Effects of steaming-made changes in physicochemical properties of Y-zeolite on cracking of bulky 1,3,5-triisopropylbenzene and coke formation

The effects of acidic properties and structural changes of Y zeolite, produced by steaming, on the zeolite cracking activity, coking tendency and distribution of various products during catalytic conversion of bulky 1,3,5-triisopropylbenzene (TIPB) are reported. NaY zeolite with framework Si/Al ratio of 2.4 was synthesized by a hydrothermal method and ammonium exchanged. The zeolite was dealuminated by a temperature-programmed steaming to form USY1 and USY2 zeolites with framework Si/Al ratio of 8.1 and 12.3 respectively. The catalysts were characterized by XRD, XRF, SEM, AAS, NH₃–TPD and N₂ adsorption–desorption techniques. The samples were in-situ activated at 748 K and evaluated by TIPB cracking at 623 K. The coke content of the catalyst beds was estimated by TPO using an FT-IR gas cell. The results of activity measurements reveal that the dealuminated zeolites lead to lower cracking activity initially; while, they exhibit higher activity at longer times. In addition, a slight modification of the window diameter of Y zeolite, as revealed by pore size distribution analyses, alters the diffusion limitation of the reactant and products through the pores of the zeolite and significantly affects the adsorbent–adsorbate interactions. TPO experiments show that compared to the precursor zeolite, lower amount of coke is formed on the dealuminated catalysts possessing lower density of acid sites. However, the coke formed on USY samples is heavier than that formed on its precursor Y zeolite. This may be attributed to the larger pores shaped in the dealuminated catalysts which in turn provide suitable places for coke formation and growth.     

Challenges, catalyst technology and catalytic solutions in resid FCC

The concurrent evolution of resid fluid catalytic cracking (RFCC) processes and catalyst technology over the years is discussed. Resid FCC catalysts today are designed making use of the following features: (a) High activity, selectivity and metals resistant zeolites; (b) Highly accessible catalyst architecture for optimal site utilization, bottoms cracking, Conradson carbon residue (CCR) conversion and easy stripping; and (c) Specially designed metal-support interaction systems to reduce the detrimental effects of metal contaminants. The future will require even more robust RFCC catalyst systems. These catalyst systems should be very accessible and effective in cracking large hydrocarbon molecules and should have the capability to handle contaminants such as metal-, sulfur-, and nitrogen-compounds. Conversion of CCR to non-coke components will be crucial in order to reduce the delta coke and hence improve the processability of heavier resids. Processability here is meant not only in terms of coke and heat balance considerations, but also involves avoiding fouling of the unit hardware by unconverted heavy hydrocarbons and coke precursors. Last, but not the least, present and future catalyst technology must be formulated and adapted to the specific commercial process unit needs and constraints, thus leading to the most cost effective solution for the refiner.     

Correlation of reactor performance with catalyst structural changes during coke formation in FCC processes

In the present study an attempt is made to relate the structural properties of Fluid Catalytic Cracking (FCC) catalysts with the process performance. Stochastic network models are employed to represent the porous structure of two catalysts with similar catalytic activity but different pore structure based on N₂ porosimetry experiments. Accordingly, reaction and deactivation are studied by means of a transient model based on percolation theory. Extension at the reactor level is achieved by employing the mixing cell in series model. The results show that at early times the catalyst with the larger surface area and pore volume shows higher conversion and yield while, at the same time, has a lower fraction of poisoned sites in the porous network. At later stages the catalyst with the higher degree of connectivity exhibits stronger resistance to structural phase transition due to pore plugging. Comparison between experimental and simulation N₂ isotherms during catalyst deactivation shows excellent agreement between model and experiment confirming the mechanism of coke formation. Further comparison with experimental results at the reactor level shows very good agreement in terms of both conversion and yield differences between the two catalysts. The close agreement between model and experiments in both catalyst structure and reactor conversion for two entirely different structures of FCC catalysts opens up the possibility of architectural design of these catalysts for optimum process performance achievement.     

