Hydrophobic surface modified aluminas and method for making thereof

Abstract

A method of producing a hydrophobic porous alumina by: i) providing a slurry comprising an alumina compound, the slurry having a pH equal to or greater than 7; ii) adding an organic composition comprising carboxylic acids with alkyl hydrocarbon chains having a carbon length less than 14 to the slurry to form an acidic modified slurry; the acidic modified slurry having a pH of between 3 and less than 7; iii) hydrothermally aging the acidic modified slurry to form a hydrothermally aged slurry; and iv) drying the hydrothermally aged slurry.

Claims

1. A method of producing a hydrophobic porous alumina comprising the steps of: i) providing a slurry comprising an alumina compound, the slurry having a pH equal to or greater than 7; ii) adding an organic composition comprising carboxylic acids with alkyl hydrocarbon chains having a carbon length less than 10, to the slurry to form an acidic modified slurry; the acidic modified slurry having a pH of between 3 and less than 7; iii) hydrothermally aging the acidic modified slurry to form a hydrothermally aged slurry; and iv) drying the hydrothermally aged slurry.

2. The method of claim 1 wherein the alumina compound includes aluminum oxide hydroxide (AlOOH), boehmite or pseudoboehmite.

3. The method of claim 1 wherein the organic composition comprises carboxylic acids with alkyl hydrocarbon chains having a carbon length of 9.

4. The method of claim 1 wherein the organic composition comprises carboxylic acids with alkyl hydrocarbon chains having a carbon length of 8 or less than 8.

5. The method of claim 1 in which the acid modified slurry has a pH of between 3.5 and 5.5.

6. The method of claim 1 wherein, the organic composition content relative to the content of alumina compound in the acidic modified slurry is between 0.5 and 10% wt.

7. A porous hydrophobic alumina prepared according to the method of claim 1.

8. A composition including a porous hydrophobic alumina prepared according to the method of claim 1 and a substrate.

9. The composition of claim 8 wherein the substrate includes polymers, crosslinked polymers, nylon resins, and acrylic resins e.g. polymethylmethlacrylate (PMMA), polystyrenes, styrene acrylate resins, polyester resins, waxes, polyethylene, polypropylene, polycarbonate, polyurethane, polyethylene terephthalate, rubber, epoxy resins, silicone, cellulose, fabric, polytetrafluoroethylene, silica glass particles, metal oxides, ceramics and carbon substrates.

10. A porous hydrophobic alumina including the following characteristics: i) an aspect ratio of between 1.80 and 5.0; ii) an average pore value between 0.55 cc/g and 2.0 cc/g; iii) a specific surface area of between 30_m.sup.2/g and 300 m.sup.2/g; and iv) an organic composition content between 0.5 and 10 wt. % relative to the content of alumina.

Description

EXPERIMENTAL

(1) The invention will now be described with reference to the following Figures and non-limiting example where:

(2) FIG. 1 is the simplified tri-dimensional graphical representation of a primary crystallite shape that can be obtained with the method of the present invention;

(3) FIG. 2 is an SEM photo that shows the particle morphology of the product of Example 1;

(4) FIG. 3 shows the product of Example 1 coated onto different substrates (silica glass particles (glass bead), nylon resin (nylon 12) and PMMA;

(5) FIG. 4 shows the morphology of particles from Example 2 from SEM;

(6) FIG. 5 shows the product of Example 2 coated onto different substrates (silica glass particles (glass bead), polystyrene, sulfonic polystyrene resin, PMMA and nylon (nylon 12)),

(7) FIG. 6 is an FTIR spectra of the Alumina formed as per Example 1;

(8) FIG. 7 is an FTIR spectra of the Alumina formed as per Example 2;

(9) FIG. 8 is an FTIR spectra of the Alumina formed as per Comparative Example 1;

(10) FIG. 9 is an FTIR spectra of the Alumina formed as per Comparative Example 2;

(11) FIG. 10 is an FTIR spectra of the Alumina formed as per Example 3;

(12) FIG. 11 is an SEM photo that shows the particle morphology of the product of Example 3; and

(13) FIG. 12 shows the product of Example 3 onto polystyrene substrate.

(14) The following terms are used in the experimental section:

(15) FTIR means Fourier Transform Infrared.

(16) DRIFT means Diffuse Reflectance Infrared Fourier Transform.

