Feed Space Velocity Research Articles

Increasing the Efficiency of Liquid Phase Alkylation of Benzene with Propylene Using the Method of Mathematical Modeling

In this study the existing problems of liquid-phase alkylation of benzene with propylene problems are indicated. The paper describes the stages alkylation of benzene with propylene mathematical model development. The model allows to define the composition of the product stream under changing of plant process parameters: temperature, benzene/propylene molar ratio and feed space velocity. The error of the model does not exceed 7.5%. «Alkylation» computer modeling system is developed in Borland Delphi 7 and the optimization module of the process parameters is called «Optimization». In Aspen HYSYS the technological scheme of rectification products alkylation of benzene with propylene using aluminum chloride catalyst was developed. Integration of computer models allowed to determine the technological modes of production, providing isopropylbenzene outlet with higher quality.

Isomerization of n-hexane on binder-free shaped platinum-containing mordenite

A catalyst has been prepared as binder-free shaped MOR-type zeolite in the H form promoted with 0.5 wt % platinum, and n-hexane conversion over this catalyst has been studied. It has been found that the selectivity for C4–C6 isoparaffins on the new catalyst is about 90% at 300°C, a feed space velocity of 1.5 h–1, and a hydrogen pressure of 3 MPa, with the hexane conversion being 80.0–83.0 wt % and the selectivity for isohexane making 83.0–86.0%. It has been shown that the new catalyst is stable for 50 h on-stream under these conditions.

Solar molten salt heated membrane reformer for natural gas upgrading and hydrogen generation: A CFD model

Parabolic trough solar collectors can be used to drive endothermic reactions, such as methane reforming, while using molten salts as a heat transfer fluid. However, linear focus concentrators can only provide temperatures under 600°C, resulting in CH4 conversions well below 50%. The equilibrium can be shifted toward much higher conversions if H2 is continuously removed from the reaction mixture via a H2-selective membrane, while simultaneously generating a high-purity H2 stream. In this study, a tube-and-shell, molten salt-heated packed bed membrane reformer (Ni/Al2O3 catalyst, 5μm supported Pd film membrane) is analyzed numerically using computational fluid dynamics and non-isothermal formulation. The effects of molten salt supply rate and reforming feed flow rate on the reformer performance, which is evaluated in terms of CH4 conversion, H2 recovery, and selectivity to CO, are investigated. Depending on operating parameters, significant temperature and concentration gradients may form in both axial and radial directions. These gradients can be prevented by adjusting feed rates in the reforming and molten salt compartments. For the optimized case, CH4 conversion of 99% and H2 recovery of 87% are predicted for the molten salt feed temperature of 600°C and reforming feed space velocity of 5000h−1, which corresponds to a power density of 1.9kW/L and a fuel heating value upgrade of 40%. A preliminary techno-economic evaluation is provided.

Multicycle Investigation of Normal Paraffin Separation from Naphtha To Improve Olefin and Aromatic Feed

A programmed control double-column adsorber was built to investigate the steady operation of the normal paraffin separation from naphtha. The naphtha from Shanghai Gaoqiao Petrochemical Company (SGPC) was separated into a raffinate oil rich in non-normal hydrocarbons and a desorption oil rich in normal paraffins, using zeolite 5A as an adsorbent. In this paper, we investigate the effects of the adsorption/desorption temperature, feed space velocity, desorption gas space velocity, and switch time on the steady separation of normal paraffins. The adsorbability observed from the breakthrough curves of normal paraffins is consistent with the adsorption energies. The optimal conditions for the adsorption/desorption process were an operation temperature of 270 °C, a naphtha feed space velocity of 90.1 h–1, a switch time of 30 min, a desorption gas N2 space velocity of 127.5 h–1, and an intermediate oil cutting time of 2 min. With the Cutting Intermediate Oil (CIO) process, the normal paraffin content in raffinate oil was 3.42% and the potential aromatic content was 12.14% higher than that of naphtha. The normal paraffin content of desorption oil was 96.61%, and the ethylene yield was 15.08% higher than that of naphtha.

