GB2042490A - Catalytic hydroisomerisation - Google Patents

Abstract

Alkylbenzenes, preferably xylenes, are hydroisomerised in the vapour phase in the presence of hydrogen and a catalyst comprising zeolite FU-1 with a minor amount, preferably in the range 0.1 to 2.0% by weight, of ruthenium. Optionally, the catalyst may also contain a second metal, for example platinum, iridium or nickel. The process is useful in isomerising xylene mixtures containing relatively large (up to 25%) amounts of ethylbenzene.

Description

SPECIFICATION Hydrocarbon conversion This invention relates to a process for the isomerisation of alkylbenzene hydrocarbons using, as catalyst, a material having some properties in common with zeolites. The material will be referred to hereinafter as "zeoliteFU-1"orsimply"FU-1".

Zeolite FU-1, its preparation and its use as a catalyst are described in our copending UK application No.

46130/76. (UK Patent Specification No 1,563,346).

The crystallographic structure of FU-1 is shown to be unique by its X-ray diffraction pattern, which includes the following characteristic lines: TABLE 1 d(A) 100 ill d(A) 100 lIlo 9.51 31 4.48 6 8.35 8 4.35 13 6.92 28 4.07 19 6.61 9 4.00 9.4 6.26 9 3.89 13 5.25 16 3.73 28 4.61 63 3.68 3 3.44 100 These lines were measured on the sodiumltetramethylammonium (TMA) form of FU-1 but we find that the pattern of the hydrogen form, as exemplified by the corresponding material from which all the TMA and all but 300 ppm w/w of Na2O has been removed differs negligibly from the above pattern. The diffraction peaks observed are very broad suggesting that FU-1, at least as so far produced, occurs in small crystallites typically 100-500 Angstrom ( ) in diameter.

The crystalline structure of FU-1, as shown by electron microscope examination, can consist of very thin sheets of angularly interlocking platelets typically 50 to 400 A thick and agglomerated into packs of total thickness in the range of 0.1 to 10 microns.

The chemical composition of FU-1 is as follows: 0.6 to 1 .4R20 . Awl203. over 5 SiO2. 0 to 40 H20 where R is a monovalent cation orlof a cation of valency n and H20 is water of hydration additional to water notionally present when R is H.

The number of molecules of SiO2 is more typically at least 10, for example in the range 15 to 300 and FU-1 appears to be most readily formed in a state of high purity when the number of molecules of SiO2 is in the range 15 to 45, for example 15 to 30. It is believed to be unusual to have hydrophobic properties at such a low SiO2 level. The upper limit for SiO2 that can exist in the FU-1 structue is not yet known.

In our UK Patent Specification No 1,563,346, we also describe replacement of cation(s) of zeolite FU-1 by any cation(s) of metals, and particularly by cations of those metals in Groups IA, IB, IIA, liB, III (including rare earths), VIIA (including manganese), VIII (including noble metals) and by lead and bismuth.

The use of zeolite FU-1 as a catalyst for xylenes isomerisation is described in our UK Patent Specification No 1, 563,346. As is well known, the aim in xylenes isomerisation is to increase the para-xylene content of the feedstock at the expense of other isomers since para-xylene is a particularly useful and valuable product. As can be seen from the description in UK Patent Specification No 1,563,346, the use of zeolite FU-1 as catalyst in the isomerisation of feedstocks comprising mainly xylenes with only small amounts of ethylbenzene leads to a useful increase in para-xylene content.Hitherto, some of the mixed xylenes feedstock available has contained relatively small amounts of ethylbenzene but it is anticipated that in the future such feedstock will become somewhat scarce and that resort will have to be made to feedstocks containing rather larger amounts of ethylbenzene, say up to about 25% ethylbenzene. It is possible to remove some of this ethylbenzene by distillation but such a step adds to the cost of the process. Clearly, it will be of considerable advantage if a larger proportion, if not all, of the ethylbenzene content of these feedstocks can be converted to xylenes, especially para-xylene.

