硫化物在OTA催化剂上催化转化性能

考察了催化裂化(FCC)汽油中硫化物和模型硫化物在OTA(Olefin To Aromatics)催化剂上的催化转化性能.结果表明FCC汽油硫化物总脱硫率为86.3 %,其中,硫醚和四氢噻吩的转化率都达到100 %,硫醇硫转化率96.6 %,噻吩硫转化率78.8 %,烷基噻吩转化率85.8 %,苯并噻吩转化率81.4 %.3-甲基噻吩在OTA催化剂上的转化产物中含有小分子(噻吩),异构硫化物(2-甲基噻吩),以及大分子异构硫化物(如2,5-二甲基噻吩、2,4-二甲基噻吩和2,3-二甲基噻吩).烷基噻吩和苯并噻吩硫化物在OTA催化剂上脱硫反应网络一方面含有直接加氢脱硫反应,另一方面经历歧化、异构化和裂解等反应.     

硫化物在纳米HZSM-5催化剂上催化转化性能及机理研究

研究了催化裂化（FCC）汽油中硫化物类型和含量，特别考察了各种硫化物在纳米HZSM-5催化剂上的催化转化性能，并探讨了硫化物的加氢脱硫转化机理。结果表明FCC汽油中硫化物主要为硫醇、噻吩、烷基取代噻吩和苯并噻吩等，其中，烷基取代噻吩占总硫化物的65％-73％。在纳米HZSM-5催化剂作用下，FCC汽油的硫化物都较易被脱除。烷基取代噻吩脱硫机理一方面含有直接加氢脱硫反应路线，另一方面含有裂解反应、烷基化反应和异构化反应路线。     

超临界甲醇中氧化脱除模型物中噻吩硫的研究

传统加氢脱硫往往难以脱除重油中的噻吩类硫化物。利用噻吩类硫化物氧化后的极性增加,在超临界甲醇条件下强化其在极性溶剂中的溶解度,可深度脱除重油中的噻吩硫。以二苯并噻吩(DBT)与十四烷为模型油,甲醇为超临界介质,考察了无催化时反应条件对超临界氧化脱硫性能的影响,不同催化氧化体系的脱硫效率。利用红外光谱、气相色谱-质谱联用对反应产物进行分析以研究脱硫机理。结果表明,在无催化时,反应温度260℃、反应压力8.5～9.0 MPa、反应时间3 h、过氧化二叔丁基作氧化剂且氧硫摩尔比为3:1时,噻吩模型物的脱硫率最高,达42%。在催化氧化体系中,催化剂用量与硫的摩尔比为1:10时催化剂使用效率最高,3种脱硫效果较好的催化氧化体系脱硫率分别达到了47%、45%、45%。FTIR、GC-MS结果表明二苯并噻吩被氧化为相应亚砜并转移至甲醇相,从而实现了硫化物的脱除。     

PY-GC法研究渣油中硫化物的热裂解性能

采用裂解气相色谱（PY-GC）方法研究渣油中的大分子硫化物的裂解性能。首先对（PY-GC）的实验条件进行优化,在此基础上,得到了可以反应渣油样品中硫化物组成和结构的裂解色谱图;通过标准物对比并结合文献对渣油裂解产物中硫化物的组成进行定性。研究发现,渣油高温裂解产物中的硫化物主要有：H2S、噻吩类、苯并噻吩类和二苯并噻吩类系列的化合物。根据模型化合物的裂解色谱分析结果,推测出渣油裂解产物中的H2S不仅来源于重油分子中硫醚类结构的裂解,而且与重油分子中噻吩、苯并噻吩和二苯并噻吩类结构的裂解有关,而渣油裂解产物中的噻吩、BT和DBT系列化合物主要来自于重油中的大分子噻吩、BT和DBT类化合物的裂解。     

C6～C8烃类转化及芳构化反应机理的研究

采用正己烷、正辛烷、环己烷、异辛烷、1-己烯和1-辛烯六种模型化合物，使用微型固定床反应器，采用FCC汽油芳构化、烷基化降烯烃OTA技术，考察烃类模型化合物在FDO催化剂上的反应活性和转化途径，进一步探讨了烃类芳构化反应机理。     

