重质油在催化剂孔道内受限扩散及其关联模型研究进展

重质油分子结构复杂、尺寸较大且容易聚集形成缔合体,致使在加氢及催化裂化催化剂孔道内存在明显的扩散阻力,显著阻碍了反应物分子与催化剂孔道内部活性位的接触,导致反应速率与转化率明显低于轻质原料。因此,研究重油分子在催化剂孔道内扩散受阻情况可以为催化剂的设计优化提供信息与指导。尽管借助仪器或膜材料能获得溶质分子的扩散性能,但与反应条件下扩散规律差别较大,因此在实际反应体系下获得重油分子在催化剂孔道中的扩散传质具有重要的现实意义。综述采用反应动力学手段获得扩散传质数据并建立受限因子关联模型及其影响因素的研究进展,从反应物选择、反应条件及催化剂等因素的优化角度对重油分子受阻扩散研究进行展望。     

分子扩散测定方法的研究进展

介绍了近年来多孔材料中分子扩散研究的发展,重点介绍了测定方法的新进展.指出多孔材料中分子扩散的研究主要集中于小分子如丁烷、异丁烷、戊烷、环戊烷、环已烷、苯、甲苯、对二甲苯、乙苯、邻二甲苯等.认为在众多方法中,重量法、程序升温脱附法、色谱法及膜池法等以其方便有效,是将来发展的重要测试方法.     

重质油在孔道内扩散传质的研究进展

内扩散广泛存在于非均相催化反应过程中。重质油因为具有更大的分子尺寸和复杂的组成结构,其在催化转化过程中通过孔道的扩散传质受到显著影响,极大降低了重质油的高效转化和催化剂的有效利用。本文重点对重质油在孔道内扩散传质的主要研究方法(隔膜池、吸附扩散和反应动力学法)和现状、孔内扩散的影响因素以及内扩散对重质油催化转化的影响等方面进行了综述,还探讨了重质油催化转化过程中扩散传质研究的发展方向。     

重油热加工技术的研究进展

介绍了国内外各种重质油热加工工艺和发展状况,分析了其特点和适应性。同时,结合我国目前重油加工的现状,基于喷动床造粒原理提出了一种重油热裂解制球形焦的新工艺,为重油热加工的发展提供了新的思路。     

分子筛中碳氢化合物扩散行为的分子模拟研究进展

分子筛催化过程中反应物、产物以及中间体等分子在分子筛孔道内的扩散行为显著影响催化剂择形催化性能、限域效应、产物选择性和稳定性等.本文总结了近二十年来分子模拟技术在分子筛扩散研究中的应用进展.首先简单介绍以分子动力学模拟为代表的分子筛扩散研究方法,然后介绍了包括烷烃、烯烃和芳烃在内的单组分以及多组分碳氢化合物在分子筛中的...     

重油催化裂化技术的研究进展

介绍了国内重油催化裂化技术的重要发展情况,包括现代重油催化裂化工艺的现状,国内外重油催化裂化的差距、国内催化裂化技术的改进,催化剂的发展,以及今后发展的方向等;同时对这些技术进步进行了分析。     

ZSM-5分子筛扩散受限问题研究进展

ZSM-5分子筛作为工业上应用较广泛的催化剂之一,一直是研究的热点。但传统的ZSM-5分子筛存在晶粒大、扩散困难和活性位点可及性差的问题,限制了在大分子催化方面的应用。对近年来通过调节凝胶化学因素和合成条件因素来改善分子筛扩散困难问题的方法和机理进行综述,并指出利用长链季铵盐作为结构导向剂能够合成具有自柱撑形貌的ZSM-5分子筛,具有良好的晶间介孔连通性,但其制备过程繁琐,成本昂贵。尿素和晶种等添加剂的引入以及二段晶化法的成功应用使得合成的成本降低,改善了晶间介孔,使得ZSM-5分子筛具有更好的扩散性能。     

重油乳化技术的研究进展

综述了国内外关于重油乳化技术的原理、设备、乳化剂选择及节能效果评价等问题的研究现状,介绍了乳化重油催化裂化方面的应用,分析了当前重油乳化技术中存在的问题,并初步探讨了其发展方向。     

