Method for directly synthesizing unsaturated aldehydes from alcohol mixtures

Patent metadata

Field	Value
Publication number	US-9365478-B2
Application number	US-201314437565-A
Country	US
Kind code	B2
Filing date	Oct 17, 2013
Priority date	Oct 29, 2012
Publication date	Jun 14, 2016
Grant date	Jun 14, 2016

Abstract

The present invention concerns a method for directly synthesizing acrolein or methacrolein from a mixture of methanol and ethanol or propanol. The method of the invention comprises two successive phases: oxidation in the presence of a selective oxidation catalyst of the light alcohols of the feedstock, then condensation by aldolization of the aldehydes formed during oxidation in the presence of a condensation catalyst (aldolization). Alternatively, the two phases can be carried out in the presence of a single catalyst, in particular in the presence of a molybdenum-based selective oxidation catalyst. These two phases can be conducted in a single reactor or in two cascade reactors.

First claim

The invention claimed is:

1. A process for the direct synthesis of an unsaturated aldehyde of formula CH 2 ═C(R)—CHO, wherein R represents H or CH 3 , from a feedstock containing an alcohol mixture comprising methanol and a second alcohol of formula R—CH 2 —CH 2 OH, the process comprising:
introducing the alcohol mixture, oxygen and an unreactive diluent gas into a reaction system comprising a solid selective oxidation catalyst chosen from molybdenum-based catalysts and optionally a solid aldol condensation catalyst, wherein said reaction system is operated in the gas phase at a temperature of between 200 and 400° C. and under a pressure of between 1 and 10 bar absolute, and wherein the alcohol mixture and the oxygen each represent at most 10% of a total volume of a reaction mixture in the reaction system, and
recovering a gaseous effluent comprising the formed unsaturated aldehyde and water, coproduced by the reaction, at an outlet of the reaction system.

2. The process as claimed in claim 1 , wherein the oxidation catalyst is represented by the general formula:
A a X b Mo c Z d O e   (I)

wherein:
A is at least one cation selected from the group consisting of the elements of Groups 1 to 16 of the Periodic Table of the Elements and the lanthanides,
X is P or Si,
Z is at least one element selected from the group consisting of W, Ti, Zr, V, Nb, Ta, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, In, Tl, Sn, Ag, As, Ge, B, Bi, La, Ba, Sb, Te, Ce and Pb,
O is oxygen,
a, b, c and d are indices consisting of integers or decimals corresponding to the following ranges:
0≦a≦9
0≦b≦2
0<c≦12
0≦d≦12
such that a+b+d>0,
and e is a number determined by the total degree of oxidation of the elements.

3. The process as claimed in claim 2 , wherein the oxidation catalyst is an iron molybdate corresponding to the general formula (I), with the value of the indices a and b being 0 and the value of the index d not being 0.

4. The process as claimed in claim 1 , wherein the condensation catalyst is selected from the group consisting of alkali metal hydroxides LiOH, NaOH, KOH, or CsOH deposited on a silica or alumina support; alkali metals and alkaline earth metals dispersed on silica, alumina, magnesia, charcoal or potassium carbonate; LiCO 3 deposited on silica; and t-BuOK deposited on xonotlite.

5. The process as claimed in claim 1 , wherein the condensation catalyst is selected from sodium silicate deposited on silica or on aluminosilicate and further comprising a metal promoter and cesium deposited on silica grafted with or doped by a zirconium compound.

6. The process as claimed in claim 1 , wherein the condensation catalyst is selected from the group consisting of
i) SiO 2 —MgO, SiO 2 —CaO, SiO 2 —SrO, SiO 2 —BaO, SiO 2 —SnO, SiO 2 —ZnO, SiO 2 —Al 2 O 3 , SiO 2 —ThO 2 , SiO 2 —TiO 2 , SiO 2 —ZrO 2 , SiO 2 —MoO 3 , SiO 2 —WO 3 , Al 2 O 3 —MgO, Al 2 O 3 —ThO 2 , Al 2 O 3 —TiO 2 , Al 2 O 3 —ZrO 2 , Al 2 O 3 —MoO 3 , Al 2 O 3 —WO 3 , ZrO 2 —ZnO, ZrO 2 —TiO 2 , TiO 2 —MgO, or ZrO 2 —SnO 2 ,
ii) hydrotalcites, hydroxyapatites, chrysolite and sepiolite, optionally doped with alkali metals and other metals,
iii) rare earth metal oxides doped with alkaline earth metals,
iv) mixed oxides of the mixed cobalt and aluminum phosphate type,
v) silicas-aluminas doped with salts of Na, K, Cs, Cd, Mg, Ca, Sr, Mn, Zn, Mo, Nb, Pb and/or Si,
vi) MgO-alumina or MgO—SiO 2 ,
vii) rare earth metals in the form of phosphates, tungstates or molybdates, and
viii) mixed oxynitrides of vanadium-aluminum, phosphorus-zirconium, phosphorus-aluminum, vanadium-aluminum-phosphorus or gallium-aluminum-phosphorus.

7. The process as claimed in claim 1 , wherein the process is carried out at a temperature of between 250 and 350° C. under a pressure of between 1 and 5 bar absolute.

8. The process as claimed in claim 1 , wherein the rate of introduction of the alcohol mixture into the reaction system is such that the total content of alcohols in the reaction medium is between 4 and 10%, expressed by volume.

9. The process as claimed in claim 1 , wherein for the alcohol mixture, the methanol/second alcohol molar ratio is between 0.8 and 2.

10. The process as claimed in claim 1 , wherein the reactions are carried out with an HSV of between 2000 and 40 000 h −1 .

11. The process as claimed in claim 1 , wherein the reactions are carried out in a single reactor with a catalytic bed comprising a single molybdenum-based oxidation catalyst or a physical mixture of a molybdenum-based oxidation catalyst and a condensation catalyst.

12. The process as claimed in claim 1 , wherein the reaction system contains both a molybdenum-based oxidation catalyst and a solid aldol condensation catalyst.

13. The process as claimed in claim 12 , wherein the reactions are carried out in a single reactor with two superimposed catalytic beds, the oxidation catalytic bed being placed upstream.

14. The process as claimed in claim 12 , wherein the reaction system comprises two reactors, the first reactor serving to simultaneously oxidize the two alcohols, and the second reactor serving for the cross-condensation of the two aldehydes contained in the outlet effluent from the first reactor and for the dehydration of the aldol formed.

Assignees

• Dubois Jean-Luc
• Capron Mickaël
• Dumeignil Franck
• Arkema France

Inventors

• Dubois Jean-Luc
• Capron Mickaël
• Dumeignil Franck

Classifications

• C07C45/75

  Reactions with formaldehyde · CPC title

• C07C47/21

  with only carbon-to-carbon double bonds as unsaturation · CPC title

• C07C45/38 Primary

  being a primary hydroxyl group · CPC title

• C07C47/22

  Acryaldehyde; Methacryaldehyde · CPC title