Yield Of Olefins Research Articles

Fe2O3@ZrO2 catalyst derived from MOF-on-MOF for direct CO2 hydrogenation to light olefins

The utilization of CO2 for the production of light olefins through catalysis with iron-based catalysts presents a viable strategy to address the challenges of carbon neutrality. In this study, we synthesized a novel hybrid catalyst Fe2O3@ZrO2, derived from the pyrolysis of dual metal–organic frameworks (NH2-MIL-88B@UiO-66). Under specific conditions (340 °C, 3.0 MPa, CO2/H2 = 1:3, 10000 mL gcat−1h−1), the Fe2O3@ZrO2 catalyst exhibited a notable space–time yield of light olefins at 12.7 mmol g−1h−1. The characterizations results show an electron transfer from ZrO2 to the Fe2O3 surface was observed at the heterointerface of Fe2O3 and ZrO2. This electron transfer mechanism was identified as advantageous for the formation of the active phase Fe5C2. This research introduces an innovative use of the hybrid Fe2O3@ZrO2 catalyst derived from MOF-on-MOF, holding significant promise in advancing the field of CO2 hydrogenation catalysts.

A Nanocrystalline ZSM‐5 for the Catalytic Cracking of Waste Cooking Oil

AbstractA series of hierarchical ZSM‐5 nanocrystalline aggregates (HNZ‐5) was synthesized using a hydrothermal method with tetrapropylammonium hydroxide as a structural guide. The HNZ‐5 samples having different Si/Al molar ratios all showed suitable hierarchical architectures and the maximum surface area was found to be 329 m2/g. The SEM image displayed the width of the individual crystal particles was ~100 nm, and its nanocrystalline clusters generated intercrystalline pores. Temperature‐programmed desorption with NH3 indicated that the total acidity of this material increased with increases in the Al3+ content to a maximum of 0.47 mmol/g at a Si/Al ratio of 15. In addition, 27Al magic angle spinning nuclear magnetic resonance spectra showed that the acid sites were associated with tetrahedral and octahedral Al sites. This HNZ‐5 was applied to the catalytic cracking of waste cooking oil model compound and gave a light olefin yield as high as 43.9 % at 550 °C. Extending the reaction time to 6000 min provided a yield of light olefins in excess of 30 %, which was higher than that achieved using traditional ZSM‐5. These data confirmed that the hierarchical pore structure of HNZ‐5 resulting from the self‐assembly of nanocrystals, together with exposed acidic sites, promoted the catalytic conversion of large molecules.

Synthesis of hierarchical Fe-incorporated ZSM-5 molecular sieves with an Fe-based metal-organic framework as a mesoporogen and iron source for catalytic pyrolysis of alkanes

To increase the yield of light olefins during the catalytic pyrolysis of alkanes, a novel hierarchical Fe-incorporated ZSM-5 molecular sieve (FeM-Z5) was synthesized using an Fe-based metal-organic framework (Fe-MOF) as a mesoporogen and iron source through the dry gel conversion (DGC) method. In contrast to the conventional method of incorporating Fe species into ZSM-5 via impregnation, the DGC method incorporates Fe species into the framework of ZSM-5, decreasing the amount of Brønsted (B) acid sites and thereby inhibiting the side reactions of hydrogen transfer during the catalytic pyrolysis of alkanes. Compared with the FeN-Z5 catalyst prepared by the DGC method with Fe(NO3)3 as an iron source, FeM-Z5 had a larger amount of strong B acid sites and more mesopores with a size range of 10–40 nm originating from the decomposition of Fe-MOF; these aspects improved n-pentane pyrolysis and ethylene and propylene diffusion. As a result, the optimal FeM-Z5 catalyst exhibited the highest yield of ethylene and propylene (33.4 wt%) and the lowest deactivation rate (0.07 %/h) among the prepared catalysts during the catalytic pyrolysis of n-pentane.

