DD297888A7 - Reforming catalyst for the conversion of gasoline hydrocarbons - Google Patents

Abstract

The invention relates to a reforming catalyst for the conversion of gasoline hydrocarbons in aromatics-rich concentrates or in hochoktanige components. The goal of obtaining a catalyst with improved selectivity and high yield stability is achieved by using a catalyst consisting of platinum- and rhenium-containing gamma-Al 2 O 3 moldings with platinum contents between 0.2 and 0.45 * atomic platinum / rhenium ratios between 0.25 and 0.65 and 0.005 to 0.1 * elements of VI. HG of the PSE, in particular Chromium contains. The advantageous effects are achieved in particular when one part of the catalyst material has higher platinum / rhenium ratios compared to the average platinum / rhenium ratio, while another part of this material has lower platinum / rhenium ratios. These different Pt / Re ratios are each realized in the same form. {Reforming catalyst; Petroleum hydrocarbons; Platinum-rhenium-containing gamma-Al 2 O 3 catalyst; Chromium; Platinum-rhenium ratio}

Description

Field of application of the invention

The invention relates to a reforming catalyst which can be used advantageously in refinery operations for the production of aromatics concentrates or fuel components of high octane number by conversion of gasoline hydrocarbons.

Characteristic of bekannton state of the art

Technically proven catalysts for the conversion of petroleum hydrocarbons under reforming are bimetallic catalysts of the system PIaUn-AI ₂ O ₃ , in particular platinum-rhenium and platinum-iridium systems. Platinum-rhenium Al ₂ O ₃ catalysts have become widely used in refining plants.

For the effective use of such catalysts, a number of activation steps are necessary, for. B. a sufficient sulfurization (DE-OS 2455375, DD-PS 203474, US-PS 3578582) or defined water contents in the reduction step (US-PS 4539307, DD-PS 241 264, DD-PS 218630).

In DE-AS 2819088 the preparation of a Pt-Re-Al ₂ O ₃ catalyst is described with good activity and activity-selectivity properties, the particular effects of a selective sulfidation up to sulfur / rhenium atomic ratios of 0.5: 1 to 1.5: 1 can be achieved. Furthermore, the use of a specific Ziegler alumina as a prerequisite for the catalytic activity is unseen.

Numerous teachings are found in connection with Pt-Re-Al ₂ O ₃ catalysts that the Re / Pt ratios should preferably be about one or less than one to achieve maximum liquid yields (eg, US Patent 3,415,737, US Pat -PS 3578582). According to US-PS 3558477, an Re / Pt ratio of less than 0.7 * ü. Rzugt. Also, by further modification with other promoting components, the beneficial effects of Re / Pt ratios of one or less one are confirmed.

According to DE-OS 2 913183, the relative cycle length of a Pt / Re catalyst could be extended if an fWPt ratio in the range of 2.25 to 4 and a highly hydrorefined raw material (sulfur contents below 0.25 ppm) is used. With significantly improved stability, there are hints for unfavorable yields (Example 3 in DE-OS 2913183). Apparently, the catalytic behavior of such catalysts is not without problems, since z. B. according to EP 83875 catalysts with increased Re contents werdp.i used only in the downstream reaction zones in the flow direction. Catalysts with increased Re contents in the first reaction zones of the catalytic reforming obviously lead to increased cleavage and yield losses. Also according to DE-OS 3038231 is a catalyst with increased Re content only in the last reaction zone.

In contrast, US Pat. No. 4,764,267 proposes a reforming process in which catalysts with increased rhenium contents corresponding to Re / Pt weight ratios greater than 1.7 are used in all reforming stages. According to this teaching, the not unproblematic peculiarities of using rhenium-rich catalysts are apparently solved by the fact that in the last reaction zones catalysts with at least 0.5 mol% higher Re content than the Re / Pt ratio in the first reaction zones , are used. The overcoming of possible undesired cleavage reactions on rhenium-rich catalysts is achieved in this case by a combination of at least two different catalysts, which must be clearly different from each other in their Re / Pt ratios.

The clearly pronounced cleavage reactions of special rhenium-rich catalyst variants are also used for the targeted reduction of the hydrogen content in hydrocarbon-containing hydrogen for special hydro-catalytic reforming.

The well-known good catalytic! Properties of the systems Pt / Re- and Pt / Ir-Al ₂ O ₃ can also be improved by further promoter components.

Thus chromium-modified Pt / Re catalysts are described in DD-PS 223077, in which a uniform distribution of the active components is to be ensured by a special impregnation, which advantageously results in the catalytic properties.

