NO744038L - - Google Patents

Description

Olefin hydration catalyst.

The present invention relates to olefin hydration catalysts.

The use of glass as a support material for catalysts

has wide coverage in the technical literature. Uemaki et al (CA 74:

75964 and 73:3^08) used e.g. glass beads as a solid diluent for a phosphoric acid-impregnated diatomaceous earth catalyst. The use of glass or quartz, as distinct from porous glass or glass-

spheres which support H-^PO^ for the preparation of a catalyst are described in Langlois et al., Petroleum Refiner 31, No. 8, 1952 and in French Patent No. 1,294,712. The use of porous glass as a support for catalysts other than olefin hydration catalysts is described in several places including French Patent No. 1,492,495

and DOS 1,814,253. The use of non-porous glass or glass beads as a catalyst support is also described in many publications including US Patent No. 2,847,475 and Romanian Patent 48,909.

It has now been found that a. improved olefin hydration catalyst can be prepared using a support of porous glass spheres with high silicon dioxide content and with structural and surface properties. The phosphoric acid-impregnated glass balls constitute an effective catalyst and have high compressive strength.

The present invention relates to an olefin hydration catalyst and more particularly to an olefin hydration catalyst comprising porous glass spheres impregnated with aqueous phosphoric acid and with a high silicon dioxide content and with specific structural and surface properties.

According to preferred embodiments of the invention,

porous glass spheres with a high silica content and with special structural and surface properties, impregnated with aqueous phosphoric acid and the resulting catalyst are used in a fixed bed in a vapor phase olefin hydration process.

The carrier is porous glass spheres with a high silicon dioxide content and is characterized by the following properties: Particle size and shape - particles, preferably spherical with Martin diameters - of 0.5~25.0 mm, preferably 2.0-4.8 mm (Martin diameter is the distance between opposite sides of the particle measured across the particle and along a line that bisects the projection area). (Martin et al, Trans. Ceram. Soc. (Eng.) 23, 61 (1924))

Thermally stable at temperatures up to 1000°C. Chemically resistant and mechanically stable to the effects of aqueous H-^POjij at concentrations up to 70% by weight at temperatures up to 270°C for up to 1000 hours.

The average compressive strength of the glass balls is determined on a "Chatillon Pellet Strength tester" which measures the minimum force required to crush a particle between parallel plates.

Suitable 'glass beads' are commercially available. An example is type "lC2" porous glass spheres. Such microporous glass catalyst supports can alternatively be produced using known methods, e.g. as described in DOS 2.309-449. Porous glass is produced by heat treating a type of glass to a point whereby microphase separation into a. silica-rich microphase and another leachable microphase are obtained, followed by cooling and then leaching of the leachable phase so that one is left with a porous structure consisting mainly of

silicon dioxide. One such glass is alkali borosilicate glass in which

the microphases are a silica-rich phase and a soda-boron oxide-rich phase. The latter phase can be leached with a mineral acid and thus leave a porous silicon dioxide structure. An example of such a glass is unfused "'Vycor" glass. The leached porous glass from "Vycor" ("Vycor code 7930") has a chemical composition of 96% silicon dioxide, 3% boron oxide and 0.5%■R20^+R02 (mainly Al20^ and Zn02) and traces of Na20 and As20 ^.

The process for making porous glass with a high silica content was first reported by Nordberg, J. Am. Ceram. Soc 27, 299-305 (1944). It has been shown (Zhdanbv et al, CA. 58:8743) that the pore volumes of the porous glasses depend on the content of alkali metal oxide in the starting glass and also on the particular alkali metal. The pore size, i.e. the pore diameters, can be regulated within a few Å by means of the temperature and the duration of a

preliminary heat treatment. (Dobychin et al, CA. 60:14228 (1964)).