Catalytic behaviour of nickel and iron metal contaminants of an FCC catalyst after oxidative and reductive thermal treatments

The catalytic effects of nickel and iron deposited on an FCC (fluidized catalytic cracking) catalyst via metal naphthenates were studied in a micro activity test (MAT) unit after both oxidative and reductive treatments of the catalyst samples.The dehydrogenation activity of nickel was found to be close to the dehydrogenation activity of vanadium – and not several times higher than that of vanadium as is often reported – when deposited on the commercial FCC catalyst used in this study followed by steam deactivation (oxidative treatment) at 760 °C. However, the dehydrogenation activity of nickel was significantly intensified after post-treatment with a CO/N₂ mixture at this temperature (reductive treatment).The results show that iron did not have a dehydrogenation activity after steaming, but had a significant dehydrogenation activity after steaming when followed by exposure to the CO/N₂ mixture at 760 °C. The results indicate that the presence of deposited iron was inducing an additional catalytic cracking activity for the FCC catalyst.It was observed that co-impregnation of equal loadings of nickel, iron and vanadium on the FCC catalyst led to a considerably higher dehydrogenation activity than could be expected from the catalytic behaviour of the separate elements. The dehydrogenation activity was however slightly reduced by the reductive treatment as the reduced dehydrogenation activity from the lower oxidation state of vanadium (V³⁺) more than compensated the increased dehydrogenation activity of iron and nickel. A slightly increased gasoline production after the reductive treatment of the co-impregnated sample was a result of the increased production of gasoline from the FCC catalyst itself, which more than compensated for the reduced gasoline production from nickel.     

Nature of nitrogen specie in coke and their role in NOx formation during FCC catalyst regeneration

NO_x emission during the regeneration of coked fluid catalytic cracking (FCC) catalysts is an environmental problem. In order to follow the route to NO_x formation and try to find ways to suppress it, a coked industrial FCC catalyst has been prepared using model N-containing compounds, e.g., pyridine, pyrrole, aniline and hexadecane–pyridine mixture. Nitrogen present in the FCC feed is incorporated as polyaromatic compounds in the coke deposited on the catalyst during cracking. Its functionality has been characterized using XPS. Nitrogen specie of different types, namely, pyridine, pyrrolic or quaternary-nitrogen (Q-N) have been discriminated. Decomposition of the coke during the catalyst regeneration (temperature programmed oxidation (TPO) and isothermal oxidation) has been monitored by GC and MS measurements of the gaseous products formed. The pyrrolic- and pyridinic-type N specie, present more in the outer coke layers, are oxidized under conditions when still large amount of C or CO is available from coke to reduced NO_x formed to N₂. “Q-N” type species are present in the inner layer, strongly adsorbed on the acid sites on the catalyst. They are combusted last during regeneration. As most of the coke is already combusted at this point, lack of reductants (C, CO, etc.) results in the presence of NO_x in the tail gas.     

CFD modeling of gas-solid flow and cracking reaction in two-stage riser FCC reactors

The Eulerian-Eulerian approach was applied to simulate the flow behavior and catalytic cracking reactions in the riser reactors of two-stage riser fluid catalytic cracking (TSRFCC) technology. A k-ε-k_p-ε_p-Θ gas-solid turbulent flow model was used, which took account of the particle turbulence and the interaction of turbulence between gas and particle phases. A 14-lump kinetics model was used for simulating cracking reactions. The approach and model were validated with both experimental results and commercial data. The distributions of particle fraction volume and velocity, as well as product yields in the TSRFCC riser reactors were first analyzed. The simulations were then carried out for optimization studies to understand the influence of the operating conditions on the performance of commercial TSRFCC riser reactors. The model and results presented here are valuable for the design and optimization of TSRFCC technology.     

FCC汽油脱硫降烯烃催化剂的烧炭再生研究

对失活的FCC汽油脱硫降烯烃催化剂FDO进行了烧炭再生处理,并用浸渍法对烧炭再生后的催化剂进行了载Ni处理。用XRD、XRF、NH₃-TPD和FT-IR等方法对所得催化剂进行了表征,采用小型固定床反应器,在温度370 ℃、压力3.0 MPa、空速3.0 h^-1和氢油体积比600的反应条件下,评价了催化剂的催化性能。结果表明,烧炭再生处理可以使失活FDO催化剂的芳构化降烯烃性能得到完全恢复,但不能完全恢复其脱硫能力。在烧炭再生的基础上进一步负载适量Ni,可以使失活FDO催化剂的芳构化降烯烃性能和脱硫能力得到令人满意的恢复。     

Catalytic degradation of waste polyolefinic polymers using spent FCC catalyst with various experimental variables

