Propylene Yield Research Articles

Catalytic performance of H-ZSM-5 zeolites for conversion of ethanol or ethylene to propylene: Effect of reaction pressure and SiO2/Al2O3 ratio

In this work, the conversions of ethanol to propylene and ethylene to propylene were investigated over H-ZSM-5 zeolite catalysts with different SiO2/Al2O3 ratios (80 and 280). The effect of operating conditions (contact time and reaction pressure) has been studied. Special attention has been paid to the effect of reaction pressure on the propylene yield, space time yield and catalyst deactivation. Results show that the H-ZSM-5(280) catalyst was more stable for the ethanol or ethylene conversion reaction. High operating pressure favors the propylene production. However, the higher pressure leads to faster coking.

Reactivity of naphtha fractions for light olefins production

The catalytic cracking of naphtha fractions for propylene production was investigated under high severity catalytic cracking conditions (high temperatures and high catalyst to oil ratio). Straight run naphtha and cracked naphtha along with a with proprietary catalyst were used, and reaction was carried out using a catalyst to oil ratio (C/O) of 3–6 at 600–650 °C and 1 atm in a micro activity testing (MAT) unit. The results from this experiments show that light cracked naphtha (LCN) gave the highest propylene yield of 18% at 650 °C, and that propylene yield depends on the naphtha fraction being used as feed. The trend for reactivity and propylene yield was as follows: light cracked naphtha > heavy straight run naphtha > light straight run naphtha > heavy cracked naphtha.

Eight-Lump Reaction Kinetic Model for the Maximizing Isoparaffin Process for Cleaning Gasoline and Enhancing Propylene Yield

The maximizing isoparaffin process for cleaning gasoline and enhancing propylene yield (MIP-CGP) is the main derived technology of catalytic cracking in China. Based on the reaction mechanism of catalytic cracking and the characteristics of MIP-CGP with two reaction zones, the eight-lump reaction kinetic model was established. The measured data was from the industrial unit. Twenty-two groups of kinetic parameters were estimated, and the model parameters were validated that the predicted values were close to measured values. The analysis of the reaction rate constants and activation energies showed that the model parameters can well reflect the reaction law. The model can predict the main product distribution and provide the referential value for the operation optimization of MIP-CGP technology.

Highly selective catalytic conversion of ethanol to propylene over yttrium-modified zirconia catalyst

The yttrium-modified zirconia catalysts were prepared by co-precipitation method. N2 adsorption/desorption method, temperature programmed desorption and X-ray diffraction were used to characterize the Y/ZrO2 catalyst. All the catalysts were tested in the conversion of ethanol to propylene. The propylene yields showed a volcano-shaped dependence on the Y amount. The maximum yield of propylene reached 44.0%. The results implied that Y/ZrO2 catalyst with tetragonal structure or bigger specific BET surface area showed better performance. Reaction pathways were suggested to be ethanol to ethylene on the acidic sites, and ethanol→acetaldehyde→acetone→propylene on the basic sites.

Production of olefinic diesel, lubricants, and propylene

HEU-1 zeolites with different SiO2/Al2O3 ratios (60–530) were in-situ synthesized and systematically evaluated in n-hexane catalytic cracking reaction. The influencing factors including SiO2/Al2O3 ratio, weight hourly space velocity and reaction temperature were investigated to optimize the light olefin yield, especially propylene. Compared to HZSM-48 and HZSM-5 zeolites with similar SiO2/Al2O3 ratios, HEU-1-300 (SiO2/Al2O3 = ca. 300), for example, displays much higher yield of ethylene plus propylene than HZSM-48 and comparable with HZSM-5. Furthermore, the propylene yield (35.6%) on it is higher than HZSM-5 by 9.0 percentage points, thus leading to higher propylene/ethylene ratio of 2.1. This excellent cracking performance of HEU-1-300 is ascribed to the combination of its moderate Brönsted acidity, due to the optimal SiO2/Al2O3 ratio, and unique framework topology. Moreover, both HEU-1 and HZSM-48 zeolites present much lower aromatics selectivity in the gas effluent than HZSM-5. For HEU-1 zeolite, it displays significant product shape selectivity due to its confined channel system, even though the large void space favors the formation of large intermediate species or aromatics precursors, while there is transition state shape selectivity for HZSM-48 structure which possesses no enough void space available to accommodate the large and complex hydrocarbons. HEU-1 topological structure also has pronounced effect on the formation and oxidation of coke deposition.

