Methods and apparatuses for separating toluene from multiple hydrocarbon streams (UOP)

CATEGORY: TOLUENE
PATENT
Methods and apparatuses for separating toluene from multiple hydrocarbon streams (UOP)
Publication number US8716545 B1
Application number US 13/712,714
Publication date May 6, 2014
Inventors Jason T. Corradi, David William Ablin
Original Assignee Uop Llc
Abstract
Methods and apparatuses for separating toluene from multiple hydrocarbon streams are provided. A method includes fractionating a first hydrocarbon stream, which includes benzene-depleted fractionation bottoms from benzene fractionation, in a first fractionation zone into a first fractionation overhead stream that includes toluene and a first fractionation bottoms. A second hydrocarbon stream, which includes toluene and is substantially free of compounds having a higher vapor pressure than toluene, is fractionated in a second fractionation zone into a second fractionation overhead stream including toluene and a second fractionation bottoms. The second fractionation zone is in liquid isolation from and in vapor communication with the first fractionation zone. The first fractionation bottoms are removed from the first fractionation zone, and the second fractionation bottoms are removed from the second fractionation zone separate from the first fractionation bottoms. The first fractionation overhead stream and the second fractionation overhead stream are combined to produce a combined fractionation overhead stream.
Description
TECHNICAL FIELD
The technical field generally relates to methods and apparatuses for separating toluene from hydrocarbon streams that include the toluene, and more particularly relates to methods and apparatuses for separating toluene from different hydrocarbon streams that include toluene.
BACKGROUND
Aromatic compounds have a multitude of uses, both as end products and as reactants for downstream processes. Methods of preparing aromatic compounds from a hydrocarbon feed are generally known in the art and include upgrading the hydrocarbon feed followed by reforming and aromatics separation. Typical upgrading techniques include hydrotreating to remove contaminants such as sulfur, nitrogen, and oxygen. After upgrading, the hydrocarbon feed is reformed in the presence of a catalyst to convert paraffins and naphthenes to a reformate that includes aromatic compounds such as xylenes, benzene, and toluene. A series of separation techniques are employed to separate the various aromatic compounds from the reformate, and numerous product streams having varying degrees of purity may be isolated for each aromatic compound in the reformate.
Toluene is a common aromatic compound that has many uses not only as an end product, but also as a process stream during production of other aromatic compounds. Toluene is generally separated from a reformate in a toluene column that is downstream of a benzene column. The toluene column fractionates benzene-depleted reformate into a toluene-containing stream and a xylene-containing stream. The toluene-containing stream can be blended with C9 or greater aromatic compounds for conversion into xylenes and benzene through disproportionation and transalkylation. The xylenes and benzene produced through disproportionation and transalkylation can be separated along with the reformate through conventional separation techniques.
Adsorption/desorption is a common separation technique that is employed for separation of xylene isomers, such as para-xylene, meta-xylene, and ortho-xylene. During adsorption/desorption, select xylene isomers, such as para-xylene or meta-xylene, are adsorbed from a xylene-containing stream that is generally depleted of benzene and toluene. Specific xylene isomers can be selectively adsorbed by selecting appropriate adsorbing material. A desorbent, which can be readily separated from adsorbed compounds through fractionation, is generally employed to remove adsorbed isomers from the adsorbent material. Raffinate from adsorption/desorption generally also includes the desorbent, and the desorbent is generally separated from the raffinate through fractionation to recover the desorbent for further use.
Due to different compositional makeup of the raffinate and the reformate, the raffinate and the reformate are generally fractionated through separate fractionation techniques to separate individual compounds therefrom. Separate fractionation is conducted even when a desorbent such as toluene is used and is present in the raffinate. For example, whereas the reformate can be fractionated in the toluene fractionation unit to produce a bottoms stream that includes a range of xylene isomers, the raffinate from adsorption/desorption is generally depleted of para- and/or meta-xylenes such that mixing of the raffinate with the reformate would dilute the content of para- and/or meta-xylenes in the bottoms stream from the toluene fractionation unit. Instead, the raffinate is separately fractionated from the reformate to produce a bottoms stream that contains any xylenes that remain after adsorption/desorption, such as ortho-xylene, and the ortho-xylene may be isomerized to produce para-xylene or meta-xylene. Separate fractionation columns and associated units such as receiver vessels and overhead pumps are thus required for fractionating the reformate separate from the raffinate.
