Catalyst for preparing fluoroethylene and 1,2difluoroethane, and preparation method
Technical Field The invention relates to a chemical catalyst and method for preparing the same, particularly relates to a method for producing ethylene and 1, 1-difluoroethane and method for preparing the catalyst. Background Art Vinyl is an important (VF) a fluorine-containing monomer, can be used for the production of polyvinyl fluoride (PVF), and fluorine-containing fine chemicals. PVF is an important one of the decorative material, the heat resistance of the invention has a prominent; low temperature resistant performance; moisture-proof heat, wash resistant, anti-salt fog performance, in addition its coating film having very good flexibility and a compound of the, wear-resistant, anti-impact properties. Various oils in the PVF, alcohols, aldehydes, ketones, esters and salts, alkali, dilute acid and other chemical pesticide products have excellent anti-corrosion performance. The PVF superior performance, can be widely applied to a solar energy, electronic, outdoor advertising, decorative internal-external wall of the building, such as aircraft interior decoration of the train. Various fluorine-containing fine chemicals, wide application, the added value is high. fluorine medicine and intermediates thereof, and intermediate fluorine agricultural chemicals , fluorine-containing surface active agent, fluorine-containing textile finishing agent, fire-extinguishing agent, chromium fog inhibitors, anti-static agent, leather treatment, release agent, lubricant, anti-rust agent, etc., belong to the fluorine-containing fine chemicals. 1, 1-difluoroethane (HFC-152a) is an important fluorine-containing organic compound, is plastic pvdf intermediate prepares, is also the current in the two carbon substitute Freon of outstanding variety. At present, to acetylene method for synthesizing VF and HFC-152a the catalyst used is mainly composed of a mercury-containing compound, a compound of cadmium, chromium-containing compound, cuprous cyanide, emissions of the composite catalyst with the metal chloride, and zinc-containing compound such as aluminum-containing compound. United States Patent US2892000 discloses name to: AND1 VINYL FLUORIDE OF MANUFACTURE, 1-DIFLUOROETHANE (vinyl and 1, 1-difluoroethane production) patented technology, the technology utilizes acetylene and hydrogen fluoride reaction, synthetic VF and HFC-152a, the catalyst is chromium compound (chromium oxide or chromium salt), however, the relatively low activity of the catalyst, in the 300 when [...] the conversion rate is only 50%, and this kind of catalyst of toxic, causing greatly to the pollution of the environment. United States Patent US2519199 discloses name to: VINYL FLUORIDES OF SYNTHESIS (fluoro ethylene synthesis) patented technology, the technology utilizes hydrogen fluoride and acetylene reaction to prepare and VF HFC-152a, is supported on the charcoal with mercury oxide or fluorinated mercury as the catalyst. However, this kind of catalyst hypertoxic, easily inactiviting, the stability is poor, and the goal the yield of the product is very low. In general, mercury-containing catalyst not only the price is expensive and over, long activating process, low yield of the product, not stable short service life, is highly toxic! Cadmium-containing catalyst and the toxicity of the cyanide catalyst was still very strong. Chromium-based catalyst is also to the environment will cause a certain degree of pollution. Single component of the aluminum-based or zinc-based catalyst, although the activity of which is quite high, but many ties the carbon quantity , thus affecting the activity and stability of catalysts, so as to affect its service life. Content of the invention The purpose of this invention is used for aiming at and vinyl producing ethyne 1, 1-difluoroethane catalyst of high cost, complicated preparation technology, poor activity, the stability is not high, the defects of the serious environmental pollution, provides a low-cost, simple preparation process, high activity, high stability and environment-friendly for producing ethylene and 1, 1-difluoroethane and method for preparing the catalyst. This invention adopts the following technical solutions: For producing ethylene and 1, 1-difluoroethane catalyst, the precursor of the catalyst active component A oxide and active