Modeling and analysis of air combustion and steam regeneration in methanol to olefins processes

Light olefins is the incredibly important materials in chemical industry.Methanol to olefins(MTO),which provides a non-oil route for light olefins production,received considerable attention in the past decades.However,the catalyst deactivation is an inevitable feature in MTO processes,and regeneration,therefore,is one of the key steps in industrial MTO processes.Traditionally the MTO catalyst is regenerated by removing the deposited coke via air combustion,which unavoidably transforms coke into carbon dioxide and reduces the carbon utilization efficiency.Recent study shows that the coke species over MTO catalyst can be regenerated via steam,which can promote the light olefins yield as the deactivated coke species can be essentially transferred to industrially useful synthesis gas,is a promising pathway for further MTO processes development.In this work,we modelled and analyzed these two MTO regeneration methods in terms of carbon utilization efficiency and technology economics.As shown,the steam regeneration could achieve a carbon utilization efficiency of 84.31%,compared to 74.74%for air combustion regeneration.The MTO processes using steam regeneration can essentially achieve the near-zero carbon emission.In addition,light olefins production of the MTO processes using steam regeneration is 12.81%higher than that using air combustion regeneration.In this regard,steam regeneration could be considered as a potential yet promising regeneration method for further MTO processes,showing not only great environmental benefits but also competitive economic performance.

Production of linear alkylbenzene over Ce containing Beta zeolites

Ce-encapsulated Beta zeolite was synthesized by a one-pot hydrothermal method with citric acid complexing Ce in the absence of Na species.Additional citric acid can effectively prevent the deposition of Ce species during the hydrothermal synthesis of zeolites,leading to uniform distribution of Ce cluster in the framework of Beta zeolites.Moreover,the sodium-free synthesis system resulted that the Brønsted acid sites were mainly located on the straight channels and external surface of Beta zeolites,improving the utilization of Brønsted acid sites.In addition,Ce encapsulated Beta zeolites showed enhanced activity and robust stability in the alkylation of benzene with 1-dodecene based on the synergistic effect between Ce species and Brønsted acid sites,which pave the way for its practical application in the production of alkylbenzene.

CO_(2)-assisted oxidation dehydrogenation of light alkanes over metal-based heterogeneous catalysts

Light olefins are important platform feedstocks in the petrochemical industry,and the ongoing global economic development has driven sustained growth in demand for these compounds.The dehydrogenation of alkanes,derived from shale gas,serves as an alternative olefins production route.Concurrently,the target of realizing carbon neutrality promotes the comprehensive utilization of greenhouse gas.The integrated process of light alkanes dehydrogenation and carbon dioxide reduction(CO_(2)-ODH)can produce light olefins and realize resource utilization of CO_(2),which has gained wide popularity.With the introduction of CO_(2),coke deposition and metal reduction encountered in alkanes dehydrogenation reactions can be effectively suppressed.CO_(2)-assisted alkanes dehydrogenation can also reduce the risk of potential explosion hazard associated with O_(2)-oxidative dehydrogenation reactions.Recent investigations into various metal-based catalysts including mono-and bi-metallic alloys and oxides have displayed promising performances due to their unique properties.This paper provides the comprehensive review and critical analysis of advancements in the CO_(2)-assisted oxidative dehydrogenation of light alkanes(C2-C4)on metal-based catalysts developed in recent years.Moreover,it offers a comparative summary of the structural properties,catalytic activities,and reaction mechanisms over various active sites,providing valuable insights for the future design of dehydrogenation catalysts.

Review of Iron-Based Catalysts for Carbon Dioxide Fischer-Tropsch Synthesis

Capturing and utilizing CO_(2)from the production process is the key to solving the excessive CO_(2)emission problem. CO_(2)hydrogenation with green hydrogen to produce olefins is an effective and promising way to utilize CO_(2)and produce valuable chemicals. The olefins can be produced by CO_(2)hydrogenation through two routes, i.e., CO_(2)-FTS (carbon dioxide Fischer- Tropsch synthesis) and MeOH (methanol-mediated), among which CO_(2)-FTS has significant advantages over MeOH in practical applications due to its relatively high CO_(2)conversion and low energy consumption potentials. However, the CO_(2)-FTS faces challenges of difficult CO_(2)activation and low olefins selectivity. Iron-based catalysts are promising for CO_(2)-FTS due to their dual functionality of catalyzing RWGS and CO-FTS reactions. This review summarizes the recent progress on iron-based catalysts for CO_(2)hydrogenation via the FTS route and analyzes the catalyst optimization from the perspectives of additives, active sites, and reaction mechanisms. Furthermore, we also outline principles and challenges for rational design of high-performance CO_(2)-FTS catalysts.

