Hydrothermally stable catalyst composition and a process for preparation thereof

Abstract

The present disclosure relates to a hydrothermally stable catalyst composition. The hydrothermally stable supported catalyst composition comprises K.sub.2CO.sub.3 impregnated on an amorphous silica-alumina support. The weight ratio of silica to alumina in the support is in the range of 0.1 to 1.5. The amount of K.sub.2CO.sub.3 is in the range of 5 wt % to 60 wt % with respect to the total catalyst composition. The catalyst composition is characterized by a pore volume in the range of 0.1 cc/g to 0.9 cc/g, a surface area in the range of 40 m.sup.2/g to 250 m.sup.2/g and an attrition index in the range of 2% to 8%. The present disclosure also relates to a process for preparing the catalyst composition. The catalyst composition provides improved hydrothermal stability, attrition resistance, high pore volume and surface area for gasifying carbonaceous feed at low temperature, as compared to a conventional catalyst composition.

Claims

1. A hydrothermally stable catalyst composition for low temperature gasification of carbonaceous feedstock, said catalyst composition comprising: a) an amorphous silica-alumina support; wherein said amorphous silica-alumina support having an average particle size in the range of 80 μm to 150 μm; wherein a weight ratio of silica to alumina in said amorphous silica-alumina support is in the range of 0.1 to 1.5; and b) K.sub.2CO.sub.3 impregnated on said amorphous silica-alumina support; wherein said K.sub.2CO.sub.3 is impregnated on said amorphous silica-alumina support in an amount in the range of 5 wt % to 60 wt % with respect to the total catalyst composition.

2. The catalyst composition as claimed in claim 1 is characterized by a pore volume in the range of 0.1 cc/g to 0.9 cc/g, a surface area in the range of 40 m.sup.2/g to 250 m.sup.2/g, pore diameter in the range of 125 to 150 Å and an attrition index in the range of 2% to 8% as measured per ASTM D5757.

3. The catalyst composition as claimed in claim 1, is stable during the hydrothermal deactivation at a temperature in the range of 750 to 850 deg C. in presence of steam environment and loss of pore volume is within 15% and loss of surface area is within 20% and change in pore diameter by 4% and attrition index is within 10%.

4. The catalyst composition as claimed in claim 1, wherein a weight ratio of silica to alumina in said amorphous silica-alumina support is in the range of 0.1 to 0.9.

5. The catalyst composition as claimed in claim 2, wherein said pore volume, said surface area, pore diameter and said attrition index of said catalyst composition is retained after gasification of the carbonaceous feedstock at a temperature up to 850 deg C.

6. A process for preparing the hydrothermally stable catalyst composition of claim 1, said process comprising the following steps: a) mixing a silica salt in water to obtain an alkaline aqueous solution; b) adding an acidic aqueous solution comprising 30% to 40% of an acid in water to said alkaline aqueous solution while maintaining the pH in the range of 8 to 9, to obtain precipitated silica; c) separating said precipitated silica to obtain silica cake; d) treating said silica cake with an acidic aqueous solution of an aluminum salt to obtain a first slurry; e) stirring said first slurry to obtain a hydrated silica alumina slurry having a pH less than 2; f) adding an aqueous solution of sodium aluminate or calcium aluminate to said hydrated silica alumina slurry to obtain a second slurry having a pH in the range of 4 to 5; g) filtering said second slurry to obtain a wet cake; h) re-slurring said wet cake in water to obtain a pumpable slurry, followed by spray drying said pumpable slurry to obtain an amorphous silica-alumina support having an average particle size in the range of 80 μm to 150 μm; and i) impregnating said support with K.sub.2CO.sub.3 to obtain a K.sub.2CO.sub.3 impregnated support, followed by drying said K.sub.2CO.sub.3 impregnated support to obtain a hydrothermally stable catalyst composition.

7. The process as claimed in claim 6, wherein said silica salt is at least one of sodium silicate and potassium silicate.

