EP1011842A4 - Catalytic conversion of gases via cation-exchangeable alumino-silicate materials - Google Patents

Abstract

A process for catalytic conversion and/or adsorption of gases inclusive of NOx, SOx, CO2, CO, dioxins and PAHs and combinations thereof wherein said gases may contain particulates which include contacting one or more of such gases with an alumino-silicate material having: (i) a primarily tetrahedrally co-ordinated aluminium as established by the fact that the 27Al Magic Angle Spinning (MAS) provides a single peak at 55-58 ppm (FWHM = ∩23 ppm) relative to Al(H¿2O)6?3+; and (ii) a cation exchange capacity of at least 1 meq 100 g-1 in aqueous solution at room temperature.

Description

TITLE "CATALYTIC CONVERSION OF GASES VIA CATION-EXCHANGEABLE ALUMINO-SILICATE MATERIALS" FIELD OF THE INVENTION THIS INVENTION relates to the use of alumino-silicate materials for the catalytic conversion and/or adsorption of gas mixtures, such as those containing nitrous oxide, nitric oxide and nitrogen dioxide (generically termed "NOx") and/or other pollutant gases including, but not limited to, SOx, C0₂, CO, dioxins and polycyclic aromatic hydrocarbons (generically termed "PAH"s) and combinations thereof. The invention also relates to any of the aforementioned gas mixtures or gases which also contain particulates.

These toxic or pollutant gases are commonly encountered as products, in varying proportions, of combustion processes in many industrial processes (e.g. the burning of coal; production of chemicals) and internal combustion engines. In the case of NOx, these alumino-silicate materials convert the environmentally hazardous chemicals into benign gases such as nitrogen and/or water and/or oxygen.

It has now been discovered that certain alumino-silicate materials, as described herein, function as a catalyst for the catalytic conversion of these gases or gas mixtures or adsorb these gases or gas mixtures. These chemical processes may generally occur at elevated temperatures between 200°C and 850°C and over a wide range of gas flow and gas composition conditions. BACKGROUND OF THE INVENTION

Currently, two commercial processes for the removal of NO_x from industrial stacks are routinely implemented. The first is based upon the use of titania catalyst often promoted by oxides of vanadia, tungsten, iron, molybdenum, cobalt, manganese, uranium, copper, chromium or niobium, which facilitates the selective catalytic reduction of NO_x by ammonia and comprehensive reviews exist on this topic (G. C. Bond and S. F. Tahir, 1991 , Appl. Catal. 71 1 ; H. Bosch and F. Janssen, 1988, Catal. Today 2 369). The reaction for this commercial process can be represented by:-

4 NO + 4 NH₃ + 0₂ - 4 N₂ + 6 H₂0.

This latter catalyst system typically operates at temperatures in the range 300-400°C and exhibits good resistance to poisoning in the presence of SOx in the exhaust gas. Commercially, the catalyst is presented as either a plate-type or honeycomb monolith operating in the parallel flow mode which serves to minimize plugging of the catalyst bed by particulates

(F. Nakajima and I. Hamada, 1996, Catal. Today 29 109). Although this catalyst shows good selectivity to the desired products, it has several drawbacks relating to its practical application. These drawbacks include a lack of abrasion resistance, a use which is limited to a low reaction temperature (< 425°C) and high cost. Moreover, the ammonia reactant contaminates fly-ash produced in the system which causes additional difficulties for long-term effective use in industrial environs. Ammonia itself is also difficult to store as it is flammable and toxic and thus, it is undesirable to use ammonia in residential areas.

Recent developments aimed at improving the performance of these latter materials include the manufacture of clay mineral interlayer compounds containing titanium oxide and vanadium or copper species (N. Yoshida and J. Kato, 1996, Jpn, Kokai Tokkyo Koho JP 08, 117, 597). Similarly, Yang and Li (R. T. Yang and W. Li, 1995, J. Catal. 155 414) examined the performance of Fe³⁺ ion-exchanged TiO₂ pillared clays. Whereas catalysts are slightly poisoned in the presence of S0₂ and H₂0 (common components of industrial flues), the activity of the pillared clay materials is enhanced by the presence of S0₂ and H₂0. It was postulated that S0₂ and H₂0 are responsible for an increase in the concentration of Bronsted acid sites on the catalyst surface - which are assumed to be central to the catalytic reaction. The second process uses zeolite materials to catalyze the aforementioned reaction between ammonia and nitric oxide, although in this instance the optimum operating temperature is notably higher (ca. 500°C). For example, the use of iron-exchanged zeolites (e.g. ZSM5) has been reported by Famos et al. (U.S. Patent 5451387) and cerium-exchanged mordenite zeolites have been described by van den Bleek et al., (Netherlands Patent Application No. NL 9302288). Cu-ZSM5 catalysts have been shown by Sullivan etal., 1996, (App. Catalysis B: Environmental 7415- 417), to exhibit comparable activity to conventional vanadia/titania SCR catalysts and Komatsu et al., 1995, (J. Phys. Chem. 99 13053), deduced from infrared spectroscopy measurements that nitrate species formed on the zeolite surface subsequently reacted with ammonia to produce product nitrogen.

The direct decomposition of nitric oxide to its elements has been a significant challenge to scientists for decades (M. Shelef, 1995, Chem. Rev. 95209-224). This reaction is a particularly attractive solution to current pollution problems since no added reductant is necessary. This reaction, although thermodynamically favorable,

NO(g) - V_ N₂ (g) + ¹ O₂ (g) ΔG = -20.7 kcal/mol (298K) had not been demonstrated in any substantial yield until recently by Iwamoto et al. (1986, J. Chem. Soc. Chem. Comm., 1272). The major breakthrough involved the discovery that Cu-ZSM5 zeolites can decompose NO_x to its elements at 500°C at a significant rate. To date, Cu-ZSM5 has been thought unique among alumino-silicate-based materials. However, it has been conceded that Cu-ZSM5 catalysts do not have sufficient activity for practical implementation (Komatsu et al., 1995, J. Phys. Chem. 99 13053). In addition, there does not appear to be any method by which the activity of Cu- ZSM5 can be increased by the required I to 2 orders of magnitude to achieve practical or commercial use (Bogner et al., 1995, Applied Catalysis B: Environmental 7 153-171). The commonly employed method to improve activity involves an increase in the operating temperature - but this results in a reduction of activity for Cu-ZSM5 (Bogner et al., 1995, supra). According to Shelef (1995, supra), the principal cause of this relatively poor activity for Cu-ZSM5 is related to the crystal structure and consequent presentation of Cu-impregnated pores to the catalyst reaction. Alternative systems which have been reported to exhibit some activity for direct NO_x decomposition include yttrium barium copper oxide superconductor (YBCO) (Shimada etal., 1988, Chem. Letts., 1997) and a stratified aluminium silicate structure, in particular, mica, which incorporates either cerium or lanthanum ions in the silicate framework (E. Hums, PCT International Publication WO96/00016). The related decomposition of nitrous oxide (N₂O) into gaseous nitrogen and oxygen can be achieved by use of anionic clay minerals such as hydrotalcites, sjogrenites and pyroaurites containing activator species such as alkali metals or alkaline earth metals (Farris et al., U.S. Patent No. 5472677).

