Catalyst as well as preparation method and application thereof

Abstract

The invention belongs to the field of catalysts and petrochemical engineering, and particularly relates to a catalyst and a preparation method and application thereof. The catalyst comprises a composite carrier and an active metal Ni loaded on the composite carrier, the composite carrier is formed by compounding a modifier and a natural mineral substance, and the modifier comprises zirconium and a rare earth metal; the natural mineral substance is selected from one or more of diatomite, sepiolite, halloysite, attapulgite, vermiculite and molybdenite; the rare earth metal is selected from one or more of yttrium, lanthanum, cerium, neodymium, samarium, europium, gadolinium and ytterbium. The catalyst provided by the invention has good structural stability, and has high activity and high selectivity in a reaction for catalytically preparing DMS. The catalyst provided by the invention shows excellent performance in a reaction for preparing DMS through DMM hydrogenation, and can effectively improve the selectivity of DMS and reduce the generation of GBL, BDO and THF.

Description

Technical Field

[0001] The invention belongs to the field of catalysts and petrochemical industry, and specifically relates to a catalyst and a preparation method and application thereof. Background Art

[0002] At present, the main production method of polybutylene succinate (PBS) is to use succinic acid or succinic anhydride and 1,4-butanediol (BDO) for direct esterification polymerization, but the molecular weight of PBS synthesized by this method is low, and its color value, mechanical properties and processing properties are difficult to meet the expected requirements, which limits the promotion and application of PBS. According to the report in the second issue of Volume 36 of "Polyester Industry", PBS produced by transesterification polymerization of dimethyl succinate (DMS) and BDO is more likely to obtain high molecular weight products, and the physical properties such as terminal carboxyl, melt index, and antioxidant properties are more in line with the requirements of downstream products. Therefore, the development of a low-cost, high-quality polymerization-grade DMS production process has broad application prospects and economic benefits.

[0003] The traditional DMS production process routes mainly include succinate esterification, catalytic hydrogenation, and electrochemical catalytic conversion. Since the succinate esterification and electrochemical catalytic methods generally use highly corrosive catalysts such as concentrated sulfuric acid, acidic resin or p-toluenesulfonic acid, and the reaction speed is slow and there are many by-products, they do not have the basis for large-scale development of industrial equipment and most of them have been eliminated. At present, the most promising industrial application method is the catalytic hydrogenation method, which usually uses maleic anhydride as a raw material. First, dimethyl maleate (DMM) is synthesized through esterification reaction, and DMM is then hydrogenated to generate DMS, and then further removed from the light and heavy to obtain DMS. The key to this process route is the hydrogenation reaction after the esterification is completed. Since DMS, BDO, tetrahydrofuran (THF) and γ-butyrolactone (GBL) can be converted into each other through reactions such as hydrogenation, hydrogenolysis or dehydration, and DMS is usually a reaction intermediate and can be easily and quickly converted into BDO, GBL or THF, it is difficult to obtain a high yield of DMS and there is no condition for separation. Although many documents have reported methods for producing various chemicals by esterification and hydrogenation using maleic anhydride as raw material, most of the products are mixtures of BDO, DMS, THF and GBL. Patent application CN104822650A discloses a method for obtaining DMS using maleic anhydride and alkanol as raw materials under the action of Pd catalyst. The content of DMS in the reactant obtained by this method is low, only 30%-55%, and distillation separation is difficult. Patent application CN102070448A discloses a method for preparing DMS using maleic anhydride as raw material, through two steps of esterification and hydrogenation, under the action of a precious metal catalyst. Only a few documents obtain DMS by hydrogenating DMM. Patent application CN117380185A, patent application CN103657693A, etc. mainly use precious metal catalysts such as Pd, Pt or Ru to prepare DMS by hydrogenation of DMM, but this type of method is not only costly, but also has low conversion rate, many side reactions, and the obtained DMS is difficult to purify and cannot reach polymerization grade. Summary of the invention

[0004] The purpose of the present invention is to provide a catalyst and a preparation method and application thereof.

[0005] In a first aspect of the present invention, a catalyst is provided, comprising a composite carrier and an active metal Ni loaded on the composite carrier, wherein the composite carrier is composited by a modifier and a natural mineral, wherein the modifier comprises zirconium and a rare earth metal; the natural mineral is selected from one or more of diatomaceous earth, sepiolite, halloysite, attapulgite, vermiculite and molybdenite; and the rare earth metal is selected from one or more of yttrium, lanthanum, cerium, neodymium, samarium, europium, gadolinium and ytterbium.

[0006] In one or more embodiments, the catalyst has one or more of the following characteristics: The modifier consists of zirconium and rare earth metal; In the modifier, the molar ratio of zirconium to rare earth metal is 1:(0.001-0.5); The content of zirconium element is 0.01-30wt% of the content of the natural mineral; The specific surface area of ​​the composite carrier is 150-450m 2 / g; The total pore volume of the composite carrier is 0.15-1.5m 3 / g; The average pore size of the composite carrier is 5-30 nm; In the catalyst, the content of the active metal Ni is 1-40wt%.

[0007] The second aspect of the present invention provides a method for preparing the catalyst according to the first aspect of the present invention, the method comprising the steps of: (1) subjecting an aqueous solution containing a zirconium salt and a rare earth metal salt to a high pressure hydrothermal method to obtain a modifier; (2) allowing the modifier and the natural mineral to form a precipitate in a dispersant, collecting the precipitate by filtration, drying, and calcining to obtain a composite carrier; (3) immersing the composite support in an aqueous solution containing a nickel salt, filtering out the solution, drying, and calcining to obtain a catalyst precursor; (4) subjecting the catalyst precursor to a reduction reaction in a reducing gas to obtain the catalyst.

[0008] In one or more embodiments, step (1) has one or more of the following features: The zirconium salt is selected from one or more of zirconium nitrate, zirconium chloride and zirconium alkoxide; The rare earth metal salt is selected from one or more of Gd(NO3)3·6H2O, Yb(NO3)3·5H2O, Y(NO3)3·4H2O, La(NO3)3·xH2O, Ce(NO3)3·6H2O, Nd(NO3)3·6H2O, Sm(NO3)3·6H2O, Eu(NO3)3·5H2O and chloride salts of rare earth metals; In the aqueous solution, the concentration of zirconium salt is 2-2.5 mol / L; In the aqueous solution, the molar ratio of zirconium to rare earth metal is 1:(0.001-0.5); The reaction pressure of the high pressure hydrothermal method is 1.0-3.0 MPa; The reaction temperature of the high pressure hydrothermal method is 110-150°C; The reaction time of the high pressure hydrothermal method is 3-24h.

[0009] In one or more embodiments, step (2) has one or more of the following features: The amount of the modifier added is such that the content of zirconium in the modifier is 0.01-30wt% of the content of the natural mineral; The condition for forming the precipitate is: stirring and dispersing the modifier and the natural mineral under heating conditions, and then standing under heating conditions until a precipitate is formed; The drying temperature is 100-150°C; The drying time is 2-48h; The calcination temperature is 150-800°C; The calcination time is 0.5-12h;

[0010] Before carrying out step (2), the natural mineral is first subjected to heat treatment and / or chemical treatment.

[0011] In one or more embodiments, step (3) has one or more of the following features: The nickel salt is selected from one or more of nickel nitrate, nickel chloride and nickel sulfate; The aqueous solution containing nickel salt also includes an organic acid; In the aqueous solution containing nickel salt, the concentration of nickel salt is 0.01-2.0 g / mL; The immersion time is 20-240min; The drying temperature is 80-120°C; The drying time is 2-12h; The calcination temperature is 150-550°C; The calcination time is 0.5-50h.

[0012] In one or more embodiments, step (4) has one or more of the following features: The reducing gas includes hydrogen and a protective gas, and the protective gas is selected from one or more of nitrogen, helium and argon; The temperature of the reduction reaction is 130-650°C; The reduction reaction system is heated to a set temperature at a heating rate not exceeding 10°C / h; After the temperature of the reduction reaction system reaches the set value, it is maintained for 4-48 hours.

[0013] The third aspect of the present invention provides a method for preparing dimethyl succinate, the method comprising step (a): under the catalytic action of a catalyst, dimethyl maleate is subjected to a hydrogenation reaction with hydrogen to obtain a crude dimethyl succinate product, wherein the catalyst is the catalyst described in the first aspect of the present invention or a catalyst prepared by the method described in the second aspect of the present invention.

[0014] In one or more embodiments, the method further comprises step (b): distilling the crude dimethyl succinate to obtain dimethyl succinate.

[0015] In one or more embodiments, step (a) has one or more of the following features: The molar ratio of dimethyl maleate to hydrogen is 1:(100-500); The reaction pressure is 1.0-10.0MPaG; The reaction temperature is 110-230°C; The gas phase space velocity of the reactor is 20000-30000 h -1 ; The conversion rate of dimethyl maleate in step (a) is ≥ 99.9%; The selectivity of dimethyl succinate in step (a) is ≥99%; In step (a), the content of γ-butyrolactone in the crude dimethyl succinate is ≤5wt%.

