A method for continuously synthesizing isoprene based on enal liquid phase method

Abstract

The present invention provides an application of a catalyst in the synthesis of isoprene by an alkenal liquid phase method; the catalyst comprises a modified rare earth phosphate catalyst; the general formula of the modified rare earth phosphate is A x B y PO4·SiO2. The present invention uses tert-butyl alcohol, methyl tert-butyl ether and formaldehyde as raw materials, synthesizes isoprene by two-stage continuous reaction, controls formaldehyde side reaction, develops multi-phase recoverable catalyst, especially uses the modified rare earth phosphate catalyst in one-stage reaction, adopts low olefin-aldehyde ratio and lower reaction temperature to reduce formaldehyde side reaction, improves olefin source utilization and product production efficiency, and saves isobutylene recovery and hydration process.

Description

Technical Field

[0001] The invention belongs to the technical field of synthesizing isoprene by enal method, relates to application of a catalyst in synthesizing isoprene by enal liquid phase method and a method for synthesizing isoprene by enal liquid phase method, and particularly relates to a method and a catalyst for continuously synthesizing isoprene by enal liquid phase method. Background Art

[0002] Isoprene is the key raw material for synthesizing isoprene rubber, and is also the basic raw material for synthesizing isoprene latex, pharmaceutical intermediates, spices and cross-linking agents, etc. At present, the main method for producing isoprene is C5 separation, and this process yield is low (less than 1.7% of the input raw material), and a rubber device of 100,000 t / a requires an ethylene device of 5 or 6 million tons to meet the supply of isoprene raw materials, and among many chemical synthesis methods, the olefin aldehyde method for synthesizing isoprene has obvious advantages economically. Russia has successively carried out the research of olefin aldehyde two-step method and one-step method (gas phase), and wherein the two-step method for synthesizing isoprene has been industrialized, although the olefin aldehyde one-step method has a short process, the product is easily refined, and each energy consumption is significantly reduced, but there is no industrialized report at present.

[0003] The key to the technology of synthesizing isoprene by enal method is to control the side reaction of formaldehyde and olefins (isobutylene, isoprene) to improve the selectivity. The reaction temperature of the one-step method is relatively high (300℃), the side reaction of formaldehyde is serious, there are many by-products, many high-boiling point compounds are generated, and olefin compounds are easily involved in the carbon formation reaction, and the yield is difficult to exceed 70%. Due to the use of tower reactors and multi-stage separation devices, the advantages of this process can only be reflected when the device scale is large. In contrast, the reaction temperature of the enal liquid phase method is mild (<200℃), the side reaction is highly controllable, and the requirements for equipment and process are low. It has many advantages: ① It reduces the consumption of raw materials and energy for isoprene production; ② It improves the ecological indicators of the production process and reduces the emission of wastewater and waste gas; ③ The product has high purity and low impurity content, which can reduce the cost of isoprene polymerization (polymerization-grade isoprene has strict control over the impurity content, usually requiring isoprene purity>99.4%, cyclopentadiene content<3μg / g, and alkyne content<10μg / g). In 1972, Sumitomo Chemical Co., Ltd. of Japan developed a one-step method for synthesizing isoprene, which uses isobutylene or tert-butyl alcohol and formaldehyde as raw materials. The reaction is carried out in liquid phase at 149-160°C, and the residence time in the reactor is 30-50 minutes. The reaction process is that isobutylene and formaldehyde condense to form intermediate products (mainly 4,4-dimethyl-1,3-dioxane, 3-methyl-1,3-butanediol, 3-methyl-3-butene-1-ol, 3-methyl-2-butene-1-ol), and the intermediate products are cracked to form isoprene. The generation and cracking of the intermediate products are carried out in the same reactor. In order to suppress side reactions, the molar ratio of formaldehyde to isobutylene or tert-butyl alcohol is 1:1.2 (Oil & Gas Journal, 1972, 70(26)). Japanese Kuraray (EP83110225.6, US4511751, US4593145) reported the process in detail, using sulfuric acid, sulfuric acid or boric acid as a catalyst, firstly introducing an acidic aqueous solution into the reactor, heating to 170-180°C, forming a pressure of about 10atm, introducing tert-butyl alcohol, formaldehyde and water at a certain rate, and after the system is stable, the pressure is about 12-20atm, and the gaseous product flows out from the top of the reactor and is collected after cooling. Control the reaction time, the molar ratio of C4 / formaldehyde>3, when the molar ratio is less than 3, the isoprene yield decreases, from the perspective of selectivity, the larger the olefin ratio, the better, but too large an olefin ratio does not significantly improve the isoprene yield, and will significantly increase the heat consumption.

[0004] Eurochem has developed a new environmentally friendly enal liquid phase process (two-stage process), which is slightly different from the above process. It uses formaldehyde and tert-butyl alcohol as raw materials to first generate DMD, and then reacts DMD with tert-butyl alcohol in the liquid phase to generate isoprene. This method can effectively improve the selectivity of formaldehyde. In 2003, the Nizhnekamsk Petrochemical Company of Russia applied the enal liquid phase process to produce isoprene on a large scale. At present, the company has replaced the original enal two-step process technology with this technology, with a production capacity of 180,000 t / a (Petrochemicals, 1(2):103-104, Fine Petrochemicals, 2012, 29, 77-82). According to the published patent (EP2157072A1), the process uses phosphoric acid as the base catalyst. The typical result is that 9L phosphoric acid solution (7%) is added to the reactor, and the temperature is raised to 110°C and 160°C respectively. 40% formaldehyde (256.6g / h) and 88% tert-butanol (860g / h) are added to reactor 1. The pressure of the reactor is 22atm. The product of reactor 1 is mixed with tert-butanol (2015.9g / h) and enters reactor 2. The pressure of reactor 2 is 12atm. The selectivity of formaldehyde and isobutylene is 75% and 82% respectively. The intermediate products 4,4-dimethyl-1,3-dioxane, 3-methyl-1,3-butanediol, 3-methyl-3-butene-1-ol, etc. are the intermediate products of the liquid phase synthesis of isoprene, and are also the key to restricting the production efficiency of isoprene. Although the high olefinic aldehyde ratio effectively inhibits the formaldehyde side reaction, it also reduces the production efficiency of the intermediate products. The recovery and hydration reuse of a large amount of isobutylene also generates more energy consumption.

[0005] Therefore, how to find a more suitable method for synthesizing isoprene by the enaldehyde method to further inhibit the occurrence of side reactions and improve production efficiency has become one of the focuses of widespread attention of forward-looking researchers in the industry. Summary of the invention

[0006] In view of this, the technical problem to be solved by the present invention is to provide an application of a catalyst in the synthesis of isoprene by an olefinic aldehyde liquid phase method and a method for synthesizing isoprene by an olefinic aldehyde liquid phase method, in particular, a method for continuously synthesizing isoprene by an olefinic aldehyde liquid phase method. The present invention designs a modified rare earth phosphate catalyst with a specific composition for the synthesis of isoprene by an olefinic aldehyde liquid phase method, which not only reduces the formaldehyde side reaction and improves the isoprene production efficiency, but also the solid phase catalyst is easier to recover for the liquid phase process, and the reaction conditions are mild, the operation is simple, and there is a prospect for large-scale synthesis.

[0007] The present invention provides the use of a catalyst in the synthesis of isoprene by an alkenal liquid phase method;

[0008] The catalyst includes a modified rare earth phosphate catalyst;

[0009] The general formula of the modified rare earth phosphate is A x By PO4·SiO2;

[0010] Among them, x is 0.7 to 1.4, y is 0.02 to 0.3;

[0011] A is one or more of La, Ce, Pr, Nd and Gd;

[0012] B is one or more of Mo, Zr, Cu, Zn, W, V and Nb.

[0013] Preferably, the catalyst is a heterogeneous catalyst;

[0014] The catalyst also includes a metal-modified hydroxyapatite catalyst;

[0015] The metal includes one or more of Cu, Ce, Fe and Zn;

[0016] The mass content of the metal in the metal-modified hydroxyapatite is 2wt% to 20wt%;

[0017] The size of the metal particles in the metal-modified hydroxyapatite is 10 to 50 nm.

[0018] Preferably, the mass content of SiO2 in the modified rare earth phosphate is 15wt% to 45wt%;

[0019] The synthesis comprises continuous synthesis;

[0020] The synthesis is specifically a two-stage synthesis;

[0021] The modified rare earth phosphate catalyst is a one-stage synthesis catalyst;

[0022] The metal-modified hydroxyapatite catalyst is a catalyst for two-stage synthesis.

[0023] The present invention also provides a method for synthesizing isoprene by an alkenal liquid phase method, comprising the following steps:

[0024] 1) feeding tert-butyl alcohol and / or methyl tert-butyl ether, a modified rare earth phosphate catalyst and formaldehyde into a first reaction device for reaction to obtain a liquid phase reaction system;

[0025] 2) sending tert-butyl alcohol and / or methyl tert-butyl ether, the metal-modified hydroxyapatite catalyst, and the liquid phase reaction system obtained in the above steps into a second reaction device for further reaction to obtain isoprene.

[0026] Preferably, the olefinic aldehyde ratio of the raw material in step 1) is (0.2-1.6):1;

[0027] The reaction temperature is 120-145°C;

[0028] The reaction time is 10 to 60 minutes;

[0029] The reaction pressure is less than or equal to 10 atm;

[0030] The feed rate in step 1) is 5-50 ml / min;

[0031] After the reaction, the solid phase catalyst is filtered to obtain a liquid phase reaction system;

[0032] The liquid phase reaction system includes 4,4-dimethyl-1,3-dioxane and 3-methyl-1,3-butanediol.

[0033] Preferably, the molar equivalent ratio of tert-butyl alcohol and / or methyl tert-butyl ether in step 2) to formaldehyde in step 1) is (2-10):1;

[0034] The feed rate in step 2) is 5-50 ml / min;

[0035] The temperature of the second reaction is 145-165°C;

[0036] The second reaction time is 10 to 60 minutes;

[0037] The pressure of the second reaction is less than or equal to 16 atm.