Accordingly, it is desirable to provide methods and apparatuses for separating toluene from multiple hydrocarbon streams, such as a hydrocarbon stream including reformate and a hydrocarbon stream including raffinate from para-xylene and/or meta-xylene adsorption/desorption processes, that enable duplication of fractionation equipment to be minimized. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.
BRIEF SUMMARY
Methods and apparatuses for separating toluene from multiple hydrocarbon streams are provided. In an embodiment, a method of separating toluene from multiple hydrocarbon streams includes fractionating a first hydrocarbon stream in a first fractionation zone into a first fractionation overhead stream and a first fractionation bottom stream. The first hydrocarbon stream includes the benzene-depleted fractionation bottom stream from benzene fractionation. The first fractionation overhead stream includes toluene. A second hydrocarbon stream different from the first hydrocarbon stream is fractionated in a second fractionation zone into a second fractionation overhead stream and a second fractionation bottom stream. The second fractionation zone is in liquid isolation from and in vapor communication with the first fractionation zone. The second hydrocarbon stream includes toluene and is substantially free of compounds that have a higher vapor pressure than toluene. The second fractionation overhead stream includes toluene. The first fractionation bottom stream is removed from the first fractionation zone, and the second fractionation bottom stream is removed from the second fractionation zone separate from the first fractionation bottom stream. The first fractionation overhead stream from the first fractionation zone and the second fractionation overhead stream from the second fractionation zone are combined to produce a combined fractionation overhead stream that includes toluene.
In another embodiment, a method of separating toluene from multiple hydrocarbon streams includes providing a benzene column for receiving a benzene-containing hydrocarbon stream that includes xylenes, benzene, and toluene. The benzene-containing hydrocarbon stream is fractionated into a benzene-containing overhead stream and a benzene-depleted fractionation bottom stream that includes xylenes and toluene. A split fractionation column is provided that includes an internal partition. The internal partition defines a first fractionation zone and a second fractionation zone in liquid isolation from and in vapor communication with the first fractionation zone. A first hydrocarbon stream is fractionated in the first fractionation zone into a first fractionation overhead stream and a first fractionation bottom stream. The first hydrocarbon stream includes the benzene-depleted fractionation bottom stream from the benzene column. The first fractionation overhead stream includes toluene and the first fractionation bottom stream includes xylenes. A second hydrocarbon stream is fractionated in the second fractionation zone into a second fractionation overhead stream and a second fractionation bottom stream. The second hydrocarbon stream includes an adsorption raffinate that is depleted of at least one of para-xylene or meta-xylene, and the adsorption raffinate includes toluene. The second hydrocarbon stream is substantially free of compounds that have a higher vapor pressure than toluene. The second fractionation overhead stream includes toluene. The first fractionation bottom stream is removed from the first fractionation zone, and the second fractionation bottom stream is removed from the second fractionation zone separate from the first fractionation bottom stream. The first fractionation overhead stream from the first fractionation zone and the second fractionation overhead stream from the second fractionation zone are combined to produce a combined fractionation overhead stream including toluene.
In another embodiment, an apparatus for separating toluene from multiple hydrocarbon streams includes a benzene column, a processing unit, and a split fractionation column. The benzene column receives a benzene-containing hydrocarbon stream that includes xylenes, benzene, and toluene. The processing unit provides a second hydrocarbon stream that includes toluene and that is substantially free of compounds that have a higher vapor pressure than toluene. The split fractionation column includes an internal partition that defines a first fractionation zone and a second fractionation zone. The second fractionation zone is in liquid isolation from and in vapor communication with the first fractionation zone. The first fractionation zone is in fluid communication with the benzene column for receiving a first hydrocarbon stream that includes a benzene-depleted fractionation bottom stream from the benzene column. The second fractionation zone is in fluid communication with the processing unit for receiving the second hydrocarbon stream.
Free Full Text Source: http://www.google.com/patents/US8716545

