Fluidized bed dehydrogenation process for light olefin production

Patent metadata

Field	Value
Publication number	US-11873276-B2
Application number	US-202117447828-A
Country	US
Kind code	B2
Filing date	Sep 16, 2021
Priority date	Sep 16, 2020
Publication date	Jan 16, 2024
Grant date	Jan 16, 2024

Abstract

The present invention discloses process and apparatus for the production of light olefins from their respective alkanes by catalytic dehydrogenation, where in the dehydrogenation reaction is carried out in multiple semi-continuously operated fluidized bed isothermal reactors, connected to a common regenerator and wherein the process is carried out in a sequence of steps in each cycle i.e., entry of hot regenerated catalyst, pre-treatment with reducing gas, dehydrogenation reaction, stripping, transfer of catalyst to regenerator and catalyst regeneration. Process cycle in each reactor starts at different times such that the catalyst inventory in the regenerator is invariable with time.

First claim

What is claimed is:

1. A process for production of light olefins by dehydrogenation of alkanes in a plurality of semi-continuously operated fluidized bed reactors A i ; (i=2, . . . n) provided with a common continuously operated catalyst regenerator (D), wherein the process comprises sequential steps:
a) feeding a hot regenerated catalyst and a pre-heated diluent stream to the plurality of semi-continuously operated fluidized bed reactors;
b) pre-treating the hot regenerated catalyst by feeding a reducing gas to the plurality of semi-continuously operated fluidized bed reactors to obtain a pre-treated catalyst;
c) feeding a pre-heated alkane feed to the plurality of semi-continuously operated fluidized bed reactors for catalytic dehydrogenation in presence of the pre-treated catalyst to obtain a product mixture comprising olefins, unreacted alkanes, product gases, and a spent catalyst;
d) separating the product mixture from the spent catalyst in reactor cyclones;
e) separating remaining hydrocarbon molecules from the spent catalyst by stripping using steam, or an inert gas and recovering stripping product gas through the reactor cyclones;
f) transferring the spent catalyst to the common continuously operated catalyst regenerator (D); and,
g) reactivating the spent catalyst in the common continuously operated catalyst regenerator by burning coke deposited on spent catalyst using air, oxygen, or an oxygen containing gas,

wherein the pre-heated diluent stream and the pre-heated alkane feed are in a molar ratio in a range of 0.1 to 5,
wherein the process in each of the plurality of semi-continuously operated fluidized bed reactors begins at a different time to maintain a constant catalyst inventory with time in the common continuously operated catalyst regenerator, and to maintain a minimum catalyst inventory in each of the plurality of semi-continuously operated fluidized bed reactors by flowing steam, or an inert gas at a minimum velocity during reactivation of the spent catalyst, wherein the process occurs in a sequence wherein a slide valve of a stand pipe opens at t=0 minutes to transfer the regenerated catalyst from the common continuously operated catalyst regenerator to the semi-continuously operated fluidized bed reactor A i−1 , and wherein a slide valve of a stand pipe B i−1 remains closed at t=0 minutes until a desired catalyst inventory is built up in the semi-continuously operated fluidized bed reactor A i−1 ,
the slide valve of the stand pipe B i opens to transfer the spent catalyst from the semi-continuously operated fluidized bed reactor A i to the common continuously operated catalyst regenerator through a lift line C i , wherein after regeneration, a slide valve of a stand pipe E i opens and the hot regenerated catalyst flows into the semi-continuously operated fluidized bed reactor A i , and wherein at the same time, the spent catalyst from the semi-continuously operated fluidized bed reactor A i+1 flows into the common continuously operated catalyst regenerator through a slide valve of a stand pipe B i+1 and the lift line C i+1 , where i=2, . . . n.

2. The process as claimed in claim 1 , wherein the semi-continuously operated fluidized bed reactors are maintained under isothermal conditions by an additional heating element (Ft).

3. The process as claimed in claim 1 , wherein the temperature of the hot regenerated catalyst entering the plurality of semi-continuously operated fluidized bed reactors is 600-800° C., and wherein the pre-heated diluent stream comprises of nitrogen, steam, or helium, and wherein the pre-heated alkane feed is sent to the plurality of semi-continuously operated fluidized bed reactors with or without diluents.

