DE2528554A1 - Ethylene and methane prodn. - by combined hydropyrolysis and cracking of higher hydrocarbons - Google Patents

Abstract

Ethylene is produced by integrated hydropyrolysis-cracking process comprising (a) reacting H2 and hydrocarbon oil (density 0.99 and Conradson 20% wt.) in mol ratio at least 1:1 (3-30:1) at 600-900(700-850) degrees C and >=5(5-100) atmos. gauge with residence time 0.60(0.5-20) secs., (b) treating effluent from hydropyrolysis in cracking zone at 750-900 degrees C(800-850 degrees C) and =2(=1) atmos. with residence time 0.01-10(0.1-1) secs., (c) sepg. effluent into H2, CH4, C2H4, C2H6 and higher hydrocarbon streams, (d) recycling H2 to stage (a) and recycling C2H6 to stage (b), and (e) recovering methane and ethylene streams. In a pref. system water is injected into first-stage hydropyrolysis zone. Higher hydrocarbon stream from stage (c) is generally hydrogenated and recycled to stage (a); alternatively aromatics may be recovered from this stream and the residue recycled (after hydrogenation) to stage (a). Process yields methane as well as ethylene with total recycle of unconverted materials.

Description

Two-st en hydropyro lysis cracking process for the production of ethylene The invention relates to a combined process for the production of ethylene. The invention relates in particular to a combined or integrated two-stage hydropyrolysis cracking or cracking process for the production of ethylene from higher hydrocarbons.

The splitting or cracking of various petroleum fractions for production of ethylene is well known. In general, fractions are used for these cracking processes in the area of Ethan. to heavy gas oil and even total crude oil as raw materials The cracking takes place in many different devices, for example heated tubular heating devices, heating devices with layers of silica, Cracking devices with fluidized bed, etc. Many procedural systems amrden also owl wrapped, which also include the recycling of various components, to increase the ethylene yields.

The invention relates to. . a summarized method of manufacture of ethylene together with methane, first in a first stage a hydrocarbon oil is hydropyrolysed in the presence of hydrogen, and then this is done at the Hydropyrolysis split material flowing off. Subsequently, the hydrogen and the ethane separated and recycled and the methane and ethylene recovered.

The invention relates to a process for the production of ethylene from higher hydrocarbons, which is characterized by the fact that one (a) a Introducing hydrocarbon oil and hydrogen into a hydropyrolysis zone of the first stage, wherein the molar ratio of hydrogen to hydrocarbon oil is at least 1/1, (b) the hydrocarbon oil in the presence of hydrogen in this zone at temperature conditions in the range of about 600 to 900 ° C, pressures of at least about 5 atmospheres and Hydropyrolysed residence times ranging from about 0.1 to 60 seconds, wherein a hydropyrolysis effluent is obtained, (c) the hydropyrolysis effluent to a cracking zone the second stage and subjects the effluent to cracking conditions such as temperatures in the range of about 750 to 900 ° C, pressures not exceeding about 2 atmospheres and dwell times in the range of about 0.01 to 10 seconds, forming a cracking zone effluent (d) the cracking zone effluent into a hydrogen stream, a methane stream, a Separates an ethylene stream, an ethane stream and a higher hydrocarbon stream, (e) recycling the hydrogen stream to the first stage hydropyrolysis zone and the ethane stream is recycled to the cracking zone of the second stage and (f) the methane stream and the ethylene stream wins.

According to the invention, a new, combined or

Integrated two-stage hydropyrolysis cracking process created, in which higher hydrocarbons including whole crude and hydrogenated coal liquids be pyrolyzed to form ethylene. In the case of the integrated procedure not only ethylene, but also methane, which in synthetic Natural gas can be used. The hydrogen and all other higher organic substances can be recycled into the process, ultimately converting them to ethylene and Methane can be converted, although it is also possible to use a heavy organic Separate electricity from which aromatic compounds such as benzene, toluene and / or can win xylenes. Will the aromatic compounds not be affected by this? If organic electricity is disposed of before recycling, it is desirable to use the electricity to hydrogenate in order to convert unsaturated compounds into saturated compounds.

