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采用溶胶-凝胶(Sol-Gel)法制备了微孔结构均匀的“SiO2/陶瓷”膜和“Mo-Co-O/SiO2/陶瓷”催化功能膜,并用XRD、SEM和孔径测定等技术进行了表征。在常压,500~700℃的条件下,在催化膜反应器(CMR)中考察了甲烷氧化制甲醇的反应。在相似的反应条件下(转化率为1.0%),用CMR(甲醇选择性1?.2%)可获得较固定床反应器(甲醇选择性4.5%)高得多的甲醇选择性。 相似文献
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用溶胶-凝胶法制备了“SiO2/陶瓷”非对称无机膜,并用该膜制备了反应气吹扫催化膜反应器(RSCMR0装置。在RSCMR上考察了甲烷一步催化氧化制甲醇反应。结果表明,在研究的范围内,增加氧气或甲烷的浓度和吹扫气的流速(即总的反应气流量)有利于提高甲醇的收率;甲醇在反应条件下的热不稳定性是影响目标反应选择性的重要原因。RSCMR较膜反应(CMR0系统能更有效地抑制甲醇的热分解,因而可得到较CMR更高 相似文献
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甲烷直接氧化制甲醇Ⅲ.反应气吹扫催化膜反应器(RSCMR) 总被引:2,自引:0,他引:2
用溶胶-凝胶法制备了“SiO_2/陶瓷”非对称无机膜,并用该膜制备了反应气吹扫催化膜反应器(RSCMR)装置。在RSCMR上考察了甲烷一步催化氧化制甲醇反应。结果表明,在研究的范围内,增加氧气或甲烷的浓度和吹扫气的流速(即总的反应气流量)有利于提高甲醇的收率;甲醇在反应条件下的热不稳定性是影响目标反应选择性的重要原因。RSCMR较膜反应器(CMR)系统能更有效地抑制甲醇的热分解,因而可得到较CMR更高的甲醇收率。当反应温度为700℃时,甲醇的收率在CMR中为0.5g/m ̄2h,在RSCMR中可达0.9g/m ̄2h。 相似文献
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正丁烷选择氧化过程中VPO体系的表面物种 总被引:4,自引:0,他引:4
用漫反射傅立叶变换红外光谱法,研究了VPO催化剂上正丁烷选择氧化制顺酐的表面物种及催化反应过程。催化剂暴露在1.5%n-C4 21%02+N2的流动混合气中,流量为50mL/min,温度100-400℃,在催化剂表面上未观察到吸附的正丁烷,但发现了吸附的顺酐和COx。同时,检测到吸附的马来酸和高活性的烯烃物种。 相似文献
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Investigation of the mechanism of n-butane oxidation on vanadium phosphorus oxide catalysts: evidence from isotopic labeling studies 总被引:1,自引:0,他引:1
The selective oxidation of n-butane to maleic acid catalyzed by vanadium phosphates (VPO) is one of the most complex partial oxidation reactions used in industry today. Numerous reaction mechanisms have been proposed in the literature, many of which have butenes, butadiene, and furan as reaction intermediates. We have developed an experimental protocol to study the mechanism of this reaction in which (13)C-isotopically labeled n-butane is flowed over a catalyst bed and the reaction products are analyzed using (13)C NMR spectroscopy. This protocol approximates the conditions found in an industrial reactor without requiring an exorbitant amount of isotopically labeled material. When [1,4-(13)C]n-butane reacted on VPO catalysts to produce maleic acid and butadiene, the isotopic labels were observed in both the 1,4 and 2,3 positions of butadiene and maleic acid. The ratio of label scrambling was typically 1:20 for the 2,3:1,4 positions in maleic acid. For butadiene, the ratio of label scrambling was consistently much higher, at 2:3 for the 2,3:1,4 positions. Because of the discrepancy in the amount of label scrambling between maleic acid and butadiene, butadiene is unlikely to be the primary reaction intermediate for the conversion of n-butane to maleic anhydride under typical industrial conditions. Ethylene was always observed as a side product for n-butane oxidation on VPO catalysts. Fully (13)C-labeled butane produced about 5-13 times as much isotopically labeled ethylene as did [1,4-(13)C]butane, indicating that ethylene was produced mainly from the two methylene carbons of n-butane. When the reaction was run under conditions which minimize total oxidation products such as CO and CO(2), the amounts of ethylene and carbon oxides produced from fully (13)C-labeled butane were almost equal. This strongly suggests that the total oxidation of n-butane on VPO catalysts involves the oxidation and abstraction of the two methyl groups of n-butane, and the two methylene groups of n-butane form ethylene. An organometallic mechanism is proposed to explain these results. 相似文献
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Mechanosynthesis and mechanochemical treatment of bismuthdoped vanadium phosphorus oxide catalysts for the partial oxidation of n-butane to maleic anhydride 总被引:1,自引:0,他引:1 下载免费PDF全文
Three Bi-doped vanadyl pyrophosphate catalysts were prepared via dihydrate route (VPD method), which consisted of different preparation methods including mechanosynthesis, mechanochemical treatment, and the conventional reflux method. The catalysts produced by the above three methods were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and temperature programmed reduction (TPR). Catalytic evaluation for the partial oxidation of n-butane to maleic anhydride (MA) was also carried out. The XRD patterns of all the Bi-doped catalysts showed the main peaks of pyrophosphate phase. Lower intensity peaks were observed for the mechanochemically treated Bi-doped catalyst (VPDBiMill) with two additional small peaks corresponding to the presence of a small amount of V5+ phase. The TPR profiles showed that the highest amount of active oxygen species, i.e, V4+–O- pair, responsible for n-butane activation, was removed from VPDBiMill. Furthermore, from the catalytic test results, the graph of selectivity to MA as a function of the conversion of n-butane demonstrated that VPDBiMill was the most selective catalyst. This suggests that the mechanochemical treatment of vanadium phosphate catalyst (VPDBiMill) is a potential method to improve the catalytic properties for the partial oxidation of n-butane to maleic anhydride. 相似文献