Optimization of the product spectrum for 1-pentene cracking on ZSM-5 using single-event methodology. Part 2: Recycle reactor

This study is the second part of a mechanistic approach to incorporate kinetics into a reactor model. The single-event kinetic modeling concept is used to optimize a recycle reactor for 1-pentene cracking on ZSM-5. A flow scheme for this kind of reactor is presented in which the reactor outlet stream is separated into C4=–C12= olefins for recycle and into the product stream consisting of propene and ethene. Since the latter only contains propene and ethene in this idealized reactor configuration, the 1-pentene feed can be selectively converted to these lower olefins. The validity of the applied single-event kinetic model to different feed olefins is shown by comparing simulated product distributions obtained for 1-hexene, 1-pentene and 1-butene as feed to own experiments and literature results. The implemented recycle reactor model is used to optimize the reaction conditions with the aim of maximizing propene yield and minimizing ethene yield from a 1-pentene feed by varying reaction temperature as well as residence time.

Enhanced metathesis of ethylene and 2-butene on tungsten incorporated ordered mesoporous silicates

Tungsten-incorporated 3D mesoporous silicates, W-KIT-6, W-KIT-5, and W-SBA-16 catalysts, outperform supported tungsten oxide catalysts (WO3/SiO2 and WO3/KIT-6) for the metathesis of ethylene and 2-butene to propene at 450°C. All catalysts exhibit steady activity and stability during 7h runs in a fixed-bed reactor. Furthermore, on all mesoporous catalysts, a maximum propylene yield was obtained at an optimum W loading at which the catalyst acidity is also maximum. Slightly delayed addition of the W source during the one-pot synthesis protocol markedly improves the propene yield on W-KIT-6 catalyst. XPS results conclusively show that this enhancement is due to preferential enrichment of active W species on the catalyst surface. Extended runs lasting five days reveal very little loss of activity even which is easily recovered by calcination in air.

Effect of Phosphorus Addition on the Performance of Hierarchical ZSM-11 Catalysts in Methanol to Propene Reaction

Hierarchical ZSM-11 zeolite (SiO2/Al2O3 = 65) was found to be an efficient catalyst in Methanol to Propene (MTP) reaction. The catalytic activity of ZSM-11-based catalysts was studied in MTP reaction, and the effect of phosphorus (P) addition has been comprehensively investigated. XRD, N2 adsorption–desorption, NH3-TPD and Py-FTIR analyses reveal that the addition of P has a remarkable influence on the physicochemical properties of the catalysts. With the incorporation of P, the Bronsted acid sites decrease significantly, but the Lewis acid sites are almost preserved. Reaction results indicate that propene selectivity is obviously improved by P addition, and the highest propene yield (20.35 wt%) is obtained over 0.2ZAlPO catalyst. Based on the characterization and reaction results, it can be concluded that the appropriate concentration and strength of acid sites on 0.2ZAlPO catalyst with maintained MEL structure results in the enhanced propene selectivity and stability.

Experimental and kinetic study of catalytic cracking of heavy fuel oil over E-CAT/MCM-41 catalyst

The catalytic cracking of heavy fuel oil was investigated over the equilibrium fluid catalytic cracking catalyst (E-Cat) as a base component with the mesoporous MCM-41 as an additive. The catalytic performance of the E-Cat/MCM-41 system was assessed in a fixed-bed MAT unit. The reaction was performed at temperatures of 500, 530, 550 and 600°C and the product distributions in both gaseous and liquid phases were studied. The yields of products including light olefins, liquefied petroleum gas (LPG), gasoline, dry gas, coke and also the conversions obtained over different temperatures were reported and some generalities discussed. The maximum yield of propylene (17.5%) was obtained at 550°C whereas the highest conversion and gasoline yield was gained at 530°C. An eight-lump kinetic model containing 11 kinetic parameters was considered. Those parameters were estimated based on experimental data at specific temperatures by fourth order Runge–Kutta algorithm and the least square method. In addition, Arrhenius equation was used to calculate apparent activation energies. The calculated data of the product yields were in a close agreement with the experimental data.

SYNTHESIS OF PROPYLENE FROM ETHANOL USING PHOSPHORUS-MODIFIED HZSM-5

Effects of phosphorus addition to HZSM-5 on ethanol conversion to propylene were evaluated. Catalysts were characterized by XRF, XRD, nitrogen adsorption, 27Al and 31P MAS NMR, n-propylamine and ammonia TPD. Increasing P content decreased the strength and density of acid total sites. Ethanol dehydration was carried out in a fixed bed reactor operating at atmospheric pressure. Conversion was around 100% for all catalysts. 1.2 wt% of P catalyst showed the highest propylene yield, and was used to evaluate temperature and ethanol partial pressure effects on the product distribution. The highest propylene accumulated productivity was obtained for an ethanol partial pressure of 0.4 atm. Propylene formation was favored in the temperature range 475-500 °C. Significant changes in the product distribution as a function of time on stream were observed at higher temperatures, suggesting stronger catalyst deactivation. The ethylene yield decreased up to 500 °C, rising significantly at 550 °C, possibly due to heavier product cracking reactions.

