FORM-2
THE PATENTS ACT, 1970
(39 of 1970)
AND
THE PATENTS RULES, 2003
COMPLETE
SPECIFICATION
(See section 10; rule 13)
AN IMPROVED PROCESS FOR PRODUCING OLEFINS FROM SYNGAS
RELIANCE INDUSTRIES LIMITED
an Indian company of,
3rd Floor, Maker Chamber-IV, 222, Nariman Point,
Mumbai 400021, Maharashtra, India
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED. 2

FIELD
The present disclosure relates to an improved process for producing olefins from syngas.
BACKGROUND
Syngas is generally a mixture of hydrogen (H2), carbon monoxide (CO). 5 However, due to process inefficiency, carbon dioxide (CO2) is also produced along with syngas. Syngas can be used in a variety of applications such as production of methanol, production of dimethyl ether (DME), production of olefins, production of ammonia, production of urea, heating, generation of steam and generation of power. Syngas can be produced by utilizing methane or natural 10 gas, liquid fuels or solid fuels such as coal, petcoke, biomass, solid wastes, and the like.
Following are the reactions or processes, illustrating the production of syngas:
i. steam reforming:

CH4 + H2O = CO + 3H2; 15
ii. partial oxidation:

2CH4 + O2 = 2CO + 4H2;
iii. coal gasification:

3C + O2 + H2O = 3CO + H2;
iv. dry reforming: 20

CH4 + CO2 = 2CO + 2H2; and
v. water-gas shift reaction:

CO + H2O H2 + CO2
The ratio of H2 and CO in syngas varies depending upon raw material and process or reaction conditions used for producing syngas. 25
Figure 1 depicts a flow-path, illustrating a conventional process for producing olefins from syngas. Syngas (1) is first converted into methanol (3). For the 3

production of methanol, syngas (1) comprising 2:1 ratio of H2 and CO is used. The syngas (1) is introduced into a water-gas shift reactor/section (50), wherein the proportion of H2 can be increased. Due to 2:1 ratio of H2 and CO requirement, the amount of CO2 (2) produced during the production of syngas (1) is significant, hence, there is a need to separate CO2 (2) from the syngas (1). 5 Therefore, the syngas (1) from the water-gas shift reactor/section (50) is introduced into a separator (100). After the separation of CO2 (2), the syngas (1), which is deficient of CO2, is introduced into a reactor (200) for producing methanol (3). The reaction for producing methanol (3) is depicted herein below:
2H2 + CO = CH3OH (methanol) 10
Methanol (3) is then introduced into a reactor (300), wherein methanol (3) is dehydrogenated to produce a stream (4) comprising olefins (5), unconverted DME (6) and H2O (7) in the reactor (300). The stream (4) is further introduced into a separator (400) for separating unconverted DME (6) and H2O (7) from stream (4) to obtain olefins (5). The separated H2O (7) and the unconverted DME 15 (6) can be further utilized for producing syngas (1) and olefins (5) respectively.
Moreover, the amount of CO2 produced during this process is significant because:
• CO2 is present in syngas; and
• syngas with low H2 and high CO need to be converted to syngas 20 comprising 2:1 ratio of H2 and CO. This can be done by water-gas shift, wherein CO is reacted with water to generate H2, and CO2 as a by-product.

A separate process equipment is required for separating carbon dioxide from syngas. Also, the amount of energy required to separate carbon dioxide from 25 syngas is more due to significant CO2 in syngas. This increases the capital expenditure (CAPEX) and operational expenditure (OPEX) of the conventional process for producing olefins. 4

Moreover, syngas comprising 2:1 ratio of H2 and CO results in the conversion of syngas to methanol at a particular temperature (in the range of 300oC to 400oC) and pressure (in the range of 60 bar to 90 bar) conditions, thereby requiring a reactor for producing methanol. Also, different process equipment like heaters and compressors are required for achieving the specific temperature and pressure 5 conditions in the reactor. This results in further increase in the capital expenditure (CAPEX) and operational expenditure (OPEX) of the conventional process for producing olefins.
Therefore, there is a need for a process for producing olefins with reduced generation and possible utilization of CO2. Further, there is a need for a process 10 for producing olefins with reduced CAPEX and OPEX of the process, which minimizes the multiple reactors operating at different temperature and pressure conditions.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment 15 herein satisfies, are as follows.
An object of the present disclosure is to provide a process with reduced generation of CO2.
Yet another object of the present disclosure is to provide a process which can inherently consume less energy along with elimination of equipment/process 20 conditions for the intermediate process.
Yet another object of the present disclosure is to separate CO2 post the DME production to minimize the energy need for separation.
Still another object of the present disclosure is to efficiently utilize separated streams like CO2, methane, ethane, and propane to produce syngas. 25 5

