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.

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.

Boosting CO_(2) hydrogenation to high-value olefins with highly stable performance over Ba and Na co-modified Fe catalyst

CO_(2)hydrogenation has been considered to be a highly promising route for the production of high-value olefins(HVOs)while also mitigating CO_(2)emissions.However,it is challenging to achieve high selectivity and maintain stable performance for HVOs(ethylene,propylene,and linear a-olefins)over a prolonged reaction time due to the difficulty in precise control of carbon coupling and rapid catalyst deactivation.Herein,we present a selective Ba and Na co-modified Fe catalyst enriched with Fe_(5)C_(2)and Fe_(3)C active sites that can boost HVO synthesis with up to 66.1%selectivity at an average CO_(2)conversion of 38%for over 500 h.Compared to traditional NaFe catalyst,the combined effect of Ba and Na additives in the NaBaFe-0.5 catalyst suppressed excess oxidation of FeCxsites by H_(2)O.The absence of Fe3O4phase in the spent NaBaFe-0.5 catalyst reflects the stabilization effect of the co-modifiers on the FeCxsites.This study provides a strategy to design Fe-based catalysts that can be scaled up for the stable synthesis of HVOs from CO_(2)hydrogenation.

Targeted Catalytic Cracking to Olefins(TCO):Reaction Mechanism,Production Scheme,and Process Perspectives

Light olefins are important organic building blocks in the chemicals industry.The main low-carbon olefin production methods,such as catalytic cracking and steam cracking,have considerable room for improvement in their utilization of hydrocarbons.This review provides a thorough overview of recent studies on catalytic cracking,steam cracking,and the conversion of crude oil processes.To maximize the production of light olefins and reduce carbon emissions,the perceived benefits of various technologies are examined.Taking olefin generation and conversion as a link to expand upstream and downstream processes,a targeted catalytic cracking to olefins(TCO)process is proposed to meet current demands for the transformation of oil refining into chemical production.The main innovations of this process include a multiple feedstock supply,the development of medium-sized catalysts,and a diameter-transformed fluidizedbed reactor with different feeding schemes.In combination with other chemical processes,TCO is expected to play a critical role in enabling petroleum refining and chemical processes to achieve low carbon dioxide emissions.

Catalyst for Increasing Ethylene and Propylene Production and Its Industrial Application in a Catalytic Pyrolysis Unit

Light olefins,particularly ethylene and propylene,are the most important building blocks for the petrochemical industry,and demand for their production has been increasing.The catalytic pyrolysis process(CPP)and the corresponding catalyst,developed by SINOPEC Research Institute of Petroleum Processing Co.,Ltd.,are designed to maximize the light olefin yield from catalytic cracking of heavy feedstocks.However,owing to the continuing degradation of feedstocks,the original catalyst can no longer maintain its activity.Herein,we describe the rational design of the new catalyst,Epylene,from a new metal-modified hierarchical ZSM-5 zeolite and matrix.Epylene was tested in the CPP unit of Shaanxi Yanchang Coal Yulin Energy and Chemical Company.A test run and base run were conducted to demonstrate the better performance of Epylene compared with the original catalyst.The properties of the feedstocks and the operating conditions in both runs were similar.The light olefin yield was increased from 33.95%to 36.50%and the coke yield was only 9.58%in the test run,which was lower than that in the base run.

Fischer-Tropsch wax catalytic cracking for the production of low olefin and high octane number gasoline: Process optimization and heat effect calculation

To produce low olefin gasoline with high octane number by Fischer-Tropsch (F-T) wax fluid catalytic cracking (FCC) process, operating conditions optimization were carried out in the pilot-scale riser and turbulent fluidized bed (TFB) FCC unit. The experimental results in the riser indicated that under the condition of low reaction temperature and regenerated catalyst temperature, large catalyst-to-oil weight ratio (C/O) and long reaction time, the gasoline olefin content could be reduced to 20.28 wt%, but there is large octane number loss owing to a great loss in high octane number olefin. Therefore, a novel FCC process using the TFB reactor was proposed to strengthen the aromatization reaction. The reaction performance of TFB reactor were investigated. The result demonstrated that the TFB reactor has more significant effect in reducing olefins and improving aromatics. At the expense of certain gasoline yield, the gasoline olefin content reduced to 23.70 wt%, aromatics content could increase to 26.79 wt% and the RON was up to 91.0. The comparison of reactor structure and fluidization demonstrated that the TFB reactor has higher catalyst bed density. The reaction heat and coke combustion heat was calculated indicating the feasibility of its industrial application of the TFB process.