Carbon nanotube templated synthesis of metal containing hierarchical SAPO-34 catalysts: Impact of the preparation method and metal avidities in the MTO reaction

Hierarchical SAPO-34 was synthesized hydrothermally using carbon nanotube as hard template and modified with Co and Ni by isomorphous substitution and impregnation methods. The prepared catalysts were characterized by XRD, SEM, TEM, XRF, UV–vis, NH3-TPD, H2-TPR, FTIR and N2 physisorption measurements and their catalytic performance was evaluated for transformation of methanol to light olefins (MTO). There were meaningful differences in terms of crystallinity, acidity, porosity and reducibility among the synthesized catalysts modified by impregnation and isomorphous substitution methods. In addition, the ethylene and propylene yields and the catalytic longevity were strongly dependent on Ni and Co avidities as well as on the modification procedure. The results indicated that compared to the unmodified hierarchical SAPO-34, the catalyst modified with Ni by means of isomorphous substitution improved the yield of ethylene while methane production was promoted over SAPO-34 impregnated with Ni. On the other hand, the Co-containing SAPO-34 samples enhanced the production of both ethylene and propylene relative to the unmodified mesostructured SAPO-34 and these modifications prolonged the catalyst lifetime. These changes in the catalytic behaviors could be ascribed to the changes in the acid sites and porous structure.

Honeywell UOP opens new catalyst production line at Shreveport, LA, facility

When a physical mixture composed of a 0.7 wt.% Pt–Sn-ZSM-5 dehydrogenation (DH) catalyst and a 42 wt.% Bi2O3/SiO2 selective hydrogen combustion (SHC) catalyst is subjected to a DH + SHC redox process operation, it gives substantially higher than equilibrium propylene yields from propane. At 540°C, atmospheric pressure and WHSV of 2 h−1, initial microreactor propylene yields from neat propane are 48.2% at about 90% selectivity, compared to equilibrium olefin yields of 20.0% at about 95% selectivity when only the DH catalyst is used. The overall propylene yield improvement is 140%. In this novel redox process arrangement no gaseous oxygen is cofed to the physical mixture; the lattice oxygen of the SHC catalyst is the sole oxidizing agent to selectively combust the hydrogen produced in situ by the dehydrogenation of the propane, catalyzed by the commingled DH catalyst. Periodic regeneration with air is necessary to replenish the lattice oxygen of the SHC catalyst depleted in the redox reaction.Although still significantly (i.e., 65%) above equlibrium, the high initial DH + SHC propylene yields are not sustainable and decline from 48.2% (first cycle) to 33.0% (tenth cycle); i.e., 2.1%/cycle; they are ascribed to the loss of Bi2O3 dispersion on the SiO2 support caused by the deep redox cycling. Shortening the redox cycle or increasing the SHC/DH catalyst ratio lessen the decline. However, the identification of a more redox stable catalyst is imperative to make the process practical. Some suggestions are provided. It is surmised that the DH + SHC redox process approach will ultimately (i.e., once a sufficiently redox stable SHC catalyst is identified) be preferred over the DH- > SHC- > DH cofed approach to improve conventional dehydrogenation processes such as the Oleflex and Catofin processes.

Catalytic cracking of n-hexane over HEU-1 zeolite for selective propylene production: Optimizing the SiO2/Al2O3 ratio by in-situ synthesis

HEU-1 zeolites with different SiO2/Al2O3 ratios (60–530) were in-situ synthesized and systematically evaluated in n-hexane catalytic cracking reaction. The influencing factors including SiO2/Al2O3 ratio, weight hourly space velocity and reaction temperature were investigated to optimize the light olefin yield, especially propylene. Compared to HZSM-48 and HZSM-5 zeolites with similar SiO2/Al2O3 ratios, HEU-1-300 (SiO2/Al2O3=ca. 300), for example, displays much higher yield of ethylene plus propylene than HZSM-48 and comparable with HZSM-5. Furthermore, the propylene yield (35.6%) on it is higher than HZSM-5 by 9.0 percentage points, thus leading to higher propylene/ethylene ratio of 2.1. This excellent cracking performance of HEU-1-300 is ascribed to the combination of its moderate Brönsted acidity, due to the optimal SiO2/Al2O3 ratio, and unique framework topology. Moreover, both HEU-1 and HZSM-48 zeolites present much lower aromatics selectivity in the gas effluent than HZSM-5. For HEU-1 zeolite, it displays significant product shape selectivity due to its confined channel system, even though the large void space favors the formation of large intermediate species or aromatics precursors, while there is transition state shape selectivity for HZSM-48 structure which possesses no enough void space available to accommodate the large and complex hydrocarbons. HEU-1 topological structure also has pronounced effect on the formation and oxidation of coke deposition.

