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1.
CuZn-based catalysts are active in production of hydrogen by methanol steam reforming. However, there is a need to have further insight on their physico-chemical properties to improve selectivity to hydrogen. Therefore, a series of CuZn/MCM-41 catalysts was synthesized by four different routes; one pot hydrothermal synthesis (OPMCM), co-impregnation (COMCM), serial impregnation (SRMCM) and copper impregnated on Zn-MCM-41 (ZNMCM). Samples of catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), inductively coupled plasma (ICP) emission spectrometry, Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). XRD revealed disruption in the ordered pore network typical in MCM-41 for all catalysts synthesized and also showed that the one pot synthesis catalyst had wide spread dispersion of Cu and Zn. SEM micrographs captured irregularly shaped particles of different sizes. While XPS showed that different Cu and Zn species were formed within the catalyst matrix. XPS also confirmed that there was wide spread dispersion and interaction of Cu and Zn with MCM-41 matrix in the OPMCM catalyst. COMCM and OPMCM demonstrated the highest activity with 88 and 65% methanol conversion with corresponding H2 selectivity of 91 and 86% respectively. They are better than SRMCM and ZNMCM which had average H2 selectivity of 19% and 31% respectively. CO selectivity was less than 1.8% for the COMCM and OPMCM catalysts. While SRMCM and ZNMCM had CO selectivity's as high as 8.9% and 7.2% respectively. The data generated shows that catalytic activity is largely affected by the nature of Cu species within the catalyst matrix.  相似文献   

2.
A novel catalyst, Nickel supported over MCM-41 coated ceramic membrane (NMC), was developed using coating method and deposition-precipitation method and applied for steam reforming of real tar in fixed bed. The effects of reaction conditions such as Ni loading amount, reaction temperature and mass ratio of steam to tar were also studied. The good dispersion of Ni nanoparticles and the strong interaction between Ni particles and the support were identified by BET, XRD, H2-TPR and SEM/EDS, resulting in the excellent performance of NMC catalysts. Maximum tar conversion of 96.4% and H2 yield of 98.7 mmol g?1 were obtained using 20NMC with a mass ratio of steam to coal tar of 2 at 800 °C. Moreover, 20 NMC exhibited a good stability in 10 h of lifetime test and the resistance of graphitic carbon formation prone to easier regeneration of catalysts illustrated by Raman spectroscopy. It indicates that the utilization of NMC catalysts for tar steam reforming is a promising way.  相似文献   

3.
In this study, sorption-enhanced ethanol steam reforming (SEESR) is investigated using a Ce-Ni/MCM-41 as a catalyst in the presence of Na or/and Zr promoted CaO-based adsorbents. Ce-Ni/MCM-41 and promoted sorbents were synthesized by wet impregnation method. The catalyst was characterized by XRD, FTIR, TGA, EFSEM, TEM, H2-TPR and N2 adsorption/desorption and promoted sorbents were studied by XRD, EFSEM, BET, TEM and TGA analysis. Sorption experiments were performed to verify sorbent activity for CO2 removing. The results indicated that with doping different promoter on CaO sorbent and also with increasing Na loading, there was an increase in BET surface area, the reduction in particle size and thereupon an enhancement in CO2 sorption capacity. Higher BET surface area, smaller particle size, and superior CO2 sorption capacity were obtained on Na-Zr-CaO sorbent. Sorption-enhanced steam reforming process of ethanol on synthesized catalyst and sorbents were performed at 600 °C and water to ethanol molar ratio of 6. The effect of sorbent to catalyst ratio and the arrangement of sorbent and catalyst (like two separated layers and the mixture of sorbent and catalyst in a single layer) were also studied. The best results were demonstrated on Na-Zr-CaO sorbent and with the separated array. Hydrogen production via a SEESR process with Na-Zr-CaO as sorbent was ∼94% that is 24% more than that of conventional ethanol steam reforming (ESR) reaction.  相似文献   

