CN112794839B

CN112794839B - Preparation method of glycolide

Info

Publication number: CN112794839B
Application number: CN202011111421.3A
Authority: CN
Inventors: 孙红影; 李进; 王炳春; 王贤彬
Original assignee: China Catalyst Holding Co ltd
Current assignee: China Catalyst Holding Co ltd
Priority date: 2020-10-16
Filing date: 2020-10-16
Publication date: 2022-12-09
Anticipated expiration: 2040-10-16
Also published as: CN112794839A

Abstract

The invention provides a preparation method of glycolide. The preparation method of the glycolide comprises the step of carrying out cyclization reaction on gaseous glycolate under the catalysis of a titanium-containing molecular sieve to obtain the product glycolide. The preparation method provided by the invention has the advantages of mild reaction conditions, high product yield, continuous operation and no need of high vacuum and high boiling point solvent.

Description

Preparation method of glycolide

Technical Field

The invention belongs to the field of catalytic reaction, and particularly relates to a preparation method of glycolide.

Background

Environmental pollution (i.e., "white contamination") caused by uncontrolled mass production of non-degradable petroleum-based plastics and abuse of disposable petroleum-based plastic articles has attracted serious worldwide attention. Biodegradable polymers based on renewable raw materials have gained many important applications in the biomedical field, such as controlled release drug carriers, absorbable surgical sutures, implantable hard tissue repair materials, etc., and can be used as environmentally friendly materials for manufacturing agricultural films, packaging materials, disposable hygiene products, disposable catering products, etc.

Polyglycolic acid (PGA) is the simplest structural linear aliphatic polyester and the earliest commercialized in vivo absorbable polymer material. Due to excellent biodegradability and tissue compatibility, the material is widely applied to the fields of absorbable sutures, suture reinforcement materials, fracture fixation materials, drug controlled release systems, tissue engineering scaffold materials and the like. In principle, glycolic acid can be produced by direct polycondensation, but it is difficult to produce a polymer having a relatively high molecular weight by direct polycondensation, and polyglycolic acid having a high molecular weight can be synthesized from glycolide.

At present, most mature and most applied glycolide synthesis methods at home and abroad mainly adopt a polycondensation-depolymerization method using glycolic acid as a raw material, which is adopted by Dupont, wu Yue chemical company in Japan and the like, but the method has harsh reaction conditions, needs to be carried out in the presence of a high-temperature, high-vacuum and high-boiling-point solvent, most of catalysts are tin-containing inorganic compounds, and the catalysts cannot be recycled after being used, so that large-scale industrial production is limited. Patent CN1266146C discloses a glycolide production method, glycolic acid oligomer and polar high-boiling point organic solvent (boiling point 230-450 ℃) are reacted under the conditions of 0.1-90KPa and 230-320 ℃, and glycolide is collected in the form of reaction distillate.

Aiming at the current development situation of the coal chemical industry in China, the advantages of the existing glycol technology and the device capacity are fully utilized to develop low-cost methyl glycolate derivative products and application, and in recent years, the synthesis method of glycolide by taking methyl glycolate as a raw material is reported, but the synthesis method is still a polycondensation-depolymerization method, the catalyst is still not recyclable, and the problems of harsh glycolide synthesis conditions and catalyst recycling are not fundamentally solved.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a method for preparing glycolide with high conversion rate and high selectivity.

The preparation method of the glycolide provided by the invention takes the titanium-containing molecular sieve as the catalyst, and the glycolide is continuously synthesized by a one-step method under the gas phase and normal pressure, so that the synthesis process of the glycolide is simplified.

The invention provides a preparation method of glycolide, which comprises the step of carrying out cyclization reaction on gaseous glycolate under the condition of catalysis of a titanium-containing molecular sieve to obtain the product glycolide.

The preparation method provided by the invention uses the glycollic ester as a raw material and the titanium-containing molecular sieve as a catalyst to synthesize the glycolide by a gas-phase normal-pressure one-step method.

