Patent Description:
Ethylene glycol is an important glycol. It is mainly used to prepare polyester fiber, polyester resin, moisture absorbent, plasticizer, surfactant, synthetic fiber, cosmetics and explosives, and can be used as solvent for dyes, inks and the like, can be formulated into engine antifreeze, gas dehydrating agent, and can be used to prepare resin. It can also be used as wetting agent for cellophane, fiber, leather and adhesive. The preparation method thereof mainly comprises chloroethanol hydrolysis method, ethylene oxide hydration method, dimethyl oxalate hydrogenation reduction method (note: coal-to-ethylene glycol method), and transesterification method (using ethylene carbonate and lower alcohols as raw materials).

The transesterification method refers to the transesterification reaction of ethylene carbonate and methanol to produce ethylene glycol and dimethyl carbonate. Dimethyl carbonate is an important green solvent, and ethylene glycol is an important raw material for synthesizing fine chemical.

However, in the prior art, a homogeneous catalyst is used to produce ethylene glycol and dimethyl carbonate through the transesterification reaction of ethylene carbonate and methanol. The homogeneous catalyst, such as methanol solution of sodium methoxide or potassium methoxide, enters the reaction system in proportion along with raw materials. Part of the catalyst will react with the carbon dioxide produced by the decomposition of ethylene carbonate to be converted into sodium carbonate. Salts such as sodium methoxide and sodium carbonate are separated from the ethylene glycol in a column bottom in the EG rectification system, and a small amount of high-grade polyalcohol is entrained. These materials become solid wastes of chemical plants and need to be delivered to those companies with processing qualifications and processing capabilities to conduct harmless treatment.

Therefore, the use of homogeneous catalyst has the disadvantages of high consumption, high production cost, difficult post-treatment and generation of solid wastes. Under the premise that the environmental protection situation is becoming more and more severe, there is an urgent market demand for green environmental protection technology.

<CIT> describes a process for producing ethylene glycol by reacting ethylene carbonate with methanol in which a heterogenous catalyst is used.

According to one aspect of the present application, there is provided a method for producing ethylene glycol using ethylene carbonate and methanol as raw materials. The method involves a transesterification process using a solid catalyst and overcomes the disadvantages of high catalyst consumption, high production cost, difficult post-treatment and generation of solid wastes when a homogeneous catalyst is used.

A method for producing ethylene glycol using ethylene carbonate and methanol as raw materials comprising following steps:.

Optionally, in step a), the pre-reaction is performed in the presence of catalyst II; wherein, the catalyst II comprises a solid catalyst.

The solid catalyst in the present application is heterogeneous catalyst.

Optionally, in step a), a weight hourly space velocity of the reactants, which is calculated as EC, ranges from <NUM> to <NUM>-<NUM>.

Optionally, in step a), a molar ratio of the ethylene carbonate to methanol ranges from <NUM>:<NUM> to <NUM>:<NUM>.

Optionally, a heating temperature in step a) ranges from <NUM> to <NUM>.

Optionally, in step b), a weight hourly space velocity of the pre-treatment material ranges from <NUM> to <NUM>-<NUM>.

Optionally, in step b), the catalytic rectification reaction is performed at a temperature ranging from <NUM> to <NUM>.

Optionally, in step b), under the condition of introducing supplementary methanol, the pre-treatment material is subjected to a catalytic rectification reaction to obtain product I and azeotropic components, wherein the azeotropic components contain dimethyl carbonate and methanol.

Optionally, the azeotropic components are extracted from a column top of a reaction rectification column, and the reflux ratio of the azeotropic components ranges from <NUM>:<NUM> to <NUM>:<NUM>.

Optionally, the shape of the solid catalyst is spherical or columnar.

Optionally, the solid catalyst is basic catalyst.

Optionally, the basic catalyst is a molecular sieve catalyst; and the molecular sieve catalyst comprises element-modified molecular sieve, wherein the element comprises at least one of an alkali metal element and an alkaline earth metal element, and the molecular sieve comprises at least one of X-type molecular sieve, and Y-type molecular sieve.

Specifically, in the molecular sieve catalyst, the content of the modification element ranges from <NUM> wt% to <NUM> wt%.

The molecular sieve catalyst (i.e., weak basic catalyst) is prepared by the following method:.

