METHOD FOR THE SYNTHESIS OF ZSM-5 ZEOLITE, AT ATMOSPHERIC PRESSURE AND AT LOW TEMPERATURE

Abstract: Method for the synthesis of ZSM-5 zeolites at atmos­ pheric pressure, at a temperature preferably from 60 to 100°C wherein: a) an aqueous solution containing a quaternary ammonium compound (QA) is added to a second aqueous solution, containing a Si compound, a Na compound and a potassium halogenide (K Hal.), according to the molar ratios: -Na₂O/SiO₂ ≧0.20 (preferably from 0.25 to 2); -H₂O/SiO₂ = from 5 to 100 (preferably from 10 to 50): -K Hal/SiO₂ = from 0.03 to 0.50; b) a third aqueous solution, containing A1 sulphate, is added to the mixture obtained according to a); c) to the mixture obtained according to b) an aqueous solution of H₂SO₄ is added; wherein the molar ratio Y = (QA/SiO₂) is from 0.02 to 0.08 and the molar ratio Z = SiO₂/A1₂O₃ is fron 25 to 210, said Y ratio and the molar ratio X = OH⁻/SiO₂ being represented by points lying within triangles limited by the following 3 straight lines: A) Y = 0.7 X; B) X = K/Z, wherein K = 4 (K being constant); C) Y = - 2/3 X + 1 - H, wherein the constant H is obtained from the expression: H = 1/2 (45/Z)⁰˙³¹⁷.

Description: The invention concerns a method for the synthesis of ZSM-5 zeolite, at atmospheric pressure and at low temperatures. Many patents (e.g. U.S. patent 3,702,886) deal with the synthesis of ZSM-5 zeolite, well known catalyst for a lot of reactions (e.g. m-xylene isomerization, toluene disproportionating, ethylbenzene synthesis and so on); U.S. patent 4,117,026 teaches, in particular, that a ZSM-5 zeolite, having a relatively large size (average size 0.5/+m and preferably from 1 to 6 t m), can be very useful in disproportionating toluene to benzene and para-xylene. The same U.S. patent (4,117,026) states however that when relatively low temperatures are used, during the zeolite preparation (e.g. 220 F,namely 1040C), said average size is rather low (o.03/'). We have now surprisingly noted that certain particular and original combinations of the operative conditions allow to obtain, in a very easy and simple way(at atmospheric pressure and within a short time) the same ZSM-5 zeolite that was synthesized, until now, only at high temperatures (and therefore at pressures higher than the atmospheric), or within very long times (in the case of a process at atmospheric pressure) or at the price of a too small size. The method, according to the invention, for the synthesis of ZSM-5 zeolites at atmospheric pressure and at temperatures preferably from 60 to 100 C, comprises the following steps: a) an aqueous solution containing a quaternary ammonium compound (QA) - e.g. tetrapropylammonium bromide [(TPA)Br] - - is added to a second aqueous solution, containing a Si compound, a Na compound, and a potassium halogenide (KHal) according to the following molar ratios: - Na O/SiO + 0.20 (preferably from 0.25 to 2); 2 2 -H20/SiO2 = from 5 to 100 (preferably from 10 to 50); - K(Hal)/SiO2 = from 0.03 to 0.50; b) a third aqueous solution, containing Al sulphate, is added to the mixture obtained according to a); c) to the mixture obtained according to b) an aqueous so lution of H SO is added; 24 wherein the molar ratio Y = (QA/SiO ) is from 0.02 to 2 0.08 and the molar ratio Z = SiO2/Al 203 is from 25 to 210, said Y ratio and the molar ratio X = OH-/SiO2 being represented by points lying within triangles limites by the following 3 straight lines: A) Y = 0.7 X; B) X = K/Z, wherein K = 4 (K being constant); C) Y = - 2/3 X + 1 - H, wherein H, constant with respect to X and Y, is obtained from the expression: H = 1/2 (45/Z) 0.317. Said (QA) quaternary compound can be replaced by an admixture of (QA) itself with an amine, according to the teachings of European patent 101183. Figure 1 is representing graphically the dritical triangles hereinabove, what is one of the features of the invention, and figure 2 is representing a narrower area, corresponding to the very gist of the invention. All the SiO2 (100%) is converted i-nto crystalline product and large outputs are possible because of the very simple apparatuses required by the synthesis; a further advantage resides in the long life of our zeolites (without re-generation), especially when exploited for disproportionating toluene or for converting methanol into propylene. The areas of figure 1 strongly decrease( ) with the decrease of the SiO2/Al2O3 ratio. The chances therefore, to obtain a ZSM-5 zeolite at atmospheric pressure, when said ratio is nearby the lowermost limits of Z, are very few and contained within well determined and very narrow boundaries. Our invention comprises obviously all those equivalent variants that donut misrepresent the gist of the invention itself; the Al sulphate e.g. can be replaced by equivalent amounts of another salt (for instance nitrate) and H2SO4 can be replaced by equivalent amounts of another acid supplier of H3O+ ions, e.g. HNO3 or H PO . The calculation of the OH ions depends on the 34 selected salt and acid; if the salt is Al sulphate and the acid H2SO4, the formula is (by moles): x = (OH)/SiO = 2Na20/SiO2 - 2/Z-2H2S04/SiO2. 2 4 During the addition of the Al3+ ions, generally in the form of sulphate or nitrate, the extension of the flocculation depends on the amount of added Al. Then, also the acid (e.g. H SO ) is added, in such an amount to get 24 a more or less thick gel; best results are reached if ** the amounts of acid decrease ( ) when the amounts of Al are increasing. The crystallization time (preferably un * approximately with exponential trend. ** within the boundaries of the figure 1 triangles. der agitation) is 3 days, according to the examples, but it is possible to reach rather good results also within shorter times. The zeolites obtained according to the invention can be used (as such or in a modified form) in admixture with suitable amounts of oxides as binders, e.g. SiO2 or A1203; a list of many other binders can be retrieved e.g. in European patent publication 36707. The regenera tion of the catalyst can be carried out in air for some hours, at 300-600 C; a steam regeneration is described in European patent publication 36704 and according to a still further method the catalyst can be regenerated by a hydrogen treatment. As to the initial activation of a zeolitic catalyst, some methods are described in Euro pean patent publications 34444 and 35830; in general it is advisable to activate the catalyst for some hours in air, at 450-7500C (preferably 540-7000C). Furthermore some conversion (e.g. methanol to propylenei exerts a stimulating activation on the zeolitic catalyst; in other words catalyst and reaction are affected each other by a mutual, reciprocal and beneficial activating action. The acid form of the zeolites (H-ZSM-5) can be very advantageously obtained when the raw product of the zeolitic synthesis is dried (e.g. at 1200C), calcined (e.g. at 540 C in air for some hours), as to remove any residual organic compound, and then exchanged with a solution containing HC1 or NH4N03; in the second case (NH4NO3) the final acid form is obtained by means of a heat-treatment, e.g. at 4000C. Other methods for the ion exchange of the zeolites are described, for