JPH0147519B2 - - Google Patents

Description

Claim 1: Preheating a hydrocarbon feedstock and a hydrogen-containing gas to reforming conditions by indirect heat exchange with the effluent from the final reaction zone in the series of reaction zones; passing through alternating series of catalytic reaction zones and heaters under reforming conditions, the number of heaters in the series being one less than the number of reaction zones, and the mixture is passed through alternating series of contact reaction zones and heaters under re-forming conditions, the number of heaters in the series being one less than the number of reaction zones, and the mixture is heated before entering the first heater. A method of reforming a hydrocarbon feedstock, the method comprising: passing a hydrocarbon feedstock through a first reaction zone.

2. The method of claim 1, wherein the rehoming conditions of each successive reaction zone are stricter than the rehomming conditions of the first zone.

3 The number of reaction zones is 4 and the number of heaters is 3.
The method according to claim 1.

4. The method of claim 1, wherein the inlet temperature of each successive reaction zone in the series is progressively higher than the inlet temperature to the immediately preceding reaction zone.

5 The inlet supply temperature of the first reaction zone is 800〓~
850° and the inlet feed temperature of each successive reaction zone is at least 900°.

6. The number of reaction zones is 4, and the inlets of the series of zones are at least 820〓, 930〓, 935〓, respectively.
〓 and 940〓.

7. The method of claim 1, wherein the molar ratio of hydrogen to hydrocarbon feedstock is from 4:1 to about 6:1.

8. The method of claim 1, wherein the pressure in each reaction zone is at least 100 psig.

9 The pressure in each reaction zone is between 150 psig and
9. The method of claim 8, wherein the pressure is 400 psig.

10. The method of claim 1, wherein the feedstock and hydrogen-containing gas are mixed before passing through a heat exchanger.

11. The method of claim 1, wherein the hydrocarbon feedstock is a petroleum naphtha fraction having a boiling point range of 106 to 390.

12. The method of claim 1, wherein each reaction zone comprises a separate reactor.

13. The method of claim 1, wherein each reaction zone is a separate zone in a common vessel.

14. The method of claim 1, wherein the hydrocarbon feed and the hydrogen-containing gas are separately preheated and then mixed.

TECHNICAL FIELD The present invention relates to contact reforming. More particularly, the present invention relates to multi-stage adiabatic catalytic reforming of petroleum feedstocks. The invention particularly relates to catalytic reforming of petroleum naphtha.

TECHNICAL BACKGROUND OF THE INVENTION Catalytic reforming is a well-known method for improving petroleum fractions into more valuable products. Catalytic reforming is applied to petroleum naphtha fractions, i.e.
It finds particular use in improving petroleum fractions boiling between 100 and 400 to increase their octane number for addition to gasoline motor fuels. Catalytic reforming is becoming increasingly important as environmental regulations tighten the use of lead additives, such as tetraethyl lead, traditionally used to increase the octane number of gasoline motor fuels. it is conceivable that.

In traditional catalytic reforming, the feedstock and hydrogen-containing gas undergo indirect heat exchange (indirect hear
(exchange) and then passed through an alternating series of heaters and reaction zones. Heater means a device for adding thermal energy to a mixture directly or indirectly from a primary energy supply facility such as a gas burner or an oil burner. In prior art systems, the number of heaters is the same as the number of reaction zones, and the feedstock and hydrogen mixture passes through the heaters before entering the first reaction zone.

Each reforming zone includes a fixed or moving bed of a suitable reforming catalyst. Alumina-based catalysts containing platinum and halogens are often used. Promoters such as rhenium, iridium or germanium can be incorporated into the catalyst along with the platinum. Reforming catalysts are well known in the art and are not further described herein.

The rehoming reaction is strongly endothermic. As a result, the temperature of the reaction mixture rapidly drops until it reaches a level at which the reforming reaction proceeds very slowly, if at all. In most cases, the reduction in temperature and consequent termination of the reforming reaction will occur before reforming is complete. To overcome this problem, it has become standard practice in the industry to perform reforming operations in successive stages in a series of reactors. Typically three or four successive reaction zones are used.

In the prior art, the feedstock is passed through a heater before or after mixing with the hydrogen-containing gas to raise the temperature of the feedstock to the reforming temperature before introducing the mixture of feedstock and hydrogen into the first reaction zone.
The effluent from the first reaction zone is reheated in the second stage of the reforming operation by passing it through a second heater before being introduced into the second reaction zone. Similarly, the effluent from the second reforming reaction zone is reheated in the third heater before being introduced into the third reaction zone in the next stage of the reforming operation. Examples of such systems are Webb US Pat. No. 3,011,768 and Greenwood et al. US Pat.
3725248 and Bonacci et al.
U.S. Pat. No. 3,899,411 (Figure 2 of Bonatskii does not show the first heater, but Bonatskii specification column 11, lines 9-14, ``naphtha is brought to reforming temperature in a suitable heater, not shown). ).

The coils for each reaction zone are mounted in a common firebox in heat exchange relationship with the hot combustion gases from the burner flame so that the feed-hydrogen mixture passes through each reaction zone's respective coil before entering each reaction zone. Possibly combining several heaters into a single device. The net result is the same.

