The process of co-production of isoprene and 3-methylbutan-1
(57) Abstract:Usage: in the petrochemical industry, in particular in the production of monomers for synthetic rubber - isoprene and 3-methylbutan-1. The essence of the invention: a process of co-production of isoprene and 3-methylbutan-1 provides a two-stage dehydrogenation of isopentane, contact condensation of the gas of the first stage dehydrogenation, the stabilization of the obtained condensate by distillation emitting in the distillate fraction containing C3-C4-hydrocarbons and 3-methylbutan-1. From the last clear rectification 3-methylbutan-1. CBM product stabilization - isopentane - isoamylene fractions divided into isopentanol returned to the first stage dehydrogenation, and isoamylenes fraction fed to the second stage dehydrogenation. The invention relates to an improved method for producing a joint production of isoprene and 3-methylbutan-1, which are used in the IC industry and petrochemistry.Closest to the claimed by its technical essence is a method of producing isoprene and 3-methylbutan-1 two-step dehydrogenation of isopentane, including contact condensation of the gas of the first stage d is it emitting in the distillate fraction, containing hydrocarbons WITH3-C4and as the product isopentane-isoamylene fractions, separation of isopentane-isoamylene faction on isopentanol returned to the first stage dehydrogenation, and isoamylenes fraction fed to the second stage dehydrogenation . The disadvantage of this method is the low quality of the obtained 3-methylbutan-1 (the content of the basic substance is not more than 80-95 wt.%), increased energy consumption at the stage extractive distillation.The aim of the invention is to improve the quality 3-methylbutan-1 and the reduction of energy consumption.This task is solved by the claimed process of co-production of isoprene and 3-methylbutan-1 two-step dehydrogenation of isopentane, including contact condensation of the gas of the first stage dehydrogenation, the stabilization obtained by contact of the gas of the first stage dehydrogenation rectification emitting in the distillate fraction containing hydrocarbons WITH3-C4and as the product isopentane-isoamylene fractions, separation of isopentane-isoamylene faction on isopentanol returned to the first stage dehydrogenation, and isoamylenes fraction fed to the second stage digitdia in the distillate together with hydrocarbons3-C4select 3-methylbutan-1 and obtained from the distillate by a clear rectification produce 3-methylbutan-1.P R I m e R 1. On the dehydrogenation serves 150 g/h isopentanol fraction composition, wt.%:
The process is carried out in a quartz flow type reactor, heated by the electric furnace, fluidized bed alimohammadi catalyst (IM-2201). The download size of the catalyst 40 cm3. The catalyst is pre-developed for 2 h in a stream of air at 650aboutWith and reduce it gradually to 580aboutC. Experiments are performed cycles. The cycle includes the dehydrogenation - 15 min, nitrogen purge - 5 min, a gradual increase in temperature up to 650aboutWith the current air - 20 min, regeneration of the catalyst in this mode, 30 minutes, lowering the temperature in a stream of air to 580aboutS - 20 min, nitrogen purge - 5 min Volumetric flow rate of nitrogen, air and raw materials is 400 h-1.Get the contact gas composition of 1 wt.%:
Piperidin Traces in the number 149,08 g/h
The percentage of raw materials, converted into coke, and 0.62 wt.%.The condensate from the first stage dehydrogenation in the number 141,35 g/h composition of 2 wt.%:
Hydrocarbons WITH52,25 served in the stabilization column on the Department MB together with the fraction of hydrocarbons WITH3-C4. This top of the column select 21,4 g/h fraction composition of 3 wt.%:
MB OF 9.30
Hydrocarbons WITH5of 0.50 and below select 119,95 g/h isopentane-isoamylene fraction composition 4 wt.%:
Hydrocarbons WITH5to 2.57 served on extractive rectification, where divided into isoamylenes fraction composition of 5 wt.%:
