Conversions of mixtures of propane and benzene on Pt,Re/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> + H-zeolite systems

The conversion of C₆H₆: C₃H₈C mixtures on mixed catalysts composed of the metal catalysts Pt,ReOx/Al₂O₃ and zeolites Y, M, and ZSM-5 in the H form was studied. The products of benzene dehydroalkylation by propane and propane dehydrogenation products are formed at 180–350°C. It has been shown that propane is activated on the metal catalysts and C₆H₆ interacts with the zeolites yielding the C₆H₇ ⁺ intermediate, which acts as an agent of proton transfer from a zeolite to a metal catalyst, and another intermediate C₉H₁₃⁺ (I). Cumene, alkylbenzenes, and propene are formed as a result of the conversion of I. A comparison of the results of the conversion of these mixtures on the composite catalysts with different zeolites shows that the formation of cumene and propene is thermally controlled and the formation of the other products is kinetically controlled. It has been concluded that the coupling of the redox properties of the metal catalysts with the acid-base properties of the zeolite catalysts facilitates the low-temperature transformations of the mixtures.     

Transformations of tetradecane on La/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> + ZSM catalysts

The behavior of La/Al₂O₃ + ZSM catalysts has been studied in the process of the hydrogen-free conversion of tetradecane. The structure and state of active centers of catalysts have been investigated using a combination of physicochemical and instrumental methods (TPD of ammonia, IR spectroscopy, electron microscopy). It was found that the catalysts are characterized by the presence of acid (Brönsted and Lewis) sites and M⁰ and Mⁿ⁺ metal centers. Lanthanum in different oxidation states can be included in the acid sites. The degree of tetradecane conversion and the product composition are determined by the SiO₂/Al₂O₃ ratio of the zeolite and the conditions of the process. The mechanism of the cracking and transformations of tetradecane on La/Al₂O₃ + ZSM catalysts is discussed.     

Exhaustive schemes for refining C<Subscript>3</Subscript>-C<Subscript>4</Subscript> hydrocarbon fractions

Exhaustive schemes for efficient refining of the C₃-C₄ hydrocarbon fraction using zeolite type Y catalysts to obtain a high-octane additive are proposed. Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 5, pp. 6–7, September–October, 2008.     

Catalytic reforming of <Emphasis Type="Italic">n</Emphasis>-heptane on platinum-tungsten supported on gamma-alumina

The mono-metallic and bi-metallic catalysts have been prepared by impregnating with solutions containing a compound of H₂PtCl₆, WO₃ and 1 ml HCl (0.1 mol). It should be noted that the catalysts’ activity and selectivity have been determined under these conditions: 450–500°C, and 15–25 atm by H₂. For converting n-heptane, the molar ratio H₂/C₇H₁₆ is 5, and LHSV is 1.5 ml/h. It has been proved that, under these experimental conditions, the conversion of n-heptane into branched aliphatic isomers is catalyzed by a bifunctional mechanism. The results indicate that in the presence of W, the catalysts have much higher selectivity and stability for isomerization reaction. At a given conversion, the bi-metallic catalysts produce much lower concentrations of cracked products. According to the tests, W modifies the support acidity resulting to the higher selectivity for isomerization and the lower one for cracking, and it also modifies the Pt properties.     

Differentiation of jurassic and cretaceous Kalmykia crudes based on C<Subscript>14</Subscript>-C<Subscript>16</Subscript> diamantanes

The distribution of hydrocarbons of diamond-like structure – C₁₀-C₁₃ adamantanes and C₁₄-C₁₆ diamantanes – in Kalmykia condensate lying in Cretaceous and Jurassic deposits was investigated by chromatography–mass spectrometry. It was shown that Jurassic and Cretaceous crudes can differ with respect to the relative distribution of C₁₅-C₁₆ methyl- and dimethyldiamantanes.     

Liquid––liquid phase equilibrium in saturated hydrocarbon – arenes C<Subscript>6</Subscript>-C<Subscript>8</Subscript> – mixed extractant systems

Experimental data are reported on liquid–liquid equilibrium in saturated hydrocarbon – C₆-C₈ arene – mixed extractant (triethylene glycol–sulfolane–water) pseudoternary systems of varying composition at 50°C. It was shown that increasing the sulfolane:TEG ratio from 21.7:78.3 to 60:40 changes the character of the bimodal curve in the phase diagram from the open to the closed type. As a result, for the same ratio of extractant and feedstock, all of the extraction indices – the degree of extraction, distribution coefficients, and arene content in the extractant – improved and the hydrocarbon fractionation factors increased.     

