651 results about "Re crystallization" patented technology

The invention relates to a purification method of penta (dimethylamino) tantalum, and relates to the technical field of purification of amino metal compounds. In a standard glove box with the oxygen content lower than 2 ppm and the water content lower than 0.01 ppm, taking a proper amount of sublimated crude product penta (dimethylamino) tantalum, putting the sublimated crude product penta (dimethylamino) tantalum into a dry and clean sample bottle, adding a solvent after water and oxygen removal to dissolve the penta (dimethylamino) tantalum, and filtering; and then cooling and crystallizing, slowly reducing the temperature until crystals are separated out, and slowly crystallizing to generate faint yellow micro-transparent crystals. After crystallization is completed, filtering is conducted again in a low-temperature state, and crystals are dried in vacuum. And after the mother liquor is desolventized to evaporate out the solvent, the recovered crude product penta (dimethylamino) tantalum can be sublimated and recycled again.

The invention discloses a preparation method of hydrogenated benvitimod and analogues thereof, and belongs to the technical field of organic synthesis. The method comprises the following steps: S1, mixing a compound I and palladium carbon in a solvent to obtain slurry; s2, under the protection of nitrogen, preheating the silicon carbide microchannel reactor to 20-70 DEG C, and then introducing hydrogen and the slurry in the step S1; the reaction temperature is 20-70 DEG C, the reaction pressure is 1-10 kg, and the retention time of the slurry is 1-20 min; and S3, carrying out solid-liquid separation, concentration, recrystallization and drying on the reaction liquid in the step S2 to obtain a compound II. The method adopts continuous flow production and is suitable for industrial production; the reaction speed is high, and the residence time does not exceed 20 min and is much shorter than overnight time in the prior art; the reaction yield is high and can reach 95% or above, and the yield of part of compounds can reach 99% or above; the catalyst dosage is small, and the reaction cost is greatly reduced.

The invention relates to the field of organic synthesis, and discloses a continuous deuteration preparation method of perdeuterated carbazole. The method comprises the following steps: taking carbazole and a deuterium source as raw materials, reacting under the catalysis conditions of a solvent and a catalyst, collecting an effluent reaction solution, cooling, filtering, concentrating and recrystallizing to obtain the perdeuterated carbazole. According to the present invention, the heavy metal chloride is adopted to catalyze the continuous reaction, the carbazole is adopted as the raw material, the hydrogen-deuterium exchange with the deuterium source is performed to synthesize the perdeuterated carbazole, the reaction condition is mild, the deuterium source is supplemented for multiple times during the reaction process so as to achieve the continuous deuteration, and the conversion rate and the yield are substantially improved. The whole reaction system is carried out in an isolated environment, no other impurities enter the reaction system, the product is free of pollution in the production process, the yield reaches 91% or above, the purity reaches 99.8% or above, and the deuteration degree reaches 99% or above. The whole process does not need high-temperature and high-pressure conditions, is relatively simple and convenient to operate, and facilitates industrial large-scale production.

To provide a method which enables inexpensive production with a high yield of lithium hydroxide with a low amount of impurities such as sodium from lithium-containing water including a lithium ion and a chloride ion.SOLUTION: A production method of lithium hydroxide includes: a crystallizing step of crystallizing lithium hydroxide (LiOH) from lithium-containing water including a lithium ion and a chloride ion; a solid-liquid separation step of performing solid-liquid separation treatment of concentrated liquid including the LiOH to obtain the LiOH as a solid product and filtrate; a carbonation step of producing lithium carbonate from the filtrate by carbonation; a lithium carbonate recovery step of evaporating at least a part of ammonia from a mixed liquid obtained in the carbonation step and performing solid-liquid separation treatment of the resultant treated liquid to obtain lithium carbonate as a solid product; a lithium hydroxide production step of converting the obtained lithium carbonate into LiOH followed by solid-liquid separation treatment to obtain an aqueous LiOH solution (1) as a liquid component; and a recrystallizing step of crystallizing LiOH from the aqueous solution (1).SELECTED DRAWING: Figure 2

