Title of Invention

A PROCESS FOR THE CONVERSION OF SOLID STARTING PARTICLES INTO SOLID INTERMEDIATE PARTICLES

Abstract

The present invention relates to a process for the conversion of solid starting particles into solid intermediate particles and the reduction of the median diameter of the intermediate particles to obtain product particles, which process involves the following steps: a) flowing a suspension of starting particles through a series of at least two conversion vessels, thereby converting at least part of the starting particles into intermediate particles, which (i) when the starting particles are amorphous, possess a degree of order, or (ii) when the starting particles possess a degree of order, possess a different order, a different degree of order, or no order, b) adding a supercritical fluid to one or more of the conversion vessels, thereby forming a supercritical suspension, and c) releasing pressure from the supercritical suspension, thereby expanding the suspension and converting the intermediate particles into prQduct particles.

Full Text

• PROCESS FOR CONVERSION AND SIZE REDUCTION OF SOLID PARTICLES The present invention relates to the conversion z: solid panicles with a certain median diameter into soiid product particles with a smaller mecian diameter. One of the most common ways cf reducing a canicie size is niilir.g. However, particles with a median diameter below about 1 micron usually cannot be obtained by regular milling procedures. Today, nanctechnclcgy is a growing research area with high expectations. This technology requires so-called nancparticies, which are defined in this specification as particles with a median particle size beiow about 1 micron. Such particles usually cannot be obtained by simpie milling of larger particles. US 5,810,257 discloses a process for pulverising a powder by suspending the powder into a fluid in a supercritical state, pressurising the suspension, injecting the fluid through a nozzle, reducing pressure in the suspension fluid, and separating the fluid from the solid particles as a gas under supercritical or subcritical conditions. Exemplified in this document is the reduction of 10-micron SiC particles to 1-micron SiC particles. The size of these particles is changed, but their chemical constitution and degree of order remain the same. US 5,921,478 discloses a method for dispersing particles by (i) feeding a mixture of a dispersoid and a solvent into a supercritical vessel, (ii) feeding a supercritical solvent into the supercritical vessel, (iii) heating and compressing the supercritical solvent to convert if from a gaseous phase state to supercritical fluid, (iv) mixing the mixture and the supercritical fluid in the supercritical vessel to obtain a supercritical mixture, and (v) introducing the supercritical mixture to an explosion-crashing tank to release the supercritical mixture to atmospheric pressure and to collide the supercritical mixture with a collision portion of the supercritical tank to effect dispersion of the dispersoid. This method results in crashing and dispersing cf the particles. The chemical constitution of the particles and their degree cf order remain the 5 same. It would be desirable, however, to be able to combine (a) changing the particles' degree cf order and (b) reducing the size cf :hese panicles to, if desired, nanometer scale in one process. The present invention provides 10 such a process. The process according to the invention relates to a combined process for the conversion of solid starting particles into solid intermediate particles and reducing the median diameter of the intermediate pa~:cies to retain prcduc: particles, which process involves the following steps: a) flowing a suspension of starting particles through a seres r at leas: two ccnverslcn vessels, thereby convening at least part ZT :he staring particles into intermediate particles, b) adding a supercritical fluid to one or more of :ne ccr.vars-cr. vessels thereby forming a supercritical suspension, and c) releasing pressure from the supercritical suspension, thereby expanding the suspension and converting the intermediate particles into product particles. The solid staring particles are either amorphous c~ possess a degree of order. During the process they are preferably converted into intermediate particles which (i) when the starting particles are amorphous, possess a degree of order, or (ii) when the starting particles possess1 a degree of order. possess a different order, a different degree of order, or no order. The term "a degree of order" is defined as the presence of a crystalline or