[0038] Preferably, the step of separating the catalyst is further included after the second reaction;

[0039] The separated liquid phase includes an oil phase and a water phase;

[0040] The height of the water phase is no more than one-half and no less than one-quarter of the height of the reaction zone of the reactor;

[0041] The height of the oil phase is no more than one-half and no less than one-quarter of the height of the reaction zone of the reactor;

[0042] In the method, the generated isobutylene is hydrated to obtain tert-butyl alcohol, and the process returns to step 1).

[0043] Preferably, the preparation method of the modified rare earth phosphate catalyst comprises the following steps:

[0044] The mixed solution of the rare earth metal soluble compound and the transition metal soluble compound is mixed with the silicide, the pH value is adjusted to obtain a precipitate, the precipitate is dried, the precipitate is subjected to step-by-step temperature ball milling with a phosphoric acid solution, and the precipitate is calcined to obtain a modified rare earth phosphate catalyst;

[0045] The rare earth metal soluble compound includes one or more of lanthanum nitrate, lanthanum chloride, cerium nitrate, cerium chloride, cerium ammonium nitrate, cerium perchlorate, praseodymium nitrate, praseodymium chloride, neodymium chloride, neodymium nitrate and gadolinium nitrate;

[0046] The transition metal soluble compound includes one or more of ammonium molybdate, molybdenum chloride, phosphomolybdic acid, zirconium nitrate, zirconium oxynitrate, copper nitrate, copper chloride, copper sulfate, copper acetate, zinc nitrate, zinc sulfate, zinc chloride, phosphotungstic acid, ammonium tungstate, tungsten chloride, ammonium metavanadate, vanadium trichloride, vanadium trichloride, niobic acid, niobium oxalate and niobium oxalate complex;

[0047] The total concentration of the metal compounds in the mixed solution is 10 to 80 g / L;

[0048] The silicide includes one or more of ethyl orthosilicate, water glass and silica sol;

[0049] The mixing temperature is 50-80°C.

[0050] Preferably, the pH value is 8 to 10;

[0051] The drying temperature is 50-80°C;

[0052] The drying time is 3 to 10 hours;

[0053] The concentration of the phosphoric acid solution is 3 to 30 g / L;

[0054] The starting and ending temperatures of the step-by-step temperature ball milling are 15 to 200° C.

[0055] The heating rate of the step-by-step heating ball mill is 1°C to 20°C;

[0056] The residence time of the step is 0.5 to 3.5 hours;

[0057] The calcination temperature is 400°C to 600°C;

[0058] The calcination time is 3 to 10 hours.

[0059] Preferably, the preparation method of the metal-modified hydroxyapatite catalyst comprises the following steps:

[0060] The hydroxyapatite is calcined, placed in a modified metal compound solution, subjected to an exchange-adsorption-deposition process, and calcined again to obtain a metal-modified hydroxyapatite catalyst;

[0061] The calcination temperature is 800-1500°C;

[0062] The calcination time is 2 to 8 hours;

[0063] The modified metal compound solution includes one or more of copper nitrate, cupric chloride, cuprous chloride, cupric sulfate, cupric oxalate, ferric nitrate, ferric chloride, ferrous nitrate, ferrous chloride, ferric bromide, ferrous bromide, ferric sulfate, ferrous sulfate, cerium nitrate, cerium chloride, cerium ammonium nitrate, cerium perchlorate, zinc chloride, zinc sulfate, zinc nitrate and zinc dihydrogen phosphate;

[0064] The ion concentration of the modified metal in the modified metal compound solution is 0.02 to 1.2 g / ml;

[0065] The pH value of the system during the exchange-adsorption-deposition process is 5 to 8;

[0066] The time of the exchange-adsorption-deposition process is 2 to 24 hours;

[0067] The re-baking temperature is 600-1300°C;

[0068] The re-roasting time is 2 to 8 hours.

[0069] The present invention provides an application of a catalyst in the synthesis of isoprene by an alkenal liquid phase method; the catalyst comprises a modified rare earth phosphate catalyst; the general formula of the modified rare earth phosphate is A x B y PO4·SiO2; wherein x is 0.7 to 1.4, y is 0.02 to 0.3; A is one or more of La, Ce, Pr, Nd and Gd; B is one or more of Mo, Zr, Cu, Zn, W, V and Nb. Compared with the prior art, the present invention aims at the deficiencies existing in the existing enaldehyde liquid phase method for synthesizing isoprene, and designs a modified rare earth phosphate catalyst specially used for the reaction process, and the catalyst is a solid phase catalyst, which is easier to recover and recycle in the liquid phase synthesis process. The modified rare earth phosphate catalyst provided by the present invention is combined with the two-stage continuous reaction synthesis process provided by the present invention, and is further combined with a modified hydroxyapatite catalyst, thereby reducing the formaldehyde side reaction, improving the isoprene production efficiency, and facilitating the recovery and recycling of the catalyst.

[0070] The present invention uses tert-butyl alcohol, methyl tert-butyl ether and formaldehyde as raw materials, and synthesizes isoprene by two-stage continuous reaction, controls the side reaction of formaldehyde, and develops a multi-phase recyclable catalyst. The first stage: low olefin-aldehyde ratio, 120-145°C, using modified rare earth phosphate (A x B yPO4·SiO2) is used as a catalyst to catalyze formaldehyde, tert-butyl alcohol, and methyl tert-butyl ether to synthesize intermediate products such as 4,4-dimethyl-1,3-dioxane and 3-methyl-1,3-butanediol. The liquid phase product is controlled to be a uniform phase. The reaction pressure is less than 10atm. The conversion rate and selectivity of tert-butyl alcohol and methyl tert-butyl ether are greater than 92%; the second stage: the intermediate product and tert-butyl alcohol and methyl tert-butyl ether are kept at 145-165°C, the olefin source is excessive, and the modified hydroxyapatite catalyst is used to convert and synthesize isoprene. The reaction pressure is less than 16atm, and the yield can reach 80%. The first stage reaction uses a low olefin aldehyde ratio and a lower reaction temperature to reduce formaldehyde side reactions, improve the utilization rate of olefin sources and product production efficiency, and omit the isobutylene recovery and hydration process.

[0071] Experimental results show that by using the catalyst provided by the present invention and a two-stage continuous reaction synthesis method, in the first stage reaction, the conversion rate and selectivity of the raw materials tert-butyl alcohol and methyl tert-butyl ether are both greater than 92%; and in the second stage reaction, by using a modified hydroxyapatite catalyst, the yield can reach 80%. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 A schematic diagram of the reaction process for continuously synthesizing isoprene by the enaldehyde liquid phase method provided by the present invention;

[0073] Figure 2 The product distribution and regulation of the process of continuous synthesis of isoprene based on the enal liquid phase method provided by the present invention 1;

[0074] Figure 3 Product distribution and regulation of the process of continuous synthesis of isoprene by the enal liquid phase method provided by the present invention 2;

[0075] Figure 4 This is a gas chromatography-mass spectrometry full component analysis diagram of the process of continuous synthesis of isoprene by the enal liquid phase method provided by the present invention. DETAILED DESCRIPTION

[0076] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the invention.

[0077] All raw materials of the present invention are not particularly limited in their sources and can be purchased from the market or prepared according to conventional methods well known to those skilled in the art.

[0078] There is no particular limitation on the purity of all raw materials in the present invention. The present invention preferably uses analytically pure raw materials or raw materials with purity requirements conventional in the field of synthesizing isoprene by the enal liquid phase method.

[0079] All raw materials and process steps of the present invention, their brands or abbreviations are conventional brands or abbreviations in the art, and each brand or abbreviation is clear and definite in the field of its related use. Those skilled in the art can purchase them from the market or prepare them by conventional methods, or implement them with corresponding equipment according to the brands, abbreviations and corresponding uses.

[0080] The present invention provides the use of a catalyst in the synthesis of isoprene by an alkenal liquid phase method;

[0081] The catalyst includes a modified rare earth phosphate catalyst;

[0082] The general formula of the modified rare earth phosphate is A x B y PO4·SiO2;

[0083] Among them, x is 0.7 to 1.4, y is 0.02 to 0.3;

[0084] A is one or more of La, Ce, Pr, Nd and Gd;

[0085] B is one or more of Mo, Zr, Cu, Zn, W, V and Nb.

[0086] In the present invention, the general formula of the modified rare earth phosphate is A x B y PO4·SiO2;

[0087] Here, x is 0.7 to 1.4, may be 0.8 to 1.3, preferably 0.9 to 1.2, and more preferably 1.0 to 1.1. y is 0.02 to 0.3, may be 0.05 to 0.25, and preferably 0.1 to 0.2.

[0088] In the present invention, A is one or more of La, Ce, Pr, Nd and Gd, and may be La, Ce, Pr, Nd or Gd.

[0089] In the present invention, B is one or more of Mo, Zr, Cu, Zn, W, V and Nb, and may be Mo, Zr, Cu, Zn, W, V or Nb.

[0090] In the present invention, the catalyst is preferably a heterogeneous catalyst.

[0091] In the present invention, the catalyst also preferably includes a metal-modified hydroxyapatite catalyst.

[0092] In the present invention, the metal preferably includes one or more of Cu, Ce, Fe and Zn, and more preferably Cu, Ce, Fe or Zn.

[0093] In the present invention, the mass content of metal in the metal-modified hydroxyapatite is preferably 2wt% to 20wt%, more preferably 5wt% to 17wt%, and more preferably 8wt% to 14wt%.

[0094] In the present invention, the size of the metal particles in the metal-modified hydroxyapatite is preferably 10 to 50 nm, more preferably 15 to 45 nm, more preferably 20 to 40 nm, and more preferably 25 to 35 nm.

[0095] In the present invention, the mass content of SiO2 in the modified rare earth phosphate is preferably 15wt% to 45wt%, more preferably 20wt% to 40wt%, and more preferably 25wt% to 35wt%.

