碳五烃催化裂解制取低碳烯烃反应性能及机理

以ZSM-5分子筛为催化剂,碳五烃混合物为裂解原料,考察温度及稀释比对碳五烃催化裂解制丙烯/乙烯反应性能的影响。结果表明:随温度升高碳五烷烃及烯烃的转化率均不断升高,但碳五烯烃的转化率远高于碳五烷烃的转化率。同时乙烯及丙烯的收率也随温度的升高而升高,空速3.06 h-1,分压23.24 k Pa时,分别由450℃的2.38%,8.84%升高到620℃时的13.86%和19.67%。另外,随稀释比的增加,碳五烯烃转化率,乙烯、丙烯及丁烯的收率不断下降,但C6烃的收率随稀释比的增加而升高。碳五烯烃催化裂解机理分析指出:碳五烯烃催化裂解过程中碳五烯烃在直接裂解生成乙烯和丙烯的同时,也可通过二聚成C10中间体,然后生成的C10中间体再发生顺次裂解反应。该机理应用于实验规律的解释,取得了满意的结果。     

增产丙烯的烯烃转化技术

（1）ABBLumus公司的OCT技术。ABBLummus公司的OCT技术将乙烯转化为丙烯的选择性近100％，将丁烯转化为丙烯的选择性为97％，丁烯总转化率为85％～92％（丁烯进料中正丁烯质量分数为50％～95％）。进料中的乙烯和丁烯可来自蒸汽裂解装置和各种炼油厂的生产过程，浓度也可不相同，丁烯也可来自乙烯二聚装置。OCT技术采用固定床反应器，催化剂是载于硅藻土上的W03和MgO。催化剂可连续再生，催化剂结焦采用氮气加空气清焦。原料中的1～丁烯在MgO作用下异构化为2-丁烯，然后与乙烯由W03歧化生成丙烯。在乙烯塔内分离出未反应的乙烯返回反应器循环使用，丙烯可以在丙烯塔内分离得到，因在反应中无丙烷生成，无须进一步提纯即可得到聚合级丙烯。     

裂解碳五主要馏分用途介绍

乙烯副产裂解碳五可得到多种高附加值化工产品，如异戊二烯、环戊二烯、间戊二烯、异戊烯、1-戊烯、2-丁炔、3-甲基-1-丁烯、环戊烷、环戊烯、异戊烷、正戊烷等；其中异戊二烯、环戊二烯（双环戊二烯）和间戊二烯这3种双烯烃含量约占一半左右。     

环烷基瓦斯油催化裂解反应规律及产品性质

利用提升管催化裂解实验装置研究了加拿大合成原油瓦斯油HGO和LGO的催化裂解反应规律和裂解产品性质。发现总低碳烯烃（乙烯、丙烯和丁烯）产率随反应温度和剂油比的增大存在最大值,随反应时间的延长而减小,随水油比的增大而升高。实验确定了HGO催化裂解的优化反应条件：反应温度620～640℃、剂油比16、反应时间2 s、水油比0.5左右。在此反应条件下,乙烯、丙烯和总低碳烯烃产率分别可达9.0%（质量）,15.8%（质量）和32.6%（质量）。催化裂解汽油馏分、柴油馏分和重油馏分含有大量的芳香烃,其中催化裂解汽油馏分总芳香烃含量在80%（质量）以上,主要是甲苯和C₈芳香烃;催化裂解柴油馏分总芳香烃含量在60%（质量）以上,主要是单环和双环芳香烃;催化裂解重油馏分总芳香烃含量在70%（质量）以上,主要是多环芳香烃。     

东营市环境空气臭氧前体物污染特征研究

为研究东营市环境空气臭氧前体物污染特征，参照《环境空气臭氧前体有机物手工监测技术要求》(试行)和《环境空气VOCs手工监测质量控制与监督检查要点》(试行)要求，对东营市2021年4～10月份环境空气进行分析，并且对环境空气VOCs组成、月浓度变化、平均浓度前10物质、臭氧生成潜势前10物质和VOCs的来源进行讨论。结果表明，2021年东营市环境空气57种臭氧前体物(PAMS)月平均浓度范围为52.02～167.88μg/L,平均浓度为98.78μg/L。其中烷烃、烯烃、炔烃、芳香烃分别占57种PAMS总浓度的63.62%,27.97%,2.47%,5.94%。平均浓度前10物质为乙烯、正丁烯、乙烷、丙烷、2-甲基戊烷、正丁烷、丙烯、异丁烷、异戊烷、正戊烷，占比74.38%,臭氧生成潜势前10物质为1-丁烯、乙烯、丙烯、顺式二戊烯、1-己烯、间/对二甲苯、2-甲基戊烷、1-戊烯、异戊二烯、邻二甲苯，占比80.5%。污染物主要来源为汽车尾气、汽油蒸汽和液态石油的挥发，芳香烃浓度主要来源于机动车尾气。     

