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1.
Effects of Calcination Temperature on the Acidity and Catalytic Performances of HZSM-5 Zeolite Catalysts for the Catalytic Cracking of n-Butane 下载免费PDF全文
The acidic modulations of a series of HZSM-5 catalysts were successfully made by calcination at different treatment temperatures, i.e. 500, 600, 650, 700 and 800 ℃, respectively. The results indicated that the total acid amounts, their density and the amount of B-type acid of HZSM-5 catalysts rapidly decreased, while the amounts of L-type acid had almost no change and thus the ratio of L/B was obviously enhanced with the increase of calcination temperature (excluding 800 ℃). The catalytic performances of modified HZSM-5 catalysts for the cracking of n-butane were also investigated. The main properties of these catalysts were characterized by means of XRD, N2 adsorption at low temperature, NH3-TPD, FTIR of pyridine adsorption and BET surface area measurements. The results showed that HZSM-5 zeolite pretreated at 800 ℃ had very low catalytic activity for n-butane cracking. In the calcination temperature range of 500-700 ℃, the total selectivity to olefins, propylene and butene were increased with the increase of calcination temperature, while, the selectivity for arene decreased with the calcination temperature.The HZSM-5 zeolite calcined at 700 ℃ produced light olefins with high yield, at the reaction temperature of 650 ℃ the yields of total olefins and ethylene were 52.8% and 29.4%, respectively. Besides, the more important role is that high calcination temperature treatment improved the duration stability of HZSM-5zeolites. The effect of calcination temperature on the physico-chemical properties and catalytic performance of HZSM-5 for cracking of n-butane was explored. It was found that the calcination temperature had large effects on the surface area, crystallinity and acid properties of HZSM-5 catalyst, which further affected the catalytic performance for n-butane cracking. 相似文献
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实验研究了装有Pt覆盖的多孔陶瓷的Swiss-Roll燃烧器的燃烧特性,分别得到了3种不同长度的催化剂基底的熄火极限,并测量3种情况下催化剂壁面及催化剂后部空间的温度。实验结果表明,3种情况中,催化剂基底长4.5mm的燃烧器可燃范围最大,所以此长度较适合此Swiss-Roll燃烧器。从温度数据可以看出来,催化剂后部空间存在反应,且受上游催化剂表面反应强度的影响。 相似文献
3.
正丁烷在金属钼酸盐催化剂上的氧化脱氢 总被引:5,自引:0,他引:5
用柠檬酸盐法合成了第一系列过渡金属(Cr,Mn,Fe,Co,Ni,Cu和Zn)及Mg的钼酸盐催化剂,研究
了它们对正丁烷氧化脱氢反应的催化作用. 结果表明,这些钼酸盐催化剂的催化性能受阳离子的影响较大. CoMoO4催化剂具有最高的催化活性和较高的选择性,其催化性能与文献报道的对正丁烷氧化脱氢反应催化性能最好的ZrP2O7和Mg3V2O8催化剂大致相当; MgMoO4催化剂虽然选择性较高,但活性较低; Cr2(MoO4)3上基本没有C4烯烃生成; 其它钼酸盐催化剂对正丁烷氧化脱氢反应的催化活性和对烯烃的选择性都较低. XRD,NH3-TPD和H2-TPR的研究结果表明,催化剂为单一的钼酸盐晶相,催化剂的性能由其氧化还原性决定而与其表面酸量没有直接关系. 通过对产物分布的分析,提出了正丁烷在CoMoO4催化剂上的氧化脱氢反应途径. 在558 ℃,正丁烷发生氧化脱氢生成正丁烯和丁二烯以及氧化燃烧生成CO2三个平行竞争反应的竞争分率分别约为75%,10%和15%. 在正丁烷转化率较高的条件下,产物中的CO2主要来自C4烯烃的再氧化反应,而CO则完全来自C4烯烃的再氧化. 相似文献
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Mingyu Chu Yu Liu Jin Gong Congyang Zhang Xuchun Wang Qixuan Zhong Linzhong Wu Prof. Yong Xu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(45):11643-11648
Butadiene (BD) is a critical raw material in chemical industry, which is conventionally produced from naphtha cracking. The fast-growing demand of BD and the limited oil reserve motivate chemists to develop alternative methods for BD production. Shale gas, which mainly consists of light alkanes, has been considered as cheap raw materials to replace oil for BD production via n-butane direct dehydrogenation (n-BDH). However, the quest for highly-efficient catalysts for n-BDH is driven by the current drawback of low BD selectivity. Here, we demonstrate a strategy for boosting the selectivity of BD by suppressing dehydroisomerization, an inevitable step in the conventional n-BDH process which largely reduces the selectivity of BD. Detailed investigations show that the addition of alkali-earth metals (e. g., Mg and Ca) into Pt-Ga2O3/S10 catalysts increases Pt dispersity, suppresses coke deposition and dehydroisomerization, and thus leads to the significant increase of BD selectivity. The optimized catalyst displays an initial BD selectivity of 34.7 % at a n-butane conversion of 82.1 % at 625 °C, which outperforms the reported catalysts in literatures. This work not only provides efficient catalysts for BD production via n-BDH, but also promotes the researches on catalyst design in heterogeneous catalysis. 相似文献
7.
