DD238998A1 - METHOD FOR PRODUCING QUALITATIVELY HIGH QUALITY PYROLYSIS USE PRODUCTS - Google Patents

Abstract

The deposits of coke-like products in pyrolysis reactors have a significant influence on the running time and thus the economy of olefin production plants. To reduce the formation of coke in the reactors, a process for the preparation of pyrolysis by-products is described, in its application without additional use of foreign inhibitors, by admixing a partially refined product from the same process to Hydrospaltabstreifer and recovery of 300C, a significant increase in life and service life of pyrolysis plants can be achieved.

Description

Field of application of the invention

The invention relates to a process for the hydro-cleavage of vacuum distillates whose distillation residues> 300 ° C boiling water can be used as high-quality pyrolysis by-products and which result in a lower deposition of coke-like products in the pyrolysis plant than is the case for distillation residues from the hydrocracking, which were made according to other procedures.

Characteristic of the known technical solutions

In connection with the search for new fields of application for hydrocracked products, a suitability for the production of lower olefins by pyrolysis was soon tested (Zchonik, SB et al.: Hydrocarbon Pocess 55 [1976] 1,149 and Phoc, A. et al .: OilGasJ.79 [1981] 4.164).

Atmospheric distillation residues which were obtained by hydrocracking of vacuum distillate fractions proved to be interesting pyrolysis starting products which yield high olefin yields (Goetzmann, S. et al.: Hydrocarbon Process.58 [1979] 6,109 and Goetzmann, S. and Zimmermann, H .: Linde reports No. 55 [1984]). Will now be above 300 ⁰ C boiling vacuum gas oil from the petroleum distillation, from the thermal treatment of petroleum residues or coal upgrading with technical hydrogen at a pressure of 10 to 25 MPa, a temperature of 360 ° C to 420 ⁰ C and a catalyst loading between 500 and 1 500: 1 treated on different catalyst systems, for example from a mixture of 5% NiO, 20% MoO ₃ or WO ₃ on X-ray amorphous aluminum silicate, resulting in products whose distillation residues lead in the pyrolysis to lower olefins to a strong deposition of coke-like products in the pyrolysis , The deposition of coke-like products, however, affects the technical operation of olefin production plants. They deteriorate the heat transfer tube wall / medium and reduce the cross section of the reaction tubes. To compensate for the resulting negative impact on the operating regime of the pyrolysis plant, a constant increase in the pipe outer wall temperature and the form is required, resulting in a higher wear and thus shorter life of the pipe system in the radiation zone of the cracking furnaces. Intermittent normal operation is required at certain intervals for the purpose of oxidative decoking of the tubes with water vapor-air mixtures, which limits the available production time and leads to a reduction in creep strength through progressive roughening of the inner reactor surface caused by high-temperature corrosion (LF Albright, US Pat. BL Crynes: Industrial and Laboratory Pyrolysis, ACS Symposium Ser. 32, Washington 1975). To avoid these deficiencies, a number of methods and methods for reducing coke formation have been proposed in the patent literature, which can be attributed to the following principles of action:

a) Passivation of the inner reactor surface, from which a catalytic effect on coke formation, by forming a thermally stable protective layer, e.g. from aluminum (US Pat. No. 3,827,967) and silicon dioxide (D.E. Brown et al., 8th Internat. Conf. on former Vapor Depos., Paris 1981)

b) Continuous renewal of the inner reactor surface by liquid films (metals or molten salts) (Su-PS 249370 and 341 320).

c) gasification of coke and its precursors with steam under the catalytic action of additionally introduced compounds, usually salts, oxides or hydroxides of alkali or Erdalkalimentallen (DE-PS 2750324 and DD-PS 133570).

d) Continuous metering of sulfur or sulfur-containing compounds (DD-PS 124422, US-PS 3848017 and 3641190) and nitrogen or phosphorus-containing compounds as coke inhibitors (SU-PS 191726 and US-PS 3852188).

All these methods, however, have disadvantages. Either the expenses for use in large systems are too high (burden of fission gas separation and Spaltgaswäschen) or additional devices for the difficult-to-control material cycles are required. In addition, the corrosive effect of additions of inorganic salts should not be underestimated.

Object of the invention.

The aim of the invention is the production of a pyrolysis byproduct of vacuum distillates from the petroleum distillation, from the thermal treatment of petroleum residues or coal refining, which shows a lower tendency to coke deposits in pyrolysis in pyrolysis to lower olefins, as conventionally produced vacuum residues from the hydrosolification and thus an increase in the duration of the plant between two Dekkokungszeiten and the lifetime of the reactors influenced by measures that do not worsen the feed-specific yields of target products.