The invention discloses a method for realizing pollution reduction and carbon reduction by phosphogypsum recycling. The method comprises the following steps: (1) washing phosphogypsum with water to remove soluble impurities, neutralizing residual acid, and calcining and activating; (2) pretreatment of the landfill leachate: magnesium salt and phosphate are added, the pH of the landfill leachate is adjusted, and free ammonia NH3 is released through low-temperature heating; (3) the pretreated landfill leachate is sprayed to capture CO2 in the flue gas, and a (NH4) 2CO3 solution is obtained; (4) fully mixing a (NH4) 2CO3 solution with the pretreated ardealite, and controlling the reaction conditions in a closed reactor, so that the ardealite and (NH4) 2CO3 are subjected to a heterogeneous reaction to generate CaCO3 and (NH4) 2SO4; and (5) product purification: carrying out solid-liquid separation on the mixed solution by adopting a multi-stage crystallization process to obtain a building material, and carrying out gradient cooling and recrystallization purification on the filtrate to obtain the nitrogen fertilizer. According to the method, recycling of the landfill leachate and the ardealite is achieved, and CO2 in the flue gas is efficiently removed.

The invention belongs to the technical field of preparation of semiconductor high-temperature protective coatings, and particularly relates to a chemical vapor infiltration method for preparing a low-residual-stress SiC high-temperature-resistant protective coating. A positive pressure chemical vapor infiltration technology is adopted, an MTS-H2 system is selected as a precursor, the molar ratio (MTS: H2 = 0.01-1) of the MTS-H2 system to the precursor is controlled, and when the working pressure is 100-400 KPa and the temperature is 1000-1600 DEG C, the SiC high-temperature-resistant protective coating which is low in residual stress and compact in structure is deposited on the surface of a recrystallized silicon carbide matrix. The SiC protective coating prepared by adopting the method is compact in structure, relatively low in residual stress and good in combination with a recrystallized silicon carbide matrix, and can play an excellent high-temperature protection role on the recrystallized silicon carbide matrix.

The invention provides a method for preparing FAPbBr3 quantum dots, which comprises the following steps: S1, preparation of a precursor solution: respectively dissolving a lead source precursor, a bromine source precursor and acid in water and stirring to obtain the precursor solution; s2, formation of nucleation sites: adding an FA precursor into the precursor solution prepared in the step S1, stirring, and reacting and crystallizing in water to form floccules capable of being used as the nucleation sites; s3, construction of a substrate layer: adding silane into the solution prepared in the step S2, stirring, heating and drying to obtain a FAPbBr3-coated SiO2 quantum dot crude product, and coating the exterior of FAPbBr3 with SiO2 generated by hydrolysis of the silane in an acidic solution to serve as the substrate layer; s4, ball-milling recrystallization: carrying out ball-milling recrystallization on the FAPbBr3-coated SiO2 quantum dot crude product prepared in the step S3; wherein the object of ball milling is a substrate layer, and the object of recrystallization is FAPbBr3 quantum dots. The solvent of the system is an aqueous solution, so that the problems of recycling, discharging and the like of organic solvents are solved.

The invention belongs to the technical field of production, separation and purification of hydroxyl carbazole, and provides a continuous flow production process of hydroxyl carbazole, which specifically comprises the following steps: (1) mixing raw materials of o-halogenated aniline, benzenediol, an organic solvent and an acid catalyst, and pumping into a first reactor for reaction; (2) sequentially performing extraction, reduced pressure distillation, recrystallization and drying treatment on the reaction liquid at the outlet of the first-stage reactor to obtain a reaction product photoreaction intermediate; (3) continuously pumping a mixed solution of the photoreaction intermediate prepared in the step (2), a photoreaction catalyst and a second solvent into a second-stage photoreactor, and carrying out photochemical reaction under the irradiation of a UV-LED light source; and (4) sequentially carrying out neutralization, reduced pressure distillation and recrystallization on the reaction liquid at the outlet of the second-stage photoreactor to obtain a hydroxyl carbazole product. By adopting the technical scheme provided by the invention, various hydroxycarbazole with high yield and high purity can be prepared, and the production period is shortened.