[0016] A fourth aspect of the present invention provides a method for preparing polybutylene succinate, the method comprising the steps of: (A) providing the catalyst described in the first aspect of the present invention, or providing a catalyst prepared by the method described in the second aspect of the present invention; (B) under the catalytic action of the catalyst, hydrogenating dimethyl maleate with hydrogen to prepare dimethyl succinate; (C) subjecting the dimethyl succinate obtained in step (B) to a polymerization reaction with 1,4-butanediol to obtain polybutylene succinate.

[0017] The present invention has the following beneficial effects: (1) The present invention uses natural minerals with rich pores as the main carrier of the catalyst. The natural mineral carrier is modified by introducing rare earth metals and zirconium elements by utilizing the large mesopore volume, large specific surface area, and excellent adsorption characteristics of the natural mineral itself. The active metal Ni is loaded on the modified natural mineral carrier to obtain the catalyst of the present invention.

[0018] While ensuring the stability of the pore structure, acid properties and mechanical strength of the catalyst, the active metal Ni can be uniformly dispersed on the surface of the carrier. The catalyst of the present invention has good structural stability and has high activity and high selectivity in the reaction of catalyzing the preparation of DMS. The catalyst of the present invention exhibits excellent performance in the reaction of hydrogenating DMM to prepare DMS, can effectively improve the selectivity of DMS, and reduce the generation of GBL, BDO and THF.

[0019] (2) The process for preparing DMS of the present invention adopts a fixed bed cold hydrogen cycle, which can effectively eliminate the hot spot temperature occurring in the hydrogenation reaction, can accurately control the temperature rise of the bed, ensure the stability and safety of the reaction, inhibit the occurrence of side reactions, improve the quality and output of the product, and can also effectively reduce energy consumption, improve production efficiency, and reduce production costs.

[0020] (3) The method for preparing DMS of the present invention can produce a high-purity, polymer-grade DMS product with a purity of ≥99.9% and a color of ≤10AHPA. Compared with PBS products prepared using conventional commercially available succinic acid and succinic anhydride as raw materials, the PBS product prepared using the DMS product of the present invention has a higher molecular weight, and the physical properties such as terminal carboxyl groups, melt index, and antioxidant properties are more in line with the requirements of downstream products. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 1 is a schematic diagram of the structure of the fixed bed reactor used in Example 1 of the present invention; wherein 1-reactor, 101-hydrogen inlet, 102-reaction raw material inlet, 103-catalyst, 104-multi-point thermometer, 105-reactant outlet. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0023] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0024] Herein, “comprising”, “including”, “containing” and similar terms encompass the meanings of “consisting essentially of” and “consisting of”. For example, when “A comprises B and C” is disclosed herein, “A consists essentially of B and C” and “A consists of B and C” should be deemed to be disclosed herein.

[0025] In this document, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible sub-ranges and individual values ​​within the range (including integers and fractions).

[0026] In this document, unless otherwise specified, percentage refers to mass percentage and ratio refers to mass ratio.

[0027] Herein, when describing embodiments or examples, it should be understood that they are not used to limit the present invention to these embodiments or examples. On the contrary, all substitutes, improvements and equivalents of the methods and materials described in the present invention can be included in the scope limited by the claims.

[0028] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0029] Herein, rare earth metals refer to metals such as scandium, yttrium, and lanthanum in Group IIIB of the periodic table, specifically including scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu), preferably one or more of yttrium, lanthanum, cerium, neodymium, samarium, europium, gadolinium, and ytterbium.

[0030] The catalyst of the present invention has the general formula Ni x -Zr y R z P and R represent rare earth metals, P represents natural minerals, x represents the mass fraction of Ni in the catalyst, which is x%, and y and z represent the molar ratio of Zr to R, which is y:z. x -Zr y R z In P, x, y, and z do not represent the content relationship between Ni and Zr, nor do they represent the content relationship between Ni and R.

[0031] Herein, since the material is natural, natural minerals usually contain trace amounts of ions or organic impurities. In order to improve the performance of natural minerals and stabilize the performance of natural minerals, those skilled in the art usually pre-treat the natural minerals before using them. The pre-treatment method of natural minerals can be selected from one or more of sintering, acid treatment and alkali treatment. Since the impurity content carried by natural minerals is less, the mass loss of the pre-treated natural minerals can be ignored.

[0032] The present invention adopts a special reactor structure, which can increase the circulating cold hydrogen to a larger flow rate without increasing the pressure difference of the reactor. Therefore, the present invention provides a reactor used in the method for preparing dimethyl succinate of the present invention. The reactor is a fixed bed reactor. Figure 1 As shown, the reactor 1 is formed by nesting two layers of inner and outer structures, the catalyst 103 is loaded in the inner cylinder of the reactor, and the outer cylinder is circulating cold hydrogen. The reaction raw materials enter the inner cylinder filled with the catalyst 103 through the reaction raw material inlet 102. The reaction liquid after the reaction is completed is discharged from the reactor 1 through the reactant outlet 105. Hydrogen enters the outer cylinder structure inside the reactor through the hydrogen inlet 101, and further reaches the center of the inner cylinder through the catalyst, and then passes through the entire catalyst bed axially. The structure of the reactor of the present invention allows the hydrogen entering the reactor 1 to be transmitted axially, so that the fluid passing area is much larger than the normal radial area, thereby achieving a large circulating cold hydrogen. The reactor can still maintain a low pressure drop. Preferably, a multi-point thermometer 104 is also provided in the reactor of the present invention. One or more multi-point thermometers 104 are arranged in the inner cylinder of the reactor through the catalyst 103.

[0033] Herein, the reactor bed temperature difference refers to the temperature difference between the reactor top temperature and the bottom discharge temperature. Those skilled in the art can measure the reactor bed temperature difference by inserting a multi-point thermometer (T) from the reactor top.

[0034] Herein, the reactor bed pressure drop refers to the difference between the reactor top pressure and the reactor bottom pressure. Those skilled in the art can measure the reactor bed pressure drop by using a pressure transmitter disposed at the reactor top and a pressure transmitter disposed at the bottom discharge.

[0035] The carrier of the catalyst of the present invention is composited by a modifier (including zirconium and rare earth metal) and a natural mineral, and is applied to the preparation of dimethyl succinate by hydrogenation of dimethyl maleate to obtain dimethyl succinate with high yield (high DMS conversion rate) and high purity (high DMS selectivity). Therefore, the present invention provides a catalyst for catalyzing the reaction of dimethyl maleate with hydrogen to prepare dimethyl succinate.

[0036] The catalyst of the present invention comprises a composite carrier and an active metal Ni loaded on the composite carrier, wherein the composite carrier is composited by a modifier and a natural mineral, wherein the modifier comprises zirconium and a rare earth metal; the natural mineral is selected from one or more of diatomaceous earth, sepiolite, halloysite, attapulgite, vermiculite and molybdenite; and the rare earth metal is selected from one or more of yttrium, lanthanum, cerium, neodymium, samarium, europium, gadolinium and ytterbium.

[0037] In some embodiments, the natural mineral is selected from one or more of diatomite, sepiolite, halloysite, attapulgite, vermiculite and molybdenite. Preferably, the natural mineral is selected from one or more of diatomite and sepiolite. Selecting the natural mineral of the present invention as one of the components of the composite carrier can make the prepared catalyst have high activity and high selectivity in the reaction of catalyzing the preparation of DMS; the catalyst shows excellent performance in the reaction of hydrogenating DMM to prepare DMS, can effectively improve the selectivity of DMS, and reduce the generation of GBL, BDO and THF.

[0038] In some embodiments, the rare earth metal is selected from one or more of yttrium, lanthanum, cerium, neodymium, samarium, europium, gadolinium and ytterbium. Preferably, the rare earth metal is selected from one or more of yttrium, lanthanum and cerium. The use of a modifier including the rare earth metal of the present invention to modify natural minerals and prepare a composite carrier can make the prepared catalyst have high activity and high selectivity in the reaction of catalyzing the preparation of DMS; the catalyst exhibits excellent performance in the reaction of hydrogenating DMM to prepare DMS, can effectively improve the selectivity of DMS, and reduce the formation of GBL, BDO and THF.

[0039] In some embodiments, the modifier is composed of zirconium and rare earth metals. Using the modifier of the present invention to modify natural minerals and prepare a composite carrier can make the prepared catalyst have high activity and high selectivity in the reaction of catalyzing the preparation of DMS; the catalyst exhibits excellent performance in the reaction of hydrogenating DMM to prepare DMS, can effectively improve the selectivity of DMS, and reduce the generation of GBL, BDO and THF.

[0040] In some embodiments, in the modifier, the molar ratio of zirconium to rare earth metal is 1:(0.001-0.5), such as 1:0.005, 1:0.008, 1:0.01, 1:0.02, 1:0.05, 1:0.08, 1:0.1, 1:0.2, 1:03, 1:0.5, preferably 1:(0.001-0.1), 1:(0.001-0.01) or 1:(0.01-0.1). Controlling the molar ratio of zirconium to rare earth metal in the modifier within the range defined in the present invention can make the prepared catalyst have high activity and high selectivity in the reaction of catalyzing the preparation of DMS; the catalyst exhibits excellent performance in the reaction of preparing DMS by hydrogenation of DMM, can effectively improve the selectivity of DMS, and reduce the formation of GBL, BDO and THF.

