No description available.

Dimethyl ether (DME), as a solution to environmental pollution and diminishing energy supplies, can be synthesized more efficiently, compared to conventional methods, using a catalytic distillation column for methanol dehydration to DME over an active and selective catalyst. In current work, using an autoclave batch reactor, a variety of commercial catalysts are investigated to find a proper catalyst for this reaction at 110-135 C and 900 kPa. Among the -Alumina, Zeolites (HY, HZSM-5 and HM) and ion exchange resins (Amberlyst 15, Amberlyst 35, Amberlyst 36 and Amberlyst 70), Amberlyst 35 and 36 demonstrate good activity for the studied reaction at the desired temperature and pressure. Then, the kinetics of the reaction over Amberlyst 35 is determined. The experimental data are described well by Langmuir-Hinshelwood kinetic expression, for which the surface reaction is the rate determining step. The calculated apparent activation energy for this study is 98 kJ/mol. / Chemical Engineering

As a byproduct of incomplete combustion, soot attracts increasing attentions as extensive researches exploring serious health and environmental effects from soot particles. Soot emission reduction requires a comprehensive understanding of the mechanism for polycyclic aromatic hydrocarbons and of soot formation and aging processes. Therefore, advanced experimental techniques and numerical simulations have been conducted to investigate this procedure. In order to investigate the effects of dimethyl ether (DME) mixing on soot particle size distribution functions (PSDFs), DME was mixed in premixed ethylene/oxygen/argon at flames at the equivalence ratio of 2.0 with a range of mixing ratio from 0% to 30% of the total carbon fed. Two series of atmospheric pressure flames were tested in which cold gas velocity was varied to obtain different flame temperatures. The evolution of PSDFs along the centerline of the flame was determined by burner stabilized stagnation probe and scanning mobility particle sizer (SMPS) techniques, yielding the PSDFs for various separation distances above the burner surface. Meanwhile, the flame temperature profiles were carefully measured by a thermocouple and the comparison to that of simulated laminar premixed burner-stabilized stagnation flame was satisfactory. Additionally, to understand the chemical role of DME mixing in soot properties, characterization measurements were conducted on soot samples using thermo-gravimetric analysis (TGA) and elemental analysis (EA). Results of the evolution of PSDFs and soot volume fraction showed that adding DME into ethylene flame could reduce soot yield significantly. The addition of DME led to the decrease of both the soot nucleation rate and the particle mass growth rate. To explain the possible mechanism for the observation, numerical simulations were performed. Although DME addition resulted in the slight increase of methyl radicals from pyrolysis, the decrease in acetylene and propargyl radicals inhibited the production of polycyclic aromatic hydrocarbons. At the same time, the addition of DME gave rise to the increase of the flame temperatures, which favored the production of OH radicals. The incremental concentration of OH radicals promoted the oxidation rate of soot particles. Additionally, soot samples from flames with higher DME mixing ratios showed higher O/C, H/C mass ratios and thus better oxidation characteristics. In summary, the addition of DME reduces soot emission in two ways: on the one hand, it inhibits soot nucleation and mass/size growth, then the production of soot particles decreases; on the other hand, it promotes soot oxidation process by increasing the concentration of OH radicals and improving the oxidation behavior of the soot particles, then more particles are oxidized. Both of them are responsible for the reduction of soot emissions at the presence of DME.

No description available.