Due to the difficulty in forming catalysts which are suitable for industrial application of the direct NO_x decomposition reaction, the selective catalytic reduction (SCR) of NOx by various hydrocarbons has been examined in depth. Hydrocarbons are often found in exhaust streams along with the NOx pollutant. In particular, the development of more fuel efficient lean burn engines for automotive applications means that the exhaust gas will become highly oxidizing in character and, thus, the challenge is to create a catalyst which can selectively reduce NOx in the presence of excess oxygen. The current commercial three-way catalyst comprising mixtures of platinum, rhodium and ceria on an alumina washcoat cannot satisfactorily reduce NOx under net oxidizing conditions (K. C.Taylor, 1993, Catal. Rev. Sci. Eng. 35457) . The use of methane has attracted attention (J. N. Amor, 1995, Catal. Today 26 147) since it is in plentiful supply, relatively cheap and usually available. Materials which show activity for the selective reduction of NOx by hydrocarbons have in the majority been metal-exchanged zeolite (Komatsu et al., 1995, supra; K. C. Taylor, 1993, supra; Bogner et al., 1995, supra). However, the influence of SO₂ and H₂O - two typical components of industrial gas emissions - has often been found to be detrimental to catalytic activity (K. C. Taylor, 1995, supra) and current estimates are that the zeolite systems are approximately a factor of four too low in activity for commercial implementation (K. C. Taylor, 1995, supra). Accordingly, even for the most promising application - that of selective catalytic reduction of NO_x - there are no commercial uses of zeolite substrates or metal exchanged zeolites. In International Publication No. WO95/00441 , reference is made to the kaolin derivatives described in this specification that such derivatives have high specific surface areas of between 45 m²/g and 400 m²/g and high cation exchange capacities of from 50-450 meq/100 g for exchange of ammonium ions when compared to the starting kaolin. It was also speculated that such properties may make the kaolin derivative a useful replacement for conventional catalysts such as those used in the rearrangement and conversion of hydrocarbons. Another application uses the loading of lanthanides and/or transition metals on the kaolin derivative in reduction-oxidation catalyzed reactions such as the dehydrogenation of methanol to methyl formate. This specification also included specific examples directed to use of the kaolin derivative wherein the alkali metal cation was exchanged with copper in relation to dehydrogenation of methanol to methyl formate at elevated temperature and dehydrogenation of ethanol to acetaldehyde at elevated temperature. However, in International Publication No. WO95/00441 , the reference to the catalysis of methanol vapour and ethanol vapour is the only example of use of a metal exchanged kaolin derivative when used for catalysis.

However, it has now been discovered that alumino-silicate materials as described herein, inclusive of kaolin amorphous derivatives as described in International Publication No. WO95/00441 can be utilized in relation to conversion, via selective catalytic reduction and/or direct decomposition of NOx gases and other toxic gases such as CO, C0₂, SOx, dioxins and PAHs to environmentally benign product(s). The mechanism for such catalysis, as exemplified in the case of catalytic conversion of NOx gases, appears to involve the electronic configuration of the exchangeable metal ion when held by the alumino-silicate derivative which appears to have a surprising effect on the overall activity of the catalyst.

SUMMARY OF THE INVENTION The alumino-silicate materials for use in the present invention have a primarily tetrahedrally co-ordinated aluminium and have a cation exchange capacity of at least 1 meq 100 g^'1 in aqueous solution at room temperature. Preferably such materials have a CEC of above 100 meq 100 g^"1 and more preferably have a CEC of between 160-900 meq 100 g^"1 and most preferably have a CEC of between 350-450 meq 100 g^"1 using methods of determination defined in previous disclosures (e.g. International Publication Nos. WO96/18576 and W096/18577).

The fact that the alumino-silicate materials have a primarily tetrahedrally co-ordinated aluminium is evidenced by the fact that the ²⁷AI Magic Angle Spinning (MAS) gives a single peak at 55-58 ppm (FWHM = -23 ppm) relative to Al (H₂0) ₆ ⁺³. The alumino-silicate materials for use in the present invention also include an exchangeable cation which is an ammonium ion or alkali metal cation which may be partly or fully exchanged by a secondary metal selected from one of the following:- the alkaline earths Mg²⁺, Ca²⁺, Sr^2* and Ba²⁺, the transition metals Cr³", Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Ag\ the heavy metals Pb²⁺, Cd²⁺, Hg²⁺; the lanthanides- Lai and NcP or the actinide U0₂ ²⁺ .

In one aspect, the alumino-silicate materials for use in the invention are amorphous in nature and thus cover kaolin amorphous derivatives or KADs as described in International Publication No. WO95/00441 or alumino-silicate derivatives (ASDs) as described in International Publication Nos. W096/18576 or W096/18577. These amorphous materials do not show any substantial long range structural ordering and have a broad hump between 14° and 40° 2Θ (or 22° and 32° 2Θ in some cases) for CuKα X-radiation. No sharp diffraction peaks are observed except those belonging to impurities. Such KADs or ASDs may be prepared by reaction of a starting alumino-silicate with MOH and/or MX where M is alkali metal and X is halide. Such compounds may have a chemical composition of the general formula,

M_p Al_qSi₂O_r(OH)_sX_t ^• uH₂O wherein 0.2 < p < 2.0, 0.5 ≤ q < 2.5, 4.0 < r < 12, 0.5 ≤ s < 4.0, 0.0 < t < 1.0 and 0.0 ≤ u < 6.0 and M is ammonium ion or alkali metal cation and X is halide wherein M as NH₄ ⁺, Na⁺, K⁺, Li⁺, Rb⁺ or Cs may be exchanged by one of the secondary metals discussed above.

In another aspect, the alkali metal alumino-silicate materials for use in the invention may comprise amorphous or poorly or partly crystalline alumino-silicates having a stuffed silica polymorph-related structure which is produced by reacting a starting alumino-silicate or a combination of aluminium oxide-containing and silicon-oxide containing compounds with an alkali oxide or alkali hydroxide containing reagent. Such stuffed silica polymorphs include kalsilite, camegieite, eucryptite or nepheline. These polymorphs are stuffed derivatives of the tridymite, cristobalite or quartz structures. Such materials are described in International Publication No. WO96/12678, which disclosure is included herein by reference.

The alumino-silicate materials for use in the invention also include modified kaolins which may be prepared from a kaolin group mineral which includes expansion and contraction of layers of the kaolin group mineral wherein these layers comprise one Si-tetrahedral sheet and one Al- octahedral sheet. Such modified kaolins and their cation-exchangeable alumino-silicate derivatives are described in International Publication No. WO97/15427, which disclosure is included herein by reference.