[0041] In some embodiments, the content of zirconium is 0.01-30wt% of the content of the natural mineral, such as 0.05wt%, 0.1wt%, 0.2wt%, 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 7wt%, 9wt%, 11wt%, 13wt%, 15wt%, 17wt%, preferably 0.5-20wt%, 1-5wt%, 5-10wt%, 5-20wt%. Controlling the content of zirconium within the range defined in the present invention can make the prepared catalyst have high activity and high selectivity in the reaction of catalyzing the preparation of DMS; the catalyst shows excellent performance in the reaction of preparing DMS by hydrogenation of DMM, can effectively improve the selectivity of DMS, and reduce the formation of GBL, BDO and THF.

[0042] In some embodiments, in the catalyst, the content of the active metal Ni is 1-40wt%, such as 2wt%, 5wt%, 8wt%, 10wt%, 13wt%, 15wt%, 18wt%, 25wt%, 30wt%, 35wt%, 40wt%, preferably 5-25wt%, 10-20wt% or 5-10wt%. Controlling the content of Ni in the catalyst within the range defined in the present invention can make the prepared catalyst have high activity and high selectivity in the reaction of catalyzing the preparation of DMS; the catalyst exhibits excellent performance in the reaction of preparing DMS by hydrogenation of DMM, can effectively improve the selectivity of DMS, and reduce the formation of GBL, BDO and THF.

[0043] The present invention also provides a composite support, which is composed of a modifier and a natural mineral. The modifier and the natural mineral are as described in any embodiment of the present invention. The catalyst prepared using the composite support has good structural stability and has high activity and high selectivity in the reaction of catalyzing the preparation of DMS. The catalyst prepared using the composite support shows excellent performance in the reaction of DMM hydrogenation to prepare DMS, which can effectively improve the selectivity of DMS and reduce the generation of GBL, BDO and THF.

[0044] The present invention also provides a method for preparing a composite carrier, the method comprising the steps of: (1) subjecting an aqueous solution containing a zirconium salt and a rare earth metal salt to a high pressure hydrothermal method to obtain a modifier; (2) allowing the modifier and the natural mineral to form a precipitate in a dispersant, collecting the precipitate by filtration, drying, and calcining to obtain a composite carrier; Step (1) and step (2) are as described in any embodiment of the present invention.

[0045] In some embodiments, the specific surface area of ​​the composite carrier is 150-450 m 2 / g, for example, 155 m 2 / g, 160m 2 / g, 165 m 2 / g, 170 m 2 / g, 175 m 2 / g, 177 m 2 / g, 180 m 2 / g, 185 m 2 / g, 187 m 2 / g, 188 m 2 / g, 200m 2 / g, 220 m 2 / g, 250 m 2 / g, 280 m 2 / g, 320 m 2 / g, 350 m 2 / g, 400 m 2 / g, preferably 150-250 m 2 / g, 170-190 m 2 / g, 177-188 m 2 / g. The use of a composite carrier having a specific surface area defined herein to prepare the catalyst of the present invention can make the prepared catalyst have high activity and high selectivity in the reaction of catalyzing the preparation of DMS; the catalyst exhibits excellent performance in the reaction of hydrogenating DMM to prepare DMS, can effectively improve the selectivity of DMS, and reduce the generation of GBL, BDO and THF.

[0046] In some embodiments, the total pore volume of the composite support is 0.15-1.5 m 3 / g, for example 0.2 m 3 / g, 0.25 m 3 / g, 0.3 m 3 / g, 0.35 m 3 / g, 0.38 m 3 / g, 0.4 m 3 / g, 0.45 m 3 / g, 0.5 m 3 / g, 0.6 m 3 / g, 0.7m 3 / g, 0.8 m 3 / g, 1.0 m 3 / g, 1.3 m 3 / g, preferably 0.3-1.0 m 3 / g, 0.35-0.5 m 3 / g. The use of a composite carrier having a total pore volume defined herein to prepare the catalyst of the present invention can make the prepared catalyst have high activity and high selectivity in the reaction of catalyzing the preparation of DMS; the catalyst exhibits excellent performance in the reaction of hydrogenating DMM to prepare DMS, can effectively improve the selectivity of DMS, and reduce the generation of GBL, BDO and THF.

[0047] In some embodiments, the average pore size of the composite support is 5-30 nm, such as 8 nm, 10 nm, 12 nm, 15 nm, 18 nm, 20 nm, 22 nm, 25 nm, 28 nm, preferably 8-20 nm, 10-12 nm, 10-15 nm. The use of a composite support having an average pore size as defined herein to prepare the catalyst of the present invention can make the prepared catalyst have high activity and high selectivity in the reaction of catalyzing the preparation of DMS; the catalyst exhibits excellent performance in the reaction of hydrogenating DMM to prepare DMS, can effectively improve the selectivity of DMS, and reduce the formation of GBL, BDO and THF.

[0048] The inventors have found that natural minerals can obtain suitable specific surface area and pore structure after being modified by rare earth metals and zirconium elements. The catalyst prepared by using the modified natural minerals as a composite carrier and loading the active metal Ni on the composite carrier shows excellent performance in the reaction of DMM hydrogenation to prepare DMS, has high catalytic activity and high selectivity, can effectively improve the selectivity of DMS, and reduce the generation of GBL, BDO and THF.

[0049] The present invention provides a method for preparing the catalyst of the present invention, the method comprising the steps of: (1) subjecting an aqueous solution containing a zirconium salt and a rare earth metal salt to a high pressure hydrothermal method to obtain a modifier; (2) allowing the modifier and the natural mineral to form a precipitate in a dispersant, collecting the precipitate by filtration, drying, and calcining to obtain a composite carrier; (3) immersing the composite support in an aqueous solution containing a nickel salt, filtering out the solution, drying, and calcining to obtain a catalyst precursor; (4) subjecting the catalyst precursor to a reduction reaction in a reducing gas to obtain the catalyst.

[0050] In some embodiments, in step (1), the zirconium salt is selected from one or more of zirconium nitrate, zirconium chloride and zirconium alkoxide. Preferably, the zirconium salt is selected from one or more of ZrOCl2, ZrO(NO3)2 and ZrCl4, such as ZrO(NO3)2.

[0051] In some embodiments, in step (1), the rare earth metal salt is selected from one or more of Gd(NO3)3·6H2O, Yb(NO3)3·5H2O, Y(NO3)3·4H2O, La(NO3)3·6H2O, Ce(NO3)3·6H2O, Nd(NO3)3·6H2O, Sm(NO3)3·6H2O, Eu(NO3)3·5H2O and chloride salts of rare earth metals. Preferably, the rare earth metal salt is selected from one or more of Ce(NO3)3·6H2O, La(NO3)3·6H2O and Y(NO3)3·4H2O.

[0052] The catalyst of the present invention is prepared by using the zirconium salt and the rare earth metal salt of the present invention, so that the prepared catalyst has high activity and high selectivity in the reaction of catalytic preparation of DMS; the catalyst shows excellent performance in the reaction of hydrogenating DMM to prepare DMS, can effectively improve the selectivity of DMS, and reduce the generation of GBL, BDO and THF.

[0053] In some embodiments, in step (1), the concentration of zirconium salt in the aqueous solution is 2-2.5 mol / L, for example, 2 mol / L, 2.2 mol / L, 2.3 mol / L, 2.5 mol / L.

[0054] In some embodiments, in step (1), the molar ratio of zirconium to rare earth metal in the aqueous solution is 1:(0.001-0.5), for example, 1:0.005, 1:0.008, 1:0.01, 1:0.02, 1:0.05, 1:0.08, 1:0.1, 1:0.2, 1:03, 1:0.5, preferably 1:(0.001-0.1), 1:(0.001-0.01) or 1:(0.01-0.1).

[0055] In some embodiments, in step (1), the reaction pressure of the high pressure hydrothermal method is 1.0-3.0 MPa, for example, 1.0 MPa, 1.5 MPa, 2.0 MPa, 2.5 MPa, 3.0 MPa, preferably 2.0-3.0 MPa.

[0056] In some embodiments, in step (1), the reaction temperature of the high pressure hydrothermal method is 110-150°C, for example, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, preferably 120-130°C.

[0057] In some embodiments, in step (1), the reaction time of the high pressure hydrothermal method is 3-24 h, for example, 3 h, 5 h, 6 h, 8 h, 10 h, 15 h, 18 h, 20 h, preferably 6-18 h.

[0058] In step (1), the concentration of zirconium salt in the aqueous solution, the molar ratio of zirconium to rare earth metal in the aqueous solution, the reaction pressure of the high-pressure hydrothermal method, the reaction temperature of the high-pressure hydrothermal method, and the reaction time of the high-pressure hydrothermal method defined in the present invention are used to prepare a modifier, and the prepared modifier is compounded with natural minerals to obtain a composite carrier suitable for the catalyst of the present invention. The use of the composite carrier to prepare the catalyst of the present invention can make the prepared catalyst have high activity and high selectivity in the reaction of catalyzing the preparation of DMS; the catalyst exhibits excellent performance in the reaction of hydrogenating DMM to prepare DMS, can effectively improve the selectivity of DMS, and reduce the generation of GBL, BDO and THF.