component B oxide, wherein for A mg, Y, Sm, in La one or more, for B Al, Zn in one kind or two kinds of, between and A B the molar ratio of 1:9-99. The catalyst precursor after inert gas pre-processing and fluorizating pre-processing may obtain the catalyst of the invention. The catalyst of the present invention prepared by precipitation method, comprising the following steps: (1) the molar ratio of the the A B to 1:9-99, a certain amount of weighed B A the compounds of the compound and, after mixing with water, by adding precipitant, the adjusted solution to pH 8-10.5, the dissolved metal ion precipitation completely, to wash until the filtrate is neutral is separated, and then in the sediments will 100-150 the oven dried under [...] 10-16h; (2) the (1) of the material after drying in, in 300-500 the roasting under [...] 2-6h, the precursor of the catalyst of the present invention; (3) the (2) catalyst precursor obtained in the preforming shapes; (4) catalyst precursor sheeting formation of an inert gas, such as at atmospheric pressure: N2, Ar, He, in 200-400 the dry the [...] 2-10h; (5) after the inert gas pre-treatment, recanalization anhydrous hydrogen fluoride in a the 200-450 [...] temperature processing 2-20h, to obtain the catalyst of the invention. In the step (1) selected from states the precipitating agent in the ammonia water, ammonium carbonate, a sodium carbonate. In the step (1) A in, the B compounds are all can be a halide, nitrate, sulfate, oxide, hydrous oxide, hydroxide of one or more than one. The catalyst of the invention can also be prepared by dipping process, comprising the following steps: (1) the molar ratio of the the A B to 1:9-99, A weighing a certain amount of the compounds of compounds and B. The proper amount of water for the compound completely dissolved A are evenly mixed after the compound B, standing 6-12h, then in 100-150 the drying temperatures [...] 10-16h; (2) the (1) of the material after drying in, in 300-500 the roasting under [...] 2-6h, the precursor of the catalyst of the present invention; (3) the (2) catalyst precursor obtained in the preforming shapes; (4) catalyst precursor sheeting formation of an inert gas, such as at atmospheric pressure: N2, Ar, He, in 200-400 the dry the [...] 2-10h; (5) after the inert gas pre-treatment, recanalization anhydrous hydrogen fluoride in a the 200-450 [...] temperature processing 2-20h, to obtain the catalyst of the invention. In the step (1) can be in compound A is halide, nitrate, sulfate, one or more than one kind of; B the compound may be an oxide, hydrous oxide, hydroxide of one or more than one. Prepared by the method of the present invention the precursor of the catalyst, comprises at least two oxide, oxide can be an oxide of Zn in or Al of one or more than one kind of and mg, Y, Sm, in La of the oxide of one or more than one, the precursor in the through the inactive gas pre-processing and fluorinated after pre-treatment, part of the oxide will be transformed into fluoride, this mixture is the catalyst of the invention. Al, Zn oxide there is a strong acid, the active center of the reaction, mg, Y, Sm, La oxide, containing a certain amount of alkaline, can weaken the carbon the emergence of the reaction, the catalyst can be in the material within the range of relatively low, having a high activity and stability, and has the preparation method is simple and easy, rapid, low price and the like, is especially suitable for acetylene french gas phase VF and HFC-152a producing fluoride, the acetylene maximum conversion is relatively high, and VF HFC-152a to the total selectivity is very high. Embodiment mode Through some in the embodiment of the catalyst of this invention for further description, but the invention is not limited to these embodiments. Embodiment 1 First weighing Al, Y mole ratio is 13:1 the AlCl3 and Y (OH)3, the AlCl3 in dissolved in a certain amount of water, then add Y (OH)3, added under stirring state (NH4)2 CO3, of the adjusted solution to pH 8, so that the dissolved Al3+ and partially dissolved Y3+ can be completely precipitated, to wash filters after the filtrate is neutral, again in 100 the lower drying temperature [...] 10h, at the 300 the roasting under [...] 4h, after the preforming is shaped, that is, to obtain the catalyst precursor (Al2 O3-Y2 O3). For this catalyst precursor N2 gas for the 300 dry the [...] 