Promotion of CO<Subscript>2</Subscript> hydrogénation to hydrocarbons in three-phase catalytic (Fe-Cu-K-Al) slurry reactors

A three-phase slurry reactor has been employed to increase the CO₂ conversion and decrease the selectivity of CO in the direct hydrogénation of CO₂ to hydrocarbons, as it is beneficial for removal of the heat generated due to highly exothermic nature of the reaction. Experiments were conducted over iron-based catalysts (Fe-Cu-K-Al, d_p,=45-75 Μm) in a slurry reactor. It was found that the slurry reactor is preferable to the fixed bed reactor. The productivity and selectivity of hydrocarbons in the slurry reactor appeared to be better than that in the fixed bed reactor for the hydrogénation of CO₂. The CO₂ conversion was increased with increasing reaction temperature (275-300 ‡C), pressure (1-2.5 MPa) or H₂/CO₂ ratio (2-5) in the three-phase slurry reactor. The CO₂ conversion was increased with increasing the amount of CO₂ fed.     

The destruction of N2O in a pulsed corona discharge reactor

The removal of N₂O by a pulsed corona reactor (PCR) was investigated. Gas mixtures containing N₂O were allowed to flow in the reactor at various levels of energy input, and for different background gases, flow rates, and initial pollutant concentrations. The reactor effluent gas stream was analyzed for N₂O, NO, NO₂, by means of an FTIR spectrometer. It was found that destruction of N₂O was facilitated with argon as the background gas; the conversion dropped and power requirements increased when nitrogen was used as the background gas.Reaction mechanisms are proposed for the destruction of N₂O in dry argon and nitrogen. Application of the pseudo-steady state hypothesis permits development of expressions for the overall reaction rate in these systems. These reaction rates are integrated into a simple reactor model for the pulsed corona discharge reactor. The reactor model brings forth the coupling between reaction rates, electrical discharge parameters, and fluid flow within the reactor. Comparison with experiment is encouraging, though the needs for additional research are clearly identified.     

Comparative study between fluidized bed and fixed bed reactors in methane reforming combined with methane combustion for the internal heat supply under pressurized condition

The effect of catalyst fluidization on the conversion of methane to syngas in methane reforming with CO₂ and H₂O in the presence of O₂ under pressurized conditions was investigated over Ni and Pt catalysts. Methane and CO₂ conversion in the fluidized bed reactor was higher than those in the fixed bed reactor over Ni_0.15Mg_0.85O catalyst under 1.0 MPa. This reactor effect was dependent on the catalyst properties. Conversion levels in the fluidized and fixed bed reactor were almost the same over MgO-supported Ni and Pt catalysts. It is suggested that this phenomenon is related to the catalyst reducibility. On a catalyst with suitable reducibility, the oxidized catalyst can be reduced with the produced syngas and the reforming activity regenerates in the fluidized bed reactor. Although serious carbon deposition was observed on Ni_0.15Mg_0.85O in the fixed bed reactor, it was inhibited in the fluidized bed reactor.     

Methyl tert-butyl ether decomposition over heteropoly acid catalyst in a cellulose acetate membrane reactor

In this study the methyl tert-butyl ether (MTBE) decomposition over H₃PW₁₂O₄₀ was carried out in a cellulose acetate membrane reactor. The permeability of methanol through the cellulose acetate membrane was about 30 and 300 times higher than that of either isobutene or MTBE, respectively. The isobutene selectivity in the fixed bed reactor was only slightly higher than the methanol selectivity due to the side reaction. In the cellulose acetate membrane reactor, however, the isobutene selectivity in the rejected stream was 68% and the methanol selectivity in the permeated stream was up to 97%. The MTBE conversion in the membrane reactor was about 7% higher than that in the membrane-free fixed bed reactor under the same reaction conditions. The enhanced performance of the membrane reactor in this reversible reaction was mainly due to the selective permeation of methanol which resulted in a methanol-deficient condition suppressing MTBE synthesis reaction.     

Improved methanol yield from methane oxidation in a non-isothermal reactor

Partial oxidation of methane to methanol was carried out homogeneously in a non-isothermal reactor that contained a non-permselective membrane. A tubular reactor was used with a smaller-diameter tubular membrane of 5 nm pore diameter alumina or 0.5 μm pore diameter metal. The membrane provided a uniform flow distribution and separated the hot reactor wall from a cooling tube located in the centre of the reactor. The cold region in the reactor rapidly quenched further reaction. The selectivity for CH₃OH formation at 4.6% conversion increased from 34 to 52% when quenching was used. The highest yield (selectivity times conversion) obtained was 3.8% at 55 MPa and 800 K. Methanol selectivity increased with increasing pressure and decreased with increasing temperature, residence time and O₂ concentration. The combined selectivity to partial oxidation products (CO, CH₃OH, CH₂O) was almost constant at 86%.     