Catalysts are involved in a very large number of processes leading to the production of industrial chemicals, fuels, pharmaceutical, and to the avoidance, as well as the clean-up of environmental pollutants. In respect to the latter aspect, efforts are being made by different stake-holders (governments, researchers, industrials, etc) in order to prevent or to minimize pollution of our cities. A notably way to reduce pollution for a friendly environment is to make use of clean fuels. After years of research work, it is only recently that dimethyl ether alone or when combined with methanol has been identified as a potential alternative clean fuel. Nonetheless, the technology used for the methanol synthesis from syngas requires high pressure (>120 atm) to reach an acceptable CO conversion. The dimethyl ether production from methanol in a separate unit makes DME more expensive than methanol. However, the transformation of syngas directly into dimethyl ether can be used to relieve the thermodynamic constraints requiring operation at high pressure. If the synthesis of methanol and dimethyl ether takes place in the same reactor, the process should, in principle, be able to operate at a much lower pressure, making it a potentially cheaper process to produce methanol and dimethyl ether. The catalysts that need to be used for this coproduction have to be catalytically stable, selective and able to catalyze the main reactions (methanol and dimethyl ether synthesis) involved in this process at the same temperature. Unfortunately, existing commercial methanol/DME catalysts are not able to function efficiently in the presence of large concentrations of water or at high temperature. Thus, it is relevant to have a catalyst satisfying the above criteria. Recently, it has been reported that a supported gold catalyst could be used for methanol synthesis; accordingly this study has developed bifunctional gold-based catalysts for the methanol and DME synthesis. This study utilized process synthesis approach to determine the optimal operating conditions for methanol/dimethyl ether production that yielded results used to drive an experimental programme to get the most useful information for designing a process route. In a comparative way and by using the feed compressor work load per unit of valuable material generated as objective function, this study showed that the system where methanol is co-produced with DME is more efficient than the one involving the production of methanol alone and this is applicable for the operating reactor temperatures of 500-700K and the loop pressure ranging from 10 to 100 atm. The catalysts systems chosen in this study were consisted in the physical mixture of gold-based catalysts incorporating respectively gamma-alumina and zeolite-Y. The gold-based catalysts were prepared by a co-precipitation method, then characterized by XRD, Raman Spectrometry and Transmission Electron Microscopy and, afterwards tested using a 1/4 inch tubular fixed bed reactor between 573 and 673K at 25 atm. Amongst the catalysts tested at 673K, and 25 atm, 5%Au/ZnO/γ-Al2O3 produced both methanol and dimethyl ether with moderate yield, whereas 5%Au/ZnO/LZ Y-52 gave high dimethyl ether selectivity (75.7%) with a production rate of 252.3 μmol.h-1.g -1 cat . The presence of hydrocarbons detected by the GC-FID in the gas products requires that further investigations be done to determine the eventual source and optimize this new catalyst system based on gold for a large scale coproduction of methanol and dimethyl ether from syngas.

