Light olefins are one of the main raw materials for the petrochemical industry. They are mainly produced by steam cracking of hydrocarbons from ethane to gasoil. The pyrolysis takes place in the ...tubular reactors, inside the firebox of the furnace, at high temperature, low pressure and a very short residence time. This is the only available industrial process exists for the production of olefins yet although there are other processes such as catalytic cracking for the production of such materials. This paper reviews the main research works done on the process in the literature in the last five decades. Three sections of the furnace and tubular reactors which are fixed inside the furnace have been described in detail. A mathematical model is presented for the simulation of the firebox and the reactor. Some of the main experimental laboratory setup systems in the world have been reviewed and parts of the results are presented and discussed. Finally, a few computer software packages for the simulation and online optimization of thermal cracking furnaces are presented.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
•Anammox activity was not affected by a decrease in temperature from 35 °C to 20 °C.•Anaerobic effluent and a temperature of 25 °C select for Ca. Anammoximicrobium.•Temperature reduction changed ...microbial community structure and diversity.•Anammox and denitrifying bacteria were both favoured at 25 °C.•Anammox removes N from municipal wastewater at typical tropical temperatures.
The effects of temperature reduction (from 35 °C to 20 °C) on nitrogen removal performance and microbial diversity of an anammox sequencing batch reactor were evaluated. The reactor was fed for 148 days with anaerobically pretreated municipal wastewater amended with nitrite. On average, removal efficiencies of ammonium and nitrite were high (96%) during the enrichment period and phases 1 (at 35 °C) and 2 (at 25 °C), and slightly decreased (to 90%) when the reactor was operated at 20 °C. Deep sequencing analysis revealed that microbial community structure changed with temperature decrease. Anammox bacteria (Ca. Brocadia and Ca. Anammoximicrobium) and denitrifiers (Burkholderiales, Myxococcales, Rhodocyclales, Xanthomonadales, and Pseudomonadales) were favoured when the temperature was lowered from 35 °C to 25 °C, while Anaerolineales and Clostridiales were negatively affected. The results support the feasibility of using the anammox process for mainstream nitrogen removal from anaerobically pretreated municipal wastewater at typical tropical temperatures.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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•Initial rate of photon absorption (IRPA) correlated to optimum catalyst concentration.•τapp provides an ideal similarity parameter for designing and scaling photocatalytic ...reactors.•τapp in the range 4.1–4.4 provides optimum catalyst and reactor performance with any photocatalyst.•Dimensionless boundary layer of photon absorption of 90% provides optimal design.•Radiative transfer phenomena correlated to IRPA, dimensionless boundary layer of photon absorption and τapp.
The concepts of “initial rate of photon absorption” (IRPA), “dimensionless boundary layer of photon absorption” and “apparent optical thickness (τapp)” are presented to evaluate the radiative transfer phenomena in solar, slurry, planar, photocatalytic reactors. The radiation field produced by suspensions of TiO2 and goethite, two photocatalysts with profoundly different optical properties used in heterogenous photocatalysis and heterogeneous photo-assisted Fenton reactions, was determined by the six-flux radiation absorption-scattering model coupled to the Henyey-Greenstein scattering phase function (SFM-HG). The concept of IRPA, defined by the differentiation at the local volumetric rate of photon absorption (LVRPA) at the reactor window boundary, is proposed as a new approach to determine the impact of catalyst loading and optical properties on the extinction of light inside a photoreactor. The IRPA showed that the extinction of light follows a second order dependency on the photocatalyst concentration while the impact of the optical properties can be expressed by a decoupled function (Ψ function). The Ψ function increased with photocatalyst concentration and approached a maximum at the same optimal photocatalyst concentration determined from the analysis of the total rate of photon absorption (TRPA) in the reactor. The analysis of TRPA and boundary layer of photon absorption redefined here in dimensionless form, as a function of τapp, determined that the most efficient rate of radiation absorption in solar powered planar reactors occurs at τapp = 4.1–4.4, with approximately 10% of the reactor width under darkness. τapp is a similarity dimensionless parameter exclusively derived from the SFM approach, which clusters the effects of photocatalyst loading, reactor dimension and photocatalyst optical properties, providing an ideal parameter for designing and scaling photocatalytic reactors operated with any kind of photocatalytic material.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•Balancing AOB and AnAOB rates is the key factor for mainstream PNA at μM DO.•Stable PNA after temperature decrease from 25 to 15 °C without acclimation.•Heterotrophs growth on dissolved organic ...carbon from cell lysis decreases effluent NO3−.•Nitrospira was the only NOB and their control was assisted by AnAOB activity.•Candidatus Kuenenia was the predominant AnAOB throughout the study.