Comparison of physically mixed and separated MgO and WO3/SiO2 catalyst for propylene production via 1-butene metathesis

We examined the catalyst bed design of MgO and WO3/SiO2 for production of propylene via metathesis of 1-butene. WO3/SiO2 was used as a bi-functional catalyst for isomerization and metathesis reactions. Addition of MgO was proposed to help improve the isomerization activity and hence the propylene yield. Experimental studies were carried out to determine activity and reaction kinetics of 1-butene isomerization over MgO isomerization catalyst and 1-butene metathesis over WO3/SiO2 bi-functional catalyst for designing a suitable catalyst bed. Two types of catalyst bed arrangement—physically mixed bed and separated bed—were considered and compared by computer simulation. The simulations reveal that adding MgO in the separated bed by packing MgO before WO3/SiO2 offers superior propylene yield to the physically mixed bed. The appropriate %MgO loading in catalyst bed which offers a maximum propylene yield was found to vary (3 and 23%), depending on operating condition.

Conversion of Y into SSZ-13 zeolites and ethylene-to-propylene reactions over the obtained SSZ-13 zeolites

Y zeolites having wide ranges of SiO2/Al2O3 ratios (silica/alumina ratios or SARs) were converted into SSZ-13 zeolites in the presence of N,N,N-trimethyl-1-adamantanamine iodide (TMAda-I) as a template. SSZ-13s with increased SARs could be obtained from Y zeolites having SARs of 5.1–80 and sodium silicate by both conventional electric (CE) and microwave (MW) heating. The syntheses conducted using MW and CE heating at 140°C were completed in 2h and 144h, respectively, because of accelerations by MW in both the nucleation and crystal growth stages. The obtained yields of SSZ-13 decreased as SARs of the starting Y zeolites increased, demonstrating the relatively easy conversion of aluminous Y into SSZ-13. The obtained SSZ-13s with wide SAR ranges (19–287) were applied as catalysts in the direct conversion of ethylene-to-propylene (ETP) to understand the effect of the SARs on the ETP performances, including the conversion of ethylene and propylene selectivity. The stability of ETP was highly dependent on the SAR of the SSZ-13 zeolites. SSZ-13s with excessively high or low SARs caused low ethylene conversion (from the beginning of the reaction) or rapid deactivation in the conversion, respectively. The propylene selectivity or yield (at a fixed ethylene conversion of 80%) generally increased with decreasing SARs (up to 19) of SSZ-13s under the studied conditions because of a steady increase in the selectivities for butenes and higher products with increasing SARs of SSZ-13s.

Full-crystalline hierarchical monolithic ZSM-5 zeolites as superiorly active and long-lived practical catalysts in methanol-to-hydrocarbons reaction

The efforts to obtain superior active and long-lived practical zeolite catalysts must be based on shaped forms rather than only powder, if considering necessary mechanical strength requirement in industrial application. The binders, incorporated as indispensable additives to keep intact of macroscopical body, are catalytically inert and their negative impacts in mass transfer are widely neglected. Here, we firstly revealed the remarkable mass transfer depression by incorporating silica sol as binders in shaped zeolitic catalyst. Then, by re-crystallizing the shaped binder/zeolite body with assistance of controlled organic template steam, the binders were converted into zeolitic phase, forming full-zeolitic monoliths. In re-crystallization, it was found obvious intra-crystalline mesopores were in situ created while maintaining high mechanical strength. A remarkable mass transfer advantage was revealed in such hierarchical monolith, which means more acid sites will be accessible after re-crystallization. Therefore, in performance evaluation, hierarchical full-zeolitic monolith demonstrated higher propylene yield and slower deactivation rate in C4 olefin cracking reaction. Moreover, highly prolonged cycle time, which was more than 2000h and three times as long as that of commercial catalyst, was realized in catalyzing methanol-to-hydrocarbons (MTH) under industrial condition. That is the first report on so long-lived zeolite catalyst without regeneration in methanol conversion reaction. Fundamental understanding in re-crystallization of monolithic material will contribute significantly to technical progress in developing more high-valued applicable catalysts and optimizing existing zeolite catalyst.

