DE2164951B2 - Process for the production of gaseous olefins - Google Patents

Description

25th

The present invention relates to a process for producing gaseous olefins from Petroleum distillate feeds.

Ethylene, propylene and butadiene, the main ones Intermediate products for a large part of the petroleum chemical industry are essentially obtained through thermal cracking of petroleum gases and distillates such as naphtha and gas oil. It exists all over the world an increasing demand for the use of these lighter components of petroleum, and it is desirable to use heavier feeds for olefin production. In the past numerous problems arose in cracking the heavier loads previously used with them prevented the economical production of light olefins. The main problems were:

1) Excessive coke build-up in the cracking lines which reduced heat transfer and thereby made higher temperatures of the "pipe skin" necessary. The excessive coke deposition also restricts the flow in the cracking lines and can ultimately lead to one Blocking lead. The coke must often be removed by so burning it out, resulting in a longer shutdown of the system

2) tar build-up in the transmission lines and heat exchangers; this reduces the effectiveness the heat recovery and requires the system to be shut down for cleaning, which in turn affects the overall effectiveness of the work

3) Yields of olefin products are compared to those from lighter feeds low, which makes an increased charge and demands on the fuel necessary; additional ovens, heat exchangers, and other equipment make a much higher initial capital investment necessary.

4) feeds from many sources contain high levels of sulfur; this is the operation of the The cracking process is not necessarily harmful, but it can add to the construction cost of the plant. Furthermore, most of the sulfur is in the liquid products that boil above 200 ° C concentrated, which is why these are less valuable as fuel oils

The object was therefore to find an advantageous process for the preparation of olefins.

The subject of the invention is the method defined by the above claim.

It is important to avoid excessive degradation of the feed in the hydrogenation (1st stage), since On the one hand, this leads to increased hydrogen consumption with the associated increased production costs would lead, but on the other hand the olefin yield would not be increased. Of the The catalysts mentioned are those made of nickel / tungsten / silica / alumina particularly suitable The catalysts mentioned can also be used in sulfided form.

The catalysts are conveniently prepared by the support with an aqueous solution of a Of each of the metals, one after the other or at the same time. Tungsten as ammonium metatungstate, cobalt as cobalt nitrate, cobalt acetate, etc., and molybdenum as ammonium molybdate be admitted. In general, it is convenient to first coat the carrier with the salt of the Impregnate metal that should be present in the finished catalyst in the highest concentration, although not critical, other methods of making the catalyst include precipitation the metals on the support from a solution of their salts and the simultaneous precipitation of the metals with the hydrated carrier material.

The catalysts are preferably before use in the reaction by contact with a stream of hydrogen at a temperature between 100-800 ⁰ C, activated preferably 300-600 ° C for a period of 1 minute to 24 hours. The sulfided catalyst form can conveniently be prepared by hydrogen is replaced by liquid tetrahydrothiophene, and then for a period of 1 minute to 24 hours, of the between 100-800 ⁰ C, preferably 300-600 ° C, catalyst kept conducting.

Although the exact structure of the active types of the above hydrogenation catalysts in their active form is not known, it is possible that the catalyst in addition to the support elemental metal, metal oxides, Metal sulfides and complex aluminum or silicon-metal compounds contains.

The liquid hourly space velocity (LHSV) of the hydrocarbon can be between 0.1-5.0, preferably 0.25-2.0.

The hydrogen is preferably about 5 to 10 times molar on a recycle basis Amount of hydrocarbon feed used and can be used to remove before recycle Hydrogen sulfide and ammonia are passed through scrubbers. However, others can as well Working methods, such as B. batch work in an autoclave can be used.

The hydrogenation can take place in a single stage or in a series of two or more stages Using the same or different catalysts can be carried out.

The cracking that follows as the 2nd stage is carried out in the usual way.

