Montmorillonite (MMT) is widely used as the catalyst in the commercial production of dimeric fatty acids (DAs). However, the dimerization activity of MMTs from different mineral sources is usually different, leading to unstable yield of DAs. In order to obtain a high and stable yield of DAs, the relationship between the dimerization activity and characteristics of MMT should be clarified. The characteristics of seven MMTs from different mineral sources, including the acidity (the type, strength, and amount of the acid sites), composition (interlayer cations, Si/Al ratio, water content, pH), and structure (basal spacing) are determined and correlated with their dimerization activity. Additionally, the relationship between dimerization activity and characteristics of MMT is quantified by nonlinear-regression. It is found that the dimerization activity of MMT is mainly influenced by its Brønsted acidity and basal spacing. Stable DA yield of around 70% on MMT is obtained at the amount of weakBrønsted acid sites of more than 0.20 mmol g −1 and basal spacing of larger than 1.50 nm. Additionally, it is found that acid treatment is an effective method to adjust the Brønsted acidity and basal spacing of MMT. Practical Applications: The positive effect of Brønsted acid sites amount and basal spacing on the activity of MMT has practical value on the selection of highly efficient MMT catalyst for DA production. In addition, some MMT with poor activity can be activated by the acid treatment method mentioned in the paper.

An innovative ball-mill reactor was designed and made to produce dimer acid continuously. Mixing and polymerization in the constructed reactor were intensified by the rotation of the cylinder and mechanical actions of small beads. A total of 3 baffles were set up to enhance radial turbulence, and 10 clapboards were sequentially installed to separate the whole reactor into 11 small reactors in series in order to make it close to a plug-flow reactor. The relationship between reaction performance and the inner components (baffles and clapboards), ball-milling medium, rotating speed, wall temperature and residence time were investigated. The crude product containing 50.6% dimer acid was obtained under the optimal conditions (zirconia beads as ball-milling medium, wall temperature 300 °C, residence time 2.16 h, rotating speed 20 rpm). Ferric and nickel ion from the reactor and the uneven residence time distribution resulted in low dimer acid production yield.

Abstract:The mass transfer and reaction kinetics of sulfuryl fluoride (SO 2 F 2 ) absorption with aqueous sodium hydroxide (NaOH) solutions were studied in an experimental double-stirred cell. Results showed that SO 2 F 2 absorption with NaOH was followed by a reaction model employing a fast pseudo-first-order. The second-order rate constant for SO 2 F 2 absorption with aqueous NaOH solutions was determined to be 1.44 m 3 /(mol·s) at 298 K. Three models were used in this chemical absorption process, and in each case, the same expression of enhancement factor was obtained. A comparison was made between the experimental enhancement factor and the value calculated from the model, and the maximum relative deviation was less than 4.2%. The proposed model expression gave a reasonable fit with the experimental values, indicating that mass transfer correlations are valid for scaling up design.

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