Hello Faisal,

Thank you for sharing these results. As I am sure you are aware, pyrolysis leads to a complex mixture of products that is sensitive to operating conditions and process design and that is very difficult to predict.accurately. A few more details would be useful (overall stoichiometry, temperature, pressure, initial fuel size and mode of injection). Also, are the furans and esters the primary products you are finding or just among many others, such as phenols, aromatic clusters, etc. Also, what are the products with the catalyst. 

All of that notwithstanding, I can offer some thoughts below rather than just asking for more details.The furans involve in-ring oxygen and esters involve carboxyl groups, neither of which occurs in the lignosulfonates of which I am aware. Assuming these structures are not in your feedstock, it seems clear that your pyrolysis conditions are aggressive enough to be rearranging molecular structure, not just breaking long chains in existing structures.  I assume your lignosulfonates have sulfate functional groups where phenolic functional groups would be in the regular lignin. It is unlikely that the aromatic rings of the lignosulfonate have been ruptured during pyrolysis since they are among the most stable portions of the macromolecule. Therefore, the sulfate group must be reacting for form the carboxy groups plus a sulfur containing light gas (H2S unless there is some additional oxygen) and the furans could be forming from either the same site or from the ether-bonded functional groups that do not contain sulfur. The catalyst may be promoting the further oxidation of these functional groups to CO, H2O, or CO2 with residual, more stable and probably more aromatic, carbon structures. 

I am not sure any of this is detailed enough to help. 

Thanks alot for the kind answer! I though to elaborate further on my experimental condition, perhaps it will help anyone who is interested. Pyrolysis was carried out to 550c at a slow heating rate of 15c/min[fixed bed reactor], lignin mass 2gram. The material was lignosulfonate with a sulfur content of 8wt%. The major compounds for non catalytic run: various Heterocyclic, a great deal phenols,Furans,Esters and some aromatics, and poly aromatics. when HZSm was applied furans and Esters was not observed and the amount of carboxylic acids decreased alot.

The amount of poly aromatic hydrocarbons was the major pyrolysis product for all catalysts to lignin mass ratio. apart from elemental analysis nothing else was known for this lignosulfonate.

The occurence of furans and esters for pyrolysis of this lignin are in agreement with some litterateurs, though no explanation for the origin of these compounds could be found. Its hard to believe that furans and lots of heterocyclic compounds are build as a result of secondary reaction and aromatic rings cleavages since the pyroylsis condition was not that aggressives for Non-catalytic run. 

Amoung the pyrolysis gases some olefines and CO&Co2, H2S were common for both catalytic and non catalytic. 

Best regards Faisal

Dear Faisal,

Generally, when you observe furans, they originate from cellulose residues in the lignin. Depending on the separation method the lignin may still contain a larger fraction of cellulose. This decomposes into furans under pyrolysis conditions. Another prominent molecule from glucose pyrolysis is levoglucosenone; maybe you detected this, too. The lignosulfonate from the pulp mills actually still contains quite a high fraction of cellulose residues, since they aim for high quality pulp with fewer lignin content. Therefore, the pulp mills rather loose a little cellulose yield, but gain higher selectivity. 

Also, the ZSM-5 needs to be freshly calcined prior use, otherwise it may contain still residues from the synthesis or adsorbates that simply accumulated. 

best regards,

 Thanks, i do find your explanation more reasonable for this material. Many thanks !