Particularly favorable process parameters are described in EP 252605 for a Pt / Re / Ir catalyst. In addition to extremely low sulfur contents in the raw material to be processed, a high content of the valuable metals in the catalyst of 0.9% by mass must be required for the process parameters which are particularly favorable with regard to the reaction pressure and the hydrogen supply. Data on yield stability are not made.

The combination of a Pt-Ir Kotalysators with additions of Cr ₂ O ₃ leads according to DD 212192 to catalysts that are characterized in addition to good activity and selectivity, by low Hydrogenolyseaktivitsten and therefore make no extreme demands on sulfurization in the start-up phase You are beyond good reactivatable. The effects described are bound to the catalyst system described and are achieved only by maintaining narrow concentration ranges for the components mentioned.

According to DD-PS 247792 fluorine-promoted platinum catalysts are proposed, which should ensure the dehydrogenative reforming in high selectivity for relatively high reaction pressures between 3 and 6 MPa. However, these reaction pressures are to be assessed as unfavorable for high reforming powers. Selective effects on Pt-Al ₂ O ₃ catalysts for the dehydrogenation of naphthenes and the dehydrocyclization of paraffins are also described for tin and lead modifications (DD-PS 138509.138559). The transfer to technically relevant raw materials is obviously still problematic because the effect is limited to very low reaction pressures. High aromatization activity, an essential partial function of a reforming catalyst, can be achieved in accordance with US Pat. No. 3,554,901 by a Pt-Pd-Co ₂ O 3 catalyst based on aluminum oxide. Due to the particular very high C ₂ OrGehalt of 5 to 25%, the use of such a catalyst leads to high aromatics, but only at the expense of relatively high gasification levels are achieved and thus adversely affect the yields of liquid hydrocarbons. The above effects are apparently bound to very low reaction pressures and extremely low space velocities. The problem of yield stability with increasing reaction temperatures remains open.

As an alternative to technically relevant pressures between 0.8 and 2 MPa a Pt / Sn / Cr-A ^ Oj catalyst is proposed according to DD-PS 224326, the Fhtin and chromium in a graded distribution having an advantageous effect. Unsatisfactory here, despite undoubtedly achieved progress selectivity decreases at elevated reaction temperatures. A similar Katalysatoryätem is also the subject of DE-AS 2460560, in the dear Pt, Sn and chloride, the elements chromium, molybdenum and manganese and small amounts of sulfur are used as catalyst promoters. The advantageous effects described are due essentially to the tin modification and give a high catalytic activity for the aromatization of n-heptane at very low reaction pressures.

Object of the invention

The aim of the invention is a reforming catalyst which is characterized by improved selectivity and high yield stability in the conversion of gasoline hydrocarbons.

Darling of the essence of the invention

The object was to improve the performance of known reforming catalysts in terms of selectivity property and yield stability in the production of aromatics-rich reformates or hochoktaniger components. This object is achieved by a reforming catalyst for the recovery of aromatic hydrocarbons or aromatically rich hochoktanigen fuel components from hydroraffinated Banzinkohlenwasserstoffgemischen under hydroreforming conditions based on platinum and rhenium-containing porous gamma A ^ GyFormlinge by inventively the catalyst at platinum contents of 2 to 4.5g / kg atomic platinum / rhenium ratios between 0.25 and 0.65 and elements of Vl. Subgroup or compounds thereof in amounts of 0.05 to 1 g / kg, based on the respective element.

In a particularly advantageous form, the catalyst has platinum contents of 2 to 3.5 g / kg average platinum / rhenium ratios between 0.30 and 0.60 and contains 0.1 to 0.8 g / kg of chiomium, calculated as chromium III-oxide. The mean platinum / rhenium ratios according to the invention at relatively low platinum contents in combination with the stated contents of chromium oxide are essential for achieving the objective. Such catalyst compositions lead to high selectivities and thus high Fiüssigausbeuten at the same time high yield stability even at high reaction temperatures. The catalysts of the invention are not associated with the disadvantages of reduced liquid yields in the production of high octane reformates as described for catalysts having higher rhenium contents compared to the platinum contents.

Further advantages in the solution according to the invention result from the fact that, while maintaining the average atomic platinum / rhenium ratio of 0.30 to 0.60 in the catalyst, proportions of the catalyst material in the range from 5 to 40% have a platinum / rhenium ratio between 0, 40 and 0.90 and have proportions of 5 to 40% such ratios between 0.1 and 0.5. It is essential that these portions of the catalyst material with different platinum / rhenium Ratio ^; , _o en each present in the same catalyst molding. In addition to the already mentioned advantages of the catalysts according to the invention, another is that no increased requirements in terms of the removal of

Heteroatomhaltigon compounds must be collected, as they are well known for bimetallic catalysts.

