FR2537152A1 - PROCESS FOR IMPROVING THE QUALITY OF THE GASOLINE OBTAINED BY CATALYTIC CRACKING - Google Patents

Abstract

THE INVENTION RELATES TO A PROCESS FOR IMPROVING THE QUALITY OF THE GASOLINE OBTAINED BY CATALYTIC CRACKING. THIS IMPROVEMENT IS OBTAINED BY PUTTING THE GASOLINE IN CONTACT WITH A CRYSTALLINE METAL SILICATE WHICH, AFTER CALCINATION FOR ONE HOUR IN AIR AT 500C HAS THE FOLLOWING PROPERTIES: A. IS THERMALLY STABLE UP TO AT LEAST 600C, BA A DIAGRAM OF DIFFRACTION X-RAYS BY THE POWDER METHOD IN WHICH THE MOST INTENSE LINES ARE THE FOUR LINES MENTIONED IN TABLE A: D (A) 11.2 0.210.0 0.23.84 0.073.72 0.06 C. IN THE FORMULA THAT REPRESENTS THE COMPOSITION OF SILICATE EXPRESSED IN MOLES OF OXIDES AND WHICH, IN ADDITION TO SIO, CONTAINS BOTH FEO AND ALO, THE SIOFEO MOLAR RATIO IS 25-90 AND THE SIOALO MOLAR RATIO IS 250-1200. PREFERENCE, AT LEAST PART OF FRACTION C.

Description

C-1- The present invention relates to a method for improving the quality

  gasoline obtained by catalytic cracking. The gasoline obtained by catalytic cracking has a high olefin content This is the reason why

  gasoline has a strong tendency to form gums.

  The gasoline obtained by catalytic cracking also has a relatively low content of aromatic compounds. This is the reason why gasoline has a relatively low octane number. Due to the properties mentioned above, the quality of the gasoline obtained The improvement in quality can be achieved by catalytic reforming, in which, in particular, the olefin content decreases and the content of aromatic compounds increases. Catalytic reforming of the gasoline obtained by catalytic cracking is the high content of sulfur compounds and nitrogen compounds of this gasoline As the presence of sulfur compounds and nitrogen in the feed has an adverse influence on the behavior usable catalysts in reforming, extreme removal of these compounds from the feed is required before that the latter may be subject to

  Catalytic reforming This requires a catalytic hydrotreatment

  lytic under extremely severe conditions although the two-step process mentioned above, in which

  gasoline is first subjected to a hydrotreatment

  lytic under extremely severe conditions and then catalytic reforming, provide an improvement

  considerable difference in the quality of the gasoline obtained

  catalytic quenching, there is an urgent need for a

  leading to the desired result in one step.

  Recently, new metallic silicates

  tallins having a special structure were obtained by

-2 2537152

  synthesis, which silicates exhibit a catalytic activity in the conversion of non-aromatic organic compounds, such as olefins, into aromatic hydrocarbons. The catalytic behavior of these silicates is very insensitive to the presence of sulfur and nitrogen compounds in the The crystalline metal silicates are characterized in that after calcination for one hour in air at 500 ° C., they have the following properties:

  a) they are thermally stable up to a time

  at least 600 ° C, b) they have an X-ray powder diffraction pattern in which the most intense lines are the four lines mentioned in the diagram.

Table A.

TABLE A

8 (0.1 nm)

11.1 0.2

0 0.2

3.84 t 0.07

3.72 0.06

  c) in the formula which represents the composition of the silicate expressed in moles of the oxides and which, in addition to Si O 2, comprises either A 1203 or Fe 203, the molar ratio

  If O 2 / A 1203 or Si O 2 / Fe 203 is greater than 10.

  In the present patent application, a crystalline silicate having a thermal stability of at least t C must be understood as being a silicate whose X-ray diffraction pattern by the powder method, during heating at a temperature of t C , rest

substantially unchanged.