In any event, the construction and operation of such heaters contributes significantly to the initial capital investment costs and to the continuous operating costs of the catalytic reforming equipment. of course,
Eliminating or minimizing such costs is highly desirable.

OBJECTS OF THE INVENTION It is therefore an object of the invention to provide an improved multi-step process for catalytic reforming of petroleum feedstocks.

Another object of the present invention is to provide a catalytic reforming process that does not require the feedstock to be passed through a heater before being introduced into the reforming reaction zone at each stage of operation.

It is another object of the present invention to provide a petroleum naphtha catalytic reforming process that does not require a heater to increase the temperature of the feedstock and hydrogen before introducing it into the first stage reforming reaction zone. .

Yet another object of the present invention is to provide a catalytic reforming process that reduces the capital and operating costs of reformer equipment.

SUMMARY OF THE INVENTION These and other objects of the present invention include preheating the feedstock and hydrogen-containing gas to reforming conditions by indirect heat exchange and reforming the mixture of the feedstock and hydrogen-containing gas. The number of catalytic reaction zones and heaters maintained at conditions is one less than the number of reaction zones in the series, providing a process in which the mixture passes through the first reaction zone before entering the first heater. This is achieved by In another aspect of the invention, the petroleum naphtha feedstock and hydrogen-containing gas are in indirect heat exchange relationship with the effluent from the final reaction zone in the series of reaction zones to raise the initial temperature of the feedstock and hydrogen to the reforming temperature. Let it pass. In another aspect of the invention, the re-forming conditions in each successive reaction zone are more severe than the re-forming conditions in the first reaction zone. The hydrocarbon feedstock and hydrogen-containing gas may be mixed before passing through the heat exchanger, or they may be heated separately and then mixed. The reaction zones may consist of individual reactors or they may consist of separate zones in a single vessel.

Surprisingly, the initial heater in a conventional multi-stage reformer can be omitted and by passing the feed-hydrogen mixture in heat exchange relationship with the effluent from the final reaction zone of the reformer. It has been found that it can be brought to rewarming temperatures.
This passes the feed mixture in heat exchange relationship with the effluent from one or more reactors, but does not allow the reforming temperature to be reached in the heat exchanger, and after leaving the heat exchanger and the first reaction It is to be distinguished from prior art devices which have to be passed through a separate heater before introduction into the zone.

[Brief explanation of drawings]

The invention will now be described in detail with reference to the accompanying drawings, which are schematic illustrations of a four-stage reforming apparatus adapted to carry out the method of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic representation of a reforming apparatus 10 consisting of a series of four reforming reaction zones designated as reactors 11, 12, 13 and 14. A feedstock such as petroleum naphtha is introduced into the reformer through inlet piping 15 by pump 16. Hydrogen-containing gas is supplied through line 17 and mixed with the feedstock. The molar ratio of hydrogen to feedstock can vary depending on the nature of the feedstock and the conditions of the reforming reaction. In most cases, the molar ratio of hydrogen to feedstock is 1:
It is between 1 and 10:1. For naphtha feedstocks treated according to the disclosed embodiments, the hydrogen/feedstock molar ratio is preferably from about 4:1 to about 6:1. The mixed feedstock is transferred to heat exchanger 18
Proceeding to step 1, the temperature of the feedstock is raised to at least 800°C in heat exchanger 18. Preferably, the temperature is increased to 825° to 850°.
From heat exchanger 18, the feedstock passes through line 19 and is introduced into the top of reactor 11.

The feedstock passes through a bed of a suitable reforming catalyst material, such as a platinum-containing alumina-based reforming catalyst, in the reactor and reacts to produce an improved product. The catalyst bed can be fixed or mobile, and the flow through this and subsequent catalyst beds in the reactor can be radial or non-radial, as desired. The temperature of the feed mixture decreases rapidly due to the strongly reforming endothermic reaction. Depending on the exact nature of the feedstock, the temperature in the first reactor will drop from about 140° to about 200°. The effluent from the reactor 11 is piped 20
through which it passes to the first heater 21 where it is reheated to the re-forming temperature. Desirably, the feedstock will be heated to a temperature of at least 875°. Preferably, heater 21 maintains the temperature of the effluent from reactor 11 between about 900°C and 930°C.
The temperature will rise to 〓. Inlet piping 22 carries the reheated and partially reformed feed to the top of second reactor 12 where it is further reformed. The temperature of the mixture drops considerably in reactor 12 as a result of the endothermic nature of the reforming reaction. Typically the effluent from reactor 12 is about
It has a temperature not higher than 800〓.

The effluent from the reactor 12 is transferred to the pipe 23 and the heater 2.
4 and pipe 25 to reactor 13, where the same basic operating sequence is repeated. The inlet temperature of the feed to reactor 13 is typically 900
higher, preferably at least higher than 935〓,
The outlet temperature is lower than 900〓. Similarly, the partially reformed feed is transferred to piping 26 and heater 2.
7 and line 28 to reactor 14, the last reactor in the series. The reactor 14 inlet temperature is typically at least about 940° and the outlet temperature is usually within 10° of the inlet temperature.

