Preparation Of A Carbon-based Solid Acid Catalyst With Hign Specific Surface Area By Biomass Wood Powder

Liquid acid catalyst is one of the most important chemical industry catalysts, be used extensively in chemical industry. It has some advantages, including strong acid, low price, high catalytic activity and so on. However, its use is wasteful and energy-inefficient, requiring separation, recycling, and treatment of waste, and easy to cause environment pollution problems. Solid acid catalyst is simple in operation, easy to woke up, and has no waste acidic liquor to drain off during reactions, friendly to environment and so on, comparing with liquid acid catalyst.The carbon-based solid acid catalyst is of strong acid, good chemical and thermal stability, low price and so on, but it has a relatively low specific surface area, which goes against the esterification of long chain acid. In order to solve this problem, a carbon-based solid acid catalyst with high specific surface area is presented in this paper. We used the hydrochloric acid with ZnCl₂ to activate biomass wood powder, then to carbonize, and finally to sulfonate or diazonium salt reduction to prepare the carbon-based solid acid. We examined the activity of the prepared carbon-based solid acid catalysts by the acetic acid, hexanoic acid, decanoic acid esterification with ethanol.The results were listed as follows:(1)The carbon-based solid acid catalyst activated by ZnCl₂ with hydrochloric acid solution is superior to the one without activated, its specific surface area is more than 1800 m2/g when ZnCl₂ solution with a concentration of 40 %, carbonization temperature of 500℃, carbonization time of 2 h.(2)Carbonization temperature on the catalytic properties is significant, when the carbonization temperature is 500℃, the density of acid catalyst is maximum to 4.43 mmol/g; the optimum conditions of sulfonation are following: the amount of concentrated sulfuric acid to the activated carbon mass ratio of 25:1, sulfonation temperature of 150℃, sulfonation time of 6 h.Solid acid catalysts prepared by different biomass wood powders have different catalytic activitives. The order is wheat straw powder <corn straw powder <walnut shell powder <pine powder, the catalyst made by pine power has the highest catalytic activity. (3)The optimum reaction conditions were determined by optimizing the parameters of esterification reaction, namely: ethanol to acid molar ratio of 10:1, catalyst dosage of 6% acid weight, esterification temperature of 80℃and the esterification time of 8 h.(4)The carbon-based solid acid catalyst prepared by the diazonium salt for the esterification of long chain acid is better than the catalyst prepared by the sulfurination.