  Research on the use of the aforementioned crystalline silicates of iron or aluminum as catalysts to improve the quality of the gasoline obtained by catalytic cracking has shown that although

  a certain reduction in the

  These changes are not sufficient to achieve the desired quality improvement. It has also been found that the catalysts have insufficient activity and stability. However, by continuing the investigations, it is not possible to obtain the desired quality improvement. found that crystalline metal silicates having the special structure of the aforementioned iron or aluminum silicates when used as catalysts to improve the quality of the gasoline obtained by catalytic cracking, exhibit excellent behavior if they comprise both iron and aluminum and if, moreover, these metals are present in the silicate in amounts such that in the formula which represents the composition of the silicate expressed in moles of the oxides, the molar ratio Si O 2 / Fe 2 03 either

  -90 and the molar ratio Si O 2 / Fe 203 is 250-1200.

  Compared with crystalline silicates of iron or aluminum

  mixed silicates of iron and aluminum

  above mentioned activities and stability

  dereally superior and give a gasoline with a considerably lower olefin

  octane considerably higher.

  The present patent application therefore relates to a process for improving the quality of the gasoline obtained by catalytic cracking, in which the gasoline is brought into contact with a crystalline metal silicate which, after calcination for one hour in air at 500 ° C. , has the properties mentioned above under a) and b) and the property that in the formula which represents the composition of the silicate expressed in moles of the oxides and which in addition to Si O 2 comprises both Fe 2 03 and A 1203, the SiO 2 / Fe 203 molar ratio is 25-90 and the

  molar ratio Si O 2 / A 1203 is 250-1200.

  In the process according to the invention, the

253? 5-2

-4-

  starting is a gasoline obtained by catalytic cracking.

  Such gasolines can very well be prepared by the application of catalytic cracking to oils

  heavy hydrocarbons, such as atmospheric gas oils.

  vacuum distillation gas oils, residues

  deasphalted vacuum and mixtures thereof

  The catalytic cracking on an industrial scale is usually carried out in a continuous manner using a plant which consists essentially of a cracking reactor.

  arranged vertically and a catalyst regenerator.

  The regenerated hot catalyst from the regenerator is suspended in the oil to be cracked and the mixture is passed through the cracking reactor in a direction from bottom to top. The deactivated catalyst is separated from the cracked product and, after stripping, transported to the regenerator The cracked product is separated into a light fraction having a high content of C 3 and C 4 olefins, a gasoline fraction and several heavy fractions, such as a light recycling oil, an average recycling oil, a heavy recycling oil and an oil

for porridge.

  Crystalline metal silicates used as-

  catalysts in the process according to the invention are defined in particular by the X-ray diffraction pattern

  by the method of the powders which they present

  nation for one hour in the air at 5000 C On this dia-

  The most intense lines must be the four lines mentioned in Table A. The complete powder X-ray diffraction pattern of a typical example of a crystalline metal silicate used in the process according to the invention. is shown in Table B. -5-

2537152 '

TABLE B

  d (0.1 nm) 11.1, 8.93 7.99 7.42 6.68 6.35, 97, 70, 56, 35

4.98 (D)

  4.60 4.35 4.25 4.07 4.00 Relative intensity 1 d (0, lnm) relative intensity

3.84 (D) 57

3.72 (D) 31

3.63 16

3.47 1

3.43 5

3.34 2

3.30 5

3.25 1

3.05 8

2.98 11

2.96 3

2.86 2

2.73 2

2.60 2

2.48 3

2.40 -2

  (D) = doublet Crystalline metal silicates may be prepared from an aqueous mixture comprising the following compounds: one or more compounds of an alkali metal (M), one or more organic nitrogen compounds (RN) which comprise an organic cation or from which an organic cation is formed during the preparation of the silicate, one or more silicon compounds, one or more compounds comprising iron in a trivalent form and one or more aluminum compounds. The preparation is carried out by maintaining the mixture at an elevated temperature until the silicate is formed and then separating the silicate crystals from the mother liquor and washing, drying and calcining the

  crystals in the aqueous mixture from which the silicas

  cates are prepared, the various compounds must be

  present in the following molar ratios, expressed

  with the exception of the organic compounds of the nitrogen in moles of the oxides: M 2 O: Si O 2 = 0.01-0.35, RN: Si O 2 = -0.02-l, 0 Si O 2: Fe 203 = 25-270 Si O 2: A 1203 = 250-2400 and H 20: If O 2 = 5-65 In the preparation of the silicates, the basic mixture from which one can start can very well be a mixture which as a compound of the nitrogen comprises an alkylammonium compound

  quaternary, such as a tetrapropylammonium compound.