利用孔径均一催化剂测定加氢脱硫条件下重油分子的有效扩散系数

采用反应-动力学法测定了加氢条件下风城减压渣油超临界萃取窄馏分在四种孔径均一催化剂(WDUPS)中的有效扩散系数。结果表明:在400℃,6.0 MPa下,重油分子在催化剂孔道中的扩散系数的数量级在10-9~10-8 cm2·s-1。随着馏分变重,各馏分的有效扩散系数均逐渐降低;随着催化剂孔径增加各馏分的有效扩散系数逐渐增加,但当孔径大于48 nm后,有效扩散系数基本不受孔径影响。受限扩散因子的计算结果表明,相比轻馏分,重馏分在催化剂孔道中的扩散更容易受到催化剂孔径的限制。     

聚合物受限结晶研究进展

在纳米尺度下,聚合物的相转变受到尺度作用、界面作用、以及化学作用的影响,与本体中的相转变行为存在着显著的差别。本文将根据受限空间的几何特点,将受限空间按一维(1D)、二维(2D)、三维(3D)划分,介绍聚合物在受限空间结晶的研究进展。     

Variation of intraparticle diffusion parameter during adsorption of p‐chlorophenol onto activated carbon made from apricot stones

The adsorption of para‐chlorophenol onto an active carbon made from waste apricot stones has been studied. The batch kinetic adsorption processes have been measured for a range of system variables including agitation rate, initial concentration of para‐chlorophenol, mass of carbon and particle size of carbon. The extent of adsorption is reported as plots of solid phase concentration against the square root of time. An intraparticle diffusion parameter is used to describe the mass transfer within the adsorbent. This parameter varies with the square root of time and can be related to the type of structure which occurs within an activated carbon. A correlation is proposed relating the process variable with the intraparticle diffusion parameter in each of the three mass transfer regions. Copyright © 2003 Society of Chemical Industry     

The adsorption of dyestuffs from aqueous solutions using activated carbon. iii. intraparticle diffusion processes

The rate of dye removal from aqueous solution has been found to vary linearly with the square root of time for much of the adsorption period. A rate parameter, k, has been defined to explain intraparticle diffusion on a quantitative basis. This rate parameter has been correlated against the process variables thus providing useful design data.     

Restrictive diffusion and hydrodesulfurization reaction of dibenzothiophenes over NiMo/SBA-15 catalysts

Macromolecular organosulfur compounds encountered resistance when diffusing in catalyst pore channels during the hydrotreating process. Quantitative insights into the effects of the catalyst pore size and the reactant molecule size on the diffusivities can guide the optimization of the catalyst structures. Herein, a heavy oil macromolecular dibenzothiophene compound, 2,8-di-(4-pentyl phenyl)dibenzothiophene (2,8-DPPDBT), was synthesized. Three NiMo-supported SBA-15 based catalysts with different pore sizes, but similar active phase dispersions were controllably fabricated. The reaction network of 2,8-DPPDBT HDS was proposed. The diffusion behaviors of 2,8-DPPDBT, along with 2,8-dimethyl dibenzothiophene (2,8-DMDBT) and dibenzothiophene (DBT) in three SBA-15 pore channels, were systematically investigated through the reaction kinetic method. A restrictive factor, F(λ), was correlated by F(λ) = (1 − λ)^8.5 to determine the relationship between the effective diffusivity and the ratio of the molecule-to-pore size (λ). This empirical correlation provided sound theoretical guidance on the design of highly efficient heavy oil hydrodesulfurization catalysts.     

