CS256996B1 - A method of alkylating phenolic compounds - Google Patents

Abstract

A method for alkylating phenolic compounds with at least one free ortho-position to hydroxyl by the action of alcohol on the phenolic compound in the gas phase at a temperature of 300 to 450 C, a pressure of 0.1 to 1.0 MPa in the presence of a solid catalyst containing iron oxide and sulfate ions, which contains a mixture of iron oxide and sulfate ions in the atomic ratio Fe:S=100:0.05 to 100:5 and at least one other oxide of an element from the group Mg, Mn, Ti, Si, Cr in an amount corresponding to the atomic ratio of the relevant element to iron in the range of 0.04 to 6.0 to 100. The selectivity of alkylation to the o-position is achieved by over 95%.

Description

The invention relates to a method for alkylating phenolic compounds with at least one free ortho-position to hydroxyl in the gas phase with a lower alcohol, especially methanol, in the presence of a solid catalyst based on iron oxides.

The processes of alkylation of phenols with lower alcohols on solid catalysts have been known for a long time, but especially in the last decade the use of catalysts based on iron oxides Fe for these purposes has been described. For example, Japanese patent application 78 101 318 describes the alkylation of phenol on a catalyst containing oxides of iron, chromium and boron with the addition of alkali metals, Japanese patent application 78 35 061 describes the use of a catalyst containing iron oxide Fe ₂ O ₃ ^and oxides of a number of other elements, especially alkaline earth elements and copper Cu, nickel Ni, chromium Cr, cobalt Co. Quite often, catalysts based on iron oxides are modified with vanadium. An example is Polish patent 105 922. In principle, the modification of alkylation catalysts with sulfate anions is also known. In particular, catalysts based on magnesium oxide MgO modified with sulfates have been described (US Pat. 4,269,735, 4,283,574). A catalyst based on iron oxide FejOj, modified with tin oxide SnO ₂ and sulfates (DOS 2,852,245) has also been tested, with which very good selectivity to the ortho-position was allegedly achieved during alkylation. Tin oxide SnO _2, however, is not a very common and available compound. The main disadvantage of catalysts based on magnesium oxide MgO, even with sulfate modification, remains the high operating temperature during alkylation and the relatively rapid coking of the catalyst associated with it.

The process according to the present invention eliminates the above-mentioned shortcomings. The essence of the invention is the finding that for the alkylation of phenols in the gas phase with high requirements for the selectivity of the reaction to the ortho position, a mixture of iron oxides modified with sulfate anions and an oxide of at least one other element from the group magnesium Mg, manganese Mn, titanium Ti, silicon Si, chromium Cr can be advantageously used. The content of sulfate anions in the catalyst is according to the present invention selected so that the atomic ratio of iron Fe:sulfur S reaches values of 100:0.05 to 100:5. Each of the other modifying elements is present in an amount corresponding to the atomic ratio of the respective element to iron in the range of 0.04:100 to 6.0:100.

The catalyst for the process according to the present invention is most suitably prepared by combining an aqueous solution of soluble iron compounds Fe and the used modifying metals, or silicon Si, with an aqueous solution of an alkaline reacting substance, most preferably a solution of ammonium carbonate (NH ₄ ) ₂ C0 ₃ or ammonia NHj. Sulfate anions can be supplied in the form of sulfate of any metal used, but it is most advantageous to start the preparation from ferrous sulfate FeSO^ and reduce the concentration of sulfate anions SO^ in the catalytic mass to the desired limit by controlled washing with water.

The alkylation in the process according to the invention is carried out in the gas phase at a temperature of 300 to 450°C and a pressure of 0.1 to 1.0 MPa. However, the most preferred conditions are a temperature in the range of 350°C to 390°C and a pressure of 0.1 MPa.

The main advantages of the process according to this invention are the use of a catalyst prepared from common and available raw materials, the possibility of using available and cheap hydrated ferrous sulfate FeSO ₄ .7H ₂ O for the preparation of the catalyst is particularly advantageous, while a high selectivity of alkylation of phenols (over 95%) to the ortho position can be achieved, some elements usable according to this invention for modification of the catalyst are also present as impurities in some types of technical ferrous sulfate FeSO^, which can be economically very advantageous.

The following examples serve to illustrate the process according to the present invention.