We have now found that it is possible to use a modified form of zeolite FU-1 as catalyst in the hydroisomerisation of mixed xylene feedstocks, especially those containing releatively large amounts of ethylbenzene.

According to the present invention a hydrocarbon conversion process comprises contacting a feed of an alkylbenzene or a mixture of alkylbenzenes under hydroisomerisation conditions in the vapour phase with hydrogen and with a catalyst comprising zeolite FU-1 with a minor amount of ruthenium and/or a ruthenium compound.

Modification of zeolite FU-1 may be effected by, for example, impregnation or ion exchange of the ruthenium and is preferably effected by contacting the zeolite with a compound of ruthenium, suitable compounds including the trichloride and dodecacarbonyltriruthenium. Complexes of ruthenium, for example H4Ru4(CO)12, H2Ru4(CO)13, [Rus (CO)16C]2- and amine complexes, for example [Ru (NH3)5N212+ are also considered suitable for contacting with the zeolite. One method of modifying the zeolite is to dissolve the required amount of ruthenium trichloride in distilled water, add zeolite FU-1 and stir the resulting suspension at room temperature. Excess water is removed and the resulting catalyst dried and pelleted.An alternative method of modifying the zeolite is to add zeolite FU-1 to a suitable amount of dodecacarbonyltriruthenium in toluene, gently agitate for a short period and then remove the toluene under vacuo. The catalyst is then dried and pelleted.

The modified zeolite FU-1 can be used per se but it is preferred to use a catalyst which is an intimate mixture of the hydrogen form of zeolite FU-1 with the modified ruthenium-containing zeolite FU-1. The relative proportions of the two components of such a mixture are likely to vary from case to case depending on the alkylbenzene feed which is being isomerised and on the amount of ruthenium in the modified zeolite component A typical mixture comprises 75 to 85% by weight of zeolite FU-1 in the hydrogen form with 25 to 15% by weight of modified zeolite FU-1 containing 0.1 to 1.0% by weight ruthenium.

The amount of ruthenium present in the catalyst for the process of this invention is at least 0.05% by weight, preferably at least 0.1% by weight, more preferably in the range of 0.1 to 2.0% by weight, although the use of catalysts containing more than 2% by weight of ruthenium is not excluded. However, it is likely that there is little additional benefit, either economic or technical, to be obtained by using catalysts containing more than 2% ruthenium.

Optionally, the catalysts may comprise zeolite FU-1 modified with ruthenium and with another metal, preferably another Group 8 metal for example platinum, nickel and iridium. The proportions present in the catalyst of each metal will vary from case to case but preferably the total amount of metal present lies in the range 0.2 to 2.0% by weight.

Suitable hydroisomerisation conditions for (the vapour phase) operation of the process of this invention include a temperature in the range 400 to 600"C, more preferably in the range 400 to 500"C, a hydrogen pressure in the range 100 to 300 psig, more preferably in the range 150 to 250 psig, a weight hourly space velocity in the range 1 to 15 hr-1, more preferably in the range 4 to 8 hr-1, and a hydrogen to hydrocarbon volume ratio in the range 2:1 to 8:1, more preferably in the range 3.5:1 to 6.5:1.

Preferably the alkylbenzene is a xylene, for example m-xylene for conversion to p-xylene, or a mixture of xylenes, possibly with ethylbenzene. The amount of ethylbenzene will depend to some extent on the source of the xylene mixture but will usually lie in the range 0 to 25% by weight of the feestock. However, we believe that the process of this invention is very suitable for feedstocks containing relatively large amounts of ethylbenzene, say in the range 6 to 25% by weight of the feedstock.

EXAMPLES Preparation of Catalyst CatalystA - A number of catalysts were prepared containing various amounts of ruthenium. In each case the required amount of ruthenium trichloride was dissolved in 10 ml distilled water. To this was added zeolite FU-1 (usually 3 to 49) and the resulting suspension was stirred at room temperature for about 30 minutes.

Excess water was then removed by evaporation over a steam bath, and the resulting catalyst was dried overnight at 120 to 1 40"C. The catalyst was formed into pellets of 1/8" diameter.

