A two-stage catalyst bed concept for conversion of carbon dioxide into methanol

Conversion of CO₂ into methanol by catalytic hydrogenation has been recognized as one of the most promising processes for stabilizing the atmospheric CO₂ level, and furthermore the methanol produced could be used as fuel or basic chemical for satisfying the large demand world-wide. The present work investigates a two-stage catalyst bed concept for conversion of CO₂ to methanol. A system with two catalyst beds instead of one single catalyst bed is developed for conversion of CO₂ to methanol. In the first catalyst bed, the synthesis gas is partly converted to methanol in a conventional water-cooled reactor. This bed operates at higher than normal operating temperature and at high yield. In the second bed, the reaction heat is used to pre-heat the feed gas to the first bed. The continuously reduced temperature in this bed provides increasing thermodynamic equilibrium potential. In this bed, the reaction rate is much lower and, consequently, so is the amount of the reaction heat. This feature results in milder temperature profiles in the second bed because less heat is liberated compared to the first bed. In this way the catalysts are exposed to less extreme temperatures and, catalyst deactivation via sintering is circumvented. In this work, a one-dimensional dynamic plug flow dynamic is used to analyze and compare the performance of two-stage bed and conventional single bed reactors. The results of this work show that the two-stage catalyst bed system can be operated with higher conversion and longer catalyst life time.     

烯烃裂解增产丙烯催化剂再生性能

由于烯烃裂解技术反应自身的特点,催化剂容易积炭失活,需要进行多次再生,因此,催化剂的再生性能对烯烃裂解技术至关重要。在实验室对中国石化中原石油化工有限责任公司烯烃裂解工业装置的ZSM-5催化剂进行了多次反应和再生试验,考察其烯烃裂解反应性能,并运用TG、XRD、NH₃-TPD、氮气物理吸附以及SEM等对再生前后的催化剂样品进行表征。结果表明,开发的烯烃裂解催化剂经过13次的反应再生过程,新鲜催化剂与再生催化剂的比表面积和孔容基本相同,烯烃转化率、丙烯及乙烯收率无明显变化,烯烃转化率仍大于73%,丙烯和乙烯收率分别大于32%和10%。且催化剂骨架结构和酸中心稳定,在多次反应与再生过程中的酸量保持不变,具有良好的再生性能。     

DQ催化剂催化丙烯共聚合

研究了DQ催化剂生产抗冲共聚物时均聚物(基体相)与共聚物(橡胶相)的相对分子质量之比(即特性黏数之比)对橡胶相分散度的影响。对于DQ催化剂,当共聚物与均聚物的特性黏数之比为2．7～3．0时,所得抗冲共聚物中橡胶粒子分散程度较好,抗冲共聚物的相对分子质量分布为7～8。     

甲醇制烯烃装置催化剂跑损的研究

对甲醇制烯烃装置反应器和再生器催化剂跑损原因进行分析,利用装置DCS在线参数及离线分析数值的相关参数,对催化剂跑损量进行定量计算,探讨稀相密度值与催化剂跑损的联系,提出预防催化剂跑损的建议,对催化剂跑损研究具有一定指导意义。     

Behaviors of coke deposition on SAPO-34 catalyst during methanol conversion to light olefins

The deposition of coke on SAPO-34 during methanol conversion to olefins at temperatures of 623–823 K was observed to be fast initially but moderate in the later stage. Micropores are blocked badly at coke contents of above 4 wt.%. The coke deposition influences olefins selectivity significantly and selectivities of ethylene plus propylene reach maximum at a coke content of about 5.7 wt.%. The coke formation can be attenuated by the presence of water, but the effect of water weakens gradually with the progress of the reaction. A model relating the coke content over SAPO-34 to cumulative amount of methanol fed to the catalysts is proposed and proved the validity to estimate the coke content on SAPO-34 at different reaction conditions. The coke deposited at different reaction temperatures has different compositions.     

Kinetic study of the methanol to olefin process on a SAPO-34 catalyst

In this paper, a new kinetic model for methanol to olefin process over SAPO-34 catalyst was developed using elementary step level. The kinetic model fits well to the experimental data obtained in a fixed bed reactor. Using this kinetic model, the effect of the most important operating conditions such as temperature, pressure and methanol space-time on the product distribution has been examined. It is shown that the temperature ranges between 400 °C and 450 °C is appropriate for propene production while the medium temperature (450 °C) is favorable for total olefin yield which is equal to 33%. Increasing the reactor pressure decreases the ethylene yield, while medium pressure is favorable for the propylene yield. The result shows that the ethylene and propylene and consequently the yield of total olefins increase to approximately 35% with decreasing the molar ratio of inlet water to methanol.     