Modification of ZSM-23 zeolite via vapor-phase transport method: Reducing the length along the unidimensional channels for enhanced catalytic performances in methanol-to-hydrocarbons

ZSM-23, a unidimensional zeolite, finds application in the methanol-to-hydrocarbons (MTH) reaction, but commonly suffers from rapid deactivation due to diffusion hindrances. Given the challenges of reducing the length along the a-axis of ZSM-23 zeolite while preserving its catalytic functions using conventional methods, this study introduces a post-modification approach inspired by the vapor-phase transport (VPT) method, wherein ZSM-23 is subjected to the vapor of an iso-propylamine (IPA) solution. The results demonstrated that the crystal lengths aligned with the micropores can be effectively reduced to less than half of the original material (115 nm vs. 289 nm), while preserving much of the microstructure and acidity. Insights into the post-treatment mechanism unveiled a coexistence of etching and re-crystallization processes during the procedure, with conditions finely adjustable by varying the concentrations of the IPA solution. The optimized modification procedure resulted in ZSM-23 zeolite demonstrating an increased C2–C4 olefin yield (62.2 % vs. 53.2 %) and enhanced stability (22 h vs. 5 h) in MTH reaction compared to the untreated sample, which can be attributed to the enhanced diffusion properties of the modified zeolite. This vapor-assisted modification protocol successfully expands the toolkit for synthesizing efficient one-dimensional zeolite for catalytic purposes.

One-pot CO2-to-olefins via methanol over In2O3-ZrO2/SAPO-34 catalysts mixtures with different spatial arrangements

The one-pot CO2 hydrogenation to lower olefins involves the integration of two catalytic reactions in a single reactor: the conversion of CO2 into methanol (CTM) and its subsequent conversion into lower olefins (MTO). This approach requires two catalysts cooperating in the same reactor, posing different challenges in terms of synergies and interactions between the two active phases. In this work, we investigate the effect of process conditions and arrangements between In2O3-ZrO2 (CTM catalyst) and SAPO-34 (MTO catalyst) on the lower olefins yield. We show that the distance between CTM and MTO active sites, studied by assessing different catalyst arrangements spanning from an intimate mixture obtained through mortar mixing to a complete segregation of the catalysts (i.e., consecutive beds), plays a key role in driving the products distribution. However, the thermodynamic equilibrium of the reverse water gas shift limits CO2 conversion in the investigated conditions. Finally, we discuss the stability of the catalytic performances: the characterization of the spent samples after ∼400 h on stream indicated the deactivation of the catalytic materials in all investigated cases, with In sintering on the methanol catalyst, and SAPO-34 losing both P and Al due to hydrothermal aging; indications of In migration on SAPO-34 were also observed when the two catalyst are in contact.

Synthesize and Characterization of Pt-supported Co-ZIF for Catalytic Hydrocracking and Hydroisomerization of n-Hexadecane

Zeolitic Imidazole Frameworks (ZIFs) are prospective porous materials as catalyst support due to their relatively large surface area, and tunability in size, structure, and porosity. Recent studies have also shown that ZIF is the best candidate for various catalytic redox reactions such as the oxidation of benzyl aromatic hydrocarbons. In this study, the synthesized Pt catalyst supported on Co-ZIF was varied by the organic ligands: imidazole, benzimidazole, and 1-(3-aminopropyl) imidazole, then followed by impregnation of Pt precursor. The catalysts were characterized its physical and chemicals properties such as Fourier Transform Infrared (FTIR), X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), and Brunauer Emmet Teller (BET), Temperature-Programmed Desorption (NH3-TPD and CO2-TPD). The prepared catalysts were evaluated for catalytic hydrocracking and hydroisomerization of n-hexadecane in a 100 ml-batch reactor. GC-MS analysis presented that the Pt/ZIF catalyst with imidazole ligands has better performance than others. Hence, the optimization of n-Hexadecane conversion was carried out by the Pt/ZIF-imidazole catalyst varying the amount of metal loading, time and temperature reaction. The results showed that the reaction temperature of 350 ºC using 20 bar H2 for 4 h and the addition of 15 wt% Pt successfully achieved 90.77% conversion and produced the highest yield of isomers and alkanes, 4.04% and 35.75%, respectively. Copyright © 2024 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Combinatorial optimization of C4 olefin production conditions based on interpretable LSSVM&TPE