Low Temperature Performance of Selective Catalytic Reduction of NO with NH3 under a Concentrated CO2 Atmosphere

Selective catalytic reduction of NOx with NH3 (NH3-SCR) has been widely investigated to reduce NOx emissions from combustion processes, which cause environmental challenges. However, most of the current work on NOx reduction has focused on using feed gas without CO2 or containing small amounts of CO2. In the future, oxy-fuel combustion will play an important role for power generation, and this process generates high concentrations of CO2 in flue gas. Therefore, studies on the SCR process under concentrated CO2 atmosphere conditions are important for future SCR deployment in oxy-fuel combustion processes. In this work, Mn- and Ce-based catalysts using activated carbon as support were used to investigate the effect of CO2 on NO conversion. A N2 atmosphere was used for comparison. Different process conditions such as temperature, SO2 concentration, H2O content in the feed gas and space velocity were studied. Under Mn-Ce/AC conditions, the results suggested that Mn metal could reduce the inhibition effect of CO2 on the NO conversion, while Ce metal increased the inhibition effect of CO2. High space velocity also resulted in a reduction of CO2 inhibition on the NO conversion, although the overall performance of SCR was greatly reduced at high space velocity. Future investigations to design novel Mn-based catalysts are suggested to enhance the SCR performance under concentrated CO2 atmosphere conditions.

A new strategy for hydrogen sulfide removal by amido-functionalized reduced graphene oxide as a novel metal-free and highly efficient nanoadsorbent

In this research, hydrogen sulfide is adsorbed on amido-functionalized reduced graphene oxide (AFRGO) as a nanoadsorbent. By the use of n-propylamine and allylamine, reduced graphene oxide (RGO) was amidated for the adsorption of hydrogen sulfide. The materials were characterized by adsorption of H2S, potentiometric titration, scanning electron microscopy (SEM), Fourier-transform infrared (FT-IR) spectroscopy, and X-ray diffraction (XRD) analysis. The effect of the operational conditions of 4000–6000 h−1 space velocities and 60,000 ppm H2S feed concentrations were examined on adsorption capacity. The results show that H2S feed concentration, space velocity, and functional groups of adsorbents have a major effect on H2S adsorption. It was also found that the temperature in the range of 30–70°C had a significant effect on H2S adsorption. The concentration of H2S adsorbed in 3 h by AFRGO containing allyl substituent, AFRGO containing propyl substituent, graphene oxide (GO), and reduced graphene oxide (RGO) were reported as 59,710, 59,650, 59,600, and 59,500 ppm, respectively. Hydrogen sulfide adsorption analysis showed that nanoadsorbents increase adsorption capacity of H2S.

Production of hydrogen by catalytic steam reforming of oxygenated model compounds on Ni-modified supported catalysts. Simulation and experimental study

Steam reforming of two representative components in the aqueous fraction of bio-oil, acetone and ethanol, was investigated over nickel based supported catalysts (Ni/Al2O3). The effect of Rh incorporation (Ni–Rh/Al2O3) and the properties of different γ-Al2O3 used as support was tested. Hydrogen-rich gas is produced at temperatures higher than 673 K in both acetone and ethanol reforming with maximum mole fraction of 0.6–0.7. The reactions involved and the possible routes were studied. Rh incorporation and nanostructured alumina affects the Ni metal size and the amount of carbon deposited onto catalysts’ surface after reforming tests; besides, acetone is also found as an important intermediate in ethanol reforming, and Rh improve hydrogen production with negligible intermediates presence. The effect of S/Acetone or S/Ethanol feed molar ratios, space velocity and temperature over acetone/ethanol conversion and over H2/CO ratio were modeled using the Matlab software in order to find the regions and the optimal operating conditions in both processes. Simulation results are consistent with the experimental data.