[0096] In the present invention, the synthesis preferably comprises continuous synthesis.

[0097] In the present invention, the synthesis is preferably a two-stage synthesis.

[0098] In the present invention, the modified rare earth phosphate catalyst is preferably a one-stage synthesis catalyst.

[0099] In the present invention, the metal-modified hydroxyapatite catalyst is preferably a catalyst for two-stage synthesis.

[0100] The present invention provides a method for synthesizing isoprene by an alkenal liquid phase method, comprising the following steps:

[0101] 1) feeding tert-butyl alcohol and / or methyl tert-butyl ether, a modified rare earth phosphate catalyst and formaldehyde into a first reaction device for reaction to obtain a liquid phase reaction system;

[0102] 2) sending tert-butyl alcohol and / or methyl tert-butyl ether, the metal-modified hydroxyapatite catalyst, and the liquid phase reaction system obtained in the above steps into a second reaction device for further reaction to obtain isoprene.

[0103] The invention firstly feeds tert-butyl alcohol and / or methyl tert-butyl ether, a modified rare earth phosphate catalyst and formaldehyde into a first reaction device for reaction to obtain a liquid phase reaction system.

[0104] In the present invention, the olefinic aldehyde ratio of the raw material in step 1) is preferably (0.2-1.6):1, more preferably (0.4-1.4):1, more preferably (0.6-1.2):1, and more preferably (0.8-1.2):1.

[0105] In the present invention, the reaction temperature is preferably 120-145°C, more preferably 125-140°C, and more preferably 130-135°C.

[0106] In the present invention, the reaction time is preferably 10 to 60 minutes, more preferably 20 to 50 minutes, and even more preferably 30 to 40 minutes.

[0107] In the present invention, the reaction pressure is preferably less than or equal to 10 atm, more preferably less than or equal to 9 atm, and more preferably less than or equal to 8 atm.

[0108] In the present invention, the feed rate in step 1) is preferably 5 to 50 ml / min, more preferably 15 to 40 ml / min, and more preferably 25 to 30 ml / min.

[0109] In the present invention, after filtering the solid phase catalyst after the reaction, preferably a liquid phase reaction system is obtained.

[0110] In the present invention, the liquid phase reaction system preferably includes 4,4-dimethyl-1,3-dioxane and 3-methyl-1,3-butanediol.

[0111] In the present invention, tert-butyl alcohol and / or methyl tert-butyl ether, the metal-modified hydroxyapatite catalyst and the liquid phase reaction system obtained in the above steps are finally sent to a second reaction device for further reaction to obtain isoprene.

[0112] In the present invention, the molar equivalent ratio of tert-butyl alcohol and / or methyl tert-butyl ether in step 2) to formaldehyde in step 1) is preferably (2-10):1, more preferably (3-9):1, more preferably (4-8):1, and more preferably (5-7):1.

[0113] In the present invention, the feed rate in step 2) is preferably 5 to 50 ml / min, more preferably 15 to 40 ml / min, and more preferably 25 to 30 ml / min.

[0114] In the present invention, the temperature of the secondary reaction is preferably 145 to 165°C, more preferably 149 to 161°C, and more preferably 153 to 157°C.

[0115] In the present invention, the re-reaction time is preferably 10 to 60 minutes, more preferably 20 to 50 minutes, and more preferably 30 to 40 minutes.

[0116] In the present invention, the pressure of the secondary reaction is preferably less than or equal to 16 atm, more preferably less than or equal to 15 atm, and more preferably less than or equal to 14 atm.

[0117] In the present invention, the second reaction preferably further includes a catalyst separation step.

[0118] In the present invention, the separated liquid phase preferably includes an oil phase and an aqueous phase.

[0119] In the present invention, the height of the aqueous phase is preferably not more than one-half, more preferably one-third, preferably not less than one-quarter, more preferably not less than one-fifth of the height of the reaction zone of the reactor.

[0120] In the present invention, the height of the oil phase is preferably not more than one half, more preferably one third, preferably not less than one quarter, more preferably not less than one fifth of the height of the reaction zone of the reactor.

[0121] In the present invention, in the method, the generated isobutylene is hydrated to obtain tert-butyl alcohol, which is preferably returned to step 1).

[0122] In the present invention, the preparation method of the modified rare earth phosphate catalyst preferably comprises the following steps:

[0123] The mixed solution of rare earth metal soluble compound and transition metal soluble compound is mixed with silicide, and the pH value is adjusted to obtain a precipitate, which is dried, ball-milled with a phosphoric acid solution by step-by-step temperature increase, and then calcined to obtain a modified rare earth phosphate catalyst.

[0124] In the present invention, the rare earth metal soluble compound preferably includes one or more of lanthanum nitrate, lanthanum chloride, cerium nitrate, cerium chloride, ammonium cerium nitrate, cerium perchlorate, praseodymium nitrate, praseodymium chloride, neodymium chloride, neodymium nitrate and gadolinium nitrate, and more preferably includes lanthanum nitrate, lanthanum chloride, cerium nitrate, cerium chloride, ammonium cerium nitrate, cerium perchlorate, praseodymium nitrate, praseodymium chloride, neodymium chloride, neodymium nitrate or gadolinium nitrate.

[0125] In the present invention, the transition metal soluble compound preferably includes one or more of ammonium molybdate, molybdenum chloride, phosphomolybdic acid, zirconium nitrate, zirconyl nitrate, copper nitrate, copper chloride, copper sulfate, copper acetate, zinc nitrate, zinc sulfate, zinc chloride, phosphotungstic acid, ammonium tungstate, tungsten chloride, ammonium metavanadate, vanadium trichloride, vanadium oxychloride, niobic acid, niobium oxalate and niobium oxalate complex, and more preferably includes ammonium molybdate, molybdenum chloride, phosphomolybdic acid, zirconium nitrate, zirconyl nitrate, copper nitrate, copper chloride, copper sulfate, copper acetate, zinc nitrate, zinc sulfate, zinc chloride, phosphotungstic acid, ammonium tungstate, tungsten chloride, ammonium metavanadate, vanadium trichloride, vanadium oxychloride, niobic acid, niobium oxalate or niobium oxalate complex.

[0126] In the present invention, the total concentration of the metal compounds in the mixed solution is preferably 10 to 80 g / L, more preferably 25 to 65 g / L, and even more preferably 40 to 50 g / L.

[0127] In the present invention, the silicide preferably includes one or more of tetraethyl orthosilicate, water glass and silica sol, and more preferably tetraethyl orthosilicate, water glass or silica sol.

[0128] In the present invention, the mixing temperature is preferably 50 to 80°C, more preferably 55 to 75°C, and even more preferably 60 to 70°C.

[0129] In the present invention, the pH value is preferably 8 to 10, more preferably 8.4 to 9.6, and more preferably 8.8 to 9.2.

[0130] In the present invention, the drying temperature is preferably 50-80°C, more preferably 55-75°C, and more preferably 60-70°C.

[0131] In the present invention, the drying time is 3 to 10 hours, preferably 4.5 to 8.5 hours, and more preferably 6 to 7 hours.

[0132] In the present invention, the concentration of the phosphoric acid solution is preferably 3 to 30 g / L, more preferably 8 to 25 g / L, and even more preferably 13 to 20 g / L.

[0133] In the present invention, the starting and ending temperatures of the step-temperature ball milling are preferably 15 to 200°C, more preferably 50 to 160°C, and even more preferably 90 to 120°C.

[0134] In the present invention, the heating rate of the step-temperature ball milling is preferably 1°C to 20°C, more preferably 5°C to 16°C, and more preferably 9°C to 12°C.

[0135] In the present invention, the residence time of the step is preferably 0.5 to 3.5 hours, more preferably 1.0 to 3.0 hours, and more preferably 1.5 to 2.5 hours.

[0136] In the present invention, the calcination temperature is preferably 400°C to 600°C, more preferably 440°C to 560°C, and more preferably 480°C to 520°C.

[0137] In the present invention, the calcination time is preferably 3 to 10 hours, more preferably 4 to 9 hours, more preferably 5 to 8 hours, and more preferably 6 to 7 hours.

[0138] In the present invention, the preparation method of the metal-modified hydroxyapatite catalyst preferably comprises the following steps:

[0139] The hydroxyapatite is calcined, placed in a modified metal compound solution, and subjected to an exchange-adsorption-deposition process, and calcined again to obtain a metal-modified hydroxyapatite catalyst.

[0140] In the present invention, the calcination temperature is preferably 800-1500°C, more preferably 950-1350°C, and even more preferably 1100-1200°C.

[0141] In the present invention, the calcination time is preferably 2 to 8 hours, more preferably 3 to 7 hours, and more preferably 4 to 6 hours.

[0142] In the present invention, the modified metal compound solution preferably includes one or more of copper nitrate, cupric chloride, cuprous chloride, cupric sulfate, cupric oxalate, ferric nitrate, ferric chloride, ferrous nitrate, ferrous chloride, ferric bromide, ferrous bromide, ferric sulfate, ferrous sulfate, cerium nitrate, cerium chloride, ammonium cerium nitrate, cerium perchlorate, zinc chloride, zinc sulfate, zinc nitrate and zinc dihydrogen phosphate, and more preferably includes copper nitrate, cupric chloride, cuprous chloride, cupric sulfate, cupric oxalate, ferric nitrate, ferric chloride, ferrous nitrate, ferrous chloride, ferric bromide, ferrous bromide, ferric sulfate, ferrous sulfate, cerium nitrate, cerium chloride, ammonium cerium nitrate, cerium perchlorate, zinc chloride, zinc sulfate, zinc nitrate or zinc dihydrogen phosphate.

[0143] In the present invention, the ion concentration of the modified metal in the modified metal compound solution is preferably 0.02 to 1.2 g / ml, more preferably 0.1 to 1.0 g / ml, more preferably 0.3 to 0.8 g / ml, and more preferably 0.5 to 0.6 g / ml.