Due to the complexity of the products from the ethanol coupling reaction, the C4 olefin yield tends to be low. Finding the optimal ethanol reaction conditions requires repeated manual experiments. In this paper, a novel learning framework based on least squares support vector machine and tree-structured parzen estimator is proposed to solve the optimization problem of C4 olefin production conditions. And shapley value is introduced to improve the interpretation ability of modeling method. The experimental results show that the proposed learning framework can obtain the combination of ethanol reaction conditions that maximized the C4 olefin yield It is nearly 17.30% higher compared to the current highest yield of 4472.81% obtained from manual experiments.

Catalytic co-pyrolysis of cabbage waste and plastics with Ni/ZSM-5 catalysis to produce aromatic-rich oil

This study investigates the selective production of aromatics through the co-pyrolysis of cabbage waste and plastics followed by catalytic reforming with Ni-modified ZSM-5. Co-pyrolysis significantly improves the inflection point (a parameter for determining thermal stability) to 251.3 °C from 232.7 °C. This process also enhances the relative yield of olefins and phenols, which are precursors for aromatic production to 25.46 and 17.23 respectively, up from 13.87 to 12.05. Furthermore, catalytic pyrolysis elevates the relative yield of aromatics to 53.4, as confirmed by Thermogravimetric Analysis (TGA) and Thermogravimetric-Fourier Transform Infrared Spectroscopy (TG-FTIR) analyses. GC-MS confirms the enhanced formation of valuable chemical precursors via co-pyrolysis such as phenols and olefines to 18.67 % and 22.13 % leading to a 63.81 % selective yield of aromatics in the final oil with 10Ni/ZSM-5. Ni modification of ZSM-5 is influential in decreasing PAH formation (7.26 % from 20.37 %), indicating that this two-step process is an effective method for transforming waste into high-quality bio-oil with enriched aromatic content.

Catalytic hydrogenolysis of polypropylene and polyethylene mixtures: Effect of temperature on liquid alkane components

This study explored the interactions between different polyolefins using a commercial Ru/C catalyst-mediated hydrogenolysis of polypropylene (PP), low-density polyethylene (LDPE), and their mixtures. The effects of the mass ratio of polyolefins to the catalyst, temperature, pressure and time on the yield of products and the internal components of liquid alkane products were studied, and the optimum conditions for solo plastic hydrogenolysis were determined. The highest liquid alkane yields of PP (46.70 %) and LDPE (70.70 %) were obtained at 250 and 210 °C, respectively. Further, the interactions between PP and LDPE during co-hydrogenolysis were observed. The temperature had a significant influence on the gaseous and liquid products, and we proposed a two-step hydrogenolysis reaction process for a mixture of polyethylene with polypropylene conducted at various temperatures. Co-hydrogenolysis provides a high-value utilization path for polyolefins that are difficult to separate during recovery.

Effects of ZrO2 crystalline phase on oxygen vacancy of GaZr oxides and their properties for CO2 hydrogenation to light olefins