Preferably, the titanium-containing molecular sieve is a titanium-containing molecular sieve with a regular structure.

The titanium-containing molecular sieve with a regular structure in the invention is a titanium-containing molecular sieve with high crystallinity and regular appearance.

Preferably, the titanium-containing molecular sieve is one or a mixture of more of TS-1, ti-MWW, ti-MOR, ti-Beta, ti-ZSM-22 and Ti-ZSM-35.

More preferably, the titanium-containing molecular sieve is one or the combination of more than two of TS-1, ti-MWW and Ti-MOR.

Preferably, the titanium-containing molecular sieve has a crystallinity of greater than 95%.

Preferably, the titanium-containing molecular sieve has a grain size of 100-3000nm, preferably 150-1500nm.

Preferably, the titanium-containing molecular sieve is of a microporous or hierarchical pore structure.

Preferably, the titanium dioxide content of the titanium-containing molecular sieve is 0.1wt% to 10wt%, preferably 1wt% to 5wt%.

Preferably, the glycolic acid ester is one or a combination of two or more of methyl glycolate, ethyl glycolate, propyl glycolate and butyl glycolate, and preferably one or two of methyl glycolate and ethyl glycolate.

Preferably, the glycolate vaporization temperature is 150-600 ℃, more preferably 200-400 ℃.

Preferably, the cyclization reaction temperature is 240-320 ℃, more preferably 250-300 ℃.

Preferably, the reaction pressure is atmospheric.

Preferably, the feed mass space velocity is from 0.5 to 5g glycolate per gram of catalyst per hour, more preferably, the feed mass space velocity is from 1 to 3g glycolate per gram of catalyst per hour.

Preferably, the catalyst and the raw material are subjected to gas phase contact reaction.

Preferably, the cyclization reaction is carried out in a fixed bed, a fluidized bed, a moving bed, an ebullating bed or an expanded bed.

The glycolide is prepared by a bulk polymerization method under the action of a tin-containing catalyst, wherein the relative weight average molecular weight of the glycolide is more than 1 x 10 ⁵ The polyglycolic acid contains stannous octoate or stannous chloride as a tin catalyst.

The preparation method of the polyglycolic acid has the polymerization reaction temperature of 150-200 ℃, the reaction pressure of 0.5-2MPa, the reaction time of 2-5h and the catalyst dosage of 200-500 mug/g.

Compared with the traditional synthesis method of firstly carrying out polycondensation and then carrying out depolymerization, the method has the advantages of mild reaction conditions, high product yield, high conversion rate of glycolate and high selectivity of glycolide. The method can be continuously carried out, high vacuum and high boiling point solvents are not needed, compared with the conventional metal compound catalyst, the catalyst used in the method is safe, environment-friendly and recyclable, and the method is more suitable for industrial production of glycolide.

Drawings

FIG. 1 is an XRD spectrum of the titanium silicalite TS-1 of example 1;

FIG. 2 is an XRD spectrum of the Ti-MWW molecular sieve of example 2;

FIG. 3 is an XRD spectrum of the titanium containing molecular sieve Ti-MOR of example 3;

FIG. 4 is an XRD spectrum of the titanium containing molecular sieve Ti-Beta of example 4;

FIG. 5 is the FI-IR spectrum of glycolide synthesized in example 6;

FIG. 6 is a 1H NMR spectrum of glycolide synthesized in example 6.

Detailed Description

The invention is described below by means of specific examples. Unless otherwise specified, all technical means used in the present invention are well known to those skilled in the art. In addition, the embodiments should be considered illustrative, and not restrictive, of the scope of the invention, which is defined solely by the claims. It will be apparent to those skilled in the art that various changes or modifications in the components and amounts of the materials used in these embodiments can be made without departing from the spirit and scope of the invention.

The invention provides a preparation method of glycolide.