Chong-Jiang Cao Xi-Zhi Yu Chang-Lin Chen Nan-Ping Xu Yan-Ru Wang Chung-Yuan Mou 《Reaction Kinetics and Catalysis Letters》2004,83(1):85-92
Sulfated zirconia catalysts promoted by gallium or aluminium were prepared and tested for n-butane isomerization. Both elements increase and stabilize the isomerization rate. Characterization results showed that the
promoting mechanism of gallium was different from that of aluminium.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
8.
Yuichi Kamiya 《Reaction Kinetics and Catalysis Letters》2005,84(2):271-278
Summary 1% of Fe-doped and undoped vanadyl pyrophosphate catalysts were prepared via dihydrate method. The catalysts have been characterised by XRD, ICP, BET and SEM. The undoped catalyst was found to be more active and selective (77.6% selectivity at about 60 % conversion at 703 K). 相似文献
9.
Promotional Effect of Bismuth as Dopant in Bi-Doped Vanadyl Pyrophosphate Catalysts for Selective Oxidation of n-Butane to Maleic Anhydride 总被引:2,自引:0,他引:2 下载免费PDF全文
Y. H. Taufiq-Yap Y. Kamiya K. P. Tan 《天然气化学杂志》2006,15(4):297-302
Bismuth-promoted (1% and 3%) vanadyl pyrophosphate catalysts were prepared by refluxing Bi(NO3)3·5H2O and VOPO4·2H2O in isobutanol. The incorporation of Bi into the catalysts lattice increased the surface area and lowered the overall V oxidation state. Profiles of temperature programmed reduction (TPR) in H2 show a significant shift of the maxima of major reduction peaks to lower temperatures for the Bi-promoted catalysts. A new peak was also observed at the low temperature region for the catalyst with 3% of Bi dopant. The addition of Bi also increased the total amount of oxygen removed from the catalysts. The reduction pattern and reactivity information provide fundamental insight into the catalytic properties of the catalysts. Bi-promoted catalysts were found to be highly active (71% and 81% conversion for 1% and 3% Bi promoted catalysts, respectively, at 703 K), as compared to the unpromoted material (47% conversion). The higher activity of the Bi-promoted catalysts is due to that these catalysts possess highly active and labile lattice oxygen. The better catalytic performance can also be attributed to the larger surface area. 相似文献
10.
Yun Hin Taufiq-Yap 《天然气化学杂志》2006,15(2):144-148
In this study, Cr and Co promoted, as well as unpromoted vanadium phosphate (VPO) catalysts were synthesized by the reaction of V2O5 and o-H3PO4 in organic medium followed by calcination in n-butane/air environment at 673 K. The physico-chemical properties and the catalytic behavior were affected by the addition of Cr and Co dopants. H2-TPR was used to investigate the nature of oxidants in the unpromoted and promoted catalysts. The results showed that both the Cr and Co promoters remarkably lowered the temperature of the reduction peak associated with V5 . The amount of oxygen species originated from the active phase, V4 , removed was significantly increased for Co and Cr-promoted catalysts. Both Cr and Co dopants improve strongly the n-butane conversion without sacrificing the MA selectivity. A good correlation was observed between the amount of oxygen species removed from V4 phase and the activity for n-butane oxidation to maleic anhydride. This suggested that V4 -O was the center for the activation of n-butane. 相似文献