The charge from the hydrogenation reaction is evaporated, for example, in the presence of steam at a weight ratio of steam to hydrocarbon of about 0.5: 1 to 2.0: 1 and at a maximum temperature between 700 and 1000 ^° C. and a residence time at this temperature between 0.01-5 seconds, preferably 0.1-2 seconds, passed through a heated zone, preferably a pipe. The products are rapidly cooled in a heat exchanger system, separated and cleaned in the usual way

In the publication by J. C Hill and LJ. Spillane in "J. At the. Chem. Soc Div. Petroleum Chem. Preprints «14 (1969), pages A13-A21, the hydrogenation of so-called "cycle oil" and subsequent steam pyrolysis of the hydrogenated product. From the Table I of this publication shows that in the hydrogenation, although the tricyclic and higher cyclic aromatics, which in the starting material in a Amount of 38% are present, are hydrogenated, but that the proportion of dicyclic aromatics of 3.9 to 7.8% and that of the monocyclic aromatics increases from 8.8 to 28.8%. This represents an approximately 30% strength Reduction of the aromatic content and this value is only half as great as that according to the invention required minimum reduction. Thus, according to this process, the more cyclic aromatic Compounds hydrogenated to form mono- or dicyclic aromatic compounds From table III it can be seen that the total yield of ethylene and propylene is about 18-25% and is therefore essential is lower than in the method according to the invention.

In the reference by M.D. Abbott et al in The Oil and Gas Journal, May 1958, See 144-152 a hydrogenation of certain petroleum fractions described, followed by a catalytic Cracking (no steam cracking) takes place This is an essential difference to the claimed one Process before, as is known, the starting materials for catalytic cracking are different Must meet conditions as starting materials for steam cracking. In particular, this is what you want End product in a catalytic cracking gasoline and light oil, with propylene eta only as by-products incurred, while ethylene and propylene are the preferred end products in steam cracking. This is possible also from Table 3 of the citation, in which propylene, ethane and propane as well as lighter products can only be obtained in an amount of about 8 to 9%. These yields are of course not comparable with those of the method according to the invention. In this reference it is stated that one The aim is to remove polyaromatic compounds during the hydrogenation, as they are necessary for the subsequent cracking are undesirable. It is also stated that the polyaromatic compounds readily become monoaromatic Let compounds hydrogenate, while these are difficult to convert into saturated compounds are. It is also stated that monoaromatic or naphthenic compounds for a catalytic Cracking processes are well suited. It cannot be inferred from this reference that one is a starting material suitable for steam cracking is obtained by considering the aromatic content Connections reduced by at least 61%. On the contrary, the impression must be created that the Presence of monoaromatic compounds - at least if followed by a catalytic crack should take place - preferred, but not disadvantageous in any case

In the reference by P, W. Sherwood "Petroleum Refiner", Vol 30, no. 11, pages 157-160, it is stated, among other things, that the best ethylene yields are obtained from crude petroleum if this has a high paraffin content; the yields can then be up to about 30%. If the starting material is more aromatic, a maximum ethylene yield of up to 15% can be obtained. This was of course already known. It is then determined that these recycle oils either have to be used as fuel oils or they can be converted back into suitable starting materials for ethylene (or gasoline) production by high pressure hydrogenation, i.e. they can be rearranged from aromatic compounds into paraffinic compounds by high pressure hydrogenation must, since, as stated, only give good ethylene yields. The presence of large amounts of paraffin in the starting material means not only a hydrogenation of the aromatic components, but also a splitting of the same (or the previously formed saturated ring structures) to paraffinic, i.e. open-chain compounds. However, this requires large amounts of hydrogen, which makes the process expensive and uneconomical. It is then stated that the more severe the pyrolysis conditions, the more aromatic compounds are obtained in the obtained by-product. Because of the high aromatic content of the by-products, they are unsuitable for recycling to cracking processes. Here, too, there is an essential difference from the present invention, since no rearrangements into paraffins should take place during the hydrogenation.

