Experimental study on coking, deactivation, and regeneration of binderless 5A zeolite during 1-hexene adsorption

Coking, deactivation, and regeneration of 5A zeolite during 1-hexene adsorption were studied on a fixed-bed adsorber and a themogravimetric analyzer. Adsorption activity measurement, scanning electron microscope (SEM) analysis, X-ray diffraction (XRD) analysis, FT-IR analysis, ¹H NMR analysis, and porosity measurement were used to reveal the mechanism of coking and deactivation of 5A zeolite, and evaluate the influences of binder on them. There are distinct increases in both coke content and deactivation degree with increasing the adsorption temperature. Deactivation degrees of zeolite increase as coke contents rise, however, they display smaller increasing rate at higher coke content. The rates of coke formation and deactivation of 5A zeolite are significantly enhanced by the binder mainly due to the fact that the activity sites offered by the amorphous compounds contained in the binder catalyze the formation of coke precursors. As compared to the coke formed in zeolite with binder, the coke in binderless zeolite is more aromatic. The coke which consists of inflammable part and nonflammable part can be oxidatively removed completely while the temperature approaches 787 K. No destruction in 5A zeolite crystal structure was observed in the regenerated binderless sample. The formation of coke during 1-hexene adsorption on zeolite can be explained using the carbonization-cyclization reaction mechanism. Furthermore, the kinetics models for formation and removal of coke were developed.     

The influence of adamantane on the reaction of n -heptane over H-Y, H-β and H-mordenite zeolites

The effect of adamantane (Ad) on the activity and selectivity of acidic zeolites Y, β and mordenite (M) in the isomerization and cracking ofn-heptane (C₇) in He at 443 K was studied.Ad was found to promote the isomerization of C₇. TheAd uptake of the zeolites, and the IR spectra obtained from the zeolite-boundAd were determined. It was found thatAd did not remain completely unconverted under the conditions of the C₇ reaction. The activity of the catalysts in the conversion ofAd increased in the sequence of H-Y<H-β<H-M. Existing data suggest that a fraction of theAd, responsible for the cocatalytic effect, can participate in hydride transfer processes and remain unconverted, while another fraction, depending on catalyst acidity, is converted to dimer and oligomers.     

Cracking of n-hexane on Na, H-mordenite: Coke poisoning

n-Hexane cracking was studied on Na, H-mordenites at 400 °C under atmospheric pressure. It was found that the degree of exchange of Na⁺ for H⁺ affected both the initial and the steady state activity of the mordenite. The deactivation by coke also varied with the degree of proton exchange of the zeolite.

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- Na, H- 400°C . , , Na⁺ H⁺. .

     

反应条件对Ni-CaO-ZrO2催化剂上CH4-CO2重整反应及积炭的影响

用共沉淀法制备了Ni-CaO-ZrO₂催化剂,并将其用于CH₄-CO₂重整反应。考察了反应温度、空速和反应物配比对催化剂性能和积炭的影响。通过热力学计算和实验表征研究发现,反应条件对CH₄-CO₂重整反应结果和积炭有重要的影响。由于高温条件同时有利于CH₄裂解和碳物种的及时消除,升高温度可以提高催化剂的活性和稳定性。增大空速则使CH₄的转化率和消碳反应的速率均降低,导致积炭量增加。同时,反应物配比对催化剂表面的积炭量也有很大影响;稍高的CO₂/CH₄摩尔比有利于抑制CH₄-CO₂重整反应过程中的积炭。     

煤质对H2/Ar等离子体热解制乙炔的影响

选取12种不同变质程度的煤，通过等离子体热解实验考察了煤的挥发分产率、煤中氧质量分数、灰分产率对乙炔收率和结焦的影响。研究结果表明，挥发分产率为30%～40%的烟煤，热解时具有较高的乙炔收率；含氧量越高的煤，生成的碳氧化物越多，相应的乙炔收率较低；煤中的矿物质与乙炔收率之间并不存在相关性，但煤中的矿物质有利于CO的生成。影响结焦量的主要因素与煤的矿物质密切相关，煤中掺入二氧化硅和天然河沙能够明显增加结焦量，改变结焦形态。     

Isomerization of m-xylene on H-mordenite and H-clinoptilolite catalysts

The catalytic properties of Hungarian natural H-mordenite and H-clinoptilolite were studied. The accompanying substances in the rock were found to be catalytically inactive in the reaction investigated. The active centers of clinoptilolite and mordenite are the OH groups with IR bands at 3610 and 3600 cm^–1, respectively. In the case of activation above 550 °C, active sites are also the Lewis centers formed during dehydroxylation. The initial rate of m-xylene isomerization can be described by a Langmuir type equation. In a single reaction step the shift of the methyl groups occurs only between two neighboring carbon atoms of the benzene ring.

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H- H-. , . — OH - 3610 3600 ^–1, . 550 °C . . - . .

     

Frequencies, anharmonicities, and dissociation energies of OH groups in H-mordenite

Harmonic frequencies, anharmonicities and dissociation energies of surface hydroxy groups in H-mordenite have been determined. The application of the Lippincott-Schroeder potential function for similar problems is proposed.

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, -. - .