The invention provides a porous magnetic hyaluronic acid microneedle for treating knee osteoarthritis and a preparation method, and relates to the technical field of biological materials. The porous magnetic hyaluronic acid microneedle for treating knee osteoarthritis comprises a needle body and a matrix layer, the needle body is a porous drug-loading autolysis hyaluronic acid microneedle body, and the matrix layer is a magnetic hyaluronic acid matrix. The invention has the following beneficial effects: 1, a soluble biocompatible microneedle structure is adopted, so that the injury caused by the breakage of a metal microneedle is avoided, and the medicine can directly reach the subcutaneous part; 2, a porous structure is constructed through ice crystal recrystallization, and the drug loading content is increased through a secondary drying technology; 3, the drug carrier is added through the nano magnetic particles, so that diffusion and absorption of drug components are promoted; 4, the operation is simple, tedious steps such as injection in the articular cavity are not needed, and the infection risk in the articular cavity is reduced; 5, batch mold production can be realized, and the production cost is reduced; 6, the administration amount is increased through microneedle perforation administration and matrix layer permeation micropore administration.

The invention belongs to the technical field of forest chemical industry and natural perfume extraction and separation, and particularly discloses a superheated steam distillation separation and recovery method for perfume components in cinnamon oil rectifying still residues. The method comprises the following steps: processing the cinnamon oil rectifying still residues by adopting a steam distillation method taking normal-pressure superheated steam as a desorption medium, carrying out condensation cooling and phase separation on distilled oil-water mixed gas, and collecting oily liquid or crystalline solid containing cinnamon spice components, and carrying out one or more physical isolation methods such as freezing crystallization, vacuum fractionation or rectification, recrystallization and the like to obtain natural cinnamon monomer spices such as o-methoxycinnamaldehyde, o-methoxycinnamic acid, phenethyl alcohol and the like. The method has the advantages of low equipment investment, simple and feasible operation, low production cost, clean and pollution-free process, good operation safety, high industrial application feasibility and the like.

The invention belongs to the technical field of active substance preparation, and particularly relates to a preparation method and application of high-purity rare ginsenoside CK. The high-purity rare ginsenoside CK with the content exceeding 95% is finally produced through the steps of combined enzymolysis, ultrafiltration, nanofiltration, multiple crystallization and the like, the production efficiency and purity of the rare ginsenoside CK are improved through the preparation method, only ethyl alcohol and water are used as solvents in the whole process, it is guaranteed that the technology is green and environmentally friendly, and the method is suitable for industrial production. The method has the advantages of simple operation, no use of harmful chemical solvents, great reduction of environmental pollution, realization of the significant cost advantage in the whole production process due to repeated use of equipment and solvents, suitableness for large-scale industrial application, and wide market prospects and economic benefits.

The invention discloses a quaternary sulfuric acid molten salt heat storage material based on salt lake resources as well as a preparation method and application of the quaternary sulfuric acid molten salt heat storage material. The preparation method comprises the following steps: freezing and recrystallizing first sulfate type salt lake raw brine to prepare sodium sulfate decahydrate; carrying out evaporative crystallization and recrystallization treatment on the second sulfate type salt lake raw brine to prepare magnesium sulfate heptahydrate; mixing the sodium sulfate decahydrate, the magnesium sulfate heptahydrate, the potassium sulfate and the calcium sulfate, heating to a first dehydration temperature at a first heating rate for first heat treatment, heating to a second dehydration temperature at a second heating rate for second heat treatment, and heating to a melt blending temperature at a third heating rate for third heat treatment, the quaternary sulfuric acid molten salt heat storage material is prepared. The quaternary sulfuric acid molten salt is prepared by a one-step method through a dehydration and coupling technology, so that high-valued utilization of sodium, potassium, magnesium and calcium resources of a salt lake is realized, the process flow is simplified, and the cost is reduced.

