NL8204837A - Lactam(s) prodn. - by rearrangement of cycloalkanone oxime(s) with boron contg. silica catalyst - Google Patents

Abstract

Lactams are prepd. by rearrangement of cycloalkanoneoximes using a heterogenous catalyst comprising a crystalline modification of silicon dioxide in which a number of Si atoms in the crystal lattice are replaced by boron atoms. Pref. in the crystal modification the amt. of boron is such that the ratio SiO2/B2O3 is greater than 3, pref. 100-500. The B-contg. catalyst may be modified with a cpd. of P, Mg, B, Sb, Ca, Ba or Sr. The rearrangement reaction is pref. carried out in the gas phase using 0.1-10g oxime per hour per g catalyst. Pref. prod. is E-caprolactam.

Description

Stamicarbon B.V.

Inventors: Petrus M.G. FREMKEN in Thorn

Marcel G.F. KROLL in Maastricht PN 3423 '1

PROCESS FOR PREPARING LACTAMS BY CONVERTING CYCLOALKANONOXIM IN LACTAM WITH A Heterogeneous CATALYST ON

BASIS OF SILICA

The invention relates to a process for the preparation of lactams by rearranging a cycloalkanone oxime with a heterogeneous silica-based catalyst.

It is known that lactams can be prepared by rearrangement of cycloalkanone oximes, having 5-12 carbon atoms, especially cydohexanone oxime, in a heterogeneous process in which the oximes are gelated over a solid catalyst. This method has the advantage over the known methods for rearranging said oximes in a homogeneous process using stoichiometric amounts of strong mineral acids, inter alia, that no ammonium sulphate is formed.

Known heterogeneous catalysts used in rearrangement of cycloalkanone oxime, especially cyclohexanone oxime, are, for example: silica gel, aluminum oxide, silica-alumina, magnesium oxide, thorium oxide, supported phosphoric acid, borum phosphate, and aluminum phosphate. These catalysts achieve only low lactam yields or appear to be unstable.

The use of borloxy oxide-containing support catalysts is known from DE-A 2844880. However, during the conversion 20 carbonaceous decomposition products are deposited on the catalyst. This limits the life of the catalyst, making it necessary to continuously add fresh catalyst to the fluid bed reactor and remove spent catalyst. The catalyst also loses boron.

It is also known to use acidic zeolites as a catalyst (J. Cat, 6, 245-252, 1966). The use of these zeolites results

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However, low yields of caprolactam and / or the catalyst have poor stability. In EP-A 56698 rights are claimed for a process for the preparation of caprolactam in which cyclohexano-noxim is passed over a zeolite, with a silica-alumina ratio of at least 12 and a constraint index of 1 to 12.

Examples of such zeolites are ZSM-5, ZSM-11 and ZSM-23. Aftereffect of this patent shows that the yield of caprolactam by this method is low and only 1-2 Z selectivity is obtained.

The object of the invention is to develop a process in which these disadvantages do not occur.

A process has now been found for rearranging cycloalkanone oxime with a heterogeneous silica-based catalyst using a boron-containing catalyst consisting of a crystalline modification of silicon dioxide in which a number of silicon atoms have been replaced in the crystal lattice of the silicon dioxide by boron atoms.

The reaction can be used in both the liquid phase and the gas phase.

Surprisingly, the use of the crystalline borosilicate results in high conversions and considerably higher yields of lactams in the rearrangement of cycloalkanone oximes. In the rearrangement of cyclohexanone oxime by the method of the invention, the selectivity to caprolactam by this new method is 55% or more, while a conversion of 100 Z is achieved. Due to the very stable installation of b3 + in the. crystalline silica structure has little or no boron loss.

A crystalline modification of silicon dioxide, in which a number of silicon atoms in the crystal lattice of the silicon dioxide have been replaced by boron atoms, is also referred to as boralite. The preparation of boralites and some of their properties are described in US patent 4269813 and in German patent application 2924915. The boron content of the boralite used as a catalyst can vary between wide limits. The amount of boron is expressed as the molar ratio between silicon dioxide and boron trioxide. The ratio is greater than 3.

The SiO 2 / B 2 O 3 ratio may be very high, but higher than 2000, 8204837 v :: 3 offers no more advantages since the number of catalytically active sites decreases sharply and the activity of the catalyst decreases. The ratio is preferably between 100 and 500.

