DE2255231A1 - PROCESS FOR THE PRODUCTION OF ISOPRENE - Google Patents

Description

Process for the production of isoprene

Priorities of November 11, 1971, U.S.A. No. 197 964

April 17, 1972, U.S.A., No. 244 847

The invention relates to an improved process for the production of isoprene by the vapor phase reaction of Methylal with isobutene or butene-2 or mixtures thereof in Presence of a BE, catalyst, isoprene being obtained in high yields and good selectivity. With help of the special catalyst according to the invention, a longer service life of the catalyst is also achieved, than with previously known methods. ·

In a particular embodiment, the invention relates on the use of metal salts as cocatalysts, converting certain ethers formed as by-products into isoprene be transferred and in this way the total yield is improved.

309021! / 1 0 28

In Japanese Patent Publication 19082/1970 the vapor phase reaction of methylal with isobutene under Formation of isoprene and isoprene precursors described, with silicon dioxide, aluminum oxide, acidic as the catalyst Clay, oxides of metals of group II or group III of the periodic table or their mixtures with silicon dioxide, Aluminum oxide or the like can be used. With the help of this process, some isoprene is formed, However, the process is characterized by a very short life of the catalyst. As in the one below In addition, as shown in Example 1, the selectivity and conversion rate drops after 15-30 Minutes are essential if this known procedure is used '-.' IrcL

According to the invention it has now been found that by using BF "on aluminum oxide or a special one, hereinafter described catalyst combination, as a catalyst in the known process described above Surprisingly, significantly longer catalyst life in conjunction with higher conversion rates and better selectivity can be achieved than when using the known catalysts.

The invention therefore relates to a method for production of isoprene by the vapor phase reaction of methylal with isbutene, butene-2 or mixtures thereof in the presence of a solid catalyst which is characterized in that as Catalyst BF, on an anhydrous inorganic oxide, is used as the carrier material.

_ rt _

3 0 9 ü,: 0/1 0 2 8

In the method according to the invention, the reaction of Me thy IaI with Isobut en in the vapor phase is carried out before ihaf t; ·. τ led by the "two reactances over a catalyst-: - ■■■ layer at elevated temperatures of 150 Ms 450 ° C : ,, '* before * ζ ί preferably 250 to 350 ° C with liquid hourly room temperature. speed (XHSV) of the reaction mixture in the range 'from about 0.1 to 25.0, preferably 1.0 to "10.0, are passed, and a product mixture is obtained which has a predominant proportion of isoprene and a small proportion of the isoprene Precursor 4-methoxy ~ 2-methyrbutene-1, contains. The isoprene can be obtained from this mixture in a simple manner by distillation. , ",

The molar ratio of isobutene to methylal in the feed stream should advantageously be in the range of about 2 to 20, in particular range from about 6 to 10, although it is therefore important that an excess of isobutene over methylal "is present, a far smaller excess is required than in the process described in the Japanese patent publication in which molar ratios of at least 15 must be applied.

While essentially pure isobutene is the preferred olefinic reactant, other olefins such as butene-2 can also be used. According to another embodiment of the invention, mixtures of C. to C.sub.8 hydrocarbons, such as olefin-containing and / or paraffin-containing hydrocarbon streams from earth refining, can be used as starting materials. which boil in the range from about -10 ° C to 40 ° 0 and contain at least 5 to 10 percent by weight isobutene and 0 to * 20 percent by weight butene-2, are used. A typically, more suitable C ₄ to C hydrocarbon stream from

-4- 2258231

petroleum refining consists of a hydrocarbon mixture, the 2 or more of the compounds isobutene, n-butene-1, η-butane, trans-butene-2, cis-butene-2, isopentane, isopentene and the like. The fact that the starting material is not based on pure isobutene or butene-2 is limited, but instead also a mixture of C. to Cc hydrocarbons, isobutene and / or butene-2 as well as other olefins and / or paraffins can be used. In this case the methylal reacts selectively with isobutene or butene-2, while the other olefins and paraffins present are only used as non-reactive diluents which do not hinder the reaction.

As indicated above, the preferred catalyst for this process is alumina coated BF-. This catalyst can be prepared according to the teachings of US Pat. No. 2,939,890, according to which essentially anhydrous gamma or theta-alumina is modified by adding about 2 to 100 percent by weight of BF ,, based on the weight of the Aluminum oxide, is brought into contact. Theta and gamma alumina are preferred, but it has been found that other substantially anhydrous inorganic oxides, as indicated in said US Pat. No. 2,939,890, in can be used in the same way for the purposes of the invention, for example silicon dioxide, titanium oxide, zirconium dioxide, Chromium oxide, zinc oxide, magnesium oxide, calcium oxide or various silicon dioxide or aluminum oxide combinations, provided that ^ these oxides are a thermally stable compound with the BF, - form.