In US-PS 3491 019 is a hydrogenation of polyaromatic compounds described in monoaromatic, d. H. Compounds in which the unsaturated Bonds are contained in a single benzene nucleus. A reduction in the total salary of aromatic compounds by at least 61% is also not achieved hydrogenated product subjected to catalytic cracking. As is well known, this is essentially the case Gasoline and no ethylene produced, so that other requirements are placed on the raw materials are considered to be according to the invention.

US Pat. No. 3,513,217 describes the hydrogenation of a petroleum fraction, in which the aromatic hydrocarbons are hydrogenated and then cracked. The main difference between the claimed process and the known process is that the starting material used for the hydrogenation should have a boiling point of up to about 218.degree. Such fractions can not be compared with the presently employed fractions with a boiling point of 300 to 65O ⁰ C. The fractions used in the known process cannot contain any significant amounts of polycyclic aromatics, since these have a significantly higher boiling point. Thus naphthalene boiling at 218 ⁰ C and the two methylnaphthalenes at about 240 to 245 ° C.

Compared to the prior art, insofar as it hydrogenated the production of suitable for steam cracking As far as petroleum fractions are concerned, the method according to the invention has significant advantages. Are z. B. polycyclic aromatics without splitting the ring

structures are only partially hydrogenated to monoaromatic compounds, such a material would be Steam cracking splits off hydrogen and converts it back into a polyaromatic material. Such a material is therefore not desirable as a starting material, however, if the hydrogenation is so carried out that a splitting of the carbocyclic ring structure takes place, then the hydrogen consumption much higher and the cost of the process increases considerably. According to the invention, however, the polycyclic Structures of the starting material are not destroyed by hydrogenation, but maintained which makes it possible to use smaller amounts to obtain hydrogen products, which in the subsequent steam cracking show very high yields

Ethylene and propylene result. From one of the literature it can be seen that one for Production of large amounts of ethylene from paraffinic compounds should start. The production However, such paraffinic starting materials are either very expensive (large hydrogen consumption) or special and particularly suitable starting materials are necessary. The process claimed enables heavy oil fractions to be produced in large quantities made usable of ethylene and propylene in excellent yields

In the following examples, the reduction in aromatic content was calculated using the following Equation:

% Aromatics in feed -% aromatics after hydrogenation % aromatics in feed

X 100 =

The following examples illustrate the present invention without restricting it.

Comparison test 1

A complete Agha January vacuum distillate having an atomic ratio of hydrogen to carbon of 1.73 and a sulfur content of 1.72 wt .-% was performed in a 26-cc quartz reactor at a maximum temperature of 830 ⁰ C cracked The analysis by physical separation and spectroscopy (including UV absorption) showed an aromatic compound content of 49% by weight.

The weight ratio of water vapor to hydrocarbon in the feed was 1: 1 with a average total molar flow of 33 moles / hr. The ethylene and propylene yields were 23 and 10 wt%, respectively, with a total cracked gas conversion of 53 wt% of the feed. The in Coke deposited in the cracking zone was equivalent to 1200 ppm of the hydrocarbon feed.

The above example, not according to the invention, serves Comparison purposes.

example 1

The catalyst was prepared by calcining alumina at a temperature of 550 ⁰ C. Then, the calcined clay was * us ammonium molybdate impregnated with an aqueous solution, evaporated to dryness, and further calcined at 55O ⁰ C. This procedure was then treated with an aqueous solution of cobalt nitrate, the catalyst was repeated then activated in a hydrogen stream for 16 hours at 400 ⁰ C.

A 250 g sample of the comparative test i used Agha January vacuum distillate in a 1 - - shaken autoclave at 350 ⁰ C and 105 atmospheres hydrogen pressure for 8 hours using 100 g of the above prepared cobalt / Moiybdän / alumina catalyst is hydrogenated. The recovered hydrogenated vacuum distillate, Sample A, had an atomic ratio of hydrogen to carbon of 1.84 and a sulfur content below 0.05% by weight. Analysis by physical separation and spectroscopy (including UV absorption) showed that the aromatic compound content was 19% by weight (reduction in aromatic content: 61.2%). This material was then cracked with steam under the conditions mentioned in comparison list test 1. The ethylene and propylene yields were 26 and 10 wt% of the feed, respectively, with a total conversion to cracked gas of 58%. There was also a substantial reduction in heavier products compared to those formed from the untreated vacuum distillate. In particular, the tar-like material condensing in the transmission line from the reactor was, in contrast to comparative test 1, only formed in half the amount. The one in the reactor zone

The amount of coke deposited was only 250 ppm of the feed.

