Subscriber access provided by UNIV OF MISSISSIPPI
Article
Prediction of Pd/C catalyst deactivation rate and assessment of optimal operating conditions of industrial hydropurification process Abbas Azarpour, Tohid Nejad Ghaffar Borhani, Sharifah Rafidah Wan Alwi, Zainuddin Abdul Manan, and Mazyar Madooli Behbehani Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.5b00925 • Publication Date (Web): 25 Jun 2015 Downloaded from http://pubs.acs.org on July 1, 2015
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.
Industrial & Engineering Chemistry Research 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 50
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
Industrial & Engineering Chemistry Research
Prediction of Pd/C Catalyst Deactivation Rate and Assessment of Optimal Operating Conditions of Industrial Hydropurification Process Abbas Azarpour, *,† Tohid Nejad Ghaffar Borhani, ‡ Sharifah Rafidah Wan Alwi, ‡ Zainuddin Abdul Manan, ‡ Mazyar Madooli Behbehani ** †
Chemical Engineering Department, Universiti Teknologi Petronas Bandar Seri Iskandar, 31750 Tronoh, Perak, Malaysia
‡
Process Systems Engineering Center (PROSPECT), Faculty of Chemical Engineering Universiti Teknologi Malaysia, 81310 Skudai, Johor, Malaysia
**
PTA/PET Process Engineering Office, Shahid Tondgooyan Petrochemical Company Petrochemical Economic Special Zone, 667 Mahshahr, Khoozestan, Iran
*
Corresponding Author: Tel.: +605 368 7638; Fax: +605 365 6176;
E-mail:
[email protected];
[email protected] (A. Azarpour).
1 ACS Paragon Plus Environment
Industrial & Engineering Chemistry Research
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
Abstract- One of the key concerns of the purification section of purified terephthalic acid (PTA) production plant is the deactivation of palladium supported on carbon (Pd/C) catalyst. In this work, the deactivation rate model of 0.5 wt.% Pd/C catalyst has been developed considering temperature, active surface area, and residual catalytic activity. Moreover, the optimal operating conditions of the industrial hydropurification process has been investigated. The results show that PTA production rate (PPR) can be improved by 5.4 percent through 18 percent increase in hydrogen flowrate. Furthermore, PPR can be increased by 7.6 percent via the temperature rise in the reaction mixture. The optimization results further reveal that PPR can be enhanced by 17.3 percent by improving the feed concentration under the normal operation by means of limiting the inlet 4-carboxybenzaldehyde concentration. The research findings can be applied in the actual working plant to enhance the efficiency of the hydropurification process. Keywords: 4-carboxybenzaldehyde, purified terephthalic acid, optimization, production rate, hydropurification, deactivation rate.
2 ACS Paragon Plus Environment
Page 2 of 50
Page 3 of 50
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
Industrial & Engineering Chemistry Research
1.
INTRODUCTION Catalytic hydrotreating (HDT) is one of the basic processes to produce high quality
products via the removal of contaminants such as sulfur, nitrogen, oxygen, and the saturated aromatic rings and olefins from the final products. The process is usually implemented in fixedbed catalytic reactors (FBCRs) where both gas and liquid phases flow concurrently through a catalyst bed based on the trickle flow regime. Meticulous design and optimization of industrial units necessitate the use of rigorous modeling tools to describe the process more realistically. This includes incorporating the process chemistry and the physical phenomena such as catalyst deactivation to accomplish the best predicting efficiency.1 The catalyst decay rate is a significant parameter to determine the appropriateness of HDT catalysts in industry.
The catalyst
deactivation rate is very important from an industrial standpoint since it influences the production rate planning and the economics. The properties of the feed, especially the low concentration of the impurities, affect the rate of deactivation.2 There are some parameters which influence the palladium catalysts deactivation like particle growth, coke transformation, coke deposition, the effect of the support material on stability, chemical poisoning, corrosion, and leaching.3 There are some challenges in the area of hydrotreating processes. Catalyst deactivation is a great concern in these processes. Various causes of hydrotreating catalysts deactivation have been recognized including metal and coke deposition, poisoning, and sintering.4-11 The other challenge is to synthesize high performance catalysts. Production of clean product to meet the ecological requirements, feed quality change, and involvement of unconventional hydrocarbon resources require the development of more active catalysts.12-19 The other issue is the feed quality control. For example, feeds with low relative solubility index produce more cokes. 3 ACS Paragon Plus Environment
Industrial & Engineering Chemistry Research
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
Moreover, feeds containing higher amount of metals cause faster deactivation of catalysts.20-24 The other concern to mention is the strict environmental regulations. Reduction of SOx and NOx is to be considered in hydrotreating processes.25,
26
The other matter is to design more
sophisticated reactors. The reactors should be designed to distribute gas and liquid uniformly, minimize thermal instability, and maximize reactor catalyst usage.27-30 The other important challenge in this filed is the prediction of kinetics parameters. The complicated calculation of these parameters might be due to coupled catalytic and thermal reactions, especially, when the deactivation of catalyst takes place.31-36 PTA production technology is broadly benefited from Amoco-MC process.37 Purified terephthalic acid (PTA) as a petrochemical product is utilized to produce polyethylene terephthalate (PET).38 PET is commercially produced from ethylene glycol (EG) and PTA. PET is widely used in the production of synthetic fibers, beverage bottles, cosmetics, household and pharmaceutical products, and food packaging film.39 The production of PTA is increasing significantly due to the considerable growth in polyesters production. In the first stage of PTA production, the oxidation of para-xylene (PX) is carried out using a combination of three ions as homogeneous catalyst, which are cobalt, manganese and bromide. Bromide is utilized as promoter. Acetic acid (AA) and air are used as solvent and oxidant. The operating conditions are around 20 atm and 200 oC. Even with high selectivity, even more than 96% that this reaction has, there are still partial oxidation products, such as para-tolualdehyde, para-toluic acid (pta), and 4carboxybenzaldehyde (4-CBA).40 4-CBA and pta are considered as the main impurities of the final crude terephthalic acid (CTA) product, which are reported in the laboratory analysis of CTA powder. The concentration ranges of 4-CBA and pta are usually 2000-3000 ppm and 3001000 ppm, respectively.
The advantage of the homogeneous catalyst is the high yield of 4 ACS Paragon Plus Environment
Page 4 of 50
Page 5 of 50
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
Industrial & Engineering Chemistry Research
production. The disadvantages of this kind of process are that bromide ions have corrosive nature, an expensive titanium reactor is required, bromide ions are not environmentally friendly, and they are dangerous to handle. Co-Y and Mn-Y zeolites were used as heterogeneous catalyst for PX oxidation, but the conversion was low. A significant result in heterogeneous catalytic oxidation of PX was achieved using neat and µ3-oxo bridged Co/Mn cluster complexes encapsulated in zeolite Y as a catalyst and AA-water as a solvent. Very high conversion was the advantage of this process. However, higher operating pressure compared with the commercial process conditions and the corrosive nature and environmental concern of AA utilization were two disadvantages of this achievement.41 In the second stage of PTA production, CTA is purified through the catalytic HDT of 4-CBA to pta in an FBCR consisting of Pd supported on carbon (Pd/C) catalyst.
PTA powder quality is evaluated in accordance with various
measurements as shown in Table 1. Table 1. Some of the specifications of PTA powder quality.42 Parameter
Specification
Unit
delta-y
1 - 10
NA
b-value
