CS227483B1 - Method of preparing methylcyclohexanol by cresol hydrogenation - Google Patents

Description

The present invention relates to a process for the production of methylcyclohexanol by hydrogenating cresol with an increased sulfur content in the gas phase in two stages on nickel supported catalyst at temperatures of 130 to 190 ° C and a molar excess of hydrogen of 50 to 100: 1.

Technical methylcyclohexanol is a mixture of three of its isomers in varying proportions, less cyclohexanol and dimethylcyclohexanols. It is most often used as a solvent, raw material in the manufacture of synthetic resins and in the production of methylcyclohexanone. It is produced by a single-stage or multi-stage catalytic hydrogenation of cresol on nickel catalysts in both the gas and liquid phases, similar to the larger amounts of phenol hydrogenation to cyclohexanol carried out.

While phenol purity has been improving recently due to the expanding production of synthetic cumene phenol, the content of impurities, mainly sulfur, in technical cresol has been steadily increasing due to the increasing sulfur content of coal and lignite tars. use a system of two reactors, the first of which is purification and partially hydrogenation.

The most commonly used industrial catalysts for the hydrogenation of cresol are Raney nickel and nickel on alumina or other support (diatomaceous earth, silica gel). Of these, more commonly used Raney nickel has higher activity and selectivity, but lower durability due to poisoning with both sulfur compounds and mercury and less use of nickel in the formation of nickel sulfide during hydrogenation. The regeneration of Raney nickel by overlapping with sodium hydroxide solution is ineffective because the NiS formed does not decompose with lye. Furthermore, the replacement of this spent catalyst in a tubular reactor is very difficult, it takes several weeks and the use of pneumatic hammers, drills or pressurized water has not proved successful. Some pipes could not be cleaned at all. The operator is then exposed for a long time to the inhalation of nickel dust from the cresol compounds. In the case of Raney nickel, it was necessary to carry out a piping reactor after three of its replacement.

Thus, with a sulfur content of cresol in hundredths of a percent or more, it is preferable to use, as a catalyst, supported nickel supported catalysts such as alumina, diatomaceous earth, chromium trioxide, and the like in a system of two serially connected alternating current reactors.

The above disadvantages of the present invention eliminate the process for the production of methylcyclohexenol by hydrogenating cresol with an increased sulfur content in the gas phase in two stages on nickel supported catalyst at temperatures of 130-190 ° C and excess hydrogen. This process consists in passing, in the first step, a mixture of cresol-hydrogen vapor through nickel on a carrier having a sulfur content of 2 to 10% by weight at a space velocity of 0.1 to 0.3 h ^-1 .

The advantage of the process according to the invention over the known processes is, in particular, a higher utilization of the catalyst in the treatment of cresol with a higher sulfur content. The prolongation of catalyst replacement periods also results in increased labor productivity and reduced catalyst replacement effort.

The reaction is carried out in excess hydrogen, the molar ratio of hydrogen to cresol may be 50 to 100: 1. A sufficiently deactivated catalyst having an average sulfur content of min. 2 wt. otherwise, the amount of undesirable front fractions (water, methylcyclohexene) in methylcyclohexenol rises above 5% by volume after passing through the second reactor.

The temperature control of the cooling water bath must be reliable and separate for both reactors At the start of the cycle with a relatively active catalyst (conversion of 90% cresol in the first stage), the temperature in the second stage must not exceed 150 ° C; at the same time it must not drop below 135 ° C, otherwise methylcyclohexanol condensation, leaching of the catalyst into the product and deterioration of the mechanical properties of the contact.

Later during the cycle and the advancing poison zone in both reactors, the temperature of the second reactor increases to 185 ° C. Under these conditions, the cresol content of methylcyclohexanol is below 0.1% by weight. and an amount of front distillates below 1 wt.