[0144] In the present invention, the pH value of the system during the exchange-adsorption-deposition process is preferably 5-8, more preferably 5.5-7.5, and more preferably 6-7.

[0145] In the present invention, the time of the exchange-adsorption-deposition process is preferably 2 to 24 hours, more preferably 6 to 20 hours, and more preferably 10 to 16 hours.

[0146] In the present invention, the re-calcination temperature is preferably 600-1300°C, more preferably 750-1150°C, and even more preferably 900-1000°C.

[0147] In the present invention, the re-calcination time is preferably 2 to 8 hours, more preferably 3 to 7 hours, and more preferably 4 to 6 hours.

[0148] See also Figure 1 , Figure 1 The present invention provides a schematic diagram of the reaction process for continuously synthesizing isoprene by the enaldehyde liquid phase method.

[0149] The present invention is a complete and detailed overall technical solution, which can better reduce the side reaction of formaldehyde and further improve the olefin source utilization rate and product production efficiency of the olefin aldehyde liquid phase method for synthesizing isoprene. The method for continuously synthesizing isoprene by the olefin aldehyde liquid phase method preferably comprises the following steps:

[0150] A method for continuously synthesizing isoprene by an aldehyde liquid phase method, which uses formaldehyde, tert-butyl alcohol and methyl tert-butyl ether as raw materials and reacts in two stages;

[0151] (1) The first stage reaction is carried out at 120-145° C., the olefinic aldehyde ratio is controlled to be 0.2-1.6, the feed rate is 5-50 ml / min, the residence time of the material in the reactor is 10-60 minutes, and intermediate products such as 4,4-dimethyl-1,3-dioxane and 3-methyl-1,3-butanediol are synthesized. The liquid phase product is a homogeneous phase. The reaction pressure is regulated to be less than 10 atm. The catalyst is retained in the first stage reactor through a filter, and the material enters the second stage reactor.

[0152] (2) tert-butyl alcohol and methyl tert-butyl ether are added, and the equivalent ratio of tert-butyl alcohol and methyl tert-butyl ether to formaldehyde is maintained at 2-10, the feed rate is 5-50 ml / min, the reaction temperature is 145-165° C., the residence time of the material is 10-60 minutes, and the reaction pressure is adjusted to be less than 16 atm; isoprene is separated, and the liquid phase is divided into oil and water phases, the water phase does not exceed one half of the reactor and is not less than one quarter; the oil phase is controlled not to exceed one half of the reactor and is not less than one quarter; the generated isobutylene is separated and returned to the first reactor through hydration.

[0153] Specifically, the catalyst used in the first stage reactor is a modified rare earth phosphate (A x B y PO4·SiO2), A is a rare earth metal La, Ce, Pr, Nd, Gd, etc. It comes from lanthanum nitrate, lanthanum chloride, cerium nitrate, cerium chloride, ammonium cerium nitrate, cerium perchlorate, praseodymium nitrate, praseodymium chloride, neodymium chloride, neodymium nitrate, gadolinium nitrate, etc. B is a transition metal Mo, Zr, Cu, Zn, W, V, Nb, etc. It comes from ammonium molybdate, molybdenum chloride, phosphomolybdic acid, zirconium nitrate, zirconium oxynitrate, copper nitrate, copper chloride, copper sulfate, copper acetate, zinc nitrate, zinc sulfate, zinc chloride, phosphotungstic acid, ammonium tungstate, tungsten chloride, ammonium metavanadate, vanadium trichloride, vanadium trichloride, niobic acid, niobium oxalate, niobium oxalate complex, etc.

[0154] Specifically, the modified rare earth phosphate catalyst can be expressed in the form of A x B y PO4·SiO2, characterized in that A is one or more rare earth metals such as La, Ce, Pr, Nd, Gd, etc., and the atomic ratio x to P is 0.7 to 1.4, B is one or more transition metals such as Mo, Zr, Cu, Zn, W, V, Nb, etc., and the atomic ratio y to P is 0.02 to 0.3, A x B y PO4 in A x B y The content of PO4·SiO2 is 15 to 45 wt%.

[0155] Specifically, the preparation process is:

[0156] (1) Dissolve soluble compounds containing rare earth metals such as La, Ce, Pr, Nd, Gd, etc. in water, add soluble compounds containing Mo, Zr, Cu, Zn, W, V, Nb, etc., the total concentration of metal compounds in the solution is 10-80 g / L, and add silicon-containing compounds such as tetraethyl orthosilicate, water glass, silica sol, etc.;

[0157] (2) stirring and mixing at 50-80° C., adjusting the pH to 8-10, filtering out the precipitate, and drying at 50-80° C. for 3-10 hours;

[0158] (3) adding a phosphoric acid solution with a concentration of 3 to 30 g / L, adopting a programmed temperature rise-ball milling method, controlling the temperature rise program from room temperature to 200° C., a heating rate of 1° C. to 20° C., and a residence time of 0.5 to 3.5 hours; calcining at 400° C. to 600° C. for 3 to 10 hours to obtain A x B y PO4·SiO2.

[0159] Specifically, the catalyst used in the second stage reactor is metal-modified hydroxyapatite, the modified metal is one or more of Cu, Ce, Fe, and Zn, the loading amount is 2 to 20 wt%, and the size of the metal particles in the catalyst is 10 to 50 nm.

[0160] Specifically, the hydroxyapatite used is a commercial product and is calcined at 800°C to 1500°C for 2 to 8 hours before use; a solution containing Cu, Ce, Fe and Zn is used for "exchange-adsorption-deposition" for 2 to 24 hours, and the ion concentration is 0.02 to 1.2 g / ml, and Cu, Ce, Fe and Zn come from copper nitrate, cupric chloride, cuprous chloride, copper sulfate, copper oxalate, ferric nitrate, ferric chloride, ferrous nitrate, ferrous chloride, ferric bromide, ferrous bromide, ferrous sulfate, ferrous sulfate, cerium nitrate, cerium chloride, ammonium cerium nitrate, cerium perchlorate, zinc chloride, zinc sulfate, zinc nitrate, zinc dihydrogen phosphate, etc.; the pH of the system is adjusted to 5 to 8, and after filtering, the solution is dried at 100°C for 3 to 8 hours, and calcined at 600°C to 1300°C for 2 to 8 hours to obtain a modified hydroxyapatite catalyst.

[0161] Furthermore, the method and catalyst for continuously synthesizing isoprene by the alkenal liquid phase method provided by the present invention more preferably include the following steps:

[0162] The enaldehyde liquid phase method for synthesizing isoprene uses formaldehyde, tert-butyl alcohol and methyl tert-butyl ether as raw materials and is divided into two stages of reaction.

[0163] (1) The first stage reaction is carried out at 120-145°C, preferably 125-140°C; the olefinic aldehyde ratio is controlled to be 0.2-1.6, preferably 0.3-1.5; the feed rate is 5-50 ml / min, preferably 10-50 ml / min; the residence time of the material in the reactor is 10-60 minutes, preferably 15-50 minutes; intermediate products such as 4,4-dimethyl-1,3-dioxane and 3-methyl-1,3-butanediol are synthesized, and the liquid phase product is a homogeneous phase. The reaction pressure is regulated to be less than 10 atm, preferably <9 atm. The catalyst is retained in the first stage reactor through a filter, and the material enters the second stage reactor.

[0164] (2) tert-butyl alcohol and methyl tert-butyl ether are added, and the equivalent ratio of tert-butyl alcohol and methyl tert-butyl ether to formaldehyde is maintained at 2-10, preferably 2.5-9.5; the feed rate is 5-50 ml / min, preferably 10-50 ml / min; the reaction temperature is 145-165° C., preferably 150-160° C.; the residence time of the material is 10-60 minutes, preferably 15-50 minutes; the reaction pressure is adjusted to be less than 16 atm, preferably <14 atm; isoprene is separated, and the liquid phase is divided into oil and water phases, the water phase does not exceed one-half of the reactor and is not less than one-quarter; the oil phase is controlled not to exceed one-half of the reactor and is not less than one-quarter; the generated isobutylene is separated and returned to the first stage reactor through hydration.

[0165] The catalyst used in the first stage reactor is modified rare earth phosphate (A x B y PO4·SiO2), A is a rare earth metal La, Ce, Pr, Nd, Gd, etc., preferably La, Ce, Pr, Nd, Gd; is derived from lanthanum nitrate, lanthanum chloride, cerium nitrate, cerium chloride, ammonium cerium nitrate, cerium perchlorate, praseodymium nitrate, praseodymium chloride, neodymium chloride, neodymium nitrate, gadolinium nitrate, etc., preferably lanthanum nitrate, lanthanum chloride, cerium nitrate, cerium chloride, ammonium cerium nitrate, cerium perchlorate, praseodymium nitrate, praseodymium chloride, neodymium chloride, neodymium nitrate, gadolinium nitrate. B is a transition metal such as Mo, Zr, Cu, Zn, W, V, and Nb, preferably Mo, Zr, Cu, Zn, W, V, and Nb, and is derived from ammonium molybdate, molybdenum chloride, phosphomolybdic acid, zirconium nitrate, zirconyl nitrate, copper nitrate, copper chloride, copper sulfate, copper acetate, zinc nitrate, zinc sulfate, zinc chloride, phosphotungstic acid, ammonium tungstate, tungsten chloride, ammonium metavanadate, vanadium trichloride, vanadium oxychloride, niobic acid, niobium oxalate, and a niobium oxalate complex, and is preferably derived from ammonium molybdenum chloride, phosphomolybdic acid, zirconium nitrate, zirconyl nitrate, copper nitrate, copper chloride, copper sulfate, copper acetate, zinc nitrate, zinc sulfate, zinc chloride, phosphotungstic acid, ammonium tungstate, tungsten chloride, ammonium metavanadate, vanadium trichloride, vanadium oxychloride, niobic acid, niobium oxalate, and a niobium oxalate complex.