Intraparticle diffusion of cadmium and zinc ions during adsorption from aqueous solution on activated carbon

The adsorption isotherms of cadmium(II) and zinc(II) onto activated carbons were obtained in a batch adsorber. The concentration decay data were obtained in a rotating basket adsorber and were interpreted by a mathematical model, which takes into account the adsorption rate, external mass transport and intraparticle diffusion. The results showed that the overall rate of adsorption of Cd(II) and Zn(II) was mainly controlled by the intraparticle diffusion which was solely due to pore volume diffusion. The contribution of the external mass transport resistance was negligible. The effective pore volume diffusivities of Cd(II) and Zn(II) were predicted reasonably well using the ionic diffusivity of the metal and the void fraction and tortuosity of activated carbon. Copyright © 2005 Society of Chemical Industry     

Insight into the intraparticle diffusion of residue oil components in catalysts during hydrodesulfurization reaction

Well‐defined and uniform pore structure catalysts were used to study the intraparticle diffusion of fractionated Saudi vacuum residue under hydrodesulfurization (HDS) reaction conditions. HDS rates of residue oil cuts with different molecular weights are determined as functions of pore size, temperature, and pressure in a trickle‐bed reactor. Credible intrinsic and bulk diffusivities of organosulfur compounds in residue oil were obtained for the first time, from the apparent and intrinsic reaction kinetic constants. Intrinsic diffusivities ranged from 2 × 10^?7 to 8 × 10^?7 cm²/s for the residual oil molecules; diffusivity decreases with increasing molecular weight of the residual oil. The intrinsic diffusivity for molecular weights ～1000 Daltons increases with pore size for pores <70 nm, but is nearly independent of pore size for pores >70 nm. The diffusivity dependences on pore size and molecular weight suggest that the onset of restricted diffusion occurs for ratios of molecular diameter to pore diameter of ～0.04. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3267–3275, 2014     

Diffusion in liquid-filled pores of activated carbon. I. Pore volume diffusion

The adsorption isotherms on activated carbon were measured for the following six systems: benzaldehyde, phenol, and potassium chloride in water; benzene, isopropylbenzene, and phenol in cyclohexane. The systems isopropylbenzene and benzene each in cyclohexane and potassium chloride in water proved to be slightly adsorbing systems, whereas the benzaldehyde and phenol each in water were highly adsorbing systems. The rate of diffusion of the slightly adsorbing solutes was interpreted by assuming that the intraparticle diffusion was due to pore volume diffusion. The results indicated that the tortuosity factor for activated carbon is 3.5. The effective pore volume diffusivity and the tortuosity factor were not affected by the concentration of the solute, solute molecular size and the particle diameter. The external mass transfer resistance was negligible when pore volume diffusion was the controlling intraparticle diffusion mechanism.     

重油生产低碳烯烃等化工品技术研究进展

当前国内炼油产能过剩,化工品如低碳烯烃及苯-甲苯-二甲苯混合物（BTX）等存在缺口,因此应推动炼油向石化的生产转变,化解过剩产能同时提高化工品供给。我国原油馏分偏重且原油重质化劣质化趋势不可逆转,因此利用重油生产低碳烯烃等化工品成为技术关键。本文介绍了重油生产低碳烯烃的催化裂解单项技术典型工艺,包括重油深度催化裂解（DCC）、催化热裂解（CPP）及重油裂解制烯烃（HCC）工艺,认为催化裂解技术的发展在于催化剂的改性与反应器型式的革新优化,下行床反应器前景更为广阔。同时,本文也介绍了从重油或原油通过加氢裂化联合催化裂解、蒸汽裂解及芳烃装置一体化生产化工品的几种国内外工艺技术及工程项目。在单项技术无法取得明显突破之前,炼化一体化生产化工品具有集约化、高效化、灵活性高及经济效益好等优势。一体化技术的重点在于重油（渣油）的深度转化,可通过渣油的加氢裂化工艺来实现。     

大孔结构重油加氢脱金属催化剂的制备、表征及重油在催化剂中有效扩散系数的求解

以大孔拟薄水铝石为原料,沥青残渣为造孔剂,经超临界干燥和焙烧得到催化剂载体,通过浸渍活性组分得到重油加氢脱金属催化剂并进行扩散实验。结果表明,制备条件对重油加氢脱金属催化剂的物性影响较大,通过对各种制备因素进行优化并对催化剂进行表征和扩散实验,进一步表明制备的催化剂具有较大的比表面积、孔容、适宜的孔分布及大孔结构,适合加工金属含量较高的原油,重油分子在添加造孔剂催化剂中的有效扩散系数变大。