Unreacted Compound Research Articles

Residual Cementing Property in Recycled Fines and Coarse Aggregates: Occurrence and Quantification

AbstractThe adhered cement mortar in coarse aggregates and fines from demolished concrete has the potential to induce a residual cementing property upon recycling. A procedure for quantifying the contribution of recycled fines to the strength gain within the new mortar matrix is proposed. The strength gain is found to be more significant in recycled aggregates and fines from brick aggregate concrete than in those from stone aggregate concrete. Isothermal calorimetry measurements indicate the existence of large heat flows immediately after wetting and a prolonged initial reaction period during the hydration of recycled fines because of the presence of unreacted cement compound fractions and depleted amounts of gypsum. This phenomenon has been further confirmed, particularly in recycled fines from brick aggregate concrete, through electron microscopy observations of the formation of new gel structures caused by rehydration. The chemical compositions determined using two independent methods indicated possibl...

Enzyme-assisted kinetic resolution of novel 2-naphthol Mannich bases

In an attempt to develop novel Selective Estrogen Receptor Modulators (SERMs) containing a chirality centre, simpler 1-((2-hydroxynaphthalen-1-yl)arylmethyl)piperidin-4-ol prototypes were synthesized as racemic mixtures via the Mannich reaction protocol from 2-naphthol, 4-piperidinol, and 10 different aromatic aldehydes. These 10 chiral Mannich bases were then resolved utilizing an enzyme-assisted chemo-, regio-, and enantioselective acetylation process. The enzyme (Novozyme 435 ®; Lipase B from Candida Antarctica) displayed exclusive chemo- and regioselectivity in acetylating the test compounds; the optical enrichment was also achieved as evidenced by measurement of the optical rotation of the mono-acetylated product and unreacted dihydroxy compound.

Intergel interpolyelectrolyte reaction and synthesis of hybdrid composites based on charged microgels and inorganic nanocrystals

We have studied the interaction between oppositely charged microparticles of polyelectrolyte hydrogels whose low-molecular-mass counterions form insoluble compounds. The intergel polyelectrolyte reaction of such polymers leads to formation of a crystalline compound in the microgel mixture phase. The asprepared samples are composites containing, along with unreacted microgel regions, the interpolyelectrolyte complex comprising the intercrystalline low-molecular-mass compound. It has been shown that both unreacted microgel regions and insoluble compound incorporated into the intergel complex can be involved in chemical modification.

Mechanism of glycolysis of nylon 6,6 and its model compound by ethylene glycol

The degradation mechanism of nylon 6,6 and its model compound hexamethylenebis(hexamide) (HMHA) by ethylene glycol (EG) was studied in detail. Glycolysis of both model compound and nylon 6,6 was carried out with stoichiometric excess of EG at high temperature (250 and 275 °C, respectively) in an autoclave reactor as a closed system. Samples were collected at predetermined intervals and characterized by FT-IR, GC–MS, and GPC. FT-IR studies of model compound glycolysis showed no significant increase in the ester band after 11 h indicating that the glycolysis reaction may have reached equilibrium. GC–MS data revealed the presence of ester as well as unreacted model compound. GC–MS data for nylon 6,6 revealed the presence of compounds having β-hydroxyethylester group, bis(β-hydroxyethyl)adipate, and δ-valerolactone as the degradation products. From GPC data, as the glycolysis time of nylon 6,6 increased, both the number average and weight average molecular weights decreased indicating that the main chain of nylon 6,6 was broken into low molecular weight compounds during glycolysis.

Two possible pathways for the release of arsenic during pyrolysis of chromated copper arsenate (CCA)-treated wood

The behavior of arsenic during pyrolysis at temperatures between 135 and 500 °C has been widely studied. We examined the release of arsenic during the pyrolysis of chromated copper arsenate (CCA)-treated wood, and here we propose two models for the volatilization of arsenic: (a) a reacted arsenic compound, chromium arsenate, in CCA-treated wood was initially decomposed to arsenic pentoxide, which then appeared to be released at around 400–500 °C as a form of arsenic trioxide; and (b) an unreacted arsenic compound, arsenic pentoxide, in CCA-treated wood was released at much lower temperatures than reacted arsenic compound, as a form of arsenic trioxide. In order to restrain the release of arsenic during pyrolysis, it is possible to pyrolyze CCA-treated wood carefully at temperatures around 300–350 °C only if the wood contains little unreacted arsenic compound. Under these conditions, almost all toxic elements remain in the pyrolysis residue, and a weight reduction of the wood of approximately 50% can be obtained. On the other hand, the release of arsenic can be achieved easily using an unreacted arsenic compound under the same pyrolysis conditions. However, in the present study it was difficult to determine the accurate release point of arsenic in both cases due to the level of experimental uncertainty.

