Aromatization of FCC Gasoline Over Modified HZSM-5 Catalyst

Zinc and phosphorus incorporated HZSM-5 catalyst was prepared by adopting incipient wet co-impregnation (Zn-P/HZSM-5). Zn-P/HZSM-5 catalyst exhibited the lowest acidity but the highest aromatization activity with stable performance in the studied period of 16 hr. The process conditions on aromatization reaction and the coke deactivation mechanism of Zn-P/HZSM-5 catalyst were studied on a small-scale, fixed bed reactor using FCC naphtha (75-120°C). The weight contents of ZnO and P₂O₅ were 2% and 4%, respectively. Results showed that Zn-P/HZSM-5 catalyst under a temperature of 450°C, liquid hourly space velocity of 1.0 h^-1, and pressure of 0.1 MPa, the conversions of olefins and alkanes are 96.77% and 88.94%, respectively, the contents of olefins, aromatics in liquid product are 6.79% and 74.57%, respectively. Carbon deposition was the major reason for catalyst deactivation due to the catalyst's good performance as a fresh catalyst after regeneration. All of the blending products fitted the standards of Chinese gasoline.     

正戊烷和甲醇共芳构化反应中Zn/ZSM-5催化剂的失活研究

对正戊烷和甲醇共芳构化反应与单独芳构化反应进行了比较,通过催化剂连续反应及再生的方法对共芳构化反应中导致Zn/ZSM-5催化剂失活的因素进行了系统的探究,并采用X射线衍射(XRD)、氨气程序升温脱附(NH3-TPD)、吡啶吸附红外光谱(Py-FTIR)、氮气吸附-脱附等方法对新鲜剂和再生后的催化剂进行了表征。结果表明：共芳构化反应相比于甲醇单独芳构化反应,催化剂失活减慢,共芳构化反应相比于正戊烷单独芳构化反应,可以得到更高的芳烃选择性;共芳构化反应中有甲醇存在时,催化剂除了积炭失活外,还存在分子筛水热脱铝失活,导致再生后的催化剂不能完全恢复原有的活性。     

直馏汽油芳构化改质催化剂结焦失活规律研究

利用等温固定床反应器研究了直馏汽油芳构化改质催化剂的结焦失活规律.试验考察了结焦量对催化剂物理性质、酸性质、活性的影响,研究了反应温度、反应时间对催化剂结焦量的影响.结果表明:随着结焦量的增加,催化剂的孔体积、比表面积、强弱酸量都有不同程度的减少,说明催化剂结焦不仅堵塞催化剂孔道,而且覆盖催化剂的部分酸中心,从而导致催化剂失活.随反应时间的延长,催化剂结焦量趋于饱和,此后,少量增加的结焦即能引起催化剂性能的显著降低.反应温度的提高能使催化剂的结焦速率迅速增加.     

低碳烃芳构化催化剂结炭规律的研究

测定了低碳烃芳构化过程中Ga-ZSM-5的活性、结炭量、结炭C/H比、酸密度等,考察了结炭量与它们间的关系,提出了Ga-ZSM-5的多层多中心结炭失活模型:(1)结炭先发生在沸石晶体外表面(结炭2％前);然后主要在孔道交叉点结炭(2—8％间);结炭8％后,一些小分子烃被阻封在孔内,构成孔内积炭。(2)对Ga-ZSM-5,酸中心先结炭,只酸中心中毒。引起的失活效应小;当它与Ga中心同时结炭时,产生协同失活效应,引起的失活较显著。     

Aromatization of FCC Gasoline Over Modified HZSM-5 Catalyst

Abstract

Zinc and phosphorus incorporated HZSM-5 catalyst was prepared by adopting incipient wet co-impregnation (Zn-P/HZSM-5). Zn-P/HZSM-5 catalyst exhibited the lowest acidity but the highest aromatization activity with stable performance in the studied period of 16 hr. The process conditions on aromatization reaction and the coke deactivation mechanism of Zn-P/HZSM-5 catalyst were studied on a small-scale, fixed bed reactor using FCC naphtha (75–120°C). The weight contents of ZnO and P₂O₅ were 2% and 4%, respectively. Results showed that Zn-P/HZSM-5 catalyst under a temperature of 450°C, liquid hourly space velocity of 1.0 h^?1, and pressure of 0.1 MPa, the conversions of olefins and alkanes are 96.77% and 88.94%, respectively, the contents of olefins, aromatics in liquid product are 6.79% and 74.57%, respectively. Carbon deposition was the major reason for catalyst deactivation due to the catalyst's good performance as a fresh catalyst after regeneration. All of the blending products fitted the standards of Chinese gasoline.     