[0059] In some embodiments, in step (2), the amount of the modifier added is such that the content of zirconium in the modifier is 0.01-30wt% of the content of the natural mineral, for example, 0.05wt%, 0.1 wt%, 0.2 wt%, 0.5 wt%, 1wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 7 wt%, 9 wt%, 11 wt%, 13 wt%, 15 wt%, 17 wt%, preferably 0.5-20wt%, 1-5 wt%, 5-10 wt%, 5-20 wt%.

[0060] In some embodiments, in step (2), the dispersant is selected from one or more of methanol, ethanol and water. In some embodiments, the dispersant is a mixture of ethanol and water; preferably, the volume ratio of ethanol to water is (0.1-10):1, such as 0.1:1, 0.2:1, 0.5:1, 1:1, 3:1, 5:1, 8:1, 10:1.

[0061] In some embodiments, in step (2), 100-500 g of natural minerals are added per liter of dispersant, for example, 100 g, 150 g, 200 g, 250 g, 300 g, 330 g, 350 g, 380 g, 400 g, 450 g, preferably 300-400 g, 330-350 g.

[0062] In step (2), the condition for forming the precipitate is: stirring and dispersing the modifier and the natural mineral under heating conditions, and then standing under heating conditions until a precipitate is formed. In some embodiments, the stirring and standing are each independently performed at 50-90°C, preferably at 50-80°C, 60-80°C, 80-90°C. Preferably, stirring is performed for 2-12 hours, such as 2 hours, 4 hours, 6 hours, 8 hours, 10 hours, 12 hours. Preferably, standing is performed for 4-48 hours, such as 8 hours, 12 hours, 18 hours, 24 hours, 30 hours, 35 hours, 40 hours.

[0063] In some embodiments, the drying temperature is 100-150°C, such as 110°C, 120°C, 130°C, 140°C, 150°C, preferably 100-120°C, 120-130°C, 120-150°C.

[0064] In some embodiments, the drying time is 2-48 h, for example 4 h, 8 h, 12 h, 15 h, 18 h, 24 h, 30 h, 36 h, 42 h, preferably 5-12 h, 2-8 h or 8-24 h.

[0065] In some embodiments, the calcination temperature is 150-800°C, for example, 150°C, 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, preferably 200-650°C, 200-450°C, 450-800°C.

[0066] In some embodiments, the calcination time is 0.5-12 h, such as 1 h, 2 h, 4 h, 6 h, 8 h, 10 h, preferably 1-8 h, 2-4 h, 4-12 h.

[0067] Before carrying out step (2), the natural mineral is first subjected to heat treatment and / or chemical treatment.

[0068] The temperature of the heat treatment is 300-800° C., preferably 500-600° C. The time of the heat treatment is 0.5-5 hours, preferably 2-4 hours. The heat treatment is carried out in an air environment.

[0069] The chemical treatment is to soak the natural mineral in an acid solution. The acid can be selected from one or more of sulfuric acid, hydrochloric acid and phosphoric acid; preferably sulfuric acid. The concentration of hydrogen ions in the acid solution is 0.1-0.8 mol / L, for example 0.2 mol / L, 0.4 mol / L, 0.6 mol / L. In some embodiments, the acid solution is an aqueous solution of acid. In some embodiments, the content of natural minerals is 1-80wt%, preferably 1-60wt%, 30-60wt%, based on the total mass of natural minerals and acid solution. The chemical treatment can be carried out at 30-150°C, preferably 50-120°C. The chemical treatment is carried out for 0.5-24h, preferably 1-16h, 5-8h. Preferably, the chemically treated natural minerals are washed to a pH of 6-7. Preferably, the chemically treated and washed natural minerals are dried.

[0070] In some embodiments, before performing step (2), the natural mineral is subjected to the above-mentioned heat treatment and chemical treatment in sequence.

[0071] In step (2), the amount of modifier added, the type of dispersant, the amount of natural mineral added, the conditions for forming a precipitate, the drying temperature, the drying time, the calcination temperature, the calcination time, and the heat treatment and / or chemical treatment method for the natural mineral defined in the present invention are used to prepare a composite carrier. The use of the composite carrier to prepare the catalyst of the present invention can make the prepared catalyst have high activity and high selectivity in the reaction of catalyzing the preparation of DMS; the catalyst exhibits excellent performance in the reaction of hydrogenating DMM to prepare DMS, can effectively improve the selectivity of DMS, and reduce the generation of GBL, BDO and THF.

[0072] In some embodiments, in step (3), the nickel salt is selected from one or more of nickel nitrate, nickel chloride and nickel sulfate, preferably nickel nitrate.

[0073] In some embodiments, in step (3), the aqueous solution containing nickel salt further comprises an organic acid. The organic acid may be selected from one or more of formic acid, acetic acid, oxalic acid and citric acid, preferably citric acid. Preferably, the aqueous solution containing nickel salt contains 0.9-35 vol% of organic acid, for example, 1 vol%, 2 vol%, 3 vol%, 5 vol%, 7 vol%, 9 vol%, 11 vol%, 15 vol%, 20 vol%, 25 vol%, 30 vol%, preferably 5-20 vol%, 5-10 vol%.

[0074] In some embodiments, the concentration of nickel salt in the aqueous solution containing nickel salt is 0.01-2.0 g / mL, for example, 0.05 g / mL, 0.08 g / mL, 0.1 g / mL, 0.3 g / mL, 0.5 g / mL, 0.8 g / mL, 0.9 g / mL, 1.0 g / mL, 1.3 g / mL, 1.5 g / mL, 1.8 g / mL, preferably 0.5-0.9 g / mL, 0.8-0.9 g / mL.

[0075] In some embodiments, the immersion time is 20-240 min, for example, 20 min, 30 min, 50 min, 80 min, 100 min, 120 min, 150 min, 180 min, 210 min, 230 min, preferably 20-120 min, 50-120 min, 80-120 min.

[0076] In step (3), parameters such as the volume of the solvent used in the impregnation, the content of the nickel salt in the solvent, the content of the organic acid in the impregnation solution, and the amount of the composite carrier can be adjusted according to the content of Ni in the catalyst to be prepared. Those skilled in the art can reasonably design the above parameters according to the mass fraction of Ni in the catalyst to be prepared.

[0077] In some embodiments, the drying temperature is 80-120°C, such as 80°C, 90°C, 100°C, 110°C, 120°C, preferably 100-120°C.

[0078] In some embodiments, the drying time is 2-12 h, for example, 2 h, 4 h, 6 h, 8 h, 10 h, 12 h, preferably 4-12 h, 4-8 h.

[0079] In some embodiments, the calcination temperature is 150-550°C, for example, 150°C, 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, preferably 170-550°C, 300-550°C, 500-550°C.

[0080] In some embodiments, the calcination time is 0.5-50 h, for example, 1 h, 2 h, 4 h, 8 h, 12 h, 15 h, 20 h, 24 h, 36 h, 48 h, preferably 1-24 h, 8-24 h, 2-8 h.

[0081] In step (3), a catalyst precursor is prepared by using the nickel salt, aqueous solution containing nickel salt, impregnation time, drying temperature, drying time, calcination temperature and calcination time defined in the present invention, and the catalyst precursor is further reduced to obtain a catalyst of the present invention having high activity and high selectivity in the reaction of catalyzing the preparation of DMS; the catalyst exhibits excellent performance in the reaction of hydrogenating DMM to prepare DMS, can effectively improve the selectivity of DMS, and reduce the generation of GBL, BDO and THF.

[0082] In some embodiments, in step (4), the reducing gas comprises hydrogen and a protective gas. The protective gas is selected from one or more of nitrogen, helium and argon, preferably nitrogen. In the reducing gas, the molar ratio of the protective gas to hydrogen is 1:(0.01-1), for example, 1:0.01, 1:0.02, 1:0.05, 1:0.08, 1:0.1, 1:0.2, 1:0.3, 1:0.5, 1:0.8, 1:0.9, preferably 1:(0.01-0.1), 1:(0.05-1) or 1:(0.05-0.1).

[0083] In some embodiments, the temperature of the reduction reaction is 130-650°C, for example, 150°C, 200°C, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C.

[0084] In some embodiments, the reduction reaction system is heated to a set temperature, and the heating rate does not exceed 10° C. / h.

[0085] In some embodiments, after the temperature of the reduction reaction system reaches the set value, it is maintained for 4-48 h, for example, 4 h, 8 h, 12 h, 18 h, 24 h, 30 h, 36 h, 42 h, preferably 6-24 h, 12-30 h.

[0086] The inventors found that the catalyst prepared by the method of the present invention exhibits excellent performance in the reaction of hydrogenating DMM to prepare DMS, has high catalytic activity and high selectivity, can effectively improve the selectivity of DMS, and reduce the generation of GBL, BDO and THF.

