Study On Higher Alcohols Synthesis Over Sulfur-tolerant Mo-based Catalysts In Slurry Reactor

Higher alcohols, synthesized from syngas based on coal or natural gas, is one of the substitutes of gasoline due to its blending with gasoline well and environmentally friendly properties ,It is now attracted more and more attention in the world. The sulfide molybdenum based catalyst is one of the most important catalyst systems for the synthesis of higher alcohols for its good performances on reaction activity and sulfur resistance. The studies to improve the activity and selectivity of the catalyst were focused on the addition of transition metals. In this paper, MoS₂ doped with K₂CO₃ and the preparation conditions of ADM modified by Ni in slurried bed reactor for the synthesis of higher alcohols were studied. The main conclusions are as follows:(1) MoS₂ doped with K₂CO₃ can improve the alcohol selectivity. The highest alcohol selectivity and space time yield were up to 20.0% and 142.1 g.kg^-1·h^-1 respectively when the ratio of K₂CO₃/MoS₂ was 0.6g/g. The alcohol selectivity and space time yield of the catalyst prepared by impregnation method were improved by 1.42% and 1.88 g.kg^-1.h^-1 respectively compared with the direct mixing method.(2) The quantity of Ni on ADM and Ni/ADM preparation conditions impacted its catalytic performance greatly. The alcohol selectivity and space time yield were up to 21.1% and 180.8 g·kg^-1·h^-1 respectively when the atomic ratio of Ni/ADM was 1/3, pH value was about 7 and calcinations temperature was 500℃in the co-precipitation process.(3) The optimal conditions for the synthesis of higher alcohols in our slurried bed reactor were: temperature 280℃, pressure 6MPa, space rate 1200h^-1, H₂/CO(volume)3, and stirring rate 900r/min.(4) The XRD peaks of MoS₂ doped with K₂CO₃ were not shifted, but its crystalline shape changed obviously according to its SEM pictures. Mo⁶⁺ was an important species for the synthesis of higher alcohols because the Mo⁶⁺ species will not increase when the ratio of K₂CO₃/MoS₂ more than 0.6g/g according to XPS characterization data. The BET surface area of Ni/ADM reached its peak value 7.96m².g^-1 and the crystallinity of NiS enhanced obviously when it was calcined at 500℃.