According to one form of the invention, the alumino-silicate materials as described above may be utilized for the stable catalytic transformation of NO_x, to N₂ and H₂O in the presence of hydrocarbons to achieve selective catalytic reduction (SCR). These materials can be produced with a variety of pore sizes and surface structures and may contain significant levels of surface-bonded metals such as copper, iron, cerium or cobalt which are active for conversion of NO_x. Alternatively, the cation- exchangeable material as described in International Publication Nos. WO95/00441 , WO96/18576, W096/18577 and W096/12678, may also effect this catalytic transformation albeit at lower levels of conversion. Furthermore, any form of the abovementioned alumino-silicate materials will effect conversion, if the gas stream contains amounts of metal ions which are active for conversion of NOx. In this form, the metal ions from the gas stream are adsorbed onto the alumino-silicate substrate wherein similar selective catalytic reduction of NOx in the presence of hydrocarbons occurs. The exchangeability of metal ions, as well as high surface area values for the metal-loaded substrate (BET values > 40 m²/g) are desirable attributes of the alumino-silicate materials with regard to subsequent catalysis performance. For example, TABLE 1 illustrates values for the cation exchange capacity (CEC) and surface area for conventional alumino- silicate materials such as ZSM5, kaolin clay and pillared clays compared with these values for the alumino-silicate materials specified in International Publication Nos. WO95/00441 , WO96/18576 and W096/18577.

The range of values shown in TABLE 1 achieved by the alumino-silicate materials described herein are significantly greater than those under trial by other practitioners for use as catalysts for NOx reduction. This combination of properties, as well as thermal stability to temperatures greater than 800°C, provides favourable conditions for these catalysis reactions with NOx. In a preferred form of the invention, these materials are stable in hydrothermal conditions wherein the presence of water at temperatures up to 600°C may otherwise cause the degradation of competing products. Surprisingly, it is the form of the metal-exchanged ion - that is, the electronic states or valences - induced by the cation-exchange process with the alumino-silicate material which influences the catalytic behaviour of these materials with respect to conversion of noxious gases such as NOx, dioxins and/or PAH or combinations, thereof. The nature of these electronic states are described herein for typical samples listed in TABLE 2 using spectroscopic and adsorption/desorption methods well-known to those skilled in the art. For specific data sets, a comparison is made with the electronic states for equivalent metal-exchanged zeolite species.

In another form of the invention, these materials may also react with NOx in the presence of toxic gases such as SOx without apparent degradation of catalytic performance due to the presence of SOx.

In another form of the invention, these materials may also react with organic gaseous compounds such as dioxins and polycyclic aromatic hydrocarbons (PAH).

The methods to make these new alumino-silicate materials are well described in previous International Publication Nos. WO95/00441 , WO96/18576, WO96/18577 and W096/12678, and can also be obtained by an alternate route as described in International Publication No. WO97/15427. For those skilled in the art, a wide choice of primary physical and chemical properties are available from this suite of new materials through appropriate choice of preparation method, or combination of preparation methods, as disclosed in these previous publications. These primary physical and chemical properties include surface area, cation exchange capacity, availability of sites, relative percentage of mesoporous and micro-porous sites and Si/AI ratios. For this description, the following summary in TABLE 2 identifies the various generic methods to produce the forms of new material(s) exemplified below by way of specific sample numbers.

Subtle variations in bulk properties within and between these various samples listed in TABLE 2 can be achieved by manipulation of the product or intermediate compound using conventional techniques well-known to those skilled in the art. For example, the extent of cation exchange achieved with the secondary process using copper nitrate solution listed in TABLE 2 may be increased or decreased substantially by variation of the molarity of the copper nitrate solution and/or the kinetics of the exchange reaction. Alternatively, other metal-loaded solutions such as cobalt acetate and copper acetate (or combinations thereof) may be used to achieve the appropriate level of copper and/or cobalt exchanged alumino-silicate material. These metal-exchanged alumino-silicate materials are suitable materials for the catalytic conversion of gases.

The nature of the metal ions on the alumino-silicate surface is best revealed by X-ray photoelectron spectroscopy (XPS). For example, XPS studies of copper-exchanged KAD materials indicate that two general types of copper species exist on the catalyst surface: those represented by a sub- band at 933.5eV being typical of copper oxide species and those represented by the sub-band at 935.5eV being typical of Cu⁺ ions incorporated in the alumino-silicate framework. It is apparent from the XPS data shown in TABLE 3 for a subset of all samples studied, that the relative concentration of the different types of copper species is controlled by the identity of the KAD substrate and hence, the method of preparation of the KAD material.

A common property identified by those skilled in the art of catalysis materials relates to the chemical composition of the substrate material which hosts the active sites for catalysis or decomposition reactions. The composition of these materials can be described in terms of bulk or surface chemistry. The general bulk chemical compositions of these new materials have been described in the previous disclosures referred to above. These bulk compositions were determined by well-known techniques, such as electron microprobe analysis and wet chemical analysis, using atomic absorption spectroscopy and/or inductively coupled plasma spectroscopy.

Surface chemistry of these new materials can be readily obtained by those skilled in the art of X-ray Photoelectron Spectroscopy (XPS). In general, this method probes the top surface layers of a catalyst material and provides quantitative data by way of comparison of spectral peak heights for calibrated standard compositions. TABLE 4 provides surface chemical compositions for a wide range of catalyst materials tested and developed for the gas applications listed below. These data have been acquired as average scans over mm-size regions of the powdered material(s) prior to trial as a catalyst. From these data, other critical characteristics such as elemental ratios can be determined. Accordingly, the Si/AI, K AI and Cu/AI ratios for a range of samples listed in this disclosure have been obtained by XPS measurement and are listed in TABLE 5. Importantly, as can be seen from the data listed in TABLE 5, the Si/AI ratio is in the range 1.0 to 1.5 for all samples which demonstrate suitable catalytic activity to NOx or which directly decompose NOx at suitable temperatures. In contrast, zeolites nominated for exhaust catalysis of NOx usually employ Si/AI ratios of >15 (Yoshimura etal., Jpn, Kokai Tokkyo Koho JP08, 108,043 (96,108.043). An example of the ratios for Cu-ZSM5 is also listed in TABLE 5. As shown in TABLE 5, the novel materials detailed in this disclosure have very low Si/AI ratios which are not easily obtainable by conventional zeolite preparation methods.

Without wishing to be bound by theory, the above characteristics of the metal-exchanged alumino-silicate materials are typical of those required for the effective chemical conversion (via catalysis), decomposition or adsorption of toxic inorganic gases such as NOx, and toxic organic gases such as dioxins and polycyclic aromatic hydrocarbons.

These alumino-silicate materials are amenable to fabrication into specific shapes or monoliths using conventional ceramics forming techniques. However, most trials of this material to date have utilized either a powdered or a pelleted form and are pretreated by high temperature calcination in flowing air at 500°C for two hours.

The process of the invention has relevance to the reduction of NOx in the presence of organic reductants at a temperature of 200-650°C wherein the NOx is adsorbed by the alumino-silicate material. The organic reductants include hydrocarbons inclusive of alkanes, alkenes, aromatics inclusive of benzene and polycyclic hydrocarbons as well as oxygen- containing organic compounds inclusive of alcohols and aldehydes. The temperature of 200-650°C is dependent upon the choice of the organic reductant. This process is applicable in relation to treatment of exhaust gases from furnaces, incinerators or vehicle exhausts.

The process of the reaction is also applicable to the reduction of NOx using nitrogen containing reductants inclusive of ammonia and urea. A temperature of between 200-650°C is applicable to the use of ammonia and a temperature of 350-500°C is applicable to the use of urea.

