Enhancing the Production of Light Olefins by Catalytic Cracking of FCC Naphtha over Mesoporous ZSM-5 Catalyst

The enhanced production of light olefins from the catalytic cracking of FCC naphtha was investigated over a mesoporous ZSM-5 (Meso-Z) catalyst. The effects of acidity and pore structure on conversion, yields and selectivity to light olefins were studied in microactivity test (MAT) unit at 600 °C and different catalyst-to-naphtha (C/N) ratios. The catalytic performance of Meso-Z catalyst was compared with three conventional ZSM-5 catalysts having different SiO₂/Al₂O₃ (Si/Al) ratios of 22 (Z-22), 27 (Z-27) and 150 (Z-150). The yields of propylene (16 wt%) and ethylene (10 wt%) were significantly higher for Meso-Z compared with the conventional ZSM-5 catalysts. Almost 90% of the olefins in the FCC naphtha feed were converted to lighter olefins, mostly propylene. The aromatics fraction in cracked naphtha almost doubled in all catalysts indicating some level of aromatization activity. The enhanced production of light olefins for Meso-Z is attributed to its small crystals that suppressed secondary and hydrogen transfer reactions and to its mesopores that offered easier transport and access to active sites.     

CrHZSM-5 Zeolites – Highly Efficient Catalysts for Catalytic Cracking of Isobutane to Produce Light Olefins

The CrHZSM-5 catalysts with trace amount of Cr were firstly used for catalytic cracking of isobutane, and the effect of Cr-loading on the catalytic performances of CrHZSM-5 catalysts for the cracking of isobutane was also studied. The results suggested that when the loading of Cr in the CrHZSM-5 catalysts was less than 0.038 mmol/g Cr, especially at Cr loading of 0.004 mmol/g, both the reactivity of isobutane cracking and the selectivity to light olefins of CrHZSM-5 samples were greatly enhanced compared with the unpromoted HZSM-5, and very high yields of olefins(C₂+C₃) and ethylene were obtained. For instance, the yield of olefins(C₂+C₃) and ethylene reached 56.1% and 30.8%, respectively, at 625 °C when 0.004 mmol/g Cr was loaded on HZSM-5 sample.     

Enhanced Production of C2–C4 Olefins Directly from Synthesis Gas

An attempt made for the selective production of C₂–C₄ olefins directly from the synthesis gas (CO + H₂) has led to the development of a dual catalyst system having a Fischer–Tropsch (K/Fe–Cu/AlOx) catalyst and cracking (H-ZSM-5) catalyst operate in consecutive dual reactors. The flow rate (space velocity) and H₂/CO molar ratio of the feed have been optimized for achieving higher CO conversions and olefin selectivities. The selectivity to C₂–C₄ olefins is further enhanced by optimizing the reaction temperature in the second reactor (cracking), where the product exhibited 51% selectivity to C₂–C₄ hydrocarbons rich in olefins (77%) with a stable time-on-stream performance in a studied period of 100 h.     

Experimental investigation and modeling of steam cracking of Fischer–Tropsch naphtha for light olefins

The characteristics of product distribution and the kinetic model for predicting the yields of the major products from steam cracking of Fischer–Tropsch (F–T) naphtha have been investigated in a pilot plant under various conditions. An analysis of the experimental data suggests that the naphtha produced via the low-temperature slurry-phase F–T process is an excellent feedstock for the production of light olefins, especially ethylene. For steam cracking of two F–T naphthas studied, ethylene is the primary product varying from 36.89 to 41.83 wt%, and the total yield of valuable light olefins (C₂H₄, C₃H₆ and 1,3-C₄H₆) is not less than 60.34 wt% under the conditions estimated. The experimental product distributions could be satisfactorily predicted by use of a detailed molecular reaction scheme which consists of a first-order primary reaction and 37 secondary reactions.     

Effect of process variables on product yield distribution in thermal catalytic cracking of naphtha to light olefins over Fe/HZSM-5

The effect of temperature, WHSV and Fe loading over HZSM-5 catalyst in thermal-catalytic cracking (TCC) of naphtha for the production of light olefins has been studied. The response surface defined by three most significant parameters is obtained from Box-Behnken design method and the optimal parameter set is found. The results show that ethylene increases with temperature, while propylene shows an optimum at 650 °C. Moderate WHSV is favorable for maximum production of light olefins. Addition of Fe to HZSM-5 has a favorable effect on the production of light olefins up to 6% of loading. Excess amount of loading decreases the conversion of naphtha, which leads to a drop in light olefin yields. The yield of light olefins (ethylene and propylene) at 670 °C, 44 hr⁻¹ and 6 wt% Fe has been increased to 5.43 wt% compared to the unmodified HZSM-5 and reaches to 42.47 wt%.     

