Catalyst Residues Research Articles

English

The purity level of biodiesel has a strong effect on fuel properties and on engine life. Therefore, a purification step is necessary. Generally, there are two accepted methods for purifying biodiesel: wet washing and dry washing. In this research, the effective parameters on wet purification of biodiesel were investigated. Three types of biodiesel wash water (tap water, distilled water and water with 3% phosphoric acid), three wet washing temperatures (30, 45 and 60°C), and three levels of water to biodiesel ratios (0.5, 1 and 1.5 v/v) were used. In order to perform the wet washing of biodiesel, a bubble washing technique was used. The catalyst, soap and water residue were considered as the criteria to choose the optimum water washing condition and were measured after the wet washing of crude biodiesel. The results showed that the best condition for catalyst and soap removal from biodiesel are acidified water, a temperature of 60°C and a water to biodiesel ratio of 1.5 (v/v). Also, the least amount of water residue in the final purified biodiesel was observed when using tap water at a temperature of 60°C and a water to biodiesel ratio of 0.5 (v/v).

Preparation of carbon nanotube monoliths by high-pressure compaction

High-pressure compaction was used to produce monolithic multiwall carbon nanotubes (MWCNTs) from different sources: (1) high-purity commercial Baytubes®, (2) chemical-vapor deposited MWCNTs without purification at the Laboratory of Production of CNT/UNIFRA, and (3) the same MWCNTs as (2) purified with HCl. Pressures of 4.0 GPa and 7.7 GPa were applied at room temperature using two different pressure-transmitting media, lead and graphite. Cylindrical monolithic MWCNTs with diameters of about 6 mm were obtained. The samples were characterized by Raman spectroscopy, X-ray diffraction, elemental analysis, N2 adsorption and transmission electron microscopy. Results showed that the best sample was obtained with MWCNTs without purification, containing residues of MgO catalyst, and using lead as the pressure-transmitting medium at 7.7 GPa. High-pressure may cause compressive stress and shear stress for the MWCNTs. The lead container, as a quasi-hydrostatic pressure-transmitting medium, provided more compressive stress than shear stress while the impurities acted as binding materials. Both helped to obtain better densification of the MWCNTs.

A Novel Zeolite-Containing Composite Material Synthesized via <i>In Situ</i> Crystallization

A novel Y zeolite-containing composite material was prepared via in situ crystallization with sepiolite and catalyst residue as starting materials, of which the BET surface area is up to 582 m2/g, the pore volume is 0.43 cm3/g, the relative crystallinity is as high as 55.7 %, the surface is smooth and regular, and Y zeolite particles are in the range of 0.4-1.0 mirons, the composite contains large number Y zeolite with more meso-macro porous structure.The alkalinity in reaction medium has a pronounced effect on the relative crystallinity of Y zeolite.

Novel electron-withdrawing π-conjugated pyrene-containing poly(phenylquinoxaline)s

65 In recent time, conjugated polymers have attracted considerable attention of researchers not only from scientific but also from a practical viewpoint due to their fundamental optoelectronic properties and application as electroactive materials for organic light emitting diodes [1], field effect transistors [2], and photovoltaic devices [3]. Conjugated polymers are prepared by Stille, Suzuki, and Yamamoto reactions using nickel (Yamamoto) and palladium (Suzuki and Stille) catalysts [4, 5]. However, the high cost of the processes and difficulties of purification from metal catalyst residues, which are undesirable impurities for optoelectronic devices, are considerable drawbacks of these reactions. New noncatalytic methods for the synthesis of high purity conjugated polymers should be developed to solve these problems. It has also been found that intense electroluminescence and high charge mobility in a polymer require a high electron– hole conduction of a medium due to charge carriers mobility and a balance of injection of carriers of both signs from opposite electrodes into the emission poly mer layer. However, the majority of conjugated poly mers provide hole transport that causes imbalance of charge injection and a poor quantum yield. The search for new efficient electron transport polymers is necessary to improve the characteristics of electrooptical devices, which is provided, in particu lar, by the introduction of electron withdrawing frag ments—triazole [6], oxodiazole [7], quinoline [8], and quinoxaline [9]—into macromolecules. The lat ter are the least studied and show higher electron withdrawing properties due to the presence of four electron withdrawing heteroatoms. π Conjugated thiophene containing poly(phenylquinoxaline)s (PPQs) have been obtained recently. These PPQs behave as excellent electron transport materials for organic light emitting diodes [10]. We prepared new conjugated pyrene containing PPQs as high purity polymers by noncatalytic polycondensation reaction to provide the balance of the hole and electron con duction. The introduction of flat structures, such as pyrene, into a conjugated polymer is supposed to enhance intermolecular electronic interaction in the solid state and result in formation of π–π stacking structures. In continuation of our studies [11, 12], we prepared and studied new bipolar pyrene containing PPQs as efficient electron hole and transport materi als and thereby synthesized, previously unknown bis(α diketone)s IV and VIII.

