Abstract: The present invention relates to a process for continuous hydrogenation of a nitro compound to the corresponding amine in a liquid reaction mixture comprising the nitro compound in the presence of a supported catalyst which comprises as the active component at least one element from groups 7 to 12 of the periodic table of the elements, wherein the hydrogenation is performed in the presence of at least one salt selected from the group consisting of the salts of the alkali metals, alkaline earth metals and of the rare earth metals and to a supported catalyst for continuous hydrogenation of a nitro compound to the corresponding amine in a liquid reaction mixture comprising the nitro compound which comprises as the active component at least one element from groups 7 to 12 of the periodic table of the elements and one salt of the alkali metals, alkaline earth metals or of the rare earth metals.

Abstract: The present invention relates to a process for continuous hydrogenation of a nitro compound to the corresponding amine in a liquid reaction mixture comprising the nitro compound in the presence of a supported catalyst which comprises as the active component at least one element from groups 7 to 12 of the periodic table of the elements, wherein the hydrogenation is performed in the presence of at least one salt selected from the group consisting of the salts of the alkali metals, alkaline earth metals and of the rare earth metals and to a supported catalyst for continuous hydrogenation of a nitro compound to the corresponding amine in a liquid reaction mixture comprising the nitro compound which comprises as the active component at least one element from groups 7 to 12 of the periodic table of the elements and one salt of the alkali metals, alkaline earth metals or of the rare earth metals.

Abstract: Process for scrubbing a crude mixture which is obtained in the nitration of toluene after separating off the nitrating acid and comprises dinitrotoluene, nitric acid, nitrogen oxides and sulfuric acid, which comprises two scrubbing steps (WS-I) and (WS-II), wherein i) in a first scrubbing step (WS-I), the crude mixture is extracted with a scrubbing acid I comprising nitric acid, nitrogen oxides and sulfuric acid in a scrub comprising at least one extraction stage, where the scrubbing acid discharged from the first extraction stage (WS-I-1) of the first scrubbing step (WS-I) has a total acid content of from 10 to 40% by weight and a content of from 80 to 350 ppm of hydrocyanic acid, giving a prescrubbed crude mixture, ii) in a second scrubbing step (WS-II), the prescrubbed crude mixture comprising dinitrotoluene is extracted with a scrubbing acid II in a scrub comprising at least one, preferably at least 2, extraction stage(s), where the scrubbing acid discharged from the first extraction stage (WS-II-1) of th

Abstract: The present invention relates to a process for workup of nitrite-comprising alkaline process wastewaters from the nitration of aromatic compounds, wherein the alkaline process wastewater is acidified by addition of acids and the offgas which comprises nitrogen oxides and escapes from the acidified process wastewater is worked up, comprising the steps of a) acidifying the process wastewater by adding acid to a pH below 5, which forms an organic phase which separates out, an acidic aqueous phase and a gaseous NOx-containing phase, and b) removing the gaseous NOx-containing phase.

Abstract: Process for scrubbing a crude mixture which is obtained in the nitration of toluene after separating off the nitrating acid and comprises dinitrotoluene, nitric acid, nitrogen oxides and sulfuric acid, which comprises two scrubbing steps (WS-I) and (WS-II), wherein i) in a first scrubbing step (WS-I), the crude mixture is extracted with a scrubbing acid I comprising nitric acid, nitrogen oxides and sulfuric acid in a scrub comprising at least one extraction stage, where the scrubbing acid discharged from the first extraction stage (WS-I-1) of the first scrubbing step (WS-I) has a total acid content of from 10 to 40% by weight and a content of from 80 to 350 ppm of hydrocyanic acid, giving a prescrubbed crude mixture, ii) in a second scrubbing step (WS-II), the prescrubbed crude mixture comprising dinitrotoluene is extracted with a scrubbing acid II in a scrub comprising at least one, preferably at least 2, extraction stage(s), where the scrubbing acid discharged from the first extraction stage (WS-II-1) of t

Abstract: A process for the preparation of dintrotoluene which comprises (a) nitrating toluene with a nitrating acid, wherein said nitrating acid is a mixture of nitric acid and sulfuric acid, in one or more nitration steps, and separating the nitrating acid from the process stream thus formed, wherein a crude mixture comprising dinitrotoluene and a fraction of said nitrating acid dissolved therein is obtained, said crude mixture further comprising at least 50 ppm of HCN, and (b) washing the crude dinitrotoluene containing mixture in one or more washing steps, wherein, before the first washing step is carried out, the crude mixture is distilled and/or stripped to remove HCN therefrom, wherein a crude dinitrotoluene containing mixture which is essentially free of HCN is obtained.

