Description:FIELD OF THE INVENTION:
The present invention relates to production of hydrocarbons. Specifically, the present invention relates to a catalyst for production of hydrocarbons from CO2 and a process for preparing the said catalyst.

BACKGROUND OF THE INVENTION:
Dwindling fossil fuels and global warming have stimulated recent research activities on the transformation of CO2. The excessive use of fossil fuels increases the emissions of CO2 into the atmosphere and contributes to global warming. Therefore, the transformation of CO2 to value-added products is a very attractive way to use a renewable, non-toxic, and abundant source of carbon.

Biogenic sources and fossil sources are two main sources of CO2 emissions. Biogenic sources involve carbon that is already in the biosphere, and it is part of the natural carbon cycle. Biogenic emissions are from either natural or human harvesting, fermentation, combustion, and decomposition of biomaterials. Fossil carbon is derived from largely human-driven combustion and processing of fossil resources like natural gas, coal, and petroleum, and involves an unsustainable transfer of carbon that has been stored in the earth’s crust for hundreds of million years into to biosphere.

Carbon capture technology can be used to obtain CO2 from different emission sources. Further, the captured CO2 can be either stored or utilized using carbon capture and storage (CCS) or carbon capture and utilization (CCU) technologies. There are three different main CO2 capture systems; Pre-combustion, post-combustion, and oxyfuel combustion related to different combustion processes. Out of them, the post-combustion technology offers a way to capture the CO2 from flue gases that come from the combustion of fossil fuels. There are many separation technologies such as membrane separation, dry regenerable adsorption, wet scrubbing, cryogenic distillation, pressure, and temperature swing adsorption that can be used to isolate the CO2 from the flue gases. CCS could face many challenges concerning the transportation and storage of CO2, as there is a possibility for leakage and contamination of groundwater if geological storage is used.
The utilization of CO2 after capturing is an attractive way to mitigate CO2 emissions. There are several processes where CO2 can be utilized such as enhanced oil recovery, mineralization, and conversion into value-added chemicals and fuels. However, CCU needs a large amount of energy for the conversion of CO2 due to its kinetic inertness and thermodynamic stability, but it could function as a part of the sustainable natural carbon cycle in the biosphere, if the cost of produced materials is equal to the cost of their production as well as possible offset costs for emissions while reducing the excess CO2 emitted into the atmosphere. Hydrogen is the second main reagent for CO2 transformation. Hydrogen itself is a renewable source of energy if it is produced from water splitting and using electricity from resources like wind, hydro and solar at low cost but its handling, storage, and transportation are challenging, considering its explosiveness and low-energy density. It would be beneficial to use hydrogen for the reduction of CO2 and in this way to store energy in the form of chemicals and fuels, which are easier to store and transport.

Therefore, the direct conversion of CO2 into hydrocarbons is an attractive route to utilize and mitigate the surplus CO2. More specifically, light hydrocarbons like olefins are the building blocks to produce modern plastic products. Currently, light olefins are produced through the cracking of hydrocarbons under high temperatures. Moreover, harnessing CO2 hydrogenation to produce liquid fuel offers an alternative method for generating transport fuel. This approach could serve as a support in anticipation of future fossil fuel shortages.

There are two main routes in indirect synthesis of hydrocarbons from CO2 which are (i) synthesis of CH3OH and subsequent transformation into hydrocarbons in different stages (Different reactor) and (ii) synthesis of CO via reverse water gas shift (RWGS) and then formation of hydrocarbons using a modified Fischer–Tropsch synthesis (FTS) process based on two reactor stages. Hydrocarbons can be synthesized using a direct route which could be more economically favorable and environmentally benign compared to indirect routes. The direct route also includes two routes: (i) Hydrocarbon synthesis over bifunctional catalysts in which CO2 is first hydrogenated into CH3OH and then hydrocarbons, and (ii) Reduction of CO2 to CO via the RWGS reaction followed by hydrogenation of CO to hydrocarbons via FTS. Further, some prior arts on CO2 hydrogenation are discussed below.
EP 3911437 A1 by National Energy Technology Laboratory discloses nano catalysts composed of iron oxide nanoparticles supported on porous interconnected carbon nanosheets (CNS) fabricated from the carbonization of potassium citrate, that are remarkably active for CO2 hydrogenation and Fischer-Tropsch to Olefins (FTO) synthesis, as well as a method for directly converting CO2 and H2 to C2-C4 olefins and direct FTO synthesis.

