Production method and device for converting glycerol into polyol and producing propanol as a by-product

Abstract

The present invention provides a production method and apparatus for converting glycerol into polyols and producing propylene glycol as a by-product, the method comprising providing a fixed-bed reactor provided with a catalyst bed; the catalyst bed having an aspect ratio of 0.01 to 2; continuously delivering raw materials glycerol, water, and hydrogen into the fixed-bed reactor, contacting the glycerol with the catalyst and reacting under the action of hydrogen to generate a mixture comprising polyols and propylene glycol; the mixture generated by the above reaction is drawn out of the fixed-bed reactor for post-processing; wherein the polyols include 1,2-propylene glycol and 1,3-propylene glycol, and the propylene glycol includes n-propyl alcohol and isopropyl alcohol. The present invention utilizes an ultra-thin catalyst bed to controllably hydrogenate glycerol into 1,3-propylene glycol and produce propylene glycol as a by-product, thereby improving the economic efficiency of industrialized production.

Description

Technical Field

[0001] The present invention relates to a production method and device for converting glycerol into polyol and producing propanol as a by-product. Background Art

[0002] Glycerol (also known as glycerol, chemical formula C3H8O3) is an important raw material in the field of fine chemicals and can be used as feed to prepare more valuable chemicals. For example, CN102388007A discloses a method for converting glycerol into polyols, wherein the polyols include propylene glycol, ethylene glycol, butanediol, etc. CN105452207A and CN104684879A both disclose a method for preparing 1,3-propylene glycol by hydrogenolysis using glycerol as a raw material. 1,3-propylene glycol has a wide range of industrial uses, for example, it can be used in inks, printing and dyeing, medicines, lubricants, antifreeze agents, etc. It can also be used as a diol for the synthesis of heterocycles, drug intermediates, etc. Another major use is as a polymer monomer to synthesize degradable polyester propylene terephthalate (PTT). The development of a low-cost 1,3-propylene glycol synthesis process is of great significance.

[0003] In the industrial production of 1,3-propylene glycol by hydrogenolysis of glycerol, maximizing the conversion rate of the raw material glycerol—that is, converting the raw material into product as much as possible—is a common method for improving economic efficiency. To increase the conversion rate of glycerol, one common approach in the prior art is to improve the catalyst. However, the catalysts used in the hydrogenolysis of glycerol to produce 1,3-propylene glycol are expensive, easily deactivated, and have poor stability. Currently, no good solution has been found. Increasing the aspect ratio of the catalyst bed is another means of increasing the glycerol conversion rate. Currently, the aspect ratio of the hydrogenation catalyst bed is typically greater than 6. However, this approach typically increases the glycerol conversion rate while reducing the selectivity for 1,3-propylene glycol, failing to increase product yield. Furthermore, the TOF (molar conversion factor of precious metals) of the hydrogenolysis reaction is significantly reduced, resulting in low economic efficiency. The prior art cannot achieve both full utilization of the glycerol raw material and high 1,3-propylene glycol selectivity and a high TOF. Summary of the Invention

[0004] An object of the present invention is to provide an industrial production method for converting glycerol into polyols and producing propanol as a by-product, thereby improving economic benefits.

[0005] Another object of the present invention is to provide a device for realizing the industrial production method of converting glycerol into polyols and producing propylene glycol as a by-product.

[0006] In one aspect, the present invention provides a method for converting glycerol into a polyol and producing propylene glycol as a by-product, the method comprising:

[0007] A fixed bed reactor is provided, wherein a catalyst bed is provided in the reactor; the height-to-diameter ratio of the catalyst bed is 0.01 to 2;

[0008] The raw materials glycerol, water, and hydrogen are continuously fed into a fixed bed reactor, where the glycerol contacts the catalyst and reacts under the action of hydrogen to produce a mixture containing polyols and propanol;

[0009] The mixture generated by the above reaction is drawn out of the fixed bed reactor for post-processing;

[0010] Wherein, the polyol includes 1,2-propylene glycol and 1,3-propylene glycol, and the propanol includes n-propanol and isopropanol.

[0011] The present invention's method for converting glycerol into polyols with the byproduct of propanol primarily utilizes an ultrathin catalyst bed to improve the economic efficiency of industrial production. The catalyst bed within the fixed-bed reactor can be a single, integrated layer or divided into multiple layers as needed.

[0012] According to a specific embodiment of the present invention, in the production method of converting glycerol into polyols and producing propanol as a by-product, the height-to-diameter ratio of the catalyst bed is 0.02 to 0.5.

[0013] According to a specific embodiment of the present invention, in the production method for converting glycerol into polyols and producing propanol as a by-product, the reaction conditions in the reactor are controlled such that the catalyst bed inlet reaction temperature is 120°C to 180°C, and the outlet temperature is 150°C to 250°C. In some more specific embodiments, the outlet temperature is no higher than 220°C. In the present invention, preferably, the outlet temperature is higher than the inlet temperature. More preferably, the outlet temperature is 10°C to 30°C higher than the inlet temperature.