Catalyst B-An intimate mixture was prepared comprising 4 parts by weight of zeolite FU-1 in the hydrogen form and 1 part by weight of zeolite FU-1 containing 0.4% ruthenium, prepared as described for catalyst A.

Catalyst C- This catalyst was prepared by adding ca 5g zeolite FU-1 (dried in nitrogen at 400"C for 4 hours) to a stirred solution of triruthenium dodecacarbonyl (ca 0.1 g) in dry toluene under an atmosphere of nitrogen.

After about 30 minutes the solvent was removed under reduced pressure to yield a yellow free-flowing powder.

EXAMPLE 1 A number of experiments were carried out in a laboratory reactor on the hydroisomerisation of xylenes using samples of catalysts A and B containing different amounts of ruthenium. Before use, the catalysts were reduced in the reactor under flowing conditions at a hydrogen pressure of 240 psig and at a temperature of 400"C. (The temperature was raised gradually to 400"C over 3 hours and then maintained at that temperature for 1 hour). A xylenes feed of the following composition was then introduced to the reactor (% by weight) Benzene 0.07 Toluene 1.88 Nonane 1.22 Ethylbenzene 22.83 Para-xylene 7.85 Meta-xylene 47.35 Ortho-xylene 18.79 The catalyst used, the reaction conditions and the results obtained using catalysts A and B are shown in Tables 2 and 3 respectively.

TABLE 2 Catalyst A Product (% by wt.) Ruthenium Time on Reaction * % % % p-xylene % (we. %) line Conditions gas naphthenes -in ethylbenzene xylene (hrs) xylenes loss loss 0.07 16 a 0.63 0.41 22.5 3.9 1.5 0.10 15 a 2.85 2.75 21.6 33.8 4.7 0.10 17 b 2.69 2.21 21.9 27.7 5.2 0.10 26 c 4.02 1.69 22.7 37.8 7.1 0.30 2 a 2.97 4.36 17.7 43.2 8.5 0.30 4 d 11.99 1.27 19.7 73.7 27.1 0.30 17 d 9.83 2.82 19.3 71.4 20.4 0.40 2 a 21.45 8.30 21.5 90.6 30.3 0.40 15 e 9.65 4.67 18.3 62.9 13.5 0.40 19 f 43.48 1.03- 18.5 84.1 49.5 XReaction Conditions WHSV Volume ratio (hr-1) hydrogen:hydrocarbon Temperature ("C) Pressure (psig) a 5 5:1 400 200 b 5 3.5:1 400 200 c 5 3.5:1 425 200 d 5 5:1 425 200 e 5 6.5:1 400 200 f 5 6.5::1 425 200 Catalyst B (compared with catalyst A) Product (% by wt.) Time % p-xylene % Catalyst on Reaction napht- in ethylbenzene xylene Type Catalyst line Conditions* gas henes xylenes loss loss (hr) B Composite of 80%Zeolite 1 a 3.15 5.59 22.7 36.0 8.0 H-FU-1 with 6 a 1.72 3.31 22.8 19.9 5.1 20%Zeolite 11 a 1.35 2.86 22.8 15.2 4.4 H-FU-1 16 b 1.49 0.8 23.4 11.8 3.5 containing 27 b 1.04 0.7 23.0 6.7 2.4 0.4% ruthenium A Zeolite H-FU-1 containing 2 a 21.5 8.3 21.5 90.6 30.3 0.4% ruthenium A Zeolite H-FU-1 containing 15 a 2.85 2.75 21.6 33.8 4.7 0.1% ruthenium *Reaction Conditions WHSV (hr-1) Volume ratio Temperature ("C) Pressure (psig) hydrogen:hydrocarbon a 5 5:1 400 200 b 5 5::1 450 200 Table 2 illustrates the point that conversion of ethylbenzene increases with the amount of ruthenium in the catalyst, although at the same time the isomerisation activity decreases somewhat and the loss of xylenes (mainly by disproportionation) increases. The applicants consider that from the experiments reported in Table 2, the optimum level of ruthenium in the catalyst is of the order of 0.1%.