This study aimed at assessing the performance and microbial community in a granular one-stage partial nitritation-anammox sequencing batch reactor (PNA-SBR) subjected to temperature transition from 25 to 15 °C without biomass acclimation. The PNA-SBR was operated by controlling the oxygen transfer rate (OTR) according to the ammonium loading rate (ALR), which resulted in micromolar (µM) bulk dissolved oxygen (DO) concentration. The applied strategy proved to be feasible to operate the one-stage PNA-SBR at mainstream conditions because it was possible to control nitritation according to anammox rate. Nitrogen removal rate (NRR) of 330.24 ± 25.36 mg N·L−1·d−1 was achieved at 25 °C. Nitratation control by µM bulk DO limited the NO3−production:NH4+removed at 0.28 ± 0.04. No instability was experienced by decreasing the temperature to 15 °C, but removal rates were adapted to the resulting anammox activity, which decreased at low temperature. After temperature transition, nitratation was kept controlled and the NO3−production:NH4+removed molar ratio remained at 0.33 ± 0.05, although anammox activity deteriorated and higher nitrate production was obtained. Sequencing analysis revealed the dominant bacterial groups in the microbial community that clustered within the phyla Planctomycetes, Proteobacteria, Chloroflexi, and Bacteroidetes. Temperature drop only affected bacterial abundance, but the main bacteria involved in nitrification and anammox processes did not change during the study. Candidatus Kuenenia was the main anammox genus. Moreover, the presence of bacterial groups associated with heterotrophic metabolism indicates denitrification might be supported by the release of dissolved organic carbon due to bacterial lysis, and lower nitrate effluent concentration could be reached in PNA reactors.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•Mo-ZSM5@SiC Structured catalytic reactor stable operation under MW heating at reaction conditions.•Acetylene formation in the MNOC reaction under MW heating.•Product distribution under MW heating is ...different than in the case of conventional heating.•Gas-solid temperature gap prevents soft‐coke formation.
The main problem to be addressed in the valorization of methane under non-oxidative conditions (MNOC) is to reduce or even avoid coke formation. In this work we report the use of microwave-assisted heating for MNOC. We have developed a system able to heat-up a Mo-ZSM5 catalyst coated on silicon carbide monolith that could operate stable for at least 19 h at reaction conditions, 700 °C. We demonstrate that under MW-heating the selectivity shifts to C2s and benzene. In contrast, the operation under conventional heating (CH) produces more coke and polyaromatics. The selective microwave heating has two effects in this reaction: i) during the activation of the catalyst the formation of the active catalytic species of Mo2C inside the microporous support is different affecting the selectivity and product distribution; ii) a gas-solid temperature gradient is established that prevents the formation of coke from PAHs in the gas phase. The MNOC process under controlled MW heating at high space velocity (3000 mL/gcat·h) gives a hydrocarbon yield of around 6% with a very low deactivation rate. These results open up new possibilities for process intensification using alternative sources of energy, as is the case of microwaves, for heating structured catalytic reactors.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•The removal efficiency and CO2 selectivity were improved in NTP catalysis.•CoMn/TiO2 provided better removal efficiency than CeMn/TiO2 in NTP catalysis.•The discharge behavior played ...a dominant role in chlorobenzene removal efficiency.•The catalysis took a prominent part in the CO2 selectivity and O3 decomposition.
The decomposition of chlorobenzene (CB) in a non-thermal plasma (NTP) catalysis combined reactor was investigated. CoMn/TiO2 and CeMn/TiO2 were prepared using a deposition–precipitation method. CB decomposition, carbon balance, selectivity of CO2, and the byproducts of NOx and O3 were investigated. NTP catalysis provided significantly better CB removal efficiency and CO2 selectivity than did the plasma alone. CoMn/TiO2 exhibited better removal efficiency than CeMn/TiO2 in the NTP-catalysis reactor, but the performance of the catalysts during the thermal catalytic oxidation was reversed without the NTP. To reveal the activity difference with CB decomposition in the NTP-catalysis hybrid system, the dielectric constant and the physicochemical properties of CoMn/TiO2 and CeMn/TiO2 were analyzed. The plasma, which was affected by the dielectric constant, played a dominant role in this hybrid system. The reducibility of the catalysts promoted the CO2 selectivity and O3 decomposition. The CoMn/TiO2 was remarkably stable in the NTP-catalysis hybrid system during extended testing.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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•Capillary reactors 0.53 and 1.6mm in diameter were coated with a Pd/ZnO catalyst.•The 2-methyl-3-butyn-2-ol semihydrogenation selectivity was above 97%.•At a coating thickness of ...6μm, the onset of internal diffusion limitations was observed.•A throughput of 28kg/day per channel can be reached according to the model.