[0014] According to a specific embodiment of the present invention, in the production method of converting glycerol into polyols and producing propanol as a by-product, the operating pressure in the reactor is controlled to be: 2Mpa to 20Mpa, preferably 4Mpa to 15Mpa.

[0015] According to a specific embodiment of the present invention, in the production method of converting glycerol into polyols and producing propylene glycol as a by-product, the mass concentration of glycerol in water in the feed is controlled to be 20%-80%, preferably 35%-60%.

[0016] According to a specific embodiment of the present invention, in the production method of converting glycerol into polyols and producing propanol as a by-product, the molar ratio of hydrogen to glycerol in the feed is controlled to be 2-30:1, preferably 5-15:1.

[0017] According to a specific embodiment of the present invention, in the production method of converting glycerol into polyols and producing propylene glycol as a by-product, the single-pass conversion rate of glycerol is controlled to be less than 60%, preferably less than 40%. In some specific embodiments, the single-pass conversion rate of glycerol is controlled to be 17% to 40% or 20% to 40%.

[0018] According to a specific embodiment of the present invention, in the production method of converting glycerol into polyols and producing propylene glycol as a by-product, the catalyst is a catalyst loaded with a precious metal. Any feasible catalyst known in the art may be used. In the present invention, a platinum catalyst commonly used in the art is preferably used. This type of catalyst is made by loading platinum on a carrier composed of one or more of tungsten oxide, zirconium oxide, aluminum oxide, or silicon oxide, typically with a platinum loading of 0.5% to 5%.

[0019] According to a specific embodiment of the present invention, in the production method of converting glycerol into a polyol and producing propanol as a by-product, the molar selectivity of 1,3-propylene glycol is 40%-63%. In some specific embodiments, the selectivity of 1,3-propylene glycol is 45%-60%. In the present invention, the reaction mixture includes, in addition to 1,3-propylene glycol, isopropyl alcohol, n-propyl alcohol, and 1,2-propylene glycol. The molar selectivities of isopropyl alcohol, n-propyl alcohol, and 1,2-propylene glycol are typically: 8%-12% for isopropyl alcohol, 25%-35% for n-propyl alcohol, and 5%-10% for 1,2-propylene glycol. When the reaction temperature is above 220 degrees Celsius, by-products other than the above four products (isopropyl alcohol, n-propyl alcohol, 1,2-propylene glycol, and 1,3-propylene glycol) are produced, and the amount of by-products increases with increasing temperature.

[0020] According to a specific embodiment of the present invention, the method for converting glycerol into polyols and producing propanol as a by-product can achieve a TOF (the number of moles of 1,3-propylene glycol per mole of precious metal per unit time) of 20-65. A TOF of 20 or greater is highly economical.

[0021] According to a specific embodiment of the present invention, in the production method of converting glycerol into polyols and producing propanol as a by-product, the post-processing includes a process of separating 1,3-propylene glycol from the reaction mixture. The post-processing may also optionally include a process of separating 1,2-propylene glycol, n-propanol, and isopropanol.

[0022] According to a specific embodiment of the present invention, in the production method of converting glycerol into polyols and producing propylene glycol as a by-product, unreacted glycerol and / or water are separated from the mixture generated by the reaction and returned to the fixed bed reactor for cyclic reaction.

[0023] On the other hand, the present invention also provides a device for realizing the production method of converting glycerol into polyols and producing propylene glycol as a by-product, the device comprising:

[0024] A fixed bed reactor is provided with a catalyst bed layer in the reactor; the height-to-diameter ratio of the catalyst bed layer is 0.01-2.

[0025] Preferably, in the fixed bed reactor of the present invention, the aspect ratio of the catalyst bed is 0.02 to 0.5.

[0026] The present invention configures an ultra-thin catalyst bed in a continuously circulating reaction system to precisely control the conversion rate of propylene glycol, thereby achieving very good selectivity for 1,3-propylene glycol (which can be greater than 45%) under high TOF (greater than or equal to 20). After the reaction liquid is separated by a set of distillation separation towers, propylene glycol is continuously re-added to the reaction system, fully utilizing the propylene glycol raw material and greatly improving the economic efficiency of industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of a production device for converting glycerol into polyols and producing propanol as a by-product, according to a specific embodiment of the present invention. DETAILED DESCRIPTION

[0028] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be understood as limiting the scope of the present invention. Unless otherwise specifically defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the relevant art. The method operations not specifically noted in the examples are carried out according to the conventional operations of the prior art in the relevant field.