1-丁烯催化裂解制丙烯和乙烯反应性能的研究

以MCM-49分子筛为催化剂,纯1-丁烯为原料,考察了反应温度对烯烃催化裂解制丙烯、乙烯反应性能的影响。选择适宜的反应温度条件能够有效地抑制副反应,从而提高丙烯、乙烯的总产率。     

硅源对ZSM-5分子筛合成和催化性能的影响

为了考察硅源对ZSM-5分子筛合成和催化性能的影响,分别采用白炭黑、硅胶、硅溶胶和单分散SiO₂为硅源合成ZSM-5分子筛,对合成的ZSM-5分子筛进行XRD、SEM、BET和NH₃-TPD表征,并以C₄烯烃为原料评价合成的ZSM-5分子筛的催化裂解性能。结果表明,以硅溶胶为硅源合成的ZSM-5分子筛具有较好的结晶度和催化活性。水热处理使分子筛酸量减少,孔容缩小,改善了分子筛的乙烯丙烯选择性。经600 ℃水热处理4 h的ZSM-5分子筛在常压、580 ℃和空速9 h^-1反应条件下,丁烯催化裂解为乙烯和丙烯平均转化率为90.2%,乙烯和丙烯总收率达61.1%。     

浅谈丙烯生产技术

综述了增产丙烯的两种途径,介绍了蒸汽裂解、催化裂化/催化裂解、丙烷脱氢、乙烯/丁烯歧化、煤(甲醇)制烯烃等工艺的基本情况,指出石油路线增产丙烯技术仍是目前丙烯生产的主要途径,催化裂化/催化裂解增产丙烯的潜能将会得到进一步释放。     

Ba-MCM-49分子筛上1-丁烯催化裂解性能的研究

以Ba-MCM-49分子筛为催化剂,纯1-丁烯为原料,考察了钡的含量,反应温度,原料空速及分压对烯烃催化裂解制丙烯、乙烯反应性能的影响。实验表明,适量的钡修饰可以在一定程度上抑制氢转移及芳构化副反应的发生,从而提高了目标产物丙烯和乙烯的选择性。     

反应温度对催化裂化汽油芳构化的研究

以中国石油兰州炼油石化公司催化汽油为原料,采用小型固定流化床为芳构化反应装置,考察了反应温度对芳构化产物收率、转化率、马达法和研究法辛烷值、气体产品组成和液体产品组成的影响规律。实验结果表明,随着反应温度的升高,干气、液化气和焦炭收率呈上升趋势,而汽油和柴油收率呈下降趋势,FCC汽油的转化率都在94%左右,且随反应温度的升高先增大后减小;乙烯、丙烯、丁烯、乙烯和总低碳烯烃收率单调增加,而乙烯、丙烯、丁烯、乙烯和丙烯和总低碳烯烃收率的增加幅度各不相同;异构烷烃和烯烃收率随着反应温度的升高逐渐减少,而芳烃的收率和选择性随着反应温度的升高逐渐增加,正构烷烃和环烷烃的收率随着温度的增加先增加后减少。     

Thermodynamic analysis of reaction pathways and equilibrium yields for catalytic pyrolysis of naphtha

The chain length and hydrocarbon type significantly affect the production of light olefins during the catalytic pyrolysis of naphtha. Herein, for a better catalyst design and operation parameters optimization, the reaction pathways and equilibrium yields for the catalytic pyrolysis of C_5–8 n/iso/cyclo-paraffins were analyzed thermodynamically. The results revealed that the thermodynamically favorable reaction pathways for n/iso-paraffins and cyclo-paraffins were the protolytic and hydrogen transfer cracking pathways, respectively. However, the formation of light paraffin severely limits the maximum selectivity toward light olefins. The dehydrogenation cracking pathway of n/iso-paraffins and the protolytic cracking pathway of cyclo-paraffins demonstrated significantly improved selectivity for light olefins. The results are thus useful as a direction for future catalyst improvements, facilitating superior reaction pathways to enhance light olefins. In addition, the equilibrium yield of light olefins increased with increasing the chain length, and the introduction of cyclo-paraffin inhibits the formation of light olefins. High temperatures and low pressures favor the formation of ethylene, and moderate temperatures and low pressures favor the formation of propylene. n-Hexane and cyclohexane mixtures gave maximum ethylene and propylene yield of approximately 49.90% and 55.77%, respectively. This work provides theoretical guidance for the development of superior catalysts and the selection of proper operation parameters for the catalytic pyrolysis of C_5–8 n/iso/cyclo-paraffins from a thermodynamic point of view.     

