JPS6127097B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a new catalyst comprising a molybdenum-containing calcined composition for the dehydrogenation of ethane to ethylene. For example, it has been customary for ethylene to be produced industrially by thermally decomposing ethane in an endothermic reaction carried out at temperatures of about 600 DEG to 1000 DEG C. (U.S. Pat. No. 3,541,179). The reaction times in such processes are very short, making it difficult or impossible to efficiently recover heat from the process stream. In addition, the construction of the furnace or reaction vessel for the high temperature reactions used requires the use of special alloys. The cracking reactions also produce relatively large amounts of low boiling byproducts such as hydrogen and methane, making recovery of ethylene from such byproducts complex and more expensive. It is possible to oxydehydrogenate ethane using a variety of oxyhalogenation catalyst systems in an exothermic reaction. However, these reactions are at least ca.
achieved only at a temperature of 600°C (U.S. Patent No.
3080435 specification). In addition, the presence of halogen atoms in this case increases the difficulty in recovering the olefin produced. Special and expensive construction materials are also required to withstand corrosion from halogens and hydrogen halides within the reaction system. Furthermore, in order to carry out the process economically, the halogen itself must be recovered and recycled. Oxydehydrogenation of certain C ₃ alkanes by an exothermic reaction at relatively high temperatures is also possible with selected catalysts containing vanadium (U.S. Pat.
3,218,368, 3,541,179 and 3,856,881) and selected catalysts containing vanadium and molybdenum (US Pat. No. 3,320,331). Also, catalyst systems containing molybdenum and vanadium are used for the gas phase oxidation of α,β-unsaturated aliphatic aldehydes, such as acrolein, to the corresponding α,β-unsaturated carboxylic acids, such as acrylic acid. It is also known that These catalyst systems contain the elements Mo, V and It contains. However, using these catalysts known prior to the proposal of the catalyst of the present invention, it was not possible to dehydrogenate, for example, ethane to ethylene at relatively low temperatures with favorable conversion (%), selectivity (%), and productivity. was impossible. Here, conversion rate, selectivity and productivity are defined as follows. Conversion rate (%) = A/Number of moles of ethane in the reaction mixture fed to the catalyst bed x 100 where A is the sum of mole-ethane-equivalents of all carbon-containing products, excluding ethane in the effluent. (carbon standard). Selectivity (or efficiency)% for ethylene (or acetic acid) = Number of moles of ethylene (or acetic acid) produced/A x 100 Productivity (production ability) of ethylene (or acetic acid)
= pounds of ethylene _{( or} acetic _acid ) produced per cubic foot _{of catalyst (} in the catalyst bed) per hour _of reaction _{time .} This is a firing composition. The Si used to form the catalyst compositions shown above is other than Si, which can be present in any carrier (support) that can be used to support the catalyst, as described below. Elements Mo, Ti, Mn, in the new catalyst of the present invention,
Bi and Si are physically present in the catalyst composition combined with oxygen and are themselves believed to be various oxides, and also chemically form oxides such as spinel and perovskite. It can also be a combination. The catalyst of the invention preferably contains the elements Mo, Ti, Mn,
Bi and Si are each produced from solutions of soluble compounds (salts, complexes, or other compounds), but Si can also be produced from colloidal sols. These solutions contain 1-7 and preferably 2-7
Preferably it is an aqueous system with a pH of 6. Solutions of the various compounds containing the elements are prepared by dissolving sufficient soluble compounds of the elements to provide the desired gram atomic proportions of each element.
These compounds of the various elements selected must be mutually soluble to the extent possible. The Si compound is usually added in the form of a colloidal silica sol. Si
If any of the selected compounds of such elements are not mutually soluble with other compounds,
They can be added last to the solution system. A catalyst composition is then prepared by removing water or other solvent from the mixture of compounds in the solution system by evaporation. When the catalyst is deposited and supported on a carrier, the desired elemental compound is usually deposited on a fine porous carrier having the following physical properties (but not limited to these): The surface area is approximately 0.1-500m ³ /g, and the apparent porosity is
30-60%, at least 90% of the pores have a pore size of 20-1500 microns, and the particle or pellet form has a diameter of about 1/8-1/16 inch. This deposition immerses the support in the final mixture of all compounds, evaporates most of the solvent, and then leaves the system at approximately
This is achieved by drying at 80-220°C for 2-60 hours. The thus dried catalyst is then calcined by heating in air or oxygen at about 220-550°C for 1/2-24 hours to give the desired
A Mo ₁ Bi _{0. 08} Ti _{0. 08} Mn _{0. 16} Si _{0. 16} composition is produced. Supports that can be used are silica, aluminum oxide, silicon carbide, zirconia, titania and mixtures thereof. In this case the supported catalyst is usually about 10-50% by weight.
of the catalyst composition, the remainder being the carrier. The molybdenum is preferably in solution in the form of an ammonium salt of molybdenum, such as ammonium para-molybdate, or in the form of an organic acid salt of molybdenum, such as acetate, oxalate, mandelate and glycolate. Introduce. Other water-soluble molybdenum compounds that can also be used are partially water-soluble molybdenum oxide, molybdic acid and molybdenum chloride. Titanium is preferably introduced into the solution in the form of a water-soluble chelate coordinated with ammonium lactate. Other water-soluble titanium compounds that can be used are betadiketone hydrochloride, titanium coordinated, bonded or complexed to carboxylic acids, amines, alcohols or alkanolamines. Manganese and bismuth are preferably introduced into the solution in the form of nitrates. Other water-soluble compounds of these elements that can be used are water-soluble chlorides and organic acid salts such as acetates, oxalates, tartrates, lactates, salicylates, formates and carbonates of such elements. be. Silicon is preferably introduced into the catalyst system in the form of an aqueous colloidal silica (SiO ₂ ) sol. For the catalyst to be most effective, Mo, Ti,
It is believed that the Mn, Bi and Si metal components are somewhat reduced below their highest possible oxidation state. This is accomplished during heat treatment of the catalyst in the presence of an organic reducing agent, such as NH ₃ or an organic complexing agent, which is introduced into the solution system that makes up the catalyst. Reduction of these catalysts can also occur in a reaction vessel in which the oxidation reaction is carried out by passing hydrogen or a hydrocarbon such as ethane, ethylene or propylene through the catalyst bed. Supported or unsupported catalysts can be used in fixed or fluidized beds. The catalyst of the present invention selectively oxydehydrogenates ethane without the addition of diluents other than water to produce ethylene and acetic acid as the final products with the following % conversion, % efficiency and productivity. It can be caused by In this case, in a normal reaction process without addition of water, 1 mol of water is produced for every mol of oxydehydrogenated ethane. The water thus produced during this reaction is approximately
0.05-0.25 mol of acetic acid is produced. However, the addition of water results in the production of an additional amount of acetic acid, approximately 0.25 to 0.95 moles per mole of ethylene produced.

【table】

[Table] Final product Conversion rate % Efficiency % Productivity

Claims (1)

[Claims] 1. A molybdenum-containing catalyst composition for the dehydrogenation of ethane to ethylene, comprising a calcined composition of the formula: Mo ₁ Bi ₀ . ₀₈ Ti _{0 . 08} Mn 0 . ₁₆ Si ₀ . ₁₆ thing.