243results about "Nitrosyl chloride" patented technology

The invention relates to the field of lithium batteries and lithium capacitors, in particular to a preparation method for difluorosulfimide lithium salt and application of the difluorosulfimide lithium salt. The preparation method for the difluorosulfimide lithium salt, provided by the invention, comprises the following steps: (1) performing fluorination reaction: synthetizing midbody difluorosulfimide from dichlorosulfimide and hydrogen fluoride under the action of a catalyst; (2) performing reaction between the difluorosulfimide obtained in the step 1 and alkaline lithium, and performing solid-liquid separation after the reaction to obtain an LiFSI product. The preparation method for the difluorosulfimide lithium salt, provided by the invention, is low in cost, few in by-product and simple in post-treatment, and the quality and the purity of the product are ensured, therefore the preparation method which is capable of obtaining the high-quality and high-purity product and is economic and practical is provided; the preparation method is suitable for industrial production.

The present invention provides a preparation method of lithium bis(fluorosulfonyl)amide. The method comprises the following steps: A) reacting chlorosulfuric acid with ammonia in the presence of an organic base to obtain organic alkali salt of bis(fluorosulfonyl)amide; B) mixing the bis(fluorosulfonyl)amide obtained in the step A) with HF for a fluorinated reaction to obtain an organic alkali salt of bis(fluorosulfonyl)amide; C) mixing the organic alkali salt of bis(fluorosulfonyl)amide obtained in the step B) with an alkaline substance for a neutralization reaction to obtain a bis(fluorosulfonyl)amid metal salt crude product; D) purifying the bis(fluorosulfonyl)amid metal salt crude product obtained in the step C) to obtain bis(fluorosulfonyl)amid metal salt; and E) mixing the bis(fluorosulfonyl)amid metal salt obtained in the step D) with a lithium reagent for a replacement reaction, so as to obtain lithium bis(fluorosulfonyl)amide. The preparation method provided by the invention has the characteristics of low raw material cost, low impurity content in the product and high yield of lithium bis(fluorosulfonyl)amide.

The present invention provids a method for producing fluorosulfonylimides more safely, rapidly and efficiently, which enables suppression of production of by-products, and fluorosulfonylimides. The method for producing a fluorosulfonylimide salt of the present invention includes a step of reacting a fluoride compound containing at least one element selected from the group consisting of elements of Group 11 to Group 15 and Period 4 to Period 6 (excluding arsenic and antimony) with a compound represented by the following general formula (I) to give a fluorosulfonylimide salt represented by the general formula (II): [Chemical Formula 1] wherein R1 denotes at least one element selected from the group consisting of elements of Group 11 to Group 15 and Period 4 to Period 6 (excluding arsenic and antimony); R3 denotes fluorine, chlorine or a fluorinated alkyl group having 1 to 6 carbon atoms; R4 denotes fluorine or a fluorinated alkyl group having 1 to 6 carbon atoms; and m denotes an integer of 2 or 3.

The invention relates to a preparation method of difluoro-sulfimide and lithium difluoro-sulfimide, and belongs to the field of fluorine chemical synthesis. The preparation method comprises the steps that difluoro-sulfimide is obtained by adding fluoro-sulfoxide into a mixture of sulfamic acid or amino sulfonyl fluoride and fluorosulfuric acid for reacting and then subjected to recrystallization and filtration which are conducted at the temperature of minus 100 DEG C to 16 DEG C and / or reduced / normal-pressure distillation and purification which are conducted at the temperature of 60 DEG C to 169 DEG C; difluoro-sulfimide and a lithium-containing substance react in a solvent to obtain lithium difluoro-sulfimide, and then recrystallization, filtration and purification are conducted. According to the preparation method, difluoro-sulfimide can be prepared through one step, lithium difluoro-sulfimide is obtained through lithiation, and the prepared products can be purified; few steps are needed, the technology is simple, the process is easy to control, the requirement on production devices is low, the production efficiency, the product yield and the purity are high, and large-scale production and application can be achieved.