2h, the anhydrous HF for the 300 under [...] 6h, to obtain the catalyst of the invention. The embodiment is applied to the prepared catalyst VF and acetylene french gas phase HFC-152a producing fluoride in, its the C2 H2 reaction activity and VF and HFC-152a selective see table 1. Embodiment 2 First weighing Al, La molar ratio of 79:1 of and aluminum rubber La (NO3)3, the La (NO3)3 in dissolved in a certain quantity of water, then add aluminum rubber , adding a stirring state (NH4)2 CO3, of the adjusted solution to pH 8, so that the dissolved La3+ and some dissolved Al3+ can be completely precipitated, to wash filters after the filtrate is neutral, the 120 the lower drying temperature [...] 12h, finally, in the 400 roasting under [...] 4h, after the preforming is shaped, that is, to obtain the catalyst precursor (Al2 O3-La2 O3). For this catalyst precursor N2 gas for the 300 dry the [...] 6h, the anhydrous HF for the 350 under [...] 4h, to obtain the catalyst of the invention. The embodiment is applied to the prepared catalyst VF and acetylene french gas phase HFC-152a producing fluoride in, its the C2 H2 reaction activity and VF and HFC-152a selective see table 1. Embodiment 3 First weighing Al, Y molar ratio of 24:1 of and aluminum rubber Y (OH)3, the aluminum rubber and Y (OH)3 water after mixing, add under the mixing state Na2 CO3, of the adjusted solution to pH 9, the partially dissolved Al3+ and Y3+ can be completely precipitated, to wash filters after the filtrate is neutral, the 150 the lower drying temperature [...] 16h, finally, in the 500 roasting under [...] 2h, after the preforming is shaped, that is, to obtain the catalyst precursor (Al2 O3-Y2 O3). For this catalyst precursor Ar gas for the 200 is dried under [...] 10h, the anhydrous HF for the 450 under [...] 2h, to obtain the catalyst of the invention. The embodiment is applied to the prepared catalyst VF and acetylene french gas phase HFC-152a producing fluoride in, its the C2 H2 reaction activity and VF and HFC-152a selective see table 1. Embodiment 4 First weighing Al, Y molar ratio of 20:1 the Al (NO3)3 and Y (NO3)3, the two first dissolved in a certain amount of water, make it fully dissolved, then the added in the state of mixing (NH4)2 CO3, of the adjusted solution to pH 8, so that the dissolved Al3+ and Y3+ can be completely precipitated, to wash filters after the filtrate is neutral, the 120 the lower drying temperature [...] 14h, finally in 300 the roasting under [...] 6h, after the preforming is shaped, that is, to obtain the catalyst precursor (Al2 O3-Y2 O3). For this catalyst precursor He gas for the 400 is dried under [...] 2h, the anhydrous HF for the 300 under [...] 4h, to obtain the catalyst of the invention. The embodiment is applied to the prepared catalyst VF and acetylene french gas phase HFC-152a producing fluoride in, its the C2 H2 reaction activity and VF and HFC-152a selective see table 1. Embodiment 5 First weighing Al, mg molar ratio of 10:1 and aluminum rubber of mg (NO3)2, the mg (NO3)2 completely dissolved in a certain amount of water, then add aluminum rubber , adding a stirring state NH3 · H2 O, of the adjusted solution to pH 10.5, the dissolved mg2+ and some dissolved Al3+ can be completely precipitated, to wash filters after the filtrate is neutral, re-in 110 the lower drying temperature [...] 16h, finally, in the 500 roasting under [...] 4h, after the preforming is shaped, that is, to obtain the catalyst precursor (Al2 O3-MgO). For this catalyst precursor N2 gas for the 300 dry the [...] 4h, the anhydrous HF for the 350 under [...] 4h, , to obtain the catalyst of the invention. The embodiment is applied to the prepared catalyst VF and acetylene french gas phase HFC-152a producing fluoride in, its the C2 H2 reaction activity and VF and HFC-152a selective see table 1. Embodiment 6 First weighing Zn, Y molar ratio of 30:1 the Zn (NO3)2 and Y (OH)3, the Zn (NO3)2 in dissolved in a certain amount of water, make it fully dissolved, then adding Y (OH)3, under the state of mixing by adding (NH4)2 CO3, of the adjusted solution to pH 8, so that the dissolved Zn2+ and some dissolved Y3+ can be completely precipitated, to wash filters after the filtrate is neutral, the 120 the lower drying temperature [...] 10h, finally, in the 500 roasting under [...] 