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.

Preparation of modified Ce-SAPO-34 catalysts and their catalytic performances of methanol to olefins

The modified Ce-SAPO-34 catalysts were prepared with three methods, i.e., the liquid ion exchange with air calcination, impregnation with air calcination and impregnation with steam calcination methods. The catalytic performances of the catalysts for methanol to olefins were investigated. The properties of the catalysts were characterized using XRD, BET, XRF, FT-IR and NH3-TPD. The results indicated that compared to the SAPO-34 catalyst the catalyst prepared with the impregnation and air calcination prolonged the lifetime by 40 min and improved the selectivity to ethylene by 5% （mol） and the catalyst prepared with the impregnation and steam calcination showed the best modification effect, prolonging the lifetime by 70 min and improving the ethylene selectivity by 10% （mol）. The catalyst prepared with the liquid ion exchange showed similar behaviour as the SAPO-34 catalyst. It was verified that the porous structure and surface acidity of these catalysts determined their catalytic behaviors.

Study on the deactivation and regeneration of the ZSM-5 catalyst used in methanol to olefins

ZSM-5 zeolite catalyst modified by a trace of metal cations shows high activity and high selectivity for the reaction of methanol to olefins （MTO）, but it inclines to deactivate during the reaction. In this paper, the mechanism of the catalyst deactivation and the regeneration method were studied by X-ray diffraction （XRD）, N2 adsorption-desorption, infrared spectra （IR）, and infrared spectra coupled with NH3 molecular probes （IR-NH3）. These characterizations indicated that coke formation was the main reason for the catalyst deactivation. To regenerate the deactivated catalyst, two methods, i.e., calcination and methanol leaching, were used. N2 adsorption-desorption, IR and IR-NH3 characteriza-tions showed that both methods can eliminate coke deposited on the catalyst and make the catalyst reactivated. XRD showed that the structure of the catalyst did not change after regeneration. Interestingly, the regenerated catalyst even showed better catalytic performance of the MTO reaction than the fresh one. Besides, the calcination regeneration can eliminate coke more completely, however, the methanol leaching method can be more easily carried out in situ in the reactor.

In situ Synthesis of SAPO-34 Zeolites in Kaolin Microspheres for a Fluidized Methanol or Dimethyl Ether to Olefins Process

SAPO-34 zeolite is considered to be an effective catalyst for methanol or dimethyl ether conversion to olefins. In this study,we developed the in situ synthesis technology to prepare SAPO-34 zeolite in kaolin micro-spheres as a catalyst for fluidized methanol or dimethyl ether to olefins process. The silicoaluminophosphate zeolite was first time reported to be synthesized in kaolin microspheres. The SAPO-34 content of synthesized catalyst was about 22% as measured by three different quantitative methods(micropore area,X-ray fluorescence and energy dispersive spectroscopy element analysis) . Most of the SAPO-34 zeolites were in nanoscale size and distributed uniformly inside the spheres. The catalytic performance was evaluated in fixed bed and fluidized bed reactors. Compared with the conventional spray-dry catalyst,SAPO/kaolin catalyst showed superior catalytic activities,bet-ter olefin selectivities(up to 94%,exclusive coke) ,and very good hydrothermal stability. The in situ synthesis of SAPO-34 in kaolin microspheres is a facile and economically feasible way to prepare more effective catalyst for fluidized MTO/DTO(methanol to olefins/dimethyl ether to olefins) process.

Light olefin production by catalytic co-cracking of Fischer–Tropsch distillate with methanol and the reaction kinetics investigation

Catalytic co-cracking of Fischer–Tropsch(FT) light distillate and methanol combines highly endothermic olefin cracking reaction with exothermic methanol conversion over ZSM-5 catalyst to produce light olefins through a nearly thermoneutral process. The kinetic behavior of co-cracking reactions was investigated by different feed conditions: methanol feed only, olefin feed only and co-feed of methanol with olefins or F–T distillate. The results showed that methanol converted to C2–C6 olefins in first-order parallel reaction at low space time, methylation and oligomerization–cracking prevailed for the co-feed of methanol and C2–C5 olefins, while for C6–C8 olefins,monomolecular cracking was the dominant reaction whether fed alone or co-fed with methanol. For FT distillate and methanol co-feed, alkanes were almost un-reactive, C3–C5 olefins were obtained as main products, accounting for 71 wt% for all products. A comprehensive co-cracking reaction scheme was proposed and the model parameters were estimated by the nonlinear least square method. It was verified by experimental data that the kinetic model was reliable to predict major product distribution for co-cracking of FT distillate with methanol and could be used for further reactor development and process design.

