Dehydrogenation Of Isopentane Research Articles

Effect of H2S co-feeding on the performance of the Fe/SiO2 catalyst for isomerization and dehydrogenation of C5-monoolefin

Isoprene was obtained by dehydrogenation, involving the isomerization of 2-methyl-2-butene into 2-methyl-1-butene. Notably, isoprene was produced through the dehydrogenation following isomerization using the Fe/SiO2 catalyst in the presence of H2S.

ISOLATION OF HIGH PURITY PIPERYLENE

Piperylene is a valuable raw material component for petrochemical synthesis, perfumery and cosmetic products, and is used as a solvent for petroleum products in the production of synthetic rubbers and latexes, and in the paint and varnish industry. Piperylene in the form of a fraction is produced in the production of isoprene by the two-stage dehydrogenation of isopentane, where it is a secondary product of the main synthesis. Isolation of commercial piperylene of high purity will allow the production of a value-added product and expand the sales market. Currently, restrictions on the production of commercial piperylene are associated with the high content of an impurity – cyclopentadiene. Previous studies by the author showed the feasibility of extracting cyclopentadiene at the stage of obtaining the catalyzate of the second stage of isoprene dehydrogenation. Simulation of the technological scheme in the application program showed that, together, the extraction of cyclopentadiene by a chemical method and a change in the technological operating mode makes it possible to isolate piperylene with a content of 99.45 % wt and CPD equal to 0.0046 % wt.

ISOLATION AND PURIFICATION OF ISOPRENE FROM CYCLOPENTADIENE

Isoprene is a basic monomer in the petrochemical industry. It is used in the synthetic rubber production for the manufacture of rubber products for the electrical, aviation and engineering industries, for the manufacture of food and medical products. In the Republic of Bashkortostan, Sintez-Kauchuk OJSC (Sterlitamak) produces isoprene by the two-stage dehydrogenation of isopentane with an annual product output of hundreds of thousands of tons. The disadvantage of this technology for producing isoprene is the significant content of impurities in raw isoprene, which seriously affect the kinetics of polymerization and the quality of the final product. Of all the impurities present in the monomer, cyclopentadiene is the most detrimental to the stereoregular polymerization process. Its content in isoprene should not exceed 0.0001 % wt. Due to the urgency of the problem, a technical solution was developed to remove cyclopentadiene impurities from monomers.Currently, there is a problem of accumulation of cyclopentadiene in the system of purification and treatment of isoprene at the operating production. The paper proposes to purify isoprene from cyclopentadiene before the stage of extractive distillation. This purification method allows to reduce the content of cyclopentadiene in the isoprene-isoamylene fraction from 0.10 % wt. to 0.00014 % wt, which reduces its concentration in all recycle flows of the isoprene isolation and purification system. To implement this solution, laboratory experiments were carried out to purify the isoamylene-isoprene fraction formed at the second stage of isopentane dehydrogenation. In order to assess the energy efficiency of the studied method for reducing cyclopentadiene, a computer model of the isoprene isolation and purification process was built in the Honeywell Unisim Design software environment.

Experience in the Development and Implementation of Chromium-Alumina Catalysts of the KDI Series for Isobutane Dehydrogenation in a Fluidized Bed

The paper summarizes the experience in the development of a microspherical chromium-alumina catalyst for isobutane dehydrogenation to isobutylene according to the technology devised at Yarsintez. The development of commercial catalysts of the KDI series based on a new boehmite support was considered. Interrelations of elemental and phase composition of the catalysts with their performance were established. A new two-step scheme for producing the boehmite support by hydrothermal treatment of the thermal decomposition product of gibbsite agglomerates with a desired size makes it possible to control its phase composition as well as the physico-mechanical characteristics of the catalysts and their catalytic properties, which allowed obtaining a series of KDI, KDI-M, and KDI-M1 catalysts. The most important steps in commercial implementation of the catalyst at PJSC Nizhnekamskneftekhim were noted. The commercial KDI-M catalyst provided a stable 33–37 % yield of isobutylene in isobutane dehydrogenation and a 30 % yield of methylbutenes in isopentane dehydrogenation. The catalyst consumption was 2–3 kg per ton of the produced isobutylene. The catalyst operation was monitored to propose a way for its improvement and optimization of the reactor instrumentation. According to the laboratory testing, a commercial sample of the KDI-M1 catalyst modified with a silicon-containing inorganic complex compound has higher activity and selectivity than previous catalysts of this series and is ready to industrial implementation.

