CN107235832B

CN107235832B - Method for producing guaiacol

Info

Publication number: CN107235832B
Application number: CN201610183357.7A
Authority: CN
Inventors: 朱贵法; 陈敏恒
Original assignee: Jiaxing Zhonghua Chemical Co ltd
Current assignee: Jiaxing Zhonghua Chemical Co ltd
Priority date: 2016-03-28
Filing date: 2016-03-28
Publication date: 2021-03-26
Anticipated expiration: 2036-03-28
Also published as: CN107235832A

Abstract

The invention discloses a method for producing guaiacol, which comprises the steps of adding a phosphorus-containing compound serving as a catalytic component into a mixed gas phase of catechol and methanol in a gas phase manner, and etherifying the catechol at a reaction temperature of not more than 275 ℃ to generate the guaiacol. The method can avoid the over-high local concentration of the phosphorus-containing compound in the reactor and prevent the carbon precipitation of the catechol, thereby ensuring that the gas-phase catalytic synthesis process of the guaiacol can be stably realized for a long time.

Description

Method for producing guaiacol

Technical Field

The invention relates to a method for producing guaiacol, in particular to gas-phase catalytic synthesis of guaiacol. The invention uses phosphorus-containing compound as catalytic component, inert solid as catalyst carrier, and realizes long-term stable guaiacol catalytic production by a specific catalyst adding method.

Background

Guaiacol (guaiacol), i.e. o-methoxyphenol, is an important intermediate in fine chemistry, widely used in the synthesis of medicines, perfumes and dyes, especially as an important raw material and intermediate in the production of perfumes (e.g. vanillin) and pharmaceuticals. The main production process of guaiacol is diazotization-hydrolysis process, i.e. the raw material o-aminoanisole is diazotized and hydrolyzed to obtain guaiacol. CN97118908.0 and CN03141536.9 both relate to diazonium salt hydrolysis process and improvement thereof, however, the diazonium salt hydrolysis process has the disadvantages of high energy consumption, much waste water, chlorine carried in the product and the like, and the quality of the final product spice or medicament is adversely affected. Current methods of guaiacol synthesis involve homogeneous and heterogeneous (gas phase) syntheses. Homogeneous synthesis has the defects of complex process, serious corrosion, high toxicity, environmental pollution and the like. Because of the above problems with homogeneous synthesis, attention has been directed to the study of heterogeneous synthesis processes, particularly the study of gas-solid phase catalytic synthesis using alcohols as alkylating agents. The heterogeneous reaction has advantages in conversion, by-products and energy consumption compared with homogeneous reaction, especially the heterogeneous reaction process for preparing guaiacol from methanol and catechol. For example, xuyan et al proposed that methanol and catechol undergo a gas phase reaction in a fixed bed reactor (xuyan et al, ZnCl2/NaY catalyzing the etherification reaction of catechol and methanol, applied chemistry, 2004,21(7): 664-.

The present inventors have found in their research that catechol has a tendency to "carbon" out of phase synthesis processes for the preparation of guaiacol from methanol and catechol by etherification. The carbon precipitation phenomenon is more obvious when the reaction time is prolonged, and the reaction process is damaged, so that the gas-phase catalytic synthesis process is difficult to realize stably for a long time. The existence of carbon precipitation has become one of the obstacles which hinder the further application and development of the process.

The reason and the influence factors of carbon precipitation are not clarified in the prior art, so that the method in the prior art cannot effectively prevent the carbon precipitation, and even if some processes have better yield and energy consumption occasionally, good process stability is difficult to realize or long-term operation cannot be ensured.

Therefore, there is a need in the art for an efficient process for the production of guaiacol that avoids the occurrence of carbon sequestration and ensures a long-term stable process.

Disclosure of Invention

The invention aims to overcome the problem of carbon precipitation in the existing guaiacol production process and provide a more effective and stable guaiacol production process.

