Benzenesulfonic Acid - an Green Efficient Esterification Catalysts for Continuous Synthesis of n-propyl Acetate

The esterification of acetic acid and n-propanol catalyzed by benzenesulfonic acid and its derivatives in the batch and continuous rectification tower was studied, in order to develop a new effective and green catalyst instead of the oxidative and corrosive sulfuric acid. A series of the comparison system with sulfuric acid was build for the targeted and fast evaluation of catalysts. The results showed that the catalytic esterification activity of p-phenolsulfonic acid and p-toluenesulfuric acid is very closed to sulfonic acid in the continuous rectification tower. Furthermore, the stability test for continuous esterification with p-toluenesulfuric acid presented that the high yield of n-propyl acetate could maintain 50 hours and stability. Therefore, p-phenolsulfonic acid and p-toluenesulfuric acid could be prospective substitutes for sulfuric acid for the continuous synthesis of n-propyl acetate in the rectification tower.

Separation and Rectification of Chloroacetyl Chloride from TiCl4

Titanium tetrachloride (TiCl4) is an important intermediate material for the preparation of titanium products. The organic impurities in TiCl4 are easily accumulated during the production of titanium sponges due to the problems of imperfect detection methods and the lack of effective control methods, resulting in a poor quality of sponge titanium. Among all impurities, chloroacetyl chloride (CAC) is the most important in TiCl4. Herein, the determination of the CAC content in TiCl4 solution, with a low detection limit of 0.633 ppm, was established by the standard addition method using Fourier transform infrared (FTIR) spectrometry. This test method presented good repeatability, excellent accuracy, and moderate precision. Furthermore, the influencing factors of CAC separation in the continuous rectification process, including the heating power (the ratio of total heating power to feed rate), reflux temperature, top tower pressure, and feed temperature were optimized based on an orthogonal experimental design. The experimental data demonstrated that the average CAC removal rate reached 78.94% ± 1.00% under the optimal distillation conditions, with 72.21% of the CAC removed via the off-gas system. Therefore, excellent control of the negative pressure of the tail gas is highly desirable for the removal of CAC impurities.

Innovation in Continuous Rectification for Tequila Production

In this study, a new process of continuous horizontal distillation at a pilot level is presented. It was applied for the first time to the rectification of an ordinario fraction obtained industrially. Continuous horizontal distillation is a new process whose design combines the benefits of both distillation columns, in terms of productivity and energy savings (50%), and distillation stills in batch, in terms of the aromatic complexity of the distillate obtained. The horizontal process of continuous distillation was carried out at the pilot level in a manual mode, obtaining five accumulated fractions of distillate that were characterized by gas chromatography (GC-FID). The tequila obtained from the rectification process in this new continuous horizontal distillation process complies with the content of methanol and higher alcohols regulated by the Official Mexican Standard (NOM-006-SCFI-2012). Continuous horizontal distillation of tequila has potential energy savings of 50% compared to the traditional process, besides allowing products with major volatile profiles within the maximum limits established by the regulation for this beverage to be obtained.

Identification of low-boiling fraction of pyrolysis oil

Composition of the low-boiling fraction of the pyrolysis oil obtained from continuous rectification has been determined by combination of capillary gas-liquid chromatography with other identification methods (catalytic hydrogenation, polymerization). In this way components have been identified which form overall 86.0 per cent (m/m) of the low-boiling fraction. The said pyrolysis oil fraction has been found to contain almost 50 per cent (m/m) of unsaturated components able of polymerization, especially methylindenes, methyl-, ethyl- and dimethylvinylbenzenes, divinylbenzenes and 1,2-dihydronaphthalene. Elution behaviour of all the identified isomeric methylindenes, divinylbenzenes and 1,2-dihydronaphthalene has been evaluated by determination of parameters of the equation Ist.phase (2) = k . Ist.phase(1) + q. The Kovats elution indices of all the identified aromatic hydrocarbons have been determined with the use of a glass capillary column wetted with Carbowax 20M at 80 °C.