US20100018900A1

US20100018900A1 - PROCESS AND APPARATUS FOR PRODUCING A REFORMATE BY INTRODUCING n-BUTANE

Info

Publication number: US20100018900A1
Application number: US12/179,542
Authority: US
Inventors: Steven L. Krupa; Mark P. Lapinski; Clayton C. Sadler
Original assignee: UOP LLC
Current assignee: Honeywell UOP LLC
Priority date: 2008-07-24
Filing date: 2008-07-24
Publication date: 2010-01-28

Abstract

One exemplary embodiment can be a process for producing a reformate by combining a stream having an effective amount of n-butane and a stream having an effective amount of naphtha for reforming. Generally, the naphtha has not less than about 95%, by weight, of one or more compounds having a boiling point of about 38—about 260° C. as determined by ASTM D86-07. The process can include introducing the combined stream to a reforming reaction zone. Typically, the combined stream has an n-butane:naphtha mass ratio of about 0.10:1.00—about 1.00:1.00.

Description

FIELD OF THE INVENTION

This invention generally relates to a process and an apparatus for producing a reformate.

DESCRIPTION OF THE RELATED ART

In naphtha reforming, it is generally desired to decrease the yield of C1-C5 products and increase the yield of aromatics. Co-feeding a liquefied petroleum gas can reduce the C1-C5 product yield and increase aromatics. However, such co-feeding has failed to identify specific components that can reduce the yield of aromatics and reduce the yield of undesirable products. Particularly, certain components in the liquefied petroleum gas can cause undesirable increases in undesirable reforming species. As a consequence, it can be beneficial to provide a co-feed that can increase aromatic yields while reducing both C5 paraffin yield and C3 yield.

SUMMARY OF THE INVENTION

One exemplary embodiment can be a process for producing a reformate by combining a stream having an effective amount of n-butane and a stream having an effective amount of naphtha for reforming. Generally, the naphtha has not less than about 95%, by weight, of one or more compounds having a boiling point of about 38—about 260° C. as determined by ASTM D86-07. The process can include introducing the combined stream to a reforming reaction zone. Typically, the combined stream has an n-butane:naphtha mass ratio of about 0.10:1.00—about 1.00:100.
Another exemplary embodiment may be a reforming apparatus for producing a reformate. The reforming apparatus can include a reforming reaction zone and a first fractionation zone. Generally, the reforming reaction zone is adapted to receive a stream rich in n-butane and a stream rich in naphtha. Usually, the naphtha has not less than about 95%, by weight, of one or more compounds having a boiling point of about 38—about 260° C. as determined by ASTM D86-07. The first fractionation zone can be adapted to produce a stream rich in at least one of methane and hydrogen, a stream rich in C1-C4, and a stream rich in C5.
A further exemplary embodiment can be a process for producing a reformate. The process can include combining a stream substantially of n-butane and a stream substantially of naphtha, and introducing the combined streams to a reforming reaction zone. Typically, the naphtha has not less than about 95%, by weight, of one or more compounds having a boiling point of about 38—about 260° C. as determined by ASTM D86-07.
The embodiments disclosed herein can provide a reduction in the production of C3, C4, and/or C5 and an increase in the total aromatic yield by co-feeding n-butane. Thus, the vapor pressure of a gasoline product may be lowered. In addition, co-feeding n-butane may be more advantageous as compared to co-feeding other light hydrocarbons.

