Vol 58, No 3 (2018)

Results of theoretical description of the reactions of concerted molecular decomposition of alkyl halides RX to olefin and HX have been analyzed. Data on quantum-chemical calculation of the transition state of these reactions are given. The results obtained by analyzing experimental data in terms of the model of intersecting parabolas have been compared. The following factors determining the reactivity of RX (X = F, Cl, Br, I) in the decomposition reactions: enthalpy of decomposition, force constants of reacting bonds, triplet repulsion, electronegativity of the reaction-center atoms, the π-bond adjacent to the reaction center, dipole–dipole interaction, and elongation of the R–X bond win the transition state, have been distinguished. The energy spectrum of partial activation energies of the concerted molecular degradation of RX has been constructed.

The group composition of hydrocarbons (HC) and hetero compounds in the products of stepwise thermolysis of asphaltenes from crude oil of the Usa oilfield at temperatures of 120, 230, 370, 500 and 750°C has been studied. The volatile thermolysis products formed at each step of the process have been studied by gas chromatography–mass spectrometry. It has been found that the main products of stepwise thermolysis of asphaltene molecules are alkylbenzenes (AB) and saturated aliphatic hydrocarbons (SAH), aromatic fragments obtained at 370°C are mainly separate structural blocks of asphaltene molecules, and benzothiophenes (BT) predominate over dibenzothiophenes (DBT) as structural units of asphaltene molecules. It has been shown that with an increase in the process temperature, the alkylbenzenes/saturated aliphatic hydrocarbons ratio (AB/SAH + Alkenes) increases by a factor of 6 to 7; the phenanthrene/alkylbenzenes (PN/AB) ratio and the polycyclic aromatic hydrocarbons/alkylbenzenes (PAH/AB) ratio decrease by ten- and twofold, respectively; and the naphthalenes/alkylbenzenes (NP/AB) ratio increases by two times.

The direction of catalytic aquathermolysis processes involving high-molecular-weight components of heavy oil has been revealed in model experiments, depending on the metal nature and the conditions of the experiments carried out at 300°C in neutral and carbon dioxide media, using oil-soluble carboxylates of the transition metals nickel, iron, cobalt, and copper as a catalyst. The yield and quality of the products formed in the presence of individual metals and their compositions have been determined. Propanol and tetralin have been studied as modifying additives. The viscosity of heavy oil in a carbon dioxide medium has been significantly reduced by using an iron-, cobalt-, and copper-containing catalyst composition together with the propanol additive, as a result of an increase in the amount of saturated and aromatic hydrocarbons and a decrease in the resin content in its composition. An increase in the value of the C₁₃–C₁₇/C₁₈–C₂₂ index can serve as a parameter for monitoring the progress of catalytic aquathermolysis processes.

Catalysts based on Ni, Co, and NiCo supported on MFI zeolites for the partial oxidation of methane and dry reforming of methane to synthesis gas have been synthesized and studied. The total metal content in the catalysts is 2 wt %. A commercial zeolite with a binder (alumina) and a binder-free zeolite synthesized by an accelerated microwave-assisted hydrothermal method are used as supports. The synthesis gas yield is 97% in the presence of Ni and NiCo catalysts supported on the MFI zeolite synthesized by the microwaveassisted hydrothermal method. The simultaneous presence of Ni and Co in the catalyst makes the sample resistant to coking during dry reforming of methane, whereas the Ni catalyst is characterized by the formation of a significant amount of carbon fibers.

The effect of temperature on the cracking of pond acid tar and acid tar neutralized with lime has been studied. The formation of H₂S or SO₂ is determined by the amount of sulfuric acid in the tar. Liquid hydrocarbons obtained from neutralized acid tar are characterized by low sulfur content.

Propane conversion to aromatic hydrocarbons (HC) on a steamed galloaluminosilicate catalyst has been studied. Dependences of the propane conversion, the selectivity of the formation of its conversion products, and the on-stream stability of galloaluminosilicate on the steaming temperature have been revealed. It has been found that steaming leads to a decrease in concentration of acid sites of different strengths, a change that has been associated with partial dealumination of the zeolite framework. Trends in the coking process on the steamed galloaluminosilicate surface in the propane conversion to aromatic hydrocarbons have been elucidated, and the origin and concentration of the condensation products formed have been determined.

The thermal degradation, under oxidative pyrolysis conditions, of two synthetic lubricating base oils, poly-α-olefin (PAO) and di-ester (DE), was investigated. The main objective of the study was to characterize their behavior in simulated “areo-engine” conditions, i.e. compared the thermal stability and identified the products of thermal decomposition as a function of exposure temperature. Detailed characterizations of products were performed with Fourier transform infrared spectrometry (FTIR), gas chromatography/ mass spectrometry (GC/MS), viscosity experiments and four-ball tests. The results showed that PAO had the lower thermal stability, being degraded at 200°C different from 300°C for DE. The degradation also effected the tribological properties of lubricating oil. Several by-products were identified during the thermal degradation of two lubricants. The majority of PAO products consisted of alkanes and olefins, while more oxygen-containing organic compounds were detected in DE samples according to the observation of GC/MS analysis. The related reaction mechanisms were discussed according to the experimental results.

High-density polyethylene (HDPE) have been widely used as materials of hollow molded articles, extrusion molded articles, films and sheets. The properties of HDPE vary depending on its application fields and processing methods thereof. Approximately 50 million tons of HDPE are produced annually around the worldwide by slurry phase processes. In this paper, the status of slurry phase polyethylene processes in China is briefly introduced. Two of the most important licensers of continuous stirred tank reactor (CSTR) type slurry phase polyethylene processes, namely, Hostalen (Licensed by Basell), CX (Licensed by Mitsui), with a dual- or three-reactor are reviewed. The merits and demerits of the examined polyethylene production technologies are discussed in detail. Catalyst is a key of polyolefin technology. It does have an extremely close relationship with the performance of polyethylene. The characteristics and disadvantages of different catalysts for the two processes are summarized for comparison, including the PZ and RZ catalysts of Mitsui, the BCH and BCE catalysts of Beijing Research Institute of Chemical Industry, the TH series catalysts of Basell. Some advices on the development and application of HDPE catalysts for the slurry process are proposed.