Applied Petrochemical Research (v.6, #4)
Aminopyridine stabilized group-IV metal complexes and their applications by Muhammad Hafeez; Muhammad Riaz (307-340).
During the last two decades, group-IV metals-based aminopyridinato complexes have attracted a tremendous research interest because of immense industrial needs for the catalyst which would be of higher activity and selectivity with lower toxicity and lower cost. Chemistry of titanium (Ti) and zirconium (Zr) complexes was more extensively explored as compared to hafnium (Hf) complexes. Direct synthesis, salt metathesis, amine elimination, alkane elimination, silyl chloride elimination, hydrogen chloride elimination and toluene elimination protocols have been used for the synthesis of group-IV metal complexes. Changes in ligand and complex design were made to optimize these catalysts for olefin polymerization. Most of these complexes have shown good catalytic activities when activated with dry methyl aluminoxane. Ligand transfer to aluminum was found in these complexes, particularly with less bulky ligands, and this ligand transfer problem was overcome by tridentate ligands but the activities of these complexes were not competitive to complexes with bidentate aminopyridinato ligands. Majority of these complexes produce high-molecular-weight polymers with broader molecular weight distributions, and Hf-complexes produce longer chain polymers than their comparative Ti and Zr aminopyridinato complexes. It could be deduced that group-IV metals inherit the potential for optimal polymerizing catalysts probably, because of their almost vacant d-orbitals, these act as hard acids which on combination with soft bases carry the opportunity to design and develop polymerization catalysts which could overcome the problems associated with existing systems.
Keywords: Group-IV polymerizing catalysts; Aminopyridinato ligands; Homogenous catalysts; Olefin polymerization
n-Heptane hydroconversion over sulfated-zirconia-supported molybdenum carbide catalysts by F. F. Oloye; A. J. McCue; J. A. Anderson (341-352).
Molybdenum carbide on sulfated zirconia was prepared by impregnation of MoO3 on sulfated zirconia to give a loading of 5 wt% followed by carburisation at 923 K in a mixture of CH4/H2 (4:1). The resulting catalyst was characterised by N2 adsorption–desorption, CO chemisorption, FTIR of pyridine adsorption, XRD, TPR, TGA, Raman and SEM–EDX. This combination of characterisation studies suggests formation of a well-dispersed Mo2C phase over tetragonal zirconia. When employed in the hydroconversion of n-heptane, high temperature and low space velocity lead to substantial cracking. However, under some conditions, an increase in the research octane number (RON) from 0 (n-heptane) to ca. 50 was attained. Between 723 and 873 K, n-heptane is mainly cracked to iso-pentane and ethane. The product distribution as a function of conversion suggests that the reaction did not simply follow a consecutive reaction pathway, but that other parallel routes were involved.
Keywords: Molybdenum carbide; Sulfated zirconia; n-heptane; Cracking; Isomerisation
Modification of USY zeolites with malic–nitric acid for hydrocracking by Ke Qiao; Xuejin Li; Yang Yang; Fazle Subhan; Xinmei Liu; Zifeng Yan; Wei Xing; Lihong Qin; Baoqin Dai; Zhihua Zhang (353-359).
The modification of commercial ultra-stable Y zeolite using malic acid (MA) and nitric acid (NA) was investigated. A series of factors including the amount of MA and NA solutions, the pH of the solutions, the treatment time, and the reaction temperature were investigated and optimized. The pore structure, acid properties, and crystal structure of modified USY zeolite were characterized by N2-adsorption, temperature-programmed desorption of ammonia (NH3-TPD), pyridine adsorbed Fourier transform infrared spectroscopy, and X-ray diffraction techniques. The as-obtained sample under the optimum conditions presents an increased secondary pore volume up to 0.202 cm3 g−1, which accounts for 45.3 % of the total pore volume, and appropriate acid properties as well as good crystallinity. Furthermore, the USY zeolite modified with different methods was also investigated, indicating that malic–nitric combined acid is an effective modifier for USY zeolite. The modified USY zeolite was used as support to prepare hydrocracking catalysts. The 140–370 °C middle distillate yield of the catalyst is 68.59 %, and middle distillate selectivity can reach up to 81.52 %. Compared with commercial catalyst, the yield and selectivity increased by 8.17 and 5.14 %, respectively.
Keywords: USY zeolite; Modification; Malic acid; Nitric acid
Adsorption desulfurization study with ionic liquid compound ZrO2/PSMIMHSO4 by Jianxiang Wu; Yilong Gao; Wei Zhang; Yueyue Tan; Aomin Tang; Yong Men; Bohejin Tang (361-366).