O gás de síntese (Syngas), proveniente do biogás gerado no tratamento anaeróbio de águas residuárias e o CO2 (presente no biogás) surgem como fontes promissoras para a obtenção de produtos de valor agregado nomeados C2-C4, tais como eteno, propileno, butano, metanol e dimetil éter (DME). Neste trabalho, catalisadores de Cu suportados em argila pilarizada foram estudados visando à produção de compostos C2-C4 a partir da hidrogenação do CO e CO2. Da mesma forma, buscou-se otimizar estes catalisadores, tanto para o processo de Fischer-Tropsch quanto para a síntese direta do DME. Primeiramente, foi avaliado o efeito dos agentes pilarizantes Al e Nb para a conversão do metanol em produtos C2-C4. Após a seleção do agente pilarizante, avaliou-se o efeito do teor de cobre (5% e 10% em massa) no catalisador bifuncional de CuZn/V-Al PILC. Finalmente, foi realizada a adição de Ce, Nb, Fe e/ou Co (5% em massa) sobre o catalisador contendo 10% de Cu suportado na argila pilarizada V-Al PILC. As reações de conversão do metanol foram realizadas em temperaturas de 250 ºC - 400 ºC/2h, sob o fluxo de 1,1 mL.h-1. As reações de hidrogenação (CO e CO2) foram realizadas nas temperaturas de 250 ºC e 300 ºC/3h, P= 40 bar e razão de H2/CO=2 e H2/CO2=3. Os catalisadores foram caracterizadas por difração de raios X (DRX) in situ e ex situ, refinamento de Rietveld, fisissorção de N2, análise da composição química (EDX), microscopia eletrônica de varredura (MEV), redução a temperatura programada (RTP-H2), oxidação do cobre com N2O (TPD-N2O), adsorção de piridina gasosa como molécula modelo para a identificação dos sítios ácidos através do FTIR (FTIR-Py), dessorção de amônia a temperatura programada (DTP- NH3), espectroscopia de absorção de raios X e espectroscopia de fotoelétrons excitados por raios X (XPS). O processo de pilarização somado à impregnação de Cu juntamente com Zn, Ce, Nb, Fe e/ou Co produziu catalisadores com diferentes propriedades estruturais e ácidas, as quais favoreceram as conversões do CO e CO2 para produtos C2-C4. O catalisador bimetálico CuFe/V-Al PILC foi o mais ativo em ambas reações de hidrogenação (CO e CO2) e o mais seletivo para a síntese de DME. Os estudos de caracterização mostraram que a baixa seletividade apresentada para a formação de DME está relacionada com a baixa densidade total de sítios ácidos e com a elevada velocidade espacial experimental. / Syngas, a gas mixture produced from biogas generated in the anaerobic treatment of wastewaters, and carbon dioxide (CO2), a biogas constituent, are promising feedstocks for obtaining value-added chemicals known as C2-C4 products, which include ethylene, propylene, butane, methanol, and dimethyl ether (DME). In this work, Cu catalysts supported on pillared clay were studied aiming at producing C2-C4 compounds from hydrogenation of CO and CO2. The studies were conducted toward optimizing the catalysts performance both for Fischer-Tropsch process and direct synthesis of DME. First, the effect of Al and Nb pillared agents on the conversion of methanol to C2-C4 products was evaluated. The pillared agent was selected and further used to evaluate the Cu content (5 to 10 wt.%) effect on the bifunctional CuZn/V Al-PILC catalyst. Finally, the addition of Ce, Nb, Fe and/or Co (5 wt.%) to the 10 wt.% Cu-containing catalyst supported on V-Al PILC pillared clay was studied. The methanol conversion was performed in the temperature range 250 - 400 °C for 2 h under flow of 1.1 mL h-1. The CO and CO2 hydrogenation reactions were carried out at 250 °C and 300 °C, respectively, for 3 h and P = 40 bar using ratios H2/CO = 2 and H2/CO2 = 3. The catalysts were characterized by means of in situ and ex situ X-ray diffraction (XRD), Rietveld refinement, N2 physisorption, chemical composition analysis (EDX), scanning electron microscopy (SEM), temperature-programmed reduction (TPR-H2), Cu oxidation with N2O (TPD-N2O) pyridine adsorption-FTIR spectroscopy (FTIR-Py), temperature-programmed NH3 desorption (TPD-NH3), and X-ray photoelectron spectroscopy (XPS). The pillaring process along with impregnation of Cu with Zn, Ce, Nb, Fe and/or Co produced catalysts with different structural and acidity properties, which favored the conversion of CO and CO2 into C2 -C4 products. The bimetallic CuFe/V-Al-PILC catalyst presented the highest catalytic activity on the CO and CO2 hydrogenation reactions, and best selectivity for DME synthesis. The low selectivity for obtaining DME was revealed to be most likely due to low total acid sites density of catalysts and high experimental spatial velocity.