For heterogeneous synthesis processes using fixed bed reactors, inert solids are used as catalyst carriers and filled in the reactor, phosphorus-containing mixtures are used as catalytic components, and in order to maintain stable catalytic activity, it is necessary to make the catalyst active components reach the surface of the catalyst carrier to exert catalytic action. The reaction temperature of this process is often above 300 c, even 400 c. The inventors have unexpectedly found in long-term process studies that: when the temperature is 300 ℃ or even above 280 ℃, the carbon precipitation phenomenon becomes obvious or occurs, and the carbon precipitation phenomenon is caused by the reactant catechol; on the other hand, when a phosphorus-containing compound (e.g., phosphoric acid, methyl phosphate, dimethyl phosphate, trimethyl phosphate, diethyl phosphate, triethyl phosphate, pyrophosphoric acid, metaphosphoric acid, polyphosphoric acid, etc.) is used as a catalytically active component, the tendency toward carbon evolution is particularly severe, and the critical temperature at which carbon evolution of catechol occurs is correspondingly lowered as the concentration of the phosphorus-containing compound increases. Without being limited by theory, the inventors speculate that it is possible that carbon evolution occurs more readily at relatively low temperatures as the local concentration of the phosphorus-containing compound in the reaction system increases relatively.

Aiming at the carbon precipitation influence factors discovered above, the inventor discovers through multiple experimental researches: the carbon precipitation phenomenon can be effectively prevented by controlling the adding mode of the phosphorus-containing compound to the reaction system; on the other hand, when the temperature of the reaction system is controlled not to exceed a certain temperature (for example, 275 ℃), the occurrence of the carbon deposition phenomenon can be effectively prevented.

To this end, the present inventors propose a process for producing guaiacol, which comprises feeding a phosphorus-containing compound as a catalytic component in a gaseous phase into a reactor containing a mixed gaseous phase of catechol and methanol, and etherifying the catechol at a reaction temperature not higher than a certain temperature to produce guaiacol.

It should be noted in particular that satisfactory results cannot be obtained if the phosphorus-containing compound as the catalytic component is directly added to the reaction vessel in the form of a liquid or solution in advance and then heated to vaporize it.

The inventors propose that the following three ways of adding the phosphorus-containing compound as the catalytic component can be used in the present invention:

i) adding the catalytic component into catechol or catechol/methanol mixture in a liquid phase, gasifying the catalytic component together with the catechol or catechol/methanol mixture and then feeding the gasified catalytic component into a reactor; or

ii) dissolving the catalytic component in methanol, and then spraying the obtained methanol solution into a reactor by using an atomization spraying device to be vaporized by catechol-methanol feed gas; or

iii) the methanol is divided into two gaseous feeds, one of which entrains catechol and simultaneously vaporizes it, the other of which entrains the catalytic component and simultaneously vaporizes it, so that the two gaseous feeds are rapidly mixed in the reactor.

Detailed Description

In one aspect of the present invention, there is provided a process for producing guaiacol, which comprises adding a phosphorus-containing compound as a catalytic component in a gaseous phase to a mixed gaseous phase of catechol and methanol.

Preferably, in the above process of the present invention, catechol is etherified in the reaction system at a reaction temperature of not more than 280 ℃ to produce guaiacol. More preferably, the etherification reaction temperature is not more than 275 ℃, not more than 270 ℃, not more than 265 ℃, not more than 260 ℃, not more than 255 ℃, not more than 250 ℃, not more than 245 ℃, not more than 240 ℃, not more than 235 ℃, not more than 230 ℃, not more than 220 ℃, not more than 210 ℃, not more than 200 ℃, not more than 195 ℃ or even not more than 190 ℃.

In the process of the present invention, the phosphorus-containing compound as the catalytic component is added in the gas phase. The phosphorus-containing compound can be added into catechol or catechol/methanol mixture in liquid phase, gasified together with catechol or catechol/methanol mixture, and then fed into the reactor; or dissolving the catalytic component in methanol, and then spraying the obtained methanol solution into the reactor by using an atomization spraying device, wherein the fog drops are vaporized by catechol-methanol feed gas; alternatively, the methanol may be fed in two gaseous phases, one of which entrains catechol and simultaneously vaporizes it, the other of which entrains the catalytic component and simultaneously vaporizes it, so that the two gaseous phases are rapidly mixed in the reactor.