金属硼化物上噻吩类型硫的原位还原深度脱硫研究

研究了噻吩类型硫在金属硼化物上的原位还原深度脱硫.实验对不同金属硼化物、镍源对硼化镍的活性影响以及还原剂用量进行了评价.结果表明,硼化镍原位脱硫活性高于其它金属硼化物;采用六水合氯化镍镍源,还原剂用量为0.64 g时,脱硫率可达99%以上.通过GC-MS、IR、XRD以及XPS分析,研究了可能的反应机理,噻吩类型硫主要通过硫原子"端链吸附"在催化剂表面,发生氢解脱硫反应;噻吩脱硫产物主要为C1、C3和C4烃类,以气体形式逸出;苯并噻吩氢解脱硫产物主要为乙基苯和C7烃类产物,二苯并噻吩脱硫产物为联苯.推测反应机理为,硫化物通过硫原子"端链吸附"在活性中心,富电子镍介入硫化物中C-S键形成加合物,高活性氢进攻α-C原子,C-S键断裂,脱除硫元素多以负二价形式保留在硼化镍中.     

改性对ZSM-5分子筛芳构化性能的影响

ZSM-5分子筛由于具有独特的择形性、良好的水热稳定性、耐酸和抗积碳性能,因而被广泛应用于芳构化过程。综述了国内外对ZSM-5分子筛芳构化催化剂的改性方法。Zn的加入不仅能促进低碳烃的芳构化反应,而且能增强催化剂的抗积碳性能。随着磷的引入,液体收率增加,芳烃含量增加。Ga离子交换改性的ZSM-5对低碳烃类的芳构化有明显的催化作用。P—Zn／HZSM-5催化剂不仅表现出较高的初活性,而且具有良好的稳定性。经水热处理的ZSM-5分子筛具有良好的芳构化稳定性。纳米HZSM-5沸石催化剂具有很强的烃类转化能力,烃类通过芳构化、异构化和烷基化等反应转化为高辛烷值的异构烷烃和芳烃。     

Co-Mo/γ-Al_2O_3催化剂上噻吩与苯并噻吩加氢脱硫动力学

采用固定床等温积分反应器,以不同组成的含硫化合物作为模型化合物,在消除催化剂内外扩散影响的基础上,考察了反应温度、苯并噻吩浓度、噻吩浓度以及硫化氢分压对加氢脱硫反应速率的影响,建立了苯并噻吩和噻吩单独加氢和共加氢的LHHW型反应动力学方程,并表明以真实的原料组成和在实际操作条件下进行动力学实验的重要性。     

柴油深度脱硫三集总一级动力学模型建立

将柴油馏分中硫化物按照其加氢脱硫反应难易程度分为三个集总,建立了柴油深度加氢脱硫反应三集总一级动力学模型。运用建立的动力学模型对柴油馏分中不同类型硫化物的反应规律以及工业上几种不同类型柴油加氢脱硫催化剂的反应性能特点进行了分析。动力学模型拟合结果表明,在脱硫率为70%时,集总1已经完全脱除,生成油中剩余未转化硫化物全部为集总2和3硫化物,且随着反应深度的加深集总3的比例逐渐提高,脱硫率达到98%后,加氢精制油剩余硫化物80%以上为集总3硫化物,4,6位含空间位阻作用的二苯并噻吩(DBT)硫化物的脱除是深度脱硫反应过程的速率控制步骤。相比于另外两个集总硫化物,集总3的脱除反应提温敏感性较差,较高的压力和较低的空速下有利于这部分硫化物的脱除。运转评价结果也表明催化剂1相比于催化剂2和3在深度加氢脱硫反应过程受热力学平衡限制作用更加明显:以原料2为反应进料,在反应压力6.0 MPa、体积空速1.0 h-1条件下催化剂1加氢脱硫生成油硫含量随反应温度变化曲线在370℃下出现拐点。而在相同压力、体积空速1.5 h-1条件下,催化剂2和3上随着反应温度的升高,产品硫含量逐渐降低,在试验的温度范围内,未出现温度拐点。催化剂2和3表现出了更好的对集总3的脱除效率以及更好的提温敏感性,更适合工业装置上深度脱硫反应过程。     

汽油和柴油中含硫化合物加氢脱硫反应机理研究进展

环境保护意识的大幅度提升促使车用燃料质量标准日益严格,为实现汽油和柴油中硫含量不断降低的目标,迫切需要研发超深度脱硫技术.目前加氢脱硫技术是大规模工业化应用的关键技术,其核心是高效催化剂的研制.介绍了FCC汽油及柴油中所含各类硫化物的加氢脱硫反应路径,主要讨论了其中难以脱除的噻吩类、苯并噻吩类、二苯并噻吩类和4,6-二...     