4h, after the preforming is shaped, that is, to obtain the catalyst precursor (ZnO-Y2 O3). In this catalyst precursor N2 gas for the 300 dry the [...] 8h, the anhydrous HF for the 200 under [...] 20h, to obtain the catalyst of the invention. The embodiment is applied to the prepared catalyst VF and acetylene french gas phase HFC-152a producing fluoride in, its the C2 H2 reaction activity and VF and HFC-152a selective see table 1. Embodiment 7 First weighing Zn, mg molar ratio of 30:1 the ZnCl2 and MgSO4, the two first dissolved in a certain amount of water, make it fully dissolved, then the added in the state of mixing NH3 · H2 O, of the adjusted solution to pH 10.5, the dissolved Zn2+ and mg2+ can be completely precipitated, to wash filters after the filtrate is neutral, the 120 the lower drying temperature [...] 14h, finally, in the 500 roasting under [...] 4h, after the preforming is shaped, that is, to obtain the catalyst precursor (ZnO-MgO). For this catalyst precursor N2 gas for the 400 is dried under [...] 4h, the anhydrous HF for the 350 under [...] 4h, to obtain the catalyst of the invention. The embodiment is applied to the prepared catalyst VF and acetylene french gas phase HFC-152a producing fluoride in, its the C2 H2 reaction activity and VF and HFC-152a selective see table 1. Embodiment 8 First weighing Al, Y, La molar ratio of 30:1:1 the Al2 (SO4)3, YCl3, La (NO3)3, dissolved in the first three are in a certain amount of water, make it fully dissolved, then the added in the state of mixing (NH4)2 CO3, of the adjusted solution to pH 8, so that the dissolved Al3+, Y3+ and La3+ can be completely precipitated, to wash filters after the filtrate is neutral, the 120 the lower drying temperature [...] 14h, finally, in the 400 roasting under [...] 4h, after the preforming is shaped, that is, to obtain the catalyst precursor (Al2 O3-Y2 O3-La2 O3). For this catalyst precursor N2 gas for the 300 dry the [...] 5h, the anhydrous HF for the 350 under [...] 4h, to obtain the catalyst of the invention. The embodiment is applied to the prepared catalyst VF and acetylene french gas phase HFC-152a producing fluoride in, its the C2 H2 reaction activity and VF and HFC-152a selective see table 1. Embodiment 9 First weighing Al, Sm molar ratio of 9:1 the γ-Al2 O3 and Sm (NO3)3, the Sm (NO3)3 in dissolved in a certain amount of water, make it fully dissolved, then adding γ-Al2 O3, standstill 10h to make it fully impregnated, the 110 the lower drying temperature [...] 12h, finally, in the 400 roasting under [...] 4h, after the preforming is shaped, that is, to obtain the catalyst precursor (Al2 O3-Sm2 O3). For this catalyst precursor N2 gas for the 300 dry the [...] 2h, the anhydrous HF for the 300 under [...] 10h, to obtain the catalyst of the invention. The embodiment is applied to the prepared catalyst VF and acetylene french gas phase HFC-152a producing fluoride in, its the C2 H2 reaction activity and VF and HFC-152a selective see table 1. Embodiment 10 First weighing Al, mg molar ratio of 20:1 and aluminum rubber of mg (NO3)2, the mg (NO3)2 in dissolved in a certain amount of water, make it fully dissolved, then adding aluminum rubber , standing 8h the fully impregnated, the 100 the lower drying temperature [...] 16h, finally in 300 the roasting under [...] 6h, after the preforming is shaped, that is, to obtain the catalyst precursor (Al2 O3-MgO). For this catalyst precursor N2 gas for the 200 is dried under [...] 10h, the anhydrous HF for the 350 under [...] 6h, to obtain the catalyst of the invention. The embodiment is applied to the prepared catalyst VF and acetylene french gas phase HFC-152a producing fluoride in, its the C2 H2 reaction activity and VF and HFC-152a selective see table 1. Embodiment 11 First weighing Zn, La molar ratio of 50:1 the ZnO and LaCl3, the LaCl3 in dissolved in a certain amount of water, make it fully dissolved, then add ZnO, and 10h to make it fully impregnated, the 120 the lower drying temperature [...] 15h, finally, in the 500 roasting under [...] 2h, after the preforming is shaped, that is, to obtain the catalyst precursor (ZnO-La2 O3). For this catalyst precursor Ar gas for the 400 is dried under [...] 4h, the anhydrous HF for the 400 under [...] 