A Comparative Study of Solvent-Free and Highly Efficient Pinene Hydrogenation over Pd on Carbon, Alumina, and Silica Supports

Abstract

Solvent-free catalytic hydrogenation of pinene over Pd on carbon, alumina, and silica supports were compared. Despite the absence of solvent, Pd catalyst on all three supports yields to a quantitative conversion of pinene to pinanes and a higher selectivity for the cis isomer (72−89%). The temperature affected similarly the selectivity of the reaction for all three catalysts in favor of the cis-pinane isomer. However, recycling of the Pd on the three tested supports varied greatly. If Pd/C and Pd/alumina were successfully recycled 13 and 14 times, respectively, Pd/silica could be used only once to convert pinenes into pinanes. Remaining very effective during all 13 cycles, Pd/C was the best catalyst/support of the three tested ones for the solvent-free hydrogenation of pinene. The influence of H 2 pressure on pinene conversion rates were investigated for Pd/C catalyst. An extremely low leaching rate of palladium in pinenes and pinanes determined by ICP/MS confirmed the heterogeneous nature of this catalytic solvent-free reaction. The hydrogenation reaction presented in this paper is an alternate environmentally friendly pathway for pinane synthesis.

The conversion of α-pinene to cis-pinane using a nickel catalyst supported on a discarded fluid catalytic cracking catalyst with an ionic liquid layer

“…Ethanol has been used as solvent in general hydrogenation reaction and especially for the pinene hydrogenation. 1 Cocker et al has studied the hydrogenation of a-pinene over Pt/C (5 wt%) catalyst with EtOH as solvent and obtained high selectivity for cis-pinane (98.5%). 44 Dorjnamjin et al have used the OH-ILs as a reducing agent which reduces the Ag ion to Ag 0 as well as a stabilizer in forming Ag nanoparticles, and the -CH 2 OH-group in OH-ILs is converted to the -CHOgroup by reducing Ag ion and protects the Ag nanoparticles at the same time.…”

“…As a natural, green, and renewable product, a-pinene has drawn great interest for applications in the pharmaceutical, bioenergy, ne chemistry, and avouring industries. 1 There are two kinds of hydrogenation products of a-pinene, namely, cis-pinane and trans-pinane, and among these two products, cis-pinane is more desirable since the content of cis-pinane in raw materials should be greater than 90% to reduce by-products and simplify post-treatments. There is a need to design and identify more effective catalysts for the selective hydrogenation of a-pinene to improve the yield of cis-pinane.…”

“…4 Selka et al achieved excellent catalytic activity and selectivity based on their studies into hydrogenation of a-pinene over Pd-based catalysts on different supports; however, the reusability of these catalysts was poor. 1 Simakova et al investigated the hydrogenation of a-pinene over 4 wt% palladium on carbon (Pd/C) as a catalyst with n-octane as a solvent. 5 Tanielyan et al used ethanol as solvent in their studies of pinene hydrogenation over anchored Wilkinson catalyst.…”

Highly selective and recyclable hydrogenation of α‐pinene catalyzed by ruthenium nanoparticles loaded on amphiphilic core–shell magnetic nanomaterials

“…To prevent the aggregation of metal nanoparticles, a stabilizer or supported catalyst is usually applied in the catalytic system . Touaibia's team has systematically studied solvent‐free hydrogenation of pinenes over heterogeneous catalysts based on different active metals (Pd, Pt, Ru, and Rh) and supports (carbon, silica and alumina), and the results show Ru/C provides the best catalytic activity under 2.75 MPa H 2 . Our research group has made some progress in the stabilization of metal nanoparticles by using some polymers such as PVA, F127, P123, and TPGS‐1000 as stabilizers .…”

“…[15,16] Touaibia's team has systematically studied solvent-free hydrogenation of pinenes over heterogeneous catalysts based on different active metals (Pd, Pt, Ru, and Rh) and supports (carbon, silica and alumina), and the results show Ru/C provides the best catalytic activity under 2.75 MPa H 2 . [17,18] Our research group has made some progress in the stabilization of metal nanoparticles by using some polymers such as PVA, F127, P123, and TPGS-1000 as stabilizers. [19][20][21][22] A high catalytic activity can be achieved under mild conditions owing to the formation of hydrophobic micellar microreactors.…”