The process of the invention is also applicable in the direct decomposition of NOx to nitrogen at a temperature of 200-850°C. The alumino-silicate material for this specific application contains Fe, Cu or Ag or other metals as described in Example 8. In relation to the process of CO₂, use is made of ASDs which are doped with or which contain basic oxides inclusive of CaO and MgO or other alkaline earth metal oxides as well as transition metal oxides inclusive of CuO, ZnO or iron oxides. This may be accomplished by reacting the alumino-silicate material (hereinafter alumino-silicate derivative or ASD) with a soluble salt of the relevant oxide such as the nitrate or the halide followed by drying and heating.

The gas containing C0₂ or CO₂ perse is passed through the ASD so that the CO₂ is adsorbed by the ASD. A suitable temperature is between room temperature and 300°C. A similar process as described above in relation to C0₂ may also apply to processing of SOx inclusive of SO₂ wherein the SOx is passed through the ASD and is adsorbed by the ASD or reduced to sulphur. Temperatures for adsorption of SO₂ are usually between 0-500°C and more suitably between room temperature and 150°C. The ASD may be doped with basic metal oxides or transition metal oxides as described above.

The process of the invention may also be applied to oxidation of SO₂ to S0₃ wherein an ASD containing Pt, Pd, Ag, Cu, Co, Mn or Cr is utilized at a temperature of 150-650°C. A similar process is used for oxidation of CO to C0₂. In the treatment of dioxins or PAHs, the ASD may contain Pt,

Pd, Ag, Cu, Co, Mn or Cr and a suitable temperature is between 250-650°C. Dioxins may be converted to H₂0, HCI and C0₂. An example in relation to treatment with dioxins is shown in Example 9.

In relation to PAHs, suitable gases which are subject to the process of the invention include anthracene, fluorene, pyrene, perylene, chrysene and naphthacene.

In the abovementioned examples, it will be appreciated that the conversion rate or percentage removal from a gas stream being treated by the catalysts of the invention depends on the temperature which is utilized and the higher the temperature utilized will result in the more efficient removal of gas pollutant from the gas stream.

In relation to stationary flues of power stations, chemical treatment plants, furnaces and the like, a conversion or removal rate of around 30-40% may apply in relation to temperatures of about 200-250°C. This conversion rate may increase to 60% in the case of 350°C. For motor vehicles, temperatures of 450-500°C may result in greater than 80% conversion and this may also apply in relation to diesels wherein a temperature of 200-600°C may be utilized.

The following examples demonstrate the various properties of these alumino-silicate materials for the catalytic conversion of gases derived from high temperature combustion.

EXAMPLES EXAMPLE 1 Decomposition of NOx

Laboratory-scale experiments were undertaken in a fixed bed micro-reactor system modified to accommodate preliminary study of NOx reduction. The various components of the micro-reactor which includes a fixed bed reactor, in situ transmission FTIR cell and DRIFTS cell integrated to an on-line mass spectrometer, gas chromatograph and a gas chromatograph-FTIR accessory are shown in FIG. 1.

The behaviour of five types of copper-exchanged materials has been investigated with regard to their activity towards NO_x decomposition.

An appropriate quantity of K-KAD was added to an aqueous solution of copper nitrate at pH 6.5 at room temperature and stirred for 2 hours. For these experiments, the following reaction parameters were:-

• catalyst temperature: 550°C

• initial NOx concentration: 2000 ppm • flow-rate (gas hourly space velocity (GHSV)): 15,000 lr¹

The conversion data in FIG. 2 for these experiments show that the copper-exchanged catalyst Cu-KAD3-1 does indeed exhibit excellent potential for direct NO_x decomposition since 100% NO _x conversion is achieved at 550°C and at flowrates approaching those of commercial conditions. The conditions employed during these preliminary trials of the copper-exchanged catalyst material are substantially more severe than those used in previous studies of Cu-ZSM5 (N. Yoshida and Y. Kato, 1996, supra). A comparison of the data presented by Iwamoto et al. (1986, supra) and calculations for these preliminary trials, reveal that the copper-exchanged catalyst material is at least an order of magnitude more active than Cu-ZSM5 under these same conditions.

The source of the enhanced catalytic activity and superior resistance to deactivation of Cu-KAD (or Cu-ASD) is associated with the nature of the copper species present on the catalyst surface. In situ FTIR studies reveal significant differences in the structure of the adsorbed species present following NO_x/O₂ exposure on Cu-ZSM5 relative to Cu-KAD or Cu- ASD as shown in FIG. 3. Importantly, this Cu-KAD or Cu-ASD catalyst promotes the formation of adsorbed nitrate, nitro and nitrito species. Adelman et al., 1996, Appl. Cat. B. 11 L1 , recently summarized the mechanism for the selective reduction of NOx with alkanes on Cu-ZSM5 zeolite and significantly emphasized the importance of adsorbed nitrate and nitro species in the reaction. Similarly, Centi et al., 1996, J. Chem. Soc. Faraday Trans. 92 5129, have also used a combination of ¹³C MAS NMR, FTIR, reactivity testing and UV-VIS-NIR reflectance spectroscopy to determine that the reaction between adsorbed nitrate species and the hydrocarbon initially results in an organonitro species which is integral to the catalytic reaction. Consequently, the promotion of the concentration of adsorbed NOx species on the Cu-KAD or Cu-ASD catalysts is beneficial to the catalytic process.

EXAMPLE 2 Spectroscopy of copper- and potassium-exchanged alumino-silicates

FTIR studies of the interaction of NO_x and O₂ were performed on copper- and potassium-exchanged KAD materials and the spectral data have been summarized as follows in TABLES 6 and 7. These data provide fundamental information on the nature of the types of surface sites available on these new materials and the role(s) of the active species at these sites in the catalysis and/or decomposition reaction with NOx gases. For comparison, similar data for Cu-ZSM5 are also tabulated.

The infrared data indicate that a combination of potassium and copper species are present in these catalysts as bands at ca. 1390-1400 cm^'1 and 1360 cm^"1 are present in both the potassium-exchanged catalyst and the copper-exchanged catalyst which was prepared from the potassium form. XPS studies support this conclusion, as it is clear that potassium exists in all the copper-exchanged samples. However, copper-exchanged samples which contain little or no exchanged potassium are similarly considered suitable materials for these catalysis or direct decomposition reactions.

EXAMPLE 3 Spectroscopy of Co-exchanged alumino-silicate materials during reaction with NOx Cobalt-exchanged alumino-silicate is similar to Cu-KAD or Cu- ASD in that it is characterized by an intrinsically high surface area, has an alumino-silicate substrate and shows potential for "over-exchange" reactions. As in Example 7 described hereinafter, Co-KAD was prepared by contacting K-KAD with a cobalt nitrate solution. An example of the superior adsorption properties of cobalt-exchanged KAD materials with respect to conventional cobalt-exchanged zeolites (e.g. Co-ZSM5) is provided by inspection of FTIR spectra which were recorded at ambient temperature following exposure of an OJ0₂ mixture to the catalyst surface. FIG. 4 gives a summary of these spectral data.

