WO2008052993A2

WO2008052993A2 - Process for production of acrolein and other oxygenated compounds from glycerol in a transported bed reactor

Info

Publication number: WO2008052993A2
Application number: PCT/EP2007/061695
Authority: WO
Inventors: Paul O'connor; Avelino Corma Camos; George Huber; Louis Andre Savanaud
Original assignee: Bioecon International Holding NV
Current assignee: Bioecon International Holding NV
Priority date: 2006-11-01
Filing date: 2007-10-30
Publication date: 2008-05-08
Anticipated expiration: 2009-05-01
Also published as: WO2008052993A3

Abstract

Disclosed is a process for the production of acrolein and other oxygenated compounds from glycerol. Use is made of an acidic catalyst in a moving bed reactor at 200 - 650°C.

Description

Invention Title

Process for production of acrolein and other oxygenated compounds from glycerol in a transported bed reactor

Field of Invention

This invention relates to a process for production of acrolein and other oxygenates from glycerol with acidic solid materials in a transported bed reactor. Background of Invention

Biodiesel production is increasing worldwide as our society looks to overcome problems caused by our dependence on fossil fuels (Bendz 2005; Knothe, Krahl et al . 2005; Huber, Iborra et al . In Press). Biodiesel, also called fatty acid methyl esters or FAME, is produced by transesterification of vegetable oils (triglycerides) and methanol with glycerol produced as a byproduct with a molar ratio of 1:1 glycerol to triglyceride (Bendz 2005; Knothe, Krahl et al . 2005; Huber, Iborra and Corma 2006). It is estimated that approximately 80 % of the biofuels in Europe are biodiesel (Bendz 2005) . Glycerol is currently a valuable by-product of biodiesel production. As biodiesel production increases the price of glycerol is projected to significantly drop, and the price of glycerol has already dropped by almost half over the last few years (McCoy 2005) . Therefore it is desirable to develop inexpensive processes for the conversion of glycerol into valuable chemicals. The glycerol by-product from a biodiesel plant contains a number of impurities including water, soaps, bases, and salts. The concentration and level of these impurities will depend on the type of process that is used for biodiesel production.

Processes for production of acrolein by dehydration of glycerol with solid acid catalysts have been known since at least 1918 (Sabatier and Gaudion 1918) . Acrolein is a valuable chemical and is used to produce a wide range of chemicals, including acrylic acid, acrylic acid esters, superabsorber polymers, and detergents. In 1918 Sabatier and Gaudion produced acrolein from glycerol by dehydration in the gas-phase with both AI2O3 and UO2 catalysts at 360 and 350⁰C, respectively (Sabatier and Gaudion 1918) . A 10 % acrolein yield was observed, with other products being ethanol, water and allyl alcohol.

In 1928 Freund patented a process for producing unsaturated organic compounds by dehydration with siliceous clays or other aluminum magnesium hydrosilicates (Freund 1928) . In one of the examples for the patent Freund observed that pure acrolein could be produced from glycerol at 180⁰C using diatomaceous silica (Freund 1928), with no indications on the by-products formed.

In 1948 Hoyt and Manninen patented a method for production of acrolein from glycerol water mixtures (Hoyt and Manninen 1951). The glycerol-water solution was treated with a solid phosphoric acid catalyst. The solid acid catalyst was prepared by impregnating 100 parts of a solid catalytic support with 3-25 parts of orthophosphoric acid, meta-phosphoric acid, pyrophosphoric acid or phosphorus pentoxide (Hoyt and Manninen 1951). According to Fougret et al . , phosphoric acid supported on Tiθ2, Siθ2 and Siθ2-Tiθ2 have H₀ (Hammett acidity function) from -3.0 to -8.2 depending on the proportion of the different forms of phosphoric acid supports (Fougret, Atkins et al . 1999). Pure AI2O3 has a H₀ around +1 (Jansen, Palmieri et al . 1996) . Therefore, it is likely that phosphoric acid support on AI2O3 would have Ho from +1 to -8.2, depending on the proportion of the different forms of phosphoric acid relative to the support. Solid phosophoric acid catalysts are well known acid catalysts, and have been used industrially since 1930(Eglorr 1936; Fougret, Atkins et al . 1999; Coetzee, Mashapa et al . 2006). In Hoyt and Manninen's patent they claim that finely divided carbon, activated carbon, coke, asbestos, silica gel and activated alumina can all be used as catalyst supports for phosphoric acid. Overall yields of 72 % of acrolein from a 95 wt% glycerol solution (5 % water) at 286 ⁰C were observed. A petroleum oil fraction, with a boiling point between 300 and 400⁰C, was used as a solvent in this reaction. They claim temperatures of 250 - 325 ⁰C are good for the dehydration reaction. The composition of the other products of this reaction is not described. In 1949 Heinemann et al . studied the dehydration of organic compounds (including glycerol) with activated bauxite catalysts (Heinemann, Wert et al . 1949). Bauxites are abundant and relatively inexpensive catalysts, used for drying and for dehydration reactions. The major components of bauxites are Al₂O₃, SiO₂, TiO₂, and Fe₂O₃. These are well known to be Lewis Acid catalysts, and it is likely that H₀ varies from +1 (the value for Al₂O₃) to -24 (value for zeolite catalysts) (Jansen, Palmieri et al . 1996; Haw 2002) . Heinemann et al . observed acrolein yields of up to 42 % from glycerol using Bauxite catalysts by gas-phase reactions at 430⁰C (Heinemann, Wert et al . 1949). In 1993, Degussa patented a process to produce acrolein by dehydration of glycerol in the liquid or gaseous phase with solid acidic catalysts (Neher, Haas et al . 1995). They claim that aqueous solutions from 10-40 wt% glycerol can be converted to acrolein at 180-340⁰C in the liquid phase or 250-340⁰C in the gaseous phase. For gas-phase dehydration they tested phosphoric acid supported on AI2O3 as a catalyst. As was said above, phosphoric acid on alumina was already shown by Hoyt et al to be an effective catalyst for acrolein production (Hoyt and