Example 2

100 g of hydrogenated vacuum distillate sample A were further in a rocking autoclave at 35O ⁰ C and 105 atmospheres hydrogen pressure for 18 hours under USAGE-Jung of 40 g of a by impregnation as in Example 1 produced 5% nickel-on-silica catalyst hydrogenated This further hydrogenated Vacuum distillate had an atomic ratio of hydrogen to carbon of 1.91 and a sulfur content below 0.02% by weight. Analysis by physical separation and spectroscopy (including UV absorption) showed an aromatic compound content below 2% by weight (reduction in aromatic content: about 96%). After steam cracking this sample under the conditions used in Comparative Test 1, the ethylene and propylene yields were 29 and 11 weight percent, respectively, and the overall cracked gas yield increased to 64%. The yields of fuel oil and tarry material were reduced to a quarter of that obtained from the untreated vacuum distillate, while the amount of coke deposited in the reactor was only 100 ppm of the feed.

Comparison test 2

A complete Kuwait vacuum distillate with an atomic ratio of hydrogen to carbon of

bo 1.74 and 2.78 wt .-% of Schwefelgshalt was performed in a 20-cc quartz reactor at a temperature of 83O ⁰ C cracked The analysis by physical separation and spectroscopy (including UV absorption) showed a content of aromatic Verbin -

b5 fertilize 52% by weight.

The weight ratio of water vapor to hydrocarbon in the feed was 1: 1 with one average hydrocarbon feed

amount of 62 g / hour The ethylene and propylene yields were 23 and 10 weight percent, respectively, with total conversion in cracked gas at 52% by weight of the feed. The coke deposited in the cracking zone corresponded to 1050 ppm of hydrocarbon feed. The sulfur content of the fuel oil was 6.8 Wt%.

This example, not according to the invention, is used for comparison purposes.

Example 3

A 200 g sample of the Kuwait vacuum distillate used in comparative test 2 was in a 1-1 shaking autoclave at 350 ^° C. and 154 atm. Hydrogen pressure for 8 hours using 50 g of the cobalt / molybdenum / alumina produced by impregnation as in Example 1 - hydrogenated catalyst.

The hydrogenated vacuum distillate obtained had an atomic ratio of hydrogen to carbon of 1.87 and a sulfur content below 400 ppm (weight). Analysis by physical separation and Spectroscopy (including UV absorption) showed an aromatic compound content of 16 % By weight (reduction in aromatic content: 69%).

This material was steam cracked under the same conditions as in Comparative Test 2. the Ethylene and propylene yields were 27 and 12 weight percent, respectively, of the feed, with 62 weight percent of the Feed were converted to cracked gas. The yields of fuel oil and tarry material were reduced to one third of the values obtained from the untreated vacuum distillate. The in Coke deposited in the cracking zone was equal to 150 ppm (weight) of the hydrocarbon feed.

Example 4

Kuwait vacuum distillate used a 200-g sample of the comparative test 2 was ⁰ C and 154 atm hydrogen g of 8 hours, using 50 in a 1-1 shaken autoclave at 35O of the nickel / tungsten prepared by impregnation as in Example 1 / silica / Hydrogenated alumina catalyst The hydrogenated vacuum distillate obtained had an atomic ratio of hydrogen to carbon of 1.95 and a sulfur content of 100 ppm (weight). Analysis by physical separation and spectroscopy (including UV absorption) showed an aromatic compound content below 2% by weight (reduction in aromatic content: 96%).