Selection of an effective catalyst for the stage isoamyl alcohol dehydration during synthesis isoprene from isopentane

The annual growth in the consumption of isoprene rubbers dictates manufacturers to searching for the new methods of its production. An intermediate product in the production of isoprene rubbers is the synthesis of a monomer - isoprene. The main industrial methods for its production in Russia are synthesis processes from isobutylene and formaldehyde and two-stage dehydrogenation of isopentane. The article analyzes and selects an effective catalyst for the stage of isoamyl alcohol dehydration in the synthesis of isoprene from isopentane.

The difference between borate and phosphate modified carbon nanotubes in isopentane oxidative dehydrogenation

Borate and phosphate modified carbon nanotubes with different loading amounts are synthesized by a facile impregnation method and used as metal-free catalyst for oxidative dehydrogenation of isopentane. When the loading of borate was less than 5wt% B2O3 decrease in isopentane conversion and increase in alkene selectivity was observed, whereas with increase in borate loading exceeding 5wt% B2O3 the conversion and selectivity remain constant. This phenomenon is significantly different from the volcanic distribution of dehydrogenation selectivity of the phosphate modified carbon nanotubes. We propose that borate modification is more selective than phosphate modification toward the blockage of defects and the inhibition of combustion reaction on the CNTs supported by X-ray photoelectron spectroscopy, temperature-programmed desorption and oxidation. The synergetic effect of borate and phosphate has not been observed in the isopentane oxidative dehydrogenation.

2-methyl-2-butene production using positional isomerization catalyzed by sulfonic acid cation exchangers

Economically efficient 2-methyl-2-butene production is an essential element of the promising isoprene manufacturing process using 2-methyl-2-butene epoxidation and the dehydration of the resulting epoxide. An efficient way of producing 2-methyl-2-butene is isopentane dehydrogenation followed by 2-methyl-2-butene recovery from the resulting C5 fraction by liquid-phase isomerization (preferably on sulfonic acid cation exchangers) and distillation.

Catalytic Dehydrogenation of Isopentane with Iridium Catalysts

Activation by adding PPh3: The catalytic dehydrogenation of isopentane to give isopentene and hydrogen with iridium catalysts on a silica gel support at 450 °C proceeds with impressive conversion when the support is impregnated with PPh3. The active species are proposed to be iridium phosphides which arise by thermal cleavage of phenyl groups.

Isopentane dehydrogenation on Pt-Sn catalysts supported on Al-Mg-O mixed oxides: effect of Al/Mg atomic ratio

A series of Mg-Al-O supports was prepared by the coprecipitation method at constant pH. The Al/Mg atomic ratio ranged from 2.06 to 4.9. The physico-chemical, as well as the surface and structural properties of the synthesized materials were strongly dependent on the Al/Mg atomic ratio. In solids with an Al/Mg atomic ratio higher than 2, a support with a mixture of Al 2O 3 and MgAl 2O 4 phases was obtained. In all the supports a non stoichiometric magnesium aluminate spinel structure (MgAl 2+ x O 4+(3/2) x ) was not detected. The supports were impregnated with Pt and Sn (0.6 and 1.2 wt.%, respectively). The resulting catalysts were evaluated in the isopentane dehydrogenation reaction at 550°C and atmospheric pressure. On the Pt-Sn catalysts which were prepared with aluminum rich supports (Al/Mg=2.4 and 4.9), TPD-H 2 results showed the presence of Pt particles (unalloyed and tin alloyed) deposited in both Al 2O 3 and MgAl 2O 4 phases. A stronger Pt-support interaction on MgAl 2O 4 phase than on Al 2O 3 phase was observed. The Pt-Sn catalyst impregnated on pure MgAl 2O 4 showed the maximum selectivity to isoamilenes. The high Al 2O 3 content supports (Al/Mg>3) bring about a higher light olefins (C 2–C 4) production, which promotes the coke formation. This process finally accelerated the catalyst deactivation. This is explained by the higher acidity of alumina compared with magnesium aluminate.