Table 3 illustrates that use of the composite catalyst (catalyst B) improves the isomerisation activity over the fully impregnated catalyst (catalyst A), the percentage of para-xylene in the xylenes for catalyst B being close to the equilibrium value of about 23.5%.

For comparison, an experiment was carried out using zeolite H-FU-1 but containing no ruthenium. The xylenes feed had the composition (% by weight) Benzene 0.02 Toluene 0.07 Nonane 2.01 Ethylbenzene 7.54 Para-xylene 9.06 Meta-xylene 53.88 Ortho-xylene 27.41 The reaction conditions used were a WHSV of 9.9 hr-1, a hydrogen: hydrocarbon volume ration of 0.73:1, a temperature of 450"C and a pressure of 100 psig. The results obtained are shown in Table 4.

TABLE 4 Product (% by wt.) %p-xylene % Time on line in - ethylbenzene xylenes (hr) gas naphthene xylenes loss loss 5 0.34 1.88 23.19 11.9 2.94 11 0.20 1.92 23.13 9.3 2.71 72 0.12 1.78 22.47 6.0 0.71 It is clear that in the absence of ruthenium, the conversion of ethylbenzene is much lower.

EXAMPLE 2 Example 1 was repeated using samples of catalyst C. The reaction conditions and results obtained are shown in Table 5.

TABLE 5 PRODUCT (% by wt) % para Ruthenium Time on Reaction xylene % Run (wt. %) line Conditions gas napht- in ethylbenzene xylene (hrs) * hene xylenes loss loss C1 0.1 1 a 0.34 0.11 20.12 5.75 1.75 18 a 0.17 0.10 20.38 4.30 1.49 C2 0.2 1 a 0.86 0.26 22.04 7.97 5.00 3 a 0.66 0.20 21.70 6.91 5.60 9 a 0.55 0.18 21.78 5.89 5.20 C3 1 4 a 2.53 0.64 21.05 24.67 3.03 20 b 4.57 1.16 19.84 38.40 6.06 35 b 2.58 0.76 20.00 25.69 3.21 39 c 3.97 1.04 22.04 35.52 5.48 44 d 1.82 0.36 19.94 15.10 2.46 56 d 1.21 0.30 20.16 11.33 1.79 C4 1 1 a 15.44 1.44 21.49 55.15 11.88 3 e 26.82 2.19 21.14 74.03 21.67 17 f 11.75 1.47 21.32 49.06 10.92 20 f 9.82 0.60 20.75 36.22 8.57 23 g 21.64 0.34 21.18 52.43 27.12 *Reaction Conditions WHSV Volume ratio Temperature Pressure (hr-') hydrogen/hydrocarbon ('C) ("C) (psig) a 5 5:1 400 200 b 12.8 5::1 400 200 c 8.0 5:1 400 200 d 12.5 6.5:1 425 200 e 5.0 6.5:1 400 200 f 5.0 5:1 425 200 9 5.0 5:1 450 200 From the results in Table 5 it can be seen that catalyst C converts more ethylbenzene relative to xylenes than do the catalysts prepared by using ruthenium trichloride (catalysts A and B). Of the runs shown in Table 5, Run C3 gives the most advantageous results.

Catalysts D, E and F- Samples of zeolite FU-1 modified by the presence of ruthenium and platinum (catalyst D), ruthenium and nickel (catalyst E) or ruthenium and iridium (catalyst F), were prepared by dissolving the required amounts of the two metals (as their respective chlorides) in distilled water. Alumina was impregnated with this solution (1.45 ml solution per gram alumina) and the alumina was kept in contact with the solution overnight. The resulting catalyst was dried at about 11 0'C for 2 to 3 hours and was then intimately mixed with the required proportion of the hydrogen form of zeolite FU-1.

EXAMPLE 3 Example 1 was repeated using samples of catalysts D, E and F. The reaction conditions used and results obtained are shown in Table 6.

