Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Reexamination Certificate
2000-08-17
2004-08-17
Silverman, Stanley S. (Department: 1754)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
C502S341000
Reexamination Certificate
active
06777373
ABSTRACT:
INTRODUCTION
This invention relates to an industrial catalyst, its preparation, and its use, especially for the production of EDC by the oxychlorination of ethylene in a fluidizable or fixed bed reactor.
BACKGROUND OF THE INVENTION
The oxychlorination of ethylene to 1,2-dichloroethane (EDC) is known to be catalysed by catalysts containing, inter alia, copper, suitably in the form of its chloride, often in admixture with alkali metal salts, and carried on an alumina support. Such catalysts have been described, as well as the related preparation methods, in several patents. The ethylene oxychlorination reaction
C
2
H
4
+2HCl+½O
2
→C
2
H
4
Cl
2
+H
2
O
exploits a catalyst whose active phase is copper chloride. The first patents claimed a simple catalyst prepared by impregnating a suitable support, often &ggr;-alumina, with a solution containing copper chloride. However, a real development of such catalyst was achieved by adding a further salt, chosen from among the alkali, alkaline-earth or rare-earth metals. Thus, binary, ternary and sometimes quaternary compositions are described in many patents, as well as different preparation methods.
A typical example of a binary composition is described in EP 041330 (PPG) and is a catalyst prepared with copper and potassium chlorides. The claims refer to a real active phase constituted by KCuCl
3
. The method of preparation is based on a co-precipitation of CuCl
2
and KCl on various supports, the preferred one being attapulgite clay. Copper content in the catalyst ranges from 4 to 12% by weight preferably between 7 to 9%. The molar ratio Cu:K is 1:1. Such a catalyst is said to be suitable for fluid bed applications.
European Patent EP 119933 (MONTEPOLIMERI) describes a binary composition based on copper and magnesium, codeposited on the support as chlorides. In this case, the preferred support is &ggr;-Al
2
O
3
, preferably with a relatively high surface area and proper pore volume. The amount of copper in the catalyst lies in the range 1-10% by weight, while the magnesium content goes from 0 to 1 mole per mole of copper. The preparation method includes the use of HCl during the dry impregnation procedure.
European Patent EP 176432 (AUSIMONT) describes a fluidizable catalyst. Copper and magnesium are the metals used and the crucial item in the preparation method is said to be the radial distribution of the active phase inside the support particles. In fact, a catalyst having less copper on the surface of the particles is claimed, with relevant reduction of sticking phenomena. Copper and magnesium content in the catalyst falls between 1 and 10% by weight, preferably between 2 and 6% for copper.
In EP 0278922 (ENICHEM SYNTHESIS) is described a catalyst for fluid bed applications and the method for its preparation based on &ggr;-alumina, Cu and alkali or alkaline earth metals. Copper content ranges from 3 to 7% by weight while from 0.01 to 4% of the aforesaid additives is included. The examples describe a &ggr;-Al
2
O
3
-supported catalyst containing Cu and Ca; a catalyst containing also Mg; and a catalyst which includes Li instead of Mg. All the catalysts were prepared by one-shot impregnation, with an aqueous solution of the salts. The oxychlorination reactions are carried out using an air-based process, operating with an oxygen excess.
U.S. Pat. No. 4,446,249, (GEON) describes the use of a catalyst containing copper on &ggr;-alumina, wherein the support is modified prior to the deposit of copper by incorporating in it from 0.5 to 3.0% by weight, based on the weight of the support, of at least one metal selected from the group consisting of potassium, lithium, rubidium, caesium, alkaline earth metals, rare earth metals and combinations thereof, by admixing a water solution salt of metal(s) with the &ggr;-Al
2
O
3
, support, drying the mix and calcining it at 350 to 600° C. for about 4 to 16 hours. However, in the example in this patent, even though the Cl/C ratio settled is near the stoichiometric value and despite the excess of oxygen (about 60% above the stoichiometric) the HCl conversion to EDC is decidely low with respect to the usual standard conversion required by and achieved in modern industrial plants (>99%).
