共查询到20条相似文献,搜索用时 15 毫秒
1.
In situ infrared spectroscopy has been used to investigate the synthesis of dimethyl carbonate (DMC) from methanol and carbon dioxide over tetragonal (t-ZrO2) and monoclinic zirconia (m-ZrO2. While similar species were observed for both catalyst phases, the dynamics of the elementary processes were different. The dissociative adsorption of methanol to form methoxide species was approximately twice as fast on m-ZrO2 as on t-ZrO2. CO2 insertion to form monomethyl carbonate, an intermediate in the synthesis of DMC, occurred more than order of magnitude more rapidly over m-ZrO. By contrast, the transfer of a methyl group from adsorbed methanol to monomethyl carbonate and the resulting formation of DMC proceeded roughly twice as fast over m-ZrO2. The observed patterns are attributed to the higher Brønsted basicity of hydroxyl groups and cus-Zr4+O2- Lewis acid/base pairs present on the surface of zirconia. 相似文献
2.
Comparison of iron-, nickel-, copper- and manganese-based oxygen carriers for chemical-looping combustion 总被引:1,自引:0,他引:1
For combustion with CO2 capture, chemical-looping combustion (CLC) with inherent separation of CO2 is a promising technology. Two interconnected fluidized beds are used as reactors. In the fuel reactor, a gaseous fuel is oxidized by an oxygen carrier, e.g. metal oxide particles, producing carbon dioxide and water. The reduced oxygen carrier is then transported to the air reactor, where it is oxidized with air back to its original form before it is returned to the fuel reactor. The feasibility of using oxygen carrier based on oxides of iron, nickel, copper and manganese was investigated. Oxygen carrier particles were produced by freeze granulation. They were sintered at 1300 °C for 4 h and sieved to a size range of 125-180 μm. The reactivity of the oxygen carriers was evaluated in a laboratory fluidized bed reactor, simulating a CLC system by exposing the sample to alternating reducing and oxidizing conditions at 950 °C for all carriers except copper, which was tested at 850 °C. Oxygen carriers based on nickel, copper and iron showed high reactivity, enough to be feasible for a suggested CLC system. However, copper oxide particles agglomerated and may not be suitable as an oxygen carrier. Samples of the iron oxide with aluminium oxide showed signs of agglomeration. Nickel oxide showed the highest reduction rate, but displayed limited strength. The reactivity indicates a needed bed mass in the fuel reactor of about 80-330 kg/MWth and a needed recirculation flow of oxygen carrier of 4-8 kg/s, MWth. 相似文献
3.
Nader Mahinpey Koorosh AsghariParissa Mirjafari 《Chemical Engineering Research and Design》2011,89(9):1873-1878
This paper presents the results of experimental investigation and analysis of challenges for utilizing enzyme bovine carbonic anhydrase for sequestration of CO2 in saline formations. Several sets of controlled bench-top experiments were conducted, and results are presented in this paper, where effects of various parameters including pH, concentration of enzyme, and temperature on enhancing hydration and subsequent precipitation of CO2 in the form of calcium carbonate were tested. A mathematical model describing the extent and rate of precipitation was developed upon analyzing the results of these tests. Subsequently, core flood tests were conducted where effect of enzyme on precipitation of CO2 in Berea cores, and its impact on porosity and permeability of the porous media were investigated. These tests indicated that the pressure drop across cores was increased about 2-4 times, which is an indication of precipitation of CO2 in the form of calcium carbonate in porous media. In addition to above tests, effect of timing and scheme of the injection on extent of CO2 precipitation in porous media was tested. It was observed that co-injection of CO2 and enzyme solution leads to higher pressure drop across the cores in tests reported here. Finally, the learning of above tests has been used to outline a series of potential challenges and propose solutions for effective utilization of enzyme bovine carbonic anhydrase for safe sequestration of CO2 in saline formations. 相似文献
4.