Liquid-phase catalytic degradation of waste polyolefinic polymers (HDPE, LDPE, PP) over spent fluid catalytic cracking (FCC) catalyst was carried out at atmospheric pressure with a stirred semi-batch operation. The effect of experimental variables, such as catalyst amount, reaction temperature, plastic types and weight ratio of mixed plastic on the yield and accumulative amount distribution of liquid product for catalytic degradation was investigated. The initial rate of catalytic degradation of waste HDPE was linearly increased with catalyst amount (4-12 wt%), while that was exponentially increased with reaction temperature (350-430 ‡C). Spent FCC catalyst in the liquid-phase catalytic degradation of polymer was not deactivated fast. The product distribution from catalytic degradation using spent FCC catalyst strongly depended on the plastic type. The catalytic degradation of mixed plastic (HDPE: LDPE: PP: PS=3: 2: 3: 1) showed lower degradation temperature by about 20 ‡C than that of pure HDPE.     

第三代降烯烃催化剂GOR-Ⅲ的开发和工业应用

针对进一步增强催化剂的降烯烃能力、汽油辛烷值不降或少降、提高重油裂化能力和改善产品的市场需求,开发了第三代降烯烃催化剂GORⅢ并进行了工业应用。工业应用结果表明,采用新型基质材料ASP、改性活性组分制备的GORⅢ催化剂降烯烃能力强,同时能在一定程度上提高稳定汽油的辛烷值,且汽油的诱导期延长,催化汽油性质有所改善。GORⅢ催化剂具有活性高、重油裂化能力强,产品选择性好,轻质油收率高等优点。     

改性Ｙ型沸石催化剂在苯和二异丙苯烷基转移反应中稳定性的研究

采用水蒸汽处理与离子交换结合的方法对ＮａＹ沸石进行了改性。通过ＴＰＤ、ＸＲＤ、比表面和孔径分布测定等方法研究了催化剂的晶相结构、孔结构及表面酸性质。使用固定床等温积分反应器对改性Ｙ型沸石催化剂在苯和二异丙苯烷基转移反应中的稳定性进行了评价,并采用无梯度反应器装置测定了上述烷基转移反应中失活催化剂的结炭量及Ｃ／Ｈ。结果表明,在烷基转移反应中具有良好稳定性的催化剂不仅需要具备一定的各类酸量,而且要具备较大的比表面积和较高的结晶度,同时还要具有适中的孔径。沸石催化剂的结构与结炭反应密切相关,不同结构的沸石催化剂,即使参与同一化学反应,催化剂上结炭反应形式亦各异。     

Two-stage cracking catalyst of amorphous silica-alumina on Y zeolite for enhanced product selectivity and suppressed coking

A novel bilayer catalyst composed of amorphous silica-alumina (ASA) layer coated on Y zeolite layer is proposed as a fluid catalytic cracking (FCC) catalyst to cause two-stage reactions of pre-cracking and deep-cracking. The bilayer catalyst (Y/ASA) is compared with the usual mixed one (ASA+Y), in catalytic cracking of a feed composed of 1,3,5-triisopropylbenzene and naphthalene. The two catalyst representations were prepared by applying layers of Y zeolite and ASA or both on inert monolith supports. Catalytic cracking experiments were carried out at 300, 350 and 400 °C. Compared to Y+ASA, Y/ASA yielded about 33% and 46% more benzene and toluene, respectively, and 18% less coke in the catalytic cracking at 350 oC. The coke of Y/ASA was less refractory than that of Y+ASA as burnt at lower temperatures, while emitting less carbon monoxide in regeneration. Y/ASA configuration shows promising features as FCC catalysts for increased bottoms cracking and suppressed coking.     

Enhancing propylene production from catalytic cracking of Arabian Light VGO over novel zeolites as FCC catalyst additives

The catalytic cracking of vacuum gas oil over fluid catalytic cracking (FCC) catalyst containing novel additives was investigated to enhance propylene yield. A conventional ZSM-5, mesoporous ZSM-5 (Meso-Z), TNU-9 and SSZ-33 zeolite were tested as additives to a commercial equilibrium USY FCC catalyst (E-Cat). Their catalytic performance was assessed in a fixed-bed micro-activity test unit (MAT) at 520 °C and various catalyst/oil ratios. The cracking activity of all E-Cat/additives did not decrease by using these additives. The highest propylene yield of 12.2 wt.% was achieved over E-Cat/Meso-Z compared with 9.0 wt.% each over E-Cat/ZSM-5 and E-Cat/TNU-9, at similar gasoline yield penalty. The enhanced production of propylene over Meso-Z is attributed to its mesopores that suppressed secondary and hydrogen transfer reactions and offered easier transport and accessibility to active sites. The lower enhancement of propylene over the large-pore SSZ-33 additive was due to its high-hydrogen transfer activity. Gasoline quality was improved by the use of all additives, as octane rating increased by 7-12 numbers for all E-Cat/additives.     