30982 0/1028

A. hs & on & eTS- ^: ir © zt & ± litia; £ teB-maximal .- & βτ ¥ using the

BF ^ catalyst given in the invention in accordance with the invention . the finding that this catalyst IeIcEt

can be reactivated in situ! simply by inge quantities on gaseous BF ^ 'in the heating zone. ne Hart Wemden. This can iseqoiem: entwetler duron intermittieröndas ο4 «ϊ ^ konyti-

F ^ nEisclien small amounts of BF ^ jnit äem -ßeak oäev άητ en '/ separate' Ziifianicung in a! -Nerite gas ,, like nitrogen, take place, · ■

Bie activity Ses catalyst nand asm ■ degree of teakti-Ti-© tion werflen leieftt anvQh'Annljm <ier amount "-äar

Examples ^ g © 33 is a difference between isoprene and ITorlfiifer. Forstüfe ^ at the beginning of a reaction ^: senr hooJa. i and is about W ? -1, ¥ enn ^ 4er catalyst is not reactivated, this ¥ er & ltnis allÄänlicn after about 10 hours to about 1 i 1 afe. ¥ hen jeäoßii .to cLiesera Zeitpmnkt or, "an I earlier Eeitpankt low Inteile at If ^, dureia the Eeaktionsisone be routed," which is ferliältnis zn of isoprene ¥ orst "fe back almost to the ia.rspr" nglieljen value gnriiokgebraßJit, addition the percentage conversion of methylal, which generally occurs during this cut of about 99% a »f B5 1 °, is set back to its original value with the help of this measure. This activation treatment can be carried out several times, until the catalyst no longer responds to the BF ^. At this point in time, the catalyst can advantageously be regenerated by heating to high temperatures sufficient to burn coke residues and, if necessary, reactivated with additional BP-

108820/1026

2265231

in order to restore the Kenge of this material in percent by weight, based on the proportion en Älmuinimmoxyd.

As taught in the aforementioned Japanese Patent Publication 19082/1970, the isoprene precursor, 4-methoxy-2-methylbutene-1, which is formed in high proportions with isoprene, can be easily converted to isoprene and can therefore be separated and combined with the starting materials are recycled to the. Increase overall yield. Another and more advantageous possibility, however, has proven to be another form of the invention, in which a cocatalyst consisting of phosphorus phosphate or lead, magnesium or barium sulfate is used together with the main catalyst. In this execution of the invention torm is the amount of precursor formed is substantially less than when used alone, the BF, -iCatalysators, that is, there is obtained a 95 $ lge selectivity for isoprene during the initial stages of the reaction when the cocatalyst is used, compared to a selectivity of 80 % when the main catalyst is used alone. In GB-PS 673 547 a 'similar reaction using metal salts in the presence of aluminum oxide is toe • chrleben. However, this patent does not teach or suggest the use of BF * in this reaction or the use of such a catalyst system in the reaction of methylene with isobutene to form isoprene. .

The ratio of the BF, catalyst to the cocatalyst should be Desirably in the range of about 1 to 25 percent by weight, preferably about 2 to 8 percent by weight of the cocatalyst, based on the total weight of the catalyst mixture lie.

3 0 9820/1028 r -

- ■ 7 - "■■ ■ 2265231

The invention is illustrated below by the following examples. The catalyst described in the Japanese patent application is used in Example 1, while the catalyst according to the invention is used in Example-4. _t A comparison of the results of the examples' Game 1 with the results obtained in Example 4 clearly shows the superiority of the catalyst system of the invention over the known catalyst with a view to the life of the catalyst and the selectivity -for the desired isoprene. In addition, it can be seen from Examples 5, 6 and 10 that by adding MgSO., Cu ₅ (PO ₄ ) ₂ or PbSO ₄ to the catalyst of Example 4, the final yield is further improved, while the addition of small amounts of BF. to the reactant feed stream (example 7), serves to maintain the catalytic life and ^ selectivity during the course of the reaction. Comparative Examples 2, 3 and 11 are placed in. to show that .weder Aluminum oxide by itself, aluminum oxide only with the addition of the metal salt, or BP, alone leads to the pronounced catalytic activity achieved according to the invention, but rather that the catalytic activity drops rapidly or the process, as when BP is used, cannot be carried out on its own 8 illustrates the novel process according to the invention under varying reaction conditions and ratios, while Example 9 shows the use of silicon dioxide-magnesium oxide al s illustrated support for BF, instead of aluminum. -