Normal hydrocarbons as a source of resin formation in the process of obtaining isoprene from isopentane

A study was made on a catalyst of dehydrogenation of olefins of the conversion of isoamylenes and other C/sub 5/ hydrocarbons (isoprene, n-pentenes, piperylene), formed during dehydrogenation of isoamylenes to isoprene. It was found that the yield of heavy products increases on transition from hydrocarbons of iso-structure to normal hydrocarbons, which is due to the greater ease of polycondensation of cyclopentadiene formed from n-pentenes and particularly from piperylene under conditions of dehydrogenation. A study was made by chromato-mass-spectrometry of the composition of heavy products of conversion of piperylene and isoprene. In contrast with the catalysate of isoprene, the catalysate of piperylene contains a significant proportion of hydrocarbons containing a five-membered ring in the molecule (dicyclopentadiene, indane, indene, methylindenes, azilene), this being due to the participation of cyclopentadiene in the formation of heavy products. In the two-stage process of dehydrogenation of isopentane to isoprene 95% normal hydrocarbons are formed on dehydrogenation of isopentane to isoamylenes. (JMT)

Optimal operation of a catalytic tubular reactor with fouling catalyst by coke deposition

The dehydrogenation of isopentane over chromia-alumina catalyst has been carried out at three isothermal levels. The catalyst fouling and the deposited coke profiles were observed in a catalytic tubular reactor. A kinetic model is proposed and the kinetic parameters have been estimated by non linear regression methods. For the dehydrogenation with catalyst fouling, the problem of finding the isothermal optimal control was formulated by a distributed maximum principle and a computational algorithm using a quasi-steady state assumption was presented. The dehydrogenation of isopentane was carried out experimentally at the evaluated isothermal optimal temperature. The observed conversion, yields and coke content profiles agreed with the evaluated ones fairly well, which suggests that the kinetic model may be useful for optimal controls.

Isopentane Dehydrogenation with Chromia-Alumina Catalyst

Dehydrogenation of isopentane over chromia-alumina catalyst of several sizes (42∼60mesh to 5mmφ×5mm) has been carried out. The catalyst. foulig by the deposited coke was observed in a fixed-bed reactor. The coke distribution in a catalyst pellet was found to be uniform. The diffusivity of the reactants within the catalyst pellet was measured and found to be a linear function of the coke content.A kinetic model was proposed and kinetic parameters were estimated by computer simulation under the condition that intraparticle diffusion was negligible. Using this kinetic model and the function of diffusivity, the effect of intraparticle diffusion on conversion and the profile of the coke content in the reactor were experimentally described.

Use of aluminium-chromium-sodium catalysts in dehydrogenation of isopentane to isopentenes

Use of aluminium-chromium-sodium catalysts in dehydrogenation of isopentane to isopentenes

KINETICS OF ISOPENTANE DEHYDROGENATION ON CHROMIA-ALUMINA CATALYST WITH CATALYST FOULING

In isopentane dehydrogenation over chroniia-alumina catalyst, the conversion of isopentane and the yield of isopentenes decreased rapidly with process time while that of isoprene did so very slowly. Coke deposition on catalyst and catalyst fouling occurred in an integral catalytic reactor, and coke distribution was observed along the axial direction of the reactor. For isopentane dehydrogenation a kinetic model in which the main reaction was consecutive and the sub-reaction was parallel is proposed. For estimating distributed kinetic parameters with catalyst fouling, an algorithm that involves two calculating steps is introduced. Applying an activity factor which accounts for catalyst fouling and which is a linear function of coke content, the kinetic parameters were estimated. Using these parameters, the changes of the concentration and the distribution of coke content with process time were simulated fairly well.