Two ionic liquids 1-methyl-imidazolium-3-propylsulfonate (PSMIM) and 1-methyl-imidazolium-3-propylsulfonate hydrosulfate (PSMIMHSO4) were synthesized. Their ZrO2, ZrOCl2 and ZrO2/SO4 2− derivatives were prepared under different condition and their desulfurization performances were studied. Then compared with traditional materials and their original materials under the same condition, the result showed that PSMIMHSO4 compounded with ZrO2 at mass ratio of 1:1 exhibited the superior desulfurization activity at 433 K for 25 min with the material/oil (m/v) of 1:10, and its desulfurization rate reached 97.4 %.
Keywords: Ionic liquid; Desulfurization; Adsorption
Vapor-phase catalytic dehydration of lactic acid to acrylic acid over nano-crystalline cerium phosphate catalysts by Nekkala Nagaraju; Vanama Pavan Kumar; Amirineni Srikanth; N. Pethan Rajan; Komandur V. R. Chary (367-377).
A series of cerium phosphate (CeP) catalysts were synthesized using precipitation method with varying Ce/P mole ratios ranging from 0.5 to 3.0 followed by calcination. The formation of cerium phosphate was confirmed by X-ray diffraction and FT-IR techniques. The catalysts were further characterized to understand the morphology, surface area by using transmission electron microscopy (TEM) and N2-sorption measurements. The acidic and basic sites were measured by CO2-TPD, NH3-TPD and ex situ pyridine FT-IR methods. These calcined CeP catalysts were employed for the dehydration of lactic acid (LA) to acrylic acid (AA) under vapor-phase reaction conditions. Among the catalysts examined, CeP catalyst with Ce/P mole ratio 2.5 (CeP(2.5)) was found to exhibit better catalytic performance with conversion of lactic acid ~100 and 64 % selectivity towards acrylic acid at optimized conditions. Time-on-stream experiments suggest that CeP(2.5) catalyst exhibited constant activity until 20 h after which a slight drop of conversion of lactic acid was noticed. The characterization studies of the spent catalysts using thermogravimetric (TG), CHNS analysis and FT-IR reveal the presence of carbonaceous species over the catalyst surface causing deactivation of the catalyst.
Keywords: Lactic acid (LA); Acrylic acid (AA); Acetaldehyde; Cerium phosphate (CeP)
Selective hydrogenation of 1,3-butadiene in presence of 1-butene under liquid phase conditions with NiPd/Al2O3 catalysts by Franklin J. Méndez; Roger Solano; Yanet Villasana; Julia Guerra; Susana Curbelo; Marcel Inojosa; Claudio Olivera-Fuentes; Joaquín L. Brito (379-387).
The catalytic performance of Al2O3-supported monometallic and bimetallic catalysts in selective hydrogenation of 1,3-butadiene in the presence of 1-butene under liquid phase conditions was studied. Bimetallic catalysts were prepared by the coimpregnation method with the required amounts of the precursors salts [Ni(NO3)2·6H2O and Pd(NH3)4Cl2·H2O] over pellet-form γ-Al2O3 with a constant content of Pd (0.5 wt%) and varying Ni/Pd atomic ratio (0.25, 0.5, 0.75, and 1) obtaining egg-shell profiles of the active components. The catalysts were characterized by X-ray diffraction, temperature-programmed techniques, such as reduction in hydrogen and desorption of ammonia, N2 physisorption, and transmission electron microscopy. The catalytic test showed that the 1,3-butadiene was selectively hydrogenated when bimetallic catalysts were used. The addition of Ni to the Pd-based catalysts suppressed n-butane formation and increased recovery of 1-butene at medium conversion. Therefore, it was observed an improved catalytic performance of the bimetallic catalysts being highest in the case of the 1NiPd/Al2O3.
Keywords: 1,3-Butadiene; Liquid-phase reactions; NiPd catalysts; Selective hydrogenation
Dehydration of emulsified lubricating oil by three fields: swirl centrifugal field, pulse electric field and vacuum temperature field by Ye Peng; Tao Liu; Haifeng Gong; Xianming Zhang (389-395).
