Nanozeolites and Process for Preparation Thereof

CROSS-REFERENCE TO RELATED APPLICATIONS

[001] This application claims the benefit of U.S. provisional application No. 60/859,249 filed November 16, 2006 which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

[002] The invention generally relates to nanozeolites and process for their manufacture.

BACKGROUND

[003] Zeolites are crystalline aluminosilicate molecular sieves with uniform pores of molecular dimensions. They are widely used as catalysts in industries. However due to the pore size constraints, their applications are limited to reactant molecules having kinetic diameter below 1.0 nm. Zeolites are usually synthesized in aqueous medium, which results in microsized crystals, therefore with negligible external surface area [1-3]. These properties impose severe limitations for their use in the conversion of bulky compounds.

[004] Recently, nanosized zeolites (less than 100 nm) have attracted considerable attention because of their potential advantages in catalysis involving the conversion of large molecules due to their high external surface area, reduced diffusion path lengths and exposed active sites. The reduction of particle size from the micrometer to the nanometer scale leads to substantial changes in the properties of materials, which have an impact on the performance of zeolites in traditional application areas such as catalysis and separation. Thus, the ratio of external to internal number of atoms increases rapidly as the particles size decreases and zeolite nanoparticles have large external surface areas and high surface activity. The external surface acidity is of importance when the zeolite is intended to be used as a catalyst in reactions involving bulky molecules. In addition, smaller zeolite crystals have reduced diffusion path lengths relative to conventional micrometer- sized zeolites [4-6]. Two general methodologies for the production of new types of zeolitic bimodal materials, overcoming the limitation of conventional zeolites.

These materials (UL-zeolites and ZCMeso-AS) are considered of potential for application in catalysis and separation, due to easier transport of guest molecules through the mesopores and shorter diffusion pathways in the zeolitic walls [4,5].

[005] There are currently two main methods to synthesize nanozeolites [6-8]: the direct synthesis and the confined space synthesis. The former method employs a hydrothermal treatment of clear zeolite gels [9,10]. To produce nanozeolites, it is desired to increase the number of zeolite nuclei and to suppress their aggregation. However, it is not easy to restrain the aggregation process: Van der Waal force and high reactivity of the external surface of zeolite precursors are two factors that favor the aggregation of precursors [6, 8- 10]. The latter method, which is called confined space synthesis, has been developed for the preparation of nanosized zeolite crystals. The synthesis is conducted within an inert matrix such as porous carbon matrices, thermo-reversible polymer hydrogels, which provides a steric hindered space for zeolite crystal growth. Because their disordered structure, therefore zeolites with rather broad size distributions were produced [11-14].

[006] Two-phase synthesis is an attractive method which has been used in the synthesis of inorganic nanoparticles such as Pt, TiO2. CdS... [17-24]. In principal, the method employs both organic solvent and water as the reaction media. The formation of nanoparticles takes place at the interface between the two phases. If the organic solvent is previously added with some capping agent such as oleic acid or stearic acid, the resulting nanoparticles capped with these agents can disperse in the solvent. In this section we discus the adoption of the two-phase synthesis for the preparation of nanozeolites.

[007] Several synthetic routes have been reported for the preparation of nanocrystalline zeolites. However, none of these attempts has produced an easy means of controlling the small size. Furthermore, the external surface of those nanocrystalline zeolitesis hydrophilic and thereby has mostly silanol groups that limit catalytic reactivity to the internal pore surface.

[008] Since the crystallization of zeolites is somewhat different and difficult compared to the synthesis of conventional inorganic particles, care should be taken in choosing the appropriate "capping agent" and solvent for the synthesis of zeolites.

[009] One of the problems in applying this method for the synthesis of this method is that oxalic acid and stearic acid are incapable of "capping" zeolite crystals. In the synthesis of inorganic nanoparticles, these acids can attach to metal atoms by coordinate bonding. Thus, a transition metal of which atom has an incomplete d sub-shell is more likely to form the complex with the acids compared to Si and Al atom in the structure of zeolites. Some surfactants such as CetylTrimethylAmmonium Bromide (CTAB), anionic surfactant sodium bis(2-ethylhexyl) sulfosuccinate or Aerosol OT (AOT) can adsorb on the surface of zeolite crystals, however, the presence of these surfactant in the synthesis of zeolites has been reported to affect the morphology of the product as well as increase the crystal size [25-27].

SUMMARY OF THE INVENTION

[010] In one aspect of the invention, there is provided a process for preparing organosilane-functionalized nanozeolites comprising i) providing an aqueous zeolite gel solution containing zeolite seeds; ii) contacting an organosilane in an organic solvent with the zeolite gel solution of step i) to produced organosilane-functionalized zeolite seeds; iii) treating the organosilane-functionalized zeolite seeds of step ii) to produce organosilane-functionalized nanozeolite crystals; and iv) isolating the organosilane- functionalized nanozeolite crystals from step iii).

[Oi l] In one aspect of the invention, there is provided a process for preparing nanozeolite comprising i) providing an aqueous zeolite gel solution containing zeolite seeds; ii) contacting an organosilane in an organic solvent with the zeolite gel solution of step i) to produced organosilane-functionalized zeolite seeds; iii) treating the organosilane-functionalized zeolite seeds of step ii) to produce organosilane- functionalized nanozeolite crystals; iv) isolating the nanozeolite crystals from step iii) and v) drying and calcining the organosilane-functionalized nanozeolite from step iv) to produce said nanozeolite.

[012] In a further aspect, there is provided a nanozeolite having a small crystal size and high specific and hydrophobic external surface areas.