  Preference is given to the use of an amine

  as an organic compound and in particular n-butylamine.

  In addition, in the preparation of the silicates, preference is given to the use of a starting mixture which, as an alkali metal compound, comprises a compound of the

  sodium and, as silicon compound, amorphous silica.

  The silicates prepared as described above comprise alkali metal ions. Using suitable exchange methods, these ions can be replaced by other cations, such as hydrogen ions or ammonium ions. Crystalline silicates used in the process according to the invention preferably have a

  alkali metal of less than 0.05% by weight.

  The process according to the invention can very well be carried out by passing the feed from bottom to top or from top to bottom through a vertically disposed reactor containing a fixed or mobile bed of crystalline metal silicate. Suitable conditions for implementing the process according to the invention is a temperature of 300-600 ° C, a pressure of 1-50 bar and a speed

253? 152 '

  The process is preferably carried out under the following conditions: a temperature of 400-500.degree. C., a pressure of 2.5-25 bar and a space velocity of 0. The process can be carried out in the presence of hydrogen, if desired. In the process according to the invention, the formation of aromatic compounds is accompanied by cracking. As a result of this cracking, the product fraction C 4 contains a considerable proportion of C 3 and C 4 olefins. that the recycling of the product fraction Cj leads to a considerable improvement in

  the selectivity and stability of the catalyst, while

  As a result, in the process according to the invention, at least a portion of the product fraction C 4 is preferably recycled. Depending on the extent to which the separation between the light fraction and the gasoline fraction

  catalytically cracked product is more or less

  However, the investigations revealed that in the process according to the invention an increase in the content of C 3 and / or C 4 olefins was observed. of

  the load results in improved selectivity of quality.

  An increase in the C 3 and / or C 4 olefin content of the filler can be obtained in various ways. Firstly, it is possible to separate the light fraction from the gasoline fraction of the cracked product.

  less completely and thus allow a

  The alternative is to separate the gasoline from the catalytic cracking product and then add additional C 3 and / or C 4 olefins for this purpose. a preference is

2535 152 '

  The use of C 3 and / or C 4 olefins which can be separated from the light fraction of a product obtained by catalytic cracking Because of its favorable effect on the improvement of the selectivity and quality, the method according to the invention is applied

  preferably to a gasoline obtained by catalytic cracking

  which has an increased content of C 3 and / or C 4 olefins.

  The invention is now illustrated with the help of

the following example.

EXAMPLE

  Four crystalline silicates (silicates 1-4) are prepared by heating mixtures of NaOH, Fe (NO 3) 3 and / or NaAlO 2, amorphous silica containing 100 ppm by weight of aluminum and C 4 H NH 2 or (C 3 H 7) 4 NOH in water in an autoclave under spontaneous pressure, with stirring, at C. In the preparation of silicates 1-3, the mixture is heated for 120 hours. of reaction, the silicates formed are separated by filtration, washed with water until the pH of the water

  of about 8 and dried at 120 ° C.

  nation for one hour in air at 5000 C, silicates 1-4 have the following properties

  (a) they are thermally stable up to a temperature

  at least 800 ° C, (b) they have an X-ray powder diffraction pattern corresponding substantially to that given in Table B and (c) they have Si O 2 / Fe 203 and If O 2 / A 1203 as mentioned in Table C.

TABLE C

  Silicate N O Si O 2 / Fe 203 Si O 2 / A 1203 i

4

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  The molar composition of the aqueous mixtures from which silicates 1-4 are prepared can be represented.

  as follows: Na 2 W (C 3 H 7) 4 NOH x C 4 H 9 NH 2 y A 1203.

  z Fe 203 If O 2 450 H 20, where v, w, x, y and z have the values mentioned in Table D.