Catalytic dehydrogenation of isopentane employing the statistical experiment planning method

On the basis of the experimental data for the process of isopentane dehydrogenation on aluminum-chromium-lithium catalysts a mathematical model was proposed, which made it possible to determine the yields of isoamylenes, isoprene, and the skeletal isomerization and cracking products in the range 530–570‡, at space velocities of 0.5–1.5 h−1, and with a variation in the catalyst composition where the chromium oxide concentration was varied from 8 to 20%, and that of lithium oxide was varied from 0.3 to 2.5%.

Catalytic Dehydrogenation of Isopentane on Al<sub>2</sub>O<sub>3</sub>-Cr<sub>2</sub>O<sub>3</sub> Catalyst

Catalytic Dehydrogenation of Isopentane on Al<sub>2</sub>O<sub>3</sub>-Cr<sub>2</sub>O<sub>3</sub> Catalyst

Oxidative dehydrogenation of isopentane in the presence of hydrobromic acid

1. The oxidative dehydrogenation of i-C5H12 with HBr, the same as in the case with Br2, is a complex process. 2. The best indices of the process were obtained on cobalt catalysts at 500° and a molar ratio of i-C5H12∶O2∶HBr∶H2O=1∶1∶2∶29 (the yields of isoprene were 24–28%, and of isopentenes ~10%, with a total selectivity of 80–82%).

Oxidative dehydrogenation of isopentane in the presence of bromine

1. A study was made of the reaction for the oxidative dehydrogenation of isopentane in the presence of bromine and cobalt-lithium-magnesium or aluminum-molybdenum-potassium catalysts, at 400–500°, and using molar ratios of i-C5H12∶Br∶O2∶N2=1∶0.00–0.7∶1.2–2.4∶3.5–7.2. 2. In the catalyzates was established the presence of the dehydrogenation products of isopentane (isoprene, isopentenes), skeletal isomerization (n-C5 hydrocarbons), a shift of the double bond (three isomeric isopentenes), and mild oxidation (ethanol, isovaleraldehyde). 3. Of all of the studied conditions, only at 500° and molar ratios of i-C5H12∶Br∶O2=1∶0.1∶1.6–2, were the highest yields of isoprene (17%) achieved on a cobalt-lithium-magnesium catalyst, and of isopentenes (24%) on an aluminum-molybdenum-potassium catalyst.

Reaction of aliphatic C5 hydrocarbons with oxygen in the gas phase

1. A study was made of the reaction of oxygen with isopentane, three isopentenes and isoprene in the absence of a catalyst at 350–550°, using a molar ratio of hydrocarbon∶oxygen=1∶1.2 -1.4. Here the total conversion of the starting hydrocarbons can reach 50–70% (at 550°). 2. Under the studied conditions the starting hydrocarbons were converted mainly to hydrocarbons with a lower molecular weight having a C1-C4 composition, and, in addition, together with other reactions that went to slight degree, there occurred dehydrogenation of isopentane to isopentenes (up to 17%), and of isopentenes to isoprene (up to 15%); isoprene underwent the greatest change of all and in a more complex manner; the oxidation reaction occurred to the greatest degree in the case of the isopentenes and isoprene.

Dehydrogenation of isopentenes by iodine

1. A study was made of the oxidative dehydrogenation of isopentenes by iodine in the presence of a solid soda acceptor. It was shown that the process occurs with a high yield of isoprene and high selectivity (75.5 and 94.2 wt.%, respectively) at molar ratios of iodine: oxygen: water vapor: isopentenes = 0.05∶1.0∶12.4∶1.0, temperature 520°C, and contact time 1.3 sec. 2. It was shown that in the dehydrogenation of isopentenes the yield of isoprene and the selectivity are commensurable in reactors filled with a solid acceptor or a quartz packing. 3. It has been established that the reaction rate for the dehydrogenation of isopentenes by iodine is significantly greater than that for the dehydrogenation of isopentane. 4. The products arising from extensive oxidation and decomposition during the dehydrogenation of isopentane are formed predominantly by side reactions of the original feedstock, and only in insignificant amounts from the intermediate product, isopentene.