     

格尔木渣油加氢反应及生焦行为的研究

选用超低沥青质含量的格尔木渣油（沥青质质量分数：0.32%）作为加氢原料,考察反应条件对加氢反应样品组分性质、胶体稳定性参数（CSP）、生焦性能的影响。结果表明,随着加氢反应温度的升高和反应时间的延长,沥青质和饱和分的含量增加,胶质和芳香分的含量减少;胶体稳定性参数降低,生焦率不断增加;胶质与沥青质的缩合度增加,芳碳率f_A不断增大;金属与杂原子在加氢过程中不断得到脱除,V比Ni更容易脱除、S比N更容易脱除;催化剂表面形成了类似石墨有序结构的炭基物质,使得催化剂的孔结构参数不断减小。在所研究的反应中,当反应温度和时间分别为420℃和5 h时,催化剂的孔结构损害最为严重,出现了较大的微孔分布。     

煤中Se、Cd在焦化过程中迁移规律的研究

利用现代分析测定仪器和实验室模拟手段,以煤及固相(焦炭)、液相焦化产物(焦油、氨水)、气相焦化产物(煤气)中有害微量元素镉(Cd)、硒(Se)为研究对象。通过测定,比较不同煤化度煤种微量元素的含量,并归纳探讨了配合煤中Cd、Se元素在焦化过程中的迁移规律。发现煤化度不同的煤中,镉元素随着煤变质程度升高而减少;硒元素含量对比:QFFM,JM和SM中含量相差不大。在模拟焦化温度1 000℃环境下,分别有45%的硒和48%的镉元素转移到焦炭中,2%的硒和7%的镉转移到氨水中,12%的硒和15%的镉转移到焦油中,并通过物料衡算,发现有41%的硒和30%的镉释放到煤气中。     

Effects of alumina phases on CO2 sorption and regeneration properties of potassium-based alumina sorbents

A range of potassium-based alumina sorbents were fabricated by impregnation of alumina with K₂CO₃ to examine the effects of the structural and textural properties of alumina on the CO₂ sorption and regeneration properties. Alumina materials, which were used as supports, were prepared by calcining alumina at various temperatures (300, 600, 950, and 1,200 °C). The CO₂ sorption and regeneration properties of these sorbents were examined during multiple tests in a fixed-bed reactor in the presence of 1 vol% CO₂ and 9 vol% H₂O. The regeneration capacities of the potassium-based alumina sorbents increased with increasing calcination temperature of alumina. The formation of KHCO₃ increased with increasing calcination temperature during CO₂ sorption, whereas the formation of KAl(CO₃)(OH)₂, which is an inactive material, decreased. These results is due to the fact that the structure of alumina by the calcination temperature is related directly to the formation of the by-product [KAl(CO₃)(OH)₂]. The structure of alumina plays an important role in enhancing the regeneration capacity of the potassium-based alumina sorbent. Based on these results, a new potassium-based sorbent using δ-Al₂O₃ as a support was developed for post-combustion CO₂ capture. This sorbent maintained a high CO₂ capture capacity of 88 mg CO₂/g sorbent after two cycles. In particular, it showed a faster sorption rate than the other potassium-based alumina sorbents examined.     

腐植酸型煤气化特性及动力学研究

以低活性福建无烟粉煤为原料,采用腐植酸型煤黏结剂,制得腐植酸型煤。比较研究型煤和无烟煤在常压条件下的气化动力学和气化特性。运用等温热重法,在900~1 150℃进行水蒸气气化实验,测定了型煤和无烟煤的反应速率、转化率与时间的关系,考察了常压下温度和煤样对气化反应的影响。采用积分缩核模型对实验数据进行拟合关联,得到煤样水蒸气气化反应的动力学参数。结果表明,型煤的气化反应活化能(102.0 kJ/mol)低于福建无烟煤(122.5 kJ/mol)。950℃下型煤的化学反应性(80.0%)优于福建无烟煤(33.0%)。型煤较福建无烟煤表现出更好的化学反应性,可代替优质块煤用于工业固定床煤气化。     

Toluene disproportionation and coking on zeolites Y modified with Lewis-connected InO acid sites

The effect of introduction of Lewis acid sites on the reactions of toluene transformation and catalysts coking has been studied over parent (Si/Al = 2.5) and dealuminated (Si/Al = 3.7) Y zeolites modified with Lewis connected InO⁺ cationic acid sites. The catalysts with prevalent amount of Brönsted acid sites (less than 40% of protons exchanged by InO⁺) possess the typical for the proton directed reaction of methyl transfer upon toluene disproportionation long period of activation, the longer the higher the concentration of bridging protons. In contrast, at predominant Lewis sites concentration, the activation period disappear, an enhanced initial activity is observed, followed by deactivation on the expense of a rapid process of accumulation of strongly held reaction products and intermediates. Their further condensation leads to catalysts aging, the faster the higher the concentration of electron acceptor Lewis acid sites. A relation has been found between the initially accelerated processes of alkyl transfer and the reinforced formation of carbonaceous deposits over the In-modified catalysts.     

Effect of carbon nanotubes dispersed in binder on properties of epoxy nanocomposite

Effect of quality parameters of starting raw materials, native carbon nanotubes (degree of defectiveness, thermal stability, morphology) on the properties of carboxylated and amidated nanotubes produced from these raw materials and on the homogeneity of a dispersion of amidated nanotubes in an epoxy oligomer was studied. The physicomechanical properties of epoxy nanocomposites produced from these dispersions were examined. It was found experimentally that an increase in the defectiveness of native nanotubes leads to a rise in the size of numerous aggregates in dispersions composed of an epoxy resin and amidated carbon nanotubes and, as a result, to deterioration of the physicomechanical characteristics of epoxy nanocomposites based on these dispersions.     

Physicochemical and pyrolysis properties of SARA fractions separated from asphalt binder

Journal of Thermal Analysis and Calorimetry - To further understand thermal properties of asphalt binder, four fractions, namely saturates, aromatics, resins and asphaltenes (SARA), were first...