Isoprene 1.46 and isopentanol fraction, which return to the first stage dehydrogenation. The dehydrogenation isoamylenes fraction (composition 5) is carried out in the flowing metal reactor filled with industrial chronolonical avodat cycles: dehydration - the regeneration. Isoamylenes fraction is diluted with steam in a ratio of 1: 20 and with the speed 144,75 g/h fed into the reactor. At the outlet of the reactor get the contact gas (excluding water) in the amount of 142,96 g/h composition of 6 wt. %:
The cyclopentadiene 0.03 Yield of isoprene on missed isoamylene was 38.7 wt. % , turned isoamylene and 88.5 wt.%. The percentage of raw material, transformed in the Cox - 1,65.Next, the resulting fraction part 6 after receiving the condensate is directed to extractive rectification, where already allocate commodity isoprene.The fraction containing 3-methylbutan-1 (part 3), is subjected to distillation, which is carried out on a laboratory column of the periodic steps in the cube which load 500 g of the indicated fractions and the temperature of the cube +30aboutAnd the top - 50aboutWith selected 187 g of a fraction consisting of 7 wt.%:
Then after selecting the specified fraction of the temperature of the cube R> Hydrocarbons WITH40,14
Decomposition DMF (particularly diethylamine) in this fraction are missing.In Cuba column remains 275 g of a fraction consisting of 9 wt.%:
Output MB at the stage of selection based on the obtained condensate (part 2) is:
F = 100% = 100% = 47.1% of wt where G3and G8- the amount taken and obtained after distillation fractions;
X2and X8content MB in fractions 2 and 8 wt.share;
W2and W3- the rate of accumulation of condensate composition 2 and 3, g/hP R I m m e R 2. The condensate from the first stage of the industrial process of dehydrogenation in the number 44978,4 kg/h composition of 1 wt.%:
Hydrocarbons WITH60,6 served in column 1, operating in the following modes:
The number teoreticheskoi number 6
power supply 65 from the Bottom of the column 1 select the isopentane-isoamylene faction in the number 36150,55 kg/h composition of 2 wt.%:
Isoprene of 2.51
Hydrocarbons WITH60,74 which is directed to the selection of the isopentane-isoamylene fraction by extractive distillation, similar to the prototype and example 1.On top of the column 1 select the faction in the number 8782,85 kg/h, the composition of 3 wt.%:
Piperidin 0,10 served in column 2, operating in the following mode.The number of theoretical
plates, 20 pcs.
The number of theoretical
plates in strengthening parts, pieces 10
power 99,5 Top of the column 2 are selected faction in the number 1837,64 kg/h of part 4 wt.%:
3MB is NY 2 select faction in the number 6945,21 kg/h composition of 5 wt.%:
n-Pentane 0,34 which is sent to the column 3, operating in the following modes:
The number of theoretical
plates, pieces 55
The number of theoretical
plates in strengthening parts, pieces of 35.5
Reflux the number 40
power 57 on Top of the column 3 are selected product fraction B in the number 479,38 kg/h composition of 6 wt.%:
Isoprene Traces From the cube column 3 select the isopentane-isoamylene fraction, which return to the stage dehydrogenation.Output MB at the stage of selection in the calculation of the resulting condensate from the first stage is:
F = 100 = a 56.88 wt.%
The products of decomposition of DMF in the product fractions are missing.The process described method can improve the quality MB (the content of the basic substance with 80-95 up 964-97 wt.%, the products of decomposition of DMF available) and to reduce the energy consumption for statification). The process of co-production of ISOPRENE AND 3-METHYLBUTAN-1 the two-stage dehydrogenation of isopentane, including contact condensation of the gas of the first stage dehydrogenation, the stabilization obtained by contact of the gas of the first stage dehydrogenation rectification emitting in the distillate fraction containing hydrocarbons, C3-C4and as the product isopentane-isoamylene fractions, separation of isopentane-isoamylene faction on isopentanol returned to the first stage dehydrogenation, and isoamylenes supplied to the second stage dehydrogenation, characterized in that on the stage condensate stabilization first stage dehydrogenation in the distillate together with the hydrocarbon, C3- C4select 3-methylbutan-1 and obtained from the distillate by a clear rectification produce 3-methylbutan-1.
FIELD: petroleum chemistry, chemical technology.
