Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
  • B01J27/24—Nitrogen compounds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/002—Mixed oxides other than spinels, e.g. perovskite
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
  • B01J27/14—Phosphorus; Compounds thereof
  • B01J27/186—Phosphorus; Compounds thereof with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
  • B01J27/195—Phosphorus; Compounds thereof with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium with vanadium, niobium or tantalum
  • B01J27/198—Vanadium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
  • B01J27/20—Carbon compounds
  • B01J27/22—Carbides
  • B01J27/224—Silicon carbide
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J35/00—Catalysts, in general, characterised by their form or physical properties
  • B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/0009—Use of binding agents; Moulding; Pressing; Powdering; Granulating; Addition of materials ameliorating the mechanical properties of the product catalyst
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
  • C07C51/16—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation
  • C07C51/21—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen
  • C07C51/215—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of saturated hydrocarbyl groups
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2523/00—Constitutive chemical elements of heterogeneous catalysts

Definitions

• It is an object of this invention is to further advance the technology of NPO catalysis by providing for a NPO catalyst combined with a thermally conductive material particularly effective for hydrocarbon oxidation.
• Figure 1 is a plot of the yield of maleic anhydride versus reaction temperature for the oxidation of n-butane using vanadium phosphorus oxide catalysts combined with boron nitride compared to phosphorus treated boron nitride and vanadium phosphorus oxide. Data from Comparative Example 2 (vanadium phosphorus oxide) and Examples 1 (vanadium phosphorus oxide supported on boron nitride are shown in this figure.
• a comparison is also made to the comparative catalyst (Comparative Example 1), vanadium phosphorus oxide supported on silicon carbide and Comparative Example 2 (vanadium phosphorus oxide).
• the catalyst of this invention comprises vanadium phosphorus oxide combined with a thermally conductive material.
• vanadium phosphorus oxide it is meant a compound containing the elements vanadium, phosphorus and oxygen, and which is catalytically active in exothermic catalytic reactions, especially hydrocarbon oxidations. Vanadium pyrophosphate is an example of such compounds that may be useful.
• the vanadium phosphorus oxide may contain promoters, especially those known to improve activity in hydrocarbon oxidations, such as those described in G. J. Hutchings, Applied Catalysis, 72 (1991), Elsevier Science Publishers B. V. -Amsterdam, pages 1-31.
• the amount of vanadium phosphorus oxide in the catalyst should be in the range of 0.1 to 90 wt %, based on the total weight of the catalyst.
• the vanadium phosphorus oxide is present in an amount of 5 to 50 wt %, and most preferably 10 to 40 wt %.
• thermally conductive materials can be used. These include silicon nitride, and boron nitride. As described in this invention, preferably boron nitride is boron nitride treated with a phosphorous containing compound.
• the catalysts can be in any form wherein vanadium phosphorus oxide is combined with, for example, or intimately associated with, the thermally conductive support. Preferably, the catalyst will comprise a "core" of the thermally conductive material, a "shell" of the vanadium phosphorus oxide compound and a transition phase intermediate between the core and the shell which contains the elements of the thermally conductive material, and vanadium, phosphorus and oxygen. However, the catalysts may also be in a form wherein the vanadium phosphorus oxide is bound to the thermally conductive material, in such a manner where no transition phase can be seen.
• a chemical reaction of the vanadium phosphorus oxide catalyst onto the thermally conductive material is preferred. Mechanical mixing of the vanadium phosphorus oxide with the thermally conductive material is also possible. Process to Prepare Catalyst
• a suspension of vanadium (IV) phosphate in a liquid medium is formed.
• the liquid medium comprises with at least one substantially anhydrous unsubstituted alcohol having 1-10 carbon atoms, 1-3 hydroxyl groups and free from olefinic double bonds.
• Vanadium phosphorus oxide precursor is prepared by mixing vanadium pentoxide with the alcohol-containing medium, and heating the mixture to form a feed of vanadium oxide reduced to a valence of between 4 and 4.6.
• the vanadium oxide feed is then contacted with a solution comprising orthophosphoric acid and at least one substantially anhydrous unsubstituted alcohol having 1-10 carbon atoms, 1-3 hydroxyl groups and free from olefinic double bonds.