Manninen 1951). Gas-phase dehydration of glycerol at 300⁰C with this catalyst gave acrolein yields of 70 and 65 % as the concentration of glycerol increased from 10 to 40 wt%

(Neher, Haas et al . 1995) . Dehydration of glycerol was also done in the liquid phase with H-ZSM-5, Na-ZSM-5, mordenite, LisPC^ and FePθ4. However acrolein yields were lower in the liquid phase than in the gas phase, with the highest liquid phase yield being 36 %.

Acrolein can also be prepared from glycerol using sub- and supercritical water (Ramayya, Brittain et al . 1987; Buhler, Dinjus et al . 2002; Ott, Bicker et al . 2006) or with homogenous catalysts (Drent and Jager 2000). The maximum acrolein yield with sub-and supercritical water was reported to be 37.5 % at 360⁰C, 25 MPa, and 470 ppm (g g^"1) of zinc sulfate by Ott et al . (Ott, Bicker et al . 2006).

All the processes described above involve solid acid catalysts and use fixed bed reactors. It is stated that the catalyst deactivation with pure feeds is low enough to carry out this type of operation (Neher, Haas et al . 1995) . Nevertheless, the presence of contaminants, especially basic contaminants from the production of biodiesel and the possible secondary reactions of glycerol cracking products may produce coke that deactivate the catalyst, which then needs to be regenerated.

The method of the present invention has a number of advantages over prior art processes. Our process can process glycerol solution in whatever concentration, with only small changes in selectivity and activity of the catalyst; it does not need any co-solvent to carry out the reaction; and continuously regenerates the catalyst so that catalyst activity can be maintained over large periods of time, even with contaminated feeds. Furthermore, the less valuable heavy by-products of the reaction can be burned inside the process, thus generating the heat that is necessary to carry out the process, as water vaporization requires large heat input. Thus, we have found that using solid acid catalysts in transported bed reactors, and working at short contact times between the gaseous products and the catalysts offer clear advantages over previous technologies from the point of view of selectivity to acrolein and other oxygenates and the continuous regeneration of the catalyst.

Summary of Invention

This invention relates to a process for the production of acrolein and other oxygenates by dehydration of glycerol.

The glycerol feed may be in the form of pure glycerol, a glycerol-water mixture, or glycerol-containing solutions produced in the transesterification of vegetable oils. The process is carried out in a transported bed reactor. The transported bed reactor preferably is part of a continuous process whereby, in a first step, salts present in the feed are removed from this by adsorption ion exchange or by evaporating the feed. The resulting feed is mixed with a catalyst and passed through a heated zone. The catalyst and reaction products are separated, and the catalyst is continuously regenerated. The catalyst used is a solid acid catalyst (either Brδnsted or Lewis acid) . ZSM-5 zeolite is preferably included as the main catalyst component. One of the requirements is the use of a transported bed at high space velocities, with continuous regeneration of the catalysts a desired embodiment.