Effects of zinc on Fe-based catalysts during the synthesis of light olefins from the Fischer-Tropsch process

Fe‐based catalysts for the production of light olefins via the Fischer‐Tropsch synthesis were modi‐fied by adding a Zn promoter using both microwave‐hydrothermal and impregnation methods. The physicochemical properties of the resulting catalysts were determined by scanning electron mi‐croscopy, the Brunauer‐Emmett‐Teller method, X‐ray diffraction, H2 temperature‐programed re‐duction and X‐ray photoelectron spectroscopy. The results demonstrate that the addition of a Zn promoter improves both the light olefin selectivity over the catalyst and the catalyst stability. The catalysts prepared via the impregnation method, which contain greater quantities of surface ZnO, exhibit severe carbon deposition following activity trials. In contrast, those materials synthesized using the microwave‐hydrothermal approach show improved dispersion of Zn and Fe phases and decreased carbon deposition, and so exhibit better CO conversion and stability.

Synthesis and characterization of an unusual snowflake-shaped ZSM-5 zeolite with high catalytic performance in the methanol to olefin reaction

The ZSM-5 zeolite with an unusual snowflake-shaped morphology was hydrothermally synthesized for the first time,and compared with common ellipsoidal and boat-like shaped samples.These samples were characterized by N2 adsorption-desorption,X-ray fluorescence spectroscopy,scanning electron microscopy,X-ray diffraction,magic angle spinning nuclear magnetic resonance,temperature-programmed desorption of ammonia,and infrared spectroscopy of pyridine adsorption.The results suggest that the BET surface area and SiO2/Al2O3 ratio of these samples are similar,while the snowflake-shaped ZSM-5 zeolite possesses more of the（101） face,and distortion,dislocation,and asymmetry in the framework,resulting in a larger number of acid sites than the conventional samples.Catalysts for the methanol to olefin（MTO） reaction were prepared by loading Ca on the samples.The snowflake-shaped Ca/ZSM-5 zeolite exhibited excellent selectivity for total light olefin（72%） and propene（39%） in MTO.The catalytic performance influenced by the morphology can be mainly attributed to the snowflake-shaped ZSM-5 zeolite possessing distortion,dislocation,and asymmetry in the framework,and lower diffusion limitation than the conventional samples.

Modulating the microstructure and surface chemistry of carbocatalysts for oxidative and direct dehydrogenation: A review

The catalytic performance of solid catalysts depends on the properties of the catalytically active sites and their accessibility to reactants, which are significantly affected by the microstructure（morphology, shape, size, texture, and surface structure） and surface chemistry（elemental components and chemical states）. The development of facile and efficient methods for tailoring the microstructure and surface chemistry is a hot topic in catalysis. This contribution reviews the state of the art in modulating the microstructure and surface chemistry of carbocatalysts by both bottom‐up and top‐down strategies and their use in the oxidative dehydrogenation（ODH） and direct dehydrogenation（DDH） of hydrocarbons including light alkanes and ethylbenzene to their corresponding olefins, important building blocks and chemicals like oxygenates. A concept of microstructure and surface chemistry tuning of the carbocatalyst for optimized catalytic performance and also for the fundamental understanding of the structure‐performance relationship is discussed. We also highlight the importance and challenges in modulating the microstructure and surface chemistry of carbocatalysts in ODH and DDH reactions of hydrocarbons for the highly‐efficient, energy‐saving,and clean production of their corresponding olefins.