催化裂化汽油加氢脱硫技术研究

主要介绍了原油中硫化物种类和催化裂化(FCC)汽油加氢脱硫反应原理,介绍了9种FCC汽油后处理脱硫工艺技术,其中催化加氢脱硫技术(HDS)在工业中得到了广泛应用,而吸附脱硫、氧化脱硫等新型工艺技术则显示出较好的发展前景。     

Laboratory Testing of FCC Catalysts and Hydrogen Transfer Properties Evaluation

The importance of fluid catalytic cracking of hydrocarbons (FCC) as a leading process in the chemical industry has been acknowledged for a long time. Present data on feedstock processing and its overall economical impact confirm such a role [1, 21. Technical, economic, and environmental concerns have played significant roles as driving forces in the research conducted on FCC matters, leading to developments that are identifiable along catalytic cracking chronology (e.g., fluid bed technology, zeolite catalyst introduction, promotor addition, octane boosting).     

Laboratory Testing of FCC Catalysts and Hydrogen Transfer Properties Evaluation

The importance of fluid catalytic cracking of hydrocarbons (FCC) as a leading process in the chemical industry has been acknowledged for a long time. Present data on feedstock processing and its overall economical impact confirm such a role [1, 21. Technical, economic, and environmental concerns have played significant roles as driving forces in the research conducted on FCC matters, leading to developments that are identifiable along catalytic cracking chronology (e.g., fluid bed technology, zeolite catalyst introduction, promotor addition, octane boosting).     

催化裂化汽油加氢精制技术研究

加氢脱硫降烯烃技术在FCC汽油加氢脱硫及烯烃饱和的同时,很好地减少汽油辛烷值损失问题。介绍了采用HDDO-01催化剂与HDDO-02催化剂组合工艺,对催化裂化汽油进行加氢处理,w（硫）〈50μg/g,汽油辛烷值损失〈2。     

FCC汽油选择性深度加氢脱硫催化剂研究

采用固定床反应器,研究了催化剂载体原料、助剂以及螯合剂(M)对FCC汽油选择性加氢脱硫催化剂的活性及选择性影响,并对催化剂进行了200 h的稳定性试验。结果表明,采用大小孔拟薄水铝石混配原料和添加硼、钙、铈制备的载体,催化剂具有适宜的酸性中心和最佳的脱硫选择性;当M/Co+Mo=0.25～0.3时,选择性为最好,在200 h的试验运转过程中,具有较高的脱硫率和较低的烯烃饱和率,其活性稳定性良好。     

催化裂化平衡剂生焦因子和生氢因子的考察

探讨了催化裂化平衡剂生焦因子和生氢因子的评价方法。考察了操作条件、平衡剂金属含量以及原料油性能对生焦因子和生氢因子的影响规律。     

A comparative study of liquid product on non-catalytic and catalytic degradation of waste plastics using spent FCC catalyst

Non-catalytic and catalytic degradation of waste plastics (high-density polyethylene (HDPE), low-density polyethylene (LDPE), polypropylene (PP) and polystyrene (PS)) using spent fluid catalytic cracking (FCC) catalyst into liquid product were comparatively studied with a stirred semi-batch reactor at 400 ‡C, under nitrogen stream. Liquid product characteristics were described by cumulative distribution as a function of lapse time of reaction, paraffin, olefin, naphthene and aromatic (PONA) composition, and also carbon number distribution on plastic type of reactant. For degradation of waste PE with relatively high degradation temperature, the effect of adding spent FCC catalyst greatly appeared on cumulative distribution of liquid product with a reaction lapse time, whereas those for waste PP and PS with low degradation temperature showed a similar trend in both non-catalytic and catalytic degradation at 400 ‡C. In PONA and carbon number distribution of liquid product, the characteristics of waste PS that was mainly degraded by end chain scission mechanism were not much altered in presence of spent FCC catalyst. However, waste polyolefinic polymer that was degraded by a random chain scission mechanism significantly differed on PONA and carbon number distribution of liquid product with or without spent FCC catalyst. The addition of spent FCC catalyst in degradation of polyolefinic polymer, which economically has a benefit in utilization of waste catalyst, significantly improved the light olefin product by its high cracking ability and also the aromatic product by cyclization of olefin as shape selectivity in micropore of catalyst.