Lubricating oil can be easily polluted by water and emulsified, thereby negatively affecting the lubricating property. Meanwhile, wasted lubricating oil, a complex composition, presents high water content and exists with emulsion. A single technological method is difficult to be satisfied for efficient demulsification and dehydration of emulsified lubricating oil. In this paper, it is proposed that the swirl centrifugal field made by hydrocyclone, pulse electric field, and vacuum temperature field are coupled to achieve the oil’s dehydration. Based on the theories, it is reasonable to use three fields for oil’s demulsification. In the experiment of three-field dehydrating, the demulsification device is divided into two parts, namely, the coupled unit of pulse electric field and hydrocyclone, and the vacuum heating unit. The structure and size of the device were optimized through numerical simulation. With two modes of single field and three-field, the experiments were carried out. Results indicated that the use of three-field was more energy efficient and faster compared with the traditional vacuum heating method only.
Keywords: Dehydration; Swirl centrifugal field; Pulse electric field; Vacuum temperature field; Emulsified lubricating oil
Red-oils in ethylene plants: formation mechanisms, structure and emulsifying properties by Fabrice Cuoq; Jérôme Vachon; Jan Jordens; Gerard Kwakkenbos (397-402).
In most ethylene plants, the caustic sections suffer from red-oils formation which results from the polyaldol condensation of some oxygenate species in basic media. These red-oils lead to solid material deposition which is generically referred to as fouling and which can cause severe energy losses or operational issues. This specific red-oil fouling can be successfully mitigated by regularly washing the caustic scrubber with a hydrocarbon washing stream which acts as a solvent. However, such washing streams can be further rerouted to the quench water system, increasing the risk of emulsion formation due to its amphiphilic components, i.e., red-oils, compromising the safe operation of the whole plant. The complexity of red-oil structures renders its analysis and characterization challenging. Consequently, there has been no study showing the effect of the type of hydrocarbon wash on the red-oils structure and its potential emulsifying properties. This study describes an in-house developed analytical technique based on UPLC-High resolution QTOF which allows characterizing hydrocarbon streams with complex mixtures of oxygenated species. This method has been successfully applied to monitor red-oil structures during a plant trial where Pyrolysis Gasoline and Toluene-Xylene hydrocarbon washes were successively applied. The data revealed that reactive compounds from the Pyrolysis Gasoline react with the polyaldol species, likely through a Diels–Alder mechanism, thus increasing the diene adduct concentration in the red-oil. It was further found that toluene-xylene washes hindered the emulsifying properties of the red-oils more effectively than Pyrolysis Gasoline washes, in that they could best inhibit the formation of polyaldols adducts.
Keywords: Caustic tower; Red-oil; Quench water; Gasoline; TX-cut; Aldol condensation; Fouling; Emulsifier; UPLC-Q-TOF
Removal and recovery of mercury from chlor-alkali petrochemical wastes using γ-Fe2O3 nanoparticles by Zahra Ramezani; Neda Pourmand; Abdolazim Behfar; Ali Momeni (403-411).
One of the main sources of mercury pollutions in Bandar Imam petrochemical company is its chlor-alkali unit. The unit uses mercury to convert sodium chloride (NaCl) to chlorine and sodium hydroxide. In this study, removal and recovery of mercury from wastewater of the chlor-alkali unit before its conversion to cake using γ-Fe2O3 nanoparticles were reported. It was shown that the magnetic nanoparticles can adsorb and remove mercury from the chlor-alkali unit wastes and the resulting sorbents effectively separated from the solution by a 1.4 T magnet. Different parameters, which could affect the adsorption process, such as the amount of nanoparticles, pH and volume of buffer, and contact time were optimized. Under the optimized conditions, 94.59 % of mercury was removed using bare nan γ-Fe2O3 with RSD of 1.7 % (n = 5). Adsorbed Hg(II) was successfully desorbed using 1 M HCl, then the resulting solution’s mercury content was reduced to elemental mercury. The elemental mercury was finally collected in a hollow glass gas chromatographic column half filled with distilled water, providing a green chemistry for reuse of mercury. The method of mercury determination was cold vapor atomic adsorption spectrometry throughout this study.
Keywords: Petrochemical waste; Chlor-alkali unit; γ-Fe2O3 nanoparticles; Mercury, remediation
Hydrogen: efficient promoter for PNP/Cr(III)/MAO catalyzed ethylene tetramerization toward 1-octene by Tao Jiang; Le Zhang; Jinlong Gao; Chengang Cao (413-417).
The effect of hydrogen addition on the catalytic activity and product selectivity of PNP/Cr(III)/MAO catalytic systems for ethylene tetramerization was investigated. The results showed that the catalytic activity could be increased twice and the polymer production could be reduced efficiently through hydrogen addition. It could be inferred from the analysis and characterization results of the products that there existed at least three sorts of catalytic active centers in the ethylene tetramerization reaction.