SUBSTANCE: crude alpha-olefin is heated, raw vinylidene olefins are isomerized in the presence of catalyst and alpha-olefin is separated from isomerized vinylidene olefin by rectification. Separation of alpha-olefin is carried out for at least two successive steps at similar temperatures on top of vat and reducing pressure of rectifying column at each following step. Condensed phase removing from top of the rectifying column at previous step is fed to feeding zone of the following step and the rectifying column at top and vat section is sprayed. For spraying the top section of column the condensed phase removing from the top of rectifying column at the same step is used and for spraying the vat section of column the vat liquid of rectifying column at the same step is used. Separated alpha-olefin is purified additionally from oxygen-containing impurities by adsorption up to polymerization degree of purity. Raw heating, isomerization, separation and adsorption are carried out in atmosphere in inert gas. The unit used for treatment of alpha-olefin includes reactor for isomerization of vinylidene olefins in raw, rectifying column wherein feeding zone is joined with reactor outlet and wherein alpha-olefin of high purity degree is removed from the column top. The unit includes also at least one rectifying column for additional treatment of alpha-olefin of high purity from isomerized vinylidene olefins and adsorption column for separation of oxygen-containing impurities in alpha-olefin of high purity wherein the column inlet is joined with the top outlet of the last rectifying column used for additional treatment of alpha-olefin of high purity and outlet is used for removing alpha-olefin of the polymerization purity degree. Invention provides enhancing quality of the end product.
EFFECT: improved method for treatment.
8 cl, 1 dwg, 1 ex
FIELD: organic chemistry, petroleum chemistry, chemical technology.
SUBSTANCE: method involves preparing ethylene and hexane-1 from butene-1 by the exchange reaction of butene-1 and the isomerization reaction of synthesized hexane-3 to hexane-1. The parent material represents a mixed butene flow wherein butene-1 is isomerized to butene-2 after separation of isobutylene followed by the isomerization reaction of butene-2 to butene-1. Butene-1 is a raw for the exchange reaction.
EFFECT: improved preparing method, simplified technology process.
32 cl, 4 tbl, 4 ex
SUBSTANCE: invention pertains to the method of obtaining 2-methyl-2-butene from isopentane, including gas phase dehydrogenation of isopentane in the dehydrogenation zone, extraction of the C5-fraction from contact gas, mainly consisting of isopentane, tert pentanes, isoprene impurities and other hydrocarbons and obtaining a stream from it, mainly consisting of 2-methyl-2-butene, with use of a liquid phase isomerisation catalyst in a C5-fraction 2-methyl-1-butene in 2-methyl-2-butene and distillation. The method is characterised by that, the above mentioned C5-fraction, possibly containing extra piperylene and 2-pentene, directly or after distillation from the larger part of 2-methyl-2-butene, undergoes liquid phase hydroisomerisation in the presence of a solid catalyst, containing group VIII metal(s), capable of simultaneous catalysing hydrogenation of pentadienes, isoprene and possibly, piperylenes, and positional isomerisation of tert pentenes, preferably with subsequent additional isomerisation of 2-methyl-1-butene in 2-methyl-2-butene on a sulfocationite catalyst, and distillation with output of a distillate stream of mainly isopentane, containing not more than 1.0% mass, preferably not more than 0.2% mass of pentadiene(s), which are mainly recirculated in the hydrogenation zone, and output from the lower part of the recirculation stream of mainly 2-methyl-2-butene with impurities of n.pentane and possibly 2-pentenes. The invention also pertains to the method of obtaining isoprene from isopentane, which involves reaction of 2-methyl-2-butene, obtained from gas phase dehydrogenation of isopentane, with hydroperoxide with further conversion of the oxide or products of hydroxylation in isoprene.
EFFECT: obtaining 2-methyl-2-butene and isoprene from isopentane.
13 cl, 8 ex, 2 tbl, 3 dwg
SUBSTANCE: invention relates to a method of dehydrogenating isopentane and isopentane-isoamylene fractions, carried out at atmospheric pressure in a water vapour medium via dehydrogenation-regeneration cycles in the fixed bed of a catalyst based on platinum and tin deposited on an aluminium-zinc spinel, characterised by that the catalyst used has average crystal size of 22-35 nm with the following content of components in wt %: platinum - 0.05-2.0, tin - 0.1-6.0, aluminium-zinc spinel - the rest. The dehydrogenation process is carried out at 560-620°C, feed space velocity of the material of 300-500 h-1 in the presence of hydrogen and water vapour. The ratio material: hydrogen : water vapour equals 1 :0.5-2.0 :5-20 mol : mol : mol.
EFFECT: use of the method enables more efficient dehydrogenation of isopentane and isopentane-isoamylene fractions.
3 cl, 14 ex, 1 tbl
SUBSTANCE: catalyst system component is obtained via mechanical activation of a solid mixture with the ratio of 2-ethyl hexanoate of group I metal:CrCl3>1:1 and heating the activated mixture to obtain the desired product. The ethylene oligomerisation catalyst system contains an organoaluminium compound of general formula AlR3, a complexing agent, a modifier, a solvent and a chromium-containing component obtained using the disclosed method. The ethylene oligomerisation method is carried out in the medium of a hydrocarbon solvent at temperature of 40-95°C and ethylene pressure of 1-5 MPa in the presence of said catalyst system.