Evaluation of solvent dearomatization effect in heavy feedstock thermal cracking to light olefin: An optimization study

Response surface method was used to study the effect of aromatic extraction of heavy feedstock in thermal cracking. N-methylpyrrolidone as the solvent performing dearomatization of feedstock was at different temperature and molar solvent to oil ratios. Temperature, flow rate and steam-to-hydrocarbon ratio were in the range of 1,053–1,143 K, 1–2 g/g, and 0.75–1.2 g/min, respectively. From the CCD studies, the effects of flow rate and coil outlet temperature were the key factors influencing the yield of light olefins. Ethylene and propylene yields increased more than 10% by dearomatization. C ₅ ⁺ decreased by 13% on average. Finally, we obtained the single maximum yield of ethylene, propylene, and simultaneous maximum yields for untreated and raffinate.     

Research of the Activity of Catalysts on the Base of H3PW12O40 in Partial Oxidative Conversion of C3–C4 alkanes

Catalysts from heteropoly acid H₃PW₁₂O₄₀ and its Cs, Na, Ba, Pb, Ca, Cd, Cr, Mn, V, La salts supported on clinoptilolite, alumosilicate are highly active in oxidative conversion of propane–butane (OCPB) mixture and formation of C₂–C₄ olefins, oxygen-containing compounds at temperatures T = 100–800 °C. Optimum yields of ethylene and propylene are achieved on heteropoly acid its Cs and Cr salts. The processes of oxidative dehydrogenation (ODPB) and cracking are concurrent in formation of olefins. High activity is caused by dispersity of supported catalysts (XRD, IRS) both formation of crystal hydrates and an amorphous phase of heteropoly acid in a condition of interaction with the carrier.     

Catalytic production of olefins using natural halloysite nanotubes

The production of C₂-C₄ olefins by deep catalytic cracking and the thermocontact pyrolysis of vacuum gas oil, commercial-grade cottonseed oil, and a vacuum gas oil-cottonseed oil 90: 10 mixture in the temperature range of 600–800°C is studied using natural halloysite extracted from kaolinite fields in the form of aluminosilicate sheets rolled in nanotubes. It is found that in the deep catalytic cracking of vacuum gas oil at 600°C using halloysite as a catalyst, the gain in the yield of ethylene is 6.4–10.1 wt %, compared to yields of this product when using ZSM-5 catalyst. Adding 10% commercial-grade cottonseed oil to the vacuum gas oil further increases the yield of ethylene by 2.2 wt % with a simultaneous 3.3 wt % rise in the yield of propylene. The cracking of pure cottonseed oil under identical conditions yields ethylene and propylene of 16.1 and 9.2 wt %, respectively. The possibility of using halloysite nanotubes as a heating surface for the thermal pyrolysis of the above feedstocks at temperatures of 700–800°C in order to obtain yields of C₂-C₃ olefins exceeding those of identical products in industry, and of reusing halloysites in the thermoconversion of the studied feedstocks via their complete regeneration, is confirmed.     

High efficient mesoporous HZSM-5 nanocatalyst development through desilication with mixed alkaline solution for methanol to olefin reaction

Methanol to olefin (MTO) process is a non-oil route for the light olefins production. We report the mesoporous and high siliceous HZSM-5 nanocatalyst development through the new desilication process including the mixed alkaline solution. The properties of nanocatalysts were characterized using TGA/DTA, XRD, ICP, FE-SEM, BET, FT-IR, and NH₃-TPD techniques. FE-SEM images represent the spherical morphology of parent nanocatalyst including smooth surface. The XRD analysis confirms that applied desilication does not change the typical MFI-type structure of ZSM-5 nanocatalysts. The BET and NH₃-TPD results show that mixed alkaline solution including 40 wt% TPAOH results in the best adjustment of textural (299.7 m²/g) and acidity (strong/weak ratio of 0.21) properties, respectively. The PHZ-NaTP0.4 nanocatalyst represents the highest methanol conversion (99.2%), propylene selectivity (48.3%), C₃ ⁼/C₂ ⁼ molar ratio (7.4) as well as lowest selectivity to C₁–C₄ alkanes (4.6%) for long time on stream (170 h). The low selectivity of light alkanes (C₁–C₄) and high total light olefins (ca. 75%) confirm the stable performance of nanocatalyst. Consequently, the developed PHZ-NaTP0.4 nanocatalyst is a high efficient MTO catalyst and can be candidate for commercial scale up.     