Brief Description of the Figure

Fig. 1 is a schematic representation of the production of acrolein from glycerol. The glycerol is first purified to remove any bases, salts or other impurities that may poison the catalyst. The catalyst is circulated from the regenerator (Reactor 1) to the glycerol dehydration transported reactor (Transported bed reactor 21), followed by the stripper (Reactor 3) , which separates the reaction products from the catalyst. The catalyst is returned to the regenerator in order to burn coke on the catalyst surface to provide process heat and regenerate the catalyst. Optionally a part of the catalyst may be recycled from the stripper to the reactor without regeneration.

Detailed Description of Invention

The present invention relates to a process for the production of dehydrated oxygenated compounds comprising contacting a glycerol-water solution containing from 10-100 wt% glycerol with an acidic solid catalyst in a moving bed reactor at 200-650⁰C.

The glycerol may be in an aqueous solution (from 10 to 100 wt% glycerol) , which definition includes pure glycerol. Specifically, the glycerol solution may be a byproduct of biodiesel production from transesterification of vegetable oils. A glycerol solution from a biodiesel process is first neutralized to remove bases and salts that may poison the catalyst. To improve downstream processing,

(additional) water may be added to the glycerol feed. The glycerol solution is contacted with a catalyst react in a moving bed reactor, typically transported by a vapor lift, as shown in Figure 1. The temperature of the moving bed reactor may range from 200-650⁰C, more specifically from 290 to 400⁰C. Contact time is in the range of 0.005 to 5 seconds. Catalyst-to-glycerol weight ratios are in the range of from 2 to 100, preferentially from 5 to 20. At a suitable height in the reactor the glycerol feed is contacted with the catalyst by convenient means, such as a multiple spray nozzles that ensure a good distribution of the feed through the reactor. Such injection devices are well known to those trained in the art of the fluid catalytic cracking processes. Gas products and catalyst are then transported through the reactor 21 to the stripper 3, where the catalyst and the gas products are separated. Separation means are the same as those used in fluid catalytic cracking. The catalyst is then passed to a regenerator where the coke is burned off the catalyst, which provides process heat for evaporating the feed (to remove salts) , as well as for carrying out the reaction, which is endothermic. The heat necessary to carry out the reaction depends on the thermal properties of the glycerol solution, in particular the water/glycerol ratio, as water and glycerol have rather different properties. As an example we present in table 1 the approximate amount of coke that needs to be generated for the process to be autothermal, in the same way a Fluid Catalytic Cracking process is autothermal. The coke yields are given as weight percent of the glycerol solution fed into the reactor and also as weight percent of the carbon in the feed. A process temperature of 350 ⁰C was assumed.

Table 1 - Coke make-up for autothermal acrolein production process at 350⁰C

As in FCC units, the reaction products preferably are separated from the catalyst in a separate reactor.

Coke removal preferably includes burning the coke in an oxygen-containing gas, such as air, whereby the required heat is produced. For example, coke may be burned off in flowing air at a temperature in the range of from 400 to 700 ⁰C.

Suitable solid acid catalysts for this process include: (1) amorphous or crystalline alumina-silicates, as for instance amorphous silica-alumina or zeolites, (2) fluid catalytic cracking catalysts, such as Y-zeolite in a silica-alumina matrix, or commercial equilibrium FCC catalysts, (3) oxidic catalysts such as AI2O3, Zrθ2, ZrSO₄, Tiθ2, Siθ2, Siθ2-Al₂θ3, and mixtures thereof; (4) supported phosphoric acid or heteropolyacid materials. Examples of suitable zeolites include ZSM-5, in particular H-ZSM-5, mordenite, montmorillonite, zeolite beta, Y-zeolite, and mixtures thereof.

Examples of supported catalysts include catalysts comprising a carrier, for example an oxidic or siliceous carrier, coated with a mono-, di-, or polybasic inorganic acid or with an acid salt of an inorganic acid. Preferred are carriers such as carbon, AI2O3, Tiθ2, or Siθ2, coated with phosphoric acid.

Examples

The following Examples are included solely to provide a more complete disclosure of the subject invention. Thus, the following Examples serve to illuminate the nature of the invention, but do not limit the scope of the invention disclosed and claimed herein in any fashion.

Data were obtained in a Microdowner unit (Corma et al. 2003) . Reactor was 1.1 meter long and had an internal diameter of 0.9 cm. Nitrogen was used as a dispersion medium for the feed and for the transport of the solid from the catalyst preheater to the reactor. Nitrogen flow was 8 weight % of the feed. "Conversion" means the glycerol conversion. Product selectivities are reported on a per carbon basis.