(17) LECO is the apparatus/method used to measure the amount of carbon of the powder.

(18) BET Equation is Brunauer-Emmett-Teller method to determine the Specific Surface area by N.sub.2 gas adsorption at temperature of 77 K.

(19) N.sub.2 adsorption method is the method used for the Pore analysis (Average Pore Diameter)

(20) SEM means Scanning Electron Microscopy.

(21) The inherent properties of the products are measured by the following methods:

(22) DRIFT spectra were registered on self-supporting powders with an FTIR Variant apparatus, 32 spectral acquisitions per sample. Information about the functional group of the organic compound is easily obtained by the presence of the band in the range of 1700-1800 cm-.sup.1. Differences became evident after reaction by the spectral behaviour in the range 1580-1590 cm-.sup.1 assigned to the organic linked to the alumina surface.

(23) Crystal size information is obtained from three diffraction peaks, the (020), the (200), the (002) peaks. These three peaks (crystal planes) are the most accessible in alumina's x-ray diffraction pattern. The ratio of the 200/020 crystal size is the aspect ratio. This ratio can only approach unity if the (200) crystal size is short relative to the (020) size. A representation of the (020), the (200) and the (002) is showed in FIG. 1. The procedure consists of: data collection, calculation of the scattering factor; and finally the x-ray diffraction profile. The data treatment and curve fitting is carried out with high accuracy and requires several hours as long collection times are required to improve the signal to noise ratio with several scans per step. This is known to a person skilled in the art. The theoretical concepts behind the calculation of the crystal sizes is known. The determination is made by measuring diffraction peak widths. The size is calculated by the Scherrer equation.
Csize=(0.94)λ(57.3)/(B cos(θ))
0.94 is a shape factor, λ is the x-ray wavelength used (1.5418 A). 57.3 is a radian/degree conversion factor. B is the full width at half maximum of the peak minus the instrumental broadening. θ is one half the diffraction angle (2θ) for the peak. The x-ray wavelength used is the weighted average of the copper Kα1 and Kα2 components.

(24) The BET surface area and pore volume data were determined by N.sub.2 adsorption according to the ASTM method. Data was collected after a heat treatment at 110° C. for 2 hours with vacuum at 1 Torr. The surface area (m.sup.2/g) was evaluated using the BET equation. The total pore volume was determined from the volume of nitrogen adsorbed at relative pressure p/p.sub.0 equal to 0.992.

(25) The samples for SEM were prepared on an SEM stub, spin coated with gold and therefore evaluated on a JEOL SEM microscope.

(26) The amount of organic composition utilized is determined by means of a carbon analyzer by using a LECO Apparatus. A sample of the powder that contains the organic composition is weighted in a crucible and combusted inside a furnace system that operates with pure oxygen to ensure the complete combustion of all organic composition in the sample, the carbon content of the sample by % weight is determined. Afterwards, the amount of organic composition on the powder (% wt) is calculated from the carbon amount by using the molecular formula.

(27) Deagglomeration tests were carried by weighting 0.5 parts of powder per 100 part of substrate in a closed container and shaken with a vortex for 5 minutes.

(28) Dispersibility tests were carried out by weighting 3 parts of powder per 100 part of liquid solvent and hand shaking for 10 minutes. For the dispersion in TEG and PEG due to the high viscosity of the liquid, 30 sec of sonication treatment in a water batch was subsequently applied in order to homogenize the dispersion. The dispersion quality was judged by observation of sedimentation behavior after 30 minutes. The % wt. of particles dispersed was also evaluated after centrifugation from the solid residue after drying at 120° C. and determined taking into account the total amount of powder initially added.

Example 1

(29) A boehmite (AlOOH) slurry from the Ziegler alcohol process having a pH of about 9.0 was prepared. The starting boehmite alumina crystallite had a blocky-like shape with size from the X-ray (020) reflex of 31 nm, 33 nm (200) and 36 nm (002), with aspect ratio 200/020 equal to 1.06.

(30) An amount of organic composition, in this case, octanoic acid (carboxylic acid having a carbon chain length of 8) equal to 7.8 parts in 100 parts of powder (0.54 mmol/g of powder) was reacted in a stirred vessel with the boehmite slurry at 105° C. for 2 hours to form an acidic modified slurry. The acid underwent fast homogenization with the alumina slurry to obtain a milky acidic modified slurry having a pH of 4.0.