instance, in U.S. patents 3,140,249; 3,140,251; 3,140,253 and in European patent publications 68,754 and 40,276. After the removal of the organic base and the conversion into the acid form, the zeolites according to the invention are endowed with a long life and a very high catalytic activity towards many reactions, in particular toluene disproportionating, benzene alkylation and aromatization of olefines; they are furthermore extraordinarily active in the conversion of methanol into any kind of hydrocarbons and particularly into olefinic and aromatic hydrocarbons, especially low molecular weight olefins. The following examples illustrate the invention without limiting, however, in any way the scope thereof. EXAMPLE I 22.80 g of granules of SiO2 (granulated silicagel from the CARLO ERBA Company) and 10.45 g of KF.2H20 were pon- red into a solution of 9.00 g of NaOH (989) in 200 cm3 of deionized water and the resulting suspension was kept at 1000C under stirring, until obtaining a clear solution, without any solid matter; after cooling down to room temperature, 37.19 g of (TPA) Br, dissolved in 150 cm3 of deionized H20, and 2.53 g of Al2 (SO ) .18H20, 4 3 dissolved in 100 cm3 of deionized H20, were added in this order. The thus obtained gel was heated at 800C and 3 drop by drop 3.00 cm of H SO (96% b.w.; density = 3 24 1.835 g/cm ) were added under gentle stirring; the composition of the mixture was (by moles): Na2O/SiO2 = 0.290; Z = SiO2/Al2O3 = 100; Y = (TAP)/SiO2 = 0.368; H2O/SiO2 = 65.80; X = OH /SiO = 0.216; KF/SiO2 = 0.292. 2 2 Tire mixture was transferred into a polytetrafluoroethy Jene flask, supplied with cooler, stirrer and thermomf- ter, and kept at 1000C for 3 days under gentle stirring and reflux; the product was filtered, repeatedly washed with deionized H20, until obtaining a neutral washing liquid (litmus paper) and dried at 1200 for 16 hours. The solid yield was 100% and the X ray analysis stated that the product was a ZSM-5 zeolite having a cristallinity degree of 100% (see Table 1); the composition of the product is on Table 1, together with the operative conditions. EXAMPLES 2 AND 3 Example 1 was repeated while using greater amounts of H2SO4 (respectively 4.00 and 4.50 cm ), whereby the 24 OH-/SiO2 ratio on Table 1 was modified. The results of examples 1-3 were similar. EXAMPLE 4 Example 1 was repeated, while lowering the amount of 3 H2SO4 to 0.76 cm , whereby the value of the OH-/SiO2 ra- tio was 0.428, thus obtaining very poor results, as can be deduced from Table 1. EXAMPLE 5 Example 1 was repeated while bringing the H2SO4 amount up to 5.90 cm ; worse results were obtained, as shown on Table 1. EXAMPLE 6 Example 1 was repeated, while modifying the amount of Al sulphate (0.60 g) and also the amount of H2SO4 (4.65 - 8 cm ); data and results are on Table 1. EXAMPLE 7 Example 1 was repeated while increasing the amount of Al sulphate to 5.06 g and decreasing the H SO amount down 3 24 to 3.15 cm ; data and results are on Table 1. EXAMPLES 8 and 9 Example 7 was repeated, while letting the amount of Al sulphate unchanged, but adding respectively 2.00 and 3 3.65 cm of H2SO4; data and results are on Table 1. EXAMPLE 10 Example 2 was repeated while lowering practically to 50% the original amount of (TPA)Br, namely to 18.60 g; data and satisfactory results are on Table 2. EXAMPLE 11 Example 10 was repeated while adding 4.50 cm3 of H2S04; data and results are on Table 2. EXAMPLE 12 Example 10 was repeated while doubling the amunts of SiO2, NaOH, (TPA)Br, Al sulphate, potassium fluoride and H SO and letting the amount of H2 0 unchanged (reduction 24 of the dilution level); data and good results are on Table 2. EXAMPLE 13 Example 12 was repeated, while adding 9.00 cm3 of H2SOd; data and results are on Table 2. EXAMPLE 14 Example 11 was repeated, while lowering down to 7.68 g the amount of (TPA)Br; data and results are on Table 2. The size average of the crystallites was 1.5'm (micrometers). EXAMPLE 15 Example 2 was repeated, while replacing the Al-sulphate by 2.85 g of the corresponding nitrate [Al(NO )3.9H2O] and replacing H2SO4 by 9.90 cm of 65% HNO3 (density 1.400 g/cm ); data and good results are on Table 2. EXAMPLE 16 A solution of Na metasilicate, prepared by dissolving 3 31.02 g of NaOH into 200 cm of deionized H20 and by adding 22.80 g of SiO2 and 10.45 g of KF.2H2O, was kept at 1000C until obtaining a clear solution, without any solid matter more; after cooling down to room temperature, 18.60 g of (TPA)Br, dissolved in 150 cm3 of deionized H2O, and 2.53 g of Al2(SO4)3.18H2O, dissolved in 100 cm of deionized H20, were added in this order. The gel thus obtained was heated at 800C and 18.98 g of H SO were 24 added, drop by drop, under gentle stirring; the synthesis steps followed then just as in Example 1. Data and results are on Table 2. EXAMPLE 17 (Comparative) 20.27 g of SiO2 granules were added to a solution of 3 8.00 g of NaOH in 200 cm of deionized H20 and the resulting suspension was kept at 1000C under stirring, until obtaining a clear solution, without any solid particle more; after cooling down to room temperature, 33.06 3 g of (TPA)Br, dissolved in 100 cm of deionized H20, and 2.53 g of Al2(SO4)3.18H2O, dissolved in 100 cm of deionized H2O (96%; density = 1.835 g/cm ) were added under gentle stirring; the composition of the mixture was (by moles): Na2O/SiO2 = 0.290; Z = SiO2/Al2O3 = 100; Y = 0.368; II O/SiO = 65.80; X = 0.216. 2 2 The mixture was transferred into a polytetrafluoroethy lene flask and kept at 1500C for 3 days under autogenous pressure; the product was then treated as in example 1. Data and results are on Table 2, where from it is possible to see that, after 3 days, the amount of solid (com pletely in crystalline form) is merely 75% of the theoretical amount; a further test, for a longer time, has shown that the 100% solid (crystalline) yield is reached only if the heating (at 1500C and without KF) is extended for a period of 5 days. EXAMPLE 18 (Exploitation of the zeolitic catalyst) A sample of H-ZSM5, prepared according to example 1, was calcined in air at 5400C for 16 h; 20 g of the calcined 3 product were suspended in 400 cm of a 0.5 M solution of NO NO and kept at 800C for 2 h under gentle stirring 43 Such treatment was identically repeated 5 times; even tally the product was filtered, washed until negative nitrate test (brucine test) and dried for 16 h at 1200C. The resulting NH -ZSM5 was decomposed, while obtaining 4 thereby H-ZSM5, by means of a calcination in à nitrogen stream, at 5400C for 16 h; 10 g of such H-ZSM5 were ad 3 mixed with 14 cm of a silica sol (commercially known as "Ketyensol AKZO", containing 40% b.w. SiO2), dried for 16 h at 120 C, then granulated and finally calcined for 16 h at 540 C. Thereafter 1.000 g of the fraction between 35 and 50 (Tyler) mesh were loaded into a titanium ("plug flow") microreactor (360 mm long; @ = 8 mm) and tested for the methanol conversion; operative conditions and product distribution are on Tables 3 and 4. EXAMPLE 19 In order to ascertain if it is possible to work with m()- re concentrated solutions, example 14 was repeated quadruplicating the amount of SiO2, NaOH, (TPA)Br, potassium fluoride