An effective route to improve the catalytic performance of SAPO-34 in the methanol-to-olefin reaction

An effective route to improve the catalytic performance of SAPO-34 in the methanol-to-olefin reaction by simple oxalic acid treatment was investigated. The samples were characterized by XRD, SEM, N2 adsorption-desorption, XRF, TG, 29Si MAS NMR and NH3-TPD techniques. The results indicated that the external surface acidity of SAPO-34 was finely tuned by oxalic acid treatment, and the selectivity to C2H4 on SAPO-34 and the catalyst lifetime in the methanol-to-olefin reaction were greatly improved.

Data-driven optimal operation of the industrial methanol to olefin process based on relevance vector machine

Methanol to olefin(MTO)technology provides the opportunity to produce olefins from nonpetroleum sources such as coal,biomass and natural gas.More than 20 commercial MTO plants have been put into operation.Till now,contributions on optimal operation of industrial MTO plants from a process systems engineering perspective are rare.Based on relevance vector machine(RVM),a data-driven framework for optimal operation of the industrial MTO process is established to fully utilize the plentiful industrial data sets.RVM correlates the yield distribution prediction of main products and the operation conditions.These correlations then serve as the constraints for the multi-objective optimization model to pursue the optimal operation of the plant.Nondominated sorting genetic algorithmⅡis used to solve the optimization problem.Comprehensive tests demonstrate that the ethylene yield is effectively improved based on the proposed framework.Since RVM does provide the distribution prediction instead of point estimation,the established model is expected to provide guidance for actual production operations under uncertainty.

Kinetics of steam regeneration of SAPO-34 zeolite catalyst in methanol-to-olefins(MTO) process

Methanol-to-olefins(MTO)is industrially applied to produce ethylene and propylene using methanol converted from coal,synthetic gas,and biomass.SAPO-34 zeolites,as the most efficient catalyst in MTO process,are subject to the rapid deactivation due to coke deposition.Recent work shows that steam regeneration can provide advantages such as low carbon dioxide emission and enhanced light olefins yield in MTO process,compared to that by air regeneration.A kinetic study on the steam regeneration of spent SAPO-34 catalyst has been carried out in this work.In doing so,we first investigated the effect of temperature on the regeneration performance by monitoring the crystal structure,acidity,residual coke properties and other structural parameters.The results show that with the increase of regeneration temperature,the compositions of residual coke on the catalyst change from pyrene and phenanthrene to naphthalene,which are normally considered as active hydrocarbon pool species in MTO reaction.However,when the regeneration temperature is too high,nitrogen oxides can be found in the residual coke.Meanwhile,as the regeneration temperature increases,the quantity of residual coke reduces and the acidity,BET surface area and pore structure of the regenerated samples can be better recovered,resulting in prolonging catalyst lifetime.We have further derived the kinetics of steam regeneration,and obtained an activation energy of about 177.8 kJ·mol^(-1).Compared that with air regeneration,the activation energy of steam regeneration is higher,indicating that the steam regeneration process is more difficult to occur.

Methylcyclopentenyl cation mediated reaction route in methanol-to-olefins reaction over H-RUB-50 with small cavity

Methylcyclopentenyl cations(MCP+)have been regarded as active intermediates during methanol conversion,however,their function mode in the reaction are still uncertain.In our recent report,trimethylcyclopentenyl cation(triMCP+)and its deprotonated counterpart(trimethylcyclopentadiene,tri MCP)were directly captured on H-RUB-50 catalyst with small cavity by the aid of in situ 13C MAS NMR spectroscopy,and their higher catalytic reactivity were clarified by 12C/13C-CH3OH isotopic switch experiment.In this contribution,an alternative route-cyclopentadienes-based cycle was applied on methanol conversion catalyzed on the H-RUB-50,in which ethene was produced with the participation of tri MCP+as critical intermediate.Then the cyclopentadienes-based cycle was predicted to be energetically favorable for ethene formation by density functional theory(DFT)calculations.The energetic comparison of paring mechanism in the aromatics-based cycle and cyclopentadienes-based cycle with the involvements of trimethylcyclopentadienyl(tri MCPdi+)and tri MCP+as the corresponding active intermediates suggests that cyclopentadienes-based cycle is a feasible route for ethene formation.Furthermore,this work highlights the importance of the steric constraint and the host-guest interaction induced by the zeolite with cavity structure in the formation of intermediates and reaction pathway.

