From last decade Bio-fuel energy hasattracted significant attention due to increased energy consumption andenvironmental issue. Biomass boonsrenewable substitutes to Fossil-fuel as a resource for production of bio-oiland valuable chemicals.
1 With the help of physical, chemical andbiological methods biomass can be converted in to wide range of valuable chemicalsources. Bio-oil, a source of greenenergy produced from fast pyrolysis of lignocellulosic biomass.2Phenolic compounds (bio-oil) from pyrolysis of biomass usually contain up to60% oxygen, deoxygenation helps to improve the heating value and stability.3Up to now, several methods such as aqueous phase reforming,4cracking5 and hydrodeoxygenation6-10 developed forupgrading of bio-oil. Generally,noble metal-based catalysts for example Pd,11,12 Pt,13,14 Rh,15 Ru4,16 andGold-based17,18 systems are still most important catalysts forHDO of biomass derived compounds even though those precious metals haveextensive applications are limited by low earth-abundance and high cost. Thereare so many studies of non-noble catalysts reported on the basis of unmodifiedand changing alkaline and noble metals activity of Co-Mo and Ni-Mo15,19-22type catalysts for hydrodeoxygenation reaction. Also, the non-noble metal likeCo and Ni usually show low activity and it required high pressure (> 2 MPa),high temperature (> 150 °C) and maximum consumption of energy inthe process. In some studies molybdenum carbide on different support used forhydrodeoxygenation reaction.
The non-noble metals did not showyet total conversion in mild condition. Therefore, alternative heterogeneous non-noble metal basecatalyst with shows high performance in mild conditions are desired for thehydrodeoxygenation of biomass. Metal-organicframeworks, a new type of porous crystalline materials which is used from pasttwo decades and their potential applications in catalysis, gas separation andstorage, sensor etc.
It is very popular because having high surface area andcontrollable structures. Researchers designed and made different functionalMOFs by changing metals and organic linkers. Zeoliteimidazolate frameworks (ZIFs) is classified as a subclass of MOFs, haveappeared as a novel type of highly porous materials, having similar advantagesof both zeolites and conventional MOFs. By using MOFs as a solid acid catalystor catalyst support several reactions have been carried out such ashydrogenation, oxidation, aldol condensation, knoevenagel condensation,Suzuki-cross coupling, Friedel-craft alkylation, transesterification reactionand epoxide ring opening reaction. Researchers mostly focused on tosynthesizing new ZIFs and investigating their applications. Recently, carbon nanotube from Zeoliteimidazolate frameworks (ZIFs) with high surface area, hierarchical pores andstable frameworks have been known superior characteristics for catalyticmaterial and support. Metal NPs based N-doped carbon containing heterogenouscatalyst showed enhanced performance because nitrogen with carbon skeletonresult in increasing basicity and hydrophilicity of catalyst which helps todeveloping better interaction between aqueous phase and substrate. In recentstudies promoting effect of N-carbon supported metal catalyst have mainly focusedon precious metals but with non-noble metal didn’t get maximum conversion inmild condition.
It is great challenge to check the promoting effect can help toincrease the conversion with non-noble metals in the mild condition. 2-methoxy-4-methylphenol (MMP) a novel molecule which have potentialfuture of biofuel is getting from hydrodeoxygenation of 4-hydroxy-3-methoxybenzaldehyde(vanillin) which is commonly found in pyrolysis oil. The hydrodeoxygenation ofvanillin always requires high temperature, high pressure and noble metals butit always form by-product HMP (4-hydroxymethyl-2-methoxyphenol) which isindication of incomplete hydrogenation of vanillin due to poor catalyticactivity of catalyst. For the HDO of vanillin, we have synthesized Zn-Co CNx(ZIFs). Herein, we describe a ZIFs whichis based on metallic Co nanoparticles (NP) and Zn(II) Lewis acid areinfrastructure in ZIFs that can selectively hydrodeoxygenation of vanillinunder relatively mild conditions, 130 °C and0.7 MPa of H2.A combination of control experiments and spectroscopic characterization of thecatalyst under relevant reaction conditions points to a synergistic effect between Zn(II) and metallicCobalt without formation of a Zn–Co alloy.