassium hydroxide or alkoxide so that a pH value in the range 6 to 14 is obtained. is in the range 500 psi to 2000 psi under a temperature in the range 150 ° C to 300 ° C and a hydrogen / glycerine molar ratio in the range 1: 1 to 10: 1. The document points out that, besides producing propylene glycol as a major compound, there is the formation of butanediols and a proportion of other diols in the range of 0.04% to 2.31%. The product purification / separation section proposed in this process comprises a step of removing the alkalizing agent by means of an ion exchange resin and by product distillation steps. In the first distillation tower, water and light alcohols are removed from the top and sent to a second distillation tower for separation. The bottom effluent from the first distillation tower flows into a plurality of small distillation towers in which the residual water and unconverted glycerin are separated. The propylene glycol enriched stream is conveyed to a distillation tower for separation of other byproducts, mainly ethylene glycol. WO 2008/057317 (Archer-Daniels-Midland Company) discloses a process for purifying propylene glycol and ethylene glycol produced from a renewable source. The process employs a polar solvent to aid in the distillation separation of the components. A mixture of polyols produced during a hydrogenolysis reaction of a renewable raw material, among many glycerin, is mixed with a polar solvent such as water, methanol, ethanol, n-propanol, n-butanol, i-butanol, alcohol. amyl, acetone, butyric acid, gluconic acid, acetic acid, lactic acid, sulfuric acid and hydrochloric acid, so that it does not form azeotrope with the mixture components for distillation. This type of distillation is known as extractive distillation and is used when the components of a mixture have low relative volatility. The polar solvent interacts differently with the components of the mixture causing a change in the relative volatility of these components and thus enables the separation to be performed.

UOP has been disclosing a process of transformation of glycerine to propylene glycol in a single stage where it uses a catalyst whose composition has not been disclosed. The process selectivity reported is 90 wt% propylene glycol in 79 wt% yield. The major byproduct is ethylene glycol, which is about 3% by weight in the reactor effluent which is subsequently separated from the medium. The propylene glycol produced has a purity of 99.5% w / w. A glycerine of 40% by weight purity may be used as a filler, dispensing the purification step depending on the initial charge characteristic. Such technology is ready to be licensed.

As it was observed, the studies progress, although it is observed among the processes mentioned above very little concern with the product separation stage. The present invention provides an alternative route for obtaining propylene glycol with optimization of the process as well as the recovery, separation and final treatment of the obtained products.

SUMMARY OF THE INVENTION

It is an object of the present invention that a process for the production of propylene glycol from glycerine, in which reactions take place in the liquid phase and glycerine is used as raw material, is specifically generated during the process of obtaining biodiesel.

Biodiesel glycerine or blonde glycerine is produced in a range of 40% to 85% purity and, to be used as a raw material for the production of propylene glycol according to the present invention, needs to be purified by purification processes normally employed. in the art, yielding a glycerine with a purity content in the range of 90% to 99% by weight.

The transformation of purified glycerin to propylene glycol is performed by a hydrogenolysis reaction which is conducted in liquid phase, where the two reaction steps occur simultaneously and in the same reactor.

In the first step the glycerol by temperature effect and catalyst is transformed into acetol and water. In the second stage, acetol, by catalyst effect and hydrogen gas, is transformed into propylene glycol.

The reactor effluent is conducted to a separation and purification section after which a high purity and low contaminant end product is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a representation of the chemical equations illustrating the transformation of glycerine from biodiesel to propylene glycol.

Figure 2 is a simplified process flowchart representation of glycerine to propylene glycol hydrogenolysis.