This material was then steamed under the conditions used in Comparative Test 2 cracked The ethylene and propylene yields were 28 and 14 wt% of the feed, respectively, with 68% of the feed had been converted to cracked gas. The yields of fuel oil and teenage products Material was reduced to a quarter of the values obtained from the untreated vacuum distillate, while the amount of coke deposited in the reactor was only 100 ppm. The sulfur content of the fuel oil was only at 300 ppm.

Example 5

A 200 g sample of the Kuwait vacuum distillate used in comparative test 2 was in a 3 l shaking autoclave at 350 ^° C. and 154 atmospheres hydrogen for 75 hours using 60 g of a cobalt / molybdenum / alumina produced by impregnation as in Example 1 Hydrogenated catalyst The hydrogenated vacuum distillate obtained had an atomic ratio of hydrogen to carbon of 1.95 and a sulfur content of 125 ppm (weight). Analysis by physical separation and spectroscopy (including UV absorption) showed an aromatic compound content of less than 2% by weight (reduction in aromatic content: over 96%).

This material was produced under the conditions of

ίο Comparison test 2 cracked with steam. The Ethylene and propylene yields were 28 and 14 wt% of the feed, respectively, with 67 wt% of the Feed were converted to cracked gas. The yields of fuel oil and tarry material were reduced to a quarter of the values obtained from the untreated vacuum distillate, while the amount of coke deposited in the reactor was only 100 ppm.

, ₀ examples

A 200 g sample of the Kuwait vacuum distillate used in comparative test 2 was in a 1-1 shaking autoclave at 350 ^° C. and 154 atmospheres hydrogen for 8 hours using 50 g of a nickel / tungsten / alumina produced by impregnation as in example 1 -Catalyst hydrogenated. The hydrogenated vacuum distillate obtained had an atomic ratio of hydrogen to carbon of 1.88 and a sulfur content below 300 ppm (weight).

Analysis by physical separation and spectroscopy (including UV absorption) showed an aromatic compound content of 15% by weight (reduction in aromatic content: approx 71%).

J5 This material was then steam cracked under the conditions of Comparative Test 2 Ethylene and propylene yields were 27 and 13 weight percent, respectively, of the feed, with 62 weight percent of the Feed were converted to cracked gas.

The yields of fuel oil and tarry material were one third of that from the untreated The values obtained in the vacuum distillate were reduced and the amount of coke deposited in the reactor was only 120 ppm.

Comparative tests 1 and 2 show the ethylene and propylene yields, the cracked gas yield and the deposition of coke from cracking a straight run wax distillate without pretreatment. The examples according to the invention show that the

so hydrogenation of the wax distillates before cracking leads to an improvement in all of the above parameters and that further not only reduces the sulfur content, but also the yields of fuel oil and tarry material were reduced. This is achieved by using a nickel / tungsten / silica / alumina catalyst The increased level of hydrogenation achieved is evident from Example 4. The level of hydrogenation is similar to Example 5, but was achieved in a much worse time

eo In all examples according to the invention was continued found that the fuel oil product is an essential lower viscosity and lower tendency to emulsify with water after condensation van. Product and diluting water vapor showed than the fuel oil produced in the comparative tests; through this pumping and handling at lower temperatures or separation and fractionation of liquid products

Claims (1)

Claim: Process for the production of gaseous olefins, in which a between 300-650 ⁰ C (at atmospheric pressure) boiling vacuum distillate at a temperature of 300-400 ° C at a pressure of 14-210 atfl in the presence of a catalyst made of nickel and / or Cobalt / molybdenum / alumina, nickel or cobalt / tungsten / alumina, nickel or cobalt / molybdenum / silica / alumina or nickel or cobalt / tungsten / silica / alumina or a sulfided form of these catalysts heated with hydrogen and that The product obtained is cracked in the customary manner in the presence of steam at elevated pressures and temperatures, characterized in that the content of aromatic, in particular polycyclic compounds is reduced by at least about 61% without significant rearrangement or significant degradation of carbon structures