[0029] Example 1

[0030] This embodiment provides a production method for converting glycerol into polyols and producing propanol as a by-product. Figure 1 As shown, the industrial production method of this embodiment mainly includes:

[0031] A fixed bed reactor 10 is provided, wherein a catalyst bed 11 is provided in the reactor; the catalyst bed 11 has an aspect ratio of 0.2; the catalyst is commercially available Pt / Al2O3, Pt / ZrO2, Pt / WO3 / Al2O3, Pt / WO3 / ZrO2, or Pt / WO3, wherein the Pt loading is approximately 1.0%;

[0032] The raw materials glycerol, water, and hydrogen (feed rate glycerol 966Kg / h / water 644Kg / h / hydrogen 1260Nm 3 / h) is continuously delivered into a fixed-bed reactor, where glycerol contacts the catalyst and reacts under the action of hydrogen to produce a mixture comprising polyols and propanol. The reaction conditions in the reactor are controlled as follows: an upstream temperature of the catalyst bed is 150° C., and a downstream temperature of 173° C.; the operating pressure in the reactor is controlled at 10 MPa; and the resulting mixture comprises: 1,2-propylene glycol, 1,3-propylene glycol, n-propanol, isopropanol, unreacted glycerol, and water.

[0033] The mixture produced by the above reaction is drawn out of the fixed-bed reactor for post-processing. In this embodiment, the mixture is drawn out of the fixed-bed reactor and then introduced into a separator 20 for separation. 1,2-Propanediol, 1,3-Propanediol, n-propanol, and isopropanol are separated from the reaction mixture as products. Unreacted glycerol and water are separated from the reaction mixture and returned to the fixed-bed reactor for a cyclic reaction. Hydrogen entrained in the reaction mixture can also be returned to the fixed-bed reactor for a cyclic reaction after being separated in the separator.

[0034] In this embodiment, the single-pass conversion rate of glycerol is 38.3%, and the TOF is 51.2.

[0035] Other embodiments

[0036] Referring to the production method for converting glycerol into polyols with the byproduct of propanol described in Example 1, experiments were conducted with varying process conditions, and the test results are reported in Table 1. In Table 1, the reactor inner diameter for Examples 1-8 was 120 cm, and the catalyst loading was adjusted based on the different bed height-to-diameter ratios. The reactor inner diameter for Comparative Example 1 was 70 cm, the reactor inner diameter for Comparative Example 2 was 28 cm, and the reactor inner diameters for Comparative Examples 3 and 4 were 22 cm. The catalyst loading for Comparative Examples 1-4 was the same as that for Example 1. The precious metal loadings for the catalysts in each of the Examples and Comparative Examples were essentially the same.

[0037] Table 1

[0038]

[0039] From the above test results, it can be seen that the selectivity of 1,3-propylene glycol in the comparative example is significantly reduced, and the utilization rate of glycerol and the economic efficiency of the product are affected.

[0040] It should be noted that the foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A production method for converting glycerol into a polyol and producing propylene glycol as a by-product, the method comprising: A fixed bed reactor is provided, wherein a catalyst bed is provided in the reactor; The height-to-diameter ratio of the catalyst bed is 0.02 to 0.5; The raw materials glycerol, water, and hydrogen are continuously fed into a fixed bed reactor, where the glycerol contacts the catalyst and reacts under the action of hydrogen to produce a mixture containing polyols and propanol; The mixture generated by the above reaction is drawn out of the fixed bed reactor for post-processing; Wherein, the polyol includes 1,2-propylene glycol and 1,3-propylene glycol, and the propanol includes n-propanol and isopropanol; The reaction conditions in the reactor are controlled as follows: the catalyst bed inlet reaction temperature is 120°C to 180°C, and the outlet temperature is 150°C to 250°C; the outlet temperature is 10°C to 30°C higher than the inlet reaction temperature; Control the operating pressure in the reactor to 2 MPa to 20 MPa; The selectivity of 1,3-propylene glycol is 40%-63%, and / or the molar conversion factor (TOF) of the catalyst is 20-65.

2. The method according to claim 1, wherein The operating pressure in the reactor is controlled to be 4 MPa to 15 MPa.

3. The method according to claim 1, wherein The mass concentration of glycerol in water during the feed is controlled to be 20%-80%.

4. The method according to claim 3, wherein: The mass concentration of glycerol in water during the feed is controlled to be 35%-60%.

5. The method according to claim 1 or 3, wherein: The molar ratio of hydrogen to glycerol in the feed is controlled to be 2-30:

1.

6. The method according to claim 5, wherein: The molar ratio of hydrogen to glycerol in the feed is controlled to be 5-15:

1.

7. The method according to claim 1, wherein The single-pass conversion rate of glycerol is controlled to be less than 60%.

8. The method according to claim 7, wherein: The single-pass conversion rate of glycerol is controlled to be 17% to 40%.

9. The method according to claim 1, wherein The catalyst is a catalyst loaded with precious metals.

10. The method according to claim 1, wherein The post-treatment includes a process of separating 1,3-propylene glycol from the mixture generated by the reaction.

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