Oxidation Of Isobutylene Research Articles

KINETIC REGULARITIES OF THE CATALYTIC OXIDATION OF ISOBUTYLENE TO METHYLACROLEIN ON AN ANTIMONY-TIN CATALYST

The parameters that determine the choice of the reactor are the reactor power, catalyst activity (intensity per unit volume), the total required amount of catalyst, the value of the adiabatic change in the temperature of the reaction mixture at complete conversion, the nature of the change in the reaction rate and selectivity with the depth of conversion, etc. the results of the theoretical optimization showed the need for the implementation of the process of partial oxidation of isobutylene to methylacrolein on an antimony-tin oxide catalyst in an isothermal reactor. To determine the optimal conditions for conducting the process on an antimony-tin catalyst, the choice of the type and main structural dimensions of the reactor for the partial catalytic oxidation of isobutylene to methylacrolein, we used the method of mathematical modeling, which is based on data on the rates of chemical transformation. To obtain quantitative characteristics, a series of experiments was carried out by influence of the composition of the reaction mixture and the rate of the oxidation of isobutylene to methylacrolein. The kinetic regularities of the process of catalytic oxidation of isobutylene to methylacrolein on an antimony-tin catalyst were recorded on a flow-type unit with a small volume reactor without a gradient. Reaching the stationary regime in this reactor occurs in 15–25 minutes

Efficient one-step oxidation of isobutylene to methacrylic acid over Mo-V-Te-Cs by integrating active lattice oxygen and suitable medium acidity.

Efficient one-step oxidation of isobutylene to methacrylic acid was achieved over a Mo-V-Te-Cs catalyst. Mo-O-V as "asymmetric lattice oxygen" brings high activity. Te and Cs provide a suitable medium acidity to enhance the selectivity. A record single-step yield of 65% for methacrylic acid was obtained from isobutylene oxidation.

Partial oxidation of isobutylene using Ni TiOx

We report an aerobic partial oxidation of isobutylene into isoprene, acetone, and para-xylene using a mesoporous Ni TiOx catalytic material. In this work, two catalysts were found to synthesize two of these three valuable products with high selectivity, with p-xylene being synthesized with a selectivity of 46.0% and isoprene being synthesized with a selectivity of 64.7%, with overall conversions of isobutylene being 34.0% and 11.9% respectively. These reactions were done at relatively low temperatures (300 °C or below) and are conducted at flow rates of 10 sccm oxygen and isobutylene. The nickel titania catalysts were studied extensively using various characterization methodologies such as TEM, Raman, XRD, and XRF.

Optimum conditions determination of methyl methacrylate obtaining over tungsten-containing catalyst

The main common methods of methyl methacrylate producing are acetoncyanohydrin method and oxidation of isobutylene and tert-butanol. Because of the significant drawbacks of these methods, it is important to develop new, alternative ways of methyl methacrylate obtaining, one of which could be aldol condensation of methyl propionate with formaldehyde in the gas phase. The actual task for today is to find out effective catalysts for this process. For this aim, methyl propionate condensation with formaldehyde was studied in the presence of B 2 O 3 -P 2 O 5 -WO 3 /SiO 2 catalyst, which previously has showed high activity in the condensation of propionic acid with formaldehyde to methacrylic acid. The paper also investigates the influence of methanol on the side reaction of methyl propionate hydrolysis; it was found that adding methanol causes a slight increase in MMA selectivity, but the yield of unsaturated products decreases, and therefore adding methanol to the reaction mixture for the MP condensation with FA over B 2 O 3 -P 2 O 5 -WO 3 /SiO 2 catalyst is impractical. The optimum conditions for MP condensation with FA, namely temperature 653 K and contact time 12 s were found. Under these conditions, in the presence of B 2 O 3 -P 2 O 5 -WO 3 /SiO 2 catalyst with an atomic ratio of components B:P:W 3:1:0.6 respectively total yield of MMA and MAA was 31.91% while their total selectivity was 32.3%.

Effect of pH Value on the Properties of Molybdenum-Based Multiphasic Oxide Catalysts in Selective Oxidation of Isobutene to Methacrolein

The effect of different pH values on Mo-Bi-Fe-Co-Mn multiphasic oxide catalysts prepared via co-precipitation methods was studied. In addition, selective oxidation of isobutylene to methacrolein (MAL) reaction was evaluated. The structures and crystal phases of the catalysts were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption, and temperature-programmed reduction of H2 (H2-TPR). The characterization results showed that the structures and properties depended on the pH during preparation. The amount of the special crystalline phase MX on the catalysts increased with increasing pH value during the preparation process. When the precipitation pH value was 7, the crystalline phase MX reached maximum levels on the corresponding sample. The conversion of isobutene and selectivity for methacrolein were 99.9% and 95.6%, respectively. When increasing the precipitation pH, the MX content decreased, and the conversion of isobutene and selectivity for methacrolein decreased. The results revealed that synergistic effects or cooperation between multiphasic oxides and the special phase MX might be important for improving catalytic performance.

