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STUDY OF HYDROGEN TRANSFER REACTIONS IN PROPANE AROMATIZATION OVER Ga MODIFIED HZSM-5 CATALYSTS 下载免费PDF全文
研究了丙烷在不同SiO2/Al2O3比值的HZSM5和Ga改性HZSM5催化剂上的芳构化转化,为探讨氢转移反应的能力,也考察了在丙烷中添加少量氢对芳构化转化的影响。结果表明,随HZSM5分子筛SiO2/Al2O3比值的减小,氢转移反应程度增大;在分子筛中引入Ga,氢转移反应能力增大。最后提出了有Ga参与的反应机理。 相似文献
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以乙烯、乙烷为探针反应分子,以混合不同锌含量的ZnO/SiO2与HZSM-5为催化剂,在不同处理条件与不同混合方式(直接混合或机械研磨)下研究高温焙烧的催化剂对乙烯、乙烷芳构化反应的影响。考察了不同含量的Zn/HZSM-5上C2H4、C2H6的芳构化反应及NaHZSM-5与ZnO/SiO2和NaZnHZSM-5与ZnO/SiO2混合催化剂高温焙烧后的C2H4芳构化反应。发现Zn/HZSM-5是一种 相似文献
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以乙烯、乙烷为探针反应分子,以混合不同锌含量的ZnO/SiO_2,与HZSM-5为催化剂,在不同处理条件与不同混合方式(直接混合或机械研磨)下研究高温焙烧的俗化剂对乙烯、乙烷芳构化反应的影响。考察了不同含量的Zn/HZSM-5上C_2H_4、C_2H_6的芳构化反应及NaHZSM-5与ZnO/SiO_2和NaZnHZSM-5与ZnO/SiO_2混合催化剂高温焙烧后的C_2H_4芳构化反应。发现Zn/HZSM-5是一种双功能催化剂,乙烯、乙烷芳构化反应的活性和选择性均与Zn/HZSM-5的双中心Zn ̄(2+)和B酸的相互匹配有密切关系,B酸和Zn ̄(2+)存在最合适匹配。而NZSM-5与ZnO/SiO_2合催化剂高温焙烧后具有Zn/HZSM-5的双功能性,HZSM-5与ZnO/SiO_2在高温下发生了固相反应。 相似文献
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考察了在具有Pentasil孔道结构的H-Ga-Si与Pt/H-Ga-Si杂原子分子筛及HZSM-5分子筛催化剂上的丙烷芳构化。Pt/H-Ga-Si有较高催化活性和芳烃选择性,用XRD、TEM和TPR等技术对催化剂进行了表征,讨论了Pt与Ga的相互作用。Pt/H-Ga-Si为双功能催化剂,Pt促进烷烃脱氢成为烯烃,还能降低丙烷裂解活性,而且可稳定骨架Ga,使其不易脱除;Ga可以提高中间烯烃转变为芳烃的选择性。H-Ga-Si与HZSM-5上的丙烷芳构化机理不同。H-Ga-Si上为丙烷脱氢机理,Ga脱去H+形成活泼正碳离子,同时由于骨架Ga与分子筛B酸位相邻,所以可提高芳烃选择性;HZSM-5上丙烷活化是经过裂化机理,再通过氢转移步骤形成芳烃。 相似文献
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低碳烃芳构化过程中HZSM—5催化剂结炭规律的研究 总被引:1,自引:0,他引:1
用GC、TPO-GC、NH3-TPD和TEM等方面,测定了丙烷在HZSM-5沸石上芳构化过程中,催化剂的活性、结炭量、结炭C/H比、酸密度等,考察了催化剂的结炭量与其它参数之间的关系。结果表明,在反应温度为873K,进料空速WHSV=5h^-1时,丙烷在HZSM-5上的结炭首先发生在沸石晶体的外表面的活性中心上;结炭量为1.8-3.4%时,主要在孔道交叉点结炭;结炭量在3.4-5.7%时,孔道已有 相似文献
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DEHYDROGENATION AND AROMATIZATION OF METHANE IN THE ABSENCE OF OXYGEN OVER DOPED Mo/HZSM-5 CATALYSTS 下载免费PDF全文
研究了在Mo/HZSM-5催化剂上添加助剂以及不同的反应预处理温度对甲烷无氧脱氢芳构化反应的影响。实验结果表明,由于第二组分的添加,Mo/HZSM-5催化剂的活性和选择性都得到了较大程度的改善。预处理温度是影响催化剂反应性能的关键因素。Mo-Ru/HZSM-5催化剂经过873K空气预处理后,甲烷在973K的转化率约为10%,催化剂的稳定性也得到较大程度的提高。TPSR实验结果表明,Ru的加入降低了芳烃生成的温度。TPO和DTA实验结果表明,在Mo-Ru/HZSM-5催化剂上可生成较多的碳物种,结合反应结果,可以认为反应过程中生成的碳物种对甲烷的无氧脱氢芳构化反应是起积极作用的 相似文献
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水蒸气存在时Mo/HZSM-5催化剂上的甲烷芳构化反应性能 总被引:2,自引:0,他引:2
研究了水蒸气存在条件下Mo/HZSM-5沸石分子筛催化剂上的甲烷芳构化反应行为,发现水蒸气的引入可以明显地降低甲烷芳构化反应的起始温度,从而在较为温和的条件下实现甲烷的活化.适量水蒸气的加入可以在一定程度上改善Mo/HZSM-5催化剂的稳定性,过量水蒸气的引入则会抑制甲烷芳构化反应.在反应温度为973 K时,引入适量的水蒸气对芳构化反应产物的分布没有明显影响在低温条件下的甲烷芳构化反应过程中检测到有乙烯生成,该结果支持了甲烷芳构化反应可能经历了乙烯这一中间产物的机理.实验结果还表明,水蒸气对催化剂上的积炭量没有明显的影响. 相似文献