Example 1 :

The glycerol solution (50/50 wt% glycerol/water) was dehydrated at 350 ⁰C and a gas residece time of 0.5 s as shown as Experiment Number 1 in Table 2. A commercial FCC additive based on ZSM-5 zeolite (ZSM-5) was used as a catalyst. It contained around 15 % zeolite and had a BET area around 70 m²/g. A clay binder was used to shape the catalyst as 60-100 μm microspheres. At these conditions an acrolein selectivity of 57 % was observed. The other major oxygenates produced were acetaldehyde, acetone, 2- hydroxypropenal (first dehydration product from glycerol) , with metacrolein, dioxanes, furans and polyols also being produced in trace amounts. The total yield of oxygenated products was 82 %.

Table 2 Operating conditions, conversion and product selectivities for micro-downer reactor experiments with ZSM-5 zeolite based catalyst

fOther oxygenates involve a wide spectrum of oxygenates including furans and dioxans with 0 to 3 methyl substituents . Example 2 :

The glycerol solution of Example 1 was dehydrated at 290⁰C (the glycerol boiling point temperature) and the following operating conditions: 290⁰C, CTO = 6.5, gas residence time 1.0 s. The ZSM-5 based catalyst of Example 1 was used

(Experiment Number 2 in Table 1) . At these conditions the acrolein selectivity was 57%. The total yield of oxygenates was 75%. Coke yield was higher (16%) due to the lower process temperature, which decreased the desorption rate from the catalyst surface.

Example 3 :

The glycerol solution was dehydrated at typical vacuum gas- oil cracking conditions (500 ⁰C, CTO = 11.7, gas residence time 0.8 s) with ZSM-5 as shown as Experiment Number 3 in Table 1. At these conditions 40 % of the glycerol was converted into acrolein, 22% to ethanal, with a total oxygenates yield of 68 %. The selectivity to oxygenates may be tuned to the most desired products by changing the operating conditions, while the conversion of glycerol to valuable products remains high.

Example 4 :

A 20% glycerol solution was dehydrated at 350 ⁰C, CTO 12, and residence time around 0.8 second. The ZSM-5 catalyst of example 1 was used. Acrolein selectivity rose to 61%, ethanal selectivity was 9 %, and total oxygenates yield was 79%. Considering the 16 % coke selectivity, the carbon selectivity to acrolein among the products that exited the reactor was 73%. Example 5 :

A 85% glycerol solution was dehydrated at similar conditions to those in example 4 (350 ⁰C, CTO 10, residence time 0.8 second) and with the same catalyst as in example 1. This concentration is typical of the glycerol solutions that are obtained from a biodiesel plant. Acrolein selectivity was 56%, ethanal selectivity was 5 % and total oxygenates yield was 74%. These tests show that it is possible to process a glycerol/water stream with a broad range of concentrations while the selectivity towards acrolein is maintained between 56 and 61%.

Example 6 :

In this test a commercial FCC equilibrium catalyst was used. It had a BET area of 110 m2/g, and contained 10 % of Y zeolite as measured by XRD. A 50% glycerol solution was dehydrated under the same conditions to those of example 3 (500 ⁰C, CTO 12, residence time 0.8s) as shown in table 3. Acrolein selectivity was 32% and ethanal selectivity 9%. Coke selectivity increased compared to the ZSM-5-based catalyst, and represented 21% with Ecat under these conditions. Among the C1-C4 gases, a significant amount of propene (5% of carbon mass balance) was detected.

Table 3 Operating conditions, conversion and product selectivities for micro-downer reactor experiments with FCC equilibrium catalyst and beta zeolite based catalyst

Example 7 :

In this example a catalyst based on beta zeolite was used. It contained 20 % beta zeolite embedded in a silica/alumina matrix, and had a BET area of 190 m2/g. A 50% glycerol solution was processed on this catalyst with the following operating conditions: 350 ⁰C, CTO 12, and residence time around 0.8 second. This sample gave a 38 % selectivity to acrolein, a 9% selectivity to ethanal and a 35% selectivity to coke. This last selectivity may be due to the high surface area of the catalyst sample.

References Cited

Bendz, K. (2005) . EU-25 Oilseeds and Products Biofuels situation in the European Union 2005, USDA Foreign Agricultural Service.

Buhler, W., E. Dinjus, et al . (2002). "Ionic reactions and pyrolysis of glycerol as competing reaction pathways in near- and supercritical water." Journal of Supercritical Fluids 22: 37-53.

Canos, A. C, L. L. A. Sauvanaud, et al . (2003). Test Unit for Studying Catalysts in Reactions Involving a Short

Contact Time Between the Catalyst and the Reagents. WO

03/043726 Al. International, Consejo Superior de

Investigaciones Cientificas.

