JPH01271489A - Isomerization of c5 and c6 paraffin utilizing distillation zone where raw material and product are united - Google Patents

Abstract

PURPOSE: To efficiently improve an octane number and to obtain a product which is useful as lead-free automobile fuel in good yielding at low cost by separating and distilling a low- boiling-point and a high-boiling-point component obtained by separating a lower hydrocarbon containing feed raw material in a distilling zone after processing them in an isomerizing zone and a reforming zone respectively.

CONSTITUTION: The feed raw material 2 containing 5-7C hydrocarbons are sent in a splitter column as the 1st column of the distilling zone 1 consisting of the 1st column 21 and a 2nd column 22 and distilled, the low-boiling-point component 6 as a side-cut distillation is led to the isomerizing zone 5 and brought into contact with an isomerizing catalyst under isomerizing conditions so selected as to increase the octane numbers of the 5-6C components, and the reaction product is sent to a separating drum 13; and a rich-hydrogen off gas stream 14 is circulated to the isomerizing zone 5, a condensed liquid 16 is sent to a stabilizer 17 to extract a light component from the column top, and a column bottom stream 18 containing a high-octane-value product is returned to the distilling zone 1. A heavy hydrocarbon stream 4 as the high-boiling-point stream, on the other hand, is sent from the bottom of the column 21 to the reforming zone 3, the condensate 10 obtained by separating the reaction product by the separating drum 7 is led to the stabilizer to extract a light component from the column top, and a product 20 having a high octane number is obtained from the column bottom.

COPYRIGHT: (C)1989,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to the catalysis of paraffinic hydrocarbons incorporating a feed fraction from an isomerization unit and a molecule unit for product recovery. Regarding isomerization technology. Also,
The present invention relates to the combination of isomerization and reforming of naphtha boiling range hydrocarbons, which combined process provides a naphtha boiling range product with sufficient octane number for use as an unleaded motor vehicle fuel.

[Background of the Invention] Modern gasoline engines require high octane gasoline. In the past, it was common to use various lead-containing additives to increase octane numbers. As the addition of lead to gasoline is gradually restricted for environmental reasons,
There is an increasing need to modify the structure of hydrocarbons blended into gasoline to achieve high octane numbers. Catalytic reforming and catalytic isomerization are two widely used octane improvement processes.

Ganlin formulations typically include hydrocarbons having boiling points from C4 to less than 205° C. at normal pressure. This range of hydrocarbons includes C4 to C6 paraffins, particularly relatively low octane C5 normal paraffins. 04~C
No. 6 hydrocarbons are the most susceptible to increasing octane numbers by the addition of lead, and have previously been improved by this method. The octane number can also be improved by changing the structure of paraffinic hydrocarbons into branched paraffins or aromatic compounds by isomerization.

C6 and heavier hydrocarbons can be catalytically reformed to increase their octane number.

Since C5 hydrocarbons are not easily converted to aromatics, it is customary to isomerize them to branched isoparaffins.

C6 hydrocarbons can be added to aromatic hydrocarbons by a dehydrocyclization reaction, but this reaction reduces liquid yield. The decrease in liquid yield is due to increased gas production and conversion of hydrocarbons to ^dense materials.

For this reason, C6 paraffin is also supplied to the isomerization device and C6
It is customary to obtain isoparaffins. That is, to improve the octane number, it is customary to use an isomerization reaction for C6 and lower boiling point hydrocarbons, and to use a reforming reaction for C7 plus and higher boiling point hydrocarbons.

It is known to convert feedstocks in the naphtha boiling range in a combined isomerization and reforming process.

U.S. Pat. No. 4,457,832 first reforms a naphtha feedstock, separates a C5-C6 paraffin fraction from the reformed product, and isomerizes the C5-C6 fraction to improve the octane number of these components. A method is adopted in which the C5-C6 isomerization product is recovered and is mixable with the reformed product. U.S. Patent Nos. 4.11N, 599 and 3,761,
No. 392 also shows an isomerization-reforming process,
There, the entire naphtha boiling range feedstock enters a first distillation zone where the feedstock is divided into a light fraction, which is fed to the isomerization zone, and a heavy fraction, which is fed to the reforming zone. . The reformed product obtained from one or more reforming zones is then subjected to additional separation and conversion, including the recovery of aromatics, which is then fed to the isomerization zone. C5-C6 hydrocarbons are obtained.

It is also known in the art to improve octane number by returning at least a portion of the normal paraffins in the isomerization zone effluent to the isomerization zone for additional addition of paraffins to isoparaffins. a separation device;
A flow for recycling C5 paraffin and/or C6 paraffin is described in The Robert A.
Handbook Petroleum Refini
ng Processes, pages 5-49.

Recycling is particularly effective because of the equilibrium relationship between the isomerization reactions of pentane and hexane.