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In this work, syngas methanation over Ni-W/TiO2-SiO2 catalyst was studied in a fluidized-bed reactor (FBR) and its performance was compared with a fixed-bed reactor (FIXBR). The effects of main operating variables including feedstock gases space velocity, coke content, bed temperature and sulfur-tolerant stability of 100 h life were investigated. The structure of the catalysts was characterized by XRD, N2 adsorption-desorption and TEM. It is found that under same space velocity from 5000 h?1 to 25000 h?1 FBR gave a higher CH4 yield, lower coke content, and lower bed temperature than those obtained in FIXBR. Ni-W/TiO2-SiO2 catalyst possessed excellent sulfur-tolerant stability on the feedstock gases less than 500 ppm H2S in FBR. The carbon deposits formed on the spent catalyst were in the form of carbon fibers in FBR, while in the form of dense accumulation distribution appearance in FIXBR. 相似文献
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Annapurna Jetty Ravichandra Potumarthi A. Gangagni Rao B. Sarva Rao S. V. Ramakrishna 《Applied biochemistry and biotechnology》2009,159(2):579-588
Oxytetracycline (OT) production using glutaraldehyde cross-linked calcium alginate immobilized cells of Streptomyces varsoviensis in continuous fluidized bed reactor (FBR) was investigated. Initially, batch experiments were carried in stirred tank reactor
(STR) and FBR using calcium alginate immobilized cells. Higher OT production of 0.45 gm/L was achieved by FBR when compared
with 0.33 g/L of OT in STR. All subsequent studies were carried out in continuous mode of operation in FBR. During 21 days
of operation, effect of glucose concentration and different dilution rates were studied. A maximum of 0.75 g/L OT was achieved
in the medium having 10 g/L of glucose concentration. The highest OT concentration of 0.92 g/L and the highest yield of OT
with respect to biomass at 0.1713 g/g were obtained at the dilution rate of 0.25 day−1. 相似文献
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Sun May Y. Nghiem Nhuan P. Davison Brian H. Webb Oren F. Bienkowski Paul R. 《Applied biochemistry and biotechnology》1998,(1):429-439
The production of ethanol from starch was studied in a fluidized-bed reactor (FBR) using co-immobilizedZymomonas mobilis and glucoamylase. The FBR was a glass column of 2.54 cm in diameter and 120 cm in length. TheZ. mobilis and glucoamylase were co-immobilized within small uniform beads (1.2-2.5 mm diameter) of κ-carrageenan. The substrate for
ethanol production was a soluble starch. Light steep water was used as the complex nutrient source. The experiments were performed
at 35κC and pH range of 4.0-5.5. The substrate concentrations ranged from 40 to 185 g/L, and the feed rates from 10 to 37
mL/min. Under relaxed sterility conditions, the FBR was successfully operated for a period of 22 d, during which no contamination
or structural failure of the biocatalyst beads was observed. Volumetric productivity as high as 38 g ethanol/(Lh), which was
74% of the maximum expected value, was obtained. Typical ethanol volumetric productivity was in the range of 15-20 g/(Lh).