[0166] The modified rare earth phosphate catalyst can be expressed in the form of A x By PO4·SiO2, A is one or more rare earth metals such as La, Ce, Pr, Nd, Gd, etc., preferably one or more of La, Ce, Pr, Nd, Gd; the atomic ratio x to P is 0.7-1.4, preferably 0.8-1.3; B is one or more transition metals such as Mo, Zr, Cu, Zn, W, V, Nb, etc., preferably one or more of Mo, Zr, Cu, Zn, W, V, Nb; the atomic ratio y to P is 0.02-0.3, preferably 0.03-0.28; A x B y PO4 in A x B y The content of PO4·SiO2 is 15 to 45 wt%, preferably 18 to 40 wt%.

[0167] The modified rare earth phosphate catalyst is prepared as follows:

[0168] (1) dissolving a soluble compound containing a rare earth metal such as La, Ce, Pr, Nd, Gd in water, adding a soluble compound containing Mo, Zr, Cu, Zn, W, V, Nb, etc., wherein the total concentration of the metal compound in the solution is 10 to 80 g / L, preferably 15 to 75 g / L; adding a silicon-containing compound such as tetraethyl orthosilicate, water glass, silica sol, preferably tetraethyl orthosilicate, water glass, silica sol;

[0169] (2) stirring and mixing at 50-80° C., preferably 55-75° C.; adjusting the pH to 8-10, filtering out the precipitate; drying at 50-80° C. for 3-10 hours, preferably 55-75° C. for 5-10 hours;

[0170] (3) adding a phosphoric acid solution with a concentration of 3 to 30 g / L, preferably 5 to 25 g / L; adopting a programmed temperature rise-ball milling method, controlling the temperature rise program from room temperature to 200° C., preferably 50° C. to 170° C.; the heating rate is 1° C. to 20° C., preferably 2° C. to 15° C.; the residence time is 0.5 to 3.5 hours, preferably 1 to 3 hours; and calcining at 400° C. to 600° C. for 3 to 10 hours to obtain A x B y PO4·SiO2, the calcination temperature is preferably 450°C to 550°C, and the calcination time is preferably 4 to 8 hours.

[0171] The catalyst used in the second stage reactor is metal-modified hydroxyapatite, the modified metal is one or more of Cu, Ce, Fe, and Zn, and the loading amount is 2 to 20 wt%, preferably 4 to 18 wt%; the size of the metal particles in the catalyst is 10 to 50 nm, preferably 15 to 45 nm.

[0172] The metal-modified hydroxyapatite is a commercial product, which is calcined at 800°C to 1500°C for 2 to 8 hours before use, preferably at 850°C to 1400°C, and for 3 to 7 hours;

[0173] (1) using a solution containing Cu, Ce, Fe, and Zn for "exchange-adsorption-deposition" for 2 to 24 hours, preferably 3 to 20 hours; the ion concentration is 0.02 to 1.2 g / ml, preferably 0.04 to 1.0 g / ml; Cu, Ce, Fe, and Zn are from copper nitrate, copper chloride, cuprous chloride, copper sulfate, copper oxalate, ferric nitrate, ferric chloride, ferrous nitrate, ferrous chloride, ferric bromide, ferrous bromide, ferric sulfate, ferrous sulfate, cerium nitrate, cerium chloride, ammonium cerium nitrate, cerium perchlorate, zinc chloride, zinc sulfate, zinc nitrate, zinc dihydrogen phosphate, etc., preferably copper nitrate, copper chloride, cuprous chloride, copper sulfate, copper oxalate, ferric nitrate, ferric chloride, ferrous nitrate, ferrous chloride, ferric bromide, ferrous bromide, ferrous sulfate, ferrous sulfate, cerium nitrate, cerium chloride, ammonium cerium nitrate, cerium perchlorate, zinc chloride, zinc sulfate, zinc nitrate, and zinc dihydrogen phosphate;

[0174] (2) adjusting the system pH to 5-8, drying at 100°C for 3-8 hours, preferably 4-7 hours after filtering; calcining at 600°C-1300°C for 2-8 hours to obtain a modified hydroxyapatite catalyst, wherein the calcination temperature is preferably 650°C-1200°C, and the calcination time is preferably 3-7 hours.

[0175] Furthermore, the method and catalyst for continuously synthesizing isoprene by the enaldehyde liquid phase method provided by the present invention effectively reduce the side reaction of formaldehyde, improve the production efficiency of isoprene, and develop an easily recyclable catalyst, and may further include the following steps:

[0176] The enaldehyde liquid phase method for synthesizing isoprene uses formaldehyde, tert-butyl alcohol and methyl tert-butyl ether as raw materials and is divided into two stages of reaction.

[0177] (1) The first stage reaction is carried out at 120-145°C, preferably 125-140°C, more preferably 130-140°C; the olefinic aldehyde ratio is controlled to be 0.2-1.6, preferably 0.3-1.5; the feed rate is 5-50 ml / min, preferably 10-50 ml / min, more preferably 10-45 ml / min; the residence time of the material in the reactor is 10-60 minutes, preferably 15-50 minutes, more preferably 15-40 minutes; intermediate products such as 4,4-dimethyl-1,3-dioxane and 3-methyl-1,3-butanediol are synthesized, and the liquid phase product is a homogeneous phase. The reaction pressure is regulated to be less than 10 atm, preferably <9 atm, more preferably <8 atm. The catalyst is retained in the first stage reactor through a filter, and the material enters the second stage reactor.

[0178] (2) tert-butyl alcohol and methyl tert-butyl ether are added to maintain an equivalent ratio of 2 to 10 with respect to formaldehyde, preferably 2.5 to 9.5, more preferably 2.8 to 9.0; the feed rate is 5 to 50 ml / min, preferably 10 to 50 ml / min, and more preferably 12 to 45 ml / min; the reaction temperature is 145 to 165° C., preferably 150 to 160° C., and more preferably 155 to 160° C.; the residence time of the material is 10 to 60 minutes, preferably 15 to 50 minutes, and more preferably 15 to 40 minutes; the reaction pressure is adjusted to be less than 16 atm, preferably <14 atm, and more preferably <12 atm; isoprene is separated, and the liquid phase is divided into oil and water phases, the water phase does not exceed one half of the reactor and is not less than one quarter; the oil phase is controlled not to exceed one half of the reactor and is not less than one quarter; the generated isobutylene is separated and returned to the first stage reactor through hydration.

[0179] The catalyst used in the first stage reactor is modified rare earth phosphate (A x B y PO4·SiO2), A is a rare earth metal La, Ce, Pr, Nd, Gd, etc., preferably La, Ce, Pr, Nd, Gd, and more preferably La, Ce, Nd, Gd; it is derived from lanthanum nitrate, lanthanum chloride, cerium nitrate, cerium chloride, ammonium cerium nitrate, cerium perchlorate, praseodymium nitrate, praseodymium chloride, neodymium chloride, neodymium nitrate, gadolinium nitrate, etc., preferably lanthanum nitrate, lanthanum chloride, cerium nitrate, cerium chloride, ammonium cerium nitrate, cerium perchlorate, praseodymium nitrate, praseodymium chloride, neodymium chloride, neodymium nitrate, gadolinium nitrate, and more preferably lanthanum nitrate, cerium nitrate, ammonium cerium nitrate, neodymium nitrate, and gadolinium nitrate. B is a transition metal such as Mo, Zr, Cu, Zn, W, V, and Nb, preferably Mo, Zr, Cu, Zn, W, V, and Nb, and more preferably Mo, Zr, Cu, W, and Nb, and is derived from ammonium molybdate, molybdenum chloride, phosphomolybdic acid, zirconium nitrate, zirconium oxynitrate, copper nitrate, copper chloride, copper sulfate, copper acetate, zinc nitrate, zinc sulfate, zinc chloride, phosphotungstic acid, ammonium tungstate, tungsten chloride, ammonium metavanadate, vanadium trichloride, vanadium trichloride, niobic acid, Niobium oxalate, niobium oxalate complex, etc. are preferably ammonium molybdate, molybdenum chloride, phosphomolybdic acid, zirconium nitrate, zirconium oxynitrate, copper nitrate, copper chloride, copper sulfate, copper acetate, zinc nitrate, zinc sulfate, zinc chloride, phosphotungstic acid, ammonium tungstate, tungsten chloride, ammonium metavanadate, vanadium trichloride, vanadium oxychloride, niobic acid, niobium oxalate, and niobium oxalate complex, and more preferably ammonium molybdate, phosphomolybdic acid, zirconium oxynitrate, copper nitrate, copper acetate, phosphotungstic acid, ammonium tungstate, tungsten chloride, niobic acid, and niobium oxalate.

[0180] The modified rare earth phosphate catalyst can be expressed in the form of A x B yPO4·SiO2, characterized in that A is one or more rare earth metals such as La, Ce, Pr, Nd, Gd, etc., preferably one or more of La, Ce, Pr, Nd, Gd, more preferably one or two of La, Ce, Nd, Gd; the atomic ratio x to P is 0.7-1.4, preferably 0.8-1.3, more preferably 0.9-1.2; B is one or more transition metals such as Mo, Zr, Cu, Zn, W, V, Nb, etc., preferably one or more of Mo, Zr, Cu, Zn, W, V, Nb, more preferably one or two of Mo, Zr, Cu, W, Nb; the atomic ratio y to P is 0.02-0.3, preferably 0.03-0.28, more preferably 0.05-0.25; A x B y PO4 in A x B y The content of PO4·SiO2 is 15 to 45 wt%, preferably 18 to 40 wt%, and more preferably 20 to 35 wt%.