[013] In a further aspect, there is provided an organosilane-functionalized nanozeolites susceptible to be produced using a process of the invention.

[014] In a further aspect, there is provided a nanozeolite susceptible to be produced using a process of the present invention.

[015] In a further aspect, there is provided a nanozeolite having a structure comprising a specific surface area of at least 500 m /g an external surface area of at least about 100 m ² /g and a crystal size of less than about lOOnm.

[016] In a further aspect, there is provided a mesoporous nanozeolite comprising a 29Si MAS NMR signal corresponding to Q4 Si(OSi)4 and substantially no signal corresponding to Q3 Si(OSi)3OH.

[017] In a further aspect, there is provided an organosilane-functionalized nanozeolite susceptible to be produced using a process of the invention.

[018] In a further aspect, there is provided an organosilane-functionalized nanozeolite comprising a 29Si MAS NMR signal corresponding to T3 R-C-Si(OSi)3.

[019] In a further aspect, there is provided a process for treating a hydrocarbon feed comprising: contacting a feed containing hydrocarbon under reaction conditions to treat said hydrocarbon with a nanozeolite as defined herein.

[020] In a further aspect, there is provided a catalytic material for use in the treatment of a hydrocarbon feed comprising at least one nanozeolite as defined herein.

BRIEF DESCRIPTION OF THE DRAWINGS

[021] Having thus generally described the nature of the invention, reference will now be made to the accompanying drawings, showing by way of illustration a preferred embodiment thereof, and in which:

Fig. 1 is a schematic representation of the single-phase synthesis method;

Fig. 2 is a schematic representation of the two-phase synthesis method;

Fig. 3 is XRD patterns of the as-made silicalite-1 samples prepared from the same synthesis solution (a) in aqueous solution using conventional method: in absence of organosilane, (b) in solvent medium (phase): in the presence of organosilane;

Fig. 4 is XRD patterns of the as-made FAU zeolite samples prepared from the same synthesis solution (a) in aqueous solution using conventional method: in absence of organosilane, (b) in solvent medium (phase): in the presence of organosilane;

Fig. 5 is a FTIR spectrum of nanosilicalite-1;

Fig. 6 is a FTIR spectrum of FAU nanozeolite;

Fig. 7 is a representative TEM micrograph of as-made nanosilicalite-1 prepared using single-phase method;

Fig. 8 is a representative TEM micrograph of as made FAU nanozeolite prepared using single-phase method;

Fig. 9 is Si MAS NMR spectra of the as made nanosilicalite-1 samples prepared from the same clear zeolite gel solution using different methods, (a): conventional method in aqueous medium without organosilane (b): single phase method in organic solvent and (c) calcined nanosilicalite- 1 ;

Fig. 10 is ²⁹ Si MAS NMR spectra of the as made FAU nanozeolite samples prepared from the same clear zeolite gel solution using different methods, (a): conventional method (b): single phase method in organic solvent;

Fig. 11 is nitrogen adsorption /desorption isotherms and BJH pore radius distribution of calcined nanosilicalite-1;

Fig. 12 is nitrogen adsorption/desorption isotherms and BJH pore radius distribution of calcined FAU nanosilicalite-1 Fig. 13 is XRD patterns of the as made silicalite-1 samples, (a) sample prepared using conventional method in aqueous medium, (b) aqueous phase, AP, (c) organic phase, OP; Fig. 14 is representative SEM micrographs of the as made silicalite-1 samples, (a) organic phase, OP and (b) aqueous phase, AP; Fig. 15 is ²⁹ Si MAS NMR spectra of the as made silicalite-1 samples, (a) aqueous phase, AP and (b) organic phase, OP;

Fig. 16. is nitrogen adsorption/desorption isotherms of the calcined nano silicalite sample recovered in the organic phase (OP);

Fig. 17 is aTEM image of the calcined silylated nanofaujasite sample.

DETAILED DESCRIPTION OF THE INVENTION

[022] The present invention relates to a new approach for the preparation of nanozeolites in a medium involving organic solvent using organosilanes, which leads to substantially uniform nanosized zeolite crystals.

[023] This can be realized by functionalization of the external surface zeolite precursors with organosilanes, as schematically represented in Figure 1. After reacting with organosilanes, the resulting organosilane-functionalized zeolite are subjected to the hydrothermal treatment to yield the nanozeolites crystals.

[024] It is known in the art that in aqueous media, zeolite precursors tend to aggregate during the crystallization, leading to the formation of undesired large zeolite crystals. To overcome this disadvantage, in this invention, an organic solvent is used as an alternative reaction medium for the hydrothermal treatment of organo-silane-functionalized zeolite.

[025] The applicants have found a novel general process for preparing nanozeolites. In particular, a single-phase and two-phase processes have been found.

[026] In the single-phase synthesis method, a proper amount of zeolite gel solution is added to an organic solvent that is a non-water miscible solvent/ water miscible solvent system containing organosilane. After a single phase is obtained, this mixture is then subjected to hydrothermal crystallization to produce uniform functionalized nanozeolites.

[027] The two-phase process, in contrast, involves the introduction of a non-water miscible organic solvent containing organosilane to the aqueous zeolite gel solution, resulting in a two-phase mixture. Upon mixing and hydrothermal treatment of this mixture, organosilane-functionalized nanozeolites are obtained in the organic phase. Larger zeolites , also hydrophobic, can be isolated from the aqueous phase (see Fig 14)

[028] Without being bound to theory, it is believed that both processes employ the use of organosilane to inhibit the crystal growth. The organic solvent act as the medium for dispersion of nanozeolites functionalized with organosilane from the aqueous phase, which lead to the complete halt of the growth process.

