分子筛负载铂催化剂上四氢萘加氢裂解反应行为

四氢萘是多环芳烃加氢转化的产物或者中间体,其加氢裂解行为和规律的研究在重芳烃转化和脱除领域有着重要的意义。采用等体积浸渍法制备得到了氧化铝负载贵金属(Pt,Ir和Pd)催化剂和酸性分子筛(MOR和ZSM-5)负载铂双功能催化剂,考察了它们催化四氢萘加氢裂解的反应行为。氧化铝为载体时金属催化剂表面主要发生加氢及脱氢反应,其中金属Pt表现出最高的加氢和脱氢活性。双功能催化剂上四氢萘发生加氢裂化、异构化、氢转移及烷基化等复杂反应,金属Pt通过氢溢流作用提高了分子筛Br?nsted酸活性从而提高催化剂加氢裂解活性和选择性,但过量金属Pt会加剧苯环加氢而不利于单环芳烃的生成。分子筛孔道的限域作用对四氢萘的反应活性及产物分布有重要影响,相比Pt/ZSM-5催化剂,Pt/MOR表现出更高的裂解活性及异构化选择性。Pt/MOR催化剂上四氢萘加氢裂解主要通过异构-裂解路径进行,异构化活性及异构体构型决定了裂解活性及产物的分布。     

煤直接液化条件下萘-四氢萘加氢转化反应行为

以纳米Fe_2O_3为催化剂,在0.5 L高压釜中考察了反应压力19 MPa下,不同反应温度(435℃~465℃)和反应时间(0 min~120 min)对萘-四氢萘体系加氢转化过程及产物分布的影响。根据实验结果和分析,建立了萘-四氢萘体系加氢转化反应机理模型,通过优化算法求解得到各反应的反应速率常数和活化能。结果表明:萘很快达到转化平衡状态,且低温和长停留时间有利于萘的加氢转化;萘的加氢反应速率高于四氢萘的脱氢反应速率,在四氢萘的加氢反应中,以异构化反应为主,主要生成甲基茚满和丁基苯。反应物萘、四氢萘、十氢萘(反)、十氢萘(顺)、1-甲基茚满、正丁基苯和烷基苯的质量分数的实验值和模拟值的相对偏差分别为4.56%,1.35%,9.60%,7.24%,8.29%,10.64%和10.07%。     

高温下工业NiW/Al2O3催化剂上萘的加氢饱和反应

在中压固定床中,高温条件下研究了工业NiW/Al2O3催化剂上硫化氢气氛中反应温度、反应压力和空速对萘加氢饱和反应过程的影响。实验结果表明,在液时空速为10—30 h-1,氢油体积比为800,高反应温度区320—380℃的实验条件下,萘加氢主要生成四氢萘和十氢萘,而进一步加氢裂化产物较少;提高反应温度,萘转化率和四氢萘的收率下降,加氢裂化产物略有升高,表明高温不利于芳环的加氢饱和;提高加氢反应压力,萘的转化率和四氢萘的芳环加氢程度提高;综合反应结果,提出了高温条件下萘加氢的简化可逆连串反应途径。     

十氢萘在HY和Beta分子筛上加氢开环的研究

采用高温高压反应釜研究了十氢萘在低硅铝比HY分子筛[n(Si)/n(Al)=3.2]、Beta分子筛n(Si)/n(Al)=9.7]和双功能催化剂Pt-HY、Pt-Beta上的加氢开环反应,考察了分子筛孔道结构及酸性质、贵金属Pt及反应温度等因素对十氢萘转化率和产物选择性的影响。结果表明,十氢萘在Beta分子筛上的转化率较高,且有大量脱氢缩合产物（DHC）生成。Pt引入HY和Beta分子筛后,初始反应速率升高,十氢萘转化率增加,C₁₀产物中开环异构比增大,Beta分子筛上的脱氢缩合反应得到抑制。反应温度升高可以提高十氢萘在HY分子筛上的转化率,使得C₁₀产物选择性下降,而开环异构比（ROP/Iso）增大。     