A study on characterization and methane dry reforming performance of Co–Ce/ZrO2 catalyst

The overall purpose of this study is to propose an effective Co-based non-PGM bimetallic carbon dioxide reforming of methane (CDRM) catalyst, and to find the optimal reaction conditions to be used in production of synthesis gas. In catalyst formulation, ZrO2, which has ability to produce surface oxygen, is used as a support. Ce is used as a promoter in order to increase oxygen storage capacity and to regulate surface oxygen transfer. Freshly reduced and spent catalysts were analyzed by SEM–EDX, HRTEM–EDX, TPO, Raman Spectroscopy and XPS. The reaction conditions were optimised through the use of an experimentally designed procedure using reaction temperature, CH4/CO2 feed ratio and space velocity as the parameters. XPS analysis of Co 2p indicated that additional oxidation of Co was limited during CDRM which may only lead to a small decrease in activity. EM measurements showed well dispersion of Co and Ce on the surface. No significant metal sintering was observed. Local changes in Co/Ce ratio were found to have pronounced effect on carbon formation. It is well known that methane dehydrogenation produces surface carbon as the side product covering the active site. The comparative analysis of extent of carbon coverage on Co and Ce sites of the freshly reduced and spent samples through metal mapping by SEM–EDX indirectly confirmed methane dehydrogenation is the primary function of Co sites, and there is no methane activation on Ce sites. A comparative evaluation of XPS Ce 3d obtained from freshly reduced and spent samples on the other hand showed the surface oxygen storage/transfer function of Ce through redox cycle. In the performance tests, high activity with stable performance was observed for 1/1CH4/CO2 feed ratio for CDRM over Co–Ce/ZrO2 catalyst.

Application of Cumene Technology Mathematical Model

The work describes the existing problems of the technological systems for cumene synthesis catalyst AlCl3. The paper describes the stages of development of the mathematical model ofbenzene alkylation with propylene. The model allows the calculation of composition of the product stream when changing process parameters of the plant: temperature, molar ratio of benzene/propylene, feed space velocity. The error of the model does not exceed 7.5%. The computer modeling system «Alkylation» is developed in Borland Delphi 7, and the module optimization of the process parameters is called «Optimization». The calculations allowed reducing the catalyst consumption in the alkylation reactor (to 10-15%) and increasing the cumene concentration in the product mixture (to 25% wt.). The concentration of n-propylbenzene in the output stream is 0.05 wt%. The recommendations for optimization of the industrial alkylation unit are presented for implementation at OJSC «Omsky Kautchuk».

Dehydrogenation of n-butane on the industrial microspherical chromia-alumina catalyst AOK-73-24 in a membrane reactor

The basic features of the catalytic membrane dehydrogenation of n-butane have been studied in a reactor with membrane modules based on Pd/Ag foil of 9.3 and 30 μm thickness and in the absence of the membrane (temperature, 500–550°C; feed space velocity, 150–1200 h−1). It has been shown that in the absence of the membrane, the dehydrogenation of n-butane occurs in the kinetic region. The membrane thickness has a significant effect on the performance of the catalytic membrane reaction, presumably, because of the difference in the rate of H2 withdrawal from the reaction mixture. In the reactor with the 9.3-μm thick Pd/Ag-foil, the reaction is controlled by the H2 formation rate. As the thickness of the palladium foil is increased to 30 μm, the reaction proceeds to the diffusion region, thereby resulting in both enhancement of selectivity for butenes and a reduction of the yield of hydrocarbon deposits.

Energy and mass intensities in hydrogen upgrading by a membrane reactor

The necessity arose in the last decennia for the redesign of industrial processes with new unit operations for addressing environmental concerns which has led to the definition of new process indexes, so-called, metrics, that together with the traditional parameters supply additional information for technology selection and identify operating conditions for making a process more profitable. Two sustainability indexes, mass and energy intensities were used in a non-conventional evaluation of the up-grading stage in hydrogen production, i.e. the water gas shift, by means of membrane reactors. Defined as the ratio between the total inlet mass and total energy involved in the reactor, with respect to the hydrogen fed and produced by the reactor, they provide useful information about material exploitation and energy efficiency. The comparative study of membrane reactor performance with respect to conventional reactors was analysed as a function of the main process variables, i.e., pressure, feed molar ratio and space velocity. The membrane reactor resulted always in being more material (20–40%) and energy (20–35%) intensive than a traditional reactor and, in most of the cases, the values of its indexes exceeded the best one of a conventional reactor, corresponding at the equilibrium.