In a specific embodiment provided by the invention, the preparation method of glycolide performs cyclization reaction on gaseous glycolate under the condition of catalysis of a titanium-containing molecular sieve to obtain the product glycolide.

The reaction formula for synthesizing glycolide by cyclizing glycolate is as follows:

r can be methyl, ethyl, n-propyl, isopropyl or n-butyl.

In a specific embodiment provided by the present invention, the titanium-containing molecular sieve is a titanium-containing molecular sieve with a regular structure.

In a specific embodiment provided by the invention, the titanium-containing molecular sieve is one or a mixture of TS-1, ti-MWW, ti-MOR, ti-Beta, ti-ZSM-22 and Ti-ZSM-35.

In a specific embodiment provided by the invention, the titanium-containing molecular sieve is one or a combination of more than two of TS-1, ti-MWW and Ti-MOR.

In one embodiment provided by the present invention, the crystallinity of the titanium-containing molecular sieve is greater than 95%.

In one embodiment of the present invention, the titanium-containing molecular sieve has a grain size of 100-3000nm, preferably 150-1500nm.

In a specific embodiment provided by the present invention, the titanium-containing molecular sieve is of a microporous or hierarchical pore structure.

In a specific embodiment provided by the present invention, the content of titanium dioxide in the titanium-containing molecular sieve is 0.1wt% to 10wt%, preferably 1wt% to 5wt%.

In one embodiment of the present invention, the glycolic acid ester is one or a combination of two or more of methyl glycolate, ethyl glycolate, propyl glycolate, and butyl glycolate, and preferably one or two of methyl glycolate and ethyl glycolate.

In one embodiment provided by the present invention, the vaporization temperature of the glycolic acid ester is 150-600 ℃, more preferably 200-400 ℃.

In one embodiment provided by the present invention, the cyclization reaction temperature is 240-320 ℃.

In one embodiment provided by the present invention, the cyclization reaction temperature is 250-300 ℃.

In one embodiment of the present invention, the reaction pressure is atmospheric pressure.

In one embodiment of the present invention, the feed mass space velocity is 0.5 to 5g of glycolate per gram of catalyst per hour.

In one embodiment of the invention, the feed mass space velocity is 1-3g glycolate/per gram catalyst per hour.

In one embodiment of the present invention, the catalyst and the raw material are subjected to a gas phase contact reaction.

In one embodiment of the present invention, the cyclization reaction is carried out in a fixed bed, a fluidized bed, a moving bed, an ebullating bed or an expanded bed.

In a specific embodiment provided by the invention, the titanium-containing molecular sieve is applied to the preparation of glycolide.

The content of titanium dioxide in the catalyst was measured by an X-ray fluorescence spectrometer (X' AXIOSmAX, pa.).

Catalyst XRD characterization by X-ray diffraction Analyzer (Pasnake, X' Pert) ³ Powder) was measured.

The glycolic acid ester is selected from any commercially available reagent, and the purity is required to be not less than 98%; the titanium-containing molecular sieve of the catalyst is selected from self-made or commercially available, and the relative crystallinity of the titanium-containing molecular sieve is more than 95 percent.

For better illustration of the present invention, the preparation of the titanium-containing molecular sieve is set forth, but is not limited to the titanium-containing molecular sieve prepared by the following method.

The synthesis method of the titanium silicalite TS-1 comprises the following steps: taking silica sol as a silicon source, tetrabutyl titanate as a titanium source and tetrapropylammonium bromide as a template agent, crystallizing at 150-200 ℃ for 12-48h, and filtering, washing, drying and roasting to obtain raw powder of the titanium-silicon molecular sieve TS-1. And (2) uniformly mixing the raw powder and sesbania powder, adding silica sol, further uniformly mixing, extruding and molding by using a bar extruding machine, drying the molded sample at 100 ℃ for 12 hours, and roasting to obtain the strip-shaped titanium silicalite TS-1.

