Patent Grant
4879264
This invention concerns a method of making catalyst precursors and catalysts containing vanadium and antimony in oxide form, the catalyst precursor so made, and microspheroidal catalyst made from such precursor. Harris et al. British specification Nos. 1,336,135 and 1,336,136 disclose making catalysts from V.sub.2 O.sub.5 and Sb.sub.2 O.sub.5 slurries that are mixed, dried and calcined. These are used to ammoxidize alkanes such as propane. Harris U.S. Pat. No. 3,860,534 has similar disclosures but the calcined catalyst is washed with water before use to remove soluble vanadium compounds. Th dried and calcined material in the Harris method, however, is relatively weak and has low abrasion resistance. More important is the fact that the Harris material in the dried state is a fine talcum powder-like material. Thus, it is not possible to spray dry the Harris slurry to obtain microspheroidal particles large enough for fluidized bed catalysis, generally in the 40-100 micron range. It is an object of the invention to provide a method of making a catalyst precursor having vanadium and antimony in oxide form, capable of being processed to form a catalyst having good hardness and attrition resistance. Another object is to provide such a precursor. A further object is to provide a method of making a hard, attrition-resistant catalyst containing vanadium and antimony in oxide form. Still another object is to provide a method of making a microspheroidal catalyst containing vanadium and antimony in oxide form, and the micropheroidal catalyst so made. Other objects, as well as aspects, features and advantages, of the present invention will become apparent from a study of the accompanying disclosure and the claims. According to one aspect of the invention there is provided a method of making a catalyst precursor having vanadium and antimony in oxide form in the atomic ratio of Sb to V in the range from 0.8 to 4, usually from 1 to 3, by aging an aqueous solution containing the monoperoxovanadium ion, VO(O.sub.2).sup.+, until a vanadium-containing sol or gel is formed, and reacting said vanadium while in said aqueous sol or gel form, with an antimony compound which contains Sb having a valence of 3, thereby reducing the average valence of the vanadium to less than 5 and oxidizing antimony to a valence state of 5. At least a portion of the Sb.sup.+3 is so oxidized, not necessarily all. According to a more specific aspect of the invention, the foregoing is accomplished by reacting H.sub.2 O.sub.2 in aqueous solution with a vanadium compound, aging the reaction solution, and then reacting the antimony compound as above stated. Thus, according to this aspect, there is provided a method of making a catalyst precursor having vanadium and antimony in oxide form in the atomic ratio of Sb to V in the range of 0.8 to 4, usually from 1 to 3, by reacting a vanadium compound with an aqueous hydrogen peroxide solution to form a dispersion containing the monoperoxovanadium ion, VO(O.sub.2).sup.+, in solution, aging the reaction solution to form a vanadium-containing sol or gel, and reacting the latter with an antimony compound which contains Sb having a valence of 3, thereby reducing the average valence of the vanadium to less than 5 and oxidizing antimony to a valence state of 5, wherein the ratio of moles of H.sub.2 O.sub.2 to atoms of V is at least 1. This ratio can be 1 or any amount over 1, but a ratio of 10 or less is usually sufficient. By the term "sol" is meant a suspension of colloidal particles. By the term "gel" is meant an intricate and substantially amorphous three-dimensional solid network dispersed in a liquid, wherein both the solid and the liquid phases are continuous. The initial vanadium compound reactant in the latter aspect of the invention can be an inorganic or an organic compound of vanadium, but is usually an inorganic compound. The vanadium in the compound can have any initial valence. A partial list of such compounds includes any oxide of vanadium, such as V.sub.2 O.sub.5, V.sub.7 O.sub.13, VO, VO.sub.2, V.sub.2 O.sub.3, V.sub.3 O.sub.7, etc.; any vanadium oxyhalide such as VOCl.sub.3, VOCl.sub.2, (VO.sub.2)Cl, VOCl, VOBr, VOBr.sub.2, VOBr.sub.3 ; any vanadium halide such as VF.sub.3, VBr.sub.3, VCL.sub.2, VCl.sub.3, VCl.sub.4, VF.sub.5 ; vamadu; sulfate; meta-vanadic acid; pyro-vanadic acid; in short, any compound of vanadium that will react with an aqueous H.sub.2 O.sub.2 solution. The vanadium compound usually used in the reaction with H.sub.2 O.sub.2 is one of the oxides. Because of availability and