Abstract: A process for the preparation of dintrotoluene which comprises (a) nitrating toluene with a nitrating acid, wherein said nitrating acid is a mixture of nitric acid and sulfuric acid, in one or more nitration steps, and separating the nitrating acid from the process stream thus formed, wherein a crude mixture comprising dinitrotoluene and a fraction of said nitrating acid dissolved therein is obtained, said crude mixture further comprising at least 50 ppm of HCN, and (b) washing the crude dinitrotoluene containing mixture in one or more washing steps, wherein, before the first washing step is carried out, the crude mixture is distilled and/or stripped to remove HCN therefrom, wherein a crude dinitrotoluene containing mixture which is essentially free of HCN is obtained.

Abstract: The invention relates to a process for scrubbing a crude mixture comprising dinitrotoluene, nitric acid, nitrogen oxides and sulfuric acid obtained in the nitration of toluene after the nitrating acid has been separated off, which comprises two scrubbing steps (SS-I) and (SS-II), wherein i) in a first scrubbing step (SS-I), the crude mixture is extracted with a scrubbing acid I comprising nitric acid, nitrogen oxides and sulfuric acid in a scrub comprising at least one extraction stage, where the scrubbing acid discharged from the first extraction stage (SS-I-1) of the first scrubbing step (SS-I) has a total acid content of from 20 to 40% by weight and a prescrubbed crude mixture is obtained, ii) in a second scrubbing step (SS-II), the prescrubbed crude mixture comprising dinitrotoluene is extracted with a scrubbing acid II in a scrub comprising at least one extraction stage, where the scrubbing acid discharged from the first extraction stage (SS-II-1) of the second scrubbing step (SS-II) has a pH of less

Abstract: A process for working up alkaline process wastewater from the nitration of aromatic compounds to mono-, di- and trinitroaromatics, said alkaline process wastewater having a pH of 7.5 to 13, comprising the steps of a) acidifying the alkaline process wastewater by adding concentrated sulfuric acid which originates from the workup of the aqueous, sulfuric acid-containing phase obtained in the nitration to a pH below 5, which forms a mixture A consisting of organic phase which separates out and acidic aqueous phase, b) contacting the mixture A with fresh sewage sludge, and c) removing the sewage sludge.

Abstract: A process for working up alkaline process wastewater from the nitration of aromatic compounds to mono-, di- and trinitroaromatics with a pH of 7.5 to 13 or a mixture W with a pH of 6 to 10 of alkaline process wastewater and the aqueous distillate of the sulfuric acid concentration, comprising the steps of a) acidifying the alkaline process wastewater or the mixture W by adding concentrated sulfuric acid which originates from the workup of the aqueous, sulfuric acid-containing phase obtained in the nitration to a pH below 2, which forms a mixture A consisting of organic phase which separates out and acidic aqueous phase, and b) extracting the mixture A with an aromatic extractant.

Abstract: A process for working up alkaline process wastewater from the nitration of aromatic compounds to mono-, di- and trinitroaromatics, said alkaline process wastewater having a pH of 7.5 to 13, comprising the steps of a) acidifying the alkaline process wastewater by adding concentrated sulfuric acid which originates from the workup of the aqueous, sulfuric acid-containing phase obtained in the nitration to a pH below 5, which forms a mixture A consisting of organic phase which separates out and acidic aqueous phase, b) contacting the mixture A with fresh sewage sludge, and c) removing the sewage sludge.

Abstract: The present invention relates to a process for workup of nitrite-comprising alkaline process wastewaters from the nitration of aromatic compounds, wherein the alkaline process wastewater is acidified by addition of acids and the offgas which comprises nitrogen oxides and escapes from the acidified process wastewater is worked up, comprising the steps of a) acidifying the process wastewater by adding acid to a pH below 5, which forms an organic phase which separates out, an acidic aqueous phase and a gaseous NOx-containing phase, and b) removing the gaseous NOx-containing phase.

Abstract: The invention relates to a foam comprising at least 70% by weight of carbon and having a mean cell size above 20 ?m, a porosity based on this cell size of from 35% to 99.5% and an open cell content above 90%, an internal surface above 50 m2/g, having cell struts whose cross section is a triangle having concave sides and having pores in the cell framework material having dimensions of from 0.2 nm to 50 nm and a volume of from 0.01 cm3/g to 0.8 cm3/g, and also to its use. It further relates to a process for producing a foam comprising at least 70% by weight of carbon by pyrolysis of polymer foams which comprise at least 30% by mass of a polymer material having a nitrogen content of more than 6% by mass and having a porosity of from 35 to 99.5% and an open cell content above 1%, have inorganics incorporated into the polymer foam and/or applied to the surface and/or are treated during and/or after the pyrolysis with water vapor and/or carbon dioxide and/or oxygen at above 400° C.

Abstract: Prepolymers which contain isocyanate groups, have an NCO content of at least 30.0% by weight and can be prepared by reacting an isocyanate mixture consisting predominantly of diphenylmethane diisocyanates and polyphenylpolymethylene polyisocyanates and having a proportion of two-ring isomers of not more than 74% by weight with at least 4-functional polyols or a mixture of polyols having a mean functionality of at least 4, where the polyols or polyol mixtures have a hydroxyl number of from 200 to 1650 mg KOH/g and a number average molecular weight of less than 1100 g/mol.