Improvement of carbon nanotube stability by high temperature oxygen/chlorine gas treatment

Carbon nanotubes are interesting for applications in numerous fields. Nevertheless the as-produced samples prepared from bulk synthesis methods contain impurities and remain entangled if neither mechanical nor chemical treatment is applied. Such treatments are known to damage the carbon nanotube structure and to reduce their stability which induces drastic diminution of their properties. We have developed a purification method based on the use of a gas-phase treatment under an oxygen/chlorine mixture at high temperature (around 1000°C). We were able to efficiently remove metal-based impurities from catalyst residue without damaging carbon nanotubes. We show that their stability is improved thanks to the presence of chlorine-containing functional groups at the carbon nanotube surface. Under the used conditions, the functionalization level remains low preserving the SWCNT structure and efficiently protects SWCNTs from combustion by oxygen.

Investigation of the effect of nano-clay type on the non-isothermal crystallization kinetics and morphology of poly(3(R)-hydroxybutyrate) PHB/clay nanocomposites

PHB is a thermoplastic biopolymer produced by fermentation of renewable resources. Secondary crystallization during storage leading to an increased degree of crystallinity is a principal reason of PHB brittleness. In addition, pure PHB has no residues of catalysts, meaning low nucleation density and slow crystallization rates, leading to the formation of large spherulites with cracks and brittleness. To overcome the brittleness of PHB, polymer composites based on PHB, plasticizers, and nano-clays A and B were prepared by solvent casting. The addition of plasticizer decreases T g from 5 to −13 °C in all composites. Furthermore, the addition of nano-clays acts as a nucleating agent to PHB. The effect of nano-clays A and B on spherulites morphology, thermal behavior, and crystal structure of PHB composites were tested by several techniques. Differential scanning calorimetry analysis shows that the addition of nano-clay A does not change the crystallization temperature and the crystallization half-time (t 1/2) of the PHB matrix but that nano-clay B accelerates the crystallization process. Thermogravimetric analysis revealed an increase in thermal stability of composites containing nano-clay B. Polarized optical microscopy showed that nano-clays serve as nucleating agents in PHB matrix. Therefore, the spherulites become smaller and the nuclei density increases at the selected crystallization temperature, compared to pure PHB.

Metathesis of cardanol over Ru catalysts supported on mesoporous molecular sieve SBA-15

The Hoveyda–Grubbs type Zhan catalysts (ZC) and Grubbs second generation catalyst (GII) were immobilized on SBA-15 mesoporous molecular sieve by non-covalent interactions and phosphine linkers, respectively. Both hybrid catalysts proved to be highly active and selective in cardanol metathesis and cardanol cross-metathesis with ethene and cis-1,4-diacetoxy-2-butene (DAB). GII/SBA-15 was less active than ZC/SBA-15, however, Ru leaching was significantly lower for GII/SBA-15 (0.5%) than for ZC/SBA-15 (2.5%). In ethenolysis of cardanol, 3-(non-8-enyl)phenol was isolated as a major product. In cross-metathesis with DAB 9-(3-hydroxyphenyl)non-2-enyl acetate and non-2-enyl acetate were formed with high selectivity. Easy catalyst–product separation and low Ru leaching provide the products (applicable as detergent precursors and fragrance and flavor agents) free from the catalyst residue.

Influence of catalyst residues on thermo-oxidative aging and thermal stability of poly(butene-1)

Isotactic poly(butene-1) (iPB) with spherical morphology was synthesized successfully with bulk precipitation polymerization without post-treatment of the products. The bulk precipitation polymerization process made it possible for iPB to be used as general plastic due to the acceptable decreased cost compared with the solution polymerization process. The influence of catalyst residues on the aging and thermal stability of iPB synthesized by bulk precipitation polymerization method was investigated by gel permeation chromatography, mechanical performance testing, thermogravimetric analysis and infrared spectroscopic analysis. Commercial iPB and the lab-made iPB with varied catalyst residue contents were studied. The results demonstrated that the catalyst residues played an important role in the aging process of the iPB. A possible mechanism of aging promotion by catalyst residues was proposed.