It is apparent that the intensities of the bands on C-0-ZSM5, which are best assigned to modes of adsorbed nitro and nitrito species (Adelman et al., 1996, J. Catal. 158 327) are very weak relative to that for all the illustrated Co-KAD materials. Again, there is also evidence for the presence of Co and potassium species as indicated by bands at ca. 1390 and 1360 cm-¹. EXAMPLE 4 Selective Catalytic Reduction and Direct Decomposition of NOx from an incinerator

Trials of the K-, Co- and Cu-based catalyst materials have been undertaken on waste gas stream from a commercial municipal incinerator in Brisbane, Australia. Waste gas streams from both the primary chamber, the ignition zone of the incinerator and the secondary chamber have been tested for high oxygen content waste in order to ensure burn conditions generated significant levels of NOx. A schematic of this incinerator system and the points of sampling for gas streams are indicated in FIG. 5. Note that sampling is not taken from the top of the exhaust stack, but rather at locations where high levels of target gases (e.g. NOx, water vapour, SOx etc.) are generated.

On the day of testing, Lurgi Pitch (a waste material supplied by an alumina refining company) was undergoing incineration. Incineration of this material resulted in the presence of significant quantities of hydrocarbon and oxygen (in addition to NOx) in the chamber. Within these gas streams, high levels of water vapour as well as hydrocarbons (primarily light hydrocarbons) and SOx are common, although for these experiments the precise levels were not monitored in all cases. Data on the hydrocarbon concentration are available for the secondary chamber (approximately 3 ppm) but hydrocarbon levels within the primary chamber fluctuate rapidly and are difficult to determine. Nevertheless, to those skilled in the art, it would be known that the hydrocarbon levels in a primary incinerator chamber are likely in excess of 500 ppm.

For all experiments, the set-up described in FIG. 6 was utilized.

In this arrangement, a plug of the catalyst material (0 -5.0-5.5 mm by 60-70 mm long) is inserted in the centre of a 900 mm long quartz tube and held in place using quartz wool. For baseline measurements, the gas stream was directed through a parallel quartz tube containing quartz wool only.

The reactor tubes were held in an 860 mm Lindberg furnace at a temperature of 500°C (± 50°C) for all cases except sample K-KAD5-15. In the case of sample K-KAD5-15, the reaction was carried out at 400°C (± 50°C). The gas stream was then conditioned for removal of particulates and moisture using a Perma Pure dryer. Concentrations of NO_x were monitored using a 0-2000 ppm Analytical Developments Company Infrared NO_x detector.

Gases were drawn through the catalyst material at a rate of 1.0 to 1.2 litres per minute {gas hourly space velocity (GHSV) - 60,000 h^'1}. Sampling times for all gases ranged from 20 minutes to 30 minutes.

These field trials on catalyst materials demonstrate that at the flow rates used and at modest temperatures, the reduction of NOx is significant and achievable. Within the suite of catalyst materials trialed, sample K-KAD3-8 shows a conversion efficiency less than 90% while all others are greater than 90%. Operation of these catalysts at different temperatures and with various combinations of hydrocarbons and/or water vapour will result in different levels of conversion efficiency. For example, as shown for sample K-KAD3-8, the comparative absence of hydrocarbons in the secondary chamber results in a lower reduction in NOx levels (conversion of - 11.5%) in the gas stream treated with this catalyst material. However, the relative absence of hydrocarbon in this case demonstrates that even at 500°C (± 50°C) direct decomposition of NO_x can occur with this catalyst material. In the examples listed for gases from the primary chamber and the ignition zone, where it is assumed the hydrocarbon level is considerably higher, the reduction of NOx in the presence of the new materials occurs by a selective catalytic reduction process. Since the materials are stable up to about 750°C and clearly operate at lower temperatures (e.g. to 400°C), there is opportunity to optimize these materials for higher conversion efficiencies under a wide range of operating conditions. EXAMPLE 5 Selective Catalytic Reduction of NOx in diesel engine exhaust Trials of the Co- and Cu-based catalyst materials have been undertaken on exhaust gas stream from a diesel engine. For all experiments, the set-up described in FIG. 6 was utilized. In this arrangement, a plug of the catalyst material (ø -5.0-5.5 mm by 60-70 mm long) is inserted in the centre of a 900 mm long quartz tube and held in place using quartz wool. For baseline measurements, the gas stream was directed through a parallel quartz tube containing quartz wool only. The reactor tubes were held in an 860 mm Lindberg furnace at a temperature of 500°C (± 50°C) for all cases. The gas stream was then conditioned for removal of particulates and moisture using a Perma Pure dryer. Concentrations of NO_x were monitored using a 0-2000 ppm Analytical Developments Company Infrared NO_x detector. Gases were drawn through the catalyst material at a rate of 1.0 to 1.2 litres per minute {gas hourly space velocity (GHSV) - 60,000 IT¹}. Sampling times for all gases were 20 minutes.

TABLE 9 presents raw and compiled data for the field trial of five Cu- and Co-based catalyst materials for the conversion of NOx from diesel exhaust.

These field trials on catalyst materials demonstrate that at the flow rates used and at modest temperatures, the reduction of NOx is significant and achievable. Within the suite of catalyst materials trialed, sample Co-KAD3-5 shows the lowest conversion efficiency at 91 % while all others are greater than 91 % conversion efficiency. Operation of these catalysts at different temperatures and with various combinations of hydrocarbons and/or water vapour will result in different levels of conversion efficiency. Additional trials of these same materials were conducted after a period of cool-down and inactivity for 24 hours or more. Subsequent trials under similar conditions to that listed for data given in TABLE 9 demonstrated that these new materials retained the capacity to reduce NOx levels from a diesel engine exhaust after sustained periods held at room temperature and ambient humid conditions.

EXAMPLE 6 Selective Catalytic Reduction of NOx in diesel engine exhaust using propene or diesel fuel Experiments were performed on a KUBOTA GV1120 diesel engine in which the exhaust from the operating engine is coupled to a gas injection system. Additional hydrocarbon is subsequently added to the exhaust stream, either as a mixture of propene in nitrogen or as diesel fuel. This mixture is then contacted with an appropriate amount of catalyst situated within a reactor tube located in a heated furnace using a similar arrangement to that shown schematically in FIG. 6. The treated gases are then analyzed by both an FTIR gas cell and, after passage through a dehumidifier, by a dedicated infrared NOx analyzer.

For the initial calibration tests, propene stream is not present, so the exhaust is drawn through an empty pipe. The two catalysts, samples Cu-KAD3-7 and Co-KAD3-7, were trialed at temperatures ranging from 380°C to 550°C. During these trials, the load on the engine is kept constant at around 75%. With the engine started, but under no load, the oxygen level in the gas stream is 14.9% whereas, with 75% load on the engine, the oxygen level is 13.0%. The NOx conversion value - due to direct decomposition - remained below 10% under these applied conditions. However, addition of propene to the exhaust analysis stream is shown to be extremely beneficial for NOx conversion values using these catalysts. FIG. 7 shows a series of experiments which document the relative NOx conversion rates for sample Cu-KAD3-7 for different amounts of propene in the gas stream. The optimum ratio of propene to NOx for maximum conversion under these conditions is shown to be approximately 4:1.