[0087] The catalyst of the present invention is prepared by using the type of reducing gas, the temperature of the reduction reaction, the heating rate of the reduction reaction, and the reaction time of the reduction reaction defined in the present invention. The prepared catalyst has high activity and high selectivity in the reaction of catalyzing the preparation of DMS; the catalyst shows excellent performance in the reaction of hydrogenating DMM to prepare DMS, can effectively improve the selectivity of DMS, and reduce the generation of GBL, BDO and THF.

[0088] In some embodiments, the catalyst is stored under the protection of a protective gas (eg, one or both of nitrogen and argon) or a liquid seal (eg, one or both of water and ethanol) isolated from air.

[0089] The present invention provides a method for preparing dimethyl succinate, which comprises the step (a): under the catalytic action of a catalyst, dimethyl maleate is subjected to a hydrogenation reaction with hydrogen to obtain a crude dimethyl succinate product, wherein the catalyst is the catalyst of the present invention or a catalyst obtained by the method of the present invention.

[0090] In some embodiments, the method further comprises step (b): distilling the crude dimethyl succinate to obtain dimethyl succinate.

[0091] In the present invention, use Figure 1 The reactor shown in the figure can control the reactor bed temperature difference and reactor bed pressure drop during the reaction process. The method of the present invention controls the bed temperature rise by circulating a large flow of cold hydrogen, eliminates the hot spot temperature of the catalyst bed, inhibits the occurrence of side reactions, and effectively improves the selectivity and conversion rate of dimethyl succinate.

[0092] In some embodiments, the reactor bed temperature difference (∆t) can be controlled to be ≤1°C, and the lowest can be ≤0.1°C.

[0093] In some embodiments, the reactor bed pressure drop (∆P) can be controlled to ≤0.2 MPa, and the lowest can be ≤0.1 MPa.

[0094] Using the Invention Figure 1 The reactor shown is used to prepare dimethyl succinate, and the reactor bed temperature difference and the reactor bed pressure drop are controlled within the range defined in this article, which can inhibit the occurrence of side reactions and effectively improve the selectivity and conversion rate of dimethyl succinate.

[0095] In step (a), the molar ratio of dimethyl maleate to hydrogen is 1:(100-500), for example 1:100, 1:150, 1:200, 1:250, 1:300, 1:350, 1:400, 1:450, 1:500, preferably 1:(100-300) or 1:(300-500).

[0096] In step (a), the reaction pressure is 1.0-10.0 MpaG, for example, 1.0 MpaG, 2 MpaG, 3 MpaG, 5 MpaG, 8 MpaG, 9 MpaG, preferably 1-5 MpaG, 3-8 MpaG.

[0097] In step (a), the reaction temperature is 110-230°C, for example, 110°C, 120°C, 130°C, 150°C, 170°C, 190°C, 210°C, 230°C, preferably 125-210°C, 110-190°C, 150-230°C, 190-230°C.

[0098] In step (a), the gas phase space velocity of the reactor is 20000-30000 h -1 , e.g. 21000 h -1 , 22000 h -1 、23000h -1 , 24000 h -1 , 25000 h -1 、27000 h -1 , 29000 h -1 .

[0099] The conversion rate of dimethyl maleate in step (a) is ≥99.9%.

[0100] The selectivity of dimethyl succinate in step (a) is ≥99%, for example ≥99.1%, ≥99.2%, ≥99.3%, ≥99.4%, ≥99.5%, ≥99.6%, ≥99.7%, ≥99.8%.

[0101] In step (a), the content of γ-butyrolactone in the crude dimethyl succinate is ≤5wt%, for example, ≤4wt%, ≤3wt%, ≤2wt%, ≤1wt%, ≤0.5wt%, ≤0.1wt%, ≤0.05wt%, ≤0.01wt%, ≤0.005wt%, ≤0.003wt%, ≤0.002wt%, ≤0.001wt%.

[0102] In step (a), the dimethyl maleate to hydrogen molar ratio, reaction pressure, reaction temperature and reactor gas phase space velocity conditions defined herein are used to prepare dimethyl succinate, which can effectively improve the conversion rate of dimethyl maleate, the selectivity of dimethyl succinate, and control the content of γ-butyrolactone in dimethyl succinate.

[0103] In step (b), the distillation is a three-stage distillation. The three-stage distillation includes a first-stage distillation. The operating pressure of the first-stage distillation is 5-50 kPaA, preferably 10-30 kPaA, 10-20 kPaA, 20-30 kPaA. The operating temperature of the first-stage distillation is 130-180°C, for example, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, preferably 145-175°C, 130-170°C, 140-165°C. The three-stage distillation includes a second-stage distillation. The operating pressure of the second stage distillation is 0.1-10 kPaA, such as 0.2 kPaA, 0.5 kPaA, 1 kPaA, 2 kPaA, 3 kPaA, 4 kPaA, 5 kPaA, 8 kPaA, preferably 0.5-6.5 kPaA, 1-5 kPaA, 1-3 kPaA. The operating temperature of the second stage distillation is 130-200°C, such as 135°C, 140°C, 145°C, 150°C, 155°C, 165°C, 170°C, 172°C, 178°C, 190°C, preferably 135-185°C, 140-180°C, 150-175°C. The three-stage distillation includes a third stage distillation. The operating pressure of the third stage distillation is 1-30 kPaA, such as 2 kPaA, 5 kPaA, 8 kPaA, 10 kPaA, 15 kPaA, 20 kPaA, 25 kPaA, 30 kPaA, preferably 1-20 kPaA. The operating temperature of the third stage distillation is 110-170°C, such as 120°C, 130°C, 135°C, 140°C, 150°C, 160°C, 168°C, 170°C, preferably 125-165°C, 130-170°C, 150-168°C.

[0104] The purity of the dimethyl succinate obtained in step (b) is ≥95wt%, for example ≥96wt%, ≥97wt%, ≥98wt%, ≥99wt%, ≥99.1wt%, ≥99.2wt%, ≥99.3wt%, ≥99.4wt%, ≥99.5wt%, ≥99.6wt%, ≥99.7wt%, ≥99.8wt%, ≥99.9wt%.

[0105] The color number of the dimethyl succinate prepared in step (b) is ≤10 APHA, for example, 10 APHA, 9 APHA, 8 APHA, 7 APHA, 6 APHA, 5 APHA, 4 APHA, 3 APHA, 2 APHA, 1 APHA, preferably 2-8 APHA, 3-5 APHA.

[0106] In step (b), the crude dimethyl succinate obtained in step (a) is further distilled under the three-stage distillation conditions defined in the present invention to obtain a dimethyl succinate product with high purity and low color number.

[0107] The present invention also provides a method for preparing polybutylene succinate, the method comprising the steps of: (A) providing a catalyst of the present invention, or providing a catalyst prepared by the method of the present invention; (B) under the catalytic action of the catalyst, hydrogenating dimethyl maleate with hydrogen to prepare dimethyl succinate; (C) subjecting the dimethyl succinate obtained in step (B) to a polymerization reaction with 1,4-butanediol to obtain polybutylene succinate.

[0108] The catalyst of the present invention, the method for preparing the catalyst of the present invention, and the method for preparing dimethyl succinate by hydrogenating dimethyl maleate are as described in any embodiment of the present invention.

[0109] In some embodiments, in step (C), the molar ratio of dimethyl succinate to 1, 4-butanediol is 1:(1-1.5), for example, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, preferably 1:(1-1.3), 1:(1-1.2).

[0110] Step (C) comprises the steps of: (C1) esterifying dimethyl succinate with 1,4-butanediol; (C2) subjecting the reaction liquid after the reaction in step (C1) to a preliminary polycondensation reaction; (C3) subjecting the reaction liquid obtained after the reaction in step (C2) to a final polycondensation reaction.

[0111] In some embodiments, the reaction pressure of the esterification reaction is 5-20 kPaG, for example, 5 kPaG, 8 kPaG, 10 kPaG, 12 kPaG, 15 kPaG, 18 kPaG, 20 kPaG, preferably 5-10 kPaG, 10-20 kPaG, 5-15 kPaG.

[0112] In some embodiments, the reaction temperature of the esterification reaction is 140-200°C, for example, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, preferably 140-160°C, 160-200°C.

[0113] In some embodiments, the reaction time of the esterification reaction is 3-10 h, for example, 3 h, 4 h, 6 h, 8 h, 10 h, preferably 3-6 h, 6-10 h, 3-8 h.

[0114] In some embodiments, the esterification reaction is terminated when the content of dimethyl succinate in the test reaction system drops below 500 ppm.

[0115] In some embodiments, the pre-polycondensation reaction is carried out under the catalysis of a polymerization catalyst. Preferably, the polymerization catalyst is a Ti-containing catalyst, preferably tetraisopropyl titanate (TtiPO, CAS: 546-68-9).

[0116] In some embodiments, the molar ratio of the polymerization catalyst to dimethyl succinate is 1:(300-500), for example 1:320, 1:340, 1:360, 1:380, 1:400, 1:420, 1:440, 1:480, preferably 1:(400-500) or 1:(300-400).

[0117] In some embodiments, the reaction temperature of the pre-polycondensation reaction is 180-250°C, such as 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, preferably 180-210°C, 210-250°C.