The utility model discloses a recrystallization device which comprises a heating cavity, a refrigeration cavity is arranged at the bottom end of the heating cavity, a top cover is arranged at the top of the heating cavity, an observation window and a handle are arranged on the top cover, a second filter cavity is arranged at the bottom end of the refrigeration cavity, the bottom end of the second filter cavity is communicated with a suction filtration barrel, and a connecting pipe is arranged on the suction filtration barrel. According to the utility model, the defects in the prior art are overcome, the raw materials do not need to be frequently transferred in the recrystallization stage through the integrated form of dissolving, filtering, cooling recrystallization and suction filtration, the recrystallization treatment efficiency is improved, and the device has higher social use value and application prospect.

The invention belongs to the technical field of chemical synthesis, and relates to a method for continuously synthesizing 4-bromo-2-p-chlorophenyl-5-trifluoromethyl pyrrole-3-nitrile by a microchannel reactor, which comprises the following steps: pumping a substrate solution to a first plate type micro-reaction module; respectively pumping the bromination reagent solution to a first plate type micro-reaction module, a second plate type micro-reaction module and a third plate type micro-reaction module to obtain a reaction base solution; the reaction base solution is introduced into a fourth plate type micro-reaction module, n-heptane is pumped to the fourth plate type micro-reaction module and a fifth plate type micro-reaction module, deionized water is pumped to the fourth plate type micro-reaction module and the fifth plate type micro-reaction module, and extract liquor is obtained; and carrying out separation, evaporation recovery and recrystallization to obtain a finished product. Through the multi-stage series design of the micro-channel reactor, catalytic bromination replaces traditional bromine oxidation and reaction-extraction in-situ integration, and the three major problems of low efficiency, serious pollution and poor safety of an intermittent process are solved.

The invention relates to the technical field of membrane separation, and particularly discloses a preparation method and a preparation device of a recrystallized silicon carbide disc membrane, and the preparation method comprises the steps of raw material preparation, burdening, molding and pressing, finishing treatment, sintering treatment and product detection. The preparation device of the recrystallized silicon carbide disc membrane comprises a shell mechanism, a controller and an internal extrusion mechanism, the controller is installed outside the shell mechanism. And the internal extrusion mechanism is arranged below the left side of the shell mechanism. According to the preparation method and the preparation device of the recrystallized silicon carbide disc type membrane, wet material extrusion forming is adopted, and then the recrystallized silicon carbide disc type membrane is processed in a sintering and shaping mode, so that the recrystallized silicon carbide disc type membrane is higher in acid and alkali resistance, corrosion resistance and hardness and has hydrophilic and oleophobic characteristics, and the porosity of the membrane is improved; materials in the kneading machine are automatically cleaned in the extruding step, so that the utilization rate of the materials is increased, and the production cost is reduced.

The invention discloses a preparation method of a compound menthol ointment. The preparation method comprises the following steps: preparing menthol and / or camphor microcrystals: coating the microcrystals with a wall material to obtain microcapsules; and mixing the menthol with a matrix and other oil-soluble active ingredients to prepare the compound menthol ointment. Camphora and / or menthol crystal grains with the average particle size of 1-10 microns are obtained by adopting a solvent replacement recrystallization method, the microcapsule is prepared by taking the camphor and / or menthol crystal grains as a core material, and after the microcapsule is broken, the oil-soluble component or skin grease of an outer matrix slowly dissolves the crystal grains, so that the camphor and / or menthol component slowly contacts with air, the volatilization of the camphor and / or menthol component is slowed down, and the effect of improving the quality of the microcapsule is achieved. Therefore, the cool skin feeling effect is prolonged.

The present invention discloses a preparation method of high-purity amino gallium, indium, and aluminum compounds, belonging to the technical field of semiconductor chips, and comprising the following steps: The first step is to prepare a lithium dimethylamide n-hexane suspension; the second step is to prepare one of crude tris(dimethylamino)gallium dimer, crude tris(dimethylamino)indium dimer, and crude tris(dimethylamino)aluminum dimer; the third step is to purify the crude tris(dimethylamino)metal compound by stepwise cooling recrystallization to obtain high-purity amino gallium, indium, and aluminum compounds; the present invention purifies the crude tris(dimethylamino)metal compound by stepwise cooling recrystallization, which not only has high efficiency and simple process, but also has a moderate crystallization rate of the product during the recrystallization process, will not form impurity encapsulation, has good crystal form of the product, and the purity is ≥99.9999% (6N), meeting the purity requirements for ALD / CVD film deposition of semiconductor chips.