EFFECT: simple method of producing a component of catalyst systems for oligomerising olefins, high output of the product when oligomerising ethylene to hexene-1, high selectivity of the process and purity of hexene-1, low probability of secondary reactions.
4 cl, 1 tbl, 16 ex
SUBSTANCE: invention relates to a method of producing 1-hexene from ethylene trimerisation method, involving use of the catalyst system consisting of chromium complex of general formula [CrCl3(H2O)((Ph2P(1.2-C6H4)P(Ph)(1.2-C6H4)CH=CR2)], where R is hydrogen or metal group, an activator is represented by methylaluminoxane and co-activator, is used as trimethylaluminium. System components are in the following molar ratio: chromium complex: MAO: TMA = 0.1% : 21.4% : 78.5%, in the solution methylcyclohexane at temperature 70-90°C, pressure of 30-40 bar. Invention provides selectivity of the process for trimerisation of ethylene 89-95% of fraction C6, made on 99.3-99.5 % of 1-hexene with high efficiency of process from 900 up to 1400 kg of the product/gCr·h and minimal formation of polymer - 0.3 wt% of all products.
EFFECT: selectivity process for trimerisation of ethylene 89-95% of fraction C6.
1 cl, 1 tbl, 13 ex
SUBSTANCE: present invention relates to an ethylene oligomerisation method. Method involves following steps: a) feeding ethylene, a solvent and catalyst composition containing catalyst and cocatalyst, into a reactor, b) oligomerisation of ethylene in reactor, c) discharging reactor effluent, containing linear alpha-olefins, including 1-butene, solvent, unconsumed ethylene, dissolved in output stream of reactor, and catalyst composition, from reactor, d) separation of ethylene and 1-butene together from rest of reactor effluent and e) recirculation of at least part of ethylene and 1-butene, separated at step d), into reactor. Equal amounts of 1-butene are removed from reactor with reactor effluent and recycled into reactor at step e).
EFFECT: use of disclosed method allows stable operation of reactor, improves heat removal and prevents clogging of reactor.
15 cl, 1 ex, 1 tbl, 3 dwg
SUBSTANCE: invention relates to a process of separating hexene-1 from the mixture obtained in the reaction of section of the ethylene trimerization process, wherein mentioned mixture comprises ethylene, solvent, catalyst and ethylene trimerization products derived, including hexene-1. The method includes at least the following steps: a) separation in the first distillation column a mixture formed by the reaction of ethylene trimerization on top fraction containing ethylene and a bottoms fraction, b) separation of at least one other distillation column at least part of the stream bottoms fraction obtained in step a) for the top fraction containing hexene-1 and butene-1, and a bottoms fraction, c) separation in the final distillation column, at least part of the fraction containing hexene-1 and butene-1, get constant in step b), at the top fraction containing mainly 1-butene and a bottoms fraction containing mainly 1-hexene, wherein in said method: at least one portion of the stream bottoms fraction obtained in step b), is recycled to the a reaction section and at least one other portion of mentioned bottom fraction obtained in step b) is used in at least one recirculation loop, connecting the reaction section and the column of mentioned step b), mentioned recirculation loop allows to cool the reaction section and provide repeated of partial evaporation in mentioned column from step b).
EFFECT: process is more energy efficient.
18 cl, 8 ex, 2 dwg
SUBSTANCE: invention relates to method for producing olefinic C3-C5 hydrocarbons by dehydrogenation of the corresponding paraffinic hydrocarbons in fluidized bed of aluminium-chromium catalyst circulating in the system including the reactor, regenerator (13), and reduction-desorption catalytic preparation after the regenerator (13) carried out by treating the catalyst with reducing gas in a countercurrent mode using horizontal sectioning grids (2). The method is characterized in that immediately after regenerator (13), treatment is carried out in directed internal catalyst circulation mode using vertical partition (6) separating fluidized bed into lifting section (14) and pressure section (15), and then in countercurrent mode with at ratio of catalyst residence time in the said modes is 0.3-3.0.
EFFECT: increasing the yields of target product.