Selective dimerization of styrene to 1,3-diphenylbutene-1 in the presence of [(acac)Pd(PAr<Subscript>3</Subscript>)<Subscript>2</Subscript>]BF<Subscript>4</Subscript>/BF<Subscript>3</Subscript>OEt<Subscript>2</Subscript> catalytic systems

Selective dimerization of styrene to 1,3-diphenylbutene-1 in the presence of [(acac)Pd(PAr₃)₂]BF₄ + BF₃OEt₂ catalytic systems, where R = C₆H₅, o-CH₃C₆H₄, p-CH₃C₆H₄, or o-CH₃OC₆H₄, has been studied. Under the optimal conditions (B/Pd = 8, T = 75°C, R = C₆H₅), the conversion of styrene to the products exceeds the conversion for the known analogs and reaches 1.5 tons of styrene/g-atom of palladium with amounts of dimers and trimers of 91 and 9%, respectively. The dimers consist of up to 100% 1,3-diphenylbutene-1 with a trans/cis isomer ratio of 95/5.     

Joint conversion of butane and hexane in the presence of supported platinum catalysts

It has been found that the joint conversion of butane and hexane over alumina-platinum catalysts opens up a new route of butane conversion yielding C₄₊ hydrocarbons with an increased yield of the C₆₊ products on a converted hexane basis. It has been shown that a necessary condition for the occurrence of this reaction is the presence of finely divided platinum in the ionic form (Pt^σ) in the catalysts. The results of catalytic testing of the samples modified with Cl⁻and F⁻ anions allowed a possible mechanism and the nature of active sites of the reaction of the joint conversion of butane and hexane to be proposed.     

Catalytic Cracking of <Emphasis Type="Italic">n</Emphasis>-Hexane and <Emphasis Type="Italic">n</Emphasis>-Heptane over ZSM-5 Zeolite: Influence of SiO<Subscript>2</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Ratio

The performance of two types of ZSM-5 zeolite catalysts (MFI-type zeolite, SiO₂/Al₂O₃ = 50 and 300) was studied in the catalytic cracking of n-hexane and n-heptane as a model compound of light naphtha for production of light olefins at 500, 550, and 600°C. The physicochemical properties of ZSM-5 catalysts were characterized by means of XRD, BET, SEM and NH₃-TPD. The influence of SiO₂/Al₂O₃ molar ratio was investigated on conversion and product selectivity. ZSM-5 zeolite yielded higher conversion in the cracking of n-hexane compared to n-heptane and maximum conversion was achieved over ZSM-5(50) at 600°C. ZSM-5(50) showed higher alkane selectivity rather than olefins. It was found that ZSM-5(300) was more desirable in terms of having significant selectivity to light olefins as well as producing high propylene to ethylene ratio. The maximum propylene to ethylene ratio of 2.7 and 2.48 was observed over ZSM-5(300) at 500°C for n-hexane and n-heptane cracking, respectively.     

Joint aromatization of butane and hexane on alumina-platinum catalysts

It has been found that the joint aromatization of C₄ and C₆ alkanes proceeds during the conversion of a butane and hexane mixture on alumina-platinum catalysts. It has been shown that a necessary condition for realization of the joint aromatization is the presence of highly dispersed platinum as ionic species (Pt^σ) and “hard” Lewis acid sites (L_z) of a catalyst. It has been determined that an optimum L_z/Pt^σ ratio for joint conversion reaction of light alkanes is from 1 to 2.     

Isomerization of <Emphasis Type="Italic">n</Emphasis>-hexane over bifunctional Pt/SO<Subscript>4</Subscript>/ZrO<Subscript>2</Subscript> catalysts

The catalytic properties of model Pt/SiO₂ and Pt/Al₂O₃ catalysts and their physical mixtures with SO₄/ZrO2 in the reaction of n-hexane isomerization have been studied. Significant effects of the influence of the platinum state on the characteristics of isomerization on the catalysts and their physical mixtures with SO₄/ZrO₂ have been revealed. The observed changes in catalytic performance of the mixed catalysts have been explained from the position of a bifunctional mechanism with the participation of ionic platinum promoting the formation of hydride ions, which play an important role in the activation of transformations of intermediates in isomerization reactions.     

Addition of CCl<Subscript>4</Subscript> to olefins catalyzed by chromium and ruthenium complexes: The influence of water as a nucleophilic additive

The feasibility of the addition of CCl₄ to linear and cyclic olefins and dienes in the presence of chromium and ruthenium complexes was established. The influence of water as a nucleophilic additive and the influence of the olefin nature, the catalyst central atom, and its ligand environment on the reaction selectivity and product yields were investigated. It was shown that the addition of water to chromium and ruthenium catalysts leads to the hydrolysis of the chloromethyl group in the resulting 1,1,1,3-tetrachloro derivatives, yielding the corresponding hydroxy derivatives and increasing the selectivity for the formation of (1 + 1) adducts, which is caused by the formation of hypochlorous acid playing the role of a coactivator of the addition of CCl₄ to alkenes.     