Assessment of the Pozzolanic Activity of a Spent Catalyst by Conductivity Measurement of Aqueous Suspensions with Calcium Hydroxide.

The pozzolanic activity of the spent catalyst produced by fluid catalytic cracking (FCC) has been studied by various methods in recent years. However, no quick and easy method has been reported for this activity based on the associated studies. In this work, the pozzolanic activity of a spent catalyst was investigated by measuring its electrical conductivity in aqueous suspensions of pozzolan/calcium hydroxide. The behavior of the FCC catalyst residue was compared to that of reactive and inert materials of similar chemical compositions. Further, the influence of temperature on the suspension was studied, and also, a new method was proposed in which the pozzolan/calcium hydroxide ratio was varied (with the initial presence of solid Ca(OH)2 in the system). It was concluded that the method is effective, fast and simple for evaluating the high reactivity of the catalyst. Therefore, this method is an alternative for the evaluation of the reactivity of pozzolanic materials.

Synthesis and characterisation of p-diethylaminomethylthiacalix[4]arene for selective recovery of platinum from automotive catalyst residue

The ability of chloroform solutions of p-diethylaminomethylthiacalix[4]arene 1 to extract platinum from HCl media was tested. As an ion-pair extractant, compound 1 had the highest platinum extraction ability among all the thiacalix[n]arene derivatives tested in this study. Compound 1 was a highly specific extractant for Pt(IV) ions from single-metal solutions and platinum-group metal solutions from automotive catalyst residue. Various conditions such as contact time, pH, concentration of 1, effect of chloride ions, effect of acidity and Pt(IV) concentration were studied. The distribution ratio of platinum ions (D) was calculated. The platinum complex stoichiometry ratio was obtained using slope analysis. The 1–Pt(IV) complex was characterised using X-ray photoelectron spectroscopy, FT-IR and 1H NMR. Finally, the Pt(IV) extraction percentage of compound 1 was compared with that of previously reported thiacalix[n]arene-based extractants.

Enhanced graphitization of c-CVD grown multi-wall carbon nanotube arrays assisted by removal of encapsulated iron-based phases under thermal treatment in argon

The effect of annealing on multi-walled carbon nanotube (MWCNT) arrays grown via catalytic Chemical Vapour Deposition (c-CVD) was studied. The treatment enabled to decrease number of defects/imperfections in the graphene walls of MWCNTs’, which was reflected in Raman spectroscopy by reduction of the ID/IG ratio by 27%. Moreover, the vertical alignment from the as-synthesized nanotube arrays was found intact after annealing. Not only graphitization of the nanotube walls occurred under annealing, but the amount of metal iron-based catalyst residues (interfering with numerous physicochemical properties, and hence applications of MWCNTs) was reduced from 9.00wt.% (for pristine MWCNTs) to 0.02wt.% as detected by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). This value, established by a new analytical protocol, is the lowest recorded by now for purified c-CVD MWCNTs and, due to operating under atmospheric pressure, medium temperature regime (as for annealing processes), reasonable time-scale and metal residue non-specificity, it could lay the foundation for commercial purification of c-CVD derived MWCNTs.

Thermooxidative aging of polydicyclopentadiene in glassy state

Thermal ageing of thin films of unstabilized polydicyclopentadiene (pDCPD) at several temperatures ranging from 120 to 30°C was investigated by means of carbonyl build up by FTIR with ammonia derivatization, double bond titration, mass uptake measurement, hydroperoxides titration by iodometry and DSC coupled with sulfur dioxide treatment. In the temperature range under investigation, pDCPD is in glassy state and it oxidizes faster than common polymers oxidized at rubbery state (e.g. polydienic elastomers). Using the kinetic analysis, these results were ascribed to increased initiation rate due to catalyst residues, some possible intramolecular processes favoring propagation, or a very low termination rate of oxidation radical chains because of the control of termination reactions by macroradical diffusion.

