NZ204691A - Catalytic reforming of gasoline using crystalline metal silicate - Google Patents

Description

New Zealand Paient Spedficaiion for Paient Number £04691 2 04 8 Px- r.. ;-v. Mb-%2\ 3o-i(.sa~ » I MiJs i y L-.n ! . a a rf-i C&tnfiti" C.sczlficaiion Filod: r=,„... C 10G 35/0^5 _ <►,>* <33-«ccofaaa»a»a*xajBa3ftBaaa f gOMAR 19831 ■ a i i i i i i iafo? .24 JUN1983.

PJ ^ ^ p II yi iu? einy No.: Date: NEW ZEALAND PATENTS ACT, 1953 COMPLETE SPECIFICATION PROCESS FOR IMPROVING THE QUALITY OF GASOLINE i&We, SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V., Carel van Bylandtlaan 30, The Hague, the Netherlands, a Netherlands Company hereby declare the invention for whichjci / we pray that a patent may be granted toxxx/us, and the method by which it is to be performed, to be particularly described in and by the following statement:- - 1 - (followed by page la) 20469 - Ic^- rnOCESS-gOR IMFPQVDJa TIIE QUALITY OF GAGQLIIlJE The invention relates to a process for improving the quality of gasoline obtained by catalytic cracking.

Gasoline obtained by catalytic cracking has a high olefins content. This is the reason why the gasoline displays a strong tendency to form gum. Gasoline obtained by catalytic cracking also has a relatively lew arcmatics content. This is the reason why the gasoline has a relatively low octane number. In view of the above-mentioned properties the quality of gasoline obtained by catalytic cracking must be improved, before it becomes eligible for use as motor gasoline. Such quality improvement may be carried out by catalytic reforming, in which, among other things, the olefins content will fall and the arcmatics content will rise. A serious drawback connected with the catalytic reforming of gasoline obtained by catalytic cracking is this gasoline's high content of sulphur compounds and nitrogen ccmpounds. Since the presence of sulphur and nitrogen compounds in the feed has a highly unfavourable effect on the performance of catalysts suitable for use in reforming, extreme removal of said compounds frcm the feed is needed before the latter can be subjected to catalytic reforming. This requires a catalytic hydrotreatment under extra severe conditions. Although the above-mentioned two-step process, in which gasoline is first subjected to a catalytic hydrotreatment under extra severe conditions and subsequently to catalytic reforming, results in a considerable quality improvement of the gasoline obtained by catalytic cracking, there is an urgent need for a process which leads to the desired end in a single step.

Recently new crystalline metal silicates having a special structure have been synthesized, which silicates shew catalytic 20469 1 activity in the conversion of non-aromatic organic compounds, such as olefins, into arcmatic hydrocarbons. The catalytic performance of these silicates is quite unsusceptible to the presence of sulphur and nitrogen ccmpounds in the feed. The crystalline metal silicates concerned are characterized in that after one hour's calcination in air at 500°C they have the following properties: a) thermally stable up to a temperature of at least 600°C, b) an X-ray pcwder diffraction pattern in which the strongest lines are the four lines mentioned in Table A.

TABLE A d(A) 11.1 + 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 SiC^, includes either or Fe^O^, the SiC^/A^O^ or the SiO^/Fe^O^, molar ratio is higher than 10.

In the present patent application a crystalline silicate having a thermal stability of at least t°C should be taken to be a silicate whose X-ray powder diffraction pattern, upon heating to a temperature of t°C, remains substantially unchanged.

