Direct conversion of glycerol to acrylic acid on WOx / ZrOx and mixed metal oxides

Abstract

Acrylic acid is produced by dehydrating glycerol over a first mixed metal oxide catalyst in the presence of oxygen and water to produce acrolein and then oxidizing the acrolein over a second mixed metal oxide catalyst in the presence of oxygen and water to produce the acrylic acid. The first mixed metal oxide catalyst comprises oxides of tungsten and zirconium. The second mixed metal oxide catalyst includes a solid catalyst having the empirical formula AaVbNcXdOe, where A is at least one element selected from the group consisting of Mo and W, N is at least one element selected from the group consisting of Te and Se, and X is selected from the group consisting of Nb, Ta, Ti, Al, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ni, Pt, Bi, B, In, Ce, As, Ge, Sn, Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Hf, Pb, P, Pm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu, Au, Ag, Re, Pr, Zn, Ga, Pd, Ir, Nd A, V, N and X are present in amounts such that the atomic ratio of A: V: N: X is a: b: c: d, where a = 1, b = 0.1 to 2, c = 0.1 to 1, d = 0.01 to 1, and e depends on the oxidation states of the other elements in the second mixed metal oxide catalyst.

Description

Technical Field

[0001] The present invention relates to a process for the direct conversion of glycerol into acrylic acid. Background Art

[0002] Various methods for preparing acrylic acid are known in the art. Most commercial acrylic acid is produced using fossil fuel-based feedstocks, such as propylene. Starting from propylene, the process for producing acrylic acid is usually carried out in a two-step process, wherein in a first step propylene is converted to acrolein, which is then converted to acrylic acid in a second step. This process is very energy-intensive, requiring temperatures of up to 360° C. Most propylene is a product of fossil fuels.

[0003] US Patent No. 9,546,124 discloses a method for preparing acrylic acid from glycerol by reacting glycerol and a carboxylic acid to produce allyl alcohol, and then oxidizing the allyl alcohol to form a mixture of 3-hydroxypropionic acid and acrylic acid.

[0004] U.S. Patent No. 9,409,847 discloses a catalyst for liquid phase oxidative dehydration of glycerol to acrylic acid using hydrogen peroxide as an oxidant. The method uses a nanocrystalline copper supported α-MnO2 catalyst.

[0005] US Patent No. 8,748,545 discloses a method for producing acrylic acid from glycerol. Glycerol is subjected to a dehydration reaction over a solid acid catalyst.

[0006] While processes exist for producing acrylic acid from glycerol, it would be desirable to produce acrylic acid from renewable materials that can be easily scaled up to commercial quantities, such as biomass-derived feedstocks. Summary of the invention

[0007] The present invention relates to a process for preparing acrylic acid from glycerol.

[0008] According to one aspect of the present invention, a method comprises: dehydrating glycerol over a first mixed metal oxide catalyst in the presence of oxygen and water to produce acrolein; and oxidizing the acrolein over a second mixed metal oxide catalyst in the presence of oxygen and water to produce acrylic acid. The first mixed metal oxide catalyst comprises oxides of tungsten and zirconium. The second mixed metal oxide catalyst comprises an oxide having the empirical formula A a V b N c X d O eA solid catalyst, wherein A is at least one element selected from the group consisting of Mo and W, N is at least one element selected from the group consisting of Te and Se, and X is at least one element selected from the group consisting of Nb, Ta, Ti, Al, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ni, Pt, Bi, B, In, Ce, As, Ge, Sn, Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Hf, Pb, P, Pm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu, Au, Ag, Re, Pr, Zn, Ga, Pd, Ir, Nd, Y, Sm, Tb, Br, Cu, Sc, Cl, F and I. A, V, N and X are present in amounts such that the atomic ratio of A:V:N:X is a:b:c:d, wherein a=1, b=0.1 to 2, c=0.1 to 1, d=0.01 to 1, and e depends on the oxidation state of the other elements in the second mixed metal oxide catalyst. DETAILED DESCRIPTION

[0009] As used herein, the terms "one", "the", "at least one", and "one or more" are used interchangeably. The terms "comprising", "including", "containing" and variations thereof do not have a limiting meaning when these terms appear in the specification and claims. Thus, for example, a mixture comprising a polymerization inhibitor can be interpreted as the mixture comprising at least one polymerization inhibitor.