Example 1 to 5

General procedure for catalyst preparation

The weighed amount of ferrous salt and salts of modifying elements (according to Table 1) was dissolved in the prepared measured amount of distilled water. The filtered solution of Fe salt prepared in the above manner (method A) or alkaline precipitating agent (method B) was introduced into the precipitation vessel. Then, with constant stirring, the solution of precipitating agent (A) or Fe salt (B) was added over 1 to 5 min. The resulting suspension was left to stand for a maximum of 4 hours, then the mother liquor was decanted and the precipitate was washed several times with distilled water at 22 °C with subsequent decantation. The amount of washing water required to wash S0 ₄ ions to the desired residual concentration in the catalyst depended on the type and quality of the starting FeSO ₄ and had to be experimentally verified in advance. The washed precipitate was filtered, the filter cake was freely dried for 10 days at laboratory temperature -20 to 25 °C in layers 2 to 4 cm thick and finally dried at a temperature of 40 to 50 °C. The dried mass was crushed to a grain size of 1 to 1.5 mm and, after adding 4 to 8 wt. % graphite, which acts as a binder, it was shaped into tablets 5.5 mm. The tablets were finally calcined for 6 h at a temperature of 450 to 550 °C. The special conditions for the preparation of the catalyst in individual cases are given in Table 1, the analytically determined atomic ratios of the individual elements in the finished catalyst are given in Table 2.

Alkylation

Alkylation was carried out in the gas phase in an integral reactor consisting of a vertical tube with an internal diameter of 40 mm, heated by an electric furnace with regulated power input and equipped with a raw material gasifier, which consists of a vertical cylindrical vessel of the same diameter as the reactor, also electrically heated. A tube with thermocouples was built into the axis of the reactor, ensuring temperature measurement in the catalytic bed. The height of the catalytic bed was 25 to 30 cm.

A solution of phenol, methanol and water was continuously fed into the evaporator (gasifier) by a plunger metering micropump. In all the examples given, a constant molar ratio of the components in the feed was chosen, namely phenol:methanol:water = 1:5:1. The conditions and results of the alkylation in individual cases are summarized in Tables 3 to 10.

Table 1

Conditions for preparing catalysts for alkylation, examples 1 to 5

Example 1 2 3 4 5 Preparation conditions Amount of FeSO ₄ -7H ₂ O (g) 2,986 1,493 2,390 2,390 688 Amount of Fe(MO ₃ ) ₃ .9H ₂ O (g) - - - - 1,500 Amount of dissolving water (1) 10.5 10.0 6.0 6.0 • - Addition of Ti(as TiO ₂ ) (g) ^and ^ - 7.5 12.0 - - Addition of Cr(M0 ₃ ) _3> 9H ₂ O (g) 40.4 20.8 31.9 38.5 - Addition of Mg(MO ₃ ) ₂ .6H ₂ O (g) 26.0 - - - - Addition of Mn(CH ₃ COO) ₂ (g) 21.0 10.8 16.5 20.0 - Water glass addition (ml - - - - 21.5 Precipitating agent 6% aqueous (nh ₄ ) ₂ co ₃ 6% aqueous 6% aqueous (nh ₄ ) ₂ co^ (nh ₄ ) ₂ co ₃ 6% aqueous (nh ₄ ) ₂ co ₃ 10% aqueous NH ₃ Amount of precipitant (ml) 4,000 2,000 6,000 6,000 3,500 Method of precipitation A A B B A Precipitate washing (N/V)' ³ ^ 7/50 8/50 7/60 6/50 7/20

Explanations: a) the addition of Ti was achieved by using FeSO ₄ .7H ₂ O, in which Ti was contained as an impurity

b) N = number of washing cycles; V = volume of washing water in one cycle (1)

Table 2

Analytically determined atomic ratios of elements in the finished catalysts according to examples 1 to 5

Example 1 2 3 4 5 Element Fe 100 100 100 100 100 Cr 1.0 1.1 1.5 1.7 - You - - - - 3.5 Mg 0.8 - - - - Mn 1.0 0.8 1.0 1.0 - Those - 1.0 0.9 - - With 2.6 1.8 2.8 0.1

Table 3

Example 1, conditions and results of alkylation of phenol

og&t-b ¹ T °c Main components of the phenolic part of the product (% wt;) ^In o-qv (%) . ^In 2.6-x <%> phenol o-cresol 2.6-x 2.4-x 2,4,6- TMF 0.121 364 17.4 50.1 26.6 0.9 0.6 65.1 3d,6 0.128 365 19.5 50.2 26.2 0.9 0.5 66.3 23.1 0.082 266 3.6 32.8 59.6 0.8 1.2 37.2 59.9 0.082 264 3.9 35.5 53.3 0.6 1.1 42.0 55.7 0.073 366 2.6 21.0 68.9 0.9 3.5 24.3 70.5 0.068 365 1.9 23.7 70.7 0.8 1.7 26.7 70.6