DEFINITIONS

As used herein, the term “stream” can be a stream including various hydrocarbon molecules, such as straight-chain, branched, or cyclic alkanes, alkenes, alkadienes, and alkynes, and optionally other substances, such as gases, e.g., hydrogen, or impurities, such as heavy metals, and sulfur and nitrogen compounds. The stream can also include aromatic and non-aromatic hydrocarbons. Moreover, the hydrocarbon molecules may be abbreviated C1, C2, C3 . . . Cn where “n” represents the number of carbon atoms in the one or more hydrocarbon molecules. Also, methane can be abbreviated “C1”, isobutane can be abbreviated “iC4”, normal butane can be abbreviated “nC4”, isopentane can be abbreviated “iC5”, and normal pentane can be abbreviated “nC5”. Furthermore, a superscript “+” or “−” may be used with an abbreviated one or more hydrocarbons notation, e.g., C3⁺ or C3⁻, which is inclusive of the abbreviated one or more hydrocarbons. As an example, the abbreviation “C3⁺” means at least one hydrocarbon molecule of three and/or more carbon atoms.
As used herein, the term “zone” can refer to an area including one or more equipment items and/or one or more sub-zones. Equipment items can include one or more reactors or reactor vessels, heaters, exchangers, pipes, pumps, compressors, and controllers. Additionally, an equipment item, such as a reactor, dryer, or vessel, can further include one or more zones or sub-zones.
As used herein, the term “rich” can mean an amount of generally at least about 50%, and preferably about 70%, by mole, of a compound or class of compounds in a stream.
As used herein, the term “substantially” can mean an amount of generally at least about 80%, preferably about 90%, and optimally about 99%, by mole, of a compound or class of compounds in a stream.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic depiction of an exemplary reforming apparatus.

FIG. 2 is a graphical depiction of total aromatic yield versus C7 paraffin conversion for co-feeds methane and n-butane.

FIG. 3 is a graphical depiction of total aromatic yield versus C7 paraffin conversion for co-feeds methane and isobutane.

FIG. 4 is a graphical depiction of iC5+nC5 and C5 olefin yield versus C7 paraffin conversion for co-feeds methane and n-butane.

FIG. 5 is a graphical depiction of iC5+nC5 and C5 olefin yield versus C7 paraffin conversion for co-feeds methane and isobutane.

FIG. 6 is a graphical depiction of iC4+nC4 and C3 yield versus C7 paraffin conversion for co-feeds methane and n-butane.

FIG. 7 is a graphical depiction of iC4+nC4 and C3 yield versus C7 paraffin conversion for co-feeds methane and isobutane.

