Title of Invention

AN IMPROVED PROCESS FOR THE PREPARATION OF ALKYL ALDEHYDES

Abstract

An improved process for the preparation of alkyl aldehydes which comprises mixing an alkene or its solution, with a transition metal complex catalyst in water immlsible solvent such as aliphatic,aromatic hydrocarbons, formaldehyde optionally in the presence of an additional ligand such as herein described, at a temperature ranging between 60-150 C, under stirring for a period of 2 to 50 hours, cooling the reaction mixture to room temperature and separating the product in the reaction mixture by conventional methods like distillation or chromatography.

Full Text

This invention relates to an improved process for the preparation of alkyl aldehydes. More particularly it relates to a process using formaldehyde and alkene in presence of organic soluble transition metal complex catalyst. The reaction comprises of two phases viz organic phase and aqueous phase. The organic phase contains olefin, either in pure form or a solution in organic solvent and water insoluble metal complex catalyst comprising of group VIII element such as Rh, Ru, Ir or Co. The aqueous phase contains 3 0% formaldehyde. In the prior art, the aldehydes products formed have a variety of applications in industries as solvents, plasticizers, detergent chemicals, fragrance chemicals, intermediates, pharmaceuticals etc. The aldehydes are generally manufactured by oxo technology (B. Cornils in "New synthesis with carbon monoxide" edited by J. Falbe, Springer Verley, New York (1980)) or by catalytic dehydrogenation of primary alcohol at high temperatures in presence of Cu or Cu-chromite catalysts and also by reduction of the acyl halides on Palladium on Barium sulfate support (Rosenmund reaction) (David Miller in Kirk Othmer's Encyclopedia of Chemical Technology Vol. 1, page 932, John Wiley & Sons, New York (1991)). Oxo technology for the manufacture of aldehydes using homogeneous catalysts are well known in which the addition of carbon monoxide and hydrogen to an olefin in the presence of metal complex catalyst soluble in the reaction medium is involved. This leads to risk associated with the handling of poisonous and explosive gases such as carbon monoxide and hydrogen. Whereas all other processes give poor yields as compared with the oxo process. In this invention, we propose the use of simple C1 molecule such as formaldehyde instead of gaseous reactants such as carbon monoxide and hydrogen used in conventional oxo technology. This reduces the risks associated with frandling of poisonous and explosive gases such as carbon monoxide and hydrogen required in the conventional oxo process. The object of the present invention, therefore is to prepare the aldehydes using alkene and formaldehyde in presence of transition metal complex catalyst and also to avoid use of synthesis gas containing carbon monoxide and hydrogen, which required in conventional oxo process for manufacture of aldehydes. Accordingly, the present invention provides an improved process for the preparation of alkyl aldehydes which comprises mixing an alkene or its solution, with a transition metal complex catalyst in water immisible solvent such as aliphatic, aromatic hydrocar- bons, formaldehyde,optionally in the presence of an additional ligand such as herein described, at a temperature ranging between 60-150°C, under stirring for a period of 2 to 50 hours, cooling the reaction mixture to room temperature and separating the product in the reaction mixture by conventional methods like distillation or chromatography. In one of the embodiments of the present invention the alkenes used contain carbon atoms in the range of 2-30 and may be selected from ethylene, propylene, 1-hexene, 1-octene, 1-dodecene or the like. In another embodiment the alkene may contain function groups like aldehydes, ketones, acids, cyanides, or the like. In yet another embodiment the water immiscible solvent may be from aliphatic and aromatic hydrocarbon solvents like hexane, heptane, octane, decane, benzene, toluene, ortho, meta, or para xylene, cyclohexane, ethyl acetate, diethyl ether, or higher alcohols. In yet another embodiment the metal complex catalyst having general formula MAXBYCZ wherein M = Transition element in group VII A such as Rh, Co, Ir, or the like, A,B,C are ligands such as aromatic or aliphatic phosphines, pyridine, pyrolidine, isoquino-line or the like, and x,y,z are the numbers of respective ligands and x + y + z ==3 and x,y,z may be vary between =>0 = In a feature of the present invention the metal complex catalyst is prepared by process described by Evans et al (Evans D., Osborne J. and Wilkinson G. in J. Chem. Soc. A 3133 (1968)) using Rhodium trichloride and triphenyl phosphine. In another feature of the process of the present invention may be carried out in the presence