Description:FIELD OF THE INVENTION
The present invention discloses method for preparation of alumina material with enhanced or modified textural properties. The method comprising treating pseudo-boehmite along with lignocellulosic biomass derived materials subjected to thermal treatments to obtain modified alumina material. The present invention further relates to use of lignocellulosic biomass derived materials having specified properties for enhancing textural properties of the alumina material.
BACKGROUND OF THE INVENTION
Alumina have long used as an industrial traditional sorbent material, carrier and catalyst support because of its many benefits, including high strength, superior heat stability, and a proper pore size distribution. The pore structure parameter and superficial physico-chemical property of alumina are crucial properties for its intended purpose. The physico-chemical properties of the alumina are determined by indexes like its grain size, pattern, and degree of crystallization during synthesis of pseudo-boehmite. The processes of making shaped alumina material by modification of pseudo-boehmite also determines the textural properties of final alumina.
In general, alumina materials have a textural property of 210-230 m2/g; pore volume of 0.4-.05 cc/g; average pore diameter of 5-7 nm. By addition of compounds like activated carbon and wheat flour, the surface area, pore volume and average pore diameter of the resultant alumina can be enhanced. However, the pores formed by addition of these would result in blind pores which are not interconnected and restrict the transportation of reactant molecules.
Some of the prior art documents discloses modification of boehmite and/or pseudo boehmite material are mentioned below:
CN104860339A relates to a boehmite and/or pseudo boehmite modification method, a modifier obtained through the method, and applications of the modifier. The method comprises: (1) calcining at least an alumina hydrate, wherein the calcining conditions comprise that the temperature is 300-950 ?, and the time is 0.5-24 h; (2) mixing the calcined product obtained in the step (1), at least a boehmite and/or pseudo boehmite, and water to obtain a mixture; (3) carrying out a hydrothermal treatment on the mixture obtained in the step (2) in a sealed reactor, wherein the hydrothermal treatment conditions comprise that the temperature is 60-250 ? and the time is 0.5-48 h; and (4) drying the product obtained in the step (3) to obtain the modified boehmite or pseudo boehmite. Compared with the modifier in the prior art, the modifier of the present invention has the following characteristics that: the modifier has the high relative crystallinity, and the alumina prepared from the modifier has the high specific surface area and the high pore volume.
CN101935060A relates to a method for preparing modified alumina sol suitable for oil ammonia column forming. The method comprises the steps of: adding SB powder (pseudo-boehmite, alpha-AOOH), a water-soluble organic compound, a small molecular additive and deionized water at one time and pulping and acidifying to prepare the modified alumina sol; and performing the oil ammonia column forming on the sol, washing with the deionized water, drying and roasting to obtain the spherical alumina carrier. The modified alumina sol prepared by the method has the advantages of low thixotropy, moderate viscosity, high fluidity, operation time of the oil ammonia column forming of 10 hours, and particularly suitability for preparing the spherical alumina carrier on a large scale by the oil ammonia column forming. The prepared alumina carrier has the advantages of uniform spheres, smooth surface, particle size of about 1.5 to 2.0mm, BET specific surface area of 200 to 400m2/g, bulk density of 0.60 to 0.86g/cm3, and pore volume of 0.45 to 0.55mL/g.
CN102701246A relates to a preparation method of high-heat stable rare-earth modified alumina, comprising the following steps of: 1) reacting pseudo-boehmite by nitric acid to generate aluminum sol; 2) taking soluble salt of lanthanum, adding de-ionized water to prepare aqueous solution with the concentration of 100-260g/l; 3) taking the aluminum sol and the soluble salt solution of the lanthanum, and mixing according to the mass ratio of Al2O3 to La2O3 being at 94-97 to 3-6 to obtain modified aluminum sol; 4) uniformly mixing an organic high polymer modifier with 2-6mol of an alkaline precipitator according to the mass ratio 5-10 to 90-95 to obtain a modified alkaline precipitator; 5) mixing the modified aluminum sol with the modified alkaline precipitator, performing co-precipitation; 6) performing vacuum filtration on a modified aluminum hydroxide gel precipitant, and washing; 7) calcining the precipitant in a muffle furnace; and 8) breaking the calcined matter obtained in the step 7) to obtain a modified alumina coating material. The preparation method of the high-heat stable rare-earth modified alumina is simple in steps, and the prepared modified alumina has good high-heat stability.
Still, there was a need to develop a method of preparation of alumina material with enhanced or modified textural properties by use of low value or discarded materials.
In bio-refinery or petrochemical refinery, lignocellulosic biomass derived materials such as lignin and biochar are considered as low value or discarded materials. The lignocellulosic biomass is an abundant source of carbon.
The present invention deals with utilization of the low valued lignocellulosic biomass derived materials as additives for enhancing textural properties of the alumina.
OBJECTIVES OF THE INVENTION
The primary objective of the present invention is to provide a method for preparation of modified alumina material.

Another objective of the present invention is to provide a method for preparation of modified alumina material with enhanced or modified textural properties.

Yet another objective of the present invention is to develop a method for preparation of modified alumina material with enhanced or modified textural properties by use of lignocellulosic biomass derived materials having specified properties.