Table Example 2, 4 , conditions and alkylation results phenol gg^t-h' ¹ T Hl. sl phenolic compounds parts v o-kv ^In 2.6x °c product (% (wt.) phenol o-cresol 2.6-x 2.4-x 2,4,6- TMF 0.166 360 5.1 36.3 57.4 0.2 0.6 41.2 57.6 0.102 355 4.8 66.7 24.6 0.7 1.6 72.6 23.7 0.075 370 4.5 23.6 67.7 0.8 2.2 25.9 68.8 0.155 372 4.7 27.4 64.8 0.5 1.2 31.3 65.6 0.022 380 7.5 34.2 55.7 0.8 1.1 38.5 57.5 0.084 380 ' 7.4 33.0 55.7* 078 1.1 38.5 57.5

Table 5

Example 5, conditions and results of alkylation of phenol

F 9-9kae ^h_1 Main components of the phenolic part v o-kv (%) ^In 2.6-x (%) T °c product (% wt.) phenol o-cresol 2.6-x 2.4-x 2,4,6- TMF 0.082 364 1.4 10.0 82.8 0.6 2.7 11.4 83.7 0.075 265 0.9 7.8 85.6 0.4 3.0 8.8 86.2 0.101 366 1.9 16.0 77.7 0.5 2.1 18.1 78.0 0.114 365 5.8 28.0 62.5 0.4 1.4 32.5 64.3 0.107 264 4.7 23.3 68.9 0.6 0.9 26.9 70.4 0.147 365 11.9 44.3 41.5 0.6 0.6 53.5 44.3 Table 6 Example 4, conditions and alkylation results phenol F -1 -1 Main components of the phenolic part in o-kr ^In 2.6x T product (% (wt.) (%) (%) °c phenol o-cresol 2.6-x 2.4-x 2,4,6- TMF 0.090 356 7.3 43.8 46.0 0.7 0.5 50.9 47.2 0.086 357 5.6 40.6 51.8 0.4 0.6 46.3 52.3 0.096 364 9.6 45.1 42.1 0.8 0.5 53.8 44.4 0.121 366 7.2 51.3 40.0 0.4 0.3 58.5 40.4 0.166 366 21.5 56.0 21.5 0.3 0.1 74.2 25.3 0.098 373 16.9 49.7 30.7 0.8 0.3 63.7 34.8 Table 7 Example 5, conditions and alkylation results phenol F „ „-1 h-1 T Main components of the phenolic part in ⁱⁿ o-kr ^In 2.6x ^9-g coffee °c product (% (wt.) (%) rule o-cresol 2.6-x 2.4-x 2,4,6- l B / TMF 0.111 360 1.1 12.1 84.3 0.3 1.3 13.6 84.0 0.216 360 16.2 43.8 38.8 0.3 0.4 55.4 43.4 0.288 360 32.7 46.9 19.6 0.1 0.2 72.3 26.7 0.250 370 5.1 24.0 69.6 0.3 0.7 27.7 70.7 0.288 370 15.3 36.5 46.8 0.2 0.4 46.1 52.3

Explanations to tables 3 to 7

-1 -1

F ^h ) specific injection of phenol per unit mass

T (°C) temperature in the catalytic bed o-cr ortho-cresol

2,6-x 2,6-xylenol

2.4-x

2,4,6-TMF ^V o-kr ^{(% mol) V} 2,6-x ^{(% mol)}

2,4-xylenol 2,4,6-trimethylphenol yield of ortho-cresol yield of 2,6-xylenol (relative to reacted phenol) (relative to reacted phenol)

Claims (1)

Process for the alkylation of phenolic compounds with at least one free ortho-position to hydroxyl by the action of an alcohol on the phenolic compound in the gas phase at a temperature of 300 to 450 ° C, p preferably 350 to 390 C, a pressure of 0.1 to 1.0 MPa in the presence of a solid catalyst containing iron oxide and sulphate ions, characterized in that the alkylation is carried out on a catalyst which is a mixture of iron oxides containing sulphate corresponding to an atomic ratio of iron Fe to sulfur S = 100: 0.05 to 100: 5 and at least one other oxide of an element of magnesium, manganese Mn, titanium Ti, silicon Si, chromium Cr, added in an amount corresponding to an atomic ratio of the element to iron of 0, 04 to 6.0 to 100.