or absence of an additional ligand. The additional ligand may be selected from aromatic or aliphatic phosphines, pyridine, pyrolidine, isoquinoline. The process of the invention is described in detail in the examples given below which are illustrative only should not be considered to limit the scope of the invention. EXAMPLE 1 The following charge consisting of aqueous and organic phases was introduced in 300 cm3 autoclave equipped with magnetic type drive for agitation. The organic phase consisted of HRh(CO)(PPh3)3 460 mg (0.5 mmol) in 60 cm3 toluene alongwith 1.65 g (6.3 mmol) of triphenyl phosphine. To this solution 30 cm3 30% formaldehyde solution in water was. added. The auto clave was pressurised with ethylene gas at 250 psig pressure. The reaction mixture was stirred at 900 rpm at 100 °C for 12 hrs. The reactor was cooled below ambient temperature and discharged. The color of organic solution was dark brown and analysis of aqueous and organic phase showed exhaustion of formaldehyde and corresponding amount of propionaldehyde was detected. The reactants and products were confirmed and analysed by GC analysis. EXAMPLE 2 The following charge consisting of aqueous and organic phases was introduced in 300 cm3 autoclave equipped with magnetic type drive for agitation. The organic phase consisted of HRh(CO)(PPh3)3 460 mg (0.5 mmol) in 55 cm3 toluene alongwith 5 cm3 ( 0.014 mol) hexene and 1.65 g (6.3 mmol) of triphenyl phosphine . To this solution 30 cm3 30% formaldehyde solution in water was added. The reaction mixture was stirred at 900 rpm at 100 °C for 24 hrs. The reactor was cooled below ambient temperature and discharged. The color of organic solution was dark brown and analysis of organic phase shows exhaustion of hexene and corresponding amount of normal and branched heptaldehydes was detected. The reactants and products were confirmed and analysed by GC analysis. EXAMPLE 3 The following charge consisting of aqueous and organic phases was introduced in 300 cm3 autoclave equipped with magnetic type drive for agitation. The organic phase consisted of HRh(CO)(PPh3)3 460 mg (0.5 mmol) in 55 cm3 toluene alongwith 5 cm (0.047 mol) styrene and 1.56 g (6.3 mmol ) of triphenyl phosphine. To this solution 30 cm 30% formaldehyde solution in water was added. The reaction mixture was stirred at 900 rpm at 100 °C for 24 hrs. The reactor was cooled below ambient temperature and discharged. The color of organic solution was dark brown and analysis of organ ic phase shows exhaustion of styrene and corresponding amount of 2 phenyl propionaldehyde and 3 phenyl propi- onaldehyde was detected. The reactants and products were confirmed and analysed by GC analysis. Present invention gives following advantages over hitherto known processes * Hydroformylation of alkenes is achieved with aqueous formaldehyde instead of carbon monoxide and hydrogen. WE CLAIM : 1. An improved process for the preparation of alkyl aldehydes which comprises mixing an alkene or its solution, with a transition metal complex catalyst in water immisible solvent such as aliphatic, aromatic hydrocarbons, formaldehyde optionally in the presence of an additional ligand such as herein described, at a temperature ranging between 60-150°C, under stirring for a period of 2 to 50 hours, cooling the reaction mixture to room temperature and separating the product in the reaction mixture by conventional methods like distillation or chromatography. 2. A process as claimed in claim 1, wherein the alkenes used contain carbon atoms in the range of 2-30 and may be selected form ethylene, propylene, 1-hexene, 1-octene, 1-dodecene. 3. A process as claimed in claims 1 to 2 wherein the alkene may contain function groups like aldehydes, ketones, acids, cyanides. 4. A process as claimed in claims 1 to 3 wherein the water immiscible solvent used for preparing solution of alkene is selected from aliphatic and aromatic hydrocarbon solvents like hexane, heptane, octane, decane, benzene, toluene, ortho, meta, or para xylene, cyclohexane, ethyl acetate, diethyl ether, or higher alcohols. 5. A process as claimed in claims 1 to 4 wherein, the metal complex catalyst is having the general formula MAXBYCZ wherein M = Transition element in group VII A such as Rh, Co, Ir, A,B,C are ligands such as aromatic or aliphatic phos-phines, pyridine, pyrolidine, isoquinoline and x,y,z are the numbers of respective ligands and x + y + z ==3 and x,y,z may be =>0 = 6. An improved process for the preparation of alkyl aldehydes substantially as herein described with reference to the examples.

Documents:

1862-del-1997-abstract.pdf

1862-del-1997-claims.pdf

1862-del-1997-complete specification [granted].pdf

1862-del-1997-correspondence-others.pdf

1862-del-1997-correspondence-po.pdf

1862-del-1997-description (complete).pdf

1862-del-1997-form-1.pdf

1862-del-1997-form-2.pdf