An investigation into the use of the above-mentioned crystalline iron or aluminium silicates as catalysts for iirproving the quality of gasoline obtained by catalytic cracking has shewn that although seme reduction in olefins content and seme increase in arcmatic content do occur, these changes are insufficient for the purpose of the desired quality improvement. 2046 9I It has furhter been found that the catalysts have insufficient activity and stability. Hcwever, continued research has revealed that crystalline metal silicates having the special structure of the iron or aluminium silicates mentioned hereinbefore when used 5 as catalysts for improving the quality of gasoline obtained by catalytic cracking, display excellent performance if they comprise both iron and aluminium and if, in addition, these metals are present in the silicate in such quantities that in the formula which represents the composition of the silicate 10 expressed in moles of the oxides, the Si02/Fe2C>2 molar ratio is 25-90 and the SiC^/A^O^ molar ratio is 250-1200. Compared with the crystalline iron or aluminium silicates the above-mentioned iron-aluminium silicates have considerably better activity and stability and provide a gasoline having a 15 considerably lower olefins content and a considerably higher octane number.

The present patent application therefore relates to a process for improving the quality of gasoline obtained by catalytic cracking, in which the gasoline is contacted with a 20 crystalline metal silicate which, after one hour1s calcination in air at 500 °C has the properties mentioned above under a) and b) as well as the property that in the formula which represents the composition of the silicate expressed in moles of the oxides and which in addition to SiC^, includes both and , the Si02/Fe2C>2 molar ratio is 25-90 and the SiC^/A^O^ molar ratio is 250-1200.

In the process according to the invention the starting material is a gasoline obtained by catalytic cracking. Such gasolines may very suitably be prepared by the application of 30 catalytic cracking to heavy hydrocarbon oils, such as atmospheric gas oils, vacuum gas oils, deasphalted vacuum residues and mixtures thereof. The feed used by preference is a gas oil. Catalytic cracking on a cormercial scale is usually carried out in a continuous process using an arrangement which consists 2 04 5 substantially of a vertically disposed cracking reactor and a catalyst regenerator. Hot, regenerated catalyst ccming frcm the regenerator is suspended in the oil to be cracked and the mixture is passed through the cracking reactor in an upward direction. The deactivated catalyst is separated frcm the cracked product and, following stripping, transported to the regenerator. The cracked product is separated into a light fraction having a high content of and olefins, a gasoline fraction and several heavy fractions, such as a light cycle oil, a middle cycle oil, a heavy cycle oil and a slurry oil.

The crystalline metal silicates used as catalysts in the process according to the invention are defined, among other things, by the X-ray pcwder diffraction pattern which they shew after one hour's calcination in air at 500°C. In this pattern the strongest lines should be the four lines mentioned in Table A. The ccmplete X-ray pcwder diffraction pattern of a typical example of a crystalline metal silicate used in the process according to the invention, is presented in Table B.

TABLE B 0 O 2046 d(A) Rel. int. d(A) Rel. int. 11.1 100 3.84 (D) 57 .0 (D) 70 3.72 (D) 31 8.93 1 3.63 16 7.99 1 3.47 1 7.42 2 3.43 6.68 7 3.34 2 6.35 11 3.30 .97 17 3.25 1 .70 7 3.05 8 .56 2.98 11 .35 2 2.96 3 4.98 (D) 6 2.86 2 4.60 4 2.73 2 4.35 2.60 2 4.25 7 2.48 3 4.07 2 2.40 2 4.00 (D) = doublet The crystalline metal silicates may be prepared starting frcm an aqueous mixture comprising the following ccmpounds: one or more compounds of an alkali metal (M) , one or more organic nitrogen compounds (RN) which include 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 aluminium ccmpounds.

The preparation is carried out by maintaining the mixture at an elevated temperature until the silicate has formed and 2 04 6 9 subsequently separating the silicate crystals from the mother liquor and washing, drying and calcining the crystals. In the aqueous mixture from which the silicates are prepared the various compounds should be present in the following molar ratios, expressed - with the exception of the organic nitrogen ccmpounds - in moles of the oxides: N^O : Si02 = 0.01-0.35, FN : Si02 = 0.02-1.0, Si02 : Fe2C>3 = 25-270, SiC>2 : = 250-2400, and H20 : Si02 = 5-65.

In the preparation of the silicates the base mixture started frcm may very suitably be a mixture which as a nitrogen compound comprises a quaternary alkylamronium compound, such as a tetrapropylaitmonium compound. Preference is given to the use of an amine as an organic nitrogen compound and in particular to n-butylamine. Further, in the preparation of the silicates preference is given to the use of a base mixture which, as an alkali metal compound comprises a sodium compound and as a silicon compound amorphous silica.

