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Process for producing oxygenated productsRelated Patent Categories: Chemistry: Fischer-tropsch Processes; Or Purification Or Recovery Of Products Thereof, Group Viii Metal Containing Catalyst Utilized For The Fischer-tropsch Reaction (i.e., Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Or Pt), Rhodium Containing CatalystProcess for producing oxygenated products description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20050282916, Process for producing oxygenated products. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] THIS INVENTION relates to a process for producing oxygenated products. More particularly, it relates to a process for producing oxygenated products from an olefin-rich feedstock. Still more particularly, the invention relates to a process for producing oxygenated products such as aldehydes and/or alcohols from an olefin-rich feedstock by means of hydroformylation. [0002] According to a first aspect of the invention, there is provided a process for producing oxygenated products from an olefin-rich feedstock, which process comprises reacting, in a hydroformylation stage, a Fischer-Tropsch derived olefinic product obtained by subjecting a synthesis gas comprising carbon monoxide (CO) and hydrogen (H.sub.2) to Fischer-Tropsch reaction conditions in the presence of an iron-based, a cobalt-based or an iron/cobalt-based Fischer-Tropsch catalyst, with carbon monoxide and hydrogen in the presence of a catalytically effective quantity of a hydroformylation catalyst and under hydroformylation reaction conditions, to produce oxygenated products comprising aldehydes and/or alcohols. [0003] The process of the first aspect of the invention is thus characterized thereby that it utilizes said Fischer-Tropsch derived olefinic product as feedstock for the hydroformylation stage. This feedstock is thus obtained by subjecting a synthesis gas comprising carbon monoxide and hydrogen to Fischer-Tropsch reaction conditions in the presence of an iron-based or a cobalt-based Fischer-Tropsch catalyst. [0004] Thus, according to a second aspect of the invention, there is provided a process for producing oxygenated products, which process comprises [0005] subjecting, in a Fischer-Tropsch reaction stage, a synthesis gas comprising carbon monoxide (CO) and hydrogen (H.sub.2) to Fischer-Tropsch reaction conditions in the presence of an iron-based, a cobalt-based or an iron/cobalt-based Fischer-Tropsch catalyst, to obtain an olefinic product; [0006] optionally, working up the olefinic product to remove unwanted components therefrom and/or to separate a particular olefinic component therefrom; and [0007] feeding the olefinic product or the olefinic component as a feedstock to a hydroformylation stage in which the feedstock is reacted with carbon monoxide and hydrogen in the presence of a catalytically effective quantity of a hydroformylation catalyst and under hydroformylation reaction conditions, to produce oxygenated products comprising aldehydes and/or alcohols. [0008] More particularly, the Fischer-Tropsch catalyst and reaction conditions may be selected to give an olefinic product having desired characteristics, depending on the particular oxygenated products required from the hydroformylation stage. Thus, for example, the catalyst and reaction conditions may be those utilized in fluidized bed reactors or reaction stages, eg those commonly known as synthol reactors, or those utilized in fixed bed reactors or reaction stages, or those utilized in slurry bed reactors or reaction stages, as hereinafter described. [0009] The predominant Fischer-Tropsch products from, for example, synthol reactors, can be olefins. These are predominantly linear and mono-methyl .alpha.-olefins, with lesser quantities of linear and mono-methyl branched internal olefins. The balance of the Fischer-Tropsch products comprise aromatics, paraffins and oxygenates such as ketones, aldehydes, alcohols, and carboxylic acids. Typically, in the olefinic product, more than one mono-methyl .alpha.-olefin isomer is present for any given carbon number, with the methyl group being present at any position along the .alpha.-olefin molecule backbone or linear hydrocarbon chain. [0010] A high degree of olefin feedstock purity and linearity have hitherto been regarded as essential for effective hydroformylation thereof; in contrast, in the present invention, it was unexpectedly found that a Fischer-Tropsch derived olefinic product, containing large amounts or proportions of additional, ie non-olefinic, components with different functional groups, as well as relatively large amounts of non-linear or branched olefins, can be used, directly or indirectly, as a hydroformylation feedstock. [0011] The Fischer-Tropsch stage olefinic product or the olefinic component as hereinbefore described can thus be used directly in the hydroformylation stage without any substantial purification or further processing thereof to remove unwanted components such as non-olefins. The non-olefinic components in single or multiple carbon number fractions of the Fischer-Tropsch stage product then act as a reaction medium and/or a solvent medium in the hydroformylation stage, and can thus have a beneficial effect in the hydroformylation stage. These non-olefinic components can ultimately be separated from the heavier hydroformylation stage products, eg by means of distillation, and used as synthetic fuels or the like. It is believed that the additional cost of processing such inert components in the hydroformylation stage is more than compensated for by the saving realized in not having to separate them from the hydroformylation stage feedstock. This is especially true for the higher olefin containing Fischer-Tropsch material, in which it may be difficult to purify and/or separate the valuable olefins from the balance of the Fischer-Tropsch products having structures and boiling points similar to the required olefins. Subjecting such material to hydroformylation conditions favouring the formation of linear products, results in selective `removal` of the olefins by their reacting to form heavier and still more valuable aldehydes and/or alcohols which in turn may be easily separated on the basis of temperature. This simplifies the beneficiation of the olefins. However, if present, organic acids should be removed as these can be deleterious to hydroformylation. [0012] However, the process of the invention also envisages that the olefinic product from the Fischer-Tropsch reaction stage can, if desired, he worked up to remove unwanted components therefrom and/or to separate a particular olefinic component therefrom, in which case this component can be used as the feedstock to the hydroformylation stage. This working up typically involves distillation, and may include conventional, vacuum, extractive or reactive distillation. Instead, or additionally, the working up may involve techniques such as membrane separation. The olefin content and distribution of the feedstock to the hydroformylation stage can thus be tailored according to the oxygenated products which are required. Thus, a discrete or multiple carbon number olefin product from the Fischer-Tropsch stage may thus be processed further to produce narrower `cuts` in which linear .alpha.