Catalytic dehydration of 2 propanol over Al2O3-Ga2O3 and Pd/Al2O3-Ga2O3 catalysts

Effect of C3-Alcohol Impurities on Alumina-Catalyzed Bioethanol Dehydration to Ethylene: Experimental Study and Reactor Modeling

The impact of feedstock impurities on catalytic process is among the crucial issues for processing real raw materials. A real and model 92%-bioethanol contaminated with 0.03–0.3% mol 1-propanol or 2-propanol were used to make ethylene on a proprietary alumina catalyst in isothermal flow reactor. We proposed a formal kinetic model to describe the impure bioethanol conversion to ethylene and byproducts and used it to evaluate the multi-tubular reactor (MTR) for 60 KTPA ethylene production. The simulated data agree well with experimental results. Under reaction-controlled conditions, C3-alcohols strongly suppress the formation of by-products and ethylene-from-ethanol, and slightly inhibit the formation of ethylene-via-ether. It is the suppression of the ethylene-via-ether route that causes a decrease in ethanol conversion. The predominant formation of ethylene-via-ether results in an increased ethylene yield but doubling the catalyst load is required to achieve conversion as for pure feedstock. 2-Propanol has a stronger effect on dehydration than 1-propanol. Diffusion inside the grain’s levels out the effect of C3-alcohols on the process in MTR, giving an ethylene yield as high as ~98% while dehydrating a contaminated 92% ethanol. However, impurities dilute ethanol and generate propylene (which contaminates target product), and these worsen feedstock consumption and ethylene productivity in MTR.

Full-spectrum nonmetallic plasmonic carriers for efficient isopropanol dehydration

Plasmonic hot carriers have the advantage of focusing, amplifying, and manipulating optical signals via electron oscillations which offers a feasible pathway to influence catalytic reactions. However, the contribution of nonmetallic hot carriers and thermal effects on the overall reactions are still unclear, and developing methods to enhance the efficiency of the catalysis is critical. Herein, we proposed a new strategy for flexibly modulating the hot electrons using a nonmetallic plasmonic heterostructure (named W₁₈O₄₉-nanowires/reduced-graphene-oxides) for isopropanol dehydration where the reaction rate was 180-fold greater than the corresponding thermocatalytic pathway. The key detail to this strategy lies in the synergetic utilization of ultraviolet light and visible-near-infrared light to enhance the hot electron generation and promote electron transfer for C-O bond cleavage during isopropanol dehydration reaction. This, in turn, results in a reduced reaction activation barrier down to 0.37 eV (compared to 1.0 eV of thermocatalysis) and a significantly improved conversion efficiency of 100% propylene from isopropanol. This work provides an additional strategy to modulate hot carrier of plasmonic semiconductors and helps guide the design of better catalytic materials and chemistries.

Catalytic Dehydration of Isopropanol to Propylene

Catalytic dehydration of isopropanol to propylene is a common reaction in laboratories to characterize the acid–base properties of catalysts. When acetone is produced, it is the sign of the presence of basic active sites, while propylene is produced on the acid sites. About 2/3rd of the world production of isopropanol is made from propylene, and the other third is made from acetone hydrogenation. Since the surplus acetone available on the market is mainly a coproduct of phenol synthesis, variations in the demand for phenol affect the supply position of acetone and vice versa. High propylene price and low demand for acetone should revive the industrial interest in acetone conversion. In addition, there is an increasing interest in the production of acetone and isopropanol from CO/CO2 via expected more environmentally friendly biochemical conversion routes. To preserve phenol process economics, surplus acetone should be recycled to propylene via the acetone hydrogenation and isopropanol dehydration routes. Some critical impurities present in petrochemical propylene are avoided in the recycling process. In this review, the selection criteria for the isopropanol dehydration catalysts at commercial scale are derived from the patent literature and analyzed with academic literature. The choice of the process conditions, such as pressure, temperature and gas velocity, and the catalysts’ properties such as pore size and acid–base behavior, are critical factors influencing the purity of propylene. Dehydration of isopropanol under pressure facilitates the downstream separation of products and the isolation of propylene to yield a high-purity “polymer grade”. However, it requires to operate at a higher temperature, which is a challenge for the catalyst’s lifetime; whereas operation at near atmospheric pressure, and eventually in a diluted stream, is relevant for applications that would tolerate a lower propylene purity (chemical grade).

Effect of crystal size on the acidity of nanometric Y zeolite: number of sites, strength, acid nature, and dehydration of 2-propanol

Crystallinity damage in acid Y zeolite affects the direct relationship between the number of acid sites or conversion of 2-propanol and the zeolite size and the selectivity of 2-propene in nanosized Y zeolite.

Durability and activity of Co2YZ (Y = Mn or Fe, Z = Ga or Ge) Heusler alloy catalysts for dehydrogenation of 2-propanol

Using dehydrogenation of 2-propanol as a test reaction for Heusler alloy catalysts, durability against oxidation and a relationship between activity and electronic structures were revealed.

Pd Modification and Supporting Effects on Catalytic Dehydration of Ethanol to Ethylene and Diethyl Ether over W/TiO2 Catalysts

In the present work, the palladium (Pd) modification and supporting effect of W/TiO₂ catalysts on catalytic ethanol dehydration to ethylene and diethyl ether were investigated. The Pd modification with different sequence of Pd and W impregnation on the catalysts was prepared by the incipient wetness impregnation technique. The catalyst characterization and activity testing revealed that the different sequence during impregnation influenced the physicochemical properties and ethanol conversion of catalyst. The differences in structure and surface properties were investigated by XRD, BET, SEM, EDX, XPS and NH₃-TPD. Upon the reaction temperature between 200 to 400°C, it was found that the conversion increased with increasing of temperature for all catalysts. The Pd incorporated into catalysts enhanced the ethanol conversion depending on the sequence of impregnation. At low temperature (ca. 200 to 300°C), diethyl ether is a major product and the Pd modification over W/TiO₂ catalyst resulted in increased diethyl ether yield. This is because an increase of ethanol conversion was obtained with Pd modification, while diethyl ether selectivity did not change. This can be attributed to the higher amount of weak acids sites present after Pd modification into catalyst. Among all catalysts, the PdW/TiO₂ catalyst (coimpregnation) achieved the highest diethyl ether yield of 41.4% at 300℃. At high temperature (ca. 350 to 400°C), ethylene is the major product. The W/Pd/TiO₂ catalyst (with sequential impregnation of Pd on TiO₂ followed by W) exhibited the highest ethylene yield of 68.1% at 400°C. It can be concluded that the modification of Pd onto W/TiO₂ upon different sequence of Pd and W impregnation can improve the diethyl ether and ethylene yield in catalytic ethanol dehydration.

The competition between dehydrogenation and dehydration reactions for primary and secondary alcohols over gallia: unravelling the effects of molecular and electronic structure via a two-pronged theoretical/experimental approach

The relative dehydrogenation/dehydration reactivity imparted by nanostructured gallium(iii) oxide on alcohols was investigated via electronic structure calculations, reactivity tests and DRIFT-IR spectroscopy.