4.
The entire experiments were conducted for microchannel methanol steam reforming, by which, the selection of catalyst, the operating parameters and the configuration of microchannels were discussed thoroughly. It was found that the higher the Cu concentration is, the more the corresponding active surface area of Cu will be, thereby improving the catalytic activity. The Cu-to-Zn ratio in Cu/ZnO/Al2O3 catalyst should be set at 1:1. The impacts of reaction temperature, feed flow rate, mixture temperature, and H2O-to-CH3OH molar ratio on the methanol conversion rate were also revealed and discussed. Characteristics of micro-reactors with various microchannels, including that 20 mm and 50 mm in length, as well as non-parallel microchannels, were investigated. It was found that the increase of microchannel length can improve the methanol conversion rate significantly. Besides, non-parallel microchannels help to maintain flow and temperature distribution uniformity, which can improve the performance of micro-reactor. In the present experiments, the presence of CO was under the condition that the methanol conversion rate was above 70%.  相似文献   

5.
Heterogeneous catalytic fixed bed usually suffers from severe limitations of mass and heat transfer. These disadvantages limit reformers to a low efficiency of catalyst utilization. Three catalyst activity distributions have been applied to force the reactor temperature profile to be near isothermal operation for maximization of methanol conversion. A plate-type reactor has been developed to investigate the influence of catalyst activity distribution on methanol steam reforming. Cold spot temperature gradients are observed in the temperature profile along the reactor axis. It has been experimentally verified that reducing cold spot temperature gradients contributes to the improvement of the catalytic hydrogen production. The lowest cold spot temperature gradient of 3 K is obtained on gradient catalyst distribution type A. This is attributed to good characteristics of local thermal effect. Low activity at the reactor inlet with gradual rise along with the reactor flow channel forms the optimal activity distribution. Hydrogen production rate of 161.3 L/h is obtained at the methanol conversion of 93.1% for the gradient distribution type A when the inlet temperature is 543 K.  相似文献   

6.
Nano-rod(R), nano-particle(P) and sponginess(S) of ceria samples were used to study catalytic performance of hydrogen production by methanol steam reforming. The samples were prepared by hydrothermal method, precipitation method, and sol-gel method, respectively, and the CuO was supported on the different morpholopy of CeO2 samples by wet impregnation. SEM, TEM, XRD, XRF, BET, H2-TPR, XPS and N2O titration methods were used to study correlation between the structure and the catalytic performance for methanol steam reforming. The results showed that the morphology of the prepared CeO2 support dramatically influenced the performance of catalysts. Due to the stronger interaction between copper oxide and ceria support, the CuO/CeO2-R catalyst had exhibited the better catalytic activity than those of the CuO/CeO2P and CuO/CeO2S catalysts. Moreover, higher Cu dispersion, lower reduction temperature of CuO, and higher content of active species Cu+ were also advantageous to raising catalytic effects. Besides, with the highest content of surface Ce3+, the CuO/CeO2-R had estimated the content of oxygen vacancy on the surface of the catalyst. The existence of surface oxygen vacancy had a positive effect on the methanol steam reforming.  相似文献   

7.
A kind of oriented linear cutting fiber sintered felt as an innovative catalyst support for methanol steam reforming was proposed. Multiple long copper fibers fabricated by cutting method were arranged in parallel and then sintered together in a mold pressing equipment under the condition of high temperature and protective gas atmosphere. The characteristics of oriented linear cutting fiber sintered felt coated with Cu/Zn/Al/Zr catalyst for methanol steam reforming were experimental investigated under different GHSVs and reaction temperatures. Results indicated that the structure of sintered felt was the key influencing factor for the reaction performances on the condition of low GHSV or reaction temperature whereas the structure of sintered felt showed little influences with high GHSV or reaction temperature. By the analysis of SEM image and ultrasonic vibration testing method, it was found that the coarse surface pattern of cutting fiber could effectively enhance the adhesion intensity between the catalyst and the copper fibers, as well as present relatively large specific surface area in the microchannels. And hence the oriented linear cutting fiber sintered felt present better performances of methanol steam reforming than the oriented linear copper wire sintered felt on the condition of low GHSV or reaction temperature.  相似文献   