Shuangchen Ma Huihui SongMengxuan Wang Jiehong YangBin Zang 《Chemical Engineering Research and Design》2013
As CO2 is the major greenhouse gas, reducing its emission has become an attentive problem in the whole world. It is very important to develop CO2 capture technology for coal-fired power plants. Using ammonia solution to absorb CO2 from the flue gas, which is expected to have advantages of low cost, high efficiency and high absorption load, has become an emerging, hot research area in recent years. However, this technology faces a troublesome problem of ammonia escape. This paper analyzes the mechanism of escaping ammonia; it is also shown the main existing methods to control the escape of ammonia. By comparison, it is concluded that controlling the source of ammonia is feasible. It is also shown that adding some organic additives can inhibit the escape of ammonia and enhance the CO2 removal to some extent at the same time. 相似文献
5.
This study was carried out to investigate the removability of polycyclic aromatic hydrocarbon (PAH) compounds existed in automotive industry treatment sludge. The impacts of temperature, UV, titanium dioxide (TiO2), and diethyl amine (DEA) were studied in a controlled device which was specifically designed for this study. Sludge samples were collected from the treatment plant of an automotive manufacturing facility in Bursa, Turkey. The ∑10 PAH concentration value in the sludge was 4480 ± 1450 ng/g dry matter (DM). ∑10 PAH removal ratio was 30% at 37°C without UV irradiation. Moreover, the PAH content in the sludge was reduced up to 65% through applying UV irradiation. This figure reached 100% by using photo-catalysts (TiO2 or DEA) at the rate of 20% of the DM of the sludge. 相似文献
6.
A thermodynamic efficiency analysis using the exergy concept is used to assess CO2 mineral sequestration process routes where electrochemical steps (electrolysis and fuel cells) are used to produce aqueous hydrochloric acid and sodium hydroxide reactant solutions. Results from three recent publications on the subject that come to different conclusions are used for this case study. It is shown that including electrolysis as one of the steps of a magnesium silicate mineral carbonation process route results in input energy requirements that will exceed the output of a fossil fuel-fired power plant that produces the CO2 that is bound to (hydro-) carbonates. At the same time, fuel cells are not efficient enough to change this. 相似文献
7.
The manufacture of heterogeneous catalysts and catalyst supports produces substantial amounts of nitrate containing aqueous effluent. The use of nitrate free precursors and an environmentally friendly process would change the manufacture so that the entire process of catalyst synthesis and use can be considered green. In this work the precipitation of titania acetylacetonate nanoparticles for use as catalytic supports using a supercritical carbon dioxide anti-solvent process was investigated over a range of conditions. The effects of 1) pressure, 2) temperature, 3) solution flowrate, 4) solution concentration of TiO(acac)2 in methanol, 5) nozzle diameter and 6) CO2/methanol flow ratio on the mean particle size and morphology were studied. Particle sizes between 27 and 78 nm were obtained and were generally string and branch-like with an amorphous nature. Pressure and temperature had little effect on the mean particle size. A decrease in the velocity of the solution flow rate led to an increase in mean particle size and to particles that exhibited greater interconnectivity. It was also observed that an increase in concentration of TiO(acac)2 in methanol led to an increase in mean particle size. The process shows promise for the production of catalysts by an environmentally acceptable route. 相似文献
8.
Ashleigh Cousins Leigh T. WardhaughPaul H.M. Feron 《Chemical Engineering Research and Design》2011,89(8):1237-1251
The energy penalty associated with solvent based capture of CO2 from power station flue gases can be reduced by incorporating process flow sheet modifications into the standard process. A review of modifications suggested in the open and patent literature identified several options, primarily intended for use in the gas processing industry. It was not immediately clear whether these options would have the same benefits when applied to CO2 capture from near atmospheric pressure combustion flue gases. Process flow sheet modifications, including split flow, rich split, vapour recompression, and inter-stage cooling, were therefore modelled using a commercial rate-based simulation package. The models were completed for a Queensland (Australia) based pilot plant running on 30% MEA as the solvent. The preliminary modelling results showed considerable benefits in reducing the energy penalty of capturing CO2 from combustion flue gases. Further work will focus on optimising and validating the most relevant process flow sheet modifications in a pilot plant. 相似文献
9.