轻烃催化裂解制低碳烯烃反应规律与原料特征化

利用小型固定床实验装置对比研究了轻烃模型化合物的催化裂解性能,从优到劣的顺序依次是正构烯烃、正构烷烃、环烷烃、异构烷烃、芳香烃。正构烷烃、异构烷烃与环烷烃催化裂解的总低碳烯烃收率有较大差别,但是总低碳烯烃选择性却均在56.57%左右。研究了直馏石脑油的催化裂解性能,发现乙丙烯收率和总低碳烯烃收率随反应温度的升高及重时空速的降低而逐渐增大;在反应温度680℃、重时空速4.32 h^-1和水油稀释比0.35的条件下,乙丙烯收率35.87%（质量）,总低碳烯烃收率为41.94%（质量）。针对轻烃催化裂解提出了原料特征化参数KF,它是原料H/C原子比、相对密度与分子量的函数,能较好地表征轻烃原料的催化裂解性能。     

乙基环己烷催化裂解制低碳烯烃反应动力学

利用小型固定床实验装置研究了乙基环己烷在基于ZSM-5分子筛介孔催化剂上的裂解性能,发现乙基环己烷具有较好的裂解性能,原料转化率在80%以上,乙丙烯收率（质量分数）可达41%,低碳烯烃收率（质量分数）接近50%,液体产物主要是苯、甲苯、二甲苯等芳香烃。同时考虑乙基环己烷催化裂解过程中的热反应与催化反应,建立了包含14个反应的动力学模型。基于4个反应温度下的裂解实验数据,求取了反应动力学模型的参数。求得的表观活化能均在90 kJ·mol^-1以下,主要组分收率的模型预测值与实验值的平均相对误差不高于10%。     

Dehydrogenative cracking of n-butane using double-stage reaction

Dehydrogenation-cracking double-stage (tandem) reaction of n-butane was studied using a Pt-Sn type dehydrogenation catalyst and a cracking catalyst (rare earth-loaded HZSM-5). n-Butane was firstly dehydrogenated to n-butene (1- and 2-butene) over the Pt-Sn catalyst loaded at the upper part of the reactor. Then n-butene was successively converted to ethylene and propylene over the cracking catalyst loaded at the lower part of the reactor. The yield of light olefins (ethylene+propylene) was 58% at 650 °C. The key to obtaining ethylene and propylene in high yield was to determine how the bimolecular reactions of olefins to aromatic and heavier products can be inhibited. It was proved that the loaded rare earths played an important role in inhibiting the bimolecular reactions.     

Secondary Cracking of C4 Hydrocarbons from Heavy Oil Catalytic Pyrolysis

For C4 hydrocarbons from heavy oil catalytic pyrolysis, the cracking behaviours on catalyst CEP‐1 and quartz sand were investigated in a confined fluidized bed reactor. C4 hydrocarbons show a good cracking ability on CEP‐1, and butene is easier to convert than butane. Only at high reaction temperatures can butane present a good cracking ability. On catalyst CEP‐1, C4 hydrocarbons can undergo not only cracking reactions, but also such reactions as hydrogen transfer, polymerization and aromatization. The conversion of C4 hydrocarbons thermal pyrolysis is high, indicating that free radical reactions play an important part in the secondary cracking of C4 hydrocarbons. The product yields of C4 hydrocarbons pyrolysis on quartz sand are usually lower than those on catalyst CEP‐1. For both catalytic pyrolysis and thermal pyrolysis of C4 hydrocarbons, the selectivity of propene is higher than that of ethene.     

Producing ethylene and propylene from natural gas via the intermediate synthesis of methyl chloride and its subsequent catalytic pyrolysis

An original two-stage process for producing ethylene and propylene from natural gas via the catalytic pyrolysis of methyl chloride produced by methane catalytic chlorination is investigated. The kinetics of the methyl chloride catalytic pyrolysis on a silicoaluminophosphate catalyst SAPO-34 is studied and the process parameters are determined, yielding selectivities of 45% and 35% for ethylene and propylene, respectively, at 70% conversion of methyl chloride. The kinetics of methane oxidative chlorination is investigated on a catalyst that is a mixture of copper, potassium, and lanthanum chlorides deposited on a carrier. Based on the results from kinetic investigations, the process of methane oxidative chlorination is tested on an experimental setup in reactors of different types, two with fluidized catalyst beds (diameters 400 and 45 mm) and one tubular (diameter 27 mm), and on a pilot setup in a two-stage adiabatic reactor (diameter 800 mm). The process is tested with oxygen supply distributed for each stage at temperatures of 300–320°C at the inlet and 400–420°C at the outlet of the catalyst bed. The selectivity for methyl chloride formation among chloromethanes is 90%. A basic scheme is developed for a chlorine-balanced process of ethylene and propylene production from natural gas, and conditions for conducting methane oxychlorination and methyl chloride pyrolysis reactions in industrial reactors are determined. The process can be implemented at plants that need ethylene to increase deliveries of vinyl chloride and are experienced in working with hydrochloric acid and chlorinated derivatives of hydrocarbons.     