8. The process as claimed in claim 6, wherein said acid is least one selected from the group consisting of sulfuric acid, hydrochloric acid and nitric acid.

9. The process as claimed in claim 6, wherein said aluminum salt is at least one of aluminum sulfate and aluminum chloride.

10. The process as claimed in any one of the claim 6, wherein said acidic aqueous solution of said aluminum salt of the process step d) is obtained by mixing said aluminum salt in 30% to 40% of an acid.

11. The process as claimed in claim 6, wherein K.sub.2CO.sub.3 is impregnated on said support by either an incipient wetness impregnation method or a multi-step impregnation method.

Description

DETAILED DESCRIPTION

(1) The hydrothermal stability of a catalyst is a critical parameter for catalytic gasification of carbonaceous feedstocks to synthesis gas, as the catalyst is expected to endure the severe hydrothermal environment (for example:—of steam and hydrogen) during the gasification of carbonaceous feedstocks. It is observed that the hydrothermal stability of the conventional support, i.e., γ-alumina is inferior under the conditions of catalytic gasification and hence, it is unable to provide stable gasification activity, which leads to reduction in carbon conversion during the steam gasification of carbonaceous feedstocks over a period of time.

(2) Typically, the pore volume and surface area of the commercially available spray dried micro sphere γ-alumina particles are <0.5 cc/g and <185 m.sup.2/g, respectively. It is observed that there is a significant loss in the pore volume and the surface area of the γ-alumina when it undergoes the hydrothermal deactivation test (particularly in the presence of steam at 800° C. and for 24 hours). The pore volume and the surface area of the γ-alumina drops to <0.28 cc/g and <65 m.sup.2/g, respectively, due to the hydrothermal deactivation. It is observed that if higher amount of active metals is loaded on to the support, a further reduction in the pore volume and surface area is obtained. Also, active metals are buried in the pores of the support and may not be accessible for the reaction.

(3) Further, it is observed that the alkali metals supported γ-alumina catalyst, when used in the gasification of carbonaceous feedstocks at high temperature in the presence of steam and hydrogen, is prone to loss of pore volume due to the phase transition of γ-alumina to a more stable α-alumina, resulting in loss of the gasification activity over a period of time. Moreover, there are several commercial supports available are not able to retain the attrition index. Further, is it observed that the alkali metals form agglomerates (alkali-alumino-silicates) with the silica-alumina matrix which is not desired.

(4) The present disclosure therefore envisages a hydrothermally stable catalyst composition and a process for preparing the same that obviates the above mentioned drawbacks.

(5) In an aspect of the present disclosure, the hydrothermally stable catalyst composition comprises an amorphous silica-alumina support; and K.sub.2CO.sub.3 impregnated on the support (the term “support” mentioned hereinafter refers to the “amorphous silica-alumina support”).

(6) In accordance with one embodiment of the present disclosure the weight ratio of silica to alumina in the support is in the range of 0.1 to 1.5. In accordance with another embodiment of the present disclosure, the weight ratio of silica to alumina in the support is in the range of 0.1 to 0.9. K.sub.2CO.sub.3 is impregnated on the amorphous silica-alumina support in an amount in the range of 5 wt % to 60 wt % with respect to the total catalyst composition.

(7) The catalyst composition is characterized by a pore volume in the range of 0.1 cc/g to 0.9 cc/g, a surface area in the range of 40 m.sup.2/g to 250 m.sup.2/g and an attrition index in the range of 2% to 8%.

(8) Particularly, the amorphous nature of silica in the silica-alumina support facilitates in resisting the phase transition of the alumina, i.e., from gamma alumina to alpha alumina.

(9) The use of the amorphous support having a high pore volume and surface area enables higher alkali (K.sub.2CO.sub.3) loadings and better alkali dispersion on the support, which in turn provides superior gasification activity.