Mixed Naphtha/Methanol Feed Used in the Thermal Catalytic/Steam Cracking (TCSC) Process for the Production of Propylene and Ethylene

Abstract  

The addition of some methanol to petroleum light naphtha used as feed in the Thermal Catalytic/Steam Cracking(TCSC) process significantly increases the product yield of C₂–C₄ olefins, particularly that of ethylene + propylene. However, over 20–25 wt% of methanol content in the naphtha feed, the beneficial effect is attenuated. At relatively high values of contact time, the (Zn–Pd) co-catalyst of the hybrid catalyst exerts noticeably its coke cleaning effect on the zeolite acid sites, particularly when methanol is present in the feed. The product weight ratio (propylene/ethylene) is not affected by such “moderate” addition of methanol and remains higher than 1.3.     

A ZSM-5-based Catalyst for Efficient Production of Light Olefins and Aromatics from Fluidized-bed Naphtha Catalytic Cracking

A ZSM-5-based catalyst was prepared by spray-dry method for fluidized-bed naphtha catalytic cracking. Multi-techniques, such as X-ray diffraction, scanning electron microscope, ²⁷Al MAS NMR, and NH₃–TPD, were employed for the investigation of ZSM-5 framework stability, framework dealumination, and catalyst acidity variation in hydrothermal treatment. Catalytic performances of fluidized-bed naphtha catalytic cracking at 630–680 °C indicated that light olefins and other value-added products could be more efficiently produced compared with the commercial process of thermal steam cracking. Long-term catalytic evaluation implied that naphtha catalytic cracking over the catalyst prepared with spray-dry method and hydrothermal treatment can be carried out at a variable reaction condition with a relatively high and stable light olefins yield.     

Electrochemical reactions of halohydrins. II. Olefins formation

2-Bromoethanol was reduced to ethylene, 1-bromo-2-propanol to propylene, and 2-bromo-l-indanol to indene on Pb or Cu electrodes with R₄N⁺ electrolytes, in DMF with and without addition of water. Material and current efficiencies were high. Hydrogen was the only by-product in all cases. It is suggested that this represents a general method for the conversion of bromohydrins to olefins.     

Kinetic modeling of oxidative dehydrogenation of propane with CO2 over MoOx/La2O3–Al2O3 in a fluidized bed

A 4-step kinetic model of CO₂-assisted oxidative dehydrogenation (ODH) of propane to C₂/C₃ olefins over a novel MoO_x/La₂O₃–γAl₂O₃ catalyst was developed. Kinetic experiments were conducted in a CREC Riser Simulator at various reaction temperatures (525–600 °C) and times (15–30 s). The catalyst was highly selective towards propylene at all combinations of the reaction conditions. Langmuir-Hinshelwood type kinetics were formulated considering propane ODH, uni- and bimolecular cracking of propane to produce a C₁-C₂ species. It was found that the one site type model adequately fitted the experimental data. The activation energy for the formation of propylene (67.8 kJ/mol) is much lower than that of bimolecular conversion of propane to ethane and ethylene (303 kJ/mol) as well as the direct cracking of propane to methane and ethylene (106.7 kJ/mol). The kinetic modeling revealed the positive effects of CO₂ towards enhancing the propylene selectivity over the catalyst.     

Modeling and analysis of the Lurgi‐type methanol to propylene process: Optimization of olefin recycle

This work proposed a strategy to improve the yield of light olefins of industrial methanol to propylene process by reducing the olefins recycled back into the main reactor and appending an olefin cracking reactor. The heterogeneous fixed‐bed model was employed to simulate the reactors with a robust mathematical procedure developed to determine the reactor configuration and the recycle flow rates of the olefins. Two methods were proposed for the modulation: the recycle ratio and species of the olefins, respectively. Results show that the yield of C₂–C₃ olefins can be improved up to 70% from the basement of about 60% when the ratio is reduced from 100% to less than 23% or when only butene apart from pentene and hexene is recycled back into the main reactor, and the latter method is more effective as its catalyst requirement is seven times less than the former's in the appended cracking reactor. © 2016 American Institute of Chemical Engineers AIChE J, 63: 306–313, 2017     

Coal flash pyrolysis: 2. Polymethylene compounds in low temperature flash pyrolysis tars

Pyrolysis of coals at low temperatures (< 600 °C) produces tars containing the precursors of the low molecular weight aliphatic hydrocarbons, such as ethylene and propylene, observed on flash pyrolysis of the coals at higher temperatures (700–800 °C). This is shown by further pyrolysis of these low temperature tars at high temperatures. Various methods, including isolation by h.p.l.c. were used to confirm the presence of straight chain paraffin and olefin pairs (C₁₄C₂₆ and above) in the low temperature tars. Pyrolysis of pure paraffins and olefins in this molecular weight range at temperatures > 700 °C produce ethylene, propylene and other cracking products similar to those obtained on flash pyrolysis of coal.     