Optionally, the molecular sieve is X-type molecular sieve and Y-type molecular sieve; and the modification element is alkali metal element and alkaline earth metal element. In the present application, a molecular sieve consisting of X-type molecular sieve and Y-type molecular sieve is used, and the molecular sieve is modified with alkali metal element and alkaline earth metal element. As solid catalyst, it improves the selectivity of ethylene glycol to <NUM>%.

Optionally, the weight ratio of the X-type molecular sieve to the Y-type molecular sieve ranges from <NUM>:<NUM> to <NUM>:<NUM>.

Specifically, an alkaline earth metal ion comprises either calcium ion or magnesium ion.

Alkali metal ion comprises either sodium ion or potassium ion.

In a specific example, a mixture comprising X-type molecular sieve and Y-type molecular sieve is mixed with a solution comprising calcium ion and sodium ion, and dried to obtain the precursor I.

Optionally, the basic catalyst is a metal oxide catalyst, and the metal oxide catalyst comprises element-modified metal oxide, wherein the element comprises at least one of alkali metals.

The metal oxide catalyst (i.e., medium basic catalyst) is prepared by the following method:.

Optionally, the metal oxide is γ-Al<NUM>O<NUM>. In the present application, alkali metal modified γ-Al<NUM>O<NUM> is used as solid catalyst, which improves the selectivity of ethylene glycol to <NUM>%.

Specifically, the content of the modification element in the metal oxide catalyst ranges from <NUM> wt% to <NUM> wt%.

In a specific example, the material comprising γ-Al<NUM>O<NUM> is mixed with a solution comprising potassium ion and cesium ion, and dried to obtain the precursor II.

In the present application, in the process of preparing the catalyst, step-by-step activation treatment can achieve the effects of high conversion rate of ethylene carbonate (above <NUM>%) and high selectivity of ethylene glycol (above <NUM>%).

The molecular sieve catalyst is a weak basic catalyst, and the metal oxide catalyst is a medium basic catalyst.

In the present application, the element-modified metal oxide is used as the catalyst, which has the effect of simpler and more efficient preparation process, and higher conversion rate of ethylene carbonate and selectivity of ethylene glycol.

Optionally, in step c), the methanol is extracted from the column top of the methanol recovery column, and the reflux ratio of the methanol ranges from <NUM>:<NUM> to <NUM>:<NUM>.

In the present application, the purpose of separating the methanol in the product I is to return the methanol to the raw material system for reuse.

Optionally, in step d), the product II is rectified under vacuum environment, with the purpose of lowering the temperature of the materials in the rectification system so that the temperature of the materials is lower than <NUM>, avoiding the polymerization of the materials at high temperature and improving the yield of ethylene glycol ; wherein the vacuum environment ranges from <NUM> to 5KPa.

Optionally, in step d), after the ethylene glycol is rectified, the light components at column top (comprising ethylene glycol and methanol) are returned to the methanol recovery column to continue the separation so as to recover methanol and ethylene glycol separately, thereby reducing the consumption of methanol as raw material and increasing the yield of ethylene glycol.

Optionally, the content of the ethylene glycol in the target product is ≥<NUM>%.

The following specifically describes the preparation process of ethylene glycol comprising:
feeding ethylene carbonate (EC) and methanol (ME) as raw materials into a static mixer according to a preset molar ratio and mixing them uniformly, after preheating the obtained mixture to temperature in a range from <NUM> to <NUM> in a preheater, feeding the preheated raw materials into a pre-reactor <NUM> to contact with a solid catalyst for performing reaction, then feeding the obtained pre-reaction products in a reaction rectification column to react with a solid catalyst in the column.

In the present application, the static mixer has the same function as a batching tank. Compared with the batching tank, it has the advantages of small size, saving equipment investment, not using mechanical stirring and saving power consumption and the like. Further, compared with the manner that feeding the raw materials separately into the preheater for preheating, the manner that mixing the raw materials in the static mixture uniformly before feeding the same in the preheater, achieves improved selectivity of ethylene glycol.

The filling rate of the solid catalyst in the reaction rectification column ranges from <NUM>% to <NUM>%. The dimethyl carbonate produced after reaction and the additional methanol supplemented from the column bottom form azeotropic components, which are extracted from the column top. The operating reflux ratio ranges from <NUM>:<NUM> to <NUM>:<NUM>, most preferably is <NUM>:<NUM>. The column bottom contains methanol (ME) and ethylene glycol (EG). The typical composition in the column bottom is ME in a range from <NUM>% to <NUM>% and EG in a range from <NUM>% to <NUM>%.