quasi-crystalline, i.e. non-amorphous, phase detectable by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), or extended X-ray adsorption fine structure (EXAFS). Normally, a degree of order will be X-ray detectable (either as a peak or as a lump), but in the case of very small crystallites (i.e. below the XRD detection limit) more advanced techniques are required to detect a degree of order: SEM, TEM, or EXAFS. On the other hand: amorphous is defined as not having a degree of order as defined above. The degree of order can be estimated for instance from the width of the XRD-peak (or lump) if the cn/stallites are X-ray detectable. The narrower this peak, the higher the degree of-order will be. A different order will follow from the detection of different cn/stal structures or morphologies by the techniques mentioned above. No order means amorphous. i he process according to the invention is carticulariv suitable *cr the crcduction of nanooarticles. Hence this prccess :an be favcuraciv acolied for the preparation of product particles with a mecia" diameter :f belcw " micron, more specifically 1-500 nm, even more specmcally celcv, '-2CC mm. and most preferably 1-100 nm. The intermediate panicles and: in most cases. a;sc me star:" particies have a larger median diameter than theproducer particles. Preferbly :he median diameter of the starring particles is above A micron, cre'e'acly accut 1-1,000 microns, more preferably 1-500 microns, and even mce preferably 1-200 microns. . . The diameter of the particles is determined by measuring :he clameter of a recresentative amount of oarticles as viewed bv e!ec::cn micrzscccv. The median diameter is the middle of the distribution: 50% of the number of particles are above the median diameter and 50% are below the median diameter. The starting, intermediate, and product panicles are crer'eraby mace of inorganic materials. The starting particles preferably are of low-cost material, such as aluminium oxides or hydroxides, e.g., bauxite, crystalline aluminium trihycrate (ATH): gibbsite, bauxite ore concentrate (BOC) or thermally treated fo~s thereof (e.g. calcined and/or flash-calcined forms); synthetic and naturai clays, such as kaolin, sepiolite, hydrofelcite, smectite, or bentonite; silica cres: such as sand or diatomaceous earth; magnesium sources, such as magnesium salts, magnesium oxides or hydroxides, e.g., brucite, magnesium parbenate, magnesium hydroxy carbonate; zirconium compounds, such as zirconia, zircon or baddeieyite; titanium oxides or hydroxides; sorbents: catalysts or catalyst precursors, for instance in the form of microspheres, i.e. scray-cried particles, etc. if desired, the starting particles may be mechanically treated 'e.g. milled) before use in the process according to the invention in order to reduce their particle size. Examples of conversions of starting particles into intermediate carticies are the conversion of a precipitated mixture of aluminium suicnate arc aiuminium nitrate into boehmite, the conversion of bauxite ore :cncen::a:e (3GC) into boehmite. the conversion of auasi-crvsialilne bce^rnite into micro-crystalline boehmite, the conversion of an inexpensive s^cate cre (such as sand) into silica or siiica-based materials, the ccr.e'slcn of a silicon source (e.g. sand, silica sol, water giass, diatcmaceous rarh,. anc a solid magnesium source (e.g. MgO, brucite, hydromagnesite or ~agnesiu~ salts) into a layered magnesium silicate, recrystailisaricn of zirccnia ores (e.g. zircon or baddeieyite) to highly cnystailine zirccnia, ccnve-rsion of a silicon source and a solid aluminium source (e.g. aiuminium oxide or hydroxide) and optionally seeds and/or templates into mciecular sieves (e.g. zeolite X, Y, or A, ZSM-type zeolite, zeolite beta, mescpcrcus molecular sieves), the conversion of solid trivalent and divalent metal sources ('e.c. an aluminium and a magnesium source) into anionic clays (e.g. hycrctaicite.;. the conversion of two solid divalent metal sources into laye-red hydroxy; (double) salts, the conversion of a silicon source and a soiic aiuminium source and optionally bentonite seeds into bentonite, and the conversion of .a silicon source, a solid aluminium source, and a solid magnesium source into smectites. Furthermore, all sorts of combinations of the above conversions can be used to form various composites, for instance anionic ciay and ccehmite-containing composites, or composites comprising anionic ciay. ocehmite. and zeolite. The product particles will generally consist of the same mats':ai as the intermediate particles, except for their smaller particle size. However, if ths^ intermediate particles are layered materials, such as anionic clays (e.g. hydrotalcite), cationic clays (e.g. smectites, kaolin, bentonite, seciciite, etc.): or layered hydroxy (double) salts, pressure release may result in delamination and/or exfoliation of the layered structure. ihe process according to the invention involves as a first step "lowing of a suscension of startinc oartides throuch a series of an east two conversion vesseis and as a last step releasing the pressure of the suspension. The timing cf the introduction of the supercritical fiuic can cavaried according to the following :hree embodiments. particles in a non-supercritical liquid under at~cspheric cr sucer-atmospheric pressure using, e.g., the first one, twc. or three conversion, vessels. Suitable non-supercritical liquids to be usee in this process include water, alcohols such as methanol, ethanci. n-orccsnei. isoorccancl, etc.. and hydrocarbon liquids such as toluene, nexane. white spirts, gasoline. In the subseauent conversion vessel, the suspension containinc the intermediate particles - optionally after its liquid content has been recucec and/or after being mechanically treated - is combined with a supercritical fluid to obtain a supercritical suspension. Next, the supercritical suspension is pumped via a nozzie or orifice into a subsequent vessel, inereby expanding the supercritical suspension and forming the product particles. In a second embodiment, supercritical fluid is added during the conversion of the starting particles into intermediate particles. Hence part of the conversion into intermediate particles takes place under supercritical conditions. Again, before combining the suspension and the supercritical fluid, the liquid content of the suspension may be reduced, e.g., by drying or dewatering, and the suspension may be subjected to a mechanical treatment (e.g. milling). After the desired degree of conversion, the supercritical suspension is pumped via a nozzle or orifice into a subsequent vessel, thereby expanding the supercritical suspension and forming the product particles. In these first two embodiments, the conversion vessels; that cces/dc net contain supercritical fluid is/are generally kept at lower pressure than the vessei(s) charged with supercritical fluid. In order to snabie large pressure differences between individual vessels, the apparatus can be ecuicoed with a high-pressure slurry pump. This ailows continuous processing. Aiternativeiy, the process can be conducted seml-ccnt;~'-.:usiy by interrupting the preparation of the intermediate carticies :-:T.C the sequence of (a) charging one of the vessels with supercritical :"iu:d and (b) expanding the supercritical suspension. During this interruption period, the conversion vessel(s) under supercritical conditions is/are disconnected from the conversion vessel(s) under non-supercritical conditions. In a third embodiment, the entire process of convening the staring particles into intermediate particles is conducted under supercritical conditions. Hence the supercritical fluid is added to the. first of the series pf at ieast two conversion vessels. Finally, after the intermediate particles have been formed, the supercritical suspension is pumped via a nozzle or orifice into a subsequent vessel, thereby expanding the' supercritical suspension ana forming the product particles. Examples of supercritical fluids include supercritical*,..£02, supercritical nitrogen, supercritical ethylene, supercritical xenon, supercritical ethane. supercritical nitrous oxide, supercritical propane, supercritical ammonia, supercritical pentane, supercritical isopropanol, supercritical methanol, supercritical toluene, and supercritical water. Supercritical CO2 is the preferred supercritical fluid to be used in the process according to the invention. C02 has a mild critical temperature-(S-^C), it is inflammable, and non-toxic. Furthermore, it can be obtained from existing industrial processes without further contribution to the greenhouse effect. Supercritical carbon dioxide has a high diffusivity, a low viscosity, sr.d a low surface tension. An additional advantage of using supercritical CC2 is that An example cf an apparatus comprising =t !eas: :,vc conversion vessels, which apparatus can thus be suitably usee in the process zi~~.e rvemicr. is the accaratus acccrdinc tc US 2QC3-CCC-!S5£L5.