Keywords: Ethylene tetramerization; 1-Octene; Hydrogen; Promoter
Selective oxidation of 4-tert-butylphenol by hydrogen peroxide in the presence of titanosilicates by R. R. Talipova; R. U. Kharrasov; M. R. Agliullin; A. D. Badikova; B. I. Kutepov (419-426).
The catalytic transformations of 4-tert-butylphenol in hydrogen peroxide solutions were investigated in the presence of crystalline and amorphous titanosilicates and titanium oxide. The TS-1 microporous crystalline titanosilicate was shown to exhibit low activity in the 4-tert-butylphenol transformation due to the steric limitations on the diffusion of the substrate molecules towards catalytic active centers. Mesoporous amorphous titanosilicates were more selective in the 4-tert-butylcatechol formation than the titanium oxide. The selectivity to 4-tert-butylcatechol in the presence of the TiO2 did not exceed 20 mol%. The maximum 53 mol% selectivity value to 4-tert-butylcatechol was shown to occur over the amorphous mesoporous titanosilicate containing 1.9 wt% of Ti, the 4-tert-butylphenol conversion value being equal to 42 mol%.
Keywords: 4-tert-butylphenol; 4-tert-butylcatechol; Hydrogen peroxide; Titanium oxide; Titanosilicate
The advantage of ceria loading over V2O5/Al2O3 catalyst for vapor phase oxidative dehydrogenation of ethylbenzene to styrene using CO2 as a soft oxidant by Venkata Ramesh Babu Gurram; Siva Sankar Enumula; Suresh Mutyala; Ramudu Pochamoni; P. S. Sai Prasad; David Raju Burri; Seetha Rama Rao Kamaraju (427-437).
The present work highlights the influence of ceria over vanadia/alumina for the oxidative dehydrogenation of ethylbenzene to styrene with CO2 as a soft oxidant. Various weight loadings (0, 3, 5, and 7 %) of ceria were incorporated into 10wt % V2O5/Al2O3 catalyst by wet impregnation process. Structural and textural characterizations of the catalysts were performed by means of powder X-ray diffraction, temperature-programmed reduction, temperature-programmed desorption of CO2, N2 adsorption–desorption analysis. Over 10 % V2O5/Al2O3, ethylbenzene conversion decreases from 62 to 49 % in a spam of 12 h. Ceria-incorporated catalyst (3 % CeO2/10 % V2O5/Al2O3) showed steady ethylbenzene conversion of nearly 65 % with a styrene selectivity of 96 % for a period of 12 h time. Improved catalytic activity observed on this catalyst can be attributed to the increase in the number of redox/active VOx species after incorporation of ceria. The redox properties of 3 % CeO2/10 % V2O5/Al2O3 and 10wt % V2O5/Al2O3 were examined by reaction of CO2 in pulses on to the partially reduced catalysts. The spent catalysts were characterized using XRD & TPR analysis to assess the reason for the deactivation of catalysts.
Keywords: Ceria; V2O5/Al2O3 ; Oxidative dehydrogenation; Ethylbenzene; CO2 as soft oxidant
CO2/CH4 separation by means of Matrimid hollow fibre membranes by Francesco Falbo; Adele Brunetti; Giuseppe Barbieri; Enrico Drioli; Franco Tasselli (439-450).
CO2/CH4 mixtures separation was investigated using Matrimid®5218 hollow fibre membranes and measuring the membrane flux feeding singly CH4 and CO2 and their mixtures, with CH4 concentration ranging from 5 to 70 %molar. Specific attention was paid to membrane properties at a high temperature (up to 75 °C) and feeding humidified streams, not yet particularly investigated, in a pressure range 400–600 kPa. The membrane properties were restored when water vapour was removed and temperature decreased stating the excellent hydro-thermal stability of these membranes. Maps of the separation performance were also calculated for a range of operating conditions wider than the experimental one paying specific attention to the feed/permeate pressure ratio further to membrane selectivity and permeance. Single and multi-stage membrane separation systems were investigated using these maps. The prepared Matrimid®5218 hollow fibres showed very good performance in terms of flux and selectivity for temperatures up to 60 °C, also in steam saturated conditions, allowing a methane concentration meeting the specification for its injection into the grid.
Keywords: CO2/CH4 separation; Hollow fibre membrane; Matrimid®5218; Membrane performance maps