High-speed color cinematography of chain self-ignition in the hydrogen, methane, and isobutylene oxidation reactions

The spatial development of chain self-ignition in the oxidation of stoichiometric mixtures of hydrogen, methane, and isobutylene with oxygen at total pressures of 10–100 Torr and T = 750–1000 K has been investigated by high-speed color cinematography. The spatial development of the chain process is governed by the properties of the reactor surface and by the heating time of the combustible mixture. A numerical simulation of the process has been carried out.

A kinetic study of oxidative dehydrogenation of isobutane to isobutylene over chromium oxide supported on lanthanum carbonate

Kinetics of oxidative dehydrogenation of isobutane to isobutylene over chromium oxide supported on lanthanum carbonate was studied. The formation rate of isobutylene was found to be first order in isobutane and zero order in oxygen concentration and the rate limiting step was the regeneration of active sites by the gas phase oxygen. The formation of CO2 was due to the consecutive oxidation of isobutylene which occurred on the same active sites used for isobutylene formation, not by the parallel oxidation of isobutane.

Mathematical modeling of the partial oxidation of hydrocarbons in a multiple-shelf reactor for the case of methylacrolein synthesis

A numerical study of the mathematical model of a multiple-shelf reactor in which the fixed beds of a porous catalyst alternate with built-in heat exchangers is performed. The possibility of carrying out the process of methylacrolein production by the partial oxidation of isobutylene by air oxygen is shown and the optimum conditions are determined.

Changes in the phase composition of a multicomponent Co-Mo-Bi-Fe-Sb-K-O catalyst under conditions of the partial oxidation of isobutylene to methacrolein: A comparison with the oxidation of propylene to acrolein

The partial oxidation of isobutylene to methacrolein on a multicomponent multiphase Co-Mo-Bi-Fe-Sb-K-O catalyst and on catalysts from which some components were absent was studied. Activity and selectivity changes in the case of isobutylene oxidation were the same as in the oxidation of propylene; however, the rate of propylene oxidation was higher than that of isobutylene oxidation. The X-ray diffraction analysis of the catalysts before and after the reaction indicated the occurrence of a number of phases in the samples: α-CoMoO4, β-CoMoO4, Fe2(MoO4)3, reduced bismuth molybdate species, MoO3, and reduced MoO x species. Under catalytic reaction conditions, redox phase transformations occurred. Iron molybdate and molybdenum oxide phases underwent the largest transformations. Of two molybdenum oxide phases, a β-Mo4O11 phase with a structure of a crystallographic shift is formed in the course of catalysis, whereas the second phase (MoO3) almost does not participate in catalysis and occurs in an excess.

Synthesis and characterization of MoVTeCeO catalysts and their catalytic performance for selective oxidation of isobutane and isobutylene

A series of Mo-based catalysts (MoVCeO, MoTeCeO, MoVTeO, and MoVTeCeO mixed metal oxides) were prepared and tested for the oxidation of isobutane and isobutylene. Characterization results (XRD, FTIR, TPR, XPS, and BET) showed that their structure and properties depend on the composition of the calcined samples. Catalytic tests showed that molybdenum may be the key element for the activation of isobutane, whereas the selective oxidation of isobutylene to methacrolein (MAL) might proceed mainly on the surface of the TeMo-containing crystalline phase. In addition, Te4+ may favor the formation of methacrylic acid (MAA). The incorporation of Ce ions may modify the redox process of the catalysts and thus influence the catalytic behaviors for the selective oxidation of isobutane. Thus, the selectivities and yields of MAL and MAA can be increased over these specially designed catalysts.

Oxidation of propylene and isobutylene in a reactor with barrier discharge

The oxidation of propylene and isobutylene in barrier-discharge plasma in the presence of octane was studied. The possible reaction mechanism was considered.

Catalytical Oxidation of Propylene and Isobutylene on Multicomponent Molybdenum Containing Contacts

AbstractFor Abstract see ChemInform Abstract in Full Text.