WO2017/130081 A1 by Sabic Global Technologies discloses processes and systems for increasing selectivity for light olefins from CO2 and H2. The catalyst includes both Fe and K. The reaction mixture of CO2 and H2 was in a molar ratio of about 1:3. The product mixture contained 30 mol % C2=C4 olefins on the carbon basis. There were two sections in the reactor where the first section contained a lower temperature section which converts CO2 to CO and the second section contained a higher temperature section which formed light olefins from CO.

CN 106031871 A by Dalian Institute of Chemical Physics discloses a method and a catalyst for the preparation of liquid fuel and light olefins from syngas. The authors disclosed a catalyst and a method for producing light olefins directly from synthesis gas by a one-step process and particularly relates to the method and catalyst for directly converting synthesis gas into light olefins by a one-step process. The provided catalysts are composite materials formed of multicomponent metal oxide composites and inorganic solid acids with hierarchical pore structures. The inorganic solid acids have a hierarchical pore structure having micropores, mesopores, and macropores. The metal composites can be mixed with or dispersed on surfaces or in pore channels of the inorganic solid acid and can catalyze the synthesis gas conversion to a C2=C4 light hydrocarbon product containing two to four carbon atoms. The single pass conversion of CO is 10%-60%. The selectivity of light hydrocarbon in all hydrocarbon products can be up to 60%-95%, wherein the selectivity of light olefins (C2=C4) is 50%-85%.

US20210163827A1 by King Abdullah University of Science and Technology discloses a method for preparing catalysts for CO2 hydrogenation into olefins. The process involves grinding Fe(NO3)3.9H2O, Na(NO3)3, and Al(NO3)3.9H2O to create a homogeneous powder mixture. Subsequently, this mixture is calcined at temperatures of 350°C and 450°C to produce a pre-catalyst. The final catalyst (M-Fe-Al2O3, 50-300 µm) is then synthesized by passing methane over the pre-catalyst, with methane acting as a reducing agent. The resulting catalyst demonstrates a 28% CO2 conversion rate with a combined selectivity of 50-60% towards light olefins and higher chain olefins.

CN 111111762 A by China Petroleum and Chemical Corp discloses the technical field of chemistry and chemical engineering and relates to a preparation method and application of a catalyst of a bifunctional catalytic system for preparing low-carbon olefin by CO2 hydrogenation. The catalyst comprised two main components of indium-based oxide and a molecular sieve, wherein the indium-based oxide is supplemented with one or more than two auxiliary agent metal oxide components, and the catalyst is prepared by the processes of dissolving, constant-temperature precipitation, filtering, washing, drying, and calcining. Then mixing the oxide with a certain amount of molecular sieve catalyst and applying the mixture to a reaction system for preparing low-carbon hydrocarbon from CO2 and H2 mixed gas.

CN 112121807 A by Ningxia University invention relates to a titanium ore catalyst, which is applied to the preparation of ethylene, propylene and butylene by CO or CO2 hydrogenation. The catalyst component comprises [LaGd] xFeyO3FeO3 Oxidation of metal. The catalyst after the compounding promotes the adsorption and the desorption of CO to a great extent and shows good low-carbon olefin selectivity in the hydrogenation reaction.

The above disclosed prior arts have many drawbacks such as use of costly materials for preparing the catalyst, multistep conversion of the CO2 to hydrocarbons, inadequate CO2 conversion and hydrocarbons (HCs) selectivity. Accordingly, there is a need for a new catalyst and process for preparing the same, wherein, the catalyst can be prepared from less costly raw materials and the catalyst has single step CO2 conversion property.

OBJECTIVES OF THE PRESENT INVENTION:

It is the primary objective of the present invention to produce hydrocarbons from CO2.

It is further objective of the present invention is to prepare a catalyst for production of hydrocarbons from CO2 and a process for preparing the said catalyst.

It is further objective of the present invention is to prepare a catalyst for production of hydrocarbons from CO2, wherein the modified clay is converted into slurry to make microspheres (ranging from 20 to 150 microns) through spray drying methods.

SUMMARY OF THE INVENTION
The present invention discloses a process for preparing a microsphere catalyst for production of hydrocarbons from CO2. The process comprises steps of preparing an activated clay by mixing a raw clay with HCL followed by filtering and washing, drying, and calcination at 500-600 oC for 1-3 hours. Thereafter, preparing the microsphere catalyst by blending the activated clay, ZrO2, NaNO3, and a binder-grade alumina.