8.
The distributed power generation of methanol steam reforming reactor combined with solid oxide fuel cell (SOFC) has the characteristics of outstanding economic advantages. In this paper, a methanol steam reforming reactor was designed which integrates catalyst combustion, vaporization and reforming. By catalyst combustion, it can achieve stable operation to supply fuel for kW-class SOFC in real time without additional heating equipment. The optimal operating condition of the reforming reactor is 523–553 K, and the steam to carbon ratio (S/C) is 1.2. To study the reforming performance, methanol steam reforming (MSR), methanol decomposition (MD), water-gas shift (WGS) were considered. Operating temperature is the greatest factor affecting reforming performance. The higher the reaction temperature, the lower the H2 and CO2, the higher the CO and the methanol conversion rate. The methanol conversion rate is up to 95.03%. The higher the liquid space velocity (LHSV), the lower the methanol conversion rate, the lowest is 90.7%. The temperature changes of the reforming reactor caused by the load change of stack takes about 30 min to reach new balance. Local hotspots within the reforming reactor lead to an excessive local temperature to test a small amount of CH4 in the reforming gas. The methanation reaction cannot be ignored at the operating temperature. The reforming gas contains 70–75% H2, 3–8% CO, 18–22% CO2 and 0.0004–0.3% CH4. Trace amounts of C2H6 and C2H4 are also found in some experiments. The reforming reactor can stably supply the fuel for up to 1125 W SOFC.  相似文献   

9.
A micro-reactor with eight non-parallel channels is proposed to improve the performance of micro-channel steam reforming of methanol. The widths of some channels in the micro-reactor vary gradually along the reactor length direction. The Zn-Cr/CeO2-ZrO2 catalyst is coated in the reformer with a certain porosity and permeability. The effects of micro-reactor structures and catalyst-coated manners on several factors are studied, including temperature distributions, velocity distributions, reactant concentrations and the methanol conversion rate. The results indicate that such a structure with a certain entrance inclination angle and channel inclination angle guarantees flow distribution uniformity in each reforming channel. Flow distribution uniformity is conducive to the increase of the methanol conversion rate. Besides, in order to measure strengths and weaknesses of different catalyst-coated manners, a wall-coated reformer and a packed-bed reformer are studied respectively. It is found that compared to the packed-bed reformer, the temperature and the methanol conversion rate in wall-coated reformer are far higher. It is necessary to find an optimal catalyst thickness that is able to reduce the CO concentration because the catalyst thickness can affect CO concentration in the product gases indirectly. The optimal inclination angles and the catalyst thickness are proposed based on the simulating results.  相似文献   

10.
The steam reforming of methanol was investigated in a catalytic Pd–Ag membrane reactor at different operating conditions on a commercial Cu/ZnO/Al2O3 catalyst. A comprehensive two-dimensional non-isothermal stationary mathematical model has been developed. The present model takes into account the main chemical reactions, heat and mass transfer phenomena in the membrane reactor with hydrogen permeation across the PdAg membrane in radial direction. Model validation revealed that the predicted results satisfy the experimental data reasonably well under the different operating conditions. Also the impact of different operating parameters including temperature, pressure, sweep ratio and steam ratio on the performance of reactor has been examined in terms of methanol conversion and hydrogen recovery. The modeling results have indicated the high performance of the membrane reactor which is related to continuous removal of hydrogen from retentate side through the membrane to shift the reaction equilibrium towards formation of hydrogen. The obtained results have confirmed that increasing the temperature improves the kinetic properties of the catalyst and increase in the membrane's H2 permeance, which results in higher methanol conversion and hydrogen production. Also it is inferred that the hydrogen recovery is favored at higher temperature, pressure, sweep ratio and steam ratio. The model prediction revealed that at 573 K, 2 bar and sweep ratio of 1, the maximum hydrogen recovery improves from 64% to 100% with increasing the steam ratio from 1 to 4.  相似文献   