In this research, used dimethyl ether as second fuel blended with diesel (mixed quantity with 10 L/min to 60 L/min, interval 10L/min), which test behavior of diesel engine and carbonyls emission investigated. The engine operated at steady-state condition of 1600 rpm, 145 Nm torque , eight kinds of carbonyls were sampling and analysis, and discuss the performance of the ozone formation potential (OFP). The results of regulated pollutant emissions, CO, THC and PM emission could increasing with the addition of DME, NOX emissions, along with the mixed rate of per minute from 10 L, 20 L, 30 L, 40 L, 50 L and 60 L of its reduction rate was 6.8%¡B8.3%¡B10.0%¡B10.6%¡B13.1% and 15.4%, shows that the DME can reduce NOX emissions. Add a various amount of dimethyl ether , which carbonyl compounds emission from the gas flow 0 L(with neat diesel), 10 L, 20 L, 30 L, 40 L, 50 L and 60 L concentrations were 2507.44 g/m3, 2665.27 g/m3, 2726.67 g/m3, 2958.07 g/m3, 4645.87 g/m3, 5470.20 g/m3 and 7279.91 g/m3; the emission factor of 143.58 mg/bhp-hr, 152.65 mg/bhp-hr, 156.62 mg/bhp-hr, 168.69 mg/bhp-hr, 266.22 mg/bhp-hr, 312.38 mg/bhp-hr and 416.36 mg/bhp-hr, shows the addition of DME will rising the carbonyl compound emissions of diesel engine. Gas of dimethyl ether (10,20,30,40,50 and 60 L/min) into the neat diesel fuel (0 L/min) as a mixture fuel additives, the effect of ozone formation potential as increase in the total ozone formation potential, 21945.93 g-O3/m3, 23698.40 g-O3/m3, 24427.46 g-O3/m3, 26672.98 g-O3/m3, 42683.69 g-O3/m3, 50519.26 g-O3/m3 and 67710.60 g-O3/m3 respectively, and ozone manufacturability will 0 L/min of 8.75 increased to 60 L/min of 9.30.

O gás de síntese (Syngas), proveniente do biogás gerado no tratamento anaeróbio de águas residuárias e o CO2 (presente no biogás) surgem como fontes promissoras para a obtenção de produtos de valor agregado nomeados C2-C4, tais como eteno, propileno, butano, metanol e dimetil éter (DME). Neste trabalho, catalisadores de Cu suportados em argila pilarizada foram estudados visando à produção de compostos C2-C4 a partir da hidrogenação do CO e CO2. Da mesma forma, buscou-se otimizar estes catalisadores, tanto para o processo de Fischer-Tropsch quanto para a síntese direta do DME. Primeiramente, foi avaliado o efeito dos agentes pilarizantes Al e Nb para a conversão do metanol em produtos C2-C4. Após a seleção do agente pilarizante, avaliou-se o efeito do teor de cobre (5% e 10% em massa) no catalisador bifuncional de CuZn/V-Al PILC. Finalmente, foi realizada a adição de Ce, Nb, Fe e/ou Co (5% em massa) sobre o catalisador contendo 10% de Cu suportado na argila pilarizada V-Al PILC. As reações de conversão do metanol foram realizadas em temperaturas de 250 ºC - 400 ºC/2h, sob o fluxo de 1,1 mL.h-1. As reações de hidrogenação (CO e CO2) foram realizadas nas temperaturas de 250 ºC e 300 ºC/3h, P= 40 bar e razão de H2/CO=2 e H2/CO2=3. Os catalisadores foram caracterizadas por difração de raios X (DRX) in situ e ex situ, refinamento de Rietveld, fisissorção de N2, análise da composição química (EDX), microscopia eletrônica de varredura (MEV), redução a temperatura programada (RTP-H2), oxidação do cobre com N2O (TPD-N2O), adsorção de piridina gasosa como molécula modelo para a identificação dos sítios ácidos através do FTIR (FTIR-Py), dessorção de amônia a temperatura programada (DTP- NH3), espectroscopia de absorção de raios X e espectroscopia de fotoelétrons excitados por raios X (XPS). O processo de pilarização somado à impregnação de Cu juntamente com Zn, Ce, Nb, Fe e/ou Co produziu catalisadores com diferentes propriedades estruturais e ácidas, as quais favoreceram as conversões do CO e CO2 para produtos C2-C4. O catalisador bimetálico CuFe/V-Al PILC foi o mais ativo em ambas reações de hidrogenação (CO e CO2) e o mais seletivo para a síntese de DME. Os estudos