Chemistry of hydrocarbon compounds – Aromatic compound synthesis – By condensation of entire molecules or entire hydrocarbyl...
Utility Patent
1999-06-09
2001-01-02
Knode, Marian C. (Department: 1764)
Chemistry of hydrocarbon compounds
Aromatic compound synthesis
By condensation of entire molecules or entire hydrocarbyl...
C585S455000, C585S456000, C585S468000
Utility Patent
active
06169219
ABSTRACT:
FIELD OF THE INVENTION
The field of the invention is the production of alkylated aromatic compounds.
BACKGROUND OF THE INVENTION
About thirty years ago, it became apparent that household laundry detergents made of branched alkylbenzene sulfonates were gradually polluting rivers and lakes. Solution of the problem led to the manufacture of detergents made of linear alkylbenzene sulfonates (LABS), which were found to biodegrade more rapidly than the branched variety. Today, detergents made of LABS are manufactured world-wide.
LABS are manufactured from linear alkyl benzenes (LAB). The petrochemical industry produces LAB by dehydrogenating linear paraffins to linear olefins and then alkylating benzene with the linear olefins in the presence of HF. This is the industry's most common process. Over the last decade, environmental concerns over HF have increased, leading to a search for substitute processes employing catalyst other than HF that are equivalent or superior to the standard process. Six of the chief criteria for a substitute process are: extent of conversion, linearity of alkylbenzenes, monoalkylbenzene selectivity, linear monoalkylbenzene selectivity, bromine index of alkylbenzenes, and color of the alkylbenzene sulfonates. At this point the definition of several terms are necessary to adequately understand and appreciate what follows.
i. Linearity.
The reaction of linear olefins with benzene in principle proceeds according to the equation,
C
6
H
6
+R
1
CH═CHR
2
→C
6
H
5
CH(R
1
)CH
2
R
2
or C
6
H
5
CH(R
2
)CH
2
R
1
.
Note that the side chain is branched solely at the benzylic carbon and contains only one branch in the chain. Although strictly speaking this is not a linear alkylbenzene, nonetheless the terminology which has grown up around the process and product in fact includes as linear alkylbenzenes those materials whose alkyl group chemically arises directly from linear olefins and therefore includes alpha-branched olefins. Because alkylation catalysts may also induce the rearrangement of olefins to give products which are not readily biodegradable, for example, alpha, alpha-disubstituted olefins which subsequently react with benzene to afford an alkyl benzene with branching at other than the benzylic carbon,
the degree to which the catalyst effects formation of linear alkyl benzenes (LAB) is another important catalyst parameter. The degree of linearity can be expressed by the equation,
D=L/M*100,
where D equals degree of linearity, L equals moles of linear monoalkyl benzene produced, and M equals moles of monoalkyl benzene produced.
ii. Alkylation conversion.
In alkylation, benzene typically is supplied in excess and therefore conversion is defined in terms of the olefin. The degree of conversion at a constant ratio of excess benzene relative to olefin and a constant temperature is a measure of a catalyst's activity in a process. The degree of conversion may be expressed by the formula,
V=C/T*100,
where V equals percent conversion, C equals moles of olefin consumed, and T equals moles olefin initially present.
iii. Monoalkylbenzene selectivity
Monoalkylbenzene selectivity is defined as the percentage of total olefin consumed under reaction conditions which appears as monoalkylbenzene and can be expressed by the equation,
S=(M/C)×100,
where S equals monoalkylbenzene selectivity, M equals moles of monoalkylbenzenes produced, and C equals moles olefin consumed. The higher the monoalkylbenzene selectivity, the more desirable is the process. An approximate measure of monoalkylbenzene selectivity is given by the equation,
S
=
weight
monoalkylbenzene
weight
total
products
×
100
where “total products” includes monoalkylbenzenes, polyalkylbenzenes, and olefin oligomers. At high selectivity (S>85%) the results calculated from the two equations are nearly identical. The after of the foregoing two equations is routinely used in commercial practice because of the difficulty in distinguishing between oligomers and polyalkylbenzenes.
