Effects of Calcination Temperature on the Acidity and Catalytic Performances of HZSM-5 Zeolite Catalysts for the Catalytic Cracking of n-Butane

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-5 zeolites. 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.

Low-temperature activation of methane over rare earth metals promoted Zn/HZSM-5 zeolite catalysts in the presence of ethylene

At low temperature of 723 K, methane can be easily activated in the presence of ethylene in the feed, and converted to higher hydrocarbons （C2-C4） and aromatics （C6-C10）, through its reaction over rare metals modified Zn/HZSM-5 zeolite catalysts without undesirable carbon oxides formation. Methane can get 37.3% conversion over the above catalysts under low temperature, and the catalysts show a longer lifetime than usual metal supported HZSM-5 zeolite catalysts without adding any rare earth metals. The effects of methane activation over various rare earth metal promoted Zn/HZSM-5 catalysts on the products and influences of several reaction conditions such as temperature, catalyst lifetime and molar ratio of CH4/C2H4 have been discussed.

Study of the Conversion of Postconsumer Polystyrene on CeO2/HZSM-5 Type Materials

The catalytic conversion of polystyrene (PS) was studied in the presence of the materials type HZSM-5, CeO2, 10% CeO2/HZSM-5 and 20% CeO2/HZSM-5, which were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and nitrogen adsorption at 77K. The catalytic tests were performed via thermogravimetric analysis (TG) at heating rates of 5, 10 and 20˚C min−1 in a temperature range from 30˚C to 900˚C. For the tests, a ratio of 30% by mass of each catalytic material mixed with PS was used and the activation energy of the degradation process was determined by the Vyazovkin method. The obtained results showed that the addition of the catalyst to the PS in general reduced its degradation temperature. The 10% CeO2/HZSM-5 catalyst showed greater efficiency, as it resulted in lower activation energy for PS degradation. Thus, the combination of CeO2 with HZSM-5 resulted in materials with potential for application in the catalytic degradation of polystyrene and the results indicate that the production of a composite material can be a good strategy to generate an increase in catalytic activity and a decrease in energy process activation.

Study on the in situ desulfurization and viscosity reduction of heavy oil over MoO_(3)–ZrO_(2)/HZSM-5 catalyst

Heavy oil is characterized by high viscosity.High viscosity makes it challenging to recover and transport.HZSM-5,MoO_(3)/HZSM-5,ZrO_(2)/HZSM-5 and MoO_(3)–ZrO_(2)/HZSM-5 catalysts were developed to promote in situ desulfurization and viscosity reduction of heavy oil.The physical and chemical properties of catalysts were characterized by XPS,XRD,TEM,NH3-TPD,etc.The effects of temperature,catalyst type and addition amount on viscosity and composition of heavy oil were evaluated.The results showed that the presence of MoO_(3)–ZrO_(2)/HZSM-5 nanoparticles during aquathermolysis could improve the oil quality by reducing the heavy fractions.It reduced viscosity by 82.56%after the reaction at 280℃ and catalyst addition of 1 wt%.The contents of resins and asphaltic in the oil samples were 5.69%lower than that in the crude oil.Sulfur content decreased from 1.45%to 1.03%.The concentration of H2S produced by the reaction was 2225 ppm.The contents of sulfur-containing functional groups sulfoxide and sulfone sulfur in the oil samples decreased by 19.92%after the catalytic reaction.The content of stable thiophene sulfur increased by 5.71%.This study provided a basis for understanding the mechanism of heavy oil desulfurization and viscosity reduction.