-olefins are concentrated; when such cuts are used as hydroformylation stage feedstock, hydroformylation products with increased linearity are obtained. [0013] While the Fischer-Tropsch reaction stage and the hydroformylation stage can be separated from each other so that the olefinic product from the Fischer-Tropsch reaction stage can be stored or transported independently of the hydroformylation stage, the Applicant envisages that the stages will preferably be integrated so that the olefinic product from the Fischer-Tropsch stage passes directly to the hydroformylation stage with at most the working up of the olefin product and possibly some intermediate storage thereof between the stages taking place. [0014] In the light of this integration, the carbon monoxide and hydrogen required for the hydroformylation can typically be in the form of synthesis gas, which can then be the same as that used in the Fischer-Tropsch stage. This has the added advantage that all the reactants in the hydroformylation stage are then essentially sulphur free since the synthesis gas is sulphur free. [0015] If alcohols are the desired hydroformylation product, then the overall H.sub.2:CO usage ratios for the Fischer-Tropsch reaction and hydroformylation stages may be approximately equal, thereby more readily facilitating integration of the gas systems of these stages. [0016] The hydroformylation stage feedstock is thus, depending on the Fischer-Tropsch reaction conditions and product workup, free of sulphur and typically contains between 35% and 100% by mass olefins. Of the total olefin content of the feedstock, between 50% and 100% by mass may be linear .alpha.-olefins, between 0% and 60% mono-methyl branched .alpha.-olefins, and between 0% and 10% linear internal olefins. [0017] The Fischer-Tropsch reaction may be effected in a fixed bed, in a slurry bed, or, preferably, in a fluidized bed reactor. The Fischer-Tropsch reaction conditions may include utilizing a reaction temperature of between 190.degree. C. and 340.degree. C., with the actual reaction temperature being largely determined by the reactor configuration. Thus, when a fluidized bed reactor is used, the reaction temperature is preferably between 300.degree. C. and 340.degree. C.; when a fixed bed reactor is used, the reaction temperature is preferably between 200.degree. C. and 250.degree. C.; and when a slurry bed reactor is used, the reaction temperature is preferably between 190.degree. C. and 270.degree. C. [0018] An inlet synthesis gas pressure to the Fischer-Tropsch reactor of between 1 and 50 bar, preferably between 15 and 50 bar, may be used. The synthesis gas may have a H.sub.2:CO solar ratio, in the fresh feed, of 1.5:1 to 2.5:1, preferably 1.8:1 to 2.2:1. A gas recycle may optionally be employed in the reactor, and the ratio of the gas recycle rate to the fresh feed rate, on a molar basis, may then be between 1:1 and 3:1, preferably between 1.5:1 and 2.5:1. A space velocity, in m.sup.3 (kg catalyst).sup.-1 hour.sup.-1, of from 1 to 20, preferably from 8 to 12, may be utilized in the reactor. [0019] In principle, an iron-based, a cobalt-based or an iron/cobalt-based Fischer-Tropsch catalyst can be used in the Fischer-Tropsch reaction stage; however, an iron-based catalyst is preferred. [0020] The iron-based Fischer-Tropsch catalyst may comprise iron and/or iron oxides which have been precipitated or fused. However, iron and/or iron oxides which have been sintered, cemented, or impregnated onto a suitable support can also be used. The iron should be reduced to metallic Fe before the Fischer-Tropsch synthesis. The iron based catalyst may contain various levels of promoters, the role of which may be to alter one or more of the activity, the stability, and the selectivity of the final catalyst. Preferred promoters are those influencing the surface area of the reduced iron (`structural promoters`), and these include oxides or metals of Mn, Ti, Mg, Cr, Ca, Si, Al, or Cu or combinations thereof. Preferred promoters for influencing product selectivities are alkali oxides of K and Na. The alkali oxide to structural promoter mass ratio may be between 0:1 and 20:1 but should preferably be between 0.1:1 and 2:1. The structural promoter content thereof, expressed as grams of structural promoter par 100 grams Fe, may be between 0 and 50 but is preferably between 0, 1 and 2 for high temperature Fischer-Tropsch applications, and between 10 and 40 for low temperature Fischer-Tropsch applications. [0021] When the Fischer-Tropsch olefinic product is obtained in a high temperature reaction stage or reactor, such as in the synthol reactor or reaction stage, which uses a fluidized bed, the iron-based Fischer-Tropsch catalyst will normally be a fused catalyst, eg. that derived by the fusion of magnetite with various levels of oxide promoters as hereinbefore described. The fused material may then be crushed or atomized to yield particles preferably having a size.ltoreq.70 .mu.m, and may be reduced with H.sub.2 prior to Fischer-Tropsch synthesis. [0022] However, when the Fischer-Tropsch olefinic product is obtained in a fixed or bed or a slurry bad using lower temperatures as hereinbefore described, the catalyst will normally be a precipitated or supported catalyst. [0023] The Fischer-Tropsch catalyst may be prepared in accordance with the methods described in the article by M. E. Dry in "Catalysis Science and Technology" (1979) Volume 1; pages 159-255, Eds J. R. Anderson and M, Boudart. This article is hence incorporated herein by reference. [0024] When a cobalt-based catalyst is used, it may comprise cobalt and/or a cobalt oxide which has been precipitated, cemented or impregnated onto a suitable support, such that the catalyst has the following composition: Continue reading about Process for producing oxygenated products... 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