iv. Linear monoalkylbenzene selectivity
Linear monoalkylbenzene selectivity is defined as the percentage of total olefin consumed under reaction conditions which appears as linear monoalkylbenzene and can be expressed by the equation,
R=(L/C)×100,
where R equals linear monoalkylbenzene selectivity, L equals moles of linear monoalkylbenzenes produced, and C equals moles olefin consumed. The higher the linear monoalkylbenzene selectivity, the more desirable is the process. Linear monoalkylbenzene selectivity is related to linearity and monoalkylbenzene lo selectivity by the equation,
R=(D×S)×100.
v. Bromine index
When an olefin alkylates benzene, the primary product is an alkyl benzene with a side chain having no points of unsaturation. However, byproducts may also form as a result of an olefin oligomerizing with another olefin, such as by the reaction,
R
1
CH═CH
2
+R
2
CH═CH
2
→(CH
3
)R
1
CHCH═CH
2
(R
2
)
In addition to dimers, trimers and tetramers may also form. All of the resultant oligomers are olefinic, as are the products of cracking an oligomer. Cracking can occur by one of several reactions and can produce not only monoolefins but also diolefins, such as by the reaction,
(CH
3
)R
1
CHCH═CH
2
(R
2
)→CH
2
═CH(R
2
)C═CH
2
+R
1
H
Thus, the oligomers can, but need not, contain a number of carbon atoms that is a multiple of the number of carbon atoms in the feed olefin. Regardless of the exact nature of the oligomers formed, a useful indication of the extent to which oligomers as opposed to alkyl benzenes are byproducts of the alkylation reaction is the product bromine index.
A standard test for bromine index is UOP Method 304-90, “Bromine Number and Bromine Index of Hydrocarbons by Potentiometric Titraition,” for which information is available from UOP LLC, 25 E. Algonquin Rd., Des Plaines, Ill. 60017, USA. It should be pointed out that there are at least three other standard test methods for bromine index, including ASTM D 1492, “Bromine Index of Aromatic Hydrocarbons by Coulometric Titration;” ASTM D 5776, “Bromine Index of Aromatic Hydrocarbons by Electrometric Titration;” and ASTM D 2710, “Bromine Index of Petroleum Hydrocarbons by Electrometric Titration.” Information on ASTM methods is available from American Society for Testing and Materials (ASTM), 100 Barr Harbor Drive, West Conshohocken, Pa., USA. UOP Method 304-90 is not equivalent,to each of these or other methods of determining bromine index, and therefore it is to be understood that, in the context of measuring bromine index when practicing this invention, only UOP Method 304-90 is to be used for measuring the bromine index. Accordingly, as used hereinafter, the term “bromine index” means bromine index as determined by UOP Method 304-90.
It is useful, when analyzing detergent alkylation streams for bromine index, to report the bromine index on a basis that is not dependent on the feed aromatic (e.g., benzene) content or the paraffin content of the stream. In the case of the feed aromatic, this is because the feed aromatic is usually provided in a molar excess to the feed olefin and this molar excess can vary over a relatively wide range, depending on the particular alkylation catalyst, the desired alkylation catalyst life, etc. The concentration of paraffins, which are generally unreactive at alkylation conditions, can similarly vary widely, depending of the source and nature of the olefinic feedstock. In order to determine the bromine index of a stream on a feed-aromatic-free and paraffin-free basis, a sample of the stream is distilled to remove the feed aromatic (e.g., benzene) Then, an aliquot position of the feed-aromatic-free remainder of the sample is analyzed according to UOP Method 304-90. An aliquot portion of the feed-aromatic-free remainder is a portion of the feed-aromatic-free remainder that has essentially the same composition as the feed-aromatic-free remainder. Next, another a
Detrick Kurt A.
Fritsch Thomas R.
Kojima Masami
Dang Thuan D.
Knode Marian C.
Moore Michael A.
Tolomei John G.
UOP LLC
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