(10) In another aspect of the present disclosure, there is provided the process for preparing the catalyst composition. The process is described herein below.

(11) A silica salt is mixed in water to obtain an alkaline aqueous solution. The silica salt is at least one of sodium silicate and potassium silicate.

(12) An acidic aqueous solution is added to the alkaline aqueous solution while maintaining the pH in the range of 8 to 9, to obtain precipitated silica. The acidic aqueous solution comprises 30% to 40% of an acid in water. In accordance with the present disclosure, the acid is least one selected from the group consisting of sulfuric acid, hydrochloric acid and nitric acid. The precipitated silica is separated to obtain silica cake. Typically, the precipitated silica is separated by filtration or decantation.

(13) The silica cake is treated with an acidic aqueous solution of an aluminum salt to obtain a first slurry, followed by stirring the first slurry to obtain a hydrated silica alumina slurry having a pH less than 2. The aluminum salt is at least one of aluminum sulfate and aluminum chloride. Typically, the acidic aqueous solution of the aluminum salt is obtained by mixing the aluminum salt in 30% to 40% of the acid (i.e., 30% to 40% of the acid in water).

(14) An aqueous solution of sodium aluminate or calcium aluminate is added to the hydrated silica alumina slurry to obtain a second slurry, followed by filtering the second slurry to obtain a wet cake. The pH of the second slurry is in the range of 4 to 5. Although sodium aluminate has been used as the base for increasing the pH in the following experiments, calcium aluminate can also be easily substituted as will be well known for a person of ordinary skilled in the art.

(15) Particularly, the wet cake obtained is not pumpable for preparing spray dried spherical particles. Therefore, the wet cake is re-slurried in water to obtain a pumpable slurry, followed by spray drying the pumpable slurry to obtain an amorphous silica-alumina support having an average particle size in the range of 80 μm to 150 μm. In an embodiment of the present disclosure, the pumpable slurry is spray dried by co-current drying. In accordance with an embodiment of the present disclosure, the average particle size of the support is 90 μm.

(16) The support is impregnated with K.sub.2CO.sub.3 to obtain a K.sub.2CO.sub.3 impregnated support, followed by drying the K.sub.2CO.sub.3 impregnated support to obtain a hydrothermally stable catalyst composition. In accordance with the present disclosure, K.sub.2CO.sub.3 is impregnated on the support by an incipient wetness impregnation method or a multi-step impregnation method.

(17) Typically, in the incipient wetness impregnation method, K.sub.2CO.sub.3 is dissolved in an aqueous or organic solution. Then the solution is added to the support preferably containing the same pore volume as the volume of the solution that was added. The solution is absorbed into the pores by capillary action. If the solution is added in excess of the support pore volume, then the solution transport changes from a capillary action process to a diffusion process, which is a slower process. The catalyst is dried and calcined to remove the volatile components present in the solution, thereby depositing K.sub.2CO.sub.3 on the surface of the support. Particularly, the mass transfer conditions are responsible for the concentration profile of K.sub.2CO.sub.3 within the pores during the process steps of impregnation and drying.

(18) The catalyst composition is used for low temperature gasification of carbonaceous feedstock using a single fluidized bed gasification system or a dual fluidized bed gasification system, which operates at a temperature in the range of 600° C. to 850° C., at a pressure in the range of 1 bar to 5 bar and in the presence of a gasifying agent (for example: —CO.sub.2 or steam), to produce synthesis gas. Moreover, the catalyst composition is stable when subjected to the gasification of carbonaceous feedstocks at a temperature of up to 800° C. for at least 24 hours in the presence of steam. The carbonaceous feedstock is at least one selected from the group consisting of petcoke, coal, biomass, wood and other carbon-containing materials.