[029] In accordance with one embodiment of the invention, there is therefore provided a process for preparing nanozeolites comprising: i) providing an aqueous zeolite gel solution containing zeolite seeds; ii) contacting an organosilane in an organic solvent with the zeolite gel solution of step i) to produced organosilane-functionalized zeolite; iii) treating the organosilane-functionalized zeolite of step ii) to produce nanozeolites crystals ; iv) isolating the nanozeolite crystals from step iii) and v) drying and calcining the nanozeolite from step iv.

[030] The amount of organosilane used in the process of the invention is not particularly limited, however to minimize the possible unnecessary loss of reagent and optimize economic component, it may be minimized.

[031] In one embodiment, the organosilane is in proportion of 5- 15% mol, preferably about 10%, with respect to the silica content in the gel.

[032] The organosilane useful to carry out the process of the invention can be defined by the general formula R-SiX3, wherein X is a leaving group and R is a lipophilic functional group. Advantageously, the leaving group is an optionally substituted alkyloxy group or a halogen, preferably an optionally substituted C 1-30 alkyloxy group, an optionally substituted Cl-IO alkyloxy group, more preferably an optionally substituted C 1-6 alkyloxy group, an optionally substituted Cl alkyloxy group, most preferably a methoxy, ethoxy or ipropyloxy.

[033] Advantageously, the R group in formula R-SiX3, is an optionally substituted Cl to 30 alkyl, an optionally substituted Cl to 20 alkyl, more preferably, an optionally substituted C3 to 16 alkyl, more preferably a (amino-C2-3 alkylamino)-C3 -alkyl or (C2-3 alkylamino)-C3-alkyl. Advantageously, the R group is hexadecyl-, 3-glycidoxypropyl-, 3-(diethylamino)propyl-, 3-(2-aminoethylamino)propyl-, 3-(2-aminoethylamino)propyl-

[034] The organic solvent useful to carry out the process of the invention comprise at least one non-water miscible solvent. In one embodiment, the organic solvent comprises at least one non-water miscible solvent and a water miscible solvent.

[035] Preferably, the non- water miscible solvent is non polar organic solvent, more preferably the non-water miscible solvent is toluene, n-hexane, n-octane, cyclohexane, diethyl ether, ethyl acetate, formamide.

[036] Advantageously, the water miscible solvent is alcohols, preferably methanol, ethanol, n-propanol, i-propanol, n-butanol, sec-butanol, ter-butanol, pentanol and more preferably n-butanol or n- pentanol.

[037] In accordance with the present invention, step ii) is comprising heating at about 40 to 100 ⁰ C, preferably about 6O ⁰ C. In one embodiment, step ii) is comprising heating for a period of about 6 to 48 hours, preferably about 24 hours. Preferably, the step ii) is comprising heating for a period of about 6 to 48 hours at about 40 to 100 ⁰ C.

[038] In accordance with the present invention, step iii) is comprising heating at 100- 200 ⁰ C.

[039] In accordance with the present invention, step iv) is comprising recovering and washing the nanozeolite crystals. In one embodiment, step iv) is comprising recovering by evaporation or centrifugation and washing with at least one solvent in which the nanozeolite crystals are substantially insoluble, preferably, the washing solvent is at least one alcoholic solvent and an aqueous solvent, more preferably the washing solvent is ethanol and water.

[040] In accordance with the present invention, the drying in step v) is comprising heating at about 60-80 ⁰ C for about 12-24 hours, preferably at about 8O ⁰ C for about 24 hours.

[041] In accordance with the present invention, the calcining in step v) is comprising heating at about 500 to 600 ⁰ C, preferably 55O ⁰ C for about 4-6 hours.

[042] In accordance with the present invention, there is provided a nonozeolite or organosilane-functionalized nanozeolites produced using a process of the present invention.

[043] In one embodiment of the invention, there is provided a nanozeolite having a structure comprising a specific surface area of at least 500 m ² /g an external surface area of at least about 100 m ² /g and a crystal size of less than about lOOnm.

[044] In one embodiment of the invention, there is provided a nanozeolite having a structure comprising a specific surface area of at least about 500 m ² /g, an external surface area of at between about 50 -200 m ² /g and a crystal size of less than about 50nm. Preferably, the external surface area is between about 100 -150 m /gl

[045] In a further embodiment, the nanozeolite has a crystal size of about 10 - 100 nm. Preferably, the crystal size is about 15 -50 nm.

[046] In a further embodiment, the nanozeolite has an external surface area is about 100 to 200 m ² /g.

[047] In one embodiment of the invention, the nanozeolites of the invention are being produced using a process as defined herein.

[048] In one embodiment, there is provided nanozeolites of the invention that are susceptible to be produced using a process as defined herein.

[049] In one embodiment, the nanozeolite described herein can be used alone, diluted, supported or shaped in any convenient way known to those skilled in the art. As such, the nanozeolite can be used as catalytic material or to prepare nanozeolite-containing catalytic material. For example, the nanozeolite can be admixed with binders (e.g. silica, alumina or mixtures or mesoporous material) and then formed into desired shapes by convenient methods. The nanozeolite of the invention can also conveniently be provided in the form of a matrix-supported catalytic material. The techniques for use of zeolites are known in the art and depend on the specific application.

[050] Processes in which zeolites are typically employed, can be conducted using nanozeolite of the present invention.

[051] In one embodiment, there is provided a process for treating a hydrocarbon feed comprising: contacting a feed containing hydrocarbon with a nanozeolite, according to the invention, under reaction conditions to treat said hydrocarbon.

