Two-Step Catalytic Hydrogenation Of Industrial Naphthalene To Decalin

Decalin, which has cis-and trans-figuration and it is colorless transparent Solut at room temperature, Cis-decalin own Large space structure, high energy, usually converted to trans-decalin. Decalin is insoluble in water, but it can miscibility with organic solvents, is widely used as organic solvent in chemical and pharmaceutical industry.Currently, decalin has been mostly obtained by naphthalene analogues or refined naphthalenes. So far the hydrogenation of industrial naphthalene to decalin has rarely been reported, which a better way is made with cost savings in mind. Consequently, it has very important significance in studying the system of hydrogenation of industrial naphthalene that makes the decalin available.A two-step hydrogenation was employed in this project for the scale-up production. The hydrogenation of naphthalene to tetralin was first catalyzed by NiMo/Al2O3 sulfide and the reaction was performed at 300℃,4 MPa, hydrogen/oil ratio of 600, liquid hourly space velocity of 4 h-1, which was the optimum technical condition. Moreover, the NiMo/Al2O3 catalyst could maintain the activity for even 180 h of continuous reaction. It was noteworthy that the sulfur content was obviously decreased from 809.34 ppm to 19.30 ppm under optimal conditions, indicating that the NiMo/Al2O3 catalyst exhibited great desulfurization ability.Based on this, the products originated from the first step hydrogenation, as substrate, which was fully hydrogenated to decalin over the Pd/Al2O3 and PtPd/SiO2-Al2O3 catalyst, respectively. It indicated that the PtPd/SiO2-Al2O3 catalyst exhibited the better activity and selectivity to decalin, extraordinarily, up to 99.9%. The optimal hydrogenation was at 200℃,4 MPa, hydrogen/oil ratio of 600, liquid hourly space velocity of 1 h-1. In addition, Comparing the influence of different process conditions to the molar ratio of cis-decalin and trans-decalin. Results show that the effect of temperature on the most significant, followed by the liquid hourly space velocity, pressure and the impact of hydrogen/oil ratio on the minimum. Additionally, the sulfide catalysts and noble metal catalysts were also characterized by means of XRD, TEM, BET, N2 adsorption. The relationship between catalyst structure properties and hydrogenation performance was established. The NiMo/Al2O3 catalyst structure-stability, the specific surface area is 171 m2/g, corresponding to pore diameter was 5 nm-10 nm, Large pore provides a Larger space for naphthalene, and The specific surface area of PtPd/SiO2-Al2O3 catalyst was 171 m2/g, Larger surface area allows a more uniform distribution of the PtPd metal particlesWhich is benificial to naphthalene hydrogenation. It is implied that the conversion of industrial naphthalene could reach to 100% and the yield of decalin could reach up to 99.9%. Expectantly, most of the sulfur in raw materials has been removed. It provides an important theoretical basis for the industrial production with a good application prospect.