Effect of CO<Subscript>2</Subscript> on the oxidation of cyclohexene by H<Subscript>2</Subscript>O<Subscript>2</Subscript> using Co<Subscript>1.5</Subscript>PW<Subscript>12</Subscript>O<Subscript>40</Subscript> catalyst

Oxidation of cyclohexene by cheap and environmentally friendly oxidants, namely H₂O₂ and CO₂ has been catalyzed by Co_1.5PW₁₂O₄₀. It has been found that the main products of the oxidation are 2-cyclohexen-l-one (enone), 2-cyclohexen-l-ol (enol) and 1, 2-cyclohexanediol (diol) with the enone as the major product. Oxidation by CO₂ along with H₂O₂ remarkably increased the conversion compared to that by CO₂ and H₂O₂ separately. This might be due to the fact that CO₂ increases the percarbonate species (HCO₄ ^?) responsible of the oxidation by oxygen transfer, which indicated that the CO₂/H₂O₂ mixture is a useful reagent system. The decrease of both the selectivity of the enone and epoxide in favor of that of diol at higher conversions indicated that the diol was formed from the epoxide by consecutive reaction and/or directly from cyclohexene.     

CO<Subscript>2</Subscript>-triggered gelation for mobility control and channeling blocking during CO<Subscript>2</Subscript> flooding processes

CO₂ flooding is regarded as an important method for enhanced oil recovery (EOR) and greenhouse gas control. However, the heterogeneity prevalently distributed in reservoirs inhibits the performance of this technology. The sweep efficiency can be significantly reduced especially in the presence of “thief zones”. Hence, gas channeling blocking and mobility control are important technical issues for the success of CO₂ injection. Normally, crosslinked gels have the potential to block gas channels, but the gelation time control poses challenges to this method. In this study, a new method for selectively blocking CO₂ channeling is proposed, which is based on a type of CO₂-sensitive gel system (modified polyacrylamide-methenamine-resorcinol gel system) to form gel in situ. A CO₂-sensitive gel system is when gelation or solidification will be triggered by CO₂ in the reservoir to block gas channels. The CO₂-sensitivity of the gel system was demonstrated in parallel bottle tests of gel in N₂ and CO₂ atmospheres. Sand pack flow experiments were conducted to investigate the shutoff capacity of the gel system under different conditions. The injectivity of the gel system was studied via viscosity measurements. The results indicate that this gel system was sensitive to CO₂ and had good performance of channeling blocking in porous media. Advantageous viscosity-temperature characteristics were achieved in this work. The effectiveness for EOR in heterogeneous formations based on this gel system was demonstrated using displacement tests conducted in double sand packs. The experimental results can provide guidelines for the deployment of the CO₂-sensitive gel system for field applications.     

Ethylene oligomerization in the presence of ZrO(OCOR)<Subscript>2</Subscript>-Al(C<Subscript>2</Subscript>H<Subscript>5</Subscript>)<Subscript>2</Subscript>Cl-Modifier catalytic system

The kinetics of ethylene oligomerization and molecular-mass distribution of resulted oligomers on ZrO(OCOR)₂-Al(C₂H₅)₂Cl and ZrO(OCOR)₂-Al(C₂H₅)₂Cl-modifier catalyst systems, where the modifier was CCl₄, vinyl acetate, or zinc stearate, were studied depending on the modifier: ZrO(OCOR)₂ and Al(C₂H₅)₂Cl: ZrO(OCOR)₂ molar ratios, ethylene pressure, temperature, and modifier nature.     

Characteristics of CO<Subscript>2</Subscript> sequestration in saline aquifers

Storage of CO2 in saline aquifers is a viable option for reducing the amount of CO2 released to the atmosphere. This paper provides an overall review of CO2 sequestration in saline aquifers. First,the principles of CO2 sequestration are presented,including CO2 phase behavior,CO2-water-rock interaction,and CO2 trapping mechanisms. Then storage capacity and CO2 injectivity are discussed as the main determinants of the storage potential of saline aquifers. Next,a site section process is addressed considering b...     

Study of a mass transfer-reaction model for SO<Subscript>2</Subscript> absorption process using LAS/H<Subscript>2</Subscript>SO<Subscript>4</Subscript> solution

A regenerative absorption process for removal of SO_x from FCC off-gas using LAS/H₂SO₄ solution as absorbant was studied and pilot-plant experiments were carried out. A mass transferreaction model for the SO₂ absorption process was established based on pilot-plant experiments, and the concentration distribution of components in the liquid film, and the partial pressure and mass transfer rate of SO₂ along the height of the absorption tower, was calculated from this model. The numerical simulation results were compared with the experimental results and proved that the model can be used for describing the SO₂ absorption process.     