Recycle the effluent from the isomerization zone! ! 41 is
A separation device for separating the straight-run naphtha feed into light and heavy fractions for the isomerization zone and reforming zone includes returning at least a portion of the isomerization zone effluent to the separation device. U.S. Pat. No. 3,018°244 shows such an arrangement in which the pentane fraction is recycled and mixed with fresh feed to remove light components from the feed and to It is fed to a series of fractionation columns for separation into a cut and a heavy fraction for isomerization and reforming.

U.S. Pat. No. 2,946,736 shows a combined isomerization and reforming flow in which at least a portion of the isomerization zone effluent is a hydrotreated naphtha feedstock and a reforming It is mixed with the zone effluent and the mixture is then fed to a fractionation column where it is separated into a light fraction and a light fraction.

This light fraction is further subjected to separation to remove imparaffins and high octane components from the normal paraffins that are fed as raw materials to the isomerization zone.

When lead additives are allowed, C5 and C6 paraffinic hydrocarbons have the greatest octane improvement with the addition of lead additives. Since te additives are relatively inexpensive, improving the octane number of 05 and C6 paraffins by isomerization is not economically attractive. As a result, many existing reformers do not have an isomerization zone and are not equipped to recycle C5 and C6 normal paraffins to improve octane numbers, but simply combine the reformer with a feedstock in the naphtha boiling range. It simply has a splitter to separate light and heavy components. Therefore, it would be highly desirable to provide a method for maximizing the octane number of C5 and C6 normal paraffins using existing separation equipment.

It is known that recycling unconverted normal paraffins to the isomerization zone increases the octane number of the isomerization zone product or the octane number of the isomerization zone product and the reforming zone product as a whole. However, the additional equipment and utilities required for recycling make octane improvement relatively expensive. Therefore, it would be beneficial to be able to increase the octane number without increasing equipment or utilities. Additional equipment is usually required, including recycling equipment including separation columns, pumps, condensers, separators and connecting pipes.

Providing such recycling facilities increases utility in the cost of the energy required to operate them. Both equipment and utilities increase the operating costs of the process, reducing the economic benefit that additional recycling can provide to improve octane, and equipment generally requires capital expenditures, whereas utilities are an over-time cost. Therefore, the reduction in utility has a significant impact on the increased economic benefits obtained by increasing the octane number of the isomerization zone product.

In addition to this, the octane number of the isomerized and reformed hydrocarbon is the octane number of the product produced in both the isomerization and reforming operations. Therefore, the target octane number for gasoline formulations can be achieved by increasing the octane number of the isomerization product, the reformed product, or both.

However, increasing the octane number of the reformed product requires more severe operating conditions, resulting in increased gas production and denser hydrocarbon production. Both of these reduce liquid yield. Therefore, it is desirable to improve the quality of the isomerization zone product to increase its octane number.

Surprisingly, the octane number of the product from the isomerization zone functions as a separation device to separate the feedstock to obtain a feed for the isomerization zone with little or no increase in utility. The improvement was avoided by returning the effluent from the isomerization zone to the fractionation zone where it was carried out and removing the isomerization product stream from the integrated fractionation zone.

Therefore, one of the objects of the present invention is to eliminate the separation equipment necessary to improve the octane number of the product obtained from the catalytic isomerization zone.

Another object of the present invention is to reduce utility costs for recovering and recycling isoparaffins and paraffin fractions from the catalytic isomerization zone.

Another object of the present invention is to provide a process that efficiently combines isomerization and reforming steps in an integrated fractional distillation step.

Yet another object of the present invention is to maximize the liquid yield of gasoline product from a combined isomerization and reforming process.

Yet another object of the invention is to provide a separator d that separates the naphtha boiling range feed into feeds for the reforming zone and the isomerization zone and a separator for recovering the isomerization zone product stream in the same separation. The purpose of this device is to combine a catalytic isomerization process and a catalytic reforming process.

In its most basic embodiment, the present invention combines a naphtha boiling range feedstock with a heavy hydrocarbon stream, which is normally used as the feed to the reforming zone, and a light hydrocarbon stream, which is the feed stream to the isomerization zone. A fractionator integrated with the light paraffin isomerization zone to recover an improved isomerization product stream from a fractionation zone that separates the hydrogen stream and simultaneously receives the effluent from the isomerization zone as a recycle stream. This is a method of operating the reserve zone.

General implementation H of the present invention can be described as a process for upgrading C and C6 baraffin components in C5 and higher boiling feedstocks to high octane components. The feedstock first enters an integrated fractionation zone where it is separated into high and low boiling components. A heavy fraction containing C7 and heavier hydrocarbons is withdrawn from the fractionation zone.

The middle distillate containing C6 and lighter hydrocarbons of low octane number is withdrawn from the fractionation zone and contacted under isomerization conditions with an isomerization catalyst in the isomerization zone, and the normal paraffins of low octane number are converted to high octane number. is converted to isoparaffins. At least a portion of the octane-enhanced effluent from the isomerization zone is recycled to the fractionation zone.

A relatively light hydrocarbon stream containing primarily C6 isoparaffins and low boiling hydrocarbons is withdrawn from the fractionation zone;
It is recovered as an isomerization zone product stream.

