Experiments were conducted to investigate the reforming of organic compounds (primarily methanol) in supercritical water at 550–700°C and 27.6MPa in a tubular Inconel 625 reactor. The results show that methanol can be completely converted to a product stream that is low in methane and near the equilibrium composition of hydrogen, carbon monoxide, and carbon dioxide. The effect of reactor temperature, feed concentration of methanol, and residence time on both conversion and product gas composition was investigated and the results are presented. Reaction pathways and potential applications of this technology are discussed. Ethanol and ethylene glycol resulted in less desirable effluent gas, with high concentrations of methane and carbon monoxide. Acetone and diesel fuel both resulted in the reactor becoming plugged.

Supercritical fluid (SCF) solvents represent a unique and powerful reaction medium because of the strong pressure dependence of their densities and solvent properties (nu, eta, delta, epsilon, and D). This offers the capability of controlling the solvent properties and reaction rates and selectivities through pressure manipulations. Transition-state theory was used herein to interpret the effect of pressure on the overall reaction rate as an apparent activation volume that can be further decomposed into various contributions: DELTA-V(app) = -RT(d ln r/dP) = DELTA-V(int)k + DELTA-V(comp)k + DELTA-V(diff)k + DELTA-V(elec)k + DELTA-V(p)pi, accounting for mechanical pressure effects, solvent compressibility, diffusional limitations, electrostatic interactions, and phase behavior effects, respectively. The present investigation emphasized the latter three and evaluated their contributions as DELTA-V(diff)k = 1090 cm3/mol for benzyl phenyl ether pyrolysis; DELTA-V(elec)k = -3700, -2600, and -220 cm3/mol for hydrolysis of dibenzyl ether, phenethyl phenyl ether, and guaiacol, respectively; and DELTA-V(p)pi = 1600 cm3/mol for dibenzyl ether pyrolysis in toluene.

The influence of supercritical solvent density on the pyrolysis of benzyl phenyl ether (BPE) in tetralin and supercritical toluene is interpreted in terms of transport limitations. Reaction at varying toluene densities highlighted the transport dependence of the BPE fission rate constant. The conversion of BPE decreased from 0.55 to 0.15 as the toluene density increased from 0.0 to 0.75. The yield and selectivity of BPE rearrangement products were also density dependent. These results were explained and modeled quantitatively in terms of the cage effect theory.

The thermolysis of benzylphenylether (BPE) was examined at 320°C in liquid, vapor, and supercritical methanol phases as a probe of the reaction mechanism. Toluene and phenol were the major products in all cases, but observed selectivities were dependent upon the reaction phase. Isotopic labeling experiments demonstrated that methanol participated in the reaction network as a hydrogen donor through a free-radical mechanism. These results are consistent with free-radical steps for neat BPE primary pyrolysis that include BPE fission followed by hydrogen abstraction and radical recombination reactions. A detailed set of 21 free-radical steps quantitatively explains the dependence of the selectivity and conversion on the phase behavior.

The extreme pressure dependence of the solvent properties—density, dielectric constant, and solubility parameter—has been exploited in the scrutiny of the mechanism of hydrolysis in supercritical water. Molecules containing the structural moiety of a saturated carbon attached to a heteroatom-containing leaving group undergo parallel pyrolysis and hydrolysis reactions in supercritical water. Herein, kinetics, labelling studies, and salt effects are used to assess likely mechanisms. Under isothermal conditions, the selectivity to the hydrolysis pathway increased with water density. Moreover, the rate constant for hydrolysis also increased with water density and with the addition of salts. An SN2 mechanism with H2O as the nucleophile appears to be the most likely candidate.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTHydrolysis in supercritical water: identification and implications of a polar transition stateGilbert L. Huppert, Benjamin C. Wu, Susan H. Townsend, Michael T. Klein, and Stephen C. PaspekCite this: Ind. Eng. Chem. Res. 1989, 28, 2, 161–165Publication Date (Print):February 1, 1989Publication History Published online1 May 2002Published inissue 1 February 1989https://pubs.acs.org/doi/10.1021/ie00086a006https://doi.org/10.1021/ie00086a006research-articleACS PublicationsRequest reuse permissionsArticle Views484Altmetric-Citations70LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTReactions in and with supercritical fluids: effect of phase behavior on dibenzyl ether pyrolysis kineticsBenjamin C. Wu, Michael T. Klein, and Stanley I. SandlerCite this: Ind. Eng. Chem. Res. 1989, 28, 3, 255–259Publication Date (Print):March 1, 1989Publication History Published online1 May 2002Published inissue 1 March 1989https://doi.org/10.1021/ie00087a001RIGHTS & PERMISSIONSArticle Views60Altmetric-Citations6LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts

The reactions of dibenzylamine (DBA) were studied neat and in methanol and water solvents. Neat pyrolysis afforded toluene and benzylidenebenzylamine (BBA) as the major low-molecular -weight products. Subsequent neat pyrolyses of BBA and benzylamine (a primary product of DBA pyrolysis) allowed formulation of a consistent free-radical mechanism for DBA reaction. Reaction in supercritical methanol yielded benzyl alcohol, benzaldehyde, and N-methylamine in addition to those products observed from neat pyrolysis.

A new method is presented for the analysis of anisotropic thin-plate bending problems. This method appears to enjoy several advantages over other numerical methods for linear problems.

An integral equation method which has been applied to thin elastic clamped plates of arbitrary plan form[1] has been extended to include arbitrary boundary conditions. Numerical difficulties which arise in the case of free boundaries have been avoided by defining an integration contour which differs from the actual plate boundary. Thus second order singularities which arise in the integrand of the equations are avoided.

The translational activities of cytoplasmic poly A(+) RNA of normal rat liver and Novikoff hepatoma cells in the wheat germ cell free system were found to be approximately 15–20 times greater than those of the corresponding nuclear poly A(+) RNA. The translationsl activities were 85 and 62 pmoles3H-leucine incorporated/µg cytoplasmic poly A(+) RNA for the liver and tumor respectively and 3–4 pmoles3H-leucine incorporated/µg nuclear poly A(+) RNA. Inasmuch as integrity of the ‘5′-cap’ of mRNA is essential for its translational activity, quantitative comparisons were made of its content in these RNA fractions. Of the total32P incorporated into the tumor cytoplasmic poly A(+) RNA, 0.41% was in the ‘5′-cap’; in nuclear poly A(+) RNA, the ‘5′-cap’ contained 0.11%. After periodate oxidation and labeling with KB3H4, m7 guanosine, the 5′-terminal nucleoside in both liver and Novikoff hepatoma nuclear poly A(+) RNA contained approximately 20% as much isotope as in the cytoplasmic poly A(+) RNA. These results suggest the lower translational activity of nuclear poly A(+) RNA is partly related to its lower content of the ‘5′-cap’. Molecular selection of poly A(+) RNA for transport out of the nucleus or further cytoplasmic processing may account for the higher percentage of the ‘5-cap’ and the greater translational activity of the cytoplasmic poly A(+) RNA. During these studies, it was also found that the m7 guanosine of the ‘5′-cap’ was not removed during translation of the mRNA in the wheat germ system; this result suggests that the ‘5′-cap’ may associate with allosteric binding sites of initiation factor(s).

Publisher Summary This chapter discusses a comparison of the nuclear and cytoplasmic messenger RNAs with respect to translational activities and their content of the cap. It reviews the probable allosteric nature of the interaction of the cap and its associated protein. The chapter also deals with the potential usefulness of the information derived from these studies in the development of a survey system for quantitative and qualitative analysis of mRNAs in tissues. It provides some new approaches to studies on mRNA r-prot (r-prot = ribosomal proteins), and some new studies on inhibitors of cap function. The translational activity of nuclear RNA (A n ) is less than that of cytoplasmic mRNA. Low translational activities of hnRNA have also been reported. The hnRNA of liver has a low translational capacity in the Krebs ascites cell-free system; the corresponding activity of cytoplasmic mRNA was not determined. The findings that hnRNA from adenovirus-infected cells can be translated only in the presence of nuclei and suggest that further processing by the nuclei was required.