The integrated method according to the invention is shown in the attached Drawing explained schematically together with certain possible features that are shown by dashed lines.

The hydrocarbon oils which are suitable for the process according to the invention can be defined as having densities below about 0.99, preferred below about 0.95, and have a Conradson carbon content of; less than about 20% by weight Vc, preferably less than about 2% by weight per year. As well as Both non-distillate and distillate hydrocarbon oils are suitable, as are them in U.S. Reissue Patent 27599 and U.S. Patent 3,363,024.

For example, crude petroleum and other oils that have similar density and volatility properties can be used as well as oils that are derive from coal like hydrogenated Coal oil. Distillate oils that are im The range from 30 to 3600c can be used. Similarly, coal tar distillates, which contain unsubstituted or hydroxy-substituted hydrocarbons are used will. Gases mainly containing butane and propane are satisfactory Feed materials. All of the substances listed above are intended to be derived from the expression "Hydrocarbon oils" are included.

The hydrocarbon oils described above are used in the hydropyrolysis zone the first stage initiated together with hydrogen. In the hydropyrolysis zone the hydrocarbon oils become pyrolytic. to lower in the presence of hydrogen Split hydrocarbons. As for the facilities required, so becomes a suitable reactor in which the hydropyrolyse can be carried out, in U.S. Patent 3,363,024 noted above. Another suitable facility is a common tubular furnace used in common cracking processes will.

The hydropyrolysis is done with a molar ratio of hydrogen too Hydrocarbon oils of at least 1/1, preferably at least 3/1, carried out. In the zone, the less coal is formed the more hydrogen is present, if other essential factors are kept constant such as temperature, the Pressure etc. Another factor to consider when determining the amount of hydrogen that which must be observed in a particular procedure is that with increasing hydrogen content, the formation of ethane favors the formation of ethylene will. This factor is important in connection with the second stage cracking, because at this stage ethane is dehydrated to ethylene. It is also important to note that the excess hydrogen passed through the integrated process and recycled must become. Taking all factors into account, it is preferred to use hydrogen to hydrocarbon oil mole ratios to work in the range of about 3/1 to 30/1.

The hydrogen for the hydropyrolysis stage is recycled the hydrogen, which is separated off in the subsequent separation stage, is supplied, as will be explained in more detail below, and additionally from a suitable external source.

The hydrogen and the hydrocarbon oil can be separated into the Hydropyrolysis step can be introduced or they can be mixed and mixed as a mixture be initiated. The hydrocarbon can be taken through an atomizing nozzle Use of hydrogen as the atomizing gas can be initiated. Is preferred the hydrocarbon oil to a temperature close to the operating temperature of the hydropyrolyse zone, for example heated to 3000C to as high as 550 ° C. The hydropyrolyse is at at a temperature in the range from 600 to 900 ° C., preferably from 700 to 850 ° C. Higher temperatures favor ethylene over Üthan. Prints of at least 5 atmospheres are used, usually pressures in the range from 5 to 100 atmospheres and preferably used in the range from 15 to 30 atmospheres. Favor lower pressures Ethylene versus ethane. Residence times in the range from 0.1 to 60 seconds are preferred 0.5 to 20 seconds are used.

Shorter residence times favor ethylene over ethane.

The coal deposition caused by side reactions in the hydropyrolysis zone can occur can be inhibited by adding a low concentration of sulfur compounds in the hydrocarbon oil feed if sulfur compounds are not yet present, for example 10 ppm. This is and is well known commonly referred to as passivation. Usually the addition takes place Sulfur compounds continuously.

An alternative to using the sulfur compounds is water or steam, albeit for the same effectiveness in inhibiting carbonization larger amounts of water are required compared to sulfur compounds. Usually up to about 3 moles of water / mole of hydrocarbon oil are effective, although larger Quantities can be used. Water not only inhibits carbonization, but it has also been found that water affects hydropyrolysis and formation favored by ethylene over ethane.