11.
CuO/ZnO/CeO2/ZrO2 nanoflowers catalyst was grown on an Al2O3 foam ceramic by a one-step hydrothermal process, while a naked Al2O3 foam ceramic and an Al2O3 foam ceramic grown with ZnO nanorods that directly impregnated into the catalyst precursor solution were also fabricated simultaneously. The morphology, composition, redox property and specific surface area of catalysts on the three ceramics were investigated in detail. The catalyst-loaded ceramics were used as catalyst supports in a microreactor to study the catalytic performance for methanol steam reforming. Results showed that the microreactor with Al2O3 support grown with nanoflowers catalyst achieved 99.8% methanol conversion rate, 0.16 mol/h H2 flow rate at 310 °C, and an inlet methanol flow rate of 0.048 mol/h. Moreover, the microreactor exhibited 92% methanol conversion rate after 30 h continuous reaction.  相似文献   

12.
The effects of distinct and simultaneous calcination and reduction (DCR & SCR) processes were determined over 10Ni/SiO2 catalyst. The results showed that the C3H8 conversion and H2 yield increased from 69% to 51% for DCR to 91% and 64% for SCR catalyst. Calcination before reduction seemed to be resulting in the construction of larger Ni particles and it may be due to partial phyllosilicates decomposition. According to the initial tests, to elevate the C3H8 conversion and H2 yield, the effects of promoters such as La, Ce, K, and Sr were examined on the catalyst performance. Activity test illustrated that K and Sr declined the propane conversion and H2 yield, however, Ce and La increased them. Synthesized catalysts were characterized using XRD, BET, H2-TPR, SEM, and TGA/DTA to determine the structural properties. Consistent with BET and XRD analysis, K and Sr had the low surface area and large Ni crystallite size, contributing to coke deposition on the catalyst surface. Among the promoted samples, La-containing catalyst showed good activity and then, in the rest of this work, 10Ni-yLa/SiO2 (y = 2, 5, 8 wt%) catalysts were examined. The results showed that 10Ni2La/SiO2 catalyst improved the particle dispersion and decreased the particle size so that specific surface area and porous volume were maximized and minimized, respectively. 10Ni2La/SiO2 catalyst at GHSV of 45000 (ml/h.gcat), the temperature of 640C, and S/C = 3 in 420 min time-on-stream showed the best performance, that is C3H8 conversion of 95% and H2 yield of 69% in propane steam reforming (PSR).  相似文献   

13.
A kind of composite material PdZnAl(HT)/MCM-48 was synthesized by dispersing PdZnAl-type hydrotalcite (denoted as PdZnAl(HT)) on mesoporous silica MCM-48. PdZnAl(HT) was confirmed to be formed on the MCM-48 in small particles, and the small PdZnAl(HT) particles easily collapsed during increasing the temperature. A kind of novel PdZn(Al)O/MCM-48 catalyst was obtained after calcining and reducing the PdZnAl(HT)/MCM-48 precursor. PdZn alloy species were formed on the PdZnAl(HT)/MCM-48 after reducing in H2 at 673 K. PdZn(Al)O/MCM-48-2 (with a mass ratio of PdZn(Al)O to MCM-48 = 1) had a large BET surface area (431 cm2 g?1) and small size of PdZn particles (4.1 nm) at the same time. In the steam reforming of methanol, the catalytic stability of PdZn(Al)O/MCM-48-2 was much higher than that of the Cu-based catalyst CuZn(Al)O at 503 K. The methanol conversion over PdZn(Al)O/MCM-48-2 greatly increased with increasing reaction temperature and reached 99% at 513 K. PdZn(Al)O/MCM-48-2 showed higher catalytic activity than PdZnAl(HT) and PdZn/MCM-48 (imp) at the same reaction temperature. The initial CO2 selectivity and H2 selectivity over PdZn(Al)O/MCM-48-2 at 503 K were 99.6 and 99.4%, respectively. Moreover, PdZn(Al)O/MCM-48-2 showed the highest rate of H2 production among various catalysts in the steam reforming of methanol. In a long-time operation, the methanol conversion over PdZn(Al)O/MCM-48-2 decreased from 75.8 to 68.5% after 50 h on stream at 503 K. The size of PdZn particles did not increase after 50 h on stream but the carbonaceous deposits on the catalyst surface caused the deactivation. The deactivated catalyst could be regenerated by calcining in the air at 723 K followed by reducing in the H2 at 673 K. The carbonaceous deposits were eliminated by calcining in the air and the PdZn active species were formed again by reducing in H2.  相似文献   