[0181] The modified rare earth phosphate catalyst is prepared as follows:

[0182] (1) dissolving a soluble compound containing a rare earth metal such as La, Ce, Pr, Nd, Gd in water, adding a soluble compound containing Mo, Zr, Cu, Zn, W, V, Nb, etc., wherein the total concentration of the metal compound in the solution is 10 to 80 g / L, preferably 15 to 75 g / L, and more preferably 18 to 70 g / L; adding a silicon-containing compound such as tetraethyl orthosilicate, water glass, and silica sol, preferably tetraethyl orthosilicate, water glass, and silica sol, and more preferably tetraethyl orthosilicate and water glass;

[0183] (2) stirring and mixing at 50-80° C., preferably 55-75° C., more preferably 60-70° C.; adjusting the pH to 8-10, filtering out the precipitate; drying at 50-80° C. for 3-10 hours, preferably 55-75° C. for 5-10 hours, more preferably 60-70° C. for 6-9 hours;

[0184] (3) adding a phosphoric acid solution with a concentration of 3 to 30 g / L, preferably 5 to 25 g / L, more preferably 8 to 20 g / L; adopting a programmed temperature rise-ball milling method, controlling the temperature rise program from room temperature to 200° C., preferably 50° C. to 170° C., more preferably 50° C. to 160° C.; the heating rate is 1° C. to 20° C., preferably 2° C. to 15° C., more preferably 2° C. to 10° C.; the residence time is 0.5 to 3.5 hours, preferably 1 to 3 hours, more preferably 1.5 to 2.5 hours; and calcining at 400° C. to 600° C. for 3 to 10 hours to obtain A x B yPO4·SiO2, the calcination temperature is preferably 450°C to 550°C, more preferably 460°C to 520°C, and the calcination time is preferably 4 to 8 hours, more preferably 4.5 to 7 hours.

[0185] The catalyst used in the second stage reactor is metal-modified hydroxyapatite, the modified metal is one or more of Cu, Ce, Fe, and Zn, and the loading amount is 2 to 20 wt%, preferably 4 to 18 wt%, and more preferably 5 to 16 wt%; the size of the metal particles in the catalyst is 10 to 50 nm, preferably 15 to 45 nm, and more preferably 20 to 40 nm.

[0186] The metal-modified hydroxyapatite is a commercial product, which is calcined at 800°C to 1500°C for 2 to 8 hours before use. The calcination temperature is preferably 850°C to 1400°C, more preferably 900°C to 1350°C, and the calcination time is preferably 3 to 7 hours, more preferably 3.5 to 6.5 hours.

[0187] (1) using a solution containing Cu, Ce, Fe, and Zn for "exchange-adsorption-deposition" for 2 to 24 hours, preferably 3 to 20 hours, and more preferably 4 to 16 hours; the ion concentration is 0.02 to 1.2 g / ml, preferably 0.04 to 1.0 g / ml, and more preferably 0.05 to 1.0 g / ml; Cu, Ce, Fe, and Zn are from copper nitrate, cupric chloride, cuprous chloride, copper sulfate, cupric oxalate, ferric nitrate, ferric chloride, ferrous nitrate, ferrous chloride, ferric bromide, ferrous bromide, ferric sulfate, ferrous sulfate, cerium nitrate, cerium chloride, cerium nitrate ammonium, cerium perchlorate, zinc chloride, zinc sulfate, zinc nitrate, zinc dihydrogen phosphate, etc., preferably copper nitrate, cupric chloride, cuprous chloride, cupric sulfate, cupric oxalate, ferric nitrate, ferric chloride, ferrous nitrate, ferrous chloride, ferric bromide, ferrous bromide, ferric sulfate, ferrous sulfate, cerium nitrate, cerium chloride, cerium ammonium nitrate, cerium perchlorate, zinc chloride, zinc sulfate, zinc nitrate, zinc dihydrogen phosphate, more preferably copper nitrate, cuprous chloride, cupric sulfate, cupric oxalate, ferric nitrate, ferrous nitrate, ferric bromide, ferrous bromide, ferric sulfate, cerium nitrate, cerium chloride, cerium ammonium nitrate, zinc chloride, zinc nitrate, zinc dihydrogen phosphate;

[0188] (2) adjusting the system pH to 5-8, drying at 100°C for 3-8 hours, preferably 4-7 hours, more preferably 4.5-6.5 hours after filtering; calcining at 600°C-1300°C for 2-8 hours to obtain a modified hydroxyapatite catalyst, wherein the calcination temperature is preferably 650°C-1200°C, more preferably 700°C-1150°C, and the calcination time is preferably 3-7 hours, more preferably 3.5-6.5 hours.

[0189] The process and parameters of the continuous synthesis of isoprene based on the enaldehyde liquid phase method provided in the above steps of the present invention are analyzed.

[0190] See also Figure 2 , Figure 2 The present invention provides product distribution and regulation 1 of the continuous synthesis of isoprene based on the enaldehyde liquid phase method.

[0191] Depend on Figure 2 It can be seen that when the reaction temperature is high, formaldehyde is excessive, the side reaction is intensified, and dark by-products or even solids are formed.

[0192] See also Figure 3 , Figure 3 The invention provides product distribution and regulation 2 of the process of continuous synthesis of isoprene by enal liquid phase method.

[0193] Depend on Figure 3 It can be seen that when the reaction temperature is low, excess formaldehyde can improve the utilization rate of olefin sources and inhibit formaldehyde side reactions.

[0194] The reaction process of continuously synthesizing isoprene by the enaldehyde liquid phase method provided in the above steps of the present invention is characterized.

[0195] See also Figure 4 , Figure 4 This is a gas chromatography-mass spectrometry full component analysis diagram of the process of continuous synthesis of isoprene by the enal liquid phase method provided by the present invention.

[0196] The above content of the present invention provides a method and catalyst for continuous synthesis of isoprene based on the enaldehyde liquid phase method. The present invention provides a modified rare earth phosphate catalyst particularly used in the reaction process of continuous synthesis of isoprene by the enaldehyde liquid phase method, and the catalyst is a solid phase catalyst, which is easier to recover and recycle in the liquid phase synthesis process. The modified rare earth phosphate catalyst provided by the present invention is combined with the two-stage continuous reaction synthesis process provided by the present invention, and further combined with a modified hydroxyapatite catalyst, thereby reducing the formaldehyde side reaction, improving the isoprene production efficiency, and easily recovering and recycling the catalyst.

[0197] The present invention uses tert-butyl alcohol, methyl tert-butyl ether and formaldehyde as raw materials, and synthesizes isoprene by two-stage continuous reaction, controls the side reaction of formaldehyde, and develops a multi-phase recyclable catalyst. The first stage: low olefin-aldehyde ratio, 120-145°C, using modified rare earth phosphate (A x B yPO4·SiO2) is used as a catalyst to catalyze formaldehyde, tert-butyl alcohol, and methyl tert-butyl ether to synthesize intermediate products such as 4,4-dimethyl-1,3-dioxane and 3-methyl-1,3-butanediol. The liquid phase product is controlled to be a uniform phase. The reaction pressure is less than 10atm. The conversion rate and selectivity of tert-butyl alcohol and methyl tert-butyl ether are greater than 92%; the second stage: the intermediate product and tert-butyl alcohol and methyl tert-butyl ether are kept at 145-165°C, the olefin source is excessive, and the modified hydroxyapatite catalyst is used to convert and synthesize isoprene. The reaction pressure is less than 16atm, and the yield can reach 80%. The first stage reaction uses a low olefin aldehyde ratio and a lower reaction temperature to reduce formaldehyde side reactions, improve the utilization rate of olefin sources and product production efficiency, and omit the isobutylene recovery and hydration process.

[0198] Experimental results show that by using the catalyst provided by the present invention and a two-stage continuous reaction synthesis method, in the first stage reaction, the conversion rate and selectivity of the raw materials tert-butyl alcohol and methyl tert-butyl ether are both greater than 92%; and in the second stage reaction, by using a modified hydroxyapatite catalyst, the yield can reach 80%.

[0199] To further illustrate the present invention, the application of a catalyst provided by the present invention in the synthesis of isoprene by an alkene aldehyde liquid phase method and a method for synthesizing isoprene by an alkene aldehyde liquid phase method are described in detail below in conjunction with examples. However, it should be understood that these examples are implemented on the premise of the technical scheme of the present invention, and detailed implementation methods and specific operating processes are given only to further illustrate the features and advantages of the present invention, rather than to limit the claims of the present invention, and the protection scope of the present invention is not limited to the following examples.

[0200] Example 1

[0201] (1) Catalyst preparation

[0202] Modified rare earth phosphate catalyst: According to the stoichiometric ratio, the catalyst La is prepared. 0.9 Cu 0.2 PO4·SiO2, wherein the SiO2 content is 65wt%. Lanthanum nitrate is dissolved in water, copper nitrate is added, the total concentration of metal compounds in the solution is 63g / L, ethyl orthosilicate is added, stirred and mixed at 60°C, the pH is adjusted to 9, the precipitate is filtered out, dried at 70°C for 8 hours, a phosphoric acid solution with a concentration of 23g / L is added, and the mixture is transferred to a ball mill, and the temperature is controlled to rise from room temperature to 200°C, the temperature rise rate is 5°C, the temperature is kept at 100°C for 2 hours, and the temperature is kept at 200°C for 2.5 hours, and the sample is calcined at 550°C for 5 hours to obtain La 0.9 Cu 0.2 PO4·SiO2.

[0203] Modified hydroxyapatite catalyst: 50g of commercial hydroxyapatite was taken, calcined at 1100℃ for 3 hours, and then "exchanged-adsorbed-deposited" with a solution of copper nitrate and cerium nitrate for 18 hours, with an ion concentration of 1.0g / ml, and the system pH was adjusted to 7; after filtration, it was dried at 100℃ for 5 hours and calcined at 1100℃ for 3 hours. The CuO in the obtained catalyst was x The loading amount is about 7wt%, CeO x The loading amount is about 14 wt%.

[0204] (2) Isoprene synthesis

[0205] Take 10g of the modified rare earth phosphate catalyst prepared above, add it to the first stage reactor, add formaldehyde and tert-butanol, control the olefinic aldehyde ratio to 1, the feed rate is 30ml / min, the residence time is 25 minutes, the reaction temperature is 135°C, and intermediate products such as 4,4-dimethyl-1,3-dioxane and 3-methyl-1,3-butanediol are synthesized. The liquid product is a homogeneous phase. The reaction pressure is adjusted to be less than 9atm. The catalyst is retained in the first stage reactor through a filter, and the material enters the second stage reactor.