A novel integrated rotary reactor for NOx reduction by CO and air preheating: NOx removal performance and mechanism

A novel integrated rotary reactor for NOx reduction by CO and air preheating (iNA reactor) was proposed. NOx removal performance was investigated in a fixed-bed reactor, which was used to simulate the working conditions change in the iNA reactor. Lab-synthesized Cu/FeCeO_x were used as the catalyst. Two different modes were tested with the iNA reactor: short cycles and long cycles. Excellent NOx removal efficiencies of over 95% and 90% for short cycles and long cycles, respectively, were observed in the iNA reactor. Moreover, compared with the constant-temperature rotary reactor, better H₂O and SO₂ resistances were also found in the iNA reactor. The reaction mechanism was proposed based on in situ diffuse reflectance infrared Fourier transform study. In the iNA process, NOx was stored as nitrates in the adsorption zone, and then decomposed rapidly by both high temperatures and CO, leading to the deep catalyst regeneration. Therefore, temperature swinging and the feed of CO were key to having high iNA reactor performance for NOx removal.     

Kinetics of the methanation of carbon dioxide over a supported Ni-La2O3 catalyst

The kinetics of the methanation of carbon dioxide was investigated using an alumina supported Ni-La₂O₂ catalyst in a differential and integral reactor. In the differential reactor the molar ratio of H₂ to CO₂ was varied from 0.6 to 30. In the integral reactor the rates were measured with up to 90% conversion. Both reactor tests were carried out at temperatures between 513 and 593 K. The experimental results were described by a Langmuir-Hinshelwood type equation. The kinetics can be explained by assuming equilibrium of dissociative carbon dioxide and hydrogen adsorption, and assuming hydrogenation of surface carbon as the rate determining step.     

Contribution to emission reduction of CO2 by a fluidized-bed membrane dual-type reactor in methanol synthesis process

In this work, a fluidized-bed membrane dual-type reactor was evaluated for CO₂ removal in methanol synthesis process. The feed synthesis gas is preheated in the tubes of the gas-cooled reactor and flowing in a counter-current mode with reacting gas mixture in the shell side. Due to the hydrogen partial pressure driving force, hydrogen can penetrate from feed synthesis gas into the reaction side through the membrane. The outlet synthesis gas from this reactor is fed to tubes of the water-cooled packed-bed reactor and the chemical reaction is initiated by the catalyst. The methanol-containing gas leaving this reactor is directed into the shell of the gas-cooled reactor and the reactions are completed in this fluidized-bed side. A two-phase dynamic model in bubbling regime of fluidization was developed in the presence of long-term catalyst deactivation. This model is used to compare the removal of CO₂ in a FBMDMR with a conventional dual-type methanol synthesis reactor (CDMR) and a membrane dual-type methanol synthesis reactor (MDMR). The simulation results show a considerable enhancement in the CO₂ conversion due to have a favourable profile of temperature and activity along the fluidized-bed membrane dual-type reactor relative to membrane and conventional dual-type reactor systems.     

Optimal oxygen concentration strategy through an isothermal oxidative coupling of methane plug flow reactor to obtain a high yield of C2 hydrocarbons

An optimal oxygen concentration trajectory in an isothermal OCM plug flow reactor for maximizing C₂ production was determined by the algorithm of piecewise linear continuous optimal control by iterative dynamic programming (PLCOCIDP). The best performance of the reactor was obtained at 1,085 K with a yield of 53.9%; while, at its maximum value, it only reached 12.7% in case of having no control on the oxygen concentration along the reactor. Also, the effects of different parameters such as reactor temperature, contact time, and dilution ratio (N₂/CH₄) on the yield of C₂ hydrocarbons and corresponding optimal profile of oxygen concentration were studied. The results showed an improvement of C₂ production at higher contact times or lower dilution ratios. Furthermore, in the process of oxidative coupling of methane, controlling oxygen concentration along the reactor was more important than controlling the reactor temperature. In addition, oxygen feeding strategy had almost no effect on the optimum temperature of the reactor. Finally, using the optimal oxygen strategy along the reactor has more effect on ethylene selectivity compared to ethane.     