The invention relates to low-alpha-ray aluminum oxide and a preparation method thereof, and belongs to the technical field of aluminum oxide powder preparation. Raw materials of the low-alpha-ray aluminum oxide comprise a sodium aluminate solution, the sodium aluminate solution contains thorium and uranium, and the method comprises the following steps: carrying out a first decomposition reaction on the sodium aluminate solution by using a first aluminum hydroxide seed crystal to obtain a first decomposition solution; carrying out solid-liquid separation on the first decomposition solution to obtain a liquid-phase substance; performing a second decomposition reaction on the liquid-phase substance by using a second aluminum hydroxide seed crystal to obtain aluminum hydroxide; dissolving aluminum hydroxide with sulfuric acid to obtain an aluminum sulfate solution; performing chemical reaction on the aluminum sulfate solution and ammonium sulfate to obtain aluminum ammonium sulfate; re-crystallizing the aluminum ammonium sulfate for multiple times to obtain high-purity aluminum ammonium sulfate; and roasting the high-purity aluminum ammonium sulfate to obtain the low-alpha-ray aluminum oxide. The purity of the low-alpha-ray aluminum oxide is greater than or equal to 99.99%, the thorium content is less than or equal to 5ppb, the uranium content is less than or equal to 5ppb, and the median particle size is adjustable in a range of 1-50 microns.

The invention discloses a method for preparing copper sulfate from PCB etching liquid, and belongs to the technical field of PCB etching liquid treatment.The method comprises the following steps that alkaline PCB etching waste liquid and acidic PCB etching waste liquid are mixed to obtain basic copper chloride precipitate; reacting the basic copper chloride precipitate with concentrated sulfuric acid to obtain a copper sulfate crude product; adding a hydrogen peroxide solution into the copper sulfate crude product solution, stirring and reacting for 0.5-2 hours, adding a precipitator to adjust the pH value to 3.5-4, and carrying out solid-liquid separation to obtain an impurity-removed solution; the impurity removal solution is introduced into an adsorption column filled with modified activated carbon, then evaporation concentration, cooling crystallization and reduced-pressure suction filtration are carried out, and copper sulfate is obtained.According to the method, the processes of acid-base neutralization, oxidation impurity removal, adsorption impurity removal and recrystallization are adopted, and the low-cost and efficient recovery and purification technology is achieved; and the recovery efficiency is improved to the maximum extent and the cost is controlled while the high purity of the product is ensured.

The invention provides a method for preparing electronic-grade copper oxide by using circuit board acidic etching waste liquid, and belongs to the field of copper resource recovery. The method comprises the following steps: sequentially carrying out impurity removal, concentration crystallization, salt-alkali reaction and cleaning on the circuit board acidic etching waste liquid, and collecting to obtain a copper hydroxide crude product; dissolving and recrystallizing to obtain a copper hydroxide refined product; a carbonized ammonia water solution is added to react with the copper hydroxide refined product, and ammonia cupric carbonate is obtained after adsorption and purification; adding a surfactant and a zinc salt additive, and stirring; drying to obtain modified basic cupric carbonate; carrying out selective etching on the modified basic cupric carbonate by adopting dilute acid to obtain basic cupric carbonate particles; and calcining the basic cupric carbonate particles at 300-500 DEG C to obtain the copper oxide powder with the honeycomb structure. According to the method, on the basis of the basic step of recovering copper resources from the circuit board acidic etching waste liquid, the treatment steps of purification, grain refinement, porous etching and the like are added, so that the purity and the activity performance of a final copper oxide product are improved, and the electronic-grade copper oxide is prepared.

The invention belongs to the technical field of perovskite solar cell material preparation, and particularly provides a simple preparation method of high-purity formamidine hydriodate with controllable crystal form, which comprises the steps of feeding, concentrating, washing, dissolving, crystallizing, washing, drying and the like. The method can be used for synthesis in a room-temperature laboratory, has few steps, is simple to operate, and obviously reduces the difficulty in process production. The crystal is separated out by cooling instead of a poor solvent for recrystallization, and the crystal form of the product can be controlled simply by a simple programmed cooling program with high operability. And meanwhile, by adding the washing procedure, the recrystallization frequency is reduced, the use of an organic solvent is greatly reduced, the post-treatment complexity of the product is also reduced, and the phenomenon that the product is heated and exposed to light in the post-treatment process to generate impurities is effectively avoided.