U.S. Pat. No. 3,624,170 (TOYO SODA) claims a ternary catalytic composition based on CuCl
2
, NaCl and MgCl
2
, the atomic ratio Cu:Na:Mg being 1:0.2-0.7:0.3-1.5. Such catalyst is claimed to avoid the deactivation caused by contamination due to FeCl
3
present inside the stainless steel reactors.
EP-A-0255156 (SOLVAY) describes ternary catalytic compositions containing a mixture of copper chloride, magnesium chloride and an alkali metal chloride which is sodium chloride or lithium chloride, used in precise proportions, which enable a good yield to be achieved in a fluidized bed process for the oxychlorination of ethylene to 1,2-dichloroethane, simultaneously reducing the corrosion of stainless steel reactors as a result, in particular, of a reduction in the sticking and clumping of the particles of catalyst. This document teaches that, for ternary compositions containing copper chloride, magnesium chloride and sodium chloride as an alkali metal chloride, a Na/Cu atomic ratio above 0.2:1 leads to problems of corrosion of the reactor. In contrast, if lithium is used as an alkali metal, no corrosion phenomenon is seen over a wide range of Li/Cu atomic ratios. However, the examples show the appearance of problems of sticking and clumping of the catalyst with compositions containing Li in an Li/Cu ratio above 0.6.
U.S. Pat. No. 4,849,393 (GEON) describes catalysts containing, besides copper chloride and an alkali metal salt, a rare earth metal salt. The catalysts contain from about 2% to about 8% by weight of copper, from about 1% to about 10% by weight of a rare earth metal salt and from about 0.25% to about 2.3% by weight of an alkali metal salt. All the salts are co-deposited on a suitable support by means of the dry impregnation procedure, to give a catalyst which allows high ethylene efficiency and low stickiness. In particular, it is stated that, using copper chloride, potassium chloride and one or more rare earth metal chlorides, an excellent catalyst for fluid bed ethylene oxychlorination is obtained.
More specific is the composition of the catalyst claimed in EP A 0375202 (ICI), in which is described a ternary catalytic composition based on copper chloride, magnesium chloride and potassium chloride. Copper content ranges from 3 to 9% by weight, while that of magnesium and potassium is from 0.2 to 3%. The preferred atomic ratios Cu:Mg:K are 1:0.2-0.9:0.2-09.
U.S. Pat. No. 5,260,247 (SOLVAY) describes a quaternary catalytic composition based on CuCl
2
, MgCl
2
, LiCl and at least one other alkali metal chloride on an inert support (Al
2
O
3
). Also in this patent the support is impregnated with the metal salts in one shot. The examples refer to an air-based oxychlorination process, operating with an oxygen excess of 36% and a Cl/C ratio of 0.95.
The catalytic activity of copper chloride supported on &ggr;-alumina towards the oxychlorination of ethylene to EDC is thus well known and it is also known that several alkali metal salts or alkaline-earth metal salts improve the performance of the catalyst in terms of selectivity and productivity in fixed and fluid bed reactors. In the latter case, the fluidization is particularly critical, especially when the Cl/C ratio is close to 1, because in these conditions the HCl excess induces the phenomenon of stickiness. In the recycle process, where the ethylene is in excess with respect to the HCl, the problem of sticking is negligible and the final target is the maximum HCl conversion achievable operating with a low excess of oxygen, thus maximizing the ethylene yield to EDC. This is also true for fixed bed applications, characterized by a reactant stream very rich in ethylene.
As far as industrial fluid bed oxychlorination reactors are concerned, the main problems are related to: fluidization of the catalyst, abrasion of the reactor, ethylene yield to ED
Caccialupi Letizia
Carmello Diego
Fatutto Pierluigi
Garilli Marco
EVC Technology AG
Johnson Edward
Silverman Stanley S.
Woodcock & Washburn LLP
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