Carbon-based solid acid catalysts were prepared using rice straw (RS) waste, and the effects of carbonization temperature and sulfonation temperature on the catalytic activity were investigated. The properties of the catalysts were characterized using thermo gravimetric (TG), scanning electron microscope (SEM), Brunauer-Emmet-Teller (BET), Fourier transform infrared spectroscopy (FT-IR), temperature-programmed desorption (TPD), and X-ray photoelectron spectroscopy (XPS), and their activities were investigated through the hydration of α-pinene. The conversion of α-pinene and the selectivity of α-terpineol reached 67.60% and 57.07% at 80 • C and atmospheric pressure in 24 h, respectively. The high catalytic capacity of the catalyst is attributed to the high acid site density and high porosity of the catalyst. TPD analysis and FT-IR spectroscopy showed that the catalyst produced by low-temperature carbonization at 300 • C followed by low-temperature sulfonation at 80 • C had abundant strong acid sites (0.82 mmol/g), which can effectively inhibit the side reactions of hydrated α-pinene. The total acidity reached 2.87 mmol/g. N 2 -physisorption analysis clearly indicated that the obtained catalysts were mesopore-predominant materials, and the S BET and V Total of catalysts reached 420.9 m 2 /g and 4.048 cm 3 /g, respectively. Preparation of the catalyst involves low energy consumption, and its cheap raw materials make the whole process simple, economical, and environmentally friendly.Catalysts 2020, 10, 213 2 of 18 the conversion of α-pinene and selectivity of α-terpineol reached 99.00% and 70.00%, respectively [3]. However, the excess of liquid acid cannot be recycled from the reaction mixture sufficiently. In addition, equipment corrosion and environmental contamination are serious problems in the traditional process of α-terpeneol preparation.The heterogeneous method generally uses a solid acid catalyst. Yang et al. studied the hydration of α-pinene using a pilot-scale jet reactor and Amberlyst 15 catalysts in aqueous ispropylamine at the temperature of 70 • C. The Amberlyst 15 catalysts showed good activity (93.12% conversion with 35.20% selectivity of α-terpineol) and the pilot-scale jet reactor increased the mass transfer between α-pinene and catalysts [4]. Maria et al. prepared inorganic oxide-supported trichloroacetic catalysts for the hydration of α-pinene. The conversion of α-pinene and selectivity of α-terpineol reached 57.00% and 75.00%, respectively. The carboxylate group of trichloroacetic acid incorporated Zr to form a six-membered ring, which facilitated the increase in the carboxylate group loaded onto the support and improved the Brönsted acidity [5]. Valente and Vital studied the hydration of α-pinene by ultra-stable Y zeolite catalysts in aqueous acetone. The conversion of α-pinene and the selectivity of α-terpineol reached 90.00% and 55.00%-60.00%, respectively. The ultra-stable Y zeolite catalysts showed increased activity and selectivity to α-terpineol because of the gradual improvement in the n...

In this study, silicoaluminophosphate (SAPO)-34 and Me (Me = Cr, Co)-modified SAPO-34 were synthesized and used as catalysts to investigate the catalytic performance by means of a probe reaction from ethanol to ethylene. The metal oxides were loaded on the SAPO-34 support via an impregnation method. The synthesized catalysts were characterized using XRD, SEM, EDX, FT-IR, NH3-TPD, BET, and TGA techniques. Compared to SAPO-34, SAPO-34 doped with metal oxides showed the same chabazite (CHA) topology. The structure and properties of the catalyst were further optimized by varying the amount of Me. The experimental results showed that Co-Cr/SAPO-34 exhibited the best catalytic performance when the reaction temperature reached 400 °C at a weight hourly space velocity (WHSV) of 3.5 h−1, for which the single-pass conversion of ethanol was determined as 99.15%, and the selectivity of ethylene was 99.4% at an optimum catalytic performance in the reaction of up to 600 min. In addition, Co-Cr/SAPO-34 exhibited better catalytic activity and anti-coking ability than pure SAPO-34, which was attributed to its enhanced pore structure and moderate acidity. It can also be concluded from the results of this experiment that the performance of the Co-Cr bimetal-supported catalyst is better than that of the Cr mono-metal catalyst.