Homo- and copolymerization of ethylene and propylene with a soluble chromium catalyst

Polymerization of ethylene and propylene was carried out with a soluble $\text{Cr(C}{}_{17}\text{H}{}_{35}\text{COO}\text{)}{}_3\text{AlEt}{}_2\text{Cl}$ catalytic system in toluene. The system was found to be active only for ehtylene polymerization. From e.s.r. measurements of the catalytic system combined with some qualitative experiments, the active species was determined to be Cr²⁺. The reason why it should be incapable of polymerization of propylene was also discussed. The catalytic system showed some activity for ethylene-propylene copolymerization to give a random copolymer with a narrow molecular weight distribution.     

Catalytic performance of CeAPSO-34 molecular sieve with various cerium content for methanol conversion to olefin

A series of CeAPSO-34s with various cerium contents was synthesized and characterized by multiple techniques such as XRD, SEM, BET, ²⁹Si MAS NMR, NH₃-TPD and CO₂-TPD. NH₃-TPD spectra showed that a number of acid sites, especially those of strong acidity, is reduced with the increasing of Ce incorporation. Incorporation of metal ions gave rise to more silica-islands in the CeAPSO-34 framework. CO₂-TPD showed that basic sites on the surface of modified samples are due to the presence of Ce-containing species incorporation into the framework of CeAPSO-34 molecular sieves. The performance of the catalysts was studied in methanol to olefin reactions at 425 °C under the atmospheric pressure. The results showed that the incorporation of cerium ions had great effects on the structure and acidity of the molecular sieves. All SAPO-34 and MeAPSO-34 molecular sieves were the very active and selective catalyst for light olefins production. Cerium incorporation improved the catalyst lifetime and favored the ethylene and propylene generation. However, an excess Ce content resulted in an inferior catalytic performance and stability. Therefore, there existed optimal cerium content for a specific SAPO-34.     

Effect of the cocatalyst on the copolymerization of ethylene and propylene with high activity Ziegler-Natta catalyst

Summary Ethylene and propylene were copolymerized in n-heptane in the presence of high activity heterogeneous Ziegler-Natta catalyst to study the effect of the cocatalyst on the microstructure and molecular weight of the copolymer. Seven aluminium alkyls of structure Al((CH₂)_nCH₃)₃, where n = 0—3, 5, 7 or 11, and one of structure Al(C(CH₃)₃)₃, were used as cocatalysts. The effect of the Al/Ti mole ratio was also studied. Modern molecular modelling techniques were used to calculate the volume of the cocatalyst and the electron density around aluminium. The size of the cocatalyst molecule was found to have a marked effect on the activity of the catalyst: the smaller the cocatalyst the higher the activity. Higher electron density around aluminium increased the randomness of the copolymer.     

轻汽油催化裂解生产丙烯催化剂的研究

采用HZSM-5和改性的HZSM-5催化剂,以抚顺石油二厂初馏点~75℃的催化裂化轻汽油馏分为原料,在实验室连续固定床反应装置上进行了催化裂化轻汽油的催化裂解反应,考察了反应条件对催化裂化轻汽油裂解及芳构化反应的影响和A l2O3作为催化剂的载体对HZSM-5催化剂上催化裂解产品分部的影响,并且考察了载镧HZSM-5催化剂上主要产品分布的影响。研究结果表明,在载镧量5%左右的催化剂上,丙烯产率比改性前下降5%、芳烃产率下降15%;当催化剂中载体组分为30%时,丙烯产率最高为38.26%,芳烃产率为26.26%,同不使用载体相比,芳烃产率下降了5.1%。     

重整重芳烃油烯烃选择性加氢催化剂的研究

研究了负载在Al₂O₃载体上的贵金属钯基催化剂对重整重芳烃油选择性加氢脱烯烃反应的性能。以重整残余重芳烃油为原料,分别对催化剂载体、贵金属负载量和助剂添加量进行考察。结果表明,700 ℃焙烧混有2%Ni的γ-Al₂O₃和负载0.2%的贵金属Pd综合效果最理想。催化剂稳定性结果表明,催化剂在500 h能保证产品溴指数在200 mg-Br·（100g^）-1以下,原料中萘环的损失在2%以下。     

高稳定性甲醇自热重整制氢Zn-Cr催化剂

研制了一种甲醇自热重整制氢Zn-Cr催化剂.催化荆甲醇制氢活性高,稳定性好.可在723～923K较宽温度范围和大空速下运行.使用时无需预还原处理,完毕无需钝化处理,易于操作.避免了铜基甲醇制氢催化剂稳定性差,责金属催化剂氢选择陛低的缺点.MOR-67催化剂在1000h长时间连续运行下,催化荆活性和选择性变化不大.而且在频繁启动停工的操作下,也具有良好的稳定性,表明适合于车载甲醇重整制氢燃料电池氢源使用.     