The process for preparing the activated clay comprises steps of mixing raw clay to 0.2 M HCl solution to prepare an acidic solution of clay, wherein the acidic solution is kept at 60-80 oC for 2-4 hours. Filtering and washing the acidic solution of clay with deionized water to bring the pH equal to 7 and a washed clay is produced. Drying the washed clay at 100-120oC for 10-14 hours to produce dried clay and calcinating the dried clay at 500-600 oC for 1-3 hours.

In an embodiment, the raw clay is 8-12 g and 0.2 M HCl solution is 180-220 ml, wherein, mixing the raw clay with HCL increases a ratio of active compounds and releases the waste metals and compounds, wherein, the active compounds are Al2O3 and iron oxide, and the waste metals and compounds are calcium and SiO2. The raw clay is selected from red mud clay, bentonite clay, kaolin clay, and a combination thereof.

The process for preparing the microsphere catalyst comprises steps of mixing activated clay, binder grade alumina, ZrO2, and NaNO3 in deionized water to form a uniform slurry. The activated clay is 70-80 g, binder grade alumina is 11-13 g, ZrO2 is 5-7 g, and NaNO3 is 0.92-0.94 g. Then milling the uniform slurry at 3D wet ball for 1-3 hours to get a milled slurry; peptizing the milled slurry with formic acid to get a peptized slurry. Then drying the peptized slurry between a temperature range of 120 – 380oC to form a spherical microsphere catalyst. Thereafter, calcinating the spherical microsphere catalyst at 400oC-500oC for 3-5 hours to form final microsphere catalyst. The final microsphere catalyst was converted into pelletized form.

The present invention discloses a microsphere catalyst comprising (a) activated clay ranging from 75 wt% to 100 wt%, (b) binder-grade alumina, ranging from 1 wt% to 16 wt% of the activated clay content, (c) Sodium nitrate (NaNO3), ranging from 0.1 wt% to 0.9 wt% of the activated clay, and (d) Zirconia (ZrO2), ranging from 3 wt% to 20 wt% of the activated clay.

BRIEF DESCRIPTION OF THE DRAWING:

The detailed description below will be better understood when read in conjunction with the appended drawings. For the purpose of assisting in the explanation of the invention, there are shown in the drawings embodiments which are presently preferred and considered illustrative.

It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown therein.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1: illustrates a SEM analysis of prepared microsphere of CO2 to hydrocarbon (CTH) catalyst.

DESCRIPTION OF THE INVENTION:
According to the main embodiment, the present invention discloses the production of hydrocarbons from the hydrogenation of CO2, wherein CO2 is first converted into CO and then into hydrocarbons.

Specifically, the present invention provides a catalyst for production of hydrocarbons from CO2 in single stage and a process for preparing the said catalyst by spray drying the modified clay. The process disclosed in the present invention is used for the synthesis of a CO2 to hydrocarbon (CTH) catalyst which can be used for CO2 conversion into hydrocarbon. This catalyst holds a potential for decarbonizing refinery and petrochemical processes.

More specifically, the texture properties of clay were modified to prepare the catalyst of the present invention. Further, the modified clay is converted into slurry to make microspheres (ranging from 20 to 150 microns) through spray drying methods. The spray-dried catalyst shows better physico-chemical properties than normal clay-prepared catalyst. The catalyst holds a potential for decarbonizing refinery and to provide feedstocks for petrochemical processes. Specifically, the said catalyst is used to prepare hydrocarbons from CO2 where more fraction was of light hydrocarbons. The process as disclosed herein involves modifying the textural properties of the catalyst and preparing microspheres to enhance CO2 conversion rates and hydrocarbon selectivity.

The process as disclosed herein comprises steps of preparing an activated clay by mixing a raw clay with HCL followed by filtering and washing, drying, and calcination at 500-600 oC for 1-3 hours. Thereafter, preparing the microsphere catalyst by blending the activated clay, ZrO2, NaNO3, and a binder-grade alumina.

The process for preparing the activated clay comprises steps of mixing raw clay to 0.2 M HCl solution to prepare an acidic solution of clay, wherein the acidic solution is kept at 60-80 oC for 2-4 hours. Filtering and washing the acidic solution of clay with deionized water to bring the pH equal to 7 and a washed clay is produced. Drying the washed clay at 100-120oC for 10-14 hours to produce dried clay and calcinating the dried clay at 500-600 oC for 1-3 hours. The mixing of the clay with HCL increases a ratio of active compounds and releases the waste metals and compounds like calcium and SiO2 without affecting the ratio of Al2O3 and iron oxide.