Polymerization Mechanism of α-Linear Olefin

The density functional theory on the level of B3LYP/6-31G was empolyed to study the chain growth mechanism in polymerization process of α-linear olefin in TiCl3/AlEt2Cl catalytic system to synthesize drag reduction agent. Full parameter optimization without symmetry restrictions for reactants, products, the possible transition states, and intermediates was calculated. Vibration frequency was analyzed for all of stagnation points on the potential energy surface at the same theoretical level. The internal reaction coordinate was calculated from the transition states to reactants and products respectively. The results showed as flloes： （i） Coordination compounds were formed on the optimum configuration of TiCl3/AlEt2Cl.（ii） The transition states were formed. The energy di？erence between transition states and the coordination compounds was 40.687 kJ/mol. （iii） Double bond opened and Ti-C（4） bond fractured, and the polymerization was completed. The calculation results also showed that the chain growth mechanism did not essentially change with the increase of carbon atom number of α-linear olefin. From the relationship between polymerization activation energy and carbon atom number of the α-linear olefin, it can be seen that the α-linear olefin monomers with 6-10 carbon atoms had low activation energy and wide range. It was optimum to synthesize drag reduction agent by polymerization.

阳离子树脂催化罗汉柏木烯异构化的研究

以阳离子交换树脂催化异构罗汉柏木烯,制备以Olefin B为主的异构化产物。对阳离子交换树脂进行筛选,确定大孔强酸性阳离子交换树脂HND-8对罗汉柏木烯的异构化有较好的催化活性与选择性;并对HND-8树脂催化下罗汉柏木烯的异构化工艺进行研究,得到最佳的工艺条件为:HND-8用量为罗汉柏木烯质量的5%,冰醋酸与罗汉柏木烯的质量比1∶2,反应温度80℃,反应时间6 h。在此条件下,Olefin B的含量为45.5%,产率为65.0%;催化剂重复使用性能良好,使用6次产物中Olefin B的得率未有明显下降。采用FTIR对催化剂进行表征。

烯式吡虫啉(olefin IMI)光解及其光解产物研究

烟碱类杀虫剂吡虫啉(imidacloprid,IMI)在环境中可代谢为生物活性提高10倍的烯式吡虫啉(olefin IMI)。研究了olefin IMI的光稳定性、光解动力学和光解代谢途径。结果表明:olefin IMI在避光条件下较为稳定,室温下放置400d后,olefin IMI含量仅减少3%;而在室内模拟日光条件下,olefin IMI易于分解,光解反应符合一级动力学方程(r>0.99),半衰期为4d。olefin IMI的光解反应存在2条主要途径:一是羟基化生成4,5-二羟基化吡虫啉,该产物进一步氧化断裂药效基团硝基亚胺基生成羰基化产物;二是直接脱去硝基基团生成胍基产物。

Production of Light Olefins from Biosyngas by Two-stage Catalytic Conversion Process via Dimethyl Ether

NiSAPO-34 and NiSAPO-34/HZSM-5 were prepared and evaluated for the performance of dimethyl ether （DME） conversion to light olefins （DTO）. The processes of two-stage light olefin production, DME synthesis and the following DTO, were also investigated using biosyngas as feed gas over Cu/Zn/A1/HZSM-5 and the optimized 2%NiSAPO-34/HZSM- 5. The results indicated that adding 2%Ni to SAPO-34 did not change its topology structure, but resulted in the forming of the moderately strong acidity with decreasing acid amounts, which slightly enhanced DME conversion activity and C2=-C3= selectiw ity. Mechanically mixing 2%NiSAPO-34 with HZSM-5 at the weight ratio of 3.0 further prolonged DME conversion activity to be more than 3 h, which was due to the stable acid sites from HZSM-5. The highest selectivity to light olefins of 90.8% was achieved at 2 h time on stream. The application of the optimized 2%NiSAPO-34/HZSM-5 in the second-stage reactor for DTO reaction showed that the catalytic activity was steady for more than 5 h and light olefin yield was as high as 84.6 g/m3syngas when the biosyngas （H2/CO/CO2/N2/CH4=41.5/26.9/14.2/14.6/2.89, vol%） with low H/C ratio of 1.0 was used as feed gas.

