DD243647A1 - CALCIUM ALUMINATE BASED CATALYST OF A SINTERED FORMAT AND METHOD OF MANUFACTURING THE SAME - Google Patents

Abstract

The invention relates to a catalyst made of a calcium aluminate-based sintered shaped article and to a method for its production. The catalyst consisting of a catalyst base of the composition 15-50 wt.% CaO, 50-85 wt.% Al 2 O 3 wt.%, 0.2 wt.% SiO 2 and a dopant of 0.1-3.0 % By weight alkali metal alkane adadate, has a compressive strength of 150 kp / cm 2, an open porosity of 30% and a heat development of 5 J / gh on contact with water and is in a one-step sintering process between 1250 and 1500C followed by calcining at about 800C preferably produced with potassium meta-, ortho- or pyro-vanadate and previously broken sintered energy-saving. The doped sinter of 1 to 5 mm, for example, for the direct conversion of higher boiling, containing S- and N-containing compounds hydrocarbon fractions by thermal-catalytic steam cracking of these feedstocks in lower olefins and monocyclic aromatics, the usual difficulties of coke and gum formation due a controlled and optimized gasification can be avoided, are used.

Description

Field of application of the invention

The invention relates to a calcium aluminate-based catalyst, which is particularly suitable for the thermal-catalytic steaming of higher-boiling, low-hydrogen hydrocarbon fractions, and to a process for its preparation.

Characteristic of the known technical solutions

Catalysts for the thermal catalytic steam cracking of hydrocarbons or hydrocarbon fractions in the boiling range of the atmospheric and vacuum gas oil are known. For example, in FRP publication 2431 983 a catalyst is described which is prepared and composed as follows: either a "refractory" calcium aluminate powder virtually free of silica, or a homogeneous mixture of the "refractory" powder and alumina, calcium oxide, beryllium oxide, Magnesium oxide, strontium oxide and / or a compound which is converted to one of these oxides by heating is kneaded with water, molded into a molded article and aged. This aged molded article is sintered at a temperature between 1150 and 1500 ° C, whereupon the thus sintered catalyst body having an open porosity greater than 30% and a pore radius above 50 nm ultimately 10 to 60Gew .-% calcium oxide, 30 to 90Gew .-% alumina , 0 to 30% by weight of beryllium oxide, magnesium oxide and / or the strontium oxide and less than 0.2% by weight of silica.

As a so-called refractory powder while a finely divided aluminum oxide cement or corresponding products are used, which are prepared by heating a mixture of alumina and calcium oxide at very high temperatures in the range of 1600 to 2000 ° C. The preparation of the actual catalyst takes place only in the second step, in which the "refractory" powder - as described - alone or a mixture with other oxides kneaded with water, aged and annealed again at temperatures ranging from 1150 to 1 500 ⁰ C. The process according to DE-OS 2431983 is extremely energy-consuming as a result of this two-fold high-temperature loading during catalyst preparation. On the other hand, it is expressly described that in the case of direct sintering of a mixture of calcium oxide and aluminum oxide, ie by a one-step process, no catalyst is used under a wide variety of conditions obtained, which has the desired activity and mechanical strength.

Similarly, DE-AS 21 58073 describes a silicon dioxide-free sintered catalyst which consists of at least about 20% by weight of one or more alkaline earth metal oxides and the balance of aluminum oxide. The preparation of the catalyst is carried out by kneading a mixture of aluminum cements, consisting of 79 wt .-% alumina and 18 wt .-% calcium oxide, with calcium carbonate and water, pelleting the kneaded mixture, drying in air at 100 ^c C and 3 bis 5 hours sintering at a temperature of 1 200 ⁰ C. Also in this case, it is due to the leading cement production, a two-stage very energy-intensive process for recovering the catalyst.

Object of the invention

It is the object of the invention to provide a powerful, mechanically, thermally and steam-stable, long-term active heterogeneous catalyst, which is suitable in particular for the steaming of hydrocarbons, whose production is substantially simplified with regard to the catalyst base body calcium aluminate and, above all, designed to save energy and furthermore by the incorporation of or doping with metal compounds additional positive effects with respect to the stability of the catalyst can be achieved even under extreme conditions of use.