~C VVC C2/C"C35. "ris apparatus may comprise a reed preparation vsssei. :r \T.:ZZ *re rr:a; sctic partiries and cp:;onaiiy seeds, caustic anc/cr acid car: be added arc mixed with liquid. Forced byway of a feed pump: the respire suspension can be !ed tc the first cf a series cf at least two, bui preferably d^ree tc five, conversion vessels. Each cf the conversion vessels may contain 'njectors"-via which additional liquid, acids, bases, seeds, and ether ingredients car be introduced - and a mixer, preferably an axial or cc-axia: mixer for instar.es a dcubie-heiix impeller or an anchor stirrer combined with an EKATO-JNTERMIG® (an impeller suitable for mixing slurries '.vith icv/ viscosity, cf which the outer blades pump downward while the inner blades pump upward). As supercritical fluids require super-atmospheric pressors (in ire case cf C02 abeve about 73 bar), the conversion vessels wearing The pressure is preferably released by spraying the supercriticai suspension through a nczzie or orifice - which may be heated to prevent freezing cv/ing io Joule-Thcmpscn cooling - into a subsequent vessel. Tin's method is also called Rapid Expansion of Supercritical Suspension (RE53). The subsequent vessel can be kept under close to atmosphere conditions or under somewhat higher pressure, e.g. 40-50 bar. The later arables a more energy-efficient and economical recycling of the supercriticai fuid. in order to enable the conversion of the starting panicles into intermediate particles, additional compounds (seeds, templates, additives, additional starting particles) may be added to one cr mere of the conversion; vessels during processing of the suspension. Furthermore. ::e temperature in each of the conversion vessels may be different. * In addition, surfactants, e.g. acetates or gluconates, can be added to the suspension in order to reduce the interaction be~.veer re ncr-3ucercr:t;cai liquid and the solid panicles and to enhance the interaction of the solid particles and the supercritical fluid. This is especially desired if cciar liquids such as water are present in the suspension. - - Further, metal additives can be added to the suspension, in croer to obtain metal-doped intermediate particles and/or .starting particles. Examples of such metal additives are compounds comprising an element selected from the group of alkaline earth metals (for instance Mg. Ca. and 3a), transition metals (for example Mn, Fe, Co, Ti, Zr, Cu, NL Zn, Mo, W, V. Sn; Nb), actinides, rare earth metals such as La and Ce, ncbie,metals such as Pi and Pdf silicon, gallium, boron, titanium, phosphcrus: and mixtures thereof. The metal additive can be added to the suspension together with the starring particles or separately, e.g., by adding the metal additive to one of the subsequent vessels. If a layered material is formed as intermediate particle, it may be desirable to have an intercalating agent present in the suspension to enable the formation of an intercalated layered material. The term Intercalating ager.f is defined as a compound that can be hosted between the layers of the layered material, thereby increasing the spacing between the layers. Examples of intercalating agents are organic compounds, such as organic . compounds comprising an aromatic ring and/or a functionality selected from the group consisting of carbonyl, carboxyl, hydroxy!, amide., ether ammonium, and ester. Examples of such compounds are amino acids (e.g. glycine serine, i-aspartic acid), oleates, gluconates, carboxymethylated carbohydrates (e.g. carboxymethyl cellulose), organic solvents (e.g. dimethyl sulphcxide, isophorone, gamma-butyrolactcr.e. n- methyipyrroiidone, 2-pyrrolidone, diglyrr.e, carprciaciarr.. fururyi aicchcl, tetrahydrofuran), quaternary ammonium oations: aikyi suic^atas (e.g. sodium dodecyl sulphate, aikyi sulphonstes (e.g. styrer.e suichcna:e: polystyrene suiphonaie), and ether ionic alky! chains :- =urac:s-:s. Examples of anionic Inorganic compounds that can be used as nterca'atlng agent are pillaring aniens such as FefCN)-3",, HVCXi": 7:C-~\ H7:3-:f": V^Cr" . V10O23"5, Mc70:>. ?Wi2OV~, 8(OH;7. [3:0:.Or/;. ^^CH;.]2;. 3405(OH)/'I H30,2-. HGa032; Cr042", Cr207:\ or Kecg!r>>r.s. The non-supercritical suspension flowing through "r,e servers" en vessels -may have a high Solids to Liquid Ratio (SLR). The SLR cf the s-scension is defined as the weight ratio of solids, including crystal waier: to 'euic in the suspension. The-optimal SLR depends en the rneolcgical bera.:cur cf the suspension, e.g. the tendency to form a gel and may ee in tr.s--ance 0.1-1.33, more preferably 0.3-1.33, even mere preferably C.5-1.22.and -most preferably 0.65-1.00. The viscosity of the rron-supereriticai suspension preferably is between 1 and 500 Pa-s at a shear rate cf 0.1 s'1. With the process according to the invention, product particles -"or various applications can be prepared. Their