[0010] As used herein, the expression of numerical ranges by endpoints includes all numbers subsumed within the range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.). For purposes of the present invention, it is understood that numerical ranges are intended to include and support all possible subranges included within that range, consistent with the understanding of one of ordinary skill in the art. For example, a range of 1 to 100 is intended to express 1.1 to 100, 1 to 99.99, 1.01 to 99.99, 40 to 6, 1 to 55, etc.

[0011] As used herein, the recitation of numerical ranges and / or values, including such recitations in the claims, may be read to include the term "about." In such cases, the term "about" refers to numerical ranges and / or values ​​that are substantially the same as those recited herein.

[0012] The process of the present invention relates to a method for producing acrylic acid from glycerol.

[0013] In the process of the present invention, glycerol is dehydrated over a first mixed metal oxide catalyst in the presence of oxygen and water to produce acrolein.

[0014] The first mixed metal oxide catalyst is a solid catalyst comprising oxides of tungsten (W) and zirconium (Zr). The first mixed metal oxide catalyst may also contain at least one additional element selected from Co, Ni, Mo, Ti or a combination thereof. When the first mixed metal oxide catalyst contains at least one additional element, tungsten and zirconium are the main metal elements present. Preferably, based on the total weight of the metals in the first mixed metal oxide catalyst, the first mixed metal oxide catalyst comprises at least 75 wt.%, preferably at least 80 wt.%, more preferably at least 85 wt.%, even more preferably at least 90 wt.%, still more preferably at least 95 wt.%, and even more preferably at least 98 wt.% of tungsten and zirconium. Based on the total weight of the metals in the first mixed metal oxide catalyst, the first mixed metal oxide may contain 100 wt.% of tungsten and zirconium. When Co, Ni, Mo, Ti or a combination thereof is present in the first mixed metal oxide catalyst, the total amount of Co, Ni, Mo and Ti may be in the range of 2 wt.% to 25 wt.% based on the total weight of the metals in the first mixed metal oxide catalyst.

[0015] Acrolein produced by dehydration of glycerol is then oxidized over a second mixed metal oxide catalyst in the presence of oxygen and water to produce acrylic acid.

[0016] The second mixed metal oxide catalyst has the empirical formula A a V b N c X d O e A solid catalyst, wherein A is at least one element selected from the group consisting of Mo and W, N is at least one element selected from the group consisting of Te and Se, and X is Nb, Ta, Ti, Al, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ni, Pt, Bi, B, In, Ce, As, Ge, Sn, Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Hf, Pb, P, Pm, E At least one element from the group consisting of u, Gd, Dy, Ho, Er, Tm, Yb, Lu, Au, Ag, Re, Pr, Zn, Ga, Pd, Ir, Nd, Y, Sm, Tb, Br, Cu, Sc, Cl, F and I, wherein A, V, N and X are present in an amount such that the atomic ratio of A:V:N:X is a:b:c:d, wherein a=1, b=0.1 to 2, c=0.1 to 1, d=0.01 to 1, and e depends on the oxidation state of the other elements. Preferably, a=1, b=0.15 to 0.45, c=0.05 to 0.45, and d=0.01 to 0.1.

[0017] Preferably, the second mixed metal oxide comprises a metal oxide having the empirical formula Aa V b N c X d O e A solid catalyst wherein A is Mo, N is Te, and X is Nb.

[0018] The process can be carried out as a two-part process, wherein the dehydration of glycerol is carried out in a first reactor or a first part of a reactor and the oxidation of acrolein is carried out in a second reactor or a second part of a reactor. Preferably, the reactor comprises a single tube or a plurality of tubes, such as a tube sheet. Preferably one or more reactors are heated.

[0019] Preferably, the process is carried out in a single reactor. More preferably, the process is carried out in a single reactor comprising a catalyst bed selected from a stacked bed or a mixed bed.

[0020] In a stacked bed, a first mixed metal oxide catalyst and a second mixed metal oxide catalyst are positioned adjacent to each other in a reactor, with the first mixed metal oxide catalyst closest to the inlet of the reactor. In this configuration, glycerol is dehydrated to form acrolein, which then enters the second mixed metal oxide catalyst to form acrylic acid.

[0021] In a mixed bed, the first mixed metal oxide catalyst and the second mixed metal oxide catalyst are mixed together in a single bed. In this configuration, the dehydration and oxidation reactions occur over the entire length of the catalyst bed.