基于赤铁矿载氧体的煤化学链燃烧试验

化学链燃烧是一种具有CO₂内分离特性的燃烧方式。以赤铁矿为载氧体,在1 kW_th级串行流化床上进行了煤化学链燃烧试验。讨论了燃料反应器温度对气体产物组分的影响;比较了各反应参数对煤气化效率、煤气化产物的转化效率及碳捕集效率的影响情况,分析了煤中硫的排放问题。试验结果表明：温度由900℃升高到985℃,燃料反应器中CO体积份额逐渐增加,CO₂体积份额逐渐减小,空气反应器中CO₂浓度呈线性下降。燃料反应器温度的升高促进煤气化效率及碳捕集效率大大提高。载氧体量和系统负荷是煤气化产物转化效率的主要影响因素,载氧体量的增加和负荷的增加分别会使煤气化产物转化效率提高和下降。燃料反应器中的硫主要以SO₂形式存在于燃料反应器,随温度的升高,SO₂浓度由515×10^-6逐渐增加到562×10^-6相似文献   

Erratum to “Influence of reactor materials on i-C4 synthesis from CO hydrogenation over ZrO2 based catalysts” [Fuel Process. Technol. 83 (1–3) (2003) 39–48]

The effect of reactor materials on the catalytic performance of the isosynthesis was investigated. Al₂O₃ and several calcium salts promoted zirconium dioxide-based catalysts were prepared by mechanical mixing method and evaluated in the isosynthesis reaction in a quartz-lined stainless-steel tubular reactor and a stainless-steel tubular reactor, respectively. It was found that stainless-steel tubular reactor seriously affected the selectivity of isosynthesis, while quartz-lined stainless-steel tubular reactor was favorable for the formation of i-C₄ hydrocarbons and suppressing the formation of CO₂. The addition of Al₂O₃ into ZrO₂ could largely enhance the activity while maintain the i-C₄ selectivity of pure ZrO₂. CaF₂ or CaSO₄, as an additive promoted the formation of i-C₄, in the meantime maintains the activity of pure ZrO₂. The influence of reaction temperatures on the catalytic performance of the catalysts in the quartz-lined stainless-steel tubular reactor was also investigated.     

Vapour phase oxidation of toluene in V/Al2O3–TiO2 catalytic reactors

The catalytic membrane reactor and the inert packed bed membrane reactor were studied in the vapour phase selective oxidation of toluene. Different feeding policies for the membrane were explored and their influence on the selectivity to the desired products (benzaldehyde and benzoic acid) was investigated. The active phase was prepared by depositing vanadium on a Al₂O₃–TiO₂ support prepared through the sol–gel technique. Higher selectivity to benzaldehyde was obtained using the catalytic membrane reactor. Differences were seen in the catalytic membrane reactor performance only when the active phase was heavily charged along the membrane cross-section.     

Effective combination of non-thermal plasma and catalyst for removal of volatile organic compounds and NOx

A plasma/catalyst hybrid reactor was designed to overcome the limits of plasma and catalyst technologies. A two-plasma/catalyst hybrid system was used to decompose VOCs (toluene) and NOx at temperature lower than 150 °C. The single-stage type (Plasma-driven catalyst process) is the system in which catalysts are installed in a non-thermal plasma reactor. And the two-stage type (Plasma-enhanced process) is the system in which a plasma and a catalyst reactor are connected in series. The catalysts prepared in this experiment were Pt/TiO₂ and Pt/Al₂O₃ of powder type and Pd/ZrO₂, Pt/ZrO₂ and Pt/Al₂O₃ which were catalysts of honeycomb type. When a plasma-driven catalyst reactor with Pt/Al₂O₃ decomposed only toluene, it removed just more 20% than the only plasma reactor but the selectivity of CO₂ was remarkably elevated as compared with only the plasma reactor. In case of decomposing VOCs (toluene) and NOx using plasma-enhanced catalyst reactor with Pt/ZrO₂ or Pt/Al₂O₃, the conversion of toluene to CO₂ was nearly 100% and about 80% of NOx was removed. This work was presented at the 6 ^th Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006.     

Partial oxidation of propane to acrolein in a membrane reactor – Experimental data and computer simulation

Acrolein is synthesized in a tubular membrane reactor with a porous membrane acting as oxygen distributor at 450–550 °C with the catalyst Ag_0.01Bi_0.85V_0.54Mo_0.45O₄ by direct partial oxidation of propane. The reaction in the membrane reactor is compared with the reaction in the classical co-feed reactor. If the oxygen is dosed through the porous reactor wall to the tube side of the reactor, higher acrolein yields and selectivities are obtained. The catalyst is located inside the tube, where the propane streams through. For the simulation – based on a kinetic model – the membrane reactor was partitioned into 14 separate sections through which the oxygen supply takes place. In accordance with the experiment the simulations show that the acrolein selectivities will increase if the oxygen is dosed through the reactor wall acting as membrane oxygen distributor.     