Effects of Light Rare Earth on Acidity and Catalytic Performance of HZSM-5 Zeolite for Catalytic Cracking of Butane to Light Olefins

The effects of rare earth（RE）on the structure,acidity,and catalytic performance of HZSM-5 zeolite were investigated.A series of RE/HZSM-5 catalysts,containing 7.54% RE（RE=La,Ce,Pr,Nd,Sm,Eu or Gd）,were prepared by the impregnation of the ZSM-5 type zeolites（Si/Al=64：1）with the corresponding RE nitrate aqueous solutions.The catalysts were characterized by means of FT-IR,UV-Vis,NH3-TPD,and IR spectroscopy of adsorbed pyridine.The catalytic performances of the RE/HZSM-5 for the catalytic cracking of mixed butane to light olefins were also measured with a fixed bed microreactor.The results revealed that the addition of light rare earth metal on the HZSM-5 catalyst greatly enhanced the selectivity to olefins,especially to propylene,thus increasing the total yield of olefins in the catalytic cracking of butane.Among the RE-modified HZSM-5 samples,Ce/HZSM-5 gave the highest yield of total olefins,and Nd/HZSM-5 gave the highest yield of propene at a reaction temperature of 600℃.The presence of rare earth metal on the HZSM-5 sample,not only modified the acidic properties of HZSM-5 including the amount of acid sites and acid type,that is,the ratio of L/B（Lewis acid/Brnsted acid）,but also altered the basic properties of it,which in turn promoted the catalytic performance of HZSM-5 for the catalytic cracking of butane.

Effects of Operating Conditions on the Catalytic Performance of HZSM-5 Zeolites in n-Pentane Cracking

In this work,n-pentane catalytic cracking over HZSM-5 zeolites was studied at 650°C under atmosphere pressure.A particular attention was paid to the measurement of n-pentane conversion,light olefins production,product distribution,coke deposit,etc.Several indexes were defined to evaluate the effects of operating conditions on the catalytic performance of HZSM-5 zeolites.It was found that decreasing the weight hourly space velocity,increasing the reactant partial pressure,and increasing the carrier gas flow rate could inhibit C-H bond breaking and enhance the C-C bond breaking and hydride transfer reactions,leading to reduced alkenes selectivity,which suppressed the formation of external coke and alleviated the deactivation of HZSM-5 zeolites.It was deduced that the catalytic stability of HZSM-5 zeolites was improved at the cost of alkenes selectivity.Compared with decreasing the weight hourly space velocity and increasing the reactant partial pressure,increasing the carrier gas flow rate could enhance the diffusion process and protect alkenes from being consumed in coke formation in order to improve the catalytic stability of HZSM-5 zeolites with less reduction of alkenes selectivity.

Properties and Characterization of Modified HZSM-5 Zeolites

Physicochemical and catalytic properties of phosphorus and boron modified HZSM-5 zeolites treated with 100% steam at 673 K were investigated. The acidity and distribution of acidic sites were studied by infrared spectroscopy using pyridine as probe molecule and temperature programmed desorption (TPD) of ammonia. The structure of the samples was characterized by XRD, and the textural properties of the catalysts were determined by nitrogen isothermal adsorption-desorption measurements and scanning electron microscopy (SEM). The XRD results show that the modified samples have no novel crystalline phase, indicating a high dispersion of phosphorus and boron species. After treatment, the microporous volume and surface area of the samples markedly decrease, implying the blockage of the channel. The nitrogen adsorption-desorption measurements suggest that the isothermal type of all samples is a combination of isothermal type I and IV, and all hysteresis loops resemble the H4-type in the IUPAC classification. The total acidity of the modified samples, determined by pyridine adsorption IR and TPD of ammonia, decreases in contrast to that of the parent HZSM-5. The conversion of n-heptane over P and B steam-modified HZSM-5 is higher than that of P and B-modified HZSM-5 zeolites but lower than that of the parent HZSM-5.

SYNTHESIS AND PROPERTIES OF A NOVEL COMPOSITE ZSM-5 ZEOLITE/VERMICULITE CATALYST

The composite ZSM—5 zeolite/vermiculite catalyst,in which tiny ZSM—5 zeolite parti- cles embedded in the vermiculite substrate,has been synthesized by hydrothermal method with vermiculite as silicon source.The catalytic behavior of resulting catalyst for xylene isomerization,propylene aromatization and toluene disproportionation is better than that of HZSM—5 zeolite.