Processes based upon solid sorbents are currently under consideration for post-combustion CO2 capture. Twenty-four different sorbent materials were examined on a laboratory scale in a cyclic temperature swing adsorption/regeneration CO2 capture process in simulated coal combustion flue gas. Ten of these materials exhibited significantly lower theoretical regeneration energies compared to the benchmark aqueous monoethanolamine, supporting the hypothesis that CO2 capture processes based upon solids may provide cost benefits over solvent-based processes. The best performing materials were tested on actual coal-fired flue gas. The supported amines exhibited the highest working CO2 capacities, although they can become poisoned by the presence of SO2. The carbon-based materials showed excellent stability but were generally categorized as having low CO2 capacities. The zeolites worked well under dry conditions, but were quickly poisoned by the presence of moisture. Although no one type of material is without concerns, several of the materials tested have theoretical regeneration energies significantly lower than that of the industry benchmark, warranting further development research. 相似文献
10.
This study investigates the adsorption performance of a number of absorbents prepared by incipient wetness impregnation of 3.85 wt% Fe, Co, Ni, Mn, Co and Ce oxides on HZSM-5 for the removal of trace NO (150–200 ppm) from a CO2 stream to produce food-grade CO2. The adsorbents were characterized using X-ray diffraction, X-ray fluorescence, and N2 adsorption with their performances evaluated in a fixed-bed flow system. The investigations revealed NO removal of better than 0.1 ppm from the CO2 stream. The breakthrough capacities of the adsorbents for NO removal in the presence of O2 were found to significantly increase. The converse was observed in the case of NO adsorption selectivity. Co/HZSM-5(25) was found to be the best adsorbent under all the conditions tested producing CO2 purities of better than 99.9999%. This is significantly higher than for Fe–Mn mixed oxides, claimed to be the best NO adsorbent reported in the literature for CO2 purification. 相似文献
11.
Coal combustion with O2/CO2 is promising because of its easy CO2 recovery, extremely low NOx emission and high desulfurization efficiency. Based on our own fundamental experimental data combined with a sophisticated data analysis, its characteristics were investigated. It was revealed that the conversion ratio from fuel-N to exhausted NO in O2/CO2 pulverized coal combustion was only about one fourth of conventional pulverized coal combustion. To decrease exhausted NO further and realize simultaneous easy CO2 recovery and drastic reduction of SOx and NOx, a new scheme, i.e. O2/CO2 coal combustion with heat recirculation, was proposed. It was clarified that in O2/CO2 coal combustion, with about 40% of heat recirculation, the same coal combustion intensity as that of coal combustion in air could be realized even at an O2 concentration of as low as 15%. Thus exhausted NO could be decreased further into only one seventh of conventional coal combustion. Simultaneous easy CO2 recovery and drastic reduction of SOx and NOx could be realized with this new scheme. 相似文献
12.
In an Endex reactor endothermic and exothermic reactions are directly thermally coupled and kinetically matched to achieve intrinsic thermal stability, efficient conversion, autothermal operation, and minimal heat losses. Applied to the problem of in-line carbon dioxide separation from flue gas, Endex principles hold out the promise of effecting a CO2-capture technology of unprecedented economic viability. In this work we describe an Endex Calcium Looping reactor, in which heat released by chemisorption of carbon dioxide onto calcium oxide is used directly to drive the reverse reaction, yielding a pure stream of CO2 for compression and geosequestration. In this initial study we model the proposed reactor as a continuous-flow dynamical system in the well-stirred limit, compute the steady states and analyse their stability properties over the operating parameter space, flag potential design and operational challenges, and suggest an optimum regime for effective operation. 相似文献
13.