A bifunctional catalyst, comprising GaZr oxide and SAPO-34 zeolite, manifests enhanced catalytic activity in CO2 hydrogenation to light olefins; nonetheless, the comprehensive analysis of the pivotal role played by the underlying structure of ZrO2 in Ga-Zr oxide has not been investigated. Herein, different crystalline structures of ZrO2 were prepared by the co-precipitation method and adopted as a support to deposit Ga to obtain ZrO2 with different ratios of monoclinic ZrO2 (m-ZrO2) to tetragonal ZrO2 (t-ZrO2) in GaZr oxides for CO2 hydrogenation to light olefins. Various characterizations demonstrated that the interface between Ga and the mixed phase of (m-t) ZrO2 produces more oxygen vacancies which favors the adsorption and activation of CO2, and the larger specific surface area and stronger H2 adsorption and dissociation capacity promote CO2 conversion. Interestingly, the GaZr oxide with high m-ZrO2 content exhibits superior catalytic activity than the GaZr oxide with high content of t-ZrO2. The highest light olefins yield (9.0%) and selectivity (77.9%) (CO free) with 27.9% CO2 conversion was achieved. In-situ DRIFT spectra further elaborated that the GaZr oxides with different ZrO2 crystalline phases follow the same reaction pathway to hydrogenate CO2 first to HCOO* and then to CH3O* on GaZr oxide surface. While compared with sole ZrO2, the introduction of Ga significantly promotes the hydrogenation of HCOO* to CH3O*, acting as a crucial reaction intermediate that subsequently diffuses into SAPO-34 pores to enhance the desired light olefins selectivity.

Developing Multifunctional Fe-Based Catalysts for the Direct Hydrogenation of CO2 in Power Plant Flue Gas to Light Olefins

The hydrogenation of carbon dioxide (CO2) to produce light olefins is one of the most promising ways to utilize CO2 in power plant flue gas. However, the low concentration of CO2 (~10%) and the existence of water steam in the flue gas pose great challenges for the catalyst design. To address these problems, we introduced a Mg promoter and hydrophobic component into the Fe-based catalyst to improve the CO2 adsorption capacity and weaken the negative effects of water. The yield of light olefins on an optimized multifunctional Fe-based catalyst increased by 37% in low-concentration CO2 hydrogenation with water steam. A variety of characterizations proved that the Mg promoter played critical roles in regulating the adsorption capacity of CO2, increasing the surface electron density of Fe species, and promoting the formation of iron carbide active sites. The hydrophobic component mainly contributed to constraining the oxidation of iron carbides via water steam. It benefited from the rational design of the catalyst, showing how our multifunctional Fe-based catalyst has great potential for practical application in CO2 utilization.

Improvement of catalyst activity in cracking of n-hexane via metal (Fe/Ga) impregnation over ZSM-12 catalyst

In this research, zeolite ZSM-12 with Si/Al ratio = 80 was synthesized by hydrothermal method. The synthesized zeolite ZSM-12 was modified using Fe and Ga metals and a combination of these two metals, 1 % iron metals (Z80-Fe) and 1 % gallium metals(Z80-Ga), and a 2 % combination of these two metals (Z80-Fe-Ga). The physicochemical properties of synthesized zeolites were evaluated and compared by XRD, EDX-dot-mapping, NH3-TPD, BET, FT-IR, and TGA analyses. The catalytic assessment of synthesized zeolites in the HTO (n-hexane to olefins) process in a fixed bed reactor under atmospheric pressure and Weight hourly space velocity (WHSV) equal to 4 h−1 at 550 °C was evaluated. Various parameters such as selectivity towards light olefins, propylene to ethylene (P/E ratio), production of light alkanes, and aromatic compounds (BTX) were investigated. The results show that using metals led to the improvement and adjustment of the acid sites of zeolite, and the highest amount of light olefin and the lowest amount of coke were obtained. The result of the n-hexane to olefin process showed that the yield of light olefins was significantly improved in all modified catalysts compared to parent zeolite MTW. Compared to other modified zeolites, Z80-Fe-Ga zeolite has the highest yield of light olefins, equal to 59 %. This zeolite performs better due to the presence of gallium and iron metals and shows the highest propylene selectivity (P/E = 2.4). In addition, according to the results of the TGA analysis, the content of coke on the Z80-Fe-Ga catalyst after the catalytic reaction is much less than that of other catalysts after the catalytic reactor test.