DETAILED DESCRIPTION

Referring to FIG. 1, a reforming apparatus 100 can include a reforming reaction zone 200, a separation zone 300, at least one fluid transfer zone 400, a first fractionation zone 500, and a second fractionation zone 600. The reforming reaction zone 200 can be any suitable reforming reaction zone.
The reforming reaction zone 200 can receive a combined stream 80. The combined stream 80 can include a stream 60 including an effective amount of n-butane, a stream 70 including an effective amount of naphtha, and a stream 350 including an effective amount of hydrogen to facilitate the one or more reactions in the reforming reaction zone 200. Preferably, the n-butane stream 60 can be rich in or substantially n-butane, and the naphtha stream 70 can be rich in or substantially naphtha. The naphtha can have not less than about 95%, by weight, of one or more compounds having a boiling point of about 38—about 260° C., as determined by ASTM D86-07. Generally, the stream 350 includes an effective amount of hydrogen to facilitate the one or more reactions in the reforming reaction zone 200. Preferably, the stream 350 is rich in or substantially hydrogen. The hydrogen stream 350 can be recycled back from the separation zone 300 and at least one fluid transfer zone 400, as hereinafter described, to be combined with the n-butane stream 60 and the naphtha stream 70.
Generally, the combined stream 80 has an n-butane:naphtha mass ratio of about 0.10:1.00—about 1.00:1.00, preferably about 0.20:1.00—about 0.50:1.00. In addition, the combined stream 80 may have a hydrogen:naphtha mole ratio of no more than about 10:1, and preferably about 2:1—about 8:1. Afterwards, the combined stream 80 can enter the reforming reaction zone 200.
The reforming reaction zone 200 can include at least one reforming reactor, preferably a plurality of reforming reactors operating in serial and/or parallel. The reforming reaction zone 200 can operate under any suitable conditions and include any suitable equipment. An exemplary reforming reaction zone 200 is disclosed by Dachos et al., UOP Platforming Process, Chapter 4.1, Handbook of Petroleum Refining Processes, editor Robert A. Meyers, 2nd edition, pp. 4.1-4.26 (1997). The reforming reaction can dehydrogenate compounds such as naphthenes, can isomerize paraffins and naphthenes, can dehydrocyclicize paraffins, and/or hydrocrack and dealkylate paraffins. The reforming reaction zone 200 can include other equipment such as furnaces and a combined feed heat exchanger.
The one or more reforming reactors orientated in serial and/or parallel flow can include any suitable reforming catalyst, such as a catalyst including a group VIII metal, a group IV a component, such as tin, and an inorganic oxide binder, such as alumina, magnesia, zirconia, chromia, titania, boria, thoria, phosphate, zinc oxide, silica, or a mixture thereof. Suitable reforming reaction catalysts are disclosed in, for example, US 2006/0102520 A1.
Generally, the reforming reaction zone 200 can operate at a temperature of about 300—about 550° C., preferably about 470—about 550° C., and more preferably about 500—about 550° C. The reforming reaction zone 200 can operate at a pressure of about 340—about 5,000 kPa, and a liquid hourly space velocity (LSHV) of about 0.1—about 20 hr⁻¹, preferably about 0.5—about 5.0 hr⁻¹based on the naphtha stream 70. The reforming reaction zone 200 can produce a reforming reaction zone effluent 210.
The separation zone 300 can receive the reforming reaction zone effluent 210 from the reforming reaction zone 200 and provide the stream 310 including hydrogen, preferably rich in or substantially hydrogen, as well as a stream 320 including one or more liquids, preferably rich in one or more liquids. The one or more liquids stream 320 can be provided to the at least one fluid transfer zone 400.
Usually, the at least one fluid transfer zone 400 includes one or more separators or flash drums as well as one or more compressors. In addition, the at least one fluid transfer zone 400 can include several heat exchangers to facilitate the separation of gas and liquid products. Generally, the liquid from the separation zone 300 can be passed through a series of vessels to further separate the liquid from the gas. Usually, the gas includes hydrogen that can either be recycled back in a stream 410 typically rich in hydrogen after being combined with the stream 310 usually rich in hydrogen to form the stream 350 typically rich in hydrogen provided to the reforming reaction zone 200. A portion of the hydrogen separated in the fluid transfer zone 400 can be removed as a hydrogen product 420 to use, e.g., in other parts of a refinery or a petrochemical complex. The separated liquid 430, which typically contains C1¹and possibly other gases such as hydrogen, can be provided to the first fractionation zone 500.
The first fractionation zone 500 can include a column 510, such as a debutanizer, to separate the C4⁻ from other components in the one or more liquids stream 430. The first fractionation zone 500 can provide a stream 540 rich in methane and/or hydrogen, a stream 560 rich in C1-C4, and a stream 580 rich in C5⁺ reformate. The column 510 can produce an overhead stream 520 that generally includes components from the streams 540 and 560. Particularly, the overhead stream 520 from the column 510 can be cooled and routed to a reflux drum 530 where the, typically vapor, stream 540 rich in methane and/or hydrogen can exit the upper portion of the reflux drum 530, and the, usually liquid, stream 560 rich in C1-C4 can exit the lower portion of the reflux drum 530. The stream 540 rich in methane and/or hydrogen can be routed to the at least one fluid transfer zone 400 where the hydrogen can either be recycled back to the reforming reaction zone 200 in the stream 410, or removed as the hydrogen product 420, as described above. The stream 580 rich in C5+ reformate can be taken from the bottom of the column 510 and routed to the gasoline pool. The stream 560 rich in C1-C4 can be routed to the second fractionation zone 600.
The second fractionation zone 600 can receive this stream 560 rich in C1-C4 to produce at least one stream 680 rich in or substantially C1-C3 and at least one stream 672 and/or 676 rich in or substantially C4. Generally, although at least one stream 680 rich in C1-C3 is depicted as being a combination of two other streams 630 and 664 hereinafter described, these streams 630 and 664 that make up the stream 680 may be provided separately to other units within the refinery.
The second fractionation zone 600 can include a first distillation column 620 and a second distillation column 660. The first distillation column 620 can receive the stream 560 to produce the first stream 630 including C1-C2, typically rich in C1-C2, as an overhead stream 630 and a bottom stream 634 including C3-C4, typically rich in C3-C4.
The second distillation column 660 can receive the bottom stream 634 of the first distillation column 620 to produce the overhead stream 664 having C3, typically rich in C3, and at least one bottom stream 676 having C4, typically rich in C4. Optionally, a side-stream 672 having isobutane, typically rich in isobutane, may also be taken. Particularly, the second distillation column 660 can be designed to provide a product that is reduced in the concentration of C3 and isobutane. As an example, the first distillation column 620 can be a de-ethanizer followed by a C3/C4 splitter column 660. As such, the second distillation column 660 can provide the side-stream 672 rich in isobutane and a bottom product 676 rich in n-butane and depleted in isobutane. Thus, the second distillation column 660 in one exemplary embodiment is a 3-way splitter where C3 is produced as an overhead product. In one preferred embodiment, the side-stream 672 includes 100%, by mole, isobutane, and the bottom product 676 includes 100%, by mole, n-butane. Optionally, the stream 676 can be recycled and at least a portion can be combined as the n-butane stream 60 with the naphtha stream 70. Alternatively, the split between isobutane and n-butane may be less severe so that the bottom stream 676 can be rich in n-butane and the side-stream 672 can be rich in isobutane. The bottom stream 676 can provide n-butane, although the stream 676 may contain some isobutane as a co-feed to the naphtha stream 70.