In an embodiment, the raw clay is 8-12 g and 0.2 M HCl solution is 180-220 ml, wherein, mixing the raw clay with HCL increases a ratio of active compounds and releases the waste metals and compounds, wherein, the active compounds are Al2O3 and iron oxide, and the waste metals and compounds are calcium and SiO2.

In another embodiment, the raw clay is 10 g and 0.2 M HCl solution is 200 ml, wherein, the raw clay is selected from red mud clay, bentonite clay, kaolin clay, and a combination thereof.

The process for preparing the microsphere catalyst comprises steps of mixing activated clay, binder grade alumina, ZrO2, and NaNO3 in deionized water to form a uniform slurry. The activated clay is 70-80 g, binder grade alumina is 11-13 g, ZrO2 is 5-7 g, and NaNO3 is 0.92-0.94 g. In another preferred embodiment, the activated clay is 75 g, binder grade alumina is 12 g, ZrO2 is 6 g, and NaNO3 is 0.93 g.

Then milling the uniform slurry at 3D wet ball for 1-3 hours to get a milled slurry; peptizing the milled slurry with formic acid to get a peptized slurry. Then drying the peptized slurry between a temperature range of 120-380oC to form a spherical microsphere catalyst. Thereafter, calcinating the spherical microsphere catalyst at 400oC-500oC for 3-5 hours to form final microsphere catalyst. The final microsphere catalyst was converted into pelletized form.

In another embodiment, milling the uniform slurry at 3D wet ball for 2 hours to get a milled slurry; peptizing the milled slurry with formic acid to get a peptized slurry. Then spray drying the peptized slurry in a co-current spray dryer unit at an inlet temperature range of 380oC and outlet temperature of 170oC to form a spherical microsphere catalyst. Thereafter, calcinating the spherical microsphere catalyst at 450oC for 4 hours to form final microsphere catalyst. The final microsphere catalyst was converted into pelletized form.

The present invention discloses a microsphere catalyst comprising (a) activated clay ranging from 75 wt% to 100 wt%, (b) binder-grade alumina, ranging from 1 wt% to 16 wt% of the activated clay content, (c) Sodium nitrate (NaNO3), ranging from 0.1 wt% to 0.9 wt% of the activated clay, and (d) Zirconia (ZrO2), ranging from 3 wt% to 20 wt% of the activated clay.

Example-1:
Activation of Clay:
As a clay red mud (RM) were purchased commercially. The received clays were treated with HCl followed by washing, drying, and calcination at 550 for 4 h.

10 g clays were added to 200 ml HCl solution (0.2 M). The resulting solution was kept at 70 oC for 3 h. The acidic solution of clay was filtered and washed with DM water to bring the pH equal to 7. The washed sample was dried at 110 oC for 12 h and calcined at 550 oC for 2 h. The mild treatment with HCl would increase the ratio of active compounds and release the waste metals and compounds like calcium and SiO2 without affecting the ratio of Al2O3 and iron oxide.

Example-2:
Preparation of catalyst:
75 g of activated RM clay and 12 g of binder grade alumina were mixed in desired DI water to form a uniform slurry, and milled at 3D wet ball for 2 h. The milled slurry was peptized with desired amount of formic acid. The peptized slurry was spray dried at an inlet temperature of 380 oC and outlet temperature of 140 oC to form a spherical microsphere in a co-current spray dryer unit. The spray-dried catalyst was calcined at 450 oC for 4 h to form the final CO2 to hydrocarbons (CTH) catalyst. The final CTH catalyst was converted into a pelletized form for evaluation in a fixed-bed reactor.

Example-3:
75 g of activated RM clay, 12 g of binder grade alumina, and 0.93 g NaNO3 were mixed in desired DI water to form a uniform slurry, and milled at 3D wet ball for 2 h. The milled slurry was peptized with desired amount of formic acid. The peptized slurry was spray dried at an inlet temperature of 380 oC and outlet temperature of 140 oC to form a spherical microsphere in a co-current spray dryer unit. The spray-dried catalyst was calcined at 450oC for 4 h to form final CO2 to hydrocarbons (CTH) catalyst. The final CTH catalyst was converted into pelletized form for evaluation in fixed-bed reactor.