The synthesis method of the titanium-silicon molecular sieve Ti-MWW comprises the following steps: using boric acid as a boron source, silica sol as a silicon source and piperidine as a template agent, crystallizing at 90-100 ℃ for 24-48h, filtering, washing and drying to obtain B-MWW, carrying out acid treatment and boron removal on the B-MWW, then carrying out secondary hydrothermal crystallization by using tetrabutyl titanate as a titanium source, crystallizing at 150-180 ℃ for 48-72h, filtering, washing, drying and roasting to obtain raw powder of the Ti-MWW molecular sieve, uniformly mixing the raw powder and sesbania powder, adding the silica sol, further uniformly mixing, extruding by using an extruding machine to form strips, drying the formed sample at 100 ℃ for 12h, and roasting to obtain the strip Ti-MWW molecular sieve.

The synthesis method of the titanium-containing molecular sieves Ti-MOR, ti-Beta, ti-ZSM-22 and Ti-ZSM-35 comprises the following steps: the method comprises the steps of taking MOR, beta, ZSM-22 and ZSM-35 as carriers, performing acid treatment, taking titanium tetrachloride as a titanium source, performing gas phase treatment for 6-24 hours at 400-600 ℃, washing, drying and roasting to obtain titanium-containing molecular sieve raw powder, uniformly mixing the raw powder and sesbania powder, adding a binder, further uniformly mixing, extruding and molding by using an extruder, drying the molded sample at 100 ℃ for 12 hours, and roasting to obtain the strip-shaped titanium-containing molecular sieve.

The synthetic reaction indexes of glycolide are conversion rate of glycolic acid ester (X) and selectivity of glycolide (S) _GO ) Methyl glycolate Linear oligomer Selectivity (S) _n ). Linear oligomers refer to dimers and trimers produced by the polymerization of methyl glycolate. The calculation method of each reaction index is as follows:

glycolate conversion X = moles of glycolate reacted/total moles of glycolate 100%;

glycolide selectivity S _GO = moles of glycolide produced by reaction/(moles of glycolate/2) 100%;

methyl glycolate linear oligomer selectivity = moles of dimer formed by reaction/(moles of glycolate reacted/2) × 100% + moles of trimer formed by reaction/(moles of glycolate reacted/3) × 100%.

Example 1 preparation of titanium silicalite TS-1

Taking silica sol (the content of silica is 30 wt%) as a silicon source, tetrabutyl titanate as a titanium source, tetrapropyl ammonium bromide as a template agent, wherein the mass ratio of the silica sol to the tetrabutyl titanate to the tetrapropyl ammonium bromide is 91.5: 4.5, crystallizing at 180 ℃ for 30 hours, filtering, washing, drying and roasting to obtain the raw powder of the titanium silicalite TS-1. And uniformly mixing 100g of raw powder and 2g of sesbania powder, adding 38g of silica sol, further uniformly mixing, extruding and molding by using a strip extruding machine, drying a molded sample at 100 ℃ for 12h, and roasting to obtain the strip-shaped titanium silicalite molecular sieve TS-1.

The XRD spectrogram of the titanium silicalite TS-1 is shown in figure 1, and the crystallinity is 99%.

Example 2 preparation of titanium silicalite Ti-MWW

Using boric acid as a boron source, silica sol (the content of silicon dioxide is 30 wt%) as a silicon source, and piperidine as a template, wherein the mass ratio of the boric acid to the silica sol to the piperidine is 20.

The XRD spectrum of the Ti-MWW titanium silicalite molecular sieve is shown in figure 2, and the crystallinity is 98%.

EXAMPLE 3 preparation of titanium containing molecular sieves Ti-MOR

Treating MOR serving as a carrier by 30% nitric acid at a solid-liquid ratio of 10:1 at 100 ℃ for 24h, filtering, washing and drying. Titanium tetrachloride is used as a titanium source, gas phase treatment is carried out for 12 hours at 500 ℃, raw powder of a titanium-containing molecular sieve is obtained through washing, drying and roasting, 100g of the raw powder and 2g of sesbania powder are uniformly mixed, 30g of silica sol is added, the mixture is further uniformly mixed and extruded into strips by a strip extruding machine to be molded, and the molded sample is dried at 100 ℃ for 12 hours and then roasted to obtain the strip-shaped titanium-containing molecular sieve.