The invention relates to the field of chemical synthesizing, in particular to a preparation method of imidodisulfuryl fluoride lithium salt. The preparation method includes the steps of firstly, allowing chlorosulfonic acid and chlorosulfonyl isocyanate to react in the presence of catalyst to obtain dichlorosulfimide; secondly, allowing dichlorosulfimide and hydrogen fluoride to react in the presence of catalyst to obtain imidodisulfuryl fluoride; thirdly, allowing imidodisulfuryl fluoride to react with compound containing lithium to obtain the imidodisulfuryl fluoride lithium salt. The preparation method has the advantages that the chlorosulfonic acid and chlorosulfonyl isocyanate are used as the raw materials in the first-step reaction, the generation of waste gases such as SO2 and HCl is avoided, and environment protection requirements are satisfied.

Disclosed is a method for producing “a salt or a complex comprising imide and an organic base”, characterized by reacting halogenated sulfuryl or halogenated phosphoryl with ammonia in the presence of an organic base. According to this method, a target imide compound can be produced in a high yield while significantly suppressing the production of by-products. Further, by reacting the obtained imide compound with an alkali metal hydroxide or an alkaline earth metal hydroxide, an imide metal salt can be easily derived.

The invention provides a method for producing hydrogen bis(fluorosulfonyl)imide (HFSI) by reacting hydrogen bis(halosulfonyl)imide (HXSI) with hydrogen fluoride, where each X is independently a nonfluoro-halide, such as Cl, Br, or I.

The invention discloses a preparation method of difluoro-sulfonyl imide lithium. The preparation method comprises the following steps: 1) under a protective atmosphere, adding a fluorizating agent into difluoro-sulfonyl imide to perform a fluorination reaction so as to obtain a mixture, wherein the fluorizating agent is one of or a combination of fluorine, a fluorine-containing mixed gas, anhydrous hydrogen fluoride, potassium fluoride, antimonic fluoride and rubidium fluoride; 2) performing reduced pressure distillation on the obtained mixture to obtain a di(fluoro-sulfonyl) imide intermediate; and 3) under a protective atmosphere, performing synthetic reaction on the obtained di(fluoro-sulfonyl) imide intermediate and a lithium source, and performing solid-liquid separation to obtain difluoro-sulfonyl imide lithium. According to the preparation method disclosed by the invention, the fluorination reaction does not need a solvent or other auxiliary agent, is less in types of adopted reagents, does not introduce a new impurity, is simple in operation, and is easy to control; the method is less in side reaction, good in fluorination effect and low in fluorination cost; and the purity and the yield of the product namely difluoro-sulfonyl imide lithium obtained by a subsequent synthetic reaction are improved on the whole, and the method has good economic and environmental benefits.

A process for producing a bis(fluorosulfonyl)imide anion compound by substituting a bis(chlorosulfonyl)imide anion compound, obtained from sulfamic acid, chlorosulfonic acid, and a halogenating agent, with fluorine is used as a process for producing a fluorine compound for use, for example, in the synthesis of battery electrolytes and ionic liquids. According to the above process, the inclusion of impurities can be reduced, and a high-purity fluorine compound of a bis(fluorosulfonyl)imide compound can be efficiently produced at a high yield. A base catalyst can be used in the reaction for substituting the bis(chlorosulfonyl)imide anion with fluorine. The base catalyst is preferably a nitrogen-containing compound.

The invention provides a purification method of lithium bis(fluorosulfonyl)imide. The method comprises the following steps of (1) dissolving a lithium bis(fluorosulfonyl)imide crude product in an organic solvent; filtering to remove insoluble substances and obtain filter liquid; (2) mixing the filter liquid and organic acid anhydride and then heating to obtain mixed liquid, wherein the organic acid anhydride has a structure shown as a formula I, and in the formula I, R1 and R2 are independently selected from C1-C5 alkyls or C1-C5 halogen alkyls; (3) performing evaporation treatment on the mixed liquid to remove the organic solvent and obtain an intermediate product; (4) crystallizing the intermediate product in a low-polarity organic solvent to obtain a lithium bis(fluorosulfonyl)imide pure product, wherein the polarity of the low-polarity organic solvent is lower than 4. The purification method provided by the invention has the advantages that the organic acid anhydride is used for removing moisture in the lithium bis(fluorosulfonyl)imide crude product; other impurities are not introduced; the recrystallization is performed through solvent polarity regulation. The purification method provided by the invention has the advantages that the process is simple; the obtained lithium bis(fluorosulfonyl)imide has high purity.