and Al sulphate, while adding 18.50 cm3 of H SO and keeping practically unaltered the water volu 24 me. Data and results are recorded on Table 5. EXAMPLE 20 Example 19 was repeated reducing to 50% the amount of (TPA)Br (15.38 g). Data and results are recorded on Table 5. EXAMPLE 21 In order to ascertain if it is possible to deal with greater volumes (and outputs), example 20 was repeated multiplying by 8 all the amounts of the reactants provided for by said example 20. Data and results are recorded on Table 5. TABLE 1 EMI12.1 EXAMPLE <SEP> 1 <SEP> 2 <SEP> 3 <SEP> 4(a) <SEP> 5(a) <SEP> 6 <SEP> 7 <SEP> 8(a) <SEP> 9(a) <tb> Reaction <SEP> mixture <tb> Na2O/SiO2 <SEP> (molar) <SEP> 0.290 <SEP> see <SEP> ex. <SEP> 1 <SEP> see <SEP> ex.1 <SEP> see <SEP> ex.1 <SEP> see <SEP> ex.1 <SEP> see <SEP> ex.1 <SEP> see <SEP> ex.1 <SEP> see <SEP> ex.7 <SEP> see <SEP> ex.7 <tb> SiO2/Al2O3 <SEP> " <SEP> 100 <SEP> " <SEP> " <SEP> " <SEP> " <SEP> 211 <SEP> 50 <SEP> " <SEP> " <tb> (TPA)/SiO2 <SEP> (*) <SEP> " <SEP> 0.368 <SEP> " <SEP> " <SEP> " <SEP> " <SEP> see <SEP> ex.1 <SEP> see <SEP> ex.1 <SEP> " <SEP> " <tb> H2O/SiO2 <SEP> " <SEP> 65.800 <SEP> " <SEP> " <SEP> " <SEP> " <SEP> " <SEP> " <SEP> " <SEP> " <tb> KF/SiO2 <SEP> " <SEP> 0.292 <SEP> " <SEP> " <SEP> " <SEP> " <SEP> " <SEP> " <SEP> " <SEP> " <tb> H2SO4 <SEP> (cm ) <SEP> 3.00 <SEP> 4.00 <SEP> 4.50 <SEP> 0.76 <SEP> 5.90 <SEP> 4.65 <SEP> 3.15 <SEP> 2.00 <SEP> 3.65 <tb> OH-/SiO2 <SEP> (molar) <SEP> 0.216 <SEP> 0.122 <SEP> 0.074 <SEP> 0:428 <SEP> 0.058(d) <SEP> 0.121 <SEP> 0.122 <SEP> 0.231 <SEP> 0.075 <tb> End <SEP> product <tb> Solid <SEP> yield <SEP> 100% <SEP> 100% <SEP> 100% <SEP> 23% <SEP> 84% <SEP> 100% <SEP> 100% <SEP> 70% <SEP> 90% <tb> <SEP> % <SEP> ZSM-5 <SEP> phase <SEP> (c) <SEP> 100% <SEP> 100% <SEP> 100% <SEP> 10%(b) <SEP> 0% <SEP> 100% <SEP> 100% <SEP> 30%(b) <SEP> 65%(b) <tb> (a) comparative; (b) + amorphous; (c) with respect to the solid; (d) the minus sign has no physical meaning but comes merely from the particular kind of calculation; (*) moles of (TPA)Br per mole of SiO2. TABLE 2 EMI13.1 EXAMPLE <SEP> 10 <SEP> 11 <SEP> 12 <SEP> 13 <SEP> 14 <SEP> 15 <SEP> 16 <SEP> 17 <SEP> (d) <tb> Na2O/SiO2 <SEP> (molar) <SEP> see <SEP> ex.2 <SEP> see <SEP> ex.10 <SEP> see <SEP> ex.10 <SEP> see <SEP> ex.12 <SEP> see <SEP> ex.11 <SEP> 0.290 <SEP> 1.00 <SEP> 0.290 <tb> SiO2/Al2O3 <SEP> " <SEP> " <SEP> " <SEP> " <SEP> " <SEP> 100 <SEP> 100 <SEP> 100 <SEP> 100 <tb> (TPA)/SiO2 <SEP> (*) <SEP> " <SEP> 0.184 <SEP> " <SEP> " <SEP> " <SEP> 0.076 <SEP> 0.368 <SEP> 0.184 <SEP> 0.368 <tb> H2O/SiO2 <SEP> " <SEP> see <SEP> ex. <SEP> 2 <SEP> see <SEP> ex. <SEP> 10 <SEP> 32,900 <SEP> " <SEP> 65.800 <SEP> 65.899 <SEP> 65.800 <SEP> 65.800 <tb> KF/SiO2 <SEP> " <SEP> " <SEP> " <SEP> 0.292 <SEP> " <SEP> 0.292 <SEP> 0.292 <SEP> 0.292 <SEP> H2SO4 <SEP> (cm ) <SEP> - <SEP> - <SEP> - <SEP> - <SEP> - <SEP> 9.90 <SEP> - <SEP> OH-/SiO2 <SEP> (molar) <SEP> 0.122 <SEP> 0.074 <SEP> 0.122 <SEP> 0.074 <SEP> 0.074 <SEP> 0.124 <SEP> 0.124 <SEP> 0.216 <tb> End <SEP> product <tb> Solid <SEP> yield <SEP> 100% <SEP> 100% <SEP> 100% <SEP> 100% <SEP> 100% <SEP> 100% <SEP> 100% <SEP> 75% <tb> ZSM-5 <SEP> phase <SEP> (c) <SEP> 100% <SEP> 100% <SEP> 100% <SEP> 100% <SEP> 100% <SEP> 100% <SEP> 100% <SEP> 100% <tb> (a) comparative; (b) + amorphous; (c) with respect to the solid; (d) T = 150 C, t = 3 days (in autocalve, under autogenous pressure); (*) moles of (TPA)Br per mole of SiO2. TABLE 3 OPEKATIVE CONDITIONS AND PRODllCT DISTRIBUTION Products % b.w. (-*) Temperature: 400 C DME (**): LHSV (*): 2 h-1 C2H4: 4.9 CH3OH conversion: 95% C3H6: 39.2 Time