Dimerization Of Isobutene Research Articles

Reactant Adsorption and Its Impact upon MTBE Synthesis on Zeolites

Zeolites show interesting properties as catalysts for MTBE synthesis from methanol and isobutene such as a high selectivity to MTBE even at a low methanol/isobutene feed ratio. In order to explain this high selectivity, the adsorption behaviors of HY and HZSM-5 zeolites and their impact on activity and selectivity for MTBE synthesis were studied. Adsorption experiments, carried out under conditions similar to those used for reaction, showed that ca. 2.5 molecules of methanol were adsorbed per acid site on HZSM-5 and HY zeolites, whereas isobutene was found to form a 1:1 adsorption complex. The excess methanol adsorbed was found to be only weakly bonded, probably via hydrogen bonds. On a commercially used resin catalyst (Amberlyst-15) equal amounts of methanol and isobutene were adsorbed. The higher methanol uptake of the zeolites was paralleled by a higher selectivity to MTBE as compared to the resin catalyst. The increased adsorption of methanol on the zeolites was concluded to play a key role in suppressing the formation of by-products due to isobutene dimerization or oligomerization by decreasing the adsorption of isobutene on the active sites and thereby keeping these sites available for reaction.

Kinetic study of isobutene dimerization catalyzed by a macroporous sulphonic acid resin

The kinetics of the liquid-phase dimerization of isobutene in the presence of a macroporous acidic resin (Lewatit K-2631, Bayer) has been studied. Rate data were obtained in a batchwise stirred tank reactor operated at 1.6 MPa and 40–60°C. The best rate model is a two-phase semiempirical one which implies the coexistence of a Langmuir-Hinshelwood-Hougen-Watson mechanism and a modified Eley-Rideal one.

Kinetic study of the oligomerization of isobutene over H-mordenite

Isobutene has been oligomerized in the liquid phase over H-mordenite in a batch reactor. The reactions were conducted at several temperatures between 313 and 413 K. At these temperatures, the reaction products were essentially dimer, trimer and tetramer. The initial rates showed that the oligomerization reaction followed a Rideal mechanism. The reaction scheme was found to be a rake scheme. The rate constants for the dimerization of isobutene and oligomers decreases with the carbon atom number of the olefin while the adsorption constant increases with the length of the hydrocarbon chain. A model for the oligomerization of the alkenes is proposed.

Kinetics of methyl tertiary butyl ether liquid phase synthesis catalyzed by ion exchange resin—I. Intrinsic rate expression in liquid phase activities

The microkinetics for the liquid phase synthesis of methyl tertiary butyl ether (MTBE) from methanol and isobutene using a macroporous sulfonic acid ion exchange resin as catalyst (Amberlyst 15, CVT resin) were determined experimentally in a continuous stirred tank reactor in the temperature range 323–363 K at 2.1 MPa. The reaction proceeds within the gel phase of the microspheres as the rate-controlling step overlapped by a multiple sorption equilibrium between components in the macropore liquid and the gel phase, where methanol is highly selectively sorbed. The experimental results can be described by a three-parameter model based on a Langmuir—Hinshelwood rate expression in liquid phase activities from the UNIQUAC method. The forward reaction is proportional to the activity ratio of isobutene to methanol (quasi-autocatalytic in methanol). The reverse reaction is first-order in MTBE and negative second-order in methanol (product inhibition). The activation energy was determined to 92.4 kJ/mol. No pressure dependence could be observed. The developed microkinetic model is independent of the degree of cross-linking of the resin in the investigated range 7.5–20% DVB by weight. The formation of isobutene dimers, the main by-product, was only observed if internal mass transfer influenced the rate of reaction.

Formation of Di‐isobutene, main by‐product of methyl tertiary butyl ethyl ether synthesis catalyzed by ion exchange resin

AbstractAn experimental set‐up is presented for the measurement of steady‐state reaction rates in the liquid phase methyl tertiary butyl ether (MTBE) synthesis from isobutene and methanol using ion exchange resin as catalyst. This apparatus was used for a separate investigation of the main side reaction, i.e., the formation of isobutene dimers (DIB), in the temperature range between 60 and 90°C. The reaction catalyzed by Amberlyst 15 (A15) showed no steady‐state behaviour, but the catalytic activity declined at a rate dependent on the reaction conditions. Time constants for activity loss were determined in the range from 3.5 to 30 h. The deactivated A15 catalyst could be regenerated through MTBE synthesis experiment. Deactivation is assumed to be caused by blocking of the microparticle gel phase by higher isobutene oligomers. The DIB formation, using 1‐butene as solvent, was of 2nd order with respect to isobutene and showed an apparent activation energy of about 40 kJ/mol.

The magnetohydrodynamic squeeze film : D. C. Kuzma, E. R. Maki and R. J. Donelly, J. Fluid Mech., 19 (3) (1964) 395–400

The growing interest of chemical and oil refining industries in the catalytic oligomerization of alkenes for the production of synthetic fuels and additives formulated around light gasoline olefins is due to recent environmental restrictions and increasing diesel demand. Furthermore, the drive towards sustainability and the emergent contribution of biorefineries for the manufacture of intermediate and platform chemicals envisages olefins produced from biomass derived alcohols as an important feedstock for subsequent oligomerization.Over the last years much work has been published on the catalytic oligomerization of propene, butene, isobutene and isoamylene over cation exchange resins, such as Amberlyst and Purolite, and others like Nafion. For instance, isobutene dimers and trimers are accepted additives for gasoline (octane booster) and diesel (cetane booster) while isobutene higher oligomers can be a source for heavier fuels and synthetic lube oils. This paper presents a deep and critical review in the field discussing the influence of the resin (resin-type and their physical and structural properties), the operating conditions and additives used (polar compounds like alcohols), upon oligomerization conversion and selectivity.

Catalytic hydrocondensation of carbon monoxide and olefins

1. An investigation was made of the dependence of the course of the hydropolymerization of isobutene under he action of CO and H2 on the proportions of the components of the original i-C4H8-H2-CO mixture. 2. With a CO content of the original mixture of up to 5% and an i-C4H8: H2ratio of 1–2 there mainly occurs destructive hydropolymerization of isobutene with formation of 2-methylalkanes and the corresponding olefins, but at i-C4H8: H2=3 there occurs true polymerization of isobutene with formation of dimers, trimers, and their hydrogenation products. 3. In the CO concentration range 7–20% Orlov-Fischer-Tropsch synthesis predominates. There is preferential formation of n-heptane and also of isobutene dimers. 4. Possible schemes for the formation of the hydrocarbons obtained are examined.

Catalytic Dimerization of Isobutene by Activated Copper Sulphide

IN previous communications1 it has been shown that copper sulphide, activated by oxidizing a part of its surface into copper sulphate, is a catalyst for the low molecular polymerization of isobutene. It has now been found that the main product of the catalytic process is a mixture of the two 2: 2: 4-trimethylpentenes which on hydrogenation were converted into 2: 2: 4-trimethylpentane. This latter compound was identified by determining the boiling point, the specific gravity, the refractive index, the melting point and the mixed melting point with an authentic sample. A detailed description of the experiments will be published elsewhere.