The methanol recovery temperature of the column top ranges from <NUM> to <NUM>, the temperature of the column bottom ranges from <NUM> to <NUM>, and the typical composition in the column reactor: ME <NUM>%, EG <NUM>%.

The packing in the reaction rectification column is CY700 gauze structured packing, with catalyst packing in the middle of the packing, and the number of theoretical plates ranges from <NUM> to <NUM>.

The packing in the methanol recovery column is CY700 structured packing, and the number of theoretical plates ranges from <NUM> to <NUM>.

The ethylene glycol rectification column is packed with stainless steel structured packing CY700, and the number of theoretical plates ranges from <NUM> to <NUM>.

The temperature of the ethylene glycol rectification column ranges from <NUM> to <NUM>, most preferably ranges from <NUM> to <NUM>, the reflux ratio of the column top ranges from <NUM> to <NUM>, most preferably ranges from <NUM> to <NUM>, and typically is <NUM>. The pressure at the column top is <NUM> KPa, and the pressure in the column reactor is <NUM> KPa.

The product extracted from the ethylene glycol rectification column <NUM> is cooled by a cooler and then extracted to a product intermediate tank. The EG content is ≥<NUM>%, typically is <NUM>%. The extraction reflux ratio is <NUM>:<NUM>.

Optionally, the method for producing ethylene glycol using ethylene carbonate and methanol as raw materials comprises following steps:.

Optionally, before heating the reactants, step a) further comprises mixing ethylene carbonate and methanol to obtain the reactants. In the present application, mixing ethylene carbonate and methanol before heating can improve the selectivity of ethylene glycol.

According to another aspect of the present application, there is provided an apparatus for producing ethylene glycol using ethylene carbonate and methanol. The apparatus comprises a raw material mixing unit, a preheating unit, a pre-reaction unit, a reaction rectification unit, a methanol recovery unit and an ethylene glycol rectification unit;.

Specifically, the apparatus comprises a raw material mixer, a preheater, a pre-reactor, a reaction rectification column, a methanol recovery column, and an ethylene glycol rectification column;.

In the present application, the function of the preheater is to raise the temperature of the material to the temperature required for the reaction. Without the preheater, the reaction cannot occur; and the pre-reactor is provided to reduce the volume of the catalyst filled in the rectification column. The reduced amount of catalyst filled in the rectification column can reduce the height of the rectification column, thereby reducing equipment investment.

Optionally, the lower end of the reaction rectification column is also provided with a methanol-supplementing inlet.

Specifically, in the present application, the methanol-supplementing inlet is provided at the lower end of the reaction rectification column, which has the effect of making the methanol in the reaction rectification system excess and improving the conversion rate of ethylene carbonate.

Optionally, the upper end of the ethylene glycol rectification column is connected with the upper end of the methanol recovery column.

In the present application, by providing a communication pipeline between the upper end of the ethylene glycol rectification column and the upper end of the methanol recovery column, the light components in the ethylene glycol rectification column can be returned to the methanol recovery column, thereby increasing yield of ethylene glycol.

Optionally, the pre-reactor is filled with catalyst II; a filling volume percentage of the catalyst II in the pre-reactor ranges from <NUM>% to <NUM>%.

Optionally, the reaction rectification column is filled with catalyst I; a filling volume percentage of the catalyst I in the reaction rectification column ranges from <NUM>% to <NUM>%.

In the present application, the term "weight hourly space velocity of reactant" refers to a ratio of the mass flow rate of ethylene carbonate to the weight of catalyst II in the pre-reactor.

The term "weight hourly space velocity of pre-treatment material" refers to a ratio of the mass flow rate of ethylene carbonate to the mass of catalyst I in the reaction rectification column.

The beneficial effects that the present application can achieve comprise:.

<FIG> is a schematic structural diagram of an apparatus for producing ethylene glycol using ethylene carbonate and methanol as raw materials provided by possible embodiments in the present application.

List of parts and reference numerals:
<NUM> static mixer; <NUM> preheater; <NUM> pre-reactor; <NUM> reaction rectification column; <NUM> methanol recovery column; <NUM> ethylene glycol rectification column;.

In the Figure, DMC is the abbreviation for dimethyl carbonate, and ME is the abbreviation for methanol.

The present application will be described in detail below with reference to the examples, but the present application is not limited to these examples. Unless otherwise specified, the raw materials in the examples of the present application are all commercially available.