In a more particular embodiment, the present invention is a method for upgrading a low octane 05 plus naphtha boiling range hydrocarbon stream to a high octane component. In this embodiment, the naphtha feed stream is sent to an integrated fractionation zone that is operated to produce a bottoms stream containing C7 plus hydrocarbons. The bottoms stream then enters a reforming zone where it contacts a reforming catalyst under reforming conditions to produce a relatively high octane reformed product stream. A side cut stream containing low octane n-hexane and lighter hydrocarbons is also available.
The integrated fractionation zone is withdrawn and sent to an isomerization zone where it is contacted with an isomerization catalyst under isomerization conditions to produce high octane 06 isoparaffins and lower boiling hydrocarbon-rich isomers. A zone effluent stream is generated. At least a portion of the isomerization zone effluent is recycled to the integrated fractionation zone. An overhead product stream containing primarily high octane 06 isoparaffins and lower boiling hydrocarbons is also produced in this integrated fractionation zone. The reformate and overhead product streams are mixed to provide a high octane gasoline stream.

DESCRIPTION OF THE DRAWINGS The accompanying drawings illustrate preferred embodiments of the invention, in which C
The feed stream in the 5+ naphtha boiling point range enters the integrated fraction 1I4i via line 2, in which zone the feed stream passes through line 4.
The reforming raw material fraction is sent to the reforming zone 3 from there, and the light fraction is divided into two light fractions flowing to lines 6 and 19. Among these, the light fraction in line 6 is the isomerization raw material fraction supplied to the isomerization zone 1i15. The effluent from the reforming zone is fed via line 8 to a separation drum 7. An off-gas stream containing a high concentration of hydrogen is conveyed from drum 7 to line 9,
A portion of it is recycled to the reforming zone in line 15.

Line 10 sends the liquid collected in drum 7 to stabilizer tower 11. The isomerization zone effluent enters separation drum 13 via line 12. Hydrogen-rich off-gas is in drum 13
and recycled via line 14 to the isomerization zone. Line 15 supplies make-up hydrogen from drum 7 to isomerization zone 5 . The liquid accumulated in the drum 13 enters the stabilizer tower 17 via the line 1G. Stabilized product liquid from column 17 enters fractionation zone [1 in line 18.

The product components of isomerization zone 5 flow from the top of fractionation zone 1 into line 19 and are mixed with reformed product removed from the bottom of stabilizer 11 in line 20 to provide a high octane gasoline blend.

[The object of the detailed description of the invention is to incorporate a feed separation device into the isomerization zone to improve octane numbers and increase liquid yield while reducing capital and utility costs. This objective is accomplished by utilizing the same separation equipment that separates the naphtha boiling range feedstock to remove at least a portion of the isohexane from the isomerization zone effluent and recover the isomerization zone product. Ru. In this manner, the octane number of the isomerization zone product can be increased with only a small capital outlay for separation equipment and without substantially increasing utility costs. Therefore, the operation of the feedstock separation equipment and isomerization zone is of primary importance to the process of the present invention.

The accompanying drawings illustrate preferred embodiments of the present invention! An embodiment is shown in which the isomerization and reforming processes are integrated. However, what is described below is not intended to limit the invention, nor does it exclude other embodiments with modifications that are possible to those skilled in the art. Additionally, many of the equipment known in these processes have been omitted from the drawings for the sake of brevity, including pumps, compressors, overhead fluid condensers, reboilers, control systems, and the like. These are omitted because they are not necessarily necessary for explaining the present invention.

One of the important requirements of the present invention is the isomerization zone.

The core of the isomerization operation is passing the feed through a reactor containing an acidic isomerization catalyst and maintained at conditions that promote paraffin isomerization. In this case it is preferred to pass the paraffin feed stream through one or more fixed beds contained in a single reaction zone. The conditions necessary to successfully operate the isomerization zone depend on both the feedstock and the catalyst used in the reaction zone. The average reactant temperature is 4
It may be about 30'C (800"F), but preferably 1
It is in the range of 00 to 320°C. A particular embodiment of the invention relates to the isomerization of C and C6 normal paraffins. The inlet temperature of the isomerization zone for these raw materials is 120 to about 315°C.
The particularly preferred range is approximately 150 to 215°C.
It is. The isomerization reaction is an exothermic reaction. 18-35°C depending on the conversion rate and the amount of benzene present in the feed material
temperature rise occurs in the isomerization zone. Benzene is hydrogenated in the isomerization zone, and since this reaction is more exothermic than the isomerization of normal paraffins, benzene has a large effect on the reaction run-off degree; the presence of benzene in the isomerization zone feed is Allowed to minimize fractionation costs.

The pressure in the isomerization zone can theoretically be maintained within a wide range with no limit, but the normal operating pressure range is
10,444 kPa (50-1500 psia).

When operated in combination with the reforming zone, the isomerization zone is preferably operated at a pressure such that a common piped vessel is available. In such cases, the isomerization zone is operated at a pressure of 3550 kPa gauge (500 psia) or less, more preferably about 1775 kPa (250 ps
It is preferred to operate at a pressure of iv).