Experimental Design-Assisted Investigation of Light Olefins Production Over Ceria-Altered HZSM-5 Catalysts by Naphtha Catalytic Steam Cracking

Abstract In this contribution, the effects of ceria loading, Si/Al ratio, and reaction temperature on the catalytic performance of HZSM-5 catalysts for production of ethylene and propylene from light naphtha were investigated. The elaborated catalysts were characterized by XRD, FTIR, SEM, and BET specific surface area. The acquired results demonstrated that HZSM-5 structure was preserved after ceria addition. XRD patterns exhibited a crystallinity degradation of HZSM-5 samples by aluminum addition. Box-Behnken experimental design was utilized with central composite design for investigation of parameters such as reaction temperature (600–700 °C), cerium loading (2–14 wt%), and Si/Al ratio (25–125) in ethylene and propylene production. Analysis of variance (ANOVA) indicated the significance of the studied parameters and the corresponding interactions. The results exhibited that the highest ethylene yield was at the highest reaction temperature, the highest cerium loading, and the lowest Si/Al ratio. The superior propylene yield was attained at the highest Si/Al ratio whereas an optimum can be found for reaction temperature and cerium loading.

Investigation of Key Factors and Their Interactions in MTO Reaction by Statistical Design of Experiments

Abstract The effects of templating agent [i. e., tetraethyl ammonium hydroxide (TEAOH), triethylamine (TEA) and morpholine (MOR)] and molar ratio of SiO2/Al2O3 and H2O/Al2O3 over SAPO-34 catalysts in methanol to olefin (MTO) reaction were studied systematically. The exact effect of main factors and their interaction were studied by response surface methodology (RSM) applying central composite design (CCD). Two empirical models for two systems, based on these preparation variables for the yield of ethylene and propylene were constructed in two CCD studies and ultimately these models showed as counter and three-dimensional (3D) diagrams. Analysis of Variance (ANOVA) applied for investigating the significance of the variables indicated that TEA and SiO2/Al2O3 content were the most significant variables in the case (1) and case (2), respectively. The maximum predicted ethylene and propylene yield was 58.57 wt. % and 30.22 wt. %, for catalyst with TEA = 0.2, TEAOH = 0.38 in case (1). For case (2), catalyst with SiO2/Al2O3 = 0.17, H2O/Al2O3 = 101.18 showed the maximum ethylene and propylene yield of 49.87 wt. % and 20.58 wt. %, respectively.

MSE-Type Zeolites: A Promising Catalyst for the Conversion of Ethene to Propene

The direct conversion of ethene to propene (ETP) is a potentially important route for the selective production of the latter olefin. Here we report that after some time on stream, H-UZM-35, an MSE-type large-pore zeolite, shows much better propene yield than H-SSZ-13, the best catalyst for the ETP reaction thus far. The key to this improvement is the presence of large cylindrical cages in H-UZM-35 that allows the easy formation of isopropylnaphthalene-based reaction centers for ETP catalysis, while being relatively resistant to coke formation. Mild dealumination was found to further mitigate catalyst deactivation.

Thermodynamic equilibrium distribution of light olefins in catalytic pyrolysis

Catalytic pyrolysis is a promising technology to produce light olefins. Gibbs free-energy minimization method was used to study the thermodynamic equilibrium distribution of olefins in catalytic pyrolysis with Aspen Plus software. The result showed that olefin systems with different carbon numbers demonstrated a similar thermodynamic equilibrium distribution. The ethene equilibrium composition increased with increasing reaction temperature and decreased with increasing total hydrocarbon pressure. By contrast, the propene equilibrium composition reached a maximum of 40wt% at 850–950K under 0.1MPa. Ethene yield and propene yield of thermodynamic equilibrium, catalytic pyrolysis and thermal pyrolysis were compared. The use of catalyst greatly increased the yields of ethene and propene, but the yields were still lower than the equilibrium data. Catalytic pyrolysis was carried out in the interaction zone where both catalytic conversion and thermal conversion were important. Propene yield was close to ethene yield at about 950K from the thermodynamic view. Given the shape-selective effect of the catalyst on branched olefins with large carbon number, the equilibrium carbon number distribution of olefins possibly shifted from large carbon numbers to low carbon numbers, resulting in enhanced ethene and propene yields.