4h, to obtain the catalyst of the invention. The embodiment is applied to the prepared catalyst VF and acetylene french gas phase HFC-152a producing fluoride in, its the C2 H2 reaction activity and VF and HFC-152a selective see table 1. Embodiment 12 First weighing Zn, Sm molar ratio of 50:1 the ZnO and SmCl3, the SmCl3 in dissolved in a certain amount of water, make it fully dissolved, then adding Sm2 O3, standstill 6h the fully impregnated, the 120 the lower drying temperature [...] 12h, finally, in the 500 roasting under [...] 4h, after the preforming is shaped, that is, to obtain the catalyst precursor (ZnO-Sm2 O3). For this catalyst precursor He gas for the 300 dry the [...] 6h, the anhydrous HF for the 200 under [...] 20h, to obtain the catalyst of the invention. The embodiment is applied to the prepared catalyst VF and acetylene french gas phase HFC-152a producing fluoride in, its the C2 H2 reaction activity and VF and HFC-152a selective see table 1. Embodiment 13 First weighing Al, Y molar ratio of 19:1 the γ-Al2 O3 and Y (NO3)3, the Y (NO3)3 in dissolved in a certain amount of water, make it fully dissolved, then adding γ-Al2 O3, standstill 8h the fully impregnated, the 150 the lower drying temperature [...] 10h, finally, in the 400 roasting under [...] 4h, after the preforming is shaped, that is, to obtain the catalyst precursor (Al2 O3-Y2 O3). For this catalyst precursor N2 gas for the 300 dry the [...] 2h, the anhydrous HF for the 450 under [...] 2h, to obtain the catalyst of the invention. The embodiment is applied to the prepared catalyst VF and acetylene french gas phase HFC-152a producing fluoride in, its the C2 H2 reaction activity and VF and HFC-152a selective see table 1. Embodiment 14 First weighing Al, Y molar ratio of 99:1 the γ-Al2 O3 and Y (NO3)3, the Y (NO3)3 in dissolved in a certain amount of water, make it fully dissolved, then adding γ-Al2 O3, standstill 12h the fully impregnated, the 120 the lower drying temperature [...] 13h, finally, in the 400 roasting under [...] 4h, after the preforming is shaped, that is, to obtain the catalyst precursor (Al2 O3-Y2 O3). This catalyst precursor with N2 gas for the 400 is dried under [...] 2h, the anhydrous HF for the 350 under [...] 4h, to obtain the catalyst of the invention. The embodiment is applied to the prepared catalyst VF and acetylene french gas phase HFC-152a producing fluoride in, its the C2 H2 reaction activity and VF and HFC-152a selective see table 1. Applying example 15 First weighing Al, La molar ratio of 19:1 the γ-Al2 O3 and La (NO3)3, the La (NO3)3 in dissolved in a certain amount of water, make it fully dissolved, then adding γ-Al2 O3, standstill 8h the fully impregnated, the 120 the lower drying temperature [...] 14h, finally, in the 500 roasting under [...] 2h, after the preforming is shaped, that is, to obtain the catalyst precursor (Al2 O3-La2 O3). For this catalyst precursor N2 gas for the 300 dry the [...] 4h, the anhydrous HF for the 300 under [...] 6h, to obtain the catalyst of the invention. The embodiment is applied to the prepared catalyst VF and acetylene french gas phase HFC-152a producing fluoride in, its the C2 H2 reaction activity and VF and HFC-152a selective see table 1. Applying example 16 First weighing Al, La molar ratio of 99:1 the γ-Al2 O3 and La (NO3)3, the La (NO3)3 in dissolved in a certain amount of water, make it fully dissolved, then adding γ-Al2 O3, standstill 10h to make it fully impregnated, the 120 the lower drying temperature [...] 10h, finally, in the 400 roasting under [...] 4h, after the preforming is shaped, that is, to obtain the catalyst precursor (Al2 O3-La2 O3). For this catalyst precursor N2 gas for the 300 dry the [...] 6h, the anhydrous HF for the 350 under [...] 4h, to obtain the catalyst of the invention. The embodiment is applied to the prepared catalyst VF and acetylene french gas phase HFC-152a producing fluoride in, its the C2 H2 reaction activity and VF and HFC-152a selective see table 1. Applying example 17 First weighing Zn, Y, Sm molar ratio of 50:2:1 the ZnO, Y (NO3)3, SmCl3, the Y (NO3)3 and SmCl3 in dissolved in a certain amount of water, make it fully dissolved, then add ZnO, and 10h to make it fully impregnated, the 120 the lower drying temperature [...] 10h, finally, in the 500 roasting under [...] 3h, after the preforming is shaped, that is, to obtain the catalyst precursor (ZnO-Y2 O3-Sm2 O3). For this catalyst precursor N2 gas for the 300 dry the [...] 2h, the anhydrous HF for the 350 under [...] 