Conversion of methanol into light olefins over ZSM-11 catalyst in a circulating fluidized-bed unit

Methanol conversion and the reaction pathway were investigated in a pilot-scale circulating fluidized-bed (CFB) unit over hierarchical ZSM-11 catalyst. Experimental results indicated that ZSM-11 catalyst was highly resistant to external coke due to the formation of mesopores. Elevated temperatures favored the production of propylene and butylene and decreased the yield of ethylene. Additionally, no direct relations were shown between the formation of ethylene and other products under different pressures, suggesting that ethylene was a primary product produced at the initial of the reaction. Methylation-cracking and oligomerization were verified as the main reaction pathway for the formation of C ₃ ⁺ alkenes., Methylation and oligomerization of olefins were dominated under high methanol partial pressure and consequently responsible for the production of higher olefins, while the b-scission of C ₇ ⁼ for propene and butylene, and C ₈ ⁼ for butylene were enhanced at low methanol partial pressure.     

Direct conversion of ethane to ethylene oxide over NiAgYO catalyst

NiAgYO catalyst prepared using sol–gel method exhibited better catalytic behavior than NiAgO for the direct conversion of ethane to ethylene oxide (EO). An optimal EO yield of 7.6% with 19.8% selectivity was obtained at 290 °C. The catalysts were characterized by X-ray diffraction (XRD), H₂ temperature-programmed reduction (H₂-TPR), O₂ temperature-programmed desorption (O₂-TPD), and X-ray photoelectron spectroscopy (XPS). The results showed that the interaction between Y and Ag made the absorbed oxygen species hold proper electrophilic character, thereby improving the performance of the NiAgYO catalyst.     

Carbon dispersed iron-manganese catalyst for light olefin synthesis from CO hydrogenation

High performance iron-manganese catalysts dispersed with carbon to produce light olefins from CO hydrogenation were prepared by sol-gel method using citric acid as precursor. The effects of carbon content on the bulk structure, the water gas shift reaction, the chain propagation ability and the activity and selectivity of the catalysts were investigated. The results showed that the catalysts were gradually reduced during the decomposition of the precursor when calcined under pure N₂. The formation of iron-manganese mixed crystallites was favored and stabilized because of the enhanced interaction of iron and manganese with increasing carbon content. During the subsequent CO hydrogenation reaction, all the catalysts showed high activity and olefin selectivity. With increasing carbon content, the water gas shift (WGS) reaction was restrained and the chain propagation ability was inhibited. Catalysts with higher carbon content showed much lighter hydrocarbon products; however, the selectivity of CH₄ was almost unchanged. This work was presented at the 7 ^th Korea-China Workshop on Clean Energy Technology held at Taiyuan, Shanxi, China, June 26–28, 2008.     

Preparation of SAPO-34 catalyst and presentation of a kinetic model for methanol to olefin process (MTO)

Conversion of methanol to light olefins (MTO) using acidic SAPO-34 molecular-sieve as the reaction catalyst was studied in a differential fixed bed reactor within the temperature range of 375-425 °C and under 4 bar pressure. The importance of MTO process is due to the increasing demand for light olefins in recent years. SAPO-34 was synthesized by hydrothermal method, applying morpholine as the template. The latter compound was then changed into protonated form by ion exchange method with ammonium chloride at 80 °C. A simple stoichiometric scheme has been presented for MTO. In addition a mechanism for this process based on Langmuir-Hinshelwood formulation has been put forward and the kinetic parameters have been evaluated as functions of temperature.     

A kinetic model for methanol conversion to hydrocarbons

We developed a detailed kinetic model for methanol conversion to hydrocarbons over zeolites. The dimethylether at equilibrium with methanol, generates carbene; it attacks the oxygenates giving light olefins, and the latter forming higher olefins. The olefins, through carbenium ions, form aromatics and paraffins. The kinetic parameters, identified by nonlinear optimization techniques, and the model predictions, agree quite well with the experiment and literature available data.     

Codimerization of ethylene with n-pentenes and propylene with n-butenes on an alkaline catalyst

• 1.1. 3-Ethylpent-1-ene is the main product of codimerization of ethylene with n-pentenes on a Na/K₂CO₃ catalyst independent of the position of the multiple bond in the initial olefin.
• 2.2. 3,4-Dimethylpent-1-ene is the main component in products of codimerization of n-butylenes with propylene; 4-methylhex-1-ene and 5-methylhex-2-ene are formed in small amounts even when butylene-2 is used as raw material.