Tin dioxide nanoparticles synthesis apparatus and tin dioxide nanoparticles process production

Abstract

A new and efficient nanoparticles synthesis apparatus and process production. More particularly, an apparatus and process applied to the synthesis of nanostructured tin dioxide. The benefits provided by the apparatus and process are applied in various gaseous reactions where occurs the formation of solid and gaseous products.

Claims

1. A nanoparticle synthesis reactor comprising: a) a reactor inlet; b) a tubular section in which one of at least two reactants flows axially; c) a gas distributor surrounding the tubular section, the gas distributor comprising a distributor inlet, a circular shape, cylindrical baffles providing flow canals, and orifices surrounding the tubular section of the reactor; and d) a powder collector, wherein the gas distributor provides an optimized radial interaction among reactant flows through a curtain of at least one of the reactants, providing kinetic enhancement of the following reaction:
A.sub.(g)+B.sub.(g).fwdarw.C.sub.(s)+D.sub.(g).

2. The reactor according to claim 1, wherein: a first of the reactants flows axially through the tubular section; and a second of the reactants enters the gas distributor through the distributor inlet, wherein the second reactant is redirected by the canals provided by the cylindrical baffles and then flows through the orifices that surround the tubular section, meeting the first reactant flow radially, synthesizing nanoparticles.

3. The reactor according to claim 1, wherein: A.sub.(g) is SnCl.sub.4(g); B.sub.(g) is H.sub.2O.sub.(g); C.sub.(s) is SnO.sub.2(s); D.sub.(g) is HCl.sub.(g); and SnO.sub.2(s) is in the form of tin dioxide nanoparticles.

4. The reactor according to claim 3, wherein the reactor maintains the reaction temperature at approximately 200 C.

5. The reactor according to claim 1, wherein the reactor provides particle size reduction of the synthesized nanoparticles and optimization of at least one of reaction conversion, reaction temperature, and reaction time.

6. The reactor according to claim 1, wherein the reactor provides particle size reduction of the synthesized nanoparticles and optimization of at least one of reaction conversion, reaction temperature, and reaction time.

7. A nanoparticle synthesis reactor comprising: a) a reactor inlet; b) a tubular section in which one of at least two reactant gases flows axially; c) a gas distributor surrounding the tubular section, the gas distributor comprising a distributor inlet, a circular shape, cylindrical baffles, and orifices surrounding the tubular section of the reactor; and d) a powder collector, wherein the gas distributor provides an optimized radial interaction among reactant flows through a curtain of at least one of the reactant gases, providing kinetic enhancement of the following reaction:
A.sub.(g)+B.sub.(g).fwdarw.C.sub.(s)+D.sub.(g).

8. The reactor according to claim 7, wherein: a first of the reactant gases flows axially through the tubular section; and a second of the reactant gases enters the gas distributor through the distributor inlet, wherein the second reactant gas is redirected by the cylindrical baffles and then flows through the orifices that surround the tubular section, meeting the first reactant gas flow radially, synthesizing nanoparticles.

9. The reactor according to claim 7, wherein: A.sub.(g) is SnCl.sub.4(g); B.sub.(g) is H.sub.2O.sub.(g); C.sub.(s) is SnO.sub.2(s); D.sub.(g) is HCl.sub.(g); and SnO.sub.2(s) is in the form of tin dioxide nanoparticles.

10. The reactor according to claim 9, wherein the reactor maintains the reaction temperature approximately 200 C.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) The attached figures represent illustrative and schematic illustrations and of the present invention, which has no bearing to restrict or limit the scope or the reach of the invention. The mentioned figures represent:

(2) FIG. 1 shows a tubular reactor provided with the gas distributor.

(3) FIG. 2 shows a detailed gas distributor.

(4) FIG. 3 shows an equilibrium versus temperature composition of the synthesis reaction.

(5) FIG. 4 shows an XRD of a SnO.sub.2 sample synthesized through the present invention.

(6) FIG. 5 shows an EDS of a SnO.sub.2 sample synthesized through the present invention.

(7) FIG. 6 shows a simplified schematic of industrial production using the present invention apparatus and process.

(8) FIG. 7 shows an equilibrium versus temperature composition of the Cl.sub.2 production reaction shown in the simplified schematic of industrial production.

(9) FIG. 8 shows an equilibrium composition versus temperature composition of the Sn chlorination reaction shown in the simplified schematic of industrial production.

(10) FIG. 9 shows a high-resolution transmission electron microscopy (HRTEM) of the sample produced by the current state of technique. Scale: 50 nm.

(11) FIG. 10 shows a high-resolution transmission electron microscopy (HRTEM) of the sample produced by the current state of technique. Scale: 10 nm.