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V. Martin J. M. M. Millet J. C. Volta 《Journal of Thermal Analysis and Calorimetry》1998,53(1):111-121
The transformation of VOHPO4·0.5H2O (VPO) precursor doped with cobalt or iron for n-butane oxidation to maleic anhydride was
investigated by thermogravimetric analysis under air and nitrogen, with and without n-butane in the flow. While almost no
effect was observed in nitrogen or air, a strong influence of the doping was observed when n-butane was added to the nitrogen
or air. This resulted in a delay of the decomposition of the precursor and a further reoxidation of the VPO catalyst, particularly
for doping with cobalt at low percentage (1%). This shows that doping can change the oxidation state of vanadium phosphorus
oxide catalysts, which can explain differences in their catalytic performances and the favourable effect of doping by cobalt.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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二甲基亚砜对钒磷氧催化剂性能的影响 总被引:1,自引:0,他引:1
在制备钒磷氧催化剂前驱体的过程中,加入高沸点溶剂二甲基亚砜(DMSO),改善了钒磷氧催化剂对正丁烷氧化制顺丁烯二酸酐的催化性能.催化性能评价实验表明,当DMSO/V(摩尔比)=0.1时,用催化剂(D0.1-VPO)制备顺酐的收率达到最大(49.4%),与没有加入DMSO的催化剂(VPO)相比其选择性由57%提高到76%,转化率达到65%.采用BET,XRD,SEM,FT-IR等方法分析,发现添加DMSO能增大催化剂的比表面积,改变催化剂前驱体择优取向和催化剂的微观形貌,形成了一些具有纳米尺度的催化剂颗粒. 相似文献
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高比表面积VPO催化剂的制备及其性质研究 总被引:4,自引:0,他引:4
利用有机相制备VPO催化剂,在制备过程中加入聚乙二醇(PEG)作为分散剂可有效提高VPO催化剂的比表面积。实验中采用两种不同分子量的聚乙二醇(PEG 6000和PEG 10000),所得VPO催化剂的比表面积分别为52与54m2/g,而不加聚乙二醇的VPO催化剂其比表面积仅为19m2/g.XRD,XPS及FTIR的结果表明,催化剂的主要晶相均为(VO)2P2O7,但两类催化剂的微观结构有所不同。正丁烷选择氧化生成马来酐的催化反应结果表明,385℃时加聚乙二醇制备的VPO催化剂其丁烷的转化率为84%~86%.马来酸酐的选择性为78%,而不加聚乙二醇制备的VPO催化剂其转化率和选择性均为71%. 相似文献
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Eichelbaum M Stösser R Karpov A Dobner CK Rosowski F Trunschke A Schlögl R 《Physical chemistry chemical physics : PCCP》2012,14(3):1302-1312
We have developed a noncontact method to probe the electrical conductivity and complex permittivity of single and polycrystalline samples in a flow-through reactor in the temperature range of 20-500 °C and in various gas atmospheres. The method is based on the microwave cavity perturbation technique and allows the simultaneous measurement of microwave conductivity, permittivity and of the catalytic performance of heterogeneous catalysts without any need for contacting the sample with electrodes. The sensitivity of the method towards changes in bulk properties was proven by the investigation of characteristic first-order phase transitions of the ionic conductor rubidium nitrate in the temperature range between 20 and 320 °C, and by studying the temperature dependence of the complex permittivity and conductivity of a niobium(V)-doped vanadium-phosphorous-oxide catalyst for the selective oxidation of n-butane to maleic anhydride. Simultaneously, the catalytic performance was probed by on line GC analysis of evolving product gases making the technique a real in situ method enabling the noninvasive investigation of electronic structure-function relationships. 相似文献
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V. A. Zazhigalov V. P. Shabel'nikov V. G. Golovatyi A. I. Pyatnitskaya G. A. Komashko 《Theoretical and Experimental Chemistry》1993,28(2):139-142
The feasibility of partially oxidizing n-butane to tetrahydrofuran in the presence of promoted V-P-O catalyst was demonstrated. Tetrahydrofuran formation was identified by means of chromatography and mass spectrometry. From the relationship between its concentration and reaction temperature tetrahydrofuran could be proposed as a possible intermediate in the transformation of n-butane into maleic anhydride.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 28, No. 2, pp. 159–162, March–April, 1992. 相似文献