Another object of the present disclosure is to provide a process for producing olefins with reduced CAPEX and OPEX of the process.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure. 5
SUMMARY
The present disclosure envisages a process for producing olefins from syngas comprising H2, CO and CO2. Typically, the ratio of H2 and CO of the syngas requirement for this process is 1:1. The syngas is contacted with at least one first catalyst, at a pre-determined temperature and at a pre-determined pressure, to 10 produce an intermediate stream comprising dimethyl ether (DME) and unconverted CO2, H2 and CO. The unconverted H2 and CO is recycled to a first catalyst section, and a portion of the separated CO2 is recycled for producing the syngas. The remaining intermediate stream is further contacted with a second catalyst, at a pre-determined temperature and at a pre-determined pressure, to 15 produce a second product stream comprising olefins, H2O, methane, ethane, and propane. H2O, methane, ethane, and propane are separated from the second product stream to obtain olefins. The separated CO2, H2O, methane, ethane, and propane are further recycled for producing the syngas.
The olefins can be at least one of ethylene and propylene. 20
The process of the present disclosure reduces the generation of CO2.
The process of the present disclosure also reduces CAPEX and OPEX of the entire process.
25 6

BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
A process for producing olefins from a gaseous mixture will now be described with the help of the accompanying drawing, in which:
Figure 1 depicts a flow-path, illustrating a conventional process for producing olefins; and 5
Figure 2 depicts a flow-path for producing olefins in accordance with the present disclosure.
A process for producing olefins from a gaseous mixture will now be described with the help of the accompanying drawing, in which:
Figure 1 depicts a flow-path, illustrating a conventional process for producing 10 olefins; and
Figure 2 depicts a flow-path for producing olefins in accordance with the present disclosure.
Table illustrates following elements of the process of the present disclosure represented by their respective reference letters: 15 Elements Reference letters
Raw material (a)
Gasifier/reformer (R)
Syngas (b)
DME reactor (D)
Intermediate stream (c)
Separator (s)
Separated portion (g)
Separated CO2 (h)
Separated H2 and CO (i)
Reactor (O)
Second product stream (d)
Fractionation column or divided wall column (Dw)
Olefins (e)
Separated stream (f)
DETAILED DESCRIPTION
2:1 ratio of H2 and CO in syngas leads to generation of an excess amount of CO2, and an excess use of H2O. Moreover, for economic viability of methanol production process, CO2 should be minimum or nil in the feed. Therefore, it is 5 necessary to completely separate or remove CO2. Separation of CO2 require bigger separation units, which consume a significant amount of energy, and H2O passes through all the equipment due to which the size of the equipment increases, thereby increasing the CAPEX and OPEX of the entire process. 8

The present disclosure, therefore, provides an improved process for producing olefins with reduced generation of CO2 and with reduced CAPEX and OPEX of the entire process.
The process for producing olefins is illustrated with reference to Figure 2. Raw material (a) is treated in a gasifier/reformer (R), typically at a temperature in the 5 range of 300ºC to 1000ºC and at a pressure in the range of 1 kg/cm2 to 80 kg/cm2, to produce syngas (b) comprising H2, CO and CO2.
The raw material (a) can be at least one of coal, petcoke, biomass, natural gas or liquid fuels.
With H2: CO of 1:1 needed for DME production, the portion of CO2 produced 10 during the production of syngas is significantly less. Additionally, the one-step DME process can handle significant CO2 in the feed, as compared to methanol process. Therefore, separation of CO2 from syngas (b) in a separate process equipment is obviated at this stage.
Syngas (b) is directly introduced into a DME reactor (D), wherein syngas (b) is 15 contacted with a first catalyst in the DME reactor (D), typically at a temperature in the range of 100ºC to 400ºC and at a pressure in the range of 1 kg/cm2 to 60 kg/cm2, to produce an intermediate stream (c) comprising dimethyl ether (DME) and unconverted CO2, H2 and CO. CO2, and the unconverted H2 and CO can be separated from the intermediate stream (c) with less energy requirement as CO2 20 concentration is relatively higher, and reduced criticality of a process equipment used for separating CO2 as a simpler separation process equipment can be used. The separated portion (g) is introduced into a separator (s) for separating CO2 (h), H2 and CO (i). The separated CO2 (h) can be recycled for producing syngas, and the separated H2 and CO (i) can be recycled to the DME reactor (D). 25
The first catalyst includes, but is not limited to, copper oxide, chromium oxide, zinc oxide and aluminium oxide. 9