[0206] 10 g of the modified hydroxyapatite catalyst prepared above was added to the second-stage reactor, tert-butanol was supplemented, the equivalent ratio of tert-butanol to formaldehyde was maintained at 8, the feed rate was 36 ml / min, the reaction temperature was 165° C., the residence time was 36 minutes, and the reaction pressure was adjusted to be less than 12 atm; isoprene was separated, and the liquid phase was divided into oil and water phases, the water phase did not exceed one half of the reactor and was not less than one quarter; the oil phase was controlled to be no more than one half of the reactor and not less than one quarter; the generated isobutylene was separated and returned to the first-stage reactor through hydration.

[0207] When the reaction was in equilibrium, the isoprene yield was calculated to be 80%, the formaldehyde selectivity was 88%, and the tert-butanol selectivity was 92%.

[0208] Example 2

[0209] (1) Catalyst preparation

[0210] Modified rare earth phosphate catalyst: According to the stoichiometric ratio, the catalyst Ce is prepared. 1.2 Zr 0.1 PO4·SiO2, wherein the SiO2 content is 60wt%. Cerium ammonium nitrate is dissolved in water, zirconium oxynitrate is added, the total concentration of metal compounds in the solution is 60g / L, silica sol is added, stirred and mixed at 55°C, the pH is adjusted to 9, the precipitate is filtered out, dried at 80°C for 6 hours, a phosphoric acid solution with a concentration of 18g / L is added, and the mixture is transferred to a ball mill. The temperature is controlled to rise from room temperature to 200°C, the temperature rise rate is 10°C, the mixture is kept at 100°C for 3 hours, kept at 200°C for 1.5 hours, and calcined at 500°C for 8 hours to obtain Ce1.2 Zr 0.1 PO4·SiO2.

[0211] Modified hydroxyapatite catalyst: 50g of commercial hydroxyapatite was taken, calcined at 800℃ for 5 hours, and then subjected to "exchange-adsorption-deposition" for 15 hours using a solution containing Cu and Zn, with an ion concentration of 0.6g / ml, and the system pH was adjusted to 7; after filtration, it was dried at 100℃ for 6 hours and calcined at 800℃ for 5 hours. The CuO in the obtained catalyst was x The loading amount is 6wt%, ZnO x The loading amount is 12wt%.

[0212] (2) Isoprene synthesis

[0213] Take 10g of the modified rare earth phosphate catalyst prepared above, add it to the first stage reactor, add formaldehyde and methyl tert-butyl ether, control the olefinic aldehyde ratio to 0.4, the feed rate is 40ml / min, the residence time is 24 minutes, the reaction temperature is 125°C, and intermediate products such as 4,4-dimethyl-1,3-dioxane and 3-methyl-1,3-butanediol are synthesized. The liquid product is a homogeneous phase. The reaction pressure is adjusted to be less than 10atm. The catalyst is retained in the first stage reactor through a filter, and the material enters the second stage reactor.

[0214] 10 g of the modified hydroxyapatite catalyst prepared above was added to the second-stage reactor, methyl tert-butyl ether was supplemented, the equivalent ratio of methyl tert-butyl ether to formaldehyde was maintained at 4, the feed rate was 25 ml / min, the reaction temperature was 155°C, the residence time was 39 minutes, and the reaction pressure was adjusted to be less than 12 atm; isoprene was separated, and the liquid phase was divided into oil and water phases, the water phase did not exceed one half of the reactor and was not less than one quarter; the oil phase was controlled to be no more than one half of the reactor and not less than one quarter; the generated isobutylene was separated and returned to the first-stage reactor through hydration.

[0215] When the reaction was in equilibrium, the isoprene yield was calculated to be 74%, the formaldehyde selectivity was 86%, and the methyl tert-butyl ether selectivity was 90%.

[0216] Example 3

[0217] (1) Catalyst preparation

[0218] Modified rare earth phosphate catalyst: According to the stoichiometric ratio, the catalyst LaPr 0.9 Mo 0.08PO4·SiO2, wherein the SiO2 content is 70wt%. Lanthanum chloride and praseodymium nitrate are dissolved in water, ammonium molybdate is added, the total concentration of metal compounds in the solution is 56g / L, silica sol is added, stirred and mixed at 65°C, the pH is adjusted to 9, the precipitate is filtered out, dried at 60°C for 5 hours, a phosphoric acid solution with a concentration of 18g / L is added, and the mixture is transferred to a ball mill. The temperature is controlled to rise from room temperature to 200°C, the temperature rise rate is 15°C, the mixture is kept at 100°C for 2.5 hours, kept at 200°C for 2 hours, and calcined at 500°C for 6 hours to obtain LaPr 0.9 Mo 0.08 PO4·SiO2.

[0219] Modified hydroxyapatite catalyst: 50g of commercial hydroxyapatite was taken, calcined at 900℃ for 5 hours, and then "exchanged-adsorbed-deposited" with a solution containing Cu and Ce for 20 hours, with an ion concentration of 0.5g / ml, and the pH of the system was adjusted to 7; after filtration, it was dried at 100℃ for 6 hours and calcined at 900℃ for 5 hours. The CuO in the obtained catalyst was x The loading amount is 5wt%, CeO x The loading amount is 16wt%.

[0220] (2) Isoprene synthesis

[0221] Take 10g of the modified rare earth phosphate catalyst prepared above, add it to the first stage reactor, add formaldehyde and tert-butanol, control the olefinic aldehyde ratio to 0.3, the feed rate is 25ml / min, the residence time is 46 minutes, the reaction temperature is 125°C, and intermediate products such as 4,4-dimethyl-1,3-dioxane and 3-methyl-1,3-butanediol are synthesized. The liquid product is a homogeneous phase. The reaction pressure is adjusted to be less than 10atm. The catalyst is retained in the first stage reactor through a filter, and the material enters the second stage reactor.

[0222] Take 10g of the modified hydroxyapatite catalyst prepared above, add it to the second stage reactor, supplement tert-butyl alcohol and methyl tert-butyl ether (volume ratio is 1:1), maintain the equivalent ratio of them to formaldehyde at 6, the feed rate is 36ml / min, the reaction temperature is 165℃, the residence time is 54 minutes, and the reaction pressure is adjusted to be less than 10atm; separate and obtain isoprene, and the liquid phase is divided into oil and water phases, the water phase does not exceed one half of the reactor and is not less than one quarter; control the oil phase to be no more than one half of the reactor and not less than one quarter; the generated isobutylene is separated and returned to the first stage reactor through hydration.

[0223] When the reaction was in equilibrium, the isoprene yield was calculated to be 70%, the formaldehyde selectivity was 82%, and the tert-butyl alcohol / methyl tert-butyl ether selectivity was 93%.

[0224] Example 4

[0225] (1) Catalyst preparation

[0226] Modified rare earth phosphate catalyst: According to the stoichiometric ratio, the catalyst Ce is prepared. 0.8 ZGar 0.06 PO4·SiO2, wherein the SiO2 content is 62wt%. Ammonium cerium nitrate is dissolved in water, zirconium nitrate and ammonium metavanadate are added, the total concentration of metal compounds in the solution is 52g / L, silica sol is added, stirred and mixed at 70°C, the pH is adjusted to 9, the precipitate is filtered out, dried at 80°C for 10 hours, a phosphoric acid solution with a concentration of 23g / L is added, and the mixture is transferred to a ball mill, and the temperature is controlled to rise from room temperature to 200°C, the temperature rise rate is 5°C, the mixture is kept at 100°C for 3 hours, kept at 200°C for 3 hours, and calcined at 450°C for 8 hours to obtain Ce 0.8 ZGar 0.06 PO4·SiO2.

[0227] Modified hydroxyapatite catalyst: 50g of commercial hydroxyapatite was calcined at 800℃ for 5 hours before use; ammonium cerium nitrate and zinc nitrate solution (ion concentration of 1.0g / ml) were added, and "exchange-adsorption-deposition" was carried out for 2-24 hours, and the pH of the system was adjusted to 7. After filtration, it was dried at 100℃ for 5 hours and calcined at 800℃ for 5 hours. The ZnO in the obtained catalyst was x The loading amount is 6wt%, CeO x The loading amount is 12wt%.

[0228] (2) Isoprene synthesis

[0229] Take 10g of the modified rare earth phosphate catalyst prepared above, add it to the first stage reactor, add formaldehyde and methyl tert-butyl ether, control the olefinic aldehyde ratio to 0.4, the feed rate is 25ml / min, the residence time is 46 minutes, the reaction temperature is 120°C, and intermediate products such as 4,4-dimethyl-1,3-dioxane and 3-methyl-1,3-butanediol are synthesized. The liquid product is a homogeneous phase. The reaction pressure is adjusted to be less than 10atm. The catalyst is retained in the first stage reactor through a filter, and the material enters the second stage reactor.

[0230] 10 g of the modified hydroxyapatite catalyst prepared above was added to the second-stage reactor, tert-butanol was supplemented, the equivalent ratio of tert-butanol to formaldehyde was maintained at 8, the feed rate was 40 ml / min, the reaction temperature was 150°C, the residence time was 34 minutes, and the reaction pressure was adjusted to be less than 10 atm; isoprene was separated, and the liquid phase was divided into oil and water phases, the water phase did not exceed one half of the reactor and was not less than one quarter; the oil phase was controlled to be no more than one half of the reactor and not less than one quarter; the generated isobutylene was separated and returned to the first-stage reactor through hydration.

[0231] When the reaction was in equilibrium, the isoprene yield was calculated to be 78%, the formaldehyde selectivity was 85%, and the tert-butyl alcohol / methyl tert-butyl ether selectivity was 88%.