Reduction of nitrogen oxides from simulated exhaust gas by using plasma–catalytic process

Removal of nitrogen oxides (NO_x) using a nonthermal plasma reactor (dielectric-packed bed reactor) combined with monolith V₂O₅/TiO₂ catalyst was investigated. The effect of initial NO_x concentration, feed gas flow rate (space velocity), humidity, and reaction temperature on the removal of NO_x was examined. The plasma reactor used can be energized by either ac or pulse voltage. An attempt was made to utilize the electrical ignition system of an internal combustion engine as a high-voltage pulse generator for the plasma reactor. When the plasma reactor was energized by the electrical ignition system, NO was readily oxidized to NO₂. Performance was as good as with ac energization. Increasing the fraction of NO₂ in NO_x, which is the main role of the plasma reactor, largely enhanced the NO_x removal efficiency. In the plasma–catalytic reactor, the increases in initial NO_x concentration, space velocity (feed gas flow rate) and humidity lowered the NO_x removal efficiency. However, the reaction temperature in the range up to 473 K did not significantly affect the NO_x removal efficiency in the presence of plasma discharge.     

Vapor phase dehydrogenation of methanol to methyl formate in the catalytic membrane reactor with Cu/SiO2/ ceramic composite membrane

The Cu/SiO₂/ceramic composite membrane was prepared on the SiO₂/ceramic mesoporous membrane by an ion exchange method, and vapor phase dehydrogenation of methanol to methyl formate in the catalytic membrane reactor was investigated. It showed much better performance in the catalytic membrane reactor than that in the fixed-bed reactor under the same reaction conditions. At 240 °C, 57.3% conversion of methanol and 50.0% yield of methyl formate were achieved in the catalytic membrane reactor and only 43.1% conversion of methanol and 36.9% yield of methyl formate were achieved in the fixed-bed reactor.     

Development of a multi-layered micro-reactor coated with Pt–Co/Al2O3 catalyst for preferential oxidation of CO

Pt–Co/Al₂O₃ catalysts were prepared with different Co/Pt weight ratios (0.3–1.8) and their performances for preferential oxidation of CO (PROX) were tested. The activity of the catalyst increased with Co/Pt weight ratio due to the increase of the area of active phase by interaction between Pt and Co species. The 13-layered micro-channel reactor was prepared by stacking the plates coated with Pt–Co/Al₂O₃ catalyst. The reactor was divided into three parts (inlet, middle, and outlet) to evaluate the performance of each part. Most of O₂ supplied was depleted at the inlet part and the temperature gradient of the reactor occurred due to the high exothermicity of oxidations of CO and hydrogen. In order to prevent hot spot and temperature gradient, the reactor with non-uniform distribution of the catalyst (partially coating the catalyst on the channels) was prepared. The prepared reactor showed uniform temperature distribution and exhibited excellent performance for PROX.     

Higher Hydrocarbon Production through Oxidative Coupling of Methane Combined with Hydrogenation of Carbon Oxides

In the production of higher hydrocarbons, combining oxidative coupling of methane (OCM) with hydrogenation of the formed carbon oxides in a separate reactor provides an alternative to the currently applied methane conversion to syngas followed by Fischer‐Tropsch synthesis. The effects of CH₄:O₂ feed ratio in the OCM reactor and partial pressures of H₂ or/and H₂O in the hydrogenation reactor were analyzed to maximize production of C₂₊ hydrocarbons and reduce CO_x formation. The highest C₂₊ yield was achieved with low CH₄:O₂ feed ratio for OCM and removal of the formed water before entering the hydrogenation reactor.     

Mixed oxygen ionic-carbonate ionic conductor membrane reactor for coupling CO2 capture with in situ methanation

CO₂ methanation is one of the vital reactions to utilize CO₂ and realize power to gas process. To decrease the CO₂ capture cost and alleviate the hot spots during the strong exothermic methanation reaction, here, we report a coupling of CO₂ capture process with in situ CO₂ methanation process through a ceramic-molten carbonate (MC) dual phase membrane reactor over the Ni-based catalyst. The performance of the membrane reactor was systematically investigated and compared with the traditional fixed-bed reactor. The results show that the performance of the membrane reactor is higher than that of the fixed-bed reactor, since the produced steam through the methanation process can be partially removed through the dual-phase membrane, which promotes the reaction shift to right side. A stability test shows no obvious degradation within 32 h. These results indicate that the membrane reactor is promising for coupling CO₂ capture with in situ methanation process.     

Direct interaction of high-temperature melt with water

The interaction of high-temperature melts formed upon combustion of F₂O₃-Al thermit in a closed volume with water was explored at initial pressures of 101 kPa and 7.5 MPa using a specially designed high-pressure SHS reactor. A maximum force recorded by a force gauge installed on the outer reactor wall was around 750 and 150 N, respectively. Upon direct contact with water, the combustion product was found to undergo dispersion into submicron particles. After completion of combustion, the gas cushion of the reactor was found to contain 70–90% hydrogen gas. The observed system behavior was associated with steam explosions arising in the reactor.