Enhancing bio-based chemical production and reducing pollutants emission through the synergistic effect of ZSM-5/CaO during hydrogen-deficient biomass pyrolysis

The study proposed the use of ZSM-5/CaO as a catalyst to simultaneously improve the quality of pyrolytic products and reduce pollutants emission during the pyrolysis of hydrogen-deficient biomass, specifically cabbage waste (CW). Variables such as pyrolysis temperature and catalysts, including 5% ZSM-5, 5% CaO and 10% ZSM-5/CaO, significantly affected biomass conversion, yield, and products composition. Thermogravimetric-Fourier transform infrared spectroscopy (TG-FTIR) analysis shows that the catalysts (5% ZSM-5, 5% CaO and 10% ZSM-5/CaO) reduced pollutants emission and increased value-added chemicals production by 24.96%, 28.5%, 17.39% and 75.04%, 71.5%, 82.1%, respectively compared to non-catalytic process as 34.18% and 65.82%. Moreover, these catalysts enhanced the relative yield of olefins, aromatics, and phenols to 23.5, 21.6, 27.6% for 5wt.%ZSM-5; 20.8, 18.7, 23.3% for 5wt.%CaO; 30.7, 38.6, 41.3% for 10wt.%ZSM-5/CaO, compared to the non-catalytic process' yield of 15.7, 10.7, 19.3%. Py/GC–MS analysis confirms that these catalysts also decreased PAH and oxygenates production to 13.5, 15.3% for 5wt.%ZSM-5; 11.8, 9.1% for 5wt.%CaO; 5.2, 4.7% for 10wt.%ZSM-5/CaO, in contrast to the non-catalytic process' 26.2, 28.7%. This confirms the synergistic effect of ZSM-5/CaO for upgrading bio-based chemicals and reducing pollutants emission.

Effect of fast heating rate and alkaline catalyst on composition and characteristic of volatile products during catalytic upgrading of oil sand bitumen

The study was devoted to exploring the fundamental study on the upgrading of Buton oil sand bitumen (OSB) via fast alkaline catalytic pyrolysis based on the fluid pyrolysis technology. The effect of fast heating rate on the composition and molecular distribution of volatile products from the high-temperature fast pyrolysis of OSB was investigated by Py-GC/TOF-MS that could simulate the fast heating rate of industrial fluid pyrolysis process. The results showed that the volatile products of OSB under heating rates ranging from 10 to 1000 °C/s had the similar species composition. It was found that there were the highest relative content of low-carbon alkenes (C2-C4) and light aromatics (C6-C8) in volatile products under the 1000 °C/s, indicating that the fast heating rate favored the production of light alkenes and aromatics. Subsequently, a laboratory-scale fluidized bed apparatus was employed to further gain insight into fast alkaline catalytic pyrolysis behaviors of OSB. The investigation on the yield distribution, fractional- and molecular-level chemical characteristic of volatile products obtained from the fast alkaline catalytic upgrading of OSB over calcium aluminate was carried out with the aid of the comparison with that over Y zeolite-based FCC catalyst and silica sand. The results revealed that three-phase products over calcium aluminate possessed the larger selectivity of C2−C4 alkenes, larger yield of light oil and the lower coke output, which were 51.88%, 45.49% and 7.96%, respectively. On basis of the chemical structure analysis of liquid products, the alkaline catalytic upgrading of OSB over calcium aluminate could heighten the content of chain alkyl structures as well as alkyl-substituents attached to aromatic ring in liquid products. This indicated that the fast heating rate and alkaline catalyst that adopted in catalytic upgrading process of OSB could play an energetic role in optimizing the composition of volatile products. The alkaline catalytic upgrading of OSB based on fluid pyrolysis technology with the fast heating rate could heighten the yield of low-carbon olefins and light oil and lessen coke yield, meanwhile modify the chemical structure characteristics of liquid products that were conducive to the generation of valuable chemicals (light alkanes and BTX) during secondary processing of liquid products.

