Dimersol-process

The Dimersol process (Erench Petroleum Institute) produces hexenes, heptenes, and octenes from propylene and linear butylene feedstocks. This process is reported to produce olefin with less branching than the corresponding polygas olefins. BASE practices this process ia Europe. 

Similar to IFP s Dimersol process, the Alphabutol process uses a Ziegler-Natta type soluble catalyst based on a titanium complex, with triethyl aluminum as a co-catalyst. This soluble catalyst system avoids the isomerization of 1-butene to 2-butene and thus eliminates the need for removing the isomers from the 1-butene. The process is composed of four sections reaction, co-catalyst injection, catalyst removal, and distillation. Reaction takes place at 50—55°C and 2.4—2.8 MPa (350—400 psig) for 5—6 h. The catalyst is continuously fed to the reactor ethylene conversion is about 80—85% per pass with a selectivity to 1-butene of 93%. The catalyst is removed by vaporizing Hquid withdrawn from the reactor in two steps classical exchanger and thin-film evaporator. The purity of the butene produced with this technology is 99.90%. IFP has Hcensed this technology in areas where there is no local supply of 1-butene from other sources, such as Saudi Arabia and the Far East. 

From these results, the Institut Fran ais du Petrole (IFF) has developed a biphasic version of its established monophasic Dimersol process , which is offered for licensing under the name Difasol process [98]. The Difasol process uses slightly acidic chloroaluminate ionic liquids with small amounts of allcylaluminiums as the solvent for the catalytic nickel center. In comparison to the established Dimersol process , the new biphasic ionic liquid process drastically reduces the consumption of Ni-cata-lyst and allcylaluminiums. Additional advantages arise from the good performance obtained with highly diluted feedstodcs and the significantly improved dimer selectivity of the Difasol process (for more detailed information see Section 5.3). 

In the homogeneous Dimersol process, the olefin conversion is highly dependent on the initial concentration of monomers in the feedstock, which limits the applicability of the process. The biphasic system is able to overcome this limitation and promotes the dimerization of feedstock poorly concentrated in olefinic monomer. 

Since the catalyst is concentrated and operates in the ionic phase, and also probably at the phase boundary, reaction volumes in the biphasic technology are much lower than in the conventional single-phase Dimersol process, in which the catalyst concentration in the reactor is low. As an example, the Difasol reactor volume can be up to 40 times lower than that classically used in the homogeneous process. 

Another example is butene dimerization catalyzed by nickel complexes in acidic chloroaluminates 14). This reaction has been performed on a continuous basis on the pilot scale by IFF (Difasol process). Relative to the industrial process involving homogeneous catalysis (Dimersol process), the overall yield in dimers is increased. Similarly, selective hydrogenation of diene can be performed in ionic liquids, because the solubility of dienes is higher than that of monoene, which is higher than that of paraffins. In the case of the Difasol process, a reduction of the volume of the reaction section by a factor of up to 40 can be achieved. This new Difasol technology enables lower dimer (e.g., octenes) production costs 14). 

The process involves reacting butenes and mixtures of propenes and butenes with either a phosphoric acid type catalyst (UOP Process) or a nickel complex-alkyl aluminum type catalyst (IFP Dimersol Process) to produce primarily hexene, heptene, and octene olefins. The reaction first proceeds through the formation of a carbocation which then combines with an olefin to form a new carbocation species. The acid proton donated to the olefin initially is then released and the new olefin forms. Hydrotreatment of the newly formed olefin species results in stable, high-octane blending components. 

Ni-catalyzed dimerization of propene and/or butenes, which was intensively studied in the 1960 s [96] and later commercialized as the Dimersol process by the Institut Franjais du Petrole (IFF). The active catalytic species is formed in situ through the reaction between a Ni(ll) source and an alkylaluminium co-catalyst. 

The soluble nickel catalyst developed by IFP for the oligomerization of alkenes applied in different Dimersol processes (see Section 13.1.3) can also be used in benzene hydrogenation to replace Raney nickel (IFP cyclohexane process).340... 

BASF s BASIL process [15] and the Dimersol process [16] have both been commercialized. The former uses the ionic liquid as a phase transfer catalyst to produce alkoxyphenylphosphines which are precursors for the synthesis of photoinitiators used in printing inks and wood coatings. The imidazole acts as a proton scavenger in the reaction of phenyl-chlorophosphines with alcohols to produce phosphines. The Dimersol process uses a Lewis acid catalyst for the dimerization of butenes to produce Cs olefins which are usually further hydroformylated giving C9 alcohols used in the manufacture of plasticizers. Several other processes are also at the pilot plant scale and some ionic liquids are used commercially as additive e.g. binders in paints. 

Difasol An improvement on the Dimersol process for dimerizing propene or butenes. The process utilizes an ionic liquid based on imidazoliniumaluminate and a nickel-based Dimersol catalyst. Developed by IFP in 1999, but not commercialized by 2005. 

The reaction is the basis of the Dimersol process for the production of octane enhancers.131 The activity of these catalysts is strongly dependent on the steric properties of the phosphine ligands, PEt3 << PPh3 < PCy3 < PPr Bu. 129... 

The ionic liquid can, for example, be added to the butene effluent from the Dimersol process to obtain octenes by butene dimerization the octene can be carbonylated (Section 4.6) and hydrogenated to wo-nonanol, used to make phthalate plasticizers. In the case of the Phillips trimerization process the use of an ionic liquid allows an easy separation of the trimers and the catalyst for recycling (see also reviews to Section 5.5). However, the industrial use as solvents of ionic liquids, containing halide species (especially anions such as Bp4, PFg, or AlCU ) has the disadvantage that they readily break down to give HX, which can adversely affect the reaction. New types of non-halide containing ionic liquids are being actively researched. 

The IFP Dimersol Process for Dimerization of Propylene into Isohexenes... 

Still another method of utilizing this chart is under the conditions which say that alkylate operation sets the value on the FCC C3 stream. For exan le if a refiner pays 25c/gal for isobutane and sells C3 alkylate into a 35c/gal gasoline market, his propylene costs out at about l8.7< /gal. This same 18.7< / gal propylene would yield gasoline at 30< /gal in the Dimersol Process thus realizing a 5c/gal profit. 

Figure 5 illustrates the simplicity of the Dimersol Process. Dried feedstock, which may vary widely in propylene composition, is charged to the reactor where soluble catalyst is added in low concentration. Close reactor temperature control is obtained by circulation of the reaction mix through a cooler which may be of the air or water type. The reaction occurs at essentially ambient temperature, allowing for the exothermic heat of reaction, and at a pressure sufficiently high to maintain a liquid phase. 

Though the economics used in this paper are based upon a 1007o new plant, the IFF Dimersol Process can be adapted to existing equipment because of its simplicity and modest operating requirements. For example, the reactor section for small to medium size units may utilize an existing LPG bullet-type vessel or an existing polymerization unit can be converted into the Dimersol Process. 

One has to be impressed with the economics of the Dimersol Process and the simplicity of the design which leads not only to ease of operation but to fast construction as well. The construction time schedule for one unit which is now under design foresees operation by the end of 1977. 

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