不同晶型In_(2)O_(3)/片状HZSM-5串联催化剂催化CO_(2)加氢制芳烃

采用水热/溶剂热法制备了不同晶型(立方相、六方相和混晶相)In_(2)O_(3),并将其与片状HZSM-5分子筛机械混合得到CO_(2)加氢制芳烃的串联催化剂,在固定床反应器上测试了其催化活性,重点讨论了串联催化剂活性组分的空间分布对其催化性能的影响。通过XRD、SEM、N2等温吸附-脱附和Py-IR等手段对催化剂的形貌、结构和表面酸性等性质进行了表征。结果表明,当In_(2)O_(3)金属氧化物与片状HZSM-5分子筛的活性位点过于接近时,迁移到分子筛中的In物种毒化了其表面酸性,导致反应中间产物甲醇无法高效转化为芳烃,致使CO_(2)转化率与芳烃选择性降低。

Preparation and Catalytic Application of Novel Water Tolerant Solid Acid Catalysts of Zirconium Sulfate/HZSM-5

Esterification of acrylic acid（AA） to produce AA esters has widespread application in the chemical industry. A series of water tolerant solid acid catalysts was prepared, and characterized by XRD, nitrogen adsorption, TGA-DTA, XPS, and ammonia adsorption FTIR. The effects of Si/Al ratio, zirconium sulfate（ZS） loading on HZSM-5 and calcination temperature on the esterification were investigated. When 20% （mass fraction） ZS is loaded on HZSM-5, the conversion of AA reaches 100%. XRD analysis indicates that ZS is highly dispersed on HZSM-5 because no crystalline structure assigned to ZS is found. Catalytic activity and hydrophobicity of ZS supported on HZSM-5 are higher compared with those of parent ZS or HZSM-5. Results show that this kind of novel catalysts is an efficient water tolerant solid acid catalyst for esterification reactions.

Effects of ZrO_2 on the Performance of CuO-ZnO-Al_2O_3/HZSM-5 Catalyst for Dimethyl Ether Synthesis from CO_2 Hydrogenation

A series of composite catalysts were prepared by the wet mixing method, and the mass ratio of CuO-ZnO-Al2O3-ZrO2 component to HZSM-5 zeolite （molar ratio of SiO2 to Al2O3 being 25） was 2：1. The CuO-ZnO-Al2O3-ZrO2 （CuO/ZnO/Al2O3=3/6/1 by weight） component was prepared by a modified ＇two-step＇ co-precipitation method. The effects of ZrO2 on the performance of CuO-ZnO-Al2O3/HZSMo5 catalyst for dimethyl ether synthesis from CO2 hydrogenation were investigated. It was found that ZrO2 improved the properties of CuO-ZnO-Al2O3/HZSM-5 as a structural promoter.

Direct amination of isobutylene over zeolite catalysts with various topologies and acidities

The atomically economic and green chemical reaction of direct amination of isobutylene to tertbutylamine, particularly under the relative mild reaction conditions available for future industrial use,was carried out over zeolite catalysts possessing different topological structures, from one dimensional to three dimensional pore system, and from small 8-member ring pore（MRP） to medium 10 MRP and further to large 12 MRP zeolites, to disclose the relationship between the zeolite properties/topologies and their amination performance systematically under the mild reaction conditions. It was discovered that the pore structure and the acidities of zeolite catalysts played crucial roles in the isobutylene amination process, and suitable pore diameter（larger than 0.5 nm or with large side pockets/cups in the outside surface） and a certain number of mid-strong acid sites are indispensable to catalyze the amination reaction,while too strong acid strength was not conducive to the process of isobutylene amination. Among them,zeolites with topologies of BEA, MFI, MEL, MWW and EUO exhibited good amination performance, with which the isobutylene conversion was higher than 12.61%（>46.42% of the equilibrium conversion） under the studied mild reaction conditions. Due to the good amination performance and the large adjustable Si/Al;ratio range, ZSM-5 was selected to further study the effect of acidity on the amination performance systematically under the mild reaction conditions, and the activity-acidity relationship in the amination process was disclosed: the amination activity（isobutylene conversion） had a linear correlation with the amount of mid-strong B acidity under the studied conditions over ZSM-5 catalyst, which can provide guidance for further developing high-efficient amination catalyst under mild reaction conditions available for future industrial use.

