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Process for the production of para-xylene

a production process and para-xylene technology, applied in the field of para-xylene production, can solve the problems of difficult separation of csub>8 /sub>aromatics, general undesirabledealkylation and hydrocracking during catalytic reforming,

Inactive Publication Date: 2012-02-02
CHEVROU USA INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

"The present invention provides a process for producing para-xylene by using a specific type of catalyst and a specific type of feedstock. The process involves a reforming reaction that produces para-xylene and meta-xylene, with a ratio of at least 0.9. The process also involves a hydrocracking reaction that forms a fraction containing at least 10 wt. % C8 paraffinic hydrocarbons. These hydrocarbons are then contacted with the reforming catalyst in a second reaction zone to produce the desired para-xylene and meta-xylene product stream. The technical effect of this invention is to provide a more efficient and selective process for producing para-xylene."

Problems solved by technology

Dealkylation and hydrocracking during catalytic reforming are generally undesirable due to the low value of the resulting light hydrocarbon products.
However, there are two major technical challenges in achieving this goal of maximizing para-xylene yield.
As a result, the para-xylene yield is limited from any refinery C8 stream unless additional processing steps are used to increase the amount of para-xylene and / or to improve the para-xylene recovery efficiency.
Secondly, the C8 aromatics are difficult to separate due to their similar chemical structures and physical properties and identical molecular weights.
However, the commercial utility of these methods depends on the efficiency, cost effectiveness and rapidity of the separation step which, as discussed above, is complicated by the chemical and physical similarity of the different C8 isomers.
However, it is difficult to use conventional fractional distillation technologies to separate ethylbenzene (EB) and the different xylene isomers because the boiling points of the four C8 aromatics fall within a very narrow range, namely from about 136° C. to about 144° C. In particular, the boiling points of para-xylene and EB are about 2° C. apart, whereas the boiling points of para-xylene and meta-xylene are only about 1° C. apart.
As a result, large equipment, significant energy consumption, and / or substantial recycles would be required for fractional distillation to provide effective C8 aromatic separation.
The above described methods are time consuming and costly.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

[0077]A naphtha feedstock comprising greater than 10% C8 paraffinic hydrocarbons, with an ASTM D-2887 simulated distillation shown in Table 1, was used as feed for the process of the invention and the following comparative examples (IBP=initial boiling point, EP=end boiling point). The feedstock composition was characterized by API, RON, and GC analysis with results given in Table 2, where B stands for benzene, T for toluene, X for all three xylene isomers and EB for ethylbenzene while PX / MX stands for the yield ratio of para-xylene to meta-xylene.

TABLE 1ASTM D-2887 simulated distillation of the feedVol. %Temperature, ° F.IBP771016830218502467027390302EP331

TABLE 2Other properties of the feedAPI57.7RON65.9C5+, wt. %99.9Benzene, wt. %0.5Toluene, wt. %1.7Ethylbenzene, wt. %1.7m-Xylene, wt. %1.1p-Xylene, wt. %0.5o-Xylene, wt. %1.1Total BTX + EB, wt. %4.9PX / MX0.46Total C8, wt. %25.4C8 paraffins, wt. %13.7C8 naphthenes, wt. %7.3

example 2

Comparative

[0078]The naphtha feed described in Example 1 was contacted in a fixed-bed reactor containing a commercial amorphous reforming catalyst comprising platinum with a rhenium promoter on an alumina support. The reaction conditions included the temperatures of 885, 895, 905 and 915° F., a pressure of 350 psig, a liquid hourly space velocity (LHSV) of 1.5 hr−1 and a molar ratio of hydrogen to hydrocarbon of 5:1.

[0079]The yield of C5+ liquid, its RON and other properties as well as the hydrogen production obtained under the aforementioned conditions are listed in Table 3, where HC stands for hydrocarbons and H2 / HC for the molar ratio of hydrogen to hydrocarbon at the reactor inlet. A PX / MX ratio of about 0.41 was obtained for all the products at these four temperatures.

TABLE 3Properties of reforming products obtained from acommercial reforming catalyst comprising platinumwith a rhenium promoter on an alumina support.Pressure, psig350LHSV, hr−11.5H2 / HC5:1Temperature, ° F.88589590...

example 3

Invention

[0080]The naphtha feed described in Example 1 was contacted in a fixed-bed reactor containing a ZSM-5 zeolite based catalyst composited with 30 wt. % alumina binder material. The ZSM-5 had a SiO2 / Al2O3 molar ratio of about 500 and was ion exchanged to the ammonium form before incorporating in a 70 wt. % zeolite on 30 wt. % alumina extrudate. The extrudate was impregnated with 0.8 wt. % Pt, 0.38 wt. % Re, 0.35 wt. % Na and 0.3 wt. % Mg by an incipient wetness procedure to make the final catalyst. The reaction conditions included the temperatures of 865, 875, 885, 895, 905 and 915° F., a pressure of 80 psig, a liquid hourly space velocity (LHSV) of 1.0 hr−1 and a molar ratio of hydrogen to hydrocarbon of 2:1.

[0081]The yield of C5+ liquid, its RON and other properties as well as the hydrogen production obtained under the aforementioned conditions are listed in Table 4. The PX / MX ratio of the products produced over the ZSM-5 zeolite based catalyst in this example ranged from 1....

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Abstract

A reforming process using a medium pore zeolite under conditions to facilitate the conversion of C8 paraffinic compounds to para-xylene is provided. Para-xylene is produced at greater than thermodynamic equilibrium concentrations using the process.

Description

FIELD OF THE INVENTION[0001]The present invention provides a process for the production of para-xylene from a C8 containing paraffinic feedstock. A shape selective catalyst comprising a medium pore zeolite with a silica to alumina ratio of at least 40:1 is used during the catalytic reaction.BACKGROUND[0002]Catalytic reforming is one of the basic petroleum refining processes for upgrading light hydrocarbon feedstocks, frequently referred to as naphtha feedstocks. Products from catalytic reforming can include high octane gasoline useful as automobile fuel, aromatics (for example benzene, toluene, xylenes and ethylbenzene), and / or hydrogen. Reactions typically involved in catalytic reforming include dehydrocylization, isomerization and dehydrogenation of naphtha range hydrocarbons, with dehydrocyclization and dehydrogenation of linear and slightly branched alkanes and dehydrogenation of cycloparaffins leading to the production of aromatics. Dealkylation and hydrocracking during catalyt...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C07C5/00
CPCC07C5/41C07C2529/40C07C5/373C07C5/322C07C15/08Y02P20/52
Inventor CHEN, CONG-YANMILLER, STEPHEN J.ZIEMER, JAMES N.LIANG, ANN J.
Owner CHEVROU USA INC
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