JPH10316975A - Catalytic reforming process for hydrocarbon and method for inhibiting coking - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit the formation of coke in a catalytic reforming apparatus. SOLUTION: In a process for catalytically reforming a hydrocarbon in the presence of a catalyst in a catalytic reforming apparatus, the formation of coke occurring on the wall of or in the inside of the apparatus is inhibited by incorporating water in an amt. of 50-100 ppm, pref. 60-90 ppm, (based on the hydrocarbon) into a raw material feed comprising a hydrocarbon and hydrogen.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for suppressing coking in an apparatus for performing catalytic reforming of hydrocarbons such as naphtha and a straight-run gasoline feedstock in the presence of a catalyst.

[0002]

BACKGROUND OF THE INVENTION Contact reforming is a process used in the petroleum industry to improve the octane number of naphtha and straight run gasoline. Contact reforming is
Dehydrogenation of cyclohexanes and the like and dehydroisomerization of alkylcyclopentanes and the like to produce aromatic compounds; n
-Isomerization of paraffins; isomerization of alkylcycloparaffins; and reactions of hydrocarbons such as hydrocracking of paraffins to produce gases and coke. Coke generated by hydrocracking accumulates on the catalyst.
Caulking is basically a heavy matter in feed oil,
Alternatively, a heavy component produced by partially polymerizing in feed oil adheres to the wall surface of the equipment, and grows by being exposed to a higher temperature for a long time to form a coke.

[0003] In catalytic reforming, a bifunctional catalyst in which platinum is supported on a porous inorganic oxide support such as alumina is used as a typical catalyst. Platinum is used by adding a reaction accelerator such as rhenium, tin, iridium, and germanium as necessary. As a porous inorganic oxide support other than alumina, bentonite, terra alba, diatomaceous earth, zeolite, silica, activated carbon, magnesia, zirconia, thoria and the like are used.

[0004] Commercial reforming processes are typically performed in either continuous or fixed bed reactors. Fixed bed reactors are usually used in semi-regenerative mode, while circulating and moving bed reactors are used in continuous reforming.

[0005] When a fixed bed reactor is used, the regeneration operation of the catalyst must be carried out periodically. The coke that has accumulated in the reactor is removed in a combustion step during catalyst regeneration. Also, in many cases, fixed bed reactors have high hydrogen / oil ratios and are operated under relatively high reaction pressures, such as 700-3,000 kPa-G, so that coke grows in the reactor. The speed of doing was also low. On the other hand, the halogen on the catalyst is in equilibrium with the moisture in the raw material. Being controlled.

On the other hand, in the moving bed type reactor, the reactor and the regenerator are separate and coke is removed by the regenerator, so that coke is not burned in the reactor. However, in many cases the hydrogen / oil ratio is relatively low,
Since the reactor is operated under a relatively low reaction pressure such as 1,000 kPa-G, the coke in the reactor is in a condition where it can easily grow.

[0007]

SUMMARY OF THE INVENTION Contact reforming,
In particular, in the continuous reforming-type contact reforming, in recent years, the conversion to aromatic hydrocarbons has been improved by significantly lowering the reaction pressure. On the other hand, due to a decrease in pressure, particularly a decrease in hydrogen partial pressure, coke (mainly, metal-catalyzed coke) has been easily generated on a wall surface or the like in the reactor. This coke grows fast,
Due to the large voids, the mechanical strength is not very high.
However, this coke induces the growth of complex and highly crystallized coke, causing mechanical damage to the reactor,
In some cases, continuation of operation may be difficult due to blockage of the flow path.

An object of the present invention is to suppress the generation of coke inside a contact reforming apparatus.

[0009]

Means for Solving the Problems In view of the problems of the prior art, the present inventors have conducted intensive studies in order to suppress coking. As a result, in the contact reforming, the feedstock comprising hydrocarbons and hydrogen was produced. 50 to 10 for hydrocarbons
It has been found that by containing water in an amount of 0 ppm by weight, metal catalyzed coke generated by the catalytic action of metal, mainly iron, can be suppressed on the inner wall and inside of the contact reforming apparatus, and the present invention has been completed. .