Reaction characteristics of maximizing light olefins and decreasing methane in C_(5) hydrocarbons catalytic pyrolysis

When converting C_(5) hydrocarbons to light olefins by catalytic pyrolysis,the generation of low value-added methane will affect the atomic utilization efficiency of C_(5) hydrocarbons.To improve the atomic utilization efficiency,different generation pathways of light olefins and methane in the catalytic pyrolysis of C_(5) hydrocarbons were analyzed,and the effects of reaction conditions and zeolite types were inves-tigated.Results showed that light olefins were mainly formed by breaking the C_(2)-C_(3) bond in the middle position,while methane was formed by breaking the C_(1)-C_(2) bond at the end.Meanwhile,it was discovered that the hydrogen transfer reaction could be reduced by about 90%by selecting MTT zeolite with 1D topology and FER zeolite with 2D topology under high weight hourly space velocity(WHSV)and high temperature operations,thus leading to the improvement of the light olefins selectivity for the catalytic pyrolysis of n-pentane and 1-pentene to 55.12% and 74.60%,respectively.Moreover,the fraction ratio of terminal C_(1)-C_(2) bond cleavage was reduced,which would reduce the selectivity of methane to 6.63%and 1.83%.Therefore,zeolite with low hydrogen transfer activity and catalytic pyrolysis process with high WHsV will be conducive to maximize light olefins and to decrease methane.

Study on the epoxidation of olefins with H_(2)O_(2)catalyzed by biquaternary ammonium phosphotungstic acid

Selective epoxidation of olefins is an important field in chemical industry.In this work,we developed a new phosphotungstic acid catalyst{[(C_8H_(17))(CH_(3))_(2)N]_(2)(CH_(2))_(3)}_(1.5){PO_(4)[WO(O_(2))_(2)]_(4)}with long carbon chain and biquaternary ammonium cation.Cyclohexene could be epoxidized to cyclohexene oxide in 96.3%conversion and 98.2%selectivity.The catalyst type,solvent type,catalyst loading,initial molar ratio,temperature,cycle performance and substrate extensibility were studied and optimized,the kinetic parameters about overall reaction and unit reaction were also calculated.Dynamic light scattering analysis was carried out to explain the different catalytic performance between catalysts with different carbon chain length.This novel catalyst and the corresponding dynamics and mechanism study could probably help the industrial application on the epoxidation of cyclohexene with H_(2)O_(2).

Core-shell-structured Composite ZSM-5@MCM-41 Catalysts:Fabrication,Characterization,and Enhanced Performance in Hexane Catalytic Cracking

A series of core-shell zeolites with a ZSM-5 zeolite core and a MCM-41 shell with varying shell thicknesses were successfully fabricated via a cetyltrimethylammonium bromide(CTAB)-directed sol-gel coating method in an ultradilute solution. Extensive characterization techniques, including XRD, TEM, N_(2) adsorption-desorption, NH_(3)-TPD, and IR measurements, confirmed the successful coating of a microporous ZSM-5 core with a mesoporous MCM-41 shell layer and were further employed to explore the textural properties and acidic properties of the samples. The hexane cracking results revealed a significant enhancement in olefin yields after introducing the MCM-41 shell to ZSM-5. Interestingly, a volcanic trend in olefin yields was observed with the increase in the shell thickness. In particular, the highest olefin yield of 51.5%, exceeding that of the core catalyst by 17.1%, was achieved when the shell thickness was controlled at 40 nm.Moreover, the catalyst lifetime investigation revealed that the core-shell composite catalyst exhibited a minimal reduction in hexane conversion of merely 3.8% over a 120 h reaction period, significantly outperforming the 11.3% reduction exhibited by the core catalyst. This remarkable catalytic performance was attributed to the passivation of external acid sites and the introduction of more developed pore channels by the shell, which effectively mitigated unwanted side reactions. The successful synthesis of these core-shell structured catalysts presents a novel strategy for improving catalytic performance in hexane cracking, in addition to serving as a solid foundation for the design of industrial catalysts for light naphtha cracking.