催化裂化汽油临氢异构化/芳构化改质过程的反应特性

采用工业Ni-Mo/Al₂O₃-HZSM-5催化剂在小型固定床加氢微反装置上对催化裂化（FCC）汽油临氢改质过程的反应特性进行了研究,通过考察反应温度、压力、空速和氢油体积比对改质后的FCC汽油烃类组成的影响,分析了汽油中不同烃类的转化性能。结果表明,氢油比对产物组成影响不大,高温、低压、低空速有利于增加芳烃的选择性,低温、高压、高空速则有利于增加异构烷烃的选择性;临氢改质后,FCC汽油的烯烃含量明显降低,芳烃和异构烷烃含量增加,因而产品汽油的辛烷值基本保持不变;全馏分、轻馏分和重馏分FCC汽油临氢改质实验结果表明,烯烃含量较高的轻馏分具有更高的转化活性;在FCC汽油临氢改质过程中,同碳数的端烯烃反应活性高于内烯烃,直链烯烃的反应活性高于支链烯烃。     

The effect of heavy aromatic sulfur compounds on sulfur in cracked naphtha

The scope of the present study was to elucidate the effect of heavy sulfur compounds, commonly found in the gas oils, on the percentage of sulfur in gasoline range during the Fluid Catalytic Cracking (FCC) process. Five model sulfur compounds commonly found in the gas oils were studied: benzothiophene, 2-methyl-benzothiophene, 3-decyl-thiophene, dibenzothiophene and 4,6-dimethyl-dibenzothiophene. In order to maintain a realistic hydrocarbon environment each one of the heavy sulfur model compounds were diluted in conventional gas oil. Their cracking behaviour were studied using a steamed deactivated FCC catalyst, while the run tests were performed in an automated Short Contact Time Microactivity Test Unit (SCT-MAT) operated at 560 °C and 12 s run time. The experimental results indicated that the long chain alkyl-thiophene (3-decyl-thiophene) is mainly responsible for the increase of sulfur amount in the gasoline range during cracking, through dealkylation and side cracking reactions for the production of thiophene and shorter chain alkyl-thiophenes, respectively. That sulfur compound was also the most reactive one with respect to desulfurization, since it was highly cracked to H₂S and decomposed to S in coke. On contrary, the polycyclic sulfur compounds did not affect the sulfur amount in gasoline, while their reactions were strongly related to their chemical structure. Thus, the main reaction pathway of the alkylated 2-methyl-benzothiophene and 4,6-dibenzothiophene during the FCC process was isomerization, while for benzothiophene and dibenzothiophene alkylation reactions were dominated.     

Transformation of olefin over Ni/HZSM-5 catalyst

Olefins in the cracked naphtha can be transformed into aromatics and isoparaffin to reduce the olefin content as well as to improve the octane number. In this work, Ni/HZSM-5 bifunctional catalyst was prepared and was characterized by nitrogen adsorption, FT-IR analysis with adsorbed pyridine as well as by X-ray powder diffraction analysis. The activity of the catalyst was investigated with the transformation of 1-hexene. The experimental results show that the main reactions occurring over Ni/HZSM-5 at relatively low temperature are cracking and isomerization of 1-hexene, which results in the high concentration of olefin in the hydrotreated product. The double-bond isomerization of 1-hexene is dominant at low temperature (<220 °C) while the skeletal isomerization is elevated at high temperature, and the aromatization activity of the Ni/HZSM-5 catalyst is promoted by high temperature. The sulfided Ni/HZSM-5 catalyst shows higher aromatization activity than the reduced one and the zeolite supported Ni catalysts show comparatively better stability than that without metal components.     