Example 1 "* - <- ■ - * -.-....-

Tn one with electrical. _f He4zv9rrlchtung equipped vertikäles Pyrex tube 4 cnr silica gel as a catalyst

309 8/0/102 8 "^ ^

contains methylal are introduced by an injection pump and isobutene in a controlled manner by a flow meter. The reaction is carried out with a ratio of isobutene to methylal of 15: 1 at 300.degree. The isobutene is introduced at a rate of 25 liquid girr / h and the methylal at a rate of 1.5 ml / h via the 4.0 cm ^{5 of} the silica gel catalyst (1HSV = 6.6; MHSV = 80). The results obtained by this reaction are shown below:

Duration conversion from selectivity to selectivity to 4- (min.) Methylal ($) isoprene ($) methoxyT2-methylbutene-1

15 85 63 17

30 40 40 40

example 2

Following the procedure of Example 1 isobutene and

Methylal over 4.0 cm ^{5 of} aluminum oxide in installments of 24 Liquigir Tt

keits-cm / h or 1.5 cnr / h, that is, the molar ratio from isobutene to methylal is about 15 and the LHSV value is 6.6. The following results are achieved:

Duration conversion from selectivity to selectivity to 4- (hours) methylal ($) isoprene {$>) methoxy-2-methylbutene-i

1.5 96 32 tracks

2.5 59 23 tracks

3-5 14 13 tracks

Example 3

Following the procedure of Example 1, 24 cnr / h Isobutene and 2.8 cm of methylal passed over a catalyst, that of aluminum oxide, that with 10 percent by weight of MgSO. is impregnated, exists (IHSV = 9.0). The following Results obtained: · '

Duration conversion of methyl selectivity selectivity to (Hours) IaI to isoprene '4-methoxy-2-methyl-

^bt1

1 47 39 O

2 29 31 11

Example 4

Following the procedure of Example 1, isobutene is passed at a rate of 24 liquid cm 2 / h and methylal at 1.5 cra / h at 300 ° C. over 4.0 cnr aluminum oxide which contains 6 percent by weight of BP ₅ . (£ HSV = _6.6; molar ratio of isobutene to methylal = I5). The following results are achieved; . ■

Duration conversion of methyl selectivity selectivity to (hours) IaI to isoprene 4-methoxy-2-methyl '

butene-1 ₍ ^

2 5 " 99 5 99 10 99 For example

ao 5

4Q

The procedure of Example 4 is repeated with the Modification that the BF, on aluminum oxide containing Ka, baly-

309820/1 023 .. _{] 0}

22b5231

sator also contains 5 percent by weight of MgSO. After 10 hours, the conversion is 99 # and the selectivity for isoprene is 80 $ and the selectivity for 4-methoxy-2-methylbutene-1 6 #.

Example 6

The procedure of Example 5 is repeated, with the modification that 10 percent by weight Cu, (P0 ₄ ) ₂ instead of MgSO. be used.

After 10 hours the conversion is 95 % and the selectivity for isoprene is 75 $ and that for 4-methoxy-2-methylbutene- 19 $

Example 7

The process steps of Example 3 are repeated, with the modification that the methylal used as the reactant additionally contains 1 percent by weight of BF. After 15 hours, the conversion is $ 99> and the selectivity for isoprene or 4-methoxy-2-methylbutene-1 is $ 60 or $ 25.

Example 8

The process steps of Example 7 are repeated, with the modification that the reactant feed is 5.8 cm / isobutene and 1.5 cm ³ / h methylal (IBSV «* 1.8, molar ratio of isobutene to methylal - 2).

After 10 hours the conversion is 95% and the selectivity for isoprene or 4-methoxy-2-methylbutene is ~ 17 % or 15%. After ^ 2 hours, the conversion 85 1 "and the selectivity for isoprene and 4-methoxy-2 ~ raethylbuten-1 $ 50 is respectively, 55 #.

BeljBfltey 9

Following the procedural measures of Example 4, isobutene At a rate of 24.0 cm / h and Methylal At a rate

309Ö2Ü / 102Ö

2.8 cm ^ / h "at 300? C passed over silicon dioxide-magnesium oxide, the 5th
achieved the following results:

BP, contains (LHSV = 6.6). Thereby fol-i

duration
(Hours)

Conversion of methyl selectivity IaI to isoprene

Selectivity to 4-methoxy-2-methylbutene-1

99 99

76 78

Example 10 "; -

The procedural steps of Example 5 are repeated, with the modification that-instead of magnesium sulfate $ 20 Lead sulfate can be used.

After 10 hours, the conversion 99 f <> and the selectivity for isoprene and 4-methoxy-2-methyl-i i together 83 °.