The XRD spectrum of the titanium-containing molecular sieve Ti-MOR is shown in figure 3, and the crystallinity is 96%.

EXAMPLE 4 preparation of titanium containing molecular sieves Ti-Beta

The method comprises the following steps of treating Beta as a carrier by 20% nitric acid, enabling the solid-to-liquid ratio to be 10.

The XRD spectrum of the titanium-containing molecular sieve Ti-Beta is shown in figure 4, and the crystallinity is 95%.

Example 5

The method comprises the steps of screening a titanium silicalite TS-1 (titanium dioxide content is 2.9 wt%) catalyst into particles of 20-40 meshes, filling 4g of the catalyst into the middle section of a fixed bed reaction tube, filling inert quartz sand into two ends of the reaction tube, wherein the vaporization temperature of methyl glycolate is 220 ℃, the reaction temperature is 280 ℃, the feeding amount of methyl glycolate is 8g/h, the reaction is carried out under normal pressure, and the reaction result is shown in table 1.

Example 6

The titanium silicalite TS-1 (titanium dioxide content is 2.9 wt%) catalyst is sieved into particles of 20-40 meshes, 4g of the catalyst is filled into the middle section of a fixed bed reaction tube, inert quartz sand is filled at two ends of the reaction tube, the vaporization temperature of methyl glycolate is 260 ℃, the reaction temperature is 280 ℃, the feeding amount of methyl glycolate is 8g/h, the reaction is carried out under normal pressure, and the reaction result is shown in table 1. Separating and purifying the obtained material to obtain glycolide, and the FI-IR spectrogram and 1H NMR spectrogram of the product are shown in figures 5 and 6 respectively.

Example 7

The method comprises the steps of screening a titanium silicalite TS-1 (titanium dioxide content is 2.9 wt%) catalyst into particles of 20-40 meshes, filling 4g of the catalyst into the middle section of a fixed bed reaction tube, filling inert quartz sand into two ends of the reaction tube, wherein the vaporization temperature of methyl glycolate is 300 ℃, the reaction temperature is 280 ℃, the feeding amount of methyl glycolate is 8g/h, the reaction is carried out under normal pressure, and the reaction result is shown in table 1.

Example 8

The titanium silicalite TS-1 (titanium dioxide content is 2.9 wt%) catalyst is sieved into particles of 20-40 meshes, 4g of the catalyst is filled into the middle section of a fixed bed reaction tube, inert quartz sand is filled at two ends of the reaction tube, the vaporization temperature of methyl glycolate is 260 ℃, the reaction temperature is 250 ℃, the feeding amount of methyl glycolate is 8g/h, the reaction is carried out under normal pressure, and the reaction result is shown in table 1.

Example 9

The titanium silicalite TS-1 (titanium dioxide content is 2.9 wt%) catalyst is sieved into particles of 20-40 meshes, 4g of the catalyst is filled into the middle section of a fixed bed reaction tube, inert quartz sand is filled at two ends of the reaction tube, the vaporization temperature of methyl glycolate is 260 ℃, the reaction temperature is 310 ℃, the feeding amount of methyl glycolate is 8g/h, the reaction is carried out under normal pressure, and the reaction result is shown in Table 1.

Example 10

The titanium silicalite TS-1 (titanium dioxide content is 2.9 wt%) catalyst is sieved into particles of 20-40 meshes, 4g of the catalyst is filled into the middle section of a fixed bed reaction tube, inert quartz sand is filled at two ends of the reaction tube, the vaporization temperature of methyl glycolate is 260 ℃, the reaction temperature is 280 ℃, the feeding amount of the methyl glycolate is 4g/h, the reaction is carried out under normal pressure, and the reaction result is shown in table 1.