Dissociation behavior of （CH4 ＋ C2H4） hydrate in the presence of sodium dodecyl sulfate

Separation of a mixture of CH4+C2H4 gas by forming hydrate in ethylene production has become of interest,and the dissociation behavior of(CH4+C2H4) hydrate is of great importance for this process. The hydrate formation rate could be increased by adding a small amount of sodium dodecyl sulfate(SDS) into water. In this work,the kinetic data of CH4(18.5 mol%) +C2H4(81.5 mol%) hydrate decomposition in the presence of 1000 mg·L-1 SDS at different temperatures and pressures were measured with the depressurizing m...     

Co-hydrotreating of straight-run diesel fraction and vegetable oil on Co(Ni)-PMo/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts

The process of co-hydrotreatment of straight-run diesel fraction (DF) and vegetable oil (VO) on Co(Ni)-PMo/Al₂O₃ catalysts prepared from H₃PMo₁₂O₄₀ and cobalt (nickel) citrate has been studied. It has been shown that under conditions close to those in the industry, the complete conversion of fatty acid triglycerides (FATG) is achieved on the catalysts of both types to give an ultraclean hydrotreating product in a 97% yield and a cetane number of 5 points above that of the hydrotreating product of the DF alone. The degree of hydrodesulfurization (HDS) is reduced more significantly on the Co-PMo/Al₂O₃ catalyst than in the case of Ni-PMo/Al₂O₃. The catalysts are more susceptible to deactivation in the hydrotreating of the blended feedstock containing VO. The Co-PMo/Al₂O₃ sample is less stable than Ni-PMo/Al₂O₃. Examination of the spent catalysts by transmission electron microscopy has shown that the average particle length of the active phase of Co-PMo/Al₂O₃ increases, whereas this increment for Ni-PMo/Al₂O₃ is insignificant, indicating higher stability of particles of the NiMoS phase. Thus, the co-hydrotreating of petroleum fractions and vegetable oil is more reasonable to carry out on NiMo/Al₂O₃ catalysts.     

Evolution of active ingredients and catalytic properties of Pt-Sn/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts in the selective deoxygenation reaction of vegetable oils

The evolution of the structure of Pt–Sn/Al₂O₃ catalysts and their catalytic properties in the reaction of the reductive deoxygenation of rapeseed oil fatty acid triglycerides (FATGs) have been studied. The catalysts were prepared by deposition from an organic solution of a mixture of platinum and tin compounds, as well as a heterometallic (PPh₄)₃[Pt(SnCl₃)₅] complex, in which platinum and tin atoms are linked by a metal–metal bond. It has been shown that the use of the heterometallic complex as a precursor with a tin to platinum molar ratio of 5 results in the formation of clusters of nanosized tin (2+; 4+) oxides and particles of a metastable PtSn_{3 ± δ} alloy on the surface of the catalyst after reductive activation. In the presence of this catalyst, the exhaustive conversion of the feed FATGs and the selectivity for hydrocarbons above 98% have been achieved. The gaseous products CO, CO₂, and CH₄ are formed in trace quantities. The results show that the deoxygenation occurs not via the known decarboxylation and decarbonylation route, but also through the step of the selective reduction of oxygen and almost complete suppression of cracking of the organic moieties of FATGs.     

Study of the coordinative nature of alkylaluminum modified Phillips CrOx/SiO2 catalyst by multinuclear solid-state NMR

Solid-state nuclear magnetic resonance spectroscopy was used to investigate the coordinative states of surface Al species on various alkylaluminum-modified Phillips CrOx/SiO2 catalysts.The alkylaluminum-modified Phillips CrOx/SiO2 catalysts were examined via ethylene homopolymerization.1H and 27Al magic angle spinning（MAS） nuclear magnetic resonance（NMR） spectra clearly demonstrated that the existing states of surface Al species in alkylaluminum-modified catalysts strongly depended on the type of alkylaluminum cocatalyst,concentration of alkylaluminum and the calcination temperature.1H MAS NMR spectra of alkylaluminum-modified Phillips CrOx/SiO2 catalysts,calcined at two different temperatures,exhibited similar trends in peak shift.1H spectra showed that with an increase of Al/Cr ratio and calcination temperature,the main peak shifted to high field,indicating that the dominant surface proton species changed from hydroxyl to ethoxyl and ethyl groups.27Al MAS NMR spectra showed the presence of three different coordination states（6-,5-,and 4-coordinated Al species） in the alkylaluminummodified Phillips catalysts.In comparison of different alkylaluminum cocatalysts,it was found that the reactivity of alkylaluminum modified Phillips catalyst decreased in the order of TEA〉DEAH〉DEAE.The amount of 4-coordinated Al species of Phillips catalysts modified by TEA,DEAE and DEAH also decreased in the order of TEA〉DEAH〉DEAE,indicating that the presence of 4-coordinated Al species is related to the polymerization activity.     