Sensitivity analysis of CO<Subscript>2</Subscript> sequestration in saline aquifers

Carbon capture and storage (CCS) technology has been considered as an important method for reducing greenhouse gas emissions and for mitigating global climate change. Three primary options are being considered for large-scale storage of CO₂ in subsurface formations: oil and gas reservoirs, deep saline aquifers, and coal beds. There are very many large saline aquifers around the world, which could make a big contribution to mitigating global warming. However, we have much less understanding of saline aquifers than oil and gas reservoirs. Several mechanisms are involved in the storage of CO₂ in deep saline aquifers, but the ultimate goal of injection of CO₂ into the aquifers containing salt water is to dissolve the CO₂ in the water. So it is important to study the solubility trapping and sensitivity factors of CO₂ in saline aquifers. This paper presents results of modeling CO₂ storage in a saline aquifer using the commercial reservoir simulator ECLIPSE. The objective of this study was to better understand the CO₂/brine phase behavior (PVT properties) and quantitatively estimate the most important CO₂ storage mechanism in brine-solubility trapping. This would provide a tool by performing theoretical and numerical studies that help to understand the feasibility of CO₂ geological storage. A 3-dimensional, 2-phase (water/gas) conceptional reservoir model used finite, homogenous and isothermal formations into which CO₂ is injected at a constant rate. The effects of main parameters were studied, including the vertical to horizontal permeability ratio k _v/k _h, salinity, and residual phase saturations. The results show that the vertical to horizontal permeability ratio has a significant effect on CO₂ storage. Moreover, more CO₂ dissolves in the brine at lower k _v/k _h values.     

A quick evaluation model for CO<Subscript>2</Subscript> flooding and sequestration

CO₂ flooding not only triggers an increase in oil production, but also reduces the amount of CO₂ released to the atmosphere (by storing it permanently in the formations). It is one of the best ways to use and store CO₂. This paper firstly selects the key factors after analyzing the factors influencing the CO₂ storage potential in the formations and oil recovery, and then introduces a series of dimensionless variables to describe reservoir characteristics. All influencing factors with varying values are calculated through a Box-Behnken experimental design. The results are interpreted by a response surface method, and then a quick screening model is obtained to evaluate the oil recovery and CO₂ storage potential for an oil reservoir. Based on the evaluation model, sensitivity analysis of each factor is carried out. Finally, research on CO₂ sequestration and flooding in a typical reservoir indicates that the evaluation model fits well with the numerical simulation, which proves that the evaluation model can provide criteria for screening attractive candidate reservoirs for CO₂ sequestration and flooding.     

Research on a novel composite gel system for CO<Subscript>2</Subscript> breakthrough

A composite gel was prepared for plugging CO2 channeling, which is a serious problem for enhanced oil recovery with CO2. A composite gel which is one of the materials for successful control of CO2 channeling during CO2 injection process was studied in this paper. SEM and nano particle size analysis were used to describe this material’s microstructure. Its effect on CO2 channeling control was evaluated with core flow experiments. Both the rheological test and core plugging experiments indicated that both acr...     

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...     

Precise model for estimating CO<Subscript>2</Subscript>—oil minimum miscibility pressure

The CO₂—oil minimum miscibility pressure (MMP) is an important parameter for screening and selecting reservoirs for CO₂ injection projects. For the highest recovery, a candidate reservoir must be capable of withstanding an average reservoir pressure greater than the CO₂—oil MMP. Knowledge of the CO₂—oil MMP is also important when selecting a model to predict or simulate reservoir performance as a result of CO₂ injection. This paper, presents a new alternating conditional expectation “ACE”-based model for estimating CO₂—oil MMP. The ACE algorithm estimates the optimal transformation that maximizes the correlation between the transformed dependent variable “CO₂—oil MMP” and the sum of the transformed independent variables that represent reservoir temperature and different components of oil composition. Predicted values of the CO₂—oil MMP from the developed ACE-based model were compared with the experimental and calculated values from the most common correlations reported in the literature for CO₂—oil MMP prediction. The results showed that the ACE-based model is superior to other commonly used correlations. Regarding other correlations, the ACE-based model yielded the highest correlation coefficient (0.9878), the lowest average relative error (0.7428%), and the lowest standard deviation of error (1.2265). The text was submitted by the author in English.     

Mono- and Bimetallic Mo(W)S<Subscript>2</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and Mo(W)S<Subscript>2</Subscript>/SBA-15 Hydrotreating Catalysts Based on SiMo<Subscript>12</Subscript> and SiW<Subscript>12</Subscript> Heteropoly Acids

Mono- and bimetallic Mo(W)S₂ catalysts supported on γ-Al₂O₃ and SBA-15 have been prepared using the Keggin heteropoly acids (HPAs) H₄SiMo₁₂O₄₀ and H₄SiW₁₂O₄₀. The catalyst samples have been analyzed by temperature-programmed reduction with hydrogen, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. Catalytic properties have been examined in the joint hydrotreating of dibenzothiophene and naphthalene on a flow-through unit. It has been shown that the use of mesoporous silica SBA-15 as a support can reduce the average length of Mo(W)S₂ particles from 4.9 to 3.7 nm and increase the average number of layers and the particle size of the active phase, changes that lead to an increase in catalytic activity by a factor of ~3 relative to the alumina-supported counterparts. The use of a mixture of SiMo₁₂HPA and SiW₁₂HPA for preparing MoW catalysts leads to a significant enhancement of catalytic activity, which is apparently due to the formation of mixed active sites.     