Example 11

The method comprises the steps of screening a titanium silicalite TS-1 (titanium dioxide content is 2.9 wt%) catalyst into particles of 20-40 meshes, filling 4g of the catalyst into the middle section of a fixed bed reaction tube, filling inert quartz sand into two ends of the reaction tube, wherein the vaporization temperature of methyl glycolate is 260 ℃, the reaction temperature is 280 ℃, the feeding amount of methyl glycolate is 16g/h, the reaction is carried out under normal pressure, and the reaction result is shown in table 1.

Example 12

The method comprises the steps of screening a titanium silicalite Ti-MWW (titanium dioxide content is 3.1 wt%) catalyst into particles of 20-40 meshes, filling 4g of the catalyst into the middle section of a fixed bed reaction tube, filling inert quartz sand into two ends of the reaction tube, wherein the vaporization temperature of methyl glycolate is 260 ℃, the reaction temperature is 280 ℃, the feeding amount of methyl glycolate is 8g/h, the reaction is carried out under normal pressure, and the reaction result is shown in table 1.

Example 13

The titanium-containing molecular sieve Ti-MOR (titanium dioxide content is 3.3 wt%) catalyst is sieved into particles of 20-40 meshes, 4g of the catalyst is filled into the middle section of a fixed bed reaction tube, inert quartz sand is filled at two ends of the reaction tube, the vaporization temperature of methyl glycolate is 260 ℃, the reaction temperature is 280 ℃, the feeding amount of the methyl glycolate is 8g/h, the reaction is carried out under normal pressure, and the reaction result is shown in Table 1.

Example 14

The titanium-containing molecular sieve Ti-Beta (titanium dioxide content is 2.7 wt%) catalyst is screened into particles of 20-40 meshes, 4g of the catalyst is filled into the middle section of a fixed bed reaction tube, inert quartz sand is filled into two ends of the reaction tube, the vaporization temperature of methyl glycolate is 260 ℃, the reaction temperature is 280 ℃, the feeding amount of methyl glycolate is 8g/h, the reaction is carried out under normal pressure, and the reaction result is shown in table 1.

Example 15

The method comprises the steps of screening a titanium silicalite TS-1 (titanium dioxide content is 2.9 wt%) catalyst into particles of 20-40 meshes, filling 4g of the catalyst into the middle section of a fixed bed reaction tube, filling inert quartz sand into two ends of the reaction tube, wherein the vaporization temperature of ethyl glycolate is 300 ℃, the reaction temperature is 300 ℃, the feeding amount of methyl glycolate is 8g/h, the reaction is carried out under normal pressure, and the reaction result is shown in table 1.

Comparative example 1

Preparing a catalyst: preparing TiO by an isometric impregnation method by using micro silica gel powder or white carbon black as a carrier and tetrabutyl titanate dissolved in isopropanol as a titanium source ₂ /SiO ₂ Catalyst, with a titanium dioxide content of 3 wt.%.

Reaction: adding TiO into the mixture ₂ /SiO ₂ The catalyst is sieved into particles of 20-40 meshes, 4g of the catalyst is filled into the middle section of a fixed bed reaction tube, inert quartz sand is filled into the two ends of the reaction tube, the vaporization temperature of methyl glycolate is 260 ℃, the reaction temperature is 280 ℃, the feeding amount of the methyl glycolate is 8g/h, the reaction is carried out under normal pressure, and the reaction result is shown in table 1.

Comparative example 2

Reaction: adding TiO into the mixture ₂ /SiO ₂ The catalyst is sieved into particles of 20-40 meshes, 4g of the catalyst is filled into the middle section of a fixed bed reaction tube, inert quartz sand is filled into two ends of the reaction tube, methyl glycolate is gasified in a nitrogen atmosphere and then enters the reaction tube together, the gasification temperature is 260 ℃, the volume fraction of the methyl glycolate is 8 percent in a mixed gas of nitrogen and the methyl glycolate, the reaction temperature is 280 ℃, the feeding amount of the methyl glycolate is 8g/h, the reaction is carried out under normal pressure, and the reaction result is shown in table 1.