Methane dehydro-aromatization over Mo/HZSM-5 catalysts in the absence of oxygen:Effect of steam-treatment on catalyst stability

The effect of steam-treatment to HZSM-5 zeolite and Mo/HZSM-5 with a steaming time range of 0.5-1 h on the catalytic performance of methane dehydro-aromatization （MDA） over Mo/HZSM-5 catalyst prepared with impregnation has been studied in detail in combination with the characterization of 1H MAS NMR technique. Both the deactivation rate constant （kd） and the Brtnsted acid sites per unit cell were calculated to quantitatively evaluate the stability of Mo/HZSM-5 catalysts treated with steam at 813 K before and after impregnation of molybdenum species, and the corresponding variation of their Brtnsted acid sites. The results reveal that a V-shape relationship between kd and the number of B 1 acid sites per unit cell is presented on Mo/HZSM-5 catalyst under the tested steam-treatment and reaction conditions.

Studies on Mo/HZSM-5 Complex Catalyst for Methane Aromatization

The influence of adding Fe, Cr, Co, and Ga into 3%Mo/HZSM-5 catalyst on methane aromatization, and the influence of additives ratio on methane conversion, selectivity to hydrocarbons and coke, as well as distribution of aromatics were investigated. The experimental results showed that the addition of Fe, Cr, Co and Ga promoted the dehydrogenation and dissociation of methane. The results of NH3-TPD indicated that the acidity of HZSM-5 was changed by adding Fe and Co components, consequently the catalytic properties of Mo/HZSM-5 were changed. It was also revealed that strong acid sites were the center of methane aromatization. The results of XRD characterization showed that the crystallinity of Mo on ZSM-5 zeolite was increased after adding Fe, Co additives.

Coking behaviors and kinetics on HZSM-5/SAPO-34 catalysts for conversion of ethanol to propylene

The coke deposition on HZSM-5/SAPO-34 composite catalysts has been studied in the conversion of ethanol to propylene. The HZSM-5/SAPO-34 composite catalysts were synthesized by hydrothermal method（ZS-HS） and fully blending（ZS-MM）. The used catalysts were characterized by XRD, N;adsorption–desorption, TGA, TPO, elemental analysis, FTIR and XPS. The coking kinetics on both ZS-HS and ZS-MM has been investigated and their coking rate equations were obtained. The used ZS-MM catalyst had higher amount of coke and lower nC:nHthan the used ZS-HS. 90% of the coke was deposited in the micropores of ZS-HS, while almost 45% of the coke located in the micropores of ZS-MM. The coke deposited on ZS-HS catalyst was mainly graphite-like carbon species, whereas dehydrogenated coke species was the major on ZS-MM. The coking activation energy of ZS-MM was lower than that of ZS-HS, and the coking rate on ZS-MM was faster than on ZS-HS. In addition, the regeneration of ZS-MM catalyst showed that it had a good hydrothermal stability. The differences on coking behaviors on the two catalysts were due to their different acidic properties and textures.