A 2.5wt.% Pd/ZnO catalytic coating has been deposited onto the inner wall of capillary reactors with a diameter of 0.53 and 1.6mm. The coatings were characterised by XRD, SEM, TEM and elemental analysis. The performance of catalytic reactors was studied in solvent-free hydrogenation of 2-methyl-3-butyn-2-ol. No mass transfer limitations was observed in the reactor with a diameter of 0.53mm up to a catalyst loading of 1.0kg(Pd)m−3. The activity and selectivity of the catalysts has been studied in a batch reactor to develop a kinetic model. The kinetic model was combined with the reactor model to describe the obtained data in a wide range of reaction conditions. The model was applied to calculate the range of reaction conditions to reach a production rate of liquid product of 10–50kg a day in a single catalytic capillary reactor.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The photo-Fenton process is intensified for degradation of carbofuran by using a tubular microreactor coiled around a florescent light. The microreactor attained 7.5 times faster degradation rate ...compared to a batch reactor operated under a LED light. At the initial Fe2+ concentration of 0.25 mM, the degradation rates in the batch reactor were fast at first, subsequently became slow, and afterward gradually increased with time regardless of light intensity. In the microreactor, the degradation rates appeared to decrease similarly to the first-order reaction despite the same initial Fe2+ concentration. A proposed kinetic model well fitted the results of both batch and microreactors by modeling that Fe3+ is photoreduced in a complex in equilibrium with Fe3+ and intermediates with carboxyl group decomposed from carbofuran.
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IJS, KILJ, NUK, PNG, UL, UM
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•Green algal-bacterial granules were obtained with illuminance ≥135 µmol m−2 s−1.•≥90 µmol m−2 s−1 illumination created an aerobic/anoxic zone in the core of granule.•High light ...intensity enhanced lipid content and affected FAMEs (C15–18) composition.•Nitratation was remarkably inhibited when exposed to illuminance ≥180 µmol m−2 s−1.•Enriched AOB and algae were the major contributors to the enhanced N and P removals.
The effects of light intensity (0–225 µmol m−2 s−1) on oxygen distribution, lipid production and biological community structure of algal-bacterial granules were investigated in six identical photo-sequencing batch reactors (with a dark/light cycle of 12 h/12 h). Typically green algal-bacterial granules could be developed at a light intensity of ≥135 µmol m−2 s−1. The lipid content was significantly increased under higher light intensity, while the percentage of saturated fatty acid methyl esters was remarkably decreased. Results showed that light intensity ≥90 µmol m−2 s−1 yielded enough O2 production from algae, creating aerobic/anoxic zone (0.3–0.6 mg-O2/L) in the core of granules and thus efficient algal-bacterial symbiosis system. Enhanced nitrogen and phosphorus removals were achieved in the reactors with stronger light illumination, probably attributable to the enrichment of ammonia oxidizing bacteria (Comamonadaceae and Nitrosomonadaceae) and algae (Navicula and Stigeoclonium). Illuminance ≥180 µmol m−2 s−1 was found to be unfavorable for Nitrospiraceae.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Renewables challenge the management of energy supply and demand due to their intermittency. A promising solution is the direct conversion of the excess electrical energy into valuable chemicals in ...electrochemical reactors that are inexpensive, scalable, and compatible with irregular availability of electrical power. Membrane-less electrolyzers, deployed on a microfluidic platform, were recently shown to hold great promise for efficient electrolysis and cost-effective operation. The elimination of the membrane increases the reactor lifetime, reduces fabrication costs, and enables the deployment of liquid electrolytes with ionic conductivities that surpass those allowed by solid membranes. Here, we demonstrate a membrane-less architecture that enables unprecedented throughput by 3D printing a device that combines components such as the flow plates and the fluidic ports in a monolithic part, while at the same time, providing tight tolerances and smooth surfaces for precise flow conditioning. We show that inertial fluidic forces are effective even in millifluidic regimes and, therefore, are utilized to control the two-phase flows inside the device and prevent cross-contamination of the products. Simulations provide insight on governing fluid dynamics of coalescing bubbles and their rapid jumps away from the electrodes and help identify three key mechanisms for their fast and intriguing return towards the electrodes. Experiments and simulations are used to demonstrate the efficiency of the inertial separation mechanism in millichannels and at higher flow rates than in microchannels. We analyze the performance of the present device for two reactions: water splitting and the chlor-alkali process, and find product purities of more than 99% and Faradaic efficiencies of more than 90%. The present membrane-less reactor - containing more efficient catalysts - provides close to 40 times higher throughput than its microfluidic counterpart and paves the way for realization of cost-effective and scalable electrochemical stacks that meet the performance and price targets of the renewable energy sector.
Separation of electrolysis products using fluidic inertial forces in a 3D printed flow cell.
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