[0118] In some embodiments, the reaction pressure of the pre-polycondensation reaction is 0.5-2 kPaA, such as 0.8 kPaA, 1 kPaA, 1.2 kPaA, 1.4 kPaA, 1.6 kPaA, 1.8 kPaA, preferably 0.5-1 kPaA, 1-2 kPaA.

[0119] In some embodiments, the reaction time of the pre-polycondensation reaction is 2-5 h, such as 3 h, 4 h.

[0120] In some embodiments, the reaction pressure of the final polycondensation reaction is 50-80 PaA, such as 55 PaA, 60 PaA, 65 PaA, 70 PaA, 75 PaA, preferably 60-80 PaA, 65-80 PaA.

[0121] In some embodiments, the reaction temperature of the final polycondensation reaction is 200-250°C, for example, 205°C, 210°C, 215°C, 220°C, 225°C, 230°C, 235°C, 240°C, preferably 225-250°C.

[0122] In some embodiments, the reaction time of the final polycondensation reaction is 1-5 h, such as 2 h, 3 h, or 4 h.

[0123] In some embodiments, the viscosity of the reaction system of the final polycondensation reaction no longer increases (ie, the viscosity of the reaction system remains stable), and the final polycondensation reaction is completed.

[0124] In some embodiments, before the esterification reaction, dimethyl succinate and 1, 4-butanediol are fully dissolved, for example, by heating, the heating can be carried out at 100-150° C., and the heating can be carried out for 0.5-5 hours.

[0125] The polybutylene succinate prepared by the method of the present invention has a terminal carboxyl content of 30-80 mol / t, for example, 35 mol / t, 40 mol / t, 45 mol / t, 50 mol / t, 55 mol / t, 60 mol / t, 65 mol / t, 70 mol / t, 75 mol / t, preferably 35-80 mol / t, 40-80 mol / t, 45-80 mol / t, 45-50 mol / t.

[0126] The melt index of polybutylene succinate prepared by the method of the present invention is 5.0-8.0 g / min, for example, 5.5 g / min, 6.0 g / min, 6.2 g / min, 6.5 g / min, 7.0 g / min, 7.5 g / min, 8.0 g / min, preferably 6.0-8.0 g / min, 6.2-8.0 g / min, 6.2-7.0 g / min.

[0127] The oxidation induction time of polybutylene succinate prepared by the method of the present invention is 60-150 min, for example, 65 min, 70 min, 75 min, 80 min, 85 min, 90 min, 95 min, 100 min, 105 min, 110 min, 115 min, 116 min, 120 min, 125 min, 130 min, 135 min, 140 min, 145 min, preferably 65-116 min, 116-150 min, 90-120 min.

[0128] The oxidation induction temperature of the polybutylene succinate prepared by the method of the present invention is 250-350°C, for example, 255°C, 260°C, 265°C, 270°C, 275°C, 280°C, 290°C, 300°C, 310°C, 320°C, 330°C, 340°C, preferably 280-320°C, 250-300°C, 290-340°C.

[0129] Polybutylene succinate is prepared by using the molar ratio of dimethyl succinate to 1, 4-butanediol, the conditions of esterification reaction, the conditions of pre-polycondensation reaction, and the conditions of final polycondensation reaction defined in this article. The physical properties of the prepared polybutylene succinate, such as terminal carboxyl groups, melt index, and antioxidant properties, are more in line with the requirements of downstream products.

[0130] Due to the advanced nature of the catalyst of the present invention and its preparation method and application, the catalyst of the present invention can be widely used in application fields such as petrochemical industry, catalyst research and development, environmental protection and energy conservation.

[0131] In the field of petrochemical industry, the present invention provides a novel modified composite support Ni-based catalyst for gas phase hydrogenation of dimethyl maleate (DMM) to produce dimethyl succinate (DMS), and provides a production process for preparing DMS by catalyzing DMM hydrogenation using the catalyst. Herein, the process for producing DMS by gas phase hydrogenation of DMM using the catalyst of the present invention has the advantages of high DMS conversion rate, high DMS selectivity, and low production cost, and can greatly reduce side reactions in the DMM hydrogenation reaction process and reduce the generation of by-products.

[0132] The present invention provides an optimized hydrogenation reaction process. The reaction process uses a reactor with a special structure, which can achieve a low pressure drop in the reactor under a high hydrogen circulation rate and eliminate the hot spot temperature of the catalyst bed. The process of the present invention has the advantages of high product purity, low energy consumption and easy control, and can greatly improve the output and quality of DMS, reduce production costs, and promote the rapid development of the biodegradable plastic PBS industry.

[0133] In the field of environmental protection and energy conservation, the method of the present invention adopts cold hydrogen circulation to strictly control the temperature rise of the bed, avoids hot spots, improves the safety and stability of the reaction, reduces energy waste, reduces carbon emissions in the production process, and is beneficial to environmental protection and sustainable development.

[0134] In summary, the method for preparing DMS of the present invention has the characteristics of high selectivity and low energy consumption, which is beneficial to reducing the waste of resources, improving resource utilization efficiency, and achieving the goal of environmental protection and energy saving.

[0135] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods in the following examples without specifying specific conditions are usually based on conventional conditions or the conditions recommended by the manufacturer. Unless otherwise stated, percentages and parts are calculated by weight.

[0136] In this paper, the specific surface area test method of the composite carrier is as follows: measured by BET method, using Japan Micoratrca BELSORP-mini x specific surface area meter, using static volume method, degassing conditions at 300 ° C for 8 h, and the specific surface area calculation method uses Brunauer–Emmett–Teller (BET) equation.

[0137] In this paper, the total pore volume and average pore size of the composite carrier are calculated by the BJH (Barrett-Joiner-Halenda) model. The average pore size of the composite carrier is equal to the result of dividing the corresponding pore volume by the corresponding specific surface area. Calculation formula: Average pore diameter P aver = k × total pore volume / specific surface area, where k is taken based on cylindrical pores, k=4.

[0138] Preparation Example 1: Preparation of Catalyst 1 (1) Preparation of zirconium-rare earth Zr1Ce 0.01 Modifier Prepare a certain amount of 2.0 mol / L ZrO(NO3)2 aqueous solution, add Ce(NO3)3·6H2O according to the molar ratio of Zr to Ce in the aqueous solution of 1:0.01, mix well and add into the high pressure reactor, increase the pressure to 3.0 MPa, react at 130℃ for 6h to obtain zirconium-rare earth Zr1Ce 0.01 Modifier, reduce to normal pressure and room temperature, and set aside.

[0139] (2) Diatomaceous earth (P) pretreatment Weigh a certain amount of purchased natural diatomite (Sichuan 1 diatomite ore, Jilin Changbai diatomite vein), first heat treat it, roast it at 600℃ in air atmosphere for 2h to eliminate the organic matter contained in the natural diatomite ore, and grind the heat-treated diatomite into a uniform powder. Then, the heat-treated diatomite powder is chemically treated in sulfuric acid to remove the alkali ions therein, and the ground powder is suspended in dilute sulfuric acid with a concentration of 0.2mol / L and a solid content of 30wt%, and stirred continuously at 50℃ for 8h. Then, filter and separate, wash with deionized water, dry the filter cake at 120℃ to constant weight, and grind it into powder.

[0140] (3) Preparation of composite carrier Zr x R y P Weigh 100 g of the diatomaceous earth treated in step (2), add 300 mL of a mixed solution of ethanol and water (volume ratio of 5:1), stir until suspended, add the modifier prepared in step (1) according to the zirconium content of 5 wt% (based on the amount of natural diatomaceous earth), stir continuously at 80°C for 4 hours, stop stirring and stand at 80°C for 24 hours until a stable colloidal precipitate is formed, remove the solvent by filtration, and then dry the precipitate at 120°C in an air atmosphere for 8 hours. Finally, calcine the carrier sample at 450°C for 4 hours to obtain a composite carrier. The specific surface area (BET) of the prepared composite carrier is 180 m 2 / g, and the total pore volume is 0.5cm 3 / g, and the average pore diameter is 12nm.

[0141] (4) Preparation of catalyst precursor Active metal Ni is loaded on the composite support by impregnation method. First, 54.2 g of Ni(NO3)2·6H2O is weighed to prepare 200 mL of nickel salt aqueous solution. Citric acid is added to the prepared nickel salt aqueous solution according to the volume ratio of nickel salt aqueous solution to citric acid of 1:0.1. The composite support is impregnated with a mixed solution of nickel salt aqueous solution and citric acid. The amount of the composite support is selected according to the amount of Ni loaded on the catalyst to be prepared in step (5). The mixture is allowed to stand for 120 minutes, and the excess solution is removed by filtration. After drying at 120°C for 4 hours, the mixture is calcined at 550°C for 8 hours in an air atmosphere to obtain a catalyst precursor.