Thus, the above advantages are accessible without much effort in Rafffineriebetrieben.

A mechanical mixture of catalyst moldings, wherein the mixed moldings in each case have different platinum / rhenium ratios, does not correspond to the present inventive solution.

The effectiveness of a catalyst material with different platinum / rhenium ratios in the same catalyst article can be further improved if in 5 to 30% of the catalyst material this ratio between 0.5 to 0.9 and in 10 to 40% of the catalyst material this ratio between 0.1 and 0.5 is.

The catalysts according to the invention make it possible to make available highly stable catalysts with very low platinum contents which, despite these low platinum contents, are advantageous for refinery practice because of their high yield stability.

The catalysts according to the invention are accessible via impregnation steps of customary porous gamma-Al ₂ O ₃ -Formlinge using in particular hexachloroplatinic acid, perrhenic acid and chromic acid from hydrochloric acid aqueous solution.

The particularly expedient form of the catalysts according to the invention with platinum / rhenium ratios deviating from the average ¹ within the same catalyst molding can be easily determined by the impregnation conditions, such as concentration of the active components in the impregnation solution, duration of the impregnation, hydrochloric acid concentration and pretreatment of Al ₂ O. ₃ shapes are guaranteed. A suitable pretreatment is, for example, a loading with steam or with carbon dioxide. Intense loading of carbon dioxide and high concentrations of hydrochloric acid in the impregnating solution lead to catalysts in which the platinum / rhenium ratios deviate only slightly from the average value. By low loading with carbon dioxide and low hydrochloric acid concentrations of catalyst moldings are obtained in danon strongly differentiated platinum / rhenium ratios in the molding present. Although the distribution ratios according to the invention can also be achieved by multiple impregnation steps, a simultaneous impregnation of all components has proven to be expedient. The platinum / rhenium ratios present in the catalysts according to the invention can easily be determined from distribution analyzes by means of electron beam microanalysis.

embodiments

Example 1 (inventive catalyst A)

500 cm ^{3 of} a gamma-Al ₂ O ₃ in the form of strand moldings with 1.3 mm diameter and a surface area of 24OmVg, a pore volume of 0.63 cmVg (prepared according to DD-PS 258714) were charged for two hours with gaseous carbon dioxide (flow rate 101 / Std.) And then covered with an impregnating solution, the 2.7 g / kg of platinum as Kexachloroplatinsäure, 5.1 g / kg of rhenium as perrhenic acid and 0.2 g / kg of Cr ₂ O ₃ as chromium-Vl acid, each based on AI ₃ O ₃ , contained. The solution was saline equivalent to 8.9 g chloride / l. After 12 hours' soaking time, the moldings were separated, dried and annealed at 820K for three hours. The analytical parameters were

platinum 2.7 g / kg Al ₂ O ₃ rhenium 4.8 g / kg Al ₂ O ₃ Platinum / rhenium 0.56 Cr ₂ O ₃ 0.19 g / kg Al ₂ O ₃ chloride 15.0 g / kg Al ₂ O ₃

The deviations from the stated Pt / Re ratio within a catalyst article were in the range of 5% relative.

Example 2 Inventive Catalyst B

The same amount of Al ₂ O ₃ as in Example 1 was for 10 minutes with 5l / hr. Treated carbon dioxide gas and then impregnated for four hours with a solution which had the following contents: 2.3 g / kg of platinum, 7.1 g / kg of rhenium and 0.15 g / kg Cr ₂ O ₃ , each based on Al ₂ O ₃ . Analogous compounds were used as in Example 1. The hydrochloric acid content corresponded to 7.1 g of chloride / I. Drying and annealing were carried out as in Example 1.

The following analytical characteristics were determined (data based on Al ₂ O ₃ ):

platinum 2.3 g / kg rhenium 6.6 g / kg Platinum / rhenium 0.35 as an average Cr ₂ O ₃ 0.15 g / kg chloride 13.9 g / kg

The following Pt-Re distribution data were determined by electron beam microanalysis: 15% of the catalyst material had an average Pt / Re ratio of 0.70 25% of the catalyst material of 0.20.

Example 3 (not according to the invention)

Based on the AI ₂ O ₃ -formten mentioned in Example 1, a catalyst with 3g / kg of platinum and rhenium, 0.2 g / kg Cr ₂ O ₃ and 4g / kg chloride according to the inventive information in DD 223077 was prepared (catalyst C).