The hydrocarbons passing through the isomerization zone are usually a mixture with hydrogen, and the ratio of the two is 0.5 hydrogen per mole of hydrocarbon.
~10 moles. The presence of hydrogen at this concentration ensures gas phase conditions and also suppresses coke deposition on the catalyst.

The isomerization reactor has a liquid hourly space velocity of 0.5 to 12. Ohr”1, but the preferred space velocity is 1.0~
6. Ohr”.

A number of suitable catalysts are known for the isomerization of paraffins. A preferred catalyst is a platinum group metal supported on a heat-resistant mei oxide. Preferably, the catalyst is used as a fixed bed in the isomerization zone.

There are no restrictions on the shape of the catalyst, which can be spherical, pellet-like, or extruded.The solid, heat-resistant oxide can be selected from a variety of materials, including silica, alumina, titanium dioxide, and mixtures of these oxides, or natural heat-resistant oxides such as bauxite, bentonite, clay, mordenite, and diatomaceous earth. Among these materials, alumina and mordenite are preferred and can be synthesized. Particularly preferred is substantially anhydrous high purity alumina.

Platinum group metals refer to noble metals other than silver and gold, which are selected from the group consisting of platinum, palladium, germanium, ruthenium, rhodium, osmium and iridium.

These metals differ in activity and selectivity, with platinum and palladium usually being preferred, with the use of platinum being most preferred.

Preferred catalysts contain less than 2 wt% of platinum group components.
However, the preferred m degree of this component is about 0.1 to 0.
5 tons%.

The platinum group components of the catalyst are present in the R-finished catalyst composition as oxides, sulfides, halides, or as elemental metals. There are several suitable methods for preparing the isomerization zone catalyst composition and incorporating the platinum group metal therein. One method is to impregnate a carrier material with an aqueous solution of a water-soluble and decomposable platinum group metal compound. Impregnation can be carried out by soaking the support material in a solution of chloroplatinic acid, ammonium chloroplatinate, bromoplatinic acid or palladium dichloride.

The use of platinum chloride has the advantage that a small amount of halogen can be introduced into the catalyst at the same time as the platinum component.

Particularly preferred isomerization catalyst compositions include sulfur-resistant compositions comprising a Group I noble metal, a hydrogen-form crystalline aluminosilicate, and a surface area of at least 580 wt/Q.
Contains a heat-resistant m-equipped compound.

The composition may also contain a catalytically effective amount of a promoter metal in addition to the Group I noble metals described above. As such a promoter metal.

Tin, lead, germanium, cobalt, nickel, iron, tungsten, chromium, molybdenum, bismuth, indium, gallium, cadmium, zinc, uranium, copper, silver,
Mention may be made of gold, tantalum, 111 or more rare earth metals and mixtures thereof. The crystalline aluminosilicate used in the present invention is a water-free silica alumina having a three-dimensional crystal lattice framework with a suitable pore structure that allows the ingress of reactants and the evacuation of products. Three-dimensional aluminosilicates include synthetic and natural silica-aluminas, including faujasites such as X-type, Y-type, ultrastable Y, L-type, omega-type and mordenite, which are essentially two-dimensional channels. This is an example of crystalline aluminosilicate. A preferred aluminosilicate material in the catalyst composition of the present invention is mordenite. The hydrogen aluminosilicate is mixed with a refractory trim oxide and formed into a catalyst composition. Shaping of the catalyst composition can be carried out by methods known in the art, including oil drop methods and extrusion methods. Hydrogen type aluminosilicate is 50 to about 99.5
*t%, preferably in an amount of 75 to 95 wt%, and the refractory inorganic oxide can be present in an amount of 0.5 to about 50 wt%
] of t%.

Many isomerization catalysts also contain halogen components. The halogen component, referred to in the art as a bound halogen, is approximately 0.05 to about 0.05 e, sw on a dry carrier''
It can be present in an amount of t%.

When the catalyst contains a halogen component, the halogen component is about 0.
The halogen component, preferably in an amount of 5 wt% or more, is usually selected from fluorine and chlorine, with chlorine being particularly preferred.

The halogen component can be incorporated into the carrier material during the process of introducing the platinum group component into the carrier material using a mixture of chloroplatinic acid and hydrogen chloride. Another method uses alumina and a drosol to form an aluminum support material that includes at least a portion of the halogen. Another method of adding halogen is to contact the calcined support material with an aqueous solution of an acid such as hydrogen chloride, hydrogen bromide or hydrogen iodide.

A highly stable isomerization catalyst is disclosed in U.S. Patent No. 2,999,07.
4@ and No. 3.649.704. Further information regarding the preparation and use of isomerization catalysts can be found in U.S. Patent No. 3,442.794, no.
, 238,319 and 4°489,216.