As described above, since the generation of coke can be suppressed inside the contact reforming apparatus, stable operation can be realized. Furthermore, the constraints imposed on the operating conditions during contact reforming in order to suppress the formation of coke,
It can be relaxed by the present invention, thereby producing more aromatic compounds and improving the octane number of gasoline.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The present invention can be applied to a reforming system in which a plurality of reaction zones are arranged in series.
Preferably, a preheater is present between the reaction zones so that the temperature of the feed to each reaction zone can be controlled. Preferably, each reaction zone is located in a separate reactor. The invention relates to a system in which at least two reactors, preferably three to five reactors, are arranged in series. Some or all of the reactors may be fixed bed reactors or moving bed reactors, but moving bed reactors provide for coking in the reactor according to the present invention. High industrial value due to suppression.

In a multi-stage reaction zone reforming system, the catalyst composition may be different in different reforming zones, but generally the catalyst is the same in all reactors. However, the capacity of the catalyst usually differs between the reaction zones. The first reactor generally has a small amount of catalyst. This is because the feedstock is rapidly cooled by the highly endothermic reaction that occurs in the first reactor. If a large amount of catalyst is present in the first reactor, the lower portion of the catalyst bed will not be used effectively because the temperature of the feed in the downstream portion of the catalyst bed will be too low.

[0013] The temperature of each reaction zone may be the same or different. The final reaction zone generally has the highest average catalyst bed temperature. Each reactor pressure is almost the same except for the difference in the degree of pressure loss in the piping. It is particularly advantageous for a desired reforming reaction that the temperature and pressure be correlated with the liquid hourly space velocity (LHSV). With different catalyst loadings and different reaction zones, the space velocity of the individual reaction zones can vary considerably.

The hydrogen and feed rate, and the temperature and pressure
By adjusting the contact reforming process conditions,
The operation of the contact reforming device is started. Driving is
Adjustment of key process variables within the following ranges will continue at optimal reforming conditions.

[0015]

[Table 1]

Regeneration methods, whether continuous or batch, are well known in the art. Such a method generally involves the following several steps. That is, a step of contacting the catalyst with an oxygen-containing gas and burning off until substantially all of the carbon is removed, and then contacting the catalyst with an oxygen-containing gas to redisperse the platinum group, a halogen adjustment step, and a catalyst. An optional step of reducing the regenerated catalyst with hydrogen gas before returning to the reactor.

The water content is determined at the entrance of the reactor
50-1 based on hydrocarbon (e.g. naphtha) as raw material
00 ppm by weight, more preferably 60 to 90 parts by weight pp
m. Water may be added to the raw material as long as it is upstream of the heating furnace of the catalytic reforming reactor, may be added to the hydrocarbon as the raw material, or may be added to the circulating hydrogen. For example, water can be easily added to hydrocarbons by blowing steam into the preheated hydrocarbons. If the water content in the hydrocarbon exceeds 100 ppm by weight, the amount of coke produced tends to increase, which is not preferable.

For example, the moisture in naphtha is often 10
４０40 ppm by weight. In this range, failure is often caused by coke generated on the contact reforming device. 0 to 20 ppm by weight of water in hydrocarbon
, The generation of coke can be suppressed to some extent. However, the operation of dehydrating hydrocarbons is economically disadvantageous because it requires installation of a drying facility and replacement of a desiccant as compared with the operation of adding water to hydrocarbons.

The moisture in the hydrocarbon feed has almost no effect on the initial activity of the catalyst. Also, for the activity degradation, there is an equilibrium between the water content in the raw material and the halogen concentration on the catalyst porous solid, and as the water content in the raw material increases, the halogen concentration becomes lower than originally desired. , May lead to deterioration of the activity. However, particularly in a continuous regeneration type apparatus, the regeneration interval of the catalyst is generally short, so that deterioration due to this cause is not a problem.

Rather, the addition of water to the raw material according to the present invention also slightly suppresses the accumulation of coke on the metal of the catalyst. In some cases, wear can be reduced. This, together with the result of the suppression of coking on the device, which is the object of the present invention, is to increase the severity of operation, such as reducing the amount of circulating hydrogen or operating at a lower reaction pressure. Connect.

The catalyst used in the reaction zone consists of a platinum group component supported on a porous solid support. Platinum is preferred as the platinum group component. Further, the porous solid carrier,
Preferably, it consists of a porous refractory inorganic oxide, for example alumina. The platinum group component is present in an amount of 0.01 to 3% by weight, preferably 0.01 to 1% by weight.