The long term stability of these catalysts under typical exhaust conditions have also been tested and is demonstrated in FIG. 8 for the sample of Co-KAD3-7. The NOx conversion level is stable and greater than 80% for periods of several hours (up to 13 hours), and significantly, the catalyst attains a similar level of activity (or NOx conversion rate) following shutdown due to cooling to temperatures below 350°C for a period of time (e.g. approximately 1.5 hours). This demonstration of reactivation after a period of time is relevant to the normal operating mode of vehicular or stationary diesel engines.

The use of propene may not be suitable for certain applications which utilize diesel engines due to considerations associated with storage of propene. Accordingly, a similar test to assess the NOx conversion efficiency of these catalysts with injection of diesel fuel into the exhaust stream has also been undertaken. As shown in FIG. 9, diesel fuel addition under these standard operating conditions resulted in NOx conversion efficiencies of approximately 70%.

EXAMPLE 7 Selective catalytic reduction of NOx with NH₃

Catalysts were prepared by the following protocol. Firstly, K- KAD was converted to NH₄ ⁺ KAD and TiCI₄ were mixed together and then the TiCI₄ was hydrolyzed by the addition of aqueous ammonia. Finally, after drying the Ti-KAD at 120° and calcination to 500°C, the Ti-KAD was impregnated with appropriate amounts of aqueous iron nitrate, niobium chloride, tin chloride, ammonium metavanadate or ammonium metatungstate. Again, this material was calcined at 500°C before use in the micro-reactor shown in FIG. 10. The preparation of the Fe-Ti-KAD, Fe-Sn- Ti-KAD, Fe-W-Ti-KAD, Fe-Nb-Ti-KAD, V-Sn-Ti-KAD and V-W-Ti-KAD catalysts described above is shown in Table 10 and the measurement of DeNOx activity is shown in Table 11. The temperature dependence of activity of the iron-based catalyst is shown in FIG. 11 and of the vanadium based catalysts is shown in FIG. 12. EXAMPLE 8 Direct NOx

Fe-KAD catalysts were prepared by exchanging K-KAD with an aqueous solution of either iron nitrate and/or iron and cerium nitrates. In order to enhance the concentration of iron and/or cerium exchanged the solution was was purged with nitrogen to remove dissolved oxygen. Different iron-KAD catalysts as described in FIG. 13 were prepared by varying the pH between 2 and 4. Results of the use of such catalysts in the direct decomposition of NOx is shown in FIG. 13. EXAMPLE 9 Reduction of dioxins from exhaust gas streams

Introduction

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), often referred to collectively as "dioxins", can be formed downstream of a combustion chamber as the gases are cooled via a process known as De Novo synthesis. This occurs in the temperature range 250-400°C by reactions between the products of incomplete combustion in the presence of a chlorine donor. Certain materials can act as catalysts in these reformation reactions. However, current research suggests that some materials may also transform dioxins and other organic micro-pollutants into non-toxic byproducts.

Of particular interst are the NO_x reduction catalysts, which have been reported in the literature as having the potential to reduce the concentration of dioxins and related micro-pollutants.

To investigate the possibility of using KADs to reduce dioxins in a gas stream, a series of experiments were performed on a pilot-scale pathological waste incinerator fitted with a shell-and-tube heat exchanger and baghouse. Experimental Apparatus

The incinerator is of the two chamber design, consisting of a primary chamber for the combustion of solid waste and a secondary chamber/afterburner for the oxidation of combustible gases and particulate matter discharged from the primary chamber. The primary chamber is of a stationary hearth design utilizing a series of rams to slowly push the waste material through the incinerator for complete ash burn-down. The secondary chamber is capable of maintaining all emissions produced in the primary chamber at a temperature of 800- 900°C for a retention time of 0.3-0.5 seconds.

The primary chamber operates under reducing (starved air) conditions. By starving the process of air, the volatile components of the waste are gasified. The combustible gases produced behave as a fuel and are mixed with air and completely oxidized in the secondary chamber.

Natural gas is used as a supplementary fuel in both chambers.

Exhaust gases exiting the secondary chamber enter an air- cooled heat exchanger, dropping the gas temperature to 200°C. This was designed to maximise dioxin formation through the De Novo process. The gases then enter a baghosue, where they are filtered prior to discharge through a stack.

It was decided to incorporate a baghouse into the experimental design for two main reasons:-

(1 ) to simulate industrial conditions (most modern incineration plants utilizing best available technology are fitted with a baghouse); and

(2) Filtering the gas stream prior to KAD minimized the possibility of misleading results due to the filtering effects of the KAD. The incineration system is depicted in FIG. 14. During the trials, the incinerator was batch fed every 10 minutes with a specially prepared waste at an average feed rate of 10 kg/hr. This waste material consisting of 30% PVC, 60% shredded newspaper and 10% by water (by weight).

For catalytic experiments, testing was conducted at a gas outlet space velocity (gas flow rate (mls/hr)/volume of catalyst (mis)) of 60,000 hr¹.

A plug of the KAD material was inserted into the centre of a quartz tube, and held in place using quartz wool. For baseline experiments, the gas stream was directed through a parallel quartz tube containing only quartz wool. Both catalysis and baseline studies were conducted simultaneously.

The parallel quartz reactor tubes were held in an 860 mm long Lindberg furnace at a temperature of 450°C (± 20°C). The temperature was regulated with a Eurotherm controller. For each test, the system was pre- conditioned for 60 minutes prior to sampling. The samples were then collected over a 60-90 minute period. Test Methods Dioxins

Sampling for PCDDs and PCDFs was performed in accordance with USEPA Method 23 - "Determination of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans from stationary sources" using twin USEPA Modified Method 5 sampling trains. Each train consisted of the following components in series: nozzle, quartz probe, heated particulate filter, condenser, XAD-2 adsorbent module, impinger bank, diaphragm pump and gas meter.

By passing the quartz probe through the Lindberg furnace prior to the particulate filter, it was possible integrate the catalysis experimental apparatus into the sampling trains.

All train components in contact with the sample were thoroughly cleaned with purified solvents prior to use. The XAD-2 resin was spiked prior to sampling with isotopically labelled PCDD and PCDF surrogate standards. The filter, resin and impinger solutions were extracted with organic solvents and the extract purified by chemical treatment and solid phase chromatographic techniques. The method of extraction and purification is based on USEPA

Methods 3540 (soxhlet extraction of solid phase), 3545 (pressurized fluid extraction of solid phase), 3510 (liquid/liquid extraction of aqueous phase), 3620 (Florisil® column) and 3640 (gas phase chromatography).

Measurement of PCDDs and PCDFs was performed using high resolution gas chromatography and low resolution mass spectrometry in accordance with USEPA Method 8280. This method provides data on all toxic 2,3,7,8-chlorinated PCDDs and PCDFs as well as totals of non-2,3,7,8- chlorinated PCDDs and PCDFs for each homologue group (tetra to octa). The total toxic equivalent (l-TEQ) for each congener was calculated using NATO (international) toxic equivalency factors (l-TEFs). The sampling/experimental apparatus is depicted in FIG. 15.

Nitrogen oxides

Nitrogen oxides were monitored in accordance with Victorian EPA Standard Analytical Procedure B12 - "Total Nitrogen Oxides", using a Testo 350 series NO/N0₂/NOx analyzer. This was calibrated using NATA certified nitric oxide (NO) span gas, and zeroed with instrument grade nitrogen. Oxygen

Oxygen concentration was monitored in accordance with Victoria EPA Standard Analytical Procedure B10 - "Oxygen (Instrumental)", using a Testo 350 series analyzer. This was calibrated using ambient air, and zeroed with instrument grade nitrogen.