Another important feature of the invention is the feedstock separation equipment and its interconnection with the isomerization zone. Although the novelty of the invention lies, at least in part, in the arrangement of the separation zone and the interconnection of the separation zone and the isomerization zone, the process of the invention does not require separate specialized equipment. Therefore, those skilled in the art of hydrocarbon processing or petroleum processing equipment design will be able to understand the nature of the equipment used in the invention and what it accomplishes, and will be able to design equipment capable of successfully carrying out the method of the invention. According to the present invention, the fractionation zone of the present invention preferably uses a tray-type column with sieve-type trays and an overhead component condensation section and a reboiler, both of conventional design. "Rich" or "enriched" means that the m degree of a specific compound or group of compounds present in a specific flow is 50
Indicates that it exceeds mol%.

Returning again to the drawing, fractionation zone 1 receives naphtha feedstock of the entire boiling point range. Suitable feedstocks contain primarily hydrocarbons from C5 plus up to a final boiling point of about 210°C, preferably up to an n boiling point of 185°C. Other hydrocarbons outside this range may also be included in the feed entering minor fractionation zone 1; the hydrocarbon species present in significant amounts in the feed include paraffins, isoparaffins, naphthenic and aromatic compounds. It is. Such feedstock can be obtained from debutanized naphtha fractions. If a reforming zone is used and both the isomerization catalyst and the reforming catalyst are sensitive to sulfur poisoning, the feedstock can be hydrotreated before introduction to the fractionation zone.

The integrated fractionation zone 1 of the present invention has two inlets for feedstock and for isomerization zone recycle and three outlets, namely for isomerization products, for isomerization feedstock and for heavy hydrocarbons. One or more fractionation columns can be used in the zero fractionation zone 1 comprising: The total number of trays in these fractionation towers is thought to be about 70. Naphtha feedstock with a full boiling point range is introduced near the middle of the fractionator, which is selected to ensure good separation of feedstock components. It is divided into a heavy hydrocarbon fraction, which contains as much as 1,000 yen, and a light hydrocarbon fraction, which has a boiling point of normal hexane or lower. This heavy stream is removed from the fractionation zone as a bottoms stream, which contains small amounts of aliphatic and aromatic C6 hydrocarbons, which are not wasted. The isomerization zone feed is a mid-boiling fraction, which is withdrawn from the fractionation zone as a sidecut. The location of the side cut is chosen to maximize the concentration of n-hexane while limiting withdrawal of C6 isoparaffins and lower boiling components. This side cut may be in liquid phase or gas phase.

Typically, a side cut is located above the raw material introduction site.

At least a portion of the effluent from the isomerization zone returns to the fractionation zone as a recycle stream. This recycle stream is rich in low boiling 05 and C6 isoparaffins and high boiling hydrocarbons such as normal C6 paraffins. Therefore,
These are introduced into the fractionation column at a position above the side cut stream withdrawal section, and the low boiling point isoparaffins are placed at the top of the column.
High-boiling normal paraffins fall to the side cut stream extraction site. It will be readily apparent to those skilled in the art to appropriately select the introduction site of the recycle stream to minimize normal C6 paraffins and maximize C6 isoparaffins in the isomerization product stream withdrawn from band I41 via line 19. Probably.

The upper end of the fractionation zone is designed to remove normal C6 components from the isomerization zone product stream.

Typically, the isomerization zone product stream is withdrawn from the fractionation column as an overhead stream. The isomerization zone product contains C6 isoparaffins and lower boiling components from the feedstock and isomerization zone recycle stream.

After passing through the isomerization zone 5, the side cut fraction flowing through line 6 enters a separator where off-gas is removed and stabilized by depropanation. A typical separation mode is shown in the drawing in which the effluent from isomerization zone 5 enters drum 13 via line 12 and a suitable cooling section collects most of the 04-plus hydrocarbons in condensation. The vapor collected in drum 13 is a hydrogen-rich off-gas stream that is recycled in line 14 to the isomerization zone.

Condensed liquid from drum 13 enters stabilizer column 17 via line 1G, and light components such as ethane and propane are withdrawn at the top, while a bottoms stream containing isomerization zone products is withdrawn via line 18. and recycled to band 1. A variation of this flow is Line 1B
The isomerization zone product is not entirely recycled to zone 1, but a portion thereof is used directly for gasoline formulation.

Such variations are implemented when existing isomerization equipment has the ability to increase the throughput through partial recycling over the throughput through full recycling. However, in order to realize the benefits of the present invention, a substantial amount of the isomerization zone effluent should be recycled on the order of about 10 w%. The isomerization zone product returns to fractionation zone 1 via line 18, which contains a substantial amount of normal C6 paraffin. %, thereby increasing the normal paraffin concentration of the side cut stream fed to the isomerization zone. the result,
The overhead product stream withdrawn from the fractionation zone via line 19 has a very low concentration of C6 normal paraffins;
5 and C6 isoparaffins. Top stream 1
The relatively high isoparaffin concentration of 9 improves the octane number over that obtained with the isomerization zone alone.

Recycling of the relatively hot isomerization zone I11 effluent is believed to provide additional heat to the fractionation zone.