[0142] (5) Preparation of 10 wt% Ni-loaded catalyst The catalyst precursor obtained in step (4) is reduced under a reducing gas to obtain a catalyst with metal Ni as the active center. The reducing gas is a mixed gas of nitrogen and hydrogen, and the molar ratio of nitrogen to hydrogen is 1:0.05. The temperature is raised to 350°C by a programmed temperature increase method, and the heating rate does not exceed 10°C / h. After reaching the set temperature, it is maintained for 24 hours and naturally cooled to room temperature to obtain a catalyst Ni with a Ni content of 10wt%. 10 -Zr1R 0.01 P, the prepared catalyst is sealed by adding deionized water and isolated from air for storage.

[0143] Preparation Example 2: Preparation of Catalyst 2 The method of Preparation Example 1 was repeated, with the only difference being that purchased sepiolite powder (from Xiangtan Sepiolite Technology Co., Ltd.) was used instead of diatomaceous earth.

[0144] The specific surface area of ​​the prepared composite carrier is 187m 2 / g, and the total pore volume is 0.42cm 3 / g, and the average pore size is 10nm.

[0145] Preparation Example 3: Preparation of Catalyst 3 The method of Preparation Example 1 was repeated, with the only difference being that Y(NO3)3·4H2O was used instead of Ce(NO3)3·6H2O.

[0146] The specific surface area of ​​the prepared composite carrier is 188m 2 / g, and the total pore volume is 0.40m 3 / g, and the average pore size is 12nm.

[0147] Preparation Example 4: Preparation of Catalyst 4 The method of Preparation Example 1 was repeated, with the only difference being that La(NO3)3·6H2O was used instead of Ce(NO3)3·6H2O.

[0148] The specific surface area of ​​the prepared composite carrier is 177m 2 / g, and the total pore volume is 0.38m 3 / g, and the average pore size is 10nm.

[0149] Preparation Example 5: Preparation of Catalyst D1 The method of Preparation Example 1 was repeated, with the only difference being that a commercial activated alumina carrier (Jiulong Chemical, JL-C-02 activated alumina) was used instead of diatomaceous earth. The activated alumina carrier did not contain a modifier. The specific surface area of ​​the activated alumina carrier was 170 m 2 / g, and the total pore volume is 0.6cm 3 / g, and the average pore size is 12nm.

[0150] Preparation Example 6: Preparation of Catalyst D2 The method of Preparation Example 1 was repeated, with the only difference being that commercial silica (Q-15 series SiO2 carrier from Fuji, Japan) was used instead of diatomaceous earth. The silica carrier did not contain a modifier. The specific surface area of ​​the silica carrier was 200 m 2 / g, total pore volume is 1.0cm 3 / g, and the average pore size is 15nm.

[0151] Example 1 The method of the present invention is as follows Figure 1 100 kg of catalyst 1 prepared in Preparation Example 1 was weighed and loaded into the fixed bed reactor. The gas phase space velocity of the reactor was set at 20000 h / min. -1Calculation, purchased dimethyl maleate (DMM) raw material (Hengli New Materials Co., Ltd.), feed components and feed conditions are shown in Table 1. The feed rate of DMM is 38kg / h, the molar ratio of DMM raw material to circulating hydrogen is 1:300, the reaction pressure is 3.0MPaG, and the reaction temperature is 190℃. The DMM feed is heated to 190℃ by the heater, and instantly vaporizes after entering the gas-liquid separator. A small amount of unvaporized heavy component impurities are separated and discharged. After gasification, the DMM and hydrogen mixture is added to the reactor from the bottom of the reactor, and the bed temperature difference of the reactor is monitored by the temperature measuring point of the reactor. The bed temperature difference of the fixed bed reactor ∆t≤0.1℃, and the bed pressure drop of the fixed bed reactor ∆P≤0.1MPa.

[0152] Table 1

[0153] The reactants are taken out from the top of the reactor, and after heat recovery, the gaseous reactants are condensed into a liquid phase to obtain a crude DMS product, which is subjected to chromatographic analysis. The conversion rate is calculated based on the consumption of DMM, and the selectivity is calculated based on the DMS content in the reaction liquid.

[0154] The crude DMS reaction liquid is sent to the distillation unit for further purification and separation. The first distillation is used to perform preliminary separation of the crude DMS, remove light components such as methanol and dimethyl ether contained in the crude DMS, and distill the light components from the top of the tower. The operating pressure is 20kPaA and the operating temperature is 165℃.

[0155] The second distillation tower is a product tower, which is used to refine the final DMS product after removing the light components. The operating pressure is 3kPaA and the temperature is 172°C. The industrial-grade DMS is produced from the top of the tower, the polymerization-grade DMS is produced in the middle, and the heavy components are discharged from the bottom of the tower. The purity of the polymerization-grade DMS is 99.93%.

[0156] The third distillation tower is a light component tower, which recovers DMS in the light component. The top of the tower is the light component and the bottom of the tower is crude DMS. The operating pressure is 10kPaA and the operating temperature is 168°C.

[0157] Example 2 The method of Example 1 was repeated, with the only difference being that Catalyst 2 prepared in Preparation Example 2 was used instead of Catalyst 1.

[0158] Example 3 The method of Example 1 was repeated, with the only difference being that Catalyst 3 prepared in Preparation Example 3 was used instead of Catalyst 1.

[0159] Example 4 The method of Example 1 was repeated, with the only difference being that Catalyst 4 prepared in Preparation Example 4 was used instead of Catalyst 1.

[0160] Comparative Example 1 The method of Example 1 was repeated, with the only difference being that Catalyst D1 obtained in Preparation Example 5 was used instead of Catalyst 1.

[0161] Comparative Example 2 The method of Example 1 was repeated, with the only difference being that Catalyst D2 prepared in Preparation Example 6 was used instead of Catalyst 1.

[0162] Test Example 1 The crude DMS product obtained in the fixed bed reactor was directly tested for composition. The contents of the various components in the crude DMS and the performance of the catalyst are shown in Table 2.

[0163] 1. DMM conversion rate and DMS purity analysis were measured using Agilent 7890 chromatograph. The chromatographic analysis method was set as follows: Chromatographic column: CP-SIL8CB 50*0.32*1.2; Detector temperature: 300°C; Inlet temperature: 250°C; Split ratio: 25:1; Column flow rate: 2.4 mL / min.

[0164] 2. The calculation method of DMM conversion rate is as follows: , X A : The conversion rate calculated based on reactant A; A1: starting mass of reactant A; A2: the remaining mass of reactant A after reaction; Reactant A was DMM.

[0165] 3. Using DMM, the catalyst selectivity is calculated according to the following formula: , S: Selectivity; B: the mass of the reaction target product B; A1: starting mass of reactant A; A2: the remaining mass of reactant A after reaction;

[0166] The target product B is DMS, and the reactant A is DMM.

[0167] Table 2

[0168] Test Example 2 The refined DMS product obtained by three-stage distillation was analyzed for composition and color number.

[0169] The content of each component in the product was detected using the same method as in Test Example 1.

[0170] The color number and content of each component of the DMS product obtained after three-stage distillation are shown in Table 3.

[0171] The color number test is based on GB3143-1982 and measured by Lovibond Tintometer PFX190.

[0172] Table 3

[0173] “Trace amount” means the amount is very small, the detection peak is almost invisible, and the content is generally less than 1ppm.

[0174] From the above analysis results of the hydrogenation reaction (Table 1), it can be seen that the catalyst of the present invention has a good hydrogenation effect, the conversion rate and selectivity are better than other catalysts, and the side reaction of generating GBL is well suppressed, which provides conditions for distillation to obtain high-purity DMS. Furthermore, the use of the fixed bed reactor of the present invention can greatly increase the cold hydrogen circulation amount without affecting the pressure drop of the reactor, thereby eliminating the hot spot temperature of the catalyst bed, effectively suppressing the generation of various by-products, and making the purity of the polymer-grade DMS obtained after distillation ≥99.9%.

[0175] Application Examples The DMS product prepared in Example 1, commercially available succinic acid (Shandong Feiyang Chemical Co., Ltd., meeting the requirements of T / HNPCIA13-2019 superior products), commercially available succinic anhydride (Henan Energy Group Hebi Coal Chemical Co., Ltd., meeting the requirements of GB34686-2017 superior products), the DMS product prepared in Comparative Example 1 and the DMS product prepared in Comparative Example 2 were used as polymerization raw materials and applied to a 200L intermittent PBS polymerization test. The indicators of commercially available succinic acid and commercially available succinic anhydride are shown in Tables 4-5.

[0176] Table 4: Commercially available succinic acid indicators

[0177] Table 5: Commercially available succinic anhydride specifications

[0178] Feeding: Add the above-mentioned polymer raw materials and BDO into the reactor at a molar ratio of 1:1.2 at the same time, stir and mix. If the dissolution is not good, heat at 140°C for 1 hour, and then add the mixed slurry into the reactor for esterification reaction.

[0179] Esterification reaction: The reaction pressure is 10kPaG, the reaction temperature is 160±2℃, the reaction liquid in the reactor is sampled every 1h, and the DMS content in the reaction liquid is analyzed. After about 6h, the DMS content drops below 500ppm, and the esterification reaction is completed after it remains stable. The reaction liquid is transferred to the pre-polycondensation reactor for pre-polycondensation reaction.