二氧化硅负载磷钨酸催化罗汉柏木烯的异构反应

甲基柏木酮为柏木系最重要的香料之一,具有珍贵的木香-麝香-龙涎香气息,其中Isomer G成分的香气最为出色,它是由罗汉柏烯先异构为Olefin B,再乙酰化得到。采用溶胶-凝胶法制备二氧化硅负载磷钨酸固体催化剂制备Olefin B,研究磷钨酸负载量、焙烧温度和焙烧时间对催化剂活性的影响,用比表面积及孔径分析(BET)、X-射线多晶衍射(XRD)进行表征;通过单因素及正交试验优化罗汉柏木烯异构反应工艺,并用气相色谱-质谱(GC-MS)联用仪对产物进行表征。研究表明:催化剂制备最佳工艺条件为磷钨酸负载量40%、焙烧温度200℃和焙烧时间3 h时,催化活性最强;异构化单因素最佳条件为反应温度70℃、反应时间7 h、溶剂质量分数50%和催化剂质量分数10%;正交试验最佳工艺条件为反应温度80℃、反应时间7 h、乙酸质量分数50%和催化剂质量分数10%,平均得率58.1%,产物Olefin B(7,10-桥亚乙基-4,4,7-三甲基-1,9-八氢化萘)的选择性为97.7%,催化剂可循环使用3次。

Catalytic epoxidation of olefin over supramolecular compounds of molybdenum oxide clusters and a copper complex

The catalytic epoxidation of olefin was investigated on two copper complex-modified molybdenum oxides with a 3D supramolecular structure, [Cu（bipy）]4[Mo15O47].2H2O （1） and [Cu1（bix）][（Cu1bix） （δ-MoVl8O26）0.5] （2） （bipy = 4,4＇-bipyridine, bix = 1,4-bis（imidazole-1-ylmethyl）benzene）. Both compounds were catalytically active and stable for the epoxidation of cyclooctene, 1-octene, and styrene with tert-butyl hydroperoxide （t-BuOOH） as oxidant. The excellent catalytic performance was attributed to the presence of stable coordination bonds between the molybdenum oxide and copper complex, which resulted in the formation of easily accessible Mo species with high electropositivity. In addition, the copper complex also acted as an active site for the activation of t-BuOOH, thus im- proving these copper complex-modified polyoxometalates.

Changing the balance of the MTO reaction dual-cycle mechanism: Reactions over ZSM-5 with varying contact times

The methanol to olefins （MTO） reaction was performed over ZSM‐5 zeolite at 300℃ under various methanol weight hourly space velocity （WHSV） values. During these trials, the catalytic perfor‐mance was assessed, in addition to the formation and function of organic compounds retained in the zeolite. Analysis of reaction effluents and confined organics demonstrated a dual‐cycle reaction mechanism when employing ZSM‐5. The extent of the hydrogen transfer reaction, a secondary reac‐tion in the MTO process, varied as the catalyst‐methanol contact time was changed. In addition, 12C/13C‐methanol switch experiments indicated a relationship between the dual‐cycle mechanism and the extent of the hydrogen transfer reaction. Reactions employing a low methanol WHSV in conjunction with a long contact time favored the hydrogen transfer reaction to give alkene products and promoted the generation and accumulation of retained organic species, such as aromatics and methylcyclopentadienes, which enhance the aromatic cycle. When using higher WHSV values, the reduced contact times lessened the extent of the hydrogen transfer reaction and limited the genera‐tion of methylcyclopentadienes and aromatic species. This suppressed the aromatic cycle, such that the alkene cycle became the dominant route during the MTO reaction.

Effects of AOS on Bt's Adhesion Amount on Vegetable Leaves and Its Insecticidal Effect

[Objectives] This study was conducted to investigate the safety of surfactants AOS and Tween 80 on Bt and their effects on Bt's adhesion amount on crop leaves and its field efficacy. [Methods] Certain concentrations of AOS and Tween 80 were added to Bt liquid to check the effects of the surfactants on Bt spore germination, the adhesion amount of Bt on vegetable leaves and the field efficacy on beet armyworm. [Results] After treatment with surfactants AOS and Tween 80, Bt spores germinated normally. After adding AOS, the adhesion amounts of Bt spores on scallion, kohlrabi, radish and Chinese cabbage leaves were 209.75, 249.00, 274.00 and 281.75, respectively, which was 3.8, 2.2, 2.0 and 1.6 times higher than the CK. After adding Tween 80, the adhesion amounts of Bt spores on scallion, kohlrabi, radish and Chinese cabbage leaves were 198.25, 203.25, 233.00 and 236.75, respectively, which were 3.6, 1.8, 1.7 and 1.4 times higher than the CK, respectively. The average field insecticidal effect of the Bt liquid reached 81.3% and 79.5% after the addition of surfactants AOS and Tween 80, respectively, while the average insecticidal effect of the CK without the addition of a surfactant was only 53.3%, which was remarkably lower than above two values. [Conclusions] Surfactants AOS and Tween 80 are safe for Bt; and the addition of surfactants AOS and Tween 80 significantly increased the amount of Bt attached to vegetable leaves, and significantly improved the control efficacy of pests on plants rich in cuticle.