The glass spheres used as carriers in the present invention must have high porosity because they must contain a substantial amount of aqueous H^PO^ and still have a dry surface. None of these conditions can be achieved if the glass is non-porous. The substantial quantity of aqueous phosphoric acid for a given batch of nickel volume or size is necessary for high catalyst activity and the dry state is necessary to avoid corrosion of H-^PO^ on the reactor walls by the catalyst being adjacent to these walls. When porous glass spheres with the above properties are incompletely saturated with a high concentration level of H-^PO^, these purposes are achieved.

A loss of phosphoric acid from the catalyst occurs during the hydration reaction due to a mechanism that is not known. One hypothesis is that a reaction takes place between ethylene and phosphoric acid in the pores so that a volatile but thermally unstable ethyl phosphate is formed. Part of this material is volatilized out of the pores before decomposition into phosphoric acid and ethylene and before its reaction with water to form alcohol and phosphoric acid. Thus, H^PO^ can be brought out of the pores. The same reaction can take place outside the pores where the high linear gas velocity allows for a much faster movement before decomposition or the reaction takes place. The process continues until the acid passes out of the reactor.

The glass sphere carrier is impregnated with phosphoric acid and this provides an olefin hydration catalyst. This can be achieved by filling the balls in a container containing aqueous phosphoric acid or by filling phosphoric acid in a container containing the balls, as desired. The container used to impregnate the beads may conveniently be the olefin hydration catalyst. Sufficient acid is used to cover the balls, which are allowed to soak in the acid for a sufficient period of time, after which the acid is allowed to drain. The soaking process can be repeated one or . several times as desired. Alternatively, the H-^PO^ solution can be injected into the glass sphere using a very small droplet size, 0.001-0.005 mm, until the carrier is saturated. At this point, the phosphoric acid content, defined as the weight in grams of 100/2-H-^PO^in one cm of catalyst, is determined. The impregnated porous,

glass balls can then be dried in a suitable way, such as with hot circulating gas, e.g. nitrogen or ethylene, at an elevated temperature so that the dry catalyst is obtained.

