Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Halogen or compound containing same
Reexamination Certificate
2002-06-28
2004-08-24
Bell, Mark L. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Halogen or compound containing same
C502S228000, C502S229000, C502S231000, C502S034000, C502S035000, C502S036000
Reexamination Certificate
active
06780815
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to fluorination catalysts. More particularly, the present invention provides methods and systems for preparing catalysts for use in the fluorination of organic compounds and processes of fluorinating organic compounds.
BACKGROUND OF THE INVENTION
There are numerous processes directed to the manufacture of fluorinated organic compounds. Many of these processes involve the reaction of an organic starting material compound, such an alkane and/or an alkene, with hydrogen fluoride (“HF”) in the presence of a fluorination catalyst to produce a desired fluorinated compound or compounds. The product stream from this type of reaction typically includes, in addition to the desired fluorinated organic compound or compounds, unreacted alkane and/or alkene starting materials and unreacted HF. It is common in such processes to separate the unreacted starting materials from the product stream and to recycle those components to the reaction step.
In many prior art processes, the reaction product also includes water. Although water is typically present in relatively minor amounts, its presence in the reaction product stream has been recognized to be undesirable. For example, U.S. Pat. No. 5,334,784—Blake, et al. discloses reacting trichloroethylene and/or 1,1,1-trifluoro-2-chloroethane with HF to produce 1,1,1,2-tetrafluoroethane, using a stoichiometric excess of HF and an increased inventory of catalyst to enhance the conversion efficiency of the process. Blake et al, however, also recognizes that water generated in the reaction or otherwise present in the reactants tends to combine with HF (because of the affinity of HF for water) and, when HF recycle is used, the water content in the product stream tends to build up. Blake et al note that the presence of significant amounts of water in the product stream gives rise to serious obstacles to further treatment of the reaction stream because of the highly corrosive nature of condensate containing HF and water.
Blake et al., and others in the field, have attempted to solve the problem of water in the reaction product by proposing the use of equipment and steps downstream of the fluorination reactor to remove water from the reaction product stream and thereby minimize the amount of water recycled with the unreacted HF.
While approaches of the type suggested by Blake et al. may have some degree of success, they are inherently ineffective in at least one important respect. More particularly, Beck et al. does not acknowledge or recognize that the presence of water generated in or otherwise present during the fluorination reaction may have a deleterious effect on the reaction itself, and the downstream removal solutions are inherently unable to address any such problems.
The present inventors have come to appreciate a need in the art for an improved process for the preparation of fluorination catalyst and a fluorination process, each of which result in improved efficiency, selectivity and/or yield of fluorinated organic compounds (hereinafter sometimes referred to as “fluorocarbons”).
SUMMARY
The present inventors have recognized that water generated during the fluorination of organic compounds has a deleterious effect not only on the downstream processing of the reaction product but also on the fluorination reaction itself. Applicants have also come to appreciate that, for at least certain embodiments of the present invention, the extent to which water is generated during the reaction of organic compounds with HF is impacted by the process that is used to prepare the catalyst, and that certain catalyst preparation methods have an unexpected and surprising ability to produce fluorination catalysts which minimize the generation of water during the fluorination of organic compounds.
Applicants have thus discovered a process for preparing fluorination catalyst which comprises exposing a catalytically active compound to an activating agent under conditions effective to achieve substantial thermal and/or water generation stability at a temperature that is at least about 80 relative percent of the operating temperature of the catalyst and a pressure that is at least about 80 relative percent of the operating pressure of the catalyst. In other words, applicants have found that it is preferred to condition the catalyst with an activating agent at or near its operating conditions, and more particularly to bring the catalyst to or near its operating temperature and pressure while removing a substantial amount, and preferably substantially all of, the water and preferably also the heat generated during the activation step.
Applicants have found that in many embodiments it is important to ensure that the catalyst is brought to a state in which it is at a substantially constant temperature under adiabatic conditions, and without exposure to temperature excursions that would be harmful to the effectiveness and/or activity of the catalyst. It is contemplated that many different combinations of steps may be used in view of the present disclosure to bring the catalyst to this desired condition in which it is ready to be used in the fluorination of organic compounds. It is highly preferred, however, that the step of exposing the catalyst to activating agent is performed without allowing the catalyst temperature to exceed about 125 relative percent of the operating temperature of the catalyst. By conditioning catalytically active compounds in accordance with the present invention, the resulting catalyst has a substantially reduced tendency to produce water when used during the fluorination of organic compounds.
As used herein, the term “catalytically active compound” is intended to refer to compounds that tend to catalyze fluorination of organic compounds and to compounds that can be converted, by the present process or others, to such compounds. It is to be understood that this term encompasses not only fresh, unused catalytically active compounds but also compounds that have been previously used as a fluorination catalyst and subsequently regenerated and/or reactivated by the present process or some other process.
As used herein, the term “substantial thermal stability” is intended to refer to conditions in which the rate of change of temperature has slowed to a substantial extent, and preferably is substantially constant for a measurable period of time, under adiabatic conditions. In other words, a catalyst has reached “substanial thermal stability” when the rate of heat generation during the conditioning step is substantially reduced, and preferably is substantially zero. As explained in more detail hereinafter, the preferred exposing step(s) of the present invention result in an exothermic reaction involving the catalyst, and “substantial thermal stability” is achieved when such exotherms are substantially dissipated. Also, substantial thermal stability as used herein produces and is coincident with a gradual reduction, preferably to a substantially constant, relatively low level, of water generated by the conditioning process or step.
As used herein, the term “operating pressure” refers to the pressure or range of pressures at which the catalyst prepared by the present methods is intended to be used, and/or is used, to fluorinate the target organic compound(s). Likewise, the term “operating temperature” refers to the temperature or range of temperatures at which the catalyst prepared by the present methods is intended to be used, and/or is used, to fluorinate the target organic compound(s).
According to one preferred embodiment, the exposing step comprises exposing the catalytically active compound to an activating agent that comprises an activating compound and an inert carrier wherein the concentration of the activating compound in the activating agent increases during at least a portion of the exposing step. According to other preferred embodiments, the temperature of the activating agent and/or the catalyst is increased at least during a portion of the exposing step. In yet other embodiments, the
Cerri Gustavo
Chiu Yuon
Stuck Jason T.
Tung Hsueh S.
Bell Mark L.
Hailey Patricia L.
Honeywell International , Inc.
Szuch Colleen D.
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