SUMMARY OF THE INVENTION
In an aspect of the present invention, the present invention discloses a method for preparation of modified alumina material, the method comprising the steps of:
a) drying a pseudo-boehmite and adding lignocellulosic biomass derived material to form a mixture;
b) preparing extrudable dough of the mixture using nitric acid as peptizing agent;
c) extruding the extrudable dough to extrudates;
d) processing the extrudates with thermal treatment to obtain the modified alumina material.
In a feature of the present invention, the lignocellulosic biomass derived material is selected from powder lignin and biochar or combination thereof; and wherein the powder lignin and biochar is obtained from pyrolysis of the lignocellulosic biomass.
In a feature of the present invention, d50 particle size of pseudo-boehmite is in the range of 5-40 µm; and wherein d50 particle size of lignocellulosic biomass derived material is at least in the range of 75-200 µm.
In a feature of the present invention, d50 particle size of the lignocellulosic biomass derived material is at least three times higher than the d50 particle size of the pseudo-boehmite.
In a feature of the present invention, weight ratio of the lignocellulosic biomass derived material to the pseudo-boehmite is in a range of 5-20.
In a feature of the present invention, the thermal treatment includes a temperature in a range of 400-550 °C and wherein the thermal treatment includes a temperature ramp of 0.5 to 2 °C/minutes.
In a feature of the present invention, carbon content in the alumina material is in a range of 1-3 wt.%.
In a feature of the present invention, the alumina material has an average pore diameter of at least 12 nm, a pore volume of at least 0.8 cc/g and a crush strength of at least 5 kg/mm.
In a feature of the present invention, the alumina material has 60-70% of pores having a pore diameter of more than 6 nm.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES
Figure 1 illustrates pore size distribution of modified alumina material of the present invention.

DETAILED DESCRIPTION OF THE INVENTION
The present invention discloses utilization of low valued lignocellulosic biomass derived materials as additives in preparation of modified alumina for enhancing textural properties of the alumina. The fused aromatic rings in the lignocellulosic biomass derived materials, i.e., lignin/biochar allow the formation of interconnected pores during thermal treatments of alumina. In this context, pseudo-boehmite (precursor to alumina material) is mixed with lignin/biochar at a certain weight ratios and particle sizes and then subjected to thermal treatments to obtain modified alumina. The resultant alumina exhibited enhance textural properties, i.e., surface area, pore volume, average pore dimeter. In particular, average pore diameter of modified alumina is enhanced to 12 nm and pore volume to 0.9 cc/g at thermal treatment of 400-550 °C.
In general, in alumina materials to achieve majority proportion of pores having pore diameter more than 10 nm, the thermal treatments should be conducted at temperatures more than 700 °C. Here in the case of lignin/biochar added to the alumina materials, 550 °C thermal treatment is sufficient to achieve the same textural properties.
Biochar is a type of charcoal that is left over from the pyrolysis of biomass. It is a light, black residue composed of ashes and carbon. “The solid material obtained from the thermochemical conversion of biomass in an oxygen-limited environment” is the definition of biochar given by the International Biochar Initiative. Rich in pyrogenic carbon, biochar is a stable solid.
Lignin is a class of intricate organic polymers which makes up important structural components of the majority of plants' support tissues. In terms of chemistry, lignins are polymers created through the cross-linking of phenolic precursors.
In an aspect of the present invention, the present invention discloses a method for preparation of modified alumina material, the method comprising the steps of:
a) drying a pseudo-boehmite and adding lignocellulosic biomass derived material to form a mixture;
b) preparing extrudable dough of the mixture using nitric acid as peptizing agent;
c) extruding the extrudable dough to extrudates;
d) processing the extrudates with thermal treatment to obtain the modified alumina material.
In an embodiment of the present invention, the lignocellulosic biomass derived material is selected from powder lignin and biochar or combination thereof; and wherein the powder lignin and biochar is obtained from pyrolysis of the lignocellulosic biomass.
In an embodiment of the present invention, d50 particle size of pseudo-boehmite is in the range of 5-40 µm; and wherein d50 particle size of lignocellulosic biomass derived material is at least in the range of 75-200 µm.
In an embodiment of the present invention, d50 particle size of the lignocellulosic biomass derived material is at least three times higher than the d50 particle size of the pseudo-boehmite.
In an embodiment of the present invention, weight ratio of the lignocellulosic biomass derived material to the pseudo-boehmite is in a range of 5-20.
In an embodiment of the present invention, the thermal treatment includes a temperature in a range of 400-550 °C and wherein the thermal treatment includes a temperature ramp of 0.5 to 2 °C/minutes.
In an embodiment of the present invention, carbon content in the alumina material is in a range of 1-3 wt.%.
In an embodiment of the present invention, the alumina material has an average pore diameter of at least 12 nm, a pore volume of at least 0.8 cc/g and a crush strength of at least 5 kg/mm.
In an embodiment of the present invention, the alumina material has 60-70% of pores having a pore diameter of more than 6 nm.
Use of the modified alumina of the present invention are:
- helps in residue hydrocracking;
- helps in residue de-metallization reaction; and
- helps in crude hydrocracking.
Advantages of the modified alumina of the present invention are:
- High surface area helps in high dispersion of active metal;
- High pore volume helps in accommodating large size reactant molecules; and
- High average pore diameter helps in minimizing coking.