H-jjPO^ which is used for impregnating the glass balls is used as an aqueous solution in which the orthophosphoric acid concentration is in the range of 12-85%, and preferably in the range of approx. 50-60%. The impregnation temperature can be in the range 20-200°C, but is preferably in the range of approx. 25-50°C. The balls are usually allowed to soak in acid for 15 minutes to 5 hours or more and preferably for approx. 2 hours. A longer period of time can be used, but is usually unnecessary. Excess liquid acid is usually allowed to drain for 0.5~2 hours. The aqueous solvent for the phosphoric acid may optionally contain ethanol and/or a small percentage of a wetting agent such as polyoxyethylene to help fill the pores in the beads with acid. The drying of the impregnated glass spheres can be achieved in any suitable manner, but is preferably effected at least partially under a flow of a suitable gas such as nitrogen or ethylene with heat supplied either externally to the reactor or by preheating the gas. The latter method is preferred. The impregnated balls can e.g. be air-dried for 3~24 hours, preferably 10-15 hours, and then oven-dried for 1-4 hours, 'preferably approx. 2 hours, at a temperature of 100-200°C, preferably approx. 110°C.. ;The extent of the drying is regulated so that the total pore volume in the spheres is not occupied by H^PO^, i.e. the carrier is not completely saturated. The volume taken up by the acid is less than 100% of the total pore volume, preferably approx. 40-85%. The degree of unsaturation will naturally vary depending on the degree of concentration of the acid used and also on the strength of the aqueous H-^PO^ solution used in the impregnation. When e.g. 55% acid is used, it is preferred that approx. 70% of the pore volume, after drying, is filled with H-^PO^. Since the carrier is not saturated, essentially all the acid is in the pores and the surface is thus dry and corrosion of the reactor walls is avoided. The catalyst according to the invention is used to hydrate olefins to alcohols and ethers. The catalyst can be used in known processes and it is particularly useful for converting monoolefins with 2-10 carbon atoms, such as ethylene, propylene and butylene. It is particularly useful in ethylene hydration to ethanol and diethyl ether. The hydration reaction usually involves passing a gaseous mixture of olefin and water in continuous contact with the catalyst at elevated temperatures and pressures. This process is in itself well known and does not need to be described in more detail here. In the preferred continuous vapor phase hydration process, a reaction temperature of 235-350°C, preferably 245-300°C, ■ a pressure of 35-105 kg/cm<2>', preferably 63-87.5 kg/cm is used <2>gauge pressure, a molar ratio between water and ethylene of 0.4-2.0, preferably 0.5_0.8, and a steam rate of 5-100, preferably 15-35 liters/min./liter of catalyst under standard conditions of 1 atmosphere pressure and oa. 25°C. Orthophosphoric acid solution is added to the reactor to replace what is lost from the reactor. The catalyst according to the invention is characterized by an average compressive strength (50 particles) of over 4.5 kg, a phosphoric acid content of 0.030-1.01, preferably 0.048-0.48 and preferably 0.16-0.48 g/cm ■ x catalyst, and a high level of activity with respect to olefin hydration to alcohols and ethers. Although the catalyst is primarily suitable for operation in a fixed bed, it can also be used in a process with a moving bed. In the above, the theory behind the invention is discussed, but the invention should of course not be limited by this theory. The following examples further illustrate the invention. Unless otherwise stated, all portion and percentage statements are based on weight. ;Example I; 228.6 g (375 ml) high silica porous glass spheres (type "1C2"; Pittsburgh Plate Glass Company) having the following properties. ; ; was immersed in 55% aqueous H-^PO^ for 2 hours at ambient temperature (23°C), then drained and dried for 3 hours at 105°C. The average compressive strength of the resulting catalyst (based on 50' particles) was 6.3 kg with 0% with a compressive strength of 0.90 kg, a free phosphoric acid content of 27.93% with. equivalent content of 0.282 g H^PO^ per cm^ of catalyst. ;300 ml (302.9 g) of this catalyst was charged into a reactor having a length of 35 cm and an internal diameter of 4.03 cm, which reactor was provided with a steel jacket. After filling the catalyst and closing the reactor, hot oil at 264°C was circulated through the jacket to heat the catalyst. When the temperature in the bed had reached 236°C, a vapor mixture of ethylene and water in a mole ratio of water to ethylene of 0.558 was passed down through the bed at a vapor rate of 30.14 standard (25°C, 1 atmosphere pressure) liters per . minute per liter of catalyst and at a pressure of 70 kg/cm 2 manometer pressure. ' Reacted waste gas was passed through a pneumatically operated valve which regulated the reaction pressure and through which the waste gas pressure was reduced to atmospheric pressure. ;As the reaction proceeded, a steady state was reached whereby the bed temperatures near the top and bottom of the bed were 265 and 271°, respectively, and the pressure was 70 kg/cm<2.>In order to measure the catalyst activity under steady state conditions, the ;-off gas was diverted and passed through a special passage for exactly 1 hour for the collection of data. The waste gas was cooled in a condenser using water at 20°C as coolant and a liquid phase condensed and this phase contained the bulk of synthesized alcohol together with water. Non-condensed gas was then passed through: a wash tower in which* liquid methanol flowed down the column in countercurrent to the gas stream to wash out ethanol and ether. These components were measured in the methanol washing solution

by gas-liquid chromatography and was also recovered by distillation. The ethylene volume in the effluent was measured. The ethanol and ether content of the condensed aqueous phase was also measured by gas-liquid chromatography and then recovered by distillation. The results after 35 hours were as follows: Yield of alcohol

and ether were 0.17 and 0.03 liters (at 20°C) per liter of catalyst per hour, respectively. The conversions of ethylene to ethanol and ether were 5.83% and 1.31%, respectively.