• the liquid medium comprises water and vanadium (IV) phosphate can be formed by the hydrochloric acid digestion of V 2 O 5 and H3PO4 in an aqueous solvent, as described, for example, in U.S. Patent 3,985,775, the disclosure of which is incorporated herein by reference.
• vanadium pentoxide, orthophosphoric acid and anhydrous alcohol of the type described above can be used in the practice of this process.
• a thermally conductive material is added to a suspension containing the vanadium phosphorus oxide precursor (formed by refluxing the mixture of V2O5 and orthophosphoric acid for 1-4 hours) under agitation.
• the thermally conductive material is maintained between a temperature between 40°C and 120°C to form vanadium (IV) phosphate combined with the thermally conductive material.
• the rapid crystallization of the vanadium (IV) phosphate should be avoided, as that would result in a mixture of crystallized vanadium (IV) phosphate and the thermally conductive material, rather than the of this invention.
• the catalysts of this invention may be further processed to impart attrition resistance by methods known in the art, such as, for example, by applying a coating of Si ⁇ 2 in accordance with U.S. Patent 4,677,084, the disclosure of which is incorporated herein by reference. This further process is particularly applied when the thermally conductive material is in the form of a fine powder.
• the catalysts of this invention are well suited for use as catalysts in exothermic reactions, especially hydrocarbon oxidations, in any type of reactor, for example, fixed bed, fluidized bed and recirculating solids reactor.
• the thermally conductive support acts as a heat sink
• the catalysts of this invention can be utilized at higher temperatures than the corresponding catalyst in the absence of thermally conductive material. More specifically, the catalyst is well suited to be efficiently utilized in fixed bed reactors with improved selectivity at high butane concentrations.
• Silicon carbide was provided in the form of grains having a particle size of ⁇ 0.3 mm. Under vigorous agitation, 10 g of silicon carbide at 80°C was added to the solution (10 g of silicon carbide) prepared according to U.S. 5,460,759 and 5,427,761 was added as a hot powder to the hot reflux containing the vanadium hydrogen phosphate hemihydrate suspension in the solvent. The temperature was increased to 130°C for approximately 15 minutes, which led to some evaporation of the solvent. When the temperature of the mixture reaches about 135°C the drying process was engaged under partial vacuum to obtain a suspension having a " mud" -like consistency, which was placed in a glass vessel and dried at 150°C for 12-15 hours in air.
• Patent 4,132,670 by heating the material to a temperature of 380°C at 3°C per minute under air flow rate of 1.5 cc per minute and held at 380°C for 2 hours. The material was then heated to a temperature of 480°C at 3°C per minute under air/butane (1.5% by volume of butane) flow rate of 3 cc per minute and held at 480°C for 15 hours. The material was allowed to cool to 420°C under air/butane (1.5% by volume of butane) flow of 17 cc per minute for 100 hours. This produced an " activated catalyst" . The activated catalyst was further stabilized by subjecting the catalyst to 200 hours of the air butane flow at 420°C. The activated catalyst contained 30 wt % vanadium phosphorus oxide; 30 wt % (VO) 2 P 2 O7, 70 wt % SiC; based on V, P determined by atomic absorption (AA).
• AA atomic absorption
• Catalytic reactions were carried out using an automated continuous flow fixed-bed microreactor system.
• the reactor consisted of a 6.35 mm o. d. stainless steel tube having an internal diameter of 4.57 mm. Heating the reactor tube was achieved by placing it in an isothermal fluidized sandbath in which silicon carbide was used as the fluidized heat transfer medium. The reactor temperature was controlled by monitoring the external microreactor wall tempreature at the midpoint of the catalyst bed. In a typical experiment, the reactor was packed with about 0.50 g of 0.125 mm to 0.5 mm particles of supported catalyst or catalyst precursor. Catalytic tests were run on the stabilized material and compared to a conventional bulk VPO catalyst, prepared in accordance with the process described in U.S. Patent 4,132,670.
• Catalyst testing was based on performance of the catalysts in the oxidation of n-butane to maleic anhydride.
• the oxidation reactions were performed at temperatures ranging from 310 to 470°C.