In one aspect of the invention, the reactor may contain a bed of inert solid catalyst support for supporting the catalyst, which may be selected from any one or more of activated carbon, alpha-alumina, silica, diatomaceous earth, silica gel, zeolite molecular sieves in the hydrogen form, aluminum phosphate molecular sieves, silicoaluminophosphate molecular sieves, montmorillonite, bentonite, ion exchange resins, iron oxide, zinc oxide, and TiO2-ZrO2, including combinations thereof. In a preferred embodiment, the inert solid catalyst support is selected from the group consisting of alpha-alumina, activated carbon, silica, diatomaceous earth, silica gel, zeolite molecular sieves in the hydrogen form, aluminum phosphate molecular sieves, aluminum silicophosphate molecular sieves, and montmorillonite. In a more preferred embodiment, the inert solid catalyst support is alpha-alumina.

The phosphorus-containing compound used as the catalytically active component in the production method of the present invention includes phosphoric acid, methyl phosphate, dimethyl phosphate, trimethyl phosphate, diethyl phosphate, triethyl phosphate, pyrophosphoric acid, metaphosphoric acid and polyphosphoric acid, and may be a combination of several of them. In a particularly preferred aspect, the phosphorus-containing catalyst in the process of the invention is phosphoric acid.

The phosphorus-containing compound used as the catalytically active component in the production process of the present invention may be added in an amount of 0.1 to 1%, preferably 0.1 to 0.9%, 0.1 to 0.8%, more preferably 0.1 to 0.7%, particularly preferably 0.2 to 0.6% and 0.2 to 0.5% by mass of the total mass of the reactants.

In a preferred aspect of the process of the invention, the reactor may be equipped with means for monitoring the temperature and/or catalyst concentration of the reaction system in real time, as well as monitoring the temperature and concentration profile in the reaction system in real time.

Examples

The following are non-limiting examples of the invention. These examples are given for illustrative purposes only and are not to be construed as limiting the invention. It will be understood by those skilled in the art that many changes and modifications may be made to the invention without departing from the spirit and scope of the invention. In the present specification and in the following examples, all concentrations are in weight percent unless otherwise indicated.

The present invention will be further described with reference to the following specific examples.

Example 1

1) Reaction device

Stainless steel fixed bed reactor, 2000mm internal diameter, charged with 5m3

Alpha-alumina spheres. Part of the liquid phase methanol is vaporized by a vaporizer and then enters a catechol saturation tower. Catechol is added into a catechol saturation tower and gasified, and is mixed with methanol steam, and the gas phase compound is heated to the reaction temperature through a superheater and then enters a reactor.

2) Method for adding catalytic component

The catalytic component is trimethyl phosphate. Part of the feed liquid phase methanol is vaporized by a vaporizer and then enters a trimethyl phosphate vaporizer. Trimethyl phosphate is added into a trimethyl phosphate vaporizer and gasified, and is mixed with methanol steam, and a gas-phase compound is heated to the reaction temperature through a superheater and then enters the reactor. The weight ratio of the feed liquid is as follows: catechol: methanol 1: 1.

3) etherification reaction

The reaction temperature is 260-263 ℃, the methanol feeding flow rate is 1300L/hr, the operation is 720 hours, carbon deposition does not exist on the surface of the alumina ball, the white color is still kept, and the reaction conversion rate and the selectivity are not changed.

Example 2

1) Reaction device

Stainless steel fixed bed reactor, 2000mm internal diameter, charged with 5m3

2) Method for adding catalytic component

The catalytic component is phosphoric acid. Part of the feed liquid phase methanol is vaporized by a vaporizer and then enters a phosphoric acid vaporizer. Phosphoric acid is added and gasified in a phosphoric acid vaporizer, is mixed with methanol steam, and a gas-phase compound is heated to the reaction temperature through a superheater and then enters the reactor.

The weight ratio of the feed liquid is as follows: catechol: methanol 1: 1.

3) etherification reaction

The reaction temperature is 260-265 ℃, the methanol feeding flow is 1500L/hr, the operation is 1440 hours, carbon deposition does not exist on the surface of the alumina ball, the white color is still kept, and the reaction conversion rate and the selectivity are not changed.

Example 3

1) Reaction device

A stainless steel single-tube reactor with an inner diameter of 32mm and a length of 1200mm, wherein the upper layer of the reactor is a gasification and preheating section and is filled with

Glass beads, 40cm in height. The middle layer of the reaction tube is a catalyst bed layer which is filled with 350cm3

Alpha-alumina spheres, 50cm in height. The lower layer of the reaction tube is a heat insulation section and is filled with

Glass beads, 40cm in height.