Example 2

228 g (275 ml) of high silica porous glass spheres (type "lC-1", Pittsburgh Plate.Glass'Company) and

with the following properties:

was immersed in 55% aqueous phosphoric acid for 3 to 5 hours at ambient temperature (23°C), drained for 2 hours and then dried for 17 hours at 105°C giving a final weight of 362.2 g, - Analysis showed that the resulting catalyst contained 34.90% free H^PO^ and that the average compressive strength was 13.55 kg. The acid content corresponds to an acid amount of 0.34 g H^PO^per. cm. catalyst.

300 ml (292.9 g) of the catalyst was added to the reactor as described in example 1, and was used as described in said example to hydrate ethylene continuously to ethanol in the vapor phase under the following conditions: pressure 70 kg/cm 2 , molar ratio of water. and ethylene 0.55,.vapor rate of reactants

29.22 liters/min./liter catalyst under standard conditions, and inlet and outlet gas temperatures of 262 and 264°C, respectively. The layer temperature. at the top and bottom of the layer were 265 and 278°C,

respectively. The results from the hydration after 2 hours were yields of alcohol and ether of 0.165 and 0.05 liters (at -20°C) per liter of catalyst per hour in conversions of ethylene to alcohol and to ether of 5.89$ and 2.03%, respectively.

Example 3

An isolated pressure reactor for experiments on a large scale is filled with porous glass spheres with a high silicon dioxide content and with properties as described in example 1.

55% aqueous H^PO^ is pumped into the reactor until the porous glass balls are completely submerged. After a stay in the acid of 2 hours, the acid is drained. The catalyst has a compressive strength, wet or dry, of over 4.5 kg. The catalyst is dried by passing dry ethylene at 110°C through the layer. The improved catalyst produced in situ in this way is used in continuous vapor phase hydration of olefin to corresponding alcohols and ethers as follows: Preheated (to about 260°C) ethylene and steam (in a molar ratio between water and ethylene of about 0 ,6) and,, later, recycled gases, are compressed to approx. 63 kg/cm abs. and is then passed continuously down through the catalyst bed at a steam rate

near 30 litres/min/litre, (at standard conditions) catalyst, causing the bed to be heated to reaction temperature and finally due to the heat of reaction to a final temperature

' at steady state. The gaseous effluent reaction mixture is cooled under pressure and the resulting liquid mixture is separated in a high pressure separator. The vapor stream from the separator is fed to an alcohol scrubber where the alcohol is washed out with water and the washed gas is fed to a recycling compressor and then (after cleaning a small stream) returned to the reactor. The washing solution is combined with the liquid phase from the high-pressure separator and is fed into an ether stripping vessel where ether and other light components are removed, sent to an off-gas compressor, then to the recycle compressor and finally recycled to the reactor.

The dilute alcohol solution from the bottom of the ether stripper is concentrated in a pre-rectification column, then catalytically hydrogenated to convert by-product carbonyl groups to alcohol groups and to saturate by-product unsaturated compounds (e.g., converting acrolein to n-butane) for easy . removal via distillation., The bottom product from the pre-rectification column is recycled to the alcohol wash column because this product essentially consists of water. After hydrogenation, the alcohol is purified

.furthermore, by extractive distillation and rectification for continuous release of a very pure alcohol product. 55% aqueous H^PO^ solution is added to the top layer to replace acid

which has been lost from the layer.

Example 4

Catalyst is prepared from 228 g (375 ml) of porous glass spheres with a high silicon dioxide content and of the type "1C-2" as in example 1. A 300 ml (303 g) supply of the catalyst is placed in the reactor as described in example 1 and used for continuous solid bed and vapor phase catalytic hydration of propylene with water to isopropanol and isopropyl ether using a modification of the method described in example 1.

After placing the catalyst and closing the reactor, hot oil at 202°C is circulated through the reactor jacket to heat the catalyst.' When the temperature in the bed reaches 200°C, a vaporous mixture of propylene and water in a molar ratio between water and propylene of 0.57 is passed down through the bed at a steam rate of 4l litres/min./litre (at standard conditions) of catalyst, at a pressure of 30.8 kg/cm gauge pressure. Reacted waste gas is passed through a pneumatically operated valve which regulates the reaction pressure and through which the waste gas pressure is reduced to atmospheric pressure.