The invention discloses a preparation method for lithium bis(fluorosulfonyl)imide. The preparation method comprises the following steps: 1) preparing fluorine sulfamide lithium; 2) preparing sulfuryl fluoride, and pumping the sulfuryl fluoride into the fluorine sulfamide lithium solution, and adding an acid-binding agent to prepare bifluorine sulfimide ammonium salt; 3) dissolving the bifluorine sulfimide ammonium salt in water solution, to obtain bifluorine sulfimide water solution through the acid resin exchange; 4) adding lithium carbonate, regulating the PH value to be neutral, filtering and removing undissolved substances, depressurizing and removing the most of the water, and adding a weak-polarity organic solvent to separate out a coarse product of the lithium bis(fluorosulfonyl)imide, further depressurizing and drying; and 5) adding a polarity solvent to the coarse product of the lithium bis(fluorosulfonyl)imide, stirring and dissolving, filtering and removing the undissolved substances, depressurizing and removing a strong-polarity solvent, and adding the weak-polarity organic solvent to perform the recrystallization, and depressurizing and drying to obtain a product after filtering. The preparation method is simple, the reaction time is short, the yield is high, and metal ion and negative ion impurities can be effectively controlled, so that the product with the high purity can be obtained.

The invention relates to the field of chemical synthesis, and concretely relates to a preparation method of lithium bis(fluorosulfonyl)imide. The preparation method of lithium bis(fluorosulfonyl)imide comprises the following steps: 1, carrying out a displacement reaction on bis(fluorosulfonyl)imide and LiX, wherein X is selected from Cl, Br and I; 2, mixing a proper amount of hydrogen chloride with a reaction solution obtained through the displacement reaction; and 3, carrying out solid-liquid separation on a reaction solution obtained in step 2, concentrating the obtained liquid phase, adding a poor solvent to crystallize, and carrying out solid-liquid separation to obtain the bis(fluorosulfonyl)imide. The preparation method of bis(fluorosulfonyl)imide allows highly pure LiFSI to be obtained, and has the advantages of realization of stable quality and high yield of the above product, effective reduction of the content of potassium ions, sodium ions, chloride ions, sulfate radicals, water and other impurities, simple operating steps, reasonable production cost, high safety, and suitableness for industrial production.

The invention discloses a preparation method of LiFSI (imidodisulfuryl fluoride lithium salt). The method comprises steps as follows: S01, HFSI (lithium fluorosulfonimide) and organic lithium salt LiR are subjected to an exchange reaction under the solvent-free condition or an organic solvent condition to produce LiFSI and organic matter HR, wherein the PKa of the organic matter HR is 0-50, the exchange reaction is performed under the condition of gas protection, and the reaction temperature is 0-60 DEG C; S02: a reactant under the solvent-free condition in S01 is added to a poor reagent to be crystallized, and LiFSI is obtained after solid-liquid separation; S03: a reactant under the organic solvent condition in S01 is subjected to solid-liquid separation, a liquid phase is concentrated, the reactant is added to a poor reagent to be crystallized, and LiFSI is obtained after solid-liquid separation. The preparation method has the characteristics of simple steps, high yield, high purity, good stability and low impurity content.

The invention discloses a preparation method of lithium bis (fluorosulfonyl) imide. The preparation method comprises the following steps: (1) in the presence of an ammonia source, an organic solvent,fluoride salt and an initial amount of sulfuryl fluoride, slowly introducing organic alkali while continuously introducing the balance of sulfuryl fluoride until the reaction is finished, and directlycarrying out reduced pressure distillation on the reaction solution to obtain an intermediate, namely the difluorosulfonyl imide salt; and (2) in the presence of an organic solvent, adding lithium oxide powder into the intermediate imidodisulfuryl fluoride salt, filtering, concentrating, adding a non-aqueous poor solvent, and crystallizing to obtain lithium bis (fluorosulfonyl) imide.