The glycolate conversion, glycolide selectivity and linear oligomer selectivity in the glycolide preparation process provided in examples 5-15 and comparative examples 1 and 2 are shown in table 1 below.

TABLE 1 results of the reaction

As can be seen from Table 1, in examples 5-15, the titanium silicalite molecular sieve is used as the catalyst to catalyze the reaction of glycolate to glycolide, compared with comparative examples 1 and 2, in which TiO is used ₂ /SiO ₂ The catalyst can be used for catalyzing glycolic acid ester reaction to generate glycolide, and the conversion rate of glycolic acid ester, the selectivity of glycolide and the selectivity of linear oligomer are all remarkably improved. Different titanium-containing catalysts are shown to affect glycolate conversion, glycolide selectivity, and linear oligomer selectivity during glycolate reaction to glycolide. Meanwhile, the glycolic acid ester conversion rate, glycolide selectivity and linear oligomer selectivity are also affected by mixing nitrogen with gasified glycolic acid ester during the reaction process.

Comparative example 6 and comparative example 1. TiO in comparative example 1 ₂ /SiO ₂ The titanium dioxide content in the catalyst is 3wt%, while the titanium dioxide content of the titanium silicalite TS-1 in example 6 is 2.9wt%, which is lower than that in comparative example 1. The conversion of glycolate in comparative example 1 was 46.5%, the glycolide selectivity was 71.3%, and the linear oligomer selectivity was 15.3%. Conversion of glycolate in example 699.4%, glycolide selectivity 93.1%, and linear oligomer selectivity 5.0%, the glycolate conversion, glycolide selectivity, and linear oligomer selectivity were all higher for example 6 than for comparative example 1.

Comparative example 6 and comparative example 2. Comparative example 2 TiO with a titanium dioxide content of 3wt% ₂ /SiO ₂ The catalyst catalyzes glycolic acid ester to react to generate glycolide, and the glycolic acid ester is gasified in nitrogen atmosphere and then enters the reaction tube together, the conversion rate of glycolic acid ester after reaction is 38.4%, the selectivity of glycolide is 90.1%, the selectivity of linear oligomer is 9.0%, and the reaction indexes are all lower than those of the reaction in embodiment 6 of the invention.

Example 16

Preparing polylactic acid: dissolving 0.009g stannous octoate in petroleum ether, adding into a stainless steel reaction kettle together with 30g glycolide, evacuating the kettle with nitrogen for at least three times, vacuumizing for 0.5h under stirring to remove petroleum ether, stopping stirring, pressurizing to 1MPa with nitrogen, heating to 180 deg.C, starting stirring, timing, reacting for 3h, stopping reaction to obtain polyglycolic acid, and determining its relative weight average molecular weight by Gel Permeation Chromatograph (GPC) to be 1.53 × 10 ⁵ 。

The above-mentioned embodiments are only for illustrating the technical idea and features of the present invention, and the purpose of the present invention is to enable those skilled in the art to understand the content of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims

1. The preparation method of glycolide is characterized in that gaseous glycolic acid ester is subjected to cyclization reaction under the condition of catalysis of a titanium-containing molecular sieve to obtain a product glycolide;

the titanium-containing molecular sieve is one or the combination of more than two of TS-1, ti-MWW, ti-MOR, ti-Beta, ti-ZSM-22 and Ti-ZSM-35.

2. The method of claim 1, wherein the titanium-containing molecular sieve is one or a combination of two or more of TS-1, ti-MWW and Ti-MOR.