TABLE D

Silicate N v W x y z

1 1 9 0.066 -

2 2.5 10 0.003 0.20

3 1 10 0.036 0.20

4 1 10 0.036 0.33

  From the silicates 1-4, 8-silicates are prepared, respectively, by boiling the silicates 1-4 with a solution of molarity 1.0 of NH 4 N0 3, washing with water, boiling again with a solution of molarity 1.0 of NH 4 NO 3, washing, drying at 120 ° C.

and calcining at 500 C.

  Silicates 5-8 are tested in six experiments (experiments 1-6) as catalysts to improve the

  quality of gasoline obtained by catalytic cracking.

  The experiments are carried out in a reactor containing a fixed bed of catalyst. All the experiments are carried out at a temperature of 450 ° C., a pressure of 5 bars and a space velocity of 0.5 kg / kg. In experiments 5 and 6, the fraction of product C 4 is recycled to a

  C 4 / gasoline molar ratio of 10: 1.

  Experiments 1-5 are carried out using a gasoline 1 Experiment 6 is carried out using a gasoline 2 obtained by mixing 93.0 parts by weight of gasoline 1 with 7.0 parts by weight of a mixture of butenes L Petrol 1 has the following properties:

253-152 1

  Composition in% by weight C 4 c 4 aromatic compounds naphthenes paraffins + olefins weight ratio olefins / paraffins

sulfur content,% by weight -

  nitrogen content, ppm by weight boiling point, C ozone index, mmol / g *

MON-0 **

  4.7 24.2 13.6 57.5 approx 50/50 0.14 4.0, 4 * The ozone index is a measure of the olefin content of gasoline Less gasoline contains

  of olefins, the lower the ozone index.

  ** MON-O is the octane number "motor" without addition

lead.

  The results of experiments 1-6 are shown in Tables EG The parameters activity, selectivity, stability and selectivity of the operation indicated in the Tables are defined as follows: Activity = (% by weight of non-aromatic C 5 compounds present in the feed) (% by weight + non-aromatic C 5 compounds present in the product) + x 100 (% by weight of C 5 nonaromatic compounds present in the feedstock) Selectivity = (% by weight of coco solids) aromatics present in the product) (% by weight of aromatic compounds present in the feed) x 100 (% by weight of non-aromatic C 5 compounds present in the feed) (% by weight + of non-aromatic C 5 compounds present in the product Instability = decrease of the activity of a test of 100 hours to a test of 350 hours Selectivity of the operation = increase of the% in weight of aromatic compounds + reduction of the weight% of fraction C 5 wl - 12- Experienced these 1-6, only experiments 4-6 are experiments according to the invention Experiments 1-3 are outside the general scope of the invention They have

  have been included in the patent application for comparison.

TABLE E

  Experiment N Silicate N Fuel load N Aromatic compounds present in the feed or in the total product, resp.% By weight C 5 + C 5 + present in the feed or in the total product, resp.% By weight Activity, average on 350 hours,% by weight Selectivity, average over 350 hours,% by weight Instability,% by weight MON-O of the filler or product

liquid, resp.

  Ozone index of the charge or liquid product, resp, mmol / g

1 2 3 4

6 7 8

1 1 1 1 1

24.2 36.8 41.0 43.3 46.7

, 79.8

82.0 79.8 74.9

39.5 42.3 48.8 60.3

44.8, 8, 2

, 4 83.2 83.2 84.8

52.5 87.4

4.0 2.0 1.1 0.6 0.3

-13-

TABLE F

  Experience N Silicate N Gasoline load N C 4 recycle Aromatic compounds present in the feedstock or total product, resp.% By weight C 5+ present in the feed or total product, resp.% By weight Activity, average over 350 hours,% by weight Selectivity, average over 350 hours,% by weight Instability,% by weight

  MCN-O of the charge or liquid product, resp.