application depends on the type cf material and the size of the particles. Nanoparticles, for instance, can find their use in, e.g., molecular electronic devices (e.g. molecular wires, cicdes: transistors, memories), sensors, nanopumps. catalysis (as cataiys:. catalyst additive, catalyst support, etc), adsorbents, coating compositions (e.g. primer, base coat and/or clear coat for metallic and/cr piastic s-bstrates): paper making, paper conserving (e.g. conserving historical documents), polymers (as fillers), etc. EXAMPLES Example 1 This Example illustrates the process according :z the Invention fcr :r.e conversion cf aluminium trihydrate and magnesium :x;ce staring cericies Into anionic ciay intermediate particles and the conversion cf these anionic ciav intermeciate oarticies into anionic ciay crocuct ~a;~ecart;c:es. 24.2 kg aluminium trihydrate (ATH M6@frcm Alcca). 25 kg MgC .Zciiihc 42~ from Martin Marietta), and 150.8 kg water were mixed in a feed preparation vessel of 250 I. The solids to licuid ratio was 2.33. The ~ciar ratio MgO/Al2o3 was 4. The suspension was pumped to the first conversion vessel. 3y way of steam injection the suspension was heated up to 170, thereby decreasing the solids to liquid ratio to 0.25.- The suspension was led through ir.e subsequent two conversion vessels with such a ficw that the average residence time was about 45 minutes. The suspension in-ail conversion vessels was agitated using a ccubie-heiix impeller at 76-33 rpm. Because of a slightly exothermic reaction the temperature increased from 170°C in the first conversion vessel to 130°C in the second one. The pressure of the whole system was controlled by a pressure valve positioned immediately beyond the third conversion vessel. The system pressure in this experiment was maintained at 12 bar. X-ray diffraction (XRD) measurements showed that a Mg-AI anionic ciay was formed. The anionic clay intermediate particles had a median particle diameter of abcut 4 microns. After the third conversion vessel, the suspension was charged into a fourth conversion vessel, which was pressurised with C02 to the desired conditions in the supercritical regime (T > 3C4.2 K: p > 73 aim; using a supercritical C02 pump. Before being charged with the supercritical 'iuid, the fourth ccnversicn vessel was disconnected mom the ccnve'sicn vessel are the creoaraticn c^the anionic clay staring cartisies was ir,:e"u?ted. ; ha resulting sucercritica; suscensicn was acitatec a: high sceed %1000 2000 mml for 10 minutes. the weight ratic co2 to h2o in the suspersice ., f • . I .... was merer man o; tnerecy recucing tne sci;cs to -;CU;G rai;c :c :5ss thar^ vassal, when was kept under close to atmosphere senditis-'s. :nerecy venting the we: CO: gas to a COo qas recovery and drying system. The cried C0: gas was recycled using a supercritical Co2: ccmcress:-cunc. According to the semi-continuous mode of this process, the thir: anc fourth conversion vessels were re-connected, the prccucticn of re pr:duct particles was resumed, and the fourth conversion vessel was ara'n chargec with startinc oarticles. The product particles collected from the last vessel were analyse: to be ;vig- .; Al anionic clay particles with a median particie size of-ess than 511 nm. Example 2 Example 1 was repeated, except that instead of supercrticai CO-, supercritical nitrogen (126 K, 33.5 atm) was used. Again, re product particles comprised Mg-Ai anionic clay and had a median par:;e size of less than 500 nm. Example 3 This Example illustrates the conversion of sodium silicate and fiasn-caicined alumina starting particles into zeolite intermediate partic;as and the conversion of these intermediate particles into zeolite product particles. 3.73 kg aqueous sodium silicate containing 28 wt% soiids (as so. particles) were mixed with 40 g aluminium CP-3 (flash-calcined aluminium trihydrate) and*2.30 kg water under atmospheric conditions to form a suspe-sicn. The sclics to liquid ratic (SLR) of this suspension was 3.2C. in ca;cuiat:ng ir.a SLR. 23 wt% cf the sodium silicate mass was counts: as sciic. the ether "2 wt% was counted as liquid. Z3M-5 seeds (10 V.T::.