The invention relates to a process for the preparation of a bis(sulphonato)imide salt of formula:(III) (SO3−)—N−—(SO3)3C+  (III)where C+ represents a monovalent cation, comprising the reaction of amidosulphuric acid of formula:(OH)—SO2—NH2  (I)with a halosulphonic acid of formula:(OH)—SO2—X  (II)where X represents a halogen atom, and comprising a reaction with a base which is a salt formed with the cation C+.The invention also relates to a process for the preparation of bis(fluorosulphonyl)imide acid of formula:F—(SO2)—NH—(SO2)—F  (V)and to a process for the preparation of lithium bis(fluorosulphonyl)imide salt of formula:F—(SO2)—N−—(SO2)—F Li+.  (VII)

The invention relates to a preparation method of difluoro lithium sulfimide. The method comprises the following step: in a saturated alkyl carbonate and / or saturated fluoroalkyl carbonate solvent, enabling dichloro lithium sulfimide to react with alkali metal fluoride serving as a fluorinating agent to obtain the difluoro lithium sulfimide under a catalytic condition of a crown ether phase-transfer catalyst adaptive to the alkaline metal fluoride. The preparation method of the difluoro lithium sulfimide disclosed by the invention is simple in process route and easy to realize industrial preparation.

The invention discloses a preparation method for coproducing bis(chlorosulfonyl)imide and lithium bis(fluorosulfonyl)imide, which comprises the following steps: S1, adding sulfuryl chloride into a first solvent, dropwisely adding octamethylcyclotetrasilazane for reaction, and carrying out purification to obtain bis(chlorosulfonyl)imide; S2, taking bis(chlorosulfonyl)imide and anhydrous hydrofluoric acid to react under the action of a catalyst to obtain bis(fluorosulfonyl)amide; and S3, taking the bis(fluorosulfonyl)amide and lithium fluoride to react in a second solvent, and carrying out purification to obtain the lithium bis(fluorosulfonyl)imide. According to the invention, proper raw materials are selected and matched with a solvent method to co-produce bis(chlorosulfonyl)imide and lithium bis(fluorosulfonyl)imide. The method has the advantages of simple preparation process, few and recyclable byproducts, high yield, no water participation in the production process, high purity of the obtained bis(chlorosulfonyl)imide and lithium bis(fluorosulfonyl)imide, no wastewater generation and green and environment-friendly process route, and is suitable for industrial production.

The invention provides a method for synthesizing lithium bis(fluorosulfonyl)imide. The synthetic method of the lithium bis(fluorosulfonyl)imide is characterized by comprising the following steps: (1) in a nitrogen atmosphere, sufficiently mixing bis(fluorosulfonyl)imide and an organic solvent, and putting a mixture into a reactor with a condenser; sequentially adding lithium fluoride and liquid-state hydrogen fluoride into the reactor and raising the temperature to react; (2) reducing the temperature of a reaction system, and decompressing and displacing by nitrogen to completely remove residual hydrogen fluoride gas, and filtering a reaction solution under the nitrogen atmosphere to remove insoluble matters, so as to obtain filtrate; (3) concentrating the filtrate by utilizing a high-vacuum decompression and desolvation method; (4) cooling a concentrated solution and adding a low-polarity solvent; recrystallizing at low temperature, and filtering and carrying out decompression and drying treatment at 40 DEG C to obtain the pure lithium bis(fluorosulfonyl)imide. The synthetic method has the advantages that used reagents are cheap and easy to obtain, a preparation process is simple, a reaction is rapid and complete, a few of byproducts are produced and are easy to remove, a post-treatment manner is simple and convenient, a product has high purity and the synthetic method is very suitable for industrial production.

The invention discloses a preparation method of bis(fluorosulfonyl)amine. The preparation method comprises the following steps of enabling SO2F2 (sulfuryl fluoride), NH4F (ammonium fluoride) and triethylamine to react to prepare organic alkaline salt of bis(fluorosulfonyl)amine; performing replacing reaction with strong acid, and performing pressure-relief distillation, so as to obtain high-puritybis(fluorosulfonyl)amine. The preparation method has the advantages that the SO2F2, the NH4F and the organic alkaline are used as the raw materials, and the FSO3H (fluorosulfonic acid) with strong corrosion property is not used as the raw material; the technology is simple, the continuous operation property is strong, the product is easy to separate and purify, the high-purity (more than or equalto 99%) bis(fluorosulfonyl)amine can be prepared, and the yield rate reaches 90% or above; the chloride ion is not used in the whole reaction process, and the product quality is stable.