Synthesis and Characterization of Dimethylthiocarbamoyl-Modified Thiacalix[n]arenes for Selective Pd(II)-Ion Extraction

In this study, two extractants, hexakis[(dimethylthiocarbamoyl)oxy]thiacalix[6]arene (1) and tetrakis[(dimethylthiocarbamoyl)oxy]thiacalix[4]arene (2), were synthesized by the reaction of dimethylthiocarbamoyl chloride with p-tert-butylthiacalix[n]arenes (n = 6 and 4) and characterized using 1H NMR and FT-IR spectroscopies, elemental analysis, and fast-atom-bombardment mass spectrometry (FAB-MS). These compounds were extensively evaluated for the extraction of Pd(II) ions from HCl media and solutions of platinum-group metals from automotive catalyst residues, using various solvents. Compounds 1 and 2 were found to have higher Pd(II)-ion extraction abilities (0.57 and 0.48 g/L, respectively) than the native p-tert-butylthiacalix[6]arene (3) and p-tert-butylthiacalix[4]arene (4) (0.46 and 0.20 g/L, respectively), using 1 mM extractant and 9.4 mM Pd(II)-ion solutions in HCl media. The extractant–Pd(II) complexes were characterized using FT-IR spectroscopy, elemental analysis, XRD, Job’s continuous method, an...

Revealing the role of catalysts in carbon nanotubes and nanofibers by scanning transmission X-ray microscopy.

The identification of effective components on the atomic scale in carbon nanomaterials which improve the performance in various applications remains outstanding challenges. Here the catalyst residues in individual carbon nanotube (CNT) and carbon nanofiber (CNF) were clearly imaged with a concurrent characterization of their electronic structure by nanoscale scanning transmission X-ray microscopy. Except for prominent catalyst nanoparticle at the tip, tiny catalyst clusters along the tube (fiber) were detected, indicating a migration of the catalysts with the growth of CNTs (CNFs). The observation provides the direct evidence on the atomic metal in CNT for oxygen reduction reported in the literature. Interaction between catalysts (Fe, Ni) and CNTs (CNFs) at the tip was also identified by comparing the X-ray absorption spectra. A deep understanding of catalyst residues such as Fe or Ni in carbon nanomaterials is very vital to growth mechanism development and practical applications.

微細回路の信頼性向上を目的としたパラジウム触媒残渣除去プロセス

微細回路の信頼性向上を目的としたパラジウム触媒残渣除去プロセス

Selective Dispersion of Large‐Diameter Semiconducting Single‐Walled Carbon Nanotubes with Pyridine‐Containing Copolymers

The purity of single-walled carbon nanotubes (SWNTs) is a key parameter for their integration in electronic, optoelectronic and photonic devices. Samples of pristine SWNTs are inhomogeneous in terms of electric behavior and diameter and contain a variety of amorphous carbon and catalyst residues. To obtain high performance devices, purification of SWNTs is required. Conjugated polymers have emerged as efficient solubilizing and sorting agents for small diameter SWNTs (HiPco tubes, 0.7 nm<Ø<1.1 nm). Nevertheless, reports on polymers able to efficiently sort large diameter SWNTs with Ø>1.1 nm are lacking. Several pyridine-containing copolymers were synthesized for this purpose and showed efficient and selective extraction of semiconducting large diameter SWNTs (PLV tubes, Ø>1.1 nm). High concentration and high purity suspensions are obtained without the use of ultracentrifugation, which gives an up-scaling potential of the method. The emission wavelength is in near infrared region around 1550 nm and fits with broadly used telecommunication wavelength window. The processes taking place at the interface were simulated by a newly designed hybrid coarse-grain model combining density functional theory and geometrical calculation to yield insights into the wrapping processes with an unprecedented level of details for such large diameter SWNTs.

Intracellular fate of carbon nanotubes inside murine macrophages: pH-dependent detachment of iron catalyst nanoparticles

BackgroundCarbon nanotubes (CNT) are a family of materials featuring a large range of length, diameter, numbers of walls and, quite often metallic impurities coming from the catalyst used for their synthesis. They exhibit unique physical properties, which have already led to an extensive development of CNT for numerous applications. Because of this development and the resulting potential increase of human exposure, an important body of literature has been published with the aim to evaluate the health impact of CNT. However, despite evidences of uptake and long-term persistence of CNT within macrophages and the central role of those cells in the CNT-induced pulmonary inflammatory response, a limited amount of data is available so far on the CNT fate inside macrophages. Therefore, the overall aim of our study was to investigate the fate of pristine single walled CNT (SWCNT) after their internalization by macrophages.MethodsTo achieve our aim, we used a broad range of techniques that aimed at getting a comprehensive characterization of the SWCNT and their catalyst residues before and after exposure of murine macrophages: X-ray diffraction (XRD), High Resolution (HR) Transmission Electron Microscopy (TEM), High Angle Annular Dark Field-Scanning TEM (HAADF-STEM) coupled to Electron Energy Loss Spectroscopy (EELS), as well as micro-X-ray fluorescence mapping (μXRF), using synchrotron radiation.ResultsWe showed 1) the rapid detachment of part of the iron nanoparticles initially attached to SWCNT which appeared as free iron nanoparticles in the cytoplasm and nucleus of CNT-exposed murine macrophages, and 2) that blockade of intracellular lysosomal acidification prevented iron nanoparticles detachment from CNT bundles and protected cells from CNT downstream toxicity.ConclusionsThe present results, while obtained with pristine SWCNT, could likely be extended to other catalyst-containing nanomaterials and surely open new ways in the interpretation and understanding of CNT toxicity.