DETAILED DESCRIPTION OF THE INVENTION

This invention deals with a process for the production of propylene glycol from glycerine, in which reactions take place in liquid phase and glycerine is specifically generated during the process of obtaining biodiesel. Glycerin produced throughout the biodiesel production process, which is used as a feedstock for the process of the present invention, initially has a purity content in the range of 40% to 85% due to the presence of numerous reaction byproducts such as for example:

- salts containing sodium, chlorine, sulfur and phosphorus which irreversibly deactivate the catalyst;

- fatty acids, phospholipids, glycerides, soaps and biodiesel residues which deactivate the pore blocking catalyst. The production of propylene glycol has as its raw material this glycerine, after purified is transformed into propylene glycol by means of a hydrogenolysis reaction, which is conducted in liquid phase, where the two reaction steps occur simultaneously and in the same reactor, or that is, the glycerol by temperature effect and catalyst is transformed into acetol and water and then by catalyst effect and hydrogen gas is transformed to propylene glycol. The chemical reactions involved in the process are shown in Figure 1.

The process for producing propylene glycol from glycerine derived from biodiesel according to the present invention can be followed with the aid of Figure 2 and basically comprises the following steps:

(a) subject glycerine from biodiesel (G) production and impurities by a purification step (P) to remove impurities (R) by a prior art purification process provided that the process provides a glycerine blonde with a purity content between 90% and 99.9% by weight;

(b) in a fixed bed adiabatic reactor operating under a downward flow, in liquid phase, proceed the hydrogenolysis reaction, where the two reaction steps occur simultaneously as follows:

^■ activating a copper chromite catalyst by passing hydrogen;

^■ pressurizing the fixed bed reactor (1) to a pressure which may be in the range of 5 to 40 bar, preferably 15 to 30 bar;

^■ raise the catalytic bed temperature to an operating temperature in the range of 180 ° C to 260 ° C;

^■ start inlet of purified glycerin with a certain water content from a loading line (12) and start inlet of hydrogen through a gas line (13), with a molar ratio of glycerine to hydrogen in the range between 1/3 and 1/50 and a spatial velocity in the range between 0.1 h ^"1 and 4.0 h ^{" 1} relative to the limiting reagent (glycerin);

c) cooling and removing the effluent preferably from the bottom of this reactor and conducting through a reaction line (11);

d) the effluent from the fixed bed reactor (1) through the reaction line (11) is cooled and enters a flash separating vessel

(2) removing a stream containing hydrogen and noncondensable light compounds by a first top stream (21) and removing liquid effluent by a first bottom stream (22);

e) the first top stream (21) from the flash separating vessel (2) enters a recycle compressor (3), which compresses the contents of this stream where part is driven by a first recycle line (31) to the fixed bed reactor (1) while another part is driven by a first purge line intended for incineration burning (32); f) the liquid effluent from the first bottom stream (22) from the flash separating vessel (2) enters a primary fractionation tower (4), which discharges by a second top stream (41) water and polar light compounds such as methanol, ethanol, n-propanol and isopropanol, while the bottom effluent is driven by a second bottom stream (42);

g) the bottom effluent from the second bottom stream (42) from the primary fractionation tower (4) enters a heavy duty removal tower (5), which removes unreacted glycerin and other heavy products formed during the hydrogenolysis reaction. which are driven by a third bottom stream (52) to destinations which may be chosen from: a second firing line (53) for incineration and power generation and a second recycle line (54) where glycerin is returned to the fixed bed reactor (1) while propylene glycol with impurities is driven by the third top stream (51); h) the effluent from the third top stream (51) from the heavy duty removal tower (5) enters a purification tower (6), which removes impurities such as ethylene glycol, 1,3-propylene glycol and a small content of heavy compounds. which are led by a fourth bottom stream (62) to the junction with the second firing line (53) for incineration and power generation, while high purity propylene glycol is obtained by the fourth top stream ( 61).

Due to the exothermicity of the reactions involved, the fixed bed reactor (1) may contain more than one catalytic bed and have a cooling system between the beds. Propylene glycol produced according to the present invention has an estimated purity of over 99% with low contaminant content.

The following is a merely illustrative example of the application of the process object of the present invention.