TABLE 6 PRODUCT (% by wt) Time % para Catalyst on Reaction xylene % Run No used line Conditions gas napht- in ethylbenzene xylene (hrs) * hene xylenes loss loss D1 80% H-FU-1 with 20% 5 a 5.4 22.51 23.3 75.3 19.7 of 0.49% Pt and 0.34% 14 a 4.03 26.44 23.3 74.5 20.9 Ru on alumina 15 b 6.38 4.58 23.3 66.4 11.8 20 c 3.69 1.28 23.3 42.6 5.6 35 d 1.9 3.64 22.5 18.7 2.6 40 e 2.09 3.36 23.0 23.0 3.2 49 e 2.91 4.88 23.6 29.7 3.4 El 80% H-FU-1 with 20% of0.29% Ni and 0.56% 3 a 12.14 11.47 19.8 81.1 33.7 Ru on alumina 11 b 87.32 1.08 17.8 99.5 88.7 F1 80% H-FU-1 with 20% 2 a 22.4 18.25 20.8 95.1 38.8 of Ir and 0.5% 3 b 92.0 0.07 21.1 100.0 97.6 Ru on alumina ' 13 f 24.01 7.21 21.8 96.7 39.7 20 g 41.17 5.06 21.0 98.3 57.2 *Reaction Conditions WHSV Volume Ratio Temperature Pressure (hr-1) hydrogen/hydrocarbon ("C) (psig) a 5 5:1 400 200 b 5 5:1 450 200 c 10 5:1 470 200 d 10 6.5:1 450 200 e 5 5:1 450 200 f 5 5:1 425 200 9 10 6.5:1 425 200 It can be seen that these bimetallic catalysts are also effective in increasing the para-xylene yield and in converting ethylbenzene, the platinum-ruthenium combination being the most effective of those tested.

However, it is possible that the use of catalysts having different proportions and overall amounts of the various metals would prove even more effective.

Claims (13)

1. A process for hydrocarbon conversion which comprises contacting a feed of an alkylbenzene or a mixture of alkylbenzenes under hydroisomerisation conditions in the vapour phase with hydrogen and with a catalyst comprising zeolite FU-1 with a minor amount of ruthenium and/or a ruthenium compound.

2. A process as claimed in claim 1 in which the catalyst comprises an intimate mixture of the hydrogen form of zeolite FU-1 with ruthenium - containing zeolite FU-1.

3. A process as claimed in claim 2 in which the intimate mixture comprises 75 to 85% by weight of zeolite FU-1 in the hydrogen form with 25 to 15% by weight of modified zeolite FU-1 containing 0.1 to 1.0% by weight ruthenium.

4. A process as claimed in any one of the preceding claims in which the amount of ruthenium present in the catalyst is at least 0.05% weight.

5. A process as claimed in claim 4 in which the amount of ruthenium present in the catalyst is in the range 0.1 to 2.0% by weight.

6. A process as claimed in any one of the preceding claims in which the catalyst comprises zeolite FU-1 modified with ruthenium and with another metal.

7. A process as claimed in claim 6 in which the catalyst comprises zeolite FU-1 modified with ruthenium and with a metal of Group 8 of the Periodic Table.

8. A process as claimed in claim 6 or 7 in which the total amount of metal present in the catalyst is in the range 0.2 to 2.0% by weight.

9. A process as claimed in any one of the preceding claims in which the hydroisomerisation conditions comprise a temperature in the range 400 to 600"C, a hydrogen pressure in the range 100 to 300 psig, a weight hourly space velocity in the range 1 to 15 hr-1, and a hydrogen to hydrocarbon volume ratio in the range 2:1 to8:1.

10. A process as claimed in any one of the preceding claims in which the feed comprises a xylene or a mixture of xylenes.

11. A process as claimed in claim 10 in which the feed also comprises ethylbenzene in addition to the xylene or mixture of xylenes.

12. A hydrocarbon conversion process substantially as hereinbefore described with reference to any one of the Examples.

13. An alkylbenzene hydrocarbon whenever produced by a process as claimed in any one of claims 1 to 12.