Subscriber access provided by University of Newcastle, Australia
Article
Slurry phase hydrocracking of residue with ultra dispersed MoS2 catalysts prepared by microemulsion methods Ravindra Prajapati, Kirtika Kohli, and Samir Kumar Maity Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.7b00216 • Publication Date (Web): 09 Mar 2017 Downloaded from http://pubs.acs.org on March 9, 2017
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
Energy & Fuels is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
Page 1 of 22
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Energy & Fuels
Slurry phase hydrocracking of residue with ultra dispersed MoS2 catalysts prepared by microemulsion methods R. Prajapati, K. Kohli, S. K. Maity * Catalyst and Conversion Division-Indian Institute of Petroleum, Dehradun, 248005, India
ABSTRACT Slurry phase hydrocracking of vacuum residue using dispersed catalyst has been investigated in this work. Liquid yield and coke formation in this process mostly depend on the catalyst particle size and its distribution. Three emulsion methods-colloidal emulsions liquid (CEL), emulsion liquid membrane (ELM) and reserve micelle (RM) are used to synthesize the dispersed MoS2 catalyst. Dynamic light scattering results show that the colloidal particle of molybdenum sulphide in RM catalyst is smaller in size and narrowly distributed compared with the catalysts prepared by CEL and ELM methods. Our SEM and TEM analysis results also support the smaller particle size of the active metal in RM catalyst. Hydrotreating and hydrocracking activities of RM catalyst are higher and it is due to its smaller particle size and its narrow distribution. Moreover, coke formation in this catalyst is very low. It is found that the residue (550OC plus hydrocarbons) are mostly converted into the middle distillates and vacuum gas oil by this catalyst. Lower mole percentage of unconsumed hydrogen in gaseous product and higher H/C ratio in liquid product also indicate the higher hydrogenation activity of RM catalyst. The total liquid yield in this catalyst is also higher suggesting the deep hydrocracking of the large hydrocarbons. Therefore, the reverse micelle emulsion is a suitable method to prepare residue hydrocracking catalyst with proper morphology.
Keywords: colloidal emulsion liquid, emulsion liquid membrane, reverse micelle, slurry phase hydrocracking
1
ACS Paragon Plus Environment
Energy & Fuels
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
INTRODUCTION The conventional supported CoMo or NiMo hydrotreating catalyst is deactivated very fast due to coke deposition on the porous support. This deactivation becomes very problematic when the feed contains high percentage of microcarbon residue or asphaltene 1–4. Slurry phase hydrocracking is one of the best options for upgradation of this type of feed. In this process, coke formation can be minimised by using proper catalyst. Mainly two type catalysts are used: homogeneous catalyst and heterogeneous solid powder catalyst. The homogeneous catalyst further divided into oil soluble and water soluble catalyst. The oil soluble catalyst is not attractive due to the higher production cost compared with the water soluble catalyst. Hematite, lignite coke and red mud were used in high amount as heterogeneous solid powder catalyst. In recent years, fine powder catalyst of Fe, Mo, Ni, Co etc becomes more attractive due to their higher cracking and lower coking activities. Various methods are use for preparation of fine dispersed catalyst such as hydrothermal, ball milling, precipitation etc.
5–8
. To achieve controlled particle size and
homogeneity of particles in the above said conventional methods are difficult. Compared with these methods, the liquid phase synthesis can provide better homogeneity, dispersion and controlled size 9. Therefore, the micro-emulsion methodology is a good option in this direction. Colloidal emulsion liquid (CEL), emulsion liquid membrane (ELM), reverse micelle (RM) are some of the micro-emulsion methods used extensively to obtain smaller particle of the catalyst. An emulsion is a colloidal system, where two immiscible liquids (one is continuous and other is dispersed phase) are co-existing. This colloidal system is thermodynamically unstable. But surfactant is generally used to get the stability of the colloidal system. The surfactant covers the dispersed phases or droplets and provides the stability. The micro-emulsion method has great advantage of having flexibility to control the morphology and nano particle size of the finished product. It can be controlled by varying water to oil ratio, oil to surfactant ratio etc. The usefulness of Cu, Fe slurry phase powder catalyst for the production of fatty alcohol was recently reviewed by Thakur et al.10. Colloidal emulsion liquid aphrons and emulsion liquid membrane are multilayered stable droplets which are surrounded by thin surfactant film 11. Reverse micelles are emulsion colloidal system in which hydrophilic phase is surrounded by single layer of surfactant in the hydrophobic phase of hydrocarbon system. These emulsion based catalysts have stability and interfacial area that make them useful in various applications such as mineral processing, protein recovery, separation of organic dyes from waste water purification etc. 12–17. CEL and ELM preparation methods were used by Dai et al.18 to synthesize the silver based catalyst. It 2
ACS Paragon Plus Environment
Page 2 of 22
Page 3 of 22
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Energy & Fuels
was noticed that these methods were very effective to prepare nano-size catalyst particles. It was also observed by authors that the silver catalyst prepared by CEL method formed granular shape whereas comparatively linear shape of silver was formed by ELM preparation method. Therefore, the dispersibility of ELM was rather less than colloidal emulsion liquid (CEL). Larger inner phase (0.2-2mm) of ELM than colloidal emulsion liquid aphrons was also reported by other 19. ELM method was also used by Somnuk et al.
20
to synthesize ceria
based catalyst having proper physico-chemical property, appropriate morphology and controlled particle size. Reverse micelle method consists of mixing the two microemulsion systems, one containing a metal salt precursor and other having precipitating agent. The nanosize precipitate is formed due to collision and coalescence of microemulsions in limited dimension of the droplets. This process has wide range of flexibility to control the size of the finished product by varying water to surfactant ratio
21
, metal concentration
22
and type of
23
surfactant employed . Smith and his group have used this method to prepare the dispersed catalysts
24–27
. They have used different metals such as Fe, Co, Ni and Mo to prepare the
micelle catalysts and pentane, hexane and toluene were used as solvents. The size of the micelle depends on the metal and it is found in the order of Ni