[052] In one embodiment, the treating of said hydrocarbon is effected by a reaction selected from the group consisting of acylation, alkylation, dimerization, oligomerization, polymerization, dewaxing, hydration, dehydration, disproportionation, hydrogenation, dehydrogenation, aromatization, selective oxidation, isomerization, hydrotreating, catalytic cracking and hydrocracking. In further embodiments, acylation is acylation of an aromatic compound and catalytic cracking is catalytic cracking of a fraction of petroleum;

[053] The term "alkyl" represents a linear, branched or cyclic hydrocarbon moiety having 1 to 30 carbon atoms, which may have one or more unsaturation in the chain, and is optionally substituted. Examples include but are not limited to methyl, ethyl, and branched or linear propyl, , butyl, pentyl, hexyl, heptyl, octyl, dodecyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosanyl (didecyl), heneicosanyl, docosanyl, tricosanyl, tetracosanyl, pentacosanyl, hexacosanyl,

heptacosanyl, octacosanyl, nonacosanyl, triacontanyl. The term alkyl is also meant to include alkyls in which one or more hydrogen atom is replaced by a halogen, ie. an alkylhalide.

[054] The term "aryl" represents a carbocyclic moiety containing at least one benzenoid-type ring (i.e., may be monocyclic or polycyclic), and which where indicated may be optionally substituted with one or more substituents. Examples include but are not limited to phenyl, tolyl, dimethylphenyl, aminophenyl, anilinyl, naphthyl, anthryl, phenanthryl or biphenyl.

[055] The term "aralkyl" represents an aryl group attached to the adjacent atom by an alkyl, alkenyl or alkynyl. Like the aryl groups, where indicated the aralkyl groups can also be optionally substituted. Examples include but are not limited to benzyl, benzhydryl, trityl, phenethyl, 3-phenylpropyl, 2-phenylpropyl, 4-phenylbutyl and naphthylmethyl.

[056] "Alkoxy" represents an alkyl which is covalently bonded to the adjacent atom through an oxygen atom. Examples include but are not limited to methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, tert-butoxy,.

[057] The term "amino" represents a derivative of ammonia obtained by substituting one or more hydrogen atom and include -NH ₂ , -NHRj and -NRjRk, wherein Rj and Rk are each independently selected from C 1 -6 alkyl, or Rj and Rk are taken together with the nitrogen to which they are attached to form a 3 to 12 membered heterocycle.

[058] "Alkylamino" represents an alkyl which is covalently bonded to the adjacent atom through a nitrogen atom and may be monoalkylamino or dialkylamino, wherein the alkyl groups may be the same or different. Examples include but are not limited to methylamino, dimethylamino, ethylamino, diethylamino, methylethylamino, propylamino, isopropylamino, butylamino, isobutylamino, sec-butylamino, tert- butylamino, pentylamino and hexylamino.

[059] "Halogen atom" is specifically a fluoride atom, chloride atom, bromide atom or iodide atom.

[060] The term "independently" means that a substituent can be the same or a different definition for each item.

[061] The term "optionally substituted" represents one or more halogen, amino, amidino, amido, azido, cyano, guanido, hydroxyl, nitro, nitroso, urea, OS(O)2Rm (wherein Rm is selected from C 1-6 alkyl, C6-10 aryl or 3-10 membered heterocycle), OS(O)2ORn (wherein Rn is selected from H, C 1-6 alkyl, C6-10 aryl or 3-10 membered heterocycle), S(O)2ORp (wherein Rp is selected from H, C 1-6 alkyl, C6-10 aryl and 3- 10 membered heterocycle), S(O)0-2Rq (wherein Rq is selected from H, C 1-6 alkyl, C6- 10 aryl or 3-10 membered heterocycle), OP(O)ORsORt, P(O)ORsORt (wherein Rs and Rt are each independently selected from H or C 1-6 alkyl), Cl-6alkyl, C6-12aralkyl, C6- lOaryl, Cl-6alkoxy, C6-12aralkyloxy, C6-10aryloxy, 3-10 membered heterocycle, C(O)Ru (wherein Ru is selected from H, C 1-6 alkyl, C6-10 aryl, C6-12 aralkyl or 3-10 membered heterocycle), C(O)ORv (wherein Rv is selected from H, C 1-6 alkyl, C6-10 aryl, C6-12 aralkyl or 3-10 membered heterocycle), NRxC(O)Rw (wherein Rx is H or C 1-6 alkyl and Rw is selected from H, C 1-6 alkyl, C6-10 aryl, C6-12 aralkyl or 3-10 membered heterocycle, or Rx and Rw are taken together with the atoms to which they are attached to form a 3 to 10 membered heterocycle) or SO2NRyRz (wherein Ry and Rz are each independently selected from H, Cl-6 alkyl, C6-10 aryl, C3-10 heterocycle or C6-12 aralkyl).

[062] The terms "leaving group" is an atom or molecule that detaches from the parent compound. Examples include halogen such as chloride, bromide and iodide, or an alkyoxy group such as methoxy.

[063] The terms "lipophilic functional group" refers to the ability of the group, in the silylated nanozeolite, to favor dispersion in the organic solvent solvents. Exemples include, without limitation, alkyl, aryl and aralkyl.

[064] The term "hydrophobic" used with reference to the nanozeolite of the invention means that the surface of the nanozeolite contains less hydroxyl hydrophilic groups compared to a nanozeolite prepared according to conventional methods.