Investigation of AFeO3 (A=Ba, Sr) Perovskites for the Oxidative Dehydrogenation of Light Alkanes under Chemical Looping Conditions.

Oxidative dehydrogenation (ODH) of light alkanes to produce C2-C3 olefins is a promising alternative to conventional steam cracking. Perovskite oxides are emerging as efficient catalysts for this process due to their unique properties such as high oxygen storage capacity (OSC), reversible redox behavior, and tunability. Here, we explore AFeO3 (A=Ba, Sr) bulk perovskites for the ODH of ethane and propane under chemical looping conditions (CL-ODH). The higher OSC and oxygen mobility of SrFeO3 perovskite contributed to its higher activity but lower olefin selectivity than its Ba counterpart. However, SrFeO3 perovskite is superior in terms of cyclic stability over multiple redox cycles. Transformations of the perovskite to reduced phases including brownmillerite A2Fe2O5 were identified by X-ray diffraction (XRD) as a cause of performance degradation, which was fully reversible upon air regeneration. A pre-desorption step was utilized to selectively tune the amount of lattice oxygen as a function of temperature and dwell time to enhance olefin selectivity while suppressing CO2 formation from the deep oxidation of propane. Overall, SrFeO3 exhibits promising potential for the CL-ODH of light alkanes, and optimization through surface and structural modifications may further engineer well-regulated lattice oxygen for maximizing olefin yield.

Regulating framework aluminum location towards boosted light olefins generation in ex-situ catalytic pyrolysis of low-density polyethylene

Amidst the global focus on recycling and treatment of waste plastics for resource sustainability, it remains an enormous challenge to convert waste plastics into light olefin. Herein, the impact of framework Al (AlF) location in ZSM-5 catalyst, controlled by regulating Al sources, on the ex-situ catalytic pyrolysis of low-density polyethylene (LDPE) has been investigated. Based on multi-techniques, such as 27Al MAS NMR, ICP-AES, Co-UV–vis-DRS, XRD, SEM, N2 adsorption-desorption, NH3-TPD, Py-IR and FTIR. It is found that the AlF located at the channel intersections show more Al pairs, and this location offers ample space for secondary reactions, which include Diels-Alder reaction, cyclization reaction and dehydrogenation reaction, resulting in the low yield of light olefins (10.6 wt%) and the generation of light alkanes and aromatics from light olefins. In contrast, AlF located in the straight and sinusoidal channels exists mainly in the form of single Al. The substantial steric hindrance for this location facilitates the cracking reaction, mainly referring to the cracking reactions of LDPE that produce light olefins and generate enhanced yield of light olefins (52.8 wt%). These results provide new perspectives towarding boosted light olefins generation in ex-situ catalytic pyrolysis of LDPE.

Effect of kaolin calcined temperature on the preparation and crystallization mechanism of SAPO-34 molecular sieve for methanol-to-olefins performance

SAPO-34 molecular sieves synthesized using calcined kaolin as partial raw material under three-stage of high-low-high temperature hydrothermal condition are explored systematically. Especially, the effect of kaolin calcination temperature on the crystallization mechanism of SAPO-34 and the methanol to olefin performance are investigated thoroughly. It is found that the sample (SP-500) synthesized by using kaolin calcined at 500 °C (MK-500) demonstrates clean cubic structure, large specific surface area and mild acidity, providing the initially activated Si and Al source for the synthesis of SAPO-34 molecular sieve due to the well scattered structure of MK-500. From the crystallization mechanism consideration, it can be proposed that the SAPO-34 molecular sieves will be controlled by the low degree of Si aggregation in metakaolin and quantity of Si (3Al,1Si) species. As a result, SP-500 displays excellent catalytic lifetime during methanol to olefin reaction for its special Si coordination environment, showing the highest stable light olefin yield of 80.6 % and a methanol conversion above 90 % for more than 720 min. In contrast, SP-800 sample with the most strong acid sites is only 390 min, even if showcasing the highest selectivity of light olefins (84.5%).