Kinetics of isobutylene oxidation on a Mo-Sb-Te-O (1 : 0.6 : 0.06) catalyst

Kinetics of isobutylene oxidation over a Mo-Sb-Te-O catalyst is studied in a flow-circulation system with the Korneichuk differential reactor. The reaction orders of methacrolein, acetic acid, acetone, and CO2 formation, as well as the order of the overall reaction of isobutylene oxidation into methacrolein, with respect to oxygen and isobutylene are determined at 613–703 K and oxygen concentrations of (0.33–13.05) x 10−3 mol/1 and isobutylene (3.2–121.9) × 10−4 mol/1. The activation energies of these reactions are determined.

Novel Re–Sb–O catalysts for the selective oxidation of isobutane and isobutylene

It was found that three crystalline Re–Sb–O compounds, SbOReO 4·2H 2O, Sb 4Re 2O 13 and SbRe 2O 6, were active for the selective catalytic oxidation of isobutane (773 K) and isobutylene (623–723 K). Among the three compounds, SbRe 2O 6 exhibited the highest catalytic activity for the selective oxidation of isobutane with a high selectivity of 83% to methacrolein (MAL)+isobutylene at the steady-state conversion of 7%. The Re–Sb–O catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and in situ laser Raman microscopy (LRM). SbRe 2O 6 decomposed to Re 2O 7 and Sb 4Re 2O 13 partly at the surface under isobutylene oxidation at 673 K, while Sb 4Re 2O 13 was stable under the reaction conditions. Under isobutane oxidation conditions at 773 K, the three Re–Sb–O compounds underwent a progressive decomposition to Sb 4Re 2O 13, Re 2O 7 and Sb 2O 4. The catalytic behavior and structural characterization of the new catalysts allowed us to refer the reactivity of the catalysts to surface Re 2O 7 species benefiting from a cooperation with Sb 4Re 2O 13.

Performance and Characterization of Novel Re−Sb−O Catalysts Active for the Selective Oxidation of Isobutylene to Methacrolein

The catalytic behavior of three well-defined Re−Sb−O compounds, SbOReO4·2H2O, Sb4Re2O13, and SbRe2O6, was investigated in the selective oxidation of isobutylene to methacrolein at 673 K. We have directed our attention to the correlation between the catalytic performance of the compounds and their structural and superficial changes undergone under the reaction conditions. For the purpose, the effects of the pretreatment conditions for the catalysts and of the isobutylene/oxygen ratio in the reaction atmosphere on the performance of the catalysts were explored. Each Re−Sb−O compound was characterized before and after the pretreatments and the catalytic reactions by X-ray diffraction, X-ray photoelectron spectrocopy, scanning electron microscopy, and in situ laser Raman microscopy. Among the three Re−Sb−O compounds, a novel SbRe2O6 compound exhibited the highest catalytic performance for selective oxidation. The compound underwent a progressive decomposition to Sb4Re2O13 and Re2O7 when pretreated or reacted at 673 K in the presence of oxygen. The decomposition was favored under more oxidative conditions, and a close parallelism between the catalytic performance and the quantity of Re2O7 stabilized at the surface of the catalyst was observed. On the other hand, the activities of pure Re2O7 and a new Sb4Re2O13 compound were very low when each of them was used as a catalyst independently. The results indicate that the reactivity of SbRe2O6 is likely due to the presence of Re2O7 at the surface, benefitting from a cooperation with Sb4Re2O13. The model also accounts for the performance of SbOReO4·2H2O. SbOReO4·2H2O decomposed to Sb4Re2O13 and Re2O7 regardless of the reaction atmosphere, which explains a higher activity of SbOReO4·2H2O than Sb4Re2O13. However, the amount of Re2O7 stabilized at the surface was smaller than that for the case of SbRe2O6, which leads to lower performances of SbOReO4·2H2O than those of SbRe2O6.

Catalytic behavior of SbRe2O6 in the selective oxidation of isobutene: the key role of the cooperation between Sb4Re2O13 and Re2O7

The catalytic performance of a novel SbRe2O6 compound has been investigated in the selective oxidation of isobutylene to methacrolein at 673 K. The initial reactivity of the catalyst strongly depended on catalyst pretreatment conditions. The catalyst was more active after pretreatments under more oxidative atmospheres. However, the activity of the catalyst always reached an identical level at the steady state, independent of the pretreatment conditions. Scanning electron microscopy and in situ confocal Raman microscopy revealed that the reactivity of SbRe2O6 was attributable to the presence at its surface of Re2O7 which benefitted from a cooperation with Sb4Re2O13. The two phases resulted from a partial decomposition of SbRe2O6 in the presence of oxygen. When deposited on Sb4Re2O13, Re2O7 was stabilized and did not volatilize under the reaction conditions. The phenomenon is likely the origin of the cooperation between Sb4Re2O13 and Re2O7.