Alireza Emadi Mehran SohrabiMahmoud Jamiolahmady Shaun IrelandGraeme Robertson 《Chemical Engineering Research and Design》2011,89(9):1783-1793
The world's dependence on heavy oil production is on the rise as the existing conventional oil reservoirs mature and their production decline. Compared to conventional oil, heavy oil is much more viscous and hence its production is much more difficult. Various thermal methods and particularly steam injection are applied in the field to heat up the oil and to help with its flow and production. However, the thermal recovery methods are very energy intensive with significant negative environmental impact including the production of large quantities of CO2. Alternative non-thermal recovery methods are therefore needed to allow heavy oil production by more environmentally acceptable methods. Injection of CO2 in heavy oil reservoirs increases oil recovery while eliminating negative impacts of thermal methods.In this paper we present the results of a series of micromodel and coreflood experiments carried out to investigate the performance of CO2 injection in an extra-heavy crude oil as a method for enhancing heavy oil recovery and at the same time storing CO2. We reveal the pore-scale interactions of CO2-heavy oil-water and quantify the volume of CO2 which can be stored in these reservoirs.The results demonstrate that CO2 injection can provide an effective and environmentally friendly alternative method for heavy oil recovery. CO2 injection can be used independently or in conjunction with thermal recovery methods to reduce their carbon footprint by injecting the CO2 generated during steam generation in the reservoirs rather than releasing it in the atmosphere. 相似文献
14.
James W. Butler C. Jim LimJohn R. Grace 《Chemical Engineering Research and Design》2011,89(9):1794-1804
One promising method for the capture of CO2 from point sources is through the usage of a lime-based sorbent. Lime (CaO) acts as a CO2 carrier, absorbing CO2 from the flue gas (carbonation) and releasing it in a separate reactor (calcination) to create a pure stream of CO2 suitable for sequestration. One of the challenges with this process is the decay in calcium utilization (CO2 capture capacity) during carbonation/calcination cycling. The reduction in calcium utilization of natural limestone over large numbers of cycles (>250) was studied. Cycling was accomplished using pressure swing CO2 adsorption in a pressurized thermogravimetric reactor (PTGA). The effect of carbonation pressure on calcium utilization was studied in CO2 with the reactor operated at 1000 °C. The pressure was cycled between atmospheric pressure for calcination, and 6, 11 or 21 bar for carbonation. Over the first 250 cycles, the calcium utilization reached a near-asymptotic value of 12.5-27.7%, depending on the cycling conditions. Pressure cycling resulted in improved long-term calcium utilization compared to temperature swing or CO2 partial pressure swing adsorption under similar conditions. An increased rate of de-pressurization caused an increase in calcium utilization, attributed to fracturing of the sorbent particle during the rapid calcination, as observed via SEM analysis. 相似文献
15.
CaO–ZrO2 prepared by co-precipitation showed to be a well-performed catalyst for the transesterification of propylene carbonate (PC)
and methanol. The characterization by X-ray powered diffraction (XRD) and Raman spectroscopy indicated that CaO was doped
into the lattice of ZrO2 to form CaO–ZrO2 solid solution. Such a solid solution was a strong solid base, which was proved by CO2 temperature program desorption (CO2-TPD). As a result, the catalyst showed high stability towards the transesterification of propylene carbonate and methanol
into dimethyl carbonate with high PC conversion, especially being subjected to the continuous production of dimethyl carbonate
at reactive distillation reactor for 250 h without any obvious loss of activity at the PC conversion of 95%. 相似文献
16.
Cristina Gutiérrez Juan Francisco Rodríguez Ignacio Gracia Antonio de Lucas 《Polymer-Plastics Technology and Engineering》2016,55(4):335-342
The recycling of polystyrene wastes by precipitation from limonene solutions using CO2 as antisolvent is an alternative and original environmentally friendly route to recover high quality wastes. The most suitable working conditions to conduct the process are selected based on the accurate knowledge of the phase equilibrium for the ternary mixture. To maximize the recycling of polymeric wastes while the consumption of CO2 and limonene is minimized, high values of pressure (≥100 bar), low values of temperature (≤30°C) and moderated concentrations of polymer (≤0.4 g PS/ml limonene) are required. 相似文献
17.