-2- 238 998 Presentation of the Essence of the Invention

The invention has for its object to develop a process for the hydro-cleavage of vacuum distillates, which provides a product whose distillation residue greater than 300 ° C boiling in the subsequent pyrolysis to lower olefins without addition of coke inhibitors or other additional measures leads to lower coke formation in the pyrolysis than in the application of hydrocracked products produced by known methods. The object is achieved by a process for the production of high quality pyrolysis by-products with low coke formation by hydrocracking of vacuum distillate at pressures of 20 to 25 MPa, average reactor temperatures of 380 ° C to 450 ° C, gas-product ratios of 750 to 1: 500: 1 and a Catalyst loading of 0.5 to 3v / vh and recovery of over 300 "C boiling components by distillation according to the invention solved by the resulting in the hydrocracking liquid fractions before distillation with 3 to 20 wt .-% of a partial stream, after passing through the first One-eighth, but at least diverted from the entry into the third eighth of the catalyst feed.

It was surprisingly found that a distillation residue produced from this mixture> 300 ⁰ C boiling, formed in the subsequent pyrolysis by more than half less coke in the reactors, as otherwise produced distillation residues.

This invention achieves progress in that this measure selectively inhibits coke formation in the pyrolysis reactors without affecting the pyrolysis reactions determining the target product yields or shifting the target product yields (Table 1), eliminating the need for additional inhibitors, and substantially modifying apparatus Hydrospalter, the subsequent distillation or in the pyrolysis system are necessary. In addition, the service life of the pyrolysis reactors increases and the number of decoking cycles decreases. embodiments

The following embodiments are based on experimental data obtained in a small scale hydrospitter and pyrolysis tests in the stainless steel laboratory reactor.

Example 1 (comparative example)

A vacuum distillate is introduced at a pressure of 20 to 25 MPa, an average reactor temperature of 430 ° ^C and a catalyst loading of 1.0 v / vh and at a gas to product ratio of 1000: 1 on a catalyst system of a mixture of 2% NiO and 15% MoO ₃ hydrogelled on X-ray amorphous aluminum silicate with technical hydrogen. The hydrosporin product is distilled and the distillation residue> 300 ⁰ C boiling used for the pyrolysis for the production of lower olefins. At 830 ° C, 0.4 s residence time, 0.2 MPa reactor exit pressure, and a water / hydrocarbon ratio of 0.6, a reactor run time, measured at the onset of pressure rise, of 6 hours was found.

Example 2 (comparative example)

A hydrosoluble product prepared under the same conditions as in Example 1, 5Ma .-% vacuum distillate, which serves as a feedstock for the hydrospray, have been mixed. After distillation, the distillation residue was subjected to pyrolysis> 300 ° C. under the conditions mentioned in Example 1. Already after 4 hours, a strong increase in pressure occurred, which led shortly thereafter to the blockage of the reactor.

Example 3 (comparative example)

To a hydrosoluble product prepared under the same conditions as in Example 1, 5% by weight of partially hydrogenated hydrocracked product which has passed through half of the catalyst layer are mixed in each case and then distilled. The respective distillation residues> 300 ° C boiling gave the same results in the pyrolysis under the conditions mentioned in Example 1.

Example 4

A hydrosoluble product prepared according to Example 1 is mixed with 5 wt .-% of a partial stream which has undergone a quarter of the catalyst layer, and then distilled. The distillation residue> 300 ° C boiling is pyrolyzed under the conditions mentioned in Example 1. A significant increase in pressure in the tubular reactor was found only after 14 hours, the blockage of the reactor began only after 15 hours.

Example 5 (Comparative Example)

A hydrosoluble product prepared according to Example 1 is mixed with 5 wt .-% of a partial stream which has passed through half of the catalyst layer and then distilled. The distillation residue> 300 ° C boiling is pyrolyzed under the conditions mentioned in Example 1. An increase in pressure in the tube reactor started after 6 hours, the blockage after 7 hours.

Table 1

Product composition after the pyrolysis of untreated (1) and according to the invention treated (2) distillation residue from the hydrocracking in% by mass.

Cleavage products (1) (2)

hydrogen 0.8 0.8 methane 10.4 10.4 ethene 34.4 34.4 propene 14.9 14.9 butadiene 5.9 6.0 benzene 7.2 7.2 toluene 3.1 3.3 pyrolysis gasoline 22.3 22.7 Pyrolyseheizöl 4.6 4.0

Table 2

Overview of the reactor runtime

Pyrolysis conditions: 830 ^° C; 0,4sec; 0.2 MPa; H ₂ O / KW ratio 0.6

Feedstock according to Example Run time of the reactor

16 hours

24 hours

3 6 hours

4 14 hours

5 7 hours

Claims (1)

Invention claim: Process for the preparation of high quality low coke formation proline feedstock by hydrocracking of vacuum distillate at pressures of 20 to 25 MPa, average reactor temperatures of 380 ° C to 450 ° C, gas product ratios of 750 to 1500: 1 and a catalyst loading of 0.5 to 3 v / vh and recovery of the over 300 ° C boiling components by distillation, characterized in that the obtained in the hydrocracking liquid fractions prior to distillation with 3 to 20 Ma .-% of a partial flow, after passing through the first eighth, but at least before Entry into the third eighth of the catalyst bed was diverted, mixed.