Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Halogen or compound containing same
Reexamination Certificate
1999-04-05
2001-01-16
Bell, Mark L. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Halogen or compound containing same
C502S060000, C502S080000, C502S084000, C502S087000, C502S243000, C502S244000, C502S344000, C502S345000
Reexamination Certificate
active
06174834
ABSTRACT:
BACKGROUND OF THE INVENTION
Oxyhydrochlorination processes wherein ethylene, hydrogen chloride, and molecular oxygen are reacted in the presence of oxychlorination catalyst to form 1,2-dichloroethane [CAS 107-06-2], are themselves well known; see U.S. Pat. Nos. 3,256,352; 3,288,868; 3,345,422; 3,378,597; 3,679,373; 4,151,212; and 4,172,052. The process is usually conducted either in a fluidized bed of oxychlorination catalyst particles at elevated temperatures in the range of from 190° C. to 350° C., or in a fixed bed of oxychlorination catalyst particles at elevated temperatures in the range of from 200° C. to 450° C. When ethylene is so oxyhydrochlorinated, satisfactorily high yields of 1,2-dichloroethane may be obtained under moderate reaction conditions. However, the product typically contains objectionable amounts of chloral, i.e., amounts in excess of about 0.2 percent by weight. In addition to being classified as a pollutant, the normal boiling point of chloral is quite close to that of 1,2-dichloroethane. Chloral is therefore both difficult and costly to remove by distillation to produce high purity 1,2-dichloroethane.
Oxychlorination catalysts have been manufactured in the past by milling attapulgus clay with water, extruding the milled clay into pellets, drying the pellets, calcining the dried pellets, grinding the dried pellets and screening to form particles of appropriate size, adding a hot aqueous solution of cupric chloride and potassium chloride to the particles, and drying to remove water and thereby form substantially dry catalyst particles. The addition of the hot aqueous solution of cupric chloride and potassium chloride to the particles is usually accomplished either by spraying the hot solution onto heated clay particles in a tumbling vessel or by spraying the hot solution into a heated fluidized bed of the particles. Rescreening may be performed to verify the correct particle size distribution.
Oxychlorination catalysts have also been made by mixing attapulgus clay, water, an aqueous solution containing cupric chloride and potassium chloride to form a slurry, drying the slurry at 160° C. for 48 hours in a forced draft oven to form a dried cake, breaking up the cake, and grinding the broken cake to −70 to +200 mesh; See, for example, U.S. Pat. No. 4,151,212. See also U.S. Pat. No. 4,172,052 which discloses drying slurries at 105° C. and grinding the resulting cakes.
SUMMARY OF THE INVENTION
A new process has now been found which produces a new oxychlorination catalyst having improved catalytic characteristics. The new catalyst when used for the oxyhydrochlorination of ethylene to form 1,2-dichloroethane has been observed to result in markedly reduced chloral formation as compared to prior catalyst where both the cupric chloride and potassium chloride were sprayed onto preformed pellets or particles. Depending upon conditions, reductions in chloral formation of from 30% to 75% have been achieved.
Accordingly, a first embodiment of the invention is a process for producing oxychlorination catalyst comprising: (a) mixing together wet support material and copper chloride or precursor thereof to form a paste, wherein the wet support material is wet clay, wet silica, wet silica gel, wet alumina, wet diatomaceous earth, or a mixture of two or more thereof; (b) removing water from the paste to produce a substantially dry mixture; and (c) calcining the substantially dry mixture at elevated temperatures of at least 600° C. to produce a calcined mixture; wherein: (d) alkali metal chloride or a precursor thereof is mixed with the wet support material and copper chloride or precursor thereof, to form the paste; or (e) an aqueous solution of alkali metal chloride or precursor thereof is applied to the paste, the substantially dry mixture, the calcined mixture, or two or more thereof, and the water of the aqueous solution is substantially removed.
A second embodiment of the invention is oxychlorination catalyst produced by the process of the first embodiment.
In an oxyhydrochlorination process wherein ethylene, hydrogen chloride, and molecular oxygen are reacted in the presence of oxychlorination catalyst to form 1,2-dichloroethane, a third embodiment of the invention is the improvement wherein the oxychlorination catalyst has been produced by the process of the first embodiment.
In an oxyhydrochlorination process wherein 1,2-dichloroethane, hydrogen chloride, and molecular oxygen are reacted in the presence of oxychlorination catalyst to form perchloroethylene and trichloroethylene, a fourth embodiment is the improvement wherein the oxychlorination catalyst has been produced by the process of the first embodiment.
DETAILED DESCRIPTION OF THE INVENTION
The support material may be any commonly used catalyst carrier, e.g., silica, silica gel, alumina, diatomaceous earth, and the like. If the catalyst is to be used in a fluidized rather than a fixed bed, silica or high silica or alkali metal silicate content clay minerals are preferred support materials, some examples of which are bentonite, kaolite, illite and attapulgite clay minerals. Alumina or high alumina content clay materials, e.g., diaspore and bauxite clays, may be used; however, these have been found to be somewhat more friable and to have a higher attrition rate when used in a fluidized bed than the predominately silica or alkali metal silicate containing clays. Of the clay minerals, attapulgus clay is particularly preferred.
The initial support material may be wet or dry, but water should be present at some point during mixing with the other materials in order to form a paste. When the support material contains insufficient water, water may be added neat, as a solvent for one or more of the added salts, or both. When the support material contains too much water, water may be removed.
The copper chloride is cupric chloride, cuprous chloride or a mixture thereof. Precursors of copper chloride are those copper compounds or metallic copper which are converted to copper chloride under the oxychlorination conditions prevailing in the oxychlorination reactor in which they are used. The more common precursors of copper chloride include copper bromide, copper iodide, copper oxide, metallic copper, and a mixture of two or more thereof. The copper bromide may be cupric bromide, cuprous bromide, or a mixture thereof. The copper iodide may be cupric iodide, cuprous iodide, or a mixture thereof. The copper oxide may be cupric oxide, cuprous oxide, or a mixture thereof. Hydrates of the various copper compounds may be used where they exist.
The alkali metal chloride may be sodium chloride, potassium chloride, lithium chloride, rubidium chloride, cesium chloride, or a mixture of two or more thereof. Potassium chloride, sodium chloride, or a mixture thereof is generally used. The preferred alkali metal chloride is potassium chloride. Precursors of alkali metal chloride are those alkali metal compounds which are converted to alkali metal chloride under the oxychlorination conditions prevailing in the oxychlorination reactor in which they are used. Exemplary precursors of the alkali metal chlorides include potassium bromide, potassium iodide, sodium bromide, sodium iodide, lithium bromide, lithium iodide, rubidium bromide, rubidium iodide, cesium bromide, cesium iodide, and mixtures of two or more thereof. Hydrates of the various alkali metal compounds may be used where they exist.
The quantity of copper chloride or precursor thereof used in the preparation of the catalyst are such that the copper content of the catalyst is from 4 to 15 percent by weight, preferably from 5 to 12 percent by weight based on the total weight of catalyst, i.e., combined weights of metal halides plus support material.
The quantity of alkali metal chloride or precursor thereof used in the preparation of the catalyst is such that the alkali metal content of the catalyst is from 2 to 12 percent by weight, preferably from 3 to 10 percent by weight based on the total weight of catalyst, i.e., combined weights of metal halides plus supp
Bell Mark L.
Hailey Patricia L.
Mitchell William C.
Morris George D.
PPG Industries Ohio Inc.
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