Development of Alkylation Toluene with Methanol for Fuel on Modified ZSM-5 Zeolites by Amphoteric Surfactant

CATEGORY: TOLUENE
Journal of Surface Engineered Materials and Advanced Technology, 2014, 4, 41-46
Development of Alkylation Toluene with Methanol for Fuel on Modified ZSM-5 Zeolites by Amphoteric Surfactant
Akila El Morsi, A. M. A. Omar, Nora Y. Almehbad
1 Egyptian Petroleum Research Institute, Cairo, Egypt
2 Najran University, Najran, Kingdom of Saudi Arabia.
drabdelazim123@yahoo.com
abdelazimomar@hotmail.com
ABSTRACT
Methylation of toluene over ZSM-5 zeolites modified by the introduction of Sr of 2.5%, 5%, and 10% by weight was studied. Experiments were performed in a fixed bed under the conditions of reaction temperatures between 300°C-500°C, liquid hour space velocity of 4 g toluene/h.g catalyst, methanol to toluene ratio 4:1, and 0.01% of N-Octyl-N-benzyl-N-methylglycine as emulsifier.
Data for conversion of toluene and selectivity towards xylene isomers showed that 2.5% Sr/ZSM-5 catalyst has the highest conversion of toluene at 500°C, and the lowest p-xylene selectivity, while 10% Sr/ZSM-5 catalyst has the highest selectivity for p-xylene production. Nevertheless, the catalyst 2.5% Sr/ZSM-5 has the highest selectivity for m-xylene. The two catalysts 2.5% and 5% Sr/ZSM-5 give nearly the same selectivity for the three xylene isomers at all conversions obtained at the reaction conditions under study.
Free Full Text Source: http://www.scirp.org/journal/PaperInformation.aspx?paperID=42459

Temperature, pressure, and bath gas composition dependence of fluorescence spectra and fluorescence lifetimes of toluene and naphthalene

CATEGORY: TOLUENE
Applied Physics B, January 2013, Volume 110, Issue 1, pp 81-93
Temperature, pressure, and bath gas composition dependence of fluorescence spectra and fluorescence lifetimes of toluene and naphthalene
Stephan Faust, Gabrielle Tea, Thomas Dreier, Christof Schulz
1. IVG, Institute for Combustion and Gasdynamics, University of Duisburg-Essen, Duisburg, Germany
2. IFP Energies nouvelles, Rueil-Malmaison, Paris, France
Abstract
Reports results of a study of time-resolved fluorescence spectra of gas-phase toluene and naphthalene upon picosecond laser excitation at 266 nm as a function of temperature, pressure, and bath gas composition (varying concentrations of N₂, O₂, and CO₂) with a temporal resolution of 50 ps.
In the temperature range under study, the fluorescence spectra of both toluene and naphthalene reveal a significant red-shift, whereas the fluorescence lifetime decreases with increasing temperature, more pronounced for toluene than for naphthalene. Increasing the total pressure of either N₂ or CO₂ from atmospheric to 10 bar leads to an increase by about 20 % (naphthalene at 373 K) and a decrease by 60 % (toluene at 575 K) in fluorescence lifetimes, respectively. As expected, at atmospheric pressure collisions with O₂ shorten the fluorescence lifetime of both toluene and naphthalene significantly, e.g., by a factor of 30 and 90 when changing O₂ partial pressure at 373 K from 0 to 0.21 bar, respectively. The fluorescence model of Koban et al. (Appl Phys B 80: 777, 2005) for the dependence of the toluene quantum yield on temperature and O₂ partial pressure at atmospheric pressure describes toluene fluorescence lifetimes well within its range of validity. The model is modified to satisfactorily predict effective toluene fluorescence lifetimes in N₂ at pressures up to 10 bar. While the fitting models have their shortcomings, this publication presents a data set of great importance for practical LIF applications, e.g., in-cylinder mixture formation diagnostics in internal combustion engines.
Full Text Source (Subscription or Fee): http://link.springer.com/article/10.1007/s00340-012-5254-8#