[0022] Preferably, the dehydration and oxidation reactions are carried out in the gas phase. The glycerol can then be condensed and separated from the by-products and unreacted glycerol. Preferably, the unreacted glycerol is recycled to the reactor.

[0023] In the dehydration of glycerol and the subsequent oxidation of the produced acrolein, oxygen may be present in the form of purified oxygen, oxygen from air, or lattice oxygen of the first mixed metal oxide catalyst and the second mixed metal oxide catalyst. Preferably, the oxygen comes from air or lattice oxygen of the first mixed metal oxide catalyst and the second mixed metal oxide catalyst. Preferably, no additional oxidant other than purified oxygen, oxygen from air, or lattice oxygen of the first mixed metal oxide catalyst and the second mixed metal oxide catalyst is present in the process.

[0024] The steps of dehydrating glycerol and oxidizing acrolein may be performed at a temperature ranging from 150°C to 450°C, preferably from 200°C to 400°C, and even more preferably from 250°C to 350°C.

[0025] The steps of dehydrating the glycerol and oxidizing the acrolein may be carried out at a pressure ranging from 1 bar to 5 bar, preferably from 1 bar to bar, and even more preferably from 1 bar to 2 bar. Most preferably, the process is carried out at atmospheric pressure.

[0026] Purification of acrylic acid may be achieved by one or more techniques known in the art, such as absorption using water or an organic solvent, extraction, fractional distillation, or melt crystallization.

[0027] Preferably, the glycerol is produced from a biomass-derived feedstock. Because all carbon atoms are present in the product acrylic acid, any biomass-derived carbon atoms in the glycerol will be present in the acrylic acid. Preferably, at least 90% by weight, more preferably at least 95% by weight, even more preferably at least 98% by weight, still more preferably at least 99% by weight, and yet more preferably 100% by weight of the acrylic acid in the product comprises carbon atoms from biomass-derived feedstock.

[0028] Example

[0029] The following examples illustrate the invention but are not intended to limit the scope of the claims.

[0030] Examples 1-5 –

[0031] In Examples 1 to 5, a feed containing glycerol-containing water having a composition shown in Table 1 was mixed with 80 sccm of air and 60 sccm of nitrogen and fed into a reactor tube including a stacked catalyst bed at 280° C. and atmospheric pressure. The stacked catalyst bed contained 3.6 cm 3 14 / 20 Mo a V b Nb c Te d 4.0cm on O 3 14 / 20 mesh WO x / ZrO x Catalyst, wherein a=1, b=0.15 to 0.45, c=0.05 to 0.45, and d=0.01 to 0.1. The reactor effluent was condensed in several traps immersed in an isopropanol / dry ice bath. The gaseous products downstream of the traps were analyzed on an SRI gas chromatograph. The condensed liquid products were analyzed on an HP 6890 gas chromatograph.

[0032] The reactor consisted of a 1 / 2" OD, 0.035" wall, 18" long 316 stainless steel tube with Swagelok fittings at each end that allowed the reactor tube to be connected to the system. The feed was supplied to each reactor via a set of Brooks mass flow controllers and a KD Scientific syringe pump or LC pump. Air and nitrogen were fed to the reactor via mass flow controllers, and a glycerol / water solution was fed via a KD Scientific LC pump. The catalyst sample was diluted 1:1 in a quartz chip and loaded into the center section (or upper and lower center sections) of the 1 / 2" OD reactor. The resulting mixed bed was supported below by quartz chips. After the catalyst / quartz chip mixture had been loaded, the remaining reactor volume was filled with quartz chips, which acted as a mixing and preheating zone. Inlet and outlet fittings were attached to the reactor tube, which was then pressure tested to 20 psig on a laboratory bench before installation in the reactor system. The reactor tube containing the catalyst was mounted in a furnace and tightly insulated to ensure adequate heat transfer.

[0033] Once the reactor tubes are installed in each reactor system, the system is isolated and pressure tested with nitrogen at 100 psig. If the reactor system does not maintain pressure, the system is depressurized (following the prescribed procedures) and all reactor fittings are tightened. The reactor system is then tested again. The process is continued until the reactor system is sealed at 100 psig. After the pressure test, the reactor is purged with nitrogen to remove residual air and the furnace temperature is raised to the initial test conditions. Once the reactor reaches the desired temperature in the flowing nitrogen, the syringe pump is started to induce the liquid feed flow and the air flow is induced at the desired flow rate. If necessary, the back pressure regulator is adjusted to maintain the desired reactor pressure. Once a complete feed flow is established, the reactor is operated (line out) for ~ 45 minutes according to the standard process before starting the experiment. The range of reaction temperature is 250°C-350°C. All experiments are carried out at atmospheric pressure.