[0180] Pre-polycondensation reaction: Tetraisopropyl titanate (TtiPO, CAS: 546-68-9) is used as a catalyst, the molar ratio of the catalyst to the polymerization raw material is 1:400, the reaction system is raised to 210°C, and maintained at a vacuum of 1 kPaA for 3 hours to obtain a pre-polycondensation product. All the reaction liquid in the pre-polycondensation reactor is sent to the final polycondensation reactor.

[0181] Final polycondensation reaction: reaction pressure is 65±2PaA, reaction temperature is 225±5℃, stirring speed is 210rpm, until the stirrer power stops increasing and slightly decreases, marking the end of final polycondensation, reaction time is about 3h. During the reaction, the stirrer speed is reduced in time to prevent excessive shear heat.

[0182] Granulation: The polycondensation product obtained in the final polycondensation reaction step is dried and then granulated to obtain the finished PBS. When the end point is reached, nitrogen is added and the material is discharged for granulation. The granulation process requires that the material be kept clean throughout the process to avoid external contamination.

[0183] Application test case The performance of the PBS prepared according to the corresponding example was tested by the following method. The test results are shown in Table 4.

[0184] The terminal carboxyl content refers to the content of carboxyl functional groups near the two ends of the PBS molecule, which is mainly used to characterize information such as the average molecular weight. The level of terminal carboxyl content directly affects the thermal stability, degradation rate and color of the product. The terminal carboxyl content is determined by titration analysis-photometry. The sample is refluxed and dissolved in a mixed solvent of o-cresol-CHCl3. After cooling, bromophenol blue is used as an indicator and titrated with sodium hydroxide-ethanol standard titrant. The terminal carboxyl content of PBS is calculated based on the consumption of the standard titrant. The formula is as follows: , Where: Indicates the volume of sodium hydroxide-ethanol standard titration solution consumed by the sample, mL; Indicates the volume of sodium hydroxide-ethanol standard titration solution consumed in blank, mL; Indicates the concentration of sodium hydroxide-ethanol standard titration solution, mol / L; Indicates the sample weight, g.

[0185] The melt index test was carried out according to ASTM-D1238 method using Ray-Ran MFR300.

[0186] The oxidation resistance was characterized by oxidation induction time and oxidation induction temperature according to ASTM D3895-14 method using TGA / DSC 3 + Type differential scanning calorimeter. In order to eliminate the thermal history of the sample during the test, the sample was first heated to 150°C at 20°C / min, kept warm for 5 minutes, and then cooled to 25°C at a rate of 20°C / min before the test conditions were met. Take a sample with a mass of 5.5±0.5 mg that meets the test conditions and heat it to 220°C in a nitrogen atmosphere. After isothermally maintaining at 220°C for 5 minutes, switch the nitrogen atmosphere to an oxygen atmosphere (both gas flow rates are 50 ml / min), and then maintain the temperature for 120 minutes, or until a peak appears in the differential scanning calorimetry (DSC) curve. Use an uncovered aluminum crucible. All samples were measured twice.

[0187] It can be seen from Table 6 that the performance of the PBS plastic prepared by using the DMS prepared in Example 1 as a raw material is better than that of the PBS prepared by using Comparative Examples 1-2, commercially available succinic acid, and commercially available succinic anhydride as raw materials.

[0188] Table 6

[0189] In summary, the use of the catalyst of the present invention and the method for producing dimethyl succinate by hydrogenating dimethyl maleate of the present invention can effectively improve the selectivity of DMS and improve the purity of the DMS product. Further, the fixed bed reactor of the present invention is used to control the bed temperature difference, which can reduce energy consumption and production costs, thereby improving the economic benefits of the production of degradable plastic PBS.

Claims

1. A catalyst, characterized in that The catalyst includes a composite carrier and an active metal Ni loaded on the composite carrier. The composite carrier is composited by a modifier and a natural mineral. The modifier includes zirconium and a rare earth metal. The natural mineral is selected from one or more of diatomaceous earth, sepiolite, halloysite, attapulgite, vermiculite and molybdenite. The rare earth metal is selected from one or more of yttrium, lanthanum, cerium, neodymium, samarium, europium, gadolinium and ytterbium.

2. The catalyst according to claim 1, characterized in that The catalyst has one or more of the following characteristics: The modifier consists of zirconium and rare earth metal; In the modifier, the molar ratio of zirconium to rare earth metal is 1:(0.001-0.5); The content of zirconium element is 0.01-30wt% of the content of the natural mineral; The specific surface area of ​​the composite carrier is 150-450m 2 / g; The total pore volume of the composite carrier is 0.15-1.5m 3 / g; The average pore size of the composite carrier is 5-30 nm; In the catalyst, the content of the active metal Ni is 1-40wt%.

3. A method for preparing the catalyst according to claim 1 or 2, characterized in that: The method comprises the steps of: (1) subjecting an aqueous solution containing a zirconium salt and a rare earth metal salt to a high pressure hydrothermal method to obtain a modifier; (2) allowing the modifier and the natural mineral to form a precipitate in a dispersant, collecting the precipitate by filtration, drying, and calcining to obtain a composite carrier; (3) immersing the composite support in an aqueous solution containing a nickel salt, filtering out the solution, drying, and calcining to obtain a catalyst precursor; (4) subjecting the catalyst precursor to a reduction reaction in a reducing gas to obtain the catalyst.

4. The method according to claim 3, characterized in that Step (1) has one or more of the following characteristics: The zirconium salt is selected from one or more of zirconium nitrate, zirconium chloride and zirconium alkoxide; The rare earth metal salt is selected from one or more of Gd(NO3)3·6H2O, Yb(NO3)3·5H2O, Y(NO3)3·4H2O, La(NO3)3·xH2O, Ce(NO3)3·6H2O, Nd(NO3)3·6H2O, Sm(NO3)3·6H2O, Eu(NO3)3·5H2O and chloride salts of the rare earth metal; In the aqueous solution, the concentration of zirconium salt is 2-2.5 mol / L; In the aqueous solution, the molar ratio of zirconium to rare earth metal is 1:(0.001-0.5); The reaction pressure of the high pressure hydrothermal method is 1.0-3.0 MPa; The reaction temperature of the high pressure hydrothermal method is 110-150°C; The reaction time of the high pressure hydrothermal method is 3-24h.

5. The method according to claim 3, characterized in that Step (2) has one or more of the following characteristics: The amount of the modifier added is such that the content of zirconium in the modifier is 0.01-30wt% of the content of the natural mineral; The condition for forming the precipitate is: stirring and dispersing the modifier and the natural mineral under heating conditions, and then standing under heating conditions until a precipitate is formed; The drying temperature is 100-150°C; The drying time is 2-48h; The calcination temperature is 150-800°C; The calcination time is 0.5-12h; Before carrying out step (2), the natural mineral is first subjected to heat treatment and / or chemical treatment.

6. The method according to claim 3, characterized in that Step (3) has one or more of the following characteristics: The nickel salt is selected from one or more of nickel nitrate, nickel chloride and nickel sulfate; The aqueous solution containing nickel salt also includes an organic acid; In the aqueous solution containing nickel salt, the concentration of nickel salt is 0.01-2.0 g / mL; The immersion time is 20-240min; The drying temperature is 80-120°C; The drying time is 2-12h; The calcination temperature is 150-550°C; The calcination time is 0.5-50h.

7. The method according to claim 3, characterized in that Step (4) has one or more of the following characteristics: The reducing gas includes hydrogen and a protective gas, and the protective gas is selected from one or more of nitrogen, helium and argon; The temperature of the reduction reaction is 130-650°C; The reduction reaction system is heated to a set temperature at a heating rate not exceeding 10°C / h; After the temperature of the reduction reaction system reaches the set value, it is maintained for 4-48 hours.

8. A method for preparing dimethyl succinate, characterized in that: The method comprises step (a): under the catalytic action of a catalyst, dimethyl maleate is subjected to a hydrogenation reaction with hydrogen to obtain a crude dimethyl succinate product, wherein the catalyst is the catalyst according to claim 1 or 2 or a catalyst obtained by the method according to any one of claims 3 to 7.

9. The method according to claim 8, characterized in that: The method further comprises step (b): distilling the crude dimethyl succinate to obtain dimethyl succinate; and / or, Step (a) has one or more of the following features: The molar ratio of dimethyl maleate to hydrogen is 1:(100-500); The reaction pressure is 1.0-10.0MPaG; The reaction temperature is 110-230°C; The gas phase space velocity of the reactor is 20000-30000 h -1 ; The conversion rate of dimethyl maleate in step (a) is ≥ 99.9%; The selectivity of dimethyl succinate in step (a) is ≥99%; In step (a), the content of γ-butyrolactone in the crude dimethyl succinate is ≤5wt%.

10. A method for preparing polybutylene succinate, characterized in that: The method comprises the steps of: (A) providing a catalyst according to claim 1 or 2, or providing a catalyst prepared by the method according to any one of claims 3 to 7; (B) under the catalytic action of the catalyst, hydrogenating dimethyl maleate with hydrogen to prepare dimethyl succinate; (C) subjecting the dimethyl succinate obtained in step (B) to a polymerization reaction with 1,4-butanediol to obtain polybutylene succinate.

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