The method and apparatus for producing ethylene glycol using ethylene carbonate and methanol as raw materials provided in the present application are as follows.

Preferably, the reaction temperature in the preheater <NUM> and the pre-reactor <NUM> ranges from <NUM> to <NUM>.

Preferably, the heterogeneous solid catalyst is a weak basic catalyst or a medium basic catalyst, and the shape thereof is spherical or columnar.

Preferably, the filling volume percentage of the heterogeneous solid catalyst in the reaction rectification column <NUM> ranges from <NUM>% to <NUM>%.

Preferably, a method for preparing the above weak basic catalyst comprises the following steps:
mixing <NUM> parts NaX molecular sieves and <NUM> parts NaY molecular sieve by weight uniformly, adding <NUM> parts calcium nitrate solution with <NUM>% weight concentration and <NUM> parts sodium carbonate solution with <NUM>% weight concentration therein and stirring evenly, drying the obtained product in an oven at <NUM> for <NUM> hours and then drying the mixture in an oven at <NUM> for <NUM> hours, then placing the dried product in a muffle furnace at <NUM> for <NUM> hours' activation, and increasing to <NUM> for <NUM> hours' activation, and after cooling down, placing the resulting product in a desiccator to cool for use.

Preferably, a method for preparing the above medium basic catalyst comprises the following steps:
slowly adding <NUM> parts potassium carbonate solution with <NUM>% weight concentration and <NUM> parts cesium nitrate solution with <NUM>% weight concentration in <NUM> parts γ-Al<NUM>O<NUM> powder, and stirring evenly, then squeezing and cutting the obtained product into strips, drying the obtained product in an oven at <NUM> for <NUM> hours and then drying the mixture in an oven at <NUM> for <NUM> hours, then placing the dried product in a muffle furnace at <NUM> for <NUM> hours' activation, and increasing to <NUM> for <NUM> hours' activation, and after cooling down, placing the resulting product in a desiccator to cool for use.

Referring to <FIG>, the method for producing ethylene glycol using ethylene carbonate and methanol as raw materials mentioned in this Example comprises following preparation apparatus and preparation processes.

The static mixer <NUM> is connected with the pre-reactor <NUM> via the preheater <NUM>, the upper part of pre-reactor <NUM> is connected with the upper portion of reaction rectification column <NUM>, the bottom of reaction rectification column <NUM> is connected with the upper part of methanol recovery column <NUM> via a process pipeline, and the lower part of the methanol recovery column <NUM> is connected with the middle part of the ethylene glycol rectification column <NUM>, the upper part of the ethylene glycol rectification column <NUM> is connected with the upper part of the methanol recovery column <NUM> to return light components therein; wherein the column bottom of the reaction rectification column <NUM> is also provided with a methanol-supplementing inlet, which is used to provide excess methanol during the catalytic rectification reaction, thereby achieving good reaction effect.

The preparation process comprises followings:.

The temperature at the column top of the methanol recovery column <NUM> is <NUM>, the temperature of the column bottom thereof is <NUM>, and the typical composition of the column bottom is: ME <NUM>%, EG <NUM>%;.

The packing in the reaction rectification column <NUM> is CY700 gauze structured packing, with catalyst packing in the middle of the packing, and the number of plates in this Example is <NUM>;.

In the ethylene glycol rectification column <NUM>, the temperature of the column bottom is <NUM>, the reflux ratio at the column top is <NUM>, the pressure at the column top is <NUM>. 2KPa, and the pressure at the column bottom is <NUM> KPa;.

The product extracted from the ethylene glycol rectification column <NUM> is cooled by a cooler and then extracted to a product intermediate tank. The EG content is ≥<NUM>%, typically is <NUM>%. The extraction reflux ratio is <NUM>:<NUM>;.

In this Example, the solid catalyst <NUM># is weak basic solid catalyst with a spherical shape and an outer diameter of <NUM>. The feeding weight hourly space velocity of the raw materials (the mass flow rate of EC/the weight of the catalyst II in the reaction rectification column, that is, the space velocity of the pretreatment material) is <NUM>-<NUM>.

The production process of the weak basic solid catalyst <NUM># is as follows: mixing <NUM> NaX molecular sieve and <NUM> NaY molecular sieve uniformly, adding <NUM> calcium nitrate solution with <NUM>% weight concentration and <NUM> sodium carbonate solution with <NUM>% weight concentration therein and stirring evenly, drying the obtained product in an oven at <NUM> for <NUM> hours and then drying the mixture in an oven at <NUM> for <NUM> hours, then placing the dried product in a muffle furnace at <NUM> for <NUM> hours' activation, and increasing to <NUM> for <NUM> hours' activation, and after cooling down, placing the resulting product in a desiccator to cool for use.