轻烃芳构化催化剂的再生

考察了轻烃移动床芳构化ZSM-5纳米级分子筛催化剂的积炭速率,研究其再生工艺条件和再生动力学。结果表明:适宜的轻烃芳构化ZSM-5催化剂再生条件为：再生温度450 ℃、再生气中氧体积分数1%、再生气/催化剂体积比2400;计算得出了芳构化ZSM-5催化剂表面积炭燃烧的动力学方程lnK_c=－3.696×10³/T－3.625,其中积炭燃烧速率对氧分压的反应级数为1.049,对催化剂积炭含量的反应级数为1.060,积炭燃烧活化能为3.121×10⁴ J/mol。烧炭动力学方程的建立为开发移动床催化剂连续再生工艺打下了基础。     

催化剂积炭失活的网络模型

采用随机网络模型模拟球形催化剂的积炭失活过程，探讨了不同的反应条件下催化剂的失活机理，得到了反应组分的有效扩散系数及反应的本征反应速率常数随积炭量的变化关系。模拟结果表明，在一定的积炭量下，催化剂的活性主要与积炭的位置及焦炭相对增长速率有关。积炭位置越靠近催化剂外表现，积炭的相对增长速率越小，催化剂的活性越低。同时，考察了异丙苯催化裂化催化剂的失活过程，与模拟结果进行了定性比较，并根据本模型对实验结果进行了分析与解释。     

苯与丙烯烷基化反应中温度对Y沸石催化剂失活的影响

研究了丙烯与苯反应中反应温度对改性Y沸石催化剂失活的影响。通过TG、元素分析、FT-IR和裂解-色质等手段,分析了失活催化剂中的"焦炭"。结果表明,在较低反应温度下,催化剂失活的原因可能是由于沸石孔口直径为0 7～0 8nm,在超笼内生成较大分子的产物或中间化合物很难扩散出去,滞留在超笼中,导致孔口堵塞;在较高反应温度下,催化剂失活原因可能是催化剂活性中心缓慢地被积碳占据,直至积碳堵塞孔口后,活性便迅速下降。     

醚后碳四在ZSM-5分子筛催化剂上的芳构化反应性能

在小型固定床试验装置考察了ZSM-5分子筛催化剂对醚后碳四芳构化反应的催化性能,并进行了催化剂长周期活性稳定性评价。结果表明：在反应温度为380 ℃、反应压力为2.0 MPa、氢油比体积比为300、质量空速为2.0 h-1的条件下,催化剂的长周期运行活性稳定,烯烃转化率大于99%,干气产率小于2%,液化气产率为57%～64%,C5+液体收率为35%～41%,芳烃产率为10%～12%。经过 984 h长周期运行后,芳构化催化剂的积炭量为11.56%。气相产物是优质的裂解制乙烯原料。     

烷烃芳构化Pt/KL催化剂失活与再生的研究

分析表征了失活催化剂的比表面积、孔体积、晶相、积炭量和Pt晶粒粒度,并与新鲜催化剂进行了比较。结果表明,积炭堵塞L分子筛孔道和Pt晶粒聚集长大是催化剂失活的主要原因。同时考察了烧炭温度对催化剂再生性能的影响。结果表明,烧炭可以有效恢复催化剂的比表面积、孔体积和反应性能,并且低温烧炭可减缓Pt晶粒的烧结,有利于催化剂的再生,适宜的烧炭温度为370℃。     

原位红外技术对芳构化催化剂HZSM－5反应过程的研究

采用原位流动红外技术测试了ＨＺＳＭ－５分子筛原粉、粘合剂氧化铝和工业芳构化催化剂中Ｂ酸及Ｌ酸的酸度，并研究了正己烷芳构化的机理及催化剂结焦失活问题。试验发现分子筛原粉以Ｂ酸为主，氧化铝以Ｌ酸为主，催化剂中Ｂ酸Ｌ酸各占一定比例；结焦后的催化剂Ｂ酸及较强Ｌ酸下降比较明显；正己烷在芳闷化过程中生成很多物种，有环己烯、取代苯等。     