NiMo/HY催化剂上四氢萘加氢裂化反应网络与热力学平衡分析

采用固定床反应器对四氢萘在NiMo/HY工业催化剂上的加氢裂化反应过程进行了研究,考察了反应温度对产物分布的影响,提出了四氢萘加氢裂化反应网络。该网络包含加氢、异构、脱氢、开环、脱烷基等12个反应,通过热力学计算,得到了这些反应的平衡常数,并据此求得各类产物的平衡收率及其随温度、压力和氢气/四氢萘（摩尔比）的变化规律。由热力学平衡分析得到的产物收率随反应条件的变化规律与实验结果较为吻合,表明本文构建的反应网络可以较好地描述NiMo/HY催化剂上的四氢萘加氢裂化反应体系。     

NiMo/HY催化剂上四氢萘加氢裂化反应网络与热力学平衡分析

采用固定床反应器对四氢萘在Ni Mo/HY工业催化剂上的加氢裂化反应过程进行了研究,考察了反应温度对产物分布的影响,提出了四氢萘加氢裂化反应网络。该网络包含加氢、异构、脱氢、开环、脱烷基等12个反应,通过热力学计算,得到了这些反应的平衡常数,并据此求得各类产物的平衡收率及其随温度、压力和氢气/四氢萘(摩尔比)的变化规律。由热力学平衡分析得到的产物收率随反应条件的变化规律与实验结果较为吻合,表明本文构建的反应网络可以较好地描述Ni Mo/HY催化剂上的四氢萘加氢裂化反应体系。     

煤高温快速液化过程中的单原子与双原子氢转移机理

氢转移对煤的加氢液化至关重要,理解氢转移机理对于改善煤液化过程具有重要意义。在微型反应釜中通过考察氢气的溶解、溶剂类型以及不同类型催化剂对煤高温快速液化的影响,揭示了煤高温快速液化过程中单原子氢和双原子氢的转移机理。结果表明,在以四氢萘、氢气为条件的高温快速液化过程中,主要的活性氢来源于溶剂所提供的单原子;在以四氢萘、氮气为条件的高温快速液化过程中,不同催化剂对溶剂提供单原子氢的影响不同。在以四氢萘和萘、氢气为条件的高温快速液化过程中,双原子氢基本未参与液化反应,溶解并不是其参与液化反应的主要影响因素。以萘为溶剂、氢气气氛下的高温快速液化过程中,双原子氢参与反应需要一定的时间。在以萘或四氢萘、氢气为条件的高温快速液化过程中通过加入一定量的催化剂,可以促使双原子氢快速参与反应。     

磷改性USY分子筛催化剂上四氢萘选择性开环反应性能

通过P改性对USY分子筛酸量进行调节,考察酸量对四氢萘选择性开环反应的影响。结果表明,P改性后USY分子筛弱酸量增加,中强酸略增,强酸基本不变,P_(0.5)-USY分子筛弱酸量增加有利于四氢萘生成不饱和开环产物。负载贵金属Pt后,Pt_(0.4)/P_(0.5)-USY催化剂上四氢萘转化率99.37%,开环选择性40.79%,贵金属Pt的引入对结焦前驱体的生成有抑制作用。     

煤液化油中低级酚生成的影响因素研究

为了探究反应温度、反应压力、催化剂添加量以及供氢溶剂对褐煤直接液化油中低级酚生成的影响以及低级酚生成的机理,利用模型化合物邻苄基苯酚在煤直接液化条件下进行加氢反应。实验结果表明:邻苄基苯酚在液化条件下主要发生桥键断裂反应生成低级酚,苯环不易被加氢饱和。温度升高对促进邻苄基苯酚桥键断裂有利;压力升高则不利于其桥键断裂;铁系催化剂添加量的增加会促进桥键断裂;供氢溶剂四氢萘相比十氢萘会抑制低级酚的生成。邻苄基苯酚加氢液化的产物以苯酚与甲苯为主,邻甲酚与苯相对较少。     