(19) Particularly, the catalyst with carbon particles deposited thereon (deactivated catalyst) from the gasifier is fed to a combustor for combusting a portion of the feed in the presence of air at a temperature in the range of 800° C. to 825° C. Due to the combustion, the deposited carbon particles are combusted to regenerate the catalyst. The regenerated catalyst (activated catalyst) is re-circulated in the gasifier. Since, the catalyst undergoes continuous deactivation and activation, it is necessary for the catalyst to have the hydrothermal stability at 850° C. for 24 hours in the presence of steam.

(20) The catalyst composition possesses features such as hydrothermal stability, attrition resistance, high pore volume and surface for better dispersion of K.sub.2CO.sub.3 (i.e., high surface area), and consistent activity for the gasification of carbonaceous feedstock.

(21) Further, K.sub.2CO.sub.3 does not form agglomerates with the silica-alumina matrix. The catalyst composition of the present disclosure is capable of retaining its pore volume and surface area during the gasification of carbonaceous feedstocks. The loss in pore volume and surface area is within 60% of the original pore volume and surface area prior to the hydrothermal deactivation, and it retains its mechanical strength, i.e., the attrition index in the range of 2% to 8%.

(22) The present disclosure is further described in light of the following laboratory scale experiments which are set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure. These laboratory scale experiments can be scaled up to industrial/commercial scale and the results obtained can be extrapolated to industrial/commercial scale.

EXPERIMENTAL DETAILS

(23) Experiment 1: Preparation of an Amorphous Silica-Alumina Support

(24) 745 g of sodium silicate was dissolved in 9000 ml water to obtain an alkaline aqueous solution of sodium silicate. 550 ml of 35% H.sub.2SO.sub.4 solution was added to the alkaline aqueous solution of sodium silicate, while maintaining pH of 9 to obtain precipitated silica. The precipitated silica was separated by filtration to obtain silica cake. An acidic aqueous solution of aluminum sulfate was prepared by mixing 354 g of aluminum sulfate in 1062 ml of water.

(25) The so obtained silica cake was added to 1240 ml of acidic aqueous solution of aluminum sulfate to obtain a first slurry. The first slurry was thoroughly stirred to obtain a hydrated silica-alumina slurry having a pH of 1. An aqueous solution of sodium aluminate was added in the hydrated silica-alumina slurry to obtain a second slurry having a pH of 5. The aqueous solution of sodium aluminate was obtained by mixing 290 g of sodium aluminate in 4000 ml of water. The second slurry was filtered on a rotary drum vacuum filter to obtain a wet cake. The wet cake was re-slurried with water to obtain a pumpable slurry. The pumpable slurry was spray dried by co-current drying to obtain a silica-alumina support.

(26) The relative proportions of silica and alumina in the final product were varied by taking different proportions of sodium silicate, aluminum sulfate and sodium aluminate. Different amorphous silica-alumina samples were prepared in which the silica to alumina ratio (SAR) was varied and further these samples were subjected to a hydrothermal deactivation (steaming) test which was carried out in a fluidized reactor at a temperature of 800° C. for 24 hours under continuous steam purging condition. The mechanical strength (which is represented by attrition index) of the support was tested on an attrition testing unit as per ASTM D5757 method for obtaining respective attrition index.

(27) Table-1a summarizes the physical properties of different amorphous silica-alumina supports prepared in accordance with the embodiments of the present disclosure, both fresh (as such) and after hydrothermal deactivation and Table-1 b summarizes the physical properties of different γ-alumina based supports of the conventional catalysts.

