Catalyst – solid sorbent – or support therefor: product or process – Regenerating or rehabilitating catalyst or sorbent – Treating with a liquid or treating in a liquid phase,...
Reexamination Certificate
2000-06-14
2003-06-17
Silverman, Stanley S. (Department: 1754)
Catalyst, solid sorbent, or support therefor: product or process
Regenerating or rehabilitating catalyst or sorbent
Treating with a liquid or treating in a liquid phase,...
C502S034000
Reexamination Certificate
active
06579821
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to catalyst reactivation methods. More particularly, this invention relates to methods for reactivating totally or partially deactivated alkylation catalysts with a reactive near-critical, critical or supercritical fluid reactivating agent.
2. Related Technology
Nomenclature
As conventionally accepted in the literature on alkylation, terms such as alkanes, paraffins and paraffinic hydrocarbons will hereinafter refer to open-chain saturated hydrocarbons. The suffix -ene is adopted for straight-chain monounsaturated hydrocarbons, so that a term such as butene refers to at least one of the compounds 1-butene and 2-butene. The suffix -ylene is hereinafter employed to refer to a monounsaturated hydrocarbon that consists of the same number of carbon atoms as expressed by the name. For example, the term butylene refers to at least one of the compounds 1-butene, 2-butene, and isobutylene, the latter compound also is known as 2-methylpropene. Terms such as alkenes, olefins and olefinic hydrocarbons generically refer to monounsaturated hydrocarbons.
The prefix iso- is generically used to refer to branched alkanes or alkenes that have one or more methyl groups only as side chains. Aromatic hydrocarbons refer to hydrocarbons that have at least one aromatic ring and to hydrocarbons which, although strictly not aromatic, contain conjugation to the extent such that they undergo alkylation reactions like aromatic compounds.
The term C
n
describes a hydrocarbon with n carbon atoms, whether the hydrocarbon is linear, branched, paraffinic, olefinic or aromatic. The notation C
n
-C
m
describes at least one hydrocarbon in the set of hydrocarbons such that the number of carbon atoms ranges from n to m for any individual hydrocarbon in the set. The notation C
n≧p
or C
p+
refers to at least one hydrocarbon with at least p carbon atoms, and it often refers to a mixture of hydrocarbons such that the number of carbon atoms is at least p for any individual hydrocarbon in the mixture.
Processes
The term alkylation generically refers to the addition of an alkyl group to a molecule that is to be alkylated. Alkylation of alkenes to produce alkylation products, or alkylate, is an addition of a saturated hydrocarbon (R—H) to an alkene to yield a saturated hydrocarbon of higher molar mass. This reaction is generically represented by the following chemical equation:
Alkylation is extensively used in the petroleum industry to produce medium- or large-mass hydrocarbons from smaller molecules. One of the more important alkylation reactions is the addition of isobutane to 2-butene to produce 2,2,4-trimethylpentane according to the following equation:
This reaction is conventionally carried out in the presence of an acid such as sulfuric acid or anhydrous hydrofluoric acid.
According to the nomenclature previously introduced, the first reactant in equation (1) is an alkane, paraffinor paraffinic hydrocarbon, whereas the second reactant in the same
is equation is an alkene, olefin, or olefinic hydrocarbon that can also correspond in that equation with an alkylene. More specifically, the paraffin which is listed as the first reactant in equation (2) is isobutane, and the alkylene which is listed as the second reactant in the same equation is 2-butene. Furthermore, equations (1) and (2) describe with varying degrees of generality paraffin alkylation, or the addition reaction of a paraffin and an olefin. Equation (2), in particular, describes the addition reaction of an isoparaffin and an olefin where the alkylate is an isoalkane.
The notation used in equation (1) describes a reaction that includes, for example, the reaction of a C
4
-C
8
paraffinic hydrocarbon with a C
2
-C
12
olefinic hydrocarbon to produce a branched paraffinic hydrocarbon. In the particular example provided by equation (2), a C
4
isoparaffin reacts with a C
4
olefin to produce a C
8
isoparaffin.