2) Method for adding catalytic component

The catalytic component is phosphoric acid, and the phosphoric acid is directly added into the feed liquid. The weight ratio of the feed liquid is as follows: catechol: methanol: phosphoric acid 1: 1. the feed liquid phase feed liquid enters the top of the reaction tube through a pump.

The phosphoric acid is gasified along with the feed liquid in the preheating section of the reaction tube.

3) Etherification reaction

The reaction temperature is 275 ℃, the feed flow is 125g/hr, the operation is 2500 hours, carbon deposition on the surface of the alumina ball is avoided, the white color is still kept, and the reaction conversion rate and the selectivity are not changed.

Example 4

1) Reaction device

Glass beads, 40cm in height.

2) Method for adding catalytic component

The catalytic component is trimethyl phosphate, and the trimethyl phosphate is directly added into the feed liquid. The weight ratio of the feed liquid is as follows: catechol: methanol 1: 1. the feed liquid phase feed liquid enters the top of the reaction tube through a pump.

The trimethyl phosphate is gasified along with the feed liquid in the preheating section of the reaction tube.

3) Etherification reaction

The reaction temperature is 265 ℃, the feeding flow rate is 120g/hr, the operation is 400 hours, carbon deposition does not exist on the surface of the alumina ball, the white color is still kept, and the reaction conversion rate and the selectivity are not changed.

Comparative example 1

1) Reaction device

Stainless steel fixed bed reactor, 2000mm internal diameter, charged with 4.6m3

Alpha-alumina spheres. The liquid phase methanol is vaporized by a vaporizer and then enters a catechol saturation tower. Catechol was added in a catechol saturation column and gasified, and mixed with methanol vapor. The gas-phase compound is heated to the reaction temperature through a superheater and then enters a reactor.

2) Method for adding catalytic component

The catalytic component is phosphoric acid. The phosphoric acid is added directly to the feed gas phase via a simple distribution device in the upper part of the reactor.

4) Etherification reaction

The reaction temperature was 265 ℃, the methanol feed rate was 1000L/hr, the operation was 480 hours, and the carbon deposition in the reactor was about 250 kg.

From the above results, it can be seen that examples 1 to 4 using the addition method of the present invention can effectively prevent the occurrence of reaction carbon deposition, and have significant technical advantages, compared to comparative example 1 in which the carbon is directly added.

Claims

1. A process for producing guaiacol, which comprises feeding a phosphorus-containing compound as a catalytic component in a gaseous phase to a reactor containing a mixed gaseous phase of catechol and methanol to etherify the catechol at a reaction temperature of not more than 275 ℃ to produce guaiacol;

wherein the phosphorus-containing compound as a catalytic component is selected from the group consisting of methyl phosphate, dimethyl phosphate, trimethyl phosphate, diethyl phosphate and triethyl phosphate and combinations thereof;

wherein the reactor comprises an inert solid catalyst carrier bed layer for loading a catalyst, and the inert solid catalyst carrier is selected from activated carbon, alpha-alumina, silicon dioxide, diatomite, silica gel, hydrogen type zeolite molecular sieve, aluminum phosphate molecular sieve, silicoaluminophosphate molecular sieve, montmorillonite, bentonite, ferric oxide, zinc oxide, TiO2-ZrO2 and a combination thereof.

2. The process of claim 1, wherein the phosphorus-containing compound is added in the following manner: the catalytic component is added into catechol or catechol/methanol mixture in liquid phase, and the catalytic component and the catechol or catechol/methanol mixture are vaporized and fed into a reactor.

3. The process of claim 1, wherein the phosphorus-containing compound is added in the following manner: the catalytic component is dissolved in methanol, and the obtained methanol solution is sprayed into a reactor by an atomization spraying device and is vaporized by catechol-methanol feed gas.

4. The process of claim 1, wherein the phosphorus-containing compound is added in the following manner: the methanol is divided into two gas phase feeds, one of which carries catechol and simultaneously vaporizes it, and the other of which carries the catalytic component and simultaneously vaporizes it, so that the two gas phases are rapidly mixed in the reactor.

5. The process according to any of the preceding claims, wherein the phosphorus-containing compound is added in an amount of 0.1-0.8% of the total mass of the reactants.

6. The method of claim 1, wherein the reactor has a means to monitor reaction system temperature and/or catalyst concentration in real time.