After in situ activation of the catalyst via hydrogen passage, the system was pressurized to approximately 20 bar with hydrogen and the operating temperature adjusted to 220 ° C. Purified glycerin containing a certain content of water and hydrogen at a 1/35 molar glycerine / hydrogen ratio with a spatial velocity of 1 h ^-1 relative to the limiting reagent (glycerin) was admitted. fixed bed operated isothermally, the reactor effluent (1) after analysis showed a glycerine conversion greater than 99% and selectivity for propylene glycol was 88.6%.

The complete reactor effluent composition of this example is listed in table 1 below:

Although the present invention has been described in its preferred embodiment, the main concept underlying the present invention which is a process for producing propylene glycol from glycerin, particularly from biodiesel glycerine, remains preserved as to its usefulness. innovative character, where those usually versed in may envisage and practice such variations, modifications, alterations, adaptations and equivalents as are appropriate and compatible with the particular working environment, without, however, departing from the scope and scope of the present invention, which are represented by the following claims.

Claims

- PROPYLENEGLYCOL PRODUCTION PROCESS FROM BIODIESEL GLYCERIN, characterized in that the glycerin used as a raw material comes specifically from a biodiesel production process, the purity of which is in the range of 90% to 99.9% by weight. and understand the following steps to take:

(a) in a fixed bed adiabatic downstream reactor operating in a liquid phase downflow, carry out the hydrogenolysis reaction, where the two reaction steps occur simultaneously;

b) remove the effluent from the bottom of this reactor (1) and drive through a reaction line (11);

c) the effluent from the fixed bed reactor (1) through the reaction line (11) is cooled and enters a flash separating vessel (2) for removal of a stream containing hydrogen and light non-condensable compounds for a first time. top stream (21) and removing liquid effluent by a first bottom stream (22);

d) the first top stream (21) from the flash separating vessel (2) enters a recycle compressor (3), which compresses the contents of this stream where part is driven by a first recycle line (31) as fixed bed reactor (1) while another part is driven by a first purge line intended for incineration burning (32);

e) the liquid effluent from the first bottom stream (22) from the flash separating vessel (2) enters a primary fractionation tower (4), which discharges by a second top stream (41) water and polar light compounds such as methanol, ethanol, n-propanol and isopropanol, while the effluent from bottom is driven by a second bottom stream (42);

f) the bottom effluent from the second bottom stream (42) from the primary fractionation tower (4) enters a heavy duty removal tower (5), which removes unreacted glycerin and other heavy products formed during the hydrogenolysis reaction. which are driven by a third bottom stream (52) to destinations which may be chosen from: a second firing line (53) for incineration and power generation and a second recycle line (54) where glycerin is returned to the fixed bed reactor (1) while propylene glycol with impurities is driven by the third top stream (51); g) the effluent from the third top stream (51) from the heavy duty removal tower (5) enters a purification tower (6), which removes impurities such as ethylene glycol, 1,3-propylene glycol and a small content of heavy compounds. which are led by a fourth bottom stream (62) to the junction with the second firing line (53) for incineration and power generation, while high purity propylene glycol is obtained by the fourth top stream ( 61).

PROPYLENGLYCOL PRODUCTION PROCESS FROM BIODIESEL GLYCERIN according to claim 1, characterized in that the fixed bed reactor (1) can contain more than one catalytic bed and has a cooling system between the beds due to exothermicity. of the reactions involved.

A process for the production of propylene glycol from glyodine glycerine according to claim 1, characterized in that the hydrogenolysis reaction is conducted in the presence of a copper chromite catalyst under the pressure of hydrogen in the range of 15 bar to 30 bar, temperature in the range of 180 ° C to 260 ° C, with a molar ratio of glycerine to hydrogen in the between 1/3 and 1/50 and a spatial velocity in the range between 0.1 h ^"1 and 4.0 h ^{" 1} with respect to the limiting reagent (glycerin).