Gas separation: processes – Solid sorption – Organic gas or liquid particle sorbed
Reexamination Certificate
1998-12-11
2002-10-22
Spitzer, Robert H. (Department: 1724)
Gas separation: processes
Solid sorption
Organic gas or liquid particle sorbed
C095S900000, C095S902000, C502S405000, C502S415000
Reexamination Certificate
active
06468329
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
This invention relates to a new adsorbent useful in selective adsorption of unsaturated hydrocarbons, the manufacture of the adsorbent and a separating process employing the same. More specifically, this invention relates to an adsorbent having a high degree of selectivity and affinity for olefin molecules and also having high adsorption capacity for olefins, and a process for producing the same. More specifically, this invention relates to an ethylene and/or propylene separation process employing a specially prepared adsorbent to effectively separate ethylene and/or propylene from a mixed gas containing ethylene and/or propylene together with a component selected from the group consisting of H
2
, He, CH
4
, C
2
H
6
, C
3
H
8
and mixtures thereof, in an efficient manner using a developed adsorbent having a high adsorptive capacity for unsaturated hydrocarbons such as ethylene and propylene.
2. Description of Related Art
Unsaturated hydrocarbons such as ethylene and propylene are basic raw materials in synthetic chemistry. These are produced by naphtha
atural gas cracking or by dehydrogenation of paraffin. Invariably these are obtained as mixtures necessitating separation before their use. Traditionally separations of ethylene from ethane and propylene from propane have been achieved by low temperature and/or high pressure distillation. These separations are highly energy intensive and difficult to achieve. Separation of mixture of ethane-ethylene is carried out by at −25° C. and 320 psig in a distillation column containing over 160 trays and propane-propylene at −30° C. and 30 psig pressure in a distillation column containing over 200 trays. It is said that separations of ethane-ethylene and propane-propylene by distillation are the largest energy consuming separation processes in petrochemical industry. Further, demand for ethylene and propylene is ever increasing.
For the past several years, various researchers have been working on the development of alternative technologies such as adsorption, chemical absorption and membrane separation processes. Of the various alternate technologies, adsorption process appears to be promising. Conventional adsorbents such as activated alumina, activated carbon, silica gel and zeolites do not show good selectivity for olefins over paraffins. Hence, development of a suitable adsorbent has become a key factor for the successful development of adsorption process.
Some of the adsorbents that have been reported for paraffin-olefin separation are crystalline CuCl; ion exchanged zeolites; polymer supported aluminum silver chloride; and copper-containing resins. Most of these adsorbents suffer from one or the other drawbacks such as slow adsorption kinetics, poor adsorption capacity, and/or selectivity. More recently Yang and Kikkinides, and CHO and coworkers have reported more promising adsorbents. Among the adsorbents reported by them, Ag
+
resin and CuCl/Al
2
O
3
showed high olefin adsorption capacity and good selectivity. However, ethylene and propylene sorption kinetics on Ag
+
resin are slow. CuCl/Al
2
O
3
is a CuCl dispersed on &ggr;-Al
2
O
3
by monolayer dispersion technique and hence, is obtained in powder form. For commercial use this adsorbent needs to be formed in to pellets which leads to reduction in adsorption capacity and selectivity. Further, adsorbent formulations prepared using Cu(I) compounds are unstable and easily get oxidized to Cu(I) leading to loss in adsorption capacity and selectivity of the adsorbent. Xie et al., have also reported a series of adsorbents containing Cu(I). These were also prepared in powder form. Hence, these adsorbents also suffer from the above mentioned drawbacks.
SUMMARY OF THE INVENTION
It has now been found that a group of solid adsorbents in the form of pellets/beads have high adsorptive capacity and selectivity for ethylene and/or propylene not known in the prior art and that they can be produced by a simple process as described below. These adsorbents comprise (i) a silver compound and (ii) a support having a sufficiently high surface area on which support said silver compound is supported. These adsorbents are highly stable and are capable of reversibly adsorbing substantial quantity of ethylene and/or propylene at room temperature. The rates of adsorption of ethylene and/or propylene are also very fast in these adsorbents.
It is an object of the present invention to provide a process for producing new highly stable solid adsorbent in pellet/bead form for selective adsorption of unsaturated hydrocarbons, which adsorbent is a composite comprising (a) a silver compound and (b) a suitable support having a sufficiently high surface area, at least a portion of said silver compound being supported by said support, and which adsorbent is obtainable by a process comprising impregnation of silver compound in a said support and heat treatment of the obtained adsorbent. Optionally the adsorbent may also contain a promoter compound.
It is another object of this invention to provide a process for the separation of ethylene and/or propylene from a mixed gas containing ethylene and/or propylene together with another component selected from such as H
2
, He, CH
4
, C
2
H
6
, C
3
H
8
and mixtures thereof, which process comprises passing a stream of said mixed gas through a mass of the adsorbent at a temperature from 0° C. to 100° C. and a pressure from 1 to 100 atmospheres, and releasing the adsorbed ethylene and/or propylene by lowering pressure and/or increasing temperature.
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Brakash Kumar
Cho Soon-Haeng
Chue Kuck-Tack
Han Sang-Sup
Kim Jong-Nam
Korea Institute of Energy Research
Ladas & Parry
Spitzer Robert H.
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