7 cl, 4 ex, 1 tbl
SUBSTANCE: method of selective hydrogenation of acetylenes and dienes in the flow of the C5 hydrocarbons include: hydrogen supply and C5-olefin-containing stream containing the linear pentenes, dienes, acetylenes and cyclopentene, in the reaction system of catalytic distillation; at the same time in the reactor system of catalytic distillation: hydrogenation of acetylenes and dienes; and fractionation C5-olefin-containing stream; removing the head of the faction that contains linear pentenes; removing the side fractions containing cyclopentene; and extract cubic faction. Also the invention relates to method of conversion of linear pentenes in propylene and selective hydrogenation of acetylenes and dienes in a stream of C5 hydrocarbons.
EFFECT: lower costs.
21 cl, 6 dwg, 2 tbl
FIELD: industrial organic synthesis.
SUBSTANCE: invention relates to production of isoprene for use in synthesis of isoprene rubber and butyl rubber used in tire industry and manufacture of general mechanical rubber goods. In the method of invention, isoprene is obtained by decomposition of 4,4-dimethyl-1,3-dioxan in reactors caused by interaction of isobutylene-containing C4 fraction with aqueous formaldehyde solution (prepared by oxidation of methanol) at elevated temperature and pressure in presence of acid catalyst to form reaction medium composed of oil and water layers followed by separation of oil layer into unreacted C4-hydrocarbons and 4,4-dimethyl-1,3-dioxan by rectification leaving bottom residue containing dioxan alcohols (high-boiling by-products to be processed into additional product), separation of water layer, condensation of 4,4-dimethyl-1,3-dioxan decomposition contact gas, and recovery of desired isoprene by rectification. Bottom residue is processed at residual pressure 0.002-0.010 MPa, elevated reflux ratio equal to 2.0-5.0, and continuous circulation of bottom fluid under lower plate of rectification column at weight ratio of circulating bottom fluid as additional product to bottom residue of 4,4-dimethyl-1,3-dioxan rectification equal to 20-35. Column distillate - low-boiling by-products are sent to 4,4-dimethyl-1,3-dioxan synthesis reactors or subjected to catalytic decomposition, separately or jointly with 4,4-dimethyl-1,3-dioxan.
EFFECT: enhanced isoprene production efficiency and reduced specific consumption of raw materials.
1 dwg, 5 ex
FIELD: industrial organic synthesis.
SUBSTANCE: invention relates to production of isoprene for use in synthesis of isoprene rubber, butyl rubber, and isoprene-containing polymers used in tire industry and manufacture of general mechanical rubber goods. In the method of invention, isoprene is obtained by decomposition of 4,4-dimethyl-1,3-dioxan on calcium phosphate catalyst comprising synthesis of 4,4-dimethyl-1,3-dioxan by interaction of isobutylene-containing C4 fraction with formaldehyde-containing blend based on methanol-free formalin obtained by oxidation of methanol followed by rectification of formalin, accomplished at elevated temperature and pressure in presence of acid catalyst followed by separation of reaction medium into oil and water layers including extraction of organic products from water layer, isolation of 4,4-dimethyl-1,3-dioxan, unreacted C4-hydrocarbons, and high-boiling by-products from oil layer, condensation of 4,4-dimethyl-1,3-dioxan decomposition contact gas and isolating from condensate isoprene, unreacted 4,4-dimethyl-1,3-dioxan, recycling isobutylene and formaldehyde-containing water, performing also withdrawal of extracted water layer to be vacuum evaporated followed by sending evaporated water layer to preparation of formaldehyde-containing blend. Evaporation of extracted water layer containing acid catalyst is carried out at temperature of boiler wall in rectification column 80-105°C and residual pressure 0.015-0.025 MPa. Distillate is mixed with above-indicated formaldehyde-containing water and resulting mixture is subjected to two-step concentration of formaldehyde. Second-step distillate, namely recycle methanol, is sent to oxidation zone. Bottom residues of the second step of formaldehyde concentration and those of the extracted water layer evaporation are combined with methanol-free formaldehyde and acid catalyst continuously supplied as replenishment, after which used as formaldehyde-containing blend in the 4,4-dimethyl-1,3-dioxan synthesis. Concentration of acid catalyst is maintained between 1.60 and 1.75 wt %.
EFFECT: increased productivity and reduced material and power consumption.
2 cl, 1 dwg, 5 ex
FIELD: industrial organic synthesis.