The effluent from the hydropyrolysis zone of the first stage is then in initiated the cracking zone of the second stage. In the second stage crack zone the effluent is split or cracked at low pressure. Temperatures in the area from 750 to 9000C, preferably from 800 to 8500C, are used.

Prints, usually not over about 2 atmospheres, and preferably not over 1 atm are used. The residence time can range from about 0.01 to 10 seconds, with 0.1 to 1 second being preferred, since the conditions are in the crack zone of the second stage are also ideal for dehydrogenating ethane to ethylene, the ethane is recycled from the separation zone into the cracking zone of the second stage. The zone of the second stage serves not only to contain the higher hydrocarbons in the effluent from the first stage hydropyrolysis zone, but also in addition, ethane, which is formed in the first and second stages, as well as dehydrate that which is recycled.

The effluent mixture from the second stage cracking zone is then worked up to recover methane and ethylene in a separation zone. Usual Process for the separation of hydrogen, methane, ethylene, ethane and higher hydrocarbons can be used. With a suitable Separation and extraction system the product mixture becomes immediate when it leaves the second stage cracking zone exits, cooled or quenched and then the cooled mixture is passed through passed a series of fractional distillation columns at low temperatures. The hydrogen is first separated and fed into the hydropyrolyse zone of the first stage, as previously mentioned, recycled.

The methane is then separated and recovered, and it can conveniently can be used as a synthetic component for natural gas. Then it becomes ethylene separated, and this can be stored or transported away as a commercial product. Ethane is next separated and sent to the second stage cracking zone as before specified, recycled.

The remaining higher hydrocarbons are then on usual Way hydrogenated to eliminate the unsaturation, and in the hydropyrolyse zone of the recycled in the first stage, where it is re-bound and converted into lower hydrocarbons and finally ethylene and methane are transferred.

The separation process described above is essentially a selective, stepwise distillation; one can also use a reverse process, i.e. a selective, gradual condensation.

Because the higher hydrocarbons have different amounts of aromatic Compounds, mainly benzene, toluene and xylenes, may contain prior to hydrogenation and recycling a further separation stage can be carried out. Such a separation can be done in a known manner to remove essentially all aromatic compounds to be separated, or only the desired components can be separated.

When essentially all aromatic compounds are separated, the remaining stream of higher hydrocarbons can be fed into the hydropyrolysis zone be recycled without hydrogenation of the first stage. However, it is preferred to use the current from higher hydrocarbons before recycling hydrogenate even if the aromatic compounds or part of the aromatic Connections have been removed.

The following examples illustrate the invention.

Example 1 A mixture of 2.3 vol / min liquid kerosene (boiling point range from 190 to 2700C and specific gravity of 2.65 vol / min liquid water and 161 vol / min hydrogen gas (molar ratio of H2 to hydrocarbon = approx 18.0) is fed into the first stage hydropyrolysis zone, as in US Pat. No. 3,363,024 described, initiated. Inlets for the recycled hydrogen and the recycled higher hydrocarbon are also contemplated. The hydropyrolysis is at a temperature in the range from 750 to 8000C, a pressure of 20.4 atü and a ventilation time of 7 to 10 seconds.

The effluent from the hydropyrolysis zone of the first stage is then depressurized passed into the cracking zone of the tubular second stage furnace. In this Zone is also provided with an inlet for recycled ethane. The split the second stage is at temperatures from 850 to 9000C, pressures from 0.7 to 1.7 atü and a dwell time of 0.1 to 0.5 seconds.

The product mixture from the second stage hydropyrolysis zone becomes rapidly cooled or quenched and transferred to a series of fractional distillation columns directed. The hydrogen is separated off and transferred to the hydropyrolysis zone of the first Stage recycled. The methane is separated and stored.

Ethylene is separated and stored. Ethane is separated and in the cracking zone of the second stage is recycled. The remaining electricity from higher Hydrocarbons are hydrogenated and transferred to the first stage hydropyrolysis zone recycled.

