Chemistry of hydrocarbon compounds – Purification – separation – or recovery – By contact with solid sorbent
Reexamination Certificate
1999-09-27
2001-04-24
Griffin, Walter D. (Department: 1764)
Chemistry of hydrocarbon compounds
Purification, separation, or recovery
By contact with solid sorbent
C585S826000, C208S31000R
Reexamination Certificate
active
06222088
ABSTRACT:
FIELD OF THE INVENTION
The subject invention relates to a process for the adsorptive separation of hydrocarbons. More specifically, the invention relates to a process for the continuous simulated countercurrent adsorptive separation of monomethyl paraffins or olefins from a mixture containing other hydrocarbons. A preferred application of the process is the separation of C
10
-C
15
monomethyl paraffins from a n-paraffin depleted kerosene boiling range fraction.
BACKGROUND OF THE INVENTION
Most of the detergents in use today are derived from precursor petrochemicals. The currently predominant precursors is linear alkyl benzene (LAB), which is commonly produced by the alkylation of benzene with a long chain linear olefin. The subject invention is directed to the production of monomethyl acyclic olefins and paraffins, which may be recovered as a product in their own right, or used in the production of various petrochemicals as through alkylation or oxygenation. The following description of the invention will mainly address the recovery and use of the monomethyl hydrocarbons in the production of detergent precursor petrochemicals, and in particular the production of alkylbenzene derived detergents.
Several quality characteristics of alkylbenzenesulfonate (ABS) detergents are set by the chemical structure of the alkyl side chain. For instance, linear alkyl groups have the advantage of increased biodegradability. Other characteristics of the detergent such as its effectiveness in hard water and its foaming tendency are also influenced by the structure of the side chain and its constituents. It has recently been determined that highly desirable detergent precursors can be formed from olefins which contain a single methyl side chain on the main alkane chain. This is a departure from the previous preference for straight chain alkanes. The subject invention is specifically directed to the production of monomethyl hydrocarbons for use in the subsequent production of these detergent precursors or ingredients.
BACKGROUND ART
The large utility of detergents and other cleaners has led to extensive development in the areas of detergent production and formulation. While detergents can be formulated from a wide variety of different compounds much of the world's supply is formulated from chemicals derived from linear alkyl benzenes. The compounds are produced in petrochemical complexes in which an aromatic hydrocarbon, typically benzene, is alkylated with an olefin of the desired structure and carbon number. Typically the olefin is actually a mixture forming a homologous series of different olefins having a range of three to five carbon numbers. The olefin(s) can be derived from several sources. For instance, they can be derived from the oligomerization of C
3
or C
4
olefins or from the polymerization of ethylene. Economics has led to the production of olefins by the dehydrogenation of the corresponding paraffin being the preferred route to produce the olefin.
Paraffins having 10 to 15 carbon atoms per molecule are found in the relatively low cost kerosene boiling range fraction of crude oils or processed fractions of crude oil, and therefore recovery of the desired paraffins from kerosene has become the leading commercial source of the olefinic precursors. The production of the olefins starts with the recovery of paraffins of the same carbon number by adsorptive separation from kerosene. The paraffins are then passed through a catalytic dehydrogenation zone wherein some of the paraffins are converted to olefins. The resultant mixture of paraffins and olefins is then passed into an alkylation zone in which the olefins are reacted with the aromatic substrate. This overall flow is shown in U.S. Pat. No. 2,477,382 issued to A. H. Lewis. A more complete description of this integrated process employing paraffin dehydrogenation and alkylation is shown in an article at page 86 of the November, 1984 edition of
Hydrocarbon Processing.
A description of the process and of the use of simulated moving bed adsorptive separation to recover the paraffins from the kerosene boiling range petroleum fraction is provided in a presentation made by R. C. Schulz et al. at the 2nd World Conference on Detergents in Montreux, Switzerland on Oct. 5-10, 1986. This shows several incidental steps in the process such as fractionation and hydrotreating. The subject invention differs from the process shown in this reference in that the paraffins recovered in the subject process are recovered from the stream labeled as the raffinate stream of the adsorptive separation unit, rather than the extract stream as shown in the reference. This is because the reference seeks to recover pure straight chain paraffins while the subject process is directed to the recovery of a branched chain paraffin. The raffinate stream of the reference can be charged into the subject process as the feed stream.
The desirability of detergents based upon mono-methyl alkylbenzenes was disclosed in PCT publication WO 99/07656. This reference also describes in general terms the recovery of the desired mono-methyl paraffins from the raffinate of an adsorptive separation zone using a second adsorptive separation zone. The reference describes several adsorbents including zeolites and silicoaluminophosphates of specific pore sizes and suggests the use of lower molecular weight n-paraffin such as heptane or octane as a desorbent.
The success of a particular adsorptive separation is determined by many factors. Predominant among these are the composition of the adsorbent (stationary phase) and desorbent (mobile phase) employed in the process. The remaining factors are basically related to process conditions. The subject process employs an adsorbent comprising a molecular sieve referred to in the art as silicalite. The use of silicalite in the adsorptive separation of paraffins is described in U.S. Pat. No. 4,956,521 issued to W. K. Volles, which is directed to the production of higher octane gasoline blending components. The use of silicalite and zeolite 5A in the separation of monomethylalkanes is described in an article in the
Journal of Chromatography,
316 (1984) 333-341. Silicalite has also been described as useful in separating normal paraffins from cyclic hydrocarbons and from branched chain hydrocarbons in U.S. Pat. Nos. 4,367,364 and 4,455,444 issued to S. Kulprathipanja and R. W. Neuzil. This separation differs from that performed in the subject process as it corresponds to that done in the previously cited article from the World Conference on Detergents, which is performed to recover normal paraffins.
The unique pore structure of silicalite has also led to efforts to employ it in the separation of linear (normal) olefins. Silicalite also has catalytic properties which can result in undesired conversion of olefins during this separation. The use of silicalite based adsorbents in the separation of linear olefins from nonlinear hydrocarbons and treatments of the silicalite to reduce its catalytic activity are described in U.S. Pat. No. 5,262,144 to McCulloch, U.S. Pat. No. 5,276,246 to McCulloch et al, and U.S. Pat. No. 5,292,990 to Kanter et al.
U.S. Pat. No. 4,992,618 issued to the applicant is directed to the use of a “pre-pulse” technique during the simulated moving bed adsorptive separation of normal paraffins from non-normal paraffins. In this technique a pulse of a non-normal hydrocarbon is injected into the adsorption zone at or just before the injection point of the feed stream. This increases the recovery of the desired normal paraffins and also improves the balance of the recovery across the carbon number distribution of the feed stream. In comparison the subject technique improves the selectivity of the separation of monomethyl paraffins from other non-normal paraffins.
SUMMARY OF THE INVENTION
The invention is an adsorptive separation process for the recovery of monomethyl paraffins or olefins from admixture with other nonnormal paraffins or olefins, e.g., cyclic and multibranched paraffins of the same carbon number. The invention is c
Griffin Walter D.
Nguyen Tam M.
Spears, Jr. John F.
Tolomei John G.
UOP LLC
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