As the reaction proceeds, a steady state is reached whereby the bed temperature near the top and bottom of the bed is 200 and 211°C, respectively, and the pressure is 30.8 kg/cm<2>. To measure catalyst activity at steady state, waste gas is diverted through a special passage for exactly 1 hour for data collection. The waste gas is cooled in a condenser using water at 20°C as coolant and a liquid phase is condensed, which phase consists of the main amount of synthesized alcohol together with water. Non-condensed gas is then passed through a washing tower in which liquid methanol flows down through the column in countercurrent to the gas flow to wash out isopropanol and isopropyl ether. These components are measured in the methanol washing material using gas-liquid chromatography and are recovered by distillation. The propylene volume in the effluent is measured. The isopropanol and isopropyl ether content in the condensed aqueous phase is also measured by gas-liquid chromatography and is then recovered by distillation. The results after about 3 hours are as follows: Yield of isopropanol is 0.31 liter (at 20°C)/liter/hour. The conversions of propylene to isopropanol and isopropyl ether are 6.03% and 0.015%, respectively. The conversion to acetone is 0.011%.

Claims (10)

1. Olefin hydration catalyst, characteri--. characterized in that it comprises phosphoric acid-impregnated porous glass spheres with a high silica content, which spheres, before impregnation, have the characteristics of particles with a Martin diameter of 0.5-25 mm, eh pore volume of 0.4-1.0 cm^/g, an average pore diameter of 30-1000 Å, a bulk density of -0.5-0.8. g/cm^, a mean compressive strength (50 particles) of over 4.5 kg, a coefficient of expansion (0-3 00 <Q> C) of 0.5-0.8 x 10~ <6> , a surface area of 50 -300 m <2> /g and a silicon dioxide content of over 95%, the amount of H-^PO^ in the catalyst being 0.03-1.01 grams of acid/liter' of catalyst and the volume taken up by phosphoric acid as an aqueous solution is less than 100% of a ball's pore volume, and in that the catalyst has a substantially phosphoric acid-free surface. 2. Catalyst according to claim 1, characterized in that the Martin diameter of a ball is 2.0-4.8 mm. 3. Catalyst according to claim 1 or 2, characterized in that the amount of H^PO^ is 0.048-0.48 grams of acid/cm- <5> catalyst. 4. Catalyst according to claim 3, characterized in that the amount of H^PO^ is 0.16-0.48 grams of acid/cm^ of catalyst. 5. Catalyst according to claims 1-4, characterized in that the phosphoric acid occupies approx. 40-85% of the pore volume in a glass sphere. 6. Process for the production of an olefin hydration catalyst comprising phosphoric acid impregnated porous glass spheres with a high silicon dioxide content, characterized by impregnation of glass" particles with a Martin diameter of 0.5-25 mm, a pore volume of 0.4-1.0 cm^/g, an average pore diameter of 30-1000.Å, ■ a volume density of 0.5 -0.8 g/cm-', an average compressive strength (50 particles) of over 4.5 kg, an expansion coefficient (0-300°C) p, 0.5-0.8 x 10 , a surface area of' 50-300 m/g and a silicon dioxide content of over 95%, with an aqueous 12-85% phosphoric acid solution, and that the spheres thus impregnated are then dried so that the acid occupies less than 100% of the total pore volume in a sphere. 7. Method according to claim 6, characterized in that the drying is regulated so that the acid occupies approx. 40-85% of the total pore volume in a sphere. 8. Procedure according to requirements. 6 or 7, characterized in that the aqueous phosphoric acid solution is a 20-70% solution. 9. Method according to claim 8, characterized in that the concentration is approx. 55% 10. Process for hydrating an olefin to the corresponding alcohol by bringing a gaseous mixture of olefin and water into contact with a catalyst, characterized in that the catalyst is used according to any of claims 1-5-