Selective oxidation of methane into synthesis gas at short contact times on low-loading platinum-ruthenium catalysts

The results of the study of Pt-Ru/2% Ce/(θ + α)-Al₂O₃ catalysts with various Pt/Ru ratios used in the process of selective methane oxidation into synthesis gas at short contact times are presented. The optimal catalyst preparation conditions have been found for the process. It has been revealed that the methane conversion at 1173 K and a contact time of 4.0-3.0 ms varies from 96 to 100% and the selectivities for hydrogen and CO are 100 and 95–100%, respectively. At a Pt: Ru molar ratio of 2: 1 or 1: 1 and τ = 3.5 ms, the maximum (100%) degree of the conversion of methane into synthesis gas via the direct route is observed; the selectivity for H₂ and CO is 100%, and the total content of the noble metals is O ≥ 0.2%.     

Activity and stereoselectivity of heterogeneous molybdenum-and tungsten-containing catalytic systems in α-olefin metathesis

The dependence of the stereoisomeric composition of symmetric olefins (the products of α-olefin metathesis) on their conversion at 27 and 60°C was studied in the presence of three different catalysts: MoCl₅/SiO₂, MoOCl₄/SiO₂, and WCl₆/SiO₂, as well as SnMe₄ as a cocatalyst. Experimental data on the stereoisomer contents of the equilibrium mixture agree well with the results of thermodynamic calculation. It was found that temperature has an effect on the equilibration rate and the composition of stereoisomers in the equilibrium mixture. The activity and stereoselectivity of these three catalyst systems in the metathesis of α-olefins were compared. The molybdenum-containing catalysts were shown to be more active than the tungsten catalysts.     

The effect of H<Subscript>2</Subscript>S on the selectivity of light alkenes in the FE-Mn-catalyzed Fischer-Tropsch synthesis

Iron-manganese oxides are prepared using a co-precipitation procedure and studied for the conversion of synthesis gas to light olefins. In particular, the effect of a range of preparation variables is investigated in details. In this investigation, sulfur absorption and effect of sulfur poisoning on Fe-Mn catalysts have been studied. In the Fischer-Tropsch synthesis process, the poisoning of the catalyst is one of the important parameters causing a decrease in the catalyst activity, declaring the sulfur compounds as virulent poisons in this process. In the present investigation, poisoning of Fe-Mn catalysts were performed in a gas circulation system and H₂S was injected into a circulation loop. The prepared catalysts were exposed to a mixture of H₂S and N₂ at about 450°C in the stainless-steel micro reactor via co-precipitation method. H₂S was produced by addition of H₂SO₄ to Na₂S × H₂O and this gas was mixed with an inert carrier gas (N₂). Comparing the activity and selectivity of fresh and poisoned catalysts, indicates that the selectivity and CO conversion are affected by high-level sulfur adsorbed on the catalysts. The results show that the CO conversion and selectivity with respect to methane production and coke formation were decreased, but the selectivity of light alkenes such as propylene was increased over poisoned catalysts. Characterization of both precursors and calcined catalysts by powder X-ray diffraction, BET specific surface area and thermal analysis methods such as TGA and DSC showed that the poisoning of Fe-Mn catalysts influenced the catalyst structure.     

Specifics of the mechanism of formation and molecular-mass distribution of hydrocarbons in fischer-tropsch synthesis on Co/SiO2 Mn+ catalysts

It was shown that molecular-mass distributions of hydrocarbons produced over Co/SiO₂ · Fe(III), Co/SiO₂ · Cr(III), and Co/SiO₂ · Zn(II) catalysts are described well by a mathematical model proposed earlier for rationalizing the distribution of products formed in the presence of a Co/SiO₂ · Zr(IV) catalyst with a probability α. This model is based on the concept that α₁-hydrocarbons are produced from alkyl intermediates and α₂-hydrocarbons (α₁ < α₂) are formed from alternative surface compounds. The primary α₁-products are olefins, and ethylene is involved in chain growth with a lower value of α. Reasons for the speculation that the difference in the pattern of molecular-mass distribution of hydrocarbons produced on cobalt and iron catalysts is due to the difference in the mechanism of formation of α₁-hydrocarbons are given.