This additional heat application reduces the reboiler load and
Contributing to utility savings, further separation between C6 inparaffins and n-hexane can be performed with little or no extra utility consumption. In fact, in some cases, the utility required to simply separate a naphtha feed stream directly into light and heavy components is slightly higher than the utility of a fractionation column to obtain the sidecut and recycle streams.

In the integrated process of the present invention, the heavy hydrocarbon stream from the bottom of the fractionation zone is sent via line 4 to the reforming zone as shown in Figure 0! ! Like a bridge, modified zone 1
The hydrocarbons entering 14 are mixed with recycled hydrogen which is sent via line 15 to the reforming zone. The reforming zone includes one or more reactors, a feed exchanger, and a heater to increase the temperature of the reactants. The reaction products from the reforming zone typically contain significant amounts of hydrogen and ethane, butane,
Containing other light components such as propane, these are conveyed in line 8 to separation drum 7 through a suitable cooling bag W1 (not shown). After separating the hydrogen-rich gas, the condensate from drum 7 is transferred to stabilizer (stripping) column 11
where light components such as ethane, butane and propane are removed overhead, while a bottoms stream consisting of hydrocarbons in the naphthenic boiling range is collected as product. As already mentioned, the reformed product stream in line 20 and the line 19
The isomerization product streams are mixed at the confluence of lines 20 and 19 to provide a high octane gasoline blend.

The reforming zone used in the present invention has a catalyst bed temperature of 400-
It is operated in the gas phase in the range of 570°C (150 to 105 G"Fl.
) is normally undesirable; other reforming conditions typically require
si, preferably about 790 kPa (100 psia)
The above pressures are included.

In the combined isomerization-reforming process, the liquid hourly space velocity is approximately 0.
．． 2 to about 10br-1, hydrogen to hydrocarbon molar ratio 0.5:
A range of 1 to 10:1 is typical, while liquid hourly space velocities range from 1.0 to 8. The reforming zone typically contains multiple catalyst beds. The catalyst bed inlet temperature is typically 515° C. (960° F.);
It is held under c.

The reforming catalyst typically comprises one or more Group I noble metals (platinum, iridium, rhodium and palladium);
Contains halogens such as chlorine and/or fluorine. These components are supported on a porous, heat resistant carrier material such as alumina. The reforming catalyst may also contain one or more additional catalytic metal components such as ruthenium, germanium or tin. Details of catalysts suitable for catalytic reforming are provided in U.S. Pat. Nos. 3,740,328 and 3,745,1
No. 12, No. 3.948,804 and No. 4,367.1
No. 37 teaches.

Preference is given to using fixed bed reactors. The catalyst can therefore be present in extruded form or in the form of pellets. In contrast, preferred shapes for catalysts for use in moving bed reactors and regenerators are approximately 1764 to 5/3 diameter.
It has a hard spherical shape of 2 inches (0,0397~G, 391 cm). Reforming catalysts are commercially available from many sources.

The configuration of the reforming zone and the composition of the catalyst used in the present invention are not essential elements of the present invention, nor do they limit the features of the present invention. Preferably, the reactor is operated at the same pressure as the isomerization zone reactor; however, in order to clarify the full background of the invention, it is worth describing another reactor system used in the reforming zone. appears to be beneficial. Such reactor systems are moving bed radial flow multi-stage reactors, which are described in U.S. Pat.
No. 652,231, No. 3,692,496, No. 3, 7
No. 06,536, No. 3,785,963, No. 3,82
No. 5.116, No. 3,839.196, No. 3.83
9.197 @ 3,854,887, No. 3.8
S111, No. 662, No. 3,918,930, No.
3.98L824, No. 4,094,814, No. 4,
No. 110,081 and No. 4,403,909. These US patents also describe catalyst regeneration and catalyst moving bed operations and equipment. This reactor system is widely used commercially for naphtha reforming.

In a moving bed system, small amounts of catalyst are periodically removed from the reactor and sent to a regeneration zone. An overview of the regeneration procedure and operating conditions are provided in the aforementioned U.S. Pat. Nos. 3,652,231 and 3,9
No. 81,824, No. 4,094,814, No. 4.09
No. 41817. The catalyst regeneration procedure includes a carbon incineration step, which typically includes a drying step and a halogenation step.

Although there are no particular limitations on the design of the fractionation zone other than the requirements necessary to obtain various fractions of the desired composition, two empty fractionation zones are shown in the drawing.

It is believed that the fractionation zone will normally consist of one large column or, as shown in the drawing, two smaller columns. Two small columns as shown may be used when applying the present invention to an existing reforming operation equipped with a separator for feedstock naphtha separation. In such equipment, an isomerization zone is added and a splitter column is used as the first column from which the reformed raw material and the isomerized raw material are taken out.
a second for receiving the recycle stream and obtaining an overhead component;
A tower is added. Alternatively, an additional column can be provided, which can be connected to the existing column by a circulation line and associated pump. This arrangement is shown in the drawing, where tower 21 is the existing tower. The overhead component from column 21 is conveyed in conduit 23 to the bottom of new column 22. Conduit 24 communicates the bottom of new column 22 with the top of existing column 21. This two-column system further includes an isomerized feed stream,
Inlets and outlets are provided for a side cut stream and a recycle stream. The locations of the side cut and recycle streams are selected in the manner described above.As shown, the recycle conduit 18 typically provides input to the bottom area of the new column 22, and is located at the side of the feedstock. The cut is typically the existing tower 2
It is extracted from near the top of the tower. The isoparaffin product is typically removed from the new column 22 as an overhead component.