The average yield was 0.49 g ethanol/g substrate consumed, which was 90% of the theoretical yield. Very low levels of glucose
were observed in the reactor, indicating that starch hydrolysis was the rate-limiting step. 相似文献
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Thermophilic ethanol fermentation of wet-exploded wheat straw hydrolysate was investigated in a continuous immobilized reactor
system. The experiments were carried out in a lab-scale fluidized bed reactor (FBR) at 70°C. Undetoxified wheat straw hydrolysate
was used (3–12% dry matter), corresponding to sugar mixtures of glucose and xylose ranging from 12 to 41 g/l. The organism,
thermophilic anaerobic bacterium Thermoanaerobacter BG1L1, exhibited significant resistance to high levels of acetic acid (up to 10 g/l) and other metabolic inhibitors present
in the hydrolysate. Although the hydrolysate was not detoxified, ethanol yield in a range of 0.39–0.42 g/g was obtained. Overall,
sugar efficiency to ethanol was 68–76%. The reactor was operated continuously for approximately 143 days, and no contamination
was seen without the use of any agent for preventing bacterial infections. The tested microorganism has considerable potential
to be a novel candidate for lignocellulose bioconversion into ethanol. The work reported here also demonstrates that the use
of FBR configuration might be a viable approach for thermophilic anaerobic ethanol fermentation. 相似文献
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HE Ren-Jin 《天然气化学杂志》1996,5(4):306-319
lntroductionNat[lralgasisanabundanresourceandtheworldreservesareestimatedtobe43trillioncubicmeers.DuetoitshightransportcostandverystablechendcalproPerty,onlylessthanlo%oftheworldproductionofnaturalgasisusedinchendcalindustriesandtheremainderisburnedasfuelforpowergeneratingandhcaing.Toincreaseitsvalueanduseitasachemicalfeedstock,naturalgasmustbeconvetaltomoreappropriatC-products.SincethepioneeringworkofKellerandBhasim(l982)atUnionCarbidell],therehasbeenconsiderableinterestinmethaneconversiont… 相似文献
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碳四烃在改性HZSM-5分子筛上芳构化研究 总被引:8,自引:0,他引:8
研究了炼厂混合C_4烃在Zn、Ga、Cr、La改性的HZSM-5分子筛催化剂上的芳构化反应,采用TPD和IR测定了催化剂的表面酸性质。结果表明,用Zn(3%)和Zn(2%)Ga(1%)改性的HZSM-5分子筛具有较好的芳构化性能;各改性HZSM-5分子筛催化剂芳构化性能变化与表面酸性有关,总酸量下降,芳构化活性下降,强B酸中心减少,深度裂解反应减少;Zn的单组分和双组分改性的HZSM-5分子筛催化剂芳构化活性的增高与表面强L酸浓度增加和吡啶吸附IR谱中的1615cm~(-1)吸收峰出现有关。 相似文献