(12) FIG. 11 shows a detailed gas distributor, perspective view.

(13) FIG. 12 shows a top schematic view of the reactor showing an illustrative or example reactant flow of two reactants through the reactor.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(14) The following is the detailed description of a preferred application of the present invention, which has no bearing to restrict or limit the scope or the reach of the invention.

(15) The reactor of the present invention is illustrated in FIGS. 1, 2, 11, and 12. In the reactor 10 of the present invention the flow of tin tetrachloride and water vapor meet radially, in order to maximize the probability of contact and the energy involved in the collision between them. The water vapor enters trough the inlet 4 located at the gas distributor 8, while the tetrachloride enters parallel to the axis of the tubular reactor 9 through the inlet 5. The tubular section 9 is provided with the distributor, built in a way that the water vapor flow is and the carrier gas passes through the cylindrical baffles 1 redirecting part of the mixture (water vapor and carrier gas) from the outer canals located at the outer section 11 to the inner canals located at the inner section 11 created by the cylindrical baffles into the lower orifices or holes 2 of the reactor (tube) 9. Thus, the mixture (water vapor and the carrier gas) is distributed evenly over the orifices or holes 2 of the tubular section 9, and then radially meet the tin tetrachloride flow.

(16) This energetic radial contact between the reagents creates a highly efficient mixture and starts the reaction that occurs rapidly along a short extension of the tube (region 3) wherein the temperature is maintained at 200 C. The tin dioxide nanoparticles are collected in the powder collector 7 located shortly after the gas distributor while the hydrogen chloride gas produced along with other gases leave the reactor 6 for subsequent treatment or reuse on the industrial production scheme as shown in FIG. 6.

(17) The perspective view of the gas distributor is shown in FIG. 11. The cylindrical baffles 1 create flow canals 11 inside the gas distributor where one of the reactants will flow from the outer canals to the inner canals until it reaches the orifices 2 and meets the other gaseous flow 12 radially. The reactant enters the gas distributor through the inlet 4. A schematic view of the reactor showing an illustrative or example reactant flow of two reactants through the reactor 10 is shown in FIG. 12, with a second reactant flowing over and under cylindrical baffles 1, through flow canals 11, and radially interacting with a first reactant in region 3 of tubular reactor 9.

(18) Tetrachloride and the water, in the liquid phase at room temperature, are volatilized through heater blankets. Then argon is used as a carrier gas to bring these reagents to the reactor gas. The heating of the reactor is done via heaters installed along the tube.

(19) Experiments carried out by the above methods, but using a traditional apparatus and reactor, produced tin dioxide nanoparticles sizes ranging from 25-45 nm, shown by the TEM images (FIGS. 9 and 10). In these early experiments the reagent flows were parallel; however, in the present invention, the flows are conducted perpendicularly, radially about the flowing reactant gas, allowing a kinetically more favorable interaction between the reagents. This was proven by the lower temperature required for the completion of the reaction. The reaction temperature decreased from 700 C. to 200 C. using the present invention.

(20) FIG. 3 shows the equilibrium composition versus temperature graph of the synthesis reaction, built from HSC Chemistry. 5 kmol H.sub.2O (g) and 1 kmol of SnCl.sub.4 (g) were calculated. Importantly, program calculations are based on closed systems. As the process of the present invention is an open system, we expect a higher conversion at lower temperatures, as evidenced in the experiments presented here, thus increasing the viability of the inventive process.

(21) The results shown here were obtained through analysis of tin dioxide samples collected at the end of the reactor and the powder filter. The following are the parameters and test results, to the date, more satisfactory.

(22) The SnO.sub.2 produced was analyzed using EDS (energy dispersive spectroscopy) and XRD (X-ray Diffraction). The crystallite size calculated using the XRD shown in FIG. 4 was approximately 3 nm. This crystallite size is much smaller than the 45 nm calculated from the gaseous reaction using a traditional reactor. The quality of the nanostructured tin dioxide gas sensor strongly improves with the decrease of particle size. The present invention apparatus also allows the reaction temperature reduction from 700 C. to 200 C. The EDS of the sample (FIG. 5) shows the strong presence of tin, confirming the purity of the sample and the high rate of conversion of the reaction system.