cost, V.sub.2 O.sub.5 is often the compound that is chosen to react with the hydrogen peroxide. Antimony compound reactants chosen to react with the monoperoxovanadium ion in making the catalyst precursor of the invention can be an organic or an inorganic compound of antimony. A partial list of such compounds includes any of the following types of compounds containing antimony having a valence of 3: any such antimony oxide such as Sb.sub.2 O.sub.3 and Sb.sub.2 O.sub.4 ; SbOCl; any such antimony halide such as SbBr.sub.3, SbCl.sub.3, SbF.sub.3 and SbI.sub.3. The antimony compound usually chosen to react with the peroxovanadium ion in either aspect of the invention is one of the antimony oxides containing antimony having a valence of 3. Because of availability and cost Sb.sub.2 O.sub.3 is ordinarily the chosen oxide. Of course, when the antimony compound is Sb.sub.2 O.sub.4, the half of the Sb that is 5-valent is not useful to effect reduction of the 5-valent vanadium. It will be understood that the method includes the embodiment where other catalyst additives are present during the process. In most cases other compounds can be added after the vanadium and antimony reaction has taken place. This includes compounds of elements such as Sn, Fe, Cu, Mg and Li, for instance. Compounds of some elements such as Ti that form peroxo compounds can also be added before or with the addition of the H.sub.2 O.sub.2, but are usually most conveniently added after the vanadium and antimony compounds have reacted, as before noted. We are aware of U.S. Pat. No. 3,984,353 wherein Sb.sub.2 O.sub.3 is contacted with H.sub.2 O.sub.2 and oxidized to Sb.sub.2 O.sub.5 and the latter is reacted with a compound of certain metals, such as the oxide, and the obtained product is dried and calcined at up to 700.degree. C. The list of second metals includes V. This process, of course, is contrary to the present process. In another aspect of the invention a catalyst precursor is provided which is the product of the process of any one of the foregoing methods. In still another aspect of the invention there is provided a process for making a catalyst which comprises drying a precursor made by one of the foregoing processes and thereafter calcining the resulting dried product at a maximum temperature in the range 650.degree. to 1000.degree. C., usually 700.degree. to 875.degree. C., and most particularly in the range from 750.degree. to 850.degree. C. When the drying is a spray drying step, the product is a microspheroidal catalyst having particle diameters including the range from 10 to 200 microns. The following examples illustrate the invention but are not to be considered in any way limiting. A catalyst was made as taught by Harris U.S. Pat. No. 3,860,534, as follows: Powdered V.sub.2 O.sub.5 (27.58 g) and Sb.sub.2 O.sub.3 (72.56 g) were slurried in 80 cc of water and 80 cc of concentrated nitric acid. The orange slurry was heated on a hotplate until nearly dry, then dried overnight at 130.degree. C. It was the heat treated at 650.degree. C. for 8 hours. It was very soft and powdery. Half of the catalyst precursor was then mixed with 1 percent of graphite, pelleted, crushed and screened to 20-35 mesh. It was activated by calcining at 810.degree. C. for 1 hour, then cooled to 500.degree. C. and taken from the oven. It was placed in a funnel and washed with warm water running through the catalyst until no color appeared in the filtrate (about 2 hours). An attrition, or particle size retention, test was carried out on a portion of the activated catalyst. The test procedure is as follows: A 2 g sample of the catalyst (20/35 mesh) is weighed accurately and placed in a 4 oz. round jar with a screw-on lid, along with 15 BB pellets (4.5 mm., Zn-plated steel). The jar is closed and placed on the rollers of a ball mill. It is then rolled for 1 hour. The contents of the jar are then placed on stacked 20/35 mesh screens to remove any pellets and the fines. The material retained on 35 mesh is then weighed. The particle size retention is reported as percent of the original weight. The particle size retention was 41%, far too low to be a viable commercial fluid bed catalyst. The same particle size retention test was carried out on an attrition resistant bismuth molybdate type catalyst composition used in commercial fluidized bed propylene ammoxidation operations, and the particle size retention was 78%.
| Number | Name | Date | Kind |
|---|---|---|---|
| 3860534 | Harris et al. | Jan 1975 | |
| 3984353 | Sergunkin et al. | Oct 1976 | |
| 4746641 | Guttmann et al. | May 1988 |