Explanation of the essence of the invention

The object is achieved by a catalyst based on a sintered calcium aluminate-based shaped article in that, according to the invention, it consists of a catalyst base consisting of 15 to 50% by mass, preferably 30% by mass, calcium oxide and 50 to 85% by mass, preferably by 70% by mass % Alumina containing less than 0.2% by weight of silica in the form of calcium aluminates 12CaO-7Al ₂ O ₃₁ CaO-Al ₂ O ₃₁ CaO ₂ A ₂ O ₃ and CaO 6 Al ₂ O ₃ , preferably CaO-Al ₂ O ₃ and CaO 2 Al ₂ O ₃ , and as a dopant from 0.1 to 3.0Ma .-% of an alkali meta, -ortho- or -pyro-vanadate, preferably of the potassium salt, is composed. In addition, alkaline earth oxides of the elements beryllium, magnesium, strontium and / or barium or their compounds, which are converted by heating into one or more of these oxides, in an amount of 0.1 to 30% by mass, may be added to the catalyst raw meal for the preparation of the catalyst. be added. The catalyst according to the invention is characterized by a compressive strength above 150 kp / cm ² , a bulk density above 1.70 g / cm ³ , a pore radius> 50 nm and an open porosity <30% and has a heat development of less than 5 J / g on contact with water. h.

The object is further achieved by a process for the preparation of the catalyst by an alumina support, preferably calcined alumina, and a calcium oxide, preferably treated calcium carbonate, alone or with addition of carriers of the oxides of the elements beryllium, magnesium, strontium and / or barium by weight, wet-chemically with the addition of water and the resulting suspension stabilizing additives, such as sulfite liquor and carboxymethyl cellulose in amounts of up to 1.5 Ma .-%, homogenized, ground to a particle size of preferably smaller θ, Ομ, ηι, spray-dried , the sprayed grain pressed at a pressing pressure greater than 300kp / cm ² to normal format similar blanks, then at temperatures between 1300 and 1 500 ⁰ C, preferably sintered at 1450 ° C, the sinter is then crushed and classified. The catalyst base body of calcium aluminate mixture with a particle size of 1 to 5 mm thus obtained is added to a doping in an amount between 0.1 and 3.0% by mass with, for example, 0.1 to 5% solution of a low-volatile alkali metal oxide. meta, -ortho- or pyro-vanadate, preferably the potassium salt, impregnated, dried and finally calcined at a preferred temperature to 800 ⁰ C. Due to the particular characteristics of the catalyst according to the invention, regarding its high compressive strength, the relatively low open porosity with significantly smaller pore diameter and the extremely low heat development on contact with water, which in practice indicates a pronounced reaction inertness towards this medium, are extremely advantageous conditions for a high abrasion resistance, a very low, caused by water vapor decay and thus overall for a high long-term activity of the product, for example when used as a cracking catalyst for higher-boiling, hydrogen-poor and possibly also heteroatom-containing hydrocarbon fractions of petroleum or carbochemical origin. An additional effect in this direction, which is directed in particular to the gasification activity and selectivity, is achieved by the doping of the crushed sintered product used as catalyst base body before it is used with the lowvolatile alkali metal alkane.

Equally advantageous is the process for preparing the catalyst characterized according to the invention. In contrast to the known processes, the sintering process in two stages - first at 1600 to 2000 ⁰ C and after the preparation of the sinter again at temperatures between 1150 and 1500 ⁰ C - perform, is to obtain the catalyst base on calcium aluminate only a single-step process according to the invention carried out in which the sintering process in favor of considerably lowered temperatures in the range between 1250 and 1500 ⁰ C. The catalyst characterized according to the invention leads to a number of economic and technical advantages, which can be summarized as follows:

- Effective production of the catalyst by the use of low-cost raw materials and a one-step processing (cryogenic sintering) with subsequent doping.

- Use for the direct conversion of high-boiling, S- and N-containing compounds containing hydrocarbon fractions (without hydro-catalytic pretreatment) in lower olefins and monocyclic aromatics, the usual difficulties of coke and gum formation are avoided by a controlled and optimized gasification.

Achieving long run times without regeneration of the catalyst and thus higher space-time yields of the catalyst layer and overall reduction in operating costs.

-3- Z43 Ö4 /

embodiments

Production of the catalyst base body

example 1

High-purity calcium carbonate and calcined alumina are wet-mechanically homogenized in a mill in a ratio corresponding to 30% by weight of calcium oxide and 70% by weight of aluminum oxide with the addition of 1% sulfite liquor and 1% carboxymethyl cellulose, followed by spray drying. The spray grain is pressed under a pressure of 400kp / cm ² to form bodies and sintered at 1400 to 145O ⁰ C. After sintering, the moldings have a strength of 213 kp / cm ² and an open porosity of 30%. The chemical analysis shows a calcium oxide content of 29.8%, an alumina content of 70% and a silicon dioxide content of less than 0.2%. As chemical compounds CaO · Al ₂ O ₃ and CaO · 2 Al ₂ O _{3 are} detected.