To provide an imide salt represented by the formulawherein, R represents a halosulfonyl group (—SO2X1 where X1 is a halogen such as fluorine, chlorine, bromine and iodine) or dihalophosphoryl group (—POX2X3 where X2 and X3 are the same or different halogens such as fluorine, chlorine, bromine and iodine), and M represents an alkali metal;with high selectivity and high efficiency by using a low-cost starting material.In the production of an imide salt, an alkali metal fluoride, a sulfuryl halide or phosphoryl halide, and ammonia or an ammonium salt are reacted. According to this method, a desired imide salt can be produced with high yield, while greatly suppressing the production of a by-product.

The invention relates to a preparation method of imidodisulfuryl fluoride lithium salt. The preparation method comprises the following steps: (1) performing a fluorination reaction of imidodisulfuryl chloride by taking a hydrogen fluoride complex salt as a fluorinating agent in the presence of a solvent, the fluorinating agent and an initiator, performing filter pressing separation at the end of the reaction, distilling filtrate under a reduced pressure to remove the solvent, and rectifying under a reduced pressure to obtain imidodisulfuryl fluoride; (2) reacting the imidodisulfuryl fluoride with a lithium compound at the temperature of 80 to 110 DEG C to obtain a crude imidodisulfuryl fluoride lithium salt. The preparation method provided by the invention has the advantages of easiness in operation of a fluorinating process route, mild conditions, high operability and easiness in implementation of industrial production; the prepared imidodisulfuryl fluoride lithium salt is 99 percent or more in purity, and is suitable for lithium batteries.

The invention discloses a preparation method of alkali metal salt of bis(fluorosulfonyl)amide. The preparation method comprises the step of carrying out fluoridation on alkali metal salt of bis(chlorosulfonyl)amide in an polar aprotic solvent by taking ion liquid as a phase transfer catalyst and alkali metal fluoride as a fluorinating agent, so as to obtain corresponding alkali metal salt of bis(fluorosulfonyl)amide. Compared with the prior art, the preparation method has the advantages that reaction conditions are mild, the yield and the purity are high, the product is easily separated and purified, the ion liquid catalyst can be recycled and reduced, and the like. The preparation method is applicable to industrial mass production.

The invention relates to a process for preparing a fluoro compound of formula:R2—(SO2)—NX—(SO2)—F   (III)comprising:(a) a first step for obtaining the chloro compound of formula:R1—(SO2)—NX—(SO2)—Cl;   (II)this first step comprising the reaction of the sulfamide of formula:R0—(SO2)—NH2   (I)with a sulfureous acid and a chlorinating agent; and(b) a second step for obtaining the fluoro compound of formula (III), this second step comprising the reaction of the chloro compound of formula (II) with anhydrous hydrofluoric acid in at least one organic solvent;in which:X represents either a hydrogen atom or a monovalent cation M;R1 represents an electron-withdrawing group having a positive Hammett parameter σp;if R1 represents Cl, then R0 represents OH; otherwise, R0 is identical to R1; andif R1 represents Cl, then R2 represents F; otherwise, R2 is identical to R1.

The invention discloses a preparation method of lithium bis (fluorosulfonyl) imide. The preparation method comprises the steps of 1 by using chlorosulfonyl isocyanate and chlorosulfonic acid as reaction raw materials, dropwisely adding to react for 5 hours, and keeping the temperature to react for 10 hours to obtain bis (chlorosulfonyl) imide; 2 putting bis (chlorosulfonyl) imide serving as a reaction raw material into a tetrafluoro reaction bottle, reacting with anhydrous hydrogen fluoride under the action of a catalyst, and generating bis (fluorosulfonyl) imide after reacting for 20 hours; and 3 putting the bis (fluorosulfonyl) imide into a reaction bottle, and reacting with lithium hydroxide or lithium carbonate under the action of a catalyst to obtain a product containing lithium bis (fluorosulfonyl) imide. The preparation method disclosed by the invention is simple to operate, easy to control and small in environmental pollution, and meanwhile, inert gas is used as a reaction environment to remove water by low-temperature drying, so that the reaction of the bis (fluorosulfonyl) imide and the final product lithium bis (fluorosulfonyl) imide with water in air is avoided, the quality of the product is ensured, and the preparation method is suitable for industrial production of the lithium bis (fluorosulfonyl) imide.