Application of suspended catalysts to the catalytic cracking of vacuum gas oil

The results of experimental studies on the application of finely dispersed catalytic compositions prepared based on the aqueous solutions of sodium silicate and Al2(SO4)3 and a suspension of zeolite NaY to the process of the catalytic cracking of the vacuum gas oil fractions of petroleum are given. It was found that the degree of conversion of a raw material into a fraction of motor fuels at a temperature of 450°C and a feed space velocity of 4.0 h−1 varied from 31.8 to 53.6% depending on the catalytic composition used, or it was higher than 90% upon the complete conversion with the recycling of the residue.

Modeling and Simulation of Hydrocracking of Fischer–Tropsch Hydrocarbons in a Catalytic Microchannel Reactor

Product quality of Fischer–Tropsch synthesis is improved by catalytic hydrocracking which converts heavy hydrocarbon fractions (wax) to commercially valuable fuels. The process is highly exothermic and requires strict temperature control; high temperatures cause overcracking to lower, commercially undesired hydrocarbons, whereas low temperatures reduce the conversions. Running hydrocracking in microchannel reactors is promising, since submillimeter dimensions lead to significant compaction that favors robust temperature control. This work investigates modeling and simulation of hydrocracking in a heat-exchange-integrated microchannel reactor involving parallel groups of square-shaped cooling and catalyst-coated reaction channels. Effects of material type and thickness of the wall separating the channels, and operating parameters (reactant and coolant feed temperatures and space velocity of the reactant stream) on reaction temperature and product distribution are investigated. Mole fractions of the product...

Coal hydrogenation under short-term reaction conditions

The results of the hydrogenation of coal from the Zashulanskoe deposit in the Chita oblast under conditions of a short reaction time (no longer than 10 min) are given. It was found that, to reach a 78–80% degree of coal conversion under the conditions of high-speed heating (∼200 K/min), the reaction time can be no longer than 10 min (the coal: paste-forming agent ratio = 50: 50), which corresponds to a feed space velocity of 2.5–3.0 kg l−1·h−1. This value, which determines the process productivity of coal hydrogenation, is higher by a factor of 3–3.5 than that under analogous conditions used in second generation processes, which were developed in the 1990s.

Effects of promoters on methane dry reforming over Ni catalyst on a mixed (a-Al2O3+TiO2-P25) support

Carbon dioxide reforming of methane to synthesis gas over Ni on a mixed (α-Al2O3 and TiO2-P25) support was investigated. The effect of adding Zr and Ce promoters to the supported catalyst was studied. Catalytic testes were performed at atmospheric pressure, flow rate of 33 ml/min and various reaction temperatures in the range of 500 and 800°C. The influence of several operating conditions such as feed ratio, space velocity and oxygen addition (that is, combined dry reforming and partial oxidation) on catalyst activity, stability and synthesis gas ratio (H2/CO) were studied. Spent and fresh catalysts were characterized by scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) techniques. The lowest carbon formation on the catalyst was attained at 800°C. Zr gave highest promotion and best stability. For the 1%Ni+0.15%Zr catalyst over 80% a- Al2O3+20% TiO2 support, the best conversions of CH4 and CO2 were 97 and 89.5%, respectively at 800°C and CO2/CH4 = 1.3. Key words: CO2 reforming, CH4, supported catalysts, coke, promoter, stability, partial oxidation.

Hydrogen Storage in a Recyclable Organic Hydride: Kinetic Modeling of Methylcyclohexane Dehydrogenation Over 1.0 wt% Pt/θ-Al2O3

The methylcyclohexane-toluene-hydrogen system is a potential solution for the implementation of a successful hydrogen economy. The dehydrogenation reaction, the backbone of the methylcyclohexane-toluene-hydrogen system, is studied over 1.0 wt% Pt/θ-Al2O3. Experiments were performed in a 1.02-cm internal diameter fixed-bed reactor. The effects of feed composition, temperature, space velocity, and pressure on conversion of methylcyclohexane were studied. An enhancement in the rate is observed with the addition of hydrogen in the feed. Both the power law kinetics and Langmuir-Hinshelwood-Hougen-Watson kinetics were employed to best fit the experimental data. Langmuir-Hinshelwood-Hougen-Watson kinetics based on single-site surface reaction kinetics were found to be appropriate to the experimental data.