The estimated accuracy is ± 5%.

The dioxn and NOx results are summarized in Tables 12 and 13. The comprehensive dioxin results are given in Tables 14-27. While the above Examples refer specifically to the use of the alumino-silicate materials as catalysts in relation to NOx and dioxins, it is to be noted the alumino-silicate materials and their catalytic action on NOx and dioxins are exemplary of heterogeneous catalysis (as defined, for example, in Chemistry, Fifth Edition by Raymond Chang, published by McGraw-Hill Inc. in 1994). Such catalysis shows the use of a solid catalyst in a gaseous reaction system whereby an oxidation reaction occurs with dioxins and a reduction reaction occurs with NOx. In similar fashion, the alumino-silicate materials of the invention will catalyze SOx as described above, CO or CO₂ as described above and PAHs. In specific regard to PAHs, Example 9 may also apply to the use of the alumino-silicate materials of the invention to PAHs as similar conditions apply.

TABLES

TABLE 1 Comparison of desirable properties for catalyst materials

TABLE 2 Summary of generic preparation methods for cation- exchanged KAD material

TABLE 3 XPS data for copper-exchanged alumino-silicate derivatives

TABLE 4 Summary of XPS analyses for a range of catalyst materials

TABLE 5 Summary of XPS data for a range of catalyst samples

TABLE 6 Summary FTIR data for copper-exchanged KAD materials and Cu-ZSM5

TABLE 7 Summary of FTIR data for adsorbed nitro, nitrito and nitrate species on selected catalyst materials

TABLE 8 Field Trials of catalyst materials: NOx reduction from incinerator emissions

TABLE 9 Field Trials of catalyst materials: NOx reduction from diesel exhaust

TABLE 10 Preparation of catalysts

TABLE 11 Measurement of DeNOx activity

Particle size of catalyst; 10-20 mesh(0.84-1.68 mm)

Amount of catalyst taken; (0.3 ml)

Gas flow rate; (0.5/min)

Space Velocity (GHSV); 100,000 lr¹

Gas composition; NO = 200 ppm, NH₃ = 240 ppm, O₂ = 3%, C0₂

12%, H₂O = 12% TABLE 12 Summary of Dioxin Results

TABLE 13

TABLE 14 Dioxin Profile for Run 1 - Baseline Study

Dry gas volume sampled = 0.952 m³ @ 20°C, 101.3 kPa and 14.9% 0₂. Dry gas volume sampled = 0.538 Nm³ @ 0°C, 101.3 kPa and 11 % O₂

TABLE 15 Dioxin Profile for Run 1 - Trial with KAD 3

Dry gas volume sampled = 0.928 m³ @ 19°C, 101.3 kPa and 14.9% 0₂. Dry gas volume sampled = 0.526 Nm³ @ 0°C, 101.3 kPa and 11 % 0₂

C

TABLE 16 Dioxin Profile for Run 2 - Baseline Study

Dry gas volume sampled = 0.935 m³ @ 23°C, 101.3 kPa and 15.1% 0₂. Dry gas volume sampled = 0.505 Nm³ @ 0°C, 101.3 kPa and 11 % 0₂

σ

C

TABLE 17 Dioxin Profile for Run 2 - Ttrial with KAD 9

Dry gas volume sampled = 1.009 m³@ 23°C, 101.3kPaand 15.1% 0₂. Dry gas volume sampled = 0.545 Nm³ @ 0°C, 101.3 kPa and 11% 0₂

0

co o

TABLE 18 Dioxin Profile for Run 3 - Baseline Study

Dry gas volume sampled = 0.889 m³ @ 22°C, 101.3 kPa and 14.0% 0₂. Dry gas volume sampled = 0.573 Nm³ @ 0°C, 101.3 kPa and 11 % 0₂

TABLE 19 Dioxin Profile for Run 3 - Trial with KAD 14

Dry gas volume sampled = 1.109 m³ @ 24°C, 101.3 kPa and 14.0% O₂. Dry gas volume sampled = 0.710 Nm³ @ 0°C, 101.3 kPa and 11 % O₂

TABLE 20 Dioxin Profile for Run 4 - Baseline Study

Dry gas volume sampled = 0.844 m³ @ 24°C, 101.3 kPa and 13.8% 0₂. Dry gas volume sampled = 0.556 Nm³ @ 0°C, 101.3 kPa and 11% 0₂

TABLE 21 Dioxin Profile for Run 4 - Trial with KAD 19

Dry gas volume sampled = 0.877 m³ @ 24°C, 101.3 kPa and 13.8% 0₂. Dry gas volume sampled = 0.578 Nm³ @ 0°C, 101.3 kPa and 11 % 0₂

*

TABLE 22 Dioxin Profile for Run 5 - Baseline Study

Dry gas volume sampled = 0.913 m³ @ 21 °C, 101.3 kPa and 14.9% 0₂. Dry gas volume sampled = 0.514 Nm³ @ 0°C, 101.3 kPa and 11 % 0₂

C

V

TABLE 23 Dioxin Profile for Run 5 - Trial with KAD 23

Dry gas volume sampled = 0.968 m³ @ 21 °C, 101.3 kPa and 14.9% 0₂. Dry gas volume sampled = 0.545 Nm³ @ 0°C, 101.3 kPa and 11 % O₂

n o

cπ

TABLE 24 Dioxin Profile for Run 6 - Baseline Study

Dry gas volume sampled = 0.965 m³ @ 21 °C, 101.3 kPa and 14.7% O₂. Dry gas volume sampled = 0.561 Nm³ @ 0°C, 101.3 kPa and 11% O₂

c r

O

TABLE 25 Dioxin Profile for Run 6 - Trial with KAD 25

Dry gas volume sampled = 0.875 m³ @ 21 °C, 101.3 kPa and 14.7% 0₂ Dry gas volume sampled = 0.509 Nm³ @ 0°C, 101.3 kPa and 11 % O₂

c

L L

TABLE 26 Dioxin Profile for Run 7 - Baseline Study

Dry gas volume sampled = 0.951 m³ @ 25°C, 101.3 kPa and 13.8% O₂. Dry gas volume sampled = 0.625 Nm³ @ 0°C, 101.3 kPa and 11% O₂

L

L

TABLE 27 Dioxin Profile for Run 7 - Trial with KAD K

Dry gas volume sampled = 0.943 m³ @ 25°C, 101.3 kPa and 13.8% 0₂. Dry gas volume sampled = 0.620 Nm³ @ 0°C, 101.3 kPa and 11% 0₂

L o

LΠ vo

LEGENDS TABLE 12

Sm³ = gas volume in dry cubic metres at 0°C, 101.3 kPa and 11 % 0₂.

TABLE 13 Nm³= gas volume in dry cubic metres at 0°C, 101.3 kPa and 7% 0₂.