A Review of Catalyst Modification and Process Factors in the Production of Light Olefins from Direct Crude Oil Catalytic Cracking

Petrochemical feedstocks are experiencing a fast growth in demand, which will further expand their market in the coming years. This is due to an increase in the demand for petrochemical-based materials that are used in households, hospitals, transportation, electronics, and telecommunications. Consequently, petrochemical industries rely heavily on olefins, namely propylene, ethylene, and butene, as fundamental components for their manufacturing processes. Presently, there is a growing interest among refineries in prioritising their operations towards the production of fuels, specifically gasoline, diesel, and light olefins. The cost-effectiveness and availability of petrochemical primary feedstocks, such as propylene and butene, can be enhanced through the direct conversion of crude oil into light olefins using fluid catalytic cracking (FCC). To achieve this objective, the FCC technology, process optimisation, and catalyst modifications may need to be redesigned. It is helpful to know that there are several documented methods of modifying traditional FCC catalysts’ physicochemical characteristics to enhance their selectivity toward light olefins’ production, since the direct cracking of crude oil to olefins is still in its infancy. Based on a review of the existing zeolite catalysts, this work focuses on the factors that need to be optimized and the approaches to modifying FCC catalysts to maximize light olefin production from crude oil conversion via FCC. Several viewpoints have been combined as a result of this research, and recommendations have been made for future work in the areas of optimising the yield of light olefins by engineering the pore structure of zeolite catalysts, reducing deactivation by adding dopants, and conducting technoeconomic analyses of direct crude oil cracking to produce light olefins.

Direct Intramolecular Coupling of Primary/Secondary Alcohols with Secondary Alcohols for Macrocyclic Alkenylation Using Ni‐Zeolite Catalyst Under Continuous‐Flow Conditions

AbstractHerein, we report the direct intramolecular coupling of primary and secondary alcohols for the selective synthesis of macrocyclic olefins in the presence of Ni‐zeolite catalyst under continuous flow. This reaction proceeds via dehydration of secondary alcohols to alkenes, which subsequently undergo intramolecular dehydrative coupling reaction with a primary alcohol to obtain moderate yields of macrocyclic olefins. This reaction is also effective for the coupling of secondary‐secondary alcohols and alkene‐alcohols to produce diverse macrocyclic olefin products. This unique approach has various advantages including step‐economy, no additives and pre‐functionalization required, inexpensive and reusable catalyst, and exemplification with 23 macrocycles in different ring sizes. The continuous flow macrocyclisation afforded higher productivity and space‐time yield than the batch reaction conditions.

Surface Modification of Fe-ZSM-5 Using Mg for a Reduced Catalytic Pyrolysis Temperature of Low-Density Polyethylene to Produce Light Olefin

Although the catalytic pyrolysis of low-density polyethylene (LDPE) to produce light olefin has shown potential industrial application advantages, it has generally suffered when using higher pyrolysis temperatures. In this work, Mg-modified Fe-ZSM-5 was used for catalytic conversion of LDPE to obtain light olefin in a fixed bed reactor. The effects of catalyst types, pyrolysis temperatures, and Mg loading on the yield of light olefin were investigated. The 1 wt% Mg loading slightly improved the yield of light olefin to 38.87 wt% at 395 °C, lowering the temperature of the pyrolysis reaction. We considered that the higher light olefin yield of Fe-Mg-ZSM-5 was attributed to the introduction of Mg, where Mg regulated the surface acidity of the catalyst, inhibited the secondary cracking reaction, and reduced coking during the pyrolysis process. Furthermore, the addition of Mg also dramatically reduced the average particle size of Fe oxides from 40 nm to 10 nm, which is conducive to a lower catalytic reaction temperature. Finally, the spent catalyst could be easily regenerated at the conditions of 600 °C in airflow with a heating rate of 10 °C/min for 1 h, and the light olefin yield remained higher than 36.71 wt% after five cycles, indicating its excellent regeneration performance.