Catalysis and inhibition of the combustion of ammonium perchlorate based solid propellants

Results of studies of the combustion of a composite solid propellant based on ammonium perchlorate are presented. The effect of additives of metal oxides is studied for the high and low-temperature decompositions, linear pyrolysis, and combustion of ammonium perchlorate, the decomposition of HClO4, isobutylene oxidation by oxygen and perchloric acid, and the combustion of propellants with various organic combustibles. It is shown that the efficiency of metal oxides in the reactions of oxidation of isobutylene and propellant combustion is related to the energy of the Me—O bond in the surface oxide layer or the enthalpy of formation of this bond. The extremal nature of the catalytic effect of metal oxides on the burning rate of the propellant is due to the small time of residence of the oxide particles in the zone of intense oxidation-reduction reactions. For this reason, the same additives of metal oxides has different effects on the combustion of the propellant with different organic, combustibles, and the most efficient catalyst can be chosen by a simplified algorithm. The potentials for affecting the composite solid propellant via gas-phase oxidation-reduction reactions is indicated by the effect of additives of organic sources of active species—amines and halides.

The interaction of Pt and SbO x in the selective oxidation of isobutylene to methacrolein

New Pt/SbO x catalysts active for the selective oxidation of iso-C 4H 10 and iso-C 4H 8 to methacrolein were investigated by pulse reactivity measurements, X-ray diffraction (XRD) analysis, and Raman spectroscopy. XRD revealed that the main oxide phase in Pt/SbO x catalysts after calcination or reaction condition was Sb 6O 13 whereas Raman spectroscopy also showed the presence of Sb 2O 3 (senarmontite). As a result of the interaction between Pt and SbO x the total oxidation chemistry of Pt was shut down, and instead a selective oxidation behavior appeared. Investigation of iso-C 4H 8 oxidation by lattice oxygen in Pt/SbO x revealed that Pt was essential for SbO x to undergo redox cycles, and that without Pt, not much SbO x was reoxidized under reaction conditions. The overall results were consistent with small Sb 2O 3 oxide crystallites forming on or around Pt particles, with small highly dispersed antimony species, possibly O=SbO y decorating the surface. These species were responsible for breaking up large Pt ensembles and suppressing the total oxidation reaction.

Oxidative cleavage of 2-methylpropene on Ir(111): double bond scission during the formation of acetone

High resolution electron energy loss spectroscopy (HREELS) and temperature-programmed reactive desorption (TPRD) techniques have been used to study the oxidation of π-bound and di-σ-bound 2-methylpropene (isobutylene) on the Ir(111) surface. For surface temperatures of less than 80 K, isobutylene adsorbs into a π-bound state on the Ir(111)-(2 × 1)O surface and into a di-σ-bound state on the bare Ir(111) surface. Isobutylene which is π-bound reacts with oxygen upon heating to yield gaseous t-butanol, acetone, water and dihydrogen as well as adsorbed acetate, η 2(C,O)-acetone, and possibly formate by 330 K. Isotopic labeling experiments indicate that gaseous acetone is not produced from an allylic intermediate. The oxidation of π-bound isobutylene is proposed to proceed through sequential O(CH 3) 2CCH 2 and O(CH 3) 2CCH 2O species. t-Butanol is produced from the former species while acetone, acetate, water, dihydrogen and formate are produced from the latter. Di-σ-bound isobutylene species are not thought to participate in the formation of acetone and acetate since no detectable amounts of adsorbed acetone or acetate and little gaseous acetone were produced from the direct oxidation of di-σ-bound isobutylene.

Preparation of SiO 2 and NiO/Al 2O 3 aerogels by supercritical CO 2 drying and their catalytic activity

Aerogels of SiO 2 and NiO/Al 2O 3 were prepared by means of sol-gel method followed by supercritical CO 2 drying. Aerogels were characterized in terms of BET surface area, pore size distribution by both nitrogen adsorption and mercury porosimetry, and TEM microscope observation in comparison with xerogels that were prepared by ambient drying of alcogel. Aerogels had higher surface area and pores in meso- and macropore size region. TEM microscopy revealed that aerogels had large pores and a highly divided state of NiO on Al 2O 3 matrix. Catalytic activity of NiO/Al 2O 3 aerogels was measured for partial oxidation of iso-butylene. Aerogel catalyst was selective to methylacrolein over acetone, whereas xerogel catalyst was not selective.