Hybrid Gas Separation Membranes Containing Star-Shaped Polystyrene with the Fullerene (C<Subscript>60</Subscript>) Core

A physicochemical study of novel hybrid polymer membranes based on polyphenylene oxide with a star-shaped modifier incorporated into the matrix has been conducted, and the transport properties of the membranes in the gas separation process have been studied. Poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) has been selected as the polymer matrix because of the low cost and high mechanical strength of this material. Star-shaped macromolecules (up to 5 wt %) containing six polystyrene arms grafted onto a fullerene(C₆₀) central core have been used as the filler. The structure and physical properties of the resulting membranes have been characterized by scanning electron microscopy, membrane density measurements, differential scanning calorimetry, and thermogravimetric analysis. Film surface has been studied by contact angle measurements. The gas separation properties of the membranes have been studied by the barometric method for the following individual gases: H₂, O₂, N₂, and CH₄. Data on the separation properties have been plotted as a Robeson diagram to compare with published data. It has been shown that the incorporation of star-shaped polystyrene into the PPO matrix leads to an improvement of the separation efficiency for selected gas pairs and an increase in selectivity compared with that of the unmodified membrane.     

Geometric structure,electronic structure,and some thermodynamic properties of C<Subscript>13</Subscript>H<Subscript>22</Subscript> trimethyl- and ethylmethyladamantanes

The structure of perhydrofluorene and its isomerization products 1,3,5-trimethyladamantane, 1,3,6-trimethyladamantane, cis-1,3,4-trimethyladamantane, trans-1,3,4-trimethyladamantane, 1-ethyl-3-methyladamantane, cis-1-ethyl-4-methyladamantane, trans-1-ethyl-4-methyladamantane, 1,2,6-trimethyladamantane, and 1,2,8-trimethyladamantane of the general formula C₁₃H₂₂ has been studied using the Becke—Lee—Yang—Parr (B3LYP) hybrid energy functional of electron density with the 6-31G* basis set. The geometric and electronic characteristics of the compounds and their total energy, transformation energies, entropies of transformations, and normal vibration frequencies have been calculated. It has been shown that the calculated Gibb free energies of formation for the perhydrofluorene isomerization products are in qualitative agreement with the experimental product composition of the isomerate.     

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.     

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.     

Supported Bifunctional Cobalt Catalysts for CO and H<Subscript>2</Subscript> Conversion to Fuel Fractions of Hydrocarbons

of Supported bifunctional cobalt catalysts for the direct conversion of synthesis gas to liquid fuelfraction hydrocarbons (HCs) have been studied. The effect of ZSM-5 zeolite in the structure of the support preformed using a boehmite binder on the catalytic and physicochemical properties of the catalysts has been examined. The synthesized catalysts exhibit high mechanical strength; therefore, they can be used in tubular Fischer–Tropsch (FT) synthesis reactors. The efficiency of the supported bifunctional Со/(Аl₂O₃–ZSM-5) catalysts is determined by the number of active metal cobalt sites, the degree of dispersion of the cobalt crystallites, and the total surface acidity. An increase in the catalyst acidity leads to an increase in the fuel fraction selectivity owing to long-chain HCs. At the same time, the activity of the catalysts decreases; therefore, a decrease in their efficiency is observed. It is assumed that this finding is attributed to the diffusion limitations between the HC synthesis and hydrotreating sites.     

Effect of Pd–Ru alloy membrane thickness on H<Subscript>2</Subscript> flux from steam reforming products

The influence of the thickness of a Pd–Ru alloy membrane on the H₂ flux from binary mixtures containing about 5 and 20% CO, CO₂, CH₄, and steam has been studied. It has been shown that with a decrease in the membrane thickness from 30 to 10 μm, the negative influence of these impurities on the H₂ flux increases. In experiments with pure H₂, it has been established that a decrease in the membrane thickness does not affect the nature of the rate-limiting step in the H₂ flow mechanism. The values for the effective activation energy of the H₂ permeability of the 30- and 10-μm membranes are 13.6 and 23.4 kJ/mol, respectively. A mathematical model describing the flow of hydrogen from binary mixtures through membranes of various thicknesses with varying temperature and pressure is 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.     

Conversion of dimethyl ether into lower olefins on a La-Zr-HZSM-5/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> zeolite catalyst

The catalytic properties of La-Zr-HZSM-5/Al₂O₃ in the synthesis of olefins from dimethyl ether (DME) were studied. It was shown by the method of temperature-programmed ammonia desorption that acid sites of medium strength are responsible for the high catalyst selectivity for lower olefins. It was found that the preliminary high-temperature treatment of zeolite or the replacement of nitrogen with steam increased not only the selectivity of the catalyst for lower olefins, but also its activity and stability. The effect of the operating parameters of the DME conversion into the lower olefins and the dependence of the catalyst activity on the number of regenerations were studied.