芳烃催化加氢反应机理的研究进展

对萘、菲、蒽及芘根据不同计算方法所得的反应活性位进行总结,对苯在金属表面的催化加氢机理-芳烃交换机理进行概括,对菲在MoS₂/Al₂O₃催化剂表面生成二氢菲的基元反应步骤和在Ni-MoS₂/Al₂O₃催化剂表面加氢生成四氢菲的过程进行总结,还给出了蒽的催化加氢反应网络图,分析了在不同催化条件下蒽是否有中环断裂情况的发生,给出了芘在RaneyNickel（W-7）催化剂表面生成二氢芘、四氢芘和六氢芘的催化加氢机理反应图,以及根据能量最低理论,判断芘发生加氢反应的优先位置情况,分别计算了芘加氢生成二氢芘、四氢芘、六氢芘和十氢芘可能存在的加氢路径。并总结了蒽、菲等多环芳烃发生催化加氢反应的规律。加深对多环芳烃催化加氢机理的研究将更好地指导重质油轻质化的进行,因此对多环芳烃催化加氢机理的研究具有重要意义。     

合成羟基功能化聚酯的研究进展

概括介绍了合成羟基功能化聚酯的几种方法,主要有线形缩聚法、开环聚合法、羟基保护和脱保护法、在聚酯的侧链中引入羟基法和酶催化聚合法。对每种合成方法的特点进行了评述：线形缩聚法的原料来源丰富、价格便宜,但是工艺条件苛刻;开环聚合法的反应时间短、产物性能较好,但是分离和回收工艺成本高;羟基保护和脱保护法的实验步骤多、产物产率低;在聚酯侧链中引入羟基法的原料不易制备、工艺成本高;酶催化聚合法的反应条件温和,但是酶的价格高、导致工艺成本高。     

Evaluation of different reaction strategies for the improvement of cetane number in diesel fuels

Cetane number improvement of diesel fuels is a difficult task that refiners will face in the near future. Aromatics saturation by deep hydrogenation is a necessary, but perhaps not sufficient step in the diesel treatment. Some researchers have proposed selective ring opening (SRO) as an additional step in the upgrading. In this work, we explore some possible reaction pathways of compounds typically found in diesel after different levels of hydrogenation, i.e. decalin (decahydronaphthalene), perhydrophenanthrene, tetralin (1,2,3,4-tetrahydronapthalene), as well as 1-ring and 2-ring aromatic phenanthrenes. We have estimated the cetane number (CN) of each individual compound involved in the reaction pathways, using an artificial neural network program that was trained with pure compound cetane numbers from a database. The results demonstrate the great challenge that reaching high CN represents. In the conversion of decalin, acidic catalysts alone are not able to yield products with CN significantly higher than the decalin feed. Similarly, no significant gain in CN can be expected with hydrogenolysis metal catalysts operating via the dicarbene mechanism. Only in the case of selective metal-catalyzed hydrogenolysis, with preferential cleavage at substituted C–C bonds, the predicted products have CN substantially higher than the decalin feed. As expected, branching has a strongly negative effect on the CN and it should be minimized. Both, metal-catalyzed di-carbenium C–C cleavage and acid-catalyzed ring contraction/ring opening combination leave branching groups in the product. Similarly, the acid-catalyzed ring opening of perhydrophenanthrene does not result in a significantly higher CN than the initial feed. The possibility of minimizing hydrogen consumption in the CN improvement process by an initial partial hydrogenation followed by ring opening was tested by using phenanthrene and tetralin as probe molecules. In the first reaction strategy, partially hydrogenated phenanthrenes (1-ring and 2-ring aromatics) were followed by ring opening of one of the saturated rings. Although this option would lead to lower overall hydrogen consumption, it results in products of much lower CNs than the ones obtained by full hydrogenation of phenanthrene. Similar results are obtained for tetralin. From this analysis, it is clear that upgrading CN of diesel requires extensive hydrogen consumption. For further upgrading, highly selective hydrogenolysis catalysts are needed in order to minimize branching and therefore obtain high CN products.     

Alkanes and solvent dimers in successive extract fractions released from coal during liquefaction in a flowing-solvent reactor