(31) The milky acidic modified slurry was dried under nitrogen flow with a nozzle spray atomizer at temperature of the in-gas of 230° C. and out-gas temperature of 90+/−5° C. by adjusting the acidic modified slurry flow rate.

(32) The resulting crystallites were thinner along the (020) axis and wider along the (200) axis, have an aspect ratio of 2.16 that shows it is platy-oblong.

(33) The BET surface area available for adsorption was 46 m.sup.2/g. The estimated number of OH groups was about 2.510.sup.20/g, which accounts for about 0.42 mmol/g of organic modification to be added.

(34) The hydrophobic porous alumina had a residual amount of organic composition measured through catalytic combustion analysis of 4.2 parts in 100 parts of powder (0.29 mmol/g powder) that is less than the estimated stoichiometric amount of 0.42 mmol/g.

(35) The organic composition was strongly bonded to the alumina compound as confirmed by the FTIR spectra FIG. 6 by the appearance of the band at 1590 cm-.sup.1, and the complete disappearance of the organic functional group band at 1700 cm-.sup.1. This was not shown in Comparative Examples 1 and 2 (FIGS. 8 and 9). The particles morphology is shown in FIG. 2.

(36) In order to measure the pore structure of the hydrophobic porous alumina, N.sub.2 adsorption method was applied on the hydrophobic porous alumina. Data was collected on heat treated samples at 110° C. for 2 hours with vacuum at 1 Torr. The specific surface area of the hydrophobic porous alumina (m.sup.2/g) was evaluated using the B.E.T. equation. The pore volume was determined from the volume of nitrogen adsorbed at saturation (evaluated at relative pressure p/p.sub.o equal to 0.992). The pore volume determined with this method was contained in pores filled up to about 269 nm.

(37) The hydrophobic porous alumina powders were deagglomerated to nanosize with single nano crystals by light blending and incorporated with different substrates including polymeric and non polymeric substrates. As can be seen from FIG. 3 the powders coat the different substrates.

(38) The particles were not wetted by water but could be wetted by hexane for example and have dispersed giving opalescent systems without sedimentation.

Example 2

(39) This example shows that it is possible to fine tune the properties of the porous hydrophobic alumina with a minor organic composition modification without changing the ability of the nanocrystallites to be deagglomerated. The porous hydrophobic alumina was prepared according to Example 1, but the amount of organic composition i.e. C8 carbon chain was decreased. The final powder had a residual amount of organic composition measured through catalytic combustion analysis of 2.6 parts in 100 parts of powder, that counts for only 0.18 mmol/g of the organic composition on surface.

(40) The organic composition was strongly bonded to the alumina compound as confirmed by the FTIR spectra, FIG. 7. The spectra is similar to the Example 1 leading to the same conclusions, and it is different from Comparative Examples 1 and 2, FIGS. 8 and 9.

(41) FIG. 4 shows the morphology of the particles. FIG. 5 shows the deagglomerated hydrophobic porous alumina on several substrates including silica glass, polystryrene, sulfonic polystyrene resin, PMMA and nylon (nylon 12).

(42) The particles were dispersed giving opalescent systems without sedimentation.

Comparative Example 1

(43) This example exemplifies the use of an organic composition including an alkyl hydrocarbon chain length of 18. An amount of an organic modifier composition which is a polymerized chain fatty acid having a carbon chain of greater than 16 was reacted in a stirred vessel with the boehmite slurry of Example 1 at 105° C. for 2 hours. The resulting mixture had a pH of 7.0.

(44) The milky mixture was dried under nitrogen flow with a nozzle spray atomizer at temperature of the inlet air of 260° C. The resulting crystallites were thinner than the starting alumina compound, the aspect ratio was 1.75. As per FIG. 8, this comparative composition had a different spectra than that of Example 1 and Example 2.

(45) The final powder had an amount of organic composition of 14 parts in 100 parts of powder (0.49 mmol/g powder) that is higher than in the Example 1 and is comparable to the stoichiometric estimated value.

Comparative Example 2

(46) This example exemplifies a modified drying operation for producing modified boehmite with an organic composition having a C18 chain by using a screen to deagglomerate particles before drying. An amount of the organic modifier composition which has been used in the Comparative Example 1 was reacted in a stirred vessel with the boehmite slurry of Comparative Example 1 at 105° C. for 2 hours. The resulting milky mixture had a pH of 7.0.