Silicon can be replaced by germanium. In the grid 5 built up from one or both of these materials, smaller amounts of the silicon and / or germanium can be replaced by aluminum, iron, chromium, vanadium, molybdenum, arsenic, manganese or gallium.

A convenient way of obtaining the crystalline modifications of silicon dioxide and boron in a simple manner is to start from pure silicon dioxide and a soluble boron compound. Useful boron compounds are boric acid, sodium borate, ammonium borate, soluble perborates and pyroborates, and soluble organic boron compounds. In the preparation, pure silica, dissolved in a tetraalkylammonium hydroxide, is heated in an autoclave with a solution of a boron compound, the crystalline product formed is removed from the autoclave, washed, dried and calcined under air. If, after the calcination, non-acid-reacting cations are still present, for example alkali metal ions, * the obtained crystalline modification is subjected to an ion exchange with solutions, which exchanges the relevant cations for acid-reacting cations, such as hydrogen ions and / or rare earth ions and / or against groups of groups that decompose on heating, for example ammonium wages, in which case hydrogen remains on the surface. In the latter case, the ion-exchanged crystalline modification is heated again. The ion exchange brings the crystalline modification into the fully catalytically active state. Particularly good results are obtained if one starts from amorphous silicon dioxide, for example aerosol.

The catalyst has a micropore system determined by crystallography, the pores of which have a uniform diameter.

The calcination has removed the organic nitrogen compounds from the pores, making them accessible. Although the yield of lactam is already considerably improved when the boralite catalyst is used, there is further improvement of the yield of lactam and the stability of the catalyst by modification of the borula-containing catalyst.

The boron-containing catalyst can be modified with a compound of an element from the group of phosphorus, magnesium, boron, antimony, calcium, barium or strontium

The modification with a phosphorus-containing compound is preferred. Preference is given to phosphorus-containing compounds from the groups of phosphoric acid, phosphines, phosphites, phosphite esters, phosphorus halides, phosphine sulfides, phosphonic acid and phosphoric esters. Examples of the phosphorus-containing compound are: phosphoric acid, diphenylphosphine, diethylchlorothiophosphine, phosphates, diphenylphosphine chloride, trimethylphosphite, ammonium hydrogen phosphate, phosphorus halides, and esters of phosphine. 70% selectivity is obtained with these modified catalysts.

The amount of phosphorus in the boron-containing catalyst can be between 0.5 and 25% by weight. The modification can take place, for example, by suspending boralite in a solution of phosphoric acid in methanol. The suspension is evaporated after reflux and the resulting solid product is dried and then heated.

The boralite can be advantageously modified by deactivating some of the acidic sites on the outer surface. A very suitable method is described in the co-filed patent application (code PN 3426). According to this method, the pores of the boralite are first made inaccessible to the deactivating agent, for example by soaking with toluene, after which the hydrogen ions are exchanged for, for example, sodium ions.

The use of the catalyst for the catalytic rearrangement of cycloalkanone oximes uses conditions known per se. When rearranging in the liquid phase, the temperature is between 70 ° C and 140 eC. The gas phase process can take place in either a fluid bed or a fixed bed mode. The rearrangement takes place at temperatures between 230 ° C and 500 eC. The cycloalkanone oxime used as a food may contain up to 10% water. The throughput rate can be between 0.1 and 10 grams of oxime per hour per gram of catalyst. Cycloalkanone oximes, for example with 5-12 carbon atoms, especially cyclohexanone oxime, can be converted to the corresponding lactam.

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The preparation of lactars by rearrangement of cycloalkanone oximes with the above-described catalysts will now be illustrated by examples without, however, being limited to the embodiments described herein.

Example 1, comparative

In a small fixed bed reactor, filled with zeolite HZSM-5 (Si02 / Al2 <> 3 - 1640, 104, respectively) and glass spheres, a solution of cyclohexanone oxime in toluene is pumped at such a speed that a spatial throughput on weight basis of 10 oxime was obtained from 1 hour ~ 1 (WHSV »1 gram of oxime per hour per gram of zeolite). A gas mixture of CO2 and H2O is also charged in the reactor. This can be achieved by passing CO2 through a water-filled saturator. The molar ratio of the feed components is oxime / toluene / CO2 / H2 O - 1.0 / 4.0 / 16.5 / 3.5. The waste gas from the reactor is condensed with a water cooler and the product obtained is analyzed by gas chromatography. The reactor temperature varies between 210 and 340 ° C. After each experiment (210, 300 and 340 ° C), the catalyst is calcined with air at 430 ° C to 540 ° C for 12 hours. A significant conversion of 20 oxime only occurs at 340 ° C. The lactam selectivity in all cases is only 1-2 percent. The same result is obtained if CO2 is replaced by N2.