4. The process as claimed in claim 1 , wherein the reducing gas is selected from the group consisting of hydrogen, methane, a hydrogen containing gas, a dry gas from an FCCU, Pressure Swing Adsorption (PSA) off-gas from Hydrogen Generation Unit (HGU), and a combination thereof.

5. The process as claimed in claim 1 , wherein the dehydrogenation reaction is carried out at a temperature in a range of 500-850° C., a pressure in a range of 0.1-3.0 bar, and wherein the hot regenerated catalyst and the pre-heated diluent stream are fed at a gas hourly space velocity (GHSV) in a range of 500-10000 h −1 .

6. The process as claimed in claim 1 , wherein the alkane feed comprises ethane, propane, iso-butane, n-butane, or a combination thereof.

7. The process as claimed in claim 6 , wherein ethane, propane, iso-butane, or n-butane are sent separately to each of the plurality of the semi-continuously operated fluidized bed reactors for simultaneous production of ethylene, propylene and butylene, respectively.

8. The process as claimed in claim 1 , wherein the plurality of semi-continuously operated fluidized bed reactors has a catalyst bed density of 500-700 kg/m 3 in a lower portion and a catalyst bed density of 20-100 kg/m 3 in an upper portion.

9. The process as claimed in claim 1 , comprising contacting the pre-treated catalyst and the pre-heated alkane feed for a period of 0.1-20 seconds.

10. The process as claimed in claim 1 , wherein 40-60 wt % of the alkane feed gets converted per pass through each of the plurality of semi-continuously operated fluidized bed reactors with an olefin selectivity of 80-97 wt %.

11. The process as claimed in claim 1 , further comprising adding a fresh catalyst and withdrawing the spent catalyst at regular intervals of time to compensate the catalyst losses from the catalyst inventory and to maintain uniform catalyst activity.

12. The process as claimed in claim 1 , wherein pre-treating the hot regenerated catalyst is characterized to enhance propylene selectivity.

13. The process as claimed in claim 1 , wherein the number of semi-continuously operated fluidized bed reactors (n) is a function of time taken for completion of one cycle of the process (t C ), time taken for the spent catalyst regeneration (t Rg ), and time taken for a transfer of the spent catalyst from each of the plurality of semi-continuously operated fluidized bed reactors to the common continuously operated catalyst regenerator or time taken for a transfer of the hot regenerated catalyst from the common catalyst to each of the plurality of semi-continuously operated fluidized bed reactors (t T ).

14. The process as claimed in claim 1 , wherein the number of semi-continuously operated fluidized bed reactors is directly proportional to the time taken for completion of one cycle of the process, and inversely proportional to the time taken for the spent catalyst regeneration and time taken for a transfer of the spent catalyst from each of the plurality of semi-continuously operated fluidized bed reactors to the common continuously operated catalyst regenerator or time taken for a transfer of the hot regenerated catalyst from the common continuously operated catalyst regenerator to each of the plurality of semi-continuously operated fluidized bed reactors.

15. The process as claimed in claim 1 , wherein the alkane feed is pre-heated to 400-700° C. in an external furnace prior to sending to the plurality of semi-continuously operated fluidized bed reactors.

16. The process as claimed in claim 1 , wherein the catalyst comprises metals or metal oxides selected from groups IA, VB, VIB, VIII, Lanthanide series, or a combination thereof; and is supported on alumina, silica, zeolite, or a combination thereof.

17. The process as claimed in claim 1 , wherein the catalyst has a temperature in a range of 600-800° C., and an average reside

Assignees

• Indian Oil Corp Ltd

Inventors

• Doosa Hima Bindu
• Subramani Saravanan
• Thakur Ram Mohan
• Nath Vineeth Venu
• LOGANATHAN Kumaresan
• Kanattukara Vijayan Bineesh
• Sau Madhusudan
• Kapur Gurpreet Singh
• RAMAKUMAR Sankara Sri Venkata

Classifications

• C07C5/333 Primary

  Catalytic processes · CPC title

• B01J8/0055

  using cyclones · CPC title

• B01J8/1836

  Heating and cooling the reactor (B01J8/42 takes precedence) · CPC title

• B01J8/24

  according to "fluidised-bed" technique (B01J8/20 takes precedence) · CPC title

• B01J38/02

  Heat treatment · CPC title