The silicates prepared as described hereinbefore comprise alkali metal ions. By using suitable exchange methods these may be replaced by other cations, such as hydrogen ions or ammonium ions. The crystalline silicates used in the process according to the invention preferably have an alkali metal content of less than 0.05 %w.

The process according to the invention may very suitably be carried out by passing the feed in an upward or downward direction through a vertically arranged reactor containing a fixed or a moving bed of the crystalline metal silicate.

Suitable conditions for carrying out the process according to the invention are a temperature of 300-600°C, a pressure of 1-50 bar and a space velocity of 0.1-10 kg.kg \h The process is preferably carried out under the following conditions: a 2 046 91 temperature of 400-500°C, a pressure of 2.5-25 bar and a space velocity of 0.2-3 kg.kg_1.h 1. The process may be carried out in the presence of hydrogen, if desired.

In the process according to the invention the formation of aroma tics is accompanied with cracking. As a result of this cracking the product fraction contains a considerable proportion of and olefins. The investigation has revealed that the recirculation of the product fraction leads to considerable improvement of the catalyst's selectivity and stability, whilst the excellent quality of the gasoline is maintained. Therefore, in the process according to the invention at least part of the product fraction is preferably recirculated.

Depending upon the degrees of thoroughness with which the separation between the light fraction and the gasoline fraction of the catalytically cracked product is carried out, the separated gasoline may contain larger or smaller proportions of and C4 olefins. The investigation has revealed that in the process according to the invention an increase in the and/or olefins content of the feed results in enhanced selectivity of the quality improvement. An increase in the and/or olefins content of the feed may be achieved in various ways. In the first place one may carry out the separation between the light fraction and the gasoline fraction of the cracked product less thoroughly and thus allow a considerable portion of the olefins usually present in the light fraction to go into the "gasoline fraction. Another option is separating the gasoline from the catalytically cracked product and subsequently adding additional and/or olefins. For this purpose preference is given to the use of and/or olefins which can be separated frcm the light fraction of a product obtained by catalytic cracking. In view of its favourable effect on selectivity and quality improvement the process according to the invention is preferably applied to a 204691 gasoline obtained by catalytic cracking which has an increased and/or olefins content.

The invention is now elucidated with the aid of the following example.

EXAMPLE Four crystalline silicates (silicates 1-4) were prepared by heating mixtures of NaGH, Fe (NO^) ^ and/or NaAlC^, amorphous silica containing 100 ppmw aluminium and C^H^NH^ or (C^H_,) ^NOH in water in an autoclave under autogenous pressure, with 10 stirring, at 150°C. In the preparation of silicates 1-3 the mixtures were heated for 24 hours. In the preparation of silicate 4 the mixture was heated for 120 hours. After cooling of the reaction mixtures the silicates formed were filtered off, washed with water until the pH of the wash water was about 8 and dried 15 at 120°C. After one hour's calcination in air at 500°C, silicates 1-4 had the following properties: a) thermally stable up to a temperature of at least 800°C, b) an X-ray powder diffraction pattern substantially corresponding with that mentioned in Table B, and c) values of the Si02/Fe2C>2 and SiC^/A^C^ molar ratios as mentioned in Table C.

TABLE C Silicate No. Si02/Fe202 SiC^/A^O^ 1 - 250 2 108 1900 3 127 600 4 79 1000 The molar composition of the aqueous mixtures frcm which silicates 1-4 were prepared may be represented as follows: v Na20 . w (C^Hy) ^NOH . x C^HgNH2 . y A^C^ . z Fe^^ . 25 SiC>2 . 450 H20, 25 where v, w, x, y and z have the values mentioned in Table D. 2 046 91 TABLE D Silicate No. v w x y z 1 1 9 - 0.066 - 2 2.5 - 0.003 0.20 3 1 - 0.036 0.20 4 1 — 0.036 0.33 From silicates 1-4 were prepared silicates 5-8, respectively, by boiling silicates 1-4 with a 1.0 molar NH^NO^ solution, washing with water, boiling again with a 1.0 molar NH^NO^ solution, washing, drying at 120°C and calcining at 500°C.

