DE2462867C2 - - Google Patents

Description

The invention relates to a method for cracking of hydrocarbons without added hydrogen. Common facilities for this purpose usually include a cracking reactor and a regenerator, the catalyst continuously circulated through these two vessels. Flow catalyst cracking has particularly significant advantages (FCC) with zeolitic catalysts receive. The catalysts of the invention are for hydrocracking using a fixed catalyst bed and an excess of added hydrogen not suitable.

There are two main types of catalytic cracking processes in use. Catalytic reforming or the Thermoforcrack process (TCC) is both in the reactor as well as a moving compact in the regenerator Catalyst bed used. Catalyst caused by deposition of carbonaceous deposits that generally referred to as "coke", proportionately becomes inactive, is continuously from the bottom of the reactor deducted in the gas oil by contact with the catalyst is cracked at elevated temperature. The used one The catalyst of the reactor becomes the upper part of a regenerator supplied in which the activity of the catalyst restored by burning the coke with air becomes. Hot regenerated catalyst is from the Bottom of the regenerator continuously to the upper part of the reactor returned to the one described first Repeat cycle.  

When working with a fluid bed or fluidized bed the catalyst follows a similar cycle. However, it is used both in the reactor and in the regenerator through upward flowing gases, namely gaseous hydrocarbons, in the reactor and in the regenerator fluidized.

The main difference in both methods is with respect to the catalyst in particle size. Pellets or pearls with a diameter of about 0.32 cm used at TCC. Fine powder, with an average Particle size of about 70 microns FCC used.

Both processes are used for printing between atmospheric Pressure and driven about 3.8 bar. Becomes hydrogen formed by the cracking reaction in a small amount. It however, becomes the reactors of the TCC and FCC units no hydrogen added. This cracking in absentia of added hydrogen is endothermic in the Contrary to the exothermic character of hydrocracking with a catalyst containing substantial amounts of hydrogenation metal contains (above 0.5 wt .-%), and in the presence a large excess of added hydrogen, as described in US Pat. No. 3,173,854.

In general, potent hydrogenation metals are used in TCC and FCC catalysts avoided. A serious problem with these catalysts occurs when feed materials are cracked that contain metals. In particular, the deposition of the metal is nickel Group VIII disadvantageous. Amounts of nickel in the order of magnitude of 0.03% by weight on the catalyst hydrogen formation to such an extent that serious problems in the treatment of the gas from the TCC and FCC processes occur.  

Catalysts used in the FCC and TCC contained acid-treated clays, amorphous silicon oxide / Alumina compositions and the like. Many Variants such as silicon dioxide / zirconium oxide, silicon oxide / Magnesium oxide and other acidic porous solids described in the literature.

Very effective catalysts have recently been made by replacing a larger portion of the older amorphous catalysts with a smaller part of an active crystalline Aluminosilicate zeolite was mixed. Typical Catalysts of this type for the FCC and TCC are in the US-PS 31 40 249 and 31 40 253 described on their Disclosure is referred to.

The FCC and TCC occur due to incomplete combustion the problem is that substantial amounts of Carbon monoxide (CO) in the flue or combustion gas stay behind. Aside from being undesirable is to release the CO into the atmosphere, these tend to Gases in addition, in pipes and chimneys of the plant to burn (by reacting the CO with residual oxygen in the flue gas), these facilities by excessive temperature can be damaged.

It has been suggested to address this issue at TCC Add small amounts of chromium oxide to the catalyst to master. This leads to some deterioration the gasoline yield, however, this impact is tolerable if this avoids the CO problem (see US Pat. No. 2,647,860).

It has also been proposed in a cracking catalyst to introduce a zeolite, which in its inner pore structure a CO-oxidizing catalyst contains, the pores are too small to the Allow feeder molecules to enter  however large enough for CO to occur (cf. U.S. Patent 33 64 136).

It is also known from US-PS 36 96 025, titanium or titanium compounds to crack catalysts during of the catalytic cracking process.

The object of the invention is to create a method for the cracking of hydrocarbons due to a high CO₂ / CO ratio in the regenerator exhaust while maintaining high selectivity of the cracking distinguished.

The invention relates to a method for cracking of hydrocarbons without added hydrogen using a catalyst from an exchanged Zeolites with a pore size that is large is enough for the entry of benzene molecules, and optionally a porous matrix of silicon dioxide, Aluminum oxide, magnesium oxide, zirconium oxide, clay or Mixtures thereof, which is characterized in that the feed material is a palladium, platinum, ruthenium, Osmium, iridium, rhodium and / or rhenium component contains that on the catalyst in an amount of 0.01 to 50 ppm of total catalyst weight as metal, to be put down.

It would be assumed that those used according to the invention strong dehydration metals in amounts that a noticeable catalytic oxidation effect that Hydrocarbons to form unsaturated Compounds would dehydrate as coke precursors are known. Surprisingly, however, Addition of the metals mentioned to FCC and TCC catalysts in amounts of 50 ppm or less is not essential Observe an increase in coke formation.  