Reaction and deactivation kinetics of methanol-to-olefins process based on a special TGA reactor

Thermax 700 thermo gravimetric analysis （TGA） instrument is introduced for the investigation of the reaction and deactivation kinetics of Methanol-to-Olefins （MTO） process with SAPO-34 catalyst.By the use of a special sample basket,the TGA instrument can be viewed as a plug flow fixed-bed reactor,while the weight change of SAPO-34 during reaction can be recorded online.Kinetic data are acquired in the temperature range of 648.2？748.2 K and space velocities of 7.08？35.91 h^-1 （WHSV）.Catalyst activity is expressed with average coke content,and selectivity for different products is related as a function of coke content and temperature.Methane is also introduced into the lumping kinetic model,and power exponent function with first-order reaction is adopted for model deduction.Exponential function is tested to give the best fit for catalyst activity and product selectivity with the highest correlation coefficient.The nicely agreed results between experimental and calculated data suggest that the overall kinetic model would be meaningful in both product distribution prediction and reactor simulation.

One-Pot Synthesis of Hierarchically Nanoporous SSZ-13 for Conversion of Methanol to Olefins

The main disadvantage of microporous SSZ-13 catalyst used in the methanol to olefins(MTO) process is its rapid deactivation due to its relatively low coke resistance. Meanwhile, the hierarchical zeolites usually exhibit improved catalytic stability thanks to their better mass transfer ability. Herein, the hierarchically nanoporous SSZ-13 zeolites were one-pot synthesized by using N,N,N-trimethyl-1-adamantanammonium hydroxide as a microporous structure directing agent and C_(18)H_(37) N^+(CH_3)_2 C_6H_(12) N^+(CH_3)_2 C_6 H_(13)(Br^-)_2(hereinafter abbreviated as C_(18-6-6) Br_2) as a mesoporogen. The hierarchically nanoporous SSZ-13 catalyst was characterized by XRD, N_2 physisorption, SEM, TEM, TG-DTG, ^(27) Al and ^(29) SiNMR spectroscopy and NH_3-TPD techniques. The results showed that the hierarchical SSZ-13 zeolite synthesized in the presence of the C_(18-6-6) Br_2 surfactant exhibits aggregates of primary nanocrystals and contains the well-developed mesopores and excellent acidity. Compared to its conventional counterpart, the hierarchical SSZ-13 zeolite has longer catalytic lifetime and higher selectivity for ethylene and propylene in the MTO reaction, which can be attributed to the synergistic effect of their good acidity and improved diffusion properties resulted from the hierarchical pore structure.

Study on Olefins Yield from Methanol Conversion over Different Catalysts

Conversion of Methanol to Olefins (MTO) under different reaction conditions was ex- perimentally investigated over different catalysts, and comparison was made between the SAPO-34 and GOR-MLC catalysts. Optimization of reaction conditions has been explored. Conversion of methanol to olefins over these catalysts under different reaction temperatures was experimentally studied. In a fixed bed micro-reactor, the influence of temperature was found to be one of the major factors. For both catalysts the olefins yield was increased significantly when water was added to the methanol feed. A temperature range of 460—480 ℃ appeared to be the optimum range suitable for methanol conversion with appropriate catalyst activity and C2—C3 olefins yield. Some other hydrocarbons appeared during the MTO reaction in the presence of the SAPO-34 catalyst, while a lot of dimethylether was formed when the GOR-MLC catalyst was used. In the course of the MTO reaction, the GOR-MLC catalyst was found to have a faster catalyst deactivation rate compared to the SAPO-34 catalyst.

A Probe into Process for Maximization of Low-carbon Olefins via Co-processing of Methanol and Heavy Oil

From the viewpoint of process specifics and thermodynamics, this article has put forward a route for maximiza- tion of low-carbon olefins via co-processing of methanol and heavy oil. Catalytic cracking experiments on co-processing of methanol and heavy oil at different ratios in a fixed fluidized bed reactor had been conducted. Test results have revealed that when 12.5% of methanol was blended to the heavy oil a good products distribution and relatively higher yield of low-carbon olefins could be obtained. The overall yield of low-carbon olefins could reach 50.16%, with the yield of ethylene, propylene and butylene equating to 5.47 %, 28.93% and 15.76 %, respectively.

Performance of Methanol-to-Olefins Catalytic Reactions by the Addition of PEG in the Synthesis of SAPO-34

SAPO-34, a silicoaluminophosphate zeolite, has been synthesized by the hydrothermal method with the addition of different molecular weights of polyethylene glycol(PEG), and has been characterized with XRD, SEM,N_2 adsorption–desorption, FT-IR, and NH_3 temperatureprogrammed desorption(NH_3-TPD). We studied SAPO-34 as a catalyst in the methanol-to-olefins(MTO) reaction, in a fixed-bed reactor. The results show that the chain length of PEG has a great influence on the particle size and morphology of SAPO-34. PEG acts as inhibitor in the crystallization process. With the increase of the chain length of PEG used in the synthesis, from a relative molecular weight of 400-6000, the morphology of SAPO-34 changes gradually from cubic to nanoplate-like and then changes to cubic again. The particle size decreases markedly at first and then increases to some extent. The catalytic stability in the MTO reaction also increases first and then decreases, with all the catalysts having almost the same selectivity to olefins. When the sample is synthesized with PEG800, the particles become nanoplate-like with a thickness of 46 nm on average, and the catalytic stability is appreciably prolonged, which is attributed to the shorter diffusion paths of the reactants in the zeolite.