of the run: 50 h liquid fraction (hydrocarbons): 55.9 TABLE 4 DISTRIBUTION OF THE PRODUCTS WITHIN THE LIQUID (HYDRO CARBONS) FRACTION (AT 250C) % b.w. PM (average mole cular weight) C 3.7 70 5 C6 38.5 84 C7 12.0 98 C8 8.8 112 C9 19.5 126 C10 13.5 140 C11 3.2 156 (*) liters/h of liquid feed per liter of (bound) zeo lite; (**) dimethyl-ether; (***) the calculation doesn't take H2O into account. TABLE 5 EMI15.1 <tb> <SEP> EXAMPLES <SEP> 19 <SEP> 20 <SEP> 21(***) <tb> Reaction <SEP> mixture <tb> Na2O/SiO2 <SEP> (molar) <SEP> see <SEP> ex.14 <SEP> see <SEP> ex.19 <SEP> see <SEP> ex.20 <tb> SiO2/Al2O3 <SEP> " <SEP> 100 <SEP> 100 <SEP> " <tb> <SEP> (TPA)/SiO2 <SEP> " <SEP> (*) <SEP> 0.076 <SEP> 0.038 <SEP> n <tb> H2O/SiO2 <SEP> " <SEP> 16.400 <SEP> s.ex.14 <SEP> " <tb> KF/SiO2 <SEP> " <SEP> - <SEP> - <SEP> " <tb> H2SO4 <SEP> (cm ) <SEP> 18.50 <SEP> s.ex.14 <SEP> " <SEP> <tb> <SEP> OH <SEP> /SiO2 <SEP> (molar) <SEP> 0.062 <SEP> <SEP> 11 <SEP> fl <SEP> <tb> <SEP> 2 <SEP> <tb> <SEP> data <SEP> survey <SEP> after <SEP> 3 <SEP> days <SEP> 3 <SEP> days <SEP> 3 <SEP> days <tb> <SEP> End <SEP> product: : <tb> <SEP> Solid <SEP> yield <SEP> 100% <SEP> 100% <SEP> 100% <tb> <SEP> % <SEP> ZSM-5 <SEP> phase <SEP> (**) <SEP> | <SEP> 100% <SEP> | <SEP> > 90% <SEP> | <SEP> 100% <tb> (*) moles of (TPA)Br per mole of SiO2. (**) with respect to the solid. (*-:'-*) greater amount of reactants (8 times with respect to example 20).

Claims: CLAIMS 1. A method for the synthesis of ZSM-5 zeolites at at mospheric pressure, at a temperature preferably from 60 to 1000C, wherein: a) an aqueous solution containing a quaternary am monium compound (QA) is added to a second aque ous solution, containing a Si compound, a Na compound and a potassium halogenide (KHal.), ac cording to the molar ratios: : - Na2O/SiO2 # 0.20 (preferably from 0.25 to 2); - H O/SiO = from 5 to 100 (preferably from 10 2 2 to 50); - K Hal/SiO2 = from 0.03 to 0.50; b) a third aqueous solution, containing Al sulpha te, is added to the mixture obtained according to a); c) to the mixture obtained according to b) an aque ous solution of HsSO4 is added; and wherein the molar ratio Y = (QA/SiO2) is from 2 0.02 to o.o8 and the molar ratio Z = SiO2/A1203 is from 25 to 210, said Y ratio and the molar ratio X = OH /SiO being represented by points lying within 2 triangles limited by the following 3 straight li nes: A) Y = 0.7 X; B) X = K/Z, wherein K = 4 (K being constant); C) Y = -2/3 X + 1 - H, wherein the constant H is obtained from the equation: H = 1/2 (45/Z) 0.317. 2. A method according to claim 1, wherein the global diluition, namely the "total H O"/SiO molar ratio, 2 2 is from 7 to 120 (preferably from 15 to 80). 3. A method according to claim 1, wherein the Al sul phate is replaced by an equivalent amount of ano ther Al compound (e.g. nitrate) and H SO is repla 24 ced by an equivalent amount of a monoprotic acid (e.g. HNO3) or of a polyprotic acid (e.g. H3P04). 4. A method according to claim 1, wherein said potas sium halogenide is selected from the group compri sing potassium chloride and potassium fluoride. 5. Use of the zeolites, obtained according to claims from 1 to 4, for an acid-catalyzed reaction, in particular for the xylenes isomerization, the to luene disproportioning and the benzene alkylation. 6. Use of the zeolites, obtained to claim from 1 to 4, for the methanol conversion to light olefines and in particular to propylene.

Inventors: GHERARDI, PAOLA, GUBITOSA, GIUSEPPE
Applicants: MONTEDISON S.P.A.
Application year: 1984
Main classification: C01B33
IPC codes: C07C6, C01B39, C07C5, C07C1, B01J29, C07C2