Thermal cracking of black oil fuel in a mixture with shale

The results of studies performed for the development of a new process of the thermal cracking of tar as a suspension with ground Baltic oil shale in order to obtain motor fuel components are reported. The experimental results suggest undoubted advantages of the process over industrial thermal cracking because the deep degradation of tar (the yields of a gasoline fraction with bp to 180°C, middle distillates with bp of 180–360°C, and feedstock for catalytic cracking with bp of 360–520°C were ~12, 43–44, and ~15–16 wt % on an initial tar basis) was achieved upon the single-stage processing of the raw material under relatively mild conditions (5 MPa, 425°C, and a feed space velocity of 1.0 h−1). The resulting coke-like products and V and Ni contained in the raw material were deposited on the mineral matter of shale and removed from the reaction zone with the liquid products of the process.

Selective Isobutene Oligomerization by Mesoporous MSU-SBEA Catalysts

Hydrolytically stable mesostructured aluminosilicates assembled from protozeolitic precursors are examined as acid catalysts in the isobutene oligomerization reaction. Steady state conversions as high as 80% at 60 °C are achieved, depending on the isobutene:butane feed composition and space velocity. Most notably, the product selectivity to dimeric C8= and trimeric C12= olefins is readily fine-tuned simply by changing the feed composition. Undesirable high molecular weight oligomers are not produced in any case. The superior catalytic performance of the mesostructured aluminosilicates in comparison to commercial USY and BEA zeolites is clearly established. The improvement in catalytic performance is attributed to a combination of textural and acidic properties, as judged by N2 adsorption and pyridine adsorption studies.

Integrated membrane system for pure hydrogen production: A Pd–Ag membrane reactor and a PEMFC

In this work, an integrated system consisting of single stage hydrogen production and a commercial PEMFC was investigated experimentally. The CO-free hydrogen fed to the PEMFC was produced in a Pd–Ag membrane reactor (MR), upgrading a syngas stream with a composition similar to that coming out of a reformer (CO 45%; H 2 50%; CO 2 4%; N 2 balance, on dry basis). The performance of the MR was evaluated in terms of CO conversion and H 2 recovery as a function of the feed pressure (up to 600 kPa) and space velocity; no sweep gas was used for promoting the H 2 permeation, since this role was assigned exclusively to the feed pressure. Special attention was paid to the analysis of the integrated system, focusing on the influence of the Pd–Ag MR operating conditions on the electrical performance of the PEMFC. The PEMFC internal crossover was also considered to have an effect on the electrical performance and this was taken into account estimating the PEMFC actual efficiency. Furthermore, the chemical efficiency of the integrated membrane plant was evaluated, considering the H 2 converted into electricity with respect to the total amount of H 2 contained in the feed mixture. An interesting performance was shown by the integrated system since the PEMFC performance was close to the power nominal value.

Cerium impregnated palm shell activated carbon (Ce/PSAC) sorbent for simultaneous removal of SO 2 and NO—Process study

The simultaneous removal of SO 2 and NO from simulated flue gas by cerium oxide supported over palm shell activated carbon (Ce/PSAC) was studied in a fixed bed adsorber. The effects of adsorber temperature, presence of humidity, feed gas concentration and space velocity were studied as the process parameter. The results were illustrated as sorption breakthrough curves. From the experimental results, it was found that at higher space velocity, the SO 2 and NO sorption capacity was reduced. Humidity enhanced the SO 2 sorption capacity but deterred the NO sorption at percentage more than 15%. Temperature played an important role in the simultaneous removal of SO 2 and NO by cerium supported over PSAC. The maximum simultaneous sorption capacity of SO 2 and NO was achieved at temperature 150 °C with 121.7 and 3.5 mg/g, respectively. This study shows that cheap biomass based activated carbon can be a potential sorbent for simultaneous removal of SO 2 and NO from flue gas.