Initially, the reforming reaction proceeds relatively easily when the feed mixture is introduced into the first reactor. This is because the concentration of non-aromatic compounds in the feed mixture is relatively high. As the reforming process passes through successive stages, the concentration of non-aromatics becomes progressively more dilute and more aggressive reaction conditions are required. Therefore, the reaction conditions in each successive reactor are usually made progressively more severe. As the reforming process approaches completion, the actual reaction volume per unit of feedstock in each reactor will be proportionately lower, and the concomitant temperature drop in each subsequent reactor will usually be lower. The extent of the temperature drop decreases in each successive reactor to facilitate heating the feedstock to progressively higher temperatures before introducing it into each successive reactor.

The pressure throughout the reactor system can be ambient or elevated. Desirably, the reforming reaction is conducted at elevated pressures ranging between 100 psi and about 600 psi. In the disclosed embodiments, the pressure typically ranges between about 150 psi and about 400 psig.

The effluent from the fourth stage reactor 14 is passed directly to the heat exchanger 18 via line 29, which is used to raise the temperature of the initial feedstock/hydrogen-containing gas mixture. Heat exchanger 18 can be any effective countercurrent type exchanger, such as a transient feed flux barrel and tube heat exchanger with either stream on the tube side. From heat exchanger 18, the reformed naphtha and hydrogen-rich gas passes through line 30 to condenser 3.
1 and thence through line 32 to a conventional separator 33, where the condensed reformate is passed from separator 33 via line 34 to further processing as desired, such as a slabilizer (not shown). communicated to process equipment. Hydrogen-containing reformer off-gas leaves separator 33 via line 35. A part of the hydrogen-containing gas is transferred to the compressor 36 and the pipe 3
7 to the hydrogen-containing gas supply pipe 17.

Hydrogen-containing reformer off-gas that does not need to be recycled can be removed via line 42 and collected or used as desired.

The catalyst material can be regenerated by known methods. If a mobile catalyst bed is used in the reaction zone, the removed catalyst can be regenerated externally. When a fixed bed of catalyst is used in a reforming reactor, the catalyst can be removed in situ by periodic substitution of a spare reactor for the reactor regenerating the catalyst or by semi-periodic shutdown of the entire regeneration system. Regeneration is possible, in which case all reactor catalysts are regenerated at once. In the last mentioned case, it is advantageous to first start the regeneration in the final zone and to preheat the oxygen-containing gas stream used to regenerate the first zone in a heat exchanger with the hot off-gas from the final zone. That's true.

Example 1 Consists of alternating series of four reactors and three heaters, with heaters located between the first and second reactors, between the second and third reactors, and between the third reactor, respectively. A hydrocarbon naphtha feedstock is charged to a catalytic reformer located between the reactor and the fourth reactor at a rate of 17,000 barrels per day (operating day). Hydrogen-rich gas also has a hydrogen to hydrocarbon feed molar ratio of 5.0
is fed into the reformer at a rate sufficient to provide a ratio of 1 to 1. The naphtha feedstock has a boiling point range of 106〓 to 390〓 and contains about 52% paraffin and about
Contains 35% naphthenic compounds. The first three reactors each contain a bed of 385 cubic feet of platinum-containing alumina-based reforming catalyst, and the fourth reactor is larger and contains a bed of 914 cubic feet of catalyst. The naphtha feedstock and hydrogen-rich gas are intimately mixed and passed through a heat exchanger where the temperature of the mixture is increased to 825°C.
The hot mixture is then passed through the first reactor where the temperature drops to 720°C. The effluent from the first reactor is heated to 938° in the first heater and then introduced into the second reactor where additional reforming occurs and the temperature of the stream is reduced to 880°. The temperature of the effluent from the second reactor is increased to 941°C in the second heater and the reheated effluent is passed to the third reactor. In the third reactor, the temperature of the stream is reduced to 918°. After leaving the third reactor, the stream is heated to 951°C in a third heater and introduced into a fourth reactor. The average reaction pressure of the system is 338 psig. The effluent leaving the fourth reactor at a temperature of 940° is passed directly through a heat exchanger to provide the heat necessary to preheat the initial feed mixture. Cool the effluent after passing through a heat exchanger, 95
The above research method separates the C ₅ ⁺ reformate product having an octane number from the recycled hydrogen-rich gas stream. Approximately 14,000 barrels of C ₅ ⁺ reformate are produced per operating day at a yield of approximately 83% by volume. .

The foregoing aspects and examples are included for illustrative purposes only and are not intended to limit the scope of the invention. It will be appreciated that many modifications of the disclosed aspects are possible. For example, instead of using individual reactors for each stage of the reforming process, separate reaction zones in a single common vessel can be used. Similarly, the heaters could be located in a single common firebox without departing from the spirit of the invention. Other modifications of the disclosed embodiments may be made by those skilled in the art. Accordingly, the scope of the invention is limited only by the scope of the claims.