Mechanical and physical performance of low alkalinity cementitious composites reinforced with recycled cellulosic fibres pulp from cement kraft bags

The objective of this work was to study the addition of cellulosic pulp in low alkalinity cement composites as well as its mechanical behavior under bending stresses before and after accelerated aging cycles. The cellulosic pulp was obtained from recycled Portland cement kraft bags used for packaging. Low alkaline cementitious matrices were tested, reducing from 80 to 85% the content of Portland cement, in order to reduce the use of the conventional raw materials, energy cost and mainly to avoid a possible alkaline degradation of the cellulosic pulps. The cement matrix resulted from the ternary blend Portland cement–gypsum–pozzolan (fly ash or catalytic cracking catalyst residue), with 50% by weight of gypsum and different percentages by weight of pozzolans. These composites were prepared in the laboratory using a slurry vacuum dewatering followed by pressing technique. The four point-bending tests were carried out to evaluate the mechanical behavior of the low alkalinity cementitious composites and composite without pozzolans at 28 days and after soak and dry accelerated aging tests. The low alkaline cement composites presented average values of modulus of rupture about 10MPa after the aging cycles, with the indication that its flexural strength was not significantly affected by the degradation tests. In addition, the average values of specific energy of these composites were also acceptable after 100 soak and dry cycles as compared to the composites with the Portland cement plain matrix. These results suggest that the use of low alkalinity ternary binder system can be an effective contribution in order to avoid the severe damage on cellulosic fibers (which occurred when traditional pure Portland cement matrix is applied).

Determination of platinum group metal catalyst residues in active pharmaceutical ingredients by means of total reflection X-ray spectrometry

The control of metal catalyst residues (i.e., platinum group metals (PGMs)) in different stages of the manufacturing processes of the active pharmaceutical ingredients (APIs) and, especially, in the final product is crucial. For API specimens, there are strict guidelines to limit the levels of metal residues based on their individual levels of safety concern. For PGMs the concentration limit has been established at 10mg/kg in the API.Therefore great effort is currently being devoted to the development of new and simple procedures to control metals in pharmaceuticals.In the present work, an analytical methodology based on benchtop total reflection X-ray fluorescence spectrometry (TXRF) has been developed for the rapid and simple determination of some PGM catalyst impurities (Rh, Pd, Ir and Pt) in different types of API samples. An evaluation of different sample treatments (dissolution and digestion of the solid pharmaceutical samples) has been carried out and the developed methodologies have been validated according to the analytical parameters to be considered and acceptance criteria for PGM determination according to the United States Pharmacopeia (USP). Limits of quantification obtained for PGM metals were in the range of 2–4mg/kg which are satisfactory according to current legislation. From the obtained results it is shown that the developed TXRF method can be implemented in the pharmaceutical industries to increase productivity of the laboratory; offering an interesting and complementary analytical tool to other atomic spectroscopic methods.

Pozzolanic reaction rate of fluid catalytic cracking catalyst residue (FC3R) in cement pastes

Fluid catalytic cracking catalyst residue (FC3R) is a waste material generated in the petroleum industry. Previous research has shown that FC3R exhibits excellent pozzolanic properties in Portland cement mixtures. The pozzolanic activity of FC3R was studied by means of thermogravimetric analysis (measurement of lime fixation) and cold hydrochloric acid treatment (quantification of FC3R reacted). A water/binder ratio of 0·40 was used in the study in the preparation of a control paste (without spent catalyst) and a 15% substituted FC3R paste. The selected curing temperatures were 20 and 40°C and several curing times were tested. The amount (grammes) of fixed lime by gramme of reacted catalyst indicated that approximately one part lime is chemically combined with 2·3 parts of spent catalyst. The combination of both study techniques allows determination of the optimal dosage in order to maximise use of this excellent pozzolan.