Process for the preparation of an olefinic product comprising ethylene and/or propylene

Patent metadata

Field	Value
Publication number	US-9505669-B2
Application number	US-201314655343-A
Country	US
Kind code	B2
Filing date	Dec 24, 2013
Priority date	Dec 28, 2012
Publication date	Nov 29, 2016
Grant date	Nov 29, 2016

Abstract

The invention provides a process for the preparation of an olefinic product comprising ethylene and/or propylene comprising: a) steam cracking a paraffinic feedstock to obtain an effluent comprising olefins; b) converting an oxygenate to obtain a gaseous effluent comprising olefins; c) subjecting both effluents to water removal and compression steps, wherein the effluents are combined before the water removal step, between the water removal and the compression steps or after the compression step to obtain a combined gaseous effluent; d) removing acid gas from the combined gaseous effluent obtained in step c), wherein the combined gaseous effluent is treated with a caustic solution in a caustic tower and a non-aqueous liquid stream comprising one or more aromatic C7 + hydrocarbons is added to the caustic solution to control the formation of red oil, to obtain a treated gaseous effluent; and e) separating the olefinic product from the treated gaseous effluent.

First claim

That which is claimed is:

1. A process for the preparation of an olefinic product comprising ethylene and/or propylene, the process comprising the following steps:
a) steam cracking a paraffinic feedstock under cracking conditions in a cracking zone to obtain a cracker effluent comprising olefins, water, carbon dioxide and carbonyl compounds including C2 + aldehyde and/or ketone;
b) contacting an oxygenate feedstock in an oxygenate conversion reaction zone with a molecular sieve-comprising catalyst at a temperature in the range of from 350 to 1000° C. to produce an oxygenate conversion effluent comprising olefins, water, carbon dioxide and carbonyl compounds including C2 + aldehyde and/or ketone;
c) subjecting both the cracker effluent and the oxygenate conversion effluent to a water removal step followed by a compression step with optional recovery of any condensed hydrocarbons in the water removal step and/or in the compression step, wherein the cracker effluent and the oxygenate conversion effluent are combined prior to the water removal step or after the water removal step and before the compression step, to obtain a combined compressed water-depleted gaseous stream comprising olefins, carbon dioxide and carbonyl compounds;
d) separating carbon dioxide from the combined compressed water-depleted gaseous stream by subjecting the gaseous stream to a caustic wash treatment in a caustic tower wherein the gaseous stream is countercurrently contacted with a caustic solution to obtain a washed gaseous stream comprising olefins; and
e) subjecting the washed gaseous stream to one or more separation steps such that at least an olefin product stream comprising ethylene and/or propylene is obtained,

wherein in step d) a non-aqueous liquid stream comprising one or more aromatic C7 + hydrocarbons is added to the caustic solution prior to contacting the caustic solution with the gaseous stream and wherein a liquid phase comprising spent caustic solution and the one or more aromatic C7 + hydrocarbons is discharged from the caustic tower and wherein the non-aqueous liquid stream comprises less than 0.1 wt % of olefinic hydrocarbons and at least part of the non-aqueous liquid stream comprising one or more aromatic C7 + hydrocarbons is recovered from the oxygenate conversion effluent in step c), and/or step e).

2. A process according to claim 1 , wherein in step d) the compressed gaseous stream is countercurrently contacted with a caustic solution in at least two stages in series before being countercurrently contacted with the water stream, wherein the gaseous stream is contacted in each stage of the at least two stages with a caustic solution having a concentration of caustic, wherein the concentration of caustic in a next stage is higher than the concentration of caustic in the stage directly preceding said next stage, wherein the non-aqueous liquid stream is added to the caustic solution of at least one stage and wherein the liquid phase comprising spent caustic solution and the one or more aromatic hydrocarbons is discharged from the first stage.

3. A process according to claim 2 , where the non-aqueous liquid stream is added to the caustic solution in the first stage.

4. A process according to claim 3 , wherein the non-aqueous liquid stream is added to the caustic solution in all of the at least two stages.

5. A process according to claim 1 , wherein the non-aqueous liquid stream consists essentially of C7-C10 hydrocarbons.

6. A process according to claim 5 , wherein the non-aqueous liquid stream consists essentially of C8-C10 hydrocarbons.

7. A process according to claim 1 , wherein the non-aqueous liquid stream comprises xylene.

8. A process according to claim 1 , wherein in step e) a stream comprising C7 + hydrocarbons is obtained and wherein the non-aqueous liquid stream comprises at least part of the stream comprising C7 + hydrocarbons.

9. A process according to claim 8 , wherein in step e) a stream comprising C8-C10 hydrocarbons is obtained, and wherein the non-aqueous liquid stream comprises at least part of the stream comprising C8-C10 hydrocarbons.

10. A process according to claim 1 , wherein the temperature of the compressed gaseous stream that is contacted with the caustic solution is at most 40° C.

11. A process according to claim 1 , wherein the caustic wash treatment is operated at a temperature of at most 50° C.

12. A process according to claim 1 , wherein the colour of the liquid phase discharged from the caustic tower or of a non-aqueous phase separated from the liquid phase is determined, and wherein the amount of non-aqueous liquid stream added to the caustic solution is controlled in accordance with the determined colour.

13. A process according to claim 12 , wherein the colour is determined by inspection through a sight glass located in a conduit for recycling or withdrawal of the liquid phase and/or a conduit for withdrawal of a non-aqueous phase separated from the liquid phase.

14. A process according to claim 1 , wherein the compressed gaseous stream obtained in step c) is heated to a temperature in the range of from 2 to 5° C. above its dew point prior to subjecting the compressed gaseous stream to the caustic wash treatment in step d).

Assignees

• Shell Oil Co

Inventors

• Van Westrenen Jeroen
• Vijayakumari Sivakumar Sadasivan

Classifications

• C07C7/005

  Processes comprising at least two steps in series · CPC title

• C07C11/06

  Propene · CPC title

• Y02P30/42

  Cross-Sectional Technologies · mapped topic

• C07C1/20 Primary

  starting from organic compounds containing only oxygen atoms as heteroatoms · CPC title

• C07C2529/00

  Catalysts comprising molecular sieves · CPC title