The invention provides a bio-based crude terephthalic acid hydrofining method, and belongs to the technical field of terephthalic acid hydrofining. The method comprises the following steps: carrying out recrystallization pretreatment on bio-based crude terephthalic acid, mixing the pretreated bio-based crude terephthalic acid with a solvent, adding a catalyst, carrying out a hydrofining reaction, replacing the solvent after the reaction is finished, carrying out recrystallization treatment on a hydrofined product, washing with water, and drying to obtain refined terephthalic acid, the method disclosed by the invention has the advantages of high impurity removal rate, mild reaction conditions and small process pollution, the refining of the bio-based crude terephthalic acid is realized, the obtained terephthalic acid can meet the requirements of an existing industrial method, and the concentration of impurities p-carboxybenzaldehyde is less than or equal to 25ppm and the concentration of methyl benzoic acid is less than or equal to 180ppm.

The invention relates to a synthesis process of an omarigliflozin intermediate, and belongs to the technical field of drug synthesis, one-step efficient conversion is adopted in the process of synthesizing the omarigliflozin intermediate, p-bromophenylhydrazine hydrochloride is used as a starting raw material, and a target product is obtained through indole cyclization, alkali precipitation and acidification crystallization. Toluene plays a role in cyclization and dehydration in a high-temperature reflux process, in a purification process of alkali precipitation and acidification crystallization, a sodium hydroxide aqueous solution is utilized to hydrolyze and convert a product into water-soluble sodium salt, the water-soluble sodium salt enters a water phase, a toluene layer containing a large amount of organic impurities and the water phase are layered in a standing and layering process, and the organic impurities in the toluene layer are removed; the preparation method comprises the following steps of: preparing a sodium salt, acidifying in a water phase by using hydrochloric acid, changing the sodium salt form of the product into an acid form, and crystallizing from the water phase, which is equivalent to recrystallization purification, so that the prepared product has higher purity, the purity is stabilized at 98% or above, and the purity of the product can meet the quality standard of medical intermediates.

The invention relates to a method for purifying an electronic-grade sulfonium salt photoacid generator. The method comprises the following steps: heating, preparing a photoacid generator stock solution, purifying through ion exchange resin, cooling, recrystallizing, carrying out solid-liquid separation, washing crystals and the like to obtain the high-purity photoacid generator, so that the metal content in the photoacid generator can be effectively reduced, the single metal content is less than 5ppb, and the yield is up to 80-90%. And mother liquor is collected and purified by resin and can be used for preparing photoacid stock solution again. The operation effectively reduces the use of an organic solvent and the generation of wastewater, can further improve the recrystallization yield, and meets the requirements of green and sustainable development.

The invention relates to the technical field of preparation of silicon carbide materials, in particular to a preparation method of high-density recrystallized silicon carbide, which comprises the following steps: 1) putting silicon carbide powder with different particle sizes, an additive and a solvent into a mixer, and fully and uniformly mixing to obtain pug for preparing the high-density recrystallized silicon carbide; the additives comprise a plasticizer, a binder, a pH regulator and a sintering aid; (2) pug is put into a kneading and extruding all-in-one machine to be subjected to pugging and forming; 3) drying the formed pug to obtain a dry blank for preparing high-density recrystallized silicon carbide; and 4) putting the dry blank into a recrystallization sintering furnace, and carrying out high-temperature sintering according to a sintering curve and a sintering atmosphere to obtain a high-density recrystallized silicon carbide product. Through optimized process parameters and an innovative preparation process, a pressureless sintering process is coupled in a recrystallization process, so that the density and the crystallization quality of the silicon carbide material are remarkably improved.