As indicated above, aromatic hydrocarbons can also be alkylated. For example, benzene can be alkylated with ethylene to produce ethylbenzene, a precursor of styrene, according to the zeolite catalyzed reaction that is described by equation (3):
Ethylbenzene yields, upon dehydrogenation, styrene, which is the simplest and most important member of a series of unsaturated aromatic compounds. The zeolite-catalyzed alkylation of benzene by ethylene has been described in a number of sources. See, for example, Kirk-Othmer Encyclopedia of Chemical Technology, Vol. 21, pp. 770-800, 3rd ed. (1983).
The olefins in equations (1)-(3) are the respective alkylating agents. Generally, in alkylation reactions, the amount of the-reactant to be alkylated exceeds the amount of the alkylating agent. Thus, when an aromatic hydrocarbon is alkylated with an olefin, it is preferred to operate with a molar ratio of the aromatic hydrocarbon to the olefin greater than 1:1, and preferably from about 2:1 to 5:1 as measured by the flow rates into the reaction zone. Similarly, it ispreferable to operate with a paraffin-to-olefin molar ratio greater than 2:1. Preferably, the paraffin-to-olefin molar ratio exceeds 3:1. However, ratios as high as 100:1 can be employed. The use of a large-pore zeolite with a Lewis acid reportedly increases the activity and selectivity of the zeolite, thus permitting effective alkylation at high olefin weight hour space velocity (OWHSV) and low isoparaffin/olefin ratio. The OWHSV is defined as the amount of olefin fed to the reactor per unit catalyst per hour (i.e., g olefin. (g catalyst)
−1
h
−1
).
The principal industrial application of paraffin alkylation is in the production of premium-quality fuels for internal combustion engines. More specifically, alkylation is mainly used to provide a high octane blending alkylate for automotive fuels that also increases the fuel sensitivity to octane-enhancing agents. Alkylate components are typically characterized by clean, low emission burning. Because of these properties, alkylate production capacity is expected to increase as specifications for gasoline become more stringent.
Most commercial alkylations rely on catalytic processes for the production of alkylate. Catalysts used in industrial alkylations have typically been strong liquid acids, such as sulfuric acid and hydrofluoric acid. Other strong acids have been used in laboratory or industrial alkylations. These acids include aluminum trichloride, and super acids such as trifluoromethanesulfonic acid.
In addition to problems related to undesired polymerization and side-reactions, liquid acid alkylation requires the use of a fairly concentrated acid and the replacement of consumed acid. For example, sulfuric acid concentration is controlled above 90% to provide optimum activity and selectivity, and hydrofluoric acid concentration is maintained in the range of 85-95%. These acids, however, are recognized hazardous materials, whose use requires the adoption of periodic hazard reviews of the operating units and the implementation of safety procedures and measures to minimize the probability of accidental releases. Other typically costly measures that must be adopted include control operations to mitigate the detrimental effects of such possible accidents.
Another drawback of the use of liquid acid catalysts is the disposal of sludge formed during alkylation. This waste sludge that is produced by sulfuric acid or hydrofluoric acid catalyzed alkylations is subject to stringent environmental regulations. The regulated waste management operations for the disposal of this sludge add considerable expenses to commercial alkylation.
The residue known as “red oil” is another product derived form liquid acid catalysis that presents disposal and recycling problems. Red oil is predominantly the conjugation product of an acid and alkylate that has to be disposed of, or recycled. Disposal presents a problem that is inherent in the storage, handling and deposit of hazardous substances. Further, recycling is also an expensive operation because it requires the implementatio
Coates Kyle
Fox Robert V.
Ginosar Daniel M.
Thompson David N.
Zalewski David J.
Bechtel Bwxt Idaho LLC
Johnson Edward M.
Silverman Stanley S.
Workman & Nydegger & Seeley
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