As described in Example 1, a chromium-free Ft / Re catalyst was prepared with the following contents: (Catalyst D)

platinum 2.5 g / kg rhenium 4.5 g / kg chloride 15 g / kg.

Example 4

The catalysts of Examples 1 to 3 were subjected in a reforming pilot plant to a comparative catalytic test under real reforming conditions. The following results were obtained:

test conditions: print 1.5MPa burden 2 v / v h Gas ratio 1000NI / I amount of catalyst 300ml

Raw material: Hydrorefined petrol 378 to 413 K boiling

Sulfur content 1 ppm

Aromatics 0.07 l / l

Naphthenes 0.38 l / l

Paraffins 0.55 l / l

Result:

Catalyst ABC

Reaction temperature K octane RON liquid yield kg / kg aromatics yield kg / kg

The catalysts A and B according to the invention operate more selectively with the result of higher aromatics yields. In addition, there is a trend of improved stability.

example

In another catalytic! Test the yield stability of the catalyst A was tested, the following conditions were set:

765 762.2 761 767 99.4 100 99.5 99.3 0,852 0,852 0.825 0.842 0,614 0.618 0.586 0,600

1.5MPa kg / kg g / kg 3v / vh 0.882 27.7 5molH ₂ / molKW 0.088 28.5. corresponding to a RON in the reformate 98 to 100 0.888 29.0 80 ml 0.883 27.6 Hydrorefined petrol 383 to 453 K Aromatics in l / l 0.10 Naphthenes in l / l 0.364 Paraffins in l / l 0.536 print Depending on the catalyst stability, the following temperature steps were dur burden to keep: gas ratio temperature Temperature Liquid yield H ₂ -Expute amount of catalyst K raw material 763 773 783 793

The numbers prove the high yield stability over a relatively wide temperature range. In prior art catalysts, represented by catalysts C and D, yield reductions at higher temperatures in the range of 20 to 40 g / kg are found under analogous conditions and comparable run times.

Example 6 (inventive catalyst E) 500 cm ^{3 of} the aluminum oxide of Example! 1 were impregnated from a supernatant (NhUhMoCV solution with 0.10 g / kg MoOa, then dried at 373K and calcined at 723K for 3 hours in air The alumina thus loaded with MoO ₃ was analogously to Example 2 with platinum, rhenium and chloride without the addition of chromic acid impregnated and after-treated in an analogous manner The following analysis values were determined

platinum 2.28 g / kg rhenium 6.63 g / kg Platinum / rhenium 0.34 as an average MoO ₃ 0.10 g / kg chloride 13.8 g / kg

The distribution data obtained by electron beam microanalysis corresponded to those given in Example 2. Catalyst E was catalytically tested under analogous conditions as in Example 4. The following results were obtained:

Catalyst E 764 Comparison! catalysatore Reaction temperature K 99.6 DD 212192 Octane RON 0,850 DE-AS 2460560 Liquid yield kg / kg 0,610 DE-AS 2819088 Aromatic yield kg / kg more capable than that EP 252 605 The catalyst E is performance Documents considered: US 3554901 US 4764 267

Claims (4)

1. reforming catalyst for the recovery of aromatic hydrocarbons or aromatic-rich hochoktanigen fuel components from hydroraffinierten Benzinkohlenwasserstoffgemischen under hydroreforming conditions based on platinum and rhenium-containing porous gamma-Al2-O ₃ -Formlinge, characterized in that the catalyst at platinum contents of 2 to 4, 5g / kg has an atomic platinum / rhenium ratio of 0.25 to 0.65 and 0.05 to 1 g / kg, based on the respective element, elements of Vl. Subgroup or their compounds contains. 2. reforming catalyst according to claim!, Characterized in that de. Catalyst at platinum contents of 2 to 3.5 g / kg platinum / rhenium ratios of 0.30 to 0.60 and levels of chromium, calculated as chromium-lll-oxide, from 0.1 to 0.8 g / kg. 3. reforming catalyst according to claim 1 and 2, characterized in that when broadening the average atomic platinum / rhenium V6rhältnisses of 0.30 to 0.60 in the catalyst 5 to 40% of the catalyst material, a platinum / rhenium ratio between 0.40 and 0.9 and 5 to 40% have such a ratio between 0.1 and 0.5, these different platinum / rhenium ratios each being in the same catalyst blank. 4. reforming catalyst according to claim 3, characterized in that 5 to 30% of the catalyst material has a platinum / rhenium ratio of 0.5 to 0.9 and 10 to 40% of Katalysatoratateriab such a ratio of 0.1 to 0.35 ,