3. The method of claim 1, wherein the titanium-containing molecular sieve has a crystallinity of greater than 95%.

4. The method of claim 2, wherein the titanium-containing molecular sieve has a crystallinity of greater than 95%.

5. The method of claim 3, wherein the titanium-containing molecular sieve has a crystallite size of 100 to 3000nm.

6. The method of claim 3, wherein the titanium-containing molecular sieve has a crystallite size of from 150 to 1500nm.

7. The method of any one of claims 1 to 6, wherein the titanium dioxide content of the titanium-containing molecular sieve is 0.1wt% to 10wt%.

8. The method of any one of claims 1 to 6, wherein the titanium dioxide content of the titanium-containing molecular sieve is 1wt% to 5wt%.

9. The production method according to any one of claims 1 to 6, wherein the glycolic acid ester is one or a combination of two or more of methyl glycolate, ethyl glycolate, propyl glycolate, and butyl glycolate.

10. The process according to claim 7, wherein the glycolic acid ester is one or a combination of two or more selected from the group consisting of methyl glycolate, ethyl glycolate, propyl glycolate and butyl glycolate.

11. The production method according to any one of claims 1 to 6, wherein the glycolic acid ester is one or both of methyl glycolate and ethyl glycolate.

12. The production method according to any one of claims 1 to 6, wherein the glycolic acid ester is vaporized into a gaseous state under heating.

13. The production method according to claim 7, wherein the glycolic acid ester is vaporized into a gaseous state under heating.

14. The production method according to claim 9, wherein the glycolic acid ester is vaporized into a gaseous state under heating.

15. The production method according to claim 12, wherein the vaporization temperature is 150 to 600 ℃.

16. The method of claim 12, wherein the vaporization temperature is 200-400 ℃.

17. The production method according to any one of claims 1 to 6, wherein the cyclization reaction temperature is 240 to 320 ℃.

18. The process according to claim 7, wherein the cyclization reaction temperature is 240 to 320 ℃.

19. The process according to claim 9, wherein the cyclization reaction temperature is 240 to 320 ℃.

20. The production method according to claim 12, wherein the cyclization reaction temperature is 240 to 320 ℃.

21. The production method according to any one of claims 1 to 6, wherein the cyclization reaction temperature is 250 to 300 ℃.

22. The production method according to any one of claims 1 to 6, wherein the reaction pressure is normal pressure.

23. The method according to claim 7, wherein the reaction pressure is atmospheric pressure.

24. The method according to claim 9, wherein the reaction pressure is atmospheric pressure.

25. The method according to claim 12, wherein the reaction pressure is normal pressure.

26. The method according to claim 17, wherein the reaction pressure is normal pressure.

27. The process of any one of claims 1 to 6, wherein the feed mass space velocity is from 0.5 to 5g of glycolate ester per gram of catalyst per hour.

28. The process according to any one of claims 1 to 6, wherein the cyclization reaction is carried out in a fixed bed, a fluidized bed, a moving bed, an ebullating bed or an expanded bed.

29. The process according to any one of claims 1 to 6, wherein the cyclization reaction is carried out in a fixed bed, a fluidized bed, a moving bed, an ebullating bed or an expanded bed.

30. The process according to claim 7, wherein the cyclization reaction is carried out in a fixed bed, a fluidized bed, a moving bed, an ebullating bed or an expanded bed.

31. The process according to claim 9, wherein the cyclization reaction is carried out in a fixed bed, a fluidized bed, a moving bed, an ebullating bed or an expanded bed.

32. The process according to claim 12, wherein the cyclization reaction is carried out in a fixed bed, a fluidized bed, a moving bed, an ebullating bed or an expanded bed.

33. The process according to claim 17, wherein the cyclization reaction is carried out in a fixed bed, a fluidized bed, a moving bed, an ebullating bed or an expanded bed.

34. The titanium-containing molecular sieve is one or the combination of more than two of TS-1, ti-MWW, ti-MOR, ti-Beta, ti-ZSM-22 and Ti-ZSM-35.