[065] With reference to Fig. 1, in which a schematic representation of single-phase process for the preparation of nanozeolites is represented, the general procedure is consisted of the following steps:

[066] Preparing an aqueous clear zeolite gel solution, which contains the zeolite seeds in form of nanoslabs (10-100 nm). Typically, processes reported in the literature can be used to prepare the gel [6-8]. This clear gel solution is heated at a suitable temperature (e.g. under reflux at 40-100 ⁰ C) for a suitable period of time (generally from about 6-48 hours) to produce zeolite seeds.

[067] To this clear zeolite gel solution, an organic solvent, suitable to produce a single phase system, containing organosilanes is added and stirred under heating conditions (generally from about under reflux at 40-100 ⁰ C for about 6-48 hours).

[068] The organic phase containing organosilane-functionalized zeolite seeds is transferred into a suitable heating device, such as an autoclave, and then heated at desired temperature for crystallization.

[069] After the crystallization, the resulting nanozeolite crystals are recovered (e.g. by centrifugation) and then washed (e.g. using sequential washings with ethanol and then with water) several times. The nanozeolite crystals are then dried (generally at about 60- 80 ⁰ C for 12-24 hours) and calcined at 550 ⁰ C for a suitable period of time (e.g. 4-6 hours).

[070] In contrast with what was previously reported in the literature, the two phase process of the invention can overcome a number of limitations, for which there was so far no solution, by using organosilane as the protecting agent of zeolite nanocrystals. The aqueous solution of zeolite precursors is added with a solution of organosilane agent in an organic solvent. As the organic solvent is insoluble in water, the organic phase stays on top of the aqueous phase . Since the external surface of precursors is rich of silanol groups, they can react with the organosilane agents at the interface between the two phases. The precursors hence are protected by organic groups which keep them from aggregation. Furthermore, because of the protecting organic groups, the precursors

become more hydrophobic and can diffuse into the organic phase. Thus the growth stage is suppressed spatially in two-phase synthesis.

[071] With reference to Fig. 2, in which a schematic representation of two-phase process for the preparation of nanozeolites is represented, the general procedure is consisted of the following steps:

[072] Preparing an aqueous clear zeolite gel solution. This clear solution was heated at a suitable temperature (e.g. under reflux at 40-100 ⁰ C) for a suitable period of time (generally from about 6-48 hours) to produce zeolite seeds.

[073] To this clear zeolite gel solution, an organic solvent, suitable to produce a single phase system, containing organosilanes is added. Since the solvent is non-water miscible, a two-phase system was obtained. This two-phase system was stirred under heating conditions (generally under reflux at about at 40-100 ⁰ C for 12 hours).

[074] The two-phase mixture is transferred into a suitable heating device, such as an autoclave, and then heated at desired temperature for crystallization.

[075] After the crystallization, the organic phase containing nanozeolite crystals is extracted. In the organic phase, the resulting nanozeolite crystals is recovered (e.g. by centrifugation) and then washed (e.g. using sequential washings with ethanol and then with water) several times. The product is then dried (generally at about 60-80 ⁰ C for 12-24 hours) and calcined at 550 ⁰ C for a suitable period of time (e.g. 4-6 hours).

[076] The present invention will be more readily understood by referring to the following examples which are given to illustrate the invention rather than to limit its scope.

[077] Characterization: The FTIR spectra were recorded using a Biorad FTS-60 spectrometer on sample wafers. Powder XRD patterns of the materials were recorded on a Philips X-ray diffractometer (PW 1010 generator and PW 1050 computer assisted goniometer) using nickel-filtered CuKa (λ = 1.5406 A) radiation, 0.0258 step size and a 1 s step time.The nitrogen adsorption/description measurements were carried out using an

Omnisorp- 100 automatic analyzer at -196 ⁰ C after degassing about 30 mg of calcined sample at 200 ⁰ C for at least 4 hours under vacuum (10 ^"4 -10 ^"5 torr). The specific surface area (S _BET ) was determined from the linear part of the BET equation (P/P _o = 0.05 - 0.15). High-resolution TEM images were obtained on a JEOL 200 CX transmission electron microscope operated at 120 kV. The samples for TEM were prepared by dispersing the fine powders of the products in slurry in ethanol onto honeycomb carbon copper grids. However, for scanning electron microscope (SEM), JEOL JSM-840 scanning electron microscope operated at 15 Kv was used. Solid-state Si MAS NMR spectra were recorded at room temperature on a Bruker ASX 300 spectrometer.

EXAMPLE 1 : SYNTHESIS OF NANOZEOLITES USING SINGLE-PHASE PROCESS

PHASE 1: Preparation of clear zeolite gel solution

[078] - Silicalite-1: In a typical recipe, 14 g of tetrapropylammonium hydroxide (TPAOH) 20% in water was added to 7.8 g of tetraorthosilicate Si(OC ₂ Hs) ₄ (TEOS). The mixture was stirred vigorously for 24 h at room temperature. The molar gel composition was: 2.68 SiO ₂ : 1 TPAOH : 168 H ₂ O.

[079] - FAU zeolite: 38.4 g solution of NaOH 0.05 N (Fischer) was diluted with 121.6 g of H ₂ O. Then 52.3 g tetramethylammonium (TMA ⁺ ) hydroxide as templating agent solution (Aldrich, 25% in water) and aluminium isopropoxide Al(OiPr) ₃ as aluminium source, (Aldrich, 98%) were added in that order, and stirred vigorously until the solution became clear at room temperature. To this solution 21.65 g of tetraorthosilicate was added. This clear solution was aged for 1-3 days under vigorous stirring at room temperature. The final molar composition was: 2.46 (TMA)20 : 0.032 Na2O : 1 A12O3 : 3.4 SiO2 : 370 H2O.