EXAMPLES
Example 1:
The comparative alumina material preparation contains the following steps.
a) A desired amount of pseudo-boehmite having a particle size of d50 of 10-25 µm was dried at 120 °C for 6 hours.
b) The pseudo-boehmite was peptized with 0.7 wt.% of HNO3 with respect to weight of pseudo-boehmite for 15 minutes. The extrudable mixture was extruded into cylindrical extrudates and aged at 30 °C for a period of 4 hours followed by drying at 120 °C for 5 hours. The dried extrudates were subjected to thermal treatments at 550 °C for 4 hours.
Example 2:
The comparative alumina material preparation contains the following steps.
a) A desired amount of pseudo-boehmite having a particle size of d50 of 10-25 µm was dried at 120 °C for 6 hours and 10 wt.% of activated carbon with respect to weight of pseudo-boehmite of particle size of 75-120 µm was systematically mixed and grounded.
b) The pseudo-boehmite and amorphous carbon mixture was peptized with 0.7 wt.% of HNO3 with respect to weight of pseudo-boehmite for 15 minutes. The extrudable mixture was extruded into cylindrical extrudates and aged at 30 °C for a period of 4 hours followed by drying at 120 °C for 5 hours. The dried extrudates are subjected to thermal treatments at 550 °C for 4 hours.
Example 3:
The alumina material of the present invention preparation procedure contains the following steps:
a) A desired amount of pseudo-boehmite having a particle size of d50 of 10-25 µm is dried at 120 °C for 6 hours and 10 wt.% of powdered lignin with a particle size of 75-120 µm is added to the dried pseudo-boehmite and systematically mixed and grounded.
b) The mixture was peptized with 0.7 wt.% of HNO3 with respect to weight of pseudo-boehmite for 15 minutes. The extrudable mixture was extruded into cylindrical extrudates and aged at 30 °C for a period of 4 hours followed by drying at 120 °C for 5 hours. The dried extrudates were subjected to thermal treatments at 550 °C for 4 hours.
Example 4:
The alumina material of the present invention preparation procedure contains the following steps:
a) A desired amount of pseudo-boehmite having a particle size of d50 of 10-25 µm is dried at 120 °C for 6 hours and 10 wt.% of powdered biochar obtained from pyrolysis of lignocellulosic biomass having a particle size of 100-150 µm was added to the dried pseudo-boehmite and systematically mixed and grounded.
b) The mixture is peptized with 0.7 wt.% of HNO3 with respect to weight of pseudo-boehmite for 15 minutes. The extrudable mixture is extruded into cylindrical extrudates and aged at 30 °C for a period of 4 hours followed by drying at 120 °C for 5 hours. The dried extrudates are subjected to thermal treatments at 550 °C for 4 hours.
Textural properties of the prepared alumina materials of the examples are given below:
Table-1
Property Example 1 Example 2 Example 3 Example 4
Surface area (m2/g) Base +10 +10 +30
Pore Volume (cc/g) Base +0.1 +0.1 +0.3
Average Pore Diameter (nm) Base Base +2 +5 , Claims:1. A method for preparation of modified alumina material, the method comprising the steps of:
a) drying a pseudo-boehmite and adding lignocellulosic biomass derived material to form a mixture;
b) preparing extrudable dough of the mixture using nitric acid as peptizing agent;
c) extruding the extrudable dough to extrudates;
d) processing the extrudates with thermal treatment to obtain the modified alumina material.
2. The method as claimed in claim 1, wherein the lignocellulosic biomass derived material is selected from powder lignin and biochar or combination thereof; and wherein the powder lignin and biochar is obtained from pyrolysis of the lignocellulosic biomass.
3. The method as claimed in claim 1, wherein d50 particle size of the pseudo-boehmite is in a range of 5-40 µm; and wherein d50 particle size of lignocellulosic biomass derived material is at least in a range of 75-200 µm.
4. The method as claimed in claim 4, wherein d50 particle size of the lignocellulosic biomass derived material is at least three times higher than the d50 particle size of the pseudo-boehmite.
5. The method as claimed in claim 1, wherein weight ratio of the lignocellulosic biomass derived material to the pseudo-boehmite is in a range of 5-20.
6. The method as claimed in claim 1, wherein the thermal treatment includes a temperature in a range of 400-550 °C, and wherein the thermal treatment includes a temperature ramp of 0.5 to 2 °C/minutes.
7. The method as claimed in claim 1, wherein carbon content in the modified alumina material is in a range of 1-3 wt.%.
8. The method as claimed in claim 1, wherein the modified alumina material has an average pore diameter of at least 12 nm, a pore volume of at least 0.8 cc/g and a crush strength of at least 5 kg/mm.
9. The method as claimed in claim 1, wherein the modified alumina material has 60-70% of pores having a pore diameter of more than 6 nm.