(28) TABLE-US-00001 TABLE 1a Characterization of different amorphous silica-alumina (SAR = SiO.sub.2: Al.sub.2O.sub.3) based supports of the present disclosure Pore Attrition S. Catalyst TSA TPV diameter index No. Support condition (m.sup.2/g) (cc/g) (°A) (%) 1 SAR = 1:8 Fresh 203 0.724 138 4.28 2 (0.12) Steamed 177 0.612 143 5.7 3 SAR = 1:3.7 Fresh 210 0.74 142 2.75 4 (0.27) Steamed 182 0.65 147 3.81 5 SAR = 1:4.8 Fresh 225 0.775 138 2.38 6 (0.20) Steamed 192 0.695 143 3.12 7 SAR = 1:3.5 Fresh 219 0.688 125 2.14 8 (0.28) Steamed 178 0.576 130 3.32 9 SAR = 1:2 Fresh 240 0.82 136 2.12 10 (0.5) Steamed 203 0.76 141 2.95 11 SAR = 1:1.4 Fresh 247 0.815 132 5.64 12 (0.7) Steamed 211 0.742 138 6.21 (TSA-total surface area, TPV-total pore volume)

(29) From Table-1a, it is evident that there is a minor reduction in the pore volume and surface area, and minor increase in the attrition index after the hydrothermal deactivation as compared to that of the fresh catalyst support. From Table-1a, it is also evident that at SiO.sub.2:Al.sub.2O.sub.3(SAR) of 0.5, the support possesses comparatively higher pore volume (0.82 cc/g), surface area (240 m.sup.2/g) and mechanical strength (attrition index <2.2).

(30) TABLE-US-00002 TABLE 1b Characterization of different γ-alumina based supports of the conventional catalysts Pore Attrition S. Catalyst TSA TPV diameter index No. Support condition (m.sup.2/g) (cc/g) (°A) (%) 1 γ-Alumina Fresh 184 0.459 99 3.4 2 Steamed 65 0.279 171 4.2 3 3% Ce on Fresh 196 0.464 95 3.8 4 γ-Alumina Steamed 124 0.435 140 4.5 5 5% Ce on Fresh 144 0.449 124 4.1 6 γ-Alumina Steamed 86 0.333 160 4.5 7 3% alumina on Fresh 130 0.407 125 3.6 8 γ-Alumina Steamed 81 0.323 158 3.9 9 5% alumina on Fresh 226 0.277 49 3.7 10 γ-Alumina Steamed 117 0.269 92 4.2 11 3% La on Fresh 224 0.396 70 5.5 12 γ-Alumina Steamed 121 0.389 136 6.7 13 Modified Fresh 231 0.432 95 4.5 14 γ-Alumina Steamed 122 0.417 137 5.8 by high digestion time

(31) From Table-1 b, it is clear that there is no significant improvement in the surface area, pore volume and attrition index of a catalyst composition obtained by impregnating varying amounts of different metals such as La and Ce on γ-Alumina as compared to the conventional catalyst (γ-Alumina).

(32) From Table-1a and Table-1b, it is evident that the surface area, pore volume and attrition index of the catalyst composition of the present disclosure is better as compared to that of the conventional γ-alumina support and conventional catalyst composition (as shown in Table-1 b).

(33) The properties such as the surface area, pore volume and attrition index are responsible for increasing the hydrothermal stability of a catalyst composition. From Table-1a and Table-1b, it is evident that these properties are better in case of the catalyst composition of the present disclosure as compared to that of the conventional γ-alumina support and conventional catalyst composition; therefore, it can be concluded that the hydrothermal stability of the catalyst composition of the present disclosure is superior as compared to of the conventional γ-alumina support.

(34) Experiment 2a: Impregnation of K.sub.2CO.sub.3 on the Silica-Alumina Support Using Wet-Impregnation Method

(35) The alkali metal supported catalyst was prepared by impregnating K.sub.2CO.sub.3 on the support, i.e., amorphous silica-alumina support (having SAR of 0.5) by using the incipient wetness impregnation method. In this method, 100 g of K.sub.2CO.sub.3 was dissolved in 90 ml water to obtain a saturated solution of K.sub.2CO.sub.3. 100 g of amorphous silica-alumina was poured into the K.sub.2CO.sub.3 saturated solution and was mixed thoroughly for 1 hour to obtain the mixture. The so obtained mixture was dried at 80° C. for 24 hours. The mixture was further dried under reduced pressure at 105° C. for 12 hours to obtain the hydrothermally stable supported catalyst composition.