B e i s p 1 e 1 2 In a hydropyrolysis zone, which is 0.96 cm (3/8 inch) stainless steel tubular reactor 0.3 in (1 ft.) In length which contains a volume of about 16 cc in the interior area that the heated Zone results will be a light naphtha (BP 85 to 1500C) at a rate of 0.034 ml / min and hydrogen at a rate of 100 ccm / min (molar ratio from hydrogen to hydrocarbon = approximately 16.2). The hydropyrolysis is at a temperature of 7500C (hot spot or hot tip), a pressure of 6.8 atmospheres and an average residence time of 2.5 seconds.

The effluent from the hydropyrolysis zone is analyzed by gas chromatography; it contains 12.4% by weight of H2, 36.3% by weight of methane, 1.1% by weight of ethylene, 41.4% by weight of Ó ethane and 9.0 weight percent higher hydrocarbons.

The effluent from the hydropyrolysis is then sent to the second cracking stage initiated, which is operated at atmospheric pressure and 800 to 850 ° C. Calculations due to the thermodynamic equilibrium at 8500C result in a product that has the following hydrocarbon distribution: 41% by weight methane, 23.4% by weight 9b Ethylene, 26.6 total 45 ethane, 4.9% by weight benzene and 4.1% by weight higher hydrocarbons.

The methane, ethylene and benzene are extracted, and the hydrogen and the higher hydrocarbons are recycled to the hydropyrolysis zone and the ethane is recycled to the second stage cracking zone.

Claims (9)

Claims Process for the production of ethylene from higher hydrocarbons, It is noted that (a) a hydrocarbon oil and hydrogen is introduced into a hydropyrolysis zone of the first stage, the molar ratio of Hydrogen to hydrocarbon oil is at least 1/1, (b) the hydrocarbon oil in the presence of hydrogen in the iEarZone at temperature conditions in the area from about 600 to 900C, pressures of at least about 5 atmospheres and dwell times hydropyrolysed in the range of about 0.1 to 60 seconds with a hydropyrolysis effluent (c) the hydropyrolysis effluent to a second stage cracking zone initiates and the effluent cracking conditions under current temperatures in the range from about 750 to 90O0c, pressures not exceeding about 2 atm and dwell times in the range of about 0.01 to 10 seconds, forming a cracking zone effluent (d) the cracking zone effluent into a hydrogen stream, a methane stream, a Separates an ethylene stream, an ethane stream and a higher hydrocarbon stream, (e) recycling the hydrogen stream to the first stage hydropyrolysis zone and recycling the ethane stream to the second stage cracking zone and (f) the methane stream and wins the ethylene stream. 2. The method according to claim 1, characterized in that g e k e n n -z e i c h n e t that the hydrocarbon oil has a density less than about 0.99 and a Conradson carbon content of less than about 20 weight percent. 3. The method according to one or more of claims 1 and 2, characterized It is not noted that the following conditions apply to hydropyrolysis be used: Temperatures ranging from about 700 to 8500C, pressures in the range of about 5 to 100 atmospheres and dwell times in the range from 0.5 to 20 seconds. 4. The method according to one or more of claims 1 to 3, characterized Note that the hydrogen to hydrocarbon oil molar ratio ranges from about 3/1 to 30/1. 5. The method according to one or more of claims 1 to 4, characterized it is not noted that in the hydropyrolysis zone of the first stage as well Water is introduced. 6. The method according to one or more of claims 1 to 5, characterized It is not noted that in the cracking zone of the second stage the following Conditions to be used: temperatures in the range of approximately 800 to 8500C, Do not print above about 1 atm and dwell times in the range of 0.1 to 1 second. 7. The method according to one or more of claims 1 to 6, characterized NOTICE that the higher carbon mass hydrogenates and becomes in the hydropyrolysis zone of the first stage is recycled. 8 The method according to one or more of claims 1 to 7, characterized it is not noted that the flow of higher hydrocarbons into one Stream of aromatic compounds and a remaining stream is separated that the stream is obtained from aromatic compounds and that the remaining stream is recycled to the hydropyrolysis zone of the first stage. 9. The method according to one or more of claims 1 to 8, characterized it is not noted that the remaining stream is to be recycled is hydrogenated. L e r s e i t e