Specifics of the deactivation of acid and zinc-containing propane aromatization catalysts

The specifics of the deactivation of acid and Zn-containing MFI catalysts in the propane aromatization reaction at high-feed space velocities (600–2400 h^?1) and temperatures (550–610°C) was studied. The kinetics of the buildup of carbonaceous products (coke) was investigated in situ during the catalytic reaction in a thermal analyzer coupled to a mass spectrometer and a gas chromatograph (TA-MS-GC). The nature of the coke was studied by means of differential thermal analysis (DTA) and elemental analysis. It was found that the buildup of heavy coke on the H-MFI zeolite takes place on the outer crystal surface and pore openings, thus leading to a decrease in the propane conversion at the beginning of the reaction. In contrast, light coke appears first and is transformed to heavy coke at later stages on Zn/H-MFI. The light coke leads to a decrease in the yield of methane, ethane, and ethylene, and the heavy coke impedes the formation of aromatic hydrocarbons.     

Modeling of Coke Formation and Catalyst Deactivation in Propane Dehydrogenation Over a Commercial Pt-Sn/γ-Al2O3 Catalyst

Propane dehydrogenation was carried over a commercial Pt-Sn/γ-Al₂O₃ catalyst at atmospheric pressure and reaction temperatures of 580, 600, and 620°C and WHSV of 11 h^?1 in an experimental tubular quartz reactor. Propane conversions were measured for catalyst time on stream of up to nine days. The amounts of coke deposited on the catalyst were measured after one, three, six, and nine days on stream using a thermogravimetric differential thermal analyzer (TG-DTA) for each reaction temperature. The coke formation kinetics was successfully described by a coke formation model based on a monolayer-multilayer mechanism. In addition, catalyst deactivation was presented by a time-dependant deactivation function. The kinetic order for monolayer coke formation was found to be two, which would support a coke formation step involving two active sites. The kinetic order for multilayer coke formation was found to be zero. The activation energy for monolayer coke formation was found to be 29.1 kJ/mol, which was lower than the activation energy of about 265.1 kJ/mol for multilayer coke formation indicating that the presence of metals can promote coke formation on the catalyst surface.     

Characteristics of Coke Deposition Over a SAPO-34 Catalyst in the Methanol-to-Olefins Reaction

The deactivation of SAPO-34 catalyst in the methanol-to-olefins process has been studied at temperatures of 400 to 475°C. The catalyst activity keeps stable before a rapid deactivation occurs at a critical coke content. The analysis of retained coke species showed that methylbenzenes were the most abundant species at lower temperatures (400°C and 425°C), while polycyclic aromatics became the dominant species at 475°C. The growth in the retained coke species with increasing temperature comes from the enhanced reactivity of methylbenzenes and methylnaphthalenes at high reaction temperature, where methylnaphthalenes may function as another active reaction centers.     

焦化蜡油催化裂化反应过程生焦特性

 利用催化裂化工业平衡催化剂RGD-1,在提升管催化裂化中试装置和小型固定流化床实验装置上研究了大庆焦化蜡油催化裂化反应过程的生焦特性。采用吡啶红外法表征了积炭催化剂的表面酸性质,并对所生成焦炭的种类进行了分析。结果表明,在与直馏蜡油相同积炭率的条件下,焦化蜡油积炭催化剂的活性损失更大。焦化蜡油催化裂化反应生成的焦炭由吸附焦C_ad、脱氢缩合焦C_dh和氢转移焦C_ht构成。C_ad由碱性氮化物在L酸中心化学吸附所形成,是导致催化剂活性大幅度下降的主要原因,在催化裂化加工焦化蜡油过程中,必须牺牲部分催化剂的L酸中心以供C_ad沉积。常规反应条件下的焦炭组成中,在催化裂化加工焦化蜡油过程中,必须牺牲部分催化剂的L酸中心以供C_ad沉积。常规反应条件下的焦炭组成中,C_ad的质量分数约占20%;C_dh是焦炭的主要来源,质量分数占总生焦量的60%左右;氢转移焦C_ht的生成量受二次反应进行的程度影响很大,适当提高反应温度、缩短反应时间能够抑制氢转移反应的进行,减少C_ht的生成量,有利于降低焦炭选择性。     