  Ozone index of the charge or liquid product, resp, mmol / g

TABLE G

  Experiment N Silicate N Petrol feed N C 4 recycle Aromatic compounds present in the feedstock or the total product, resp.% By weight C + compounds present in the feedstock or the total product, resp,% by weight Increased compounds aromatic,% by weight Decrease of the compounds in C 5,% by weight Selectivity of the operation 1 1 no yes

24.2 46.7 48.5

, 3 74.9 77.1

, 59.8

52.5

, 87.4

57.2 87.3

4.0 0.3 0.4

1 1

Yes

2 2

Yes

24.2 48.5 22.2

47.0

, 3 77.1 88.6 76.8

  24.3 18.2 1.3 24.8 11.8 2.1 MON-O of the feedstock or total product, resp 84.0 87.3 Ozone number of feed or total product, resp, mmol / g 4.0 0.4

, 87.2

4.2 0.3

253 I 52

  Referring to the results mentioned in the

  Tables E-G, we can notice the following.

Table E

  Silicate-5 (aluminum silicate) is not used

  It can be read as a catalyst for the present purpose because this silicate has a very low average activity, a very low average selectivity and a very low stability and, moreover, it gives a gasoline having a moderate octane number.

  and a very high olefin content.

  Silicate 6 (iron silicate) is not very useful

  readable for the present purpose because this silicate has a very low average activity and, moreover, gives a gasoline having a moderate octane number and a high olefin content. Silicate 7 (mixed silicate of iron and aluminum, outside the general scope of the invention) is not very useful as a catalyst for the present purpose, because this silicate has a very low average activity and, moreover, gives a gasoline with a moderate octane number and a

  relatively high olefin content.

  Silicate 8 (mixed silicate of iron and aluminum

  according to the invention) is excellently usable as a cata-

  lyser for the present purpose This silicate has a very high average activity, a high average selectivity and a very high stability In addition, the silicate gives a gasoline having a very high octane number and a very low

olefin content.

Table F

  Recycling the C 4 product fraction gives a higher average selectivity and higher stability while the very high average activity and the very high

  product quality are maintained.

Table C

  When a gasoline-of a higher butene content is used as a filler, then, for an increase

_ 15-

  Compared with the content of aromatic compounds, a much lower loss of compounds is obtained, in other words a higher selectivity of the quality improvement. At the same time, a very high quality of the product is maintained. . 2531 i SI

Claims (8)

  A process for improving the quality of a gasoline obtained by catalytic cracking, characterized in that the gasoline is brought into contact with a crystalline metal salt which, after calcination for one hour in air at 500 ° C., has the following properties:   a) it is thermally stable up to a temperature of   at least 600 o C, b) it has an X-ray diffraction pattern by the powder method in which the strongest lines are the four lines mentioned in Table A: TABLE A d (0.1 nm) 11.2 0.2 10.0 0.2 3.84 0.07 3.72 0.06   c) in the formula which represents the composition of the silicate expressed in moles of the oxides and which, in addition to Si O 2, comprises both Fe 203 and A 1203, the molar ratio Si O 2 / Fe 203 is 25-90 and the molar ratio Si O 2 / A 1203 is 250-1200.   A process according to claim 1, characterized in that the crystalline metal silicate has a content of   alkali metal of less than 0.05% by weight.   A process according to one of claims 1 and 2,   characterized in that it is carried out at a temperature of 300-600 C, a pressure of 1-50 bar and a speed space of 0.1-10 kg kg 1 h 1.   A process according to one of claims 1 to 3,   characterized in that at least a portion of the fraction of product C 4 is recycled. 253 1152 l -1 7-   A process according to one of claims 1 to 4,   characterized in that it is applied to a gasoline obtained by catalytic cracking which has an increased C 3 and / or C 4 olefins.   A process according to claim 5, characterized in that the increase in the olefin content of the gasoline has been achieved by separating the C 4 fraction from the gasoline fraction of the cracked product in such a way that at least a portion of the olefins which in general are removed together with the C 4 fraction spend in the fraction of gasoline.   A process according to claim 5, characterized   in that the increase in the   gasoline by adding C 3 and / or C 4 olefins from an outside source.   8 The improved quality essence obtained by a   process according to one of claims 1 to 7.