(36) Experiment 2b: Impregnation of K.sub.2CO.sub.3 on the Silica-Alumina Support Using Multi-step Impregnation Method

(37) In multi-step impregnation method, an active metal is impregnated on the support in a stage wise manner in which a fraction of the total amount of the active metal is impregnated at each stage.

(38) In this method, 10 wt % of K.sub.2CO.sub.3 was impregnated at every successive stage and the catalyst was dried in each impregnation stage.

(39) Different amounts of K.sub.2CO.sub.3 impregnated on the support are illustrated in Table-2a.

(40) TABLE-US-00003 TABLE 2a Ratio of K.sub.2CO.sub.3 to support in accordance with the present disclosure K.sub.2CO.sub.3 Support Alkali (K) (56.58% of Alkali (K)/ (%) (%) K.sub.2CO.sub.3) Support Ratio 5 95 2.83 0.03 10 90 5.66 0.06 20 80 11.32 0.14 30 70 16.98 0.24 40 60 22.63 0.38 50 50 28.29 0.57 60 40 33.95 0.85

(41) Table-2b summarizes the properties of K.sub.2CO.sub.3 supported on the amorphous silica-alumina support (having SAR of 0.5) prepared by impregnating 10 wt % to 60 wt % of K.sub.2CO.sub.3 on the silica-alumina support using the single step and multi-step impregnation methods of the present disclosure.

(42) TABLE-US-00004 TABLE 2b Comparison of the characteristics of K.sub.2CO.sub.3 supported on the amorphous silica-alumina support prepared using the single step and multi-step impregnation methods of the present disclosure K.sub.2CO.sub.3 impregnated No. on the support i.e. Pore of amorphous dia- S. Preparation equal silica:alumina TSA TPV meter No. method steps (SAR = 0.5) (m.sup.2/g) (cc/g) (°A) 1 Support (SAR = 0.5) 240 0.82 136 alone 2 Single step 1 10 wt % K.sub.2CO.sub.3 220 0.74 140 3 impregnation 1 20 wt % K.sub.2CO.sub.3 189 0.62 143 4 1 30 wt % K.sub.2CO.sub.3 160 0.49 147 5 1 40 wt % K.sub.2CO.sub.3 125 0.36 145 6 1 50 wt % K.sub.2CO.sub.3 95 0.24 149 7 1 60 wt % K.sub.2CO.sub.3 48 0.12 152 8 Multi step 2 20 wt % K.sub.2CO.sub.3 196 0.85 143 9 impregnation 3 30 wt % K.sub.2CO.sub.3 173 0.55 151 10 4 40 wt % K.sub.2CO.sub.3 145 0.44 138 11 5 50 wt % K.sub.2CO.sub.3 118 0.34 140 12 6 60 wt % K.sub.2CO.sub.3 95 0.26 144 13 2 40 wt % K.sub.2CO.sub.3 134 0.39 140 14 3 60 wt % K.sub.2CO.sub.3 80 0.21 142

(43) From Table-2b, it is observed that the pore volume and the surface area decrease with increase in the loading of K.sub.2CO.sub.3. However, for a given loading of K.sub.2CO.sub.3, the surface area and pore volume are higher in case of the multi-step impregnation method as compared to that of the single step impregnation method. In case of multi-step impregnation, the active component (K.sub.2CO.sub.3) covers the pore walls and is filled in the pores of the support, thereby resulting in less decrease in the pore volume and surface area as compared to that of the single step impregnation method. This multi-step impregnation is expected to provide better metal dispersion throughout the support due to the controlled loading of active metal in step-wise manner. Moreover, the interaction of K.sub.2CO.sub.3 and the support does not result in a significant change in the mesoporous structure of the support.

