Reactor and process for producing alkyl (meth)acrylates

Patent metadata

Field	Value
Publication number	US-11858890-B2
Application number	US-202217804057-A
Country	US
Kind code	B2
Filing date	May 25, 2022
Priority date	May 28, 2021
Publication date	Jan 2, 2024
Grant date	Jan 2, 2024

Abstract

A novel process can be used for a heterogeneously catalysed oxidation reaction, in the presence of a pulverulent noble metal-containing catalyst, where (meth)acrolein, an alkyl alcohol, in particular methanol, and an oxygen-containing gas are converted to an alkyl (meth)acrylate, in particular methyl (meth)acrylate. A corresponding reactor suitable for performing the reaction is also useful. The process allows for an effective retention of the particulate catalyst and the continuous discharge of fines fractions of the catalyst powder which are present, particularly in a fresh catalyst batch as a consequence of its preparation. Such fines fractions may also be produced by abrasion during the reaction. The process allows for effective recycling, recovery, and utilization of these discharged catalyst fractions.

First claim

The invention claimed is:

1. A process for producing alkyl (meth)acrylates, comprising:
reacting (meth)acrolein with an alkyl alcohol in a reactor, in the presence of an oxygen-containing gas and a particulate, pulverulent catalyst in a liquid phase, to obtain an alkyl (meth)acrylate;
wherein a reaction medium is discharged from the reactor during the reaction, wherein the reaction medium comprises a first portion of the catalyst and a product solution, wherein the first portion of the catalyst is discharged in a classifying manner,
wherein a second portion of the catalyst remaining in the reactor has a higher particle size distribution compared to the first portion of the catalyst,
wherein the first portion of the catalyst is collected in at least one filter,
wherein, optionally, the first portion of the catalyst is at least partially recycled into the reactor, and
wherein, optionally, the first portion of the catalyst is at least partially removed and sent to a workup for recovery of at least one employed catalyst metal of the catalyst.

2. The process according to claim 1 , wherein the catalyst is a fresh catalyst which comprises gold or palladium as a central active oxidation metal in a concentration of between 0.1% by weight and 10% by weight, based on a total weight of the catalyst, wherein the catalyst includes a further support material,
wherein particles of the catalyst have a size of 0.1 to 300 μm, wherein more than 95% by volume of the particles present have a size of less than 200 μm, and
wherein more than 50% by volume of the particles have a size between 10 and 90 μm, and
wherein a fines fraction of the particles in the reactor having a size of 0.1 μm to 10 μm is less than 10% by volume.

3. The process according to claim 1 , wherein less than 0.5% by weight per hour of the catalyst present in the reactor is discharged from the reactor,
wherein in the second portion of the catalyst remaining in the reactor after 1000 operating hours, more than 98% by volume of all catalyst particles have a particle size greater than 10 μm,
wherein the first portion of the catalyst is collected in the at least one filter which allows retention of particles of 1 to 30 μm in size, and
wherein catalyst particles retained in further filters downstream of an inclined settler are to an extent of more than 50% by volume of particles smaller than 30 μm.

4. The process according to claim 1 , wherein the catalyst has an average particle size distribution of 30 to 100 μm, and wherein a fines fraction of the first portion of the catalyst discharged in the reaction medium has an average particle size distribution of 1 to 15 μm.

5. The process according to claim 1 , wherein the alkyl alcohol is methanol and the alkyl (meth)acrylate is methyl methacrylate (MMA).

6. The process according to claim 5 , wherein the first portion of the catalyst comprises at least 50% by volume of particles smaller than 30 μm and is continuously discharged from the reactor, and is supplied to the at least one filter in a suspended form in the reaction medium containing the MMA, methacrylic acid, water, and the methanol.

7. The process according to claim 5 , wherein the reaction medium exiting the reactor has an MA content of more than 20% by weight and less than 50% by weight, has a water content of between 1% and 15% by weight, and contains less than 20% by weight of unconverted methacrolein.

8. The process according to claim 1 , wherein the reaction medium is discharged to a combination of at least one classifying sedimentation apparatus and at least 2 filters continuously traversed by the reaction medium, and
wherein a first filter of the at least 2 filters after the at least one classifying sedimentation apparatus has a lower retention capacity than a subsequent second filter of the at least 2 filters.

9. The process according to claim 8 , wherein the at least one classifying sedimentation apparatus is installed within a reactor shell of the reactor, and wherein at least one downstream filter is arranged outside the reactor shell.

10. The process according to claim 1 , wherein a final filter upstream of a next process operation has a retention capacity for particles smaller than 10 μm, with a result that less than 1 ppm of catalyst particles having a diameter greater than 10 μm pass into the next process operation.

11. The process according to claim 1 , wherein the reactor has a ratio of diameter to height of a gasified liquid level of between 1:1 and 1:50,
wherein the reactor contains a zone A and at least one zone B, and wherein present at a transition from zone A to each of the at least one zone B are internals which homogenize flow of a reaction mixture upon entry of the reaction mixture into the at least one zone B, wherein a ratio of a volume of zone A to a total volume of all of the at least one zone B is greater than 1 and less than 500.

12. The process according to claim 1 , wherein the reactor comprises one or more feed conduits through which mixtures of the alkyl alcohol and the (meth)acrolein may be supplied.

13. The process according to claim 8 , wherein the at least one classifying sedimentation apparatus, in a zone C of the reactor, consists of a plurality of channel-like profiles, tubes, of lamellae having an angle of inclination to a horizontal, wherein each have the same pressure at an inlet.

14. The process according to claim 13 , wherein the at least one classifying sedimentation apparatus is an inclined settler.

15. The process according to claim 8 , wherein the at least one classifying sedimentation apparatus is a hydrocyclone.

16. The process according to claim 11 , wherein relatively large catalyst particles are retained in a separation apparatus and are recycled into the at least one zone B,
wherein relatively small catalyst particles are collected using at least one filter apparatus, and
wherein zone A in a lower portion of the reactor is actively supplied with the oxygen-containing gas via nozzles or gasification apparatuses, and simultaneously the at least one zone B comprises no apparatuses for active gasification of the reaction mixture.

17. The process according to claim 11 , wherein a stirring means or a vertically conveying pump is arranged in zone A and wherein zone A and the at least one zone B are separated from one another by the internals, wherein the internals at the transition from zone A to each of the at least one zone B largely prevent entry of gas bubbles into the at least one zone B.

18. The process according to claim 1 , wherein an average particle size of the catalyst based on volume distribution is between 50 and 120 μm.

19. The process according to claim 10 , wherein the next process operation is a distillation, a degassing, a phase separation, or an extraction.

20. The process according to claim 17 , wherein the internals are dividing walls.

Assignees

• Roehm Gmbh

Inventors

• Krill Steffen
• Ait Aissa Belaid
• Rühling Andreas
• Stitou Mounir
• Gräff Andreas
• Merker Olaf

Classifications

• B01J2235/30

  Scanning electron microscopy; Transmission electron microscopy · CPC title

• B01J2219/00481

  by the use of moving stirrers within the reaction vessels · CPC title

• B01J19/1856

  placed in parallel · CPC title

• B01J35/51

  Spheres · CPC title

• B01J35/397

  Egg shell like · CPC title