• Anhydrous phosphoric acid was prepared in the inert atmosphere drybox by mixing 257.4 g of 85 + % phosphoric acid (J. T. Baker and Co., Phillipsburg, NJ) with 99.6 g of anhydrous phosphorus pentoxide (J. T. Baker). The anhydrous phosphoric acid was then added to the addition funnel, brought outside of the drybox, and attached to the round bottom flask. The vanadium pentoxide and alcohols were held at reflux temperatures for one hour. Anhydrous phosphoric acid was then added dropwise over a period of two hours. Following this procedure, the reflux continued for a period of fifteen additional hours. The precipitated solids were then filtered in a buchner funnel and dried in flowing nitrogen at 80-125°C for a period of 16 hours to yield the catalyst precursor.
• the precursor was calcined and activated in a small, 4 cm fluidized bed reactor. Prior to the activation, fine particles were sieved out on a 400 mesh screen.
• the calcination/activation procedure was accomplished using the following conditions: a) 25-390°C in air b) 390°C, 1 hour in air c) 390°C 1 hour is 1.5% butane/air d) 390-460°C, 20 minutes in 1.5% butane/air e) 460-460°C, 18 hours in 1.5% butane/air f) 460-420°C in 1.5% butane/air g) 420-360°C in 1.5% butane/air h) 360-25°C in 2 .
• the solution was heated to 100°C and maintained at this temperature until all of the phosphoric acid was dissolved.
• the phosphoric acid/boron nitride mixture was stirred for 30 minutes.
• the resulting material was (not filtered) dried at 120°C in air and washed three times in water to extract any excess phosphoric acid.
• the material was calcined at 150°C for 12 hours in air to provide phosphorus-modified boron nitride.
• Vanadium phosphorus oxide precursor in isobutanol was prepared in the same manner as in Comparative Example 1.
• the phosphorus-modified boron nitride was added to the vanadium (IV) phosphate mixture under agitation at a temperature between 100°C and 150°C to form vanadium phosphorus precursor supported on the phosphorus-modified boron nitride (VPO/PIBN).
• the supported vanadium phosphorus oxide precursor was subjected to activation in accordance with the teachings of U.S. Patent 4,132,670, by heating the material to a temperature of 380°C at 3°C per minute under air flow rate of 1.5 cc per minute and held at 380°C for 2 hours. The material was then heated to a temperature of 480°C at 3°C per minute under air/butane (1.5% by volume of butane) flow rate of 3 cc per minute and held at 480°C for 15 hours. The material was allowed to cool to 420°C under air/butane (1.5% by volume of butane) flow of 17 cc per minute for 100 hours. This produced an " activated catalyst" .
• a vanadium phosphorus oxide catalyst was prepared in the same manner with untreated boron nitride.
• the treated and untreated boron nitride catalysts contained 30 wt % vanadium phosphorus oxide. Catalytic testing was carried out as described above in Comparative
• vanadium phosphorus oxide supported on untreated boron nitride also shows improvement in higher temperature performance (above 425°C) compared to vanadium phosphorus oxide (Comparative Example 2), but this improvement is not as pronounced as it is for the vanadium phosphorus oxide supported on phosphated boron nitride (Example 1).
• EXAMPLE 2 Exactly the same procedure was followed to prepare VPO on non- phosphated boron nitride. As shown in Figure 1, this material showed an increase in maleic anhydride yield, but tended to level off at about 20%. It still showed improvement over VPO catalyst (Comparative Example 2), which did not contain boron nitride at temperatures above about 420°C, as indicated in Figure 1 and as described above.
• Catalytic testing was carried out as described above in Comparative Example 1 for vanadium phosphorus oxide supported on SiC. These testing protocols were applied to conventional VPO catalyst (Comparative Example 2), vanadium phosphorus oxide supported silicon nitride (Example 3) and the catalyst of Comparative Example 1 (vanadium phosphorus oxide supported on silicon carbide). The percentage yield of maleic anhydride versus temperature is shown in Figure 2 for these catalysts. As can be seen from Figure 2, the catalyst of Example 3 exhibits superior higher temperature performance (above 425°C) compared with vanadium phosphorus oxide (Comparative Example 2). This behavior is similar to that observed from catalysts prepared in Example 1 (vanadium phosphorus oxide supported on phosphated boron nitride), in which the percentage yield to maleic anhydride increases with temperature, up to 470°C.

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• 2000
  • 2000-04-14 CN CN00806259A patent/CN1347342A/zh active Pending
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