(44) Experiment 3: Gasification Activity

(45) The gasification activity of the hydrothermally stable silica-alumina supported catalyst of the present disclosure (i.e. K.sub.2CO.sub.3 supported on the amorphous silica-alumina support [wherein SAR=0.5]) was verified by carrying out the steam gasification of petcoke (1 g) at a temperature of 700° C. with a catalyst to coke ratio of 50, for a time period of 10 minutes in a fixed fluid bed reactor. The catalytic steam gasification activity of the petcoke was verified by using a laboratory-scale fixed fluid bed reactor set-up consisting of a vertical tubular reactor (30 cm length and 4 cm width) and a steam generator, which was heated with the help of an electric split furnace. Studies were conducted under catalytic conditions in which the reactor was loaded with a mixture of 1 g of petcoke and 50 g of the hydrothermally stable silica-alumina supported catalyst prepared in Experiment 1.

(46) The loaded reactor was then kept in the split furnace and heated up to the reaction temperature of 700° C. under nitrogen gas (inert gas) flow. Once the desired reaction temperature of 700° C. was attained, nitrogen supply to the reactor was replaced with steam at a flow rate of 0.3 g/min. The pressure was maintained at 1 bar in the presence of steam as a gasifying agent, the fluidized bed superficial velocity was maintained at 0.5 m/s, the catalyst to feed ratio was 50 and the molar ratio of gasifying agent to the carbonaceous feedstock was 2. The total product gas was collected in a water displacement system and further analyzed with the help of gas chromatography (GC). The amount of the gas produced depends on the reaction rate/carbon conversion, which is dependent on the catalyst effectiveness at a given operating condition. The steam supply of the reactor was stopped after 15 minutes. The un-reacted petcoke was burnt with air and the total combustion product gas was also collected and its composition was measured. Further, the carbon content in the combustion product gas (in terms of CO.sub.2 and CO gases) was calculated to estimate the remaining carbon which did not react during the steam gasification of petcoke. Further, the complete mass balance and precise carbon conversion of steam gasification was verified from the composition analysis of the product gases of both gasification and combustion reactions.

(47) Table-3a summarizes the gasification activity of the hydrothermally stable silica-alumina catalyst compositions of the present disclosure. Particularly, Table-4a provides a comparative analysis of the gasification activity when 50 wt % of K.sub.2CO.sub.3 was impregnated on the amorphous silica-alumina support (SAR=0.5) prepared by the single impregnation step method and 60 wt % of K.sub.2CO.sub.3 was impregnated on the amorphous silica-alumina support (SAR=0.5) prepared by the multi-step impregnation method.

(48) TABLE-US-00005 TABLE 3a Comparison of the gasification activity and the properties of the catalyst composition of the present disclosure, i.e., K.sub.2CO.sub.3 supported on the amorphous silica-alumina support before and after hydrothermal deactivation Surface Pore Attrition Reaction Carbon Metal Impregnation Catalyst area volume index time & conversion loading technique Support condition (m.sup.2/g) (cc/g) (%) temperature (%) 60 wt % Multi-step Amorphous Fresh 95 0.26 3.6 10 min & 100 of Impregnation silica: Steamed 48 0.14 4.2 700° C. 92 K.sub.2CO.sub.3 alumina 50 wt % Single-step (SAR = 0.5) Fresh 95 0.24 3.42 10 min & 100 of Impregnation Steamed 40 0.11 4.1 700° C. 85 K.sub.2CO.sub.3

(49) From Table-3a, it is evident that the silica-alumina supported catalyst of the present disclosure is capable of retaining its activity even after the hydrothermal deactivation. Hence, the supported catalyst of the present disclosure has improved properties such as hydrothermal stability, attrition resistance, high pore volume/surface area, and the catalyst is capable of sustaining the gasification activity at low temperature (700° C.) even after hydrothermal deactivation as compared to that of the conventional K.sub.2CO.sub.3 supported γ-alumina catalyst.