TABLES 14-27 ng = nanograms (10^"9 grams)

Sm³ = Gas volume in dry cubic metres at 0°C, 101.3 kPa and 11 % O₂ l-TEF = International toxic equivalency factor l-TEQ = International toxic equivalent based on the 2,3,7,8-TCDD congener

FIG. 1

Combined micro-analysis/vibrational spectroscopic facility.

FIG. 2 Comparison of NO_x Decomposition on (a) Cu-ZSM5 (squares) and (b) Cu-

KAD3-1 (circles).

FIG. 3

FTIR spectra obtained after exposure of NO_x (1300 ppm)O₂ (1.7%) to (a) Cu-

ZSM5 and (b) Cu-KAD3-5. FIG. 4

FTIR spectra of adsorbates produced after NO_x (1300 ppm)/0₂ (1.7%) to (a)

CoKAD3-1 , (b) CoKAD3-5, (c) CoKAD3-7, (d) CoKAD¹/₂-13, (e) CoKAD5-16 and (f) Co-ZSM5 (Si/AI ratio 40:1 ).

FIG. 5 Schematic of incinerator configuration and sampling points for gases.

FIG. 6

Schematic of experimental set-up for field trials.

FIG. 7

NOx conversion from a diesel exhaust as a function of propene ignited. FIG. 8

Lifetime study of catalyst efficiency during diesel engine operation. FIG. 9

Catalyst Performance with diesel injected into line. NOx conversion from diesel exhaust, with and without diesel fuel addition.

FIG. 10 Micro-reactor system employed for de NOx studies.

FIG. 11

NOx reduction with NH₃ using iron-based catalysts.

FIG. 12

NOx reduction with NH₃ using Vanadium-based catalysts. FIG. 13

Direct decomposition of NOx.

FIG. 14

Pilot scale incineration system.

FIG. 15 Sampling/experimental apparatus comprising USEPA MM5 sampling train with integrated catalyst reactor.

Claims

1. A process for catalytic conversion and/or adsorption of gases inclusive of NOx, SOx, CO₂, CO, dioxins and PAHs and combinations thereof wherein said gases may contain particulates which include contacting one or more of such gases with an alumino-silicate material having:-

(i) a primarily tetrahedrally co-ordinated aluminium as established by the fact that the ²⁷AI Magic Angle

Spinning (MAS) provides a single peak at 55-58 ppm

(FWHM = ~ 23 ppm) relative to AI(H₂O)₆ ³⁺; and (ii) a cation exchange capacity of at least 1 meq 100g^"1 in aqueous solution at room temperature.

2. A process as claimed in Claim 1 for reduction of NOx in the presence of organic reductant(s) at a temperature of 200-650°C wherein NOx is adsorped by the alumino-silicate material. 3. A process as claimed in Claim 2 wherein said organic reductant(s) is selected from hydrocarbons inclusive of alkanes, alkenes and aromatics.

4. A process as claimed in Claim 2 wherein said organic reductant(s) is selected from alcohols and aldehydes. 5. A process as claimed in Claim 2 wherein the organic reductant(s) are selected from alkenes or alcohols.

6. A process as claimed in Claim 1 wherein for reduction of NOx in the presence of nitrogen containing reductant(s) inclusive of urea or ammonia at a temperature of 200-650°C. 7. A process as claimed in Claim 6 wherein the nitrogen containing reductant is urea at a temperature of 350-500°C.

8. A process as claimed in Claim 6 wherein the nitrogen containing reductant is ammonia at a temperature of 200-650°C.

9. A process as claimed in Claim 1 wherein NOx is directly decomposed to nitrogen at a temperature of 200-850°C in the presence of the alumino-silicate material containing Fe, Cu or Ag.

10. A process as claimed in Claim 1 wherein the C0₂ in the presence of the alumino-silicate material doped with a basic metal oxide or transition metal oxide is adsorbed by the alumino-silicate material.

11. A process as claimed in Claim 10 wherein the basic oxide is CaO or MgO.

12. A process as claimed in Claim 10 wherein the transition metal oxide is selected from CuO, ZnO or iron oxides.

13. A process as claimed in Claim 1 used for the oxidation of CO to C0₂ wherein the alumino-silicate material contains Pt, Pd, Ag, Cu, Co, Mn or Cr at a temperature of 150-650°C.

14. A process as claimed in Claim 1 used for the reduction of S0₂ to sulphur wherein SO₂ is adsorped by the alumino-silicate material containing basic metal oxides inclusive of MgO or CaO or transition metal oxides inclusive of CuO, ZnO or iron oxides at a temperature of 0-500°C. 15. A process as claimed in Claim 14 wherein the temperature is between room temperature and 150°C.

16. A process as claimed in Claim 1 used for the oxidation of SO₂ to SO₃ wherein the alumino-silicate material contains Pt, Pd, Ag, Cu, Co, Mn or Cr at a temperature of 150-650°C. 17. A process as claimed in Claim 1 used for conversion of dioxins to carbon dioxide, water and hydrogen chloride wherein the dioxins are adsorbed by the alumino-silicate material at a temperature of 150-650°C.

18. A process as claimed in Claim 17 used for conversion of PAHs wherein the PAHs are catalyzed by the alumino-silicate material at a temperature of 150-650°C.

19. A process as claimed in any preceding claim wherein the gases are passed through a plug of the alumino-silicate material in a conduit.

20. A process as claimed in Claim 19 wherein the alumino-silicate materials have a CEC of above 100 meq 100 g^"1. 21. A process as claimed in Claim 20 wherein the alumino-silicate materials have a CEC of between 160-900 meq 100 g^"1.

22. A process as claimed in Claim 21 wherein the CEC is 350-450 meq 100 g^"1.

23. A process as claimed in Claim 19 wherein the alumino-silicate material has an exchangeable cation which is ammonium ion or alkali metal cation which is partly or fully exchanged by one of the following alkaline earths Mg²⁺, Ca²⁺, Sr^2* and Ba²⁺, the transition metals Cr³", Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Ag⁺, the heavy metals Pb²⁺, Cd²⁺, Hg^2*; the lanthanides- La³⁺ and Nd³⁺ or the actinide UO₂ ²⁺.

24. A process as claimed in Claim 19 wherein the alumino-silicate materials are amorphous not showing any substantial long range structural ordering and having a broad hump between 14° and 40° 2Θ for CuKα radiation.

25. A process as claimed in Claim 24 wherein such amorphous materials are prepared by reaction of a starting alumino-silicate with MOH and/or MX where M is alkali metal and X is halide.

26. A process as claimed in Claim 19 wherein the alumino-silicate materials are amorphous or poorly or partly crystalline alumino-silicates having a stuffed silica polymorph-related structure which is produced by reacting a starting alumino-silicate or a combination of aluminium oxide containing and silicon oxide containing compounds with an alkali oxide or alkali hydroxide containing reagent.

27. A process as claimed in Claim 19 wherein the alumino-silicate materials include modified kaolins which are prepared from a kaolin group mineral which includes expansion and contraction of layers of the kaolin group mineral wherein these layers comprise one Si-tetrahedral sheet and one Al-octahedral sheet.

28. A process as claimed in Claim 19 wherein the Si/AI ratio of the alumino-silicate materials is within the ratio 1.0-1.5.

29. A process as claimed in Claim 19 wherein the conduit comprises two or more spaced plugs of alumino-silicate material.