SUBSTANCE: invention relates to production of isoprene for use in synthesis of isoprene rubber and butyl rubber used in tire industry and manufacture of general mechanical rubber goods. In the method of invention, isoprene is obtained by decomposition of 4,4-dimethyl-1,3-dioxan on calcium phosphate catalyst comprising synthesis of 4,4-dimethyl-1,3-dioxan by interaction of isobutylene-containing C4 fraction with aqueous formaldehyde solution in presence of acid catalyst to form reaction medium composed of oil and water layers followed by separation of oil layer into unreacted C4-hydrocarbons and 4,4-dimethyl-1,3-dioxan by rectification leaving bottom residue containing dioxan alcohols (high-boiling dioxan alcohols to be processed into additional product), separation of water layer, condensation of contact gas, and recovery of desired isoprene. Low-boiling part of hydrocarbons distilled off in processing of bottom residue of 4,4-dimethyl-1,3-dioxan rectification is separated and thus obtained lower product is discharged as a mixture of high-boiling dioxan alcohols, which constitute additional desired product, whereas upper product is combined with formaldehyde-containing blend fed into 4,4-dimethyl-1,3-dioxan synthesis zone. Acid catalyst utilized in synthesis of 4,4-dimethyl-1,3-dioxan is mixture of oxalic and phosphoric acids at weight ratio between 2:1 and 1:1, whereas summary concentration of acids in formaldehyde-containing blend is maintained between 1.5 and 2.5 wt %. Remaining high-boiling fraction of hydrocarbons taken off in processing of bottom residue of 4,4-dimethyl-1,3-dioxan rectification, which are mixture of heavy residue and high-boiling alcohols, are taken off in the form of by-product.
EFFECT: enhanced isoprene production efficiency and reduced corrosion of technique, clogging with salts and tars, produced useful dioxan alcohols, and reduced specific consumption of raw materials.
1 dwg, 3 ex
FIELD: hydrogenation-dehydrogenation catalysts.
SUBSTANCE: invention relates to catalysts used in isoamylenes-into-isoprene dehydrogenation process and contains, wt %: iron oxide 62-75.4, potassium carbonate 12-21.5, chromium oxide 1-3, potassium hydroxide 0.5-2.5, sulfur 0.1-2.0, ammonium nitrate 0.1-2.0, silicon dioxide 1-5, calcium carbonate 1-5, and cerium nitrate 1-3.
EFFECT: increased mechanical strength, resistance to saturated steam and moisture, and stability during long-time operation.
FIELD: industrial organic synthesis.
SUBSTANCE: first stage of the process comprises synthesis of 4,4-dimethyl-1,3-dioxan via isobutylene/formaldehyde condensation in presence of acid catalyst at 80-100ºC and pressure 1.6-2.0 MPa. Product and high-boiling by-product mixture are isolated from oil layer of reaction mixture. 4,4-Dimethyl-1,3-dioxan is then decomposed on calcium phosphate catalyst at 290-380°C and pressure 0.12-0.16 MPa in presence of water steam. Contact gas is further processed to produce isoprene. High-boiling by-product mixture is distilled on two in series connected vacuum rectification columns. On the first column, 60-70% of distillate is recovered based on the weight of feed. Second distillation on the second column gives second distillate (75-90%) and bottom product, which is recycled into 4,4-dimethyl-1,3-dioxan synthesis zone. Second-column distillate is decomposed into isoprene on ceramic filling at 400-450°C and pressure 0.12-0.16 MPa in presence of water steam supplied at (2-5):1 weight ratio to high-boiling by-product mixture. Contact gas obtained after decomposition of this mixture is processed jointly with contact gas obtained after decomposition of dimethyldioxan.
EFFECT: reduced amount of process waste and increased production of isoprene without increase in consumed raw material.
3 cl, 1 dwg, 1 tbl, 4 ex
FIELD: industrial organic synthesis.
SUBSTANCE: first stage of the process comprises synthesis of 4,4-dimethyl-1,3-dioxan via isobutylene/formaldehyde condensation in presence of acid catalyst at 80-100ºC and pressure 1.6-2.0 MPa. Product and high-boiling by-product mixture are isolated from oil layer of reaction mixture. 4,4-Dimethyl-1,3-dioxan is then decomposed on calcium phosphate catalyst at 290-380ºC and pressure 0.12-0.16 MPa in presence of water steam. Contact gas is further processed to produce isoprene. High-boiling by-product mixture is distilled on vacuum rectification column to give distillate in amount 30-35% of the weight of feed. Distillate is passed to heterogeneous-phase catalytic decomposition into isoprene on ceramic filling at 400-450°C and pressure 0.12-0.16 MPa in presence of water steam supplied at (2-5):1 weight ratio to high-boiling by-product mixture. Contact gas obtained after decomposition of this mixture is processed jointly with contact gas obtained after decomposition of dimethyldioxan.