The method mentioned in this example uses ethylene carbonate and methanol as raw materials to produce ethylene glycol. The preparation apparatus is the same as that in Example <NUM>. The preparation process is as follows:.

The operations of the methanol recovery column <NUM> and the ethylene glycol rectification column <NUM> are the same as those in Example <NUM>.

In this Example, the solid catalyst <NUM># is a medium basic solid catalyst with a spherical shape and an outer diameter of <NUM>. The feeding weight hourly space velocity (calculated by EC) is <NUM>-<NUM>.

The production process of the solid catalyst <NUM># is as follows: slowly adding <NUM> potassium carbonate solution with <NUM>% weight concentration and <NUM> cesium nitrate solution with <NUM>% weight concentration in <NUM> γ-Al<NUM>O<NUM> powder, and stirring evenly, then squeezing and cutting the obtained product into strips, drying the obtained product in an oven at <NUM> for <NUM> hours and then drying the mixture in an oven at <NUM> for <NUM> hours, then placing the dried product in a muffle furnace at <NUM> for <NUM> hours' activation, and increasing to <NUM> for <NUM> hours' activation, and after cooling down, placing the resulting product in a desiccator to cool for use.

The preparation apparatus in this comparative example is partly identical to those in Example <NUM>, and the identical contents will not be repeated.

The specific preparation process of ethylene glycol is as follows:
feeding respectively EC and methanol as the raw materials into an agitator-containing mixing tank with a solvent of <NUM> from the top thereof according to the molar ratio of <NUM>:<NUM>, and feeding the sodium methoxide as catalyst (in the form of 30wt% sodium methoxide solution, the weight ratio of sodium methoxide to EC is <NUM>) into the mixing tank through the other inlet of the mixing tank. The mixing tank has a stirring speed of <NUM> rpm/h. The lower part of the mixing tank is connected with a feeding pump which is used to feed the material to the reaction rectification column <NUM>. The reaction rectification column is filled with CY gauze packing, and the supplemented methanol from the column bottom promotes EC conversion. The materials at the column bottom of the reaction rectification column enter the methanol recovery column <NUM>, the methanol at the column top of the methanol recovery column <NUM> returns to the batching system, and the materials at the column bottom thereof enter the EG rectification column <NUM>. The material at the column top of the EG rectification column returns to the feeding line of the methanol recovery column <NUM>, the EG product is extracted from the column, and the material containing the sodium methoxide as catalyst is regularly extracted from the column bottom. Because the sodium methoxide can react with the carbon dioxide generated by the decomposition of ethylene carbonate to be converted into sodium carbonate, sodium methoxide and sodium carbonate and the like salts are separated from the ethylene glycol from the column bottom in the EG rectification system, and a small amount of higher polyalcohol is entrained. These materials become solid wastes of chemical plants. In this comparative example, <NUM> tons of solid wastes are generated every year. The solid waste needs to be delivered to a qualified unit for harmless treatment.

Taking the production apparatus with an annual output of 3500T ethylene glycol as an example, the effect comparison among Example <NUM>, Example <NUM> and the conventional homogeneous catalyst in the prior art is shown in Table <NUM>.

In the present application, the 3500t/a EG production apparatus uses a total of <NUM> tons of solid catalyst. The solid catalyst has a lifespan of <NUM> years, that is, <NUM> tons of solid catalysts need to be replaced every year on average. These catalysts are also solid hazardous wastes that require qualified units to process. Compared with the homogeneous catalyst, the homogeneous catalyst produces <NUM> tons of solid wastes per year.

Claim 1:
A method for producing ethylene glycol using ethylene carbonate and methanol as raw materials comprising following steps:
a) performing pre-reaction of heated reactants to obtain a pre-treatment material, the reactants comprising ethylene carbonate and methanol;
b) subjecting the pre-treatment material to a catalytic rectification reaction to obtain a material stream I;
c) separating methanol from the material stream I to obtain a material stream II;
d) subjecting the material stream II to rectification to obtain a target product, the target product comprising ethylene glycol;
wherein, the catalytic rectification reaction is performed in the presence of a catalyst I;
the catalyst I comprising a solid catalyst.