14.
Oxidative steam reforming of methanol over monometallic gold (Au) and bimetallic Au-copper (Cu) supported on ceria-zirconia (CeO2ZrO2) was examined over the temperature range of 200–400 °C in a fixed-bed reactor. The composition of CeO2ZrO2 supports was also studied for their catalytic activity. The Au/Ce0.75Zr0.25O2 catalyst exhibited the highest methanol (CH3OH) conversion level (96.7%) and hydrogen (H2) yield (59.7%) due to the formation of a homogeneous Ce1-xZrxO2 solid solution. When Cu was introduced in the Au catalysts, all of the bimetallic catalysts presented a better stability for CH3OH conversion as well as H2 yield in comparison to the monometallic catalysts, which was due to the partial electron transfer from Cu to Au metals. The performance of the AuCu/Ce0.75Zr0.25O2 catalysts, which was evaluated under identical conditions, was ranked in the order: 3Au1Cu > 1Au3Cu > 1Au1Cu.  相似文献   

15.
Steam reforming of methanol is investigated numerically considering both heat and mass transfer of the species in a packed bed microreactor. The numerical results are shown to be in good agreement with experimental data [M.T. Lee, R. Greif, C.P. Grigoropoulos, H.G. Park, F.K. Hsu, J. Power Sources Transport in, 166 (2007) 194–201] with a BASF F3-01(CuO/ZnO/Al2O3) catalyst. A correlation for the conversion efficiency of methanol has been obtained as a function of the operating temperature and a dimensionless time parameter which represents the ratio of the characteristic time of the methanol flow to the time for chemical reaction. The results show that for the constant wall temperature condition the steam reforming process of methanol results in a nearly uniform temperature throughout the microreactor over the range of operating conditions.  相似文献   

16.
In this study, cerium promoted copper-based catalysts were synthesized via conventional and surfactant-assisted impregnation methods using KIT-6 as a new support material. The catalytic activity of the prepared catalysts was investigated in the methanol steam reforming (MSR). The characterization results revealed the incorporation of cerium oxide and employing the surfactant-assisted impregnation method effectively controlled the size of copper particles and also improved the uniform distribution of the metal species. Among all catalysts, the CeCu/KIT-6 catalyst which was prepared using the surfactant-assisted impregnation method exhibited the best catalytic performance of about 92% methanol conversion, 99% H2 selectivity and only 0.9% CO selectivity at 300 °C. The CeCu/KIT-6 samples showed no significant change in catalytic activity after 24 h, demonstrating that the use of 3D-mesoporous KIT-6 support significantly improved the stability of metal-based catalysts.  相似文献   