EXAMPLES

The following examples are intended to further illustrate the disclosed embodiments. These illustrations of the embodiments are not meant to limit the claims to the particular details of these examples. These examples can be based on engineering calculations and actual operating experience with similar processes.
Tests are conducted by comparing a co-feed of methane (C1) and naphtha, a co-feed of normal butane or n-butane (nC4) and naphtha, and a co-feed of isobutane (iC4) and naphtha, which may be referred to as a co-feed of, respectively, methane, n-butane, and isobutane. Each test is conducted in a pilot plant using the same reforming catalyst made in accordance with US 2006/0102520 A1. The pilot plant is operated to minimize catalyst de-activation during the test. The catalyst has a chloride content of about 1% by weight. The feedstock is a commercial naphtha with an endpoint of 160° C. The methane, n-butane, and isobutane are provided as pure components. The feed contains 1.1 weight ppm sulfur on a naphtha plus methane basis, or a naphtha plus n-butane or isobutane basis for the respective methane, n-butane, or isobutane co-feed tests. These conditions can provide a sulfur level at the reactor inlet typical of a commercial unit reactor. The temperature of the reactor is varied from 510-540° C. to obtain performance data at different conversion levels of the feedstock. The parameters for the co-feed of methane, n-butane, and isobutane are depicted below in Table 1:

TABLE 1

		nC4	iC4
Parameter	C1 Co-Feed	Co-Feed	Co-Feed

C1, nC4 or iC4 to Naphtha Mass	0.072	0.26	0.26
Ratio (gram/gram)
C1, nC4 or iC4 to Naphtha Mole	0.488	0.488	0.488
Ratio (mole/mole)
LHSV on Naphtha	2.75	2.75	2.75
(hr⁻¹)
LHSV on Naphtha + nC4 or iC4	Not	3.67	3.71
(hr⁻¹)	Applicable
Hydrogen:Hydrocarbon Mole Ratio	8.0	8.0	8.0
Based on Naphtha (mole/mole)
Hydrogen:(Naphtha + nC4 or iC4)	8.0	5.4	5.4
Mole Ratio
(mole/mole)
Pressure (kPa)	446	446	446

The following formula is used to calculate the yield of, respectively, methane, n-butane, isobutane, or hydrogen (each “selected species” collectively abbreviated “ss”) in the reactor product:
Y _ss=(P _ss −L _ss)/N*100%

Y_ss=net mass yield of methane, n-butane, isobutane, or hydrogen based on a naphtha feed;
P_ss=mass flow of methane, n-butane, isobutane, or hydrogen in the reactor effluent;
L_ss=mass flow of methane, n-butane, or isobutane co-feed, or the hydrogen feed; and
N=mass flow of a naphtha feed.

