Self-neutralizing in situ Acid Catalysts from CO2

Abstract

Acids are the most common industrial catalysts but have the disadvantage of requiring post-reaction neutralization and salt disposal. We show the catalytic use of self-neutralizing acids. Carbon dioxide interacts with water and amines to form carbonic acid and carbamates. A similar interaction occurs with alcohols to form alkylcarbonic acids. All three solvent systems provide in situ acid formation for catalysis which can be easily neutralized by removal of carbon dioxide. However, water has poor organic solubility and amines form salts so only alkylcarbonic acids combine good organic solubility with simple neutralization via depressurization. The use of in situ acid also completely eliminates the solid salt wastes associated with many acid processes. To elucidate how to implement these systems in place of a standard acid system we compare the reaction rates of several alkylcarbonic acids with diazodiphenylmethane (DDM). We report also the effect of CO 2 pressure on reaction rate of DDM as well as measure the dielectric constant of these systems. Finally, a Hammett plot is used to identify the dominant step in alkylcarbonic acid catalysis.

An insight into the use of dimethylphenyl carbamate cyclofructan 7 chiral stationary phase in supercritical fluid chromatography: The basic comparison with HPLC

“…As has already been published, the components of mobile phase can interact with CSP in different ways . One of the possible interactions in SFC is the reaction of CO 2 with the free hydroxyl groups of CSP and formation of carboxylic group . The other possibility is adsorption of the alcoholic component of the mobile phase on CSP.…”

Fractioned High Pressure Extraction of Anthocyanins from Elderberry (Sambucus nigra L.) Pomace

“…The dissolved CO 2 negatively affected ESE yields (decrease of 1-7%); and so, the possible positive influence of the enhanced transport properties of gas-expanded liquids (Chamblee et al 2004) and the decrease in the solvent mixture pH were not so significant as the negative influence of the decrease in the solvent polarity that happened when CO 2 was added to the solvent (Weikel et al 2006). However, an increase of TA contents, from 105 to 149 mg g −1 for in natura pomace and from 111 to 120 mg g −1 for dried pomace (Table 1), occurred for the CO 2 -EtOH-H 2 O gas-expanded mixtures; so, not only the higher solvent mixture density and polarity but also the solvent's pH drop can have important roles in the extraction of these polar substances (West et al 2001).…”

Reversible Uptake of COS, CS2, and SO2: Ionic Liquids with O‐Alkylxanthate, O‐Alkylthiocarbonyl, and O‐Alkylsulfite Anions

“…[12] Therefore, the stabilizing effect of these bases should also work for the reactions of these gases with alcohols. Alkylcarbonic acids, formed by the reaction of CO 2 with alcohol, are unstable in the absence of a base and are known to readily decarboxylate unless under CO 2 pressure, [13][14][15] and the same instability was expected for COS and CS 2 derivatives. [12] It has recently been shown that alkylcarbonic acids can be reversibly trapped as liquid alkylcarbonate salts when in the presence of amidines and guanidines [this is the basis of the CO 2 BOLs, Eq.…”