Conversion of methanol into light olefins over ZSM-11 catalyst in a circulating fluidized-bed unit

Methanol conversion and the reaction pathway were investigated in a pilot-scale circulating fluidized-bed (CFB) unit over hierarchical ZSM-11 catalyst. Experimental results indicated that ZSM-11 catalyst was highly resistant to external coke due to the formation of mesopores. Elevated temperatures favored the production of propylene and butylene and decreased the yield of ethylene. Additionally, no direct relations were shown between the formation of ethylene and other products under different pressures, suggesting that ethylene was a primary product produced at the initial of the reaction. Methylation-cracking and oligomerization were verified as the main reaction pathway for the formation of C ₃ ⁺ alkenes., Methylation and oligomerization of olefins were dominated under high methanol partial pressure and consequently responsible for the production of higher olefins, while the b-scission of C ₇ ⁼ for propene and butylene, and C ₈ ⁼ for butylene were enhanced at low methanol partial pressure.     

流化催化裂化汽油改质和增产低碳烯烃的研究

采用GL型催化剂,在小型固定流化床实验装置上考察了反应温度、剂油比、空速和水油比等操作条件对流化催化裂化(FCC)汽油催化改质汽油的产品分布、低碳烯烃(丁烯、丙烯和乙烯)产率和族组成的影响。实验结果表明,在一定反应条件下,FCC汽油通过催化改质可以降低烯烃含量,提高芳烃含量和辛烷值,在满足新汽油标准的同时提高了低碳烯烃的产率。此外,较高的反应温度、剂油比和水油比以及较低的空速有利于FCC汽油催化改质和增产低碳烯烃。     

Methanol-to-olefins over FeHZSM-5: Further transformation of products

The catalytic activity of FeHZSM-5 was investigated for the conversion of both methanol and mixed C₃° + C₄ hydrocarbons. For methanol conversion at WHSV = 1 h^− 1 and 470 °C, 0.35% FeHZSM-5 showed increased selectivity for propylene and C₂⁼–C₄⁼ olefins by 21% and 4%, respectively, compared with HZSM-5. The selectivity of propane and butylene decreased. High temperature favored the conversion of C₃° + C₄ mixture while the selectivity of ethene + propylene achieved a maximum at 470 °C. Improved olefins selectivity for methanol conversion was attributed to FeHZSM-5 with more weak acid but less strong acid amount and to further transformation of the products.     

Epoxidation of a Series of C2–C6 Olefins in the Gas Phase

Epoxidation of ethylene, propylene, 2‐methylpropene, trans‐2‐butene, 2‐methyl‐2‐butene, and 2,3‐dimethyl‐2‐butene were carried out in a flow‐through reactor in the homogeneous gas phase at pressures of 0.25–1.0 bar in the temperature range of 250–375 °C. Residence times in the reactor varied from 8.3 to 38 ms. The oxidizing agent needed in the feed gas is ozone. The O₃ efficiency (reacted olefin/initial O₃) was found to be strongly dependent on the reactivity of the olefin used. For C₄–C₆ olefins, the O₃ efficiency was better than 75 % in each case. For 2‐methyl‐2‐butene and 2,3‐dimethyl‐2‐butene, the O₃ efficiency exceeded the theoretical value of 100 % considerably. The selectivity to epoxide was about 90 % independent of the olefin used. Under conditions of nearly total olefin conversion, the high selectivity to the epoxide has been retained as unchanged. There were no indications for consecutive reactions of the epoxides.     

Characterization of AlPO4-based molecular sieves and methanol conversion to light olefins

Of the AlPO₄-based molecular sieves, A1PO₄, SAPOs, and MeAPOs of different pore sizes were prepared at 100-200°C by a hydrothermal crystallization method. This study was purposed to maximize the yield of light olefins through methanol conversion. Crystal structure was confirmed by means of XRD and SEM, and acidity was examined by TPD and IR of adsorbed ammonia on the catalysts. It was found that SAPO-34 exhibited more than 90% selectivity for light olefins such as ethylene, propylene, and butylene due to shape selectivity through small pores, although it had a strong acidity. MeAPO-34 exhibited slightly lower selectivity for light olefins than SAPO-34 and different product distribution, depending on the electronegativity of the metal in its framework. SAPO17 and SAPO-44, which have the same pore size with SAPO-34 but different pore structure from SAPO-34, showed less selectivity for light olefins than SAPO-34.