Example 11 . - ■ ■ -

This experiment is carried out using the procedural steps of Example 4 carried out, but BE, without aluminum oxide or any other solid catalyst is used. and the reaction in a closed system at 150 ° G and a pressure of 12.6 kg / cm. Through the Reaction, a black viscous material is formed resembles a polymer. .-

When the reaction is carried out at 0 ° C, it becomes the main product 1,3-dimethoxy-3-methylbutene was obtained.

Example 12

After the process steps of Example 1, a mixed, C _{/ ä} to C, - Q3 contains refines and paraffins.

· -.- ■■■ 3ü9ü> 0 / I 02B

12 -

-12- 2265231

Product stream from petroleum refining with a content of 12 $> isobutene at a rate of 24 liquid cnr / h and methylal at a rate of 1.5 cm ⁵ / h at 300 ° C over 4.0 cm ^ aluminum oxide, the 6 # BP ₅ contains, headed. (LHSV = 6.6, molar ratio of isobutene to methylal = 2). After 10 hours the conversion of methylal is $ 70 and the selectivity for isoprene is 65 % and that for 4-methoxy-2-methylbutene-1 is $ 7. The remaining constituents of the refinery hydrocarbon stream, other than isobutene, are recovered essentially unchanged.

Example 15

The procedure of Example 12 is repeated, with the modification that instead of the C. to C.sub.1 refinery hydrocarbon stream, a hydrocarbon stream containing 50 % isobutene and 50% isobutane is used. (LHSV = 6.6, molar ratio of isobutene to methylal = 8). After 10 hours, the conversion of methylal 95 f and the selectivity for isoprene is 73% and the 4-methoxy-2-methylbutene-1 # 13 ♦ The isobutane is recovered unchanged.

Example 14 ,

Following the process steps of Example 4, with the modification that butene-2 is used instead of isobutene, methylal (1.5 cm ⁵ / h) and butene-2 (24 liquid ^{cm 5} / h) at 300 ° C. over 4 cm ^{3 passed} aluminum oxide, which contains 6 # BF ₅ (LHSV = 6.6, molar ratio of 2-butene to methylal = 15).

After 8 hours, the conversion is 50 % and the combined selectivity for isoprene and 4-methoxy-2-methylbutene-1 together is $ 60.

■ - 13 ? ■ · 3 0 9 8 2t) / - (υ 2 b

22SS231

aam $ 60. ». . ·.

Example 15

After the process steps of Example 4, but under Use of silicon dioxide-magnesium oxide or silicon-aluminum oxide instead of aluminum oxide as a carrier for BP, the following results are achieved after 8 hours: * "" '.

Conversion of methyl selectivity for selectivity for

IaI isoprene 4-methoxy-2-methylbutene-1

Si-Al Si-Mg , Si-Al Si-Mg Si-Al Si-Mg 99 98 74 71 8 '.11

"- 14 -3098 20 / j02S

Claims (8)

225523Ί PATENT CLAIMS LV. Process for the preparation of isoprene by the vapor phase reaction of methylal with isobutene, butene-2 or mixtures thereof in the presence of a solid catalyst, characterized in that the catalyst used for the reaction is BF ^ on an anhydrous inorganic oxide. 2. The method according to claim 1, characterized in that isobutene and butene-2 in the form of a C. to Ct-- Hydrocarbon mixture containing olefins and paraffins are used that contain at least 5 percent by weight isobutene and 0 to 20 percent by weight butene-2 contains. 3. The method according to claim 1 or 2, characterized in that a catalyst is used, deT at least 2 percent by weight BP, based on aluminum oxide on the weight of the aluminum oxide, 4. Verfahröii according to claim 1 to 3, characterized g © - k θ χι η ζ eich η 3 t that asked the implementation methylal 30 9Ü2 0/10 ^ B - 15 - and isobutene or butene-2 in a liquid hourly space velocity from 0.1. to 25.0, preferably 1.0 to 10.0, are passed over the catalyst. 5- The method according to claim 1 to 4, characterized in that the reaction in a molar ratio from isobutene or 2-butene to methylal in the range from about 2 to 20, preferably about 6 to 12, carried out will. '■■.-.- 6. * The method according to claim 1 to 7, characterized in that after the start of the reaction additional BP, is introduced into the reaction zone. 7. The method according to claim 1 to 6, characterized in that the reaction in the presence of MgSO ₄ , BaSO _4,. PbSO ₄ or Cu (PO ₄ ) ₂ is carried out as cocatalyst. 8. The method according to claim 7, characterized in that g e k e η η that the goocatalyst in an amount of about 1 to 25 percent by weight, preferably 2 to 8 percent by weight, based on the total weight of the catalyst mixture, is used. 30982 0/1028