Types of alkanes present in liquefaction product fractions released from coal during successive time—temperature intervals were examined by g.c.—m.s. Experiments were carried out in a flowing-solvent reactor where solubilized products are continuously removed from the reaction zone; tetralin, quinoline and hexadecane were used as the solvent. At 450°C (with 400 s holding) total conversions in tetralin, quinoline and hexadecane were 82.5, 74.7 and 24 wt% (daf), respectively. In tetralin, alkanes were released from coal more readily and at lower temperatures than in quinoline or hexadecane; m.s. signal intensities fell rapidly with increasing reaction temperature. In quinoline, lower intensities of alkane peaks were observed than in tetralin, although the trend with temperature was similar. In hexadecane however, the trend of intensity with temperature was reversed compared with liquefaction in tetralin or in quinoline; the range of alkanes detected was also smaller than in tetralin or in quinoline. The presence of alkenes in the hexadecane extracts suggested a pyrolytic mechanism for the thermal breakdown. Isoprenoid alkanes, pristane and phytane, were detected in the tetralin and quinoline extracts but not those prepared in hexadecane. Materials present in product mixtures and thought to originate with each solvent were briefly investigated: dimers were the most prominent species in tetralin extracts, with only low-intensity dimers being found in quinoline extracts and no apparent formation of higher homologues from hexadecane. These results were compared with the pattern of alkane release from coal during liquefaction in tetralin in a conventional minibomb reactor and in the pentane-soluble fraction of the total (unfractionated) extract from the F-S reactor.     

Upgrading of tall oil to fuels and chemicals over HZSM-5 catalyst using various diluents

The upgrading of crude tall oil (CTO) to fuels and chemicals was studied at atmospheric pressure and in the temperature range 370 to 440°C in a fixed bed microreactor containing HZSM-5. The oil was co-fed with diluents such as tetralin, methanol and steam. High oil conversions of the order of 80–90 wt. % were obtained using tetralin and methanol as diluents but with steam the conversion only ranged between 36 to 70 wt. %. The maximum concentration of gasoline range aromatic hydrocarbons in the liquid product was 52 and 57 wt. % with tetralin and steam but only 39 wt. % with methanol. The amount of gas product in most of the runs was 1–4 wt.%. A reaction scheme is postulated based on the results.     

Comparative study of the hydrogenation of tetralin on supported Ni, Pt, and Pd catalysts

The hydrogenation of tetralin in the vapor phase has been investigated over Ni, Pt, and Pd catalysts to determine the evolution of the trans- and cis-decalin products as a function of conversion over the different catalysts. The concentration of each isomer in the product may be important in subsequent ring opening steps if cetane number improvement is desired. The cis-decalin isomer is preferred to open the naphthenic ring in a selective way instead of multiple cracking. However, thermodynamically, this isomer is the least favored; so, kinetic control is the only solution. By selecting the proper catalyst and operating conditions, one could keep the trans/cis-decalin ratio low. In this study, we have prepared a series of supported metal catalysts and tested them in a flow reactor at 3540 kPa and 548 K. Kinetic parameters for the hydrogenation of tetralin and the cis-to-trans-decalin isomerization over the various catalysts investigated were obtained by fitting the data with a generalized Langmuir–Hinshelwood model.

The kinetic analysis revealed that the relative rates of tetralin hydrogenation, as well as the cis-to-trans isomerization are greatly affected by adsorption site competition of decalin and tetralin, which in turn has different magnitudes over the different catalysts. At tetralin conversions above 30%, the Ni catalyst yields the lowest trans/cis-decalin ratio. In contrast, the trans/cis ratio on Pd catalyst remains constant at all conversion levels and is highest at low tetralin conversion. It is concluded that the trans/cis ratio is a combination of the intrinsic selectivity of each isomer and the isomerization reaction.     

四氢萘加氢裂化集总模型的建立与考察

选用国产３８２５加氢裂化催化剂，利用ＷＦ８０００Ａ型连续流动固定床微型反应器，以四氢萘为模型化合物，研究了重质馏分加氢型裂化集总动力学，根据原料，生成物的性质和沸点差异，建立了四氢萘加氢裂化七集总反应网络。     

Reaction mechanism of coal hydrogenation: 1. Two-ring solvent system

Taiheiyo coal was hydrogenated in naphthalene, tetralin and decalin under 10 MPa (initial pressure) of hydrogen or nitrogen with stabilized nickel as catalyst at 400 °C for 15 min. Preasphaltene, asphaltene and oil conversions and the conversion of the solvents were measured. The hydrogen absorbed by coal from molecular hydrogen and from the donor solvent was calculated. The main reaction route appears to be the direct hydrogenation of coal by molecular hydrogen, with the side reaction via solvent by molecular hydrogen occurring only slightly, when an active catalyst such as stabilized nickel is present.