Silicates 5-8 were tested in six experiments (Experiments 1-6) as catalysts for improving the quality of gasoline obtained by catalytic cracking. The experiments were carried out in a reactor containing a fixed catalyst bed. All the experiments were carried out at a temperature of 450°C, a pressure of 5 bar 10 and a space velocity of 0.5 kg.kg ^".h In Experiments 5 and 6 the product fraction was recirculated at a /gasoline molar ratio of 10:1.

Experiments 1-5 were applied to a gasoline 1. Experiment 6 was applied to a gasoline 2 which had been obtained by mixing 15 93.0 pbw of gasoline 1 with 7.0 pfcw of a mixture of butenes. Gasoline 1 had the following properties: 2 04-691 Canposition in %w: aramatics 24.2 naphthenes 13.6 paraffins + olefins 57.5 olefins/paraffins weight ratio approx. 50/50 sulphur content, %w 0.14 nitrogen content, ppmw 60 final boiling point, °C 244 ik ozone number, mmole/g 4.0 *★ MON-O 80.4 ★ The ozone number is a measure of the olefins content of the gasoline. According as the gasoline contains fewer olefins, the ozone number will be lower.

** MCN-0 is the motor octane number without the addition of lead.

The results of Experiments 1-6 are given in Tables E-G. The parameters activity, selectivity, stability and selectivity of the operation given in the Tables are defined as follows: Activity = (%w C,+ non-arcmatics present in feed)-(%w C* non-aromatics present in product) 5 5 x 100 (%w C,. non-aromatics present in feed) Selectivity - (%w arcmatics present in product) - (%w arcmatics present in feed) x 100 (%w C,- non-aromatics present in feed)-(%w non-arcmatics present in product) i i-^ Instability = decrease in activity from run hour 100 to run hour 350. 1 N> O \0 2 04691 Selectivity of the operation = increase in %w arcmatics decrease in %w Cc+ fraction 5 Of Experiment 1-6 only Experiments 4-6 are experiments according to the invention. Experiments 1-3 fall outside the scope of the invention. They have been included in the patent application for comparison. 204691 - 13 -TABLE E Experiment No. - 1 Silicate No. - 5 Feed gasoline No. 11 Arcmatics present in feed or total product, resp., %w 24.2 36.8 41.0 43.3 46.7 C,+ present in feed or total product, resp., %w 95.3 79.8 82.0 79.8 74.9 Activity averaged over 350 hours, %w - 39.5 42.3 48.8 60.3 Selectivity averaged over 350 hours, %w - 44.8 55.8 55.2 52.5 Instability, %w 65 38 39 33 MON-O of feed or liquid product, resp. 80.4 83.2 83.2 84.8 87.4 Ozone number of feed or liquid product, resp. mmole/g 4.0 2.0 1.1 0.6 0.3 2 046 9 TABLE F Experiment No.

Silicate No.

Feed gasoline No. recirculation Arcmatics present in feed or total product, resp., %w C,+ present in feed or total product, resp., %w Activity averaged over 350 hours, %w Selectivity averaged over 350 hours, %w Instability, %w MCN-0 of feed or liquid product, resp.

Ozone number of feed or liquid product, resp. imiole/g 4 5 8 8 1 11 no yes 24.2 46.7 48.5 95.3 74.9 77.1 60.3 59.8 52.5 57.2 33 27 80.4 87.4 87.3 4.0 0.3 0.4 2 04 6 TABLE G Experiment No. Silicate No.