《分离科学与技术》2012,47(6):850-866
Methanol is an important raw material in industry and is commonly produced from syngas. The stoichiometric ratio (H2–CO2)/(CO + CO2) of the methanol synthesis reactor feed stream must be adjusted to approximately 2.1. In this study, the replacement of the solvent unit within a coal to methanol process by a pressure swing adsorption (PSA) unit is proposed. The PSA produces a hydrogen enriched stream, to adjust the stoichiometric ratio of the methanol feed stream, and simultaneously captures the carbon dioxide for future sequestration. The feed flow rate is sub divided into eight 4-bed PSA units, operated with a defined phase lag between them in order to flatten the products (composition and flow rate) oscillations. The results show that the stoichiometric adjustment is possible and that oscillations on the products flow rate and composition are reduced to less than 3%. A carbon dioxide stream of 95.15% is obtained with a recovery of 94.2% and a productivity of 82.7 mol CO2/kg/day. The power consumption of the global process is 119.7 MW, which includes the requirements for the rinse stream (64.4 MW) and the compression of the CO2 product to 110 bar for sequestration (55.3 MW). 相似文献
18.
A novel method of direct synthesis of dimethyl carbonate from methanol and carbon dioxide catalyzed by zirconia 总被引:5,自引:0,他引:5
Keiichi Tomishige Tomohiro Sakaihori Yoshiki Ikeda Kaoru Fujimoto 《Catalysis Letters》1999,58(4):225-229
Dimethyl carbonate was synthesized from methanol and CO2 with high selectivity using ZrO2 catalysts. In this reaction, the amount of dimethyl ether and CO was below the detection limit. The catalytic activity seems
to be related to acid–base pair sites of the ZrO2 surface from the results of temperature‐programmed desorption of NH3 and CO2.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
19.
Hyun Jin Ryu Kyeong Keun Oh Young Soo Kim 《Journal of Industrial and Engineering Chemistry》2009,15(4):471-475
Microalgae fix CO2 as energy source and afford biomass and high valued products such as carotenoids, pigments, proteins, and vitamins that can be used for the production of nutraceuticals, pharmaceuticals, animal feed additives, cosmetics, etc. Carbon dioxide is the sole source of carbon and it is supplied continuously for the microalgal cultivation. But undissolved CO2 is lost by outgassing and sufficient dissolved CO2 should be provided to avoid carbon limitation. The effect of CO2 mass transfer with different CO2 concentrations, aeration rate of gas, bubble size, baffle type and baffle number on the growth of Chlorella sp. AG10002 was investigated and the optimized conditions for the enhancement of biomass productivity were determined. We confirm that these results can be provided as basic data to improve the CO2 mass transfer ability for the high density culture of Chlorella sp. and some microalgae having commercial value. 相似文献
20.
Daria Surovtseva 《Chemical Engineering Research and Design》2011,89(9):1752-1757
This project is a trial conducted under contract with CO2CRC, Australia of a new CO2 capture technology that can be applied to integrated gasification combined cycle power plants and other industrial gasification facilities. The technology is based on combination of two low temperature processes, namely cryogenic condensation and the formation of hydrates, to remove CO2 from the gas stream. The first stage of this technology is condensation at −55 °C where CO2 concentration is expected to be reduced by up to 75 mol%. Remaining CO2 is captured in the form of solid hydrate at about 1 °C reducing CO2 concentration down to 7 mol% using hydrate promoters. This integrated cryogenic condensation and CO2 hydrate capture technology hold promise for greater reduction of CO2 emissions at lower cost and energy demand. Overall, the process produced gas with a hydrogen content better than 90 mol%. The concentrated CO2 stream was produced with 95-97 mol% purity in liquid form at high pressure and is available for re-use or sequestration. The enhancement of carbon dioxide hydrate formation and separation in the presence of new hydrate promoter is also discussed. A laboratory scale flow system for the continuous production of condensed CO2 and carbon dioxide hydrates is also described and operational details are identified. 相似文献