de caracterização mostraram que a baixa seletividade apresentada para a formação de DME está relacionada com a baixa densidade total de sítios ácidos e com a elevada velocidade espacial experimental. / Syngas, a gas mixture produced from biogas generated in the anaerobic treatment of wastewaters, and carbon dioxide (CO2), a biogas constituent, are promising feedstocks for obtaining value-added chemicals known as C2-C4 products, which include ethylene, propylene, butane, methanol, and dimethyl ether (DME). In this work, Cu catalysts supported on pillared clay were studied aiming at producing C2-C4 compounds from hydrogenation of CO and CO2. The studies were conducted toward optimizing the catalysts performance both for Fischer-Tropsch process and direct synthesis of DME. First, the effect of Al and Nb pillared agents on the conversion of methanol to C2-C4 products was evaluated. The pillared agent was selected and further used to evaluate the Cu content (5 to 10 wt.%) effect on the bifunctional CuZn/V Al-PILC catalyst. Finally, the addition of Ce, Nb, Fe and/or Co (5 wt.%) to the 10 wt.% Cu-containing catalyst supported on V-Al PILC pillared clay was studied. The methanol conversion was performed in the temperature range 250 - 400 °C for 2 h under flow of 1.1 mL h-1. The CO and CO2 hydrogenation reactions were carried out at 250 °C and 300 °C, respectively, for 3 h and P = 40 bar using ratios H2/CO = 2 and H2/CO2 = 3. The catalysts were characterized by means of in situ and ex situ X-ray diffraction (XRD), Rietveld refinement, N2 physisorption, chemical composition analysis (EDX), scanning electron microscopy (SEM), temperature-programmed reduction (TPR-H2), Cu oxidation with N2O (TPD-N2O) pyridine adsorption-FTIR spectroscopy (FTIR-Py), temperature-programmed NH3 desorption (TPD-NH3), and X-ray photoelectron spectroscopy (XPS). The pillaring process along with impregnation of Cu with Zn, Ce, Nb, Fe and/or Co produced catalysts with different structural and acidity properties, which favored the conversion of CO and CO2 into C2 -C4 products. The bimetallic CuFe/V-Al-PILC catalyst presented the highest catalytic activity on the CO and CO2 hydrogenation reactions, and best selectivity for DME synthesis. The low selectivity for obtaining DME was revealed to be most likely due to low total acid sites density of catalysts and high experimental spatial velocity.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22763号 / 工博第4762号 / 新制||工||1745(附属図書館) / 京都大学大学院工学研究科都市環境工学専攻 / (主査)教授 高岡 昌輝, 教授 清水 芳久, 准教授 大下 和徹 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

CO2 activation and conversion mediated by transition metal (TM) catalysts were investigated. Homogeneous catalysis of the reverse water gas shift reaction CO2+H2→H2O+CO was studied as a means to reduce CO2.  β-diketiminato metal models L'MI ( L' =C3N2H5-; M = first-row TMs) were considered as potential catalysts. The thermodynamics of prototypical reaction pathways were simulated using B3LYP/aug-cc-pVTZ. Results show that middle series metal complexes result in more thermodynamically favorable properties; therefore, more detailed thermodynamic and kinetic studies were carried out for Mn, Fe, and Co complexes. On the other hand, heterogeneous catalysis of the reduction of CO2 to CO was carried out on Fe, Co, Ni, and Cu surfaces, using the PBE functional. Reaction barriers were calculated using the climbing image nudged elastic band method. Late 3d and 4d transition metal ion (Fe, Co, Ni, Cu, Ru, Rh, Pd, and Ag) mediated activation of dimethyl ether was studied to investigate the intrinsic catalytic properties of metals for C-O bond cleavage. A set of density functional theory (DFT) methods (BLYP, B3LYP, M06, M06-L, B97-1, B97-D, TPSS, and PBE) with aug-cc-pVTZ basis sets was calibrated with CCSD(T)/CBS calculations on reaction energies and barriers.