This product does not need to be distilled for most applications. When the activity of the catalyst in the second stage is lost, which results in a rapid increase in the cresol content in methylcyclohexanol of more than 5% by weight, the completely depleted catalyst is dumped from the first reactor and the reactor is filled with fresh. The next cycle is repeated in the reverse order of the reactors.

The spilled catalyst contains up to 30 wt. NiS, which represents a high utilization of nickel in the catalyst to remove sulfur from the feedstock. Catalyst replacement in the reactor takes one day without much physical effort. The elongation of the cycle over the overlapped Raney nickel in the first stage is 2.5 to 3.5 times more without catalyst replacement.

In the following examples, unless otherwise indicated, percentages are by weight.

He did

Technical cresol of 1, 2 wt. phenol, 11.5% o-cresol, 55.0% m-cresol, 27.8% p-cresol, 4.5% xylenols (from phenolic compounds), 0.1% water, 0.04% sulfur,

0.03% of the pyridine bases are fed to an evaporator at an average of 175 kg / h at an evaporator temperature of 157-163 ° C, saturated with hydrogen circulating at 3000 nP / h (under normal conditions) and at a pressure of 1.5 MPa.

The vapor of cresol with hydrogen (1:88 molar ratio) passes through two tubular reactors filled with catalysts. Each of the reactors has a tube volume of 1.28 m ³ , jacket cooling on the principle of evaporation of steam condensate and stainless steel mesh on the head and bottom.

The catalyst is filled up to a height of 0.75 to 1 m from the level evenly into all pipes.

In the first reactor, 860 kg of nickel-on-alumina catalyst having a bulk density of 0.74 kg / l and a sulfur content of 4% by weight are partially consumed. and nickel 39%; in the second reactor there is fresh tableted nickel on alumina in an amount of 750 kg, with a bulk density of 0.65 kg / l, a nickel content of 44% by weight.

At the start of production (the first 20 t of methylcyclohexanol produced), cresol dosing is 170 kg / h at a choke temperature of 157 ° C, the temperature of the first reactor is 160 ° C, the reaction mixture-cresol- 10%, methylcyclohexanol 90%, the temperature of the second reactor is 140 ° C, product composition - 0.01% cresol, distillate fractions 1.3% (v / v).

In the main production stage (20 to 320 t of methylcyclohexanol), the cresol feed rate is 180 kg / h at a choke temperature of 162 ° C, the temperature in the first reactor is 160 to 175 ° C, temperature, second reactor 140-175 ° C, product composition 0.0-0.03 wt. cresol, 0.8% (v / v) after distillation.

In the third phase (320 to 330 t of methylcyclohexanol) the cresol feed is 145 kg / h, the choke temperature is 156 ° C, the temperature of the first reactor is 170 ° C, the cresol content in the reaction mixture is 74% after the first stage. of the product 0.1-5% cresol.

330 tonnes of methylcyclohexanol were produced throughout the cycle. The cresol content was monitored by colorimetric reaction with aminoantipine, the front fractions from the distillation curve to 160 ° C (containing water, methylcyclohexane and about 20% methylcyclohexanol). Catalyst replacement in the first reactor took 24 hours and the spent catalyst contained 8.5% sulfur.

Example 2

The procedure is the same as in Example 1 except that fresh tableted nickel on kieselguhr with a nickel content of 46%, a bulk density of 1.05 kg / l and partially deactivated nickel on kieselguhr with a sulfur content of 5% were used as catalyst in the second reactor. . Cresol contained 0.05% sulfur. The methylcyclohexanol produced contained 0 to 0.05% cresol and 0.8% front parts.

Claims (1)

SUBJECT OF THE INVENTION A process for the production of methylcyclohexanol by hydrogenating cresol with an increased sulfur content in the gas phase in two stages on nickel supported catalyst at temperatures of 130 to 190 ° C in excess hydrogen, characterized in that in the first stage a sulfur content of 2 to 10% by weight at a space velocity of 0.1 to 0.3 h ^-1 .