Example-4:
75 g of activated RM clay, 12 g of binder grade alumina, and 6 g ZrO2 were mixed in desired DI water to form uniform slurry, and milled at 3D wet ball for 2 h. The milled slurry was peptized with desired amount of formic acid. The peptized slurry was spray dried at an inlet temperature of 380 oC and outlet temperature of 170 oC to form a spherical microsphere in a co-current spray dryer unit. The spray-dried catalyst was calcined at 450 oC for 4 h to form final CO2 to hydrocarbons (CTH) catalyst. The final CTH catalyst was converted into pelletized form for evaluation in fixed bed reactor.

Example-5:
75 g of activated RM clay, 12 g of binder grade alumina, 6 g ZrO2, and 0.93 g NaNO3 were mixed in desired DI water to form uniform slurry, and milled at 3D wet ball for 2 h. The milled slurry was peptized with desired amount of formic acid. The peptized slurry was spray dried at an inlet temperature of 380 oC and outlet temperature of 170 oC to form a spherical microsphere in a co-current spray dryer unit. The spray-dried catalyst was calcined at 450oC for 4 h to form final CO2 to hydrocarbons (CTH) catalyst. The final CTH catalyst was converted into pelletized form for evaluation in a fixed bed reactor.

Example-6:
A reference catalyst was prepared using the wet impregnation method. A mixture consisting of 75 g of activated RM clay, 12 g of binder grade alumina, 6 g of ZrO2, and 0.93 g of NaNO3 was mixed in deionized water to create a uniform slurry. The slurry was stirred at 75 °C on a hot plate until it reached a paste form. The catalyst paste was then subjected to drying at 120 °C for 12 h and calcination at 450 °C for 4 h to produce the final CO2 to hydrocarbons (CTH) catalyst. The final CTH catalyst was converted into pelletized form for evaluation in a fixed-bed reactor.

Example-7:
Below table 1 provides Physico-chemical properties of prepared catalysts

Table 1
Catalysts Surface area (m2/g) PV (cc/g) Particle diameter (nm)
RM Clay 33.1 0.07 5.9
Activated RM clay 54.5 0.09 6.4
Example 5 72.1 0.14 8.3
Example 6 57.4 0.10 6.7

Example-8:
A catalyst was loaded into a fixed-bed high-pressure reactor. The catalysts were initially activated within a N2 atmosphere at 400°C for a duration of 2 h, followed by reduction in a 10% H2 in N2 atmosphere for 1 h at 380°C. Reactants CO2 and H2 were subsequently introduced into the fixed-bed reactor in a molar ratio of 1:3. To facilitate the formation of hydrocarbons from CO2 and H2, the temperature was maintained at 380°C, while the pressure was set at 30 bar. The reaction is carried out for 20 h under the condition of 12000 h-1 space velocity, the reaction product mentioned in Table 2, was analyzed in gas chromatography. The unconverted CO and CO2 can be recycled again in the reactor after the separation of HCs from the stream.

Example-9:
The catalytic performance of CO2 hydrogenation into hydrocarbons at 380°C and 30 bar are tabulated below in table 2. Wherein, table 2 discloses catalytic performance of CO2 hydrogenation into hydrocarbons at 380°C and 30 bar over examples 2, 3, 4, 5, and 6 catalysts.

Table 2
Catalysts CO2 Conv. HCs Sel. CO Sel.
(%) Hydrocarbons distributions (Sel. %)
(C2-C4= + C2-C4o) C5+ CH4
Example -2 32.5 28.8 71.2 46.0 10.2 43.8
Example -3 37.1 33.2 66.8 59.4 15.7 24.9
Example -4 40.9 37.7 62.3 66.4 16.2 17.4
Example -5 46.0 40.4 59.6 72.2 15.3 12.5
Example -6 39.7 34.3 65.7 65.3 14.2 20.5

A review of Table 1 reveals that the texture properties of activated Red Mud (RM) clay improved after HCl treatment. The percentage of active components, such as iron oxide and Al2O3, increased in the composition after HCl treatment. Furthermore, the texture properties of the spray-dried catalyst obtained from Example 5 showed improvement compared to activated Red Mud (RM) clay and the Example 6 catalyst, prepared using wet impregnation.

A review of Table 2 indicates the CO2 conversion and hydrocarbons selectivity increased over spray dried catalyst having a composition of Red Mud (RM) clay, binder grade alumina, sodium nitrate, and monoclinic ZrO2. In addition, the methane selectivity decreased over the catalyst obtained from example 5. It is therefore established that the present invention provides a process to prepare a spray-dried microsphere catalyst which enhances the selectivity of hydrocarbons (HCs) in comparison to a catalyst prepared from a well-established wet impregnation method.