PHASE 2: Functionalization and crystallization in organic medium

[080] 10 g of zeolite gel solution was added to 500 ml of a solution of toluene containing n-butanol (30% wt) and. An organosilane, e.g. hexadecyltrimethoxysilane, was in a proportion of 10% mol in regards to the silica content in the gel. After vigorous

stirring at 40-80 ⁰ C for 12-48 h under reflux, a mixture of only one clear liquide phase was obtained. This mixture was then transferred to an autoclave for further hydrothermal treatment at 15O ⁰ C for 3 days and 180 ⁰ C for 1 day for faujasite and silicalite- 1 , respectively. The product is recovered by evaporation or centrifugation, washed with ethanol and then with water for several times, dried at 60-80 ⁰ C for 12-24 hours and calcined at 55O ⁰ C for 4-6 hours.

Characterization

[081] The XRD patterns of the as made nanozeolite samples prepared from silylated seeds are shown in Figure 3b. The samples prepared from the same clear zeolite gel solution in aqueous solution without organosilane (conventional method) was used as a reference (Figure 3a). The XRD pattern of the nanosilicalite- 1 sample is identical to that of the reference, indicating the MFI structure of this nanosilicalite- 1 sample. However, there is a clear broadening of the reflections, which is attributed to small crystals. In addition, no significant peak at 2θ = 20-30° which is characteristic of amorphous phase was observed indicating a relative high crystallinity of this sample.

[082] A similar trend was also observed for the nanofaujasite sample (Figure IB). Furthermore, the FT-IR spectra of both as made nanosilicalite- 1 and nanofaujasite match well with the typical FTIR peaks assigned to silicalite- 1 and zeolite Y, respectively' ²⁰ ' ²¹ I

[083] The XRD pattern of the nanosilicalite- 1 synthesized using this single-phase method at 170°C for 24 h is shown in Figure 3b. The XRD pattern of the large crystals prepared from the same zeolite gel solution in aqueous solution without organosilane (conventional method) is used as a reference in Figure 3 a). The XRD pattern of the nanosilicalite- 1 synthesized using the single-phase method is identical to that of the reference, indicating the MFI structure of this sample. There is a clear broadening of the reflections from the sample, which is attributed to small crystals. Furthermore, the sample is highly crystalline, i.e., the XRD pattern of this sample does not appear to contain a broad feature around 2θ = 20-30° which is characteristic of amorphous SiO2 phase.

[084] A similar trend was also observed for the nanofaujasite sample (Figure 4). The XRD pattern of the as made FAU sample synthesized at 15O ⁰ C for 3 days using the same methods is shown in Figure 4. The XRD pattern of the nanofaujasite sample is similar to that of samples prepared from the same zeolite gel solution using conventional method (the reference sample), implying the FAU structure of this sample. The fact that the peaks are broaden indicates the small size of the crystals.

[085] Figure 5 shows the FTIR spectrum of the nanosilicalite sample before calcination. The peak height and position are identical to those of MFI structure. The peak at 450 cm ^"1 is assigned to the structure insensitive internal TO ₄ (T = Si or Al). The peak around 550 cm ^"1 is attributed to the vibration of double 5-rings in MFI lattice. However, two adjacent peaks (544 and 555 cm ^"1 ) are observed. According to [15] the presence of these two peaks indicates the formation of nanozeolites. The peak at 790 cm ^"1 is assigned to external linkage symmetric stretching. The peaks at 1080 and 1220 cm ^"1 are assigned to internal tetrahedral asymmetrical stretching and external linkage asymmetrical stretching respectively. It should be noted that the intensity of peak at 790 cm ^"1 attributed to the vibration of the external silanol groups is very low. This suggests that most of the external silanol groups have been functionalized with the organosilane.

[086] The FT-IR spectrum of the nanofaujasite sample before calcination is shown in Figure 6. The peak at 460 cm ^"1 is assigned to the structure insensitive internal TO ₄ (T = Si or Al) tetrahedral bending peak of zeolite Y. The peak at 565 cm ^'1 is attributed to the double ring external linkage peak assigned to zeolite Y. The peaks at 685 and 775 cm ^" are assigned to external linkage symmetrical stretching and internal tetrahedral symmetrical stretching respectively. Furthermore, the peaks at 1010 and 1080 cm ^"1 are assigned to internal tetrahedral asymmetrical stretching and external linkage asymmetrical stretching respectively. Overall, the FT-IR spectrum of this sample matches well with the typical FTIR absorption peaks of zeolite Y [3].

[087] In order to verify the crystal size of the zeolite samples, the transmission electron micrographs (TEM) technique was used. A representative micrograph of the as made nanosilicalite- 1 also sample is shown in Figure 7. A small average crystal size of about

20 nm was observed. It is also seen that the crystal size distribution appears very uniform. Figure 8 also shows the TEM image of the FAU nanozeolite sample. The TEM image of this sample clearly indicates highly nanozeolites with uniform size of 30 nm. Furthermore, this samples is composed of discrete particles rather than aggregates. Based on the fact that zeolilte precursors functionalized with organosilane were highly dispersed in the organic medium thus they were protected from aggregation during the crystallization.

[088] ²⁹ Si MAS NMR technique was used to monitor the functionalization of the silanol groups on the surface of the zeolite nanocrystals. The ²⁹ Si MAS NMR spectrum was carried out on the as-made samples (before calcination). The ²⁹ Si MAS NMR spectrum of the zeolite synthesis using the conventional method was also performed for comparison.