Example 2, comparative

According to the procedure of Example 1, cyclohexanone oxime 25 is rearranged while the oxime / toluene / CO2 / H2 O ratio is 1.0 / 3.0 / 7.0 / 1.0. The conversion of the oxime is 100 l, while the lactam selectivity is only 1%. The results are shown in Table 1.

Example 3 A fixed-bed reactor, filled with 3.14 grams of H-boralite

(S102 / B203 - 220) is fed with a stream of the following molar composition: oxime / toluene / N2 / H20 - 1.0 / 3.0 / 7.0 / 1.4. The oxide solution in toluene is placed in a glass bead filled evaporator at 215 eC

8204837 6 Gas phase and mixed with a gaseous N2 / H2O mixture. The WHSV is 0.79 grams of oxime per hour per gram of boralite. The reactor temperature is 340 ° C. The conversion of the oxime is 100%, while the selectivity to caprolactam is 58%. The results are included in Table 1.

Example 4 to 6

In these experiments performed analogously to Example 3, the oxime / toluene / N2 / H 2 O ratio was slightly changed to 1.0 / 3.0 / 7.0 / 1.0. The temperatures are 355 eC, 385 10 ° C and 400 ° C, respectively. The results are shown in Table 1.

Example 7

In this experiment, which is analogous to Example 3, the unmodified boralite catalyst has been replaced by a phosphoric acid-modified boralite catalyst. The oxime conversion is 100% while the lactam selectivity is 70%.

The modification was effected by suspending 4.88 grams of boralite in a solution of 0.25 grams of 85% H3PO4 in 75 ml of methanol. The suspension is evaporated after refluxing for 16 hours and the resulting solid product is dried at 125 ° C and then heated to 540 ° C.

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Table 1

Example Catalyst Temperature WISV Conversion Selectivity ° C hr- * Z (capro-lactam)% on converted oxim 13) HZSH-5 340 1 90 2 10 23) HZSM-5 340 0.79 100 1 3 H-Boralite D 340 0.79 100 58 4 H-Boralite 355 1.26 100 62 5 H-Boralite 385 0.84 100 65 6 H-Borallite 400 1.05 100 65 15 7 P-Boralite2) 340 0.79 100 70 1) H -Boralite is unmodified Boralite 2) P-Boralite is phosphoric acid-modified Boralite 3) Not according to the invention 8204837

Claims (10)

8 PN 3423 1. Process for the preparation of lactams by rearrangement of cycloalkanone oximes with a heterogeneous silica-based catalyst, characterized in that a boron-containing catalyst is used, which consists of a crystalline modification of silicon dioxide in which a number of crystals in the crystal lattice of the silicon dioxide silicon atoms have been replaced by boron atoms. Process according to claim 1, characterized in that the amount of boron in the crystalline modification expressed as the molar ratio of the oxides SIO2 / B2O3 is greater than 3. Process according to claims 1-2, characterized in that the amount of boron in the crystalline modification expressed as the molar ratio of the oxides SiO 2 / B 2 O 3 is between 100 and 500. 4. Process according to claims 1-3, characterized in that the boron-containing catalyst is modified with a compound of an element from the group of phosphorus, magnesium, boron, antimony, calcium, barium or strontium. 5. Process according to claim 4, characterized in that the boron-containing catalyst is modified with a phosphorus-containing compound. Process according to claims 1 to 5, characterized in that the rearrangement of cycloalkanone oxime with a heterogeneous catalyst takes place in the gas phase. 7. A method according to claim 6, characterized in that the throughput is between 0.1 and 10 grams of oxime per hour per gram. Process according to claims 1-7, characterized in that the cycloalkanone oxime is cyclohexanone oxime. 9. ε-caprolactam obtained by any one of methods 1-8. 10. Process according to the invention for the conversion of cycloalkanoxoxime to lactam as described in the introduction and illustrated in the examples. VNP / MS 8204837