(23) FIG. 6 illustrates a simplified diagram of an industrial SnO.sub.2 nanoparticles production. The first reactor performs the SnO.sub.2 synthesis, receiving the reagents SnCl.sub.4 and water vapor. The SnO.sub.2 is collected and the co-product of this reaction, the gaseous HCl, is taken to the second reactor. The reactor for generation of Cl.sub.2 receives atmospheric air, whose oxygen reacts with HCl to form water, which is discarded, and chlorine gas (Cl.sub.2) according to the reaction:
4HCl.sub.(g)+O.sub.2(g)=2H.sub.2O+2Cl.sub.2(g)

(24) The thermodynamic study shown in FIG. 7 points toward almost 100% conversion at low temperatures (room temperature), contributing to the viability of the energy cost. 1 kmol of HCl (g) and 2 kmol O.sub.2 (g) were calculated. In this case the reaction is also gaseous, and the interaction between the reactants is crucial. Therefore, a reactor equivalent to the one used for the SnO.sub.2 synthesis also present benefits being used in the generation of Cl.sub.2.

(25) However, it should be noted that reactions involving hydrochloric acid are complicated due to waste of materials and environmental damage. If it is not of interest to perform the chlorination of tin for producing tin tetrachloride, the HCl itself is already a salable product. So, it is possible to collect the HCl right after the first reactor.

(26) Again it is important to remember that the program used for thermodynamic studies performs its calculations based on a closed system. As shown by the results of experimental line, the practical results were thermodynamically more promising than the theoretical. The satisfactory theoretical calculations presented here for the industrial system are an indication that the same may occur at larger scales and in other reactions, since they also occur in open systems. Table 1 below shows the thermodynamic data of the Cl.sub.2 synthesis reaction at different temperatures.

(27) TABLE-US-00001 TABLE 1 thermodynamic data of the Cl.sub.2 synthesis reaction at different temperatures. 4HCl(g) + O2(g) = 2H2O + 2Cl2(g) T deltaH deltaS deltaG C kcal cal/K kcal K Log(K) 0.000 51.678 99.649 24.459 3.726E+019 19.571 100.000 47.049 83.665 15.830 1.871E+009 9.272 200.000 45.134 79.130 7.694 3.583E+003 3.554 300.000 42.720 74.526 0.005 1.004E+000 0.002 400.000 39.092 68.705 7.156 4.746E003 2.324 500.000 35.388 63.573 13.764 1.285E004 3.891 600.000 31.740 59.136 19.894 1.047E005 4.980 700.000 28.156 55.249 25.609 1.771E006 5.752 800.000 24.630 51.799 30.958 4.951E007 6.305 900.000 21.159 48.706 35.981 1.979E007 6.704 1000.000 17.738 45.908 40.709 1.026E007 6.989

(28) The Cl.sub.2 generated is then transported to the third reactor, which also receives metallic tin in order to react with the Cl.sub.2, producing the SnCl.sub.4 required for the SnO.sub.2 synthesis reaction in the first reactor. The chlorination of tin is highly exothermic, requiring the cooling of the reactor in order to achieve a higher yield. Thus water is used, which in addition to performing the cooling of the third reactor, uses the energy of chlorination to be vaporized and reacted with SnCl.sub.4 in the first reactor.

(29) FIG. 8 shows the thermodynamic study of chlorination. 1 kmol Sn (s) and kmol 2 Cl.sub.2 (g) were calculated. The reaction has a conversion close to 100% from ambient temperature to 740 C. Table 2 presents the thermodynamic data of chlorination of tin at different temperatures.

(30) TABLE-US-00002 TABLE 2 Tin chlorination thermodynamic data for different temperatures Sn + 2Cl2(g) = SnCl4(g) T deltaH deltaS deltaG C kcal cal/K kcal K Log(K) 0.000 114.376 31.251 105.840 4.900E+084 84.690 100.000 114.295 30.999 102.728 1.484E+060 60.171 200.000 114.231 30.846 99.636 1.062E+046 46.026 300.000 115.884 34.124 96.326 5.411E+036 36.733 400.000 115.792 33.976 92.921 1.482E+030 30.171 500.000 115.691 33.837 89.530 2.042E+025 25.310 600.000 115.588 33.712 86.153 3.680E+021 21.566 700.000 115.486 33.601 82.787 3.925E+018 18.594 800.000 115.386 33.503 79.432 1.506E+016 16.178 900.000 115.290 33.417 76.086 1.498E+014 14.176 1000.000 115.198 33.342 72.748 3.084E+012 12.489

(31) Thus, the only reagents that need to be continually provided to this industrial production system are metallic tin, atmospheric air and water, substances much cheaper than those used in other synthesis methods.

(32) The low temperature requirements for the SnO.sub.2 synthesis and the energy reuse in order to vaporize the water also provides advantages over other methods as well.

(33) Those skilled in the art will appreciate the fact that the process object of the present invention applied to the production of nanoparticles, preferably nanoparticles of SnO.sub.2, has industrial reproducibility, and provides several advantages over other synthesis methods. The benefits of reduced temperature and time required for the reaction is generally applicable to other gaseous reactions, also encompassed by the present invention.