[089] Figure 9 shows the NMR spectra of nanosilicalite-1 samples prepared using conventional method (a) and the single-phase method (b). For the sample (a) two peaks at 110 ppm and 100 ppm which are characteristic of Q4 (Si(0Si)4) and Q3 (HOSi(OSi)3), respectively were observed. However, for the sample (b) only one main peak at approximately 110 ppm which is assigned to Q4 (Si(0Si)4) was observed. In addition, a new peak at -68 ppm is present and is assigned to R-C-Si-(OSi)3 species, which is the result from the reaction between the silicon in the organosilane and the surface silanol groups during the zeolite synthesis. Hence the NMR result has also confirmed the silylating reaction on the external surface of nanosilicalites-1. This also suggests the silanization on the external surface of nanosilicalites-1, which acts to heal defect sites (e.g., silanol groups) in the zeolite surface. Furthermore this calcined sample also shows essentially a single resonance peak Q ⁴ at ~ -110 ppm. Thus, it can be concluded that the presence of only one resonance Q ⁴ even after calcination of the silylated silicalite-1 sample suggests its hydrophobic surface character.

[090] Similar results were also obtained for the silylated (or functionalized) nanofaujasite sample. Figure 10 also shows the ²⁹ Si MAS NMR spectra of the as-made faujasite prepared in aqueous medium in absence of organosilane (conventional method) and silylated faujasite samples. For the silylated sample, besides the resonance peaks at -

88 ppm, -95 ppm, -100 ppm and -103 ppm corresponding to Si(3Al), Si(2Al), Si(IAl) and Si(OAl), respectively. The peak attributed to R-C-Si-(OSi) ₃ species at -65 ppm was also observed. This peak at -65 ppm is absent in the faujasite sample prepared in aqueous medium in absence of organosilane (Figure 10a). As seen in Figure 10b, for the silylated faujasite sample, Q ⁴ signals became much broader with higher intensity as compared to those of the faujasite one. This means that the silanization led to the transformation of Q ³ to Q ⁴ silicon species during the crystallization.

[091] It is remarkable that the presence of Q3 species was not detected in the NMR spectrum of the functionalized nanosilicalite-1 samples. However, for the silicalite reference sample prepared by the conventional method, the peak at about -100 ppm which is assigned to the silanol group (SiO) ₃ OH was observed. This remark was also noticed in the spectrum of FAU nanozeolite as compared to that of the reference sample. In general, Q3 species in FAU structure can be detected at -82.0 ppm (Si(OAl)3(OH)), - 87.0 ppm (Si(OAl)2(OSi)(OH)), -92.8 ppm (Si(OAl)(OSi)2(OH)), and -97.5 ppm (Si(SiO)3(OH). As seen in, for the functionalized FAU nanozeolite sample, Q4 signals became much broader with higher intensity as the Q3 signals decrease, compared to those of the reference. Without being bound to theory, it is believe that the protection of nanozeolites with organosilane led to the transformation of Q3 species to Q4. The nanozeolites became hydrophobic as the hydroxyl groups were replaced by the organic ones.

[092] Table 1 summarized the physico-chemical properties of the series of zeolite samples prepared in solvent medium in presence of organosilane and prepared in aqueous medium in absence of organosilane (conventional method). Surface area and pore volume of nanozeolites were determined using nitrogen adsorption/desorption isotherms. Figure 11 shows the N ₂ adsorption/desorption isotherms and the BJH pore radius distribution of the calcined nanosilicalite-1 sample. At low relative P/Po pressure, a steep rise in uptake, followed by a flat curve, corresponds to filling of micropores with nitrogen. An inflection at higher pressures (e.g. in P/Po range from 0.7-0.9) is characteristic of capillary condensation and is related to the range of mesopores. The specific surface area is 570

m ² /g and the external surface area based on t-plot calculation is 150 m ² /g. This high external surface value indicates the small crystal size of the sample.

[093] Table 1. Physicochemical properties of the calcined silylated nanozeolite and zeolite samples prepared from the same zeolite gel, in solvent medium in the presence of organosilane, and in aqueous medium in absence of organosilane, respectively.

[094] Figure 12 shows the nitrogen adsorption/desorption isotherms and the BJH pore radius distribution of the calcined FAU nanozeolite sample. The specific surface area of the sample is very high, e.g. 545 m ² /g. The external surface area is of a high value of 96 m ² /g, which also implies the presence of nanozeolites in the sample.

EXAMPLE 2: SYNTHESIS OF NANOZEOLITES USING TWO-PHASE PROCESS [095] To demonstrate this process, the synthesis of nanosilicalite-1 was carried out. The organosilane reagent used in this study was hexadecyltrimethoxysilane. This organosilane reagent was chosen because of the large sizes so that the functionalization occurs only on external surfaces. Toluene was chosen as the organic solvent since it can dissolve the organosilane. After crystallization the products in the Organic Phase and Aqueous Phase were recovered separately by centrifugation and were denoted as OP and AP sample, respectively.

PHASE 1: Preparation of clear zeolite gel solution

[096] The gel solution was prepared in a manner similar to what is described in example 1.

PHASE 2: Functionalization and crystallization in organic medium

[097] For the synthesis of nanosilicalite-1, typically, 21.8 g of clear zeolite gel solution, which was previously prepared phase 1, was heated at 8O ⁰ C for 12 h, the obtained solution was added with 93 g of a solution of toluene containing 1.22% wt hexadecyltrimethoxysilane, resulting in a two-phase mixture. After stirring for 12 hours at 60 ⁰ C, the organic phase mixture was transferred into an autoclave; and heated at 160- 180 ⁰ C for 24 hours. The product is recovered by evaporation or centrifugation, washed with ethanol and then with water for several times, dried at 60-80 ⁰ C for 12-24 hours and calcined at 55O ⁰ C for 4-6 hours.