SOLVENT PARTICIPATION OF WITTIG OLEFINATION REACTION IN METHANOL

Wittig reaction in methanol was investigated, and a possible mechanism was proposed.

Progress in the Field of Converting Methanol into Light Olefins over the ZSM-5 Zeolite Catalyst

Technical progress in the field of conversion of methanol into ethylene and propylene over the ZSM-5 catalyst was summarized. The economical analysis of the technology, the mechanism of chemical reaction and reaction kinetics were introduced. The factors including the effect of the operating conditions,the influence of catalyst preparation conditions and modification of ZSM-5 zeolite on the reaction and coke formation were also discussed.

Significant Breakthrough in Industrial Test of the "Methanol to Olefins" Process Developed by Dalian Institute of Chemical Physics,Chinese Academy of Sciences

A process of ＂Methanol or Dimethylether to Olefins＂ developed by Dalian Institute of Chemical Physics （DICP）, designated as the DMTO process, has attained great success in industrial scaling up testing. DICP, by collaborating with the Xinxing Coal Chemical Co., Ltd. of Shaanxi Province and the Luoyang Petrochemical Engineering Co. of the SINOPEC Group, operated successfully a 50t（methanol）/d unit for the conversion of methanol to lower olefins, with a methanol conversion of close to 100%, and a selectivity to lower olefins（ethylene, propylene and butylenes） of higher than 90%. On 23rd August, the industrial test project has passed a state appraisal. The experts of the Appraisal Group, headed by Prof. YUAN Qingtang, academician of Chinese Academy of Engineering, drew the conclusions that the DMTO process, by utilizing a proprietary SAPO-34 catalyst system and a recycling fluidized bed reaction system for the production of lower olefins from methanol, is the first unit in the world having a capacity of producing nearly ten thousand tons lower olefins per year. The technological level of the industrial test is at a leading position internationally. This accomplishment will provide a sound base for the subsequent commercialization of the DMTO process.

Commercial Demonstration Unit for Manufacture of Aromatics from Toluene and Methanol with Coproduction of Low-Carbon Olefins Will Be Set Up

On November 29,2013 the Shaanxi Coal Chemicals Technology Engineering Center,Ltd.(SCCTEC),the CNOOC Huizhou Refining and Chemical Company and the SINOPEC Luoyang Engineering Company,Ltd.signed an agreement on cooperation in development of

Kinetic Modeling of Methanol to Olefins(MTO)Process on SAPO-34 Catalyst

A kinetic model of MTO process over the SAPO-34 catalyst considering the effect of water and coke deposition has been proposed.The model takes into account three steps of the MTO reaction in which the products cover 5 lumped components.The water in the feed not only reduces the concentration of methanol but also alleviates the deactivation of SAPO-34 catalyst.The kinetic parameters have been estimated by the least square method.It has been proved that the calculated values in the kinetic model are in good agreement with the experimental values.

Co/SAPO-34催化剂在MTO反应中催化性能和积炭行为

针对SAPO-34分子筛在MTO反应中烯烃选择性低和易于酸性积炭失活的问题,通过等体积浸渍法向SAPO-34分子筛孔道内引入金属Co,系统考察了Co的加入量对Co/SAPO-34催化剂在MTO反应中的催化性能和积炭行为的影响。结果表明金属Co可以作为脱氢反应中心位点,削弱氢离子转移作用,抑制烷烃的生成,进而有效提高反应烯烃选择性;同时Co金属的引入可以精密调控SAPO-34分子筛表面酸中心强度,提高弱酸/强酸比例,进而削弱强酸中心的积炭作用,抑制催化剂的积炭失活。结合NH_(3)-TPD、H_(2)-TPD、氮气物理吸脱附、TG、XPS、GC-MS等表征方法,深入探讨Co/SAPO-34催化剂在MTO反应中的积炭行为,发现多甲基苯类关键积炭前体优先沉积于微孔和强酸位点,并显著促进稠环芳烃的生成,而相对较大的孔体积以及适量的弱酸浓度可以协同促进积炭前体的分解转化,抑制稠环芳烃等硬积炭物种的形成。积炭速率计算表明,具有适量酸性和孔道结构的Co 0.5/SAPO-34的甲醇转化率及低碳烯烃选择性最高,催化寿命最长。