The lower limit of metal component on the catalyst is preferably 0.1 ppm and the upper limit preferably 20 ppm, especially 15 ppm.

The term "metal component" here means that Metal itself or a metal ion or a metal compound, like an oxide, sulfide, halide, sulfate or other compounds that are characterized by the addition of the metal or a metal compound to the catalyst surrender.

It is surprising to find that the used Metal components, although they are for molecules of Feeding are easily accessible, not a disadvantage Show effect when in the amounts according to the invention be used.

The catalyst of the invention, the metal component contains a particularly large reduction the CO content of the flue or combustion gases of FCC units. This is improved by a CO₂ / CO ratio compared to a cracking catalyst, that contains no metal component. The Metal components are of particular advantage in Catalysts, the silicon oxide, aluminum oxide, magnesium oxide, Zirconia, clay and combinations thereof contain. They are particularly advantageous in composite catalysts from active crystalline Aluminosilicate zeolites in a porous Matrix, such as a matrix obtained from clay. Other Types of matrices include silicon oxide, aluminum oxide, Magnesium oxide, zirconium oxide and mixtures thereof.  

The used in such composite catalysts Zeolites are those that are able access to the feed molecules to be cracked to allow a condition that is met if it Have pore openings that are large enough to hold benzene molecules allow access. The one for this Purpose most commonly used on an industrial scale are the zeolites X and Y, the pore openings of about Have 8 to 9 Å units. Zeolites with pore openings less than about 6 Å units do not allow the entry of the benzene molecules, and this is why for the implementation of standard crack feeds not used. Crystalline aluminosilicates are preferred used that exchanged with rare earths are.  

An oil-soluble or oil-dispersible compound of the metal is added in an appropriate amount to the hydrocarbon feed, such as a gas oil feed, to be introduced into the catalyst when the feed is cracked. Such compounds include metal diketonates, carbonyls, metallocenes, olefin complexes having 2 to 20 carbon atoms, acetylene complexes, alkyl or arylphosphine complexes and carboxylates having 1 to 20 carbon atoms. Specific examples are platinum acetylacetonate, tris (acetylacetonato) rhodium (III), trÿodoiridium (III) - tricarbonyl, π- cyclopentadienylrhenium (I) tricarbonyl, ruthenocene, π- cyclopentadienylosmium (I) dicarbonyldimer, dichloro (IIhylene ((ethylene) palladium π- Cyclopentadienyl) (ethylene) rhodium (I), diphenylacetylene-bis (triphenylphosphino) - platinum (0), bromomethyl-bis (triethylphosphino) palladium (II), tetrakis (triphenylphosphino) - palladium (0), chlorocarbonyl-bis (triphenylphosphino ) iridium (I), palladium acetate and palladium naphthenate.

The feed materials using the catalysts of the invention can be cracked, include all common hydrocarbon feeds, like naphthas, gas oil, light and heavy distillates, Residue oils and the like  

example

It became the equilibrium catalyst, which consists of a commercial FCC unit was used. A broad section of a mid-continent gas oil feed was at 498 ° C, a catalyst to oil ratio of 3 and a catalyst residence time of 2.4 min. The catalyst was regenerated in place in two stages, that air over the catalyst at a rate of 25 cm³ / min / g catalyst at 538 ° C and atmospheric pressure for 8 min and the gas was collected.

Then the same gas oil, but now containing platinum acetylacetonate dissolved therein in sufficient quantity, was introduced into the cracker under the same conditions except for a slightly higher temperature to provide 1 ppm of platinum on the catalyst. The catalyst was regenerated again. The platinum-containing feed was then cracked again over the same catalyst and the catalyst again regenerated. The following results were obtained:

The catalyst contained the smallest component Pore size of a rare earth-exchanged Y zeolite.

The research showed that even at such low Concentrations of added metal component such as 0.01 ppm the CO₂ / CO ratio during the regeneration is increased.  

If the catalyst with the added metal component contains a lot of this metal component, which goes beyond the amount according to the invention can by mixing such a catalyst in the Use, d. H. either cracking and / or regeneration with such a cracking catalyst, which contains less or no metal component Total mixture with a sufficient amount of metal component can be obtained according to the invention.

From the work results obtained according to the invention it can be seen that the cracking catalysts according to the invention in converting hydrocarbons into are equally effective while in the regeneration stage the CO₂ / CO outflow conditions are extremely cheaper than with catalysts without added metal component. The type of catalyst the type of feed material and / or practice the way of introducing the components no adverse effects on the regeneration effectiveness out.

Claims (1)

The process for cracking of hydrocarbons without added hydrogen, using a catalyst of an exchanged zeolite having a pore size which is large enough for the entry of benzene molecules and optionally a porous matrix of silica, alumina, magnesia, zirconia, clay, or mixtures thereof, characterized characterized in that the feed contains a palladium, platinum, ruthenium, osmium, iridium, rhodium and / or rhenium component, which on the catalyst in an amount of 0.01 to 50 ppm of the total catalyst weight, calculated as metal, be put down.