Abstract: Thermally stable rigid foams based on isocyanate can be produced by reacting a) polyisocyanates with b) compounds containing at least two hydrogen atoms which can react with isocyanate groups, c) water, in the presence of d) physically acting blowing agents, in the presence or absence of e) catalysts and auxiliaries and/or additives, wherein the component b) comprises bi) at least one polyether alcohol having a functionality of at least 1.5 and a hydroxyl number of from 10 to 100 mg KOH/g in an amount of from 0.2 to 80% by mass, based on b), and bii)at least one polyester alcohol in an amount of from 5 to 90% by mass, based on b), the water c) is present in an amount of at most 2% by mass, based on the sum of the components b) to e), and the component d) used comprises hydrocarbons and/or fluorine-containing hydrocarbons in an amount of from 5 to 30% by mass, based on the sum of the components b) to e).

Abstract: Storage-stable, blowing agent-containing halogen-free emulsions for producing rigid foams based on isocyanate comprise a) compounds containing hydrogen atoms which are reactive toward isocyanate groups, b) water, c) physically acting, halogen-free blowing agents and, if desired, d) auxiliaries and/or additives which are customary in polyurethane chemistry, wherein the component a) comprises polyether alcohols having a functionality of greater than 1.5 and a hydroxyl number of from 10 to 100 mg KOH/g in an amount of from 0.2% by mass to 80% by mass, based on the mass of the component a), and the halogen-free, physically acting blowing agents c) used are hydrocarbons having from 3 to 10 carbon atoms.

Abstract: A microcellular PU elastomer having improved dynamic-mechanical properties and based on an isocyanate component consisting essentially of 4,4'-MDI and also further customary constituents has, after heating at from 100 to 120.degree. C. for from 8 to 24 hours, a melting range of from 130.degree. C. as the minimum lower limit to 230.degree. C. as a minimum upper limit, measured by differential scanning calorimetry (DSC) at a heating rate of 20.degree. C./min, and a urea content of from 14 to 18% by weight.A process is also provided for preparing such a microcellular PU elastomer having improved dynamic mechanical properties. The microcellular PU elastomers can be used for producing damping elements.

Abstract: A microcellular PU elastomer having improved dynamic mechanical properties and based on an isocyanate component consisting essentially of 4,4'-MDI and further customary constituents has a physicochemical structure which, in the gel permeation chromatograph (GPC) of a solution of the microcellular polyurethane elastomer prepared at 90.degree. C. in N,N-dimethylformamide containing 1 percent of di-n-butylamine measured against polymethyl methacrylate (PMMA) as standard, displays a signal occurring in addition to low molecular weight main signal and comprising one or more peaks at an (apparent) molar mass of greater than 250,000 g/mol which becomes smaller or disappears on addition of lithium chloride to this solution, and a urea content of from 14 to 18% by weight.A process is also provided for preparing such a microcellular PU elastomer having improved dynamic mechanical properties. The microcellular PU elastomers can be used for producing damping elements.

Abstract: Blowing agent-containing emulsions comprisea) compounds containing hydrogen atoms which are reactive toward isocyanates,b) blowing agents,c) catalysts, auxiliaries and/or additives which are customary in polyurethane chemistry, wherein the blowing agents b) are present as an emulsion in the components a) and c), and polyester alcohols having the following structure are used as emulsification aids: ##STR1## where m=0-15n=0-1o=0-15p=0-1q=0-15r=0-1s=0-15t=0-1u=0-10v=0-15x=1-5y=1-4 or mixtures of 1-3 where r+n.noteq.0z=0-3z.sub.i =0.1-3R.sub.1 is an aliphatic structure without OH groups, based on the structure of polyhydric alcohols, preferably ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol and dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,3-butanediol, trimethylolpropane, trimethylol ethane, glycerol, pentaerythritol, where these substances can also be used as any mixture with one another in the esterification and R.sub.

Abstract: In a process for producing rigid polyurethane foams having improved heat distortion resistance and reduced thermal conductivity by reactinga) polyisocyanates withb) compounds containing hydrogen atoms reactive toward isocyanates, in the presence ofc) water, and, if desired,d) physically acting blowing agents ande) catalysts and known auxiliaries and/or additives, the compounds b) containing hydrogen atoms reactive toward isocyanates are a polyol mixture comprisingb1) a polyol which can be prepared by addition of ethylene oxide and/or propylene oxide onto a hexitol or a hexitol mixture, with the total hexitol content of the polyol mixture being from 15 to 30% by weight, based on the polyol mixture, andb2) a polyol which can be prepared by addition of ethylene oxide and/or propylene oxide onto one or more aromatic amines, with the total amine content of the polyol mixture being from 1 to 10% by weight, based on the polyol mixture, and the amount of the polyol mixture in the component b) is from 60 to 100 parts