Promotion effects of alkali metals on iron molybdate catalysts for CO_(2)catalytic hydrogenation

CO_(2)hydrogenation is an attractive way to store and utilize carbon dioxide generated by industrial processes,as well as to produce valuable chemicals from renewable and abundant resources.Iron catalysts are commonly used for the hydrogenation of carbon oxides to hydrocarbons.Iron-molybdenum catalysts have found numerous applications in catalysis,but have been never evaluated in the CO_(2)hydrogenation.In this work,the structural properties of iron-molybdenum catalysts without and with a promoting alkali metal(Li,Na,K,Rb,or Cs)were characterized using X-ray diffraction,hydrogen temperatureprogrammed reduction,CO_(2)temperature-programmed desorption,in-situ^(57)Fe Mossbauer spectroscopy and operando X-ray adsorption spectroscopy.Their catalytic performance was evaluated in the CO_(2)hydrogenation.During the reaction conditions,the catalysts undergo the formation of an iron(Ⅱ)molybdate structure,accompanied by a partial reduction of molybdenum and carbidization of iron.The rate of CO_(2)conversion and product selectivity strongly depend on the promoting alkali metals,and electronegativity was identified as an important factor affecting the catalytic performance.Higher CO_(2)conversion rates were observed with the promoters having higher electronegativity,while low electronegativity of alkali metals favors higher light olefin selectivity.

Water-based synthesis of nanoscale hierarchical metal-organic frameworks:Boosting adsorption and catalytic performance

The combination of nano sizes,large pore sizes and green synthesis is recognized as one of the most crucial and challenging problems in constructing metal-organic frameworks(MOFs).Herein,a water-based strategy is proposed for the synthesis of nanoscale hierarchical MOFs(NH-MOFs)with high crystallinity and excellent stability.This approach allows the morphology and porosity of MOFs to be fine tuned,thereby enabling the nanoscale crystal generation and a well-defined hierarchical system.The aqueous solution facilitates rapid nucleation kinetics,and the introduced modulator acts as a deprotonation agent to accelerate the deprotonation of the organic ligand as well as a structure-directing agent(SDA)to guide the formation of hierarchical networks.The assynthesized NH-MOFs(NH-ZIF-67)were assessed as efficient adsorbents and heterogeneous catalysts to facilitate the diffusion of guest molecules,outperforming the parent microZIF-67.This study focuses on understanding the NH-MOF growth rules,which could allow tailor-designing NH-MOFs for various functions.

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。

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。

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%。

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%。

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。

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.

Effect of manganese on the catalytic performance of an iron-manganese bimetallic catalyst for light olefin synthesis

A systematic study was carried out to investigate the promotion effect of manganese on the performance of a coprecipitated iron-manganese bimetallic catalyst for the light olefins synthesis from syngas. The catalyst samples were characterized by N2 physisorption, transmis- sion electron microscopy （TEM）, X-ray photoelectron spectroscopy （XPS）, powder X-ray diffraction （XRD）, Mossbauer spectroscopy, H2- differential thermogravimetric analysis （H2-DTG）, CO temperature-programmed reduction （CO-TPR） and CO2 temperature-programmed des- orption （CO2-TPD）. The Fischer-Tropsch synthesis （FTS） performance of the catalyst was measured at 1.5 MPa, 250 ℃ and syngas with H2/CO ratio of 2.0. The characterization results indicated that the addition of manganese decreases the catalyst crystallite size, and improves the catalyst BET surface area and pore volume. The presence of manganese suppresses the catalyst reduction and carburization in H2, CO and syngas, respectively. The addition of manganese improves the catalytic activity of water-gas shift reaction and suppresses the oxidation of iron carbides in the FTS reaction. The incorporation of manganese improves the catalyst surface basicity and results in a significant improvement in the selectivities to light olefins and heavy hydrocarbons （C5＋）, and furthermore an inhibition of methane formation in FTS. The pure iron catalyst （Mn-00） has the highest initial FTS catalytic activity （65%） and the lowest selectivity （17.35 wt%） to light olefins （C2=-C4=）. The addition of an appropriate amount of manganese can improve the catalyst FTS activity.