罗汉柏木烯异构化反应工艺

以柏木油为原料,对柏木油中罗汉柏木烯异构化生成Olefin B的催化剂种类及影响因素进行了对比研究。结果表明:以五氧化二磷为催化剂,m(柏木油)∶m(冰醋酸)∶m(五氧化二磷)=15∶7∶1,反应温度为60～70℃,反应时间为4～5 h,罗汉柏木烯转化率为96.5%,其中Olefin B的产率为24%。

Charge compensation dominates the distribution of silica in SAPO-34

The distribution of Si atoms in the SAPO-34 framework determines its acidity and catalytic effects.This was investigated using the charge balance between the inorganic framework and trapped template ions.Three types of templates,which yielded R~＋,2R~＋ and 2R^（2＋） positive charges in the cages of SAPO-34,were obtained from single crystal data and they were used to direct the synthesis of SAPO-34 with different Si contents and formation of isolated Si atoms and Si islands in the lattice.The concentration limits of SiO2 in the gel for constituting isolated Si atoms were calculated and verified experimentally.Si islands,including 5-Si,8-Si,11-Si,14-Si island were described on the basis of host-guest charge compensation.An overall view of the distribution of Si atoms in SAPO-34 was given and a criterion for the strength and density of acid sites in SAPO-34 for it to be an efficient catalyst for MTO was made available.

Production of Low-carbon Light Olefins from Catalytic Cracking of Crude Bio-oil

Low-carbon light olefins are the basic feedstocks for the petrochemical industry. Catalytic cracking of crude bio-oil and its model compounds （including methanol, ethanol, acetic acid, acetone, and phenol） to light olefins were performed by using the La/HZSM-5 catalyst. The highest olefins yield from crude bio-oil reached 0.19 kg/（kg crude bio-oil）. The reaction conditions including temperature, weight hourly space velocity, and addition of La into the HZSM-5 zeolite can be used to control both olefins yield and selectivity. Moderate adjusting the acidity with a suitable ratio between the strong acid and weak acid sites through adding La to the zeolite effectively enhanced the olefins selectivity and improved the catalyst stability. The production of light olefins from crude bio-oil is closely associated with the chemical composition and hydrogen to carbon effective ratios of feedstock. The comparison between the catalytic cracking and pyrolysis of bio-oil was studied. The mechanism of the bio-oil conversion to light olefins was also discussed.

多聚磷酸催化罗汉柏木烯异构化反应工艺

以柏木油为原料,对柏木油中罗汉柏木烯异构化生成Olefin B的催化剂种类及影响因素进行了对比研究。结果表明,以多聚磷酸为催化剂,质量比为柏木油∶冰醋酸∶多聚磷酸=45∶18∶8,反应温度为50℃,反应时间为3h,Olefin B含量可达10.3%,产率25.8%。

New Trends in Olefin Production

Most olefins （e.g., ethylene and propylene） will continue to be produced through steam cracking （SC） ofhydrocarbons in the coming decade. In an uncertain commodity market, the chemical industry is investingvery little in alternative technologies and feedstocks because of their current lack of economic viability,despite decreasing crude oil reserves and the recognition of global warming. In this perspective, some of themost promising alternatives are compared with the conventional SC process, and the major bottlenecks ofeach of the competing processes are highlighted. These technologies emerge especially from the abundanceof cheap propane, ethane, and methane from shale gas and stranded gas. From an economic point of view,methane is an interesting starting material, if chemicals can be produced from it. The huge availability ofcrude oil and the expected substantial decline in the demand for fuels imply that the future for proventechnologies such as Fischer-Tropsch synthesis （FFS） or methanol to gasoline is not bright. The abundance ofcheap ethane and the large availability of crude oil, on the other hand, have caused the SC industry to shiftto these two extremes, making room for the on-purpose production of light olefins, such as by the catalyticdehydrogenation of orooane.