(50) Table-3b provides a comparison between the gasification activity of the conventional fresh catalyst, i.e., 50% K.sub.2CO.sub.3 on γ-alumina and the hydrothermally deactivated conventional catalyst.

(51) TABLE-US-00006 TABLE 3b Comparison of the gasification activity of the conventional alkali supported catalyst (γ-Alumina) under different conditions fresh and steamed (hydrothermal deactivation) Reaction Catalyst/ Carbon Supported Catalyst time Temperature coke conversion catalyst condition (minutes) (° C.) (g/g) (%) 50% K.sub.2CO.sub.3 Fresh 15 700 50 85.6 on γ-Alumina Steamed 45

(52) From Table-3b, it is clear that upon deactivation of the conventional supported catalyst (γ-alumina) a significant loss in gasification activity is observed because of the low surface area and pore volume of the catalyst after the hydrothermal deactivation i.e. γ-alumina support loses its pore volume and surface area. From Tables-3a and 3b, it can be concluded that the gasification activity of the fresh and steamed catalyst composition of the present disclosure is significantly higher as compared to that of the conventional alkali supported catalyst (γ-Alumina).

(53) Experiment 4: Re-Usability of the Hydrothermally Stable Catalyst

(54) The re-suability of the hydrothermally stable catalyst of the present disclosure (i.e., alkali supported on the amorphous silica-alumina support [SAR=0.5]) was verified by carrying out the steam gasification of petcoke (1 g) at a temperature of 700° C. with a catalyst to coke ratio of 50, for 10 minutes in a fixed fluid bed reactor, similar to the process described in Experiment-3. The hydrothermally stable catalyst was prepared by impregnating the 50% of K.sub.2CO.sub.3 on the amorphous silica-alumina support (SAR=0.5) by using the multi-step impregnation method as explained in Experiment-2. Further, the catalyst was hydrothermally deactivated prior to its use in this experiment. After the completion of each reaction, the used catalyst was collected and re-used for the next reaction and this was repeated 5 times. The results of re-usability are tabulated in Table-4.

(55) Table-4 summarizes the gasification activity of the five reactions which were carried out under similar conditions in the presence the same catalyst (re-used catalyst).

(56) TABLE-US-00007 TABLE 4 Re-usability of the hydrothermally deactivated catalyst, i.e., 50 wt % of K.sub.2CO.sub.3 supported on the amorphous silica-alumina support (SAR = 0.5) 1.sup.st 2.sup.nd 3.sup.rd 4.sup.th 5.sup.th Usage Usage Usage Usage Usage Carbon Conversion (%) 89 87 88 87 89

(57) From Table-4, it is evident that the catalyst of the present disclosure is capable of sustaining the gasification activity, i.e., the gasification activity is consistent, during the steam gasification of petcoke at a temperature of 700° C., and can be re-used.

(58) From the above experiments, it can be concluded that the gasification activity of the catalyst composition of the present disclosure is high and it exhibits regenerability, i.e., it is capable of retaining its activity without any decay, as compared to that of the conventional catalyst. It can also be concluded that the catalyst composition does not lose its properties such as pore volume, surface area and attrition resistance even after hydrothermal deactivation, thereby enabling higher loading of K.sub.2CO.sub.3 on the amorphous silica-alumina support.

(59) Technical Advances and Economical Significance

(60) The present disclosure described herein above has several technical advantages including, but not limited to, the realization of a hydrothermally stable catalyst composition that: possess properties such as high hydrothermal stability, pore volume, surface area, and mechanical strength; and is capable of retaining the gasification activity even after hydrothermal deactivation, at significantly lower temperature.

(61) Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

(62) The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results. While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Variations or modifications to the formulation of this invention, within the scope of the invention, may occur to those skilled in the art upon reviewing the disclosure herein. Such variations or modifications are well within the spirit of this invention.

(63) The numerical values given for various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the invention unless there is a statement in the specification to the contrary.

(64) While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the disclosure. These and other changes in the preferred embodiment of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.