- v/ere added. The suspension was heated to. 170C and keci a: this temcerat.i-e 3CC minutes. The suspension was agitated us^ng a ccucre-heiix impeller at 73- The so-formed zeciite intermediate particles had and;an ::ame:er z: about 7 microns. The suspension was charged into a second vessei, which was pressurised with CO2 to :he desired conditions in the superoriticai regime (T > 3C4.2 K. p > 73 atm), using a supercritical C02 pump. The resulting supercritical -suspension was agitated at high speed (1,000-2.CCQ mm) icr MZ minuies. The weight ratio CO? to H20 in the suspension was higher than 5. thereby reducing the solids to liquid ratio to iess than 0.033. * Next, the suspension was released through a nczzie into a third vessel, which was kept under close to atmospheric conditions, thereby venting the wet CO2 gas to a CO2 gas recover/ and dn/ing system. The cried CO2 gas was recycled using a supercritical CO2 compressor/pump. The product particles collected from the third vessel were analysed to be ZSM-5 with a Silica to Alumina Ratio (SAR) of 55. 80% cf these product particles had a particle size of below 1 micron. Example 4 i —'i Examples 1 and 2 were repeated, except that before being charged to the fourth conversion vessel, the suspension was dswatered using a high-pressure filtration step, thereby reducing the water content (LOI) of-the suspension to iess than 10 wt%. This increased the superoriticai fluid-to-water ratio in the fourth conversion vessel. Example 5 Example 3 was repeated, except that before being charged to the second vessel, the suspension was dewatered using a high-pressure filtration step, thereby reducing the water content (LOI) of the suspension to less than 10 wt%. This increased the supercritical fluid-to-water ratio in the second vessel. Example 6 Examples 1-5 were repeated, with sodium gluconate being added to the suspension. Example 7 Examples 1-6 were repeated, except that before being released into the vessel under close to atmospheric conditions, the supercritical suspension was first released into a 'vessel under somewhat higher pressure (in the case of supercritical C02: 40-50 bar), thereby enabling more energy-efficienl and economical recycling of the supercritical fluid. CLAIMS 1. Process for the "conversion of solid starting particles into solid intermediate particles and the reduction of the median diameter of the intermediate particles to obtain product particles, which process involves the following steps: a) flowing a suspension of starting particles through a series of at least two conversion vessels, thereby converting at least part of the starting particles into intermediate particles, which i) when the starting particles are amorphous, possess a degree of order, or (ii) when the starting particles possess a degree of order, possess a different order, a different degree of order, or no order, b) adding a supercritical fluid to one or more of the conversion vessels, thereby forming a supercritical suspension, and c) releasing pressure from the supercritical suspension, thereby expanding the suspension and converting the intermediate particles into product particles. 2. Process according to claim 1 wherein the solid product particles have a median diameter of below 1 micron. 3. Process according to claim 1 wherein the solid product particles have a median diameter of 1-500 nm. 4. Process according to-claim 3 wherein the solid product particles have a median diameter of 1-200 nm. 5. Process according to any one of the preceding claims wherein the solid starting particles are inorganic solid particles. 6. Process according to any one of the preceding claims wherein,-vthe intermediate particles comprise a material selected from the group consisting of anionic clay, smectite, zeolite, boehmite, silica, cationic clays, layered hydroxy salts, and combinations thereof. 7. Process according to any _one of the pracatind claims wherein the supercritical fluid is supercritical carbon dioxide. 8. Process according to any one of the preceding claims wherein at least par: cf the conversion of the starting particles into the intermediate particles takes place under supercritical conditions. 9. Process according to any one of the preceding claims wherein the supercritical suspension is added to the first cf the series of conversion vessels. 10. Process according to any of claims 1-7 wherein the supercritical fluid is added to the suspension of starting particles after conversion of the starting panicles into the intermediate particles!

Documents:

1095-CHENP-2005 ABSTRACT.pdf

1095-CHENP-2005 CORRESPONDENCE OTHERS.pdf

1095-CHENP-2005 CORRESPONDENCE PO.pdf

1095-CHENP-2005 FORM 1.pdf

1095-CHENP-2005 FORM 2.pdf

1095-CHENP-2005 PETITIONS.pdf

1095-chenp-2005-abstract.pdf

1095-chenp-2005-claims.pdf

1095-chenp-2005-correspondnece-others.pdf

1095-chenp-2005-correspondnece-po.pdf

1095-chenp-2005-description(complete).pdf

1095-chenp-2005-drawings.pdf

1095-chenp-2005-form 1.pdf

1095-chenp-2005-form 26.pdf

1095-chenp-2005-form 3.pdf

1095-chenp-2005-form 5.pdf

1095-chenp-2005-others.pdf

1095-chenp-2005-pct.pdf