Feed gasoline No. recirculation - yes - yes Arcmatics present in feed or total product, resp., %w 24.2 48.5 22.2 47.0 C+ present in feed or total product, resp., %w 95.3 77.1 88.6 76.8 Increase of arcmatics, %w 24.3 24.8 Decrease of Cc+, %w 18.2 11.8 o Selectivity of operation 1.3 2.1 MCN-0 of feed or total product, resp. 80.4 87.3 80.3 87.2 Ozone number of feed or total product, resp. imiole/g 4.0 0.4 4.2 0.3 2 04691 Referring to the results mentioned in Tables E-G the following may be remarked.

Table E Silicate 5 (aluminium silicate) is not suitable as catalyst for the present purpose, since this silicate has a very low average activity, a lew average selectivity and a very low stability and, in addition, it provides a gasoline with a moderate octane number and a very high olefins content.

Silicate 6 (iron silicate) is not very suitable as catalyst for the present purpose, since this silicate has a very low average activity and, in addition provides a gasoline with a moderate octane number and a high olefins content.

Silicate 7 (iron-aluminium silicate, outside the scope of the invention) is not very suitable as catalyst for the present purpose, since this silicate has a low average activity and, in addition, provides a gasoline with a moderate octane number and a relatively high olefins content.

Silicate 8 (iron-aluminium silicate according to the invention) is excellently suitable as catalyst for the present purpose. The silicate has a very high average activity, a high average selectivity and a very high stability. In addition, the silicate provides a gasoline with a very high octane number and a very low olefins content.

Table F Recirculation of the product fraction results in a higher average selectivity and a higher stability whilst, the very* high average activity and very high product quality are maintained.

Table G When a gasoline with a higher butenes content is used as the feed, then, at a comparable increase in arcmatics content, a much smaller loss of C^+ is attained, in other words a higher selectivity of the quality improvement. Meanwhile the very high product quality is maintained. yo^c{ ( 204601

Claims (9)

WHAT WE CLAIM IS:

1. A process for improving the quality of a gasoline obtained by catalytic cracking, characterized in that the gasoline is contacted with a crystalline metal silicate which, after one hour's calcination in air at 500°C, has the following properties: 5 a) thermally stable up to a temperature of at least 600 °C, b) an X-ray pcwcler diffraction pattern in which the strongest lines are the four lines mentioned in Table A. TABLE A d(A) 11.2 ± 0.2 10.0 ± 0.2 3.84 ± 0.07 3.72 ± 0.06 c) in the formula which represents the ccrposition of the silicate expressed in moles of the oxides and which, in 10 addition to SiC>2, includes both Fe2°3 A12°3' the Si02/Fe2C>2 molar ratio is 25-90 and the Si02/Al203 molar ratio is 250-1200.

2. A process as claimed in claim 1, characterized in that the crystalline metal silicate has an alkali metal content of less 15 than 0.05 %w.

3. A process as claimed in claim 1 or 2, characterized in that it is carried out at a temperature of 300-600°C a pressure of 1-50 bar and a space velocity of 0.1-10 kg.kg~"*.h~*.

4. A process as claimed in any one of claims 1-3, characterized in that at least part of the Cj product fraction, which is present in the product obtained according to the process of any one of claims 1 to 3, is recirculated.

5. A process as claimed in any one of claims 1-4, characterized in that it is applied to a gasoline obtained by catalytic cracking which has an increased C^ and/or C^ olefins content. 2 046 91 - 18 -

6. A process as claimed in claim 5, characterized in that the increase of the olefins content of the gasoline has come about by carrying out the separation between the C^~ fraction and the gasoline fraction of the cracked product in such a manner 5 that at least part of the olefins which as a rule are withdrawn together with the fraction, go into the gasoline fraction.

7. A process as claimed in claim 5, characterized in that the increase of the olefins content of the gasoline has carte about by adding and/or olefins frcm an external source. 10

8. A process for irrproving the quality of a gasoline obtained by catalytic cracking, as claimed in claim 1, and substantially as described hereinbefore with reference to Experiments 4-6 of the example.

9. Gasoline of improved quality obtained according to a 15 process as described in claim 8. LJATED THIS DAY OF 19§3 A. J. PAHK & SON °0" AGENTS FCH THE APPLICANTS JUM9&