异丙苯裂化催化剂ASTRA-MB1积炭失活机理

通常催化剂的积炭失活由两种情况引起：活性位被覆盖和孔被堵塞。在热重分析仪上以异丙苯裂化反应为模型反应，采用CCAP（恒碳Arrhenius关系图）技术探讨了裂化催化剂SATRA-MB1的积炭失活机理，得到了反应速率常数和有效扩散系数随积炭量的变化规律。结果表明，当反应温度低于573K时，也的堵塞对催化剂的活性影响较大，当反应温度高于623K时，积炭主要发生在催化剂的外表面，其上的活性位被覆盖是造成催化剂失活的主要原因。理论上，通过降低催化剂粒径以增加其外表面的活性位数目，是提高催化剂利用率的有效途径。     

Deactivation features of gallium-containing zeolites in the propane aromatization process

Conversion of propane to aromatic hydrocarbons on Ga-containing zeolite catalysts prepared by various methods has been examined, and their comparative stability against deactivation has been analyzed. It has been shown that the Ga-containing zeolite catalysts exhibit high activity and stability in propane conversion to aromatic hydrocarbons. Specific features of the formation of carbon deposits on the surface of Ga-containing zeolites in the propane aromatization reaction have been revealed using the techniques of temperature-programmed desorption of ammonia, low-temperature adsorption of nitrogen, differential thermal analysis, high-resolution transmission electron microscopy, and characteristic X-ray spectroscopy radiation. It has been found that the coke deposited on the catalyst has an almost homogeneous structure and is characterized by relatively low degree of polycondensation.     

纳米HZSM-5沸石催化剂上催化裂化轻汽油的芳构化

利用小型固定床加压反应器在纳米 HZSM-5沸石催化剂上进行了流化催化裂化(FCC)轻汽油(馏出温度小于等于85℃的馏分)的芳构化反应。实验结果表明,在反应温度为360～400℃、反应压力为1.0～3.0 MPa、重时空速为1.0～4.0 h~(-1)、V(H_2)∶V(原料)为260、反应时间48 h 的条件下,FCC 轻汽油中的 C_5~+烯烃转化率为39.11%～97.92%,产物中芳烃净增量为2.59%～19.05%,说明 FCC 轻汽油可在纳米 HZSM-5沸石催化剂上有效进行芳构化反应。汽油收率低和催化剂失活快是 FCC轻汽油在纳米 HZSM-5沸石催化剂上进行芳构化反应需要解决的两个主要问题。对纳米 HZSM-5沸石催化剂进行必要的改性处理及脱除原料中的二烯烃杂质呵以改进 FCC 轻汽油芳构化催化剂的性能。     

Aromatization Reaction of Liquefied Petroleum Gas

Abstract

The aromatization reaction of liquefied petroleum gas has been studied by using Huabei liquefied petroleum gas as raw material and LBO-A as catalyst, and the four lumped kinetics models network have been put up forward on the basis of lumped theory and the aromatization reaction mechanism. In the network, the aromatization reaction species were firstly lumped into C₄, propylene, low-molecular hydrocarbon, liquid, and coke. A mathematical method is first introduced to study on the product distribution of liquefied petroleum gas aromatization reaction. The results from experimental data are in accordance with the quantitatively analytical conclusions drawn from the calculated data.     

酸性及酸量对甲醇制丙烯催化剂性能影响及再生工艺研究

考察了积炭焙烧及离子交换前后酸性和酸量的变化对失活MTP催化剂催化性能的影响,同时对失活催化剂进行了离子交换再生工艺研究。除了MTP催化剂表面积炭堵塞分子筛内孔通道入口导致催化剂失活,积炭覆盖催化剂部分酸性位以及工艺蒸汽中Na＋扩散至催化剂表面,部分取代H质子的位置,从而使催化剂酸性下降也是导致MTP催化剂失活的原因。积炭失活可通过焙烧恢复活性,而催化剂碱金属中毒只能通过离子交换恢复催化剂酸性的手段得以再生。采用焙烧脱炭和离子交换去除碱金属毒物的再生方法,失活催化剂MTP反应性能得以基本恢复,反应470h后,甲醇转化率保持在99％以上,丙烯选择性可达46％。