Empirical modeling of normal/cyclo-alkanes pyrolysis to produce light olefins

Due to the complexity of feedstock, it is challenging to build a general model for light olefins production. This work was intended to simulate the formation of ethylene, propene and 1,3-butadiene in alkanes pyrolysis by referring the effects of normal/cyclo-structures. First, the pyrolysis of n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, cyclohexane, methylcyclohexane, n-hexane and cyclohexane mixtures, and n-heptane and methylcyclohexane mixtures were carried out at 650-800℃, and a particular attention was paid to the measurement of ethylene, propene and 1,3-butadiene. Then, pseudo-first order kinetics was taken to characterize the pyrolysis process, and the effects of feedstock composition were studied. It was found that chain length and cyclo-alkane content can be qualitatively and quantitively represented by carbon atom number and pseudo-cyclohexane content, which made a significant difference on light olefins formation. Furthermore, the inverse proportional/quadratic function, linear function and exponential function were proposed to simulate the effects of chain length, cycloalkane content and reaction temperature on light olefins formation, respectively. Although the obtained empirical model well reproduced feedstock conversion, ethylene yield and propene yield in normal/cyclo-alkanes pyrolysis, it exhibited limitations in simulating 1,3-butadiene formation. Finally, the accuracy and flexibility of the present model was validated by predicting light olefins formation in the pyrolysis of multiple hydrocarbon mixtures. The prediction data well agreed with the experiment data for feedstock conversion, ethylene yield and propene yield, and overall characterized the changing trend of 1,3-butadiene yield along with reaction temperature, indicating that the present model could basically reflect light olefins production in the pyrolysis process even for complex feedstock.     

葵花杆的热解特性及热解产物分析

为充分利用生物质葵花杆,采用同步热分析仪以升温速率为影响因素对葵花杆的热解特性进行研究,利用Coats-Redfern积分法计算主要阶段热解动力学参数,并采用气相色谱/质谱联用仪对热解产物进行了定量分析.研究结果表明:葵花杆的热解过程可分为预热干燥、主要热解及炭化3个阶段;随着升温速率的增大,葵花杆热解的TG曲线向高温...     

Catalytic production of olefins using natural halloysite nanotubes

The production of C₂-C₄ olefins by deep catalytic cracking and the thermocontact pyrolysis of vacuum gas oil, commercial-grade cottonseed oil, and a vacuum gas oil-cottonseed oil 90: 10 mixture in the temperature range of 600–800°C is studied using natural halloysite extracted from kaolinite fields in the form of aluminosilicate sheets rolled in nanotubes. It is found that in the deep catalytic cracking of vacuum gas oil at 600°C using halloysite as a catalyst, the gain in the yield of ethylene is 6.4–10.1 wt %, compared to yields of this product when using ZSM-5 catalyst. Adding 10% commercial-grade cottonseed oil to the vacuum gas oil further increases the yield of ethylene by 2.2 wt % with a simultaneous 3.3 wt % rise in the yield of propylene. The cracking of pure cottonseed oil under identical conditions yields ethylene and propylene of 16.1 and 9.2 wt %, respectively. The possibility of using halloysite nanotubes as a heating surface for the thermal pyrolysis of the above feedstocks at temperatures of 700–800°C in order to obtain yields of C₂-C₃ olefins exceeding those of identical products in industry, and of reusing halloysites in the thermoconversion of the studied feedstocks via their complete regeneration, is confirmed.     

Coal flash pyrolysis: 1. An indication of the olefin precursors in coal by CP/MAS 13C n.m.r. spectroscopy

The results reported indicate that the low molecular weight olefins (ethylene, propylene and butadiene) which are major gaseous hydrocarbon products of flash pyrolysis of coal derive from the same precursors in coal, whereas methane, benzene and other pyrolysis products are mainly formed from different components in the coal. CP/MAS ¹³C n.m.r. spectra suggest that the olefin precursors are long-chain polymethylene structures (chemical shift 31 ppm), either chemically bound or mechanically trapped in the coal and thus not solvent-extractable.