Characterization

[098] Figure 13 shows the X-ray powder pattern of the AP and OP samples recovered in the aqueous phase and organic phase, respectively; and the reference synthesized using the conventional method in aqueous solution in the absence of organosilane. The XRD patterns of the AP and OP samples are identical to that of the reference, indicating the MFI structure of the samples.

[099] The crystal size of the samples was investigated by scanning electron microscope (SEM) technique (Figure 14). The crystal size of OP (Organic Phase) sample was very small, ranging from 20 - 50nm. In contrast, large crystals of 5μm were observed in SEM micrograph of the AP (Aqueous Phase) sample.

[0100] Without being bound to theory, it is believed that the difference between the two samples suggest the effect of the oganosilanes agent on the crystal size of the product. Silanol sites on zeolites are located on the external surface and therefore the quantity of silanol sites is related to the zeolite crystal size. The large external surface of nanocrystalline zeolites provides significantly more silanol sites that are available for

chemical functionalization than for zeolites with larger crystal sizes and smaller external surface areas. The nanocrystalline zeolites can be much more extensively functionalized than zeolites with larger crystal sizes. Therefore, only the functionalized nanozeolites were sufficiently hydrophobic to disperse into the organic phase whereas the large nanocrystals with lower degree of functionalization remained in the aqueous phase.

[0101] The ²⁹ Si MAS NMR analysis of the dried (as made) AP and OP samples also appears to support this proposition (Figure 15). The peaks at the range of 60-80 ppm, which indicates the presence of C-Si bond, were only found on the NMR spectrum of the as-made OP sample. However, these NMR peaks were absent for the as-made AP sample

[0102] This suggest that a higher external surface of nanocrystalline zeolites provides significantly more silanol sites available for chemical functionalization than that for zeolites with larger crystal sizes (e.g., smaller external surface area). The nanocrystalline zeolites can be much more extensively functionalized than zeolites with larger crystal sizes. Therefore, only the functionalized nanozeolites were sufficiently hydrophobic to disperse into the organic phase whereas the large nanocrystals with lower degree of functionalization remained in the aqueous phase.

[0103] Figure 16 shows the N2 adsorption/desorption isotherms of the calcined OP sample prepared from the two-phase synthesis. The specific surface area is 520 m ² /g, the external surface area based on t-plot calculation is 106 m ² /g. This high external surface value also indicates the small crystal size of the sample.

[0104] Table 2: Physicochemical properties of the calcined silylated nanozeolite and zeolite samples prepared from the same clear zeolite gel, using the two-phase[a] and conventional[b] methods.

AP: aqueous phase; ;OP: organic phase; [a] see example 2; [b] see example 3

EXAMPLE 3: PREPARATION OF NANOZEOLITE USING CONVENTIONAL METHOD

[0105] The conventional synthesis of the zeolites in aqueous medium was carried out according to the procedure described in the literature [references 7, 15, 28]. After being filled with the same starting faujasite gel solution for the single-phase and two-phase methods, the Teflon-lined stainless steel autoclave was completely sealed and heated in a convection oven at 150 ⁰ C for 3 days. The solid product was recovered by centrifugation, washed several times with distilled water, dried over night at 80 ⁰ C. The products were synthesized using this conventional method, were denoted as reference or conventional silicalite-1 samples.

EXAMPLE 4 WATER ADSORPTION CAPACITY

[0106] Samples of 2g of each of A) calcined silylated FAU nanozeolite prepare in example 1 and B) calcined conventional zeolite prepared as in example 3 were outgassed at 200 ⁰ C for 16 hours, and then placed in a desiccator for 24 hours at 25 ⁰ C, a open beaker of HCl solution was also placed in the desiccator. The pressure of water vapor was adjusted by changing the HCl content. For this experiment, a solution of HCl 30% was used, corresponding to the pressure of water vapor of 7.52 mmHg at 25 ⁰ C (Perry's Chemical Engineers' Handbook, McGraw Hill 1999). The adsoption I calculated by weight difference before and after physi-sorption of water. As shown in table 3, the

adsorption of water in sample A), corresponding to one embodiment of the invention, is substantially less that the conventional "hydrophilic" zeolite.

Table 3

Sample A) SiO ₂ /Al ₂ O ₃ = 4.3 5.01% (wt)

Sample B) SiO ₂ ZAl ₂ O ₃ = 4.3 9.54% (wt)

[0107] Finally, it is thus expected with these materials which should allow catalysis to be extended to larger molecules, not converted in conventional zeolites because of spatial restrictions. Moreover, the relatively short diffusion pathways due to the small uniform zeolite size are expected to improve masse transfer and catalytic reaction efficiency and minimize channel blocking.

[0108] These two methods is believed to be applicable to the synthesis of silicalite-1 and FAU nanozeolites and could be applied to the synthesis of other types of zeolites such as BEA, , TS-I, MOR, , zeolite Beta, zeolite Y (including "ultra stable Y"-USY), mordenite, Zeolite L, ZSM-5, ZSM-Il, ZSM- 12, ZSM-20, Theta-1, ZSM-23, ZSM-34, ZSM-35, ZSM-48, SSZ-32, PSH-3, MCM-22, MCM-49, MCM-56, ITQ-I, ITQ-2, ITQ- 4, ITQ-21, SAPO-5, SAPO-I l, SAPO-37, Breck-6, ALPO ₄ -5,

[0109] While the invention has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modifications and this application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth, and as follows in the scope of the appended claims.

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