Other components besides the platinum group components can be present on the porous solid support. Tin can be added, for example, to 0.1.
It is particularly preferred that it be present in an amount of from 0.01 to 5% by weight and from 0.01 to 2% by weight. Tin significantly improves the yields obtained with platinum-containing catalysts. In general, the reforming action of the catalyst is activated by the addition of halides, especially fluorides or chlorides. Halides provide a limited amount of acidity to the catalyst, which is advantageous for most reforming operations. The catalyst activated with halide has a total halide content of 0.1 to 3% by weight,
The preferred halide is chloride.

The catalyst used in the reaction zone can be, for example, a granular catalyst. This catalyst has, for example, a diameter
Generally, it is 1 to 3 mm, preferably 1.5 to 2 mm, but these values are not restrictive. The catalyst may have a spherical shape. The bulk density of the catalyst is generally 0.4 to
1, preferably 0.5 to 0.9, more particularly 0.55 to 0.
8, but these values are not restrictive.

The feed, that is, the charged raw material is about 27
It is a hydrocarbonaceous stream in the gasoline boiling range of ~ 220 ° C. Such raw materials include straight run naphtha, cracked naphtha,
Examples include, but are not limited to, those derived from both petroleum and synthetic sources, such as Fischer-Tropsch naphtha, coal-derived naphtha, and the like.

Typical feeds are hydrocarbons having about 5 to 12, more preferably about 5 to about 9 carbon atoms. Naphtha or petroleum fractions having a boiling point in the range of about 27-220 ° C, preferably about 50-190 ° C, contain carbon numbers in these ranges. Thus, a typical fraction is usually about 20-
About 80% by volume of both linear and branched paraffins in the range of about C5 to C12; about 10 to 80% by volume of naphthenes in the range of about C6 to C12; and about 5 to 20% by volume of about C6-C1
It contains desirable aromatics belonging to the range of 2.

Generally, although hydrogen is produced by catalytic reforming, hydrogen separated from the effluent of any reaction zone, usually the final reaction zone, is recycled to the first or subsequent reaction zone. Is common. Hydrogen can be mixed with the feed prior to contacting with the catalyst. Increasing the hydrogen / oil ratio can reduce coke production. Hydrogen is preferably introduced into the reforming reaction zone at a rate of 0.5 to 20 moles per mole of feed. Hydrogen may be a mixture with light hydrocarbon gas.

[0027]

EXAMPLES Next, examples of the present invention and comparative examples will be described, but the present invention is not limited to these examples.

The apparatus, catalyst and moisture measuring method employed in the examples or comparative examples of the present invention are as follows. (Reaction tube) The specification of the catalyst reaction tube is 605 mm in overall length, 10 mm in inner diameter, and made of SUS316. (Catalyst) 400 g of γ-alumina sieved to 10 to 16 mesh is collected and impregnated with water to fill the pores. Next, 720 cc of an aqueous solution of 8.5 × 10 ⁻³ mol / l chloroplatinic acid and 1.7 × 10 ⁻² mol / l stannic chloride /
600cc of a 0.1 mol / l hydrochloric acid aqueous solution is added, and the mixture is evaporated to dryness on a sand bath. Then, after drying at 120 ° C. overnight, baking is performed at 400 ° C. for 1 hour. BET of the resulting catalyst
The specific surface area was 200 m ² / g, and the pore volume determined by the nitrogen adsorption method was 0.8 cc / g. This is previously done at 500 ° C for 1
After hydrogen reduction for an hour, it was used for a catalytic reaction test. (Water content measurement method) The water content in desulfurized heavy naphtha was measured by Karl Fischer coulometric titration.

Table 2 shows the properties and composition of naphtha.

[0030]

[Table 2]

(Reaction Method and Product Analysis Method) A raw material hydrocarbon whose water content has been adjusted in advance is supplied to an evaporator at a constant rate (eg, 3.1 g / h) by a micropump. The raw material preheated and vaporized in the evaporator is supplied at a constant preheated flow rate (for example,
(21 ml / min), and the mixture is sent to a catalytic reaction tube heated in an electric furnace. When evaluating the catalytic reaction performance, the catalyst reaction tube is designed to give a predetermined temperature distribution to the catalyst layer in order to predict the reaction performance in a moving bed type commercial apparatus. The temperature was adjusted to 515 ° C. When evaluating the amount of coke generated, the temperature of the metal test piece was set to 570 ° C. to promote coking. The processing amount was set to the liquid hourly space velocity = 1.1 h ^-1 . A part of the product gas obtained by the contact reforming was introduced into a gas chromatograph at 195 ° C., and the gas composition was analyzed.