One-step DME process requires H2: CO ratio of 1:1, which leads to smaller water-gas shift reaction and lower water consumption and CO2 generation. As the portion of CO2 in the syngas is lower; the one-step DME process can handle syngas without removing CO2.
The intermediate stream (c) is introduced into a reactor (O) and contacted with a 5 second catalyst in the reactor (O), typically at a temperature in the range of 200ºC to 600ºC and at a pressure in the range of 0.5 kg/cm2 to 10 kg/cm2, to produce a second product stream (d) comprising olefins, H2O, unreacted DME, methane, ethane, and propane.
The second catalyst includes, but is not limited to, molecular sieve catalysts. 10
In accordance with one embodiment of the present disclosure, the second catalyst is at least one selected from the group consisting of zeolites, aluminophosphate (ALPO) molecular sieves, and silicoaluminophosphate (SAPO) molecular sieves, as well as substituted forms thereof.
In accordance with another embodiment of the present disclosure, the second 15 catalyst is ZSM-5.
The second product stream (d) is introduced into a fractionation column or a divided wall column (Dw) for separating, H2O, unreacted DME, methane, ethane, and propane from the second product stream (d) to obtain olefins (e) and a separated stream (f). 20
The separated CO2, H2O, methane, ethane, and propane can be recycled into the reformer for producing syngas by at least one of dry reforming, bi-reforming, or tri-reforming, wherein syngas with higher H2 and CO is produced as compared to gasification.
Dry reforming of natural gas is depicted herein below: 25
CH4 + CO2 = 2CO + 2H2O
Moreover, the amount of raw materials required for producing syngas (b) is reduced, since the separated methane, ethane and propane are utilized for producing syngas which is significantly rich in H2. Also, the separated unreacted DME can be recycled into the DME reactor (D) for producing the intermediate stream (c). 5
In accordance with one embodiment of the present disclosure, a portion of the separated CO2 is recycled into the reformer and a remaining portion of the separated CO2 is vented out to the atmosphere.
Moreover, the amount of H2O generated in the reactor (O) can be approximately 50% less as compared to that generated conventionally during the production of 10 olefins from syngas comprising 2:1 ratio of H2 and CO.
In accordance with one embodiment of the present disclosure, the second product stream (d) can be introduced into a de-methanation column (not shown in Figure 2) for separating methane contained therein.
As described herein above, syngas (b) comprising 1:1 ratio of H2 and CO is 15 utilized for producing olefins (e). Due to 1:1 ratio of H2 and CO:
• the amount of raw materials required for producing syngas (b) is reduced, because the separated CO2, methane, ethane and propane are utilized for producing syngas which is significantly rich in H2;
• the amount of CO2 produced during the production of syngas (b) and 20 water-gas shift reaction is significantly less, and one step DME process can accommodate CO2 in the feed, which leads to smaller and less severe CO2 separating process equipment post DME;
• the intermediate step of methanol production of obviated, thereby eliminating the use of a reactor for producing methanol; 25
• efficient separation of the streams by divided wall column may lead to even more reduction in energy need for separation and saving in the CAPEX of the entire process; and
11

• the amount of water being circulated from gasification to olefins would significantly reduce which leads to reduced volume of many intermediate sections.

Due to the above mentioned factors, CAPEX can be significantly reduced and OPEX can reduce upto 30% as compared to that of the conventional process.
TECHNICAL ADVANCES AND ECONOMICAL SIGNIFICANCE
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of an improved process that: 10
• reduces generation of CO2 during the process for producing olefins;
• utilizes CO2 in olefins production;
• reduces energy needs for separating products;
• reduces energy needs for separating CO2;
• reduces circulation of H2O in the process with lower water-gas shift 15 reaction; and
• reduces CAPEX and OPEX for producing olefins.

The disclosure has been described with reference to the accompanying embodiments which do not limit the scope and ambit of the disclosure. The description provided is purely by way of example and illustration. 20
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. 25 12

The foregoing description of the specific embodiments so fully revealed the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended 5 within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with 10 modification within the spirit and scope of the embodiments as described herein.
WE CLAIM:
1. An improved process for producing olefins from syngas, said improved process comprising the following steps:
a) treating raw material, at a temperature in the range of 300ºC to 1000ºC and at a pressure in the range of 1 kg/cm2 to 80 kg/cm2, to 5 produce said syngas comprising H2, CO and CO2, wherein the ratio of H2 and CO in said syngas is 1:1, wherein said raw material is at least one selected from the group consisting of coal, petcoke, biomass, natural gas and liquid fuels;
b) contacting said syngas with at least one first catalyst, at a 10 temperature in the range of 100ºC to 400ºC and at a pressure in the range of 1 kg/cm2 to 60 kg/cm2, to produce an intermediate stream comprising dimethyl ether (DME), unconverted CO2, H2, and CO, wherein said at least one first catalyst is selected from the group consisting of chromium oxide, zinc oxide and aluminium oxide; 15
c) separating a portion of CO2, H2, and CO from said intermediate stream and recycling the separated portion of CO2 the step 1) for producing said syngas and recycling the separated portion of H2, and CO for producing said DME;
d) contacting said intermediate stream with at least one second 20 catalyst, at a temperature in the range of 200ºC to 600ºC and at a pressure in the range of 0.5 kg/cm2 to 10 kg/cm2, to produce a second product stream comprising olefins, H2O, methane, ethane, and propane, wherein said at least one second catalyst is ZSM-5;
e) separating H2O, methane, ethane and propane from said second 25 product stream to obtain said olefins; and
f) recycling the separated CO2, methane, ethane and propane to reforming for producing said syngas.

2. The improved process as claimed in claim 1, wherein said olefins is at least one of ethylene and propylene.

3. The improved process as claimed in claim 1, wherein the separated CO2 is recycled to the step a), for producing said syngas by reforming at least 5 one of:
• natural gas; and
• one of the separated methane, ethane, and propane, with CO2.