The invention discloses a preparation process of high-purity dotenorad, and belongs to the technical field of organic synthesis route design and raw material medicine and intermediate preparation. Benzothiazole is used as a starting material, reduction, acylation, amide condensation, oxidation, demethylation and other reactions are sequentially carried out, a dotenorad crude product is synthesized, and the required crystal form is obtained through recrystallization. The raw materials of the preparation method are cheap, easy to obtain and high in stability, the defect that the raw materials of other preparation processes are poor in stability is overcome, and the preparation method is convenient to operate and suitable for industrial production; the total yield of the prepared dotenorad in each step is 66.80%, and the purity of the dotenorad can reach 99.99%.

The invention belongs to the technical field of food processing, and particularly relates to a preparation method and application of resistant starch. By optimizing drying process parameters (temperature, humidity control and the like), the damage of spray drying (high-temperature hydrogen bond damage), vacuum freeze drying (water loss of a crystal channel caused by sublimation of ice crystals) and traditional hot air drying (untimely loss of bound water caused by unregulated moisture distribution) to the starch double-helix structure in the prior art is effectively avoided. By maintaining a moisture environment required by recrystallization of starch molecules, ordered arrangement of starch chains is promoted, the relative crystallinity of the resistant starch is remarkably improved, and the problems of incomplete crystal structure and limited digestion resistance caused by an existing drying process are solved; and a key technical support is provided for large-scale application in the fields of baked foods, meal replacement products, pharmaceutical preparations and the like.

To provide a method for manufacturing a graphite crucible hard to be exhausted even when put at high temperature.SOLUTION: A method for manufacturing a single crystal growth graphite crucible, capable of growing the single crystal on the main surface of a seed crystal substrate by a sublimation recrystallization method comprises: the molding step of molding a raw material including coke mainly constituted of needle coke and binder pitch; the calcination step of calcining the molded molding to obtain a calcined product; the first impregnation calcination step of performing the impregnation and calcination of additional binder pitch once or more to the calcined product to obtain an impregnation calcination product; the graphitization step of heating and graphitizing the impregnation calcination product at 2000°C or more to obtain a graphitization product; and the second impregnation calcination step of performing the impregnation and calcination of additional binder pitch once or more to the graphitization product.SELECTED DRAWING: Figure 1

The invention discloses a method for preparing vitamin D2 with high conversion rate and high selectivity, and belongs to the technical field of organic photosynthesis reaction.The method comprises the steps that an ergosterol solution passes through a first-stage illumination reactor, the illumination wavelength is controlled to be 254 nm, the illumination time is 20-25 min, and an ergosterol ring-opening product reaction solution is obtained through a first photoreaction; the ergosterol ring-opening product reaction liquid passes through a second-stage illumination reactor, the illumination wavelength is controlled to be 365-415 nm, the illumination time is 30-35 min, and a VD2 precursor reaction liquid is obtained through a second photoreaction; the VD2 precursor reaction liquid is heated and converted into VD2 converted oil; and carrying out esterification, crystallization, hydrolysis and recrystallization on the VD2 conversion oil to obtain a VD2 finished product. According to the method, the conversion rate of ergosterol and the selectivity of a target product can be remarkably improved, the purity of a VD2 finished product is improved, the impurity content is reduced, and the VD2 impurity limit requirement specified by European Pharmacopoeia is met.

Disclosed in the present application are a non-noble metal-based bifunctional catalyst, a preparation method therefor, and the use thereof. The non-noble metal-based bifunctional catalyst comprises a support and an active component; the support is a hydrogen-type ZSM-48 molecular sieve; the active component comprises an active element, the active element being selected from among at least one of Fe, Co and Ni, and the dispersion of the active component being 5.5-40%. The catalyst is prepared by preparing an aluminum source, a templating agent, an inorganic base, a metal precursor and water into a mother solution, and then adding the parent ZSM-48 molecular sieve to the mother solution to be subjected to hydrothermal crystallization at a certain temperature. An one-step recrystallization policy is used to simultaneously construct metal sites and acid sites of the bifunctional catalyst. The bifunctional catalyst prepared by the method has advantages of high metal dispersion and good stability, and exhibits excellent catalytic activity and target product yields in chain alkane isomerization reactions.