Method for producing acrolein and/or acrylic acid from glycerol
The invention relates to the production of acrolein and/or acrylic acid from glycerol, and more particularly to a method for continuous production of a stream comprising acrolein by dehydration of glycerol, comprising cycles of reaction and regeneration of a dehydration catalyst.
1. A method for continuous production of a stream comprising acrolein, comprising the steps of:
a) reacting a gaseous reaction stream comprising glycerol, by contacting said gaseous reaction stream with a solid acid catalyst in a reactor zone maintained at a temperature in the range from 250° C. to 350° C. to obtain a stream comprising acrolein,
b) regenerating said solid catalyst with a gaseous regeneration stream comprising oxygen, wherein:
(i) step (b) is carried out at a regeneration temperature equal to within plus or minus 10° C. the reaction temperature of step (a), and
(ii) controlling and maintaining a hot spot of the catalyst during step (b) so that the hot spot does not exceed 50° C. above the temperature of the reactor zone containing the catalyst in regeneration mode, and
(iii) step (a) and step (b) are applied simultaneously, each on at least one reactor zone in the form of cycles in reaction mode and in regeneration mode offset from one zone to another.
2. The method of claim 1 wherein step (a) and step (b) are carried out on two or more catalyst zones placed in at least two reactors in parallel, each reactor being supplied separately.
3. The method of claim 1 wherein step (a) and step (b) are carried out in one reactor comprising at least 2 catalyst zones, each zone being supplied separately.
4. The method of claim 3 wherein the number of catalyst zones operating in reaction mode is equal to the number of zones operating in regeneration mode.
5. The method of claim 3 wherein the number of catalyst zones operating in reaction mode is greater than the number of zones operating in regeneration mode.
6. The method of claim 1 wherein the regeneration stream contains water.
7. The method of claim 1 wherein an increasing temperature gradient is applied to the reactor zone, or to the heat-transfer fluid providing thermostatic control of the reactor zone, for the entire duration of step (b) during regeneration mode between 1 and 30° C. between the start and end of step (b).
8. The method of claim 1 wherein the oxygen content in the regeneration stream is below 10 vol % throughout step (b).
9. The method of claim 1 wherein the oxygen content in the regeneration stream increases during regeneration, with a first part in which the oxygen content is below 10 vol % and a second part in which the oxygen content is from 9 to 22 vol %.
10. A method for producing acrylic acid from glycerol comprising a first step of continuous production of a stream comprising at least acrolein by the method of claim 1 and a step of oxidation of acrolein to acrylic acid.