The existing condensing device at the top of column 21 can be adapted to contribute to the reflux requirements at the top of column 22.

Also, a pump for the conduit 24 and an accompanying 1lItX
Apart from the 1 system, the reboilers, pumps, etc. already installed for operating the existing column 21 are usually also suitable for operating the two units in combination. Therefore, the installation of an extra tower 22 can be realized with a small investment.

Whether additional separation capacity for additional fractions is obtained in a new separation zone or in a separation zone modified as described above, the additional effluent stream increases the overall utility. It can be obtained without any particular increase. Perform additional fractional separation,
The advantages of high octane numbers thereby obtained are illustrated in the examples below, which are based on studies and engineering calculations of commercial reformer and isomerization unit operations. The example below considers two cases. The examples are six examples illustrating the present invention which combines isomerization and reforming with an integrated fractionation zone as shown in the drawings.
is a comparative example that simply combines an isomerization zone and a reforming zone, where the feedstock is divided into the isomerization zone feedstock and the reforming zone feedstock, and each feed fraction is sent to each zone. It passes through only once and is mixed into the net product.

The composition of the feedstock on each side is given in Table 1 in moles/hr; this feedstock is obtained from crude oil with a boiling point of 2
It is made of hydrocarbons at 00°C and has undergone hydrogenation treatment to remove sulfur and nitrogen compounds. The feedstock is 24,000 barrels/day (3816 m3) on each side.
/day) was supplied to the first fractionating column.

Table 1 Normal butane 7.5C5 isoparaffin 126.9 Normal pentane 1g9. IC5 Naphthene
173C6 isoparaffin
213.8 normal hexane
200.3 benzene
25.0C6 Naphthene 205
．． 0C physoparaffin 215.0 Normal heptane 250. OC7 naphthene 100.0 toluene
50. From OC8 and this! ! Heavy fraction 900.0 Example 1 According to the invention, the feedstock is fed to a fractionator in tray 10. This fractionating column boiler load 41.588BTυ/
hr, :) Densor load 2788 BTII/hr
operated by.

The raw material for the reformer having the composition shown in Table 2 is discharged from the bottom of the fractionation column at approximately 16,800 barrels/day (267 barrels/day).
1 m3/day) to the reforming zone.

A catalyst supporting platinum and rhenium is used on the alumina carrier, and the average pressure is 250 psia (1825 kPa).
, average temperature 515°C (960°F), liquid hourly velocity 1.2
The reforming operation carried out under the conditions of 1.7 wt% hydrogen, 17.6 wt% light gas, and 20 wt% mixture of butane and pentane.
．． 5 wt%, C6 and heavier hydrocarbons 60,2t
Produces a modified product consisting of %. C4 and heavier hydrocarbons are recovered in an amount of 10.400 barrels/day (1654 m3/day) resulting in a reformed product for gasoline blending with a research octane number of 99.0.

Table 2 Reformer For isomerization Isomerization Fractionation tower supply Side recycle tower Top fraction Cut Cru Component normal butane 1.5
43.7 49.7 Benzene 4
．． 9 20.1 4.9 - C8 and heavier fractions 898.3 +, 7 - The other side cut stream serving as the feed stream to the isomerization zone is 12,
000 barrels/day (2035 m3/day) is withdrawn from the fractionator and fed to the isomerization zone.

The relative composition of this side cut stream is shown in Table 2 in moles/hr. In the isomerization zone, the hydrocarbons are mixed with a platinum alumina catalyst containing s, % chlorine and a liquid hourly space velocity of 1. O
hr". The processing conditions in the isomerization zone include a hydrogen to hydrocarbon ratio of 2.1 and a pressure of 450 DSiO (3204 k
Pa) is included. When the side cut stream is processed in the isomerization zone, 12,800 barrels per day (
At a flow rate of 2035 m/day), a product is obtained, the relative composition of which is stabilized by excluding C3 and lighter components, is shown in Table 2. The isomerized product is recycled back to the fractionation column.

A mixture of lighter feed components and isomerization products is withdrawn from the top of the fractionation column, the relative composition of which is shown in Table 2. This overhead stream, upgraded by the isomerization zone effluent, has a research octane number of 86.3. Then, when the overhead fraction is mixed with the reformed product, 17,540 barrels/day (2
7119 m3/day).

Example ■ To demonstrate the benefits of recycling each isomerization zone product to a fractionation zone, as in the process of the present invention, the feedstock is simply separated and each feed fraction is transferred to its respective processing zone once. In this example, the results obtained when only 100% of the total amount of light is allowed to pass are evaluated.