17.
Methanol steam reforming (MSR) is deemed to be an effective way for hydrogen production and Pd/ZnO catalyst were found to exhibit high activity in this reaction. However, their activities are strongly related to the preparations methods. In most cases, these catalysts are synthesized by impregnation or co-precipitation methods, aiming to change the dispersion and stability of Pd nanoparticle to get better performance. Here we report an efficient Pd/ZnO catalyst that was synthesized with zeolitic imidazolate framework-8 (ZIF-8) as the precursor, on which Pd ions was supported after NaHB4 reduction. Typically, when the catalyst reduced at 300 °C for 2 h, the methanol conversion could reach 97–98% and the CO2 selectivity is around 86.3% under the reaction condition of 0.1 MPa, water/CH3OH = 1.2:1 (mol ratio), WHSVmethanol = 43152ml/gcat*h, catalyst = 0.1 g, our catalyst was found to show much better performance than other Pd@ZnO catalysts prepared by other methods, especially in terms of selectivity which is particularly important for hydrogen fuel cell application considering that Pt electrode could be poisoned by even trace amount of CO. It turned out that the large surface area, enough holes, evenly distributed PdZn alloy activity sites and abundant oxygen vacancies lead to the overall excellent performance of our catalyst.  相似文献   

18.
Dry reforming of methane (DRM) is considered a promising reforming technology that converts natural gas in the Natuna Sea into synthesis gas, which can be further utilized to produce beneficial chemicals such as olefins, alcohols, and liquid hydrocarbons. However, the challenges in commercializing the DRM process are carbon deposition and sintering of the catalyst at high temperatures, because of which the catalyst is easily deactivated. This study aimed to test the activity and stability of MCM-41-based catalysts for the DRM; determine the effect of promoter type on the activity and stability of MCM-41-based catalysts; and determine the effect of base promoter addition on the amount of carbon deposition. MCM-41-based catalysts were synthesized using incipient wetness impregnation method. XRD, N2 Physisorption, H2-TPR, CO2-TPD, and TGA analysis were conducted to determine the physicochemical properties of the catalysts. The catalysts activity was tested in a fixed-bed reactor, under atmospheric pressure at 700 °C. Overall, all catalysts exhibited good stability for 240 min. Moreover, catalysts with Mg and Ca promoters showed the highest CH4 and CO2 conversion among all catalysts. Ni–Mg/MCM-41 catalyst yielded 72% CH4 conversion and 54% CO2 conversion, meanwhile Ni–Ca/MCM-41 yielded 69% CH4 conversion and 55% CO2 conversion. Furthermore, MCM-41-based catalysts with base promoter produced small amount of carbon deposition.  相似文献   

19.
Methanol steam reforming (MSR) holds great potential for mobile hydrogen production, but it still requires an active and stable catalyst. In this work, we report a high-performance ZnZr-0.5 composite oxide catalyst for this reaction, with a hydrogen production rate of 2.80 mol·gcat?1·h?1 and CO2 selectivity of 99.6% at a methanol space velocity of 22,762 mL·gcat?1·h?1. It also exhibits superior long-term durability in the TOS test for more than 100 h. Such good activity results from a synergistic effect of ZnO–ZrO2 dual sites. ZrO2 is capable of stabilizing and storing more CH3O1 and HCOO1 intermediates while ZnO is in charge of the dehydrogenation of these key intermediates. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and chemisorption results reveal that the MSR reaction experiences successively the hydrolysis of methyl formate and dehydrogenation of formate. More importantly, it is found that H2O significantly promotes the dehydrogenation of HCOO1 intermediate by directly participating in this reaction from pulse chemisorption experiments.  相似文献   

20.
A novel approach for the hydrogen production which integrated methanol steam reforming and fluidized bed reactor (FBR) was proposed. The reaction was carried out over Cu/ZnO/Al2O3 catalysts. The critical fluidized velocities under different catalyst particle sizes and masses were obtained. The influences of the operating parameters, including that of H2O-to-CH3OH molar ratio, feed flow rate, reaction temperature, and catalyst mass on the performance of methanol steam reforming were investigated in FBR to obtain the optimum experimental conditions. More uniform temperature distribution, larger surface volume ratio and longer contacting time can be achieved in FBR than that in fixed bed reactor. The results indicate that the methanol conversion rate in FBR can be as high as 91.95% while the reaction temperatures is 330 °C, steam-to-carbon molar ratio is 1.3, and feed flow rate is 540 ml/h under the present experiments, which is much higher than that in the fixed bed.  相似文献   

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