The following formula is used to calculate the yield of species (i) in the reactor product, where (i) is a component other than methane, isobutane, n-butane, or hydrogen in the reactor effluent:
Y _i =P _i /N*100%

Y_i=net mass yield of species based on a naphtha feed;
P_i=mass flow of species in the reactor effluent; and
N=mass flow of naphtha feed.

Referring to FIGS. 2-7, the yields of various compounds are compared for the co-feeds of methane (C1), n-butane (nC4), and isobutane (iC4) and are plotted versus C7 paraffin conversion. The yields for the co-feeds n-butane and isobutane are calculated using the same experimental computations and statistical methods, and are compared against a baseline of feeding naphtha with a methane co-feed. The methane co-feed test is used as a reference to ensure that the same naphtha residence time in the reactor and the same hydrogen partial pressure are used in both experiments. Use of the methane co-feed in the reference experiment allows for these process variables to be held constant while using methane with minimal reactivity under reforming conditions. With these process variables controlled, any yield differences can be attributed to the effect of n-butane or isobutane on the reactions in the reforming reaction zone. A line of best fit is drawn through some of the data points.
Referring to FIGS. 2-3, comparisons are made of the yield of total aromatics for a methane co-feed, an n-butane co-feed, and an isobutane co-feed. As depicted, the n-butane co-feed provides a higher aromatic yield than when co-feeding methane. In marked contrast, referring to FIG. 3, an isobutane co-feed yields less total aromatic yield as compared to the same methane co-feed reference.
Referring to FIGS. 4-5, the sum of isopentane (iC5) and n-pentane (nC5) (may be referred to collectively hereinafter as “C5 paraffins”), and C5 olefin yields for a methane co-feed, an n-butane co-feed, and an isobutane co-feed are compared. As depicted in FIG. 4, a co-feed of n-butane can yield substantially the same amount of C5 paraffins and C5 olefin as a co-feed of methane. However, as depicted in FIG. 5, a co-feed of isobutane can yield higher amounts of C5 paraffins as compared to a co-feed of methane. Particularly, the co-feeding of n-butane yields a lower yield of C5 paraffins as compared to a co-feed isobutane whereas a co-feed of isobutane yields higher amounts of undesirable C5 paraffins. Generally, it is preferred for a reformate product to have less C5 paraffin compounds.
Referring to FIGS. 6-7, a propane plus propylene (collectively may be abbreviated “C3”) yield and iC4 plus nC4 (collectively may be referred to as “C4 paraffins”) yield are compared for a methane co-feed, an n-butane co-feed, and an isobutane co-feed. Referring to FIG. 6, the n-butane co-feed yields superior results with respect to C4 paraffins yield, namely a lower yield as compared to co-feeding methane. In marked contrast, referring to FIG. 7, the co-feed of isobutane demonstrates higher yields of C3 and C4 paraffins as compared to the n-butane co-feed in FIG. 6. Generally, it is preferred for a reformate product to have less C3 and C4 paraffins.
As a consequence, the above testing demonstrates, unexpectedly, the superiority of co-feeding n-butane as compared to isobutane with respect to increasing aromatic content and reducing the undesirable amounts of C3-C5, which are generally undesirable in a reformate product used for, e.g., gasoline. Moreover, the benefit of co-feeding n-butane can be particularly advantageous if existing n-butane is available to provide to the reforming unit without additional capital expense.
Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.
In the foregoing, all temperatures are set forth in degrees Celsius, all parts and percentages are by weight, and all pressure units are absolute, unless otherwise indicated.
From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.