(Evaluation of Reaction Performance) Since the apparatus employed in the embodiment of the present invention is of a fixed bed type, estimation for predicting the reaction performance in a moving bed type apparatus was performed to evaluate the reaction performance. In this method, an integrated value up to a predetermined time is averaged over time from data on the change over time of the reaction result obtained by a fixed bed type apparatus. The term "predetermined time" means a time during which the amount of coke on the catalyst is equivalent to that of the catalyst at the outlet of the moving bed apparatus. This time corresponds to the catalyst residence time of the moving bed type device, so that a longer time means that the regeneration frequency of the catalyst is less. In Table 3, the residence time is shown as a ratio to the case where the water content in naphtha is 12 ppm by weight and 1.0.

(Evaluation of Amount of Coke Generated on Metal Sample) In order to evaluate the easiness of forming coke, a metal piece was inserted immediately after the catalyst layer using the above-mentioned catalyst reaction tube. The amount of coke produced was determined from the weight increase before and after the reaction of this metal piece.
(Including free coke in the layer containing the metal flakes). Mild steel (SS400), which has no chromium oxide film formed on it and has direct iron exposure to the environment, was used to promote the formation of metal catalyzed coke. The reaction pressure was set to 100 kPa-G in order to promote the formation of coke.

(Embodiment 1) 5 for naphtha and 5 for naphtha
0 wt ppm of water was contained and the amount of coke produced was evaluated at a reaction pressure of 100 kPa-G for 41 hours. Table 3 shows the reaction results. (Examples 2 and 3) The amount of coke produced was evaluated in the same manner as in Example 1 except that the concentration of water in naphtha was changed to the values shown in Table 3. Example 4 A catalytic reaction was carried out at a water concentration in naphtha of 55 ppm by weight and a reaction pressure of 350 kPa-G. The reaction results are shown in Table 3.

(Comparative Examples 1-4) The concentration of water in naphtha was
The amount of coke generated was evaluated in the same manner as in Example 1 except that the values were changed to the values shown in Table 3. (Comparative Examples 5 and 6) A catalytic reaction was carried out in the same manner as in Example 4 except that the concentration of water in naphtha was changed to the value shown in Table 3.

[0036]

[Table 3]

In particular, Examples 1, 2, and 3 and Comparative Examples 2, 3, and 4
As can be seen from the above, by setting the content of water in naphtha to be not less than 50 ppm by weight and not more than 100 ppm by weight, the amount of coke generated on metal was significantly reduced. In Comparative Example 1, the amount of coke generated on the metal was reduced, but a naphtha drying operation was required. Further, when Example 4 is compared with Comparative Examples 5 and 6, Example 4 of the present invention is different from Comparative Examples 5 and 6 in terms of aromatic yield, C _{5 +} yield, hydrogen generation amount, and residence time. On the other hand, there is no inferiority in terms of processing efficiency.

[0038]

As described above, according to the present invention,
In the contact reforming, by adding an appropriate amount of water to the raw material or the recycle gas, it is possible to suppress coke growing on the wall surface or inside the contact reforming device. Moreover, the operation of drying the charged raw materials is not required. As a result, the stability of the continuous regeneration contact reforming operation is improved, and operation under severer conditions is also possible, so that production of an aromatic compound, improvement in octane number, and the like become possible. Therefore, the industrial value of the present invention is extremely high.

Claims (2)

[Claims] 1. A method for catalytically reforming a hydrocarbon in the presence of a catalytic reforming catalyst in a catalytic reforming apparatus, the method comprising the steps of: A process for contact reforming of hydrocarbons, characterized in that it contains water in an amount of from 50 to 100 ppm by weight. 2. In a contact reforming apparatus, when a hydrocarbon is subjected to catalytic reforming in the presence of a catalyst for catalytic reforming, a feedstock containing the hydrocarbon and hydrogen is contained in the raw material containing the hydrocarbon and hydrogen. A method for suppressing coking, characterized by suppressing coke generated inside the contact reforming device by adding water in an amount of 50 to 100 ppm by weight.