Electron microscopic study on pyrolysis of CCA (chromium, copper and arsenic oxide)-treated wood

The effectiveness of pyrolysis as a possible technique for disposing of CCA (chromium, copper and arsenic oxide)-treated wood was studied. A CCA-treated sample given an extra heat treatment at 450 °C for 10 min was thoroughly investigated in order to establish the details of the reaction in which arsenic is captured in the pyrolysis residue prior to volatilization. Composition and structure of the metal compounds in the pyrolysis residue were examined by transmission electron microscopy (TEM). A large number of particles were found of variable diameter between 10 and 100 nm. The smaller ones were mostly spherical, sometimes faceted. The larger ones were lumpy. CCA compounds and their reaction products like Cr 2As 4O 12 and As 2O 3 were identified in conventional TEM by selected area electron diffraction. In high resolution, the nanoparticles exhibited lattice fringes as indication of their monocrystalline character, fitting, e.g., the d 2 1 0 =0.204 nm of Cr. The volatility of arsenic during pyrolysis of CCA-treated wood was measured by XRF (X-ray fluorescence) analysis at temperatures up to 500 °C and at times up to 1 h. Weight change and arsenic content of the pyrolysis residue were measured after dissolution in HNO 3. More than 20% of arsenic was already lost at 300 °C, which may have been caused mainly by the volatilization of the unreacted arsenic compound after reduction of As(V) in As 2O 5 to As(III) in As 2O 3. Arsenic is probably released as As 4O 6, which is very difficult to capture and toxic. By an additional heat treatment, this reduction can be prevented and the dry separation of the metals may be allowed.

Iron-Catalyzed Cocurrent Flow Destruction and Dechlorination of Chlorobenzene During Gasification

Iron-treated char was used in an attempt to catalyze chlorobenzene destruction in the ChemChar thermal waste gasification process. The contribution to the destruction removal efficiency (DRE) of chlorobenzene from gasification per se was increased from 99.75% when char was used in the gasifier bed to >99.99% when char treated with iron was used. This clearly satisfies the EPA requirement of 99.99% (4-nines) destruction. Furthermore, other operations in the total system including condensation of condensable matter from the gas stream, filtration of the dried gas over a char filter, and secondary combustion of the product gas contribute to additional removal of unreacted parent compound and byproducts, so that the DRE should easily be increased to 99.9999% (6-nines). The primary mechanism for chlorobenzene dechlorination was determined to involve the reduction of chlorobenzene by reaction with nascent hydrogen. Nascent hydrogen is produced through the water−gas shift reaction, which is believed to be cataly...

Thin film deposition in glow discharges fed with hexamethyldisilazane-oxygen mixtures

Thin films deposited in glow discharges fed with hexamethyldisilazane-oxygen-argon mixtures at low substrate temperature have been studied by means of in situ X-ray photoelectron spectroscopy. The results have been compared with those obtained with tetraethoxysilane-oxygen plasmas. It has been found that hexamethyldisilazane, even if less oxidisable, is strongly fragmented in the plasma phase. The oxygen atoms produced by plasma dissociation promote decrease of nitrogen, carbon and hydrogen content of the film but are not able to form oxygenated nitrogen compounds. The results are in agreement with a deposition mechanism composed of different gas-gas and gas-surface reactions as previously found for tetraethoxysilane. The main difference is that in the present work the homogeneous activation reaction of unreacted compound by means of oxygen atoms is important even when the oxygen content of the feed is low. When the oxygen content of the film is high, the chemical composition of the film surface is slightly different from that of the bulk.