Claims

1. A process for producing a reformate by combining a stream comprising an effective amount of n-butane and a stream comprising an effective amount of naphtha for reforming, wherein the naphtha has not less than about 95%, by weight, of one or more compounds having a boiling point of about 38—about 260° C. as determined by ASTM D86-07, comprising:

A) introducing the combined stream to a reforming reaction zone wherein the combined stream has an n-butane:naphtha mass ratio of about 0.10:1.00—about 1.00:1.00.

2. The process according to claim 1, wherein the combined stream has an n-butane:naphtha mass ratio of about 0.20:1.00—about 0.50:1.00.

3. The process according to claim 1, wherein the reforming reaction zone has a temperature of about 300—about 550° C.

4. The process according to claim 1, wherein the reforming reaction zone has a temperature of about 470—about 550° C.

5. The process according to claim 1, wherein the reforming reaction zone has a pressure of about 340—about 5,000 kPa and a liquid hourly space velocity based on a naphtha feed of about 0.1—about 20 hr⁻¹.

6. The process according to claim 1, wherein the reforming reaction zone has a liquid hourly space velocity based on a naphtha feed of about 0.5—about 5.0 hr⁻¹.

7. The process according to claim 1, further comprising providing a stream with an effective amount of hydrogen for reforming to the reforming reaction zone.

8. The process according to claim 7, wherein the reforming reaction zone has a pressure of about 340—about 5,000 kPa and a liquid hourly space velocity based on a naphtha feed of about 0.1—about 20 hr⁻¹, and the combined stream has an isopentane:naphtha mass ratio of about 0.20:1.00—about 0.50:1.00.

9. The process according to claim 8, wherein the reforming reaction zone has a temperature of about 470—about 550° C.

10. A reforming apparatus for producing a reformate, comprising:

1) a reforming reaction zone adapted to receive a stream rich in n-butane and a stream rich in naphtha wherein the naphtha has not less than about 95%, by weight, of one or more compounds having a boiling point of about 38—about 260° C. as determined by ASTM D86-07; and

2) a first fractionation zone adapted to produce a stream rich in at least one of methane and hydrogen, a stream rich in C1-C4, and a stream rich in C5⁺.

11. The reforming apparatus according to claim 10, further comprising:

at least one fluid transfer zone adapted to receive the stream rich in methane and/or hydrogen, which in turn comprises hydrogen and at least a portion of the hydrogen is recycled to the reforming reaction zone.

12. The reforming apparatus according to claim 10, further comprising:

a second fractionation zone adapted to receive the stream rich in C1-C4 and produce at least one stream rich in C1-C3 and at least one stream rich in C4.

13. The reforming apparatus according to claim 12, wherein the second fractionation zone further comprises:

a first distillation column; and

a second distillation column;

wherein the first distillation column produces a first stream rich in C1-C2 and a bottom stream, and the second distillation column is adapted to receive the bottom stream and produce an overhead stream rich in C3, a side-stream rich in isobutane, and a bottom stream rich in n-butane.

14. The reforming apparatus according to claim 12, wherein the reforming reaction zone is adapted to receive at least a portion of the bottom stream of the second distillation column.

15. The reforming apparatus according to claim 13, wherein the bottom stream is substantially n-butane.

16. A process for producing a reformate, comprising:

A) combining a stream substantially of n-butane and a stream substantially of naphtha wherein the naphtha has not less than about 95%, by weight, of one or more compounds having a boiling point of about 38—about 260° C. as determined by ASTM D86-07, and introducing the combined stream to a reforming reaction zone.

17. The process according to claim 16, wherein the combined stream has an n-butane:naphtha mass ratio of about 0.10:1.00—about 1.00:1.00.

18. The process according to claim 16, wherein the combined stream has an n-butane:naphtha mass ratio of about 0.20:1.00—about 0.50:1.00.

19. The process according to claim 16, wherein the reforming reaction zone has a temperature of about 300—about 550° C.

20. The process according to claim 16, wherein the reforming reaction zone has a pressure of about 340—about 5,000 kPa and a liquid hourly space velocity based on a naphtha feed of about 0.1—about 20 hr⁻¹.