(47) A screen pack was installed on the line to the nozzle dryer to remove clots or agglomerates. The milky mixture was dried under air flow with a nozzle spray atomizer at temperature of the inlet air of 260° C. The resulting crystallites were thinner than the starting alumina compound, the aspect ratio was 1.69.

(48) The final powder had an amount of organic composition of 14 parts in 100 parts of powder (0.49 mmol/g powder). The FTIR spectra, FIG. 9, has similar features to Comparative Example 1.

(49) The properties of the modified aluminas (AlOOH-M) of Examples 1 and 2 and Comparative Examples 1 and 2 are summarized in Table 1.

(50) TABLE-US-00001 TABLE 1 Properties of the Aluminas of the Examples and Comparative Examples AlOOH—M AlOOH—M AlOOH—M AlOOH—M boehmite modified boehmite modified boehmite modified boehmite modified Unit Example 1 Example 2 Comparative Example 1 Comparative Example 2 Carbon chain C8 C8 C18 C18 Csize 020 Nm 25 27 32 32 Csize 200 Nm 54 56 56 54 Csize 002 Nm 27 32 35 33 Aspect Ratio 2.16 2.07 1.75 1.68 200/020 Organic composition % wt 4.2 2.6 14 14 content Specific Surface m2/g 51 52 28 27 Area BET Pore Volume Cc/g 0.94 0.85 0.51 0.51 Dispersibility Hexane Propylene Hexane Hexane carbonate Propanediol PEG TEG

(51) From Table 1 it is clear that the process of the present invention produces modified alumina where the morphology of the crystals has an oblong shape. This is clear as the aspect ratio of the modified alumina is greater than 1.80. The crystals become more oblong with the use of a carboxylic acid having a carbon chain of 8 (Example 1 and Example 2 versus Comparative Examples 1 and 2) and require less than the stoichiometric value of the organic composition. The products of Examples 1 and 2 have a higher surface area and pore volume when compared with the Comparative Examples 1 and 2.

Example 3

(52) The following example describes the use of an organic composition having an amino group and an alkyl carbon chain of 6. A weighted amount of Leucine (amino acid with alkyl chain of 6) was added to water and stirred at room temperature until a not-completely clear solution was obtained. The not-completely clear solution was mixed with a boehmite (AlOOH) slurry from the Ziegler alcohol process of Example 1 in a vessel operating at a suitable revolution rate of low RPM at 105° C. for 2 hours. The pH was in the range of 5.5-6.0. The slurry was dried using a spray atomizer to obtain a final powder with an amount of organic composition of 8.9 parts in 100 parts of powder (0.68 mmol/g).

(53) The powders had a BET surface area of 37 m.sup.2/g and pore volume of 0.73 Cc/g.

(54) The FTIR spectra, FIG. 10, had similar features of Example 1 in the region of about 1580 cm-1.

(55) 3 g of powder with 100 g of PEG were agitated for 10 minutes. After 30 minutes no sedimentation occurred.

(56) The mixture was centrifuged and the solid residue was evaluated after drying at 120° C. The % wt. of particles that remained in the supernatant after centrifugation with respect to the total amount initially added was 99% wt, which showed that particles were highly dispersible.

(57) FIG. 11 shows the alumina particle morphologies and FIG. 12 shows the deagglomerated alumina particles on polystryrene.

(58) In another procedure the preparation with Leucine was carried out with the same starting reagent solution and in the same mixing vessel under a revolution rate of higher RPM. After reaction the powder, which had essentially the same surface area as above, 37.3 m.sup.2/g, had a pore volume of 0.53 cc/g. Thus if an appropriate mixing rate is applied in the vessel, the pore volume may be adjusted being as much higher as the mixing rate is lowered.

(59) Although specific embodiments of the invention have been described herein in some detail, this has been done solely for the purposes of explaining the various aspects of the invention, and is not intended to limit the scope of the invention as defined in the claims which follow. Those skilled in the art will understand that the embodiment shown and described is exemplary, and various other substitutions, alterations and modifications, including but not limited to those design alternatives specifically discussed herein, may be made in the practice of the invention without departing from its scope.