Mechanism study of deep-UV irradiated poly(methyl methacrylate)-azide resist system

Abstract The photochemical reactions of resist films consisting of poly(methyl methacrylate) (PMMA) and aromatic azide at high concentraton (25 wt.%) were studied. Both p-azidobenzoic acid (PABA) and 2,6-bis(4-azidylbenzylidene)-4-methyl cyclohexanone(2,6-bisazide) were used as the azide compounds. Chemical analysis carried out on the photoproducts of deep-UV irradiated PMMA-azide films revealed them to consist of unreacted azide compound, primary amine, azo dye, and PMMA with pendant secondary amines formed by nitrene insertion reactions. It is concluded that formation of secondary amines resulting from nitrene insertion to the PMMA chain were mainly responsible for both the dissolution rate retardation and the image reversal observed in the exposed PMMA-azide resist.

On the active site of the Phillips catalyst for ethylene polymerization

The FTIR spectra of CO adsorbed on the chromium(II)-A surface compound (the active site of the Phillips catalyst) before and after short polymerization with ethylene have been reexamined. No difference in the CO spectra of the room temperature triplet at 2190, 2185, and 2179 cm −1 was found for that part of chromium which reacts with ethylene compared to the CO spectra of the unreacted surface compound. The same result was observed with the low temperature CO IR triplet at 2120, 2100, and 2035 cm −1. After low temperature polymerization with ethylene a new CO IR band at 2176.82 cm −1 was observed. After high temperature reaction with ethylene a symmetrical and rather sharp CO IR band at 2171.52 cm −1 was noted at room temperature instead. It is concluded that in both cases rather well-structured chromium surface compounds are formed. The CO IR bands of the room temperature triplet shifted from 2190.79, 2184.74 and 2178.69 cm −1 to 2192.28, 2185.03, and 2180.76 cm −1 after seven oxidation (800 °C, O 2)/reduction (350 °C, CO) cycles. The CO IR bands of the low temperature triplet (−145 °C) separated into two triplets with higher (2121.12, 2102.06, and 2040.37 cm −1) and lower (2117.12, 2098.47 and 2031.34 cm −1) positions than the original one. It is concluded that the surface structure of the support has a rather large influence on the electronic density of the chromium(II) surface ions.

Metathesis and reduction reactions of nitroso compounds with metal carbenes and metal carbonyls

Reaction of nitroso compounds with metal-carbene complexes and metal carbonyls has been investigated. These reactions lead to reduction of the nitroso compounds, primarily to the corresponding azo- and azoxy compounds. Metal-nitrene complexes have been proposed as intermediates in these reactions. These intermediates couple rapidly with the unreacted nitroso compound, or enter into nitrene-like reactions with external or internal trapping agents. Reaction of metal carbonyls with nitrosoarenes and photolysis has been found to be an effective method for the reduction of nitrosoarenes to azoxyarenes, with few problems resulting from overreduction to amines or azo compounds.

2184. Excitation of high-frequency oscillations in a plasma with accelerating Hall layer: V I Arefev and K P Kirdyashev,Zh Tekh Fiz,45 (3), 19s75, 527–535 ( in Russian)

The FTIR spectra of CO adsorbed on the chromium(II)-A surface compound (the active site of the Phillips catalyst) before and after short polymerization with ethylene have been reexamined. No difference in the CO spectra of the room temperature triplet at 2190, 2185, and 2179 cm−1 was found for that part of chromium which reacts with ethylene compared to the CO spectra of the unreacted surface compound. The same result was observed with the low temperature CO IR triplet at 2120, 2100, and 2035 cm−1. After low temperature polymerization with ethylene a new CO IR band at 2176.82 cm−1 was observed. After high temperature reaction with ethylene a symmetrical and rather sharp CO IR band at 2171.52 cm−1 was noted at room temperature instead. It is concluded that in both cases rather well-structured chromium surface compounds are formed. The CO IR bands of the room temperature triplet shifted from 2190.79, 2184.74 and 2178.69 cm−1 to 2192.28, 2185.03, and 2180.76 cm−1 after seven oxidation (800 °C, O2)/reduction (350 °C, CO) cycles. The CO IR bands of the low temperature triplet (−145 °C) separated into two triplets with higher (2121.12, 2102.06, and 2040.37 cm−1) and lower (2117.12, 2098.47 and 2031.34 cm−1) positions than the original one. It is concluded that the surface structure of the support has a rather large influence on the electronic density of the chromium(II) surface ions.