Study on attrition of spherical-shaped Mo/HZSM-5 catalyst for methane dehydro-aromatization in a gas–solid fluidized bed

As a potential methane efficient conversion process,non-oxidative aromatization of methane in fluidized bed requires a catalyst with good attrition resistance,especially in the states of high temperature,longtime rapid movement and chemical reaction.Existing evaluation methods for attrition resistance,such as ASTM D5757 and Jet Cup test,are targeted for fresh catalysts at ambient temperature,which cannot well reflect the real process.In this study,spherical-shaped Mo/HZSM-5 catalyst prepared by dipping and spray drying was placed in a self-made apparatus for attrition testing,in which the catalyst attrition under different system temperatures,running time and process factors was investigated with percent mass loss(PML),particle size-mass distribution(PSMD)and scanning electron microscope(SEM).Carbon deposition on the catalyst before and after activation,aromatization and regeneration was analyzed by thermogravimetry(TG),and the attrited catalysts were evaluated for methane dehydro-aromatization(MDA).The results show that the surface abrasion and body breakage of catalyst particles occur continuously,with the increase of system temperature and running time,and make the PML rise gradually.The process factors of activation,aromatization and regeneration can cause the catalyst attrition and carbon deposits,which broaden the PSMD in varying degrees,and the carbon-substances on catalysts greatly improve their attrition resistance at high temperature.Catalyst attrition has a certain influence on its catalytic performance,and the main reasons point to particle breakage and fine powder escape.

Catalyst activity comparison of alcohols over zeolites

Alcohol transformation to transportation fuel-range hydrocarbon over HZSM-5 （SIO2/A1203 = 30） catalyst was studied at 360 C and 300 psig. Product distributions and catalyst life were compared between methanol, ethanol, 1-propanol and 1-butanol as a feed. The catalyst life for 1-propanol and l-butanol was more than double compared with that for methanol and ethanol. For all the alcohols studied, the product distributions （classified to paraffin, olefin, naphthene, aromatic and naphthalene compounds） varied with time on stream （TOS）. At 24 h TOS, liquid product from 1-propanol and 1-butanol transformation primarily contains higher olefin compounds. The alcohol transformation process to higher hydrocarbon involves a complex set of reaction pathways such as dehydration, oligomerization, dehydrocyclization and hydrogenation. Compared with ethylene generated from methanol and ethanol, oligomerization of propylene and butylene has a lower activation energy and can readily take place on weaker acidic sites. On the other hand, dehydrocyclization of the oligomerized products of propylene and butylene to form the cyclic compounds requires the sites with stronger acid strength. Combination of the above mentioned reasons are the primary reasons for olefin rich product generated in the later stage of the time on stream and for the extended catalyst life time for 1-propanol and 1-butanol compared with methanol and ethanol conversion over HZSM-5.

Effect of Rare Earths on n-Hexane Aromatization over HZSM-5 Catalyst

The cracking and aromatization of n hexane over H ZSM 5 modified by various rare earths were investigated by means of continuous flow micro reactor. The surface properties of modified H ZSM 5 catalysts were obtained from IR, XRD and XPS. The results show that the rare earths enhance the aromatizing properties of the catalysts which are prepared by mechanical mixture method. The results of n hexane cracking and aromatization are correlated with the acidity. The Brnsted acidic sites are the active sites of n hexane aromatization, while Lewis acid site plays an important role in n hexane cracking.

清洁法制备全结晶ZSM-5分子筛催化剂及其催化性能

在无额外添加碱金属或碱土金属的体系中,以氨水为模板剂,成功制备全结晶ZSM-5分子筛催化剂。晶化结束后,采用闪蒸技术回收晶化残液中的氨水,回收率高达85%,并且实现了回收氨水的循环再利用,连续回用3次仍然可以得到高结晶的分子筛催化剂。表征结果表明,通过优化合成配方,在晶化温度为170℃,晶化时间为6 h的条件下,制备的全结晶ZSM-5分子筛催化剂具有晶体形貌规整、晶间孔丰富、活性中心状态好、机械强度高(108 N·cm^(-1))等优点。在稀乙烯和苯气相烷基化制乙苯反应中,全结晶ZSM-5分子筛催化剂表现出优异的活性、选择性、稳定性及再生性能,关键杂质二甲苯含量仅为(350~400)μL·L^(-1),完全可以满足工业应用需求。