8h, to obtain the catalyst of the invention. The embodiment is applied to the prepared catalyst VF and acetylene french gas phase HFC-152a producing fluoride in, its the C2 H2 reaction activity and VF and HFC-152a selective see table 1. Table 1. Embodiment 1-17 catalyst to C2 H2 HFC-152a the activity and VF and the selectivity of the (HF:C2 H2 = 2.5: 1, vhsv: 900h-1) The invention relates to a catalyst for producing fluorothene and 1,1-difluoroethane and a preparation method thereof. The oxide of an active component A and the oxide of an active component B form the former body of the catalyst, wherein A is one or more than one of Mg, Y, Sm and La, B is one or two of Al and Zn, the mol ratio between A and B is 1:9-99, and the catalyst is obtained through the pretreatment of inert gas and the fluorination pretreatment. The catalyst is prepared by a precipitation method or an immersion method. The former body of the catalyst is obtained after the treatment at a certain temperature, and the catalyst is then obtained through the treatment of inert gas and anhydrous hydrogen fluoride. The catalyst which has the advantages of low cost, simple preparation process, high activity, high stability and the like is particularly suitable for the gas phase fluorination production of fluorothene and 1,1-difluoroethane through an acetylene method. 1. For producing ethylene and 1, 1-difluoroethane catalyst, characterized in that the catalyst is formed by active component A oxide and active component B oxide precursor, wherein for A mg, Y, Sm, in La one or more, for B Al, Zn in one kind or two kinds of, between and A B the molar ratio of 1:9-99; and pre-treated with an inert gas to make pre-fluoride. 2. Claim 1 the preparation method of the catalyst, characterized in that the precipitation method, comprising the following steps: (1) the molar ratio of the the A B to 1:9-99, a certain amount of weighed B A the compounds of the compound and, after mixing with water, by adding precipitant, the adjusted solution to pH 8-10.5, the dissolved metal ion precipitation completely, to wash until the filtrate is neutral is separated, and then in the sediments will 100-150 the oven dried under [...] 10-16 hours; (2) the (1) of the material after drying in, in 300-500 the roasting under [...] 2-6 hours, the precursor of the catalyst of the present invention; (3) the (2) catalyst precursor obtained in the preforming shapes; (4) catalyst precursor sheeting formation at atmospheric pressure in an inert gas 200-400 the dry the [...] 2-10h; (5) after the inert gas pre-treatment, recanalization anhydrous hydrogen fluoride in a the 200-450 [...] temperature processing 2-20 hours, to obtain the catalyst of the invention. 3. Preparation method of the catalyst according to Claim 2, characterized in that in the step (1) selected from states the precipitating agent in the ammonia water, ammonium carbonate, a sodium carbonate; step (4) of the inert gas is selected from the group in N2, Ar, He a in. 4. Preparation method of the catalyst according to Claim 2, characterized in that in the step (1) in A, B compounds are the halide, nitrate, sulfate, oxide, hydrous oxide, hydroxide of one or more than one. 5. Claim 1 the preparation method of the catalyst, characterized in that through the dipping method, comprising the following steps: (1) the molar ratio of the the A B to 1:9-99, A weighing a certain amount of the compounds of compounds and B. The proper amount of water for the compound completely dissolved A are evenly mixed after the compound B, standing 6-12 hours, then in 100-150 the drying temperatures [...] 10-16 hours; (2) the (1) of the material after drying in, in 300-500 the roasting under [...] 2-6 hours, the precursor of the catalyst of the present invention; (3) the (2) catalyst precursor obtained in the preforming shapes; (4) catalyst precursor sheeting formation at atmospheric pressure in an inert gas 200-400 the dry the [...] 2-10h; (5) after the inert gas pre-treatment, recanalization anhydrous hydrogen fluoride in a the 200-450 [...] temperature processing 2-20 hours, to obtain the catalyst of the invention. 6. Preparation method of the catalyst according to Claim 5, characterized in that in the step (1) in the compound A is halide, nitrate, sulfate, one or more than one kind of; B compound as the oxide, hydrous oxide, hydroxide of one or more than one kind of; step (4) of the inert gas is selected from the group in N2, Ar, He a in.