A mixture of sulphamic acid, a halogenated sulphonic acid and thionyl chloride is heated to allow the reaction to proceed, to thereby produce first intermediate products. The first intermediate products are then subjected to reaction with an alkali metal fluoride MF to produce second intermediate products. The second intermediate products is then subjected to reaction with the alkali metal fluoride MF in a polar solvent to obtain a desired product MN(SO2F)2 (where M is an alkali metal).

The present invention relates to a novel method for preparing lithium bis(fluorosulfonyl)imide and, more specifically, to a method for preparing lithium bis(fluorosulfonyl)imide, capable of simply and economically preparing lithium bis(fluorosulfonyl)imide, which is a lithium salt to be used in an electrolyte solution for a lithium secondary battery, in a high yield and with high purity. According to the present invention, the novel method for preparing lithium bis(fluorosulfonyl)imide can resolve the problem of a conventional technique by reacting a bis(chlorosulfonyl)imide compound, which is a starting material, with a fluorination reagent, and then immediately treating the same with an alkali reagent without purification or concentration, and has an effect of enabling lithium bis(fluorosulfonyl)imide to be simply and economically prepared in a high yield and with high purity.

The invention discloses a preparation method of high-purity imidodisulfuryl fluoride lithium. The preparation method includes the steps: taking imidodisulfuryl fluoride salt (MFSI) with the purity higher than or equal to 99.9% as a raw material, and performing replacement reaction on the imidodisulfuryl fluoride salt (MFSI) and lithium sulfonate (RSO3Li) in ester, ketone, alcohol, ether, carbonicester or nitrile reaction solvents to obtain imidodisulfuryl fluoride lithium salt crude solution; filtering and concentrating the crude solution, adding ether organic solvents into concentrated solution, filtering and concentrating the concentrated solution, adding low-polarity non-proton organic solvents into the concentrated solution, and performing standing, crystallization and drying to obtain the high-purity imidodisulfuryl fluoride lithium. R in the lithium sulfonate (RSO3Li) is Ar or CnHxFyOz, n>=1, x, y and z>=0, the R is adjusted according to the solubility of the imidodisulfuryl fluoride salt (MFSI) in reaction solvents. In the preparation steps, anhydrous operation is performed under protection of inert gas. The preparation method has the advantages of simple process, wide substrate selectivity, low cost and high product purity.

The invention belongs to the technical field of preparation of electrolyte salts used for electrochemical devices, and specifically relates to a preparation method with advantages of safe reaction process, simple operation method, high product production capacity, simple post-treatment, applicability to large-scale production and capability of obtaining high-purity difluorosulfonylimide salt meeting the use requirements of electronic chemicals. The preparation method comprises the following steps: (1) introducing dichlorosulfonylimide and fluorine-containing gas into a micro-channel reactor, and carrying out a reaction at 36 to 120 DEG C for 60 to 600 s so as to obtain difluorosulfonylimide; (2) adding the obtained difluorosulfonylimide and an oxide of alkali metal or an oxide of alkaline-earth metal into an organic solvent, and carrying out a reaction at minus 20 to 10 DEG C for 1 to 12 h so as to obtain the difluorosulfonylimide salt.

The invention discloses a method for preparing bis(fluorosulfonyl)imide salt. The method comprises the following steps: reacting bis(chlorosulfonyl)imide and a fluorination reagent to obtain bis(fluorosulfonyl)imide; and reacting the bis(fluorosulfonyl)imide and an alkali metal salt chelator to obtain the corresponding bis(fluorosulfonyl)imide salt. The method provided by the invention does not need the use HF and other high-activity compounds, and is simple and safe in preparation process, thereby being suitable for industrialization application.

The invention belongs to the technical field of fluorochemical industry, and particularly relates to methods for preparing imidodisulfuryl fluoride and alkali metal salt thereof. The method for preparing imidodisulfuryl fluoride comprises the steps of mixing imidodisulfuryl chloride with ether-nHF complex, conducting stirring reaction for 1-20 h at 0-100 DEG C, and conducting reduced pressure distillation after reaction to obtain imidodisulfuryl fluoride. The method for preparing alkali metal salt of imidodisulfuryl fluoride comprises the step of mixing imidodisulfuryl fluoride with MF for reaction under ball milling to obtain a crude product of alkali metal salt of imidodisulfuryl fluoride, wherein reaction temperature is 10-30 DEG C, reaction time is 2-20 h, and M is Li, Ma or K. The technical scheme is safe, efficient and suitable for industrial production.