EFFECT: reduced amount of process waste and increased production of isoprene without increase in consumed raw material.
3 cl, 1 tbl, 4 ex
FIELD: organic chemistry, chemical technology.
SUBSTANCE: invention relates to technology for preparing isoprene that is a monomer in synthesis of polyisoprene, butyl rubber, isoprene-containing polymers used in tire industry and rubber-technical articles and can be used in petrochemical industry. Proposed method for preparing isoprene involves decomposition of 4,4-dimethyl-1,3-dioxane on calcium-phosphate catalyst and involves synthesis of 4,4-dimethyl-1,3-dioxane by interaction of isobutylene-containing C4-fraction with formaldehyde aqueous solution in the presence of acid catalyst to form reaction mass consisting of oily and aqueous layers. Then oily layer is separated to isolate unreacted C4-hydrocarbons and 4,4-dimethyl-1,3-dioxane by rectification and removal of vat residue containing high-boiling dioxane alcohols and other by-side products, separation by rectification and isolation of floating reagent-oxal and absorbent that involves also processing aqueous layer and the following isolation the main product - isoprene from hydrocarbon condensate. Vat residue after rectification of 4,4-dimethyl-1,3-dioxane is separated by rectification for two stages carried out successively in in-line connected columns and bottom product from the first stage - heavy residue with ignition point 130-155°C is removed as floating reagent-oxal. Upper product from the first stage is fed for processing to the second stage and upper product from the second stage - light-boiling part of high-boiling by-side products is fed for decomposition completely on calcium-phosphate catalysts separately or in common with 4,4-dimethyl-1,3-dioxane. Bottom product from the second stage is fed to the synthesis process of 4,4-dimethyl-1,3-dioxane as recycle. Upper product from the second stage in processing by rectification of vat residue of rectification of 4,4-dimethyl-1,3-dioxane is fed for preparing absorbent only in case of stopping decomposition reactors with high-boiling by-side products or reactors wherein 4,4-dimethyl-1,3-dioxane is decomposed. In stopping reactors with decomposition of high-boiling by-side products upper product of the second stage is removed as recycle to synthesis of 4,4-dimethyl-1,3-dioxane and as absorbent component removing in the amount 25-35% of mass of vat residue of rectification of 4,4-dimethyl-1,3-dioxane feeding to the first stage. In stopping reactors with decomposition of high-boiling products and if necessary a mixture of dioxane alcohols, in particular, hydroxyisopropyl-4,4-dioxane-1,3, methyl-4-hydroxyethyldioxane-1,3 and dimethyl-4,4-hydroxymethyl-5-dioxane-1,3 are removed additionally as a bottom product of the second stage. Invention provides enhancing effectiveness in using waste - high-boiling by-side products, preparing additional amount of isoprene from them and enhancing regulation of the process.
EFFECT: improved preparing method.
4 cl, 1 dwg, 6 ex
FIELD: petrochemical processes.
SUBSTANCE: tert-butyl alcohol, 4,4-dimethyl-1,3-dioxan and/or formaldehyde are fed into reaction zone in the form of homogenous mixture with recycled aqueous solution of acid catalyst, which mixture is preliminarily prepared in a separate apparatus at heated to 80-90°C and said aqueous acid solution freed of organics is preliminarily passed through cationite at volume flow rate 15-20 h-1. Process is conducted at elevated temperature and pressure exceeding pressure of water steam at this temperature, and at molar excess of tert-butyl alcohol relative to summary amount of formaldehyde in hollow apparatus mounted coaxially over shell-and-tube heat exchanger and provided with circulation pipe connecting top part of hollow apparatus to bottom part of shell-and-tube heat exchanger, diameter of this pipe being at least three times lass than that of hollow reactor. Circulating factor at least 100 h-1 is achieved with the aid of pump installed in feed supply line into bottom part of hollow apparatus. Reaction products and part of aqueous acid solution are removed from the top of hollow apparatus in one stream passed into separator.
EFFECT: simplified technology and increased yield of isoprene.
1 dwg, 3 tbl, 3 ex