[0034] Comparative Example 1 and Comparative Example 2

[0035] Comparative Examples 1 and 2 were prepared in a similar manner to Examples 1 to 5, except that a single mixed metal catalyst was used. A feed comprising water containing 20.97 wt % glycerol was mixed with 80 sccm air and 60 sccm nitrogen and fed at 280° C. and atmospheric pressure to a reactor comprising 3.6 cm 2 of the catalyst used in Examples 1 to 5. 3The reactor was condensed in a reactor tube containing a single bed of 14 / 20 mesh MoVNbTeO catalyst. The reactor effluent was condensed in several traps immersed in an isopropanol / dry ice bath. The gaseous products downstream of the traps were analyzed on an SRI GC. The condensed liquid products were analyzed on an HP 6890 GC.

[0036] Table 1

[0037]

Claims

1. A method, comprising: dehydrating glycerol over a first mixed metal oxide catalyst in the presence of oxygen and water to produce acrolein, oxidizing the acrolein over a second mixed metal oxide catalyst in the presence of oxygen and water to produce acrylic acid, wherein the first mixed metal oxide catalyst comprises oxides of tungsten and zirconium, and Wherein the second mixed metal oxide catalyst comprises a solid catalyst having the following empirical formula: A a V b N c X d O e in: A is at least one element selected from the group consisting of Mo and W, N is at least one element selected from the group consisting of Te and Se, and X is at least one element selected from the group consisting of Nb, Ta, Ti, Al, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ni, Pt, Bi, B, In, Ce, As, Ge, Sn, Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Hf, Pb, P, Pm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu, Au, Ag, Re, Pr, Zn, Ga, Pd, Ir, Nd, Y, Sm, Tb, Br, Cu, Sc, Cl, F and I, wherein A, V, N and X are present in an amount such that the atomic ratio of A:V:N:X is a:b:c:d, wherein a=1, b=0.1 to 2, c=0.1 to 1, d=0.01 to 1, and e depends on the oxidation state of the other elements in the second mixed metal oxide catalyst.

2. The method according to claim 1, wherein the steps of dehydrating the glycerol and oxidizing the acrolein are performed in a single reactor.

3. The process of claim 2, wherein the single reactor comprises the first mixed metal oxide catalyst and the second mixed metal oxide catalyst in a single bed selected from a stacked bed and a mixed bed.

4. The method of claim 3, wherein the single reactor comprises the first mixed metal oxide catalyst and the second mixed metal oxide catalyst in a stacked bed.

5. The method according to any one of the preceding claims, wherein the oxygen is present in the form of purified oxygen, air or lattice oxygen of the mixed metal oxide.

6. A method according to any one of the preceding claims, wherein the process is carried out in the gas phase.

7. The process according to any one of the preceding claims, wherein the oxygen in the steps of dehydrating the glycerol and oxidizing the acrolein and / or the lattice oxygen of the first and second mixed metal oxide catalysts are the only oxidants present in the process.

8. The process according to any one of the preceding claims, wherein the acrylic acid is produced from a biomass-derived feedstock.

9. The method of claim 8, wherein at least 90% of the carbon atoms in the acrylic acid are derived from biomass-derived feedstock.

10. A method according to any one of the preceding claims, wherein A is Mo, N is Te, and X is Nb.

11. The method according to any one of the preceding claims, a=1, b=0.15 to 0.45, c = 0.05 to 0.45, and d = 0.01 to 0.

1.

12. The process according to any one of the preceding claims, wherein the steps of dehydrating the glycerol and oxidizing the acrolein are carried out at a pressure ranging from 1 bar to 5 bar.

13. The process according to any one of the preceding claims, wherein the steps of dehydrating the glycerol and oxidizing the acrolein are carried out at a temperature ranging from 150°C to 450°C.

14. The process according to any one of the preceding claims, wherein the steps of dehydrating the glycerol and oxidizing the acrolein are performed in a single step.

15. A process according to any one of the preceding claims, further comprising recycling unreacted glycerol to the dehydration step.

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