In example 6, the incorporation of ZrO2 and binder-grade alumina into clay led to a slight enhancement in surface area, pore volume, and pore diameter. Conversely, in example 5, employing the spray dryer technique for catalyst synthesis resulted in notable improvements in surface area, pore volume, and pore diameter, showcasing significant differences compared to other methods.

The spray-drying process yielded microspheres ranging from 20 to 150 µm, ensuring the uniform distribution of both catalyst and promoter active sites. This distribution facilitated efficient absorption and activation of CO2. The inclusion of ZrO2 further augmented oxygen vacancies, enhancing the adsorption of both CO2 and H2. Additionally, it promoted the dispersion of active sites within the clay, facilitating the formation of CO and hydrocarbons.

The inclusion of Na promoter enhanced the reduction of active sites within the clay, crucial for CO production. Additionally, Na promotion facilitated chain growth while mitigating methane selectivity. The microsphere catalyst as prepared in the present invention has CO2 conversion up to 46 % with 40.4 % hydrocarbons (HCs) selectivity.
, Claims:1. A process for preparing a microsphere catalyst for production of hydrocarbons from CO2, wherein the process comprises steps of:
preparing an activated clay by mixing a raw clay with HCL followed by filtering and washing, drying, and calcination at 500-600 oC for 1-3 hours; and
preparing the microsphere catalyst by mixing the activated clay, ZrO2, NaNO3, and a binder-grade alumina.

2. The process as claimed in claim 1, wherein, preparing the activated clay comprises steps of:
mixing raw clay to 0.2 M HCl solution to prepare an acidic solution of clay, wherein the acidic solution is kept at 60-80 oC for 2-4 hours;
filtering and washing the acidic solution of clay with deionized water to bring the pH equal to 7 and a washed clay is produced;
drying the washed clay at 100-120oC for 10-14 hours to produce a dried clay; and
calcinating the dried clay at 500-600 oC for 1-3 hours.

3. The process as claimed in claim 1-2, wherein, raw clay is 8-10 g and 0.2 M HCl solution is 180-220 ml, wherein, mixing the raw clay with HCL increases a ratio of active compounds and releases the waste metals and compounds, wherein, the active compounds are Al2O3 and iron oxide, and the waste metals and compounds are calcium and SiO2.

4. The process as claimed in claim 3, wherein, the raw clay is selected from red mud clay, Bentonite clay, kaolin clay, and a combination thereof.

5. The process as claimed in claim 1, wherein, preparing the microsphere catalyst comprises steps of:
mixing activated clay, binder grade alumina, ZrO2, and NaNO3 in deionized water to form a uniform slurry;
milling the uniform slurry at 3D wet ball for 1-3 hours to get a milled slurry; peptizing the milled slurry with formic acid to get a peptized slurry, wherein, the formic acid is 1 to 10% of binder grade alumina;
drying the peptized slurry between a temperature range of 120 oC to 380oC to form a spherical microsphere catalyst; and
calcinating the spherical microsphere catalyst at 400oC-500oC for 3-5 hours to form final microsphere catalyst.

6. The process as claimed in claim 5, wherein, activated clay is 70-80 g, binder grade alumina is 11-13 g, ZrO2 is 5-7 g, NaNO3 is 0.92-0.94 g, and deionized water is 2 to 3 times of a total solid weight of activated clay, binder grade alumina, ZrO2 and NaNO3.

7. The process as claimed in claim 5, wherein, drying the peptized slurry comprises spray drying in a co-current spray dryer unit at an inlet temperature of 380oC and outlet temperature of 170oC.

8. The process as claimed in claim 5, wherein, the final microsphere catalyst is converted into pelletized form.

9. A microsphere catalyst comprising:
(a) activated clay ranging from 75 wt% to 100 wt%;
(b) binder-grade alumina, ranging from 1 wt% to 16 wt% of the activated clay content;
(c) Sodium nitrate (NaNO3), ranging from 0.1 wt% to 0.9 wt% of the activated clay; and
(d) Zirconia (ZrO2), ranging from 3 wt% to 20 wt% of the activated clay.

10. The microsphere catalyst as claimed in claim 9, wherein, the microsphere catalyst has a particle size ranging from 20 to 150 µm.

11. The microsphere catalyst as claimed in claim 9, wherein, the microsphere catalyst has CO2 conversion up to 46 % with 40.4 % hydrocarbons (HCs) selectivity.