[0232] Example 5

[0233] (1) Catalyst preparation

[0234] Modified rare earth phosphate catalyst: According to the stoichiometric ratio, the catalyst Nd 0.9 ikB 0.06 PO4·SiO2, wherein the SiO2 content is 63wt%. Neodymium nitrate is dissolved in water, ammonium molybdate and niobium oxalate are added, the total concentration of metal compounds in the solution is 66g / L, ethyl orthosilicate is added, stirred and mixed at 75°C, the pH is adjusted to 9, the precipitate is filtered out, dried at 70°C for 8 hours, a phosphoric acid solution with a concentration of 18g / L is added, and the mixture is transferred to a ball mill, and the heating program is controlled from room temperature to 200°C, the heating rate is 10°C, the mixture is kept at 100°C for 3 hours, kept at 200°C for 2 hours, and calcined at 550°C for 8 hours to obtain Nd 0.9 ikB 0.06 PO4·SiO2.

[0235] Modified hydroxyapatite catalyst: 50g of commercial hydroxyapatite was calcined at 1000℃ for 5 hours before use; copper oxalate, cerium nitrate, and zinc nitrate solution (ion concentration of 0.9g / ml) were added, and "exchange-adsorption-deposition" was performed for 18 hours. The pH of the system was adjusted to 7, and the catalyst was dried at 100℃ for 7 hours after filtration and calcined at 1100℃ for 3 hours. x The loading amount is 5wt%, CeO x The loading amount of ZnO is 11wt%. x The loading amount is 5wt%.

[0236] (2) Isoprene synthesis

[0237] Take 10g of the modified rare earth phosphate catalyst prepared above, add it to the first stage reactor, add formaldehyde and tert-butanol, control the olefinic aldehyde ratio to 0.4, the feed rate is 36ml / min, the residence time is 30 minutes, the reaction temperature is 140°C, and intermediate products such as 4,4-dimethyl-1,3-dioxane and 3-methyl-1,3-butanediol are synthesized. The liquid product is a homogeneous phase. The reaction pressure is adjusted to be less than 10atm. The catalyst is retained in the first stage reactor through a filter, and the material enters the second stage reactor.

[0238] 10 g of the modified hydroxyapatite catalyst prepared above was added to the second-stage reactor, tert-butanol was supplemented, the equivalent ratio of tert-butanol to formaldehyde was maintained at 5, the feed rate was 53 ml / min, the reaction temperature was 155°C, the residence time was 32 minutes, and the reaction pressure was adjusted to be less than 12 atm; isoprene was separated, and the liquid phase was divided into oil and water phases, the water phase did not exceed one half of the reactor and was not less than one quarter; the oil phase was controlled to be no more than one half of the reactor and not less than one quarter; the generated isobutylene was separated and returned to the first-stage reactor through hydration.

[0239] When the reaction was in equilibrium, the isoprene yield was calculated to be 76%, the formaldehyde selectivity was 81%, and the tert-butanol selectivity was 92%.

[0240] The above is a detailed introduction to a method and catalyst for continuous synthesis of isoprene based on the enaldehyde liquid phase method provided by the present invention. The principles and implementation methods of the present invention are described in detail using specific examples herein. The description of the above embodiments is only used to help understand the method and its core ideas of the present invention, including the best mode, and also enables any technician in the field to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, the present invention can also be improved and modified in several ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims, and may include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements that are not different from the textual expression of the claims, or if they include equivalent structural elements that are not substantially different from the textual expression of the claims, then these other embodiments should also be included in the scope of the claims.

Claims

1. Application of catalyst in the synthesis of isoprene by enal liquid phase method; The catalyst includes a modified rare earth phosphate catalyst; The general formula of the modified rare earth phosphate is A x B y PO4·SiO2; in, x is 0.7~1.4, y is 0.02~0.3; A is one or more of La, Ce, Pr, Nd and Gd; B is one or more of Mo, Zr, Cu, Zn, W, V and Nb; The synthesis is specifically a two-stage synthesis; The modified rare earth phosphate catalyst is a one-stage synthesis catalyst; The catalyst also includes a metal-modified hydroxyapatite catalyst; The metal includes one or more of Cu, Ce, Fe and Zn; The metal-modified hydroxyapatite catalyst is a catalyst for two-stage synthesis.

2. The use according to claim 1, characterized in that: The catalyst is a heterogeneous catalyst; The mass content of the metal in the metal-modified hydroxyapatite is 2wt%~20wt%; The size of the metal particles in the metal-modified hydroxyapatite is 10-50 nm.

3. The use according to claim 2, characterized in that: In the modified rare earth phosphate, the mass content of SiO2 is 15 wt%~45wt%; The synthesis includes continuous synthesis.

4. A method for synthesizing isoprene by an alkenal liquid phase method, characterized in that: The following steps are involved: 1) tert-butyl alcohol and / or methyl tert-butyl ether, a modified rare earth phosphate catalyst and formaldehyde are fed into a first reaction device for reaction to obtain a liquid phase reaction system; The general formula of the modified rare earth phosphate is A x B y PO4·SiO2; Among them, x is 0.7~1.4, y is 0.02~0.3; A is one or more of La, Ce, Pr, Nd and Gd; B is one or more of Mo, Zr, Cu, Zn, W, V and Nb; 2) sending tert-butyl alcohol and / or methyl tert-butyl ether, the metal-modified hydroxyapatite catalyst, and the liquid phase reaction system obtained in the above steps into a second reaction device for further reaction to obtain isoprene; The metal in the metal-modified hydroxyapatite catalyst includes one or more of Cu, Ce, Fe and Zn.

5. The method according to claim 4, characterized in that The olefinic aldehyde ratio of the raw material in step 1) is (0.2-1.6): 1; The reaction temperature is 120-145°C; The reaction time is 10 to 60 minutes; The reaction pressure is less than or equal to 10 atm; The feed rate in step 1) is 5-50 ml / min; After the reaction, the solid phase catalyst is filtered to obtain a liquid phase reaction system; The liquid phase reaction system includes 4,4-dimethyl-1,3-dioxane and 3-methyl-1,3-butanediol.

6. The method according to claim 4, characterized in that The molar equivalent ratio of tert-butyl alcohol and / or methyl tert-butyl ether in step 2) to formaldehyde in step 1) is (2-10):1; The feed rate in step 2) is 5-50 ml / min; The temperature of the second reaction is 145-165°C; The time for the second reaction is 10 to 60 minutes; The pressure of the second reaction is less than or equal to 16 atm.

7. The method according to claim 4, characterized in that The step of separating the catalyst is also included after the second reaction; The separated liquid phase includes an oil phase and a water phase; The height of the water phase is no more than one-half and no less than one-quarter of the height of the reaction zone of the reactor; The height of the oil phase is no more than one-half and no less than one-quarter of the height of the reaction zone of the reactor; In the method, the generated isobutylene is hydrated to obtain tert-butyl alcohol, and the process returns to step 1).

8. The method according to claim 4, characterized in that The preparation method of the modified rare earth phosphate catalyst comprises the following steps: The mixed solution of the rare earth metal soluble compound and the transition metal soluble compound is mixed with the silicide, the pH value is adjusted to obtain a precipitate, the precipitate is dried, the precipitate is subjected to step-by-step temperature ball milling with a phosphoric acid solution, and the precipitate is calcined to obtain a modified rare earth phosphate catalyst; The rare earth metal soluble compound includes one or more of lanthanum nitrate, lanthanum chloride, cerium nitrate, cerium chloride, cerium ammonium nitrate, cerium perchlorate, praseodymium nitrate, praseodymium chloride, neodymium chloride, neodymium nitrate and gadolinium nitrate; The transition metal soluble compound includes one or more of ammonium molybdate, molybdenum chloride, phosphomolybdic acid, zirconium nitrate, zirconium oxynitrate, copper nitrate, copper chloride, copper sulfate, copper acetate, zinc nitrate, zinc sulfate, zinc chloride, phosphotungstic acid, ammonium tungstate, tungsten chloride, ammonium metavanadate, vanadium trichloride, vanadium trichloride, niobic acid, niobium oxalate and niobium oxalate complex; The total concentration of the metal compounds in the mixed solution is 10-80 g / L; The silicide includes one or more of ethyl orthosilicate, water glass and silica sol; The mixing temperature is 50-80°C.

9. The method according to claim 8, characterized in that The pH value is 8 to 10; The drying temperature is 50-80°C; The drying time is 3 to 10 hours; The concentration of the phosphoric acid solution is 3-30 g / L; The starting and ending temperatures of the step-by-step temperature ball milling are 15-200°C; The heating rate of the step-by-step heating ball mill is 1°C to 20°C; The residence time of the step is 0.5 to 3.5 hours; The calcination temperature is 400°C to 600°C; The calcination time is 3 to 10 hours.

10. The method according to claim 4, characterized in that The preparation method of the metal-modified hydroxyapatite catalyst comprises the following steps: The hydroxyapatite is calcined, placed in a modified metal compound solution, subjected to an exchange-adsorption-deposition process, and calcined again to obtain a metal-modified hydroxyapatite catalyst; The calcination temperature is 800-1500°C; The calcination time is 2 to 8 hours; The modified metal compound solution includes one or more of copper nitrate, cupric chloride, cuprous chloride, cupric sulfate, cupric oxalate, ferric nitrate, ferric chloride, ferrous nitrate, ferrous chloride, ferric bromide, ferrous bromide, ferric sulfate, ferrous sulfate, cerium nitrate, cerium chloride, cerium ammonium nitrate, cerium perchlorate, zinc chloride, zinc sulfate, zinc nitrate and zinc dihydrogen phosphate; The ion concentration of the modified metal in the modified metal compound solution is 0.02-1.2 g / ml; The pH value of the system during the exchange-adsorption-deposition process is 5-8; The time of the exchange-adsorption-deposition process is 2 to 24 hours; The re-baking temperature is 600-1300°C; The re-roasting time is 2 to 8 hours.

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