Therefore, the feedstock shown in Table 1 was supplied to the 36-tray separation column at the same flow rate as in the example, and the total amount was 4188 BTU/h.
r no! J wheeler load and 31888Ttl/hr (
D Has a capacitor load. This separation column provides a bottom fraction containing relatively heavy hydrocarbons and an overhead fraction containing relatively light hydrocarbons, the relative molar compositions of which are shown in Table 3.

Table 3 Reformer for isomerization Stabilized feed fraction
Feed fraction Isomerization product normal butane
7.5 17.3 Benzene 4.0 21.0
0. OC8 and heavier components 899.9
- The heavy hydrocarbon fraction is fed to the reformer at 18,900 barrels/day (268,717 days). The reformer operation was the same as in Example I except that the conditions were more severe.

The reaction in the reformer produces 1.9wt% hydrogen and 20% light gas.
．． 7wt%, mixture of butane and pentane 23.5wt%
A product consisting of 56.9 wt% of , C6 and heavier hydrocarbons is obtained. In this case, C4 and heavier hydrocarbons are recovered at a flow rate of 9330 barrels/day (14 g3 m37 days) to provide a research process 102 octane gasoline blending reformate stream.

The top distillate is 7080 barrels/day (1126m” 7 days)
enters the isomerization zone at a flow rate of . Except for the lower throughput, the isomerization zone operates substantially the same as that of the previous example. Treatment of the overhead fraction in an isomerization zone followed by removal and stabilization of C3 and lighter hydrocarbons results in 71
An amount of 20 barrels/day (032 m3/day) is obtained of the isomerization zone effluent, which has an octane number of 83.1 and the relative composition is shown in Table 3. The stabilized reformed product and isomerization zone effluent are mixed and a stream of butane is added to adjust the vapor pressure to approximately 9 ps i, resulting in a research octane number of 95.4 and a motor octane number of 87. Gasoline with O is 16, Goo barrels/day (254413/day)
generated.

Compared to Example H, the inventive process practiced in Example I produces an additional 940 barrels/day (150 m37 days) of gasoline product with the same motor octane number. Also, Example I
The utility required to operate a fractionator to obtain a large number of fractions is slightly lower than that required for a simple separation such as in Example (3). It is therefore surprising that by recycling the isomerization zone w1 effluent to a fractionation column that yields multiple fractions, an additional amount of liquid product can be obtained at the same motor octane number. Of course, in the conventional process, the throughput increases with the addition of the recycle flow, and a correspondingly large isomerization zone is required. However, operation of large isomerization zones requires only a slight increase in utility. Therefore, the benefits of the present invention can be obtained only at the expense of enlarging the feed separation column and increasing the capacity of the isomerization zone.

[Brief explanation of the drawing]

The accompanying drawing is a flow diagram illustrating a preferred embodiment of the method of the invention.

Claims (1)

Claims: 1. a) feeding a feedstock containing C_5, C_6 and C_7 hydrocarbons to a fractionation zone to separate it into high-boiling components and low-boiling components; b) from said fractionation zone; c) withdrawing a relatively heavy bottoms stream containing C_7 plus hydrocarbons; c) withdrawing from said fractionation zone an intermediate sidecut stream enriched in low-octane normal hexane and low-boiling range hydrocarbons, which is isomerized; C_5 and C_6 in the band
contacting an isomerization catalyst under isomerization conditions selected to increase the octane number of the components; d) subjecting a recycle stream comprising at least a portion of the high octane effluent from said isomerization zone to said fractional distillation; e) high octane C_5 and C_ from said fractionation zone;
A method for increasing the octane number of the C_5 and C_6 components of said feed stream comprising withdrawing a relatively light overhead product stream containing 6 isoparaffins and low boiling hydrocarbons. 2. The process of claim 1, wherein the feedstock contains a hydrocarbon stream in the naphtha boiling range from C_5 plus to a final boiling point of 205°C. 3. Feeding a relatively heavy bottoms stream to a reforming zone where it is contacted with a reforming catalyst under reforming conditions selected to produce a high octane effluent; 3. A process as claimed in claim 1 or 2 in which the stream is mixed with said relatively light overhead product stream to obtain a gasoline product stream. 4. a) feeding a hydrocarbon feed stream with a low octane number in the C_5 plus to naphtha boiling range to a fractionation zone to separate it into high boiling components and low boiling components; b) extracting C7 hydrocarbons from this fractionation zone; c) contacting the bottoms stream in the reforming zone with a reforming catalyst under reforming conditions such that a high octane reformed product stream is produced; d) extracting a side cut stream containing n-hexane and low-boiling hydrocarbons from the fractionation zone and feeding it to an isomerization zone; e) isomerizing the side cut stream under isomerization conditions in the isomerization zone; f) supplying at least a portion of the isomerization zone effluent as a recycle stream to a fractionation zone; g) withdrawing from the fractionation zone a high octane overhead product stream comprising C_6 isoparaffins and low boiling hydrocarbons. 5. Mixing at least a portion of said overhead stream with a reforming zone product to obtain a high octane gasoline product stream.
Method described.