Coetzee, J. E., T. N. Mashapa, et al . (2006). "An improved solid phosphoric acid catalyst for alkene oligomerization in a Fischer-Tropsch refinery." App . Catal. A 308: 204-209.

Drent, E. and W. W. Jager (2000) . Hydrogenolysis of Glycerol. US Patent 6080898. USA, Shell Oil Company.

Eglorr, G. (1936). Ind. Eng. Chem. 28 (12) : 1461-1467.

Fougret, C. M., M. P. Atkins, et al . (1999). "Influence of the carrier on the catalytic performance of impregnated phosphoric acid in the hydration of ethylene." App. Catal. A 181: 145-156.

Freund, E. (1928). Production of Unsaturated Organic Compounds. US Patent 1672378. USA, Chemische Fabrik Auf Actien.

Haw, J. F. (2002) . "Zeolite acid strength and reaction mechanisms in catalysis." Phys . Chem. Chem. Phys . 4: 5431-5441. Heinemann, H., R. W. Wert, et al . (1949). "Organic

Dehydration Reactions Using Activated Bauxite."

Industrial and Engineering Chemistry 41(12): 2928- 2931.

Hoyt, H. E. and T. H. Manninen (1951) . Production of Acrolein from Glycerol. US Patent 2558520. USA, U.S. Industrial Chemicals.

Huber, G. W., S. Iborra, Corma, A. (2006). "Synthesis of transportation fuels from biomass: chemistry, catalysts and engineering." Chemial Reviews.

Jansen, S., M. Palmieri, et al . (1996). "Acid catalysts based on Cu/Ru alumina: conversion of butyraldehyde to dibutyl ether." J. Catal . 163(2): 262-270.

Knothe, G., J. Krahl, et al . (2005). The Biodiesel Handbook. Champaign, Illinois, AOCS Press.

McCoy, M. (2005). "An Unlikely Impact." Chem. Eng. News. 83 (8) : 19-20.

Neher, A., T. Haas, et al . (1995). Process for the production of acrolein. US Patent 5387720. USA, Degussa Aktiengesellschaft .

Ott, L., M. Bicker, et al . (2006). "Catalytic dehydration of glycerol in sub- and supercritical water: a new chemical process for acrolein production." Green Chemistry 8: 214-220.

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Claims

1. A process for the production of dehydrated oxygenated compounds comprising contacting a glycerol-water solution containing from 10-100 wt% glycerol with an acidic solid catalyst in a moving bed reactor at 200-650⁰C.

2. The process of claim 1 wherein the dehydrated oxygenated compounds comprise acrolein.

3. The process of claim 1 or 2 wherein the contact time of the glycerol-water solution with the catalyst is in the range of 0.005 to 5 seconds.

4. The process of any one of the preceding claims wherein the catalyst to glycerol weight ratio is in the range of 2 to 100.

5. The process according to any one of the preceding claims wherein the glycerol-water solution is a byproduct of a transesterification of vegetable oils.

6. The process according to any one of the preceding claims wherein the acidic solid catalyst comprises a zeolite selected from the group consisting of H-ZSM-5, mordenite, montmorillonite, zeolite beta, Y-zeolite, and mixtures thereof.

7. The process according to any one of the preceding claims wherein the acidic solid catalyst comprises a Y- zeolite in a silica-alumina matrix.

8. The process according to any one of the preceding claims wherein the acidic catalyst comprises AI2O3, ZTO₂, ZrSO₄, TiO₂, SiO₂, SiO₂-Al₂O₃, or mixtures thereof.

9. The process according to any one of the preceding claims wherein the acidic solid catalyst comprises an oxidic or siliceous carrier coated with a mono-,di-, or polybasic inorganic acid, or with an acid salt of an inorganic acid.

10. The process according to claim 9 wherein the solid acid catalyst comprises Al₂O₃, carbon, TiO₂ or SiO₂ coated with phosphoric acid.

11. The process according to any one of the preceding claims wherein the moving bed reactor is a fluid catalytic cracker and the glycerol solution is co-fed into the reactor with vacuum gas-oil.

12. The process according to any one of the preceding claims wherein the solid acid catalyst has a carbon deposit .

13. The process according to any one of the preceding claims wherein the reaction products are separated from the catalyst in a separate reactor.

14. The process according to any one of the preceding claims comprising an additional step of removing coke from the catalyst in flowing air at 400-700⁰C.

15. The process according to any one of the preceding claims comprising an additional step of adding water to the glycerol feed.

16. The process according to any one of the preceding claims comprising an additional step of removing impurities from the glycerol feed by neutralization.

17. The process according to any one of the preceding claims comprising an additional step of removing impurities from the glycerol feed by ion exchange.