The shaped bodies are crushed and classified; as a catalyst is preferably a grain size of 2 to 5 mm into consideration.

Example 2

Calcium oxide, calcined alumina and magnesium oxide are wet mechanically homogenized in a ratio corresponding to 20% by weight of calcium oxide, 10% by weight of magnesium oxide and 70% by weight of aluminum oxide in the presence of sulfite liquor and carboxymethyl cellulose and prepared analogously to Example 1. The strength of the moldings after sintering is 210kp / cm ² , the open porosity at 28%. The chemical analysis gives the following composition:

19.7% calcium oxide 9.8% magnesium oxide

70.2% alumina <0.1% silica.

The shaped bodies are crushed and classified; The catalyst used is preferably a grain size of 2 to 5 mm. Doping of the catalyst main body

Example 3

The doping of Kataiysatorgrundkörpers carried out with a solution which is prepared by entering the stoichiometric amount of vanadium pentoxide in 1 N potassium hydroxide. After immersing in a 1% derCalciumaluminatstücke Kaliumorthovanadatlösung, drying the wet shape at 80 ⁰ C and calcination at 800 ⁰ C, the catalyst shows a weight increase of 2.5%. Preliminary dilution of the potassium orthovanadate solution with 2 volumes of water results in a weight gain of 0.8% in a second approach.

Example 4

The Kataiysatorgrundkörpers with potassium pyrovanadate is doped with a solution which is prepared by introducing a obtained at 900 ° C from 5.6 parts by weight of potassium carbonate and 3.6 parts by weight of vanadium pentoxide melt in water. After immersion derCalciumaluminatstücke strength in eine3 Kaliumpyrovanadatlösung%, drying the wet pieces at 80 ⁰ C and calcination at 800 ⁰ C, the catalyst shows a weight increase of 2%. A previous dilution of the potassium pyrovanadate solution with 1 or 2 parts by volume of water leads to further increases in weight gains of 1.0 and 0.66%.

Claims (4)

Invention claim: A calcium aluminate-based sintered shaped article catalyst particularly suitable for thermally catalytic steaming of higher boiling, low-hydrogen hydrocarbon fractions, characterized in that the catalyst consists of a catalyst base of the composition 15 to 50% by mass, preferably 30% by mass of calcium oxide and 50% up to 85% by mass, preferably around 70% by mass, aluminum oxide containing less than 0.2% by mass of silicon dioxide in the form of the calcium aluminates 12 CaO 7 Al ₂ O ₃ , CaO Al ₂ O ₃ , CaO.Al ₂ O ₃ and CaO · 6 Al ₂ O ₃ , preferably CaO Al ₂ O ₃ and CaO · 2 Al ₂ O ₃ , and 0.1 to 3.0 mass% of an alkali metal meta, ortho or pyro vanadate , Preferably the potassium salt, as a dopant. 2. Catalyst according to item!, Characterized in that the catalyst additionally contains 0.1 to 30 wt .-% of the oxides of the elements beryllium, magnesium, strontium and / or barium in the form of the oxides themselves or their compounds with alumina. 3. Catalyst according to item 1 and 2, characterized in that the catalyst has a compressive strength above 150kp / cm ² , a density above 1.70 g / cm ³ , a pore radius> 50nm and an open porosity <30% and in contact with water a heat development 5 5J / g · h shows. 4. A process for the preparation of the catalyst according to claim 1 to 3, characterized in that an alumina carrier, preferably calcined alumina, and a calcium oxide carrier, preferably prepared calcium carbonate, alone or with addition of carriers of the oxides of the elements beryllium, magnesium, Strontium and / or barium dosed by weight, wet-chemical with the addition of water and the suspension stabilizing additives, preferably sulfite liquor and carboxymethyl cellulose in amounts of up to 1.5Ma .-%, homogenized, ground to a particle size of preferably less than 60 ^ m, spray-dried , pressed at a pressure greater than 200 kp / cm ² to normal format similar blanks, then sintered at temperatures between 1 300 and 1 500 ° C, preferably 1450 °, then crushed and classified and ultimately the resulting catalyst base of calcium aluminate mixture with a particle size between 1 and 5mm by soaking with a L solution of a low-volatile alkali metal salt, preferably the potassium meta-, pyro-or -ortho- vanadate, followed by drying and calcining at 8O ⁰ C, preferably in an amount between 0.1 and 3.0 wt .-% is doped.