Retrofitting of Fixed-Bed Heterogeneous Reactors for Glucose Isomerization

A retrofitting strategy is proposed here that can enhance the conversion level while significantly reducing the pressure drop in fixed-bed glucose isomerization reactors. The proposed strategy utilizes hollow support matrix for enzyme immobilization instead of commonly used solid spherical support. The absence of core in hollow catalytic support helps to lower diffusional resistances, thus ensuring a better utilization of the catalytic material. This leads to higher conversion in the reactor. Moreover, the use of hollow packing yields high bed void fraction, which helps to substantially lower the pressure drop. Specifying the proposed hollow support matrix as being either cylindrical or ring shaped, a rigorous heterogeneous model for the glucose isomerization reactor is developed here. The model validity is first tested by using reported experimental data for spherical support. Using the present model, the reactor performance can be optimized in terms of shape parameters of the proposed hollow support for enzyme immobilization.     

Thiophene conversion under mild conditions over a ZSM-5 catalyst

Refiners are nowadays actively considering the post-treating FCC gasoline processes as a viable and less costly approach for meeting sulfur environmental regulations. Most promising catalytic desulfurization processes do not require hydrogen addition, including between others the use of zeolites as adsorbents/catalysts. This type of desulfurization leads to the formation of significant amounts of coke, requiring keeping high catalyst activity a continuous twin fluidized bed system (fluidized-bed reactor, fluidized bed regenerator). This study evaluates the catalytic conversion of thiophene and/or thiophene in n-octane mixtures. Catalytic experiments are carried out in the CREC riser simulator under mild conditions, using H-ZSM5 zeolite dispersed in a silica matrix. The experimental results obtained demonstrate a higher selective conversion of thiophene over n-octane. It is shown that thiophene conversion proceeds via ring opening and alkylation yielding H₂S, alkyl-thiophenes, benzothiophene, and coke, with no measurable thiophene saturation or dimerization reactions observed. The experimental results are also supported with an extensive thermodynamic analysis that includes all the possible thiophene conversion pathways over zeolites. On this basis and using as a reference the observable measurable species, a reaction network is proposed to represent the thiophene catalytic conversion under the suggested gasoline post treatment conditions.     

Purification of hydrocarbons from aromatic sulfur compounds by supercritical carbon dioxide extraction

Supercritical carbon dioxide extraction to purify samples of model hydrocarbons (tetralin, decalin, and tetradecane) containing various aromatic sulfur compounds (benzothiophene, dibenzothiophene, and 4,6-dimethydibenzothiophene) was studied. The influence of extraction temperature and pressure was investigated for the extraction from a tetralin-dibenzothiophene system in the range of 293-353 K and 8-15 MPa, and it was found that the amount of tetralin extracted increased with an increase in carbon dioxide density, while the separation factor decreased with an increase in carbon dioxide density. High recovery and high separation factor values for the tetralin-dibenzothiophene system were obtained under 10 MPa at 313 K. Higher separation factor was obtained for tetralin than decalin and tetradecane, containing 4,6-dimethyldibenzothiophene than that containing dibenzothiophene.     

Pressure and temperature effects on the hydrogenation of coal-derived asphaltene

Pressure and temperature effects on hydrogenation reactions were examined using coal-derived asphaltene at 390,420 and 450 °C, under 3 and 10 MPa of hydrogen partial pressure. Higher conversion was obtained at higher reaction temperatures. Benzene-insoluble material (Bl) was formed at higher temperatures especially at low hydrogen pressure, this Bl being one-third of the reaction product at 450 °C. From structural analysis of unreacted asphaltenes and product oils, at 390 °C, it was concluded that smaller molecular components convert to oil initially and the larger molecules remain as unreacted asphaltene. Under higher hydrogen pressure for all temperatures carbon aromaticity (f_a) and number of aromatic ring per structural unit (R_aus) in unreacted asphaltenes were lower than those under lower hydrogen pressure suggesting that hydrogenation of the aromatic nucleus was promoted by higher pressure. At lower hydrogen pressure, R_aus for asphaltenes at higher temperature is larger than that at lower temperature. This suggests that at lower hydrogen pressure, dehydrogenation or condensation reactions occur more easily. A large effect at higher hydrogen pressure was a reduction in the extent of condensation reactions. Higher reaction temperatures contribute to splitting of bridged linkages so reducing molecular size and degree of aromatization.